Alpha(1D)-adrenergic receptor insensitivity is associated with alterations in its expression and distribution in cultured vascular myocytes

A new oxime synthesized from Senecio nutans SCh. Bip (chachacoma) reduces calcium influx in the vascular contractile response in rat aorta

Senecio nutans Sch. Bip is an endemic plant commonly employed in the Andes culture to counteract the effects of mountain sickness, and its bioactive molecules could provide new drugs for treating hypertension. The purpose was to determine whether the vascular response of the plant bioactive molecules, such as (5-acetyl-6-hydroxy-2-isopropenyl-2,3-dihydrobenzofurane; Sn-I), could be improved by a simple structural modification to synthesize oximes (Ox-Sn-I). We characterized both compounds using IR and NMR spectroscopy and Heteronuclear Multiple Quantum Coherence (HMQC). We investigated vascular relaxation mechanisms in response to Sn-I and Ox-Sn-I using rat aorta and vascular smooth muscle cells (A7r5) as experimental models. Preincubation of aortic rings with Sn-I (10-5 M) significantly (p < 0.001) decreased the contractile effect in response to phenylephrine (PE) and potassium chloride (KCl). The sensitivity (EC50) to PE significantly (p < 0.01) decreased in the presence of Sn-I (10-5 M), but not with Ox-Sn-I. Sn-I significantly (p < 0.001) reduced the PE-induced contraction under calcium-free conditions. When A7r5 cells were preincubated with Sn-I and Ox-Sn-I (10-5 M), both compounds blunted the increase in intracellular Ca2+ induced by KCl. 2,3-Dihydrobenzofurane derived from S. nutans (Sn-I) reduces the contractile response probably by blocking Ca2+ entry through voltage-gated Ca2+ channels (VGCC) in vascular smooth cells. This effect also causes relaxation in rat aorta mediated by reduction of intracellular Ca2+ concentration, rather than an increase of NO generation in endothelial vascular cells.

Impact of Normal and Overweight Pregnancy in GLUT4 and Glucose-Dependent Vascular Contractility

INTRODUCTION

Obesity during pregnancy can contribute to hypertensive complications through changes in glucose utilization. We investigated the impact of vascular glucose uptake, GLUT4 density, and endothelium on agonist-induced vasoconstriction in the aortas of overweight pregnant rats.

METHODS

Isolated aortic rings with or without endothelium from pregnant or nonpregnant rats fed a standard (SD) or hypercaloric diet (HD) were contracted with phenylephrine or serotonin (10-9 to 10-4M) using standard (11 mm) or without (0 mm) glucose Krebs solution. GLUT4 density in the aortas was measured using the en face method.

RESULTS

Aortas from overweight pregnant animals (PHD) showed increased Phe-induced vasoconstriction (p < 0.05 vs. pregnant standard diet [PSD]), which was endothelium-independent. The contraction decreased significantly in the absence of glucose. In contrast, vessels from pregnant SD rats maintained their contraction in glucose-free Krebs solution. 5-HT increases PHD aortic contraction only in the absence of glucose. The fetal aortas from PHD mothers showed blunted vasoconstriction. Overweight significantly reduced GLUT4 expression in maternal and fetal aortas (p < 0.05 vs. PSD).

CONCLUSIONS

Aortic contractility is independent of glucose uptake during healthy pregnancy. In contrast, overweight pregnancy increases contractility. This increase depends directly on smooth muscle glucose uptake and inversely on GLUT-4 density. The increased contraction observed in the vasculature of overweight mothers was inverted in the fetal aortas.

Effects of Genetic Mutation Sites in ADR Genes on Modern Chickens Produced and Domesticated by Artificial Selection

Associations between neurotransmitters, adrenergic receptor (ADR) mutations, and behaviors in chickens produced and domesticated by artificial selection remain unclear. This study investigates the association of neurotransmitters and ADR mutations with egg laying and cockfighting-behaviors associated with significantly different breeding backgrounds-in Shaver Brown and Shamo chickens. Accordingly, the whole sequences of nine ADR genes were determined, and nine amino acid-specific mutation sites from five genes (ADRα1A: S365G, ADRα1D: T440N, ADRα2A: D273E, ADRβ1: N443S, S445N, ADRβ3: R342C, Q404L, and P406S) were extracted. Evolutionary analysis showed that these mutations were not ancestrally derived. These results confirm that the mutations at these sites were artificially selected for domestication and are breed specific. N_ST population analysis confirmed a difference in the degree of genetic differentiation between the two populations in seven genes. The results further confirm differences in the degree of genetic differentiation between the two populations in Shaver Brown (ADRA1B and ADRA1D) and Shamo (ADRA1A and ADRA2B) chickens, indicating that the ADR gene differs between the two breeds. The effects of artificial selection, guided by the human-driven selection of desirable traits, are reflected in adrenaline gene mutations. Furthermore, certain gene mutations may affect domestication, while others may affect other traits in populations or individuals.

