Histochemical and Electron Microscopic Study on Motor Neurone Degeneration Following Transient Spinal Cord Ischaemia at Normothermic Conditions in Rabbits

Erythropoietin preconditioning improves clinical and histologic outcome in an acute spinal cord ischemia and reperfusion rabbit model

OBJECTIVE

This study examined effects and functional outcome of recombinant human erythropoietin (rhEPO) and carbamylated erythropoietin fusion protein (cEPO-FC) preconditioning in a rabbit model for spinal cord ischemia and resulting paraplegia. This model was chosen because only a small surgical effect is needed to cause paraplegia in rabbits, which facilitates postoperative observation of animals.

METHODS

Anesthetized but spontaneously breathing New Zealand White rabbits randomly received cEPO-FC (50 μg/kg; n = 8), rhEPO (5000 IU/kg; n = 10), or vehicle (control; n = 10) 30 minutes before and after infrarenal aortic clamping. Ideal clamping time of 22 minutes was identified from preceding clamping tests (15-25 minutes). Postoperative observation time was 96 hours. Spinal cord function was assessed by neurologic evaluation of hind limb motor function every 12 hours using a modified Tarlov score. Spinal cord tissue damage was evaluated after 96 hours using hematoxylin and eosin, elastica van Gieson, Nissl, Masson-Goldner, and hemosiderin staining. Plasma levels of cell senescence markers stathmin, chitinase 1/3, elongation factor 1-α were determined.

RESULTS

Rabbits that received rhEPO showed significant improvement of spontaneous lower limb movements until 36 hours of reperfusion and improved histologic scores upon examination of the lumbar spinal cord compared with the control group. In contrast, cEPO-FC treatment showed comparable outcome to the control group concerning movements of the lower limbs and histology. Senescence markers were elevated in the control group, but not in the treatment groups, except for chitinase 3 in the rhEPO group. Only stathmin showed no significant effect. Markers for senescence might increase after acute ischemic injury. Attenuation of senescence markers might not come alone from improvement of the spinal cord.

CONCLUSIONS

Preconditioning with rhEPO attenuates ischemia/reperfusion injury of the spinal cord, whereas the carbamylated derivative (cEPO-FC) showed no positive effect on spinal cord function.

Transient ischemia-induced changes of excitatory amino acid carrier 1 in the ventral horn of the lumbar spinal cord in rabbits

OBJECTIVES

To examine temporal changes of EAAC1 immunoreactivity and its protein level in the spinal ventral horn after transient ischemia in the rabbit to investigate the correlation between neuronal cell death and EAAC1 in the ventral horn of spinal cord.

METHODS

White rabbits weighing 2.5-3.0 kg were anesthetized with a mixture of 2.5% isoflurane in 30% oxygen and 70% nitrous oxide, and the abdominal aortic artery below the left renal artery was occluded for 15 minutes. At designated times after reperfusion, the immunohistochemical and Western blot analysis for EAAC1 was conducted using tissues of the seventh lumbar spinal segment.

RESULTS

EAAC1 immunoreactivity was detected in the neurons of the normal spinal cord. EAAC1 immunoreactivity and protein level reduced significantly 30 minutes after ischemia/reperfusion, but EAAC1 immunoreactivity and protein level again increased by 80% versus sham 3 hours after ischemia. At this time point, neurological defect in hindlimb was also detected. Thereafter, EAAC1 immunoreactivity and protein levels remained to be attenuated in the ventral horn of spinal cord until 48 hours after ischemia.

CONCLUSION

The significant change in EAAC1 expression and motor defects at early time after transient spinal cord ischemia relates to the acute events following ischemia/reperfusion. These results indicate that EAAC1 has an important role in the modulation of glutamate homeostasis in ischemic neurons in the spinal ventral horn.

Sodium 4-phenylbutyrate protects against spinal cord ischemia by inhibition of endoplasmic reticulum stress

OBJECTIVE

Delayed paraplegia after operation on the thoracoabdominal aorta is considered to be related to vulnerability of motor neurons to ischemia. Previous studies have demonstrated the relationship between neuronal vulnerability and endoplasmic reticulum (ER) stress after transient ischemia in the spinal cord. The aim of this study was to investigate whether sodium 4-phenylbutyrate (PBA), a chemical chaperone that reduces the load of mutant or unfolded proteins retained in the ER during cellular stress, can protect against ischemic spinal cord damage.

METHODS

Spinal cord ischemia was induced in rabbits by direct aortic cross-clamping (below the renal artery and above the bifurcation) for 15 minutes at normothermia. Group A (n = 6) was a sham operation control group. In group B (n = 6) and group C (n = 6), vehicle or 15 mg/kg/h of sodium 4-PBA was infused intravenously, respectively, from 30 minutes before the induction of ischemia until 30 minutes after reperfusion. Neurologic function was assessed at 8 hours, and 2 and 7 days after reperfusion with a Tarlov score. Histologic changes were studied with hematoxylin-eosin staining. Immunohistochemistry analysis for ER stress-related molecules, including caspase12 and GRP78 were examined.

