Piezo1 drives microgravity-induced ANP secretion via calcium-JNK/c-Jun signaling in primary rat atrial cardiomyocytes

Weightlessness exposure during spaceflight induces cardiovascular deconditioning, including orthostatic intolerance (PSOI) upon re-exposure to gravity, partly attributed to dysregulated atrial natriuretic peptide (ANP) secretion. While ANP elevation occurs acutely in microgravity, the upstream mechanosensitive pathways regulating this response remain poorly understood. This study investigated the role of the mechanosensitive ion channel Piezo1 and the JNK/c-Jun signaling pathway in ANP regulation under simulated weightlessness. Primary rat atrial cardiomyocytes were exposed to simulated microgravity (SM) using a rotary cell culture system. Experimental groups included: Control, SM, SM treated with the stretch-activated channel (SAC) inhibitor streptomycin (STR), SM treated with the JNK inhibitor SP600125, SM with Piezo1 knockdown via lentiviral shRNA (performed prior to SM exposure), and normal gravity treated with the Piezo1 agonist Yoda1. ANP expression, JNK/c-Jun pathway activation, Piezo1 expression, and intracellular calcium levels were assessed using Western blot, RT-PCR, and flow cytometry. SM significantly increased ANP expression and activated the JNK/c-Jun pathway. Both STR and SP600125 suppressed SM-induced JNK phosphorylation and ANP upregulation. SM also increased Piezo1 expression and intracellular calcium. Piezo1 knockdown effectively prevented SM-induced JNK/c-Jun activation, ANP upregulation, and the increase in intracellular calcium, achieving an effect comparable to that of STR and SP600125. Conversely, Yoda1, a Piezo1 activator, mimicked the SM response under normal gravity by activating JNK/c-Jun and increasing ANP expression. STR inhibited SM-induced upregulation of Piezo1 expression. SP600125 blocked JNK/c-Jun activation and ANP upregulation but failed to prevent SM-induced calcium elevation. Short-term simulated weightlessness upregulates ANP expression in atrial cardiomyocytes via activation of the Piezo1 channel. Piezo1 mediates this effect by increasing intracellular calcium and subsequently activating the JNK/c-Jun signaling pathway. These findings identify Piezo1 as a critical upstream mechanosensor for microgravity-induced ANP dysregulation and highlight its potential as a therapeutic target for mitigating associated cardiovascular deconditioning, such as PSOI.