Tyrosine Hydroxylase Protein Levels Research Articles

Treatment Of Magnesium-L-Threonate Elevates The Magnesium Level In The Cerebrospinal Fluid And Attenuates Motor Deficits And Dopamine Neuron Loss In A Mouse Model Of Parkinson's disease.

PurposeEpidemiology research has demonstrated that magnesium (Mg) deficiency is associated with a high incidence of Parkinson’s disease (PD). It is known that the systemic administration of MgSO4 is not able to elevate the Mg concentration in cerebrospinal fluid (CSF). This study aims to verify the protective effect of magnesium-L-threonate (MgT) in 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) mouse model.MethodsC57BL/6J mice were orally administered MgT or MgSO4 for 4 weeks, and received MPTP in the third week. After analysis of open-field and rotarod tests on the last day, tyrosine hydroxylase (TH) immunopositive cells and protein levels were quantified in the substantia nigra pars compacta (SNpc) and striatum. The expression of inducible nitric oxide synthase (iNOS) level was evaluated. Mg concentration in serum and CSF was measured after oral administration of MgSO4 or MgT in normal mice. Mg concentration in the CSF was increased in the mice treated with MgT but not MgSO4.ResultsThe total distance and mean speed in open-field tests, and the time spent on rotarod in the MgT group were increased, compared with MPTP group. The MgT treatment but not MgSO4 dose-dependently attenuated the loss of TH-positive neurons, and the reduction of the TH expression in the SNpc. The MgT treatment also inhibited the expression of iNOS as measured by immunohistochemistry and Western blots. Double-immunofluorescence staining of TH and iNOS showed iNOS-positive cells were collocalized for TH-positive cells.ConclusionThe treatment with MgT is associated with an increase of Mg in the CSF. MgT, rather than MgSO4, can significantly attenuate MPTP-induced motor deficits and dopamine (DA) neuron loss.

Loss of PTEN-induced kinase 1 (Pink1) reduces hippocampal tyrosine hydroxylase and impairs learning and memory

Phosphatase and tensin homolog (PTEN)-induced kinase 1 (Pink1) is involved in mitochondrial quality control, which is essential for maintaining energy production and minimizing oxidative damage from dysfunctional/depolarized mitochondria. Pink1 mutations are the second most common cause of autosomal recessive Parkinson's disease (PD). In addition to characteristic motor impairments, PD patients also commonly exhibit cognitive impairments. As the hippocampus plays a prominent role in cognition, we tested if loss of Pink1 in mice influences learning and memory. While wild-type mice were able to perform a contextual discrimination task, age-matched Pink1 knockout (Pink1−/−) mice showed an impaired ability to differentiate between two similar contexts. Similarly, Pink1−/− mice performed poorly in a delayed alternation task as compared to age-matched controls. Poor performance in these cognitive tasks was not the result of overt hippocampal pathology. However, a significant reduction in hippocampal tyrosine hydroxylase (TH) protein levels was detected in the Pink1−/− mice. This decrease in hippocampal TH levels was also associated with reduced DOPA decarboxylase and dopamine D2 receptor levels, but not post-synaptic dopamine D1 receptor levels. These presynaptic changes appeared to be selective for dopaminergic fibers as hippocampal dopamine beta hydroxylase, choline acetyltransferase, and tryptophan hydroxylase levels were unchanged in Pink1−/− mice. Administration of the dopamine D1 receptor agonist SKF38393 to Pink1−/− mice was found to improve performance in the context discrimination task. Taken together, our results show that Pink1 loss may alter dopamine signaling in the hippocampus, which could be a contributing mechanism for the observed learning and memory impairments.

Exposure to deltamethrin in adolescent mice induced thyroid dysfunction and behavioral disorders.