QiShenYiQi ameliorates salt-induced hypertensive nephropathy by balancing ADRA1D and SIK1 expression in Dahl salt-sensitive rats

BACKGROUND

Hypertension is a leading risk factor for developing kidney disease. Current single-target antihypertensive drugs are not effective for hypertensive nephropathy, in part due to its less understood mechanism of pathogenesis. We recently showed that QiShenYiQi (QSYQ), a component-based cardiovascular Chinese medicine, is also effective for ischemic stroke. Given the important role of the brain-heart-kidney axis in blood pressure control, we hypothesized that QSYQ may contribute to blood pressure regulation and kidney protection in Dahl salt-sensitive hypertensive rats.

METHODS

The therapeutic effects of QSYQ on blood pressure and kidney injury in Dahl salt-sensitive rats fed with high salt for 9 weeks were evaluated by tail-cuff blood pressure monitoring, renal histopathological examination and biochemical indicators in urine and serum. RNA-seq was conducted to identify QSYQ regulated genes in hypertensive kidney, and RT-qPCR, immunohistochemistry, and Western blotting analysis were performed to verify the transcriptomics results and validate the purposed mechanisms.

RESULTS

QSYQ treatment significantly decreased blood pressure in Dahl salt-sensitive hypertensive rats, alleviated renal tissue damage, reduced renal interstitial fibrosis and collagen deposition, and improved renal physiological function. RNA-seq and subsequent bioinformatic analysis showed that the expression of ADRA1D and SIK1 genes were among the most prominently altered by QSYQ in salt-sensitive hypertensive rat kidney. RT-qPCR, immunohistochemistry and Western blotting results confirmed that the mRNA and protein expression levels of alpha-1D adrenergic receptor (ADRA1D) in the kidney tissue of the QSYQ-treated rats were markedly down-regulated, while the mRNA and protein levels of salt inducible kinase 1 (SIK1) were significantly increased.

CONCLUSION

QSYQ not only lowered blood pressure, but also alleviated renal damage via reducing the expression of ADRA1D and increasing the expression of SIK1 in the kidney of Dahl salt-sensitive hypertensive rats.

N-glycosylation of α1D-adrenergic receptor N-terminal domain is required for correct trafficking, function, and biogenesis

G protein-coupled receptor (GPCR) biogenesis, trafficking, and function are regulated by post-translational modifications, including N-glycosylation of asparagine residues. α1D-adrenergic receptors (α1D-ARs) - key regulators of central and autonomic nervous system function - contain two putative N-glycosylation sites within the large N-terminal domain at N65 and N82. However, determining the glycosylation state of this receptor has proven challenging. Towards understanding the role of these putative glycosylation sites, site-directed mutagenesis and lectin affinity purification identified N65 and N82 as bona fide acceptors for N-glycans. Surprisingly, we also report that simultaneously mutating N65 and N82 causes early termination of α1D-AR between transmembrane domain 2 and 3. Label-free dynamic mass redistribution and cell surface trafficking assays revealed that single and double glycosylation deficient mutants display limited function with impaired plasma membrane expression. Confocal microscopy imaging analysis and SNAP-tag sucrose density fractionation assays revealed the dual glycosylation mutant α1D-AR is widely distributed throughout the cytosol and nucleus. Based on these novel findings, we propose α1D-AR transmembrane domain 2 acts as an ER localization signal during active protein biogenesis, and that α1D-AR N-terminal glycosylation is required for complete translation of nascent, functional receptor.

Norepinephrine stimulation of alpha1D-adrenoceptor promotes proliferation of pulmonary artery smooth muscle cells via ERK-1/2 signaling

