Soluble epoxide hydrolase inhibition enhances anti-inflammatory and antioxidative processes, modulates microglia polarization, and promotes recovery after ischemic stroke

Novel molecular mechanism driving neuroprotection after soluble epoxide hydrolase inhibition: Insights for Alzheimer's disease therapeutics

BACKGROUND

Neuroinflammation is widely recognized as a significant hallmark of Alzheimer's disease (AD). To combat neuroinflammation, the inhibition of the soluble epoxide hydrolase (sEH) enzyme has been demonstrated crucial. Importantly, sEH inhibition could be related to other neuroprotective pathways described in AD.

AIMS

The aim of the study was to unveil new molecular pathways driving neuroprotection through sEH, we used an optimized, potent, and selective sEH inhibitor (sEHi, UB-SCG-51).

MATERIALS AND METHODS

UB-SCG-51 was tested in neuroblastoma cell line, SH-SY5Y, in primary mouse and human astrocytes cultures challenged with proinflammatory insults and in microglia cultures treated with amyloid oligomers, as well as in mice AD model (5XFAD).

RESULTS

UB-SCG-51 (10 and 30 μM) prevented neurotoxic reactive-astrocyte conversion in primary mouse astrocytes challenged with TNF-α, IL-1α, and C1q (T/I/C) combination for 24 h. Moreover, in microglial cultures, sEHi reduced inflammation and glial activity. In addition, UB-SCG-51 rescued 5XFAD cognitive impairment, reducing the number of Amyloid-β plaques and Tau hyperphosphorylation accompanied by a reduction in neuroinflammation and apoptotic markers. Notably, a transcriptional profile analysis revealed a new pathway modulated by sEHi treatment. Specifically, the eIF2α/CHOP pathway, which promoted the endoplasmic reticulum response, was increased in the 5XFAD-treated group. These findings were confirmed in human primary astrocytes by combining sEHi and eIF2α inhibitor (eIF2αi) treatment. Besides, combining both treatments resulted in increased in C3 gene expression after T/I/C compared with the group treated with sEHi alone in cultures.

DISCUSSION

Therefore, sEHi rescued cognitive impairment and neurodegeneration in AD mice model, based on the reduction of inflammation and eIF2α/CHOP signaling pathway.

CONCLUSIONS

In whole, our results support the concept that targeting neuroinflammation through sEH inhibition is a promising therapeutic strategy to fight against Alzheimer's disease with additive and/or synergistic activities targeting neuroinflammation and cell stress.

Inhibition of soluble epoxide hydrolase as a therapeutic approach for blood-brain barrier dysfunction

The blood-brain barrier (BBB) is a protective semi-permeable structure that regulates the exchange of biomolecules between the peripheral blood and the central nervous system (CNS). Due to its specialized tight junctions and low vesicle trafficking, the BBB strictly limits the paracellular passage and transcellular transport of molecules to maintain the physiological condition of brain tissues. BBB breakdown is associated with many CNS disorders. Soluble epoxide hydrolase (sEH) is a hydrolase enzyme that converts epoxy-fatty acids (EpFAs) to their corresponding diols and is involved in the onset and progression of multiple diseases. EpFAs play a protective role in the central nervous system via preventing neuroinflammation, making sEH a potential therapeutic target for CNS diseases. Recent studies showed that sEH inhibition prevented BBB impairment caused by stroke, hemorrhage, traumatic brain injury, hyperglycemia and sepsis via regulating the expression of tight junctions. In this review, the protective actions of sEH inhibition on BBB and potential mechanisms are summarized, and some important questions that remain to be resolved are also addressed.

Phytosome Supplements for Delivering Gymnema inodorum Phytonutrients to Prevent Inflammation in Macrophages and Insulin Resistance in Adipocytes

