Important Chemical Mediator Research Articles

Structural Study Reveals That Ser-354 Determines Substrate Specificity on Human Histidine Decarboxylase

Histamine is an important chemical mediator for a wide variety of physiological reactions. L-histidine decarboxylase (HDC) is the primary enzyme responsible for histamine synthesis and produces histamine from histidine in a one-step reaction. In this study, we determined the crystal structure of human HDC (hHDC) complexed with the inhibitor histidine methyl ester. This structure shows the detailed features of the pyridoxal-5'-phosphate inhibitor adduct (external aldimine) at the active site of HDC. Moreover, a comparison of the structures of hHDC and aromatic L-amino acid (L-DOPA) decarboxylase showed that Ser-354 was a key residue for substrate specificity. The S354G mutation at the active site enlarged the size of the hHDC substrate-binding pocket and resulted in a decreased affinity for histidine, but an acquired ability to bind and act on L-DOPA as a substrate. These data provide insight into the molecular basis of substrate recognition among the group II pyridoxal-5'-phosphate-dependent decarboxylases.

Interleukin-1 beta influences on lysyl oxidases and matrix metalloproteinases profile of injured anterior cruciate ligament and medial collateral ligament fibroblasts

The anterior cruciate ligament (ACL) is known to have a poor healing ability, especially in comparison with the medial collateral ligament (MCL) which can heal relatively well. Interleukin-1beta (IL-1β) is considered to be an important chemical mediator in the acute inflammatory phase of ligament injury. The role of IL-1β-induced expressions of lysyl oxidases (LOXs) and matrix metalloproteinases (MMPs), which respectively facilitate extracellular matrix (ECM) repair and degradation, is poorly understood. In this study, we aim to determine the intrinsic differences between ACL and MCL by characterising the differential expressions of LOXs and MMPs in response to IL-1β in the injury process. Semi-quantitative polymerase chain reaction (PCR), quantitative real-time PCR, Western blot, and zymography were performed. We detected high expressions of IL-1β-induced LOXs in normal ACL and MCL. Then, we found IL-1β induced injured MCL to express more LOXs than injured ACL (up to 2.85-fold in LOX, 2.58-fold in LOXL-1, 1.89-fold in LOXL-2, 2.46-fold in LOXL-3 and 2.18-fold in LOXL-4). Meanwhile, we found IL-1β induced injured ACL to express more MMPs than injured MCL (up to 1.72-fold in MMP-1, 1.95-fold in MMP-2, 2.05-fold in MMP-3 and 2.3-fold in MMP-12). The further protein results coincided with gene expressions above. Lower expressions of LOXs and higher expressions of MMPs might help to explain the poor healing ability of ACL.

Abstract 3284: Organ-specific Gst-pi expression in new metastatic androgen-independent prostate cancer animal model

