Establishment of a local cooling model against spinal cord ischemia representing prolonged induction of heat shock protein

Is thoracic aortic disease a growing problem in Japan?

An article by Okita was recently published in General Thoracic and Cardiovascular Surgery. The paper thoroughly reviewed the surgical treatments for thoracic aortic disease in Japan. Valve-sparing aortic root operation, cerebral protection during aortic arch aneurysmectomy, and spinal cord protection during thoracoabdominal aneurysm repair are discussed in the present editorial.

Autophagy-mediated stress response in motor neurons after hypothermic spinal cord ischemia in rabbits

OBJECTIVE

The development of spinal cord injury is believed to be related to the vulnerability of spinal motor neurons to ischemia. However, the mechanisms underlying this vulnerability have not been fully investigated. Previously, we reported that spinal motor neurons are lost likely due to autophagy and that local hypothermia prevents such spinal motor neuron death. Therefore, we investigated the role of autophagy in normothermic and hypothermic spinal cord ischemia using an immunohistochemical analysis of Beclin 1 (BCLN1; B-cell leukemia 2 protein [Bcl-2] interacting protein), Bcl-2, and γ-aminobutyric acid type-A receptor-associated protein (GABARAP), which are considered autophagy-related proteins.

METHODS

We used rabbit normothermic and hypothermic transient spinal cord ischemia models using a balloon catheter. Neurologic function was assessed according to the Johnson score, and the spinal cord was removed at 8 hours and 1, 2, and 7 days after reperfusion, and morphologic changes were examined using hematoxylin and eosin staining. A Western blot analysis and histochemical study of BCLN1, Bcl-2, and GABARAP, and double-labeled fluorescent immunocytochemical studies were performed.

RESULTS

There were significant differences in the physiologic function between the normothermic model and hypothermic model after the procedure (P < .05). In the normothermic model, most of the motor neurons were selectively lost at 7 days of reperfusion (P < .001 compared with the sham group), and they were preserved in the hypothermic model (P = .574 compared with the sham group). The Western blot analysis revealed that the sustained expression of the autophagy markers, BCLN1 and GABARAP, was observed (P < .001 compared with the sham group) and was associated with neuronal cell death in normothermic ischemic conditions. In hypothermic ischemic conditions, the autophagy inhibitory protein Bcl-2 was powerfully induced (P < .001 compared with the sham group) and was associated with blunted expression of BCLN1 and GABARAP and neuronal cell survival. The double-label fluorescent immunocytochemical study revealed that immunoreactivitiy for BCLN1, Bcl-2, and GABARAP was induced in the same motor neurons.

CONCLUSIONS

These data suggest that the prolonged induction of autophagy might be a potential factor responsible for delayed motor neuron death, and the induction of the autophagy inhibitory protein Bcl-2 using hypothermia might limit autophagy and protect against delayed motor neuron death.

Rapid ischemic preconditioning with a short reperfusion time prevents delayed paraplegia in a rabbit model

BACKGROUND

Surgery for thoracic and thoracoabdominal aortic aneurysms can be complicated by a significant incidence of neurogenic deficits due to spinal cord ischemia. In this study, we investigated whether ischemic preconditioning (IPC) improves neurologic outcome in a rabbit model.

METHODS

Forty rabbits underwent infrarenal aortic occlusion. The IPC group (n = 20) had 10 minutes of aortic occlusion to induce spinal cord ischemia, 40 minutes of reperfusion, and 30 minutes of ischemia, whereas the control group (n = 20) had only 30 minutes of ischemia. Tarlov scoring (0, paraplegia; 4, normal) was used to evaluate neurologic functions 7 days later, and spinal cord segments (L4-L6) were stained with hematoxylin and eosin for histologic evaluation.

RESULTS

Complete paraplegia (grade 0) occurred in 15 (75%) of the 20 control animals, whereas in the IPC group, 13 (65%) of 20 animals were completely normal (grade 4) (P < .05).

CONCLUSION

IPC is beneficial for protecting against neurologic damage after transient aortic occlusion in a rabbit model; however, the protective mechanisms are not clear.

ONO-5046 attenuation of delayed motor neuron death and effect on the induction of brain-derived neurotrophic factor, phosphorylated extracellular signal–regulated kinase, and caspase3 after spinal cord ischemia in rabbits

OBJECTIVE

The mechanism of spinal cord injury is believed to be related to the vulnerability of spinal motor neuron cells to ischemia. The aim of this study was to investigate whether ONO-5046, a specific inhibitor of neutrophil elastase that can attenuate tissue or organ injury in various pathologic conditions, could protect against ischemic spinal cord damage.

METHODS

After induction of spinal ischemia, ONO-5046 or vehicle was injected intravenously. Cell damage was analyzed by counting the number of motor neurons. To investigate the mechanism by which ONO-5046 prevents ischemic spinal cord damage, we observed the immunoreactivity of CPP32 (caspase3), brain-derived neurotrophic factor, and phosphorylated extracellular signal-regulated kinase.

