Abstract
The effect of a chum salmon egg lectin (CSL3) on tight junction (TJ) of Caco-2 cell monolayers was investigated. The lectin opened TJ as indicated by the decrease of the transepithelial electrical resistance (TER) value and the increase of the permeation of lucifer yellow, which is transported via the TJ-mediated paracellular pathway. The effects of CSL3 were inhibited by the addition of 10 mM L-rhamnose or D-galactose which were specific sugars for CSL3. The lectin increased the intracellular Ca2+ of Caco-2 cell monolayers, that could be inhibited by the addition of L-rhamnose. The fluorescence immunostaining of β-actin in Caco-2 cell monolayers revealed that the cytoskeleton was changed by the CSL3 treatment, suggesting that CSL3 depolymerized β-actin to cause reversible TJ structural and functional disruption. Although Japanese jack bean lectin and wheat germ lectin showed similar effects in the decrease of the TER values and the increase of the intracellular Ca2+, they could not be inhibited by the same concentrations of simple sugars, such as D-glucose and N-acetyl-D-glucosamine.
Highlights
Lectins are a group of non-catalytic sugar-binding proteins that are widely distributed in varying amounts in most common foods [1,2]
The present study investigated the effects of a chum salmon egg lectin, CSL3, on tight junction (TJ) of Caco-2 cell monolayers in more detail, to gain insight concerning the function of food lectins
Caco-2 cell monolayers were incubated with various concentrations of CSL3 for 2–6 h and their transepithelial electrical resistance (TER) values were measured (Figure 2A)
Summary
Lectins are a group of non-catalytic sugar-binding proteins that are widely distributed in varying amounts in most common foods [1,2]. Such lectins as the legume type have tolerance against heating, acidic pH and proteolytic digestion; the digestive tract is constantly exposed to the biologically active lectins contained in fresh and processed foods [3,4,5]. We have shown that lectins contained in foodstuff had varying modulating effects on the transport system of human intestinal Caco-2 cell monolayers [13,14,15]. The present study investigated the effects of a chum salmon egg lectin, CSL3, on TJ of Caco-2 cell monolayers in more detail, to gain insight concerning the function of food lectins. The effects of Japanese jack bean lectin (CGA) and wheat germ lectin (WGA) were examined
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