alpha-Melanocyte-related tripeptide, Lys-D-Pro-Val, ameliorates endotoxin-induced nuclear factor kappa B translocation and activation: evidence for involvement of an interleukin-1 beta(193-195) receptor antagonism in the alveolar epithelium

The potential anti-inflammatory role of alpha -melanocyte-stimulating hormo ne (alpha -MSH)-related tripeptide, lysine(11)-D-proline-valine(13) (KDPV), an analogue of interleukin (IL)-1 beta (193-195) and an antagonist of IL-1 beta /prostaglandin E-2, is not well characterized in the alveolar epithel ium. In a model of foetal alveolar type II epithelial cells in vitro, we sh owed that lipopolysaccharide endotoxin (LPS) differentially, but selectivel y, induced the nuclear subunit composition of nuclear factor kappaB(1) (NF- kappaB(1)) (p50), RelA (p65) and c-Rel (p75), in parallel to up-regulating the DNA-binding activity (supershift indicating the presence of the p50-p65 complex), LPS accelerated the degradation of inhibitory kappaB-alpha (I ka ppaB-alpha), accompanied by enhancing its phosphorylation in the cytosolic compartment but not in the nucleus. KDPV suppressed, in a dose-dependent ma nner, the nuclear localization of p50, p65 and p75, an effect that led to t he subsequent inhibition of NF-kappaB activation. Interleukin-1 receptor an tagonist (IL-1ra) decreased the nuclear abundance of p50, p65 and p75, and subsequently depressed the DNA-binding activity induced by LPS. Analysis of the mechanism involved in the KDPV- and IL-1ra-mediated inhibition of NF-k appaB nuclear localization revealed a reversal in I kappaB-alpha phosphoryl ation and degradation, followed by cytosolic accumulation. LPS induced endo genous IL-1 beta biosynthesis in a time-dependent manner; the administratio n of exogenous recombinant human interleukin 1 (rhIL-1) resulted in a dose- dependent activation of NF-kappaB. KDPV and IL-1ra abrogated the effect of rhIL-1. Pretreatment with the non-steroidal anti-inflammatory drug (NSAID) indomethacin, an inhibitor of cyclo-oxygenase, blocked the LPS-induced acti vation of NF-kappaB, These results indicate the involvement of prostanoid-d ependent (NSAID-sensitive) and IL-1-dependent (IL-1ra-sensitive) mechanisms mediating LPS-induced NF-kappaB translocation and activation, a pathway th at is regulated, in part, by a negative feedback mechanism transduced throu gh I kappaB-alpha, the major cytosolic inhibitor of NF-kappaB.