Inhibition of cerebral ischemia/reperfusion injury-induced apoptosis:nicotilforin and JAK2/STAT3 pathway

Nicotilforin is a lfavonoid extracted from Carthamus tinctorius. Previous studies have shown its cerebral protective effect, but the mecha-nism is undeifned. In this study, we aimed to determine whether nicotilforin protects against cerebral ischemia/reperfusion injury-induced apoptosis through the JAK2/STAT3 pathway. hTe cerebral ischemia/reperfusion injury model was established by middle cerebral artery occlusion/reperfusion. Nicotilforin (10 mg/kg) was administered by tail vein injection. Cell apoptosis in the ischemic cerebral cortex was examined by hematoxylin-eosin staining and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Bcl-2 and Bax expres-sion levels in ischemic cerebral cortex were examined by immunohistochemial staining. Additionally, p-JAK2, p-STAT3, Bcl-2, Bax, and caspase-3 levels in ischemic cerebral cortex were examined by western blot assay. Nicotilforin altered the shape and structure of injured neurons, decreased the number of apoptotic cells, down-regulates expression of p-JAK2, p-STAT3, caspase-3, and Bax, decreased Bax immunoredactivity, and increased Bcl-2 protein expression and immunoreactivity. hTese results suggest that nicotilforin protects against cerebral ischemia/reperfusion injury-induced apoptosis via the JAK2/STAT3 pathway.     

特异性抑制JAK2/STAT3信号通路对大鼠急性脑缺血再灌注损伤后COX-2和VEGF表达水平的影响

目的 探讨特异性抑制蛋白酪氨酸激酶2/信号转导与激活子3(JAK2/STAT3)信号通路对急性脑缺血再灌注损伤大鼠脑组织环氧合酶-2(COX-2)和血管内皮生长因子(VEGF)表达水平的影响。方法 采用线栓法制备大鼠急性大脑中动脉闭塞再灌注模型; 大鼠随机分为假手术组、模型组和给药组; 给药组大鼠于再灌注前5 min腹腔注射JAK2/STAT3信号通路抑制剂AG490(1 mg/kg),其余2组给予等量生理盐水; 再灌注24 h后各组行神经功能缺损评分,用氯化三苯基四氮唑(TTC)染色法检测大鼠脑梗死体积,用实时荧光定量PCR(RT-qPCR)检测脑组织中JAK2、STAT3、环氧合酶2(COX-2)和血管内皮生长因子(VEGF)的mRNA相对表达水平,用蛋白印迹(Western blot)检测脑组织磷酸化JAK2(p-JAK2)、磷酸化STAT3(p-STAT3)、COX-2和VEGF的蛋白相对表达水平。结果 与假手术组比较,模型组大鼠神经功能缺损评分、脑梗死体积、JAK2和STAT3的mRNA,p-JAK2和p-STAT3蛋白、COX-2的mRNA和蛋白相对表达水平均显著升高(P<0.05),VEGF的mRNA和蛋白相对表达水平显著降低(P<0.05); 与模型组比较,给药组大鼠神经功能缺损评分、脑梗死体积、JAK2和STAT3的mRNA、p-JAK2和p-STAT3蛋白、COX-2的mRNA和蛋白相对表达水平均显著降低(P<0.05),VEGF的mRNA和蛋白相对表达水平显著升高(P<0.05)。结论 特异性抑制JAK2/STAT3信号通路可能通过降低脑组织中COX-2表达和促进VEGF表达来保护大鼠急性脑缺血再灌注损伤。     

PI3K/akt, JAK/STAT and MEK/ERK pathway inhibition protects retinal ganglion cells via different mechanisms after optic nerve injury

