Restoring mitochondrial cardiolipin homeostasis reduces cell death and promotes recovery after spinal cord injury

Alterations in phospholipids have long been associated with spinal cord injury (SCI). However, their specific roles and signaling cascades in mediating cell death and tissue repair remain unclear. Here we investigated whether alterations of cardiolipin (CL), a family of mitochondrion-specific phospholipids, play a crucial role in mitochondrial dysfunction and neuronal death following SCI. Lipidomic analysis was used to determine the profile of CL alteration in the adult rat spinal cord following a moderate contusive SCI at the 10th thoracic (T10) level. Cellular, molecular, and genetic assessments were performed to determine whether CL alterations mediate mitochondrial dysfunction and neuronal death after SCI, and, if so, whether reversing CL alteration leads to neuroprotection after SCI. Using lipidomic analysis, we uncovered CL alterations at an early stage of SCI. Over 50 distinct CL species were identified, of which 50% showed significantly decreased abundance after SCI. The decreased CL species contained mainly polyunsaturated fatty acids that are highly susceptible to peroxidation. In parallel, 4-HNE, a lipid peroxidation marker, significantly increased after SCI. We found that mitochondrial oxidative stress not only induced CL oxidation, but also resulted in CL loss by activating cPLA₂ to hydrolyze CL. CL alterations induced mitochondrial dysfunction and neuronal death. Remarkably, pharmacologic inhibition of CL alterations with XJB-5-131, a novel mitochondria-targeted electron and reactive oxygen species scavenger, reduced cell death, tissue damage and ameliorated motor deficits after SCI in adult rats. These findings suggest that CL alteration could be a novel mechanism that mediates injury-induced neuronal death, and a potential therapeutic target for ameliorating secondary SCI.

Transhemispheric remodeling the motor cortex promotes forelimb recovery after mouse spinal cord injury

Understanding the reorganization of neural circuits spared after spinal cord injury in the motor cortex and spinal cord would provide insights for developing therapeutics. Using optogenetic mapping, we demonstrated a transhemispheric recruitment of neural circuits in the contralateral cortical M1/M2 area to improve the impaired forelimb function after a cervical 5 right-sided hemisection in mice, a model mimicking the human Brown-Séquard syndrome. This cortical reorganization can be elicited by a selective cortical optogenetic neuromodulation paradigm. Areas of whisker, jaw, and neck, together with the rostral forelimb area, on the motor cortex ipsilateral to the lesion were engaged to control the ipsilesional forelimb in both stimulation and nonstimulation groups 8 weeks following injury. However, significant functional benefits were only seen in the stimulation group. Using anterograde tracing, we further revealed a robust sprouting of the intact corticospinal tract in the spinal cord of those animals receiving optogenetic stimulation. The intraspinal corticospinal axonal sprouting correlated with the forelimb functional recovery. Thus, specific neuromodulation of the cortical neural circuits induced massive neural reorganization both in the motor cortex and spinal cord, constructing an alternative motor pathway in restoring impaired forelimb function.

[Spatiotemporal evolution of COVID-19 epidemic in the early phase in China]

Objective: Based on the geographic information systems, we exploreed the spatiotemporal clustering and the development and evolution of COVID-19 epidemic at prefectural level in China from the time when the epidemic was discovered to the time when the lockdown ended in Wuhan. Methods: The information and data of the confirmed COVID-19 cases from December 8, 2019 to April 8, 2020 were collected from 367 prefectures in China for a spatial autocorrelation analysis with software GeoDa, and software ArcGIS was used to visualize the results. Software SatScan was used for spatiotemporal scanning analysis to visualize the hot-spot areas of the epidemic. Results: The incidence of new cases of COVID-19 had obvious global autocorrelation and the partial autocorrelation results showed that incidence of COVID-19 had different spatial distribution at different times from December 8, 2019 to March 4, 2020. There was no significant difference in global autocorrelation coefficient from March 5, 2020 to April 8, 2020. The statistical analysis of spatiotemporal scanning identified two kinds of spatiotemporal clustering areas, the first class clustering areas included 10 prefectures, mainly distributed in Hubei, from January 13 to February 25, 2020. The secondary class clustering areas included 142 prefectures, mainly distributed in provinces in the north and east of Hubei, from January 23 to February 1, 2020. Conclusions: There was a clear spatiotemporal correlation in the distribution of the outbreaks in the early phase of COVID-19 epidemic (December 8, 2019-March 4, 2020) in China. With the decrease of the case and effective prevention and control measures, the epidemics had no longer significant correlations among areas from March 5 to April 8. The study results showed relationship with time points of start and adjustment of emergency response at different degree in provinces. Furthermore, improving the early detection of new outbreaks and taking timely and effective prevention and control measures played an important role in blocking the transmission.

Inhibition of Cytosolic Phospholipase A2 Has Neuroprotective Effects on Motoneuron and Muscle Atrophy after Spinal Cord Injury

Surviving motoneurons undergo dendritic atrophy after spinal cord injury (SCI), suggesting an important therapeutic target for neuroprotective strategies to improve recovery of function after SCI. Our previous studies showed that cytosolic phospholipase A₂ (PLA₂) may play an important role in the pathogenesis of SCI. In the present study, we investigated whether blocking cytosolic PLA₂ (cPLA₂) pharmacologically with arachidonyl trifluoromethyl ketone (ATK) or genetically using cPLA₂ knockout (KO) mice attenuates motoneuron atrophy after SCI. C57BL/6 mice received either sham or contusive SCI at the T10 level. At 30 min after SCI, mice were treated with ATK or vehicle. Four weeks later, motoneurons innervating the vastus lateralis muscle of the quadriceps were labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed in three dimensions. Soma volume, motoneuron number, lesion volume, and tissue sparing were also assessed, as were muscle weight, fiber cross-sectional area, and motor endplate size and density. ATK administration reduced percent lesion volume and increased percent volume of spared white matter, compared to the vehicle-treated control animals. SCI with or without ATK treatment had no effect on the number or soma volume of quadriceps motoneurons. However, SCI resulted in a decrease in dendritic length of quadriceps motoneurons in untreated animals, and this decrease was completely prevented by treatment with ATK. Similarly, vastus lateralis muscle weights of untreated SCI animals were smaller than those of sham surgery controls, and these reductions were prevented by ATK treatment. No effects on fiber cross-sectional areas, motor endplate area, or density were observed across treatment groups. Remarkably, genetically deleting cPLA₂ in cPLA₂ KO mice attenuated dendritic atrophy after SCI. These findings suggest that, after SCI, cord tissue damage and regressive changes in motoneuron and muscle morphology can be reduced by inhibition of cPLA₂, further supporting a role for cPLA₂ as a neurotherapeutic target for SCI treatment.

Laminin-coated multifilament entubulation, combined with Schwann cells and glial cell line-derived neurotrophic factor, promotes unidirectional axonal regeneration in a rat model of thoracic spinal cord hemisection

Biomaterial bridging provides physical substrates to guide axonal growth across the lesion. To achieve efficient directional guidance, combinatory strategies using permissive matrix, cells and trophic factors are necessary. In the present study, we evaluated permissive effect of poly (acrylonitrile-co-vinyl chloride) guidance channels filled by different densities of laminin-precoated unidirectional polypropylene filaments combined with Schwann cells, and glial cell line-derived neurotrophic factor for axonal regeneration through a T10 hemisected spinal cord gap in adult rats. We found that channels with filaments significantly reduced the lesion cavity, astrocytic gliosis, and inflammatory responses at the graft-host boundaries. The laminin coated low density filament provided the most favorable directional guidance for axonal regeneration which was enhanced by co-grafting of Schwann cells and glial cell line-derived neurotrophic factor. These results demonstrate that the combinatorial strategy of filament-filled guiding scaffold, adhesive molecular laminin, Schwann cells, and glial cell line-derived neurotrophic factor, provides optimal topographical cues in stimulating directional axonal regeneration following spinal cord injury. This study was approved by Indiana University Institutional Animal Care and Use Committees (IACUC #:11011) on October 29, 2015.

