NO Production In Endothelial Cells Research Articles

Endothelial Hemoglobin Alpha Mediates Iron Regulation of Endothelial Nitric Oxide

Iron deficiency anemia (IDA) is a common comorbidity in cardiovascular disease. Previous clinical studies have found iron deficiency anemia (IDA) increases endothelial NO signaling and attributed this change to the reduction in circulating hemoglobin. However, it has been shown in ex vivo preparations that endothelial NO signaling is unaffected by the presence of erythrocytes suggesting changes in circulating hemoglobin do not alter NO signaling. Our lab has previously shown the hemoglobin-α (Hbα) is expressed in the endothelium of small arteries and scavenges NO. We hypothesized endothelial Hbα, rather than blood hemoglobin is responsible for the increased NO signaling in IDA. We first tested this hypothesis in a mouse model of IDA in which we were able to replete vascular iron stores. Male and female C57BL/6 mice were fed an iron deficient (2-6 ppm Fe) or nutrient matched control diet (48 ppm Fe) beginning at weaning. IDA mice underwent phlebotomies (10% blood volume) at 9 and 11 weeks old. To restore vascular iron stores, a subset of IDA mice received a single i.p. injection of iron dextran (FeDex; 20 mg/kg) at 12 weeks. All measurements were taken one week later. As expected, IDA mice had low blood hemoglobin, and FeDex did not rescue the anemia but did rescue vascular iron stores as measured by ferritin light chain protein. To investigate NO signaling, we used laser speckle contrast imaging to measure changes in in vivo blood flow in response to the NO synthase inhibitor L-NAME. The magnitude of the response to L-NAME is an indicator of NO signaling. IDA mice exhibited an exaggerated response to L-NAME indicating increased NO signaling. FeDex treatment restored the L-NAME response back to control levels suggesting reduced vascular iron stores, rather than the anemia itself increased NO signaling. In order to investigate the role of endothelial Hbα, we repeated these studies in endothelial specific Hbα knockout mice (Hba1fl/fl-Cdh5-CreERT2+). Lack of endothelial Hbα did not prevent the increased response to L-NAME in IDA mice but did prevent the rescue by FeDex. This suggests a model in which endothelial Hba participates in regulating NO in response to iron but not the increased NO in IDA. Because Hbα does not explain the initial increase in NO, we have begun investigating other anemia-associated NO stimulators. Erythropoetin (EPO) is known to stimulate NO production in endothelial cells and is elevated in our anemia model regardless of FeDex treatment. Future work will investigate the role of EPO in regulating NO in IDA. University of Virginia Basic and Translational Research Training Grant T32 007284 (LSD, MAL, SAL); NIH HL088554; LaunchPad; Lipedema Foundation; AHA Predoctoral Fellowship (MAL). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Dual effect of amitriptyline in the control of vascular tone: Direct blockade of calcium channel in smooth muscle cells and reduction of TLR4-dependent NO production in endothelial cells

Background and purposeAmitriptyline (AM) is a classical and typical tricyclic antidepressant drug. Despite its well-known effects on the nervous system, it has been described to work as a TLR4 antagonist and several clinical works suggested some unexpected cardiovascular effects. The role of amitriptyline on vascular tone is not clear, thus we hypothesized that amitriptyline has a double effect on vascular tone by both endothelial TLR4-dependent nitric oxide down-regulation and calcium channel blockade in smooth muscle cells. Experimental approachChanges in isometric tension were recorded on a wire myograph. NO production was evaluated by fluorescence microscopy and flow cytometry in the mouse aorta and EAhy926 cells using DAF fluorescence intensity. Calcium influx was evaluated in A7r5 cells by flow cytometry. Western blot was used to analyze eNOS and nNOS phosphorylation. Key resultsAM reduced PE-induced contraction by calcium influx diminution in smooth muscle cells (F/F0 = 225.6 ± 15.9 and 118.6 ± 17.6 to CT and AM, respectively). AM impaired Ach-dependent vasodilation (Emax = 95.8 ± 1.4; 78.1 ± 1.8; 60.4 ± 2.9 and −7.4 ± 1.0 for CT, 0.01, 0,1 and 1 μmol/L AM, respectively) through reduction of calcium influx and NO availability and TLR4 antagonism in a concentration-dependent manner. AM or TLR4 gene deletion significantly reduced NO production (Fluorescence = 9503 ± 871.7, 2561 ± 282, 4771 ± 728 and 1029 ± 103 to CT, AM, TLR4−/− and AM + TLR4−/−, respectively) by an increase in nNOSser852 and reduction in eNOSser1177 phosphorylation in endothelial cells. Conclusions and implicationsOur data show that amitriptyline impaired vascular function through two different mechanisms: blockade of TLR4 in endothelial cells and consequent decrease in NO production and calcium influx reduction in smooth muscle and endothelial cells. We also suggest, for the first time, nNOS activity reduction by AM in non-neuronal cells.

