Mechanism of amphotericin B resistance in clinical isolates of Leishmania donovani.

Abstract

The clinical value of amphotericin B, the mainstay therapy for visceral leishmaniasis in sodium antimony gluconate-nonresponsive zones of Bihar, India, is now threatened by the emergence of acquired drug resistance, and a comprehensive understanding of the underlying mechanisms is the need of the hour. We have selected an amphotericin B-resistant clinical isolate which demonstrated 8-fold-higher 50% lethal doses (LD(50)) than an amphotericin B-sensitive strain to explore the mechanism of amphotericin B resistance. Fluorimetric analysis demonstrated lower anisotropy in the motion of the diphenylhexatriene fluorescent probe in the resistant strain, which indicated a higher fluidity of the membrane for the resistant strain than for the sensitive strain. The expression patterns of the two transcripts of S-adenosyl-l-methionine:C-24-Δ-sterol methyltransferase and the absence of ergosterol, replaced by cholesta-5,7,24-trien-3β-ol in the membrane of the resistant parasite, indicate a decreased amphotericin B affinity, which is evidenced by decreased amphotericin B uptake. The expression level of MDR1 is found to be higher in the resistant strain, suggesting a higher rate of efflux of amphotericin B. The resistant parasite also possesses an upregulated tryparedoxin cascade and a more-reduced intracellular thiol level, which helps in better scavenging of reactive oxygen species produced by amphotericin B. The resistance to amphotericin B was partially reverted by the thiol metabolic pathway and ABC transporter inhibitors. Thus, it can be concluded that altered membrane composition, ATP-binding cassette transporters, and an upregulated thiol metabolic pathway have a role in conferring amphotericin B resistance in clinical isolates of Leishmania donovani.

• Authors: Bidyut Purkait, Ashish Kumar, Nilay Nandi, Abul Hasan Sardar, Sushmita Das, Sudeep Kumar, Krishna Pandey, Vidyananda Ravidas, Manish Kumar, Tripti De, Dharmendra Singh, Pradeep Das
• Journal: Antimicrobial agents and chemotherapy (Antimicrob Agents Chemother) Vol. 56 Issue 2 Pg. 1031-41 (Feb 2012) ISSN: 1098-6596 [Electronic] United States
• PMID: 22123699 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• ATP-Binding Cassette Transporters
• Antiprotozoal Agents
• Membrane Lipids
• Protozoan Proteins
• Sulfhydryl Compounds
• Amphotericin B

Topics

• ATP-Binding Cassette Transporters (metabolism)
• Amphotericin B (pharmacology)
• Animals
• Antiprotozoal Agents (pharmacology)
• Cell Line
• Drug Resistance
• Gene Expression Regulation
• Humans
• India
• Leishmania donovani (drug effects, isolation & purification)
• Leishmaniasis, Visceral (parasitology)
• Membrane Fluidity
• Membrane Lipids (chemistry)
• Parasitic Sensitivity Tests
• Protozoan Proteins (genetics, metabolism)
• Sulfhydryl Compounds (metabolism)