PPARδ Is Required for Exercise to Attenuate Endoplasmic Reticulum Stress and Endothelial Dysfunction in Diabetic Mice

Linagliptin in combination with insulin suppresses apoptotic unfolded protein response in ovaries exposed to type 1 diabetes

Type 1 diabetes mellitus (T1DM) is one of the main causes of ovarian atresia, but its molecular effect on the ovaries is not fully understood. Accumulating evidence suggests that T1DM causes excessive endoplasmic reticulum (ER) stress and insufficient adaptive unfolded protein response that triggers proapoptotic signaling pathways in ovarian tissue. In addition, problems such as amenorrhea and infertility, which are frequently seen in women with T1DM, continue despite the intensification of insulin therapy and improvement of metabolic control. Therefore new, and adjunctive treatments for women with T1DM need to be explored. We aimed to examine how the use of linagliptin, which has blood sugar-lowering effects and high antioxidant activity, together with insulin affects the expression levels of proteins and genes that play a role in ER stress in type 1 diabetic mouse ovaries. Eighty-four Balb/C 6-week-old female mice were randomly divided into seven groups: control, vehicle, diabetes + insulin, diabetes + linagliptin, diabetes + linagliptin + insulin, diabetes + TUDCA, and diabetes + TUDCA + insulin. TUDCA (an inhibitor of ER stress) groups are positive control groups created to compare linagliptin groups in terms of ER stress. Linagliptin and TUDCA were given by oral gavage and 1U insulin was administered subcutaneously for 2 weeks. A significant decrease was observed in the MDA and NOX1 levels and the number of atretic follicles in the ovaries of the diabetes + linagliptin + insulin group compared to the diabetes + insulin group. The use of linagliptin and insulin increased the expression of pro-survival XBP1s transmembrane protein and decreased the expression of proapoptotic ATF4, pJNK1/2, cleaved caspase 12, and cleaved caspase 3 in mouse ovaries. Our study provides new therapeutic evidence that linagliptin administered in addition to insulin induces ER stress mechanism-dependent survival in ovaries with type 1 diabetes.

Effect of reactive oxygen, nitrogen, and sulfur species on signaling pathways in atherosclerosis

Atherosclerosis is a chronic inflammatory disease in which fats, lipids, cholesterol, calcium, proliferating smooth muscle cells, and immune cells accumulate in the intima of the large arteries, forming atherosclerotic plaques. A complex interplay of various vascular and immune cells takes place during the initiation and progression of atherosclerosis. Multiple reports indicate that tight control of reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS) production is critical for maintaining vascular health. Unrestricted ROS and RNS generation may lead to activation of various inflammatory signaling pathways, facilitating atherosclerosis. Given these deleterious consequences, it is important to understand how ROS and RNS affect the signaling processes involved in atherogenesis. Conversely, RSS appears to exhibit an atheroprotective potential and can alleviate the deleterious effects of ROS and RNS. Herein, we review the literature describing the effects of ROS, RNS, and RSS on vascular smooth muscle cells, endothelial cells, and macrophages and focus on how changes in their production affect the initiation and progression of atherosclerosis. This review also discusses the contribution of ROS, RNS, and RSS in mediating various post-translational modifications, such as oxidation, nitrosylation, and sulfation, of the molecules involved in inflammatory signaling.

Exercise Attenuates Myocardial Ischemia-Reperfusion Injury by Regulating Endoplasmic Reticulum Stress and Mitophagy Through M2 Acetylcholine Receptor

Aims: Adaptive changes in the heart by exercise have been shown to reduce the risk of cardiovascular disease, and M2 Acetylcholine receptor (M2AChR), a receptor abundantly present on cardiac parasympathetic nerves, is closely associated with the development of cardiovascular disease. The present study intends to investigate whether exercise can regulate endoplasmic reticulum stress (ERS) and mitophagy through M2AChR to resist myocardial ischemia-reperfusion (I/R) injury and to elucidate its mechanism of action. Results: Exercise enhanced parasympathetic nerve function and increased myocardial M2AChR protein expression in I/R rats. In addition, it promoted the protein expression of MFN2 and inhibited the expression of Drp1, Chop, PINK1/Parkin, and PERK/eIF2α/ATF4 signaling pathways, effectively reducing mitophagy, ERS, and apoptosis. At the cellular level, 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR) reduced hypoxia/reoxygenation (H/R)-induced ERS through the downregulated expression of PERK/eIF2α/ATF4 pathway proteins in H9C2 cardiomyocytes. When intervened with M2AChR inhibitors, the levels of ERS and phosphorylation levels of the PERK/eIF2α/ATF4 pathway were increased in H/R cells. Innovation and Conclusion: Exercise intervention activated the parasympathetic state in rats. It inhibited myocardial mitophagy and ERS levels, and reduced myocardial apoptosis through M2AChR, thereby resisting I/R-induced myocardial injury and improving cardiac function. Antioxid. Redox Signal. 40, 209-221.

Follistatin-like 1 protects endothelial function in the spontaneously hypertensive rat by inhibition of endoplasmic reticulum stress through AMPK-dependent mechanism

OBJECTIVE

Endothelial dysfunction is a critical initiating factor in the development of hypertension and related complications. Follistatin-like 1 (FSTL1) can promote endothelial cell function and stimulates revascularization in response to ischemic insult. However, it is unclear whether FSTL1 has an effect on ameliorating endothelial dysfunction in spontaneously hypertensive rats (SHRs).

METHODS

Wistar Kyoto (WKY) and SHRs were treated with a tail vein injection of vehicle (1 mL/day) or recombinant FSTL1 (100 μg/kg body weight/day) for 4 weeks. Blood pressure was measured by tail-cuff plethysmograph, and vascular reactivity in mesenteric arteries was measured using wire myography.

RESULTS

We found that treatment with FSTL1 reversed impaired endothelium-dependent relaxation (EDR) in mesenteric arteries and lowered blood pressure of SHRs. Decreased AMP-activated protein kinase (AMPK) phosphorylation, elevated endoplasmic reticulum (ER) stress markers, increased reactive oxygen species (ROS), and reduction of nitric oxide (NO) production in mesenteric arteries of SHRs were also reversed by FSTL1 treatment. Ex vivo treatment with FSTL1 improved the impaired EDR in mesenteric arteries from SHRs and reversed tunicamycin (ER stress inducer)-induced ER stress and the impairment of EDR in mesenteric arteries from WKY rats. The effects of FSTL1 were abolished by cotreatment of compound C (AMPK inhibitor).

CONCLUSIONS

These results suggest that FSTL1 prevents endothelial dysfunction in mesenteric arteries of SHRs through inhibiting ER stress and ROS and increasing NO production via activation of AMPK signaling.

Inhibitory Effect of PPARδ Agonist GW501516 on Proliferation of Hypoxia-induced Pulmonary Arterial Smooth Muscle Cells by Regulating the mTOR Pathway

OBJECTIVE

This study aimed to investigate the effects of the peroxisome proliferator-activated receptor δ (PPARδ) agonist GW501516 on the proliferation of pulmonary artery smooth muscle cells (PASMCs) induced by hypoxia, in order to search for new drugs for the treatment and prevention of pulmonary vascular remodeling.

METHODS

PASMCs were incubated with different concentrations of GW501516 (10, 30, 100 nmol/L) under the hypoxic condition. The proliferation was determined by a CCK-8 assay. The cell cycle progression was analyzed by flow cytometry. The expression of PPARδ, S phase kinase-associated protein 2 (Skp2), and cell cycle-dependent kinase inhibitor p27 was detected by Western blotting. Then PASMCs were treated with 100 nmol/ L GW501516, 100 nmol/L mammalian target of rapamycin (mTOR) inhibitor rapamycin and/or 2 µmol/L mTOR activator MHY1485 to explore the molecular mechanisms by which GW501516 reduces the proliferation of PASMCs.

RESULTS

The presented data demonstrated that hypoxia reduced the expression of PPARδ in an oxygen concentration- and time-dependent manner, and GW501516 decreased the proliferation of PASMCs induced by hypoxia by blocking the progression through the G0/G1 to S phase of the cell cycle. In accordance with these findings, GW501516 downregulated Skp2 and upregulated p27 in hypoxia-exposed PASMCs. Further experiments showed that rapamycin had similar effects as GW501516 in inhibiting cell proliferation, arresting the cell cycle, regulating the expression of Skp2 and p27, and inactivating mTOR in hypoxia-exposed PASMCs. Moreover, MHY1485 reversed all the beneficial effects of GW501516 on hypoxia-stimulated PASMCs.

CONCLUSION

GW501516 inhibited the proliferation of PASMCs induced by hypoxia through blocking the mTOR/Skp2/p27 signaling pathway.

The role of oxidative stress in diabetes mellitus-induced vascular endothelial dysfunction

Diabetes mellitus is a metabolic disease characterized by long-term hyperglycaemia, which leads to microangiopathy and macroangiopathy and ultimately increases the mortality of diabetic patients. Endothelial dysfunction, which has been recognized as a key factor in the pathogenesis of diabetic microangiopathy and macroangiopathy, is characterized by a reduction in NO bioavailability. Oxidative stress, which is the main pathogenic factor in diabetes, is one of the major triggers of endothelial dysfunction through the reduction in NO. In this review, we summarize the four sources of ROS in the diabetic vasculature and the underlying molecular mechanisms by which the pathogenic factors hyperglycaemia, hyperlipidaemia, adipokines and insulin resistance induce oxidative stress in endothelial cells in the context of diabetes. In addition, we discuss oxidative stress-targeted interventions, including hypoglycaemic drugs, antioxidants and lifestyle interventions, and their effects on diabetes-induced endothelial dysfunction. In summary, our review provides comprehensive insight into the roles of oxidative stress in diabetes-induced endothelial dysfunction.

