Atrial natriuretic peptide stimulates autophagy/mitophagy and improves mitochondrial function in chronic heart failure

Mitochondrial dysfunction, causing increased reactive oxygen species (ROS) production, is a molecular feature of heart failure (HF). A defective antioxidant response and mitophagic flux were reported in circulating leucocytes of patients with chronic HF and reduced ejection fraction (HFrEF). Atrial natriuretic peptide (ANP) exerts many cardiac beneficial effects, including the ability to protect cardiomyocytes by promoting autophagy. We tested the impact of ANP on autophagy/mitophagy, altered mitochondrial structure and function and increased oxidative stress in HFrEF patients by both ex vivo and in vivo approaches. The ex vivo study included thirteen HFrEF patients whose peripheral blood mononuclear cells (PBMCs) were isolated and treated with αANP (10^-11 M) for 4 h. The in vivo study included six HFrEF patients who received sacubitril/valsartan for two months. PBMCs were characterized before and after treatment. Both approaches analyzed mitochondrial structure and functionality. We found that levels of αANP increased upon sacubitril/valsartan, whereas levels of NT-proBNP decreased. Both the ex vivo direct exposure to αANP and the higher αANP level upon in vivo treatment with sacubitril/valsartan caused: (i) improvement of mitochondrial membrane potential; (ii) stimulation of the autophagic process; (iii) significant reduction of mitochondrial mass-index of mitophagy stimulation-and upregulation of mitophagy-related genes; (iv) reduction of mitochondrial damage with increased inner mitochondrial membrane (IMM)/outer mitochondrial membrane (OMM) index and reduced ROS generation. Herein we demonstrate that αANP stimulates both autophagy and mitophagy responses, counteracts mitochondrial dysfunction, and damages ultimately reducing mitochondrial oxidative stress generation in PBMCs from chronic HF patients. These properties were confirmed upon sacubitril/valsartan administration, a pivotal drug in HFrEF treatment.

Diagnostic value of cardiac natriuretic peptide on pulmonary hypertension in systemic sclerosis: A systematic review and meta-analysis

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a major cause of morbidity and mortality in systemic sclerosis (SSc). Many risk factors and predictors of outcomes have been identified in these patients. B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP) serum levels are often elevated in SSc patients with early PAH. We conducted this systematic review and meta-analysis to estimate the diagnostic value of BNP/NT-proBNP in systemic sclerosis secondary pulmonary arterial hypertension (SSc-PAH).

METHODS

A systematic search was performed through PubMed, Embase, and Cochrane Library databases up to January 30, 2021. Stata 16.0 (Stata Corp, College Station, TX) was used to conduct the meta-analysis.

RESULTS

A total of 9 studies involving 220 SSc-PAH patients and 259 non-SSc-PAH controls were included. The values of sensitivity and specificity using BNP and NT-ProBNP as diagnostic tools were pooled in the diagnostic meta-analysis. The overall performance of BNP/NT-ProBNP detection was: pooled sensitivity, 0.67 (95% CI: 0.52 to 0.79); pooled specificity, 0.84 (95% CI: 0.75 to 0.91); pooled positive likelihood ratio, 4.3 (95% CI: 3 to 6.1); and pooled negative likelihood ratio, 0.39 (95% CI: 0.28 to 0.55). The subgroup analysis showed similar results. Funnel plots indicate that there is no evidence for publication bias.

CONCLUSIONS

Our results revealed that NT-proBNP has certain diagnostic value for PAH due to its better specificity and moderate sensitivity, but its clinical application value remains suboptimal and can not be a stand-alone decision-making diagnostic tool of SSc-PAH.

Effects of aging on the secretory apparatus in the right atrial cardiomyocytes of rats

The cardiac atria secrets polypeptide hormones usually called natriuretic peptides (NPs). These substances play a relevant role in the blood pressure regulation. The objective of the study was to estimate the effects of aging on the secretory apparatus of NPs in cardiomyocytes of the right atrium. Twenty male Wistar rats were studied: 10 young animals aged 3 months old (237 ± 27 g; mean ± SD) and 10 old animals aged 20 months old (450 ± 68 g; mean ± SD). The systolic blood pressure was verified instants before the moment of the euthanasia. Electron micrographs were prepared to quantify the area and density of the NP granules and the relative volumes of the endoplasmic reticulum, Golgi complex, and mitochondria. In addition, the number of pores per 10 μm of karyotheca was another variable evaluated. The significance of the results between the two groups evaluated was analyzed by the Student's t test (p < 0.05). The cardiomyocytes obtained from animals of the old group showed decreased in sectional area and density of secretory granules of NP and lower relative volume of endoplasmic reticulum, Golgi complex, and mitochondria compared with the young rats. Moreover, the quantitative density of nuclear pores was significantly lower compared with the youngers. CONCLUSION: Aging causes hypotrophy of the cardiomyocytes of right atrium, similar to what occurs in ventricular cardiomyocytes.