Until the beginning of this century, neurons of the supraoptic nucleus (SON) were repeatedly shown to express tyrosine hydroxylase (TH) in salt loaded rats. However, its role remains unsolved due to methodological problems. Given that these issues can now be solved using transgenic mice and more advanced methods, the aim of this study was to reproduce the salt loading models used in rats, in C57BL/6 mice and transgenic mice expressing the green fluorescent protein gene under the TH promoter. Our study also attempted to identify a model that would most significantly increase TH synthesis in vasopressinergic neurons. This was assessed with immunocytochemistry by measuring the number of TH-immunoreactive neurons in the SON and the intraneuronal content of TH-immunoreactive material in individual neurons. In the first model, when using 3% NaCl as drinking water, the highest number of TH-immnopositive neurons was detected on the 3rd day, while the intraneuronal TH content did not change. In the second model, 10 hours after the intraperitoneal administration of 8.5% NaCl (experiment) or 0.9% NaCl (control), the number of TH-immunopositive neurons was significantly higher than in the first model. Moreover, the intraneuronal content of TH increased. Additional PCR analysis showed in the second model an increase in the expression of the TH gene and genes of some transcription factors (Sp1, Atf4, c-Fos, c-Jun) that initiate the TH gene expression in SON. Thus, we developed and characterized a salt loading model in mice with the highest level of TH synthesis, which will be used in the future to assess the functional significance of this protein.

Group-living insects like the pea aphid, Acythosiphon pisum, use population density as a key signal to regulate behavior, but the underlying mechanisms of individual responses remain unclear. This study employed a novel dual-color system to precisely track individual aphid behavior across a density gradient. We found that aphid behavioral responses are not linear but are triggered at critical density thresholds, which differ depending on the aphid's initial state (settled or active). As density increased, aphids exhibited significantly greater movement and reduced reproductive output, with a key behavioral shift toward dispersal occurring above 1.25 individuals/cm2 (1: 11 group). To investigate the molecular basis for this shift, we analyzed the expression of genes related to three key monoamine neurotransmitters. The results showed a strong positive correlation between population density, locomotor activity, and the expression of the tyramine β-hydroxylase (TBH) gene, which is critical for octopamine synthesis. Conversely, the expression of the serotonin-related gene tryptophan hydroxylase (TPH) decreased, while the dopamine-related gene Tyrosine hydroxylase (TH) showed no clear trend. These findings suggest that aphids utilize a "threshold-triggered" model to rapidly shift from a settled to a dispersal state, a process primarily mediated by the monoamine neurotransmitters system. This provides a new perspective on the self-regulation mechanisms of insect populations.

Genetic and clinical profile of a Brazilian cohort of dopa-responsive dystonia.

The dopamine (DA) system is central to mood regulation, motivation, and reward processing, making it a critical focus for understanding Major Depressive Disorder (MDD). While the dopaminergic system's role in MDD pathophysiology has been acknowledged, gaps remain in linking specific receptor subtypes and genetic factors to depression-like phenotypes. This study explores the interplay between dopamine receptor subtypes (D1-D5) and associated genetic variations, particularly focusing on receptor heterodimers and polymorphisms influencing dopamine biosynthesis, signalling, and metabolism. A comprehensive review of molecular mechanisms highlights key findings; alterations in D1-D2 heterodimers contribute to mood dysregulation; D3 receptor downregulation correlates with depressive behaviour; and genetic polymorphisms, including those in tyrosine hydroxylase and dopamine transporter (DAT) genes, influence dopamine levels and receptor functions. Emerging data from neuroimaging and animal models confirm the pivotal role of dopamine receptor subtypes in MDD, offering insights into their therapeutic targeting. Here, we show that dopaminergic dysfunction underpins MDD's pathophysiology, with receptor-specific mechanisms presenting novel drug targets. Understanding these pathways facilitates precision medicine approaches, bridging the gap between genetic predisposition and receptor pharmacology, and paving the way for tailored antidepressant strategies with improved efficacy and reduced side effects.

