Anti-inflammatory Activity of Magnesium Isoglycyrrhizinate Through Inhibition of Phospholipase A2/Arachidonic Acid Pathway

Glycyrrhiza glabra (licorice) has been known to possess various pharmacological properties including anti-inflammatory, antioxidants, antiviral, and hepatoprotective activities. Magnesium isoglycyrrhizinate (MgIG), a magnesium salt of 18-α glycyrrhizic acid stereoisomer, is clinically used for the treatment of inflammatory liver diseases. However, the mechanism by which MgIG exerts its anti-inflammatory effects remains unknown. In the present study, we investigated the inhibitory potential of MgIG in phospholipase A 2 (PLA 2 )/arachidonic acid (AA) pathway and release of the pathway-generated inflammatory lipid mediators in RAW264.7 macrophages. Results revealed that MgIG suppressed LPS-induced activation of PLA 2 and production of AA metabolites such as prostaglandin E 2 (PGE 2 ), prostacyclin (PGI 2 ), thromboxane 2 (TXB 2 ), and leukotrienes (LTB 4 ) in macrophages. Furthermore, LPS-induced AA-metabolizing enzymes including COX-2, COX-1, 5-LOX, TXB synthase, and PGI 2 synthase were significantly inhibited by MgIG. Taken together, our data suggest that modulation of cyclooxygenase (COXs) and 5-lipoxygenase (LOX) pathways in AA metabolism could be a novel mechanism for the anti-inflammatory effects of MgIG.