Gymnema inodorum (GI) is a leafy green vegetable found in the northern region of Thailand. A GI leaf extract has been developed as a dietary supplement for metabolic diabetic control. However, the active compounds in the GI leaf extract are relatively nonpolar. This study aimed to develop phytosome formulations of the GI extract to improve the efficiencies of their phytonutrients in terms of anti-inflammatory and anti-insulin-resistant activities in macrophages and adipocytes, respectively. Our results showed that the phytosomes assisted the GI extract's dispersion in an aqueous solution. The GI phytocompounds were assembled into a phospholipid bilayer membrane as spherical nanoparticles about 160-180 nm in diameter. The structure of the phytosomes allowed phenolic acids, flavonoids and triterpene derivatives to be embedded in the phospholipid membrane. The existence of GI phytochemicals in phytosomes significantly changed the particle's surface charge from neutral to negative within the range of -35 mV to -45 mV. The phytosome delivery system significantly exhibited the anti-inflammatory activity of the GI extract, indicated by the lower production of nitric oxide from inflamed macrophages compared to the non-encapsulated extract. However, the phospholipid component of phytosomes slightly interfered with the anti-insulin-resistant effects of the GI extract by decreasing the glucose uptake activity and increasing the lipid degradation of adipocytes. Altogether, the nano-phytosome is a potent carrier for transporting GI phytochemicals to prevent an early stage of T2DM.

Sex-Specific Response of the Brain Free Oxylipin Profile to Soluble Epoxide Hydrolase Inhibition

Oxylipins are the oxidation products of polyunsaturated fatty acids and have been implicated in neurodegenerative disorders, including dementia. Soluble epoxide hydrolase (sEH) converts epoxy-fatty acids to their corresponding diols, is found in the brain, and its inhibition is a treatment target for dementia. In this study, male and female C57Bl/6J mice were treated with an sEH inhibitor (sEHI), trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB), for 12 weeks to comprehensively study the effect of sEH inhibition on the brain oxylipin profile, and modulation by sex. Ultra-high-performance liquid chromatography-tandem mass spectrometry was used to measure the profile of 53 free oxylipins in the brain. More oxylipins were modified by the inhibitor in males than in females (19 versus 3, respectively) and favored a more neuroprotective profile. Most were downstream of lipoxygenase and cytochrome p450 in males, and cyclooxygenase and lipoxygenase in females. The inhibitor-associated oxylipin changes were unrelated to serum insulin, glucose, cholesterol, or female estrous cycle. The inhibitor affected behavior and cognitive function as measured by open field and Y-maze tests in males, but not females. These findings are novel and important to our understanding of sexual dimorphism in the brain's response to sEHI and may help inform sex-specific treatment targets.

Aflatoxin B1 exposure disrupts the intestinal immune function via a soluble epoxide hydrolase-mediated manner

Aflatoxin B1 (AFB1) contamination in food and feed leads to severe global health problems. Acting as the frontier immunological barrier, the intestinal mucosa is constantly challenged by exposure to foodborne toxins such as AFB1 via contaminated diets, but the detailed toxic mechanism and endogenous regulators of AFB1 toxicity are still unclear. Here, we showed that AFB1 disrupted intestinal immune function by suppressing macrophages, especially M2 macrophages, and antimicrobial peptide-secreting Paneth cells. Using an oxylipinomics approach, we identified that AFB1 immunotoxicity is associated with decreased epoxy fatty acids, notably epoxyeicosatrienoic acids, and increased soluble epoxide hydrolase (sEH) levels in the intestine. Furthermore, sEH deficiency or inhibition rescued the AFB1-compromised intestinal immunity by restoring M2 macrophages as well as Paneth cells and their-derived lysozyme and α-defensin-3 in mice. Altogether, our study demonstrates that AFB1 exposure impairs intestinal immunity, at least in part, in a sEH-mediated way. Moreover, the present study supports the potential application of pharmacological intervention by inhibiting the sEH enzyme in alleviating intestinal immunotoxicity and associated complications caused by AFB1 global contamination.

Soluble Epoxide Hydrolase as a Therapeutic Target for Neuropsychiatric Disorders

It has been found that soluble epoxide hydrolase (sEH; encoded by the EPHX2 gene) in the metabolism of polyunsaturated fatty acids (PUFAs) plays a key role in inflammation, which, in turn, plays a part in the pathogenesis of neuropsychiatric disorders. Meanwhile, epoxy fatty acids such as epoxyeicosatrienoic acids (EETs), epoxyeicosatetraenoic acids (EEQs), and epoxyeicosapentaenoic acids (EDPs) have been found to exert neuroprotective effects in animal models of neuropsychiatric disorders through potent anti-inflammatory actions. Soluble expoxide hydrolase, an enzyme present in all living organisms, metabolizes epoxy fatty acids into the corresponding dihydroxy fatty acids, which are less active than the precursors. In this regard, preclinical findings using sEH inhibitors or Ephx2 knock-out (KO) mice have indicated that the inhibition or deficiency of sEH can have beneficial effects in several models of neuropsychiatric disorders. Thus, this review discusses the current findings of the role of sEH in neuropsychiatric disorders, including depression, autism spectrum disorder (ASD), schizophrenia, Parkinson’s disease (PD), and stroke, as well as the potential mechanisms underlying the therapeutic effects of sEH inhibitors.

