Neuroprotective Effects of Oxymatrine via Triggering Autophagy and Inhibiting Apoptosis Following Spinal Cord Injury in Rats.

Spinal cord injury (SCI) is a devastating neurological disorder characterized by high morbidity and disability. However, there is still a lack of effective treatments for it. The identification of drugs that promote autophagy and inhibit apoptosis in neurons is critical for improving patient outcomes following SCI. Previous studies have shown that increasing the activity of silent information regulator 1 (SIRT1) and downstream protein AMP-activated protein kinase (AMPK) in rat models of SCI is highly neuroprotective. Oxymatrine (OMT), a quinolizidine alkaloid, has exhibited neuroprotective effects in various central nervous system (CNS) diseases. However, its explicit effect and molecular mechanism in SCI are still unclear. Herein, we aimed to investigate the therapeutic effects of OMT and explore the potential role of autophagy regulation following SCI in rats. A modified compressive device (weight 35 g, time 5 min) was applied to induce moderate SCI in all groups except the sham group. After treatment with drugs or vehicle (saline), our results indicated that OMT treatment significantly reduced the lesion size, promoted survival of motor neurons, and subsequently attenuated motor dysfunction following SCI in rats. OMT significantly enhanced autophagy activity, inhibited apoptosis in neurons, and increased SIRT1 and p-AMPK expression levels. Interestingly, these effects of OMT on SCI were partially prevented by co-treatment with SIRT1 inhibitor EX527. Furthermore, combining OMT with the potent autophagy inhibitor chloroquine (CQ) could effectively abolish its promotion of autophagic flux. Taken together, these data revealed that OMT exerts a neuroprotective role in functional recovery against SCI in rats, and these effects are potentially associated with OMT-induced activation of autophagy via the SIRT1/AMPK signaling pathway.

Epidural Spinal Cord Stimulation Promotes Motor Functional Recovery by Enhancing Oligodendrocyte Survival and Differentiation and by Protecting Myelin after Spinal Cord Injury in Rats.

Epidural spinal cord stimulation (ESCS) markedly improves motor and sensory function after spinal cord injury (SCI), but the underlying mechanisms are unclear. Here, we investigated whether ESCS affects oligodendrocyte differentiation and its cellular and molecular mechanisms in rats with SCI. ESCS improved hindlimb motor function at 7 days, 14 days, 21 days, and 28 days after SCI. ESCS also significantly increased the myelinated area at 28 days, and reduced the number of apoptotic cells in the spinal white matter at 7 days. SCI decreased the expression of 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNPase, an oligodendrocyte marker) at 7 days and that of myelin basic protein at 28 days. ESCS significantly upregulated these markers and increased the percentage of Sox2/CNPase/DAPI-positive cells (newly differentiated oligodendrocytes) at 7 days. Recombinant human bone morphogenetic protein 4 (rhBMP4) markedly downregulated these factors after ESCS. Furthermore, ESCS significantly decreased BMP4 and p-Smad1/5/9 expression after SCI, and rhBMP4 reduced this effect of ESCS. These findings indicate that ESCS enhances the survival and differentiation of oligodendrocytes, protects myelin, and promotes motor functional recovery by inhibiting the BMP4-Smad1/5/9 signaling pathway after SCI.

Time representation of mitochondrial morphology and function after acute spinal cord injury.

Changes in mitochondrial morphology and function play an important role in secondary damage after acute spinal cord injury. We recorded the time representation of mitochondrial morphology and function in rats with acute spinal cord injury. Results showed that mitochondria had an irregular shape, and increased in size. Mitochondrial cristae were disordered and mitochondrial membrane rupture was visible at 2-24 hours after injury. Fusion protein mitofusin 1 expression gradually increased, peaked at 8 hours after injury, and then decreased to its lowest level at 24 hours. Expression of dynamin-related protein 1, amitochondrial fission protein, showed the opposite kinetics. At 2-24 hours after acute spinal cord injury, malondialdehyde content, cytochrome c levels and caspase-3 expression were increased, but glutathione content, adenosine triphosphate content, Na(+)-K(+)-ATPase activity and mitochondrial membrane potential were gradually reduced. Furthermore, mitochondrial morphology altered during the acute stage of spinal cord injury. Fusion was important within the first 8 hours, but fission played a key role at 24 hours. Oxidative stress was inhibited, biological productivity was diminished, and mitochondrial membrane potential and permeability were reduced in the acute stage of injury. In summary, mitochondrial apoptosis is activated when the time of spinal cord injury is prolonged.

