Glutathione S-transferase 3, mitochondrial
glutathione transferase activity
Biosynthesis of prostaglandin 15dPGJ<sub>2</sub> -glutathione and 15dPGJ<sub>2</sub>-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<sub>2</sub> and can lead to shunting of PGH<sub>2</sub> into the prostaglandin D<sub>2</sub> (PGD<sub>2</sub>)/15-deoxy-Δ<sup>12,14</sup>-prostaglandin J<sub>2</sub> (15dPGJ<sub>2</sub>) pathway. 15dPGJ<sub>2</sub> 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<sub>2</sub> via conjugation with GSH, to form 15dPGJ<sub>2</sub>-glutathione (15dPGJ<sub>2</sub>-GS) and 15dPGJ<sub>2</sub>-cysteine (15dPGJ<sub>2</sub>-Cys) conjugates and to characterize the effects of mPGES-1 inhibition on the PGD<sub>2</sub>/15dPGJ<sub>2</sub> pathway in mouse and human immune cells. Our results demonstrate the formation of PGD<sub>2</sub>, 15dPGJ<sub>2</sub>, 15dPGJ<sub>2</sub>-GS, and 15dPGJ<sub>2</sub>-Cys in RAW264.7 cells after lipopolysaccharide stimulation. Moreover, 15dPGJ<sub>2</sub>-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<sub>2</sub> conjugates. In contrast to inhibition of cyclooxygenase, which leads to blockage of the PGD<sub>2</sub>/15dPGJ<sub>2</sub> pathway, we found that inhibition of mPGES-1 preserves PGD<sub>2</sub> and its metabolites. Collectively, this study highlights the formation of 15dPGJ<sub>2</sub>-GS and 15dPGJ<sub>2</sub>-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.