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Browning, a white to brown-like (beige) adipocyte conversion, offers a promising therapeutic strategy for the treatment of human obesity. In the present study, the effects of sodium salicylate, a nonsteroidal anti-inflammatory drug, on adipocyte browning were investigated. We found sodium salicylate altered the macrophage phenotype to M2 in RAW264.7 cells, mediated by up-regulation of heme oxygenase-1 (HO-1), and sodium salicylate-treated conditioned medium from macrophages (Sal-M2 CM) induced browning of fully differentiated 3T3-L1 adipocytes. Conversely, the conditioned medium obtained from macrophages when treated with sodium salicylate in the presence of either ZnPP (a HO-1 inhibitor) or HO-1 siRNA did not induce browning. In association with macrophage HO-1 induction by sodium salicylate, iron production also increased, and deferoxamine (an iron chelator) blunted the browning effects of Sal-M2 CM, suggesting that iron may play a role in the Sal-M2 CM-induced browning. The in vivo browning effects of sodium salicylate were confirmed in ob/ob mice, whereas in vivo macrophage depletion by clodronate as well as HO-1 blockade by either ZnPP or adeno-associated virus carrying HO-1 shRNA (AAV-HO-1 shRNA) attenuated the browning effects of sodium salicylate. These results reveal sodium salicylate induces browning in vitro and in vivo by up-regulating HO-1 thus promoting M2 polarization., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Hyperacusis, an exaggerated, sometimes painful perception of loudness even for soft sounds, is a poorly understood distressing condition. While the involvement of modified gain of central auditory neurons and the influence of nonauditory brain regions are well-documented, the issue of where in the auditory system these abnormalities arise remains open, particularly when hyperacusis comes without sensorineural hearing loss. Here we used acute intraperitoneal administration of sodium salicylate (150 mg/kg) in rats, enough to produce > 10-dB decrease in acoustic startle threshold with mild hearing loss at low frequencies (<10 kHz). Anesthesia, necessary for middle-ear-reflex (MEMR) threshold measurements, abolished the olivocochlear efferent reflex but not the MEMR acting on frequencies < 10 kHz, and its mean threshold increased from 55 dB SPL in controls to 80 dB SPL in salicylate-treated animals 60-90 minutes after injection, with an about 3-dB increase in acoustic energy reaching the cochlea. The mean latencies of auditory brainstem-evoked responses (ABR) conspicuously decreased after salicylate, by 0.25 millisecond at 6 kHz at every level, a frequency-dependent effect absent above 12 kHz. A generic model of loudness based upon cross-frequency coincidence detection predicts that with such timing changes, a transient sound may seem as loud at <40 dB SPL as it does in controls at >60 dB SPL. Candidate circuits able to act at the same time on the startle reflex, the MEMR and ABRs may be serotoninergic, as salicylate is known to increase brain serotonin and 5-HT neurons participate in MEMR and ABR circuits., (Copyright © 2019 IBRO. Published by Elsevier Ltd. All rights reserved.)

Following noise overexposure and tinnitus-induction, fusiform cells of the dorsal cochlear nucleus (DCN) show increased spontaneous firing rates (SFR), increased spontaneous synchrony and altered stimulus-timing-dependent plasticity (StDP), which correlate with behavioral measures of tinnitus. Sodium salicylate, the active ingredient in aspirin, which is commonly used to induce tinnitus, increases SFR and activates NMDA receptors in the ascending auditory pathway. NMDA receptor activation is required for StDP in many brain regions, including the DCN. Blocking NMDA receptors can alter StDP timing rules and decrease synchrony in DCN fusiform cells. Thus, systemic activation of NMDA receptors with sodium salicylate should elicit pathological changes to StDP, thereby increasing SFR and synchrony and induce tinnitus. Herein, we examined the action of salicylate in tinnitus generation in guinea pigs in vivo by measuring tinnitus using two behavioral measures and recording single-unit responses from DCN fusiform cells pre- and post-salicylate administration in the same animals. First, we show that animals administered salicylate show evidence of tinnitus using both behavioral paradigms, cross-validating the tests. Second, fusiform cells in animals with tinnitus showed increased SFR, synchrony and altered StDP timing rules, like animals with noise-induced tinnitus. These findings suggest that alterations to fusiform-cell plasticity are an essential component of tinnitus, regardless of induction technique., (Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.)

The central gain model of hyperacusis proposes that loss of auditory input can result in maladaptive neuronal gain increases in the central auditory system, leading to the over-amplification of sound-evoked activity and excessive loudness perception. Despite the attractiveness of this model, and supporting evidence for it, a critical test of the central gain theory requires that changes in sound-evoked activity be explicitly linked to perceptual alterations of loudness. Here we combined an operant conditioning task that uses a subject's reaction time to auditory stimuli to produce reliable measures of loudness growth with chronic electrophysiological recordings from the auditory cortex and inferior colliculus of awake, behaviorally-phenotyped animals. In this manner, we could directly correlate daily assessments of loudness perception with neurophysiological measures of sound encoding within the same animal. We validated this novel psychophysical-electrophysiological paradigm with a salicylate-induced model of hearing loss and hyperacusis, as high doses of sodium salicylate reliably induce temporary hearing loss, neural hyperactivity, and auditory perceptual disruptions like tinnitus and hyperacusis. Salicylate induced parallel changes to loudness growth and evoked response-intensity functions consistent with temporary hearing loss and hyperacusis. Most importantly, we found that salicylate-mediated changes in loudness growth and sound-evoked activity were correlated within individual animals. These results provide strong support for the central gain model of hyperacusis and demonstrate the utility of using an experimental design that allows for within-subject comparison of behavioral and electrophysiological measures, thereby making inter-subject variability a strength rather than a limitation., (Copyright © 2018. Published by Elsevier Ltd.)

Previous studies have indicated that sodium salicylate (SS) can cause hearing abnormalities through affecting the central auditory system. In order to understand central effects of the drug, we examined how a single intraperitoneal injection of the drug changed the level of subunits of the type-B γ-aminobutyric acid receptor (GABAB receptor) in the rat's inferior colliculus (IC). Immunohistochemical and western blotting experiments were conducted three hours following a drug injection, as previous studies indicated that a tinnitus-like behavior could be reliably induced in rats within this time period. Results revealed that both subunits of the receptor, GABABR1 and GABABR2, reduced their level over the entire area of the IC. Such a reduction was observed in both cell body and neuropil regions. In contrast, no changes were observed in other brain structures such as the cerebellum. Thus, a coincidence existed between a structure-specific reduction in the level of GABAB receptor subunits in the IC and the presence of a tinnitus-like behavior. This coincidence likely suggests that a reduction in the level of GABAB receptor subunits was involved in the generation of a tinnitus-like behavior and/or used by the nervous system to restore normal hearing following application of SS., (Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.)