Recently we unexpectedly found that PI3K/akt, JAK/STAT and MEK/ERK pathway inhibitors enhanced retinal ganglion cell (RGC) survival after optic nerve (ON) axotomy in adult rat, a phenomenon contradictory to conventional belief that these pathways are pro-survival. In this study we showed that: (i) the RGC protection was pathway inhibition-dependent; (ii) inhibition of PI3K/akt and JAK/STAT, but not MEK/ERK, activated macrophages in the eye, (iii) macrophage removal from the eye using clodronate liposomes significantly impeded PI3K/akt and JAK/STAT inhibition-induced RGC survival and axon regeneration whereas it only slightly affected MEK/ERK inhibition-dependent protection; (iv) in the absence of recruited macrophages in the eye, inhibition of PI3K/akt or JAK/STAT did not influence RGC survival; and (v) strong PI3K/akt, JAK/STAT and MEK/ERK pathway activities were located in RGCs but not macrophages after ON injury. In retinal explants, in which supply of blood-derived macrophages is absent, MEK/ERK inhibition promoted RGC survival whereas PI3K/akt or JAK/STAT inhibition had no effect on RGC viability. However, MEK/ERK inhibition exerted opposite effects on the viability of purified adult RGCs at different concentrations in vitro, suggesting that this pathway may be bifunctional depending on the level of pathway activity. Our data thus demonstrate that inhibition of the PI3K/akt or JAK/STAT pathway activated macrophages to facilitate RGC protection after ON injury whereas the two pathways per se did not modulate RGC viability under the injury conditions (in the absence of the pathway activators). In contrast, the MEK/ERK pathway inhibition protected RGCs via macrophage-independent mechanism(s).     

Aldehyde dehydrogenase 2 overexpression inhibits neuronal apoptosis after spinal cord ischemia/reperfusion injury

Aldehyde dehydrogenase 2(ALDH_2)is an important factor in inhibiting oxidative stress and has been shown to protect against renal ischemia/reperfusion injury.Therefore,we hypothesized that ALDH_2 could reduce spinal cord ischemia/reperfusion injury.Spinal cord ischemia/reperfusion injury was induced in rats using the modified Zivin’s method of clamping the abdominal aorta.After successful model establishment,the agonist group was administered a daily consumption of 2.5%alcohol.At 7 days post-surgery,the Basso,Beattie,and Bresnahan score significantly increased in the agonist group compared with the spinal cord ischemia/reperfusion injury group.ALDH_2expression also significantly increased and the number of apoptotic cells significantly decreased in the agonist group than in the spinal cord ischemia/reperfusion injury group.Correlation analysis revealed that ALDH_2 expression negatively correlated with the percentage of TUNEL-positive cells(r=-0.485,P0.01).In summary,increased ALDH_2 expression protected the rat spinal cord against ischemia/reperfusion injury by inhibiting apoptosis.     

Ginsenoside Rd inhibits apoptosis following spinal cord ischemia/reperfusion injury

Ginsenoside Rd has a clear neuroprotective effect against ischemic stroke. We aimed to verify the neuroprotective effect of ginsenoside Rd in spinal cord ischemia/reperfusion injury and explore its anti-apoptotic mechanisms. We established a spinal cord ischemia/reperfusion injury model in rats through the occlusion of the abdominal aorta below the level of the renal artery for 1 hour. Successfully established models were injected intraperitoneally with 6.25, 12.5, 25 or 50 mg/kg per day ginsenoside Rd. Spinal cord morphology was observed at 1, 3, 5 and 7 days after spinal cord ischemia/reperfusion injury. Intraperitoneal injection of ginsenoside Rd in ischemia/reperfusion injury rats not only improved hindlimb motor function and the morphology of motor neurons in the anterior horn of the spinal cord, but it also reduced neuronal apoptosis. The optimal dose of ginsenoside Rd was 25 mg/kg per day and the optimal time point was 5 days after ischemia/ reperfusion. Immunohistochemistry and western blot analysis showed ginsenoside Rd dose-de- pendently inhibited expression of pro-apoptotic Caspase 3 and down-regulated the expression of the apoptotic proteins ASK1 and JNK in the spinal cord of rats with spinal cord ischemia/reper- fusion injury. These findings indicate that ginsenoside Rd exerts neuroprotective effects against spinal cord ischemia/reperfusion injury and the underlying mechanisms are achieved through the inhibition of ASK1-JNK pathway and the down-regulation of Caspase 3 expression.     

