The Application of Peptide Nucleic Acids (PNA) in the Inhibition of Proprotein Convertase Subtilisin/Kexin 9 (PCSK9) Gene Expression in a Cell-Free Transcription/Translation System

Proprotein convertase subtilisin/kexin 9 (PCSK9) is a protein that plays a key role in the metabolism of low-density lipoprotein (LDL) cholesterol. The gain-of-function mutations of the PCSK9 gene lead to a reduced number of surface LDL receptors by binding to them, eventually leading to endosomal degradation. This, in turn, is the culprit of hypercholesterolemia, resulting in accelerated atherogenesis. The modern treatment for hypercholesterolemia encompasses the use of biological drugs against PCSK9, like monoclonal antibodies and gene expression modulators such as inclisiran-a short, interfering RNA (siRNA). Peptide nucleic acid (PNA) is a synthetic analog of nucleic acid that possesses a synthetic peptide skeleton instead of a phosphate-sugar one. This different structure determines the unique properties of PNA (e.g., neutral charge, enzymatic resistance, and an enormously high affinity with complementary DNA and RNA). Therefore, it might be possible to use PNA against PCSK9 in the treatment of hypercholesterolemia. We sought to explore the impact of three selected PNA oligomers on PCSK9 gene expression. Using a cell-free transcription/translation system, we showed that one of the tested PNA strands was able to reduce the PCSK9 gene expression down to 74%, 64%, and 68%, as measured by RT-real-time PCR, Western blot, and HPLC, respectively. This preliminary study shows the high applicability of a cell-free enzymatic environment as an efficient tool in the initial evaluation of biologically active PNA molecules in the field of hypercholesterolemia research. This cell-free approach allows for the omission of the hurdles associated with transmembrane PNA transportation at the early stage of PNA selection.

Antibody-Based Therapeutics for Atherosclerosis and Cardiovascular Diseases

Cardiovascular disease is the leading cause of death worldwide, and its prevalence is increasing due to the aging of societies. Atherosclerosis, a type of chronic inflammatory disease that occurs in arteries, is considered to be the main cause of cardiovascular diseases such as ischemic heart disease or stroke. In addition, the inflammatory response caused by atherosclerosis confers a significant effect on chronic inflammatory diseases such as psoriasis and rheumatic arthritis. Here, we review the mechanism of action of the main causes of atherosclerosis such as plasma LDL level and inflammation; furthermore, we review the recent findings on the preclinical and clinical effects of antibodies that reduce the LDL level and those that neutralize the cytokines involved in inflammation. The apolipoprotein B autoantibody and anti-PCSK9 antibody reduced the level of LDL and plaques in animal studies, but failed to significantly reduce carotid inflammation plaques in clinical trials. The monoclonal antibodies against PCSK9 (alirocumab, evolocumab), which are used as a treatment for hyperlipidemia, lowered cholesterol levels and the incidence of cardiovascular diseases. Antibodies that neutralize inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-17, and IL-12/23) have shown promising but contradictory results and thus warrant further research.

Personalized medicine in lipid-modifying therapy

The choice of lipid-modifying treatment is largely based on the absolute level of cardiovascular risk and baseline lipid profile. Statins are the first-line treatment for most patients requiring reduction of low-density-lipoprotein cholesterol (LDL-C) and ezetimibe and proprotein convertase subtilisin/kexin type 9 inhibitors can be added to reach LDL-C targets. Statins have some adverse effects that are somewhat predictable based on phenotypic and genetic factors. Fibrates or omega-3 fatty acids can be added if triglyceride levels remain elevated. The RNA-targeted therapeutics in development offer the possibility of selective liver targeting for specific lipoproteins such as lipoprotein(a) and long-term reduction of LDL-C with infrequent administration of a small-interfering RNA may help to overcome the problem of adherence to therapy.

State of the art in diagnostics of ischemic heart disease and current recommended therapeutic approach

Several changes have occurred during last few years in diagnostics and treatment of the ischemic heart disease, especially due to introduction of so called high-sensitive troponins, implementation of new antiplatelet drugs, using of drug-eluting stents in percutaneous coronary interventions or novel definitions of acute myocardial infarction types. The European Society of Cardiology and Czech Society of Cardiology established new recommendations for management of both acute and chronic forms of the ischemic heart disease. Recently discovered inhibitors of the PCSK9 molecule that have been slowly introduced in the clinical practice represent a breakthrough in the treatment of dyslipidemia. Future research will certainly aim at detection of early forms of the atherosclerotic involvement of the coronary arteries.

Role of Proprotein Convertase Subtilisin/Kexin Type 9 in the Pathogenesis of Graves' Orbitopathy in Orbital Fibroblasts

BACKGROUND

The proprotein convertase subtilisin/kexin type 9 (PCSK9) has been implicated in the pathogenesis of inflammatory diseases. We sought to investigate the role of PCSK9 in the pathogenesis of Graves' orbitopathy (GO) and whether it may be a legitimate target for treatment.

