Endothelium-derived Hyperpolarizing Factor Research Articles

Evaluation of the component’s contribution in endothelium-dependent acetylcholine-induced relaxation of the rat aorta

The regulation of rat aorta vascular tone involves various factors, including endothelium-derived hyperpolarization factor (EDHF), nitric oxide (NO), prostaglandins, and sensory nerves. While these elements can function independently, their pathways intersect at various points, complicating the assessment of their individual contributions. The aim of this study was to establish the numerical contributions of EDHF, NO, prostaglandins, and also the effect of the sensory nerve on acetylcholine-induced relaxation on the background of phenylephrine preconstriction using contraction and relaxation measurements in Wistar rat thoracic aorta. EDHF, whose action is mediated through potassium channels, emerges as a crucial regulator. Blockage of inward rectifier potassium (KIR) channels integral to EDHF significantly abolishes 50% of the relaxation amplitude in comparison to control conditions. Endothelial TRPV4 channel, exhibiting a fine-tuning role, contributes to a 25% reduction in the amplitude of acetylcholine-induced relaxation in comparison to control relaxation. NO demonstrates its vasodilatory prowess, with NO blockage eliminating 77% of the residual relaxation effect after KIR blockage. Blockage of prostaglandin functions, modulated by cyclooxygenase 1, reduces relaxation by 44% in comparison to control relaxation. Desensitization of sensory nerves with capsaicin, shows a minor yet significant role, in the reduction of acetylcholine-induced relaxation amplitude by 10%. In conclusion, we established that the main element of acetylcholine-induced relaxation is EDHF with approximately 50% of relaxation amplitude depending on it.

Nitric oxide, endothelium-derived hyperpolarizing factor, and smooth muscle-dependent mechanisms contribute to magnesium-dependent vascular relaxation in mouse arteries.

Magnesium (Mg2+ ) is a vasorelaxant. The underlying physiological mechanisms driving this vasorelaxation remain unclear. Studies were designed to test the hypothesis that multiple signaling pathways including nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) in endothelial cells as well as Ca2+ antagonization and TRPM7 channels in vascular smooth muscle cells mediate Mg2+ -dependent vessel relaxation. To uncover these mechanisms, force development was measured exvivo in aorta rings from mice using isometric wire myography. Concentration responses to Mg2+ were studied in intact and endothelium-denuded aortas. Key findings were confirmed in second-order mesenteric resistance arteries perfused exvivo using pressure myography. Effects of Mg2+ on NO formation were measured in Chinese Hamster Ovary (CHO) cells, isolated mesenteric vessels, and mouse urine. Mg2+ caused a significant concentration-dependent relaxation of aorta rings. This relaxation was attenuated significantly in endothelium-denuded aortas. The endothelium-dependent portion was inhibited by NO and cGMP blockade but not by cyclooxygenase inhibition. Mg2+ stimulated local NO formation in CHO cells and isolated mesenteric vessels without changing urinary NOx levels. High extracellular Mg2+ augmented acetylcholine-induced relaxation. SKCa and IKCa channel blockers apamin and TRAM34 inhibited Mg2+ -dependent relaxation. The endothelium-independent relaxation in aorta rings was inhibited by high extracellular Ca2+ . Combined blockade of NO, SKCa , and IKCa channels significantly reduced Mg2+ -dependent dilatation in mesenteric resistance vessels. In mouse conductance and resistance arteries Mg2+ -induced relaxation is contributed by endothelial NO formation, EDHF pathways, antagonism of Ca2+ in smooth muscle cells, and additional unidentified mechanisms.

Roles of endothelial and smooth muscle cell dysfunction and vasa vasorum in vasomotor disorders in ischemia with no obstructive coronary artery disease

Recently, the importance has emerged of ischemia with no obstructive coronary artery disease (INOCA), for which endothelial and vascular smooth muscle cell (VSMC) dysfunctions and alterations in coronary vasa vasorum are involved. Regarding endothelial vasodilator functions, both endothelium-derived nitric oxide and endothelium-derived hyperpolarizing factor play important roles in modulating vascular tone, especially in the microcirculation. Recent studies have suggested systemic endothelial dysfunction in INOCA. Regarding VSMC dysfunction, Rho-kinase has been identified as a key molecular mechanism of VSMC hyperconstriction in INOCA. Finally, recent advances of coronary imaging have demonstrated the important role of altered adventitial vasa vasorum functions in INOCA.