Abstract Introduction: Prostate cancer is major leading cause of death in western world. And elucidating the mechanisms of metastasis in prostate cancer, particularly to the bone, is a major issue for treatment of this malignancy. Reactive oxygen species (ROS) have been identified as important chemical mediators in cell growth and differentiation, and glutathione oxidation-reduction (redox) system is the main mechanism against ROS in human body. We established a new metastatic model of prostate cancer, using new cell line, and we investigated the role of glutathione redox system in the androgen-independent prostate cancer. Methods: A new cell line, PCai1, was established from the androgen-independent cancer derived from transgenic rat model for adenocarcinoma of the prostate (TRAP), and investigated its metastatic potential in nude mice. By cDNA microarray analysis in our model, glutathione S-transferase Pi (Gst-pi), which was the major component protein of glutathione redox system, had higher expression in androgen independent prostate cancer. Therefore, effects of Gst-pi knocked down in vitro with iRNA strategy were analyzed in PCai1 cells, and the quantification of ROS was performed by DCFH assay. In addition, to evaluate roles of Gst-pi in castration-resistant cell proliferation, Gst-pi siRNA transfected PCai1 cells were transplanted subcutaneously in castrated or normal nude mice. Results: Gst-pi-siRNA in vitro significantly suppressed cell proliferation rate of PCai1. In addition, high levels of intracellular ROS were recognized in the Gst-pi knockout. Strong expression of Gst-pi was realized castration-resistant prostate cancer specimen, while no tumor was stained in hormone naïve prostate cancer. PCai1 frequently formed metastatic lesions in the lung and lymph nodes after orthotopic implantation in the prostate. Intravenous injections of PCai1, metastasis to lung and bone were obvious. Tumors metastasized in the bone marrow after intravenous injection expressed high levels of Gst-pi, while metastatic lesions in the lung and lymph nodes failed to express Gst-pi as seen in cases of the orthotopic implantation. Knock down of Gst-pi expression of PCai1 significantly inhibited tumor growth of PCai1 compared to negative controls in castrated mice. On the other hand, Gst-pi expression did not affect tumor growth in non-castrated mice Conclusion: Establishment of a new metastatic prostate cancer model allows for the systematic analysis of genetic and molecular characteristics of human tumors. And these results suggest that glutathione redox system can regulate cancer cell growth in androgen free environment. Gst-pi expression of the prostate cancers are dependent on metastatic site, and that Gst-pi has an important role in adapting prostate cancer for growth and metastasis involving an alteration of ROS signals. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3284. doi:1538-7445.AM2012-3284

ChemInform Abstract: Drug Discovery for Improvement of Chronic Kidney Disease and Cardiovascular Disease

AbstractReview: 40 refs.

Drug Discovery for Improvement of Chronic Kidney Disease and Cardiovascular Disease

Chronic kidney disease (CKD) has been increasingly recognized as a major public health problem in the world. Recent studies have showed that CKD is an independent risk factor for the occurrence of cardiovascular disease (CVD). Reactive oxygen species (ROS), generated by reduction-oxidation actions, have been generated by reduction-oxidation actions, recognized as the important chemical mediators that regulate signal transduction in various cells including vascular smooth muscle cells (VSMC) and mesangial cells (MC). It has been showed that increase in ROS generation may relate to a risk for CVD and CKD. In addition, ROS mediate activation of mitogen-activated protein (MAP) kinases, extracellular signal-regulated kinase 1/2, c-Jun N-terminal kinase, p38, and big MAP kinase 1, in various cells leading to change in gene expressions. Control of the oxidative stress and ROS-mediated alterations of signaling molecules including MAP kinases may provide new therapeutic strategy against CKD and CVD. In this review, we summarize mainly our data regarding the pharmacological effects of renin-angiotensin-aldosterone system blockers, bioflavonoids and adiponectin in VSMC and MC. Also we review the data on a possible new class drug against oxidative stress to improve CKD and CVD.

Histamine regulates cyclooxygenase 2 gene activation through Orai1-mediated NFκB activation in lung cancer cells

Histamine, an important chemical mediator, has been shown to regulate inflammation and allergic responses. Stimulation of histamine receptors results in a significant increase in cytoplasmic Ca 2+, which could be mediated by inositol trisphosphate (IP 3)-dependent store-operated Ca 2+ channels (SOC). However, the link between histamine-mediated signaling and activation of inflammatory genes such as cyclooxygenase 2 ( COX-2) is still unknown. Our study indicated that the COX-2 protein was highly expressed in human lung cancer cells. Following stimulation with 10 μM of histamine, both store-operated Ca 2+ entry (SOCE) and COX-2 gene expression were evoked. Histamine-mediated COX-2 activation can be prevented by 2-APB and SKF-96365, SOC channel inhibitors. In addition, deletion analysis of the COX-2 promoter suggested that the region between −80 bp and −250 bp, which contains NFκB binding sites, is the key element for histamine-mediated signaling. Knocking down ORAI1, one of the essential molecules of store-operated calcium channels, attenuated histamine-mediated COX-2 expression and NFκB activation. These results indicated that ORAI1-mediated NFκB activation was an important signaling pathway, responsible for transmitting histamine signals that trigger inflammatory reactions.

