Patients with acute pancreatitis complicated by organ failure show highly aberrant monocyte signaling profiles assessed by phospho-specific flow cytometry. Crit Care Med. 2010;38:1702-1708. [PMID: 20512034 DOI: 10.1097/ccm.0b013e3181e7161c]

Prognostic significance of organ failure and infected pancreatic necrosis in acute pancreatitis: An updated systematic review and meta-analysis

OBJECTIVES

In patients with acute pancreatitis (AP), minimally invasive treatment and the step-up approach have been widely used to deal with infected pancreatic necrosis (IPN) in the last decade. It is unclear whether IPN has become a less important determinant of mortality relative to organ failure (OF). We aimed to statistically aggregate recent evidence from published studies to determine the relative importance of IPN and OF as determinants of mortality in patients with AP (PROSPERO: CRD42020176989).

METHODS

Relevant studies were sourced from MEDLINE and EMBASE databases. Relative risk (RR) or weighted mean difference (WMD) was analyzed as outcomes. A two-sided P value of less than 0.05 was regarded as statistical significance.

RESULTS

Forty-three studies comprising 11 601 patients with AP were included. The mortality was 28% for OF patients and 24% for those with IPN. Patients with OF without IPN had a significantly higher risk of mortality compared to those with IPN but without OF (RR 3.72, P < 0.0001). However, patients with both OF and IPN faced the highest risk of mortality. Additionally, IPN increased length of stay in hospital for OF patients (WMD 28.75, P = 0.032).

CONCLUSION

Though IPN remains a significant concern, which leads to increased morbidity and longer hospital stay, it is a less critical mortality determinant compared to OF in AP.

Circulating monocytes in acute pancreatitis

Acute pancreatitis is a common gastrointestinal disease characterized by inflammation of the exocrine pancreas and manifesting itself through acute onset of abdominal pain. It is frequently associated with organ failure, pancreatic necrosis, and death. Mounting evidence describes monocytes - phagocytic, antigen presenting, and regulatory cells of the innate immune system - as key contributors and regulators of the inflammatory response and subsequent organ failure in acute pancreatitis. This review highlights the recent advances of dynamic change of numbers, phenotypes, and functions of circulating monocytes as well as their underling regulatory mechanisms with a special focus on the role of lipid modulation during acute pancreatitis.

Infectious Complications of Acute Pancreatitis Is Associated with Peripheral Blood Phagocyte Functional Exhaustion

BACKGROUND

Infected pancreatic necrosis is one of the most severe complications of acute pancreatitis (AP). The development of secondary infection doubles the risk of death during the late stage of necrotizing pancreatitis. Phagocytes play a major role in AP pathogenesis, as well as in local and systemic complications of the disease.

AIMS

We aimed to investigate the relationship between quantitative and functional indices of circulating phagocyte at the time of admission and onset of infectious complications in patients with AP afterward.

METHODS

A post hoc analysis of 97 patients with AP was conducted. The metabolic state of peripheral blood neutrophils and monocytes was analyzed based on their phagocytic activity and generation of reactive oxygen species (ROS), which were determined by flow cytometry on admission. The clinical end point was marked by onset of infectious complications of AP.

RESULTS

On admission, baseline values and reactivity reserve of monocyte and neutrophil phagocytic activity in AP patients, who developed septic complications, were substantially decreased, whereas monocyte ROS generation was dramatically increased as compared to the group without infectious processes. ROC curve was obtained both for neutrophil and monocyte phagocytosis reactivity reserve expressed as modulation coefficient values and categorized as the risk factor of infectious complications, showing an area under curve of 0.95 (P < 0.0001) and 0.84 (P < 0.0001), respectively.

CONCLUSIONS

Early (at the time of admission) detection of quantitative and functional indices of circulating phagocytes can be useful for the prediction of septic complications in SAP patients.

Blood Leukocyte Signaling Pathways as Predictors of Severity of Acute Pancreatitis

OBJECTIVES

Clinical practice lacks biomarkers to predict the severity of acute pancreatitis (AP). We studied if intracellular signaling of circulating leukocytes could predict persistent organ dysfunction (OD) and secondary infections in AP.

