Objective: To investigate the activation effects of interleukin-13 (IL-13) on human lung fibroblast and to elucidate the impact of beclomethasone dipropionate (BDP) or budesonide (BUD) on IL-13 fibroblast activation.
Methods: Human embryo lung fibroblasts (HELF) were stimulated by recombinant human IL-13 (20 ng/ml) for 72 h with or without increasing concentrations of BDP or BUD (10(-8) to 10(-5) mol/L). The supernatants were collected for the measurement of eotaxin and IL-6. Fibroblast proliferation was assessed with the MTT [3-(4, 5-dimcthylthioazol-2-yl)-2, 5-diphenyl-tetrazolium bromide] assay. The expression of alpha-smooth muscle actin (alpha-SMA) was measured with Western blot and RT-PCR.
Results: The average concentrations of IL-6 and eotaxin were (20 +/- 2) ng/L and (64 +/- 25) ng/L in the supernatant of un-stimulated HELF. After the stimulation with IL-13, IL-6 and eotaxin levels significantly increased to (140 +/- 8) ng/L and (340 +/- 51) ng/L, respectively. The IL-6 levels in HELF stimulated with IL-13 in the presence of 10(-8), 10(-7), 10(-6) or 10(-5) mol/L BDP, were (112 +/- 14), (83 +/- 5), (77 +/- 6) and (53 +/- 6) ng/L, respectively. BDP also showed a dose-dependent inhibition on IL-13-induced eotaxin levels. Similarly, HELF stimulated with IL-13 in the presence of 10(-8) to 10(-5) mol/L BUD showed a markedly decrease in IL-6 release to (55 +/- 14), (42 +/- 5), (40 +/- 3), (32 +/- 6) ng/L, compared to those from cells cultured with IL-13 alone. Meanwhile, the concentrations of eotaxin were significantly decreased to (287 +/- 59), (263 +/- 57), (235 +/- 58) or (183 +/- 43) ng/L. Treatment with BDP or BUD also inhibited IL-6 mRNA expression in HELF induced by IL-13. IL-13 increased HELF proliferation and interestingly, this effect was further enhanced by BDP or BUD treatment. Furthermore, IL-13 induced fibroblasts transdifferentiation into myofibroblasts characterized by a strong expression of alpha-SMA. Neither BDP nor BUD reduced the alpha-SMA protein or mRNA expression induced by IL-13 treatment.
Conclusions: BDP or BUD possessed a diversified regulation of human lung fibroblasts in response to IL-13 stimulation. The inhibitory effect of BDP or BUD on IL-13 induced IL-6 and eotaxin release in fibroblast may contribute to the attenuation of IL-13 induced subepithelial fibrosis. However, BDP or BUD does not inhibit fibroblast proliferation nor their transdifferentiation into myofibroblasts.