Effects of the histamine H1 antagonist chlorcyclizine on rat fetal palate development

BACKGROUND: The effects of histamine H1 antagonist chlorcyclizine on rat palate development were characterized following in utero exposure. METHODS: To identify the optimum dose for inducing cleft palate, pregnant rats were administered 30, 60, or 90 mg/kg chlorcyclizine on Gestation Days 11 to 14. Fetal palate gene expression was also assessed after 90 mg/kg chlorcyclizine at 8, 15 and 30 hours post‐dose on Gestation Day 14 using microarray and qRT‐PCR. RESULTS: Rats in the 60‐ and 90‐mg/kg groups exhibited adverse clinical signs and body weight loss. Rats in the 90‐mg/kg group also demonstrated increases in late resorptions and decreases in fetal weight. Effects in the low‐dose group were limited to decreases in body weight gain. Fetal assessment on Gestation Day 21 revealed that findings were limited to the 60‐ and 90‐mg/kg groups, and included cleft palate (80% of litters for both groups), high arched palate, small nose, micrognathia, high domed head, digits shortened/absent and small limb. The fetal incidence of cleft palate was higher at 90 mg/kg, thus this dose was selected to assess palate gene expression. The altered genes associated with chlorcyclizine‐induced cleft palate included Wnt5a, Bmp2, Bmp4, Fgf10, Fgfr2, Msx1, and Insig1 but the magnitude of the change was relatively small (1.5‐ to 2‐fold). CONCLUSIONS: Expression of several genes involved in palate, limb and digit development was altered in the fetal palate following in utero exposure to chlorcyclizine. The subtle perturbation and interplay of these genes may have profound effects on the dynamics of fetal palate development. Birth Defects Res (Part B) 89:474–484, 2010. © 2010 Wiley‐Liss, Inc.     

Characterization of histamine H1-receptor on rat hepatocytes

The binding sites for [3H]pyrilamine in isolated rat hepatocytes were characterized. Scatchard analysis revealed two kinds of binding sites in hepatocytes, a high-affinity site and a low-affinity one. The rates of binding of the radioligand with the high-affinity binding site and its dissociation were rapid. The specificity of the sites for various histamine antagonists indicated that the high-affinity [3H]pyrilamine binding site is representative of the histamine H1 receptor. Treatment of hepatocytes with protease or phospholipase A2 significantly decreased the maximum binding capacity of the high-affinity site without affecting its dissociation constant, suggesting that the binding site is proteinaceous and is sensitive to a change in the lipid moiety of the membrane. Hepatocytic cyclic AMP and cyclic GMP were not significantly modulated by incubating hepatocytes with histamine. Thus, the action of histamine on hepatocytes might not be mediated by the cyclic nucleotides.     

血小板活化因子对大鼠卵巢颗粒细胞垂体腺苷酸环化酶激活肽mRNA表达的影响及调节机制

目的：探讨血小板活化因子（PAF）对大鼠卵巢颗粒细胞垂体腺苷酸环化酶激活肽（PACAP）mRNA表达的影响及其可能调节机制,旨在寻找PAF在卵巢中的作用靶点。方法：原代培养卵巢颗粒细胞,用放射免疫分析（RIA）及逆转录．聚合酶链反应（RT-PCR）方法检测颗粒细胞雌二醇分泌情况及其PACAP mRNA表达变化．结果：PAF对PACAP mRNA表达无明显影响,但与hCG共同作用可促进PACAP mRNA的表达：Forkolin可使PACAP mRNA表达升高。结论：PAF可通过对hCG的允许作用间接促进大鼠卵巢颗粒细胞PACAP mRNA表达,hCG的促进作用可能是通过cAMP—PKA途径介导的。     

电针对大鼠脑内雌激素受体蛋白及其mRNA表达的影响

本文应用放射免疫分析（ＲＩＡ）、ＲＮＡ点杂交和Ｎｏｒｔｈｅｒｎ ｂｌｏｔ、单克隆抗体免疫组织化学和计算机图像处理技术研究电针对切除卵巢大鼠脑内雌激素受体（ＥＲ）蛋白和ｍＲＮＡ表达的影响。以探讨针刺作用的分子生物学机理。结果表明,切除卵巢可导致血雌二醇（Ｅ２）水平降低,动物脑内ＥＲ蛋白和ｍＲＮＡ的表达增强;电针实验穴位后,去卵巢大鼠血的Ｅ２含量明显增加,脑内ＥＲ蛋白和ｍＲＮＡ表达受到明显抑制。正常大     