Exendin-4 Enhances Motor Function Recovery via Promotion of Autophagy and Inhibition of Neuronal Apoptosis After Spinal Cord Injury in Rats.

Autophagy occurs prior to apoptosis and plays an important role in cell death regulation during spinal cord injury (SCI). This study aimed to determine the effects and potential mechanism of the glucagon-like peptide-1 (GLP-1) agonist extendin-4 (Ex-4) in SCI. Seventy-two male Sprague Dawley rats were randomly assigned to sham, SCI, 2.5 µg Ex-4, and 10 µg Ex-4 groups. To induce SCI, a 10-g iron rod was dropped from a 20-mm height to the spinal cord surface. Ex-4 was administered via intraperitoneal injection immediately after surgery. Motor function evaluation with the Basso Beattie Bresnahan (BBB) locomotor rating scale indicated significantly increased scores (p < 0.01) in the Ex-4-treated groups, especially 10 µg, which demonstrated the neuroprotective effect of Ex-4 after SCI. The light chain 3-II (LC3-II) and Beclin 1 protein expression determined via western blot and the number of autophagy-positive neurons via immunofluorescence double labeling were increased by Ex-4, which supports promotion of autophagy (p < 0.01). The caspase-3 protein level and neuronal apoptosis via transferase UTP nick end labeling (TUNEL)/NeuN/DAPI double labeling were significantly reduced in the Ex-4-treated groups, which indicates anti-apoptotic effects (p < 0.01). Finally, histological assessment via Nissl staining demonstrated the Ex-4 groups exhibited a significantly greater number of surviving neurons and less cavity (p < 0.01). To our knowledge, this is the first study to indicate that Ex-4 significantly enhances motor function in rats after SCI, and these effects are associated with the promotion of autophagy and inhibition of apoptosis.

Acetyl-L-carnitineameliorates mitochondrial damage and apoptosis following spinal cord injury in rats.

Acetyl-l-carnitine (ALC) facilitates the entry and exit of fatty acids from mitochondria and plays an essential role in energy metabolism. Although ALC is known to exert neuroprotective effects in multiple neurological diseases, its effects on spinal cord injury (SCI)-induced mitochondrial impairments and apoptosis remain unclear. In this study, we aimed to evaluate the putative effects of ALC on mitochondrial dysfunction and apoptosis induced by SCI in a rodent model. Our results indicate that SCI elicits dynamic alternations in the expression of mitochondria-related proteins. Transmission electron microscopy analysis showed that ALC administration abrogated key ultrastructural abnormalities in mitochondria at 24h after SCI by maintaining mitochondrial length, reducing the number of damaged mitochondria, and reversing mitochondrial score (P<0.05 compared with SCI group). In addition, ALC administration maintained the mitochondrial membrane potential and mitochondrial Na(+)-K(+)-ATPase activity following SCI (P<0.05 compared with SCI group). ALC administration reversed the downregulation of mitofusin 1 (Mfn1), Mfn2, Bcl-2, and the upregulation of dynamin-related protein 1 (Drp1), mitochondrial fission 1 (Fis1), Bcl-2-associated X protein (Bax) and cytosol cytochrome c (cyto-CytC) induced by SCI (P<0.05 compared with SCI group). Finally ALC administration greatly reduced the percentage of apoptotic cells compared with the SCI group (P<0.01). In conclusion, our findings demonstrated that ALC ameliorated SCI-induced mitochondrial structural alternations, mitochondrial dysfunction, and apoptosis.

Curcumin improves the integrity of blood-spinal cord barrier after compressive spinal cord injury in rats.

Previous studies have shown that curcumin (Cur) can produce potent neuroprotective effects against damage due to spinal cord injury (SCI). However, whether Cur can preserve the function of the blood-spinal cord barrier (BSCB) is unclear. The present study was performed to investigate the mechanism underlying BSCB permeability changes, which were induced by treatment with Cur (75, 150, and 300 mg/kg, i.p.) after compressive SCI in rats. BSCB permeability was evaluated by Evans blue leakage. Motor recovery of rats with SCI was assessed using the Basso, Beattie, and Bresnahan scoring system every day until the 21st days post-injury. The protein levels of heme oxygenase-1 (HO-1), tight junction protein, and inflammatory factors were analyzed by western blots. The expression of the inflammatory factors tumor necrosis factor-α (TNF-α) and nuclear factor-kappaB (NF-κB) mRNA was determined with reverse transcription-polymerase chain reactions. Treatment with Cur (150 and 300 mg/kg) significantly reduced Evans blue leakage into the spinal cord tissue at 24h after SCI. Cur (150 mg/kg) significantly increased HO-1 protein expression. The levels of TNF-α and NF-κB mRNA and protein greatly increased at 24h after SCI, and this increase was significantly attenuated by Cur treatment. ZO-1 and occludin expression was upregulated by Cur (150 mg/kg) treatment after SCI, and this effect was blocked by the HO-1 inhibitor zinc protoporphyrin. Long-term effects of Cur on motor recovery after SCI were observed. Our results indicated that Cur can improve motor function after SCI, which could correlate with improvements in BSCB integrity.

