Correlation between Neurotransmitters (Dopamine, Epinephrine, Norepinephrine, Serotonin), Prognostic Nutritional Index, Glasgow Prognostic Score, Systemic Inflammatory Response Markers, and TNM Staging in a Cohort of Colorectal Neuroendocrine Tumor Patients.

Neuroendocrine tumors are uncommon in the gastrointestinal system but can develop in the majority of the body's epithelial organs. Our goal was to examine the presence and clinical application of serum dopamine (DA), serotonin (ST), norepinephrine (NE), and epinephrine (EPI), in addition to determining the significance of the Prognostic Nutritional Index (PNI), Glasgow Prognostic Score (GPS), and systemic inflammatory response (SIR) markers as a prognostic factor for patients with colorectal neuroendocrine tumors (CR-NETs), in various tumor-node-metastasis (TNM) stages. We also wanted to identify the possible connection between them. This study included 25 consecutive patients who were diagnosed with CR-NETs and a control group consisting of 60 patients with newly diagnosed colorectal cancer (CRC). We used the Enzyme-Linked Immunosorbent Assay (ELISA) technique. This study revealed that CR-NET patients showed significantly higher serum levels of DA compared to CRC patients. We showed that serum DA was present in the early stages of CR-NETs, with increasing levels as we advanced through the TNM stages. Moreover, we found a close relationship between the levels of DA and the inflammation and nutritional status of the CR-NET patients in this study. CR-NET patients from the PNI < 47.00 subgroup had a higher level of DA than those from the PNI ≥ 47.00 subgroup. Pearson's correlation analysis revealed correlations between DA, PNI, and the neutrophil/lymphocyte ratio (NLR) and the platelet/lymphocyte ratio (PLR). Both hematological indices were negatively correlated with albumin (ALB). Our investigation's findings relating to the PNI, GPS, SIR, and DA indicate that these tools can be markers of nutritional and systemic inflammatory status, are simple to use, and are repeatable. Further research on this topic could provide valuable insights into which biomarkers to incorporate into clinical practice for the management of CR-NET patients.

Dopamine production in neurotensin receptor 1 neurons is required for diet-induced obesity and increased day eating on a high-fat diet.

OBJECTIVE: This study aimed to determine a dopaminergic circuit required for diet-induced obesity in mice. METHODS: We created conditional deletion mutants for tyrosine hydroxylase (TH) using neurotensin receptor 1 (Ntsr1) Cre and other Cre drivers and measured feeding and body weight on standard and high-fat diets. We then used an adeno-associated virus to selectively restore TH to the ventral tegmental area (VTA) Ntsr1 neurons in conditional knockout (cKO) mice. RESULTS: Mice with cKO of Th using Vglut2-Cre, Cck-Cre, Calb1-Cre, and Bdnf-Cre were susceptible to obesity on a high-fat diet; however, Ntsr1-Cre Th cKO mice resisted weight gain on a high-fat diet and did not experience an increase in day eating unlike their wild-type littermate controls. Restoration of TH to the VTA Ntsr1 neurons of the Ntsr1-Cre Th cKO mice using an adeno-associated virus resulted in an increase in weight gain and day eating on a high-fat diet. CONCLUSIONS: Ntsr1-Cre Th cKO mice failed to increase day eating on a high-fat diet, offering a possible explanation for their resistance to diet-induced obesity. These results implicate VTA Ntsr1 dopamine neurons as promoting out-of-phase feeding behavior on a high-fat diet that could be an important contributor to diet-induced obesity in humans.

Mechanistic Insight into Intestinal α-Synuclein Aggregation in Parkinson's Disease Using a Laser-Printed Electrochemical Sensor.

