Toll-Like Receptor Signaling in Ischemic Brain Injury

Ischaemic brain injury triggers innate immune responses that profoundly influence tissue damage and recovery. Toll-like receptors (TLRs), notably TLR4, expressed on resident microglia and infiltrating leucocytes, recognise endogenous danger signals released by necrotic cells. Engagement of TLR4 recruits the adaptor protein MyD88, leading to activation of nuclear factor-κB (NF-κB) and transcription of pro-inflammatory cytokines and chemokines. Although this acute inflammatory cascade exacerbates blood–brain barrier disruption, neuronal apoptosis and oedema, it also primes reparative processes in the subacute phase. Cross-talk with autophagy, interferon pathways and metabolic regulators further shapes outcome. A detailed understanding of TLR temporal dynamics and downstream effectors offers avenues for targeted interventions to limit infarct expansion and support neural repair.

Research from Nature Portfolio

Recent studies have demonstrated that preconditioning strategies can modulate TLR4 signalling to confer neuroprotection. Brief exposure to isoflurane vapour prior to cerebral ischaemia was found to downregulate TLR4 and its adaptor MyD88 in microglia, attenuating NF-κB activation. This reduction in microglial release of interleukin-1β and tumour necrosis factor-α led to smaller infarct volumes, diminished neuronal apoptosis and improved functional outcomes. Mechanistic analyses revealed upregulation of the NF-κB inhibitor IκB-α as central to this protective effect, suggesting a template for precise modulation of TLR-mediated inflammation in stroke.

Toll-Like Receptor Signaling in Ischemic Brain Injury publication trend

The graph below shows the total number of articles in toll-like receptor signaling in ischemic brain injury across all publications each year (not limited to Nature Index journals).

Technical terms

Toll-Like Receptor (TLR): A class of pattern-recognition receptors that detect damage- or pathogen-associated molecular patterns and initiate inflammatory signalling.

MyD88: Myeloid differentiation primary response 88, an adaptor protein that links activated TLRs to downstream kinases culminating in NF-κB activation.

NF-κB (Nuclear Factor-κB): A transcription factor that regulates genes involved in inflammation, cell survival and immunity.

Microglia: Innate immune cells of the central nervous system responsible for surveillance, phagocytosis and modulation of neuroinflammation.

Aptamer: A short, single-stranded nucleic acid sequence that binds specifically to a target protein to modulate its function.

References

1. Polydopamine-modified black phosphorus nanosheet drug delivery system for the treatment of ischemic stroke. Regenerative Biomaterials (2024).
2. Salvianolic acid C attenuates cerebral ischemic injury through inhibiting neuroinflammation via the TLR4-TREM1-NF-κB pathway. Chinese Medicine (2024).
3. Cerebroprotective Effects of the TLR4-Binding DNA Aptamer ApTOLL in a Rat Model of Ischemic Stroke and Thrombectomy Recanalization. Pharmaceutics (2024).
4. Crosstalk Between Autophagy and Inflammation in Chronic Cerebral Ischaemia. Cellular and Molecular Neurobiology (2023).
5. Isoflurane preconditioning provides neuroprotection against stroke by regulating the expression of the TLR4 signalling pathway to alleviate microglial activation. Scientific Reports (2015).