Smooth muscle signalling pathways in health and disease

STELLATE GANGLION BLOCK REVERSES PHSML-INDUCED VASCULAR HYPOREACTIVITY THROUGH INHIBITING AUTOPHAGY-MEDIATED PHENOTYPIC TRANSFORMATION OF VSMCs

ABSTRACT

Posthemorrhagic shock mesenteric lymph (PHSML) return-contributed excessive autophagy of vascular smooth muscle cells (VSMCs) is involved in vascular hyporeactivity, which is inhibited by stellate ganglion block (SGB) treatment. The contractile phenotype of VSMCs transforms into a synthetic phenotype after stimulation with excessive autophagy. Therefore, we hypothesized that SGB ameliorates PHSML-induced vascular hyporeactivity by inhibiting autophagy-mediated phenotypic transformation of VSMCs. To substantiate this hypothesis, a hemorrhagic shock model in conscious rats was used to observe the effects of SGB intervention or intravenous infusion of the autophagy inhibitor 3-methyladenine (3-MA) on intestinal blood flow and the expression of autophagy- and phenotype-defining proteins in mesenteric secondary artery tissues. We also investigated the effects of intraperitoneal administration of PHSML intravenous infusion and the autophagy agonist rapamycin (RAPA) on the beneficial effect of SGB. The results showed that hemorrhagic shock decreased intestinal blood flow and enhanced the expression of LC3 II/I, Beclin 1, and matrix metalloproteinase 2, which were reversed by SGB or 3-MA treatment. In contrast, RAPA and PHSML administration abolished the beneficial effects of SGB. Furthermore, the effects of PHSML or PHSML obtained from rats treated with SGB (PHSML-SGB) on cellular contractility, autophagy, and VSMC phenotype were explored. Meanwhile, the effects of 3-MA on PHSML and RAPA on PHSML-SGB were observed. The results showed that PHSML, but not PHSML-SGB, incubation decreased VSMC contractility and induced autophagy activation and phenotype transformation. Importantly, 3-MA administration reversed the adverse effects of PHSML, and RAPA treatment attenuated the effects of PHSML-SGB incubation on VSMCs. Taken together, the protective effect of SGB on vascular reactivity is achieved by inhibiting excessive autophagy-mediated phenotypic transformation of VSMCs to maintain their contractile phenotype.

Extracellular nucleotides in smooth muscle contraction

Extracellular nucleotides and nucleosides are crucial signalling molecules, eliciting diverse biological responses in almost all organs and tissues. These molecules exert their effects by activating specific nucleotide receptors, which are finely regulated by ectonucleotidases that break down their ligands. In this comprehensive review, we aim to elucidate the relevance of extracellular nucleotides as signalling molecules in the context of smooth muscle contraction, considering the modulatory influence of ectonucleotidases on this intricate process. Specifically, we provide a detailed examination of the involvement of extracellular nucleotides in the contraction of non-vascular smooth muscles, including those found in the urinary bladder, the airways, the reproductive system, and the gastrointestinal tract. Furthermore, we present a broader overview of the role of extracellular nucleotides in vascular smooth muscle contraction.

Fiber alignment in 3D collagen networks as a biophysical marker for cell contractility

Cells cultured in 3D fibrous biopolymer matrices exert traction forces on their environment that induce deformations and remodeling of the fiber network. By measuring these deformations, the traction forces can be reconstructed if the mechanical properties of the matrix and the force-free matrix configuration are known. These requirements limit the applicability of traction force reconstruction in practice. In this study, we test whether force-induced matrix remodeling can instead be used as a proxy for cellular traction forces. We measure the traction forces of hepatic stellate cells and different glioblastoma cell lines and quantify matrix remodeling by measuring the fiber orientation and fiber density around these cells. In agreement with simulated fiber networks, we demonstrate that changes in local fiber orientation and density are directly related to cell forces. By resolving Rho-kinase (ROCK) inhibitor-induced changes of traction forces, fiber alignment, and fiber density in hepatic stellate cells, we show that the method is suitable for drug screening assays. We conclude that differences in local fiber orientation and density, which are easily measurable, can be used as a qualitative proxy for changes in traction forces. The method is available as an open-source Python package with a graphical user interface.

Lymphatic muscle cells are unique cells that undergo aging induced changes

Lymphatic muscle cells (LMCs) within the wall of collecting lymphatic vessels exhibit tonic and autonomous phasic contractions, which drive active lymph transport to maintain tissue-fluid homeostasis and support immune surveillance. Damage to LMCs disrupts lymphatic function and is related to various diseases. Despite their importance, knowledge of the transcriptional signatures in LMCs and how they relate to lymphatic function in normal and disease contexts is largely missing. We have generated a comprehensive transcriptional single-cell atlas-including LMCs-of collecting lymphatic vessels in mouse dermis at various ages. We identified genes that distinguish LMCs from other types of muscle cells, characterized the phenotypical and transcriptomic changes in LMCs in aged vessels, and uncovered a pro-inflammatory microenvironment that suppresses the contractile apparatus in advanced-aged LMCs. Our findings provide a valuable resource to accelerate future research for the identification of potential drug targets on LMCs to preserve lymphatic vessel function as well as supporting studies to identify genetic causes of primary lymphedema currently with unknown molecular explanation.

Non-Excitatory Amino Acids, Melatonin, and Free Radicals: Examining the Role in Stroke and Aging

The aim of this review is to explore the relationship between melatonin, free radicals, and non-excitatory amino acids, and their role in stroke and aging. Melatonin has garnered significant attention in recent years due to its diverse physiological functions and potential therapeutic benefits by reducing oxidative stress, inflammation, and apoptosis. Melatonin has been found to mitigate ischemic brain damage caused by stroke. By scavenging free radicals and reducing oxidative damage, melatonin may help slow down the aging process and protect against age-related cognitive decline. Additionally, non-excitatory amino acids have been shown to possess neuroprotective properties, including antioxidant and anti-inflammatory in stroke and aging-related conditions. They can attenuate oxidative stress, modulate calcium homeostasis, and inhibit apoptosis, thereby safeguarding neurons against damage induced by stroke and aging processes. The intracellular accumulation of certain non-excitatory amino acids could promote harmful effects during hypoxia-ischemia episodes and thus, the blockade of the amino acid transporters involved in the process could be an alternative therapeutic strategy to reduce ischemic damage. On the other hand, the accumulation of free radicals, specifically mitochondrial reactive oxygen and nitrogen species, accelerates cellular senescence and contributes to age-related decline. Recent research suggests a complex interplay between melatonin, free radicals, and non-excitatory amino acids in stroke and aging. The neuroprotective actions of melatonin and non-excitatory amino acids converge on multiple pathways, including the regulation of calcium homeostasis, modulation of apoptosis, and reduction of inflammation. These mechanisms collectively contribute to the preservation of neuronal integrity and functions, making them promising targets for therapeutic interventions in stroke and age-related disorders.

The importance of dystrophin and the dystrophin associated proteins in vascular smooth muscle

This review details the role of dystrophin and the dystrophin associated proteins (DAPs) in the vascular smooth muscle. Dystrophin is most comprehensively studied in the skeletal muscle due to serious symptoms found related to the skeletal muscle of patients with muscular dystrophy. Mutations in the dystrophin gene, or DAPs genes, result in a wide range of muscular dystrophies. In skeletal muscle, dystrophin is known to act to as a cytoskeletal stabilization protein and protects cells against contraction-induced damage. In skeletal muscle, dystrophin stabilizes the plasma membrane by transmitting forces generated by sarcomeric contraction to the extracellular matrix (ECM). Dystrophin is a scaffold that binds the dystroglycan complex (DGC) and has many associated proteins (DAPs). These DAPs include sarcoglycans, syntrophins, dystroglycans, dystrobrevin, neuronal nitric oxide synthase, and caveolins. The DAPs provide biomechanical support to the skeletal or cardiac plasma membrane during contraction, and loss of one or several of these DAPs leads to plasma membrane fragility. Dystrophin is expressed near the plasma membrane of all muscles, including cardiac and vascular smooth muscle, and some neurons. Dystrophic mice have noted biomechanical irregularities in the carotid arteries and spontaneous motor activity in portal vein altered when compared to wild type mice. Additionally, some studies suggest the vasculature of patients and animal models with muscular dystrophy is abnormal. Although the function of dystrophin and the DAPs in vascular smooth muscle is not thoroughly established in the field, this review makes the point that these proteins are expressed, and important and further study is warranted.

How vascular smooth muscle cell phenotype switching contributes to vascular disease

Vascular smooth muscle cells (VSMCs) are the most abundant cell in vessels. Earlier experiments have found that VSMCs possess high plasticity. Vascular injury stimulates VSMCs to switch into a dedifferentiated type, also known as synthetic VSMCs, with a high migration and proliferation capacity for repairing vascular injury. In recent years, largely owing to rapid technological advances in single-cell sequencing and cell-lineage tracing techniques, multiple VSMCs phenotypes have been uncovered in vascular aging, atherosclerosis (AS), aortic aneurysm (AA), etc. These VSMCs all down-regulate contractile proteins such as α-SMA and calponin1, and obtain specific markers and similar cellular functions of osteoblast, fibroblast, macrophage, and mesenchymal cells. This highly plastic phenotype transformation is regulated by a complex network consisting of circulating plasma substances, transcription factors, growth factors, inflammatory factors, non-coding RNAs, integrin family, and Notch pathway. This review focuses on phenotypic characteristics, molecular profile and the functional role of VSMCs phenotype landscape; the molecular mechanism regulating VSMCs phenotype switching; and the contribution of VSMCs phenotype switching to vascular aging, AS, and AA. Video Abstract.

