Surgical resection of lung cancer inhibits mRNA expression of GOT2 gene encoding kynurenine aminotransferase in leukocytes

INTRODUCTION AND OBJECTIVE

Lung cancer is the most common malignant tumour. More than 80% of all diagnosed cases are non-small cell carcinoma which can be effectively treated by radical resection. Despite significant progress in the field of diagnostic and therapeutic methods, the results of lung cancer treatment are still unsatisfactory. Lung cancer is detected relatively late, which leads to an unfavourable prognosis. Kynurenine aminotransferases are an important element of the kynurenine pathway of tryptophan metabolism, which has recently aroused great interest from the aspect of possible use as a target point of personalized therapies in malignant tumours.The aim of the study was to analyze the expression of the selected gene of kynurenine aminotransferases GOT 2 at the mRNA level in peripheral blood leukocytes of patients with lung cancer.

MATERIAL AND METHODS

The mRNA expression of the GOT 2 gene was tested on blood samples from 50 patients treated surgically for non-small cell lung cancer.The control group consisted of 15 healthy individuals.The determination of mRNA expression of the GOT 2 gene was performed using the real-time PCR method.The GAPDH gene was used as the endogenous reference level.

RESULTS

The mRNA expression of the GOT2 gene on the 6th day after surgery was statistically significantly lower than before surgery (p = 0,05). In the study group, the average LogRQ mRNA expression of the GOT2 gene before the procedure was 0.192082±0.292174 in woman. This was statistically significantly higher than in men whose average LogRQ mRNA expression of the GOT2 gene before the procedure was 0.004210±0.235065 (p=0.0183).

CONCLUSIONS

Surgical resection of lung cancer results in inhibition of GOT2 mRNA expression in leukocytes. Further studies are expected to show whether it may be used as a target point for personalized therapies in lung cancer.

Kynurenine aminotransferase isoforms display fiber-type specific expression in young and old human skeletal muscle

Conversion of kynurenine (KYN) to kynurenic acid (KYNA) is the main pathway for free tryptophan degradation in skeletal muscle and has emerged as an important mechanism of how exercise is linked to promotion of mental health. Metabolism of KYN to KYNA mainly depends on the expression of kynurenine aminotransferases (KATs) that is under control of the mitochondria biogenesis regulator PGC-1α. We therefore hypothesized that expression of KATs would vary between muscle fibers that differ in mitochondrial content, i.e. oxidative type I vs more glycolytic type II muscle fibers. Moreover, we tested the hypothesis that KAT expression differs with age. Single muscle fibers were isolated from biopsies taken from the vastus lateralis muscle in young and old healthy subjects. In young and old subjects the abundance of KAT I, KAT III and KAT IV was greater in Type I than Type II fibers without age-dependent difference in the KAT isoform expressions. The link to mitochondrial content was further seen as the expression of KAT IV correlated to mitochondrial cytochrome c oxidase IV (COX IV) abundance in both fiber types. In conclusion, we describe for the first time the expression pattern of KAT isoforms with respect to specific fiber types and age in human skeletal muscle.

D-Cycloserine lowers kynurenic acid formation--new mechanism of action

D-Cycloserine, known as a partial agonist at the glycine modulatory site of the glutamatergic N-methyl-D-aspartate (NMDA) receptor, exerts anticonvulsive activities and improves cognitive function. The present study evaluates the action of D-cycloserine with respect to the biosynthetic machinery of kynurenic acid (KYNA) synthesis e.g. the activity of enzymes synthesizing KYNA, kynurenine aminotransferases I, kynurenine aminotransferase II and kynurenine aminotransferase III (KAT I, KAT II and KAT III) in the rat liver and brain, and human frontal cortex in the presence of the anti-mycobacterial drug D-cycloserine, in an in vitro study. We found that D-cycloserine blocked dose-dependent and significantly KAT I, II and III activities in rat liver and brain homogenates. Furthermore, the inhibitory effect of KYNA formation was observed in the frontal cortex homogenate of human post mortem tissue, as well. D-Cycloserine, at 63.7 µM concentration blocked significantly KAT II, I and III (53.2, 66.1 and 71.3% of control, P<0.001) activities in the human frontal cortex homogenate. Obtained data indicate that D-cycloserine exerts notable biochemical properties to block KYNA synthesis. Lowering of KYNA content due to D-cycloserine inhibition of KATs activities can free up more glycine sites for the actions of D-cycloserine. On the other site, it needs to be clarified, if the postulated mechanism for D-cycloserine to act as a partial agonist at the glycine site of the NMDA receptor could be mainly due to KAT's inhibition. We propose that this mechanism(s) might play a role in the improvement of memory, cognition and/or delusion in Alzheimer's, HIV-1 infected patients and schizophrenia patients.