Postnatal development of extracellular matrix and vascular function in small arteries of the rat.

Introduction: Vascular extracellular matrix (ECM) is dominated by elastic fibers (elastin with fibrillin-rich microfibrils) and collagens. Current understanding of ECM protein development largely comes from studies of conduit vessels (e.g., aorta) while resistance vessel data are sparse. With an emphasis on elastin, we examined whether changes in postnatal expression of arteriolar wall ECM would correlate with development of local vasoregulatory mechanisms such as the myogenic response and endothelium-dependent dilation. Methods: Rat cerebral and mesenteric arteries were isolated at ages 3, 7, 11, 14, 19days, 2months, and 2years. Using qPCR mRNA expression patterns were examined for elastin, collagen types I, II, III, IV, fibrillin-1, and -2, lysyl oxidase (LOX), and transglutaminase 2. Results: Elastin, LOX and fibrillar collagens I and III mRNA peaked at day 11-14 in both vasculatures before declining at later time-points. 3D confocal imaging for elastin showed continuous remodeling in the adventitia and the internal elastic lamina for both cerebral and mesenteric vessels. Myogenic responsiveness in cannulated cerebral arteries was detectable at day 3 with constriction shifted to higher intraluminal pressures by day 19. Myogenic responsiveness of mesenteric vessels appeared fully developed by day 3. Functional studies were performed to investigate developmental changes in endothelial-dependent dilation. Endothelial-dependent dilation to acetylcholine was less at day 3 compared to day 19 and at day 3 lacked an endothelial-derived hyperpolarizing factor component that was evident at day 19. Conclusion: Collectively, in the rat small artery structural remodeling and aspects of functional control continue to develop in the immediate postnatal period.

17α-ethinylestradiol modulates endothelial function in ovariectomized rat carotid arteries

17α-ethinylestradiol (EE2), a derivative of 17β-estradiol (E2), is a potent estrogenic substance that is used as the estrogenic component of oral contraceptives (OCPs). However, women who take OCPs have an increased risk of cardiovascular events. Since few studies have examined EE2 endothelial effects, we explored the effects of EE2 on endothelial function in ovariectomized and isoflavone-free rats. After ovariectomy, 12-week-old female Sprague-Dawley rats were assigned to EE2, E2 or control groups. After 16 weeks, the EE2 and E2 groups were orally administered EE2 (8.3 μg/day) and E2 (12.6 μg/day) for 4 weeks, respectively. At 18 weeks, endothelial denudation of the left common carotid arteries was performed, and they were harvested at 20 weeks. The rats in the EE2 and E2 groups exhibited significantly decreased body weights and significantly increased uterine weights, respectively, but no differences were observed between the EE2 and E2 groups. The EE2 and E2 groups showed significantly enhanced acetylcholine-induced endothelium-dependent relaxation, with apamin plus charybdotoxin inhibiting only the EE2 group. Endothelial nitric oxide (NO) synthase expression was significantly higher in the EE2 group than in the control, but lower than in the E2 group. The intima-to-media ratio of denuded arteries was significantly lower in the E2 group than in the other groups, suggesting that NO decreased in the EE2 group compared to the E2 group. We conclude that EE2 has a weaker ability than E2 to produce NO and, for the first time, we demonstrate the ability of EE2 to enhance the activity of endothelial-derived hyperpolarizing factor.

Alterations in Vessel Hemodynamics Across Uncomplicated Pregnancy.

