Simone A. Thair

PCSK9 is a critical regulator of the innate immune response and septic shock outcome

Inhibition of PCSK9 function is associated with an increase in pathogen lipid clearance, a decrease in the innate immune inflammatory response, and an improvement in septic shock clinical outcome. An Enemy of Translation Despite nearly 100 clinical trials, potential drugs against murine-derived therapeutic targets for sepsis—a deadly condition caused by overactivation of the innate immune response to microbial infection—have been immune to translation. But humans and microbes have long coexisted fairly symbiotically and have come to share certain biological pathways. Now, Walley et al. show that both host- and pathogen-derived lipids use clearance mechanisms that highlight a well-known protein—proprotein convertase subtilisin/kesin type 9 (PCSK9)—as a possible therapeutic target for selected sepsis patients. The authors show that, compared to wild-type mice, Pcsk9 knockout mice displayed a dampening of various pathophysiological responses to a lipopolysaccharide (LPS) in the cell wall of Gram-negative bacteria. Also, PCSK9 protein inhibited LPS uptake by human liver cells, a crucial step in systemic LPS clearance. Pharmacological inhibition of PCSK9 enhanced survival of mice with polymicrobial peritonitis, a sepsis model. Last, PCSK9 loss-of-function genetic variants were associated with improved survival in septic shock patients. Drugs that reduce serum cholesterol by inhibiting PCSK9 are being studied in clinical trials as treatments for cardiovascular disease. Then, new work suggests that PCSK9-targeted drugs should be tested in clinical trials with sepsis patients who carry the PCSK9 gain-of-function variant. A decrease in the activity of proprotein convertase subtilisin/kexin type 9 (PCSK9) increases the amount of low-density lipoprotein (LDL) receptors on liver cells and, therefore, LDL clearance. The clearance of lipids from pathogens is related to endogenous lipid clearance; thus, PCSK9 may also regulate removal of pathogen lipids such as lipopolysaccharide (LPS). Compared to controls, Pcsk9 knockout mice displayed decreases in inflammatory cytokine production and in other physiological responses to LPS. In human liver cells, PCSK9 inhibited LPS uptake, a necessary step in systemic clearance and detoxification. Pharmacological inhibition of PCSK9 improved survival and inflammation in murine polymicrobial peritonitis. Human PCSK9 loss-of-function genetic variants were associated with improved survival in septic shock patients and a decrease in inflammatory cytokine response both in septic shock patients and in healthy volunteers after LPS administration. The PCSK9 effect was abrogated in LDL receptor (LDLR) knockout mice and in humans who are homozygous for an LDLR variant that is resistant to PCSK9. Together, our results show that reduced PCSK9 function is associated with increased pathogen lipid clearance via the LDLR, a decreased inflammatory response, and improved septic shock outcome.

β2-Adrenergic Receptor Gene Polymorphism Is Associated with Mortality in Septic Shock

RATIONALE The CysGlyGln haplotype of the beta(2)-adrenergic receptor gene (ADRB2) is functional and associated with altered responses to adrenergic agonists in patients with asthma. Whether this functional haplotype alters outcome in patients receiving adrenergic agonists in septic shock is unknown. OBJECTIVES To determine whether genetic variation of ADRB2 influences outcome in septic shock. METHODS Two cohorts of patients with septic shock were studied: a single center (St. Pauls Hospital [SPH]) cohort (n = 589) and the Vasopressin and Septic Shock Trial (VASST) cohort (n = 616). The A allele of the rs1042717 G/A polymorphism is in complete linkage disequilibrium with the CysGlyGln haplotype of ADRB2; therefore, rs1042717 was genotyped. Modulation by norepinephrine and salbutamol of IL-6 production by stimulated in vitro lymphoblastoid cells was measured by genotype. MEASUREMENTS AND MAIN RESULTS Patients who had the AA genotype of rs1042717 displayed increased 28-day mortality in SPH (adjusted hazard ratio, 2.23; 95% confidence interval, 1.33-3.72; P = 0.0022), and this result was replicated in VASST (adjusted hazard ratio 2.82; 95% confidence interval, 1.56-5.09; P = 0.0006). This genotypic effect was eliminated in patients treated with acute low-dose corticosteroids. In all patients, the AA genotype was associated with more organ dysfunction. Patients with the AA genotype had a higher heart rate (SPH; P < 0.05; VASST; P < 0.05) and required a higher norepinephrine dose over Days 1 through 3 (VASST; P < 0.05). The AA genotype was associated with decreased norepinephrine and salbutamol inhibition of IL-6 production by stimulated lymphoblastoid cells in vitro (P < 0.05). CONCLUSIONS The AA genotype of ADRB2 rs1042717, identifying homozygotes for the CysGlyGln haplotype, was associated with increased mortality and more organ dysfunction in septic shock.

