Fig. 5

TXNIP and inflammatory pathways: Role of MSG and quercetin in the development of pulmonary fibrosis through balance in redox and myofibroblast differentiation (A-D). Data were expressed as Mean ± SEM. Significance level based on one-way ANOVA, P ≤ 0.05. Significance level based on Tukey’s post hoc test (n = 5): NC vs. MSG: a, NC vs. QL/QM/QH: b, QL vs. QM vs. QH: c, QL/QM/QH vs. MSG + QL/MSG + QM/MSG + QH: d, MSG vs. MSG + QL: e, MSG vs. MSG + QM: f, MSG vs. MSG + QH: g, MSG + QL vs. MSG + QM vs. MSG + QH: h [*P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, NS: not significant]. The cytoarchitectonic view of lung tissues was also depicted in this figure, which shows the restorative impact of quercetin in the MSG-induced altered cytomorphology by HE (HE), Picrosirius red (PSR), and Masson’s trichrome (MT) staining. Histological examination of lung tissue in NC, MSG, and two graded concentrations of quercetin with or without MSG showed the variants in terms of structure integrity and fibrotic responses. Normal alveolar structures with minimal inflammatory infiltration were seen in the NC group by hematoxylin and eosin staining (HE). On the other hand, the MSG group presented intense pulmonary fibrosis, whose histological appearance was disturbed due to higher collagen deposition and inflammatory cell infiltration in all of the used staining methods. Interstitial edema and inflammation were mainly emphasized under HE staining (HE), whereas Picrosirius red staining (PSR) indicated the existence of thick fibers that represent fibrotic remodeling. Areas stained with Masson’s trichrome revealed an increase compared with controls (MT). The treatment at two concentrations of quercetin has not shown any alterations of the lung histology compared with the NC group, indicating that this compound has limited or no significant influence on the lung independently. However, quercetin + MSG offered protective and significantly reduced the level of fibrotic changes with all the stainings ; thus, there is evidence that although quercetin itself does not produce marked remodeling of lung tissue, it effectively rescues from the pathological effects of MSG and saves the structure and attenuates inflammatory responses.