Modulation of the IL-1 cytokine network in keratinocytes by intracellular IL-1 alpha and IL-1 receptor antagonist.
The IL-1 cytokine network in epidermal cells was studied in vitro, using the spontaneously transformed HaCAT human keratinocyte line. Intracellular (ic) IL-1 alpha and IL-1 receptor antagonist protein (IL-1Ra) following cell lysis were readily identified assayed using a capture ELISA; whereas in culture supernatants IL-1Ra was not detected, and IL-1 alpha was present at only very low levels. Confluent cultures of HaCAT cells were shown to provide optimal conditions for the study, since confluence increased the icIL-1Ra:IL-1 alpha ratio to a level as seen in vivo, which was independent of Ca2+ concentration in the culture medium. The IL-1Ra extracted from HaCAT cell lysates was functionally active, as demonstrated in the mouse thymocyte co-proliferation assay which could be blocked using a rabbit anti-IL-1Ra antibody. Transforming growth factor-beta (TGF-beta 1) stimulated a dose-dependent increase in HaCAT cell IL-1 alpha without changing IL-1Ra concentration, with a resultant reduction in the icIL-1Ra: IL-1 alpha ratio from 320:1 to 100:1. Similarly, TGF-alpha, interferon-gamma (IFN-gamma), IL-6, and tumour necrosis factor-alpha (TNF-alpha) substantially increased HaCAT cell IL-1 alpha, but had no effect on the IL-1Ra, with a concomitant reduction in the icIL-1Ra:IL-1 alpha ratio. In contrast to their effects on monocytes, IL-4 and IL-10 at biologically active levels had no effect on IL-1 alpha, IL-1Ra or the icIL-1Ra: IL-1 alpha ratio in confluent HaCAT cells. Hydrocortisone reduced IL-1 alpha to below the limit of sensitivity of the ELISA, and induced a small increase in IL-1Ra of questionable biological significance. Thus, regulation of the IL-1 cytokine network in keratinocytes involves modulation of icIL-1 alpha rather than of icIL-1Ra levels, and is markedly different from that noted in monocytes.
Phillips
W G
WG
Kennedy Institute of Rhematology Sunley Division, St Thomas' Hospital, London, UK.
Feldmann
M
M
Breathnach
S M
SM
Brennan
F M
FM
D002118:Calcium / Q000378:metabolism / Q000502:physiology; D002452:Cell Count; D002460:Cell Line; D002461:Cell Line, Transformed; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000494:pharmacology* / Q000502:physiology*; D015603:Keratinocytes / Q000187:drug effects / Q000502:physiology*; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors*; D012795:Sialoglycoproteins / Q000187:drug effects / Q000502:physiology*
C507763:IL1RN protein, human; C507764:Il1rn protein, mouse; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D017472:Receptors, Interleukin-1; D012795:Sialoglycoproteins; D002118:Calcium; D006854:Hydrocortisone