Voltage-gated Ca2+ channel activity modulates smooth muscle cell calcium waves in hamster cremaster arterioles

Coronary Spasm Due to Pulsed Field Ablation: A State-of-the-Art Review

With the ever-growing population of patients undergoing cardiac ablation with pulsed electric fields, there is a need to understand secondary effects from the therapy. Coronary artery spasm is one such effect that has recently emerged as the subject of further investigation in electrophysiology literature. This review aims to elucidate the basic anatomy underlying vascular spasm due to pulsed electric fields and the effects of irreversible electroporation on coronary arteries. This review also aims to gather the current preclinical and clinical data regarding the physiology and function of coronary arteries following electroporation.

CaV3.1 channels facilitate calcium wave generation and myogenic tone development in mouse mesenteric arteries

The arterial myogenic response to intraluminal pressure elicits constriction to maintain tissue perfusion. Smooth muscle [Ca2+] is a key determinant of constriction, tied to L-type (CaV1.2) Ca2+ channels. While important, other Ca2+ channels, particularly T-type could contribute to pressure regulation within defined voltage ranges. This study examined the role of one T-type Ca2+ channel (CaV3.1) using C57BL/6 wild type and CaV3.1-/- mice. Patch-clamp electrophysiology, pressure myography, blood pressure and Ca2+ imaging defined the CaV3.1-/- phenotype relative to C57BL/6. CaV3.1-/- mice had absent CaV3.1 expression and whole-cell current, coinciding with lower blood pressure and reduced mesenteric artery myogenic tone, particularly at lower pressures (20-60 mmHg) where membrane potential is hyperpolarized. This reduction coincided with diminished Ca2+ wave generation, asynchronous events of Ca2+ release from the sarcoplasmic reticulum, insensitive to L-type Ca2+ channel blockade (Nifedipine, 0.3 µM). Proximity ligation assay (PLA) confirmed IP3R1/CaV3.1 close physical association. IP3R blockade (2-APB, 50 µM or xestospongin C, 3 µM) in nifedipine-treated C57BL/6 arteries rendered a CaV3.1-/- contractile phenotype. Findings indicate that Ca2+ influx through CaV3.1 contributes to myogenic tone at hyperpolarized voltages through Ca2+-induced Ca2+ release tied to the sarcoplasmic reticulum. This study helps establish CaV3.1 as a potential therapeutic target to control blood pressure.

In Silico, In Vitro, and Ex Vivo Biological Activity of Some Novel Mebeverine Precursors

Irritable bowel syndrome (IBS) is a functional gastroenterological disorder with complex pathogenesis and multifaceted therapy approaches, aimed at alleviating clinical symptoms and improving the life quality of patients. Its treatment includes dietary changes and drugs from various pharmacological groups such as antidiarrheals, anticholinergics, serotonin receptor antagonists, targeting chloride ion channels, etc. The present article is focused on the synthesis and biological evaluation of some mebeverine precursors as potential antispasmodics.

METHODS

In silico analysis aimed at predicting the pharmacodynamic profile of the compounds was performed. Based on these predictions, ex vivo bioelectrical activity (BEA) and immunohistochemical effects of the compounds were established. A thorough biological evaluation of the compounds was conducted assessing their in vitro antimicrobial and cytotoxic activity.

RESULTS

All the newly synthesized compounds exerted drug-like properties, whereby 3-methyl-1-phenylbutan-2-amine 3 showed a significant change in BEA due to Ca²⁺ channel regulation, Ca²⁺ influx modulation, and a subsequent change in smooth muscle cell response. The immunohistochemical studies showed a good correlation with the obtained data on the BEA, defining amine 3 as a leader structure. No cytotoxicity to human malignant leukemic cell lines (LAMA-84, K-562) was observed for all tested compounds.

CONCLUSION

Based on the experimental results, we outlined 3-methyl-1-phenylbutan-2-amine 3 as a potential effective choice for orally active long-term therapy of IBS.