K+ channels in the coronary microvasculature of the ischemic heart

Ischemic heart disease is the leading cause of death and a major public health and economic burden worldwide with expectations of predicted growth in the foreseeable future. It is now recognized clinically that flow-limiting stenosis of the large coronary conduit arteries as well as microvascular dysfunction in the absence of severe stenosis can each contribute to the etiology of ischemic heart disease. The primary site of coronary vascular resistance, and control of subsequent coronary blood flow, is found in the coronary microvasculature, where small changes in radius can have profound impacts on myocardial perfusion. Basal active tone and responses to vasodilators and vasoconstrictors are paramount in the regulation of coronary blood flow and adaptations in signaling associated with ion channels are a major factor in determining alterations in vascular resistance and thereby myocardial blood flow. K+ channels are of particular importance as contributors to all aspects of the regulation of arteriole resistance and control of perfusion into the myocardium because these channels dictate membrane potential, the resultant activity of voltage-gated calcium channels, and thereby, the contractile state of smooth muscle. Evidence also suggests that K+ channels play a significant role in adaptations with cardiovascular disease states. In this review, we highlight our research examining the role of K+ channels in ischemic heart disease and adaptations with exercise training as treatment, as well as how our findings have contributed to this area of study.

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.

The Network Pharmacology Study of Dahuang Fuzi Decoction for Treating Incomplete Intestinal Obstruction

Objective

To explore the mechanism of Dahuang Fuzi decoction in the treatment of incomplete intestinal obstruction (IIO) based on network pharmacology and molecular docking.

Methods

The chemical components of Rhubarb, Aconite, and Asarum were searched by the Traditional Chinese Medicine Systems Pharmacology database, where the possible active components were screened by oral bioavailability and drug likeness as filtering indicators. The relevant targets in the Swiss Target Prediction database were obtained according to the structure of the chemical components confirmed by the PubChem database. Disease targets of IIO were collected using GeneCards and OMIM databases. We obtained the cross-target using VENNY to capture the common targets. PPI analysis was performed on the intersection genes combined with Cytoscape 3.7.2. Gene Ontology (GO) function enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were carried out by David database. The core targets and active ingredients were molecularly docked through AutoDock Vina software to predict the detailed molecular mechanism of Dahuang Fuzi decoction for treating IIO.

Results

There are 45 active components in Dahuang Fuzi decoction, with 709 corresponding targets, 538 IIO targets, and 97 common targets, among which kaempferol, deltoin, and eupatin are the main active ingredients. 10 core targets were obtained by protein-protein interaction network analysis. Through GO enrichment analysis, it was found that Dahuang Fuzi decoction may be involved in biological processes such as signal transduction, anti-apoptosis, promotion of gene expression, regulation of cell proliferation, and differentiation. Besides, KEGG pathway analysis revealed that it mainly relates to PI3K-AKT signal pathway and HIF-1 signal pathway, etc. Molecular docking results showed that the active ingredients of Dahuang Fuzi decoction possess a good binding activity with the core targets.

Conclusion

Dahuang Fuzi decoction may act on target genes such as TNF, IL6, AKT1, VEGFA, SRC, EGFR, and STAT3 through active ingredients such as kaempferol, deltoin, and eupatin to regulate signaling pathways such as PI3K-AKT and HIF-1 and reduce the expression of various inflammatory factors such as TNF-α, IL-6, iNOS, and COX-2 to play a role in the treatment of IIO.

Glucose-6-phosphate dehydrogenase and MEG3 controls hypoxia-induced expression of serum response factor (SRF) and SRF-dependent genes in pulmonary smooth muscle cell

Although hypoxia induces aberrant gene expression and dedifferentiation of smooth muscle cells (SMCs), mechanisms that alter dedifferentiation gene expression by hypoxia remain unclear. Therefore, we aimed to gain insight into the hypoxia-controlled gene expression in SMCs. We conducted studies using SMCs cultured in 3% oxygen (hypoxia) and the lungs of mice exposed to 10% oxygen (hypoxia). Our results suggest hypoxia upregulated expression of transcription factor CP2-like protein1, krüppel-like factor 4, and E2f transcription factor 1 enriched genes including basonuclin 2 (Bcn2), serum response factor (Srf), polycomb 3 (Cbx8), homeobox D9 (Hoxd9), lysine demethylase 1A (Kdm1a), etc. Additionally, we found that silencing glucose-6-phosphate dehydrogenase (G6PD) expression and inhibiting G6PD activity downregulated Srf transcript and hypomethylation of SMC genes (Myocd, Myh11, and Cnn1) and concomitantly increased their expression in the lungs of hypoxic mice. Furthermore, G6PD inhibition hypomethylated MEG3, a long non-coding RNA, gene and upregulated MEG3 expression in the lungs of hypoxic mice and in hypoxic SMCs. Silencing MEG3 expression in SMC mitigated the hypoxia-induced transcription of SRF. These findings collectively demonstrate that MEG3 and G6PD codependently regulate Srf expression in hypoxic SMCs. Moreover, G6PD inhibition upregulated SRF-MYOCD-driven gene expression, determinant of a differentiated SMC phenotype.

NLRP3 inflammasome links vascular senescence to diabetic vascular lesions

Vascular senescence is inextricably linked to the onset and progression of cardiovascular diseases (CVDs), which are the main cause of mortality in people with Type 2 diabetes (T2DM). Previous studies have emphasized the importance of chronic aseptic inflammation in diabetic vasculopathy. Here, we found the abnormal activation of NLRP3 inflammasome in the aorta of both old and T2DM mice by immunofluorescence and Western Blot analysis. Histopathological and isometry tension analysis showed that the presence of T2DM triggered or aggravated the increase of vascular aging markers, as well as age-associated vascular impairment and vasomotor dysfunction, which were improved by NLRP3 deletion or inhibition. Differential expression of aortic genes links to senescence activation and vascular remodeling supports the favorable benefits of NLRP3^-/- during T2DM. In vitro results based on primary mice aortic endothelial cells (MAECs) and vascular smooth muscle cells (VSMCs) demonstrate that NLRP3 deficiency attenuated premature senescence and restored proliferation and migration capability under-stimulation, and partially ameliorated replicative senescence. These results provide an insight into the critical role of NLRP3 signaling in T2DM-induced vascular aging and loss of vascular homeostasis, and provide the possibility that targeting NLRP3 inflammasome might be a promising strategy to prevent diabetic vascular senescence and associated vascular lesions.

Wei Chang An pill regulates gastrointestinal motility in a bidirectional manner

CONTEXT

Wei Chang An (WCA) is a commercial prescription developed for the coordination of gastrointestinal movement.

OBJECTIVE

To investigate the role of WCA in the regulation of diarrhoea and constipation in rats.

MATERIAL AND METHODS

The diarrhoea and constipation models were prepared by gavage of Folium senna and diphenoxylate hydrochloride. Rats were randomized equally (n = 6) into the normal group given saline daily, the positive group given Pinaverium Bromide (13.5 mg/kg) or Sennoside A (0.1 mg/kg) and three WCA-treated groups (22, 44, and 88 mg/kg) by gavage daily for 7 consecutive days. The effects of WCA were assessed by a series of faecal symptoms and histopathology. Gastrointestinal parameters were determined by ELISA. The effect of WCA on gastrointestinal tissues was evaluated by strip assay. Expression of ROCK-1 and MLCK was measured by RT-PCR and Western blotting.

RESULTS

Data from Bristol stool form scale, diarrhoea index, visceral sensitivity, defaecation time, and intestinal propulsive rate showed that WCA protected rats against diarrhoea and constipation (p < 0.01). The up-regulation of Substance P and 5-hydroxytryptamine in diarrhoea rats and down-regulation of Substance P and vasoactive intestinal polypeptide in constipation rats were inhibited by WCA (p < 0.05). WCA stimulated the gastrointestinal strip contractions but inhibited ACh-induced contractions (p < 0.01). The decreased ROCK-1 and MLCK expression in diarrhoea rats and increased in constipation rats were suppressed by WCA (p < 0.01).

CONCLUSIONS

WCA has both antidiarrhea and anti-constipation effects, suggesting its bidirectional role in gastrointestinal modulation, and providing evidence of WCA for irritable bowel syndrome treatment.

