A. Moutabarrik et al., INTERLEUKIN-6 AND INTERLEUKIN-6 RECEPTOR ARE EXPRESSED BY CULTURED GLOMERULAR EPITHELIAL-CELLS, Scandinavian journal of immunology, 40(2), 1994, pp. 181-186
Interleukin-6 (IL-6) has been extensively studied in mesangial cells b
ut little is known about the expression of this cytokine and its recep
tor in glomerular epithelial cells (GEC). IL-6 was detected in the cul
ture supernatants of human GEC and its production was enhanced in time
and dose dependent manner by lipopolysaccharide (LPS), interleukin-1
beta (IL-1 beta) and tumour necrosis alpha (TNF-alpha). Quiescent, ser
um-starved GEC did not express clearly IL-6 mRNA. Stimulation of cells
with LPS, TNF-alpha or IL-1 beta resulted in an increase of detectabl
e IL-6 mRNA. Interestingly, it was found that IL-6 induced its own mRN
A attesting that this cytokine was secreted in autocrine fashion by GE
C. GEC expressed IL-6 receptor (IL-6R) as demonstrated directly by the
existence of IL-6R mRNA detected by northern blotting. Stimulation of
GEC by pro-inflammatory mediators such as LPS increased the expressio
n of IL-6R mRNA. The soluble form of IL-6 receptor (sIL-6R) was not de
tectable in the culture supernatants harvested from untreated or cytok
ine-treated cells. We investigated further, whether IL-6 may influence
growth of cultured GEC. Incubation of GEC with recombinant (r) IL-6 r
esulted in a dose dependent increase in H-3 thymidine incorporation in
dicating that IL-6 acts as an autocrine growth factor for GEC. We conc
lude that GEC are a potent source of IL-6, the local excessive express
ion of IL-6 and its receptor may play a substantive role in the regula
tion of processes which appear critical to the initiation of progressi
ve glomerular disease such as cell proliferation.