Deltamethrin (DM) has become one of the most widely used insecticides in the world due to its low toxicity, high efficiency and low persistence in soil. However, it is still unknown whether DM exposure has any effects on the Hypothalamic-Pituitary-Thyroid (HPT) axis in adolescent mice. In this study, the open field test and circadian activity test showed that DM exposure increased activity. There was no significant difference between the groups in the light/dark box test and nest building test. Forced swimming test showed that after 6 and 12 mg kg-1 DM exposure 28 days, the immobility time was increased and the swimming time was reduced. After 6 mg kg-1 DM treatment, the thyroid stimulating hormone (TSH) content increased, and thyrotropin releasing hormone (TRH), triiodothyronine (T3) and thyroxine (T4) decreased. After exposure to 6 and 12 mg kg-1 DM, mRNA levels of HPT axis-related genes were destroyed. The histological examination showed that, the DM groups mice thyroid tissues appeared expanded thyroid follicles, scanty colloid and hyperplastic thyroid cells. Western blot results showed that the expression level of tyrosine hydroxylase (TH) protein decreased and the content of dopamine transporter (DAT) protein increased in DM treated mice striatum. Collectively, our results indicated that DM exposure could induce thyroid dysfunction and behavioral disorders in adolescent mice.

Norepinephrine upregulates the expression of tyrosine hydroxylase and protects dopaminegic neurons against 6-hydrodopamine toxicity

As a classic neurotransmitter in the brain, norepinephrine (NE) also is an important modulator to other neuronal systems. Using primary cultures from rat ventral mesencephalon (VM) and dopaminergic cell line MN9D, the present study examined the neuroprotective effects of NE and its effects on the expression of tyrosine hydroxylase (TH). The results showed that NE protected both VM cultures and MN9D cells against 6-hydroxydopamine-caused apoptosis, with possible involvement of adrenal receptors. In addition, treatment with NE upregulated TH protein levels in dose- and time-dependent manner. Further experiments to investigate the potential mechanisms underlying this NE-induced upregulation of TH demonstrated a marked increase in protein levels of the brain-derived neurotrophic factor (BDNF) and the phosphorylated extracellular signal-regulated protein kinase 1 and 2 (pERK1/2) in VM cultures treated with NE. In MN9D cells, a significantly increase of TH and pERK1/2 protein levels were observed after their transfection with BDNF cDNA or exposure to BDNF peptides. Treatment of VM cultures with K252a, an antagonist of the tropomyosin-related kinase B, blocked the upregulatory effects of NE on TH, BDNF and pERK1/2. Administration of MEK1 & MEK2 inhibitors also reversed NE-induced upregulation of TH and pERK1/2. Moreover, ChIP assay showed that treatment with NE or BDNF increased H4 acetylation in the TH promoter. These results suggest that the neuroprotection and modulation of NE on dopaminergic neurons are mediated via BDNF and MAPK/ERK pathways, as well as through epigenetic histone modification, which may have implications for the improvement of therapeutic strategies for Parkinson's disease.

Angiotensin II mediates the axonal trafficking of tyrosine hydroxylase and dopamine β-hydroxylase mRNAs and enhances norepinephrine synthesis in primary sympathetic neurons.

