Objective      To determine the effects of the dysfunction of sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP) on the expression of inflammatory cytokines

IL-1β and monocyte chemoattractant protein-1 (MCP-1)

in THP-1 macrophages

and investigate whether its pro-inflammatory effect depends on its mediated regulation of cholesterol homeostasis.       Methods      Gene transfection was used to over-express or knock-down SCAP in THP-1 macrophages. After THP-1 macrophages were treated with inflammatory stimulus

LPS (1 μg/mL) or translocation inhibitor

betulin (3 μmol/L

a chemical which inhibits SCAP translocation from endoplasmic reticulum to Golgi specifically). The THP-1 macrophages were divided into control group

SCAP over-expression group

SCAP knocking-down group

SCAP knocking-down plus LPS group

and SCAP over-expression plus betulin group. The mRNA expression of SCAP

HMGCoAR

pro-IL-1β and MCP-1 were determined after over-expression or knocking-down of SCAP by real-time PCR. The accumulation of neutral lipid droplets in the cells was observed by Oil Red O staining. The contents of intracellular total cholesterol (TC)

free cholesterol (FC) and cholesterol ester (CE) were determined by quantitative assays. The protein expression of SCAP and pro-IL-1β

and the mature IL-1β level in the supernatants were measured by Western blotting.       Results      Over-expression of SCAP significantly increased the expression of HMGCoAR

pro-IL-1β and MCP-1 at mRNA level (P0.01)

the contents of intracellular pro-IL-1β and mature IL-1β in the supernatants (P0.05)

and intracellular TC accumulation and CE contents in SCAP over-expressed macrophages. Knocking-down SCAP dramatically decreased the expression of HMGCoAR

pro-IL-1β and MCP-1 at mRNA level (P0.05)

the contents of intracellular pro-IL-1β and mature IL-1β in the supernatants (P0.05)

and intracellular TC accumulation and CE contents in SCAP knocking-down macrophages. The expression of MCP-1 and pro-IL-1β and the content of mature IL-1β were lower in the knocking-down plus LPS group than the LPS group (P0.05). Betulin treatment effectively suppressed the mRNA expression of HMGCoAR (P0.05) and decreased the contents of intracellular TC and CE (P0.05)

but had no effect on the expression of pro-IL-1β and MCP-1 and level of mature IL-1β in the supernatants (P0.05).       Conclusion      Cholesterol sensor SCAP dysfunction promotes the expression of IL-1β and MCP-1

and enhances the production and secretion of mature IL-1β. Our findings suggest that this new function of SCAP is independent of its mediated regulation of cholesterol homeostasis.