The protective effect of salvianolic acid B on blood-spinal cord barrier after compression spinal cord injury in rats.

Salvianolic acid B (Sal B), a bioactive compound isolated from the Chinese medicinal herb danshen, is commonly used for the prevention and treatment of cardiovascular disease. The present study was performed to investigate the effect of Sal B on the blood-spinal cord barrier (BSCB) after spinal cord injury (SCI) in a rat model. Sal B (1, 10, and 50 mg/kg i.v.) was administered to rats immediately following SCI. The permeability of the BSCB and spinal cord tissue water content were evaluated. Additionally, the expression levels of tight junction proteins and heme oxygenase-1 (HO-1) were monitored by Western blot analysis. Enzyme-linked immunosorbent assay analysis of spinal cord tissue homogenates was performed 24 h post-SCI to evaluate the expression of inflammation-related cytokines. In addition, the motor recovery of SCI rats was assessed using the Basso, Beattie, and Bresnahan scoring system. Compared to the SCI group, rats treated with Sal B (10, 50 mg/kg) exhibited significantly reduced spinal cord tissue water content and BSCB permeability. Further, the motor function of rats was also greatly improved by Sal B administration. The expression of pro-inflammatory factors TNF-α and NF-κB was found to be greatly increased 24 h post-SCI, and this upregulation was significantly attenuated by Sal B treatment. The expression of ZO-1 and occludin was upregulated by Sal B (10 mg/kg) treatment after SCI, and this effect was blocked by the HO-1 inhibitor ZnPP. Taken together, our results clearly indicate that Sal B attenuates SCI by promoting the repair of the damaged BSCB, demonstrating that this molecule is a novel and promising therapeutic agent for human SCI.

Mitochondrial fusion and fission after spinal sacord injury in rats.

Responsible for orchestrating cellular energy production, mitochondria are central to the maintenance of life and the gatekeepers of cell death. Its morphology is dynamic and controlled by continual and balanced fission and fusion events. In this study, we analyzed the mitochondrial dynamics and functions after spinal cord injury in rats and further to discuss the mechanisms of the mitochondria regulated cell injury during SCI. Using adult rat spinal cord injury model, it was found that the absolute number of mitochondria per area was significantly less and the individual mitochondrial cross-sectional area was significantly greater in the neurons of rats in SCI group than in the sham-operated group at 3h and 6h after SCI, and the reverse pattern at 12h and 24h after SCI. The results from Western blot and RT-PCR assays showed that the protein and mRNA levels of mitochondrial fusion-related genes (Mfn1 and Mfn2) decreased and fission-related genes (Drp1 and Fis1) increased at 3h and 6h after SCI. At 12h and 24h after SCI the reverse pattern of Mfn1, Mfn2, Drp1 and Fis1 expression was found. Taken together the results of the present study showed the mitochondrial tendency of elongation and fusion in the injured spinal cord at 3h and 6h after SCI, and the tendency of mitochondrial fission at 12h and 24h after SCI in our SCI models of rat. These findings have important implications for our understanding of the mechanisms of mitochondrial dynamics and functions after SCI injury. And mitochondrial fusion may potentially be used as a target for improving spinal cord function in the first 6h after SCI. Mitochondrial fusion may be inhibited at 12-24h after SCI for improving functional outcomes following SCI.

The effect of cigarette smoke exposure on spinal cord injury in rats.

