Comparative effects of methylprednisolone and tetracosactide (ACTH1-24) on ischemia/reperfusion injury of the rabbit spinal cord

Abstract

Introduction: Tetracosactide is an engineered peptide that applies the same biological impacts as the endogenous adrenocorticotropic hormone. Previous studies indicated that tetracosactide has anti-inflammatory, antioxidant and neurotrophic activity. In this study, we hypothesized that tetracosactide may have protective effects in spinal cord ischemia-reperfusion injury.

Material and methods: Rabbits were randomized into the accompanying four groups of eight animals each: group 1 (control), group 2 (ischemia), group 3 (methylprednisolone) and group 4 (tetracosactide). In the control group, just a laparotomy was performed. In the various groups, the spinal cord ischemia model was made by the impediment of the aorta only caudal to the renal vein. Neurological assessment was conducted with the Tarlov scoring system. Levels of myeloperoxidase, malondialdehyde and catalase were analyzed, similar to the activities of xanthine oxidase and caspase-3. Histopathological and ultrastructural assessments were additionally performed.

Results: After ischemia-reperfusion injury, increments were found in the tissue myeloperoxidase levels (p < 0.001), malondialdehyde levels (p < 0.001), xanthine oxidase action (p < 0.001) and caspase-3 movement (p < 0.001). Conversely, both serum and tissue catalase levels were diminished (p < 0.001 for both). After the administration of tetracosactide, declines were seen in the tissue myeloperoxidase levels (p < 0.001), malondialdehyde levels (p = 0.003), xanthine oxidase action (p < 0.001) and caspase-3 movement (p < 0.001). Conversely, both the serum and tissue catalase levels were expanded (p < 0.001). Besides, tetracosactide treatment indicated enhanced results related to the histopathological scores (p < 0.001), the ultra-structural score (p = 0.008) and the Tarlov scores (p < 0.001).

Conclusions: The findings showed for the first time that tetracosactide shows significant neuroprotective activity against ischemia-reperfusion injury of the spinal cord.

Keywords: adrenocorticotropic hormone; ischemia-reperfusion; methylprednisolone; neuroprotection; spinal cord; tetracosactide.

Figure 1

Flow diagram showing the study design

Figure 2

Photomicrographs of 5 μm spinal cord tissue sections from the different study groups (H&E, 10× obj.). A – Control group (n = 8), showing normal spinal cord parenchyma. B – Ischemia group (n = 8), showing degenerated neurons (filled arrows) in the edematous surface. C – MP group (n = 8), showing less degenerated neurons (filled arrows); note the normal neurons (hollow arrows). D – ACTH group (n = 8), showing less degenerated neurons (filled arrows), and more normal neurons (hollow arrows). The spinal cord tissues were protected from injury

Figure 3

Graphs showing the histopathological (A, B), ultrastructural (C) and neurological examination results (D) of the groups (n = 8 for each group). A – Comparison of the histopathology scores among the groups. The horizontal lines in the middle of each box represent the median, while the top and bottom borders of the box represent the 25th and 75th percentiles, respectively. The whiskers above and underneath the box represent the highest and lowest levels observed. B – Correlation of the number of normal neurons in the anterior horn among the groups. The box in the middle of each whisker shows the arithmetic mean, while the whiskers above and below the box indicate the +1 SD and –1 SD levels, respectively. C – Bar graph demonstrating the after-effects of the ultrastructural investigation. D – Comparison of the Tarlov scores among the groups. The horizontal lines in the middle of each box represent the median, while the top and bottom borders of the box indicate the 25th and 75th percentiles, respectively. The whiskers above and below the box mark the maximum and minimum levels observed MP – methylprednisolone, ACTH – adrenocorticotropic hormone.

Figure 4

Transmission electron microscopy of the groups. A – Electron micrograph from the control group (n = 8) showing ultrastructurally normal myelinated axons (m) (original magnification 5000×, scale bar is 2 μm long). B – Electron micrograph from the ischemia group (n = 8) showing the small, medium-sized, and large axons with separations in myelin configuration (*) (original magnification 5000×, scale bar is 2 μm long). C – Electron micrograph from the MP group (n = 8) showing separations in myelin configurations (*) in small, medium-sized and large myelinated axons (original magnification 5000×, scale bar is 2 μm long). n – nucleus of a neuron. D – Electron micrograph from the ACTH group (n = 8) indicating medium-sized myelinated axons with gentle division in myelin configuration (*) and ultrastructurally normal small and medium-sized myelinated axons (m) (original amplification 5000×, scale bar is 2 μm long)