Adenosine/A2B Receptor Signaling Ameliorates the Effects of Aging and Counteracts Obesity.
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ABSTRACT:
SUBMITTER: Gnad T
PROVIDER: S-EPMC7437516 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:High fat diet and its induced changes in glucose homeostasis, inflammation and obesity continue to be an epidemic in developed countries. The A2b adenosine receptor (A2bAR) is known to regulate inflammation. We used a diet-induced obesity murine knockout model to investigate the role of this receptor in mediating metabolic homeostasis, and correlated our findings in obese patient samples.Administration of high fat, high cholesterol diet (HFD) for sixteen weeks vastly upregulated the expression of the A2bAR in control mice, while A2bAR knockout (KO) mice under this diet developed greater obesity and hallmarks of type 2 diabetes (T2D), assessed by delayed glucose clearance and augmented insulin levels compared to matching control mice. We identified a novel link between the expression of A2bAR, insulin receptor substrate 2 (IRS-2), and insulin signaling, determined by Western blotting for IRS-2 and tissue Akt phosphorylation. The latter is impaired in tissues of A2bAR KO mice, along with a greater inflammatory state. Additional mechanisms involved include A2bAR regulation of SREBP-1 expression, a repressor of IRS-2. Importantly, pharmacological activation of the A2bAR by injection of the A2bAR ligand BAY 60-6583 for four weeks post HFD restores IRS-2 levels, and ameliorates T2D. Finally, in obese human subjects A2bAR expression correlates strongly with IRS-2 expression.Our study identified the A2bAR as a significant regulator of HFD-induced hallmarks of T2D, thereby pointing to its therapeutic potential.
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Project description:The A(2B) adenosine receptor (AR) has emerged as a unique member of the AR family with contrasting roles during acute and chronic disease states. We utilized zinc-finger nuclease technology to create A(2B)AR gene (Adora2b)-disrupted rats on the Dahl salt-sensitive (SS) genetic background. This strategy yielded a rat strain (SS-Adora2b mutant rats) with a 162-base pair in-frame deletion of Adora2b that included the start codon. Disruption of A(2B)AR function in SS-Adora2b mutant rats was confirmed by loss of agonist (BAY 60-6583 or NECA)-induced cAMP accumulation and loss of interleukin-6 release from isolated fibroblasts. In addition, BAY 60-6583 produced a dose-dependent increase in glucose mobilization that was absent in SS-Adora2b mutants. Upon initial characterization, SS-Adora2b mutant rats were found to exhibit increased body weight, a transient delay in glucose clearance, and reduced proinflammatory cytokine production following challenge with lipopolysaccharide (LPS). In addition, blood pressure was elevated to a greater extent (?15-20 mmHg) in SS-Adora2b mutants as they aged from 7 to 21 weeks. In contrast, hypertension augmented by Ang II infusion was attenuated in SS-Adora2b mutant rats. Despite differences in blood pressure, indices of renal and cardiac injury were similar in SS-Adora2b mutants during Ang II-augmented hypertension. We have successfully created and validated a new animal model that will be valuable for investigating the biology of the A(2B)AR. Our data indicate varying roles for A(2B)AR signaling in regulating blood pressure in SS rats, playing both anti- and prohypertensive roles depending on the pathogenic mechanisms that contribute to blood pressure elevation.