The effect of chronic administration of sodium salicylate (NaSal) on the excitability and synaptic plasticity of the rodent hippocampus was investigated. Repeated systemic treatment with NaSal reliably induced tolerance to the anti-nociceptive effect of NaSal (one i.p. injection per day for 6 consecutive days). Following chronic NaSal or vehicle treatment, a series of electrophysiological experiments on acute hippocampal slices (focusing on the CA1 circuitry) were tested whether tolerance to NaSal would augment pentylenetetrazol (PTZ)-induced long-term potentiation (LTP) and /or epileptic activity, and whether the augmentation was the same after priming activity with a natural stimulus pattern prior to PTZ. We noted an altered synaptic input-to-spike transformation, such that neuronal firing increased after a given synaptic drive. Population spike-LTP (PS-LTP) was increased in the NaSal-tolerant animals, but only when it was induced via a combination of electrical stimulation (theta pattern primed-burst stimulation) and the transient application of PTZ. Identifying and understanding these changes in neuronal excitability and synaptic plasticity following chronic salicylate treatment could prove useful in the clinical diagnosis or treatment of chronic aspirin-induced, or even idiopathic, seizure activity., (Copyright © 2015 Elsevier B.V. All rights reserved.)

We previously identified salicylate as a novel catalytic inhibitor of human DNA topoisomerase II (topo II; EC 5.99.1.3) that preferentially targets the alpha isoform by interfering with topo II-mediated DNA cleavage. Many pharmaceuticals and compounds found in foods are salicylate-based. We have now investigated whether these are also catalytic inhibitors of topo II and the structural determinants modulating these effects. We have determined that a number of hydroxylated benzoic acids attenuate doxorubicin-induced DNA damage signaling mediated by the ATM protein kinase and inhibit topo II decatenation activity in vitro with varying potencies. Based on the chemical structures of these and other derivatives, we identified unique properties influencing topo II inhibition, including the importance of substitutions at the 2'- and 5'-positions. We extended our findings to a number of salicylate-based pharmaceuticals including sulfasalazine and diflunisal and found that both were effective at attenuating doxorubicin-induced DNA damage signaling, topo II DNA decatenation and they blocked stabilization of doxorubicin-induced topo II cleavable complexes in cells. In a manner similar to salicylate, we determined that these agents inhibit topo II-mediated DNA cleavage. This was accompanied by a concomitant decrease in topo II-mediated ATP-hydrolysis. Taken together, these findings reveal a novel function for the broader class of salicylate-related compounds and highlight the need for additional studies into whether they may impact the efficacy of chemotherapy regimens that include topo II poisons., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Parkinson's disease (PD) is the second most common neurodegenerative disorder manifesting in motor, cognitive and behavioral anomalies. Loss of dopaminergic neurons in the substantia nigra region of the brain is the hallmark feature of PD, which is attributed to oxidative and inflammatory stress besides other diverse factors and hence drugs targeting these pathways hold promise as neuro-therapeutics. The anti-oxidative as well as anti-inflammatory properties of sodium salicylate (SS), suggest its neuroprotective potentials in PD. Since PD is a progressive neurodegenerative disorder, the mechanistic basis for utilizing SS as a neuroprotectant in PD could be better understood in the chronic models. The present study utilizes a rotenone-based model of PD to evaluate the neuro-modulatory efficacy of SS. Subcutaneous injection of rotenone (2mg/kg body weight) was given to male SD rats every day, for a period of 5 weeks, which developed all the essential features of PD in these animals. Simultaneously, another group was injected SS intraperitoneally at the dose of 100mg/kg body weight, in addition to the rotenone. In the animals receiving rotenone+SS, significant improvement was observed in the various characteristic hallmarks of PD such as dopamine and tyrosine hydroxylase levels as well as the motor dysfunction symptoms. It attenuated the reactive oxygen species levels significantly but failed to reduce the levels of protein carbonylation and lipid peroxidation. However, SS effectively abridged the levels of inflammatory mediators like cyclooxygenase-2 (COX-2), nuclear factor kappa B and inducible nitric oxide synthase. Correspondingly, a significant decrease in the levels of pro-inflammatory cytokines interleukin-6, interleukin-1β and tumor necrosis factor-α was also observed following SS co-treatment. Thus, neuroprotective efficacy of SS in this chronic model of PD can be largely attributed to its anti-inflammatory effects rather than its free radical-scavenging properties., (Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.)

Effects of morphine on synaptic transmission and plasticity in the hippocampus area CA1 following in vivo sodium salicylate and the potential molecular mechanism were investigated. Population spikes (PS) were recorded from stratum pylamidale of area CA1 following stimulation of Schaffer collaterals in slices taken from control and sodium salicylate injected rats. To induce long term potentiation (LTP), a 100Hz tetanic stimulation was used. Acute in vitro morphine increased baseline PS amplitude in control slices but not in slices taken from sodium salicylate treated rats. In vivo chronic salicylate did slightly decrease and/or destabilize LTP of CA1 synaptic transmission. We also found that mRNA of NR2A subunit of NMDA receptor was reduced in the hippocampus of sodium salicylate treated rats as compared to control ones. Following LTP induction, the mRNA of NR2A and PP1 (protein phosphatase 1) in slices taken from salicylate-treated rats were more than those of control ones. After long-term exposure to in vitro morphine, high frequency stimulation (HFS) decreased NR2A mRNA level significantly in sodium salicylate treated slices. It is concluded that in vivo sodium salicylate causes tolerance to excitatory effect of morphine and changes the ability of HFS to induce PS LTP in the hippocampus area CA1 in vitro. These changes in synaptic response may be due to alterations in NR2A and PP1 expression., (Copyright © 2011 Elsevier B.V. All rights reserved.)

