A key role for tetrahydrobiopterin-dependent endothelial NOS regulation in resistance arteries: studies in endothelial cell tetrahydrobiopterin-deficient mice

Intermedin protects peritubular capillaries by inhibiting eNOS uncoupling through AMPK/GTPCH-I/BH4 pathway and alleviate CKD following AKI

BACKGROUND

Even after recovery of kidney function following AKI, progression to CKD may still occur, characterized by a reduction in peritubular capillaries (PTC) and subsequent kidney fibrosis. Reactive oxygen species (ROS) from uncoupled eNOS are suspected to damage endothelial cells and cause PTC rarefaction observed in AKI-CKD. Intermedin (IMD) inhibits eNOS uncoupling by activating AMPK, but its impact on AKI-CKD transition remains unclear.

METHODS

We utilized IMD-deficient (IMD-/-) mice to explore its effects on AKI-CKD transition, PTC density, endothelial damage, and kidney ROS in a kidney ischemia/reperfusion injury (IRI) model. To elucidate its protective mechanism for PTCs, we subsequently investigated the effects of IMD on endothelial cells and ROS using a hypoxia/reoxygenation (HR) model with human umbilical vein endothelial cells (HUVECs). Finally, we investigated the influence of IMD on AMPK/GTPCH-I/BH4/eNOS to explore its mechanism in alleviating oxidative stress.

RESULTS

Compared with IMD+/+ littermate sham controls, PTC density was significantly reduced in IMD-/- sham mice, with significantly increased oxidative stress. Post-AKI, both IMD+/+ and IMD-/- mice demonstrated substantial declines in kidney function and histology, along with significant fibrosis, PTC reduction, and heightened oxidative stress. Moreover, the severity of kidney damage in IMD-/- mice following AKI was considerably more pronounced than in IMD+/+ mice. HR significantly induced eNOS uncoupling and oxidative stress in HUVECs. Treatment with IMD effectively inhibited eNOS uncoupling and ROS production, achieving levels comparable to the antioxidant N-acetylcysteine. The inhibitory effect of IMD on eNOS uncoupling was abrogated when L-NAME was introduced after HR. HR significantly impaired AMPK activation, which could be reversed by IMD. Additional experiments with inhibitors of GTPCH-I and AMPK, and exogenous BH4, confirmed that IMD protects endothelial cells by activating AMPK/GTPCH-I/BH4, thereby inhibiting eNOS uncoupling and ROS production.

CONCLUSION

We concluded that IMD inhibits AKI-CKD transition by protecting endothelial cells of PTC via AMPK/GTPCH-I/BH4/eNOS pathway.

Unlocking the potential of photobiomodulation therapy for brain neurovascular coupling: The biological effects and medical applications

Photobiomodulation (PBM) therapy stands as an innovative neurostimulation modality that has demonstrated both efficacy and safety in improving brain function. This therapy exerts multifaceted influences on neurons, blood vessels, and their intricate interplay known as neurovascular coupling (NVC). Growing evidence indicates that NVC may present a promising target for PBM intervention. However, the detailed mechanisms underlying its therapeutic benefits remain to be fully understood. This review aims to elucidate the potential metabolic pathways and signaling cascades involved in the modulatory effects of PBM, while also exploring the extensive repertoire of PBM applications in neurologic and psychiatric conditions. The prospects of PBM within the realm of NVC investigation are intensively considered, providing deeper insights into the powerful capabilities of PBM therapy and its potential to revolutionize neurostimulation treatments.

Mechanisms underlying targeted mitochondrial therapy for programmed cardiac cell death

Heart diseases are common clinical diseases, such as cardiac fibrosis, heart failure, hypertension and arrhythmia. Globally, the incidence rate and mortality of heart diseases are increasing by years. The main mechanism of heart disease is related to the cellular state. Mitochondrion is the organ of cellular energy supply, participating in various signal transduction pathways and playing a vital role in the occurrence and development of heart disease. This review summarizes the cell death patterns and molecular mechanisms associated with heart disease and mitochondrial dysfunction.

Promotion of nitric oxide production: mechanisms, strategies, and possibilities

The discovery of nitric oxide (NO) and the role of endothelial cells (ECs) in its production has revolutionized medicine. NO can be produced by isoforms of NO synthases (NOS), including the neuronal (nNOS), inducible (iNOS), and endothelial isoforms (eNOS), and via the non-classical nitrate-nitrite-NO pathway. In particular, endothelium-derived NO, produced by eNOS, is essential for cardiovascular health. Endothelium-derived NO activates soluble guanylate cyclase (sGC) in vascular smooth muscle cells (VSMCs), elevating cyclic GMP (cGMP), causing vasodilation. Over the past four decades, the importance of this pathway in cardiovascular health has fueled the search for strategies to enhance NO bioavailability and/or preserve the outcomes of NO's actions. Currently approved approaches operate in three directions: 1) providing exogenous NO, 2) promoting sGC activity, and 3) preventing degradation of cGMP by inhibiting phosphodiesterase 5 activity. Despite clear benefits, these approaches face challenges such as the development of nitrate tolerance and endothelial dysfunction. This highlights the need for sustainable options that promote endogenous NO production. This review will focus on strategies to promote endogenous NO production. A detailed review of the mechanisms regulating eNOS activity will be first provided, followed by a review of strategies to promote endogenous NO production based on the levels of available preclinical and clinical evidence, and perspectives on future possibilities.

Nur77 mitigates endothelial dysfunction through activation of both nitric oxide production and anti-oxidant pathways

BACKGROUND

Nur77 belongs to the member of orphan nuclear receptor 4A family that plays critical roles in maintaining vascular homeostasis. This study aims to determine whether Nur77 plays a role in attenuating vascular dysfunction, and if so, to determine the molecular mechanisms involved.

METHODS

Both Nur77 knockout (Nur77 KO) and Nur77 endothelial specific transgenic mice (Nur77-Tg) were employed to examine the functional significance of Nur77 in vascular endothelium in vivo. Endothelium-dependent vasodilatation to acetylcholine (Ach) and reactive oxygen species (ROS) production was determined under inflammatory and high glucose conditions. Expression of genes was determined by real-time PCR and western blot analysis.

RESULTS

In response to tumor necrosis factor alpha (TNF-α) treatment and diabetes, the endothelium-dependent vasodilatation to Ach was significantly impaired in aorta from Nur77 KO as compared with those from the wild-type (WT) mice. Endothelial specific overexpression of Nur77 markedly prevented both TNF-α- and high glucose-induced endothelial dysfunction. Compared with WT mice, after TNF-α and high glucose treatment, ROS production in aorta was significantly increased in Nur77 KO mice, but it was inhibited in Nur77-Tg mice, as determined by dihydroethidium (DHE) staining. Furthermore, we demonstrated that Nur77 overexpression substantially increased the expression of several key enzymes involved in nitric oxide (NO) production and ROS scavenging, including endothelial nitric oxide synthase (eNOS), guanosine triphosphate cyclohydrolase 1 (GCH-1), glutathione peroxidase-1 (GPx-1), and superoxide dismutases (SODs). Mechanistically, we found that Nur77 increased GCH1 mRNA stability by inhibiting the expression of microRNA-133a, while Nur77 upregulated SOD1 expression through directly binding to the human SOD1 promoter in vascular endothelial cells.

CONCLUSION

Our results suggest that Nur77 plays an essential role in attenuating endothelial dysfunction through activating NO production and anti-oxidant pathways in vascular endothelium. Targeted activation of Nur77 may provide a novel therapeutic approach for the treatment of cardiovascular diseases associated with endothelial dysfunction.

