Cytokine induction of iNOS and sPLA(2) in immortalized astrocytes (DITNC):Response to genistein and pyrrolidine dithiocarbamate

Using an immortalized astrocyte cell line (DITNC), we showed that lipopolys accharide (LPS), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1 beta (IL-1 beta) but not interferon-alpha (IFN-alpha) could individually i nduce secretory phospholipase A(2) (sPLA(2)) mRNA and enzymatic activity. H owever, induction of inducible nitric oxide synthase (iNOS) mRNA and NO pro duction by cytokines required the presence of IFN-gamma. Using a three-cyto kine mixture (TNF-alpha, IL-1 beta, and IFN-gamma) that could maximally ind uce both iNOS and sPLA(2), the increase in these mRNA species reached a max imum by 4-8 h, followed by a decline up to 48 h. L-N-6-(1-Iminoethyl)lysine acetate (L-NIL) inhibited cytokine-induced NO production with IC50 of 25 m u M, but this compound did not affect iNOS mRNA, Furthermore, L-NIL, exerte d no effect on sPLA(2) mRNA or sPLA(2) activity. Pyrrolidine dithiocarbamat e (PDTC), an inhibitor for NF-kappa B, was more effective in inhibiting iNO S mRNA and NO production than for sPLA(2). Surprisingly, genistein inhibite d both NO production and sPLA(2) activity with IC50 of 72 mu M and 88 mu M, respectively. On the other hand, daidzein, a genistein analog lacking tyro sine kinase inhibitor activity, was not effective in inhibition of NO produ ction at 250 mu M. These results demonstrate distinct pathways for inductio n of iNOS and sPLA(2) in DITNC cells by cytokines and shed new insight on t ranscriptional regulation for these two mRNA species.