Histamine N-methyltransferase Research Articles

Brain histamine improves colonic hyperpermeability through the basal forebrain cholinergic neurons, adenosine A2B receptors and vagus nerve in rats

Intestinal barrier dysfunction, leaky gut, is implicated in various diseases, including irritable bowel syndrome (IBS) and neurodegenerative conditions like Alzheimer's disease. Our recent investigation revealed that basal forebrain cholinergic neurons (BFCNs), critical for cognitive function, receive signals from butyrate and orexin, playing a role in regulating intestinal barrier function through adenosine A2B signaling and the vagus. This study explores the involvement and function of brain histamine, linked to BFCNs, in the regulation of intestinal barrier function. Colonic permeability, assessed by quantifying absorbed Evans blue in rat colonic tissue, showed that histamine did not affect increased colonic permeability induced by LPS when administered subcutaneously. However, intracisternal histamine administration improved colonic hyperpermeability. Elevating endogenous histamine levels in the brain with SKF91488, a histamine N-methyltransferase inhibitor, also improved colonic hyperpermeability. This effect was abolished by intracisternal chlorpheniramine, an histamine H1 receptor antagonist, not ranitidine, an H2 receptor antagonist. The SKF91488-induced improvement in colonic hyperpermeability was blocked by vagotomy, intracisternal pirenzepine (suppressing BFCNs activity), or alloxazine (an adenosine A2B receptor antagonist). Additionally, intracisternal chlorpheniramine injection eliminated butyrate-induced improvement in colonic hyperpermeability. These findings suggest that brain histamine, acting via the histamine H1 receptor, regulates intestinal barrier function involving BFCNs, adenosine A2B signaling, and the vagus. Brain histamine appears to centrally regulate intestinal barrier function influenced by butyrate, differentiating its actions from peripheral histamine in conditions like IBS, where mast cell-derived histamine induces leaky gut. Brain histamine emerges as a potential pharmacological target for diseases associated with leaky gut, such as dementia and IBS.

Dihydroergotamine Increases Histamine Brain Levels and Improves Memory in a Scopolamine-Induced Amnesia Model.

The beneficial effects of increasing histamine levels on memory have acquired special interest due to their applicability to psychiatric conditions that cause memory impairments. In addition, by employing drug repurposing approaches, it was demonstrated that dihydroergotamine (DHE), an FDA drug approved to treat migraines, inhibits Histamine N Methyl Transferase (HNMT), the enzyme responsible for the inactivation of histamine in the brain. For this reason, in the present work, the effect of DHE on histamine levels in the hippocampus and its effects on memory was evaluated, employing the scopolamine-induced amnesia model, the Novel Object Recognition (NOR) paradigm, and the Morris Water Maze (MWM). Furthermore, the role of histamine 1 receptor (H1R) and histamine 2 receptor (H2R) antagonists in the improvement in memory produced by DHE in the scopolamine-induced amnesia model was evaluated. Results showed that the rats that received DHE (10 mg/kg, i.p.) showed increased histamine levels in the hippocampus after 1 h of administration but not after 5 h. In behavioral assays, it was shown that DHE (1 mg/kg, i.p.) administered 20 min before the training reversed the memory impairment produced by the administration of scopolamine (2 mg/kg, i.p.) immediately after the training in the NOR paradigm and MWM. Additionally, the effects in memory produced by DHE were blocked by pre-treatment with pyrilamine (20 mg/kg, i.p.) administered 30 min before the training in the NOR paradigm and MWM. These findings allow us to demonstrate that DHE improves memory in a scopolamine-induced amnesia model through increasing histamine levels at the hippocampus due to its activity as an HNMT inhibitor.

Sexually Dimorphic Effects of Histamine Degradation by Enteric Glial Histamine N-Methyltransferase (HNMT) on Visceral Hypersensitivity.

