Postischemic Treatment Research Articles

Post-ischemic modest hypothermia (35°C) combined with intravenous magnesium is more effective at reducing CA1 neuronal death than either treatment used alone following global cerebral ischemia in rats

In this study, we investigated the efficacy of pre- and 2 h post-ischemic magnesium treatment with different durations of modest hypothermia (35°C) induced immediately or 2 h following global cerebral ischemia in rats. In experimental group 1, rats received an intravenous loading dose (LD) of 360 μmol/kg MgSO 4 immediately before ischemia followed by a 48 h intravenous infusion (IVI) at 120 μmol/kg/h. Immediately post-ischemia, body temperature was lowered to 35°C for 6 h or maintained at 37°C. In experimental group 2, 2 h after ischemia, rats received the MgSO 4 LD/IVI and/or had their body temperature lowered to 35°C for 6, 12 or 24 h. In experimental group 1, ischemic rats receiving 6 h of modest hypothermia demonstrated 9.4% CA1 neuronal survival, whereas rats treated with magnesium alone or magnesium and 6 h of modest hypothermia demonstrated 5.1% and 37.9% neuronal survival, respectively. In experimental group 2, ischemic rats receiving 6, 12 or 24 h of modest hypothermia demonstrated 6.1, 5 and 43% CA1 neuronal survival, respectively. Rats treated with magnesium and 6, 12 or 24 h of modest hypothermia demonstrated 8.1, 9 and 76% neuronal survival, respectively. Our findings demonstrate that post-ischemic treatment with a 24 h duration of modest hypothermia and magnesium is more effective than either treatment used alone.

Ibandronate for Prevention of Femoral Head Deformity After Ischemic Necrosis of the Capital Femoral Epiphysis in Immature Pigs

Femoral head deformity is the most serious sequela of ischemic necrosis of the immature femoral head. The purpose of this study was to determine if a highly potent antiresorptive agent, ibandronate, can inhibit bone resorption during the repair of the infarcted femoral head and thus alter the repair process. We hypothesized that preservation of the trabecular framework by inhibiting osteoclastic bone resorption would minimize the development of deformity in a piglet model of ischemic necrosis. The effect of ibandronate on long-bone growth was also assessed. Ischemic necrosis of the right femoral head was produced in twenty-four piglets by placing a ligature tightly around the femoral neck. The animals were divided into three groups according to whether they received saline solution, prophylactic treatment, or post-ischemia treatment. The contralateral, untreated femoral heads from the animals that had received saline solution served as the normal control group. At eight weeks, the femoral heads were assessed for deformity with radiography and for trabecular bone indices with histomorphometry. Also, the length of femur from the untreated side was measured on the radiographs and compared among the groups. Radiographic assessment showed that the epiphyseal quotient, determined by dividing the maximum height of the osseous epiphysis by the maximum diameter, was better preserved in the prophylactic (p < 0.001) and post-ischemia (p = 0.02) treatment groups than in the group treated with saline solution. Histomorphometric assessment also showed that the trabecular bone indices were better preserved in the prophylactic and the post-ischemia treatment groups than in the group treated with saline solution (p < 0.01). The mean femoral length on the untreated side of the animals treated with ibandronate was reduced compared with the length on the untreated side of the animals that had received saline solution (p </= 0.01). Ibandronate preserves the trabecular structure of the osseous epiphysis and prevents femoral head deformity during the early phase of repair of ischemic necrosis in the piglet model.

IBANDRONATE FOR PREVENTION OF FEMORAL HEAD DEFORMITY AFTER ISCHEMIC NECROSIS OF THE CAPITAL FEMORAL EPIPHYSIS IN IMMATURE PIGS

