Determination of Bioactive Compound Kynurenic Acid in Linum usitatissimum L.

Kynurenic acid (KYNA) is a bioactive compound exhibiting multiple actions and positive effects on human health due to its antioxidant, anti-inflammatory and neuroprotective properties. KYNA has been found to have a beneficial effect on wound healing and the prevention of scarring. Despite notable progress in the research focused on KYNA observed during the last 10 years, KYNA's presence in flax (Linum usitatissimum L.) has not been proven to date. In the present study, parts of flax plants were analysed for KYNA synthesis. Moreover, eight different cultivars of flax seeds were tested for the presence of KYNA, resulting in a maximum of 0.432 µg/g FW in the seeds of the cultivar Jan. The level of KYNA was also tested in the stems and roots of two selected flax cultivars: an oily cultivar (Linola) and a fibrous cultivar (Nike). The exposure of plants to the KYNA precursors tryptophan and kynurenine resulted in higher levels of KYNA accumulation in flax shoots and roots. Thus, the obtained results indicate that KYNA might be synthesized in flax. The highest amount of KYNA (295.9 µg/g dry weight [DW]) was detected in flax roots derived from plants grown in tissue cultures supplemented with tryptophan. A spectroscopic analysis of KYNA was performed using the FTIR/ATR method. It was found that, in tested samples, the characteristic KYNA vibration bands overlap with the bands corresponding to the vibrations of biopolymers (especially pectin and cellulose) present in flax plants and fibres.

Binge-like mephedrone treatment induces memory impairment concomitant with brain kynurenic acid reduction in mice.

While mephedrone (4-methylmethcathinone), a synthetic cathinone derivative, is widely abused by adolescents and young adults, the knowledge about its long-term effects on memory processes is limited. Kynurenic acid (KYNA) is a neuroactive metabolite of the kynurenine pathway of tryptophan degradation. KYNA is considered an important endogenous modulator influencing physiological and pathological processes, including learning and memory processes. The aim of this study was to determine whether (A) binge-like mephedrone administration (10.0 and 30.0 mg/kg, intraperitoneally, in 4 doses separated by 2 h) induces memory impairments, assessed 2, 8 and 15 days after mephedrone cessation in the passive avoidance test in mice, and whether (B) KYNA is involved in these memory processes. To clarify the role of KYNA in the mephedrone effects, its production in the murine brain in vivo, and in cortical slices in vitro, as well as the activities of kynurenine aminotransferases (KATs) I and II were assessed. Furthermore, cell line experiments were conducted to investigate the effects of mephedrone on normal human brain cells. Our results showed memory impairments 8 and 15 days after binge-like mephedrone administration. At the same time, reduction in the KYNA level in the murine brain was noted. In vitro studies showed no effect of mephedrone on the production of KYNA in cortical slices or on the activity of the KAT I and II enzymes. Finally, exposure of normal cells to mephedrone in vitro resulted in a modest reduction of cell viability and proliferation.

Evidence against involvement of kynurenate branch of kynurenine pathway in pathophysiology of Fuchs' dystrophy and keratoconus.

Kynurenine aminotransferases (KAT) are enzymes catalyzing formation of kynurenic acid (KYNA) from kynurenine. KYNA is a Janus-faced molecule of high biological activity. On the one hand KYNA was identified as a UV filter and neuroprotectant with free radical scavenging properties, but on the other hand it may contribute to photodamage of lens proteins resulting in cataract formation. Fuchs endothelial corneal dystrophy (FECD) and keratoconus (KC) are common, vision threatening corneal dystrophies whose etiology is not fully understood. In our previous works, we confirmed the presence of KATs in the human cornea together with GPR35, a receptor for KYNA. This prompted us to investigate the potential changes in the expression of three isoforms: KAT I, KAT II, and KAT III in normal and FECD- and KC-affected corneas. Immunohistochemistry accompanied by gene expression data mining revealed that the levels of neither KAT I, KAT II, nor KAT III are affected in FECD and KC. This constitutes evidence against the involvement of KATs in the pathophysiology of FECD and KC.

Content of tryptophan and kynurenines in serum and milk of dairy cows with mastitis caused by Streptococcus spp.

