Resolvin D1 controls inflammation initiated by glutathione-lipid conjugates formed during oxidative stress

Torachrysone-8-O-β-d-glucoside mediates anti-inflammatory effects by blocking aldose reductase-catalyzed metabolism of lipid peroxidation products

Aldose reductase (AR) is an important enzyme involved in the reduction of various aldehyde and carbonyl compounds, including the highly reactive and toxic 4-hydroxynonenal (4-HNE), which has been linked to the progression of various pathologies such as atherosclerosis, hyperglycemia, inflammation, and tumors. AR inhibitors have potential therapeutic benefits for these diseases by reducing lipid peroxidation and mitigating the harmful effects of reactive aldehydes. In this study, we found that torachrysone-8-O-β-d-glucoside (TG), a natural product isolated from Polygonum multiflorum Thunb., functions as an effective inhibitor of AR, exhibiting potent effects in clearing reactive aldehydes and reducing inflammation. TG up-regulated the mRNA levels of several antioxidant factors downstream of NRF2, especially glutathione S-transferase (GST), which is significantly increased, thus detoxifying 4-HNE by facilitating the conjugation of 4-HNE to glutathione, forming glutathione-4-hydroxynonenal (GS-HNE). By employing a combination of molecular docking, cellular thermal shift assay, and enzyme activity experiments, we demonstrated that TG exhibited strong binding affinity with AR and inhibited its activity and blocked the conversion of GS-HNE to glutathionyl-1,4-dihydroxynonene (GS-DHN), thereby preventing the formation of protein adducts and inducing severe cellular damage. This study provides novel insights into the anti-inflammatory mechanisms of AR inhibitors and offers potential avenues for developing therapeutic strategies for AR-related pathologies. Our findings suggest that TG, as an AR inhibitor, may hold promise as a therapeutic agent for treating conditions characterized by excessive lipid peroxidation and inflammation. Further investigations are needed to fully explore the clinical potential of TG and evaluate its efficacy in the treatment and management of these complex diseases.

Specialized Pro-Resolving Mediators Derived from N-3 Polyunsaturated Fatty Acids: Role in Metabolic Syndrome and Related Complications

Significance: Metabolic syndrome (MetS) prevalence continues to grow and represents a serious public health issue worldwide. This multifactorial condition carries the risk of hastening the development of type 2 diabetes (T2D), non-alcoholic fatty liver disease (NAFLD), and cardiovascular diseases (CVD). Another troubling aspect of MetS is the requirement of poly-pharmacological therapy not devoid of side effects. Therefore, there is an urgent need for prospecting alternative nutraceuticals as effective therapeutic agents for MetS. Recent Advances: Currently, there is an increased interest in understanding the regulation of metabolic derangements by specialized pro-resolving lipid mediators (SPMs), especially those derived from the long chain n-3 polyunsaturated fatty acids. Critical Issues: The SPMs are recognized as efficient modulators that are capable of inhibiting the production of pro-inflammatory cytokines, blocking neutrophil activation/recruitment, and inducing non-phlogistic (anti-inflammatory) activation of macrophage engulfment and removal of apoptotic inflammatory cells and debris. The aim of the present review is precisely to first underline key concepts relative to SPM functions before focusing on their status and actions on MetS components (e.g., obesity, glucose dysmetabolism, hyperlipidemia, hypertension) and complications such as T2D, NAFLD, and CVD. Future Directions: Valuable data from preclinical and clinical investigations have emphasized the SPM functions and influence on oxidative stress- and inflammation-related MetS. Despite these promising findings obtained without compromising host defense, additional efforts are needed to evaluate their potential therapeutic applications and further develop practical tools to monitor their bioavailability to cope with cardiometabolic disorders. Antioxid. Redox Signal. 37, 54-83.

Resolvin D1 prevents cadmium chloride-induced memory loss and hippocampal damage in rats by activation/upregulation of PTEN-induced suppression of PI3K/Akt/mTOR signaling pathway

This study evaluated the protective effect of resolvin D1 (RVD1) against cadmium chloride (CdCl₂ )-induced hippocampal damage and memory loss in rats and investigated if such protection is mediated by modulating the PTEN/PI3K/Akt/mTOR pathway. Adult male Wistar rats (n = 18/group) were divided as control, control + RVD1, CdCl₂ , CdCl₂  + RVD1 and CdCl₂  + RVD1 + bpV(pic), a PTEN inhibitor. All treatments were conducted for 4 weeks. Resolvin D1 improved the memory function as measured by Morris water maze (MWM), preserved the structure of CA1 area of the hippocampus, and increased hippocampal levels of RVD1 in the CdCl₂ -treated rats. Resolvin D1 also suppressed the generation of reactive oxygen species (ROS), tumour necrosis factor-α and interleukine-6 (IL-6), inhibited nuclear factor κB (NF-κB) p65, stimulated levels of glutathione (GSH), manganese superoxide dismutase (MnSOD), and Bcl2 but reduced the expression of Bax and cleaved caspase 3 in hippocampi of CdCl₂ -treated rats. Concomitantly, it stimulated levels and activity of PTEN and reduced the phosphorylation (activation) of PI3K, Akt and mTOR in hippocampi of CdCl₂ -treated rats. In conclusion, RVD1 attenuates CdCl₂ -induced memory loss and hippocampal damage in rats mainly by activating PTEN-induced suppression of PI3K/Akt/mTOR, an effect that seems secondary to its' anti-oxidant and anti-inflammatory potential.

Resolvin D1 protects against cadmium chloride-induced memory loss and hippocampal damage in rats: A comparison with docosahexaenoic acid

BACKGROUND

Intoxication with cadmium (Cd) ions leads to hippocampal damage and cognitive impairment. However, omega-3 polyunsaturated fatty acids (n-3 PUFAs) exert neuroprotective effects in different animal models of neurodegeneration.

PURPOSE

This study compared the neuroprotective effect of the n-3 PUFA, docosahexaenoic acid (DHA), and its downstream metabolite, resolvin D1 (RVD1), on hippocampal damage and memory deficits in cadmium chloride (CdCl₂)-treated rats.

RESEARCH DESIGN

Control or CdCl₂ (0.5 mg/kg)-treated rats were subdivided into three groups (n = 18/each) and treated for 6 weeks as follows: (1) fed control diet, (2) fed DHA-rich diets (0.7 g/100 g), or (3) treated with RVD1 (0.2 μg/kg, i.p).

RESULTS

Treatment with a DHA-rich diet or RVD1 significantly increased the levels of docosahexaenoic acid and RVD1, respectively, in the hippocampal of CdCl₂-treated rats without affecting the reduction in the expression of the 15-lipooxygenase-1 (ALOX15). These effects were associated with improvements in rats' memory function and hippocampal structure, as well as a redction in the hippocampal levels of reactive oxygen species (ROS), malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), nuclear localization of the nuclear factor-kappa beta p65 (NF-κB p65), and expression of cleaved caspase-3. Concomitantly, hippocampi of both groups of rats showed significantly higher levels of Bcl-2, superoxide dismutase (SOD), and glutathione (GSH), as well as enhanced nuclear levels of the nuclear factor erythroid 2-related factor 2 (Nrf-2). The effects of RVD1 on all these markers in the CdCl₂-induced rats were more profound than those of DHA. Also, the increase in the nuclear protein levels of Nrf-2 and the decrease in the levels of Bax and nuclear protein levels of NF-κB p65 were only seen in the hippocampal of CdCl₂ + RVD1-treated rats.

CONCLUSION

RVD1 is more powerful than DHA in preventing CdCl₂-induced memory loss and hippocampal damage in rats.

Specialized Pro-Resolving Lipid Mediators in Neonatal Cardiovascular Physiology and Diseases

Cardiovascular disease remains a leading cause of mortality worldwide. Unresolved inflammation plays a critical role in cardiovascular diseases development. Specialized Pro-Resolving Mediators (SPMs), derived from long chain polyunsaturated fatty acids (LCPUFAs), enhances the host defense, by resolving the inflammation and tissue repair. In addition, SPMs also have anti-inflammatory properties. These physiological effects depend on the availability of LCPUFAs precursors and cellular metabolic balance. Most of the studies have focused on the impact of SPMs in adult cardiovascular health and diseases. In this review, we discuss LCPUFAs metabolism, SPMs, and their potential effect on cardiovascular health and diseases primarily focusing in neonates. A better understanding of the role of these SPMs in cardiovascular health and diseases in neonates could lead to the development of novel therapeutic approaches in cardiovascular dysfunction.

