The JNK2-NLRP3 nexus in atrial fibrillation and its anti-AF therapeutic potentials

Excessive binge alcohol intake is a well-recognized risk factor for atrial fibrillation (AF), the most common arrhythmia with a high morbidity and mortality, yet current therapies have suboptimal effectiveness. [While aging is an unavoidable AF risk factor, alcohol as a secondary stressor exacerbates AF risk in the aging population.] Clinical data suggest that one-third of all new-onset AF cases are related to alcohol intoxication and alcohol abuse brings a high AF risk even in people without co-existing cardiovascular diseases. It is a classic concept that enhanced inflammation contributes to alcohol-caused organ damage, which could also lead to AF. However, the ineffectiveness of the anti-inflammation therapies in AF patients has demonstrated the urgent need to understand the detailed underlying mechanisms of inflammation-associated AF and explore novel anti-AF therapeutic targets. The goal of this proposal is to fill this knowledge gap by establishing a previously unrecognized crosstalk between the pro-inflammatory signaling pathways and the stress kinase JNK2 in AF pathogenesis. In human donor atria, binge alcohol exposure increased pro-inflammatory TNFα and IL1β-NLRP3 signaling along with activated JNK2. And TNFα or IL1β significantly enhanced diastolic SR Ca2+ leak and triggered activities (Ca2+ waves and delayed after depolarizations), while either JNK2 or NLRP3 inhibition effectively alleviated those triggered activities, suggesting a crosstalk between JNK2 and pro-inflammatory signaling. However, we found that only TNFα, but not IL1β, activates cJNK2. Yet, TNFα is known to upregulate IL1β signaling, which could explain the involvement of NLRP3 in TNFα-induced triggered activities. But why JNK2 is not influenced by IL1β yet is critically involved in IL1β-NLRP3-mediated Ca2+ mishandling remains completely unknown. [This proposal is thus aimed to establish a novel and potentially paradigm-shifting and translationally important link between the JNK2-NLRP3 nexus (as a pathological nodal point; it has never been revealed before) and a complex web of co-existing pro-inflammatory pathways in AF pathogenesis and most importantly, testing therapeutic potentials of targeting this pathological nexus as a novel anti-AF approach.] Our multi-discipline team will use a unique diversified approach (molecular biochemistry to single channel/myocytes/whole-heart electrophysiology in animal models/human donor hearts) to systematically address two Specific Aims 1) Determine the underlying mechanisms of the JNK2-NLRP3 feedback loop in atrial Ca2+ mishandling; 2) Establish the functional contribution of JNK2 and/or pro-inflammatory signaling pathways in binge alcohol-evoked arrhythmic activities and AF pathogenesis. The scientific premise of this proposal is strong because it integrates important functional measurements and fundamental mechanistic studies along with appropriate alternative approaches. [Cardiac specific interventions (in vivo atrial gene transfer & genetic modification & target-specific pharmacological inhibition) that limit cJNK2 and/or NLRP3-inflammasome activity will be used as proof-in-principal studies to prove the JNK2-NLRP3 feedback loop in AF pathogenesis and shed new light on future development of anti-AF therapeutic strategies and new drug discovery.]