Aggregated deposits of the protein α-synuclein and depleting levels of dopamine in the brain correlate with Parkinson's disease development. Treatments often focus on replenishing dopamine in the brain; however, the brain might not be the only site requiring attention. Aggregates of α-synuclein appear to accumulate in the gut years prior to the onset of any motor symptoms. Enteroendocrine cells (specialized gut epithelial cells) may be the source of intestinal α-synuclein, as they natively express this protein. Enteroendocrine cells are constantly exposed to gut bacteria and their metabolites because they border the gut lumen. These cells also express the dopamine metabolic pathway and form synapses with vagal neurons, which innervate the gut and brain. Through this connection, Parkinson's disease pathology may originate in the gut and spread to the brain over time. Effective therapeutics to prevent this disease progression are lacking due to a limited understanding of the mechanisms by which α-synuclein aggregation occurs in the gut. We previously proposed a gut bacterial metabolic pathway responsible for the initiation of α-synuclein aggregation that is dependent on the oxidation of dopamine. Here, we develop a new tool, a laser-induced graphene-based electrochemical sensor chip, to track α-synuclein aggregation and dopamine level over time. Using these sensor chips, we evaluated diet-derived catechols dihydrocaffeic acid and caffeic acid as potential inhibitors of α-synuclein aggregation. Our results suggest that these molecules inhibit dopamine oxidation. We also found that these dietary catechols inhibit α-synuclein aggregation in STC-1 enteroendocrine cells. These findings are critical next steps to reveal new avenues for targeted therapeutics to treat Parkinson's disease, specifically in the context of functional foods that may be used to reshape the gut environment.

Expression Profiles of Dopamine-Related Genes and miRNAs Regulating Their Expression in Breast Cancer.

This study aimed to assess the expression profile of messenger RNA (mRNA) and microRNA (miRNA) related to the dopaminergic system in five types of breast cancer in Polish women. Patients with five breast cancer subtypes were included in the study: luminal A (n = 130), luminal B (n = 196, including HER2-, n = 100; HER2+, n = 96), HER2+ (n = 36), and TNBC (n = 43); they underwent surgery, during which tumor tissue was removed along with a margin of healthy tissue (control material). The molecular analysis included a microarray profile of mRNAs and miRNAs associated with the dopaminergic system, a real-time polymerase chain reaction preceded by reverse transcription for selected genes, and determinations of their concentration using enzyme-linked immunosorbent assay (ELISA). The conducted statistical analysis showed that five mRNAs statistically significantly differentiated breast cancer sections regardless of subtype compared to control samples; these were dopamine receptor 2 (DRD2), dopamine receptor 3 (DRD3), dopamine receptor 25 (DRD5), transforming growth factor beta 2 (TGF-ß-2), and caveolin 2 (CAV2). The predicted analysis showed that hsa-miR-141-3p can regulate the expression of DRD2 and TGF-ß-2, whereas hsa-miR-4441 is potentially engaged in the expression regulation of DRD3 and DRD5. In addition, the expression pattern of DRD5 mRNA can also be regulated by has-miR-16-5p. The overexpression of DRD2 and DRD3, with concomitant silencing of DRD5 expression, confirms the presence of dopaminergic abnormalities in breast cancer patients. Moreover, these abnormalities may be the result of miR-141-3P, miR-16-5p, and miR-4441 activity, regulating proliferation or metastasis.

Dopamine-Functionalized, Red Carbon Quantum Dots for In Vivo Bioimaging, Cancer Therapeutics, and Neuronal Differentiation.

One of the crucial requirements of quantum dots for biological applications is their surface modification for very specific and enhanced biological recognition and uptake. Toward this end, we present the green synthesis of bright, red-emitting carbon quantum dots derived from mango leaf extract (mQDs). These mQDs are conjugated electrostatically with dopamine to form mQDs-dopamine (mQDs:DOPA) bioconjugates. Bright-red fluorescence of mQDs was used for bioimaging and uptake in cancerous and noncancerous cell lines, tissues, and in vivo models like zebrafish. mQDs exhibited the highest uptake in brain tissue compared to the heart, kidney, and liver. mQD:DOPA conjugates killed breast cancer cells and increased uptake in epithelial RPE-1 cells and zebrafish. Additionally, mQDs:DOPA promoted neuronal differentiation of SH-SY5Y cells to differentiated neurons. Both mQDs and mQDs:DOPA exhibited the potential for higher collective cell migrations, implicating their future potential as next-generation tools for advanced biological and biomedical applications.

Laccase-Treated Polystyrene Surfaces with Caffeic Acid, Dopamine, and L-3,4-Dihydroxyphenylalanine Substrates Facilitate the Proliferation of Melanocytes and Embryonal Carcinoma Cells NTERA-2.

