LTA

Lipoteichoic acid (LTA), a component of the Gram-positive bacterial cell wall, exhibits potent immunomodulatory properties. However, it is highly unstable and susceptible to degradation under gastrointestinal conditions, which limits its in vivo functional application. In this study, LTA from theLactobacillus johnsonii was encapsulated into chitosan-tripolyphosphate (CS-TPP) nanoparticles for the first time, establishing a robust delivery system. The resulting LTA@CS-TPP nanoparticles displayed uniform nano size, favorable stability, high encapsulation efficiency, and sustained release behavior. Simulated digestion assays demonstrated that nanoencapsulation effectively protected LTA from gastric degradation and enabled controlled release in the intestinal phase. Cellular experiments showed that LTA@CS-TPP enhanced antioxidative stress defenses, reduced intracellular ROS levels, and alleviated LPS-induced inflammatory injury. Immunofluorescence analysis further revealed that LTA@CS-TPP significantly suppressed NF-κB activation and nuclear translocation, suggesting interference with the TLR₄/MyD88/NF-κB signaling cascade. Compared with free LTA, nanoencapsulation not only preserved but also amplified its bioactivity, whereas blank CS-TPP nanoparticles exerted minimal effects. Collectively, these findings provide the first evidence of chitosan-based nanoencapsulation of LTA and highlight its potential as a bioactive delivery platform for inflammation modulation, laying the groundwork for future oral administration studies with promising applications in functional foods and therapeutic strategies.

Heat stress compromises the intestinal mucosal barrier, whereas bifidobacteria preserve its structural integrity. L-theanine (LTA) elevates intestinal Bifidobacterium abundance in heat-stressed mice, thereby alleviating barrier damage. This protection may occur through heat shock factor 1 (Hsf1) regulation, though the precise mechanism requires further elucidation. We investigated the mechanism for the protective effect of L-theanine against heat stress: the LTA protects the intestinal mucosal barrier to alleviate heat stress through Hsf1 and is mediated by Bifidobacterium for Hsf1 regulation. These investigations employed LTA interventions in heat-stressed MODE-K cells, Hsf1-knockout mice, pseudo-germ-free mice, and LTA-Bifidobacterium longum (BL) co-culture experiments. In heat-stressed MODE-K cells, LTA intervention significantly increased cell viability, improved mucosal barrier function, and inhibited Hsf1 and its target proteins Hsp70 and Hsph1. These effects were no longer observed in the Hsf1-inhibited cells but were enhanced in the Hsf1-overexpressing cells. Consistently, LTA failed to protect the intestinal mucosal barrier in heat-stressed Hsf1-knockout mice. In pseudo-germ-free mice and co-culture experiments, BL improved intestinal morphology, protected mucosal barrier function, and suppressed Hsf1 and its target proteins. The effects of L-theanine and BL were superior to those of BL alone. These findings indicate that L-theanine protects the intestinal mucosal barrier in a manner dependent on Bifidobacterium and the Hsf1 signaling pathway.