CYP2C8-derived epoxyeicosatrienoic acids decrease oxidative stress-induced endothelial apoptosis in development of atherosclerosis: Role of Nrf2 activation

Paeoniflorin confers ferroptosis resistance by regulating the gut microbiota and its metabolites in diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is closely related to ferroptosis, a new type of cell death that mainly manifests as intracellular iron accumulation and lipid peroxidation. Paeoniflorin (PA) helps to improve impaired glucose tolerance, influences the distribution of the intestinal flora, and induces significant resistance to ferroptosis in several models. In this study, we found that PA improved cardiac dysfunction in mice with DCM by alleviating myocardial damage, resisting oxidative stress and ferroptosis, and changing the community composition and structure of the intestinal microbiota. Metabolomics analysis revealed that PA-treated fecal microbiota transplantation affected metabolites in DCM mice. Based on in vivo and in vitro experiments, 11,12-epoxyeicosatrienoic acid (11,12-EET) may serve as a key contributor that mediates the cardioprotective and antiferroptotic effects of PA-treated fecal microbiota transplantation (FMT) in DCM mice.NEW & NOTEWORTHY This study demonstrated for the first time that paeoniflorin (PA) exerts protective effects in diabetic cardiomyopathy mice by alleviating myocardial damage, resisting ferroptosis, and changing the community composition and structure of the intestinal microbiota, and 11,12-epoxyeicosatrienoic acid (11,12-EET) may serve as a key contributor in its therapeutic efficacy.

Trigeminal Nerve Stimulation Improves Cerebral Macrocirculation and Microcirculation After Subarachnoid Hemorrhage: An Exploratory Study

BACKGROUND

Delayed cerebral ischemia (DCI) is the most consequential secondary insult after aneurysmal subarachnoid hemorrhage (SAH). It is a multifactorial process caused by a combination of large artery vasospasm and microcirculatory dysregulation. Despite numerous efforts, no effective therapeutic strategies are available to prevent DCI. The trigeminal nerve richly innervates cerebral blood vessels and releases a host of vasoactive agents upon stimulation. As such, electrical trigeminal nerve stimulation (TNS) has the capability of enhancing cerebral circulation.

OBJECTIVE

To determine whether TNS can restore impaired cerebral macrocirculation and microcirculation in an experimental rat model of SAH.

METHODS

The animals were randomly assigned to sham-operated, SAH-control, and SAH-TNS groups. SAH was induced by endovascular perforation on Day 0, followed by KCl-induced cortical spreading depolarization on day 1, and sample collection on day 2. TNS was delivered on day 1. Multiple end points were assessed including cerebral vasospasm, microvascular spasm, microthrombosis, calcitonin gene-related peptide and intercellular adhesion molecule-1 concentrations, degree of cerebral ischemia and apoptosis, and neurobehavioral outcomes.

RESULTS

SAH resulted in significant vasoconstriction in both major cerebral vessels and cortical pial arterioles. Compared with the SAH-control group, TNS increased lumen diameters of the internal carotid artery, middle cerebral artery, and anterior cerebral artery, and decreased pial arteriolar wall thickness. Additionally, TNS increased cerebrospinal fluid calcitonin gene-related peptide levels, and decreased cortical intercellular adhesion molecule-1 expression, parenchymal microthrombi formation, ischemia-induced hypoxic injury, cellular apoptosis, and neurobehavioral deficits.

CONCLUSION

Our results suggest that TNS can enhance cerebral circulation at multiple levels, lessen the impact of cerebral ischemia, and ameliorate the consequences of DCI after SAH.

Soluble Epoxide Hydrolase Inhibition Protected against Diabetic Cardiomyopathy through Inducing Autophagy and Reducing Apoptosis Relying on Nrf2 Upregulation and Transcription Activation

Background

Many patients with diabetes die from diabetic cardiomyopathy (DCM); however, effective strategies for the prevention or treatment of DCM have not yet been clarified.

Methods

Leptin receptor-deficient (db/db) mice were treated with either the soluble epoxide hydrolase (sEH) inhibitor AUDA or vehicle alone. A virus carrying Nrf2 shRNA was used to manipulate Nrf2 expression in db/db mice. Cardiac structures and functions were analyzed using echocardiography and hemodynamic examinations. Primary cardiomyocytes cultured under high glucose and high fat (HGHF) conditions were used to conduct in vitro loss-of-function assays after culture in the presence or absence of AUDA (1 μM). Fluorescence microscopy-based detection of mCherry-GFP-LC3 was performed to assess autophagic flux.