This study presents the effects of treating polystyrene (PS) cell culture plastic with oxidoreductase enzyme laccase and the catechol substrates caffeic acid (CA), L-DOPA, and dopamine on the culturing of normal human epidermal melanocytes (NHEMs) and human embryonal carcinoma cells (NTERA-2). The laccase-substrate treatment improved PS hydrophilicity and roughness, increasing NHEM and NTERA-2 adherence, proliferation, and NHEM melanogenesis to a level comparable with conventional plasma treatment. Cell adherence dynamics and proliferation were evaluated. The NHEM endpoint function was quantified by measuring melanin content. PS surfaces treated with laccase and its substrates demonstrated the forming of polymer-like structures. The surface texture roughness gradient and the peak curvature were higher on PS treated with a combination of laccase and substrates than laccase alone. The number of adherent NHEM and NTERA-2 was significantly higher than on the untreated surface. The proliferation of NHEM and NTERA-2 correspondingly increased on treated surfaces. NHEM melanin content was enhanced 6-10-fold on treated surfaces. In summary, laccase- and laccase-substrate-modified PS possess improved PS surface chemistry/hydrophilicity and altered roughness compared to untreated and plasma-treated surfaces, facilitating cellular adherence, subsequent proliferation, and exertion of the melanotic phenotype. The presented technology is easy to apply and creates a promising custom-made, substrate-based, cell-type-specific platform for both 2D and 3D cell culture.

Oleic acid reduces oxidative stress in rat brain induced by some anticancer drugs.

Oleic acid (OA) is a monounsaturated compound with many health-benefitting properties such as obesity prevention, increased insulin sensitivity, antihypertensive and immune-boosting properties, etc. The aim of this study was to analyze the effect of oleic acid (OA) and some anticancer drugs against oxidative damage induced by nitropropionic acid (NPA) in rat brain. Six groups of Wistar rats were treated as follows: Group 1, (control); group 2, OA; group 3, NPA + OA; group 4, cyclophosphamide (CPP) + OA; group 5, daunorubicin (DRB) + OA; and group 6, dexrazoxane (DXZ) + OA. All compounds were administered intraperitoneally route, every 24 h for 5 days. Their brains were extracted to measure lipoperoxidation (TBARS), H2O2, Ca+2, Mg+2 ATPase activity, glutathione (GSH) and dopamine. Glucose, hemoglobin and triglycerides were measured in blood. In cortex GSH increased in all groups, except in group 2, the group 4 showed the highest increase of this biomarker. TBARS decrease, and dopamine increase in all regions of groups 4, 5 and 6. H2O2 increased only in cerebellum/medulla oblongata of group 5 and 6. ATPase expression decreased in striatum of group 4. Glucose increased in group 6, and hemoglobin increased in groups 4 and 5. These results suggest that the increase of dopamine and the antioxidant effect of oleic acid administration during treatment with oncologic agents could result in less brain injury.

Striatal GDNF Neurons Chemoattract RET-Positive Dopamine Axons at Seven Times Farther Distance Than Medium Spiny Neurons.

Glial cell line-derived neurotrophic factor (GDNF) is among the strongest dopamine neuron function- and survival-promoting factors known. Due to this reason, it has clinical relevance in dopamine disorders such as Parkinson's disease and schizophrenia. In the striatum, GDNF is exclusively expressed in interneurons, which make up only about 0.6% of striatal cells. Despite clinical significance, histological analysis of striatal GDNF system arborization and relevance to incoming dopamine axons, which bear its receptor RET, has remained enigmatic. This is mainly due to the lack of antibodies able to visualize GDNF- and RET-positive cellular processes; here, we overcome this problem by using knock-in marker alleles. We find that GDNF neurons chemoattract RET+ axons at least seven times farther in distance than medium spiny neurons (MSNs), which make up 95% of striatal neurons. Furthermore, we provide evidence that tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis, is enriched towards GDNF neurons in the dopamine axons. Finally, we find that GDNF neuron arborizations occupy approximately only twelve times less striatal volume than 135 times more abundant MSNs. Collectively, our results improve our understanding of how endogenous GDNF affects striatal dopamine system function.

