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Abstract Many chronic disease symptomatologies involve desynchronized sleep-wake cycles, indicative of disrupted biorhythms. This can be interrogated using body temperature rhythms, which have circadian as well as sleep-wake behavior/environmental evoked components. Here, we investigated the association of wrist temperature amplitudes with a future onset of disease in the UK Biobank one year after actigraphy. Among 425 disease conditions (range n = 200-6728) compared to controls (range n = 62,107-91,134), a total of 73 (17%) disease phenotypes were significantly associated with decreased amplitudes of wrist temperature (Benjamini-Hochberg FDR q

Abstract Background Lipids may influence cellular penetrance by viral pathogens and the immune response that they evoke. We deeply phenotyped the lipidomic response to SARs‐CoV‐2 and compared that with infection with other pathogens in patients admitted with acute respiratory distress syndrome to an intensive care unit (ICU). Methods Mass spectrometry was used to characterise lipids and relate them to proteins, peripheral cell immunotypes and disease severity. Results Circulating phospholipases (sPLA2, cPLA2 (PLA2G4A) and PLA2G2D) were elevated on admission in all ICU groups. Cyclooxygenase, lipoxygenase and epoxygenase products of arachidonic acid (AA) were elevated in all ICU groups compared with controls. sPLA2 predicted severity in COVID‐19 and correlated with TxA2, LTE4 and the isoprostane, iPF2α‐III, while PLA2G2D correlated with LTE4. The elevation in PGD2, like PGI2 and 12‐HETE, exhibited relative specificity for COVID‐19 and correlated with sPLA2 and the interleukin‐13 receptor to drive lymphopenia, a marker of disease severity. Pro‐inflammatory eicosanoids remained correlated with severity in COVID‐19 28 days after admission. Amongst non‐COVID ICU patients, elevations in 5‐ and 15‐HETE and 9‐ and 13‐HODE reflected viral rather than bacterial disease. Linoleic acid (LA) binds directly to SARS‐CoV‐2 and both LA and its di‐HOME products reflected disease severity in COVID‐19. In healthy marines, these lipids rose with seroconversion. Eicosanoids linked variably to the peripheral cellular immune response. PGE2, TxA2 and LTE4 correlated with T cell activation, as did PGD2 with non‐B non‐T cell activation. In COVID‐19, LPS stimulated peripheral blood mononuclear cell PGF2α correlated with memory T cells, dendritic and NK cells while LA and DiHOMEs correlated with exhausted T cells. Three high abundance lipids – ChoE 18:3, LPC‐O‐16:0 and PC‐O‐30:0 – were altered specifically in COVID. LPC‐O‐16:0 was strongly correlated with T helper follicular cell activation and all three negatively correlated with multi‐omic inflammatory pathways and disease severity. Conclusions A broad based lipidomic storm is a predictor of poor prognosis in ARDS. Alterations in sPLA2, PGD2 and 12‐HETE and the high abundance lipids, ChoE 18:3, LPC‐O‐16:0 and PC‐O‐30:0 exhibit relative specificity for COVID‐19 amongst such patients and correlate with the inflammatory response to link to disease severity.

Previous efforts to study the circadian clock using scRNA-seq have relied on time course designs that treat cell collection time as a proxy for circadian time. Here, the authors introduce a statistical method to infer circadian timing directly from expression, enabling researchers to study circadian phase heterogeneity.

Optimal lung repair and regeneration are essential for recovery from viral infections, including influenza A virus (IAV). We have previously demonstrated that acute inflammation and mortality induced by IAV is under circadian control. However, it is not known whether the influence of the circadian clock persists beyond the acute outcomes. Here, we utilize the UK Biobank to demonstrate an association between poor circadian rhythms and morbidity from lower respiratory tract infections, including the need for hospitalization and mortality after discharge; this persists even after adjusting for common confounding factors. Furthermore, we use a combination of lung organoid assays, single-cell RNA sequencing, and IAV infection in different models of clock disruption to investigate the role of the circadian clock in lung repair and regeneration. We show that lung organoids have a functional circadian clock and the disruption of this clock impairs regenerative capacity. Finally, we find that the circadian clock acts through distinct pathways in mediating lung regeneration — in tracheal cells via the Wnt/β-catenin pathway and through IL-1β in alveolar epithelial cells. We speculate that adding a circadian dimension to the critical process of lung repair and regeneration will lead to novel therapies and improve outcomes.

