Synthesis of Glycyrrhizin Analogues as Hmgb1 Inhibitors and Their Activity Against Sepsis in Acute Kidney Injury

Glycyrrhizin (GL) is one of the antagonists of highly conserved nuclear protein(HMGB1). Research shows that the glycosyl of GL is an important pharmacophore for GL binding to HMGB1, and it is the determinant of mechanism of action. To get the HMGB1 inhibitors with higher activity and good pharmacokinetic properties, two classes of GL analogues containing C-N glycoside bond were synthesized, and their anti-inflammatory, anti-oxidative stress and anti-septic kidney injury were evaluated. The results are as follows. First, in the anti-inflammatory assay, all the compounds inhibited NO release in some degree; among them, compound 6 displayed the strongest NO inhibitory effect with IC50 value of 15.9 μM, and compound 15 with IC50 value of 20.2 μM was the next.The two compounds not only dec IL-1β and TNF-α levels in RAW264.7 cells and HK-2 cells, but also downregulated the levels of NLRP3, P-NF-κB p65 and HMGB1 in activated HK-2 cells in a dose-dependent manner. Second, in the renal protection assay with H2O2-stimulated HK-2 cells line, they reduced MDA level and increased SOD level in HK-2 cells; additionally, they also inhibited the HK-2 cells apoptosis and downregulated the Caspase-1 p20 level. Third, in the in vivo activity tests of the septic mouse, they showed the same activities as in vitro, decreasing the IL-1β, TNF-α, MDA, blood creatinine (Scr) and urea nitrogen (BUN) in serum, and increasing SOD levels in a dose-dependent manner. The immunoblotting results also showed the two compounds downregulated the levels of HMGB1, P-NF-κB p65, NLRP3 and Caspase-1 p20 protein. All in all, the two compounds improved the renal injury of septic mice, and alleviated the tube wall structure damage and renal tubular dilation in kidney, which further proved by H&E staining. This suggests the two compounds have septic acute kidney injury activity, and they will be potential therapeutic drugs for septic acute kidney injury.