Modeling Disease Progression: Angiotensin II Indirectly Inhibits Nitric Oxide Production via ADMA Accumulation in Spontaneously Hypertensive Rats

Angiotensin Regulation of Vascular Homeostasis: Exploring the Role of ROS and RAS Blockers

Extensive research has been conducted to elucidate and substantiate the crucial role of the Renin-Angiotensin System (RAS) in the pathogenesis of hypertension, cardiovascular disorders, and renal diseases. Furthermore, the role of oxidative stress in maintaining vascular balance has been well established. It has been observed that many of the cellular effects induced by Angiotensin II (Ang II) are facilitated by reactive oxygen species (ROS) produced by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. In this paper, we present a comprehensive overview of the role of ROS in the physiology of human blood vessels, specifically focusing on its interaction with RAS. Moreover, we delve into the mechanisms by which clinical interventions targeting RAS influence redox signaling in the vascular wall.

Ecklonia cava extracts decrease hypertension-related vascular calcification by modulating PGC-1α and SOD2

Vascular calcification (VC) is induced by a decrease in sirtuin 3 (SIRT3) and superoxide dismutase (SOD)2 and increases mitochondrial reactive oxygen species (mtROS), eventually leading to mitochondrial dysfunction and phenotype alterations in vascular smooth muscle cells (VSMCs) into osteoblast-like cells in hypertension. Ecklonia cava extract (ECE) is known to increase peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α) and SOD2. In this study, we evaluated the effect of ECE on decreasing VC by increasing PGC-1α which increased SOD2 activity and decreased mtROS in an in vitro VSMC model of treating serums from Wistar Kyoto (WKY), spontaneous hypertensive rats (SHRs), and ECE-treated SHRs. Furthermore, the decreasing effect of ECE on VC was evaluated with an in vivo SHR model. PGC-1α expression, SIRT3 expression, and SOD2 activity were decreased by the serum from the SHRs and increased by the serum from the ECE-treated SHRs in the VSMCs. PGC-1α silencing eliminated those increases. mtROS generation and mitochondrial DNA (mtDNA) damage increased in the SHRs but decreased with ECE. Mitochondrial fission increased in the SHRs but decreased by ECE. Mitochondrial fusion, mitophagy, and mitochondrial biogenesis were decreased in the SHRs but increased by ECE. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and calcium deposition in the medial layer of the aorta increased in the SHRs but decreased with ECE. Therefore, ECE decreases VC via the upregulation of PGC-1α and SIRT3, which increases SOD2 activity. Activated SOD2 decreases mtDNA damage and mtROS generation, which sequentially decreases NADPH oxidase activity and changes the mitochondrial dynamics, thereby decreasing VC.

Overexpression of dimethylarginine dimethylaminohydrolase 1 protects from angiotensin II-induced cardiac hypertrophy and vascular remodeling

Cardiovascular complications are the leading cause of death, and elevated levels of asymmetric dimethyarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, are implicated in their pathophysiology. We investigated the role of dimethylarginine dimethylaminohydrolase 1 (DDAH1), an enzyme hydrolyzing ADMA, in prevention of cardiovascular remodeling during hypertension. We hypothesized that the animals overexpressing DDAH1 will be protected from angiotensin II (ANG II)-induced end organ damage. Angiotensin II (ANG II) was infused in two doses: 0.75 and 1.5 mg/kg/day in DDAH1 transgenic mice (DDAH1 TG) and wild-type (WT) littermates for 2 or 4 wk. Echocardiography was performed in the first and fourth weeks of the infusion, systolic blood pressure (SBP) was measured weekly, and cardiac hypertrophy and vascular remodeling was assessed by histology. Increase in SBP after 1 wk of ANG II infusion was not different between the groups, whereas TG mice had lower SBP at later time points. TG mice were protected from cardiovascular remodeling after 2 wk of ANG II infusion in the high dose and after 4 wk in the moderate dose. TG mice had higher left ventricular lumen-to-wall ratio, lower cardiomyocyte cross-sectional area, and less interstitial fibrosis compared with WT controls. In aorta, TG mice had less adventitial fibrosis, lower medial thickness with preserved elastin content, lower counts of inflammatory cells, lower levels of active matrix metalloproteinase-2, and showed better endothelium-dependent relaxation. We demonstrated that overexpression of DDAH1 protects from ANG II-induced cardiovascular remodeling and progression of hypertension by preserving endothelial function and limiting inflammation.NEW & NOTEWORTHY We showed that overexpression of dimethylarginine dimethylaminohydrolase 1 (DDAH1) protects from angiotensin II-induced cardiovascular damage, progression of hypertension, and adverse vascular remodeling in vivo. This protective effect is associated with decreased levels of asymmetric dimethylarginine, preservation of endothelial function, inhibition of cardiovascular inflammation, and lower activity of matrix metalloproteinase-2. Our findings are highly clinically relevant, because they suggest that upregulation of DDAH1 might be a promising therapeutic approach against angiotensin II-induced end organ damage.

