Ziprasidone triggers inflammasome signaling via PI3K-Akt-mTOR pathway to promote atrial fibrillation.

BACKGROUND: Second-generation antipsychotics increase the risk of atrial fibrillation. This study explores whether the atypical antipsychotic ziprasidone triggers inflammasome signaling, leading to atrial arrhythmia. METHODS: Electromechanical and pharmacological assessments were conducted on the rabbit left atria (LA). The patch-clamp technique was used to measure ionic channel currents in single cardiomyocytes. Detection of cytosolic reactive oxygen species production was performed in atrial cardiomyocytes. RESULTS: The duration of action potentials at 50 % and 90 % repolarization was dose-dependently shortened in ziprasidone-treated LA. Diastolic tension in LA increased after ziprasidone treatment. Ziprasidone-treated LA showed rapid atrial pacing (RAP) triggered activity. PI3K inhibitor, Akt inhibitor and mTOR inhibitor abolished the triggered activity elicited by ziprasidone in LA. The NLRP3 inhibitor MCC950 suppressed the ziprasidone-induced post-RAP-triggered activity. MCC950 treatment reduced the reverse-mode Na+/Ca2+ exchanger current in ziprasidone-treated myocytes. Cytosolic reactive oxygen species production decreased in ziprasidone-treated atrial myocytes after MCC950 treatment. Protein levels of inflammasomes and proinflammatory cytokines, including NLRP3, caspase-1, IL-1ß, IL-18, and IL-6 were observed to be upregulated in myocytes treated with ziprasidone. CONCLUSIONS: Our findings suggest ziprasidone induces atrial arrhythmia, potentially through upregulation of the NLRP3 inflammasome and enhancement of reactive oxygen species production via the PI3K/Akt/mTOR pathway.

Lemnalol Modulates the Electrophysiological Characteristics and Calcium Homeostasis of Atrial Myocytes.

Sepsis, an inflammatory response to infection provoked by lipopolysaccharide (LPS), is associated with high mortality, as well as ischemic stroke and new-onset atrial arrhythmia. Severe bacterial infections causing sepsis always result in profound physiological changes, including fever, hypotension, arrhythmia, necrosis of tissue, systemic multi-organ dysfunction and finally death. LPS challenge-induced inflammatory responses during sepsis may increase the likelihood of the arrhythmogenesis. Lemnalol is known to possess potent anti-inflammatory effects. This study examined whether Lemnalol (0.1 µM) could modulate the electrophysiological characteristics and calcium homeostasis of atrial myocytes under the influence of LPS (1µg/mL). Under challenge with LPS, Lemnalol-treated LA myocytes, had a longer AP duration at 20%, 50% and 90% repolarization of the amplitude, compared to the LPS-treated cells. LPS-challenged LA myocytes showed increased late sodium current, Na+-Ca2+ exchanger current, transient outward current, rapid component of delayed rectifier potassium current, tumor necrosis factor-α, NF-κB and increased phosphorylation of ryanodine receptor (RyR), but a lower L-type Ca2+ current than the control LA myocytes. Exposure to Lemnalol reversed the LPS-induced effects. The LPS-treated and control groups of LA myocytes, with or without the existence of Lemnalol. showed no apparent alterations in the sodium current amplitude or Cav1.2 expression. The expression of sarcoendoplasmic reticulum calcium transport ATPase (SERCA2) was reduced by LPS treatment, while Lemnalol ameliorated the LPS-induced alterations. The phosphorylation of RyR was enhanced by LPS treatment, while Lemnalol attenuated the LPS-induced alterations. In conclusion, Lemnalol modulates LPS-induced alterations of LA calcium homeostasis and blocks the NF-κB pathways, which may contribute to the attenuation of LPS-induced arrhythmogenesis.