Generation of Guanine–Thymidine Cross-Links in DNA by Peroxynitrite/Carbon Dioxide

Nitrosoperoxycarbonate derived from the combination of carbon dioxide and peroxynitrite is an important chemical mediator of inflammation. In aqueous solutions, it rapidly decomposes to the reactive species CO(3)(•-) and (•)NO(2) radicals that are known to initiate the selective oxidation and nitration of guanine in DNA. We have previously demonstrated that the reactions of carbonate radical anions with guanine in 2'-deoxyoligoribonucleotides generate a previously unknown intrastrand cross-linked guanine-thymine product G*-T* with a covalent bond between the C8 (G*) and the thymine N3 (T*) atoms (Crean Nucleic Acids Res. 2008, 36, 742-755). In this work, we demonstrate that G*-T* cross-linked products are also formed when peroxynitrite (0.1 mM) reacts with native DNA in aqueous solutions (pH 7.5-7.7) containing 25 mM carbon dioxide/bicarbonate, in addition to the well-known nitration/oxidation products of guanine such as 8-nitroguanine (8-nitro-G), 5-guanidino-4-nitroimidazole (NIm), 8-oxo-7,8-dehydroguanine (8-oxo-G), and spiroiminodihydantoin (Sp). The yields of these products, after enzymatic digestion with P1 nuclease and alkaline phosphatase to the nucleotide level and reversed phase HPLC separation, were compared with those obtained with the uniformly, isotopically labeled (15)N,(13)C-labeled 2'-deoxy oligoribonucleotides 5'-dGpT and 5'-dGpCpT. The d(G*pT*) and d(G*-T*) cross-linked products derived from the di- and trioligonucleotides, respectively, were used as standards for identifying the analogous lesions in calf thymus DNA by isotope dilution LC-MS/MS methods in the selected reaction monitoring mode. The NIm and 8-nitro-G are the major products formed (∼0.05% each), and lesser amounts of 8-oxo-G (∼0.02%) and d(G*pT*) and d(G*-T*) enzymatic digestion products (∼0.002% each) were found. It is shown that the formation of d(G*pT*) enzyme digestion product can arise only from intrastrand cross-links, whereas d(G*-T*) can arise from both interstrand and intrastrand cross-linked products.

IL-16 Variability and Modulation by Antiallergic Drugs in a Murine Experimental Allergic Rhinitis Model

Background: Interleukin-16 (IL-16) is a cytokine that induces selective migration of CD4+ cells and participates in inflammatory diseases including allergic rhinitis. Histamine and prostaglandin D₂ are important chemical mediators of allergic inflammation, and antiallergic drugs are commonly used for the treatment of allergic rhinitis. It remains unknown whether treatment with the drugs affects IL-16. Objective: We evaluated the variability of IL-16 and the effects of the antiallergic drugs fexofenadine (40 mg/kg/day) and ramatroban (30 mg/kg/day) on IL-16 in an OVA-sensitized BALB/c murine experimental allergic rhinitis model. Methods: We measured the expression level of IL-16 protein in the mouse nasal septal mucosa by immunohistochemistry, and the serum level of IL-16 by ELISA. Several other parameters associated with allergic rhinitis (nasal symptoms, OVA-specific IgE, eosinophil and T cell infiltration) were also measured. Results: Local and systemic expressions of IL-16 were significantly increased in OVA-sensitized mice when compared to the nonsensitized group. Fexofenadine and ramatroban significantly inhibited the following OVA-induced allergic features when compared to the nontreated sensitized group: sneezing, nasal rubbing, eosinophil infiltration, IL-16 expressions in nasal tissue, and serum IL-16 level. Serum OVA-specific IgE and local T cell infiltration were reduced, but they did not reach significant values. Conclusions: These results suggest that IL-16 was both systemically and locally upregulated in the murine allergic rhinitis model and that IL-16 changed in parallel to allergic state by treatment with the drugs.

