Insulin potentiates the anticonvulsive activity of phenytoin against maximal electroshock-induced seizures in mice.

INTRODUCTION: The limitations imposed by the blood-brain barrier (BBB) on the sufficient accumulation of antiepileptic drugs (AEDs) in the epileptogenic focus is considered the major cause of the high percentage of morbidity and mortality cases among epilepsy patients. This study aimed at examining the potential effect of insulin on the anticonvulsant action of phenytoin (PHT) in the mouse maximal electroshock-induced seizure model. SUBJECTS AND METHODS: PHT was administered orally in single doses either alone or in combination with insulin given as single intraperitoneal injections. To assess the anticonvulsant activity of PHT, the ED50 values were calculated. The current strength (CS50) threshold for insulin was also estimated. The animals were sacrificed, and the brains were removed to measure their PHT concentrations in the brain. RESULTS: It has been demonstrated that insulin (in all used doses) has no effect on the CS50 but can cause a significant increase in concentrations of PHT in the brain and potentiate the antiepileptic efficiency of this drug in electroshock-induced models of epilepsy in mice. CONCLUSIONS: The combination of insulin with PHT may be of great importance for developing new treatment possibilities following further investigations with other animal models of epilepsy and preclinical studies. Further research is also needed to explore the concentrations of PHT in the brain and the anticonvulsant activity of this drug against maximal electroshock seizures in diabetic mice.

Apigenin inhibits infectious bronchitis virus replication in ovo.

OBJECTIVE: Infectious bronchitis virus (IBV), for which no effective drugs are available, is among the most important causes of economic loss within the poultry industry. Apigenin is a flavonoid that can be isolated from plants. Apigenin has low toxicity with anti-viral activity. However, the effects of apigenin against IBV remain unclear. MATERIALS AND METHODS: Thus, here we investigate the anti-viral effect of apigenin on IBV using 10 day-old embryonated eggs by determining the virus titer by embryo infective doses50 (EID50/mL) and determining IBV genomes copy number (per µL) of allantoic fluid. RESULTS: We found that apigenin protected embryonated eggs from IBV. Additionally, apigenin reduced the log titer of the IBV with a significant correlation of up to 9.4 times at 2 µg/egg. Also, apigenin appears to significantly reduce IBV genomes copy number (per µL) in the allantoic fluid. CONCLUSIONS: Apigenin may be a promising approach for the treatment of IBV, since it protects embryonated eggs from IBV in ovo and suppresses viral replication.

Punicalagin and zinc (II) ions inhibit the activity of SARS-CoV-2 3CL-protease in vitro.

OBJECTIVE: Coronavirus 2019 (COVID-19) has now been declared as a worldwide pandemic. Currently, no drugs have been endorsed for its treatment; in this manner, a pressing need has been developed for any antiviral drugs that will treat COVID-19. Coronaviruses require the SARS-CoV-2 3CL-Protease (3CL-protease) for cleavage of its polyprotein to yield a single useful protein and assume a basic role in the disease progression. In this study, we demonstrated that punicalagin, the fundamental active element of pomegranate in addition to the combination of punicalagin with zinc (Zn) II, appear to show powerful inhibitory activity against SARS-CoV-2. MATERIALS AND METHODS: The 3CL protease assay kit was used to quantify 3CL protease action. The tetrazolium dye, MTS, was used to evaluate cytotoxicity. RESULTS: Punicalagin showed inhibitory action against the 3CL-protease in a dose-dependent manner, and IC50 was found to be 6.192 µg/ml for punicalagin. Punicalagin (10 µg/mL) demonstrated a significant inhibitory activity toward 3CL-protease activity (p < 0.001), yet when punicalagin is combined with zinc sulfate monohydrate (punicalagin/Zn-II) extremely strong 3CL-protease activity (p < 0.001) was obtained. The action of 3CL-protease with punicalagin/Zn-II was decreased by approximately 4.4-fold in contrast to only punicalagin (10 µg/mL). Likewise, we did not notice any significant cytotoxicity caused by punicalagin, Zn-II, or punicalagin/Zn-II. CONCLUSIONS: We suggest that these compounds could be used as potential antiviral drugs against COVID-19.

Nigella sativa oil and thymoquinone ameliorate albuminuria and renal extracellular matrix accumulation in the experimental diabetic rats.