Abstract The circadian clock in animals and humans plays crucial roles in multiple physiological processes. Disruption of circadian homeostasis causes detrimental effects. Here, it is demonstrated that the disruption of the circadian rhythm by genetic deletion of mouse brain and muscle ARNT‐like 1 (Bmal1) gene, coding for the key clock transcription factor, augments an exacerbated fibrotic phenotype in various tumors. Accretion of cancer‐associated fibroblasts (CAFs), especially the alpha smooth muscle actin positive myoCAFs, accelerates tumor growth rates and metastatic potentials. Mechanistically, deletion of Bmal1 abrogates expression of its transcriptionally targeted plasminogen activator inhibitor‐1 (PAI‐1). Consequently, decreased levels of PAI‐1 in the tumor microenvironment instigate plasmin activation through upregulation of tissue plasminogen activator and urokinase plasminogen activator. The activated plasmin converts latent TGF‐β into its activated form, which potently induces tumor fibrosis and the transition of CAFs into myoCAFs, the latter promoting cancer metastasis. Pharmacological inhibition of the TGF‐β signaling largely ablates the metastatic potentials of colorectal cancer, pancreatic ductal adenocarcinoma, and hepatocellular carcinoma. Together, these data provide novel mechanistic insights into disruption of the circadian clock in tumor growth and metastasis. It is reasonably speculated that normalization of the circadian rhythm in patients provides a novel paradigm for cancer therapy.

The COVID-19 Committee of the Lincei Academy has reviewed the scientific evidence supporting the efficacy and safety of existing and new drugs/biologics for the preventing and treating of COVID-19 and its complications. This position paper reports what we have learned in the field in the past 2 years. The focus was on, but not limited to, drugs and neutralizing monoclonal antibodies, anti-SARS-CoV-2 agents, anti-inflammatory and immunomodulatory drugs, complement inhibitors and anticoagulant agents. We also discuss the risks/benefit of using cell therapies on COVID-19 patients. The report summarizes the available evidence, which supports recommendations from health authorities and panels of experts regarding some drugs and biologics, and highlights drugs that are not recommended, or drugs for which there is insufficient evidence to recommend for or against their use. We also address the issue of the safety of drugs used to treat underlying concomitant conditions in COVID-19 patients. The investigators did an enormous amount of work very quickly to understand better the nature and pathophysiology of COVID-19. This expedited the development and repurposing of safe and effective therapeutic interventions, saving an impressive number of lives in the community as well as in hospitals.

Formation of specialized pro-resolving lipid mediators (SPMs) such as lipoxins or resolvins usually involves arachidonic acid 5-lipoxygenase (5-LO, ALOX5) and different types of arachidonic acid 12- and 15-lipoxygenating paralogues (15-LO1, ALOX15; 15-LO2, ALOX15B; 12-LO, ALOX12). Typically, SPMs are thought to be formed via consecutive steps of oxidation of polyenoic fatty acids such as arachidonic acid, eicosapentaenoic acid or docosahexaenoic acid. One hallmark of SPM formation is that reported levels of these lipid mediators are much lower than typical pro-inflammatory mediators including the monohydroxylated fatty acid derivatives (e.g., 5-HETE), leukotrienes or certain cyclooxygenase-derived prostaglandins. Thus, reliable detection and quantification of these metabolites is challenging. This paper is aimed at critically evaluating i) the proposed biosynthetic pathways of SPM formation, ii) the current knowledge on SPM receptors and their signaling cascades and iii) the analytical methods used to quantify these pro-resolving mediators in the context of their instability and their low concentrations. Based on current literature it can be concluded that i) there is at most, a low biosynthetic capacity for SPMs in human leukocytes. ii) The identity and the signaling of the proposed G-protein-coupled SPM receptors have not been supported by studies in knock-out mice and remain to be validated. iii) In humans, SPM levels were neither related to dietary supplementation with their ω-3 polyunsaturated fatty acid precursors nor were they formed during the resolution phase of an evoked inflammatory response. iv) The reported low SPM levels cannot be reliably quantified by means of the most commonly reported methodology. Overall, these questions regarding formation, signaling and occurrence of SPMs challenge their role as endogenous mediators of the resolution of inflammation.