In the sympatho-adrenal system, angiotensin II (Ang II) acts as a key neuromodulatory component. At sympathetic nerve terminals, Ang II influences sympathetic transmission by enhancing norepinephrine (NE) synthesis, facilitating NE release and inhibiting NE uptake. Previously, it was demonstrated that tyrosine hydroxylase (TH) mRNA is trafficked to the distal axons of primary superior cervical ganglia (SCG) neurons, directed by a cis-acting regulatory element (i.e. zipcode) located in the 3'UTR of the transcript. Results of metabolic labeling studies established that the mRNA is locally translated. It was further shown that the axonal trafficking of the mRNA encoding the enzyme plays an important role in mediating dopamine (DA) and NE synthesis and may facilitate the maintenance of axonal catecholamine levels. In the present study, the hypothesis was tested that Ang II induces NE synthesis in rat primary SCG neurons via the modulation of the trafficking of the mRNAs encoding the catecholamine synthesizing enzymes TH and dopamine β-hydroxylase (DBH). Treatment of SCG neurons with the Ang II receptor type 1 (AT1R) agonist, L-162,313, increases the axonal levels of TH and DBH mRNA and protein and results in elevated NE levels. Conversely, treatment of rat SCG neurons with the AT1R antagonist, Eprosartan, abolished the L-162,313-mediated increase in axonal levels of TH and DBH mRNA and protein. In a first attempt to identify the proteins involved in the Ang II-mediated axonal transport of TH mRNA, we used a biotinylated 50-nucleotide TH RNA zipcode as bait in the affinity purification of TH zipcode-associated proteins. Mass spectrometric analysis of the TH zipcode ribonucleoprotein (RNP) complex immune-purified from SCG neurons led to the identification of 163 somal and 127 axonal proteins functionally involved in binding nucleic acids, the translational machinery or acting as subunits of cytoskeletal and motor proteins. Surprisingly, immune-purification of the TH axonal trafficking complex, results in the acquisition of DBH mRNA, suggesting that these mRNAs maybe transported to the axon together, possibly in the same RNP complex. Taken together, our results point to a novel mechanism by which Ang II participates in the regulation of axonal synthesis of NE by modulating the local trafficking and expression of TH and DBH, two key enzymes involved in the catecholamine biosynthetic pathway.

Chronic unpredictable mild stress-induced behavioral changes are coupled with dopaminergic hyperfunction and serotonergic hypofunction in mouse models of depression

Accumulating evidence shows that stressful events evoke molecular alterations in the brain, considered a pathology in major depressive disorder (MDD). However, the abnormalities of neurotransmissions as well as intracellular signaling pathways affected by chronic stress in brain have not been fully explored. We investigated the effect of chronic unpredictable mild stress (CUMS) on the emotional behaviors, dopaminergic and serotoninergic function, and intracellular signaling in the nucleus accumbens, hippocampus and prefrontal cortex. Male C57BL/6J mice were exposed to CUMS for 4 weeks. CUMS was shown to induce hyperactivity in a novel environment, decrease interaction time in the social interaction test, prolong feeding latency in the novelty suppressed feeding test and enhance immobility in the forced swimming test. The levels of dopamine, its metabolites and turnover, and protein level of tyrosine hydroxylase (TH) were increased by CUMS in the nucleus accumbens (NAc). The level of serotonin and protein levels of tryptophan hydroxylase (TPH) and TH were decreased by CUMS in the hippocampus (HPC) and prefrontal cortex (PFC). Accompanying the increase in dopaminergic function, phosphorylation levels of extracellular signal-regulated kinases (ERK), protein kinase B (Akt) and cAMP response element-binding protein (CREB) were increased by CUMS in the NAc. Administration of fluoxetine (selective serotonin re-uptake inhibitor: 20 mg/kg i.p.) and aripiprazole (dopamine D2 receptor partial agonist: 0.1 mg/kg i.p.) during CUMS, prevented behavioral changes and increase of dopamine level in the NAc. These data suggest that CUMS-induced depression-like behaviors are coupled with dopaminergic hyperfunction in the NAc and serotonergic hypofunction in the HPC and PFC.

Differential methylation of enhancer at IGF2 is associated with abnormal dopamine synthesis in major psychosis

Impaired neuronal processes, including dopamine imbalance, are central to the pathogenesis of major psychosis, but the molecular origins are unclear. Here we perform a multi-omics study of neurons isolated from the prefrontal cortex in schizophrenia and bipolar disorder (n = 55 cases and 27 controls). DNA methylation, transcriptomic, and genetic-epigenetic interactions in major psychosis converged on pathways of neurodevelopment, synaptic activity, and immune functions. We observe prominent hypomethylation of an enhancer within the insulin-like growth factor 2 (IGF2) gene in major psychosis neurons. Chromatin conformation analysis revealed that this enhancer targets the nearby tyrosine hydroxylase (TH) gene responsible for dopamine synthesis. In patients, we find hypomethylation of the IGF2 enhancer is associated with increased TH protein levels. In mice, Igf2 enhancer deletion disrupts the levels of TH protein and striatal dopamine, and induces transcriptional and proteomic abnormalities affecting neuronal structure and signaling. Our data suggests that epigenetic activation of the enhancer at IGF2 may enhance dopamine synthesis associated with major psychosis.

