469605 Antibacterial Activity of Catechins Against Aggregatibacter Actinomycetemcomitans
Antibacterial Activity of Catechins against Aggregatibacter actinomycetemcomitans
Virulence factors are molecules produced by pathogenic bacteria that allow them to establish a niche within the host. These molecules include adhesions, enzymes, and toxins, among many others. Our lab is focused on inhibiting the action of toxins for the development of antivirulence strategies to treat bacterial infections. The gram-negative bacterium Aggregatibacter actinomycetemcomitans (A.a.) produces numerous virulence factors, including a leukotoxin (LtxA), which selectively kills host immune cells. It has been reported that catechins, polyphenols extracted from green tea leaves, have antibacterial properties against A.a. However, the mechanism by which catechins interact with both the bacteria and mammalian cells has not yet been uncovered. In this project, six common catechins were used: (-) catechin (C), epicatechin (EC), epigallocatechin (EGC), gallocatechin gallate (GCg), epigallocatechin gallate (EGCg) and epicatechin gallate (ECg) to correlate inhibition of LtxA activity with the catechins¡¯ ability to alter the host membrane properties. In addition, the effect of the six catechins on bacterial membrane properties was examined. Our results indicate that the galloylated catechins significantly alter membrane fluidity in both model membranes and target cell (THP-1) membranes, while non-galloyated catechins have little effect on membrane fluidity. These changes appear to be caused by the catechins alone, as there are no changes in the cell membrane cholesterol composition after incubation with the catechins. Two of these galloyated catechins, EGCg and GCg, inhibit the ability of LtxA to kill target cells, while the non-galloylated catechins do not, suggesting that the ability of the catechins to alter target cell membrane fluidity plays a role in their inhibition of toxin activity. Our current work is focused on better understanding this relationship as well as investigating the effects of the catechins on bacterial cell membrane properties to better define their antibacterial properties.