Effects of the green tea catechin (−)-epigallocatechin gallate on Trypanosoma brucei

Abstract

The current pharmacopeia to treat the lethal human and animal diseases caused by the protozoan parasite Trypanosoma brucei remains limited. The parasite's ability to undergo antigenic variation represents a considerable barrier to vaccine development, making the identification of new drug targets extremely important. Recent studies have demonstrated that fatty acid synthesis is important for growth and virulence of Trypanosoma brucei brucei, suggesting this pathway may have therapeutic potential. The first committed step of fatty acid synthesis is catalyzed by acetyl-CoA carboxylase (ACC), which is a known target of (-)-epigallocatechin-3-gallate (EGCG), an active polyphenol compound found in green tea. EGCG exerts its effects on ACC through activation of AMP-dependent protein kinase, which phosphorylates and inhibits ACC. We found that EGCG inhibited TbACC activity with an EC50 of 37 μM and 55 μM for bloodstream form and procyclic form lysates, respectively. Treatment with 100 μM EGCG induced a 4.7- and 1.7- fold increase in TbACC phosphorylation in bloodstream form and procyclic lysates. EGCG also inhibited the growth of bloodstream and procyclic parasites in culture, with a 48 h EC50 of 33 μM and 27 μM, respectively, which is greater than the EGCG plasma levels typically achievable in humans through oral dosing. Daily intraperitoneal administration of EGCG did not reduce the virulence of an acute mouse model of T. b. brucei infection. These data suggest a reduced potential for EGCG to treat T. brucei infections, but suggest that EGCG may prove to be useful as a tool to probe ACC regulation.

Regulation of Trypanosoma brucei Acetyl Coenzyme A Carboxylase by Environmental Lipids

“…Total TbACC protein levels were determined by SA-HRP blotting after the 32 P signal decayed to background. As we observed previously ( 21 ), [ 32 P]orthophosphate labeling of TbACC-myc immunoprecipitates demonstrated that TbACC was phosphorylated in PFs ( Fig. 3A , upper left panel).…”

“…ACC is regulated by phosphorylation in a diverse array of organisms, from yeast to humans. TbACC was identified as a phosphoprotein by proteomics ( 20 ), and we showed that treatment of PF and BF lysates with (–)-epigallocatechin gallate (EGCG), a bioactive compound in green tea, resulted in increased TbACC phosphorylation and decreased TbACC activity in cell lysates ( 21 ). Taken together, these observations suggested that TbACC may be subject to phosphoregulation in response to some stimuli.…”

Anti–trypanosomal effect of Peristrophe bicalyculata extract on Trypanosoma brucei brucei–infected rats

“…Although we cannot ascertain the reasons for the sudden drop, some pathophysiological mechanisms may be involved. It has been reported that lipids serve as an important source of energy for T. brucei [31,32] , thus, the lowering of the serum lipids and cholesterol as observed in the present study could, partly, be the result of trypanosomal utilization of the molecules. Thus, the continuous utilization of these molecules from the blood stream could be a contributory factor to lowering of the serum levels of lipids and cholesterol.…”

“…Also, it is known that blood-stream trypanosomes scavenge blood glucose for energy [31] , which could cause hypoglycemia in the trypanosome-infected animal. Although blood glucose level was not determined in this study, hypoglycemia can undoubtedly result in increased catabolism of lipids and cholesterol in order to meet some strategic energy needs in the body of the host animal [31,32] . Consequently, this could lead to decrease in serum levels of these molecules as observed in the present study.…”

“…Reports have shown that lipids play important roles in the pathogenesis of trypanosomiasis [31,32] . From the findings in this study, it is reasonable to infer that T. brucei infection causes significant decrease in the serum levels of cholesterol, high density lipoprotein, triacylglycerol and low density lipoprotein.…”