Maternal exercise represses Nox4 via SIRT1 to prevent vascular oxidative stress and endothelial dysfunction in SHR offspring

Maternal exercise during pregnancy has emerged as a potentially promising approach to protect offspring from cardiovascular disease, including hypertension. Although endothelial dysfunction is involved in the pathophysiology of hypertension, limited studies have characterized how maternal exercise influences endothelial function of hypertensive offspring. In this study, pregnant spontaneously hypertensive rats and Wistar-Kyoto rats were assigned either to a sedentary lifestyle or to swimming training daily, and fetal histone deacetylase-mediated epigenetic modification and offspring vascular function of mesenteric arteries were analyzed. Maternal exercise ameliorated the impairment of acetylcholine-induced vasodilation without affecting sodium nitroprusside-induced vasodilation in mesenteric arteries from the hypertensive offspring. In accordance, maternal exercise reduced NADPH oxidase-4 (Nox4) protein to prevent the loss of nitric oxide generation and increased reactive oxygen species production in mesenteric arteries of hypertensive offspring. We further found that maternal exercise during pregnancy upregulated vascular SIRT1 (sirtuin 1) expression, leading to a low level of H3K9ac (histone H3 lysine 9 acetylation), resulting in the transcriptional downregulation of Nox4 in mesenteric arteries of hypertensive fetuses. These findings show that maternal exercise alleviates oxidative stress and the impairment of endothelium-dependent vasodilatation via SIRT1-regulated deacetylation of Nox4, which might contribute to improved vascular function in hypertensive offspring.

Targeting cytokine-like protein FAM3D lowers blood pressure in hypertension

Current antihypertensive options still incompletely control blood pressure, suggesting the existence of uncovered pathogenic mechanisms. Here, whether cytokine-like protein family with sequence similarity 3, member D (FAM3D) is involved in hypertension etiology is evaluated. A case-control study exhibits that FAM3D is elevated in patients with hypertension, with a positive association with odds of hypertension. FAM3D deficiency significantly ameliorates angiotensin II (AngII)-induced hypertension in mice. Mechanistically, FAM3D directly causes endothelial nitric oxide synthase (eNOS) uncoupling and impairs endothelium-dependent vasorelaxation, whereas 2,4-diamino-6-hydroxypyrimidine to induce eNOS uncoupling abolishes the protective effect of FAM3D deficiency against AngII-induced hypertension. Furthermore, antagonism of formyl peptide receptor 1 (FPR1) and FPR2 or the suppression of oxidative stress blunts FAM3D-induced eNOS uncoupling. Translationally, targeting endothelial FAM3D by adeno-associated virus or intraperitoneal injection of FAM3D-neutralizing antibodies markedly ameliorates AngII- or deoxycorticosterone acetate (DOCA)-salt-induced hypertension. Conclusively, FAM3D causes eNOS uncoupling through FPR1- and FPR2-mediated oxidative stress, thereby exacerbating the development of hypertension. FAM3D may be a potential therapeutic target for hypertension.

Cardiomyocyte tetrahydrobiopterin synthesis regulates fatty acid metabolism and susceptibility to ischaemia-reperfusion injury

NEW FINDINGS

What is the central question of this study? What are the physiological roles of cardiomyocyte-derived tetrahydrobiopterin (BH4) in cardiac metabolism and stress response? What is the main finding and its importance? Cardiomyocyte BH4 has a physiological role in cardiac metabolism. There was a shift of substrate preference from fatty acid to glucose in hearts with targeted deletion of BH4 synthesis. The changes in fatty-acid metabolic profile were associated with a protective effect in response to ischaemia-reperfusion (IR) injury, and reduced infarct size. Manipulating fatty acid metabolism via BH4 availability could play a therapeutic role in limiting IR injury.

ABSTRACT

Tetrahydrobiopterin (BH4) is an essential cofactor for nitric oxide (NO) synthases in which its production of NO is crucial for cardiac function. However, non-canonical roles of BH4 have been discovered recently and the cell-specific role of cardiomyocyte BH4 in cardiac function and metabolism remains to be elucidated. Therefore, we developed a novel mouse model of cardiomyocyte BH4 deficiency, by cardiomyocyte-specific deletion of Gch1, which encodes guanosine triphosphate cyclohydrolase I, a required enzyme for de novo BH4 synthesis. Cardiomyocyte (cm)Gch1 mRNA expression and BH4 levels from cmGch1 KO mice were significantly reduced compared to Gch1flox/flox (WT) littermates. Transcriptomic analyses and protein assays revealed downregulation of genes involved in fatty acid oxidation in cmGch1 KO hearts compared with WT, accompanied by increased triacylglycerol concentration within the myocardium. Deletion of cardiomyocyte BH4 did not alter basal cardiac function. However, the recovery of left ventricle function was improved in cmGch1 KO hearts when subjected to ex vivo ischaemia-reperfusion (IR) injury, with reduced infarct size compared to WT hearts. Metabolomic analyses of cardiac tissue after IR revealed that long-chain fatty acids were increased in cmGch1 KO hearts compared to WT, whereas at 5 min reperfusion (post-35 min ischaemia) fatty acid metabolite levels were higher in WT compared to cmGch1 KO hearts. These results indicate a new role for BH4 in cardiomyocyte fatty acid metabolism, such that reduction of cardiomyocyte BH4 confers a protective effect in response to cardiac IR injury. Manipulating cardiac metabolism via BH4 could play a therapeutic role in limiting IR injury.

Endothelial cell vasodilator dysfunction mediates progressive pregnancy-induced hypertension in endothelial cell tetrahydrobiopterin deficient mice

BACKGROUND AND PURPOSE

Pregnancy-associated vascular remodelling is essential for both maternal and fetal health. We have previously shown that maternal endothelial cell tetrahydrobiopterin (BH4) deficiency causes poor pregnancy outcomes. Here, we investigated the role and mechanisms of endothelial cell-mediated vasorelaxation function in these outcomes.

EXPERIMENTAL APPROACH

The vascular reactivity of mouse aortas and uterine arteries from non-pregnant and pregnant endothelial cell-specific BH4 deficient mice (Gch1fl/flTie2cre mice) was assessed by wire myography. Systolic blood pressure was assessed by tail cuff plethysmography.

KEY RESULTS

In late pregnancy, systolic blood pressure was significantly higher (∼24 mmHg) in Gch1fl/flTie2cre mice compared with wild-type littermates. This was accompanied by enhanced vasoconstriction and reduced endothelial-dependent vasodilation in both aorta and uterine arteries from pregnant Gch1fl/flTie2cre mice. In uterine arteries loss of eNOS-derived vasodilators was partially compensated by upregulation of intermediate and large-conductance Ca2+-activated K+ channels. In rescue experiments, oral BH4 supplementation alone did not rescue vascular dysfunction and pregnancy-induced hypertension in Gch1fl/flTie2cre mice. However, combination with the fully reduced folate, 5-methyltetrahydrofolate (5-MTHF), restored endothelial cell vasodilator function and blood pressure.

CONCLUSIONS AND IMPLICATIONS

We identify a critical requirement for maternal endothelial cell Gch1/BH4 biosynthesis in endothelial cell vasodilator function in pregnancy. Targeting vascular Gch1 and BH4 biosynthesis with reduced folates may provide a novel therapeutic target for the prevention and treatment of pregnancy-related hypertension.