ResolvinD1 Protects the Airway Barrier Against Injury Induced by Influenza A Virus Through the Nrf2 Pathway

Airway barrier damage and excessive inflammation induced by influenza A virus (IAV) are associated with disease progression and prognosis. ResolvinD1 (RvD1) is a promising lipid mediator with critical protection against infection in the lung. However, whether RvD1 protects against IAV-induced injury and the underlying mechanisms remain elusive. In this study, primary normal human bronchial epithelial (pNHBE) cells were isolated and co-cultured with IAV and/or RvD1. Then, the expressions of E-cadherin, Zonula occludins-1, inflammatory mediators and proteins in Nrf2-dependent pathway were detected. To further explore the mechanisms, Nrf2 short hairpin RNA (Nrf2 shRNA) was applied in pNHBE cells. Furthermore, mice were infected with IAV, and were subsequently treated with RvD1. We found that IAV downregulated expressions of E-cadherin, Zonula occludins-1, Nrf2 and HO-1, upregulated the phosphorylation of NF κ B p65 and IKBα, levels of IL-8 and TNF-α, as well as ROS production. RvD1 reversed these damaging effects induced by IAV. However, when Nrf2 expression was suppressed with shRNA in pNHBE cells, the protective effects of RvD1 on IAV-induced injury were inhibited. In vivo studies further demonstrated that RvD1 could alleviate barrier protein breakdown and reduce airway inflammatory reactions. Collectively, the study demonstrated that RvD1 could play dual beneficial roles in protecting airway epithelium barrier function and reducing inflammation via the Nrf2 pathway, which may provide a better treatment option for influenza A virus infection.

Impact of Parenteral Lipid Emulsion Components on Cholestatic Liver Disease in Neonates

Total parenteral nutrition (TPN) is a life-saving intervention for infants that are unable to feed by mouth. Infants that remain on TPN for extended periods of time are at risk for the development of liver injury in the form of parenteral nutrition associated cholestasis (PNAC). Current research suggests the lipid component of TPN is a factor in the development of PNAC. Most notably, the fatty acid composition, vitamin E concentration, and presence of phytosterols are believed key mediators of lipid emulsion driven PNAC development. New emulsions comprised of fish oil and medium chain triglycerides show promise for reducing the incidence of PNAC in infants. In this review we will cover the current clinical studies on the benefit of fish oil and medium chain triglyceride containing lipid emulsions on the development of PNAC, the current constituents of lipid emulsions that may modulate the prevalence of PNAC, and potential new supplements to TPN to further reduce the incidence of PNAC.

Salivary Redox Biomarkers in the Course of Caries and Periodontal Disease

Caries are a pathological process of extracorporeal nature, characterized by demineralization of inorganic substances as well as proteolysis triggered by acids produced by bacteria present in dental plaque, as a result of metabolism of sugars of both external and internal origin. Periodontal disease, on the other hand, is a multifactorial degenerative disease associated with inflammation, involving a group of tissues that surround the dental cervix and root of the tooth. It is believed that one of the mechanisms in the etiopathogenesis of caries and periodontitis are disorders of local and/or general oxidative stress (OS) parameters. Numerous clinical studies have confirmed the relationship between oxidative stress markers and oral diseases. In most analyzed studies, technical and biological variability was so high that none of the markers so far has proven suitable for routine clinical use. The aim of systematic reviews of the literature is to present the existing studies on OS parameters, mainly concerning the activity of antioxidant enzymes in saliva of patients with caries and periodontitis.

Specialized pro-resolving mediators: It's anti-oxidant stress role in multiple disease models

Oxidative stress-related injury is a negative state caused by the imbalance between oxidation and antioxidant effects in the internal environment of the body. Oxidative stress has been confirmed to be an important factor in aging and a variety of diseases and the inhibition of inappropriate oxidative stress responses are important for maintaining normal physiological functions. Recently, considerable attention has been focused on specialized pro-resolving mediators(SPMs). SPMs are endogenous mediators derived from polyunsaturated fatty acids, which have multiple protective effects such as anti-inflammation, pro-resolution, and promoting tissue damage repair, etc. Moreover, the role of SPMs on oxidative stress has been extensively researched and provides a possible treatment method. In the current study, we review the positive role of SPMs in oxidative stress-related disease and outline the possible involved mechanism, thus providing the theoretical support for a better understanding of the roles of SPMs in oxidative stress and the theoretical basis for finding targets for the oxidative stress-related diseases.

Resolvin D1 Protects Against Ischemia/Reperfusion-Induced Acute Kidney Injury by Increasing Treg Percentages via the ALX/FPR2 Pathway

Aims

To evaluate whether Resolvin D1 attenuates ischemia/reperfusion-induced (IRI) acute kidney injury (AKI) via affecting Tregs.

Materials and Methods

The IRI-AKI mouse model was established, and RvD1 was injected into the mouse tail vein. Further, the renal function, histological changes, injury markers and serum cytokines were detected at 24 and 72 h after IRI. Flow cytometry was used to categorize regulatory T cells (Tregs) in the spleen and kidney. Treg cells were stripped with the anti-CD25 antibody blocker PC61 to assess its role in the protective effect of RvD1 on IRI mice. CD4⁺ T cells were obtained from spleen monocytes by magnetic bead sorting and differentiated into induced Treg (iTreg) cells. The effect of RvD1 on iTreg cell differentiation was observed in vitro. In addition, neutralizing antibodies against the orphan receptor G-protein-coupled receptor 32 (anti-GPR32) and LXA4 receptor (anti-ALX/FPR2), both RvD1 receptor blockers, were used to evaluate the effect of RvD1 on iTreg cell differentiation. Boc-1, an ALX/FPR2 receptor inhibitor, was administered via the tail vein to observe its effects on the ameliorative efficacy of RvD1 in IRI-AKI mice in vivo.

Results

In vivo, RvD1 increased Treg percentages, alleviated renal tubular injury and reduced the serum levels of IFN-γ, TNF-α and IL-6 in IRI-AKI mice, while PC61 depleted the number of Tregs and reversed the protective effects of RvD1. In vitro, RvD1 induced the generation of iTregs. Importantly, preincubation with anti-ALX/FPR2 neutralizing antibodies but not with anti-GPR32 neutralizing antibodies, abrogated the enhancement activity of RvD1 on iTregs. In addition, in vivo blockade of the receptor ALX/FPR2 by Boc-1 reversed the beneficial effects of RvD1 on the splenic and kidney Treg percentages, renal tubular injury and serum IFN-γ, TNF-α, and IL-6 levels.

Conclusion

Our study demonstrates that RvD1 protects against IRI-AKI by increasing the percentages of Tregs via the ALX/FPR2 pathway.

Self-defense of macrophages against oxidative injury: Fighting for their own survival

Activated macrophages play a central role in both the development and resolution of inflammation. These immune cells need to be functional in harmful conditions with high levels of reactive oxygen and nitrogen species that can damage their basic cell components, which may alter their metabolism. An excessive accumulation of these cell alterations drives macrophages inexorably to cell death, which has been associated to the development of several inflammatory diseases and even with aging in a process termed as "immunosenescence". Macrophages, however, exhibit a prolonged survival in this hostile environment because they equip themselves with a complex network of protective mechanisms. Here we provide an overview of these self-defense mechanisms with special attention being paid to bioactive lipid mediators, NRF2 signaling and metabolic reprogramming.

Anti-inflammatory effects of resolvins in diabetic nephropathy: Mechanistic pathways

The incidence of diabetes mellitus is growing rapidly. The exact pathophysiology of diabetes is unclear, but there is increasing evidence of the role of the inflammatory response in both developing diabetes as well as its complications. Resolvins are naturally occurring polyunsaturated fatty acids that are found in fish oil and sea food that have been shown to possess anti-inflammatory actions in several tissues including the kidneys. The pathways by which resolvins exert this anti-inflammatory effect are unclear. In this review we discuss the evidence showing that resolvins can suppress inflammatory responses via at least five molecular mechanisms through inhibition of the nucleotide-binding oligomerization domain protein 3 inflammasome, inhibition of nuclear factor κB molecular pathways, improvement of oxidative stress, modulation of nitric oxide synthesis/release and prevention of local and systemic leukocytosis. Complete understanding of these molecular pathways is important as this may lead to the development of new effective therapeutic strategies for diabetes and diabetic nephropathy.

