Objective: To study the experimental efficacy of Qushi Huayu Decoction (祛湿化瘀方,QHD) on protein and gene expression of cathepsin B (ctsb) in HepG2 cells induced by free fatty acids (FFAs).Methods: The model of HepG2 steatosis and tumor necrosis factor-α (TNF-α) secretion was induced by long-chain FFAs.HepG2 cells were divided into 4 groups: control group (group C),model group (group M),low-dose QHD group (group L) and high-dose QHD group (group H ).Long-chain FFAs were added to groups M,L and H.The 10% blank-control serum was added to group C and M,while 5% and 10% QHD-containing sera were added to group L and H,respectively.The levels of serum TNF-α and cellular triglyceride (TG) were detected.Cellular p-IκB and ctsb expression were detected using Western blot and PCR.The expression and distribution of ctsb were observed by immunofluorescence.Results: After incubating with FFA for 24 h,TG deposition in HepG2,TNF-α content in cell supernatant,the protein expression of cellular ctsb and P-IκB,as well as mRNA expression of ctsb increased markedly in group M compared with group C (P<0.05,P<0.01).Compared with group M,TG deposition,the expression of cellular ctsb,P-IκB and ctsb mRNA in groups L and H,as well as TNF-α content in group H,decreased significantly (P<0.05).Cell immunochemical fluorescence studies showed that ctsb was released from lysosomes and distributed in the cytoplasm extensively and diffusedly after being stimulated with FFA.In this study,these above-mentioned changes were inhibited markedly in groups L and H.Conclusion: QHD might have a direct inhibitory effect on the ctsb target in the FFA-ctsb-TNFα pathway of hepatic lipotoxicity. Objective: To study the experimental efficacy of Qushi Huayu Decoction on protein and gene expression of cathepsin B (ctsb) in HepG2 cells induced by free fatty acids (FFAs). Methods: The model of HepG2 steatosis and tumor necrosis factor-α (TNF-α) secretion was induced by long-chain FFAs.HepG2 cells were divided into 4 groups: control group (group C), model group (group M), low-dose QHD group ) and high-dose QHD group (group H). Long-chain FFAs were added to groups M, L and H. The 10% blank-control serum was added to group C and M while 5% and 10% QHD-containing sera were added to group L and H, respectively. These levels of serum TNF-α and cellular triglyceride (TG) were detected. Cellular p-IκB and ctsb expression were detected using Western blot and PCR. Expression and distribution of ctsb were observed by immunofluorescence. Results: After incubating with FFA for 24 h, TG deposition in HepG2, TNF-α content in cell supernatant, the protein expression of cell Taken together with group M, TG deposition, the expression of cellular ctsb, P-IκB (P <0.05, P <0.01) and ctsb mRNA in groups L and H, as well as TNF-α content in group H, decreased significantly (P <0.05). Cell immunochemical fluorescence studies showed that ctsb was released from lysosomes and distributed in the cytoplasm extensively and diffusedly after being stimulated with FFA. this study, these above-mentioned changes were made markedly in groups L and H. Confluence: QHD might have a direct inhibitory effect on the ctsb target in the FFA-ctsb-TNFα pathway of hepatic lipotoxicity.