Signal Transduction Mechanisms Involved in Ischemic Preconditioning in the Rat Retina in vivo

BackgroundRecombinant human relaxin-2 (serelaxin), which has organ-protective actions mediated via its cognate G protein–coupled receptor relaxin family peptide receptor 1 (RXFP1), has emerged as a potential agent to treat fibrosis. Studies have shown that serelaxin requires the angiotensin II (AngII) type 2 receptor (AT2R) to ameliorate renal fibrogenesis in vitro and in vivo. Whether its antifibrotic actions are affected by modulation of the AngII type 1 receptor (AT1R), which is expressed on myofibroblasts along with RXFP1 and AT2R, is unknown.MethodsWe examined the signal transduction mechanisms of serelaxin when applied to primary rat renal and human cardiac myofibroblasts in vitro, and in three models of renal- or cardiomyopathy-induced fibrosis in vivo.ResultsThe AT1R blockers irbesartan and candesartan abrogated antifibrotic signal transduction of serelaxin via RXFP1 in vitro and in vivo. Candesartan also ameliorated serelaxin’s antifibrotic actions in the left ventricle of mice with cardiomyopathy, indicating that candesartan’s inhibitory effects were not confined to the kidney. We also demonstrated in a transfected cell system that serelaxin did not directly bind to AT1Rs but that constitutive AT1R–RXFP1 interactions could form. To potentially explain these findings, we also demonstrated that renal and cardiac myofibroblasts expressed all three receptors and that antagonists acting at each receptor directly or allosterically blocked the antifibrotic effects of either serelaxin or an AT2R agonist (compound 21).ConclusionsThese findings have significant implications for the concomitant use of RXFP1 or AT2R agonists with AT1R blockers, and suggest that functional interactions between the three receptors on myofibroblasts may represent new targets for controlling fibrosis progression.

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Room F, 10/16/2000 9: 00 AM - 11: 00 AM (PS) Heat Shock Protein Expression and Ischemic Preconditioning in the In Vivo Rat Retina

Anesthesiology ◽

10.1097/00000542-200009001-00706 ◽

2000 ◽

Vol 93 (3A) ◽

pp. A-706

Author(s):

Steven Roth ◽

Charles Zhang ◽

Afzal Shaikh ◽

Elise Krecji ◽

Chris Yang

Keyword(s):

Heat Shock ◽

Heat Shock Protein ◽

Protein Expression ◽

Ischemic Preconditioning ◽

Rat Retina ◽

Heat Shock Protein Expression

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Role of the β1-Adrenergic Pathway in Anesthetic and Ischemic Preconditioning against Myocardial Infarction in the Rabbit Heart In Vivo

Anesthesiology ◽

10.1097/00000542-200609000-00014 ◽

2006 ◽

Vol 105 (3) ◽

pp. 503-510 ◽

Cited By ~ 55

Author(s):

Markus Lange ◽

Thorsten M. Smul ◽

Christoph A. Blomeyer ◽

Andreas Redel ◽

Karl-Norbert Klotz ◽

...

Keyword(s):

