The pathogenesis of septic shock

Identification of S1PR3 gene signature involved in survival of sepsis patients

BACKGROUND

Sepsis is a life-threatening complication of infection that rapidly triggers tissue damage in multiple organ systems and leads to multi-organ deterioration. Up to date, prognostic biomarkers still have limitations in predicting the survival of patients with sepsis. We need to discover more prognostic biomarkers to improve the sensitivity and specificity of the prognosis of sepsis patients. Sphingosine-1-phosphate (S1P) receptor 3 (S1PR3), as one of the S1P receptors, is a prospective prognostic biomarker regulating sepsis-relevant events, including compromised vascular integrity, antigen presentation, and cytokine secretion. Until now, no S1PR3-related prognostic gene signatures for sepsis patients have been found.

METHODS

This study intends to obtain an S1PR3-associated gene signature from whole blood samples to be utilized as a probable prognostic tool for patients with sepsis.

RESULTS

We obtained an 18-gene S1PR3-related molecular signature (S3MS) from the intersection of S1PR3-associated genes and survival-associated genes. Numerous important immunity pathways that regulate the progression of sepsis are enriched among our 18 genes. Significantly, S3MS functions greatly in both the discovery and validation cohort. Furthermore, we demonstrated that S3MS obtains significantly better classification performance than random 18-gene signatures.

CONCLUSIONS

Our results confirm the key role of S1PR3-associated genes in the development of sepsis, which will be a potential prognostic biomarker for patients with sepsis. Our results also focus on the classification performance of our S3MS as biomarkers for sepsis, which could also provide an early warning system for patients with sepsis.

Low-dose plasmid DNA treatment increases plasma vasopressin and regulates blood pressure in experimental endotoxemia

Background

Although plasmid DNA encoding an antigen from pathogens or tumor cells has been widely studied as vaccine, the use of plasmid vector (without insert) as therapeutic agent requires further investigation.

Results

Here, we showed that plasmid DNA (pcDNA3) at low doses inhibits the production of IL-6 and TNF-α by lipopolysaccharide (LPS)-stimulated macrophage cell line J774. These findings led us to evaluate whether plasmid DNA could act as an anti-inflammatory agent in a Wistar rat endotoxemia model. Rats injected simultaneously with 1.5 mg/kg of LPS and 10 or 20 μg of plasmid DNA had a remarkable attenuation of mean arterial blood pressure (MAP) drop at 2 hours after treatment when compared with rats injected with LPS only. The beneficial effect of the plasmid DNA on MAP was associated with decreased expression of IL-6 in liver and increased concentration of plasma vasopressin (AVP), a known vasoconstrictor that has been investigated in hemorrhagic shock management. No difference was observed in relation to nitric oxide (NO) production.

Conclusion

Our results demonstrate for the first time that plasmid DNA vector at low doses presents anti-inflammatory property and constitutes a novel approach with therapeutic potential in inflammatory diseases.

Síndrome de disfunção de múltiplos órgãos induzida por sepse: estudo experimental em ratos

RACIONAL: A principal causa de morte em pacientes com sepse em cirurgia é a síndrome de disfunção de múltiplos órgãos. Assim, modelos experimentais que simulem alterações orgânicas da sepse em humanos são necessários. OBJETIVO: Apresentar dois modelos que induzem a síndrome de disfunção de múltiplos órgãos e comparar as alterações induzidas por inoculação endovenosa de 36UE de lipopolissacarídeo ou célula viável de Escherichia coli, em relação à: mortalidade e sobrevivência; nível de lipopolissacarídeo; liberação de fator de necrose tumoral alfa; alterações hematológicas e das funções hepática e renal. MÉTODO: Este estudo teve duração de sete dias e utilizou-se nele 50 ratos Wistar machos, divididos em três grupos: controle, lipopolissacarídeo e Escherichia coli. Os grupos experimento eram inoculados e separados em dois subgrupos, com inoculação a cada 24 ou 48 horas. No sétimo dia eram procedidas coletas de sangue e análise histopatológica de fígado, rins e pulmões. RESULTADOS: Houve sobrevivência de dez animais no grupo controle; zero no bacteriano de 24 horas e seis no de 48 horas; dez no lipopolissacarídeo de 24 horas e seis no de 48 horas. Nos grupos experimentais, os níveis de lipopolissacarídeo, fator de necrose tumoral alfa, leucócitos, plaquetas, bastonetes e as alterações renais e hepáticas foram superiores ao grupo controle. Houve alterações histopatológicas no grupo bacteriano. CONCLUSÃO: Os dois modelos de sepse induziram síndrome de disfunção de múltiplos órgãos, contudo a administração de 36UE de endotoxina a cada 48 horas pode ser utilizada com vantagens sobre os demais por não induzir morte em número significativo durante o período de sete dias.