Background: Femoral head deformity is the most serious sequela of ischemic necrosis of the immature femoral head. The purpose of this study was to determine if a highly potent antiresorptive agent, ibandronate, can inhibit bone resorption during the repair of the infarcted femoral head and thus alter the repair process. We hypothesized that preservation of the trabecular framework by inhibiting osteoclastic bone resorption would minimize the development of deformity in a piglet model of ischemic necrosis. The effect of ibandronate on long-bone growth was also assessed. Methods: Ischemic necrosis of the right femoral head was produced in twenty-four piglets by placing a ligature tightly around the femoral neck. The animals were divided into three groups according to whether they received saline solution, prophylactic treatment, or post-ischemia treatment. The contralateral, untreated femoral heads from the animals that had received saline solution served as the normal control group. At eight weeks, the femoral heads were assessed for deformity with radiography and for trabecular bone indices with histomorphometry. Also, the length of femur from the untreated side was measured on the radiographs and compared among the groups. Results: Radiographic assessment showed that the epiphyseal quotient, determined by dividing the maximum height of the osseous epiphysis by the maximum diameter, was better preserved in the prophylactic (p < 0.001) and post-ischemia (p = 0.02) treatment groups than in the group treated with saline solution. Histomorphometric assessment also showed that the trabecular bone indices were better preserved in the prophylactic and the post-ischemia treatment groups than in the group treated with saline solution (p < 0.01). The mean femoral length on the untreated side of the animals treated with ibandronate was reduced compared with the length on the untreated side of the animals that had received saline solution (p ≤ 0.01). Conclusions: Ibandronate preserves the trabecular structure of the osseous epiphysis and prevents femoral head deformity during the early phase of repair of ischemic necrosis in the piglet model. Clinical Relevance: Administration of an anti-osteolytic agent, ibandronate, during the fragmentation stage of Legg-Calvé-Perthes disease may prevent early flattening of the osseous epiphysis. Additional preclinical studies are needed to determine the optimum dose and delivery of the drug to prevent the deformity while minimizing its effect on long-bone growth. Studies are also needed to determine the long-term effects of ibandronate in terms of preventing deformity.

Inhibition of iNOS activity by 1400W decreases glutamate release and ameliorates stroke outcome after experimental ischemia

It has been shown that the reversed operation of glutamate transporters when ATP levels fall accounts for most glutamate release induced by severe cerebral ischemia. Nitric oxide (NO) is formed after ischemia and causes ATP depletion. Our purpose is to test if NO release from inducible NO synthase (iNOS) after stroke may cause a delayed glutamate release due to ATP depletion that might underlie progression of the ischemic infarct. We have studied the effect of the highly selective inhibitor of iNOS activity 1400W on brain ATP levels, extracellular glutamate, and stroke outcome after transient focal cerebral ischemia in rats. To induce focal ischemia, the middle cerebral artery (MCA) was occluded by using the intraluminal thread technique (tMCAO). 1400W was administered, after tMCAO, by using an Alzet osmotic pump to yield a drug delivery rate of 2.5 mg/kg/h. Results. Postischemic treatment with 1400W induced a reduction in the neurofunctional impairment and in the total volume of brain infarct. Western blot analysis showed ischemia-induced expression of iNOS. Treatment with 1400W partially prevented delayed ATP reduction and produced inhibition of the subsequent delayed increase in glutamate levels caused by the ischemic insult. Our data indicate that 1400W improves stroke outcome, an effect concomitant to the inhibition of both ischemia-induced decrease in brain ATP levels and increase in glutamate release. These results provide evidence indicating that the expression of iNOS induced by ischemia may contribute to the progression of the ischemic infarct and have important therapeutic implications for the management of stroke.

Post-ischemic Treatment with Toki-Shakuyaku-San (Tang-Gui-Shao-Yao-San) Prevents the Impairment of Spatial Memory Induced by Repeated Cerebral Ischemia in Rats

Previously we have reported that Toki-shakuyaku-san (TSS) ameliorated the impairment of spatial memory induced by single cerebral ischemia (1 x 10 minutes) and scopolamine, a muscarinic receptor antagonist. In this experiment, we studied the effect of TSS on repeated cerebral ischemia (2 x 10 minutes, 1-hour interval) induced impairment of spatial memory and neuronal injury in rats. The 8-day post-ischemic treatment with TSS (30-300 mg/kg) was administered p.o. once per day. TSS dose-dependently prevented the impairment of spatial memory, neuronal death and TUNEL positive cells induced by repeated cerebral ischemia. In order to determine the mechanism of TSS, we also studied the effect of TSS on GluR2 mRNA, one of the glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) receptor subunits. Repeated cerebral ischemia significantly decreased GluR2 flop mRNA at 1 and 3 days after the occlusion. TSS (300 mg/kg) significantly suppressed the decrease in GluR2 flop at 3 days after repeated cerebral ischemia. These results suggested that the TSS has neuroprotective action which may be indirectly mediated by the AMPA receptor, and TSS may be beneficial for the treatment of cerebrovascular dementia.