It has been shown that the sympathetic nervous system is activated in pulmonary arterial hypertension (PAH). Norepinephrine (NE) levels are increased by chemoreflex-dependent sympathetic overactivation and involved in pulmonary vascular remodeling. However, the underlying mechanisms of the remodeling induced by NE are poorly understood. In this study, we found that, in vivo, the expression of tyrosine hydroxylase and the concentration of plasma NE were increased in PAH rats compared with normal rats. Increases in ventricular hypertrophy and medial width of the pulmonary arteries were reversed by prazosin, α₁-adrenoceptor (α₁-AR) antagonists, in PAH rats. Elevated expression of α_1D-AR was detected in PAH rats. In addition, prazosin reduced the increasing expression of PCNA, CyclinA and CyclinE induced by hypoxia. In vitro, MTT assay, flow cytometry, Western blotting and immunofluorescence were performed to investigate the effects of NE on proliferation of pulmonary artery smooth muscle cells (PASMCs). We revealed that NE promoted PASMCs viability, increased the expression of PCNA, CyclinA and CyclinE, made more cells from G₀/G₁ phase to G₂/M+S phase and enhanced the microtubule formation. Above NE-induced changes could be suppressed by BMY 7378, an inhibitor of α_1D-AR. Furthermore, ERK-1/2 pathway was activated by NE. U0126, a specific inhibitor for ERK-1/2, attenuated the NE-induced proliferation of PASMCs under normoxia and hypoxia. Taken together, our results suggest that NE which stimulates α_1D-AR promotes proliferation of PASMCs and the effect is, at least in part, mediated via the ERK-1/2 pathway.

Arterial relaxation is coupled to inhibition of mitochondrial fission in arterial smooth muscle cells: comparison of vasorelaxant effects of verapamil and phentolamine

Mitochondria are morphologically dynamic organelles which undergo fission and fusion processes. Our previous study found that arterial constriction was always accompanied by increased mitochondrial fission in smooth muscle cells, whereas inhibition of mitochondrial fission in smooth muscle cells was associated with arterial relaxation. Here, we used the typical vasorelaxants, verapamil and phentolamine, to further confirm the coupling between arterial constriction and mitochondrial fission in rat aorta. Results showed that phentolamine but not verapamil induced vasorelaxation in phenylephrine (PE)-induced rat thoracic aorta constriction. Verapamil, but not phentolamine, induced vasorelaxation in high K⁺ (KPSS)-induced rat thoracic aorta constriction. Pre-treatment with phentolamine prevented PE- but not KPSS-induced aorta constriction and pre-treatment with verapamil prevented both PE- and KPSS-induced aorta constriction. Transmission electron microscopy (TEM) results showed that verapamil but not phentolamine inhibited KPSS-induced excessive mitochondrial fission in aortic smooth muscle cells, and verapamil prevented both PE- and KPSS-induced excessive mitochondrial fission in aortic smooth muscle cells. Verapamil inhibited KPSS-induced excessive mitochondrial fission in cultured vascular smooth muscle cells (A10). These results further demonstrate that arterial relaxation is coupled to inhibition of mitochondrial fission in arterial smooth muscle cells.

Mitochondrial Fission of Smooth Muscle Cells Is Involved in Artery Constriction

Mitochondria are dynamic organelles and continuously undergo fission and fusion processes. Mitochondrial fission is involved in multiple physiological or pathological processes, but the role of mitochondrial fission of smooth muscle cells in artery constriction is unknown. The role of mitochondrial fission of smooth muscle cells in arterial function was investigated by measuring the tension of rat mesenteric arteries and thoracic aorta and by evaluating mitochondrial fission, mitochondrial reactive oxygen species, and cytosolic [Ca²⁺]_i in rat vascular smooth muscle cells. Mitochondrial fission inhibitors mdivi-1 and dynasore antagonized phenylephrine- and high K⁺-induced constriction of rat mesenteric arteries. Mdivi-1 relaxed phenylephrine-induced constriction, and mdivi-1 pretreatment prevented phenylephrine-induced constriction in mice, rat aorta, and human mesenteric arteries. Phenylephrine- and high K⁺-induced increase of mitochondrial fission in smooth muscle cells of rat aorta and the increase was inhibited by mdivi-1. Mdivi-1 inhibited high K⁺-induced increases of mitochondrial fission, mitochondrial reactive oxygen species, and cytosolic [Ca²⁺]_i in rat vascular smooth muscle cells. Prechelation of cytosolic Ca²⁺ prevented high K⁺-induced cytosolic [Ca²⁺]_i increase, mitochondrial fission, and mitochondrial reactive oxygen species overproduction. Mitochondria-targeted antioxidant mito-TEMPO antagonized phenylephrine- and high K⁺-induced constriction of rat mesenteric arteries. Nitroglycerin and ROCK (Rho-associated protein kinase) inhibitor Y27632, the 2 vasodilators with different vasorelaxant mechanisms, relaxed high K⁺-induced vasoconstriction and inhibited high K⁺-induced mitochondrial fission. In conclusion, the mitochondrial fission of smooth muscle cells is involved in artery constriction.

