Uremic toxin-induced pathological signaling in sinus node cells is attenuated by probenecid

Uremic toxins, including indoxyl sulfate (IS) and p-cresyl sulfate (PCS), contribue to cardiac fibrosis and maladaptive remodeling in chronic kidney disease (CKD). Although their roles in ventricular and vascular pathology are well established, their effects on sinus node cells and the associated molecular alterations remain poorly defined. Understanding how the uremic milieu affects sinus node cell homeostasis may provide insight into CKD-associated conduction abnormalities.

To investigate uremic toxin-induced stress responses, H9C2 cardiomyocytes were used as a comparative cardiac stress-model, whereas primary sinus node cells served as the principal pacemaker-relevant model. Both cell types were treated with IS and PCS. Profibrotic, pro-apoptotic, and stress-related signaling pathways were evaluated by protein and mRNA analyses, together p38 and ERK activation. In parallel, a CKD mouse model was generated by 2-week adenine feeding, and sinus node cells were isolated for molecular analysis. The effects of probenecid were examined in cultured cells and ex vivo using primary sinus node cells isolated from adenine-fed mice. Results IS and PCS induced profibrotic, pro-apoptotic, and remodeling-associated signaling in both H9C2 cardiomyocytes and primary sinus node cells, indicating activation of shared cardiac stress pathways. Conclusions regarding pacemaker-relevant molecular alterations were based primarily on primary sinus node cell findings, including cells isolated from 2-week adenine-fed mice., In primary sinus node cells, uremic toxin exposure increased fibronectin accumulation, altered the Bax/Bcl-2 balance, and activated p38 and ERK signaling, whereas TBX3 expression remained unchanged. changes occurred without overt loss of this pacemaker identity marker. These findings indicate apoptosis-associated, profibrotic, and stress-responsive molecular alterations rather than direct evidence of functional pacemaker impairment. Sinus node cells isolated from adenine-fed mice showed similar remodeling-associated molecular marker changes. Probenecid attenuated fibronectin accumulation, Bax/Bcl-2 imbalance, and stress kinase activation in primary sinus node cells, with similar effects observed ex vivo in cells isolated from adenine-fed mice.

These findings suggest that uremic toxin-driven stress signaling is associated with molecular remodeling signatures in sinus node cells under CKD-related conditions. Although the functional consequences of these molecular alterations were not assessed, probenecid attenuated uremic toxin-associated profibrotic, pro-apoptotic, and stress kinase signaling, suggesting that targeting molecular stress pathways may help strategy sinus node cell homeostasis in CKD.