Matrix metalloproteinase inhibitor properties of tetracyclines: therapeutic potential in cardiovascular diseases

Matrix metalloproteinases (MMPs) are a family of proteases best known for their capacity to proteolyse several proteins of the extracellular matrix. Their increased activity contributes to the pathogenesis of several cardiovascular diseases. MMP-2 in particular is now considered to be also an important intracellular protease which has the ability to proteolyse specific intracellular proteins in cardiac muscle cells and thus reduce contractile function. Accordingly, inhibition of MMPs is a growing therapeutic aim in the treatment or prevention of various cardiovascular diseases. Tetracyclines, especially doxycycline, have been frequently used as important MMP inhibitors since they inhibit MMP activity independently of their antimicrobial properties. In this review we will focus on the intracellular actions of MMPs in some cardiovascular diseases including ischemia and reperfusion (I/R) injury, inflammatory heart diseases and septic shock; and explain how tetracyclines, as MMP inhibitors, have therapeutic actions to treat such diseases. We will also briefly discuss how MMPs can be intracellularly regulated and activated by oxidative stress, thus cleaving several important proteins inside cells. In addition to their potential therapeutic effects, MMP inhibitors may also be useful tools to understand the biological consequences of MMP activity and its respective extra- and intracellular effects.

Activated protein C utilizes the angiopoietin/Tie2 axis to promote endothelial barrier function

Activated protein C (APC) is an anticoagulant, approved as a treatment for severe sepsis, that can prevent apoptosis, inflammation, and vascular leakage. The aim of this study was to investigate whether APC protects endothelial barrier function through the angiopoietin (Ang)/Tie2 axis. APC significantly up-regulated gene and protein expression of Tie2 and Ang1 in a dose (0.01-10 microg/ml)- and time (0.5-24 h)-dependent manner in human umbilical vein endothelial cells (HUVECs). Interestingly, it markedly inhibited Ang2 with an IC(50) of approximately 0.1 microg/ml. HUVEC permeability, measured using Evans blue dye transfer, was significantly reduced in the presence of APC, and, in concordance, the tight junction associated protein zona occludens (ZO)-1 was up-regulated and localized peripherally around cells, compared with controls. Smooth muscle cell migration toward APC-stimulated HUVECs was elevated compared with unstimulated cells. Blocking antibodies and small interfering (si) RNA treatment, compared with isotype (IgG) or scrambled siRNA controls, showed that APC requires 3 receptors, the endothelial protein C receptor, protease-activated receptor 1, and Tie2 to perform all these barrier stabilization functions. In summary, this study demonstrates that APC has novel effects on the Ang/Tie2 axis, which enhance endothelial barrier function and are likely to contribute to its therapeutic effect in sepsis and other diseases associated with vascular leakage.-Minhas, N., Xue, M., Fukudome, K., Jackson, C. J. Activated protein C utilizes the angiopoietin/Tie2 axis to promote endothelial barrier function.

