Toll-Like Receptor-Mediated Neuroinflammation and Its Role in Neurocognitive Functions

Toll-like receptors (TLRs) are a family of pattern recognition receptors that recognise both pathogen-associated and damage-associated molecular patterns. While their expression was initially believed to be restricted to immune cells, accumulating evidence now demonstrates their presence across multiple neural cell types. Due to their significant involvement in neuroinflammatory and neurodegenerative processes, TLRs have garnered growing attention for their potential contributions to neurocognitive disorders, including Alzheimer's disease, Parkinson's disease, stroke, amyotrophic lateral sclerosis, and other forms of dementia. Potential treatment targets for lowering neuroinflammation and slowing the evolution of neurocognitive diseases include TLR signalling pathways, namely the MYD88-dependent and TRIF-dependent cascades. To initiate signalling, Toll-like receptors (TLRs) recruit specific adaptor molecules that activate the transcription factors NF-κB and IRFs, which regulate the induction of innate immune responses. Over the past decade, a combination of genetic, biochemical, structural, cellular, and bioinformatics approaches has been utilised to elucidate the detailed molecular mechanisms underlying TLR signalling. These studies have clarified how TLRs interact with cytosolic innate immune sensors to orchestrate effective immunological reactions. The function of different TLRs expressed in various brain immune cells and their contribution to the pathophysiology of neuroinflammation are described. This paper discusses the involvement of TLRs in autoimmune and neuroinflammatory circumstances like multiple sclerosis (MS), bacterial meningitis, viral encephalitis, stroke, Alzheimer's disease, and Parkinson's disease. It is intended for TLR biologists and immunologists studying neuroinflammation, as well as neuroscientists delving into central nervous system processes mediated by TLRs.