Proresolving Lipid Mediators: Endogenous Modulators of Oxidative Stress

Specialized proresolving mediators (SPMs) are a novel class of endogenous lipids, derived by ω-6 and ω-3 essential polyunsaturated fatty acids such as arachidonic acid (AA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) that trigger and orchestrate the resolution of inflammation, which is the series of cellular and molecular events that leads to spontaneous regression of inflammatory processes and restoring of tissue homeostasis. These lipids are emerging as highly effective therapeutic agents that exert their immunoregulatory activity by activating the proresolving pathway, as reported by a consistent bulk of evidences gathered in the last two decades since their discovery. The production of reactive oxygen (ROS) and nitrogen (RNS) species by immune cells plays indeed an important role in the inflammatory mechanisms of host defence, and it is now clear that oxidative stress, viewed as an imbalance between such species and their elimination, can lead to many chronic inflammatory diseases. This review, the first of its kind, is aimed at exploring the manifold effects of SPMs on modulation of reactive species production, along with the mechanisms through which they either inhibit molecular signalling pathways that are activated by oxidative stress or induce the expression of endogenous antioxidant systems. Furthermore, the possible role of SPMs in oxidative stress-mediated chronic disorders is also summarized, suggesting not only that their anti-inflammatory and proresolving properties are strictly associated with their antioxidant role but also that these endogenous lipids might be exploited in the treatment of several pathologies in which uncontrolled production of ROS and RNS or impairment of the antioxidant machinery represents a main pathogenetic mechanism.

Development of an Optimized LC-MS Method for the Detection of Specialized Pro-Resolving Mediators in Biological Samples

The cardioprotective and anti-inflammatory effects of long chain omega-3 polyunsaturated fatty acids (n3 PUFA) are believed to be partly mediated by their oxygenated metabolites (oxylipins). In the last two decades interest in a novel group of autacoids termed specialized pro-resolving mediators (SPMs) increased. These are actively involved in the resolution of inflammation. SPMs are multiple hydroxylated fatty acids including resolvins, maresins, and protectins derived from the n3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as well as lipoxins derived from arachidonic acid (ARA). In the present paper, we developed an LC-MS/MS method for a comprehensive set of 18 SPMs derived from ARA, EPA, and DHA and integrated it into our targeted metabolomics platform. Quantification was based on external calibration utilizing five deuterated internal standards in combination with a second internal standard for quality assessment of sample preparation in each sample. The tandem mass spectrometric parameters were carefully optimized for sensitive and specific detection. The influence of source parameters of the used AB Sciex 6500 QTRAP instrument as well as electronic parameters and the selection of transitions are discussed. The method was validated/characterized based on the criteria listed in the European Medicines Agency (EMA) guideline on bioanalytical method validation and method performance is demonstrated regarding recovery of internal standards (between 78 ± 4% and 87 ± 3% from 500 μL of human serum) as well as extraction efficacy of SPMs in spiked plasma (intra-day accuracy within ±20 and ±15% at 0.1 and 0.3 nM in plasma, respectively). Based on the lower limit of quantification of 0.02-0.2 nM, corresponding to 0.18-2.7 pg on column, SPMs were generally not detectable/quantifiable in plasma and serum supporting that circulating levels of SPMs are very low, i.e., <0.1 nM in healthy subjects. Following septic shock or peritonitis, SPMs could be quantified in the samples of several patients. However, in these studies with a small number of patients no clear correlation with severity of inflammation could be observed.

The Lipid Mediator Resolvin D1 Reduces the Skin Inflammation and Oxidative Stress Induced by UV Irradiation in Hairless Mice

UV irradiation-induced oxidative stress and inflammation contribute to the development of skin diseases. Therefore, targeting oxidative stress and inflammation might contribute to reduce skin diseases. Resolvin D1 (RvD1) is a bioactive metabolite generated during inflammation to actively orchestrate the resolution of inflammation. However, the therapeutic potential of RvD1 in UVB skin inflammation remains undetermined, which was, therefore, the aim of the present study. The intraperitoneal treatment with RvD1 (3-100 ng/mouse) reduced UVB irradiation-induced skin edema, myeloperoxidase activity, matrix metalloproteinase 9 activity, and reduced glutathione depletion with consistent effects observed with the dose of 30 ng/mouse, which was selected to the following experiments. RvD1 inhibited UVB reduction of catalase activity, and hydroperoxide formation, superoxide anion production, and gp91phox mRNA expression. RvD1 also increased the Nrf2 and its downstream targets NQO1 and HO-1 mRNA expression. Regarding cytokines, RvD1 inhibited UVB-induced production of IL-1β, IL-6, IL-33, TNF-α, TGF-β, and IL-10. These immuno-biochemical alterations by RvD1 treatment had as consequence the reduction of UVB-induced epidermal thickness, sunburn and mast cell counts, and collagen degradation. Therefore, RvD1 inhibited UVB-induced skin oxidative stress and inflammation, rendering this resolving lipid mediator as a promising therapeutic agent.

Role of Toll-like receptor 4/oxidant-coupled activation in regulating the biosynthesis of omega-3 polyunsaturated fatty acid derivative resolvin D1 in primary murine peritoneal macrophage

We have previously shown that reactive oxygen species (ROS) as prooxidants can activate Toll-like receptor 4 (TLR4) with the potential to initiate, propagate and maintain "sterile" inflammation of innate immunity, which plays a mediatory role in a host of human disease states. We now present new evidence that ROS can also activate TLR4 to counter the inflammatory phenotype by increasing the production of resolvin D1 (RvD1), which is a specialized anti-inflammatory and pro-resolving lipid mediator. We used primary murine peritoneal macrophages (pM) derived from both TLR4-WT and TLR4-KO mice as a cellular model. We used potassium peroxychromate (PPC) as a direct in vitro source of exogenous ROS. PPC treatment increased intracellular ROS levels, which decreased intracellular total antioxidant capacity, thus suggesting an enhanced cellular oxidative stress. PPC and LPS-EK (a TLR4-specific agonist) increased pro-inflammatory TNFα production with noeffect on IL-10, an anti-inflammatory cytokine. Treatment with the prooxidant increased the expression of 12 lipoxygenase (12-LOX) and 5-lipoxygenase (5-LOX) only in pM derived from TLR4 WT but not in pM from TLR4-KO mice. 5-LOX and 12-LOX are the key enzymes in the RvD1 biosynthetic pathway. In addition, PPC increased the expression of RvD1 receptor, a member of G-protein-coupled receptor only in pM from TLR4-WT mice. Our data support the involvement of TLR4-mediated oxidant-induced pro-inflammatory phenotypes that are in opposition to the production of anti-inflammatory/pro-resolution phenotypes in macrophages. Now, we show that through TLR4 activation, exogenous oxidants can play a role both in producing proinflammatory phenotypes at the same time that it enhances resolution of inflammation to maintain a state of cellular homeostasis and prevent tissue damage/disease.

Resolvin D1 attenuates liver ischaemia/reperfusion injury through modulating thioredoxin 2-mediated mitochondrial quality control

BACKGROUND AND PURPOSE

Liver ischaemia and reperfusion (IR) injury is a sterile inflammatory response involving production of ROS. Mitochondrial homeostasis is maintained by mitochondrial quality control (QC). Thioredoxin (TRX) 2 is a key mitochondrial redox-sensitive protein. Resolvin D1 (RvD1), a specialized pro-resolving lipid mediator, exerts anti-inflammatory and antioxidant activities. We investigated mechanisms of RvD1 protection against IR-induced oxidative damage to the liver, focusing on TRX2-mediated mitochondrial QC.

EXPERIMENTAL APPROACH

Mice underwent partial warm IR. RvD1 was administered 1 h before ischaemia and immediately prior to reperfusion. Human liver carcinoma HepG2 cells were exposed to hypoxia/reoxygenation and transfected with TRX2 siRNA. Immunohistochemistry, Western blotting and enzyme assays were used to follow changes in mitochondrial structure and function.

KEY RESULTS

RvD1 attenuated hepatocellular damage following IR, assessed by serum aminotransferase activities and histology. RvD1 reduced mitochondrial swelling, lipid peroxidation and glutamate dehydrogenase release. Impaired activities of mitochondrial complexes I and III were restored by RvD1. RvD1 enhanced expression of the mitophagy-related protein, Parkin and inhibited accumulation of PTEN-induced putative kinase 1. RvD1 restored levels of mitochondrial biogenesis proteins including PPARγ coactivator 1α, nuclear respiratory factor 1 and mitochondrial transcription factor A and mtDNA level. RvD1 attenuated the increase in levels of the mitochondrial fission-related protein, dynamin-related protein 1. IR reduced TRX2 levels while increasing TRX2 association with TRX-interacting protein. RvD1 attenuated these changes. The regulatory effects of RvD1 on mitochondrial QC were abolished by TRX2 knockdown.

