The Central Role of Proprotein Convertase Subtilisin/Kexin Type 9 in Septic Pathogen Lipid Transport and Clearance

Aerosol Toxicokinetics: A Framework for Unraveling Toxicological Dynamics from Air to the Body

Exposure to atmospheric aerosols threatens human health and is yet to be effectively addressed globally. Aerosol toxicity strongly depends upon components whose chemical profiles and concentrations can constantly evolve throughout atmospheric transformation, inhalation, distribution, metabolism, and excretion. Despite the abundant studies on aerosol components and their toxic effects, the dynamics in component concentrations and related biological effects from air to the body remain unclear. Here, we propose a conceptual toxicokinetic framework to mathematically deduce the bioavailable concentration from the changing bulk concentration of aerosol constituents in the atmosphere. The biological effects of single or multiple components are further predicted via toxicodynamic modeling according to their bioavailable concentrations. Atmospheric concentrations of toxic composition can in turn be regulated by risk-based guidelines, aiming to alleviate in vivo toxic effects. This perspective demonstrates how serial toxicokinetic-toxicodynamic equations bridge the knowledge gap between ambient aerosols and associated toxic effects in human bodies. The prediction from an inhalation perspective also allows connecting with the exposomes from aggregate exposure pathways. We call for the development of the model validity and integrate quantitative adverse outcome pathways to apply for exposure-disease modeling, providing novel insights into air quality policymaking and public health management.

Lipopolysaccharide, arbiter of the gut-liver axis, modulates hepatic cell pathophysiology in alcoholism

Over the last four decades, clinical research and experimental studies have established that lipopolysaccharide (LPS)-a component of the outer membrane of gram-negative bacteria-is a potent hepatotoxic molecule in humans and animals. Alcohol abuse is commonly associated with LPS endotoxemia. This review highlights LPS molecular structures and modes of release from bacteria, plasma LPS concentrations, induction of microbiota dysbiosis, disruption of gut epithelial barrier, and translocation of LPS into the portal circulation impacting the pathophysiology of hepatic cells via the gut-liver axis. We describe and illustrate the portal vein circulation and its distributaries draining the gastrointestinal tract. We also elaborate on the gut-liver axis coupled with enterohepatic circulation that represents a bidirectional communication between the gut and liver. The review also updates the data on how circulating LPS is cleared in a coordinated effort between Kupffer cells, hepatocytes, and liver sinusoidal endothelial cells. Significantly, the article reviews and updates the modes/mechanisms of action by which LPS mediates the diverse pathophysiology of Kupffer cells, hepatocytes, sinusoidal endothelial cells, and hepatic stellate cells primarily in association with alcohol consumption. Specifically, we review the intricate linkages between ethanol, microbiota dysbiosis, LPS production, gut-liver axis, and pathophysiology of various hepatic cells. The maintenance of the gut barrier structural and functional integrity and microbiome homeostasis is essential in mitigating alcoholic liver disease and improving liver health.

Low LDL cholesterol and risk of bacterial and viral infections: observational and Mendelian randomization studies

Aims

Low levels of LDL cholesterol may be associated with risk of infectious disease. We tested the hypothesis that low LDL cholesterol due to genetic variation in the LDLR, PCSK9, and HMGCR genes and a polygenic LDL cholesterol score is associated with risk of infectious diseases in the general population.

Methods and results

Using observational and Mendelian randomization designs, we examined associations of low plasma LDL cholesterol with risk of bacterial and viral infections in 119 805 individuals from the Copenhagen General Population Study/Copenhagen City Heart Study, 468 701 from the UK Biobank, and up to 376 773 from the FinnGen Research Project. Observationally, low LDL cholesterol concentrations were associated with risk of hospitalization for both bacterial and viral infections. In genetic analyses, a 1 mmol/L lower LDL cholesterol was associated with lower plasma PCSK9 {-0.55 nmol/L [95% confidence interval (CI): -1.06 to -0.05]; P = 0.03}, leucocyte count [-0.42 × 109/L (-0.61 to -0.24); P < 0.001], and high-sensitivity C-reactive protein [-0.44 mg/L (-0.79 to -0.09); P = 0.014]. Using an LDLR, HMGCR, and PCSK9 score, a 1 mmol/L lower LDL cholesterol was associated with risk ratios of 0.91 (95% CI: 0.86-0.97; P = 0.002) for unspecified bacterial infection, of 0.92 (0.87-0.97; P = 0.004) for diarrhoeal disease, and of 1.15 (1.03-1.29; P = 0.012) for unspecified viral infections and 1.64 (1.13-2.39; P = 0.009) for HIV/AIDS. Using a polygenic LDL cholesterol score largely showed similar results and in addition a lower risk of 0.85 (0.76-0.96; P = 0.006) for bacterial pneumonia and 0.91 (0.82-0.99; P = 0.035) for sepsis.

Conclusion

Genetically low LDL cholesterol concentrations were associated with lower concentration of markers of inflammation; lower risk of hospitalization for unspecified bacterial infections, infectious diarrhoeal diseases, bacterial pneumonia, and sepsis; and higher risk of viral infections and HIV/AIDS.

High-Density Lipoprotein Predicts Intrahospital Mortality in Influenza

Background: Although it is known that high-density lipoprotein (HDL) exerts important anti-inflammatory effects and that low HDL plasma concentrations represent a negative prognostic marker in bacterial infections and sepsis, not much is known about possible implications of HDL in acute viral infections such as influenza. Methods: We performed a retrospective, single-centre analysis of influenza patients hospitalised during the 2018/19 and 2019/20 influenza seasons and analysed the impact of HDL concentrations on inflammation and mortality. Results: 199 influenza patients (173 male patients) were admitted during the 2018/19 and 2019/20 influenza seasons with a mortality rate of 4.5%. HDL was significantly lower in deceased patients (median HDL 21 (IQR 19-25) vs. 35 (IQR 28-44) mg/dL; p = 0.005). Low HDL correlated with increased inflammation and HDL was an independent negative predictor regarding mortality after correction for age and the number of comorbidities both overall (OR = 0.890; p = 0.008) and in male patients only (OR = 0.891; p = 0.009). Conclusions: Low HDL upon hospital admission is associated with increased inflammation and is an independent predictor for increased mortality in male patients with influenza A.

Proprotein Convertase Subtilisin Kexin 9 Inhibitor in Severe Sepsis and Septic Shock Patients in a Phase II Prospective Cohort Study-Preliminary Results

Sepsis is a life-threatening organ dysfunction syndrome caused by a dysregulated host response to infection that has a high mortality rate. Proprotein convertase subtilisin kexin 9 (PCSK9) is a serine protease secreted by the liver. Its binding to the low-density lipoprotein (LDL) receptor enhances its degradation, causing an increase in LDL levels in the blood. Objectives: Administering a PCSK9 inhibitor leading to an increase in lipid uptake by the liver may positively affect septic patients due to the increased removal of endotoxins. Methods: This preliminary study aimed to examine the safety of PCSK9 inhibitor use in septic and septic shock patients. We treated five septic patients in the intensive care unit with 300 mg of alirocumab following serious adverse events for 28 days. Results: Four of our patients did not experience any adverse events, and all of them survived. One patient died after discharge from the intensive care unit, and this death was presumably not related to the study drug. The patients rapidly recovered from the inflammatory stage of sepsis. Conclusions: Alirocumab appears safe in severe sepsis and septic shock patients. The outcome data are promising. Only a basic safety profile can be assessed based on this pilot study. Further study with a PCSK-9 inhibitor in septic or septic shock patients is required to further determine its benefit in ICU patients.

