Curcumin prevents leptin-induced tight junction dysfunction in intestinal Caco-2 BBe cells

Maintaining tight junction (TJ) integrity in the intestine is critical for nutrient absorption, host defense, and host immunity. While leptin secreted from adipose tissue is associated with obesity and obesity-related intestinal inflammation, the role of luminal leptin in intestinal TJ function is elusive. Here, we examined the role of leptin in intestinal TJ function in Caco-2 BBe cells and further explored the function of curcumin (CCM) in leptin-induced TJ dysfunction. Apical leptin, but not basolateral leptin, treatment at a concentration of 100 ng/ml deteriorated TJ function in Caco-2 BBe cells. Leptin-impaired TJ alteration was resulted from induction of leptin receptor-dependent JAK2/STAT3 signaling pathway and its-related PI3K/Akt/ERK1/2 signaling pathways. Apical leptin also lowered the expression levels of genes encoding TJ-associated proteins such as zonula occludens-3, claudin-5, and occludin, and elevated expression of pro-inflammatory genes such as IL-6 and TNF-α. Leptin-impaired TJ junction in Caco-2 BBe cells was blunted by a 30-min CCM pretreatment through inhibition of leptin receptor-dependent signaling pathway, and its-associated induction of expression of genes encoding TJ-associated proteins and pro-inflammatory cytokines. Our results elucidate a novel function of luminal leptin in intestinal TJ dysfunction, and further identify CCM as an effective dietary compound that prevents leptin-impaired TJ function in intestinal cells.