Src/p38 MAPK pathway in spinal microglia is involved in mechanical allodynia induced by peri-sciatic administration of recombinant rat TNF-α

Our previous work has shown that peri-sciatic administration of recombinant rat TNF-α (rrTNF) induces mechanical allodynia and up-regulation of TNF-α in the spinal dorsal horn of rats; however, the underlying mechanisms remain unknown. In the current study, we found that the levels of phosphorylated Src-family kinases (p-SFKs) and phosphorylated p38 mitogen-activated protein kinase (p-p38 MAPK) were significantly increased in bilateral lumbar spinal dorsal horn on day 3 after rrTNF administration. Double immunofluorescence staining revealed that p-SFKs and p-p38 MAPK were nearly restricted to the microglia. Intrathecal delivery of SFKs inhibitor PP2 or p38 MAPK inhibitor SB203580, started 30 min before rrTNF administration and given once daily thereafter for 7 days, blocked mechanical allodynia in bilateral hind paws and increase of TNF-α expression in the spinal dorsal horn. Moreover, PP2 inhibited the up-regulation of p-p38 MAPK induced by rrTNF. We also found that intrathecal injection of TNF-α neutralization antibody alleviated mechanical allodynia in bilateral hind paws and suppressed up-regulation of p-SFKs and p-p38 MAPK. These results suggest that activation of the SFKs/p38 MAPK pathway in microglia and subsequent TNF-α expression in the spinal dorsal horn may contribute to the mechanical hyperalgesic state induced by peri-sciatic administered rrTNF.     

蛛网膜下腔出血后大鼠基底动脉p38MAPK信号传导途径研究

目的探讨蛛网膜下腔出血(SAH)后大鼠基底动脉中p38丝裂原活化蛋白激酶(p38MAPK)信号传导通路的活化情况以及与脑血管痉挛(CVS)的关系。方法通过枕大池二次注血方法制作大鼠SAH模型,以免疫组化方法和逆转录酶-多聚酶链反应分析,分别从蛋白、基因水平分析SAH后基底动脉中p38MAPK信号传导通路的活化情况。结果 SAH后大鼠基底动脉逐渐出现痉挛。基底动脉磷酸化p38MAPK表达逐渐增加,3 d时达高峰并持续至第5 d,14 d时恢复正常。p38MAPK基因表达在注血后1 d明显增加,逐渐增加,于5 d时达高峰,14 d仍维持较高水平。结论SAH后大鼠基底动脉中p38MAPK信号传导通路激活,可能诱导CVS的发生。     

ATP induces long-term potentiation of C-fiber-evoked field potentials in spinal dorsal horn: the roles of P2X4 receptors and p38 MAPK in microglia

Many studies have shown that adenosine triphosphate (ATP), as a neurotransmitter, is involved in plastic changes of synaptic transmission in central nervous system. In the present study, we tested whether extracellular ATP can induce long-term potentiation (LTP) of C-fiber-evoked field potentials in spinal dorsal horn. The results showed the following: (1) ATP at a concentration of 0.3 mM induced spinal LTP of C-fiber-evoked field potentials, lasting for at least 5 h; (2) spinal application of 2',3'-O-(2,4,6-trinitrophenyl)adenosine-5-triphosphate (TNP-ATP; an antagonist of P2X(1-4) receptors), but not pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS; an antagonist of P2X(1,2,3,5,7) receptors), 30 min before ATP blocked ATP-induced LTP, indicating that ATP may induce spinal LTP by activation of P2X(4) receptors; (3) at 60 min after LTP induction the level of phospho-p38 mitogen-activated protein kinase (p-p38 MAPK) was significantly elevated and at 180 min after LTP the number of P2X(4) receptors increased significantly; both p-p38 and P2X(4) receptors were exclusively co-located with the microglia marker, but not with neuronal or astrocyte marker; (4) spinal application of TNP-ATP but not PPADS prevented p38 activation; (5) spinal application of SB203580, a p38 MAPK inhibitor, prevented both spinal LTP and the upregulation of P2X(4) receptors. The results suggested that ATP may activate p38 MAPK by binding to intrinsic P2X(4) receptors in microglia, and subsequently enhance the expression of P2X(4) receptors, contributing to spinal LTP.     

