Prevention of delayed neuronal death in gerbil hippocampus by a novel vinca alkaloid derivative (vinconate)

SIRT1 exerts neuroprotective effects by attenuating cerebral ischemia/reperfusion-induced injury via targeting p53/microRNA-22

The aim of this study was to investigate whether the SIRT1 exerts neuroprotective effects by attenuating cerebral ischemia/reperfusion-induced injury (CIRI) via targeting p53/microRNA-22. We found that the overexpression of sirtuin 1 (SIRT1) decreased the infarct volume, suppressed p53 protein expression and activated microRNA-22 expression following CIRI. An injection of lipopolysaccharide (LPS, 1 mg/ml; Sigma, St. Louis, MO USA) into the corpus callosum was used to induce CIRI in rats. The infarct volume and neurological deficit score were used to examine the effects of SIRT1 on CIRI. Furthermore, the overexpression of SIRT1 was found to suppress caspase-3 activity, inhibit the activation of the Bax signaling pathway, reduce tumor necrosis factor-α (TNF-α) and interleukin (IL)-6) activity, decrease cyclooxygenase (COX)‑2 and inducible nitric oxide synthase (iNOS) protein expression, and increase IL-10 activity following CIRI. Following the downregulation of SIRT1, p53 protein expression was significantly increased, microRNA-22 expression was inhibited, caspase-3 activity was increased and the Bax signaling pathway was activated. In addition, the activity of TNF-α and IL-6 was was enhanced, COX-2 and iNOS protein expression was increased, and IL-10 activity was reduced following CIRI. Thus, the data from our study suggest that SIRT1 attenuates CIRI by targeting the p53/microRNA-22 axix, while suppressing apoptosis, inflammation, COX-2 and iNOS expression.

Vinconate, a cognitive enhancer, and PI turnover-phospholipase C systems in the brain

The molecular mechanisms for the stimulation of inositol 1-phosphate (IP1) formation by vinconate were investigated using preparations of rat brain. Vinconate (10(-8)-10(-3) M) dose-dependently inhibited the binding of [3H]quinuclidinyl benzilate ([3H]QNB) to muscarinic acetylcholine receptors and its IC50 value for [3H]QNB binding was 1.7 x 10(-5) M. The rightward shift of carbachol displacement curve of [3H]QNB binding by GTP (10(-4) M) was completely abolished by vinconate (10(-5) M). Carbachol (10(-8)-10(-2) M) increased [3H]IP1 formation in a dose-dependent manner and the carbachol-induced [3H]IP1 formation was significantly accentuated by vinconate (10(-5) M). The enhancement of [3H]IP1 accumulation by vinconate was inhibited by approximately 50% in the presence of atropine (10(-5) M), although phentolamine and ketanserin had no effects on the stimulatory effect of vinconate on [3H]IP1 formation. Vinconate showed no alteration in the binding of [3H]guanosine 5'-(beta, gamma-imino) triphosphate ([3H]Gpp(NH)p) to the crude synaptic membranes. The enhancement of phosphatidylinositol 4,5-biphosphate (PIP2)-specific phospholipase C (PLC) activity by GTP was unaffected in the presence of 10(-3) M vinconate, whereas vinconate alone dose-dependently enhanced the activities of both PIP2-specific and cytosolic PLC. These results suggest that vinconate may induce the facilitation of phosphatidylinositide (PI) turnover via the stimulation of muscarinic acetylcholine receptors, the enhancement of coupling between muscarinic acetylcholine receptors and GTP-binding protein, and the direct activations of PIP2-specific and cytosolic PLC.

Effects of vinconate on neurotransmitter receptor systems in aged rat brain

We investigated the effects of age and (±)-methyl-3-ethyl-2,3,3a,4-tetrahydro-1 H-indolo[3,2,1-de][1,5]naphthyridine-6-carboxylate hydrochloride (vinconate), an indolonaphthyridine derivative, on neurotransmitter receptor systems in the rat brain using quantitative receptor autoradiography. [(3)H]Quinuclidinyl benzilate (QNB), [(3)H]hemicholinium-3 (HC) and [(3)H]muscimol were used to label acetylcholine receptors, high-affinity choline uptake sites and γ-aminobutyric acid(A) (GABA(A)) receptors, respectively. [(3)H]QNB, [(3)H]HC and [(3)H]muscimol binding decreased in any brain areas of 24-month-old (aged) rats in comparison with 6-month-old (adult) animals. Chronic treatment with vinconate (10 and 30 mg/kg, i.p., once a day for 4 weeks) partly ameliorated the reduction in [(3)H]QNB, [(3)H]HC and [(3)H]muscimol biding in aged rat brains. This effect was especially noted in [(3)H]muscimol binding. The results suggest that vinconate may have beneficial effects on age-related changes in neurotransmitter receptor systems.

