Intrastriatal administration of erythropoietin protects dopaminergic neurons and improves neurobehavioral outcome in a rat model of Parkinson's disease

Erythropoietin (EPO), a hematopoietic cytokine, has recently been demonstrated to protect nigral dopaminergic neurons in a mouse model of Parkinson's disease (PD). In the present study, we tested the hypothesis that recombinant human erythropoietin (rhEPO) could protect dopaminergic neurons and improve neurobehavioral outcome in a rat model of PD. rhEPO (20 units in 2 microl of vehicle) was stereotaxically injected into one side of the striatum. 6-hydroxydopamine (6-OHDA) was injected into the same side 1 day later. Another group of rats received rhEPO (5000 u/kg, i.p.) daily for 8 days, and unilateral injection of 6-OHDA in the striatum 3 days after systemic administration of rhEPO. We observed that intrastriatal administration, but not systemic administration of rhEPO significantly reduced the degree of rotational asymmetry. The rhEPO-treated rats also showed an improvement in skilled forelimb use when compared with control rats. The number of tyrosine hydroxylase (TH)-immunoreactive (IR) neurons in the ipsilateral substantia nigra (SN) was significantly larger in intrastriatal rhEPO-treated rats than that in control rats. TH-IR fibers in the 6-OHDA-lesioned striatum were also increased in the intrastriatal rhEPO-treated rats when compared with control rats. In addition, there were lower levels of expression of major histocompatibility complex (MHC) class II antigens and a smaller number of activated microglia in the ipsilateral SN in intrastriatal rhEPO-treated rats than that in control rats at 2 weeks, suggesting that intrastriatal injection of rhEPO attenuated 6-OHDA-induced inflammation in the ipsilateral SN. Our results suggest that intrastriatal administration of rhEPO can protect nigral dopaminergic neurons from cell death induced by 6-OHDA and improve neurobehavioral outcome in a rat model of PD. Anti-inflammation may be one of mechanisms responsible for rhEPO neuroprotection.     

Selective inhibition of cyclooxygenase-2 exacerbates methamphetamine-induced dopamine depletion in the striatum in rats

Neuroinflammatory processes associated with induction of cyclooxygenase (COX) have been implicated in the deleterious events resulting in neurodegeneration. The present study was designed to investigate the impact of acute methamphetamine (MA) administration on COX expression and prostaglandin E2 (PGE₂) production, and to evaluate the effect of selective COX-2 inhibition using celecoxib in MA-induced degeneration of dopaminergic terminal and cell apoptosis in the striatum. Male Sprague–Dawley rats were treated with either a neurotoxic regimen of methamphetamine hydrochloride (5 mg/kg, i.p., every 2 h for four injections) with or without celecoxib (7.5 mg/kg) or vehicle. COX-1 expression was not affected by MA, while both COX-2 protein expression and number of COX-2 positive cells in striatum were significantly reduced 24 h after MA treatment. However, after 72 h, a significant upregulation of COX-2 protein was detected. PGE₂ production was correlated with altered COX-2 levels. NFkappa-B (NFκB), a key regulator of COX-2 expression, was activated 72 h after MA administration, and was accompanied by increased Ikappa B (IκB) phosphorylation. Animals receiving MA exhibited an increase in apoptotic cells and notable reductions in dopamine (DA) content (63.9%) in immunoreactivity of tyrosine hydroxylase (TH) and neuron specific microtubule-associated protein 2 (MAP2) in striatum. Administration of celecoxib exacerbated MA-induced DA depletion, and did not affect MA-induced MAP2 damage, apoptosis or proliferation of glial cells. Our findings suggest that COX-2 containing cells are targets of the damage during earlier stages of MA-related neurotoxicity, and that the selective inhibition of COX-2 enzyme is harmful rather than protective. The COX-2 induction appears during the recovery period, and NFκB activation may be an important mechanism.     

