Vascular Smooth Muscle Relaxation Research Articles

Methylene Blue in Metformin Intoxication: Not Just Rescue But Also Initial Treatment.

Metformin (MTF) is a widely used oral antidiabetic medication. Regardless the reason, high doses of MTF cause lactic acidosis as a result of its effects on mitochondrial ATP production and no-mediated vascular smooth muscle relaxation. Metformin-associated lactic acidosis can be life-threatening despite all treatments. Methylene blue (MB) has the potential to reverse the toxic effects of MTF through its effects on both the mitochondrial respiratory chain and nitric oxide production. The use of MB in MTF intoxication has only been reported in a limited number of cases. Herein, we present a 16-year-old female patient who attempted suicide by ingesting high doses of MTF. Supportive treatments, such as vasopressor, inotropic treatments, and sodium bicarbonate, were started in the patient who developed fluid-resistant hypotension after pediatric intensive care unit admission. Because of rising lactate levels, Continuous renal replacement therapy (CRRT) was started immediately. Despite all treatments, hypotension and hyperlactatemia persisted; MB was given as a rescue therapy. Noticeable hemodynamic improvement was observed within 30 minutes of initiating MB infusion, allowing a gradual decrease in the doses of inotropic infusions within the first hour of therapy. Patient's cardiovascular support was discontinued on the second day, and she was discharged on the fifth day. We speculate that, considering the mechanisms of MTF toxicity and the mechanisms of action of MB, it is suggested that early administration of MB, not only as a rescue treatment but as the initial approach to MTF poisoning in combination with other treatments, may result in improved outcomes.

286 Evaluation of Serotonin as a Vasorelaxant in Ovine Saphenous Artery and Vein

Abstract Herbivores that consume ergot alkaloids frequently suffer from vasoconstriction that can result in a myriad of symptoms that can range from necrosis of peripheral tissues to fetal intra-uterine growth restriction. As part of a larger study screening compounds that may mitigate the vasoconstrictive effects of ergot alkaloids, the objective of this experiment was to evaluate serotonin (5-HT) as vasorelaxant in the ovine saphenous artery and vein. Blood vessels were collected from a total mixed breed market rams (n = 16; approximate BW = 58 kg) at slaughter, cleaned of surrounding adipose and connective tissue, sliced into 2-mm cross-sections, and mounted in a multimyograph. Artery and vein cross-sections were equilibrated to 1 g tension in continuously gassed (95% O2/5% CO2) Krebs-Henseleit buffer (pH 7.4; 37.5 °C) for 90 min, precontracted with 0.0001 M phenylephrine for 15 min, exposed to concentrations of 5-HT that ranged from 1 x 10-9 to 1 x 10-4 M for a 5-min interval. Response data were normalized to the 0.0001 M phenylephrine response and were analyzed as a completely randomized design in SAS. The lateral saphenous vein (n = 5 lambs) relaxed to increasing concentrations of 5-HT (P < 0.05) with 65 to 75 % relaxation occurring at 1 x 10-7 M through 1 x 10-4 5-HT. Conversely, the lateral saphenous artery (n = 6 lambs) contracted in response to increasing concentrations of 5-HT (P < 0.05) resulting in a 255% increase from the phenylephrine response by the 1 x 10-4 M addition. In a subsequent experiment, saphenous veins from the remaining lambs (n = 5) were treated the same, but in place of increasing concentrations of 5-HT, saphenous veins were exposed to increasing concentrations of selective 5-HT receptor agonists to determine the receptor subtypes involved in the previously observed vasorelaxation. Agonists for receptors 5-HT2B (BW 723C86; α-methyl-5-(2-thienylmethoxy)-1H-indole-3-ethanamine hydrochloride), 5-HT4 (BIMU-8; 2,3-Dihydro-N-[(3-endo)-8-methyl-8-azabicyclo[3.2.1]oct-3-yl]-3-(1-methylethyl)-2-oxo-1H-benzimidazole-1-carboxamide hydrochloride), and 5-HT7 (LP44; 4-[2-(methylthio)phenyl]-N-(1,2,3,4-tetrahydro-1-naphthalenyl)-1-piperazinehexanamide, monohydrochloride) were used. These 5-HT receptor subtypes were selected based on their association with vascular smooth muscle relaxation. While all three 5-HT receptor subtypes resulted in vasorelaxation (P < 0.05), the 5-HT2B agonist only stimulated a maximal relaxation of 32% compared with the agonists for 5-HT4 and 5-HT7 that resulted in maximal relaxation of 68% and 50%, respectively. The agonist for 5-HT4 produced the greatest relaxation in the ovine lateral saphenous vein and should be targeted in subsequent research. It is likely that the combined effect of binding multiple receptor subtypes contributes to the overall effect of 5-HT. The focus on development of ergot alkaloid mitigation strategies should consider the divergent responses of arteries and veins to serotonin in peripheral tissues.

