HUMAN PERITONEAL MESOTHELIAL CELLS SYNTHESIZE INTERLEUKIN-8 - SYNERGISTIC INDUCTION BY INTERLEUKIN-1-BETA AND TUMOR-NECROSIS-FACTOR-ALPHA

The present study demonstrates the synthesis and secretion of the neut rophil-activating peptide/interleukin-8 (IL-8) by cultured human perit oneal mesothelial cells (HPMC) and examines the regulation of its prod uction by other cytokines. Unstimulated HPMC under growth-arrested con ditions released IL-8 in a constitutive and time-dependent manner. Sti mulation of HPMC with IL-1beta or TNF-alpha resulted in a time- and do se-dependent IL-8 generation; after 24 hour the levels induced by IL-1 beta and TNF-alpha (both at 1000 pg/ml) were (mean +/- SEM, n = 5) 101 +/- 266 (z = 2.023; P < 0.01) and 35 +/- 8.09 (z = 2.023; P < 0.01) r espectively. This release was inhibited following coincubation with th e relevant anti-cytokine antibody or preincubation with either cyclohe ximide or actinomycin D. Treatment of HPMC with IL-1beta or TNF-alpha resulted in increased levels of IL-8-specific mRNA. Stimulation of HPM C with combinations of IL-1beta and TNF-alpha resulted in a synergisti c, increase in IL-8 release. This effect was significant al combined d oses of IL-1beta (50 pg/ml) and TVF-alpha (500 pg/ml) and above, when the release of IL-8 was 88 +/- 27% above the additive IL-8 release val ues (z = 2.20; P < 0.01). Western blot analysis using specific anti-IL -8 antibody demonstrated the presence of two major immunoreactive band s between 9 and 10 kd, in HPMC culture supernatants. These data demons trate that HPMC synthesize IL-8 and that its release can be regulated as a result of induction of mRNA expression and de novoprotein synthes is by other cytokines.