Forskolin inhibits expression of inducible nitric oxide synthase mRNA via inhibiting the mitogen activated protein kinase in C6 cells

This study has demonstrated the mechanism of protein kinase A (PKA)-dependent inhibition of astrocytic nitric oxide production and inducible NO synthase mRNA expression induced by lipopolysaccharide. In C6 glioma cells, the stimulation with lipopolysaccharide (LPS; 1 microg/ml) evoked increases of nitric oxide (NO) production, NO synthase (iNOS) mRNA expression, phosphorylation of p38 mitogen activated protein kinase (p-p38), and the activation of NF kappa B. LPS-induced NO production and iNOS mRNA expression were inhibited by the pretreatment with forskolin (FSK; 5 microM) in a dose-dependent manner, and which were reversed by PKA inhibition by compound H89. Furthermore, LPS-induced increases of p-p38, but not activation of NF kappa B, were also reduced by FSK and H89 reversed the FSK-induced inhibition response. The dose-dependent inhibition of NO production and iNOS mRNA expression by compound SB203580 (p38 inhibitor) suggests the participation of p38 in PKA-dependent inhibition of LPS-induced NO production and iNOS mRNA expression. However, the activation of NF kappa B by LPS also not affected by SB203580. Therefore, our results suggest that, in C6 glioma cells, LPS-induced NO production and iNOS gene expression may be regulated by PKA pathway through the reduction of activity of p38 kinase. This inhibitory role of PKA may not involve the activation of NF kappa B.     

Effects of peripheral inflammation on activation of p38 mitogen-activated protein kinase in the rostral ventromedial medulla

In the present study, the activation of p38 mitogen-activated protein kinase (p38 MAPK) in the rostral ventromedial medulla (RVM) following the injection of complete Freund's adjuvant (CFA) into the rat hindpaw was examined in order to clarify the mechanisms underlying the dynamic changes in the descending pain modulatory system after peripheral inflammation. Phospho-p38 MAPK-immunoreactive (p-p38 MAPK-IR) neurons were observed in the nucleus raphe magnus (NRM) and nucleus reticularis gigantocellularis pars alpha (GiA). Inflammation induced the activation of p38 MAPK in the RVM, with a peak at 30 min after the injection of CFA into the hindpaw, which lasted for 1 h. In the RVM, the number of p-p38 MAPK-IR neurons per section in rats killed at 30 min after CFA injection (19.4+/-2.0) was significantly higher than that in the naive group (8.4+/-2.4) [p<0.05]. At 30 min after CFA injection, about 40% of p-p38 MAPK-IR neurons in the RVM were serotonergic neurons (tryptophan hydroxylase, TPH, positive) and about 70% of TPH-IR neurons in the RVM were p-p38 MAPK positive. The number of p-p38 MAPK- and TPH-double-positive RVM neurons in the rats with inflammation was significantly higher than that in naive rats [p<0.05]. These findings suggest that inflammation-induced activation of p38 MAPK in the RVM may be involved in the plasticity in the descending pain modulatory system following inflammation.     

Magnolol protects against trimethyltin-induced neuronal damage and glial activation in vitro and in vivo

Trimethyltin (TMT), an organotin with potent neurotoxic effects by selectively damaging to hippocampus, is used as a tool for creating an experimental model of neurodegeneration. In the present study, we investigated the protective effects of magnolol, a natural biphenolic compound, on TMT-induced neurodegeneration and glial activation in vitro and in vivo. In HT22 murine neuroblastoma cells, TMT induced necrotic/apoptotic cell death and oxidative stress, including intracellular reactive oxygen species (ROS), protein carbonylation, induction of heme oxygenase-1 (HO-1), and activation of all mitogen-activated protein kinases (MAPKs) family proteins. However, magnolol treatment significantly suppressed neuronal cell death by inhibiting TMT-mediated ROS generation and activation of JNK and p38 MAPKs. In BV-2 microglial cells, magnolol efficiently attenuated TMT-induced microglial activation via suppression of ROS generation and activation of JNK, p38 MAPKs, and nuclear factor-κB (NF-κB) signaling. In an in vivo mouse study, TMT induced massive neuronal damage and enhanced oxidative stress at day 2. We also observed a concomitant increase in glial cells and inducible nitric oxide synthase (iNOS) expression on the same day. These features of TMT toxicity were reversed by treatment of magnolol. We observed that p-JNK and p-p38 MAPK levels were increased in the mouse hippocampus at day 1 after TMT treatment and that magnolol blocked TMT-induced JNK and p38 MAPK activation. Magnolol administration prevented TMT-induced hippocampal neurodegeneration and glial activation, possibly through the regulation of TMT-mediated ROS generation and MAPK activation.     