Spinosin ameliorates insulin resistance by suppressing reactive oxygen species-associated inflammation.

Objective(s):Spinosin is the predominant C-glycoside flavonoid derived from the seeds of Zizyphus jujuba var. Spinosa (Rhamnaceae). The present study aimed to investigate the effects of spinosin on insulin resistance (IR) in vascular endothelium.Materials and Methods:The anti-IR effect of spinosin was evaluated in a high-fat diet (HFD) treated mice model. The effects of spinosin pretreatment on reactive oxygen species (ROS)-associated inflammation in Human umbilical vein endothelial cells (HUVEC) were evaluated by western blot analysis and reverse transcription-polymerase chain reaction. The effect of spinosin on insulin-mediated endothelium-dependent vasodilation of rat aortae was further evaluated. Results:Spinosin at 20 mg/kg alleviates increased mice’s body weight, fasting serum glucose, oral glucose tolerance, serum insulin, insulin resistance index, and serum lipid of HFD-treated mice. Spinosin at 20 μM suppressed ROS overproduction, and inhibited ROS-related HUVEC inflammation by inhibiting mRNA expression of tumor necrosis factor-α and interleukin-6. In addition, spinosin at 0.1 μM showed a vasodilation effect of isoprenaline-pretreated rat aortae and increased insulin-mediated NO production in endothelial cells. These effects were shown to be related to the spinosin regulating serine/tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) facilitated/phosphoinositide 3-kinase (PI3K) signaling. Conclusion:Spinosin may ameliorate IR and ROS-associated inflammation, and increase endothelial NO production by mediating IRS-1/PI3K/endothelial nitric oxide synthase (eNOS) pathway.

Human Tissue Kallikrein 1 Is Downregulated in Elderly Human Prostates and Possesses Potential In Vitro Antioxidative and Antifibrotic Effects in Rodent Prostates.

Objective The aim of the present study was to investigate the protective effects and mechanisms of KLK1 on aging-related prostate alterations and search clues about the application of KLK1 to the treatment of human BPH. Methods Thirty-six rats including 26 male wild-type SD rats and 10 transgenic rats were fed to 3- or 18-month-old and divided into three groups: young WTR (yWTR) as the control (n = 16), aged WTR (aWTR) (n = 10), and aged TGR (aTGR) (n = 10). The prostates of the three groups of rats (10 rats per group) were harvested to evaluate the levels of KLK1 expression, oxidative stress, fibrosis, and involved signaling pathways, such as NO/cGMP, COX-2/PTGIS/cAMP, and TGF-β1/RhoA/ROCK1, via quantitative PCR, Western blot, histological examinations, and ELISA. Moreover, the remaining 6 yWTRs were sacrificed to obtain primary prostate fibroblast and aortic endothelial cells, and a coculture system was built with the cells for the verification of above signaling pathways in vitro. And the direct effects of bradykinin on prostate cells were detected by MTT experiment. Prostate specimens of 47 patients (age from 48 to 92 years) undergoing BPH surgery were collected after approval. Histological examinations and KLK1 IHC were preformed to analyze the relationship between KLK1 expression and age and prostate fibrosis. Results The human KLK1 gene only existed and was expressed in aTGR. The prostate of young rats expressed more KLK1 than the aged and the expression of KLK1 in prostate decreased with age in humans (r = −0.347, P = 0.018). Compared to the aWTR group, the yWTR and aTGR groups showed milder fibrosis, less oxidative stress, upregulated NO/cGMP, and COX-2/PTGIS/cAMP signaling pathways and inhibited TGF-β1/RhoA/ROCK1 signaling pathway. In the coculture system, KLK1 suppressed TGF-β1-mediated fibroblast-to-myofibroblast transdifferentiation via cleaving LMWK to produce the BK which upregulate eNOS expression and NO production in endothelial cells. BK not only slightly stimulated the proliferation ability of prostatic stromal cells but also upregulated iNOS and inhibited TGF-β1 expression in them. Conclusion KLK1 protects prostate from oxidative stress and fibrosis via amplified NO/cGMP signal in aged rats. The decrease of KLK1 expression with aging is laying the groundwork for the application of KLK1 to the treatment of human BPH. The current experimental data showed that the side effects of KLK1 on the prostate cell were not obvious.