[Research progresses in the cytoskeleton and its functions in osteoblasts]

Osteoblasts are cells that are in charge of bone formation and play an important role in bone remodeling. Cytoskeleton is widely found in eukaryotic cells, and not only plays an important role in maintaining the order of cell morphology and internal structure, but also may be involved in mechanotransduction, the regulation of cell differentiation, proliferation, apoptosis, migration and the expression of related genes. The studies on the function of the cytoskeleton in osteoblasts may provide new ideas for dental fields in such aspects as guided bone regeneration, orthodontic tooth movement, distraction osteogenesis and postoperative bone healing. This article reviewed the research progresses about cytoskeleton in osteoblasts.

Disrupting nNOS-PSD95 Interaction Improves Neurological and Cognitive Recoveries after Traumatic Brain Injury

Excessive activation of N-methyl-D-aspartate receptors (NMDARs) and the resulting neuronal nitric oxide synthase (nNOS) activation plays a crucial role in the pathogenesis of traumatic brain injury (TBI). However, directly inhibiting NMDARs or nNOS produces adverse side effects because they play key physiological roles in the normal brain. Since interaction of nNOS-PSD95 is a key step in NMDAR-mediated excitotoxicity, we investigated whether disrupting nNOS-PSD95 interaction with ZL006, an inhibitor of nNOS-PSD95 interaction, attenuates NMDAR-mediated excitotoxicity. In cortical neuronal cultures, ZL006 treatment significantly reduced glutamate-induced neuronal death. In a mouse model of controlled cortical impact (CCI), administration of ZL006 (10 mg/kg, i.p.) at 30 min postinjury significantly inhibited nNOS-PSD95 interaction, reduced TUNEL- and phospho-p38-positive neurons in the motor cortex. ZL006 treatment also significantly reduced CCI-induced cortical expression of apoptotic markers active caspase-3, PARP-1, ratio of Bcl-2/Bax, and phosphorylated p38 MAPK (p-p38). Functionally, ZL006 treatment significantly improved neuroscores and sensorimotor performance, reduced somatosensory and motor deficits, reversed CCI-induced memory deficits, and attenuated cognitive impairment. Histologically, ZL006 treatment significantly reduced the brain lesion volume. These findings collectively suggest that blocking nNOS-PSD95 interaction represents an attractive strategy for ameliorating consequences of TBI and that its action is mediated via inhibiting neuronal apoptosis and p38 MAPK signaling.

Descending motor circuitry required for NT-3 mediated locomotor recovery after spinal cord injury in mice

Locomotor function, mediated by lumbar neural circuitry, is modulated by descending spinal pathways. Spinal cord injury (SCI) interrupts descending projections and denervates lumbar motor neurons (MNs). We previously reported that retrogradely transported neurotrophin-3 (NT-3) to lumbar MNs attenuated SCI-induced lumbar MN dendritic atrophy and enabled functional recovery after a rostral thoracic contusion. Here we functionally dissected the role of descending neural pathways in response to NT-3-mediated recovery after a T9 contusive SCI in mice. We find that residual projections to lumbar MNs are required to produce leg movements after SCI. Next, we show that the spared descending propriospinal pathway, rather than other pathways (including the corticospinal, rubrospinal, serotonergic, and dopaminergic pathways), accounts for NT-3-enhanced recovery. Lastly, we show that NT-3 induced propriospino-MN circuit reorganization after the T9 contusion via promotion of dendritic regrowth rather than prevention of dendritic atrophy.

Bisperoxovanadium Mediates Neuronal Protection through Inhibition of PTEN and Activation of PI3K/AKT-mTOR Signaling after Traumatic Spinal Injuries

Although mechanisms involved in progression of cell death in spinal cord injury (SCI) have been studied extensively, few are clear targets for translation to clinical application. One of the best-understood mechanisms of cell survival in SCI is phosphatidylinositol-3-kinase (PI3K)/Akt and associated downstream signaling. Clear therapeutic efficacy of a phosphatase and tensin homologue (PTEN) inhibitor called bisperoxovanadium (bpV) has been shown in SCI, traumatic brain injury, stroke, and other neurological disease models in both neuroprotection and functional recovery. The present study aimed to elucidate mechanistic influences of bpV activity in neuronal survival in in vitro and in vivo models of SCI. Treatment with 100 nM bpV(pic) reduced cell death in a primary spinal neuron injury model (p < 0.05) in vitro, and upregulated both Akt and ribosomal protein S6 (pS6) activity (p < 0.05) compared with non-treated injured neurons. Pre-treatment of spinal neurons with a PI3K inhibitor, LY294002 or mammalian target of rapamycin (mTOR) inhibitor, rapamycin blocked bpV activation of Akt and ribosomal protein S6 activity, respectively. Treatment with bpV increased extracellular signal-related kinase (Erk) activity after scratch injury in vitro, and rapamycin reduced influence by bpV on Erk phosphorylation. After a cervical hemicontusive SCI, Akt phosphorylation decreased in total tissue via Western blot analysis (p < 0.01) as well as in penumbral ventral horn motor neurons throughout the first week post-injury (p < 0.05). Conversely, PTEN activity appeared to increase over this period. As observed in vitro, bpV also increased Erk activity post-SCI (p < 0.05). Our results suggest that PI3K/Akt signaling is the likely primary mechanism of bpV action in mediating neuroprotection in injured spinal neurons.

Functional and Histological Gender Comparison of Age-Matched Rats after Moderate Thoracic Contusive Spinal Cord Injury

Spinal cord injury (SCI) afflicts hundreds of thousands of Americans, and most SCI (∼80%) occurs in males. In experimental animal models, however, many studies used females. Funding agencies like the National Institutes of Health recommend that new proposed studies should include both genders due to variations in gender response to injuries, diseases, and treatments. However, cost and considerations for some animal models, such as SCI, affect investigators in adapting to this recommendation. Research has increased comparing gender effects in various disease and injury models, including SCI. However, most studies use weight-matched animals, which poses issues in comparing results and outcomes. The present study compared histologic and functional outcomes between age-matched male and female Sprague-Dawley rats in a moderate thoracic contusion SCI model. Cresyl violet and eosin staining showed no significant differences in lesion volume between genders after 9 weeks post-SCI (p > 0.05). Luxol fast blue-stained spared myelin was similar between genders, although slightly greater (∼6%) in spared myelin, compared with cord volume (p = 0.044). Glial reactivity and macrophage labeling in the lesion area was comparable between genders, as well. Basso, Beattie, Bresnahan (BBB) functional scores were not significantly different between genders, and Hargreaves thermal hyperalgesia and Gridwalk sensorimotor analyses also were similar between genders, compared with uninjured gender controls. Analysis of covariance showed weight did not influence functional recovery as assessed through BBB (p = 0.65) or Gridwalk assessment (p = 0.63) in this study. In conclusion, our findings suggest age-matched male and female rats recover similarly in a common clinically relevant SCI model.

