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Chelators have the potential to treat the underlying cause of Alzheimer’s disease (AD), but their therapeutic use is hampered by their poor targeting and poor permeability to the brain and/or toxic effects. Here, we report a new strategy for designing site-activated chelators targeting both acetylcholinesterase (AChE) and monoamine oxidase (MAO). We demonstrated that our lead 2inhibited both AChE and MAO in vitro, but with little affinity for metal (Fe, Cu, and Zn) ions. Compound 2can be activated by inhibition of AChE to release an active chelator M30. M30has been shown to be able to modulate amyloid precursor protein regulation and β-amyloid reduction, suppress oxidative stress, and passivate excess metal ions (Fe, Cu, and Zn). Compound 2was less cytotoxic and more lipophilic than the brain-permeable chelator M30. Our new strategy is relatively simple and generally produces small and simple molecules with drug-like properties; it thus holds a potential use in designing site-activated multifunctional chelators with safer and more efficacious properties for treating other metal-related diseases such as Parkinson’s disease and cancer where specific elimination of metals in cancer cells is required.

Increasing evidence suggests that oxidative stress (OS)-induced pancreatic beta-cell impairments is involved in diabetes and diabetic complications. Our group has recently synthesized two multifunctional nontoxic, lipophilic, iron-chelating drugs, 5-{N-methyl-N-propargylaminomethyl}-8-hydroxyquinoline (M30) and 5-{4-propargylpiperazin-1-ylmethyl}-8-hydroxyquinoline (HLA20), for the treatment of various OS-mediated pathogeneses. These compounds contain the N-propargylamine cytoprotective moiety of the antiparkinsonian drug rasagiline (Azilect) and the iron-complexing component 8-hydroxyquinoline. The aim of this research was to evaluate the protective effect of the multifunctional iron-chelating drugs on rat insulin-producing pancreatic beta-cells (INS-1E and RINm) against OS-induced cytotoxicity. We found that M30 and HLA20 markedly and dose-dependently inhibited H(2)O(2)-induced cytotoxicity, associated with decreased intracellular reactive oxygen species formation and increased catalase activity. In accordance, the catalase inhibitor 3-amino-1,2,4-triazol blocked the protective action of M30 against H(2)O(2)-induced damage. Both compounds significantly increased the levels of the iron-responsive protein transferrin receptor indicating their iron-chelating effect. Further mechanistic studies showed that M30 and HLA20 attenuated H(2)O(2)-induced mitochondrial membrane potential loss, decreased the release of cytochrome c into the cytoplasm, and inhibited the activation of caspase-3, suggesting that these drugs may produce cytoprotective effects via the preservation of mitochondrial function. These results indicate that the novel drugs, M30 and HLA20 display significant cytoprotective activity against OS-induced cytotoxicity in insulin producing beta-cells, which might be of therapeutic use in the treatment of diabetes mellitus.

Reactive oxygen species are heavily involved in the pathogenesis of diabetes mellitus (DM) because the insulin-producing beta cells are particularly vulnerable to free-radical-mediated cytotoxicity. Catalytic anti-oxidants have been successfully applied for attenuation of DM and its consequences, but most recent research revealed that preventing the nitration of vital proteins/enzymes might be an even more powerful strategy. We now report an unprecedented efficiency of manganese(III) corroles regarding the protection of rat pancreatic beta cells against intracellular nitration by peroxynitrite and subsequent cell death. A comparison between analogous corroles and porphyrin metal complexes reveals significant superiority of the former in all examined aspects. This is particularly true for the positively-charged manganese(III) corrole, which decomposes peroxynitrite fast enough and through a unique catalytic mechanism that is devoid of potentially nitrating reaction intermediates.

