Hepatocytic lipocalin-2 controls HDL metabolism and atherosclerosis via Nedd4-1-SR-BI axis in mice.

High-density lipoprotein (HDL) metabolism is regulated by complex interplay between the scavenger receptor group B type 1 (SR-BI) and multiple signaling molecules in the liver. Here, we show that lipocalin-2 (Lcn2) is a key regulator of hepatic SR-BI, HDL metabolism, and atherosclerosis. Overexpression of human Lcn2 in hepatocytes attenuates the development of atherosclerosis via SR-BI in western-diet-fed Ldlr-/- mice, whereas hepatocyte-specific ablation of Lcn2 has the opposite effect. Mechanistically, hepatocyte Lcn2 improves HDL metabolism and alleviates atherogenesis by blocking Nedd4-1-mediated SR-BI ubiquitination at K500 and K508. The Lcn2-improved HDL metabolism is abolished in mice with hepatocyte-specific Nedd4-1 or SR-BI deletion and in SR-BI (K500A/K508A) mutation mice. This study identifies a regulatory axis from Lcn2 to HDL via blocking Nedd4-1-mediated SR-BI ubiquitination and demonstrates that hepatocyte Lcn2 may be a promising target to improve HDL metabolism to treat atherosclerotic cardiovascular diseases.

Hippo-YAP/MCP-1 mediated tubular maladaptive repair promote inflammation in renal failed recovery after ischemic AKI.

Acute kidney injury (AKI) is associated with significant morbidity and its chronic inflammation contributes to subsequent chronic kidney disease (CKD) development. Yes-associated protein (YAP), the major transcriptional coactivator of the Hippo pathway, has been shown associated with chronic inflammation, but its role and mechanism in AKI-CKD transition remain unclear. Here we aimed to investigate the role of YAP in AKI-induced chronic inflammation. Renal ischemia/reperfusion (I/R) was used to induce a mouse model of AKI-CKD transition. We used verteporfin (VP), a pharmacological inhibitor of YAP, to treat post-IRI mice for a period, and evaluated the influence of YAP inhibition on long-term outcomes of AKI. In our results, severe IRI led to maladaptive tubular repair, macrophages infiltration, and progressive fibrosis. Following AKI, the Hippo pathway was found significantly altered with YAP persistent activation. Besides, tubular YAP activation was associated with the maladaptive repair, also correlated with interstitial macrophage infiltration. Monocyte chemoattractant protein 1 (MCP-1) was found notably upregulated with YAP activation. Of note, pharmacological inhibition of YAP in vivo attenuated renal inflammation, including macrophage infiltration and MCP-1 overexpression. Consistently, in vitro oxygen-glucose deprivation and reoxygenation (OGD/R) induced YAP activation and MCP-1 overproduction whereas these could be inhibited by VP. In addition, we modulated YAP activity by RNA interference, which further confirmed YAP activation enhances MCP-1 expression. Together, we concluded tubular YAP activation with maladaptive repair exacerbates renal inflammation probably via promoting MCP-1 production, which contributes to AKI-CKD transition.

6-mT 0-120-Hz magnetic fields differentially affect cellular ATP levels.

Adenosine triphosphate (ATP), an indispensable molecule that provides energy for essentially all cellular processes, has been shown to be affected by some magnetic fields (MFs). Although people are frequently exposed to various static and power frequency MFs in their daily lives, the exact effects of these MFs of different frequencies have not been systematically investigated. Here, we tested 6-mT MFs with 0, 50, and 120 Hz for their effects on cellular ATP levels in 11 different cell lines. We found that the 6-mT static magnetic field (SMF) either does not affect or increase cellular ATP levels, while 6-mT 50-Hz MF either does not affect or decrease cellular ATP levels. In contrast, 6-mT 120-Hz MF has variable effects. We examined the mitochondrial membrane potential (MMP) as well as reactive oxygen species (ROS) in four different cell lines, but did not find their direct correlation with ATP levels. Although none of the ATP level changes induced by these three different frequencies of 6-mT MFs are dramatic, these results may be used to explain some differential cellular responses of various cell lines to different frequency MFs.