BACKGROUND: Clostridioides difficile infection (CDI) is a debilitating nosocomial disease. Postmenopausal women may have an increased risk of CDI, suggesting estrogen influence. Soybean products contain a representative estrogenic isoflavone, genistein. METHODS: The anti-inflammatory and antiapoptotic effects of genistein were determined using primary human cells and fresh colonic tissues. The effects of oral genistein therapy among mice and hamsters were evaluated. RESULTS: Within 10 days of CDI, female c57BL/6J mice in a standard environment (regular diet) had a 50% survival rate, while those with estrogen depletion and in an isoflavone-free environment (soy-free diet) had a 25% survival rate. Oral genistein improved their 10-day survival rate to 100% on a regular diet and 75% in an isoflavone-free environment. Genistein reduced macrophage inflammatory protein-1α (MIP-1α) secretion in fresh human colonic tissues exposed to toxins. Genistein inhibited MIP-1α secretion in primary human peripheral blood mononuclear cells, abolished apoptosis and BCL-2-associated X (BAX) expression in human colonic epithelial cells, and activated lysine-deficient protein kinase 1 (WNK1) phosphorylation in both cell types. The anti-inflammatory and antiapoptotic effects of genistein were abolished by inhibiting estrogen receptors and WNK1. CONCLUSIONS: Genistein reduces CDI disease activity by inhibiting proinflammatory cytokine expression and apoptosis via the estrogen receptor/G-protein estrogen receptor/WNK1 pathways.

BACKGROUND: Clostridium difficile infection (CDI) is a debilitating nosocomial infection. C. difficile produces toxins A and B, which cause inflammation. Existing therapies have issues with recurrence, cost, and safety. We aim to discover a safe, effective, and economical nonmicrobiological therapeutic approach against CDI. METHODS: We included human primary peripheral blood mononuclear cells (PBMCs), fresh human colonic explants, and humanized HuCD34-NCG mice. Toxin A+B+ VPI 10463 and A-B+ ribotype 017 C. difficile strains were used. We used single-cell RNA profiling and high-throughput screening to find actionable toxin B-dependent pathways in PBMCs. RESULTS: Histamine 1 receptor-related drugs were found among the hit compounds that reversed toxin-mediated macrophage inflammatory protein (MIP) 1α expression in PBMCs. We identified loratadine as the safest representative antihistamine for therapeutic development. Loratadine inhibited toxin B-induced MIP-1α secretion in fresh human colonic tissues. Oral loratadine (10 mg/kg/d) maintained survival, inhibited intestinal CCl3 messenger RNA expression, and prevented vancomycin-associated recurrence in the VPI 10463-infected mice and ribotype 017-infected hamsters. Splenocytes from loratadine-treated mice conferred anti-inflammatory effects to the VPI 10463-infected T/B-cell--deficient Rag-/- mice. Oral loratadine suppressed human MIP-1α expression in monocytes/macrophages in toxin B-expressing ribotype 017-infected humanized HuCD34-NCG mice. CONCLUSIONS: Loratadine may be repurposed to optimize existing therapies against CDI.