Differential alterations in cardiovascular responses during the progression of polymicrobial sepsis in the mouse

Decoding molecular signature on heart of septic mice with distinct left ventricular ejection fraction

Dysregulated cardiac function after sepsis in intensive care unit is known to predict poor long-term outcome and increase mortality. Their pathological feature and molecular mechanism remain unclear. We observed that septic patients with depressed left ventricular ejection fraction (LVEF) have the highest in-hospital and 28 days mortality comparing to patients with hyperdynamic LVEF or with heart failure with preserved LVEF. Echocardiograms reveal that survivors post cecum ligation and puncture (CLP) on rodents have stable LVEF and non-survivors have fluctuated LVEF at CLP early phase. CLP-induced mice fall into three groups based on LVEF 24 h post-surgery: high-, low-, and normal-LVEF. Transcriptomic and proteomic analyses identify jointly and distinctively changed genes, proteins and biologically essential pathways in left ventricles from three CLP groups. Notably, transmission electron microscopy shows different mitochondrial and sarcomere defects associated with LVEF variances. Together, this study systematically characterizes the molecular, morphological, and functional alterations in CLP-induced cardiac injury.

The bone is the major source of high circulating intact fibroblast growth factor-23 in acute murine polymicrobial sepsis induced by cecum ligation puncture

Fibroblast growth factor-23 (FGF23), a bone-produced hormone, plays a critical role in mineral homeostasis. Human diseases associated with excessive intact circulating FGF23 (iFGF23) result in hypophosphatemia and low vitamin D hormone in patients with normal kidney function. In addition, there is accumulating evidence linking FGF23 with inflammation. Based on these studies and the frequent observation of hypophosphatemia among septic patients, we sought to elucidate further the relationship between FGF23 and mineral homeostasis in a clinically relevant murine polymicrobial sepsis model. Medium-severity sepsis was induced by cecum ligation puncture (CLP) in adult CD-1 mice of both sexes. Healthy CD-1 mice (without CLP) were used as controls. Forty-eight hours post-CLP, spontaneous urine was collected, and serum, organs and bones were sampled at necropsy. Serum iFGF23 increased ~20-fold in CLP compared to control mice. FGF23 protein concentration was increased in the bones, but not in spleen or liver of CLP mice. Despite the ~20-fold iFGF23 increase, we did not observe any significant changes in mineral homeostasis or parathyroid hormone levels in the blood of CLP animals. Urinary excretion of phosphate, calcium, and sodium remained unchanged in male CLP mice, whereas female CLP mice exhibited lower urinary calcium excretion, relative to healthy controls. In line with renal FGF23 resistance, expression of phosphate-, calcium- and sodium-transporting proteins did not show consistent changes in the kidneys of male and female CLP mice. Renal expression of the co-receptor αKlotho was downregulated in female, but not in male CLP mice. In conclusion, our data demonstrate that the dramatic, sex-independent rise in serum iFGF23 post-CLP was mainly caused by an upregulation of FGF23 secretion in the bone. Surprisingly, the upsurge in circulating iFGF23 did not alter humoral mineral homeostasis in the acutely septic mice. Hence, the biological function of elevated FGF23 in sepsis remains unclear and warrants further studies.

Will mesenchymal stem cells be future directions for treating radiation-induced skin injury?

Radiation-induced skin injury (RISI) is one of the common serious side effects of radiotherapy (RT) for patients with malignant tumors. Mesenchymal stem cells (MSCs) are applied to RISI repair in some clinical cases series except some traditional options. Though direct replacement of damaged cells may be achieved through differentiation capacity of MSCs, more recent data indicate that various cytokines and chemokines secreted by MSCs are involved in synergetic therapy of RISI by anti-inflammatory, immunomodulation, antioxidant, revascularization, and anti-apoptotic activity. In this paper, we not only discussed different sources of MSCs on the treatment of RISI both in preclinical studies and clinical trials, but also summarized the applications and mechanisms of MSCs in other related regenerative fields.

Ghrelin as an Anti-Sepsis Peptide: Review

Sepsis continues to produce widespread inflammation, illness, and death, prompting intensive research aimed at uncovering causes and therapies. In this article, we focus on ghrelin, an endogenous peptide with promise as a potent anti-inflammatory agent. Ghrelin was discovered, tracked, and isolated from stomach cells based on its ability to stimulate release of growth hormone. It also stimulates appetite and is shown to be anti-inflammatory in a wide range of tissues. The anti-inflammatory effects mediated by ghrelin are a result of both the stimulation of anti-inflammatory processes and an inhibition of pro-inflammatory forces. Anti-inflammatory processes are promoted in a broad range of tissues including the hypothalamus and vagus nerve as well as in a broad range of immune cells. Aged rodents have reduced levels of growth hormone (GH) and diminished immune responses; ghrelin administration boosts GH levels and immune response. The anti-inflammatory functions of ghrelin, well displayed in preclinical animal models of sepsis, are just being charted in patients, with expectations that ghrelin and growth hormone might improve outcomes in patients with sepsis.

The role of lipoprotein-associated phospholipase A2 in acute kidney injury of septic mice

Background

This experiment aimed to investigate the role and mechanism of lipoprotein-associated phospholipase A2 (Lp-PLA2) in kidney injury in septic mice induced by cecal ligation and perforation (CLP).

Methods

Male BALB/c mice were randomly divided into two groups: sham-operation group (Sham group) and septic group (CLP group). The septic model was simulated by cecal ligation and puncture method, but only cecal ligation was used for the sham operation group. The whole serum and renal tissue samples of the mice were collected 24 hours after modeling in both groups. Hematoxylin-eosin (HE) staining was used to observe the pathological changes of renal tissue, the renal injury score was recorded, and the creatinine (Cr) and blood urea nitrogen (BUN) levels were detected by automatic biochemical analyzer, while the serum Lp-PLA2 level was detected by enzyme-linked immunosorbent assay (ELISA). The 7-day survival rate and the survival curve of the two groups were statistically analyzed.

Results

Compared with the Sham group, the pathological score of renal injury in the CLP Group was higher, the level of Lp-PLA2 in serum was significantly increased (all P<0.01), and the expression of Lp-PLA2 in renal tissue was significantly elevated (all P<0.01). Furthermore, the 7-day survival rate of the Sham group was 90%, while that of CLP group was 25%.

Conclusions

The expression level of Lp-PLA2 in blood and kidney tissue of septic mice was increased and correlated with prognosis. However, the predictive value of Lp-PLA2 for prognosis in septic mice needs further study.

Deletion of the adenosine A2A receptor increases the survival rate in a mice model of polymicrobial sepsis

We aim to investigate the role of A_2A receptor in peritonitis-related sepsis by injection of a fecal solution (FS) as a model of polymicrobial infection. C57/black J6 wild-type (WT) and A_2A-deficient mice (A_2AKO) were exposed to sepsis induced by intraperitoneal injection of a FS (FS-induced peritonitis) or instead was injected with saline buffer (Sham). Survival rate and sepsis score were measured up to 48 h. The presence of bacteria in tissue homogenates was analyzed. Telemetry and speckle laser Doppler were used for systemic blood pressure and peripheral blood perfusion analysis, respectively. Histological analysis and identification of active caspase 3 were performed in selected organs, including the liver. The survival rate of A_2AKO mice exposed to FS-induced peritonitis was significantly higher, and the sepsis score was lower than their respective WT counterpart. Injection of FS increases (50 to 150 folds) the number of colonies forming units in the liver, kidney, blood, and lung in WT mice, while these effects were significantly attenuated in A_2AKO mice exposed to FS-induced peritonitis. A significant reduction in both systolic and diastolic blood pressure, as well as in the peripheral perfusion was observed in WT and A_2AKO mice exposed to FS-induced peritonitis. Although, these last effects were significantly attenuated in A_2AKO mice. Histological analysis showed a large perivascular infiltration of polymorphonuclear in the liver of WT and A_2AKO mice exposed to FS-induced peritonitis, but again, this effect was attenuated in A_2AKO mice. Finally, high expression of active caspase 3 was found only in the liver of WT mice exposed to FS-induced peritonitis. The absence of the A_2A receptor increases the survival rate in mice exposed to polymicrobial sepsis. This outcome was associated with both hemodynamic compensation and enhanced anti-bacterial response.