RESULTS

ONO-5046 eased the functional deficits and increased the number of motor neurons after ischemia. The induction of caspase3 was significantly reduced by ONO-5046 treatment. Furthermore, the expressions of brain-derived neurotrophic factor and phosphorylated extracellular signal-regulated kinase were prolonged.

CONCLUSION

ONO-5046 may protect motor neurons from ischemic injury by reducing caspase3 and prolonging the expressions of brain-derived neurotrophic factor and phosphorylated extracellular signal-regulated kinase. ONO-5046 may be a strong candidate for use as a therapeutic agent in the treatment of ischemic spinal cord injury.

MCI-186 reduces oxidative cellular damage and increases DNA repair function in the rabbit spinal cord after transient ischemia

BACKGROUND

Paraplegia is a serious complication of operations on the thoracic and thoracoabdominal aorta. To investigate the mechanism by which motor neurons are damaged during these operations, we have reported a rabbit model of spinal cord ischemia. We also tested whether a free radical scavenger MCI-186 that is useful for treating ischemic damage in the brain can protect against ischemic spinal cord damage.

METHODS

Fifteen minutes of ischemia was induced, then MCI-186 or vehicle was injected intravenously. Cell damage was analyzed by observing the function of the lower limbs and by counting the number of motor neurons. To investigate the mechanism by which MCI-186 prevents ischemic spinal cord damage, we observed the immunoreactivity of 8-hydroxy-2'-deoxyguanosine as an oxidative DNA damage marker and redox effector as a DNA repair marker.

RESULTS

In sham control, 8-hydroxy-2'-deoxyguanosine was not observed, and the nuclear expression of redox effector was observed. In vehicle injection group (group I), the nuclear expression of 8-hydroxy-2'-deoxyguanosine was observed at 1 and 2 days after reperfusion. The nuclear expression of redox effector was observed at 8 hours and 1 day, and disappeared at 2 days after transient ischemia. In MCI-186 injection group (group M), the nuclear expression of 8-hydroxy-2'-deoxyguanosine was not observed, and redox effector was observed at 8 hours and 1 and 2 days.

CONCLUSIONS

These results suggest that redox effector decreased in motor neurons after transient ischemia and this reduction preceded oxidative DNA damage. MCI-186 works as a radical scavenger and reduced oxidative DNA damage, so redox effector did not disappear. MCI-186 could be a strong candidate for a use as a therapeutic agent in the treatment of ischemic spinal cord injury.

Mediators of ischemic preconditioning identified by microarray analysis of rat spinal cord

Spinal ischemia is a frequent cause of paralysis. Here we explore the biological basis of ischemic preconditioning (IPC), the phenomenon in which a brief period of ischemia can confer protection against subsequent longer and normally injurious ischemia, to identify mediators of endogenous neuroprotection. Using microarrays, we examined gene expression changes induced by brief spinal ischemia using a rat balloon occlusion model. Among the nearly 5000 genes assayed, relatively few showed two-fold changes, and three groups stood out prominently. The first group codes for heat shock protein 70, which is induced selectively and robustly at 30 min after brief ischemia, with increases up to 100-fold. A second group encodes metallothioneins 1 and 2. These mRNAs are increased at 6 and 12 h after ischemia, up to 12-fold. The third group codes for a group of immediate-early genes not previously associated with spinal ischemia: B-cell translocation gene 2 (BTG2), the transcription factors early growth response 1 (egr-1) and nerve growth factor inducible B (NGFI-B), and a mitogen-activated protein kinase phosphatase, ptpn16, an important cell signaling regulator. These mRNAs peak at 30 min and return to baseline or are decreased 6 h after ischemia. Several other potentially protective genes cluster with these induced mRNAs, including small heat shock proteins, and many have not been previously associated with IPC. These results provide both putative mediators of IPC and molecular targets for testing preconditioning therapies.

MCI-186 prevents spinal cord damage and affects enzyme levels of nitric oxide synthase and Cu/Zn superoxide dismutase after transient ischemia in rabbits

OBJECTIVE

The mechanism of spinal cord injury is believed to be related to the vulnerability of spinal motor neuron cells against ischemia. We tested whether MCI-186, which is useful for treating ischemic damage in the brain, can protect against ischemic spinal cord damage.

METHODS

After induction of ischemia, MCI-186 or vehicle was injected intravenously. Cell damage was analyzed by observing the function of the lower limbs and by counting the number of motor neurons. To investigate the mechanism by which MCI-186 prevents ischemic spinal cord damage, we observed the immunoreactivity of Cu/Zn superoxide dismutase, neuronal nitric oxide synthase, and endothelial nitric oxide synthase.

RESULTS

MCI-186 eased the functional deficits and increased the number of motor neurons after ischemia. The induction of neuronal nitric oxide synthase was significantly reduced by the treatment with MCI-186. Furthermore, the increase in the induction of endothelial nitric oxide synthase and Cu/Zn superoxide dismutase was more pronounced.

