Mesencephalic Cultures Research Articles

Neurotoxicity of cerebro-spinal fluid from patients with Parkinson's disease on mesencephalic primary cultures as an in vitro model of dopaminergic neurons.

Parkinson's disease is a degenerative disorder of the central nervous system. In spite of extensive research, neither the cause nor the mechanisms have been firmly established thus far. One assumption is that certain toxic substances may exist in the cerebro-spinal fluid (CSF) of Parkinson's disease patients. To confirm the neurotoxicity of CSF and study the potential correlation between neurotoxicity and the severity of Parkinson's disease, CSF was added to cultured cells. By observation of cell morphology, changes in the levels of lactate dehydrogenase, the ratio of tyrosine hydroxylase-positive cells, and the expression of tyrosine hydroxylase mRNA and protein, the differences between the two groups were shown. The created in vitro model of dopaminergic neurons using primary culture of mouse embryonic mesencephalic tissue is suitable for the study of neurotoxicity. The observations of the present study indicated that CSF from Parkinson's disease patients contains factors that can cause specific injury to cultured dopaminergic neurons. However, no obvious correlation was found between the neurotoxicity of CSF and the severity of Parkinson's disease.

Neuroprotection of Dopaminergic Neurons by Herbal Acupuncture in and Models of Parkinson’s Disease Induced by MPP+/MPTP Toxicity

Objectives : This study was designed to investigate the neuroprotective effects of HominisPlacenta (HP)on dopaminergic neurons. Methods : We examined the effect of invitro administration of HP against 1-methyl-4-phenylpyridinium(MPP+)-induced dopaminergic cell loss in primary mesencephalic culture and also used behavioral tests and performed analysis in the striatum and the substantia nigra of mouse brain, to confirm the effect of HP on dopaminergic neurons in an invivo 1-methyl-4-phenyl1,2,3,6-tetrahydropyridine(MPTP)-induced PD mouse model. Animals were assigned to four groups: (1) Group 1(vehicle-treatedgroup), (2) Group 2(MPTPonlytreated group), (3) Group 3(MPTP+ saline-treated/ST36 group), and (4) Group 4(MPTP+HP-treated/ST36 group). HP at 20 μ L of 48 mg/kg dose was injected at ST36 for 4 weeks at 2-day intervals. MPTP in saline was injected intraperitoneally each day for 5 days from the 8th treatment of HP. We performed the pole test and rota-rod test on the first and seventh day after the last MPTP injection. To investigate the effect of HP on dopaminergic neurons, we performed analysis in the striatum and the substantia nigra of mouse brain after treatment with HP and/or MPTP. Results : Treatment with HP had no influence on cell proliferation and caused no cell toxicity in PC12 and HT22 cells. Our study showed that HP significantly prevented cell loss and protected neurites against MPP+ toxicity. Although the invivo treatment of HP herbal acupuncture at ST36 showed a tendency to improve movement ability and protected dopaminergic cells and fibers in the substantia nigra and the striatum, it did not show significant changes compared with the MPTP treated group. Conclusions : These data suggest that HP could be a potential treatment strategy in neurodegenerative diseases such as Parkinson’s disease.

Targeting cyclin D3/CDK6 activity for treatment of Parkinson's disease.