CONCLUSIONS AND IMPLICATIONS

We suggest that RvD1 ameliorated IR-induced hepatocellular damage by regulating TRX2-mediated mitochondrial QC.

AT-RVD1 repairs mouse lung after cigarette smoke-induced emphysema via downregulation of oxidative stress by NRF2/KEAP1 pathway

Long-term exposure to cigarette smoke (CS) results in alveolar parenchyma destruction due to chronic inflammatory response and the imbalance between oxidants and antioxidants, and proteases and antiproteases. Emphysema is the main symptom of chronic obstructive pulmonary disease. Current treatment focuses on relieving respiratory symptoms, and inflammation resolution failure is an important pathophysiological element of the disease. Specialized pro-resolving mediators (SPMs) synthesized endogenously during resolution processes demonstrated beneficial effects in murine models of airway inflammation. Here, we aimed to test the SPM AT-RvD1 in a murine model of CS-induced emphysema. AT-RvD1 restored elastic fibers and lung morphology, with reduction in MMP-3, neutrophils, and myeloperoxidase activity and increases in macrophages and IL-10 levels. AT-RvD1 also decreased levels of oxidative stress markers and ROS via upregulation of the Nrf2/Keap1 pathway. Therefore, we suggest that AT-RvD1 causes pro-resolutive action in our murine model of CS-induced emphysema by upregulation of the Nrf2/Keap1 pathway.

Enzymatic and non-enzymatic detoxification of 4-hydroxynonenal: Methodological aspects and biological consequences

4-Hydroxynonenal (HNE), an electrophilic end-product deriving from lipid peroxidation, undergoes a heterogeneous set of biotransformations including enzymatic and non-enzymatic reactions. The former mostly involve red-ox reactions on the HNE oxygenated functions (phase I metabolism) and GSH conjugations (phase II) while the latter are due to the HNE capacity to spontaneously condense with nucleophilic sites within endogenous molecules such as proteins, nucleic acids and phospholipids. The overall metabolic fate of HNE has recently attracted great interest not only because it clearly determines the HNE disposal, but especially because the generated metabolites and adducts are not inactive molecules (as initially believed) but show biological activities even more pronounced than those of the parent compound as exemplified by potent pro-inflammatory stimulus induced by GSH conjugates. Similarly, several studies revealed that the non-enzymatic reactions, initially considered as damaging processes randomly involving all endogenous nucleophilic reactants, are in fact quite selective in terms of both reactivity of the nucleophilic sites and stability of the generated adducts. Even though many formed adducts retain the expected toxic consequences, some adducts exhibit well-defined beneficial roles as documented by the protective effects of sublethal concentrations of HNE against toxic concentrations of HNE. Clearly, future investigations are required to gain a more detailed understanding of the metabolic fate of HNE as well as to identify novel targets involved in the biological activity of the HNE metabolites. These studies are and will be permitted by the continuous progress in the analytical methods for the identification and quantitation of novel HNE metabolites as well as for proteomic analyses able to offer a comprehensive picture of the HNE-induced adducted targets. On these grounds, the present review will focus on the major enzymatic and non-enzymatic HNE biotransformations discussing both the molecular mechanisms involved and the biological effects elicited. The review will also describe the most important analytical enhancements that have permitted the here discussed advancements in our understanding of the HNE metabolic fate and which will permit in a near future an even better knowledge of this enigmatic molecule.

HNE and cholesterol oxidation products in colorectal inflammation and carcinogenesis

Consistent experimental data suggest the importance of inflammation-associated oxidative stress in colorectal cancer (CRC) pathogenesis. Inflammatory bowel disease with chronic intestinal inflammation is now considered a precancerous condition. Oxidative stress is an essential feature of inflammation. Activation of redox-sensitive pro-inflammatory cell signals and inflammatory mediators concur to establish a pro-tumoral environment. In this frame, lipid oxidation products, namely 4-hydroxynonenal and oxysterols, can be produced in big quantity so as to be able to exert their function as inducers of cell signaling pathways of proliferation and survival. Notably, an important source of these two compounds is represented by a high fat diet, which is undoubtedly a risk factor for inflammation and CRC development. Current evidence for the emerging implication of these two oxidized lipids in inflammation and CRC development is discussed in this review.

Resolvin D1 Programs Inflammation Resolution by Increasing TGF-β Expression Induced by Dying Cell Clearance in Experimental Autoimmune Neuritis

Experimental autoimmune neuritis (EAN) is the animal model of human acute inflammatory demyelinating polyradiculoneuropathies (AIDP), an auto-immune inflammatory demyelination disease of the peripheral nervous system (PNS) and the world's leading cause of acute autoimmune neuromuscular paralysis. EAN and AIDP are characterized by self-limitation with spontaneous recovery; however, endogenous pathways that regulate inflammation resolution in EAN and AIDP remain elusive. A pathway of endogenous mediators, especially resolvins and clearance of apoptotic cells, may be involved. Here, we determined that resolvin D1 (RvD1), its synthetic enzyme, and its receptor were greatly increased in PNS during the recovery stage of EAN. Both endogenous and exogenous RvD1 increased regulatory T (Treg) cell and anti-inflammatory macrophage counts in PNS, enhanced inflammation resolution, and promoted disease recovery in EAN rats. Moreover, RvD1 upregulated the transforming growth factor-β (TGF-β) level and pharmacologic inhibition of TGF-β signaling suppressed RvD1-induced Treg cell counts, but not anti-inflammatory macrophage counts, and RvD1-improved inflammation resolution and disease recovery in EAN rats. Mechanistically, the RvD1-enhanced macrophage phagocytosis of apoptotic T cells leading to reduced apoptotic T-cell accumulation in PNS induced TGF-β production and caused Treg cells to promote inflammation resolution and disease recovery in EAN. Therefore, these data highlight the crucial role of RvD1 as an important pro-resolving molecule in EAN and suggest its potential as a therapeutic target in human neuropathies.

SIGNIFICANCE STATEMENT

Experimental autoimmune neuritis (EAN) is the animal model of human acute inflammatory demyelinating polyradiculoneuropathies, an auto-immune inflammatory demyelination disease of the peripheral nervous system (PNS) and the world's leading cause of acute autoimmune neuromuscular paralysis. Here, we demonstrated that resolvin D1 (RvD1) promoted macrophage phagocytosis of apoptotic T cells in PNS, thereby upregulating transforming growth factor-β by macrophages, increased local Treg cell counts, and finally promoted inflammation resolution and disease recovery in EAN. These data highlight the crucial role of RvD1 as an important pro-resolving molecule in EAN and suggest that it has potential as a therapeutic target in human neuritis.

Resolvin D1 Alleviates the Lung Ischemia Reperfusion Injury via Complement, Immunoglobulin, TLR4, and Inflammatory Factors in Rats

Lung ischemia-reperfusion injury (LIRI) is still an unsolved medical issue, which negatively affects the prognosis of many lung diseases. The aim of this study is to determine the effects of RvD1 on LIRI and the potential mechanisms involved. The results revealed that the levels of complement, immunoglobulin, cytokines, sICAM-1, MPO, MDA, CINC-1, MCP-1, ANXA-1, TLR4, NF-κBp65, apoptosis index, and pulmonary permeability index were increased, whereas the levels of SOD, GSH-PX activity, and oxygenation index were decreased in rats with LIRI. Except for ANXA-1, these responses induced by LIRI were significantly inhibited by RvD1 treatment. In addition, LIRI-induced structure damages of lung tissues were also alleviated by RvD1 as shown by H&E staining and transmission electron microscopy. The results suggest that RvD1 may play an important role in protection of LIRI via inhibition of complement, immunoglobulin, and neutrophil activation; down-regulation of TLR4/NF-κB; and the expression of a variety of inflammatory factors.

Impact of non-surgical periodontal therapy on saliva and serum levels of markers of oxidative stress

OBJECTIVE

The purpose of this study was to determine the effect of non-surgical periodontal treatment on markers of oxidative stress in saliva and serum in patients with chronic periodontitis.

