Current trends in inflammatory and immunomodulatory mediators in sepsis

Hepatic PPARα is critical in the metabolic adaptation to sepsis

BACKGROUND & AIMS

Although the role of inflammation to combat infection is known, the contribution of metabolic changes in response to sepsis is poorly understood. Sepsis induces the release of lipid mediators, many of which activate nuclear receptors such as the peroxisome proliferator-activated receptor (PPAR)α, which controls both lipid metabolism and inflammation. We aimed to elucidate the previously unknown role of hepatic PPARα in the response to sepsis.

METHODS

Sepsis was induced by intraperitoneal injection of Escherichia coli in different models of cell-specific Ppara-deficiency and their controls. The systemic and hepatic metabolic response was analyzed using biochemical, transcriptomic and functional assays. PPARα expression was analyzed in livers from elective surgery and critically ill patients and correlated with hepatic gene expression and blood parameters.

RESULTS

Both whole body and non-hematopoietic Ppara-deficiency in mice decreased survival upon bacterial infection. Livers of septic Ppara-deficient mice displayed an impaired metabolic shift from glucose to lipid utilization resulting in more severe hypoglycemia, impaired induction of hyperketonemia and increased steatosis due to lower expression of genes involved in fatty acid catabolism and ketogenesis. Hepatocyte-specific deletion of PPARα impaired the metabolic response to sepsis and was sufficient to decrease survival upon bacterial infection. Hepatic PPARA expression was lower in critically ill patients and correlated positively with expression of lipid metabolism genes, but not with systemic inflammatory markers.

CONCLUSION

During sepsis, Ppara-deficiency in hepatocytes is deleterious as it impairs the adaptive metabolic shift from glucose to FA utilization. Metabolic control by PPARα in hepatocytes plays a key role in the host defense against infection.

LAY SUMMARY

As the main cause of death in critically ill patients, sepsis remains a major health issue lacking efficacious therapies. While current clinical literature suggests an important role for inflammation, metabolic aspects of sepsis have mostly been overlooked. Here, we show that mice with an impaired metabolic response, due to deficiency of the nuclear receptor PPARα in the liver, exhibit enhanced mortality upon bacterial infection despite a similar inflammatory response, suggesting that metabolic interventions may be a viable strategy for improving sepsis outcomes.

Neutrophil Activation During Septic Shock

In addition to their well-known role as the cellular mediators of immunity, key other roles have been identified for neutrophils during septic shock. Importantly, neutrophils indeed play a critical role in the recently described immunothrombosis concept and in septic shock-induced coagulopathy. Septic shock is one of the most severe forms of infection, characterized by an inadequate host response to the pathogenic organism. This host response involves numerous defense mechanisms with an intense cellular activation, including neutrophil activation. Neutrophils are key cells of innate immunity through complex interactions with vascular cells and their activation may participate in systemic tissue damages. Their activation also leads to the emission of neutrophil extracellular traps, which take part in both pathogen circumscription and phagocytosis, but also in coagulation activation. Neutrophils thus stand at the interface between hemostasis and immunity, called immunothrombosis.The present review will develop a cellular approach of septic shock pathophysiology focusing on neutrophils as key players of septic shock-induced vascular cell dysfunction and of the host response, associating immunity and hemostasis. We will therefore first develop the role of neutrophils in the interplay between innate and adaptive immunity, and will then highlight recent advances in our understanding of immunothrombosis septic shock-induced coagulopathy.

Sodium tanshinone IIA sulfonate attenuates cardiac dysfunction and improves survival of rats with cecal ligation and puncture-induced sepsis

Cardiac dysfunction, a common consequence of sepsis, is the major contribution to morbidity and mortality in patients. Sodium tanshinone IIA sulfonate (STS) is a water-soluble derivative of Tanshinone IIA (TA), a main active component of Salvia miltiorrhiza Bunge, which has been widely used in China for the treatment of cardiovascular and cerebral system diseases. In the present study, the effect of STS on sepsis-induced cardiac dysfunction was investigated and its effect on survival rate of rats with sepsis was also evaluated. STS treatment could significantly decrease the serum levels of C-reactive protein (CRP), procalcitonin (PCT), cardiac troponin I (cTn-I), cardiac troponin T (cTn-T), and brain natriuretic peptide (BNP) in cecal ligation and puncture (CLP)-induced) septic rats and improve left ventricular function, particularly at 48 and 72 h after CLP. As the pathogenesis of septic myocardial dysfunction is attributable to dysregulated systemic inflammatory responses, several key cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10) and high mobility group protein B1 (HMGB1), were detected to reveal the possible mechanism of attenuation of septic myocardial dysfunction after being treated by STS. Our study showed that STS, especially at a high dose (15 mg·kg^-1), could efficiently suppress inflammatory responses in myocardium and reduce myocardial necrosis through markedly reducing production of myocardial TNF-α, IL-6 and HMGB1. STS significantly improved the 18-day survival rate of rats with sepsis from 0% to 30% (P < 0.05). Therefore, STS could suppress inflammatory responses and improve left ventricular function in rats with sepsis, suggesting that it may be developed for the treatment of sepsis.

Chestnut Shell Extract Modulates Immune Parameters in the Rainbow Trout Oncorhynchus mykiss

In this study, chestnut (Castanea sativa) shell was extracted with different solvents, and immunomodulatory activity was investigated in an in vitro model system using blood and intestinal leukocytes of Oncorhynchus mykiss. Gallic acid (GA) was used as a standard. Chestnut shell extract (CSE) and GA readily entered both blood and intestinal leukocytes. Superoxide anion production and phagocytosis were decreased by low doses of CSE and increased with high doses. CSE and GA differently regulated cytokine expression in blood and intestinal leukocytes. High doses of CSE upregulated IL-1β, TNF-α, and IL-10 in intestinal leukocytes and IL-10 in blood leukocytes. Low doses of CSE upregulated IL-1β and TNF-α in blood leukocytes. GA appeared to be effective only in blood leukocytes. The effects of CSE on pro- and anti-inflammatory cytokines seemed to suggest an alert effect of the immune defense system against a possible infectious agent. The less evident effect of GA in comparison to CSE could have been attributable to the synergistic and/or additive effects of polyphenols in the latter. The immune-stimulating activity of CSE reported here could be useful for future practical applications in fish health.

Dexmedetomidine inhibits astrocyte pyroptosis and subsequently protects the brain in in vitro and in vivo models of sepsis

Sepsis is life-threatening and often leads to acute brain damage. Dexmedetomidine, an α₂-adrenoceptor agonist, has been reported to possess neuroprotective effects against various brain injury but underlying mechanisms remain elusive. In this study, in vitro and in vivo models of sepsis were used to explore the effects of dexmedetomidine on the inflammasome activity and its associated glia pyroptosis and neuronal death. In vitro, inflammasome activation and pyroptosis were found in astrocytes following lipopolysaccharide (LPS) exposure. Dexmedetomidine significantly alleviated astrocyte pyroptosis and inhibited histone release induced by LPS. In vivo, LPS treatment in rats promoted caspase-1 immunoreactivity in astrocytes and caused an increase in the release of pro-inflammatory cytokines of IL-1β and IL-18, resulting in neuronal injury, which was attenuated by dexmedetomidine; this neuroprotective effect was abolished by α₂-adrenoceptor antagonist atipamezole. Dexmedetomidine significantly reduced the high mortality rate caused by LPS challenge. Our data demonstrated that dexmedetomidine may protect glia cells via reducing pyroptosis and subsequently protect neurons, all of which may preserve brain function and ultimately improve the outcome in sepsis.

Streptococcal toxic shock syndrome caused by β-hemolytic streptococci: Clinical features and cytokine and chemokine analyses of 15 cases

OBJECTIVES

β-Hemolytic streptococci occasionally cause severe infections such as necrotizing fasciitis and streptococcal toxic shock syndrome (STSS). Here, we conducted a prospective study to investigate the production of cytokines and chemokines in patients with STSS to explore its pathogenesis in survivors and fatal cases.

METHODS

From January 2013 through August 2015, all culture results from normally sterile sites were prospectively followed and screened for STSS. Clinical characteristics of the patients with STSS were evaluated and compared between survivors and fatal cases. Serum samples were collected on admission for quantification of various cytokines and chemokines. Bacterial strains were categorized by Lancefield grouping and analyzed for the emm type, and presence of speA, speB, speC, and speF.

RESULTS

Fifteen patients received diagnosis of STSS. The median age of the patients was 60-year-old, and the mortality rate was 40% despite intensive treatment. Nine strains were categorized as group A, two belonged to group G, and four to group B. Group A contained various emm genotypes. Unexpectedly, potent proinflammatory cytokine levels such as TNF-α and IL-1β were not significantly elevated, and comparison with surviving patients showed that IL-6, IL-8, and MCP-1 levels were significantly decreased and creatine kinase level was significantly elevated in fatally ill cases.

