Specialized proresolving mediator resolvin E1 corrects the altered cystic fibrosis nasal epithelium cilia beating dynamics.

In cystic fibrosis (CF), impaired mucociliary clearance leads to chronic infection and inflammation. However, cilia beating features in a CF altered environment, consisting of dehydrated airway surface liquid layer and abnormal mucus, have not been fully characterized. Furthermore, acute inflammation is normally followed by an active resolution phase requiring specialized proresolving lipid mediators (SPMs) and allowing return to homeostasis. However, altered SPMs biosynthesis has been reported in CF. Here, we explored cilia beating dynamics in CF airways primary cultures and its response to the SPMs, resolvin E1 (RvE1) and lipoxin B4 (LXB4). Human nasal epithelial cells (hNECs) from CF and non-CF donors were grown at air-liquid interface. The ciliary beat frequency, synchronization, orientation, and density were analyzed from high-speed video microscopy using a multiscale Differential Dynamic Microscopy algorithm and an in-house developed method. Mucins and ASL layer height were studied by qRT-PCR and confocal microscopy. Principal component analysis showed that CF and non-CF hNEC had distinct cilia beating phenotypes, which was mostly explained by differences in cilia beat organization rather than frequency. Exposure to RvE1 (10 nM) and to LXB4 (10 nM) restored a non-CF-like cilia beating phenotype. Furthermore, RvE1 increased the airway surface liquid (ASL) layer height and reduced the mucin MUC5AC thickness. The calcium-activated chloride channel, TMEM16A, was involved in the RvE1 effect on cilia beating, hydration, and mucus. Altogether, our results provide evidence for defective cilia beating in CF airway epithelium and a role of RvE1 and LXB4 to restore the main epithelial functions involved in the mucociliary clearance.

Specialized pro-resolving mediators enhance the clearance of dead cells.

The failure to resolve inflammation underpins to several prevalent diseases, like atherosclerosis, and so identifying ways to boost resolution is unmet clinical needs. The resolution of inflammation is governed by several factors such as specialized pro-resolving mediators (SPMs) that counter-regulate pro-inflammatory pathways and promote tissue repair without compromising host defense. A major function of nearly all SPMs is to enhance the clearance of dead cells or efferocytosis. As such, phagocytes, such as macrophages, are essential cellular players in the resolution of inflammation because of their ability to rapidly and efficiently clear dead cells. This review highlights the role of SPMs in the clearance of apoptotic and necroptotic cells and offers insights into how targeting efferocytosis may provide new treatments for non-resolving diseases, like atherosclerosis.

Specialized pro-resolving mediators as modulators of immune responses.

Specialized pro-resolving mediators (SPMs) are endogenous small molecules produced mainly from dietary omega-3 polyunsaturated fatty acids by both structural cells and cells of the active and innate immune systems. Specialized pro-resolving mediators have been shown to both limit acute inflammation and promote resolution and return to homeostasis following infection or injury. There is growing evidence that chronic immune disorders are characterized by deficiencies in resolution and SPMs have significant potential as novel therapeutics to prevent and treat chronic inflammation and immune system disorders. This review focuses on important breakthroughs in understanding how SPMs are produced by, and act on, cells of the adaptive immune system, specifically macrophages, B cells and T cells. We also highlight recent evidence demonstrating the potential of SPMs as novel therapeutic agents in topics including immunization, autoimmune disease and transplantation.

Resolvin D2 limits atherosclerosis progression via myeloid cell-GPR18.

