ABSTRACT
Voltage-gated proton channels (Hv1/VSOP), encoded by Hvcn1, are important regulator of reactive oxygen species (ROS) production in many types of immune cells. While in vitro studies indicate that Hv1/VSOP regulates ROS production by maintaining pH homeostasis, there are few studies investigating the functional importance of Hv1/VSOP in vivo. In the present study, we first show that Hv1/VSOP is functionally expressed in liver resident macrophage, Kupffer cells, regulating the hepatic oxidative stress in vivo. Our immunocytochemistry and electrophysiology data showed that Hvcn1 is specifically expressed in Kupffer cells, but not in hepatocytes. Furthermore, Hvcn1-deficiency drastically altered the hepatic oxidative stress. The Hvcn1-deficient mice showed high blood glucose and serum insulin but normal insulin sensitivity, indicating that these phenotypes were not linked to insulin resistance. Transcriptome analysis indicated that the gene expression of glycogen phosphorylase (Pygl) and Glucose-6-phosphatase, catalytic subunit (G6pc) were upregulated in Hvcn1-deficient liver tissues, and quantitative PCR confirmed the result for Pygl. Furthermore, we observed higher amount of glucose-6-phosphate, a key sugar intermediate for glucose in Hvcn1-deficient liver than WT, suggesting that glucose production in liver is accelerated in Hvcn1-deficient mice. The present study sheds light on the functional importance of Kupffer cells in hepatic oxidative stress and its potential relationship with glucose metabolism.
Subject(s)
Glucose/metabolism , Ion Channels/metabolism , Kupffer Cells/metabolism , Liver/metabolism , Oxidative Stress/physiology , Animals , Cell Line , Cell Line, Tumor , Hep G2 Cells , Hepatocytes/metabolism , Humans , Insulin Resistance/physiology , Male , Mice , Mice, Inbred C57BL , Protons , Reactive Oxygen Species/metabolism , Up-Regulation/physiologyABSTRACT
AIM: Adiponectin (APN) is an adipocyte-derived bioactive molecule with antiatherogenic properties. We previously reported that cystatin C (CysC) abolished the anti-atherogenic effects of APN. We aimed to elucidate the clinical significance of CysC-APN complex in patients with coronary artery disease (CAD). METHODS: We enrolled 43 stable CAD male patients to examine the relationship between CysC-APN complex and coronary plaque characteristics. Serum was immunoprecipitated by the anti-APN antibody and immunoblotted by the anti-CysC antibody to demonstrate the presence of CysC-APN complexes in vivo. To confirm their binding in vitro, HEK293T cell lysates overexpressing myc-APN and FLAG-CysC were immunoprecipitated with an anti-myc or anti-FLAG antibody, followed by immunoblotting with an anti-APN or anti-CysC antibody. RESULTS: CysC was identified as a specific co-immunoprecipitant with APN by the anti-APN antibody in human serum. In vitro, FLAG-CysC was co-immunoprecipitated with myc-APN by the anti-myc antibody and myc-APN was co-immunoprecipitated with FLAG-CysC by the anti-FLAG antibody. Among CAD patients, serum CysC-APN complex levels negatively correlated with fibrotic components of coronary plaques and positively correlated with either necrotic or lipidic plus necrotic components. Plaque burden negatively correlated with serum APN levels but not serum CysC-APN complex levels. Serum CysC levels had no association with plaque characteristics. In multivariate analysis, CysC-APN complex levels were identified as the strongest negative factor for fibrotic components and the strongest positive factor for both necrotic and lipidic plus necrotic components. CONCLUSION: Measuring serum CysC-APN complex levels is helpful for evaluating coronary plaque instability in CAD patients.
