Gu Seob Roh

Resveratrol Attenuates Obesity-Associated Peripheral and Central Inflammation and Improves Memory Deficit in Mice Fed a High-Fat Diet

Obesity-induced diabetes is associated with chronic inflammation and is considered a risk factor for neurodegeneration. We tested the hypothesis that an AMP-activated protein kinase activator, resveratrol (RES), which is known to exert potent anti-inflammatory effects, would attenuate peripheral and central inflammation and improve memory deficit in mice fed a high-fat diet (HFD). C57BL/6J mice were fed an HFD or an HFD supplemented with RES for 20 weeks. Metabolic parameters in serum were evaluated, and Western blot analysis and immunohistochemistry in peripheral organs and brain were completed. We used the Morris water maze test to study the role of RES on memory function in HFD-treated mice. RES treatment reduced hepatic steatosis, macrophage infiltration, and insulin resistance in HFD-fed mice. In the hippocampus of HFD-fed mice, the protein levels of tumor necrosis factor-α and Iba-1 expression were reduced by RES treatment. Choline acetyltransferase was increased, and the phosphorylation of tau was decreased in the hippocampus of HFD-fed mice upon RES treatment. In particular, we found that RES significantly improved memory deficit in HFD-fed mice. These findings indicate that RES reverses obesity-related peripheral and central inflammation and metabolic derangements and improves memory deficit in HFD-fed diabetic mice.

Curcumin attenuates the kainic acid-induced hippocampal cell death in the mice.

Kainic acid (KA) induced oxidative stress is associated with hippocampal cell death. Recent studies suggest that curcumin, a potent antioxidant, may provide protection for KA-induced oxidative stress. We investigated the effects of curcumin treatment on hippocampal reactive astrocytes in mice with KA-induced seizures. Eighteen hours after curcumin treatment, mice were treated with KA (30 mg/kg, i.p.), and then sacrificed after a further 48 h. Using cresyl violet staining and TUNEL analysis, histological evaluation revealed cell death in the KA-treated hippocampus. However, marked cell death was not observed in mice treated with curcumin. In addition, curcumin treatment reduced the KA-induced immunoreactivity of caspase-3. Similarly, immunoreactivity analyses indicated that KA causes upregulation of hippocampal GFAP, eNOS, and HO-1 levels, all of which were reduced in animals those received the curcumin treatment. Our findings indicate that curcumin is a potent inhibitor of reactive astrocyte expression and thus, prevents hippocampal cell death. These results also support its potential for use in the treatment of neurodegenerative diseases.

Heme Oxygenase-1 Protects Rat Kidney from Ureteral Obstruction via an Antiapoptotic Pathway

This study examined the functional significance of heme oxygenase-1 (HO-1) expression on renal injury induced by ureteral obstruction in the rat kidney. Male Sprague-Dawley rats were divided into three groups, after which unilateral ureteral obstruction (UUO) was performed: untreated (group 1), treated with 30 mg/kg body wt hemin (group 2), and treated with 50 microg/kg body wt zinc (alpha) protoporphyrin eta (ZnPP) and 30 mg/kg hemin (group 3). After 7 and 14 d, histologic changes and the expression of HO-1, Bcl-2, Bad, TGF-beta, and cleaved caspase-3 were examined. Tubular lumens were dilated and epithelial cells were flattened on day 7 after UUO. Interstitial fibrosis and separation of the tubules were markedly increased on day 14. In contrast, the kidneys that were treated with hemin exhibited minimal interstitial fibrosis and flattening of epithelial cells on day 7 and fewer changes on day 14 than in the controls. However, treatment with ZnPP, an inhibitor of HO enzyme activity, eliminated the beneficial effect of hemin on interstitial fibrosis and tubular dilation. Increased HO-1 expression was associated with increased Bcl-2. In the ZnPP-treated rats, Bcl-2 signals were decreased compared with the hemin group. The level of proapoptotic Bad was not changed in any group. The positive cells for cleaved caspase-3 were significantly increased in renal tubular epithelial cells and tubulointerstitial cells in the obstructed rats, and hemin treatment decreased the caspase-3 activation. This study demonstrates that upregulation of HO-1 provides protection against renal injury that follows UUO. This effect is dependent on modulation of the antiapoptotic pathway by HO-1 expression.