Prompt Administration of Antibiotics and Fluids in the Treatment of Sepsis: A Murine Trial

OBJECTIVES

Sepsis, the acute organ dysfunction caused by a dysregulated host response to infection, poses a serious public health burden. Current management includes early detection, initiation of antibiotics and fluids, and source control as necessary. Although observational data suggest that delays of even a few hours in the initiation of antibiotics or IV fluids is associated with survival, these findings are controversial. There are no randomized data in humans, and prior animal studies studied time from experimental manipulation, not from the onset of clinical features of sepsis. Using a recently developed murine cecal ligation and puncture model that precisely monitors physiologic deterioration, we hypothesize that incremental hourly delays in the first dose of antibiotics, in the first bolus of fluid resuscitation, or a combination of the two at a clinically relevant point of physiologic deterioration during polymicrobial sepsis will shorten survival.

DESIGN

Randomized laboratory animal experimental trial.

SETTING

University basic science laboratory.

SUBJECTS

Male C57BL/6J, female C57BL/6J, aged (40-50 wk old) male C57BL/6J, and BALB/C mice.

INTERVENTIONS

Mice (n = 200) underwent biotelemetry-enhanced cecal ligation and puncture and were randomized after meeting validated criteria for acute physiologic deterioration. Treatment groups consisted of a single dose of imipenem/cilastatin, a single bolus of 30 mL/kg fluid resuscitation, or a combination of the two. Mice were allocated to receive treatment at the time of meeting deterioration criteria, after a 2-hour delay or after a 4-hour delay.

MEASUREMENTS AND MAIN RESULTS

Hourly delays in the initiation of antibiotic therapy led to progressively shortened survival in our model (p < 0.001). The addition of fluid resuscitation was unable to rescue animals, which received treatment 4 hours after meeting enrollment criteria. Systemic inflammation was increased, and host physiology was increasingly deranged with hourly delays to antibiotics.

CONCLUSIONS

We conclude that antibiotic therapy is highly time sensitive, and efforts should be made to deliver this critical therapy as early as possible in sepsis, perhaps extending into the first point of medical contact outside the hospital.

Glutamine Administration in Early or Late Septic Phase Downregulates Lymphocyte PD-1/PD-L1 Expression and the Inflammatory Response in Mice With Polymicrobial Sepsis

BACKGROUND

Sepsis is a severe inflammatory response to infection. Excessive compensation to inflammation leads to dysregulated immune response that ultimately results in organ damage and lethality of sepsis. This study administered glutamine (GLN) in the early or late phase of sepsis to investigate its effects on regulating leukocyte programmed cell death 1 (PD-1) and its ligand (programmed cell death ligand 1 [PD-L1]) expression, macrophage function, inflammation, and acute kidney injury in sepsis.

METHODS

Mice were randomly assigned to cecal ligation and puncture (CLP) or sham-operated groups. Septic mice were respectively injected once with saline or 0.75 g GLN/kg body weight at 3 or 10 hours post-CLP via tail vein. All mice were sacrificed 24 hours after CLP.

RESULTS

Sepsis enhanced the percentage of interferon-γ-expressing and interleukin (IL)-17A-expressing CD4⁺ T cells, expression of PD-1 on T cells, and PD-L1 on B cells and monocytes. Inflammatory mediator messenger RNA (mRNA) expression in kidney tissues and proapoptotic caspase-3 mRNA expression in mesenteric lymph nodes were also upregulated. GLN administration decreased plasma IL-6 level, downregulated the percentage of IL-17A-expressing CD4⁺ T cells, attenuated macrophage dysfunction, decreased caspase-3 mRNA expression, and reduced PD-1/PD-L1 expression by T and B cells. Histological findings also showed that kidney damage was attenuated. GLN administered at 3 and 10 hours after CLP offered nearly equal effects on PD-1/PD-L1 and inflammatory mediator expression after CLP.

CONCLUSIONS

These findings suggest that a single dose of GLN administration in either the early or late phase during sepsis promotes a more balanced immune regulation and reduced systemic and kidney inflammatory responses in mice.

Thioredoxin-1 attenuates sepsis-induced cardiomyopathy after cecal ligation and puncture in mice

BACKGROUND

Sepsis is a leading cause of mortality among patients in intensive care units across the USA. Thioredoxin-1 (Trx-1) is an essential 12 kDa cytosolic protein that, apart from maintaining the cellular redox state, possesses multifunctional properties. In this study, we explored the possibility of controlling adverse myocardial depression by overexpression of Trx-1 in a mouse model of severe sepsis.

METHODS

Adult C57BL/6J and Trx-1Tg/+ mice were divided into wild-type sham (WTS), wild-type cecal ligation and puncture (WTCLP), Trx-1Tg/+sham (Trx-1Tg/+S), and Trx-1Tg/+CLP groups. Cardiac function was evaluated before surgery, 6 and 24 hours after CLP surgery. Immunohistochemical and Western blot analysis were performed after 24 hours in heart tissue sections.

RESULTS

Echocardiography analysis showed preserved cardiac function in the Trx-1Tg/+ CLP group compared with the WTCLP group. Similarly, Western blot analysis revealed increased expression of Trx-1, heme oxygenase-1 (HO-1), survivin (an inhibitor of apoptosis [IAP] protein family), and decreased expression of thioredoxin-interacting protein (TXNIP), caspase-3, and 3- nitrotyrosine in the Trx-1Tg/+CLP group compared with the WTCLP group. Immunohistochemical analysis showed reduced 4-hydroxynonenal, apoptosis, and vascular leakage in the cardiac tissue of Trx-1Tg/+CLP mice compared with mice in the WTCLP group.

CONCLUSIONS

Our results indicate that overexpression of Trx-1 attenuates cardiac dysfunction during CLP. The mechanism of action may involve reduction of oxidative stress, apoptosis, and vascular permeability through activation of Trx-1/HO-1 and anti-apoptotic protein survivin.

Downregulation of PI3K-γ in a mouse model of sepsis-induced myocardial dysfunction

A key component during sepsis is the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway, of which the PI3K-γ isoform is a major regulator in many inflammatory responses. However, the role of PI3K-γ in the development of sepsis-induced myocardial dysfunction (SIMD) is unknown. In this study, we established a model of SIMD induced by lipopolysaccharide (LPS), subsequently used the selective inhibitor LY294002 and AS605240 to block the effect of PI3K and PI3K-γ, respectively. Cardiac function was evaluated by echocardiography, hearts were obtained for histological and protein expression examinations. ELISA was used to measure the serum levels of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), cardiac troponin I (cTnI) and heart-type fatty acid binding protein (H-FABP). LPS-treated mice showed an increase to cardiac inflammation, myocardial damage and production of TNF-α, IL-6, NF-κB, cTnI and H-FABP. Administration of AS605240 to LPS-treated mice reduced some patho-physiological characteristics of SIMD and reduced TNF-α, IL-6, cTnI and H-FABP production. However, administration of LY294002 did not improve those same conditions. The results showed that PI3K-γ is likely a crucial element in SIMD by regulating the PI3K/Akt pathway, and become a new marker of myocardial injury. Inhibition of PI3K-γ might be a potential therapeutic target in SIMD.

Alpha-Lipoic Acid Attenuates Oxidative Damage in Organs After Sepsis

Sepsis progression is linked with the imbalance between reactive oxygen species and antioxidant enzymes. Thus, the aim of this study was to evaluate the effect of alpha-lipoic acid (ALA), a powerful antioxidant, in organs of rats submitted to sepsis. Male Wistar rats were subjected to sepsis by cecal ligation puncture (CLP) and treated with ALA or vehicle. After CLP (12 and 24 h), the myeloperoxidase (MPO) activity, protein and lipid oxidative damage, and antioxidant enzymes in the liver, kidney, heart, and lung were evaluated. ALA was effective in reducing MPO activity, lipid peroxidation in the liver, and protein carbonylation only in the kidney in 12 h after CLP. In 12 h, SOD activity increased in the kidney and CAT activity in the liver and kidney with ALA treatment. Thus, ALA was able to reduce the inflammation and oxidative stress in the liver and kidney after sepsis in rats.

