Lethal Shock Research Articles

PNU-282987 Improves the Hemodynamic Parameters by Alleviating Vasopermeability and Tissue Edema in Dogs Subjected to a Lethal Burns Shock

Excessive inflammation and high vasopermeability can lead to blood volume loss and tissue edema, which can affect the resuscitation and prognosis for serious burn patients. In this experiment, we investigated the effect of PNU-282987, an α7 nicotine cholinergic receptor agonist on the hemodynamic parameters and survival rate by inhibiting vasopermeability and tissue edema during the fluid resuscitation for lethal burn shock. Forty Beagle dogs with intubation of the carotid artery and jugular vein 24 hours before the injury were subjected to 50% TBSA full-thickness burns, and were randomly divided into following four groups: no resuscitation group (group NR), venous fluid resuscitation group (group R), PNU-282987 treatment group (group P), and fluid resuscitation group plus PNU-282987 group (group RP), with 10 dogs in each group. Hemodynamic variables and biochemical parameters were determined with animals in a conscious and cooperative state. The plasma volume and the vasopermeability were determined by indocyanine green and fluorescein isothiocyanate-dextran, respectively. The level of tumor necrosis factor-α and interleukin-1β in plasma, and the water content of different organs were also determined. The mean arterial pressure, cardiac output, and plasma volume of all dogs decreased significantly, and the lung extravascular water index and pulmonary vascular permeability index increased remarkably after burn. The hemodynamic parameters deteriorated continually in group N dogs, and then anuria, hyperlactacidemia, and multiple organ dysfunctions developed. The mean arterial pressure and cardiac output of dogs in group R and group RP returned to preinjury levels at 48 hours postburn. The lung extravascular water index and pulmonary vascular permeability in group R were higher than those before preinjury. The dogs in group RP were found to have a significant increase in plasma volume and urine output, and a remarkable decrease in the levels of tumor necrosis factor-α, interleukin-1α, lactic acid, and organ functions compared with those of group R (P <.05). The survival rate of RP group (100%; 10/10) was significantly higher than that of group N (0; 0/10), group P (20%; 2/10), and group R (60%; 6/10). PNU-282987 combined with intravenous fluid resuscitation significantly improved hemodynamics and the survival rate in the early period after this lethal burn shock. The mechanism may be attributable to the lowering of the level of proinflammatory mediators, amelioration of vasopermeability-induced visceral edema, less of blood volume loss, and protection of vital organs through activation of cholinergic anti-inflammatory pathway.

Preventing rheumatic fever: M-protein based vaccine

Group A beta hemolytic streptococcus (GAS), the organism which initiates rheumatic fever (RF) continues to be sensitive to penicillin. However, penicillin cannot prevent RF if the preceding sore throat is asymptomatic in more than 70 percent children. Prevention of rheumatic fever (RF) may be possible only with the use of a vaccine. Efforts to design a vaccine based on emm gene identification of GAS, M-protein going on for more than 40 years, is unlikely to succeed. M-protein is strain specific. Infection with one strain does not provide immunity from infection with another strain. Based on the emm gene identification, of 250 or more identified strains of GAS, the distribution is heterogenous and keeps changing. The M-protein gene sequence of the organism tends to mutate. A vaccine prepared from available strains may not be effective against a strain following mutation.Lethal toxic shock syndrome due to GAS infection has been described with organisms without identifiable or functional M-protein. M-protein has been excluded as the antigen responsible for acute glomerulonephritis (GN). Therefore M-protein plays no role in one suppurative (toxic shock syndrome) and one non-suppurative (acute GN) manifestation due to GAS infection. Lastly there is no direct evidence to indicate that M-protein is involved in inducing RF. The role of M-protein and the GAS component resulting in the suppurative manifestations of GAS infections like pyoderma, septic arthritis or necrotizing fasciitis etc is unknown. For a vaccine to be effective, an epitope of the streptococcus which is stable and uniformly present in all strains, needs to be identified and tested for its safety and efficacy. The vaccine if and when available is expected to prevent GAS infection. Preventing GAS infection will prevent all the suppurative as well as non-suppurative manifestations including RF.

