Analysis of the mechanism of the tight-junctional permeability increase by capsaicin treatment on the intestinal Caco-2 cells.

In a previous experiment (Isoda et al., 2001), we showed that the tight-junctional (TJ) permeability increase in Caco-2 cells during capsaicin exposure was through binding of the capsaicin molecule to a capsaicin receptor-like protein. In the present study, we examined how actin, which modulates TJ permeability, is influenced by capsaicin. We showed that after treatment of the Caco-2 cells with capsaicin, the volume of F-actin decreased. Moreover, we also examined protein kinase C (PKC) and heat shock protein 47 (HSP47), which act as probable second messengers in causing TJ permeability increase. We showed that after capsaicin treatment, HSP47 was activated. However, PKC activity was the same in both control and treatment setups. These results suggest that, while PKC is not involved, it is highly possible that HSP47plays a role in TJ permeability increase in intestinal Caco-2 cells exposed to capsaicin.