The Effect of Metformin on Radiation-Induced Lung Fibrosis in Mice

Figure 1.. Metformin effects on body and lung weights. (A) Mice appearance and chest albinism, red arrow: white fur; (B) The curve of body weight during the experiments; (C) The anatomy of lung tissue; (D) The lung wet weight to body weight ratio (LWW/BW) among the groups. The results are presented as mean ± SD. b P < 0.01 vs Control group, d P < 0.01 vs IR group.

Figure 2.. Metformin improved radiation-induced pathological changes in the lungs. (A) Representative images of hematoxylin-eosin staining and the comparison of pathological scores, a: alveolus, as: alveolar septa, red arrow: alveolar hemorrhage; (B) Representative images of Masson’s Trichrome staining and the comparison of fibrotic scores, black arrow: thickening of alveolar septa. The results are presented as mean ± SD. a P < 0.05 vs Control group, b P < 0.01 vs Control group, c P < 0.05 vs IR group, d P < 0.01 vs IR group, e P < 0.05 vs L-Met group.

Figure 3.. Metformin mitigated radiation-induced lung fibrosis. (A)-(C) Representative images (40×) of immunohistochemical staining of Collagen-I, Samd2, and TGF-β1 and the percentages of their positive cells, black arrow: Collagen-I, Samd2, and TGF-β1 posotive cells. (D) Representative images of western blot of Collagen-I, Samd2, and TGF-β1 and their quantified calculation of protein expression. The results are presented as mean ± SD. a P < 0.05 vs Control group, b P < 0.01 vs Control group, c P < 0.05 vs IR group, d P < 0.01 vs IR group, e P < 0.05 vs L-Met group, f P < 0.01 vs L-Met group.

Figure 4.. Metformin suppressed radiation-induced inflammation response in lung tissue, bronchoalveolar lavage fluid (BALF) , and serum. (A) The production of cytokines high-mobility group box 1 (HMGB1), interleukin-1 beta (IL-β1), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) in the lung tissue. (B) Cytokines levels in bronchoalveolar lavage fluid (BALF). (C) Cytokines levels in serum. The results are presented as mean ± SD. aP < 0.05 vs Control group, bP < 0.01 vs Control group, cP < 0.05 vs IR group, dP < 0.01 vs IR group, eP < 0.05 vs L-Met group.

Figure 5.. Metformin reduced inflammation response via high-mobility group box 1(HMGB1)/toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) pathway in the lung tissue. (A) Representative images of western blot of HMGB1, TLR4, myeloid differentiation primary response protein 88 (MyD88), NF-κB, and interleukin-1 beta in the lung tissues and their quantified calculation of protein expression. (B) mRNA expression levels of HMGB1, TLR4, and NF-κB in lung tissues. The results are presented as mean ± SD. aP < 0.05 vs Control group, bP < 0.01 vs Control group, cP < 0.05 vs IR group, dP < 0.01 vs IR group.

Figure 6.. The effects of metformin on intestinal gut microbiota. (A)-(C) The indexes of the abundance and diversity of intestinal gut microbiota bacterial, including the observed species number, Chao1 index, and Shannon index. (D) Principal coordinate analysis (PCA) of gut microbiomes. (E) Principal component analysis (PCoA) of gut microbiomes. (F) The differences in intestinal bacterial structure at the genus level among the groups (G) The relative abundance of bacterial flora at the genus level. (H) The relative abundance of lactobacillus. (I) The relative abundance of Lachnospiraceae-NK4A136. The results are presented as mean ± SD. a P < 0.05 vs Control group, b P < 0.01 vs Control group, c P < 0.05 vs IR group, eP < 0.05 vs L-Met group.

Figure 7.. Potential mechanisms of radiation-induced lung fibrosis mitigation by metformin. Draw by Figdraw.