Histamine is a neuromodulator that affects gut motility and visceral sensitivity through intrinsic and extrinsic neural pathways, yet the mechanisms regulating histamine availability in these pathways remain poorly understood. Here, we show that enteric glia contribute to histamine clearance in the enteric nervous system (ENS) through their expression of the enzyme histamine N-methyltransferase (HNMT). Glial HNMT expression was initially assessed using immunolabeling and gene expression, and functionally tested using CRISPR-Cas9 to create a Cre-dependent conditional Hnmt ablation model targeting glia. Immunolabeling, calcium imaging, and visceromotor reflex recordings were used to assess the effects on ENS structure and visceral hypersensitivity. Immunolabeling and gene expression data show that enteric neurons and glia express HNMT. Deleting Hnmt in Sox10+ enteric glia increased glial histamine levels and altered visceromotor responses to colorectal distension in male mice, with no effect in females. Interestingly, deleting glial Hnmt protected males from histamine-driven visceral hypersensitivity. These data uncover a significant role for glial HNMT in histamine degradation in the gut, which impacts histamine-driven visceral hypersensitivity in a sex-dependent manner. Changes in the capacity of glia to clear histamines could play a role in the susceptibility to developing visceral pain in disorders of the gut-brain interaction.

Importance of solvents role in molecular and electronic properties, DFT, spectroscopic, electron-hole transition, chemical reactivity, topology and molecular docking investigations of (±)-2-(2-{4-[(4-chlorophenyl)-phenylmethyl] piperazin-1-yl} ethoxy)ethanol

The phenyl-substituted piperazine derivative molecule was taken into consideration in the current investigation of the organic drug molecule (±)-2-(2-{4-[(4-chlorophenyl)-phenylmethyl] piperazin-1-yl} ethoxy) ethanol (CPE), evaluating the spectral characterization using both simulated and recorded FT-IR, FT-Raman, and UV spectral studies. The theoretical computations have been conducted using DFT/B3LYP/6–311++G(d,p)as a basis set. The stable optimized structure was attained by selecting suitable dihedral angles using PES analysis and molecular geometrical parameters were obtained and matched with the available literature data. The vibrational assignments along with the PED contributions were obtained and matched with the recorded values. The electronic properties were analyzed for the various solvents and found that acetone possesses a lesser band energy gap of 5.3637 eV implies the stability of the header composite. Further, the UV–Vis spectra for the various solvents and corresponding parameters were obtained along with excitation analysis with electron-hole isosurface contributions. The maximum absorption wavelength of the CPE obtained in the liquid phase and the recorded wavelength compared with the simulated data. Intermolecular reliability of the molecule emanating from hyperconjugative interactions of charge delocalization by NBO analysis. The accomplishment of nucleophilic and electrophilic regions of the solvents such as acetone, water, and DMSO was implemented using Molecular Electrostatic Potential (MEP) for the molecule. Electron localization function (ELF) Localized orbital locator (LOL) and Reduced density Gradient (RDG) were attained using the above-mentioned basis set for the topological behavior of the title molecule. According to molecular docking studies, the amino acid residues present at the active site region of the ligand (CPE) are particularly suited to Histamine N-methyltransferase (HNMT) with suitable targets (PDB: 2AOT,1JQD, and 2AOU) and the minimum binding energy for the receptor target is 2AOU is −6.90 kcal/mol respectively.

Novel single nucleotide polymorphism biomarkers to predict opioid effects for cancer pain.

There have been few studies on predictive biomarkers that may be useful to select the most suitable opioids to optimize therapeutic efficacy in individual patients with cancer pain. We recently investigated the efficacy of morphine and oxycodone using single nucleotide polymorphisms (SNPs) of the catechol-O-methyltransferase (COMT) rs4680 gene as a biomarker (RELIEF study). To explore additional biomarkers that may enable the selection of an appropriate opioid for individual patients with cancer pain, three SNPs were examined: C-C motif chemokine ligand 11 (CCL11; rs17809012), histamine N-methyltransferase (HNMT; rs1050891) and transient receptor potential V1 (TRPV1; rs222749), which were screened from 74 pain-related SNPs. These SNPs, which were identified as being significantly associated with the analgesic effect of morphine, were then used to genotype the 135 patients in the RELIEF study who had been randomized into a morphine group (n=69) or an oxycodone group (n=66). The present study then assessed whether the SNPs could also be used as selective biomarkers to predict which opioid(s) might be the most suitable to provide pain relief for patients with cancer. Oxycodone tended to provide superior analgesic effects over morphine in patients carrying the genotype AA for the CCL11 rs17809012 SNP (P=0.012 for interaction), suggesting that it could serve as a potential biomarker for personalized analgesic therapy for patients suffering with cancer pain.

Renal Histaminergic System and Acute Effects of Histamine Receptor 2 Blockade on Renal Damage in the Dahl Salt-Sensitive Rat.