Advances and Challenges in Sepsis Management: Modern Tools and Future Directions

Sepsis, a critical condition marked by systemic inflammation, profoundly impacts both innate and adaptive immunity, often resulting in lymphopenia. This immune alteration can spare regulatory T cells (Tregs) but significantly affects other lymphocyte subsets, leading to diminished effector functions, altered cytokine profiles, and metabolic changes. The complexity of sepsis stems not only from its pathophysiology but also from the heterogeneity of patient responses, posing significant challenges in developing universally effective therapies. This review emphasizes the importance of phenotyping in sepsis to enhance patient-specific diagnostic and therapeutic strategies. Phenotyping immune cells, which categorizes patients based on clinical and immunological characteristics, is pivotal for tailoring treatment approaches. Flow cytometry emerges as a crucial tool in this endeavor, offering rapid, low cost and detailed analysis of immune cell populations and their functional states. Indeed, this technology facilitates the understanding of immune dysfunctions in sepsis and contributes to the identification of novel biomarkers. Our review underscores the potential of integrating flow cytometry with omics data, machine learning and clinical observations to refine sepsis management, highlighting the shift towards personalized medicine in critical care. This approach could lead to more precise interventions, improving outcomes in this heterogeneously affected patient population.

Proteomic Evolution from Acute to Post-COVID-19 Conditions

Many COVID-19 survivors have post-COVID-19 conditions, and females are at a higher risk. We sought to determine (1) how protein levels change from acute to post-COVID-19 conditions, (2) whether females have a plasma protein signature different from that of males, and (3) which biological pathways are associated with COVID-19 when compared to restrictive lung disease. We measured protein levels in 74 patients on the day of admission and at 3 and 6 months after diagnosis. We determined protein concentrations by multiple reaction monitoring (MRM) using a panel of 269 heavy-labeled peptides. The predicted forced vital capacity (FVC) and diffusing capacity of the lungs for carbon monoxide (DLCO) were measured by routine pulmonary function testing. Proteins associated with six key lipid-related pathways increased from admission to 3 and 6 months; conversely, proteins related to innate immune responses and vasoconstriction-related proteins decreased. Multiple biological functions were regulated differentially between females and males. Concentrations of eight proteins were associated with FVC, %, and they together had c-statistics of 0.751 (CI:0.732-0.779); similarly, concentrations of five proteins had c-statistics of 0.707 (CI:0.676-0.737) for DLCO, %. Lipid biology may drive evolution from acute to post-COVID-19 conditions, while activation of innate immunity and vascular regulation pathways decreased over that period. (ProteomeXchange identifiers: PXD041762, PXD029437).

Pharmacologic and Genetic Downregulation of Proprotein Convertase Subtilisin/Kexin Type 9 and Survival From Sepsis

OBJECTIVES

Treatments that prevent sepsis complications are needed. Circulating lipid and protein assemblies-lipoproteins play critical roles in clearing pathogens from the bloodstream. We investigated whether early inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) may accelerate bloodstream clearance of immunogenic bacterial lipids and improve sepsis outcomes.

DESIGN

Genetic and clinical epidemiology, and experimental models.

SETTING

Human genetics cohorts, secondary analysis of a phase 3 randomized clinical trial enrolling patients with cardiovascular disease (Evaluation of Cardiovascular Outcomes After an Acute Coronary Syndrome During Treatment With Alirocumab [ODYSSEY OUTCOMES]; NCT01663402), and experimental murine models of sepsis.

PATIENTS OR SUBJECTS

Nine human cohorts with sepsis (total n = 12,514) were assessed for an association between sepsis mortality and PCSK9 loss-of-function (LOF) variants. Incident or fatal sepsis rates were evaluated among 18,884 participants in a post hoc analysis of ODYSSEY OUTCOMES. C57BI/6J mice were used in Pseudomonas aeruginosa and Staphylococcus aureus bacteremia sepsis models, and in lipopolysaccharide-induced animal models.

INTERVENTIONS

Observational human cohort studies used genetic PCSK9 LOF variants as instrumental variables. ODYSSEY OUTCOMES participants were randomized to alirocumab or placebo. Mice were administered alirocumab, a PCSK9 inhibitor, at 5 mg/kg or 25 mg/kg subcutaneously, or isotype-matched control, 48 hours prior to the induction of bacterial sepsis. Mice did not receive other treatments for sepsis.

MEASUREMENTS AND MAIN RESULTS

Across human cohort studies, the effect estimate for 28-day mortality after sepsis diagnosis associated with genetic PCSK9 LOF was odds ratio = 0.86 (95% CI, 0.67-1.10; p = 0.24). A significant association was present in antibiotic-treated patients. In ODYSSEY OUTCOMES, sepsis frequency and mortality were infrequent and did not significantly differ by group, although both were numerically lower with alirocumab vs. placebo (relative risk of death from sepsis for alirocumab vs. placebo, 0.62; 95% CI, 0.32-1.20; p = 0.15). Mice treated with alirocumab had lower endotoxin levels and improved survival.

CONCLUSIONS

PCSK9 inhibition may improve clinical outcomes in sepsis in preventive, pretreatment settings.

A pharmacoproteomic landscape of organotypic intervention responses in Gram-negative sepsis

Sepsis is the major cause of mortality across intensive care units globally, yet details of accompanying pathological molecular events remain unclear. This knowledge gap has resulted in ineffective biomarker development and suboptimal treatment regimens to prevent and manage organ dysfunction/damage. Here, we used pharmacoproteomics to score time-dependent treatment impact in a murine Escherichia coli sepsis model after administering beta-lactam antibiotic meropenem (Mem) and/or the immunomodulatory glucocorticoid methylprednisolone (Gcc). Three distinct proteome response patterns were identified, which depended on the underlying proteotype for each organ. Gcc enhanced some positive proteome responses of Mem, including superior reduction of the inflammatory response in kidneys and partial restoration of sepsis-induced metabolic dysfunction. Mem introduced sepsis-independent perturbations in the mitochondrial proteome that Gcc counteracted. We provide a strategy for the quantitative and organotypic assessment of treatment effects of candidate therapies in relationship to dosing, timing, and potential synergistic intervention combinations during sepsis.

DHCR7 Expression Predicts Poor Outcomes and Mortality From Sepsis

This is a study of lipid metabolic gene expression patterns to discover precision medicine for sepsis.

OBJECTIVES

Sepsis patients experience poor outcomes including chronic critical illness (CCI) or early death (within 14 d). We investigated lipid metabolic gene expression differences by outcome to discover therapeutic targets.

DESIGN SETTING AND PARTICITPANTS

Secondary analysis of samples from prospectively enrolled sepsis patients (first 24 hr) and a zebrafish endotoxemia model for drug discovery. Patients were enrolled from the emergency department or ICU at an urban teaching hospital. Enrollment samples from sepsis patients were analyzed. Clinical data and cholesterol levels were recorded. Leukocytes were processed for RNA sequencing and reverse transcriptase polymerase chain reaction. A lipopolysaccharide zebrafish endotoxemia model was used for confirmation of human transcriptomic findings and drug discovery.

MAIN OUTCOMES AND MEASURES

The derivation cohort included 96 patients and controls (12 early death, 13 CCI, 51 rapid recovery, and 20 controls) and the validation cohort had 52 patients (6 early death, 8 CCI, and 38 rapid recovery).

RESULTS

The cholesterol metabolism gene 7-dehydrocholesterol reductase (DHCR7) was significantly up-regulated in both derivation and validation cohorts in poor outcome sepsis compared with rapid recovery patients and in 90-day nonsurvivors (validation only) and validated using RT-qPCR analysis. Our zebrafish sepsis model showed up-regulation of dhcr7 and several of the same lipid genes up-regulated in poor outcome human sepsis (dhcr24, sqlea, cyp51, msmo1, and ldlra) compared with controls. We then tested six lipid-based drugs in the zebrafish endotoxemia model. Of these, only the Dhcr7 inhibitor AY9944 completely rescued zebrafish from lipopolysaccharide death in a model with 100% lethality.