The Effect of Atypical Antipsychotic Drugs on the Neurotrophic Factors Gene Expression in the MPTP Model of Parkinson’s Disease

Atypical antipsychotics (AAP) are used in the therapy of Parkinson’s disease (PD) for elimination of psychotic symptoms. As the brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) and cerebral dopamine neurotrophic factor (CDNF) play a crucial role in the PD treatment, the aim of our study was the investigation of the effects of chronic treatment with commonly used AAP, clozapine and quetiapine, on the motor behavior and the BDNF, GDNF and CDNF genes expression in the mouse brain in the PD model produced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Clozapine and quetiapine (1 mg/kg, i.p.) were administered 48 hours after the last MPTP injection, and treatment continued for the following 16 days. Then animals were euthanized, substantia nigra (SN), striatum (St) and hippocampus (Hc) were extracted for RT-PCR and tyrosine hydroxylase (TH) western blot assessment. MPTP treatment led to 50% depletion in the TH protein level in the St. MPTP caused significant decrease in both BDNF and GDNF mRNA level in the Hc and St, respectively. At the same time, increase in the GDNF expression in the MPTP + clozapine group in the SN was found. MPTP caused dramatic decrease in the CDNF mRNA level in the SN with simultaneous increase in the St. Both clozapine and quetiapine decreased it to a normal level in the St. The effect of AAP clozapine and quetiapine on the GDNF and CDNF genes expression in the pharmacological model of PD has been shown for the first time.

Tyrosine hydroxylase phosphorylation invivo.

Tyrosine hydroxylase (TH) is the rate-limiting enzyme in the synthesis of the catecholamines dopamine, noradrenaline and adrenaline. One of the major mechanisms for controlling the activity of TH is protein phosphorylation. TH is phosphorylated at serine residues 8, 19, 31 and 40. There have been a number of previous reviews focused on TH phosphorylation invitro and insitu. This review on TH phosphorylation invivo has three main sections focusing on: (1) the methods used to investigate TH phosphorylation invivo, including the animals used, the sacrifice procedures, the tissue preparation, the measurement of TH protein levels and TH phosphorylation and the measurement of TH activation. (2) The regulation of TH phosphorylation and its consequences invivo, including the kinases and phosphatases acting on TH, the stoichiometry of TH phosphorylation, the proteins that bind TH and TH subcellular location. (3) The acute and prolonged TH phosphorylation changes in specific catecholaminergic tissues, including the adrenal medulla, the nigrostriatal pathway and the mesolimbic pathway.

Minocycline Protects against Rotenone-Induced Neurotoxicity Correlating with Upregulation of Nurr1 in a Parkinson's Disease Rat Model.

The aim of this study was to investigate the effect of minocycline in rats with rotenone-induced Parkinson's disease (PD). The open field test was performed to determine the motor ability of the rats. Double immunofluorescence staining was used to detect the expression of tyrosine hydroxylase (TH) and Nurr1 in the substantia nigra (SN) of rats. The relative protein levels of TH, Nurr1, and the total- and phosphorylated-cAMP-response element binding protein (CREB) were determined by western blot analysis. The production of reactive oxygen species (ROS) and nitric oxide (NO) was detected by commercial kits. After exposure to rotenone for 28 days, rats exhibited decreased ambulation and rearing frequency and prolonged immobility time with loss of TH positive neurons in the SN. The phosphorylation levels of CREB and Nurr1 expression decreased significantly accompanied with the release of ROS and NO. Minocycline alleviated the motor deficits of rats lesioned by rotenone and elevated the expression of TH, as well as suppressing the release of ROS and NO in the SN. That was in line with the elevated phosphorylation levels of CREB and Nurr1 expression. In conclusion, our present study showed minocycline protected against neurotoxicity in a rotenone-induced rat model of PD, which was correlated with upregulation of Nurr1.