Аrginine – biological role, biosynthesis and whey consumption

The article summarizes actual information about L-arginine (Arg), which is the semi-essential amino acid. L-arginine is classified as an essential amino acid for birds, carnivores and young mammals and a conditionally essential amino acid for adults. L-arginine plays very important role in the plant and animal body metabolism. It metabolically interconvertible with the amino acids proline and glutamate and also is the precursor of a large number of crucial metabolites. It is serves as a precursor for synthesis of molecules of great biological importance, including proteins, L-ornithine, polyamines, agmatine, creatine and urea, which is important in the urea cycle. The main importance of L-arginine is attributed to its role as a precursor for the synthesis of nitric oxide (NO), a free radical molecule that is synthesized in all mammalian cells from L-arginine by NO synthase. NO appears to be a major form of the endothelium-derived relaxing factor. So, L−arginine plays a special role in vascular system, where it is a source of endogenous nitric oxide, which is blood vessels dilator. The use of supplements with L-arginine is appropriate in the prevention and treatment of metabolic diseases. Thanks to relaxation of vascular smooth muscles, it takes part in regulation of blood vessels tone. Treatment by arginine as a medicine improves functions of cardiovascular system. L-Аrginine there is in plant and animal food and in seafood. L-arginine has a wide and varied application such as animal feeding, cosmetology, medical field. In recent years arginine production has been increasing. L−Arginine is obtained by hydrolysis of proteins, with the help of chemical and microbiological synthesis. Microbiological synthesis of L-arginine is the most promising and economically advantageous. Modern microbial technologies use monosubstrates and mixed substrates. Bacteria can synthesize all 20 proteinogenic amino acids, including the nine essential amino acids required for mammalian growth. In general, enzymes involved in the biosynthesis of amino acids are essential for the growth and survival of bacteria. Peat cause great scientific interest. Peat is a natural media for growing symbiotic microorganisms, and has advantages over other types of natural feedstocks. We obtained a peat-based bio-substrate using an inorganic sulfur-containing compound. As a result of bio-substrate composting the content arginine and some other amino asides increased. This bio-substrate was used in resіaches as a feed additive for broiler chickens. Under the action of the feed additive the metabolism in the body of chісkens, growth and live weight gain improved.

Effect of hypoandrogenism on expression of transient receptor potential vanilloid channels in rat penile corpus cavernosum and erectile function.

Hypoandrogenism is a cause of erectile dysfunction (ED). Vascular smooth muscle cell contraction and relaxation are regulated by TRPV1-4 channels. However, the influence of hypoandrogenism on TRPV1-4 and its relationship with erectile function remain unclear. To reveal whether hypoandrogenism affects erectile function by influencing TRPV1-4 expression in the corpus cavernosum of rats. Male Sprague-Dawley rats (N = 36) aged 8 weeks were assigned to 6 groups at random (n = 6): sham operation, castrated, castrated + testosterone replacement, sham operation + transfection, castrated + transfection, and castrated + empty transfection. Four weeks after castration, 20μL of lentiviral vector (1 × 108 TU/mL) carrying the TRPV4 gene was injected into the penile cavernous tissue of the transfection groups. One week after transfection, the maximum intracavernous pressure (ICPmax)/mean arterial pressure (MAP) and the content of TRPV1-4, phosphorylated eNOS (p-eNOS)/eNOS, and nitric oxide (NO) in penile cavernous tissue of each group were measured. Under low androgen conditions, TRPV4 expression in endothelial cells in the rat penile cavernosum was sharply reduced, resulting in a decrease in p-eNOS/eNOS and NO content, which could inhibit erectile function. In rat penile cavernous tissue, TRPV1-4 was expressed in the cell membranes of endothelial cells and smooth muscle cells. The ICPmax/MAP and the content of TRPV4, p-eNOS/eNOS, and NO end product nitrite level in rat penile cavernous tissue was markedly reduced in the castrated group as compared with the sham group (P < .05). The ICPmax/MAP and the content of TRPV4, p-eNOS/eNOS, and NO end product nitrite level in rat penile cavernous tissue were markedly improved in the castrated + transfection group vs the castrated group (P < .01). Upregulation of TRPV4 expression in penile cavernosum tissue might be a viable therapeutic for ED caused by hypoandrogenism. The specific mechanism of TRPV4 in ED needs to be further verified by androgen receptor or TRPV4 gene knockout experiments. Hypoandrogenism may cause ED by reducing the expression of TRPV4 in rat penile cavernous tissue. Upregulation of TRPV4 expression in penile cavernous tissue can increase the ratio of p-eNOS/eNOS and NO levels and ameliorate the erectile function of castrated rats.