Signal Transduction ◽

Coronary Artery ◽

Infarct Size ◽

Ischemic Preconditioning ◽

Myocardial Infarct ◽

Coronary Artery Occlusion ◽

Artery Occlusion ◽

Myocardial Infarct Size ◽

Area At Risk

Background Anesthetic and ischemic preconditioning share similar signal transduction pathways. The authors tested the hypothesis that the beta1-adrenergic signal transduction pathway mediates anesthetic and ischemic preconditioning in vivo. Methods Pentobarbital-anesthetized (30 mg/kg) rabbits (n = 96) were instrumented for measurement of systemic hemodynamics and subjected to 30 min of coronary artery occlusion and 3 h of reperfusion. Sixty minutes before occlusion, vehicle (control), 1.0 minimum alveolar concentration desflurane, or sevoflurane, and esmolol (30.0 mg x kg(-1) x h(-1)) were administered for 30 min, respectively. Administration of a single 5-min cycle of ischemic preconditioning was instituted 35 min before coronary artery occlusion. In separate groups, the selective blocker esmolol or the protein kinase A inhibitor H-89 (250 microg/kg) was given alone and in combination with desflurane, sevoflurane, and ischemic preconditioning. Results Baseline hemodynamics and area at risk were not significantly different between groups. Myocardial infarct size (triphenyltetrazolium staining) as a percentage of area at risk was 61 +/- 4% in control. Desflurane, sevoflurane, and ischemic preconditioning reduced infarct size to 34 +/- 2, 36 +/- 5, and 23 +/- 3%, respectively. Esmolol did not alter myocardial infarct size (65 +/- 5%) but abolished the protective effects of desflurane and sevoflurane (57 +/- 4 and 52 +/- 4%, respectively) and attenuated ischemic preconditioning (40 +/- 4%). H-89 did not alter infarct size (60 +/- 4%) but abolished preconditioning by desflurane (57 +/- 5%) and sevoflurane (61 +/- 1%). Ischemic preconditioning (24 +/- 7%) was not affected by H-89. Conclusions The results demonstrate that anesthetic preconditioning is mediated by the beta1-adrenergic pathway, whereas this pathway is not essential for ischemic preconditioning. These results indicate important differences in the mechanisms of anesthetic and ischemic preconditioning.

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MECHANISMS OF ISCHEMIC PRECONDITIONING IN THE RAT RETINA in VIVO

Anesthesia & Analgesia ◽

10.1097/00000539-199902001-00240 ◽

1999 ◽

Vol 88 (Supplement) ◽

pp. 241S

Author(s):

S. Roth ◽

B. Li ◽

K. Houamed

Keyword(s):

Ischemic Preconditioning ◽

Rat Retina

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Vasopressin V2-receptor mobile fraction and ligand-dependent adenylate cyclase activity are directly correlated in LLC-PK1 renal epithelial cells.

The Journal of Cell Biology ◽

10.1083/jcb.114.1.53 ◽

1991 ◽

Vol 114 (1) ◽

pp. 53-60 ◽

Cited By ~ 28

Author(s):

D A Jans ◽

R Peters ◽

P Jans ◽

F Fahrenholz

Keyword(s):

Signal Transduction ◽

Epithelial Cells ◽

Lateral Diffusion ◽

Camp Production ◽

Lateral Mobility ◽

Renal Epithelial Cells ◽

Transduction Mechanisms ◽

Mobile Fraction ◽

Temperature Pretreatment

The role of hormone receptor lateral mobility in signal transduction was studied using a cellular system in which the receptor mobile fraction could be reversibly modulated to largely varying extents. The G-protein-coupled vasopressin V2-type receptor was labeled in LLC-PK1 renal epithelial cells using a fluorescent analogue of vasopressin, and receptor lateral mobility measured using fluorescence microphotolysis (fluorescence photobleaching recovery). The receptor mobile fraction (f) was approximately 0.9 at 37 degrees C and less than 0.1 at 10 degrees C, in accordance with previous studies. When cells were incubated for 1 h at 4 degrees C without hormone, and then warmed up to 37 degrees C and labeled with the vasopressin analogue, f increased from approximately 0.4 to 0.8 over approximately 1 h. The apparent lateral diffusion coefficient was not markedly affected by temperature pretreatment. Studies with radiolabeled vasopressin indicated that temperature pretreatment influenced neither receptor number nor binding/internalization kinetics. F-actin staining revealed that temperature change resulted in reversible changes of cytoskeletal structure. The maximal rate of in vivo cAMP production at 37 degrees C in response to vasopressin, but not to forskolin (receptor-independent agonist), was also markedly influenced by preincubation of cells at 4 degrees C, thus paralleling the effects of temperature preincubation on f. A linear correlation between f and maximal cAMP production was observed, suggesting that the receptor mobile fraction is a key parameter in hormone signal transduction in vivo. We conclude that mobile receptors are required to activate G-proteins, and discuss the implications of this for signal transduction mechanisms.

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