Melatonin treatment affects changes in adrenal gene expression of catecholamine biosynthesizing enzymes and norepinephrine transporter in the rat model of chronic-stress-induced depression.

This study investigated the effects of melatonin treatment on adrenal catecholamine content, synthesis, uptake, and vesicular transport induced by the chronic unpredictable mild stress (CUMS) model of depression in rats. This entailed quantifying the norepinephrine, epinephrine, mRNA, and protein levels of tyrosine hydroxylase (TH), dopamine-β-hydroxylase (DBH), phenylethanolamine N-methyltransferase (PNMT), norepinephrine transporter (NET), and vesicular monoamine transporter 2 (VMAT2) in the adrenal medulla. CUMS caused a significant depletion of norepinephrine stores and protein levels of TH, DBH, and NET, whereas the gene expression of PNMT was increased. It was observed that melatonin treatment in the CUMS rats prevented the stress-induced decrease in norepinephrine content and the protein expression of TH, DBH, and NET in the adrenal medulla of chronically stressed rats. The present study demonstrates the stimulatory effect of melatonin on adrenomedullary synthesis, the uptake and content of catecholamine in the rat model of chronic stress-induced depression.

Baicalin regulates the dopamine system to control the core symptoms of ADHD

We aimed to test the therapeutic effects of baicalin on attention deficit hyperactivity disorder (ADHD) in an animal model and to explain the potential mechanism. We investigated the therapeutic effects and mechanisms of baicalin in a spontaneously hypertensive rat (SHR) model of ADHD depending on the dopamine (DA) deficit theory. In this study, fifty SHRs were randomly divided into five groups: methylphenidate (MPH), baicalin (50 mg/kg, 100 mg/kg, or 150 mg/kg), and saline-treated. Ten Wistar Kyoto (WKY) rats were used as controls. All rats were orally administered the treatment for four weeks. Motor activity, spatial learning and memory ability were assessed with the open-field and Morris water-maze tests. The mRNA and protein levels of tyrosine hydroxylase (TH), vesicular monoamine transporter 2 (VMAT2), synaptosomal-associated protein of molecular mass 25kD (SNAP25) and synataxin 1a in synaptosomes were detected with real-time polymerase chain reaction (PCR) and Western blot. In addition, DA levels were measured in the prefrontal cortex and striatum. The results indicated that both MPH and baicalin at doses of 150 mg/kg and 100 mg/kg significantly decreased the hyperactivity and improved the spatial learning memory deficit in the SHRs and increased the synaptosomal mRNA and protein levels of TH, SNAP25, VMAT2 and synataxin 1a compared with saline treatment. MPH significantly increased DA levels in both the prefrontal cortex (PFC) and striatum, while baicalin significantly increased DA levels only in the striatum. The results of the present study showed that baicalin treatment was effective for controlling the core symptoms of ADHD. Baicalin increased DA levels only in the striatum, which suggested that baicalin may target the striatum. The increased DA levels may partially be attributed to the increased mRNA and protein expression of TH, SNAP25, VMAT2, and syntaxin 1a. Therefore, these results suggested that the pharmacological effects of baicalin were associated with the synthesis, vesicular localization, and release of DA and might be effective in treating ADHD. However, further studies are required to better understand the molecular mechanisms underlying these findings.

NLRP3 inflammasome pathway is involved in olfactory bulb pathological alteration induced by MPTP.