We recently reported that propargylamine derivatives such as rasagiline (Azilect) and its S-isomer TVP1022 are neuroprotective. The aim of this study was to test the hypothesis that the neuroprotective agents TVP1022 and propargylamine (the active moiety of propargylamine derivatives) are also cardioprotective. We specifically investigated the protective efficacy of TVP1022 and propargylamine in neonatal rat ventricular myocytes (NRVM) against apoptosis induced by the anthracycline chemotherapeutic agent doxorubicin and by serum starvation. We demonstrated that pretreatment of NRVM cultures with TVP1022 or propargylamine attenuated doxorubicin-induced and serum starvation-induced apoptosis, inhibited the increase in cleaved caspase 3 levels, and reversed the decline in Bcl-2/Bax ratio. These cytoprotective effects were shown to reside in the propargylamine moiety. Finally, we showed that TVP1022 neither caused proliferation of the human cancer cell lines HeLa and MDA-231 nor interfered with the anti-cancer efficacy of doxorubicin. These results suggest that TVP1022 should be considered as a novel cardioprotective agent against ischemic insults and against anthracycline cardiotoxicity and can be coadministered with doxorubicin in the treatment of human malignancies.

Parkinson's disease (PD) has been modeled in humans, lower primates, and to a lesser extent in some other vertebrates by the administration of the potent neurotoxin 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP). The MPTP model has thus drawn considerable attention during the past 15 years, as a system to search for anti-PD drugs. It has been previously reported that a Parkinsonian syndrome can be elicited in the common goldfish (Carassius auratus) by a single dose of MPTP. This protocol describes the relatively simple and inexpensive MPTP model of PD in goldfish. The procedure takes 14–30 d, depending on how many animals are tested and on the planned study. The accessibility of the goldfish nervous system, neural density, the evolutionary equivalent subcortical circuitry and the greatly abbreviated blood–brain barrier of the goldfish brain, make it an attractive system for study of PD as well as potential drugs for therapy.

Green tea extract and its main polyphenol constituent (‐)‐epigallocatechin‐3‐gallate (EGCG) possess potent neuroprotective activity in cell culture and mice model of Parkinson's disease. The central hypothesis guiding this study is that EGCG may play an important role in amyloid precursor protein (APP) secretion and protection against toxicity induced by β‐amyloid (Aβ). The present study shows that EGCG enhances (~6‐fold) the release of the non‐amyloidogenic soluble form of the amyloid precursor protein (sAPPα) into the conditioned media of human SH‐SY5Y neuroblastoma and rat pheochromocytoma PC12 cells. sAPPα release was blocked by the hydroxamic acid‐based metalloprotease inhibitor Ro31–9790, which indicated mediation via α‐secretase activity. Inhibition of protein kinase C (PKC) with the inhibitor GF109203X, or by down‐regulation of PKC, blocked the EGCG‐induced sAPPα secretion, suggesting the involvement of PKC. Indeed, EGCG induced the phosphorylation of PKC, thus identifying a novel PKC‐dependent mechanism of EGCG action by activation of the non‐amyloidogenic pathway. EGCG is not only able to protect, but it can rescue PC12 cells against the β‐amyloid (Aβ) toxicity in a dose‐dependent manner. In addition, administration of EGCG (2 mg/kg) to mice for 7 or 14 days significantly decreased membrane‐bound holoprotein APP levels, with a concomitant increase in sAPPα levels in the hippocampus. Consistently, EGCG markedly increased PKCα and PKCε in the membrane and the cytosolic fractions of mice hippocampus. Thus, EGCG has protective effects against Aβ‐induced neurotoxicity and regulates secretory processing of non‐amyloidogenic APP via PKC pathway.

