Detection of Proteins on Blot Transfer Membranes

α1A-Subtype adrenergic agonist therapy for the failing right ventricle

Failure of the right ventricle (RV) is a serious disease with a poor prognosis and limited treatment options. Signaling by α₁-adrenergic receptors (α₁-ARs), in particular the α_1A-subtype, mediate cardioprotective effects in multiple heart failure models. Recent studies have shown that chronic treatment with the α_1A-subtype agonist A61603 improves function and survival in a model of left ventricular failure. The goal of the present study was to determine if chronic A61603 treatment is beneficial in a RV failure model. We used tracheal instillation of the fibrogenic antibiotic bleomycin in mice to induce pulmonary fibrosis, pulmonary hypertension, and RV failure within 2 wk. Some mice were chronically treated with a low dose of A61603 (10 ng·kg^-1·day^-1). In the bleomycin model of RV failure, chronic A61603 treatment was associated with improved RV fractional shortening and greater in vitro force development by RV muscle preparations. Cell injury markers were reduced with A61603 treatment (serum cardiac troponin I, RV fibrosis, and expression of matrix metalloproteinase-2). RV oxidative stress was reduced (using the probes dihydroethidium and 4-hydroxynonenal). Consistent with lowered RV oxidative stress, A61603 was associated with an increased level of the cellular antioxidant superoxide dismutase 1 and a lower level of the prooxidant NAD(P)H oxidase isoform NOX4. In summary, in the bleomycin model of RV failure, chronic A61603 treatment reduced RV oxidative stress, RV myocyte necrosis, and RV fibrosis and increased both RV function and in vitro force development. These findings suggest that in the context of pulmonary fibrosis, the α_1A-subtype is a potential therapeutic target to treat the failing RV.NEW & NOTEWORTHY Right ventricular (RV) failure is a serious disease with a poor prognosis and no effective treatments. In the mouse bleomycin model of RV failure, we tested the efficacy of a treatment using the α_1A-adrenergic receptor subtype agonist A61603. Chronic A61603 treatment improved RV contraction and reduced multiple indexes of RV injury, suggesting that the α_1A-subtype is a therapeutic target to treat RV failure.

Immunoblotting and Immunodetection

Immunoblotting (western blotting) is used to identify specific antigens recognized by polyclonal or monoclonal antibodies. This unit provides protocols for all steps, starting with solubilization of the protein samples, usually by means of SDS and reducing agents. Following solubilization, the material is separated by SDS-PAGE and the antigens are electrophoretically transferred to a membrane, a process that can be monitored by reversible staining with Ponceau S. The transferred proteins are bound to the surface of the membrane, providing access to immunodetection reagents. After nonspecific binding sites are blocked, the membrane is probed with the primary antibody and washed. The antibody-antigen complexes are tagged with fluorophores, horseradish peroxidase, or alkaline phosphatase coupled to a secondary anti-IgG antibody, and detected using appropriate fluorescent imaging technologies or with chromogenic or luminescent substrates. Finally, membranes may be stripped and reprobed. © 2017 by John Wiley & Sons, Inc.

Immunoblotting and Immunodetection

Immunoblotting (western blotting) is used to identify specific antigens recognized by polyclonal or monoclonal antibodies. This unit provides protocols for all steps, starting with solubilization of the protein samples, usually by means of SDS and reducing agents. Following solubilization, the material is separated by SDS-PAGE and the antigens are electrophoretically transferred to a membrane, a process that can be monitored by reversible staining with Ponceau S. The transferred proteins are bound to the surface of the membrane, providing access to immunodetection reagents. After nonspecific binding sites are blocked, the membrane is probed with the primary antibody and washed. The antibody-antigen complexes are tagged with fluorophores, horseradish peroxidase, or alkaline phosphatase coupled to a secondary anti-IgG antibody, and detected using appropriate fluorescent imaging technologies or with chromogenic or luminescent substrates. Finally, membranes may be stripped and reprobed.

Cardiac function is not significantly diminished in hearts isolated from young caveolin-1 knockout mice

Matrix metalloproteinases (MMPs) are known to degrade components of the extracellular matrix. More recently, in myocardial oxidative stress injury including ischemia-reperfusion, MMP-2 is activated and degrades troponin I and α-actinin. MMP activity is regulated at several levels. We recently showed that MMP-2 is localized in the caveolae of cardiomyocytes and is negatively regulated by caveolin-1 (Cav-1). The caveolin scaffolding domain of Cav-1 inhibits MMP-2 proteolytic activity in vitro, and Cav-1(-/-) mouse hearts have increased MMP-2 activity compared with controls. Whether this increase in MMP-2 activity translates to impaired cardiac function is unknown. Hearts isolated from Cav-1(-/-) mice and their wild-type controls were perfused as isolated working hearts and physiologically challenged with increasing increments of left atrial preload (7-22.5 mmHg). The hearts were then pharmacologically challenged with increasing concentrations of isoproterenol (0.1-100 nM). Functionally, the Cav-1(-/-) hearts were similar to the controls in heart rate, peak systolic pressure, developed pressure, and rate pressure product. At higher preload pressures, the Cav-1(-/-) hearts outperformed the control hearts. Coronary flow was significantly higher in Cav-1(-/-) hearts under all conditions. The highest concentration of isoproternol increased the heart rate of Cav-1(-/-) hearts more than in controls. Western blot analysis revealed no significant changes in troponin I or α-actinin between Cav-1(-/-) hearts and their controls. There was a significant loss of MMP-2 from both knockout and control hearts during the perfusion. In summary, despite the loss of Cav-1, Cav-1(-/-) hearts show similar or better cardiac function compared with wild-type hearts following physiological challenge or β-adrenergic stimulation in vitro, and this appears unrelated to changes in MMP-2.