CONCLUSION

Our results indicate that reduced production of proinflammatory cytokines and chemokines may be involved in STSS pathogenesis and critical for prognosis of patients with STSS.

Integrating molecular pathogenesis and clinical translation in sepsis-induced acute respiratory distress syndrome

Sepsis-induced acute respiratory distress syndrome (ARDS) has high morbidity and mortality and arises after lung infection or infection at extrapulmonary sites. An aberrant host response to infection leads to disruption of the pulmonary alveolar-capillary barrier, resulting in lung injury characterized by hypoxemia, inflammation, and noncardiogenic pulmonary edema. Despite increased understanding of the molecular biology underlying sepsis-induced ARDS, there are no targeted pharmacologic therapies for this devastating condition. Here, we review the molecular underpinnings of sepsis-induced ARDS with a focus on relevant clinical and translational studies that point toward novel therapeutic strategies.

Resolvin D1 Promotes SIRT1 Expression to Counteract the Activation of STAT3 and NF-κB in Mice with Septic-Associated Lung Injury

Resolvin D1 (RvD1) is a novel endogenous docosahexaenoic acid (DHA)-derived lipid mediators, which possesses a dual role of anti-inflammation and promotes inflammation resolution. The aim of the present study was to assess the effects of RvD1 on cecal ligation and puncture (CLP) model of sepsis and explore the underlying mechanism. Six-to-eight-week-old male C57BL/6 mice were randomly divided into following three groups: sham-operated group (SO), CLP model group (CLP), and CLP+RvD1 group (RvD1). The SO group underwent the sham operation. The RvD1 groups were administered RvD1 (10-ng/g body weight) by penile vein injection, but the CLP groups were administered the same volume of vehicle (PBS) after CLP. We assessed the survival benefit of RvD1 in CLP-induced septic mice for 7 days. After 24 h, mice were sacrificed, bronchoalveolar lavage fluids (BALF) was collected for proinflammatory cytokines assay, and albumin assay and the lung tissues were harvested for histologic analysis, myeloperoxidase (MPO) activity and the expression of Sirtuin 1 (SIRT1), signal transducers, and activators of transcription 3 (STAT3), nuclear factor-κB (NF-κB), and mitogen-activated protein kinases (MAPKs). RvD1 treatment increased the survival time in mice with sepsis induced by CLP, reducing the MPO activity and albumin level at 24 h. The levels of inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6) in BALF were significantly decreased by RvD1. RvD1 promoted SIRT1 expression and suppressed the activation of NF-κB, STAT3, ERK, and p38 in lung tissues of septic mice. These results suggest that RvD1 may improve survival and attenuate the degree of lung inflammation reaction in mice with CLP by suppressing STAT3, NF-κB, ERK, and p38 expressions through a mechanism partly dependent on SIRT1.

Metabolomics analysis of gut barrier dysfunction in a trauma-hemorrhagic shock rat model

Intestinal barrier dysfunction has been implicated in the development of multiorgan dysfunction syndrome caused by the trauma-hemorrhagic shock (THS). However, the mechanisms underlying THS-induced gut barrier injury are still poorly understood. In the present study, we used the metabolomics analysis to test the hypothesis that altered metabolites might be related to the development of THS-induced barrier dysfunction in the large intestine. Under the induction of THS, gut barrier failure was characterized by injury of permeability and mucus layer, which were companied by the decreased expression of zonula occludens-1 in the colon and increased levels of inflammatory factors including tumor necrosis factor-α, interferon-γ, interleukin (IL)-6, and IL-1β in the serum. A total of 16 differential metabolites were identified in colonic tissues from THS-treated rats compared with control rats. These altered metabolites included dihydroxy acetone phosphate, ribose-5-phosphate, fructose, glyceric acid, succinic acid, and adenosine, which are critical intermediates or end products that are involved in pentose phosphate pathway, glycolysis, and tricarboxylic acid cycle as well as mitochondrial adenosine triphosphate biosynthesis. These findings may offer important insight into the metabolic alterations in THS-treated gut injury, which will be helpful for developing effective metabolites-based strategies to prevent THS-induced gut barrier dysfunction.

Orexins as Novel Therapeutic Targets in Inflammatory and Neurodegenerative Diseases

Orexins [orexin-A (OXA) and orexin-B (OXB)] are two isoforms of neuropeptides produced by the hypothalamus. The main biological actions of orexins, focused on the central nervous system, are to control the sleep/wake process, appetite and feeding, energy homeostasis, drug addiction, and cognitive processes. These effects are mediated by two G protein-coupled receptor (GPCR) subtypes named OX1R and OX2R. In accordance with the synergic and dynamic relationship between the nervous and immune systems, orexins also have neuroprotective and immuno-regulatory (i.e., anti-inflammatory) properties. The present review gathers recent data demonstrating that orexins may have a therapeutic potential in several pathologies with an immune component including multiple sclerosis, Alzheimer's disease, narcolepsy, obesity, intestinal bowel diseases, septic shock, and cancers.

KPT-330, a potent and selective CRM1 inhibitor, exhibits anti-inflammation effects and protection against sepsis

Sepsis, a systemic inflammatory response caused by infection or injury, is still one of the most important causes of death in clinical patients. The ongoing search for the pathogenesis of sepsis and novel therapeutic methods are highly urgent. In this study, we hypothesized that KPT330, a potent and specific small molecule inhibitor of CRM1, could reduce inflammation and attenuate the severity of sepsis. In LPS-induced sepsis model in vivo, administration of KPT330 increased survival rate and ameliorated LPS-induced lung injury, with suppressed levels of TNF-α, IL-6 and HMGB1 in the circulation and decreased macrophage and PMN subpopulations in peritoneal cavity. In vitro investigations showed that KPT330 dose-dependently inhibited LPS-triggered proinflammatory cytokines production including TNF-α, IL-6 and HMGB1 in macrophages. Furthermore, KPT330 treatment significantly suppressed TNF-α and IL-6 mRNA expression and inhibited HMGB1 necleocytoplasmic translocation by inhibiting CRM1 distribution. Moreover, the mechanism analysis demonstrated that KPT330 exerted anti-inflammation effects by inhibiting the production of pro-inflammatory cytokines through suppressing activation of NF-κB and p38 signaling. Thus, pharmacologic stimulation of KPT330 may present a promising therapeutic strategy for sepsis.

Deficiency of receptor-interacting protein kinase 3 (RIPK3) attenuates inflammation and organ injury in neonatal sepsis

INTRODUCTION

Sepsis is the third leading cause of morbidity and mortality in neonates. Sepsis in neonates is characterized as the systemic inflammation owing to infection within the first 28days after birth. The molecular mechanism causing the exaggerated inflammation phenotype in neonates has not been completely elucidated. Receptor interacting protein kinase 3 (RIPK3) is a protein identified as a mediator in programmed necrosis or necroptosis. We hypothesize that RIPK3 could be responsible for the inflammatory response in neonates and that deficiency in the RIPK3 protein attenuates inflammation and organ injury in neonatal sepsis.

METHODS

Male and female C57BL6 wild-type (WT) and RIPK3 knock-out (KO) newborn mice aged 5-7days (3-4g body weight) were injected intraperitoneally with 0.9mg/g cecal slurry (CS). At 10h after injection, the newborns were euthanized and blood, the lungs and gut tissues were collected.

RESULTS

At 10h after CS injection, serum cytokines IL-6 and IL-1β in the WT mice were increased by 511- and 43-fold whereas in KO mice, these levels were increased by 166-fold and 22-fold, respectively. Lung IL-1β in the WT mice increased by 7-fold after CS injection whereas only a 4-fold increase was seen in the KO mice. In the lungs of CS injected KO mice, the injury score, MIP-2 mRNA, myeloperoxidase (MPO) activity and TUNEL staining were significantly reduced by 76%, 70%, 26% and 74%, respectively compared to the CS WT mice. Gut TUNEL staining was also reduced by 80%.

CONCLUSION

The deficiency in RIPK3 attenuated serum and lung cytokines, lung injury and neutrophil infiltration and lung and gut apoptosis. These data suggest that RIPK3, in part, is responsible for the systemic inflammatory response in neonatal sepsis.

