Experimental and proteomics evidence revealed the protective mechanisms of Shemazhichuan Liquid in attenuating neutrophilic asthma.

Background: Neutrophilic asthma (NA) is one of the most important phenotypes of non-Th2 asthma and is often insensitive to glucocorticoid therapy, making current treatment difficult. Shemazhichuan Liquid (SMZCL), a Chinese medicine compound preparation, has unique advantages in the treatment of asthma. However, the underlying mechanisms of SMZCL in treating NA are not fully understood.

Purpose: The efficacy and underlying mechanisms of SMZCL on NA were investigated by TMT-labeled quantitative proteomics analysis and in vivo and in vitro experiments.

Methods: NA mouse model was constructed by OVA/CFA sensitization followed by a 10-day challenge with 5 % OVA. Lung histopathology, leukocyte counts and cell sorting counts, inflammatory cytokines levels, as well as expression of autophagy markers were then assessed. The specific pathways and proteins of SMZCL for treating NA were further illustrated through TMT-based quantitative proteomics. In addition, RAW264.7 cells were induced by LPS to further explore the mechanism of the main active ingredient of SMZCL on autophagy pathway.

Results: In vivo, SMZCL contributed to attenuating airway inflammation and collagen disposition, markedly reduced the number of leukocytes, especially neutrophils in bronchoalveolar lavage fluid (BALF), as well as decreased IgE and inflammatory cytokine levels (TNF-α, IL-1β, IL-6 and IL-8) in BALF and serum. Besides, SMZCL elevated the levels of LC3 and ATG5 while inhibiting the expression of p62 and mTOR. Mzb1 and Rab3ip were identified as the critical overlapping DEPs whose expression was inhibited by SMZCL and rapamycin. KEGG enrichment analysis showed that necroptosis process was a key pathway for SMZCL to treat NA airway inflammation. IHC and WB results confirmed that SMZCL and rapamycin inhibited the phosphorylation of RIPK1, PIPK3 and MLKL. In vitro, ATG5 and LC3 proteins were obviously increased while p-mTOR expression was inhibited after amygdalin treatment.

Conclusion: SMZCL attenuated airway inflammation in NA mainly through inhibition of the mTOR pathway, along with inhibition of the necroptosis pathway regulated by the RIPK1/RIPK3/MLKL axis and inhibition of Mzb1 and Rab3ip expression.