Cytotoxicity of absorption enhancers in Caco-2 cell monolayers

This study was performed to evaluate the utility of absorption enhancers wi th reference to mucosal cell cytotoxicity. Overall assessment of the damage to plasma, lysosomal and nuclear membranes by three absorption enhancers, sodium deoxycholate, sodium caprate and dipotassium glycyrrhizinate, was pe rformed on Caco-2 cell monolayers. The cytotoxicities of sodium deoxycholate (0.02-0.1% w/v), sodium caprate ( 0.1-0.5% w/v) and dipotassium glycyrrhizinate (0.5-2% w/v) were evaluated b y the trypan blue-exclusion test, the protein-release test, the neutral-red assay, the DNA-propidium iodide staining test and the test for recovery of transepithelial electrical resistance (TEER) up to 24 h after treatment wi th each enhancer. Sodium dodecyl sulphate (SDS; 0.1% w/v), a potent surfact ant, was used as positive control. SDS at this level was significantly cyto toxic whereas dipotassium glycyrrhizinate was not cytotoxic in any tests. R esults from the trypan blue-exclusion and protein-release tests showed that high concentrations of sodium caprate (0.5% w/v) and sodium deoxycholate ( 0.1% w/v) were significantly cytotoxic to the plasma membrane. The neutral- red assay, an indicator of damage to lysosomal membranes, revealed that 0.5 % (w/v) sodium caprate had no effect whereas the uptake of neutral red was slightly increased by treatment with 0.1% (w/v) sodium deoxycholate, implyi ng that the compound had cell-growth-enhancing activity. Nuclear-membrane d amage, as evaluated by the DNA-propidium iodide staining test, was severe i n cell monolayers treated with 0.5% (w/v) sodium caprate compared with that induced by 0.1% (w/v) sodium deoxycholate. In the TEER recovery test, TEER failed to recover 29 h after treatment with 0.5% (w/v) sodium caprate and 0.1% (w/v) SDS, but recovered after treatment with 0.1% (w/v) sodium deoxyc holate. The recovery of TEER might be related to nuclear membrane damage an d cell-growth-enhancing activity. These results indicate that of the three classes of enhancer, dipotassium g lycyrrhizinate was not cytotoxic and that high concentrations of sodium cap rate and sodium deoxycholate could damage plasma and nuclear membranes.