Dose proportionality and bioavailability of quinoxaline-based JNK inhibitor after single oral and intravenous administration in rats.

The dose proportionality and bioavailability of the potential anti-inflammatory and neuroprotective JNK inhibitor 11H-indeno[1,2-b]quinoxalin-11-one oxime (IQ-1) were evaluated by comparing pharmacokinetic parameters after single oral (25, 50 and 100 mg/kg) and intravenous (1 mg/kg) IQ-1 administration in rats.IQ-1 and its major metabolite ketone 11H-indeno[1,2-b]quinoxalin-11-one (IQ-18) were isolated from plasma samples by liquid-liquid extraction. IQ-1 (E-isomer) and IQ-18 were simultaneously quantified in plasma by the validated method of liquid chromatography with triple quadrupole mass spectrometry (HPLC-MS/MS).The absolute bioavailability of IQ-1 was < 1.5%. Cmax values were 24.72 ± 4.30, 25.66 ± 7.11 and 37.61 ± 3.53 ng/mL after single oral administration of IQ-1 at doses of 25, 50 and 100 mg/kg, respectively. IQ-1 exhibited dose proportionality at 50-100 mg/kg dose levels, whereas its pharmacokinetics was not dose proportional over the range of 25-50 mg/kg. IQ-18 demonstrated the invariance of the dose-normalized Cmax.In this study we systematically elucidated the absorption characteristics of IQ-1 in rat gastrointestinal tract and provided better understanding of IQ-1 pharmacology for the future development of a new formulations and therapeutic optimisation.

Neuroprotective Effects of a Novel Inhibitor of c-Jun N-Terminal Kinase in the Rat Model of Transient Focal Cerebral Ischemia.

A novel specific inhibitor of c-Jun N-terminal kinase, 11H-indeno[1,2-b]quinoxalin-11-one oxime sodium salt (IQ-1S), has a high affinity to JNK3 compared to JNK1/JNK2. The aim of this work was to study the mechanisms of neuroprotective activity of IQ-1S in the models of reversible focal cerebral ischemia (FCI) in Wistar rats. The animals were administered with an intraperitoneal injection of IQ-1S (5 and 25 mg/kg) or citicoline (500 mg/kg). Administration of IQ-1S exerted a pronounced dose-dependent neuroprotective effect, not inferior to the effects of citicoline. Administration of IQ-1S at doses of 5 and 25 mg/kg reduced the infarct size by 20% and 50%, respectively, 48 h after FCI, whereas administration of citicoline reduced the infarct size by 34%. The administration of IQ-1S was associated with a faster amelioration of neurological status. Control rats showed a 2.0-fold increase in phospho-c-Jun levels in the hippocampus compared to the corresponding values in sham-operated rats 4 h after FCI. Administration of IQ-1S at a dose of 25 mg/kg reduced JNK-dependent phosphorylation of c-Jun by 20%. Our findings suggest that IQ-1S inhibits JNK enzymatic activity in the hippocampus and protects against stroke injury when administered in the therapeutic and prophylactic regimen in the rat model of FCI.

An improved three-vessel occlusion model of global cerebral ischemia in rats.

We developed an improved three-vessel occlusion model of global cerebral ischemia in rats. This method consists in cessation of cerebral blood flow by accessing a. carotis communis sinistra through the ventral surface of the neck as well as tr. brachiocephalicus and a. subclavia sinistra through the first intercostal space, bypassing the pleural cavity and excluding pneumothorax. After the occlusion of the vessels that resulted in interruption of their blood flow, according to laser-Doppler flowmetry, there was a sharp decline in local cerebral blood flow in the visual cortex to 4±1% of the initial level. After restoring the level of local cerebral blood flow at the 5th minute, 10th minute, 20th minute and 24th hour of reperfusion, the levels of local cerebral blood flow were 51±7%, 41±5%, 35±8% and 54±9% of the initial level, respectively. Histo-quantitative analysis of changes in neurons of the hippocampus of rats showed that after ischemic injury, the numerical density of neurons in hippocampal zone CA1 in the observed 1mm2 region decreased by 29%, 22%, and 35%, respectively, compared to sham-operated animals (p<0.05). By the first day after global cerebral ischemia, the experimental group had shown a mean neurological deficit score equal to 7.5±1.0 and 7.9±0.7 points, followed by a decrease up to score 6.5±1.1 and 5.9±0.7 on the third day, 4.6±0.8 and 4.7±0.5 on the fifth day (on chloral hydrate and propofol anesthesia correspondently).

Neuroprotective effects of p-tyrosol after the global cerebral ischemia in rats.

BACKGROUND: Salidroside is a biologically active compound derived from Rhodiola rosea L. Studies showed that salidroside after i.v. injection is extensively metabolized to p-tyrosol and only trace amounts of salidroside are found in the brain tissue. OBJECTIVE: The aim of the study was to investigate the neuroprotective effects of p-tyrosol in the global cerebral ischemia-reperfusion (GCI) model. STUDY DESIGN: A total of 103 Wistar rats were assigned to groups of sham-operated (n=10), control (n=42), p-tyrosol-treated (n=36), and pentoxifylline-treated (n=15) animals. The rats of control, p-tyrosol-treated, and pentoxifylline-treated groups received intravenously 0.9% NaCl solution, 2% solution of p-tyrosol in doses of 5mg/kg, 10mg/kg, and 20mg/kg, and pentoxifylline in a dose of 100mg/kg, respectively, daily for 5 days. Rats were examined at days 1, 3, and 5 after GCI. After evaluation of neurological deficit, animals were euthanized for morphological and biochemical characterization. METHODS: Rats of control, p-tyrosol-treated, and pentoxifylline-treated groups were exposed to three-vessel model of GCI. Neurological deficit, numeric density of neurons in hippocampal CA1 region, and percentage of neurons with focal and total chromatolysis were studied. Biochemical study assessed contents of conjugated dienes and fluorescent products in brain homogenate. RESULTS: In control group, only 50.0% of rats survived by day 5 after the GCI; 38.1% of survived animals had severe neurologic deficit. In brain tissue of PTX-treated rats, the levels of diene conjugates and fluorescent products were 79% and 73%, respectivley, at day 5 compared with control. Differences in diene conjugates were statistically significant compared with control. The survival rate of animals treated with 20mg/kg p-tyrosol was 82.3% at day 5 after GCI. In p-tyrosol-treated GCI rats, the numeric density of neurons in the hippocampal CA1 region was higher by 31% compared with control. The percentage of neurons with focal and total chromatolysis decreased by 27% and 43%, respectively. At day 5 after GCI, the levels of conjugated dienes and fluorescent products were significantly lower (by 37% and 45%, respectively) in group of animals treated with 20mg/kg p-tyrosol compared with control. Moderate neuroprotective effects of 5mg/kg p-tyrosol administration were documented only at day 5 after GCI. In case of 10mg/kg p-tyrosol administration, neuroprotection was documented sooner: at day 1 or 3 after GCI. However, administration of 5 and 10mg/kg p-tyrosol did not affect animal survival. CONCLUSION: Course administration of intravenous p-tyrosol in a dose of 20mg/kg increased survival, reduced neurological deficit after GCI, attenuated neuronal damage in the hippocampus, and attenuated lipid peroxidation in brain tissue in animals subject to GCI with reperfusion.