Neuromelanin (NM) is a granular, dark brown pigment produced in some but not all of the dopaminergic neurons of the human substantia nigra (SN). In Parkinson's disease (PD) the pigmented dopaminergic neurons of the SN degenerate, suggesting that this process is related to the presence of NM. As yet it is unknown whether NM in the parkinsonian brain differs from that found in healthy tissue and thus may fulfil a different role within this tissue. The function of NM within the pigmented neurons is unknown but other melanins are believed to play a protective role via attenuation of free radical damage. Experimental evidence suggests that NM may also exhibit this characteristic, possibly by direct inactivation of free radical species or via its ability to chelate transition metals, such as iron. NM has the ability to bind a variety of metals, seven per cent of isolated NM is reported to consist of Fe, Cu, Zn and Cr. Iron is of particular interest as this metal is highly concentrated within the SN. Up to 20 per cent of the total iron contained in the SN from normal subjects is bound within NM. Further, it was demonstrated that NM contains a protein component and that iron is bound to NM in the ferric form. Increased tissue iron found in the parkinsonian SN may saturate iron-chelating sites on NM, and a looser association between iron and NM may result in an increased, rather than decreased, production of free radical species. It is hypothesized that this redox-active iron could be released and involved in a Fenton-like reaction leading to an increased production of oxidative radicals. The resultant radical-mediated cytotoxicity may contribute to cellular damage observed in PD.

Our recent studies have demonstrated that green tea polyphenol (−)-epigallocatechin-3-gallate (EGCG) exerts neuroprotective/neurorescue effects against ß-amyloid toxicity and protects neuronal cells from 1-methyl-4-phenyl-1,2,3,6-tetrahydropy-ridinium ion (MPP+) and 6-hydroxydopaminein vitro, or fromN-methyl-4-phenyl-1,2,3,6-tetrahdropyridine-(MPTP-) induced nigral dopaminergic neuronal loss in mice. In the present study, we report that EGCG (0.1 and 1 μM) significantly protects rat pheochromocytoma PC12 cells from apoptosis induced by serum support withdrawal, suggesting that EGCG may play a role in the growth of PC12 cells, where it stimulates survival-promoting pathways.

Studies from our laboratory have demonstrated that the major green tea polyphenol, (-)-epigallocatechin 3-gallate (EGCG), exerts potent neuroprotective actions in the mice model of Parkinson's disease. These studies were extended to neuronal cell culture employing the parkinsonism-inducing neurotoxin, 6-hydroxydopamine (6-OHDA). Pretreatment with EGCG (0.1-10 microm) attenuated human neuroblastoma (NB) SH-SY5Y cell death, induced by a 24-h exposure to 6-OHDA (50 microm). Potential cell signaling candidates involved in this neuroprotective effect were further examined. EGCG restored the reduced protein kinase C (PKC) and extracellular signal-regulated kinases (ERK1/2) activities caused by 6-OHDA toxicity. However, the neuroprotective effect of EGCG on cell survival was abolished by pretreatment with PKC inhibitor GF 109203X (1 microm). Because EGCG increased phosphorylated PKC, we suggest that PKC isoenzymes are involved in the neuroprotective action of EGCG against 6-OHDA. In addition, gene expression analysis revealed that EGCG prevented both the 6-OHDA-induced expression of several mRNAs, such as Bax, Bad, and Mdm2, and the decrease in Bcl-2, Bcl-w, and Bcl-x(L). These results suggest that the neuroprotective mechanism of EGCG against oxidative stress-induced cell death includes stimulation of PKC and modulation of cell survival/cell cycle genes.

Chronic inflammatory processes are associated with the pathophysiology of Alzheimer's disease (AD), and it has been proposed that treatment with non-steroidal anti-inflammatory drugs (NSAIDs) reduces the risk for AD. Here we report that various NSAIDs, such as the cyclooxygenase inhibitors, nimesulide, ibuprofen and indomethacin, as well as thalidomide (Thal) and its non-teratogenic analogue, supidimide, significantly stimulated the secretion of the non-amyloidogenic alpha-secretase form of the soluble amyloid precursor protein (sAPP alpha) into the conditioned media of SH-SY5Y neuroblastoma and PC12 cells. These NSAIDs markedly reduced the levels of the cellular APP holoprotein, further accelerating non-amyloidogenic processes. sAPP alpha release, induced by nimesulide and Thal, was modulated by inhibitors of protein kinase C and Erk mitogen-activated protein (MAP) kinase. Furthermore, in results complementary to the inhibitor studies, we show for the first time that NSAIDs can activate the Erk MAP kinase signaling cascade, thus identifying a novel pharmacology mechanism of NSAIDs. Our findings suggest that NSAIDs and Thal might prove useful to favor non-amyloidogenic APP processing by enhancing alpha-secretase activity, thereby reducing the formation of amyloidogenic derivatives, and therefore are of potential therapeutic value in AD.