Preventive effect of Y-27632, a selective Rho-kinase inhibitor, on ischemia/reperfusion-induced acute renal failure in rats

We evaluated the effects of Y-27632 [(+)-( R)- trans-4-(1-aminoethyl)- N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate], a selective Rho-kinase inhibitor, on ischemic acute renal failure. Ischemic acute renal failure in rats was induced by clamping the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after the contralateral nephrectomy. Y-27632 administration (1, 10, and 100 μg/kg, i.p.) before ischemia dose-dependently attenuated the ischemia/reperfusion-induced renal dysfunction and histological damage, such as tubular necrosis. The ischemia/reperfusion-induced renal dysfunction was also overcome by postischemic treatment with Y-27632 at 100 μg/kg, i.p. Myeloperoxidase activity in the kidney after ischemia/reperfusion was significantly increased, being the maximal level at 6 h after the reperfusion, and this increase was also suppressed by Y-27632 (100 μg/kg, i.p.). These results indicate that Y-27632 prevents the development of ischemia/reperfusion-induced acute renal failure, and the effect is related to the suppression of the enhanced myeloperoxidase activity in an early phase after reperfusion, thereby suggesting that the Rho/Rho-kinase pathway plays a key role in the pathogenesis of ischemic acute renal failure.

A two-hour window for hypothermic modulation of early events that impact delayed opening of the rat blood-brain barrier after ischemia.

Opening of the blood-brain barrier (BBB) and consequent edema are known to intensify 24-72 h after ischemic stroke, and research on potential ameliorative therapies in animal models may lead to improved clinical treatments to prevent brain swelling and the secondary damage it causes. In this study, post-ischemic hypothermia treatment, which is an established neuroprotective strategy, was examined for its ability to prevent delayed BBB opening in a rat model of global ischemia. Anesthetized, normothermic SD rats (340-380 g) underwent 20 min of two-vessel (carotid) occlusion plus hypotension (2VO ischemia, between 0900-1100 h). Marked cortical BBB leakiness, which developed overnight, was indicated at sacrifice 24 h post-2VO by an average six- to eightfold increase above baseline in transfer constant values (K(i) ) for rate of blood to brain diffusion of intravenously delivered [(3)H]sucrose. A post-2VO treatment involving whole body cooling to 31.5 degrees-32.5 degrees C, maintenance for 6 h and rewarming to normothermia, significantly reduced BBB leakiness at 24 h, whether cooling was initiated immediately after reperfusion, or after a 1-h delay, but not after 2-h delay. Immediate hypothermia treatment reduced overall tissue injury at 24 h as evidenced by an assay of mitochondrial succinate dehydrogenase activity, and also reduced brain edema. By contrast, treatment of rats with the anti-inflammatory drugs cyclosporine A or minocycline offered no protection of BBB or mitochondria. It is concluded that hypothermic alteration of critical events during the first 2 h after prolonged ischemia powerfully mitigates the BBB damage and associated events that normally develop 24 h later.

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Astragaloside IV protects against ischemic brain injury in a murine model of transient focal ischemia

Astragalus membranaceus is a herbal medicine that has been used clinically in stroke patients in China for decades, but its potential neuroprotective effect against ischemic brain injury has not been experimentally tested. In this study, we investigated the effect of Astragaloside IV, a purified extract from Astragalus membranaceus, in a murine model of focal cerebral ischemia/reperfusion produced by transient (1.5 h) middle cerebral artery occlusion. As determined at 72 h after ischemia, post-ischemic treatment of Astragaloside IV (20 or 40 mg/kg) markedly and significantly ( P<0.03 vs. vehicle-treated animals) reduced infarct volume. Astragaloside IV treatment also decreased the levels of malondialdehyde, an indicator of lipid peroxidation, and increased the levels of the antioxidant enzymes glutathione peroxidase and superoxide dismutase in ischemic tissues. The results presented here provide the first evidence of a neuroprotective effect of Astragaloside IV in the model of ischemic brain injury. We suggest that the anti-infarction effect by Astragaloside IV may be derived at least in part from its antioxidant properties.

Sustained blockade of brain AT1 receptors before and after focal cerebral ischemia alleviates neurologic deficits and reduces neuronal injury, apoptosis, and inflammatory responses in the rat.

