Secoisolariciresinol diglucoside ameliorates muscarinic acetylcholine receptor mediated activation of NLRP3 inflammasome in cardiomyocytes

BACKGROUND: Secoisolariciresinol diglucoside (SDG), the main lignan found in flaxseed, contributes to cardioprotection. However, its molecular mechanism of action remains unknown. NOD-like receptor protein containing domain 3 (NLRP3), a critical mediator in inflammatory pathways, is one of the key players in cardiovascular disease progression and is a promising target for cardioprotective interventions. This study investigated the immunomodulatory effect of SDG in regulating acetylcholine receptor-mediated activation of the NLRP3 inflammasome. METHODS AND RESULTS: HL-1 mouse cardiomyocytes were treated with carbachol, a cholinergic agonist, and analyzed for the expression and activation of NLRP3 family members (NLRP3, ASC, Caspase-1, IL-18, and IL-1beta). Investigations included preconditioning with SDG, NF-kappa B (NF-κB) inhibitor, or antagonists for acetylcholine receptors. NLRP3 components and NF-κB were analyzed by immunostaining and immunofluorescence. Caspase-1 activity and gasdermin D expression were studied as the functional endpoints of NLRP3 activation. Carbachol induced the activation of NLRP3 inflammasomes in HL-1 cardiomyocytes. Pre-treatment with SDG significantly attenuated the carbachol-induced activation of NLRP3 inflammasome. NLRP3 activation was also subdued in the presence of atropine, and NF-κB activation inhibitor, confirming the role of the muscarinic receptor and the NF-κB pathway, respectively. CONCLUSION: The study revealed the beneficial therapeutic properties of SDG as an anti-inflammatory agent that can help prevent NLRP3-induced inflammation. Further, the findings highlight the pro-inflammatory property of muscarinic cholinergic system, in contrast to the known nicotinic cholinergic anti-inflammatory system.