METHODS

A venous blood sample was taken from 174 patients with AP 72 hours or less from onset of symptoms and 31 healthy controls. Phosphorylation levels (p) of appropriately stimulated signal transducer and activator of transcription 1 (STAT1), STAT6, nuclear factor-κB (NF-κB), Akt, and nonstimulated STAT3 in monocytes, neutrophils, and lymphocytes was measured using phosphospecific flow cytometry.

RESULTS

The patients showed higher pSTAT3 and lower pSTAT1, pSTAT6, pNF-κB, and pAkt than healthy controls. pSTAT3 in all leukocyte subtypes studied increased, and pSTAT1 in monocytes and T cells decreased in an AP severity-wise manner. In patients without OD at sampling, high pSTAT3 in monocytes and T lymphocytes were associated with development of persistent OD. In patients with OD, low interleukin-4-stimulated pSTAT6 in monocytes and neutrophils and Escherichia coli-stimulated pNF-κB in neutrophils predicted OD persistence. High pSTAT3 in monocytes, CD8+ T cells, and neutrophils; low pSTAT1 in monocytes and T cells; and low pNF-κB in lymphocytes predicted secondary infections.

CONCLUSIONS

Leukocyte STAT3, STAT1, STAT6, and NF-κΒ phosphorylations are potential predictors of AP severity.

Time course of signaling profiles of blood leukocytes in acute pancreatitis and sepsis

Activation of intracellular signaling pathways in circulating leukocytes represents an early step in systemic immune-inflammatory response occurring e.g. in acute pancreatitis (AP) and sepsis. Previously, we found aberrations in the phosphorylation of leukocyte signaling proteins in patients with sepsis or AP (measured <48 h from hospital admission) resembling each other and associating with AP severity. Of these patients, those with sepsis or severe AP complicated by persistent organ dysfunction (OD+, n = 17) and patients with moderately severe AP (OD-, n = 6) were followed up in this study by measuring the phosphorylations at two additional time points (2-4 and 5-8 days after the initial sample) using phosphospecific whole blood flow cytometry. Twenty-eighty healthy subjects served as controls (HC). Constitutive STAT3 phosphorylation (pSTAT3) declined in monocytes and neutrophils of OD-/OD + and in lymphocytes of OD + and remained higher in OD- than HC. Monocytes of OD-/OD + showed low pSTAT3 and pSTAT1 levels in response to IL-6 through follow-up. Monocyte pNF-κB levels in response to TNF, LPS and E. coli in OD+, to E. coli in OD-, and lymphocyte pNF-κB levels in response to TNF in OD- increased during follow-up but remained lower than in HC, and neutrophil pNF-κB levels in response to TNF declined in OD-. Phorbol myristate acetate + Ca²⁺ ionophore-stimulated pERK1/2 decreased in neutrophils of OD-/OD+. To conclude, in patients with moderately severe or severe AP or sepsis, improvement and molecular events contributing to OD can be assessed at the level of blood leukocyte signaling.

Multiple Organ Dysfunction Syndrome

Multiple organ dysfunction syndrome (MODS) is one of the most common syndromes of critical illness and the leading cause of mortality among critically ill patients. Multiple organ dysfunction syndrome is the clinical consequence of a dysregulated inflammatory response, triggered by clinically diverse factors with the main pillar of management being invasive organ support. During the last years, the advances in the clarification of the molecular pathways that trigger, mitigate, and determine the outcome of MODS have led to the increasing recognition of MODS as a distinct disease entity with distinct etiology, pathophysiology, and potential future therapeutic interventions. Given the lack of effective treatment for MODS, its early recognition, the early intensive care unit admission, and the initiation of invasive organ support remain the most effective strategies of preventing its progression and improving outcomes.

