Histamine as an autocrine regulator of leukemic cell proliferation

Guanidines: Synthesis of Novel Histamine H3R Antagonists with Additional Breast Anticancer Activity and Cholinesterases Inhibitory Effect

This study examines the properties of novel guanidines, designed and synthesized as histamine H₃R antagonists/inverse agonists with additional pharmacological targets. We evaluated their potential against two targets viz., inhibition of MDA-MB-231, and MCF-7 breast cancer cells viability and inhibition of AChE/BuChE. ADS10310 showed micromolar cytotoxicity against breast cancer cells, combined with nanomolar affinity at hH₃R, and may represent a promising target for the development of an alternative method of cancer therapy. Some of the newly synthesized compounds showed moderate inhibition of BuChE in the single-digit micromolar concentration ranges. H₃R antagonist with additional AChE/BuChE inhibitory effect might improve cognitive functions in Alzheimer's disease. For ADS10310, several in vitro ADME-Tox parameters were evaluated and indicated that it is a metabolically stable compound with weak hepatotoxic activity and can be accepted for further studies.

In vitro effects of histamine receptor 1 antagonists on proliferation and histamine release in canine neoplastic mast cells

Canine mastocytomas (MCTs) are characterized by rapid proliferation of neoplastic mast cells (MCs) and clinical signs caused by MC-derived mediators. In dogs suffering from MCT, histamine receptor 1 (HR1) antagonists are frequently used to control mediator-related clinical symptoms. Previous studies have shown that the HR1 antagonists loratadine and terfenadine exert some growth-inhibitory effects on neoplastic MCs. We examined whether other HR1 antagonists used in clinical practice (desloratadine, rupatadine, cyproheptadine, dimetindene, diphenhydramine) affect proliferation and survival of neoplastic MCs. Furthermore, we analysed whether these HR1 antagonists counteract IgE-dependent histamine release from a MC line harbouring a functional IgE-receptor. HR1 antagonists were applied on two canine MC lines, C2 and NI-1, and on primary MCs obtained from three MCT samples. The HR1 antagonists desloratadine, rupatadine and cyproheptadine were found to be more potent in decreasing proliferation of C2 and NI-1 cells when compared with dimetindene and diphenhydramine. Similar effects were seen in primary neoplastic MCs, except for diphenhydramine, which exerted more potent growth-inhibitory effects than the other HR1 antagonists. Drug-induced growth-inhibition in C2 and NI-1 cells was accompanied by apoptosis. Loratadine, desloratadine and rupatadine also suppressed IgE-dependent histamine release in NI-1 cells. However, drug concentrations required to elicit substantial effects on growth or histamine release were relatively high (>10 µM). Therefore, it remains unknown whether these drugs or similar, more potent, HR1-targeting drugs can suppress growth or activation of canine neoplastic MCs in vivo.

Deletion and down-regulation of HRH4 gene in gastric carcinomas: a potential correlation with tumor progression

BACKGROUND

Histamine is an established growth factor for gastrointestinal malignancies. The effect of histamine is largely determined locally by the histamine receptor expression pattern. Histamine receptor H4 (HRH4), the newest member of the histamine receptor family, is positively expressed on the epithelium of the gastrointestinal tract, and its function remains to be elucidated. Previously, we reported the decreased expression of HRH4 in colorectal cancers and revealed its correlation with tumor proliferation. In the current study, we aimed to investigate the abnormalities of HRH4 gene in gastric carcinomas (GCs).

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed H4R expression in collected GC samples by quantitative PCR, Western blot analysis, and immunostaining. Our results showed that the protein and mRNA levels of HRH4 were reduced in some GC samples, especially in advanced GC samples. Copy number decrease of HRH4 gene was observed (17.6%, 23 out of 131), which was closely correlated with the attenuated expression of H4R. In vitro studies, using gastric cancer cell lines, showed that the alteration of HRH4 expression on gastric cancer cells influences tumor growth upon exposure to histamine.

CONCLUSIONS/SIGNIFICANCE

We show for the first time that deletion of HRH4 gene is present in GC cases and is closely correlated with attenuated gene expression. Down-regulation of HRH4 in gastric carcinomas plays a role in histamine-mediated growth control of GC cells.

Attenuated expression of HRH4 in colorectal carcinomas: a potential influence on tumor growth and progression

BACKGROUND

Earlier studies have reported the production of histamine in colorectal cancers (CRCs). The effect of histamine is largely determined locally by the histamine receptor expression pattern. Recent evidence suggests that the expression level of histamine receptor H4 (HRH4) is abnormal in colorectal cancer tissues. However, the role of HRH4 in CRC progression and its clinical relevance is not well understood. The aim of this study is to evaluate the clinical and molecular phenotypes of colorectal tumors with abnormal HRH4 expression.

