Involvement of dopaminergic neuronal cystatin C in neuronal injury-induced microglial activation and neurotoxicity

Abstract

Factors released from injured dopaminergic (DA) neurons may trigger microglial activation and set in motion a vicious cycle of neuronal injury and inflammation that fuels progressive DA neurodegeneration in Parkinson's disease. In this study, using proteomic and immunoblotting analysis, we detected elevated levels of cystatin C in conditioned media (CM) from 1-methyl-4-phenylpyridinium and dieldrin-injured rat DA neuronal cells. Immunodepletion of cystatin C significantly reduced the ability of DA neuronal CM to induce activation of rat microglial cells as determined by up-regulation of inducible nitric oxide synthase, production of free radicals and release of proinflammatory cytokines as well as activated microglia-mediated DA neurotoxicity. Treatment of the cystatin C-containing CM with enzymes that remove O- and sialic acid-, but not N-linked carbohydrate moieties markedly reduced the ability of the DA neuronal CM to activate microglia. Taken together, these results suggest that DA neuronal cystatin C plays a role in the neuronal injury-induced microglial activation and neurotoxicity. These findings from the rat DA neuron-microglia in vitro model may help guide continued investigation to define the precise role of cystatin C in the complex interplay among neurons and glia in the pathogenesis of Parkinson's disease. Cystatin C and the vicious cycle of neuronal injury and microglial activation The impact of factors released from neurons under stress on brain immune cells may be relevant to neuropathogenesis. In a rat cell-based model, among proteomically identified secretome proteins from toxicant-injured dopamine neurons, cystatin C was found to facilitate microglial activation and neurotoxicity. Dopamine neuronal cystatin C and/or related proteins may be key mediators of neuroinflammation and neurodegeneration. © 2012 The Authors. Journal of Neurochemistry © 2012 International Society for Neurochemistry.