The aim of the study was to investigate serum and milk concentrations of tryptophan (TRP), kynurenine (KYN) and kynurenic acid (KYNA), and activity of indoleamine 2,3-dioxygenase (IDO) in cows suffering from mastitis caused by Streptococcus spp. The blood and milk samples were collected from Holstein-Friesian cows farmed in the Lublin region of Poland. It was found that TRP was lower in cows with mastitis both in serum and milk. KYN was lower in serum but not in milk. KYNA was not significantly altered in diseased cows both in serum and milk. The activity of IDO calculated as KYN to TRP ratio was unchanged in serum but was markedly elevated in milk of cows with mastitis. Our findings may have important implications for diagnosis of mastitis in cows because an increase of activity of IDO and reduction of TRP in milk might be a valuable early marker predicting the occurrence of the disease.

Kynurenic acid and cancer: facts and controversies.

Kynurenic acid (KYNA) is an endogenous tryptophan metabolite exerting neuroprotective and anticonvulsant properties in the brain. However, its importance on the periphery is still not fully elucidated. KYNA is produced endogenously in various types of peripheral cells, tissues and by gastrointestinal microbiota. Furthermore, it was found in several products of daily human diet and its absorption in the digestive tract was evidenced. More recent studies were focused on the potential role of KYNA in carcinogenesis and cancer therapy; however, the results were ambiguous and the biological activity of KYNA in these processes has not been unequivocally established. This review aims to summarize the current views on the relationship between KYNA and cancer. The differences in KYNA concentration between physiological conditions and cancer, as well as KYNA production by both normal and cancer cells, will be discussed. The review also describes the effect of KYNA on cancer cell proliferation and the known potential molecular mechanisms of this activity.

Tryptophan Pathway Abnormalities in a Murine Model of Hereditary Glaucoma.

BACKGROUND: It has been shown that a possible pathogenetic mechanism of neurodegeneration in the mouse model of glaucoma (DBA/2J) may be an alteration of kynurenic acid (KYNA) in the retina. This study aimed to verify the hypothesis that alterations of tryptophan (TRP) metabolism in DBA/2J mice is not limited to the retina. METHODS: Samples of the retinal tissue and serum were collected from DBA/2J mice (6 and 10 months old) and control C57Bl/6 mice of the same age. The concentration of TRP, KYNA, kynurenine (KYN), and 3-hydroxykynurenine (3OH-K) was measured by HPLC. The activity of indoleamine 2,3-dioxygenase (IDO) was also determined as a KYN/TRP ratio. RESULTS: TRP, KYNA, L-KYN, and 3OH-K concentration were significantly lower in the retinas of DBA/2J mice than in C57Bl/6 mice. 3OH-K concentration was higher in older mice in both strains. Serum TRP, L-KYN, and KYNA concentrations were lower in DBA/2J than in age-matched controls. However, serum IDO activity did not differ significantly between compared groups and strains. CONCLUSIONS: Alterations of the TRP pathway seem not to be limited to the retina in the murine model of hereditary glaucoma.

An efficient method for production of kynurenic acid by Yarrowia lipolytica.

Kynurenic acid (KYNA) is a compound derived from the tryptophan catabolic pathway. Antioxidant and neuroprotective properties have been confirmed for KYNA, which makes it an interesting and important metabolite of biomedical significance. In the present study, the yeast Yarrowia lipolytica was tested for KYNA biosynthesis. The results showed that Y. lipolytica strain S12 is able to produce KYNA in high concentrations (up to 21.38 µg/ml in culture broth and 494.16 µg/g cell dry weight in biomass) in optimized conditions in a medium supplemented with tryptophan. Different conditions of culture growth, including the source of carbon, its concentration and pH value of the medium, as well as the influence of an inhibitor or precursor of KYNA synthesis, were analysed. The obtained data confirmed the presence of KYNA metabolic pathway in the investigated yeast. To our best knowledge, this is the first study that reports KYNA production in the yeast Y. lipolytica in submerged fermentation.

The presence and distribution of G protein-coupled receptor 35 (GPR35) in the human cornea - Evidences from in silico gene expression analysis and immunodetection.

We provide the evidence for G protein-coupled receptor 35 (GPR35) presence and distribution in the human cornea. The initial data on GPR35 gene expression were retrieved from microarray repositories and were further confirmed by western blotting and immunohistochemical analysis. Immunoblotting suggested that GPR35 exists predominantly as a dimer in corneal tissue. Moreover, corneal tissues were significantly richer in GPR35 compared to the adjacent sclera. Immunoreactivity for GPR35 was detected in normal corneas, keratoconus and Fuchs' dystrophy, mainly in the corneal epithelium and endothelium. In corneas with Fuchs' dystrophy, less intensive immunoreactivity for GPR35 in endothelium was revealed. The physiological relevance of this phenomenon requires further investigation.