Results

The sEH inhibitor AUDA significantly attenuated ventricular remodeling and ameliorated cardiac dysfunction in db/db mice. Interestingly, AUDA upregulated Nrf2 expression and promoted its nuclear translocation in db/db mice and the HGHF-treated cardiomyocytes. Additionally, AUDA increased autophagy and decreased apoptosis in db/db mice heart. Furthermore, the administration of AUDA promoted autophagic flux and elevated LC3-II protein level in the presence of bafilomycin A1. However, AUDA-induced autophagy was abolished, and the antiapoptotic effect was partially inhibited upon Nrf2 knockdown.

Conclusion

Our findings suggest that the sEH inhibitor AUDA attenuates cardiac remodeling and dysfunction in DCM via increasing autophagy and reducing apoptosis, which is relevant to activate Nrf2 signaling pathway.

Differential Effects of sEH Inhibitors on the Proliferation and Migration of Vascular Smooth Muscle Cells

Epoxyeicosatrienoic acid (EET) is a cardioprotective metabolite of arachidonic acid. It is known that soluble epoxide hydrolase (sEH) is involved in the metabolic degradation of EET. The abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) play important roles in the pathogenesis of atherosclerosis and restenosis. Thus, the present study investigated the effects of the sEH inhibitor 12-(((tricyclo(3.3.1.13,7)dec-1-ylamino)carbonyl)amino)-dodecanoic acid (AUDA) on platelet-derived growth factor (PDGF)-induced proliferation and migration in rat VSMCs. AUDA significantly inhibited PDGF-induced rat VSMC proliferation, which coincided with Pin1 suppression and heme oxygenase-1 (HO-1) upregulation. However, exogenous 8,9-EET, 11,12-EET, and 14,15-EET treatments did not alter Pin1 or HO-1 levels and had little effect on the proliferation of rat VSMCs. On the other hand, AUDA enhanced the PDGF-stimulated cell migration of rat VSMCs. Furthermore, AUDA-induced activation of cyclooxygenase-2 (COX-2) and subsequent thromboxane A2 (TXA₂) production were required for the enhanced migration. Additionally, EETs increased COX-2 expression but inhibited the migration of rat VSMCs. In conclusion, the present study showed that AUDA exerted differential effects on the proliferation and migration of PDGF-stimulated rat VSMCs and that these results may not depend on EET stabilization.

Orally Active Epoxyeicosatrienoic Acid Analogs

Biologically active epoxyeicosatrienoic acid (EET) regioisomers are synthesized from arachidonic acid by cytochrome P450 epoxygenases of endothelial, myocardial, and renal tubular cells. EETs relax vascular smooth muscle and decrease inflammatory cell adhesion and cytokine release. Renal EETs promote sodium excretion and vasodilation to decrease hypertension. Cardiac EETs reduce infarct size after ischemia-reperfusion injury and decrease fibrosis and inflammation in heart failure. In diabetes, EETs improve insulin sensitivity, increase glucose tolerance, and reduce the renal injury. These actions of EETs emphasize their therapeutic potential. To minimize metabolic inactivation, 14,15-EET agonist analogs with stable epoxide bioisosteres and carboxyl surrogates were developed. In preclinical rat models, a subset of agonist analogs, termed EET-A, EET-B, and EET-C22, are orally active with good pharmacokinetic properties. These orally active EET agonists lower blood pressure and reduce cardiac and renal injury in spontaneous and angiotensin hypertension. Other beneficial cardiovascular actions include improved endothelial function and cardiac antiremodeling actions. In rats, EET analogs effectively combat acute and chronic kidney disease including drug- and radiation-induced kidney damage, hypertension and cardiorenal syndrome kidney damage, and metabolic syndrome and diabetes nephropathy. The compelling preclinical efficacy supports the prospect of advancing EET analogs to human clinical trials for kidney and cardiovascular diseases.

Modulation of mitochondrial dysfunction and endoplasmic reticulum stress are key mechanisms for the wide-ranging actions of epoxy fatty acids and soluble epoxide hydrolase inhibitors

The arachidonic acid cascade is arguably the most widely known biologic regulatory pathway. Decades after the seminal discoveries involving its cyclooxygenase and lipoxygenase branches, studies of this cascade remain an active area of research. The third and less widely known branch, the cytochrome P450 pathway leads to highly active oxygenated lipid mediators, epoxy fatty acids (EpFAs) and hydroxyeicosatetraenoic acids (HETEs), which are of similar potency to prostanoids and leukotrienes. Unlike the COX and LOX branches, no pharmaceuticals currently are marketed targeting the P450 branch. However, data support therapeutic benefits from modulating these regulatory lipid mediators. This is being approached by stabilizing or mimicking the EpFAs or even by altering the diet. These approaches lead to predominantly beneficial effects on a wide range of apparently unrelated states resulting in an enigma of how this small group of natural chemical mediators can have such diverse effects. EpFAs are degraded by soluble epoxide hydrolase (sEH) and stabilized by inhibiting this enzyme. In this review, we focus on interconnected aspects of reported mechanisms of action of EpFAs and inhibitors of soluble epoxide hydrolase (sEHI). The sEHI and EpFAs are commonly reported to maintain homeostasis under pathological conditions while remaining neutral under normal physiological conditions. Here we provide a conceptual framework for the unique and broad range of biological activities ascribed to epoxy fatty acids. We argue that their mechanism of action pivots on their ability to prevent mitochondrial dysfunction, to reduce subsequent ROS formation and to block resulting cellular signaling cascades, primarily the endoplasmic reticulum stress. By stabilizing the mitochondrial - ROS - ER stress axis, the range of activity of EpFAs and sEHI display an overlap with the disease conditions including diabetes, fibrosis, chronic pain, cardiovascular and neurodegenerative diseases, for which the above outlined mechanisms play key roles.

