Circumventricular organ apelin receptor knockdown decreases blood pressure and sympathetic drive responses in the spontaneously hypertensive rat

The central site(s) mediating the cardiovascular actions of the apelin-apelin receptor (APJ) system remains a major question. We hypothesized that the sensory circumventricular organs (CVOs), interfacing between the circulation and deeper brain structures, are sites where circulating apelin acts as a signal in the central nervous system to decrease blood pressure (BP). We show that APJ gene (aplnr) expression was elevated in the CVOs of spontaneously hypertensive rats (SHRs) compared to normotensive Wistar Kyoto (WKY) controls, and that there was a greater mean arterial BP (MABP) decrease following microinjection of [Pyr(1)]apelin-13 to the CVOs of SHRs compared to WKY rats. Lentiviral APJ-specific-shRNA (LV-APJ-shRNA) was used to knockdown aplnr expression, both collectively in three CVOs and discretely in individual CVOs, of rats implanted with radiotelemeters to measure arterial pressure. LV-APJ-shRNA-injection decreased aplnr expression in the CVOs and abolished MABP responses to microinjection of [Pyr(1)]apelin-13. Chronic knockdown of aplnr in any of the CVOs, collectively or individually, did not affect basal MABP in SHR or WKY rats. Moreover, knockdown of aplnr in any of the CVOs individually did not affect the depressor response to systemic [Pyr(1)]apelin-13. By contrast, multiple knockdown of aplnr in the three CVOs reduced acute cardiovascular responses to peripheral [Pyr(1)]apelin-13 administration in SHR but not WKY rats. These results suggest that endogenous APJ activity in the CVOs has no effect on basal BP but that functional APJ in the CVOs is required for an intact cardiovascular response to peripherally administered apelin in the SHR

THE CONCISE GUIDE TO PHARMACOLOGY 2021/22: G protein-coupled receptors

The Concise Guide to PHARMACOLOGY 2021/22 is the fifth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of nearly 1900 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes over 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/bph.15538. G protein-coupled receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2021, and supersedes data presented in the 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate

Characterization of the antiproliferative signal mediated by the somatostatin receptor subtype sst5

We investigated cell proliferation modulated by cholecystokinin (CCK) and somatostatin analogue RC-160 in CHO cells bearing endogenous CCK(A) receptors and stably transfected by human subtype sst5 somatostatin receptor. CCK stimulated cell proliferation of CHO cells. This effect was suppressed by inhibitor of the soluble guanylate cyclase, LY 83583, the inhibitor of the cGMP dependent kinases, KT 5823, and the inhibitor of mitogen-activated protein (MAP) kinase kinase, PD 98059. CCK treatment induced an increase of intracellular cGMP concentrations, but concomitant addition of LY 83583 virtually suppressed this increase. CCK also activated both phosphorylation and activity of p42-MAP kinase; these effects were inhibited by KT 5823. All the effects of CCK depended on a pertussis toxin-dependent G protein. Somatostatin analogue RC-160 inhibited CCK-induced stimulation of cell proliferation but it did not potentiate the suppressive effect of the inhibitors LY 83583 and KT 5823. RC-160 inhibited both CCK-induced intracellular cGMP formation as well as activation of p42-MAP kinase phosphorylation and activity. This inhibitory effect was observed at doses of RC-160 similar to those necessary to occupy the sst5 recombinant receptor and to inhibit CCK-induced cell proliferation. We conclude that, in CHO cells, the proliferation and the MAP kinase signaling cascade depend on a cGMP-dependent pathway. These effects are positively regulated by CCK and negatively influenced by RC-160, interacting through CCK(A) and sst5 receptors, respectively. These studies provide a characterization of the antiproliferative signal mediated by sst5 receptor

Spatial and temporal variability of water quality in the Nile delta

Dysfunction of the apelinergic system, comprised of the neuropeptide apelin mediating its effects via the G protein-coupled apelin receptor (APJ), may underlie the onset of cardiovascular disease such as hypertension. Apelin expression is increased in the rostral ventrolateral medulla (RVLM) in spontaneously hypertensive rats (SHRs) compared to Wistar-Kyoto (WKY) normotensive rats, however, evidence that the apelinergic system chronically influences mean arterial blood pressure (MABP) under pathophysiological conditions remains to be established. In this study we investigated, in conscious unrestrained rats, whether APJ contributes to MABP and sympathetic vasomotor tone in the progression of two models of hypertension – SHR and L-NAME-treated rats – and whether APJ contributes to the development of hypertension in pre-hypertensive SHR. In SHR we showed that APJ gene (aplnr) expression was elevated in the RVLM, and there was a greater MABP increase following microinjection of [Pyr1]apelin-13 to the RVLM of SHR compared to WKY rats. Bilateral microinjection of a lentiviral APJ-specific-shRNA construct into the RVLM of WKY, SHR, and L-NAME-treated rats, chronically implanted with radiotelemeters to measure MABP, decreased aplnr expression in the RVLM and abolished acute [Pyr1]apelin-13-induced increases in MABP. However, chronic knockdown of aplnr in the RVLM did not affect MABP in either SHR or L-NAME-treated rats. Moreover, knockdown of aplnr in the RVLM of prehypertensive SHR did not protect against the development of hypertension. These results show that endogenous apelin, acting via APJ, is not involved in the genesis or maintenance of hypertension in either animal model used in this study