Dysregulated inflammation-resolution programs are associated with atherosclerosis progression. Resolvins, in part, mediate inflammation-resolution programs. Indeed, Resolvin D2 (RvD2) activates GPR18, a G-protein-coupled receptor, and limits plaque progression, though the cellular targets of RvD2 remain unknown. Here, we developed a humanized GPR18 floxed ("fl/fl") and a myeloid (Lysozyme M Cre) GPR18 knockout (mKO) mouse. We functionally validated this model by assessing efferocytosis in bone marrow-derived macrophages (BMDMs) and found that RvD2 enhanced efferocytosis in the fl/fl, but not in the mKO BMDMs. To understand the functions of RvD2-GPR18 in atherosclerosis, we performed a bone marrow transfer of fl/fl or mKO bone marrow into Ldlr-/- recipients. For these experiments, we treated each genotype with either Vehicle/PBS or RvD2 (25 ng/mouse, 3 times/week for 3 weeks). Myeloid loss of GPR18 resulted in significantly more necrosis, increased cleaved caspase-3+ cells and decreased percentage of Arginase-1+ -Mac2+ cells without a change in overall Mac2+ plaque macrophages, compared with fl/fl➔Ldlr-/- transplanted mice. RvD2 treatment decreased plaque necrosis, the percent of cleaved caspase-3+ cells and increased the percent of Arginase-1+ -Mac2+ cells in fl/fl➔Ldlr-/- mice, but not in the mKO➔Ldlr-/- transplanted mice. These results suggest that GPR18 plays a causal role in limiting atherosclerosis progression and that RvD2's ability to limit plaque necrosis is in part dependent on myeloid GRP18.

Continuous infusion of resolvin D2 in combination with Angiotensin-II show contrary effects on blood pressure and intracardiac artery remodeling.

Specialized pro-resolving mediators (SPMs) are key effectors of resolution of inflammation. This is highly relevant for cardiac and vessel remodeling, where the net inflammatory response contributes to determine disease outcome. Herein, we used a mice model of angiotensin (Ang)-II-induced hypertension to study the effect of the SPM Resolvin D2 (RvD2), on hypertension and cardiac remodeling. By using subcutaneous osmotic minipumps, mice were treated with PBS or Ang-II in combination with or without RvD2 for two weeks. Mice receiving RvD2 gained less blood pressure increase compared to Ang-II alone. Surprisingly, however, examination of intracardiac arteries revealed that RvD2 treatment in combination with Ang-II exacerbated Ang-II-induced fibrosis. Measures of vascular smooth muscle cell dedifferentiation correlated with the level of vascular remodeling, indicating that this dedifferentiation, including increased proliferation and migration, is a contributing factor. RNA sequencing of left ventricle cardiac tissue supported these findings as pathways related to cell proliferation and cell differentiation were upregulated in mice treated with Ang-II in combination with RvD2. Additionally, the RNA sequencing also showed upregulation of pathways related to SPM metabolism. In line with this, Mass spectrometry analysis of lipid mediators showed reduced cardiac levels of the arachidonic acid derived metabolite leukotriene E4 in RvD2 treated mice. Our study suggests that continuous infusion through osmotic minipumps should not be the recommended route of RvD2 administration in future studies.

Resolvin D1 attenuated liver injury caused by chronic ethanol and acute LPS challenge in mice.

Alcohol-associated liver disease (ALD) is a major health problem with limited effective treatment options. Alcohol-associated hepatitis (AH) is a subset of severe ALD with a high rate of mortality due to infection, severe inflammation, and ultimately multi-organ failure. There is an urgent need for novel therapeutic approaches to alleviate the human suffering associated with this condition. Resolvin D1 (RvD1) promotes the resolution of inflammation and regulates immune responses. The current study aimed to test the therapeutic efficacy and mechanisms of RvD1-mediated effects on liver injury and inflammation in an experimental animal model that mimics severe AH in humans. Our data demonstrated that mice treated with RvD1 had attenuated liver injury and inflammation caused by EtOH and LPS exposure by limiting hepatic neutrophil accumulation and decreasing hepatic levels of pro-inflammatory cytokines. In addition, RvD1 treatment attenuated hepatic pyroptosis, an inflammatory form of cell death, via downregulation of pyroptosis-related genes such as GTPase family member b10 and guanylate binding protein 2, and reducing cleavage of caspase 11 and gasdermin-D. In vitro experiments with primary mouse hepatocytes and bone marrow-derived macrophages confirmed the effectiveness of RvD1 in the attenuation of pyroptosis. In summary, our data demonstrated that RvD1 treatment provided beneficial effects against liver injury and inflammation in an experimental animal model recapitulating features of severe AH in humans. Our results suggest that RvD1 may be a novel adjunct strategy to traditional therapeutic options for AH patients.

The bioenergetics of traumatic brain injury and its long-term impact for brain plasticity and function.