Sildenafil for congenital heart diseases induced pulmonary hypertension, a meta-analysis of randomized controlled trials

BackgroundSildenafil was first prescribed for angina pectoris and then for erectile dysfunction from its effects on vascular smooth muscle relaxation and vasodilatation. Recently, sildenafil has been proposed for congenital heart diseases induced pulmonary hypertension, which constitutes a huge burden on children's health and can attribute to fatal complications due to presence of unoxygenated blood in the systemic circulation. Therefore, our meta-analysis aims to further investigate the safety and efficacy of sildenafil on children population.MethodsWe searched the following electronic databases: PubMed, Cochrane CENTRAL, WOS, Embase, and Scopus from inception to April 20th, 2022. Randomized controlled trials that assess the efficacy of using sildenafil in comparison to a placebo or any other vasodilator drug were eligible for inclusion. The inverse variance method was used to pool study effect estimates using the random effect model. Effect sizes are provided in the form of mean difference (MD) with 95% confidence intervals (CI).ResultsOur study included 14 studies with (n = 849 children) with a mean age of 7.9 months old. Sildenafil showed a statistically significant decrease over placebo in mean and systolic pulmonary artery pressure (PAP) with MD -7.42 (95%CI [-13.13, -1.71], P = 0.01) and -8.02 (95%CI [-11.16, -4.88], P < 0.0001), respectively. Sildenafil revealed a decrease in mean aortic pressure and pulmonary artery/aortic pressure ratio over placebo with MD -0.34 (95%CI [-2.42, 1.73], P = 0.75) and MD -0.10 (95%CI [-0.11, -0.09], P < 0.00001), respectively. Regarding post corrective operations parameters, sildenafil had a statistically significant lower mechanical ventilation time, intensive care unit stay, and hospital stay over placebo with MD -19.43 (95%CI [-31.04, -7.81], s = 0.001), MD -34.85 (95%CI [-50.84, -18.87], P < 0.00001), and MD -41.87 (95%CI [-79.41, -4.33], P = 0.03), respectively. Nevertheless, no difference in mortality rates between sildenafil and placebo with OR 0.25 (95%CI 0.05, 1.30], P = 0.10) or tadalafil with OR 1 (95%CI 0.06, 17.12], P = 1).ConclusionSildenafil is a well-tolerated treatment in congenital heart diseases induced pulmonary hypertension, as it has proven its efficacy not only in lowering both PAP mean and systolic but also in reducing the ventilation time, intensive care unit and hospital stay with no difference observed regarding mortality rates.

Rosuvastatin relaxes rat thoracic aorta, pulmonary artery, and trachea via nitric oxide, prostanoids, and potassium channels

Purpose: This study aimed to determine the functional effects and mechanisms of the action of rosuvastatin on vascular and tracheal smooth muscle tissues. &#x0D; Materials and Methods: Vascular and tracheal rings (2-3 mm) isolated from the thoracic aortas, pulmonary arteries, and tracheas of Wistar Albino male rats (250-300 g) were placed in chambers in the isolated tissue bath system. As the resting tension, 1 g was selected. Vascular rings contracted with 10-6 M phenylephrine after a 90-minute equilibration period. Tracheal rings contracted with 10-5 M acetylcholine. After the contraction was steady, rosuvastatin (10-8-10-4 M) was cumulatively applied to the vascular and tracheal rings. The defined experimental methodology was repeated following the incubation of selective inhibitors of signaling pathways and K+ channel blockers to ascertain rosuvastatin's functional effect mechanisms. &#x0D; Results: In the precontracted rat vascular and tracheal rings, rosuvastatin induced concentration-dependent relaxation. The maximal relaxation level in vessel samples was 96%. On the other hand, the maximal relaxation level in tracheal samples was found to be 75%. The vasorelaxant effects of rosuvastatin were dramatically attenuated by endothelium removal, L-NAME treatment, and indomethacin incubation (up to 27%). With the incubation of tetraethylammonium, glyburide, 4-Aminopyridine, and anandamide, rosuvastatin-mediated vascular smooth muscle relaxation levels were significantly decreased (up to 38%). Moreover, With the incubation of tetraethylammonium, glyburide, and 4-Aminopyridine rosuvastatin-mediated tracheal smooth muscle relaxation levels were significantly decreased (up to 30%). &#x0D; Conclusion: Rosuvastatin has a noticeable relaxing effect on the vascular and tracheal smooth muscles. The vasorelaxant effect of rosuvastatin involves intact endothelium, nitric oxide, prostanoids, and K+ channels (BKCa, KV, and KATP channels). Furthermore, nitric oxide, prostanoids, BKCa channels, KV channels, and KATP channels play a role in rosuvastatin-induced tracheal smooth muscle relaxation

β3 Receptor Signaling in Pregnant Human Myometrium Suggests a Role for β3 Agonists as Tocolytics.