Vasopressin Compared with Norepinephrine Augments the Decline of Plasma Cytokine Levels in Septic Shock

RATIONALE Changes in plasma cytokine levels may predict mortality, and therapies (vasopressin versus norepinephrine) could change plasma cytokine levels in early septic shock. OBJECTIVES Our hypotheses were that changes in plasma cytokine levels over 24 hours differ between survivors and nonsurvivors, and that there are different effects of vasopressin and norepinephrine on plasma cytokine levels in septic shock. METHODS We studied 394 patients in a randomized, controlled trial of vasopressin versus norepinephrine in septic shock. We used hierarchical clustering and principal components analysis of the baseline cytokine concentrations to subgroup cytokines; we then compared survivors to nonsurvivors (28 d) and compared vasopressin- versus norepinephrine-induced changes in cytokine levels over 24 hours. MEASUREMENTS AND MAIN RESULTS A total of 39 plasma cytokines were measured at baseline and at 24 hours. Hierarchical clustering and principal components analysis grouped cytokines similarly. Survivors (versus nonsurvivors) had greater decreases of overall cytokine levels (P < 0.001). Vasopressin decreased overall 24-hour cytokine concentration compared with norepinephrine (P = 0.037). In less severe septic shock, the difference in plasma cytokine reduction over 24 hours between survivors and nonsurvivors was less pronounced than that seen in more severe septic shock. Furthermore, vasopressin decreased interferon-inducible protein 10 and granulocyte colony-stimulating factor more than did norepinephrine in less severe septic shock, whereas vasopressin decreased granulocyte-macrophage colony-stimulating factor in patients who had more severe shock. CONCLUSIONS Survivors of septic shock had greater decreases of cytokines, chemokines and growth factors in early septic shock. Vasopressin decreased 24-hour plasma cytokine levels more than did norepinephrine. The vasopressin-associated decrease of cytokines differed according to severity of shock. Clinical trial registered with www.controlled-trials.com (ISRCTN94845869).

A Single Nucleotide Polymorphism in NF-κB Inducing Kinase Is Associated with Mortality in Septic Shock

We tested the hypothesis that single nucleotide polymorphisms (SNPs) within genes of the NF-κB pathway are associated with altered clinical outcome of septic shock patients. We genotyped 59 SNPs in the NF-κB pathway in a discovery cohort of septic shock patients (St. Paul’s Hospital [SPH], N = 589), which identified the C allele of rs7222094 T/C within MAP3K14 (NF-κB inducing kinase; NIK) associated with increased 28-d mortality (uncorrected p = 0.00024, Bonferroni corrected p = 0.014). This result was replicated in a second cohort of septic shock patients (Vasopressin and Septic Shock Trial [VASST; N = 616]) in which the CC genotype of rs7222094 was associated with increased 28-d mortality (Cox regression: SPH cohort hazard ratio [HR], 1.35; 95% confidence interval [CI], 1.12–1.64; p = 0.002 Caucasian only; and VASST cohort HR, 1.24; 95% CI, 1.00–1.52; p = 0.048 Caucasian only). Patients having the CC genotype of rs7222094 in SPH experienced more renal and hematological dysfunction (p = 0.003 and p = 0.011), while patients of the VASST cohort with the rs7222094 CC genotype showed the same trend toward more renal dysfunction. In lymphoblastoid cell lines, we found the rs7222094 genotype most strongly associated with mRNA expression of CXCL10, a chemokine regulated by NF-κB. Accordingly, we measured CXCL10 protein levels and found that the CC genotype of rs7222094 was associated with significantly lower levels than those of the TT genotype in lymphoblastoid cell lines (p < 0.05) and in septic shock patients (p = 0.017). This suggests that the CC genotype of NIK rs7222094 is associated with increased mortality and organ dysfunction in septic shock patients, perhaps due to altered regulation of NF-κB pathway genes, including CXCL10.