Possible cell death mechanisms for pars compacta nigro-striatal dopamine neurons in Parkinson’s disease include oxidative stress, inflammatory processes, nitric oxide, iron accumulation, glutamate toxicity and diminished neurotrophic factor responses. There is a notion that Parkinson’s disease is not a single disorder but a syndrome that can be initiated by several factors. Because of limitations of biochemical methods in the global analysis of neuronal death, a full picture of events has not been established. However, recently developed cDNA microarray or microchips, in which the global expression of thousands of genes can be assessed simultaneously, is changing the prospect for understanding the disease process, its progression, response to drugs, etc. The neurotoxin N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is considered the most valid model of Parkinson’s disease. We employed the technique of cDNA microarray gene expression to determine the mechanism of action of MPTP in mouse substantia nigra. Also, we studied neuroprotective processes induced by several compounds, including R-apomorphine and the green tea polyphenol epigallo-catechin-3-gallate (EGCG). This was done in two ways: (1) the time-dependent acute effect of MPTP, for determining which of the initial genes might lead to dopamine neuron death and (2) gene expression at the time of MPTP-induced dopamine neuron death. We observed that early (acute MPTP) gene expression differs from effects seen at the time of death (chronic MPTP), and that early gene changes are crucial for setting into action genes that eventually cause dopamine neuron death. Furthermore, this process is a cascade of “domino” effects, some of which were previously established by biochemical means. However, our findings show an additional large number of events previously unknown. The neuroprotective drugs reversed some but not all of the gene expression, suggesting involvement of these genes in the neurodegenerative process. Because of the profound complexity of “domino” effect it is now reasonable to understand why a single neuroprotective drug has not shown clinical neuroprotective efficacy. Future multi neuroprotective drugs may be necessary for treatment of not only Parkinson’s disease, but other neurodegenerative diseases (e.g. Alzheimer’s disease) and detrimental states (e.g. ischaemia).

Rasagiline [N‐propargyl‐1R(+)‐aminoindan], was examined for its monoamine oxidase (MAO) A and B inhibitor activities in rats together with its S(−)‐enantiomer (TVP 1022) and the racemic compound (AGN‐1135) and compared to selegiline (1‐deprenyl). The tissues that were studied for MAO inhibition were the brain, liver and small intestine.While rasagiline and AGN1135 are highly potent selective irreversible inhibitors of MAO in vitroand in vivo, the S(−) enantiomer is relatively inactive in the tissues examined.The in vitroIC50values for inhibition of rat brain MAO activity by rasagiline are 4.43±0.92 nM(type B), and 412±123 nM(type A). The ED50values for ex vivoinhibition of MAO in the brain and liver by a single dose of rasagiline are 0.1±0.01, 0.042±0.0045 mg kg−1respectively for MAO‐B, and 6.48±0.81, 2.38±0.35 mg kg−1respectively for MAO‐A.Selective MAO‐B inhibition in the liver and brain was maintained on chronic (21 days) oral dosage with ED50values of 0.014±0.002 and 0.013±0.001 mg kg−1respectively.The degree of selectivity of rasagiline for inhibition of MAO‐B as opposed to MAO‐A was similar to that of selegiline. Rasagiline was three to 15 times more potent than selegiline for inhibition of MAO‐B in rat brain and liver in vivoon acute and chronic administration, but had similar potency in vitro.These data together with lack of tyramine sympathomimetic potentiation by rasagiline, at selective MAO‐B inhibitory dosage, indicate that this inhibitor like selegiline may be a useful agent in the treatment of Parkinson's disease in either symptomatic or L‐DOPA adjunct therapy, but lack of amphetamine‐like metabolites could present a therapeutic advantage for rasagiline.