Bacterial Toxins-Staphylococcal Enterotoxin B.

Staphylococcal enterotoxin B is one of the most potent bacterial superantigens that exerts profound toxic effects upon the immune system, leading to stimulation of cytokine release and inflammation. It is associated with food poisoning, nonmenstrual toxic shock, atopic dermatitis, asthma, and nasal polyps in humans. Currently, there is no treatment or vaccine available. Passive immunotherapy using monoclonal antibodies made in several different species has shown significant inhibition in in vitro studies and reduction in staphylococcal enterotoxin B-induced lethal shock in in vivo studies. This should encourage future endeavors to develop these antibodies as therapeutic reagents.

Diagnostic Value Of Serum Level Of Soluble CD14-Subtype In Febrile Neutropenia In Patients With Hematologic Disorders

Background Febrile neutropenia (FN) is a common and potentially fatal complication that can occur during intensive chemotherapy in patients with hematologic disorders. Identification of the cause of FN is very difficult due to the poor diagnostic performance of blood cultures. Thus, the standard of care for FN has been a fever-driven approach with the use of broad-spectrum antibiotics, likely resulting in over-treatment, poor cost-effectiveness, and induction of drug-resistance in bacteria. A novel diagnostic method is needed to improve these problems. CD14, one of the surface markers in monocytes/macrophages, is a lipopolysaccharide-binding protein complex receptor. Some recent studies reported that a fragment released into the blood—soluble CD14-subtype (sCD14-ST)—is promising as a new diagnostic biomarker of infection, especially sepsis (Endo S, et al. J Infect Chemother. 2012;18:891-7). However, the utility of this test in FN is unknown. Methods We prospectively examined the diagnostic value of serum sCD14-ST in patients with hematological disorders who developed FN after chemotherapy or hematopoietic cell transplantation between November 2010 and February 2012. Neutropenia was defined as a neutrophil count of less than 500/μL or less than 1,000/μL with an expected decline to less than 500/μL. Fever was defined as an axillary temperature ≥ 37.5 °C based on a single measurement. Serum was collected within the first 72 hours after the onset of FN in all episodes. During some episodes, serum was collected as a control at the onset of fever, or before chemotherapy when the subjects were afebrile, in accordance with the protocol. Serum sCD14-ST was measured by the two-step enzyme-linked immunosorbent assay using recombinant sCD14-ST as the standards (Yaegashi Y, et al. J Infect Chemother. 2005;11:234-8). Patients with FN were classified into the following four groups: fever of unknown origin, local infection, bacteremia without hypotension, or septic shock. Results A total of 43 patients were eligible and 75 febrile episodes were evaluable. The median age of the patients (44% were male) was 45 years (range: 16–65). Seventy-five blood samples were collected within 72 hours after onset of fever (31 from 0–24 hours, 34 from 24–48 hours, and 10 from 48–72 hours), 12 while afebrile before chemotherapy, and 25 at the onset of fever. The corresponding serum sCD14-ST measurements were termed sCD14-ST&lt;72hr, sCD14-STcon, and sCD14-STonset, respectively. The underlying diseases included acute leukemia (56%), myelodysplastic syndrome (9%), non-Hodgkin’s lymphoma (16%) and others (19%). The median neutrophil count at study enrollment was 67/μL (range 0 to 962). The types of treatment prior to study entry included 49 (65%) chemotherapies, one (1%) autologous hematopoietic cell transplant, and 18 (24%) allogeneic hematopoietic cell transplants. The mean sCD14-STonset value (790 pg/ml, range: 364–1582, n=25) was significantly higher than that for sCD14-STcon (436 pg/ml, range: 262–846, n=12) [unpaired t-test, P&lt;0.001]. In 12 patients with control data, sCD14-ST&lt;72hr was significantly higher than sCD14-STcon (paired t-test, P&lt;0.001). In 25 patients with onset data, sCD14-ST&lt;72hr was significantly higher than sCD14-STonset (paired t-test, P&lt;0.047). The median sCD14-ST&lt;72hrwith fever of unknown origin (n=31), local infection (n=27), bacteremia without hypotension (n=9), septic shock (n=5) and others (n=3) was 680 (314–1986) pg/ml, 763 (348–2615), 782 (482–1550), 1359 (493–2115), and 738 (387–1402), respectively. Conclusion Serum levels of sCD14-ST may be a sensitive indicator of the development of FN. Within 72 hours of the onset of FN, serum levels of sCD14-ST appeared to increase. In addition, sCD14-ST might be a useful marker in detecting potentially lethal septic shock. Further prospective research in a large cohort is warranted to determine not only the diagnostic performance of this test but also its clinical utility as a tool for guiding antibiotic use, including the administration, timing and completion of these drugs in FN. Disclosures: Nakamae: Mochida Pharmaceutical Co., LTD.: Research Funding.

