High-tryptophan diet mitigates parvalbumin-induced allergic responses via gut microbiome remodeling and immune modulation.

Parvalbumin-induced food allergy model in BALB/c mice were established to investigate the intervention effect of high- tryptophan (Trp) diet on allergic responses. Trp suppressed histamine and IL-6 release from the sensitized KU812 cells, effectively mitigated parvalbumin-induced cellular sensitization. High-Trp diet alleviated allergic symptoms, reduced the organ index of the spleen and serum specific IgE, IgG, IgG1 and IgG2a levels, alongside suppressed Th2-type immune responses in mice. Meanwhile, Trp not only influenced the relative abundance of allergy-related gut microbiome, such as Faecalibaculum, Romboutsia, Lachnoclostridium unclassified_f__Lachnospiracea and norank_f__Ruminococcaceae, but also increased the production of short-chain fatty acids. Meanwhile, Trp enhanced the expression of intestinal tight junction proteins, repaired the impaired intestinal barrier in allergic mice, and also induced the phosphorylation of STAT3 and enhanced the expression of Reg3γ, then may activated the AhR/IL-22 signal pathway in murine intestinal epithelial cells. These findings demonstrated that high-Trp diet mitigated parvalbumin-induced allergic responses were responsible for gut microbiome remodeling and immune modulation.