Identification of genes and pathways associated with multiple organ dysfunction syndrome by microarray analysis

Multiple organ dysfunction syndrome (MODS) is characterized by the development of progressive physiological dysfunction of ≥2 organs or organ systems and is responsible for the majority of the morbidity and mortality among patients in intensive care units. The aim of the present study was to investigate the potential genes and pathways associated with MODS. The microarray dataset GSE60088 was downloaded from the Gene Expression Omnibus and used to identify differentially expressed genes (DEGs) between organ tissues (lung, liver and kidney) obtained from a murine model of MODS and healthy controls. The interactions between DEGs in lungs, liver and kidneys were revealed by Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. Furthermore, protein‑protein interaction (PPI) data for DEGs were obtained from the Search Tool for the Retrieval of Interacting Genes and a PPI network was constructed. Additionally, DEGs that were common among the three organs were screened and transcription factors that regulated them were predicted using the iRegulon plugin. A total of 943, 267 and 227 DEGs were identified in lung, liver and kidney samples, respectively, between mice with MODS and healthy controls. In lung and liver samples, two pathways that were enriched with DEGs were identified and were common between lung and liver samples, including 'cytokine‑cytokine receptor interaction' and 'Jnk‑STAT signaling pathway', and examples of DEGs associated with these pathways include C‑X‑C motif chemokine ligand (Cxcl)1 and Cxcl10, and signal transducer and activator of transcription (Stat)1, respectively. Furthermore, two common pathways were identified in liver and kidney samples, which included 'MAPK signaling pathway' and 'p53 signaling pathway', and DEGs associated with these pathways included growth arrest and DNA damage‑inducible α. A total of 18 DEGs were common among lung, liver and kidney tissues, including CCAAT/enhancer binding protein β (Cebpb) and olfactomedin‑like 1 (Olfml1). Cebpb modulated various other DEGs, such as Cxcl1, and Olfml1 was regulated by Stat5A. These genes and pathways may serve roles in the progression of MODS and may be considered to be potential therapy targets for MODS.

Monocyte programmed death ligand-1 expression is an early marker for predicting infectious complications in acute pancreatitis

Background

Acute pancreatitis (AP) is a life-threatening disease that requires early identification of patients at risk of developing infectious complications. Immunosuppression is an initial event that is key to AP pathogenesis. The programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) system is reported to mediate evasion of host immune surveillance in many diseases; however, the relationship between PD-1/PD-L1 expression and these parameters or infectious complications in AP has not been elucidated. This study was conducted to determine whether PD-1 and PD-L1 are upregulated and to reveal the relationship between PD-1/PD-L1 expression and the development of infectious complications in AP.

Methods

Sixty-three patients with AP and 32 sex- and age-matched healthy control subjects were prospectively enrolled. On days 1 and 3 after the onset of AP, we measured PD-1 expression in peripheral CD4⁺ T cells and PD-L1 and human leukocyte antigen-DR (HLA-DR) expression in CD14⁺ monocytes using flow cytometry. Plasma interleukin (IL)-10 levels were measured by enzyme-linked immunosorbent assay.

Results

Compared with healthy volunteers, the percentages of PD-1-expressing CD4⁺ lymphocytes and PD-L1-expressing CD14⁺ monocytes were increased in patients with AP on days 1 and 3 after onset, especially those with infectious complications. Moreover, increased PD-1/PD-L1 expression was associated with increased occurrence of infectious complications, decreased circulating lymphocytes, and increased plasma IL-10 concentration. Multivariate regression analysis indicated that the increased percentage of PD-L1-expressing CD14⁺ monocytes was an independent risk factor for infectious complications in AP. Area under the ROC curve analysis showed the combination of Acute Physiology and Chronic Health Evaluation II score and PD-L1 and HLA-DR expression in CD14⁺ monocytes had high accuracy in predicting infectious complications in patients with AP.

Conclusions

The PD-1/PD-L1 system plays an essential role in the early immunosuppression of AP. PD-L1 expression in CD14⁺ monocytes may be a new marker for predicting risk of infectious complications in patients with AP.

