Cell cycle inhibitor enhances the resolution of HSV-1-induced proinflammatory response in murine microglial cells

Herpes simplex encephalitis remains one of the most devastating intracranial infections despite available antiviral treatment, with sequelae secondary to a persistent inflammatory response. Recently, cyclin-dependent kinases (CDKs) have been found to act as cellular targets for antiviral drugs. However, the pharmacological effects of CDK inhibitors on glial cell function in herpes simplex encephalitis have not been elucidated. The aim of this work was to determine the influence of olomoucine on microglial activation during the inflammatory response after herpes simplex virus 1(HSV-1) infection.

Microglial cells were treated with various concentrations of olomoucine after HSV-1 infection. The expression change of cyclin D1 and myeloid cell leukemia 1 (Mcl-1) in microglia were detected by Western blot analysis. Flow cytometry was used to assess the apoptosis ratio of microglial cells among the groups of control, HSV-1 infected and olomoucine treated with or without zVAD-fmk. ELISA was adopted to analyse cytokines in the supernatant. We used semiquantitative reverse transcription polymerase chain reaction to detect HSV glycoprotein D gene.

The following are the results of this work: (1) olomoucine reduced HSV-1-induced proliferation associated cyclin D1 expression; (2) olomoucine also induced microglial cells apoptosis early at 24 hours post-infection and inhibited the release of proinflammatory cytokine and chemokine, including tumor necrosis factor alpha and monocyte chemoattractant protein 1; and (3) olomoucine-induced apoptosis was caspase-dependent, and it also reduced the antiapoptotic protein Mcl-1.

Our conclusion is that microglial cells are targets for olomoucine and that modulation of glial response and inflammation may be an appendant mechanism of CDK inhibitor-mediated neuroprotection in HSV-1 encephalitis.