CONCLUSIONS

DHCR7, an important cholesterol metabolism gene, was up-regulated in poor outcome sepsis patients warranting external validation. This pathway may serve as a potential therapeutic target to improve sepsis outcomes.

DHCR7 Expression Predicts Poor Outcomes and Mortality from Sepsis

Objective: Sepsis patients experience poor outcomes including chronic critical illness (CCI) or early death (within 14 days). We investigated lipid metabolic gene expression differences by outcome to discover therapeutic targets. Design: Secondary analysis of samples from prospectively enrolled sepsis patients and a zebrafish sepsis model for drug discovery. Setting: Emergency department or ICU at an urban teaching hospital. Patients: Sepsis patients presenting within 24 hours. Methods: Enrollment samples from sepsis patients were analyzed. Clinical data and cholesterol levels were recorded. Leukocytes were processed for RNA sequencing (RNA-seq) and reverse transcriptase polymerase chain reaction (RT-qPCR). A lipopolysaccharide (LPS) zebrafish sepsis model was used for confirmation of human transcriptomic findings and drug discovery. Measurements and Main Results: There were 96 samples in the derivation (76 sepsis, 20 controls) and 52 in the validation cohort (sepsis only). The cholesterol metabolism gene 7-Dehydrocholesterol Reductase ( DHCR7) was significantly upregulated in both derivation and validation cohorts in poor outcome sepsis compared to rapid recovery patients and in 90-day non-survivors (validation only) and validated using RT-qPCR analysis. Our zebrafish sepsis model showed upregulation of dhcr7 and several of the same lipid genes upregulated in poor outcome human sepsis (dhcr24, sqlea, cyp51, msmo1 , ldlra) compared to controls. We then tested six lipid-based drugs in the zebrafish sepsis model. Of these, only the Dhcr7 inhibitor AY9944 completely rescued zebrafish from LPS death in a model with 100% lethality. Conclusions: DHCR7, an important cholesterol metabolism gene, was upregulated in poor outcome sepsis patients warranting external validation. This pathway may serve as a potential therapeutic target to improve sepsis outcomes.

Modulation of vascular endothelial inflammatory response by proprotein convertase subtilisin-kexin type 9

BACKGROUND AND AIMS

Endotoxins carried within LDL are cleared from the circulation via hepatic LDL receptor (LDLR)-mediated endocytosis. Proprotein convertase subtilisin-kexin type 9 (PCSK9) reduces this clearance by down-regulating LDLR density on hepatocytes. In addition to hepatocytes, vascular endothelial cells also express receptor targets of PCSK9, including LDLR. Therefore, we hypothesized that PCSK9 may regulate vascular endothelial cell uptake of lipopolysaccharide (LPS) and alter the vascular endothelial cell inflammatory response.

METHODS AND RESULTS

We found that LPS is internalized by human umbilical vein vascular endothelial cells (HUVECs) and LPS uptake dose-dependently increased with increasing LDL concentration. Intracellular LPS co-localized with LDL. PCSK9 and, separately, blocking antibodies against LDLR, dose-dependently decreased the vascular endothelial cell uptake of LPS and, furthermore, inhibition of endocytosis using Dynasore blocked LPS uptake. In contrast, blocking antibodies against TLR4 did not alter LPS uptake. PCSK9 decreased the LPS-induced proinflammatory response (IL-6 and IL-8 gene expression and protein secretion, and VCAM-1/ICAM-1 expression) in vascular endothelial cells. In addition, a decrease in PCSK9 and increase in LDLR, mediated by triciribine or siPCSK9, increased LPS uptake and the LPS-induced proinflammatory response. Similar results were also found in aortic vascular tissue from Pcsk9^-/- mice after LPS injection.

CONCLUSIONS

Our data suggest that, similar to PCSK9 treatment in hepatocytes, PCSK9 reduces vascular endothelial cell uptake of LPS via LDLR-mediated endocytosis. Consequently, PCSK9 decreases the LPS-induced proinflammatory response in vascular endothelial cells. These results raise the possibility that PCSK9 inhibition may have additional effects on vascular endothelial inflammation via this alternative pathway, beyond the known effects of PCSK9 inhibition on LDL lowering and hepatic endotoxin clearance.

Molecular and cellular biology of PCSK9: impact on glucose homeostasis

Proprotein convertase substilisin/kexin 9 (PCSK9) inhibitors (PCSK9i) revolutionised the lipid-lowering therapy. However, a risk of type 2 diabetes mellitus (T2DM) is evoked under PCSK9i therapy. In this review, we summarise the current knowledge on the link of PCSK9 with T2DM. A significant correlation was found between PCSK9 and insulin, homeostasis model assessment (HOMA) of insulin resistance and glycated haemoglobin. PCSK9 is also involved in inflammation. PCSK9 loss-of-function variants increased T2DM risk by altering insulin secretion. Local pancreatic low PCSK9 regulates β-cell LDLR expression which in turn promotes intracellular cholesterol accumulation and hampers insulin secretion. Nevertheless, the association of PCSK9 loss-of-function variants and T2DM is inconsistent. InsLeu and R46L polymorphisms were associated with T2DM, low HOMA for β-cell function and impaired fasting glucose, while the C679X polymorphism was associated with low fasting glucose in Black South African people. Hence, we assume that the impact of these variants on glucose homeostasis may vary depending on the genetic background of the studied populations and the type of effect caused by those genetic variants on the PCSK9 protein. Accordingly, these factors should be considered when choosing a genetic variant of PCSK9 to assess the impact of long-term use of PCSK9i on glucose homeostasis.

Colivelin, a synthetic derivative of humanin, ameliorates endothelial injury and glycocalyx shedding after sepsis in mice

Endothelial dysfunction plays a central role in the pathogenesis of sepsis-mediated multiple organ failure. Several clinical and experimental studies have suggested that the glycocalyx is an early target of endothelial injury during an infection. Colivelin, a synthetic derivative of the mitochondrial peptide humanin, has displayed cytoprotective effects in oxidative conditions. In the current study, we aimed to determine the potential therapeutic effects of colivelin in endothelial dysfunction and outcomes of sepsis in vivo. Male C57BL/6 mice were subjected to a clinically relevant model of polymicrobial sepsis by cecal ligation and puncture (CLP) and were treated with vehicle or colivelin (100-200 µg/kg) intraperitoneally at 1 h after CLP. We observed that vehicle-treated mice had early elevation of plasma levels of the adhesion molecules ICAM-1 and P-selectin, the angiogenetic factor endoglin and the glycocalyx syndecan-1 at 6 h after CLP when compared to control mice, while levels of angiopoietin-2, a mediator of microvascular disintegration, and the proprotein convertase subtilisin/kexin type 9, an enzyme implicated in clearance of endotoxins, raised at 18 h after CLP. The early elevation of these endothelial and glycocalyx damage biomarkers coincided with lung histological injury and neutrophil inflammation in lung, liver, and kidneys. At transmission electron microscopy analysis, thoracic aortas of septic mice showed increased glycocalyx breakdown and shedding, and damaged mitochondria in endothelial and smooth muscle cells. Treatment with colivelin ameliorated lung architecture, reduced organ neutrophil infiltration, and attenuated plasma levels of syndecan-1, tumor necrosis factor-α, macrophage inflammatory protein-1α and interleukin-10. These therapeutic effects of colivelin were associated with amelioration of glycocalyx density and mitochondrial structure in the aorta. At molecular analysis, colivelin treatment was associated with inhibition of the signal transducer and activator of transcription 3 and activation of the AMP-activated protein kinase in the aorta and lung. In long-term outcomes studies up to 7 days, co-treatment of colivelin with antimicrobial agents significantly reduced the disease severity score when compared to treatment with antibiotics alone. In conclusion, our data support that damage of the glycocalyx is an early pathogenetic event during sepsis and that colivelin may have therapeutic potential for the treatment of sepsis-associated endothelial dysfunction.