Immunopathogenesis of pancreatitis

The conventional view of the pathogenesis of acute and chronic pancreatitis is that it is due to a genetic- or environment-based abnormality of intracellular acinar trypsinogen activation and thus to the induction of acinar cell injury that, in turn, sets in motion an intra-pancreatic inflammatory process. More recent studies, reviewed here, present strong evidence that while such trypsinogen activation is likely a necessary first step in the inflammatory cascade underlying pancreatitis, sustained pancreatic inflammation is dependent on damage-associated molecular patterns-mediated cytokine activation causing the translocation of commensal (gut) organisms into the circulation and their induction of innate immune responses in acinar cells. Quite unexpectedly, these recent studies reveal that the innate responses involve activation of responses by an innate factor, nucleotide-binding oligomerization domain 1 (NOD1), and that such NOD1 responses have a critical role in the activation/production of nuclear factor-kappa B and type I interferon. In addition, they reveal that chronic inflammation and its accompanying fibrosis are dependent on the generation of IL-33 by injured acinar cells and its downstream induction of T cells producing IL-13. These recent studies thus establish that pancreatitis is quite a unique form of inflammation and one susceptible to newer, more innovative therapy.

Intra-Abdominal Pressure Reduction After Percutaneous Catheter Drainage Is a Protective Factor for Severe Pancreatitis Patients With Sterile Fluid Collections

OBJECTIVES

Severe acute pancreatitis (SAP) is a fatal disease with natural course of early SAP (ESAP) and late SAP (LSAP) phases. Peripancreatic percutaneous catheter drainage (PCD) is effective in management of LSAP. Although our previous study indicates that intra-abdominal PCD ahead of peripancreatic PCD benefits ESAP patients with sterile fluid collections, the mechanism is still uncovered.

METHODS

According to therapeutic results, 452 SAP patients who underwent PCD were divided into sterile group (248 cases), secondary infection group (145 cases), and primary infection group (59 cases).

RESULTS

The mortality was 4.1%, 10.9%, and 18.6%, respectively. Logistic-regression analysis indicated that multiorgan dysfunction syndrome (odds ratio [OR], 1.717; 95% confidence interval [95% CI], 1.098-2.685; P = 0.018), catheters located intra-abdominally (OR, 0.511; 95% CI, 0.296-0.884; P = 0.016), and intra-abdominal hypertension (OR, 1.534; 95% CI, 1.016-2.316; P = 0.042) were predictors for infection after PCD. Receiver operating characteristics curve delineated that decrease of intra-abdominal pressure (IAP) of more than 6.5 mm Hg after PCD had the ability to predict infection with sensitivity of 84.0% and specificity of 79.5%.

CONCLUSIONS

Intra-abdominal PCD for acute sterile fluid collections seems to be an effective option rather than peripancreatic PCD. Patients with a significant decrease of IAP had a lower incidence of infection and better alleviation of organ failure.

The role of Card9 overexpression in peripheral blood mononuclear cells from patients with aseptic acute pancreatitis

Activated mononuclear cells are an early event in the course of severe acute pancreatitis (SAP). To date, the molecular mechanism triggering peripheral blood mononuclear cells (PBMCs) is poorly understood. The aim of this paper was to determine the potential role of Card9 in SAP. We collected data from 72 subjects between January 2013 and June 2014. Subsequently, PBMCs were isolated on day 1, 3 and 5 of pancreatitis. Immunofluorescence staining, quantitative real‐time PCR, Western blotting, immunoprecipitation and ELISA were used to determine the role of Card9 in SAP. Microbial culture showed that SAP patients at the early period did not develop any bacteria and fungi infection. Card9 expression in SAP patients was higher than that in mild acute pancreatitis and volunteer healthy controls, up to the peak on day 1. The monocyte‐derived cytokines interleukin (IL)‐17, IL‐1β, IL‐6 and tumour necrosis factor‐α mediated by the induction of Card9 markedly increased in SAP patients compared with the control group. Furthermore, the inducible formation of Card9‐Bcl10 complex was found in PBMCs, which may be involved in nuclear factor kappa B (NF‐κB) and p38 activation in SAP. Receiver operating characteristic curve indicated that Card9 levels had a high sensitivity of 87.5% and specificity of 67.7%, showing the close correlation with SAP patients. Card9 overexpression was firstly found in aseptic SAP, which may be played an important role in NF‐κB and p38 activation in PBMCs. It also provided the new insights into therapeutic interventions by targeting monocytes activation in SAP patients.

