Exendin-4 Improves Nonalcoholic Fatty Liver Disease by Regulating Glucose Transporter 4 Expression in ob/ob Mice

Exendin-4 (Ex-4), a glucagon-like peptide-1 receptor (GLP-1R) agonist, has been known to reverse hepatic steatosis in ob/ob mice. Although many studies have evaluated molecular targets of Ex-4, its mechanism of action on hepatic steatosis and fibrosis has not fully been determined. In the liver, glucose transporter 4 (GLUT4) is mainly expressed in hepatocytes, endothelial cells and hepatic stellate cells (HSCs). In the present study, the effects of Ex-4 on GLUT4 expression were determined in the liver of ob/ob mice. Ob/ob mice were treated with Ex-4 for 10 weeks. Serum metabolic parameters, hepatic triglyceride levels, and liver tissues were evaluated for hepatic steatosis. The weights of the whole body and liver in ob/ob mice were reduced by long-term Ex-4 treatment. Serum metabolic parameters, hepatic steatosis, and hepatic fibrosis in ob/ob mice were reduced by Ex-4. Particularly, Ex-4 improved hepatic steatosis by enhancing GLUT4 via GLP-1R activation in ob/ob mice. Ex-4 treatment also inhibited hepatic fibrosis by decreasing expression of connective tissue growth factor in HSCs of ob/ob mice. Our data suggest that GLP-1 agonists exert a protective effect on hepatic steatosis and fibrosis in obesity and type 2 diabetes.

Curcumin Attenuates Radiation-Induced Inflammation and Fibrosis in Rat Lungs

A beneficial radioprotective agent has been used to treat the radiation-induced lung injury. This study was performed to investigate whether curcumin, which is known to have anti-inflammatory and antioxidant properties, could ameliorate radiation-induced pulmonary inflammation and fibrosis in irradiated lungs. Rats were given daily doses of intragastric curcumin (200 mg/kg) prior to a single irradiation and for 8 weeks after radiation. Histopathologic findings demonstrated that macrophage accumulation, interstitial edema, alveolar septal thickness, perivascular fibrosis, and collapse in radiation-treated lungs were inhibited by curcumin administration. Radiation-induced transforming growth factor-beta1 (TGF-beta1), connective tissue growth factor (CTGF) expression, and collagen accumulation were also inhibited by curcumin. Moreover, western blot analysis revealed that curcumin lowered radiation-induced increases of tumor necrosis factor-alpha (TNF-alpha), TNF receptor 1 (TNFR1), and cyclooxygenase-2 (COX-2). Curcumin also inhibited the nuclear translocation of nuclear factor-kappa B (NF-kappaB) p65 in radiation-treated lungs. These results indicate that long-term curcumin administration may reduce lung inflammation and fibrosis caused by radiation treatment.

Pak1/LIMK1/Cofilin Pathway Contributes to Tumor Migration and Invasion in Human Non-Small Cell Lung Carcinomas and Cell Lines

Squamous cell carcinoma (SCC) and adenocarcinoma (AC) are the major histological types of non-small cell lung carcinoma (NSCLC). Although both SCCs and ACs have been characterized histologically and clinically, the precise mechanisms underlying their migration and invasion are not yet known. Here, we address the involvement in NSCLC of the p21-associated kinase1 (Pak1)/LIM kinase1 (LIMK1)/cofilin pathway, which recently has been reported to play a critical role in tumor migration and invasion. The Pak1/LIMK1/cofilin pathway was evaluated in tumors from SCC (n=35) and AC (n=35) patients and in SCC- and AC-type cell lines by western blotting, immunohistochemistry, and in vitro migration and invasion assays. The levels of phosphorylated Pak1, LIMK1, and cofilin in lung tumor tissues from SCC patients were increased as compared to normal tissues. In addition, immunohistochemistry showed greater expression of phosphorylated cofilin in SCC tissues. Expression of phosphorylated Pak1 and LIMK1 proteins was also significantly higher in SCC-type cells than in AC-type cells. Moreover, migration and invasion assays revealed that a higher percentage of SCC type cells exhibited migration and invasion compared to AC type cells. Migration was also decreased in LIMK1 knockdown SK-MES-1 cells. These findings suggest that the activation of the Pak1/LIMK1/cofilin pathway could preferentially contribute to greater tumor migration and invasion in SCC, relative to that in AC.

