Apoptosis Mechanisms in Mycobacterium Tuberculosis Infections

Mycobacterium tuberculosis infection engages a dynamic interplay between host cell apoptosis and bacterial survival strategies. Programmed cell death limits pathogen spread by sequestering bacilli within apoptotic bodies, whereas M. tuberculosis has evolved mechanisms to inhibit or delay apoptosis, thereby enhancing intracellular persistence. Central to this balance are the intrinsic and extrinsic apoptotic pathways: the intrinsic route is triggered by cellular stressors that promote mitochondrial outer membrane permeabilisation (MOMP), cytochrome c release and activation of Caspase-9, whereas the extrinsic route is initiated by death receptor ligation and subsequent Caspase-8 activation. M. tuberculosis modulates these pathways via secretion of virulence factors such as ESAT-6 and chorismate mutase, which interfere with mitochondrial integrity and downregulate pro-apoptotic Bcl-2 family members. Conversely, host responses including endoplasmic reticulum (ER) stress and engagement of Toll-like receptors can stimulate pro-apoptotic mediators such as CHOP and Bax, promoting macrophage apoptosis and enhancing antigen presentation. The interplay between apoptosis and alternative death modalities such as necroptosis further shapes granuloma formation, bacterial clearance and disease pathogenesis. Understanding these mechanisms offers pathways to therapeutic intervention, from small-molecule inhibitors that restore intrinsic apoptosis to immunomodulatory agents that tip the host–pathogen equilibrium towards bacterial eradication.

Research from Nature Portfolio

Recent studies have highlighted the role of endoplasmic reticulum stress in directing apoptotic responses within M1-polarised macrophages during M. tuberculosis infection. Elevated expression of ER stress sensors such as CHOP and phosphorylated eIF2α has been shown to trigger mitochondrial apoptosis and enhance bacterial clearance. Furthermore, host-directed therapy investigations have demonstrated that corticosteroid treatment can inhibit p38 MAPK-mediated mitochondrial permeability transition, shifting infected cells away from necrotic death and favouring caspase-dependent apoptosis, thereby reducing inflammation and limiting bacillary dissemination.

Apoptosis Mechanisms in Mycobacterium Tuberculosis Infections publication trend

The graph below shows the total number of articles in apoptosis mechanisms in mycobacterium tuberculosis infections across all publications each year (not limited to Nature Index journals).

Technical terms

Apoptosis: programmed cell death conserving membrane integrity and driven by caspase activation.

Intrinsic apoptotic pathway: mitochondria-mediated cell death initiated by internal stress signals, culminating in cytochrome c release and Caspase-9 activation.

Extrinsic apoptotic pathway: death receptor-triggered apoptosis initiated at the cell surface by ligands such as TNF, leading to Caspase-8 activation.

Endoplasmic reticulum (ER) stress: cellular condition arising from accumulation of misfolded proteins, which can activate apoptotic signalling via CHOP.

Caspases: family of cysteine proteases that orchestrate apoptotic execution through substrate cleavage.

Bcl-2 family proteins: regulators of mitochondrial membrane permeability that modulate apoptosis by promoting or preventing cytochrome c release.

Mitochondrial outer membrane permeabilisation (MOMP): pivotal event in intrinsic apoptosis leading to cytochrome c efflux and downstream caspase activation.

Toll-like receptor 2 (TLR2): pattern recognition receptor that senses mycobacterial components and influences apoptotic signalling.

References

1. A secreted form of chorismate mutase (Rv1885c) in Mycobacterium bovis BCG contributes to pathogenesis by inhibiting mitochondria-mediated apoptotic cell death of macrophages. Journal of Biomedical Science (2023).
2. Combination of MCL-1 and BCL-2 inhibitors is a promising approach for a host-directed therapy for tuberculosis. Biomedicine & Pharmacotherapy (2023).
3. Early secretory antigen target of 6-kDa of Mycobacterium tuberculosis inhibits macrophage apoptosis and host defense via TLR2. Respiratory Research (2025).
4. Roles of endoplasmic reticulum stress-mediated apoptosis in M1-polarized macrophages during mycobacterial infections. Scientific Reports (2016).
5. Corticosteroids inhibit Mycobacterium tuberculosis-induced necrotic host cell death by abrogating mitochondrial membrane permeability transition. Nature Communications (2019).