Metabolomics analysis reveals changes related to pseudocyst formation induced by iron depletion in Trichomonas vaginalis

Abstract

Background Iron is an essential element for cellular functions, such as energy metabolism. Trichomonas vaginalis, a human urogenital tract pathogen, is capable of surviving in the environment without sufficient iron supplementation. Pseudocysts (cyst-like structures) are an environmentally tolerated stage of this parasite while encountering undesired conditions, such as iron deficiency. We demonstrated that iron deficiency induces more active glycolysis but a drastic downregulation of hydrogenosomal energy metabolic enzymes. Therefore, the metabolic direction of pyruvate is still controversial. Methods In the present work, we conducted an LC‒MS-based metabolomics analysis to obtain accurate insights into the enzymatic events of T. vaginalis under iron-depleted (ID) conditions. Results First, we showed the possible digestion of glycogen, cellulose polymerization, and accumulation of raffinose family oligosaccharides (RFOs). Second, a medium-chain fatty acid (MCFA) capric acid was elevated, whereas most detected C18 fatty acids were reduced significantly. Third, amino acids were mostly reduced, especially alanine, glutamate, and serine. There were 33 dipeptides that showed significant accumulation in ID cells, which was probably associated with the decrease in amino acids. Our results indicated that glycogen was metabolized as the carbon source, and the structural component cellulose was synthesized at same time. The decrease in C18 fatty acids implied possible incorporation in the membranous compartment for pseudocyst formation. The decrease in amino acids accompanied by an increase in dipeptides implied incomplete proteolysis. These enzymatic reactions (alanine dehydrogenase, glutamate dehydrogenase, and threonine dehydratase) were likely to be involved in ammonia release. Conclusion These findings highlighted the possible glycogen utilization, cellulose biosynthesis, and fatty acid incorporation in pseudocyst formation, as well as NO precursor ammonia production induced by iron-depleted stress.