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In the present study, we hypothesized that hypoxia-inducible factor 1α (HIF-1α)-mediated mitophagy plays a protective role in ischemia/reperfusion (I/R)-induced acute kidney injury (AKI). Mitophagy was evaluated by measuring the changes of mitophagy flux, mitochondria DNA copy number, and the changes of mitophagy-related proteins including translocase of outer mitochondrial membrane 20 (TOMM20), cytochrome c oxidase IV (COX IV), microtubule-associated protein 1 light chain 3B (LC3B), and mitochondria adaptor nucleoporin p62 in HK2 cells, a human tubular cell line. Results show that HIF-1α knockout significantly attenuated hypoxia/reoxygenation (H/R)-induced mitophagy, aggravated H/R-induced apoptosis, and increased the production of reactive oxygen species (ROS). Similarly, H/R induced significantly increase in Bcl-2 19-kDa interacting protein 3 (BNIP3), a downstream regulator of HIF-1α. Notably, BNIP3 overexpression reversed the inhibitory effect of HIF-1α knockout on H/R-induced mitophagy, and prevented the enhancing effect of HIF-1α knockout on H/R-induced apoptosis and ROS production. For in vivo study, we established HIF-1αflox/flox; cadherin-16-cre mice in which tubular HIF-1α was specifically knockout. It was found that tubular HIF-1α knockout significantly inhibited I/R-induced mitophagy, and aggravated I/R-induced tubular apoptosis and kidney damage. In contrast, adenovirus-mediated BNIP3 overexpression significantly reversed the decreased mitophagy, and prevented enhanced kidney damage in tubular HIF-1α knockout mice with I/R injury. In summary, our study demonstrated that HIF-1α-BNIP3-mediated mitophagy in tubular cells plays a protective role through inhibition of apoptosis and ROS production in acute kidney damage.

Background: This study aimed to explore the feasibility of guiding the application of metoprolol succinate in patients with moderate to severe heart failure (HF) through monitoring plasma brain natriuretic peptide (BNP) levels., Methods: A total of 195 patients with moderate to severe HF (NYHA Functional Class III to IV) were selected and randomized into two groups: an observation group and a BNP group. The groups were established to observe the clinical conditions and establish plasma BNP levels to guide the application of metoprolol succinate. The average start-up of metoprolol succinate and average dose of metoprolol succinate after one month, as well as the recurrence rate and mortality of HF during hospital stay were compared between the two groups., Results: Start-up of metoprolol succinate was shorter in the BNP group than in the observation group [(5.89 ± 1.76) d vs. (7.03 ± 2.08) d, p < 0.01], but no significant differences in recurrence rate (26.60% vs. 23.91%, p > 0.05) and mortality (6.38% vs. 5.43%, p > 0.05) of HF were observed between the two groups. The average dose of metoprolol succinate after one month was higher in the BNP group compared with that of the observation group [(47.65 ± 13.09) mg/d vs. (35.08 ± 11.08) mg/d, p < 0.01]., Conclusions: Although monitoring plasma BNP might have limited the clinical impact on the change of left ventricular ejection fraction, recurrence of HF or mortality within 1 month, it could safely facilitate early use and up-titration of the metoprolol succinate in patients with moderate to severe HF., Key Words: BNP; Heart failure; β receptor blocker.