MATERIALS AND METHODS

In total, 25 patients, who were diagnosed with generalized chronic periodontitis (11 females and 14 males), and 26 systemically and periodontally healthy individuals (15 females and 11 males) were included. The plaque index (PI), gingival index (GI), probing pocket depth (PPD), attachment loss (AL), gingival recession (GR), and bleeding on probing (BOP) were recorded at baseline and 6 weeks later. Malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), and 4-hydroxy-2-nonenal (4-HNE) were assessed in saliva and serum samples before and after the non-surgical treatment by enzyme-linked immune sorbent assay (ELISA).

RESULTS

In the group with chronic periodontitis, all clinical parameters were significantly higher compared to the control group at baseline (p < 0.001). Periodontal treatment reduced plaque, gingival inflammation, and pocket depth significantly (p < 0.001). At baseline, salivary 8-OHdG was significantly higher in chronic periodontitis (p < 0.001) and reduced significantly subsequent to the periodontal treatment (p < 0.001). Salivary MDA and serum 4-HNE were significantly higher in the patients with periodontitis compared to the control group (p < 0.001). Periodontal treatment did not significantly change the levels of 4-HNE and salivary MDA (p = 0.503, p = 0.093).

CONCLUSIONS

Salivary 8-OHdG and MDA may be associated with local impact of periodontal disease, while 4-HNE may be associated with systemic impact of chronic periodontitis.

CLINICAL RELEVANCE

Clinical intervention in periodontitis may be beneficial for periodontitis patients' systemic oxidative stress control, and using lipidic agents for the use of anti-inflammatory/pro-resolving processes for blocking the actions of arachidonic acid cascade can enable some late therapeutic strategies in order to lead oxidative stress-induced inflammation.

Resolvin D1, resolvin D2 and maresin 1 activate the GSK3β anti-inflammatory axis in TLR4-engaged human monocytes

Pro-resolving, docosahexaenoic acid-derived mediators have recently emerged as important potential therapeutic agents for the amelioration of complications arising from inflammation, such as vascular disease, asthma, acute lung injury and colitis. While resolvin D1 (RVD1), resolvin D2 (RVD2) and maresin 1 (MaR1) are established pro-resolvins, their mechanisms of action remain unclear. Here we show that, in LPS-stimulated primary human monocytes, RVD1, RVD2 and MaR1 each suppress the release of pro-inflammatory cytokines (TNF, IL-1β, IL-8) and the innate/adaptive bridging cytokine, IL-12 p40, while simultaneously augmenting the production of the anti-inflammatory cytokine, IL-10. Such resolving activity is accompanied by the increased phosphorylation (enhanced anti-inflammatory state) of glycogen synthase kinase 3β (GSK3β) along with increased phosphorylation (activation) of Akt, SGK1 and CREB but not MAPK-related molecules. Gain and loss of function experiments confirm a key role for GSK3β and CREB in the anti-inflammatory actions of resolvins. These results suggest that induction of the GSK3β anti-inflammatory axis is a common mechanism of action for RVD1, RVD2 and MaR1.

Enhanced Resolution of Hyperoxic Acute Lung Injury as a result of Aspirin Triggered Resolvin D1 Treatment

Acute lung injury (ALI), which presents as acute respiratory failure, is a major clinical problem that requires aggressive care, and patients who require prolonged oxygen exposure are at risk of developing this disease. Although molecular determinants of ALI have been reported, the molecules involved in disease catabasis associated with oxygen toxicity have not been well studied. It has been reported that lung mucosa is rich in omega-3 fatty acid dicosahexanoic acid (DHA), which has antiinflammatory properties. Aspirin-triggered resolvin D1 (AT-RvD1) is a potent proresolution metabolite of DHA that can curb the inflammatory effects in various acute injuries, yet the effect of AT-RvD1 on hyperoxic acute lung injury (HALI) or in the oxygen toxicity setting in general has not been investigated. The effects of AT-RvD1 on HALI were determined for the first time in 8- to 10-week-old C57BL/6 mice that were exposed to hyperoxia (≥95% O2) for 48 hours. Mice were given AT-RvD1 (100 ng) in saline or a saline vehicle for 24 hours in normoxic (≈21% O2) conditions after hyperoxia. Lung tissue and bronchoalveolar lavage (BAL) fluid were collected for analysis associated with proinflammatory signaling and lung inflammation. AT-RvD1 treatment resulted in reduced oxidative stress, increased glutathione production, and significantly decreased tissue inflammation. AT-RvD1 treatment also significantly reduced the lung wet/dry ratio, protein in BAL fluid, and decreased apoptotic and NF-κB signaling. These results show that AT-RvD1 curbs oxygen-induced lung edema, permeability, inflammation, and apoptosis and is thus an effective therapy for prolonged hyperoxia exposure in this murine model.

Untargeted Plasma Metabolomics Identifies Endogenous Metabolite with Drug-like Properties in Chronic Animal Model of Multiple Sclerosis

We performed untargeted metabolomics in plasma of B6 mice with experimental autoimmune encephalitis (EAE) at the chronic phase of the disease in search of an altered metabolic pathway(s). Of 324 metabolites measured, 100 metabolites that mapped to various pathways (mainly lipids) linked to mitochondrial function, inflammation, and membrane stability were observed to be significantly altered between EAE and control (p < 0.05, false discovery rate <0.10). Bioinformatics analysis revealed six metabolic pathways being impacted and altered in EAE, including α-linolenic acid and linoleic acid metabolism (PUFA). The metabolites of PUFAs, including ω-3 and ω-6 fatty acids, are commonly decreased in mouse models of multiple sclerosis (MS) and in patients with MS. Daily oral administration of resolvin D1, a downstream metabolite of ω-3, decreased disease progression by suppressing autoreactive T cells and inducing an M2 phenotype of monocytes/macrophages and resident brain microglial cells. This study provides a proof of principle for the application of metabolomics to identify an endogenous metabolite(s) possessing drug-like properties, which is assessed for therapy in preclinical mouse models of MS.

Resolvin D1 Reduces Emphysema and Chronic Inflammation

Chronic obstructive pulmonary disease is characterized, in part, by chronic inflammation that persists even after smoking cessation, suggesting that a failure to resolve inflammation plays an important role in the pathogenesis of the disease. It is widely recognized that the resolution of inflammation is an active process, governed by specialized proresolving lipid mediators, including lipoxins, resolvins, maresins, and protectins. Here, we report that proresolving signaling and metabolic pathways are disrupted in lung tissue from patients with chronic obstructive pulmonary disease, suggesting that supplementation with proresolving lipid mediators might reduce the development of emphysema by controlling chronic inflammation. Groups of mice were exposed long-term to cigarette smoke and treated with the proresolving mediator resolvin D1. Resolvin D1 was associated with a reduced development of cigarette smoke-induced emphysema and airspace enlargement, with concurrent reductions in inflammation, oxidative stress, and cell death. Interestingly, resolvin D1 did not promote the differentiation of M2 macrophages and did not promote tissue fibrosis. Taken together, our results suggest that cigarette smoking disrupts endogenous proresolving pathways and that supplementation with specialized proresolving lipid mediators is an important therapeutic strategy in chronic lung disease, especially if endogenous specialized proresolving lipid mediator signaling is impaired.

4-Hydroxy-nonenal-A Bioactive Lipid Peroxidation Product

This review on recent research advances of the lipid peroxidation product 4-hydroxy-nonenal (HNE) has four major topics: I. the formation of HNE in various organs and tissues, II. the diverse biochemical reactions with Michael adduct formation as the most prominent one, III. the endogenous targets of HNE, primarily peptides and proteins (here the mechanisms of covalent adduct formation are described and the (patho-) physiological consequences discussed), and IV. the metabolism of HNE leading to a great number of degradation products, some of which are excreted in urine and may serve as non-invasive biomarkers of oxidative stress.

Biological Roles of Resolvins and Related Substances in the Resolution of Pain

Endogenous pain-inhibitory substances have rarely been found. A group of powerful pain suppressor molecules that are endogenously generated are now emerging: resolvins and related compounds including neuroprotectins and maresins. These molecules began to be unveiled in a series of inflammation studies more than a decade ago, rapidly shifting the paradigm that explains the mechanism for the inflammatory phase switch. The resolution phase was considered a passive process as proinflammatory mediators disappeared; it is now understood to be actively drawn by the actions of resolvins. Surprisingly, these substances potently affect the pain state. Although this research area is not fully matured, consistently beneficial outcomes have been observed in a various in vivo and in vitro pain models. Furthermore, multiple hypotheses on the neuronal and molecular mechanisms for alleviating pain are being tested, deriving inspiration from existing inflammation and pain studies. This paper serves as a brief summary of the proresolving roles of resolvins and related lipid mediators in inflammation and also as a review for accumulated information of their painkilling actions. This also includes potential receptor-mediated mechanisms and discusses future scientific perspectives. Further diverse approaches will help to construct a hidden axis of natural protection principles and establish proofs of concept for pain relief.