Leucyl/Cystinyl Aminopeptidase Gene Variants in Septic Shock

BACKGROUND Vasopressin is an essential peptide hormone regulating cardiovascular homeostasis and an adjunctive vasopressor therapy for septic shock. METHODS We tested for association between single nucleotide polymorphisms (SNPs) in vasopressin pathway genes and altered outcome in derivation (n = 589) and replication (n = 616) cohorts of patients with septic shock. The primary outcome was 28-day mortality and the secondary outcome was vasopressin clearance. In a third cardiac surgical cohort (n = 977), we tested for locus-specific heritability of serum sodium concentrations. RESULTS Of 17 tested tag SNPs in five vasopressin pathway genes (arginine vasopressin [AVP], arginine vasopressin receptor 1A and 1B [AVPR1A, AVPR1B], leucyl/cystinyl aminopeptidase [LNPEP], and oxytocin receptor [OXTR]), rs18059 in LNPEP (also known as vasopressinase) was associated with 28-day mortality in the derivation cohort (P = .037). Therefore, we resequenced the 160-kb haplotype block encompassing the LNPEP gene, including rs18059, and genotyped the 230 identified SNPs in the derivation cohort. The strongest signal was found for LNPEP rs4869317 (adjusted P = .044). The rs4869317 TT genotype was associated with increased 28-day mortality in the derivation cohort (51.0% [TT] vs 34.5% [AA/AT]; adjusted hazard ratio [HR], 1.58; 95% CI, 1.21-2.06; P = .00073) and the replication cohort (38.6% vs 29.6%; HR, 1.36; 95% CI, 1.03-1.80; P = .030). We found that the TT genotype was associated with increased plasma vasopressin clearance (P = .028), and the rs4869317 genotype accounted for 80% of the variance of serum sodium concentrations (locus-specific heritability) in cardiac surgical patients. CONCLUSIONS The genetic variation in LNPEP (vasopressinase) is associated with 28-day mortality in septic shock and is associated with biologic effects on vasopressin clearance and serum sodium regulation. Further confirmation in additional cohorts is required.

Association of angiotensin II type 1 receptor-associated protein gene polymorphism with increased mortality in septic shock.