PCSK9 is associated with mortality in patients with septic shock: data from the ALBIOS study

BACKGROUND

Pro-protein convertase subtilisin/kexin 9 (PCSK9) is a proenzyme primarily known to regulate low-density lipoprotein receptor re-uptake on hepatocytes. Whether PCSK9 can concurrently trigger inflammation or not remains unclear. Here, we investigated the potential association between circulating levels of PCSK9 and mortality in patients with severe sepsis or septic shock.

METHODS

Plasma PCSK9 levels at days 1, 2 and 7 were measured in 958 patients with severe sepsis or septic shock previously enrolled in the Albumin Italian Outcome Sepsis (ALBIOS) trial. Correlations between levels of PCSK9 and pentraxin 3 (PTX3), a biomarker of disease severity, were evaluated with ranked Spearman's coefficients. Cox proportional hazards models were used to assess the association of PCSK9 levels at day 1 with 28- and 90-day mortality.

RESULTS

Median plasma PCSK9 levels were 278 [182-452] ng mL-1 on day 1. PCSK9 correlated positively with PTX3 at the three time-points, and patients with septic shock within the first quartile of PCSK9 showed higher levels of PTX3. Similar mortality rates were observed in patients with severe sepsis across PCSK9 quartiles. Patients with septic shock with lower PCSK9 levels on day 1 (within the first quartile) showed the highest 28- and 90-day mortality rate as compared to other quartiles.

CONCLUSION

In our sub-analysis of the ALBIOS trial, we found that patients with septic shock presenting with lower plasma PCSK9 levels experienced higher mortality rate. Further studies are warranted to better evaluate the pathophysiological role of PCSK9 in sepsis.

Study protocol for a multicentre, prospective cohort study of the association of angiotensin II type 1 receptor blockers on outcomes of coronavirus infection

INTRODUCTION

The COVID-19 epidemic grows and there are clinical trials of antivirals. There is an opportunity to complement these trials with investigation of angiotensin II type 1 receptor blockers (ARBs) because an ARB (losartan) was effective in murine influenza pneumonia.

METHODS AND ANALYSIS

Our innovative design includes: ARBs; alignment with the WHO Ordinal Scale (primary endpoint) to align with other COVID-19 trials; joint longitudinal analysis; and predictive biomarkers (angiotensins I, 1-7, II and ACE1 and ACE2). Our hypothesis is: ARBs decrease the need for hospitalisation, severity (need for ventilation, vasopressors, extracorporeal membrane oxygenation or renal replacement therapy) or mortality of hospitalised COVID-19 infected adults. Our two-pronged multicentre pragmatic observational cohort study examines safety and effectiveness of ARBs in (1) hospitalised adult patients with COVID-19 and (2) out-patients already on or not on ARBs. The primary outcome will be evaluated by ordinal logistic regression and main secondary outcomes by both joint longitudinal modelling analyses. We will compare rates of hospitalisation of ARB-exposed versus not ARB-exposed patients. We will also determine whether continuing ARBs or not decreases the primary outcome. Based on published COVID-19 cohorts, assuming 15% of patients are ARB-exposed, a total sample size of 497 patients can detect a proportional OR of 0.5 (alpha=0.05, 80% power) comparing WHO scale of ARB-exposed versus non-ARB-exposed patients.

ETHICS AND DISSEMINATION

This study has core institution approval (UBC Providence Healthcare Research Ethics Board) and site institution approvals (Health Research Ethics Board, University of Alberta; Comite d'etique de la recerche, CHU Sainte Justine (for McGill University and University of Sherbrook); Conjoint Health Research Ethics Board, University of Calgary; Queen's University Health Sciences & Affiliated Hospitals Research Ethics Board; Research Ethics Board, Sunnybrook Health Sciences Centre; Veritas Independent Research Board (for Humber River Hospital); Mount Sinai Hospital Research Ethics Board; Unity Health Toronto Research Ethics Board, St. Michael's Hospital). Results will be disseminated by peer-review publication and social media releases.

TRIAL REGISTRATION NUMBER

NCT04510623.

Transendothelial transport of lipoproteins

The accumulation of low-density lipoproteins (LDL) in the arterial wall plays a pivotal role in the initiation and pathogenesis of atherosclerosis. Conversely, the removal of cholesterol from the intima by cholesterol efflux to high density lipoproteins (HDL) and subsequent reverse cholesterol transport shall confer protection against atherosclerosis. To reach the subendothelial space, both LDL and HDL must cross the intact endothelium. Traditionally, this transit is explained by passive filtration. This dogma has been challenged by the identification of several rate-limiting factors namely scavenger receptor SR-BI, activin like kinase 1, and caveolin-1 for LDL as well as SR-BI, ATP binding cassette transporter G1, and endothelial lipase for HDL. In addition, estradiol, vascular endothelial growth factor, interleukins 6 and 17, purinergic signals, and sphingosine-1-phosphate were found to regulate transendothelial transport of either LDL or HDL. Thorough understanding of transendothelial lipoprotein transport is expected to elucidate new therapeutic targets for the treatment or prevention of atherosclerotic cardiovascular disease and the development of strategies for the local delivery of drugs or diagnostic tracers into diseased tissues including atherosclerotic lesions.

Quantitative and Qualitative Assessments of Cholesterol Association With Bacterial Infection Type in Sepsis and Septic Shock

BACKGROUND

Reduced cholesterol levels are associated with increased organ failure and mortality in sepsis. Cholesterol levels may vary by infection type (gram negative vs positive), possibly reflecting differences in cholesterol-mediated bacterial clearance.

METHODS

This was a secondary analysis of a combined data set of 2 prospective cohort studies of adult patients meeting Sepsis-3 criteria. Infection types were classified as gram negative, gram positive, or culture negative. We investigated quantitative (levels) and qualitative (dysfunctional high-density lipoprotein [HDL]) cholesterol differences. We used multivariable logistic regression to control for disease severity.

RESULTS

Among 171 patients with sepsis, infections were gram negative in 67, gram positive in 46, and culture negative in 47. Both gram-negative and gram-positive infections occurred in 11 patients. Total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and HDL cholesterol (HDL-C) levels were lower for culture-positive sepsis at enrollment (TC, P < .001; LDL-C, P < .001; HDL-C, P = .011) and persisted after controlling for disease severity. Similarly, cholesterol levels were lower among culture-positive patients at 48 hours (TC, P = .012; LDL-C, P = .029; HDL-C, P = .002). Triglyceride (TG) levels were lower at enrollment (P =.033) but not at 48 hours (P = .212). There were no differences in dysfunctional HDL. Among bacteremic patients, cholesterol levels were lower at enrollment (TC, P = .010; LDL-C, P = .010; HDL-C, P ≤ .001; TG, P = .005) and at 48 hours (LDL-C, P = .027; HDL-C, P < .001; TG, P = .020), except for 48 hour TC (P = .051). In the bacteremia subgroup, enrollment TC and LDL-C were lower for gram-negative versus gram-positive infections (TC, P = .039; LDL-C, P = .023).

CONCLUSION

Cholesterol levels are significantly lower among patients with culture-positive sepsis and bacteremia.

