Qingfei Tongluo Jiedu Formula Regulates M2 Macrophage Polarization via the Butyric Acid-GPR109A-MAPK Pathway for the Treatment of Mycoplasma pneumoniae Pneumonia

<b>Background</b>: <i>Mycoplasma pneumoniae</i> pneumonia (MPP) is a common community-acquired pneumonia in children. Increasing drug resistance highlights the need for more effective treatments with fewer side effects. The Qingfei Tongluo Jiedu formula (QTJD) has demonstrated clinical efficacy against MPP; however, its underlying mechanisms remain unclear. This study aimed to explore the mechanism of QTJD on MPP using network pharmacology and in vitro experiments. <b>Methods</b>: Network pharmacology was used to identify the active compounds and signaling pathways of QTJD in MPP. QTJD-containing serum was prepared, and primary mouse lung and bone marrow cells were isolated to examine the effects of QTJD on macrophage polarization through butyric acid. Cell viability assays, flow cytometry, and quantitative reverse transcription-polymerase chain reaction were performed. GPR109^-/- cells were used to confirm the receptor mediating butyric acid's action, and Western blotting was employed to assess the MAPK signaling pathway. <b>Results</b>: QTJD promoted macrophage polarization and alleviated the inflammatory response caused by <i>Mycoplasma pneumoniae</i>. High-performance liquid chromatography-electrospray ionization mass spectrometry combined with network pharmacology identified 20 active compounds. Protein-protein interaction analysis revealed 10 core target, including JUN and Tumor Necrosis Factor (TNF), while enrichment analysis highlighted pathways such as Mitogen-Activated Protein Kinase (MAPK) and Phosphoinositide 3-Kinase-Protein Kinase B. Experimental validation demonstrated that QTJD reduced M1 markers (CD86, CXCL10) by increasing butyrate levels (<i>p</i> < 0.01) and enhanced M2 markers (CD206, Arg-1, MRC-1), promoting M2 polarization. QTJD inhibited ERK1/2, p38, and JNK1/2 (<i>p</i> < 0.01). In GPR109A^-/- mice macrophages, QTJD suppressed p38 and JNK1/2 (<i>p</i> < 0.01) but showed no effect on ERK1/2 (<i>p</i> > 0.05), confirming involvement of the butyrate-GPR109A-MAPK pathway. <b>Conclusions</b>: QTJD effectively alleviates MPP by regulating macrophage polarization through the butyrate-GPR109A-MAPK pathway. Future studies should explore how QTJD modulates pulmonary immunity through gut microbiota and butyrate production and elucidate its immunoregulatory mechanisms along the gut-lung axis using multi-omics approaches.