Resveratrol activates AMPK and suppresses LPS-induced NF-kappaB-dependent COX-2 activation in RAW 264.7 macrophage cells / 대한해부학회지

AMP-activated protein kinase (AMPK), an enzyme involved in energy homeostasis, regulates inflammatory responses, but its precise mechanisms are not fully understood. Recent evidence has shown that resveratrol (RES), an AMPK activator, reduces prostaglandin E2 production in lipopolysaccharide (LPS)-treated microglia. Here, we examined the effect of RES on nuclear factor kappa B (NF-kappaB) dependent cyclooxygenase (COX)-2 activation in LPS-treated RWA 264.7 macrophages. We found that treatment with RES increased AMPK activation. AMPK and acetyl CoA carboxylase phosphorylation were attenuated in cells treated with LPS+RES, compared to cells treated with LPS alone. RES inhibited tumor necrosis factor (TNF)-alpha and TNF receptor 1 in LPS-treated cells. Finally, RES inhibited LPS-induced NF-kappaB translocation into the nucleus and COX-2 expression. Moreover, the effects of 5-aminoimidazole-4-carboxamide ribose and compound C were consistent with the effects of RES in LPS-treated cells. Taken together, these results suggest that the anti-inflammatory action of RES in RAW 264.7 macrophages is dependent on AMPK activation and is associated with inhibition of the LPS-stimulated NF-kappaB-dependent COX-2 signaling pathway.

Phosphorylation of 14-3-3zeta at serine 58 and neurodegeneration following kainic acid-induced excitotoxicity / 대한해부학회지

Oxidative stress-induced cell death leads to phosphorylation of 14-3-3zeta at serine 58. 14-3-3zeta is detected at significant levels in cerebrospinal fluid after kainic acid (KA)-induced seizures. Here we examined temporal changes in 14-3-3zeta phosphorylation in the hippocampus and amygdala of mice after KA treatment. Mice were killed at 2, 6, 24, or 48 h after KA (30 mg/kg) injection. We observed an increase in TUNEL and Fluoro-Jade B (FJB)-stained neurons in the hippocampus and amygdala of KA-treated mice. Phospho (p)-14-3-3zeta and p-JNK expression was increased in the hippocampus 2 and 6 h after KA treatment, respectively. In immunohistochemical analysis, p-14-3-3zeta-positive cells were present in the CA3 region of the hippocampus and the central nucleus of amygdala (CeA) of KA-treated mice. Thus, phosphorylation of 14-3-3zeta at serine 58 may play an important role in KA-induced hippocampal and amygdaloid neuronal damage.

Streptozotocin-induced Diabetes Increases the Adiponectin-mediated AMP-activated Protein Kinase Cascade in the Hippocampus of Mice / 대한해부학회지

Adiponectin is an adipocyte-derived protein with anti-diabetic and anti-angiogenesis properties that improves both glucose metabolism and insulin resistance via the adenosine monophosphate-activated protein kinase (AMPK) cascade. Diabetic cognitive deficits are correlated with dysregulation of energy metabolism in the hippocampus. In the present study, we investigated the expression of adiponectin-mediated AMPK cascade proteins in the hippocampus of streptozotocin (STZ)-induced diabetic mice. Diabetes was induced by STZ (55 mg/kg) injection intraperitoneally. Twenty-four weeks after induction of diabetes, mice were sacrificed. Results showed that decreased serum adiponectin levels and increased expression of hippocampal adiponectin receptor 1 (AdipoR1) was expressed in diabetic mice. Phosphorylated AMPK, acetyl CoA carboxylase (ACC), and eNOS expression levels were increased in the hippocampus of diabetic mice. The immunoreactivity of glucose transporter 1 in the endothelium of hippocampal blood vessels was also increased. These results indicate that adiponectin-mediated AMPK cascade activation may play a role in catabolic process that is involved in diabetic neurodegeneration.