To explore the protective effect of Angelica sinensis polysaccharide(ASP)on leptospiro-sis induced by pathogenic Leptospira infection,the golden hamster model of leptospirosis was se-lected for the experiment.The Leptospira and Leptospira+ASP groups were intraperitoneally injected with Leptospira interrogans serovar Lai strain 56601(1 × 10 6 per hamster).After infec-tion,the Leptospira+ASP group was injected intraperitoneally with ASP(50 mg/kg)for three consecutive days,while the Leptospira group was injected intraperitoneally with normal saline for three days.The experiment employed methods such as daily observation of the clinical symptoms of golden hamsters,statistics of the survival status of each group of golden hamsters,pathological damage of liver,kidney,and lung,bacterial load in organs,and the expression of inflammatory cy-tokines(IL-1β and TNF-α).The results indicated that ASP could effectively alleviate the clinical symptoms of the infected hamsters,enhance the survival rate,ameliorate the pathological damage of the body,reduce the bacterial load in various organs,and mitigate tissue inflammation.This study demonstrated for the first time that ASP has a protective effect on leptospirosis,providing medication guidance for the clinical treatment of leptospirosis.

To explore the protective effect of Angelica sinensis polysaccharide(ASP)on leptospiro-sis induced by pathogenic Leptospira infection,the golden hamster model of leptospirosis was se-lected for the experiment.The Leptospira and Leptospira+ASP groups were intraperitoneally injected with Leptospira interrogans serovar Lai strain 56601(1 × 10 6 per hamster).After infec-tion,the Leptospira+ASP group was injected intraperitoneally with ASP(50 mg/kg)for three consecutive days,while the Leptospira group was injected intraperitoneally with normal saline for three days.The experiment employed methods such as daily observation of the clinical symptoms of golden hamsters,statistics of the survival status of each group of golden hamsters,pathological damage of liver,kidney,and lung,bacterial load in organs,and the expression of inflammatory cy-tokines(IL-1β and TNF-α).The results indicated that ASP could effectively alleviate the clinical symptoms of the infected hamsters,enhance the survival rate,ameliorate the pathological damage of the body,reduce the bacterial load in various organs,and mitigate tissue inflammation.This study demonstrated for the first time that ASP has a protective effect on leptospirosis,providing medication guidance for the clinical treatment of leptospirosis.

Leptospirosis is a global natural zoonotic infectious disease.Research shows that short-chain fatty acids,metabolites of gut microbiota,are involved in host immune regulation and affect disease progression.This experiment was conducted to investigate the role of short-chain fatty acids in leptospirosis.The results showed that supplementation of short-chain fatty acid butyric acid could significantly improve the survival rate of leptospirosis in hamsters.In vitro experiments showed that butyric acid treatment inhibited the expression of Cat and Gsr genes in macrophages after infection with Leptospira,but enhanced the expression of NOX1 and NOX4 genes.At the same time,butyric acid treatment enhanced macrophage ROS levels after leptospirosis infection,and high levels of ROS enhanced the bactericidal function of macrophages.In vivo experiments al-so confirmed that butyric acid protects hamsters against acute leptospirosis by regulating ROS production.Collectively,the short-chain fatty acid butyric acid,a metabolite of gut microbiota,en-hances the bactericidal function of macrophages by regulating ROS expression,thereby protecting the host against leptospirosis.