p38丝裂原活化蛋白激酶在实验性蛛网膜下腔出血后早期脑损伤中的作用

目的探讨p38丝裂原活化蛋白激酶(p38MAPK)在蛛网膜下腔出血(SAH)后早期脑损伤(EBI)中的作用。方法成年雄性SD大鼠随机分配至对照组、SAH组及p38MAPK干预组,每组18只。采用血管内穿刺法制作SAH模型,干预组于术前30 min经侧脑室注射p38MAPK特异性抑制剂SB203580,造模后24 h处死。观察各组大鼠脑含水量和神经功能评分,RT-PCR及免疫组化检测脑组织p38MAPK表达。结果与对照组相比,SAH组大鼠脑含水量(t=-196.35,P0.01)及p38 MAPK的mRNA水平(t=-24.75,P0.01)均明显升高,神经功能评分明显减低(t=201.08,P0.01)。与SAH组相比,干预组脑含水量(t=75.67,P0.01)及p38 MAPK的mRNA水平(t=9.43,P0.01)均明显下降,神经功能评分明显升高(t=-81.68,P0.01)。免疫组化示SAH组及干预组均有p38MAPK表达,但干预组较SAH组表达水平明显下降(t=-3.37,P0.01)。结论 p38 MAPK在EBI形成机制中起重要作用,有望成为防治EBI的药物作用新靶点。     

Cross-talk between cell cycle induction and mitochondrial dysfunction during oxidative stress and nerve growth factor withdrawal in differentiated PC12 cells

Neuronal death has been reported to involve mitochondrial dysfunction and cell cycle reentry. In this report, we used Nerve Growth Factor (NGF)-differentiated PC12 cells to investigate mechanisms linking mitochondrial dysfunction and cell cycle activation during neuronal death induced by NGF withdrawal and/or oxidative stress. We found that loss of survival following H(2) O(2) -induced oxidative stress or NGF deprivation was preceded by a decrease in mitochondrial membrane potential (ΔΨm), increase in reactive oxygen species (ROS), and up-regulation of cyclin D1 and phosphorylation (Ser-780) of protein retinoblastoma (P-pRb), without an increase of proliferation rates. Treatment with H(2) O(2) , but not NGF deprivation, also induced the phosporylation (Ser-10) of p27(kip1) and the appearance of a cleaved P-p27(kip1) fragment of about 15 kDa. The extent of cell cycle activation appeared to be inversely correlated to the duration of toxic stimuli (pulse/continuous). H(2) O(2) -induced mitogenic responses appeared to be mediated by induction of P-MAPK and P-Akt and were blocked by p38MAPK and JNK inhibitors as well as by the CDK inhibitor flavopiridol (Flav) and by sodium selenite (Sel), a component of selenoproteins, including glutathione peroxidases. Inhibition of p38MAPK and JNK, instead, did not affect cyclin D1 changes following NGF deprivation. Finally, both Flav hydrochloride and Sel partially prevented mitochondrial dysfunction and cell death following NGF withdrawal or H(2) O(2) toxicity, but not during oxidative stress in the absence of NGF. Taken together, these data suggest that H(2) O(2) -induced oxidative stress can determine distinct patterns of mitogenic responses as a function of mitochondrial dysfunction depending on 1) intensity/duration of stress stimuli and/or 2) presence of NGF.     

p38 activation in uninjured primary afferent neurons and in spinal microglia contributes to the development of neuropathic pain induced by selective motor fiber injury