In this study, we examined whether cigarette smoke has neuroprotective or toxic effects on spinal cord injury (SCI). Male Sprague-Dawley rats were included in the study and received either cigarette smoke exposure or fresh air exposure. Twenty-four hours after the last cigarette smoke or fresh air exposure, all rats were injured at thoracic level 12 (T12), using an established static compression model. Our data showed that the cigarette smoke group had higher water content; higher permeability of the blood-spinal cord barrier (BSCB); higher malondialdehyde (MDA) levels, aquaporin-4 (AQP4) and hypoxia-inducible factor 1-alpha (HIF-1α) protein expression, and mRNA levels; and lower glutathione (GSH) levels than the control group values at 12 h, 24 h, and 48 h after SCI. There was no significant difference in these between the cigarette smoke group and the control group at 0 h after SCI. The results of the Basso, Beattie, and Bresnahan (BBB) hindlimb locomotor rating scale showed that rats in the cigarette smoke group had greater dysfunction in hindlimb movement than did rats in control group from 2 to day 6 after SCI. The extent of recovery did not make any difference from day 7 to day 10 after SCI between the cigarette smoke group and the control group. These results suggested that cigarette smoke can reinforce the oxidative stress injury via HIF-1α and AQP4 in the early stage after SCI. It is possible that cigarette smoke exposure does not affect SCI recovery in the long term; however, it can aggravate the edema and deteriorate BSCB disruption via HIF-1α and AQP4 in the early stage after SCI. More studies will be essential to consider this hypothesis and elucidate the mechanisms involved.

2-Methoxyestradiol inhibits the up-regulation of AQP4 and AQP1 expression after spinal cord injury.

The study investigated the mechanism of the up-regulation of aquaporin-4 (AQP4) and aquaporin-1 (AQP1) expression induced by spinal cord injury (SCI). Using adult rat spinal cord injury model, it was found that up-regulation of hypoxia inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), AQP4, and AQP1 in response to spinal cord injury was greatly antagonized by 2-methoxyestradiol (2ME2), which can post-transcriptionally inhibit the expression of HIF-1α. VEGF alone significantly increased the extravasation of Evans blue and up-regulated the levels of AQP4 protein expression in the injured spinal cord issue, but the levels of AQP1 expression were not significantly changed. Taken together, our results suggest that expression of AQP4 and AQP1 is correlated with up-regulation of HIF-1α after SCI through the mechanisms that were dependent and independent of the VEGF signaling pathway, respectively. And the inhibitor of HIF-1α is a novel promising therapeutic agent for human SCI-induced edema in the future.

Neuroprotective effect of baicalin on compression spinal cord injury in rats.

The current study was performed to investigate the effect of baicalin (BC) on spinal cord injury (SCI) in rat. BC (10, 30 and 100mg/kg, i.p., respectively) was administered to rats immediately and every 24h following SCI. The BC therapy (100mg/kg) dramatically decreased (1) the water content of spinal cord tissue (by dry-wet weight method), (2) the permeability of blood-spinal cord barrier (measured by Evans blue), (3) oxidant stress (malondialdehyde values and glutathione levels evaluation), (4) proinflammatory cytokines expression (tumor necrosis factor-α and NF-κB) (5) and apoptosis (measured by Bax, Bcl-2 and Caspase-3 expression). And the treatment with BC also significantly improved the recovery of limb function (evaluated by motor recovery score). Taken together, our results clearly indicate that BC possesses potent anti-inflammatory and anti-apoptotic properties, attenuates the SCI and is a new promising therapeutic agent for human SCI in the future.

The effect of aminoguanidine on compression spinal cord injury in rats.

The current study was performed to investigate the effect of aminoguanidine (AG) on spinal cord injury (SCI) in rat. AG (75, 150 and 300mg/kg, i.p. respectively ) was administered to rats immediately following SCI. It was found that AG (150mg/kg) significantly reduced spinal cord water content and improved motor function, however, AG at the doses of 75 and 300mg/kg had no effect. Compared to SCI group without treatment, AG at the dosage of 150mg/kg induced a reduction in the permeability of blood-spinal cord barrier (BSCB) after injury 48h (from 59.8+/-5.5microl/g to 39.8+/-3.8microl/g), a 38% decrease of Malondialdehyde (MDA) values and a 1-fold increase of the Glutathione (GSH) levels at 12h after SCI. And the expression of inducible nitric oxide synthase (iNOS) protein reached a peak at 24h after injury, which was significantly attenuated by treatment with AG (150mg/kg). In addition, the expression of AQP4 protein was down-regulated by the treatment of AG (150mg/kg) at 24h after SCI, and the changes still lasted at 48h after injury. Our results indicated that AG could induce spinal cord edema clearance and improve motor function, which could be correlated with antioxidative property, the down-regulation of iNOS and AQP4 protein expression after SCI.