Tyrosine Hydroxylase Activity in Discrete Brain Regions of Depression Model Rats

Abstract: Tyrosine hydroxylase (TH) activity was measured in discrete brain regions of rats during short-term forced running stress (FRS). TH activity was also determined in a depression-like state and in a recovered state after a long-term FRS. Under the short-term FRS, the TH activity showed a significant increase in the locus ceruleus, certain limbic regions and tuberoinfundibular system. In the depression-like state, however, there was a significant decrease in the locus ceruleus and certain limbic regions, but a significant increase was seen in the median eminence. The TH activity in recovered rats showed no difference from the level in the controls. These findings demonstrate an adaptive increase in the TH activity in relation to stress, and may also indicate a failure of adaptation in the depression-like state.     

Lithium Chloride Induces the Expression of Tyrosine Hydroxylase in hNT Neurons

In the present study, several doses of lithium chloride were tested for their ability to induce the expression of tyrosine hydroxylase (TH) in neurons derived from a human teratocarcinoma cell line (hNT) after 5 and 10 days in vitro (DIV). Following immunocytochemical staining for tyrosine hydroxylase, the percentage of TH-positive neurons was determined and morphometric analysis, including mean soma profile area and neuritic length, was performed. hNT neurons responded to lithium treatment in a dose-dependent manner. In 5 DIV, the most effective dose of lithium chloride (1.0 mM) increased the number of TH-positive neurons approximately sixfold. In addition, both TH-positive hNT neuron mean soma profile area and neurite length were significantly larger than controls by 60 and 70%, respectively. Moreover, even after withdrawal of lithium chloride on day 5, the number of TH-positive neurons in 10 DIV cultures remained significantly increased. These data suggest that hNT cells are indeed responsive to lithium exposure and may serve as a continual source of TH-expressing neurons in new therapeutic approaches to degenerative brain disease.     

死亡相关蛋白小分子干扰RNA对帕金森病大鼠黑质酪氨酸羟化酶表达的影响

目的:利用动物模型探讨死亡相关蛋白(FADD)小分子干扰RNA(siRNA)对帕金森病(PD)大鼠黑质酪氨酸羟化酶(TH)表达的影响。方法:40只雄性Wistar大鼠随机分为4组。经立体定向定位黑质,PD组:注入6-羟基多巴(6-OHDA);siRNA组:注入FADD siRNA2次后再注入6-OHDA;SiRNA阴性对照组:注入FADD siRNA阴性对照物2次后再注入6-OHDA;正常对照组:注入抗坏血酸生理盐水。各组大鼠术后4周处死,取鼠的术侧中脑黑质,利用原位杂交检测FADD、TH mRNA表达。结果:PD组与正常对照组比较FADD mRNA表达显著增加(P<0.01);siRNA组与PD组比较FADD mRNA表达显著减少(P<0.05);siRNA阴性对照组与正常对照组比较FADD mRNA表达量无显著差异(P>0.05)。PD组与正常对照组比较TH mRNA表达显著减少(P<0.01);siRNA组与PD组比较TH mRNA表达显著增加(P<0.05);siRNA阴性对照组与正常对照组比较TH mRNA表达量差异无统计学意义(P>0.05)。结论:FADDsiRNA可能通过抑制凋亡对PD大鼠模型有一定的保护和治疗作用。     

Intrastriatal 6-OHDA Lesion Differentially Affects Dopaminergic Neurons in the Ventral Tegmental Area of Prenatally Stressed Rats

Exposure to a variety of stressful events during the last week of pregnancy in rats interferes with the correct progeny development, which in turn leads to delays in motor development, impaired adaptation to stressful conditions, altered sexual behaviour, learning deficits, neuronal development and brain morphology. Many of these alterations have been attributed to changes in dopamine (DA) neurotransmission and occur primarily in the mesolimbic system. We found that prenatally stressed offspring showed higher levels of cells expressing tyrosine hydroxylase (TH) in the ventral tegmental area (VTA) and that these cells were more susceptible to a neurochemical insult with 6-hydroxy-DA (6-OHDA) in adulthood. Moreover, prenatally stressed rats presented differences in terms of the number and asymmetry of neuronal nitric oxide synthase-expressing cells in the VTA and nucleus accumbens, respectively. Similar to the results described for TH-expressing cells, the nitrergic systems were differentially regulated after 6-OHDA lesion in control and prenatally stressed rats. These results indicated that prenatal stress affects the dopaminergic and nitrergic systems in the mesolimbic pathway. In addition, we propose that the mesolimbic areas are more susceptible than the motor areas to a neurochemical insult during adult life.     

