Biosynthesis of prostaglandin 15dPGJ(2) -glutathione and 15dPGJ(2)-cysteine conjugates in macrophages and mast cells via MGST3

Inhibition of microsomal prostaglandin E synthase-1 (mPGES-1) results in decreased production of proinflammatory PGE(2) and can lead to shunting of PGH(2) into the prostaglandin D(2) (PGD(2))/15-deoxy-Δ(12,14)-prostaglandin J(2) (15dPGJ(2)) pathway. 15dPGJ(2) forms Michael adducts with thiol-containing biomolecules such as GSH or cysteine residues on target proteins and is thought to promote resolution of inflammation. We aimed to elucidate the biosynthesis and metabolism of 15dPGJ(2) via conjugation with GSH, to form 15dPGJ(2)-glutathione (15dPGJ(2)-GS) and 15dPGJ(2)-cysteine (15dPGJ(2)-Cys) conjugates and to characterize the effects of mPGES-1 inhibition on the PGD(2)/15dPGJ(2) pathway in mouse and human immune cells. Our results demonstrate the formation of PGD(2), 15dPGJ(2), 15dPGJ(2)-GS, and 15dPGJ(2)-Cys in RAW264.7 cells after lipopolysaccharide stimulation. Moreover, 15dPGJ(2)-Cys was found in lipopolysaccharide-activated primary murine macrophages as well as in human mast cells following stimulation of the IgE-receptor. Our results also suggest that the microsomal glutathione S-transferase 3 is essential for the formation of 15dPGJ(2) conjugates. In contrast to inhibition of cyclooxygenase, which leads to blockage of the PGD(2)/15dPGJ(2) pathway, we found that inhibition of mPGES-1 preserves PGD(2) and its metabolites. Collectively, this study highlights the formation of 15dPGJ(2)-GS and 15dPGJ(2)-Cys in mouse and human immune cells, the involvement of microsomal glutathione S-transferase 3 in their biosynthesis, and their unchanged formation following inhibition of mPGES-1. The results encourage further research on their roles as bioactive lipid mediators.