Novel strategies to target proprotein convertase subtilisin kexin 9: beyond monoclonal antibodies

Since the discovery of the role of proprotein convertase subtilisin kexin 9 (PCSK9) in the regulation of low-density lipoprotein cholesterol (LDL-C) in 2003, a paradigm shift in the treatment of hypercholesterolaemia has occurred. The PCSK9 secreted into the circulation is a major downregulator of the low-density lipoprotein receptor (LDLR) protein, as it chaperones it to endosomes/lysosomes for degradation. Humans with loss-of-function of PCSK9 exhibit exceedingly low levels of LDL-C and are protected from atherosclerosis. As a consequence, innovative strategies to modulate the levels of PCSK9 have been developed. Since 2015 inhibitory monoclonal antibodies (evolocumab and alirocumab) are commercially available. When subcutaneously injected every 2-4 weeks, they trigger a ∼60% LDL-C lowering and a 15% reduction in the risk of cardiovascular events. Another promising approach consists of a liver-targetable specific PCSK9 siRNA which results in ∼50-60% LDL-C lowering that lasts up to 6 months (Phases II-III clinical trials). Other strategies under consideration include: (i) antibodies targeting the C-terminal domain of PCSK9, thereby inhibiting the trafficking of PCSK9-LDLR to lysosomes; (ii) small molecules that either prevent PCSK9 binding to the LDLR, its trafficking to lysosomes or its secretion from cells; (iii) complete silencing of PCSK9 by CRISPR-Cas9 strategies; (iv) PCSK9 vaccines that inhibit the activity of circulating PCSK9. Time will tell whether other strategies can be as potent and safe as monoclonal antibodies to lower LDL-C levels.

Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Is Not Induced in Artificial Human Inflammation and Is Not Correlated with Inflammatory Response

Lipoproteins, as well as proprotein convertase subtilisin/kexin type 9 (PCSK9), have been shown to play a key role in the innate immune response. However, knowledge about the role and kinetics of PCSK9 in human inflammation is currently insufficient. This study aimed to investigate the interaction between inflammation and lipid metabolism, including the possible role of PCSK9. A single-blinded, placebo-controlled cross-over study using the human endotoxin model was performed.

Lipoproteins, as well as proprotein convertase subtilisin/kexin type 9 (PCSK9), have been shown to play a key role in the innate immune response. However, knowledge about the role and kinetics of PCSK9 in human inflammation is currently insufficient. This study aimed to investigate the interaction between inflammation and lipid metabolism, including the possible role of PCSK9. A single-blinded, placebo-controlled cross-over study using the human endotoxin model was performed. Ten healthy men received lipopolysaccharide (LPS) or placebo on two different study days after overnight fasting. Lipoproteins as well as PCSK9 were measured repetitively over 48 h. PCSK9 plasma concentrations were not induced by LPS infusion, and no correlation between PCSK9 plasma concentrations and the degree of inflammation could be identified. The observed low-density lipoprotein (LDL) response to inflammation was more complex than anticipated, especially in the very early phase after the inflammatory stimulus. Baseline concentrations of LDL, as well as high-density lipoprotein (HDL), correlated negatively with inflammatory response. Our data suggest that the lipoprotein response to inflammation is independent of PCSK9. The proposed elevations of PCSK9 and suspected correlations between PCSK9 levels and inflammatory response are not supported by our data. (This study has been registered at ClinicalTrials.gov under registration no. NCT03392701.)

Cholesteryl Ester Transfer Protein Influences High-Density Lipoprotein Levels and Survival in Sepsis

RATIONALE

High-density lipoprotein (HDL) cholesterol (HDL-C) levels decline during sepsis, and lower levels are associated with worse survival. However, the genetic mechanisms underlying changes in HDL-C during sepsis, and whether the relationship with survival is causative, are largely unknown.

OBJECTIVES

We hypothesized that variation in genes involved in HDL metabolism would contribute to changes in HDL-C levels and clinical outcomes during sepsis.

METHODS

We performed targeted resequencing of HDL-related genes in 200 patients admitted to an emergency department with sepsis (Early Infection cohort). We examined the association of genetic variants with HDL-C levels, 28-day survival, 90-day survival, organ dysfunction, and need for vasopressor or ventilatory support. Candidate variants were further assessed in the VASST (Vasopressin versus Norepinephrine Infusion in Patients with Septic Shock Trial) cohort (n = 632) and St. Paul's Hospital Intensive Care Unit 2 (SPHICU2) cohort (n = 203).

MEASUREMENTS AND MAIN RESULTS

We identified a rare missense variant in CETP (cholesteryl ester transfer protein gene; rs1800777-A) that was associated with significant reductions in HDL-C levels during sepsis. Carriers of the A allele (n = 10) had decreased survival, more organ failure, and greater need for organ support compared with noncarriers. We replicated this finding in the VASST and SPHICU2 cohorts, in which carriers of rs1800777-A (n = 35 and n = 12, respectively) had significantly reduced 28-day survival. Mendelian randomization was consistent with genetically reduced HDL levels being a causal factor for decreased sepsis survival.

CONCLUSIONS

Our results identify CETP as a critical regulator of HDL levels and clinical outcomes during sepsis. These data point toward a critical role for HDL in sepsis.

Biomarkers of Infection and Sepsis

The role of biomarkers for detection of sepsis has come a long way. Molecular biomarkers are taking front stage at present, but machine learning and other computational measures using bigdata sets are promising. Clinical research in sepsis is hampered by lack of specificity of the diagnosis; sepsis is a syndrome with no uniformly agreed definition. This lack of diagnostic precision means there is no gold standard for this diagnosis. The final conclusion is expert opinion, which is not bad but not perfect. Perhaps machine learning will displace expert opinion as the final and most accurate definition for sepsis.

Association of Serum PCSK9 Levels with Antibiotic Resistance and Severity of Disease in Patients with Bacterial Infections Admitted to Intensive Care Units

BACKGROUND

The results of several studies have suggested that infections and sepsis, either bacterial or viral, might be associated with elevated plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) levels. Since there are no data on PCSK9 levels and antibiotic resistance or the severity of disease in patients with bacterial infections in intensive care units, the aim of this study was to investigate whether any such associations exist.

METHODS

100 patients (46 males, mean age 67.12 ± 1.34 years) with bacterial infections who were staying in an intensive care unit (ICU) longer than 48 h but less than 7 days and who were not receiving corticosteroids were analyzed. Their serum levels of albumin, C-reactive protein, glucose, lactate, blood urea nitrogen, prothrombin (international normalized ratio), total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, PCSK9, and procalcitonin were measured. The severity of the patients' condition was assessed by using the Glasgow Coma Scale (GCS), the Sequential Organ Failure Assessment (SOFA), and the Acute Physiology and Chronic Health Evaluation II (APACHE II) scales.

RESULTS

Using a hierarchical regression modeling approach, no significant association was found between PCSK9 levels and either the severity of disease (APACHE II, SOFA, and GCS) indices or resistance to antibiotics.

CONCLUSION

The results suggest that there is no association between PCSK9 levels and resistance to antibiotics or the condition of patients hospitalized in intensive care units.

Molecular regulation of plasma lipid levels during systemic inflammation and sepsis

PURPOSE OF REVIEW

Sepsis is a common syndrome of multiorgan system dysfunction caused by a dysregulated inflammatory response to an infection and is associated with high rates of mortality. Plasma lipid and lipoprotein levels and composition change profoundly during sepsis and have emerged as both biomarkers and potential therapeutic targets for this condition. The purpose of this article is to review recent progress in the understanding of the molecular regulation of lipid metabolism during sepsis.

RECENT FINDINGS

Patients who experience greater declines in high-density lipoprotein during sepsis are at much greater risk of succumbing to organ failure and death. Although the causality of these findings remains unclear, all lipoprotein classes can sequester and prevent the excessive inflammation caused by pathogen-associated lipids during severe infections such as sepsis. This primordial innate immune function has been best characterized for high-density lipoproteins. Most importantly, results from human genetics and preclinical animal studies have suggested that several lipid treatment strategies, initially designed for atherosclerosis, may hold promise as therapies for sepsis.