We have previously reported that pretreatment of human lymphoblastoid cells with the hydroxyl radical scavenger, N-acetyl cysteine, attenuates doxorubicin-induced DNA damage signalling through the ATM protein kinase. We sought to extend these studies to examine the effects of other hydroxyl radical scavengers in human breast cancer cells. Using MCF-7 cells, we observed that doxorubicin treatment triggered autophosphorylation of ATM on serine 1981 and the ATM-dependent activation of its downstream effectors p53, Chk2, and SMC1. Furthermore, we demonstrate that this effect was attenuated by pretreatment of cells with the hydroxyl radical scavengers sodium benzoate, sodium salicylate and, to a lesser extent, N-acetyl cysteine, but not Trolox™. Intriguingly, these effects were independent of doxorubicin's ability to redox cycle, were observed with multiple classes of topoisomerase II poisons, but did not represent a general damage-attenuating response. In addition, the observed effects were independent of the ability of sodium salicylate to inhibit cyclooxygenase-2 or NFκB. We demonstrate that sodium salicylate prevented doxorubicin-induced DNA double-strand break generation, which was attributable to inhibition of doxorubicin-stabilized topoisomerase IIα-DNA cleavable complex formation in vivo. Using topoisomerase IIα-DNA cleavage and decatenation assays, we determined that sodium salicylate is a catalytic inhibitor of topoisomerase IIα. Consistent with the observed inhibition of double-strand break formation, pretreatment of cells with sodium salicylate attenuated doxorubicin and etoposide cytotoxicity. These results demonstrate a novel mechanism of action for sodium salicylate and suggest that further study on the mechanism of topoisomerase II inhibition and the effects of related therapeutics on doxorubicin and etoposide cytotoxicity are warranted., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Chemopreventive non-steroidal anti-inflammatory drugs (NSAIDs) exhibit diverse pharmacological and biological activities mainly through their inhibitory effect on cyclooxygenase (COX). However, COX-independent mechanisms involving kinase inhibition have been proposed to explain certain therapeutic effects of NSAIDs. Here, we explored the potential relationship between chemopreventive NSAIDs and DNA damage responses induced by treatment with topoisomerase-targeting drugs. (1) Sodium salicylate, a non-COX-selective NSAID, was shown to reduce DNA damage-induced RPA and p53 phosphorylation. (2) The formation of enzyme cleavable complexes by topoisomerase-targeting drugs was not affected in the presence of sodium salicylate. (3) The attenuating effect of NSAIDs on the DNA damage responses is COX-2-independent, since COX-2-selective inhibitors failed to inhibit DNA damage-induced phosphorylation of replication protein A (RPA) and p53. (4) This COX-2-independent attenuating effect was mediated through interference of neither nuclear factor kappa B nor extracellular signal-regulated kinase pathways. (5) The activation of ataxia telangiectasia mutated (ATM) kinase and DNA-dependent protein kinase (DNA-PK), two key signal transducers upstream of RPA and p53, was found to be significantly reduced with sodium salicylate treatment. (6) Most importantly, sodium salicylate and other NSAIDs directly inhibited kinase activity of ATM and DNA-PK. The extent of inhibition on the kinase activity also correlated with the degree of attenuation on the DNA damage responses. (7) Unexpectedly, sodium salicylate showed a p53-independent protection effect on topoisomerase-mediated cell killing. Together, our study provides evidence that NSAIDs exhibit a novel COX-independent modulating activity of NSAIDs on the DNA damage responses and it is through inhibition of phosphoinositide 3-kinase-like kinases., ((c) 2010 Elsevier B.V. All rights reserved.)

Aspirin is used as chemopreventive agents in a variety of human cancer cells including those of colon, lung, breast, and leukemia. Sodium salicylate (NaSal, the natural deacetylated form of aspirin) induced cell cycle arrest and apoptosis in a dose-dependent manner in A549 cells; high dose (20mM) of NaSal-induced apoptosis, whereas low dose (2-10mM) induced cell cycle arrest. We found that NaSal-activated Akt/PKB, ERK1/2, and p38MAPK signal cascades. Twenty micromolar of NaSal-induced apoptotic response of A549 cells was enhanced by the PI3K inhibitors (LY294002 and wortmannin) and in a less extent by the MEK1/2 inhibitors (U0126 and PD98059), whereas it was suppressed by the p38MAPK inhibitor (SB203580). Furthermore, simultaneous inhibition of the Akt/PKB and ERK1/2 signal cascades could lower the dose of NaSal to induce apoptosis to 2mM in A549 lung cancer cells. Similar enhancement was observed in cells treated with 2mM NaSal and 100muM genistein, an inhibitor of receptor tyrosine kinases (RTKs) that are upstream of PI3K and MEK1/2 signaling. We further demonstrated that NAG-1 plays a key role in apoptosis by NaSal-based combined treatment. Collectively, our findings indicate that inhibition of the pro-survival Akt/PKB and ERK1/2 signaling may increase the chemopreventive effects of NaSal and combined treatment of two natural compounds (NaSal and genistein) results in a highly synergistic induction of apoptosis, thereby increasing the chemopreventive effects of NaSal against cancer.

The nonselective contact herbicide, paraquat (PQ), is a strong pneumotoxicant, especially due to its accumulation in the lung through a polyamine uptake system and to its capacity to induce redox cycling, leading to oxidative stress-related damage. In the present study, we aimed to investigate the occurrence of apoptotic events in the lungs of male Wistar rats, 24, 48, and 96 h after PQ exposure (25 mg/kg ip) as well as the putative healing effects provided by sodium salicylate [(NaSAL), 200 mg/kg ip] when administered 2 h after PQ. PQ exposure resulted in marked lung apoptosis, in a time-dependent manner, characterized by the "ladder-like" pattern of DNA observed through electrophoresis and by the presence of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL)-positive cells (TPC) as revealed by immunohistochemistry. The two main caspase cascades (the extrinsic receptor-mediated and the intrinsic mitochondria-mediated) and the expressions of p53 and activator protein-1 (AP-1) were also evaluated, to obtain an insight into apoptotic cellular signaling. PQ-exposed rats suffered a time-dependent increase of caspase-3 and caspase-8 and a decrease of caspase-1 activities in lungs compared to the control group. A marked mitochondrial dysfunction evidenced by cytochrome c (Cyt c) release was also observed as a consequence of PQ exposure. In addition, fluorescence electrophoretic mobility shift assay (fEMSA) revealed a transcriptional induction of the p53 and AP-1 transcription factors in a time-dependent manner as a consequence of PQ exposure. NaSAL treatment resulted in the remission of the observed apoptotic signaling and consequently of lung apoptosis. Taken together, the present results showed that PQ activates several events involved in the apoptotic pathways, which might contribute to its lung toxicodynamics. NaSAL, a recently implemented antidote for PQ intoxications, proved to protect lungs from PQ-induced apoptosis.

Cyclooxygenase-2 (COX-2) overexpression is associated with cancer. One potential mechanism is DNA damage caused by COX-2 derived oxidants. Since DNA in proliferating cells is highly vulnerable to oxidative damage and mutation, we propose that COX-2 transactivation by exogenous stimuli is suppressed in proliferating cells compared to quiescent cells. In this review, we provide evidence for reduced COX-2 transcriptional expression in response to phorbol esters (PMA), lipopolysaccharide (LPS), interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha). Our results show that COX-2 transcription in proliferating fibroblasts is suppressed by a small molecular weight compound produced by proliferating cells. By contrast, COX-2 expression in response to exogenous stimuli is robust in quiescent cells. The quiescent cells in human body may play a primary role in mounting response to exogenous stimuli. Salicylate inhibits COX-2 transcriptional activation in quiescent cells but not in serum-driven proliferating cells by blocking C/EBPbeta DNA binding. These studies suggest that COX-2 expressions in quiescent and proliferating cells are regulated by different mechanisms. Further investigations into their transcriptional control mechanisms will have great impact on the fundamental understanding of the division of cell functions between quiescent and proliferating cells and the design of novel therapeutic strategies.