Histamine is involved in the immune response, vasodilation, neurotransmission, and gastric acid secretion. Although elevated histamine levels and increased expression of histamine metabolizing enzymes have been reported in renal disease, there is gap in knowledge regarding the mechanisms of histamine-related pathways in the kidney. We report here that all four histamine receptors, as well as enzymes responsible for metabolism of histamine are expressed in human and rat kidney tissues. In this study, we hypothesized that the histaminergic system plays a role in salt-induced kidney damage in Dahl Salt-Sensitive (DSS) rat, a model characterized with inflammation-driven renal lesions. To induce renal damage related to salt-sensitivity, DSS rats were challenged with a 21 days of high salt diet (HS, 4% NaCl); normal salt diet (NS, 0.4% NaCl) fed rats were used as a control. We observed lower histamine decarboxylase (HDC), and higher histamine N-methyltransferase (HNMT) levels in HS diet-fed rats, indicative of a shift in the histaminergic tone; metabolomics showed higher histamine and histidine levels in the kidneys HS diet-fed rats, while plasma levels for both compounds were lower. Acute systemic inhibition of histamine receptor 2 (HR2) in the DSS rat revealed that it lowered vasopressin receptor 2 and AQP2 abundance in the kidney. In summary, we established here the existence of the local histaminergic system, revealed a shift in the renal histamine balance during salt-induced kidney damage, and provided evidence that blockage of HR2 in the DSS rat affects water balance and urine concentrating mechanisms.

Target Class Profiling of Small-Molecule Methyltransferases.

Target class profiling (TCP) is a chemical biology approach to investigate understudied biological target classes. TCP is achieved by developing a generalizable assay platform and screening curated compound libraries to interrogate the chemical biological space of members of an enzyme family. In this work, we took a TCP approach to investigate inhibitory activity across a set of small-molecule methyltransferases (SMMTases), a subclass of methyltransferase enzymes, with the goal of creating a launchpad to explore this largely understudied target class. Using the representative enzymes nicotinamide N-methyltransferase (NNMT), phenylethanolamine N-methyltransferase (PNMT), histamine N-methyltransferase (HNMT), glycine N-methyltransferase (GNMT), catechol O-methyltransferase (COMT), and guanidinoacetate N-methyltransferase (GAMT), we optimized high-throughput screening (HTS)-amenable assays to screen 27,574 unique small molecules against all targets. From this data set, we identified a novel inhibitor which selectively inhibits the SMMTase HNMT and demonstrated how this platform approach can be leveraged for a targeted drug discovery campaign using the example of HNMT.

Drug Repurposing to Inhibit Histamine N-Methyl Transferase.

Lower activity of the histaminergic system is associated with neurological disorders, including Alzheimer's disease (AD). Thus, the enhancement of histaminergic neurotransmission by inhibition of histamine N-methyl transferase (HNMT), which degrades histamine, appears as an important approach. For this purpose, rigid and flexible molecular docking studies of 185 FDA-approved drugs with the HNMT enzyme were carried out to select two compounds to perform molecular dynamics (MD) simulations to evaluate the binding free energies and stability of the enzyme-drug complexes. Finally, an HNMT inhibition assay was performed to corroborate their effect towards HNMT. Molecular docking studies with HNMT allowed the selection of dihydroergotamine and vilazodone since these molecules showed the lowest Gibbs free energy values. Analysis of the binding mode of vilazodone showed interactions with the binding pocket of HNMT with Glu28, Gln143, and Asn283. In contrast, dihydroergotamine binds to the HNMT active site in a different location, apparently because it is overall the more rigid ligand compared to flexible vilazodone. HNMT inhibitory activity for dihydroergotamine and vilazodone was corroborated (IC50 = 72.89 μM and 45.01 μM, respectively) by in vitro assays. Drug repurposing of HNMT was achieved by employing computational studies.