Remodeling of lumbar motor circuitry remote to a thoracic spinal cord injury promotes locomotor recovery

Retrogradely-transported neurotrophin signaling plays an important role in regulating neural circuit specificity. Here we investigated whether targeted delivery of neurotrophin-3 (NT-3) to lumbar motoneurons (MNs) caudal to a thoracic (T10) contusive spinal cord injury (SCI) could modulate dendritic patterning and synapse formation of the lumbar MNs. In vitro, Adeno-associated virus serotype two overexpressing NT-3 (AAV-NT-3) induced NT-3 expression and neurite outgrowth in cultured spinal cord neurons. In vivo, targeted delivery of AAV-NT-3 into transiently demyelinated adult mouse sciatic nerves led to the retrograde transportation of NT-3 to the lumbar MNs, significantly attenuating SCI-induced lumbar MN dendritic atrophy. NT-3 enhanced sprouting and synaptic formation of descending serotonergic, dopaminergic, and propriospinal axons on lumbar MNs, parallel to improved behavioral recovery. Thus, retrogradely transported NT-3 stimulated remodeling of lumbar neural circuitry and synaptic connectivity remote to a thoracic SCI, supporting a role for retrograde transport of NT-3 as a potential therapeutic strategy for SCI.

Protective Effects of Estradiol and Dihydrotestosterone following Spinal Cord Injury

Spinal cord injury (SCI) results in lesions that destroy tissue and disrupt spinal tracts, producing deficits in locomotor and autonomic function. We previously demonstrated that motoneurons and the muscles they innervate show pronounced atrophy after SCI, and these changes are prevented by treatment with testosterone. Here, we assessed whether the testosterone active metabolites estradiol and dihydrotestosterone have similar protective effects after SCI. Young adult female rats received either sham or T9 spinal cord contusion injuries and were treated with estradiol, dihydrotestosterone, both, or nothing via Silastic capsules. Basso-Beattie-Bresnahan locomotor testing was performed weekly and voiding behavior was assessed at 3 weeks post-injury. Four weeks after SCI, lesion volume and tissue sparing, quadriceps muscle fiber cross-sectional area, and motoneuron dendritic morphology were assessed. Spontaneous locomotor behavior improved after SCI, but hormone treatments had no effect. Voiding behavior was disrupted after SCI, but was significantly improved by treatment with either estradiol or dihydrotestosterone; combined treatment was maximally effective. Treatment with estradiol reduced lesion volume, but dihydrotestosterone alone and estradiol combined with dihydrotestosterone were ineffective. SCI-induced decreases in motoneuron dendritic length were attenuated by all hormone treatments. SCI-induced reductions in muscle fiber cross-sectional areas were prevented by treatment with either dihydrotestosterone or estradiol combined with dihydrotestosterone, but estradiol treatment was ineffective. These findings suggest that deficits in micturition and regressive changes in motoneuron and muscle morphology seen after SCI are ameliorated by treatment with estradiol or dihydrotestosterone, further supporting a role for steroid hormones as neurotherapeutic agents in the injured nervous system.

Anatomical and functional effects of lateral cervical hemicontusion in adult rats

PURPOSE

Cervical injuries are the most common form of spinal cord injury (SCI), and are often complicated by pathological secondary damage. Therefore, cervical SCI is of great clinical importance for understanding pathology and potential therapies. Here we utilize a weight drop cervical hemi-contusion injury model using a NYU/MASCIS impactor that produced graded anatomical and functional deficits.

METHODS

Three groups of rats were established: 1) Sham (laminectomy only) (n = 6), 12.5 mm weight drop (n = 10), and 25 mm weight drop (n = 10) SCI groups. Forelimb functional assessments of grooming ability, cereal manipulation, and forepaw adhesive removal were performed weekly after injury. Using transcranial magnetic motor evoked potentials (tcMMEPs), supraspinal motor stimulations were recorded in both forelimbs and hindlimbs at 5 and 28d post-injury. Lesion volume and myelinated tissue area were assessed through histological analysis.

RESULTS

A 12.5 mm weight drop height produced considerable tissue damage compared to Sham animals, while a 25 mm drop induced even greater damage than the 12.5 mm drop (p < 0.05). Forelimb functional assessments showed that increased injury severity and tissue damage was correlated to the degree of forelimb functional deficits. Interestingly, the hindlimbs showed little to no motor function loss. Upon tcMMEP stimulation, surprisingly little motor signal was recorded in the hindlimbs despite outward evidence of hindlimb motor recovery.

CONCLUSIONS

Our findings highlight a correlation between anatomical damage and functional outcome in a graded cervical hemi-contusion model, and support a loss of descending motor control from supraspinal inputs and intraspinal plasticity that promote spontaneous hindlimb functional recovery in this model.

Automated monitoring of early neurobehavioral changes in mice following traumatic brain injury

Traumatic brain injury often causes a variety of behavioral and emotional impairments that can develop into chronic disorders. Therefore, there is a need to shift towards identifying early symptoms that can aid in the prediction of traumatic brain injury outcomes and behavioral endpoints in patients with traumatic brain injury after early interventions. In this study, we used the SmartCage system, an automated quantitative approach to assess behavior alterations in mice during an early phase of traumatic brain injury in their home cages. Female C57BL/6 adult mice were subjected to moderate controlled cortical impact (CCI) injury. The mice then received a battery of behavioral assessments including neurological score, locomotor activity, sleep/wake states, and anxiety-like behaviors on days 1, 2, and 7 after CCI. Histological analysis was performed on day 7 after the last assessment. Spontaneous activities on days 1 and 2 after injury were significantly decreased in the CCI group. The average percentage of sleep time spent in both dark and light cycles were significantly higher in the CCI group than in the sham group. For anxiety-like behaviors, the time spent in a light compartment and the number of transitions between the dark/light compartments were all significantly reduced in the CCI group than in the sham group. In addition, the mice suffering from CCI exhibited a preference of staying in the dark compartment of a dark/light cage. The CCI mice showed reduced neurological score and histological abnormalities, which are well correlated to the automated behavioral assessments. Our findings demonstrate that the automated SmartCage system provides sensitive and objective measures for early behavior changes in mice following traumatic brain injury.

Treadmill training induced lumbar motoneuron dendritic plasticity and behavior recovery in adult rats after a thoracic contusive spinal cord injury

Spinal cord injury (SCI) is devastating, causing sensorimotor impairments and paralysis. Persisting functional limitations on physical activity negatively affect overall health in individuals with SCI. Physical training may improve motor function by affecting cellular and molecular responses of motor pathways in the central nervous system (CNS) after SCI. Although motoneurons form the final common path for motor output from the CNS, little is known concerning the effect of exercise training on spared motoneurons below the level of injury. Here we examined the effect of treadmill training on morphological, trophic, and synaptic changes in the lumbar motoneuron pool and on behavior recovery after a moderate contusive SCI inflicted at the 9th thoracic vertebral level (T9) using an Infinite Horizon (IH, 200 kDyne) impactor. We found that treadmill training significantly improved locomotor function, assessed by Basso-Beattie-Bresnahan (BBB) locomotor rating scale, and reduced foot drops, assessed by grid walking performance, as compared with non-training. Additionally, treadmill training significantly increased the total neurite length per lumbar motoneuron innervating the soleus and tibialis anterior muscles of the hindlimbs as compared to non-training. Moreover, treadmill training significantly increased the expression of a neurotrophin brain-derived neurotrophic factor (BDNF) in the lumbar motoneurons as compared to non-training. Finally, treadmill training significantly increased synaptic density, identified by synaptophysin immunoreactivity, in the lumbar motoneuron pool as compared to non-training. However, the density of serotonergic terminals in the same regions did not show a significant difference between treadmill training and non-training. Thus, our study provides a biological basis for exercise training as an effective medical practice to improve recovery after SCI. Such an effect may be mediated by synaptic plasticity, and neurotrophic modification in the spared lumbar motoneuron pool caudal to a thoracic contusive SCI.