G protein-coupled receptors in the hypothalamic paraventricular and supraoptic nuclei – serpentine gateways to neuroendocrine homeostasis

G protein-coupled receptors (GPCRs) are the largest family of transmembrane receptors in the mammalian genome. They are activated by a multitude of different ligands that elicit rapid intracellular responses to regulate cell function. Unsurprisingly, a large proportion of therapeutic agents target these receptors. The paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus are important mediators in homeostatic control. Many modulators of PVN/SON activity, including neurotransmitters and hormones act via GPCRs – in fact over 100 non-chemosensory GPCRs have been detected in either the PVN or SON. This review provides a comprehensive summary of the expression of GPCRs within the PVN/SON, including data from recent transcriptomic studies that potentially expand the repertoire of GPCRs that may have functional roles in these hypothalamic nuclei. We also present some aspects of the regulation and known roles of GPCRs in PVN/SON, which are likely complemented by the activity of ‘orphan’ GPCRs

Relative mRNA abundance for <i>apela</i>, <i>apelin</i> and <i>aplnr</i> quantified by RNA-Seq in microdissected rat kidney tubules.

<p>Relative mRNA abundance for <i>apela</i>, <i>apelin</i> and <i>aplnr</i> quantified by RNA-Seq in microdissected rat kidney tubules.</p

Autoradiographic film images of ISHH with antisense-<i>apela</i> probes in kidneys from adult male <i>aplnr</i> wildtype (WT) (A,C) and knockout (KO)(B) mice.

<p>As in the rat kidney, <i>apela</i> labelling in the mouse kidney is mainly located in the inner medulla (IM) with weaker labelling in the inner stripe of the outer medulla (ISOM). There is also weak, scattered labelling in the cortex (arrowed). Background sense <i>apela</i> probe labelling is shown in (<b>C</b>), where the image contrast was increased in Image J to show the outline of the tissue. Pseudocolour scale bar is shown in (<b>B</b>). The sections were exposed to film for 5 weeks and images were processed as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0183094#pone.0183094.g003" target="_blank">Fig 3</a>. Scale bar = 500μm.</p

RNAscope with <i>aplnr</i> probes in CHO-B78 (rat APJ) and non-transfected CHO cell cultures.

<p>In <b>(A)</b> clear, punctate <i>aplnr</i> labelling is present in the cytoplasm of the majority of CHO-B78 cells with cell-cell variability in the levels of expression. Strongly (open arrow), moderately (arrows) and unlabelled (arrowheads) <i>aplnr</i> cells in CHO-B78 cultures are shown in (<b>B</b>). <b>(C)</b> shows negative control probe on CHO-B78 cells, while the lack of <i>aplnr</i> labelling in non-transfected CHO cells is shown in <b>(D)</b>. Scale bar = 25μm.</p

<i>Apela</i>, <i>apelin</i> and <i>aplnr</i> expression in the adult rat heart ventricle and kidney by branched-chain ISHH.

<p>The tissues were hybridized with RNAscope probes and processed in one day. Positive <i>apela</i>, <i>apelin</i> and <i>aplnr</i> and negative control staining of the heart is shown in (<b>A, B</b>) and (<b>C</b>), respectively. In (<b>A</b>) <i>aplnr</i>-expressing cells (green dots; labelled 1–6 with green arrows) are widely distributed in the heart myocardium. The rare cells express only <i>apela</i> (red dots; labelled 7 with a red arrow). Some cells are labelled with both <i>aplnr</i> + <i>apelin</i> (white dots) probes (labelled 8–10 with yellow arrows). A few cells express <i>aplnr</i> + <i>apela</i> + <i>apelin</i> (labelled 11 with a white arrow) or <i>aplnr</i> + <i>apela</i> (labelled 12 with a purple arrow). (<b>B</b>) is an enlargement of the dotted area outlined in (<b>A</b>). There was no labelling with negative control probes in all three channels in the heart ventricles (<b>C</b>) where * denotes vessel. In the kidney inner medulla (<b>D</b>) the vast majority of cell expressing <i>apela</i> (red dots; labelled 1–8 with red arrows) do not express <i>aplnr</i> (green dots) or <i>apelin</i> (yellow dots). Some cells express both <i>aplnr</i> + <i>apela</i> transcripts (labelled 9 with a purple arrow) while <i>aplnr</i> + <i>apelin</i> cells are more common (labelled 10–13 with yellow arrows). The rare cell exhibits <i>apela</i> + <i>apelin</i> + <i>aplnr</i> labelling (14; white arrow). Removing the DAPI channel in (<b>E</b>) (corresponding image of (<b>D</b>)) highlights the distinction between <i>apela</i> (red) and <i>aplnr</i>/<i>apelin</i> expression (green and yellow, respectively) in the kidney. (<b>F</b>) is an enlargement of the dotted area outlined in (<b>D</b>). In (<b>G</b>) the red channel diffuse background is enhanced to clearly show the renal tubular <i>apela</i> (red) labelling. (<b>H</b>) shows <i>aplnr</i> expression (white dots; e.g., arrowed) in a glomerulus (partial boundaries shown by dotted line). The images are representative of results obtained from the hearts and kidneys of 3 and 4 rats, respectively. DAPI counterstaining is shown in blue. Scale bar = 50μm.</p