Compelling evidence shows that the adjacent uninjured primary afferents play an important role in the development of neuropathic pain after nerve injury. The underlying mechanisms, however, are largely unknown. In the present study, the selective motor fiber injury was performed by L5 ventral root transection (L5 VRT), and p38 activation in dorsal root ganglia (DRG) and L5 spinal dorsal horn was examined. The results showed that phospho-p38 immunoreactivity (p-p38-IR) was increased in both L4 and L5 DRGs, starting on day 1 and persisting for nearly 3 weeks (P<0.05) following L5 VRT and that the activated p38 was confined in neurons, especially in IB4 positive C-type neurons. L5 VRT also induced p38 activation in L5 spinal dorsal horn, occurred at the first day after the lesion and lasted for 2 weeks (P<0.05). The activated p38 is restricted entirely in spinal microglia. In contrast, selective injury of sensory neurons by L5 dorsal root transection (L5 DRT) failed to induce behavioral signs of neuropathic pain and activated p38 only in L5 DRG but not in L4 DRG and L5 spinal dorsal horn. Intraperitoneal injection of thalidomide, an inhibitor of TNF-alpha synthesis, prevented p38 activation in DRG and spinal cord. Intrathecal injection of p38 inhibitor SB203580, starting before L5 VRT, inhibited the abnormal pain behaviors. Post-treatment with SB203580 performed at the 1st day or at the 8th day after surgery also reduced established neuropathic pain. These data suggest that p38 activation in uninjured DRGs neurons and in spinal microglia is necessary for the initiation and maintenance of neuropathic pain induced by L5 VRT.     

p38MAPK信号通路在小胶质细胞激活介导多巴胺能神经元变性中的作用研究

目的:研究p38丝裂原激活蛋白激酶(p38MAPK)在脂多糖(LPS)诱导小胶质细胞激活介导多巴胺(DA)能神经元变性中的作用。方法:脑立体定位注射LPS于大鼠脑黑质,Western blot印记法检测不同时间点(0、0.5h、1h、6h、12h)黑质p38磷酸化水平。酪氨酸羟化酶(Tyrosine hydroxylase,TH)免疫组织化学染色观察蛋白激酶(MAPK)特异性抑制剂SB203580预处理后LPS对DA能神经元变性的影响。结果:黑质注射LPS后,Western blot结果显示p38MAPK总体蛋白水平在各组均存在表达,无显著性差异(P>0.05),而其磷酸化p-p38MAPK却发生了明显变化。正常对照组和PBS注射侧几乎无p-p38的表达,LPS注射后30min,p-p38即有少量的表达;1h表达量增加;6h表达量达高峰;12h后表达量逐渐下降。与PBS对照侧相比,LPS注入黑质导致TH阳性细胞数下降至38%;SB203580预处理可以显著增加TH+细胞数达63%(P<0.05)。结论:p38MAPK信号通路参与了LPS诱导小胶质细胞激活介导DA能神经元变性,可通过阻断信号通路来减轻LPS诱导DA能神经元变性,为PD治疗提供新的思路。     

Down‐regulation of Bcl‐2 enhances autophagy activation and cell death induced by mitochondrial dysfunction in rat striatum

In vivo administration of the mitochondrial inhibitor 3‐nitropropionic acid (3‐NP) produces striatal pathology mimicking Huntington's disease (HD). However, the mechanisms of cell death induced by metabolic impairment are not fully understood. Previous studies showed that 3‐NP triggered p53‐depedent autophagy activation and cell death. The present study investigated the contribution of the Bcl‐2 signaling pathway to autophagy activation and cell death induced by 3‐NP. Rat striatum was intoxicated with 3‐NP by stereotaxic injection. 3‐NP up‐regulated the expression of the autophagic protein beclin 1 but down‐regulated the expression of the antiapoptotic protein Bcl‐2. Pretreatment with the autophagy inhibitor 3‐methyladenine (3‐MA) significantly inhibited the 3‐NP‐induced alterations in beclin 1 and Bcl‐2 protein levels. Similarly, the 3‐NP‐induced decline in Bcl‐2 was also prevented by the lysosomal inhibitor E64, indicating degradation of Bcl‐2 by lysosomes. In agreement with the time course of 3‐NP‐induced cell death, an increase in the release of cytochrome c from mitochondria was observed. 3‐MA also attenuated the 3‐NP‐induced release of cytochrome c. On the other hand, 3‐NP‐induced elevations in proapoptotic protein Bax and autophagic protein beclin 1 and LC3‐II were significantly enhanced by the Bcl‐2‐specific inhibitor HA14‐1. Furthermore, HA14‐1 increased the release of cytochrome c and 3‐NP‐induced striatal damage. These results suggest that induction of autophagy leads to degradation of Bcl‐2. Meanwhile, down‐regulation of Bcl‐2 amplifies autophagy activation and apoptotic signaling. Bcl‐2 thus plays important roles in mitochondria dysfunction‐induced apoptotic death of stritatal neurons by modulating both autophagic and apoptotic processes. © 2009 Wiley‐Liss, Inc.     