Oxidative Regulation of Vascular Cav1.2 Channels Triggers Vascular Dysfunction in Hypertension-Related Disorders

Blood pressure is determined by cardiac output and peripheral vascular resistance. The L-type voltage-gated Ca²⁺ (Ca_v1.2) channel in small arteries and arterioles plays an essential role in regulating Ca²⁺ influx, vascular resistance, and blood pressure. Hypertension and preeclampsia are characterized by high blood pressure. In addition, diabetes has a high prevalence of hypertension. The etiology of these disorders remains elusive, involving the complex interplay of environmental and genetic factors. Common to these disorders are oxidative stress and vascular dysfunction. Reactive oxygen species (ROS) derived from NADPH oxidases (NOXs) and mitochondria are primary sources of vascular oxidative stress, whereas dysfunction of the Ca_v1.2 channel confers increased vascular resistance in hypertension. This review will discuss the importance of ROS derived from NOXs and mitochondria in regulating vascular Ca_v1.2 and potential roles of ROS-mediated Ca_v1.2 dysfunction in aberrant vascular function in hypertension, diabetes, and preeclampsia.

Dynamics of capillary blood flow responses to acute local changes in oxygen and carbon dioxide concentrations

Objectives: We aimed to quantify the magnitude and time transients of capillary blood flow responses to acute changes in local oxygen concentration ([O₂]), and carbon dioxide concentration ([CO₂]) in skeletal muscle. Additionally, we sought to quantify the combined response to both low [O₂] and high [CO₂] to mimic muscle microenvironment changes at the onset of exercise. Methods: 13 Sprague Dawley rats were anaesthetized, mechanically ventilated, and instrumented with indwelling catheters for systemic monitoring. The extensor digitorum longus muscle was blunt dissected, and reflected over a microfluidic gas exchange chamber in the stage of an inverted microscope. Four O₂ challenges, four CO₂ challenges, and a combined low O₂ (7-2%) and high CO₂ (5-10%) challenges were delivered to the surface with simultaneous visualization of capillary blood flow responses. Recordings were made for each challenge over a 1-min baseline period followed by a 2-min step change. The combined challenge employed a 1-min [O₂] challenge followed by a 2-min change in [CO₂]. Mean data for each sequence were fit using least-squared non-linear exponential models to determine the dynamics of each response. Results: 7-2% [O₂] challenges decreased capillary RBC saturation within 2 s following the step change (46.53 ± 19.56% vs. 48.51 ± 19.02%, p < 0.0001, τ = 1.44 s), increased RBC velocity within 3 s (228.53 ± 190.39 μm/s vs. 235.74 ± 193.52 μm/s, p < 0.0003, τ = 35.54 s) with a 52% peak increase by the end of the challenge, hematocrit and supply rate show similar dynamics. 5-10% [CO₂] challenges increased RBC velocity within 2 s following the step change (273.40 ± 218.06 μm/s vs. 276.75 ± 215.94 μm/s, p = 0.007, τ = 79.34s), with a 58% peak increase by the end of the challenge, supply rate and hematocrit show similar dynamics. Combined [O₂] and [CO₂] challenges resulted in additive responses to all microvascular hemodynamic measures with a 103% peak velocity increase by the end of the collection period. Data for mean responses and exponential fitting parameters are reported for all challenges. Conclusion: Microvascular level changes in muscle [O₂] and [CO₂] provoked capillary hemodynamic responses with differing time transients. Simulating exercise via combined [O₂] and [CO₂] challenges demonstrated the independent and additive nature of local blood flow responses to these agents.

Salvianolic acid A from Danhong Injection induces vasorelaxation by Regulating L-type calcium channel in isolated mouse arteries

ETHNOPHARMACOLOGICAL RELEVANCE

Danhong injection (DHI), which is a Chinese clinical prescription consists of Radix et Rhizoma Salviae Miltiorrhizae (Salvia miltiorrhiza Bge., Labiatae, Danshen in Chinese) and Flos Carthami (Carthamus tinctorius L., Compositae, Honghua in Chinese)(Plant names have been checked with http://www.theplantlist.org on March 1st, 2022), has been mainly used in the clinical therapy of cardiovascular diseases, including hypertension in China for many years.