Background/Objectives: Neurotransmitters such as dopamine and serotonin are critical regulators of mood, cognition, and neuronal homeostasis. This study aimed to evaluate the neuropharmacological potential of Hawaiian plants by investigating their ability to modulate the expression of tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH), key enzymes in neurotransmitter biosynthesis. Methods: A total of 108 aqueous and methanolic extracts of Hawaiian plants were screened for cytotoxicity against PC-12 and Neuro-2A cells using the MTT assay. Fifty-six non-toxic extracts were selected and further analyzed for TH and TPH expression via quantitative real-time PCR (qPCR). Results: Several extracts significantly upregulated TH and TPH expression without inducing cytotoxicity. Extracts derived from Morinda citrifolia, Pipturus albidus, and Hedychium coronarium showed the most notable activity, suggesting their potential to enhance dopaminergic and serotonergic pathways. Conclusions: The findings highlight the promise of native Hawaiian flora as sources of neuroactive compounds that may support neuroprotection and regeneration. These results provide a foundation for in vivo studies and further exploration of novel neurotherapeutic agents.

Catecholamines (CA) are considered to play key roles in acute stress responses, but they also regulate important functions of the nervous, immune, and endocrine systems and are essential for body homeostasis and health. In Swiss mice (an outbred strain) with haploinsufficiency of the tyrosine hydroxylase gene (Th, TH-HZ), which encodes the rate-limiting enzyme of catecholamine synthesis, impairments in homeostatic system functions and a reduced lifespan have been reported. Moreover, these homeostatic alterations are exacerbated when these animals are exposed to acute restraint stress. Nonetheless, the effects of this genetic modification on an inbred strain, such as C57BL/6J, are undetermined. Given that the genetic background of mice can affect the phenotype of any genetic modification, this work aimed to characterize how behavioral responses, immunity, and the oxidative state in C57BL/6J mice are altered by Th haploinsufficiency under basal conditions after being subjected to 10 min of acute restraint stress. Sex differences were also considered. Compared with their WT counterparts, TH-HZ C57BL/6J animals exhibit behavioral impairments, immunosenescence, and oxidative stress under basal conditions. After stress, TH-HZ animals (both sexes) exhibit deteriorated behavior and immune functions. Therefore, Th haploinsufficiency in the inbred C57BL/6J strain triggers impairments in behavior, immunity, and the redox state. These findings corroborate the role of CA in maintaining regulatory system functions and highlight the importance of mouse strains in basic research.

One of the earliest changes associated with Alzheimer's disease (AD) is the loss of catecholaminergic terminals in the cortex and hippocampus originating from the Locus Coeruleus (LC). This decline leads to reduced catecholaminergic neurotransmitters in the hippocampus, affecting synaptic plasticity and spatial memory. However, it is unclear whether restoring catecholaminergic transmission in the terminals from the LC may alleviate the spatial memory deficits associated with AD. This study aims to investigate the effects of optogenetic stimulation of LC catecholaminergic projections on alleviating spatial memory and synaptic plasticity deficits associated with AD. We conducted experiments using a 12-month-old 3xTgAD mouse model (AD-TH) that expresses Cre recombinase under the control of the tyrosine hydroxylase (TH) gene. This model enabled us to photostimulate the terminals from the LC in the hippocampal CA1 region before performing two different spatial memory tasks and inducing long-term plasticity. Optogenetic stimulation successfully reversed the impairment of spatial memory retrieval in aging AD-TH mice. Furthermore, this stimulation restored levels of catecholaminergic neurotransmitters in the hippocampus and enhanced synaptic plasticity, as demonstrated by a long-term potentiation (LTP) protocol. These findings suggest a critical role for the LC-hippocampal CA1 catecholaminergic circuitry in disrupting synaptic plasticity and the spatial memory deficits characteristic of the early stages of AD. The study highlights the potential for targeting LC catecholaminergic pathways as a therapeutic strategy to improve cognitive deficits experienced by AD patients.

Gestational exposure to fenvalerate induces attention-deficit hyperactivity disorder-like behaviors partially through altered DNA hydroxymethylation in the fetal midbrain of weaning offspring.

Repeated treatment with JWH-018 progressively increases motor activity and aggressiveness in male mice: involvement of CB1 cannabinoid and D1/D2 dopaminergic receptors.