Early induction of secondary injury factors causing activation of calpain and mitochondria-mediated neuronal apoptosis following spinal cord injury in rats

To investigate a potential relationship between calpain and mitochondrial damage in spinal cord injury (SCI), a 40 gram-centimeter force (g-cm) injury was induced in rats by a weight-drop method and allowed to progress for 4 hr. One-centimeter segments of spinal cord tissue representing the adjacent rostral, lesion, and adjacent caudal areas were then removed for various analyses. Calcium green 2-AM staining of the lesion and penumbra sections showed an increase in intracellular free calcium (Ca(2+)) levels following injury, compared with corresponding tissue sections from sham-operated (control) animals. Western blot analysis showed increased calpain expression and activity in the lesion and penumbra segments following SCI. Double-immunofluorescent labeling indicated that increased calpain expression occurred in neurons in injured segments. Western blot analysis also showed an increased Bax:Bcl-2 ratio, indicating the induction of the mitochondria-mediated cell death pathway in the lesion and penumbra. The morphology of mitochondria was altered in lesion and penumbra following SCI: mostly hydropic change (swelling) in the lesion, with the penumbra shrunken or normal. At 4 hr after induction of injury, a substantial amount of cytochrome c had been released into the cytoplasm, suggesting a trigger for apoptosis through caspase 3 activation. Neuronal death after 4 hr of injury was detected by a combined TUNEL and double-immunofluoresence assay in the lesion and penumbra sections of injured cord, compared with sham controls. These results suggest that an early induction of secondary factors is involved in the pathogenesis of SCI. The increased Ca(2+) levels could activate calpain and mediate mitochondrial damage leading to neuronal death in lesion and penumbra following injury. Thus, secondary injury processes mediating cell death are induced as early as 4 hr after the injury, and calpain and caspase inhibitors may provide neuroprotection.     

Regulatory T cells promote functional recovery after spinal cord injury by alleviating microglia inflammation via STAT3 inhibition

Background

Immediately after spinal trauma, immune cells, and proinflammatory cytokines infiltrate the spinal cord and disrupt the focal microenvironment, which impedes axon regeneration and functional recovery. Previous studies have reported that regulatory T cells (Tregs) enter the central nervous system and exert immunosuppressive effects on microglia during multiple sclerosis and stroke. However, whether and how Tregs interact with microglia and modulate injured microenvironments after spinal cord injury (SCI) remains unknown.

Method

Regulatory T cells spatiotemporal characteristics were analyzed in a mouse contusion SCI model. Microglia activation status was evaluated by immunostaining and RNA sequencing. Cytokine production in injured spinal cord was examined using Luminex. The role of STAT3 in Treg–microglia crosstalk was investigated in a transwell system with isolated Tregs and primary microglia.

Results

Regulatory T cells infiltration of the spinal cord peaked on day 7 after SCI. Treg depletion promoted microglia switch to a proinflammatory phenotype. Inflammation-related genes, such as ApoD, as well as downstream cytokines IL-6 and TNF-α were upregulated in microglia in Treg-depleted mice. STAT3 inhibition was involved in Treg–microglia crosstalk, and STAT3 chemical blockade improved function recovery in Treg-depleted mice.

Conclusion

Our results suggest that Tregs promote functional recovery after SCI by alleviating microglia inflammatory reaction via STAT3.     

Senegenin inhibits neuronal apoptosis after spinal cord contusion injury

Senegenin has been shown to inhibit neuronal apoptosis, thereby exerting a neuroprotective effect. In the present study, we established a rat model of spinal cord contusion injury using the modiifed Allen’s method. Three hours after injury, senegenin (30 mg/g) was injected into the tail vein for 3 consecutive days. Senegenin reduced the size of syringomyelic cavities, and it substantially reduced the number of apop-totic cells in the spinal cord. At the site of injury, Bax and Caspase-3 mRNA and protein levels were decreased by senegenin, while Bcl-2 mRNA and protein levels were increased. Nerve ifber density was increased in the spinal cord proximal to the brain, and hindlimb motor function and electrophysiological properties of rat hindlimb were improved. Taken together, our results suggest that senegenin exerts a neuroprotective effect by suppressing neuronal apoptosis at the site of spinal cord injury.     

Apigenin inhibits fibrous scar formation after acute spinal cord injury through TGFβ/SMADs signaling pathway