Localization and function of histamine H3 receptor in the nasal mucosa

Histamine is an important chemical mediator of allergic rhinitis (AR). Histamine H(3) receptors (H(3)R) are located on cholinergic and NANC neurons of the myenteric plexus, and activation of H(3)R regulates gastric acid secretion. However, little is known about the localization and function of H(3)R in the upper airway. The objective of this study was to examine the localization and possible function of H(3)R in the nasal mucosa. We extracted total RNA from the inferior turbinate mucosa of patients with AR. H(3)R mRNA and beta-actin mRNA were amplified by RT-PCR. We used immunohistochemistry to examine localization of H(3)R protein in the inferior turbinate mucosa excised during clinically indicated surgery. We used alcian blue/periodic acid-shiff staining to examine the effects of the H(3)R agonist (R)-alpha-methylhistamine and the H(3)R antagonist thioperamide on secretion from rat submucosal glands. H(3)R protein was expressed around submucosal gland cells. Thioperamide induced degranulation in the submucosal gland in the nasal septum. The present results suggest that H(3)R is localized mainly around submucosal glands, and that H(3)R plays an important role in the secretion of submucosal glands in the nose.

Molecular cloning and characterization of chicken prostaglandin E receptor subtypes 2 and 4 (EP 2 and EP 4)

Prostaglandin E 2 (PGE 2) is an important chemical mediator responsible for regulation of many vital physiological processes. Four receptor subtypes have been identified to mediate its biological actions. Among these subtypes, prostaglandin E receptor subtypes 2 and 4 (EP 2 and EP 4), both coupled to cAMP-protein kinase A (cAMP-PKA) signaling pathway, are proposed to play crucial roles under both physiological and pathological conditions. Though both receptors were extensively studied in mammals, little is known about their functionality and expression in non-mammalian species including chicken. In present study, the full-length cDNAs for chicken EP 2 and EP 4 receptors were first cloned from adult chicken ovary and testis, respectively. Chicken EP 2 is 356 amino acids in length and shows high amino acid identity to that of human (61%), mouse (63%), and rat (61%). On the other hand, the full-length cDNA of EP 4 gene encodes a precursor of 475 amino acids with a high degree of amino acid identity to that of mammals, including human (87%), mouse (86%), rat (84%), dog (85%), and cattle (83%), and a comparatively lower sequence identity to zebrafish (52%). RT-PCR assays revealed that EP 2 mRNA was expressed in all tissues examined including the oviduct, while EP 4 expression was detected only in a few tissues. Using the pGL3-CRE-luciferase reporter system, we also demonstrated that PGE 2 could induce luciferase activity in DF-1 cells expressing EP 2 and EP 4 in dose-dependent manners (EC 50: <1 nM), confirming that both receptors could be activated by PGE 2 and functionally coupled to the cAMP-PKA signaling pathway. Together, our study establishes a molecular basis to understand the physiological roles of PGE 2 in target tissues of chicken.

Nasal Allergic Response Mediated by Histamine H3 Receptors in Murine Allergic Rhinitis

Histamine is one of the most important chemical mediators causing nasal allergic symptoms, and H1 receptor antagonist have been used as the treatment first choice in nasal allergy. The presence of H3 receptors has also been determined in the human nasal mucosa, but few studies have investigated the involvement of H3 receptors in nasal allergy. We used a murine allergic model to investigate the presence of nasal mucosa H3 receptor mRNA and any H3 receptor agonist or antagonist influences on clinical nasal allergic symptoms. H3 receptor mRNA in nasal mucosa was investigated by reverse-transcription polymerase chain reaction. OVA-sensitized mice were given an intraperitoneal injection of H3 receptor agonist or antagonist, and clinical nasal allergic symptoms were scored over 10 minutes after nasal provocation of OVA. Inhibition of nasal allergic symptoms was also examined using an H1 receptor antagonist alone and using a both an H3 receptor agonist and an H1 receptor antagonist. H3 receptor mRNA was identified in the murine nasal mucosa. The H3 receptor agonist (R)-alpha-metylhistamine significantly inhibited clinical nasal allergic symptoms of OVA-sensitized mice. The H3 receptor agonist and H1 receptor antagonist inhibited clinical nasal allergic symptoms in the murine allergic model more strongly than the single drug. The foregoing results indicate that H3 receptors are involved in modulation of nasal allergy. H3 receptor agonists can also be useful as a novel therapeutic approach in nasal allergy. Both H3 receptor agonist and H1 receptor antagonist may be more effective than a single drug.