Endogenous N-terminal Domain Cleavage Modulates α1D-Adrenergic Receptor Pharmacodynamics

The α1D-adrenergic receptor (ADRA1D) is a key regulator of cardiovascular, prostate, and central nervous system functions. This clinically relevant G protein-coupled receptor has proven difficult to study, as it must form an obligate modular homodimer containing the PDZ proteins scribble and syntrophin or become retained in the endoplasmic reticulum as non-functional protein. We previously determined that targeted removal of the N-terminal (NT) 79 amino acids facilitates ADRA1D plasma membrane expression and agonist-stimulated functional responses. However, whether such an event occurs in physiological contexts was unknown. Herein, we report the ADRA1D is subjected to innate NT processing in cultured human cells. SNAP near-infrared imaging and tandem-affinity purification revealed the ADRA1D is expressed as both full-length and NT truncated forms in multiple human cell lines. Serial truncation mapping identified the cleavage site as Leu(90)/Val(91) in the 95-amino acid ADRA1D NT domain, suggesting human cells express a Δ1-91 ADRA1D species. Tandem-affinity purification MS/MS and co-immunoprecipitation analysis indicate NT processing of ADRA1D is not required to form scribble-syntrophin macromolecular complexes. Yet, label-free dynamic mass redistribution signaling assays demonstrate that Δ1-91 ADRA1D agonist responses were greater than WT ADRA1D. Mutagenesis of the cleavage site nullified the processing event, resulting in ADRA1D agonist responses less than the WT receptor. Thus, we propose that processing of the ADRA1D NT domain is a physiological mechanism employed by cells to generate a functional ADRA1D isoform with optimal pharmacodynamic properties.

Bladder smooth muscle organ culture preparation maintains the contractile phenotype

Smooth muscle cells, when subjected to culture, modulate from a contractile to a secretory phenotype. This has hampered the use of cell culture for molecular techniques to study the regulation of smooth muscle biology. The goal of this study was to develop a new organ culture model of bladder smooth muscle (BSM) that would maintain the contractile phenotype and aid in the study of BSM biology. Our results showed that strips of BSM subjected to up to 9 days of organ culture maintained their contractile phenotype, including the ability to achieve near-control levels of force with a temporal profile similar to that of noncultured tissues. The technical aspects of our organ culture preparation that were responsible, in part, for the maintenance of the contractile phenotype were a slight longitudinal stretch during culture and subjection of the strips to daily contraction-relaxation. The tissues contained viable cells throughout the cross section of the strips. There was an increase in extracellular collagenous matrix, resulting in a leftward shift in the passive length-tension relationship. There were no significant changes in the content of smooth muscle-specific α-actin, calponin, h-caldesmon, total myosin heavy chain, protein kinase G, Rho kinase-I, or the ratio of SM1 to SM2 myosin isoforms. Moreover the organ cultured tissues maintained functional voltage-gated calcium channels and large-conductance calcium-activated potassium channels. Therefore, we propose that this novel BSM organ culture model maintains the contractile phenotype and will be a valuable tool for the use in cellular/molecular biology studies of bladder myocytes.

Alpha-dystrobrevin-1 recruits alpha-catulin to the alpha1D-adrenergic receptor/dystrophin-associated protein complex signalosome

α(1D)-Adrenergic receptors (ARs) are key regulators of cardiovascular system function that increase blood pressure and promote vascular remodeling. Unfortunately, little information exists about the signaling pathways used by this important G protein-coupled receptor (GPCR). We recently discovered that α(1D)-ARs form a "signalosome" with multiple members of the dystrophin-associated protein complex (DAPC) to become functionally expressed at the plasma membrane and bind ligands. However, the molecular mechanism by which the DAPC imparts functionality to the α(1D)-AR signalosome remains a mystery. To test the hypothesis that previously unidentified molecules are recruited to the α(1D)-AR signalosome, we performed an extensive proteomic analysis on each member of the DAPC. Bioinformatic analysis of our proteomic data sets detected a common interacting protein of relatively unknown function, α-catulin. Coimmunoprecipitation and blot overlay assays indicate that α-catulin is directly recruited to the α(1D)-AR signalosome by the C-terminal domain of α-dystrobrevin-1 and not the closely related splice variant α-dystrobrevin-2. Proteomic and biochemical analysis revealed that α-catulin supersensitizes α(1D)-AR functional responses by recruiting effector molecules to the signalosome. Taken together, our study implicates α-catulin as a unique regulator of GPCR signaling and represents a unique expansion of the intricate and continually evolving array of GPCR signaling networks.