Inhibition of matrix metalloproteinase activity in vivo protects against vascular hyporeactivity in endotoxemia

Persistent arterial hypotension is a hallmark of sepsis and is believed to be caused, at least in part, by excess nitric oxide (NO). NO can combine with superoxide to produce peroxynitrite, which activates matrix metalloproteinases (MMPs). Whether MMP inhibition in vivo protects against vascular hyporeactivity induced by endotoxemia is unknown. Male Sprague-Dawley rats were administered either bacterial lipopolysaccharide (LPS, 4 mg/kg ip) or vehicle (pyrogen-free water). Later (30 min), animals received the MMP inhibitor doxycycline (4 mg/kg ip) or vehicle (pyrogen-free water). After LPS injection (6 h), animals were killed, and aortas were excised. Aortic rings were mounted in organ baths, and contractile responses to phenylephrine or KCl were measured. Aortas and plasma were examined for MMP activity by gelatin zymography. Aortic MMP and inducible nitric oxide synthase (iNOS) were examined by immunoblot and/or immunohistochemistry. Doxycycline prevented the LPS-induced development of ex vivo vascular hyporeactivity to phenylephrine and KCl. iNOS protein was significantly upregulated in aortic homogenates from endotoxemic rats; doxycycline did not alter its level. MMP-9 activity was undetectable in aortic homogenates from LPS-treated rats but significantly upregulated in the plasma; this was attenuated by doxycycline. Plasma MMP-2 activities were unchanged by LPS. Specific MMP-2 activity was increased in aortas from LPS-treated rats. This study demonstrates the in vivo protective effect of the MMP inhibitor doxycycline against the development of vascular hyporeactivity in endotoxemic rats.

Alexidine and chlorhexidine bind to lipopolysaccharide and lipoteichoic acid and prevent cell activation by antibiotics

OBJECTIVES

Many antibiotics used to treat infections cause release of immunostimulatory cell wall components from bacteria. Therefore, a combination of antimicrobial and endotoxin-neutralizing activity is desired to prevent inflammation induced by destroyed bacteria. Chlorhexidine and alexidine are amphipathic bisbiguanides and could neutralize bacterial membrane components as stimulators of Toll-like receptors (TLRs).

METHODS

Binding of chlorhexidine and alexidine to lipopolysaccharide (LPS) and lipoteichoic acid (LTA) was determined by fluorescence displacement assay and isothermal calorimetric titration. Neutralization of the biological effect of LPS and LTA on TLR-activated cellular activation was determined by NF-kappaB reporter luciferase activation on cells transfected with specific TLRs and NO production of murine macrophages in the presence of isolated agonists and antibiotic-treated bacteria.

RESULTS

Alexidine and chlorhexidine bind not only to LPS but also to LTA from Gram-positive bacteria. Alexidine has a higher affinity than chlorhexidine for both compounds. Calorimetric titration shows an initial endothermic contribution indicating participation of hydrophobic interactions in LPS binding, while binding to LTA displayed initial exothermic contribution. Both compounds prevent cell activation of TLR4 and TLR2 by LPS and LTA, respectively. The addition of both compounds suppressed NO production by macrophages in the presence of bacteria treated with different types of antibiotics.

CONCLUSIONS

Chlorhexidine and alexidine suppress bacterial membrane-induced cell activation at concentrations two orders of magnitude lower than that used in topical applications. Combining biocides with different types of antibiotics prevented macrophage activation in the presence of bacteria and demonstrated the potential of chlorhexidine and alexidine to suppress inflammatory responses caused by activation of TLRs.

Endothelial dependence of matrix metalloproteinase-mediated vascular hyporeactivity caused by lipopolysaccharide

Septic shock remains the leading cause of death in intensive care units in North America. Recent evidence implicates matrix metalloproteinases (MMP) in the pathogenesis of sepsis. MMP activity is upregulated in blood vessels exposed to bacterial lipopolysaccharide (LPS) or pro-inflammatory cytokines and contributes to vascular hyporeactivity to vasoconstrictors. The exact mechanism of MMP-mediated vascular hyporeactivity is unknown. We investigated the contribution of the endothelium in the MMP response to LPS-mediated vascular hyporeactivity in vitro. Tone induced by phenylephrine in isolated rat aortic rings with either intact or denuded endothelium was measured in the presence of LPS for 6 h. These rings were incubated with the nitric oxide (NO) synthase inhibitor, N(G)-nitro-l-arginine methyl ester (l-NAME), to determine whether NO synthase was involved in the response, or the MMP inhibitors, doxycycline or GM6001. MMP activity was measured after 6 h. LPS caused a greater reduction of phenylephrine-induced tone in endothelium-intact rings versus endothelium-denuded rings, indicating both endothelium-independent and -dependent mechanisms for LPS-induced vascular hyporeactivity. l-NAME abolished the response to LPS in both endothelium-intact and endothelium-denuded rings. MMP inhibitors prevented the LPS-induced loss of tone in endothelium-intact but not endothelium-denuded rings. LPS caused significantly greater MMP-2 activity in endothelium-intact aortae which was attenuated by doxycycline. MMP-2 activity in endothelium-denuded aortae was unchanged by LPS. The vascular endothelium contributes to MMP-mediated vascular dysfunction induced by LPS. The protective effect of MMP inhibition is endothelium-dependent and is a novel mechanism by which MMPs contribute to vascular dysfunction.

