Discovery of Topoisomerase I Inhibitor Nitidine Derivatives with IL-10 Enhancing Activity for the Treatment of Sepsis

Nitidine chloride (NC) is a natural product that promotes the expression of interleukin-10 (IL-10) in macrophages by inhibiting topoisomerase I (TopoI) under stimulation by lipopolysaccharides (LPSs) and can be used in the treatment of sepsis. However, NC's poor water solubility limits its applications. This study aimed to design and synthesize a series of derivatives by simplifying the A- and E-rings in the structure of NC and introducing oxygen-containing groups, using NC as the lead compound. In this work, the ability of NC and its derivatives to induce IL-10 secretion and inhibit TopoI was evaluated. The water solubility of the compounds was determined in phosphate-buffered saline. An LPS-induced sepsis in mice was prepared to assess the activity of the compounds in vivo. Our data suggested that compound 6F showed better activity in inducing IL-10 secretion and inhibiting TopoI, and its water solubility was at least 500-fold higher than that of NC. When septic mice were given 6F (3 mg/kg), their survival rate was comparable to those treated with NC. Based on our findings, 6F may be a new drug candidate for the treatment of sepsis.