Induction of KLF2 by Exercise Activates eNOS to Improve Vasodilatation in Diabetic Mice

Diabetic endothelial dysfunction associated with diminished endothelial nitric oxide (NO) synthase (eNOS) activity accelerates the development of atherosclerosis and cardiomyopathy. However, the approaches to restore eNOS activity and endothelial function in diabetes remain limited. The current study shows that enhanced expression of Krüppel-like factor 2 (KLF2), a shear stress-inducible transcription factor, effectively improves endothelial function through increasing NO bioavailability. KLF2 expression is suppressed in diabetic mouse aortic endothelium. Running exercise and simvastatin treatment induce endothelial KLF2 expression in db/db mice. Adenovirus-mediated endothelium-specific KLF2 overexpression enhances both endothelium-dependent relaxation and flow-mediated dilatation, while it attenuates oxidative stress in diabetic mouse arteries. KLF2 overexpression increases the phosphorylation of eNOS at serine 1177 and eNOS dimerization. RNA-sequencing analysis reveals that KLF2 transcriptionally upregulates genes that are enriched in the cyclic guanosine monophosphate-protein kinase G-signaling pathway, cAMP-signaling pathway, and insulin-signaling pathway, all of which are the upstream regulators of eNOS activity. Activation of the phosphoinositide 3-kinase-Akt pathway and Hsp90 contributes to KLF2-induced increase of eNOS activity. The present results suggest that approaches inducing KLF2 activation, such as physical exercise, are effective to restore eNOS activity against diabetic endothelial dysfunction.

ARTICLE HIGHLIGHTS

Exercise and statins restore the endothelial expression of Krüppel-like factor 2 (KLF2), which is diminished in diabetic db/db mice. Endothelium-specific overexpression of KLF2 improves endothelium-dependent relaxation and flow-mediated dilation through increasing nitric oxide bioavailability. KLF2 promotes endothelial nitric oxide synthase (eNOS) coupling and phosphorylation in addition to its known role in eNOS transcription. KLF2 upregulates the expression of several panels of genes that regulate eNOS activity.

ER stress decreases exosome production through adiponectin/T-cadherin-dependent and -independent pathways

Exosomes, extracellular vesicles (EVs) produced within cells, mediate both the disposal of intracellular waste and communication with distant cells, and they are involved in a variety of disease processes. Although disease modifications of exosome cargos have been well studied, it has been poorly investigated how disease processes, such as endoplasmic reticulum (ER) stress, affect EV production. We previously reported that adiponectin, an adipocyte-secreted salutary factor, increases systemic exosome levels through T-cadherin-mediated enhancement of exosome biogenesis. In the present study, we demonstrated that adiponectin/T-cadherin-dependent EV production was susceptible to ER stress and that low-dose tunicamycin significantly reduced EV production in the presence, but not in the absence, of adiponectin. Moreover, pharmacological or genetic activation of inositol-requiring enzyme 1α, a central regulator of ER stress, downregulated T-cadherin at the mRNA and protein levels as well as attenuated EV production. In addition, adiponectin/T-cadherin-independent EV production was attenuated under ER stress conditions. Repeated administration of tunicamycin to mice decreased circulating small EVs without decreasing tissue T-cadherin expression. Mechanistically, inositol-requiring enzyme 1α activation by silencing of the X-box binding protein 1 transcription factor upregulated the canonical interferon pathway and decreased EV production. The interferon pathway, when it was activated by polyinosinic-polycytidylic acid, also significantly attenuated EV production. Thus, we concluded that ER stress decreases exosome production through adiponectin/T-cadherin-dependent and -independent pathways.

A review of the signaling pathways of aerobic and anaerobic exercise on atherosclerosis

Atherosclerosis (AS), a chronic inflammatory vascular disease with lipid metabolism abnormalities, is one of the major pathological bases of coronary heart disease. As people's lifestyles and diets change, the incidence of AS increases yearly. Physical activity and exercise training have recently been identified as effective strategies for lowering cardiovascular disease (CVD) risk. However, the best exercise mode to ameliorate the risk factors related to AS is not clear. The effect of exercise on AS is affected by the type of exercise, intensity, and duration. In particular, aerobic and anaerobic exercise are the two most widely discussed types of exercise. During exercise, the cardiovascular system undergoes physiological changes via various signaling pathways. The review aims to summarize signaling pathways related to AS in two different exercise types and provide new ideas for the prevention and treatment of AS in clinical practice.

Jatrorrhizine Improves Endothelial Function in Diabetes and Obesity through Suppression of Endoplasmic Reticulum Stress

Jatrorrhizine (JAT) is one of the major bioactive protoberberine alkaloids found in rhizoma coptidis, which has hypoglycemic and hypolipidemic potential. This study aimed to evaluate the vasoprotective effects of JAT in diabetes and obesity and the underlying mechanism involved. Mouse aortas, carotid arteries and human umbilical cord vein endothelial cells (HUVECs) were treated with risk factors (high glucose or tunicamycin) with and without JAT ex vivo and in vitro. Furthermore, aortas were obtained from mice with chronic treatment: (1) control; (2) diet-induced obese (DIO) mice fed a high-fat diet (45% kcal% fat) for 15 weeks; and (3) DIO mice orally administered JAT at 50 mg/kg/day for the last 5 weeks. High glucose or endoplasmic reticulum (ER) stress inducer tunicamycin impaired acetylcholine-induced endothelium-dependent relaxations (EDRs) in mouse aortas, induced oxidative stress in carotid arteries and HUVECs, downregulated phosphorylations of Akt at Ser473 and eNOS at Ser1177 and enhanced ER stress in mouse aortas and HUVECs, and these impairments were reversed by cotreatment with JAT. JAT increased NO release in high-glucose-treated mouse aortas and HUVECs. In addition, chronic JAT treatment restored endothelial function with EDRs comparable to the control, increased Akt/eNOS phosphorylation, and attenuated ER stress and oxidative stress in aortas from DIO mice. Blood pressure, glucose sensitivity, fatty liver and its morphological change, as well as plasma levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) and plasma lipid profile, were also normalized by JAT treatment. Collectively, our data may be the first to reveal the vasoprotective effect of JAT that ameliorates endothelial dysfunction in diabetes and obesity through enhancement of the Akt/eNOS pathway and NO bioavailability, as well as suppression of ER stress and oxidative stress.

ADAM17 cleaves the insulin receptor ectodomain on endothelial cells and causes vascular insulin resistance

Inflammation and vascular insulin resistance are hallmarks of type 2 diabetes (T2D). However, several potential mechanisms causing abnormal endothelial insulin signaling in T2D need further investigation. Evidence indicates that the activity of ADAM17 (a disintegrin and metalloproteinase-17) and the presence of insulin receptor (IR) in plasma are increased in subjects with T2D. Accordingly, we hypothesized that in T2D, increased ADAM17 activity sheds the IR ectodomain from endothelial cells and impairs insulin-induced vasodilation. We used small visceral arteries isolated from a cross-sectional study of subjects with and without T2D undergoing bariatric surgery, human cultured endothelial cells, and recombinant proteins to test our hypothesis. Here, we demonstrate that arteries from subjects with T2D had increased ADAM17 expression, reduced presence of tissue inhibitor of metalloproteinase-3 (TIMP3), decreased extracellular IRα, and impaired insulin-induced vasodilation versus those from subjects without T2D. In vitro, active ADAM17 cleaved the ectodomain of the IRβ subunit. Endothelial cells with ADAM17 overexpression or exposed to the protein kinase-C activator, PMA, had increased ADAM17 activity, decreased IRα presence on the cell surface, and increased IR shedding. Moreover, pharmacological inhibition of ADAM17 with TAPI-0 rescued PMA-induced IR shedding and insulin-signaling impairments in endothelial cells and insulin-stimulated vasodilation in human arteries. In aggregate, our findings suggest that ADAM17-mediated shedding of IR from the endothelial surface impairs insulin-mediated vasodilation. Thus, we propose that inhibition of ADAM17 sheddase activity should be considered a strategy to restore vascular insulin sensitivity in T2D.NEW & NOTEWORTHY To our knowledge, this is the first study to investigate the involvement of ADAM17 in causing impaired insulin-induced vasodilation in T2D. We provide evidence that ADAM17 activity is increased in the vasculature of patients with T2D and support the notion that ADAM17-mediated shedding of endothelial IRα ectodomains is a novel mechanism causing vascular insulin resistance. Our results highlight that targeting ADAM17 activity may be a potential therapeutic strategy to correct vascular insulin resistance in T2D.