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Project description:The cAMP-elevating A(2b) adenosine receptor (A(2b)AR) controls inflammation via its expression in bone marrow cells.Atherosclerosis induced by a high-fat diet in apolipoprotein E-deficient mice was more pronounced in the absence of the A(2b)AR. Bone marrow transplantation experiments indicated that A(2b)AR bone marrow cell signals alone were not sufficient to elicit this effect. Intriguingly, liver expression of the A(2b)AR in wild-type mice was vastly augmented by a high-fat diet, raising the possibility that this upregulation is of functional significance. A(2b)AR genetic ablation led to elevated levels of liver and plasma cholesterol and triglycerides and to fatty liver pathology typical of steatosis, assessed by enzymatic assays and analysis of liver sections. Western blotting and quantitative polymerase chain reaction revealed elevated expression of the following molecules in the liver of A(2b)AR-null mice: the transcription factor sterol regulatory element binding protein-1 (SREBP-1) and its 2 downstream targets and regulators of lipogenesis, acetyl CoA carboxylase and fatty acid synthase. Pharmacological activation or inhibition of A(2b)AR in primary hepatocytes confirmed the regulation of SREBP-1 by this receptor. A(2b)AR-mediated changes in cAMP were found to regulate levels of the transcriptionally active form of SREBP-1. Finally, adenovirally mediated restoration of the A(2b)AR in the liver of A(2b)AR-null mice reduced the lipid profile and atherosclerosis. Similarly, in vivo administration of the A(2b)AR ligand BAY 60-6853 in control mice on a high-fat diet reduced the lipid profile and atherosclerosis.This study provides the first evidence that the A(2b)AR regulates liver SREBP-1, hyperlipidemia, and atherosclerosis, suggesting that this receptor may be an effective therapeutic target.
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Project description:Hypertension is the most prevalent life-threatening disease worldwide and is frequently associated with chronic kidney disease (CKD). However, the molecular basis underlying hypertensive CKD is not fully understood.We sought to identify specific factors and signaling pathways that contribute to hypertensive CKD and thereby exacerbate disease progression.Using high-throughput quantitative reverse-transcription polymerase chain reaction profiling, we discovered that the expression level of 5'-ectonucleotidase (CD73), a key enzyme that produces extracellular adenosine, was significantly increased in the kidneys of angiotensin II-infused mice, an animal model of hypertensive nephropathy. Genetic and pharmacological studies in mice revealed that elevated CD73-mediated excess renal adenosine preferentially induced A2B adenosine receptor (ADORA2B) production and that enhanced kidney ADORA2B signaling contributes to angiotensin II-induced hypertension. Similarly, in humans, we found that CD73 and ADORA2B levels were significantly elevated in the kidneys of CKD patients compared with normal individuals and were further elevated in hypertensive CKD patients. These findings led us to further discover that elevated renal CD73 contributes to excess adenosine signaling via ADORA2B activation that directly stimulates endothelin-1 production in a hypoxia-inducible factor-?-dependent manner and underlies the pathogenesis of the disease. Finally, we revealed that hypoxia-inducible factor-? is an important factor responsible for angiotensin II-induced CD73 and ADORA2B expression at the transcriptional level.Overall, our studies reveal that angiotensin II-induced renal CD73 promotes the production of renal adenosine that is a prominent driver of hypertensive CKD by enhanced ADORA2B signaling-mediated endothelin-1 induction in a hypoxia-inducible factor-?-dependent manner. The inhibition of excess adenosine-mediated ADORA2B signaling represents a novel therapeutic target for the disease.
| S-EPMC3886128 | biostudies-literature
Project description:Acute pulmonary inflammation is still a frightening complication in intensive care units. In our previous study, we determined that heme oxygenase (HO)-1 had anti-inflammatory effects in pulmonary inflammation. Recent literature has emphasized a link between HO-1 and the nucleotide adenosine. Since adenosine A2A- and A2B-receptors play a pivotal role in pulmonary inflammation, we investigated their link to the enzyme HO-1. In a murine model of pulmonary inflammation, the activation of HO-1 by hemin significantly decreased polymorphonuclear leukocyte (PMN) migration into the lung. This anti-inflammatory reduction of PMN migration was abolished in A2A- and A2B-knockout mice. Administration of hemin significantly reduced chemokine levels in the BAL of wild-type animals but had no effects in A2A-/- and A2B-/- mice. Microvascular permeability was significantly attenuated in HO-1-stimulated wild-type mice, but not in A2A-/- and A2B-/- mice. The activity of HO-1 rose after LPS inhalation in wild-type animals and, surprisingly, also in A2A-/- and A2B-/- mice after the additional administration of hemin. Immunofluorescence images of animals revealed alveolar macrophages to be the major source of HO-1 activity in both knockout strains-in contrast to wild-type animals, where HO-1 was also significantly augmented in the lung tissue. In vitro studies on PMN migration further confirmed our in vivo findings. In conclusion, we linked the anti-inflammatory effects of HO-1 to functional A2A/A2B-receptor signaling under conditions of pulmonary inflammation. Our findings may explain why targeting HO-1 in acute pulmonary inflammation has failed to prove effective in some patients, since septic patients have altered adenosine receptor expression.
