Lactobacillus paracasei normalizes muscle hypercontractility in a murine model of postinfective gut dysfunction

Background & Aims: The effects of probiotics on gut dysfunction in postinfective irritable bowel syndrome are unknown. We tested whether probiotics influence persistent muscle hypercontractility in mice after recovery from infection with Trichinella spiralis and analyzed the underlying mechanisms. Methods: Mice were gavaged with Lactobacillus paracasei, Lactobacillus johnsonii, Bifidobacterium longum, or Bifidobacterium lactis in spent culture medium from days 10 to 21 after infection. Additional mice received heat-inactivated Lactobacillus paracasei, Lactobacillus paracasei-free spent culture medium, or heat-inactivated Lactobacillus paracasei-free spent culture medium. Lactobacilli enumeration, immunohistochemistry, and cytokine detection (enzyme-linked immunosorbent assay) were performed. Mice were also treated with Lactobacillus paracasei or Lactobacillus paracasei-free spent culture medium from days 18 to 28 after infection. Contractility was measured on days 21 and 28 after infection. Results: Lactobacillus paracasei, but not Lactobacillus johnsonii, Bifidobacterium lactis, or Bifidobacterium longum, attenuated muscle hypercontractility. This was associated with a reduction in the Trichinella spiralis-associated T-helper 2 response and a reduction in transforming growth factor-beta1, cyclooxygenase-2, and prostaglandin E-2 levels in muscle. Attenuation of muscle hypercontractility by Lactobacillus paracasei-free spent culture medium was abolished after heat treatment. Improvement of muscle hypercontractility at day 28 after infection was also observed after the administration of Lactobacillus paracasei or Lactobacillus paracasei-free spent culture medium from day 18 after infection. Conclusions: Probiotics show strain-dependent attenuation of muscle hypercontractility in an animal model of postinfective irritable bowel syndrome. This likely occurs via both a modulation of the immunologic response to infection and a direct effect of Lactobacillus paracasei or a heat-labile metabolite on postinfective muscle hypercontractility. Lactobacillus paracasei may be useful in the treatment of postinfective irritable bowel syndrome.