In the present study, we investigate whether a long-term blockade of brain AT1 receptors in male Wistar rats before and after ischemic injury exerts neuroprotective effects and modulates apoptosis and inflammatory responses, which are associated with the post-ischemic progression of brain damage. The AT1 receptor antagonist irbesartan was continuously infused intracerebroventricularly using osmotic minipumps over a 5-day period before and for 3 or 7 days after middle cerebral artery occlusion (MCAO) for 90 minutes. Neurologic status was evaluated daily, starting 24 hours after MCAO. After MCAO (3 and 7 days), brains were removed for the measurement of infarct size and immunohistochemical evaluation of apoptosis and accumulation of reactive microglia and macrophages. Treatment with irbesartan before ischemia improved motor functions, whereas post-ischemic treatment improved sensory functions. Blockade of brain AT1 receptors reduced the infarct size on days 3 and 7 after MCAO. In the peri-infarct cortex, irbesartan treatment decreased the number of apoptotic cells on day 3 and attenuated the invasion of activated microg-lia and macrophages on days 3 and 7 after ischemia. Long-term blockade of brain AT1 receptors improves the recovery from cerebral ischemia. Antiapoptotic mechanisms and inhibition of post-ischemic inflammation are involved in the AT1 receptor blockade-induced neuroprotective effects in ischemic brain tissue.

Effect of Brain-Derived Neurotrophic Factor Treatment and Forced Arm Use on Functional Motor Recovery After Small Cortical Ischemia

Both the administration of growth factors and physical therapy such as forced arm use (FAU) are promising approaches to enhance recovery after stroke. We explored the effects of these therapies on behavioral recovery and molecular markers of regeneration after experimental ischemia. Rats were subjected to photothrombotic ischemia: sham (no ischemia), control (ischemia), brain-derived neurotrophic factor (BDNF; ischemia plus BDNF, 20 microg), and FAU (ischemia plus FAU, 1-sleeve plaster cast ipsilateral limb). Animals survived 1 or 6 weeks and underwent behavioral testing (Rotarod, beam balance, adhesive removal, plantar test, neuroscore). After the rats were killed, brain sections were immunostained for semiquantitative analysis of MAP1B, MAP2, synaptophysin, GFAP expression, and quantification of infarct volumes. Infarct volumes were not different between the groups 1 or 6 weeks after ischemia. BDNF-treated animals had better functional motor recovery (Rotarod, beam balance, neuroscore) compared with all other groups (P<0.05). There was no significant adverse effect of early FAU treatment on motor recovery, although sensorimotor function (adhesive removal test) was impaired (P<0.05). There were no differences between groups as measured by nociception of the left and right forepaw (plantar test). BDNF treatment transiently induced MAP1B expression in the ischemic border zone and synaptophysin expression within the contralateral cortex 6 weeks after ischemia (P<0.05). Both BDNF and FAU reduced astrogliosis compared with controls (P<0.05). Postischemic intravenous BDNF treatment improves functional motor recovery after photothrombotic stroke and induces widespread neuronal remodeling. Early FAU treatment after stroke does not increase infarct size, impairs sensorimotor function, but leaves motor function unchanged. Postischemic astrogliosis was reduced by both treatments.

Glutathione protects the rat liver against reperfusion injury after prolonged warm ischemia.

To evaluate the potential of postischemic intravenous infusion of the endogenous antioxidant glutathione (GSH) to protect the liver from reperfusion injury following prolonged warm ischemia. The release of reactive oxygen species (ROS) by activated Kupffer cells (KC) and leukocytes causes reperfusion injury of the liver after warm ischemia. Therefore, safe and cost-effective antioxidant strategies would appear a promising approach to prevent hepatic reperfusion injury during liver resection, but need to be developed. Livers of male Lewis rats were subjected to 60, 90, or 120 minutes of normothermic ischemia. During a 120 minutes reperfusion period either GSH (50, 100 or 200 micromol/h/kg; n= 6-8) or saline (n= 8) was continuously administered via the jugular vein. Postischemic GSH treatment significantly prevented necrotic injury to hepatocytes as indicated by a 50-60% reduction of serum ALT and AST. After 1 hour of ischemia and 2 hours of reperfusion apoptotic hepatocytes were rare (0.50 +/- 0.10%; mean +/- SD) and not different in GSH-treated animals (0.65 +/- 0.20%). GSH (200 micromol GSH/h/kg) improved survival following 2 hours of ischemia (6 of 9 versus 3 of 9 rats; P < 0.05). Intravital fluorescence microscopy revealed a nearly complete restoration of sinusoidal blood flow. This was paralleled by a reduction of leukocyte adherence to sinusoids and postsinusoidal venules. Intravenous GSH administration resulted in a 10- to 40-fold increase of plasma GSH levels, whereas intracellular GSH contents were unaffected. Plasma concentrations of oxidized glutathione (GSSG) increased up to 5-fold in GSH-treated animals suggesting counteraction of the vascular oxidant stress produced by activated KC. Intravenous GSH administration during reperfusion of ischemic livers prevents reperfusion injury in rats. Because GSH is well tolerable also in man, this novel approach could be introduced to human liver surgery.

