Tryptophan-kynurenine pathway metabolite levels were altered in MTLE-HS
We have also quantified the TKP metabolites namely TRP, KYN, KYNA, QUIN and neurotransmitters glutamate and GABA in tissues obtained from the surgically resected hippocampal samples obtained from patients with MTLE-HS and compared it with autopsy control hippocampus tissues. The concentration of TRP was significantly reduced (Figure 2a) in the hippocampal samples. Although KYN concentration was not significantly altered (Figure 2b), but that of KYNA was significantly reduced in the hippocampal samples (Figure 2d). The tryptophan kynurenine ratio was also significantly reduced in the hippocampal samples (Figure 2c). The concentration of QUIN was significantly enhanced in the hippocampal samples (Figure 2e). The ratio of QUIN and KYNA was also significantly enhanced in the hippocampal samples (Figure 2f). The concentration of glutamate (Figure 2g), GABA (Figure 2h) and glutamate GABA ratio (Figure 2i), neither of those was significantly altered between the two groups.
To investigate the de novo synthesis pattern of KYNA and QUIN in tissues, 300 µM thick slices were prepared from the surgically resected hippocampus tissues and tumour periphery non-seizure control tissues, incubated in ACSF (artificial cerebrospinal fluid) containing 200 µM KYN (saturating concentration), precursor of both KYNA and QUIN, and incubated at 30°C in a water bath for 2 hours (Turski et al., 1989). At the end of the incubation period, the ACSF was aliquoted; KYNA and QUIN were estimated by HPLC and LC-MS/MS respectively. We observed a similar pattern of results as earlier. The de novo synthesis of KYNA was significantly reduced in the hippocampal samples obtained from patients with MTLE-HS (Figure 2j). Similarly, the de novo synthesis of QUIN was significantly enhanced in the hippocampal samples obtained from patients with MTLE-HS (Figure 2k).