Baicalin attenuates angiotensin II-induced blood pressure elevation and modulates MLCK/p-MLC signaling pathway

Scutellaria baicalensis Georgi is an extensively used medicinal herb for the treatment of hypertension in traditional Chinese medicine. Baicalin, is an important flavonoid in Scutellaria baicalensis Georgi extracts, which exhibits therapeutic effects on anti-hypertension, but its underlying mechanisms remain to be further explored. Therefore, we investigated the effects and molecular mechanisms of Baicalin on anti-hypertension. In vivo studies revealed that Baicalin treatment significantly attenuated the elevation in blood pressure, the pulse propagation and thickening of the abdominal aortic wall in C57BL/6 mice infused with Angiotensin II (Ang II). Moreover, RNA-sequencing and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses identified 537 differentially expressed transcripts and multiple enriched signaling pathways (including vascular smooth muscle contraction and calcium signaling pathway). Consistently, we found that Baicalin pretreatment significantly alleviated the Ang II induced constriction of abdominal aortic ring, while promoted NE pre-contracted vasodilation of abdominal aortic ring at least partly dependent on L-type calcium channel. In addition, Ang II stimulation significantly increased cell viability and PCNA expression, while were attenuated after Baicalin treatment. Moreover, Baicalin pretreatment attenuated Ang II-induced intracellular Ca2+ release, Angiotensin II type 1 receptor (AT1R) expression and activation of MLCK/p-MLC pathway in vascular smooth muscle cells (VSMCs). The present work further addressed the pharmacological and mechanistic insights on anti-hypertension of Baicalin, which may help better understand the therapeutic effect of Scutellaria baicalensis Georgi on anti-hypertension.

Endolysosomal Ca2+ signaling in cardiovascular health and disease

An increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i) regulates a plethora of functions in the cardiovascular (CV) system, including contraction in cardiomyocytes and vascular smooth muscle cells (VSMCs), and angiogenesis in vascular endothelial cells and endothelial colony forming cells. The sarco/endoplasmic reticulum (SR/ER) represents the largest endogenous Ca²⁺ store, which releases Ca²⁺ through ryanodine receptors (RyRs) and/or inositol-1,4,5-trisphosphate receptors (InsP₃Rs) upon extracellular stimulation. The acidic vesicles of the endolysosomal (EL) compartment represent an additional endogenous Ca²⁺ store, which is targeted by several second messengers, including nicotinic acid adenine dinucleotide phosphate (NAADP) and phosphatidylinositol 3,5-bisphosphate [PI(3,5)P₂], and may release intraluminal Ca²⁺ through multiple Ca²⁺ permeable channels, including two-pore channels 1 and 2 (TPC1-2) and Transient Receptor Potential Mucolipin 1 (TRPML1). Herein, we discuss the emerging, pathophysiological role of EL Ca²⁺ signaling in the CV system. We describe the role of cardiac TPCs in β-adrenoceptor stimulation, arrhythmia, hypertrophy, and ischemia-reperfusion injury. We then illustrate the role of EL Ca²⁺ signaling in VSMCs, where TPCs promote vasoconstriction and contribute to pulmonary artery hypertension and atherosclerosis, whereas TRPML1 sustains vasodilation and is also involved in atherosclerosis. Subsequently, we describe the mechanisms whereby endothelial TPCs promote vasodilation, contribute to neurovascular coupling in the brain and stimulate angiogenesis and vasculogenesis. Finally, we discuss about the possibility to target TPCs, which are likely to mediate CV cell infection by the Severe Acute Respiratory Disease-Coronavirus-2, with Food and Drug Administration-approved drugs to alleviate the detrimental effects of Coronavirus Disease-19 on the CV system.

Signalling mechanisms in the cardiovascular protective effects of estrogen: With a focus on rapid/membrane signalling

In modern society, cardiovascular disease remains the biggest single threat to life, being responsible for approximately one third of worldwide deaths. Male prevalence is significantly higher than that of women until after menopause, when the prevalence of CVD increases in females until it eventually exceeds that of men. Because of the coincidence of CVD prevalence increasing after menopause, the role of estrogen in the cardiovascular system has been intensively researched during the past two decades in vitro, in vivo and in observational studies. Most of these studies suggested that endogenous estrogen confers cardiovascular protective and anti-inflammatory effects. However, clinical studies of the cardioprotective effects of hormone replacement therapies (HRT) not only failed to produce proof of protective effects, but also revealed the potential harm estrogen could cause. The "critical window of hormone therapy" hypothesis affirms that the moment of its administration is essential for positive treatment outcomes, pre-menopause (3-5 years before menopause) and immediately post menopause being thought to be the most appropriate time for intervention. Since many of the cardioprotective effects of estrogen signaling are mediated by effects on the vasculature, this review aims to discuss the effects of estrogen on vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) with a focus on the role of estrogen receptors (ERα, ERβ and GPER) in triggering the more recently discovered rapid, or membrane delimited (non-genomic), signaling cascades that are vital for regulating vascular tone, preventing hypertension and other cardiovascular diseases.

Investigation of ethnomedicinal use of Commiphora leptophloeos (Mart.) J. B. Gillett (Burseraceae) in treatment of diarrhea

ETHNOPHARMACOLOGICAL RELEVANCE

Commiphora leptophloeos (Mart.) J.B. Gillett, popularly known as "imburana", "imburana-de-cheiro" or "imburana-de-espinho", has been used in folk medicine for the treatment of gastrointestinal diseases, such as diarrhea. The indian tribes "Kairir-Shokó and shokó use the bark to treat diarrhea. However, there is no scientific evidence to justify the therapeutic use of this species.

AIM OF THE STUDY

To investigate the ethnomedicinal use of Commiphora leptophloeos, with respect to the antimicrobial, antisecretory, antimotility and antispasmodic activities of the crude ethanolic extract obtained from its leaves (CL-EtOH_L) and the mechanism underlying this action in rodents.

MATERIAL AND METHODS

In the evaluation of antibacterial and antifungal activities was determined the minimum inhibitory concentration (MIC) of the extract, against different strains of bacteria and fungi. All experimental protocols were approved by the Animal Ethics Committee of the Federal University of Paraíba (045/2016). In addition, behavioral screening and acute toxicity assessment of CL-EtOH_L were performed in female mice (n = 6). In the investigation of antidiarrheal activity (n = 6), frequency of defecation and number of liquid stools, were classified during 4 h, and intestinal fluid and transit were measured. In addition, the antispasmodic effect on rat ileum (n = 5) was also investigated.

RESULTS

The ethanolic extract is rich in flavonoids and the main were identified as C-glycosylated flavonoids (isoorientin, orientin, and vitexin). In the evaluation of antimicrobial and antifungal activity, the extract showed moderate efficacy only against the tested strains of Candida krusei ATCC-6258, Candida parapsilosis ATCC-22019 and Candida glabrata ATCC-90030. The extract had no toxic effect until 2000 mg/kg. In castor oil-induced diarrhea, CL-EtOH_L inhibited, in a dose-dependent manner, both total defecation frequency (ED₅₀ = 380.4 ± 145.4 mg/kg) and the number of watery stools (ED₅₀ = 151.2 ± 76.3 mg/kg). The extract showed no effect on fluid accumulation or normal intestinal transit. On the other hand, when the animals were pretreated with castor oil, the extract decreased the distance traveled by the activated charcoal (ED₅₀ = 177.0 ± 50.3 mg/kg). In the investigation of antispasmodic effect, CL-EtOH_L antagonized the contractions induced by KCl 30 mM (IC₅₀ = 208.2 ± 25.9 μg/mL) and CCh 10^-6 M (IC₅₀ = 95. ± 22.0 μg/mL). To verify the participation of muscarinic receptors in this effect, cumulative carbachol curves were performed in the absence and presence of the extract, and a non-competitive pseudo-irreversible antagonism of these receptors was observed.

CONCLUSION

The data indicate that ethanol extract obtained from the leaves of Commiphora leptophloeos has an antidiarrheal effect due to inhibition of the intestinal motility and antispasmodic effect, through the antagonism of muscarinic receptors. In addition, we suggest that flavonoids isolated from CL-EtOH_L may be responsible for antidiarrheal activity of this extract. This explains its ethnomedicinal use in the treatment of diarrhea.

Mechanism of α1-Adrenergic Receptor-Induced Increased Contraction of Rat Mesenteric Artery in Aging Hypertension Rats

INTRODUCTION

Vasoconstriction is triggered by an increase in intracellular-free calcium concentration. Growing evidence indicates that contraction is also regulated by calcium-independent mechanisms involving RhoA-Rho kinase (ROCK), protein kinase C (PKC), and so on. In this study, we studied the changes of vascular reactivity as well as the underlying signaling pathways in aging spontaneously hypertensive rats (SHRs).

METHODS

The artery tension induced by α1-adrenergic receptor activator (α1-AR) phenylephrine (PE) was measured in the absence or presence of myosin light chain kinase (MLCK), PKC, and ROCK inhibitors. The α1-AR, PKC, ROCK, phosphorylation of myosin light chain (MLC), and PKC-potentiated phosphatase inhibitors of 17 kDa (CPI-17) of rat mesenteric arteries were analyzed at the mRNA level or protein level.

RESULTS

The vascular tension measurements showed that there was a significant increase in the mesenteric artery contraction induced by PE in old SHR. MLCK inhibitor ML-7 can similarly inhibit PE-induced vasoconstriction. PKC inhibitor GF109203X has the weakest inhibitory effect on PE-induced contraction in old SHR. At the presence of ROCK inhibitor H1152, PE-induced contraction was significantly reduced in young Wistar-Kyoto (WKY) rats, but this phenomenon disappeared in other rats. Furthermore, in old SHR the protein expression of α1-AR decreased and phosphorylation of MLC and CPI-17 were upregulated and MLC phosphatase (MLCP) activity was significantly lower. The expressions of PKC were upregulated in SHR and old rats. In addition, the expression of ROCK-1 was decreased and ROCK-2 was significantly upregulated with age in SHR.

