Role of age, Rho-kinase 2 expression, and G protein-mediated signaling in the myogenic response in mouse small mesenteric arteries

Functional, Structural and Proteomic Effects of Ageing in Resistance Arteries

The normal ageing process affects resistance arteries, leading to various functional and structural changes. Systolic hypertension is a common occurrence in human ageing, and it is associated with large artery stiffening, heightened pulsatility, small artery remodeling, and damage to critical microvascular structures. Starting from young adulthood, a progressive elevation in the mean arterial pressure is evidenced by clinical and epidemiological data as well as findings from animal models. The myogenic response, a protective mechanism for the microcirculation, may face disruptions during ageing. The dysregulation of calcium entry channels (L-type, T-type, and TRP channels), dysfunction in intracellular calcium storage and extrusion mechanisms, altered expression of potassium channels, and a change in smooth muscle calcium sensitization may contribute to the age-related dysregulation of myogenic tone. Flow-mediated vasodilation, a hallmark of endothelial function, is compromised in ageing. This endothelial dysfunction is related to increased oxidative stress, lower nitric oxide bioavailability, and a low-grade inflammatory response, further exacerbating vascular dysfunction. Resistance artery remodeling in ageing emerges as a hypertrophic response of the vessel wall that is typically observed in conjunction with outward remodeling (in normotension), or as inward hypertrophic remodeling (in hypertension). The remodeling process involves oxidative stress, inflammation, reorganization of actin cytoskeletal components, and extracellular matrix fiber proteins. Reactive oxygen species (ROS) signaling and chronic low-grade inflammation play substantial roles in age-related vascular dysfunction. Due to its role in the regulation of vascular tone and structural proteins, the RhoA/Rho-kinase pathway is an important target in age-related vascular dysfunction and diseases. Understanding the intricate interplay of these factors is crucial for developing targeted interventions to mitigate the consequences of ageing on resistance arteries and enhance the overall vascular health.

Vascular mechanotransduction

This review aims to survey the current state of mechanotransduction in vascular smooth muscle cells (VSMCs) and endothelial cells (ECs), including their sensing of mechanical stimuli and transduction of mechanical signals that result in the acute functional modulation and longer-term transcriptomic and epigenetic regulation of blood vessels. The mechanosensors discussed include ion channels, plasma membrane-associated structures and receptors, and junction proteins. The mechanosignaling pathways presented include the cytoskeleton, integrins, extracellular matrix, and intracellular signaling molecules. These are followed by discussions on mechanical regulation of transcriptome and epigenetics, relevance of mechanotransduction to health and disease, and interactions between VSMCs and ECs. Throughout this review, we offer suggestions for specific topics that require further understanding. In the closing section on conclusions and perspectives, we summarize what is known and point out the need to treat the vasculature as a system, including not only VSMCs and ECs but also the extracellular matrix and other types of cells such as resident macrophages and pericytes, so that we can fully understand the physiology and pathophysiology of the blood vessel as a whole, thus enhancing the comprehension, diagnosis, treatment, and prevention of vascular diseases.

Arterial myogenic response and aging

The arterial myogenic response is an inherent property of resistance arteries. Myogenic tone is crucial for maintaining a relatively constant blood flow in response to changes in intraluminal pressure and protects delicate organs from excessive blood flow. Although this fundamental physiological phenomenon has been extensively studied, the underlying molecular mechanisms are largely unknown. Recent studies identified a crucial role of mechano-activated angiotensin II type 1 receptors (AT1R) in this process. The development of myogenic response is affected by aging. In this review, we summarize recent progress made to understand the role of AT1R and other mechanosensors in the control of arterial myogenic response. We discuss age-related alterations in myogenic response and possible underlying mechanisms and implications for healthy aging.

Inhibition of ROCK ameliorates pulmonary fibrosis by suppressing M2 macrophage polarisation through phosphorylation of STAT3

BACKGROUND

Emerging evidence provides mechanistic insights into the pathogenesis of pulmonary fibrosis (PF), and rare anti-PF therapeutic method has promising effect in its treatment. Rho-associated coiled-coil kinases (ROCK) inhibition significantly ameliorates bleomycin-induced PF and decreases macrophage infiltration, but the mechanism remains unclear. We established bleomycin and radiation-induced PF to identify the activity of WXWH0265, a newly designed unselective ROCK inhibitor in regulating macrophages.

