Abstract： Objective To determine the effects of nuclear factor-KB(NF-кB)on peroxisome proliferator activated receptor γ(PPARγ)expression in the murine macrophage cell line Ana-1.based on the investigation of the PPARγ expression stimulated by lipopolysaccharide(LPS).Methods Aas-1 cells were divided randomly into seven groups:control group,LPS groups(cells were activated by 0.1 mg/L LPS for 1,2,4,8 hours respectively),SN50 group(cells were stimulated by 50 mg/L SN50 for 4 hours)and NF-кB high expression plasmid transfeeted group.PPARγ and tumor necrosis factor-α(TNF-α)tuRNA levels were assayed by reverse transcription-polymerase chain reaction(RT-PCR)and the TNF-d protein was measured by enzyme linked immunosorbent assay(ELISA)after being activated by LPS.The eukaryotic expression vector of murine NF-кB p65 gene was constructed and stably transfected into Ana-1 cells with DOTAP liposome.The PPARγ expression and NF-кB p65 transloeation as stimulated by LPS and SN50 were assayed by Western blotting.Results Expressions of both PPARγ mRNA and protein were downregulated when cells were stimulated by LPS,which were accompanied with the activity of NF-кB and TNF-α in Ana-1 cells (all P<0.05).The eukaryotie expression vectors containing murine p65 gene were successfully constructed and stably transfected into Ana-1 cells.LPS stimulation and NF-кB p65 gene overexpression resulting in upregulation of p65 could downregulate PPARγ expression in Ana-1 cells(r=-0.91 3,P<0.05).But downregulation of NF-кB by SN50 could upregulate PPARγ expression in the nucleus(r=-0.959,P<0.05).Conclusion LPS can markedly decrease the expression of PPARγ in Ana-1 cells,which may be related to its activity of enhancing NF-кB.NF-кB p65 gene can control PPARγ expression in the reverse direction in Ana-1 cells.