TV3326 [(N-propargyl-(3R) aminoindan-5-yl)-ethyl methyl carbamate] is a novel aminoindan derivative possessing both cholinesterase (ChE) and monoamine oxidase (MAO)-inhibitory activity. In doses of 35–100 μmol/kg administered orally to rats, it inhibits ChE by 25%–40% and antagonises scopolamine-induced impairments in spatial memory. After daily oral administration of 75 μmol/kg for 2 weeks, TV3326 inhibits MAO-A and -B in the brain by ~80% but has little or no effect on the enzymes in the intestine or liver. This reduces the likelihood of it producing the “cheese effect” if administered with tyramine-containing foods or beverages. TV3326 has activity in the forced-swim test, consistent with that of known antidepressants. Both TV3326 and its S- isomer, TV3279, which inhibits ChE but lacks MAO-inhibitory activity, have neuroprotective effects against a variety of insults in PC12 cells and in vivo. TV3326 significantly reduces hippocampal cell damage caused by global ischaemia in gerbils and the cerebral oedema induced by closed head injury in mice and speeds recovery of their motor and memory deficits. These pharmacological actions of TV3326 could clearly be of clinical importance for the treatment of Alzheimer's disease, and the drug is currently in development for this purpose. Drug Dev. Res. 50:216–222, 2000. © 2000 Wiley-Liss, Inc.

TV3326 [(N‐propargyl‐(3R) aminoindan‐5‐yl)‐ethyl methyl carbamate] is a novel aminoindan derivative possessing both cholinesterase (ChE) and monoamine oxidase (MAO)‐inhibitory activity. In doses of 35–100 μmol/kg administered orally to rats, it inhibits ChE by 25%–40% and antagonises scopolamine‐induced impairments in spatial memory. After daily oral administration of 75 μmol/kg for 2 weeks, TV3326 inhibits MAO‐A and ‐B in the brain by ∼80% but has little or no effect on the enzymes in the intestine or liver. This reduces the likelihood of it producing the “cheese effect” if administered with tyramine‐containing foods or beverages. TV3326 has activity in the forced‐swim test, consistent with that of known antidepressants. Both TV3326 and its S‐ isomer, TV3279, which inhibits ChE but lacks MAO‐inhibitory activity, have neuroprotective effects against a variety of insults in PC12 cells and in vivo. TV3326 significantly reduces hippocampal cell damage caused by global ischaemia in gerbils and the cerebral oedema induced by closed head injury in mice and speeds recovery of their motor and memory deficits. These pharmacological actions of TV3326 could clearly be of clinical importance for the treatment of Alzheimer's disease, and the drug is currently in development for this purpose. Drug Dev. Res. 50:216–222, 2000. © 2000 Wiley‐Liss, Inc.

Degenerative diseases of the central nervous system (CNS) frequently have a predilection for specific cell populations. An explanation for the selective vulnerability of particular neuronal populations and the mechanisms of cell death remains, as yet, elusive. Partial elucidation of the processes underlying the selective action of neurotoxic substances such as iron, 6-hydroxydopamine (6-OHDA), glutamate, kainic acid, quinolinic acid or l-methyl-4-phenyl-l,2,3,6-tetrahydropyridine (MPTP), has revealed possible molecular mechanisms for neurodegeneration. Hypotheses regarding the neurotoxic mechanisms of these substances have evolved based on our understanding of the pathogenesis of cell death in neurodegenerative disorders and have been the rationale for neuroprotective approaches. Various experimental models have demonstrated that monoamine oxidase type B (MAO-B) inhibitors and dopamine agonists exert a neuroprotective effect at the cellular, neurochemical and functional levels, however as yet it has not been possible to demonstrate an unequivocal neuroprotective effect of these substances in clinical studies. This does not suggest, however, that the pathogenetic processes underlying neurodegenerative disorders are not amenable to neuroprotective treatment.