Over the past decades, there have been numerous fatalities resulting from accidental or voluntary ingestion of the widely used herbicide paraquat dichloride (methyl viologen; PQ). Considering that the main target organ for PQ toxicity is the lung and involves the production of reactive oxygen and nitrogen species, inflammation, disseminated intravascular coagulation, and activation of transcriptional regulatory mechanisms, it may be hypothesized that an antidote against PQ poisonings should counteract all these effects. For this purpose, sodium salicylate (NaSAL) may constitute an adequate therapeutic drug, due to its ability to modulate inflammatory signaling systems and to prevent oxidative stress. To test this hypothesis, NaSAL (200 mg/kg ip) was injected in rats 2 h after exposure to a toxic dose of PQ (25 mg/kg, ip). NaSAL treatment caused a significant reduction in PQ-induced oxidative stress, platelet activation, and nuclear factor (NF)-kappaB activation in lung. In addition, histopathological lesions induced by PQ in lung were strongly attenuated and the oxidant-induced increases of glutathione peroxidase and catalase expression became absent. These effects were associated with a full survival of the PQ-treated rats (extended for more than 30 days) in comparison with 100% of mortality by Day 6 in animals exposed only to PQ, suggesting that NaSAL constitutes an important and valuable therapeutic drug to be used against PQ-induced toxicity. Indeed, NaSAL constitutes the first compound with such degree of success (100% survival).

Salicylates and nonsteroidal anti-inflammatory drugs (NSAIDs) induce apoptosis in a variety of cancer cells, including those of colon, prostate, breast, and leukemia. We examined the effects of sodium salicylate (NaSal) on reactive oxygen species (ROS) production and the association of these effects with apoptotic tumor cell death. We demonstrate that NaSal mediates ROS production followed by a decrease in mitochondrial membrane potential (deltapsi(m)), release of cytochrome c, and activation of caspase-9 and caspase-3. However, expression of Bcl-2 or Bcl-x(L) prevents ROS production and subsequent loss of deltapsi(m), thereby inhibiting apoptotic cell death. The presence of ROS scavengers and an inhibitor of NADPH oxidase or expression of a dominant negative form of Rac1 blocks ROS production, deltapsi(m) collapse, and the subsequent activation of caspases. These observations indicate that NaSal mediates ROS production critical in the triggering of apoptotic tumor cell death through a Rac1-NADPH oxidase-dependent pathway. Our data collectively imply that NaSal-induced ROS are key mediators of deltapsi(m) collapse, which leads to the release of cytochrome c followed by caspase activation, culminating in tumor apoptosis.

Aspirin (acetylsalicylic acid) is one of the most widely used drugs worldwide. It acetylates cyclooxygenases thereby irreversibly blocking the conversion of arachidonic acid to prostanoids. Biotransformation of aspirin yields salicylate, a compound that possesses similar anti-inflammatory potency as aspirin but lacks aspirin's inhibitory effect on the activity of isolated cyclooxygenase. This article is aimed at providing an overview about the often conflicting results concerning the mechanisms of action of aspirin and sodium salicylate. At present, there is no common agreement about the extent to which salicylate contributes to aspirin's anti-inflammatory properties, as well as there is still no final conclusion reached about the mechanisms of action of sodium salicylate. Several possible sites of action of salicylate have been suggested: It has been shown that in intact cells-but not in purified enzyme preparations-, sodium salicylate inhibits prostanoid biosynthesis. This effect seems to be prevented in the presence of high concentrations of arachidonic acid, which has been shown to interfere with inhibition by salicylate of cyclooxygenase-2-mediated prostanoid formation in vitro. Other possible sites of action that are not directly related to cyclooxygenase inhibition have been suggested based on observations made in vitro using high concentrations of aspirin and sodium salicylate. These effects target intracellular signaling mechanisms such as kinases, including the mitogen activated protein-kinases (MAPK) cascade. With the exception of reported salicylate-induced activation of p38 MAPK, observed effects are usually inhibitory. This may be one reason for the observation that, downstream to kinases, inhibitory effects of salicylates have been observed on several nuclear transcription factors, such as nuclear transcription factor kappa B (NF-kB) or activator protein 1 (AP-1). Several reports have also shown interference by salicylates with the expression of cyclooxygenase-2, which, depending on experimental models, can be observed as inhibitory but also stimulatory effects. Antioxidant properties of salicylates, adenosine release induced by sodium salicylate and aspirin-triggered lipoxin formation are additional mechanisms that may contribute to anti-inflammatory properties of aspirin and/or sodium salicylate. An additional focus of this review is the discussion of interactions between aspirin, sodium salicylate and other non-steroidal anti-inflammatory drugs (NSAIDs), which are of particular relevance in the gastro-intestinal and cardiovascular systems.

The effects of salicylate on the phosphorylation and nuclear translocation of signal transducers and activators of transcription (STATs) induced by interferon-gamma (IFN-gamma) were studied in rat cardiac fibroblasts as a possible model for the anti-inflammatory effects of salicylate on this signaling pathway. Salicylate inhibited the tyrosine phosphorylation of both STAT1 and STAT3, but had a more pronounced effect on STAT3 activation. Salicylate pretreatment prevented both the nuclear translocation and the DNA-binding activity of STAT1 and STAT3, assessed by immunoblotting and gel shift assays, respectively. In addition to causing phosphorylation at tyrosine residues, IFN-gamma also phosphorylated STAT3 and STAT1 at serine 727. Salicylate attenuated both tyrosine and serine phosphorylations of STAT3, and also suppressed extracellular signal-regulated kinase (ERK) activation, implicating the effect of salicylate on ERK as a possible mechanism for attenuating STAT3 activation. The possibility that salicylate might affect signaling cascades by altering the redox state of the cells was examined, and its effects differed from those of other reducing agents. Salicylate did attenuate the effects of hydrogen peroxide on STAT phosphorylation, consistent with a mechanism involving an interaction between salicylate and reactive oxygen species within the cell.