Switch of histamine receptor expression from H2 to H1 during differentiation of monocytes into macrophages

It is known that histamine suppresses gene expression and synthesis of tumor necrosis factor alpha (TNF-alpha) induced by lipopolysaccharide (LPS) in human peripheral blood mononuclear monocytes (HPM) or alveolar macrophages via histamine H2 receptors. We investigated the effect of histamine and differentiation in macrophages on the expression and secretion of TNF-alpha, TNF-alpha-converting enzyme (TACE), and histamine H1 and H2 receptors by use of a leukemia cell line, U937, and HPM. Differentiation of U937 and HPM cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) enhanced the H1 receptor expression and rather suppressed the H2 receptor, resulting in up-regulation of the histamine-induced expression and secretion of TNF-alpha, modulated via TACE. Therefore, histamine failed to inhibit up-regulated expression of TNF-alpha induced by LPS in macrophages. The switch from H2 to H1 receptors during differentiation in the monocyte/macrophage lineage could participate in the pathogenic processes of atherosclerosis and inflammatory reactions in the arterial wall.     

Conformationally-restricted ligands for the histamine H1 receptor

Potent H1-antagonistic activity in a series of novel indeno[2,1-c]pyridines and their 4-arylpiperidinol precursors is reported; one compound shows an in vitro activity four times that of the standard mepyramine that it was screened against. Their failure to translate this protection to in vivo tests is discussed.     

Effects of low-intensity prolonged exercise on PGC-1 mRNA expression in rat epitrochlearis muscle

We previously reported that the peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) mRNA in rat epitrochlearis muscle was increased after swimming exercise training. In the present study, we demonstrated further that PGC-1 mRNA expression in the epitrochlearis muscle of 4-5-week-old male Sprague-Dawley rats was increased after a 6-h acute bout of low-intensity swimming exercise. With this increase, the expression level was approximately 8-fold of control and immersion group rats that stayed for 6-h in warm water, maintained at the identical temperature of the swimming barrel (35 degrees C) (p<0.01). Second, PGC-1 mRNA expression in the muscle was found to have increased 6-h after 30 10-s tetani contractions were induced by in vitro electrical stimulation. Finally, PGC-1 mRNA expression in the muscle incubated for 18-h with 0.5mM 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR: a 5' AMP-activated protein kinase (AMPK) activator) was elevated to approximately 3-fold of the control muscle (n=6, p<0.001). AMPK activity in epitrochlearis muscle after the swimming was also found to be elevated to approximately 4-fold of the pre-exercise value (p<0.001). These results may suggest that an acute bout of low-intensity prolonged swimming exercise directly enhances the PGC-1 mRNA expression in the activated muscle during exercise, possibly through, at least in part, an AMPK-related mechanism.     

Expression analysis of the histamine H(3) receptor in developing rat tissues.

Endogenous histamine is involved in tissue growth and cell proliferation. In accordance with a putative function of the H(3) receptor in this mitogenic effect, we show that H(3)-receptor mRNAs are expressed together with those of the histamine-synthesizing enzyme in the embryonic liver and adipose tissue, and in various epithelia. Finally, we show that activation of recombinant H(3) receptors enhances MAP kinase activity.     

Effects of histamine H1 antagonist dithiaden on acetic acid-induced colitis in rats.

To assess the possible involvement of mast cells and/or their mediators in inflammatory bowel diseases, the effect of the histamine H1 antagonist Dithiaden was studied on a model of acetic acid-induced colitis in rats. Dithiaden pretreatment by intracolonic administration was found to reduce the extent of acute inflammatory colonic injury. This was manifested by a decrease in the score of gross mucosal injury, by lowered colonic wet weight and by diminished myeloperoxidase activity reflecting reduced leukocyte infiltration. Vascular permeability and gamma-glutamyl transpeptidase activity, elevated by acetic acid exposure, were decreased after Dithiaden pretreatment. The results indicate that locally administered Dithiaden may protect the colonic mucosa against an acute inflammatory attack by interfering with the action of the major mast cell mediator histamine.     

