Tryptophan catabolites and their impact on multiple sclerosis progression

Accumulating evidence demonstrates involvement of tryptophan metabolites and in particular activation of the kynurenine pathway (KP) in neurocognitive disorders under CNS inflammatory conditions. The KP is involved in several brain-associated disorders including Parkinson’s disease, AIDS dementia, Alzheimer’s disease, Huntington’s disease, amyotrophic lateral sclerosis, schizophrenia, and brain tumors. Our review is an attempt to address any relevant association between dysregulation of KP and multiple sclerosis (MS), an inflammatory CNS disorder that ultimately leads to demyelinated brain areas and severe neurological deficits. Modulation of KP is a new topic for the field of MS and warrants further research. The availability of potential KP modulators approved for MS may shed some light into the therapeutic potential of KP antagonists for the treatment of MS patients.