The acetylenic selective monoamine oxidase (MAO) type B suicide inhibitor, l-deprenyl (l-selegiline), has proved to be a useful adjuvant to L-dopa therapy and monotherapy of Parkinson's disease. Although not all features of its antiParkinson action are known, studies that used brains obtained at autopsy from patients who took l-deprenyl show that the selective inhibition of MAO-B with a concomitant increase of phenylethylamine and dopamine, but not of serotonin or noradrenaline, in the basal ganglia may be responsible for its mode of action. The increased life expectancy noted in patients with Parkinson's disease who received long-term therapy (9 years in an uncontrolled study) is another unexpected feature of the drug. These exciting data, if confirmed in other long-term clinical trials, may herald a neuroprotective approach to the treatment of this degenerative disease. More recent studies indicate that Parkinson's disease may eventually turn out to be a neurotoxic event resulting from oxidative stress?induced free radical species in the substantia nigra. Thus selective MAO-B inhibitors could represent a unique class of drugs, having symptomatic actions with possible neuroprotective and neurorescue actions in one.Clinical Pharmacology and Therapeutics (1994) 56, 725–733; doi:10.1038/clpt.1994.202

l-Deprenyl is a selective, irreversible monoamine oxidase (MAO) type B inhibitor. Dopamine is a relatively good MAO-B substrate in the human brain. Because Parkinson's disease is characterized by a decrease in dopaminergic neurotransmission in the basal ganglia, the selective inhibition of MAO-B should lead to diminished metabolism of dopamine in the nigrostriatal system and a significant increase in the concentration of the neurotransmitter. MAO-B inhibition explains the clinical efficacy of l-deprenyl in the treatment of Parkinson's disease and the prevention of the conversion of protoxins such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, which is oxidized by MAO-B and can cause a parkinsonian syndrome, to their active neurotoxin. In addition, l-deprenyl appears to exhibit other biochemical actions that are independent of its MAO-B activity. These actions may be the basis of the neuroprotective effects of l-deprenyl and may include the inhibition of oxidative stress, an indirect influence on the polyamine binding site of the N-methyl-d-aspartate receptor and the stimulation of neurotrophic factors.Clinical Pharmacology and Therapeutics (1994) 56, 734–741; doi:10.1038/clpt.1994.203

Neither the physiological function of sigma (σ) receptors nor the cellular mechanism responsible for the pharmacological effects of σreceptor ligands is known. We now report that σreceptor ligands noncompetitively inhibit nicotine‐stimulated catecholamine release from bovine adrenal chromaffin cells in a concentration‐dependent and reversible manner. The rank order of potency of ligands to inhibit nicotine‐stimulated catecholamine release is significantly correlated (P< 0.005) with that observed in radioligand binding assays selective for the σ1receptor subtype. This naltrexone‐insensitive effect is paralleled by an inhibition of nicotine‐stimulated increases in [Ca2+]i. Sigma ligands were without effect on catecholamine release or [Ca2+]iin the absence of nicotine. In addition, nicotine accelerated the association of the σreceptor selective radioligand, [3H](+)pentazocine, to adrenal medullary homogenates while having no effect on the rate of ligand dissociation, consistent with a σligand binding site closely associated with and allosterically modulated by the nicotinic acetylcholine receptor. Thus, the actions of agonists at the nicotinic acetylcholine receptor in bovine chromaffin cells are modulated by σ1receptor selective ligands.—Paul, I. A., Basile, A. S., Rojas, E., Youdim, M. B. H., De Costa, B., Skolnick, P., Pollard, H. B., Kuijpers, G. A. J. Sigma receptors modulate nicotinic receptor function in adrenal chromaffin cells. FASEB J.7: 1171‐1178; 1993.