METHODS

The PCSK9 was compared between GO (n=11) and normal subjects (n=7) in orbital tissue explants using quantitative real-time PCR, and in cultured interleukin-1β (IL-1β)-treated fibroblasts using western blot. Western blot was used to identify the effects of PCSK9 inhibition on IL-1β-induced pro-inflammatory cytokines production and signaling molecules expression as well as levels of adipogenic markers and oxidative stress-related proteins. Adipogenic differentiation was identified using Oil Red O staining. The plasma PCSK9 concentrations were compared between patients with GO (n=44) and healthy subjects (n=26) by ELISA.

RESULTS

The PCSK9 transcript level was higher in GO tissues. The depletion of PCSK9 blunted IL-1β-induced expression of intercellular adhesion molecule 1 (ICAM-1), IL-6, IL-8, and cyclooxygenase-2 (COX-2) in GO and non-GO fibroblasts. The levels of activated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and phosphorylated forms of Akt and p38 were diminished when PCSK9 was suppressed in GO fibroblasts. Decreases in lipid droplets and attenuated levels of peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer-binding protein β (C/EBPβ), and leptin as well as hypoxia-inducible factor 1α (HIF-1α), manganese superoxide dismutase (MnSOD), thioredoxin (Trx), and heme oxygenase-1 (HO-1) were noted when PCSK9 was suppressed during adipocyte differentiation. The plasma PCSK9 level was significantly higher in GO patients and correlated with level of thyrotropin binding inhibitory immunoglobulin (TBII) and the clinical activity score (CAS).

CONCLUSIONS

PCSK9 plays a significant role in GO. The PCSK9 inhibition attenuated the pro-inflammatory cytokines production, oxidative stress, and fibroblast differentiation into adipocytes. PCSK9 may serve as a therapeutic target and biomarker for GO.

Meta-analysis of Randomized Controlled Trials Assessing the Impact of Proprotein Convertase Subtilisin/Kexin Type 9 Antibodies on Mortality and Cardiovascular Outcomes

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition by monoclonal antibodies has been shown to reduce low density lipoprotein (LDL-C) but its effects on cardiovascular (CV) outcomes have not been fully described. The aim of this study is to assess the impact of PCSK9 inhibition on mortality and CV outcomes by pooling data from all available randomized clinical trials (RCT) of PCSK9 inhibitors. We conducted a comprehensive search of electronic databases, up to December 1, 2018, for all RCTs comparing PCSK9 inhibition to placebo or ezetimibe in patients with hypercholesterolemia or coronary artery disease receiving maximally tolerated statin for primary or secondary prevention of mortality and cardiovascular outcomes. We used random-effects meta-analyses to summarize the studies. We retained 23 RCTs having included 88,041 patients in primary and secondary prevention. The follow-up ranged from 6 to 36 months. PCSK9 inhibition was not significantly associated with reductions in total mortality (odds ratio [OR] 0.91, 95% confidence interval [CI] 078 to 1.06; p = 0.22) and CV mortality (OR 0.95, 95% CI 0.84 to 1.07; p = 0.37). In contrast, PCSK9 inhibition was associated with reductions in myocardial infarction (OR 0.80, 95% CI 0.71 to 0.91; p <0.0001), stroke (OR 0.75, 95% CI 0.65 to 0.85; p <0.0001), and coronary revascularization (OR 0.82, 95% CI 0.77 to 0.88; p <0.0001). In conclusion, PCSK9 inhibition was associated with reductions in myocardial infarction, stroke, and coronary revascularization. Future analyses may identify high-risk patients who may benefit more from these agents and longer follow-up of current or new trials may show a mortality benefit.

Inhibiting PCSK9 - biology beyond LDL control

Clinical trials have unequivocally shown that inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) efficaciously and safely prevents cardiovascular events by lowering levels of LDL cholesterol. PCSK9 in the circulation is derived mainly from the liver, but the protein is also expressed in the pancreas, the kidney, the intestine and the central nervous system. Although PCSK9 modulates cholesterol metabolism by regulating LDL receptor expression in the liver, in vitro and in vivo studies have suggested that PCSK9 is involved in various other physiological processes. Although therapeutic PCSK9 inhibition could theoretically have undesired effects by interfering with these non-cholesterol-related processes, studies of individuals with genetically determined reduced PCSK9 function and clinical trials of PCSK9 inhibitors have not revealed clinically meaningful adverse consequences of almost completely eradicating PCSK9 from the circulation. The clinical implications of PCSK9 functions beyond lipid metabolism in terms of wanted or unwanted effects of therapeutic PCSK9 inhibition therefore appear to be limited. The objective of this Review is to describe the physiological role of PCSK9 beyond the LDL receptor to provide a rational basis for monitoring the effects of PCSK9 inhibition as these drugs gain traction in the clinic.

[Cholesterol-lowering treatment with PCSK9-inhibitors]

Monoclonal antibodies inhibiting proprotein convertase subtilisin-kexin type 9 constitute a new class of lipid-lowering drugs. Currently, evolocumab and alirocumab are marketed. A recent cardiovascular outcome study with evolocumab has shown a cardiovascular (CV) event reduction of 15% in high-risk individuals at very low levels of low-density lipoproteins. The adverse event profile up to two years is mild. Treatment is very costly, and data on CV endpoints are still limited. Treatment is restricted to patients at very high risk of getting CV diseases and on a maximal tolerated statin and ezetimibe treatment in addition to dietary intervention.