The protective role of neuregulin-1: A potential therapy for sepsis-induced cardiomyopathy

The extremely high mortality of sepsis in intensive care units, caused primarily by sepsis-induced cardiomyopathy, is a pressing issue. Current studies have revealed the importance of the neuregulin-1 (NRG-1)/ErbB signaling axis at the cardiovascular level and the positive effect of NRG-1 on cardiac function in patients with heart failure. To investigate the protective mechanism of NRG-1 against myocardial injury in septic rats, a cecal ligation and puncture (CLP) model was applied. Animals were administered either a vehicle or recombinant human NRG-1 (rhNRG-1, 10μg/kg). Their survival rates were noted 24h after CLP. The hemodynamic method was used to evaluate their cardiac function. The myocardial morphology was observed. An enzyme-linked immunosorbent assay was used to detect the level of cardiac troponin-T (cTn-T), cytokines, and angiotensin II (Ang II) in the serum and myocardium. Compared with the vehicle, rhNRG-1 improved survival of rats and prevented hemodynamic derangement, as reflected in the increased mean arterial pressure, left ventricular systolic pressure, ±dp/dt max, and decreased left ventricular end-diastolic pressure (P<0.05). Furthermore, the serum levels of cTn-T and pro-inflammatory cytokines (tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and IL-6) were significantly increased in vehicle-treated rats but reduced in rhNRG-1-treated rats. The latter also showed decreased concentration of macrophage inhibitory factor and Ang II in the myocardium (P<0.05). These results suggest that NRG-1 improved cardiac function and protected cardiomyocytes of rats from CLP-induced sepsis by suppressing the immune inflammatory response and excessive activation of the renin-angiotensin-aldosterone system. Ultimately, NRG-1 increased the survival rate of rats.

Impaired heart rate regulation and depression of cardiac chronotropic and dromotropic function in polymicrobial sepsis

The scope of cardiac pathophysiology in sepsis has not been fully defined. Accordingly, we evaluated the effects of sepsis on heart rate (HR), HR variability, and conduction parameters in a murine model of sepsis. Electrocardiograms were recorded noninvasively from conscious mice before and after cecal ligation and puncture (CLP) or sham surgery. Responses of isolated atria to tyramine and isoproterenol were quantified to assess the functional state of sympathetic nerves and postjunctional sensitivity to adrenergic stimulation. Cecal ligation and puncture mice had lower HR compared with sham at 16 to 18 h postsurgery (sham, 741 ± 7 beats/min; CLP, 557 ± 31 beats/min; n = 6/group; P < 0.001), and there was significant prolongation of the PR, QRS, and QTc intervals. Slowing of HR and conduction developed within 4 to 6 h after CLP and were preceded by a decrease in HR variability. Treatment of CLP mice with isoproterenol (5 mg/kg, intraperitoneally) at 25 h after surgery failed to increase HR or decrease conduction intervals. The lack of in vivo response to isoproterenol cannot be attributed to hypothermia because robust chronotropic and inotropic responses to isoproterenol were evoked from isolated atria at 25 °C and 30 °C. These findings demonstrate that impaired regulation of HR (i.e., reduced HR variability) develops before the onset of overt cardiac rate and conduction changes in septic mice. Subsequent time-dependent decreases in HR and cardiac conduction can be attributed to hypothermia and would contribute to decreased cardiac output and organ perfusion. Because isolated atria from septic mice showed normal responsiveness to adrenergic stimulation, we conclude that impaired effectiveness of isoproterenol in vivo can be attributed to reversible effects of systemic factors on adrenergic receptors and/or postreceptor signaling.

Altered L-type Ca2+ channel activity contributes to exacerbated hypoperfusion and mortality in smooth muscle cell BK channel-deficient septic mice

We determined the contribution of vascular large conductance Ca2+-activated K+ (BK) and L-type Ca2+ channel dysregulation to exaggerated mortality in cecal ligation/puncture (CLP)-induced septic BK channel β1-subunit knockout (BK β1-KO, smooth muscle specific) mice. CLP-induced hemodynamic changes and mortality were assessed over 7 days in wild-type (WT) and BK β1-KO mice that were either untreated, given volume resuscitation (saline), or saline + calcium channel blocker nicardipine. Some mice were euthanized 24 h post-CLP to measure tissue injury and vascular and immune responses. CLP-induced hypotension was similar in untreated WT and BK β1-KO mice, but BK β1-KO mice died sooner. At 24 h post-CLP (mortality latency in BK β1-KO mice), untreated CLP-BK β1-KO mice showed more severe hypothermia, lower tissue perfusion, polymorphonuclear neutrophil infiltration-independent severe intestinal necrosis, and higher serum cytokine levels than CLP-WT mice. Saline resuscitation improved survival in CLP-WT but not CLP-BK β1-KO mice. Saline + nicardipine-treated CLP-BK β1-KO mice exhibited longer survival times, higher tissue perfusion, less intestinal injury, and lower cytokines versus untreated CLP-BK β1-KO mice. These improvements were absent in treated CLP-WT mice, although saline + nicardipine improved blood pressure similarly in both septic mice. At 24 h post-CLP, BK and L-type Ca2+ channel functions in vitro were maintained in mesenteric arteries from WT mice. Mesenteric arteries from BK β1-KO mice had blunted BK/enhanced L-type Ca2+ channel function. We conclude that vascular BK channel deficiency exaggerates mortality in septic BK β1-KO mice by activating L-type Ca2+ channels leading to blood pressure-independent tissue ischemia.

Adjuvant potential of selegiline in attenuating organ dysfunction in septic rats with peritonitis

Selegiline, an anti-Parkinson drug, has antioxidant and anti-apoptotic effects. To explore the effect of selegiline on sepsis, we used a clinically relevant animal model of polymicrobial sepsis. Cecal ligation and puncture (CLP) or sham operation was performed in male rats under anesthesia. Three hours after surgery, animals were randomized to receive intravenously selegiline (3 mg/kg) or an equivalent volume of saline. The administration of CLP rats with selegiline (i) increased arterial blood pressure and vascular responsiveness to norepinephrine, (ii) reduced plasma liver and kidney dysfunction, (iii) attenuated metabolic acidosis, (iv) decreased neutrophil infiltration in liver and lung, and (v) improved survival rate (from 44% to 65%), compared to those in the CLP alone rats. The CLP-induced increases of plasma interleukin-6, organ superoxide levels, and liver inducible nitric oxide synthase and caspase-3 expressions were ameliorated by selegiline treatment. In addition, the histological changes in liver and lung were significantly attenuated in the selegiline -treated CLP group compared to those in the CLP group. The improvement of organ dysfunction and survival through reducing inflammation, oxidative stress and apoptosis in peritonitis-induced sepsis by selegiline has potential as an adjuvant agent for critical ill.

Pulmonary microvascular albumin leak is associated with endothelial cell death in murine sepsis-induced lung injury in vivo

Sepsis is a systemic inflammatory response that targets multiple components of the cardiovascular system including the microvasculature. Microvascular endothelial cells (MVEC) are central to normal microvascular function, including maintenance of the microvascular permeability barrier. Microvascular/MVEC dysfunction during sepsis is associated with barrier dysfunction, resulting in the leak of protein-rich edema fluid into organs, especially the lung. The specific role of MVEC apoptosis in septic microvascular/MVEC dysfunction in vivo remains to be determined. To examine pulmonary MVEC death in vivo under septic conditions, we used a murine cecal ligation/perforation (CLP) model of sepsis and identified non-viable pulmonary cells with propidium iodide (PI) by intravital videomicroscopy (IVVM), and confirmed this by histology. Septic pulmonary microvascular Evans blue (EB)-labeled albumin leak was associated with an increased number of PI-positive cells, which were confirmed to be predominantly MVEC based on specific labeling with three markers, anti-CD31 (PECAM), anti-CD34, and lectin binding. Furthermore, this septic death of pulmonary MVEC was markedly attenuated by cyclophosphamide-mediated depletion of neutrophils (PMN) or use of an anti-CD18 antibody developed for immunohistochemistry but shown to block CD18-dependent signaling. Additionally, septic pulmonary MVEC death was iNOS-dependent as mice lacking iNOS had markedly fewer PI-positive MVEC. Septic PI-positive pulmonary cell death was confirmed to be due to apoptosis by three independent markers: caspase activation by FLIVO, translocation of phosphatidylserine to the cell surface by Annexin V binding, and DNA fragmentation by TUNEL. Collectively, these findings indicate that septic pulmonary MVEC death, putatively apoptosis, is a result of leukocyte activation and iNOS-dependent signaling, and in turn, may contribute to pulmonary microvascular barrier dysfunction and albumin hyper-permeability during sepsis.