Inhibition of GSDMD-dependent pyroptosis decreased methamphetamine self-administration in rats.

It is widely believed that the activation of the central dopamine (DA) system is crucial to the rewarding effects of methamphetamine (METH) and to the behavioral outcomes of METH use disorder. It was reported that METH exposure induced gasdermin D (GSDMD)-dependent pyroptosis in rats. The membrane pore formation caused by METH-induced pyroptosis may also contribute to the overflow of DA into the extracellular space and subsequently increase the DA levels in the brain. The present study firstly investigated whether the membrane pore information induced by GSDMD-dependent pyroptosis was associated with the increased DA levels in the ventral tegmental area (VAT) and nucleus accumbens (NAc) of rats self-administering METH and SY-SH5Y cells treated by METH. Subsequently, the effect of pore formation blockade or genetic inhibition of GSDMD on the reinforcing and motivational effect of METH was determined in rats, using the animal model of METH self-administration (SA). METH exposure significantly increased the activity of NLRP1/Cas-1/GSDMD pathway and the presence of pyroptosis, accompanied by the significantly increased DA levels in VTA and NAc. Moreover, intraperitoneal injections of disulfiram (DSF) or microinjection of rAAV-shGSDMD into VTA/NAc significantly reduced the reinforcing and motivational effect of METH, accompanied by the decreased level of DA in VTA and NAc. The results provided novel evidence that METH-induced pyroptosis could increase DA release in VTA and NAc via the NLRP1/Cas-1/GSDMD pathway. Additionally, membrane pores or GSDMD blockade could significantly reduce the reinforcing and motivational effect of METH. In conclusion, blocking GSDMD and membrane pore formation could be a promising potential target for the development of agents to treat METH use disorder.

Darpp-32 is regulated by dopamine and is required for the formation of GABAergic neurons in the developing telencephalon.

DARPP-32 (dopamine and cAMP-regulated phosphoprotein Mr. 32 kDa) is a phosphoprotein that is modulated by multiple receptors integrating intracellular pathways and playing roles in various physiological functions. It is regulated by dopaminergic receptors through the cAMP/protein kinase A (PKA) pathway, which modulates the phosphorylation of threonine 34 (Thr34). When phosphorylated at Thr34, DARPP-32 becomes a potent protein phosphatase-1 (PP1) inhibitor. Since dopamine is involved in the development of GABAergic neurons and DARPP-32 is expressed in the developing brain, it is possible that DARPP-32 has a role in GABAergic neuronal development. We cloned the zebrafish darpp-32 gene (ppp1r1b) gene and observed that it is evolutionarily conserved in its inhibitory domain (Thr34 and surrounding residues) and the docking motif (residues 7-11 (KKIQF)). We also characterized darpp-32 protein expression throughout the 5 days post-fertilization (dpf) zebrafish larval brain by immunofluorescence and demonstrated that darpp-32 is mainly expressed in regions that receive dopaminergic projections (pallium, subpallium, preoptic region, and hypothalamus). We demonstrated that dopamine acutely suppressed darpp-32 activity by reducing the levels of p-darpp-32 in the 5dpf zebrafish larval brain. In addition, the knockdown of darpp-32 resulted in a decrease in the number of GABAergic neurons in the subpallium of the 5dpf larval brain, with a concomitant increase in the number of DAergic neurons. Finally, we demonstrated that darpp-32 downregulation during development reduced the motor behavior of 5dpf zebrafish larvae. Thus, our observations suggest that darpp-32 is an evolutionarily conserved regulator of dopamine receptor signaling and is required for the formation of GABAergic neurons in the developing telencephalon.

A pathophysiological biomarker combination separates Lewy body from non-Lewy body neurogenic orthostatic hypotension ​.