Examination of Kynurenine Toxicity on Corneal and Conjunctival Epithelium: In vitro and in vivo Studies.

Kynurenine (KYN) is a metabolite of tryptophan, proposed for the treatment of corneal diseases. Our goal was to evaluate the effects of KYN on normal human corneal and conjunctival epithelial cells in vitro and the re-epithelization of corneal erosion in rabbits. In our study, we used corneal (10.014 pRSV-T) and conjunctival (HC0597) epithelium cell cultures. KYN was applied at a concentration range of 1-100 µM for 24 and 48 h. We examined the effects on cellular metabolism, viability, interleukin-1ß (IL-1ß), IL-6, IL-10 secretion, cytoskeleton organization and transwell migration ability. Following a bilateral corneal de-epithelialization, the rabbits received drops containing 1% KYN and a saline solution to the contralateral control eye, 5 times daily. Digital images were analyzed using the EPCO 2000 software. The metabolic activity of cells was slightly decreased by KYN in the corneal but not in the conjunctival epithelium. The viability of both epithelia was improved by KYN; it caused alterations in the secretion of IL-6 and IL-10 but not IL-1ß. It had no impact on both epithelia morphology and the organization of the cellular cytoskeleton. KYN stimulated the formation of pseudopodia projections in both epithelia in vitro, which may be important in terms of wound healing. However, there were no differences in the re-epithelization rate in vivo. At the tested concentrations, KYN was not toxic for the corneal and the conjunctival epithelium in vitro and did not affect corneal re-epithelization in rabbits in vivo. Our results suggest that KYN may be taken into consideration for the treatment of ocular disorders.

Tryptophan, kynurenine, kynurenic acid concentrations and indoleamine 2,3-dioxygenase activity in serum and milk of dairy cows with subclinical mastitis caused by coagulase-negative staphylococci.

The aim of the study was to investigate serum and milk concentrations of tryptophan (TRP), kynurenine (KYN), kynurenic acid (KYNA), and indoleamine 2,3-dioxygenase (IDO) activity in cows suffering from subclinical mastitis caused by coagulase-negative staphylococci (MSCNS). TRP and kynurenines were determined by high-performance liquid chromatography (HPLC), and IDO activity was calculated as the KYN/TRP ratio. The blood and milk samples were collected from 40 midlactation Holstein-Fresian cows from two herds in the Lublin region in Poland. In the milk samples from 20 cows with subclinical mastitis, coagulase-negative staphylococci were isolated and in the milk obtained from healthy cows growth of microorganisms was not detected. TRP, KYN and KYNA concentrations were significantly lower in milk of cows with MSCNS compared to control animals (4.47 vs. 7.24 µM, 0.14 vs. 0.21 µM, 1.58 vs. 2.18 nM, respectively). There was no statistically significant difference in TRP and KYNA concentrations in serum between the studied animal groups (32.97 vs. 39.29 µM, 31.3 vs. 26.5 nM, respectively). In turn, the level of KYN was lower in the serum (0.81 vs. 1.13 µM) of cows with mastitis compared to healthy ones. No statistically significant differences in IDO activity, both in serum and in milk (25.24 and 27.55, 28.56 and 27.17, respectively) was revealed between the studied groups. These findings may have potential implications for diagnosis of mastitis in cows because reduction of these parameters in milk might be a marker predicting the occurrence of the disease.

The presence of kynurenine aminotransferases in the human cornea: Evidence from bioinformatics analysis of gene expression and immunohistochemical staining.

PURPOSE: Kynurenine aminotransferases (KATs) catalyze the synthesis of kynurenic acid (KYNA), a compound of significant biological activity. The aim of this study is to investigate the presence and distribution of KAT immunoreactivity in the healthy human cornea. METHODS: Data on gene expression in human eye structures were extracted from public microarray experiments using Genevestigator software. Immunohistochemistry was conducted using polyclonal antibodies against KAT I, II, and III on sections of eight enucleated eyes from patients with choroidal melanoma. RESULTS: Bioinformatics analysis showed that all four KAT isoforms were actively transcribed in the cornea and the conjunctiva. Immunohistochemical analysis revealed the presence of KAT I, II, and III in all examined corneal sections. The corneal endothelium showed the strongest reactivity for all three KAT isoforms. There was a slight positive staining of the corneal stroma for KAT I and II. KAT III immunoreactivity was found only in the stroma of the limbal region. In the corneal epithelium, the expression of all three KAT isoforms showed a specific pattern of the stain with fine squatter granules throughout the cytoplasm. This reactivity was more pronounced in the basal cell layers. The intermediate cell layers showed only faint immunoreactivity, and occasionally, there was no staining. KAT I, II, and III were also present in the adjacent limbal conjunctiva. CONCLUSIONS: The results indicate that kynurenine can be metabolized to KYNA in the corneal epithelium, stroma, and endothelium.