METHODS

Immunoblotting, real-time PCR, immunofluorescence and immunohistochemistry assays were adopted to examine HRH4 expression in case-matched CRC samples (n = 107) and adjacent normal tissues (ANTs). To assess the functions of HRH4 in CRC cells, we established stable HRH4-transfected colorectal cells and examined cell proliferation, colony formation, cell cycle and apoptosis in these cells.

RESULTS

The protein levels of HRH4 were reduced in most of the human CRC samples regardless of grade or Dukes classification. mRNA levels of HRH4 were also reduced in both early-stage and advanced CRC samples. In vitro studies showed that HRH4 over-expression caused growth arrest and induced expression of cell cycle proteins in CRC cells upon exposure to histamine through a cAMP -dependent pathway. Furthermore, HRH4 stimulation promoted the 5-Fu-induced cell apoptosis in HRH4-positive colorectal cells.

CONCLUSION

The results from the current study supported previous findings of HRH4 abnormalities in CRCs. Expression levels of HRH4 could influence the histamine-mediated growth regulation in CRC cells. These findings suggested a potential role of abnormal HRH4 expression in the progression of CRCs and provided some new clues for the application of HRH4-specific agonist or antagonist in the molecular therapy of CRCs.

Decreased hormone content of immune cells in children during acute lymphocytic leukemia (ALL) - effect of treatment

Histamine, serotonin and triiodothyronine (T3) content of different circulating lymphocyte subsets of leukemic (acute lymphocytic leukemia, ALL) and non-leukemic (control) children were investigated by multicolor flow cytometry. The hormone contents of the cells were followed from the time of diagnosis till the end of treatment. Each hormone could be detected in every time in the investigated cell types, although the amounts of them changed during the treatment.T lymphocytes: Significantly lower amount of serotonin was found in each T cell subsets (Th, Tc and activated T lymphocytes) of leukemic children compared to the healthy control group at the time of diagnosis and it was permanently low during the maintenance therapy. The decreased amount of serotonin could be demonstrated in Tc and Th cells even at one year after the end of treatment. However, there was no alteration in the histamine and T3 content of T cell subsets in the time of diagnosis, but significant decrease was detected during the maintenance therapy and after treatment.NK cells: The serotonin and T3 contents of NK cells (both NK and NKT subsets) were significantly lower at the time of diagnosis and during the maintenance therapy. Similar decrease was detected in the case of serotonin in B cells. Although there was no difference in the T3 content of B cells at the time of diagnosis, significantly lower amounts could be detected during the therapy compared to the healthy control group. The serotonin concentration remained low for years after the end of treatment, both in B and NK cells. These observations might have diagnostic and prognostic importance.

H1-receptor antagonists terfenadine and loratadine inhibit spontaneous growth of neoplastic mast cells

OBJECTIVE

In mast cell (MC) neoplasms, clinical problems requiring therapy include local aggressive and sometimes devastating growth of MCs and mediator-related symptoms. A key mediator of MCs responsible for clinical symptoms is histamine. Therefore, use of histamine receptor (HR) antagonists is an established approach to block histamine effects in these patients.

MATERIALS AND METHODS

We screened for additional beneficial effects of HR antagonists and asked whether any of these agents would also exert growth-inhibitory effects on primary neoplastic MCs, the human MC line HMC-1, and on two canine MC lines, C2 and NI-1.

RESULTS

We found that the HR1 antagonists terfenadine and loratadine suppress spontaneous growth of HMC-1, C2, and NI-1 cells, as well as growth of primary neoplastic MCs in all donors tested (human patients, n = 5; canine patients, n = 8). The effects of both drugs were found to be dose-dependent (IC(50): terfenadine, 1-20 μM; loratadine, 10-50 μM). Both agents also produced apoptosis in neoplastic MCs and augmented apoptosis-inducing effects of two KIT-targeting drugs, PKC412 and dasatinib. The other HR1 antagonists (fexofenadine, diphenhydramine) and HR2 antagonists (famotidine, cimetidine, ranitidine) tested did not exert substantial growth-inhibitory effects on neoplastic MCs. None of the histamine receptor blockers were found to modulate cell-cycle progression in neoplastic MCs.

CONCLUSIONS

The HR1 antagonists terfenadine and loratadine, in addition to their antimediator activity, exert in vitro growth-inhibitory effects on neoplastic MCs. Whether these drugs (terfenadine) alone, or in combination with KIT inhibitors, can also affect in vivo neoplastic MC growth remains to be determined.