PURPOSE: Neurogenic orthostatic hypotension (nOH) results from deficient reflexive delivery of norepinephrine to cardiovascular receptors in response to decreased cardiac venous return. Lewy body (LB) forms of nOH are characterized by low 18F-dopamine-derived radioactivity (a measure of cardiac noradrenergic deficiency), olfactory dysfunction by the University of Pennsylvania Smell Identification Test (UPSIT), and increased deposition of alpha-synuclein (α-syn) in dermal sympathetic noradrenergic nerves by the α-syn-tyrosine hydroxylase (TH) colocalization index. This observational, cross-sectional study explored whether combinations of these biomarkers specifically identify LB forms of nOH. METHODS: Clinical laboratory data were reviewed from patients referred for evaluation at the National Institutes of Health for chronic autonomic failure between 2011 and 2023. The cutoff value for low myocardial 18F-dopamine-derived radioactivity was 6000 nCi-kg/cc-mCi, for olfactory dysfunction an UPSIT score ≤ 28, and for an increased α-syn-TH colocalization index ≥ 1.57. RESULTS: A total of 44 patients (31 LB, 13 non-LB nOH) had data for all three biomarkers. Compared to the non-LB group, the LB nOH group had low myocardial 18F-dopamine-derived radioactivity, low UPSIT scores, and high α-syn-TH colocalization indexes (p < 0.0001 each). Combining the three biomarkers completely separated the groups. Cluster analysis identified two distinct groups (p < 0.0001) independently of the clinical diagnosis, with one cluster corresponding exactly to LB nOH. CONCLUSION: LB forms of nOH feature cardiac noradrenergic deficiency, olfactory dysfunction, and increased α-syn-TH colocalization in skin biopsies. Combining the data for these variables efficiently separates LB from non-LB nOH. Independently of the clinical diagnosis, this biomarker triad identifies a pathophysiologically distinct cluster of nOH patients.

Using microdialysis to monitor dopaminergic support of limb-use control following mesencephalic neurosphere transplantation in a rodent model of Parkinson's Disease.

Controlled nigrostriatal dopamine release supports effective limb use during locomotion coordination that becomes compromised after this pathway deteriorates in Parkinson's Disease (PD). How dopamine release relates to active ongoing behavior control remains unknown. Restoring proper release strategy appears important to successful PD treatment with transplanted dopamine-producing stem cells. This is suggested by apparently distinct behavioral support from tonic or phasic release and corresponding requirements of requisite afferent control exhibited by intact nigrostriatal neurons. Our laboratory previously demonstrated that transplanted dopaminergic cells can elicit skilled movement recovery known to depend on phasic dopamine release. However, efforts to measure this movement-related dopamine release yielded seemingly paradoxical, incongruent results. In response, here we explored whether those previous observations derived from rapid reuptake transport into either transplanted cells or residual, lesion-surviving terminals. We confirmed this using minimal reuptake blockade during intrastriatal microdialysis. After unilateral dopamine depletion, rats received transplants and were subjected to our swimming protocol. Among dopamine-depleted and transplanted rats, treatment supported restoration of limb movement symmetry. Interestingly, subsequent reuptake-restricted microdialysis confirmed distinct swimming-induced dopamine increases clearly occurred among these lesioned/transplanted subjects. Thus, phasic firing control appears to contribute to transplant-derived recovery in Parkinsonian animals.

An implantable piezoelectric ultrasound stimulator (ImPULS) for deep brain activation.

Precise neurostimulation can revolutionize therapies for neurological disorders. Electrode-based stimulation devices face challenges in achieving precise and consistent targeting due to the immune response and the limited penetration of electrical fields. Ultrasound can aid in energy propagation, but transcranial ultrasound stimulation in the deep brain has limited spatial resolution caused by bone and tissue scattering. Here, we report an implantable piezoelectric ultrasound stimulator (ImPULS) that generates an ultrasonic focal pressure of 100 kPa to modulate the activity of neurons. ImPULS is a fully-encapsulated, flexible piezoelectric micromachined ultrasound transducer that incorporates a biocompatible piezoceramic, potassium sodium niobate [(K,Na)NbO3]. The absence of electrochemically active elements poses a new strategy for achieving long-term stability. We demonstrated that ImPULS can i) excite neurons in a mouse hippocampal slice ex vivo, ii) activate cells in the hippocampus of an anesthetized mouse to induce expression of activity-dependent gene c-Fos, and iii) stimulate dopaminergic neurons in the substantia nigra pars compacta to elicit time-locked modulation of nigrostriatal dopamine release. This work introduces a non-genetic ultrasound platform for spatially-localized neural stimulation and exploration of basic functions in the deep brain.

