Salivary Histamine Levels in Patients with Oral Lichen Planus Lesions

Background and Objectives: An oral lichen planus (OLP) chronic lesion refers to a group of oral potentially malignant disorders (OPMDs) that still lack a proper understanding from the point of view of relevant biomarkers for diagnostics and prognosis. The aim of the study was to assess the salivary histamine levels in patients with oral lichen planus lesions. Materials and Methods: The study included a group of 76 patients with oral lichen planus. General diseases and medication taken, smoking habits, severity of pain assessed using a visual analogue scale (VAS), oral hygiene status, and duration of OLP were evaluated. ELISA diagnostics for histamines in saliva levels were assessed. Results: The histamine levels in the OLP group were higher (0.468) in comparison with the control group (0.056), without a statistically significant value p = 0.090 (Mann-Whitney U Test). The median age of 76 OLP patients was 63 years (min 22.0-max. 81), with the biological sex being 80.3% females and 15 19.7% males. The average duration of OLP lesion presence was 29.4 months (SD 37.1) and the median value was 14.5 months. The median of the VAS was 3.0. OLP assessment in accordance with the Malhotra methodology showed the highest frequency-30.3% for only two of the point areas involved and 17.1% for three points. Clinical assessment of the different OLP grades, severity, and oral site involvement and the VAS in correlation with histamine salivary levels showed a lack of statistical significance in the investigated population. Conclusions: Undertaking further research could provide further possibilities for searching for general factors in OLP development.

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.

Histamine deficiency inhibits lymphocyte infiltration in the submandibular gland of aged mice via increased anti-aging factor Klotho

OBJECTIVES

Histidine decarboxylase (HDC), a histamine synthase, is expressed in various tissues and is induced by proinflammatory cytokines such as TNFα. As they age, C57BL/6 mice show auto-antibody deposition and lymphocyte infiltration into various tissues, including salivary glands. However, the mechanism underlying cell infiltration and the change in HDC expression in salivary glands with aging remain unclear. Thus, we aimed to elucidate the relationship between histamine and inflammaging.

METHODS

We investigated the change in histology and HDC expression in the major salivary glands (parotid, submandibular, and sublingual) of 6-week- and 9-month-old wild-type mice. We also determined the histological changes, cytokine expression, and anti-aging factor Klotho in the salivary glands of 9-month-old wild-type and HDC-deficient (HDC-KO) mice.

RESULTS

Cell infiltration was observed in the submandibular gland of 9-month-old wild-type mice. Although most cells infiltrating the submandibular glands were CD3-positive and B220-positive lymphocytes, CD11c-positive and F4/80-positive monocyte lineages were also detected. HDC, TNFα, and IL-1β mRNA expression increased in the submandibular gland of 9-month-old wild-type mice. The expression of PPARγ, an anti-inflammatory protein, declined in 9-month-old wild-type mice, and Klotho expression increased in 9-month-old HDC-KO mice. Immunohistochemistry showed that Klotho-positive cells disappeared in the submandibular gland of 9-month-old wild-type mice, while Klotho was detected in all salivary glands in HDC-KO mice of the same age.

CONCLUSION

Our findings demonstrate the multifunctionality of histamine and can aid in the development of novel therapeutic methods for inflammatory diseases such as Sjogren's syndrome and age-related dysfunctions.

Cimetidine-induced androgenic failure causes cell death and changes in actin, EGF and V-ATPase immunoexpression in rat submandibular glands

Submandibular gland (SMG) is responsive to androgens via androgen receptor (AR). We verified whether cimetidine induces androgenic dysfunction in SMG, and evaluated the structural integrity, cell death and immunoexpression of actin, EGF and V-ATPase in androgen-deficient SMG. Male rats received cimetidine (CMTG) and control animals (CG) received saline. Granular convoluted tubules (GCTs) diameter and number of acinar cell nuclei were evaluated. TUNEL and immunofluorescence reactions for detection of AR, testosterone, actin, EGF and V-ATPase were quantitatively analysed. In CG, testosterone immunolabelling was detected in acinar and ductal cells cytoplasm. AR-immunolabelled nuclei were observed in acinar cells whereas ductal cells showed AR-immunostained cytoplasm, indicating a non-genomic AR action. In CMTG, the weak testosterone and AR immunoexpression confirmed cimetidine-induced androgenic failure. A high cell death index was correlated with decreased number of acinar cells, GCTs diameter and EGF immunoexpression under androgenic dysfunction. Actin immunofluorescence decreased in the SMG cells, but an increased and diffuse cytoplasmic V-ATPase immunolabelling was observed in striated ducts, suggesting a disruption in the actin-dependent V-ATPase recycling due to androgenic failure. Our findings reinforce the androgenic role in the maintenance of SMG histophysiology, and point to a potential clinical use of cimetidine against androgen-dependent glandular tumour cells.

