PLA2G2A inhibition by Aristolochic acid IVa suppresses colonic inflammation in experimental colitis

Aristolochic acid IVa (AAIVa), a bioactive analogue derived from Aristolochiaceae herbs traditionally used in Chinese medicine, exhibits potent anti-inflammatory properties without the known toxicities associated with other aristolochic acids. This study aimed to elucidate AAIVa's specific interaction with phospholipase A2 (PLA₂) isoforms and evaluate its immunopharmacological potential in dextran sulfate sodium (DSS)-induced colitis, a model of inflammatory bowel disease (IBD).

Computational docking and experimental validations, including Drug Affinity Responsive Target Stability and Cellular Thermal Shift Assay, demonstrated selective binding of AAIVa to PLA2G2A, a secreted PLA₂ isoform upregulated in IBD and implicated in arachidonic acid-mediated inflammation, with dose-dependent enzymatic inhibition (IC₅₀ = 58 μM). In BALB/c mice subjected to 4.25% DSS for 10 days, oral administration of AAIVa (30 mg/kg/day) significantly ameliorated disease severity, as evidenced by improved Disease Activity Index scores (p < 0.05 on days 9-10), restored colon length (10.54 ± 0.12 cm vs. 8.99 ± 0.15 cm in DSS group, p < 0.05), reduced histopathological damage, and decreased myeloperoxidase expression. Mechanistically, AAIVa suppressed colonic PLA₂ activity by 43%, lowered arachidonic acid levels, and inhibited pro-inflammatory responses in LPS-stimulated RAW264.7. The anti-inflammatory effects of AAIVa were attenuated by recombinant PLA2G2A or genetic overexpression of Pla2g2a, whereas exogenous arachidonic acid supplementation reversed both its anti-inflammatory activity and its modulation of M2 macrophage polarization.

These findings suggest that AAIVa targets PLA2G2A and its downstream lipid pathway to attenuate inflammation and shape macrophage phenotypes in experimental colitis, highlighting its therapeutic potential in IBD.