SMPD1 Inhibition Attenuates Abdominal Aortic Aneurysm via Ceramide-Mediated NLRP3 Inflammatory Pathway

BACKGROUND: Abdominal aortic aneurysm (AAA) is a lethal cardiovascular disease with high heritability but no effective pharmacotherapy. We aimed to identify and experimentally validate AAA-associated proteins with causal genetic support as therapeutic targets. METHODS: We integrated large-scale AAA genome-wide association study and plasma proteomic data to identify causal proteins using Mendelian randomization, with validation in an independent cohort, colocalization, and multivariable Mendelian randomization single-cell RNA sequencing and cell isolation experiments identified the cellular source of SMPD1 (sphingomyelin phosphodiesterase 1) in AAA. Using recombinant SMPD1 and the inhibitor ASM-IN-1, we assessed the effects of SMPD1 in vitro on primary aortic endothelial cells and aortic smooth muscle cells and in vivo on AAA pathogenesis in PPE (porcine pancreatic elastase)-induced and angiotensin II-induced mouse models. We also assessed the role of ceramide (d18:1/16:0) in SMPD1‑driven AAA by measuring plasma ceramide levels, exogenous ceramide administration, and ASM‑IN‑1 rescue experiments. Therapeutic inhibition of SMPD1 with the Food and Drug Administration-approved drug amitriptyline was also assessed in vivo. RESULT: Mendelian randomization analysis identified 46 plasma proteins with causal genetic evidence for AAA, of which 6 (IL6R [interleukin-6 receptor], PCSK9 [proprotein convertase subtilisin/kexin type 9], NFKB1 [nuclear factor kappa B subunit], MMP1 [matrix metalloproteinase-1], TIMD4 [T-cell immunoglobulin and mucin domain-containing 4], and SMPD1) were validated. SMPD1 robustly colocalized with AAA susceptibility, an effect specifically mediated by ceramide (d18:1/16:0). SMPD1 was upregulated in AAA mice and originated from adventitial fibroblasts. Functional studies showed that SMPD1 promotes AAA by suppressing proliferation, inducing apoptosis/autophagy in endothelial cells and smooth muscle cells, amplifying inflammation, and promoting smooth muscle cell phenotypic switching. Moreover, SMPD1 drives AAA via the ceramide‑mediated NLRP3 inflammatory pathway. Pharmacological inhibition of SMPD1 with amitriptyline attenuated AAA progression. CONCLUSIONS: Integrated Mendelian randomization and experimental evidence identified SMPD1 as a novel AAA driver through the ceramide (d18:1/16:0)-mediated NLRP3 pathway, establishing SMPD1 as a promising therapeutic target.