An Ultramicroelectrode Electrochemistry and Surface Plasmon Resonance Coupling Method for Cell Exocytosis Study.

Exocytosis of a single cell has been extensively researched in recent years due to its close association with numerous diseases. However, current methods only investigate exocytosis at either the single-cell or multiple-cell level, and a method for simultaneously studying exocytosis at both levels has yet to be established. In this study, a combined device incorporating ultramicroelectrode (UME) electrochemistry and surface plasmon resonance (SPR) was developed, enabling the simultaneous monitoring of single-cell and multiple-cell exocytosis. PC12 cells were cultured directly on the SPR sensing Au film, with a carboxylated carbon nanopipette (c-CNP) electrode employed for electrochemical detection in the SPR reaction cell. Upon exocytosis, the released dopamine diffuses onto the inner wall of c-CNP, undergoing an electrochemical reaction to generate a current peak. Concurrently, exocytosis can also induce changes in the refractive index of the Au film surface, leading to the SPR signal. Consequently, the device enables real-time monitoring of exocytosis from both single and multiple cells with a high spatiotemporal resolution. The c-CNP electrode exhibited excellent resistance to protein contamination, high sensitivity for dopamine detection, and the capability to continuously monitor dopamine exocytosis over an extended period. Analysis of both SPR and electrochemical signals revealed a positive correlation between changes in the SPR signal and the frequency of exocytosis. This study introduces a novel method and platform for the simultaneous investigation of single-cell and multiple-cell exocytosis.

Ventral Tegmental Area Amylin Receptor Activation Differentially Modulates Mesolimbic Dopamine Signaling in Response to Fat versus Sugar.

Amylin, a pancreatic hormone that is cosecreted with insulin, has been highlighted as a potential treatment target for obesity. Amylin receptors are distributed widely throughout the brain and are coexpressed on mesolimbic dopamine neurons. Activation of amylin receptors is known to reduce food intake, but the neurochemical mechanisms behind this remain to be elucidated. Amylin receptor activation in the ventral tegmental area (VTA), a key dopaminergic nucleus in the mesolimbic reward system, has a potent ability to suppress intake of palatable fat and sugar solutions. Although previous work has demonstrated that VTA amylin receptor activation can dampen mesolimbic dopamine signaling elicited by random delivery of sucrose, whether this is also the case for fat remains unknown. Herein we tested the hypothesis that amylin receptor activation in the VTA of male rats would attenuate dopamine signaling in the nucleus accumbens core in response to random intraoral delivery of either fat or sugar solutions. Results show that fat solution produces a greater potentiation of accumbens dopamine than an isocaloric sucrose solution. Moreover, activation of VTA amylin receptors elicits a more robust suppression of accumbens dopamine signaling in response to fat solution than to sucrose. Taken together these results shed new light on the amylin system as a therapeutic target for obesity and emphasize the reinforcing nature of high-fat/high-sugar diets.

Approach/Avoidance Behavior to Novel Objects is Correlated with the Serotonergic and Dopaminergic Systems in the Brown Rat (Rattus norvegicus).

The brown rat (Rattus norvegicus) is known to show three types of behavioral responses to novel objects. Whereas some rats are indifferent to novel objects, neophobic and neophilic rats show avoidance and approach behavior, respectively. Here, we compared the dopaminergic, serotonergic, and noradrenergic systems immunohistochemically among these rats. Trapped wild rats and laboratory rats were first individually exposed to the novel objects in their home cage. Wild rats were divided into neophobic and indifferent rats depending on their behavioral responses. Similarly, laboratory rats were divided into neophilic and indifferent rats. Consistent with the behavioral differences, in the paraventricular nucleus of the hypothalamus, Fos expression in corticotropin-releasing hormone-containing neurons was higher in the neophobic rats than in the indifferent rats. In the anterior basal amygdala, the neophobic rats showed higher Fos expression than the indifferent rats. In the posterior basal amygdala, the neophobic and neophilic rats showed lower and higher Fos expressions than the indifferent rats, respectively. When we compared the neuromodulatory systems, in the dorsal raphe, the number of serotonergic neurons and Fos expression in serotonergic neurons increased linearly from neophobic to indifferent to neophilic rats. In the ventral tegmental area, Fos expression in dopaminergic neurons was higher in the neophilic rats than in the indifferent rats. These results demonstrate that approach/avoidance behavior to novel objects is correlated with the serotonergic and dopaminergic systems in the brown rat. We propose that the serotonergic system suppresses avoidance behavior while the dopaminergic system enhances approach behavior to novel objects.