Neuroprotection and its molecular mechanism following spinal cord injury

Acute spinal cord injury initiates a complex cascade of molecular events termed ‘secondary injury’, which leads to progressive degeneration ranging from early neuronal apoptosis at the lesion site to delayed degeneration of intact white matter tracts, and, ultimately, expansion of the initial injury. These secondary injury processes include, but are not limited to, inflammation, free radical-induced cell death, glutamate excitotoxicity, phospholipase A₂ activation, and induction of extrinsic and intrinsic apoptotic pathways, which are important targets in developing neuroprotective strategies for treatment of spinal cord injury. Recently, a number of studies have shown promising results on neuroprotection and recovery of function in rodent models of spinal cord injury using treatments that target secondary injury processes including inflammation, phospholipase A₂ activation, and manipulation of the PTEN-Akt/mTOR signaling pathway. The present review outlines our ongoing research on the molecular mechanisms of neuroprotection in experimental spinal cord injury and briefly summarizes our earlier findings on the therapeutic potential of pharmacological treatments in spinal cord injury.

Biphasic bisperoxovanadium administration and Schwann cell transplantation for repair after cervical contusive spinal cord injury

Schwann cells (SCs) hold promise for spinal cord injury (SCI) repair; however, there are limitations for its use as a lone treatment. We showed that acute inhibition of the phosphatase and tensin homolog deleted on chromosome ten (PTEN) by bisperoxovanadium (bpV) was neuroprotective and enhanced function following cervical hemicontusion SCI. We hypothesized that combining acute bpV therapy and delayed SC engraftment would further improve neuroprotection and recovery after cervical SCI. Adult female Sprague-Dawley (SD) rats were randomly sorted into 5 groups: sham, vehicle, bpV, SC transplantation, and bpV+SC transplantation. SCs were isolated from adult green fluorescent protein (GFP)-expressing SD rats (GFP-SCs). 200 μg/kg bpV(pic) was administered intraperitoneally (IP) twice daily for 7 days post-SCI in bpV-treated groups. GFP-SCs (1×10(6) in 5 μl medium) were transplanted into the lesion epicenter at the 8th day post-SCI. Forelimb function was tested for 10 weeks and histology was assessed. bpV alone significantly reduced lesion (by 40%, p<0.05) and cavitation (by 65%, p<0.05) and improved functional recovery (p<0.05) compared to injury alone. The combination promoted similar neuroprotection (p<0.01 vs. injury); however, GFP-SCs alone did not. Both SC-transplanted groups exhibited remarkable long-term SC survival, SMI-31(+) axon ingrowth and RECA-1(+) vasculature presence in the SC graft; however, bpV+SCs promoted an 89% greater axon-to-lesion ratio than SCs only. We concluded that bpV likely contributed largely to the neuroprotective and functional benefits while SCs facilitated considerable host-tissue interaction and modification. The combination of the two shows promise as an attractive strategy to enhance recovery after SCI.

A semicircular controlled cortical impact produces long-term motor and cognitive dysfunction that correlates well with damage to both the sensorimotor cortex and hippocampus

Animal models of traumatic brain injury (TBI) are essential for testing novel hypotheses and therapeutic interventions. Unfortunately, due to the broad heterogeneity of TBI in humans, no single model has been able to reproduce the entire spectrum of these injuries. The controlled cortical impact (CCI) model is one of the most commonly used models of contusion TBI. However, behavioral evaluations have revealed transient impairment in motor function after CCI in rats and mice. Here we report a new semicircular CCI (S-CCI) model by increasing the impact tip area to cover both the motor cortex and hippocampal regions in adult mice. Mice were subjected to S-CCI or CCI using an electromagnetic impactor (Impactor One, MyNeuroLab; semicircular tip: 3mm radius; CCI tip diameter: 3mm). We showed that S-CCI, at two injury severities, significantly decreased the neuroscore and produced deficits in performance on a rotarod device for the entire duration of the study. In contrast, the CCI induced motor deficits only at early stages after the injury, suggesting that the S-CCI model produces long-lasting motor deficits. Morris water maze test showed that both CCI and S-CCI produced persisting memory deficits. Furthermore, adhesive removal test showed significant somatosensory and motor deficits only in the S-CCI groups. Histological analysis showed a large extent of cortical contusion lesions, including both the sensory and motor cortex, and hippocampal damage in the S-CCI. These findings collectively suggest that the current model may offer sensitive, reliable, and clinically relevant outcomes for assessments of therapeutic strategies for TBI.

Cytosolic phospholipase A2 protein as a novel therapeutic target for spinal cord injury

Objective

The objective of this study was to investigate whether cytosolic phospholipase A₂ (cPLA₂), an important isoform of PLA₂ that mediates the release of arachidonic acid, plays a role in the pathogenesis of spinal cord injury (SCI).

Methods

A combination of molecular, histological, immunohistochemical, and behavioral assessments were used to test whether blocking cPLA₂ activation pharmacologically or genetically reduced cell death, protected spinal cord tissue, and improved behavioral recovery after a contusive SCI performed at the 10th thoracic level in adult mice.

Results

SCI significantly increased cPLA₂ expression and activation. Activated cPLA₂ was localized mainly in neurons and oligodendrocytes. Notably, the SCI-induced cPLA₂ activation was mediated by the extracellular signal-regulated kinase signaling pathway. In vitro, activation of cPLA₂ by ceramide-1-phosphate or A23187 induced spinal neuronal death, which was substantially reversed by arachidonyl trifluoromethyl ketone, a cPLA₂ inhibitor. Remarkably, blocking cPLA₂ pharmacologically at 30 minutes postinjury or genetically deleting cPLA₂ in mice ameliorated motor deficits, and reduced cell loss and tissue damage after SCI.

Interpretation

cPLA₂ may play a key role in the pathogenesis of SCI, at least in the C57BL/6 mouse, and as such could be an attractive therapeutic target for ameliorating secondary tissue damage and promoting recovery of function after SCI.

Characterizing phospholipase A2-induced spinal cord injury-a comparison with contusive spinal cord injury in adult rats

To assess whether phospholipase A2 (PLA2) plays a role in the pathogenesis of spinal cord injury (SCI), we compared lesions either induced by PLA2 alone or by a contusive SCI. At 24-h post-injury, both methods induced a focal hemorrhagic pathology. The PLA2 injury was mainly confined within the ventrolateral white matter, whereas the contusion injury widely affected both the gray and white matter. A prominent difference between the two models was that PLA2 induced a massive demyelination with axons remaining in the lesion area, whereas the contusion injury induced axonal damage and myelin breakdown. At 4 weeks, no cavitation was found within the PLA2 lesion, and numerous axons were myelinated by host-migrated Schwann cells. Among them, 45% of animals had early transcranial magnetic motor-evoked potential (tcMMEP) responses. In contrast, the contusive SCI induced a typical centralized cavity with reactive astrocytes forming a glial border. Only 15% of rats had early tcMMEP responses after the contusion. BBB scores were similarly reduced in both models. Our study indicates that PLA2 may play a unique role in mediating secondary SCI likely by targeting glial cells, particularly those of oligodendrocytes. This lesion model could also be used for studying demyelination and remyelination in the injured spinal cord associated with PLA2-mediated secondary SCI.