Role of lipid mediators in the regulation of oxidative stress and inflammatory responses in dairy cattle

Periparturient dairy cows experience an increased incidence and severity of several inflammatory-based diseases such as mastitis and metritis. Factors associated with the physiological adaptation to the onset of lactation can impact the efficiency of the inflammatory response at a time when it is most needed to eliminate infectious pathogens that cause these economically important diseases. Oxidative stress, for example, occurs when there is an imbalance between the production of oxygen radicals during periods of high metabolic demand and the reduced capabilities of the host's antioxidant defenses. The progressive development of oxidative stress in early lactation cows is thought to be a significant underlying factor leading to dysfunctional inflammatory responses. Reactive oxygen species (ROS) are also produced by leukocytes during inflammation resulting in positive feedback loops that can further escalate oxidative stress during the periparturient period. During oxidative stress, ROS can modify polyunsaturated fatty acids (PUFA) associated with cellular membranes, resulting in the biosynthesis of oxidized products called oxylipids. Depending on the PUFA substrate and oxidation pathway, oxylipids have the capacity of either enhancing or resolving inflammation. In mediating their effects, oxylipids can directly or indirectly target sites of ROS production and thus control the degree of oxidative stress. This review discusses the evidence supporting the roles of oxylipids in the regulation of oxidative stress and the subsequent development of uncontrolled inflammatory responses. Further, the utility of some of the oxylipids as oxidative stress markers that can be exploited in developing and monitoring therapies for inflammatory-based diseases in dairy cattle is discussed. Understanding of the link between some oxylipids and the development or resolution of oxidative stress could provide novel therapeutic targets to limit immunopathology, reduce antibiotic usage, and optimize the resolution of inflammatory-based diseases in periparturient dairy cows.

14,15-Epoxyeicosatrienoic acid suppresses cigarette smoke condensate-induced inflammation in lung epithelial cells by inhibiting autophagy

Epoxyeicosatrienoic acids (EETs) are metabolic products of free arachidonic acid, which are produced through cytochrome P-450 (CYP) epoxygenases. EETs have anti-inflammatory, antiapoptotic, and antioxidative activities. However, the effect of EETs on cigarette smoke-induced lung inflammation is not clear. Autophagy is believed to be involved in the pathogenesis of chronic obstructive pulmonary disease. In addition, nuclear erythroid-related factor 2 (Nrf2), a transcription factor that regulates many antioxidant genes, is thought to regulate antioxidant defenses in several lung diseases. In addition, interaction between EETs, autophagy, and Nrf2 has been reported. The aim of this study was to explore the effect of 14,15-EET on cigarette smoke condensate (CSC)-induced inflammation in a human bronchial epithelial cell line (Beas-2B), and to determine whether the underlying mechanisms involved in the regulation of Nrf2 through inhibition of autophagy. Autophagy and expression of autophagy signaling pathway proteins (LC3B, p62, PI3K, Akt, p-Akt, and p-mTOR) and anti-inflammatory proteins (Nrf2 and HO-1) were assessed via Western blot analysis. Autophagosomes and autolysosomes were detected by adenoviral mRFP-GFP-LC3 transfection. Inflammatory factors (IL-6, IL-8, and MCP-1) were detected by ELISA. Lentiviral vectors carrying p62 short hairpin RNA were used to interfere with p62 expression to evaluate the effect of p62 on Nrf2 expression. Nrf2 expression was determined through immunocytochemistry. 14,15-EET treatment resulted in a significant reduction in IL-6, IL-8, and MCP-1 secretion, and increased accumulation of Nrf2 and expression of HO-1. In addition, 14,15-EET inhibited CSC-induced autophagy in Beas-2B cells. The mechanism of the anti-inflammatory effect of 14,15-EET involved inhibition of autophagy and an increase in p62 levels, followed by translocation of Nrf2 into the nucleus, which then upregulated expression of the antioxidant enzyme HO-1. 14,15-EET protects against CSC-induced lung inflammation by promoting accumulation of Nrf2 via inhibition of autophagy.

