While a number of studies have documented the importance of microglia in central nervous system (CNS) response to injury, infection and disease, little is known regarding its role in viral encephalitis. We therefore, exploited an experimental model of Japanese Encephalitis, to better understand the role played by microglia in Japanese Encephalitis Virus (JEV) infection. Lectin staining performed to assess microglial activation indicated a robust increase in reactive microglia following infection. A difference in the topographic distribution of activated, resting, and phagocytic microglia was also observed. The levels of various proinflammatory mediators, such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (Cox-2), IL-6, IL-1beta, TNF-alpha, and MCP-1 that have been implicated in microglial response to an activational state was significantly elevated following infection. These cytokines exhibited region selective expression in the brains of infected animals, with the highest expression observed in the hippocampus. Moreover, the expression of neuronal specific nuclear protein NeuN was markedly downregulated during progressive infection indicating neuronal loss. In vitro studies further confirmed that microglial activation and subsequent release of various proinflammatory mediators induces neuronal death following JEV infection. Although initiation of immune responses by microglial cells is an important protective mechanism in the CNS, unrestrained inflammatory responses may result in irreparable brain damage. Our findings suggest that the increased microglial activation following JEV infection influences the outcome of viral pathogenesis. It is likely that the increased microglial activation triggers bystander damage, as the animals eventually succumb to infection.

Despite recent advances in understanding molecular mechanisms involved in glioblastoma progression, the prognosis of the most malignant brain tumor continues to be dismal. Because the flavonoid kaempferol is known to suppress growth of a number of human malignancies, we investigated the effect of kaempferol on human glioblastoma cells. Kaempferol induced apoptosis in glioma cells by elevating intracellular oxidative stress. Heightened oxidative stress was characterized by an increased generation of reactive oxygen species (ROS) accompanied by a decrease in oxidant-scavenging agents such as superoxide dismutase (SOD-1) and thioredoxin (TRX-1). Knockdown of SOD-1 and TRX-1 expression by small interfering RNA (siRNA) increased ROS generation and sensitivity of glioma cells to kaempferol-induced apoptosis. Signs of apoptosis included decreased expression of Bcl-2 and altered mitochondrial membrane potential with elevated active caspase-3 and cleaved poly(ADP-ribose) polymerase expression. Plasma membrane potential and membrane fluidity were altered in kaempferol-treated cells. Kaempferol suppressed the expression of proinflammatory cytokine interleukin-6 and chemokines interleukin-8, monocyte chemoattractant protein-1, and regulated on activation, normal T-cell expressed and secreted. Kaempferol inhibited glioma cell migration in a ROS-dependent manner. Importantly, kaempferol potentiated the toxic effect of chemotherapeutic agent doxorubicin by amplifying ROS toxicity and decreasing the efflux of doxorubicin. Because the toxic effect of both kaempferol and doxorubicin was amplified when used in combination, this study raises the possibility of combinatorial therapy whose basis constitutes enhancing redox perturbation as a strategy to kill glioma cells. [Mol Cancer Ther 2007;6(9):2544 -53]

Rosmarinic acid (RA) reduced the mortality of mice infected with Japanese encephalitis virus (JEV). Significant decreases in viral loads (P < 0.001) and proinflammatory cytokine levels (P < 0.001) were observed in JEV-infected animals treated with RA compared to levels in infected mice without treatment, at 8 to 9 days postinfection.

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-Effect of Tinospora cordifolia extract on modulation of hepatoprotective and immunostimulatory functions in carbon tetrachloride (CCl 4 ) intoxicated mature rats is reported here. Administration of CCl 4 (0.7 ml/kg body weight for 7 days) produces damage in the liver as evident by estimation of enzymes such as serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transminase (SGPT) and alkaline phosphatase (ALP) as well as serum bilirubin level. CCl 4 administration also causes immunosuppressive effects as indicated by phagocytic capacity, chemotactic migration and cell adhesiveness of rat peritoneal macrophages. However, treatment with T. cordifolia extract (100 mg/kg body weight for 15 days) in CCl 4 intoxicated rats was found to protect the liver, as indicated by enzyme level in serum. A significant reduction in serum levels of SGOT, SGPT, ALP, bilirubin were observed following T. cordifolia treatment during CCl 4 intoxication. Treatment with T. cordifolia extract also deleted the immunosuppressive effect of CCl 4 , since a significant increment in the functional capacities of rat peritoneal macrophages (PMφ) was observed following T. cordifolia treatment. The results of our experiment suggest that treatment by T. cordifolia extract may be the critical remedy for the adverse effect of CCl 4 in liver function as well as immune functions.

While a number of studies have documented the neurotropism of Japanese encephalitis virus (JEV), little is known regarding the molecular mechanism of neuronal death following viral infection. The tumor necrosis factor receptor (TNFR)-associated death domain (TRADD) has been suggested to be the crucial signal adaptor that mediates all intracellular responses from TNFR-1. Using mouse (Neuro2a) and human (SK-N-SH) neuroblastoma cell lines, we have shown that the altered expression of TNFR-1 and TRADD following JEV infection regulates the downstream apoptotic cascades. Activation of TRADD led to mitochondria-mediated neuronal apoptosis. As TRADD-knockout animals or deficient cell lines are unavailable, it has been difficult to definitively address the physiological role of TRADD in diseases pathology following JEV infection. We circumvented this problem by silencing TRADD expression with small-interfering RNA (siRNA) and have found that TRADD is required for TNFR-1-initiated neuronal apoptosis following in vitro infection with JEV. Interestingly, siRNA against TRADD also decreased the viral load in Neuro2a cells. Furthermore, siRNA against TRADD increased the survival of JEV-infected mice by altering the expression of pro apoptotic versus antiapoptotic molecules. These studies show that the engagement of TNFR-1 and TRADD following JEV infection plays a crucial role in neuronal apoptosis.

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