Kynurenic Acid Induces Impairment of Oligodendrocyte Viability: On the Role of Glutamatergic Mechanisms.

Kynurenic acid (KYNA) is an end stage product of tryptophan metabolism with a variety of functions in the human body, both in the central nervous system (CNS) and in other organs. Although its activity in the human brain has been widely studied and effects on neural cells were emphasized, the effect of KYNA on oligodendroglial cells remains unknown. Present study aims at describing the activity of high concentration of KYNA in OLN-93 cells. The inhibition of OLN-93 oligodendrocytes viability by KYNA in a medium with reduced serum concentration has been demonstrated. Although decreased metabolic activity of KYNA treated OLN-93 cells was shown, the cells proliferation was not altered. KYNA treatment did not alter morphology as well as expression level of cell cycle and proliferation regulating proteins. Furthermore, glutamate receptor antagonists and agonists did not alter the inhibitory effect of KYNA on viability of OLN-93 oligodendrocytes. This study contributes to the elucidation of effects of KYNA on oligodendrocytes in vitro, yet further analyses are necessary to explain the mechanisms behind the damage and loss of myelin sheaths.

The effect of kynurenic acid on the synthesis of selected cytokines by murine splenocytes - in vitro and ex vivo studies.

Kynurenic acid (KYNA), a secondary product of the kynurenine pathway of tryptophan degradation, known mainly as an endogenous neuroprotectant, shows also immunotropic properties. Some quantities of KYNA are present in food and are effectively absorbed in the gastrointestinal tract. Since the spleen is an important target of dietary immunomodulators, the aim of the study was to determine the effect of exogenous KYNA on murine splenocytes. Splenocytes isolated from adult BALB/c mice were used in the study. Firstly, the effect of increasing KYNA concentrations (0-5 mM) on the viability, and proliferative and cytokine response (interleukin 1ß [IL-1ß], IL-6, IL-10, tumor necrosis factor α [TNF-α]) of murine splenocytes under in vitro conditions was determined. Then, proliferative and cytokine responses were determined in cells derived from animals receiving kynurenic acid in drinking water at concentrations of 2.5, 25, or 250 mg/l for 7-14 days. Cytokine levels were measured using commercial immunoassay (ELISA) kits, and cell viability and proliferation was determined with MTT reduction assay. Exogenous KYNA was characterised by a low level of cytotoxicity towards murine splenocytes, and was well tolerated by the animals receiving it in drinking water. As expected, it exhibited anti-inflammatory action towards the activated splenocytes, under both in vitro and ex vivo conditions. Surprisingly, however, KYNA itself influenced the activity of resting, non-stimulated cells, exerting an immunostimulant effect in vitro, and an immunosuppressive effect under ex vivo conditions. The obtained results indicate not only anti-inflammatory, but also more complex, immunomodulating properties of KYNA, which require more detailed investigation.

Kynurenic acid inhibits colon cancer proliferation in vitro: effects on signaling pathways.

Kynurenic acid (KYNA), a tryptophan metabolite, inhibits proliferation of several cancer cell lines including colon cancer, renal cancer and glioblastoma cells. Previous studies reported that inhibitory properties of KYNA may be related to interactions of KYNA with cell cycle regulators and signaling proteins. However, the exact molecular interaction of KYNA with signaling pathways in colon cancer cells has not been studied to date. The molecular mechanism of KYNA activity towards colon cancer cells may be of great importance taking into consideration that KYNA is present in several tissues and physiological fluids, including gastrointestinal tract, and it is also present in various products of human diet. In this study, the inhibitory effect of KYNA on activation of phosphoinositide 3-kinase/Akt (PI3K/Akt) and mitogen-activated protein kinase (MAPK) signaling pathways in colon adenocarcinoma HT-29 cells was revealed. KYNA decreased phosphorylation of Akt, ERK 1/2 and p38 kinases in HT-29 cells. Interestingly, the study revealed also unexpected effect of KYNA on Wnt pathway in HT-29 cells. KYNA in millimolar concentrations increased protein expression of ß-catenin. However, the nuclear translocation of ß-catenin in HT-29 cells exposed to KYNA was not observed. Moreover, KYNA 1 mM increased antiproliferative properties of inhibitors of signaling pathways: wortmannin, PD98059, SB202190 and IWR-1. Taking into consideration these results, KYNA may be seen as a potential chemopreventive agent in colon cancer or supportive agent in standard cancer chemotherapy. However, the interactions between KYNA, Wnt signaling pathway and ß-catenin need further studies to exclude potential effect of KYNA on colon carcinogenesis.