A novel role of kallikrein-related peptidase 8 in the pathogenesis of diabetic cardiac fibrosis

Rationale: Among all the diabetic complications, diabetic cardiomyopathy, which is characterized by myocyte loss and myocardial fibrosis, is the leading cause of mortality and morbidity in diabetic patients. Tissue kallikrein-related peptidases (KLKs) are secreted serine proteases, that have distinct and overlapping roles in the pathogenesis of cardiovascular diseases. However, whether KLKs are involved in the development of diabetic cardiomyopathy remains unknown.The present study aimed to determine the role of a specific KLK in the initiation of endothelial-to-mesenchymal transition (EndMT) during the pathogenesis of diabetic cardiomyopathy.

Methods and Results-By screening gene expression profiles of KLKs, it was found that KLK8 was highly induced in the myocardium of mice with streptozotocin-induced diabetes. KLK8 deficiency attenuated diabetic cardiac fibrosis, and rescued the impaired cardiac function in diabetic mice. Small interfering RNA (siRNA)-mediated KLK8 knockdown significantly attenuated high glucose-induced endothelial damage and EndMT in human coronary artery endothelial cells (HCAECs). Diabetes-induced endothelial injury and cardiac EndMT were significantly alleviated in KLK8-deficient mice. In addition, transgenic overexpression of KLK8 led to interstitial and perivascular cardiac fibrosis, endothelial injury and EndMT in the heart. Adenovirus-mediated overexpression of KLK8 (Ad-KLK8) resulted in increases in endothelial cell damage, permeability and transforming growth factor (TGF)-β1 release in HCAECs. KLK8 overexpression also induced EndMT in HCAECs, which was alleviated by a TGF-β1-neutralizing antibody. A specificity protein-1 (Sp-1) consensus site was identified in the human KLK8 promoter and was found to mediate the high glucose-induced KLK8 expression. Mechanistically, it was identified that the vascular endothelial (VE)-cadherin/plakoglobin complex may associate with KLK8 in HCAECs. KLK8 cleaved the VE-cadherin extracellular domain, thus promoting plakoglobin nuclear translocation. Plakoglobin was required for KLK8-induced EndMT by cooperating with p53. KLK8 overexpression led to plakoglobin-dependent association of p53 with hypoxia inducible factor (HIF)-1α, which further enhanced the transactivation effect of HIF-1α on the TGF-β1 promoter. KLK8 also induced the binding of p53 with Smad3, subsequently promoting pro-EndMT reprogramming via the TGF-β1/Smad signaling pathway in HCAECs. The in vitro and in vivo findings further demonstrated that high glucose may promote plakoglobin-dependent cooperation of p53 with HIF-1α and Smad3, subsequently increasing the expression of TGF-β1 and the pro-EndMT target genes of the TGF-β1/Smad signaling pathway in a KLK8-dependent manner.

Conclusions: The present findings uncovered a novel pro-EndMT mechanism during the pathogenesis of diabetic cardiac fibrosis via the upregulation of KLK8, and may contribute to the development of future KLK8-based therapeutic strategies for diabetic cardiomyopathy.

[Mechanisms of chronic stress influence on the brain hemodynamic in persons with employment-related chronic stress]

OBJECTIVE

To discuss the mechanisms by which chronic psychosocial stress (CPSS) affects the parameters of cerebral blood flow.

MATERIAL AND METHODS

One hundred and sixty locomotive machinists (LM) and machinist assistants (MA), whose profession is rated as one of the most stressful, were enrolled in this study. The control group consisted of 100 healthy volunteers. The activity of the stressor system was assessed by the levels of stress hormones in serum (ACTH, cortisol, adrenaline). The functional state of the endothelium was assessed by secretion of nitric oxide and endothelin-1. Doppler ultrasound was used to measure the linear velocity of blood flow in the cerebral vessels, the size of the intima-media complex of the common carotid artery, and the results of the endothelium-dependent vasodilation. Blood pressure was monitored daily.

RESULTS

The action of CPSS is accompanied by the persistent increase in the serum cortisol levels. This process contributes to the development of vasoconstriction with the initiation of endothelial dysfunction with impaired production of nitric oxide and increased secretion of endothelin-1 and the formation of arterial hypertension. With progression of these processes, there is a decrease in cerebral blood flow. The observed increase in the size of the intima-media complex of the common carotid artery correlates with the severity of arterial hypertension and endothelial dysfunction.