The interactions of sodium salicylate and the selective cyclooxygenase-2 inhibitors N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide (NS-398) and 5.5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5II)-furanone (DFU), dexamethasone and the nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine methylester (L-NAME) were examined in ischaemia-reperfusion damage and adaptive protection in the rat stomach. Ischaemia-reperfusion damage was substantially aggravated by pretreatment with NS-398 (4 mg/kg), DFU (2 mg/kg), dexamethasone (1 mg/kg) or L-NAME (3 and 10 mg/kg). Salicylate (0.01-0.05 mg/kg) reversed the aggravating effect of NS-398, DFU and dexamethasone, while the effect of L-NAME was counteracted by L-arginine (twice 400 mg/kg) but not salicylate (0.05 or 10 mg/kg). Instillation of 20% ethanol prevented mucosal damage induced by 70% ethanol. This adaptive gastroprotection was abolished by pretreatment with NS-398 (1 mg/kg), DFU (0.2 mg/kg) or L-NAME (10 mg/kg). Salicylate (0.01-0.05 mg/kg) reversed the inhibition of protection by NS-398 and DFU, while the effect of L-NAME (10 mg/kg) was antagonized by L-arginine (100 mg/kg) but not salicylate (0.05 mg/kg). The precise mechanism of the functional antagonism between extremely low doses of salicylate and selective cyclooxygenase-2 inhibitors remains to be investigated.

The effects of salicylate on the expression of cyclooxygenases, and on prostaglandin E(2) biosynthesis were examined in human peripheral blood mononuclear cells. Peripheral blood mononuclear cells were incubated in the presence of endotoxin, which induced expression of cyclooxygenase-2 protein, and caused a time-dependent increase of immunoreactive prostaglandin E(2) in the supernatant. The cycooxygenase-2 selective inhibitor N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide (NS-398, 1 microM) suppressed the endotoxin-induced increase of prostaglandin E(2), without significantly affecting the expression of cyclooxygenase-1 or cyclooxygenase-2. In peripheral blood mononuclear cells exposed to endotoxin (18 h), 1.0 and 3.0 mM sodium salicylate reduced the prostaglandin E(2) concentration of the supernatant, and, at the same time, stimulated cyclooxygenase-2 expression. After a subsequent 2 h incubation of peripheral blood mononuclear cells in drug-free medium, prostaglandin E(2) concentrations in samples that had been exposed to endotoxin together with 1.0 or 3.0 mM salicylate were significantly higher than in samples exposed to endotoxin alone. These results show that salicylate can enhance the expression of cyclooxygenase-2 in endotoxin-exposed peripheral blood mononuclear cells and at the same time reduce prostaglandin E(2) formation. After washout and removal of salicylate-induced cyclooxygenase inhibition, increased cyclooxygenase-2 expression resulted in enhanced prostaglandin E(2) formation. It seems possible that under certain conditions salicylate-induced stimulation of cyclooxygenase-2 expression may contribute to its clinical pharmacological profile.

Nitric oxide (NO) has been proposed to play a role in a variety of inflammatory diseases. Sodium salicylate (NaSal) is the most commonly used anti-inflammatory agent. We investigated whether NaSal can diminish the production of NO in TM4 Sertoli cells. TM4 Sertoli cells produced a small amount of NO upon treatment with recombinant interferon-gamma (rIFN-gamma). The effect of rIFN-gamma was enhanced markedly by the addition of recombinant TNF-alpha (rTNF-alpha) in a dose-dependent manner. NaSal (10 and 20 mM) significantly inhibited NO production from TM4 Sertoli cells induced by rIFN-gamma plus rTNF-alpha. In addition, rIFN-gamma in combination with rTNF-alpha showed a marked increase of the expression of inducible NO synthase (iNOS) protein. Western blot analysis revealed that NaSal (10 and 20 mM) blocked a step of iNOS protein synthesis. The rIFN-gamma plus rTNF-alpha-induced nuclear factor-kappaB (NF-kappaB) activation was significantly blocked by NaSal (10 and 20 mM). On the other hand, neither staurosporine nor polymyxin B significantly inhibited NO production from TM4 Sertoli cells induced by rIFN-gamma plus rTNF-alpha. The present results indicate that NaSal inhibits rIFN-gamma plus rTNF-alpha-induced NO production in TM4 Sertoli cells via the signal transduction pathway of NF-kappaB activation.

Solid dispersion and crystallization of a very slightly water-soluble drug, allopurinol, were prepared using urea, sodium salicylate and beta-cyclodextrin (beta-CD) as carriers. The spectroscopic infra-red (IR), differential scanning calorimetry (DSC) and powder X-ray diffractometry (PXRD) data indicate a role of these carriers in decreasing the crystallinity of allopurinol and complexing abilities. Solid dispersion and crystallization of the drug with these carriers were used in suppository formulations to investigate their role in enhancement of drug release through the membrane barrier. The bases used included Suppocire AM and the mixture of polyethylene glycols (PEGs). The release rates of allopurinol from lipophilic and hydrophilic suppository bases were examined and compared with those obtained for their inclusion compounds incorporated in the same bases. The prepared suppositories were evaluated for in-vitro drug release, when fresh and on storage. The release of pure allopurinol from the lipophilic base was remarkably higher than that from the hydrophilic one. The release of allopurinol from lipophilic as well as hydrophilic bases was significantly enhanced by crystallization of the drug from 5% w/v of sodium salicylate. Allopurinol crystallized from sodium salicylate, showed enhanced release reaching about 100% in 1 h from the Suppocire AM base. The obtained data from these experiments proved the superiority of the PEG formulations containing coevaporates of the drug to sodium salicylate, ratio 1:1, or of the drug to beta-CD, ratio 1:2; T(90%),12 and 36 min, respectively. A significant decrease of uric acid excretion in rabbits was observed after rectal administration of suppositories containing allopurinol crystallized from sodium salicylate.

Aspirin (acetylsalicylic acid), and its main metabolite sodium salicylate, have been shown to protect neurons from excitotoxic cell death in vitro. The objective of our study was to investigate the possible neuroprotective effects of sodium salicylate in vivo in rats with kainic acid-induced seizures, a model for temporal lobe epilepsy in human patients. Male Sprague-Dawley rats received intraperitoneal injections of kainic acid either alone, or with sodium salicylate given before and for 40h after kainic acid injections. The control group received either phosphate-buffered saline or sodium salicylate without co-administration of kainic acid. Animals developed status epilepticus, which was aborted 1.5-2h later with diazepam. On day 3 following kainic acid-induced seizures, animals received bromodeoxyuridine to measure cellular proliferation, and were killed under anesthesia 24h later. Brains were removed, sectioned, and analysed for gross histological changes, evidence of hemorrhage, DNA fragmentation, cellular proliferation, and microglial immunohistochemistry. We report that sodium salicylate did not protect neurons from seizure-induced cell death, and to the contrary, it caused focal hemorrhage and cell death in the hippocampal formation and the entorhinal/piriform cortex of rats with kainic acid-induced seizures. Hemorrhage was never observed in animals that received vehicle, kainic acid or sodium salicylate only, which indicated that sodium salicylate exerted its effect only in animals with seizures, and was confined to select regions of the brain that undergo seizure activity. Large numbers of cells displaying DNA fragmentation were detected in the hippocampal formation, entorhinal/piriform cortex and the dorsomedial thalamic nucleus of rats that received kainic acid or kainic acid in combination with sodium salicylate. Bromodeoxyuridine immunohistochemistry revealed large numbers of proliferating cells in and around the areas with most severe neural injury induced by kainic acid or kainic acid co-administered with sodium salicylate. These same brain regions displayed intense staining with a microglia-specific marker, an indication of microglial activation in response to brain damage. In all cases, the degree of cell death, cell proliferation and microglia staining was more severe in animals that received the combination of kainic acid and sodium salicylate when compared to animals that received kainic acid alone. We hypothesize that our findings are attributable to sodium salicylate-induced blockade of cellular mechanisms that protect cells from calcium-mediated injury. These initial observations may have important clinical implications for patients with epilepsy who take aspirin while affected by these conditions, and should promote further investigation of this relationship.

