MURINE ENCEPHALITOGENIC LYMPHOID-CELLS INDUCE NITRIC-OXIDE SYNTHASE IN PRIMARY ASTROCYTES

A cytokine-inducible form of nitric oxide synthase (iNOS), capable of producing large quantities of nitric oxide (NO), can be induced in man y cell types. We demonstrate that conditioned medium from encephalitog enic myelin basic protein-sensitized lymphoid cells (MBP-CM) induces t he expression of iNOS in primary cultures of murine astrocytes in a ti me- and concentration-dependent manner. iNOS mRNA was detected by reve rse transcriptase-polymerase chain reaction (RT-PCR) as early as 3 h p ost-exposure. Accumulation of nitrite into the astrocyte culture mediu m, an indirect measure of NO, was measurable 3 h post-exposure, platea ued at 24 h, and was prevented by the simultaneous administration of t he NOS inhibitors, L-N-G-nitroarginine methyl ester, N-G-nitro-L-argin ine or aminoguanidine. Astrocyte expression of iNOS protein, detected by immunohistochemistry and immunoprecipitation/Western blot, was prev ented by inhibitors of RNA or protein metabolism, consistent with its dependence on de novo protein synthesis.