Multimodal Optical Imaging to Investigate Spatiotemporal Changes in Cerebrovascular Function in AUDA Treatment of Acute Ischemic Stroke

Administration of 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA) has been demonstrated to alleviate infarction following ischemic stroke. Reportedly, the main effect of AUDA is exerting anti-inflammation and neovascularization via the inhibition of soluble epoxide hydrolase. However, the major contribution of this anti-inflammation and neovascularization effect in the acute phase of stroke is not completely elucidated. To investigate the neuroprotective effects of AUDA in acute ischemic stroke, we combined laser speckle contrast imaging and optical intrinsic signal imaging techniques with the implantation of a lab-designed cranial window. Forepaw stimulation was applied to assess the functional changes via measuring cerebral metabolic rate of oxygen (CMRO₂) that accompany neural activity. The rats that received AUDA in the acute phase of photothrombotic ischemia stroke showed a 30.5 ± 8.1% reduction in the ischemic core, 42.3 ± 15.1% reduction in the ischemic penumbra (p < 0.05), and 42.1 ± 4.6% increase of CMRO₂ in response to forepaw stimulation at post-stroke day 1 (p < 0.05) compared with the control group (N = 10 for each group). Moreover, at post-stroke day 3, increased functional vascular density was observed in AUDA-treated rats (35.9 ± 1.9% higher than that in the control group, p < 0.05). At post-stroke day 7, a 105.4% ± 16.4% increase of astrocytes (p < 0.01), 30.0 ± 10.9% increase of neurons (p < 0.01), and 65.5 ± 15.0% decrease of microglia (p < 0.01) were observed in the penumbra region in AUDA-treated rats (N = 5 for each group). These results suggested that AUDA affects the anti-inflammation at the beginning of ischemic injury and restores neuronal metabolic rate of O₂ and tissue viability. The neovascularization triggered by AUDA restored CBF and may contribute to ischemic infarction reduction at post-stroke day 3. Moreover, for long-term neuroprotection, astrocytes in the penumbra region may play an important role in protecting neurons from apoptotic injury.

Association of rs11780592 Polymorphism in the Human Soluble Epoxide Hydrolase Gene (EPHX2) with Oxidized LDL and Mortality in Patients with Diabetic Chronic Kidney Disease

Soluble epoxide hydrolase 2 (EPHX2) is an enzyme promoting increased cellular apoptosis through induction of oxidative stress (OS) and inflammation. The EPHX2 gene which encodes soluble EPHX2 might be implicated in the pathogenesis and development of OS and atherosclerosis. We aimed to assess the possible association between two functional polymorphisms of the EPHX2 gene (rs2741335 and rs11780592) with oxidized LDL (ox-LDL), carotid atherosclerosis, mortality, and cardiovascular (CV) disease in 118 patients with diabetic chronic kidney disease (CKD). At baseline, ox-LDL and carotid intima-media thickness (cIMT) were evaluated and all patients were followed for seven years with outcomes all-cause mortality and CV events. rs11780592 EPHX2 polymorphism was associated with ox-LDL, cIMT, albuminuria, and hypertension. Compared to AG and GG, AA homozygotes had higher values of albuminuria, ox-LDL, and cIMT (p = 0.046, p = 0.003, and p = 0.038, respectively). These associations remained significant, even after grouping for the G allele. After the follow-up period, 42/118 patients died (30/60 with AA genotype, 11/42 with AG genotype, and 1/12 with GG genotype) and 49/118 experienced a new CV event (fatal or nonfatal). The Kaplan-Meier analysis revealed that patients with the AA genotype exhibited a significantly higher mortality risk, compared to patients with AG and GG genotypes (p = 0.006). This association became even stronger, when AG and GG genotypes were grouped (AA vs. AG/GG, p = 0.002). AA homozygotes were strongly associated with all-cause mortality in both univariate (hazard ratio (HR) = 2.74, confidence interval (CI) = 1.40-5.35, p = 0.003) and multivariate Cox regression analysis (HR = 2.61, CI = 1.32-5.17, p = 0.006). In conclusion, our study demonstrated that genetic variations of EPHX2 gene were associated with increased circulating ox-LDL, increased cIMT, and all-cause mortality in diabetic CKD. Since EPHX2 regulates the cholesterol efflux and the oxidation of LDL in foam cells and macrophages, our study suggests that a genetic basis to endothelial dysfunction and OS might be present in diabetic CKD.