Discovery of Small Molecule RIP1 Kinase Inhibitors for the Treatment of Pathologies Associated with Necroptosis.

Potent inhibitors of RIP1 kinase from three distinct series, 1-aminoisoquinolines, pyrrolo[2,3-b]pyridines, and furo[2,3-d]pyrimidines, all of the type II class recognizing a DLG-out inactive conformation, were identified from screening of our in-house kinase focused sets. An exemplar from the furo[2,3-d]pyrimidine series showed a dose proportional response in protection from hypothermia in a mouse model of TNFα induced lethal shock.

Staphylococcal and Streptococcal Superantigens: Basic Biology of Conserved Protein Toxins

Staphylococcus aureus and Streptococcus pyogenes are gram-positive bacteria that possess great pathogenic potential in humans, causing numerous maladies such as arthritis, cutaneous infections, endocarditis, enterocolitis, food poisoning, pharyngitis, pneumonia, rheumatic fever, surgical site infections, and toxic shock. These prevalent pathogens produce various virulence factors that include the staphylococcal enterotoxins (SEs), toxic shock syndrome toxin-1 (TSST-1), and streptococcal pyrogenic exotoxins (SPEs). Minute (picomolar) amounts of these structurally-similar superantigens (SAgs) elicit high levels of proinflammatory cytokines and chemokines that can induce fever, hypotension, and lethal shock. In vitro and in vivo models have provided important tools for studying the biological effects of, and potential vaccines plus therapeutics against, these related protein toxins. This review will delve into the known physical and biological properties of the SEs, TSST-1, and SPEs. The reader will hopefully derive a general appreciation of these wonderfully-complex, structurally-similar toxins produced by S. aureus and S. pyogenes.

Valproic acid for the treatment of hemorrhagic shock: a dose-optimization study

BackgroundValproic acid (VPA) has been shown to improve survival in animal models of hemorrhagic shock at a dose of 300 mg/kg. Our aim was to identify the ideal dose through dose-escalation, split-dosing, and dose de-escalation regimens. Materials and methodsRats were subjected to sublethal 40% hemorrhage and treated with vehicle or VPA (dose of 300, 400, or 450 mg/kg) after 30 min of shock. Acetylated histones and activated proteins from the PI3K–Akt–GSK-3β survival pathway at different time points were quantified by Western blot analysis. In a similar model, a VPA dose of 200 mg/kg followed 2 h later by another dose of 100 mg/kg was administered. Finally, animals were subjected to a lethal 50% hemorrhage and VPA was administered in a dose de-escalation manner (starting at dose of 300 mg/kg) until a significant drop in percent survival was observed. ResultsLarger doses of VPA resulted in greater acetylation of histone 3 and increased activation of PI3K pathway proteins. Dose-dependent differences were significant in histone acetylation but not in the activation of the survival pathway proteins. Split-dose administration of VPA resulted in similar results to a single full dose. Survival was as follows: 87.5% with 300 and 250 mg/kg of VPA, 50% with 200 mg/kg of VPA, and 14% with vehicle-treated animals. ConclusionsAlthough higher doses of VPA result in greater histone acetylation and activation of prosurvival protein signaling, doses as low as 250 mg/kg of VPA confer the same survival advantage in lethal hemorrhagic shock. Also, VPA can be given in a split-dose fashion without a reduction in its cytoprotective effectiveness.