Effect of vinconate on the extracellular levels of dopamine and its metabolites in the rat striatum: microdialysis studies

The effects of (+/-)-methyl-3-ethyl-2,3,3 alpha, 4-tetrahydro-1H- indolo[3,2,1-de][1,5]naphthyridine-6-carboxylate hydrochloride (vinconate), an indolonaphthyridine derivative, on the extracellular levels of dopamine and its metabolites in the rat striatum were examined using brain microdialysis. Single administration of vinconate (10, 100 mg/kg i.p.) increased the extracellular level of dopamine and its metabolites. This enhancing effect of vinconate was antagonized by scopolamine (10 microM), a muscarinic receptor antagonist, which was added to the perfusate from 30 min before vinconate treatment. These findings suggest that vinconate, even when systemically administered, enhances the endogenous release of dopamine in the striatum, probably via the stimulation of presynaptic muscarinic receptors.

Involvement of brain serotonergic function in lidocaine-induced convulsions in mice

Influences of drug-induced manipulations of central serotonergic function on lidocaine- and pentylenetetrazol (PTZ)-induced convulsions were examined in mice. Agents that suppressed serotonergic transmission increased, whereas drugs that facilitated serotonin (5-HT) function decreased the incidence of lidocaine-induced convulsions. These treatments had similar influences on the incidence of PTZ-induced convulsions. Lidocaine (10(-5)-10(-3) M) reduced the stimulation evoked [3H]5-HT release from cortical slices, followed with an increased spontaneous [3H] overflow at higher concentrations. These results may suggest that brain 5-HT neurons are causally involved as inhibitory neurons in lidocaine-induced convulsions as in the case of PTZ-induced convulsions.

Non-competitive antagonism by hirsuteine of nicotinic receptor-mediated dopamine release from rat pheochromocytoma cells

Effects of hirsuteine, an indole alkaloid extracted from Uncaria genus, on nicotine- and high K-induced responses were investigated in rat pheochromocytoma PC12 cells. Hirsuteine (300 nM-10 microM) inhibited dopamine release evoked by 100 microM nicotine in a concentration-dependent manner. Hirsuteine did not produce a parallel shift of the concentration-response relationship curve for nicotine, but reduced maximal dopamine release. Dopamine release evoked by 60 and 155 mM KCl was also inhibited by hirsuteine, but the concentration necessary for significant inhibition was higher (more than 10 microM). Under whole cell voltage-clamp, hirsuteine reversibly inhibited inward currents activated by 100 microM nicotine. The current inhibition was slightly accelerated by hyperpolarization. The results suggest that hirsuteine non-competitively antagonizes nicotine-evoked dopamine release by blocking ion permeation through nicotinic receptor channel complexes. The blockade of Ca channels, which are activated during nicotine-evoked depolarization, may not play a major role in the antagonism.

Effect of vinconate against regional age-related changes in the gerbil brain

We investigated age-related changes in the binding sites of muscarinic acetylcholine, forskolin, adenosine 3',5'-cyclic monophosphate (cAMP), and of a voltage-dependent L-type calcium channel blocker in the gerbil brain using receptor autoradiography. [3H]Quinuclidinyl benzilate (QNB), [3H]forskolin, [3H]cAMP, and [3H]PN200-110 were used to label muscarinic receptors, adenylate cyclase, cAMP-dependent protein kinase, and L-type calcium channels, respectively. In middle-aged animals (16-month-old gerbils), [3H]QNB, [3H]PN200-110, [3H]forskolin, and [3H]cAMP binding sites were elevated in the hippocampal region compared with that of young gerbils (4 weeks old). Further, a significant elevation in [3H]forskolin binding was seen in the nucleus accumbens. In contrast, [3H]QNB, [3H]PN200-110, and [3H]forskolin binding sites were reduced in the cerebellum, neocortex and thalamus, and hypothalamus in middle-aged animals, respectively. [3H]cAMP binding was not altered in other regions except for an elevation in the hippocampus. Thus, the age-related alterations in receptor binding may proceed by different mechanisms in various brain regions. Chronic vinconate treatment partly modulated the age-related alterations in [3H]QNB, [3H]forskolin, and [3H]cAMP binding in the hippocampus, but not that of [3H]PN200-110. Vinconate also regulated the age-related changes in [3H]forskolin binding in the nucleus accumbens. These results indicate that the age-related alterations in the binding sites of muscarinic acetylcholine, forskolin, cAMP, and L-type calcium channel blocker occur in particular in the hippocampus. Further, they suggest that a novel vinca alkaloid derivative, vinconate, can partly modulate age-related changes in these binding sites.