Electron Microscopy of Colocalization of GABA and Tyrosine Hydroxylase Expression in Rat Olfactory Bulb Transplants

Juxtaglomerular (JG) neurons of rat olfactory bulb (OB) are a subset of inhibitory interneurons within the OB, acting via lateral inhibition to modulate the afferent input of the primary olfactory nerve. The JG neurons, composed of periglomerular, external tufted, and short axon cells, have been found to express various neurotransmitters, including γ-amino butyric acid (GABA) and dopamine. A specific set of neurons within the periglomerular population have also been shown to coexpress these neurotransmitters. Deafferentation or functional odor deprivation of the normal OB causes a loss of tyrosine hydroxylase (TH) (the rate limiting enzyme in the dopamine synthesis pathway) expression within the JG cell population, but appears to have no effect on GABA levels. Our laboratory has developed a transplantation model to further study the effects of deafferentation and subsequent reinnervation within this system. Sections from transplant (TX) OBs were reacted for GABA and TH using immunocytochemical localization protocols and studied by electron microscopy. Numerous neuronal populations were found to be either TH or GABA positive in this study, with a specific subpopulation showing colocalization of both. Although the architecture of the TX OB is somewhat disrupted and the TH- and GABA-positive cells were not as uniform in their arrangement as they are in the normal OB, we found that these cells in the TX OB were morphologically similar to the JG cells of normal OB. Positively labeled profiles were also found to receive and form numerous synaptic contacts with both host olfactory nerve axons as well as with the processes of donor neurons. These synaptic contacts were within areas that resemble the glomeruli of normal OB, suggesting that lateral inhibition may occur within the TX OB as it does in the normal. The coexpression of GABA and TH within specific neurons also indicates that a unique population of JG neurons that occur in normal OB are also found within this transplanted system as well.     

Dieldrin对PC12细胞的增殖及酪氨酸羧化酶mRNA表达的影响

目的 :观察有机氯杀虫剂dieldrin对培养的PC12细胞增殖及对其酪氨酸羟化酶mRNA(THmRNA)表达的影响 ,探讨该毒物致帕金森病 (PD)的可能机制。方法 :以MPP+ 为阳性对照 ,用不同浓度 (10 -4 ～ 1mmol·L-1)的MPP+ 和dieldrin分别于预PC12细胞 2 4h后计细胞数 ,并采用半定量逆转录聚合酶链式反应 (RT PCR)方法测定THmRNA表达的改变。结果 :(1)MPP+ 和dieldrin对PC12细胞均有毒性 ,1mmol·L-1的MPP+ 可使细胞数减少至对照组的 45 % (P <0 0 1) ,低于此浓度的MPP+ 对细胞增殖无影响 ;但 0 1mmol·L-1的dieldrin就可使细胞数减少至对照组的 3 0 % (P <0 0 1) ,1mmol·L-1的dieldrin使PC12细胞全部死亡。 (2 )MPP+ 和dieldrin均可降低THmRNA的表达。 0 1mmol·L-1MPP+ 和dieldrin使细胞THmRNA的表达分别下降至对照组的 69 3 % (P >0 0 5 )和 61 7% (P <0 0 1)。结论 :Dieldrin不仅具有与MPP+ 相同的抑制培养的PC12细胞的增殖及THmRNA表达的作用 ,而且其对细胞的毒性强于MPP+ ,提示dieldrin是一种潜在的致PD物质 ,其与PD的关系值得进一步研究     

Inhibitory Actions of Acute Estradiol Treatment on the Activity and Quantity of Tyrosine Hydroxylase in the Median Eminence of Ovariectomized Rats