JAK-STAT signaling pathway and acute pancreatitis

The pathogenesis of acute pancreatitis has long been an important research topic. In acute pancreatitis, cytokines and growth factors bind to Janus kinase (JAK) related receptors, and activate JAKs. The activated JAKs phosphorylate the tyrosine residues of the receptor. The downstream signal transducers and activators of transcription (STAT) then bind to the specific site of the phosphorylated JAK receptor complexes, leading to the activation of STATs. The activated STATs detach from the receptor complexes and translocate to the nucleus to regulate the expression of Bcl-2, Bcl-X(L), Mcl-1 and other genes, thereby participating in the pathogenesis of pancreatitis. Such signal transduction can be terminated by the dephosphorylation of STATs. At present, more and more clinical experiments and animal studies have shown that the JAK-STAT pathway is closely related with acute pancreatitis. In this article, we will review the structure, distribution, and function of JAK-STAT signaling pathway as well as the role of JAK-STAT signaling pathway in the pathogenesis of acute pancreatitis.

Immune-modulating therapy in acute pancreatitis: Fact or fiction

Acute pancreatitis (AP) is one of the most common diseases of the gastrointestinal tract, bearing significant morbidity and mortality worldwide. Current treatment of AP remains unspecific and supportive and is mainly targeted to aggressively prevent systemic complications and organ failure by intensive care. As acute pancreatitis shares an indistinguishable profile of inflammation with sepsis, therapeutic approaches have turned towards modulating the systemic inflammatory response. Targets, among others, have included pro- and anti-inflammatory modulators, cytokines, chemokines, immune cells, adhesive molecules and platelets. Even though, initial results in experimental models have been encouraging, clinical implementation of immune-regulating therapies in acute pancreatitis has had a slow progress. Main reasons include difficulty in clinical translation of experimental data, poor understanding of inflammatory response time-course, flaws in experimental designs, need for multimodal approaches and commercial drawbacks. Whether immune-modulation in acute pancreatitis remains a fact or just fiction remains to be seen in the future.

Remote ischemic preconditioning as treatment for non-ischemic gastrointestinal disorders: Beyond ischemia-reperfusion injury

Common gastrointestinal diseases such as radiation enteritis (RE), acute pancreatitis, inflammatory bowel diseases (IBD) and drug-induced hepatotoxicity share pathophysiological mechanisms at the molecular level, mostly involving the activation of many pathways of the immune response, ultimately leading to tissue injury. Increased oxidative stress, inflammatory cytokine release, inflammatory cell infiltration and activation and the up-regulation of inflammatory transcription factors participate in the pathophysiology of these complex entities. Treatment varies in each specific disease, but at least in the cases of RE and IBD immunosuppressors are effective. However, full therapeutic responses are not always achieved. The pathophysiology of ischemia-reperfusion (IR) injury shares many of these mechanisms. Brief and repetitive periods of ischemia in an organ or limb have been shown to protect against subsequent major IR injury in distant organs, a phenomenon called remote ischemic preconditioning (RIP). This procedure has been shown to protect the gut, pancreas and liver by modulating many of the same inflammatory mechanisms. Since RIP is safe and tolerable, and has shown to be effective in some recent clinical trials, I suggest that RIP could be used as a physiologically relevant adjunct treatment for non-ischemic gastrointestinal inflammatory conditions.

