Pimitespib, an HSP90 inhibitor, augments nifuroxazide-induced disruption in the IL-6/STAT3/HIF-1α autocrine loop in rats with bleomycin-challenged lungs: Evolutionary perspective in managing pulmonary fibrosis.

Idiopathic pulmonary fibrosis is a fatal lung disorder in which the etiology and pathogenesis are still unobvious. Effective treatments are urgently needed considering that lung transplantation is the only treatment that could improve outcomes. This study aimed to investigate the therapeutic significance of the dual administration of pimitespib, an HSP90 inhibitor, and nifuroxazide, a STAT3 inhibitor, against bleomycin-induced pulmonary fibrosis in rats. Our results revealed that pimitespib/nifuroxazide inhibited bleomycin-induced alterations in the structure and the function of the lungs. They demonstrated significant decreases in the BALF total and differential cell counts, LDH activity, and total protein. Concurrently, there was a reduction in the accumulation of collagen as proved by decreased hydroxyproline and the gene expression of COL1A1 accompanied by lower levels of PDGF-BB, TIMP-1, and TGF-β. The levels of IL-6 were also downregulated. Pimitespib-induced inhibition of HSP90 led to subsequent inhibition of HIF-1α and STAT3 client proteins since the closed HSP90 would not enclose its client proteins. Therefore, pimitespib resulted in the repression of HIF-1α/CREB-p300 HAT as well as the STAT3/CREB-p300 HAT nuclear interactions. On the other hand, nifuroxazide resulted in a notable decline in pSTAT3 and HIF-1α levels. Subsequently, the combined effects of both drugs led to a substantial reduction in ECM deposition. Herein, pimitespib augmented nifuroxazide-induced disruption in the IL-6/STAT3/HIF-1α autocrine loop. Our findings also disclose that this novel loop is a promising therapeutic attack site for possible pulmonary fibrosis repression studies. Therefore, the use of pimitespib/nifuroxazide embodies an evolutionary perspective in managing pulmonary fibrosis.