Organic Cation Transporters in Brain Histamine Clearance: Physiological and Psychiatric Implications

Histamine acts as a neurotransmitter in the central nervous system and is involved in numerous physiological functions. Recent studies have identified the causative role of decreased histaminergic systems in various neurological disorders. Thus, the brain histamine system has attracted attention as a therapeutic target to improve brain function. Neurotransmitter clearance is one of the most important processes for the regulation of neuronal activity and is an essential target for diverse drugs. Our previous study has shown the importance of histamine N-methyltransferase for the inactivation of brain histamine and the intracellular localization of this enzyme; the study indicated that the transport system for the movement of positively charged histamine from the extracellular to intracellular space is a prerequisite for histamine inactivation. Several studies on in vitro astrocytic histamine transport have indicated the contribution of organic cation transporter 3 (OCT3) and plasma membrane monoamine transporter (PMAT) in histamine uptake, although the importance of these transporters in in vivo histamine clearance remains unknown. Immunohistochemical analyses have revealed the expression of OCT3 and PMAT on neurons, emphasizing the importance of investigating neuronal histamine uptake. Further studies using knockout mice or fast-scan cyclic voltammetry will accelerate the research on histamine transporters. In this review article, we summarize histamine transport assays and describe the candidate transporters responsible for histamine transport in the brain.

Membrane Transporters in Human Parotid Gland-Targeted Proteomics Approach

Salivary glands provide secretory functions, including secretion of xenobiotics and among them drugs. However, there is no published information about protein abundance of drug transporters measured using reliable protein quantification methods. Therefore, mRNA expression and absolute protein content of clinically relevant ABC (n = 6) and SLC (n = 15) family member transporters in the human parotid gland, using the qRT-PCR and liquid chromatography‒tandem mass spectrometry (LC−MS/MS) method, were studied. The abundance of nearly all measured proteins ranged between 0.04 and 0.45 pmol/mg (OCT3 > MRP1 > PEPT2 > MRP4 > MATE1 > BCRP). mRNAs of ABCB1, ABCC2, ABCC3, SLC10A1, SLC10A2, SLC22A1, SLC22A5, SLC22A6, SLC22A7, SLC22A8, SLCO1A2, SLCO1B1, SLCO1B3 and SLCO2B1 were not detected. The present study provides, for the first time, information about the protein abundance of membrane transporters in the human parotid gland, which could further be used to define salivary bidirectional transport (absorption and secretion) mechanisms of endogenous compounds and xenobiotics.

Molecular Regulation of Histamine Synthesis

Histamine is a critical mediator of IgE/mast cell-mediated anaphylaxis, a neurotransmitter and a regulator of gastric acid secretion. Histamine is a monoamine synthesized from the amino acid histidine through a reaction catalyzed by the enzyme histidine decarboxylase (HDC), which removes carboxyl group from histidine. Despite the importance of histamine, transcriptional regulation of HDC gene expression in mammals is still poorly understood. In this review, we focus on discussing advances in the understanding of molecular regulation of mammalian histamine synthesis.

Histamine stimulates secretion of extracellular vesicles with nucleotidase activity in rat submandibular gland

BACKGROUND

Extracellular vesicles released by different cells have been isolated from diverse fluids including saliva. We previously reported that rat submandibular glands secrete nanovesicles that catalyze hydrolysis of ATP, ADP and AMP, which are actors of the purinergic signaling system along with adenosine. Extracellular nucleotides like ATP and adenosine are involved in the regulation of inflammatory processes and apoptosis. Histamine, a widely distributed biogenic amine, is involved in inflammatory response.

OBJECTIVE

To test if activation of histamine receptors in rat submandibular gland promotes changes in the release of vesicles with nucleotidase activity that could modulate purinergic signaling.

METHODS

Rat submandibular glands were incubated in the absence or presence of histamine and JNJ7777120, an antagonist for H₄ receptors. Extracellular vesicles were isolated from incubation media by differential centrifugation. Vesicular nucleotidase activity was measured following Pi release by 3mM MgATP, MgADP or MgAMP.

RESULTS

Histamine increased the release of vesicles with nucleotidase activity in a concentration dependent manner. JNJ7777120 significantly reduced this effect. Vesicular nucleotidases obtained in the absence or presence of histamine promoted Pi production from ATP, ADP and AMP.

CONCLUSION

The results show a relationship between histamine and the regulation of purinergic signaling, which could be important in the modulation of inflammatory processes.