AimTo investigate the effect of apigenin on fibrous scar formation after mouse spinal cord injury (SCI).MethodsThe pneumatic impactor strike method was used to establish an SCI model. Mice were intraperitoneally injected with 5 mg/kg or 20 mg/kg apigenin daily for 28 days after SCI. The Basso Mouse Scale (BMS) score, hematoxylin–eosin staining, and immunohistochemical staining were used to assess the effect of apigenin on scar formation and motor function recovery. Western blotting and qRT‐PCR were used to detect the expression of fibrosis‐related parameters in spinal cord tissue homogenates. NIH‐3 T3 cells and mouse primary spinal cord fibroblasts, α‐Smooth muscle actin (α‐SMA), collagen 1, and fibronectin were used to evaluate apigenin''s effect in vitro. Western blotting and immunofluorescence techniques were used to study the effect of apigenin on TGFβ/SMADs signaling.ResultsApigenin inhibited fibrous scar formation in the mouse spinal cord and promoted the recovery of motor function. It reduced the expression of fibroblast‐related parameters and increased the content of nerve growth factor in vivo, decreasing myofibroblast activation and collagen fiber formation by inhibiting TGFβ‐induced SMAD2/3 phosphorylation and nuclear translocation in vitro.ConclusionApigenin inhibits fibrous scar formation after SCI by decreasing fibrosis‐related factor expression through TGFβ/SMADs signaling.     

JAK/STAT信号转导通路在IGF-1抑制左旋多巴诱导的多巴胺能神经元凋亡中的作用

目的 探讨胰岛素样生长因子1(IGF-1)通过JAK/STAT信号转导通路对左旋多巴诱导的多巴胺能神经元凋亡的保护作用.方法 应用100μg/L β神经生长因子(β-NGF)将体外常规培养的PC12细胞诱导分化为多巴胺能神经元.MTT比色法筛选左旋多巴的神经损伤浓度和IGF-1的神经保护浓度(150μmol/L、100nmol/L),实验分为4组:(1)左旋多巴+IGF-1组;(2)左旋多巴+IGF-1+AG490组,AG490(10 μmol/L)在给予左旋多巴和IGF-1前20 min加人;(3)左旋多巴组;(4)对照组.Western blotting检测4组细胞P-JAK2、P-STAT3蛋白表达,Hoechst33258染色和流式细胞仪分别检测细胞凋亡和凋亡率.结果 Westen blotting法检测显示对照组和左旋多巴组P-JAK2、P-STAT3蛋白表达阴性,而左旋多巴+IGF-1组和左旋多巴+IGF-1+AG490组表达阳性.左旋多巴+IGF.1+AG490组P.JAK2、P.STAT3表达强度低于左旋多巴+IGF.1组,差异有统计学意义(P<0.05):Hoechst33258染色结果显示左旋多巴组细胞核固缩及碎裂最明显,较多凋亡小体形成,而左旋多巴+IGF-1组与左旋多巴+IGF-1+AG490组仅有少量凋亡小体形成.流式细胞仪检测显示4组多巴胺能神经元凋亡率不同,差异有统计学意义(F=180.991,P=0.000);与对照组比较,另3组细胞凋亡率均增高,差异有统计学意义(P<0.05);其中左旋多巴组细胞凋亡率最高,其次为左旋多巴+IGF-1+AG490组、左旋多巴+IGF-1组.结论 大剂量左旋多巴对多巴胺能神经元具有毒性作用.IGF-1对左旋多巴诱导的神经细胞毒性作用呈保护作用,JAK2/STAT3信号转导通路参与了此过程.

Abstract：

Objective To explore the protective effect of insulin-like growth factor 1 (IGF-1) on apoptosis of dopaminergic neurons induced by L-dopa via JAK/STAT signaling pathway. Methods PC12 cells were induced to differentiate into dopaminergic neurons with 100 μg/L β-NGF; MTT assay was employed to identify the changes in the viability of PC12 cells following L-dopa treatment at 0, 10,20, 50, 100, 150 and 200 μmol/L, and the different concentrations of IGF-1 at 0, 10, 25, 50 and 100 nmol/L with the same concentration of L-dopa (150 μmol/L); Western blotting was used to detect the levels of P-JAK2/P-STAT3 in PC12 cells treated with PBS (controls), L-dopa, L-dopa+IGF-1 and L-dopa+IGF-1+AG490 for 24 h, and then the apoptosis rate was assessed by flow cytometry and Hchest33258 staining. Results Western blotting showed that the expressions of P-JAK2 and P-STAT3 were detected in the L-dopa+IGF-1 and L-dopa+IGF-1+AG490 treatment groups but not in the control group or L-dopa treatment group; the expression of P-STAT3 in the L-dopa+IGF-1+AG490 treatment group was obviously lower than that in the L-dopa+IGF-1 treatment group (P<0.05). Hchest33258 staining indicated that L-dopa treatment group had the most obvious karyopyknosis and karyorrhexis,much more apoptotic bodies than the L-dopa+IGF-1 and L-dopa+IGF-1+AG490 treatment groups. Flow cytometry showed that the apoptosis rate was significantly different among the 4 groups (F=180.991,P=0.000): as compared with the control group, the other 3 groups had a higher apoptosis rate (P<0.05);L-dopa treatment group (38.13 ±2.54 %) enjoyed the highest level, followed by L-dopa+IGF-1 +AG490treatment group (25.60±1.30 %) and L-dopa+IGF-1 treatment group (20.17±1.54 %). Conclusion L-dopa has toxic effect on PC12 cells; IGF-1 could protect the PC12 cells from the neurotoxic effect of L-dopa and JAK2/STAT3 signaling pathway is activated in this procedure.     