METHODS

Bleomycin-induced PF was induced by intratracheal instillation and radiation-induced PF was induced by bilateral thoracic irradiation. Histopathological techniques (haematoxylin and eosin, Masson's trichrome and immunohistochemistry) and hydroxyproline were used to evaluate PF severity. Western blot, quantitative real-time reverse transcription-polymerase chain reaction and flow cytometry were performed to explore the underlying mechanisms. Bone marrow-derived macrophages (BMDMs) were used to verify their therapeutic effect. Clodronate liposomes were applied to deplete macrophages and to identify the therapeutic effect of WXWH0265.

RESULTS

Therapeutic administration of ROCK inhibitor ameliorates bleomycin-induced PF by inhibiting M2 macrophages polarisation. ROCK inhibitor showed no significant anti-fibrotic effect in macrophages-depleted mice. Treatment with WXWH0265 demonstrated superior protection effect in bleomycin-induced PF compared with positive drugs. In radiation-induced PF, ROCK inhibitor effectively ameliorated PF. Fibroblasts co-cultured with supernatant from various M2 macrophages phenotypes revealed that M2 macrophages stimulated by interleukin-4 promoted extracellular matrix production. Polarisation of M2 macrophages was inhibited by ROCK inhibitor treatment in vitro. The p-signal transducer and activator of transcription 3 (STAT3) in lung tissue and BMDMs was significantly decreased in PF in vivo and vitro after treated with ROCK inhibitors.

CONCLUSION

Inhibiting ROCK could significantly attenuate bleomycin- and radiation-induced PF by regulating the macrophages polarisation via phosphorylation of STAT3. WXWH0265 is a kind of efficient unselective ROCK inhibitor in ameliorating PF. Furthermore, the results provide empirical evidence that ROCK inhibitor, WXWH0265 is a potential drug to prevent the development of PF.

Vascular calcium signalling and ageing

Changes in cellular Ca²⁺ levels have major influences on vascular function and blood pressure regulation. Vascular smooth muscle cells (SMCs) and endothelial cells (ECs) orchestrate vascular activity in distinct ways, often involving highly specific fluctuations in Ca²⁺ signalling. Ageing is a major risk factor for cardiovascular diseases, but the impact of ageing per se on vascular Ca²⁺ signalling has received insufficient attention. We reviewed the literature for age-related changes in Ca²⁺ signalling in relation to vascular structure and function. Vascular tone dysregulation in several vascular beds has been linked to abnormal expression or activity of SMC voltage-gated Ca²⁺ channels, Ca²⁺ -activated K⁺ channels or TRPC6 channels. Some of these effects were linked to altered caveolae density, microRNA expression or 20-HETE abundance. Intracellular store Ca²⁺ handling was suppressed in ageing mainly via reduced expression of intracellular Ca²⁺ release channels, and Ca²⁺ reuptake or efflux pumps. An increase in mitochondrial Ca²⁺ uptake, leading to oxidative stress, could also play a role in SMC hypercontractility and structural remodelling in ageing. In ECs, ageing entailed diverse effects on spontaneous and evoked Ca²⁺ transients, as well as structural changes at the EC-SMC interface. The concerted effects of altered Ca²⁺ signalling on myogenic tone, endothelium-dependent vasodilatation, and vascular structure are likely to contribute to blood pressure dysregulation and blood flow distribution deficits in critical organs. With the increase in the world's ageing population, future studies should be directed at solving specific ageing-induced Ca²⁺ signalling deficits to combat the imminent accelerated vascular ageing and increased risk of cardiovascular diseases.

Effect of age on the vascular proteome in middle cerebral arteries and mesenteric resistance arteries in mice