The effects of acute estradiol (E₂) treatment on both the activity of tyrosine hydroxylase (TH) in the median eminence and the serum level of prolactin (PRL) were investigated. Twelve-day-ovariectomized rats were injected with 17β-E₂ (25μg sc) at 1100 h and sacrificed hourly from 1200 to 2300 h. TH activity was quantified by measuring the amount of exogenous tyrosine converted to L-DOPA in vitro by aliquots of median eminence homogenates. Serum PRL levels were evaluated by radioimmunoassay. A biphasic response of TH activity to treatment was observed: an immediate decrease occurred—preceding and accompanying a rise in serum PRL—followed by an increase beyond control levels 2 h after the maximal release of PRL. The increase in TH activity could be prevented by the pretreatment of rats with a specific rat PRL antiserum, suggesting it was not due to E₂ per se but rather mediated by the E₂-induced PRL elevation. To pin-point the process underlying the E₂-induced decrease in TH activity, we evaluated the kinetic parameters of TH in the median eminence as well as its quantity (by Western blot analysis) in the median eminence and arcuate nucleus. Finally, we used a sensitive dot-blot assay to quantify specific TH messenger ribonucleic acid in the arcuate nucleus. The decrease in TH activity after E₂ treatment paralleled an immediate decrease in the affinity of TH for its pterin cofactor (6-MPH4), while V_max remained unchanged. A decrease in the amount of TH protein in the arcuate nucleus and median eminence as well as in the TH messenger ribonucleic acid level in the arcuate nucleus was also observed, but the latency of these effects precluded a major involvement in the immediate decline of TH activity. Therefore, when observed separately from those of PRL, E₂ effects on TH in tuberoinfundibular dopaminergic neurons are clearly inhibitory consisting of a ‘deactivation’ of the enzyme together with a reduction of its synthesis.     

Tyrosine Hydroxylase Replacement in Experimental Parkinson's Disease with Transvascular Gene Therapy

Summary: Transvascular gene therapy of Parkinson''s disease (PD) is a new approach to the gene therapy of PD and involves the global distribution of a therapeutic gene to brain after an intravenous administration and transport across the blood-brain barrier (BBB). This is enabled with the development of a nonviral gene transfer technology that encapsulates plasmid DNA inside pegylated immunoliposomes or PILs. An 85- to 100-nm liposome carries the DNA inside the nanocontainer, and the liposome surface is conjugated with several thousand strands of 2000-Da polyethyleneglycol (PEG). This PEGylation of the liposome stabilizes the structure in the blood stream. The liposome is targeted across the BBB via attachment to the tips of 1-2% of the PEG strands of a receptor-specific monoclonal antibody (mAb) directed at a BBB receptor, such as the insulin receptor or transferrin receptor (TfR). Owing to the expression of the insulin receptor or the TfR on both the BBB and the neuronal plasma membrane, the PIL is able to reach the neuronal nuclear compartment from the circulation. Brain-specific expression is possible with the combined use of the PIL gene transfer technology and brain-specific gene promoters. In the 6-hydroxydopamine rat model of experimental PD, striatal tyrosine hydroxylase (TH) activity is completely normalized after an intravenous administration of TfRmAb-targeted PILs carrying a TH expression plasmid. A treatment for PD may be possible with dual gene therapy that seeks both to replace striatal TH gene expression with TH gene therapy, and to halt or reverse neurodegeneration of the nigro-striatal tract with neurotrophin gene therapy.     

Association between Antipsychotics-Induced Restless Legs Syndrome and Tyrosine Hydroxylase Gene Polymorphism

Objective

Restless legs syndrome (RLS) has been reported to be more prevalent in schizophrenic patients who take antipsychotics. The cause of RLS is unknown but associated with dopaminergic deficiency. Tyrosine hydroxylase (TH) is the enzyme responsible for catalyzing the conversion of L-tyrosine to DOPA. The purpose of this study is to determine whether the TH gene Val81Met polymorphism is associated with antipsychotic-induced RLS.

Methods

One hundred ninety Korean schizophrenic patients were evaluated by the diagnostic criteria of the International RLS Study Group (IRLSSG). The genotyping was performed by PCR-based methods.

Results

Of the one hundred ninety schizophrenic patients, 44 (23.2%) were found to have RLS. Although there were no significant associations between TH genotypes or allele frequencies and RLS, when separate analyses were performed by sex (male or female), we detected significant differences in the frequencies of the genotype (χ²=6.15, p=0.046) and allele (χ²=4.67, p=0.031) of the TH gene Val81Met polymorphism between those with and without RLS in the female patients.

Conclusion

These findings suggest that the TH gene Val81Met SNP might be associated with antipsychotic-induced RLS in female schizophrenic patients.     