Cotransplantation of Glial Restricted Precursor Cells and Schwann Cells Promotes Functional Recovery after Spinal Cord Injury

Oligodendrocyte (OL) replacement can be a promising strategy for spinal cord injury (SCI) repair. However, the poor posttransplantation survival and inhibitory properties to axonal regeneration are two major challenges that limit their use as donor cells for repair of CNS injuries. Therefore, strategies aimed at enhancing the survival of grafted oligodendrocytes as well as reducing their inhibitory properties, such as the use of more permissive oligodendrocyte progenitor cells (OPCs), also called glial restricted precursor cells (GRPs), should be highly prioritized. Schwann cell (SC) transplantation is a promising translational strategy to promote axonal regeneration after CNS injuries, partly due to their expression and secretion of multiple growth-promoting factors. Whether grafted SCs have any effect on the biological properties of grafted GRPs remains unclear. Here we report that either SCs or SC-conditioned medium (SCM) promoted the survival, proliferation, and migration of GRPs in vitro. When GRPs and SCs were cografted into the normal or injured spinal cord, robust survival, proliferation, and migration of grafted GRPs were observed. Importantly, grafted GRPs differentiated into mature oligodendrocytes and formed new myelin on axons caudal to the injury. Finally, cografts of GRPs and SCs promoted recovery of function following SCI. We conclude that cotransplantation of GRPs and SCs, the only two kinds of myelin-forming cells in the nervous system, act complementarily and synergistically to promote greater anatomical and functional recovery after SCI than when either cell type is used alone.

PTEN/PI3K and MAPK signaling in protection and pathology following CNS injuries

Brain and spinal cord injuries initiate widespread temporal and spatial neurodegeneration, through both necrotic and programmed cell death mechanisms. Inflammation, reactive oxidation, excitotoxicity and cell-specific dysregulation of metabolic processes are instigated by traumatic insult and are main contributors to this cumulative damage. Successful treatments rely on prevention or reduction of the magnitude of disruption, and interfering with injurious cellular responses through modulation of signaling cascades is an effective approach. Two intracellular signaling pathways, the phosphatase and tensin homolog (PTEN)/phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling cascades play various cellular roles under normal and pathological conditions. Activation of both pathways can influence anatomical and functional outcomes in multiple CNS disorders. However, some mechanisms involve inhibiting or enhancing one pathway or the other, or both, in propagating specific downstream effects. Though many intracellular mechanisms contribute to cell responses to insult, this review examines the evidence exploring PTEN/PI3K and MAPK signaling influence on pathology, neuroprotection, and repair and how these pathways may be targeted for advancing knowledge and improving neurological outcome after injury to the brain and spinal cord.

Neuroprotective effects of testosterone on motoneuron and muscle morphology following spinal cord injury

Treatment with testosterone is neuroprotective/neurotherapeutic after a variety of motoneuron injuries. Here we assessed whether testosterone might have similar beneficial effects after spinal cord injury (SCI). Young adult female rats received either sham or T9 spinal cord contusion injuries and were implanted with blank or testosterone-filled Silastic capsules. Four weeks later, motoneurons innervating the vastus lateralis muscle of the quadriceps were labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed in three dimensions. Soma volume, motoneuron number, lesion volume, and tissue sparing were also assessed, as were muscle weight, fiber cross-sectional area, and motor endplate size and density. Contusion injury resulted in large lesions, with no significant differences in lesion volume, percent total volume of lesion, or spared white or gray matter between SCI groups. SCI with or without testosterone treatment also had no effect on the number or soma volume of quadriceps motoneurons. However, SCI resulted in a decrease in dendritic length of quadriceps motoneurons in untreated animals, and this decrease was completely prevented by treatment with testosterone. Similarly, the vastus lateralis muscle weights and fiber cross-sectional areas of untreated SCI animals were smaller than those of sham-surgery controls, and these reductions were both prevented by testosterone treatment. No effects on motor endplate area or density were observed across treatment groups. These findings suggest that regressive changes in motoneuron and muscle morphology seen after SCI can be prevented by testosterone treatment, further supporting a role for testosterone as a neurotherapeutic agent in the injured nervous system.

MicroRNA in central nervous system trauma and degenerative disorders

MicroRNAs (miRNAs) are a novel class of small noncoding RNAs that negatively regulate gene expression at the posttranscriptional level by binding to the 3'-untranslated region of target mRNAs leading to their translational inhibition or sometimes degradation. MiRNAs are predicted to control the activity of at least 20-30% of human protein-coding genes. Recent studies have demonstrated that miRNAs are highly expressed in the central nervous system (CNS) including the brain and spinal cord. Although we are currently in the initial stages of understanding how this novel class of gene regulators is involved in neurological biological functions, a growing body of exciting evidence suggests that miRNAs are important regulators of diverse biological processes such as cell differentiation, growth, proliferation, and apoptosis. Moreover, miRNAs are key modulators of both CNS development and plasticity. Some miRNAs have been implicated in several neurological disorders such as traumatic CNS injuries and neurodegenerative diseases. Recently, several studies suggested the possibility of miRNA involvement in neurodegeneration. Identifying the roles of miRNAs and their target genes and signaling pathways in neurological disorders will be critical for future research. miRNAs may represent a new layer of regulators for neurobiology and a novel class of therapeutic targets for neurological diseases.

Phospholipase A2 and its molecular mechanism after spinal cord injury

Phospholipases A(2) (PLA(2)s) are a diverse family of lipolytic enzymes which hydrolyze the acyl bond at the sn-2 position of glycerophospholipids to produce free fatty acids and lysophospholipids. These products are precursors of bioactive eicosanoids and platelet-activating factor which have been implicated in pathological states of numerous acute and chronic neurological disorders. To date, more than 27 isoforms of PLA(2) have been found in the mammalian system which can be classified into four major categories: secretory PLA(2), cytosolic PLA(2), Ca(2+)-independent PLA(2), and platelet-activating factor acetylhydrolases. Multiple isoforms of PLA(2) are found in the mammalian spinal cord. Under physiological conditions, PLA(2)s are involved in diverse cellular responses, including phospholipid digestion and metabolism, host defense, and signal transduction. However, under pathological situations, increased PLA(2) activity, excessive production of free fatty acids and their metabolites may lead to the loss of membrane integrity, inflammation, oxidative stress, and subsequent neuronal injury. There is emerging evidence that PLA(2) plays a key role in the secondary injury process after traumatic spinal cord injury. This review outlines the current knowledge of the PLA(2) in the spinal cord with an emphasis being placed on the possible roles of PLA(2) in mediating the secondary SCI.

Differential expression of sPLA2 following spinal cord injury and a functional role for sPLA2-IIA in mediating oligodendrocyte death

After the initial mechanical insult of spinal cord injury (SCI), secondary mediators propagate a massive loss of oligodendrocytes. We previously showed that following SCI both the total phospholipase activity and cytosolic PLA(2)-IV alpha protein expression increased. However, the expression of secreted isoforms of PLA(2) (sPLA(2)) and their possible roles in oligodendrocyte death following SCI remained unclear. Here we report that mRNAs extracted 15 min, 4 h, 1 day, or 1 month after cervical SCI show marked upregulation of sPLA(2)-IIA and IIE at 4 h after injury. In contrast, SCI induced down regulation of sPLA(2)-X, and no change in sPLA(2)-IB, IIC, V, and XIIA expression. At the lesion site, sPLA(2)-IIA and IIE expression were localized to oligodendrocytes. Recombinant human sPLA(2)-IIA (0.01, 0.1, or 2 microM) induced a dose-dependent cytotoxicity in differentiated adult oligodendrocyte precursor cells but not primary astrocytes or Schwann cells in vitro. Most importantly, pretreatment with S3319, a sPLA(2)-IIA inhibitor, before a 30 min H(2)O(2) injury (1 or 10 mM) significantly reduced oligodendrocyte cell death at 48 h. Similarly, pretreatment with S3319 before injury with IL-1 beta and TNFalpha prevented cell death and loss of oligodendrocyte processes at 72 h. Collectively, these findings suggest that sPLA(2)-IIA and IIE are increased following SCI, that increased sPLA(2)-IIA can be cytotoxic to oligodendrocytes, and that in vitro blockade of sPLA(2) can create sparing of oligodendrocytes in two distinct injury models. Therefore, sPLA(2)-IIA may be an important mediator of oligodendrocyte death and a novel target for therapeutic intervention following SCI.

