PTGS1 and chronic kidney disease: While the mRNA levels of COX-1, COX-2, and AKR1C18 were unchanged, the mRNA level of 15-PGDH was significantly reduced in CKD kidneys of Alox15−/− mice when compared with those of WT mice (Fig. 8b, P = 0.0325), that potentially lead to the increase in PGD2 in CKD kidneys of Alox15−/− mice.