👤 Kaloyan Takov

PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibition is a potent cholesterol-lowering strategy. This study examined the effects of PCSK9 monoclonal antibodies (mAbs) and high-intensity statins beyond low-density lipoprotein cholesterol reduction, which are not fully defined, particularly in patients with acute myocardial infarction (MI). Proteomic and lipidomic analyses were conducted on plasma from 265 patients with acute MI from the PACMAN-AMI (Effects of the PCSK9 Antibody Alirocumab on Coronary Atherosclerosis in Patients With Acute Myocardial Infarction) randomized, placebo-controlled PCSK9 mAb trial and 34 patients without MI with hyperlipidemia from the Vienna Lipid Clinic registry, also receiving PCSK9 mAbs. Discovery proteomics revealed changes in apolipoproteins and increased PCOLCE (procollagen C-endopeptidase enhancer 1) levels in both the PCSK9 mAb and placebo groups after MI. UK Biobank data confirmed PCOLCE and PCSK9 upregulation as associated with statin use. Hepatoma cell experiments demonstrated a dose-dependent PCOLCE induction on statin treatment. Compared with placebo (statins only), PCSK9 mAb therapy resulted in greater reductions in APOB (apolipoprotein B), APOE (apolipoprotein E), APOC2 (apolipoprotein C2), and APOC3 (apolipoprotein C3), as shown by targeted proteomics. Mediation analysis indicated that these changes were largely explained by low-density lipoprotein cholesterol lowering. Lipidomics identified more pronounced reductions in cholesteryl esters, ceramides, sphingomyelins, phosphatidylcholines, triglycerides, and diglycerides in PCSK9 mAb-treated patients with MI. Results were largely consistent in patients without MI. However, levels of LPA (apolipoprotein[a]), the characteristic protein component of lipoprotein(a), remained unchanged in PCSK9 mAb-treated patients with MI, since a rise of LPA was observed in the placebo group post-MI. Most apolipoprotein changes after PCSK9 mAb therapy following MI were mediated by low-density lipoprotein cholesterol lowering. Statin use is associated with increased circulating PCOLCE, with hepatoma cell experiments supporting a predominant hepatic origin. Combining PCSK9 mAbs with high-intensity statins mitigates post-MI increases in lipoprotein(a). URL: https://www.clinicaltrials.gov; Unique identifier: NCT03067844. Show less

High-density lipoprotein (HDL) levels are reduced in patients with coronavirus disease 2019 (COVID-19), and the extent of this reduction is associated with poor clinical outcomes. While lipoproteins are known to play a key role during the life cycle of the hepatitis C virus, their influence on coronavirus (CoV) infections is poorly understood. In this study, we utilize cross-linking mass spectrometry (XL-MS) to determine circulating protein interactors of the severe acute respiratory syndrome (SARS)-CoV-2 spike glycoprotein. XL-MS of plasma isolated from patients with COVID-19 uncovered HDL protein interaction networks, dominated by acute-phase serum amyloid proteins, whereby serum amyloid A2 was shown to bind to apolipoprotein (Apo) D. XL-MS on isolated HDL confirmed ApoD to interact with SARS-CoV-2 spike but not SARS-CoV-1 spike. Other direct interactions of SARS-CoV-2 spike upon HDL included ApoA1 and ApoC3. The interaction between ApoD and spike was further validated in cells using immunoprecipitation-MS, which uncovered a novel interaction between both ApoD and spike with membrane-associated progesterone receptor component 1. Mechanistically, XL-MS coupled with data-driven structural modeling determined that ApoD may interact within the receptor-binding domain of the spike. However, ApoD overexpression in multiple cell-based assays had no effect upon viral replication or infectivity. Thus, SARS-CoV-2 spike can bind to apolipoproteins on HDL, but these interactions do not appear to alter infectivity. Show less

Proprotein convertase subtilisin/kexin type 9 (PCSK9) circulates in a free and lipoprotein-bound form, yet the functional consequence of the association between PCSK9 and high-density lipoprotein (HDL) remains unexplored. This study sought to interrogate the novel relationship between PCSK9 and HDL in humans. Comparing lipoprotein and apolipoprotein profiles by nuclear magnetic resonance and targeted mass spectrometry measurements with PCSK9 levels in the community-based Bruneck (n=656) study revealed a positive association of plasma PCSK9 with small HDL, alongside a highly significant positive correlation between plasma levels of PCSK9 and apolipoprotein-C3, an inhibitor of lipoprotein lipase. The latter association was replicated in an independent cohort, the SAPHIR study (n=270). Thus, PCSK9-HDL association was determined during the postprandial response in two dietary studies (n=20 participants each, 8 times points). Peak triglyceride levels coincided with an attenuation of the PCSK9-HDL association, a loss of apolipoprotein-C3 from HDL and lower levels of small HDL as measured by nuclear magnetic resonance. Crosslinking mass spectrometry (XLMS) upon isolated HDL identified PCSK9 as a potential HDL-binding partner. PCSK9 association with HDL was confirmed through size-exclusion chromatography and immuno-isolation. Quantitative proteomics upon HDL isolated from patients with coronary artery disease (n=172) returned PCSK9 as a core member of the HDL proteome. Combined interrogation of the HDL proteome and lipidome revealed a distinct cluster of PCSK9, phospholipid transfer protein, clusterin and apolipoprotein-E within the HDL proteome, that was altered by sex and positively correlated with sphingomyelin content. Mechanistically, HDL facilitated PCSK9-mediated low-density lipoprotein receptor degradation and reduced low-density lipoprotein uptake through the modulation of PCSK9 internalisation and multimerisation. This study reports HDL as a binder of PCSK9 and regulator of its function. The combination of -omic technologies revealed postprandial lipaemia as a driver of PCSK9 and apolipoprotein-C3 release from HDL. Show less