Expression of non-mast cell histidine decarboxylase in tumor-associated microvessels in human esophageal squamous cell carcinomas

Histamine is produced by mast cells and many other types of cells. The role of histamine released from mast cells in promoting tumor angiogenesis has been intensively studied; however, the role of non-mast cell histamine in regulating tumor angiogenesis has been largely ignored. In this study, tissue specimen sections from 43 patients with esophageal squamous cell carcinoma (ESCC) and normal esophageal biopsies from 17 heath individuals obtained from a high incidence area of north China were used to assess changes in microvessel density (MVD) and non-mast cell L-histidine decarboxylase (HDC) (the only rate-limiting enzyme that catalyzes the formation of histamine from L-histidine) expression in the tumor microenvironment by immunohistochemistry (IHC). In addition, the cellular characterization of non-mast cell HDC-positive cells in microvessels was examined by double IHC combined with HDC/CD34 and HDC/PCNA antibodies. These IHC analyses revealed a significantly increased HDC-positive MVD in ESCC as compared with normal controls, which accounted for approximately 61% of CD34-labeled general MVD in ESCC. Furthermore, IHC in serial sections and double IHC showed that most of these HDC-positive cells were CD34-positive endothelial cells in microvessels with an increased proliferative capacity. Thus, our results suggest that non-mast cell histamine expressed in endothelial cells of microvessels could be an additional cellular source and might play a role in regulating angiogenesis in ESCC.

Development of a high-throughput screening assay for chemical effects on proliferation and viability of immortalized human neural progenitor cells

There is considerable public concern that the majority of commercial chemicals have not been evaluated for their potential to cause developmental neurotoxicity. Although several chemicals are assessed annually under the current developmental neurotoxicity guidelines, time, resource, and animal constraints prevent testing of large numbers of chemicals using this approach. Thus, incentive is mounting to develop in vitro methods to screen chemicals for their potential to harm the developing human nervous system. As an initial step toward this end, the present studies evaluated an automated, high-throughput method for screening chemical effects on proliferation and viability using ReNcell CX cells, a human neural progenitor cell (hNPC) line. ReNcell CX cells doubled in approximately 36 h and expressed the neural progenitor markers nestin and SOX2. High-throughput assays for cell proliferation (5-bromo-2'-deoxyuridine incorporation) and viability (propidium iodide exclusion) were optimized and tested using known antiproliferative compounds. The utility of this in vitro screen was evaluated further using a set of compounds containing eight known to cause developmental neurotoxicity and eight presumably nontoxic compounds. Six out of eight developmental neurotoxicants significantly inhibited ReNcell CX cell proliferation and/or viability, whereas two out of eight nontoxic chemicals caused only minimal effects. These results demonstrate that chemical effects on cell proliferation and viability can be assessed via high-throughput methods using hNPCs. Further development of this approach as part of a strategy to screen compounds for potential effects on nervous system development is warranted.

Safety of levocetirizine treatment in young atopic children: An 18-month study

There are more than 40 H(1)-antihistamines available worldwide. Most of these medications have never been optimally studied in prospective, randomized, double-masked, placebo-controlled trials in children. The aim was to perform a long-term study of levocetirizine safety in young atopic children. In the randomized, double-masked Early Prevention of Asthma in Atopic Children Study, 510 atopic children who were age 12-24 months at entry received either levocetirizine 0.125 mg/kg or placebo twice daily for 18 months. Safety was assessed by: reporting of adverse events, numbers of children discontinuing the study because of adverse events, height and body mass measurements, assessment of developmental milestones, and hematology and biochemistry tests. The population evaluated for safety consisted of 255 children given levocetirizine and 255 children given placebo. The treatment groups were similar demographically, and with regard to number of children with: one or more adverse events (levocetirizine, 96.9%; placebo, 95.7%); serious adverse events (levocetirizine, 12.2%; placebo, 14.5%); medication-attributed adverse events (levocetirizine, 5.1%; placebo, 6.3%); and adverse events that led to permanent discontinuation of study medication (levocetirizine, 2.0%; placebo, 1.2%). The most frequent adverse events related to: upper respiratory tract infections, transient gastroenteritis symptoms, or exacerbations of allergic diseases. There were no significant differences between the treatment groups in height, mass, attainment of developmental milestones, and hematology and biochemistry tests. The long-term safety of levocetirizine has been confirmed in young atopic children.