At present, treatment for Parkinson's disease (PD) is only symptomatic; therefore, it is important to identify new targets tackling the molecular causes of the disease. We previously found that lymphoblasts from sporadic PD patients display increased activity of the cyclin D3/CDK6/pRb pathway and higher proliferation than control cells. These features were considered systemic manifestations of the disease, as aberrant activation of the cell cycle is involved in neuronal apoptosis. The main goal of this work was to elucidate whether the inhibition of cyclin D3/CDK6-associated kinase activity could be useful in PD treatment. For this purpose, we investigated the effects of two histone deacetylase (HDAC) inhibitors, suberoylanilide hydroxamic (SAHA) acid and sodium butyrate (NaB), and the m-TOR inhibitor rapamycin on cell viability and cyclin D3/CDK6 activity. Moreover, the potential neuroprotective action of these drugs was evaluated in 6-hydroxy-dopamine (6-OHDA) treated dopaminergic SH-SY5Y cells and primary rat mesencephalic cultures. Here, we report that both compounds normalized the proliferative activity of PD lymphoblasts and reduced the 6-OHDA-induced cell death in neuronal cells by preventing the over-activation of the cyclin D3/CDK6/pRb cascade. Considering that these drugs are already used in clinic for treatment of other diseases with good tolerance, it is plausible that they may serve as novel therapeutic drugs for PD. We report here that peripheral cells from Parkinson's disease (PD) patients show an enhanced proliferative activity due to the activation of cyclin D3/CDK6-mediated phosphorylation of retinoblastoma protein (pRb). Treatment of PD lymphoblasts with inhibitors of histone deacetylases like suberoylanilide hydroxamic acid (SAHA) and sodium butyrate (NaB), or with rapamycin, inhibitor of mechanistic target of rapamycin (mTOR) normalized the proliferation of PD lymphoblasts by preventing the over-activation of the cyclin D3/CDK6/pRb cascade. These drugs were shown to have neuroprotective effects in both human neuroblastoma SH-SY5Y cells and primary rat mid-brain dopaminergic neuronal cultures toxicity induced by 6-hidroxydopamine. Considering that these drugs are already used in clinic for treatment of other diseases with good tolerance, it seems reasonable to believe that the repositioning of these drugs toward PD holds promise as a novel therapeutic strategy.

Anti-inflammatory effects of BHBA in both in vivo and in vitro Parkinson's disease models are mediated by GPR109A-dependent mechanisms.

BackgroundAccumulating evidence suggests that neuroinflammation plays an important role in the progression of Parkinson’s disease (PD). Excessively activated microglia produce several pro-inflammatory enzymes and pro-inflammatory cytokines, leading to damage to surrounding neurons and eventually inducing neurodegeneration. Therefore, the inhibition of microglial overactivation may be a potential therapeutic strategy to prevent the further progression of PD. β-Hydroxybutyric acid (BHBA) has been shown to suppress lipopolysaccharide (LPS)-induced inflammation in BV-2 cells and to protect dopaminergic neurons in previous studies, but the underlying mechanisms remain unclear. Thus, in this study, we further investigated this mechanism in LPS-induced in vivo and in vitro PD models.MethodsFor the in vitro experiments, primary mesencephalic neuron-glia cultures were pretreated with BHBA and stimulated with LPS. [3H]dopamine (DA) uptake, tyrosine hydroxylase-immunoreactive (TH-ir) neurons and morphological analysis were evaluated and analyzed in primary mesencephalic neuron-glia cultures. In vivo, microglial activation and the injury of dopaminergic neurons were induced by LPS intranigral injection, and the effects of BHBA treatment on microglial activation and the survival ratio and function of dopaminergic neurons were investigated. Four our in vitro mechanistic experiment, primary microglial cells were pretreated with BHBA and stimulated with LPS; the cells were then assessed for the responses of pro-inflammatory enzymes and pro-inflammatory cytokines, and the NF-κB signaling pathway was evaluated and analyzed.ResultsWe found that BHBA concentration-dependently attenuated the LPS-induced decrease in [3H]DA uptake and loss of TH-ir neurons in the primary mesencephalic neuron/glia mixed culture. BHBA treatment significantly improved the motor dysfunction of the PD model rats induced by intranigral injection of LPS, and this beneficial effect of BHBA was attributed to the inhibition of microglial overactivation and the protection of dopaminergic neurons in the substantia nigra (SN). Our in vitro mechanistic study revealed that the inhibitory effect of BHBA on microglia was mediated by G-protein-coupled receptor 109A (GPR109A) and involved the NF-κB signaling pathway, causing the inhibition of pro-inflammatory enzyme (iNOS and COX-2) and pro-inflammatory cytokine (TNF-α, IL-1β, and IL-6) production.ConclusionsIn conclusion, the present study supports the effectiveness of BHBA in protecting dopaminergic neurons against inflammatory challenge.

Rapamycin protects dopaminergic neurons against rotenone-induced cell death in primary mesencephalic cell culture.