Activation of p38 MAPK participates in brain ischemic tolerance induced by limb ischemic preconditioning by up-regulating HSP 70

This study investigates whether activation of p38 MAPK by the up-regulation of HSP 70 participates in the induction of brain ischemic tolerance by limb ischemic preconditioning (LIP). Western blot and immunohistochemical assays indicated that p38 MAPK activation occurred earlier than HSP 70 induction in the CA1 region of the hippocampus after LIP. P-p38 MAPK expression was up-regulated at 6 h and reached its peak 12 h after LIP, while HSP 70 expression was not significantly increased until 1 day and peaked 2 days after LIP. Neuropathological evaluation by thionin staining showed that quercetin (4 ml/kg, 50 mg/kg, intraperitoneal injection), an inhibitor of HSP 70, blocked the protective effect of LIP against delayed neuronal death that is normally induced by lethal brain ischemic insult, indicating that HSP 70 participates in the induction of brain ischemic tolerance by LIP. Furthermore, SB 203580, an inhibitor of HSP 70, inhibited HSP 70 activation in the CA1 region of the hippocampus induced by LIP either with or without the presence of subsequent brain ischemic insult. Based on the above results, it can be concluded that activation of p38 MAPK participates in the brain ischemic tolerance induced by LIP at least partly by the up-regulation of HSP 70 expression.     

大鼠蛛网膜下腔出血致多器官功能障碍综合征延髓内脏带FOS蛋白的表达及迷走神经的作用研究

目的 观察大鼠蛛网膜下腔出血(SAH)致多器官功能障碍综合征(MODS)并/不并迷走神经切断时延髓内脏带(MVZ)FOS蛋白的表达规律,探讨MVZ和迷走神经在SAH致MODS中的可能调控机制.方法 Willis环注血法建立SAH致MODS模型,膈下迷走神经切断法阻断迷走神经,免疫组织化学法检测MVZ内FOS蛋白的表达.结果 (1)SAH组和SAH+SDV组MVZ内FOS阳性表达明显高于正常对照组、假手术组、SDV组(P<0.01).但SAH+SDV组明显少于SAH组(P<0.01),两组FOS蛋白表达均在24h达峰.(2)SAH组和SAH+SDV组各时相点各脏器存在不同程度的炎性损害,以24～36h病理改变最显著,与FOS蛋白的表达峰值一致,而且SAH+SDV组的炎性损害较SAH组更明显、持久.结论 (1)SAH后各周围脏器的炎性改变与MVZ内FOS蛋白的表达规律相一致,提示MVZ参与了SAH后周围脏器功能的调控,是SAH致MODS的直接调控中枢之一;(2)膈下迷走神经切断增加了SAH后MODS的发生率,增强了SAH所致的周围脏器的炎性损害,提示迷走神经在SAH致MODS时对周围脏器具有潜在的保护作用.

