MECHANISM OF WARMING AND INVIGORATING KIDNEY YANG IN PROTECTING PULMONARY FIBROSIS BY INHIBITING SMAD AND STAT3 SIGNALING PATHWAY

Feiran Li¹, Guanyu Wang², Qizheng Han³, Caiqing Zhang^{1, 4, *}

¹First Clinical Medical College, Shandong University of Traditional Chinese Medicine, Jinan, 250000, China - ²Department of Health Care, Jinan Huaiyin People's Hospital, Jinan, 250000, China - ³Pulmonary and Critical Care Medicine, Shandong Province's Second General Hospital (Shandong Province ENT Hospital), Jinan, 250000, China - ⁴Pulmonary and Critical Care Medicine, Shandong Province's Second General Hospital (Shandong Province ENT Hospital), Shandong University of Traditional Chinese Medicine, Jinan, 250000, China

Background and aim: Pulmonary fibrosis is a kind of pulmonary disease, including heterogeneous groups of various interstitial lung diseases. We explore whether the warming and tonifying kidney yang can inhibit Smad and STAT3 signaling pathways, thus inhibiting the occurrence of pulmonary fibrosis.

Methods: To explore the mechanism of warming and tonifying kidney yang in protecting pulmonary fibrosis by inhibiting Smad and STAT3 signaling pathways, SD rats (6-8 weeks old, weight 200 ± 20g) were purchased from an experimental animal company. All feeding procedures were conducted according to the nursing guidelines of the national institutes of health. Further, the experiment and treatment were conducted by following the NIH experimental animal nursing and using guidelines. The pulmonary fibrosis model was induced by bleomycin. According to the experimental requirements, the rats were divided into control, induction, and treatment groups. The expressions of EMT, Smad, and STAT3 were analyzed by Western blot and immunohistochemistry. 

Result: The pulmonary function of rats was detected by BUXCO pulmonary function test system. The lung sections of rats were observed by trichrome staining with hematoxylin-eosin and Masson. The expressions of the markers COL1A1, COL3A1, CTGF, and TGF-β in rats were analyzed using RT-qPCR. Moreover, TNF-α, IL-1 β, and IL-6 levels in bronchoalveolar lavage fluid were detected by enzyme-linked immunosorbent assay. The protein expression of P-Smad and P-STAT3 in the induction group was higher than those in the control group; also, it decreased in the treatment group compared with the induced group (P<0.05). Immunohistochemistry showed that warming and tonifying kidney yang inhibited the activation of P-Smad and P-STAT3. The lung resistance, dynamic pulmonary compliance, and vital capacity of the treatment group were lower than those in the control group (P<0.05). The HE staining and Ashcroft scores in the induction group were higher than those in the control group (P<0.05), and those in the treatment group were lower than those in the induction group (P<0.05). The expression of mRNA in the induction group was higher than that in the control group, and the expression of ctl1a1, ctl3a1, CTGF, and TGF-β in the treatment group were lower than those in the induction group (P<0.05). The levels of TNF- α, L-1 β, and IL-6 in the induction group were higher than those in the control group (P<0.05), and the levels of TNF-α, L-1 β, and IL-6 in the treatment group were lower than those in the induction group (P<0.05). Compared to the control group, the expression of E-cadherin decreased and α-SMA increased (P<0.05) in the induction group. Also, compared with the induction group, the expression of E-cadherin increased, and α-SMA decreased (P<0.05) in the treatment group. 

Conclusion: Warming and tonifying kidney yang could improve the process of pulmonary fibrosis in rats by inhibiting the activation of Smad and STAT3. Thus, the method of warming and tonifying kidney yang may be a promising candidate strategy to treat pulmonary fibrosis.