alpha-Crystallin downregulates the expression of TNF-alpha and iNOS by activated rat retinal microglia in vitro and in vivo.

ABSTRACT

PURPOSE: Inhibition of microglial activation has become an important strategy to attenuate neurotoxic damage to the central nervous system. We evaluated the effects of alpha-crystallin on the production of cytokines in lipopolysaccharides (LPS) and optic nerve injury-activated retinal microglia. METHODS: Microglia were collected from retinas of newborn rats, cultured and treated with LPS in vitro. Microglia were also activated by an optic nerve crush in vivo. Pretreatments with and without alpha-crystallin were performed in cultured cells, and by intravitreal injection in adult rats. Expression of tumor necrosis factor-alpha (TNF-alpha), nitric oxide (NO) and inducible NOS synthase (iNOS) were measured by RT-PCR, ELISA, Western blot and the nitrate reductase method. RESULTS: Activated microglia significantly upregulated TNF-alpha and iNOS mRNA expression and protein production in vitro. An optic nerve crush also increased expression of retinal iNOS and TNF-alpha protein. Treatment with alpha-crystallin in vitro and in vivo downregulated their expression. CONCLUSION: The protective effect of alpha-crystallin may be due to its effect on microglia via a downregulation in the expression and release of 2 key immune regulatory and inflammatory molecules TNF-alpha and iNOS.