CONCLUSION

In aging hypertension, the expression/activity of PKC or ROCK-2/CPI-17 excessively increased, MLCP activity decreased and MLC phosphorylation enhanced, leading to increased α1-AR-induced vasoconstriction.

Regulation of smooth muscle contractility by the epithelium in rat tracheas: role of prostaglandin E2 induced by the neurotransmitter acetylcholine

Background

Previous studies have suggested the involvement of epithelium in modulating the contractility of neighboring smooth muscle cells. However, the mechanism underlying epithelium-derived relaxation in airways remains largely unclear. This study aimed to investigate the mechanism underlying epithelium-dependent smooth muscle relaxation mediated by neurotransmitters.

Methods

The contractile tension of Sprague-Dawley (SD) rat tracheal rings were measured using a mechanical recording system. Intracellular Ca²⁺ level was measured using a Ca²⁺ fluorescent probe Fluo-3 AM, and the fluorescence signal was recorded by a laser scanning confocal imaging system. The prostaglandin E₂ (PGE₂) content was measured using an enzyme-linked immunosorbent assay kit.

Results

We observed that the neurotransmitter acetylcholine (ACh) restrained the electric field stimulation (EFS)-induced contraction in the intact but not epithelium-denuded rat tracheal rings. After inhibiting the muscarinic ACh receptor (mAChR) or cyclooxygenase (COX), a critical enzyme in prostaglandin synthesis, the relaxant effect of ACh was attenuated. Exogenous PGE₂ showed a similar inhibitory effect on the EFS-evoked contraction of tracheal rings. Moreover, ACh triggered phospholipase C (PLC)-coupled Ca²⁺ release from intracellular Ca²⁺ stores and stimulated COX-dependent PGE₂ production in primary cultured rat tracheal epithelial cells.

Conclusions

Collectively, this study demonstrated that ACh induced rat tracheal smooth muscle relaxation by promoting PGE₂ release from tracheal epithelium, which might provide valuable insights into the cross-talk among neurons, epithelial cells and neighboring smooth muscle cells in airways.

Human Dental Pulp-Derived Mesenchymal Stem Cell Potential to Differentiate into Smooth Muscle-Like Cells In Vitro

Previous studies have shown that mesenchymal stem cells (MSCs) derived from various tissue sources can be differentiated into smooth muscle-like cells (SMLCs) in vitro. In this paper, dental pulp-derived mesenchymal stem cells (DPSCs) were evaluated for their differentiation ability towards smooth muscle-like cells (SMLCs) under the effect of widely used cytokines (TGF-β1 and PDGF-BB) with special focus on different culturing environments. For this purpose, both the commercially used culturing plates (Norm-c) and 0.1% gelatin-precoated (Gel-c) plates were used. Isolated cells displayed plastic adherence, pluripotency and cell surface marker profiling, and adipogenic and osteogenic differentiation potential with lineage specific marker expression. Differentiated cells induced under different culturing plates showed successful differentiation into SMLCs by positively expressing smooth muscle cell (SMC) specific markers both at the mRNA and protein levels. Gelatin coating could substantially enhance DPSC differentiation potential than Norm-c-induced cells. However, the absence of mature marker MHY-11 by immunostaining results from all treatment groups further indicated the development of immature and synthetic SMLCs. Finally, it was concluded that DPSC differentiation ability into SMLCs can be enhanced under cytokine treatment as well as by altering the cellular niche by precoating the culturing plates with suitable substrates. However, to get fully functional, contractile, and mature SMLCs, still many different cytokine cocktail combinations and more suitable coating substrates will be needed.

In vitro and in silico studies of 8(17),12E,14-labdatrien-18-oic acid in airways smooth muscle relaxation: new molecular insights about its mechanism of action

In the field of experimental pharmacology, researchers continuously investigate new relaxant agents of the airway smooth muscle cells (ASMCs), since the pathophysiology of respiratory illnesses, such as asthma, involves hyperresponsiveness and changes in ASMC homeostasis. In this scenario, labdane-type diterpenes, like forskolin (FSK), are a class of compounds known for their relaxing action on smooth muscle cells (SMCs), being this phenomenon related to the direct activation of AC-cAMP-PKA pathway. Considering the continuous effort of our group to study the mechanism of action and prospecting for compounds isolated from natural sources, in this paper, we presented how the diterpene 8(17),12E,14-labdatrien-18-oic acid (LBD) promotes relaxant effect on ASMC, performing in vitro experiments using isolated guinea pig trachea and in silico molecular docking/dynamics simulations. In vitro experiments showed that in the presence of aminophylline, FSK and LBD had their relaxant effect potentiated (EC₅₀ from 1.4 ± 0.2 × 10^-5 M to 1.5 ± 0.3 × 10^-6 M for LBD and from 2.0 ± 0.2 × 10^-7 M to 6.4 ± 0.4 × 10^-8 M for FSK) while in the presence of Rp-cAMPS this effect was attenuated (EC₅₀ from 1.4 ± 0.2 × 10^-5 M to 3 × 10^-4 M for LBD and from 2.0 ± 0.2 × 10^-7 to 3.1 ± 1.0 × 10^-6 M for FSK). Additionally, in silico simulations evidenced that the lipophilic character of LBD is probably responsible for its stability on AC binding site. LBD presented two preferential orientations, where the double bonds of the isoprene moiety as well as the unique polar group (carboxylic acid) in this compound form important anchoring points. In this sense, we consider that the LBD can interact stabilizing the catalytic dimmer of AC as the FSK, although less efficiently.

New insights into RhoA/Rho-kinase signaling: a key regulator of vascular contraction

While Rho-signalling controlling vascular contraction is a canonical mechanism, with the modern approaches used in research, we are advancing our understanding and details into this pathway are often uncovered. RhoA-mediated Rho-kinase is the major regulator of vascular smooth muscle cells and a key player manoeuvring other functions in these cells. The discovery of new interactions, such as oxidative stress and hydrogen sulphide with Rho signalling are emerging addition not only in the physiology of the smooth muscle, but especially in the pathophysiology of vascular diseases. Likewise, the interplay between ageing and Rho-kinase in the vasculature has been recently considered. Importantly, in smooth muscle contraction, this pathway may also be affected by sex hormones, and consequently, sex-differences. This review provides an overview of Rho signalling mediating vascular contraction and focuses on recent topics discussed in the literature affecting this pathway such as ageing, sex differences and oxidative stress.

Regulation of smooth muscle contraction by monomeric non-RhoA GTPases

Smooth muscle contraction in the cardiovascular system, airways, prostate and lower urinary tract is involved in the pathophysiology of many diseases, including cardiovascular and obstructive lung disease plus lower urinary tract symptoms, which are associated with high prevalence of morbidity and mortality. This prominent clinical role of smooth muscle tone has led to the molecular mechanisms involved being subjected to extensive research. In general smooth muscle contraction is promoted by three major signalling pathways, including the monomeric GTPase RhoA pathway. However, emerging evidence suggests that monomeric GTPases other than RhoA may be involved in signal transduction in smooth muscle contraction, including Rac GTPases, cell division control protein 42 homologue, adenosine ribosylation factor 6, Ras, Rap1b and Rab GTPases. Here, we review these emerging functions of non-RhoA GTPases in smooth muscle contraction, which has now become increasingly more evident and constitutes an emerging and innovative research area of high clinical relevance.

Introduction to ion channels and calcium signaling in the microcirculation

The microcirculation is the network of feed arteries, arterioles, capillaries and venules that supply and drain blood from every tissue and organ in the body. It is here that exchange of heat, oxygen, carbon dioxide, nutrients, hormones, water, cytokines, and immune cells takes place; essential functions necessary to maintenance of homeostasis throughout the life span. This chapter will outline the structure and function of each microvascular segment highlighting the critical roles played by ion channels in the microcirculation. Feed arteries upstream from the true microcirculation and arterioles within the microcirculation contribute to systemic vascular resistance and blood pressure control. They also control total blood flow to the downstream microcirculation with arterioles being responsible for distribution of blood flow within a tissue or organ dependent on the metabolic needs of the tissue. Terminal arterioles control blood flow and blood pressure to capillary units, the primary site of diffusional exchange between blood and tissues due to their large surface area. Venules collect blood from capillaries and are important sites for fluid exchange and immune cell trafficking. Ion channels in microvascular smooth muscle cells, endothelial cells and pericytes importantly contribute to all of these functions through generation of intracellular Ca²⁺ and membrane potential signals in these cells.

