# Modulation of the Kynurenine Pathway: A New Approach for Treating Neurodegeneration

**Authors:** Julia K. Banaszkiewicz, Anna Kukiełka, Elżbieta Kudyk, Łucja J. Walczak, Katarzyna Wicha-Komsta, Mariola Herbet, Iwona Piątkowska-Chmiel, Grzegorz Nowicki, Carmen E. Mielnik, Tomasz Kocki

PMC · DOI: 10.3390/life16020266 · 2026-02-03

## TL;DR

This paper explores how targeting the kynurenine pathway could offer new treatments for neurodegenerative diseases like Parkinson’s and Alzheimer’s.

## Contribution

The paper introduces novel strategies for modulating the kynurenine pathway to increase neuroprotective metabolites and reduce neurotoxic ones.

## Key findings

- Modulating the kynurenine pathway can help restore CNS homeostasis and reduce neurodegeneration.
- Pharmacological and non-pharmacological strategies show promise in preclinical studies.
- Combination and targeted therapies are emerging as effective approaches.

## Abstract

Neurodegenerative diseases, such as Parkinson’s and Alzheimer’s, are becoming an increasingly serious challenge for modern medicine because of the significant increase in incidence and the narrow range of effective therapeutic strategies. In recent years, the kynurenine pathway, which is one of the main pathways of tryptophan metabolism, responsible for the synthesis of products that act oppositely in the CNS including neurotoxic (quinolinic acid) and neuroprotective products, has gained increasing recognition as a potential therapeutic target. Abnormalities in the production of these metabolites, causing a disruption of homeostasis in the CNS, often lead to the development of inflammation, which can cause oxidative stress or neuronal death. This paper aims to discuss strategies useful in modulation of the kynurenine pathway, based on increasing the production of neuroprotective metabolites and reducing the synthesis of neurotoxic compounds, as well as to outline the progress in preclinical and clinical studies and the challenges encountered in these studies, among others, in the search for new KP inhibitors. The pharmacological (IDO and KMO inhibitors) and non-pharmacological (physical activity, diet) strategies are discussed, as well as new approaches from combination and targeted therapies. Together with the results of preclinical studies, they demonstrate the high utility of this target in the treatment of neurodegeneration. Despite its promising activity, further key studies are needed to fully understand the mechanisms involved in metabolism, which may translate into increased efficacy of developed therapies in the future.

