Kynurenine metabolic balance is disrupted in the hippocampus following peripheral lipopolysaccharide challenge

Table 1 Peripheral inflammation increases flux through the kynurenine pathway of tryptophan metabolism

Metabolite	Concentration (μM)		t test
Metabolite	Saline	24 h LPS	p value
Tryptophan	94.93 (7.1)	119.53 (3.9)	p < 0.01
Kynurenine	0.83 (0.08)	2.40 (0.2)	p < 0.001
3-Hydroxykynurenine (3-HK)	0.16 (0.02)	0.27 (0.04)	p < 0.001
3-Hydroxyanthranilic acid (3-HAA)	3.99 (0.3)	4.87 (0.4)	n.s.
Quinolinic acid (QA)	0.98 (0.06)	0.97 (0.07)	n.s.
Kynurenic acid (KA)	0.24 (0.03)	0.27 (0.01)	n.s.
Kynurenine/tryptophan ratio	0.0092 (0.0004)	0.020 (0.005)	p < 0.001
3-HK/KA ratio	0.55 (0.04)	1.08 (0.07)	p < 0.001

Kynurenine pathway metabolites (μM) were assessed by LC/MS in the plasma 24 h following saline or LPS treatment. Metabolites measured include tryptophan, kynurenine, 3-hydroxykynurenine (3-HK), 3-hydroxyanthranilic acid (3-HAA), quinolinic acid (QA), and kynurenic acid (KA). Kynurenine/tryptophan and 3-HK/KA ratios were calculated. Data represent sample means (SEM) and were analyzed using a t test (results denoted in table). n = 7–12 samples/group, n.s. not significant