Comparison of the Temporal Programs Regulating Tyrosine Hydroxylase and Enkephalin Expressions in TIDA Neurons of Lactating Rats Following Pup Removal and then Pup Return

Dopamine (DA) and enkephalin (ENK) release from the tuberoinfundibular dopaminergic neurons (TIDA) into the hypophysial portal circulation is fundamentally different under non-lactating and lactating conditions. The aim of this experiment was to compare the effect of a brief interruption then resumption of suckling on the temporal program of tyrosine hydroxylase (TH; rate-limiting enzyme of dopamine synthesis) and ENK regulation in dams. On post partum day 10, pups were removed for a 4-h period from a group of the dams then returned for 4- and 24-h periods. It was examined whether such a brief interruption of suckling provokes full up-regulation of TH and down-regulation of ENK, and whether reinitiation of suckling limits the extent to which TH up- and ENK down-regulate. At the end of experiment, the animals were decapitated. In situ hybridization was used to examine the expression of TH and ENK mRNA in the arcuate nucleus where TIDA neurons reside. The results showed that, on one hand, the removal of pups induced TH up-regulation, on the other hand, ENK expression also increased 8 h after removal of pups and then started to slowly decline. In dams whose sucklings were reinitiated both TH and ENK mRNAs were up-regulated at least for a day. ENK expression responded more slowly to the removal of pups than expression of TH, and after reinitiation of suckling, the temporal program of regulation of both TH and ENK expressions ran parallel in the first 24 h.     

Lactacystin对酪氨酸羟化酶基因和蛋白表达的影响

目的:探讨lactacystin对酪氨酸羟化酶(TH)基因及蛋白表达的影响。方法:在大鼠单侧黑质致密部(SNc)立体定向注射蛋白酶体抑制剂lactacystin 0 .2、2、8μg抑制α- synuclein的降解,对照组注射等量生理盐水,观察大鼠自主行为和阿扑吗啡诱导的旋转行为变化;应用免疫组化观察黑质细胞-αsynuclein和TH蛋白表达;采用RT- PCR方法测定黑质细胞THmRNA的表达。结果:注射lactacystin 0 .2 μg组未见异常;2和8μg组大鼠出现进行性的运动迟缓、少动、头向对侧倾斜、震颤,但后者更加明显并出现阿扑吗啡诱导的向对侧旋转运动;给药后3周注射lactacystin 2和8μg组大鼠黑质细胞α-synuclein表达分别较对照组高出5 6.71% (P <0 .0 1)和12 2 .16% (P <0 .0 0 1) ;部分细胞胞质内出现αsynuclein免疫反应呈强阳性的Lewy小体;THmRNA和蛋白的表达分别较对照组减少了63 .3 4% (P <0 .0 0 1)、60 .5 5 % (P <0 .0 5 )和81.95 % (P <0 .0 0 1)、89.5 3 % (P <0 .0 1)。结论:lactacystin对中脑黑质细胞TH基因及蛋白表达均有显著的抑制作用,参与了lactacystin所致的帕金森病发病机制。     

Cyclosporin A Attenuates the Decrease in Tyrosine Hydroxylase Immunoreactivity in Nigrostriatal Dopaminergic Neurons and in Striatal Dopamine Content in Rats with Intrastriatal Injection of 6-Hydroxydopamine

To explore new therapeutic strategies for Parkinson's disease, we studied the possible protective effect of an immunosuppressant, cyclosporin A (CsA), treatment on changes in dopaminergic function in rats with intrastriatal injections of 6-hydroxydopamine (6-OHDA). Four weeks after injection of 6-OHDA, dopamine (DA) and dihydroxyphenylacetic acid in the striatum were depleted by 70–80%, and repeated high-dose CsA (20 mg/kg) treatment for 1 week significantly protected against these depletions. Tyrosine hydroxylase immunoreactivity (TH-IR) of the cell bodies in the substantia nigra pars compacta (SNc) ipsilateral to the injection were lower than on the contralateral side at 4 weeks but not at 1 week after 6-OHDA injection. The number of TH-positive cell bodies in the SNc decreased to 64% but CsA treatment increased this to 87%. The staining of microglia in the SN with OX42 andGriffonia simplicifoliaB₄isolectin was intense at 3 days and gradually decreased by 28 days after injection. At 3 and 7 days after injection, the microglial staining in the SN was prominent and equal both in the 6-OHDA group and in ascorbic acid (SA)-injected controls. By 28 days postinjection, the staining had decreased to control levels in the SA group but was still above the control in the 6-OHDA group. CsA treatment did not affect this staining in either group. These results suggest that CsA protects against 6-OHDA-induced injury of nigrostriatal DA neurons by a mechanism not involving microglia.     