The Effect of Tauroursodeoxycholic Acid (TUDCA) Treatment on Pregnancy Outcomes and Vascular Function in a Rat Model of Advanced Maternal Age

Advanced maternal age (≥35 years) increases the risk of vascular complications in pregnancy that can result in fetal growth restriction and preeclampsia. Endoplasmic reticulum (ER) stress has been linked to adverse pregnancy outcomes in these complicated pregnancies. However, the role of ER stress in advanced maternal age is not known. We hypothesize that increased ER stress contributes to altered vascular function and poor pregnancy outcomes, and that treatment with the ER-stress inhibitor TUDCA will improve pregnancy outcomes. First, young and aged non-pregnant/pregnant rats were used to assess ER stress markers in mesenteric arteries; mesenteric artery phospho-eIF2α and CHOP expression were increased in aged dams compared to young dams. In a second study, young and aged control and TUDCA-treated dams were studied on gestational day (GD) 20 (term = 22 days). TUDCA treatment was provided via the drinking water throughout pregnancy (GD0-GD20; calculated dose of 150 mg/kg/day TUDCA). ER stress markers were quantified in mesenteric arteries, blood pressure was measured, pregnancy outcomes were recorded, mesenteric and main uterine arteries were isolated and vascular function was assessed by wire myography. Aged dams had increased phospho-eIF2α and CHOP expression, reduced fetal weight, reduced litter size, and impaired uterine artery relaxation. In the aged dams, TUDCA treatment reduced phospho-eIF2α and CHOP expression, reduced blood pressure, improved fetal body weight, and tended to improve uterine artery function compared to control-treated aged dams. In conclusion, our data illustrate the role of ER stress, as well as TUDCA as a potential therapeutic that may benefit pregnancy outcomes in advanced maternal age.

3,4′,5-Trimethoxy-trans-stilbene Alleviates Endothelial Dysfunction in Diabetic and Obese Mice via Activation of the AMPK/SIRT1/eNOS Pathway

3,4′,5-trimethoxy-trans-stilbene (TMS) is a methoxylated derivative of resveratrol. Previous studies showed the vaso-protective effects of resveratrol; nevertheless, research on this derivative is scarce. The current study aimed to explore whether TMS can alleviate endothelial dysfunction in diabetic and obese mice, along with the underlying mechanisms. Thoracic aortas isolated from male C57BL/6J mice and primary cultures of rat aortic endothelial cells were treated with high glucose with or without TMS. High glucose exposure impaired acetylcholine-induced endothelium-dependent relaxations, down-regulated NO bioavailability and the AMP-activated protein kinase (AMPK)/Sirtuin 1 (SIRT1)/endothelial nitric oxide synthase (eNOS) pathway, increased endoplasmic reticulum (ER) stress and oxidative stress, which were reversed by TMS treatment. Moreover, the protective effects of TMS were abolished by Compound C (AMPK inhibitor), and EX527 (SIRT1 inhibitor). The mice were fed with high-fat diet (60% kcal% fat) for 14 weeks to establish a diabetic and obese model, and were orally administered TMS (10 mg/kg/day) in the last 4 weeks. Chronic TMS treatment alleviated endothelial dysfunction via enhancing the AMPK/SIRT1/eNOS pathway and attenuated oxidative stress and ER stress in aortas of diet-induced obese mice. In summary, our study reveals the potent vaso-protective effect of TMS and its therapeutic potential against endothelial dysfunction in metabolic disorders.

Activation of AMPK/miR-181b Axis Alleviates Endothelial Dysfunction and Vascular Inflammation in Diabetic Mice

Hyperglycemia in diabetes mellitus impairs endothelial function and disrupts microRNA (miRNA) profiles in vasculature, increasing the risk of diabetes-associated complications, including coronary artery disease, diabetic retinopathy, and diabetic nephropathy. miR-181b was previously reported to be an anti-inflammatory mediator in vasculature against atherosclerosis. The current study aimed to investigate whether miR-181b ameliorates diabetes-associated endothelial dysfunction, and to identify potential molecular mechanisms and upstream inducer of miR-181b. We found that miR-181b level was decreased in renal arteries of diabetic patients and in advanced glycation end products (AGEs)-treated renal arteries of non-diabetic patients. Transfection of miR-181b mimics improved endothelium-dependent vasodilation in aortas of high fat diet (HFD)/streptozotocin (STZ)-induced diabetic mice, accompanied by suppression of superoxide overproduction and vascular inflammation markers. AMPK activator-induced AMPK activation upregulated miR-181b level in human umbilical vein endothelial cells (HUVECs). Chronic exercise, potentially through increased blood flow, activated AMPK/miR-181b axis in aortas of diabetic mice. Exposure to laminar shear stress upregulated miR-181b expression in HUVECs. Overall, our findings highlight a critical role of AMPK/miR-181b axis and extend the benefits of chronic exercise in counteracting diabetes-associated endothelial dysfunction.

Sarco/Endoplasmic Reticulum Ca2+ ATPase 2 Activator Ameliorates Endothelial Dysfunction; Insulin Resistance in Diabetic Mice

Background: Sarco/endoplasmic reticulum Ca2+-ATPase2 (SERCA2) is impaired in various organs in animal models of diabetes. The purpose of this study was to test the effects of an allosteric SERCA2 activator (CDN1163) on glucose intolerance, hepatosteatosis, skeletal muscle function, and endothelial dysfunction in diabetic (db/db) mice. Methods: Either CDN1163 or vehicle was injected intraperitoneally into 16-week-old male control and db/db mice for 5 consecutive days. Results: SERCA2 protein expression was decreased in the aorta of db/db mice. In isometric tension measurements of aortic rings from db/db mice treated with CDN1163, acetylcholine (ACh)-induced relaxation was improved. In vivo intraperitoneal administrations of CDN 1163 also increased ACh-induced relaxation. Moreover, CDN1163 significantly decreased blood glucose in db/db mice at 60 and 120 min during a glucose tolerance test; it also decreased serum insulin levels, hepatosteatosis, and oxygen consumption in skeletal muscle during the early period of exercise in db/db mice. Conclusions: CDN1163 directly improved aortic endothelial dysfunction in db/db mice. Moreover, CDN1163 improved hepatosteatosis, skeletal muscle function, and insulin resistance in db/db mice. The activation of SERCA2 might be a strategy for the all the tissue expressed SERCA2a improvement of endothelial dysfunction and the target for the organs related to insulin resistance.

Targeting endothelial dysfunction and inflammation

Vascular endothelium maintains vascular homeostasis through liberating a spectrum of vasoactive molecules, both protective and harmful regulators of vascular tone, structural remodeling, inflammation and atherogenesis. An intricate balance between endothelium-derived relaxing factors (nitric oxide, prostacyclin and endothelium-derived hyperpolarizing factor) and endothelium-derived contracting factors (superoxide anion, endothelin-1 and constrictive prostaglandins) tightly regulates vascular function. Disruption of such balance signifies endothelial dysfunction, a critical contributor in aging and chronic cardiometabolic disorders, such as obesity, diabetes, hypertension, dyslipidemia and atherosclerotic vascular diseases. Among many proposed cellular and molecular mechanisms causing endothelial dysfunction, oxidative stress and inflammation are often the pivotal players and they are naturally considered as useful targets for intervention in patients with cardiovascular and metabolic diseases. In this article, we provide a recent update on the therapeutic values of pharmacological agents, such as cyclooxygenase-2 inhibitors, renin-angiotensin-system inhibitors, bone morphogenic protein 4 inhibitors, peroxisome proliferator-activated receptor δ agonists, and glucagon-like peptide 1-elevating drugs, and the physiological factors, particularly hemodynamic forces, that improve endothelial function by targeting endothelial oxidative stress and inflammation.

Repeated glucose spikes and insulin resistance synergistically deteriorate endothelial function and bardoxolone methyl ameliorates endothelial dysfunction

Background

Both insulin resistance and postprandial glucose spikes are known for their potential to induce vascular endothelial dysfunction in individuals with metabolic syndrome. However, these factors are inextricable, and therefore, their relative contributions to inducing endothelial dysfunction remain elusive. In this study, we aimed to disentangle the effects of these factors and clarify whether bardoxolone methyl (CDDO-Me), a novel nuclear factor erythroid 2-related factor 2 (Nrf2) activator, protects against glucose spike-induced endothelial dysfunction.

Methods

We induced glucose spikes twice daily for a duration of 1 week to rats fed a standard/control diet (CD) and Western-type diet (WTD). Endothelium-dependent relaxation (EDR) was evaluated using isolated thoracic aortas. Gene expression and dihydroethidium (DHE)-fluorescence studies were carried out; the effect of CDDO-Me on aortic endothelial dysfunction in vivo was also evaluated.

Results

Neither WTD-induced insulin resistance nor pure glucose spikes significantly deteriorated EDR. However, under high-glucose (20 mM) conditions, the EDR of thoracic aortas of WTD-fed rats subjected to glucose spikes was significantly impaired. In this group of rats, we observed significantly enhanced DHE fluorescence as a marker of reactive oxygen species, upregulation of an oxidative stress-related gene (NOX2), and downregulation of an antioxidant gene (SOD2) in the thoracic aortas. As expected, treatment of the thoracic aorta of this group of rats with antioxidant agents significantly improved EDR. We also noted that pretreatment of aortas from the same group with CDDO-Me attenuated endothelial dysfunction, accompanied by a correction of the redox imbalance, as observed in gene expression and DHE fluorescence studies.

Conclusions

For the first time, we showed that insulin resistance and glucose spikes exert a synergistic effect on aortic endothelial dysfunction. Furthermore, our study reveals that CDDO-Me ameliorates endothelial dysfunction caused by glucose spikes in a rat model of metabolic syndrome.