Lipoteichoic acid from Staphylococcus aureus directly affects cardiomyocyte contractility and calcium transients

Lipoteichoic acid (LTA) is the key pathogenic factor of gram-positive bacteria and contributes significantly to organ dysfunction in sepsis, a frequent complication in critical care patients. We hypothesized that LTA directly affects cardiomyocyte function, thus contributing to cardiac failure in sepsis. This study was designed to evaluate the effects of LTA on contractile properties and calcium-transients of isolated adult rat cardiomyocytes. When myocytes were exposed to LTA for 1h prior to analysis, the amplitudes of calcium-transients as well as sarcomere shortening increased to 130% and 142% at 1 Hz stimulation frequency. Relengthening of sarcomeres as well as decay of calcium-transients was accelerated after LTA incubation. Exposure to LTA for 24 h resulted in significant depression of calcium-transients as well as of sarcomere shortening compared to controls. One of the major findings of our experiments is that LTA most likely affects calcium-handling of the cardiomyocytes. The effect is exacerbated by reduced extracellular calcium, which resembles the clinical situation in septic patients. Functionally, an early stimulating effect of LTA with increased contractility of the cardiomyocytes may be an in vitro reflection of early hyperdynamic phases in clinical sepsis. Septic disorders have been shown to induce late hypodynamic states of the contractile myocardium, which is also supported at the single-cell level in vitro by results of our 24h-exposure to LTA.

Scavenger receptor class a plays a central role in mediating mortality and the development of the pro-inflammatory phenotype in polymicrobial sepsis

Sepsis is a frequent complication in critical illness. The mechanisms that are involved in initiation and propagation of the disease are not well understood. Scavenger receptor A (SRA) is a membrane receptor that binds multiple polyanions such as oxidized LDL and endotoxin. Recent studies suggest that SRA acts as a pattern recognition receptor in the innate immune response. The goal of the present study was to determine the role of SRA in polymicrobial sepsis. SRA deficient (SRA^−/−) and C57BL/6JB/6J (WT) male mice were subjected to cecal ligation and puncture (CLP) to induce polymicrobial sepsis. NFκB activity, myeloperoxidase activity, and co-association of SRA with toll like receptor (TLR) 4 and TLR2 was analyzed in the lungs. Spleens were analyzed for apoptosis. Serum cytokines and chemokines were assayed. Blood and peritoneal fluid were cultured for aerobic and anaerobic bacterial burdens. Long term survival was significantly increased in SRA^−/− septic mice (53.6% vs. 3.6%, p<0.05) when compared to WT mice. NFκB activity was 45.5% lower in the lungs of SRA^−/− septic mice versus WT septic mice (p<0.05). Serum levels of interleukin (IL)-5, IL-6, IL-10 and monocyte chemoattractant protein −1 were significantly lower in septic SRA^−/− mice when compared to septic WT mice (p<0.05). We found that SRA immuno-precipitated with TLR4, but not TLR2, in the lungs of WT septic mice. We also found that septic SRA^−/− mice had lower bacterial burdens than WT septic mice. SRA deficiency had no effect on pulmonary neutrophil infiltration or splenocyte apoptosis during sepsis. We conclude that SRA plays a pivotal, and previously unknown, role in mediating the pathophysiology of sepsis/septic shock in a murine model of polymicrobial sepsis. Mechanistically, SRA interacts with TLR4 to enhance the development of the pro-inflammatory phenotype and mediate the morbidity and mortality of sepsis/septic shock.

Trauma and other critical illnesses can progress to septic shock. The mechanisms that result in this progression are not understood. For this reason, there are no proven treatments available, and the mortality rate from sepsis remains quite high. We have found that mice that lack a certain cell surface protein, scavenger receptor A, have a higher rate of survival from a surgically induced sepsis than those that have the receptor. Previously, this receptor has been found to play a role in atherosclerosis, and more recently, to play a role in the immune response to infection. In this study we have found that in addition to improved survival, mice without scavenger receptor A have fewer bacteria in their abdominal cavities and in their blood. They also have lower levels of inflammation. We demonstrated that scavenger receptor A interacts with another protein involved in inflammation and infection, toll like receptor 4. This interaction might be one mechanism for the effects seen in mice without scavenger receptor A. These studies provide a better understanding of the underlying mechanisms of sepsis. Drugs that target scavenger receptor A could result in better therapies for sepsis.

Activation of myocardial phosphoinositide-3-kinase p110α ameliorates cardiac dysfunction and improves survival in polymicrobial sepsis

Phosphoinositide-3-kinase (PI3K)/Akt dependent signaling has been shown to improve outcome in sepsis/septic shock. There is also ample evidence that PI3K/Akt dependent signaling plays a crucial role in maintaining normal cardiac function. We hypothesized that PI3K/Akt signaling may ameliorate septic shock by attenuating sepsis-induced cardiac dysfunction. Cardiac function and survival were evaluated in transgenic mice with cardiac myocyte specific expression of constitutively active PI3K isoform, p110α (caPI3K Tg). caPI3K Tg and wild type (WT) mice were subjected to cecal ligation/puncture (CLP) induced sepsis. Wild type CLP mice showed dramatic cardiac dysfunction at 6 hrs. Septic cardiomyopathy was significantly attenuated in caPI3K CLP mice. The time to 100% mortality was 46 hrs in WT CLP mice. In contrast, 80% of the caPI3K mice survived at 46 hrs after CLP (p<0.01) and 50% survived >30 days (p<0.01). Cardiac caPI3K expression prevented expression of an inflammatory phenotype in CLP sepsis. Organ neutrophil infiltration and lung apoptosis were also effectively inhibited by cardiac PI3k p110α expression. Cardiac high mobility group box–1 (HMGB-1) translocation was also inhibited by caPI3K p110α expression. We conclude that cardiac specific activation of PI3k/Akt dependent signaling can significantly modify the morbidity and mortality associated with sepsis. Our data also indicate that myocardial function/dysfunction plays a prominent role in the pathogenesis of sepsis and that maintenance of cardiac function during sepsis is essential. Finally, these data suggest that modulation of the PI3K/p110α signaling pathway may be beneficial in the prevention and/or management of septic cardiomyopathy and septic shock.

Pharmacological targets in the renal peritubular microenvironment: implications for therapy for sepsis-induced acute kidney injury

One of the most frequent and serious complications to develop in septic patients is acute kidney injury (AKI), a disorder characterized by a rapid failure of the kidneys to adequately filter the blood, regulate ion and water balance, and generate urine. AKI greatly worsens the already poor prognosis of sepsis and increases cost of care. To date, therapies have been mostly supportive; consequently there has been little change in the mortality rates over the last decade. This is due, at least in part, to the delay in establishing clinical evidence of an infection and the associated presence of the systemic inflammatory response syndrome and thus, a delay in initiating therapy. A second reason is a lack of understanding regarding the mechanisms leading to renal injury, which has hindered the development of more targeted therapies. In this review, we summarize recent studies, which have examined the development of renal injury during sepsis and propose how changes in the peritubular capillary microenvironment lead to and then perpetuate microcirculatory failure and tubular epithelial cell injury. We also discuss a number of potential therapeutic targets in the renal peritubular microenvironment, which may prevent or lessen injury and/or promote recovery.

TLR2 ligands attenuate cardiac dysfunction in polymicrobial sepsis via a phosphoinositide 3-kinase-dependent mechanism

Myocardial dysfunction is a major consequence of septic shock and contributes to the high mortality of sepsis. In the present study, we examined the effect of Toll-like receptor 2 (TLR2) ligands, peptidoglycan (PGN), and Pam3CSK4 (Pam3) on cardiac function in cecal ligation and puncture (CLP)-induced sepsis in mice. We also investigated whether the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway is involved in the effect of TLR2 ligands on cardiac function in CLP mice. PGN was administered to C57B6/L mice 1 h before the induction of CLP. Sham surgically operated mice served as a control. Cardiac function indexes (rate of change in left ventricular pressure, stroke work, cardiac output, and ejection fraction) were examined by a microconductance pressure catheter. Cardiac function was significantly decreased 6 h after CLP-induced sepsis compared with sham-operated control. In contrast, PGN administration attenuated CLP-induced cardiac dysfunction. Importantly, the therapeutic treatment with Pam3 1 h after CLP also significantly attenuated cardiac dysfunction in CLP mice. However, the beneficial effect of TLR2 ligands on cardiac dysfunction in CLP-mice was abolished in TLR2-deficient mice. PGN administration significantly increased the levels of phospho-Akt and phospho-GSK-3beta in the myocardium compared with the levels in untreated CLP mice. PI3K inhibition abolished the PGN-induced attenuation of cardiac dysfunction in CLP mice. In conclusion, these data demonstrate that the administration of TLR2 ligands, PGN, or Pam3 attenuates cardiac dysfunction in septic mice via a TLR2/PI3K-dependent mechanism. More significantly, Pam3 therapeutic treatment will have a potential clinical relevance.