Targeting junctional adhesion molecule-C ameliorates sepsis-induced acute lung injury by decreasing CXCR4+ aged neutrophils

Sepsis is a severe inflammatory condition associated with high mortality. Transmigration of neutrophils into tissues increases their lifespan to promote deleterious function. Junctional adhesion molecule-C (JAM-C) plays a pivotal role in neutrophil transmigration into tissues. We aim to study the role of JAM-C on the aging of neutrophils to cause sepsis-induced acute lung injury (ALI). Sepsis was induced in C57BL/6J mice by cecal ligation and puncture (CLP) and JAM-C expression in serum was assessed. Bone marrow-derived neutrophils (BMDN) were treated with recombinant mouse JAM-C (rmJAM-C) ex vivo and their viability was assessed. CLP-operated animals were administrated with either isotype IgG or anti-JAM-C Ab at a concentration of 3 mg/kg and after 20 h, aged neutrophils (CXCR4⁺ ) were assessed in blood and lungs and correlated with systemic injury and inflammatory markers. Soluble JAM-C level in serum was up-regulated during sepsis. Treatment with rmJAM-C inhibited BMDN apoptosis, thereby increasing their lifespan. CLP increased the frequencies of CXCR4⁺ neutrophils in blood and lungs, while treatment with anti-JAM-C Ab significantly reduced the frequencies of CXCR4⁺ aged neutrophils. Treatment with anti-JAM-C Ab significantly reduced systemic injury markers (alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase) as well as systemic and lung inflammatory cytokines (IL-6 and IL-1β) and chemokine (macrophage inflammatory protein-2). The blockade of JAM-C improved lung histology and reduced neutrophil contents in lungs of septic mice. Thus, reduction of the pro-inflammatory aged neutrophils by blockade of JAM-C has a novel therapeutic potential in sepsis-induced ALI.

The protective role of human ghrelin in sepsis: Restoration of CD4 T cell proliferation

Decrease of CD4 T cell numbers causes immunosuppression in sepsis. We previously showed the beneficial role of ghrelin in sepsis. We hypothesize that the protective outcome of ghrelin in sepsis is mediated partially through the restoration of CD4 T cells’ proliferation. Sepsis was induced in mice by cecal ligation and puncture (CLP). The percentage of CD4 T cells in spleen was assessed by flow cytometry and their proliferation was determined by carboxyfluorescein succinimidyl ester (CSFE). Compared to sham mice, the percentages of splenic CD4 T cells were reduced by 20%, 21%, and 29% at day 1, 2 and 3 after CLP, respectively. Human ghrelin was given to 3 day septic mice by s.c. injection at 5 and 24 h after CLP. Treatment with ghrelin restored the loss of CD4 T cells by increasing their proliferation in septic mice. The expression of cyclin D1 and B1 was significantly increased, while the expression of p57 was decreased in ghrelin-treated mice compared to vehicle-treated mice in sepsis. Treatment with human ghrelin significantly increased the p-AKT levels in the spleen compared to vehicle-treated septic mice. Human ghrelin plays an important role in reestablishing the proliferation of CD4 T cells and serves as a promising therapeutic agent in sepsis.

Upregulation of microRNA-335-5p reduces inflammatory responses by inhibiting FASN through the activation of AMPK/ULK1 signaling pathway in a septic mouse model

Sepsis, as a systemic inflammatory response syndrome (SIRS) subtype, is generally characterized by infection. Emerging evidence has highlighted dysregulated microRNAs (miRNAs) are involved in the progression of sepsis. The aim of the study was to investigate the effects of miR-335-5p on inflammatory responses in a septic mouse model. The hypothesis was subsequently asserted that the FASN gene and AMPK/ULK1 signaling pathway may participate in the regulation of miR-335-5p. A septic mouse model was established in order to validate the effect of miR-335-5p on the inflammatory response by means of suppressing the endogenous expression of FASN by siRNA against FASN in endothelial cells. A target prediction program and luciferase activity was employed to ascertain as to whether miR--335-5p targets FASN. The levels of inflammatory factors including IL-6 and IL-1β were determined by means of ELISA assay. RT-qPCR and western blot analysis were used to determine the AMPK/ULK1 signaling pathway-, apoptosis- and autophagy-related genes. Flow cytometry was employed in order to evaluate sepsis-induced cell apoptosis in response to miR-335-5p and FASN alternations. FASN was identified as a target gene of miR--335-5p. Gain- and loss-of-function studies revealed that miR-335-5p acted to enhance autophagy, reduce cell apoptosis, promote cell cycle entry in endothelial cells, and reduce inflammatory response through the modulation of pro- and anti-apoptotic factors in endothelial cells. The effect of miR-335-5p on endothelial cells was increased when FASN was suppressed by siRNA as well as when the AMPK/ULK1 signaling pathway was activated, suggesting that miR-335-5p influences sepsis by targeting and inhibiting FASN, and activating the AMPK/ULK1 signaling pathway. Our study provides evidence indicating that overexpressed miR-335-5p enhances autophagy by targeting FASN through activation of the AMPK/ULK1 signaling pathway working to alleviate the inflammatory response in septic mouse models, emphasizing the value of the functional upregulation of miR-335-5p as therapeutic strategy for sepsis.

Mechanism of membrane pore formation by human gasdermin-D

Gasdermin‐D (GSDMD), a member of the gasdermin protein family, mediates pyroptosis in human and murine cells. Cleaved by inflammatory caspases, GSDMD inserts its N‐terminal domain (GSDMD^Nterm) into cellular membranes and assembles large oligomeric complexes permeabilizing the membrane. So far, the mechanisms of GSDMD^Nterm insertion, oligomerization, and pore formation are poorly understood. Here, we apply high‐resolution (≤ 2 nm) atomic force microscopy (AFM) to describe how GSDMD^Nterm inserts and assembles in membranes. We observe GSDMD^Nterm inserting into a variety of lipid compositions, among which phosphatidylinositide (PI(4,5)P2) increases and cholesterol reduces insertion. Once inserted, GSDMD^Nterm assembles arc‐, slit‐, and ring‐shaped oligomers, each of which being able to form transmembrane pores. This assembly and pore formation process is independent on whether GSDMD has been cleaved by caspase‐1, caspase‐4, or caspase‐5. Using time‐lapse AFM, we monitor how GSDMD^Nterm assembles into arc‐shaped oligomers that can transform into larger slit‐shaped and finally into stable ring‐shaped oligomers. Our observations translate into a mechanistic model of GSDMD^Nterm transmembrane pore assembly, which is likely shared within the gasdermin protein family.

Outgrowing the Immaturity Myth: The Cost of Defending From Neonatal Infectious Disease

Newborns suffer high rates of mortality due to infectious disease-this has been generally regarded to be the result of an "immature" immune system with a diminished disease-fighting capacity. However, the immaturity dogma fails to explain (i) greater pro-inflammatory responses than adults in vivo and (ii) the ability of neonates to survive a significantly higher blood pathogen burden than of adults. To reconcile the apparent contradiction of clinical susceptibility to disease and the host immune response findings when contrasting newborn to adult, it will be essential to capture the entirety of available host-defense strategies at the newborn's disposal. Adults focus heavily on the disease resistance approach: pathogen reduction and elimination. Newborn hyperactive innate immunity, sensitivity to immunopathology, and the energetic requirements of growth and development (immune and energy costs), however, preclude them from having an adult-like resistance response. Instead, newborns also may avail themselves of disease tolerance (minimizing immunopathology without reducing pathogen load), as a disease tolerance approach provides a counterbalance to the dangers of a heightened innate immunity and has lower-associated immune costs. Further, disease tolerance allows for the establishment of a commensal bacterial community without mounting an unnecessarily dangerous immune resistance response. Since disease tolerance has its own associated costs (immune suppression leading to unchecked pathogen proliferation), it is the maintenance of homeostasis between disease tolerance and disease resistance that is critical to safe and effective defense against infections in early life. This paradigm is consistent with nearly all of the existing evidence.

B-1a cells protect mice from sepsis-induced acute lung injury

BACKGROUND

Sepsis morbidity and mortality are aggravated by acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Mouse B-1a cells are a phenotypically and functionally unique sub-population of B cells, providing immediate protection against infection by releasing natural antibodies and immunomodulatory molecules. We hypothesize that B-1a cells ameliorate sepsis-induced ALI.

METHODS

Sepsis was induced in C57BL/6 mice by cecal ligation and puncture (CLP). PBS or B-1a cells were adoptively transferred into the septic mice intraperitoneally. After 20 h of CLP, lungs were harvested and assessed by PCR and ELISA for pro-inflammatory cytokines (IL-6, IL-1β) and chemokine (MIP-2) expression, by histology for injury, by TUNEL and cleaved caspase-3 for apoptosis, and by myeloperoxidase (MPO) assay for neutrophil infiltration.

RESULTS

We found that septic mice adoptively transferred with B-1a cells significantly decreased the mRNA and protein levels of IL-6, IL-1β and MIP-2 in the lungs compared to PBS-treated mice. Mice treated with B-1a cells showed dramatic improvement in lung injury compared to PBS-treated mice after sepsis. We found apoptosis in the lungs was significantly inhibited in B-1a cell injected mice compared to PBS-treated mice after sepsis. B-1a cell treatment significantly down-regulated MPO levels in the lungs compared to PBS-treated mice in sepsis. The protective outcomes of B-1a cells in ALI was further confirmed by using B-1a cell deficient CD19-/- mice, which showed significant increase in the lung injury scores following sepsis as compared to WT mice.