A Missense Mutation in the HMNT Gene Responsible for Autosomal Recessive Intellectual Disability in an Iranian Family with Consanguineous Marriage

Background and Aims: One of the neurotransmitters in the brain is Histamine which acts as several biological mechanism regulators like inflammation, gastric acid secretion, and neuromodulation. Inactivation of Histamine occurs by histamine N-methyltransferase (HNMT) enzyme. The HNMT transfers a methyl group from S-adenosyl-L-methionine to Histamine and is the main process for the termination of neurotransmission actions of Histamine in the mammalian central nervous system.
 Materials and Methods: In this case, a family was referred to the genetic clinic to diagnose the cause of their disorder. The clinical form, pedigree, and questionnaire were completed for the family, and the parents gave their written consent for all tests and photographs publication. Both siblings have moderate learning and intellectual disability. Whole exome sequencing was performed and Sanger sequencing for co-segregation was used.
 Results: Bioinformatics analysis revealed a homozygous missense variant in HNMT (c.623T>C p.Leu208Pro) which causes non-syndromic autosomal recessive intellectual disability in this consanguineous family. Analysis of segregation confirmed this mutation. P.Leu208Pro mutation reduces the stability of the protein, which reduces the inactivation of Histamine.
 Conclusion: HNMT should be considered an important gene in the genetic evaluation of consanguineous families with intellectual disability.

Histamine intolerance (HIT)

Histamine intolerance (HIT) is food intolerance of non-immunological origin, and it results from an imbalance between the consumption of histamine with food and the organism ability to metabolize it. The patients with HIT were found to have a significantly reduced concentration of histamine-degrading enzymes, diamine oxidase (DAO) and histamine N-methyltransferase (HNMT). Factors which have been identified that are conducive to histamine intolerance are: genetic factors, dysbacteriosis, chronic diseases – especially allergic and intestinal diseases, chronic infections, mastocytosis and some drug use. Clinical symptoms of histamine excess may affect various organs and systems - the most common are skin symptoms (pruritis, erythema) nausea, vomiting, abdominal pain, diarrhea, headaches and sometimes severe reactions with shortness of breath, arrhythmias, blood pressure drop, and even cardiac arrest. Diagnostic methods in HIT utilize determination of serum DAO, determination of histamine metabolites in urine, measurement of the histamine wheal in the 50th minute of the skin prick test (SPT), gastroscopy with intestinal biopsy, diagnostic and therapeutic test, oral histamine-challenge test and genetic tests. The mainstay of histamine intolerance treatment if a low-histamine diet. Patients should avoid products belonging to the three groups of food: containing large amounts of histamine, histamine liberators, and products inhibiting the activity of DAO. Additionally, supplements containing DAO and antihistamines can be used.

Food-derived antioxidant ergothioneine improves sleep difficulties in humans

• Volunteers with reported high anxiety and sleep complaints daily took ergothioneine (EGT) for 4 weeks. • A questionnaire survey showed that EGT significantly ameliorate sleeping difficulties. • Electroencephalograph measurements showed that ingesting EGT resulted in a significant improvement in objective sleep quality. • Metabolome analysis suggested that EGT reduces consumption of antioxidant substances while enhancing lipid metabolism. Sleep disorders interfere with daily life and are associated with the development of various diseases. Here, we evaluated the effect of orally ingested ergothioneine (EGT) on improving sleep quality. We conducted a randomized, placebo-controlled, double-blind, parallel-group comparison study. A 20 mg EGT or placebo capsule was ingested daily for 4 weeks by volunteers with reported high anxiety and sleep complaints. A survey showed that EGT significantly ameliorates sleeping difficulties. Electroencephalograph measurements showed that EGT intake increases the N2 stage, while decreasing the N1 stage in non-REM sleep and the frequency of waking after sleep onset. Serum metabolome analysis suggested that EGT reduces serum glutamate as well as the consumption of antioxidant and anti-inflammatory substances while enhancing lipid metabolism. Molecular targeting assays revealed that EGT inhibits histamine N-methyltransferase and aldehyde dehydrogenase activity and binding to α3β4 nicotinic acetylcholine receptor. Hence, EGT may improve sleep difficulties via multiple mechanisms of action.