CONCLUSION

These results indicate that MCI-186 may protect motor neurons from ischemic injury by reducing neuronal nitric oxide synthase and increasing endothelial nitric oxide synthase. MCI-186 may be a strong candidate for use as a therapeutic agent in the treatment of ischemic spinal cord injury.

Topical head cooling during rewarming after experimental hypothermic circulatory arrest

BACKGROUND

The aim of this study was to evaluate the potential neuroprotective effect of topical head cooling during the first 2 postoperative hours after experimental hypothermic circulatory arrest.

METHODS

Twenty pigs underwent a 75-minute period of hypothermic circulatory arrest and were randomly assigned to rewarming to 37 degrees C or to undergo topical cooling of the head for 2 hours from the start of rewarming followed by a period of external rewarming to 37 degrees C.

RESULTS

The 7-day survival rate was 70% in the control group and 60% in the topical head cooling group. Despite brain tissue oxygenation, intracranial pressures, mixed oxygen venous saturation, oxygen consumption, and extraction tended to be favorable in the topical head cooling group as a clear effect of mild hypothermia. The latter group had significantly higher postoperative brain lactate and pyruvate ratios, and lactate and glucose ratios. Furthermore, the topical head cooling group had worse fluid balance throughout the postoperative period. Brain histopathologic scores were comparable with the study groups, but among 7-days survivors these scores tended to be worse in the topical head cooling group.

CONCLUSIONS

Topical cooling of the head during the first 2 postoperative hours after experimental hypothermic circulatory arrest does not appear to provide any neuroprotective effect.

Heme oxygenase and nitric oxide synthase mediate cooling-associated protection against TNF-alpha-induced microcirculatory dysfunction and apoptotic cell death

Local cooling protects against TNF-alpha-induced injury by attenuating inflammation-associated microcirculatory dysfunction and leukocytic response. Mechanisms of protection, however, are not fully understood. We studied whether the metabolites of the HO and NOS pathway, exerting potent vasodilatory, antioxidant, and anti-apoptotic properties, are involved in tissue cryoprotection. In animals pretreated with L-NAME or SnPP-IX, cooling-associated abrogation of TNF-alpha-induced microcirculatory dysfunction was abolished. Combined L-NAME/SnPP-IX pretreatment did not cause greater blunting than seen when each mediator system was inhibited separately. In SnPP-IX- but not L-NAME-pretreated animals, transient hypothermia failed to reduce TNF-alpha-mediated leukocyte adherence. Vice versa, treatment of TNF-alpha-exposed animals with either the NO donor l-arginine or the HO-1 inductor hemin mimicked cooling-associated tissue protection except for failure of l-arginine to abrogate the inflammatory leukocyte response. The efficiency of cooling to inhibit TNF-alpha-induced apoptotic cell death was blunted in SnPP-IX-, L-NAME-, and SnPP-IX/L-NAME-pretreated animals. Coadministration of Trolox in SnPP-IX-treated animals partly attenuated leukocyte adherence and cell apoptosis, implying that the HO pathway metabolite biliverdin contributes to the salutary effects of cooling. Thus, our study provides evidence that metabolites of the HO and the NOS pathway mediate the cooling-associated protection of inflamed tissue. Biliverdin rather than CO and NO mediates the anti-inflammatory action, whereas a coordinated function of the gaseous monoxides prevents microcirculatory dysfunction and apoptotic cell death.

Reduction of spinal cord injury with pentobarbital and hypothermia in a rabbit model

OBJECTIVES

to evaluate the effects of hypothermia and pentobarbital on spinal cord ischaemia induced in a rabbit model.

MATERIALS AND METHODS

thirty-two rabbits, allocated into four equal groups, had the infrarenal aorta clamped distal to the left renal artery and above the iliac bifurcation for 40 min. Groups 3 and 4 had infusion of 15 mg/kg of pentobarbital intravenously for 5 min, 15 min before the cross-clamping. Groups 2 and 4 had infusion of 20 ml of Ringer's lactate (LR) solution at 3 degrees C for 3 min during aortic cross clamp into the isolated aortic segment. Group 1 was untreated and served as control. Postoperative functions of spinal cord were assessed.

RESULTS

paraplegia occurred in all rabbits in Group 1, in one in each of Groups 2 and 3, whereas no paraplegia was observed in Group 4. In addition 2 and 3 animals of Groups 2 and 3, respectively revealed varying degree of neurological disturbances, whereas all animals of Group 4 had normal function. This difference between Groups 2, 3, and 4 vs Group 1 was significant (p<0.002). So was the difference between Groups 2 and 4 (p=0.03), whereas the difference between Groups 3 and 4 was not significant.

CONCLUSIONS

hypothermia and pentobarbital was more effective than hypothermia alone for prevention of spinal cord ischaemia in a rabbit model.