MicroRNA-31 regulating apoptosis by mediating the phosphatidylinositol-3 kinase/protein kinase B signaling pathway in treatment of spinal cord injury

Apoptosis is a highly conservative energy demand program for non-inflammatory cell death, which is extremely significant in normal physiology and disease. There are many techniques used for studying apoptosis. MicroRNA (miRNA) is closely related to cell apoptosis, and especially microRNA-31 (miR-31) is involved in apoptosis by regulating a large number of target genes and signaling pathways. In many neurological diseases, cell apoptosis or programmed cell death plays an important role in the reduction of cell number, including the reduction of neurons in spinal cord injuries. In recent years, the phosphoinositol 3-kinase/AKT (PI3K/AKT) signal pathway, as a signal pathway involved in a variety of cell functions, has been studied in spinal cord injury diseases. The PI3K/AKT pathway directly or indirectly affects whether apoptosis occurs in a cell, thereby affecting a significant intracellular event sequence. This paper reviewed the interactions of miR-31 target sites in the PI3K/AKT signaling pathway, and explored new ways to prevent and treat spinal cord injury by regulating the effect of miR-31 on apoptosis.     

Involvement of mitochondrial signaling pathways in the mechanism of Fas-mediated apoptosis after spinal cord injury

Activation of the Fas receptor has been recently linked to apoptotic cell death after spinal cord injury (SCI). Although it is generally considered that Fas activation mediates apoptosis predominantly through the extrinsic pathway, we hypothesized that intrinsic mitochondrial signaling could be involved in the underlying mechanism of Fas-induced apoptosis after SCI. In the present study, we utilized the Fejota^TM clip compression model of SCI at T5–6 in C57BL/6 Fas-deficient ( lpr ) and wild-type mice. Complementary studies were conducted using an in vitro model of trauma or a Fas-activating antibody to induce apoptosis in primary neuronal–glial mixed spinal cord cultures. After in vivo SCI, lpr mice, in comparison with wild-type mice, exhibited reduced numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells at the lesion, reduced expression of truncation of Bid (tBid), apoptosis-inducing factor, activated caspase-9 and activated caspase-3, and increased expression of the antiapoptotic proteins Bcl-2 and Bcl-xL. After in vitro neurotrauma or the induction of Fas signaling by the Jo2 activating antibody, lpr spinal cord cultures showed an increased proportion of cells retaining mitochondrial membrane integrity and a reduction of tBid expression, caspase-9 and caspase-3 activation, and TUNEL-positive cells as compared to wild-type spinal cord cultures. The neutralization of Fas ligand (FasL) protected against traumatically induced or Fas-mediated caspase-3 activation and the loss of mitochondrial membrane potential and tBid expression in wild-type spinal cord cultures. However, in lpr spinal cord cultures, FasL neutralization had no protective effects. In summary, these data provide direct evidence for the induction of intrinsic mitochondrial signaling pathways following Fas activation after SCI.     

