Stretch In Vascular Smooth Muscle Cells Research Articles

Transient receptor potential channel-dependent myogenic responsiveness in small-sized resistance arteries.

It is well documented that the inherent ability of small arteries and arterioles to regulate intraluminal diameter in response to alterations in intravascular pressure determines peripheral vascular resistance and blood flow (termed myogenic response or pressure-induced vasoconstriction/dilation). This autoregulatory property of resistance arteries is primarily originated from mechanosensitive vascular smooth muscle cells (VSMCs). There are diverse biological apparatuses in the plasma membrane of VSMCs that sense mechanical stimuli and generate intracellular signals for the contractility of VSMCs. Although the roles of transient receptor potential (TRP) channels in pressure-induced vasoconstriction are not fully understood to date, TRP channels that are directly activated by mechanical stimuli (e.g., stretch of VSMCs) or indirectly evoked by intracellular molecules (e.g., inositol trisphosphate) provide the major sources of Ca2+ (e.g., Ca2+ influx or release from the sarcoplasmic reticulum) and in turn, evoke vascular reactivity. This review sought to summarize mounting evidence over several decades that the activation of TRP canonical, TRP melastatin, TRP vanilloid, and TRP polycystin channels contributes to myogenic vasoconstriction.

Abstract 259: Phenotype Switch and Altered Mechanosignaling in Vascular Smooth Muscle Cells From Marfan Syndrome Mice

Background: Mechanisms whereby fibrillin-1 gene mutations promote aortic aneurysms in Marfan Syndrome (MFS) are complex. Vascular smooth muscle cells (VSMC) are crucial to aneurysm pathophysiology through (1) support of mechanical homeostasis, in which contractile VSMC connect extracellular matrix to shield synthetic VSMC against high mechanical loads and (2) key effects of synthetic VSMC on extracellular matrix organization. However, little is known about VSMC phenotypic adaptation and response to mechanical loading in MFS development. Methods: We investigated phenotypic patterns and response to cyclic stretch in VSMC cultured from aortae of wild-type (WT) mice or MFS mice bearing mgΔ lpn mutation, which develop aortic dilation/thickening from the first month of age, accelerated after 6 months. We studied VSMC from 8-9 week-old mice to focus on early disease stages. VSMC remained either static or underwent 10% cyclic stretching (1Hz, 8h). Protein expression/morphology were evaluated by Western and confocal analyses. We also performed Traction Force Microscopy to assess force distribution profile. Results: There were significant phenotypic changes in MFS-VSMC vs. WT, with loss of fusiform shape and enhanced spreading, promoting ≈7-fold increased in cell area vs. WT (p<0.001, n=5) and >60% decrease in calponin expression vs. WT (p<0.05, n=3). Also, MFS-VSMC had a 10-fold greater expression of endoplasmic reticulum stress marker Grp78 (n=2). Cyclic stretch promoted expected increase in synthetic phenotype markers in WT-VSMC but an opposing contractile phenotype switch in MFS-VSMC, with decreased calponin and pFAK expression and increased stress fiber buildup. Cyclic stretch promoted similar increase in Grp78 expression in WT vs. MFS-VSMC. MFS-VSMC showed ca.60% lower capacity to generate adhesive force and extracellular matrix contractile momentum (p<0.003, n=10), associated with lower deformation energy in vitro (9,16 vs. 1,67 pJ, p<0.004, n=6). Conclusions: MFS associate with important deregulation of VSMC phenotypic adaptations, which may impact on their force development and disrupt force distribution in aorta.

Temporal phosphoproteomics to investigate the mechanotransduction of vascular smooth muscle cells in response to cyclic stretch