Effect of oral administration of kynurenic acid on the activity of the peripheral blood leukocytes in mice.

Kynurenic acid (KYNA), an endogenous tryptophan metabolite, is a selective ligand of the GPR35 receptor, expressed mainly on the immune cells. In inflammatory conditions, by affecting this receptor, KYNA inhibits the synthesis of pro-inflammatory cytokines and probably protects tissues from oxidative damage. However, we lack data regarding the effect of exogenous KYNA on the activity of immune cells in healthy individuals. The objective of this study has been to determine the influence of kynurenic acid administered to mice in different doses (2.5, 25 or 250 mg/l) and for different time periods (3, 7, 14, 28 days) in drinking water, on the activity of their peripheral blood leukocytes. The determinations comprised the proliferative activity of lymphocytes (MTT assay) and the phagocytic activity as well as the respiratory burst activity of granulocytes and monocytes (Phagotest, Phagoburst). It was only the lowest KYNA dose that influenced the mitogenic response of lymphocytes, namely by increasing the proliferation of T cells. The impact on the phagocytic activity was varied with KYNA dose and administration time. However, all the KYNA doses significantly lowered the activity of oxidative burst in phagocytes, which was probably associated with its antioxidant properties. In the light of the research results, kynurenic acid may find applications as an immuno-modulating agent able to correct an excessive or insufficient response of phagocytizing cells, protecting an organism from oxidative stress.

Loop diuretics inhibit kynurenic acid production and kynurenine aminotransferases activity in rat kidneys.

BACKGROUND: Loop diuretics became a cornerstone in the therapy of hypervolemia in patients with chronic kidney disease or heart failure. Apart from the influence on water and electrolyte balance, these drugs were shown to inhibit tissue fibrosis and renin-angiotensin-system activity. The kynurenine (KYN) pathway products are suggested to be uremic toxins. Kynurenic acid (KYNA) is synthesized by kynurenine aminotransferases (KATs) in the brain and periphery. The cardiovascular and renal effects of KYNA are well documented. However, high KYNA levels have been correlated with the rate of kidney damage and its complications. Our study aimed to assess the effect of loop diuretics, ethacrynic acid, furosemide, and torasemide on KYNA synthesis and KATs activity in rat kidneys in vitro. METHODS: Quantitative analyses of KYNA were performed using fluorimetric HPLC detection. Additionally, molecular docking studies determined the possible interactions of investigated compounds with an active site of KAT I and KAT II. RESULTS: All studied drugs inhibited KYNA production in rat kidneys in vitro at 0.5-1.0 mmol/l concentrations. Only ethacrynic acid at 1.0 mmol/l concentration significantly lowered KAT I and KAT II activity in kidney homogenates, whereas other drugs were ineffective. Molecular docking results indicated the common binding site for each of the studied loop diuretics and KYNA. They suggested possible residues involved in their binding to the active site of both KAT I and KAT II model. CONCLUSIONS: Our study reveals that loop diuretics may decrease KYNA synthesis in rat kidneys in vitro. The presented results warrant further research in the context of KYN pathway activity regulation by loop diuretics.

The Effects of Kynurenic Acid in Zebrafish Embryos and Adult Rainbow Trout.

Kynurenic acid (KYNA) is a metabolite of tryptophan formed on the kynurenine pathway. Its pharmacological effects are relatively well characterized in mammals, whereas its role in fish is poorly understood. Therefore, the aim of the study was to expand the knowledge of KYNA's presence inside a fish's body and its impact on fish development and function. The study was performed on zebrafish larvae and adult rainbow trout. We provide evidence that KYNA is present in the embryo, larva and mature fish and that its distribution in organs varies considerably. A study of KYNA's effect on early larval development suggests that it can accelerate larval maturation, especially under conditions that are suboptimal for fish growth. Moreover, KYNA in concentrations over 1 mM caused morphological impairment and death of larvae. However, long-lasting exposure of larvae to subtoxic concentrations of KYNA does not affect the behavior of 5-day-old larvae kept under standard optimal conditions. We also show that ingestion of KYNA-supplemented feed can lead to KYNA accumulation, particularly in the pyloric caeca of mature trout. These results shed new light on the relevance of KYNA and provide new impulse for further research on the importance of the kynurenine pathway in fish.