Metformin for Cardiovascular Protection, Inflammatory Bowel Disease, Osteoporosis, Periodontitis, Polycystic Ovarian Syndrome, Neurodegeneration, Cancer, Inflammation and Senescence: What Is Next?

Diabetes is accompanied by several complications. Higher prevalence of cancers, cardiovascular diseases, chronic kidney disease (CKD), obesity, osteoporosis, and neurodegenerative diseases has been reported among patients with diabetes. Metformin is the oldest oral antidiabetic drug and can improve coexisting complications of diabetes. Clinical trials and observational studies uncovered that metformin can remarkably prevent or alleviate cardiovascular diseases, obesity, polycystic ovarian syndrome (PCOS), osteoporosis, cancer, periodontitis, neuronal damage and neurodegenerative diseases, inflammation, inflammatory bowel disease (IBD), tuberculosis, and COVID-19. In addition, metformin has been proposed as an antiaging agent. Numerous mechanisms were shown to be involved in the protective effects of metformin. Metformin activates the LKB1/AMPK pathway to interact with several intracellular signaling pathways and molecular mechanisms. The drug modifies the biologic function of NF-κB, PI3K/AKT/mTOR, SIRT1/PGC-1α, NLRP3, ERK, P38 MAPK, Wnt/β-catenin, Nrf2, JNK, and other major molecules in the intracellular signaling network. It also regulates the expression of noncoding RNAs. Thereby, metformin can regulate metabolism, growth, proliferation, inflammation, tumorigenesis, and senescence. Additionally, metformin modulates immune response, autophagy, mitophagy, endoplasmic reticulum (ER) stress, and apoptosis and exerts epigenetic effects. Furthermore, metformin protects against oxidative stress and genomic instability, preserves telomere length, and prevents stem cell exhaustion. In this review, the protective effects of metformin on each disease will be discussed using the results of recent meta-analyses, clinical trials, and observational studies. Thereafter, it will be meticulously explained how metformin reprograms intracellular signaling pathways and alters molecular and cellular interactions to modify the clinical presentations of several diseases.

Endothelial TRPV4-eNOS coupling as a vital therapy target for treatment of hypertension

BACKGROUND AND PURPOSE

Reduced nitric oxide (NO) level and activity are signs of endothelial dysfunction, which is important in mediating blood pressure up-regulation. Previously, we demonstrated that transient receptor potential channel V4 (TRPV4) could form functional complex with other proteins to mediate vasodilation in the Endothelial cells (ECs). But how TRPV4 interacts with the NO pathway in larger arteries requires further exploration.

EXPERIMENTAL APPROACH

We used single-cell RNA-sequencing to find the CD106⁺ TRPV4^high NOS3^high ECs. The TRPV4-eNOS interaction was verified by co-immunoprecipitation and Immunofluorescence resonance energy transfer (FRET), and their binding site was found by site-directed mutagenesis. Endothelium-specific TRPV4 knockout (TRPV4_EC ^-/- ) mice were used to study the effect of the TRPV4-eNOS interaction on blood pressure. A small molecule, JNc-463 was designed through molecular docking technology.

KEY RESULTS

We uncovered CD106⁺ TRPV4^high NOS3^high ECs in the mouse aorta, which they could regulate vasodilation via a TRPV4-eNOS interaction, and they were essential to regulate blood pressure. The TRPV4-eNOS interaction markedly decreased during the process of hypertension. We further attempted to identify the molecules re-join the TRPV4-eNOS interaction and develop a small-molecule drug, JNc-463, which could increase the TRPV4-eNOS interaction to enhance vasodilation, and exert antihypertensive effects in mice.

CONCLUSION AND IMPLICATIONS

This is the first study integrating single-cell RNA-Seq, single-cell functional study and drug screening in aorta. We identified a subpopulation of CD106⁺ TRPV4^high NOS3^high ECs, in which an impaired TRPV4-eNOS interaction was important in the progress of hypertension and we designed a small molecule, JNc-463 to improve the impaired TRPV4-eNOS interaction in hypertension.

The pleiotropic peroxisome proliferator activated receptors: Regulation and therapeutics

The Peroxisome proliferator-activated receptors (PPARs) are key regulators of metabolic events in our body. Owing to their implication in maintenance of homeostasis, both PPAR agonists and antagonists assume therapeutic significance. Understanding the molecular mechanisms of each of the PPAR isotypes in the healthy body and during disease is crucial to exploiting their full therapeutic potential. This article is an attempt to present a rational analysis of the multifaceted therapeutic effects and underlying mechanisms of isotype-specific PPAR agonists, dual PPAR agonists, pan PPAR agonists as well as PPAR antagonists. A holistic understanding of the mechanistic dimensions of these key metabolic regulators will guide future efforts to identify novel molecules in the realm of metabolic, inflammatory and immunotherapeutic diseases.

A GLP-1 analog lowers ER stress and enhances protein folding to ameliorate homocysteine-induced endothelial dysfunction

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular diseases and increases mortality in type 2 diabetic patients. HHcy induces endoplasmic reticulum (ER) stress and oxidative stress to impair endothelial function. The glucagon-like peptide 1 (GLP-1) analog exendin-4 attenuates endothelial ER stress, but the detailed vasoprotective mechanism remains elusive. The present study investigated the beneficial effects of exendin-4 against HHcy-induced endothelial dysfunction. Exendin-4 pretreatment reversed homocysteine-induced impairment of endothelium-dependent relaxations in C57BL/6 mouse aortae ex vivo. Four weeks subcutaneous injection of exendin-4 restored the impaired endothelial function in both aortae and mesenteric arteries isolated from mice with diet-induced HHcy. Exendin-4 treatment lowered superoxide anion accumulation in the mouse aortae both ex vivo and in vivo. Exendin-4 decreased the expression of ER stress markers (e.g., ATF4, spliced XBP1, and phosphorylated eIF2α) in human umbilical vein endothelial cells (HUVECs), and this change was reversed by cotreatment with compound C (CC) (AMPK inhibitor). Exendin-4 induced phosphorylation of AMPK and endothelial nitric oxide synthase in HUVECs and arteries. Exendin-4 increased the expression of endoplasmic reticulum oxidoreductase (ERO1α), an important ER chaperone in endothelial cells, and this effect was mediated by AMPK activation. Experiments using siRNA-mediated knockdown or adenoviral overexpression revealed that ERO1α mediated the inhibitory effects of exendin-4 on ER stress and superoxide anion production, thus ameliorating HHcy-induced endothelial dysfunction. The present results demonstrate that exendin-4 reduces HHcy-induced ER stress and improves endothelial function through AMPK-dependent ERO1α upregulation in endothelial cells and arteries. AMPK activation promotes the protein folding machinery in endothelial cells to suppress ER stress.

Panax Notoginseng Protects against Diabetes-Associated Endothelial Dysfunction: Comparison between Ethanolic Extract and Total Saponin

Previous studies revealed a cardioprotective potential of Panax notoginseng to relieve acute myocardial infarction and focal cerebral ischemia-reperfusion. However, whether P. notoginseng protects endothelial function in diabetes and the underlying mechanisms remain to be explored. P. notoginseng contains several chemical components including saponins, which are commonly believed as the major bioactive ingredients. The present study was aimed to examine and compare the vaso-protective effects of the ethanolic extract of P. notoginseng (PNE) and total saponin (PNS). Both aortas and carotid arteries were isolated from male C57BL/6J mice for ex vivo treatment with risk factors (high glucose or tunicamycin) with and without the presence of PNS and PNE. Diabetic model was established by feeding the mice with a high-fat diet (45% kcal% fat) for 12 weeks, while PNS and PNE were administrated by oral gavage at 20 mg/kg/day for another 4 weeks. Ex vivo exposure to high glucose impaired acetylcholine-induced endothelium-dependent relaxations in mouse aortas, decreased phosphorylation of AMPK and eNOS, and induced endoplasmic reticulum (ER) stress and oxidative stress. These effects were reversed by cotreatment of PNS and PNE with PNS being more potent. Furthermore, the vaso-protective effects were abolished by Compound C (AMPK inhibitor). Chronic treatment with PNS and PNE improved endothelium-dependent relaxations and alleviated ER stress and oxidative stress in aortas from high-fat diet-induced obese mice. PNE was more effective to improve glucose sensitivity and normalize blood pressure in diabetic mice. The present results showed that PNS and PNE reduced ER stress and oxidative stress and, subsequently, improved endothelial function in diabetes through AMPK activation. This study provides new inspiration on the therapeutic potential of P. notoginseng extract against vascular diseases associated with metabolic disorders.

Physical Exercise Protects Against Endothelial Dysfunction in Cardiovascular and Metabolic Diseases

Increasing evidence shows that endothelial cells play critical roles in maintaining vascular homeostasis, regulating vascular tone, inhibiting inflammatory response, suppressing lipid leakage, and preventing thrombosis. The damage or injury of endothelial cells induced by physical, chemical, and biological risk factors is a leading contributor to the development of mortal cardiovascular and cerebrovascular diseases. However, the underlying mechanism of endothelial injury remains to be elucidated. Notably, no drugs effectively targeting and mending injured vascular endothelial cells have been approved for clinical practice. There is an urgent need to understand pathways important for repairing injured vasculature that can be targeted with novel therapies. Exercise training-induced protection to endothelial injury has been well documented in clinical trials, and the underlying mechanism has been explored in animal models. This review mainly summarizes the protective effects of exercise on vascular endothelium and the recently identified potential therapeutic targets for endothelial dysfunction.

