The role of kynurenine and kynurenine metabolites in psoriasis

Objectives: Psoriasis is a widespread immunological disease characterised by inflammation and primarily associated with skin and joint symptoms. The kynurenine pathway significantly influences inflammation and immune system activity. The aim of this study is to determine serum concentrations of kynurenine metabolites in patients with psoriasis and investigate their correlation with disease severity. Methods: This study included 30 participants with psoriasis and 30 individuals without the disease as healthy controls. Serum levels of tryptophan, kynurenine, 3-OH anthranilic acid, quinolinic acid, 3-OH kynurenine, and kynurenic acid were determined by liquid chromatography-mass spectrometry (LC-MS/MS). Results: Serum levels of kynurenic acid (p<0.001), tryptophan (p<0.001) and the tryptophan/kynurenine ratio (TKR) (p<0.001) were statistically significantly lower in psoriasis patients than in healthy controls, while levels of quinolinic acid (p=0.007) and kynurenine (p=0.001) were significantly higher. The psoriasis area severity index (PASI) correlated positively with 3-hydroxykynurenine and kynurenic acid. Conclusions: Kynurenine metabolites are associated with the pathophysiology of psoriasis and could serve as valuable candidate markers for monitoring inflammation.