Effects of <i>In Vitro</i> Fermented <i>Pleurotus eryngii</i> on Intestinal Barrier Integrity and Immunomodulation in a Lipopolysaccharide-Induced Colonic Model

<b>Background</b>: This study investigates the impact of fermentation supernatants (FSs) from <i>Pleurotus eryngii</i> whole mushrooms (PEWS), as well as its subcomponents, digested (PEWSD) and extracted (PEWSE) forms, on intestinal barrier function and immune modulation in lipopolysaccharide (LPS) -stimulated Caco-2 cells. <b>Methods</b>: Gene expression of tight junction (TJs) genes, cytokines, and key immune/metabolic receptors was assessed via qRT-PCR, while cytokine protein levels were measured using ELISA to explore post-transcriptional regulation. <b>Results</b>: LPS challenge significantly downregulated TJs <i>zonula occludens</i>-1 (<i>ZO-1</i>,) <i>occludin</i>, and <i>claudin-1</i>, compromising epithelial integrity. Treatment with FS-PEWS notably restored <i>ZO-1</i> and <i>occludin</i> expression, outperforming FS-PEWSD and FS-PEWSE, which only partially mitigated the LPS-induced damage. FS-PEWS further demonstrated potent immunomodulatory effects, upregulating anti-inflammatory <i>IL-10</i> and pro-inflammatory cytokines such as <i>IL-8</i> and <i>TNF-α</i>. The activation of key receptors like <i>TLR-2</i> and <i>mTOR</i> suggests that FS-PEWS modulates critical immune and metabolic pathways, such as <i>NF-kB</i> signaling, to maintain immune homeostasis. Although mRNA expression of pro-inflammatory cytokines was altered, no corresponding protein release was detected, suggesting potential post-transcriptional regulation. <b>Conclusions</b>: FS-PEWS preserves intestinal barrier integrity and modulates immune responses, particularly in low-grade inflammation, highlighting the whole food matrix’s role in enhancing its bioactivity and functional food potential.