Proteomic analysis of apoptotic and oncotic pancreatic acinar AR42J cells treated with caerulein

This study aims to determine the differentially expressed proteins in the pancreatic acinar cells undergoing apoptosis and oncosis stimulated with caerulein to explore different cell death process of the acinar cell. AR42J cells were treated with caerulein to induce cell model of acute pancreatitis. Cells that were undergoing apoptosis and oncosis were separated by flow cytometry. Then differentially expressed proteins in the two groups of separated cells were detected by shotgun liquid chromatography-tandem mass spectrometry. The results showed that 11 proteins were detected in both apoptosis group and oncosis group, 17 proteins were detected only in apoptosis group and 29 proteins were detected only in oncosis group. KEGG analysis showed that proteins detected only in apoptosis group were significantly enriched in 10 pathways, including ECM-receptor interaction, cell adhesion molecules, and proteins detected only in oncosis group were significantly enriched in three pathways, including endocytosis, base excision repair, and RNA degradation. These proteins we detected are helpful for us to understand the process of cell death in acute pancreatitis and may be useful for changing the death mode of pancreatic acinar cells, thus attenuating the severity of pancreatitis.

Detection of muramyl dipeptide-sensing pathway defects in monocytes of patients with Crohn's disease using phospho-specific whole blood flow cytometry

Peripheral blood mononuclear cells of Crohn's disease (CD) patients with the common 1007fs mutation of the caspase recruitment domain-containing 15/nucleotide-binding oligomerization domain-containing 2 (CARD15/NOD2) gene show impaired nuclear factor kappa B (NF-κB) activation in response to muramyl dipeptide (MDP), as determined by Western blotting. We applied phospho-specific flow cytometry to examine NF-κB and p38 activation in whole blood monocytes of 16 CD patients with or without the 1007fs and previously described rare mutations of the CARD15 gene, and healthy reference subjects. Aliquots of whole blood were supplemented with MDP (0-1000 ng/mL), incubated for 10-40 min and processed for flow cytometry. Bacterial lipopolysaccharide (LPS) was used as a positive control agonist. We found that NF-κB and p38 phosphorylation induced by MDP was not detectable in monocytes of patients homozygous for the CARD15 1007fs mutation, while those induced by LPS were normal. We also determined MDP-induced NF-κB phosphorylation levels in nuclear extracts of mononuclear cells separated from blood using enzyme-linked immunosorbent assay (ELISA), and observed that the levels decreased in a 1007fs mutation-dose dependent manner. We conclude that phospho-specific whole blood flow cytometry provides a means to study phosphorylation of NF-κB and p38 in clinical samples and can be applied to screening of CD patients homozygous for the CARD15 1007fs mutation.

Patients with acute pancreatitis complicated by organ dysfunction show abnormal peripheral blood polymorphonuclear leukocyte signaling

BACKGROUND/OBJECTIVES

Circulating polymorphonuclear leukocytes (PMNLs) may contribute to development of organ dysfunction in acute pancreatitis (AP). We outlined aberrations in PMNL signaling profiles in patients with AP complicated by organ dysfunction and immune suppression.

METHODS

Study comprised 13 patients treated at intensive care unit due to severe AP complicated by vital organ dysfunction. Mean proportion (SEM) of HLA-DR-positive monocytes was 55.0% (4.1%). 13 healthy volunteers served as reference subjects. Phosphorylation of PMNL NFκB, p38, ERK1/2 and STAT3, -5 and -6 was determined using whole blood flow cytometry. Transmigration of PMNLs was studied using endothelial EA-HY cell monolayer.

RESULTS

Proportions of NFκB phosphorylation-positive PMNLs were lower in the patients' than in reference subjects' blood samples supplemented with tumor necrosis factor. p38 phosphorylation was normal while ERK1/2 phosphorylation was decreased. STAT3 was constitutively activated in five patients. Proportion of patients' pSTAT6-positive cells was normal while fluorescence intensity was decreased. STAT5 phosphorylation was normal. Transmigration of patients' PMNLs was increased.

CONCLUSIONS

In patients with AP complicated by organ dysfunction proportion of pNFκB-positive PMNLs is decreased. This impairs patients' defense mechanisms against infection. Despite immune suppression, PMNL transmigration was increased and p38 phosphorylation capacity was not depressed, which may contribute to end organ inflammation and dysfunction.

