Thymosin β4 reduces IL-17-producing cells and IL-17 expression, and protects lungs from damage in bleomycin-treated mice

Thymosin beta 4 (T beta 4) is a highly conserved peptide with immunomodulatory properties. In this research we investigated the effects of T beta 4 on the bleomycin-induced lung damage in CD-1 mice and the changes in the number of IL-17-producing cells as well as the IL-17 expression in the lung. Male CD-1 mice were treated with bleomycin (1 mg/kg) in the absence or the presence of T beta 4 (6 mg/kg delivered intra-peritoneally on the day of bleomycin treatment and for 2 additional doses). After sacrifice one week later, lung histology, measurement of collagen content of the lung, Broncho Alveolar Lavage Fluid (BALF) analysis, evaluation of IL17-producing cells in the blood as well as RT-PCR and IHC in the lung tissue were performed. As expected, bleomycin-induced inflammation and lung damage were substantially reduced by T beta 4 treatment in CD-1 mice, as shown by the significant reduction of (i) leukocytes in BALF, (ii) histological evidence of the lung damage, and (iii) total collagen content in the lung. Importantly, the bleomycin-induced increase in the number of IL17-producing cells in the blood was significantly blocked by T beta 4. Accordingly, IHC and RT-PCR results demonstrated that T beta 4 substantially inhibited bleomycin-induced IL-17 over-expression in the lung tissue. This is the first report showing that a decreased amount of IL17-producing cells and inhibited IL-17 expression in the lung with T beta 4 treatment correlate with its anti-inflammatory and anti-fibrotic effects.