OBJECTIVE: Increasing evidence suggests that Nigella sativa oil (NSO) and its principal bioactive constituents, thymoquinone (TQ), exhibit antioxidant, antihyperglycemic and renoprotective effects in streptozotocin (STZ)-induced diabetes in rats. However, the potential molecular mechanisms by which NSO and TQ may exert their actions in the diabetic kidney are still poorly characterized. This study was designed to investigate the effect of NSO and TQ treatment on the albuminuria, podocyte injury and the complex systems controlling the extracellular matrix proteins accumulation and angiogenesis in the STZ-induced model of diabetic nephropathy. MATERIALS AND METHODS: Adult female Wistar rats were divided into four experimental groups (control, untreated STZ-diabetic, and NSO or TQ treated STZ-diabetic rats). The treated rats received 2 mL/kg NSO or 50 mg/kg TQ via oral gavage once a day for 10 weeks. RESULTS: The results showed that the albuminuria and the kidney weight/body weight ratio were increased in the diabetic rats compared with the control animals and they were significantly ameliorated by the treatment with NSO or TQ. The real-time PCR showed that the NSO and TQ treatment prevented diabetes-induced downregulation of mRNA expression of the podocyte-specific marker (podocin) as well as the mRNA overexpressions of collagen IV, transforming growth factor-ß1 (TGF-ß1) and vascular endothelial growth factor-A (VEGF-A) in the diabetic kidney. These results were also confirmed by immunohistochemistry. CONCLUSIONS: NSO and TQ treatment decreased albuminuria in the experimental models of the diabetic nephropathy by the preservation of the podocyte function; along with the suppression of enhanced extracellular matrix gene expression through interfering with TGF-ß1 production and angiogenesis.

Cardiac autonomic dysfunction in young obese males is not associated with disturbances in pituitary-thyroid axis hormones.

OBJECTIVE: Obesity has been associated with hypothyroidism and cardiac autonomic dysfunction. The present study aimed to investigate whether cardiac autonomic dysfunction in young obese males might be related to an underlying thyroid disturbance. PATIENTS AND METHODS: On the basis of body mass index (BMI), 40 participants were grouped into normal weight group (NW; BMI = 18.5-25 kg/m(2); n = 15), over weight group (OW; BMI = 25-29.9 kg/m(2); n = 12) and obese group (OB; BMI ≥ 30 kg/m(2); n = 13). Electrocardiogram was recorded using PowerLab system and the time and frequency domain measures of heart rate variability (HRV) were calculated. Fasting blood samples were drawn for measurement of serum thyroid stimulating hormone (TSH), total thyroxin (TT4) and total triiodothyronine (TT3) concentrations. RESULTS: The levels of TSH, TT4 and TT3 were not significantly different between the groups. The frequency domain HRV parameter reflecting parasympathetic tone (high-frequency normalized units, HFnu) was significantly reduced in OB group. The parameters which reflect sympathetic activation (Heart rate, low-frequency normalized units; LFnu and the LF/HF ratio) were significantly increased in the OB group. HFnu was significantly and negatively correlated with BMI, waist hip ratio and body fat percentage, whereas LFnu and LF/HF ratio were significantly and positively correlated with the above mentioned parameters. No significant relationships were noted between the HRV parameters and the levels of TSH or thyroid hormones. CONCLUSIONS: Cardiac autonomic dysfunction in obese young adult males is not linked with underlying thyroid disturbance.

NMDA-induced 45Ca release in the dentate gyrus of newborn rats: in vivo microdialysis study.

This in vivo study, aimed at detecting the N-methyl-D-aspartate (NMDA) evoked Ca(2+)-induced Ca(2+) release from intracellular stores in the neonatal rat brain, demonstrates that the application of 5 mM N-methyl-D-aspartate via a microdialysis probe for 20 min to the dentate gyrus (DG) of halotane-anesthetized 7 day-old (postnatal day 7, PND 7) rats induces a prolonged decrease in Ca(2+) concentration in an initially calcium-free dialysis medium, indicative of a drop in the extracellular concentration of Ca(2+) and Ca(2+) influx to neurons. In parallel experiments, a huge NMDA-evoked release of 45Ca from the pre-labeled endogenous Ca(2+) pool was observed and interpreted as the expression of intracellular Ca(2+) release. Dantrolene (100 microM) significantly inhibited the NMDA-induced 45Ca release, whereas 250 microM ryanodine exerted an unspecific biphasic effect. Autoradiographic and immunocytochemical detection of ryanodine receptors and calbindin D(28K), respectively, in the hippocampal region of PND 7 rats displayed a pronounced expression of [3H]ryanodine binding sites in the DG, but only a slight immunoreactivity of calbindin D(28K). Plastic changes in neurons or excitotoxic neuronal damage induced by the activation of NMDA receptors are mediated by Ca(2+) signals, resulting from an influx of extracellular Ca(2+), and also in some neurons, from the release of intracellular Ca(2+). Our previous in vivo microdialysis experiments visualized NMDA-evoked 45Ca release in the adult rat dentate gyrus, attributable to Ca(2+)-induced Ca(2+) release from the ryanodine-sensitive pool. An additional role of calbindin in the mechanism of this phenomenon has been suggested. This aspect has not been studied in vivo in newborn rats. Our present results indicate that the release of 45Ca from the prelabeled intracellular, dantrolene-sensitive Ca(2+) pool in the DG neurons of immature rats, most probably representing a phenomenon of Ca(2+)-induced Ca(2+) release, significantly participates in the generation of NMDA receptor-mediated intracellular Ca(2+) signals, whereas the role of calbindin D(28K) in the mechanism of 45Ca release is negligible.