Mitochondria provide the energy to keep cells alive and functioning and they have the capacity to influence highly complex molecular events. Mitochondria are essential to maintain cellular energy homeostasis that determines the course of neurological disorders, including traumatic brain injury (TBI). Various aspects of mitochondria metabolism such as autophagy can have long-term consequences for brain function and plasticity. In turn, mitochondria bioenergetics can impinge on molecular events associated with epigenetic modifications of DNA, which can extend cellular memory for a long time. Mitochondrial dysfunction leads to pathological manifestations such as oxidative stress, inflammation, and calcium imbalance that threaten brain plasticity and function. Hence, targeting mitochondrial function may have great potential to lessen the outcomes of TBI.

Resolvin and lipoxin metabolism network regulated by Hyssopus Cuspidatus Boriss extract in asthmatic mice.

Resolvin (Rv) and lipoxin (Lx) play important regulative roles in the development of several inflammation-related diseases. The dysregulation of their metabolic network is believed to be closely related to the occurrence and development of asthma. The Hyssopus Cuspidatus Boriss extract (SXCF) has long been used as a treatment for asthma, while the mechanism of anti-inflammatory and anti-asthma action targeting Rv and Lx has not been thoroughly investigated. In this study, we aimed to investigate the effects of SXCF on Rv, Lx in ovalbumin (OVA)-sensitized asthmatic mice. The changes of Rv, Lx before and after drug administration were analyzed based on high sensitivity chromatography-multiple response monitoring (UHPLC-MRM) analysis and multivariate statistics. The pathology exploration included behavioral changes of mice, IgE in serum, cytokines in BALF, and lung tissue sections stained with H&E. It was found that SXCF significantly modulated the metabolic disturbance of Rv, Lx due to asthma. Its modulation effect was significantly better than that of dexamethasone and rosmarinic acid which is the first-line clinical medicine and the main component of Hyssopus Cuspidatus Boriss, respectively. SXCF is demonstrated to be a potential anti-asthmatic drug with significant disease-modifying effects on OVA-induced asthma. The modulation of Rv and Lx is a possible underlying mechanism of the SXCF effects.

The impact of Resolvin E1 on bone regeneration in critical-sized calvarial defects of rat model-A gene expression and micro-CT analysis.

OBJECTIVE: To investigate, in vivo, the effect of local application of Resolvin E1 (RvE1) on the bone regeneration of critical-size defects (CSDs) in Wistar rats utilizing gene expression and micro-computed tomographic (micro-CT) analysis. BACKGROUND: The inflammation-resolving actions of RvE1 are well established. The molecular mechanism of its bone-regenerative actions has been of significant interest in recent years; however, there is limited information regarding the same. MATERIALS AND METHODS: Thirty Wistar rats with a 5 mm induced critical-size calvarial defect were randomly allocated into four groups: no treatment/negative control (n = 5), treatment using bovine bone grafts/positive control (n = 5), treatment using local delivery of RvE1 (n = 11) and treatment using RvE1 mixed with bovine bone graft (n = 9). After 4 weeks, RNA isolation, complementary DNA synthesis and real-time polymerase chain reaction were used for genetic expression of alkaline phosphatase (ALP), osteocalcin (OCN) and osteopontin (OPN). The rats were sacrificed after 12 weeks and micro-CT imaging was performed to analyse the characteristics of the newly formed bone (NFB). The data were analysed using ANOVA and the least significant difference tests (α ≤ .05). RESULTS: The RvE1 + bovine graft group had statistically highest mean NFB (20.75 ± 2.67 mm3 ) compared to other groups (p < .001). Similarly, RvE1 + bovine graft group also demonstrated statistically highest mean genetic expression of ALP (31.71 ± 2.97; p = .008) and OPN (34.78 ± 3.62; p < .001) compared to negative control and RvE1 groups. CONCLUSION: Resolvin E1 with adjunct bovine bone graft demonstrated an enhanced bone regeneration compared to RvE1 or bovine graft alone in the calvarial defect of Wistar rats.

Resolvin D1 alleviates apoptosis triggered by endoplasmic reticulum stress in IPEC-J2 cells.