During the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, providing safe in-person schooling has been a dynamic process balancing evolving community disease burden, scientific information, and local regulatory requirements with the mandate for education. Considerations include the health risks of SARS-CoV-2 infection and its post-acute sequelae, the impact of remote learning or periods of quarantine on education and well-being of children, and the contribution of schools to viral circulation in the community. The risk for infections that may occur within schools is related to the incidence of SARS-CoV-2 infections within the local community. Thus, persistent suppression of viral circulation in the community through effective public health measures including vaccination is critical to in-person schooling. Evidence suggests that the likelihood of transmission of SARS-CoV-2 within schools can be minimized if mitigation strategies are rationally combined. This article reviews evidence-based approaches and practices for the continual operation of in-person schooling.

The circadian clock affects immune responses, but its role in influenza infection is not well understood. Here, Sengupta et al. show that time of infection and the circadian clock have no effect on lung virus titers, but affect inflammation, morbidity and mortality.

The use of nonsteroidal anti-inflammatory drugs inhibiting COX-1/2 is associated with an increased risk of heart failure. Here the authors show that mPGES-1, a therapeutic target downstream of COX enzymes, protects from cardiac ischemia/reperfusion injury, limiting leukocyte-endothelial interactions and preserving microvascular perfusion partly via the endothelial EP4 receptor.

In modern society, more and more people suffer from circadian disruption, which in turn affects health. But until now, there are no widely accepted therapies for circadian disorders. Rhythmic feeding behavior is one of the most potent non-photic zeitgebers, thus it has been suggested that it was important to eat during specific periods of time (time-restricted feeding, TRF) so that feeding is aligned with environmental cues under normal light/dark conditions. Here, we challenged mice with a 6 h advanced shift, combined with various approaches to TRF, and found that food restricted to the second half of the nights after the shift facilitated adaptation. This coincided with improved resilience to sepsis. These results raise the possibility of reducing the adverse responses to jet lag by subsequent timing of food intake.

Understanding the clinical risk factors for COVID-19 disease severity and outcomes requires a combination of data from electronic health records and patient reports. To facilitate the collection of patient-reported data, as well as accelerate and standardize the collection of data about host factors, we have constructed a COVID-19 survey. This survey is freely available to the scientific community to send electronically for patients to complete online. This patient survey is designed to be comprehensive, yet not overly burdensome, to gather data useful for a range of clinical investigations, and to accommodate a wide variety of implementation settings including at a COVID-19 testing site, at home during infection or after recovery, and/or for individuals while they are hospitalized. A widely adopted standardized survey that can be implemented online with minimal resources can serve as a critical tool for combining and comparing data across studies to improve our understanding of COVID-19 disease.

The significant morbidity and mortality associated with severe acute respiratory syndrome coronavirus 2 infection has underscored the need for novel antiviral strategies. Lipids play essential roles in the viral life cycle. The lipid composition of cell membranes can influence viral entry by mediating fusion or affecting receptor conformation. Upon infection, viruses can reprogram cellular metabolism to remodel lipid membranes and fuel the production of new virions. Furthermore, several classes of lipid mediators, including eicosanoids and sphingolipids, can regulate the host immune response to viral infection. Here, we summarize the existing literature on the mechanisms through which these lipid mediators may regulate viral burden in COVID-19. Furthermore, we define the gaps in knowledge and identify the core areas in which lipids offer therapeutic promise for severe acute respiratory syndrome coronavirus 2.