Endothelial cell-specific roles for tetrahydrobiopterin in myocardial function, cardiac hypertrophy, and response to myocardial ischemia-reperfusion injury

The cofactor tetrahydrobiopterin (BH4) is a critical regulator of nitric oxide synthase (NOS) function and redox signaling, with reduced BH4 implicated in multiple cardiovascular disease states. In the myocardium, augmentation of BH4 levels can impact on cardiomyocyte function, preventing hypertrophy and heart failure. However, the specific role of endothelial cell BH4 biosynthesis in the coronary circulation and its role in cardiac function and the response to ischemia has yet to be elucidated. Endothelial cell-specific Gch1 knockout mice were generated by crossing Gch1fl/fl with Tie2cre mice, generating Gch1fl/flTie2cre mice and littermate controls. GTP cyclohydrolase protein and BH4 levels were reduced in heart tissues from Gch1fl/flTie2cre mice, localized to endothelial cells, with normal cardiomyocyte BH4. Deficiency in coronary endothelial cell BH4 led to NOS uncoupling, decreased NO bioactivity, and increased superoxide and hydrogen peroxide productions in the hearts of Gch1fl/flTie2cre mice. Under physiological conditions, loss of endothelial cell-specific BH4 led to mild cardiac hypertrophy in Gch1fl/flTie2cre hearts. Endothelial cell BH4 loss was also associated with increased neuronal NOS protein, loss of endothelial NOS protein, and increased phospholamban phosphorylation at serine-17 in cardiomyocytes. Loss of cardiac endothelial cell BH4 led to coronary vascular dysfunction, reduced functional recovery, and increased myocardial infarct size following ischemia-reperfusion injury. Taken together, these studies reveal a specific role for endothelial cell Gch1/BH4 biosynthesis in cardiac function and the response to cardiac ischemia-reperfusion injury. Targeting endothelial cell Gch1 and BH4 biosynthesis may provide a novel therapeutic target for the prevention and treatment of cardiac dysfunction and ischemia-reperfusion injury.NEW & NOTEWORTHY We demonstrate a critical role for endothelial cell Gch1/BH4 biosynthesis in coronary vascular function and cardiac function. Loss of cardiac endothelial cell BH4 leads to coronary vascular dysfunction, reduced functional recovery, and increased myocardial infarct size following ischemia/reperfusion injury. Targeting endothelial cell Gch1 and BH4 biosynthesis may provide a novel therapeutic target for the prevention and treatment of cardiac dysfunction, ischemia injury, and heart failure.

Endothelial cyclin I reduces vulnerability to angiotensin II-induced vascular remodeling and abdominal aortic aneurysm risk

BACKGROUND

Retinoblastoma protein (Rb) supports vasoprotective E2F Transcription Factor 1 (E2f1)/Dihydrofolate Reductase (Dhfr) pathway activity in endothelial cells. Cyclin I (Ccni) promotes Cyclin-Dependent Kinase-5 (Cdk5)-mediated Rb phosphorylation. Therefore, we hypothesized that endothelial Ccni may regulate cardiovascular homeostasis, vessel remodeling, and abdominal aortic aneurysm (AAA) formation.

METHODS

Aortic CCNI mRNA expression was analyzed in the Gene Expression Omnibus (GEO) GSE57691 cohort consisting of AAA patients (n = 39) and healthy controls (n = 10). We employed wild-type (WT) mice and endothelial Ccni knockout (Ccnifl/flTie2-Cre) mice to conduct in vivo and ex vivo experimentation using an Angiotensin (Ang) II hypertension model and a CaCl2 AAA model. Mice were assessed for Rb/E2f1/Dhfr signaling, biopterin (i.e., biopterin [B], dihydrobiopterin [BH2], and tetrahydrobiopterin [BH4]) production, cardiovascular homeostasis, vessel remodeling, and AAA formation.

RESULTS

Aortic CCNI mRNA expression was downregulated in AAA patients. Both Ang II- and CaCl2-induced WT mice showed aortic Ccni upregulation coupled with vasculoprotective upregulation of Rb/E2f1/Dhfr signaling and biopterins. Endothelial Ccni knockout downregulated medial Rb/E2f1/Dhfr signaling and biopterins in Ang II-induced hypertensive mice, which exacerbated eNos uncoupling and H2O2 production. Endothelial Ccni knockout impaired in vivo hemodynamic responses and endothelium-dependent vasodilatation in ex vivo mesenteric arteries in response to Ang II. Endothelial Ccni knockout exacerbated mesenteric artery remodeling and AAA risk in response to Ang II and CaCl2.

CONCLUSIONS

Endothelial Ccni acts as a critical negative regulator of eNos uncoupling-mediated ROS generation and thereby reduces vulnerability to hypertension-induced vascular remodeling and AAA development in mice.

Measurement of Tetrahydrobiopterin in Animal Tissue Samples by HPLC with Electrochemical Detection-Protocol Optimization and Pitfalls

Tetrahydrobiopterin (BH4) is an essential cofactor of all nitric oxide synthase isoforms, thus determination of BH4 levels can provide important mechanistic insight into diseases. We established a protocol for high-performance liquid chromatography/electrochemical detection (HPLC/ECD)-based determination of BH4 in tissue samples. We first determined the optimal storage and work-up conditions for authentic BH4 and its oxidation product dihydrobiopterin (BH2) under various conditions (pH, temperature, presence of antioxidants, metal chelators, and storage time). We then applied optimized protocols for detection of BH4 in tissues of septic (induced by lipopolysaccharide [LPS]) rats. BH4 standards in HCl are stabilized by addition of 1,4-dithioerythritol (DTE) and diethylenetriaminepentaacetic acid (DTPA), while HCl was sufficient for BH2 standard stabilization. Overnight storage of BH4 standard solutions at room temperature in HCl without antioxidants caused complete loss of BH4 and the formation of BH2. We further optimized the protocol to separate ascorbate and the BH4 tissue sample and found a significant increase in BH4 in the heart and kidney as well as higher BH4 levels by trend in the brain of septic rats compared to control rats. These findings correspond to reports on augmented nitric oxide and BH4 levels in both animals and patients with septic shock.

Endothelial cell-derived tetrahydrobiopterin prevents aortic valve calcification

AIMS

Tetrahydrobiopterin (BH4) is a critical determinant of the biological function of endothelial nitric oxide synthase. The present study was to investigate the role of valvular endothelial cell (VEC)-derived BH4 in aortic valve calcification.

METHODS AND RESULTS

Plasma and aortic valve BH4 concentrations and the BH4:BH2 ratio were significantly lower in calcific aortic valve disease patients than in controls. There was a significant decrease of the two key enzymes of BH4 biosynthesis, guanosine 5'-triphosphate cyclohydrolase I (GCH1) and dihydrofolate reductase (DHFR), in calcified aortic valves compared with the normal ones. Endothelial cell-specific deficiency of Gch1 in Apoe-/- (Apoe-/-Gch1fl/flTie2Cre) mice showed a marked increase in transvalvular peak jet velocity, calcium deposition, runt-related transcription factor 2 (Runx2), dihydroethidium (DHE), and 3-nitrotyrosine (3-NT) levels in aortic valve leaflets compared with Apoe-/-Gch1fl/fl mice after a 24-week western diet (WD) challenge. Oxidized LDL (ox-LDL) induced osteoblastic differentiation of valvular interstitial cells (VICs) co-cultured with either si-GCH1- or si-DHFR-transfected VECs, while the effects could be abolished by BH4 supplementation. Deficiency of BH4 in VECs caused peroxynitrite formation increase and 3-NT protein increase under ox-LDL stimulation in VICs. SIN-1, the peroxynitrite generator, significantly up-regulated alkaline phosphatase (ALP) and Runx2 expression in VICs via tyrosine nitration of dynamin-related protein 1 (DRP1) at Y628. Finally, folic acid (FA) significantly attenuated aortic valve calcification in WD-fed Apoe-/- mice through increasing DHFR and salvaging BH4 biosynthesis.

CONCLUSION

The reduction in endothelial-dependent BH4 levels promoted peroxynitrite formation, which subsequently resulted in DRP1 tyrosine nitration and osteoblastic differentiation of VICs, thereby leading to aortic valve calcification. Supplementation of FA in diet attenuated hypercholesterolaemia-induced aortic valve calcification by salvaging BH4 bioavailability.