Induction of thermotolerance through heat acclimation in lablab bean (Dolichos lablab)

The acclimation of plants to moderately high temperature plays an important role in inducing plant tolerance to subsequent lethal temperatures. This study was performed to investigate the effects of heat acclimation and sudden heat stress on the antioxidant and metabolic profile of lablab bean (Dolichos lablab). Following separate pretreatments with heat acclimation (35°C) and NaCl (100 mM), seedlings of lablab bean were exposed to heat stress at 45°C for 5 h and then recovered at 25°C for five days. Pre-treated seedlings performed better under heat stress than the control and it could be associated with the observed increased levels of sugars, proline, glutathione and ascorbate; and increased activities of Peroxidase (POX), glutathione reductase (GR) and ascorbate peroxidase (APX) than just heat shocked seedlings. Seedling growth was dramatically reduced under heat stress but heat acclimation and NaCl pre-treatment were effective in imparting thermoprotection against the lethal heat shock. Key words: Acclimation, antioxidants, catalase, Dolichos lablab, glutathione reductase, heat stress, peroxidase, proline, sugar.

Pyruvate Ringer's Solution Corrects Lactic Acidosis and Prolongs Survival during Hemorrhagic Shock in Rats

BackgroundLactic acidosis is a life-threatening complication of hemorrhagic shock. There is no ideal therapy for it in the clinical setting. ObjectiveThis study was designed to investigate whether pyruvate Ringer's solution could treat hypoxic lactic acidosis associated with lethal hemorrhagic shock in rats. MethodsA total of 54 rats were subjected to hemorrhagic shock with mean arterial pressure (MAP) of 40 mm Hg for 1 h. They were then randomly divided into three groups (n = 18 each): Group N had no fluid resuscitation; Group L received lactated Ringer's solution infusion; and Group P received pyruvate Ringer's solution infusion. The survival rate was investigated after 24 h. In addition, a second set of 54 rats was selected for blood sampling, with identical methods for shock and resuscitation being followed, to determine arterial pH, blood gas analysis, lactate, pyruvate, and organs' enzyme activities at various time points. The MAP was monitored for 6 h in both populations. ResultsPyruvate Ringer's solution significantly increased the survival rate of rats subjected to fatal shock and receiving pyruvate Ringer's solution (Group P) by 1.5 times the survival rate in Group L at 24 h after fluid resuscitation (55.6% vs. 22.2%, respectively; p < 0.05). Pyruvate infusion maintained a higher MAP and fully corrected severe acidosis 1 h after resuscitation in comparison to the lactated infusion, and markedly decreased blood lactate levels and the lactate-to-pyruvate ratio 4 h after resuscitation. It also significantly improved serum markers of organ dysfunction. ConclusionPyruvate Ringer's solution efficiently treated hypoxic lactic acidosis and significantly increased the survival rate in rats with lethal hemorrhagic shock. Pyruvate Ringer's solution is potentially applicable to clinical resuscitation in humans.

TLR stimulation initiates a CD39-based autoregulatory mechanism that limits macrophage inflammatory responses

AbstractSepsis is a highly fatal disease caused by an initial hyperinflammatory response followed by a state of profound immunosuppression. Although it is well appreciated that the initial production of proinflammatory cytokines by macrophages accompanies the onset of sepsis, it remains unclear what causes the transition to an immunosuppressive state. In this study, we reveal that macrophages themselves are key regulators of this transition and that the surface enzyme CD39 plays a critical role in self-limiting the activation process. We demonstrate that Toll-like receptor (TLR)-stimulated macrophages modulate their activation state by increasing the synthesis and secretion of adenosine triphosphate (ATP). This endogenous ATP is paradoxically immunosuppressive due to its rapid catabolism into adenosine by CD39. Macrophages lacking CD39 are unable to transition to a regulatory state and consequently continue to produce inflammatory cytokines. The importance of this transition is demonstrated in a mouse model of sepsis, where small numbers of CD39-deficient macrophages were sufficient to induce lethal endotoxic shock. Thus, these data implicate CD39 as a key “molecular switch” that allows macrophages to self-limit their activation state. We propose that therapeutics targeting the release and hydrolysis of ATP by macrophages may represent new ways to treat inflammatory diseases.

