Critical Roles For The Immunoproteasome In The Pathogenesis Of Toxoplasmic Encephalitis

Toxoplasma gondii(T.gondii)is an obligate intracellular parasite that infects a wide range of avian and mammalian species and can cause severe diseases.As T.gondii has the characteristics of neurotropic cells,it can break through the blood-brain barrier of mice and reach the brain,causing inflammation.The ubiquitin-proteasome system(UPS)has critical roles in the regulation of inflammatory responses.However,it is not clear whether immunoproteasome subunits are involved in the regulation of the inflammatory responses in the brain of mice infected with T.gondii.To investigate the role of immunoproteasome in toxoplasmic encephalitis,mice were infected intraperitoneally with T.gondii PLK strain.Immunohistochemical method and nested PCR were used to detect T.gondii in the brain of mice.It proved that the mouse model of T.gondii infection was established successfully.In order to study the pathological damage caused by T.gondii infection on the brain of mice,the immunohistochemistry results showed that T.gondii infection induced the expression and activation of microglia and astrocytes.The expressions of pro-inflammatory factors IFN-??TNF-??IL-6 and IL-1? were significantly increased by real time PCR after T.gondii infection.Real time PCR and Western Blot results showed that immunoproteasome were up-regulated following T.gondii infection.Double immunofluorescence staining results showed that immunoproteasome can be detected in microglia,astrocytes and neurons.These results suggested that immunoproteasome played an important role in toxoplasmic encephalitis.In order to further study the role of immunoproteasome in toxoplasmic encephalitis,the proteasome inhibitors MG-132 and LMP10 knockout mice were selected to carry out follow-up experiments.The results showed that the levels of cerebral immunoproteasome and proinflammatory cytokines were significantly lower in the MG-132 treated infected mice and PLK-infected knockout mice than in the infection group and the wild-type infection group.These results suggested that immunoproteasome played an important role in the inflammatory process of T.gondii infection in the brain.This study laid a foundation for the study on the pathogenesis of toxoplasmosis central nervous system diseases.