Meloxicam reduces lipopolysaccharide-induced degeneration of dopaminergic neurons in the rat substantia nigra pars compacta

Inflammation is believed to play an important role in the etiology and pathogenesis of Parkinson's disease (PD). However, experimental and epidemiological evidences from various non-steroidal anti-inflammatory drugs, including cyclooxygenase-2 (COX-2) inhibitors, seem contradictive. Using the intranigral lipopolysaccharide (LPS) rat model, we show that meloxicam, a preferential COX-2 inhibitor, diminishes the activation of OX-42-immunoreactive (ir) microglia and reduces the loss of tyrosine hydroxylase (TH)-ir dopamine (DA) neurons in the substantia nigra pars compacta (SNpc) that is normally induced by exposure to LPS. Double-labelling immunohistochemistry identified that activated microglia rather than intact resting microglia are the main intracellular venues for COX-2 expression. These findings suggest that inhibition of COX-2 activity in activated microglial cells may be potentially neuroprotective for DA neurons in the SNpc.     

脑血疏口服液灌胃对帕金森病模型大鼠黑质内神经炎症反应的影响

目的:研究脑血疏口服液对帕金森病(PD)模型大鼠黑质内神经炎症的抑制作用,以及对黑质多巴胺(DA)能神经元的保护作用。方法:应用立体定向注射技术,向大鼠脑右侧纹状体内注射6-羟多巴胺制备PD模型。将PD模型大鼠随机分为PD组、雷沙吉兰组和脑血疏口服液高、中、低剂量干预组,每组10只;另选10只正常大鼠作为对照组。采用免疫组织化学法检测各组大鼠黑质DA能神经元(酪氨酸羟化酶(TH)阳性)、小胶质细胞(CD11b阳性)、星形胶质细胞(GFAP阳性)形态变化。Western Blot法检测中脑黑质环氧化酶-2(COX-2)和肿瘤坏死因子-α(TNF-α)的变化。结果:大鼠行为学检测和黑质TH免疫组织化学染色显示,中剂量组的干预效果最好。免疫组织化学显示,与对照组相比,PD组的星形胶质细胞、小胶质细胞、TNF-α阳性细胞和COX-2阳性细胞均明显增加,TH阳性细胞数量明显减少,经中剂量的脑血疏口服液干预后,两种胶质细胞、TNF-α和COX-2阳性细胞数量均减少,TH阳性细胞增多。Western Blot显示,与PD组比较,中剂量组和雷沙吉兰组GFAP、CD11b、TNF-α和COX-2蛋白表达量显著减少(P0.05),而中剂量组与雷沙吉兰组比较上述蛋白表达均无显著差异(P0.05)。结论:脑血疏口服液可能通过抑制PD大鼠黑质胶质细胞的异常激活,减少炎性因子分泌而发挥神经保护作用。     

血管活性肠肽对帕金森病大鼠黑质胶质细胞活化及相关炎性因子释放的影响

目的探讨血管活性肠肽(VIP)对帕金森病(PD)大鼠模型中脑黑质胶质细胞活化及相关炎性因子表达的影响。方法将6-羟多巴胺(6-OHDA)定向注入大鼠右侧纹状体制备PD模型。32只制备成功的PD大鼠随机分为VIP组和模型组,VIP组大鼠腹腔注射VIP 1ml(20μg/L),另10只正常大鼠为对照组。分别采用免疫组织化学、Western blotting、RT-PCR方法观察大鼠中脑黑质多巴胺(DA)能神经元、小胶质细胞、星形胶质细胞的数量和形态变化以及肿瘤坏死因子α(TNF-α)和环氧化酶2(COX-2)的表达变化。结果模型组大鼠黑质损毁侧小胶质细胞即白细胞分化抗原11b(CD11b)阳性细胞,数量较对照组明显增加(P0.05)并呈阿米巴样改变,星形胶质细胞(GFAP阳性细胞)数量明显增加(P0.05),炎性因子表达水平也明显上升(P0.05),DA能神经元数量较对照组明显下降(P0.05);与模型组相比,VIP组大鼠损毁侧黑质小胶质细胞和星形胶质细胞数量明显下降(P0.05),炎性因子表达水平显著降低(P0.05),DA能神经元数量较模型组增加(P0.05)。结论 VIP对帕金森病大鼠黑质小胶质细胞和星形胶质细胞的活化具有抑制作用,并可减少相关炎症因子的表达,从而保护黑质DA能神经元。     