Aging is associated with hypertension and brain blood flow dysregulation, which are major risk factors for cardiovascular and neurodegenerative diseases. Structural remodeling, endothelial dysfunction, or hypercontractility of resistance vessels may cause increased total peripheral resistance and hypertension. Recent studies showed that G protein- and RhoA/Rho-kinase pathways are involved in increased mean arterial pressure (MAP) and arterial tone in middle-aged mice. We aimed to characterize the age-dependent changes in the vascular proteome in normal laboratory mice using mass spectrometry and bioinformatics analyses on middle cerebral arteries and mesenteric resistance arteries from young (3 months) vs. middle-aged (14 months) mice. In total, 31 proteins were significantly affected by age whereas 172 proteins were differentially expressed by vessel type. Hierarchical clustering revealed that 207 proteins were significantly changed or clustered by age. Vitamin B6 pathway, Biosynthesis of antibiotics, Regulation of actin cytoskeleton and Endocytosis were the top enriched KEGG pathways by age. Several proteins in the RhoA/Rho-kinase pathway changed in a manner consistent with hypertension and dysregulation of cerebral perfusion. Although aging had a less profound effect than vessel type on the resistance artery proteome, regulation of actin cytoskeleton, including the RhoA/Rho-kinase pathway, is an important target for age-dependent hypertension.

Vascular Stiffening Mediated by Rho-Associated Coiled-Coil Containing Kinase Isoforms

Background

The pathogenesis of vascular stiffening and hypertension is marked by non‐compliance of vessel wall because of deposition of collagen fibers, loss of elastin fibers, and increased vascular thickening. Rho/Rho‐associated coiled‐coil containing kinases 1 and 2 (ROCK1 and ROCK2) have been shown to regulate cellular contraction and vascular remodeling. However, the role of ROCK isoforms in mediating pathogenesis of vascular stiffening and hypertension is not known.

Methods and Results

Hemizygous Rock mice (Rock1^+/− and Rock2^+/−) were used to determine the role of ROCK1 and ROCK2 in age‐related vascular dysfunction. Both ROCK activity and aortic stiffness increased to a greater extent with age in wild‐type mice compared with that of Rock1^+/− and Rock2^+/− mice. As a model for age‐related vascular stiffening, we administered angiotensin II (500 ng/kg per minute) combined with nitric oxide synthase inhibitor, L‐N^ω‐nitroarginine methyl ester (0.5 g/L) for 4 weeks to 12‐week‐old male Rock1^+/− and Rock2^+/− mice. Similar to advancing age, angiotensin II/L‐N^ω‐nitroarginine methyl ester caused increased blood pressure, aortic stiffening, and vascular remodeling, which were attenuated in Rock2^+/−, and to a lesser extent, Rock1^+/− mice. The reduction of aortic stiffening in Rock2^+/− mice was accompanied by decreased collagen deposition, relatively preserved elastin content, and less aortic wall hypertrophy. Indeed, the upregulation of collagen I by transforming growth factor‐β1 or angiotensin II was greatly attenuated in Rock2^−/− mouse embryonic fibroblasts.

Conclusions

These findings indicate that ROCK1 and ROCK2 mediate both age‐related and pharmacologically induced aortic stiffening, and suggest that inhibition of ROCK2, and to a lesser extent ROCK1, may have therapeutic benefits in preventing age‐related vascular stiffening.

Myogenic autoregulation in bone marrow arterioles and in vivo intramedullary pressure in femora of conscious, female Long Evans rats

OBJECTIVES

The ability to regulate skeletal blood flow is critical for the maintenance of bone. The myogenic response is essential for regulating tissue blood flow. Myogenic responsiveness in bone marrow arterioles has not yet been determined. Furthermore, the literature is disparate regarding intramedullary pressures (IMP) within bone. The purposes of this study were to (1) determine whether bone marrow arterioles have myogenic activity and (2) assess if the autoregulatory zone corresponds with IMP. Also, this study provides detailed methodology on dissecting and isolating bone marrow arterioles for functional assessment.

METHODS

Experiment 1: Femoral shafts of female Long Evans rats were catheterized to assess in vivo IMP. Experiment 2: Bone marrow arterioles from female Long Evans rats were cannulated. Active and passive myogenic responses were determined.

RESULTS

In vivo intramedullary pressure averaged 32 ± 3 mmHg, intramedullary pulse pressure averaged 5.28 ± 0.03 mmHg, and the mean maximal diameter and wall thickness of the bone marrow arterioles were 96 ± 7 µm and 18 ± 2 µm, respectively. An active myogenic response was observed and differed (p < .001) from the passive curve.

CONCLUSION

Bone marrow arterioles have myogenic responsiveness and the autoregulatory zone corresponded with the range of IMP (15-51 mmHg) within the femoral diaphysis of conscious animals.

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.

