Association between circulatory microRNA-218 expression, serum PCSK9 levels, inflammatory markers, and monocyte subsets in coronary artery disease patients: impact of statin therapy
Authors: Desouky Dina A. , Nosair Nahla A. , Sherif Dalia E. , El-Magd Mohammed A. , Salama Mohamed K. 
Published: June 2024

Abstract
Background
Proprotein convertase subtilisin/kexin type-9 (PCSK9), an enzyme produced mainly by hepatocytes and breaks low-density lipoprotein receptor (LDL-R), inflammatory markers [toll like receptor 4 (TLR4), high mobility group box 1 (HMGB1), tumor necrosis factor alpha (TNFα), c-reactive protein (CRP)], and monocyte subtypes are associated with coronary artery disease (CAD) pathogenesis. The circulating microRNA-218 (miR-218) can relieve CAD through the suppression of HMGB1 in monocyte-derived inflammatory cytokines. Herein, we explored the association between circulatory miR-218 expression and serum levels of PCSK9, inflammatory markers, and monocyte subtypes in statin and non-statin CAD patients. This study involved 91 healthy (control) and 91 stable CAD participants which were subdivided into no-statin (NS, n = 25), low-statin (LS, n = 25), and high-statin (HS, n = 41) groups. low-density lipoprotein cholesterol (LDL-C) and CRP serum levels were calorimetrically determined. Serum levels of PCSK9, TLR4, HMGB1, and TNFα were detected by ELISA, while monocyte subsets [classical (CM), intermediate (IM), non-classical (NC)] were calculated by flow cytometry. Circulatory miR-218 expression was detected by real-time PCR.

Results
The CAD group had significantly lower miR-218 expression and significantly higher levels of PCSK9, inflammatory markers (HMGB1, CRP, TLR4, and TNFα), and IM% than the control group. Among CAD patients, LS and HS groups had significantly lower miR-218 expression, LDL-C levels, and inflammatory markers and significantly higher levels of PCSK9 than the NS group. The HS group exhibited the lowest miR-218 expression and inflammatory markers and the highest PCSK9 levels. However, there were no significant changes in IM% among statin and non-statin groups. In the three CAD groups, miR-218 showed a significantly negative correlation with PCSK9 and inflammatory markers (HMGB1, CRP, TLR4, and TNFα), while this expression exhibited a significantly negative correlation with CM%, IM%, and NCM% only in the NS group. Results of multivariable linear regression indicated a correlation between miR-218 and five independent variables (PCSK9, HMGB1, CRP, TLR4, and TNFα) in the total statin (LS + HS) group, and eight independent variables (PCSK9, HMGB1, CRP, TLR4, and TNFα, CM%, IM%, NCM%) in the NS group. Provided that all other independent variables are constant, miR-218 expression was significantly correlated to CRP (Beta = 0.234) and PCSK9 (Beta =  − 0.875) in the total statin group; TLR4 (Beta =  − 0.554) in the LS group; HMGB1 (Beta =  − 0.507) in the HS group; and CRP (Beta =  − 0.745) in the NS group.

Conclusions
Statin-treated CAD patients have a unique negative correlation between miR-218 and PCSK9, HMGB1, and TLR4, and subsequently with CAD progress. Therefore, it could be recommended to combine activators of miR-218 and inhibitors of PCSK9, HMGB1, and TLR4 with statin to efficiently treat CAD.