Pregnancy is marked by the onset of rapid hemodynamic alterations in order to accommodate the needs of the developing fetus. Arterial stiffness is an independent predictor of cardiovascular events and mortality, and its measurement in clinical practice has been recommended. It follows a U-shaped curve in uncomplicated pregnancy, decreasing to a nadir in mid-pregnancy and rising at term. Systemic vasodilation occurs due to elevated nitric oxide, prostacyclin, endothelium-derived hyperpolarizing factor, estrogen, progesterone, and relaxin. Vascular resistance decreases to a nadir in mid-pregnancy, while endothelial function is enhanced starting in the first trimester. Plasma volume increases by about 50%, and total red blood cell mass increases by up to 40%. Cardiac output increases by up to 45%, at first due primarily to elevated stroke volume, then mainly due to increased heart rate. Along with echocardiography, cardiac magnetic resonance imaging is safe for use in pregnancy. It may assess cardiac function more accurately than echocardiography, and may be indicated in specific clinical cases. Moreover, blood pressure decreases to a nadir in mid-pregnancy and rises to near preconception values postpartum. An appreciation of the vascular changes occurring in healthy pregnancy can aid in the prediction and diagnosis of pregnancy complications, such as preeclampsia and other hypertensive disorders of pregnancy, and inform treatment. In particular, noninvasive arterial stiffness/hemodynamics assessment provides unique clinical information beyond blood pressure and traditional maternal characteristics, and can signal a need for further testing, or be used in combination with other tests to predict or diagnose complications of pregnancy.

S-11-5: CLINICAL IMPLICATION OF FMD

A healthy endothelium maintains vascular tone and structure by regulating the balance between vasodilation and vasoconstriction, growth inhibition and growth promotion, antithrombosis and prothrombosis, anti-inflammation and proinflammation, and also antioxidation and pro-oxidation. The vascular endothelium is involved in the release of various vasodilators, including nitric oxide (NO), prostaglandins, and endothelium-derived hyperpolarizing factor as well as vasoconstrictors. NO plays an important role in the regulation of vascular tone, the inhibition of platelet aggregation, and the suppression of smooth muscle cell proliferation. Cardiovascular diseases are associated with endothelial dysfunction. In addition, endothelial dysfunction is an early feature of atherosclerosis and vascular diseases in humans. Therefore, it is clinically important to estimate the degree of endothelial dysfunction. Several methods have been used to assess endothelial function in humans. Measurement of flow-mediated vasodilation (FMD) using an ultrasound is noninvasive and is an accurate indicator of NO production. Measurement of FMD is widely performed as an index of conduit artery endothelial function. Several investigators have shown that FMD is an independent predictor for cardiovascular outcomes. It is thought that FMD is useful for surrogate endpoint of cardiovascular outcomes and index of atherosclerotic treatment. However, the evaluation technique by the FMD measurement system still requires skills in measurement of the vessel diameter by an ultrasound system, and is difficult to handle. In addition, there is a problem in that the technique requires a large-scale apparatus and lacks in simplicity. In this session, we would like to explain in detail concerning the methods of assessing and clinical importance of endothelial function, especially FMD.

Effect of Nonsteroidal Mineralocorticoid Receptor Blocker Esaxerenone on Vasoreactivity to an Endothelial Stimulator in Superior Mesenteric Arteries of Type 2 Diabetic Goto-Kakizaki Rat.

Endothelial dysfunction contributes to cardiometabolic disorders, including hypertension, obesity, and type 2 diabetes. Esaxerenone is a selective, nonsteroidal, high-affinity mineralocorticoid receptor blocker recently approved in Japan for the treatment of hypertension. Although imbalanced signaling between vasorelaxant and vasocontractile factors induced by endothelial stimulation is often observed in type 2 diabetic vessels, the effects of esaxerenone on endothelium-dependent responses in type 2 diabetes remain unclear. The aim of this study was to investigate the effect of esaxerenone on endothelium-dependent responses in superior mesenteric arteries isolated from type 2 diabetic Goto-Kakizaki (GK) rats. It was found that esaxerenone (3 mg/kg/d for 4 weeks, per os (p.o.)) partially ameliorated acetylcholine (ACh)-induced endothelium-derived hyperpolarizing factor (EDHF)-type relaxation and NS309, a potent activator of small- and intermediate-conductance Ca2+-activated K+ channels, -induced relaxation, and reduced ACh-induced endothelium-derived contracting factor (EDCF)-mediated contraction. These results suggest that esaxerenone ameliorates endothelial function through increased EDHF signaling and suppressed EDCF signaling.

