Flavivirus-mediated inflammation causes neuronal death, but whether the infected neurons can evoke an innate immune response to elicit their own protection, is unknown. In an earlier study we have shown that neuronal RIG-I, play a significant role in inducing production and release of molecules that are related to inflammation. In this study, using a neuronal cell line, we show that RIG-I acts with STING in a concerted manner following its interaction with Japanese encephalitis viral RNA to induce a type 1 interferon response. Knock-down of STING showed that the expressions of various inflammatory signaling molecules were down-regulated along with increased intracellular viral load. Alternatively, over-expressing STING decreased intracellular viral load. Our results indicate that at the sub-cellular level, interaction between the pattern recognition receptor RIG-I and the adapter molecule STING, is a major contributor to elicit immunological responses involving the type 1 interferons in neurons following JEV infections.

TAR DNA-binding protein 43 (TDP-43) is a major component in aggregates of ubiquitinated proteins in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). Here we report that lipopolysaccharide (LPS)-induced inflammation can promote TDP-43 mislocalization and aggregation. In culture, microglia and astrocytes exhibited TDP-43 mislocalization after exposure to LPS. Likewise, treatment of the motoneuron-like NSC-34 cells with TNF-alpha (TNF-α) increased the cytoplasmic levels of TDP-43. In addition, the chronic intraperitoneal injection of LPS at a dose of 1mg/kg in TDP-43A315T transgenic mice exacerbated the pathological TDP-43 accumulation in the cytoplasm of spinal motor neurons and it enhanced the levels of TDP-43 aggregation. These results suggest that inflammation may contribute to development or exacerbation of TDP-43 proteinopathies in neurodegenerative disorders.

BackgroundNeuroinflammation associated with Japanese encephalitis (JE) is mainly due to the activation of glial cells with subsequent release of proinflammatory mediators from them. The recognition of viral RNA, in part, by the pattern recognition receptor retinoic acid-inducible gene I (RIG-I) has been indicated to have a role in such processes. Even though neurons are also known to express this receptor, its role after JE virus (JEV) infections is yet to be elucidated.Methodology/Principal FindingsUpon infecting murine neuroblastoma cells and primary cortical neurons with JEV the expression profile of key proinflammatory cyto/chemokines were analyzed by qRT-PCR and bead array, both before and after ablation of RIG-I. Immunoblotting was performed to evaluate the levels of key molecules downstream to RIG-I leading to production of proinflammatory mediators. Changes in the intracellular viral antigen expression were confirmed by intracellular staining and immunoblotting. JEV infection induced neuronal expression of IL-6, IL-12p70, MCP-1, IP-10 and TNF-α in a time-dependent manner, which showed significant reduction upon RIG-I ablation. Molecules downstream to RIG-I showed significant changes upon JEV-infection, that were modulated following RIG-I ablation. Ablation of RIG-I in neurons also increased their susceptibility to JEV.Conclusions/SignificanceIn this study we propose that neurons are one of the potential sources of proinflammatory cyto/chemokines in JEV-infected brain that are produced via RIG-I dependent pathways. Ablation of RIG-I in neurons leads to increased viral load and reduced release of the cyto/chemokines.

Japanese encephalitis (JE) is an arboviral disease common in Southeast Asia encompassing a population of 3 billion people. Periodic outbreak of JE takes hundreds of lives. Children are major victims of JE. About one third of JE patients die, and many of the survivors suffer from permanent neuropsychiatric sequel, owing to the lack of specific therapeutic measure. Curcumin is a naturally occurring phenolic compound extracted from Curcuma longa L. Previous studies have reported that curcumin possesses strong antioxidant, anti-inflammatory, antiviral activity. We used Neuro2a cell line and infected them with JE virus. The infected cells were treated with varying doses of curcumin. Cell viability, reactive oxygen species (ROS) production within the cells, and change in cellular membrane integrity were studied. The changes in expression of some signaling and stress-related proteins were also assessed. We also studied the inhibitory role of curcumin on the production of infective viral particles by dysregulation of the ubiquitin-proteasome system. In this study, we found that curcumin imparts neuroprotection in vitro, probably by decreasing cellular reactive oxygen species level, restoration of cellular membrane integrity, decreasing pro-apoptotic signaling molecules, and modulating cellular levels of stress-related proteins. We have also shown that curcumin, by inhibition of ubiquitin-proteasome system causes reduction in infective viral particle production from previously infected neuroblastoma cells.