AMPK phosphorylates PPARδ to mediate its stabilization, inhibit glucose and glutamine uptake and colon tumor growth

Peroxisome proliferator-activated receptor δ (PPARδ) is a nuclear receptor transcription factor that plays an important role in the regulation of metabolism, inflammation, and cancer. In addition, the nutrient-sensing kinase 5'AMP-activated protein kinase (AMPK) is a critical regulator of cellular energy in coordination with PPARδ. However, the molecular mechanism of the AMPK/PPARδ pathway on cancer progression is still unclear. Here, we found that activated AMPK induced PPARδ-S50 phosphorylation in cancer cells, whereas the PPARδ/S50A (nonphosphorylation mimic) mutant reversed this event. Further analysis showed that the PPARδ/S50E (phosphorylation mimic) but not the PPARδ/S50A mutant increased PPARδ protein stability, which led to reduced p62/SQSTM1-mediated degradation of misfolded PPARδ. Furthermore, PPARδ-S50 phosphorylation decreased PPARδ transcription activity and alleviated PPARδ-mediated uptake of glucose and glutamine in cancer cells. Soft agar and xenograft tumor model analysis showed that the PPARδ/S50E mutant but not the PPARδ/S50A mutant inhibited colon cancer cell proliferation and tumor growth, which was associated with inhibition of Glut1 and SLC1A5 transporter protein expression. These findings reveal a new mechanism of AMPK-induced PPARδ-S50 phosphorylation, accumulation of misfolded PPARδ protein, and inhibition of PPARδ transcription activity contributing to the suppression of colon tumor formation.

Down-regulation of AMPK/PPARδ signalling promotes endoplasmic reticulum stress-induced endothelial dysfunction in adult rat offspring exposed to maternal diabetes

AIMS

Exposure to maternal diabetes is associated with increased prevalence of hypertension in the offspring. The mechanisms underlying the prenatal programming of hypertension remain unclear. Because endoplasmic reticulum (ER) stress plays a key role in vascular endothelial dysfunction in hypertension, we investigated whether aberrant ER stress causes endothelial dysfunction and high blood pressure in the offspring of dams with diabetes.

METHODS AND RESULTS

Pregnant Sprague-Dawley rats were intraperitoneally injected with streptozotocin (35 mg/kg) or citrate buffer at Day 0 of gestation. Compared with control mother offspring (CMO), the diabetic mother offspring (DMO) had higher blood pressure and impaired endothelium-dependent relaxation in mesenteric arteries, accompanied by decreased AMPK phosphorylation and PPARδ expression, increased ER stress markers, and reactive oxygen species (ROS) levels. The inhibition of ER stress reversed these aberrant changes in DMO. Ex vivo treatment of mesenteric arteries with an AMPK agonist (A769662) or a PPARδ agonist (GW1516) improved the impaired EDR in DMO and reversed the tunicamycin-induced ER stress, ROS production, and EDR impairment in mesenteric arteries from CMO. The effects of A769662 were abolished by co-treatment with GSK0660 (PPARδ antagonist), whereas the effects of GW1516 were unaffected by Compound C (AMPK inhibitor).

CONCLUSION

These results suggest an abnormal foetal programming of vascular endothelial function in offspring of rats with maternal diabetes that is associated with increased ER stress, which can be ascribed to down-regulation of AMPK/PPARδ signalling cascade.

Exercise training mitigates ER stress and UCP2 deficiency-associated coronary vascular dysfunction in atherosclerosis

Endoplasmic reticulum (ER) stress and uncoupling protein-2 (UCP2) activation are opposing modulators of endothelial dysfunction in atherosclerosis. Exercise reduces atherosclerosis plaques and enhances endothelial function. Our aim was to understand how exercise affects ER stress and UCP2 activation, and how that relates to endothelial dysfunction in an atherosclerotic murine model. Wild type (C57BL/6, WT) and apolipoprotein-E-knockout (ApoE^tm1Unc, ApoE KO) mice underwent treadmill exercise training (EX) or remained sedentary for 12 weeks. Acetylcholine (ACh)-induced endothelium-dependent vasodilation was determined in the presence of an eNOS inhibitor (L-NAME), UCP2 inhibitor (genipin), and ER stress inducer (tunicamycin). UCP2, ER stress markers and NLRP3 inflammasome signaling were quantified by western blotting. p67^phox and superoxide were visualized using immunofluorescence and DHE staining. Nitric oxide (NO) was measured by nitrate/nitrite assay. ACh-induced vasodilation was attenuated in coronary arterioles of ApoE KO mice but improved in ApoE KO-EX mice. Treatment of coronary arterioles with L-NAME, tunicamycin, and genipin significantly attenuated ACh-induced vasodilation in all mice except for ApoE KO mice. Exercise reduced expression of ER stress proteins, TXNIP/NLRP3 inflammasome signaling cascades, and Bax expression in the heart of ApoE KO-EX mice. Further, exercise diminished superoxide production and NADPH oxidase p67^phox expression in coronary arterioles while simultaneously increasing UCP2 expression and nitric oxide (NO) production in the heart of ApoE KO-EX mice. Routine exercise alleviates endothelial dysfunction in atherosclerotic coronary arterioles in an eNOS, UCP2, and ER stress signaling specific manner, and resulting in reduced TXNIP/NLRP3 inflammasome activity and oxidative stress.

Roles and Therapeutic Implications of Endoplasmic Reticulum Stress and Oxidative Stress in Cardiovascular Diseases

In different pathological states that cause endoplasmic reticulum (ER) calcium depletion, altered glycosylation, nutrient deprivation, oxidative stress, DNA damage or energy perturbation/fluctuations, the protein folding process is disrupted and the ER becomes stressed. Studies in the past decade have demonstrated that ER stress is closely associated with pathogenesis of obesity, insulin resistance and type 2 diabetes. Excess nutrients and inflammatory cytokines associated with metabolic diseases can trigger or worsen ER stress. ER stress plays a critical role in the induction of endothelial dysfunction and atherosclerosis. Signaling pathways including AMP-activated protein kinase and peroxisome proliferator-activated receptor have been identified to regulate ER stress, whilst ER stress contributes to the imbalanced production between nitric oxide (NO) and reactive oxygen species (ROS) causing oxidative stress. Several drugs or herbs have been proved to protect against cardiovascular diseases (CVD) through inhibition of ER stress and oxidative stress. The present article reviews the involvement of ER stress and oxidative stress in cardiovascular dysfunction and the potential therapeutic implications.

Coptisine Attenuates Diabetes-Associated Endothelial Dysfunction through Inhibition of Endoplasmic Reticulum Stress and Oxidative Stress

Coptisine is the major bioactive protoberberine alkaloid found in Rhizoma Coptidis. Coptisine reduces inflammatory responses and improves glucose tolerance; nevertheless, whether coptisine has vasoprotective effect in diabetes is not fully characterized. Conduit arteries including aortas and carotid arteries were obtained from male C57BL/6J mice for ex vivo treatment with risk factors (high glucose or tunicamycin) and coptisine. Some arterial rings were obtained from diabetic mice, which were induced by high-fat diet (45% kcal% fat) feeding for 6 weeks combined with a low-dose intraperitoneal injection of streptozotocin (120 mg/kg). Functional studies showed that coptisine protected endothelium-dependent relaxation in aortas against risk factors and from diabetic mice. Coptisine increased phosphorylations of AMPK and eNOS and downregulated the endoplasmic reticulum (ER) stress markers as determined by Western blotting. Coptisine elevates NO bioavailability and decreases reactive oxygen species level. The results indicate that coptisine improves vascular function in diabetes through suppression of ER stress and oxidative stress, implying the therapeutic potential of coptisine to treat diabetic vasculopathy.

γ-Oryzanol Improves Exercise Endurance and Muscle Strength by Upregulating PPARδ and ERRγ Activity in Aged Mice

SCOPE

γ-Oryzanol, a well-known antioxidant, has been used by body builders and athletes to boost strength and increase muscle gain, without major side effects. However, the effect of γ-Oryzanol on sarcopenia and the underlying molecular mechanism is poorly understood.

RESULTS

Aged mice fed with the γ-Oryzanol diet do not show significant changes in muscle weight, but show increased running endurance as well as improved grip strength. The expression and activity of PPARδ and ERRγ are increased in skeletal muscle of γ-Oryzanol supplemented mice. γ-Oryzanol upregulates oxidative muscle fibers by MEF2 transcription factor, and PGC-1α and ERRα expressions. Fatty acid oxidation related genes and mitochondria biogenesis are upregulated by γ-Oryzanol. In addition, γ-Oryzanol inhibits TGF-β-Smad-NADPH oxidase 4 pathway and inflammatory cytokines such as TNF-α, IL-1β, IL-6, and p65 NF-κB subunit, which cause skeletal muscle weakness. Collectively, γ-Oryzanol attenuates muscle weakness pathway and increases oxidative capacity by increasing PPARδ and ERRγ activity, which contributes to enhance strength and improve oxidative capacity in muscles, consequently enhancing exercise capacity in aged mice. Particularly, γ-Oryzanol directly binds to PPARδ.

