Macrophage metallothioneins participate in the antileishmanial activity of antimonials

SYNOPSISO_ST_ABSBackgroundC_ST_ABSHost cell functions that participate in the pharmacokinetics and pharmacodynamics (PK/PD) of pentavalent antimonials for treatment of American cutaneous leishmaniasis (CL) are critical for drug efficacy. ObjectivesIn this study, we investigated whether macrophage mechanisms of xenobiotic detoxification contribute to drug-dependent elimination of intracellular Leishmania. MethodsTranscriptomes of primary macrophages from CL patients (n=6), exposed ex vivo to Leishmania infection and SbV were generated. Candidate genes were selected and validated using short harping RNA interference (shRNA) in THP-1 cells. ResultsStrong induction of metallothionein (MT) genes was observed upon Leishmania infection and exposure to SbV, with 7 MT genes (MT1 and MT2 family members) appearing within the top 20 up-regulated genes. Tandem knockdown (KD) of MT2-A and MT1-E, 1F, and 1X in THP-1 cells was achieved using a pan-MT shRNA., Intracellular parasite survival after SbV exposure was unaffected in tandem-KD cells, and this was a consequence of strong transcriptional upregulation of MTs by infection and SbV, overcoming the KD effect. Gene silencing of the metal transcription factor-1 (MTF-1) abrogated expression of MT1 and MT2-A genes. Upon exposure to SbV, intracellular survival of Leishmania in MTF-1KD cells was significantly enhanced (p [≤] 0.05). ConclusionsMTs are potent scavengers of heavy metals, and central elements of the mammalian cell machinery for xenobiotic detoxification. Results from this study highlight the participation of macrophage MTs in Sb-dependent parasite killing, revealing novel strategies for host-targeted optimization of antileishmanial drugs.