Immature dendritic cell-derived exosomes rescue septic animals via milk fat globule epidermal growth factor-factor VIII [corrected]

Sepsis, a highly lethal systemic inflammatory syndrome, is associated with increases of proinflammatory cytokines (e.g., TNF-alpha, HMGB1) and the accumulation of apoptotic cells that have the potential to be detrimental. Depending on the timing and tissue, prevention of apoptosis in sepsis is beneficial; however, thwarting the development of secondary necrosis through the active removal of apoptotic cells by phagocytosis may offer a novel anti-sepsis therapy. Immature dendritic cells (IDCs) release exosomes that contain milk fat globule EGF factor VIII (MFGE8), a protein required to opsonize apoptotic cells for phagocytosis. In an experimental sepsis model using cecal ligation and puncture, we found that MFGE8 levels decreased in the spleen and blood, which was associated with impaired apoptotic cell clearance. Administration of IDC-derived exosomes promoted phagocytosis of apoptotic cells and significantly reduced mortality. Treatment with recombinant MFGE8 was equally protective, whereas MFGE8-deficient mice suffered from increased mortality. IDC exosomes also attenuated the release of proinflammatory cytokines in septic rats. Liberation of HMGB1, a nuclear protein that contributes to inflammation upon release from unengulfed apoptotic cells, was prevented by MFGE8-mediated phagocytosis in vitro. We conclude that IDC-derived exosomes attenuate the acute systemic inflammatory response in sepsis by enhancing apoptotic cell clearance via MFGE8.

VX-166: a novel potent small molecule caspase inhibitor as a potential therapy for sepsis

Introduction

Prevention of lymphocyte apoptosis by caspase inhibition has been proposed as a novel treatment approach in sepsis. However, it has not been clearly demonstrated that caspase inhibitors improve survival in sepsis models when dosed post-insult. Also, there are concerns that caspase inhibitors might suppress the immune response. Here we characterize VX-166, a broad caspase inhibitor, as a novel potential treatment for sepsis.

Methods

VX-166 was studied in a number of enzymatic and cellular assays. The compound was then tested in a murine model of endotoxic shock (lipopolysaccharide (LPS), 20 mg/kg IV) and a 10 d rat model of polymicrobial sepsis by caecal ligation and puncture (CLP).

Results

VX-166 showed potent anti-apoptotic activity in vitro and inhibited the release of interleukin (IL)-1beta and IL-18. In the LPS model, VX-166 administered 0, 4, 8 and 12 h post-LPS significantly improved survival in a dose-dependent fashion (P < 0.0028). In the CLP model, VX-166 continuously administered by mini-osmotic pump significantly improved survival when dosed 3 h after insult, (40% to 92%, P = 0.009). When dosed 8 h post-CLP, VX-166 improved survival from 40% to 66% (P = 0.19). Mode of action studies in the CLP model confirmed that VX-166 significantly inhibited thymic atrophy and lymphocyte apoptosis as determined by flow cytometry (P < 0.01). VX-166 reduced plasma endotoxin levels (P < 0.05), suggesting an improved clearance of bacteria from the bloodstream. Release of IL-1beta in vivo or T-cell activation in vitro were moderately affected.

Conclusions

Our studies enhance the case for the use of caspase inhibitors in sepsis. VX-166 itself has promise as a therapy for the treatment of sepsis in man.

Approach to the patient with sepsis

This article reviews the current understanding of sepsis, severe sepsis, and septic shock. The article details definitions and epidemiology pertinent to the sepsis syndrome. A brief discussion of mechanisms of disease is followed a description of organ-specific failures related to sepsis. A concise review of the latest treatment options for each organ dysfunction is provided.

Caffeine restores myocardial cytochrome oxidase activity and improves cardiac function during sepsis

OBJECTIVE

Impaired mitochondrial function is a potential cause of sepsis-associated myocardial depression. Cytochrome oxidase (CcOX), the terminal oxidase of the electron transport chain, is inhibited in the septic heart. Caffeine increases CcOX activity by increasing cyclic adenosine monophosphate and protein kinase A activity. We hypothesized that caffeine will restore myocardial CcOX activity, increase cardiac function, and improve survival during sepsis.

DESIGN

Prospective randomized controlled study.

SETTING

University hospital-based laboratory.

SUBJECTS

One hundred twenty Sprague-Dawley male rats.

INTERVENTIONS

Sprague-Dawley male rats underwent cecal ligation and puncture (CLP) or sham operation. At 24 and 48 hours, rats underwent intraperitoneal injection of either caffeine (7.5 mg/kg, the equivalent of 1-1.5 cups of coffee) or equal volume of saline.

MEASUREMENTS AND MAIN RESULTS

One hour following the 48-hour injection, steady-state CcOX kinetic activity was measured in isolated mitochondria and normalized to citrate synthase activity. Cardiac function was assessed using an isolated rat heart preparation and survival was tracked to 96 hours. CLP significantly decreased myocardial CcOX activity, oxygen consumption, left ventricular pressure, and pressure developed during isovolumic contraction (+dP/dt) and relaxation (-dP/dt). Caffeine restored CcOX activity and increased left ventricular pressure and +/-dP/dt toward sham values following CLP. Survival significantly improved following CLP in caffeine-injected animals compared with saline injection.

CONCLUSION

Caffeine may be a novel therapy to treat sepsis-associated myocardial depression.

beta-Blockers in sepsis: reexamining the evidence

Sepsis remains the leading cause for noncardiac intensive care unit deaths in the United States. Despite recent advances in the treatment of this devastating condition, mortality and morbidity remain unacceptably high. Sepsis is characterized by a multitude of pathophysiological changes that include inflammation, metabolic derangements, hemodynamic alterations, and multiorgan dysfunction. Unfortunately, several studies of treatment modalities aimed at correcting one or more of the underlying derangements have led to disappointing results. New treatment modalities are needed. beta-Receptor blockers have long been used for a variety of conditions such as coronary artery disease, congestive heart failure, and arterial hypertension. Recent data suggest that beta-blocker effects on metabolism, glucose homeostasis, cytokine expression, and myocardial function may be beneficial in the setting of sepsis. Although treating a potentially hypotensive condition with a drug with antihypertensive properties may initially seem counterintuitive, the metabolic and immunomodulatory properties of beta-blockers may be of benefit. It is the purpose of this review to discuss the effects of beta-blockers on the following: (1) metabolism, (2) glucose regulation, (3) the inflammatory response, (4) cardiac function, and (5) mortality in sepsis.

Leukocyte Dectin-1 expression is differentially regulated in fungal versus polymicrobial sepsis

OBJECTIVE

To examine peripheral leukocyte Dectin-1 regulation in clinically relevant models of fungal and polymicrobial sepsis.

DESIGN

Prospective animal study.

SETTING

University medical school research laboratory.

SUBJECTS

Age, weight, and sex matched ICR/HSD mice.

INTERVENTIONS

Mice were infected with Candida albicans (1 x 10, intravenously) or were subjected to cecal ligation and puncture to induce polymicrobial sepsis.

MEASUREMENTS

Blood, spleen, and peritoneal exudate were harvested and leukocytes were isolated. Leukocytes were evaluated for membrane-associated Dectin-1 expression and cell phenotype by flow cytometry.

MAIN RESULTS

In C. albicans infection, Dectin-1-positive blood and splenic leukocytes were increased from 23.5% to 58.9% over the course of infection. The increased percentage of Dectin-1-expressing cells was primarily attributable to neutrophilia. However, the amount of Dectin-1 expressed by blood and splenic neutrophils in C. albicans-infected mice was decreased by a range of 49.0% to 53.3%. C. albicans infection also resulted in an infiltration of Dectin-1-positive macrophages and neutrophils into the kidney. In contrast, polymicrobial sepsis decreased blood leukocyte Dectin-1-expressing cells by up to 51.4%. This reduction was due to a decrease in Dectin-1-positive neutrophils in the periphery. However, the percentage of Dectin-1-expressing cells in the peritoneal cavity increased by 774% with cecal ligation and puncture. Treatment of isolated neutrophils with three soluble glucans, mannan, lipopolysaccharide, or a variety of cytokines revealed that glucans, alone or in combination, were the only treatment that resulted in a decrease in Dectin-1-positive neutrophils.

CONCLUSIONS

We conclude that peripheral leukocyte Dectin-1 expression is differentially regulated in fungal vs. polymicrobial sepsis. These data demonstrate that leukocyte Dectin-1 levels are modulated in response to infections of fungal and nonfungal origin.