Endothelial Progenitor Cells and Rheumatoid Arthritis: Response to Endothelial Dysfunction and Clinical Evidences

Rheumatoid Arthritis (RA) is a chronic autoimmune inflammatory disease characterized by the swelling of multiple joints, pain and stiffness, and accelerated atherosclerosis. Sustained immune response and chronic inflammation, which characterize RA, may induce endothelial activation, damage and dysfunction. An equilibrium between endothelial damage and repair, together with the preservation of endothelial integrity, is of crucial importance for the homeostasis of endothelium. Endothelial Progenitor Cells (EPCs) represent a heterogenous cell population, characterized by the ability to differentiate into mature endothelial cells (ECs), which contribute to vascular homeostasis, neovascularization and endothelial repair. A modification of the number and function of EPCs has been described in numerous chronic inflammatory and auto-immune conditions; however, reports that focus on the number and functions of EPCs in RA are characterized by conflicting results, and discrepancies exist among different studies. In the present review, the authors describe EPCs' role and response to RA-related endothelial modification, with the aim of illustrating current evidence regarding the level of EPCs and their function in this disease, to summarize EPCs' role as a biomarker in cardiovascular comorbidities related to RA, and finally, to discuss the modulation of EPCs secondary to RA therapy.

Blocking endothelial TRPV4-Nox2 interaction helps reduce ROS production and inflammation, and improves vascular function in obese mice

Obesity induces inflammation and oxidative stress, and ultimately leads to vasodilatory dysfunction in which Transient receptor potential vanilloid type 4 (TRPV4) and Nicotinamide Adenine Dinucleotide Phosphate Oxidase (Nox2) have been reported to be involved. However, little attention has been paid to the role of the TRPV4-Nox2 complex in these problems. The purpose of this study was to figure out the role of the TRPV4-Nox2 complex in obesity-induced inflammation, oxidative stress, and vasodilatory dysfunction. Using fluorescence resonance energy transfer and immunoprecipitation assays, we found enhanced TRPV4 and Nox2 interactions in obese mice. Using q-PCR, fluorescent dye dihydroethidium staining, and myotonic techniques, we found that obesity caused inflammation, oxidative stress, and vasodilatory dysfunction. Using adeno-associated viruses, we found that enhancement or attenuation of TRPV4-Nox2 interaction altered the vaso-function. Based on these findings, we found a small-molecule drug, M12, that interrupted the TRPV4-Nox2 interaction, thereby reducing inflammatory factors and reactive oxygen species production and helping to restore the vasodilatory function. In summary, our results revealed a new mechanism by which obesity-induced inflammation, oxidative stress, and vasodilatory dysfunction is caused by enhanced TRPV4-Nox2 interactions. Using M12 to interrupt the TRPV4-Nox2 interaction may have anti-inflammatory and anti-oxidative stress effects and help restore vasodilatory function and thus provide a new therapeutic approach to obesity.

Ligustilide Prevents Radiation Enteritis by Targeting Gch1/BH4/eNOS to Improve Intestinal Ischemia

There is a high incidence of radiation enteritis (RE) after abdominal radiotherapy. The occurrence of RE seriously affects the treatment and quality of life of patients; however, its pathogenesis is complex and there are no effective drugs for its prevention or treatment. Intestinal ischemia plays an important role in the occurrence of enteritis. Previous studies have shown that targeting GTP-cyclohydrolase 1 (Gch1) to improve intestinal ischemia could be a new strategy to prevent and treat RE. A high content of the naturally occurring phthalide derivative ligustilide (LIG) has been found in the plant drug Rhizoma Ligustici Chuanxiong for the treatment of cardiovascular diseases. The purpose of this study was to evaluate the protective effects of LIG on RE. Ionizing radiation (IR) rat and endothelial cell models were used to observe and record rat body weights and stool morphologies, measure intestinal blood perfusion by laser Doppler blood flow imaging, determine the diastolic functions of mesenteric arteries, detect the levels of Gch1/BH₄/eNOS pathway-related proteins and regulatory molecules in the mesenteric arteries and endothelial cells, and predict affinity by molecular docking technology. The results showed that LIG significantly improved the body weights, loose stools, intestinal villi lengths, intestinal perfusion and vasodilatory functions of IR rats. LIG also significantly improved Gch1 protein and BH₄ levels in the mesenteric arteries and endothelial cells after IR, increased the NO content, reduced superoxide accumulation, and improved p-eNOS (Ser1177) levels in endothelial cells. LIG has good affinity for Gch1, which significantly improves its activity. These results indicate that LIG is the preferred compound for the prevention and treatment of RE by improving intestinal ischemia through the Gch1/BH₄/eNOS pathway. This study provides a theoretical basis and new research ideas for the development of new drugs for RE.

Porphyromonas gingivalis infection alters Nrf2-phase II enzymes and nitric oxide in primary human aortic endothelial cells

BACKGROUND

Periodontal disease (PD) is known to be associated with endothelial dysfunction in patients with coronary artery and/or cardiovascular disease. In our study, we sought to explore the virulence of P. gingivalis (Pg) affecting glycogen synthase kinase 3 beta (GSK-3β)/nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/tetrahydrobiopterin (BH₄ )/ nitric oxide synthase (NOS) expression in primary human aortic endothelial cells (pHAECs).

METHODS

pHAECs were infected for 48 hours with Pg in vitro using the Human oxygen-Bacteria anaerobic coculture technique. Cell viability was determined, and target gene expression changes were evaluated by quantitative real-time polymerase chain reaction at the end of each incubation period.

RESULTS

Pg impaired pHAEC viability 24 hours post-infection. Pg infection reduced mRNA expression levels of endothelial NOS (eNOS), Nrf2, and Phase II enzymes (heme oxygenase-1, catalase, superoxide dismutase-1) in a time-dependent manner. Significant (P <0.05) increase in the inflammatory markers (interleukin [IL]-1β, IL-6, and tumor necrosis factor-α) were observed in the medium as well as in the infected cells. Interestingly, inducible NOS mRNA levels showed a significant (P <0.05) increase at 12 hours and 24 hours and were reduced at later time points. BH₄ (cofactor of eNOS) biosynthesis enzyme dihydrofolate reductase (DHFR, salvage pathway) mRNA levels showed a significant (P <0.05) decrease, while mRNA levels of GSK-3β were elevated.

CONCLUSIONS

These results suggest that periodontal bacterial infection may cause significant changes in the endothelial GSK-3β/BH₄ /eNOS/Nrf2 pathways, which may lead to impaired vascular relaxation. Greater understanding of the factors that adversely affect endothelial cell function could contribute to the development of new therapeutic compounds to treat PD-induced vascular diseases.

Revisiting pharmacology of oxidative stress and endothelial dysfunction in cardiovascular disease: Evidence for redox-based therapies

According to the latest Global Burden of Disease Study data, non-communicable diseases in general and cardiovascular disease (CVD) in particular are the leading cause of premature death and reduced quality of life. Demographic shifts, unhealthy lifestyles and a higher burden of adverse environmental factors provide an explanation for these findings. The expected growing prevalence of CVD requires enhanced research efforts for identification and characterisation of novel therapeutic targets and strategies. Cardiovascular risk factors including classical (e.g. hypertension, diabetes, hypercholesterolaemia) and non-classical (e.g. environmental stress) factors induce the development of endothelial dysfunction, which is closely associated with oxidant stress and vascular inflammation and results in CVD, particularly in older adults. Most classically successful therapies for CVD display vasoprotective, antioxidant and anti-inflammatory effects, but were originally designed with other therapeutic aims. So far, only a few 'redox drugs' are in clinical use and many antioxidant strategies have not met expectations. With the present review, we summarise the actual knowledge on CVD pathomechanisms, with special emphasis on endothelial dysfunction, adverse redox signalling and oxidative stress, highlighting the preclinical and clinical evidence. In addition, we provide a brief overview of established CVD therapies and their relation to endothelial dysfunction and oxidative stress. Finally, we discuss novel strategies for redox-based CVD therapies trying to explain why, despite a clear link between endothelial dysfunction and adverse redox signalling and oxidative stress, redox- and oxidative stress-based therapies have not yet provided a breakthrough in the treatment of endothelial dysfunction and CVD.

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.