CONCLUSIONS

CPSS leads to a decrease in cerebral blood flow and subsequent development of endothelial dysfunction and arterial hypertension, which are related to high levels of stress hormones circulating in the blood. These processes lead to functional failure of the vascular endothelium.

Asymmetric dimethylarginine: An crucial regulator in tissue fibrosis

Fibrosis is a reparative process with very few therapeutic options to prevent its progression to organ dysfunction. Chronic fibrotic diseases contribute to an estimated 45% of all death in the industrialized world. Asymmetric dimethylarginine (ADMA), an endothelial nitric oxide synthase inhibitor, plays a crucial role in the pathogenesis of various cardiovascular diseases associated with endothelial dysfunction. Recent reports have focused on ADMA in the pathogenesis of tissue fibrosis. This review discusses the current knowledge about ADMA biology, its association with risk factors of established fibrotic diseases and the potential pathophysiological mechanisms implicating ADMA in the process of tissue fibrosis.

l-proline supplementation improves nitric oxide bioavailability and counteracts the blood pressure rise induced by angiotensin II in rats

We evaluated whether l-proline (Pro) supplementation improves redox status and nitric oxide (NO) bioavailability and prevents or delays angiotensin II (AngII)-induced hypertension. Male Sprague-Dawley rats were distributed to four experimental groups: Pro + AngII (Pro-Ang), Pro + Saline (Pro-Sal), Vehicle + AngII (Veh-Ang) and Veh + Saline (Veh-Sal). Pro solution (2 g.kg^-1·day^-1) or water (vehicle) were orally administered, from day 0 to day 21. AngII (200 ng.kg^-1.min^-1) or saline were infused (s.c.) from day 7 to day 21. Systolic blood pressure (SBP) was measured by the tail-cuff method. From day 20-21, animals were kept on metabolic cages for 24h-urine collection. On day 21, urine and blood were collected for further quantification of redox status biomarkers, NO-related markers (urinary nitrates and nitrites, U-NOx; plasma asymmetric dimethylarginine, P-ADMA), metabolic and renal parameters. Pro prevented the AngII-induced SBP rise [mean (95% CI), Day 19: Pro-AngII, 137 (131; 143) vs. Veh-AngII, 157 (151; 163) mm Hg, P < 0.001]. Pro-AngII rats also had increased values of U-NOx, systemic and urinary total antioxidant status (TAS), urinary H₂O₂ and plasma urea, as well as reduced P-ADMA and unaltered urinary isoprostanes. Plasma Pro was inversely correlated with P-ADMA (r = -0.52, p = 0.0009) and positively correlated with urinary TAS (r = 0.55, p = 0.0005) which, in turn, was inversely correlated with P-ADMA (r = -0.56, p = 0.0004). Furthermore, urinary H₂O₂ values decreased across P-ADMA tertiles (p for linear trend = 0.023). These results suggest that Pro reduces P-ADMA levels and improves redox status, thereby increasing NO bioavailability and counteracting the AngII-induced SBP rise. H₂O₂ and TAS modulation by Pro may contribute to the reduced P-ADMA concentration.

Impaired Endothelial Function in Hereditary Angioedema During the Symptom-Free Period

Introduction: The presence of coronary endothelial dysfunction was previously shown in Hereditary Angioedema (HAE) patients. The aim of our study was to evaluate the effect of HAE on systemic endothelial function and whether there was a relationship among endothelial function, asymmetric dimethylarginine (ADMA) -which is a strong inhibitor of nitric oxide synthesis-, and disease severity scores.

Methods: Twenty-four HAE patients (18 females, aged 47.9 ± 2 years) without factors known to interfere with endothelial function were studied and compared with 24 healthy peers age- and gender-matched. Endothelial function was assessed by means of non-invasive finger plethysmography (reactive hyperaemia index: RHI) and ADMA levels by high-performance liquid chromatography. HAE severity scores have been calculated according to published literature.

Results: In HAE patients RHI was lower (2.03 ± 0.46 vs. 2.82 ± 0.34, p < 0.0001) and ADMA higher (0.636 ± 7 vs. 585 ± 5 micromol/L, p < 0.01) than in controls. A statistically significant inverse correlation was revealed between RHI and patients' ADMA levels (r = −0.516, p = 0.009) as well as between RHI and patients' chronological age (r = −0.49, p = 0.015). A statistically significant correlation between RHI and ADMA was confirmed even when excluding the possible influence of cholesterol (r = −0.408, p = 0.048). No other significant correlations were found with the examined laboratory and clinical parameters (chronological age, age at disease onset, disease duration, severity scores, and gender).

Conclusion: The dysfunction previously shown in HAE patients at the coronary arteries seems to involve the peripheral vessels as well, without a correlation with disease severity.