AIM OF THE STUDY

Cardiovascular diseases (CVDs) are the major causes of death all around the world. Due to the various stimulation, a series of vasoconstrictor substances are secreted to regulate the vasoconstriction function and then change blood pressure. The representative substances leading to abnormal vasoconstriction include renin-angiotensin system, endothelin, vasopressin and adrenaline, which act on the corresponding receptors on vascular smooth muscle to constrict blood vessels. Finally, blood pressure increases, followed by a series of cardiovascular diseases, including hypertension. However, little is known about Danhong injection's specific vasodilating mechanisms and active substances. The aims of the study were to determine the vasodilating substances of Danhong injection and explain its molecular mechanism of vasodilation.

MATERIALS AND METHODS

The effects of DHI and its active components on vascular tension were measured by myograph system in the aortic or mesenteric rings of mice. Based on this, the pharmacodynamic substances were analyzed and effective molecules were found. Combined with multiple types of vascular myograph experiments and network pharmacological analysis, the molecular pathway was preliminarily determined. With molecular biology experiments, it was verified that the relevant mechanisms were closely related to calcium-mediated vasoconstriction in smooth muscle cells.

RESULTS

DHI could relax endothelium-removed aortic rings pre-constricted with PE and 3 possible active vasodilator substances, including salvianolic acid A, salvianolic acid B and danshensu, were screened out by network pharmacology and vascular myograph experiments, among which the effects of salvianolic acid A were dominant. Meanwhile, salvianolic acid A could dilate mesenteric artery in a pressure-dependent manner. Interestingly, salvianolic acid A could still relax the vascular rings under the stimulation of KCl and Bayk8644, two agonists of L-type calcium channel. By contrast, inhibitors of Kir, Kv, Katp and BKCa channels did not block the effect of salvianolic acid A on vasodilation. Salvianolic acid A alleviated Ca²⁺ transient, referring to changes of intracellular calcium, induced by PE, Bayk8644 and high K⁺ in the VSMCs. Salvianolic acid A could partially restore the vasodilation function of vascular smooth muscle damaged by AngII and ET-1 induced hypertension situation.

CONCLUSIONS

Our results indicate that salvianolic acid A is the major vasodilator substance in DHI and the vasorelaxation pharmacology mechanism involved in inhibiting the L-type calcium channel signaling in smooth muscle cell. Hence, there are potential therapeutic effects of taking salvianolic acid A preparation which may be beneficial to protect cardiovascular system and reduce blood pressure.

Therapeutic Benefits of Pomegranate Flower Extract: A Novel Effect That Reduces Oxidative Stress and Significantly Improves Diastolic Relaxation in Hyperglycemic In Vitro in Rats