Two Weeks Of Remote Ischemic Preconditioning Improved Cutaneous Microvascular Responses To Post-occlusive Reactive Hyperemia

PURPOSE: Repeated remote ischemic preconditioning (RIPC), induced by intermittent periods of ischemia and reperfusion in a limb body, improves non-nitric oxide (NO)-mediated endothelial-dependent cutaneous vasodilation. Post-occlusive reactive hyperemia (PORH) occurs following the release of a brief arterial occlusion and is principally mediated by non-NO mediated vasodilatory factors such as prostaglandins, sensory nerve axon reflex, and endothelium-derived hyperpolarizing factors (EDHFs). However, the role of repeated bouts of RIPC on the PORH response is unknown. The purpose of this study was to test whether two weeks of RIPC improves PORH elicited cutaneous microvascular hyperemia responses. METHODS: The study was conducted with twenty-one participants (Control; 24 ± 5 yr old, 4 M/4F, n = 8, RIPC; 22 ± 2 yr old, 7 M/6F, n = 13). The RIPC group received RIPC daily sessions over a two-week period (3 intervals of 4 days with RIPC followed by a 1 day break). Each RIPC session consisted of 4 repetitions of 5-minute arm blood flow occlusion interspersed by 5-minute reperfusion. PORH was elicited by brachial artery occlusion for 5 minutes by inflating an arm cuff to 200 mmHg, and the cutaneous hyperemic response was measured after cuff release. Skin blood flow measurements were collected with laser speckle contrast image (LSCI) before and after the repeated RIPC intervention. The control group did not receive RIPC but underwent repeated PORH measurements two weeks later. RESULTS: Both Time to Peak (Tp) and max/time improved after two weeks of RIPC (Tp; 16.5 ± 2.1 vs.15.2 ± 2.9 s, Pre vs. Post, p < 0.05, max/time; 0.11 ± 0.03 vs. 0.13 ± 0.04 CVC/s, Pre vs. Post, p < 0.05). The control group did not change after 2 weeks. CONCLUSIONS: These data suggest that non-NO mediated vasodilator responses in the skin microvasculature may be affected with 2 weeks of repeated RIPC.

Effect of Oral Contraceptive Phase on Mechanisms of Cutaneous Microvascular Function

While the effect of oral contraceptive (OC) use on endothelial function has been previously studied, precise mechanisms of endothelial function in this group of women remains unclear. The purpose of this study was to investigate the contribution of cyclooxygenase (COX), endothelial‐derived hyperpolarizing factors (EDHF), and nitric oxide (NO) to cutaneous microvascular function in women during the low hormone (LH) and high hormone (HH) phases of OC. Five young, healthy women taking monophasic, combined OC of any generation visited the lab twice: once during the LH (d 1‐2 of placebo pills) and once during the HH phase (d 3‐6+ of active pills). Participants were instrumented with three microdialysis fibers, and each site was randomized as control (lactated Ringer's), COX inhibition (10 mM ketorolac), or EDHF inhibition (50 mM tetraethylammonium, TEA). Laser‐Doppler flowmetry and local heaters were used to measure skin blood flow and induce local thermal hyperemia, respectively. Each site was heated from 33°C to 39°C at a rate of 0.1°C/sec. Once a plateau to local heating was established, 20 mM L‐NAME, a NO synthase inhibitor, was infused at each site to quantify NO‐dependent vasodilation. Maximal vasodilation was induced by heating the skin to 43°C and infusing 28 mM sodium nitroprusside. Data are mean ± SD. For baseline, there was a main effect of OC phase (p = 0.03) and treatment (p &lt; 0.001) but no interaction effect (p = 0.21) such that baseline was increased at COX‐inhibited sites (23 ± 3 %CVCmax) compared with control (14 ± 6 %CVCmax; p = 0.03) during the HH phase. For initial peak, there was a main effect of treatment (p &lt; 0.001) but no effect of OC phase (p = 0.99) or interaction effect (p = 0.59) such that initial peak was decreased at EDHF‐inhibited sites during the HH phase (17 ± 6 %CVCmax) compared with control (51 ± 23 %CVCmax; p = 0.02). For local heating plateau, there was a main effect of treatment (p &lt; 0.001) but no effect of OC phase (p = 0.28) or interaction effect (p = 0.21) such that plateau was decreased at EDHF‐inhibited sites during both phases (LH: 18 ± 12 %CVCmax; HH: 20 ± 9 %CVCmax) compared with respective control (LH: 63 ± 13 %CVCmax; HH: 67 ± 23 %CVCmax) and ketorolac sites (LH: 58 ± 21 %CVCmax; HH: 71 ± 12 %CVCmax; all comparisons: p &lt; 0.01). For %NO, there was no observed effect of OC phase (p = 0.77), treatment (p = 0.21), or interaction (p = 0.09). While not statistically significant, there was a large effect size for %NO between LH and HH phases at control sites (LH: 72 ± 15 %NO; HH: 50 ± 23 %NO; Cohen’s d = 1.05). During the LH phase, large effect sizes were observed between control and TEA (48 ± 14 %NO; d = 1.65) sites and control and ketorolac (54 ± 22 %NO; d = 0.96) sites. During the HH phase, a large effect size was observed between control and ketorolac (69 ± 17 %NO; d = 0.94) sites. These preliminary data suggest mechanisms underlying endothelial function vary across OC phase in women. While overall endothelial function (i.e., magnitude of local heating plateau) is similar between OC phases, there may be basal constriction (i.e., increased baseline with COX inhibition) and reduced NO‐dependent dilation during the HH phase. This shift in mechanisms underlying endothelial function in women using OC may contribute to cardiovascular health outcomes.

