E. Hystolica EhADH2 Enzyme as Anti-Amoebic Target (2007 - Present)

Investigator:  Avelina Espinosa, Roger Williams University 

Abstract:  The intestinal protozoan Entamoeba histolytica is a major cause of morbidity and mortality worldwide, causing fifty million cases of diarrhea and one hundred thousand deaths per year. Amoebiasis is primarily treated with metronidazole. Metronidazole has toxic side effects, neurological complications, and metronidazole-resistant E. histolytica strains have been developed. These concerns have prompted the search for alternative therapeutic agents. One promising approach is the development of novel anti-metabolites. Entamoeba histolytica lacks mitochondria and obtains its energy from the fermentation of glucose. Entamoeba histolytica alcohol dehydrogenase 2 (EhADH2), a bifunctional enzyme with both aldehyde dehydrogenase (ALDH) and alcohol dehydrogenase (ADH) activities, constitutes a key enzyme in this pathway. EhADH2 is required for the growth and survival of E. histolytica, suggesting this enzyme could be a target for new anti-amoebic drugs. The goal of this study is to search for alternative non-toxic drugs that inhibit the growth of E. histolytica trophozoites, by specifically affecting the EhADH2 enzyme. Three specific aims will help achieve this goal: 1. Identify candidate chemicals with inhibitory capabilities against EhADH2. Test potential inhibitors in vitro using an Escherichia coli AdhE deficient strain, and later in vivo using Entamoeba histolytica trophozoites. Useful candidates will be effective in inhibiting the enzymatic activity of EhADH2 in vitro, killing trophozoites with little or no effect to mammalian enzymes. 2. Define the structure and catalytic function of EhADH2 with the purpose of designing specific anti-amoebic agents. To achieve this goal, the analysis of EhADH2 (wild-type and mutants) in combination with inhibitors, using kinetic, spectrophotometric, computer modeling, and x-ray crystallography will be performed. 3. Determine the toxicity of EhADH2 in mammalian cells. To evaluate the toxicity of these drugs, various concentrations of drugs will be tested in liver and intestine culture cells. EC50 standard procedures will be used.

Publications

2008 - 2009

Espinosa, A., Perdrizet, G., Paz-y-Miño C., Lanfranchi, R., Monichan, P. 2009. Effects of iron depletion on Entamoeba histolytica alcohol dehydrogenase 2 (EhADH2) and trophozoite growth: Implications for antiamoebic therapy. J. Antimicrob. Chemother., Epub 2009 Feb 13.

Presentations

2008- 2009

Espinosa, A., Rowley, D., Perdrizet, G., Paz-y-Miño C.G., Phay, M., Von Riesen, D., Socha, A. 2008. Broad strategies to find alternative antiamebic treatments. 57th American Society of Tropical Medicine and Hygiene Meeting, New Orleans, LA, December 11-14.

Espinosa, A. 2009. Co-evolutionary dialogue between hosts and pathogens. International Course “Darwin and Biomedicine” organized by the University of the Americas, Quito, Ecuador, January 15-16.

Espinosa A. 2009. Horizontal gene transfer and microbial evolution. International Course “Darwin and Biomedicine” organized by the University of the Americas, Quito, Ecuador, January 15-16.

Phay, M., Austin, K., Von Riesen, D., Espinosa, A. 2008. 1-N-substituted cyclized pyrazoline analogues of thiosemicarbazones as potential antiamebic drugs. 3rd Annual Biology New England South Meeting, Bristol, RI, December 2.

Ryke, E., Socha, A., Rowley, D., Espinosa, A. 2008. Marine actinomycetes extracts have anti-amebic properties against an Entamoeba histolytica clinical isolate. 3rd Annual Biology New England South Meeting, Bristol, RI, December 2.

Espinosa A. 2008. Could iron sequestration be used to treat amebiasis? The New England Association of Parasitologists 11th Meeting, New Grafton, MA, October 18.

Perdrizet, G., Espinosa, A. 2008. Improved purification and preliminary inhibition of the bifunctional Entamoeba histolytica alcohol dehydrogenase 2 EhADH2. 59th International Society of Protozoologists Meeting, Halifax, Nova Scotia, July 21-26.

Espinosa, A., Perdrizet, G., Paz-y-Miño C.G., Lanfranchi, R. 2008. Iron starvation as potential treatment for amebiasis. Gordon Research Conference on Biology of Host-Parasite Interactions, Newport, RI, June 22-27.

2007 - 2008

Espinosa, A., Arnold, S. 2007. Life in the gut traits of ameba dehydrogenases. Joint meeting of Phycological Society of America and International Society of Protozoology, Providence, RI, August 5-9.

Arnold, S., Espinosa, A. 2007. Metal dependence of EhADH2 biochemical analyses. Biology New England South Undergraduate Meeting, Bristol, RI, November 30.

Espinosa, A. 2007. Molecular and biochemical characterization of Entamoeba histolytica alcohol dehydrogenase 2 (EhADH2) and the novel E. invadens bifunctional alcohol dehydrogenase (EiADHE). North East Regional IDeA Conference, Burlington, VT, August 15-17.

Perdrizet, G., Espinosa, A. 2007. Purification of bifunctional Entamoeba histolytica alcohol dehydrogenase 2. Biology New England South Undergraduate Meeting, Bristol, RI, November 30.

Perdrizet, G., Espinosa, A. 2007. Purification of an amoebic bifunctional dehydrogenase to find novel anti-amoebic therapies. Biology New England South Undergraduate meeting, Bristol, RI, November 30.

Espinosa, A. 2007. Surviving in the gut: parasites & commensals. Lynn Margulis Symposia, Amherst, MA, July 31.

Perdrizet, G., Farrell, L., Espinosa, A. 2007. Biochemical characterization of Entamoeba histolytica alcohol dehydrogenase 2 (EhADH2) and a novel E. invadens bifunctional alcohol dehydrogenase (EiADHE). Joint meeting of Phycological Society of America and International Society of Protozoology, Providence, RI, August 5-9.

2006 - 2007

Espinosa, A., Ashmore, A., Fitzsimmons-Diaz, C., Roberto, M. 2006. Identification of a novel bifunctional EhADH2-like enzyme in Entamoeba invadens. Gordon Research Conference: The Biology of Host-Parasite Interactions, Newport, RI, June 25-29.

Espinosa, A. 2006. Identification of a novel bifunctional EhADH2-like enzyme in Entamoeba invadens. East Coast Protozoology Meeting, Troy, NY, June 6-8. 

Espinosa, A. 2006. Using eukaryotic parasites to understand the origin and evolution of anaerobic metabolism. Undergraduate Programs Research Retreat, Providence, RI, December 1.

Espinosa, A., McKee, K., Ashmore, A. 2006. The biochemical characterization of a novel Entamoeba invadens bifunctional alcohol dehydrogenase (EiADHE). ASTMH meeting, Atlanta, GA, November 12-15.

2005 - 2006

Espinosa, A. 2005. A glycolitic enzyme as target for antiamoebic agents: EhADH2, Seminar Series NYU, Department of Parasitology, October 14.

2004 - 2005

Espinosa, A., Clark, D., Stanley, S.L. 2005. Entamoeba histolytica alcohol dehydrogenase 2 (EhADH2) as a target for anti-amoebic agents. Keystone Symposia Drugs Against Protozoan Parasites Conference X6.