Protective effect of vinconate on ischemia-induced neuronal damage in the rat hippocampus

The protective effect of vinconate, a vinca alkaloid derivative, on ischemia-induced neuronal damage was investigated using a model of rat forebrain ischemia caused by occlusion of four vessels. Hippocampal cell loss was observed histologically and neurochemically 5 days after 10 min of ischemia. Treatment with vinconate (50 and 200 mg/kg i.p.) before cerebral ischemia significantly suppressed neuronal cell loss in the hippocampal CA1 region and the decrease in the content of neuroactive amino acids in the hippocampus. The release of neuroactive amino acids in the hippocampus was significantly increased by cerebral ischemia. Pretreatment with vinconate (50 and 200 mg/kg i.p.) significantly attenuated the increased release of glutamic acid and aspartic acid, but not the release of gamma-aminobutyric acid (GABA), taurine and glycine. This suppressive effect of vinconate was antagonized by scopolamine (10(-5) M). The addition of vinconate (10(-11)-10(-4) M) had no effect on the binding of [3H]MK-801. These results indicate that pretreatment with vinconate attenuates the ischemia-induced release of excitatory amino acids into the extracellular space of the hippocampus via the stimulation of presynaptic muscarinic acetylcholine receptors. The present results also suggest that this suppressive effect of vinconate on the release of excitatory amino acids (glutamic acid and aspartic acid) may play a crucial role in the protective action of this agent against ischemia-induced neuronal damage in the hippocampus.

Age-related alterations in second-messenger systems in the gerbil brain: autoradiographic analysis and effect of vinconate

Age-related alterations in binding sites of major second-messenger systems in the gerbil brain were analyzed by receptor autoradiography using [3H]phorbol 12,13-dibutyrate (PDBu), and [3H]inositol 1,4,5-trisphosphate (IP3). In middle-aged gerbils (16 months old), the reduction of PDBu-binding sites was noticed in various brain regions compared with young animals (4 weeks old). By contrast, the elevation of IP3-binding sites was seen in most of brain regions except for the reduction in the cerebellum in the middle-aged animals. Chronic treatment with vinconate partly regulated the age-related changes in the binding sites of these second messengers. The result demonstrates the age-related alterations in the binding sites of an intracellular second-messenger system. Furthermore, they suggest that vinconate partly modulates the age-related alterations in the bindings of second messengers.

Effects of vinconate, a novel vinca alkaloid, on spatial learning deficits induced by the basal forebrain lesion in rats

We investigated the effects of vinconate, a novel vinca alkaloid, on spatial learning deficits induced by the basal forebrain (BF) lesion in rats. Bilateral BF lesions were produced by injecting ibotenic acid (6 micrograms/0.5 microliter/side). In BF-lesioned rats, impairment of spatial learning in escaping onto the platform during training and decrease in spatial bias during the spatial probe trial in Morris's water maze task were both observed. Vinconate (5 and 10 mg/kg) treatment shortened the increase of escape latency to the platform in BF-lesioned rats and significantly reversed the decrease in spatial bias induced by the BF lesion. Vinconate (10 mg/kg) attenuated the decrease in choline acetyltransferase activity in the frontoparietal cortex caused by the BF lesion. The present study suggests that vinconate has an antiamnesic effect on the BF-lesion-induced amnesia by ameliorating the dysfunction in cholinergic neurons.

