A novel polysaccharide from Ligusticum chuanxiong attenuates cardiac hypertrophy by targeting ferroptosis through the SIRT3-mediated deacetylation of Foxo3a.

BACKGROUND: Pathological cardiac hypertrophy is a maladaptive response to pressure overload that frequently leads to heart failure, highlighting the urgent need for effective therapies. Plant-derived polysaccharides are promising bioactive candidates due to their safety and pleiotropic effects. Although Ligusticum chuanxiong has long been used for cardiovascular diseases, the structural features and mechanisms of its polysaccharides in cardiac hypertrophy remain unclear. PURPOSE: To isolate and characterize a novel polysaccharide from Ligusticum chuanxiong and elucidate its protective effects and molecular mechanism against pressure overload-induced cardiac hypertrophy. STUDY-DESIGN/METHODS: A homogeneous polysaccharide (FL-D2N1) was purified and structurally characterized by FT-IR, monosaccharide analysis, glycosidic linkage analysis, NMR, and SEC-MALLS-RI. Its in vivo cardioprotective effects were evaluated in TAC-induced heart failure mice by assessing cardiac function, hypertrophy, fibrosis, and ferroptosis. Transcriptomic profiling and mechanistic validation identified key pathways. In vitro, Ang II-stimulated cardiomyocytes were used to examine mitochondrial function, ferroptosis, mitophagy, dynamics, and energy metabolism. The SIRT3/Foxo3a axis was validated using pharmacological tools, immunofluorescence, immunoprecipitation, and SIRT3 siRNA. RESULTS: A novel galactan-type polysaccharide, FL-D2N1, was successfully isolated from Ligusticum chuanxiong rhizomes, exhibiting a weight-average molecular weight of 94.376 kDa and adopting a compact spherical conformation in aqueous solution. Structural elucidation revealed a highly branched architecture featuring a backbone of →6)-β-D-Galp-(1→, →3)-β-D-Galp-(1→, and →3,6)-β-D-Galp-(1→ residues, with α-L-Araf-(1→ units as side chains. In TAC-induced mice, FL-D2N1 administration markedly enhanced cardiac function, alleviated ventricular remodeling, diminished hypertrophy and fibrosis, and inhibited myocardial ferroptosis, as evidenced by decreased MDA and iron accumulation and restored GSH levels. Transcriptomic analysis coupled with mechanistic validation pinpointed SIRT3 as a central hub regulating FL-D2N1-conferred cardioprotection. FL-D2N1 upregulated SIRT3 expression alongside its deacetylase activity, facilitating Foxo3a deacetylation and subsequent transcriptional modulation of antioxidant and anti-ferroptotic programs. Functionally, FL-D2N1 enhanced PINK1/Parkin-mediated mitophagy, restored mitochondrial dynamics via MFN2 upregulation and Drp1 Ser616 dephosphorylation, preserved mitochondrial ultrastructure and membrane potential, reduced mitochondrial ROS overproduction, and improved mitochondrial respiratory function. Notably, SIRT3 silencing using specific siRNA abrogated the protective effects of FL-D2N1 on ferroptosis suppression, mitophagy enhancement, and mitochondrial preservation, confirming the indispensable function of the SIRT3/Foxo3a axis in its mechanism of action. CONCLUSION: FL-D2N1, a novel galactan from Ligusticum chuanxiong, attenuates pathological cardiac hypertrophy by suppressing ferroptosis and preserving mitochondrial quality control via the SIRT3/Foxo3a axis. This structurally defined natural polysaccharide represents a promising candidate for preventing and treating cardiac hypertrophy and heart failure.