6. The efficacy of combination therapy surpassed that of monotherapy in addressing inflammation and fibrosis associated with silicosis.
Following the combined application of PFD and BIBF, the inflammatory lesions in the lung tissue of advanced silicosis mice were reduced, and the infiltration of inflammatory cells decreased compared to the use of either drug alone (Fig 7A, B), indicating a stronger effect when used in combination. Moreover, levels of crucial inflammatory factors such as IL-1β (Fig 7C, D), IL-6 (Fig 7E, F), and TNF-α (Fig 7G) were also found to decrease. In terms of pulmonary fibrosis, the combined administration exhibited a more potent and effective improvement in fibrotic conditions compared to monotherapy, leading to a reduction in fibrotic lesions and a decrease in collagen deposition (Fig 8A, B). Furthermore, the mRNA and protein levels of key fibrotic factors, such as FN-1 (Fig 8C, E, F) and COL-I (Fig 8D, E, F), were reduced. Additionally, the combined treatment effectively reduced the levels of HYP (Fig 8G), implying an overall decrease in fibrosis. The above results demonstrated the advantages of combined drug administration in limiting silica-induced inflammation and fibrosis, and the effects were consistent for both high and low doses.
Clinical reports have indicated that both PFD and BIBF have certain side effects, including gastrointestinal reactions, skin diseases, hepatotoxicity and so on. Therefore, we assessed the drug toxicity of the low-dose combined therapy regimen, which is most likely to be used in clinical settings. The results showed that compared to silica group, low-dose combined therapy did not exhibit a significant trend of weight loss. In fact, the rate of weight loss was even lower than that observed with high-dose PFD or high-dose BIBF (Fig S1A). However, it is worth noting that the combined administration increased levels of liver function markers ALT (Fig S1B) and AST (Fig S1C) compared to silicosis group, although the changes were not significant when compared to the use of monotherapy. Additionally, there was no apparent structural damage or alteration observed in liver tissue. Moreover, no conspicuous damage to kidney tissues or small intestine tissues was observed (Fig S1D). In conclusion, it can be inferred that the efficacy and safety of low-dose combined administration are reasonably assured, thus recommending its prospective utilization in future anti-fibrotic treatments.