Preterm labor leading to preterm birth is the leading cause of infant morbidity and mortality. At the present time, nothing can reliably halt labor once it begins. The knowledge that agonists of the β2 adrenergic receptor relax airway smooth muscle and are effective in the treatment of asthma led to the notion that β2 mimetics would prevent preterm birth by relaxing uterine smooth muscle. The activation of cAMP-dependent protein kinase by β2 receptors is unable to provide meaningful tocolysis. The failure of β2 agonists such as ritodrine and terbutaline to prevent preterm birth suggests that the regulation of uterine smooth muscle is disparate from that of airway. Other smooth muscle quiescent-mediating molecules, such as nitric oxide, relax vascular smooth muscle in a cGMP-protein kinase G-dependent manner; however, nitric oxide activation of protein kinase G fails to explain the relaxation of the myometrium to nitric oxide. Moreover, nitric oxide-mediated relaxation is blunted in preterm labor, and thus, for this reason and because of the fall in maternal blood pressure, nitric oxide cannot be employed as a tocolytic. The β3 adrenergic receptor-mediated relaxation of the human myometrium is claimed to be cAMP-dependent protein kinase-dependent. This is scientifically displeasing given the failure of β2 agonists as tocolytics and suggests a non-canonical signaling role for β3AR in myometrium. The addition of the β3 agonist mirabegron to pregnant human myometrial strips in the tissue bath relaxes oxytocin-induced contractions. Mirabegron stimulates nitric oxide production in myometrial microvascular endothelial cells, and the relaxation of uterine tissue in vitro is partially blocked by the addition of the endothelial nitric oxide synthase blocker Nω-Nitro-L-arginine. Recent data suggest that both endothelial and smooth muscle cells respond to β3 stimulation and contribute to relaxation through disparate signaling pathways. The repurposing of approved medications such as mirabegron (Mybetriq™) tested in human myometrium as uterine tocolytics can advance the prevention of preterm birth.

Increased plasma renin by vasodilators promotes the progression of abdominal aortic aneurysm.

Background: It is well-accepted that antihypertensive therapy is the cornerstone of treatment for abdominal aortic aneurysm (AAA) patients with hypertension. Direct-acting vasodilators were used in the treatment of hypertension by directly relaxing vascular smooth muscle but may have destructive effects on the aortic wall by activating the renin-angiotensin system axis. Their roles in AAA disease remain to be elucidated. In this study, we used hydralazine and minoxidil, two classical direct-acting vasodilators, to investigate their influence and potential mechanisms on AAA disease. Methods and results: In this study, we investigated the plasma renin level and plasma renin activity in AAA patients. Simultaneously, age and gender ratio-matched patients diagnosed with peripheral artery disease and varicose veins were selected as the control group using a ratio of 1:1:1. Our regression analysis suggested both the plasma renin level and plasma renin activity are positively associated with AAA development. In view of the well-established relationship between direct-acting vasodilators and increased plasma renin concentration, we established a porcine pancreatic elastase-infused AAA mouse model, followed by oral administration of hydralazine (250mg/L) and minoxidil (120mg/L) to investigate effects of direct-acting vasodilators on AAA disease. Our results suggested both hydralazine and minoxidil promoted the progression of AAA with increased aortic degeneration. Mechanistically, the vasodilators aggravated aortic inflammation by increased leukocyte infiltration and inflammatory cytokine secretion. Conclusion and relevance: The plasma renin level and plasma renin activity are positively associated with AAA development. Direct vasodilators aggravated experimental AAA progression, which raised cautionary concerns about their applications in AAA disease.

Supplementation with Nitric Oxide Precursors for Strength Performance: A Review of the Current Literature.

Nitric-oxide-stimulating dietary supplements are widely available and marketed to strength athletes and weightlifters seeking to increase muscle performance and augment training adaptations. These supplements contain ingredients classified as nitric oxide (NO) precursors (i.e., "NO boosters"). Endogenous NO is generated via a nitric oxide synthase (NOS)-dependent pathway and a NOS-independent pathway that rely on precursors including L-arginine and nitrates, with L-citrulline serving as an effective precursor of L-arginine. Nitric oxide plays a critical role in endothelial function, promoting relaxation of vascular smooth muscle and subsequent dilation which may favorably impact blood flow and augment mechanisms contributing to skeletal muscle performance, hypertrophy, and strength adaptations. The aim of this review is to describe the NO production pathways and summarize the current literature on the effects of supplementation with NO precursors for strength and power performance. The information will allow for an informed decision when considering the use of L-arginine, L-citrulline, and nitrates to improve muscular function by increasing NO bioavailability.

