Effects of Fenofibrate and Gemfibrozil on Kynurenic Acid Production in Rat Kidneys In Vitro: Old Drugs, New Properties

Kidney dysfunction significantly increases the cardiovascular risk, even in cases of minor functional declines. Hypertriglyceridemia is the most common lipid abnormality reported in patients with kidney disorders. PPAR-α (peroxisome proliferator-activated receptor-α) agonists called fibrates are the main agents used to lower triglyceride levels. Kynurenic acid (KYNA) is a tryptophan (Trp) derivative directly formed from L-kynurenine (L-KYN) by kynurenine aminotransferases (KATs). KYNA is classified as a uremic toxin, the level of which is correlated with kidney function impairments and lipid abnormalities. The aim of this study was to analyze the effect of the most commonly used triglyceride-lowering drugs, fenofibrate and gemfibrozil, on KYNA production and KAT activity in rat kidneys in vitro. The influence of fenofibrate and gemfibrozil on KYNA formation and KAT activity was tested in rat kidney homogenates in vitro. Fenofibrate and gemfibrozil at 100 µM-1 mM significantly inhibited KYNA synthesis in rat kidney homogenates. Both fibrates directly affected the KAT I and KAT II isoenzyme activities in a dose-dependent manner at similar concentrations. The presented results reveal the novel mechanism of action of fibrates in the kidneys and suggest their potential role in kidney function protection beyond the well-known anti-hyperlipidemic effect.

Differences in the dynamics of changes in the concentration of kynurenic acid in the blood serum of depressed patients treated with electroconvulsive therapy

BACKGROUND

Nowadays, depression is a serious clinical problem, as the prevalence of its various forms increases and there are growing numbers of patients with severe forms of depression and treatment-refractory depression. Depressed patients have been observed to have decreased levels of kynurenic acid (KYNA), which is the only endogenous antagonist of ionotropic N-methyl-D-aspartate (NMDA) receptors. The aim of this study was to identify subgroups of patients differing in the dynamics of changes in KYNA concentration during electroconvulsive therapy (ECT).

SUBJECTS AND METHODS

The study included 32 patients with an ICD-10 diagnosis of a major depressive episode receiving ECT treatment and 48 healthy volunteers. Blood serum KYNA concentrations were determined using HPLC-based methods, and clinical assessment was performed using the Montgomery-Åsberg Depression Rating Scale (MADRS) and the Clinical Global Impressions (CGI) Scale.

RESULTS

Three subgroups of patients with depression were identified which differed in baseline KYNA levels and in the dynamics of changes in blood serum KYNA concentrations during and after ECT.

CONCLUSIONS

The largest number of patients with clinical improvement (83%) was observed in the subgroup with significantly lower pre-treatment, treatment and post-treatment KYNA concentrations than those determined in the control group. This subgroup of patients also showed the lowest dynamics of changes in KYNA concentrations during ECT. Clinical improvement was observed in 75% of depressed patients who had insignificantly lower pre-treatment levels of KYNA and slightly higher levels of this acid after 6 and 12 ECT sessions than controls. The smallest number of patients with clinical improvement (50%) was observed in the subgroup of patients who had similar pre-treatment and treatment concentrations of KYNA to controls and whose post-treatment concentrations of KYNA were significantly lower than those of healthy individuals.

Blood serum concentrations of kynurenic acid in patients diagnosed with recurrent depressive disorder, depression in bipolar disorder, and schizoaffective disorder treated with electroconvulsive therapy

OBJECTIVES

The aim of the present study was to compare blood serum kynurenic acid (KYNA) concentrations measured before ECT and after 1, 6 and 12 electroconvulsive treatment (ECT) sessions in patients with diagnoses of recurrent depressive disorder (RDD), depression in bipolar disorder (DBD) and schizoaffective disorder (SAD).

METHODS

The study group comprised of 50 patients with ICD-10 diagnoses of RDD, DBD and SAD. Blood serum KYNA concentrations were determined and clinical assessment was performed using the MADRS and the GAF scale.

RESULTS

Significant differences were found in blood serum KYNA levels between RDD, DBD and SAD patients treated with electroconvulsive therapy and healthy controls: 1) KYNA concentrations in DBD patients measured before ECT and after 12 ECT sessions were significantly lower than in the control group; 2) KYNA concentrations in the serum of RDD patients measured before ECT and after one and 12 ECT sessions were significantly lower than in the control group, while those measured after 6 ECT session did not differ significantly from KYNA concentrations in healthy controls; 3) higher pre-treatment blood serum concentrations of KYNA in DBD patients correlated with a higher number of illness phases and poorer general functioning before treatment; 4) significant relationships were found between higher blood serum concentrations of KYNA in RDD patients after 1 ECT session and male gender, and between higher KYNA concentrations after 6 ECT sessions and increased depression and poorer functioning before treatment in those patients.