The effect of unilateral cryptorchidism on prolactin binding to the testes was studied in the rat. Cryptorchidism was rendered surgically for 3 weeks and 3, 6 and 9 weeks later prolactin binding was measured in testicular homogenates. Prolactin binding to the cryptorchid testes decreased significantly at 3 weeks with a further decrease at 6 and 9 weeks. Binding by the contralateral testes decreased at 3 weeks and increased at 6 and 9 weeks. To examine the possible mechanism of these changes one group of rats was treated for 5 weeks with testosterone and another with hCG. Testosterone treatment resulted in a significant fall in prolactin binding to normal, cryptorchid and contralateral testes. hCG also produced a slight but significant reduction in prolactin binding. To study the effect of surgical relocation of the testes into the scrotum, orchiopexy was performed in another group of rats. Orchiopexy increased prolactin binding only if performed 3 weeks after cryptorchidism. At 6 and 9 weeks after cryptorchidism orchiopexy did not increase prolactin binding. Treatment of cryptorchid rats with prolactin for 5 weeks induced an increase in prolactin binding to control, cryptorchid and contralateral testes. It is concluded that testicular atrophy follows upon placement of a testis within the peritoneal cavity. This atrophy lowers the total amount of prolactin binding and increases binding to the contralateral testes. Intratesticular concentration of testosterone may play a major role in the decrease of prolactin binding. Orchiopexy improves prolactin binding only if performed before 6 weeks of age. Administration of prolactin augments prolactin binding to the testes, irrespective of their location.

A significant body of evidence has been provided to support the hypothesis that oxidant stress may be responsible for the degeneration of dopaminergic neurons in the substantia nigra pars compacta in Parkinson's disease. Apomorphine, a dopamine D1/D2‐receptor agonist in the clinical therapy of Parkinson's disease, has been found to be a potent antioxidant and to prevent free radical reaction in rat brain mitochondrial fraction. In this article we show that 1–10 μM of apomorphine protects rat pheochromocytoma (PC12) cells from the toxic effects of H2O2(0.6 mM) and the neurotoxin 6‐hydroxydopamine (150 μM). These effects were not exhibited by ascorbic acid, desferal, lisuride, or bromocriptine. Although pergolide exhibited some protection of PC12 cells against H2O2toxicity, it was not as potent as apomorphine. In light of the present findings and the clinical reports that parkinsonian patients on long‐term apomorphine stabilize clinically and can be weaned off L‐dopa, one may assume that apomorphine can exert a neuroprotective activity via its potent antioxidant properties.

Previous studies have described the close similarity of the GH binding protein to the liver membrane GH receptor. Since GH regulates its own liver receptors, we examined the effects of short- and long-term hGH therapy on GH binding protein in children with GH deficiency. Six GH-deficient children received their first hGH dose ever, and the pharmacodynamics of serum GH was followed for 12 h, along with measurements of GH binding protein activity. Over the first 6 h, serum GH and GH binding protein activity exhibited a parallel increase, followed by gradual decrease. At 8 h, some of the patients exhibited an apparent second peak in GH binding protein, despite the continuous decrease in serum hGH. During the period of hGH treatment, serum GH binding protein increased progressively over a period of 6 months. In a second uncontrolled group of 7 GH-deficient patients who had been treated with hGH for 30-36 months, GH binding protein activity was also significantly higher than pretreatment values. We suggest that the short-term pharmacodynamic changes probably represent the endogenous turnover of the GH receptor, whereas the elevated GH binding protein activity on hGH treatment may reflect up-regulation of the GH receptor.