RESULTS

The mean Tarlov scores were 4.0 in every group at 8 hours, but were 4.0, 2.5, and 3.9 at 2 days; and 4.0, 0.7, and 4.0 at 7 days in groups A, B, and C, respectively. The numbers of intact motor neurons at 7 days after reperfusion were 47.4, 21.5, and 44.9 in groups A, B, and C, respectively. There was no significant difference in terms of viable neurons between groups A and C. Caspase12 and GRP78 immunoreactivities were induced in motor neurons in group B, whereas they were not observed in groups A and C.

CONCLUSION

Reduction in ER stress-induced spinal cord injury was achieved by the administration of 4-PBA. 4-PBA may be a strong candidate for use as a therapeutic agent in the treatment of ischemic spinal cord injury.

New insights into mitochondrial structure during cell death

Mitochondria play a pivotal role in the cascade of events associated with cell death pathways that are involved with several forms of neurodegeneration. Recent findings show that in the Bax/Bak-dependent pathway of apoptosis, the release of cytochrome c from mitochondria is a consequence of two carefully coordinated events: opening of crista junctions triggered by OPA1 oligomer disassembly and formation of outer membrane pores. Both steps are necessary for the complete release of pro-apoptotic proteins. The remodeling of mitochondrial structure accompanies this pathway, including mitochondrial fission, and cristae and crista junction alterations. Yet, there is controversy surrounding the timing of certain remodeling events and whether they are necessary early events required for the release of pro-apoptotic factors or are simply a downstream after-effect. Here, we analyze the current knowledge of mitochondrial remodeling during cell death and discuss what structural alterations occur to this organelle during neurodegeneration, focusing on the higher resolution structural correlates obtained by electron microscopy and electron tomography.

The selective poly(ADP)ribose-polymerase 1 inhibitor INO1001 reduces spinal cord injury during porcine aortic cross-clamping-induced ischemia/reperfusion injury

OBJECTIVE

It is well-established that poly(ADP)ribose-polymerase (PARP) assumes major importance during ischemic brain damage, and the selective PARP-1 inhibitor PJ34 reduced spinal cord damage in murine aortic occlusion-induced ischemia/reperfusion injury. We investigated the effect of the PARP-1 inhibitor INO1001 on aortic-occlusion-related porcine spinal cord injury.

DESIGN AND SETTING

Prospective, randomized, controlled experimental study in an animal laboratory.

PATIENTS AND PARTICIPANTS

Ten anesthetized, mechanically ventilated, and instrumented pigs.

INTERVENTIONS

Animals underwent 45 min of thoracic aortic cross-clamping after receiving vehicle (n=5) or intravenous INO1001 (n=5, total dose 4 mg/kg administered both before clamping and during reperfusion). During reperfusion continuous intravenous norepinephrine was incrementally adjusted to maintain blood pressure at or above 80% of the preclamping level. Plasma INO1001 levels were analyzed by HPLC. After 4[Symbol: see text]h of reperfusion spinal cord biopsy samples were analyzed for neuronal damage (hematoxyline-eosine and Nissl staining), expression of the cyclin-dependent kinase inhibitor genes p21 and p27 (immunohistochemistry), and apoptosis (terminal deoxynucleotidyl transferase mediated nick end labeling assay).

MEASUREMENTS AND RESULTS

Plasma INO1001 levels were 0.8-2.3 and 0.30-0.76 mM before and after clamping, respectively. While 3-5% of the spinal cord neurons were irreversibly damaged in the INO1001 animals, the neuronal cell injury was three times higher in the control group. Neither p21 and p27 expression nor apoptosis showed any intergroup difference.

CONCLUSIONS

The selective PARP-1 inhibitor INO1001 markedly reduced aortic occlusion-induced spinal cord injury. Given the close correlation reported in the literature between morphological damage and impaired spinal cord function, INO1001 may improve spinal cord recovery after thoracic aortic cross-clamping.

Degradation of spectrin via calpains in the ventral horn after transient spinal cord ischemia in rabbits

In the present study, we investigated chronological changes of mu-calpain, m-calpain and cleaved spectrin alphaII immunoreactivity in the ventral horn after transient spinal cord ischemia to investigate relationship between calpains and vulnerability to ischemia using abdominal aorta occlusion model in rabbits. Spinal cord sections at the level of L(7) were immunostained with calpains and cleaved spectrin alphaII monoclonal antibodies. mu-Calpain and m-calpain immunoreactivity was significantly increased in the ischemic ventral horn at 30 min and 1 h after ischemia/reperfusion, respectively. Thereafter, they were decreased with time after ischemia/reperfusion: at 48 h after ischemia, their immunoreactivities nearly disappeared in the ischemic ventral horn. Cleaved spectrin alphaII immunoreactivity was significantly increased in the ventral horn of spinal cord at 12 h after ischemia/reperfusion, and thereafter, its immunoreactivity was decreased with time after ischemia/reperfusion. In addition, spectrin alphaII protein level (280 kDa) was decreased from 12 h after ischemia/reperfusion; in contrast, cleaved spectrin alphaII protein level (150 kDa) was significantly increased at 12 h after ischemia/reperfusion. In conclusion, our observations in this study indicate that calpain is associated with neuronal degeneration in the ventral horn at early time after transient spinal cord ischemia via the proteolysis of spectrin alphaII.