CONCLUSIONS

Results show that KYNA concentrations in all diagnostic groups were lower before ECT (not statistically significant for the SAD group) and that there were no significant changes in those concentrations (compared with the baseline) during ECT.

Changes in the levels of kynurenic acid and selected proinflammatory cytokines after pharmacological treatment and electroconvulsive therapy (ECT) in patients with depressive disorder

The aim of the present study was to compare the concentrations of KYNA, 3-OH-KYN and the cytokines TNF-α and IL-6 in patients with depression vs. healthy controls as well as in patients with depression treated pharmacologically vs. those treated using ECT. We also evaluated the relationship between the concentrations of KYNA, 3-OH-KYN and the cytokines TNF-α and IL-6 and clinical improvement measured on the MADRS scale in patients treated pharmacologically and those treated with ECT.

Subjects and methods: The study group comprised 29 patients aged 28 to 60 years with a diagnosis of a major depressive episode. Eleven of the patients received pharmacological treatment and 18 were treated with ECT.

Patients were assayed for serum levels of KYNA and the cytokines IL-6 and TNF-α. Clinical improvement was measured on the MADRS depression rating scale and the clinical global impression (CGI) scale.

Results: Significant differences were found in KYNA levels between depressive patients and healthy controls. Pharmacological treatment significantly contributed to the increase in KYNA levels and ECT – to the increase in TNF-α levels in depressive patients.

Conclusions:

[POL-PAVTI--Polish report on transcatheter pulmonary artery valve implantation of Melody-Medtronic prosthesis in the first 14 patients in Poland]

AIM

To assess the early results of the pulmonary artery valve transcatheter implantation (PAVTI) in pts included into POL-PAVTI registry. Detailed medical and economic analyses were performed.

METHODS

Pulmonary artery valve implantation was performed in 14 pts (9 men), aged 16-31 (mean 24.6 +/- 4.8) years, with pulmonary homograft dysfunction after total repair of tetralogy of Fallot (4 pts), pulmonary atresia (2 pts), pulmonary stenosis (1 pt), common arterial trunk type I (1 pt), Ross procedure (3 pts) and TGA - Rastelli operation (3 pts). Eleven pts underwent in the past 2-5 surgical or/and catheter interventions. Indication for PAVTI was based on clinical evaluation and echocardiographic studies. Assessment of morphological and functional features of the right ventricle (RV) and homograft with the use of cardiac magnetic resonance (CMR) was performed in 10 cases. Pulmonary stenosis (max. pulmonary gradient 32-119, mean 72 +/- 28 mmHg) was observed in 13 pts and/or significant pulmonary regurgitation in 10 pts. The procedure was performed in general anesthesia. The deployment of a valved stent in the pulmonary valve position was preceded by a metal stent implantation. Results were evaluated by echocardiography two days after the procedure and one month later. Four patients were evaluated 6 months after procedure.

RESULTS

Time of the procedure varied 60-190 (mean 127 +/- 35) min, time of fluoroscopy ranged 12-31 (mean 21 +/- 11) min. PAVTI was successfully performed in all pts without serious complications. Patients were discharged from the hospital 48-293 (mean 120 +/- 71) h after procedure. Significant reduction of pulmonary gradient after the procedure assessed by echocardiography was observed on the second day (20-60, mean 38 +/- 12 mmHg, p < 0.0001) and one month (19-52, mean 34 +/- 9 mmHg, p < 0.0001). Mild pulmonary regurgitation was observed in 2 pts. In 5 pts evaluated 6 months after procedure haemodynamic parameters were unchanged; no late complications were observed. Average cost of the procedure including a price of the valve (82 000 PLN) was 98 000 PLN.

CONCLUSIONS

Pulmonary artery valve transvascular implantation is an effective and safe method of non-surgical treatment for patients with homograft dysfunction. Cost-effectiveness is approvable.

Exhaled nitric oxide concentration in patients after heart transplantation

Nitric oxide (NO) is present in exhaled air in humans and its level may decrease in heart diseases. In the present study we prospectively investigated how heart transplantation treated with oral immunosuppresive drugs based on ciclosporine A influences the exhaled NO concentration (exNO). The study was performed in 17 patients after heart transplantation in various time after procedure and 15 nonsmoking healthy volunteers as a control group. Patients after heart transplantation were free of clinical signs of rejection. End-tidal concentration of exNO was measured by the use of a chemiluminescence method. We found no statistically significant differences in the exNO level between patients after heart transplantation and healthy controls (6.81+/-2.70 part per billion (ppb) in the transplant group vs. 6.01+/-3.43 ppb in the control group). We conclude that heart transplantation and immunosuppresive therapy do not influence the exhaled NO concentration.

