AIM: To elucidate the anti-inflammatory mechanism of an intestinal neuropeptide, sulfated cholecystolkinin octapeptide (sCCK-8), the effects of sCCK-8 on lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNF-alpha) mRNA expression and NF-kappaB activity in pulmonary interstitial macrophages (PIMs) were studied. METHODS: PIMs from rat were stimulated with LPS (1mg (.) L-1) in the presence or absence of sCCK-8 (10(-8)-10(-6)mol (.) L-1) or/and CCK receptor antagonist proglumide (2 mg (.) L-1). The expression of TNF-alpha mRNA was assayed by reverse transcription polymerase chain reaction (RT-PCR) at 3h of the stimulation, and nuclear factor-kappaB (NF-kappaB) binding activity was analyzed by electrophoretic mobility shift assay (EMSA) at 1 h of stimulation. The IkappaB-alpha protein level in the cytoplasma at 30 min of the stimulation was detected by Western blot. RESULTS: SCCK-8, at concentrations from 10(-8) mol (.) L-1 to 10(-6) mol (.) L-1 obviously inhibited LPS-Induced TNF-alpha mRNA expression and NF-kappaB binding activity in a dose-dependent manner, P<0.05, P<0.01. Stimulation PIMs with LPS resulted in a reduction of IkappaB-alpha protein level, P<0.01, which was elevated by sCCK-8, P<0.05. The effects of sCCK-8 on NF-kappaB activity and IkappaB protein level were attenuated by CCK receptor antagonist proglumide, P<0.01. CONCLUSION: SCCK-8 inhibits LPS-induced TNF-alpha mRNA expression by regulating NF-kappaB activity in rat PIMs, which is mediated through CCK receptors and inhibiting IkappaB-alpha degradation. This represents one of the antlinflammatory mechanisms of sCCK-8.