CONCLUSIONS

Our results demonstrate a novel therapeutic potential of B-1a cells to treat sepsis-induced ALI.

The relative resistance of children to sepsis mortality: from pathways to drug candidates

Attempts to develop drugs that address sepsis based on leads developed in animal models have failed. We sought to identify leads based on human data by exploiting a natural experiment: the relative resistance of children to mortality from severe infections and sepsis. Using public datasets, we identified key differences in pathway activity (Pathprint) in blood transcriptome profiles of septic adults and children. To find drugs that could promote beneficial (child) pathways or inhibit harmful (adult) ones, we built an in silico pathway drug network (PDN) using expression correlation between drug, disease, and pathway gene signatures across 58,475 microarrays. Specific pathway clusters from children or adults were assessed for correlation with drug‐based signatures. Validation by literature curation and by direct testing in an endotoxemia model of murine sepsis of the most correlated drug candidates demonstrated that the Pathprint‐PDN methodology is more effective at generating positive drug leads than gene‐level methods (e.g., CMap). Pathway‐centric Pathprint‐PDN is a powerful new way to identify drug candidates for intervention against sepsis and provides direct insight into pathways that may determine survival.

Inhibition of necroptosis attenuates lung injury and improves survival in neonatal sepsis

BACKGROUND

Neonatal sepsis represents a unique therapeutic challenge owing to an immature immune system. Necroptosis is a form of programmed cell death that has been identified as an important mechanism of inflammation-induced cell death. Receptor-interacting protein kinase 1 plays a key role in mediating this process. We hypothesized that pharmacologic blockade of receptor-interacting protein kinase 1 activity would be protective in neonatal sepsis.

METHODS

Sepsis was induced in C57BL/6 mouse pups (5-7 days old) by intraperitoneal injection of adult cecal slurry. At 1 hour after cecal slurry injection, the receptor-interacting protein kinase 1 inhibitor necrostatin-1 (10 µg/g body weight) or vehicle (5% dimethyl sulfoxide in phosphate buffered saline) was administered via retro-orbital injection. At 20 hours after cecal slurry injection, blood and lung tissues were collected for various analyses.

RESULTS

At 20 hours after sepsis induction, vehicle-treated pups showed a marked increase in serum levels of interleukin 6, interleukin 1-beta, and interleukin 18 compared to sham. With necrostatin-1 treatment, serum levels of interleukin 6, interleukin 1-beta, and interleukin 18 were decreased by 77%, 81%, and 63%, respectively, compared to vehicle. In the lungs, sepsis induction resulted in a 232-, 10-, and 2.8-fold increase in interleukin 6, interleukin 1-beta, and interleukin 18 mRNA levels compared to sham, while necrostatin-1 treatment decreased these levels to 40-, 4-, and 0.8-fold, respectively. Expressions of the neutrophil chemokines keratinocyte chemoattractant and macrophage-inflammatory-protein-2 were also increased in the lungs in sepsis, while necrostatin-1 treatment decreased these levels by 81% and 61%, respectively, compared to vehicle. In addition, necrostatin-1 treatment significantly improved the lung histologic injury score and decreased lung apoptosis in septic pups. Finally, treatment with necrostatin-1 increased the 7-day survival rate from 0% in the vehicle-treated septic pups to 29% (P = .11).

CONCLUSION

Inhibition of receptor-interacting protein kinase 1 by necrostatin-1 decreases systemic and pulmonary inflammation, decreases lung injury, and increases survival in neonatal mice with sepsis. Targeting the necroptosis pathway might represent a new therapeutic strategy for neonatal sepsis.

Inhibitor of Tec kinase, LFM-A13, decreases pro-inflammatory mediators production in LPS-stimulated RAW264.7 macrophages via NF-κB pathway

Tec kinase, a prototypical member of the Tec tyrosine kinases family, was shown to mainly govern lymphocyte proliferation. In the present study, we investigated the role of Tec kinase in acute inflammatory response in lipopolysaccharide (LPS) challenge. First, we demonstrate that Tec kinase activity was observed in RAW264.7 macrophages exposed to LPS. Tec and phosphorylated Tec expression were upregulated in a dose- and time-dependent manner after LPS stimulation. LPS increased monocyte chemotactic protein (MCP)-1 secretion and intercellular adhesion molecule (ICAM)-1 expression, and increasing mRNA expression was consistently observed. LPS also induced IκBα phoshporylaytion and its degradation, increased NF-κB p65 phoshporylaytion and translocation to nuclei in RAW264.7 cells. Pretreatment with LFM-A13 decreased LPS-induced cytokines and chemokines production and mRNA levels, blocked NF-κB transactivation. These effects of LPS were also prevented by Tec-siRNA. Additionally, LFM-A13 or Tec-siRNA obviously inhibited LPS-induced TGFβ-activated kinase 1(TAK1) phosphorylation. Taken together, our results suggest that Tec kinase involves in acute inflammation process in LPS-stimulated RAW264.7 cells, at least mediated by activating TAK1/ NF-κB signal pathway.

CIRP increases ICAM-1+ phenotype of neutrophils exhibiting elevated iNOS and NETs in sepsis

Sepsis represents uncontrolled inflammation due to an infection. Cold-inducible RNA-binding protein (CIRP) is a stress-induced damage-associated molecular pattern (DAMP). A subset of neutrophils expressing ICAM-1⁺ neutrophils was previously shown to produce high levels of reactive oxygen species. The role of CIRP for the development and function of ICAM-1⁺ neutrophils during sepsis is unknown. We hypothesize that CIRP induces ICAM-1 expression in neutrophils causing injury to the lungs during sepsis. Using a mouse model of cecal ligation and puncture (CLP)-induced sepsis, we found increased expression of CIRP and higher frequencies and numbers of ICAM-1⁺ neutrophils in the lungs. Conversely, the CIRP^-/- mice showed significant inhibition in the frequencies and numbers of ICAM-1⁺ neutrophils in the lungs compared to wild-type (WT) mice in sepsis. In vitro treatment of bone marrow-derived neutrophils (BMDN) with recombinant murine CIRP (rmCIRP) significantly increased ICAM-1⁺ phenotype in a time- and dose-dependent manner. The effect of rmCIRP on increasing frequencies of ICAM-1⁺ neutrophils was significantly attenuated in BMDN treated with anti-TLR4 Ab or NF-κB inhibitor compared, respectively, with BMDN treated with isotype IgG or DMSO. The frequencies of iNOS producing and neutrophil extracellular traps (NETs) forming phenotypes in rmCIRP-treated ICAM-1⁺ BMDN were significantly higher than those in ICAM-1^- BMDN. Following sepsis the ICAM-1⁺ neutrophils in the lungs showed significantly higher levels of iNOS and NETs compared to ICAM-1^- neutrophils. We further revealed that ICAM-1 and NETs were co-localized in the neutrophils treated with rmCIRP. CIRP^-/- mice showed significant improvement in their survival outcome (78% survival) over that of WT mice (48% survival) in sepsis. Thus, CIRP could be a novel therapeutic target for regulating iNOS producing and NETs forming ICAM-1⁺ neutrophils in the lungs during sepsis.

Mesenchymal stem cells decrease lung inflammation during sepsis, acting through inhibition of the MAPK pathway

Background

Sepsis is a severe medical condition that ranks among the top 10 causes of death worldwide and which has permanently high incidence rates. Mesenchymal stem cells (MSCs) have been found to be potent modulators of immune responses. More importantly, there is evidence that MSCs have a beneficial effect on preclinical models of polymicrobial sepsis. However, the changes caused by the MSCs in the effector cells of the host immune system remain unclear.

Methods

A mouse model of sepsis (male C57BL/6 mice) with three experimental groups was used for experiments in vivo: a control group, an untreated septic group, and a septic group treated with MSCs. In vitro experiments were performed using a cell line of pulmonary macrophages (RAW 264.7) co-cultured with MSCs and stimulated with lipopolysaccharide (LPS).

Results

In vivo we demonstrated that treatment with MSCs was able to reduce the expression of cyclooxygenase-2 (COX-2) and nuclear factor kappa B (NF-κB), and thereby decrease the production of inflammatory cytokines. In vitro experiments using a co-culture of macrophages with MSCs showed a decrease in COX-2 and NF-κB, and showed that this reduction was directly related to the ability of MSCs to inhibit phosphorylation of ERK, RSK, and p38, enzymes that belong to the family of mitogen-activated protein kinases (MAPKs).

Conclusions

This study demonstrated that MSCs are able to inhibit the MAPK pathway activation, modulating the inflammatory response during sepsis. This understanding that MSCs can remodel the response of host cells and improve the course of sepsis is essential for developing new treatments for this pathology.