## Full-text entities

- **Genes:** TDO2 (tryptophan 2,3-dioxygenase) [NCBI Gene 6999] {aka HYPTRP, TDO, TO, TPH2, TRPO}, Iba1 (induction of brown adipocytes 1) [NCBI Gene 114737], GOT2 (glutamic-oxaloacetic transaminase 2) [NCBI Gene 2806] {aka DEE82, KAT4, KATIV, KYAT4, mitAAT}, IDO2 (indoleamine 2,3-dioxygenase 2) [NCBI Gene 169355] {aka INDOL1}, GRIN1 (glutamate ionotropic receptor NMDA type subunit 1) [NCBI Gene 2902] {aka DEE101, GluN1, MRD8, NDHMSD, NDHMSR, NMD-R1}, IL10 (interleukin 10) [NCBI Gene 3586] {aka CSIF, GVHDS, IL-10, IL10A, TGIF}, APP (amyloid beta precursor protein) [NCBI Gene 351] {aka AAA, ABETA, ABPP, AD1, APPI, CTFgamma}, TNF (tumor necrosis factor) [NCBI Gene 7124] {aka DIF, IMD127, TNF-alpha, TNFA, TNFSF2, TNLG1F}, IL1B (interleukin 1 beta) [NCBI Gene 3553] {aka IL-1, IL1-BETA, IL1F2, IL1beta}, TH (tyrosine hydroxylase) [NCBI Gene 7054] {aka DYT14, DYT5b, TYH}, AHR (aryl hydrocarbon receptor) [NCBI Gene 196] {aka FVH3, RP85, bHLHe76}, NFKB1 (nuclear factor kappa B subunit 1) [NCBI Gene 4790] {aka CVID12, EBP-1, KBF1, NF-kB, NF-kB1, NF-kappa-B1}, HSD17B6 (hydroxysteroid 17-beta dehydrogenase 6) [NCBI Gene 8630] {aka HSE, RODH, SDR9C6}, SNCA (synuclein alpha) [NCBI Gene 6622] {aka NACP, PARK1, PARK4, PD1}, IDO1 (indoleamine 2,3-dioxygenase 1) [NCBI Gene 3620] {aka IDO, IDO-1, INDO}, PPARGC1A (PPARG coactivator 1 alpha) [NCBI Gene 10891] {aka LEM6, PGC-1(alpha), PGC-1alpha, PGC-1v, PGC1, PGC1A}, MAPT (microtubule associated protein tau) [NCBI Gene 4137] {aka DDPAC, FTD1, FTDP-17, MAPTL, MSTD, MTBT1}, BACE1 (beta-secretase 1) [NCBI Gene 23621] {aka ASP2, BACE, HSPC104}, Kmo (kynurenine 3-monooxygenase) [NCBI Gene 98256], Bdnf (brain derived neurotrophic factor) [NCBI Gene 12064], IL18 (interleukin 18) [NCBI Gene 3606] {aka IGIF, IL-18, IL-1g, IL1F4}, cn (cinnabar) [NCBI Gene 35724] {aka CG1555, Dmel\CG1555, Dmel\cn, KMO}, CRP (C-reactive protein) [NCBI Gene 1401] {aka PTX1}, IL6 (interleukin 6) [NCBI Gene 3569] {aka BSF-2, BSF2, CDF, HGF, HSF, IFN-beta-2}, Syp (synaptophysin) [NCBI Gene 20977] {aka A230093K24Rik, Syn, p38}, NLRP3 (NLR family pyrin domain containing 3) [NCBI Gene 114548] {aka AGTAVPRL, AII, AVP, C1orf7, CIAS1, CLR1.1}, Ido1 (indoleamine 2,3-dioxygenase 1) [NCBI Gene 15930] {aka Ido, Indo}, GFAP (glial fibrillary acidic protein) [NCBI Gene 2670] {aka ALXDRD}, TSTD1 (thiosulfate sulfurtransferase like domain containing 1) [NCBI Gene 100131187] {aka KAT}, KYNU (kynureninase) [NCBI Gene 8942] {aka KYNUU, VCRL2}, KMO (kynurenine 3-monooxygenase) [NCBI Gene 8564] {aka dJ317G22.1}, CASP1 (caspase 1) [NCBI Gene 834] {aka ICE, IL1BC, P45}, IL1RN (interleukin 1 receptor antagonist) [NCBI Gene 3557] {aka CRMO2, DIRA, ICIL-1RA, IL-1RN, IL-1ra, IL-1ra3}, SLC7A5 (solute carrier family 7 member 5) [NCBI Gene 8140] {aka 4F2LC, CD98, D16S469E, E16, LAT1, MPE16}, PYCARD (PYD and CARD domain containing) [NCBI Gene 29108] {aka ASC, CARD5, TMS, TMS-1, TMS1}, KYAT3 (kynurenine aminotransferase 3) [NCBI Gene 56267] {aka CCBL2, KAT3, KATIII}, SYP (synaptophysin) [NCBI Gene 6855] {aka MRX96, MRXSYP, XLID96}, Kmo (kynurenine 3-monooxygenase) [NCBI Gene 59113], AADAT (aminoadipate aminotransferase) [NCBI Gene 51166] {aka KAT2, KATII, KYAT2}, KYAT1 (kynurenine aminotransferase 1) [NCBI Gene 883] {aka CCBL1, GTK, KAT1, KATI}, IFNG (interferon gamma) [NCBI Gene 3458] {aka IFG, IFI, IMD69}, ACHE (acetylcholinesterase (Yt blood group)) [NCBI Gene 43] {aka ACEE, ARACHE, N-ACHE, YT}, HTT (huntingtin) [NCBI Gene 3064] {aka HD, IT15, LOMARS}
- **Diseases:** chronic inflammation (MESH:D007249), MTDLs (MESH:D015161), neurodegeneration (MESH:D019636), neuroinfectious diseases (MESH:D004194), injury to (MESH:D014947), sleep disorders (MESH:D012893), mitochondrial damage (MESH:D028361), balance disturbances (MESH:D014832), PD (MESH:D010300), neurotoxic (MESH:D020258), addiction (MESH:D019966), behavioral abnormalities (MESH:D001523), KP dysfunction (MESH:D001304), Alzheimer Disease (MESH:D000544), cancer (MESH:D009369), Intestinal dysbiosis (MESH:D064806), HD (MESH:D006816), diabetes (MESH:D003920), autism (MESH:D001321), anxiety (MESH:D001007), vitamin B6 deficiency (MESH:D026681), schizophrenia (MESH:D012559), neuroinflammation (MESH:D000090862), Lewy bodies (MESH:D020961), CNS diseases (MESH:D002493), neurological diseases (MESH:D020271), obesity (MESH:D009765), paralysis (MESH:D010243), stroke (MESH:D020521), genetic disorder (MESH:D030342), seizures (MESH:D012640), metabolic diseases (MESH:D008659), motor deficits (MESH:D009461), hyperactivity (MESH:D006948), spinal cord injury (MESH:D013119), sedative (MESH:C535788), cholinergic (MESH:C535672), synaptic degeneration (MESH:D012183), autoimmune demyelinating disease (MESH:D020278), neurofibrillary tangles (MESH:D055956), ALS (MESH:D000690), reactive gliosis (MESH:D005911), death (MESH:D003643), demyelination (MESH:D003711), brain injury (MESH:D001930), Hypertension (MESH:D006973), resting tremor (MESH:D014202), bradykinesia (MESH:D018476), cardiovascular disease (MESH:D002318), infection (MESH:D007239), EAE (MESH:D004679), psychotic symptoms (MESH:D011618), loss of neuronal function (MESH:D006315), tauopathies (MESH:D024801), insulin resistance (MESH:D007333), muscle tone disorders (MESH:D009122), type 2 diabetes (MESH:D003924), degeneration of dopaminergic neurons (MESH:D009410), autoimmune encephalomyelitis (MESH:D004681), depression (MESH:D003866)
- **Chemicals:** quinones (MESH:D011809), fat (MESH:D005223), methionine (MESH:D008715), beta-hydroxybutyrate (MESH:D020155), PA (MESH:D011478), cuprizone (MESH:D003471), T (MESH:D014316), BFF-122 (MESH:C551951), pyridoxine (MESH:D011736), oxygen (MESH:D010100), sulfate (MESH:D013431), homovanillic acid (MESH:D006719), piperidines (MESH:D010880), KYNA (MESH:D007736), succinimide (MESH:C032620), nitrogen (MESH:D009584), isoleucine (MESH:D007532), Sulfonamide (MESH:D013449), cannflavin A (MESH:C045457), Nicotinylalanine (MESH:C071261), cyclohexanes (MESH:D003510), BFF-816 (MESH:C000622260), alanine (MESH:D000409), epinephrine (MESH:D004837), 4-chloro-3-HAA (MESH:C026381), carbon (MESH:D002244), XA (MESH:C028330), tyrosine (MESH:D014443), imidazole (MESH:C029899), leucine (MESH:D007930), tanshinone IIA (MESH:C021751), 6-OHDA (MESH:D016627), 2-(3,4-dimethoxybenzenesulfonylamino)-4-(3-nitrophenyl)-5-(piperidin-1-yl)methylthiazole (MESH:C560311), nicotinamide (MESH:D009536), imidazoles (MESH:D007093), Edaravone (MESH:D000077553), thiazoles (MESH:D013844), ferulic acid (MESH:C004999), catechol (MESH:C034221), indoles (MESH:D007211), wakayin (MESH:C508208), acetylcholine (MESH:D000109), 3,4',5-trihydroxystilbene (MESH:D000077185), NMDA (MESH:D016202), 4-phenylimidazole (MESH:C033023), PIC (MESH:C030614), 4-Chlorokynurenine (MESH:C027883), glutamate (MESH:D018698), Inulin (MESH:D007444), indazole (MESH:D007191), alkaloid (MESH:D000470), FO (MESH:D005395), KYN (MESH:D007737), ketone bodies (MESH:D007657), ethanol (MESH:D000431), m-nitrobenzoylalanine (MESH:C086214), 3-HK (MESH:C005045), QUIN (MESH:D017378), glycine (MESH:D005998), hydrogen peroxide (MESH:D006861)
- **Species:** Bifidobacterium longum (species) [taxon 216816], Pigmentiphaga sp. (species) [taxon 1977564], Escherichia coli (E. coli, species) [taxon 562], Sinomenium acutum (species) [taxon 152363], Caenorhabditis elegans (species) [taxon 6239], Mus musculus (house mouse, species) [taxon 10090], Dactylicapnos scandens (species) [taxon 1406284], Saccharomyces cerevisiae (baker's yeast, species) [taxon 4932], Desulfovibrio (genus) [taxon 872], Bifidobacterium animalis subsp. lactis (subspecies) [taxon 302911], Lactobacillus acidophilus (species) [taxon 1579], Pseudomonas fluorescens (species) [taxon 294], Bifidobacterium longum subsp. infantis (subspecies) [taxon 1682], Lacticaseibacillus casei (species) [taxon 1582], Danio rerio (leopard danio, species) [taxon 7955], Rattus norvegicus (brown rat, species) [taxon 10116], Ianthella quadrangulata (species) [taxon 1162752], Bacteria Latreille et al. 1825 (Bacteria stick insect, genus) [taxon 629395], Cricetinae (hamsters, subfamily) [taxon 10026], Turicibacter (genus) [taxon 191303], Homo sapiens (human, species) [taxon 9606], Parasutterella (genus) [taxon 577310], Bifidobacterium bifidum (species) [taxon 1681], Cavia porcellus (domestic guinea pig, species) [taxon 10141], Salvia miltiorrhiza (Chinese salvia, species) [taxon 226208], Streptococcus salivarius (species) [taxon 1304], Streptococcus thermophilus (species) [taxon 1308], Limosilactobacillus reuteri (species) [taxon 1598], gut metagenome (species) [taxon 749906], Drosophila melanogaster (fruit fly, species) [taxon 7227], Lactiplantibacillus plantarum (species) [taxon 1590]
- **Cell lines:** HepG2 — Homo sapiens (Human), Hepatoblastoma, Cancer cell line (CVCL_0027), R6/2 — Mus musculus (Mouse), Hybridoma (CVCL_9233), PC12 — Rattus norvegicus (Rat), Rat adrenal gland pheochromocytoma, Cancer cell line (CVCL_0481), BV2 — Mus musculus (Mouse), Transformed cell line (CVCL_0182)

## Figures

2 figures with captions in the complete paper: https://tomesphere.com/paper/PMC12941932/full.md

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Source: https://tomesphere.com/paper/PMC12941932