The clinical course of acute pancreatitis and the inflammatory mediators that drive it

Acute pancreatitis (AP) is a common emergency condition. In the majority of cases, it presents in a mild and self-limited form. However, about 20% of patients develop severe disease with local pancreatic complications (including necrosis, abscess, or pseudocysts), systemic organ dysfunction, or both. A modern classification of AP severity has recently been proposed based on the factors that are causally associated with severity of AP. These factors are both local (peripancreatic necrosis) and systemic (organ failure). In AP, inflammation is initiated by intracellular activation of pancreatic proenzymes and/or nuclear factor-κB. Activated leukocytes infiltrate into and around the pancreas and play a central role in determining AP severity. Inflammatory reaction is first local, but may amplify leading to systemic overwhelming production of inflammatory mediators and early organ failure. Concomitantly, anti-inflammatory cytokines and specific cytokine inhibitors are produced. This anti-inflammatory reaction may overcompensate and inhibit the immune response, rendering the host at risk for systemic infection. Currently, there is no specific treatment for AP. However, there are several early supportive treatments and interventions which are beneficial. Also, increasing the understanding of the pathogenesis of systemic inflammation and the development of organ dysfunction may provide us with future treatment modalities.

Signalling profiles of circulating leucocytes in patients recovered from reactive arthritis

OBJECTIVES

Reactive arthritis (ReA) is a sterile joint inflammation triggered by a remote infection and associated with human leucocyte antigen (HLA)-B27. Its pathogenesis is unknown, but abnormal response to microbial structures or endogenous inflammatory mediators may be involved. We studied responses in leucocyte signalling profiles in patients with previous ReA after a full recovery.

METHOD

The study comprised 10 HLA-B27-positive healthy subjects with a history of Yersinia enterocolitica-triggered ReA (B27+ReA+) and 20 healthy reference subjects, of whom 10 carried HLA-B27 (B27+ReA-) and 10 did not (B27-ReA-). Phosphospecific fluorescent monoclonal antibodies and flow cytometry were used to determine activation of nuclear factor kappa B (NF-κB), signal transducers and activators of transcription (STATs) 1, 3, 5, and 6, and two mitogen-activated protein (MAP) kinases, p38 and extracellular signal-regulated kinase (ERK)1/2, in monocytes, lymphocytes, lymphocyte subsets, and neutrophils. B27+ReA+ and B27-ReA- whole-blood samples were incubated with Yersinia with or without infliximab to study the role of tumour necrosis factor (TNF) in lymphocyte subset activation. Samples of the three subject groups were studied using soluble bacterial or endogenous stimuli. Fluorescence levels were determined as relative fluorescence units (RFU) and the proportion of positively fluorescing cells.

RESULTS

The intracellular activation of circulating leucocytes in response to soluble stimuli was consistently comparable in B27+ReA+, B27+ReA-, and B27-ReA- subjects. Infliximab inhibited Yersinia-induced lymphocyte NF-κB phosphorylation similarly in B27+ReA+ and B27-ReA- groups.

CONCLUSIONS

ReA susceptibility is not reflected in leucocyte signalling profiles elicited by phlogistic stimuli. However, the possibility remains that aberrations occur in response to combinations of stimuli, such as those associated with leucocyte adhesion.

STAT3 regulates monocyte TNF-alpha production in systemic inflammation caused by cardiac surgery with cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass (CPB) surgery initiates a controlled systemic inflammatory response characterized by a cytokine storm, monocytosis and transient monocyte activation. However, the responsiveness of monocytes to Toll-like receptor (TLR)-mediated activation decreases throughout the postoperative course. The purpose of this study was to identify the major signaling pathway involved in plasma-mediated inhibition of LPS-induced tumor necrosis factor (TNF)-α production by monocytes.