Nitric oxide and nursing: a review

AIMS AND OBJECTIVES

This paper, therefore, aimed to review published literature in this area of pharmacological exploitation, to look at the therapeutic applications and clinical relevance and, by so doing, provide an accessible source for nurses to gain insight into the role of nitric oxide in the clinical setting.

BACKGROUND

Nitric oxide is a chemical mediator fundamental in the maintenance of adequate tissue perfusion and effective cardiovascular function; a major endogenous regulator of vascular tone. The use of nitrates are well established as pharmacological agents but it is only recently that it has been recognized that they act as a source of nitric oxide. Although widely addressed within the medical literature, there appears to be a paucity of nursing literature that explores either its physiological action, or its relevance to nursing practice.

CONCLUSIONS

This literature review provides an overview of the use of nitric oxide and its implications for nursing practice and patient outcomes.

RELEVANCE TO CLINICAL PRACTICE

Knowledge of nitric oxide and its action is pertinent to nurses across diverse specialities. It helps in understanding the principles of many nitrogen-derived medications which nurses administer to their patients on a daily basis. In terms of oral medication, this is demonstrated by greater insights into the action of nitrates, the appreciation of surprising developments in medications such as sildenafil and the development of new drug opportunities such as nitric oxide-non-steroidal anti-inflammatory drugs. Equally, the use of inhaled nitric oxide therapy in adult and neonatal critical care units appears to be an increasingly valuable source of treatment. A particular research challenge is found in the attempt at nitric oxide inhibition in the management of septic shock. The authors argue that understanding such esoteric areas of therapeutic developments is increasingly to be part of the repertoire of knowledge and skills for nurses in the 21st century.

Increased ICAM-1 expression causes endothelial cell leakiness, cytoskeletal reorganization and junctional alterations

Tumor necrosis factor (TNF)-induced ICAM-1 in endothelial cells (EC) promotes leukocyte adhesion. Here we report that ICAM-1 also effects EC barrier function. Control- or E-selectin-transduced human dermal microvascular EC (HDMEC) form a barrier to flux of proteins and to passage of current (measured as transendothelial electrical resistance or TEER). HDMEC transduced with ICAM-1 at levels comparable to that induced by TNF show reduced TEER, but do so without overtly changing their cell junctions, cell shape, or cytoskeleton organization. Higher levels of ICAM-1 further reduce TEER, increase F/G-actin ratios, rearrange the actin cytoskeleton to cause cell elongation, and alter junctional zona occludens 1 and vascular endothelial-cadherin staining. Transducing with ICAM-1 lacking an intracellular region also reduces TEER. TNF-induced changes in TEER and shape follow a similar time course as ICAM-1 induction; however, the fall in TEER occurs at lower TNF concentrations. Inhibiting NF-kappaB activation blocks ICAM-1 induction; TEER reduction, and shape change. Specific small-interfering RNA knockdown of ICAM-1 partially inhibits TNF-induced shape change. We conclude that moderately elevated ICAM-1 expression reduces EC barrier function and that expressing higher levels of ICAM-1 affects cell junctions and the cytoskeleton. Induction of ICAM-1 may contribute to but does not fully account for TNF-induced vascular leak and EC shape change.