We have reported previously that axonal degeneration in specific brain regions occurs in rats infected with the parasite Trypanosoma brucei. These degenerative changes occur in spatiotemporal association with over-expression of pro-inflammatory cytokine messenger RNAs in the brain. To test how aspirin-like anti-inflammatory drugs might alter the disease process, we fed trypanosome-infected rats with 200mg/kg of sodium salicylate (the first metabolite of aspirin) daily in their drinking water. Sodium salicylate treatment in uninfected rats did not cause any neural damage. However, sodium salicylate treatment greatly exacerbated neurodegeneration in trypanosome-infected rats, resulting in extensive terminal and neuronal cell body degeneration in the cortex, hippocampus, striatum, thalamus, and anterior olfactory nucleus. The exaggerated neurodegeneration, which occurred in late stages of infection, was temporally and somewhat spatially associated with a late-appearing enhancement of messenger RNA expression of interleukin-1beta, interleukin-1beta converting enzyme, tumor necrosis factor-alpha, and inhibitory factor kappaBalpha in the brain parenchyma. Restricted areas showed elevations in messenger RNA expression of interleukin-1 receptor antagonist, interleukin-6, inducible nitric oxide synthase, interferon-gamma, and inducible cyclooxygenase. The association suggests that increased production of pro-inflammatory cytokines in the brain may be an underlying mechanism for neural damage induced by the chronic sodium salicylate treatment. Furthermore, the results reveal a serious complication in using aspirin-like drugs for the treatment of trypanosome infection.

Gentle handling of small rodents leads to an emotional fever characterized by a 1-2 degrees C rise in colonic temperature associated with peripheral vasoconstriction and inhibition of this response after administration of salicylate. Because vagotomy has been recently shown to hinder microbial fever, we wanted to know whether emotional fever would also be suppressed by vagotomy in rats. The completeness of subdiaphragmatic vagotomy was verified on the basis of gastric dilation after a 24-h fast. Gentle handling produced fevers of equal magnitude: colonic temperature ca. +1.6 degrees C, in vagotomized and + 1.5 degrees C sham-vagotomized rats. On the other hand, intraperitoneal salicylate (300 mg x kg(-1)) largely prevented the fever response caused by gentle handling. It was concluded that the afferent message in the vagus is not necessary for emotional fever.

Oxidative stress plays a central role in the pathogenesis of Parkinson's disease (PD). L-DOPA, the gold standard in PD therapy, may paradoxically contribute to the progression of the disease because of its pro-oxidant properties. The issue, however, is controversial. In this study, we evaluated peripheral markers of oxidative stress in normal subjects, untreated PD patients and PD patients treated only with L-DOPA. We also measured platelet and plasma levels of L-DOPA, 3-O-methyldopa (the long-lasting metabolite of the drug), and dopamine. We found that isolated platelets of treated PD patients form higher amounts of 2,3-dihydroxybenzoate, an index of hydroxyl radical generation, than platelets of controls or untreated patients. In treated patients, platelet levels of 2,3-dihydroxybenzoate were positively correlated with platelet levels of L-DOPA, 3-O-methyldopa, and with the score of disease severity. Disease severity was correlated with platelet and plasma levels of L-DOPA, as well as with the daily intake of the drug. No significant differences in platelet levels of cytosolic and mitochondrial isoforms of the antioxidant enzyme superoxide dismutase were found between PD patients, either treated or untreated, and controls. Our findings lend further support to the hypothesis that L-DOPA might promote free radical formation in PD patients.

1. Effects of acetaminophen and sodium salicylate on hydoxyl radical elimination were studied using an electron-spin-resonance spin-trapping method. The effects of these agents on lipid peroxidation of the human erythrocyte membrane were also investigated by the thiobarbituric acid method. 2. Acetaminophen and sodium salicylate depressed hydroxyl radical generated by Cu2+/H2O2. 3. Acetaminophen inhibited Cu2+/H2O2-dependent lipid peroxidation; however, sodium salicylate enhanced Cu2+/H2O2-dependent lipid peroxidation.

1. The effects of rilmakalim, a potassium channel opener, were studied on rabbit cardiac Purkinje, ventricular muscle and atrial fibers, with the use of conventional microelectrode techniques. 2. Rilmakalim (0.24-7.2 microM) shortened, in a concentration-dependent manner, the action potential duration (APD) in Purkinje and ventricular muscle without affecting other parameters of the action potential. Pinacidil (30-300 microM) also decreased the APD of Purkinje fibers. 3. Rilmakalim (2.4 microM) and cromakalim (100 microM) hyperpolarized and abolished abnormal automaticity of cardiac Purkinje fibers pretreated with barium (0.2-0.3 mM). Glibenclamide (5 microM) blocked the hyperpolarizing effect. 4. Stable early afterdepolarizations induced in Purkinje fibers by berberine (100 microM) were reversibly blocked by rilmakalim (2.4 microM), which also suppressed late afterdepolarizations induced in Purkinje fibers treated with ouabain (0.3-0.5 microM). 5. The rate of spontaneous discharges of the rabbit sinoatrial node was not affected by rilmakalim (7.2 microM) or by pinacidil (100 microM). Both agents were also unable to affect the APD of atrial muscle fibers. 6. In cardiac Purkinje fibers, tetraethylammonium (TEA; 20 mM) significantly reduced the effects of rilmakalim (2. 4 microM) on the APD. However, neither TEA nor glibenclamide (100 microM) reduced the shortening of the APD induced by dinitrophenol (30 microM) or by salicylate (1 mM).