Methyl-2-acetamidoacrylate, an ethyl pyruvate analog, decreases sepsis-induced acute kidney injury in mice

We tested the anti-inflammatory agent methyl-2-acetamidoacrylate (M2AA), an ethyl pyruvate analog, in a cecal ligation-and-puncture (CLP) model of sepsis in CD-1 mice. M2AA administration at the time of CLP improved survival, renal function, kidney histology, liver injury, and splenocyte apoptosis, and lowered cytokine levels (TNF-alpha, IL-6, IFN-gamma, and IL-10). When M2AA treatment was delayed 6 h (but not 12 h), M2AA still significantly reduced kidney dysfunction, liver injury, splenocyte apoptosis, and cytokine levels. NF-kappaB, a M2AA target, was transiently activated in spleen, peaking at 6 h; kidney and liver NF-kappaB increased steadily with a plateau at 12-24 h. M2AA reduced NF-kappaB activation in spleen at 6 h and in kidney and liver at 24 h. Splenectomy diminished the ability of M2AA to reduce cytokines, especially IL-6, but M2AA still decreased kidney and liver dysfunction, suggesting that splenic NF-kappaB is not central to M2AA action. In contrast, beneficial effects of chloroquine on cytokines and organ damage were neutralized by splenectomy, demonstrating a spleen-specific chloroquine target. Because M2AA and chloroquine act differently, we tested this combination. Survival at 96 h was highest with combination therapy (57%) vs. chloroquine (38%), M2AA (47.6%), or vehicle (5%). The benefit of combination therapy over chloroquine or M2AA alone did not reach statistical significance, indicating potential mechanistic overlap. We conclude that the transient target(s) for M2AA responsible for the narrow 6-h therapeutic window is not splenic NF-kappaB. Identifying this new target and downstream signaling pathways could lengthen the therapeutic window and improve combination therapy with chloroquine.

Endotoxin downregulates peroxisome proliferator-activated receptor-gamma via the increase in TNF-alpha release

The nuclear receptor peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is anti-inflammatory in a cell-based system and in animal models of endotoxemia. We have shown that PPAR-gamma gene expression is downregulated in macrophages after lipopolysaccharide (LPS) stimulation. However, it remains unknown whether hepatic PPAR-gamma is altered in sepsis and, if so, whether LPS directly downregulates PPAR-gamma. To study this, rats were subjected to sepsis by cecal ligation and puncture (CLP). Hepatic tissues were harvested at 5, 10, and 20 h after CLP. PPAR-gamma gene expression and protein levels were determined by RT-PCR and Western blot analysis, respectively. The results showed that PPAR-gamma gene expression decreased at 10 and 20 h and that its proteins levels were reduced at 20 h after CLP. PPAR-gamma levels were also decreased in animals that were administered LPS. To determine the direct effects of LPS on PPAR-gamma downregulation, LPS binding agent polymyxin B (PMB) was administered intramuscularly after CLP. The administration of PMB significantly reduced plasma levels of endotoxin, but it did not prevent the downregulation of PPAR-gamma expression. We found that circulating levels of TNF-alpha still remained significantly elevated in PMB-treated septic animals. We, therefore, hypothesize that the decrease of PPAR-gamma expression is TNF-alpha dependent. To investigate this, Kupffer cells (KCs) were isolated from normal rats and stimulated with LPS or TNF-alpha. TNF-alpha significantly attenuated PPAR-gamma gene expression in KCs. Although LPS decreased PPAR-gamma in KCs, the downregulatory effect of LPS was blocked by the addition of TNF-alpha-neutralizing antibodies. Furthermore, the administration of TNF-alpha-neutralizing antibodies to animals before the onset of sepsis prevented the downregulation of PPAR-gamma in sepsis. We, therefore, conclude that LPS downregulates PPAR-gamma expression during sepsis via an increase in TNF-alpha release.

Cytochrome c oxidase dysfunction in sepsis

Sepsis, the principal cause of death in critically ill patients, is associated with impaired oxygen extraction by tissues. One possible explanation is the development of mitochondrial dysfunction and ineffective oxygen utilization. This abnormality has been termed cytopathic hypoxia. This may be caused by an abnormality in the transport of electrons down the cytochrome chain on the mitochondrial inner membrane. In this article we review our studies on abnormalities in the function of complex IV (cytochrome oxidase), the final electron acceptor in this chain. In addition, we provide evidence that administration of cytochrome c may overcome these abnormalities and provide a novel therapeutic alternative.

Mitochondrial resuscitation with exogenous cytochrome c in the septic heart

OBJECTIVE

Mitochondrial dysfunction may play a role in the pathogenesis of sepsis-induced organ dysfunction. Respiratory-chain deficiencies that occur in sepsis, however, have never been shown to cause organ failure or to be reversible. Cytochrome oxidase uses electrons donated by its substrate, cytochrome c, to reduce oxygen to H2O. In the septic heart, cytochrome oxidase is competitively inhibited. We hypothesized that cytochrome oxidase inhibition coupled with reduced substrate availability is a reversible cause of sepsis-associated myocardial depression.

DESIGN

Prospective observational study aimed to overcome myocardial cytochrome oxidase inhibition with excess cytochrome c and improve cardiac function.

SETTING

University hospital-based laboratory.

SUBJECTS

Seventy-five C57Bl6 male mice.

INTERVENTIONS

Mice underwent cecal ligation and double puncture, sham operation, or no operation. Exogenous cytochrome c or an equal volume of saline was intravenously injected at the 24-hr time point. All animals were evaluated 30 mins after injection.

MEASUREMENTS AND MAIN RESULTS

Exogenous cytochrome c readily repleted cardiac mitochondria with supranormal levels of substrate (>1.6 times baseline), restored heme c content, and increased cytochrome oxidase kinetic activity. This increased left ventricular pressure and increased pressure development during isovolumic contraction (dP/dtmax) and relaxation (dP/dtmin) by >45% compared with saline injection.

CONCLUSION

Impaired oxidative phosphorylation is a cause of sepsis-associated myocardial depression, and mitochondrial resuscitation with exogenous cytochrome c overcomes cytochrome oxidase inhibition and improves cardiac function.

A cardiovascular drug rescues mice from lethal sepsis by selectively attenuating a late-acting proinflammatory mediator, high mobility group box 1

The pathogenesis of sepsis is mediated in part by bacterial endotoxin, which stimulates macrophages/monocytes to sequentially release early (e.g., TNF, IL-1, and IFN-gamma) and late (e.g., high mobility group box 1 (HMGB1) protein) proinflammatory cytokines. The recent discovery of HMGB1 as a late mediator of lethal sepsis has prompted investigation for development of new experimental therapeutics. We found that many steroidal drugs (such as dexamethasone and cortisone) and nonsteroidal anti-inflammatory drugs (such as aspirin, ibuprofen, and indomethacin) failed to influence endotoxin-induced HMGB1 release even at superpharmacological concentrations (up to 10-25 microM). However, several steroid-like pigments (tanshinone I, tanshinone IIA, and cryptotanshinone) of a popular Chinese herb, Danshen (Salvia miltiorrhiza), dose dependently attenuated endotoxin-induced HMGB1 release in macrophage/monocyte cultures. A water-soluble tanshinone IIA sodium sulfonate derivative (TSNIIA-SS), which has been widely used as a Chinese medicine for patients with cardiovascular disorders, selectively abrogated endotoxin-induced HMGB1 cytoplasmic translocation and release in a glucocorticoid receptor-independent manner. Administration of TSNIIA-SS significantly protected mice against lethal endotoxemia and rescued mice from lethal sepsis even when the first dose was given 24 h after the onset of sepsis. The therapeutic effects were partly attributable to attenuation of systemic accumulation of HMGB1 (but not TNF and NO) and improvement of cardiovascular physiologic parameters (e.g., decrease in total peripheral vascular resistance and increase in cardiac stroke volume) in septic animals. Taken together, these data re-enforce the pathogenic role of HMGB1 in lethal sepsis, and support a therapeutic potential for TSNIIA-SS in the treatment of human sepsis.