BACKGROUND: Resolvin D1 (RvD1), a specialized pro-resolving lipid mediator (SPM), is derived from docosahexaenoic acid (DHA). It plays a key role in actively resolving inflammatory responses, which further reduces small intestinal damage. However, its regulation of the apoptosis triggered by endoplasmic reticulum (ER) stress in intestinal epithelial cells is still poorly understood. The intestinal porcine epithelial cells (IPEC-J2) were stimulated with tunicamycin to screen an optimal stimulation time and concentration to establish an ER stress model. Meanwhile, RvD1 (0, 1, 10, 20, and 50 nM) cytotoxicity and its impact on cell viability and the effective concentration for reducing ER stress and apoptosis were determined. Finally, the effects of RvD1 on ER stress and associated apoptosis were furtherly explored by flow cytometry analysis, AO/EB staining, RT-qPCR, and western blotting. RESULTS: The ER stress model of IPEC-J2 cells was successfully built by stimulating the cells with 1 µg/mL tunicamycin for 9 h. Certainly, the increased apoptosis and cell viability inhibition also appeared under the ER stress condition. RvD1 had no cytotoxicity, and its concentration of 1 nM significantly decreased cell viability inhibition (p= 0.0154) and the total apoptosis rate of the cells from 14.13 to 10.00% (p= 0.0000). RvD1 at the concentration of 1 nM also significantly reduced the expression of glucose-regulated protein 78 (GRP-78, an ER stress marker gene) (p= 0.0000) and pro-apoptotic gene Caspase-3 (p= 0.0368) and promoted the expression of B cell lymphoma 2 (Bcl-2, an anti-apoptotic gene)(p= 0.0008). CONCLUSIONS: Collectively, the results shed light on the potential of RvD1 for alleviating apoptosis triggered by ER stress, which may indicate an essential role of RvD1 in maintaining intestinal health and homeostasis.

The relationship between serum resolvin D1, NLRP3, cytokine levels, and adolescents with first-episode medication-naïve major depressive disorder.

BACKGROUND: Inflammation has become a critical pathological mechanism of Major Depressive Disorder (MDD). NLRP3 is a critical inflammatory pathway to maintain the immune balance. Recently, preclinical evidence showed that Resolvin D1 might potentially offer a new option for antidepressant treatment due to its protective effects through the inhibition of neuroinflammation. However, whether they have clinical value in the diagnosis and treatment evaluation of adolescent depression was unclear. METHODS: Forty-eight untreated first-episode adolescent patients with moderate to severe major depressive disorder, as well as 30 healthy adolescents (HCs, age and gender-matched), were enrolled for this study. Their ages ranged from 13 to 18 (15.75 ± 1.36) years. The patients were treated with fluoxetine for 6-8 weeks. HDRS-17 was used to evaluate the severity of depressive symptoms. Venous blood samples were collected at baseline for the two groups and at the time-point of post-antidepressant treatment for the patients. Serum concentrations of RvD1, NLRP3, IL-1ß, IL-18, and IL-4 were measured by enzyme-linked immunosorbent assays (ELISA) pre- and post-fluoxetine treatment. RESULTS: Serum levels of RvD1 and anti-inflammatory cytokine IL-4 were significantly elevated in adolescents with MDD compared to healthy adolescents, but no significant difference in NLRP3, IL-1ß, and IL-18 between the two groups. Meanwhile, RvD1 (positively) and IL-4 (negatively) were correlated with the severity of symptoms (HDRS-17 scores) after adjusting age, gender, and BMI. Interestingly, fluoxetine treatment significantly reduced the serum levels of RvD1, NLRP3, IL-1ß, and IL-18 in MDD adolescents but increased the levels of IL-4 relative to baseline. Furthermore, we observed that serum levels of RvD1 might be an excellent distinguishing indicator for depression and healthy adolescents. CONCLUSIONS: Our study is the first to compare RvD1 and NLRP3 between adolescent MDD and HCs. Our findings of reactive increase of RvD1 in adolescent MDD comprised a novel and critical contribution. Our results showed the presence of inflammation resolution unbalanced in adolescents with MDD and indicated that RvD1 might be an ideal biomarker for diagnosing and treating adolescent MDD.

Resolvin D1 level during different trimesters of pregnancy for predicting the risk of fetal growth retardation in elderly pregnancy.