Vascular smooth muscle cells (VSMCs) are exposed to mechanical cyclic stretch in vivo, which play important roles in maintenance of vascular homeostasis and regulation of pathological vascular remodeling. Reversible protein phosphorylation is crucial for intracellular signaling transduction. However, the dynamic phosphorylated profile induced by cyclic stretch in VSMCs is still unclear. Using the stable isotope labeling by amino acid in cell culture, VSMCs were labeled and exposed to 10% physiological cyclic stretch in vitro at 1.25Hz for 0min, 15min, 30min, 1h and 6h, respectively. Using TiO2 beads and liquid chromatography tandem mass spectrometry, the temporal phosphoproteomic profiles in response to cyclic stretch were then detected. Bioinformatics analysis including fuzzy c-means clustering, functional classifications, and Ingenuity Pathway Analysis were applied to further reveal the potential mechanotranduction networks. The results indicated that protein kinase C (PKCs) family, Rho-associated coiled-coil containing protein kinase 1 (ROCK1) and Akt may participate in cyclic-stretch induced VSMC functions. Cyclic stretch repressed the expression of ROCK1, while it had no significant effect on the phosphorylation of PKCα/βII, PKCζ/λ and PKCδ/θ. PKCθ was activated first at short time-phase (15min and 30min), and again at long time-phase (6h, 12h and 24h). The activation of p-PKCμ was immediate and short-term, similar to p-Akt. Our present in vitro work hence revealed that cyclic stretch activates complex mechanotransduction networks, suggesting that novel mechanoresponsive molecules, i.e., PKCθ, PKCμ, and ROCK1, may participate in the mechanotransduction and modulation VSMC functions.

Regulation of resistin by cyclic mechanical stretch in cultured rat vascular smooth muscle cells

Resistin has a potential role in atherosclerosis; however, the molecular mechanism underlying the increase in resistin expression in atherosclerosis remains unclear. As mechanical stretch plays an important role in atherosclerosis, in the present study we sought to investigate the cellular and molecular mechanisms underlying the regulation of resistin by cyclic mechanical stretch in VSMCs (vascular smooth muscle cells). VSMCs from thoracic aorta of adult Wistar rats were cultured and subjected to cyclic stretch. Cyclic mechanical stretch significantly increased resistin protein and mRNA expression as compared with control cells without stretch. The specific p38 MAPK (mitogen-activated protein kinase) inhibitor SB203580, the antioxidant N-acetylcysteine and p38 MAPK siRNA (small interfering RNA) attenuated the induction of resistin protein by cyclic stretch. Cyclic stretch significantly increased the phosphorylation of p38 MAPK, whereas pre-treatment with SB203580 and N-acetylcysteine significantly inhibited this effect. Cyclic stretch significantly increased ROS (reactive oxygen species) production, and pre-treatment with N-acetylcysteine significantly inhibited stretch-induced ROS production. Cyclic stretch also increased STAT3 (signal transducer and activator of transcription 3)-binding activity and resistin promoter activity, and resistin promoter activity was abolished when STAT3 in the promoter area was mutated. Pre-treatment with SB203580 and N-acetylcysteine significantly attenuated resistin promoter activity induced by cyclic stretch. Cyclic stretch increased the secretion of AngII (angiotensin II) and resistin from cultured VSMCs. Exogenous AngII increased resistin expression, and AngII receptor inhibition attenuated this effect. In conclusion, cyclic mechanical stretch increases resistin expression in cultured rat VSMCs. Stretch-induced resistin expression is mediated through ROS, and the p38 MAPK and STAT3 pathways. Therefore resistin induced by cyclic stretch may contribute to the pathogenesis of atherosclerosis under haemodynamic overload.Key

Gq-coupled receptors as mechanosensors mediating myogenic vasoconstriction

Despite the central physiological function of the myogenic response, the underlying signalling pathways and the identity of mechanosensors in vascular smooth muscle (VSM) are still elusive. In contrast to present thinking, we show that membrane stretch does not primarily gate mechanosensitive transient receptor potential (TRP) ion channels, but leads to agonist-independent activation of G(q/11)-coupled receptors, which subsequently signal to TRPC channels in a G protein- and phospholipase C-dependent manner. Mechanically activated receptors adopt an active conformation, allowing for productive G protein coupling and recruitment of beta-arrestin. Agonist-independent receptor activation by mechanical stimuli is blocked by specific antagonists and inverse agonists. Increasing the AT(1) angiotensin II receptor density in mechanically unresponsive rat aortic A7r5 cells resulted in mechanosensitivity. Myogenic tone of cerebral and renal arteries is profoundly diminished by the inverse angiotensin II AT(1) receptor agonist losartan independently of angiotensin II (AII) secretion. This inhibitory effect is enhanced in blood vessels of mice deficient in the regulator of G-protein signalling-2. These findings suggest that G(q/11)-coupled receptors function as sensors of membrane stretch in VSM cells.