Myocardin Is Involved in Mesothelial-Mesenchymal Transition of Human Pleural Mesothelial Cells

Pleural fibrosis is characterized by severe inflammation of the pleural space and pleural reorganization. Subsequent thickening of the visceral pleura contributes to lung stiffness and impaired lung function. Pleural mesothelial cells (PMCs) can become myofibroblasts via mesothelial-mesenchymal transition (MesoMT) and contribute to pleural organization, fibrosis, and rind formation. However, the mechanisms that underlie MesoMT remain unclear. Here, we investigated the role of myocardin in the induction of MesoMT. Transforming growth factor β (TGF-β) and thrombin induced MesoMT and markedly upregulated the expression of myocardin, but not myocardin-related transcription factor A (MRTF-A) or MRTF-B, in human PMCs (HPMCs). TGF-β stimulation notably induced the nuclear translocation of myocardin in HPMCs, whereas nuclear translocation of MRTF-A and MRTF-B was not observed. Several genes under the control of myocardin were upregulated in cells undergoing MesoMT, an effect that was accompanied by a dramatic cytoskeletal reorganization of HPMCs consistent with a migratory phenotype. Myocardin gene silencing blocked TGF-β- and thrombin-induced MesoMT. Although myocardin upregulation was blocked, MRTF-A and MRTF-B were unchanged. Myocardin, α-SMA, calponin, and smooth muscle myosin were notably upregulated in the thickened pleura of carbon black/bleomycin and empyema mouse models of fibrosing pleural injury. Similar results were observed in human nonspecific pleuritis. In a TGF-β mouse model of pleural fibrosis, PMC-specific knockout of myocardin protected against decrements in lung function. Further, TGF-β-induced pleural thickening was abolished by PMC-specific myocardin knockout, which was accompanied by a marked reduction of myocardin, calponin, and α-SMA expression compared with floxed-myocardin controls. These novel results show that myocardin participates in the development of MesoMT in HPMCs and contributes to the pathogenesis of pleural organization and fibrosis.

Vascular smooth muscle contraction in hypertension

Hypertension is a major risk factor for many common chronic diseases, such as heart failure, myocardial infarction, stroke, vascular dementia, and chronic kidney disease. Pathophysiological mechanisms contributing to the development of hypertension include increased vascular resistance, determined in large part by reduced vascular diameter due to increased vascular contraction and arterial remodelling. These processes are regulated by complex-interacting systems such as the renin-angiotensin-aldosterone system, sympathetic nervous system, immune activation, and oxidative stress, which influence vascular smooth muscle function. Vascular smooth muscle cells are highly plastic and in pathological conditions undergo phenotypic changes from a contractile to a proliferative state. Vascular smooth muscle contraction is triggered by an increase in intracellular free calcium concentration ([Ca²⁺]_i), promoting actin–myosin cross-bridge formation. Growing evidence indicates that contraction is also regulated by calcium-independent mechanisms involving RhoA-Rho kinase, protein Kinase C and mitogen-activated protein kinase signalling, reactive oxygen species, and reorganization of the actin cytoskeleton. Activation of immune/inflammatory pathways and non-coding RNAs are also emerging as important regulators of vascular function. Vascular smooth muscle cell [Ca²⁺]_i not only determines the contractile state but also influences activity of many calcium-dependent transcription factors and proteins thereby impacting the cellular phenotype and function. Perturbations in vascular smooth muscle cell signalling and altered function influence vascular reactivity and tone, important determinants of vascular resistance and blood pressure. Here, we discuss mechanisms regulating vascular reactivity and contraction in physiological and pathophysiological conditions and highlight some new advances in the field, focusing specifically on hypertension.

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

ETHNOPHARMACOLOGICAL RELEVANCE

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

AIM OF THE STUDY

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Isolation and culture of vascular smooth muscle cells from rat placenta

We developed a new separation method for isolating placental vascular smooth muscle cells (PVSMCs) from a rat in this study. Our method used the magnetic force between a magnet and ferrous ferric oxide (Fe3 O 4 ) to make the separation and extraction processes easier and more efficient. From the first to sixth generation, the cells isolated using this protocol were identified as smooth muscle cells (SMCs) by their immunoreactivity to the SMC markers and by the "hill and valley" morphology. PVSMCs were exposed to angiotensin II (1 μmol/L) and resulted in sharply increased intracellular Ca 2+ concentration. Furthermore, activation of protein kinase C (PKC) increased concomitantly with a decrease in calponin expression. These results indicate that the isolated cells had biological activity. Our method of isolating PVSMCs from rat leads to isolation of cultured cells with activity and high purity. The approach will be useful in research studies on placental vascular diseases.

Invertebrate troponin: Insights into the evolution and regulation of striated muscle contraction

The troponin complex plays a central role in regulating the contraction and relaxation of striated muscles. Among the three protein subunits of troponin, the calcium receptor subunit, TnC, belongs to the calmodulin family of calcium signaling proteins whereas the inhibitory subunit, TnI, and tropomyosin-binding/thin filament-anchoring subunit, TnT, are striated muscle-specific regulatory proteins. TnI and TnT emerged early in bilateral symmetric invertebrate animals and have co-evolved during the 500-700 million years of muscle evolution. To understand the divergence as well as conservation of the structures of TnI and TnT in invertebrate and vertebrate organisms adds novel insights into the structure-function relationship of troponin and the muscle type isoforms of TnI and TnT. Based on the significant growth of genomic database of multiple species in the past decade, this focused review studied the primary structure features of invertebrate troponin subunits in comparisons with the vertebrate counterparts. The evolutionary data demonstrate valuable information for a better understanding of the thin filament regulation of striated muscle contractility in health and diseases.

Muscarinic m2 receptor-mediated actin polymerization via PI3 kinase γ and integrin-linked kinase in gastric smooth muscle

BACKGROUND

Actin polymerization plays an important role in smooth muscle contraction. Integrin-linked kinase (ILK) was shown to mediate actin polymerization in airway smooth muscle. The role of ILK in actin polymerization in response to m2 receptor activation was not in gastric smooth muscle.

METHODS

Phosphorylation of paxillin, neuronal Wiskott-Aldrich syndrome protein (N-WASp), and association of paxillin with GEF proteins (Cool2/αPix [Cool2/PAK-interacting exchange factor alpha], Cool1/βPix [Cool1/PAK-interacting exchange factor beta], and DOCK 180 [Dedicator of cytokinesis]) and N-WASp with Arp2/3 complex were measured by western blot. Activation of Cdc42 was determined using an antibody for activated Cdc42. Actin polymerization was measured as an increase in F-actin/G-actin ratio.

RESULTS

Phosphorylation of paxillin, an association of paxillin with GEF proteins, Cdc42 activity, and actin polymerization were increased in response to m2 receptor activation in gastric smooth muscle cells. The increases in paxillin phosphorylation, Cdc42 activity, and actin polymerization were inhibited by a PI3Kγ inhibitor (AS-605240), ILK siRNA, and ILK dominant negative mutant (ILK [R211]). Increase in actin polymerization was also inhibited by Cdc42 dominant negative mutant (Cdc42 [T17N]). Increases in the association of paxillin with GEF proteins, phosphorylation of N-WASp and its association with Arp2/3 complex were inhibited by ILK (R211).

CONCLUSION

In gastric smooth muscle cells, activation of PI3Kγ by muscarinic m2 receptors causes ILK-dependent phosphorylation of paxillin, an association of paxillin with Cdc42 GEF proteins and activation of Cdc42, which, in turn, causes phosphorylation of N-WASp and its association with Arp2/3 complex leading to actin polymerization.

Anti-hypertensive mechanisms of cyclic depsipeptide inhibitor ligands for Gq/11 class G proteins

Augmented vasoconstriction is a hallmark of hypertension and is mediated partly by hyper-stimulation of G protein couple receptors (GPCRs) and downstream signaling components. Although GPCR blockade is a key component of current anti-hypertensive strategies, whether hypertension is better managed by directly targeting G proteins has not been thoroughly investigated. Here, we tested whether inhibiting G_q/11 proteins in vivo and ex vivo using natural cyclic depsipeptide, FR900359 (FR) from the ornamental plant, Ardisia crenata, and YM-254890 (YM) from Chromobacterium sp. QS3666, or it's synthetic analog, WU-07047 (WU), was sufficient to reverse hypertension in mice. All three inhibitors blocked G protein-dependent vasoconstriction, but to our surprise YM and WU and not FR inhibited K⁺-induced Ca²⁺ transients and vasoconstriction of intact vessels. However, each inhibitor blocked whole-cell L-type Ca²⁺ channel current in vascular smooth muscle cells. Subcutaneous injection of FR or YM (0.3 mg/kg, s.c.) in normotensive and hypertensive mice elicited bradycardia and marked blood pressure decrease, which was more severe and long lasting after the injection of FR relative to YM (FR_t1/2 ≅ 12 h vs. YM_t1/2 ≅ 4 h). In deoxycorticosterone acetate (DOCA)-salt hypertension mice, chronic injection of FR (0.3 mg/kg, s.c., daily for seven days) reversed hypertension (vehicle SBP: 149 ± 5 vs. FR SBP: 117 ± 7 mmHg), without any effect on heart rate. Our results together support the hypothesis that increased LTCC and G_q/11 activity is involved in the pathogenesis of hypertension, and that dual targeting of both proteins can reverse hypertension and associated cardiovascular disorders.