Natural resolution of inflammation

Inflammation is a protective response essential for maintaining human health and for fighting disease. As an active innate immune reaction to challenge, inflammation gives rise to clinical cardinal signs: rubor, calor, dolor, tumor and functio laesa. Termination of acute inflammation was previously recognized as a passive process; a natural decay of pro-inflammatory signals. We now understand that the natural resolution of inflammation involves well-integrated, active, biochemical programs that return tissues to homeostasis. This review focuses on recent advances in the understanding of the role of endogenous lipid mediators that modulate cellular fate and inflammation. Biosynthesis of eicosanoids and other lipids in exudates coincides with changes in the types of inflammatory cells. Resolution of inflammation is initiated by an active class switch in lipid mediators, such as classic prostaglandins and leukotrienes, to the production of proresolution mediators. Endogenous pro-resolving lipid mediators, including arachidonic acid-derived lipoxins, aspirin-triggered lipoxins, ω3-eicosapentaenoic acid-derived resolvins of the E-series, docosahexaenoic acid-derived resolvins of the D-series, protectins and maresins, are biosynthesized during the resolution phase of acute inflammation. Depending on the type of injury and the type of tissue, the initial cells that respond are polymorphonuclear leukocytes, monocytes/macrophages, epithelial cells or endothelial cells. The selective interaction of specific lipid mediators with G protein-coupled receptors expressed on innate immune cells (e.g. G protein-coupled receptor 32, lipoxin A4 receptor/formyl peptide receptor2, chemokine-like receptor 1, leukotriene B4 receptor type 1 and cabannoid receptor 2) induces cessation of leukocyte infiltration; vascular permeability/edema returns to normal with polymorphonuclear neutrophil death (mostly via apoptosis), the nonphlogistic infiltration of monocyte/macrophages and the removal (by macrophages) of apoptotic polymorphonuclear neutrophils, foreign agents (bacteria) and necrotic debris from the site. While an acute inflammatory response that is resolved in a timely manner prevents tissue injury, inadequate resolution and failure to return tissue to homeostasis results in neutrophil-mediated destruction and chronic inflammation. A better understanding of the complex mechanisms of lipid agonist mediators, cell targets and actions allows us to exploit and develop novel therapeutic strategies to treat human inflammatory diseases, including periodontal diseases.

Endogenously generated omega-3 fatty acids attenuate vascular inflammation and neointimal hyperplasia by interaction with free fatty acid receptor 4 in mice

Background

Omega‐3 polyunsaturated fatty acids (ω3 PUFAs) suppress inflammation through activation of free fatty acid receptor 4 (FFAR4), but this pathway has not been explored in the context of cardiovascular disease. We aimed to elucidate the involvement of FFAR4 activation by ω3 PUFAs in the process of vascular inflammation and neointimal hyperplasia in mice.

Methods and Results

We used mice with disruption of FFAR4 (Ffar4^−/−), along with a strain that synthesizes high levels of ω3 PUFAs (fat‐1) and a group of crossed mice (Ffar4^−/−/fat‐1), to elucidate the role of FFAR4 in vascular dysfunction using acute and chronic thrombosis/vascular remodeling models. The presence of FFAR4 in vascular‐associated cells including perivascular adipocytes and macrophages, but not platelets, was demonstrated. ω3 PUFAs endogenously generated in fat‐1 mice (n=9), but not in compound Ffar4^−/−/fat‐1 mice (n=9), attenuated femoral arterial thrombosis induced by FeCl₃. Neointimal hyperplasia and vascular inflammation in the common carotid artery were significantly curtailed 4 weeks after FeCl₃ injury in fat‐1 mice (n=6). This included greater luminal diameter and enhanced blood flow, reduced intima:media ratio, and diminished macrophage infiltration in the vasculature and perivascular adipose tissue compared with control mice. These effects were attenuated in the Ffar4^−/−/fat‐1 mice.

Conclusions

These results indicate that ω3 PUFAs mitigate vascular inflammation, arterial thrombus formation, and neointimal hyperplasia by interaction with FFAR4 in mice. Moreover, the ω3 PUFA–FFAR4 pathway decreases inflammatory responses with dampened macrophage transmigration and infiltration.

4-Hydroxynonenal in the pathogenesis and progression of human diseases

Metastable aldehydes produced by lipid peroxidation act as 'toxic second messengers' that extend the injurious potential of free radicals. 4-hydroxy 2-nonenal (HNE), a highly toxic and most abundant stable end product of lipid peroxidation, has been implicated in the tissue damage, dysfunction, injury associated with aging and other pathological states such as cancer, Alzheimer, diabetes, cardiovascular and inflammatory complications. Further, HNE has been considered as a oxidative stress marker and it act as a secondary signaling molecule to regulates a number of cell signaling pathways. Biological activity of HNE depends on its intracellular concentration, which can differentially modulate cell death, growth and differentiation. Therefore, the mechanisms responsible for maintaining the intracellular levels of HNE are most important, not only in the defense against oxidative stress but also in the pathophysiology of a number of disease processes. In this review, we discussed the significance of HNE in mediating various disease processes and how regulation of its metabolism could be therapeutically effective.

Protective actions of aspirin-triggered (17R) resolvin D1 and its analogue, 17R-hydroxy-19-para-fluorophenoxy-resolvin D1 methyl ester, in C5a-dependent IgG immune complex-induced inflammation and lung injury

Increasing evidence suggests that the novel anti-inflammatory and proresolving mediators such as the resolvins play an important role during inflammation. However, the functions of these lipid mediators in immune complex-induced lung injury remain unknown. In this study, we determined the role of aspirin-triggered resolvin D1 (AT-RvD1) and its metabolically stable analog, 17R-hydroxy-19-para-fluorophenoxy-resolvin D1 methyl ester (p-RvD1), in IgG immune complex-induced inflammatory responses in myeloid cells and injury in the lung. We show that lung vascular permeability in the AT-RvD1- or p-RvD1-treated mice was significantly reduced when compared with values in mice receiving control vesicle during the injury. Furthermore, i.v. administration of either AT-RvD1 or p-RvD1 caused significant decreases in the bronchoalveolar lavage fluid contents of neutrophils, inflammatory cytokines, and chemokines. Of interest, AT-RvD1 or p-RvD1 significantly reduced bronchoalveolar lavage fluid complement C5a level. By EMSA, we demonstrate that IgG immune complex-induced activation of NF-κB and C/EBPβ transcription factors in the lung was significantly inhibited by AT-RvD1 and p-RvD1. Moreover, AT-RvD1 dramatically mitigates IgG immune complex-induced NF-κB and C/EBP activity in alveolar macrophages. Also, secretion of TNF-α, IL-6, keratinocyte cell-derived chemokine, and MIP-1α from IgG immune complex-stimulated alveolar macrophages or neutrophils was significantly decreased by AT-RvD1. These results suggest a new approach to the blocking of immune complex-induced inflammation.

Glutathionylated products of lipid peroxidation: A novel mechanism of adipocyte to macrophage signaling

Obesity-associated insulin resistance has long been linked to both increased adipocyte oxidative stress as well as the presence of inflammatory changes in adipose tissue, including the infiltration and activation of tissue-resident macrophages. In order to investigate the connections between obesity-associated oxidative stress in adipocytes and increased inflammation in adipose tissue associated with the development of insulin resistance, our laboratory recently demonstrated that adipocytes form glutathionylated products of oxidative stress including glutathionyl-4-hydroxy-2-nonenal (GS-HNE) and glutathionyl-1,4-dihydroxynonene (GS-DHN). The abundance of both GS-HNE and GS-DHN were increased in the visceral adipose tissue of ob/ob mice and diet-induced obese, insulin-resistant mice. Further, these products of lipid peroxidation were shown to induce inflammatory changes in macrophages. Finally, in a mouse model, overproduction of GS-HNE was associated with increased fasting glucose levels and moderately impaired glucose tolerance. Together, these findings suggest a novel mechanism by which obesity-induced oxidative stress in adipocytes may lead to activation of tissue-resident macrophages. As adipose tissue inflammation has been shown to play an important role in the development of insulin resistance, further study of this pathway may lead to potential interventions to attenuate the metabolic consequences of obesity.