Small Vessel Disease: Ancient Description, Novel Biomarkers.

Small vessel disease (SVD) is one of the most frequent pathological conditions which lead to dementia. Biochemical and neuroimaging might help correctly identify the clinical diagnosis of this relevant brain disease. The microvascular alterations which underlie SVD have common origins, similar cognitive outcomes, and common vascular risk factors. Nevertheless, the arteriolosclerosis process, which underlines SVD development, is based on different mechanisms, not all completely understood, which start from a chronic hypoperfusion state and pass through a chronic brain inflammatory condition, inducing a significant endothelium activation and a consequent tissue remodeling action. In a recent review, we focused on the pathophysiology of SVD, which is complex, involving genetic conditions and different co-morbidities (i.e., diabetes, chronic hypoxia condition, and obesity). Currently, many points still remain unclear and discordant. In this paper, we wanted to focus on new biomarkers, which can be the expression of the endothelial dysfunction, or of the oxidative damage, which could be employed as markers of disease progression or for future targets of therapies. Therefore, we described the altered response to the endothelium-derived nitric oxide-vasodilators (ENOV), prostacyclin, C-reactive proteins, and endothelium-derived hyperpolarizing factors (EDHF). At the same time, due to the concomitant endothelial activation and chronic neuroinflammatory status, we described hypoxia-endothelial-related markers, such as HIF 1 alpha, VEGFR2, and neuroglobin, and MMPs. We also described blood–brain barrier disruption biomarkers and imaging techniques, which can also describe perivascular spaces enlargement and dysfunction. More studies should be necessary, in order to implement these results and give them a clinical benefit.

An Externally-Applied, Natural-Mineral-Based Novel Nanomaterial IFMC Improves Cardiopulmonary Function under Aerobic Exercise.

Nanotechnology has widespread applications in sports; however, there are very few studies reporting the use of nanotechnology to enhance physical performance. We hypothesize that a natural-mineral-based novel nanomaterial, which was developed from Japanese hot springs, might overcome the limitations. We examined if it could enhance physical performance. We conducted a treadmill exercise test on 18 students of athletic clubs at Fukushima University, Japan, and measured heart rate, oxygen consumption, maximal oxygen consumption, CO production, and respiratory quotient 106 times in total. The results showed that the elevation of heart rate was significantly suppressed in the natural-mineral-based nanomaterial group, while no differences were observed in oxygen consumption, maximal oxygen consumption, CO production, and respiratory quotient between groups. To our knowledge, this result is the first evidence where an improvement of cardiovascular and pulmonary functions was induced by bringing a natural-mineral-based nanomaterial into contact with or close to a living body without pharmacological intervention or physical intervention. This could open new avenue of biomedical industries even in an eco-friendly direction. The precise mechanisms remain a matter for further investigation; however, we may assume that endothelial NO synthase, hemoglobin and endothelium-derived hyperpolarizing factor are deeply involved in the improvement of cardiovascular and pulmonary functions.