Regulation of gastric smooth muscle contraction via Ca2+-dependent and Ca2+-independent actin polymerization

In gastrointestinal smooth muscle, acetylcholine induced muscle contraction is biphasic, initial peak followed by sustained contraction. Contraction is regulated by phosphorylation of 20 kDa myosin light chain (MLC) at Ser¹⁹, interaction of actin and myosin, and actin polymerization. The present study characterized the signaling mechanisms involved in actin polymerization during initial and sustained muscle contraction in response to muscarinic M3 receptor activation in gastric smooth muscle cells by targeting the effectors of initial (phospholipase C (PLC)-β/Ca²⁺ pathway) and sustained (RhoA/focal adhesion kinase (FAK)/Rho kinase pathway) contraction. The initial Ca²⁺ dependent contraction and actin polymerization is mediated by sequential activation of PLC-β1 via Gα_q, IP₃ formation, Ca²⁺ release and Ca²⁺ dependent phosphorylation of proline-rich-tyrosine kinase 2 (Pyk2) at Tyr⁴⁰². The sustained Ca²⁺ independent contraction and actin polymerization is mediated by activation of RhoA, and phosphorylation of FAK at Tyr³⁹⁷. Both phosphorylation of Pyk2 and FAK leads to phosphorylation of paxillin at Tyr¹¹⁸ and association of phosphorylated paxillin with the GEF proteins p21-activated kinase (PAK) interacting exchange factor α, β (α and β PIX) and DOCK 180. These GEF proteins stimulate Cdc42 leading to the activation of nucleation promoting factor N-WASP (neuronal Wiskott-Aldrich syndrome protein), which interacts with actin related protein complex 2/3 (Arp2/3) to induce actin polymerization and muscle contraction. Acetylcholine induced muscle contraction is inhibited by actin polymerization inhibitors. Thus, our results suggest that a novel mechanism for the regulation of smooth muscle contraction is mediated by actin polymerization in gastrointestinal smooth muscle which is independent of MLC₂₀ phosphorylation.

Calponin-3 is critical for coordinated contractility of actin stress fibers

Contractile actomyosin bundles, stress fibers, contribute to morphogenesis, migration, and mechanosensing of non-muscle cells. In addition to actin and non-muscle myosin II (NMII), stress fibers contain a large array of proteins that control their assembly, turnover, and contractility. Calponin-3 (Cnn3) is an actin-binding protein that associates with stress fibers. However, whether Cnn3 promotes stress fiber assembly, or serves as either a positive or negative regulator of their contractility has remained obscure. Here, we applied U2OS osteosarcoma cells as a model system to study the function of Cnn3. We show that Cnn3 localizes to both NMII-containing contractile ventral stress fibers and transverse arcs, as well as to non-contractile dorsal stress fibers that do not contain NMII. Fluorescence-recovery-after-photobleaching experiments revealed that Cnn3 is a dynamic component of stress fibers. Importantly, CRISPR/Cas9 knockout and RNAi knockdown studies demonstrated that Cnn3 is not essential for stress fiber assembly. However, Cnn3 depletion resulted in increased and uncoordinated contractility of stress fibers that often led to breakage of individual actomyosin bundles within the stress fiber network. Collectively these results provide evidence that Cnn3 is dispensable for the assembly of actomyosin bundles, but that it is required for controlling proper contractility of the stress fiber network.

KV channels and the regulation of vascular smooth muscle tone

VSMCs in resistance arteries and arterioles express a diverse array of K_V channels with members of the K_V 1, K_V 2 and K_V 7 families being particularly important. Members of the K_V channel family: (i) are highly expressed in VSMCs; (ii) are active at the resting membrane potential of VSMCs in vivo (-45 to -30 mV); (iii) contribute to the negative feedback regulation of VSMC membrane potential and myogenic tone; (iv) are activated by cAMP-related vasodilators, hydrogen sulfide and hydrogen peroxide; (v) are inhibited by increases in intracellular Ca²⁺ and vasoconstrictors that signal through G_q -coupled receptors; (vi) are involved in the proliferative phenotype of VSMCs; and (vii) are modulated by diseases such as hypertension, obesity, the metabolic syndrome and diabetes. Thus, K_V channels participate in every aspect of the regulation of VSMC function in both health and disease.

Levobupivacaine-induced vasoconstriction involves caldesmon phosphorylation mediated by tyrosine kinase-induced ERK phosphorylation

The goals of this study were to examine the cellular signaling pathways associated with the phosphorylation of caldesmon, the phosphorylation-dependent inhibitory protein of myosin phosphatase (CPI-17), and the 20-kDa regulatory light chain of myosin (MLC₂₀) induced by levobupivacaine in isolated rat aortas. The effects of genistein, tyrphostin 23, GF109203X, PD98059, Y-27632, 1-butanol, and ML-7 HCl on levobupivacaine-induced contraction were assessed. The effect of genistein on the simultaneous calcium-tension curves induced by levobupivacaine was examined. The effects of GF109203X, genistein, PD98059 and extracellular signal-regulated kinase (ERK) siRNA on levobupivacaine-induced caldesmon phosphorylation were investigated. The effect of genistein on the ERK and tyrosine phosphorylation induced by levobupivacaine was examined. The effect of GF109203X, PD98059, Y-27632, SP600125, and ML-7 HCl on the levobupivacaine-induced phosphorylation of CPI-17 and MLC₂₀ were investigated. Genistein, tyrphostin 23, GF109203X, PD98059, Y-27632, ML-7 HCl, and 1-butanol attenuated levobupivacaine-induced contraction. Genistein caused a right downward shift of the calcium-tension curves induced by levobupivacaine. Genistein attenuated levobupivacaine-induced phosphorylation of protein tyrosine, ERK and caldesmon. PD98059, ERK siRNA and GF109203X attenuated levobupivacaine-induced caldesmon phosphorylation. GF109203X, Y-27632, SP600125, ML-7 HCl and PD98059 attenuated CPI-17 phosphorylation and MLC₂₀ phosphorylation induced by levobupivacaine. These results suggest that levobupivacaine-induced caldesmon phosphorylation contributing to levobupivacaine-induced contraction is mediated by a pathway involving ERK, which is activated by tyrosine kinase or protein kinase C (PKC). The phosphorylation of CPI-17 and MLC₂₀ induced by levobupivacaine is mediated by cellular signaling pathways involving PKC, Rho-kinase, and c-Jun NH₂-terminal kinase or PKC, Rho-kinase, ERK, and myosin light chain kinase.

Evolving mechanisms of vascular smooth muscle contraction highlight key targets in vascular disease

Vascular smooth muscle (VSM) plays an important role in the regulation of vascular function. Identifying the mechanisms of VSM contraction has been a major research goal in order to determine the causes of vascular dysfunction and exaggerated vasoconstriction in vascular disease. Major discoveries over several decades have helped to better understand the mechanisms of VSM contraction. Ca2+ has been established as a major regulator of VSM contraction, and its sources, cytosolic levels, homeostatic mechanisms and subcellular distribution have been defined. Biochemical studies have also suggested that stimulation of Gq protein-coupled membrane receptors activates phospholipase C and promotes the hydrolysis of membrane phospholipids into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 stimulates initial Ca2+ release from the sarcoplasmic reticulum, and is buttressed by Ca2+ influx through voltage-dependent, receptor-operated, transient receptor potential and store-operated channels. In order to prevent large increases in cytosolic Ca2+ concentration ([Ca2+]c), Ca2+ removal mechanisms promote Ca2+ extrusion via the plasmalemmal Ca2+ pump and Na+/Ca2+ exchanger, and Ca2+ uptake by the sarcoplasmic reticulum and mitochondria, and the coordinated activities of these Ca2+ handling mechanisms help to create subplasmalemmal Ca2+ domains. Threshold increases in [Ca2+]c form a Ca2+-calmodulin complex, which activates myosin light chain (MLC) kinase, and causes MLC phosphorylation, actin-myosin interaction, and VSM contraction. Dissociations in the relationships between [Ca2+]c, MLC phosphorylation, and force have suggested additional Ca2+ sensitization mechanisms. DAG activates protein kinase C (PKC) isoforms, which directly or indirectly via mitogen-activated protein kinase phosphorylate the actin-binding proteins calponin and caldesmon and thereby enhance the myofilaments force sensitivity to Ca2+. PKC-mediated phosphorylation of PKC-potentiated phosphatase inhibitor protein-17 (CPI-17), and RhoA-mediated activation of Rho-kinase (ROCK) inhibit MLC phosphatase and in turn increase MLC phosphorylation and VSM contraction. Abnormalities in the Ca2+ handling mechanisms and PKC and ROCK activity have been associated with vascular dysfunction in multiple vascular disorders. Modulators of [Ca2+]c, PKC and ROCK activity could be useful in mitigating the increased vasoconstriction associated with vascular disease.

Gene expression profiles of ion channels and receptors in mouse resistance arteries: Effects of cell type, vascular bed, and age

OBJECTIVE

Receptors and ion channels of smooth muscle cells (SMCs) and endothelial cells (ECs) are integral to the regulation of vessel diameter and tissue blood flow. Physiological roles of ion channels and receptors in skeletal muscle and mesenteric arteries have been identified; however, their gene expression profiles are undefined. We tested the hypothesis that expression profiles for ion channels and receptors governing vascular reactivity vary with cell type, vascular bed, and age.

METHODS

Mesenteric and superior epigastric arteries were dissected from Old (24-26 months) and Young (3-6 months) C57BL/6J mice. ECs and SMCs were collected for analysis with custom qRT-PCR arrays to determine expression profiles of 80 ion channel and receptor genes. Bioinformatics analyses were applied to gain insight into functional interactions.

RESULTS

We identified 68 differences in gene expression with respect to cell type, vessel type, and age. Heat maps illustrate differential expression, and distance matrices predict patterns of coexpression. Gene networks based upon protein-protein interaction datasets and KEGG pathways illustrate biological processes affected by specific differences in gene expression.

