Inhibition of the renin-angiotensin system in patients with COPD and pulmonary hypertension

Nephrectomy and high-salt diet inducing pulmonary hypertension and kidney damage by increasing Ang II concentration in rats

BACKGROUND

Chronic kidney disease (CKD) is a significant risk factor for pulmonary hypertension (PH), a complication that adversely affects patient prognosis. However, the mechanisms underlying this association remain poorly understood. A major obstacle to progress in this field is the lack of a reliable animal model replicating CKD-PH.

METHODS

This study aimed to establish a stable rat model of CKD-PH. We employed a combined approach, inducing CKD through a 5/6 nephrectomy and concurrently exposing the rats to a high-salt diet. The model's hemodynamics were evaluated dynamically, alongside a comprehensive assessment of pathological changes in multiple organs. Lung tissues and serum samples were collected from the CKD-PH rats to analyze the expression of angiotensin-converting enzyme 2 (ACE2), evaluate the activity of key vascular components within the renin-angiotensin-aldosterone system (RAAS), and characterize alterations in the serum metabolic profile.

RESULTS

At 14 weeks post-surgery, the CKD-PH rats displayed significant changes in hemodynamic parameters indicative of pulmonary arterial hypertension. Additionally, right ventricular hypertrophy was observed. Notably, no evidence of pulmonary vascular remodeling was found. Further analysis revealed RAAS dysregulation and downregulated ACE2 expression within the pulmonary vascular endothelium of CKD-PH rats. Moreover, the serum metabolic profile of these animals differed markedly from the sham surgery group.

CONCLUSIONS

Our findings suggest that the development of pulmonary arterial hypertension in CKD-PH rats is likely a consequence of a combined effect: RAAS dysregulation, decreased ACE2 expression in pulmonary vascular endothelial cells, and metabolic disturbances.

Novel insights on the pulmonary vascular consequences of COVID-19

In the last few months, the number of cases of a new coronavirus-related disease (COVID-19) rose exponentially, reaching the status of a pandemic. Interestingly, early imaging studies documented that pulmonary vascular thickening was specifically associated with COVID-19 pneumonia, implying a potential tropism of the virus for the pulmonary vasculature. Moreover, SARS-CoV-2 infection is associated with inflammation, hypoxia, oxidative stress, mitochondrial dysfunction, DNA damage, and lung coagulopathy promoting endothelial dysfunction and microthrombosis. These features are strikingly similar to what is seen in pulmonary vascular diseases. Although the consequences of COVID-19 on the pulmonary circulation remain to be explored, several viruses have been previously thought to be involved in the development of pulmonary vascular diseases. Patients with preexisting pulmonary vascular diseases also appear at increased risk of morbidity and mortality. The present article reviews the molecular factors shared by coronavirus infection and pulmonary vasculature defects, and the clinical relevance of pulmonary vascular alterations in the context of COVID-19.

Effects of acrolein on aldosterone release from zona glomerulosa cells in male rats

A positive correlation between smoking and hypertension has been well established. Acrolein is a major toxic volatile compound found in cigarette smoke. Human exposure to low levels of acrolein is unavoidable due to its production in daily activities, such as smoke from industrial, hot oil cooking vapors, and exhaust fumes from vehicles. The toxicity and the action mechanism of acrolein to induce apoptosis have been extensively studied, but the effects of acrolein on hypertension are still unknown. The present study aimed to examine the effects of acrolein on aldosterone release both in vivo and in vitro. Male rats were divided into three groups, and intraperitoneally injected with normal saline, or acrolein (2mg/kg) for 1 (group A-1) or 3 (group A-3) days, respectively. After sacrificing, rat blood samples were obtained to measure plasma aldosterone and angiotensin II (Ang II) levels. Zona glomerulosa (ZG) cells were prepared from rat adrenal cortex, and were incubated with or without stimulants. We found that the serum aldosterone was increased by 1.2-fold (p<0.05) in A-3 group as compared to control group. Basal aldosterone release from ZG cells in A-3 group was also increased significantly. Moreover, acrolein enhanced the stimulatory effects of Ang II and 8-bromo-cyclic AMP on aldosterone secretion from ZG cells prepared in both A-1 and A-3 groups. Furthermore, the enzyme activity of P450scc, the rate-limiting step of aldosterone synthesis, was elevated after acrolein injection. Plasma level of Ang II was increased in both A-1 and A-3 groups. These results suggested that acrolein exposure increased aldosterone production, at least in part, through elevating the level of plasma Ang II and stimulating steroidogenesis pathways.