The pomegranate flower is an ancient herb in traditional Chinese medicine with multiple properties. Recent studies have shown that pomegranate flower extract is beneficial, especially for hyperglycemia. In this experiment, we investigated the diastolic effect of pomegranate flower polyphenol (PFP) extract on the isolated thoracic aorta of rats in both the absence and presence of high glucose levels. Isotonic contractile forces were recorded from aortic rings (about 3 mm in length) from rats using the BL-420F Biological Function Test System. Tissues were precontracted with 60 mM KCl to obtain maximum tension under 1.0 g load for 1 hour before the balance was achieved, and the fluid was changed every 15 minutes. PFP (700 mg/L-900 mg/L) showed a concentration-dependent relaxant effect on the aortic rings; vasodilation in the endothelium-intact was significantly higher than that in the de-endothelialized segments (P < 0.01). The endothelium-dependent vasorelaxant effect of PFP was partially attenuated by K+ channel blockers, tetraethylammonium (TEA), glibenclamide (Glib), and BaCl2, as well as L-NAME (eNOS inhibitor) on the denuded endothelium artery ring. Concentration-dependent inhibition of PFP on releasing intracellular Ca2+ in the Ca2+-free solution and vasoconstriction of CaCl2 in Ca2+-free buffer plus K+ (60 mM) was observed. In addition, PFP (0.1-10 mg/L) showed significant inhibition of acetylcholine-induced endothelial-dependent relaxation in the aorta of rats in the presence of high glucose (44 mmol/L). Nevertheless, the vasodilating effect of PFP was inhibited by atropine and L-NAME. The results indicated that PFP-induced vasodilation was most likely related to the antioxidant effects through enhanced NO synthesis, as well as the blocking of K+ channels and inhibition of extracellular Ca2+ entry. In conclusion, these observations showed that PFP ameliorates vasodilation in hyperglycemic rats. Hence, our results suggest that PFP supplementation may be beneficial for hypertensive patients with diabetes.

Calcium-Dependent Ion Channels and the Regulation of Arteriolar Myogenic Tone

Arterioles in the peripheral microcirculation regulate blood flow to and within tissues and organs, control capillary blood pressure and microvascular fluid exchange, govern peripheral vascular resistance, and contribute to the regulation of blood pressure. These important microvessels display pressure-dependent myogenic tone, the steady state level of contractile activity of vascular smooth muscle cells (VSMCs) that sets resting arteriolar internal diameter such that arterioles can both dilate and constrict to meet the blood flow and pressure needs of the tissues and organs that they perfuse. This perspective will focus on the Ca²⁺-dependent ion channels in the plasma and endoplasmic reticulum membranes of arteriolar VSMCs and endothelial cells (ECs) that regulate arteriolar tone. In VSMCs, Ca²⁺-dependent negative feedback regulation of myogenic tone is mediated by Ca²⁺-activated K⁺ (BK_Ca) channels and also Ca²⁺-dependent inactivation of voltage-gated Ca²⁺ channels (VGCC). Transient receptor potential subfamily M, member 4 channels (TRPM4); Ca²⁺-activated Cl⁻ channels (CaCCs; TMEM16A/ANO1), Ca²⁺-dependent inhibition of voltage-gated K⁺ (K_V) and ATP-sensitive K⁺ (K_ATP) channels; and Ca²⁺-induced-Ca²⁺ release through inositol 1,4,5-trisphosphate receptors (IP₃Rs) participate in Ca²⁺-dependent positive-feedback regulation of myogenic tone. Calcium release from VSMC ryanodine receptors (RyRs) provide negative-feedback through Ca²⁺-spark-mediated control of BK_Ca channel activity, or positive-feedback regulation in cooperation with IP₃Rs or CaCCs. In some arterioles, VSMC RyRs are silent. In ECs, transient receptor potential vanilloid subfamily, member 4 (TRPV4) channels produce Ca²⁺ sparklets that activate IP₃Rs and intermediate and small conductance Ca²⁺ activated K⁺ (IK_Ca and sK_Ca) channels causing membrane hyperpolarization that is conducted to overlying VSMCs producing endothelium-dependent hyperpolarization and vasodilation. Endothelial IP₃Rs produce Ca²⁺ pulsars, Ca²⁺ wavelets, Ca²⁺ waves and increased global Ca²⁺ levels activating EC sK_Ca and IK_Ca channels and causing Ca²⁺-dependent production of endothelial vasodilator autacoids such as NO, prostaglandin I₂ and epoxides of arachidonic acid that mediate negative-feedback regulation of myogenic tone. Thus, Ca²⁺-dependent ion channels importantly contribute to many aspects of the regulation of myogenic tone in arterioles in the microcirculation.

Myogenic Tone in Peripheral Resistance Arteries and Arterioles: The Pressure Is On!