Psychosis in Spinocerebellar Ataxias: a Case Series and Study of Tyrosine Hydroxylase in Substantia Nigra

Spinocerebellar ataxias are a genetically heterogeneous group of degenerative diseases typically characterized by progressive ataxia and to various degrees, neuropathy, amyotrophy, and ocular abnormalities. There is increasing evidence for non-motor manifestations associated with cerebellar syndromes including cognitive and psychiatric features. We studied a retrospective clinical case series of eight subjects with spinocerebellar ataxias (SCAs) 2, 3, 7, and 17, all displaying features of psychosis, and also measured tyrosine hydroxylase (TH) staining of the substantia nigra (SN) at autopsy, among four of the subjects. We hypothesized that increased dopamine production in the SN may underlie the pathophysiology of psychosis in SCAs, given evidence of increased dopamine production in the SN in schizophrenia, as measured by TH staining. We analyzed differences in TH staining between the SCA psychosis cohort (n = 4), a heterogeneous ataxic cohort without psychosis (n = 22), and non-diseased age- and sex-matched control group (n = 12). SCA subjects with psychosis did not differ significantly in TH staining versus ataxic cases without psychosis. There was, however, increased TH staining in the ataxic cohort with and without psychosis (n = 26), compared to non-diseased controls (n = 12). Psychotic features were similar across subjects, with the presence of delusions, paranoia, and auditory hallucinations. Our findings are preliminary because of small numbers of subjects and variable neuropathology; however, they suggest that psychosis is a clinical feature of SCAs and may be under-recognized. While the underlying pathophysiology remains to be fully established, it may be related to extra-cerebellar pathology, including a possible propensity for increased dopamine activity in the SN.     

db-cAMP对胚胎干细胞来源的神经细胞酪氨酸羟化酶mRNA水平的影响

目的：体外诱导胚胎干细胞（ES细胞）定向分化为多巴胺能神经元并促进其长期存活和特性维持。方法：以全反式维甲酸（ATRA）诱导ES细胞定向分化为神经细胞,培养液中加入双丁酰基环腺苷磷酸（db-cAMP）继续培养,RT-PCR方法检测酪氨酸羟化酶基因（TH基因）和survivin基因的mRNA水平变化。结果：db-cAMP可上调ES细胞来源的神经细胞中TH基因的mRNA水平,在实验早期还可上调survivin基因的mRNA水平。结论：db-cAMP可以促进ES细胞来源的多巴胺能神经元的存活和特性维持,抗凋亡可能是其作用机制之一。     

Ontogenetic Serotoninergic Lesioning Alters Histaminergic Activity in Rats in Adulthood

The aim of this study was to determine histamine content in the brain and the effect of histamine receptor antagonists on behavior of adult rats lesioned as neonates with the serotonin (5-HT) neurotoxin 5,7-dihydroxytryptamine (5,7-DHT). At 3 days after birth Wistar rats were pretreated with desipramine (20 mg/kg ip) before bilateral icv administration of 5,7-DHT (37.5 μg base on each side) or saline—ascorbic (0.1%) vehicle (control). At 10 week levels of 5-HT and its metabolite 5-hydroxyindole acetic acid (5-HIAA) were determined in frontal cortex, striatum, and hippocampus by an HPLC/ED technique. In the hypothalamus, frontal cortex, hippocampus and medulla oblongata, the level of histamine was analyzed by an immunoenzymatic method. Behavioral observations (locomotion, exploratory-, oral-, and stereotyped activity) were performed, and effects of DA receptor agonists (SKF 38393, apomorphine) and histamine receptor antagonists S(+)chlorpheniramine (H₁), cimetidine (H₂), and thioperamide (H₃) were determined. We confirmed that 5,7-DHT profoundly reduced contents of 5-HT and 5-HIAA in the brain in adulthood. Histamine content was also reduced in all examined brain regions. Moreover, in 5,7-DHT-lesioned rats the locomotor and oral activity responses to thioperamide were altered, and apomorphine-induced stereotype was intensified. From the above, we conclude that an intact central serotoninergic system modulates histamine H₃ receptor antagonist effects on the dopaminergic neurons in rats.