Calf Spleen Extractive Injection (CSEI), a small peptides enriched extraction, induces human hepatocellular carcinoma cell apoptosis via ROS/MAPKs dependent mitochondrial pathway

Calf Spleen Extractive Injection (CSEI), a small peptides enriched extraction, performs immunomodulatory activity on cancer patients suffering from radiotherapy or chemotherapy. The present study aims to investigate the anti-hepatocellular carcinoma effects of CSEI in cells and tumor-xenografted mouse models. In HepG2 and SMMC-7721 cells, CSEI reduced cell viability, enhanced apoptosis rate, caused reactive oxygen species (ROS) accumulation, inhibited migration ability, and induced caspases cascade and mitochondrial membrane potential dissipation. CSEI significantly inhibited HepG2-xenografted tumor growth in nude mice. In cell and animal experiments, CSEI increased the activations of pro-apoptotic proteins including caspase 8, caspase 9 and caspase 3; meanwhile, it suppressed the expressions of anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) and anti-oxidation proteins, such as nuclear factor-erythroid 2 related factor 2 (Nrf2) and catalase (CAT). The enhanced phosphorylation of P38 and c-JunN-terminalkinase (JNK), and decreased phosphorylation of extra cellular signal-regulated protein kinase (ERKs) were observed in CSEI-treated cells and tumor tissues. CSEI-induced cell viability reduction was significantly attenuated by N-Acetyl-l-cysteine (a ROS inhibitor) pretreatment. All data demonstrated that the upregulated oxidative stress status and the altered mitogen-activated protein kinases (MAPKs) phosphorylation contributed to CSEI-driven mitochondrial dysfunction. Taken together, CSEI exactly induced apoptosis in human hepatocellular carcinoma cells via ROS/MAPKs dependent mitochondrial pathway.

Hormetic and regulatory effects of lipid peroxidation mediators in pancreatic beta cells

Nutrient sensing mechanisms of carbohydrates, amino acids and lipids operate distinct pathways that are essential for the adaptation to varying metabolic conditions. The role of nutrient-induced biosynthesis of hormones is paramount for attaining metabolic homeostasis in the organism. Nutrient overload attenuate key metabolic cellular functions and interfere with hormonal-regulated inter- and intra-organ communication, which may ultimately lead to metabolic derangements. Hyperglycemia and high levels of saturated free fatty acids induce excessive production of oxygen free radicals in tissues and cells. This phenomenon, which is accentuated in both type-1 and type-2 diabetic patients, has been associated with the development of impaired glucose tolerance and the etiology of peripheral complications. However, low levels of the same free radicals also induce hormetic responses that protect cells against deleterious effects of the same radicals. Of interest is the role of hydroxyl radicals in initiating peroxidation of polyunsaturated fatty acids (PUFA) and generation of α,β-unsaturated reactive 4-hydroxyalkenals that avidly form covalent adducts with nucleophilic moieties in proteins, phospholipids and nucleic acids. Numerous studies have linked the lipid peroxidation product 4-hydroxy-2E-nonenal (4-HNE) to different pathological and cytotoxic processes. Similarly, two other members of the family, 4-hydroxyl-2E-hexenal (4-HHE) and 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), have also been identified as potential cytotoxic agents. It has been suggested that 4-HNE-induced modifications in macromolecules in cells may alter their cellular functions and modify signaling properties. Yet, it has also been acknowledged that these bioactive aldehydes also function as signaling molecules that directly modify cell functions in a hormetic fashion to enable cells adapt to various stressful stimuli. Recent studies have shown that 4-HNE and 4-HDDE, which activate peroxisome proliferator-activated receptor δ (PPARδ) in vascular endothelial cells and insulin secreting beta cells, promote such adaptive responses to ameliorate detrimental effects of high glucose and diabetes-like conditions. In addition, due to the electrophilic nature of these reactive aldehydes they form covalent adducts with electronegative moieties in proteins, phosphatidylethanolamine and nucleotides. Normally these non-enzymatic modifications are maintained below the cytotoxic range due to efficient cellular neutralization processes of 4-hydroxyalkenals. The major neutralizing enzymes include fatty aldehyde dehydrogenase (FALDH), aldose reductase (AR) and alcohol dehydrogenase (ADH), which transform the aldehyde to the corresponding carboxylic acid or alcohols, respectively, or by biding to the thiol group in glutathione (GSH) by the action of glutathione-S-transferase (GST). This review describes the hormetic and cytotoxic roles of oxygen free radicals and 4-hydroxyalkenals in beta cells exposed to nutritional challenges and the cellular mechanisms they employ to maintain their level at functional range below the cytotoxic threshold.