Protective effects of methylprednisolone–cyclophosphamide treatment on bleomycin-induced pulmonary fibrosis

Background Methylprednisolone (MP) and cyclophosphamide (CTX) combination treatment has shown great benefits in improving pulmonary fibrosis (PF) and high safety. Currently, the mechanism underlying the effects of MP-CTX on improving PF remains unclear. This study determined the effects of MP-CTX combination treatment on the modulation of inflammation, oxidative stress, and T-cell immunity in PF. Methods PF rat models were induced by bleomycin stimulation. MP (3?mg/kg) and MP-CTX (MP: 3?mg/kg; CTX: 8?mg/kg) combination were administered in the PF?+?MP and PF?+?MP?+?CTX groups, respectively. Transmission electron microscopy, hematoxylin and eosin staining, Ashcroft score, and Masson trichrome staining were performed to measure lung morphology in PF. Enzyme-linked immunosorbent assay and quantitative polymerase chain reaction assay were performed to quantify inflammatory factors. Malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-PX) levels were determined using commercial kits. α-Smooth muscle actin (SMA) and collagen I levels were determined using western blotting and immunohistochemistry. The T-cell count was evaluated using flow cytometry. Results MP-CTX reduced lung injury, collagen deposition, and α-SMA and collagen I levels in a bleomycin-induced PF rat model. Additionally, MP-CTX decreased the levels of MDA and inflammatory factors (tumor necrosis factor-α, interleukin-1β, and interleukin-6) but increased the activities of SOD and GSH-PX. Furthermore, MP-CTX changed T-cell types in lung tissues, such as increasing CD4 + CD25 + Foxp3 + cell count. Conclusions MP-CTX combination treatment improved the degree of PF by reducing inflammation and oxidative stress and improving T-cell immunity. These findings provide novel insights into the mechanisms underlying the effects of MP-CTX on PF.

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