Preconditioning of physiological cyclic stretch inhibits the inflammatory response induced by pathologically mechanical stretch in alveolar epithelial cells

The aim of the present study was to investigate the effects of preconditioning of physiological cyclic stretch (CS) on the overexpression of early pro-inflammatory cytokines [including tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-8] during the inflammatory response induced by pathologically mechanical stretch in lung epithelial cells, and to determine its molecular mechanism of action. Cells were subjected to 5% CS for various durations (0, 15, 30, 60 and 120 min) prior to 6 h treatment with pathological 20% CS. In a separate experiment, cells were preconditioned with physiological 5% CS or incubated with a nuclear factor (NF)-κB inhibitor, pyrroldine dithiocarbamate (PDTC). The expression levels of inflammatory mediators were measured using reverse transcription-quantitative polymerase chain reaction. NF-κB was quantified using western blot analysis. Preconditioning with physiological 5% CS for 30, 60 and 120 min was demonstrated to significantly attenuate the release of pathologically mechanical stretch-induced early pro-inflammatory cytokines (TNF-α, IL-1β and IL-8) in alveolar epithelial cells (P<0.05) and significantly reduce the expression of NF-κB (P<0.05). Peak suppression was observed in cells preconditioned for 60 min. In the second set of experiments, it was demonstrated that mechanical stretch-induced release of TNF-α, IL-1β and IL-8 was significantly inhibited by both PDTC pretreatment and 5% CS pretreatment alone (all P<0.05). Furthermore, significant inhibition was also observed when both 5% CS pretreatment and PDTC pretreatment was used on mechanical stretch-induced cells (P<0.05), which was markedly greater than the inhibition induced by either pretreatment alone. The present findings suggest that preconditioning with physiological 5% CS is able to inhibit the inflammatory response induced by pathologically mechanical stretch in alveolar epithelial cells. These anti-inflammatory effects are induced, at least in part, by suppressing the NF-κB signaling pathway.

Myeloperoxidase-derived 2-chlorofatty acids contribute to human sepsis mortality via acute respiratory distress syndrome

Sepsis-associated acute respiratory distress syndrome (ARDS) is characterized by neutrophilic inflammation and poor survival. Since neutrophil myeloperoxidase (MPO) activity leads to increased plasma 2-chlorofatty acid (2-ClFA) levels, we hypothesized that plasma concentrations of 2-ClFAs would associate with ARDS and mortality in subjects with sepsis. In sequential consenting patients with sepsis, free 2-ClFA levels were significantly associated with ARDS, and with 30-day mortality, for each log increase in free 2-chlorostearic acid. Plasma MPO was not associated with either ARDS or 30-day mortality but was correlated with 2-ClFA levels. Addition of plasma 2-ClFA levels to the APACHE III score improved prediction for ARDS. Plasma 2-ClFA levels correlated with plasma levels of angiopoietin-2, E selectin, and soluble thrombomodulin. Endothelial cells treated with 2-ClFA responded with increased adhesion molecule surface expression, increased angiopoietin-2 release, and dose-dependent endothelial permeability. Our results suggest that 2-ClFAs derived from neutrophil MPO-catalyzed oxidation contribute to pulmonary endothelial injury and have prognostic utility in sepsis-associated ARDS.

Blood platelets and sepsis pathophysiology: A new therapeutic prospect in critically [corrected] ill patients?

Beyond haemostasis, platelets have emerged as versatile effectors of the immune response. The contribution of platelets in inflammation, tissue integrity and defence against infections has considerably widened the spectrum of their role in health and disease. Here, we propose a narrative review that first describes these new platelet attributes. We then examine their relevance to microcirculatory alterations in multi-organ dysfunction, a major sepsis complication. Rapid progresses that are made on the knowledge of novel platelet functions should improve the understanding of thrombocytopenia, a common condition and a predictor of adverse outcome in sepsis, and may provide potential avenues for management and therapy.

Immune Function in Critically Ill Dogs

Background

People with critical illness (CI) commonly develop various forms of immune dysfunction, however, there is limited information concerning immune dysfunction in dogs with CI.

Hypothesis

The immune response in CI dogs differs from that of healthy dogs.

Animals

Immunologic variables were compared between 14 dogs with CI, defined as APPLE_fast score of >20 points, admitted to the University of Missouri Veterinary Health Center Small Animal Clinic Intensive Care Unit and healthy controls (n = 15).

Methods

Cohort study evaluating constitutive and lipopolysaccharide (LPS)‐stimulated TNF‐α, IL‐6, and IL‐10 production, phagocytosis of opsonized E. coli and respiratory burst capacity after opsonized E. coli or phorbol 12‐myristate 13‐acetate (PMA) stimulation, peripheral blood lymphocyte phenotype, and monocyte expressions of HLA‐DR and TLR‐4.

Results

Lipopolysaccharide‐stimulated leukocyte TNF‐α (median, Q1, Q3; CI, 49, 49, 120; control, 655, 446, 1174 pg/mL; P = < 0.001), IL‐6 (median, Q1, Q3; CI, 49, 49, 64; control, 100, 49, 166 pg/mL; P = 0.029), and IL‐10 (CI, 49, 49, 56; control, 96, 49, 203 pg/mL; P = 0.014) production and both E. coli (median, Q1, Q3; CI, 60.5, 43, 88.5; control, 86.6, 81, 89.2%; P = 0.047) and PMA (CI, 40, 11.7, 70; control, 93, 83, 97.6%; P = < 0.001)‐stimulated respiratory burst capacity significantly decreased in CI dogs. Percentage of monocytes expressing TLR‐4 greater in the CI dogs (median, Q1, Q3; CI, 46.9, 24.3, 64.2; control, 16.4, 9.4, 26.2%; P = 0.005).

Conclusion

These findings suggest dogs with CI develop immune system alterations that result in reduced respiratory burst function and cytokine production despite upregulation of TLR‐4.

Early septic insult in neonatal pigs increases serum and urinary soluble Fas ligand and decreases kidney function without inducing significant renal apoptosis

Apoptosis of renal tubular and glomerular cells during kidney disease involves activation of Fas ligand (FasL)-dependent death pathway. The significance of FasL in neonates with septic acute kidney injury (AKI) is unresolved, but an increase in renal FasL production, and/or infiltration of circulating FasL into the kidneys may occur following initial septic insult. Here, we examined whether soluble Fas ligand (sFasL) levels are altered during early phase of septic AKI in neonates. Six hours of polymicrobial sepsis elicited by cecal ligation and puncture (CLP) elevated serum C-reactive protein (CRP) (a bacteremia and sepsis marker) concentration in anesthetized and mechanically ventilated neonatal pigs. Serum creatinine and urea nitrogen concentrations were increased by ∼39% and 46%, respectively, following 6 h of CLP in the pigs. The urinary level of NGAL, an early marker of AKI was also elevated by ∼71% in the septic pigs. The basal concentration of sFasL in the serum and urine of neonatal pigs was similar. Six hours of CLP significantly increased serum and urine sFasL levels in the pigs by ∼24% and 68%, respectively. However, there was no evidence of caspase activation to suggest an induction of cellular apoptotic process in the kidneys of the septic pigs. These findings suggest that an increase in circulating and urinary sFasL during early septic AKI in neonatal pigs is not associated with renal apoptosis.

Modulation of alveolar macrophage innate response in proinflammatory-, pro-oxidant-, and infection- models by mint extract and chemical constituents: Role of MAPKs

There is a continuing need for discovering novel primary or adjunct therapeutic agents to treat inflammatory conditions and infections. Natural products have inspired the discovery of several modern therapeutics; however, there is a paucity of mechanistic information on their mode of action. This study investigated the therapeutic potential and mode of action of corn mint's (Mentha arvensis) leaf extract (ME) in alveolar macrophages (AMs) challenged with model pro-inflammatory (LPS), pro- oxidant (LPS or H₂O₂), and infection (Mycobacterium) agents and contribution of its dominant constituents rosmarinic acid, l-menthol, and l-menthone. LPS-induced inflammatory response in the murine AM cell line MH-S was significantly reduced in terms of pro-inflammatory cytokines (TNF-α, IL-1α) and nitric oxide (NO) when pre- or post-treated with ME. The ME pretreatment of macrophages led to a significant increase (P≤0.05) in phagocytic activity toward Mycobacterium smegmatis and a greater pathogen clearance in 24h in both ME pre-treated (P≤0.05) and post-treated cells. Significant attenuation (P≤0.01) of reactive oxygen species (ROS) production in LPS- or H₂O_2-treated macrophages by pretreatment with whole mint extract (ME) was accounted for in part by the mint constituents rosmarinic acid and l-menthone. Attenuation of pro-inflammatory response by ME pretreatment coincided with the significant reduction in total and phosphorylated JNK1/2, decrease in total p38, and increase in phospho-ERK1/2 thereby implying a role of differential modulation of MAPKs. Taken together, the results demonstrate that corn mint leaf components cause potent anti-inflammatory, anti-oxidant, and anti-infection effects in AMs via suppression of the production of cytokines/soluble mediators and ROS and increased pathogen clearance, respectively. To our knowledge, this is the first report on the mode of action of corn mint targeting the alveolar macrophages and on the potential role of MAPKs in immunomodulation by this product.