Menthol-induced activation of TRPM8 receptors increases cutaneous blood flow across the dermatome.

Topical menthol-based analgesics increase skin blood flow (SkBF) through transient receptor potential melastatin 8 (TRPM8) receptor-dependent activation of sensory nerves and endothelium-derived hyperpolarization factors. It is unclear if menthol-induced TRPM8 activation mediates a reflex change in SkBF across the dermatome in an area not directly treated with menthol. The purpose of this study was to determine the effects of localized topical menthol application on SkBF across a common dermatome. We hypothesized that SkBF would be increased with menthol at the site of application and across the dermatome (contralateral limb) through a spinal reflex mechanism. In a double blind, placebo controlled, cross-over design, 15 healthy participants (7 men; age=22±1yrs) were treated with direct application (3ml over 8×13cm) of 5% menthol gel (Biofreeze™) or placebo gel on the L4 dermatome, separated by 48h. Red blood cell flux was measured using laser Doppler flowmetry over the area of application, on the contralateral leg of the same dermatome, and in a separate dermatome (L5/S1) to serve as control. Cutaneous vascular conductance was calculated for each measurement site (CVC=flux/MAP). At baseline there were no differences in CVC between menthol and placebo gels, or among sites (all p>0.05). After 30±6min, CVC increased at the treated site with menthol (0.12±0.02 vs. 1.36±0.19flux/mmHg, p<0.01) but not the placebo (0.10±0.01 vs. 0.18±0.04flux/mmHg, p=0.91). There was a modest increase in CVC at the contralateral L4 dermatome with menthol gel (0.16±0.04 vs. 0.29±0.06flux/mmHg, p<0.01), but not placebo (0.11±0.02 vs. 0.15±0.03flux/mmHg, p=0.41). There was no effect on SkBF from either treatments at the L5/S1 control dermatome (both, p>0.05), suggesting the lack of a systemic response. In conclusion, menthol containing topical analgesic gels increased SkBF at the treated site, and modestly throughout the dermatome. These data suggest menthol-induced activation of the TRPM8 receptors induces an increase in SkBF across the area of common innervation through a localized spinal reflex mechanism.

How do we kNOw the individual contribution of eNOS and nNOS for cerebral blood flow regulation?

How do we kNOw the individual contribution of eNOS and nNOS for cerebral blood flow regulation?

Hypothetical Mechanism of Exercise-Induced Acute Kidney Injury Associated with Renal Hypouricemia.

Renal hypouricemia (RHUC) is a hereditary disease that presents with increased renal urate clearance and hypouricemia due to genetic mutations in the urate transporter URAT1 or GLUT9 that reabsorbs urates in the renal proximal tubule. Exercise-induced acute kidney injury (EIAKI) is known to be a complication of renal hypouricemia. In the skeletal muscle of RHUC patients during exhaustive exercise, the decreased release of endothelial-derived hyperpolarization factor (EDHF) due to hypouricemia might cause the disturbance of exercise hyperemia, which might increase post-exercise urinary urate excretion. In the kidneys of RHUC patients after exhaustive exercise, an intraluminal high concentration of urates in the proximal straight tubule and/or thick ascending limb of Henle’s loop might stimulate the luminal Toll-like receptor 4–myeloid differentiation factor 88–phosphoinositide 3-kinase–mammalian target of rapamycin (luminal TLR4–MyD88–PI3K–mTOR) pathway to activate the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome and may release interleukin-1β (IL-1β), which might cause the symptoms of EIAKI.

