Reductive Power Generated by Mycobacterium leprae Through Cholesterol Oxidation Contributes to Lipid and ATP...

Area of Science:

• Microbiology and Infectious Diseases
• Cell Biology
• Biochemistry

Background:

• Mycobacterium leprae, the causative agent of leprosy, infects Schwann cells and induces lipid droplet accumulation.
• Lipid droplets are recruited to M. leprae-containing phagosomes, suggesting a role in delivering host lipids to the bacteria.
• M. leprae possesses the capacity to oxidize cholesterol, a key step in its metabolic pathway within host cells.

Purpose of the Study:

• To investigate the biochemical significance of cholesterol oxidation in M. leprae pathogenesis within Schwann cells.
• To identify the specific enzyme responsible for cholesterol oxidation in M. leprae.
• To evaluate the therapeutic potential of targeting M. leprae's cholesterol oxidation pathway.

Main Methods:

• Assessed LDL-cholesterol uptake and localization in M. leprae-infected Schwann cells using fluorescence microscopy.
• Utilized Mycobacterium smegmatis mutant strains complemented with M. leprae genes to identify the cholesterol-oxidizing enzyme.
• Investigated the effect of inhibiting M. leprae 3β-hydroxysteroid dehydrogenase (3β-HSD) activity on bacterial survival.

Main Results:

• M. leprae infection enhances LDL-cholesterol uptake by Schwann cells, with close association observed between bacteria and internalized cholesterol.
• The gene ml1942, encoding 3β-hydroxysteroid dehydrogenase (3β-HSD), was identified as responsible for cholesterol oxidation, not ml0389 (cholesterol oxidase).
• 3β-HSD activity generates NADH and NADPH, essential for M. leprae's respiratory chain and cell wall lipid biosynthesis (PDIM, PGL-I).
• Inhibition of M. leprae 3β-HSD activity significantly decreased intracellular bacterial survival.

Conclusions:

• Cholesterol accumulation and delivery to intracellular M. leprae within Schwann cells are confirmed.
• Cholesterol oxidation via 3β-HSD is a critical pathway for M. leprae pathogenicity.
• M. leprae 3β-HSD represents a promising drug target for combination therapy to shorten leprosy treatment and reduce nerve damage.