Role of Oxygen Free Radical in the Expression of Interleukin-8 andInterleukin-1beta Gene in Mononuclear Phagocytic Cells

Kang, Min Jong; Kim, Jae Yeol; Park, Jae Seok; Lee, Seung Joon; Yoo, Chul Gyu; Kim, Young Whan; Han, Sung Koo; Shim, Young Soo

Abstract

BACKGROUND
Oxygen free radicals have generally been considered as cytotoxic agents. On the other hand, recent results suggest that small nontoxic amounts of these radicals may act a role in intracellular signal transduction pathway and many efforts to reveal the role of these radicals as secondary messengers have been made. It is evident that the oxygen radicals are released by various cell types in response to extracellular stimuli including LPS, TNF, IL-1 and phorbol esters, all of which translocate the transcription factor NFkappaB from cytoplasm to nucleus by releasing an inhibitory protein subunit, MB. Activation of NFkappaB is mimicked by exposure to mild oxidant stress, and inhibited by agents that remove oxygen radicals. It means the cytoplasmic form of the inducible tanscription factor NFkappaB might provide a physiologically important target for oxygen radicals. At the same time, it is well known that LPS induces the release of oxygen radicals in neutrophil with the activation of NFkappaB. From above facts, we can assume the expression of IL-8 and IL-1beta gene by LPS stimulation may occur through the activation of NFkappaB, which is mediated through the release of MB by increasing amounts of oxygen radicals. But definitive evidence is lacking about the role of oxygen free radicals in the expression of IL-8 and IL-1beta gene in mononuclear phagocytic cells. We conducted a study to determine whether oxygen radicals act a role in the expression of IL-8 and IL-1beta gene in mononuclear phagocytic cells. METHOD: Human peripheral blood monocytes were isolated from healthy volunteers. Time and dose relationship of H2O2-induced IL-8 and IL-1beta mRNA expression was observed by Northern blot analysis. To evaluate the role of oxygen radicals in the expression of IL-8 and IL-1beta mRNA by LPS stimulation, pretreatment of various antioxiants including PDTC, TMTU, NAC, ME, Desferrioxamine were done and Northern blot analysis for IL-8 and IL-1beta mRNA was performed.
RESULTS
In PBMC, dose and time dependent expression of IL-8 and IL-1beta mRNA by exogenous H2O2 was not observed. But various antioxidants suppressed the expression of LPS-induced IL-8 and IL-1beta mRNA expression of PBMC and the suppressive activity was most prominant when the pretreatment was done with TMTU.
CONCLUSION
Oxygen free radical may have some role in the expression of IL-8 and IL-1beta mRNA of PBMC but that radical might not be H2O2.