Parkinson's disease is the most common movement disorder, characterized by a progressive and extensive loss of dopaminergic neurons in the substantia nigra pars compacta and their terminals in the striatum. So far, only symptomatic treatment is available, and no cure or disease-modifying drugs exist. The present study was designed to investigate the neuroprotective effect of rapamycin, an autophagy inducer, on dopaminergic neurons against rotenone-induced cell death in primary mesencephalic cell culture. Primary mesencephalic cell cultures were prepared from embryonic mouse mesencephala (OFI/SPF, Vienna, Austria) at gestation day 14. Four sets of cultures were treated as follows: one was run as an untreated control, a second one was treated with 20 nM rotenone on the 10th day in vitro (DIV) for 48 h, a third one was co-treated with 20 nM rotenone and rapamycin (1, 10, 100, 1000 nM) on the 10th DIV for 48 h, and a fourth one was treated with rapamycin alone (1, 10, 100, 1000 nM) on the 10th DIV for 48 h. On the 12th DIV, cultures were subjected to immunohistochemistry against tyrosine hydroxylase and to fluorescence staining using LysoTracker Deep Red, JC-1 and DAPI stains. Exposure of such cultures to 20 nM rotenone on the 10th DIV for 48 h reduced the number of dopaminergic neurons by 41% and increased the release of lactate dehydrogenase (LDH) by 178% above untreated controls. Rapamycin (1, 10, 100, 1000 nM) added together with rotenone from the 10th to 12th DIV spared dopaminergic neurons by 17% and reduced the release of LDH by 64% at the concentration of 100 nM compared to rotenone-treated cultures. Activation of an autophagic process by rapamycin was demonstrated by LysoTracker Deep Red fluorescent dye, as indicated by a shift to increased red fluorescence. Rapamycin also significantly elevated the mitochondrial membrane potential (Δψm), as shown by an increase of the red:green fluorescence ratio of JC-1. Increased apoptotic cell death due to rotenone was lowered by rapamycin, as shown by the blue-fluorescent DAPI nucleic acid stain. Our study indicates for the first time that rapamycin, known as an autophagy inducer, protected dopaminergic neurons against rotenone-induced cell death in primary mesencephalic cell culture.

Cabergoline protects dopaminergic neurons against rotenone-induced cell death in primary mesencephalic cell culture.

In the present study, primary mesencephalic cell cultures prepared from embryonic mouse mesencephala were used to investigate the neuroprotective effect of cabergoline, an ergoline D2 receptor agonist, against the pesticide and neurotoxin rotenone relevant to Parkinson disease (PD). Treatment of cultures with cabergoline alone significantly increased the number of tyrosine hydroxylase immunoreactive (THir) neurons and reduced the release of lactate dehydrogenase (LDH) into the culture medium compared to untreated controls. Against rotenone toxicity, cabergoline significantly rescued degenerating THir neurons, reduced the release of LDH into the culture medium and improved the morphology of surviving THir neurons. The neuroprotective effects afforded by cabergoline were independent of dopaminergic stimulation as blocking of dopamine receptors by the dopamine receptor antagonist sulpiride did not prevent them. Furthermore, rotenone-induced formation of reactive oxygen species (ROS) was significantly reduced by cabergoline. Although cabergoline increased the glutathione (GSH) content in the culture, the protective effect for dopaminergic neurons seemed not to be predominantly mediated by increasing GSH, as depletion of GSH by L-buthionine-(S,R)-sulfoximine (BSO), a GSH biosynthesis inhibitor, did not prevent cabergoline-mediated neuroprotection of THir neurons in rotenone-treated cultures. Moreover, cabergoline significantly increased the ATP/protein ratio in primary mesencephalic cell cultures when added alone or prior to rotenone treatment. These results indicate a neuroprotective effect of cabergoline for dopaminergic neurons against rotenone toxicity. This effect was independent of dopamine receptor stimulation and was at least partially mediated by reducing ROS production and increasing the ATP/protein ratio.

Cocaine Causes Apoptotic Death in Rat Mesencephalon and Striatum Primary Cultures.

