Abstract
Purpose: :
Interleukin-11 (IL-11), a pleiotrophic cytokine, acts as an anti-inflammatory and cytoprotective agent. Expression and the roles of IL-11 are not known in retinal and corneal tissues in the eye. In the present study, we investigated the production of IL-11 by retinal and corneal cells and its regulation by cytokines.
Methods: :
Primary cultures of human retinal pigment epithelial cells (HRPE), choroid fibroblasts (HCHF), corneal fibroblasts (HCRF) and corneal epithelial cell line (HCE) were used in this study. Microarray analysis of HRPE cells treated with TGF-β was performed using GeneChip Human genome U133 plus 2.0 array (Affymetrix). Confluent cultures were treated with IFN-γ, TNF-α, IL-1 or TGF-β in serum free medium for 24 h. Culture supernatants were used for the analysis of secreted IL-11 by ELISA. Conventional and Real time PCR were used for the gene expression studies. JAK and TGF-βR1 inhibitors were used to delineate the IFN-γ and TGF-β effects. Chemical inhibitors for NFkB and MAPK were used to study TNF-α and IL-1 signal transduction pathways.
Results: :
Microaaray analysis revealed 17 fold upregulation of IL-11 in addition to some known growth factors (VEGF, PDGF, CTGF). These results prompted us to investigate the expression of IL-11 in Ocular cells. IL-11 is not secreted constitutively by both retinal and corneal cells. TNF-α and IL-1 significantly increased secretion of IL-11 in HRPE, HCHF and HCRF cells. IFN-γ down regulated TNF-α and IL-1 induced IL-11 secretion by HRPE (1899 Vs 433 pg/ml) and HCRF (1258 Vs 325 pg/ml). In contrast, TGF-β induced IL-11 secretion by HRPE was not inhibited by IFN-γ. TGF-β induced very high levels of IL-11 in HCRF (> 4000 pg/ml) that is not inhibited by IFN-γ. TGF-β induced IL-11 secretion was completely abolished in HRPE and HCRF cells by TGF-β receptor 1 inhibitor. JAK-1, inhibitor of JAK-STAT pathway significantly reversed inhibitory effects of IFN-γ on IL-11 secretion.
Conclusions: :
We report here, for the first time, that IL-11is produced by retinal and corneal cells. While TNF-α and IL-1 up regulate IL-11 expression, IFN-γ down regulated this IL-11 induction. TGF-β also upregulated IL-11 production by retinal and corneal cells. The enhanced secretion of IL-11, a known anti-inflammatory and cytoprotective cytokine, may help to reduce / prevent pathological injury caused by inflammatory diseases in the cornea and retina.
Keywords: cytokines/chemokines • immunomodulation/immunoregulation • inflammation