CONCLUSIONS

These are the first findings showing that γ-Oryzanol enhances skeletal muscle function in aged mice by regulating PPARδ and ERRγ activity without muscle gain.

Regulation of blood-brain barrier permeability by Salvinorin A via alleviating endoplasmic reticulum stress in brain endothelial cell after ischemia stroke

Inhibition of endoplasmic reticulum (ER) stress reduces blood-brain barrier (BBB) injury caused by ischemia/reperfusion (I/R), with indistinct mechanisms. Salvinorin A (SA) relieves I/R-induced BBB leakage; however, whether it is related to the suppression of ER stress is yet unclear. To address this question, we have used both a rat model of middle cerebral artery occlusion (MCAO) and human brain microvascular endothelial cells (HBMECs) with oxygen-glucose deprivation (OGD). SA was injected by tail vein at the terminal of ischemia; Norbinaltorphimine (NB), a kappa opioid antagonist, was administered 30 min prior to SA; 4-phenylbutyric acid (4-PBA), an ER stress inhibitor, was injected intraperitoneally after the onset of ischemia; adenylate-activated protein kinase (AMPK)-specific small interfering RNAs (siRNAs) were transfected to HBMECs before OGD. The assessment was as follows: infarct volume, brain water gain, Evans blue leakage, and modified neurological severity score (mNSS) after MCAO; HBMECs apoptosis rate and permeability, ER stress-related protein, and reactive oxygen species (ROS) and calcium levels after OGD. The results showed that SA significantly reduced the BBB leakage in vivo; SA relieved the apoptotic rates and ER stress in HBMECs, protected the permeability of HBMECs, and reduced ROS and calcium ion level after OGD. Moreover, the SA function was blocked by NB in vivo and AMPK- siRNAs in vitro. We conclude that SA mitigated BBB damage and HBMEC injury after I/R and alleviated ER stress in endothelial cells via AMPK pathway.

Role of the Peroxisome Proliferator Activated Receptors in Hypertension

Nuclear receptors represent a large family of ligand-activated transcription factors which sense the physiological environment and make long-term adaptations by mediating changes in gene expression. In this review, we will first discuss the fundamental mechanisms by which nuclear receptors mediate their transcriptional responses. We will focus on the PPAR (peroxisome proliferator-activated receptor) family of adopted orphan receptors paying special attention to PPARγ, the isoform with the most compelling evidence as an important regulator of arterial blood pressure. We will review genetic data showing that rare mutations in PPARγ cause severe hypertension and clinical trial data which show that PPARγ activators have beneficial effects on blood pressure. We will detail the tissue- and cell-specific molecular mechanisms by which PPARs in the brain, kidney, vasculature, and immune system modulate blood pressure and related phenotypes, such as endothelial function. Finally, we will discuss the role of placental PPARs in preeclampsia, a life threatening form of hypertension during pregnancy. We will close with a viewpoint on future research directions and implications for developing novel therapies.

The Endocannabinoid System and PPARs: Focus on Their Signalling Crosstalk, Action and Transcriptional Regulation

Peroxisome proliferator-activated receptors (PPARs) are a family of nuclear receptors including PPARα, PPARγ, and PPARβ/δ, acting as transcription factors to regulate the expression of a plethora of target genes involved in metabolism, immune reaction, cell differentiation, and a variety of other cellular changes and adaptive responses. PPARs are activated by a large number of both endogenous and exogenous lipid molecules, including phyto- and endo-cannabinoids, as well as endocannabinoid-like compounds. In this view, they can be considered an extension of the endocannabinoid system. Besides being directly activated by cannabinoids, PPARs are also indirectly modulated by receptors and enzymes regulating the activity and metabolism of endocannabinoids, and, vice versa, the expression of these receptors and enzymes may be regulated by PPARs. In this review, we provide an overview of the crosstalk between cannabinoids and PPARs, and the importance of their reciprocal regulation and modulation by common ligands, including those belonging to the extended endocannabinoid system (or "endocannabinoidome") in the control of major physiological and pathophysiological functions.

Effects of 4-phenylbutyric acid on the development of diabetic retinopathy in diabetic rats: regulation of endoplasmic reticulum stress-oxidative activation

There are good evidences suggesting that endoplasmic reticulum (ER) stress can be one of the contributing factors in the development of diabetic retinopathy. The present study was designed to investigate the effect of chemical chaperone 4-phenylbutyric acid (4-PBA) in alleviating the ER stress, and diabetic retinopathy in type 2 diabetic rats. Treatment of diabetic rats with 4-PBA, increased the antioxidant capacity, reduced the levels of lipid peroxidation, organised the state of apoptosis and regulated the ER stress - oxidative activation in retinal tissue. Also there was an improvement in the histological picture of retinal specimens compared to untreated diabetic rats. It was concluded that 4-PBA is a promising therapeutic agent for ER stress diseases such as diabetic retinopathy.

The Anti-atherogenic Role of Exercise Is Associated With the Attenuation of Bone Marrow-Derived Macrophage Activation and Migration in Hypercholesterolemic Mice

An early event in atherogenesis is the recruitment and infiltration of circulating monocytes and macrophage activation in the subendothelial space. Atherosclerosis subsequently progresses as a unresolved inflammatory disease, particularly in hypercholesterolemic conditions. Although physical exercise training has been a widely accepted strategy to inhibit atherosclerosis, its impact on arterial wall inflammation and macrophage phenotype and function has not yet been directly evaluated. Thus, the aim of this study was to investigate the effects of aerobic exercise training on the inflammatory state of atherosclerotic lesions with a focus on macrophages. Hypercholesterolemic LDL-receptor-deficient male mice were subjected to treadmill training for 8 weeks and fed a high-fat diet. Analyses included plasma lipoprotein and cytokine levels; aortic root staining for lipids (oil red O); macrophages (CD68, MCP1 and IL1β); oxidative (nitrotyrosine and, DHE) and endoplasmic reticulum (GADD) stress markers. Primary bone marrow-derived macrophages (BMDM) were assayed for migration activity, motility phenotype (Rac1 and F-actin) and inflammation-related gene expression. Plasma levels of HDL cholesterol were increased, while levels of proinflammatory cytokines (TNFa, IL1b, and IL6) were markedly reduced in the exercised mice. The exercised mice developed lower levels of lipid content and inflammation in atherosclerotic plaques. Additionally, lesions in the exercised mice had lower levels of oxidative and ER stress markers. BMDM isolated from the exercised mice showed a marked reduction in proinflammatory cytokine gene expression and migratory activity and a disrupted motility phenotype. More importantly, bone marrow from exercised mice transplanted into sedentary mice led to reduced atherosclerosis in the recipient sedentary mice, thus suggesting that epigenetic mechanisms are associated with exercise. Collectively, the presented data indicate that exercise training prevents atherosclerosis by inhibiting bone marrow-derived macrophage recruitment and activation.

AMPK upregulates KCa2.3 channels and ameliorates endothelial dysfunction in diet-induced obese mice

The opening of endothelial small-conductance calcium-activated potassium channels (K_Ca2.3) is essential for endothelium-dependent hyperpolarization (EDH), which predominantly occurs in small resistance arteries. Adenosine monophosphate-activated protein kinase (AMPK), an important metabolic regulator, has been implicated in regulating endothelial nitric oxide synthase activity. However, it was unclear whether AMPK regulated endothelial K_Ca2.3-mediated EDH-type vasodilation. Using bioinformatics analysis and myograph system, we investigated the regulation by AMPK of K_Ca2.3 in human umbilical vein endothelial cells (HUVECs) or mouse second-order mesenteric resistance arteries. In HUVECs, AMPK activation either by activators (AICAR, A769662 and MK-8722) or expression of the constitutively active form of AMPK significantly upregulated K_Ca2.3 expression. Such effects were abolished by AMPK inhibitor (compound C) or AMPK α1-/α2-siRNA, extracellular-signal-regulated-kinase 5 (ERK5) inhibitor (ERK5-IN-1), and specific siRNA to myocyte-enhancer factor 2 (MEF2) or krüppel-like factor 2/4 (KLF2/4). K_Ca2.3 expression was significantly reduced in mesenteric resistance arteries in AMPKα2 knockout mice when compared with littermate control mice. Furthermore, in high-fat diet fed mice, 2-week treatment with AICAR restored endothelial K_Ca2.3 expression in mesenteric resistance arteries with improved endothelial dysfunction. Our results demonstrate that activation of AMPK upregulates K_Ca2.3 channel expression through the ERK5-MEF2-KLF2/4 signaling pathway in vascular endothelium, which contributes to benefits through K_Ca2.3-mediated EDH-type vasodilation in mesenteric resistance arteries.