To study cocaine's toxic effects in vitro, we have used primary mesencephalic and striatal cultures from rat embryonic brain. Treatment with cocaine causes a dramatic increase in DNA fragmentation in both primary cultures. The toxicity induced by cocaine was paralleled with a concomitant decrease in the microtubule associated protein 2 (MAP2) and/or neuronal nucleus protein (NeuN) staining. We also observed in both cultures that the cell death caused by cocaine was induced by an apoptotic mechanism, confirmed by TUNEL assay. Therefore, the present paper shows that cocaine causes apoptotic cell death and inhibition of the neurite prolongation in striatal and mesencephalic cell culture. These data suggest that if similar neuronal damage could be produced in the developing human brain, it could account for the qualitative or quantitative defects in neuronal pathways that cause a major handicap in brain function following prenatal exposure to cocaine.

RhoA inhibition by C3 prevents dopaminergic neuronal degeneration in rotenone induced neurotoxicity

Parkinson disease (PD) is a complex neurodegenerative disorder characterized by a progressive loss of dopaminergic neurons. Mitochondrial dysfunction, oxidative stress or protein misfolding may underlie this process. Rotenone, a natural substance widely used as a pesticide, produces selective degeneration of dopaminergic neurons. Rotenone is a membrane-permeable compound that has two known molecular targets in the cell: it inhibits complex I in the mitochondrial respiratory chain and depolymerizes microtubules. Microtubule depolymerization would disrupt vesicular transport and cause the accumulation of vesicles in the soma. RhoA, a member of the Rho GTP-binding proteins, activates several effector proteins which target actin, actomyosin and microtubules. Here, we use an in vitro rotenone-induced PD mouse model to verify the neuroprotective effects of C3, an exoenzyme produced by Clostridium botulinum that inactivates RhoA by ADP-ribosylation. Mesencephalic cell cultures from CD1 mice were performed, at D.I.V. 6 the cells were treated with or without 2.5 μg/ml of C3; 4 hours later 25 nM of Rotenone was added. 24 hours later [3H] dopamine uptake and immunocytochemistry with anti-TH and anti-RhoA antibodies were performed. In TH+ neurons Rotenone reduced dopamina uptake to 45% and activated RhoA that was found at level of the cell membrane. Pre-treatment with C3 was able to protect mesencephalic cells from rotenone toxicity to about 40% preventing the traslocation of RhoA from the cytoplasm to the plasma membrane as observed by confocal analysis of immunostained cells. Our data indicate that the inhibition of RhoA by C3 is able to partially rescue the rotenone induced damage by probably preventing microtubules depolymerization.

Nogo-A and its functions beyond axonal inhibition: the controversial role of Nogo-A in Parkinson's disease.

Nogo-A belongs to the reticulon family (RTN4) and is generally assumed to be one of the most potent myelin associated neurite outgrowth inhibitors in the central nervous system (CNS). Together with other inhibitors such as the myelin associated glycoprotein (MAG), oligodendrocyte myelin glycoprotein (OMgp), several semaphorins and ephrins as well as chondriotin sulphate proteoglycans, Nogo-A contributes to a nonpermissive environment in the brain and spinal cord. Based on their seminal observation that neurons grown in close proximity to CNS derived oligodendrocytes showed a robust decrease in neurite outgrowth and number of processes, Schwab and Caroni (1988) postulated for nonpermissive substrate properties present in the CNS myelin. In further studies, they identified a high molecular weight component from the CNS myelin called NI-250 which was later renamed Nogo-A. In the course it could be demonstrated that Nogo-A is expressed on the surface of oligodendrocytes and is responsible for the inhibition of axonal sprouting. Since the nonpermissive environment plays a very important role in brain injuries and neurodegenerative diseases, Nogo-A and its receptors were extensively studied.

Inhibition of i-NOS but not n-NOS protects rat primary cell cultures against MPP(+)-induced neuronal toxicity.