CTRP13 Preserves Endothelial Function by Targeting GTP Cyclohydrolase 1 in Diabetes

Endothelial dysfunction plays a crucial role in the progress of diabetic vasculopathy. C1q/tumor necrosis factor-related protein 13 (CTRP13) is a secreted adipokine that can ameliorate atherosclerosis and vascular calcification. However, the role of CTRP13 in regulating endothelial function in diabetes has yet to be explored. In this study, CTRP13 treatment improved endothelium-dependent relaxation in the aortae and mesenteric arteries of both db/db mice and streptozotocin-injected mice. CTRP13 supplement also rescued the impaired endothelium-dependent relaxation ex vivo in the db/db mouse aortae and in high glucose (HG)-treated mouse aortae. Additionally, CTRP13 treatment reduced reactive oxygen species overproduction and improved nitric oxide (NO) production and endothelial NO synthase (eNOS) coupling in the aortae of diabetic mice and in HG-treated human umbilical vein endothelial cells. Mechanistically, CTRP13 could increase GTP cyclohydrolase 1 (GCH1) expression and tetrahydrobiopterin (BH4) levels to ameliorate eNOS coupling. More importantly, CTRP13 rescued HG-induced inhibition of protein kinase A (PKA) activity. Increased PKA activity enhanced phosphorylation of the peroxisome proliferator-activated receptor α and its recruitment to the GCH1 promoter, thus activating GCH1 transcription and, ultimately, endothelial relaxation. Together, these results suggest that CTRP13 preserves endothelial function in diabetic mice by regulating GCH1/BH4 axis-dependent eNOS coupling, suggesting the therapeutic potential of CTRP13 against diabetic vasculopathy.

Oxidative Stress and Inflammation, Key Targets of Atherosclerotic Plaque Progression and Vulnerability: Potential Impact of Physical Activity

Atherosclerosis, a complex cardiovascular disease, is a leading cause of mortality and morbidity worldwide. Oxidative stress and inflammation are both involved in the development of atherosclerotic plaque as they increase the biological processes associated with this pathology, such as endothelial dysfunction and macrophage recruitment and adhesion. Atherosclerotic plaque rupture leading to major ischemic events is the result of vulnerable plaque progression, which is a result of the detrimental effect of oxidative stress and inflammation on risk factors for atherosclerotic plaque rupture, such as intraplaque hemorrhage, neovascularization, and fibrous cap thickness. Thus, both are key targets for primary and secondary interventions. It is well recognized that chronic physical activity attenuates oxidative stress in healthy subjects via the improvement of antioxidant enzyme capacities and inflammation via the enhancement of anti-inflammatory molecules. Moreover, it was recently shown that chronic physical activity could decrease oxidative stress and inflammation in atherosclerotic patients. The aim of this review is to summarize the role of oxidative stress and inflammation in atherosclerosis and the results of therapeutic interventions targeting them in both preclinical and clinical studies. The effects of chronic physical activity on these two key processes are then reviewed in vulnerable atherosclerotic plaques in both coronary and carotid arteries.

Say NO to ROS: Their Roles in Embryonic Heart Development and Pathogenesis of Congenital Heart Defects in Maternal Diabetes

Congenital heart defects (CHDs) are the most prevalent and serious birth defect, occurring in 1% of all live births. Pregestational maternal diabetes is a known risk factor for the development of CHDs, elevating the risk in the child by more than four-fold. As the prevalence of diabetes rapidly rises among women of childbearing age, there is a need to investigate the mechanisms and potential preventative strategies for these defects. In experimental animal models of pregestational diabetes induced-CHDs, upwards of 50% of offspring display congenital malformations of the heart, including septal, valvular, and outflow tract defects. Specifically, the imbalance of nitric oxide (NO) and reactive oxygen species (ROS) signaling is a major driver of the development of CHDs in offspring of mice with pregestational diabetes. NO from endothelial nitric oxide synthase (eNOS) is crucial to cardiogenesis, regulating various cellular and molecular processes. In fact, deficiency in eNOS results in CHDs and coronary artery malformation. Embryonic hearts from diabetic dams exhibit eNOS uncoupling and oxidative stress. Maternal treatment with sapropterin, a cofactor of eNOS, and antioxidants such as N-acetylcysteine, vitamin E, and glutathione as well as maternal exercise have been shown to improve eNOS function, reduce oxidative stress, and lower the incidence CHDs in the offspring of mice with pregestational diabetes. This review summarizes recent data on pregestational diabetes-induced CHDs, and offers insights into the important roles of NO and ROS in embryonic heart development and pathogenesis of CHDs in maternal diabetes.

Marsdenia tenacissima extract dilated small mesenteric arteries via stimulating endothelial nitric oxide synthase and inhibiting calcium influx

ETHNOPHARMACOLOGICAL RELEVANCE

Marsdenia tenacissima is a traditional Chinese medicine that is known to be effective in combating cancer as well as reducing blood pressure. The efficacy and mechanisms of Marsdenia tenacissima in treating cancer have been well described. However, the potential vasoactivities of Marsdenia tenacissima remain poorly known.

AIM OF THE STUDY

To determine the vasoactive effects of the water-soluble part of marsdenia tenacissima in mesenteric resistance arteries of the mice, and to explore the underlying mechanisms.

MATERIALS AND METHODS

Isometric vessel tension study was used to examine the effects of marsdenia tenacissima extract (MTE) on vasodilation of the mesenteric arteries of mice. KCl, phenylephrine (PE) and 9,11-Dideoxy-11α,9α-epoxymethanoprostaglandin F2α (U46619) were used as vasoconstrictors. Y27632, Nitro-L-arginine methyl ester hydrochloride (L-NAME) and indomethacin were used to explore the underlying mechanisms for the vasoactivities of MTE. Western blot and nitric oxide (NO) assay were used to evaluate the effects of MTE on the activities of endothelial nitric oxide synthase (eNOS).

RESULTS

MTE (5-50 mg/mL), but not vehicle, dose-dependently relaxed the mesenteric arteries constricted with KCl, PE or U46619, in which relaxations to KCl were more pronounced than that to PE or U46619. Pre-incubation of the vessels with MTE (40 mg/mL) reduced the vasoconstrictions caused by calcium influx. Decreasing calcium sensitivity by inhibition of Rho kinase (ROCK) significantly augmented the vasorelaxation of MTE. While, inhibition of endothelial cells by pre-incubation with L-NAME (300 μM) and indomethacin (10 μM) or denudating endothelial cells attenuated vasorelaxations of MTE to KCl, and with a larger potency, to U46619. In both human umbilical vein endothelial cells (HUVECs) and human heart microvascular endothelial cells (HMECs), the phosphorylations of eNOS and the production of NO were significantly enhanced after treatment of MTE for 2, 5, 10, 30 min.

CONCLUSIONS

MTE, the water-soluble part of marsdenia tenacissima, was effective in relaxing mesenteric resistance arteries via inhibiting calcium influx and stimulating eNOS activities.

Knockout of dihydrofolate reductase in mice induces hypertension and abdominal aortic aneurysm via mitochondrial dysfunction

Hypertension and abdominal aortic aneurysm (AAA) are severe cardiovascular diseases with incompletely defined molecular mechanisms. In the current study we generated dihydrofolate reductase (DHFR) knockout mice for the first time to examine its potential contribution to the development of hypertension and AAA, as well as the underlying molecular mechanisms. Whereas the homozygote knockout mice were embryonically lethal, the heterozygote knockout mice had global reduction in DHFR protein expression and activity. Angiotensin II infusion into these animals resulted in substantially exaggerated elevation in blood pressure and development of AAA, which was accompanied by excessive eNOS uncoupling activity (featured by significantly impaired tetrahydrobiopterin and nitric oxide bioavailability), vascular remodeling (MMP2 activation, medial elastin breakdown and adventitial fibrosis) and inflammation (macrophage infiltration). Importantly, scavenging of mitochondrial reactive oxygen species with Mito-Tempo in vivo completely abrogated development of hypertension and AAA in DHFR knockout mice, indicating a novel role of mitochondria in mediating hypertension and AAA downstream of DHFR deficiency-dependent eNOS uncoupling. These data for the first time demonstrate that targeting DHFR-deficiency driven mitochondrial dysfunction may represent an innovative therapeutic option for the treatment of AAA and hypertension.