Olfactory bulb, as one of sensory organs opening to the outside, is susceptible to toxic environment and easy to deteriorate. Recent studies in Parkinson's disease (PD) patients and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys have shown that abnormal α-synuclein is accumulated in the olfactory glomeruli, suggesting that the lesions of PD are not only confined to the substantia nigra (SN) but also located in the olfactory bulb. Thus, olfactory bulb might be the region of onset in PD pathogenesis and a targeted region for diagnosis and treatment of PD. However, the relationship between olfactory bulb and pathogenesis of PD remains unclear. In the present study, we investigated the inflammatory pathological alterations in olfactory bulb and the underlying mechanisms in chronic MPTP mice. Mice were treated with MPTP/P, i.e., MPTP (25 mg/kg, s.c.) plus probenecid (250 mg/kg, i.p.) every 4 days, for ten times. The mice displayed typical parkinsonian syndrome. Then we examined their olfactory function and the pathologic changes in olfactory bulb. The mice showed obvious olfactory dysfunction in a buried pellet test. Immunohistochemical studies revealed that tyrosine hydroxylase (TH) protein levels were significantly decreased, whereas abnormal α-synuclein was significantly increased in the olfactory bulbs. Furthermore, the olfactory bulbs in MPTP/P-treated mice showed significantly increased levels of interleukin-1β (IL-1β), caspase-1, glial fibrillary acidic protein (GFAP), Toll receptor 4 (TLR4), phosphorylation of p65, as well as activated molecules of NOD-like receptor protein 3 (NLRP3) that were associated with neuroinflammation. Our results demonstrate that MPTP/P-caused olfactory bulb damage might be related to NLRP3-mediated inflammation.

Feeding-produced subchronic high plasma levels of uric acid improve behavioral dysfunction in 6-hydroxydopamine-induced mouse model of Parkinson's disease.

The development of Parkinson's disease (PD) involves the degeneration of dopaminergic neurons caused by oxidative stress. Accumulating clinical evidence indicates that high blood levels of uric acid (UA), an intrinsic antioxidative substance, are associated with reduced risk of PD. However, this hypothesis has not been confirmed by in-vivo experiments. The present study investigated the effects of UA on behavioral abnormalities in the development of PD. We used unilateral 6-hydroxydopamine-lesioned mice, which were fed on a diet containing 1% UA and 2.5% potassium oxonate (an uricase inhibitor) to induce hyperuricemia. A significant elevation in UA levels was found in groups that were fed a UA diet. The 6-hydroxydopamine-lesioned mice showed impaired rotarod performance and increased apomorphine-induced contralateral rotations. These behavioral abnormalities were significantly reversed by feeding a UA diet for 1 week before and 5 weeks after surgery (subchronic hyperuricemia). These behavioral improvements occurred in parallel with recovery of tyrosine hydroxylase protein levels in the lesioned striatal side. The present study with a dietary hyperuricemia mice model confirms that UA exerts a neuroprotective effect on dopaminergic neuronal loss, improving motor dysfunction and ameliorating PD development.

The effects of rotenone on TH, BDNF and BDNF-related proteins in the brain and periphery: Relevance to early Parkinson’s disease

Loss of dopaminergic neurons in the substantia nigra (SN) is one of the pathological hallmarks in Parkinson’s disease (PD). This neuron loss is accompanied by reduced protein and activity levels of tyrosine hydroxylase (TH), the rate-limiting enzyme of catecholamine synthesis. Reduced nigral brain-derived neurotrophic factor (BDNF) has been postulated to contribute to the loss of nigral dopaminergic neurons in PD by causing a lack of trophic support. Prior to this nigral cell loss many patients develop non-motor symptoms such as hyposmia, constipation and orthostatic hypotension. We investigated how TH, BDNF and BDNF related receptors are altered in the SN, olfactory bulb, adrenal glands and colon (which are known to be affected in PD) using rotenone-treated rats. Rotenone was administered to Sprague-Dawley rats at a dose of 2.75 mg/kg, 5 days/week for 4 weeks, via intraperitoneal injections. Rats underwent behavioural testing, and tissues were collected for western blot and ELISA analysis. This rotenone treatment induced reduced rears and distance travelled in the rearing and open field test, respectively but caused no impairments in forced movement (rotarod test). The SN had changes consistent with a pro-apoptotic state, such as increased proBDNF but no change in TH; whereas, the colon had significantly reduced TH and increased sortilin. Thus, our results indicate further investigation is warranted for this rotenone-dosing paradigm’s capacity for reproducing the early stage of PD, as we observed impairments in voluntary movement and pathology in the colon without overt motor symptoms or nigral dopaminergic loss.