Dopamine and its precursor levodopa inactivate SARS-CoV-2 main protease by forming a quinoprotein.

Many studies show either the absence, or very low levels of, SARS-CoV-2 viral RNA and/or antigen in the brain of COVID-19 patients. Reports consistently indicate an abortive infection phenomenon in nervous cells despite the fact that they contain the SARS-CoV-2 receptor, ACE2. Dopamine levels in different brain regions are in the range of micromolar to millimolar concentrations. We have shown that sub-micromolar to low micromolar concentrations of dopamine or its precursor (levodopa) time- and dose-dependently inhibit the activity of SARS-CoV-2 main protease (Mpro), which is vital for the viral life cycle, by forming a quinoprotein. Thiol detection coupled with the assessment of Mpro activity suggests that among the 12 cysteinyl thiols, the active site, Cys145-SH, is preferentially conjugated to the quinone derived from the oxidation of dopamine or levodopa. LC-MS/MS analyses show that the Cys145-SH is covalently conjugated by dopamine- or levodopa-o-quinone. These findings help explain why SARS-CoV-2 causes inefficient replication in many nerve cell lines. It is well recognized that inhaled pulmonary drug delivery is the most robust therapy pathway for lung diseases. CVT-301 (orally inhaled levodopa) was approved by the FDA as a drug for Parkinson's patients prior to the outbreak of COVID-19 in 2018. Based on the fact that SARS-CoV-2 causes inefficient replication in the CNS with abundant endogenous Mpro inhibitor in addition to the current finding that levodopa has an Mpro-inhibitory effect somewhat stronger than dopamine, we should urgently investigate the use of CVT-301 as a lung-targeting, COVID-19, Mpro inhibitor.

Theobromine improves hyperactivity, inattention, and working memory via modulation of dopaminergic neural function in the frontal cortex of spontaneously hypertensive rats.

Attention-deficit/hyperactivity disorder (ADHD) is a developmental disorder and dopaminergic dysfunction in the prefrontal cortex (PFC) may play a role. Our previous research indicated that theobromine (TB), a methylxanthine, enhances cognitive function in rodents via the PFC. This study investigates TB's effects on hyperactivity and cognitive function in stroke-prone spontaneously hypertensive rats (SHR), an ADHD animal model. Male SHRs (6-week old) received a diet containing 0.05% TB for 40 days, while control rats received normal diets. Age-matched male Wistar-Kyoto rats (WKY) served as genetic controls. During the TB administration period, we conducted open-field tests and Y-maze tasks to evaluate hyperactivity and cognitive function, then assessed dopamine concentrations and tyrosine hydroxylase (TH), dopamine receptor D1-5 (DRD1-5), dopamine transporter (DAT), vesicular monoamine transporter-2 (VMAT-2), synaptosome-associated protein-25 (SNAP-25), and brain-derived neurotrophic factor (BDNF) expressions in the PFC. Additionally, the binding affinity of TB for the adenosine receptors (ARs) was evaluated. Compared to WKY, SHR exhibited hyperactivity, inattention and working memory deficits. However, chronic TB administration significantly improved these ADHD-like behaviors in SHR. TB administration also normalized dopamine concentrations and expression levels of TH, DRD2, DRD4, SNAP-25, and BDNF in the PFC of SHR. No changes were observed in DRD1, DRD3, DRD5, DAT, and VMAT-2 expression between SHR and WKY rats, and TB intake had minimal effects. TB was found to have affinity binding to ARs. These results indicate that long-term TB supplementation mitigates hyperactivity, inattention and cognitive deficits in SHR by modulating dopaminergic nervous function and BDNF levels in the PFC, representing a potential adjunctive treatment for ADHD.