Glucan phosphate attenuates cardiac dysfunction and inhibits cardiac MIF expression and apoptosis in septic mice

Myocardial dysfunction is a major consequence of septic shock and contributes to the high mortality of sepsis. We have previously reported that glucan phosphate (GP) significantly increased survival in a murine model of cecal ligation and puncture (CLP)-induced sepsis. In the present study, we examined the effect of GP on cardiac dysfunction in CLP-induced septic mice. GP was administered to ICR/HSD mice 1 h before induction of CLP. Sham surgically operated mice served as control. Cardiac function was significantly decreased 6 h after CLP-induced sepsis compared with sham control. In contrast, GP administration prevented CLP-induced cardiac dysfunction. Macrophage migration inhibitory factor (MIF) has been implicated as a major factor in cardiomyocyte apoptosis and cardiac dysfunction during septic shock. CLP increased myocardial MIF expression by 88.3% ( P < 0.05) and cardiomyocyte apoptosis by 7.8-fold ( P < 0.05) compared with sham control. GP administration, however, prevented CLP-increased MIF expression and decreased cardiomyocyte apoptosis by 51.2% ( P < 0.05) compared with untreated CLP mice. GP also prevented sepsis-caused decreases in phospho-Akt, phospho-GSK-3β, and Bcl-2 levels in the myocardium of septic mice. These data suggest that GP treatment attenuates cardiovascular dysfunction in fulminating sepsis. GP administration also activates the phosphoinositide 3-kinase/Akt pathway, decreases myocardial MIF expression, and reduces cardiomyocyte apoptosis.

Simvastatin improves sepsis-induced mortality and acute kidney injury via renal vascular effects

Acute kidney injury (AKI) occurs in about half of patients in septic shock and the mortality of AKI with sepsis is extremely high. An effective therapeutic intervention is urgently required. Statins are 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors that also have pleiotropic actions. They have been reported to increase the survival of septic or infectious patients. But the effect of simvastatin, a widely used statin, on sepsis-induced AKI is unknown. The effects of simvastatin and tumor necrosis factor (TNF)-alpha neutralizing antibody were studied in a clinically relevant model of sepsis-induced AKI using cecal ligation and puncture (CLP) in elderly mice. Simvastatin significantly improved CLP-induced mortality and AKI. Simvastatin attenuated CLP-induced tubular damage and reversed CLP-induced reduction of intrarenal microvascular perfusion and renal tubular hypoxia at 24 h. Simvastatin also restored towards normal CLP-induced renal vascular protein leak and serum TNF-alpha. Neither delayed simvastatin therapy nor TNF-alpha neutralizing antibody improved CLP-induced AKI. Simvastatin improved sepsis-induced AKI by direct effects on the renal vasculature, reversal of tubular hypoxia, and had a systemic anti-inflammatory effect.

Direct molecular and spectroscopic evidence for increased ammonia removal capacity of skeletal muscle in acute liver failure

BACKGROUND/AIMS

It has been proposed that, in acute liver failure, skeletal muscle adapts to become the principle organ responsible for removal of blood-borne ammonia by increasing glutamine synthesis, a reaction that is catalyzed by the cytosolic ATP-dependent enzyme glutamine synthetase. To address this issue, glutamine synthetase expression and activities were measured in skeletal muscle of rats with acute liver failure resulting from hepatic devascularization.

METHODS

Glutamine synthetase protein and gene expression were investigated using immunoblotting and semi-quantitative RT-PCR analysis. Glutamine synthetase activity and glutamine de novo synthesis were measured using, respectively, a standard enzymatic assay and [13C]-nuclear magnetic resonance spectroscopy.

RESULTS

Glutamine synthetase protein (but not gene) expression and enzyme activities were significantly up-regulated leading to increased de novo synthesis of glutamine and increased skeletal muscle capacity for ammonia removal in acute liver failure. In contrast to skeletal muscle, expression and activities of glutamine synthetase in the brain were significantly decreased.

CONCLUSIONS

These findings demonstrate that skeletal muscle adapts, through a rapid induction of glutamine synthetase, to increase its capacity for removal of blood-borne ammonia in acute liver failure. Maintenance of muscle mass together with the development of agents with the capacity to stimulate muscle glutamine synthetase could provide effective ammonia-lowering strategies in this disorder.

An essential role for complement C5a in the pathogenesis of septic cardiac dysfunction

Defective cardiac function during sepsis has been referred to as “cardiomyopathy of sepsis.” It is known that sepsis leads to intensive activation of the complement system. In the current study, cardiac function and cardiomyocyte contractility have been evaluated in rats after cecal ligation and puncture (CLP). Significant reductions in left ventricular pressures occurred in vivo and in cardiomyocyte contractility in vitro. These defects were prevented in CLP rats given blocking antibody to C5a. Both mRNA and protein for the C5a receptor (C5aR) were constitutively expressed on cardiomyocytes; both increased as a function of time after CLP. In vitro addition of recombinant rat C5a induced dramatic contractile dysfunction in both sham and CLP cardiomyocytes, but to a consistently greater degree in cells from CLP animals. These data suggest that CLP induces C5aR on cardiomyocytes and that in vivo generation of C5a causes C5a–C5aR interaction, causing dysfunction of cardiomyocytes, resulting in compromise of cardiac performance.

INFLAMMATORY/CARDIOVASCULAR-METABOLIC RESPONSES IN A RAT MODEL OF BURN INJURY WITH SUPERIMPOSED INFECTION

Infection remains the major cause of morbidity and mortality in burn patients. Furthermore, the use of antibiotics in such patients has led to the prevalence of antibiotic-resistant microbial infections; one such infection in intensive care unit turns out to be caused by the enterococcal organisms. Our laboratory studies have used a rat model of bum injury and Enterococcus faecalis infection. Sprague-Dawley male rats ( approximately 250 g) were initially given an intragastric gavage of the antibiotic ciprofloxacin for 3 days. This procedure allowed for decontamination of intestine of gram-negative and some gram-positive organisms. The remainders of the gram-positive organisms were, to a large extent, Enterococci. After the decontamination procedure, rats were intra-abdominally inoculated with E. faecalis; inoculation involved preparation of sterilized rat fecal pellets impregnated with E. faecalis (10 colony-forming units) and their implants through a midline abdominal wall incision. Some of the rats that were implanted with the fecal pellets were subject to full-thickness skin bums ( approximately 30% total body surface area; 95 degrees C water for 7 s). Sham abdominal infection rats received a sterile pellet only; sham bum procedure consisted of exposing the skin to room temperature water. All sham and bum and/or E. faecalis infection procedures were carried out on rats under pentobarbital anesthesia. Inflammation and innate host defense-related responses were assessed via measurements of neutrophil effector responses, i.e., oxygen anion free radical (O2)/eIastase production, CD11b/CD18 expression, apoptosis, and tissue infiltration. Determining epithelial lactulose permeability, microvascular albumin leakage, and epithelial tight junction integrity assessed the status of intestinal function/structural derangements. The animals' metabolic and cardiovascular integrity was evaluated determining blood pH, p02, pC02, heart rate, respiratory rate, blood pressure, and cardiac output. Whereas the aforementioned measurements were carried out at 24 to 48 h postbum injury with and without the Enterococcal infection, animal mortality was determined for up to 5 days after the experimental injuries. The results of the studies indicated that whereas bum or E. faecalis infection alone did not produce significant mortality, the dual insult with bum and E. faecalis infection resulted in significant animal death accompanied by relatively more profound metabolic and cardiovascular derangements. Inappropriately heightened neutrophil effector responses were present with bum alone as well as with the dual bum and infection complications. These studies suggest that animal models of bum injury with Enterococcal infection complications simulate the adverse outcomes bum patients infected with Enterococcal organisms.

Evidence of myocardial hibernation in the septic heart*

OBJECTIVE

Myocardial hibernation is an adaptive response to ischemia and hypoxia. Hibernating cardiomyocytes are reversibly hypocontractile and demonstrate characteristic metabolic and ultrastructural changes. These include a switch in primary substrate utilization from fatty acids to glucose, up-regulation of the myocardial specific glucose transporters (GLUT1 and GLUT4), and glycogen deposition within and between cardiomyocytes. We hypothesized that myocardial hibernation may underlie sepsis-associated myocardial depression.

DESIGN

Prospective observational study aimed at identifying the characteristic changes of hibernation in the septic heart.

SETTING

University hospital-based laboratory.

SUBJECTS

Forty-three C57Bl6 male mice.

INTERVENTIONS

Mice underwent cecal ligation and double puncture, sham operation, or no operation and were evaluated 48 hrs after the procedure.

MEASUREMENTS AND MAIN RESULTS

Using novel, clinically relevant technology such as magnetic resonance imaging, positron emission tomography, and single photon emission computed tomography imaging, we found septic mice to have diminished cardiac performance, increased myocardial glucose uptake, increased steady-state levels of myocardial GLUT4, and increased deposits of glycogen, recapitulating the changes during hibernation. Importantly, these changes occurred in the setting of preserved arterial oxygen tension and myocardial perfusion.