Resistance arteries and downstream arterioles in the peripheral microcirculation contribute substantially to peripheral vascular resistance, control of blood pressure, the distribution of blood flow to and within tissues, capillary pressure, and microvascular fluid exchange. A hall-mark feature of these vessels is myogenic tone. This pressure-induced, steady-state level of vascular smooth muscle activity maintains arteriolar and resistance artery internal diameter at 50–80% of their maximum passive diameter providing these vessels with the ability to dilate, reducing vascular resistance, and increasing blood flow, or constrict to produce the opposite effect. Despite the central importance of resistance artery and arteriolar myogenic tone in cardiovascular physiology and pathophysiology, our understanding of signaling pathways underlying this key microvascular property remains incomplete. This brief review will present our current understanding of the multiple mechanisms that appear to underlie myogenic tone, including the roles played by G-protein-coupled receptors, a variety of ion channels, and several kinases that have been linked to pressure-induced, steady-state activity of vascular smooth muscle cells (VSMCs) in the wall of resistance arteries and arterioles. Emphasis will be placed on the portions of the signaling pathways underlying myogenic tone for which there is lack of consensus in the literature and areas where our understanding is clearly incomplete.

Myorelaxant Effect of the Dysphania ambrosioides Essential Oil on Sus scrofa domesticus Coronary Artery and Its Toxicity in the Drosophila melanogaster Model

PURPOSE

Alternative methods for the use of animals in research have gained increasing importance, due to assessments evaluating the real need for their use and the development of legislation that regulates the subject. The principle of the 3R's (replacement, reduction and refinement) has been an important reference, such that in vitro, ex vivo and cord replacement methods have achieved a prominent place in research.

METHODS

Therefore, due to successful results from studies developed with these methods, the present study aimed to evaluate the myorelaxant effect of the Dysphania ambrosioides essential oil (EODa) using a Sus scrofa domesticus coronary artery model, and the toxicity of both the Dysphania ambrosioides essential oil and its major constituent, α-terpinene, against Drosophila melanogaster in toxicity and negative geotaxis assays.

RESULTS

The EODa relaxed the smooth muscle of swine coronary arteries precontracted with K⁺ and 5-HT in assays using Sus scrofa domesticus coronary arteries. The toxicity results presented LC₅₀ values of 1.546 mg/mL and 2.282 mg/mL for the EODa and α-terpinene, respectively, thus showing the EODa and α-terpinene presented toxicity to these dipterans, with the EODa being more toxic.

CONCLUSIONS

Moreover, the results reveal the possibility of using the EODa in vascular disease studies since it promoted the relaxation of the Sus scrofa domesticus coronary smooth muscle.

Ion channels and myogenic activity in retinal arterioles

Retinal pressure autoregulation is an important mechanism that protects the retina by stabilizing retinal blood flow during changes in arterial or intraocular pressure. Similar to other vascular beds, retinal pressure autoregulation is thought to be mediated largely through the myogenic response of small arteries and arterioles which constrict when transmural pressure increases or dilate when it decreases. Over recent years, we and others have investigated the signaling pathways underlying the myogenic response in retinal arterioles, with particular emphasis on the involvement of different ion channels expressed in the smooth muscle layer of these vessels. Here, we review and extend previous work on the expression and spatial distribution of the plasma membrane and sarcoplasmic reticulum ion channels present in retinal vascular smooth muscle cells (VSMCs) and discuss their contribution to pressure-induced myogenic tone in retinal arterioles. This includes new data demonstrating that several key players and modulators of the myogenic response show distinctively heterogeneous expression along the length of the retinal arteriolar network, suggesting differences in myogenic signaling between larger and smaller pre-capillary arterioles. Our immunohistochemical investigations have also highlighted the presence of actin-containing microstructures called myobridges that connect the retinal VSMCs to one another. Although further work is still needed, studies to date investigating myogenic mechanisms in the retina have contributed to a better understanding of how blood flow is regulated in this tissue. They also provide a basis to direct future research into retinal diseases where blood flow changes contribute to the pathology.