RationaleThe development of inhibitors of microsomal prostaglandin (PG)E2 synthase-1 (mPGES-1) was driven by the promise of attaining antiinflammatory agents with a safe cardiovascular profile because of the possible diversion of the accumulated substrate, PGH2, towards prostacyclin (PGI2).ObjectivesWe studied the effect of the human mPGES-1 inhibitor, AF3485 (a benzamide derivative) on prostanoid biosynthesis in human whole blood in vitro. To characterize possible off-target effects of the compound, we evaluated: i)the impact of its administration on the systemic biosynthesis of prostanoids in a model of complete Freund's adjuvant (CFA)-induced monoarthritis in rats; ii) the effects on cyclooxygenase (COX)-2 expression and the biosynthesis of prostanoids in human monocytes and human umbilical vein endothelial cells (HUVECs) in vitro.MethodsProstanoids were assessed in different cellular models by immunoassays. The effect of the administration of AF3485 (30 and 100 mg/kg,i.p.) or celecoxib (20mg/kg, i.p.), for 3 days, on the urinary levels of enzymatic metabolites of prostanoids, PGE-M, PGI-M, and TX-M were assessed by LC-MS.ResultsIn LPS-stimulated whole blood, AF3485 inhibited PGE2 biosynthesis, in a concentration-dependent fashion. At 100μM, PGE2 levels were reduced by 66.06 ± 3.30%, associated with a lower extent of TXB2 inhibition (40.56 ± 5.77%). AF3485 administration to CFA-treated rats significantly reduced PGE-M (P < 0.01) and TX-M (P < 0.05) similar to the selective COX-2 inhibitor, celecoxib. In contrast, AF3485 induced a significant (P < 0.05) increase of urinary PGI-M while it was reduced by celecoxib. In LPS-stimulated human monocytes, AF3485 inhibited PGE2 biosynthesis with an IC50 value of 3.03 µM (95% CI:0.5–8.75). At 1μM, AF3485 enhanced TXB2 while at higher concentrations, the drug caused a concentration-dependent inhibition of TXB2. At 100 μM, maximal inhibition of the two prostanoids was associated with the downregulation of COX-2 protein by 86%. These effects did not involve AMPK pathway activation, IkB stabilization, or PPARγ activation. In HUVEC, AF3485 at 100 μM caused a significant (P < 0.05) induction of COX-2 protein associated with enhanced PGI2 production. These effects were reversed by the PPARγ antagonist GW9662.ConclusionsThe inhibitor of human mPGES-1 AF3485 is a novel antiinflammatory compound which can also modulate COX-2 induction by inflammatory stimuli. The compound also induces endothelial COX-2-dependent PGI2 production via PPARγ activation, both in vitro and in vivo, which might translate into a protective effect for the cardiovascular system.

The biosynthesis of eicosanoids occurs enzymatically via lipoxygenases, cyclooxygenases, and cytochrome P450, or through nonenzymatic free radical reactions. The enzymatic routes are highly enantiospecific. Chiral separation and high-sensitivity detection methods are required to differentiate and quantify enantioselective HETEs in complex biological fluids. We report here a targeted chiral lipidomics analysis of human blood using ultra-HPLC-electron capture (EC) atmospheric pressure chemical ionization/high-resolution MS. Monitoring the high-resolution ions formed by the fragmentation of pentafluorobenzyl derivatives of oxidized lipids during the dissociative EC, followed by in-trap fragmentation, increased sensitivity by an order of magnitude when compared with the unit resolution MS. The 12(S)-HETE, 12(S)-hydroxy-(5Z,8E,10E)-heptadecatrienoic acid [12(S)-HHT], and 15(S)-HETE were the major hydroxylated nonesterified chiral lipids in serum. Stimulation of whole blood with zymosan and lipopolysaccharide (LPS) resulted in stimulus- and time-dependent effects. An acute exposure to zymosan induced ∼80%of the chiral plasma lipids, including 12(S)-HHT, 5(S)-HETE, 15(R)-HETE, and 15(S)-HETE, while a maximum response to LPS was achieved after a long-term stimulation. The reported method allows for a rapid quantification with high sensitivity and specificity of enantiospecific responses to in vitro stimulation or coagulation of human blood.

Two prostaglandin (PG) H synthases encoded by Ptgs genes, colloquially known as cyclooxygenase (COX)-1 and COX-2, catalyze the formation of PG endoperoxide H2, the precursor of the major prostanoids. To address the functional interchangeability of these two isoforms and their distinct roles, we have generated COX-2>COX-1 mice whereby Ptgs2 is knocked in to the Ptgs1 locus. We then “flipped” Ptgs genes to successfully create the Reversa mouse strain, where knock-in COX-2 is expressed constitutively and knock-in COX-1 is lipopolysaccharide (LPS) inducible. In macrophages, flipping the two Ptgs genes has no obvious impact on COX protein subcellular localization. COX-1 was shown to compensate for PG synthesis at high concentrations of substrate, whereas elevated LPS-induced PG production was only observed for cells expressing endogenous COX-2. Differential tissue-specific patterns of expression of the knock-in proteins were evident. Thus, platelets from COX-2>COX-1 and Reversa mice failed to express knock-in COX-2 and, therefore, thromboxane (Tx) production in vitro and urinary Tx metabolite formation in COX-2>COX-1 and Reversa mice in vivo were substantially decreased relative to WT and COX-1>COX-2 mice. Manipulation of COXs revealed isoform-specific compensatory functions and variable degrees of interchangeability for PG biosynthesis in cells/tissues.