Upregulation of angiotensin converting enzyme 2 by shear stress reduced inflammation and proliferation in vascular endothelial cells

BackgroundShear stress (SS) and renin-angiotensin system (RAS) play important roles in endothelium homeostasis. Previous studies demonstrated that pulsatile shear stress (PSS) reduced the expression and activity of angiotensin-converting enzyme (ACE), however, the effect of SS on angiotensin-converting enzyme 2 (ACE2) expression is unclear. Methods and resultsWe exposed cultured endothelial cells (ECs) to distinct patterns of SS for indicated time points, Western blot and RT-PCR were used to determine the ACE2 expression; En Face staining was used to detect ACE2 expression in vivo; cell proliferation and apoptosis were determined by BrdU staining and TUNEL staining, respectively; the production of NO was detected by a commercial kit; the promoter activity of ACE2 was determined by a Dual-Luciferase Reporter Assay System, inhibitors of ACE2 and signaling pathway were added to the medium 1 h prior for PSS. Our data showed PSS induced a sustained ACE2 expression, but OSS only induced a transient ACE2 expression. The PSS-induced ACE2 expression was higher than that of OSS both in vitro and in vivo. The PSS-induced ACE2 was involved in inhibiting proliferation and inflammation, as well as promoting NO production in ECs. PSS significantly increased ACE2 expression at transcriptional level via activating AMPKα2-KLF2 pathway. ConclusionsOur results suggest PSS promotes ACE2 expression via AMPKα2-KLF2 pathway to maintain the normal EC functions.

CR6-interacting factor 1 deficiency reduces endothelial nitric oxide synthase activity by inhibiting biosynthesis of tetrahydrobiopterin

Downregulation of CR6 interacting factor 1 (CRIF1) has been reported to induce mitochondrial dysfunction, resulting in reduced activity of endothelial nitric oxide synthase (eNOS) and NO production in endothelial cells. Tetrahydrobiopterin (BH4) is an important cofactor in regulating the balance between NO (eNOS coupling) and superoxide production (eNOS uncoupling). However, whether the decreased eNOS and NO production in CRIF1-deficient cells is associated with relative BH4 deficiency-induced eNOS uncoupling remains completely unknown. Our results showed that CRIF1 deficiency increased eNOS uncoupling and depleted levels of total biopterin and BH4 by reducing the enzymes of BH4 biosynthesis (GCH-1, PTS, SPR, and DHFR) in vivo and vitro, respectively. Supplementation of CRIF1-deficient cells with BH4 significantly increased the recovery of Akt and eNOS phosphorylation and NO synthesis. In addition, scavenging ROS with MitoTEMPO treatment replenished BH4 levels by elevating levels of GCH-1, PTS, and SPR, but with no effect on the level of DHFR. Downregulation of DHFR synthesis regulators p16 or p21 in CRIF1-deficient cells partially recovered the DHFR expression. In summary, CRIF1 deficiency inhibited BH4 biosynthesis and exacerbated eNOS uncoupling. This resulted in reduced NO production and increased oxidative stress, which contributes to endothelial dysfunction and is involved in the pathogenesis of cardiovascular diseases.

Antihypertensive Effects of Rg3-Enriched Korean Vitamin Ginseng in Spontaneously Hypertensive Rats

Ginseng is well known to treat various diseases. Ginsenoside Rg3 exhibits a variety of pharmacological activities including cardiovascular protective effects. Vitamins utilized as supplements have minimal interactions with other drugs making them attractive targets for therapeutics. Here, we prepared Rg3-enriched Korean ginseng catalyzed by vitamin (REKVG) and evaluated its ability to improve hypertension in spontaneously hypertensive rats (SHRs). The ginsenoside content in both Korean Red ginseng (KRG) and REKVG were analyzed using high-performance liquid chromatography (HPLC). Male SHRs and Wistar-Kyoto rats (WKYs) were randomly divided into 6 groups (WKY saline, WKY KRG, WKY REKVG, SHR saline, SHR KRG, and SHR REKVG). KRG and REKVG were orally administered once daily to the rats at a dose of 10 mg/kg for 6 weeks, and blood pressure was measured in live rats using the tail-cuff method. Human umbilical vein endothelial cells were used for the in vitro experiment. HPLC chromatograms revealed that the concentration of ginsenoside Rg3 in REKVG was much higher than that in KRG. The administration of REKVG significantly decreased the systolic blood pressure in SHRs at the end of 6 weeks as compared to KRG. Further, REKVG use resulted in a dose-dependent increase in Akt and endothelial nitric oxide synthase (eNOS) phosphorylation and NO production in endothelial cells. In addition, the administration of REKVG significantly increased Akt and eNOS phosphorylation and increased plasma NO levels in SHRs. We conclude that REKVG effectively lowers the blood pressure in rats and therefore could be considered for use in preventing or improving hypertension.

