Carbon dioxide abolishes the reverse Pasteur effect in Leishmania major promastigotes

Area of Science:

• Parasitology
• Biochemistry
• Microbiology

Background:

• Leishmania major is a protozoan parasite responsible for leishmaniasis.
• Understanding parasite metabolism is crucial for developing novel therapeutic strategies.
• Glucose metabolism is a primary energy source for many protozoan parasites.

Purpose of the Study:

• To identify and quantify the metabolic products of Leishmania major promastigotes.
• To investigate the effects of varying oxygen and carbon dioxide concentrations on glucose metabolism.
• To elucidate the regulatory mechanisms governing glucose consumption and product formation.

Main Methods:

• Incubation of Leishmania major promastigotes with [1-13C]glucose and [U-14C]glucose.
• Identification of released products using nuclear magnetic resonance (NMR) spectroscopy.
• Measurement of glucose consumption and product formation under aerobic, anaerobic, and hypoxic conditions.
• Quantitative carbon balance analysis.

Main Results:

• Aerobic conditions yielded acetate, succinate, pyruvate, D-lactate, glycerol, and CO2.
• Anaerobic conditions led to altered product ratios and alanine production.
• Hypoxic and anaerobic glucose consumption decreased significantly but were restored by 5% CO2.
• CO2 and low O2 concentrations were identified as key regulators of L. major glucose metabolism.
• Under anaerobic conditions, all consumed glucose carbons were accounted for by identified products.

Conclusions:

• Leishmania major exhibits significant metabolic flexibility in response to oxygen and CO2.
• Carbon dioxide and low oxygen levels play critical regulatory roles in the parasite's glucose metabolism.
• The findings provide insights into the metabolic pathways of Leishmania major, potentially informing drug development.