Macrophage-targeted versus free calcitriol as host-directed adjunct therapy against Mycobacterium tuberculosis infection in mice is bacteriostatic and mitigates tissue pathology.

Host-directed therapy (HDT) with vitamin D in tuberculosis (TB) is beneficial only if the subject is deficient in vitamin D. We investigated pulmonary delivery of 1,25-dihydroxy vitamin D3 (calcitriol) in mice infected with Mycobacterium tuberculosis (Mtb). We made two kinds of dry powder inhalations (DPI)- soluble particles or poly(lactide) (PLA) particles. We compared treatment outcomes when infected mice were dosed with a DPI alone or as an adjunct to standard oral anti-TB therapy (ATT). Mice infected on Day 0 were treated between Days 28-56 and followed up on Days 57, 71, and 85. Neither DPI significantly reduced Mtb colony forming units (CFU) in the lungs. Combining DPI with ATT did not significantly augment bactericidal activity in the lungs, but CFU were 2-log lower in the spleen. CFU showed a rising trend on stopping treatment, sharper in groups that did not receive calcitriol. Lung morphology and histology improved markedly in animals that received PLA DPI; with or without concomitant ATT. Groups receiving soluble DPI had high mortality. DPI elicited cathelicidin, interleukin (IL)-1 and induced autophagy on days 57, 71, and 85. Macrophage-targeted calcitriol is therefore bacteriostatic, evokes innate microbicidal mechanisms, and mitigates pathology arising from the host response to Mtb.

Transcriptional regulation of suppressors of cytokine signaling during infection with Mycobacterium tuberculosis in human THP-1-derived macrophages and in mice.

Mycobacterium tuberculosis (Mtb) infection leads to upregulation of Suppressors of Cytokine signaling (SOCS) expression in host macrophages (Mϕ). SOCS proteins inhibit cytokine signaling by negatively regulating JAK/STAT. We investigated this host-pathogen dialectic at the level of transcription. We used phorbol-differentiated THP-1 Mϕ infected with Mtb to investigate preferential upregulation of some SOCS isoforms that are known to inhibit signaling by IFN-γ, IL-12, and IL-6. We examined time kinetics of likely transcription factors and signaling molecules upstream of SOCS transcription, and survival of intracellular Mtb following SOCS upregulation. Our results suggest a plausible mechanism that involves PGE2 secretion during infection to induce the PKA/CREB axis, culminating in nuclear translocation of C/EBPß to induce expression of SOCS1. Mtb-infected Mϕ secreted IL-10, suggesting a mechanism of induction of STAT3, which may subsequently induce SOCS3. We provide evidence of temporal variation in SOCS isoform exspression and decay. Small-interfering RNA-mediated knockdown of SOCS1 and SOCS3 restored the pro-inflammatory milieu and reduced Mtb viability. In mice infected with Mtb, SOCS isoforms persisted across Days 28-85 post infection. Our results suggest that differential temporal regulation of SOCS isoforms by Mtb drives the host immune response towards a phenotype that facilitates the pathogen's survival.

Atorvastatin Potentially Reduces Mycobacterial Severity through Its Action on Lipoarabinomannan and Drug Permeability in Granulomas.

The majority of preclinical research has shown that Mycobacterium tuberculosis can modify host lipids in various ways. To boost its intramacrophage survival, M. tuberculosis causes host lipids to build up, resulting in the development of lipid-laden foam cells. M. tuberculosis binds to and enters the macrophage via the cell membrane cholesterol. Aggregation of cholesterol in the cell wall of M. tuberculosis and an increase in vascularity at the granuloma site reduce the permeability of rifampicin and isoniazid concentrations. However, very few studies have assessed the effect of statins on drug penetration. Here, we used atorvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, to observe its effect on the bacterial burden by increasing the drug concentration at the infection site. We looked into how atorvastatin could be used in conjunction with first-line drugs to promote drug permeation. In this study, we detected an accumulation of drugs at the peripheral sites of the lungs and impaired drug distribution to the diseased sites. The efficacy of antituberculosis drugs, with atorvastatin as an adjunct, on the viability of M. tuberculosis cells was demonstrated. A nontoxic statin dosage established phenotypic and normal granuloma vasculature and showed an additive effect with rifampicin and isoniazid. Our data show that statins help to reduce the tuberculosis bacterial burden. Our findings reveal that the bacterial load is connected with impaired drug permeability resulting from lipid accumulation in the bacterial cell wall. Statin therapy combined with antituberculosis medications have the potential to improve treatment in tuberculosis patients. IMPORTANCE Mycobacterium tuberculosis binds to and enters the macrophage via the cell membrane cholesterol. M. tuberculosis limits phagosomal maturation and activation without engaging in phagocytosis. Aggregation of cholesterol in the cell wall of M. tuberculosis and an increase in the vascularity at the granuloma site reduce the permeability of rifampicin and isoniazid concentrations. However, very few studies have assessed the effect of statins on drug penetration, which can be increased through a reduction in cholesterol and vascularity. Herein, we used atorvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, to observe its effect on bacterial burden through increasing the drug concentration at the infection site. Our main research goal is to diminish mycobacterial dissemination and attenuate bacterial growth by increasing drug permeability.