Antenatal maternal hypoxic stress: adaptations in fetal lung Renin-Angiotensin system

Antenatal maternal hypoxia (AMH) can lead to intrauterine growth restriction (IUGR), as well as idiopathic pulmonary hypertension of newborn and adult, the latter of which may be a consequence of alterations in the local pulmonary renin-angiotensin system (RAS). Little is known of these adaptations, however. Thus, we tested the hypothesis that antenatal maternal hypoxia is associated with alterations in gene and protein expression of the pulmonary renin-angiotensin system, which may play an important role in pulmonary disorders in the offspring. In FVB/NJ mice, we studied messenger RNA (mRNA) and protein expression, as well as promoter DNA methylation and microRNA (miRNA) levels in response to 48 hours hypoxia (10.5% O(2)) at 15.5 day post coitum (DPC). In response to AMH, the pulmonary mRNA levels of angiotensin-converting enzyme (ACE) 1.2, ACE-2, and angiotensin II type 1b (AT-1b) receptors were increased significantly, as compared to controls (N = 4). In response to antenatal hypoxia, pulmonary protein levels of renin and ACE-2 also were increased significantly, whereas ACE-1 protein expression was reduced. In fetal lungs, we also observed reduced expression of the miRNAs: mmu-mir -199b, -27b, -200b, and -468 that putatively increase the translation of renin, ACE-1, ACE-2, and AT-1 receptors, respectively. In response to AMH, promoter methylation of ACE was unchanged. We conclude that AMH leads to changes in expression of pulmonary RAS of fetal mice. The possible implications of these changes for the regulation of pulmonary vascular contractility in later life remain to be explored.

Prevention of pulmonary hypertension by Angiotensin-converting enzyme 2 gene transfer

In spite of recent advancements in the treatment of pulmonary hypertension, successful control has yet to be accomplished. The abundant presence of angiotensin-converting enzyme 2 (ACE2) in the lungs and its impressive effect in the prevention of acute lung injury led us to test the hypothesis that pulmonary overexpression of this enzyme could produce beneficial outcomes against pulmonary hypertension. Monocrotaline (MCT) treatment of mice for 8 weeks resulted in significant increases in right ventricular systolic pressure, right ventricle:left ventricle plus septal weight ratio, and muscularization of pulmonary vessels. Administration of a lentiviral vector containing ACE2, 7 days before MCT treatment prevented the increases in right ventricular systolic pressure (control: 25+/-1 mm Hg; MCT: 44+/-5 mm Hg; MCT+ACE2: 26+/-1 mm Hg; n=6; P<0.05) and right ventricle:left ventricle plus septal weight ratio (control: 0.25+/-0.01; MCT: 0.31+/-0.01; MCT+ACE2: 0.26+/-0.01; n=8; P<0.05). A significant attenuation in muscularization of pulmonary vessels induced by MCT was also observed in animals overexpressing ACE2. These beneficial effects were associated with an increase in the angiotensin II type 2 receptor:angiotensin II type 1 receptor mRNA ratio. Also, pulmonary hypertension-induced increases in proinflammatory cytokines were significantly attenuated by lentiviral vector-containing ACE2 treatment. Furthermore, ACE2 gene transfer in mice after 6 weeks of MCT treatment resulted in a significant reversal of right ventricular systolic pressure. These observations demonstrate that ACE2 overexpression prevents and reverses right ventricular systolic pressure and associated pathophysiology in MCT-induced pulmonary hypertension by a mechanism involving a shift from the vasoconstrictive, proliferative, and fibrotic axes to the vasoprotective axis of the renin-angiotensin system and inhibition of proinflammatory cytokines.