Endothelial TrkB receptor activation controls vascular tone of rat middle cerebral artery

Little is known on the cerebrovascular BDNF (brain-derived neurotrophic factor)/TrkB (tropomyosin related kinase B) pathway. This study investigated the contribution of endogenous endothelial BDNF to the control of vascular tone of rat middle cerebral artery (MCA) and the capacity of exogenous agonist of TrkB receptors to induce their relaxation. Endothelial cells constitutively expressed both BDNF and activated TrkB receptors. Supporting endothelial BDNF as an autocrine regulator of basal myogenic tone, incubation of MCA with the TrkB antagonist cyclotraxin B induced contraction as observed with incubation in the presence of inhibitors of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) production. Exposure of MCA with the TrkB agonist LM22A-4 that increased expression of TrkB receptors phosphorylated at tyrosine 816 induced relaxation of preconstricted MCA (EC50 6.7 × 10−8 mol/L) as efficiently than acetylcholine (EC50 5.3 × 10−8 mol/L). Finally, endothelium removal, exposure to a TrkB antagonist or to inhibitors of NO and EDHF production prevented the relaxant effect of LM22A-4. In conclusion, our study identified endothelial BDNF as a new autocrine regulator of vascular tone of MCA, thus making the endothelial BDNF/TrkB pathway an attractive target for strategies aiming to improve blood supply to the brain.

Tofacitinib improved peripheral endothelial dysfunction and brain-derived neurotrophic factor levels in the rat adjuvant-induced arthritis model.

This study aimed to explore the effect of Tofacitinib on endothelial dysfunction and cerebral levels of brain-derived neurotrophic factor (BDNF) in the adjuvant-induced arthritis (AIA) rat model. Tofacitinib (10 mg/kg twice a day) or vehicle was administered from the first signs of inflammation. Arthritis scores were daily monitored while other parameters including endothelial function assessed from aortic rings, radiographic scores, blood pressure, heart rate, circulating levels of triglycerides, cholesterol, and interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), IL-17A, and cerebral BDNF levels were determined after 3 weeks of treatment. A group of non-AIA rats served as controls. In AIA rats, as compared with vehicle, Tofacitinib significantly reduced arthritis and radiographic scores, decreased total cholesterol and low-density lipoprotein cholesterol (LDL-C), but changed neither blood pressure nor heart rate and proinflammatory cytokines levels. It also fully restored acetylcholine (Ach)-induced relaxation (p < 0.05) through increased nitric oxide (NO) synthase activity, reduced BH4 deficiency and O2 -° production, decreased cyclo-oxygenase-2 (COX-2)/arginase activities, and enhanced endothelium-derived hyperpolarizing factor (EDHF) production. These effects translated into a decrease in atherogenic index and an elevation of BDNF levels in the prefrontal cortex (p < 0.05) and hippocampus (p < 0.001). The present study identified Tofacitinib as an efficient therapeutic option to reduce cardiovascular risk and improve BDNF-dependent cognition in arthritis.

Reduced Function of Endothelial Nitric Oxide and Hyperpolarization in Artery Grafts with Poor Runoff

BackgroundThe endothelium regulates vascular tonus by releasing nitric oxide (endothelium-derived nitric oxide, EDNO) and hyperpolarizing factor (endothelium-derived hyperpolarizing factor, EDHF). In vein grafts with poor runoff, lack of function of these factors causes severe intimal hyperplasia. This study evaluated how the functions of EDNO and EDHF are altered in artery grafts under poor runoff conditions. Materials and MethodsThe right common carotid arteries of rabbits were excised and implanted in their original positions as autogenous grafts under normal runoff conditions (“nonoccluded grafts”) or poor runoff conditions (“poor runoff grafts”). Histochemical changes, acetylcholine (ACh)-induced effects on endothelium-dependent relaxation and smooth muscle cell (SMC) hyperpolarization were examined. ResultsBoth artery graft types displayed negligible intimal hyperplasia. In the absence and presence of an EDNO synthase inhibitor, ACh-induced relaxation was lower in grafts with poor runoff than in nonoccluded grafts. Furthermore, ACh-induced but not nonreceptor agonist A23187-induced SMC hyperpolarization was lower in the poor runoff graft group than in the nonoccluded graft group. ConclusionsUnlike in those in vein grafts, the functions of EDNO and EDHF in autogenous carotid artery grafts under poor runoff conditions were reduced but partly maintained. In such artery grafts, intimal hyperplasia caused by surgical operation was not present. These results may explain some of the mechanisms underlying the improved patency of artery grafts compared with vein grafts.