The Post-ischemic Administration of 3-[2-[4-(3-Chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1H-indazole Dihydrochloride 3.5 Hydrate (DY-9760e), a Novel Calmodulin Antagonist, Prevents Delayed Neuronal Death in Gerbil Hippocampus

The novel calmodulin (CaM) antagonist DY-9760e (3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate) with an apparent neuroprotective effect in vivo preferentially inhibits neuronal nitric oxide synthase (nNOS), Ca2+/CaM-dependent protein kinase IIα (CaMKIIα), and calcineurin in vitro. In the present study, we investigated the molecular mechanism underlying its neuroprotective effect with the gerbil transient forebrain ischemia model, by focusing on its inhibition of these Ca2+/CaM-dependent enzymes. Post-ischemic DY-9760e treatment (5 mg/kg, i.p.) immediately after 5-min ischemia significantly reduced the delayed neuronal death in the hippocampal CA1 region. CaMKIIα was transiently autophosphorylated immediately after reperfusion with concomitant sustained decrease in its total amounts in the Triton X-100-soluble fractions. Calcineurin activity, accessed by the phosphorylation state of dopamine- and cAMP-regulated phosphoprotein of Mr 32,000 (DARPP-32) at Thr34, was elevated at 6 h after reperfusion. Post-treatment of DY-9760e had no effects on both CaMKIIα and DARPP-32 phosphorylation at 6 h after reperfusion. However, DY-9760e significantly inhibited nitrotyrosine formation, as a biomarker of NO, and in turn, peroxynitrite (ONOO-) production. These results suggest that DY-9760e primarily inhibits Ca2+/CaM-dependent neuronal NOS, without any effects on CaMKII and calcineurin, and the inhibition of NO production possibly accounts for its neuroprotective action in brain ischemic injury.

A novel and selective Na +/Ca 2+ exchange inhibitor, SEA0400, improves ischemia/reperfusion-induced renal injury

We evaluated the effects of SEA0400 (2-[4-[(2,5-difluorophenyl)methoxy]phenoxy]-5-ethoxyaniline), a novel and selective Na +/Ca 2+ exchange inhibitor, on ischemic acute renal failure. Ischemic acute renal failure in rats was induced by clamping the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after the contralateral nephrectomy. SEA0400 administration (0.3, 1 and 3 mg/kg, i.v.) before ischemia dose-dependently attenuated the ischemia/reperfusion-induced renal dysfunction and histological damage such as tubular necrosis. SEA0400 pretreatment at the higher dose suppressed the increment of renal endothelin-1 content after reperfusion. The ischemia/reperfusion-induced renal dysfunction was also overcome by post-ischemia treatment with SEA0400 at 3 mg/kg, i.v. In in vitro study, SEA0400 (0.2 and 1 μM) protected cultured porcine tubular cells (LLC-PK 1) from hypoxia/reoxygenation-induced cell injury. These findings support the view that Ca 2+ overload via the reverse mode of Na +/Ca 2+ exchange, followed by endothelin-1 overproduction, plays an important role in the pathogenesis of ischemia/reperfusion-induced renal injury. The possibility exists that a selective Na +/Ca 2+ exchange inhibitor such as SEA0400 is useful as effective therapeutic agent against ischemic acute renal failure in humans.

Assessment of the relative contribution of COX-1 and COX-2 isoforms to ischemia-induced oxidative damage and neurodegeneration following transient global cerebral ischemia.

