Architecture, permeability, disruption dynamics and remodeling of tight junction proteins: Implications for performance, health, and welfare of the broiler chicken.

Tight junction (TJ) proteins are a diverse group of proteins that play crucial roles in the formation and function of TJs, a specialized cell-to-cell junction found in the epithelial and endothelial cells for regulating selective permeability of the paracellular pathway, controlling the passage of ions, molecules, and cells across the cell layers. Transmembrane proteins like claudins, occludins, and angulins primarily form the TJ strands. Cytoplasmic plaque proteins, like zonula occludens, connect transmembrane proteins to the actin cytoskeleton, while scaffolding proteins like membrane-associated guanylate kinase inverted (MAGI) and protein associated with LIN7 1 (Pals1) aid in the TJ assembly. Claudins and occludins establish potential barriers in the paracellular pathway, dictating selective permeability and interaction with calcium ions to determine molecule selectivity. Transcellular transport, facilitated by transporter proteins and ion channels, complements this process. Aquaporins regulate water permeability, while calcium-mediated signaling ensures TJ function in response to physiological responses. Nutrient deficiency, oxidative stress, disease, inflammatory mediators, extreme temperatures, gluten sensitivity, and toxins may damage TJ proteins through various pathways resulting in compromised gut barrier integrity, increased permeability of the paracellular pathway, invasions of pathogens, and impaired blood-brain barrier leading to systemic infections, inflammation, and tissue damage. Strategies, including use of prebiotics, probiotics, vitamins, minerals, omega-3 fatty acids, toxin binders, and improved management practices like optimal stocking density, ventilation, lighting, and temperature have been identified to enhance and remodel altered TJ functions. These integrated approaches may stimulate beneficial gut microbes, reduce inflammation, support epithelial cell health, regulate immune responses, and ensure TJ integrity for maintaining a healthy gut barrier for increased productivity, health, and welfare of the broiler chicken.