184: THE INJECTION OF INTRA-ARTERIAL VASODILATOR FOR THE TREATMENT OF VASOPRESSOR EXTRAVASATION

Introduction: We described a case where vasopressor extravasation occurred and was mitigated immediately utilizing two novel techniques. This discussion highlights the importance of learning and understanding the rapid execution of treatment modalities in cases of subcutaneous extravasation of vasopressors. Description: A 67-year-old female with coronary artery disease, hypertension, anemia, and recurrent upper gastrointestinal bleeding presented to the emergency department after suffering cardiac arrest at her home. The patient was intubated and ACLS protocol was followed. The patient regained spontaneous circulation after 50 minutes. She was extremely hypotensive so a Norepinephrine infusion was started. Her hand distal to the IV became cyanotic which indicated that Norepinephrine extravasated and was causing severe vasoconstriction. We stopped the infusion of Levophed and a central line was placed.We intentionally placed an arterial line distal to the site through the brachial artery. We injected nitroprusside, a direct vasodilator, through the arterial line which is very uncommon in the ICU as medications are usually injected through the vein, not the artery. We did this in order to deliver nitroprusside directly to the forearm and hand to dilate vessels. We injected 25mg of nitroprusside and the hand immediately turned red and restored circulation. Discussion: Intracoronary nitroprusside, a vasoactive drug, has been used off-label for coronary vasospasms and is commonly used to treat congestive heart failure. Nitroprusside can effectively dilate small arteries and veins, selectively relax vascular smooth muscle and reduce peripheral vascular resistance, temporarily change hemodynamic variables, reduce blood pressure, relieve the cardiac load, and increase cardiac output.3 In the case of vasopressor extravasation, it is important to dilate the vessels in order to flush out the Norepinephrine. It is extremely difficult to perform randomized trials on vasopressor extravasation treatments due to the rare emergency nature and the non-uniformity in the methods of treatment. Although there is no literature on the use of Nitruprosside as a treatment for vasopressor extravasation, its usage in our patient’s treatment was able to successfully, and safely, salvage her hand.

Accumulation of Adipocytes in Penile Corpus Cavernosum May Contribute to Venous Leakage and Veno-Occlusive Dysfunction in Patients with Testosterone Deficiency and Erectile Dysfunction

In 2005, we reported that, in the animal model, androgen deprivation resulted in significant changes in the structural elements of the penile corpus cavernosum (CC), including: (1) atrophy of the trabecular smooth muscle, (2) increased deposition of connective tissue, and (3) accumulation of adipocytes in the sub-tunical region. These structural alterations, together with reported decreases in the expression and activity of endothelial nitric oxide synthase (eNOS) and neural nitric oxide synthase (nNOS), are believed to contribute to reduced blood inflow and increased blood outflow, contributing to veno-occlusive dysfunction and erectile dysfunction (ED). More recently, several clinical studies have documented accumulation of adipocytes in the sub-tunical region of the corpora cavernosa from patients with ED, supporting findings reported in the animal models. Here, we summarize the observations from basic and clinical research and advance the hypothesis that testosterone deficiency contributes to significant changes in the structural integrity of the CC, resulting in atrophy of the trabecular smooth muscle and contributing to reduced vascular smooth muscle relaxation and diminished blood inflow into the penis, resulting in a failure to fill. In addition, atrophy of the trabecular smooth muscle, accumulation of adipocytes in the sub-tunical region, and increased deposition of connective tissue contribute to veno-occlusive dysfunction and a failure to maintain erection. It is postulated that testosterone treatment in men with testosterone deficiency may reverse the structural alterations in the CC and improve erectile function.

AKG/OXGR1 promotes skeletal muscle blood flow and metabolism by relaxing vascular smooth muscle

Abstract In response to contraction during exercise, skeletal muscle growth and metabolism are dynamically regulated by nerve action, blood flow, and metabolic feedback. α-Ketoglutarate (AKG), a bioactive intermediate in the tricarboxylic acid cycle released during exercise, has been shown to promote skeletal muscle hypertrophy. However, the underlying mechanism of AKG in regulating skeletal muscle development and metabolism is still less known. 2-Oxoglutarate receptor 1 (OXGR1), the endogenous AKG receptor, is found to be distributed in the vascular smooth muscle (VSM) of skeletal muscles. OXGR1 knockout results in skeletal muscle atrophy, accompanied by decreased expression of myosin heavy chain I (MyHC I), capillary density, and endurance exercise capacity. Furthermore, the study found that dietary AKG supplementation increased mice endurance exercise distance, MyHC I/MyHC IIb ratio, arteriole, and capillary densities in skeletal muscle. Meanwhile, acute AKG administration gradually increased the blood flow in the lower limbs. Further, by using OXGR1 global knockout and OXGR1 VSM-specific (MYH11-Cre × OXGR1-FloxP) knockdown models, we found that OXGR1 in VSM is essential for AKG-induced improvement of skeletal muscle performances. According to the in vitro study, AKG expanded the cell area in VSM with a decreased intracellular pH by OXGR1. Our results demonstrated a novel role of AKG/OXGR1 in VSM of skeletal muscle to regulate blood flow and then enhance slow muscle fiber conversion and capillarization. These findings provide a theoretical basis for the AKG/OXGR1 signaling pathway to maintain human muscle function and improve meat production and livestock and poultry meat quality.