The flavanoide caffeic acid phenethyl ester blocks 6-hydroxydopamine-induced neurotoxicity

Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive loss of dopaminergic (DA) neurons of the substantia nigra pars compacta. 6-Hydroxydopamine (6-OHDA) is specific to dopaminergic neurons in intrastriatal rodent models. It induces neuronal death either via uncoupling mitochondrial oxidative phosphorylation resulting in energy deprivation or alternatively, is associated with its ability to produce hydrogen peroxide, hydroxyl and superoxide radicals. Caffeic acid phenethyl ester (CAPE), an antioxidant flavanoid, has antiviral, anti-inflammatory, antioxidant, and immunomodulatory properties. Recent studies have shown that CAPE has also a neuroprotective effects in ischemia and low potassium-induced neuronal apoptotic models. In cerebellar granule neurons CAPE significantly blocks 6-OHDA mediated cell death (70 microM) in a dose-dependent manner. Furthermore, CAPE was able to modulate the Ca(2+)-induced release of cyctochrome c in isolated liver mitochondria. Caspase-3 activation following 6-OHDA treatment was markedly inhibited in the presence of CAPE. Although the molecular mechanisms associated with CAPE's neuroprotective effects remain to be elucidated in more detail, our results clearly demonstrate a considerable neuroprotective effect of CAPE. Since a mitochondrial insult is a major cause for the degeneration of nigral neurons in PD, we hypothesize that propolis derivatives, in particular CAPE, may have a neuroprotective effect on those cells and may be a promising drug candidate to be taken into in vivo models of PD.     

6-Hydroxydopamine as a tool to understand adaptive immune system-induced dopamine neurodegeneration in Parkinson's disease

Abstract

Context: Neuroimmunological response is associated with neurodegeneration in the human substantia nigra (SN) in Parkinson’s disease (PD).

Objective: To explore the possibility that the neurotoxin, 6-hydroxydopamine (6-OHDA), could be used as a tool in mice to understand the immune response in PD.

Materials and methods: We employed unilateral administration of 6-OHDA into the mouse SN. At 1 week, 2 weeks and 4 weeks post-injection, we used immunohistochemistry for the markers Iba-1 and gp91PHOX to investigate activated microglia in the SN. To examine the adaptive immune response, we used immunohistochemistry for CD3-positive T-lymphocytes, CD45R-positive B-lymphocytes and anti-mouse immunoglobulin-G (IgG). Dopamine neuron loss was examined using immunohistochemistry for the dopamine neuron marker, tyrosine hydroxylase.

Results: Compared to vehicle, 6-OHDA administration induced an intense IgG deposition in the SN as well as increased infiltration of both T- and B- lymphocytes into the injected side of the midbrain. The adaptive immune response was associated with extensive destruction of dopamine neurons and extensive microglial activation at every time point in the 6-OHDA groups.

Conclusion: Our results suggest that 6-OHDA administration in mice can a potential tool for understanding mechanisms underlying adaptive immune activation-induced neurodegeneration in PD.     

