Effects of Anti-inflammatory Medication on Indoleamine 2,3 Dioxygenase Activity

Objective: To study the effects of anti-inflammatory medication on Indoleamine Indoleamine 2,3 (IDO)


INTRODUCTION
Tryptophan is a precursor of serotonin & kynurenine pathway metabolites, in which metabolization takes place in kidney cells, liver cells and CNS. Tryptophan 2,3-dioxygenase and indolamine 2,3-dioxygenase metabolized 95% Tryptophan [1,2]. Kynurenine pathway is triggered by social stress, depression and inflammatory elements [3]. At present, numerous factors produced by Mesenchymal stromal cells (MSCs) or as a reaction with target immune cells like indoleamine2,3-dioxygenase (IDO), PGE2, interleukin10, proinflammatory cytokines secreted by T-cells stimulates IDO [10]. Kynurenine pathway plays a key role in producing nicotinamide adenine dinucleotide, which means that it regulates immune response & essential constituent of behavioral changes in depression and schizophrenic patients. Kynurenine metabolism is altered by workout, electroconvulsive treatment & NSAIDs [11].
Indomethacin cox-2 inhibitor exhibited raised IDO1 inhibitory activity, which is beneficial for the malignant cells immunotherapy by suppressing interleukin-10 & prostaglandin E2 [19,20]. In this investigational study we want to evaluate the effects of indomethacin on IDO activities.

MATERIALS AND METHODS
This study took place in biochemistry department & endorsement was taken from ethical committee of KU [18]. Wistar rats of 150-250 gm weight were used in this investigational study & were kept in coops at room temperature, one week earlier the start of experiment. Rats were separated into three groups, six rats per group. Control group get 3 ml (ethanol:saline 1:2 ratio) orally, treated groups get Indomethacin(Adamjee Pharmaceutical) (50mg/1000gm/3ml) orally & sacrificed after 3.5 hr and 3 days correspondingly. Frozen sections of brain were weighed and homogenized in12% 2ml HClO 4 & 1ml ice-cold water solution per gm of brain tissue for 1 min, them left in ice-cold tubes for 10 min. Then centrifuge for 10 min at 4 0 C, then 0.5 ml portion of filtrate were used to find out IDO enzyme activity by evaluating ratio of KYN/TRP in blood serum and CNS [21]. L-tryptophan and Kynurenine were purchased from Sigma chemicals.
For data analysis one-way ANOVA followed by Tukey's test used. Variance between the two groups were considered significant when P<0.05.

DISCUSSION
IDO controls the L-Tryptophan levels, and neurotoxic metabolites. Its hyperactivity raised level of kynurenine pathway metabolites especially 3-hydroxykynurenine and quinolinic acid. Enzyme activity can be calculated by (KYN/TRP) proportion. IDO act as main immunoregulator & transforms tryptophan into kynurenine, which causes cytotoxicity and apoptosis in tumor histology [15,16]. Indomethacin cox-2 inhibitor exhibited raised IDO1 inhibitory activity, which is beneficial for the malignant cells immunotherapy by suppressing interleukin-10 & prostaglandin E2 [19,20].
Our results showed that acute treatment of Indomethacin inhibits serum IDO but chronic treatment shows induction of IDO. Our outcomes showed the induction of Indoleamine 2,3 dioxygenase by releasing pro-inflammatory cytokines. It had insignificant impact on CNS Indoleamine 2,3 dioxygenase activity but CNS Tryptophan & kynurenine levels become raised after the indomethacin therapy. Similar results are observed by [19,20] who said that it inhibits IDO activity. Previously it was reported that Diclofenac Sodium prevents hepatic tryptophan-2,3-dioxygenase enzyme activity in chronic therapy, whereas augments CNS Indoleamine 2,3 dioxygenase activity following both acute and chronic Diclofenac Sodium therapy, resulting in raised cerebral kynurenic acid and/or quinolinic acid concentrations [22]. Furthermore similar results are also observed by [23] that indomethacin therapy (50mg/kg, intra peritoneally, 3.5hr) raised the concentration of CNS kynurenic acid participates in Schizophrenia.

CONCLUSION
It is concluded that indomethacin has insignificant impact on CNS Indoleamine 2,3 dioxygenase activity but inhibits serum IDO activity.

DISCLAIMER
The products used for this research are commonly and predominantly use products in our area of research and country. There is absolutely no conflict of interest between the authors and producers of the products because we do not intend to use these products as an avenue for any litigation but for the advancement of knowledge. Also, the research was not funded by the producing company rather it was funded by personal efforts of the authors.

CONSENT
It is not applicable.

ETHICAL APPROVAL
As per international standard or university standard written ethical approval has been collected and preserved by the author(s).