METHODOLOGY/PRINCIPAL FINDINGS

Pediatric patients that underwent CPB-assisted surgical correction of simple congenital heart defects were enrolled (n = 38). Peripheral blood mononuclear cells (PBMC) and plasma samples were isolated at consecutive time points. Patient plasma samples were added back to monocytes obtained pre-operatively for ex vivo LPS stimulations and TNF-α and IL-6 production was measured by flow cytometry. LPS-induced p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-κB activation by patient plasma was assessed by Western blotting. A cell-permeable peptide inhibitor was used to block STAT3 signaling. We found that plasma samples obtained 4 h after surgery, regardless of pre-operative dexamethasone treatment, potently inhibited LPS-induced TNF-α but not IL-6 synthesis by monocytes. This was not associated with attenuation of p38 MAPK activation or IκB-α degradation. However, abrogation of the IL-10/STAT3 pathway restored LPS-induced TNF-α production in the presence of suppressive patient plasma.

CONCLUSIONS/SIGNIFICANCE

Our findings suggest that STAT3 signaling plays a crucial role in the downregulation of TNF-α synthesis by human monocytes in the course of systemic inflammation in vivo. Thus, STAT3 might be a potential molecular target for pharmacological intervention in clinical syndromes characterized by systemic inflammation.

The first step in utilizing immune-modulating therapies: immune status determination

Recently, a single center study conducted by Oiva and coworkers and published in Critical Care demonstrated that phospho-specific whole blood flow cytometry could be used to assess activated signaling pathways in leukocytes isolated from pancreatitis patients. The authors demonstrated that this methodology had the potential to determine the current status of a patient's immune state. Although the experimental cohort was clinically homogeneous, the observed data were heterogeneous. Altogether, these results suggest that prior to administering immune-modulatory therapies in inflammatory diseases, it will be beneficial to first determine immune status. Rapid results from whole blood phospho-specific flow cytometry may allow for determination of immune status, improve early diagnosis, and provide a rational basis for immunomodulatory therapies.

Acute pancreatitis with organ dysfunction associates with abnormal blood lymphocyte signaling: controlled laboratory study

Introduction

Severe acute pancreatitis is associated with systemic inflammation, compensatory immune suppression, secondary infections, vital organ dysfunction, and death.

Our study purpose was to delineate signaling profiles of circulating lymphocytes in acute pancreatitis complicated by organ dysfunction.

Methods

Sixteen patients with acute pancreatitis, dysfunction of vital organ(s), and immune suppression (proportion of HLA-DR Human Leukocyte Antigen - DR - positive monocytes < 80%) participated. Healthy volunteers served as reference subjects. Using phospho-specific whole blood flow cytometry we studied lymphocyte phosphorylation of nuclear factor-κB (NFκB), mitogen-activated protein kinases p38 and extracellular signal-regulated kinases (ERK)1/2, and signal transducers and activators of transcription (STATs) 1, 3, and 6. Statistical comparisons were performed with the Wilcoxon-Mann-Whitney test.

Results

In blood samples supplemented with tumor necrosis factor, E. coli or S. aureus, phosphorylation levels of NFκB were lower and levels of p38 were higher in patients with acute pancreatitis than healthy subjects. Low NFκB activation involved CD3+CD4+ and CD3+CD8+ lymphocytes. ERK1/2 phosphorylation induced by co-stimulation with phorbol 12-myristate 13-acetate and calcium ionophore A23187 was depressed in patients. STAT3 was constitutively activated in patients' CD3+CD4+ and CD3+CD8+ lymphocytes. Also, IL-6-induced STAT1 phosphorylation was impaired while IL-4-induced STAT6 phosphorylation was enhanced.

Conclusions

Lymphocytes of patients with acute pancreatitis, organ dysfunction and immune suppression show impaired NFκB activation, which increases infection risk and enhanced p38 activation, which sustains inflammation. Secondly, they indicate constitutive STAT3 activation, which may favor Th17 lineage of CD4+ lymphocyte differentiation. Thirdly, they reveal impaired STAT1 activation and enhanced STAT6 activation, denoting a shift from Th1 towards Th2 differentiation.