San-Huang-Xie-Xin-Tang reduces lipopolysaccharides-induced hypotension and inflammatory mediators

San-Huang-Xie-Xin-Tang (SHXT) is a traditional Chinese medicinal formula containing Coptidis rhizoma, Scutellariae radix and Rhei rhizoma. The present study aimed to determine the preventive effects of standardized SHXT on lipopolysaccharides (LPS)-induced arterial hypotension, protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), cytokines formation and prostaglandin E2 (PGE2) production. LPS-induced activation of iNOS has been recognized to increase cytokines and nitric oxide, some of them play predominant roles in sepsis. Intravenous injection of LPS (10 mg/kg) caused a marked decrease of the mean arterial pressure in normotensive rats. However, the LPS-induced arterial hypotension was inhibited by SHXT (0.01 and 0.03 g/kg), when it was given 30 min before LPS. Moreover, plasma level of cytokines and PGE2 were lowered by SHXT. In RAW 264.7 cells, SHXT (20-200 microg/ml) dose-dependently inhibited LPS (1 microg/ml)-induced iNOS and COX-2 expression, and it also significantly decreased LPS-induced cytokines in a dose-dependent manner. In conclusion, our data suggest that SHXT prevented LPS-induced arterial hypotension, which might be mediated through its inhibition activities on the expression of iNOS and COX-2, cytokines formation and PGE2 production. Therefore, its protection activity against LPS-induced arterial hypotension and inflammatory mediators release might be beneficial in the treatment of endotoxin shock and/or associated inflammation.

Urgosedin Inhibits Hypotension, Hypoglycemia, and Pro-Inflammatory Mediators Induced by Lipopolysaccharide

Urgosedin is a newly synthesized compound especially with serotonergic and alpha-adrenergic blocking actions. In rat isolated thoracic aorta, urgosedin competitively antagonized norepinephrine-, clonidine-, and serotonin-induced vasocontractions in a concentration-dependent manner. In radioligand binding experiments, urgosedin had significant binding affinities on alpha1/alpha2, 5-HT1A, 5-HT1B and 5-HT2A receptors. Intravenous injection of lipopolysaccharide (LPS) produced a biphasic hypotension in normotensive rats. Although intravenous injection of urgosedin caused minor depressor actions in the normotensive Wistar rat, urgosedin significantly attenuated the secondary prolonged hypotension produced by LPS. The plasma levels of cytokines (IL-1beta, IL-6, TNF-alpha, and IFN-gamma) and hypoglycemia induced by LPS were also reduced by urgosedin. Moreover, the acute survival rates (350 minutes) of endotoxic shock increased from 0% (LPS group) to 100% in the groups pretreated with urgosedin. In RAW264.7 cells, urgosedin inhibited LPS-induced inducible nitric oxide synthase (iNOS) expression. In conclusion, our data suggest that urgosedin was a newly potent serotonergic and mild alpha-adrenergic blocking agent. Its prevention of LPS-induced hypotension and hypoglycemia might partially mediate through its inhibition activities on the iNOS expression and cytokines formation. Urgosedin might be an effective pharmacological agent against LPS-induced hypotension, hypoglycemia, and the formation of pro-inflammatory mediators.

Case review: septic shock in the pregnant patient

This case study involves a 36-year-old female at 15 weeks gestation who presented with severe lower abdominal pain post amniocentesis and subsequently deteriorated into a state of septic shock whilst in the ED. The circumstances surrounding this patient's presentation and subsequent clinical course are presented. The assessment and management of septic shock is also described with specific consideration to this patient's pregnant state.

Biological mediators of acute inflammation

Inflammation may be defined as the normal response of living tissue to injury or infection. It is important to emphasize two components of this definition. First, that inflammation is a normal response and, as such, is expected to occur when tissue is damaged. Indeed, if injured tissue did not exhibit signs of inflammation this would be considered abnormal. Secondly, inflammation occurs in living tissue, hence the need for an adequate blood supply to the tissues in order for an inflammatory response to be exhibited. The inflammatory response may be triggered by mechanical injury, chemical toxins, invasion by microorganisms, and hypersensitivity reactions. Three major events occur during the inflammatory response: the blood supply to the affected area is increased substantially, capillary permeability is increased, and leucocytes migrate from the capillary vessels into the surrounding interstitial spaces to the site of inflammation or injury. The inflammatory response represents a complex biological and biochemical process involving cells of the immune system and a plethora of biological mediators. Cell-to-cell communication molecules known collectively as cytokines play an extremely important role in mediating the process of inflammation. An extensive exposition of this complex phenomenon is beyond the scope of this article. Rather, the author provides a review of inflammation, an overview of the role of certain biological mediators in inflammation, and a discussion of the implications of certain biological response modifiers in clinical practice.