KCNQ5 activation by tannins mediates vasorelaxant effects of barks used in Native American botanical medicine.

Tree and shrub barks have been used as folk medicine by numerous cultures across the globe for millennia, for a variety of indications, including as vasorelaxants and antispasmodics. Here, using electrophysiology and myography, we discovered that the KCNQ5 voltage-gated potassium channel mediates vascular smooth muscle relaxant effects of barks used in Native American folk medicine. Bark extracts (1%) from Birch, Cramp Bark, Slippery Elm, White Oak, Red Willow, White Willow, and Wild Cherry each strongly activated KCNQ5 expressed in Xenopus oocytes. Testing of a subset including both the most and the least efficacious extracts revealed that Red Willow, White Willow, and White Oak KCNQ-dependently relaxed rat mesenteric arteries; in contrast, Black Haw bark neither activated KCNQ5 nor induced vasorelaxation. Two compounds common to the active barks (gallic acid and tannic acid) had similarly potent and efficacious effects on both KCNQ5 activation and vascular relaxation, and this together with KCNQ5 modulation by other tannins provides a molecular basis for smooth muscle relaxation effects of Native American folk medicine bark extracts.

The differential roles of the two NO-GC isoforms in adjusting airway reactivity.

The enzyme, nitric oxide-sensitive guanylyl cyclase (NO-GC), is activated by binding NO to its prosthetic heme group and catalyzes the formation of cGMP. The NO-GC is primarily known to mediate vascular smooth muscle relaxation in the lung, and inhaled NO has been successfully used as a selective pulmonary vasodilator. In comparison, NO-GC's impact on the regulation of airway tone is less acknowledged and, most importantly, little is known about the issue that NO-GC signaling is accomplished by two isoforms: NO-GC1 and NO-GC2, implying the existence of distinct "cGMP pools." Herein, we investigated the functional role of the NO-GC isoforms in respiration by measuring lung function parameters of isoform-specific knockout (KO) mice using noninvasive and invasive techniques. Our data revealed the participation and ongoing influence of NO-GC1-derived cGMP in the regulation of airway tone by showing that respiratory resistance was enhanced in NO-GC1-KOs and increased more pronouncedly after the challenge with the bronchoconstrictor methacholine. The tissue resistance and stiffness of NO-GC1-KOs were also higher because of narrowed airways that cause tissue distortion. Contrariwise, NO-GC2-KOs displayed reduced tissue elasticity, elastic recoil, and airway reactivity to methacholine, which did not even increase in an ovalbumin model of asthma that induced hyperresponsiveness in NO-GC1-KOs. In addition, conscious NO-GC2-KOs showed a higher breathing rate with a shorter duration of inspiration and expiration time, which remained faster even in the presence of bronchoconstrictors that slow down breathing. Thus, we provide evidence of two distinct NO/cGMP pathways in airways, accomplished by either NO-GC1 or NO-GC2, adjusting differentially the airway reactivity.

PATHOPHYSIOLOGICAL PRINCIPLES UNDERLYING THE EFFECT OF SACUBITRIL-VALSARTAN ON HYPERTENSION-INDUCED CARDIOVASCULAR REMODELING

Myocardial remodeling is a process executed by cardiomyocytes, other cells within the myocardium (i.e, endothelial cells, fibroblasts, pericytes, and immune cells), and cells recruited from the circulation (e.g, immune and inflammatory cells) in response to mechanical and non-mechanical stimuli. As a result, the composition, volume, and physiology of cardiomyocytes, the interstitial matrix, and the coronary vessels undergo interrelated changes. These changes detrimentally affect the clinical outcomes of patients with hypertensive heart disease (HHD), due to the risk of fibrillation and increased ventricular stiffness leading to systolic or diastolic dysfunction. Therefore, to reduce cardiovascular remodeling is the main aim for the overall clinical care of these patients.Several drugs, such as angiotensin-converting enzyme inhibitors, beta blockers, and aldosterone antagonists, have been consistently shown to decrease remodeling in animal models and in clinical trials, and are currently widely used to decrease myocardial remodeling. A combination of sacubitril, a neprilysin inhibitor, and valsartan, an angiotensin receptor antagonist, which has positive clinical outcomes in patients with heart failure with reduced ejection fraction, has recently gained public and scientific attention for patients with heart failure with preserved ejection fraction. By promoting the accumulation of natriuretic peptides, which have natriuretic and vascular smooth muscle relaxant properties and by reducing the effects of the renin-angiotensin-aldosterone system, the combination of these two drugs has cardioprotective and antihypertensive effects and reduces cardiovascular fibrosis. It is noteworthy, that sacubitril/valsartan showed a better effect on cardiac remodeling and reversal fraction compared with ACE inhibitor perindopril in rats. However, these are only preliminary data and more extensive studies should be conducted in both experimental and clinical settings in order to fully reveal the mechanisms of action of the drug in the management of various types of arterial hypertension.