N-methyl-D-aspartate receptor-mediated, calcium-induced calcium release in rat dentate gyrus/CA4 in vivo.

Previously, by using in vivo microdialysis, we demonstrated a huge release of 45Ca2+ from prelabeled tissues to dialysate that was evoked by application of N-methyl-D-aspartate (NMDA) to the rat dentate gyrus (DG) and sector 4 of the cornu ammonis. To establish the mechanism of this phenomenon, in the present study, we characterized its NMDA receptor dependence, investigated the mechanism of 45Ca2+ removal from the cells, and evaluated the possible involvement of calcium-binding protein calbindin D28k and of ryanodine receptors. Microdialysis experiments demonstrated a dose-response relation between NMDA and 45Ca2+ release and sensitivity of this phenomenon to inhibition by 10 microM MK-801 and 5 mM 5-(N,N-dimethyl)-amiloride, thus indicating the NMDA receptor dependence and a role of Na+/Ca2+ exchanger in mediating 45Ca2+ release from cells. Immunocytochemical experiments confirmed that DG granule cells in the investigated inbred rat strain are strongly calbindin D28k-immunopositive, indicating probable involvement of this protein. However, microdialysis studies demonstrated that NMDA-evoked 45Ca2+ release was suppressed by 100 microM dantrolene and 250 microM ryanodine, whereas 50 microM ryanodine stimulated this effect. This points to a key role in the investigated phenomenon of calcium-induced calcium release (CICR) via ryanodine receptors. To our knowledge, this is the first in vivo demonstration of NMDA-evoked CICR. We postulate the usefulness of microdialysis in such studies.

Effects of caffeine on NMDA-evoked 45Ca2+ release in the rate dentate gyrus in vivo.

Caffeine in 10(-2) M concentration per se activates ryanodine receptors (RyR) in vitro, thereby increasing the intracellular concentration of Ca2+ ([Ca2+]i). In general opinion, caffeine applied in vivo in much lower doses does not affect [Ca2+]i in neurones. However, it was recently demonstrated that caffeine in low concentrations in vitro potentiates evoked Ca2+ release in neurones via RyR. Microdialysis of the rat dentate gyrus (DG), combined with measurement of 45Ca2+ efflux, has been used in our laboratory to study in vivo NMDA-evoked calcium induced calcium release (CICR) via RyR. The aim of the present microdialysis study was to investigate in vivo effects of caffeine, applied systemically in a pharmacologically-relevant dose, and locally in the dialysis medium in very high concentration, on the NMDA-evoked CICR in DG neurones. To ensure steady brain concentration of caffeine, its systemic (i.p.) administration in a dose of 40 mg/kg was followed by a continuous i.p. infusion of 80 micrograms/kg/min and application of 0.4 mM caffeine in the dialysis medium. The results demonstrated that in the rat DG, local administration of 50 mM caffeine significantly stimulates a spontaneous 45Ca2+ efflux and its release induced by 5 mM NMDA. However, systemic administration of caffeine had no effect on spontaneous and NMDA-induced 45Ca2+ release in the rat DG, which supports the view that caffeine, applied in vivo, even in high doses, does not influence CICR in brain neurones.

Insulin impairs the anticonvulsive activity of carbamazepine against maximal electroshock-induced seizures in mice.

In view of the data indicating that insulin can modify penetration of some drugs across cell membranes and tissue barriers, particularly the blood-brain barrier, the aim of the present study was to evaluate the effect of insulin on both the anticonvulsant activity and the brain concentration of carbamazepine in mice suffering from seizures induced by maximal electroshock. The antiepileptic drug was administered per os in single doses either alone or in combination with insulin given as single intraperitoneal injections. To assess the anticonvulsant activity of carbamazepine the ED50 values were calculated. The results indicate that insulin given in doses up to 2 units/kg did not affect the convulsive threshold, whereas insulin applied at 2 units/kg led to a significant reduction in the anticonvulsant activity of carbamazepine, as judged by an increase in the ED50 value from 16.2 to 41.3 mg/kg. This effect was accompanied by the marked reduction in both the brain and blood concentrations of the drug. It is likely, therefore, that the inhibitory activity of insulin on the anticonvulsive function of carbamazepine is related not only to the effect of the former on the blood-brain transport of the latter, but also to insulin-induced modulation of the serum concentration of the drug.