CD28: Direct and Critical Receptor for Superantigen Toxins

Every adaptive immune response requires costimulation through the B7/CD28 axis, with CD28 on T-cells functioning as principal costimulatory receptor. Staphylococcal and streptococcal superantigen toxins hyperstimulate the T-cell-mediated immune response by orders of magnitude, inducing a lethal cytokine storm. We show that to elicit an inflammatory cytokine storm and lethality, superantigens must bind directly to CD28. Blocking access of the superantigen to its CD28 receptor with peptides mimicking the contact domains in either toxin or CD28 suffices to protect mice effectively from lethal shock. Our finding that CD28 is a direct receptor of superantigen toxins broadens the scope of microbial pathogen recognition mechanisms.

Efficacy of Two FDA-Approved Drug Combination in a Mouse Model of Staphylococcal Enterotoxin B-Induced Shock

Staphylococcal enterotoxin B (SEB) causes lethal shock by potently stimulating the host immune response. Dexamethasone and N-acetyl cysteine (NAC) are anti-inflammatory and antioxidative drugs, respectively, which can independently modulate immune function. Dexamethasone was previously shown to be effective in preventing SEB-induced shock models only if administered early and in multiple doses for a long duration. In this study, dexamethasone and NAC were used in tandem and protected mice (75%) against SEB-induced lethal shock. Hypothermia and weight loss elicited by SEB were also diminished by this novel combination treatment. The levels of monocyte chemoattractant protein-1, interleukin-2, interleukin-6, and mouse gamma interferon in lung tissue after intranasal exposure to SEB were also significantly reduced in mice given a combination of dexamethasone and NAC versus controls.

The Soluble Guanylate Cyclase Activator BAY 58-2667 Protects against Morbidity and Mortality in Endotoxic Shock by Recoupling Organ Systems

Sepsis and septic shock are associated with high mortality rates and the majority of sepsis patients die due to complications of multiple organ failure (MOF). The cyclic GMP (cGMP) producing enzyme soluble guanylate cyclase (sGC) is crucially involved in the regulation of (micro)vascular homeostasis, cardiac function and, consequently, organ function. However, it can become inactivated when exposed to reactive oxygen species (ROS). The resulting heme-free sGC can be reactivated by the heme- and nitric oxide (NO)-independent sGC activator BAY 58-2667 (Cinaciguat). We report that late (+8 h) post-treatment with BAY 58-2667 in a mouse model can protect against lethal endotoxic shock. Protection was associated with reduced hypothermia, circulating IL-6 levels, cardiomyocyte apoptosis, and mortality. In contrast to BAY 58-2667, the sGC stimulator BAY 41-2272 and the phosphodiesterase 5 inhibitor Sildenafil did not have any beneficial effect on survival, emphasizing the importance of the selectivity of BAY 58-2667 for diseased vessels and tissues. Hemodynamic parameters (blood pressure and heart rate) were decreased, and linear and nonlinear indices of blood pressure variability, reflective for (un)coupling of the communication between the autonomic nervous system and the heart, were improved after late protective treatment with BAY 58-2667. In conclusion, our results demonstrate the pivotal role of the NO/sGC axis in endotoxic shock. Stabilization of sGC function with BAY 58-2667 can prevent mortality when given in the correct treatment window, which probably depends on the dynamics of the heme-free sGC pool, in turn influenced by oxidative stress. We speculate that, considering the central role of sGC signaling in many pathways required for maintenance of (micro)circulatory homeostasis, BAY 58-2667 supports organ function by recoupling inter-organ communication pathways.