White mulberry fruit polysaccharides enhance endothelial nitric oxide production to relax arteries in vitro and reduce blood pressure in vivo

Mulberry fruit polysaccharides have demonstrated excellent anti-inflammatory, antioxidant, hypolipidemic, and hypoglycemic properties. This study tested the effect of white mulberry fruit polysaccharides (WMFPs) on blood pressure. WMFPs induced endothelium-dependent relaxation in rat mesenteric arteries and NO production in endothelial cells, both of which were reversed by the NO synthase inhibitor Nω-nitro-l-arginine methyl ester hydrochloride, a phosphoinositide 3-kinase inhibitor LY294002, a cell-permeable Ca2+ chelator (1,2-bis (o-aminophenoxy) ethane-N,N,N’,N’-tetraacetic acid (acetoxymethyl ester)), and inhibitors of molecules downstream of NO, including the soluble guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, the potassium channel inhibitor tetraethylammonium chloride, the large conductance calcium-activated potassium channel-specific inhibitor iberiotoxin, and the KATP channel inhibitor glibenclamide. Intravenous injection of WMFPs reduced mean arterial blood pressure in both normotensive Sprague-Dawley and spontaneously hypertensive rats through enhanced endothelial NO production. This study demonstrated that WMFPs induce endothelium-dependent relaxation in rat mesenteric arteries to regulate blood pressure, suggesting that development of WMFPs as a novel antihypertensive agent is warranted.

Light-induced formation of NO in endothelial cells by photoactivatable NADPH analogues targeting nitric-oxide synthase

BackgroundNitric-oxide synthases (NOS) catalyze the formation of NO using NADPH as electron donor. We have recently designed and synthesized a new series of two-photon absorbing and photoactivatable NADPH analogues (NT). These compounds bear one or two carboxymethyl group(s) on the 2′- or/and 3′-position(s) of the ribose in the adenosine moiety, instead of a 2′-phosphate group, and differ by the nature of the electron donor in their photoactivatable chromophore (replacing the nicotinamide moiety). Here, we addressed the ability of NTs to photoinduce eNOS-dependent NO production in endothelial cells. MethodsThe cellular fate of NTs and their photoinduced effects were studied using multiphoton fluorescence imaging, cell viability assays and a BODIPY-derived NO probe for NO measurements. The eNOS dependence of photoinduced NO production was addressed using two NOS inhibitors (NS1 and L-NAME) targeting the reductase and the oxygenase domains, respectively. ResultsWe found that, two compounds, those bearing a single carboxymethyl group on the 3′-position of the ribose, colocalize with the Golgi apparatus (the main intracellular location of eNOS) and display high intracellular two-photon brightness. Furthermore, a eNOS-dependent photooxidation was observed for these two compounds only, which is accompanied by a substantial intracellular NO production accounting for specific photocytotoxic effects. ConclusionsWe show for the first time that NT photoactivation efficiently triggers electron flow at the eNOS level and increases the basal production of NO by endothelial cells. General significanceEfficient photoactivatable NADPH analogues targeting NOS could have important implications for generating apoptosis in tumor cells or modulating NO-dependent physiological processes.

Sigma‐1 receptor agonists elicit arteriolar dilation via Akt/eNOS activation, and also have endothelial barrier protective properties

Sigma‐1 receptors (σ1) have previously gained considerable attention pertaining to neuroprotection through its actions on calcium homeostasis, and the mitochondria‐associated ER membrane domain. Our laboratory recently showed that the σ1 agonist afobazole causes an endothelial NO‐dependent decrease in contraction amplitude. However, little is known about the mechanisms and functions of σ1 receptor in endothelial cells. In the current study, we investigated how σ1 agonists impact brain arteriolar tone and the Akt/eNOS pathway. Parenchymal arterioles were isolated from brains of Sprague‐Dawley rats and mounted onto glass micropipettes in a 37 °C bath containing albumin‐physiological salt solution. The nonselective σ agonist afobazole was applied to the bath at concentrations of 50, 100, 150, 200, and 250 μM in the presence or absence of the σ1 antagonist BD1047. The selective σ1 agonist, PRE‐084 was used to stimulate human umbilical vein endothelial cells (HUVEC), in which phosphorylation of endothelial NO synthase (eNOS) or Akt phosphorylation on their activation sites (S1177 and S473, respectively) were evaluated by western blotting. NO production was measured by fluorescence microscopy in cells loaded with the indicator dye DAF‐FM. Trans‐endothelial electrical resistance (TER) was used to determine the ability of PRE‐084 to attenuate disruption of endothelial barrier function caused by the the mitochondrial function inhibitors CCCP and antimycin‐A, or the inflammatory cytokine IL‐1β. The results show that afobazole significantly dilated rat brain arterioles, which was inhibited by the σ1 antagonist BD‐1047. Selective activation of σ1 with PRE‐084 significantly increased eNOS phosphorylation on S1177 and this was diminished in the presence of BD‐1047. Akt phosphorylation on S473 following PRE‐084 treatment was also enhanced. In addition, afobazole and PRE‐084 enhanced NO production in endothelial cells. PRE‐084 significantly attenuated decreases in TER caused by IL‐1β or CCCP, but not antimycin‐A, suggesting a potential barrier‐protective role for σ1 receptor, with some limitations that may be related to the source of mitochondrial dysfunction during inflammation. Collectively, our results suggest that σ1 receptor activation can cause vasodilation via the Akt/eNOS pathway in endothelial cells, and that σ1 may enhance endothelial barrier function under inflammatory conditions.Support or Funding InformationSupported by NIH grant R01GM120774.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Nitric Oxide‐Mediated Nanomolar Vasodilator Potencies of Glycosylated Anthocyanins do not Correlate with Redox Potential

