Magnolin Promotes PINK1-Parkin-mediated Mitophagy in Diffuse Large B-cell Lymphoma Cells via PPAR-γ Pathway

Diffuse large B-cell lymphoma (DLBCL) is both genetically and phenotypically heterogeneous, yet precise treatment strategies are insufficient. Magnolin, a natural compound derived from the Magnolia plant, has been clinically used for its anti-allergic, anti-inflammatory, antihypertensive, and antibacterial effects. Recent studies have shown its promising therapeutic effects in tumor treatment. However, the anti-tumor effects of Magnolin in DLBCL remain unverified.

This study aimed to elucidate the effects of Magnolin in DLBCL and reveal the underlying molecular mechanisms in vitro.

DLBCL cell lines, including LY1 and LY10, were used in the study. The drug library screening (n = 1746) was used to screen effective anti-lymphoma drugs and its synergetic anti-tumor drugs. The intricate molecular mechanism of Magnolin was explored using network pharmacology and molecular docking analyses. Using the drug affinity responsive target stability (DARTS) assay, the potential of Magnolin to target peroxisome proliferator-activated receptor gamma (PPAR-γ) was explored. Mitochondrial membrane potential (MMP), superoxide and the colocalization of mitochondria and lysosomes were evaluated by confocal microscopy. Co-immunoprecipitation (CO-IP) and immunofluorescence were performed to verify the PPAR-γ interactive proteins.

Through the drug library screening (n = 1746), Magnolin was identified as an effective anti-tumor drug for DLBCL, which effectively inhibited the progression of DLBCL through inhibiting cell viability, proliferation, and inducing cell cycle arrest (LY1, IC50=53 μM, LY10, IC50=42 μM). Besides, Magnolin treatment resulted in a decrease in mitochondrial membrane potential and an increase in MitoSOX in DLBCL. The colocalization of mitochondria with autophagosomes and lysosomes was increased after Magnolin treatment, indicating the activation of mitophagy pathway. The mitophagy inducer carbonyl cyanide 3-chlorophenylhydrazone (CCCP) enhanced the anti-tumor effect of Magnolin. Moreover, Magnolin was found to exert synergetic anti-tumor effects with Venetoclax in DLBCL based on the drug library screening and cell viability assays. Mechanistically, we identified PPAR-γ as a downstream molecule of Magnolin through network pharmacology and molecular docking analyses. Using DARTS, CO-IP and immunofluorescent assays, Magnolin was found to exert anti-lymphoma effects by directly binding to PPAR-γ, thereby increasing expression of PPAR-γ and promoting its transfer from nuclei to cytoplasm. In addition, PPAR-γ could interact with PINK1 in DLBCL, and then promoted mitophagy by activating PINK1-Parkin pathway.

In summary, our findings firstly identified the anti-tumor effects of Magnolin in DLBCL cells and highlighted that Magnolin promoted mitophagy in DLBCL cells through activating PPAR-γ/PINK1-Parkin pathway, which proposed a novel therapeutic strategy for DLBCL treatment.