Abstract：

Objective To investigate FOS protein expression in the medullary visceral zone( MVZ) of the rats following subarachnoid hemorrhage ( SAH) complicated with multiple organ dysfunction syndrome ( MODS ) which complicated or uncomplicated by vagotomy,and to discuss the possible pathogenesis of MVZ and vagus nerve in the rats following SAH complicated with MODS. Methods SAH was induced in rats by injecting arterial blood through the circle of willis. The vagus never was blocked in rats from subdlaphragamatic vagotomy. The area density of positive staining expressing FOS protein were analyzed for the relative content of immunohistochemistry. Results (1) In the MVZ, the expression in FOS protein in SAH and SAH + SDV groups were all obviously more than control group, sham-operative group and SDV group ( P < 0. 01). But the expression in SAH + SDV group were fewer and sparser than SAH group( P < 0. 01) . FOS protein expressed in SAH and SAH + SDV groups showed time progress and reached peak at 24h after SAH. (2) After SAH there are various inflammatory lesions on the organ tissue at every time point in SAH group and SAH + SDV group. The organ has significantly pathological changes at 24 ～ 36h point which is at equal pace the regularity of the expression of FOS protein. But the inflammatory lesions in SAH + SDV group was more serious and persistent than that in SAH group. Conclusions ( 1) There was the consistency between FOS protein expression and histological changes of each organ after SAH. It cued that MVZ may be one of the direct regulative centre after SAH by MODS. ( 2 ) Subdlaphragamatic vagotomy can add the incidences of MODS after SAH and can aggravate the imflamming lesions of peri-organs. Vagus never can protect peri-organs potatially when SAH complicated by MODS.     

依达拉奉对SAH大鼠JNK信号通路及海马区神经细胞自噬的影响

目的探讨依达拉奉对蛛网膜下腔出血大鼠JNK信号通路及海马区神经细胞自噬的影响。方法雄性SD大鼠40只,随机等分为假手术组(Sham组)、SAH模型组、依达拉奉治疗组(Edaravone组)、JNK抑制剂组(SP600125组)。改良血管内穿刺法制成大鼠SAH模型;SP600125组于建模前30min,侧脑室注射SP600125(3μg/μl,10μl);Edaravone组于建模后5mg/kg Edaravone腹腔注射,12 h后重复给药。24h处死,检测各组海马区神经元形态、数量及Beclin-1、LC3-Ⅱ、p-JNK蛋白的变化。结果与Sham组相比,SAH组海马区神经元排列紊乱、细胞多呈三角锥形、存活数量明显减少,(P0.05);Beclin-1、LC3-Ⅱ、p-JNK表达升高,(P0.05)。与SAH组相比,Edaravone组、SP600125组神经元坏死率明显下降、形态正常细胞数增多,(P0.05);Beclin-1、LC3-Ⅱ、p-JNK表达明显降低,(P0.05)。结论依达拉奉可降低SAH大鼠海马区神经元Beclin-1和LC3-Ⅱ表达,减轻SAH后早期脑损伤,其可能是JNK通路依赖性的。     

Pink1 deficiency attenuates astrocyte proliferation through mitochondrial dysfunction,reduced akt and increased p38 mapk activation,and downregulation of egfr

PINK1 (PTEN induced putative kinase 1), a familial Parkinson's disease (PD)‐related gene, is expressed in astrocytes, but little is known about its role in this cell type. Here, we found that astrocytes cultured from PINK1‐knockout (KO) mice exhibit defective proliferative responses to epidermal growth factor (EGF) and fetal bovine serum. In PINK1‐KO astrocytes, basal and EGF‐induced p38 activation (phosphorylation) were increased whereas EGF receptor (EGFR) expression and AKT activation were decreased. p38 inhibition (SB203580) or knockdown with small interfering RNA (siRNA) rescued EGFR expression and AKT activation in PINK1‐KO astrocytes. Proliferation defects in PINK1‐KO astrocytes appeared to be linked to mitochondrial defects, manifesting as decreased mitochondrial mass and membrane potential, increased intracellular reactive oxygen species level, decreased glucose‐uptake capacity, and decreased ATP production. Mitochondrial toxin (oligomycin) and a glucose‐uptake inhibitor (phloretin) mimicked the PINK1‐deficiency phenotype, decreasing astrocyte proliferation, EGFR expression and AKT activation, and increasing p38 activation. In addition, the proliferation defect in PINK1‐KO astrocytes resulted in a delay in the wound healing process. Taken together, these results suggest that PINK1 deficiency causes astrocytes dysfunction, which may contribute to the development of PD due to delayed astrocytes‐mediated repair of microenvironment in the brain.     