Calafate is an endemic Patagonian shrub (Berberis Microphylia); its berries are rich in polyphenols, including 3‐glycosylated anthocyanins (GA, delphinidin, petunidin or malvidin) or mono or disaccharide conjugated quercetin (Q). The chemical profile of Calafate berries is well characterized and indicates its high redox potential; pharmacological properties are virtually unknown. From ethno‐pharmaceutical reports we hypothesized that Calafate polyphenols are vasodilators and ascertained whether this effect is related to their cell antioxidant activity (CAA).Vascular responses of GA and Q were assessed perfusing the intact rat arterial mesenteric bed or following endothelium denudation. The role of NO was assessed in mesenteries perfused with an eNOS inhibitor (L‐NNA). Luminally accessible NO was determined by chemiluminescence; intracellular NO was quantified by DAF fluorescence in isolated mesentery endothelial cells. Antioxidant capacity was quantified either by 1,1‐Diphenyl‐2‐picryl‐hydrazyl antioxidant assay (DPPH) or by CAA assessment. Extracellular ATP was assessed by chloroacetaldehyde derivatization to yield fluorescent purines; the nucleotide is related to NO production in endothelial cells.GA proved potent vasodilators with EC50s of 84.1 ± 0.3, 65.8 ± 0.4 and 17.7 ± 0.1 nM, respectively; aglycones exhibited similar EC50s. The maximal effect of GA did not exceed 56 ± 3.7% efficacy compared to acetylcholine (EC50 was 43.4 ± 0.1 nM with 100% efficacy) while the Q EC50 was 12.8 ± 0.1 μM, with 99 ± 4.1%. The GA‐induced vasodilatation was totally endothelium‐dependent; while the Q response showed partial endothelium‐dependence. The degree of GA vasodilatation correlated with luminal NO (r2 = 0.83), confirming NO as the final intracellular signal. 30 μM Q increased both extracellular ATP secretion from endothelial cells plus intracellular DAF‐fluorescence (P<0.05), an indication that part of the Q response involves NO as the final effector. While Q exhibited the highest antioxidant effect in both the DPPH or CAA (p<0.01), the GA showed a 60‐fold lower potential than Q in the CAA test, indicating that the CAA is not related to its vasodilator profile, which apparently relies on eNOS allosteric modulation.In sum, GA are novel and potent endothelium‐dependent vasodilators, linked to modulation of NO production.Support or Funding InformationFunded by FONDECYT 117‐0842 and 21141226 to CC and CEDENNA FB0807This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A769662 Inhibits Insulin-Stimulated Akt Activation in Human Macrovascular Endothelial Cells Independent of AMP-Activated Protein Kinase.

Protein kinase B (Akt) is a key enzyme in the insulin signalling cascade, required for insulin-stimulated NO production in endothelial cells (ECs). Previous studies have suggested that AMP-activated protein kinase (AMPK) activation stimulates NO synthesis and enhances insulin-stimulated Akt activation, yet these studies have largely used indirect activators of AMPK. The effects of the allosteric AMPK activator A769662 on insulin signalling and endothelial function was therefore examined in cultured human macrovascular ECs. Surprisingly, A769662 inhibited insulin-stimulated NO synthesis and Akt phosphorylation in human ECs from umbilical veins (HUVECs) and aorta (HAECs). In contrast, the AMPK activators compound 991 and AICAR had no substantial inhibitory effect on insulin-stimulated Akt phosphorylation in ECs. Inhibition of AMPK with SBI-0206965 had no effect on the inhibition of insulin-stimulated Akt phosphorylation by A769662, suggesting the inhibitory action of A769662 is AMPK-independent. A769662 decreased IGF1-stimulated Akt phosphorylation yet had no effect on VEGF-stimulated Akt signalling in HUVECs, suggesting that A769662 attenuates early insulin/IGF1 signalling. The effects of A769662 on insulin-stimulated Akt phosphorylation were specific to human ECs, as no effect was observed in the human cancer cell lines HepG2 or HeLa, as well as in mouse embryonic fibroblasts (MEFs). A769662 inhibited insulin-stimulated Erk1/2 phosphorylation in HAECs and MEFs, an effect that was independent of AMPK in MEFs. Therefore, despite being a potent AMPK activator, A769662 has effects unlikely to be mediated by AMPK in human macrovascular ECs that reduce insulin sensitivity and eNOS activation.

