Induction of autophagy and autophagic cell death in damaged neural tissue after acute spinal cord injury in mice

Systemic bisperoxovanadium activates Akt/mTOR, reduces autophagy, and enhances recovery following cervical spinal cord injury

Secondary damage following primary spinal cord injury extends pathology beyond the site of initial trauma, and effective management is imperative for maximizing anatomical and functional recovery. Bisperoxovanadium compounds have proven neuroprotective effects in several central nervous system injury/disease models, however, no mechanism has been linked to such neuroprotection from bisperoxovanadium treatment following spinal trauma. The goal of this study was to assess acute bisperoxovanadium treatment effects on neuroprotection and functional recovery following cervical unilateral contusive spinal cord injury, and investigate a potential mechanism of the compound's action. Two experimental groups of rats were established to 1) assess twice-daily 7 day treatment of the compound, potassium bisperoxo (picolinato) vanadium, on long-term recovery of skilled forelimb activity using a novel food manipulation test, and neuroprotection 6 weeks following injury and 2) elucidate an acute mechanistic link for the action of the drug post-injury. Immunofluorescence and Western blotting were performed to assess cellular signaling 1 day following SCI, and histochemistry and forelimb functional analysis were utilized to assess neuroprotection and recovery 6 weeks after injury. Bisperoxovanadium promoted significant neuroprotection through reduced motorneuron death, increased tissue sparing, and minimized cavity formation in rats. Enhanced forelimb functional ability during a treat-eating assessment was also observed. Additionally, bisperoxovanadium significantly enhanced downstream Akt and mammalian target of rapamycin signaling and reduced autophagic activity, suggesting inhibition of the phosphatase and tensin homologue deleted on chromosome ten as a potential mechanism of bisperoxovanadium action following traumatic spinal cord injury. Overall, this study demonstrates the efficacy of a clinically applicable pharmacological therapy for rapid initiation of neuroprotection post-spinal cord injury, and sheds light on the signaling involved in its action.

Autophagy impairment in a mouse model of neuropathic pain

Autophagy is an intracellular membrane trafficking pathway controlling the delivery of cytoplasmic material to the lysosomes for degradation. It plays an important role in cell homeostasis in both normal settings and abnormal, stressful conditions. It is now recognised that an imbalance in the autophagic process can impact basal cell functions and this has recently been implicated in several human diseases, including neurodegeneration and cancer.

Here, we investigated the consequences of nerve injury on the autophagic process in a commonly used model of neuropathic pain. The expression and modulation of the main autophagic marker, the microtubule-associated protein 1 light chain 3 (LC3), was evaluated in the L4-L5 cord segment seven days after spinal nerve ligation (SNL). Levels of LC3-II, the autophagosome-associated LC3 form, were markedly higher in the spinal cord ipsilateral to the ligation side, appeared to correlate with the upregulation of the calcium channel subunit α2δ-1 and were not present in mice that underwent sham surgery. However, LC3-I and Beclin 1 expression were only slightly increased. On the contrary, SNL promoted the accumulation of the ubiquitin- and LC3-binding protein p62, which inversely correlates with autophagic activity, thus pointing to a block of autophagosome turnover.

Our data showed for the first time that basal autophagy is disrupted in a model of neuropathic pain.