Nitrative stress is a key component of the pathogenic process in Parkinson's disease (PD), but the relative roles of constitutive neuronal nitric oxide synthase (n-NOS) and inducible nitric oxide synthase (i-NOS) in glial cells remain unresolved. We have investigated the effects of a range of concentrations of the selective n-NOS inhibitor ARR17477, and the selective i-NOS inhibitor 1400W, on MPP(+)-induced cell death in foetal ventral mesencephalic (VM) dopaminergic cultures. MPP(+) induced a loss of TH-positive neurones accompanied by an increase in immunoreactivity for GFAP and OX-6 as markers of astrocytes and activated microglia, respectively, and induced i-NOS immunoreactivity. Unexpectedly, MPP(+) treatment did not induce 3-NT immunoreactivity in the cultures. ARR17477 and 1400W alone had no effect on the number of TH-positive cells or on the number of GFAP or OX-6 positive cells. ARR17477 did not prevent the MPP(+)-induced decrease in TH-positive neurones and had no effect on the increased number of GFAP- and OX-6-positive cells. By contrast, 1400W caused a concentration-dependent preservation of TH-positive neurones in the presence of MPP(+). It also significantly reduced the number of OX-6-immunoreactive cells and there was a small reduction in GFAP immunoreactivity. The results suggest a major role for i-NOS-mediated nitrative stress in microglia in MPP(+)-induced dopaminergic cell death and this may have important implications for developing neuroprotective strategies for PD.

Maneb-induced dopaminergic neuronal death is not affected by loss of mitochondrial complex I activity: results from primary mesencephalic dopaminergic neurons cultured from individual Ndufs4+/+ and Ndufs4-/- mouse embryos.

Primary cultures from embryonic mouse ventral mesencephalon are widely used for investigating the mechanisms of dopaminergic neuronal death in Parkinson's disease models. Specifically, single mouse or embryo cultures from littermates can be very useful for comparative studies involving transgenic mice when the neuron cultures are to be prepared before genotyping. However, preparing single mouse embryo culture is technically challenging because of the small number of cells present in the mesencephalon of each embryo (150 000-300 000), of which only 0.5-5% are tyrosine hydroxylase-positive, dopaminergic neurons. In this study, we optimized the procedure for preparing primary mesencephalic neuron cultures from individual mouse embryos. Mesencephalic neurons were dissociated delicately, plated on Aclar film coverslips, and incubated in DMEM supplemented with fetal bovine serum for 5 days and then N2 supplement was added for 1 day, which resulted in the best survival of dopaminergic neurons from each embryo. Using this optimized method, we prepared mesencephalic neuron cultures from single Ndufs4 or Ndufs4 embryos and investigated the role of mitochondrial complex I in maneb-induced dopamine neuron death. Our results suggest that maneb toxicity to dopamine neurons is not affected by the loss of mitochondrial complex I activity in Ndufs4 cultures.

Targeted toxicants to dopaminergic neuronal cell death.

Parkinson's disease (PD ) is mainly characterized by a progressive degeneration of dopaminergic neurons in the substantia nigra resulting in chronic deficits in motor functions. Administration of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP ) produces PD symptoms and recapitulates the main features of PD in human and animal models. MPTP is converted to 1-methyl-4-phenylpyridine (MPP+ ), which is the active toxic compound that selectively destroys dopaminergic neurons. Here, we describe methods and protocols to evaluate MPTP/MPP+-induced dopaminergic neurodegeneration in both murine primary mesencephalic cultures and animal models. The ability of MPTP/MPP+ to cause dopaminergic neuronal cell death is assessed by immunostaining of tyrosine hydroxylase (TH).

Neuronal differentiation dictates estrogen-dependent survival and ERK1/2 kinetic by means of caveolin-1.