Commutative regulation between endothelial NO synthase and insulin receptor substrate 2 by microRNAs

Endothelial NO synthase (eNOS) expression is regulated by a number of transcriptional and post-transcriptional mechanisms, but the effects of competing endogenous RNAs (ceRNAs) on eNOS mRNA and the underlying mechanisms are still unknown. Our bioinformatic analysis revealed three highly expressed eNOS-targeting miRNAs (miR-15b, miR-16, and miR-30b) in human endothelial cells (ECs). Among the 1103 mRNA targets of these three miRNAs, 15 mRNAs share a common disease association with eNOS. Gene expression and correlation analysis in patients with cardiovascular diseases identified insulin receptor substrate 2 (IRS2) as the most correlated eNOS-ceRNA. The expression levels of eNOS and IRS2 were coincidentally increased by application of laminar shear but reduced with eNOS or IRS2 siRNA transfection in human ECs, which was impeded by Dicer siRNA treatment. Moreover, luciferase reporter assay showed that these three miRNAs directly target the 3'UTR of eNOS and IRS2. Overexpression of these three miRNAs decreased, whereas inhibition of them increased, both mRNA and protein levels of eNOS and IRS2. Functionally, silencing eNOS suppressed the Akt signal pathway, while IRS2 knockdown reduced NO production in ECs. Thus, we identified eNOS and IRS2 as ceRNAs and revealed a novel mechanism explaining the coincidence of metabolic and cardiovascular diseases.

Endothelium-dependent vasodilatory effect of Smilax china Linn. water extract via PI3K/Akt signaling

Objective: The objective of this study was to investigate the pharmacological effect of Smilax china Linn. water extract (SCLWE) on vascular relaxation and its underlying biochemical mechanisms.Methodology: Isolated rat aortic rings were pre-constricted with phenylephrine (PE). This was followed by the cumulative addition of SCLWE. The effect of endothelial nitric oxide and PI3K/Akt on the SCLWE-induced vasodilation was investigated by the pretreatment of endothelium-intact aortic strips with or without NG-nitro-L-arginine methyl ester (L-NAME) or wortmanin before constriction with PE.Results: Treatment of PE (1 μM)-pre-contracted aortic strips with SCLWE induced endothelium-dependent relaxation, which was attenuated by L-NAME and wortmanin. Further studies using HUVECs indicated that nitrite production, eNOS and PI3K/PKB (Akt) phosphorylations were increased after exposure to SCLWE but was attenuated by pretreatment with wortmanin.Conclusion: These results suggest that SCLWE induces vasodilation by augmenting NO production in endothelial cells via PI3K/Akt-dependent eNOS phosphorylation.

Endothelial/Nitric Oxide Regulation of Brown Adipose Tissue Activating Lipokine, 12, 13-diHOME and Its Antiatherogenic Actions

Activation of brown adipose tissue (BAT) has been shown to decrease atherosclerosis due to its systemic actions to improve insulin sensitivity and facilitate weight loss. However, the direct effect of BAT cytokines on vascular arterial function and atherosclerosis has not been studied. We have reported that enhancing insulin’s action on the endothelial cells (EC) by overexpressing IRS1 to the EC on ApoE-/- background (ECIRS1/ApoE-/- mice) greatly increased insulin induced NO production and decreased atherosclerosis. ECIRS1 mice exhibited significant increases in BAT mass and activation when exposed to cold temperature (5°C), in parallel with elevation of BAT lipokine, 12,13-diHOME levels at basal, regular chow (RD) or high fat diet (HFD) compared to wild type mice (WT) by 188±33% and 187±39%, respectively, (P<0.01). Recently, 12,13 diHOME has been reported to activate BAT (Nat. Med, 2017. Elevation of 12, 13 diHOME induced by cold temperature was inhibited by L-NAME, an inhibitor of NO. In EC, the addition of 12,13-diHOME increase pAkt from 1-100nM, but without affecting peNOS and pErk. However, oxLDL-induced pErk activity and VCAM-1 expression were reduced in 12,13-diHOME (1nM) treated EC. Further, 12,13-diHOME also increased intracellular calcium concentration with parallel elevation in NO production in EC. Functionally, 12,13-diHOME(1nM-10nM) increased vascular relaxation in myography experiments significantly by 7.5%-24%. Using antibody arrays for assessing the effects of 12,13-diHOME on NO production in EC, signaling studies showed 12,13-diHOME activated mTOR, CREB and HSP27 (by 50, 2.5, and 4 fold, respectively) and down-regulated tyrosine-protein kinase (HCK) and GSK3α/β (by 30% and 26%, p<0.05) in EC. These studies for the first time showed that insulin’s action in EC can regulate BAT lipokine 12,13-diHOME expression in a positive feedback loop to increase NO and increase vasodilation with associated decrease in atherosclerosis. Disclosure K. Park: None. Q. Li: None. M. Lynes: None. H. Yokomizo: None. T. Shinjo: None. R. St-Louis: None. J. Fu: None. C. Rask-Madsen: Research Support; Self; Novo Nordisk A/S. Y. Tseng: Other Relationship; Self; Chugai Pharmaceutical Co., Ltd.. Research Support; Self; MedImmune. G.L. King: Research Support; Self; Sanofi-Aventis.