Both cyclooxygenase (COX)-1 and COX-2, encoded by Ptgs1 and Ptgs2, function coordinately during inflammation. But the relative contributions and compensations of COX-1 and COX-2 to inflammatory responses remain unanswered. We used three engineered mouse lines where the Ptgs1 and Ptgs2 genes substitute for one another to discriminate the distinct roles and interchangeability of COX isoforms during systemic inflammation. In macrophages, kidneys, and lungs, “flipped” Ptgs genes generate a “reversed” COX expression pattern, where the knock-in COX-2 is expressed constitutively and the knock-in COX-1 is lipopolysaccharide inducible. A panel of eicosanoids detected in serum and kidney demonstrates that prostaglandin (PG) biosynthesis requires native COX-1 and cannot be rescued by the knock-in COX-2. Our data further reveal preferential compensation of COX isoforms for prostanoid production in macrophages and throughout the body, as reflected by urinary PG metabolites. NanoString analysis indicates that inflammatory networks can be maintained by isoform substitution in inflamed macrophages. However, COX-1>COX-2 macrophages show reduced activation of inflammatory signaling pathways, indicating that COX-1 may be replaced by COX-2 within this complex milieu, but not vice versa. Collectively, each COX isoform plays a distinct role subject to subcellular environment and tissue/cell-specific conditions, leading to subtle compensatory differences during systemic inflammation.

Prescription ω-3 fatty acid ethyl ester supplements are commonly used for the treatment of hypertriglyceridemia. However, the metabolic profile and effect of the metabolites formed by these treatments remain unknown. Here we utilized unbiased metabolomics to identify 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) as a significant metabolite of the ω-3-acid ethyl ester prescription Lovaza™ in humans. Administration of CMPF to mice before or after high-fat diet feeding at exposures equivalent to those observed in humans increased whole-body lipid metabolism, improved insulin sensitivity, increased beta-oxidation, reduced lipogenic gene expression, and ameliorated steatosis. Mechanistically, we find that CMPF acutely inhibits ACC activity, and induces long-term loss of SREBP1c and ACC1/2 expression. This corresponds to an induction of FGF21, which is required for long-term steatosis protection, as FGF21KO mice are refractory to the improved metabolic effects. Thus, CMPF treatment in mice parallels the effects of human Lovaza™ supplementation, revealing that CMPF may contribute to the improved metabolic effects observed with ω-3 fatty acid prescriptions.

Objective: Excess ethanol consumption has serious pathologic consequences. In humans, repeated episodes of binge drinking can lead to liver damage and have adverse effects on other organs such as pancreas and brain. Long term chronic consumption of ethanol can also result in progressive alcoholic liver disease and cirrhosis. Fibroblast growth factor 21 (FGF21) is a metabolic regulator with multiple physiologic functions. FGF21 is a novel biomarker for non-alcoholic fatty liver disease (NAFLD) in humans and limits hepatotoxicity in mice. Therefore, we explored the possibility that FGF21 plays a role in response to ethanol consumption in both humans and mice. Methods: We used a binge drinking paradigm in humans to examine the effect of acute ethanol consumption on circulating FGF21. We adapted this paradigm to evaluate the acute response to ethanol in mice. We then examined the role of FGF21 on liver pathology in two models of chronic ethanol consumption in both wild type (WT) mice and mice lacking FGF21 (FGF21-KO). Results: Acute ethanol consumption resulted in a robust induction of serum FGF21 after 6 h in both humans and mice. Serum ethanol peaked at 1 h in both species and was cleared by 6 h. Ethanol clearance was the same in WT and FGF21-KO mice, indicating that FGF21 does not play a major role in ethanol metabolism in a binge paradigm. When FGF21-KO mice were fed the Lieber–DeCarli diet, a high fat diet supplemented with ethanol, a higher mortality was observed compared to WT mice after 16 days on the diet. When FGF21-KO mice consumed 30% ethanol in drinking water, along with a normal chow diet, there was no mortality observed even after 16 weeks, but the FGF21-KO mice had significant liver pathology compared to WT mice. Conclusions: Acute or binge ethanol consumption significantly increases circulating FGF21 levels in both humans and mice. However, FGF21 does not play a role in acute ethanol clearance. In contrast, chronic ethanol consumption in the absence of FGF21 is associated with significant liver pathology alone or in combination with excess mortality, depending on the type of diet consumed with ethanol. This suggests that FGF21 protects against long term ethanol induced hepatic damage and may attenuate progression of alcoholic liver disease. Further study is required to assess the therapeutic potential of FGF21 in the treatment of alcoholic liver disease.

