Fig. 9

Downregulation of CYP4X1 by a PD-1/PD-L1 inhibitor inactivates PPARα and forms a positive feedback loop in colonic macrophages. In the B16F10 melanoma model, the mice were intraperitoneally administered with the PD-1/PD-L1 inhibitor BMS-1 (0, 5 and 10 mg/kg) every 2 days for 6 times (n = 10). A CYP4X1 mRNA and protein levels in colonic macrophages. B The level of 14,15-EET-EA in colonic macrophages was determined by liquid chromatography tandem-mass spectrometry (LC-MS/MS). C In the B16F10 melanoma model, the wild type (WT) and Cyp4x1 knockout mice (Cyp4x1^−/−) mice were intraperitoneally administered with BMS-1 (10 mg/kg) every two days for 6 times (n = 10). The production of 14,15-EET-EA in colonic macrophages was determined by LC-MS/MS. D M1 factors (IL-1β and TNF-α) in colonic macrophages were determined by ELISA. E Representative images of TUNEL assay of cardiac tissues and corresponding quantification analysis. Scale bars, 50 μm. F The serum levels of creatine kinase (CK), lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB) and aspartate transaminase (AST). G PPARα mRNA and protein levels in colonic macrophages. H HL-1 cardiomyocytes were treated with the conditioned medium (CM) from the peritoneal macrophages (PNMS) in the mice treated with PD-1/PD-L1 inhibitor plus 14,15-EET-EA (n = 5). I PPARα mRNA and protein levels in the PNMS. J M1 factors (IL-1β and TNF-α) in the PNMS. K Representative images of TUNEL assay of HL-1 cardiomyocytes and corresponding quantification analysis. Scale bars, 50 μm. The values are presented as the mean ± standard error of the mean. ^*P < 0.05, ^**P < 0.01 vs. control, WT or BMS-1