Abstract
Systemic hypertension increases cardiac workload causing cardiomyocyte hypertrophy and increased cardiac fibrosis. An underlying feature is increased production of reactive oxygen species. Redox-sensitive ASK1 (apoptosis signal-regulating kinase 1) activates stress-regulated protein kinases (p38-MAPK [mitogen-activated protein kinases] and JNKs [c-Jun N-terminal kinases]) and promotes fibrosis in various tissues. Here, we determined the specificity of ASK1 signaling in the heart, with the hypothesis that ASK1 inhibitors may be used to manage fibrosis in hypertensive heart disease. Using immunoblotting, we established that moderate levels of H2O2 activate ASK1 in neonatal rat cardiomyocytes and perfused rat hearts. ASK1 was activated during ischemia in adult rat hearts, but not on reperfusion, consistent with activation by moderate (not high) reactive oxygen species levels. In contrast, IL (interleukin)-1β activated an alternative kinase, TAK1 (transforming growth factor-activated kinase 1). ASK1 was not activated by IL1β in cardiomyocytes and activation in perfused hearts was due to increased reactive oxygen species. Selonsertib (ASK1 inhibitor) prevented activation of p38-MAPKs (but not JNKs) by oxidative stresses in cultured cardiomyocytes and perfused hearts. In vivo (C57Bl/6J mice with osmotic minipumps for drug delivery), selonsertib (4 mg/[kg·d]) alone did not affect cardiac function/dimensions (assessed by echocardiography). However, it suppressed hypertension-induced cardiac hypertrophy resulting from angiotensin II (0.8 mg/[kg·d], 7d), with inhibition of Nppa/Nppb mRNA upregulation, reduced cardiomyocyte hypertrophy and, notably, significant reductions in interstitial and perivascular fibrosis. Our data identify a specific reactive oxygen species→ASK1→p38-MAPK pathway in the heart and establish that ASK1 inhibitors protect the heart from hypertension-induced cardiac remodeling. Thus, targeting the ASK1→p38-MAPK nexus has potential therapeutic viability as a treatment for hypertensive heart disease.
Highlights
Abstract —Systemic hypertension increases cardiac workload causing cardiomyocyte hypertrophy and increased cardiac fibrosis
ASK1 is activated in mouse models of pressure-overload,[14] ischemia/ reperfusion,[18] myocardial infarction,[14] and hypertension induced by Ang II,[19] all of which are associated with increased ROS
Activation of ASK1 compared with an alternative MAP3K (TAK1) was assessed by immunoblotting with antibodies to the activation loop phosphorylation sites
Summary
Abstract —Systemic hypertension increases cardiac workload causing cardiomyocyte hypertrophy and increased cardiac fibrosis. The p38 (p38-MAPK [mitogen-activated protein kinases]) and JNK (c-Jun N-terminal kinases) cascades are key modulators of the cell survival versus apoptosis/death balance. Both are Hypertension is available at https://www.ahajournals.org/journal/hyp. These are phosphorylated/activated by upstream MAP3Ks (MKK kinases) which are more numerous, potentially responding selectively to specific stresses.[12] The greater diversity at the MAP3K level provides increased potential for selective targeting Two such kinases are MAP3K5 (ASK1 [apoptosis signal-regulating kinase 1]) and MAP3K7 (TAK1 [transforming growth factor–activated kinase 1]), each of which has been placed upstream of both p38-MAPKs and JNKs in noncardiac cells where they regulate cell death responses.[13]. Therapies targeting ASK1 are in development,[21] and cardiac ASK1 is an attractive target for heart failure.[22]
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