The goal of this study was to determine if serotonergic activity, which is impaired in depression, regulates the phosphorylation of glycogen synthase kinase-3b (GSK3b) in mouse brain in vivo. GSK3b is inhibited by phosphorylation on serine-9 and is a target of the mood stabilizer lithium. Following administration to mice of d-fenfluramine to stimulate serotonin (5HT) release and reduce its reuptake, and clorgyline to inhibit 5HT catabolism, levels of phospho-Ser9-GSK3b were 300-400% of control levels in the prefrontal cortex, hippocampus, and striatum. Treatment with monoamine reuptake inhibitors fluoxetine and imipramine also increased the level of phospho-Ser9-GSK3b. Using receptor selective agonists and antagonists, 5HT1A receptors were found to mediate increases, and 5HT2 receptors decreases, in phospho-Ser9-GSK3b levels. This indicates that serotonergic regulation of the phosphorylation of GSK3b is achieved by a balance between the opposing actions of these 5HT receptor subtypes. These findings demonstrate for the first time that serotonergic activity regulates the phosphorylation of GSK3b and show that this regulation occurs in mammalian brain in vivo. These results raise the possibility that impaired inhibitory control of GSK3b may occur in conditions where serotonergic activity is dysregulated, such as in mood disorders.

Glycogen synthase kinase-3 (GSK3) has been recognized as an important enzyme that modulates many aspects of neuronal function. Accumulating evidence implicates abnormal activity of GSK3 in mood disorders and schizophrenia, and GSK3 is a potential protein kinase target for psychotropics used in these disorders. We previously reported that serotonin, a major neurotransmitter involved in mood disorders, regulates GSK3 by acutely increasing its N-terminal serine phosphorylation. The present study was undertaken to further determine if atypical antipsychotics, which have therapeutic effects in both mood disorders and schizophrenia, can regulate phospho-Ser-GSK3 and inhibit its activity. The results showed that acute treatment of mice with risperidone rapidly increased the level of brain phospho-Ser-GSK3 in the cortex, hippocampus, striatum, and cerebellum in a dose-dependent manner. Regulation of phospho-Ser-GSK3 was a shared effect among several atypical antipsychotics, including olanzapine, clozapine, quetiapine, and ziprasidone. In addition, combination treatment of mice with risperidone and a monoamine reuptake inhibitor antidepressant imipramine or fluoxetine elicited larger increases in brain phospho-Ser-GSK3 than each agent alone. Taken together, these results provide new information suggesting that atypical antipsychotics, in addition to mood stabilizers and antidepressants, can inhibit the activity of GSK3. These findings may support the pharmacological mechanisms of atypical antipsychotics in the treatment of mood disorders.

Background-Bipolar disorder has been linked to alterations in the multifunctional enzyme glycogen synthase kinase-3β (GSK3β). The mood stabilizer lithium inhibits GSK3β in vitro and in mouse brain, and this is currently the strongest known potential therapeutic target of lithium. We tested whether lithium modified GSK3β in vivo or in vitro in peripheral blood mononuclear cells (PBMCs) from healthy control and bipolar disorder subjects.

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Oxidized low-density lipoprotein- (Ox-LDL-) induced autophagy dysfunction in human vascular endothelial cells contributes to the development of atherosclerosis (AS). Resveratrol (RSV) protects against Ox-LDL-induced endothelium injury. The objective of this study was to determine the mechanisms underlying Ox-LDL-induced autophagy dysfunction and RSV-mediated protection in human umbilical vein endothelial cells (HUVECs). The results showed that Ox-LDL suppressed the expression of sirtuin 1 (SIRT1) and increased LC3-II and sequestosome 1 (p62) protein levels without altering p62 mRNA levels in HUVECs. Pretreatment with bafilomycin A1 (BafA1) to inhibit lysosomal degradation abrogated the Ox-LDL-induced increase in LC3-II protein level. Ox-LDL increased colocalization of GFP and RFP puncta in mRFP-GFP-tandem fluorescent LC3- (tf-LC3-) transfected cells. Moreover, Ox-LDL decreased the expression of mature cathepsin D and attenuated cathepsin D activity. Pretreatment with RSV increased the expression of SIRT1 and LC3-II and increased p62 protein degradation. RSV induced RFP-LC3 aggregation more than GFP-LC3 aggregation. RSV restored lysosomal function and promoted Ox-LDL degradation in HUVECs. All the protective effects of RSV were blocked after SIRT1 was knocked down. These findings demonstrated that RSV upregulated the expression of SIRT1, restored lysosomal function, enhanced Ox-LDL-induced impaired autophagic flux, and promoted Ox-LDL degradation through the autophagy-lysosome degradation pathway in HUVECs.

Oxidized low‐density lipoprotein (Ox‐LDL) may induce apoptosis and dysfunction of vascular endothelial cells, contributing to the initiation and development of atherosclerosis and lectin‐like oxidized low‐density lipoprotein receptor‐1 (LOX‐1) plays a central role in Ox‐LDL uptake in the course of atherogenesis. Humanin (HN), a mitochondrial‐derived peptide, was recently demonstrated to exert a protective role against endothelial dysfunction and Ox‐LDL‐induced progression of atherosclerosis. The HN analog HNGF6A (HNG) modulates cholesterol metabolism in macrophage RAW 264.7 cells. However, whether HNG affects Ox‐LDL metabolism in endothelial cells is unknown. In this study, we investigated the effect of HNG on Ox‐LDL accumulation in human umbilical vein endothelial cell (HUVEC) and its underlying mechanisms. HUVEC were preincubated with HNG for 1 h before addition of Ox‐LDL. Total cholesterol content was measured by using a tissue total cholesterol assay kit and flow cytometry. Cell viability was measured by CCK8 assay. Protein content was examined by Western blot assays. Flow cytometry was used to identify apoptotic cells. Flow cytometry and tissue total cholesterol assays showed that HNG reduced Ox‐LDL accumulation in HUVEC. In addition, HNG inhibited Ox‐LDL‐induced apoptosis of HUVEC. Western blot results showed that HNG reduced LOX‐1 protein content. However, when LOX‐1 was knocked down or inhibited, the effect of HNG in reducing Ox‐LDL aggregation and apoptosis in HUVEC disappeared. Our study demonstrated that HNG reduces lipid aggregation and apoptosis in HUVEC in a LOX‐1‐dependent manner.

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