Objective:Angiotensin II and its postreceptor signaling are crucial in regulating vasomotor tone. The objective of this study was to test the hypothesis that single nucleotide polymorphisms in angiotensin II pathway genes alter outcome of septic shock. Design:Genetic association study and in vitro experiment. Setting:Intensive care units at academic teaching centers. Patients:Derivation and validation septic shock cohorts (n = 589 and n = 616, respectively) and a coronary artery bypass surgery cohort (n = 551). Interventions:Patients with septic shock in the derivation cohort were genotyped for tag single nucleotide polymorphisms: angiotensin-converting enzyme (six single nucleotide polymorphisms), angiotensin II receptor type 1 (five single nucleotide polymorphisms), and angiotensin II type 1 receptor-associated protein (three single nucleotide polymorphisms), which is a negative regulator of angiotensin II receptor type 1. Patients in the septic shock replication cohort and the coronary artery bypass graft cohort were genotyped for the angiotensin II type 1 receptor-associated protein rs11121816. Measurements and Main Results:The primary outcome variable was 28-day mortality. Secondary outcome variables were blood pressure and heart rate. Angiotensin II type 1 receptor-associated protein messenger RNA expression was measured in genotyped lymphoblastoid cells in vitro. Patients with septic shock patients the GG genotype of angiotensin II type 1 receptor-associated protein rs11121816 had increased 28-day mortality in the derivation cohort (54.8% vs. 41.4%; adjusted hazard ratio, 1.46; 95% confidence interval, 1.09–1.93; p = .010 [all ethnicities]; p = .050 [white]) and in the replication cohort (43.8% vs. 32.3%; hazard ratio, 1.42; 95% confidence interval, 1.03–1.98; p = .035 [all ethnicities]; p = .037 [white]). Patients having the GG genotype had decreased mean arterial pressure (98.3% of other genotype, p = .058 [derivation cohort]; 97.7%, p = .00060 [replication cohort]) and increased heart rate (104.1%, p = .023 [derivation cohort], 102.9%, p = nonsignificant [replication cohort]). GG genotype patients undergoing coronary artery bypass grafting had decreased postoperative mean arterial pressure and increased postoperative heart rate (p < .05). GG genotype lymphoblastoid cells had 2.0-fold higher angiotensin II type 1 receptor-associated protein messenger RNA expression (p < .05). Conclusions:For angiotensin II type 1 receptor-associated protein, the negative regulator of angiotensin II receptor type 1, the GG genotype of rs11121816 was associated with increased angiotensin II type 1 receptor-associated protein expression, decreased blood pressure, and increased heart rate as well as increased 28-day mortality in septic shock.

Molecular Mechanisms of Sepsis

In cancer, therapies are targeted at 6 important pathways. In sepsis, there is ongoing controversy regarding the number and relative roles of pathways that are activated or repressed and which are important in the progression from health to death. Adding to complexity, there is interaction of pathways, there are differences in temporal pattern of up and down-regulation of pathways and there are different responses of pathways to therapies of sepsis. In this review, we define four key pathways of sepsis: (1) inflammation and immunity, (2) coagulation and fibrinolysis, (3) apoptosis, and (4) endocrine. Each of these pathways can impair endothelial function, a unifying aspect of the pathophysiology of sepsis. There are few studies of interactions of pathways except for the interacttion of inflammation/immunity with coagulation/fibrinolysis. Successful treatment of cancer requires that cancer therapies interrupt several key pathways of cancer. Accordingly, we suggest that successful treatment of sepsis will require therapies that interrupt several key pathways of sepsis. Perhaps the paucity of approved therapies for sepsis is related in part to the underevaluation of novel pathways, to lack of understanding of interactions of pathways and to lack of interruption of key pathways of sepsis.

Cytokines and Signaling Molecules Predict Clinical Outcomes in Sepsis

Introduction Inflammatory response during sepsis is incompletely understood due to small sample sizes and variable timing of measurements following the onset of symptoms. The vasopressin in septic shock trial (VASST) compared the addition of vasopressin to norepinephrine alone in patients with septic shock. During this study plasma was collected and 39 cytokines measured in a 363 patients at both baseline (before treatment) and 24 hours. Clinical features relating to both underlying health and the acute organ dysfunction induced by the severe infection were collected during the first 28 days of admission. Hypothesis Cluster analysis of cytokines identifies subgroups of patients at differing risk of death and organ failure. Methods Circulating cytokines and other signaling molecules were measured using a Luminex multi-bead analyte detection system. Hierarchical clustering was performed on plasma values to create patient subgroups. Enrichment analysis identified clinical outcomes significantly different according to these chemically defined patient subgroups. Logistic regression was performed to assess the importance of cytokines for predicting patient subgroups. Results Plasma levels at baseline produced three subgroups of patients, while 24 hour levels produced two subgroups. Using baseline cytokine data, one subgroup of 47 patients showed a high level of enrichment for severe septic shock, coagulopathy, renal failure, and risk of death. Using data at 24 hours, a larger subgroup of 81 patients that largely encompassed the 47 baseline subgroup patients had a similar enrichment profile. Measurement of two cytokines, IL2 and CSF2 and their product were sufficient to classify patients into these subgroups that defined clinical risks. Conclusions A distinct pattern of cytokine levels measured early in the course of sepsis predicts disease outcome. Subpopulations of patients have differing clinical outcomes that can be predicted accurately from small numbers of cytokines. Design of clinical trials and interventions may benefit from consideration of cytokine levels.