6-羟多巴诱导大鼠黑质的持续胶质细胞反应

本研究将40μg6- 羟多巴注射到SD大鼠一侧纹状体制作Parkinson病动物模型,研究黑质反应性神经胶质增生在Par kinson病发病过程中的可能作用。筛选成功的模型大鼠,术后12周处死。应用免疫荧光双标记法检测模型大鼠黑质胶质细胞对多巴胺能神经元损伤的反应。结果显示:在注射后12周,损伤侧黑质仍然存在明显的星形胶质细胞反应和小胶质细胞激活。此外,小胶质小结和淋巴细胞浸润的存在提示在注射后12周的注射侧黑质内依然有多巴胺能神经元死亡。结论: 6 -羟多巴对大鼠黑质多巴胺能神经元的急性损伤可以通过胶质细胞反应从而对多巴胺能神经元产生长期的毒性作用。     

Parkin protects human dopaminergic neuroblastoma cells against dopamine-induced apoptosis

Parkinson's disease (PD) is characterized by the selective degeneration of dopaminergic (DA) neurons in substantia nigra pars compacta (SNpc). A combination of genetic and environmental factors contributes to such a specific loss. Among the five PD-linked genes identified so far, parkin, a protein-ubiquitin E3 ligase, appears to be the most prevalent genetic factor in PD. Although a variety of substrates have been identified for parkin, none of them is selectively expressed in nigral DA neurons. It remains unclear how accumulation of these substrates in the absence of functional parkin may cause the selective death of DA neurons in SNpc. Here, we show that overexpression of parkin protected human DA neuroblastoma cell line (SH-SY5Y) against apoptosis induced by DA or 6-OHDA, but not by H(2)O(2) or rotenone. Parkin significantly attenuated dopamine-induced activation of c-Jun N-terminal kinase (JNK) and caspase-3. It also decreased the level of reactive oxygen species (ROS) and protein carbonyls in the cell. Inhibiting DA uptake through dopamine transporter or treating the cell with antioxidants significantly reduced oxidative stress and dopamine toxicity. Furthermore, PD-linked mutations of parkin significantly abrogated the protective effect of wild-type parkin, as well as its ability to suppress ROS and protein carbonylation. These results suggest that parkin protects against dopamine toxicity by decreasing oxidative stress and ensuing activation of apoptotic programs such as the JNK/caspase pathway. This protective function of parkin, which is greatly attenuated by its PD-linked mutations, may be uniquely important for the survival of DA neurons, as they are constantly threatened by oxyradicals produced during dopamine oxidation.     

GDNF reduces oxidative stress in a 6-hydroxydopamine model of Parkinson's disease

Many current theories of Parkinson's disease (PD) suggest that oxidative stress is involved in the neurodegenerative process. Potential neuroprotective agents could protect neurons through inherent antioxidant properties or through the upregulation of the brain's antioxidant defenses. Glial cell line-derived neurotrophic factor (GDNF) has been shown to protect and restore dopamine neurons in experimental models of PD and to improve motor function in human patients. This study was designed to investigate GDNF's effect on oxidative stress in a model of PD. GDNF or vehicle was injected into the right striatum of male Fischer-344 rats. Three days later 6-OHDA or saline was injected into the same striatum. The striatum and substantia nigra from both sides of the brain were removed 24h after 6-OHDA or saline injection and analyzed for the oxidative stress markers protein carbonyls and 4-hydroxynonenal. Both markers were significantly reduced in GDNF+6-OHDA treated animals compared to vehicle+6-OHDA treated animals. In addition, in animals allowed to recover for 3.5-4 weeks after the 6-OHDA administration, the GDNF led to significant protection against loss of striatal and nigral tissue levels of dopamine. These results suggest that the protective effects of GDNF against 6-OHDA involve a reduction in oxidative stress.     