Estrogens promote a plethora of effects in the CNS that profoundly affect both its development and mature functions and are able to influence proliferation, differentiation, survival and neurotransmission. The biological effects of estrogens are cell-context specific and also depend on differentiation and/or proliferation status in a given cell type. Furthermore, estrogens activate ERK1/2 in a variety of cellular types. Here, we investigated whether ERK1/2 activation might be influenced by estrogens stimulation according to the differentiation status and the molecular mechanisms underling this phenomenon. ERK1/2 exert an opposing role on survival and death, as well as on proliferation and differentiation depending on different kinetics of phosphorylation. Hence we report that mesencephalic primary cultures and the immortalized cell line mes-c-myc A1 express estrogen receptor α and activate ERK1/2 upon E2 stimulation. Interestingly, following the arrest of proliferation and the onset of differentiation, we observe a change in the kinetic of ERKs phosphorylation induced by estrogens stimulation. Moreover, caveolin-1, a main constituent of caveolae, endogenously expressed and co-localized with ER-α on plasma membrane, is consistently up-regulated following differentiation and cell growth arrest. In addition, we demonstrate that siRNA-induced caveolin-1 down-regulation or disruption by means of ß-cyclodextrin treatment changes ERK1/2 phosphorylation in response to estrogens stimulation. Finally, caveolin-1 down-regulation abolishes estrogens-dependent survival of neurons. Thus, caveolin-1 appears to be an important player in mediating, at least, some of the non-genomic action of estrogens in neurons, in particular ERK1/2 kinetics of activation and survival.

Differences in receptor binding affinity of several phytocannabinoids do not explain their effects on neural cell cultures

Phytocannabinoids are potential candidates for neurodegenerative disease treatment. Nonetheless, the exact mode of action of major phytocannabinoids has to be elucidated, but both, receptor and non-receptor mediated effects are discussed. Focusing on the often presumed structure–affinity-relationship, Ki values of phytocannabinoids cannabidiol (CBD), cannabidivarin (CBDV), cannabichromene (CBC), cannabigerol (CBG), cannabinol (CBN), THC acid (THCA) and THC to human CB1 and CB2 receptors were detected by using competitive inhibition between radioligand [3H]CP-55,940 and the phytocannabinoids. The resulting Ki values to CB1 range from 23.5μM (THCA) to 14,711μM (CBDV), whereas Ki values to CB2 range from 8.5μM (THCA) to 574.2μM (CBDV). To study the relationship between binding affinity and effects on neurons, we investigated possible CB1 related cytotoxic properties in murine mesencephalic primary cell cultures and N18TG2 neuroblastoma cell line. Most of the phytocannabinoids did not affect the number of dopaminergic neurons in primary cultures, whereas propidium iodide and resazurin formation assays revealed cytotoxic properties of CBN, CBDV and CBG. However, THC showed positive effects on N18TG2 cell viability at a concentration of 10μM, whereas CBC and THCA also displayed slightly positive activities. These findings are neither linked to structural characteristics nor to the receptor binding affinity therewith pointing to another mechanism than a receptor mediated one.

Increased neurotrophic factor levels in ventral mesencephalic cultures do not explain the protective effect of osteopontin and the synthetic 15-mer RGD domain against MPP + toxicity

The synthetic 15-mer arginine-glycine-aspartic acid (RGD) domain of osteopontin (OPN) is protective in vitro and in vivo against dopaminergic cell death and this protective effect may be mediated through interaction with integrin receptors to regulate neurotrophic factor levels. We now examine this concept in rat primary ventral mesencephalic (VM) cultures. 1-Methyl-4-phenylpyridinium (MPP+) exposure reduced tyrosine hydroxylase (TH)-positive cell number and activated glial cells as shown by increased glial fibrillary acidic protein (GFAP), oxycocin-42 (OX-42) and ectodermal dysplasia 1 (ED-1) immunoreactivity. Both OPN and the RGD domain of OPN were equally protective against MPP+ toxicity in VM cultures and both increased glial-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) levels. The effects of OPN and the RGD domain were accompanied by a decrease in numbers of activated microglia but with no change in astrocyte number. However, full-length OPN and the RGD domain of OPN remained protective against MPP+ toxicity in the presence of a GDNF neutralising antibody. This suggests that increased GDNF levels do not underlie the protective effect observed with OPN. Rather, OPN's protective effect may be mediated through decreased glial cell activation.

