Sgk1 regulates desmoglein 1 expression levels in oligodendrocytes in the mouse corpus callosum after chronic stress exposure.

Major depression, one of the most prevalent mental illnesses, is thought to be a multifactorial disease related to both genetic and environmental factors. However, the genes responsible for and the pathogenesis of major depression at the molecular level remain unclear. Recently, we reported that stressed mice with elevated plasma corticosterone levels show upregulation and activation of serum glucocorticoid-regulated kinase (Sgk1) in oligodendrocytes. Active Sgk1 causes phosphorylation of N-myc downstream-regulated gene 1 (Ndrg1), and phospho-Ndrg1 increases the expression of N-cadherin, α-catenin, and ß-catenin in oligodendrocytes. This activation of the Sgk1 cascade results in morphological changes in the oligodendrocytes of nerve fiber bundles, such as those present in the corpus callosum. However, little is known about the molecular functions of the traditional and/or desmosomal cadherin superfamily in oligodendrocytes. Therefore, in this study, we aimed to elucidate the functions of the desmosomal cadherin superfamily in oligodendrocytes. Desmoglein (Dsg) 1, Dsg2, and desmocollin 1 (Dsc1) were found to be expressed in the corpus callosum of mouse brain, and the expression of a subtype of Dsg1, Dsg1c, was upregulated in oligodendrocytes after chronic stress exposure. Furthermore, Dsg1 proteins were localized around the plasma membrane regions of oligodendrocytes. A study in primary oligodendrocyte cultures also revealed that chronic upregulation of Sgk1 by dexamethasone administration is involved in upregulation of Dsg1c mRNA. These results may indicate that chronic stress induced Sgk1 activation in oligodendrocytes, which increases Dsg1 expression near the plasma membrane. Thus, Dsg1 upregulation may be implicated in the molecular mechanisms underlying the morphological changes in oligodendrocytes in response to chronic stress exposure.

Interaction of Lipoplex with Albumin Enhances Gene Expression in Hepatitis Mice.

Understanding the in vivo fate of lipoplex, which is composed of cationic liposomes and DNA, is an important issue toward gene therapy. In disease conditions, the fate of lipoplex might change compared with the normal condition. Here, we examined the contribution of interaction with serum components to in vivo transfection using lipoplex in hepatitis mice. Prior to administration, lipoplex was incubated with serum or albumin. In the liver, the interaction with albumin enhanced gene expression in hepatitis mice, while in the lung, the interaction with serum or albumin enhanced it. In normal mice, the interaction with albumin did not enhance hepatic and pulmonary gene expression. Furthermore, hepatic and pulmonary gene expression levels of albumin-interacted lipoplex were correlated with serum transaminases in hepatitis mice. The albumin interaction increased the hepatic accumulation of lipoplex and serum tumor necrosis factor-α level. We suggest that the interaction with albumin enhanced the inflammation level after the administration of lipoplex in hepatitis mice. Consequently, the enhancement of the inflammation level might enhance the gene expression level. Information obtained in the current study will be valuable toward future clinical application of the lipoplex.

Association of cholesterol uptake capacity, a novel indicator for HDL functionality, and coronary plaque properties: An optical coherence tomography-based observational study.

BACKGROUND: Cholesterol efflux from atherosclerotic lesion is a key function of high-density lipoprotein (HDL). Recently, we established a simple, high-throughput, cell-free assay to evaluate the capacity of HDL to accept additional cholesterol, which is herein referred to as "cholesterol uptake capacity (CUC)". OBJECTIVE: To clarify the cross-sectional relationship between CUC and coronary plaque properties. METHODS: We enrolled 135 patients to measure CUC and assess the morphological features of angiographic stenosis by optical coherence tomography (OCT). We estimated the extent of the lipid-rich plaque by multiplying the mean lipid arc by lipid length (lipid index). The extent of the OCT-detected macrophage accumulation in the target plaque was semi-quantitatively estimated using a grading system. RESULTS: Lipid-rich plaque lesions were identified in 125 patients (92.6%). CUC was inversely associated with the lipid index (R = -0.348, P < 0.0001). In addition, CUC was also inversely associated with macrophage score (R = -0.327, P < 0.0001). Conversely, neither circulating levels of HDL cholesterol nor apoA1 showed a similar relationship. CONCLUSIONS: We demonstrated that CUC was inversely related to lipid-rich plaque burden and the extent of macrophage accumulation, suggesting that CUC could be useful for cardiovascular risk stratification.

