The many faces of sepsis-induced vascular failure

Variants in TNF and NOS3 (eNOS) genes associated with sepsis in adult patients

BACKGROUND

Sepsis is a life-threatening condition caused by a dysregulated host response to infections and is a leading cause of death in hospitalized patients. The present study aimed to elucidate the possible association between sepsis and the tumor necrosis factor (TNF) gene -308G/A (rs1800629) polymorphism, as well as endothelial nitric oxide synthase (eNOS, NOS3) gene -786T/C (rs2070744), 4a/4b (27 bp-VNTR in intron 4, rs61722009) and 894G/T (Glu298Asp, rs1799983) polymorphisms.

METHODS

In total, 188 septic adult cases and 188 healthy controls were enrolled. Genomic DNAs from the controls and patients were analyzed by polymerase chain reaction and restriction fragment length polymorphism methods.

RESULTS

There were significant associations between the G/G genotype and G allele of the TNF -308G/A (rs1800629) polymorphism in the sepsis group (p < 0.001). The presence of the T/C genotype (p = 0.002) and C allele (p = 0.001) of the -786T/C (rs2070744) was markedly associated with an increased risk of sepsis. However, no significant associations were found with 4a/4b (27 bp-VNTR in intron 4, rs61722009) and 894G/T (Glu298Asp, rs1799983) polymorphisms. Higher 4bGC and lower 4bTT haplotype frequencies were associated with sepsis.

CONCLUSIONS

Our results strongly suggest that TNF gene (-308G/A, rs1800629) and NOS3 gene -786T/C (rs2070744) polymorphisms may modify individual susceptibility to sepsis in the Turkish population.

Association between increased arterial stiffness and clinical outcomes in patients with early sepsis: a prospective observational cohort study

Background

Conduit arteries, especially the aorta, play a major role in ensuring efficient cardiac function and optimal microvascular flow due to their viscoelastic properties. Studies in animals and on isolated arteries show that acute systemic inflammation can cause aortic stiffening which affects hemodynamic efficiency. Carotid-femoral pulse wave velocity, a measure of aortic stiffness, may be useful as a bedside investigational method in patients with early sepsis admitted to intensive care, as circulatory changes can lead to multiple organ failure and increased mortality. This study aims to investigate arterial stiffness in early sepsis and its association with clinical outcomes.

Methods

This prospective observational study included adult patients with severe sepsis or septic shock admitted to our intensive care unit (n = 45). Their carotid-femoral pulse wave velocity was measured within 24 h of admission. We assessed the progression of multiple organ as well as cardiovascular failure by sequential SOFA scores. Prediction models for the progression of multiple organ and cardiovascular failure were constructed using multivariate logistic regression with pulse wave velocity and vasopressor use as predictors. A Cox proportional hazards model was used to examine the relationship between pulse wave velocity and survival time.

Results

The median pulse wave velocity for the cohort was 14.6 (8.1–24.7) m/s. There was no association between pulse wave velocity and the progression of multiple organ failure, before or after adjustment for vasopressor use. No association was found between pulse wave velocity and subsequent improvement in cardiovascular failure in the subgroup of patients who had cardiovascular instability at baseline. Cox regression and survival analyses with age, APACHE II, and baseline SOFA as confounders showed a shorter hospital survival time for patients with pulse wave velocity > 24.7 m/s (HR = 9.45, 95% CI 1.24–72.2; P = 0.03).

Conclusions

Patients with severe sepsis and septic shock admitted to intensive care have higher arterial stiffness than in the general population. No convincing association was found between pulse wave velocity at admission and the progression of multiple organ or cardiovascular failure, although the group with pulse wave velocity > 24.7 m/s had shorter survival time.

Electronic supplementary material

The online version of this article (10.1186/s40635-019-0252-3) contains supplementary material, which is available to authorized users.