SUMMARY

Lipid and lipoprotein metabolism undergoes significant changes during sepsis. An improved understanding of the molecular regulation of these changes may lead to new opportunities for the treatment of sepsis.

Emerging role of proprotein convertase subtilisin/kexin type-9 (PCSK-9) in inflammation and diseases

Proprotein convertase subtilisin/kexin type-9 (PCSK9) is most recognized serine protease for its role in cardiovascular diseases (CVD). PCSK9 regulates plasma low-density lipoprotein cholesterol (LDL-C) levels by selectively targeting hepatic LDL receptors (LDLR) for degradation, thereby serving as a potential therapeutic target for CVD. New pharmacological agents under development aim to lower the risk of CVD by inhibiting PCSK9 extracellularly, although secondary effects of this approach are not yet studied. Here we review the history of PCSK9 and rationale behind developing inhibitors for CVD. Importantly, we summarized the studies investigating the role and impact of modulated PCSK9 levels in inflammation, specifically in sepsis, rheumatoid arthritis and other chronic inflammatory conditions. Furthermore, we summarized studies that investigated the interactions of PCSK9 with pro-inflammatory pathways, such as scavenger receptor CD36 and thrombospondin 1 (TSP-1) in inflammatory diseases. This review highlights the conflicting role that PCSK9 plays in different inflammatory disease states and postulates that any unwanted effects of PCSK9 inhibition in early clinical testing should critically be examined.

Impact of PCSK9 loss-of-function genotype on 1-year mortality and recurrent infection in sepsis survivors

Background

Reduced activity of proprotein convertase subtilisin/kexin type 9 (PCSK9) has been associated with decreased short-term death in patients with septic shock. Whether PCSK9 genotype influences long-term outcomes in sepsis survivors is unknown.

Methods

We evaluated the impact of PCSK9 loss-of-function (LOF) genotype on both 1-year mortality and infection-related readmission (IRR) after an index sepsis admission. The Derivation cohort included 342 patients who survived 28 days after a sepsis admission in a tertiary hospital (Vancouver/Canada, 2004–2014), while an independent Validation cohort included 1079 septic shock patients admitted at the same hospital (2000–2006). All patients were genotyped for three common missense PCSK9 LOF variants rs11591147, rs11583680, rs562556 and were classified in 3 groups: Wildtype, single PCSK9 LOF, and multiple PCSK9 LOF, according to the number of LOF alleles per patient. We also performed a meta-analysis using both cohorts to investigate the effects of PCSK9 genotype on 90-day survival.

Findings

In the Derivation cohort, patients carrying multiple PCSK9 LOF alleles showed lower risk for the composite outcome 1-year death or IRR (HR: 0.40, P = 0.006), accelerated reduction on neutrophil counts (P = 0.010), and decreased levels of PCSK9 (P = 0.037) compared with WT/single LOF groups. Our meta-analysis revealed that the presence of multiple LOF alleles was associated with lower 90-day mortality risk (OR = 0.69, P = 0.020).

Interpretation

The presence of multiple PCSK9 LOF alleles decreased the risk of 1-year death or IRR in sepsis survivors. Biological measures suggest this may be related to an enhanced resolution of the initial infection.

Funding

Canadian Institutes of Health Research (PJT-156056).

PCSK9: A novel inflammation modulator in atherosclerosis?

Proprotein convertase subtilisin/kexin 9 (PCSK9) is the ninth member of the secretory serine protease family. It binds to low-density lipoprotein receptor (LDLR) for endocytosis and lysosome degradation in the liver, resulting in an increasing in circulating LDL-cholesterol (LDL-c) level. Since a PCSK9 induced increase in plasma LDL-c contributes to atherosclerosis, PCSK9 inhibition has become a new strategy in preventing and treating atherosclerosis. However, in addition to the effect of PCSK9 on elevating blood LDL-c levels, accumulating evidence shows that PCSK9 plays an important role in inflammation, likely representing another major mechanism for PCSK9 to promote atherosclerosis. In this review, we discuss the association of PCSK9 and inflammation, and highlight the specific effects of PCSK9 on different vascular cellular components involved in the atherosclerotic inflammation. We also discuss the clinical evidence for the association between PCSK9 and inflammation in atherosclerotic cardiovascular disease. A better understanding of the direct association of PCSK9 with atherosclerotic inflammation might help establish a new role for PCSK9 in vascular biology and identify a novel molecular mechanism for PCSK9 therapy.

The Understanding and Management of Organism Toxicity in Septic Shock

The toxicity caused by different organisms in septic shock is substantially complex and characterized by an intricate pathogenicity that involves several systems and pathways. Immune cells' pattern recognition receptors initiate the host response to pathogens after the recognition of pathogen-associated molecular patterns. In essence, the subsequent activation of downstream pathways may progress to infection resolution or to a dysregulated host response that represents the hallmark of organ injury in septic shock. Likewise, the management of organism toxicity in septic shock is complicated and comprises a multiplicity of suitable targets. In this review, the classic immune responses to pathogens are discussed as well as other factors that are relevant in the pathogenicity of septic shock, including sepsis-induced immune suppression, inflammasome activation, intestinal permeability, and the role of lipids and proprotein convertase subtilisin/kexin type 9. Current therapies aiming to eliminate the organisms causing septic shock, recent and ongoing trials in septic shock treatment, and potential new therapeutic strategies are also explored.

Role of lipoproteins and proprotein convertase subtilisin/kexin type 9 in endotoxin clearance in sepsis

PURPOSE OF REVIEW

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition is a recent high-impact cardiovascular intervention aimed at reducing low-density lipoprotein (LDL) cholesterol levels. Notably, pathogen lipids are also carried in lipoprotein particles and are cleared by hepatocyte LDL receptors. Therefore, the role of PCSK9 in sepsis is reviewed.

RECENT FINDINGS

Endogenous PCSK9 decreases clearance of LDL cholesterol by decreasing the number of LDL receptors on hepatocytes. Similarly, PCSK9 decreases clearance of pathogen lipids, such as endotoxin, carried in LDL. Pathogen lipids, such as lipopolysaccharide (LPS) from gram-negative organisms or lipoteichoic acid from gram-positive organisms, are carried in high-density lipoprotein, LDL, and very low-density lipoprotein particles. Transfer proteins that handle pathogen lipids (e.g., LPS binding protein) are homologous to transfer proteins that handle cholesterol (e.g., phospholipid transfer protein, cholesterol ester transfer protein). Reduction in PCSK9 function results in increased LPS clearance, a decreased inflammatory response, and improved clinical outcomes in mice. PCSK9 inhibition improves survival in septic mice. Similarly, humans who carry loss-of-function variants of the PCSK9 gene have increased survival in sepsis.

SUMMARY

PCSK9 inhibition may be a useful strategy to increase pathogen lipid clearance in the treatment of patients with sepsis.

Differential Expression of PCSK9 Modulates Infection, Inflammation, and Coagulation in a Murine Model of Sepsis

INTRODUCTION

Proprotein convertase subtilisin/kexin type 9 (PCSK9) targets lipoprotein receptors for degradation, thereby reducing hepatic lipid clearance. PCSK9 inhibition reduces mortality in septic mice, presumably through increased hepatic clearance of pathogen lipids due to increased lipoprotein receptor concentrations. However, PCSK9 overexpression in vivo has not been studied in sepsis. Therefore, this study aimed to evaluate the effects of differential PCSK9 expression on systemic infection, inflammation, and coagulation in sepsis.