Effect of long-term administration of Tadalafil on arteriosclerosis: A prospective cohort study

ABSTRACT Introduction Tadalafil is a phosphodiesterase type 5 (PDE-5) inhibitor, and it is used globally as a highly effective and safe drug for the treatment of erectile dysfunction (ED) and lower urinary tract symptom (LUTS). Tadalafil relieve ED or LUTS by relaxing vascular smooth muscle and increasing blood flow to the lower urinary tract tissue. PDE is distributed in pelvic organs, including the corpus spongiosum of the penis and the urethra and prostate, as well as in the lung, heart, and vascular smooth muscle. In other words, PDE is distributed throughout the body. Thus, we hypothesized that the administration of tadalafil might reduce not only systemic arteriosclerosis but also ischemia of the lower urinary tract. Objective To prospectively investigate whether the long-term administration of tadalafil, which is commonly used for erectile dysfunction, could reduce arteriosclerosis. Methods This study included 85 patients who presented to one of three hospitals with lower urinary tract symptoms. Tadalafil was administered daily (5 mg/d), and pulse wave velocity was measured before administration and at weeks 12, 24, 36, and 48. The International Prostate Symptom Score, Overactive Bladder Symptom Score, and Erection Hardness Score were simultaneously assessed at the same time points. Further sub analyses were performed in patients with a high risk of cardiovascular events, those aged 75 years or older, and those younger than 75 years. The Wilcoxon signed rank test was used for statistical analysis. Results Compared with pretreatment values, the pulse wave velocity did not show any statistically significant decrease at any time point. However, the three aforementioned scores significantly improved compared. The group at high risk of cardiovascular events showed significant improvement at weeks 24 and 36, whereas the 75 years or older group showed significant improvement at only week 24. Conclusions The long-term administration of tadalafil (5 mg daily) reduced arteriosclerosis or inhibited its progression, and relieved dysuria and improved erectile function. In particular, the drug was revealed to be more effective in patients at a high risk of cardiovascular events and those aged 75 years or older. Hence, tadalafil may have the potential to be used as an anti-aging medicine, although further studies with longer observation periods are needed to confirm its effectiveness and safety. Disclosure Work supported by industry: no.

101 Adrenergic Receptor Expression Is Increased in Carotid Smooth Muscle from Severely Burned Rats

IntroductionSevere burn disrupts cardiovascular function which can lead to critical shock. To counteract cardiovascular collapse, there is a systemic increase of catecholamines released in response to severe burn. Previous studies showed that β1- adrenergic receptor (AR)_ protein expression was significantly increased in the cardiac right ventricles (RV) following burn injury, which is correlated with compromised cardiac dysfunction. Vascular smooth muscle contraction served to modulate blood pressure and improve circulatory perfusion. We hypothesize that ARs expression in major arteries are modified to initiate vascular functional changes following severe burn. In the current study, we report temporal ARs expression in murine carotid artery smooth muscle following severe burn.MethodsThirty-four adult Sprague-Dawley male rats received a 40% total body surface area (TBSA) scald burn followed by fluid resuscitation using the Parkland formula. Control animals received a sham burn procedure. Animals were serially euthanized between 6 hours and 14 days after burn and endothelium-intact common carotid arteries were harvested for histological analysis.ResultsImmunohistochemical staining data demonstrated expression of adrenergic receptors (AR) (α1, α2, β1, and β2) were differentially changed in response to injury over time. α1a-AR expression significantly increased within the carotid artery tunica media 7-days after burn (p< 0.05). As a negative feedback of inhibitory of norepinephrine signaling, AR-α2a expression did not significantly change. AR-β1 expression also had no change over time after burn. Interestingly, functioning to relax vascular smooth muscle, a significant elevation of β2-AR expression within the carotid artery tunica media was observed only at 1-day after burn (p< 0.05).ConclusionsIn summary, immunohistochemistry showed that carotid arterial adrenergic receptor expressions of α1a-AR and β2-AR are significantly altered in response to severe burn, which may contribute to vascular contractility in burn rats.

FoxO4 controls sGCβ transcription in vascular smooth muscle.

