Cyclosporin‐A treatment attenuates delayed cytoskeletal alterations and secondary axotomy following mild axonal stretch injury

Abstract

Following central nervous system trauma, diffuse axonal injury and secondary axotomy result from a cascade of cellular alterations including cytoskeletal and mitochondrial disruption. We have examined the link between intracellular changes following mild/moderate axonal stretch injury and secondary axotomy in rat cortical neurons cultured to relative maturity (21 days in vitro). Axon bundles were transiently stretched to a strain level between 103% and 106% using controlled pressurized fluid. Double-immunohistochemical analysis of neurofilaments, neuronal spectrin, alpha-internexin, cytochrome-c, and ubiquitin was conducted at 24-, 48-, 72-, and 96-h postinjury. Stretch injury resulted in delayed cytoskeletal damage, maximal at 48-h postinjury. Accumulation of cytochrome-c and ubiquitin was also evident at 48 h following injury and colocalized to axonal regions of cytoskeletal disruption. Pretreatment of cultures with cyclosporin-A, an inhibitor of calcineurin and the mitochondrial membrane transitional pore, reduced the degree of cytoskeletal damage in stretch-injured axonal bundles. At 48-h postinjury, 20% of untreated cultures demonstrated secondary axotomy, whereas cyclosporin A-treated axon bundles remained intact. By 72-h postinjury, 50% of control preparations and 7% of cyclosporin A-treated axonal bundles had progressed to secondary axotomy, respectively. Statistical analyses demonstrated a significant (p < 0.05) reduction in secondary axotomy between treated and untreated cultures. In summary, these results suggest that cyclosporin-A reduces progressive cytoskeletal damage and secondary axotomy following transient axonal stretch injury in vitro.

Experimental models of traumatic axonal injury

“…Due to the accessibility of cultured cells and precise control of the extracellular environment, effects on cell viability can be readily assessed and the biochemical mechanisms underlying neuroprotection can be investigated. 89,90 Despite the simplifications inherent in these in vitro models, many researchers believe that in vitro models will continue to complement the in vivo models and have considerable potential in studies addressing the mechanisms of axonal dysfunction and degeneration. 7,11 3.…”

Progress of Research on Diffuse Axonal Injury after Traumatic Brain Injury

“…DAI is often accompanied by other brain injuries, and this has caused patients severe brain damage or even placed them in a persistent vegetative state. According to reports made in recent years, the mortality rate of DAI is 42%–62% [1, 2]. DAI has been as an independent category of disease accepted by neurosurgery academic.…”

Diffuse axonal injury: Novel insights into detection and treatment

“…Both CsA and FK506 could reduce progressive cytoskeletal damage and inhibit secondary axotomy. 34,35 However, the CsA treatment reduced the density of damaged axons that exhibited neurofilament compaction (NFC), while FK506 failed to attenuate NFC, suggesting that non-calpain-mediated mechanisms are operant and that additional therapeutic agents targeting NFC may be necessary. 36 There are few published studies that examine which dosage of CsA is effective in attenuating secondary progression to axotomy in the injured axon.…”