Protective effect of vinconate, a novel vinca alkaloid derivative, on glucose utilization and brain edema in a new rat model of middle cerebral artery occlusion

1. We investigated the effect of a novel vinca alkaloid derivative, vinconate, against brain damage after focal ischemia induced by a middle cerebral artery (MCA) occlusion in rats. 2. Persistent focal ischemia was induced by 6 hr, and vinconate (50 and 100 mg/kg) was given intraperitoneally twice 10 min and 3 hr after MCA occlusion. 3. Focal ischemia produced the disturbance of glucose metabolism, the increase of water content and the impairment of protein synthesis in the surrounding occluded MCA territory. 4. Vinconate was effective in preventing marked reduction of cerebral glucose utilization in the areas surrounding the occluded MCA territory. 5. Vinconate significantly reduced an increase of water content in the surrounding the occluded MCA territory. 6. Preliminary L-[methyl-14C]methionine autoradiographic study also indicated that vinconate can partly prevent a severe impairment of protein synthesis after focal ischemia. 7. The results indicate that vinconate may ameliorate the disturbance of glucose metabolism, brain edema and the impairment of protein synthesis after persistent focal ischemia, and they also suggest that vinconate has a beneficial effect against brain damage.

Protective effect of a novel vinca alkaloid derivative, vinconate, against alterations in binding sites of second messengers after transient cerebral ischemia in gerbils

1. We investigated the alterations in binding sites of three major second messengers, phorbol 12,13-dibutyrate, inositol 1,4,5-trisphosphate and forskolin following transient cerebral ischemia in gerbils, and examined the effects of a novel vinca alkaloid derivative, vinconate against the alterations in the binding of the second messengers following ischemia. 2. Transient cerebral ischemia produced by bilateral occlusion of the common carotid arteries was induced for 10 min, and intraperitoneal administration of vinconate (100 mg/kg and 300 mg/kg) was given 10 min before ischemia. 3. Morphological study indicated that transient ischemia can produce severe neuronal damage in striatum, hippocampal CA1 sector and hippocampal CA3 sector. 4. Transient cerebral ischemia caused the postischemic alterations in the binding of three second messengers. 5. The postischemic alterations in the binding of second messengers were ameliorated by pretreatment with vinconate. This effect was especially observed in the striatum which was most vulnerable to ischemia. 6. These findings are discussed in relation to the mechanism of ischemic neuronal damage.

Effects of vinconate on spatial learning impairments induced by medial septal lesion in rats

We investigated the effects of vinconate, a novel vinca alkaloid, on spatial learning deficits induced by medial septal (MS) lesion in rats. MS lesion was produced by passing an anodal DC current. In vehicle-treated MS-lesioned rats impairment of spatial learning was observed, shown by a decrease in correct choices and an increase in total errors during training in a radial arm maze task. Vinconate (10 mg/kg) treatment alleviated the decrease in correct choices and the increase in total errors induced by MS lesion. Vinconate (5 and 10 mg/kg) treatment showed a tendency to reverse the decrease in choline acetyltransferase activity in the hippocampus caused by MS lesion. The present study suggests that vinconate has an anti-amnesic effect on MS lesion-induced amnesia by ameliorating the dysfunction in cholinergic (ACh) neurons.

Comparative protective effects of vinconate, baclofen, and pentobarbital against neuronal damage following repeated brief cerebral ischemia in the gerbil brain

We investigated the neuroprotective effects of vinconate (a vinca alkaloid derivative), baclofen (a GABAB receptor agonist), or pentobarbital (a GABAA receptor-effector) on neuronal damage following repeated brief cerebral ischemia in the gerbils. The animals were allowed to survive for 7 days after two or three 2-min ischemic insults induced by bilateral occlusion of the common carotid arteries. Morphological changes were evaluated in hippocampal CA1 sector and selectively vulnerable areas after two or three 2-min ischemic insults at 1-h intervals, respectively. Pretreatment with vinconate significantly reduced histopathological neuronal damage to the hippocampal CA1 sector following two 2-min ischemic insults. However, pretreatment with baclofen and pentobarbital failed to prevent neuronal damage. Pretreatment with vinconate also prevented neuronal damage to the frontal cortex, parietal cortex, and striatum following three 2-min ischemic insults. Nevertheless, this drug failed to prevent neuronal damage to the hippocampal CA1 sector and the thalamus. Results suggest that vinconate, a vica alkaloid derivative, can prevent neuronal damage after repeated brief cerebral ischemia, but not GABAergic agents, such as baclofen and pentobarbital. These findings are of interest in relation to the mechanisms of neuronal damage induced by repeated brief cerebral ischemia.

