LPS inhibits arginase-1 expression in macrophages by up-regulating activity of cytochrome P450 1A1 epoxidase

Abstract

Objective To explore the regulative effect and mechanism of cytochrome P450 1A1 (CYP1A1) on regulating lipopolysaccharide (LPS)-induced arginase-1 (Arg-1) expression in macrophages. Methods After mouse macrophage-like cell line RAW264.7 (RAW) was treated with 10 mg/L LPS for 0, 12 and 24 h, respectively (n=3 for each time point), the expression of CYP1A1 and Arg-1 at mRNA and protein levels were measured by RT-PCR and Western blotting. Negative control RAW(NC/RAW) cells, CYP1A1-overexpression RAW (CYP1A1/RAW) cells, CYP1A1-knockout RAW (CYP1A1 KO/RAW) cells and CYP1A1 hydroxylase-activity mutant RAW (CYP1A1m/RAW) cells were constructed, respectively, and then the cells were treated with LPS and further detected with RT-PCR and Western blotting for the expression and activation levels of Arg-1 and signal transducer and activators of transcription-6 (STAT6). Then STAT 6 inhibitor AS1517499 was added to treat the CYP1A1 KO/RAW cells and NC/RAW cells, and the mRNA and protein expression of Arg-1 was measured again after LPS or PBS treatment. CYP1A1 epoxidase inhibitor, nordihydroguaiaretic acid (NDGA) and 12 (S)-HETE were introduced to treat normal RAW cells, the mRNA and protein levels of Arg-1 and activity of STAT6 were detected after LPS or PBS treatment. Results LPS-induced CYP1A1 and Arg-1 were highly expressed in staggering peaks in RAW cells (P 0.05), while CYP1A1 epoxidase-activity inhibitor NDGA enhanced Arg-1 expression and STAT6 activation (P < 0.05). Conclusion CYP1A1 can inhibit Arg-1 expression by reducing STAT6 activation in LPS-induced macrophages, and CYP1A1 hydroxylase-activity or its proinflammatory metabolism 12(S)-HETE has no effect on this regulation, while CYP1A1 epoxidase-activity may be involved in this effect.

Keywords

• cytochrome p450 1a1
• lipopolysaccharide
• macrophages
• arginase-1