1. Treatment of rats with sodium valproate (100, 200 and 400 mg/kg i.p.) reduced the paw oedema induced by carrageenan by 36, 15 and 48%, respectively, within 3 h . 2. The effect produced by the higher dose (400 mg/kg) was equivalent to that produced by indomethacin (100 mg/kg). At 100 and 400 mg/kg, sodium valproate decreased the granuloma formation by a significant level. Similar doses of sodium valproate did not affect the rectal temperature in yeast-fevered mice, except with a dose of 200 mg/kg, which showed a significant decrease at 180 and 240 min posttreatment. 3. In comparison, sodium salicylate reduced the hyperthermia very significantly throughout the study period. 4. In normothermic mice, the rectal temperature changed only with a 400 mg/kg dose, but did not respond to lower SV doses. 5. The results indicate that sodium valproate, useful clinically as an epileptic drug, may have a potential therapeutic use as a mild antiinflammatory agent.

The effects of interleukin-1 beta on the mechanical nociceptive threshold in rat were examined using the paw-pressure test. An intracerebroventricular (i.c.v.) injection of interleukin-1 beta at doses of 10 and 100 pg/rat caused hyperalgesia to mechanical stimuli. Higher doses of interleukin-1 beta (1 and 10 ng/rat) induced an analgesic effect. The coadministration of the interleukin-1 receptor antagonist completely antagonized the hyperalgesic and analgesic effects of interleukin-1 beta. An i.c.v. injection of alpha-helical-corticotropin-releasing factor [9-41] 15 min prior to interleukin-1 beta administration completely blocked the hyperalgesic and analgesic effects of interleukin-1 beta. An i.c.v. injection of sodium salicylate 15 min prior to interleukin-1 beta administration inhibited the hyperalgesic effect of interleukin-1 beta, but not the analgesic effect. These results suggest that interleukin-1 beta produces biphasic effects on the mechanical nociceptive threshold through the interleukin-1 receptor in the brain and that a corticotropin-releasing factor-mediated pathway is involved. Furthermore, the hyperalgesic effect of interleukin-1 beta may be mediated by prostaglandins.

The central administration of immune cytokines such as interleukin-1 (IL-1) and interferon-alpha (IFN-alpha) results in the suppression of peripheral cellular immunity, which depends, at least partly, on the sympathetic nervous activity. An intrathird cerebroventricular (I3V) infusion of recombinant human IL-1 beta (rhIL-1 beta) (1-5 ng/rat) elicited a dose-dependent increase in the electrical activity of the splenic sympathetic nerve in urethane and alpha-chloralose anesthetized rats. The effect of rhIL-1 beta (1 ng/rat) was completely blocked by pretreatment with an IL-1 receptor antagonist (1 microgram/rat, I3V 10 min before rhIL-1 beta), sodium salicylate (1 microgram/rat), or alpha-melanocyte stimulating hormone (alpha-MSH) (400 ng/rat). Furthermore, an antagonist of corticotropin-releasing factor (CRF), alpha-helical CRF9-41 (2 micrograms/rat), completely abolished the rhIL-1 beta-induced increase in the splenic nerve activity, although an I3V infusion of CRF (1 microgram/rat) excited it. These results suggest that IL-1 beta in the brain activates splenic sympathetic activity by its receptor-mediated and prostaglandin-dependent action that is sensitive to alpha-MSH, depending on CRF system. Our findings, together with the previous results, suggest that the splenic sympathetic nerve represents one of the communication channels from the brain to the immune system.

Sodium salicylate and other non-steroidal anti-inflammatory drugs (NSAIDs) inhibit neutrophil functions via unknown mechanisms. To examine their site of action in the neutrophil we have studied discrete events within the plasma membrane which depend upon the normal function of a GTP binding protein (G protein). We demonstrated that sodium salicylate and piroxicam inhibit neutrophil activation in response to stimuli which require signal transduction via a G protein (e.g. formyl-methionine-leucine-phenylalanine) but have no effect on stimuli which do not (e.g. phorbol myristate acetate, ionomycin). NSAIDs blocked the ADP-ribosylation of the pertussis toxin substrate in human neutrophils. This effect was associated with the capacity of NSAIDs to block pertussis toxin-dependent inhibition of neutrophil functions. Finally, NSAIDs inhibited the binding of GTP gamma S, a stable analog of GTP, to purified neutrophil membrane preparations. The data indicate that salicylate and other NSAIDs interact with a G protein in the neutrophil plasmalemma and thereby uncouple post-receptor signaling events.

Effects of recombinant interferon alpha (rhIFN alpha) and interleukin-1 beta (rhIL-1 beta) on the activity of glucose-responsive and glucose-unresponsive neurons in the ventromedial hypothalamus (VMH) were investigated with rat tissue slice preparations. While the majority of neurons which increased the activity in response to a rise in glucose concentration were excited by perfusion of rhIFN alpha (100-5000 U/ml) and rhIL-1 beta (40-160 ng/ml), most of the neurons which increased their activity to a fall in glucose concentration were inhibited by rhIFN beta. The majority of glucose-unresponsive neurons were not affected by the cytokines. These neuronal responses are appropriate in explaining the anorexia induced by IFN alpha and IL-1. Concurrent application of sodium salicylate, an inhibitor of prostaglandin synthesis, blocked both the increase and decrease in activities of VMH neurons by rhIL-1 beta, but not those by rhIFN alpha. Alpha-melanocyte stimulating hormone (alpha-MSH) (8 x 10(-9)-6.4 x 10(-7) M), an endogenous antipyretics and a possible antagonist of IL-1 at lymphocytes, specifically depressed the responses to rhIL-1 beta, but not those to rhIFN alpha. As has been previously shown in preoptic and anterior hypothalamic neurons, naloxone could block the responses of VMH neurons to rhIFN alpha, suggesting the opioid receptor mediation of IFN alpha's actions on the VMH neurons.

Psychological stress results in a rise in body temperature. Here we report that in rats, hyperthermia induced by open-field stress can be blocked by administration of the antipyretic drug sodium salicylate. These data suggest that this rise in body temperature is a true fever, perhaps mediated by prostaglandins.

Effects of E. coli endotoxin and sodium salicylate (Sal) on single-unit activity of thermosensitive neurons recorded in slices of preoptic and anterior hypothalamic area (PO/AH) were studied in vitro. Perfusion of endotoxin-containing Krebs-Ringer's solution or local application of endotoxin in the immediate vicinity of recording neurons decreased and increased the firing rate of 31 of 34 warm-sensitive neurons and a cold-sensitive neuron, but had no effect on the majority of thermally insensitive neurons. In about half of warm-sensitive neurons the inhibitory response to endotoxin was preceded by a transient increase in firing rate. The pyrogen-induced decrease in firing rate in warm-sensitive neurons was reversibly blocked or attenuated by local application of Sal in a dose-dependent manner. The results are consistent with the view that pyrogen and Sal act in the PO/AH to produce fever and antipyresis, respectively, by appropriately offsetting the activity of thermosensitive neurons.