Role of secretory phospholipase a(2) in CNS inflammation: implications in traumatic spinal cord injury

Secretory phospholipases A(2) (sPLA(2)s) are a subfamily of lipolytic enzymes which hydrolyze the acyl bond at the sn-2 position of glycerophospholipids to produce free fatty acids and lysophospholipids. These products are precursors of bioactive eicosanoids and platelet-activating factor (PAF). The hydrolysis of membrane phospholipids by PLA(2) is a rate-limiting step for generation of eicosanoids and PAF. To date, more than 10 isozymes of sPLA(2) have been found in the mammalian central nervous system (CNS). Under physiological conditions, sPLA(2)s are involved in diverse cellular responses, including host defense, phospholipid digestion and metabolism. However, under pathological situations, increased sPLA(2) activity and excessive production of free fatty acids and their metabolites may lead to inflammation, loss of membrane integrity, oxidative stress, and subsequent tissue injury. Emerging evidence suggests that sPLA(2) plays a role in the secondary injury process after traumatic or ischemic injuries in the brain and spinal cord. Importantly, sPLA(2) may act as a convergence molecule that mediates multiple key mechanisms involved in the secondary injury since it can be induced by multiple toxic factors such as inflammatory cytokines, free radicals, and excitatory amino acids, and its activation and metabolites can exacerbate the secondary injury. Blocking sPLA(2) action may represent a novel and efficient strategy to block multiple injury pathways associated with the CNS secondary injury. This review outlines the current knowledge of sPLA(2) in the CNS with emphasis placed on the possible roles of sPLA(2) in mediating CNS injuries, particularly the traumatic and ischemic injuries in the brain and spinal cord.

Focal phospholipases A2 group III injections induce cervical white matter injury and functional deficits with delayed recovery concomitant with Schwann cell remyelination

Phospholipases A(2) (PLA(2)) are group of enzymes that hydrolyze membrane phospholipids at the sn-2 position. PLA(2) are present in the brain and spinal cord and are implicated in several neurological disorders. Previously, we showed that PLA(2) activity increases following traumatic spinal cord injury and injection of group III secretory PLA(2) (sPLA(2)-III) demyelinates spinal cord axons. Here, we demonstrate that injections of sPLA(2)-III into the cervical dorsolateral funiculus (DLF) resulted in dose-dependent demyelination, loss of oligodendrocytes and astrocytes, as well as axonopathy. Additionally, spared axons within the lesion were remyelinated by Schwann cells between weeks 2 and 3. To assess functional loss and recovery, we employed a modified "Staircase Test" pellet retrieval device and footprint analysis of forelimb function during locomotion. Pellet retrieval assessment sensitively detected the dose dependent lesion and its recovery after sPLA(2)-III injections with greater sensitivity than footprint analysis. We believe that this is the first report of a reaching task being able to discriminate between various grades of cervical white matter damage and varying extents of recovery. Thus, our results indicate that sPLA(2)-III can create white matter pathologies that are remyelinated by Schwann cells 2 to 3 weeks after injury. Additionally, the pellet retrieval test is a sensitive and quantifiable method for assessing the dysfunction and later recovery mediated by sPLA(2)-III injections.

β-Tubulin Is a More Suitable Internal Control thanβ-Actin in Western Blot Analysis of Spinal Cord Tissues after Traumatic Injury

Western blot is a widely used method for determining specific protein levels. To control and correct for loading error, an internal control is often used. To date, two housekeeping geneâcoded proteins (i.e., beta-actin and beta-tubulin) are widely used as internal controls in the Western blot analysis. However, no information is available concerning the stability of their expressions in response to a traumatic injury to the central nervous system (CNS). If so, their use as an internal control may have a negative impact on data acquisition, analysis, and interpretation. Using Western blot analysis, we demonstrated that spinal cord injury (SCI) induced a significant increase in beta-actin expression which peaked at 7 days post-SCI (2.48-fold). Coefficient of variation (CV) analysis showed that the CV of beta-actin expression was 43.79 +/- 4.67%, significantly higher than that of six loadings from a single sample (6.5 +/- 0.9%, p < 0.01), indicating that increased expression of beta-actin was a result of SCI, instead of a loading error. In contrast, no statistically significant difference was found in beta- tubulin expression following SCI, compared with sham-operated controls. The CV of beta-tubulin expression following SCI was 14.3 beta 3.96%, significantly less than that of the beta-actin expression (43.79 +/- 4.67%; p < 0.01). Taken together, our study suggests that beta-actin whose expression increases following SCI is not a suitable internal control for Western blot analysis of spinal cord tissues following a traumatic injury. In contrast, beta-tubulin, whose expression was not significantly affected by SCI, is a better choice for the internal control.

A novel role of phospholipase A2in mediating spinal cord secondary injury

OBJECTIVE

To investigate whether phospholipase A2 (PLA2) plays a role in the pathogenesis of spinal cord injury (SCI).

METHODS

Biochemical, Western blot, histological, immunohistochemical, electron microscopic, electrophysiological, and behavior assessments were performed to investigate (1) SCI-induced PLA2 activity, expression, and cellular localization after a contusive SCI; and (2) the effects of exogenous PLA2 on spinal cord neuronal death in vitro and tissue damage, inflammation, and function in vivo.

RESULTS

After SCI, both PLA2 activity and cytosolic PLA2 expression increased significantly, with cytosolic PLA2 expression being localized mainly in neurons and oligodendrocytes. Both PLA2 and melittin, an activator of endogenous PLA2, induced spinal neuronal death in vitro, which was substantially reversed by mepacrine, a PLA2 inhibitor. When PLA2 or melittin was microinjected into the normal spinal cord, the former induced confined demyelination and latter diffuse tissue necrosis. Both injections induced inflammation, oxidation, and tissue damage, resulting in corresponding electrophysiological and behavioral impairments. Importantly, the PLA2-induced demyelination was significantly reversed by mepacrine.

INTERPRETATION

PLA2, increased significantly after SCI, may play a key role in mediating neuronal death and oligodendrocyte demyelination following SCI. Blocking PLA2 action may represent a novel repair strategy to reduce tissue damage and increase function after SCI.

Group II Phospholipase A(2) Activity and Its Molecular Regulation in Rat Heart during Sepsis

Changes of activity and content of myocardial group II phospholipase A(2) and its mRNA transcription and stability during rat sepsis were investigated. Results showed that, compared with control group,myocardial group II phospholipase A(2) activity in early and late sepsis decreased by 25.0%(P<0.05) and increased by 47.6%(P<0.01),respectively group II phospholipase A(2) protein concentration reduced by 27.0% and augmented by 48.0%(P<0.01),respectively. Myocardial group II phospholipase A(2) mRNA transcription rate and content showed similar two-phases changes. The mRNA transcription rate during early and late sepsis decreased by 45.0% and increased by 70.0%(P<0.01),respectively. The mRNA content decreased by 34.1% in early sepsis and increased by 157.0% in late sepsis(P<0.01), respectively. The half-life of group II phospholipase A(2) mRNA remained unchanged notably during early and late stage of sepsis. These data suggest that myocardial group II phospholipase A(2) activity decreased in early stage of sepsis and increased in its late stage, and these changes were regulated transcriptionally.