51: Toll-like receptor stimulated macrophages intrinsically control inflammatory cytokine production via CD39-based mechanism

Sepsis is a highly fatal disease caused by an initial hyper-inflammatory response followed by a state of profound immunosuppression. Moreover, a coinciding switch in macrophage activation states has been observed in septic individuals over time. While, it is well-understood that the initial production of pro-inflammatory cytokines by macrophages accompanies the onset of sepsis, it remains unclear what drives the development of anti-inflammatory cytokines and the transition to an immunosuppressive state in macrophages. In this study, we demonstrate that macrophages themselves are key regulators of this transition, and that the surface enzyme CD39 plays a critical role in self-limiting the activation process. Here, we reveal that toll-like receptor (TLR)-stimulated macrophages modulate their activation state by increasing the synthesis and secretion of adenosine triphosphate (ATP). We further demonstrate that macrophage-derived ATP is paradoxically immunosuppressive due to its rapid catabolism into adenosine by CD39. Macrophages lacking CD39 are unable to transition to a regulatory state and consequently continue to produce inflammatory cytokines. The importance of this transition was demonstrated in a mouse model of sepsis, where the presence of CD39-deficient macrophages was sufficient to induce lethal endotoxic shock. Thus, these data implicate CD39 as a key molecular switch that allows macrophages to intrinsically regulate their activation state. We propose that therapeutics targeting the release and hydrolysis of ATP by macrophages may represent new ways to treat inflammatory diseases.

The soluble guanylate cyclase activator BAY 58-2667 protects against morbidity and mortality in endotoxic shock by recoupling organ systems

Sepsis and septic shock are associated with high mortality rates and the majority of sepsis patients die due to complications of multiple organ failure (MOF). The cyclic GMP (cGMP) producing enzyme soluble guanylate cyclase (sGC) is crucially involved in the regulation of (micro)vascular homeostasis, cardiac function and, consequently, organ function. However, it can become inactivated when exposed to reactive oxygen species (ROS). The resulting heme-free sGC can be reactivated by the heme- and nitric oxide (NO)-independent sGC activator BAY 58-2667 (Cinaciguat). We report that late (+8 h) posttreatment with BAY 58-2667 in a mouse model can protect against lethal endotoxic shock. Protection was associated with reduced hypothermia, circulating IL-6 levels, cardiomyocyte apoptosis, and mortality. In contrast to BAY 58-2667, the sGC stimulator BAY 41-2272 and the phosphodiesterase 5 inhibitor Sildenafil did not have any beneficial effect on survival, emphasizing the importance of the selectivity of BAY 58-2667 for diseased vessels and tissues. Hemodynamic parameters (blood pressure and heart rate) were decreased, and linear and nonlinear indices of blood pressure variability, reflective for (un)coupling of the communication between the autonomic nervous system and the heart, were improved after late protective treatment with BAY 58-2667. In conclusion, our results demonstrate the pivotal role of the NO/sGC axis in endotoxic shock. Stabilization of sGC function with BAY 58-2667 can prevent mortality when given in the correct treatment window, which probably depends on the dynamics of the heme-free sGC pool, in turn influenced by oxidative stress. We speculate that, considering the central role of sGC signaling in many pathways required for maintenance of (micro)circulatory homeostasis, BAY 58-2667 supports organ function by recoupling inter-organ communication pathways.

Looped Host Defense Peptide CLP-19 Binds to Microtubules and Inhibits Surface Expression of TLR4 on Mouse Macrophages

The looped host defense peptide CLP-19 is derived from a highly functional core region of the Limulus anti-LPS factor and exerts robust anti-LPS activity by directly interacting with LPS in the extracellular space. We previously showed that prophylactic administration of CLP-19 even 20 h prior to LPS challenge might significantly increase the survival rate in a lethal endotoxin shock mouse model. Such an effect may be associated with immune regulation of CLP-19. To investigate the underlying mechanisms, peptide affinity chromatography, immunofluorescence, and Western blotting procedures were used to identify α- and β-tubulin as direct and specific binding partners of CLP-19 in the mouse macrophage cell line RAW 264.7. Bioinformatic analysis using the AutoDock Vina molecular docking and PyMOL molecular graphics system predicted that CLP-19 would bind to the functional residues of both α- and β-tubulin and would be located within the groove of microtubules. Tubulin polymerization assay revealed that CLP-19 might induce polymerization of microtubules and prevent depolymerization. The immunoregulatory effect of CLP-19 involving microtubules was investigated by flow cytometry, immunofluorescence, and Western blotting, which showed that CLP-19 prophylactic treatment of RAW 264.7 cells significantly inhibited LPS-induced surface expression of TLR4. Taken together, these results suggest that CLP-19 binding to microtubules disrupts the dynamic equilibrium of microtubules, reducing the efficacy of microtubule-dependent vesicular transport that would otherwise translocate TLR4 from the endoplasmic reticulum to the cell surface.