Angiotensin type 1 receptor blockage reduces l-dopa-induced dyskinesia in the 6-OHDA model of Parkinson's disease. Involvement of vascular endothelial growth factor and interleukin-1β

Non-neuronal factors such as angiogenesis and neuroinflammation may play a role in l-dopa induced dyskinesias (LID). Vascular endothelial growth factor (VEGF) and proinflammatory cytokines such as interleukin-1β (IL-1β) have been found to be involved in LID. The renin–angiotensin system (RAS) is involved in the inflammatory response and VEGF synthesis via type 1 (AT1) receptors. However, it is not known whether the RAS plays a role in LID and whether AT1 antagonists could constitute a useful therapy against LID. In this study, we investigated whether manipulation of brain RAS is effective in preventing LID. Blocking AT1 receptors with candesartan significantly reduces LID in the 6-OHDA rat model. Chronic dopaminergic denervation induces an increase in striatal levels of VEGF and IL-1β. Dyskinetic animals showed significantly higher levels of VEGF and IL-1β in the lateral striatum and the substantia nigra, as revealed by western blot and real time-PCR analyses. Interestingly, animals treated with both candesartan and l-dopa displayed significantly lower levels of VEGF, IL-1β and dyskinesia than those treated with l-dopa alone. The stimulatory effect of angiotensin II (AII) on VEGF expression was confirmed by the addition of AII to primary mesencephalic cultures and intraventricular administration of AII in rats. The results of the present study reveal for the first time that blockage of AT-1 receptors reduces LID. A candesartan-induced decrease in VEGF and IL-1β may be responsible for the beneficial effects, suggesting the brain RAS as a new target for LID treatment in PD patients.

Developmental exposure to the organochlorine insecticide endosulfan damages the nigrostriatal dopamine system in male offspring

The contribution of environmental toxicants to the etiology and risk of Parkinson's disease (PD) has been clearly established, with organochlorine insecticides routinely shown to damage the nigrostriatal dopamine pathway. Although PD is generally considered an adult onset disease, it has been postulated that exposure to environmental contaminants or other factors early in life during critical periods of neurodevelopment could alter the dopaminergic circuit and predispose individuals to developing PD. Recent epidemiological evidence has found exposure to the organochlorine insecticide endosulfan to be a risk factor for PD. However, the specific dopaminergic targets or vulnerable developmental time points related to endosulfan exposure have not been investigated. Thus, we sought to investigate dopaminergic neurotoxicity following developmental exposure to endosulfan as well as following an additional challenge with MPTP. Our in vitro findings demonstrate a reduction in SK-N-SH cells and ventral mesencephalic primary cultures after endosulfan treatment. Using an in vivo developmental model, exposure to endosulfan during gestation and lactation caused a reduction in DAT and TH in the striatum of male offspring. These alterations were exacerbated following subsequent treatment with MPTP. In contrast, exposure of adult mice to endosulfan did not elicit dopaminergic damage and did not appear to increase the vulnerability of the dopamine neurons to MPTP. These findings suggest that development during gestation and lactation represents a critical window of susceptibility to endosulfan exposure and development of the nigrostriatal dopamine system. Furthermore, these exposures appear to sensitize the dopamine neurons to additional insults that may occur later in life.

Inhibition of the microglial response is essential for the neuroprotective effects of Rho-kinase inhibitors on MPTP-induced dopaminergic cell death

Several recent studies have shown that activation of the RhoA/Rho-associated kinase (ROCK) pathway is involved in the MPTP-induced dopaminergic cell degeneration and possibly in Parkinson's disease. ROCK inhibitors have been suggested as candidate neuroprotective drugs for Parkinson's disease. However, the mechanism responsible for the increased survival of dopaminergic neurons after treatment with ROCK inhibitors is not clear. We exposed primary (neuron-glia) mesencephalic cultures, cultures of the MES 23.5 dopaminergic neuron cell line and primary mesencephalic cultures lacking microglial cells to the dopaminergic neurotoxin MPP+ and the ROCK inhibitor Y-27632 in order to study the effects of ROCK inhibition on dopaminergic cell loss and the length of neurites of surviving dopaminergic neurons. In primary (neuron-glia) cultures, simultaneous treatment with MPP+ and the ROCK inhibitor significantly reduced the loss of dopaminergic neurons. In the absence of microglia, treatment with the ROCK inhibitor did not induce a significant reduction in the dopaminergic cell loss. Treatment with the ROCK inhibitor induced a significant decrease in axonal retraction in primary cultures with and without microglia and in cultures of the MES 23.5 neuron cell line. In conclusion, inhibition of microglial ROCK is essential for the neuroprotective effects of ROCK inhibitors against cell death induced by the dopaminergic neurotoxin MPP+. In addition, ROCK inhibition induced a direct effect against axonal retraction in surviving neurons. However, the latter effect was not sufficient to cause a significant increase in the survival of dopaminergic neurons after treatment with MPP+.