Immunohistochemical localization of histamine receptor subtypes in human inferior turbinates.

Histamine is an important chemical mediator in allergic rhinitis and plays an important role in eliciting the nasal symptoms of the disorder. However, the immunohistochemical localization of histamine receptor subtypes (H1R, H2R, H3R, and H4R) in human nasal mucosa is unknown. There are also no prior studies of H3R and H4R in human nasal mucosa. The objective of this study was to examine the distribution of histamine receptor subtypes in the human inferior turbinates by an immunohistochemical method. H1R was localized primarily in the epithelium, vessels, and nerves. H2R was localized primarily in the epithelium and the glands. H3R and H4R were clearly distributed on the nerves. In addition, H1R, H3R, and H4R were clearly localized on the same nerves. This result indicates that H1R, H3R, and H4R adjoin and regulate each other in the same nerves. All histamine receptor subtypes may play some role in patients with allergic rhinitis.

H 1-antihistamines : More relevant than ever in the treatment of allergic disorders

Histamine is an important chemical mediator of inflammation, vasodilation, increased vascular permeability, decreased peripheral resistance, airway smooth muscle contraction, and sensory nerve stimulation causing itching. It also plays a significant role in neurotransmission and in cardiac function. In allergic rhinoconjunctivitis and urticaria, there is strong evidence for the role of H 1-antihistamine treatment. In asthma, additional dose–response studies, including higher doses of antihistamines than those used in allergic rhinitis, are needed to determine the role of antihistamines. In atopic dermatitis, the itch-relieving topical glucocorticoid-sparing effects of H 1-antihistamines also require further documentation. The potential benefits of each H 1-antihistamine should be weighed against the potential risks, and second-generation H 1-antihistamines with excellent, well-documented safety records should be used in preference to older, less safe H 1-antihistamines. Second-generation H 1-antihistamines are more relevant than ever in the treatment of allergic disorders.

Montelukast in the Treatment of Children with Moderate-To-Severe Atopic Dermatitis: A Pilot Study

Purpose to the Study. The role of leukotrienes in the pathogenesis of atopic dermatitis (AD) is uncertain. This double-blind, placebo-controlled crossover study addressed the efficacy of the leukotriene receptor antagonist montelukast in moderate to severe AD.Study Population. Fifteen patients (ages 6–16) with moderate to severe AD despite conventional therapy consisting of at least a class II steroid, soap substitutes, and emollients.Methods. Disease severity was evaluated by grading 8 areas of the body (head/neck, front of the trunk, the back, genitalia, and 4 limbs) on a scale of 0 to 3. A score of at least 40 was required to be enrolled in the study. The extent of disease was calculated by estimating the percentage of the body surface involvement. Patients were examined by the same physician on a biweekly basis and completed questionnaires to assess the impact of AD on daily life, as well as the effect of disease on relationships with family members and social life. There was a 2-week run-in period during which standardized topical treatment was initiated. Patients were randomized to receive either 5 mg montelukast or placebo daily for 4 weeks. There was a 2-week washout period before crossover for the second phase.Results. Eleven patients completed the study with 6 in group A (placebo first) and 5 in group B (drug first). Despite randomization, the baseline median disease severity score between groups was significantly different, group A 52 and group B 78 (P = .018). Group B had a significant decrease in the disease severity (P = .05) during the drug phase. There was also an increase in disease severity during the placebo phase, however, severity scores did not return to baseline. Group A had improvement during both the placebo and drug phase (P = .075 and .029, respectively). Patient index scores and extent of disease did not change significantly for either group.Conclusion. This pilot study shows that leukotrienes may be important mediators in AD and leukotriene receptor antagonists (LRAs) may be suitable adjuvant therapy in those patients with severe disease.Reviewers’ Comments. Although leukotrienes are important chemical mediators in asthma and allergic rhinitis, their role in the pathogenesis of AD is not as clear. This study suggests that they may have a role in AD and that LRAs may provide some clinical benefit. In practice, some patients do seem to improve although the responses have not been overwhelming, which is consistent with the results of this study. It may be worth a try in patients with severe disease and, in addition, patients who are started on an LRA for their asthma may experience some improvement in their AD.