Toll-Like Receptor 4 Reduces Oxidative Injury via Glutathione Activity in Sheep

Toll-like receptor 4 (TLR4) is an important sensor of Gram-negative bacteria and can trigger activation of the innate immune system. Increased activation of TLR4 can lead to the induction of oxidative stress. Herein, the pathway whereby TLR4 affects antioxidant activity was studied. In TLR4-overexpressing sheep, TLR4 expression was found to be related to the integration copy number when monocytes were challenged with lipopolysaccharide (LPS). Consequently, production of malondialdehyde (MDA) was increased, which could increase the activation of prooxidative stress enzymes. Meanwhile, activation of an antioxidative enzyme, glutathione peroxidase (GSH-Px), was increased. Real-time PCR showed that expression of activating protein-1 (AP-1) and the antioxidative-related genes was increased. By contrast, the expression levels of superoxide dismutase 1 (SOD1) and catalase (CAT) were reduced. In transgenic sheep, glutathione (GSH) levels were dramatically reduced. Furthermore, transgenic sheep were intradermally injected with LPS in each ear. The amounts of inflammatory infiltrates were correlated with the number of TLR4 copies that were integrated in the genome. Additionally, the translation of γ-glutamylcysteine synthetase (γ-GCS) was increased. Our findings indicated that overexpression of TLR4 in sheep could ameliorate oxidative injury through GSH secretion that was induced by LPS stimulation. Furthermore, TLR4 promoted γ-GCS translation through the AP-1 pathway, which was essential for GSH synthesis.

Changes in the relative inflammatory responses in sheep cells overexpressing of toll-like receptor 4 when stimulated with LPS

BACKGROUND

Many groups of Gram-negative bacteria cause diseases harmful to sheep. TLR4 is an important Toll-like receptor (TLR) which responds to common Gram-negative bacterial infections. Activation of TLR4 leads to the induction of inflammatory responses, which is a linkage between the innate and adaptive immune systems. A vector pTLR4-3S was constructed to overexpress TLR4 gene in sheep. In this study, effects of TLR4 overexpression on inflammation response under LPS stimulated were addressed in vivo and in vitro.

METHODOLOGY/PRINCIPAL FINDINGS

Sheep fetal fibroblasts were transfected with expression vector pTLR4-3S. Transgenic sheep were produced by microinjection of the constructed plasmids into fertilized eggs. Fetal fibroblasts, monocyte-macrophage and fibroblasts isolated from the transgenic sheep were stimulated by LPS. After that immunoactive factors (TNF-α, IL-10, IL-6, IL-8, IFN-γ), nitric oxide, phagocytize ability and adhesion were detected. Furthermore, transgenic sheep were intradermal injected of LPS in ear and observed pathological changes by HE strain. Overexpression of TLR4 gene was observed on transgenic cells and individuals. In vitro, TLR4 overexpression transgenic cells secreted Th1 and Th2 inducing cytokines with a strong LPS mediated inflammation response and promoting the secretion of nitric oxide, and then recovered to initial level. The phagocytosis index of monocyte/macrophage in transgenic sheep was higher than that of non-transgenic sheep (P<0.05). In vivo, tissue sections showed that transgenic individuals launched inflammation response more quickly.

CONCLUSIONS/SIGNIFICANCE

Overexpression of TLR4 in transgenic sheep enhanced the clearance of invaded microbe through secretion of cytokines, activation of macrophage, oxidation damage and infiltration of neutrophil.

Endothelial nitric oxide synthase 894G→T but not -786T→C gene polymorphism is associated with organ dysfunction and increased mortality in patients with severe sepsis

BACKGROUND

Endothelial nitric oxide synthase (eNOS) -786T→C and 894G→T polymorphisms have been associated with eNOS dysfunction, which might further compromise microcirculatory blood flow during sepsis and increase the risk of organ injury. The purpose of this study is to investigate the association of those two eNOS gene polymorphisms with the severity of organ dysfunction and outcome in patients with severe sepsis.

METHODS

A cohort of patients with severe sepsis was studied and genotyped for eNOS -786T→C and 894G→T polymorphisms. Acute Physical and Chronic Health Evaluation score, the Sequential Organ Failure Assessment score, with or without shock, and the outcomes were compared in patients with different genotypes.