In Systemic Sclerosis, a Unique Long Non Coding RNA Regulates Genes and Pathways Involved in the Three Main Features of the Disease (Vasculopathy, Fibrosis and Autoimmunity) and in Carcinogenesis

Systemic sclerosis (SSc) is an autoimmune disease characterized by three main features: vasculopathy, immune system dysregulation and fibrosis. Long non-coding RNAs (lncRNAs) may play a role in the pathogenesis of autoimmune diseases and a comprehensive analysis of lncRNAs expression in SSc is still lacking. We profiled 542,500 transcripts in peripheral blood mononuclear cells (PBMCs) from 20 SSc patients and 20 healthy donors using Clariom D arrays, confirming the results by Reverse Transcription Polymerase-chain reaction (RT-PCR). A total of 837 coding-genes were modulated in SSc patients, whereas only one lncRNA, heterogeneous nuclear ribonucleoprotein U processed transcript (ncRNA00201), was significantly downregulated. This transcript regulates tumor proliferation and its gene target hnRNPC (Heterogeneous nuclear ribonucleoproteins C) encodes for a SSc-associated auto-antigen. NcRNA00201 targeted micro RNAs (miRNAs) regulating the most highly connected genes in the Protein-Protein interaction (PPI) network of the SSc transcriptome. A total of 26 of these miRNAs targeted genes involved in pathways connected to the three main features of SSc and to cancer development including Epidermal growth factor (EGF) receptor, ErbB1 downstream, Sphingosine 1 phosphate receptor 1 (S1P1), Activin receptor-like kinase 1 (ALK1), Endothelins, Ras homolog family member A (RhoA), Class I Phosphoinositide 3-kinase (PI3K), mammalian target of rapamycin (mTOR), p38 mitogen-activated protein kinase (MAPK), Ras-related C3 botulinum toxin substrate 1 (RAC1), Transforming growth factor (TGF)-beta receptor, Myeloid differentiation primary response 88 (MyD88) and Toll-like receptors (TLRs) pathways. In SSc, the identification of a unique deregulated lncRNA that regulates genes involved in the three main features of the disease and in tumor-associated pathways, provides insight in disease pathogenesis and opens avenues for the design of novel therapeutic strategies.

Mast cell tetrahydrobiopterin contributes to itch in mice

GTP cyclohydrolase (GCH1) governs de novo synthesis of the enzyme cofactor, tetrahydrobiopterin (BH4), which is essential for biogenic amine production, bioactive lipid metabolism and redox coupling of nitric oxide synthases. Overproduction of BH4 via upregulation of GCH1 in sensory neurons is associated with nociceptive hypersensitivity in rodents, and neuron-specific GCH1 deletion normalizes nociception. The translational relevance is revealed by protective polymorphisms of GCH1 in humans, which are associated with a reduced chronic pain. Because myeloid cells constitute a major non-neuronal source of BH4 that may contribute to BH4-dependent phenotypes, we studied here the contribution of myeloid-derived BH4 to pain and itch in lysozyme M Cre-mediated GCH1 knockout (LysM-GCH1-/- ) and overexpressing mice (LysM-GCH1-HA). Unexpectedly, knockout or overexpression in myeloid cells had no effect on nociceptive behaviour, but LysM-driven GCH1 knockout reduced, and its overexpression increased the scratching response in Compound 48/80 and hydroxychloroquine-evoked itch models, which involve histamine and non-histamine dependent signalling pathways. Mechanistically, GCH1 overexpression increased BH4, nitric oxide and hydrogen peroxide, and these changes were associated with increased release of histamine and serotonin and degranulation of mast cells. LysM-driven GCH1 knockout had opposite effects, and pharmacologic inhibition of GCH1 provided even stronger itch suppression. Inversely, intradermal BH4 provoked scratching behaviour in vivo and BH4 evoked an influx of calcium in sensory neurons. Together, these loss- and gain-of-function experiments suggest that itch in mice is contributed by BH4 release plus BH4-driven mediator release from myeloid immune cells, which leads to activation of itch-responsive sensory neurons.

New Therapeutic Implications of Endothelial Nitric Oxide Synthase (eNOS) Function/Dysfunction in Cardiovascular Disease

The Global Burden of Disease Study identified cardiovascular risk factors as leading causes of global deaths and life years lost. Endothelial dysfunction represents a pathomechanism that is associated with most of these risk factors and stressors, and represents an early (subclinical) marker/predictor of atherosclerosis. Oxidative stress is a trigger of endothelial dysfunction and it is a hall-mark of cardiovascular diseases and of the risk factors/stressors that are responsible for their initiation. Endothelial function is largely based on endothelial nitric oxide synthase (eNOS) function and activity. Likewise, oxidative stress can lead to the loss of eNOS activity or even “uncoupling” of the enzyme by adverse regulation of well-defined “redox switches” in eNOS itself or up-/down-stream signaling molecules. Of note, not only eNOS function and activity in the endothelium are essential for vascular integrity and homeostasis, but also eNOS in perivascular adipose tissue plays an important role for these processes. Accordingly, eNOS protein represents an attractive therapeutic target that, so far, was not pharmacologically exploited. With our present work, we want to provide an overview on recent advances and future therapeutic strategies that could be used to target eNOS activity and function in cardiovascular (and other) diseases, including life style changes and epigenetic modulations. We highlight the redox-regulatory mechanisms in eNOS function and up- and down-stream signaling pathways (e.g., tetrahydrobiopterin metabolism and soluble guanylyl cyclase/cGMP pathway) and their potential pharmacological exploitation.

Tetrahydrobiopterin improves endothelial function in patients with cystic fibrosis

Cystic fibrosis (CF) is a genetic disorder associated with vascular endothelial dysfunction. Nitric oxide (NO) plays a major role in maintaining vascular function, and tetrahydrobiopterin (BH4) is a critical determinant of NO bioavailability. Thus the purpose of this study was to investigate the effects of oral administration of BH4 on endothelial function in patients with CF. Twenty-nine patients with CF (18 ± 8 yr old) and 29 healthy matched controls were recruited. Patients with CF participated in a randomized trial where they received a 5 mg/kg dose of oral BH4 (BH4-5; n = 17) or a 20 mg/kg dose of oral BH4 (BH4-20; n = 12). On a separate visit, a subset of patients from each group was retested following a placebo (PLC; n = 9). Brachial artery flow-mediated dilation (FMD) was used to evaluate vascular endothelial function, and a plasma sample was obtained before and 3 h after treatment. Cultured endothelial cells were treated with plasma to assess NO bioavailability. Baseline FMD was lower in patients compared with controls (5.7 ± 3.4 vs. 8.4 ± 3.5%, respectively, P = 0.005). No change in FMD was observed following PLC or BH4-5 (∆FMD: -0.8 ± 1.9% and -0.5 ± 2.5%; P = 0.273 and 0.132, respectively). Treatment with BH4-20, however, resulted in significant improvements in FMD (∆FMD: 1.1 ± 1.4%) compared with BH4-5 ( P = 0.023) and PLC ( P = 0.017). Moreover, BH4-20 significantly decreased endothelial cell superoxide production and increased NO production. These data suggest that a single oral dose of BH4 at 20 mg/kg improves vascular endothelial function in patients with CF, likely via increased endothelial NO synthase coupling. These findings support the hypothesis that loss of BH4 bioactivity contributes, in part, to endothelial dysfunction in patients with CF. NEW & NOTEWORTHY For the first time, the present study documents that a single dose of oral BH4 can improve vascular endothelial function in patients with cystic fibrosis (CF), and our in vitro data suggest this is via decreasing uncoupled nitric oxide. These data provide insight into the important role of BH4 bioactivity in vascular dysfunction and provide the foundation for further investigation into the chronic effects of BH4 treatment in patients with CF.