Calcitonin Gene Related Peptide, Adrenomedullin, and Adrenomedullin 2 Function in Uterine Artery During Human Pregnancy.

Calcitonin gene-related peptide (CGRP) and its family members adrenomedullin (ADM) and adrenomedullin 2 (ADM2; also known as intermedin) support vascular adaptions in rat pregnancy. This study aimed to assess the relaxation response of uterine artery (UA) for CGRP, ADM, and ADM2 in nonpregnant and pregnant women and identify the involved mechanisms. (1) Segments of UA from nonpregnant women that were precontracted with U46619 (1μM) in vitro are insensitive to the hypotensive effects of CGRP, ADM, and ADM2; (2) CGRP, ADM, and ADM2 (0.1-100nM) dose dependently relax UA segments from pregnant women with efficacy for CGRP > ADM = ADM2; (3) the relaxation responses to CGRP, ADM, and ADM2 are differentially affected by the inhibitors of nitric oxide (NO) synthase (L-NAME), adenylyl cyclase (SQ22536), apamin, and charybdotoxin; (4) UA smooth muscle cells (UASMC) express mRNA for calcitonin receptor-like receptor (CRLR) and receptor activity modifying protein (RAMP)1 and RAMP2 but not RAMP3; (5) receptor heterodimer comprising CRLR/RAMP1 and CRLR/RAMP2 but not CRLR/RAMP3 is present in UA; (6) soluble fms-like tyrosine kinase (sFLT-1) and TNF-α treatment decrease the expression of RAMP1 mRNA (P < 0.05) in UASMC; and (7) sFLT-1 treatment impairs the association of CRLR with all 3 peptides while TNF-α inhibits the interaction of CGRP but not ADM or ADM2 with CRLR in UASMC (P < 0.05). Relaxation sensitivity of UA for CGRP, ADM, and ADM2 is increased during pregnancy via peptide-specific involvement of NO system and endothelium-derived hyperpolarizing factors; vascular disruptors such as sFLT-1 and TNFα adversely impact their receptor system in UASMC.

Endothelium-Derived Hyperpolarizing Factor (EDHF) Mediates Acetylsalicylic Acid (Aspirin) Vasodilation of Pregnant Rat Mesenteric Arteries.

Acetylsalicylic acid (aspirin) exhibits a broad range of activities, including analgesic, antipyretic, and antiplatelet properties. Recent clinical studies also recommend aspirin prophylaxis in women with a high risk of pre-eclampsia, a major complication of pregnancy characterized by hypertension. We investigated the effect of aspirin on mesenteric resistance arteries and found outdiscovered the molecular mechanism underlying this action. Aspirin (10−12–10−6 M) was tested on pregnant rat mesenteric resistance arteries by a pressurized arteriography. Aspirin was investigated in the presence of several inhibitors of: (a) nitric oxide synthase (L-NAME 2 × 10−4 M); (b) cyclooxygenase (Indomethacin, 10−5 M); (c) Ca2+-activated K+ channels (Kca): small conductance (SKca, Apamin, 10−7 M), intermediate conductance (IKca, TRAM34, 10−5 M), and big conductance (BKca, paxilline, 10−5 M); and (d) endothelial-derived hyperpolarizing factor (high KCl, 80 mM). Aspirin caused a concentration-dependent vasodilation. Aspirin-vasodilation was abolished by removal of endothelium or by high KCl. Furthermore, preincubation with either apamin plus TRAM-34 or paxillin significantly attenuated aspirin vasodilation (p < 0.05). For the first time, we showed that aspirin induced endothelium-dependent vasodilation in mesenteric resistance arteries through the endothelial-derived hyperpolarizing factor (EDHF) and calcium-activated potassium channels. By activating this molecular mechanism, aspirin may lower peripheral vascular resistance and be beneficial in pregnancies complicated by hypertension.