[Influence of myocardial ischemia/reperfusion in vitro on nuclear envelope NTPase activity and mRNA export in the cardiomyocyte of rabbits]

AIM

To study the alteration of nuclear envelope associated NTPase activity and mRNA nucleocytoplasmic transport in rabbit cardiomyocyte following in vitro ischemia and reperfusion.

METHODS

The model of myocardial perfusion in rabbit was used to produce myocardial I/R injury and cardiomyocyte nuclear envelope vesicles were prepared by density gradient centrifugation for the assay of mRNA transport rate and NTPase activity.

RESULTS

NTPase activity was reduced and mRNA transport rate was significantly decreased in I/R (P < 0.01) but not in ischemia group( P > 0.05).

CONCLUSION

The nuclear envelope vesicles had been injured following ischemia and reperfusion and resulted in NTPase activity reduced and egress of mRNA interrupted, and therefore may lead to decreasing of protein synthesis.

[The changes in the heart and erythrocyte L-arginine transport of spontaneously hypertensive rats]

Changes of L-arginine/nitric oxide pathway in heart and of L arginine transport in erythrocytes and their relationship were investigated in spontaneously hypertensive rats (SHR). 12 and 16 weeks old SHR, 16 weeks old SHR with captopril treatment for 4 weeks and 16 weeks old Wistar-Kyoto (WKY) rats were used. L arginine transport of myocardial ventricular tissue and erythrocytes, total nitric oxide synthase (tNOS) activity, nitrite and nitrate (NO(2) + NO(3)) and cyclic GMP (cGMP) content in myocardium were measured. The result showed that in myocardial ventricular tissue of SHR L-arginine transport decreased significantly with V(max) of the high-affinity transport being decreased by 24.3% (P<0.05, 12W group), 36.4% (P<0.01, 16W group) as compared with WKY group. Michaelis constant (K(m)) of low affinity transport was significantly lower than that of WKY group. NO(2) + NO(3) and cGMP content were respectively decreased by 24.6%, 19.8% (P>0.05, P<0.05, 12W group), 52.5%, 60.4% (P<0.05, P<0.01, 16W group) and 14.8%, 23% (P>0.05, P<0.05, SHR+C group) as compared with WKY group. But the K(m) of L-arginine high-affinity transport and the V(max) of low affinity transport and tNOS activity were not significantly changed. In erythrocytes, the changes of L-arginine transport coincided with those of myocardial tissue. The V(max) had significant positive correlation with the V(max) of high-affinity transport in myocardial tissue, r=0.5606, P=0.01 and had negative correlation with left ventricular weight to body weight radio, r=0.6231,P<0.01. These results indicate that the activity of L-arginine/nitric oxide pathway inhibited in myocardial tissue of SHR. The correlation between the inhibitory degree of L-arginine/nitric oxide pathway and the degree of ventricular hypertrophy is negative. The changes of L-arginine transport in erythrocytes coincide with those in myocardium.

[Inhibition of ERK1/2 activity and c-fos mRNA after coronary artery balloon injury by intracoronary radiation in swine]

The effect of intracoronary radiation on extracellular signal regulated kinase 1/2 (ERK1/2) activity and c-fos mRNA after coronary artery balloon injury was investigated in swine. Twenty three swines were randomly divided into a radiation group and a control group after coronary balloon over stretch. The dilated segments in the radiation group were exposed to a dose of 20 Gy by a catheter based radiation system. The animals were sacrificed at 3 (6 swines from each group) and 30 days (6 swines from radiation group and 5 from control group) after the operation. The injured segments were processed to examine c-fos gene expression by reverse transcription polymerase chain reaction (RT PCR) and to measure the activity of ERK1/2 biochemically. Intracoronary radiation decreased significantly the ERK1/2 activity and gene expression of c-fos in the radiation treated animals 3 days after coronary balloon injury (20.5%,P<0.01; 47.7%,P<0.05), but neither ERK1/2 activity nor c-fos gene expression was significantly affected by endovascular radiation in animals 30 days after balloon injury. Therefore, both ERK1/2 and c-fos may be involved in inhibiting restenosis.

Basic fibroblast growth factor increases nitric oxide and endothelin production in rat aorta

The study was undertaken to investigate the effect of basic fibroblast growth factor (bFGF) on aortic production of nitric oxide (NO) and endothelin of aorta in spontaneously hypertensive rats (SHR) and WKY rats. Rat aortas were cut into vessel slices and incubated with 10 or 100 ng/ml bFGF for 6 hours. Nitric oxide synthase (NOS) activity in aortic slices and contents of NO(-)(2) and endothelin in the medium were determined. The results showed that NOS activity in aortic slices of SHR was 17.6% lower than that of WKY (P<0.01). NO(-)(2) and endothelin contents in the medium of SHR aortic slices were 59.7% lower and 37.4% higher than those of WKY aortic slices. Upon the exposure of low and high doses of bFGF, NOS activity in the aorta of SHR was increased by 29.7% and 59.6% (both P<0.01),respectively, while the NO(-)(2) contents in the medium were increased respectively by 28.2% (P<0.05) and 70.5% (P<0.01). Aortic endothelin production was increased by 24.1% and 44.5% (both P<0.01) respectively while the NOS activity in the aorta of WKY was increased by 24.4% and 53.7% (both P<0.01). NO(-)(2) contents in the medium were augmented by 18.8% (P<0.05)and 25.9% (P<0.01), respectively. Aortic endothelin production was increased by 84.1% and 93.1% (both P<0.01). It is concluded that bFGF may modulate the production of NO and endothelin in both SHR and WKY rats.

[Plasmid pcDNA3 enhances Ca(2+) transport of sarcoplasmic reticulum in ischemic skeletal muscle of rats]

The effects of plasmid pcDNA3 on Ca(2+) transport of sarcoplasmic reticulum (SR) in ischemic skeletal muscle was investigated. The results show that Ca(2+) transport (including Ca(2+) uptake and Ca(2+) release) rate of SR in ischemic skeletal muscle was markedly increased compared with that in non-ischemic muscle (P<0.01 or P<0.05). After plasmid pcDNA3 bound to the DNA binding proteins of SR, Ca(2+) transport of SR was further increased. The results suggest that the effect of plasmid DNA on the ability of Ca(2+) transport in SR of ischemic skeletal muscle is the same as is observed in normal skeletal muscle. The pathophysiological significance of the present finding deserves further exploration.

Effect of batroxobin against dog heart ischemia/reperfusion injury

AIM

To study the effect of batroxobin(Bat) on dog heart ischemia/reperfusion (I/R) injury.

METHODS

Dog heart I/R injury was induced by occluding the left anterior descending coronary artery for 30 min and restoring blood perfusion for 90 min. Bat was intravenously injected before heart ischemia and 15 min before reperfusion. Plasma creatine kinase (CK), lactate dehydrogenase (LDH), and myocardial malondiaedehyde (MDA) concentrations were measured. The pathologic changes of I/R myocardium were observed.