Proteomic characterisation reveals active Wnt-signalling by human multipotent stromal cells as a key regulator of beta cell survival and proliferation

AIMS/HYPOTHESIS

Novel strategies to stimulate the expansion of beta cell mass in situ are warranted for diabetes therapy. The aim of this study was to elucidate the secretome of human bone marrow (BM)-derived multipotent stromal cells (MSCs) with documented islet regenerative paracrine function. We hypothesised that regenerative MSCs will secrete a unique combination of protein factors that augment islet regeneration.

METHODS

Human BM-derived MSCs were examined for glucose-lowering capacity after transplantation into streptozotocin-treated NOD/severe combined immunodeficiency (SCID) mice and segregated into samples with regenerative (MSC^R) vs nonregenerative (MSC^NR) capacity. Secreted proteins associated with islet regenerative function were identified using stable isotope labelling with amino acids in cell culture (SILAC)-based quantitative proteomics. To functionally validate the importance of active Wnt signalling, we stimulated the Wnt-signalling pathway in MSC^NR samples during ex vivo expansion using glycogen synthase kinase 3 (GSK3) inhibition (CHIR99201), and the conditioned culture media (CM) generated was tested for the capacity to support cultured human islet cell survival and proliferation in vitro.

RESULTS

MSC^R showed increased secretion of proteins associated with cell growth, matrix remodelling, immunosuppressive and proangiogenic properties. In contrast, MSC^NR uniquely secreted proteins known to promote inflammation and negatively regulate angiogenesis. Most notably, MSC^R maintained Wnt signalling via Wnt5A/B (~2.5-fold increase) autocrine activity during ex vivo culture, while MSC^NR repressed Wnt signalling via Dickkopf-related protein (DKK)1 (~2.5-fold increase) and DKK3 secretion. Inhibition of GSK3 activity in MSC^NR samples increased the accumulation of nuclear β-catenin and generated CM that augmented beta cell survival (13% increases) and proliferation when exposed to cultured human islets.

CONCLUSIONS/INTERPRETATION

Maintenance of active Wnt signalling within human MSCs promotes the secretion of matricellular and proangiogenic proteins that formulate a niche for islet regeneration.

Akt Signaling Pathway in Macrophage Activation and M1/M2 Polarization

Macrophages become activated initiating innate immune responses. Depending on the signals, macrophages obtain an array of activation phenotypes, described by the broad terms of M1 or M2 phenotype. The PI3K/Akt/mTOR pathway mediates signals from multiple receptors including insulin receptors, pathogen-associated molecular pattern receptors, cytokine receptors, adipokine receptors, and hormones. As a result, the Akt pathway converges inflammatory and metabolic signals to regulate macrophage responses modulating their activation phenotype. Akt is a family of three serine-threonine kinases, Akt1, Akt2, and Akt3. Generation of mice lacking individual Akt, PI3K, or mTOR isoforms and utilization of RNA interference technology have revealed that Akt signaling pathway components have distinct and isoform-specific roles in macrophage biology and inflammatory disease regulation, by controlling inflammatory cytokines, miRNAs, and functions including phagocytosis, autophagy, and cell metabolism. Herein, we review the current knowledge on the role of the Akt signaling pathway in macrophages, focusing on M1/M2 polarization and highlighting Akt isoform-specific functions.

To What Extent Are the Terminal Stages of Sepsis, Septic Shock, Systemic Inflammatory Response Syndrome, and Multiple Organ Dysfunction Syndrome Actually Driven by a Prion/Amyloid Form of Fibrin?

A well-established development of increasing disease severity leads from sepsis through systemic inflammatory response syndrome, septic shock, multiple organ dysfunction syndrome, and cellular and organismal death. Less commonly discussed are the equally well-established coagulopathies that accompany this. We argue that a lipopolysaccharide-initiated (often disseminated intravascular) coagulation is accompanied by a proteolysis of fibrinogen such that formed fibrin is both inflammatory and resistant to fibrinolysis. In particular, we argue that the form of fibrin generated is amyloid in nature because much of its normal α-helical content is transformed to β-sheets, as occurs with other proteins in established amyloidogenic and prion diseases. We hypothesize that these processes of amyloidogenic clotting and the attendant coagulopathies play a role in the passage along the aforementioned pathways to organismal death, and that their inhibition would be of significant therapeutic value, a claim for which there is considerable emerging evidence.

Exendin-4-assisted adipose derived mesenchymal stem cell therapy protects renal function against co-existing acute kidney ischemia-reperfusion injury and severe sepsis syndrome in rat

This study tested the hypothesis that combined therapy with exendin-4 (Ex4) and autologous adipose-derived mesenchymal stem cells (ADMSCs) was superior to either alone for protecting renal function against acute kidney ischemia-reperfusion (IR; 40-min ischemia/27-h reperfusion) injury when complicated by sepsis syndrome (SS; by cecal-ligation-puncture). Adult-male Sprague-Dawley rats (n=40) were equally divided into group 1 (sham-control), group 2 (IR-SS), group 3 (IR-SS + Ex4, 10 μg/kg subcutaneously 30 min after reperfusion and daily for 3 days), group 4 [IR-SS + ADMSC (1.2 × 10⁶)], and group 5 (IR-SS + Ex4 + ADMSC). The circulating levels of BUN and creatinine and the ratio of urine protein to creatinine were highest in group 2, lowest in group 1, significantly higher in groups 3 and 4 than group 5, and significantly higher in group 3 than in group 4 (all P<0.0001). Microscopic findings of kidney injury score, inflammatory cells (CD14+, F4/80+), and expressions of glomerular-damage indicators (FSP-1+/WT-1+) and renal tubular-damage indicators (KIM-1+/snail+) showed an identical pattern, whereas expressions of indices of glomerular-integrity (ZO-1+/p-cadherin+/podocin+/synaptopodin+) and angiogenesis (CD31+/vWF+/number of small vessels) biomarkers demonstrated an opposite pattern, to that of creatinine level (all P<0.001). Protein expressions of inflammatory (MMP-9/IL-1ß/TNF-α/TLR-2/TLR-4), apoptotic (cleaved caspase-3/PARP/mitochondrial Bax), and oxidative-stress (NOX-1/NOX-2/oxidized protein) biomarkers exhibited an identical pattern, whereas anti-inflammatory (IL-10/IL-4) biomarkers displayed an opposite pattern, to that of creatinine level (all P<0.001). In conclusion, combined Ex4 and ADMSC therapy significantly protected kidney from acute IR-SS injury.

EFFECT OF LIPOPOLYSACCHARIDE OF ESCHERICHIA COLI ON PHAGOCYTE AND METABOLIC ACTIVITY OF MICE BLOOD NEUTROPHILS WITH INDUCED IMMUNE DEFICIENCY

Aim. Experimental evaluation of effect of E. coli LPS fractions on phagocyte and metabolic activity of blood neutrophils of laboratory mice with induced immune deficiency. Materials and methods. Phagocyte activity was evaluated by phagocyte number (PN), phagocyte index (PI) and integral phagocyte index (IPI), intensity of metabolism and energetic processes of enzyme systems - by test of tetrazolium nitro blue (TNB), mean cytochemical coefficient (MCC) in spontaneous and induced tests and stimulation index (SI). Results. LPS-3 substance administration into mice with secondary immune deficiency has resulted in a significantly highest increase of PN (15.8%), IPI (17.7%), TNB-IN (10.3%), cytochemical coefficients MCC-IN (u.) and IS (u.) - 14.8 and 10.9%, respectively, compared with the parameters of immune deficient mice that had received licopid. Conclusion. Some fractions of E. coli M17 polysaccharide have immune stimulating activity.

B-1a Cells Protect Mice from Sepsis: Critical Role of CREB

Bacterial sepsis is a serious life-threatening condition caused by an excessive immune response to infection. B-1 cells differ from conventional B-2 cells by their distinct phenotype and function. A subset of B-1 cells expressing CD5, known as B-1a cells, exhibits innate immune activity. Here we report that B-1a cells play a beneficial role in sepsis by mitigating exaggerated inflammation through a novel mechanism. Using a mouse model of bacterial sepsis, we found that the numbers of B-1a cells in various anatomical locations were significantly decreased. Adoptive transfer of B-1a cells into septic mice significantly attenuated systemic inflammation and improved survival, whereas B-1a cell-deficient CD19^-/- mice were more susceptible to infectious inflammation and mortality. We also demonstrated B-1a cells produced ample amounts of IL-10 which controlled excessive inflammation and the mice treated with IL-10-deficient B-1a cells were not protected against sepsis. Moreover, we identified a novel intracellular signaling molecule, cAMP-response element binding protein (CREB), which serves as a pivotal transcription factor for upregulating IL-10 production by B-1a cells in sepsis through its nuclear translocation and binding to putative responsive elements on IL-10 promoter. Thus, the benefit of B-1a cells in bacterial sepsis is mediated by CREB and the identification of CREB in B-1a cells reveals a potential avenue for treatment in bacterial sepsis.

