Intrinsic-mediated caspase activation is essential for cardiomyocyte hypertrophy

Abstract

Cardiomyocyte hypertrophy is the cellular response that mediates pathologic enlargement of the heart. This maladaptation is also characterized by cell behaviors that are typically associated with apoptosis, including cytoskeletal reorganization and disassembly, altered nuclear morphology, and enhanced protein synthesis/ translation. Here, we investigated the requirement of apoptotic caspase pathways in mediating cardiomyocyte hypertrophy. Cardiomyocytes treated with hypertrophy agonists displayed rapid and transient activation of the intrinsic-mediated cell death pathway, characterized by elevated levels of caspase 9, followed by caspase 3 protease activity. Disruption of the intrinsic cell death pathway at multiple junctures led to a significant inhibition of cardiomyocyte hypertrophy during agonist stimulation, with a corresponding reduction in the expression of known hypertrophic markers (atrial natriuretic peptide) and transcription factor activity [myocyte enhancer factor-2, nuclear factor kappa B (NF-κB)]. Similarly, in vivo attenuation of caspase activity via adenoviral expression of the biologic effector caspase inhibitor p35 blunted cardiomyocyte hypertrophy in response to agonist stimulation. Treatment of cardiomyocytes with procaspase 3 activating compound 1, a small-molecule activator of caspase 3, resulted in a robust induction of the hypertrophy response in the absence of any agonist stimulation. These results suggest that caspase-dependent signaling is necessary and sufficient to promote cardiomyocyte hypertrophy. These results also confirm that cell death signal pathways behave as active remodeling agents in cardiomyocytes, independent of inducing an apoptosis response.

Caspase 3 cleavage of Pax7 inhibits self-renewal of satellite cells

“…To determine whether caspase 3 is important to this process, we injected the tibialis anterior (TA) muscle with an adenovirus containing a p35-IRES-GFP vector (or GFP alone as a control). The baculovirus p35 protein is a potent biologic inhibitor of caspase 3/7 activity, which we have previously used for in vivo characterization of caspase activity in the heart (19). Infection with the p35-containing virus (Adp35) at 2 d post-cardiotoxin (CTX) injury resulted in a significant reduction in the minimal Feret's diameter (with the majority of fibers measuring between 10-20 μm; 30.03 ± 2.27%) compared with control (AdGFP)-treated muscle (17.33 ± 4.52% of fibers between 10-20 μm) at 14 d postinjury ( Fig.…”

Expression of executioner procaspases and their activation by a procaspase-activating compound in chronic lymphocytic leukemia cells

“…First, in prior reports (Putinski et al 16 and Wang et al 17 ), activation of procaspase-3 before procaspase-9 was observed by the parent compound PAC-1. Second, although zinc ion binding sites have been identified on procaspase-9, 36 zymogen procaspase-9 exists as a monomer, and activation by zinc ion chelation requires dimerization.…”

“…PAC-1 (chemically, ortho-hydroxy N-acyl hydrazone) is the founding member of this class of compounds, and has shown promise in vitro, 11,13,14 in vivo, 11,15 and as a tool for studying procaspase-3 activation in various systems. 16,17 PAC-1 inhibited growth in primary colon tumors and mouse xenograft models, 11 through zinc ion chelation of executioner procaspase-3 and -7. 12 Recently, a next-generation PAC-1 combinatorial library of 837 compounds was designed and synthesized to identify more potent and cancer cell-selective apoptosis inducers.…”

Doxorubicin-induced chronic dilated cardiomyopathy—the apoptosis hypothesis revisited

“…As nicely shown by single cell imaging and quantitative systems biology studies of apoptosis, such sub-lethal caspase-3 activity can arise when tipping the balance for expression of proteins relevant in the post-MOMP pathway from pro-apoptotic to anti-apoptotic ones [31,68,69]. Indeed, a recent study also demonstrated that apoptosome dependent, sub-lethal caspase-activity can also lead, and even is essential, in a model of cardiomyocyte hypertrophic remodeling [70]. Specifically using hypertrophy inducing agonists, these study authors demonstrated that caspase-9 and caspase-3 were activated in the cardiomyocytes at an extent that was too low to induce apoptosis.…”