CHI3L1 (YKL-40) is expressed in human gliomas and regulates the invasion, growth and survival of glioma cells

Chitinase 3‐like 1 (CHI3L1) is a secreted glycoprotein that has pleiotropic activity in aggressive cancers. In our study, we examined the expression and function of CHI3L1 in glioma cells. CHI3L1 was highly expressed in human glioma tissue, whereas its expression in normal brain tissue was very low. CHI3L1 suppression by shRNA reduced glioma cell invasion, anchorage‐independent growth and increased cell death triggered by several anticancer drugs, including cisplatin, etoposide and doxorubicin, whereas CHI3L1 overexpression had the opposite effect in glioma cells. Because the invasive nature of glioma cells plays a critical role in the high morbidity of glioma, we have further defined the role of CHI3L1 in the process of glioma invasion. Downregulation of CHI3L1 results in decreased cell–matrix adhesion and causes a marked increase in stress fiber formation and cell size with fewer cellular processes. Furthermore, the expression and activity of matrix metalloproteinase‐2 was also decreased in glioma cells in which CHI3L1 was knocked down. Taken together, these results suggest that CHI3L1 plays an important role in the regulation of malignant transformation and local invasiveness in gliomas. Thus, targeting the CHI3L1 molecule may be a potential therapeutic molecular target for gliomas.

Ketogenic diet-induced peroxisome proliferator-activated receptor-γ activation decreases neuroinflammation in the mouse hippocampus after kainic acid-induced seizures

Similar to fasting, the ketogenic diet (KD) has anti-inflammatory effects and protects against excitotoxicity-mediated neuronal cell death. Recent studies have shown that peroxisome proliferator-activated receptor (PPAR)γ has anti-inflammatory effects in seizure animal models. However, the exact mechanisms underlying the anti-inflammatory effects of the KD have not been determined for seizures. Here we investigated the effect of the KD and acetoacetate (AA) on neuroinflammation in a seizure animal model and glutamate-treated HT22 cells, respectively. Mice were fed the KD for 4 weeks and sacrificed 2 or 6h after KA injection. The KD reduced hippocampal tumor necrosis factor alpha (TNF-α) levels and nuclear factor (NF)-κB translocation into the nucleus 2h after KA treatment. KD-induced PPARγ activation was decreased by KA in neurons as assessed by western blotting and immunofluorescence. Finally, the KD inhibited cyclooxygenase (COX)-2 and microsomal prostaglandin E(2) synthase-1 (mPGES-1) expression in the hippocampus 6h after KA treatment. AA treatment also protected against glutamate-induced cell death in HT22 cells by reducing TNF-α and PPARγ-mediated COX-2 expression. Thus, the KD may inhibit neuroinflammation by suppressing a COX-2-dependent pathway via activation of PPARγ by the KD or AA.

Adiponectin protects hippocampal neurons against kainic acid-induced excitotoxicity

Neuronal damage after seizure is correlated with blood-brain barrier (BBB) leakage. Adiponectin (Ad) has shown protective effects on endothelial function. In this study, we investigated the effects of Ad on cell survival and BBB integrity in the mouse hippocampus after kainic acid (KA) treatment. Twenty-four hours after intracerebroventricular injection of recombinant Ad, mice were treated with KA, and then sacrificed 48 h later. Decreased serum Ad and increased hippocampal Ad receptor 1 in the hippocampus of KA-treated mice were prevented by Ad pretreatment. Using cresyl violet staining, TUNEL analysis, and immunostaining for caspase-3, histological evaluation revealed that the marked cell death noted in the hippocampus of KA-treated mice was not observed in KA-treated mice pretreated with Ad. Impairment of the BBB, which was demonstrated by the presence of IgG, was inhibited by Ad pretreatment. Immunohistochemical analysis indicated that KA caused up-regulation of hippocampal VEGF, eNOS, and NF-kappaB levels, all of which were reduced in animals that received Ad pretreatment. These data indicate that Ad preserves the integrity of the BBB and has neuroprotective effects in an animal model of seizures.