Exercise as medicine for COVID-19: On PPAR with emerging pharmacotherapy

Coronavirus disease 2019 (COVID-19) may have a metabolic origin given strong links with risk factors such as lipids and glucose and co-morbidities such as obesity and type 2 diabetes mellitus. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein mediates viral cellular entry via the ACE2 receptor. The cytoplasmic tail of this spike protein is heavily palmitoylated. Emerging studies suggest that SARS-CoV-2 alters lipid metabolism in the lung epithelial cells by modulating peroxisome proliferator-activated receptor alpha (PPARα), possibly contributing to lipotoxicity, inflammation and untoward respiratory effects. Disruption of this process may affect palmitoylation of SARS-CoV spike protein and thus infectivity and viral assembly. COVID-19 is also increasingly being recognized as a vascular disease, with several studies noting prominent systemic endothelial dysfunction. The pathogenesis of endothelial dysfunction may also be linked to COVID-19-mediated metabolic and inflammatory effects. Herein, exercise will be compared to fenofibrate as a possible therapeutic strategy to bolster resilience against (and help manage recovery from) COVID-19. This paper will explore the hypothesis that exercise may be a useful adjuvant in a setting of COVID-19 management/rehabilitation due to its effects on PPARα and vascular endothelial function.

Procyanidin B2 mitigates endothelial endoplasmic reticulum stress through a PPARδ-Dependent mechanism

Hyperglycemia-induced endothelial endoplasmic reticulum (ER) stress is implicated in the pathophysiology of diabetes and its vascular complications. Procyanidins are enriched in many plant foods and have been demonstrated to exert several beneficial effects on diabetes, cardiovascular and other metabolic diseases. In the present study, we investigated the effect of procyanidin B2 (PCB2), the most widely distributed natural procyanidin, on ER stress evoked by high glucose in endothelial cells (ECs) and the underlying mechanisms. We showed that PCB2 mitigated the high glucose-activated ER stress pathways (PERK, IRE1α and ATF6) in human vascular ECs. In addition, we found that PCB2 attenuated endothelial ER stress via the activation of peroxisome proliferator-activated receptor δ (PPARδ). We demonstrated that PCB2 directly bound to and activated PPARδ. Conversely, GSK0660, a selective PPARδ antagonist, attenuated the suppressive effect of PCB2 on the ER stress signal pathway. Functionally, PCB2 ameliorated the high glucose-impaired endothelium-dependent relaxation in mouse aortas. The protective effect of PCB2 on vasodilation was abolished in the aortas pretreated with GSK0660 or those from the EC-specific PPARδ knockout mice. Moreover, the protective effects of PCB2 on ER stress and endothelial dysfunction required the inter-dependent actions of PPARδ and AMPK. Collectively, we demonstrated that PCB2 mitigated ER stress and ameliorated vasodilation via a PPARδ-mediated mechanism beyond its classic action as a scavenger of free radicals. These findings further highlighted the novel roles of procyanidins in intervening the ER stress and metabolic disorders related to endothelial dysfunction.

Up-regulation of Thioredoxin 1 by aerobic exercise training attenuates endoplasmic reticulum stress and cardiomyocyte apoptosis following myocardial infarction

Exercise training (ET) has been reported to reduce oxidative stress and endoplasmic reticulum (ER) stress in the heart following myocardial infarction (MI). Thioredoxin 1 (Trx1) plays a protective role in the infarcted heart. However, whether Trx1 regulates ER stress of the infarcted heart and participates in ET-induced cardiac protective effects are still not well known. In this work, H9c2 cells were treated with hydrogen peroxide (H₂O₂) and recombinant human Trx1 protein (TXN), meanwhile, adult male C57B6L mice were used to establish the MI model, and subjected to a six-week aerobic exercise training (AET) with or without the injection of Trx1 inhibitor, PX-12. Results showed that H₂O₂ significantly increased reactive oxygen species (ROS) level and the expression of TXNIP, CHOP and cleaved caspase12, induced cell apoptosis; TXN intervention reduced ROS level and the expression of CHOP and cleaved caspase12, and inhibited cell apoptosis in H₂O₂-treated H9c2 cells. Furthermore, AET up-regulated endogenous Trx1 protein expression and down-regulated TXNIP expression, restored ROS level and the expression of ER stress-related proteins, inhibited cell apoptosis as well as improved cardiac fibrosis and heart function in mice after MI. PX-12 partly inhibited the AET-induced beneficial effects in the infarcted heart. This study demonstrates that Trx1 attenuates ER stress-induced cell apoptosis, and AET reduces MI-induced ROS overproduction, ER stress and cell apoptosis partly through up-regulating of Trx1 expression in mice with MI.

Stearoyl-CoA Desaturase-1 Attenuates the High Shear Force Damage Effect on Human MG63 Osteosarcoma Cells

Mechanical regulation is known as an important regulator in cancer progression and malignancy. High shear force has been found to inhibit the cell cycle progression and result in cell death in various cancer cells. Stearoyl-CoA desaturase (SCD)-1, one of the important lipogenic enzymes, has recently been indicated as a potential pharmaceutical target in cancer therapy. In this study, we determined whether the cell fate control of shear force stimulation is through regulating the SCD-1 expression in cancer cells. Human MG63 osteosarcoma cells were used in this study. 2 and 20 dynes/cm² shear forces were defined as low and high intensities, respectively. A SCD-1 upregulation in human MG63 osteosarcoma cells under 20, but not 2, dynes/cm² shear force stimulation was shown, and this induction was regulated by Smad1/5 and peroxisome proliferator-activated receptor δ (PPARδ) signaling. Moreover, gene knockdown of PPARδ and SCD-1 in human MG63 osteosarcoma cells attenuated the differentiation inhibition and resulted in much more cell death of high shear force initiation. The present study finds a possible auto-protective role of SCD-1 upregulation in high shear force-damaged human MG63 osteosarcoma cells. However, its detailed regulation in the cancer fate decision of high shear force should be further examined.

Endogenous hydrogen sulfide improves vascular remodeling through PPARδ/SOCS3 signaling

Introduction

Mounting evidences demonstrated the deficiency of hydrogen sulfide (H₂S) facilitated the progression of cardiovascular diseases. However, the exact effects of H₂S on vascular remodeling are not consistent.

Objectives

This study aimed to investigate the beneficial role of endogenous H₂S on vascular remodeling.

Methods

CSE inhibitor, DL-propargylglycine (PPG) was used to treat mice and vascular smooth muscle cells (VSMCs). Sodium hydrosulfide (NaHS) was given to provide hydrogen sulfide. Vascular tension, H&E staining, masson trichrome staining, western blot and CCK8 were used to determine the vascular remodeling, expressions of inflammatory molecules and proliferation of VSMCs.

Results

The deficiency of endogenous H₂S generated vascular remodeling with aggravated active and passive contraction, thicken aortic walls, collagen deposition, increased phosphorylation of STAT3, decreased production of PPARδ and SOCS3 in aortas, which were reversed by NaHS. PPG inhibited expression of PPARδ and SOCS3, stimulated the phosphorylation of STAT3, increased inflammatory molecules production and proliferation rate of VSMCs which could all be corrected by NaHS supply. PPARδ agonist GW501516 offered protections similar to NaHS in PPG treated VSMCs. Aggravated active and passive contraction in PPG mice aortas, upregulated p-STAT3 and inflammatory molecules, downregulated SOCS3 and phenotype transformation in PPG treated VSMCs could be corrected by PPARδ agonist GW501516 treatment. On the contrary, PPARδ antagonist GSK0660 exhibited opposite effects on vascular contraction in aortas, expressions of p-STAT3 and SOCS3 in VSMCs compared with GW501516.

Conclusion

In a word, endogenous H₂S protected against vascular remodeling through preserving PPARδ/SOCS3 anti-inflammatory signaling pathway. Deficiency of endogenous H₂S should be considered as a risk factor for VSMCs dysfunction.

Pharmacological management of vascular endothelial dysfunction in diabetes: TCM and western medicine compared based on biomarkers and biochemical parameters

Diabetes, a worldwide health concern while burdening significant populace of countries with time due to a hefty increase in both incidence and prevalence rates. Hyperglycemia has been buttressed both in clinical and experimental studies to modulate widespread molecular actions that effect macro and microvascular dysfunctions. Endothelial dysfunction, activation, inflammation, and endothelial barrier leakage are key factors contributing to vascular complications in diabetes, plus the development of diabetes-induced cardiovascular diseases. The recent increase in molecular, transcriptional, and clinical studies has brought a new scope to the understanding of molecular mechanisms and the therapeutic targets for endothelial dysfunction in diabetes. In this review, an attempt made to discuss up to date critical and emerging molecular signaling pathways involved in the pathophysiology of endothelial dysfunction and viable pharmacological management targets. Importantly, we exploit some Traditional Chinese Medicines (TCM)/TCM isolated bioactive compounds modulating effects on endothelial dysfunction in diabetes. Finally, clinical studies data on biomarkers and biochemical parameters involved in the assessment of the efficacy of treatment in vascular endothelial dysfunction in diabetes was compared between clinically used western hypoglycemic drugs and TCM formulas.