Resolvin D1 (RvD1) is potentially associated with fetal growth retardation (FGR) through alleviating maternal inflammation and its linkage with several pregnancy complications. Thus, this study detected RvD1 levels at different trimesters of pregnancy, aiming to investigate its role in predicting FGR risk of elderly pregnant women. This prospective, observational cohort study enrolled 165 elderly pregnant women aged ≥35 years. Serum RvD1 was detected at 10-13 weeks (early pregnancy), 20-23 weeks (middle pregnancy), and 30-33 weeks (late pregnancy) of gestational week by enzyme-linked immunosorbent assay. RvD1 was varied among different trimesters of pregnancy in elderly pregnant women (p < 0.001). FGR occurred in 25 (15.2%) women in this study. RvD1 at early (p = 0.009), middle (p = 0.002), and late (p = 0.003) pregnancy was decreased in women with FGR versus those without. By multivariate analysis, RvD1 at middle pregnancy (odds ratio (OR): 0.477, p < 0.001), pre-pregnancy body mass index (OR: 0.763, p = 0.025), and gestational diabetes mellitus (yes versus no) (OR: 0.071, p = 0.031) were independently correlated with declined FGR risk. While age (OR: 1.382, p = 0.009) was independently associated with elevated risk of FGR. Furthermore, the combination of these independent factors as a predictive model exhibited a good potential for assessing FGR risk (area under the curve: 0.802, 95% confidence interval: 0.711-0.894). In conclusion, RvD1 at different trimesters of pregnancy is negatively linked with the risk of FGR, whose level at middle pregnancy serves as an independent factor for FGR risk in elderly pregnant women.

Specialized pro-resolution mediators in the bladder: effects of resolvin E1 on diabetic bladder dysfunction in the type 1 diabetic male Akita mouse model.

BACKGROUND: One of the most common, but least studied, diabetic complication is diabetic bladder dysfunction. Current therapies include glucose control and symptom-based interventions. However, efficacy of these therapies is mixed and often have undesirable side effects. Diabetes is now known to be a chronic inflammatory disease. Specialized pro-resolving mediators are a class of compounds that promote the resolution of inflammation and have been shown to be effective in treating chronic inflammatory conditions. In this study we examine the ability of resolvin E1 to improve signs of diabetic bladder dysfunction. METHODS: Male Akita mice (Type 1 diabetic) develop hyperglycemia at 4 weeks and signs of bladder underactivity by 15 weeks. Starting at 15 weeks, mice were given one or two weeks of daily resolvin E1 and compared to age-matched wild type and untreated Akita mice. RESULTS: Resolvin E1 did not affect diabetic blood glucose after one week, although there was a slight decrease after two weeks. Diabetes decreased body weight and increased bladder weights and this was not affected by resolvin E1. Evan's blue dye extravasation (an indirect index of inflammation) was dramatically suppressed after one week of resolvin E1 treatment, but, surprisingly, had returned to diabetic levels after two weeks of treatment. Using cystometry, untreated Akita mice showed signs of underactivity (increased void volumes and intercontraction intervals). One week of resolvin E1treatment restored these cystometric findings back to control levels. After two weeks of treatment, cystometric changes were changed from controls but still significantly different from untreated levels, indicating a durable treatment effect even in the presence of increased inflammation at 2 weeks. CONCLUSIONS: Resolvin E1 has a beneficial effect on diabetic bladder dysfunction in the type 1 diabetic male Akita mouse model.

Advances in the Chemistry and Biology of Specialised Pro-Resolving Mediators (SPMs).

This review article assembles key recent advances in the synthetic chemistry and biology of specialised pro-resolving mediators (SPMs). The major medicinal chemistry developments in the design, synthesis and biological evaluation of synthetic SPM analogues of lipoxins and resolvins have been discussed. These include variations in the top and bottom chains, as well as changes to the triene core, of lipoxins, all changes intended to enhance the metabolic stability whilst retaining or improving biological activity. Similar chemical modifications of resolvins are also discussed. The biological evaluation of these synthetic SPMs is also described in some detail. Original investigations into the biological activity of endogenous SPMs led to the pairing of these ligands with the FPR2/LX receptor, and these results have been challenged in more recent work, leading to conflicting results and views, which are again discussed.

Uncovering the Power of GPR18 Signalling: How RvD2 and Other Ligands Could Have the Potential to Modulate and Resolve Inflammation in Various Health Disorders.