The effect of intrastriatal single injection of GDNF on the nigrostriatal dopaminergic system in hemiparkinsonian rats: behavioral and histological studies using two different dosages

Glial cell line-derived neurotrophic factor (GDNF) is a member of the transforming growth factor-beta superfamily and acts as a neurotrophic factor for the nigrostriatal dopamine (DA) system. Although previous studies have shown that pretreatment with GDNF could prevent degenerative changes of nigrostriatal DA system by DA neurotoxin 6-hydroxydopamine (6-OHDA), it is not really known whether GDNF can induce recovery of nigrostriatal DA system after partial lesioning by 6-OHDA. Substantia nigra has been commonly chosen as injection site for GDNF but a limited number of studies have used striatum as injection site where neural transplantation is commonly performed. Unilateral intrastriatal administration of 6-OHDA was performed in Sprague-Dawley rats to create partial lesion of the nigrostriatal DA system. These hemiparkinsonian model rats received a 10- or 100-microg single injection of human recombinant GDNF into the same portion of the striatum 4 weeks after 6-OHDA treatment. Both animals that received a 10- or 100-microg single injection of GDNF showed decreased apomorphine-induced rotation at 2 weeks after injection. More potent and prolonged functional recovery was observed in animals receiving 100 microg of GDNF than in those receiving 10 microg of GDNF. Tyrosine hydroxylase (TH) immunocytochemistry revealed that TH positive DA fiber density in the striatum and the number of DA cell bodies in the substantia nigra were greater in animals receiving 10 or 100 microg of GDNF than those receiving saline. These immunocytochemical results have also shown that 100 microg of GDNF was more potent than 10 microg of GDNF. These morphological and functional results indicate that GDNF treatment 4 weeks after 6-OHDA lesioning could induce recovery of nigrostriatal DA system. Striatum was a good site for GDNF administration for hemiparkinsonian rats and a single injection of 100 microg of GDNF was more potent than 10 microg of GDNF.     

Selective cyclooxygenase-2 blocker delays healing of esophageal ulcers in rats and inhibits ulceration-triggered c-Met/hepatocyte growth factor receptor induction and extracellular signal-regulated kinase 2 activation

Nonsteroidal anti-inflammatory drugs, both nonselective and cyclooxygenase-2 (COX-2) selective, delay gastric ulcer healing. Whether they affect esophageal ulcer healing remains unexplored. We studied the effects of the COX-2 selective inhibitor, celecoxib, on esophageal ulcer healing as well as on the cellular and molecular events involved in the healing process. Esophageal ulcers were induced in rats by focal application of acetic acid. Rats with esophageal ulcers were treated intragastrically with either celecoxib (10 mg/kg, once daily) or vehicle for 2 or 4 days. Esophageal ulceration triggered increases in: esophageal epithelial cell proliferation; expression of COX-2 (but not COX-1); hepatocyte growth factor (HGF) and its receptor, c-Met; and activation of extracellular signal-regulated kinase 2 (ERK2). Treatment with celecoxib significantly delayed esophageal ulcer healing and suppressed ulceration-triggered increases in esophageal epithelial cell proliferation, c-Met mRNA and protein expression, and ERK2 activity. In an ex vivo organ-culture system, exogenous HGF significantly increased ERK2 phosphorylation levels in esophageal mucosa. A structural analog of celecoxib, SC-236, completely prevented this effect. These findings indicate that celecoxib delays esophageal ulcer healing by reducing ulceration-induced esophageal epithelial cell proliferation. These actions are associated with, and likely mediated by, down-regulation of the HGF/c-Met-ERK2 signaling pathway.     

The dopamine agonist cabergoline provides neuroprotection by activation of the glutathione system and scavenging free radicals