Arginine and the metabolic regulation of nitric oxide synthesis in cancer

Nitric oxide (NO) is a signaling molecule that plays important roles in diverse biological processes and thus its dysregulation is involved in the pathogenesis of various disorders. In cancer, NO has broad and sometimes dichotomous roles; it is involved in cancer initiation and progression, but also restricts cancer proliferation and invasion, and contributes to the anti-tumor immune response. The importance of NO in a range of cellular processes is exemplified by its tight spatial and dosage control at multiple levels, including via its transcriptional, post-translational and metabolic regulation. In this Review, we focus on the regulation of NO via the synthesis and availability of its precursor, arginine, and discuss the implications of this metabolic regulation for cancer biology and therapy. Despite the established contribution of NO to cancer pathogenesis, the implementation of NO-related cancer therapeutics remains limited, likely due to the challenge of targeting and inducing its protective functions in a cell- and dosage-specific manner. A better understanding of how arginine regulates the production of NO in cancer might thus support the development of anti-cancer drugs that target this key metabolic pathway, and other metabolic pathways involved in NO production.

Endothelial Cell Tetrahydrobiopterin Modulates Sensitivity to Ang (Angiotensin) II-Induced Vascular Remodeling, Blood Pressure, and Abdominal Aortic Aneurysm

GTPCH (GTP cyclohydrolase 1, encoded by Gch1) is required for the synthesis of tetrahydrobiopterin; a critical regulator of endothelial NO synthase function. We have previously shown that mice with selective loss of Gch1 in endothelial cells have mild vascular dysfunction, but the consequences of endothelial cell tetrahydrobiopterin deficiency in vascular disease pathogenesis are unknown. We investigated the pathological consequence of Ang (angiotensin) II infusion in endothelial cell Gch1 deficient (Gch1fl/fl Tie2cre) mice. Ang II (0.4 mg/kg per day, delivered by osmotic minipump) caused a significant decrease in circulating tetrahydrobiopterin levels in Gch1fl/fl Tie2cre mice and a significant increase in the Nω-nitro-L-arginine methyl ester inhabitable production of H2O2 in the aorta. Chronic treatment with this subpressor dose of Ang II resulted in a significant increase in blood pressure only in Gch1fl/fl Tie2cre mice. This finding was mirrored with acute administration of Ang II, where increased sensitivity to Ang II was observed at both pressor and subpressor doses. Chronic Ang II infusion in Gch1fl/fl Tie2ce mice resulted in vascular dysfunction in resistance mesenteric arteries with an enhanced constrictor and decreased dilator response and medial hypertrophy. Altered vascular remodeling was also observed in the aorta with an increase in the incidence of abdominal aortic aneurysm formation in Gch1fl/fl Tie2ce mice. These findings indicate a specific requirement for endothelial cell tetrahydrobiopterin in modulating the hemodynamic and structural changes induced by Ang II, through modulation of blood pressure, structural changes in resistance vessels, and aneurysm formation in the aorta.

Porphyromonas gingivalis induced inflammatory responses and promoted apoptosis in lung epithelial cells infected with H1N1 via the Bcl‑2/Bax/Caspase‑3 signaling pathway

The aim of the present study was to investigate the effects of Porphyromonas gingivalis (P. gingivalis) on inflammatory cytokine and nitic oxide (NO) production in lung epithelial cells infected with H1N1, and the underlying mechanisms. Lung epithelial cells were co-infected with P. gingivalis and H1N1. The concentrations of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 were detected via an ELISA, and the concentration of NO was detected by the nitrate reductive enzymatic method at 4, 8, 12 and 24 h following infection. The expression levels of inducible NO synthase (iNOS) was detected by western blotting. The apoptotic rate of lung epithelial cells was detected by flow cytometry. The relative protein expression levels of B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax) and caspase-3 in lung epithelial cells were detected by western blotting. Compared with the control group, the concentration of the inflammatory cytokines TNF-α, IL-1β and IL-6 exhibited a significant increase (P<0.05) in the viral-infected, bacterial-infected and co-infected groups. The concentration of NO also increased significantly (P<0.05), along with the rise in the expression levels of iNOS (P<0.05) and the increase in the apoptosis rate of lung epithelial cells (P<0.05). The relative expression levels of caspase-3 and Bax proteins were increased significantly in the viral- and bacterial-infected groups when compared with the control. The relative expression levels of Bcl-2 protein exhibited a significant decrease in lung epithelial cells following the co-infection with P. gingivalis and H1N1 compared with the control (P<0.05). The results of the present study revealed that the combination of P. gingivalis and H1N1 infection in lung epithelial cells may promote the production of inflammatory cytokines and increase NO production, leading to increased levels of apoptosis in lung epithelial cells via the Bcl-2/Bax/caspase-3 signaling pathway.

17β-Estradiol Promotes Angiogenesis of Rat Cardiac Microvascular Endothelial Cells In Vitro

Background

The formation of new blood vessels, known as angiogenesis, is critical for recovery from ischemic heart disease, and estrogen is considered an important factor in this process. Here, we investigated the effects of 17β-estradiol (17β-E₂) on proliferation and migration of cardiac microvascular endothelial cells (CMECs) in vitro.

Material/Methods

Rat CMECs were isolated and cultured with 17β-E2 (0.001–1 μmol/l) in the absence or presence of the estrogen antagonist tamoxifen. Then, the expression level of estrogen receptor alpha was evaluated by using immunofluorescence assay, RT-PCR, and Western blot. Cell proliferation was detected by methyl thiazolyl tetrazolium analysis and the cell migration was verified by a scraping assay and quantified by a Transwell chamber assay. CMEC differentiation was examined using a tube formation assay. Vascular endothelial growth factor (VEGF) secretion was detected by enzyme-linked immunosorbent assay.

Results

CMECs exhibited homogenous, polygonal, exhibited contact inhibition, and had characteristically ovoid nuclei with 1 or 2 nucleoli, and the cytoplasm exhibited red fluorescence after staining for von Willebrand factor. 17β-E2 treatment upregulated estrogen receptor alpha expression in CMECs. 17β-E2 treatment significantly promoted the proliferation, migration, tubular structure formation, and VEGF secretion in CMECs. The maximal proliferation occurred in the presence of 0.01 μmol/l 17β-E2. Furthermore, estrogen and VEGF were found to synergistically stimulate angiogenesis.

Conclusions

Our data show that 17β-E2 promotes angiogenesis in vitro and suggests that estrogen treatment as a novel therapeutic modality in the management of arterial insufficiency.

MicroRNA-126 Priming Enhances Functions of Endothelial Progenitor Cells under Physiological and Hypoxic Conditions and Their Therapeutic Efficacy in Cerebral Ischemic Damage

Endothelial progenitor cells (EPCs) have shown the potential for treating ischemic stroke (IS), while microRNA-126 (miR-126) is reported to have beneficial effects on endothelial function and angiogenesis. In this study, we investigated the effects of miR-126 overexpression on EPCs and explore the efficacy of miR-126-primed EPCs (EPC^miR-126) in treating IS. The effects of miR-126 overexpression on EPC proliferation, migratory, tube formation capacity, reactive oxygen species (ROS) production, and nitric oxide (NO) generation were determined. In in vivo study, the effects of EPC^miR-126 on the cerebral blood flow (CBF), neurological deficit score (NDS), infarct volume, cerebral microvascular density (cMVD), and angiogenesis were determined. Moreover, the levels of circulating EPCs (cEPCs) and their contained miR-126 were measured. We found (1) miR-126 overexpression promoted the proliferation, migration, and tube formation abilities of EPCs; decreased ROS; and increased NO production of EPCs via activation of PI3K/Akt/eNOS pathway; (2) EPC^miR-126 was more effective than EPCs in attenuating infarct volume and NDS and enhancing cMVD, CBF, and angiogenesis; and (3) infusion of EPC^miR-126 increased the number and the level of miR-126 in cEPCs. Our data indicate that miR-126 overexpression enhanced the function of EPCs in vitro and in vivo.