Developmental expression of the GABAA receptor alpha 1 subunit mRNA in the rat brain

Recent studies have suggested that the GABAA, receptor complex, the site of action of the inhibitory neurotransmitter gamma amino-butyric acid (GABAA) and the anxiolytic benzodiazepines, is heterogeneous. Moreover, its composition may change during development. To better understand the molecular basis of receptor heterogeneity, the levels and distribution of the mRNA encoding the alpha 1 receptor subunit were examined in the developing and adult rat brain with quantitative in situ hybridization histochemistry. Our studies demonstrate that alpha 1 subunit mRNA expression changes during ontogeny. At late embryonic stages and in the first postnatal week, low levels of the mRNA were detected in the cortex, inferior colliculus, and hippocampus. The mRNA levels in these regions increased during the second and third postnatal weeks. Furthermore, a dramatic change in the distribution of the alpha 1 subunit mRNA was seen in the second postnatal week when the message first became detectable in the cerebellar cortex. During subsequent development and in the mature brain, the alpha 1 subunit mRNA was most abundant in the cerebellum, olfactory bulb, and inferior colliculus, although the absolute levels of mRNA varied by as much as sixfold in selected brain regions. The mature distribution of alpha 1 subunit mRNA, along with its temporal appearance in the cerebellum, suggests that this subunit is a constituent of the Type 1 benzodiazepine site of the GABAA receptor complex. Furthermore, the onset of alpha 1 subunit mRNA expression in the cerebellar cortex coincides with a period of extensive synapse formation, raising the possibility that synaptic interactions modulate the appearance of this GABAA receptor subunit in the cerebellum.     

Effects of H1 and H2 receptor antagonists on Tetrahymena.

In Tetrahymena pyriformis the phagocytotic rate increases in response to histamine, but neither the H1 antagonist phenindamine nor the H2 antagonist metiamide stimulate phagocytosis. The H1 antagonist counteracts the effect of histamine, whereas the H2 antagonist does not. The histamine receptor of Tetrahymena is of H1-type, since it cannot distinguish between histamine and antagonists which are closely related to it chemically. It does, however, distinguish between histamine and the chemically unrelated H1 antagonist, phenindamine. The H2 antagonist does not interact with the receptor.     

Hormonal regulation of LH receptor mRNA and expression in the rat ovary.

Agonist-induced changes in expression and mRNA levels of luteinizing hormone (LH) receptors were compared during stimulation of ovarian follicular maturation and luteinization by gonadotropic hormones. Three major species of LH receptor mRNA, 5.8, 2.6 and 2.3 kb, were present throughout differentiation and changed similarly, the 5.8 kb species being consistently more abundant than the smaller forms. The increased expression of plasma-membrane LH receptors in preovulatory follicles and luteinized ovaries and their homologous down-regulation during follicular and luteal desensitization were closely correlated with the steady-state receptor mRNA levels. The reappearance of LH receptors following desensitization during the luteal stage was preceded by an increase in mRNA levels. These studies have demonstrated that the expression of LH receptors during follicular maturation, ovulation and desensitization is related to the prevailing levels of receptor mRNA in the ovary.     

Effects of H1 and H2 histamine receptor antagonists on positive feed-back effect of estrogen on LH in prepubertal female rats

The aim of the present study was to determine whether histaminergic central mechanisms which exert a well known effect on gonadotrophin secretion are involved in the development of the positive feed-back effect of estrogen-progesterone (E-P) on LH secretion that normally occurs in female rats about 20-22 days old. The administration of histamine H2 (cimetidine and ranitidine) or H1 (diphenhydramine) receptor blocking agents did not modify the onset of the LH release response to E-P. Nevertheless cimetidine, ranitidine and diphenhydramine potentiated the LH release induced by ovarian steroids at 23 days of age. These results appear to indicate that histaminergic pathways are involved in the magnitude of the LH response to E-P in prepubertal female rats rather than in the maturation of this mechanism.     

Linking agonist binding to histamine H1 receptor activation

G protein-coupled receptors (GPCRs) constitute a large and functionally diverse family of transmembrane proteins. They are fundamental in the transfer of extracellular stimuli to intracellular signaling pathways and are among the most targeted proteins in drug discovery. The detailed molecular mechanism for agonist-induced activation of rhodopsin-like GPCRs has not yet been described. Using a combination of site-directed mutagenesis and molecular modeling, we characterized important steps in the activation of the human histamine H1 receptor. Both Ser3.36 and Asn7.45 are important links between histamine binding and previously proposed conformational changes in helices 6 and 7. Ser3.36 acts as a rotamer toggle switch that, upon agonist binding, initiates the activation of the receptor through Asn7.45. The proposed transduction involves specific residues that are conserved among rhodopsin-like GPCRs.     

