Hypoxia and heat stress affect epithelial integrity in a Caco-2/HT-29 co-culture

Abstract

Hypoxia and hyperthermia, which can be induced by high environmental temperature or strenuous exercise, are two common stressors that affect intestinal epithelial integrity and lead to multiple clinical symptoms. In this study, we developed an in-vitro intestinal monolayer model using two human colonic epithelial cell lines, Caco-2 and HT-29, co-cultured in Transwell inserts, and investigated the effects of heat treatment and/or hypoxia on the epithelial barrier function. The monolayer with a ratio of 9:1 (Caco-2:HT-29) showed high trans-epithelial electrical resistance (TEER), low Lucifer Yellow permeability and high mucin production. Hyperthermia and/or hypoxia exposure (2 h) triggered heat shock and oxidative stress responses. HSP-70 and HSF-1 protein levels were up-regulated by hyperthermia, which were further enhanced when hyperthermia was combined with hypoxia. Increased HIF-1α protein expression and Nrf2 nuclear translocation was only caused by hypoxia. Hyperthermia and/or hypoxia exposure disrupted the established monolayer by increasing paracellular permeability, decreasing ZO-1, claudin-3 and occludin protein/mRNA expression, while enhancing E-cadherin protein expression. Tight junction protein distribution in the monolayer was also modulated by the hyperthermia and/or hypoxia exposure. In addition, transcription levels of mucin genes, MUC-2 and MUC-5AC, were increased after 2 h of hyperthermia and/or hypoxia exposure. In conclusion, this Caco-2/HT-29 cell model is valid and effective for studying detrimental effects of hyperthermia and/or hypoxia on intestinal barrier function and related heat shock and oxidative stress pathways and can be used to investigate possible interventions to reverse hyperthermia and/or hypoxia-induced intestinal epithelial injury.

Novel organic selenium source hydroxy-selenomethionine counteracts the blood-milk barrier disruption and inflammatory response of mice under heat stress

“…In addition, our study showed that the TEER of the cells was significantly lower than CON group after 1 h of heat stress but then recovered, and the difference was extremely significant compared with the CON group. This result is also consistent with the previous studies, which have demonstrated that heat stress treatment decreases TEER in models of monolayer cell barriers, such as the epithelial barrier of intestine, endothelia, blood-brain, and lung (49)(50)(51)(52).…”

Junctional complexes in epithelial cells: sentinels for extracellular insults and intracellular homeostasis

“…It is known that multiple junctional components are highly sensitive to stress and insults. For example, heat shock or oxidative stress can lead to disordered or reduced localization of tight junction proteins claudin-3, occludin, and ZO-1 on the cell membrane and increase their localization in the cytoplasm [130,131]. Heat shock can also reduce the localization of the desmosome adaptor protein plakophilin 3 on desmosomes and lead to the recruitment of plakophilins 3 to stress granules in the cytoplasm [132].…”

Exercise in hypobaric hypoxia increases markers of intestinal injury and symptoms of gastrointestinal distress

“…In addition, at increasing altitudes there is a decrease in the partial pressure of oxygen resulting in hypoxaemia, a lower than normal blood oxygen level. Together hypoperfusion and hypoxaemia result in hypoxic and ischaemia–reperfusion stress which has the potential to injure intestinal epithelial cells and disrupt tight junction protein complexes, resulting in increased intestinal permeability (Lian et al., 2021; van Wijck et al., 2011). This is problematic because increased intestinal permeability allows for luminal contents, including Gram‐negative bacteria containing lipopolysaccharides (LPS), to leak from the intestinal tract where they interact with local innate immune cells (macrophages and monocytes).…”