Prostaglandin E (PGE) has been hypothesized to be an endogenous regulator of carbohydrate metabolism because it decreases human insulin secretion and carbohydrate tolerance. This report compares the effects of four inhibitors of PGE synthesis on the acute insulin response to glucose and subsequent glucose disappearance rates. Ibuprofen, acetylsalicylic acid and sodium salicylate treatments in normal volunteers were associated with augmented insulin secretion and improved glucose tolerance while indomethacin had the opposite effects. In view of these findings and the known effects of PGE on carbohydrate metabolism, we suggest that the effects of indomethacin may have been due to an action of the drug other than inhibiting PGE synthesis.

Effects of recombinant human interleukin-1 beta (rhIL-1 beta) on the single activity of thermosensitive and thermally insensitive neurons in the preoptic and anterior hypothalamus (PO/AH) were investigated in the rat's brain tissue slices. RhIL-1 beta (2.8 X 10(-9)-1.2 X 10(-8) M) decreased the activity in 19 of 27 warm-sensitive neurons and excited 2 of 3 cold-sensitive neurons, but had no effect on the majority (22 of 32) of thermally insensitive neurons. The neuronal responses to local rhIL-1 beta could be observed in a Ca2+ free/high Mg2+ solution, suggesting the postsynaptic actions of rhIL-1 beta. The actions of rhIL-1 beta on thermosensitive neurons were blocked or attenuated by concurrent application of sodium salicylate, but not by naloxone. The results suggest that centrally formed IL-1 beta may induce fever by its actions on PO/AH thermosensitive neurons, which do not involve the opioid receptor mechanisms.

The rectal temperature of male rats was measured in a thermoneutral environment (25 degrees C) and at ambient temperatures of 15 and 35 degrees C. Unless otherwise specified all drugs were administered intracerebroventricularly (i.c.v.) and all results are reported for the thermoneutral environment. Exposure to 15 degrees C did not affect the rectal temperature but exposure to 35 degrees C produced hyperthermia. At 15 and 25 degrees C, 20 mug GABA produced hyperthermia which was longer lasting at the former ambient temperature. GABA (20 mug) prevented the hyperthermic effect of exposure to 35 degrees C and produced hypothermia in animals maintained at this temperature for 1 hr. A low dose (1 mug) of NA produced hyperthermia and a higher dose (mug) hypothermia. In rats pretreated with sodium salicylate (i.p.), 20 mug GABA and 1 mug NA produced hypothermia instead of hyperthermia, suggesting the release of PGE in mediating hyperthermia. The hypothermic effect of 10 mug NA and of GABA observed at 35 degrees C was blocked by phentolamine, an indication of the possibility of alpha-adrenoceptor mediation.

Cooling mother rats by means of sodium salicylate injections did not curtail the intervals between maternal contact bouts. To the contrary, the interbout intervals were prolonged, suggesting that the relief from hyperthermia is a necessary but not a sufficient condition for the reinitiation of pup contact by mother rats. The ability of sodium salicylate to suppress maternal temperature suggests that pyrogenic and lactational increases in temperature may have some common feature.

Administration of prostaglandin synthetase inhibitors to pregnant does and dams in late gestation was followed by in utero contraction of the fetal ductus arteriosus when studied by the whole-body freezing method. In the rat this contraction was well established within 6 h and persisted up to 36 h following 15 mg/kg indomethacin p.o. No effect was observed in the 18 d rat fetus but fetuses at 20 d and 22 d of gestation responded significantly to indomethacin. Doses of indomethacin approaching clinical usage (2.5 mg/kg also caused a positive response in utero. The rat was found to be sensitive also to sodium salicylate and in the rabbit both indomethacin and sodium salicylate were effective. Exposure in utero to prostaglandin synthetase inhibitors with resulting contraction of the ductus may seriously disturb cardiac function in the fetus.

The effect of an antipyretic drug administered directly into the preoptic-anterior hypothalamus was measured in order to investigate the role of fever on mortality of bacterially infected mammals. New Zealand white rabbits (Oryctolagus cuniculus) were injected intravenously with Pasteurella multocida and either sodium salicylate or a control solution was infused directly into the preoptic-anterior hypothalamus. Both groups developed fevers, but the fever of the rabbits infused with the antipyretic was reduced by 50% during the initial stage of infection. Hypothalamic sodium salicylate infusions produced a lower average fever than control infusions over an initial 5 hour period of infection, reducing average 5 hour fevers from 1.56 degrees C to 0.72 degrees C. All of the infected rabbits infused with sodium salicylate died whereas only 29% of the infected control rabbits died. Rabbits receiving sodium salicylate alone did not die. The increased mortality could possibly be the result of a fulminating infection caused by rapidly multiplying bacteria during the initial, attenuated phase of the febrile course in the salicylate-treated rabbits.

The cyclooxygenase inhibitors indomethacin, piroxicam, ibuprofen, naproxen and flurbiprofen failed to block rat paw oedema induced by PAF-acether, whereas aspirin and sodium salicylate were effective. Two mixed cyclooxygenase and lipoxygenase inhibitors NDGA, BW 755C and dexamethasone reduced oedema in a dose - dependently. The selective PAF-acether antagonist, BN 52021, was effective against PAF-acether at 5 - 20 mg/kg. The lipoxygenase derivates may be involved in paw oedema induced by PAF-acether in the rat and the inhibition produced by aspirin and by sodium salicylate should involve mechanisms other than the cyclooxygenase pathway.

Acute inflammation of the colon (cecitis) was produced in hamsters by daily subcutaneous administration of an antibiotic for 3 days. The following prostaglandins completely prevented the cecitis: 16,16-dimethyl-PGE2, 15(R)-15-methyl-PGE2, and 2-acetyl-2-decarboxy-15(S)-15-methyl-PGF2 alpha. PGF2 beta was less active. The synthesis of 2-acetyl-2-decarboxy-15(S)-methyl-PGF2 alpha is described. Castor oil also prevented the cecitis and peanut oil exerted partial protection. Since these oils contain linoleic acid, a precursor of PGE1, protection may have been due to endogenous formation of that prostaglandin. A partial block of the protective effect of castor oil by treatment with indomethacin supports such mechanism. The tissue level of endogenous prostaglandins seems to exert protection since administration of cyclooxygenase inhibitors, indomethacin and aspirin, markedly increased the incidence of cecitis. Magnesium sulfate given orally and sodium salicylate given subcutaneously reduced the incidence of cecitis only partially. The following agents were inactive: loperamide, an antidiarrheic agent; carbachol, a cholinergic and diarrheogenic agent, atropine, an anticholinergic agent; and acetazolamide, a carbonic anhydrase inhibitor. These results, show that certain prostaglandins, which have been shown earlier to be cytoprotective for the stomach and the small intestine, are cytoprotective for the large intestine as well.