Mechanism validation of recuperating lung decoction for COPD: Targeting the TLR4/PI3K/Akt/mTOR signaling pathway to mitigate smoke- and LPS-induced pulmonary inflammation.

ETHNOPHARMACEUTICAL RELEVANCE: Chronic obstructive pulmonary disease (COPD) is categorized as "wheezing syndrome" or "lung distension" in traditional Chinese medicine (TCM). COPD is characterized by deficiency, blood stasis, and phlegm turbidity. Recuperating Lung Decoction (RLD), a TCM formula developed from the ancient Chinese formula SiJunZi Decoction, possesses effects of tonifying deficiency, removing blood stasis, and dispelling phlegm. Our team has long employed RLD for COPD treatment with positive outcomes. Although the mechanisms by which RLD alleviates COPD are not fully understood, further investigation is needed.

AIM OF THE RESEARCH: To explore RLD's anti-inflammatory effects and their potential mechanism in COPD model.

MATERIALS AND METHODS: Using network pharmacology, we preliminarily predicted the biological functions and mechanisms underlying the anti-inflammatory response of RLD. Compounds were analyzed by UHPLC-QE-MS. COPD mouse model was developed through concurrent cigarette smoke exposure and lipopolysaccharide challenge. We examined the general condition (including body weight, food intake, and total symptom and sign score), lung tissue pathology, lung function, and levels of inflammatory mediators and oxidative stress indicators in mice with COPD. Finally, the potential anti-inflammatory mechanism of RLD was validated using Reverse Transcription-polymerase chain reaction and Western blotting techniques.

RESULTS: RLD significantly improved the total symptom and sign score in COPD mice. It also reduced inflammatory cytokine levels and alleviated oxidative stress damage. Histopathological analysis revealed that RLD mitigated inflammatory cell infiltration, alveolar enlargement, rupture or fusion, and small airway epithelial hyperplasia or edema in COPD mice. Furthermore, RLD improved lung function. Additionally, RLD decreased the transcriptional activity of TLR4, PI3K, Akt, and mTOR, along with activation ratios of TLR4/GAPDH, p-PI3K/PI3K, p-Akt/Akt, and p-mTOR/mTOR. In summary, the regulation of the TLR4/PI3K/Akt/mTOR signaling pathway is a crucial mechanism underlying RLD's anti-inflammatory effects.

CONCLUSION: RLD alleviates airway inflammation in COPD, and its mechanism of action could potentially involve downregulating the TLR4/PI3K/Akt/mTOR axis. These observations present experimental corroboration supporting the clinical application of RLD.