Histamine H3 and H4 receptor ligands modify vascular histamine levels in normal and arthritic large blood vessels in vivo

Growing evidence associates histamine with arthritis, but its implication in shaping vascular function in chronic inflammation remains largely elusive. This study explored the involvement of vascular histamine in the extra-articular responses in peripheral large blood vessels using a rat model of adjuvant-induced arthritis. Histamine levels were increased in the abdominal aorta and the inferior vena cava of arthritic animals. Contrary to the H1 receptor antagonist dimetindene, histamine induction was observed following administration of the H3 and H4 receptor ligands GSK334429 and JNJ7777120, respectively. In arthritis, prophylactic treatment with GSK334429 partially attenuated the clinical signs and restored basal histamine levels only in the abdominal aorta. This study is the first to implicate the H3 and H4 receptors in a concerted constitutive regulation of basal vascular histamine in the rat large blood vessels and to identify the H3 receptor as a component that may influence arterial histamine during the onset of arthritis.

Histidine Decarboxylase Deficiency Prevents Autoimmune Diabetes in NOD Mice

Recent evidence has highlighted the role of histamine in inflammation. Since this monoamine has also been strongly implicated in the pathogenesis of type-1 diabetes, we assessed its effect in the nonobese diabetic (NOD) mouse model. To this end, we used mice (inactivated) knocked out for the gene encoding histidine decarboxylase, the unique histamine-forming enzyme, backcrossed on a NOD genetic background. We found that the lack of endogenous histamine in NOD HDC(-/-) mice decreased the incidence of diabetes in relation to their wild-type counterpart. Whereas the proportion of regulatory T and myeloid-derived suppressive cells was similar in both strains, histamine deficiency was associated with increased levels of immature macrophages, as compared with wild-type NOD mice. Concerning the cytokine pattern, we found a decrease in circulating IL-12 and IFN-γ in HDC(-/-) mice, while IL-6 or leptin remained unchanged, suggesting that histamine primarily modulates the inflammatory environment. Paradoxically, exogenous histamine given to NOD HDC(-/-) mice provided also protection against T1D. Our study supports the notion that histamine is involved in the pathogenesis of diabetes, thus providing additional evidence for its role in the regulation of the immune response.

Histamine H4 receptor in oral lichen planus

OBJECTIVES

Oral lichen planus (OLP) is an autoimmune disease characterized by a band-like T-cell infiltrate below the apoptotic epithelial cells and degenerated basement membrane. We tested the hypothesis that the high-affinity histamine H4 receptors (H4 Rs) are downregulated in OLP by high histamine concentrations and proinflammatory T-cell cytokines.

MATERIALS AND METHODS

Immunohistochemistry and immunofluorescence staining, image analysis and quantitative real-time polymerase chain reaction of tissue samples and cytokine-stimulated cultured SCC-25 and primary human oral keratinocytes.

RESULTS

H4 R immunoreactivity was weak in OLP and characterized by mast cell (MC) hyperplasia and degranulation. In contrast to controls, H4 R immunostaining and MC counts were negatively correlated in OLP (P = 0.003). H4 R agonist at nanomolar levels led to a rapid internalization of H4 Rs, whereas high histamine concentration and interferon-γ decreased HRH4 -gene transcripts.

CONCLUSION

Healthy oral epithelial cells are equipped with H4 R, which displays a uniform staining pattern in a MC-independent fashion. In contrast, in OLP, increased numbers of activated MCs associate with increasing loss of epithelial H4 R. Cell culture experiments suggest a rapid H4 R stimulation-dependent receptor internalization and a slow cytokine-driven decrease in H4 R synthesis. H4 R may be involved in the maintenance of healthy oral mucosa. In OLP, this maintenance might be impaired by MC degranulation and inflammatory cytokines.

Nascent histamine induces α-synuclein and caspase-3 on human cells

Histamine (Hia) is the most multifunctional biogenic amine. It is synthetized by histidine decarboxylase (HDC) in a reduced set of mammalian cell types. Mast cells and histaminergic neurons store Hia in specialized organelles until the amine is extruded by exocytosis; however, other immune and cancer cells are able to produce but not store Hia. The intracellular effects of Hia are still not well characterized, in spite of its physiopathological relevance. Multiple functional relationships exist among Hia metabolism/signaling elements and those of other biogenic amines, including growth-related polyamines. Previously, we obtained the first insights for an inhibitory effect of newly synthetized Hia on both growth-related polyamine biosynthesis and cell cycle progression of non-fully differentiated mammalian cells. In this work, we describe progress in this line. HEK293 cells were transfected to express active and inactive versions of GFP-human HDC fusion proteins and, after cell sorting by flow cytometry, the relative expression of a large number of proteins associated with cell signaling were measured using an antibody microarray. Experimental results were analyzed in terms of protein-protein and functional interaction networks. Expression of active HDC induced a cell cycle arrest through the alteration of the levels of several proteins such as cyclin D1, cdk6, cdk7 and cyclin A. Regulation of α-synuclein and caspase-3 was also observed. The analyses provide new clues on the molecular mechanisms underlying the regulatory effects of intracellular newly synthetized Hia on cell proliferation/survival, cell trafficking and protein turnover. This information is especially interesting for emergent and orphan immune and neuroinflammatory diseases.