ObjectivesTo explore the evaluation of abnormal regeneration of hepatic autonomic nerve in type 2 diabetes (T2DM) patients after partial hepatectomy by non-invasive sweat gland function detection.MethodsThe contents of tyrosine hydroxylase (TH) and protein gene product 9.5 (PGP 9.5) in regenerating liver tissue were quantified both in db/db mice (diabetes mice) and healthy control (db/+) mice with immunohistochemical method. Sweat gland function of the footpad in left hind foot was tested with iodine and starch reagents. The PGP 9.5 in sweat gland of the footpad in right hind foot was also examine. Analyze the correlation between the sweat gland function of mice’s footpad and the specific nerve markers in the regenerating liver.ResultsNerve fibers immunoreactive to TH and PGP 9.5 were both observed in the two groups. There was no significant difference between the two groups in PTs (positive portal tracts, PTs). On the contrary, there was a significant difference between db/ + and db/db groups in the positive TH nerve fiber density (t = 4.682, P = 0.000) and the positive PGP 9.5 nerve fiber density (t = 4.149, P = 0.000). There was a significant difference between the two groups in the number of sweating spots (t = 6.530, P = 0.000). Furthermore, the difference between the two groups in the PGP 9.5 positive fibers of sweat gland nerve fiber density (SGNFD) (t = 3.647, P = 0.001) was significant. Both the PGP 9.5 positive fibers in sweat gland of footpad and sweating spots were significantly correlated with the PGP 9.5 positive fibers in liver.ConclusionsThere is probably a correlation between the function of sweat gland in footpad and the function of autonomic nerve in liver, which will potentially establish a new standard or judgment for the preoperative evaluation and prognosis of partial hepatectomy in T2DM patients.

Dopa-responsive dystonia (DRD) has a broad, clinical, and genetically heterogeneous spectrum; its manifestations include parkinsonism, dystonia, tremor, and other movement disorders. The severity of DRD ranges from mild to fatal encephalopathy. DRD is caused by recessive mutations in the TH gene. This article is a systematic review (SR) of all reports of patients with DRD, including the first Mexican cases and other phenotypes associated with variants in the gene encoding tyrosine hydroxylase (TH), from its first description to the first quarter of 2024. The SR followed the PRISMA guidelines in five databases (Scopus, MEDLINE, PubMed Central, LILACS, and Scielo). Sixty-two publications were selected. They included 179 patients with TH deficiency, but only 143 included clinical descriptions. The age of onset was infantile regardless of phenotype, and there was a delay in age at diagnosis (t = -7.139, P < 0.001). Encephalopathy was the earliest presentation, and psychomotor retardation was common in all forms of TH deficiency. Multiple motor manifestations may be present, including dystonia, parkinsonism, gait disturbances, and others. Response to dopaminergic replacement therapy (DRT) has been reported in 143 patients (good in 64.3%, moderate in 23.7%, and poor in 12%). The compound heterozygous genotype was the most common (61.45%) for the biallelic variants of the TH gene. In addition, data from 6 cases with heterozygous variants are described. This is the most comprehensive review of TH deficiency cases and shows that these phenotypes are rare, have a wide neurological phenotypic variability, are often infantile-onset, and respond well to DRT.

Prolactin (PRL) regulates its own secretion by short-loop feedback to tuberoinfundibular dopaminergic (TIDA) neurons. PRL-induced cellular mechanisms in the regulation of tyrosine hydroxylase (TH) are not completely understood. The objectives were to (1) examine PRL-induced, time-dependent hypothalamic changes in JAK2-STAT5B signaling, TH activity, TH phosphorylation state and Th mRNA levels, and (2) evaluate direct influences of PRLR-STAT5B signaling on Th promoter activity. Ovariectomized rats were administered ovine PRL. JAK2 and STAT5 phosphorylation in the mediobasal hypothalamus peaked at 15 and 30-60 min, respectively. TH Ser40 phosphorylation in the median eminence was increased between 2 and 72 h, correlating with increased dihydroxyphenylalanine (DOPA) accumulation. Th mRNA levels in TIDA neurons were unchanged up to 72 h but elevated by 7 days. PRL did not alter Th promoter activity in CAD cells, and STAT5B did not bind three putative Gamma Interferon Activation Sites (GAS) elements. We conclude that PRL initiates an integrated cascade of cellular mechanisms in TIDA neurons, including JAK2-STAT5B activation, TH Ser40 phosphorylation coupled to increased TH activity, followed by a delayed rise in Th gene expression. PRL-induced changes in Th gene expression are not the result of STAT5-mediated transactivation but likely result from enduring changes in TIDA neuronal activity.