[Newborn life threatening respiratory failure treatment with extracorporeal membrane oxygenation]

THE AIM of the study was to show first results of newborn life threatening respiratory failure treatment with extracorporeal membrane oxygenation (ECMO) in Poland.

MATERIAL

Nine newborns were treated with extracorporeal membrane oxygenation in Silesian Center for Heart Diseases. Newborns were born in 38 week of gestational age (36-41 weeks) with mean birth weight of 3490 g. Reasons for the referral were: meconium aspiration syndrome, infection, and pulmonary hypertension. Each newborn fulfilled an Extracorporeal Life Support Organization (ELSO) criteria for extracorporeal membrane oxygenation.

RESULTS

seven out of nine of patients treated with extracorporeal membrane oxygenation survived. Full clinical stabilization was reached about 6th hour of treatment. Mean extracorporeal oxygenation time was 162 hours. For eight newborns veno-venous method was applied and for one newborn veno-arterial method. Roller pump was used in 7 cases and centrifugal pomp in one case. Five newborns had uneventful treatment. During extracorporeal membrane oxygenation therapy we have observed several complications: PDA, hemorrhagic complications, renal failure, arterial hypertension, septicemia, tubing rupture.

CONCLUSIONS

extracorporeal oxygenation is an effective method of treatment for newborn life threatening respiratory failure. Obtained results do not differ much from Extracorporeal Life Support Organization register results. The most essential problem for extracorporeal membrane oxygenation therapy is correct qualification, early referral, safe transportation as well as the development of centers providing ECMO treatment.

Increased brain quinolinic acid production in mice infected with a hamster neurotropic measles virus

In order to examine the status of quinolinic acid (QUIN) metabolism in a model of delayed excitotoxic neurodegeneration, the de novo production of QUIN from 3-hydroxyanthranilic acid was assessed in brain homogenates and brain slices of mice injected with hamster neurotropic measles virus. In the hippocampus, which presents exclusive nerve cell loss in this model, the activity of 3-hydroxyanthranilic acid oxygenase, an astrocytic enzyme responsible for the biosynthesis of QUIN, was increased 3.3-fold by 7 days after virus inoculation. Less dramatic increases were observed in the cerebral cortex and the striatum, while cerebellar enzyme activity was not different from control values. In the same brain homogenates, no changes occurred in the activities of kynurenine aminotransferase, the biosynthetic enzyme of the neuroprotectant kynurenic acid, and of the astrocytic marker glutamine synthetase. At 7 days postinoculation, hippocampal slices from virus-treated animals, when exposed to 3-hydroxyanthranilic acid, produced 18 times more QUIN than slices from control animals. Notably, a significant increase was also seen 3 days postinoculation, i.e., at a time when astrocytes had started to proliferate but prior to the onset of neurodegeneration (Eur. J. Neurosci. 3:66-71, 1991). These data suggest that astrocyte-derived QUIN may play a causative role in the occurrence of hippocampal nerve cell loss in measles virus-infected mice.

[Polycythemia]

On the basis of own material, the authors discuss the epidemiology, clinical picture, and results of treatment of newborns with polycythaemia. An analysis shows that the blood hyperviscosity syndrome is an underestimated cause of many pathological signs in newborns.

Quinolinate-like neurotoxicity produced by aminooxyacetic acid in rat striatum

The endogenous tryptophan metabolite quinolinic acid elicits in rodent brain a pattern of neuronal degeneration which resembles that caused by L-glutamate. Its qualities as a neurotoxic agent raised the hypothesis that quinolinic acid might be involved in the pathogenesis of human neurodegenerative disorders. Kynurenic acid, another endogenous tryptophan metabolite and preferential N-methyl-D-aspartate (NMDA) antagonist, has been shown to block quinolinic acid neurotoxicity. Here we report that microinjections of aminooxyacetic acid (AOAA), an inhibitor of kynurenine transaminase and of other pyridoxal phosphate-dependent enzymes, into the rat striatum produce neuronal damage resembling that caused by quinolinic acid. AOAA-induced striatal lesions can be prevented by kynurenic acid and the selective NMDA antagonist 2-amino-7-phosphonoheptanoic acid. These results suggest that AOAA produces excitotoxic lesions by depleting brain concentrations of kynurenic acid (inhibition of synthetic enzyme) or due to impairment of intracellular energy metabolism (depletion of cell energy resources). The concept of deficient neuroprotection due to metabolic defects might help to clarify the pathogenesis of human neurodegenerative disorders and to develop strategies that may be useful in their treatment.