CONCLUSIONS

Differences in gene expression profiles are most pronounced between microvascular ECs and SMCs with subtle variations between vascular beds and age groups.

Elastomeric sensor surfaces for high-throughput single-cell force cytometry

As cells with aberrant force-generating phenotypes can directly lead to disease, cellular force-generation mechanisms are high-value targets for new therapies. Here, we show that single-cell force sensors embedded in elastomers enable single-cell force measurements with ~100-fold improvement in throughput than was previously possible. The microtechnology is scalable and seamlessly integrates with the multi-well plate format, enabling highly parallelized time-course studies. In this regard, we show that airway smooth muscle cells isolated from fatally asthmatic patients have innately greater and faster force-generation capacity in response to stimulation than healthy control cells. By simultaneously tracing agonist-induced calcium flux and contractility in the same cell, we show that the calcium level is ultimately a poor quantitative predictor of cellular force generation. Finally, by quantifying phagocytic forces in thousands of individual human macrophages, we show that force initiation is a digital response (rather than a proportional one) to the proper immunogen. By combining mechanobiology at the single-cell level with high-throughput capabilities, this microtechnology can support drug-discovery efforts for clinical conditions associated with aberrant cellular force generation.

Large-scale profiling of signalling pathways reveals an asthma specific signature in bronchial smooth muscle cells

Background

Bronchial smooth muscle (BSM) cells from asthmatic patients maintain in vitro a distinct hyper-reactive (“primed”) phenotype, characterized by increased release of pro-inflammatory factors and mediators, as well as hyperplasia and/or hypertrophy. This “primed” phenotype helps to understand pathogenesis of asthma, as changes in BSM function are essential for manifestation of allergic and inflammatory responses and airway wall remodelling.

Objective

To identify signalling pathways in cultured primary BSMs of asthma patients and non-asthmatic subjects by genome wide profiling of differentially expressed mRNAs and activated intracellular signalling pathways (ISPs).

Methods

Transcriptome profiling by cap-analysis-of-gene-expression (CAGE), which permits selection of preferentially capped mRNAs most likely to be translated into proteins, was performed in human BSM cells from asthmatic (n=8) and non-asthmatic (n=6) subjects and OncoFinder tool were then exploited for identification of ISP deregulations.

Results

CAGE revealed >600 RNAs differentially expressed in asthma vs control cells (p≤0.005), with asthma samples showing a high degree of similarity among them. Comprehensive ISP activation analysis revealed that among 269 pathways analysed, 145 (p<0.05) or 103 (p<0.01) are differentially active in asthma, with profiles that clearly characterize BSM cells of asthmatic individuals. Notably, we identified 7 clusters of coherently acting pathways functionally related to the disease, with ISPs down-regulated in asthma mostly targeting cell death-promoting pathways and up-regulated ones affecting cell growth and proliferation, inflammatory response, control of smooth muscle contraction and hypoxia-related signalization.

Conclusions

These first-time results can now be exploited toward development of novel therapeutic strategies targeting ISP signatures linked to asthma pathophysiology.

Regional Heterogeneity in the Regulation of Vasoconstriction in Arteries and Its Role in Vascular Mechanics

Vasoconstriction and vasodilation play important roles in the circulatory system and can be regulated through different pathways that depend on myriad biomolecules. These different pathways reflect the various functions of smooth muscle cell (SMC) contractility within the different regions of the arterial tree and how they contribute to both the mechanics and the mechanobiology. Here, we review the primary regulatory pathways involved in SMC contractility and highlight their regional differences in elastic, muscular, and resistance arteries. In this way, one can begin to assess how these properties affect important biomechanical and mechanobiological functions in the circulatory system in health and disease.

Matrix Metalloproteinase-2 Activity is Associated with Divergent Regulation of Calponin-1 in Conductance and Resistance Arteries in Hypertension-induced Early Vascular Dysfunction and Remodelling

Matrix metalloproteinase (MMP)-2 participates in hypertension-induced maladaptive vascular remodelling by degrading extra- and intracellular proteins. The consequent extracellular matrix rearrangement and phenotype switch of vascular smooth muscle cells (VSMCs) lead to increased cellular migration and proliferation. As calponin-1 degradation by MMP-2 may lead to VSMC proliferation during hypertension, the hypothesis of this study is that increased MMP-2 activity contributes to early hypertension-induced maladaptive remodelling in conductance and resistance arteries via regulation of calponin-1. The main objective was to analyse whether MMP-2 exerts similar effects on the structure and function of the resistance and conductance arteries during early hypertension. Two-kidney, one-clip (2K-1C) hypertensive male rats and corresponding controls were treated with doxycycline (30 mg/kg/day) or water until reaching one week of hypertension. Systolic blood pressure was increased in 2K-1C rats, and doxycycline did not reduce it. Aortas and mesenteric arteries were analysed. MMP-2 activity and expression were increased in both arteries, and doxycycline reduced it. Significant hypertrophic remodelling and VSMC proliferation were observed in aortas but not in mesenteric arteries of 2K-1C rats. The contractility of mesenteric arteries to phenylephrine was increased in 2K-1C rats, and doxycycline prevented this alteration. The potency of phenylephrine to contract aortas of 2K-1C rats was increased, and doxycycline decreased it. Whereas calponin-1 expression was increased in 2K-1C mesenteric arteries, calponin-1 was reduced in aortas. Doxycycline treatment reverted changes in calponin-1 expression. MMP-2 contributes to hypertrophic remodelling in aortas by decreasing calponin-1 levels, which may result in VSMC proliferation. On the other hand, MMP-2-dependent increased calponin-1 in mesenteric arteries may contribute to vascular hypercontractility in 2K-1C rats. Divergent regulation of calponin-1 by MMP-2 may be an important mechanism that leads to maladaptive vascular effects in hypertension.

TRPC Channels in Health and Disease

This chapter offers a brief introduction of the functions of TRPC channels in non-neuronal systems. We focus on three major organs of which the research on TRPC channels have been most focused on: kidney, heart, and lung. The chapter highlights on cellular functions and signaling pathways mediated by TRPC channels. It also summarizes several inherited diseases in humans that are related to or caused by TRPC channel mutations and malfunction. A better understanding of TRPC channels functions and the importance of TRPC channels in health and disease should lead to new insights and discovery of new therapeutic approaches for intractable disease.

Physiological vs. pharmacological signalling to myosin phosphorylation in airway smooth muscle

KEY POINTS

Smooth muscle myosin regulatory light chain (RLC) is phosphorylated by Ca²⁺ /calmodulin-dependent myosin light chain kinase and dephosphorylated by myosin light chain phosphatase (MLCP). Tracheal smooth muscle contains significant amounts of myosin binding subunit 85 (MBS85), another myosin phosphatase targeting subunit (MYPT) family member, in addition to MLCP regulatory subunit MYPT1. Concentration/temporal responses to carbachol demonstrated similar sensitivities for bovine tracheal force development and phosphorylation of RLC, MYPT1, MBS85 and paxillin. Electrical field stimulation releases ACh from nerves to increase RLC phosphorylation but not MYPT1 or MBS85 phosphorylation. Thus, nerve-mediated muscarinic responses in signalling modules acting on RLC phosphorylation are different from pharmacological responses with bath added agonist. The conditional knockout of MYPT1 or the knock-in mutation T853A in mice had no effect on muscarinic force responses in isolated tracheal tissues. MLCP activity may arise from functionally shared roles between MYPT1 and MBS85, resulting in minimal effects of MYPT1 knockout on contraction.

ABSTRACT

Ca²⁺ /calmodulin activation of myosin light chain kinase (MLCK) initiates myosin regulatory light chain (RLC) phosphorylation for smooth muscle contraction with subsequent dephosphorylation for relaxation by myosin light chain phosphatase (MLCP) containing regulatory (MYPT1) and catalytic (PP1cδ) subunits. RLC phosphorylation-dependent force development is regulated by distinct signalling modules involving protein phosphorylations. We investigated responses to cholinergic agonist treatment vs. neurostimulation by electric field stimulation (EFS) in bovine tracheal smooth muscle. Concentration/temporal responses to carbachol demonstrated tight coupling between force development and RLC phosphorylation but sensitivity differences in MLCK, MYPT1 T853, MYPT1 T696, myosin binding subunit 85 (MBS85), paxillin and CPI-17 (PKC-potentiated protein phosphatase 1 inhibitor protein of 17 kDa) phosphorylations. EFS increased force and phosphorylation of RLC, CPI-17 and MLCK. In the presence of the cholinesterase inhibitor neostigmine, EFS led to an additional increase in phosphorylation of MYPT1 T853, MYPT1 T696, MBS85 and paxillin. Thus, there were distinct pharmacological vs. physiological responses in signalling modules acting on RLC phosphorylation and force responses, probably related to degenerate G protein signalling networks. Studies with genetically modified mice were performed. Expression of another MYPT1 family member, MBS85, was enriched in mouse, as well as bovine tracheal smooth muscle. Carbachol concentration/temporal-force responses were similar in trachea from MYPT1^SM+/+ , MYPT1^SM-/- and the knock-in mutant mice containing nonphosphorylatable MYPT1 T853A with no differences in RLC phosphorylation. Thus, MYPT1 T853 phosphorylation was not necessary for regulation of RLC phosphorylation in tonic airway smooth muscle. Furthermore, MLCP activity may arise from functionally shared roles between MYPT1 and MBS85, resulting in minimal effects of MYPT1 knockout on contraction.