Effect of interleukin-2 on neurogliocyte and neuron apoptosis in rat models of acute spinal cord injury

BACKGROUND： lnterleukin-2 （IL-2） may influence the growth and survival of nerve cells following spinal cord injury and resuscitate the proliferation and maturation of oligodendrocytes. OBJECTIVE： To observe the effect of IL-2 on neuronal apoptosis of neurogliocytes at different times following acute spinal cord injury in rats. DESIGN, TIME AND SETTING： A randomized grouping trial based on cellular morphology was performed at the Institute of Traumatic Orthopedics of Shandong Province between October 2004 and January 2006. MATERIALS： A total of 72 adult, male, Sprague Dawley rats were included in this study and were divided into a control group and an IL-2 group. The Bcl-2 monoclonal antibody and TUNEL kit were purchased from Wunan Boster Biological Technology Corporation. METHODS： Spinal cord injury was induced in all the rats by dropping a weight from a height of 25 cm onto the exposed spinal cord at vertebral levels T7-11, thus producing a mild lesion. Immediately following the modeling, the rats were injected with daily IL-2 （10 uL） intramuscularly （the IL-2 group）. Other rats received an injection of physiological saline 0.5 mL/d （the control group）. MAIN OUTCOME MEASURES： Bcl-2 immunohistochemistry was applied to detect the Bcl-protein and positive cell expression. The TUNEL method was used to count the number of apoptotic cells. RESULTS： The expression level of Bcl-2 proteins increased significantly in spinal cord tissues during the first day after acute spinal cord injury, reaching a peak on days 3 and days 8 in the control and IL-2 groups, respectively. They were more prevalent in neurogliocytes than in neurocytes, and then began to decrease on day 14. From then until day 21, less expression was detected （P 〈 0.05）. In the control group, many apoptotic cells existed after 24 hours, and most of them were gliocytes; apoptotic cells reached a peak after 3-8 days. They then decreased gradually until day 21, when a small number of cells were still available. In the IL-2 grou     

BDA皮质脊髓束神经顺行示踪在大鼠脊髓损伤模型中的应用

目的本研究采用生物素标记葡聚糖(Biotin Dextran Amine,BDA)顺行示踪技术来观察大鼠皮质脊髓束(CST)在中枢神经系统中的走行及脊髓损伤后的表现特征。方法20只雌性成年Sprague-Dawley大鼠,分为脊髓损伤组(n=10)和损伤对照组(n=10)。在相当于T7椎板水平用做好标记的显微剪刀剪断脊髓的后2/3。对照组动物术中仅咬除棘突、椎板,不切断脊髓。术后第15 d,所有动物通过立体定向开颅,将10％BDA溶液注入右侧的感觉运动区皮质内。BDA注射2周后,取出大脑和脊髓组织,采用自由漂浮法行BDA染色显影。实验动物于脊髓损伤术前、术后3d、1周、2周、4周采用Basso、Beatlie、Bresnahan(BBB)评分法测量运动功能,所得数据采用两组均数比较t检验进行统计学处理。结果1.脊髓损伤组动物双后肢瘫痪,BBB运动功能评分明显低于损伤对照组,统计学比较差异十分显著(P<0.01);2.BDA顺行示踪显示大脑皮层BDA注射区内见大脑皮层的锥体细胞及其发出的轴突呈阳性染色,BDA阳性染色的皮质脊髓束神经纤维在中脑、桥脑及延髓的腹侧面行走,但在锥体交叉后皮质脊髓束主要(约99％)在对侧脊髓白质的后索中行走。在致伤组动物中,位于脊髓白质后索中的皮质脊髓束纤维在脊髓损伤处终止;在对照组皮质脊髓束纤维染色可一直延伸至L1水平。结论BDA顺行神经     

Induction of neuronal phenotypes from NG2+ glial progenitors by inhibiting epidermal growth factor receptor in mouse spinal cord injury

Besides neural stem cells, some glial cells, such as GFAP+ cells, radial glia, and oligodendrocyte progenitor cells can produce neuronal cells. Attractively, NG2+ glial progenitors exhibit lineage plasticity, and they rapidly proliferate and differentiate in response to central nervous system (CNS) injuries. These attributes of NG2+ glial progenitors make them a promising source of neurons. However, the potential of neuronal regeneration from NG2+ glial progenitors in CNS pathologies remains to be investigated. In this study, we showed that antagonizing epidermal growth factor receptor (EGFR) function with EGFR inhibitor caused a significant number of proliferative NG2+ glial progenitors to acquire neuronal phenotypes in contusive spinal cord injury (SCI), which presumably led to an accumulation of newly generated neurons and contributed to the improved neural behavioral performance of animals. In addition, the neuronal differentiation of glial progenitors induced by EGFR inhibitor was further confirmed with two different cell lines either in vitro or through ex vivo transplantation experiment. The inhibition of EGFR signaling pathway under the gliogenic conditions could induce these cells to acquire neuronal phenotypes. Furthermore, we find that the Ras‐ERK axis played a key role in neuronal differentiation of NG2+ glial progenitors upon EGFR inhibition. Taken together, our studies suggest that the EGFR inhibitor could promote neurogenesis post SCI, mainly from the NG2+ glial progenitors. These findings support the possibility of evoking endogenous neuronal replacement from NG2+ glial progenitors and suggest that EGFR inhibition may be beneficial to CNS trauma. © 2012 Wiley Periodicals, Inc.     