CONCLUSIONS

Sepsis-associated cardiac dysfunction may reflect hibernation. Furthermore, such down-regulation of cellular function may underlie sepsis-induced dysfunction in other organ systems.

Renal blood flow in sepsis

Introduction

To assess changes in renal blood flow (RBF) in human and experimental sepsis, and to identify determinants of RBF.

Method

Using specific search terms we systematically interrogated two electronic reference libraries to identify experimental and human studies of sepsis and septic acute renal failure in which RBF was measured. In the retrieved studies, we assessed the influence of various factors on RBF during sepsis using statistical methods.

Results

We found no human studies in which RBF was measured with suitably accurate direct methods. Where it was measured in humans with sepsis, however, RBF was increased compared with normal. Of the 159 animal studies identified, 99 reported decreased RBF and 60 reported unchanged or increased RBF. The size of animal, technique of measurement, duration of measurement, method of induction of sepsis, and fluid administration had no effect on RBF. In contrast, on univariate analysis, state of consciousness of animals (P = 0.005), recovery after surgery (P < 0.001), haemodynamic pattern (hypodynamic or hyperdynamic state; P < 0.001) and cardiac output (P < 0.001) influenced RBF. However, multivariate analysis showed that only cardiac output remained an independent determinant of RBF (P < 0.001).

Conclusion

The impact of sepsis on RBF in humans is unknown. In experimental sepsis, RBF was reported to be decreased in two-thirds of studies (62 %) and unchanged or increased in one-third (38%). On univariate analysis, several factors not directly related to sepsis appear to influence RBF. However, multivariate analysis suggests that cardiac output has a dominant effect on RBF during sepsis, such that, in the presence of a decreased cardiac output, RBF is typically decreased, whereas in the presence of a preserved or increased cardiac output RBF is typically maintained or increased.

Endothelin receptor antagonist bosentan improves survival in a murine caecal ligation and puncture model of septic shock

The role of endothelin peptides was evaluated on survival and organ injury in a model of polymicrobial sepsis, induced by caecal ligation and puncture with particular emphasis on the timing of the administration of its blocker bosentan in Swiss albino mice (20-40 g). The cardiovascular response pattern in this experimental model was characterized by an early, "hyperdynamic" phase starting at 5 h, followed by a late but "hypodynamic" phase that commence after 20 h, provided that the animals are "resuscitated" by injecting 1 ml of saline i.p. at the end of the surgery. However, if saline resuscitation is omitted, then only hypodynamic pattern is observed starting at 5 h without any hyperdynamic phase. Thus, mice were first allocated into saline-resuscitated or unresuscitated groups and endothelin receptor antagonist bosentan (30 mg kg(-1), i.p., either 5 or 20 h after caecal ligation and puncture) was then administered. The control animals received the solvent of bosentan (i.e., saline: %0.9 NaCl, w/v). The survival rates in each group (n=14) were recorded over the following 144 h. In unresuscitated mice, the overall survival at 144 h was 14.3% in controls while bosentan treatment at 5 h (78.6%, P=0.0018) or 20 h (64.3%, P=0.0183) have both significantly improved the survival. However, in saline-resuscitated mice, bosentan administered at 20 h has significantly improved the survival (71.4%, P=0.0213) while its administration at 5 h has yielded exactly the same percent of survival (i.e., 21.4%) as observed in control animals. The beneficial effects of bosentan in preventing the tissue injury due to caecal ligation and puncture were also observed histopathologically in liver, spleen and kidney. Therefore, we concluded that the blockade of endothelin receptors by using bosentan during the later (hypodynamic) stages of septic shock is a promising therapeutic manoeuvre.

Leukocyte apoptosis and its significance in sepsis and shock

Sepsis and multiple organ failure continue to be significant problems among trauma, burn, and the critically ill patient population. Thus, a number of laboratories have focused on understanding the role of altered apoptotic cell death in contributing to immune and organ dysfunction seen in sepsis and shock. Immune cells that undergo altered apoptotic changes include neutrophils, macrophages, dendritic cells, as well as various lymphocyte populations. Evidence of epithelial as well as endothelial cell apoptotic changes has also been reported. Although mediators such as steroids, tumor necrosis factor, nitric oxide, C5a, and Fas ligand (FasL) appear to contribute to the apoptotic changes, their effects are tissue- and cell population-selective. As inhibiting Fas-FasL signaling (e.g., gene deficiency, Fas fusion protein, or Fas short interfering RNA administration), caspase inhibition (caspase mimetic peptides), and/or the overexpression of downstream antiapoptotic molecules (e.g., Bcl-2, Akt) improve survival of septic mice, it not only demonstrates the pathological significance of this process but points to novel targets for the treatment of sepsis.

Cecal ligation and puncture versus colon ascendens stent peritonitis: two distinct animal models for polymicrobial sepsis

Colon ascendens stent peritonitis (CASP) and cecal ligation and puncture (CLP), two animal models designed to closely mimic the clinical course of intra-abdominal sepsis, were compared. In the past, immunomodulatory therapies developed in animal studies failed to be successful in humans. As a consequence, the established animal sepsis models were criticized. It has been proposed that present models had to be reevaluated, and new, clinically more relevant models should be evolved. CLP procedure was performed puncturing once (CLP[1]) or twice (CLP[2]) the ligated cecum of C57BL/6 mice. In the CASP model, a stent with defined diameter was surgically inserted into the ascending colon. Survival, bacterial load, immunohistochemistry, and serum cytokine levels were analyzed in the groups. Survival after CASP procedure correlated strongly with the stent diameter, whereas the number of punctures in CLP did not significantly change survival rate. Bacterial loads of peritoneal lavage, liver, and lung, as well as serum cytokine levels (tumor necrosis factor, interleukin 1 beta, interleukin 10) steadily increased from 6 to 24 h after the CASP procedure. In contrast, continuously low amounts of bacteria and cytokines were found in CLP mice at any point of time. Twenty-four hours after CLP surgery, the ligated cecum was covered by adhesive small bowel loops, whereas in CASP mice, the intestinal leakage was then still present. The CASP model mimics closely the clinical course of diffuse peritonitis with early and steadily increasing systemic infection and inflammation (systemic inflammatory response syndrome). In contrast, CLP reveals a model of intra-abdominal abscess formation with sustained and minor signs of systemic inflammation.

CARDIAC TROPONIN I LEVELS ARE A RISK FACTOR FOR MORTALITY AND MULTIPLE ORGAN FAILURE IN NONCARDIAC CRITICALLY ILL PATIENTS AND HAVE AN ADDITIVE EFFECT TO THE APACHE II SCORE IN OUTCOME PREDICTION

Cardiac troponin I (cTnI) is a specific marker of myocardial damage used in the diagnosis of acute coronary syndrome (ACS). Recent studies have shown that cTnI levels can also be elevated in patients without ACS, such as in sepsis and trauma patients, and that this is associated with an adverse prognosis. We have evaluated the clinical implications and prognostic significance of serum cTnI levels in noncardiac critically ill patients in a prospective observational study in a general medical intensive care unit at a tertiary-level hospital. A total of 108 consecutive patients without ACS or other cardiac disease was enrolled. Serum cTnI levels were measured on admission using enzyme-linked immunoabsorbant assay kits. Clinical laboratory parameters and outcome were compared between patients with elevated and normal cTnI levels. The prognostic significance of cTnI levels and the Acute Physiology And Chronic Health Evaluation (APACHE) II score was also analyzed. Forty-nine patients (45%) had elevated cTnI levels and 59 (55%) had normal levels. Compared with patients with normal cTnI levels, patients with elevated levels had a higher incidence of new failure of two or more organs, had a lower left ventricular ejection fraction during admission, were more likely to be associated with bacteremia, and had a higher intensive care unit mortality; they also had a significantly shorter survival over a 180-day follow up, before and after stratification by the APACHE II score. Multiple organ failure was the leading cause of mortality in patients with elevated cTnI levels. By multivariate analysis, elevated cTnI levels, a high APACHE II score, and underlying cancer were the three most important independent predictors for a shorter survival. Combination analysis showed a shorter survival in patients with a high APACHE II score plus elevated cTnI levels than in patients with a high APACHE II score or elevated cTnI levels alone. In conclusion, elevated serum cTnI levels is a risk factor for multiple organ failure and mortality in noncardiac critically ill patients, and the cTnI levels and APACHE II score have an additive effect in outcome prediction.