HIF-1α-BNIP3-mediated mitophagy in tubular cells protects against renal ischemia/reperfusion injury.

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.

Application of polyhydroxyalkanoate (PHA) synthesis regulatory protein PhaR as a bio-surfactant and bactericidal agent.

Polyhydroxyalkanoates (PHA), a family of diverse bio-polyesters, are produced by many bacteria as an energy and carbon storage material. PHA synthesis regulatory protein PhaR was reported to attach on the surface of intracellular PHA granules for convenience of synthesis regulation. PhaR was found to have an amphiphilic property. However, no study was conducted to exploit this property for applications as bio-surfactant and bactericide agent. Purified PhaR showed a higher emulsification ability than that of the widely used chemical surfactants including SDS, Tween 20, sodium oleate, and liquefied detergent (LD). PhaR also showed a higher emulsification ability than bio-surfactants rhamnose and PHA granules associated protein termed phasin or PhaP. Non-purified PhaR, namely, the native inclusion bodies and cell lysates, also demonstrated to be an excellent surfactant. PhaR was found highly stable even at 95 °C. In addition, PhaR was revealed to be a promising bactericidal agent against Gram positive and negative bacteria. PhaR can be conveniently produced by recombinant Escherichia coli. It has shown to be a bio-surfactant with excellent emulsification ability and strong bactericidal capacity at elevated temperature as high as 95 °C. Therefore, PhaR could be used in areas including food, beverage, pharmaceutical and cosmetics industries.