Colonic tissues in Inflammatory Bowel Disease (IBD) patients exhibit oxygen deprivation and activation of hypoxia-inducible factor 1α and 2α (HIF-1α and HIF-2α), which mediate cellular adaptation to hypoxic stress. Notably, macrophages and neutrophils accumulate preferentially in hypoxic regions of the inflamed colon, suggesting that myeloid cell functions in colitis are HIF-dependent. By depleting ARNT (the obligate heterodimeric binding partner for both HIFα subunits) in a murine model, we demonstrate here that myeloid HIF signaling promotes the resolution of acute colitis. Specifically, myeloid pan-HIF deficiency exacerbates infiltration of pro-inflammatory neutrophils and Ly6C+ monocytic cells into diseased tissue. Myeloid HIF ablation also hinders macrophage functional conversion to a protective, pro-resolving phenotype, and elevates gut serum amyloid A levels during the resolution phase of colitis. Therefore, myeloid cell HIF signaling is required for efficient resolution of inflammatory damage in colitis, implicating serum amyloid A in this process.

Summary: An inducible gene expression program is a hallmark of the host inflammatory response. Recently, long intergenic non-coding RNAs (lincRNAs) have been shown to regulate the magnitude, duration, and resolution of these responses. Among these is lincRNA-Cox2, a dynamically regulated gene that broadly controls immune gene expression. To evaluate the in vivo functions of this lincRNA, we characterized multiple models of lincRNA-Cox2-deficient mice. LincRNA-Cox2-deficient macrophages and murine tissues had altered expression of inflammatory genes. Transcriptomic studies from various tissues revealed that deletion of the lincRNA-Cox2 locus also strongly impaired the basal and inducible expression of the neighboring gene prostaglandin-endoperoxide synthase (Ptgs2), encoding cyclooxygenase-2, a key enzyme in the prostaglandin biosynthesis pathway. By utilizing different genetic manipulations in vitro and in vivo, we found that lincRNA-Cox2 functions through an enhancer RNA mechanism to regulate Ptgs2. More importantly, lincRNA-Cox2 also functions in trans, independently of Ptgs2, to regulate critical innate immune genes in vivo. : Elling et al. utilize a number of lincRNA-Cox2 genetic models to show that lincRNA-Cox2 can regulate its neighboring gene Ptgs2 (Cox2) through an enhancer RNA mechanism. They generate a lincRNA-Cox2 splicing-deficient mouse and confirm that lincRNA-Cox2 functions in trans to regulate immune genes following LPS-induced endotoxic shock. Keywords: lincRNA-Cox2, innate immunity, Ptgs2, inflammation, CRISPR/Cas9, CRISPRi

For almost two decades, pioglitazone has been prescribed primarily to prevent and treat insulin resistance in some type 2 diabetic patients. In this review, we trace the path to discovery of pioglitazone as a thiazolidinedione compound, the glitazone tracks through the regulatory agencies, the trek to molecular agonism in the nucleus and the binding of pioglitazone to the nuclear receptor PPAR gamma. Given the rise in consumption of pioglitazone in T2D patients worldwide and the increased number of clinical trials currently testing alternate medical uses for this drug, there is also merit to some reflection on the reported adverse effects. Going forward, it is imperative to continue investigations into the mechanisms of actions of pioglitazone, the potential of glitazone drugs to contribute to unmet needs in complex diseases associated with the dynamics of adaptive homeostasis, and also the routes to minimizing adverse effects in every-day patients throughout the world.