IFN-α Negatively Regulates the Expression of Endothelial Nitric Oxide Synthase and Nitric Oxide Production: Implications for Systemic Lupus Erythematosus.

Systemic lupus erythematosus (SLE) is a known risk factor for endothelial dysfunction. Murine and human lupus studies revealed a role for IFN-α in vascular abnormalities associated with impaired blood vessel dilation. However, the impact of IFN-α on mediators that induce vasodilation and modulate inflammation, including endothelial NO synthase (eNOS) and NO bioavailability, are unknown. The objectives of this study were to determine how IFN-α promotes endothelial dysfunction in SLE, focusing on its regulation of eNOS and NO production in endothelial cells. We demonstrate that IFN-α promotes an endothelial dysfunction signature in HUVECs that is characterized by transcription suppression and mRNA instability of eNOS complemented by upregulation of MCP1 and VCAM1 These changes are associated with IFN-inducible gene expression. IFN-α impairs insulin-mediated NO production, and altered gene expression resulted from eNOS instability, possibly due to enhanced miR-155 expression. IFN-α significantly impaired NO production in insulin-stimulated HUVECs. IFN-α treatment also led to enhanced neutrophil adhesion. Our study introduces a novel pathway by which IFN-α serves as a proatherogenic mediator through repression of eNOS-dependent pathways. This could promote the development of endothelial dysfunction and cardiovascular disease in SLE.

Computational analysis of interactions of oxidative stress and tetrahydrobiopterin reveals instability in eNOS coupling

In cardiovascular and neurovascular diseases, an increase in oxidative stress and endothelial dysfunction has been reported. There is a reduction in tetrahydrobiopterin (BH4), which is a cofactor for the endothelial nitric oxide synthase (eNOS), resulting in eNOS uncoupling. Studies of the enhancement of BH4 availability have reported mixed results for improvement in endothelial dysfunction. Our understanding of the complex interactions of eNOS uncoupling, oxidative stress and BH4 availability is not complete and a quantitative understanding of these interactions is required. In the present study, we developed a computational model for eNOS uncoupling that considers the temporal changes in biopterin ratio in the oxidative stress conditions. Using the model, we studied the effects of cellular oxidative stress (Qsupcell) representing the non-eNOS based oxidative stress sources and BH4 synthesis (QBH4) on eNOS NO production and biopterin ratio (BH4/total biopterins (TBP)). Model results showed that oxidative stress levels from 0.01 to 1nM·s−1 did not affect eNOS NO production and eNOS remained in coupled state. When the Qsupcell increased above 1nM·s−1, the eNOS coupling and NO production transitioned to an oscillatory state. Oxidative stress levels dynamically changed the biopterin ratio. When Qsupcell increased from 1 to 100nM·s−1, the endothelial cell NO production, TBP levels and biopterin ratio reduced significantly from 26.5 to 2nM·s−1, 3.75 to 0.002μM and 0.99 to 0.25, respectively. For an increase in BH4 synthesis, the improvement in NO production rate and BH4 levels were dependent on the extent of cellular oxidative stress. However, a 10-fold increase in QBH4 at higher oxidative stresses did not restore the NO-production rate and the biopterin ratio. Our mechanistic analysis reveals that a combination of enhancing tetrahydrobiopterin level with a reduction in cellular oxidative stress may result in significant improvement in endothelial dysfunction.

Racial Differences in CRP Receptor and Influence on eNOS Bioactivity and NO Production in Endothelial Cells

BackgroundC‐reactive protein (CRP) is an independent biomarker of inflammation and cardiovascular disease (CVD). CRP interacts directly with endothelial cells. CRP decreases endothelial nitric oxide synthase (eNOS) expression and bioactivity and decreases nitric oxide (NO) production. Race/ethnicity is significantly associated with CRP and CVD risks. Thus, the purpose of this study was to assess the racial differences concerning the CRP‐induced biological effects in endothelial cells.MethodsHuman umbilical vein endothelial cells (HUVECs) from four African American (AA) donors and four Caucasian (CA) donors were cultured and incubated with CRP to assess its effects on eNOS bioactivity and NO production measured in cell culture media.ResultsAA and CA HUVECs responded differently to CRP incubation. We report significant increase in FcγRIIB receptor expression under both basal and CRP incubation conditions in AA HUVECs cells (~2‐fold difference, p < .01, Fig 1). This may contribute to the racial differences of CRP‐induced effects on endothelial cells with AA HUVECs showing greater impairment of eNOS expression and bioactivity (~2‐fold decrease, p < .01, Fig 2) and reduced NO production basally (CA: 11.09 ± 1.002 AA: 8.254 ± 0.5285 μmol/L; mean ± SEM, p=0.04). CRP incubation reduced NO production significantly in both AA and CA (CA: 3.947 ± 0.7360 AA: 2.756 ± 0.4368 μmol/L, p <.0001, Fig 3).ConclusionA better understanding of the racial differences in endothelial function will help to improve CVD prevention and treatment. The results suggest that the racial differences in CRP‐induced pro‐inflammatory and pro‐atherogenic biological effects on endothelial cells may be partially due to the differential expression of FcγRIIB receptor which may contribute to the disproportionate CVD rates in AA.Support or Funding InformationACSM Doctoral Student Research Grant to Chenyi Ling