METHODS

Wild-type, PCSK9 knockout (KO), and transgenic (Tg) mice that overexpress PCSK9 were subjected to sham surgery or cecal ligation and puncture (CLP). Bacterial loads were measured in lungs, peritoneal cavity fluid, and blood. Organ pathology was assessed in lungs, liver, and kidneys. Lung myeloperoxidase activity, and plasma concentrations of alanine aminotransferase (ALT), creatinine, cell-free DNA (cfDNA), protein C, thrombin-antithrombin (TAT) complexes, interleukin (IL)-6, and IL-10 were also measured 6 h postoperatively. Morbidity was assessed for 16 h following CLP.

RESULTS

Overexpression of PCSK9 in mice increased liver and kidney pathology, plasma IL-6, ALT, and TAT concentrations during sepsis, whereas PCSK9 KO mice exhibited reduced bacterial loads, lung and liver pathology, myeloperoxidase activity, plasma IL-10, and cfDNA during CLP-induced sepsis. All septic mice had reduced plasma levels of protein C, but the protein C ratio relative to normal was significantly decreased in PCSK9 Tg mice. Dyspnea, cyanosis, and overall grimace scores were greatest in septic mice overexpressing PCSK9, whereas PCSK9 KO mice retained core body temperature during sepsis.

CONCLUSION

These findings demonstrate that PCSK9 deficiency confers protection against systemic bacterial dissemination, organ pathology, and tissue inflammation, particularly in the lungs and liver, while PCSK9 overexpression exacerbates multi-organ pathology as well as the hypercoagulable and pro-inflammatory states in early sepsis.

Associations of lipoproteins with cardiovascular and infection-related outcomes in patients receiving hemodialysis

BACKGROUND

In hemodialysis (HD) patients, higher lipid levels are associated with lower mortality. Lipid-lowering therapy does not reduce all-cause mortality or cardiovascular (CV) mortality. Lipoproteins play a role in the innate immune system. Our objective was to determine whether protection from infection might counterbalance adverse CV outcomes associated with lipoproteins.

METHODS

We examined associations between serum apolipoprotein (Apo) A1, B, C2, C3, high-density lipoprotein and low-density lipoprotein (LDL) cholesterol and triglyceride levels and infectious mortality or hospitalization, CV mortality or hospitalization, and all-cause mortality in 433 prevalent HD patients. Cox models with time-varying apolipoprotein concentrations collected every 6 months for up to 2 years were used for analyses.

RESULTS

Median follow-up time for all-cause mortality was 2.7 years (25th-75th percentile range: 2.2-3.4 years). One hundred seventy-nine (41%) patients had an infection-related event. In multivariable models, higher Apo B and LDL were associated with lower risks of infection-related outcomes (hazard ratio Apo B 0.92 [95% confidence interval 0.86-0.99 per 10 mg/dL, P = .03]; hazard ratio LDL 0.93 [95% confidence interval 0.87-1.00 per 10 mg/dL, P = .05]). Sixty-three (15%) participants had a CV-related event. No significant associations were observed between lipoproteins and CV outcomes. Eighty-seven (20%) participants died. Higher Apo A1, Apo B, and Apo C3 were associated with lower risks of all-cause mortality. There was no interaction between the use of lipid-lowering medication and any of the outcomes.

CONCLUSION

Associations of lipoproteins with lower risk of serious infection accompanied by no significant association with CV events may help to explain the paradoxical association between lipids and survival and lack of benefit of lipid-lowering therapies in HD.

Update of Sepsis in the Intensive Care Unit

Sepsis, the most common cause of admission to an intensive care unit (ICU), has had an increased incidence and prevalence over the last years with a simultaneous decrease in its short-term mortality. Sepsis survivors are more frequently discharged from hospital and often experience long-term outcomes such as late mortality, immune dysfunction, secondary infections, impaired quality of life, and unplanned readmissions. Early recognition and management of sepsis have challenged emergency care and critical care physicians and nurses. New sepsis definitions were produced and the Surviving Sepsis Campaign (SSC) 2016 was updated recently. Although hospital readmissions after sepsis are common, associated risk factors and how to manage patients who survive an episode of sepsis still need clarification. The immune dysfunction caused by sepsis/septic shock is complex, persistent, affects inflammatory and anti-inflammatory systems, and might be associated with long-term outcomes of sepsis. Several randomized controlled trials (RCT) that analyzed new (and old) interventions in sepsis/septic shock are discussed in this review in parallel with the SSC 2016 recommendations and other guidelines when relevant. RCTs addressing incidence, treatment, and prevention of important sepsis-associated organ dysfunction such as the acute respiratory distress syndrome, acute kidney injury, and brain dysfunction are highlighted. Finally, we briefly discuss the need for novel targets, predictive biomarkers, and new designs of RCTs in sepsis.

PCSK9 inhibitors - from discovery of a single mutation to a groundbreaking therapy of lipid disorders in one decade

Hypercholesterolemia is one of the main risk factors for coronary heart disease and significantly contributes to the high mortality associated with cardiovascular diseases. Statin therapy represents the gold standard in the reduction of low-density lipoprotein cholesterol concentration. Nevertheless, many patients still cannot achieve the recommended target levels, due to either inadequate effectiveness or intolerance of these drugs. Monoclonal antibodies that inhibit proprotein convertase subtilisin/kexin type 9 (PCSK9) have emerged as a promising option in lipid-lowering treatment. After confirmation of their efficacy and safety in clinical trials, evolocumab and alirocumab received approval from the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) for introduction into clinical practice. In this review, we present a history of the development and mechanisms of action, as well as the results of the most important studies concerning PCSK9 inhibitors.

Curcumin Protects Against Intestinal Origin Endotoxemia in Rat Liver Cirrhosis by Targeting PCSK9

Intestinal origin endotoxemia always occurs in severe liver injury. The aim of the current study was to test antiendotoxemia effect of curcumin on tetrachloride (CCl₄ )-induced liver cirrhosis rats, and to elucidate the underlying molecular mechanism. Rat cirrhosis models were constructed with CCl₄ subcutaneous injections with curcumin (200 mg/kg/d) administered via gavages for 12 wk until the rats were sacrificed. We found that the administration of curcumin improved the physiological condition pertaining to activity index and temperature, and ameliorated the liver injury in CCl₄ -induced cirrhosis rats. Enzyme-linked immunosorbent assay (ELISA) and real-time quantitative polymerase chain reaction (qRT-PCR) showed that curcumin could reduce c-reaction protein levels and inflammatory cytokine (TNF-α, IL-1β, IL-6, and CINC-1/IL-8) concentrations in peripheral serum and liver tissue. Furthermore, curcumin treatment decreased lipopolysaccharide (LPS) levels in peripheral vein, but not in portal vein. As low-density lipoprotein receptor (LDLR) is the important receptor on the surface of hepatocyte during LPS detoxification process, we used qRT-PCR, western blot, and immunohistochemistry (IHC), finding that curcumin significantly increased LDLR protein levels, but not gene levels in the liver tissues. We also tested proprotein convertase subtilisin/kexin type 9 (PCSK9), one negative regulator of LDLR, by qRT-PCR, western blot, and IHC. The results showed that PCSK9 significantly decreased both gene and protein levels in the rat liver tissues of curcumin treatment. Thus, we concluded that curcumin could function to protect against intestinal origin endotoxemia by inhibiting PCSK9 to promote LDLR expression, thereby enhancing LPS detoxification as one pathogen lipid through LDLR in the liver.

Comparing expression and activity of PCSK9 in SPRET/EiJ and C57BL/6J mouse strains shows lack of correlation with plasma cholesterol

Objective

Low-density lipoprotein receptor (LDLR) and proprotein convertase subtilisin/kexin type 9 (PCSK9) are opposing regulators of plasma LDL-cholesterol levels. The PCSK9 gene exhibits many single or compound polymorphisms within or among mammalian species. This is case between the SPRET/EiJ (SPRET) and C57BL/6J (B6) mouse strains. We examined whether these polymorphisms could be associated with differential expression and activity of their respective PCSK9 molecules.