Highly sensitive myosin phosphorylation analysis in the renal afferent arteriole

The regulation of smooth muscle contraction and relaxation involves phosphorylation and dephosphorylation of regulatory proteins, particularly myosin. To elucidate the regulatory mechanisms, analyzing the phosphorylation signal transduction is crucial. Although a pharmacological approach with selective inhibitors is sensitive and a useful technique, it leads to speculation regarding a signaling pathway but does not provide direct evidence of changes at a molecular level. We developed a highly sensitive biochemical technique to analyze phosphorylation by adapting Phos-tag SDS-PAGE. With this technique, we successfully analyzed myosin light chain (LC₂₀) phosphorylation in tiny renal afferent arterioles. In the rat afferent arterioles, endothelin-1 (ET-1) induced diphosphorylation of LC₂₀ at Ser19 and Thr18 as well as monophosphorylation at Ser19 via ET_B receptor activation. Considering that LC₂₀ diphosphorylation can decrease the rate of dephosphorylation and thus relaxation, we concluded that LC₂₀ diphosphorylation contributes, at least in part, to the prolonged contraction induced by ET-1 in the renal afferent arteriole.

T-type voltage-gated Ca2+ channels do not contribute to the negative feedback regulation of myogenic tone in murine superior epigastric arteries

T-type voltage-gated Ca2+ channels (CaV3.2 VGCC) have been hypothesized to control spontaneous transient outward currents (STOCs) through large-conductance Ca2+-activated K+ channels (BKCa), and contribute to the negative-feedback regulation of myogenic tone. We tested this hypothesis in superior epigastric arteries (SEAs) isolated from male C57BL/6 mice. SEAs were isolated and enzymatically dissociated to obtain single smooth muscle cells (SMCs) for whole-cell recording of paxilline-sensitive (PAX, 1 μmol/L) STOCs at -30 mV, or cannulated and studied by pressure myography (80 cm H2O, 37°C). The CaV3.2 blocker Ni2+ (30 μmol/L) had no effect on STOC amplitude (20.1 ± 1.7 pA vs. 20.6 ± 1.7 pA; n = 12, P = 0.6), but increased STOC frequency (0.79 ± 0.15 Hz vs. 1.21 ± 0.22 Hz; n = 12, P = 0.02). Although Ni2+ produced concentration-dependent constriction of isolated, pressurized SEAs (logEC50 = -5.8 ± 0.09; Emax = 72 ± 5% constriction), block of BKCa with PAX had no effect on vasoconstriction induced by 30 μmol/L Ni2+ (in the absence of PAX = 66 ± 4% constriction vs. in the presence of 1 μmol/L PAX = 65 ± 4% constriction; n = 7, P = 0.06). In contrast to Ni2+, the nonselective T-type blocker, mibefradil, produced only vasodilation (logEC50 = -6.9 ± 0.2; Emax = 74 ± 8% dilation), whereas the putative T-type blocker, ML218, had no significant effect on myogenic tone between 10 nmol/L and 10 μmol/L (n = 6-7, P = 0.59). Our data do not support a role for CaV3.2 VGCC in the negative-feedback regulation of myogenic tone in murine SEAs and suggest that Ni2+ may constrict SEAs by means other than block of CaV3.2 VGCC.

Membrane depolarization activates BK channels through ROCK-mediated β1 subunit surface trafficking to limit vasoconstriction

Membrane depolarization of smooth muscle cells (myocytes) in the small arteries that regulate regional organ blood flow leads to vasoconstriction. Membrane depolarization also activates large-conductance calcium (Ca²⁺)-activated potassium (BK) channels, which limits Ca²⁺ channel activity that promotes vasoconstriction, thus leading to vasodilation. We showed that in human and rat arterial myocytes, membrane depolarization rapidly increased the cell surface abundance of auxiliary BK β1 subunits but not that of the pore-forming BKα channels. Membrane depolarization stimulated voltage-dependent Ca²⁺ channels, leading to Ca²⁺ influx and the activation of Rho kinase (ROCK) 1 and 2. ROCK1/2-mediated activation of Rab11A promoted the delivery of β1 subunits to the plasma membrane by Rab11A-positive recycling endosomes. These additional β1 subunits associated with BKα channels already at the plasma membrane, leading to an increase in apparent Ca²⁺ sensitivity and activation of the channels in pressurized arterial myocytes and vasodilation. Thus, membrane depolarization activates BK channels through stimulation of ROCK- and Rab11A-dependent trafficking of β1 subunits to the surface of arterial myocytes.

Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles

Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.

A Lipid Emulsion Reverses Toxic-Dose Bupivacaine-Induced Vasodilation during Tyrosine Phosphorylation-Evoked Contraction in Isolated Rat Aortae

The goal of this in vitro study was to examine the effect of a lipid emulsion on toxic-dose bupivacaine-induced vasodilation in a model of tyrosine phosphatase inhibitor sodium orthovanadate-induced contraction in endothelium-denuded rat aortae and to elucidate the associated cellular mechanism. The effect of a lipid emulsion on vasodilation induced by a toxic dose of a local anesthetic during sodium orthovanadate-induced contraction was examined. In addition, the effects of various inhibitors, either bupivacaine alone or a lipid emulsion plus bupivacaine, on protein kinase phosphorylation induced by sodium orthovanadate in rat aortic vascular smooth muscle cells was examined. A lipid emulsion reversed the vasodilation induced by bupivacaine during sodium orthovanadate-induced contraction. The lipid emulsion attenuated the bupivacaine-mediated inhibition of the sodium orthovanadate-induced phosphorylation of protein tyrosine, c-Jun NH₂-terminal kinase (JNK), myosin phosphatase target subunit 1 (MYPT1), phospholipase C (PLC) γ-1 and extracellular signal-regulated kinase (ERK). These results suggest that a lipid emulsion reverses toxic-dose bupivacaine-induced vasodilation during sodium orthovanadate-induced contraction via the activation of a pathway involving either tyrosine kinase, JNK, Rho-kinase and MYPT1 or tyrosine kinase, PLC γ-1 and ERK, and this reversal is associated with the lipid solubility of the local anesthetic and the induction of calcium sensitization.

Reduced Biaxial Contractility in the Descending Thoracic Aorta of Fibulin-5 Deficient Mice

The precise role of smooth muscle cell contractility in elastic arteries remains unclear, but accumulating evidence suggests that smooth muscle dysfunction plays an important role in the development of thoracic aortic aneurysms and dissections (TAADs). Given the increasing availability of mouse models of these conditions, there is a special opportunity to study roles of contractility ex vivo in intact vessels subjected to different mechanical loads. In parallel, of course, there is a similar need to study smooth muscle contractility in models that do not predispose to TAADs, particularly in cases where disease might be expected. Multiple mouse models having compromised glycoproteins that normally associate with elastin to form medial elastic fibers present with TAADs, yet those with fibulin-5 deficiency do not. In this paper, we show that deletion of the fibulin-5 gene results in a significantly diminished contractility of the thoracic aorta in response to potassium loading despite otherwise preserved characteristic active behaviors, including axial force generation and rates of contraction and relaxation. Interestingly, this diminished response manifests around an altered passive state that is defined primarily by a reduced in vivo axial stretch. Given this significant coupling between passive and active properties, a lack of significant changes in passive material stiffness may help to offset the diminished contractility and thereby protect the wall from detrimental mechanosensing and its sequelae.

Matrix metalloproteinase (MMP)-2 decreases calponin-1 levels and contributes to arterial remodeling in early hypertension

Increased matrix metalloproteinase (MMP)-2 is implicated in the vascular remodeling of hypertension. Calponin-1 is a contractile protein, and its absence is associated with vascular smooth muscle cell (VSMC) phenotype switch, which leads to migration and remodeling. We evaluated whether increased MMP-2 activity precedes chronic vascular remodeling by decreasing calponin-1 and inducing VSMC proliferation. Sham or two kidney-one clip (2K1C) rats were treated with doxycycline at 30mg/kg/day. Systolic blood pressure was increased in the 2K1C rats after 1 and 2weeks post-surgery, and doxycycline was effective to reduce it only at 2weeks of hypertension (p<0.05). Increased activity of MMP-2 was observed in aortas from 2K1C at 1 and 2weeks of hypertension, followed by increased VSMC proliferation, and those effects were abolished by treating 2K1C rats with doxycycline (p<0.05). Increased aortic media to lumen ratio started to emerge in 2K1C rats at 1week of hypertension, and it was established by 2weeks. MMP-2 and calponin-1 co-localized in the cytosol of VSMC. Aortas from 2K1C rats showed a significant reduction in calponin-1 levels at 1week of hypertension, and doxycycline prevented its loss (p<0.05). However, at 2weeks of hypertension, calponin-1 was upregulated in 2K1C (p<0.05 vs. Sham groups). The mRNA levels of calponin-1 were not altered in the aortas of 2K1C at 1week of hypertension. MMP-2 may contribute to the post-translational decrease in calponin-1, thus culminating in hypertension-induced maladaptive arterial remodeling.