Amyloidogenic Medin Induces Endothelial Dysfunction and Vascular Inflammation Through the Receptor for Advanced Glycation Endproducts

AimsMedin is a common amyloidogenic protein in humans, especially in older individuals. It has been implicated in the development of arterial degenerative changes associated with vascular aging. The mechanisms underlying medin‐induced vascular injury remain unknown. The aims are to assess medin's effects on human peripheral and central arteriole endothelial function, nitrative stress and vascular inflammation and identify potential mechanisms of injury.Methods and ResultsEx‐vivo human adipose and leptomeningeal arterioles were exposed (1 hour) to medin (0.1, 1 or 5 μM) without or with FPS‐ZM1 (100 μM, receptor for advanced endglycation products [RAGE]‐specific inhibitor) and endothelial function (acetylcholine dilator response) was compared to baseline control. Medin's effect on adipose arteriole smooth muscle function was tested by comparing post‐exposure dilator response to DETA NONOate (a nitric oxide [NO] donor) compared to baseline response. Human umbilical vein endothelial cells were exposed to medin (20 hours) without or with FPS‐ZM1 and oxidative and nitrative stress, cell viability and pro‐inflammatory signaling measures were obtained. Medin caused impaired endothelial function (versus baseline response to 10−4 M acetylcholine: −38.6±6.7% and −35.0±8.9% in adipose and leptomeningeal arterioles, respectively, each p<0.05) in human adipose and leptomeningeal arterioles. Medin did not affect adipose arteriole dilator response to DETA NONOate. Medin‐induced endothelial dysfunction was reversed by RAGE inhibitor. Medin decreased endothelial cell NO production and cell viability, increased peroxynitrite, superoxide production and profoundly increased gene and protein expression of interleukin‐6 and interleukin‐8 via activation of nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NFκB). These effects were reversed by RAGE inhibitor.ConclusionsMedin causes human microvascular endothelial dysfunction, oxidative and nitrative stress and pro‐inflammatory signaling mediated via RAGE. The discovery of this novel mechanism of injury may have implications in our understanding of and development of treatments to reverse vascular aging.Support or Funding InformationThe work was supported by National Institutes Health (NIA R21AG044723, NINDS U24NS072026, NIA P30AG19610, NIA RO1AG019795); Veterans Affairs Merit grant (I01BX007080); British Heart Foundation (FS/12/61/29877); the Arizona Department of Health Services (contrast 211002); the Arizona Biomedical Research Commission (4001, 0011, 05‐901 and 1001); Michael J. Fox Foundation for Parkinson's Research and Amyloidosis Foundation. The study was based on work supported by the Department of Veterans Affairs and VA employment.

AMP-Activated Protein Kinase Attenuates High Salt-Induced Activation of Epithelial Sodium Channels (ENaC) in Human Umbilical Vein Endothelial Cells

Recent studies suggest that the epithelial sodium channel (ENaC) is expressed in the endothelial cells. To test whether high salt affects the NO production via regulation of endothelial ENaC, human umbilical vein endothelial cells (HUVECs) were incubated in solutions containing either normal or high sodium (additional 20 mM NaCl). Our data showed that high sodium treatment significantly increased α-, β-, and γ-ENaC expression levels in HUVECs. Using the cell-attached patch-clamp technique, we demonstrated that high sodium treatment significantly increased ENaC open probability (P O). Moreover, nitric oxide synthase (eNOS) phosphorylation (Ser 1177) levels and NO production were significantly decreased by high sodium in HUVECs; the effects of high sodium on eNOS phosphorylation and NO production were inhibited by a specific ENaC blocker, amiloride. Our results showed that high sodium decreased AMP-activated kinase (AMPK) phosphorylation in endothelial cells. On the other hand, metformin, an AMPK activator, prevented high sodium-induced upregulation of ENaC expression and P O. Moreover, metformin prevented high salt-induced decrease in NO production and eNOS phosphorylation. These results suggest that high sodium stimulates ENaC activation by negatively modulating AMPK activity, thereby leading to reduction in eNOS activity and NO production in endothelial cells.