Effects of cytochrome P450 1A1 on nitric oxide production in lipopolysaccharide-induced macrophages / 中华危重病急救医学

ABSTRACT

Objective:To determine the effects of cytochrome P450 1A1 (CYP1A1) on nitric oxide (NO) production in lipopolysaccharide (LPS)-induced macrophages and the underlying mechanism.Methods:The peritoneal macrophages (PMs) were isolated from healthy C57BL/6 mice and stimulated with 10 mg/L LPS to establish inflammatory response model. The CYP1A1 mRNA and protein expressions in the cells were determined. The mouse macrophages RAW264.7 cell line with CYP1A1 overexpression (CYP1A1/RAW) were cultured in vitro, and they were stimulated by 10 mg/L LPS at logarithmic phase. The negative control-expressed RAW264.7 cells (NC/RAW) were established. The protein and mRNA expressions of activator protein-1 (AP-1) and inducible nitric oxide synthase (iNOS) in the cells as well as the content of NO in the cell supernatant were determined. The RAW264.7 cells were cultured in vitro, and they were stimulated by 10 mg/L LPS and 100 nmol/L 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] only or in combination at logarithmic phase. The blank control group was set up. The expression of iNOS mRNA in the cells and NO content in the cell supernatant were determined to observe whether the effect of CYP1A1 on LPS induced NO production in macrophages was related to 12(S)-HETE produced by metabolism. The RAW264.7 cells with CYP1A1 overexpression and hydroxylase activity mutation (CYP1A1m/RAW) were cultured in vitro, and they were stimulated by 10 mg/L LPS at logarithmic phase. The CYP1A1/RAW cell control group was set up. The iNOS mRNA expression in the cells and NO content in the cell supernatant were determined to observe the effect of hydroxylase activity of CYP1A1 in regulating NO production in macrophages. Results:Compared with the phosphate buffered saline (PBS) control group, the CYP1A1 mRNA expressions were elevated significantly from 2 hours after LPS stimulation and reached a peak at 12 hours [CYP1A1 mRNA (2 -&Delta;&Delta;Ct) 6.41±0.98 vs. 1.00±0.00, P < 0.05], while CYP1A1 protein expressions were increased from 6 hours after LPS stimulation and reached a peak at 24 hours, suggesting that CYP1A1 expression might be involved in LPS-induced macrophage over-activation. Compared with NC/RAW+LPS group, the iNOS mRNA expressions and NO contents both increased in CYP1A1/RAW+LPS group and reached a peak after 12 hours and 24 hours, respectively [12-hour iNOS mRNA (2 -&Delta;&Delta;Ct) 54.42±8.21 vs. 24.22±3.89, 24-hour NO (μmol/L) 66.52±4.09 vs. 41.42±2.09, both P < 0.05], while the iNOS protein expression and AP-1 phosphorylation also enhanced, suggesting that CYP1A1 might increase NO production by promoting AP-1 activation and iNOS expression. LPS and 12(S)-HETE stimulation only or in combination had no effect on iNOS mRNA expression and NO production, and no significant difference was found between the 12 (S)-HETE+LPS group and LPS group [12-hour iNOS mRNA (2 -&Delta;&Delta;Ct) 34.24±4.07 vs. 34.35±4.01, 24-hour NO (μmol/L) 44.02±3.14 vs. 44.56±3.21, both P > 0.05], suggesting that the regulation of CYP1A1 on NO production might not be induced by 12 (S)-HETE. There was no significant difference in the iNOS mRNA expressions or NO content between the CYP1A1m/RAW+LPS group and CYP1A1/RAW+LPS group [12-hour iNOS mRNA (2 -&Delta;&Delta;Ct) 52.11±6.84 vs. 50.21±5.19, 24-hour NO (μmol/L) 60.42±4.14 vs. 52.01±5.12, both P > 0.05], suggesting that CYP1A1 hydroxylase activity deficiency showed no effect on NO production. Conclusions:LPS stimulation significantly increases CYP1A1 expression in macrophages. CYP1A1 overexpression promotes NO production by activated macrophages through AP-1/iNOS pathway, while hydroxylase-deficiency or 12(S)-HETE has no effect on this regulation.