Objective To evaluate the role of caveolin-1 (Cav-1) in penehyclidine hydrochioride (PHC)-induced inhibition of lipopolysaccharide(LPS)-induced activation of Toll-like receptor 4 (TLR4) /p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway in macrophages of mice.Methods Macrophages of mice were seeded in 6 em diameter dishes (5 ml per dish) and divided into 5 groups (n=20 each) using a random number table:Scr-siRNA group (S group),Scr-siRNA + LPS group (LPS group),Ser-siRNA+LPS +PHC group (LPS+P group),Cav-1-siRNA+LPS group (C+LPS group) and Cav-1-siRNA+LPS+PHC group (C+LPS+P group).Macrophages were transfected with Scr-siRNA for 24 h in S,LPS and LPS+P groups and with Smart pool Cav-1 siRNAs for 24 h in C+LPS and C+LPS+P groups.LPS at the final concentration of 1 μg/ml was added after the end of transfection,and macrophages were then incubated for 2 h in LPS,LPS+P,C+LPS and C+LPS+P groups.In LPS+P and C+LPS+P groups,PHC at the final concentration of 2 μg/ml was added at 2 h of incubation with LPS,and macrophages were then incubated for 2 h.The expression of Cav-1 and TLR4 was detected by Western blot.The expression of p38 MAPK was determined by immunofluorescence.The level of tumor necrosis factor-alpha (TNF-α) in the culture medium was determined by enzyme-linked immunosorbent assay.The activity of myeloperoxidase (MPO) in macrophages was measured by colorimetry.Results Compared with group S,the expression of TLR4 and p38 MAPK was significantly up-regulated,and the concentration of TNF-α in the culture medium and activity of MPO were increased in the other four groups,the expression of Cav-1 was significantly downregulated in LPS and C+LPS groups (P ＜0.05),and no significant change was found in the expression of Cav-1 in group LPS+P (P＞0.05).Compared with group LPS,the expression of Cav-1 was significantly up-regulated,the expression of TLR4 and p38 MAPK was down-regulated,and the concentration of TNF-α in the culture medium and activity of MPO were decreased in group LPS+P,and the expression of Cay-1 was significantly down-regulated,the expression of TLR4 and p38 MAPK was up-regulated,and the concentration of TNF-α in the culture medium and activity of MPO were increased in group C+LPS (P＜0.05).Compared with group LPS+P,the expression of Cav-1 was significantly down-regulated,the expression of TLR4 and p38 MAPK was up-regulated,and the concentration of TNF-α in the culture medium and activity of MPO were increased in group C+LPS+P (P＜0.05).Compared with group C+LPS,the expression of Cav-1 was significantly up-regulated,the expression of TLR4 and p38 MAPK was down-regulated,and the concentration of TNF-α in the culture medium and activity of MPO were decreased in group C+LPS+P (P＜0.05).Conclusion The mechanism by which PHC inhibits LPS-induced activation of TLR4/p38 MAPK signaling pathway in macrophages is related to up-regulating Cav-1 expression in mice.