Oxidants and tyrosine phosphorylation: role of acute and chronic oxidative stress in T-and B-lymphocyte signaling.

The cellular response to an extracellular signal starts with the induction of a signaling cascade that transmits the signal through the cytoplasm to the nucleus, resulting in the activation of transcription factors that activate specific target genes. The signaling cascade involves a series of biochemical modifications that include phosphorylation events on tyrosine residues due to the activation of specific protein kinases. Recently, evidence accumulated that reactive oxygen species, including hydrogen peroxide, superoxide, and the hydroxyl radical, are important chemical mediators that regulate the transduction of signals from the membrane to the nucleus by modulating the protein activity by oxidation and reduction. In this report, the redox regulation of signaling involving protein tyrosine kinase activity, in particular in T- and B-lymphocyte signaling, is reviewed.

Discovery of leukotrienes and development of antileukotriene agents

This article presents information on the origin of leukotrienes (LTs) and the development of antileukotriene (anti-LT) agents. After reading this article, readers should have an understanding of the chemical mediators involved in the pathogenesis of asthma, the structural features of LTs, and the role of anti-LTs in the management of asthma symptoms. Studies considered relevant and appropriately controlled were used. Only literature in the English language was reviewed. Material was taken from academic/scholarly journals and abstracts. One of the important chemical mediators implicated in the pathogenesis of asthma is the slow-reacting substance of anaphylaxis, which was subsequently found to comprise LTs C4, D4, and E4. 5-lipoxygenase products from arachidonic acid metabolism, LTs are released from the lung tissue of asthmatic patients and purified human lung mast cells by antigens. The LTs directly induce contraction of bronchial smooth muscle. The use of anti-LT agents, particularly the receptor antagonists zafirlukast and montelukast and the biosynthesis inhibitor zileuton, reverses the bronchoconstrictive effects of LTs and significantly improve asthma symptoms. Extensive in vitro and in vivo evidence supports the role of LTs in the pathogenesis of asthma. Their discovery has had a significant impact on treatment strategies, including the use of anti-LT agents, for the management of asthma.

Development for the analysis of reactive oxygen species using capillary electrophoresis with laser‐induced fluorescence detection

AbstractReactive oxygen species (ROS) have been identified as important chemical mediators that regulate signal transduction pathways. Today, the importance of ROS in pathological events has become increasingly apparent. To monitor the ROS in biological systems, various techniques such as cytochrome c peroxidase assay and malonaldialdehyde detection were developed and used clinically. However, these methods are very laborious and time‐consuming. Therefore, in this study, we developed a capillary electrophoresis (CE)‐based ROS monitoring technique using dihydrorhodamine 123 (DHR‐123). DHR‐123 is a nonfluorescent compound, and can be oxidized irreversibly and rapidly by ROS to rhodamine 123 (Rho‐123), which is a fluorescent dye. Upon detecting the amount of the fluorescence from Rho‐123, we could indirectly quantify the amount of ROS generation in biological systems. Determination of Rho‐123 was performed in an uncoated silica capillary (27 cm×75 μm i.d.) using a CE system with laser‐induced fluorescence detection. Optimum conditions for the Rho‐123 detection were 50 mM borate buffer (pH 10.0), running at 20°C, and 5 s injection. This method allowed the detection of Rho‐123 with a detection limit around 50 pM. We also applied this developed method to the analysis of intracellular ROS level in methamphetamine (MA) treated PC12 cells. © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 327–331, 2001

Structure, function, and regulation of leukotriene A4 hydrolase.