Nasal application of kisspeptin-54 mitigates motor deficits by reducing nigrostriatal dopamine loss in hemiparkinsonian rats.

Parkinson's Disease is a progressive neurodegenerative disorder characterized by motor symptoms resulting from the loss of nigrostriatal dopaminergic neurons. Kisspeptins (KPs) are a family of neuropeptides that are encoded by the Kiss-1 gene, which exert their physiological effects through interaction with the GPR54 receptor. In the current investigation, we investigated the prospective protective effects of central KP-54 treatments on nigrostriatal dopaminergic neurons and consequent motor performance correlates in 6-hydroxydopamine (6-OHDA)-lesioned rats. Male adult Sprague Dawley rats underwent stereotaxic injection of 6-OHDA into the right medial forebrain bundle to induce hemiparkinsonism. Following surgery, rats received chronic central treatments of nasal or intracerebroventricular KP-54 (logarithmically increasing doses) for seven consecutive days. Motor performance was evaluated seven days post-surgery utilizing the open field test and catalepsy test. The levels of dopamine in the striatum were determined with mass spectrometry. Immunohistochemical analysis was conducted to assess the immunoreactivities of tyrosine hydroxylase (TH) and the GPR54 in the substantia nigra. The dose-response curve revealed a median effective dose value of ≈3 nmol/kg for both central injections. Due to its non-invasive and effective nature, nasal administration was utilized in the second phase of our study. Chronic administration of KP-54 (3nmol/kg, nasally) significantly protected 6-OHDA-induced motor deficits. Nasal KP-54 attenuated the loss of nigrostriatal dopaminergic neurons induced by 6-OHDA. Additionally, significant correlations were observed between motor performance and nigrostriatal dopamine levels. Immunohistochemical analysis demonstrated the localization of the GPR54 within TH-positive nigral cells. These findings suggest the potential efficacy of central KP-54 on motor impairments in hemiparkinsonism.

Epithelium-derived 6-nitrodopamine modulates noradrenaline-induced contractions in human seminal vesicles.

AIMS: To evaluate the basal release of 6-nitrodopamine (6-ND) from human isolated seminal vesicles (HISV) and to characterize its action and origin. MAIN METHODS: Left HISV obtained from patients undergoing prostatectomy surgery was suspended in a 3-mL organ bath containing warmed (37 °C) and gassed (95%O2:5%CO2) Krebs-Henseleit's solution (KHS) with ascorbic acid. An aliquot of 2 mL of the supernatant was used to quantify catecholamines by LC-MS/MS. For functional studies, concentration-responses curves to catecholamines were obtained, and pEC50 and Emax values were calculated. Detection of tyrosine hydroxylase and S100 protein were also carried out by both immunohistochemistry and fluorescence in-situ hybridization assays (FISH). KEY FINDINGS: Basal release of 6-ND was higher than the other catecholamines (14.76 ± 14.54, 4.99 ± 6.92, 3.72 ± 4.35 and 5.13 ± 5.76 nM for 6-ND, noradrenaline, adrenaline, and dopamine, respectively). In contrast to the other catecholamines, the basal release of 6-ND was not affected by the sodium current (Nav) channel inhibitor tetrodotoxin (1 µM; 10.4 ± 8.9 and 10.4 ± 7.9 nM, before and after tetrodotoxin, respectively). All the catecholamines produced concentration-dependent HISV contractions (pEC50 4.1 ± 0.2, 4.9 ± 0.3, 5.0 ± 0.3, and 3.9 ± 0.8 for 6-ND, noradrenaline, adrenaline, and dopamine, respectively), but 6-ND was 10-times less potent than noradrenaline and adrenaline. However, preincubation with very low concentration of 6-ND (10-8 M, 30 min) produced significant leftward shifts of the concentration-response curves to noradrenaline. Immunohistochemical and FISH assays identified tyrosine hydroxylase in tissue epithelium of HISV strips. SIGNIFICANCE: Epithelium-derived 6-ND is the major catecholamine released from human isolated seminal vesicles and that modulates smooth muscle contractility by potentiating noradrenaline-induced contractions.