Human adipose tissue-derived mesenchymal stem cells protect kidneys from cisplatin nephrotoxicity in rats

Cisplatin has multiple cellular targets and modes of action that lead to nephrotoxicity. This suggests novel therapies that act at multiple cisplatin target sites may be effective. We tested whether human adipose tissue-derived mesenchymal stem cells (Ad-MSCs) can affect multiple target sites and protect against cisplatin-induced kidney damage. Rats were divided into four groups: control, infused with Ad-MSCs, injected with cisplatin, and cisplatin followed by infusion of Ad-MSCs. Animal survival and renal function were decreased and histological damage was increased in cisplatin-treated rats at day 3. Infusion of Ad-MSCs ameliorated renal dysfunction and tissue injury caused by cisplatin, leading to increased survival. Apoptotic cell death in the kidney was significantly reduced by infusion of Ad-MSCs. Activation of p53, JNK, and ERK and the expression of inflammation-related molecules were also decreased in the kidney that received Ad-MSCs. Very few Ad-MSCs were detected in the kidney. Conditioned medium from cultured Ad-MSCs had renal-protective functions in vivo and in vitro. Renal dysfunction and tissue damage caused by cisplatin were significantly reduced in rats treated with Ad-MSCs-conditioned medium. The viability of cultured renal proximal tubular cells exposed to cisplatin was also improved by coculture with Ad-MSCs or with conditioned medium. Release of proinflammatory mediators induced by cisplatin was inhibited in coculture with Ad-MSCs. Our results show that human Ad-MSCs exert a paracrine-protective effect on cisplatin nephrotoxicity at multiple target sites and suggest that human Ad-MSCs might be a new therapeutic approach for patients with acute kidney injury.

Ethanol-induced oxidative stress is mediated by p38 MAPK pathway in mouse hippocampal cells

It has been known that ethanol causes neuronal cell death through oxidative stress. Ethanol itself and reactive oxygen species (ROS) produced by ethanol modulate intracellular signaling pathways including mitogen-activated protein kinase (MAPK) cascades. This study was conducted to examine the impact of ethanol on MAPK signaling in HT22 cells. Ethanol (100 and 400mM) caused activation of ERK, p38 MAPK, and JNK. ERK activation occurred in early time and p38 MAPK activation was evident when ERK activation was diminished. Specific inhibitor of p38 MAPK (SB203580) protected HT22 cells against ethanol, which was accompanied by an inhibition of ROS accumulation. However, inhibitors of ERK (U0126) and JNK (SP600125) had no effects on ethanol-induced neuronal cell death when they are treated with ethanol for 24h. These results suggest that p38 MAPK may have important roles in ROS accumulation during ethanol-induced oxidative stress in HT22 cells.

Suppression by ethanol of male reproductive activity.

Ethanol has been known to suppress reproductive activity in laboratory animals and humans through the inhibition of luteinizing hormone (LH) release by reduction of gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus. There are, however, little data is available regarding the effect of ethanol on GnRH gene expression. Thus, the present study was designed to evaluate the effect of ethanol on GnRH gene expression and reproductive activity at all levels of the hypothalamus-pituitary-gonad (HPG) axis simultaneously. To this end, ethanol (3 g/kg i.p., 15% v/v in saline) was administered to adult male rats for 10 days. Serum levels of LH and testosterone were significantly decreased by ethanol. Using Northern blot analysis and in situ hybridization, the present study showed the reduction in GnRH mRNA levels in the hypothalamus by prolonged ethanol administration. The content of LH in the anterior pituitary was also significantly reduced by ethanol. In addition, steroidogenic acute regulatory protein (StAR) mRNA levels were significantly decreased by ethanol, suggesting a cause for the reduced production of testosterone under this condition. These results indicate that ethanol affects the HPG axis at all the levels. Especially, suppressed GnRH mRNA levels in the hypothalamus of ethanol-treated rats strongly demonstrated that hypothalamus is the major action site of ethanol on the HPG axis. Decreased serum LH level may affect the steroidogenesis in the testis, at least in part, through the inhibition of StAR gene expression that induces part of dysfunctions of reproductive activity.

Resveratrol blocks diabetes-induced early vascular lesions and vascular endothelial growth factor induction in mouse retinas.

Purpose:  Vessel leakage and loss of pericytes are early signs of diabetic retinopathy (DR), which leads to vision loss. Upregulation of the vascular endothelial growth factor (VEGF) during diabetes plays a key role in mediating these vascular lesions. The aim of this study is to investigate the effects of resveratrol, a natural plant‐derived phytoalexin, on vascular damage and VEGF induction in mouse retinas of early diabetes.