Functional Characterization of the Canine Heme-Regulated eIF2α Kinase: Regulation of Protein Synthesis

The heme-regulated inhibitor (HRI) negatively regulates protein synthesis by phosphorylating eukaryotic initiation factor-2α (eIF2α) thereby inhibiting protein translation. The importance of HRI in regulating hemoglobin synthesis in erythroid cells makes it an attractive molecular target in need of further characterization. In this work, we have cloned and expressed the canine form of the HRI kinase. The canine nucleotide sequence has 86%, 82%, and 81% identity to the human, mouse, and rat HRI, respectively. It was noted that an isoleucine residue in the ATP binding site of human, rat, and mouse HRI is replaced by a valine in the canine kinase. The expression of canine HRI protein by in vitro translation using wheat germ lysate or in Sf9 cells using a baculovirus expression system was increased by the addition of hemin. Following purification, the canine protein was found to be 72 kD and showed kinase activity determined by its ability to phosphorylate a synthetic peptide substrate. Quercetin, a kinase inhibitor known to inhibit mouse and human HRI, inhibits canine HRI in a concentration-dependent manner. Additionally, quercetin is able to increase de novo protein synthesis in canine reticulocytes. We conclude that the canine is a suitable model species for studying the role of HRI in erythropoiesis

Histamine receptors in GtoPdb v.2021.3

Histamine receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Histamine Receptors [80, 173]) are activated by the endogenous ligand histamine. Marked species differences exist between histamine receptor orthologues [80]. The human and rat H3 receptor genes are subject to significant splice variance [12]. The potency order of histamine at histamine receptor subtypes is H3 = H4 > H2 > H1 [173]. Some agonists at the human H3 receptor display significant ligand bias [182]. Antagonists of all 4 histamine receptors have clinical uses: H1 antagonists for allergies (e.g. cetirizine), H2 antagonists for acid-reflux diseases (e.g. ranitidine), H3 antagonists for narcolepsy (e.g. pitolisant/WAKIX; Registered) and H4 antagonists for atopic dermatitis (e.g. adriforant; Phase IIa) [173] and vestibular neuritis (AUV) (SENS-111 (Seliforant, previously UR-63325), entered and completed vestibular neuritis (AUV) Phase IIa efficacy and safety trials, respectively) [216, 8]

Histamine receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

Histamine receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Histamine Receptors [75, 163]) are activated by the endogenous ligand histamine. Marked species differences exist between histamine receptor orthologues [75]. The human and rat H3 receptor genes are subject to significant splice variance [12]. The potency order of histamine at histamine receptor subtypes is H3 = H4 > H2 > H1 [163]. Some agonists at the human H3 receptor display significant ligand bias [171]. Antagonists of all 4 histamine receptors have clinical uses: H1 antagonists for allergies (e.g. cetirizine), H2 antagonists for acid-reflux diseases (e.g. ranitidine), H3 antagonists for narcolepsy (e.g. pitolisant/WAKIX; Registered) and H4 antagonists for atopic dermatitis (e.g. ZPL-3893787; Phase IIa) [163] and vestibular neuritis (AUV) (SENS-111 (Seliforant, previously UR-63325), entered and completed vestibular neuritis (AUV) Phase IIa efficacy and safety trials, respectively) [205, 8]

Histamine receptors in GtoPdb v.2023.1

Histamine receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Histamine Receptors [80, 174]) are activated by the endogenous ligand histamine. Marked species differences exist between histamine receptor orthologues [80]. The human and rat H3 receptor genes are subject to significant splice variance [12]. The potency order of histamine at histamine receptor subtypes is H3 = H4 > H2 > H1 [174]. Some agonists at the human H3 receptor display significant ligand bias [183]. Antagonists of all 4 histamine receptors have clinical uses: H1 antagonists for allergies (e.g. cetirizine), H2 antagonists for acid-reflux diseases (e.g. ranitidine), H3 antagonists for narcolepsy (e.g. pitolisant/WAKIX; Registered) and H4 antagonists for atopic dermatitis (e.g. adriforant; Phase IIa) [174] and vestibular neuritis (AUV) (SENS-111 (Seliforant, previously UR-63325), entered and completed vestibular neuritis (AUV) Phase IIa efficacy and safety trials, respectively) [217, 8]

Species-dependent smooth muscle contraction to Neuromedin U and determination of the receptor subtypes mediating contraction using NMU1 receptor knockout mice

1. The peptide ligand neuromedin U (NMU) has been implicated in an array of biological activities, including contraction of uterine, intestinal and urinary bladder smooth muscle. However, many of these responses appear to be species-specific. This study was undertaken to fully elucidate the range of smooth muscle-stimulating effects of NMU in rats, mice and guinea-pigs, and to examine the extent of the species differences. In addition, the NMU1 receptor knockout mouse was used to determine which receptor subtype mediates the contractile responses generated by NMU in the mouse. 2. A range of isolated organ in vitro bioassays were carried out, which were chosen to re-confirm previous literature reports (uterine and stomach fundus contraction) and also to explore potentially novel smooth muscle responses to NMU. This investigation uncovered a number of previously unidentified NMU-mediated responses: contraction of rat lower esophageal sphinster (LES), rat ileum, mouse gallbladder, enhancement of electrically evoked contractions in rat and mouse vas deferens, and a considerable degree of cross-species differences. 3. Studies using the NMU1 receptor knockout mice revealed that in the mouse fundus and gallbladder assays the NMU contractile response was mediated entirely through the NMU1 receptor subtype, whereas, in assays of mouse uterus and vas deferens, the response to NMU was unchanged in the NMU1 receptor knockout mouse, suggesting that the NMU response may be mediated through the NMU2 receptor subtype. NMU receptor subtype-selective antagonists are required to further elucidate the role of the individual receptor subtypes

An assay to evaluate the long-term effects of inflammatory mediators on murine airway smooth muscle: evidence that TNFα up-regulates 5-HT(2A)-mediated contraction

1. Asthma research is arguably limited by an absence of appropriate animal models to study the pharmacology of inflammatory mediators that affect airway hyperresponsiveness and remodelling. Here we assessed an assay based on mouse tracheal segments cultured for 1–32 days, and investigated contractile responses mediated by muscarinic and 5-hydroxytryptamine (5-HT) receptors following long-term exposure to tumour necrosis factor-alpha (TNFα). 2. Following culture, in the absence of TNFα, maximum contractile responses to KCl and carbachol were similar, with an increase in response up to day two and a decrease to a stable level after 8 days. Maximal relaxations to isoprenaline were not affected by the culture procedure. The potency of KCl and isoprenaline increased throughout the study. DNA microarray data revealed that global gene expression changes were greater when tissues were introduced to culture than when they were maintained in culture. The morphology of smooth muscle cells was maintained throughout the culture period. 3. 5-HT induced a weak contraction in both fresh and cultured (up to 8 days) segments. Culture with TNFα produced a time- and concentration-dependent increase in the maximal contraction to 5-HT, evidently mediated by 5-HT(2A) receptors, whereas, the potency for carbachol was reduced. 4. In conclusion, the phenotype of airway smooth muscle remained largely intact during the culture period, even though minor changes were obtained during the first days of culture. The time-dependent effect of TNFα indicates the importance of studying the long-term effect of cytokines on the smooth muscle cells in relation to airway hyperresponsiveness and remodelling