Screening and Structure-Activity Relationship of Potential Compounds against Proposed Targets of COVID-19 Infection

Background: With reference to COVID-19 pandemic prevailing across the globe, chloroquine and hydroxychloroquine were reported as effective against the disease to some extent. This effectiveness can be attributed to the glycosylation interruption of the Angiotensin-converting enzyme 2 (ACE2) receptor, which is a known target for SARS-CoV-2 entery. On the other hand, studies suggest that the inhibition of ACE2 can be lethal in certain cases, thereby causing cardiovascular disorders, especially in patients already suffering from heart-related diseases. Methods: In this study, the most probable targets (other than ACE2) have been proposed for the treatment of COVID-19 infection by taking chloroquine and hydroxychloroquine as reference drugs. SwissTargetPrediction and PASSonline tools were used in order to achieve this objective. Known drugs against each target possessing close relation to either viral infections or lung disorders were assessed from the DrugBank database, and simultaneous efficacy of these drugs towards other proposed targets has been analyzed. By taking the most effective drugs as a reference, similar compounds were screened from the ChEMBL library by using the SwissSimilarity tool. Finally, molecular docking studies were performed through MOE software by using screened compounds against proposed targets. Results: Four most probable targets have been proposed, which include chemokine receptors (CCRs), dipeptidyl peptidase 4 (DPP4), muscarinic acetylcholine receptors (CHRMs), and histamine Nmethyltransferase (HNMT). Furthermore, it has been evaluated that quinacrine and vildagliptin are effective against most of the proposed targets. By taking vildagliptin as well as quinacrine as reference drugs, further eight compounds with similar effectiveness against these targets have been screened from the ChEMBL library. Molecular docking studies with CCR5, DPP4, and CHRM5 suggest that the quinacrine and its analogue (ChEMBL1782742) as well as vildagliptin and its analogue (ChEMBL511785) are the most suitable compounds as HITs for these targets. Conclusions: It has been established that the quinacrine, ChEMBL1782742, vildagliptin, ChEMBL511785, mavorixafor, atropine, and N-(2-aminoethyl)-1-aziridineethanamine in descending order can be considered as effective drugs for the treatment of COVID-19 infection.

Contribution of astrocytic histamine N-methyltransferase to histamine clearance and brain function in mice

Brain histamine acts as a neurotransmitter in the regulation of various brain activities. Previous studies have shown that histamine N-methyltransferase (HNMT), a histamine-metabolizing enzyme, controls brain histamine concentration and brain function. However, the relative contribution of astrocytic or neuronal HNMT to the regulation of the histaminergic system is still inconclusive. Here, we phenotyped astrocytes-specific HNMT knockout (cKO) mice to clarify the involvement of astrocytic HNMT in histamine clearance and brain function.First, we performed histological examinations using HNMT reporter mice and showed a wide distribution of HNMT in the brain and astrocytic HNMT expression. Then, we created cKO mice by Cre-loxP system and confirmed that HNMT expression in cKO primary astrocytes was robustly decreased. Although total HNMT level in the cortex was not substantially different between control and cKO brains, histamine concentration after histamine release was elevated in cKO cortex. In behavioral tests, impaired motor coordination and lower locomotor activity were observed in the cKO mice. However, anxiety-like behaviors, depression-like behaviors, and memory functions were not altered by astrocytic HNMT disruption. Although sleep analysis demonstrated that the quantity of wakefulness and sleep did not change, the increased power density of delta frequency during wakefulness indicated lower cortical activation in cKO mice. These results demonstrate that astrocytic HNMT contributes to histamine clearance after histamine release in the cortex and plays a role in the regulation of motor coordination, locomotor activity, and vigilance state.

Diamine oxidase knockout mice are not hypersensitive to orally or subcutaneously administered histamine

ObjectiveTo evaluate the contribution of endogenous diamine oxidase (DAO) in the inactivation of exogenous histamine, to find a mouse strain with increased histamine sensitivity and to test the efficacy of rhDAO in a histamine challenge model.MethodsDiamine oxidase knockout (KO) mice were challenged with orally and subcutaneously administered histamine in combination with the β-adrenergic blocker propranolol, with the two histamine-N-methyltransferase (HNMT) inhibitors metoprine and tacrine, with folic acid to mimic acute kidney injury and treated with recombinant human DAO. Core body temperature was measured using a subcutaneously implanted microchip and histamine plasma levels were quantified using a homogeneous time resolved fluorescence assay.ResultsCore body temperature and plasma histamine levels were not significantly different between wild type (WT) and DAO KO mice after oral and subcutaneous histamine challenge with and without acute kidney injury or administration of HNMT inhibitors. Treatment with recombinant human DAO reduced the mean area under the curve (AUC) for core body temperature loss by 63% (p = 0.002) and the clinical score by 88% (p < 0.001). The AUC of the histamine concentration was reduced by 81%.ConclusionsInactivation of exogenous histamine is not driven by enzymatic degradation and kidney filtration. Treatment with recombinant human DAO strongly reduced histamine-induced core body temperature loss, histamine concentrations and prevented the development of severe clinical symptoms.