抑制低密度脂蛋白受体相关蛋白2表达对Alzheimer's病细胞模型丝裂原活化蛋白激酶信号通路影响的机制研究

目的探讨低密度脂蛋白受体相关蛋白2(LRP2)在β淀粉样蛋白(Aβ)诱导的Alzheimer’s病(AD)细胞模型中的表达情况,及调控LRP2表达后对神经元存活影响及其对丝裂原活化蛋白激酶(MAPKs)信号通路的影响。方法采用20μmol Aβ1-42处理的神经母细胞瘤(SH-SY5Y)细胞作为AD细胞模型。采用Western blotting法检测LRP2蛋白表达情况。Scrambled siRNA和LRP2 siRNA(si LRP2)分别转染SH-SY5Y细胞48 h,随后予以Aβ1-42处理24 h,采用噻唑蓝比色法检测细胞活力,流式细胞仪检测细胞凋亡情况,Western blotting法检测ERK、p38及JNK的磷酸化水平。结果si LRP2+Aβ组细胞活力显著低于SC+Aβ组(P<0.05)。与处理前比较,Aβ1-42处理后LRP2蛋白表达水平显著降低(P<0.05)。与空白对照组比较,siRNA-1组、siRNA-2组LRP2 mRNA及蛋白表达水平均显著降低(P<0.05~0.01)。SC+Aβ组细胞凋亡率显著低于si LRP2+Aβ组(P<0.01)。SC+Aβ组及si LRP2+Aβ组(p-ERK1/2)/ERK与SC组及si LRP2组比较,差异无统计学意义(均P>0.05)。与SC+Aβ组相比,si LRP2+Aβ组(p-ERK1/2)/ERK亦无统计学差异(P>0.05)。SC+Aβ组及si LRP2+Aβ组p-p38/p38显著高于SC组及si LRP2组(均P<0.01)。与SC+Aβ组相比,si LRP2+Aβ组p-p38/p38无统计学差异(P>0.05)。SC+Aβ组及si LRP2+Aβ组p-JNK/JNK显著高于SC组及si LRP2组(均P<0.01)。与SC+Aβ组比较,si LRP2+Aβ组p-JNK/JNK显著增高(P<0.01)。未经JNK抑制剂处理的SC组、si LRP2组细胞的Cleaved Caspase-3相对表达与经JNK抑制剂处理的细胞差异无统计学意义(均P>0.05)。结论抑制LRP2后促进Aβ诱导的细胞凋亡,并且这种效应与ERK、p38磷酸化无明显相关,与JNK磷酸化相关,但JNK抑制剂不能逆转LRP2抑制导致的凋亡增加,提示JNK信号通路可能不直接发挥作用。     

NF-κB,ERK, p38 MAPK and JNK contribute to the initiation and/or maintenance of mechanical allodynia induced by tumor necrosis factor-alpha in the red nucleus

Previous studies have demonstrated that tumor necrosis factor-alpha (TNF-α) in the red nucleus (RN) plays facilitated roles in the development of abnormal pain. Here, the roles of nuclear factor-kappa B (NF-κB), extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) in TNF-α-evoked mechanical allodynia were investigated. Repeated microinjection of recombinant rat TNF-α (20 ng daily for 3 days) into the unilateral RN of normal rats induced a significant mechanical allodynia in the contralateral but not ipsilateral hind paw at the fifth day and disappeared 24 h later. Re-injection of a single bolus of 20 ng TNF-α into the same RN reproduced this mechanical allodynia within 30 min, which was used as a pain model for further experiments. Immunohistochemistry demonstrated that NF-κB, phospho-ERK (p-ERK) and p-p38 MAPK in the RN were significantly up-regulated at 1 h after TNF-α microinjection, the up-regulations of NF-κB and p-ERK but not p-p38 MAPK remained at high levels till 4 h later. A significant up-regulation of p-JNK occurred at 4 h (but not 1 h) after TNF-α microinjection, which was later than those of NF-κB, p-ERK and p-p38 MAPK. Pre-treatment with NF-κB inhibitor PDTC, ERK inhibitor PD98059 or p38 MAPK inhibitor SB203580 at 30 min before TNF-α microinjected into the RN completely prevented TNF-α-evoked mechanical allodynia. Pre-treatment with JNK inhibitor SP600125 did not prevent but reversed TNF-α-evoked mechanical allodynia during the subsequent detection time. Post-treatment with PDTC, PD98059 or SP600125 (but not SB203580) at 4 h after TNF-α microinjected into the RN significantly reversed TNF-α-evoked mechanical allodynia. These results further prove that TNF-α in the RN plays a crucial role in the development of abnormal pain, and the algesic effect of TNF-α is initiated through activating NF-κB, ERK and p38 MAPK. The later maintenance of TNF-α-evoked mechanical allodynia mainly relies on the activation of NF-κB, ERK and JNK, but not p38 MAPK.     

