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

Endothelial Rho kinase controls blood vessel integrity and angiogenesis

Background

The Rho kinases 1 and 2 (ROCK1/2) are serine-threonine specific protein kinases that control actin cytoskeleton dynamics. They are expressed in all cells throughout the body, including cardiomyocytes, smooth muscle cells and endothelial cells, and intimately involved in cardiovascular health and disease. Pharmacological ROCK inhibition is beneficial in mouse models of hypertension, atherosclerosis, and neointimal thickening that display overactivated ROCK. However, the consequences of endothelial ROCK signaling deficiency in vivo remain unknown. To address this issue, we analyzed endothelial cell (EC) specific ROCK1 and 2 deletions.

Methods

We generated Cdh5-CreERT2 driven, tamoxifen inducible loss of function alleles of ROCK1 and ROCK2 and analyzed mouse survival and vascular defects through cellular, biochemical, and molecular biology approaches.

Results

We observed that postnatal or adult loss of endothelial ROCK1 and 2 was lethal within a week. Mice succumbed to multi-organ hemorrhage that occurred because of loss of vascular integrity. ECs displayed deficient cytoskeletal actin polymerization that prevented focal adhesion formation and disrupted junctional integrity. Retinal sprouting angiogenesis was also perturbed, as sprouting vessels exhibited lack of polymerized actin and defective lumen formation. In a three-dimensional endothelial sprouting assay, combined knockdown of ROCK1/2 or knockdown or ROCK2 but not ROCK1 led to reduced sprouting, lumenization and cell polarization defects caused by defective actin and altered VE-cadherin dynamics. The isoform specific role of endothelial ROCK2 correlated with ROCK2 substrate specificity for FAK and LIMK. By analyzing single and three allele mutants we show that one intact allele of ROCK2 is sufficient to maintain vascular integrity in vivo.

Conclusion

Endothelial ROCK1 and 2 maintain junctional integrity and ensure proper angiogenesis and lumen formation. The presence of one allele of ROCK2 is sufficient to maintain vascular growth and integrity. These data indicate the need of careful consideration for the use of ROCK inhibitors in disease settings.

Aberrant activation of TGF-β/ROCK1 enhances stemness during prostatic stromal hyperplasia

Benign prostatic hyperplasia (BPH) is a multifactorial disease in which abnormal growth factor activation and embryonic reawakening are considered important factors. Here we demonstrated that the aberrant activation of transforming growth factor β (TGF-β)/Rho kinase 1 (ROCK1) increased the stemness of BPH tissue by recruiting mesenchymal stem cells (MSCs), indicating the important role of embryonic reawakening in BPH. When TGF-β/ROCK1 is abnormally activated, MSCs are recruited and differentiate into fibroblasts/myofibroblasts, leading to prostate stromal hyperplasia. Further research showed that inhibition of ROCK1 activation suppressed MSC migration and their potential for stromal differentiation. Collectively, our findings suggest that abnormal activation of TGF-β/ROCK1 regulates stem cell lineage specificity, and the small molecule inhibitor GSK269962A could target ROCK1 and may be a potential treatment for BPH.

Mechanical Regulation of Retinal Vascular Inflammation and Degeneration in Diabetes

Vascular inflammation is known to cause degeneration of retinal capillaries in early diabetic retinopathy (DR), a major microvascular complication of diabetes. Past studies investigating these diabetes-induced retinal vascular abnormalities have focused primarily on the role of molecular or biochemical cues. Here we show that retinal vascular inflammation and degeneration in diabetes are also mechanically regulated by the increase in retinal vascular stiffness caused by overexpression of the collagen-cross-linking enzyme lysyl oxidase (LOX). Treatment of diabetic mice with LOX inhibitor β-aminopropionitrile (BAPN) prevented the increase in retinal capillary stiffness, vascular intracellular adhesion molecule-1 overexpression, and leukostasis. Consistent with these anti-inflammatory effects, BAPN treatment of diabetic mice blocked the upregulation of proapoptotic caspase-3 in retinal vessels, which concomitantly reduced retinal capillary degeneration, pericyte ghost formation, and the diabetes-induced loss of contrast sensitivity in these mice. Finally, our in vitro studies indicate that retinal capillary stiffening is sufficient to increase the adhesiveness and neutrophil elastase-induced death of retinal endothelial cells. By uncovering a link between LOX-dependent capillary stiffening and the development of retinal vascular and functional defects in diabetes, these findings offer a new insight into DR pathogenesis that has important translational potential.

ARTICLE HIGHLIGHTS

Serum Malondialdehyde-Oxidized Low-Density Lipoprotein Level Is Associated with Arterial Stiffness by Cardio-Ankle Vascular Index in Coronary Artery Bypass Graft Patients

A high malondialdehyde-oxidized low-density lipoprotein (MDA-oxLDL) level is associated with atherosclerotic cardiovascular diseases and major adverse cardiovascular events. A higher cardio-ankle vascular index (CAVI) is independently associated with an increased risk of cardiovascular events, cardiovascular mortality, myocardial infarction, and stroke in patients with cardiovascular risk. Thus, this study aimed to evaluate the relationship between serum MDA-oxLDL levels and CAVI in patients with triple-vessel coronary artery disease who underwent coronary artery bypass graft (CABG) surgery. Fasting blood samples and baseline characteristics were obtained from 88 patients who had undergone CABG. A commercialized enzyme-linked immunosorbent assay was used to measure MDA-oxLDL levels. An automatic pulse wave analyzer was used to measure CAVI values, and each side of CAVI values of ≥9 was designated as arterial stiffness. In total, 47 participants were assigned to the arterial stiffness group. More patients had diabetes mellitus, were older, and had higher serum MDA-oxLDL levels in the arterial stiffness group than in the control group. A multivariate logistic regression analysis disclosed that MDA-oxLDL and diabetes mellitus were independent predictors of arterial stiffness. Moreover, according to the Spearman's correlation analysis, the serum MDA-oxLDL level was positively associated with both left and right CAVI. Serum MDA-oxLDL levels were positively associated with arterial stiffness in patients who had undergone CABG.

Aging of the Arterial System

Aging of the vascular system is associated with deep changes of the structural proprieties of the arterial wall. Arterial hypertension, diabetes mellitus, and chronic kidney disease are the major determinants for the loss of elasticity and reduced compliance of vascular wall. Arterial stiffness is a key parameter for assessing the elasticity of the arterial wall and can be easily evaluated with non-invasive methods, such as pulse wave velocity. Early assessment of vessel stiffness is critical because its alteration can precede clinical manifestation of cardiovascular disease. Although there is no specific pharmacological target for arterial stiffness, the treatment of its risk factors helps to improve the elasticity of the arterial wall.