Background/Aims: Induced pluripotent stem (iPS) cells generated from accessible adult cells of patients with genetic diseases open unprecedented opportunities for exploring the pathophysiology of human diseases in vitro. Catecholaminergic polymorphic ventricular tachycardia type 1 (CPVT1) is an inherited cardiac disorder that is caused by mutations in the cardiac ryanodine receptor type 2 gene (RYR2) and is characterized by stress-induced ventricular arrhythmia that can lead to sudden cardiac death in young individuals. The aim of this study was to generate iPS cells from a patient with CPVT1 and determine whether iPS cell-derived cardiomyocytes carrying patient specific RYR2 mutation recapitulate the disease phenotype in vitro. Methods: iPS cells were derived from dermal fibroblasts of healthy donors and a patient with CPVT1 carrying the novel heterozygous autosomal dominant mutation p.F2483I in the RYR2. Functional properties of iPS cell derived-cardiomyocytes were analyzed by using whole-cell current and voltage clamp and calcium imaging techniques. Results: Patch-clamp recordings revealed arrhythmias and delayed afterdepolarizations (DADs) after catecholaminergic stimulation of CPVT1-iPS cell-derived cardiomyocytes. Calcium imaging studies showed that, compared to healthy cardiomyocytes, CPVT1-cardiomyocytes exhibit higher amplitudes and longer durations of spontaneous Ca²⁺ release events at basal state. In addition, in CPVT1-cardiomyocytes the Ca²⁺-induced Ca²⁺-release events continued after repolarization and were abolished by increasing the cytosolic cAMP levels with forskolin. Conclusion: This study demonstrates the suitability of iPS cells in modeling RYR2-related cardiac disorders in vitro and opens new opportunities for investigating the disease mechanism in vitro, developing new drugs, predicting their toxicity, and optimizing current treatment strategies.

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Activation of neuronal nicotinic acetylcholine receptors (nAChR) provides neuroprotection against different toxic stimuli that often lead to overproduction of reactive oxygen species (ROS) and cell death. ROS production has been related with disease progression in several neurodegenerative pathologies such as Alzheimer's or Parkinson's diseases. In this context, we investigated here if the exposure of bovine chromaffin cells to the potent nAChR agonist epibatidine protected against rotenone (30 micromol/L) plus oligomycin (10 micromol/L) (rot/oligo) toxicity, an in vitro model of mitochondrial ROS production. Epibatidine induced a concentration- and time-dependent protection, which was maximal at 3 mumol/L after 24 h. Pre-incubation with dantrolene (100 micromol/L) (a blocker of the ryanodine receptor channel), chelerythrine (1 micromol/L) (a protein kinase C inhibitor), or PD98059 (50 micromol/L) (a MEK inhibitor), aborted epibatidine-elicited cytoprotection. Mitochondrial depolarization, ROS, and caspase 3 active produced by rot/oligo were also prevented by epibatidine. Epibatidine doubled the amount of heme oxygenase-1 (HO-1), a critical cell defence enzyme against oxidative stress. Furthermore, the HO-1 inhibitor Sn(IV) protoporphyrin IX dichloride reversed the epibatidine protecting effects and HO-1 inducer Co (III) protoporphyrin IX dichloride exhibited neuroprotective effects by itself. The results of this study point to HO-1 as the cytoprotective target of nAChR activation through the following pathway: endoplasmic reticulum Ca(2+)-induced Ca(2+)-release activates the protein kinase C/extracellular regulated kinase/HO-1 axis to mitigate mitochondrial depolarization and ROS production. This study provides a mechanistic insight on how nAChR activation translates into an antioxidant and antiapoptotic signal through up-regulation of HO-1.