Induction of seizures and initiation of epileptogenesis by pilocarpine in zebrafish larvae.

Objective: Preclinical models of seizures and epilepsy in rodents contributed substantially to the discovery of currently available antiseizure medications. These were also broadly used for investigation of processes of epileptogenesis. Nevertheless, rodent models pose some limitations, thus, new models using alternative species are in high demand. The aim of this study was to describe a new model of seizures/epilepsy induced by the cholinomimetic agent, pilocarpine (PILO), in larval zebrafish. Methods: Local field potential (LFP) recordings were conducted to analyze electroencephalographic discharges and correlate it with larval behavior. Hematoxylin and eosin (H&E) staining, as well as TUNEL staining were performed to analyze morphology and apoptosis, respectively. Real-time quantitative polymerase chain reaction (qRT-PCR) was undertaken for gene expression analysis. Results: Acute exposure to PILO, in a concentration-dependent manner, induces electroencephalographic discharges in larval zebrafish, which behaviorally manifest as decreased locomotion and moving time, but enhanced movement velocity. The PILO-induced seizure-like activity is behaviorally distinct from this induced by the application of chemoconvulsant pentylenetetrazole (PTZ). Zebrafish larvae previously exposed to PILO (2 h), after a washing out period, exhibit spontaneous, unprovoked discharges and apoptotic changes in their brains. Significance: Here, we comprehensively investigated a new model of PILO-induced seizures/epilepsy in larval zebrafish. We propose that this model may be used to study epileptogenesis and for antiseizure drug screening purposes.

Fetal Sex as Moderating Factor for the Relationship Between Maternal Childhood Trauma and Salivary Kynurenic Acid and Tryptophan in Pregnancy: A Pilot Study.

Traumatic experiences and fetal development influence tryptophan (TRP) and its neuroactive byproduct, kynurenic acid (KYNA). Maternal TRP metabolite levels during pregnancy vary by fetal sex, with higher concentrations in mothers carrying male fetuses. This pilot study aimed to explore the relationship between offspring sex, maternal childhood trauma, and maternal salivary KYNA and TRP levels during pregnancy. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine KYNA and TRP levels in maternal saliva samples collected from 35 late-pregnancy participants. Maternal childhood trauma was assessed using the Childhood Trauma Questionnaire, including subscales for emotional abuse, physical abuse, sexual abuse, emotional neglect, and physical neglect. Among mothers pregnant with boys, salivary KYNA significantly correlated with physical and emotional neglect, and salivary TRP with emotional neglect. No significant correlations were found in mothers who delivered female offspring. Significant associations of childhood trauma and offspring sex were found for salivary KYNA but not TRP concentrations. Mothers with higher trauma levels who delivered boys exhibited higher levels of salivary KYNA compared to those with lower trauma levels. Moreover, mothers with higher trauma levels who delivered boys had higher salivary KYNA levels than those with higher trauma levels who delivered girls. This pilot study provides evidence of an association between maternal childhood trauma and TRP metabolism, measured in saliva, especially in mothers pregnant with boys. However, longitudinal studies with larger sample sizes are required to confirm these results.

Developmental Exposure to Kynurenine Affects Zebrafish and Rat Behavior.

Proper nutrition and supplementation during pregnancy and breastfeeding are crucial for the development of offspring. Kynurenine (KYN) is the central metabolite of the kynurenine pathway and a direct precursor of other metabolites that possess immunoprotective or neuroactive properties, with the ultimate effect on fetal neurodevelopment. To date, no studies have evaluated the effects of KYN on early embryonic development. Thus, the aim of our study was to determine the effect of incubation of larvae with KYN in different developmental periods on the behavior of 5-day-old zebrafish. Additionally, the effects exerted by KYN administered on embryonic days 1-7 (ED 1-7) on the behavior of adult offspring of rats were elucidated. Our study revealed that the incubation with KYN induced changes in zebrafish behavior, especially when zebrafish embryos or larvae were incubated with KYN from 1 to 72 h post-fertilization (hpf) and from 49 to 72 hpf. KYN administered early during pregnancy induced subtle differences in the neurobehavioral development of adult offspring. Further research is required to understand the mechanism of these changes. The larval zebrafish model can be useful for studying disturbances in early brain development processes and their late behavioral consequences. The zebrafish-medium system may be applicable in monitoring drug metabolism in zebrafish.