We investigated the relative contribution of COX-1 and/or COX-2 to oxidative damage, prostaglandin E2 (PGE2) production and hippocampal CA1 neuronal loss in a model of 5 min transient global cerebral ischemia in gerbils. Our results revealed a biphasic and significant increase in PGE2 levels after 2 and 24-48 h of reperfusion. The late increase in PGE2 levels (24 h) was more potently reduced by the highly selective COX-2 inhibitor rofecoxib (20 mg/kg) relative to the COX-1 inhibitor valeryl salicylate (20 mg/kg). The delayed rise in COX catalytic activity preceded the onset of histopathological changes in the CA1 subfield of the hippocampus. Post-ischemia treatment with rofecoxib (starting 6 h after restoration of blood flow) significantly reduced measures of oxidative damage (glutathione depletion and lipid peroxidation) seen at 48 h after the initial ischemic episode, indicating that the late increase in COX-2 activity is involved in the delayed occurrence of oxidative damage in the hippocampus after global ischemia. Interestingly, either selective inhibition of COX-2 with rofecoxib or inhibition of COX-1 with valeryl salicylate significantly increased the number of healthy neurons in the hippocampal CA1 sector even when the treatment began 6 h after ischemia. These results provide the first evidence that both COX isoforms are involved in the progression of neuronal damage following global cerebral ischemia, and have important implications for the potential therapeutic use of COX inhibitors in cerebral ischemia.

Post-ischemic treatment with cannabidiol prevents electroencephalographic flattening, hyperlocomotion and neuronal injury in gerbils

The potential activity of cannabidiol, a non-psychoactive constituent of marijuana, in preventing damage caused by cerebral ischemia was studied. Cannabidiol (1.25–20 mg/kg) was given 5 min after 10 min bilateral carotid occlusion in freely-moving awake gerbils. Seven days after ischemia, it antagonized the electroencephalographic flattening of total spectral power, with a dose-dependent bell-shaped curve; the neuroprotective effect was greatest with 5 mg/kg. One day after ischemia cannabidiol completely antagonized ischemia-induced hyperlocomotion, at all doses. Rectal temperature did not change during the first hour after occlusion. Histological examination showed complete survival of CA1 neurons in cannabidiol-treated gerbils. These findings suggest a potential therapeutic role of cannabidiol in cerebral ischemia, though the clear mechanism of action remains to be elucidated.

Post-treatment with a novel PARG inhibitor reduces infarct in cerebral ischemia in the rat

Poly(ADP-ribose) is synthesized from nicotinamide adenine dinucleotide (NAD +) by poly(ADP-ribose) polymerase (PARP) and degraded by poly(ADP-ribose) glycohydrolase (PARG). Overactivation of the poly(ADP-ribose) pathway increases nicotinamide and decreases cellular NAD +/ATP, which leads to cell death. Blocking poly(ADP-ribose) metabolism by inactivating PARP has been shown to reduce ischemia injury. We investigated whether disrupting the poly(ADP-ribose) cycle by PARG inhibition could achieve similar protection. We demonstrate that either pre- or post-ischemia treatment with 40 mg/kg of N-bis-(3-phenyl-propyl)9-oxo-fluorene-2,7-diamide, a novel PARG inhibitor, significantly reduces brain infarct volumes by 40–53% in a rat model of focal cerebral ischemia. Our result provides the first evidence that PARG inhibitors can ameliorate ischemic brain damage in vivo, in support of PARG as a new therapeutic target for treating ischemia injury.

Cardioprotection with pre‐ and postischemic adenosine and A3 receptor activation: Differing mechanisms and effects on necrosis versus stunning

AbstractThe importance of pre‐ versus postischemic treatment in adenosine‐mediated cardioprotection is unclear. We characterized effects of pre‐ and postischemic adenosine or A3 adenosine receptor (A3AR) agonism in Langendorff perfused mouse hearts subjected to 20 min global ischemia and 45 min reperfusion. In untreated hearts, diastolic pressure remained elevated at 21±2 mmHg, ventricular pressure development recovered to 75±3 mmHg (50% of pre‐ischemia), and 24±3 IU/ lactate dehydrogenase (LDH) was lost. Adenosine (50 µM) treatment prior to ischemia reduced LDH efflux by 40% (15±2 IU/g) yet exerted only modest effects on recovery of force (83±2 mmHg). Additional treatment during the first 15 min reperfusion was no more effective in reducing LDH efflux (14±2 IU/g) but further limited contractile dysfunction (93±2 mmHg). Continued treatment throughout 45 min reperfusion most effectively limited LDH efflux (10±1 IU/g) and contractile dysfunction (124±6 mmHg). Some protection was also observed with treatment during reperfusion only (16±1 IU/g and 106±3 mmHg). Effects of pre‐ and postischemic adenosine on necrosis and contractile dysfunction were not mimicked by pre‐ and postischemic A3AR agonism with 100 nM 2‐chloro‐N6‐(3‐iodobenzyl)‐adenosine‐5′‐N‐methyluronamide (Cl‐IB‐MECA), or mitochondrial KATP channel activation with 50 µM diazoxide. Protection with Cl‐IB‐MECA and diazoxide was less than with adenosine, maximal with treatment during ischemia alone, and absent with treatment during reperfusion alone. Data indicate antinecrotic effects of adenosine are primarily mediated prior to and during ischemia and are consistent with A3AR and mitochondrial KATP channel activation. In contrast, protection against contractile dysfunction involves other mechanisms and is enhanced with prolonged postischemic treatment. Drug Dev. Res. 58:447–453, 2003. © 2003 Wiley‐Liss, Inc.