Kaempferol Attenuates LPS-Induced Striatum Injury in Mice Involving Anti-Neuroinflammation, Maintaining BBB Integrity, and Down-Regulating the HMGB1/TLR4 Pathway

Neuroinflammation has been demonstrated to be linked with Parkinson’s disease (PD), Alzheimer’s disease, and cerebral ischemia. Our previous investigation had identified that kaempferol (KAE) exerted protective effects on cortex neuron injured by LPS. In this study, the effects and possible mechanism of KAE on striatal dopaminergic neurons induced by LPS in mice were further investigated. The results showed that KAE improved striatal neuron injury, and increased the levels of tyrosine hydroxylase (TH) and postsynaptic density protein 95 (PSD95) in the striatum of mice. In addition, KAE inhibited the production of pro-inflammatory cytokines, including interleukin 1β (IL-1β), interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), reduced the level of monocyte chemotactic protein-1 (MCP-1), intercellular cell adhesion molecule-1 (ICAM-1), and cyclooxygenase-2 (COX-2) in the striatum tissues. Furthermore, KAE protected blood-brain barrier (BBB) integrity and suppressed the activation of the HMGB1/TLR4 inflammatory pathway induced by LPS in striatum tissues of mice. In conclusion, these results suggest that KAE may have neuroprotective effects against striatum injury that is induced by LPS and the possible mechanisms are involved in anti-neuroinflammation, maintaining BBB integrity, and down-regulating the HMGB1/TLR4 pathway.

The effect of atypical antipsychotic drugs on the neurotrophic factors gene expression in the MPTP model of Parkinson's disease

Atypical antipsychotics (AAP) are used in the therapy of Parkinson’s disease (PD) for elimination of psychotic symptoms. As the brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) and cerebral dopamine neurotrophic factor (CDNF) play a crucial role in the PD treatment, the aim of our study was the investigation of the effects of chronic treatment with commonly used AAP, clozapine and quetiapine, on the motor behavior and the BDNF, GDNF and CDNF genes expression in the mouse brain in the PD model produced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Clozapine and quetiapine (1 mg/kg, i.p.) were administered 48 hours after the last MPTP injection, and treatment continued for the following 16 days. Then animals were euthanized, substantia nigra (SN), striatum (St) and hippocampus (Hc) were extracted for RT-PCR and tyrosine hydroxylase (TH) western blot assessment. MPTP treatment led to 50% depletion in the TH protein level in the St. MPTP caused significant decrease in both BDNF and GDNF mRNA level in the Hc and St, respectively. At the same time, increase in the GDNF expression in the MPTP + clozapine group in the SN was found. MPTP caused dramatic decrease in the CDNF mRNA level in the SN with simultaneous increase in the St. Both clozapine and quetiapine decreased it to a normal level in the St. The effect of AAP clozapine and quetiapine on the GDNF and CDNF genes expression in the pharmacological model of PD has been shown for the first time.

MAPKs and NF-κB-mediated acrylamide-induced neuropathy in rat striatum and human neuroblastoma cells SY5Y.

