Probiotic component enhances macrophage's protective innate immune functions and protects against sepsis in rats

Probiotics are nonpathogenic microorganisms or their components which play a beneficial role to the host innate immune system. Sepsis is a systemic inflammatory response to infections or injury. Currently, prevention and treatment of sepsis are still a major challenge in the clinical practice. Here we first investigated the protective role of a bacterial free probiotic component (PC) in polymicrotial sepsis induced by cecal ligation and puncture (CLP). Briefly, PC was prepared from Lactobacillus sp. (ATCC#53103). Rats (Sprague‐Dawley) were respectively fed with PC or the vehicle for 5 days, subjected to CLP, and continuously treated with PC or vehicle after CLP on a daily basis. In CLP group, about 70% of animals were died within 9 days. In contrast, only 25% of animals were died after CLP in “PC + CLP” group. The data suggested that oral delivery of PC protects against CLP‐induced death. Furthermore, we found that the PC‐induced protection was associated with an increase in bacterial clearance in the liver. To explore underlying mechanisms through which PC protects against sepsis, we studied whether PC targets macrophages (MΦ). We found that MΦ derived from PC‐treated rats had the enhanced‐capacity on cytokine production in response to LPS or PC stimulation. Treatment of MΦ with PC resulted in up‐regulating expression of antimicrobial molecules in MΦ and enhancing bactericidal activity of the cells. Together the data suggested that PC enhances the protective innate immune capacity of MΦ, which may result in protection against sepsis. Study funding: NIH, IDPA, Batts Family.