Hepatocyte SHP-1 is a Critical Modulator of Inflammation During Endotoxemia

Liver hepatocytes (Hep) are known to be central players during the inflammatory response to systemic infection. Interestingly, the protein tyrosine phosphatases (PTP) SHP-1, has been recognized as a major regulator of inflammation; however their implication in the control of Hep-mediated inflammatory response is still unknown. To study its implication in the regulation of the Hep-mediated inflammatory response during endotoxemia, Cre-Lox mice with a Hep-specific Ptpn6 deletion (Ptpn6^H-KO) were injected with LPS. In contrast to the wild-type mice (Ptpn6^f/f) that started to die by 24 hrs post-inoculation, the Ptpn6^H-KO mice exhibited mortality by 6 hrs. In parallel, higher amounts of metabolic markers, pro-inflammatory mediators and circulating cytokines were detected in Ptpn6^H-KO mice. Primary Hep obtained from Ptpn6^H-KO, also showed increased secretion of pro-inflammatory cytokines and nitric oxide (NO) comparatively to its wild type (Ptpn6^f/f) counterpart. Pharmacological approaches to block TNF-α and NO production protected both the Ptpn6^f/f and the Ptpn6^H-KO mice against deadly LPS-mediated endotoxemia. Collectively, these results establish hepatocyte SHP-1 is a critical player regulating systemic inflammation. Our findings further suggest that SHP-1 activation could represent a new therapeutic avenue to better control inflammatory-related pathologies.

The Toll-Like Receptor 4 Antagonist Eritoran Protects Mice from Lethal Filovirus Challenge

The 2013-2016 outbreak of Ebola virus (EBOV) in West Africa, which has seen intermittent reemergence since it was officially declared over in February of 2016, has demonstrated the need for the rapid development of therapeutic intervention strategies. Indirect evidence has suggested that the EBOV infection shares several commonalities associated with the onset of bacterial sepsis, including the development of a "cytokine storm." Eritoran, a Toll-like receptor 4 (TLR4) antagonist, was previously shown to result in protection of mice against lethal influenza virus infection. Here, we report that eritoran protects against the lethality caused by EBOV and the closely related Marburg virus (MARV) in mice. Daily administration of eritoran reduced clinical signs of the disease and, unexpectedly, resulted in reduced viral titers. Analysis of peripheral blood indicated that eritoran reduced granulocytosis despite an apparent increase in the percentage of activated neutrophils. Surprisingly, the increased survival rate and reduced viremia were not accompanied by increased CD3⁺ T lymphocytes, as lymphopenia was more pronounced in eritoran-treated mice. Overall, a global reduction in the levels of multiple cytokines, chemokines, and free radicals was detected in serum, suggesting that eritoran treatment may alleviate the severity of the "cytokine storm." Last, we provide compelling preliminary evidence suggesting that eritoran treatment may alter the kinetics of cytokine responses. Hence, these studies are the first to demonstrate the role of TLR4 in the pathogenesis of EBOV disease and indicate that eritoran is a prime candidate for further evaluation as a clinically viable therapeutic intervention strategy for EBOV and MARV infections.IMPORTANCE A hallmark of bacterial sepsis is the uncontrolled activation of the TLR4 pathway, which is the primary cause of the pathological features associated with this disease. Considering the importance of TLR4 signaling in bacterial sepsis and the remarkable pathological similarities associated with infections caused by filoviruses Ebola virus (EBOV) and Marburg virus (MARV), we assessed the ability of eritoran, a TLR4 antagonist, to protect mice against these viruses. Here, we show that eritoran effectively promotes survival of mice of filovirus infection, as 70% and 90% of mice receiving daily eritoran treatment survived lethal EBOV and MARV infections, respectively. Eritoran treatment resulted in a remarkable global reduction of inflammatory mediators, which is suggestive of the mechanism of action of this therapeutic treatment. These studies are the first to show the critical importance of the TLR4 pathway in the pathogenesis of filovirus infection and may provide a new avenue for therapeutic interventions.

Treatment with milk fat globule epidermal growth factor-factor 8 (MFG-E8) reduces inflammation and lung injury in neonatal sepsis

BACKGROUND

Sepsis remains one of the leading causes of infant death worldwide. It is characterized by uncontrolled inflammatory responses due to proven bacterial infection. Despite improvement in supportive care and the availability of effective antibiotics, no specific therapy targeting the dysregulated inflammatory response is available for neonatal sepsis. Milk fat globule epidermal growth factor-factor 8 (MFG-E8) is a secretory glycoprotein abundantly present in human milk. MFG-E8 suppresses the systemic inflammatory responses in adult murine injury models by improving the clearance of dying cells. We hypothesized that exogenous administration of recombinant mouse MFG-E8 could inhibit the exaggerated inflammatory response and lung injury in a murine model of neonatal sepsis.

METHODS

Neonatal sepsis was induced in 5- to 7-day-old male and female C57BL6 mice using an intraperitoneal injection of cecal slurry. At 1 hour after sepsis induction, a single dose of 40 μg/kg recombinant mouse MFG-E8 or vehicle was administered via retro-orbital injection. All neonates were returned to their mothers as a group. At 10 hours after cecal slurry injection, pups were killed and blood and lung tissues were collected. Control mice underwent a similar procedure with the exception of cecal slurry intraperitoneal injection.

RESULTS

Serum lactate dehydrogenase, IL-1β, and IL-6 were significantly increased 10 hours after cecal slurry injection. Treatment with recombinant mouse MFG-E8 decreased these levels by 30%, 56%, and 37%, respectively. Lung morphology was significantly compromised in the vehicle group after cecal slurry injection, whereas the recombinant mouse MFG-E8-treated groups demonstrated a 48% improvement in the lung injury score. Lung IL-6 and MIP-2 protein levels were significantly reduced with recombinant mouse MFG-E8 treatment. Lung neutrophil infiltration as observed by Gr-1 staining and, TUNEL-positive cells were also significantly reduced with recombinant mouse MFG-E8 treatment.

CONCLUSION

Treatment with recombinant mouse MFG-E8 attenuated inflammation and lung injury in murine neonatal sepsis. Thus, MFG-E8 could be developed as a possible therapy for neonatal sepsis.

Differentially expressed miRNAs in sepsis-induced acute kidney injury target oxidative stress and mitochondrial dysfunction pathways

Objective

To identify specific miRNAs involved in sepsis-induced AKI and to explore their targeting pathways.

Methods

The expression profiles of miRNAs in serum from patients with sepsis-induced AKI (n = 6), sepsis-non AKI (n = 6), and healthy volunteers (n = 3) were investigated by microarray assay and validated by quantitative PCR (qPCR). The targets of the differentially expressed miRNAs were predicted by Target Scan, mirbase and Miranda. Then the significant functions and involvement in signaling pathways of gene ontology (GO) and KEGG pathways were analyzed. Furthermore, eight miRNAs were randomly selected out of the differentially expressed miRNAs for further testing by qPCR.

Results

qPCR analysis confirmed that the expressions levels of hsa-miR-23a-3p, hsa-miR-4456, hsa-miR-142-5p, hsa-miR-22-3p and hsa-miR-191-5p were significantly lower in patients with sepsis compared with the healthy volunteers, while hsa-miR-4270, hsa-miR-4321, hsa-miR-3165 were higher in the sepsis patients. Statistically, miR-4321; miR-4270 were significantly upregulated in the sepsis-induced AKI compared with sepsis-non AKI, while only miR-4321 significantly overexpressed in the sepsis groups compared with control groups. GO analysis showed that biological processes regulated by the predicted target genes included diverse terms. They were related to kidney development, regulation of nitrogen compound metabolic process, regulation of cellular metabolic process, cellular response to oxidative stress, mitochondrial outer membrane permeabilization, etc. Pathway analysis showed that several significant pathways of the predicted target genes related to oxidative stress. miR-4321 was involved in regulating AKT1, mTOR and NOX5 expression while miR-4270 was involved in regulating PPARGC1A, AKT3, NOX5, PIK3C3, WNT1 expression. Function and pathway analysis highlighted the possible involvement of miRNA-deregulated mRNAs in oxidative stress and mitochondrial dysfunction.

Conclusion

This study might help to improve understanding of the relationship between serum miRNAs and sepsis-induced AKI, and laid an important foundation for further identification of the potential mechanisms of sepsis-induced AKI and oxidative stress and mitochondrial dysfunction.

