Elucidation of Cellular Mechanisms Involved in Experimental Paromomycin Resistance in Leishmania donovani

Abstract

dLeishmania donovani is the causative agent of the potentially fatal disease visceral leishmaniasis (VL). Chemotherapeutic options available to treat VL are limited and often face parasite resistance, inconsistent efficacy, and toxic side effects. Paromomycin (PMM) was recently introduced to treat VL as a monotherapy and in combination therapy. It is vital to understand the mechanisms of PMM resistance to safeguard the drug. In the present study, we utilized experimentally generated PMM-resistant L. donovani to elucidate the mechanisms of resistance and parasite biology. We found increased membrane fluidity accompanied by decreased intracellular drug accumulation in the PMM-resistant parasites. There were marked increases in gene expression of ATP-binding cassette (ABC) transporters (MDR1 and MRPA) and protein phosphatase 2A that evince increased drug efflux. Further, evaluation of parasite tolerance toward host leishmanicidal mechanisms revealed PMM-resistant parasites as being more tolerant to nitrosative stress at the promastigote and amastigote stages. The PMM-resistant parasites also predicted a better survival capacity, as indicated by resistance to complement-mediated lysis and increased stimulation of host interleukin-10 (IL-10) expression. The susceptibilities of PMM-resistant isolates to other antileishmanial agents (sodium antimony gluconate and miltefosine) remained unchanged. The data implicated the roles of altered membrane fluidity, decreased drug accumulation, increased expression of ABC transporters, and greater tolerance of parasites to host defense mechanisms in conferring PMM resistance in Leishmania.

The LABCG2 Transporter from the Protozoan Parasite Leishmania Is Involved in Antimony Resistance

“…The role of ABC transporters in resistance to different compounds has been studied previously (5,(19)(20)(21). As mentioned above, the Leishmania LABCG2 transporter is involved in the PS externalization required for macrophage infection (10).…”

“…In order to uphold the suggestion that Sb III is a potential substrate for LABCG2, the intracellular accumulation of antimony metal ions in L. major lines was measured after different durations (10,20,30, and 60 min) by ICP-MS (Fig. 2a).…”

Leishmanicidal Activities of Novel Methylseleno-Imidocarbamates

“…Several genes have been described to be involved in virulence and resistance to therapy (22,(25)(26)(27). Therefore, some of those genes related to treatment resistance and parasite virulence were also assessed.…”

“…September 2015 Volume 59 Number 9 aac.asm.org 5709 Antimicrobial Agents and Chemotherapy on May 12, 2018 by guest http://aac.asm.org/ expression may be affected by our compounds at 2.5 M 2b and 3 M 4b for 24 h. Recent data have reported the role of ABC transporters in conferring drug resistance in Leishmania (22). In our experimental settings, both drugs slightly increased gene expression (ϳ1.3-to 1.5-fold compared to the levels in untreated parasites) of ABC transporter, but without statistical significance (P Ͼ 0.05) (Fig.…”

“…5A). Next, we studied the quinonoid dihydropteridine reductase (QDPR) gene, a gene whose high levels throughout the parasite infectious cycle may contribute to virulence (22). It has been suggested that parasite QDPR may be a useful target for chemotherapy (23).…”