LianZhiXiaoYan Formula alleviates LPS-induced chronic pneumonia via regulating metabolic reprogramming through SIRT3-SDH-SUCNR1 signaling pathway.

Ethnopharmacological relevance: Recurrent or persistent respiratory tract infection may progress to chronic pneumonia or other debilitating sequelae in the absence of appropriate therapeutic interventions, seriously compromising the patients' quality of life. LianZhiXiaoYan Formula (LZXYF), a Chinese prescription composed of Chinese medical herbs Andrographis herba (ChuanXinLian) and Radix helicteris (ShanZhiMa), possesses efficiency of clearing heat and detoxifying, and shown a good therapeutic effect on respiratory infectious diseases, but its mechanism of action is not clear.

Aim of the study: Aim to evaluate the therapeutic efficacy of LZXYF in treatment of CP and investigate its molecular and physiological mechanisms.

Materials and methods: The therapeutic effects of LZXYF on CP was evaluated in an LPS-induced murine model by assessing the pulmonary function, lung histopathology, and biochemical indicators. To explore the mechanism of LZXYF, the lung metabolomics and the components of LZXYF distributed in lung were analyzed by UHPLC-Q-TOF-MS/MS. The impact of LZXYF on SIRT3-SDH-SCUNR1 pathway was investigated using RT-qPCR and Western blot, and the interaction between LZXYF and SIRT3 was verified via CETSA. LPS-induced LLC cell and succinate-induced RAW264.7 cell were employed to investigate the effect and mechanism of LZXYF on metabolic reprogramming and inflammation regulation, with selective inhibition of SIRT3 and SUCNR1, respectively.

Results: LZXYF treatment improved pulmonary function as demonstrated by increased Tidal volume, enhanced Minute ventilation, elevated Peak expiratory flow rate, and reduced Timed inspiration (P < 0.05). Moreover, histopathological analysis revealed that LZXYF treatment attenuated emphysema and airway remodeling, concomitant with reduced the levels of TGF-β and HYP (P < 0.01). Metabolomics demonstrated that LZXYF treatment restored 38 dysregulated metabolites in CP mice, primarily involving tryptophan, histidine, lysine and arginine metabolic pathways. Correlation analysis of 16 lung-distributed components and the 38 differential metabolites further indicated that LZXYF alleviated CP through SIRT3 signaling pathway mediated metabolic reprogramming. We further demonstrated that LZXYF could up-regulate SIRT3 to enhance the activities of SDH (P < 0.01), a metabolic enzyme in TCA cycle, thereby regulating metabolic reprogramming and inhibiting the activation of SUCNR1 to prevent succinate-induced inflammation responses (P < 0.01). Furthermore, we elucidated that the active components of LZXYF exerted ameliorated effects by up-regulating SIRT3 expression in LPS or 3-TYP induced LLC cell metabolic reprogramming, which revealed SIRT3 as a critical molecular target for LZXYF to improve metabolic reprogramming and suppress inflammatory responses induced by succinate.

Conclusion: LXZYF could ameliorate CP through up-regulating SIRT3, which enhances TCA cycle and suppresses succinate-mediated inflammation. This study provides new insight into the therapeutic potential of LZXYF for CP treatment.