FIG 1.
Inhibition of macrophage FAO restricts intracellular Mtb growth. (A) In the carnitine shuttle, long-chain fatty acids that have been activated to acyl-CoA derivatives are converted to acylcarnitines by CPT1 at the outer mitochondrial membrane. Etomoxir and oxfenicine inhibit CPT1. Acylcarnitines are transported across the mitochondrial membrane by a dedicated translocase. In the mitochondria, CPT2 converts acylcarnitines back to acyl-CoA and carnitine. Acyl-CoA chains then undergo β-oxidation, successively generating acetyl-CoA that enters the TCA cycle. Trimetazidine inhibits 3-ketoacyl-CoA thiolase, which catalyzes the release of acetyl-CoA from the acyl-CoA chain. (B to D) Survival of Mtb (H37Rv) in BMDMs that were untreated or treated for 72 h with 2 mM metformin (MET) or indicated concentrations of etomoxir (ETM), (B), trimetazidine (TMZ) (C), or oxfenicine (OXF) (D). (E) Survival of Mtb in BMDMs from Cpt2 KO (Cpt2fl/fl LysM-Cre+) and littermate controls (Cpt2fl/f Cre-, wild type [Wt]) 4, 72, and 120 hpi. (F) Survival of Mtb in BMDMs from Cpt2 cKO and Wt controls treated with ETM, TMZ, or vehicle control for 72 h. CFU are expressed as a percentage of the WT untreated control. (G) PMA-differentiated THP-1 cells were infected with Mtb and treated with ETM or TMZ for 72 hpi prior to enumerating CFU. In panels B to G, data show means ± standard error of means (SEM) (error bars) from at least two independent experiments. Statistical significance by one-way ANOVA (B to D, F, and G) or unpaired Student’s t test with Welch’s correction (E) is indicated as follows: **, P ≤ 0.009; ***, P = 0.0003; ****, P < 0.0001; NS, not significant. (H) Cpt2 cKO mice and littermate controls were infected by aerosol with 100 to 200 Mtb CFU per animal, and lung CFU were enumerated 7 days postinfection. Data are expressed as a percentage of the control value from two independent experiments. Data are means ± SEM. *, P = 0.01 calculated using Mann-Whitney test. (I) TMZ was tested in mice that were infected with Mtb (day 1 CFU = 3,552) and treated for the first 2 weeks of infection at the indicated doses. Plots show mean lung CFU after 2 weeks of TMZ treatment (16.8 or 50 mg/kg/day). **, P = 0.02 calculated with Mann-Whitney test. (J) Mice were infected by aerosol with 155 Mtb for 5 weeks and then were treated with TMZ or saline control for 2 weeks, and total lung CFU were enumerated. **, P ≤ 0.005 calculated using Mann-Whitney test. See also Fig. S1 and S2 in the supplemental material. wpi, week postinfection.