Activation of Ca2+/calmodulin-dependent protein kinase II α in the spinal cords of rats with clip compression injury

A comparative analysis of differentially expressed genes in rostral and caudal regions after spinal cord injury in rats

The initial mechanical damage of a spinal cord injury (SCI) triggers a progressive secondary injury cascade, which is a complicated process integrating multiple systems and cells. It is crucial to explore the molecular and biological process alterations that occur after SCI for therapy development. The differences between the rostral and caudal regions around an SCI lesion have received little attention. Here, we analyzed the differentially expressed genes between rostral and caudal sites after injury to determine the biological processes in these two segments after SCI. We identified a set of differentially expressed genes, including Col3a1, Col1a1, Dcn, Fn1, Kcnk3, and Nrg1, between rostral and caudal regions at different time points following SCI. Functional enrichment analysis indicated that these genes were involved in response to mechanical stimulus, blood vessel development, and brain development. We then chose Col3a1, Col1a1, Dcn, Fn1, Kcnk3, and Nrg1 for quantitative real-time PCR and Fn1 for immunostaining validation. Our results indicate alterations in different biological events enriched in the rostral and caudal lesion areas, providing new insights into the pathology of SCI.

Methane Suppresses Microglial Activation Related to Oxidative, Inflammatory, and Apoptotic Injury during Spinal Cord Injury in Rats

OBJECTIVE

We investigated the hypothesis that methane-rich saline (MS) can be used to repair spinal cord injury (SCI) in a rat model through suppressing microglial activation related to oxidative, inflammatory, and apoptotic injury.

METHODS

MS was injected intraperitoneally in rats after SCI. Hematoxylin-eosin (HE) staining, oxidative stress, inflammatory parameters, and cell apoptosis were detected 72 h after SCI to determine the optimal dose. Then, we investigated the protective mechanisms and the long-term effects of MS on SCI. HE and microglial activation were observed. Neurological function was evaluated by the Basso, Beattie, and Bresnahan (BBB) scale.

RESULTS

MS can significantly decrease infarct area and inhibit oxidative stress, inflammation, and cell apoptosis 72 h following SCI. The MS protective effect at a dose of 20 ml/kg was better. Moreover, MS can significantly suppress microglial activation related to oxidative and inflammatory injury after SCI and improve hind limb neurological function.

CONCLUSION

MS could repair SCI and reduce the release of oxidative stress, inflammatory cytokines, and cell apoptosis produced by activated microglia. MS provides a novel and promising strategy for the treatment of SCI.

Lentiviral-Mediated Netrin-1 Overexpression Improves Motor and Sensory Functions in SCT Rats Associated with SYP and GAP-43 Expressions

Spinal cord injury (SCI), as a major cause of disability, usually causes serious loss of motor and sensory functions. As a bifunctional axonal guidance cue, netrin-1 can attract axons via the deleted in colorectal cancer (DCC) receptors and repelling others via Unc5 receptors, but its exact role in the recovery of motor and sensory function has not well been studied, and the mechanisms remains elusive. The aim of this experiment is to determine whether lentiviral (LV)-mediated overexpression of netrin-1 or RNA interference (RNAi) can regulate the functional recovery in rats subjected to spinal cord transection (SCT). Firstly, two lentiviral vectors including Lv-exNtn-1 (netrin-1 open reading frame (ORF)) and Lv-shNtn-1 (netrin-1 sh) were constructed and injected into spinal cords rostral and caudal to the transected lesion site. Overexpressing netrin-1 enhanced significantly locomotor function, and reduced thermal and mechanical stimuli in vivo, compared with the control, while silencing netrin-1 did not significantly change the situation. Western blot and immunostaining analysis confirmed that netrin-1 ORF treatment not only effectively increased the expression level of netrin-1, also up-regulated the level of synaptophysin (SYP) in spinal cord rostral to the lesion, but also enhanced growth-associated protein-43 (GAP-43) expression in spinal cord caudal to the lesion site. Comparatively, knockdown of netrin-1 did not give rise to positive findings in our experimental condition. These findings therefore pointed that Lv-mediated netrin-1 overexpression could promote motor and sensory functional recoveries following SCT, and the underlying mechanisms were associated with SYP and GAP-43 expressions. The present study therefore provided a novel strategy for the treatment of SCI and explained the possible mechanisms for the functional improvement.

Motor and histological findings in a model of sci: comparison between posterior and lateral clips

Objective: To evaluate the locomotor and histological impact on the spinal cord comparing lateral and posterior clip placement. Method: Randomized experimental trial. Twenty female Wistar rats, weighing between 250 and 300 grams and aged 12-14 weeks were randomized in two groups according to the placement of the clip: lateral group (N=10) and posterior group (N=10). After exposing the thoracic segment of the spine (T8-T10), a laminectomy was performed at the T9 level under microscopic view. The spinal cord injury was made using a 5 mm long aneurysm clip with a closing pressure of 50 grams. Locomotor behavior was evaluated by the Basso, Beattie and Bresnahan scale in days 1, 7, 14, 21, and 28 after surgery. The area of injury was assessed by histological analysis and measured by a software. Results: The histological evaluation showed a larger mean area of 4.8±1mm² of lesion (P=0.03) in the lateral group when compared with the posterior group mean area of 2.3±2mm². There was no significant difference between lateral and posterior groups with respect to locomotor scores from day 1 to 28 (P=0.361). Conclusion: The lesion area observed in the spinal cord histology after lateral placement of a clip was significantly bigger than in the posterior placement. The motor evaluation showed similar BBB scores regardless of the type of clamping method.

Ca2+/calmodulin-dependent protein kinase II alpha is required for the initiation and maintenance of opioid-induced hyperalgesia

Repeated administration of opioids not only leads to tolerance and dependence, but also results in nociceptive enhancement called opioid-induced hyperalgesia (OIH). Nociceptive mediators involved in OIH generation remain poorly understood. In the present study, we tested the hypothesis that Ca(2+)/calmodulin-depent protein kinase II (CaMKIIalpha) is critical for OIH. Opioid-induced hyperalgesia was produced by repeated morphine administration or pellet implantation in mice. Correlating with the development of tactile allodynia and thermal hyperalgesia, spinal CaMKIIalpha activity was significantly increased in OIH. KN93, a CaMKII inhibitor, dose- and time-dependently reversed OIH and CaMKII activation without impairing locomotor coordination. To elucidate the specific CaMKII isoform involved, we targeted CaMKIIalpha by using small interfering RNA and demonstrated that knockdown of spinal CaMKIIalpha attenuated OIH. Furthermore, morphine failed to induce OIH in CaMKIIalpha(T286A) point mutant mice, although wild-type littermate mice developed robust OIH after repeated treatments with morphine. These data implicate, for the first time, an essential role of CaMKIIalpha as a cellular mechanism leading to and maintaining opioid-induced hyperalgesia.