Cortisol-Mediated Disruption of Intestinal Tight Junction Proteins

Chronic psychological stress is frequently reported by patients with functional gut disorders, yet the direct mechanistic link between hypothalamic-pituitary-adrenal (HPA) axis activation and intestinal barrier dysfunction had not been characterised in humans. This study combined an in vitro intestinal epithelial cell model (Caco-2 monolayer) with an in vivo human crossover design using the standardised Trier Social Stress Test (TSST) — a validated protocol for inducing acute cortisol elevation under controlled conditions.

Eighty-four adults (42 high cortisol responders, 42 low-responder controls) provided intestinal biopsies before and 48 hours after TSST stress induction. Tight junction protein expression (claudin-1, occludin, ZO-1) was quantified by Western blot and immunofluorescence. In high-stress responders, cortisol elevation dose-dependently reduced tight junction protein expression by 28–41% across all three proteins (p<0.001). A parallel treatment arm of 24 high-stress responders who received Lactobacillus helveticus R0052 supplementation for 4 weeks prior to TSST stress showed 60% attenuation of tight junction downregulation (p=0.004), providing the first human evidence that specific probiotic supplementation can meaningfully buffer HPA-axis-mediated gut barrier disruption.