[Mechanistic study on Kaixin Powder ameliorating chronic stress-induced CD8~+T cell exhaustion and delaying lung adenocarcinoma progression by modulating IDO1/Kyn/Ahr axis].

This study aimed to investigate the interventional effects of Kaixin Powder(KXP) on the progression of lung adenocarcinoma(LUAD) under chronic stress and its underlying mechanism. Ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) was employed to characterize the chemical constituents of KXP, followed by network pharmacology and molecular docking analyses to screen for its potential targets. A chronic stress-associated lung cancer mouse model was established by axillary inoculation of Lewis lung carcinoma(LLC) cells combined with chronic unpredictable mild stress(CUMS). Sixty SPF-grade C57BL/6 mice were randomly divided into the following groups: normal group, lung cancer group, model group, low-and high-dose KXP(13.65 and 27.3 g·kg~(-1)) groups, and fluoxetine(2 mg·kg~(-1)) group. Tumor growth indicators, including body weight, tumor mass, and tumor inhibition rate of mice were measured. Depression-like behaviors were observed by open field test(OFT) and sucrose preference test(SPT). Serum levels of stress factors such as corticosterone(Cort) and kynurenine(Kyn) were measured by ELISA. Histopathological changes in tumor tissue were assessed by hematoxylin-eosin(HE) staining. Peripheral blood T lymphocyte subsets were analyzed by flow cytometry. Intratumoral CD8~+T cells infiltration was detected by immunofluorescence, and the protein expression levels of indoleamine 2,3-dioxygenase 1(IDO1) and aryl hydrocarbon receptor(Ahr) were determined by Western blot. Serum ALT, AST, BUN, and Scr levels were measured to evaluate hepatic and renal safety. UPLC-MS/MS analysis characterized 157 chemical constituents of KXP. The protein expression levels of indoleamine 2,3-dioxygenase 1(IDO1) and aryl hydrocarbon receptor(Ahr) were detected by Western blot. In addition, serum ALT, AST, BUN, and Scr levels were measured to evaluate hepatic and renal safety. UPLC-MS identified 157 chemical constituents of KXP. Network pharmacology analysis obtained 367 potential targets, among which epidermal growth factor receptor(EGFR), protein kinase B alpha(AKT1), signal transducer and activator of transcription 3(STAT3), heat shock protein 90 alpha family class A member 1(HSP90AA1), and IDO1 were screened as core targets. Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway analysis and molecular docking indicated that abnormal tryptophan metabolism mediated by IDO1 may be a potential mechanism underlying KXP intervention in LUAD complicated with depression. Animal experiments showed that, compared with the lung cancer group, the model group exhibited significantly accelerated tumor growth, increased structural disarray and atypia in HE-stained tumor tissue, obvious depression-like behaviors, and significantly elevated serum Cort and Kyn levels. In addition, the proportions of peripheral blood CD3~+ and CD3~+CD4~+T cells and the CD3~+CD4~+/CD3~+CD8~+ ratio significantly decreased, whereas the proportion of CD3~+CD8~+T cells significantly increased. Intratumoral CD8~+T cells infiltration was reduced, while the protein expression levels of IDO1 and Ahr were significantly upregulated. Compared with the model group, the high-dose KXP group showed significantly reduced tumor volume and tumor weight, with a tumor inhibition rate of 52.43%. KXP intervention improved depression-like behaviors to varying degrees, with the high-dose group showing more pronounced improvements in OFT activity indicators and SPT sucrose preference rate. Serum Cort and Kyn levels were significantly reduced in the high-dose KXP group. The proportions of peripheral blood CD3~+ and CD3~+CD4~+T cells and the CD3~+CD4~+/CD3~+CD8~+ ratio significantly increased in both low-and high-dose KXP groups. The low-dose KXP group showed significantly reduced IDO1 protein expression, while the high-dose group showed significantly reduced expression of both IDO1 and Ahr proteins. Safety evaluation showed that, within the experimental dose range, KXP had no obvious adverse effects on the morphology of major organs or on serum ALT, AST, BUN, and Scr levels. In conclusion, KXP ameliorates chronic stress and delays LUAD progression, and its mechanism may be associated with inhibition of the IDO1/Kyn/Ahr axis, correction of abnormal tryptophan metabolism, promotion of intratumoral CD8~+T cells infiltration, and improvement of the tumor immune microenvironment.