Mate competition encourages individuals to modulate characters involved in mating success. Adult Iberian red deer (Cervus elaphus hispanicus) males show a dark ventral patch (DVP) that plays a central role in mating rivalry, whose size and chemical compounds varied according to the level of male-male competition within the population. In the pigmentation of the DVP appears, after urinary excretion, a molecule called DOPEG originating from the metabolism of norepinephrine, leading us to investigate whether differential expression mechanisms of key genes dopamine B-hydroxylase (DBH) and tyrosine hydroxylase (TH), encoding enzymes catalyzing the process can be sensitive to different competitive population situations and responsible for the plastic development of the DVP in red deer. We found that social environment with higher intrasexual competition, where male invest more in sexual traits, was associated with increased levels of DBH and TH transcripts, while Dopamine showed reversed values. We found alternative splicing for the TH gene, although differences between social environments appeared just related to expression levels. Our results support the internal cause of trait modulation based on differential gene expression in relation to the conditions of intrasexual competition in social environment. We propose the quantification of DBH transcripts as a molecular biomarker of male red deer reproductive activity.

BackgroundDopaminergic neurotransmission is involved in several important issues for determination of our behaviour including motivation, decision-making, and motor-control. Therefore, its dysfunction is deeply involved in movement disorders and neuro-psychiatric disorders.Aims & ObjectivesDopamine is synthesized from tyrosine by the action of tyrosine hydroxylase (TH). While TH is known to be a rate-limiting enzyme for the dopamine synthesis, we found that the metabolism of dopamine in the nerve terminal was different from that in the cell body (1,2). Besides, the mice overexpressing the active-form of TH using a micro-injection of AAV-Th into the midbrain showed a dramatically enhanced locomotor activity induced by methamphetamine (METH), while the dopamine levels in the nucleus accumbens (NAc) were almost unchanged. Our findings suggest that the levels of the TH activity rather than the dopamine contents would affect the METH responses.ResultsHere, we examined the locomotor activity induced by METH in heterozygous Th-knockout mice, in which the TH expression levels are about half of the wild-type while the dopamine levels were not decreased in the brain. We found that the locomotor activities of the heterozygous Th-knockout mice were less than that of the wild-type. Next, we administered a TH inhibitor, a-methyl-p-tyrosine (AMPT) to the mice. Administration of AMPT dose-dependently reduced the locomotor activities to METH.Discussion & ConclusionThese results showed that the METH responses were affected by the TH activity and expression levels, and suggest that the TH activity would be a drug-target for patients suffered from addiction disorders by altering the metabolism of dopamine.References1)TOKUOKA, H., MURAMATSU, S., SUMI-ICHINOSE, C., SAKANE, H., KOJIMA, M., ASO, Y., NOMURA, T., METZGER, D. &ICHINOSE, H. 2011. Compensatory regulation of dopamine after ablation of the tyrosine hydroxylase gene in the nigrostriatal projection. J Biol Chem, 286, 43549-58.2)NAGO-IWASHITA, Y., MORIYA, Y., HARA, S., OGAWA, R., AIDA, R., MIYAJIMA, K., SHIMURA, T., MURAMATSU, S. I., IDE, S., IKEDA, K. &ICHINOSE, H. 2023. Overexpression of tyrosine hydroxylase in dopaminergic neurons increased sensitivity to methamphetamine. Neurochem Int, 164,105491.