Exercise training induces eNOS coupling and restores relaxation in coronary arteries of heart failure rats

Exercise training (ET) has emerged as a nonpharmacological therapy for cardiovascular diseases because of its helpful milieu for improving vascular function. The aim of the present study was to assess whether ET reverses the alterations in vascular reactivity observed in heart failure (HF)-related coronary arteries and to elucidate the molecular mechanisms involved in these adjustments. Male Wistar rats were subjected to either coronary artery ligation or sham operation. Four weeks after the surgery, rats were divided into two groups: untrained HF (UHF) and exercise-trained HF (THF). ET was conducted on a treadmill for 8 wk. An untrained SO group was included in the study as a normal control. ET restored the impaired acetylcholine (ACh)- and sodium nitroprusside-induced relaxation in coronary arteries to levels of the control. Oxidative stress and reduced nitric oxide (NO) production were observed in UHF, whereas ET restored both parameters to the levels of the control. Expression levels of endothelial NO synthase (eNOS) and soluble guanylyl cyclase subunits were increased in coronary arteries of UHF rats but reduced in THF rats. Tetrahydrobiopterin restored ACh-induced NO production in the UHF group, indicating that eNOS was uncoupled. ET increased the eNOS dimer-to-monomer ratio and expression of GTP cyclohydrolase 1, thus increasing NO bioavailability. Taken together, these findings demonstrate that ET reverses the dysfunction of the NO/soluble guanylyl cyclase pathway present in coronary arteries of HF rats. These effects of ET are associated with increased GTP cyclohydrolase 1 expression, restoration of NO bioavailability, and reduced oxidative stress through eNOS coupling.

NEW & NOTEWORTHY The present study provides a molecular basis for the exercise-induced improvement in coronary arteries function in heart failure. Increasing the expression of GTP cyclohydrolase 1, the rate-limiting enzyme in the de novo biosynthesis of tetrahydrobiopterin, exercise training couples endothelial nitric oxide synthase, reduces oxidative stress, and increases nitric oxide bioavailability and sensitivity in coronary arteries of heart failure rats.

Role of glutathione biosynthesis in endothelial dysfunction and fibrosis

Glutathione (GSH) biosynthesis is essential for cellular redox homeostasis and antioxidant defense. The rate-limiting step requires glutamate-cysteine ligase (GCL), which is composed of the catalytic (GCLc) and the modulatory (GCLm) subunits. To evaluate the contribution of GCLc to endothelial function we generated an endothelial-specific Gclc haplo-insufficient mouse model (Gclc e/+ mice). In murine lung endothelial cells (MLEC) derived from these mice we observed a 50% reduction in GCLc levels compared to lung fibroblasts from the same mice. MLEC obtained from haplo-insufficient mice showed significant reduction in GSH levels as well as increased basal and stimulated ROS levels, reduced phosphorylation of eNOS (Ser 1177) and increased eNOS S-glutathionylation, compared to MLEC from wild type (WT) mice. Studies in mesenteric arteries demonstrated impaired endothelium-dependent vasodilation in Gclc(e/+) male mice, which was corrected by pre-incubation with GSH-ethyl-ester and BH4. To study the contribution of endothelial GSH synthesis to renal fibrosis we employed the unilateral ureteral obstruction model in WT and Gclc(e/+) mice. We observed that obstructed kidneys from Gclc(e/+) mice exhibited increased deposition of fibrotic markers and reduced Nrf2 levels. We conclude that the preservation of endothelial GSH biosynthesis is not only critical for endothelial function but also in anti-fibrotic responses.

Does endothelial tetrahydrobiopterin control the endothelial NO synthase coupling state in arterial resistance arteries?

LINKED ARTICLE

This article is a Commentary on Chuaiphichai S, Crabtree MJ, McNeill E, Hale AB, Trelfa L, Channon KM et al. (2017). A key role for tetrahydrobiopterin-dependent endothelial NOS regulation in resistance arteries: studies in endothelial cell tetrahydrobiopterin-deficient mice. Br J Pharmacol 174: 657-671. https://doi.org/10.1111/bph.13728.

Transgenic overexpression of GTP cyclohydrolase 1 in cardiomyocytes ameliorates post-infarction cardiac remodeling

GTP cyclohydrolase 1 (GCH1) and its product tetrahydrobiopterin play crucial roles in cardiovascular health and disease, yet the exact regulation and role of GCH1 in adverse cardiac remodeling after myocardial infarction are still enigmatic. Here we report that cardiac GCH1 is degraded in remodeled hearts after myocardial infarction, concomitant with increases in the thickness of interventricular septum, interstitial fibrosis, and phosphorylated p38 mitogen-activated protein kinase and decreases in left ventricular anterior wall thickness, cardiac contractility, tetrahydrobiopterin, the dimers of nitric oxide synthase, sarcoplasmic reticulum Ca²⁺ release, and the expression of sarcoplasmic reticulum Ca²⁺ handling proteins. Intriguingly, transgenic overexpression of GCH1 in cardiomyocytes reduces the thickness of interventricular septum and interstitial fibrosis and increases anterior wall thickness and cardiac contractility after infarction. Moreover, we show that GCH1 overexpression decreases phosphorylated p38 mitogen-activated protein kinase and elevates tetrahydrobiopterin levels, the dimerization and phosphorylation of neuronal nitric oxide synthase, sarcoplasmic reticulum Ca²⁺ release, and sarcoplasmic reticulum Ca²⁺ handling proteins in post-infarction remodeled hearts. Our results indicate that the pivotal role of GCH1 overexpression in post-infarction cardiac remodeling is attributable to preservation of neuronal nitric oxide synthase and sarcoplasmic reticulum Ca²⁺ handling proteins, and identify a new therapeutic target for cardiac remodeling after infarction.

A key role for tetrahydrobiopterin-dependent endothelial NOS regulation in resistance arteries: studies in endothelial cell tetrahydrobiopterin-deficient mice

BACKGROUND AND PURPOSE

The cofactor tetrahydrobiopterin (BH4) is a critical regulator of endothelial NOS (eNOS) function, eNOS-derived NO and ROS signalling in vascular physiology. To determine the physiological requirement for de novo endothelial cell BH4 synthesis for the vasomotor function of resistance arteries, we have generated a mouse model with endothelial cell-specific deletion of Gch1, encoding GTP cyclohydrolase 1 (GTPCH), an essential enzyme for BH4 biosynthesis, and evaluated BH4-dependent eNOS regulation, eNOS-derived NO and ROS generation.

EXPERIMENTAL APPROACH

The reactivity of mouse second-order mesenteric arteries was assessed by wire myography. High performance liquid chromatography was used to determine BH4, BH2 and biopterin. Western blotting was used for expression analysis.

KEY RESULTS

Gch1fl/fl Tie2cre mice demonstrated reduced GTPCH protein and BH4 levels in mesenteric arteries. Deficiency in endothelial cell BH4 leads to eNOS uncoupling, increased ROS production and loss of NO generation in mesenteric arteries of Gch1fl/fl Tie2cre mice. Gch1fl/fl Tie2cre mesenteric arteries had enhanced vasoconstriction to U46619 and phenylephrine, which was abolished by L-NAME. Endothelium-dependent vasodilatations to ACh and SLIGRL were impaired in mesenteric arteries from Gch1fl/fl Tie2cre mice, compared with those from wild-type littermates. Loss of eNOS-derived NO-mediated vasodilatation was associated with increased eNOS-derived H2 O2 and cyclooxygenase-derived vasodilator in Gch1fl/fl Tie2cre mesenteric arteries.

CONCLUSIONS AND IMPLICATIONS

Endothelial cell Gch1 and BH4-dependent eNOS regulation play pivotal roles in maintaining vascular homeostasis in resistance arteries. Therefore, targeting vascular Gch1 and BH4 biosynthesis may provide a novel therapeutic target for the prevention and treatment of microvascular dysfunction in patients with cardiovascular disease.