Hyperglycemia-induced transcriptional regulation of ROCK1 and TGM2 expression is involved in small artery remodeling in obese diabetic Göttingen Minipigs

Obesity and diabetes in humans are associated with hypertrophic remodeling and increased media:lumen ratio of small resistance arteries, which is an independent predictor of cardiovascular events. In order to minimize increases in media:lumen ratio, hypertrophic remodeling should be accompanied by outward remodeling. We aimed to investigate the mechanisms of structural remodeling in small pial arteries (PAs) and terminal mesenteric arteries (TMAs) from obese Göttingen Minipigs with or without diabetes. Göttingen Minipigs received either control diet (lean control (LC)), high fat/high fructose/high cholesterol diet (FFC), or FFC diet with streptozotocin (STZ)-induced diabetes (FFC/STZ) for 13 months. At the end of the study (20 months), we assessed body weight, fasting plasma biochemistry, passive vessel dimensions, mRNA expression (matrix metallopeptidases 2/9 (MMP2, MMP9), tissue inhibitor of metallopeptidase 1 (TIMP1), transglutaminase 2 (TGM2), Rho-kinase 1 (ROCK1), TGFβ-receptor 2 (TGFBR2), and IGF1-receptor (IGFR1) genes), and immunofluorescence in PAs and TMAs. We performed multiple linear correlation analyses using plasma values, structural data, and gene expression data. We detected outward hypertrophic remodeling in TMAs and hypertrophic remodeling in PAs from FFC/STZ animals. ROCK1 and TGM2 genes were up-regulated in PAs and TMAs from the FFC/STZ group. Passive lumen diameter (PLD) of TMAs was correlated with plasma values of glucose (GLU), fructosamine (FRA), total cholesterol (TC), and triglycerides (TGs). ROCK1 and TGM2 expressions in TMAs were correlated with PLD, plasma GLU, fructosamine, and TC. ROCK1 and TGM2 proteins were immunolocalized in the media of PAs and TMAs, and their fluorescence levels were increased in the FFC/STZ group. Hyperglycemia/hyperlipidemia is involved in regulation of ROCK1 and TGM2 expression leading to outward remodeling of small resistance arteries in obese diabetic Göttingen Minipigs.

Rho-kinase inhibitor coupled to peptide-modified albumin carrier reduces portal pressure and increases renal perfusion in cirrhotic rats

Rho-kinase (ROCK) activation in hepatic stellate cells (HSC) is a key mechanism promoting liver fibrosis and portal hypertension (PTH). Specific delivery of ROCK-inhibitor Y-27632 (Y27) to HSC targeting mannose-6-phosphate-receptors reduces portal pressure and fibrogenesis. In decompensated cirrhosis, presence of ascites is associated with reduced renal perfusion. Since in cirrhosis, platelet-derived growth factor receptor beta (PDGFRβ) is upregulated in the liver as well as the kidney, this study coupled Y27 to human serum albumin (HSA) substituted with PDGFRβ-recognizing peptides (pPB), and investigated its effect on PTH in cirrhotic rats. In vitro collagen contraction assays tested biological activity on LX2 cells. Hemodynamics were analyzed in BDL and CCl₄ cirrhotic rats 3 h, 6 h and 24 h after i.v. administration of Y27pPBHSA (0.5/1 mg/kg b.w). Phosphorylation of moesin and myosin light chain (MLC) assessed ROCK activity in liver, femoral muscle, mesenteric artery, kidney and heart. Three Y27 molecules were coupled to pPBHSA as confirmed by HPLC/MS, which was sufficient to relax LX2 cells. In vivo, Y27pPBHSA-treated rats exhibited lower portal pressure, hepatic vascular resistance without effect on systemic vascular resistance, but a tendency towards lower cardiac output compared to non-treated cirrhotic rats. Y27pPBHSA reduced intrahepatic resistance by reduction of phosphorylation of moesin and MLC in Y27pPBHSA-treated cirrhotic rats. Y27pPBHSA was found in the liver of rats up to 6 hours after its injection, in the HSC demonstrated by double-immunostainings. Interestingly, Y27pPBHSA increased renal arterial flow over time combined with an antifibrotic effect as shown by decreased renal acta2 and col1a1 mRNA expression. Therefore, targeting the ROCK inhibitor Y27 to PDGFRβ decreases portal pressure with potential beneficial effects in the kidney. This unique approach should be tested in human cirrhosis.