Temporal profile of the effects of pretreatment with brief cerebral ischemia on the neuronal damage following secondary ischemic insult in the gerbil: cumulative damage and protective effects

We examined the response of the gerbil brain to secondary ischemic insult following pretreatment with brief ischemia at intervals of 5 min, 1 and 6 h, 1, 2, 4, 7 and 14 days. Two minutes of bilateral carotid artery occlusion produced no histopathological brain damage, whereas 3 min of occlusion caused a moderate to severe reduction in the number of hippocampal CA1 pyramidal cells. Two-minute occlusion followed by 3-min occlusion at 5-min, 1- and 6-h intervals resulted in almost complete destruction of CA1 neurons. Additional neuronal damage was observed in the striatum at a 1-h interval and in the thalamus and the neocortex at 1- and 6-h intervals. The neuronal damage was most severe at a 1-h interval. Two-minute ischemia followed by 3-min ischemia at intervals of 1, 2, 4 and 7 days, however, caused a marked protective effect, and the hippocampal CA1 neurons were preserved. The protective effect was not observed at a 14-day interval and following pretreatment with 1-min ischemia. Thus, pretreatment with brief ischemia leads to complex responses of the brain to secondary ischemic insult; cumulative damage at intervals of 1-6 h and protective effects at intervals of 1-7 days.

Prevention of abnormal calcium accumulation in postischemic gerbil brain by vinconate

We investigated the effect of vinconate on ischemia-induced calcium accumulation in the gerbil brain. The animals were allowed to survive for 7 days after 10 min of ischemia. Abnormal calcium accumulation was evaluated in the gerbil brain after ischemia. Following 10 min ischemia, abnormal calcium accumulation was found in the neocortex, the striatum, the hippocampus, the thalamus, the substantia nigra and the inferior colliculus. Intraperitoneal administration of vinconate (100 mg/kg) immediately after 10 min of ischemia significantly reduced the areas of abnormal calcium accumulation only in the striatum. However, the application of vinconate (100 and 300 mg/kg) 10 min before ischemia dose-dependently decreased the areas of abnormal calcium accumulation in the striatum, the thalamus and the substantia nigra. Morphological observation revealed neuronal damage in the identical sites of the abnormal calcium accumulation. Furthermore, a autoradiographic study using 14C-vinconate showed that this drug easily penetrates the blood-brain barrier and especially localizes in the striatum and the thalamus after 5 min ischemia. The result suggests that vinconate reduces the areas of abnormal calcium accumulation in the postischemic gerbil brain. This effect seems to be mediated via the height distribution in the brain following ischemia.

Neuronal damage and calcium accumulation following repeated brief cerebral ischemia in the gerbil

We investigated the distribution of neuronal damage following brief cerebral transient ischemia and repeated ischemia at 1-h intervals in the gerbil, using light microscopy and 45Ca autoradiography as a marker for detection of ischemic damage. The animals were allowed to survive for 7 days after ischemia induced by bilateral carotid artery occlusion. Following 2-min ischemia, neuronal damage determined by abnormal calcium accumulation was not observed in the forebrain regions. Following 3-min ischemia, however, abnormal calcium accumulation was recognized only in the hippocampal CA1 sector and part of the striatum. Two 2-min ischemic insults caused extensive abnormal calcium accumulation in the dorsolateral part of striatum, the hippocampal CA1 sector, the thalamus, the substantia nigra and the inferior colliculus. The ischemic insults were more severe than that of a single 3-min ischemia. However, three 1-min ischemic insults caused abnormal calcium accumulation only in the striatum. On the other hand, three 2-min ischemic insults caused severe abnormal calcium accumulation in the brain. The abnormal calcium accumulation was found in the dorsolateral part of striatum, the hippocampal CA1 sector, the thalamus, the medial geniculate body, the substantia nigra and the inferior colliculus. Gerbils subjected to three 3-min ischemic insults revealed most severe abnormal calcium accumulation. Marked calcium accumulation was seen not only in the above sites, but also spread in the neocortex, the septum and the hippocampal CA3 sector. Morphological study after transient or repeated ischemia indicated that the distribution and frequency of the neuronal damage was found in the sites corresponding to most of the regions of abnormal calcium accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)