Milk fat globule-epidermal growth factor-factor VIII attenuates sepsis-induced acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is most commonly caused by sepsis in critically ill patients, and it is associated with high morbidity and mortality. The pathophysiology of sepsis-induced AKI is generally accepted to include direct inflammatory injury, endothelial cell dysfunction, and apoptosis. Milk fat globule-epidermal growth factor-factor VIII (MFG-E8) is a secretory glycoprotein with a known role in the enhancement of apoptotic cell clearance and regulation of inflammation. We hypothesize that administration of recombinant mouse MFG-E8 (rmMFG-E8) can protect mice from kidney injuries caused by sepsis.

METHODS

Sepsis was induced in 8-wk-old male C57BL/6 mice by cecal ligation and puncture (CLP). rmMFG-E8 or phosphate-buffered saline (vehicle) was injected intravenously at a dosage of 20 μg/kg body weight at time of CLP (n = 5-8 mice per group). After 20 h, serum and renal tissue were harvested for various analyses. The renal injury markers blood urea nitrogen (BUN) and creatinine were determined by enzymatic and chemical reactions, respectively. The gene expression analysis was carried out by real-time quantitative polymerase chain reaction.

RESULTS

At 20 h after CLP, serum levels of BUN and creatinine were both significantly increased in the vehicle group compared with the sham group, whereas the mice treated with rmMFG-E8 had a significant reduction in BUN and creatinine levels by 28% and 24.1%, respectively (BUN: 197.7 ± 23.6 versus 142.3 ± 20.7 mg/dL; creatinine: 0.83 ± 0.12 versus 0.63 ± 0.06 mg/dL; P < 0.05). Expressions of novel biomarkers of renal tissue injury neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 were also significantly downregulated by 58.2% and 95%, respectively, after treatment with rmMFG-E8. Proinflammatory cytokine interleukin-6 and tumor necrosis factor-α messenger RNA (mRNA) were significantly reduced by 50.8% and 50.3%, respectively, in rmMFG-E8-treated mice compared with vehicle-treated mice. The mRNA levels of the chemokines keratinocyte chemoattractant and macrophage inhibitory protein-2 were reduced by 85.1% and 78%, respectively, in mice treated with rmMFG-E8 compared with the vehicle mice. In addition, the expression of intercellular cell adhesion molecule-1 and platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) mRNA was downregulated by 35.6% and 77.8%, respectively, in rmMFG-E8-treated mice compared with the vehicle animals (P < 0.05).

CONCLUSIONS

Treatment with rmMFG-E8 reduces renal tissue injury induced by sepsis through inhibiting the production of proinflammatory cytokines and chemokine, as well as through the activation of endothelial cells. Thus, MFG-E8 may have a therapeutic potential for treating AKI induced by sepsis.

Recent Insights into the Molecular Mechanisms Underlying Pyroptosis and Gasdermin Family Functions

Pyroptosis is an inflammatory form of cell death that not only protects multicellular organisms from invading pathogenic bacteria and microbial infections, but can also lead to sepsis and lethal septic shock if overactivated. Here, we present an overview of recent developments within the pyroptosis field, beginning with the discovery of Gasdermin D (GSDMD) as a substrate of caspase-1 and caspase-11 upon detection of cytosolic lipopolysaccharide (LPS). Cleavage releases the N-terminal domain of GSDMD, causing it to form cytotoxic pores in the plasma membrane of cells. We further discuss the implications for the rest of the gasdermin (GSDM) family, which are emerging as mediators of programmed cell death in a variety of processes that regulate cellular differentiation and proliferation.

Selective Biological Responses of Phagocytes and Lungs to Purified Histones

Histones invoke strong proinflammatory responses in many different organs and cells. We assessed biological responses to purified or recombinant histones, using human and murine phagocytes and mouse lungs. H1 had the strongest ability in vitro to induce cell swelling independent of requirements for toll-like receptors (TLRs) 2 or 4. These responses were also associated with lactate dehydrogenase release. H3 and H2B were the strongest inducers of [Ca2+]i elevations in phagocytes. Cytokine and chemokine release from mouse and human phagocytes was predominately a function of H2A and H2B. Double TLR2 and TLR4 knockout (KO) mice had dramatically reduced cytokine release induced in macrophages exposed to individual histones. In contrast, macrophages from single TLR-KO mice showed few inhibitory effects on cytokine production. Using the NLRP3 inflammasome protocol, release of mature IL-1β was predominantly a feature of H1. Acute lung injury following the airway delivery of histones suggested that H1, H2A, and H2B were linked to alveolar leak of albumin and the buildup of polymorphonuclear neutrophils as well as the release of chemokines and cytokines into bronchoalveolar fluids. These results demonstrate distinct biological roles for individual histones in the context of inflammation biology and the requirement of both TLR2 and TLR4.

Immunoparalysis: Clinical and immunological associations in SIRS and severe sepsis patients

INTRODUCTION

This study was designed to identify changes in the monocytic membrane marker HLA-DR and heat shock proteins (HSPs) in relation to T-regulatory cells (T-regs) and other immunological marker changes in patients with systemic inflammatory response syndrome (SIRS) or sepsis/septic shock.

METHODS

Healthy volunteers, intensive care unit (ICU) patients with SIRS due to head injury and ICU patients with severe sepsis/septic shock were enrolled in the current study. Determination of CD14+/HLA-DR+ cells, intracellular heat-shock proteins and other immunological parameters were performed by flow cytometry and RT-PCR techniques as appropriate. Univariate and multivariate analysis examined associations of CD14/HLA-DR, HSPs, T-regs and suppressor of cytokine signalling (SOCS) proteins with SIRS, sepsis and outcome.

RESULTS

Fifty patients (37 with severe sepsis and 13 with SIRS) were enrolled, together with 20 healthy volunteers used as a control group. Compared to healthy individuals, patients with SIRS and severe sepsis showed progressive decline of their CD14/HLA-DR expression (0% to 7.7% to 50% within each study subpopulation, p<0.001). Mean fluorescent intensity (MFI) levels of HSP70 and HSP90 on monocytes and polymorphonuclear cells were significantly higher in SIRS patients compared to controls and fell significantly in severe sepsis/septic shock patients (p<0.05 for all comparisons). There was no statistically significant difference between subgroups for levels of T-regulatory cells or relative copies of Suppressor of Cytokine Signalling 3 (SOCS3) proteins. In univariate models percent of CD14/HLA-DR was associated with mortality (OR: 1.8 95%CI 1.02-3.2, p=0.05), while in multivariate models after adjusting for CD14/HLA-DR only younger age and lower Acute Physiology and Chronic Health Evaluation II (APACHE II) scores were associated with increased chances of survival (beta -0.05, OR 0.9, 95% CI 0.9-0.99, p=0.038 for age and beta -0.11, OR 0.89, 95% CI 0.8-0.99, p=0.037 for APACHE II score).

CONCLUSIONS

Significant associations with SIRS and sepsis were found for CD14/HLA-DR expression and monocyte and polymorphonuclear cell levels of HSP70 and 90. The role of these biomarkers in assessing the prognosis of sepsis needs to be further explored and validated in prospective studies.

MFG-E8-derived peptide attenuates adhesion and migration of immune cells to endothelial cells

Milk fat globule-epidermal growth factor-factor 8 (MFG-E8) plays an immunomodulatory role in inflammatory diseases. MFG-E8-derived short peptide (MSP68) greatly reduces neutrophil infiltration and injury in the lung during sepsis. In this study, we examined the effect of MSP68 on chemotaxis of various immune cells and its regulatory mechanism. Bone marrow-derived neutrophils (BMDNs) from C57BL/6 mice, human monocyte THP-1 cell line, and human T lymphocyte Jurkat cell line were used for adhesion and migration assays using a Transwell method in the presence of MSP68. Treatment with MSP68 significantly inhibited the BMDN and THP-1 cell but not Jurkat cell adhesion on the TNF-α-stimulated pulmonary artery endothelial cell (PAEC) monolayer dose-dependently. MSP68 also significantly reduced BMDN adhesion on VCAM-1-coated wells dose dependently. Surface plasmon resonance (SPR) analysis revealed that MSP68 efficiently recognized integrin α₄β₁ (receptor for VCAM-1) at the dissociation constant (K_D) of 1.53 × 10^-7 M. These findings implicate that MSP68 prevents neutrophil adhesion to the activated endothelial cells by interfering with the binding between integrin α₄β₁ on neutrophils and VCAM-1 on endothelial cells. Moreover, MSP68 significantly attenuated the migration of BMDN and THP-1 cells but not Jurkat cells to their chemoattractants. Pretreatment with MSP68 inhibited the transmigration of BMDNs across the PAECs toward chemoattractants, fMLP, MIP-2, and complement fragment 5a (C5a) dose-dependently. Finally, we identified that the activation of p38 MAPK in BMDNs by fMLP was inhibited by MSP68. Thus, MSP68 attenuates extravasation of immune cells through the endothelial cell lining into inflamed tissue, implicating MSP68 to be a novel, therapeutic agent for inflammatory diseases caused by excessive immune cell infiltration.