Nitric oxide (NO) binds soluble guanylyl cyclase β (sGCβ) to produce cGMP and relax vascular smooth muscle cells (SMCs) needed for vasodilation. Although the regulation of NO-stimulated sGC activity has been well characterized at the posttranslational level, the mechanisms that govern sGC transcription remain incompletely understood. Recently, we identified Forkhead box subclass O (FoxO) transcription factors as essential for expression of sGC; however, the specific FoxO family member responsible for the expression of sGCβ in SMC remains unknown. Using FoxO shRNA knockdown adenovirus treatment in rat aortic SMCs, we show that FoxO1 or FoxO3 knockdown causes greater than twofold increases in Gucy1a3 and Gucy1b3 mRNA expression, without changes in NO-dependent cGMP production or cGMP-dependent phosphorylation. FoxO4 knockdown produced a 50% decrease in Gucy1a3 and Gucy1b3 mRNA with 70% loss of sGCα and 50% loss of sGCβ protein expression. Knockdown of FoxO4 expression decreased cGMP production and downstream protein kinase G-dependent phosphorylation more than 50%. Triple FoxO knockdown exacerbated loss of sGC-dependent function, phenocopying previous FoxO inhibition studies. Using promoter luciferase and chromatin immunoprecipitation assays, we find that FoxO4 acts as a transcriptional activator by directly binding several FoxO DNA motifs in the promoter regions of GUCY1B3 in human aortic SMCs. Collectively, our data show FoxO4 is a critical transcriptional regulator of sGCβ expression in SMC.NEW & NOTEWORTHY One of the key mechanisms of vascular smooth muscle cell (SMC) dilation occurs through nitric oxide (NO)-dependent induction of soluble guanylyl cyclase (sGC) by means of its β-subunit. Herein, we are the first to identify Forkhead box subclass O protein 4 (FoxO4) as a key transcriptional regulator of GUCY1B3 expression, which codes for sGCβ protein in human and animal SMCs. This discovery will likely have important implications for the future usage of antihypertensive and vasodilatory therapies which target NO production, sGC, or FoxO transcription factors.

Changes of BKCA current and vascular reactivity in vascular smooth muscle of thoracic aorta and mesenteric artery in type 2 diabetic rats.

The relationship between large conductance calcium activated potassium channel (BKCa) and vascular lesions in type 2 diabetes mellitus (T2DM) was investigated by observing vascular reactivity of thoracic aorta and mesenteric artery and the current changes of BKCa in vascular smooth muscle cells (VSMCs). The thoracic aorta and mesenteric artery of T2DM rats were isolated, the whole cell perforated patch clamp experiment and single channel patch clamp experiment of acute enzyme separation of thoracic aorta and mesenteric artery smooth muscle cells were performed to measure the membrane capacitance and the amplitude of macro current. And the vascular ring experiment was performed to observe the change of relaxation percentage. The results showed that the amplitude of BKCa current in vascular smooth muscle cells of diabetic rats was higher than that of the control group. The channel current had outward rectifying characteristics. BKCa is related to vascular reactivity and smooth muscle relaxation in T2DM rats. The opening probability of BKCa in VSMCs of diabetic rats was significantly increased. This study suggests that BKCa may be a new target for diabetic vascular disease.

The associations between central serous chorioretinopathy and muscle relaxants: A case-control study.

To evaluate the role of muscle-relaxants as risk factors for the development of central serous chorioretinopathy (CSC) - the second most common retinopathy in our settings; despite multiple risk factors seen in our patients, 21% were initially labelled as idiopathic. Retrospective case-control study at a tertiary hospital in the United Arab Emirates, where we reviewed the medical records of 273 patients with CSC examined between 2010 and 2019 for use of muscle-relaxants including tolperisone/eperisone, carisoprodol and gabapentin/pregabalin within a year of onset/recurrence of the disease. Intake of drugs with known association with CSC (including corticosteroids/sympathomimetics) was also recorded. Two hundred eighty-six subjects with adverse events seen at the same institute during the same study period served as controls. Odds ratios, Chi-Square tests and multivariate logistic regression were carried out to determine any associations with the muscle-relaxants and other pharmacological confounders - corticosteroids/sympathomimetics. Muscle relaxants may increase the risk of CSC as evident on multivariate regression analysis (OR: 2.55; confidence interval [CI]: 1.208-5.413); the significance was retained on removing the 6 subjects who had corticosteroids/sympathomimetics (OR: 2.30; CI: 1.073-4.939). Univariate analysis yielded an OR of 2.52 for muscle relaxants (CI: 1.2149-5.2276), 2.96 for eperisone/tolperisone (CI: 1.3531-6.5038), and 6.26 for eperisone as an individual agent (CI: 1.8146-21.6252). We found muscle relaxants to be associated factors of CSC regardless of inclusion of corticosteroids/sympathomimetics (P < 0.05). Among individual classes of muscle relaxants in this study, only eperisone/tolperisone posed a significant risk (P < 0.05). The vascular smooth muscle relaxation could be the possible mechanism that affects the choroidal blood flow and indirectly predisposes to CSC.