Up-regulating lncRNA OIP5-AS1 protects neuron injury against cerebral hypoxia-ischemia induced inflammation and oxidative stress in microglia/macrophage through activating CTRP3 via sponging miR-186-5p

BACKGROUND

Inflammation and oxidative stress is closely associated with the development of ischemic brain stroke. Opa-interacting protein 5 antisense RNA 1 (OIP5-AS1), a novel identified long non-coding RNA (lncRNA), has been suggested to play an important role in the development of many types of human cancers. However, the functional involvement of OIP5-AS1 in ischemic stroke is still unknown.

METHODS

Quantitative real-time polymerase chain reaction and /or western blot were conducted to determine the expression profiles of OIP5-AS1, C1q/TNF-related protein 3 (CTRP3) and miR-186-5p in the serum of stroke patients, as well as in the ischemic penumbra of rats with middle cerebral artery occlusion/reperfusion (MCAO/R) injury and microglial cells treated with oxygen glucose deprivation/re-oxygenation (OGD/R). Upon selective regulation of OIP5-AS1 and miR-186-5p, the inflammation and oxidative stress responses in microglia/macrophage as well as neurologic functions in MCAO/R rats were detected. Furthermore, the interactions between OIP5-AS1 and miR-186-5p, miR-186-5p and CTRP3 were investigated by RNA immunoprecipitation (RIP) assay, luciferase report assay and bioinformation anaylsis.

RESULTS

We observed markedly increased infarct volume, neuronal apoptosis, inflammation and oxidative stress responses in the infarcted lesions of MCAO/R rats, in line with down-regulated levels of OIP5-AS1 and CTRP3 while up-regulated miR-186-5p. Functional studies demonstrated that up-regulation of OIP5-AS1 attenuated infarct volume, neuronal apoptosis, microglia/macrophage inflammation and oxidative stress responses induced by MCAO/R or OGD/R. In terms of mechanism, we revealed that OIP5-AS1-miR-186-5p-CTRP3 axis played a vital role in modulating microglia/macrophage activation and neuronal apoptosis.

CONCLUSION

Up-regulating lncRNA OIP5-AS1 protects neuron injury against MCAO/R induced inflammation and oxidative stress in microglia/macrophage through activating CTRP3 via sponging miR-186-5p.

Soluble epoxide hydrolase inhibition improves cognitive function and parenchymal artery dilation in a hypertensive model of chronic cerebral hypoperfusion

OBJECTIVE

Parenchymal arterioles (PAs) regulate perfusion of the cerebral microcirculation, and impaired PA endothelium-dependent dilation occurs in dementia models mimicking chronic cerebral hypoperfusion (CCH). Epoxyeicosatrienoic acids (EETs) are vasodilators; their actions are potentiated by soluble epoxide hydrolase (sEH) inhibition. We hypothesized that chronic sEH inhibition with trifluoromethoxyphenyl-3 (1-propionylpiperidin-4-yl) urea (TPPU) would prevent cognitive dysfunction and improve PA dilation in a hypertensive CCH model.

METHODS

Bilateral carotid artery stenosis (BCAS) was used to induce CCH in twenty-week-old male stroke-prone spontaneously hypertensive rats (SHSRP) that were treated with vehicle or TPPU for 8 weeks. Cognitive function was assessed by novel object recognition. PA dilation and structure were assessed by pressure myography, and mRNA expression in brain tissue was assessed by qRT-PCR.

RESULTS

TPPU did not enhance resting cerebral perfusion, but prevented CCH-induced memory deficits. TPPU improved PA endothelium-dependent dilation but reduced the sensitivity of PAs to a nitric oxide donor. TPPU treatment had no effect on PA structure or biomechanical properties. TPPU treatment increased brain mRNA expression of brain derived neurotrophic factor, doublecortin, tumor necrosis factor-alpha, sEH, and superoxide dismutase 3, CONCLUSIONS: These data suggest that sEH inhibitors may be viable treatments for cognitive impairments associated with hypertension and CCH.