Exercise training ameliorates cerebrovascular dysfunction in a murine model of Alzheimer's disease: role of the P2Y2 receptor and endoplasmic reticulum stress

Cerebrovascular dysfunction is a critical risk factor for the pathogenesis of Alzheimer's disease (AD). The purinergic P2Y2 receptor and endoplasmic reticulum (ER) stress are tightly associated with vascular dysfunction and the pathogenesis of AD. However, the protective effects of exercise training on P2Y2 receptor- and ER stress-associated cerebrovascular dysfunction in AD are mostly unknown. Control (C57BL/6, CON) and AD (APP/PS1dE9, AD) mice underwent treadmill exercise training (EX). 2-MeS-ATP-induced dose-dependent vasoreactivity was determined by using a pressurized posterior cerebral artery (PCA) from 10-12-mo-old mice. Human brain microvascular endothelial cells (HBMECs) were exposed to laminar shear stress (LSS) at 20 dyn/cm² for 30 min, 2 h, and 24 h. The expression of P2Y2 receptors, endothelial nitric oxide synthase (eNOS), and ER stress signaling were quantified by Western blot analysis. Notably, exercise converted ATP-induced vasoconstriction in the PCA from AD mice to vasodilation in AD+EX mice to a degree commensurate to the vascular reactivity observed in CON mice. Exercise reduced the expression of amyloid peptide precursor (APP) and increased the P2Y2 receptor and Akt/eNOS expression in AD mice brain. Mechanistically, LSS increased the expression of both P2Y2 receptor and eNOS protein in HBMECs, but these increases were blunted by a P2Y2 receptor antagonist in HBMECs. Exercise also reduced the expression of aberrant ER stress markers p-IRE1, p/t-eIF2α, and CHOP, as well as Bax/Bcl-2, in AD mice brain. Collectively, our results demonstrate for the first time that exercise mitigates cerebrovascular dysfunction in AD through modulating P2Y2 receptor- and ER stress-dependent endothelial dysfunction.NEW & NOTEWORTHY A limited study has investigated whether exercise training can improve cerebrovascular function in Alzheimer's disease. The novel findings of the study are that exercise training improves cerebrovascular dysfunction through enhancing P2Y2 receptor-mediated eNOS signaling and reducing ER stress-associated pathways in AD. These data suggest that exercise training, which regulates P2Y2 receptor and ER stress in AD brain, is a potential therapeutic strategy for Alzheimer's disease.

Omentin-1 protects against high glucose-induced endothelial dysfunction via the AMPK/PPARδ signaling pathway

High glucose-induced endothelial dysfunction is a critical initiating factor in the development of diabetic vascular complications. Omentin-1 has been regarded as a novel biomarker of endothelial function in subjects with type-2 diabetes (T2D); however, it is unclear whether omentin-1 has any direct effect in ameliorating high glucose-induced endothelial dysfunction. In the present study, we analyzed the effect of omentin-1 on high glucose-induced endothelial dysfunction in isolated mouse aortas and mouse aortic endothelial cells (MAECs). Vascular reactivity in aortas was measured using wire myography. The expression levels of AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor δ (PPARδ), Akt, endothelial nitric-oxide synthase (eNOS), and endoplasmic reticulum (ER)-stress markers in MAECs were determined by Western blotting. The production of reactive oxygen species (ROS) and nitric oxide (NO) was assessed by diluted fluoroprobe, 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) and 4-amino-5-methylamino-2',7'-difluorofluorescein (DAF-FM DA), respectively. We found that ex vivo treatment with omentin-1 reversed impaired endothelial-dependent relaxations (EDR) in mouse aortas after high-glucose insult. Elevated ER-stress markers, oxidative stress, and reduction of NO production induced by high glucose in MAECs were reversed by omentin-1 treatment. Omentin-1 also effectively reversed tunicamycin-induced ER stress responses in MAECs, as well as ameliorated impairment of endothelial-dependent relaxation in mouse aortas. Moreover, omentin-1 increased AMPK phosphorylation with a subsequent increase in PPARδ expression, while also restoring the decreased phosphorylation of Akt and eNOS. The effects of omentin-1 were abolished by cotreatment of compound C (AMPK inhibitor) and GSK0660 (PPARδ antagonist). These data indicate that omentin-1 protects against high glucose-induced vascular-endothelial dysfunction through inhibiting ER stress and oxidative stress and increasing NO production via activation of AMPK/PPARδ pathway.

Endoplasmic Reticulum Stress and Mitochondrial Function in Airway Smooth Muscle

Inflammatory airway diseases such as asthma affect more than 300 million people world-wide. Inflammation triggers pathophysiology via such as tumor necrosis factor α (TNFα) and interleukins (e.g., IL-13). Hypercontraction of airway smooth muscle (ASM) and ASM cell proliferation are major contributors to the exaggerated airway narrowing that occurs during agonist stimulation. An emergent theme in this context is the role of inflammation-induced endoplasmic reticulum (ER) stress and altered mitochondrial function including an increase in the formation of reactive oxygen species (ROS). This may establish a vicious cycle as excess ROS generation leads to further ER stress. Yet, it is unclear whether inflammation-induced ROS is the major mechanism leading to ER stress or the consequence of ER stress. In various diseases, inflammation leads to an increase in mitochondrial fission (fragmentation), associated with reduced levels of mitochondrial fusion proteins, such as mitofusin 2 (Mfn2). Mitochondrial fragmentation may be a homeostatic response since it is generally coupled with mitochondrial biogenesis and mitochondrial volume density thereby reducing demand on individual mitochondrion. ER stress is triggered by the accumulation of unfolded proteins, which induces a homeostatic response to alter protein balance via effects on protein synthesis and degradation. In addition, the ER stress response promotes protein folding via increased expression of molecular chaperone proteins. Reduced Mfn2 and altered mitochondrial dynamics may not only be downstream to ER stress but also upstream such that a reduction in Mfn2 triggers further ER stress. In this review, we summarize the current understanding of the link between inflammation-induced ER stress and mitochondrial function and the role played in the pathophysiology of inflammatory airway diseases.

Imbalance of ER and Mitochondria Interactions: Prelude to Cardiac Ageing and Disease?

Cardiac disease is still the leading cause of morbidity and mortality worldwide, despite some exciting and innovative improvements in clinical management. In particular, atrial fibrillation (AF) and heart failure show a steep increase in incidence and healthcare costs due to the ageing population. Although research revealed novel insights in pathways driving cardiac disease, the exact underlying mechanisms have not been uncovered so far. Emerging evidence indicates that derailed proteostasis (i.e., the homeostasis of protein expression, function and clearance) is a central component driving cardiac disease. Within proteostasis derailment, key roles for endoplasmic reticulum (ER) and mitochondrial stress have been uncovered. Here, we describe the concept of ER and mitochondrial stress and the role of interactions between the ER and mitochondria, discuss how imbalance in the interactions fuels cardiac ageing and cardiac disease (including AF), and finally assess the potential of drugs directed at conserving the interaction as an innovative therapeutic target to improve cardiac function.

Pharmacological basis and new insights of resveratrol action in the cardiovascular system

Resveratrol (trans-3,4',5-trihydroxystilbene) belongs to the family of natural phytoalexins. Resveratrol first came to our attention in 1992, following reports of the cardioprotective effects of red wine. Thereafter, resveratrol was shown to exert antioxidant, anti-inflammatory, anti-proliferative, and angio-regulatory effects against atherosclerosis, ischaemia, and cardiomyopathy. This article critically reviews the current findings on the molecular basis of resveratrol-mediated cardiovascular benefits, summarizing the broad effects of resveratrol on longevity regulation, energy metabolism, stress resistance, exercise mimetics, circadian clock, and microbiota composition. In addition, this article also provides an update, both preclinically and clinically, on resveratrol-induced cardiovascular protection and discusses the adverse and inconsistent effects of resveratrol reported in both preclinical and clinical studies. Although resveratrol has been claimed as a master anti-aging agent against several age-associated diseases, further detailed mechanistic investigation is still required to thoroughly unravel the therapeutic value of resveratrol against cardiovascular diseases at different stages of disease development. LINKED ARTICLES: This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc.

Free fatty acid-induced H2O2 activates TRPM2 to aggravate endothelial insulin resistance via Ca2+-dependent PERK/ATF4/TRB3 cascade in obese mice

Transient Receptor Potential Melastatin-2 (TRPM2) is a nonselective cation channel mediating Ca²⁺ influx in response to oxidative stress. Given that insulin resistance-related endothelial dysfunction in obesity attributes to fatty-acid-induced reactive oxygen species (ROS) overproduction, in this study, we addressed the possible role of TRPM2 in obesity-related endothelial insulin resistance and the underlying mechanisms. Whole-cell patch clamp technique, intracellular Ca²⁺ concentration measurement, western blot, vasorelaxation assay, and high-fat diet (HFD)-induced obese model were employed to assess the relationship between TRPM2 and endothelial insulin response. We found that both the expression and activity of TRPM2 were higher in endothelial cells of obese mice. Palmitate rose a cationic current in endothelial cells which was inhibited or enlarged by TRPM2 knockdown or overexpression. Silencing of TRPM2 remarkably improved insulin-induced endothelial Akt activation, nitric oxide synthase (eNOS) phosphorylation and nitric oxide (NO) production, while TRPM2 overexpression resulted in the opposite effects. Furthermore, TRPM2-mediated Ca²⁺ entry, CaMKII activation and the following activation of PERK/ATF4/TRB3 cascade were involved in the mechanism of obesity or palmitate-induced endothelial insulin resistance. Notably, in vivo study, knockdown of TRPM2 with adeno-associated virus harboring short-hairpin RNA (shRNA) against TRPM2 alleviated endothelial insulin resistance and ameliorated endothelium-dependent vasodilatation in obese mice. Thus, these results suggest that TRPM2-activated Ca²⁺ signaling is necessary to induce insulin resistance-related endothelial dysfunction in obesity. Downregulation or pharmacological inhibition of TRPM2 channels may lead to the development of effective drugs for treatment of endothelial dysfunction associated with oxidative stress state.