Administration of different steroid hormones in vivo has distinct and specific effects on the MAO activity of the adrenal medulla. In an effort to reconstitute these effects in defined cells, we have isolated endothelial cells and chromaffin cells from the bovine adrenal medulla and tested each cell type for sensitivity to these steroids. As in the intact animal, we found that endothelial cell MAO activity was stimulated 1.5‐ to 2.5‐fold by 10 μM progesterone, hydrocortisone, and dexamethasone, inhibited by ca. 50% by 17‐α‐estradiol, but unaffected by testosterone. The type of MAO in the endothelial cells was found to be exclusively of the A type. The chromaffin cells had MAO B exclusively and were inert to treatment with dexamethasone. The mode of action of the various steroids on MAO A activity in endothelial cells seemed to be that of affecting the number of MAO molecules, as binding of [3H]pargyline, an MAO inhibitor, changed in proportion to changes in enzyme activity. Consistently, the kinetic parameters for MAO A showed changes in Vmaxbut not Kmunder all conditions. The specificity of steroid action on MAO A activity was also supported by the fact that steroid‐induced changes in total cell division ([14C]thy‐midine incorporation) and total protein synthesis ([14C]leucine incorporation) were seen after changes in MAO A. We conclude that the differential effects of steroids on MAO activity in the intact adrenal medulla can be reproduced in cultured adrenal medullary endothelial cells but not in chromaffin cells. Therefore we suggest that the action of these steroid hormones on the intact adrenal medulla may be restricted to the endothelial cell component of this tissue.—Youdim, M. B. H.; Banerjee, D. K.; Kelner, K.; Offutt, L.; Pollard, H. B. Steroid regulation of MAO activity in the adrenal medulla. FASEB J.3: 1753‐1759; 1989.

A significant body of evidence has been provided to support the hypothesis that oxidant stress may be responsible for the degeneration of dopaminergic neurons in the substantia nigra pars compacta in Parkinson's disease. Apomorphine, a dopamine D1/D2‐receptor agonist in the clinical therapy of Parkinson's disease, has been found to be a potent antioxidant and to prevent free radical reaction in rat brain mitochondrial fraction. In this article we show that 1–10 µM of apomorphine protects rat pheochromocytoma (PC12) cells from the toxic effects of H2O2(0.6 mM) and the neurotoxin 6‐hydroxydopamine (150 µM). Neither of these effects were exhibited by ascorbic acid, desferal, lisuride, or bromocriptine. Although pergolide exhibited some protection of PC12 cells against H2O2toxicity, it was not as potent as apomorphine. In light of the present findings and the clinical reports that parkinsonian patients on long‐term apomorphine therapy stabilize clinically and can be weaned off L‐dopa, one may assume that apomorphine can exert a neuroprotective activity by way of its potent antioxidant properties.

Clinical studies in schizophrenia patients have shown that adding a selective serotonin reuptake inhibitor (SSRI) to antipsychotics can ameliorate negative symptoms that frequently resist standard treatments. It has been proposed that this combined treatment produces a ‘net effect’, different from that of the individual drugs and possibly common to that of the atypical antipsychotic, clozapine, which also ameliorates negative symptoms. The present study was initiated to determine the molecular events in the rat frontal cortex resulting from combined treatment of fluvoxamine and haloperidol compared to clozapine. Rats were allocated to five groups and received a daily intraperitoneal injection with one of the following: haloperidol (1 mg/kg), fluvoxamine (11 mg/kg), clozapine (11 mg/kg), haloperidol (1 mg/kg) plus fluvoxamine (11 mg/kg), or vehicle for 30 d. cDNA arrays were used to screen a broad range of genes in the frontal cortex. Several of the most prominent alterations were taken for analysis in real-time RT–PCR and their related proteins were examined by the Western-blotting technique. The gene expression profile of the combined fluvoxamine plus haloperidol treatment was different from that of the individual drugs. Moreover, clozapine showed some degree of homology with the dual treatment. The protein expression changes, specific to the combined treatment, included glutamic acid decarboxylase (GAD67) and protein kinase Cß (PKCß). The latter showed a similar trend following clozapine treatment. The present findings support the existence of a unique mechanism for SSRI–antipsychotic combination, different from that of the individual drugs and suggest that it may involve modification of the gamma aminobutyric acid (GABA) system.