Thymic Stromal Lymphopoietin Signaling Pathway Inhibition Attenuates Airway Inflammation and Remodeling in Rats with Asthma.

BACKGROUND/AIMS: Thymic stromal lymphopoietin (TSLP) is a cytokine that plays diverse roles in the regulation of immune responses. However, a detailed understanding of the TSLP signaling pathway in asthma remains elusive. In this study, we aimed to investigate the role of the TSLP signaling pathway in asthma and its effect on airway inflammation and remodeling. METHODS: Forty Sprague Dawley (SD) rats were evenly classified into control, asthma, IgG2a mAb and anti-TSLP mAb groups. Ovalbumin (OVA)-induced asthma models were successfully established. Blood, bronchoalveolar lavage fluid (BALF) and lung tissue samples were prepared. Total BALF leukocytes were counted, and the proportions of different leukocyte types were determined. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry were performed to determine the mRNA and protein levels of TSLP, OX40L, α-smooth muscle actin (α-SMA, a marker of airway remodeling in asthma) and collagen I in the plasma. Enzyme-linked immunosorbent assay (ELISA) was carried out to measure the concentrations of TSLP, OX40L, and other inflammatory factors, such as interferon (IFN)-γ, interleukin (IL)-4, IL-5 and IL-13, in the plasma. RESULTS: Compared with the control group, there were more leukocytes, increased EOS and LYM proportions, higher Underwood and PAS scores, increased WTt, WTm, WAt/A0, WAm/WAt, WTt/R0, WTm/WTt, TSLP, OX40L, a-SMA and collagen I mRNA and protein levels, and higher SLP, OX40L, IL-4, IL-5 and IL-13 levels, but lower MON proportions and IFN-γ levels in the asthma and IgG2a mAb groups. Compared with the asthma and IgG2a mAb groups, there were less leukocytes, decreased EOS and LYM proportions, lower Underwood and PAS scores, decreased WTt, WTm, WAt/A0, WAm/WAt, WTt/R0, WTm/WTt, TSLP, OX40L, a-SMA and Collagen I mRNA and protein levels, and lower levels of SLP, OX40L, IL-4, IL-5 and IL-13, but higher MON proportions and IFN-γ levels in the anti-TSLP mAb group. WTm and WTt were positively associated with the TSLP, OX40L, α-SMA and collagen-I levels in the rat lung tissues. CONCLUSION: The results indicate that TSLP may be an important contributor for asthma development as TSLP signaling blockade attenuates airway inflammation and remodeling in asthmatic rats.