A comparison of epinephrine and arginine vasopressin on the respiratory system response in a rat model of lethal anaphylactic shock

A comparison of epinephrine and arginine vasopressin on the respiratory system response in a rat model of lethal anaphylactic shock

P12 Clarithromycin expands CD11b+Gr–1+ cells to protect against LPS-induced lethal shock and polymicrobial sepsis

P12 Clarithromycin expands CD11b+Gr–1+ cells to protect against LPS-induced lethal shock and polymicrobial sepsis

Epigenetics in sepsis: targeting histone deacetylases

Severe sepsis and septic shock are lethal complications of infection, characterised by dysregulated inflammatory and immune responses. Our understanding of the pathogenesis of sepsis has improved markedly in recent years, but unfortunately has not been translated into efficient treatment strategies. Epigenetic mechanisms such as covalent modification of histones by acetylation are master regulators of gene expression under physiological and pathological conditions, and strongly impact on inflammatory and host defence responses. Histone acetylation is controlled by histone acetyltransferases and histone deacetylases (HDACs), which affect gene expression also by targeting non-histone transcriptional regulators. Numerous HDAC inhibitors (HDACi) are being tested in clinical trials, primarily for the treatment of cancer. We performed the first comprehensive study of the impact of HDACi on innate immune responses in vitro and in vivo. We showed that HDACi act essentially as negative regulators of the expression of critical immune receptors and antimicrobial pathways in innate immune cells. In agreement, HDACi impaired phagocytosis and killing of bacteria by macrophages, and increased susceptibility to non-severe bacterial and fungal infections. Strikingly, proof-of-principle studies demonstrated that HDACi protect from lethal toxic shock and septic shock. Overall, our observations argue for a close monitoring of the immunological and infection status of patients treated with HDACi, especially immunocompromised cancer patients. They also support the concept of pharmacological inhibitors of HDACs as promising drugs to treat inflammatory diseases, including sepsis.

Pre-treatment with low-dose endotoxin prolongs survival from experimental lethal endotoxic shock: Benefit for lethal peritonitis by Escherichia coli

Although LPS tolerance is well-characterized, it remains unknown if it is achieved even with single doses of lipopolysaccharide (LPS) and if it offers protection against lethal bacterial infections. To this end, C57B6 mice were assigned to groups A (sham); B (saline i.p followed after 24h by i.p 30mg/kg LPS); and C (3mg/kg LPS i.p followed after 24h by i.p 30mg/kg LPS). Survival was monitored and animals were sacrificed early after lethal challenge for measurement of tumour necrosis factor-alpha (TNFα) in serum; isolation of splenocytes and cytokine stimulation; and flow-cytometry for apoptosis and TREM-1. Experiments were repeated with mice infected i.p by Escherichia coli after challenging with saline or LPS. Mortality of group B was 72.2% compared with 38.9% of group C (p: 0.020). Serum TNFα of group C was lower than group B. Expression of TREM-1 of group C on monocytes/neutrophils was greater than group B. Release of TNFα, of IFNγ and of IL-17 from splenocytes of group C was lower than group B and the opposite happened for IL-10 showing evidence of cellular reprogramming. In parallel, apoptosis of circulating lymphocytes and of splenocytes of group C was greater compared with group B. Pre-treatment of mice challenged by E. coli with low dose LPS led to 0% mortality compared with 90% of saline pre-treated mice; in these mice, splenocytes improved over-time their capacity for release of IFNγ. It is concluded that single low doses of LPS lead to early reprogramming of the innate immune response and prolong survival after lethal E. coli challenge.