Impaired neuronal functions and cell death within ailments such as neurodegenerative Parkinson's disease pose significant challenges due to their complex pathophysiology and limited treatment options. In this landscape, innovative materials with unique physicochemical properties that ameliorate the debilitated neuronal functions are critically required. Neuronal functions rely on the conduction of nerve impulses, a process that can be effectively targeted using advanced materials that exhibit conducive properties essential for modulating neural activity. For their semiconductor characteristics, combined with well-suited biocompatibility, graphitic carbon nitride (g-C3N4) nanosheets provide promising avenues for such neurotherapeutic applications. Our multidisciplinary study investigates the potential of g-C3N4 nanosheets in promoting neuronal differentiation and network formation across in vitro and in vivo systems. SH-SY5Y cells exposed to g-C3N4 demonstrated enhanced neuronal differentiation and neuritic outgrowth over a chronic 21-days period, accompanied by an increased intracellular Ca2+ influx, pivotal for dopamine biosynthesis, as evidenced by the upregulated expression of vesicular monoamine transporter 2 (VMAT2), aromatic l-amino acid decarboxylase (AADC), and tyrosine hydroxylase (TH) genes. Utilizing transgenic Caenorhabditis elegans model expressing human α-synuclein, we observed the neuroprotective potential of g-C3N4, as evidenced by reduced protein aggregation and improved dopaminergic functions. In the pursuit of exploring the mechanism of g-C3N4-induced neuronal stimulation, the semiconducting nature of g-C3N4 came forth, which was further validated using theoretical (in silico) models. These models demonstrated an increase in the chemical potential of the material upon the application of electrical biases. Studying Ca2+ channel inhibition, we also observed that phenotypic and molecular effects were the outcomes of the stimulation caused due to the presence of g-C3N4 nanosheets. Our findings, supported by experimental and in silico studies, suggest that g-C3N4 nanosheets can effectively modulate neuronal behavior through their semiconducting properties, offering promising avenues for therapeutic interventions in neurodegenerative diseases.

Neurodegeneration is the progressive loss of structure or function of neuronal cells and ultimately loss of neurons by death, particularly in neuropsychiatric disorders such as Alzheimer’s, Parkinson’s, and Huntington’s diseases...This study was conducted to evaluate the improvement of cognitive deficit and related mechanism of the leaf extract of Ilex kudingcha C.J.Tseng (IKE) on a mice model of trimethyltin (TMT)-induced neurodegeneration. Male Swiss albino mice were orally administered IKE (at doses of 270 and 540 mg/kg) or distilled water continuously for 7 days, followed by a single injection of TMT (2.6 mg/kg; i.p). The IKE administration was continued throughout the experimental period. From the 28th day after treatment, behavioral tests were performed to assess memory improvement effects in TMT mice. After completing the behavioral tests, hippocampal tissues were dissected for analysis of changes in the expression of the PIK3R2, IRS1, and TH genes using Real-time PCR. The results showed that IKE (270 and 540 mg/kg) improved memory deficits and enhanced fearbased learning and memory in TMT mice using novel object recognition and passive avoidance tests. Gene expression analysis revealed that IKE restored the downregulation of PIK3R2 but did not alter the expression of IRS1 and tyrosine hydroxylase (TH) genes. These findings suggest IKE improves memory deficit in TMT-induced neurodegenerative mice, partly via the restoration of PIK3R2, which is critical for neuronal protection against damage caused by TMT.

Tyrosine hydroxylase (TH) catalyzes hydroxylation of L-tyrosine to L-3,4-dihydroxyphenylalanine, the initial and rate-limiting step in the synthesis of dopamine, noradrenaline, and adrenaline. Mutations in the human TH gene are associated with hereditary motor disorders. The common C886T mutation identified in the mouse Th gene results in the R278H substitution in the enzyme molecule. We investigated the impact of this mutation on the TH activity in the mouse midbrain. The TH activity in the midbrain of Mus musculus castaneus (CAST) mice homozygous for the 886C allele was higher compared to C57BL/6 and DBA/2 mice homozygous for the 886T allele. Notably, this difference in the enzyme activity was not associated with changes in the Th gene mRNA levels and TH protein content. Analysis of the TH activity in the midbrain in mice from the F2 population obtained by crossbreeding of C57BL/6 and CAST mice revealed that the 886C allele is associated with a high TH activity. Moreover, this allele showed complete dominance over the 886T allele. However, the C886T mutation did not affect the levels of TH protein in the midbrain. These findings demonstrate that the C886T mutation is a major genetic factor determining the activity of TH in the midbrain of common laboratory mouse strains. Moreover, it represents the first common spontaneous mutation in the mouse Th gene whose influence on the enzyme activity has been demonstrated. These results will help to understand the role of TH in the development of adaptive and pathological behavior, elucidate molecular mechanisms regulating the activity of TH, and explore pharmacological agents for modulating its function.