RESULTS

Bat reduced the mortality rate of I/R dog (I/R group 65.0% vs Bat-I group 30.0% and Bat-II group 28.6%, P < 0.05). Myocytes of I/R heart showed intracellular edema, damaged mitochondria, and concentrated nucleus. Bat decreased these changes. In Bat-I and Bat-II group, plasma CK and LDH level were reduced, the +dp/dtmax and -dp/dtmax at 30 min after ischemia and 90 min after reperfusion were elevated, and left ventricular end dilation pressure (LVEDP) was lowered. The myocardial MDA contents were decreased by 42.3% and 38.1% (P < 0.01) in Bat-I and Bat-II group, respectively.

CONCLUSION

Bat may exert an apparent role against dog heart ischemia/reperfusion injury and improve myocardial function.

[Involvement of calcineurin-dependent signal pathway in the angiotensin II-induced cardiac myocyte hypertrophy]

The present study was undertaken to observe the role of calcineurin (CaN)-dependent signaling pathway in the angiotensin II (Ang II)-induced cardiac myocyte hypertrophy. In cultured myocardial cells of neonatal rats, Ang II was used to stimulate hypertrophy and CaN-pathway blocked by CsA(an inhibitor of CaN). 3H-leucine incorporation, and activities of CaN, mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) were investigated. The results showed that 3H-leucine incorporation of Ang II-stimulated myocardial cells was 46% higher than control (P < 0.01), which could be inhibited by CsA (0.5-5 micrograms/ml) and PD098059(an inhibitor of MAPK). CaN and PKC activities of Ang II-stimulated myocardial cells were 39% and 280% higher than control (P < 0.001) respectively, while no significant increase in MAPK activities was observed. CsA could reverse the increase of CaN activity, but had no effect on PKC. It is concluded that the CaN-dependent signaling pathway may play an important role in the development of the Ang II-induced cardiac myocyte hypertrophy.

[Alteration of ryanodine receptors in cardiac sarcoplasmic reticulum and nuclear envelope of rats during sepsis]

To investigate changes of ryanodine receptors in the sarcoplasmic reticulum (SR) and the nuclear envelope (NE) of rat cardiac myocytes during sepsis induced by cecal ligation and puncture (CLP), myocardial SR and NE were fractionated with density gradient centrifugation and the characteristic of ryanodine receptor was assayed with a method of radioreceptor binding assay. The result showed that Bmax of ryanodine receptors in cardiac SR was increased by 23% during early sepsis (9 h after CLP), but decreased by 38% during late sepsis (18 h after CLP). Bmax of ryanodine receptors in cardiac NE, on the other hand, was increased by 100% and 160% during early and late sepsis respectively. Kd of ryanodine binding to SR and NE remained unchanged during sepsis. These results demonstrated up-regulation of ryanodine receptors in SR occurred during early sepsis and down-regulation of these receptors in SR occurred during late sepsis, while up-regulation of ryanodine receptors in NE occurred during both the early and the late sepsis.

Role of endogenous carbon monoxide in the pathogenesis of hypotension during septic shock

A sepsis model induced by cecal ligation and puncture was used to study the role of endogenous carbon monoxide in hypotension pathogenesis of rats during septic shock. After administration of zinc deuteroporphyrin 2,4-bisglycol (ZnDPBG),an inhibitor of heme oxygenase (HO),blood pressure (BP),HO activity and carbon monoxide (CO) release from vascular muscle tissue were measured. The results showed that BP of sepsis rats, including systolic and diastolic arterial BP, decreased significantly while HO activity and CO content were significantly increased. In contrast, after administration of ZnDPBG, BP of sepsis rats was significantly increased while the HO activity and CO production were significantly decreased. These findings suggest that HO activity and CO release within vascular musculature are increased during septic shock; inhibition of HO may elevate BP of rats during septic shock through a decrease of endogenous CO production. It is concluded that endogenous CO derived from vascular muscle cells plays an important role in regulating vascular tone, and the up-regulation of HO activity followed by subsequent CO production contributes to hypotension pathogenesis during septic shock.

Role of endogenous carbon monoxide in hypertension pathogenesis of rats

The present study investigated the contribution of endogenous heme oxygenase (HO)/carbon monoxide (CO) system to hypertension pathogenesis of rats. Zinc deuteroporphyrin 2,4-bisglycol (ZnDPBG), an inhibitor of heme oxygenase (HO), was used to inhibit HO activity in vivo. It was found that the blood pressure of rats with HO inhibition was significantly elevated, and plasma levels of adrenaline, noradrenaline, endothelin, nitrate and nitrite were significantly increased. HO activity and HbCO formation within vascular smooth muscle tissues were significantly inhibited after administration of ZnDPBG. Furthermore, administration of exogenous CO into HO inhibiting rats led to MABP decrease, but injection of HO substrate, heme-L-lysinate, had no effect on HO inhibition-induced hypertension. In spontaneously hypertensive rats, injection of exogenous CO resulted in a significant decrease of MABP, and heme-L-lysinate had a similar effect with exogenous CO. These data show that HO/CO system has an anti-hypertension biological action, suggesting that endogenous CO plays an important role in hypertension pathogenesis.

[Inhibition of signal transduction pathways of endothelin-1-induced proliferation of vascular smooth muscle cells by nitric oxide]

The signal transduction pathways of the inhibitory effect of nitric oxide (NO) on endothelin (ET)-induced proliferation of vascular smooth muscle cells (VSMCs) were studied. 3H-thymidine (TdR) incorporation, mitogen-activated protein kinase (MAPK) activity and protein kinase C (PKC) activity of cultured VSMCs of rabbits thoracic aorta were measured in the presence of either NO precursor L-arginine (L-Arg) or NO donor 3-morpholino sydnonimine-hydrochloride (SIN-1), or ET-1 alone or with L-Arg or SIN-1. The results show: (1) ET-1 (10(-8) mol/L) significantly increased VSMCs 3H-TdR incorporation (5 times, P < 0.01), MAPK activity (4 times, P < 0.01) and PKC activity (3 times, P < 0.01), as compared with control. L-Arg or SIN-1 alone was without effect on 3H-TdR incorporation, MAPK activity and PKC activity. (2) When ET-1 and L-Arg (2, 5, 10 mmol/L) were simultaneously administered, 3H-TdR incorporation and activity of both MAPK and PKC were all significantly decreased in comparison with the ET group. (3) When ET-1 + SIN-1 (5, 10, 50 mumol/L), the effects coincide with those of the ET-1 + L-Arg groups. These findings indicate that NO inhibition of the signal transduction pathways of the ET-1-induced proliferation of VSMCs may be mediated by the inhibition of ET-1-induced activation of both PKC and MAPK.

[Impairment in the phosphorylation of Ca(2+)-transport ATPase of rat liver endoplasmic reticulum during sepsis]

The phosphorylation of Ca(2+)-transport ATPase of rat liver endoplasmic reticulum (ER) during early and late septic shock induced by cecum ligation and puncture (CLP) was investigated by determining incorporation of [gamma-32P] ATP into Ca(2+)-ATP phosphoprotein intermediate. Hepatic endoplasmic reticulum was isolated by differential centrifugation with sucrose density gradient. The Ca(2+)-ATPase phosphoprotein intermediate was identified by SDS-PAGE. The results showed that the phosphorylation of Ca(2+)-ATPase (115 kD) was decreased respectively by 15-23% (P < 0.05) and 17-27% (P < 0.05) at 9 h (early sepsis) and 18 h (late sepsis), following the CLP in the rough, intermediate and smooth ER preparations. Kinetic analysis using rough ER showed that the Vmax for Ca2+ and for ATP for the phosphorylation of Ca(2+)-ATPase were decreased dramatically during early and late sepsis, but without changes in the K(m) values. These results demonstrate that the phosphorylation of the phosphoprotein intermediate of Ca(2+)-ATPase in rat liver was impaired during different phases of sepsis.