Impact of the clinically approved Petasites hybridus extract Ze 339 on intestinal mechanisms involved in the handling of histamine

In patients with histamine intolerance accumulated or ingested histamine causes a broad range of undesirable symptoms. Food-derived histamine is degraded by intestinal diamine oxidase (DAO) and histamine-N-methyltransferase (HNMT), while the organic cation transporter 3 (OCT3) contributes to the transcellular flux of histamine. Anecdotal evidence from patients with HIT suggests an improvement of symptoms related to histamine intolerance after intake of Ze 339, a lipophilic CO2-extract prepared from the leaves of Petasites hybridus. Thus, it was the aim of this study to investigate the influence of Ze 339 on DAO, HNMT and OCT3 using Caco-2 and MDCKII cells. Even though Ze 339 reduced mRNA levels of HNMT and DAO, there was no change in protein expression. Ze 339 changed neither the basal release nor the enzymatic activity of DAO. Testing the interaction of Ze 339 with the transcellular histamine transport, we observed a significant increase in the basal to apical flux in presence of high Ze 339 concentrations at the early phases of the experiment. Testing the influence of Ze 339 on OCT3-mediated histamine uptake in overexpressing MDCKII cells revealed a dose-dependent inhibition with an estimated IC50 of 26.9 ug/mL for the extract. In conclusion, we report an effect of Ze 339 on transcellular histamine transport, where inhibition of OCT3 may contribute.

Development of a Transdermal Delivery System for Tacrine

Tacrine has several mechanisms of action. The putative primary mechanism of action of tacrine for Alzheimer's disease is reversible inhibition of acetylcholinesterase (AChE), which thus slows the breakdown of the chemical messenger acetylcholine (ACh) in the brain. Tacrine also inhibits butyrylcholinesterase activity. In accumulation, tacrine blocks sodium and potassium channels. Tacrine also acts as a histamine N-methyltransferase inhibitor. This study was carried out to develop matrix based transdermal patches containing Tacrine to overcome the first pass metabolism and to reduce frequency of dosing compared to oral route. . Matrix type of transdermal patches was developed by using Methocel K4M, Methocel K15M, Methocel K100M and Xanthan gum polymers. Transdermal patches were prepared by employing solvent casting method. Drug excipients compatibility studies were carried out by using FTIR, and it was observed that there were no interactions. Formulations were prepared with the varying concentrations polymers ranging from F1-F16, and all the formulations were evaluated for various physical parameters Physical appearance, Flatness, Weight variation, Thickness, Folding endurance, Drug content, Moisture uptake, Moisture content and Swelling study and all the results were found to be within the pharmacopeial limits, invitro drug release studies by using dialysis membrane. Among all the 16 Tacrine transdermal patches formulations F5 formulations which contain Methocel K15M 100 mg had shown 97.61% % cumulative drug release within 12 hours.

HNMT Upregulation Induces Cancer Stem Cell Formation and Confers Protection against Oxidative Stress through Interaction with HER2 in Non-Small-Cell Lung Cancer.