Heat shock protein 60: an endogenous inducer of dopaminergic cell death in Parkinson disease.

BackgroundIncreasing evidence suggests that inflammation associated with microglial cell activation in the substantia nigra (SN) of patients with Parkinson disease (PD) is not only a consequence of neuronal degeneration, but may actively sustain dopaminergic (DA) cell loss over time. We aimed to study whether the intracellular chaperone heat shock protein 60 (Hsp60) could serve as a signal of CNS injury for activation of microglial cells.MethodsHsp60 mRNA expression in the mesencephalon and the striatum of C57/BL6 mice treated with MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and the Hsp60/TH mRNA ratios in the SN of PD patients and aged-matched subjects were measured. To further investigate a possible link between the neuronal Hsp60 response and PD-related cellular stress, Hsp60 immunoblot analysis and quantification in cell lysates from SH-SY5Y after treatment with 100 μM MPP+ (1-methyl-4-phenylpyridinium) at different time points (6, 12, 24 and 48 hours) compared to control cells were performed. Additional MTT and LDH assay were used. We next addressed the question as to whether Hsp60 influences the survival of TH+ neurons in mesencephalic neuron-glia cultures treated either with MPP+ (1 μM), hHsp60 (10 μg/ml) or a combination of both. Finally, we measured IL-1β, IL-6, TNF-α and NO-release by ELISA in primary microglial cell cultures following treatment with different hHsp60 preparations. Control cultures were exposed to LPS.ResultsIn the mesencephalon and striatum of mice treated with MPTP and also in the SN of PD patients, we found that Hsp60 mRNA was up-regulated. MPP+, the active metabolite of MPTP, also caused an increased expression and release of Hsp60 in the human dopaminergic cell line SH-SY5Y. Interestingly, in addition to being toxic to DA neurons in primary mesencephalic cultures, exogenous Hsp60 aggravated the effects of MPP+. Yet, although we demonstrated that Hsp60 specifically binds to microglial cells, it failed to stimulate the production of pro-inflammatory cytokines or NO by these cells.ConclusionsOverall, our data suggest that Hsp60 is likely to participate in DA cell death in PD but via a mechanism unrelated to cytokine release.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) Is Selectively Toxic to Primary Dopaminergic Neurons In Vitro

Parkinson's disease (PD) is the second most common neurodegenerative disease. Much data has linked the etiology of PD to a variety of environmental factors. The majority of cases are thought to arise from a combination of genetic susceptibility and environmental factors. Chronic exposures to dietary factors, including meat, have been identified as potential risk factors. Although heterocyclic amines that are produced during high-temperature meat cooking are known to be carcinogenic, their effect on the nervous system has yet to be studied in depth. In this study, we investigated neurotoxic effects of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a highly abundant heterocyclic amine in cooked meat, in vitro. We tested toxicity of PhIP and the two major phase I metabolites, N-OH-PhIP and 4'-OH-PhIP, using primary mesencephalic cultures from rat embryos. This culture system contains both dopaminergic and nondopaminergic neurons, which allows specificity of neurotoxicity to be readily examined. We find that exposure to PhIP or N-OH-PhIP is selectively toxic to dopaminergic neurons in primary cultures, resulting in a decreased percentage of dopaminergic neurons. Neurite length is decreased in surviving dopaminergic neurons. Exposure to 4'-OH-PhIP did not produce significant neurotoxicity. PhIP treatment also increased formation of oxidative damage markers, 4-hydroxy-2-nonenal (HNE) and 3-nitrotyrosine in dopaminergic neurons. Pretreatment with N-acetylcysteine was protective. Finally, treatment with blueberry extract, a dietary factor with known antioxidant and other protective mechanisms, prevented PhIP-induced toxicity. Collectively, our study suggests, for the first time, that PhIP is selectively toxic to dopaminergic neurons likely through inducing oxidative stress.