Histidine decarboxylase expression in pancreatic endocrine cells and related tumors

Histidine decarboxylase (HDC) is an enzyme for decarboxylating l-histidine to histamine and is expressed in various types of cells including neuroendocrine tumors. Recent findings have demonstrated a high percentage of HDC immunoreactivity in many neuroendocrine tumors, including carcinoid tumors, small cell carcinomas of the lung, pheochromocytomas, and medullary carcinomas of the thyroid. HDC immunostaining was applied to pancreatic islet cells and related tumors to explore possible expression of HDC as a wide spectrum marker for neuroendocrine differentiation. A total of 24 cases (22 pancreatic endocrine neoplasms, one small cell carcinoma of the pancreas, and one mixed exocrine-endocrine carcinoma) along with normal pancreatic tissue were immunostained with the anti-HDC antibody. In a normal pancreas, a double immunostaining revealed possible colocalization of HDC with glucagon- or insulin-positive cells in the islets. Seventeen of 22 pancreatic endocrine neoplasms (77%) were found to be positive for HDC, and no distinct relation to hormonal activity was observed. One small cell carcinoma was strongly positive to HDC. One non-functional tumor with mixed exocrine and endocrine components showed a diffuse positive immunostaining for HDC, and some neoplastic glucagon- or somatostatin (SRIF)-positive cells coexpressed HDC. In conclusion, we demonstrated that the majority of pancreatic endocrine tumors expressed HDC, and we suggest that HDC is a wider new marker for neuroendocrine differentiation.

Skin reactivity to histamine and expression of histamine receptors mRNA in lymphocytes of healthy subjects and non-small-cell lung cancer patients before and after surgery

Histamine modulates an immunological response through stimulation of appropriate receptor--H1R proinflammatory or H2R suppressive. The participation of histamine in regulation of an immunological response in the course of neoplastic disease is determined by the expression of particular receptor. The aim of our work was the investigation of the expression of mRNA of two types of histamine receptors in peripheral blood lymphocytes and the evaluation of skin-prick test with histamine in lung cancer patients before and after surgery. The investigation was performed on 15 patients qualified to surgery before and 7-10 days after treatment and on 12 healthy subjects. Reverse transcriptase polymerase chain reaction (RT-PCR) with primers labeled with fluorescent dyes was performed. Intensity of fluorescence was expressed as relative fluorescence units (RFU). The data were analysed using ABI Prism 310 GeneScan collection software Version 3.1. Skin-prick test with histamine was evaluated after 10 min by measuring the diameter of the weal. The expression of H1R and H2R mRNA in healthy subjects was not significantly different in contrast to the lung cancer patients in which a significant prevalence of H2R mRNA expression was observed before surgery and only slightly decreased after (P < 0.001). Skin-prick test--negative in one patient before surgery, after treatment was positive in all patients and the diameter of histamine weal was significantly increased (P < 0.001). One may assume that the prevalence of the expression of H2R mRNA in patients reflects the status of immunosuppression caused by cancer. Since histamine exerts its suppressive activity trough H2R it seems reasonably to include the antagonists of this receptor to the cancer therapy which may restore a relative balance between accessibility of both types of histamine receptors.

Inhibition of human primary melanoma cell proliferation by histamine is enhanced by interleukin-6

BACKGROUND

Interleukin-6 (IL-6) is a bifunctional growth factor in malignant melanoma; its expression increases during the malignant progression of the disease. Histamine, detected in large amounts in normal and pathological proliferating tissues, is an important paracrine and autocrine regulator of normal and tumour cell proliferation as well.

MATERIALS AND METHODS

We investigated the presence and function of IL-6 and histamine in the WM35 primary human melanoma cell line with respect to their direct role in cell proliferation and their regulatory interactions.

RESULTS

IL-6 inhibited the proliferation of WM35 melanoma cells and increased significantly the expression of histidine decarboxylase as well as histamine production. It had dose-dependent effects on the proliferation: high concentration (10-5 M) was inhibitory through H1 histamine receptors while low histamine concentration acting on H2 receptors, with a simultaneous increase of cAMP, enhanced colony formation in the monolayer. Furthermore, IL-6 increased the H1- but decreased the H2-histamine receptor expression of the melanoma cells. On the other hand, histamine was locally synthesized by the WM35 melanoma cells.

CONCLUSION

We suggest that the growth arrest induced by IL-6 is in part mediated by its dual action on histamine: a shift toward H1 receptor predominance and an elevation of locally produced histamine with prevalent action on the inhibitory response triggered through the H1 receptor. These findings suggest a local cross-talk between histamine and IL-6 in the regulation of melanoma growth.