Combined nimodipine and citicoline reduce infarct size, attenuate apoptosis and increase bcl-2 expression after focal cerebral ischemia

Cerebral ischemia triggers a multitude of pathophysiological and biochemical events that separately affect the evolution of focal ischemia and, therefore, stroke treatment should logically employ all known neuroprotective agents. We hypothesized that a treatment combining nimodipine and citicoline might have a potential neuroprotective effect. To assess this idea, Sprague–Dawley rats underwent transient bilateral common carotid artery ligation with simultaneous middle cerebral artery occlusion for 60 min. Four treatment groups were established. Animals received either: a) saline (control group); b) intracarotid nimodipine infusion during 30 min in the ischemia-reperfusion (nimodipine group); c) i.p. postischemic citicoline injections once daily for 7 days (citicoline group); or d) intracarotid nimodipine bolus during ischemia-reperfusion plus i.p. postichemic citicoline injections (combination group). They were killed after either 7 or 3 days after reperfusion. In the first case, the volume of the infarcted tissue was studied by a stereological procedure and in the second case, in situ end-labeling of nuclear DNA fragmentation (TUNEL) and Bcl-2 expression were employed to determine the level of apoptosis. The infarct volume was significantly reduced in both the nimodipine and the citicoline treatment groups after 7 days of reperfusion; combination of both drugs produced an additive effect. After 3 days of reperfusion, the number of Bcl-2-positive neurons was significantly increased while that of TUNEL-positive cells significantly decreased at the infarct border in the combined-treatment animals. Our findings demonstrate a neuroprotective effect from an acute single dose of nimodipine during ischemia-reperfusion and prolonged post-ischemic treatment with citicoline in a model of focal cerebral ischemia. These results suggest that a possible mechanism of neuroprotective action would be mediated by increased Bcl-2 expression and decreased apoptosis within the boundary zone of the infarct together with neutralization of the ischemia-reperfusion injury.

Platelet activation in patients with congestive heart failure: Do we have enough evidence to consider clopidogrel?

Our understanding of the pathogenesis of congestive heart failure (CHF) has improved remarkably in recent years. However, despite better knowledge and novel pharmaceutical strategies, this disease is still one of the most brutal killers in the Western world. The pathophysiology of CHF is complex, and much of our comprehension revolves strictly around the neurohormonal and mechanical mechanisms involved. It has been suggested that CHF is associated with altered hemostasis, but whether a prothrombotic state contributes to the pathogenesis and progression of the disease is still not well known. The purpose of this review article is to discuss our current knowledge of platelet activation in patients with CHF and the potential role of antiplatelet agents in preventing these hemostatic abnormalities. Clopidogrel is an established medication that reduces the incidence of stroke, myocardial ischemia, or vascular death. It is currently the drug of choice in the prophylaxis of subacute stent thrombosis and postischemic stroke treatment. Promising results of the most resent trials (Clopidogrel versus Aspirin in Patients at Risk of Ischemic Events [CAPRIE] and Clopidogrel in Unstable angina to prevent Recurrent Events [CURE]) may expand future indications of this ADP receptor antagonist for prevention of thrombotic complications in the CHF population. Currently conducted clinical trials (Warfarin and Antiplatelet Therapy in Chronic Heart Failure [WATCH] and Plavix Use for Treatment of Congestive Heart Failure [PLUTO-CHF] should clarify the role of clopidogrel in these patients. (Am Heart J 2003;145:397-403.)