Free radicals are involved in the pathogenesis and/or progression of Parkinson's disease (PD). Several ergot derivative dopamine (DA) agonists have been reported to scavenge free radicals in vitro and to show a neuroprotective effect in vivo. We investigated the in vitro free radical scavenging and antioxidant activities of cabergoline, a long-acting ergot DA agonist, as well as its ability to activate glutathione (GSH), catalase (Cat) and superoxide dismutase (SOD) activating effects and its in vivo neuroprotective properties against 6-hydroxydopamine (6-OHDA) intracerebroventricularly (i.c.v.) in mice. The striatal DA turnover induced by i.c.v. injection of 6-OHDA was completely normalized by pretreatment with cabergoline. Moreover, cabergoline scavenged free radicals in vitro and significantly reduced lipid peroxidation in vitro and in vivo. Furthermore, daily administration of cabergoline to mice significantly increased striatal GSH levels by activation of RNA expressions of GSH-related enzymes, although striatal Cat and SOD activities did not change. In addition, our present results suggest that repeated administration of cabergoline attenuates both 6-OHDA-induced nigrostriatal DAergic dysfunction and DA neuronal cell death, since cabergoline also had a neuroprotective effect in the immunohistochemical experiment. In conclusion, our findings indicate that the multiple antioxidant mechanisms of cabergoline, such as activation of the GSH system and the direct free radical scavenging activity, may explain the neuroprotective effect of this ergot DA agonist.     

硫辛酸对MPTP诱导的小鼠帕金森病模型的神经保护作用

目的:探讨α-硫辛酸(alpha-lipoic acid,ALA)在1-甲基-4-苯基-1,2,3,6-四氢吡啶(1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine,MPTP)诱导的小鼠帕金森病(Parkinson disease,PD)模型中的神经保护作用。方法:建立MPTP诱导的PD小鼠模型后,通过旷场实验、悬绳实验和转棒实验评估ALA对PD小鼠运动缺陷的影响;通过免疫组化检测ALA对PD小鼠黑质和纹状体多巴胺能神经元的影响;通过高效液相色谱检测ALA对PD小鼠纹状体多巴胺(dopamine,DA)及其代谢产物3,4-二羟基苯乙酸(3,4-dihydroxyphenylacetic acid,DOPAC)释放的影响;通过免疫荧光检测ALA对PD小鼠黑质中小胶质细胞活化以及小胶质细胞中诱导型一氧化氮合酶(inducible nitric oxide synthase,iNOS)表达的影响;通过Western blot检测ALA对PD小鼠纹状体中酪氨酸羟化酶(tyrosine hydroxylase,TH)和促炎分子白细胞介素1β(interleukin-1β,IL-1β)、肿瘤坏死因子α(tumor necrosis factor-α,TNF-α)和环氧合酶2(cyclooxygenase-2,COX-2)表达的影响。结果:行为学实验结果显示,ALA治疗显著增加PD小鼠总移动距离、平均运动速度和悬线实验评分(P<0.05),显著降低转棒实验的下落潜伏期(P<0.01)。免疫组化结果显示,ALA治疗显著增加黑质和纹状体中TH的表达水平(P<0.01)。高效液相色谱结果显示,ALA治疗显著增加纹状体DA和DOPAC的释放水平(P<0.01)。免疫荧光结果显示,ALA治疗显著降低黑质中小胶质细胞的活化和小胶质细胞的iNOS阳性细胞数(P<0.01)。Western blot结果显示,ALA治疗显著增加纹状体中TH的表达,显著降低IL-1β、TNF-α和COX-2表达(P<0.01)。结论:ALA在MPTP诱导的PD小鼠中发挥神经保护作用,能降低小胶质细胞活化,减轻多巴胺能神经元损伤、神经炎症和运动缺陷。     

Glucagon-like peptide 1 receptor stimulation reverses key deficits in distinct rodent models of Parkinson's disease

Background

It has recently become apparent that neuroinflammation may play a significant role in Parkinson's disease (PD). This is also the case in animal paradigms of the disease. The potential neuroprotective action of the glucagon-like peptide 1 receptor (GLP-1R) agonist exendin-4 (EX-4), which is protective against cytokine mediated apoptosis and may stimulate neurogenesis, was investigated In paradigms of PD.

Methods

Two rodent 'models' of PD, 6-hydroxydopamine (6-OHDA) and lipopolysaccaride (LPS), were used to test the effects of EX-4. Rats were then investigated in vivo and ex vivo with a wide range of behavioural, neurochemical and histological tests to measure integrity of the nigrostriatal system.