Inflammation and its resolution as determinants of acute coronary syndromes

Inflammation contributes to many of the characteristics of plaques implicated in the pathogenesis of acute coronary syndromes. Moreover, inflammatory pathways not only regulate the properties of plaques that precipitate acute coronary syndromes but also modulate the clinical consequences of the thrombotic complications of atherosclerosis. This synthesis will provide an update on the fundamental mechanisms of inflammatory responses that govern acute coronary syndromes and also highlight the ongoing balance between proinflammatory mechanisms and endogenous pathways that can promote the resolution of inflammation. An appreciation of the countervailing mechanisms that modulate inflammation in relation to acute coronary syndromes enriches our fundamental understanding of the pathophysiology of this important manifestation of atherosclerosis. In addition, these insights provide glimpses into potential novel therapeutic interventions to forestall this ultimate complication of the disease.

Transient receptor potential ion channels: powerful regulators of cell function

OBJECTIVE

This article reviews the current understanding of transient receptor potential ion channels (TRP channels) in health and disease.

BACKGROUND

Transient receptor potential ion channels are a group of 27 channels that are expressed in all tissues. These channels play important roles in surgically important problems, such as chronic pain, susceptibility to infection, hypothermia, and some cancers.

METHODS

A literature search was performed. This review focuses on the role of TRP channels in a few surgically important disease processes, such as pain, inflammation, airway diseases, and malignant melanomas. In addition, we discuss some of the structural properties that are important for the activation of TRP channels.

RESULTS

TRPA1 and TRPV1 are expressed on pain fibers and play an important role in the development of chronic pain, such as chemotherapy-related neuropathic pain. Deletion of TRPA1 and TRPV1 suppresses the development of chronic pain, and blockers of TRPA1 and TRPV1 show promise as a new class of painkillers. Furthermore, several TRP channels are expressed on immune cells. Macrophages express at least 3 different TRP channels, and the properly balanced activation of all these channels together allows normal macrophage function. Deletion of any of these channels results in impaired macrophage function and increased susceptibility to infection. Because several of these TRP channels on macrophages are temperature sensitive, they may comprise the link for hypothermia-related infectious complications in trauma, and to a lesser degree, in elective surgical patients.

CONCLUSIONS

Transient receptor potential ion channels are involved in several surgically important disease processes. Activation or blockade of these channels offers new therapeutic opportunities. Pharmacologic activation or blockade of TRP channels may offer new treatment options in surgical patients for the management of pain and infections.

Resolvins: Endogenously-Generated Potent Painkilling Substances and their Therapeutic Perspectives

The efficacy of many of pain-relieving drugs is based on mechanisms by which the drugs interfere with the body’s natural pain-mediating pathways. By contrast, although it is less popular, other drugs including opioids exert more powerful analgesic actions by augmenting endogenous inhibitory neural circuits for pain mediation. Recently, a novel endogenous pain-inhibitory principle was suggested and is now attracting both scientific and clinical attentions. The central players for the actions are particular body lipids: resolvins. Although research is in the preclinical phase, multiple hypotheses have actively been matured regarding the potency and molecular and neural processes of the analgesic effects of these substances. Consistently, accumulating experimental evidence has been demonstrating that treatment with these lipid substances is strongly effective at controlling diverse types of pain. Treatment of resolvins does not appear to disturb the body homeostasis as severely as many other therapeutic agents that interrupt the body’s natural signaling flow, which enables us to predict their fewer adverse effects. This paper serves as a review of currently documented painkilling actions of resolvins, summarizes the potential cellular and receptor-mediated mechanisms to date, and discusses the many clinical uses for these therapeutic lipids that have not yet been tested. Future scientific efforts will more concentrate to unveil such aspects of the substances and to construct clear proofs of concept for pain relief.

Glutathionylated lipid aldehydes are products of adipocyte oxidative stress and activators of macrophage inflammation

Obesity-induced insulin resistance has been linked to adipose tissue lipid aldehyde production and protein carbonylation. Trans-4-hydroxy-2-nonenal (4-HNE) is the most abundant lipid aldehyde in murine adipose tissue and is metabolized by glutathione S-transferase A4 (GSTA4), producing glutathionyl-HNE (GS-HNE) and its metabolite glutathionyl-1,4-dihydroxynonene (GS-DHN). The objective of this study was to evaluate adipocyte production of GS-HNE and GS-DHN and their effect on macrophage inflammation. Compared with lean controls, GS-HNE and GS-DHN were more abundant in visceral adipose tissue of ob/ob mice and diet-induced obese, insulin-resistant mice. High glucose and oxidative stress induced production of GS-HNE and GS-DHN by 3T3-L1 adipocytes in a GSTA4-dependent manner, and both glutathionylated metabolites induced secretion of tumor necrosis factor-α from RAW 264.7 and primary peritoneal macrophages. Targeted microarray analysis revealed GS-HNE and GS-DHN induced expression of inflammatory genes, including C3, C4b, c-Fos, igtb2, Nfkb1, and Nos2. Transgenic overexpression of GSTA4 in mouse adipose tissue led to increased production of GS-HNE associated with higher fasting glucose levels and moderately impaired glucose tolerance. These results indicated adipocyte oxidative stress results in GSTA4-dependent production of proinflammatory glutathione metabolites, GS-HNE and GS-DHN, which may represent a novel mechanism by which adipocyte dysfunction results in tissue inflammation and insulin resistance.

Maternal omega-3 fatty acid intake increases placental labyrinthine antioxidant capacity but does not protect against fetal growth restriction induced by placental ischaemia-reperfusion injury

Placental oxidative stress plays a key role in the pathophysiology of several placenta-related disorders. Oxidative stress occurs when excess reactive oxygen species (ROS) damages cellular components, an outcome limited by antioxidant enzymes; mitochondrial uncoupling protein 2 (UCP2) also limits ROS production. We recently reported that maternal dietary omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation reduced placental oxidative damage and enhanced fetal and placental growth in the rats. Here, we examined the effect of n-3 PUFAs on placental antioxidant defences and whether n-3 PUFA supplementation could prevent growth restriction induced by placental ischaemia-reperfusion (IR), a known inducer of oxidative stress. Rats were fed either standard or high-n-3 PUFA diets from day 1 of pregnancy. Placentas were collected on days 17 and 22 in untreated pregnancies (term=day 23) and at day 22 following IR treatment on day 17. Expression of several antioxidant enzyme genes (Sod1, Sod2, Sod3, Cat, Txn1 and Gpx3) and Ucp2 was measured by quantitative RT-PCR in the placental labyrinth zone (LZ) and junctional zone (JZ). Cytosolic superoxide dismutase (SOD), mitochondrial SOD and catalase (CAT) activities were also analyzed. Maternal n-3 PUFA supplementation increased LZ mRNA expression of Cat at both gestational days (2- and 1.5-fold respectively; P<0.01) and female Sod2 at day 22 (1.4-fold, P<0.01). Cytosolic SOD activity increased with n-3 PUFA supplementation at day 22 (1.3-fold, P<0.05). Sod1 and Txn1 expression decreased marginally (30 and 22%, P<0.05). JZ antioxidant defences were largely unaffected by diet. Despite increased LZ antioxidant defences, maternal n-3 PUFA supplementation did not protect against placental IR-induced growth restriction of the fetus and placental LZ.

Novel biphasic role of resolvin D1 on expression of cyclooxygenase-2 in lipopolysaccharide-stimulated lung fibroblasts is partly through PI3K/AKT and ERK2 pathways

Fibroblasts, far frombeing merely bystander cells, are known to play a specific role in inflammation resolution after an acute injury. As the endogenous “braking signal,” resolvins possess potent anti-inflammatory and proresolution actions. We demonstrated that the expression of COX-2 protein was significantly peaked initially at 6 hours but then also at 48 hours after LPS stimulation in lung fibroblasts. PGE₂ levels also peaked at 6 hours, and PGD₂ levels were increased and peaked at 48 hours. However, no significant change in the protein expression of COX-1 was observed after treatment with LPS in lung fibroblasts. Exogenous resolvin D1 inhibited the first peak of COX-2 expression as well as the production of PGE₂ induced by LPS. In contrast, exogenous resolvin D1 increased the second peak of COX-2 expression as well as the production of PGD₂ induced by LPS. In addition, resolvin D1 inhibited COX-2 expression at 6 hours, which was partly through PI3K/AKT and ERK2 signalling pathways.