Regulation of the expression of the rat angiotensin II receptor mRNA.

Regulation of the expression levels of the rat angiotensin II receptor mRNA in the adrenal, aorta, kidney, and brain was assessed by the competitive polymerase chain reaction method. The bilateral nephrectomy or the administration of Dup753 markedly reduced the expression levels of this receptor mRNA in the adrenal and brain stem, but not in the kidney nor aorta. A continuous infusion of angiotensin II increased the expression level of this receptor mRNA in the adrenal but not in the other tissues. It is suggested that the expression level of this receptor mRNA in the adrenal is dependent on the renin angiotensin aldosterone system.     

组胺H3受体研究进展

组胺H3受体作为突触前自身受体和异身受体,广泛分布于中枢和外周组织,抑制组胺的释放和合成,调节多种神经递质的释放,组胺H3受体是G蛋白偶联受体家族成员,激活后由G蛋白介导,通过调控N型Ca^2 通道,产生生物学效应,组胺H3受体在中枢和外周器官有着重要的生理功能,对心功能,胃酸分泌,觉醒的睡眠,认知和记忆,惊厥抽搐等都有调节作用。     

Autoimmune disease-associated histamine receptor H1 alleles exhibit differential protein trafficking and cell surface expression

Structural polymorphisms (L263P, M313V, and S331P) in the third intracellular loop of the murine histamine receptor H(1) (H(1)R) are candidates for Bphs, a shared autoimmune disease locus in experimental allergic encephalomyelitis and experimental allergic orchitis. The P-V-P haplotype is associated with increased disease susceptibility (H(1)R(S)) whereas the L-M-S haplotype is associated with less severe disease (H(1)R(R)). In this study, we show that selective re-expression of the H(1)R(S) allele in T cells fully complements experimental allergic encephalomyelitis susceptibility and the production of disease-associated cytokines while selective re-expression of the H(1)R(R) allele does not. Mechanistically, we show that the two H(1)R alleles exhibit differential cell surface expression and altered intracellular trafficking, with the H(1)R(R) allele being retained within the endoplasmic reticulum. Moreover, we show that all three residues (L-M-S) comprising the H(1)R(R) haplotype are required for altered expression. These data are the first to demonstrate that structural polymorphisms influencing cell surface expression of a G protein-coupled receptor in T cells regulates immune functions and autoimmune disease susceptibility.     

H2 histaminic receptors in rat cerebral cortex. 1. Binding of [3H]histamine

Saturable binding of [3H]histamine in equilibrium with homogenates of rat cerebral cortex reveals Hill coefficients between 0.4 and 1.0, depending upon the conditions. Data from individual experiments are well described assuming one or two classes of sites. Only the sites of higher affinity (KP1 = 3.9 +/- 0.5 nM) are observed when binding is measured by isotopic dilution at a low concentration of the radioligand (less than 1.5 nM) in the presence of magnesium or by varying the concentration of the radioligand. The sites of lower affinity (KP2 = 221 +/- 26 nM) appear during isotopic dilution at higher concentrations of the radioligand or at lower concentrations either upon the addition of guanylyl imidodiphosphate (GMP-PNP) or upon the removal of magnesium. Estimates of the second- and first-order rate constants for association and dissociation of [3H]histamine agree well with KP1. Apparent capacities corresponding to KP1 and KP2 are of the order of 100 ([R1]t) and 1300 pmol/g of protein ([R2]t), respectively. Simple interconversion cannot account for the changes in binding that occur upon adding GMP-PNP or removing magnesium, since the increase in [R2]t exceeds the decrease in [R1]t. Moreover, the apparent amount of high-affinity complex exhibits a biphasic dependence on the concentration of [3H]histamine; an increase at low concentrations is offset by a decrease that occurs at higher concentrations. The latter appears to be positively cooperative and concomitant with formation of the low-affinity complex. These and other observations indicate that the binding of histamine is inconsistent with models commonly invoked to rationalize the binding of agonists to neurohumoral receptors. GMP-PNP and magnesium reciprocally alter capacity at the sites of higher affinity, however, and the reduction caused by GMP-PNP reflects a substantial increase in the rate constant for dissociation at the sites that appear to be lost. The sites labeled by [3H]histamine thus reveal the properties of neurohumoral receptors linked to a nucleotide-specific G/F protein.