Mechanism of PCSK9-Mediated Macrophage Activation via the CAP1/NF-κB Pathway in CAWS-Induced Kawasaki Disease Vasculitis

Proprotein convertase subtilisin/kexin type 9 (PCSK9) acts as a pleiotropic modulator of inflammation. This study aimed to investigate the role and underlying mechanism of PCSK9 in Kawasaki disease (KD)-associated vasculitis. A Candida albicans water-soluble fraction (CAWS)-induced murine vasculitis model (n = 5-8 mice per group) and CAWS-stimulated RAW 264.7 macrophages (n = 3-8 independent experiments) were used. PCSK9 was pharmacologically inhibited in vivo with SBC-115076 and in vitro with PF-06446846. Vascular pathology, inflammatory markers, macrophage polarization, and signaling pathways were evaluated using hematoxylin-eosin (H&E) staining, immunofluorescence (IF), Western blot, quantitative real-time polymerase chain reaction (qRT-PCR), and RNA Sequencing (RNA-seq). CAP1 overexpression was performed via lentiviral Infection in RAW 264.7 cells to further validate its functional role. PCSK9 expression was significantly upregulated (two-fold) in the coronary arteries of CAWS-treated mice, and PCSK9 was predominantly co-localized with macrophages. Pharmacological inhibition of PCSK9 attenuated coronary arteritis, reduced the inflammatory infiltrate fraction by 54%, attenuated systemic inflammation, and decreased cardiac macrophage infiltration by 89%. In vitro, PCSK9 blockade suppressed CAWS-induced M1 macrophage polarization, as shown by reduced expression of the markers CD86 (by 96%) and iNOS (by 60%), and decreased secretion of the pro-inflammatory cytokines TNF-α (by 80%), IL-1β (by 86%), and IL-6 (by 89%). Transcriptomic analysis identified the NF-κB pathway as a key downstream signaling pathway. Mechanistically, PCSK9 inhibition downregulated CAP1 (adenylyl cyclase-associated protein 1) expression by 64% and suppressed NF-κB p65 nuclear translocation by 91% in macrophages. Importantly, CAP1 overexpression reversed the inhibitory effects of PCSK9 blockade on p65 nuclear translocation, M1 polarization, and inflammatory cytokine production. PCSK9 promotes KD-like vasculitis by activating the CAP1-mediated NF-κB pathway in macrophages, thereby driving pro-inflammatory responses. Pharmacological inhibition of PCSK9 attenuates vascular immunopathology, highlighting PCSK9 as a potential therapeutic target for KD.