Acetylsalicylic Acid reduces the severity of dextran sodium sulfate-induced colitis and increases the formation of anti-inflammatory lipid mediators

The role of non-steroidal anti-inflammatory drugs in inflammatory bowel disease is controversial, as they have been implicated in disease aggravation. Different from other cyclooxygenase inhibitors, acetylsalicylic acid (ASA) enhances the formation of anti-inflammatory and proresolution lipoxins derived from arachidonic acid as well as resolvins from omega-3 polyunsaturated fatty acids such as docosahexaenoic acid (DHA). In this study, we examined the effect of ASA on murine dextran sodium sulfate colitis. A mouse magnetic resonance imaging (MRI) protocol and post mortem assessment were used to assess disease severity, and lipid metabolites were measured using liquid chromatography-coupled tandem mass spectrometry. Decreased colitis activity was demonstrated by phenotype and MRI assessment in mice treated with ASA, and confirmed in postmortem analysis. Analysis of lipid mediators showed sustained formation of lipoxin A4 and an increase of DHA-derived 17-hydroxydocosahexaenoic acid (17-HDHA) after treatment with ASA. Furthermore, in vitro experiments in RAW264.7 murine macrophages demonstrated significantly increased phagocytosis activity after incubation with 17-HDHA, supporting its proresolution effect. These results show a protective effect of ASA in a murine colitis model and could give a rationale for a careful reassessment of ASA therapy in patients with inflammatory bowel disease and particularly ulcerative colitis, possibly combined with DHA supplementation.

Resolvin D1 reduces deterioration of tight junction proteins by upregulating HO-1 in LPS-induced mice

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) is characterized by increased pulmonary permeability with high mortality. Resolvin D1 (RvD1), which has potent anti-inflammatory and pro-resolving activity, can attenuate pulmonary edema in the animal model of ALI. However, the mechanism underlying the protection of RvD1 on pulmonary edema is still unknown. Here we explore the effects and mechanism of RvD1 on the disruption of tight junction protein that results in the permeability edema in a model of lipopolysaccharide (LPS)-induced ALI. The severity of pulmonary edema was assessed by wet-to-dry rate and Evans blue infiltration; expressions of tight junction (TJ) proteins occludin and zona occludin-1 (ZO-1) were examined by immunofluorescence staining and western blot; mRNA in lung tissue was studied by real time-PCR; the TUNEL kit was performed for the detection of apoptosis of pulmonary barrier. Twenty-four hours after LPS inhalation by mice, wet-to-dry rate and Evans blue infiltration indicated that pretreatment with RvD1 relieved the pulmonary edema and pulmonary capillary permeability. Moreover, RvD1 attenuated the LPS-induced deterioration of TJ protein ZO-1 and occludin significantly. And we found that RvD1 increased heme oxygenase-1 (HO-1) expression contributed to the protection on the deterioration of TJs. In addition, we found that RvD1 could reduce pulmonary cellular apoptosis in LPS-induced mice. In conclusion, RvD1 possesses the ability that relieves the pulmonary edema and restores pulmonary capillary permeability and reduces disruption of TJs in LPS-induced ALI of mice, at least in part, by upregulating HO-1 expression.

Unesterified docosahexaenoic acid is protective in neuroinflammation

Docosahexaenoic acid (22:6n-3) is the major brain n-3 polyunsaturated fatty acid and it is possible that docosahexaenoic acid is anti-inflammatory in the brain as it is known to be in other tissues. Using a combination of models including the fat-1 transgenic mouse, chronic dietary n-3 polyunsaturated fatty acid modulation in transgenic and wild-type mice, and acute direct brain infusion, we demonstrated that unesterified docosahexaenoic acid attenuates neuroinflammation initiated by intracerebroventricular lipopolysaccharide. Hippocampal neuroinflammation was assessed by gene expression and immunohistochemistry. Furthermore, docosahexaenoic acid protected against lipopolysaccharide-induced neuronal loss. Acute intracerebroventricular infusion of unesterified docosahexaenoic acid or its 12/15-lipoxygenase product and precursor to protectins and resolvins, 17S-hydroperoxy-docosahexaenoic acid, mimics anti-neuroinflammatory aspects of chronically increased unesterified docosahexaenoic acid. LC-MS/MS revealed that neuroprotectin D1 and several other docosahexaenoic acid-derived specialized pro-resolving mediators are present in the hippocampus. Acute intracerebroventricular infusion of 17S-hydroperoxy-docosahexaenoic acid increases hippocampal neuroprotectin D1 levels concomitant to attenuating neuroinflammation. These results show that unesterified docosahexaenoic acid is protective in a lipopolysaccharide-initiated mouse model of acute neuroinflammation, at least in part, via its conversion to specialized pro-resolving mediators; these docosahexaenoic acid stores may provide novel targets for the prevention and treatment(s) of neurological disorders with a neuroinflammatory component. Our study shows that chronically increased brain unesterified DHA levels, but not solely phospholipid DHA levels, attenuate neuroinflammation. Similar attenuations occur with acute increases in brain unesterified DHA or 17S-HpDHA levels, highlighting the importance of an available pool of precursor unesterified DHA for the production of enzymatically derived specialized pro-resolving mediators that are critical in the regulation of neuroinflammation.

Resolvin D1 protects periodontal ligament

Resolution agonists are endogenous mediators that drive inflammation to homeostasis. We earlier demonstrated in vivo activity of resolvins and lipoxins on regenerative periodontal wound healing. The goal of this study was to determine the impact of resolvin D1 (RvD1) on the function of human periodontal ligament (PDL) fibroblasts, which are critical for wound healing during regeneration of the soft and hard tissues around teeth. Primary cells were cultured from biopsies obtained from three individuals free of periodontal diseases. Peripheral blood mononuclear cells were isolated by density gradient centrifugation from whole blood of healthy volunteers. PGE2, leukotriene B4 (LTB4), and lipoxin A4 (LXA4) in culture supernatants were measured by ELISA. The direct impact of RvD1 on PDL fibroblast proliferation was measured and wound closure was analyzed in vitro using a fibroblast culture "scratch assay." PDL fibroblast function in response to RvD1 was further characterized by basic FGF production by ELISA. IL-1β and TNF-α enhanced the production of PGE2. Treatment of PDL cells and monocytes with 0.1-10 ng/ml RvD1 (0.27-27 M) reduced cytokine induced production of PGE2 and upregulated LXA4 production by both PDL cells and monocytes. RvD1 significantly enhanced PDL fibroblast proliferation and wound closure as well as basic FGF release. The results demonstrate that anti-inflammatory and proresolution actions of RvD1 with upregulation of arachidonic acid-derived endogenous resolution pathways (LXA4) and suggest resolution pathway synergy establishing a novel mechanism for the proresolution activity of the ω-3 docosahexaenoic acid-derived resolution agonist RvD1.

D-series resolvin attenuates vascular smooth muscle cell activation and neointimal hyperplasia following vascular injury

Recent evidence suggests that specialized lipid mediators derived from polyunsaturated fatty acids control resolution of inflammation, but little is known about resolution pathways in vascular injury. We sought to determine the actions of D-series resolvin (RvD) on vascular smooth muscle cell (VSMC) phenotype and vascular injury. Human VSMCs were treated with RvD1 and RvD2, and phenotype was assessed by proliferation, migration, monocyte adhesion, superoxide production, and gene expression assays. A rabbit model of arterial angioplasty with local delivery of RvD2 (10 nM vs. vehicle control) was employed to examine effects on vascular injury in vivo. Local generation of proresolving lipid mediators (LC-MS/MS) and expression of RvD receptors in the vessel wall were assessed. RvD1 and RvD2 produced dose-dependent inhibition of VSMC proliferation, migration, monocyte adhesion, superoxide production, and proinflammatory gene expression (IC50≈0.1-1 nM). In balloon-injured rabbit arteries, cell proliferation (51%) and leukocyte recruitment (41%) were reduced at 3 d, and neointimal hyperplasia was attenuated (29%) at 28 d by RvD2. We demonstrate endogenous biosynthesis of proresolving lipid mediators and expression of receptors for RvD1 in the artery wall. RvDs broadly reduce VSMC responses and modulate vascular injury, suggesting that local activation of resolution mechanisms expedites vascular homeostasis.