| S-EPMC5742329 | biostudies-literature
Project description:The A2b adenosine receptor (A2bAR) is highly abundant in bone marrow macrophages and vascular smooth muscle cells (VSMC). To examine the functional significance of this receptor expression, we applied a femoral artery injury model to A2bAR knockout (KO) mice and showed that the A2bAR prevents vascular lesion formation in an injury model that resembles human restenosis after angioplasty. While considering related mechanisms, we noted higher levels of TNF-alpha, an up-regulator of CXCR4, and of VSMC proliferation in the injured KO mice. In accordance, CXCR4, which is known to attract progenitor cells during tissue regeneration, is up-regulated in lesions of the KO mice. In addition, aortic smooth muscle cells derived from A2bAR KO mice display greater proliferation in comparison with controls. Bone marrow transplantation experiments indicated that the majority of the signal for lesion formation in the null mice originates from bone marrow cells. Thus, this study highlights the significance of the A2bAR in regulating CXCR4 expression in vivo and in protecting against vascular lesion formation.
| S-EPMC2206615 | biostudies-literature
Project description:Central to inflammatory bowel disease (IBD) pathogenesis is loss of mucosal barrier function. Emerging evidence implicates extracellular adenosine signaling in attenuating mucosal inflammation. We hypothesized that adenosine-mediated protection from intestinal barrier dysfunction involves tissue-specific signaling through the A2B adenosine receptor (Adora2b) at the intestinal mucosal surface. To address this hypothesis, we combined pharmacologic studies and studies in mice with global or tissue-specific deletion of the Adora2b receptor. Adora2b(-/-) mice experienced a significantly heightened severity of colitis, associated with a more acute onset of disease and loss of intestinal epithelial barrier function. Comparison of mice with Adora2b deletion on vascular endothelial cells (Adora2b(fl/fl)VeCadCre(+)) or intestinal epithelia (Adora2b(fl/fl)VillinCre(+)) revealed a selective role for epithelial Adora2b signaling in attenuating colonic inflammation. In vitro studies with Adora2b knockdown in intestinal epithelial cultures or pharmacologic studies highlighted Adora2b-driven phosphorylation of vasodilator-stimulated phosphoprotein (VASP) as a specific barrier repair response. Similarly, in vivo studies in genetic mouse models or treatment studies with an Adora2b agonist (BAY 60-6583) recapitulate these findings. Taken together, our results suggest that intestinal epithelial Adora2b signaling provides protection during intestinal inflammation via enhancing mucosal barrier responses.