RESULTS

One hundred seventeen patients fulfilled with inclusion criteria were enrolled from nine intensive care units of academic hospital in Beijing. In comparison with the GG genotype, patients with the GT genotype (894G→T) had a trend toward an increase in the frequency of shock (87% vs. 68.1%, p=0.071) and significantly fewer days to shock onset (p<0.05). Those patients also had significantly higher Acute Physical and Chronic Health Evaluation II scores (p<0.05), Sequential Organ Failure Assessment scores (p<0.001), and mortality at both 7 days and 28 days (p<0.001). Multivariate analyses identified the GT genotype (894G→T) as an independent risk factor for outcome in patients with severe sepsis. However, we found that the eNOS -786T→C polymorphism was not associated with severity of disease or mortality of patients with sepsis.

CONCLUSIONS

Carriage of the GT genotype at 894 of eNOS gene was associated with the occurrence of shock and impaired organ function.

The critically ill injured patient

Patients admitted to the ICU after severe trauma require frequent procedures in the operating room, particularly in cases where a damage control strategy is used. The ventilatory management of these patients in the operating room can be particularly challenging. These patients often have severely impaired respiratory mechanics because of acute lung injury and abdominal compartment syndrome. Consequently, the pressure and flow generation capabilities of standard anesthesia ventilators may be inadequate to support ventilation and gas exchange. This article presents the problems that may be encountered in patients who have severe abdominal and lung injuries, and the current management concepts used in caring for these patients in the critical care setting, to provide guidelines for the anesthetist faced with these patients in the operating room.

Preclinical trial of L-arginine monotherapy alone or with N-acetylcysteine in septic shock

OBJECTIVE

L-arginine supplementation in sepsis is controversial. Septic shock has been alternatively viewed as an L-arginine-deficient state or as a syndrome caused by excess nitric oxide, an end-product of L-arginine metabolism.

DESIGN

Randomized, placebo-controlled, and double-blinded (investigators, veterinarians, and pharmacists).

SETTING

Laboratory.

SUBJECTS

Purpose-bred, 1- to 2-yr-old, 10- to 12-kg beagles.

INTERVENTIONS

The effects of parenteral L-arginine alone or in combination with N-acetylcysteine were compared with vehicle alone in a well-characterized canine model of Escherichia coli peritonitis. Two doses were studied that delivered approximately 1.5-fold (10 mg x kg(-1) x hr(-1)) and 15-fold (100 mg x kg(-1) x hr(-1)) the L-arginine dose typically administered with standard total parenteral nutrition. Animals in the low- and high-dose L-arginine arms were further randomized to receive vehicle alone or N-acetylcysteine (20 mg x kg(-1) x hr(-1)) as an antioxidant to prevent peroxynitrite formation.

MEASUREMENTS AND MAIN RESULTS

The main measurements were hemodynamics, plasma arginine and ornithine, serum nitrate/nitrite, laboratory studies for organ injury, and survival. Both doses of L-arginine similarly increased mortality (p = .02), and worsened shock (p = .001 for reduced mean arterial pressure). These effects were associated with significant increases in plasma arginine (p = .0013) and ornithine (p = .0021). In addition, serum nitrate/nitrite (p = .02), liver enzymes (p = .08), and blood urea nitrogen/creatinine ratios (p = .001) rose, whereas arterial pH (p = .001) and bicarbonate levels (p = .001) fell. N-acetylcysteine did not significantly decrease any of the harmful effects of L-arginine. Thus, parenteral L-arginine monotherapy was markedly harmful in animals with septic shock.

CONCLUSIONS

These findings suggest that supplemental parenteral L-arginine, at doses above standard dietary practices, should be avoided in critically ill patients with septic shock.

