ObjectiveTo investigate the molecular mechanisms by which Wenyang Jiedu granules （WYJD） alleviate influenza A virus （IAV）-induced pneumonia based on single-cell transcriptome sequencing. MethodsThirty female BALB/c mice were randomly divided into a blank control group （Control）， IAV group， and WYJD low-， medium-， and high-dose groups （WYJD-L， WYJD-M， WYJD-H； 2.925， 5.85， 11.7 g·kg^-1， n=6）. Except for the Control group， all other groups were intranasally inoculated with IAV subtype H1N1 （A/PR/8/34） to establish an infection model. Two hours after modeling， drug administration was initiated and continued for 5 consecutive days， with daily monitoring of body weight and general condition. On day 6， mice were sacrificed and samples were collected. Lung index was calculated， and histopathological examination of lung tissue was performed. Lung tissues from the Control， IAV， and WYJD-H groups were subjected to single-cell transcriptome sequencing （n=3）， focusing on type I alveolar epithelial cells （AT1） to analyze changes in gene expression and signaling pathways. Western blot was used to detect the expression changes of relevant proteins to validate the single-cell sequencing results. ResultsCompared with the Control group， the IAV group exhibited significantly decreased body weight （P<0.05） and significantly increased lung index （P<0.05）. Compared with the IAV group， all WYJD-treated groups exhibited significantly increased body weight （P<0.01） and significantly decreased lung index （P<0.01）. Single-cell sequencing analysis revealed that WYJD inhibited overactivation of interferon and inflammatory signaling pathways in AT1 cells after IAV infection， including interferon-γ response， interferon-α response， tumor necrosis factor-α/nuclear factor-κB （TNF-α/NF-κB）， and interleukin-6/Janus kinase/signal transducer and activator of transcription 3 （IL-6/JAK/STAT3） pathways. Compared with the Control group， the number of AT1 cells in the IAV group showed a decreasing trend. Compared with the IAV group， the WYJD-H group showed an increasing trend， although neither difference was statistically significant. Further analysis of AT1 cell subpopulation gene expression showed that， compared with the Control group， the IAV group exhibited increased expression of pro-apoptotic genes FAS cell surface death receptor （FAS） and cyclin-dependent kinase inhibitor 1A （CDKN1A）， a significant increase in tumor protein p53 （Tp53） expression （P<0.05）， and significant decreases in expression of the AT1 marker gene advanced glycosylation end-product-specific receptor （AGER） and membrane structural gene caveolin1 （CAV1） （P<0.05， P<0.01）. Compared with the IAV group， the WYJD-H group showed significantly decreased expression of FAS， CDKN1A， and Tp53 （P<0.05， P<0.01）， and significantly increased expression of AGER and CAV1 （P<0.05， P<0.01）. Regarding interferon response-related genes， compared with the Control group， the IAV group showed increased expression of interferon-stimulated gene 15 （ISG15）， interferon-induced protein with tetratricopeptide repeats 3 （IFIT3）， signal transducer and activator of transcription 2 （STAT2）， bone marrow stromal cell antigen 2 （BST2）， and C-X-C motif chemokine ligand 10 （CXCL10）， with a significant increase in 2′，5′-oligoadenylate synthetase-like protein 1 （OASL1） （P<0.05）. Compared with the IAV group， the WYJD-H group showed significantly decreased expression of all the above genes， with highly significant differences for ISG15， IFIT3， STAT2， BST2， and OASL1 （P<0.01）， and a significant difference for CXCL10 （P<0.05）. Among inflammation-related genes， compared with the Control group， the IAV group showed significantly increased expression of intercellular adhesion molecule 1 （ICAM1）， tumor necrosis factor alpha-induced protein 3 （TNFAIP3）， keratin 8 （KRT8）， tumor necrosis factor receptor superfamily member 1A （TNFRSF1A）， and TNFRSF1B （P<0.01）， and increased expression of NFKBIA， a negative regulator of NF-κB （P<0.05）. Compared with the IAV group， the WYJD-H group showed significantly decreased expression of KRT8 and TNFRSF1B （P<0.05）， while ICAM1， NFKBIA， TNFAIP3， and TNFRSF1A showed decreasing trends without statistical significance. Western blot validation showed that， compared with the Control group， protein expression levels of ISG15， FAS， p53， and phosphorylated p65 （p-p65） in lung tissue of the IAV group were significantly increased （P<0.05， P<0.01）. Compared with the IAV group， the WYJD-H group showed significantly decreased expression of these proteins （P<0.05， P<0.01）. ConclusionWYJD may alleviate viral pneumonia by targeting gene expression in AT1 cells， inhibiting overactivated interferon and inflammatory signaling pathways after IAV infection， and downregulating pro-apoptotic signaling， thereby reducing alveolar epithelial injury.