Paclitaxel is a widely used anticancer drug for ovarian, lung, breast, and stomach cancers; however, its clinical use is often limited by the side effects of peripheral neuropathy. This study evaluated the effects of Cyperus rotundus (C. rotundus) extract and its active metabolite, α-cyperone, on paclitaxel-induced neuropathic pain. The oral administration of C. rotundus extract at doses of 500 mg/kg and intraperitoneal administration of α-cyperone at doses of 480 and 800 μg/kg prevented both the development of cold and mechanical pain. The gene and protein expressions of tyrosine hydroxylase and noradrenergic receptors (α1- and α2-adrenergic), which were upregulated by paclitaxel, were significantly downregulated in the C. rotundus extract-treated group. In the locus coeruleus region of the mouse brain, C. rotundus extract administration also reduced the elevated expression of tyrosine hydroxylase induced by paclitaxel. The concentration of α-cyperone in C. rotundus extract was quantified using high-performance liquid chromatography (HPLC). In the group treated with α-cyperone, at levels corresponding to its content in C. rotundus, both cold and mechanical allodynia were effectively prevented. This study suggests that α-cyperone shows potential as a preventive agent for paclitaxel-induced neuropathic pain.

The present study investigates the neuroprotective effects of the sea urchin Paracentrotus lividus gonadal extract on rotenone-induced neurotoxicity in a Parkinson's disease (PD) rat model. Parkinson's disease, characterized by the progressive loss of dopaminergic neurons in the substantia nigra (SN), is exacerbated by oxidative stress and neuroinflammation. The study involved fifty Wistar rats divided into five groups: control, dimethyl sulfoxide (DMSO) control, Paracentrotus lividus gonadal extract-treated, rotenone-treated, and combined rotenone with Paracentrotus lividus gonadal extract-treated. Behavioral assessments included the rotarod and open field tests, while biochemical analyses measured oxidative stress markers (malondialdehyde (MDA), nitric oxide (NO), glutathione (GSH)), antioxidants (superoxide dismutase (SOD), catalase (CAT)), pro-inflammatory cytokines (interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α)), and neurotransmitters (dopamine (DA), levodopa (L-Dopa)). Histological and immunohistochemical analyses evaluated the neuronal integrity and tyrosine hydroxylase (TH) and alpha-synuclein expression. The results showed that Paracentrotus lividus gonadal extract significantly mitigated rotenone-induced motor deficits and improved locomotor activity. Biochemically, the extract reduced oxidative stress and inflammation markers while enhancing antioxidant levels. Histologically, it restored neuronal integrity and reduced alpha-synuclein accumulation. Molecularly, it increased tyrosine hydroxylase and dopa decarboxylase gene expression, essential for dopamine synthesis. These findings suggest that Paracentrotus lividus gonadal extract exerts neuroprotective effects by modulating oxidative stress, neuroinflammation, and dopaminergic neuron integrity, highlighting its potential as a therapeutic agent for Parkinson's disease.

In insects, tyrosine hydroxylase (TH) plays essential roles in cuticle tanning and cuticle pigmentation. Plagiodera versicolora (Coleoptera: Chrysomelidae) is a leaf-eating forest pest in salicaceous trees worldwide. However, the function of PverTH in P. versicolora is still unknown. In this study, we obtained a PverTH gene from transcriptome analysis. The expression analysis of PverTH showed that the highest expression was found in epidermis of larvae. In this study, we used RNA interference (RNAi) technology to knockdown the PverTH gene. The results showed that ingestion of dsTH led to cuticle coloration became lighter in larvae, pupae and adults. Knockdown of PverTH gene inhibited larval growth, and consequently caused higher mortality. In addition, RNAi of TH disrupted the cuticle tanning, caused lower pupation rate, lower eclosion rate and higher deformity rate. This study indicates that PverTH is vital for the cuticular pigments and cuticle tanning. Moreover, this research suggested that the development of PverTH gene as a potential target gene to control P. versicolora.