Results

EX-4 (0.1 and 0.5 μg/kg) was given seven days after intracerebral toxin injection. Seven days later circling behaviour was measured following apomorphine challenge. Circling was significantly lower in rats given EX-4 at both doses compared to animals given 6-OHDA/LPS and vehicle. Consistent with these observations, striatal tissue DA concentrations were markedly higher in 6-OHDA/LPS + EX-4 treated rats versus 6-OHDA/LPS + vehicle groups, whilst assay of L-DOPA production by tyrosine hydroxylase was greatly reduced in the striata of 6-OHDA/LPS + vehicle rats, but this was not the case in rats co-administered EX-4. Furthermore nigral TH staining recorded in 6-OHDA/LPS + vehicle treated animals was markedly lower than in sham-operated or EX-4 treated rats. Finally, EX-4 clearly reversed the loss of extracellular DA in the striata of toxin lesioned freely moving rats.

Conclusion

The apparent ability of EX-4 to arrest progression of, or even reverse nigral lesions once established, suggests that pharmacological manipulation of the GLP-1 receptor system could have substantial therapeutic utility in PD. Critically, in contrast to other peptide agents that have been demonstrated to possess neuroprotective properties in pre-clinical models of PD, EX-4 is in current clinical use in the management of type-II diabetes and freely crosses the blood brain barrier; hence, assessment of the clinical efficacy of EX-4 in patients with PD could be pursued without delay.     

miR-126 contributes to Parkinson's disease by dysregulating the insulin-like growth factor/phosphoinositide 3-kinase signaling

Dopamine (DA) neurons in sporadic Parkinson's disease (PD) display dysregulated gene expression networks and signaling pathways that are implicated in PD pathogenesis. Micro (mi)RNAs are regulators of gene expression, which could be involved in neurodegenerative diseases. We determined the miRNA profiles in laser microdissected DA neurons from postmortem sporadic PD patients' brains and age-matched controls. DA neurons had a distinctive miRNA signature and a set of miRNAs was dysregulated in PD. Bioinformatics analysis provided evidence for correlations of miRNAs with signaling pathways relevant to PD, including an association of miR-126 with insulin/IGF-1/PI3K signaling. In DA neuronal cell systems, enhanced expression of miR-126 impaired IGF-1 signaling and increased vulnerability to the neurotoxin 6-OHDA by downregulating factors in IGF-1/PI3K signaling, including its targets p85β, IRS-1, and SPRED1. Blocking of miR-126 function increased IGF-1 trophism and neuroprotection to 6-OHDA. Our data imply that elevated levels of miR-126 may play a functional role in DA neurons and in PD pathogenesis by downregulating IGF-1/PI3K/AKT signaling and that its inhibition could be a mechanism of neuroprotection.     

Immunohistochemical changes of nigrostriatal tyrosine hydroxylase and dopamine transporter in the golden hamster after a single intrastriatal injection of 6-hydroxydopamine

One of the most important models for analyzing the pathomorphological aspects of Parkinson's disease (PD) is the 6-hydroxydopamine (6-OHDA) model where lesions of the nigrostriatal axis are observed when 6-OHDA is intrastriatally injected.Despite the widespread use in rats, only few studies about the toxicity of 6-OHDA have been carried out in other species. In the present study, we evaluated for the first time the effects of a single intrastriatal injection of 6-OHDA (20 μg dissolved in 2 μl of vehicle) in the young-adult golden hamster (GH). Significant decreases in tyrosine hydroxylase (TH)-positive area and dopamine transporter (DAT)-positive area were found in the ipsilateral striatum 3 days after the injection. These decreases in immunoreactivity continued for 7 days and a recovery trend was found at days 15 and 21 post injection. On the other hand, no effect of injection was found on the contralateral side. In the substantia nigra pars compacta (SNpc), a significant decrease in the number of TH-positive cells appeared one week after the injection with the peak in the loss of TH-positive immunoreactivity being recorded two weeks post-injection.On the basis of the results herein reported, we believe that the GH is a suitable model for studying the patterns of spontaneous recovery of striatal axons following the 6-OHDA intrastriatal injection.     