Acrylamide (ACR) is a potent neurotoxin that can be produced during high-temperature food processing, but the underlying toxicological mechanism remains unclear. In this study, the detrimental effects of ACR on the striatal dopaminergic neurons and the roles of mitogen-activated protein kinases (MAPKs) and nuclear factor κB (NF-κB) in ACR-induced neuronal apoptosis were investigated. Acute ACR exposure caused dopaminergic neurons loss and apoptosis as revealed by decreased tyrosine hydroxylase (TH)-positive cells and TH protein level and increased terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive cells in the striatum. ACR-decreased glutathione content, increased levels of malondialdehyde, proinflammatory cytokines tumor necrosis factor α, and interleukin 6. In addition, nuclear NF-κB and MAPKs signaling pathway with c-Jun N-terminal kinase (JNK) and p38 were activated by ACR. Specific inhibitors were used to explore the roles of MAPKs and NF-κB pathways in ACR-induced apoptosis in SH-SY5Y cells. Pretreatment with JNK-specific inhibitors SP600125 markedly upregulated the reduced B-cell lymphoma 2 (Bcl-2) content and downregulated the increased Bcl-2-associated Xprotein (Bax) level and thereby eventually reduced the proportions of early and late apoptotic cells induced by ACR, while p38 suppression by SB202190 only reversed the decrease in Bcl-2 expression. Inhibition of NF-κB by BAY 11-7082 markedly upregulated Bax level and decreased Bcl-2 expression, and eventually increasing the proportions of neuronal apoptosis compared with that in ACR alone. These results suggested that JNK contributed to ACR-induced apoptosis, while NF-κB acted as a protective regulator in response to ACR-induced neuropathy. This study helps to offer a deeper insight into the mechanism of ACR-induced neuropathy.

Regulation of tyrosine hydroxylase in periodontal fibroblasts and tissues by obesity-associated stimuli.

Tyrosine hydroxylase (TH) catalyzes the rate-limiting step in the synthesis of catecholamines and has been connected to aggravated progression of periodontal disease under chronic stress. Obesity is known to increase the risk of periodontitis and adipokines have been suggested to be a pathomechanistic link. This study examines if obesity-associated stimuli have regulatory effects on TH levels in periodontal cells and tissues. Human periodontal ligament fibroblasts were cultured in the presence of leptin or visfatin for up to 2days. Untreated cells served as control. TH regulation was analyzed by real-time PCR, immunocytochemistry and ELISA. TH gene expression in periodontal tissues of normal-weight and obese rodents was determined. Examination of gingival biopsies from rats and patients with and without periodontal disease was performed by real-time PCR or immunohistochemistry. For statistics, ANOVA and post hoc tests were applied (p < 0.05). In vitro, TH gene expression and protein levels were increased by leptin and visfatin. In vivo, TH gene expression was upregulated in periodontal tissues of obese rodents as compared to normal-weight animals. Additionally, increased TH gene expression was found in rat gingival biopsies with experimental periodontitis. Human gingival biopsies from sites of periodontitis confirmed the animal data by demonstrating elevated TH levels at periodontally diseased sites. This study provides original evidence that obesity-associated stimuli induce a TH upregulation in periodontal cells and tissues. Since TH levels were also increased at periodontitis sites, our in vitro and animal findings suggest that this enzyme could represent a pathomechanism whereby obesity contributes to periodontitis.

COA-Cl induces dopamine release and tyrosine hydroxylase phosphorylation: In vivo reverse microdialysis and in vitro analysis

We found that local perfusion of COA-Cl (0.1, 0.4, or 1.0 mM) into the dorsal striatum of living mice produced a significant and dose-dependent increase in extracellular DA levels, with the highest dose of 1.0 mM COA-Cl producing an approximately 5-fold increase in DA. Consistent with in vivo findings, 0.1 and 0.2 mM COA-Cl significantly and dose-dependently enhanced DA release 3.0 to 5.0-fold in PC12 cells, an in vitro model of DA-responsive neurons. Interestingly, the increase in striatal DA levels by COA-Cl in vivo was similar in magnitude to that observed in PC12 cells. Treatment with 0.1 mM COA-Cl significantly increased both Ser31 and Ser40 phosphorylation of tyrosine hydroxylase (TH) in PC12 cells, and Ser40 phosphorylation in iCell neurons, without altering total TH protein levels. Further, we examined whether COA-Cl could stimulate neurite outgrowth in PC12 cells and iCell neurons and found that COA-Cl significantly induced neurite outgrowth in both cell lines. Our results provide the first evidence that COA-Cl can stimulate dose-dependent DA release and activation of TH phosphorylation, suggesting that COA-Cl may be a promising therapeutic candidate for the treatment of neurological dysfunction associated with low DA.