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Project description:PurposeThe identification of genes with synthetic lethality in the context of mutant TP53 is a promising strategy for the treatment of basal-like triple negative breast cancer (TNBC). This study investigated regulators of mutant TP53 (R248Q) in basal-like TNBC and their impact on tumorigenesis.Experimental designTNBC cells were analyzed by RNA-seq, and synthetic-lethal shRNA knock-down screening, to identify genes related to the expression of mutant TP53. A tissue microarray of 232 breast cancer samples, that included 66 TNBC cases, was used to assess clinicopathological correlates of tumor protein expression. Functional assays were performed in vitro and in vivo to assess the role of ADORA2B in TNBC.ResultsTranscriptome profiling identified ADORA2B as up-regulated in basal-like TNBC cell lines with R248Q-mutated TP53, with shRNA-screening suggesting the potential for a synthetic-lethal interaction between these genes. In clinical samples, ADORA2B was highly expressed in 39.4% (26/66) of TNBC patients. ADORA2B-expression was significantly correlated with ER (P < 0.01), PgR (P = 0.027), EGFR (P < 0.01), and tumor size (P = 0.037), and was an independent prognostic factor for outcome (P = 0.036). In line with this, ADORA2B-transduced TNBC cells showed increased tumorigenesis, and ADORA2B knockdown, along with mutant p53 knockdown, decreased metastasis both in vitro and in vivo. Notably, the cytotoxic cyclic peptide SA-I suppressed ADORA2B expression and tumorigenesis in TNBC cell lines.ConclusionsADORA2B expression increases the oncogenic potential of basal-like TNBC and is an independent factor for poor outcome. These data suggest that ADORA2B could serve as a prognostic biomarker and a potential therapeutic target for basal-like TNBC.
| S-EPMC6195371 | biostudies-literature
Project description:Although acute lung injury contributes significantly to critical illness, resolution often occurs spontaneously via activation of incompletely understood pathways. We recently found that mechanical ventilation of mice increases the level of pulmonary adenosine, and that mice deficient for extracellular adenosine generation show increased pulmonary edema and inflammation after ventilator-induced lung injury (VILI). Here, we profiled the response to VILI in mice with genetic deletions of each of the 4 adenosine receptors (ARs) and found that deletion of the A2BAR gene was specifically associated with reduced survival time and increased pulmonary albumin leakage after injury. In WT mice, treatment with an A2BAR-selective antagonist resulted in enhanced pulmonary inflammation, edema, and attenuated gas exchange, while an A2BAR agonist attenuated VILI. In bone marrow-chimeric A2BAR mice, although the pulmonary inflammatory response involved A2BAR signaling from bone marrow-derived cells, A2BARs located on the lung tissue attenuated VILI-induced albumin leakage and pulmonary edema. Furthermore, measurement of alveolar fluid clearance (AFC) demonstrated that A2BAR signaling enhanced amiloride-sensitive fluid transport and elevation of pulmonary cAMP levels following VILI, suggesting that A2BAR agonist treatment protects by drying out the lungs. Similar enhancement of pulmonary cAMP and AFC were also observed after beta-adrenergic stimulation, a pathway known to promote AFC. Taken together, these studies reveal a role for A2BAR signaling in attenuating VILI and implicate this receptor as a potential therapeutic target during acute lung injury.
| S-EPMC2532979 | biostudies-literature
Project description:The adenosine A2b receptor (A2bR) was considered to play an oncogenic role in many human malignancies. However, the expression and molecular function of A2bR in bladder urothelial carcinoma (BUC) have not been well elucidated. Herein, we found that the expression of A2bR was higher than other adenosine receptors in BUC tissues and cells, and it was upregulated in BUC tissues compared with matched normal bladder tissues. Furthermore, high expression of A2bR was associated with poor prognosis of patients with BUC. In addition, suppression of A2bR inhibited the proliferation, migration and invasion of BUC cells and arrested the cell cycle at the G1 phase. Finally, we demonstrated that downregulation of A2bR inhibited the proliferation, migration and invasion of BUC in part via the MAPK signaling pathway, increasing the levels of P21 but decreasing the levels of cyclin B1, D, E1, MMP-2 and MMP-9. Overexpression of MMP-2 could rescue BUC cells migration and invasion. Thus, the present study indicates that A2bR may play a potential oncogenic role in BUC progression and act as a potential biomarker to identify BUC patients with poor clinical outcomes.
| S-EPMC5564722 | biostudies-literature