Mitochondrial Dysfunction and Inflammaging in Heart Failure: Novel Roles of CYP-Derived Epoxylipids

Age-associated changes leading to a decline in cardiac structure and function contribute to the increased susceptibility and incidence of cardiovascular diseases (CVD) in elderly individuals. Indeed, age is considered a risk factor for heart failure and serves as an important predictor for poor prognosis in elderly individuals. Effects stemming from chronic, low-grade inflammation, inflammaging, are considered important determinants in cardiac health; however, our understanding of the mechanisms involved remains unresolved. A steady decline in mitochondrial function is recognized as an important biological consequence found in the aging heart which contributes to the development of heart failure. Dysfunctional mitochondria contribute to increased cellular stress and an innate immune response by activating the NLRP-3 inflammasomes, which have a role in inflammaging and age-related CVD pathogenesis. Emerging evidence suggests a protective role for CYP450 epoxygenase metabolites of N-3 and N-6 polyunsaturated fatty acids (PUFA), epoxylipids, which modulate various aspects of the immune system and protect mitochondria. In this article, we provide insight into the potential roles N-3 and N-6 PUFA have modulating mitochondria, inflammaging and heart failure.

Pharmacological inhibition of soluble epoxide hydrolase attenuates chronic experimental autoimmune encephalomyelitis by modulating inflammatory and anti-inflammatory pathways in an inflammasome-dependent and -independent manner

We aimed to determine the effect of soluble epoxide hydrolase (sEH) inhibition on chronic experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS), associated with changes in inflammasome-dependent and -independent inflammatory and anti-inflammatory pathways in the CNS of mice. C57BL/6 mice were used to induce chronic EAE by using an injection of MOG_35-55 peptide/PT. Animals were observed daily and scored for EAE signs for 25 days after immunization. Following the induction of EAE, the scores were increased after 9 days and reached peak value as determined by ≥ 2 or ≤ 3 with 8% mortality rate on day 17. On day 17, mice were administered daily PBS, DMSO, or TPPU (a potent sEH inhibitor) (1, 3, or 10 mg/kg) until the end of the study. TPPU only at 3 mg/kg dose decreased the AUC values calculated from EAE scores obtained during the disease compared to EAE and vehicle control groups. On day 25, TPPU also caused an increase in the PPARα/β/γ and NLRC3 proteins and a decrease in the proteins of TLR4, MyD88, NF-κB p65, p-NF-κB p65, iNOS/nNOS, COX-2, NLRC4, ASC, caspase-1 p20, IL-1β, caspase-11 p20, NOX subunits (gp91^phox and p47^phox), and nitrotyrosine in addition to 14,15-DHET and IL-1β levels compared to EAE and vehicle control groups. Our findings suggest that pharmacological inhibition of sEH attenuates chronic EAE likely because of enhanced levels of anti-inflammatory EETs in addition to PPARα/β/γ and NLRC3 expression associated with suppressed inflammatory TLR4/MyD88/NF-κB signalling pathway, NLRC4/ASC/pro-caspase-1 inflammasome, caspase-11 inflammasome, and NOX activity that are responsible for inflammatory mediator formation in the CNS of mice.

Protective Effects of the Soluble Epoxide Hydrolase Inhibitor 1-Trifluoromethoxyphenyl-3-(1-Propionylpiperidin-4-yl) Urea in a Rat Model of Permanent Middle Cerebral Artery Occlusion

Acute ischemic stroke is a serious disease that endangers human health. In our efforts to develop an effective therapy, we previously showed that the potent, highly selective inhibitor of soluble epoxide hydrolase called 1-trifuoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) protects the brain against focal ischemia in rats. Here we explored the mechanism of TPPU action by assessing whether it could preserve blood-brain barrier integrity and reduce apoptosis in the brain during permanent middle cerebral artery occlusion in male Sprague-Dawley rats. TPPU administration at the onset of stroke and once daily thereafter led to smaller infarct volume and brain edema as well as milder neurological deficits. TPPU significantly inhibited the activity of soluble epoxide hydrolase and matrix metalloproteases 2 and 9, reducing 14,15-DHET levels, while increasing expression of tight junction proteins. TPPU decreased numbers of apoptotic cells by down-regulating the pro-apoptotic proteins BAX and Caspase-3, while up-regulating the anti-apoptotic protein BCL-2. Our results suggest that TPPU can protect the blood-brain barrier and reduce the apoptosis of brain tissue caused by ischemia.