Background: The treatment of non-small-cell lung cancer (NSCLC) involves platinum-based chemotherapy. It is typically accompanied by chemoresistance resulting from antioxidant properties conferred by cancer stem cells (CSCs). Human epidermal growth factor receptor 2 (HER2) enhances CSCs and antioxidant properties in cancers, including NSCLC. Methods: Here, we elucidated the role of histamine N-methyltransferase (HNMT), a histamine metabolism enzyme significantly upregulated in NSCLC and coexpressed with HER2. HNMT expression in lung cancer tissues was determined using quantitative reverse transcription PCR (RT-qPCR). A publicly available dataset was used to determine HNMT’s potential as an NSCLC target molecule. Immunohistochemistry and coimmunoprecipitation were used to determine HNMT–HER2 correlations and interactions, respectively. HNMT shRNA and overexpression plasmids were used to explore HNMT functions in vitro and in vivo. We also examined miRNAs that may target HNMT and investigated HNMT/HER2’s role on NSCLC cells’ antioxidant properties. Finally, how HNMT loss affects NSCLC cells’ sensitivity to cisplatin was investigated. Results: HNMT was significantly upregulated in human NSCLC tissues, conferred a worse prognosis, and was coexpressed with HER2. HNMT depletion and overexpression respectively decreased and increased cell proliferation, colony formation, tumorsphere formation, and CSCs marker expression. Coimmunoprecipitation analysis indicated that HNMT directly interacts with HER2. TARGETSCAN analysis revealed that HNMT is a miR-223 and miR-3065-5p target. TBHp treatment increased HER2 expression, whereas shHNMT disrupted the Nuclear factor erythroid 2-related factor 2 (Nrf2)/ hemeoxygenase-1 (HO-1)/HER2 axis and increased reactive oxygen species accumulation in NSCLC cells. Finally, shHNMT sensitized H441 cells to cisplatin treatment in vitro and in vivo. Conclusions: Therefore, HNMT upregulation in NSCLC cells may upregulate HER2 expression, increasing tumorigenicity and chemoresistance through CSCs maintenance and antioxidant properties. This newly discovered regulatory axis may aid in retarding NSCLC progression and chemoresistance.

Pumpkin seed oil and zinc attenuate chronic mild stress perturbations in the cerebral cortex of rats

PurposeThis study aims to investigate the potential of pumpkin seed oil (PSO) and zinc to attenuate oxidative stress and neuroinflammation caused by chronic mild stress (CMS) in the cerebral cortex of male rats.Design/methodology/approachThe rats were submitted to stress for six weeks and then the behavior of the rats was tested by forced swimming test (FST) and novel cage test. The treated groups were given venlafaxine (20 mg/kg), pumpkin seed oil (40 mg/kg) and zinc (4 mg/kg). The cortex homogenate was used for the detection of the oxidative stress parameters, the concentration of neurotransmitters, tumor necrosis factor-α (TNF-α) and interleukin 1β (IL-1β), Na+/K+-ATPase activity, and the expression of histamine N-methyltransferase (Hnmt) and tyrosine hydroxylase (Th).FindingsCMS causes a significant increase in immobility time in the FST and a significant decrease in the number of rearing in the novel cage test. CMS group showed a significant increase in alanine aminotransferase (ALT) activity, levels of cortisol, TNF-α, IL-1β, nitric oxide and malondialdehyde. CMS caused a significant decrease in the concentrations of serotonin, GABA, norepinephrine, and the activities of glutathione peroxidase, catalase, superoxide dismutase and Na+/K+-ATPase. CMS caused a marked reduction in the expression of Hnmt and Th in the cortex. PSO and zinc attenuated the Na+/K+-ATPase activity, oxidative parameters and neuroinflammation induced by the CMS, and this was reflected by the elevation of the concentration of neurotransmitters and reduction of cortisol and ALT, in addition to the behavior normalization. PSO and zinc attenuated the CMS by improving the antioxidant milieu and anti-inflammatory status of the cerebral cortex.Originality/valueThere are no studies on the effect of pumpkin seed oil on depression

神経細胞に発現するヒスタミン代謝酵素の重要性について

神経細胞に発現するヒスタミン代謝酵素の重要性について

Inhibition of Astrocytic Histamine N-Methyltransferase as a Possible Target for the Treatment of Alzheimer's Disease.

Alzheimer’s disease (AD) represents the principal cause of dementia among the elderly. Great efforts have been established to understand the physiopathology of AD. Changes in neurotransmitter systems in patients with AD, including cholinergic, GABAergic, serotoninergic, noradrenergic, and histaminergic changes have been reported. Interestingly, changes in the histaminergic system have been related to cognitive impairment in AD patients. The principal pathological changes in the brains of AD patients, related to the histaminergic system, are neurofibrillary degeneration of the tuberomammillary nucleus, the main source of histamine in the brain, low histamine levels, and altered signaling of its receptors. The increase of histamine levels can be achieved by inhibiting its degrading enzyme, histamine N-methyltransferase (HNMT), a cytoplasmatic enzyme located in astrocytes. Thus, increasing histamine levels could be employed in AD patients as co-therapy due to their effects on cognitive functions, neuroplasticity, neuronal survival, neurogenesis, and the degradation of amyloid beta (Aβ) peptides. In this sense, the evaluation of the impact of HNMT inhibitors on animal models of AD would be interesting, consequently highlighting its relevance.