Abstract
Salmonella typhimurium, a Gram-negative food-borne pathogen, induces impairment in intestinal mucosal barrier function frequently. The injury is related to many factors such as inflammation, oxidative stress, tight junctions and flora changes in the host intestine. Musca domestica cecropin (Mdc), a novel antimicrobial peptide containing 40 amino acids, has potential antibacterial, anti-inflammatory, and immunological functions. It remains unclear exactly whether and how Mdc reduces colonic mucosal barrier damage caused by S. typhimurium. Twenty four 6-week-old male mice were divided into four groups: normal group, control group (S. typhimurium-challenged), Mdc group, and ceftriaxone sodium group (Cs group). HE staining and transmission electron microscopy (TEM) were performed to observe the morphology of the colon tissues. Bacterial load of S. typhimurium in colon, liver and spleen were determined by bacterial plate counting. Inflammatory factors were detected by enzyme linked immunosorbent assay (ELISA). Oxidative stress levels in the colon tissues were also analyzed. Immunofluorescence analysis, RT-PCR, and Western blot were carried out to examine the levels of tight junction and inflammatory proteins. The intestinal microbiota composition was assessed via 16s rDNA sequencing. We successfully built and evaluated an S. typhimurium-infection model in mice. Morphology and microcosmic change of the colon tissues confirmed the protective qualities of Mdc. Mdc could inhibit colonic inflammation and oxidative stress. Tight junctions were improved significantly after Mdc administration. Interestingly, Mdc ameliorated intestinal flora imbalance, which may be related to the improvement of tight junction. Our results shed a new light on protective effects and mechanism of the antimicrobial peptide Mdc on colonic mucosal barrier damage caused by S. typhimurium infection. Mdc is expected to be an important candidate for S. typhimurium infection treatment.
Highlights
Salmonella typhimurium is an important Gram-negative foodborne pathogen with a broad host range including humans and animals, and causes diseases ranging from gastroenteritis and diarrhea to life-threatening systemic infections (Wan et al, 2018), resulting in one million human deaths annually (Balasundaram et al, 2017)
We elucidate how antimicrobial peptide (AMP) Musca domestica cecropin (Mdc) improve the damage of colonic mucosal barrier by regulating intestinal flora for the first time, other common functions of AMPs have been verified
There are many Salmonella infection models that can be used to study different types of intestinal injury (Santos et al, 2001), the S. typhimurium infection model used in this experiment is usually used to establish colonic mucosal lesions (Manja et al, 2003)
Summary
Salmonella typhimurium is an important Gram-negative foodborne pathogen with a broad host range including humans and animals, and causes diseases ranging from gastroenteritis and diarrhea to life-threatening systemic infections (Wan et al, 2018), resulting in one million human deaths annually (Balasundaram et al, 2017). Owing to their metabolic versatility, Salmonella can colonize as multicellular aggregates on various surfaces, enhancing virulence levels through biofilm formations that often resist antibiotic therapy (Faccone et al, 2018; Kuang et al, 2018; Ridge et al, 2018; Wan et al, 2018). A relative increase in some inflammatory factors may attenuate zonula occluding protein expression, leading to intestinal barrier dysfunction, and promotion of intestinal inflammation in the colonic mucosa (Ogawa et al, 2018)
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