Cholesterol Uptake Capacity: A New Measure of HDL Functionality for Coronary Risk Assessment.

BACKGROUND: Recent studies have shown that the cholesterol efflux capacity of HDL is a better predictor of cardiovascular disease (CVD) than HDL cholesterol. However, the standard procedures used for measuring cholesterol efflux capacity involve radioisotope-labeled cholesterol and cultured macrophages. Thus, a simpler method to measure HDL functionality is needed for clinical application. METHODS: We established a cell-free assay system to evaluate the capacity of HDL to accept additional cholesterol, which we named cholesterol "uptake capacity," using fluorescently labeled cholesterol and an anti-apolipoprotein A1 antibody. We quantified cholesterol uptake capacity of apolipoprotein B (apoB)-depleted serum samples from patients with coronary artery disease who had previously undergone revascularization. RESULTS: This assay system exhibited high reproducibility (CV <10%) and a short processing time (<6 h). The myeloperoxidase-mediated oxidation of apoB-depleted serum impaired cholesterol uptake capacity. Cholesterol uptake capacity correlated significantly with cholesterol efflux capacity (r2 = 0.47, n = 30). Furthermore, cholesterol uptake capacity correlated inversely with the requirement for revascularization because of recurrence of coronary lesions in patients with optimal control of LDL cholesterol (P < 0.01, n = 156). A multivariate analysis adjusted for traditional coronary risk factors showed that only cholesterol uptake capacity remained significant (odds ratio, 0.48; 95% CI, 0.29-0.80; P = 0.0048). CONCLUSIONS: Cholesterol uptake capacity assay evaluates the functionality of HDL in a sensitive and high-throughput manner without using radioisotope label and cells. This assay system could be used for the assessment of CVD risk in the clinical settings.

Family M42 aminopeptidase from the syntrophic bacterium Symbiobacterium thermophilum: characterization using recombinant protein.

The chromosomal DNA of the syntrophic thermophile Symbiobacterium thermophilum contains open reading frames of the genes encoding family M42 aminopeptidases, Pep1079, Pep1080, and Pep1081. To characterize these peptidases, the genes were cloned into Escherichia coli and overexpressed. Our experiments using the recombinant proteins confirmed that Pep1079, Pep1080, and Pep1081 are components of arginyl or lysinyl aminopeptidases that require Co²+ for enzymatic activity. Coexistence of Pep1079 and Pep1080 is necessary for expressing high peptidase activity. Pep1081 enhances the activity of Pep1079 and Pep1080.

Plasma corticosterone activates SGK1 and induces morphological changes in oligodendrocytes in corpus callosum.

Repeated stressful events are known to be associated with onset of depression. Further, stress activates the hypothalamic-pituitary-adrenocortical (HPA) system by elevating plasma cortisol levels. However, little is known about the related downstream molecular pathway. In this study, by using repeated water-immersion and restraint stress (WIRS) as a stressor for mice, we attempted to elucidate the molecular pathway induced by elevated plasma corticosterone levels. We observed the following effects both, in vivo and in vitro: (1) repeated exposure to WIRS activates the 3-phosphoinositide-dependent protein kinase (PDK1)-serum glucocorticoid regulated kinase (SGK1)-N-myc downstream-regulated gene 1 (NDRG1)-adhesion molecule (i.e., N-cadherin, α-catenin, and ß-catenin) stabilization pathway via an increase in plasma corticosterone levels; (2) the activation of this signaling pathway induces morphological changes in oligodendrocytes; and (3) after recovery from chronic stress, the abnormal arborization of oligodendrocytes and depression-like symptoms return to the control levels. Our data strongly suggest that these abnornalities of oligodendrocytes are possibly related to depression-like symptoms.