Nitric oxide post-transcriptionally up-regulates LPS-induced IL-8 expression through p38 MAPK activation

Nitric oxide (NO(.-)) contributes to vascular collapse in septic shock and regulates inflammation. Here, we demonstrate in lipopolysaccharide (LPS)-stimulated human THP-1 cells and monocytes that NO(.-) regulates interleukin (IL)-8 and tumor necrosis factor alpha (TNF-alpha) by distinct mechanisms. Dibutyryl-cyclic guanosine 5'-monophosphate (cGMP) failed to simulate NO(.-)-induced increases in TNF-alpha or IL-8 production. In contrast, dibutyryl-cyclic adenosine monophosphate blocked NO(.-)-induced production of TNF-alpha (P=0.009) but not IL-8. NO(.-) increased IL-8 (5.7-fold at 4 h; P=0.04) and TNF-alpha mRNA levels (2.2-fold at 4 h; P=0.037). However, nuclear run-on assays demonstrated that IL-8 transcription was slightly decreased by NO(.-) (P=0.08), and TNF-alpha was increased (P=0.012). Likewise, NO(.-) had no effect on IL-8 promoter activity (P=0.84) as measured by reporter gene assay. In THP-1 cells and human primary monocytes treated with actinomycin D, NO(.-) had no effect on TNF-alpha mRNA stability (P>0.3 for both cell types) but significantly stabilized IL-8 mRNA (P=0.001 for both cell types). Because of its role in mRNA stabilization, the p38 mitogen-activated protein kinase (MAPK) pathway was examined and found to be activated by NO(.-) in LPS-treated THP-1 cells and human monocytes. Further, SB202190, a p38 MAPK inhibitor, was shown to block NO(.-)-induced stabilization of IL-8 mRNA (P<0.02 for both cell types). Thus, NO(.-) regulates IL-8 but not TNF-alpha post-transcriptionally. IL-8 mRNA stabilization by NO(.-) is independent of cGMP and at least partially dependent on p38 MAPK activation.

Adjacent sequence controls the response polarity of nitric oxide-sensitive Sp factor binding sites

Nitric oxide (NO*) and cAMP-dependent protein kinase (PKA) inhibitors up-regulate tumor necrosis factor alpha (TNFalpha) by decreasing Sp1 binding to a proximal GC box element. Here, elements flanking GC boxes were tested for their role in determining whether Sp sites act as activators or repressors. Promoter studies in receptive human cell lines demonstrated that NO* down-regulated endothelial NO* synthase (eNOS) but up-regulated TNFalpha. Like TNFalpha, Sp1 binding to the eNOS promoter was decreased by NO* and a PKA inhibitor, H89, and increased by a PKA activator, dibutyryl cAMP (Bt2cAMP). For either promoter, mutation of Sp sites abolished NO* responses. In contrast, mutation of an upstream AP1 site in the TNFalpha promoter (not present in eNOS) maintained NO* responsiveness, but reversed the direction of NO* and cAMP effects. Using artificial constructs, NO* increased transcription when Sp and AP1 sites were both present (TNFalpha-like response), but decreased it when the adjacent AP1 site was disrupted (eNOS-like response). NO*, H89, and Bt2cAMP were found to produce reciprocal protein binding changes at contiguous AP1 and Sp sites (p < 0.0001 for an interaction). Chromatin immunoprecipitation assays demonstrated that Sp1 and to a lesser extent Sp3 bound to the GC box regions of eNOS and TNFalpha in intact cells. Thus, this NO*- and cAMP-responsive regulatory module has a Sp site sensor variably coupled to an adjacent element that determines response polarity. These results define a composite element that can utilize secondary inputs to convert off signals to on, thereby conferring complex functionalities to the same DNA binding motif.

New concepts in sepsis

An estimated 750,000 cases of severe sepsis occur annually in the United States, and the mortality rate is about 30%. As a condition that disproportionately affects the elderly and is related to invasive and immunosuppressive healthcare, increases in the frequency of sepsis are anticipated. The complex pathophysiology of sepsis encompasses the interplay of pro- and anti-inflammatory mediators, activated circulating and resident inflammatory cells, disrupted coagulation, endothelial activation and injury, vasodilatation and vascular hyporesponsiveness to vasoactive mediators, cardiac dysfunction, and cellular dysoxia. Current management of severe sepsis includes eradication of infection through source control and antimicrobial therapy, aggressive and targeted shock resuscitation that includes fluid administration, correction of anemia, vasopressor support, modest inotropic therapy, infusion of human recombinant activated protein C to selected patients, and compulsive supportive care to manage organ dysfunction and to avoid complications.