Modulation of CD73 by Betulinic acid antagonizes nucleotide metabolic dysregulation in silica nanoparticle-induced pulmonary fibrosis

Silica nanoparticles (SiNPs) exposure presents a growing public-health concern. The mechanisms driving SiNPs-induced pulmonary fibrosis and effective interventions remain unclear. This study investigated the contribution of CD73 to SiNPs-induced pulmonary fibrosis and evaluated the therapeutic mechanism of the natural compound Betulinic acid. We employed a mouse model of SiNPs-induced pulmonary fibrosis and achieved CD73 knockdown in mouse lung tissue via AAV5-mediated delivery. Fibrosis severity was evaluated by imaging, pulmonary function testing, and histopathology. We profiled metabolic alterations and interrogated the CD73-ADO-A2AR signaling axis and M2-macrophage polarization using untargeted metabolomics. Complementary in vitro experiments validated pathway function. Finally, the potential association between BA and CD73 and BA’s efficacy were assessed by network pharmacology, molecular docking, and in vitro functional assays. Metabolomic analysis revealed that SiNPs exposure disturbed nucleotide metabolism in mouse lung tissue. We therefore further explored the potential role of CD73, a nucleotide-metabolising enzyme, in SiNPs-triggered pulmonary fibrosis. Our results suggested that lung-wide CD73 knockdown attenuated lung-function impairment, reduced collagen deposition, and dampened SiNPs-induced macrophage M2-polarisation. SiNPs were found to up-regulate CD73, leading to ADO accumulation alongside increased A2AR expression, which may contribute to M2-macrophage polarisation, fibroblast activation and extracellular-matrix deposition. Betulinic acid (BA) ameliorated SiNPs-driven dysregulation within the CD73/ADO/A2AR pathway, reduced ADO accumulation, and suppressed subsequent macrophage M2-polarisation, thereby exerting anti-fibrotic effects in both in vitro and in vivo models. Together, these results suggest that SiNPs may drive macrophage M2-polarisation and pulmonary fibrosis partly through the CD73-ADO-A2AR axis, and that BA can dampen excessive activation of this pathway, representing a potential therapeutic strategy for SiNPs-related pulmonary fibrosis.