High adenosine plasma concentration as a prognostic index for outcome in patients with septic shock

OBJECTIVE

Sepsis and septic shock are a common cause of mortality in critically ill patients. Many substances have been implicated in the pathophysiology of these syndromes. We postulated that adenosine may be implicated in the sepsis- or septic shock-induced blood pressure failure. Indeed, this nucleoside is a strong endogenous vasodilating agent released by endothelial cells and myocytes under circumstances of metabolic stress, such as during critical illness.

DESIGN

A prospective, comparative observational study.

SETTING

The adult intensive care unit of a tertiary care university hospital.

PATIENTS

We measured adenosine plasma concentration (APC) in patients with severe sepsis (n = 11), in patients with septic shock (n = 14), in patients with hemorrhagic traumatic shock (n = 14), and in 12 healthy volunteers. APC was evaluated every 12 hrs over 3 days.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

At study entry, we found that APC was higher in patients with septic shock (mean +/- so = 8.4 +/-3.5 micromol/L) than in patients with hemorrhagic traumatic shock (1.1 +/- 0.6 micromol/L) and controls (0.8 +/- 0.3 micromol/L). Intermediate values (3.9 +/- 1.9 micromol/L) were found in patients with severe sepsis. APC in patients with traumatic shock did not differ from controls. In the course of the hospitalization, for both sepsis and septic shock patients, APC decreased significantly but remained higher than controls 72 hrs after entry into the study. In the septic shock group, APC was significantly higher in the nonsurvivor group (n = 6) than in the survivor group (n = 8), whatever the time of sample collection and assay.

CONCLUSIONS

High adenosine plasma concentrations are found in patients with septic shock but not during traumatic shock, or in healthy volunteers. Intermediate values of circulating adenosine are found in patients with severe sepsis. APC may be a prognostic index for outcome in septic patients, with much higher values being found in nonsurvivors.

Lipopolyamines: novel antiendotoxin compounds that reduce mortality in experimental sepsis caused by gram-negative bacteria

The interactions of lipopolyamines, a class of structurally unique compounds currently being used as transfection (lipofection) agents, with lipopolysaccharide (LPS) have been characterized. Our studies have demonstrated that 1,3-di-oleoyloxy-2-(6-carboxyspermyl)-propylamide), available commercially as DOSPER, binds to purified LPS with an affinity of about 1/10 that of polymyxin B. This essentially nontoxic compound inhibits, in a dose-dependent manner, LPS-induced activation of the Limulus clotting cascade and the production of tumor necrosis factor alpha (TNF-alpha) interleukin-6 (IL-6), and nitric oxide from LPS-stimulated J774.A1 cells, a murine macrophage-like cell line. Cytokine inhibition is paralleled by decreased steady-state levels of TNF-alpha and IL-6 mRNA and inhibits the nuclear translocation of nuclear factor kappa B. These findings suggest that the lipopolyamine compound sequesters LPS, thereby blocking downstream cellular activation events that lead to the production of proinflammatory mediators. Administration of DOSPER to D-galactosamine-sensitized mice challenged either with LPS or with Escherichia coli organisms provided significant protection against lethality both with and without antibiotic chemotherapy. Partial protection is evident in LPS-challenged mice treated with DOSPER as late as 2 to 4 h following the endotoxin challenge. A greater degree of protection is observed in E. coli-challenged animals receiving ceftazidime than in those receiving imipenem, which is probably attributable to the higher levels of LPS released in vivo by the former antibiotic. Potent antiendotoxic activity, low toxicity, and ease of synthesis render the lipopolyamines candidate endotoxin-sequestering agents of potential significant therapeutic value.