Therapeutic Benefits Of The Group B3Vitamin Nicotinamide In Mice With Lethal Endotoxemia And Polymicrobial Sepsis

Objective To investigate the therapeutic effects of NAM in murinemodels of endotoxemia and sepsis, provide novel strategies for thetreatment of sepsis. Methods Endotoxemic liver injury was induced byintraperitoneal injection of lipopolysaccharide (LPS) into D-Galactosamine(DGal)-sensitized mice，LPS at a dose of10ug/kg，D-Gal at a dose of700mg/kg. Lethal endotoxemia was induced by intraperitoneal administrationof LPS at a dose of20mg/kg. Polymicrobial sepsis was induced by cecalligation and puncture (CLP). The pre-protective and therapeutic benefits ofNAM in LPS/D-Gal exposed mice，mice were treated with vehicle orvarious doses of NAM（100mg/kg,200mg/kg，400mg/kg）at30min beforeLPS/D-Gal exposure or NAM (400mg/kg) was injected at various timepoints (1h,3h,6h) after LPS/d-Gal exposure. Survival was monitored andthe percent survival rate was expressed as Kaplan–Meier survival curves.Blood and liver samples were harvested at6h after LPS/d-Gal exposure.The serum levels of alanine aminotransferase (ALT) and aspartateaminotransferase (AST) were determined，hepatic caspase-3, caspase-8and caspase-9activities were determined. Liver sections were stained withhematoxylin–eosin for morphological evaluation and liver apoptosis wasdetermined by TUNEL assay. Blood samples were harvested at1.5h afterLPS/d-Gal exposure and TNF-α level in serum was determined. In lethaldose of lipopolysaccharide exposed mice, mice were treated with vehicle orNAM (400mg/kg) was injected at30min before or1h after LPS challenge.Survival was monitored and the percent survival rate was expressed asKaplan–Meier survival curves. Blood samples were harvested at3h afterLPS challenge, the levels of TNF-α and IL-6in serum were determined.Blood and lung samples were harvested at12h after LPS challenge, thelevels of ALT, BUN in serum were determined，lung samples stained withhematoxylin–eosin for morphological evaluation. And the W/D weightratio of lung tissues were determined，too. In sepsis model, NAM (400mg/kg) was injected at1h after CLP, survival was monitored and thepercent survival rate was expressed as Kaplan–Meier survival curves.Results In mice challenged with LPS/D-Gal, treatment with NAMsignificantly deceased serum aminotransferases level and alleviated hepaticlesions. NAM also reduced serum tumor necrosis factor-α level andattenuated apoptosis in liver, as assessed by terminal deoxynucleotidyltransferase-mediated nucleotide nick end labeling (TUNEL) staining andmeasurements of caspases activities. Survival analysis indicated that NAMreduced the mortality rate of LPS/D-Gal-challenged mice. In mice with lethal endotoxemia, NAM reduced serum level of pro-inflammatorycytokines and multiple organ damage as evidenced by improvedmorphological lesion, reduced lung wet to dry ratio as well as decreasedserum level of aminotransferase and blood urea nitrogen. In survivalanalysis, treatment with NAM increased the survival rate of mice withlethal endotoxemiaor and CLP-induced polymicrobial sepsis. ConclusionTaken together, treatment with NAM might provide therapeutic benefits insepsis, which attenuated inflammatory injury and improved the survivalrate.