Delayed pharmacological pre-conditioning effect of mitochondrial ATP-sensitive potassium channel opener on neurologic injury in a rabbit model of spinal cord ischemia

Ischemic postconditioning reduces spinal cord ischemia-reperfusion injury through ATP-sensitive potassium channel

STUDY DESIGN

Animal study.

OBJECTIVES

Explore the neuroprotective effect of remote limb ischemic postconditioning (Post C) in spinal cord ischemic reperfusion injury (SCII) and related mechanisms.

SETTING

Anesthesiology Laboratory of Southwest Medical University.

METHODS

We established a rabbit SCII model and processed it with Post C. To evaluate the neural function, spinal cord tissue was taken 48 h later, normal neurons were evaluated by HE staining, and the expression of ATP-sensitive potassium channel (K_ATP) marker molecule Kir6.2 was detected by Western blot. Immunofluorescence detection of spinal cord Iba-1 expression, ELISA detection of M1 type microglia marker iNOS and M2 type microglia marker Arg, and Western blot detection of NF-κB and IL-1β expression. Through these experiments, we will explore the protective effect of Post C in SCII, observe the changes in the protective effect after using K_ATP blockers, and verify that Post C can play a neuroprotective effect in SCII by activating K_ATP.

RESULTS

We observed that Post C significantly improved exercise ability and the number of spinal motor neurons in the SCII model. Microglia are activated and expression of M₁ microglia in the spinal cord was decreased, while M₂ was increased. This neuroprotective effect was reversed by the nonspecific K_ATP inhibitor.

CONCLUSION

Post C has a neuroprotective effect on SCII, and maybe a protective effect produced by activating K_ATP to regulate spinal microglia polarization and improve neuroinflammation.

Aprikalim a potassium adenosine triphosphate channel opener reduces neurologic injury in a rabbit model of spinal cord ischemia

BACKGROUND

Potassium adenosine triphosphate (KATP) channel openers have been involved in the enhancement of ischemic tolerance in various tissues. The purpose of the present study is to evaluate the effects of aprikalim, a specific KATP channel opener, on spinal cord ischemic injury.

METHODS

Fifty-four rabbits were randomly assigned to three groups: group 1 (n = 18, sham operation), group 2 (n = 18, 30 min of normothermic aortic cross-clamping) and group 3 (n = 18, aprikalim 100 μg/kg was administered 15 min before 30 min of normothermic aortic cross-clamping). Neurologic evaluation was performed according to the modified Tarlov scale. Six animals from each group were sacrificed at 24, 48 and 168 h postoperatively. The lumbar spinal cords were harvested and examined histologically. The motor neurons were counted and the histologic lesions were scored (0-3, 3: normal).

RESULTS

Group 3 (aprikalim group) had better Tarlov scores compared to group 2 at all-time points (P < 0.025). The histologic changes were proportional to the Tarlov scores and group 3 had better functional outcome as compared to group 2 at 168 h (number of neurons: 21.2 ± 4.9 vs. 8.0 ± 2.7, P < 0.001 and histologic score: 1.67 ± 1.03 vs. 0.50 ± 0.55, P = 0.03). Although aprikalim exhibited improved effect on clinical and histologic neurologic outcome when compared to normothermic spinal cord ischemia, animals in group 3 had worse Tarlov score, reduced number of motor neurons and worse histologic score when compared to group 1 (sham operation) at 168 h (P = 0.003, P = 0.001 and P = 0.019 respectively).

CONCLUSION

Aprikalim reduces the severity of spinal cord ischemic injury in a rabbit model of spinal cord ischemia.

Neuroprotective role of ATP-sensitive potassium channels in cerebral ischemia

ATP-sensitive potassium (K(ATP)) channels are weak, inward rectifiers that couple metabolic status to cell membrane electrical activity, thus modulating many cellular functions. An increase in the ADP/ATP ratio opens K(ATP) channels, leading to membrane hyperpolarization. K(ATP) channels are ubiquitously expressed in neurons located in different regions of the brain, including the hippocampus and cortex. Brief hypoxia triggers membrane hyperpolarization in these central neurons. In vivo animal studies confirmed that knocking out the Kir6.2 subunit of the K(ATP) channels increases ischemic infarction, and overexpression of the Kir6.2 subunit reduces neuronal injury from ischemic insults. These findings provide the basis for a practical strategy whereby activation of endogenous K(ATP) channels reduces cellular damage resulting from cerebral ischemic stroke. K(ATP) channel modulators may prove to be clinically useful as part of a combination therapy for stroke management in the future.