Resolvins, maresins, and protectins can be formed from fish oils. These specialized pro-resolving mediators (SPMs) have been implicated in the resolution of inflammation. Synthetic versions of such SPMs exert anti-inflammatory effects in vitro and when administered to animal models. However, their importance as endogenous products formed in sufficient amounts to exert anti-inflammatory actions in vivo remains speculative. We biased our ability to detect SPMs formed in healthy volunteers by supplementing fish oil in doses shown previously to influence blood pressure and platelet aggregation under placebo-controlled conditions. Additionally, we sought to determine the relative formation of SPMs during an acute inflammatory response and its resolution, evoked in healthy volunteers by bacterial lipopolysaccharide (LPS). Bioactive lipids, enzymatic epoxyeicosatrienoic acids (EETs), and free radical-catalyzed prostanoids [isoprostanes (iPs)] formed from arachidonic acid and the fish oils, served as comparators. Despite the clear shift from ω-6 to ω-3 EETs and iPs, we failed to detect a consistent signal, in most cases, of SPM formation in urine or plasma in response to fish oil, and in all cases in response to LPS on a background of fish oil. Our results question the relevance of these SPMs to the putative anti-inflammatory effects of fish oils in humans.

Niacin (nicotinic acid) has been used for decades as a lipid-lowering drug. The clinical use of niacin to treat dyslipidemic conditions is limited by its side effects. Niacin, along with fibrates, are the only approved drugs which elevate high density lipoprotein cholesterol (HDLc) along with its effects on low density lipoprotein cholesterol (LDLc) and triglycerides. Whether niacin has a beneficial role in lowering cardiovascular risk on the background of well-controlled LDLc has not been established. In fact, it remains unclear whether niacin, either in the setting of well-controlled LDLc or in combination with other lipid-lowering agents, confers any therapeutic benefit and if so, by which mechanism. The results of recent trials reject the hypothesis that simply raising HDLc is cardioprotective. However, in the case of the clinical trials, structural limitations of trial design complicate their interpretation. This is also true of the most recent Heart Protection Study 2-Treatment of HDLc to Reduce the Incidence of Vascular Events (HPS2-THRIVE) trial in which niacin is combined with an antagonist of the D prostanoid (DP) receptor. Human genetic studies have also questioned the relationship between cardiovascular benefit and HDLc. It remains to be determined whether niacin may have clinical utility in particular subgroups, such as statin intolerant patients with hypercholesterolemia or those who cannot achieve a sufficient reduction in LDLc. It also is unclear whether a potentially beneficial effect of niacin is confounded by DP antagonism in HPS2-THRIVE.

Isoprostanes (iPs) are prostaglandin-like molecules derived from autoxidation of polyunsaturated fatty acids (PUFAs). Urinary iP levels have been used as indices of in vivo lipid peroxidation. Thus far, it has only been possible to measure iPs derived from arachidonic acid in urine, because levels of iPs/neuroprostanes (nPs) derived from ω3-PUFAs have been found to be below detection limits of available assays. Because of the interest in ω3-PUFA dietary supplementation, we developed specific methods to measure nPF4α-VI and iPF3α-VI [derived from 4,7,10,13,16,19-docosahexaenoic acid (DHA) and 5,8,11,14,17-eicosapentaenoic acid (EPA)] using a combination of chemical synthesis, gas chromatography/mass spectrometry (GC/MS), and liquid chromatography tandem mass spectrometry (LC/MS/MS). Although nPF4α-VI was below the detection limit of the assay, we conclusively identified iPF3α-VI in human urine by GC/MS and LC/MS/MS. The mean levels in 26 subjects were ∼300 pg/mg creatinine. Our failure to detect nPF4α-VI may have been due to its rapid metabolism by β-oxidation to iPF3α-VI, which we showed to occur in rat liver homogenates. In contrast, iPF3α-VI is highly resistant to β-oxidation in vitro. Thus iPF3α-VI can be formed by two mechanisms: i) direct autoxidation of EPA, and ii) β-oxidation of nPF4α-VI, formed by autoxidation of DHA. This iP may therefore serve as an excellent marker for the combined in vivo peroxidation of EPA and DHA.

The prostanoids are a family of lipid mediators generated by the action of cyclooxygenase on a 20-carbon unsaturated fatty acid, arachidonic acid. Prostanoids are generated widely in response to diverse stimuli and, acting in a paracrine or autocrine manner, play important roles in normal physiology and disease. This review summarizes the current knowledge on prostanoid generation and the roles of individual mediators, their biosynthetic pathways, and their receptors in health and disease.