Inhibition of superoxide production in B lymphocytes by rac antisense oligonucleotides.

Rac1 and Rac2 gene products are small GTP-binding proteins showing 92% homology to each other. According to recent studies performed in cell-free systems, Rac1 and Rac2 proteins may be involved in the activation of NADPH-oxidase, the superoxide-generating enzymatic complex active in phagocytes. Epstein-Barr virus (EBV) transformed B lymphocytes, which express rac1 and rac2 genes, also efficiently release superoxide anions when triggered by various cell surface stimuli. To investigate the regulatory role of Rac proteins in living cells, we analyzed superoxide production in response to cross-linking of surface immunoglobulins or phorbol ester treatment in human EBV-transformed B lymphocytes pretreated with Rac sense and antisense oligonucleotides. We report here that (i) the rac protein content estimated by immunoblotting can be decreased by 60% in Rac antisense pretreated cells and (ii) a strong (50-60%), dose-dependent inhibition of superoxide production is observed in antisense pretreated cells whereas cells pretreated with sense oligonucleotide are unaffected. The data presented show, for the first time in whole cells, that superoxide production is modulated by the Rac protein content, thus demonstrating the physiological role of Rac proteins in the regulation of NADPH-oxidase.