Methods

Liver expression of LDLR and PCSK9 transcripts were assessed by RT-PCR, and that of their corresponding proteins by immunoblotting. Purified recombinant PCSK9 proteins were assayed for their ability to degrade LDLR. Pcsk9 gene proximal promoters were tested for activation of a luciferase reporter gene.

Results

SPRET and B6 mice carried comparable levels of plasma cholesterol in spite of the fact that SPRET mice expressed less PCSK9 and more LDLR in liver. There were indels and single-base differences between their Pcsk9 cDNA and promoter sequences. Ex vivo, SPRET PCSK9 protein was less secreted but was more active at degrading LDLR. Its gene promoter was more active at driving expression of the luciferase reporter.

Conclusions

Collectively, these results suggest that, compared to the B6 mouse, the SPRET mouse may represent an example of absence of direct correlation between PCSK9 and cholesterol levels in plasma, due to genetic variations leading to reduced secretion of PCSK9 associated with greater LDLR-degrading activity.

The role of genetics and antibodies in sepsis

During the course of sepsis when immunosuppression predominates, the concentrations of circulating immunoglobulins (IGs) are decreased and this is associated with adverse outcomes. The production of IGs as response to invasive bacterial pathogens takes place through a complex pathway starting from the recognition of the antigen (Ag) by innate immune cells that process and present Ags to T cells. The orchestration of T-helper (Th) lymphocyte responses directs specific B cells and ends with the production of IGs by plasma cells. All molecules implicated in this process are encoded by genes bearing single nucleotide polymorphisms (SNPs). Meta-analysis of case-control studies have shown that the carriage of minor frequency SNPs of CD14, TLR2 and TNF is associated with increased sepsis risk. The ambiguity of results of clinical trials studying the clinical efficacy of exogenous IG administration in sepsis suggests that efficacy of treatment should be considered after adjustment for SNPs of all implicated genes in the pathway of IG production.

New developments in proprotein convertase subtilisin-kexin 9's biology and clinical implications

PURPOSE OF REVIEW

High levels of LDL-cholesterol (LDL-C) are directly associated with devastating cardiovascular complications. Statins downregulate cholesterol synthesis and upregulate hepatic mRNA levels of LDL receptor (LDLR) and proprotein convertase subtilisin-kexin 9 (PCSK9), a validated enhancer of LDLR protein degradation. Herein, we summarize recent discoveries of the biological properties of PCSK9 in both health and disease states.

RECENT FINDINGS

PCSK9 downregulation of the LDLR protein likely explains the observed protective effect of the loss of PCSK9 in reducing lipoprotein(a) and incidence of septic shock. Injectable inhibitory PCSK9 monoclonal antibodies are now prescribed to hypercholesterolemic patients that do not reach target levels of LDL-C with available drugs. PCSK9 also reduces the levels of other receptors, for example, VLDL receptor (VLDLR), ApoER2, CD36, and CD81. The efficacy of the upregulation of LDLR and VLDLR cell surface levels in the absence of PCSK9 is both tissue and sex dependent. As LDLR, CD81, and VLDLR are hepatitis C receptors, PCSK9 may protect against certain viral infections.

SUMMARY

New functions of PCSK9 and other receptor targets are beginning to emerge to explain the observed changes in LDL-C and triglycerides. The effect of PCSK9 loss-of-function on glucose metabolism, factors that regulate the expression of PCSK9, and the roles of PCSK9 in other tissues, for example, intestine, kidney, and brain require further investigations.

Lipopolysaccharide Is Cleared from the Circulation by Hepatocytes via the Low Density Lipoprotein Receptor

Sepsis is the leading cause of death in critically ill patients. While decreased Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) function improves clinical outcomes in murine and human sepsis, the mechanisms involved have not been fully elucidated. We tested the hypothesis that lipopolysaccharide (LPS), the major Gram-negative bacteria endotoxin, is cleared from the circulation by hepatocyte Low Density Lipoprotein Receptors (LDLR)—receptors downregulated by PCSK9. We directly visualized LPS uptake and found that LPS is rapidly taken up by hepatocytes into the cell periphery. Over the course of 4 hours LPS is transported towards the cell center. We next found that clearance of injected LPS from the blood was reduced substantially in Ldlr knockout (Ldlr-/-) mice compared to wild type controls and, simultaneously, hepatic uptake of LPS was also reduced in Ldlr-/- mice. Specifically examining the role of hepatocytes, we further found that primary hepatocytes isolated from Ldlr-/- mice had greatly decreased LPS uptake. In the HepG2 immortalized human hepatocyte cell line, LDLR silencing similarly resulted in decreased LPS uptake. PCSK9 treatment reduces LDLR density on hepatocytes and, therefore, was another independent strategy to test our hypothesis. Incubation with PCSK9 reduced LPS uptake by hepatocytes. Taken together, these findings demonstrate that hepatocytes clear LPS from the circulation via the LDLR and PCSK9 regulates LPS clearance from the circulation during sepsis by downregulation of hepatic LDLR.

PCSK9 inhibition as an emerging lipid lowering therapy: Unanswered questions

Although statins have been used for the treatment of hypercholesterolemia for more than two decades, cardiovascular disease (CVD), which is related at least in part to high levels of low-density lipoprotein cholesterol (LDL-C), is the number one cause of death in Europe and the USA. Several studies have shown that the reduction in cardiovascular (CV) events is proportional to the absolute LDL-C lowering achieved with statins. In the quest for further reduction in LDL-C and CV events, new drugs that mainly support statin action have emerged. Since 2003, with the discovery of proprotein convertase subtilisin/kexin type 9 (PCSK9), which is a key factor in the LDL clearance pathway, new modalities, mainly in the form of monoclonal antibodies that block this protein (PCSK9 inhibitors), have reached phase III of clinical development with very promising efficacy and safety data. With a mean further reduction of LDL-C levels of ∼60% beyond that achieved with statins, the PCSK9 inhibitors set the bar even lower in terms of LDL-C levels. This review manuscript addresses important questions about the efficacy, safety and clinical use of PCSK9 inhibitors to evaluate the role of these agents in reducing CV risk.

PCSK9 inhibitors and cardiovascular disease: heralding a new therapeutic era

PURPOSE OF REVIEW

The first monoclonal antibodies targeting proprotein convertase subtilisin/kexin type 9 (PCSK9) have been approved for clinical use. This timely review highlights recent developments.

RECENT FINDINGS

Low-density lipoprotein cholesterol (LDL-C) is the primary driver of atherosclerosis and the key target for intervention. Yet despite best treatment including statins, attaining sufficient LDL-C lowering can be problematic for high cardiovascular risk patients. The development of PCSK9 inhibitors, driven by novel genetic and mechanistic insights, offers an answer. Removal of circulating PCSK9 increases LDL receptor availability, and thus markedly decreases plasma LDL-C levels (by ∼50-60%), and is additive to the lipid lowering effects of statins and ezetimibe. PCSK9 inhibition also reduces (by 25-30%) plasma levels of lipoprotein(a), a causal factor in atherosclerotic vascular disease, suggestive of partial catabolism of lipoprotein(a) by LDL receptors. The ODYSSEY and PROFICIO (Programme to Reduce LDL-C and Cardiovascular Outcomes Following Inhibition of PCSK9 In Different Populations) clinical trial programmes involving a wide range of high-risk patients, including statin intolerant patients, have confirmed the consistency of the LDL response, even with concomitant high-intensity statin or nonstatin therapy. Extensive evidence to date attests to a favourable safety and tolerability profile for these innovative agents.

SUMMARY

The new pharmacotherapeutic era of PCSK9 inhibition is upon us, promising major reduction in cardiovascular events across a wide spectrum of high-risk patients.