The resolution of inflammation is the primary domain of specialised pro-resolving mediators (SPMs), which include resolvins, protectins, and their forms synthesised under the influence of aspirin and the maresins. The role of these SPMs has been discussed by many authors in the literature, with particular reference to neuroinflammation and significant neurological disorders. This review discusses the role of G protein-coupled receptor 18 (GPR18), resolvin D2 (RvD2) activity, and the GPR18-RvD2 signalling axis, as well as the role of small molecule ligands of GPR18 in inflammation in various health disorders (brain injuries, neuropathic pain, neurodegenerative/cardiometabolic/cardiovascular/gastrointestinal diseases, peritonitis, periodontitis, asthma and lung inflammation, Duchenne muscular dystrophy, SARS-CoV-2-induced inflammation, and placenta disorders. The idea of biological intervention through modulating GPR18 signalling is attracting growing attention because of its great therapeutic potential. With this paper, we aimed to present a comprehensive review of the most recent literature, perform a constructive view of data, and point out research gaps.

Eosinophil Phenotypes Are Functionally Regulated by Resolvin D2 during Allergic Lung Inflammation.

Eosinophils (Eos) reside in multiple organs during homeostasis and respond rapidly to an inflammatory challenge. Although Eos share chemical staining properties, they also demonstrate phenotypic and functional plasticity that is not fully understood. Here, we used a murine model of allergic lung inflammation to characterize Eos subsets and determine their spatiotemporal and functional regulation during inflammation and its resolution in response to resolvin D2 (RvD2), a potent specialized proresolving mediator. Two Eos subsets were identified by CD101 expression with distinct anatomic localization and transcriptional signatures at baseline and during inflammation. CD101low Eos were predominantly located in a lung vascular niche and responded to allergen challenge by moving into the lung interstitium. CD101high Eos were predominantly located in bronchoalveolar lavage (BAL) and extravascular lung, only present during inflammation, and had transcriptional evidence for cell activation. RvD2 reduced total Eos numbers and changed their phenotype and activation by at least two distinct mechanisms: decreasing interleukin 5-dependent recruitment of CD101low Eos and decreasing conversion of CD101low Eos to CD101high Eos. Collectively, these findings indicate that Eos are a heterogeneous pool of cells with distinct activation states and spatiotemporal regulation during resolution of inflammation and that RvD2 is a potent proresolving mediator for Eos recruitment and activation.

Characteristic fragmentation of polyunsaturated fatty acids with allylic vicinal diols in positive-ion LC/ESI-MS/MS.

A characteristic fragmentation was observed for PUFAs that contain allylic vicinal diol groups (resolvin D1, D2, D4, E3, lipoxin A4, B4, and maresin 2), which were derivatized with N,N-dimethylethylenediamine (DMED), in positive-ion ESI-MS/MS. The findings indicate that when these compounds contain an allylic hydroxyl group that is located distal to the terminal DMED moiety in the case of resolvin D1, D4, and lipoxin A4, an aldehyde (-CH=O) is predominately formed, which arises from the breakdown in between vicinal diols, whereas, in the case of an allylic hydroxyl group that is located proximal to the DMED moiety, as in resolvin D2, E3, lipoxin B4, and maresin 2, an allylic carbene (-CH=CH-CH:) is formed. These specific fragmentations could be used as diagnostic ions for characterizing the above seven PUFAs. As a result, it was possible to detect resolvin D1, D2, E3, lipoxin A4, and B4 in sera (20 µl) obtained from healthy volunteers by multiple-reaction monitoring using LC/ESI-MS/MS.

Lipid mediator resolvin D2 inhibits ATP currents in rat primary sensory neurons.