PI3K／Akt信号通路对神经元机械性损伤诱导的自噬调节作用

目的研究机械性神经元损伤后自噬的发生情况以及磷脂酰肌醇3激酶（P13K）／蛋白激酶B（Akt,即PKB）信号通路对其发挥的调节作用。方法小鼠皮层神经元原代培养2W后,采用机械性神经元损伤模型,通过蛋白印迹法（Westernblot）定量分析损伤后不同时间点自噬相关分子微管相关蛋白轻链3（LC3）I／II、Beclin-1和Akt蛋白磷酸化的表达情况;使用不同浓度的P13K抑制剂LY294002预处理神经元1h后给予机械性损伤,通过Westernblot来研究自噬相关分子LC3I／Ⅱ和Beclin-1的表达情况。结果自噬相关分子LC311于机械性神经元损伤后3h表达开始逐渐增加,而Beclin-1无明显变化;p-Akt的表达于损伤后3h达到高峰,此后逐渐恢复到正常水平;用P13K抑制剂LY294002预处理神经元,可以使损伤后神经元的自噬相关分子LC3lI和Beclin-1的表达上调。结论机械性神经元损伤可以诱导自噬发生,且PI3K／Akt信号通路在其中可能发挥调节作用。     

Evidence for the role of PI(3) -kinase-AKT-eNOS signalling pathway in secondary inflammatory process after spinal cord compression injury in mice

Endothelial nitric oxide synthase (eNOS) is a dynamic enzyme tightly controlled by co‐ and post‐translational lipid modifications, phosphorylation and regulated by protein–protein interactions. In this study we have pharmacologically modulated the activation of eNOS, at different post‐translational levels, to assess the role of eNOS‐derived NO and regulatory mechanisms in tissue damage associated with spinal cord injury (SCI). SC trauma was induced by the application of vascular clips (force of 24 g) to the dura via a four‐level T5–T8 laminectomy. SCI in mice resulted in severe trauma characterized by oedema, neutrophil infiltration, and production of inflammatory mediators, tissue damage and apoptosis. LY294002, an inhibitor of phosphatidylinositol 3‐kinase that initiates Akt‐catalysed phosphorylation of eNOS on Ser1179, was administered 1 h before the induction of SCI; 24 h after SCI sections were taken for histological examination and for biochemical studies. In this study we clearly demonstrated that pre‐treatment with LY294002 reversed the increased activation of eNOS and Akt observed following SCI, and developed a severe trauma characterized by oedema, tissue damage and apoptosis (measured by TUNEL staining, Bax, Bcl‐2 and Fas‐L expression). Histological damage also correlated with neutrophil infiltration, assessed as myeloperoxidase activity. Overall these results suggest that activation of the Akt pathway in SC tissue subject to SCI is a protective event, triggered in order to protect the injured tissue through a fine tuning of the endothelial NO pathway.     

Rho激酶抑制剂对大鼠脑缺血再灌注后JAK2/STAT3信号传导通路的影响

目的 研究JAK2/STAT3信号通路在脑缺血再灌注损伤后的表达情况,并观察Rho激酶抑制剂Y-27632对其调控作用.方法 建立大鼠脑缺血再灌注模型,应用免疫组织化学染色法检测P-JAK2、P-STAT3在梗死区的表达水平,Tunel法检测神经细胞凋亡数量,观察P-JAK2、p-STAT3表达水平与神经元凋亡的相关性.结果 脑缺血再灌注后P-JAK2以及P-STAT3表达均上调,给予P-JAK2抑制剂以及Y-27632后,P-JAK2、P-STAT3的表达均受到抑制,同时减少了神经元凋亡数量,与模型组比较,差异均有统计学意义（P＜0.05）.结论 脑缺血再灌注后JAK2/STAT3信号通路激活,Y-27632可能通过抑制该通路的激活起到减少神经元凋亡,减轻神经功能缺损等脑保护作用.