Leukotrienes are important chemical mediators in a variety of inflammatory and allergic conditions, including those affecting the respiratory system. These signaling molecules can be divided into two groups: the proinflammatory leukotriene B 4 (LTB 4 ) and the spasmogenic leukotrienes C 4 . D 4 , and E 4 , also termed cysteinyl-leukotrienes (1). LTB 4 is one of the most powerful chemotactic agents known to date and acts via specific seven-transmembrane, G protein-coupled surface receptors on the target cells (2). The profile of the biological properties of LTB 4 makes it a key component in the complex network of soluble and cell-bound factors that govern the development and maintenance of inflammation. Hence, LTB 4 has been proposed to play a role in a variety of acute and chronic inflammatory diseases such as arthritis, dermatoses, inflammatory bowel disease (IBD), and chronic obstructive pulmonary disease (COPD). In particular, LTB 4 seems to play a role in the recruitment of inflammatory cells to the site of tissue injury. This article gives a brief overview of the biochemistry and molecular biology of LTA 4 hydrolase, the enzyme catalyzing the final step in the biosynthesis of LTB 4 .

Significant Increase in Prostaglandin E-Main Urinary Metabolite by Laxative Administration: Comparison with Ulcerative Colitis

Objective: To assess the production of prostaglandin E₂, an important chemical mediator in diarrhea induced by laxative administration, a prostaglandin E-main urinary metabolite (7α-hydroxy-5,11-diketotetranor-prosta-1,16-dioic acid, PGE-MUM) was measured in healthy volunteers and compared with the values of patients with ulcerative colitis. Methods: PGE-MUM was determined by a simplified immunoassay of bicyclic PGE-MUM and analyzed for the influence of laxative administration and active/remission phases of ulcerative colitis. Results: Administration of laxatives induced a significant increase in PGE-MUM in healthy volunteers. A significant elevation was also found in the active as compared with the remission phase of ulcerative colitis. The PGE-MUM levels were significantly correlated with our modified Talstad scores, clinical disease activity indices in ulcerative colitis. It was confirmed by time course studies of individual patients that changes in PGE-MUM correlated well with colitis activity. Conclusion: Laxative administration induces production of prostaglandin E₂ as one of the chemical mediators, although its production grade is relatively low as compared with ulcerative colitis in the active phase.

Expression and localization of histamine H 2 receptor messenger RNA in human nasal mucosa

Background: Histamine is an important chemical mediator in allergic rhinitis. Histamine H 2 receptor (H 2 R) stimulation controls histamine release and mediates mucus secretion, suggesting that H 2 R might play some role in allergic rhinitis. Objective: The objective of this study was to examine whether H 2 R mRNA expression is increased in patients with allergic rhinitis compared with normal subjects and to determine the localization of H 2 R mRNA in the human nasal mucosa. Methods: We extracted RNA from scrapings of the inferior turbinate mucosa of 11 patients with allergic rhinitis. H 2 R and β-actin mRNA were amplified by RT-PCR. In situ hybridization with a digoxigenin-labeled H 2 R cRNA probe was performed on surgical specimens of nasal turbinate of patients with allergic rhinitis. Results: The mean ± SD of H 2 R/β-actin ratios were 0.12 ± 0.16 for the scrapings of normal subjects and 0.35 ± 0.20 for the scrapings of patients with allergic rhinitis; the difference was statistically significant ( P < .01). H 2 R mRNA was localized in the epithelium, serous cells, and mucous cells. Conclusion: These data suggest that H 2 R mRNA is localized in the epithelium and the submucosal glands and that increased H 2 R may be playing some role in patients with allergic rhinitis. (J Allergy Clin Immunol 1999;103:944-9.)