Resolvin D2 (RvD2), an endogenous lipid mediator derived from docosahexaenoic acid, has been demonstrated to have analgesic effects. However, little is known about the mechanism underlying RvD2 in pain relief. Herein, we demonstrate that RvD2 targeted the P2X3 receptor as an analgesic. The electrophysiological activity of P2X3 receptors was suppressed by RvD2 in rat dorsal root ganglia (DRG) neurons. RvD2 pre-application dose-dependently decreased α,ß-methylene-ATP (α,ß-meATP)-induced inward currents. RvD2 remarkably decreased the maximum response to α,ß-meATP, without influencing the affinity of P2X3 receptors. RvD2 also voltage-independently suppressed ATP currents. An antagonist of the G protein receptor 18 (GPR18), O-1918, prevented the RvD2-induced suppression of ATP currents. Additionally, intracellular dialysis of the Gαi/o -protein antagonist pertussis toxin (PTX), the PKA antagonist H89, or the cAMP analog 8-Br-cAMP also blocked the RvD2-induced suppression. Furthermore, α,ß-meATP-triggered depolarization of membrane potential along with the action potential bursts in DRG neurons were inhibited by RvD2. Lastly, RvD2 attenuated spontaneous nociceptive behaviors as well as mechanical allodynia produced by α,ß-meATP in rats via the activation of the peripheral GPR18. These findings indicated that RvD2 inhibited P2X3 receptors in rat primary sensory neurons through GPR18, PTX-sensitive Gαi/o -proteins, and intracellular cAMP/PKA signaling, revealing a novel mechanism that underlies its analgesic effects by targeting P2X3 receptors.

Modeling human heterogeneity of obesity with diversity outbred mice reveals a fat mass-dependent therapeutic window for resolvin E1.

Resolvin E1 (RvE1), a specialized pro-resolving mediator (SPM), improves glucose homeostasis in inbred mouse models of obesity. However, an impediment toward translation is that obesity is a highly heterogenous disease in which individuals will respond very differently to interventions such as RvE1. Thus, there is a need to study SPMs in the context of modeling the heterogeneity of obesity that is observed in humans. We investigated how RvE1 controls the concentration of key circulating metabolic biomarkers using diversity outbred (DO) mice, which mimic human heterogeneity. We first demonstrate that weights of DO mice can be classified into distinct distributions of fat mass (i.e., modeling differing classes of obesity) in response to a high-fat diet and in the human population when examining body composition. Next, we show RvE1 administration based on body weight for four consecutive days after giving mice a high-fat diet led to approximately half of the mice responding positively for serum total gastric inhibitory polypeptide (GIP), glucagon, insulin, glucose, leptin, and resistin. Interestingly, RvE1 improved hyperleptinemia most effectively in the lowest class of fat mass despite adjusting the dose of RvE1 with increasing adiposity. Furthermore, leptin levels after RvE1 treatment were the lowest in those mice that were also RvE1 positive responders for insulin and resistin. Collectively, these results suggest a therapeutic fat mass-dependent window for RvE1, which should be considered in future clinical trials. Moreover, the data underscore the importance of studying SPMs with heterogenous mice as a step toward precision SPM administration in humans.

Resolvin E3 ameliorates high-fat diet-induced insulin resistance via the phosphatidylinositol-3-kinase/Akt signaling pathway in adipocytes.

Obesity-associated type 2 diabetes mellitus is associated with the development of insulin resistance. Among several metabolites, resolvins that are metabolites of eicosapentaenoic acid have been shown to exert insulin-sensitizing effects; however, the role of resolvin E3 (RvE3) in glucose metabolism has not been studied. In this study, the effect of RvE3 on glucose metabolism in mice with high-fat diet-induced obesity and 3T3L1 adipocytes was studied. C57BL/6 mice fed a high-fat diet were administered RvE3, for which insulin tolerance, oral glucose tolerance tests, and the homeostasis model assessment of insulin resistance, were performed. RvE3 treatment significantly improved insulin sensitivity and glucose tolerance and regulated protein kinase B (Akt) phosphorylation in the adipose tissue. Moreover, RvE3 treatment enhanced the insulin-stimulated glucose transporter 4 (Glut4) translocation, glucose uptake, phosphatidylinositol-3-kinase (PI3K) activity, and Akt phosphorylation in 3T3L1 adipocytes, whereas a PI3K inhibitor inhibited the enhanced insulin-stimulated glucose uptake induced by RvE3. These findings indicate that RvE3 likely improves insulin sensitivity, resulting in the upregulation of glucose uptake in adipocytes by activating the PI3K/Akt signaling pathways. Collectively, the findings of this study show that RvE3 may play a role in glucose homeostasis and could be used as a potential therapeutic target for developing treatments for obesity-associated diabetes.