Antiparkinsonian drugs memantine and trihexyphenidyl potentiate the anticonvulsant activity of valproate against maximal electroshock-induced seizures

Memantine increased the threshold for electroconvulsions, when administered at 1.0-6.0 mg/kg (i.p.) and given in subthreshold doses of 0.0156, 0.0625, 0.125 and 0.5 mg/kg (i.p.) potentiated the protective efficacy of valproate, against maximal electroshock (50 mA)-induced seizures in mice, lowering the ED50 from 235 to 197, 172, 164 and 130 mg/kg, respectively. Trihexyphenidyl, applied in doses of 30 and 50 mg/kg (i.p.), did not influence the electroconvulsive threshold per se but when combined with valproate, strongly enhanced its anticonvulsant activity against maximal electroshock-induced seizures lowering the ED50 from 206 to 103 and 46 mg/kg, respectively. The chimney test and retention testing in mice revealed that administration of memantine at 0.5 mg/kg (i.p.) or trihexyphenidyl at 30 mg/kg (i.p.) together with valproate in doses of 130 or 103 mg/kg (i.p.), respectively, resulted in motor impairment and caused impairment of long-term memory, similar to the effects of valproate alone, when applied at its ED50 against maximal electroshock. Neither memantine nor trihexyphenidyl altered the total level of valproate in plasma. It may be concluded that the potentiation of the anticonvulsant activity of valproate, by memantine and trihexyphenidyl, is not associated with a pharmacokinetic interaction.

Aminooxyacetic acid produces excitotoxic lesions in the rat striatum

The neuropathological, biochemical, and behavioral effects of intrastriatal injection of aminooxyacetic acid (AOAA), a non-specific transaminase inhibitor, were examined in rats. AOAA, 0.1-1 mumol, produced neuronal damage when injected into the striatum of adult rats but failed to damage the striatum of 6-d-old or decorticated rats. AOAA-induced (0.25 mumol-1 mumol) striatal lesions in adult rats displayed excitotoxic characteristics and could be prevented by the N-methyl-D-aspartate (NMDA) receptor antagonists (-)-2-amino-7-phosphono-heptanoate (AP7; 0.25 mumol) or kynurenate (KYNA; 0.5 mumol), but not by the non-NMDA antagonist 2,3-dihydroxy-6-nitro-7-sulphamoyl-benzo(F)quinoxaline (NBQX; 0.25 mumol). AOAA produced a dose-dependent reduction in striatal L-glutamate decarboxylase activity, as measured 14 d following intrastriatal injection, which could also be prevented by AP7 or KYNA, but not by NBQX. These findings suggest that AOAA-induced lesions are preferentially mediated by activation of the NMDA subtype of excitatory amino acid receptors. Behavioral studies revealed that the cataleptic response to haloperidol, 2 mg/kg, was decreased whereas the cataleptic response to arecoline, 15 mg/kg, and morphine, 15 mg/kg, was potentiated in AOAA lesioned animals 14 d following bilateral intrastriatal injections of AOAA, 0.25 and 1 mumol. In rats which received unilateral intrastriatal injection of AOAA, 0.1-1 mumol, apomorphine, 0.5 mg/kg, induced circling towards the lesioned side. Rats which received AP7, 0.25 mumol, or KYNA, 0.5 mumol, coadministered with AOAA, 0.25 mumol, behaved as vehicle-treated controls, while those which received NBQX, 0.25 mumol, and AOAA, 0.25 mumol, had behavioral patterns similar to those subjected to AOAA alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of MK-801 on the anticonvulsant activity of antiepileptics

MK-801 (a potent non-competitive antagonist of N-methyl-D-aspartic acid-mediated events) in subcutaneous doses of 0.1 and 0.2 mg/kg increased the threshold for electroconvulsions and in doses of 0.0031 and 0.0125 mg/kg enhanced the protective activity of valproate against maximal electroshock-induced convulsions in mice. Valproate-induced side-effects (evaluated by means of dark-avoidance acquisition and retention testing and the chimney test) at its ED50 against maximal electroshock (i.e. 268 mg/kg) were pronounced whereas they were absent in the case of a combined treatment with MK-801 (0.0125 mg/kg) and valproate (91 mg/kg). This treatment provided 50% protection against maximal electroshock-induced seizures. Moreover, MK-801 (0.0125 and 0.05 mg/kg) potentiated the anticonvulsant action of phenobarbital, reducing phenobarbital-induced motor impairment totally at 0.05 mg/kg, but did not influence the protection offered by carbamazepine and diphenylhydantoin at 0.05 mg/kg. The N-methyl-D-aspartic acid antagonist did not affect the total plasma levels of either valproate or phenobarbital (as measured by immunofluorescence), so a pharmacokinetic interaction, in terms of total plasma levels at least, is unlikely to be involved in the observed effects. The finding that the combined treatment of MK-801 with valproate or phenobarbital, apart from the distinct potentiation of their anticonvulsant activities, is devoid of side-effects should be carefully considered.