Exploiting the therapeutic potential of microRNAs in viral diseases: expectations and limitations.

New therapeutic approaches are urgently needed for serious diseases, including cancer, cardiovascular diseases, viral infections, and others. A recent direction in drug development is the utilization of nucleic acid-based therapeutic molecules, such as antisense oligonucleotides, ribozymes, short interfering RNA (siRNA), and microRNA (miRNA). miRNAs are endogenous, short, non-coding RNA molecules. Some viruses encode their own miRNAs, which play pivotal roles in viral replication and immune evasion strategies. Conversely, viruses that do not encode miRNAs may manipulate host cell miRNAs for the benefits of their replication. miRNAs have therefore become attractive tools for the study of viral pathogenesis. Lately, novel therapeutic strategies based on miRNA technology for the treatment of viral diseases have been progressing rapidly. Although this new generation of molecular therapy is promising, there are still several challenges to face, such as targeting delivery to specific tissues, avoiding off-target effects of miRNAs, reducing the toxicity of the drugs, and overcoming mutations and drug resistance. In this article, we review the current knowledge of the role and therapeutic potential of miRNAs in viral diseases, and discuss the limitations of these therapies, as well as strategies to overcome them to provide safe and effective clinical applications of these new therapeutics.

Identification of a nonsynonymous polymorphism in the SVEP1 gene associated with altered clinical outcomes in septic shock.

Objectives:Mortality from septic shock is highly heritable. The identification of causal genetic factors is insufficient. To discover key contributors, we first identified nonsynonymous single-nucleotide polymorphisms in conserved genomic regions that are predicted to have significant effects on protein function. We then test the hypothesis that these nonsynonymous single-nucleotide polymorphisms across the genome alter clinical outcome of septic shock. Design:Genetic-association study plus in vitro experiment using primary cells plus in silico analysis using genomic DNA and protein database. Setting:Twenty-seven ICUs at academic teaching centers in Canada, Australia, and the United States. Patients:Patients with septic shock of European ancestry (n = 520). Interventions:Patients with septic shock were genotyped for 843 nonsynonymous single-nucleotide polymorphisms in conserved regions of the genome and are predicted to have damaging effects from the protein sequence. Measurements and Main Results:The primary outcome variable was 28-day mortality. Secondary outcome variables were organ dysfunction. Productions of adhesion molecules including interleukin-8, growth-regulated oncogene-&agr;, monocyte chemoattractant protein-1, and monocyte chemoattractant protein-3 were measured in human umbilical vein endothelial cells after SVEP1 gene silencing by RNA interference. Patients with septic shock having the SVEP1 C allele of nonsynonymous single-nucleotide polymorphism, SVEP1 c.2080A>C (p. Gln581His, rs10817033), had a significant increase in the hazard of death over the 28 days (hazard ratio, 1.72; 95% CI, 1.31–2.26; p = 9.7 × 10–5) and increased organ dysfunction and needed more organ support (p < 0.05). Silencing SVEP1 significantly increased interleukin-8, growth-regulated oncogene-&agr;, monocyte chemoattractant protein-1, monocyte chemoattractant protein-3 production in human umbilical vein endothelial cells under lipopolysaccharide stimulation (p < 0.01). Conclusions:C allele of SVEP1 c.2080A>C (p. Gln581His) single-nucleotide polymorphism, a non-synonymous single-nucleotide polymorphism in conserved regions and predicted to have damaging effects on protein structure, was associated with increased 28-day mortality and organ dysfunction of septic shock. SVEP1 appears to regulate molecules of the leukocyte adhesion pathway.