Angiotensin II Directly Increases Endothelial Calcium and Nitric Oxide in Kidney and Brain Microvessels In Vivo With Reduced Efficacy in Hypertension

BACKGROUND

The vasoconstrictor effects of angiotensin II via type 1 angiotensin II receptors in vascular smooth muscle cells are well established, but the direct effects of angiotensin II on vascular endothelial cells (VECs) in vivo and the mechanisms how VECs may mitigate angiotensin II-mediated vasoconstriction are not fully understood. The present study aimed to explore the molecular mechanisms and pathophysiological relevance of the direct actions of angiotensin II on VECs in kidney and brain microvessels in vivo.

METHODS AND RESULTS

Changes in VEC intracellular calcium ([Ca2+]i) and nitric oxide (NO) production were visualized by intravital multiphoton microscopy of cadherin 5-Salsa6f mice or the endothelial uptake of NO-sensitive dye 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate, respectively. Kidney fibrosis by unilateral ureteral obstruction and Ready-to-use adeno-associated virus expressing Mouse Renin 1 gene (Ren1-AAV) hypertension were used as disease models. Acute systemic angiotensin II injections triggered >4-fold increases in VEC [Ca2+]i in brain and kidney resistance arterioles and capillaries that were blocked by pretreatment with the type 1 angiotensin II receptor inhibitor losartan, but not by the type 2 angiotensin II receptor inhibitor PD123319. VEC responded to acute angiotensin II by increased NO production as indicated by >1.5-fold increase in 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate fluorescence intensity. In mice with kidney fibrosis or hypertension, the angiotensin II-induced VEC [Ca2+]i and NO responses were significantly reduced, which was associated with more robust vasoconstrictions, VEC shedding, and microthrombi formation.

CONCLUSIONS

The present study directly visualized angiotensin II-induced increases in VEC [Ca2+]i and NO production that serve to counterbalance agonist-induced vasoconstriction and maintain residual organ blood flow. These direct and endothelium-specific angiotensin II effects were blunted in disease conditions and linked to endothelial dysfunction and the development of vascular pathologies.

Association of positive pre-transplant angiotensin II type 1 receptor antibodies with clinical outcomes in lung transplant recipients

INTRODUCTION

Autoantibodies against the angiotensin II type 1 receptor (AT1R-Ab) have been previously associated with de novo donor-specific antibody (DSA) formation in lung transplantation. However, data regarding the clinical significance of AT1R-Ab in long-term graft function after lung transplantation are lacking.

METHODS

Seventy-one patients who underwent lung transplantation between July 2016 and January 2020 were enrolled in this study. We examined the relationship between pre-transplant AT1R-Ab levels and graft function, clinical outcomes, and human leukocyte antigen (HLA) DSA levels during the first 3 years post-transplantation.

RESULTS

Seventeen (23.9%) patients were AT1R-Ab-positive, and 54 (76.1%) were AT1R-Ab-negative. The median antibody value of the AT1R-Ab-positive group was 18 [18-22.5] U/mL, while that of the AT1R-Ab-negative group was 5.1 [3.5-8.0] U/mL (p < 0.001). There was no significant difference in the median acute cellular rejection (ACR) scores between the two groups (median [interquartile range] 1 [0.8-3] vs. 0.7 [0-1]; p = 0.145). However, there was a significant difference in the distribution of the ACR scores between the two groups (p = 0.015). Most (41.2%) patients in the pre-transplant AT1R-positive group scored above 1. The incidence of de novo DSA was also higher in AT1R-Ab-positive than in AT1R-Ab-negative patients (52.9% vs. 20.4%, p = 0.009). The incidence of chronic lung allograft dysfunction (CLAD) within 3 years was significantly higher in AT1R-Ab-positive than in AT1R-Ab-negative patients (58.3% vs. 11.8%; p < 0.001). In the multivariate Cox regression analysis, AT1R-Ab positivity (hazard ratio, 9.46; 95% confidence interval, 2.89-30.94; p < 0.001) was significantly associated with early CLAD. Furthermore, Kaplan-Meier analysis showed that AT1R-Ab-positive patients had a shorter survival time (χ2 = 39.62, p < 0.001).

CONCLUSION

High AT1R-Ab levels in the pre-transplant serum of lung recipients were associated with the development of de novo HLA-DSA, ACR, early CLAD, and short survival.

Morphological and Functional Remodeling of Vascular Endothelium in Cardiovascular Diseases

The vascular endothelium plays a vital role during embryogenesis and aging and is a cell monolayer that lines the blood vessels. The immune system recognizes the endothelium as its own. Therefore, an abnormality of the endothelium exposes the tissues to the immune system and provokes inflammation and vascular diseases such as atherosclerosis. Its secretory role allows it to release vasoconstrictors and vasorelaxants as well as cardio-modulatory factors that maintain the proper functioning of the circulatory system. The sealing of the monolayer provided by adhesion molecules plays an important role in cardiovascular physiology and pathology.

The intracellular renin-angiotensin system: Friend or foe. Some light from the dopaminergic neurons

The renin-angiotensin system (RAS) is one of the oldest hormone systems in vertebrate phylogeny. RAS was initially related to regulation of blood pressure and sodium and water homeostasis. However, local or paracrine RAS were later identified in many tissues, including brain, and play a major role in their physiology and pathophysiology. In addition, a major component, ACE2, is the entry receptor for SARS-CoV-2. Overactivation of tissue RAS leads several oxidative stress and inflammatory processes involved in aging-related degenerative changes. In addition, a third level of RAS, the intracellular or intracrine RAS (iRAS), with still unclear functions, has been observed. The possible interaction between the intracellular and extracellular RAS, and particularly the possible deleterious or beneficial effects of the iRAS activation are controversial. The dopaminergic system is particularly interesting to investigate the RAS as important functional interactions between dopamine and RAS have been observed in the brain and several peripheral tissues. Our recent observations in mitochondria and nucleus of dopaminergic neurons may clarify the role of the iRAS. This may be important for the developing of new therapeutic strategies, since the effects on both extracellular and intracellular RAS must be taken into account, and perhaps better understanding of COVID-19 cell mechanisms.