Lipoprotein(a) Triggers CD36-Dependent IL-6/RhoA-GTP Axis Activation and Epigenetic Regulation of miRNA Expression in Coronary Artery Spasm

Background: Lipoprotein(a) [Lp(a)]-induced inflammation contributes to coronary artery spasm (CAS) by contraction of vascular smooth muscle cells. However, the interaction between Lp(a) and soluble CD36 (sCD36)/interleukin(IL)-6/RAS Homolog Family Member A(RhoA)-GTP signaling pathway has not been evaluated. Methods: We investigated the relevance of Lp(a)/CD36 signaling in CAS patient monocyte-derived macrophages (PMDMs) and human coronary artery smooth muscle cell (HCASMC) line using expression profile correlation analyses, molecular docking, RNA sequencing, flow cytometry, immunoblotting and quantitative reverse transcription polymerase chain reaction. Results: Plasma Lp(a) and sCD36 levels in 41 CAS patients were significantly higher (p = 0.001) and positively correlated (r2 = 0.3145, p < 0.001), a trend not observed in 36 non-CAS controls. RNA-sequencing indicated a significant co-overexpression of CD36 and RhoA in Lp(a)-treated CAS PMDMs and HCASMCs, of which the mRNA and protein expression of CD36 and RhoA were significantly enhanced (p < 0.001) dose-dependently. Lp(a) rather than LDL preferentially induced CD80+ PMDM (M1) polarization. In HCASMCs, the CD36 knockdown using either short hairpin RNA or natural biflavonoid amentoflavone suppressed Lp(a)-upregulated protein expression of CD36, RhoA-GTP, IL-6, tumor necrosis factor(TNF)-α, nuclear factor(NF)-κB and CD80; however, overexpressed CD36 increased their levels. Lp(a) decreased and amentoflavone increased the epigenetic expression of CD36 inhibitors, miR-335-5p and miR-448, respectively. Reciprocally, miRNA inhibitor or mimic could magnify or diminish Lp(a)-induced CD36, TNF-α, NF-κB and IL-6 expressions on HCASMCs, respectively. Conclusions: Elevated Lp(a) levels upregulate the CD36-dependent TNF-α/NF-κB/IL-6/RhoA-GTP signaling pathway in CAS PMDMs and HCASMCs, indicating that Lp(a)/CD36 inflammatory signaling, HCASMC activation and macrophage M1 polarization mediate CAS development.