Background and objective: With the worldwide emergence of highly drug-resistant tuberculosis (TB), novel agents that have direct antimycobacterial effects or that enhance host immunity are urgently needed. Curcumin is a polyphenol responsible for the bright yellow-orange colour of turmeric, a spice derived from the root of the perennial herb Curcuma longa. Curcumin is a potent inducer of apoptosis-an effector mechanism used by macrophages to kill intracellular Mycobacterium tuberculosis (MTB). Methods: An in vitro human macrophage infection model was used to determine the effects of curcumin on MTB survival. Results: We found that curcumin enhanced the clearance of MTB in differentiated THP-1 human monocytes and in primary human alveolar macrophages. We also found that curcumin was an inducer of caspase-3-dependent apoptosis and autophagy. Curcumin mediated these anti-MTB cellular functions, in part, via inhibition of nuclear factor-kappa B (NFκB) activation. Conclusion: Curcumin protects against MTB infection in human macrophages. The host-protective role of curcumin against MTB in macrophages needs confirmation in an animal model; if validated, the immunomodulatory anti-TB effects of curcumin would be less prone to drug resistance development.

Pure nicotine impairs macrophage killing of Mycobacterium tuberculosis (MTB), but it is not known whether the nicotine component in cigarette smoke (CS) plays a role. Moreover, the mechanisms by which nicotine impairs macrophage immunity against MTB have not been explored. To neutralize the effects of nicotine in CS extract, we used a competitive inhibitor to the nicotinic acetylcholine receptor (nAChR)-mecamylamine-as well as macrophages derived from mice with genetic disruption of specific subunits of nAChR. We also determined whether nicotine impaired macrophage autophagy and whether nicotine-exposed T regulatory cells (Tregs) could subvert macrophage anti-MTB immunity. Mecamylamine reduced the CS extract increase in MTB burden by 43%. CS extract increase in MTB was also significantly attenuated in macrophages from mice with genetic disruption of either the α7, β2, or β4 subunit of nAChR. Nicotine inhibited autophagosome formation in MTB-infected THP-1 cells and primary murine alveolar macrophages, as well as increased the intracellular MTB burden. Nicotine increased migration of THP-1 cells, consistent with the increased number of macrophages found in the lungs of smokers. Nicotine induced Tregs to produce transforming growth factor-β. Naive mouse macrophages co-cultured with nicotine-exposed Tregs had significantly greater numbers of viable MTB recovered with increased IL-10 production and urea production, but no difference in secreted nitric oxide as compared with macrophages cocultured with unexposed Tregs. We conclude that nicotine in CS plays an important role in subverting macrophage control of MTB infection.

Silencing of interleukin-32 (IL-32) in a differentiated human promonocytic cell line impairs killing of Mycobacterium tuberculosis (MTB) but the role of IL-32 in vivo against MTB remains unknown. To study the effects of IL-32 in vivo, a transgenic mouse was generated in which the human IL-32γ gene is expressed using the surfactant protein C promoter (SPC-IL-32γTg). Wild-type and SPC-IL-32γTg mice were infected with a low-dose aerosol of a hypervirulent strain of MTB (W-Beijing HN878). At 30 and 60 d after infection, the transgenic mice had 66% and 85% fewer MTB in the lungs and 49% and 68% fewer MTB in the spleens, respectively; the transgenic mice also exhibited greater survival. Increased numbers of host-protective innate and adaptive immune cells were present in SPC-IL-32γTg mice, including tumor necrosis factor-alpha (TNFα) positive lung macrophages and dendritic cells, and IFN-gamma (IFNγ) and TNFα positive CD4 + and CD8 + T cells in the lungs and mediastinal lymph nodes. Alveolar macrophages from transgenic mice infected with MTB ex vivo had reduced bacterial burden and increased colocalization of green fluorescent protein-labeled MTB with lysosomes. Furthermore, mouse macrophages made to express IL-32γ but not the splice variant IL-32β were better able to limit MTB growth than macrophages capable of producing both. The lungs of patients with tuberculosis showed increased IL-32 expression, particularly in macrophages of granulomas and airway epithelial cells but also B cells and T cells. We conclude that IL-32γ enhances host immunity to MTB.cytokine | transgenic mouse | tuberculosis | host immunity | interleukin-32

The discovery of antibiotics was one of the crowning achievements of the 20th century, revolutionizing the treatment of infectious disease. However, widespread improper use of antibiotics has led to the development of antibiotic-resistant bacteria, resulting in a healthcare crisis and the urgent need to develop new effective antibiotics. Moreover, current antibiotic therapies are inefficient in treating biofilm-protected and intracellular organisms such as Mycobacterium tuberculosis (Mtb) and non-tuberculous mycobacteria. Herein, we present a strategy for the construction of macromolecular antimicrobial compounds using a catalyst-free, polyaddition polymerization process of monomers derived from poly­(ethylene terephthalate) (PET) refuse. The initial depolymerization of PET refuse via aminolysis is highly amenable and scalable process to access a broad array of functional tertiary amine-containing terephthalamide polymer-grade monomers. This new monomer platform was subsequently used to construct antimicrobial cationic polyionenes via a polyaddition polymerization. The composition and structure of the antimicrobial polyionenes were varied to study their antimicrobial activity against a broad spectrum of pathogenic microbes including Mtb. Polymers with optimized compositions have potent antimicrobial activity with low minimum inhibitory concentrations of 3.9–15.8 μg/mL against microbes including Mtb and high selectivity for microbes over mammalian cells. Similarly, activity against Mtb ranged from 2 to 16 μg/mL, while values for Mycobacterium avium and Mycobacterium abscessus were higher. In addition, antimicrobial polyionenes were able to target and kill M. avium residing inside human macrophages. Overall, PET refuse was successfully used as a feedstock to generate new functional terephthalamide monomers for new macromolecular antimicrobial polyionenes. These polyionenes are promising candidate agents to treat difficult-to-treat bacterial and mycobacterial infections that are currently resistant to existing antibiotics.

Rationale: The association between non-tuberculous mycobacterial lung disease and alpha-1-antitrypsin (AAT) deficiency is likely due, in part, to underlying emphysema or bronchiectasis. But there is increasing evidence that AAT itself enhances host immunity against microbial pathogens and thus deficiency could compromise host protection. Objectives: The goal of this project is to determine if AAT could augment macrophage activity against non-tuberculous mycobacteria. Methods: We compared the ability of monocyte-derived macrophages cultured in autologous plasma that were obtained immediately before and soon after AAT infusion—given to individuals with AAT deficiency—to control an ex vivo Mycobacterium intracellulare infection. Measurements and Main Results: We found that compared to pre-AAT infused monocyte-derived macrophages plus plasma, macrophages, and contemporaneous plasma obtained after a session of AAT infusion were significantly better able to control M. intracellulare infection; the reduced bacterial burden was linked with greater phagosome-lysosome fusion and increased autophagosome formation/maturation, the latter due to AAT inhibition of both M. intracellulare –induced nuclear factor-kappa B activation and A20 expression. While there was a modest increase in apoptosis in the M. intracellulare -infected post-AAT infused macrophages and plasma, inhibiting caspase-3 in THP-1 cells, monocyte-derived macrophages, and alveolar macrophages unexpectedly reduced the M. intracellulare burden, indicating that apoptosis impairs macrophage control of M. intracellulare and that the host protective effects of AAT occurred despite inducing apoptosis. Conclusion: AAT augments macrophage control of M. intracellulare infection through enhancing phagosome-lysosome fusion and autophagy.