Neuroinflammation mediated by IL-1β increases susceptibility of dopamine neurons to degeneration in an animal model of Parkinson's disease

Background

The etiology of Parkinson's disease (PD) remains elusive despite identification of several genetic mutations. It is more likely that multiple factors converge to give rise to PD than any single cause. Here we report that inflammation can trigger degeneration of dopamine (DA) neurons in an animal model of Parkinson's disease.

Methods

We examined the effects of inflammation on the progressive 6-OHDA rat model of Parkinson's disease using immunohistochemistry, multiplex ELISA, and cell counting stereology.

Results

We show that a non-toxic dose of lipopolysaccharide (LPS) induced secretion of cytokines and predisposed DA neurons to be more vulnerable to a subsequent low dose of 6-hydroxydopamine. Alterations in cytokines, prominently an increase in interleukin-1beta (IL-1β), were identified as being potential mediators of this effect that was associated with activation of microglia. Administration of an interleukin-1 receptor antagonist resulted in significant reductions in tumor necrosis factor-α and interferon-γ and attenuated the augmented loss of DA neurons caused by the LPS-induced sensitization to dopaminergic degeneration.

Conclusion

These data provide insight into the etiology of PD and support a role for inflammation as a risk factor for the development of neurodegenerative disease.     

Microglial responses to dopamine in a cell culture model of Parkinson's disease

Activated microglia appear to selectively attack dopamine (DA) neurons in the Parkinson's disease (PD) substantia nigra. We investigated potential mechanisms using culture models. As targets, human SH-SY5Y cells were left undifferentiated (UNDIFF) or were differentiated with retinoic acid (RA) or RA plus brain-derived neurotrophic factor (RA/BDNF). RA/BDNF-treated cells were immunoreactive for tyrosine hydroxylase and the DA transporter, took up exogenous DA, and released DA after K(+) stimulation. Undifferentiated and RA-treated cells lacked these characteristics of a DA phenotype. Co-culture of target cells with human elderly microglia resulted in elevated toxicity in DA phenotype (RA/BDNF) cells. Lipopolysaccharide (LPS) plus K(+)-stimulated DA release enhanced toxicity by 500-fold. DA induced microglial chemotaxis in Boyden chambers. Spiperone inhibited this effect. Cultured human elderly microglia expressed mRNAs for D1-D4 but not D5 DA receptors. The microglia, as well as PD microglia in situ, were also immunoreactive for D1-D4 but not D5 DA receptors. These findings demonstrate that activated microglia express DA receptors, and suggest that this mechanism may play a role in the selective vulnerability of DA neurons in PD.     

Dopamine in the lateral caudate-putamen of the rat is essential for somatosensory orientation

The present study examined the possible localization of somatosensory orientation in the caudate-putamen (CP) of the rat. In the first experiment, 6-hydroxydopamine (6-OHDA) was injected into either the anterodorsal (AD), anteroventral (AV), posterodorsal (PD), or posteroventral (PV) CP. Only rats with PV-CP 6-OHDA injections showed impaired orientation scores. However, these PV injections often caused widespread CP dopamine (DA) depletions, and no specific CP region appeared to be particularly associated with somatosensory orientation. In the second experiment, multiple injections of 6-OHDA were directed toward the medial or lateral halves of the CP to assess their relative contributions directly. DA depletions confined to the lateral (but not medial) CP resulted in orientation deficits; these deficits were greater than would be predicted from the volume of CP/DA loss. Furthermore, the magnitude of the DA fluorescence loss in the lateral CP was more highly correlated with the orientation impairment than was the medial CP fluorescence loss. Thus the lateral CP contributes to sensorimotor functions to a greater extent than does the medial CP, but the volume of CP/DA depletion also appears important.