Protein Phosphatase 2A Activation Attenuates Acute Myocardial Injury in Takotsubo Syndrome by Modulating Ferroptosis and Mitochondrial Injury in Cardiomyocytes
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Background
Takotsubo syndrome (TTS) is an acute stress-induced cardiomyopathy characterized by transient left ventricular dysfunction. Despite its reversible nature, TTS is associated with substantial morbidity and mortality in the acute phase, and no specific treatments are available. The precise molecular mechanisms that connect catecholamine stress to reversible myocardial injury are not fully understood. PP2A, a holoenzyme with serine/threonine phosphatase activity, plays a vital role in normal cardiac development, and its dysregulation has been associated with heart disease. Its role in TTS and its potential as a therapeutic target remain completely unknown.
Methods
Analysis of public multi-omics datasets from stress cardiomyopathy (SCM) and experimental models of TTS, along with treatment of cardiomyocytes with human TTS plasma, was used to investigate a potential role for protein phosphatase 2A (PP2A) in stress-induced myocardial injury. To clarify the functional impact of manipulating PP2A activity in TTS, we used a series of disease relevant cell based and in vivo models, leveraging both genetic and pharmacological approaches to modulate PP2A activity in cardiomyocytes and in mice. To gain mechanistic insights into how PP2A influences TTS pathology and downstream signaling pathways, RNA sequencing, stress-responsive iron handling, mitochondrial function, and cardiac phenotypes were thoroughly evaluated in both in vivo and in vitro studies.
Results
PP2A activity was markedly reduced in cardiac tissues from mice with isoprenaline-induced TTS, as well as in isoprenaline-treated cardiomyocytes. Genetic or pharmacological inhibition of PP2A worsened catecholamine-induced cardiac dysfunction and myocardial injury. Most notably, pharmacological activation of PP2A using an orally bioavailable small-molecule activator strongly mitigated myocardial damage and enhanced cardiac function in TTS models. Mechanistically, PP2A inactivation promoted JNK-MAPK signaling and dysregulated stress-responsive iron-handling pathways, leading to ferritinophagy-mediated ferroptosis and mitochondrial dysfunction. Pharmacological JNK inhibition effectively rescued myocardial injury caused by PP2A deficiency in two TTS animal models and in cardiomyocytes.
Conclusions
PP2A inactivation is a key molecular event linking catecholamine stress to myocardial injury in TTS. Restoring PP2A activity or inhibiting downstream JNK attenuates ferritinophagy-dependent stress responses and mitochondrial dysfunction, providing a unifying mechanistic framework and highlighting the PP2A-JNK axis as a potential target for short-term intervention during the acute phase of TTS.
CLINICAL PERSPECTIVE
What Is New?
• Protein phosphatase 2A (PP2A) activity is acutely suppressed during the early phase of Takotsubo syndrome (TTS), with preferential involvement of the apical myocardium, closely mirroring the disease’s characteristic clinical phenotype.
• Downstream of PP2A inactivation, catecholamine stress triggers JNK-MAPK signaling activation and dysregulated stress-responsive iron handling, including ferritinophagy-mediated ferroptosis and mitochondrial dysfunction in cardiomyocytes.
• Pharmacological restoration of PP2A activity or downstream inhibition of JNK mitigates acute myocardial injury and preserves cardiac function, thereby establishing the PP2A-JNK axis as a central stress-responsive pathway in TTS.
What Are the Clinical Implications?
• Identification of PP2A inactivation as a key molecular event highlights a novel opportunity for targeted intervention during the acute phase.
• Studies in preclinical animal TTS models provide the first evidence that illuminates the therapeutic potential of a small-molecule PP2A activator as a strategy for acute TTS and may serve as a broad cardioprotective strategy in settings where cardiac dysfunction is implicated.
• Targeting downstream JNK signaling, which is activated by PP2A inactivation, emerges as an additional mechanism-based strategy for attenuating acute myocardial injury in TTS.