Differential activation of MAPK in injured and uninjured DRG neurons following chronic constriction injury of the sciatic nerve in rats

To investigate the intracellular signal transduction pathways involved in the pathophysiological mechanisms of neuropathic pain after partial nerve injury, we examined the activation of extracellular signal-regulated protein kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) in the dorsal root ganglion (DRG) in the chronic constriction injury (CCI) model. The CCI induced an increase in the phosphorylation of ERK in predominantly injured medium-sized and large-sized DRG neurons and in satellite glial cells. Treatment with the MAPK kinase 1/2 inhibitor, U0126, suppressed CCI-induced mechanical allodynia and partially reversed the increase in neuropeptide Y (NPY) expression in damaged DRG neurons. In contrast, the CCI induced the activation of p38, mainly in uninjured small-to-medium-diameter DRG neurons and in satellite glial cells. The p38 inhibitor, SB203580, reversed the CCI-induced heat hyperalgesia and also the increase in brain-derived neurotrophic factor (BDNF) expression in intact DRG neurons. On the other hand, the nerve growth factor (NGF)-induced increase in BDNF expression in small-to-medium-diameter neurons was reversed by SB203580, whereas the anti-NGF-induced increase in NPY in medium-sized and large-sized neurons was partially blocked by U0126. Taken together, our results demonstrate that the activation of ERK and p38 and also the changes in NPY and BDNF expression may occur in different populations of DRG neurons after CCI, partially through alterations in the target-derived NGF. These changes in injured and intact primary afferents are likely to have a substantial role in pathological states, and MAPK pathways in nociceptors may be potential targets for the development of novel analgesics.     

Role of autophagy in early brain injury after experimental subarachnoid hemorrhage

Autophagy is a self-degradative process and it plays a housekeeping role in removing misfolded or aggregated proteins, clearing damaged organelles, and eliminating intracellular pathogens. Previous studies have demonstrated that autophagy pathway was activated in brain after experimental subarachnoid hemorrhage (SAH); however, the role of autophagy in the pathogenesis of early brain injury (EBI) following SAH remains unknown. Experiment 1 aimed to investigate the time–course of the autophagy in the cortex following SAH. In experiment 2, we chose the maximum time pointof autophagy activation and assessed the effects of rapamycin (RAP, autophagy activator) and 3-methyladenine (3-MA, autophagy inhibitor) on regulation of EBI. All SAH animals were subjected to injection of 0.3 ml fresh arterial, nonheparinized blood into prechiasmatic cistern in 20 s. As a result, microtubule-associated protein light chain-3 (LC3), a biomarker of autophagosome, and beclin-1, a Bcl-2-interacting protein required for autophagy, were significantly increased at the early stage of SAH and their expressions peaked at 24 h after SAH. In RAP-treated group, the early brain damage such as brain edema, blood–brain barrier (BBB) impairment, cortical apoptosis, and clinical behavior scale was significantly ameliorated in comparison with vehicle-treated SAH rats. Conversely, 3-MA decreased expression of LC3 and beclin-1, increased the average value of brain edema and BBB disfunction, and aggravated neurological deficits. Our results suggest that autophagy pathway is activated in the brain after SAH and may play a beneficial role to EBI development.