Involvement of the fractalkine pathway in the pathogenesis of childhood hemolytic uremic syndrome

Assessment of interleukin-10 promoter variant (-1082A/G) and cytokine production in patients with hemolytic uremic syndrome

Introduction

Hemolytic uremic syndrome (HUS) is a condition that results in acute kidney failure mainly in children, which is caused by Shiga toxin-producing Escherichia coli and inflammatory response. Although anti-inflammatory mechanisms are triggered, studies on the implication in HUS are scarce. Interleukin-10 (IL-10) regulates inflammation in vivo, and the interindividual differences in its expression are related to genetic variants. Notably, the single nucleotide polymorphism (SNP) rs1800896 -1082 (A/G), located in the IL-10 promoter, regulates cytokine expression.

Methods

Plasma and peripheral blood mononuclear cells (PBMC) were collected from healthy children and HUS patients exhibiting hemolytic anemia, thrombocytopenia, and kidney damage. Monocytes identified as CD14⁺ cells were analyzed within PBMC by flow cytometry. IL-10 levels were quantified by ELISA, and SNP -1082 (A/G) was analyzed by allele-specific PCR.

Results

Circulating IL-10 levels were increased in HUS patients, but PBMC from these patients exhibited a lower capacity to secrete this cytokine compared with those from healthy children. Interestingly, there was a negative association between the circulating levels of IL-10 and inflammatory cytokine IL-8. We observed that circulating IL-10 levels were threefold higher in HUS patients with -1082G allele in comparison to AA genotype. Moreover, there was relative enrichment of GG/AG genotypes in HUS patients with severe kidney failure.

Discussion

Our results suggest a possible contribution of SNP -1082 (A/G) to the severity of kidney failure in HUS patients that should be further evaluated in a larger cohort.

Human Glomerular Endothelial Cells Treated With Shiga Toxin Type 2 Activate γδ T Lymphocytes

The hemolytic uremic syndrome associated with diarrhea, a consequence of Shiga toxin (Stx)-producing Escherichia coli infection, is a common cause of pediatric acute renal failure in Argentina. Stx type 2a (Stx2a) causes direct damage to renal cells and induces local inflammatory responses that involve secretion of inflammatory mediators and the recruitment of innate immune cells. γδ T cells constitute a subset of T lymphocytes, which act as early sensors of cellular stress and infection. They can exert cytotoxicity against infected and transformed cells, and produce cytokines and chemokines. In this study, we investigated the activation of human peripheral γδ T cells in response to the incubation with Stx2a-stimulated human glomerular endothelial cells (HGEC) or their conditioned medium, by analyzing in γδ T lymphocytes, the expression of CD69, CD107a, and perforin, and the production of TNF-α and IFN-γ. In addition, we evaluated by confocal microscopy the contact between γδ T cells and HGEC. This analysis showed an augmentation in cellular interactions in the presence of Stx2a-stimulated HGEC compared to untreated HGEC. Furthermore, we observed an increase in cytokine production and CD107a expression, together with a decrease in intracellular perforin when γδ T cells were incubated with Stx2a-treated HGEC or their conditioned medium. Interestingly, the blocking of TNF-α by Etanercept reversed the changes in the parameters measured in γδ T cells incubated with Stx2a-treated HGEC supernatants. Altogether, our results suggest that soluble factors released by Stx2a-stimulated HGEC modulate the activation of γδ T cells, being TNF-α a key player during this process.

Pathogenic role of inflammatory response during Shiga toxin-associated hemolytic uremic syndrome (HUS)

Hemolytic uremic syndrome (HUS) is defined as a triad of noninmune microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. The most frequent presentation is secondary to Shiga toxin (Stx)-producing Escherichia coli (STEC) infections, which is termed postdiarrheal, epidemiologic or Stx-HUS, considering that Stx is the necessary etiological factor. After ingestion, STEC colonize the intestine and produce Stx, which translocates across the intestinal epithelium. Once Stx enters the bloodstream, it interacts with renal endothelial and epithelial cells, and leukocytes. This review summarizes the current evidence about the involvement of inflammatory components as central pathogenic factors that could determine outcome of STEC infections. Intestinal inflammation may favor epithelial leakage and subsequent passage of Stx to the systemic circulation. Vascular damage triggered by Stx promotes not only release of thrombin and increased fibrin concentration but also production of cytokines and chemokines by endothelial cells. Recent evidence from animal models and patients strongly indicate that several immune cells types may participate in HUS physiopathology: neutrophils, through release of proteases and reactive oxygen species (ROS); monocytes/macrophages through secretion of cytokines and chemokines. In addition, high levels of Bb factor and soluble C5b-9 (sC5b-9) in plasma as well as complement factors adhered to platelet-leukocyte complexes, microparticles and microvesicles, suggest activation of the alternative pathway of complement. Thus, acute immune response secondary to STEC infection, the Stx stimulatory effect on different immune cells, and inflammatory stimulus secondary to endothelial damage all together converge to define a strong inflammatory status that worsens Stx toxicity and disease.

Hemodialysis-related changes in phenotypical features of monocytes

Hemodialysis (HD) patients exhibit chronic inflammation and leukocyte activation. We investigated the surface-marker profile of monocytes by flow cytometry to assess the chronic effect of uremia and the acute effect of dialysis on their phenotypical and functional features in 16 healthy controls (CON) and 15 HD patients before and after a polysulfone-based dialysis session. Median fluorescence intensities were analyzed indicating expression of CD14, CD16, integrins (CD11b, CD18), chemokine receptors (CCR2, CX3CR1), scavenger receptors (CD36, CD163) and Toll-like receptor-2 (TLR2). Before and after dialysis, HD patients harbour 0.9-fold less CD14⁺⁺CD16^- (Mo1), 1.8-fold more CD14⁺⁺CD16⁺ (Mo2) and CD14⁺CD16⁺⁺ (Mo3) monocytes than CON. HD patients' Mo1 showed elevated expression of CD11b (1.7-fold), CD18 (1.2-fold) and CD36 (2.1-fold), whereas CD163 expression was reduced in Mo1 and Mo2 (0.6-fold) compared to CON. These markers remained unaffected by dialysis. CX3CR1 expression on Mo2 and Mo3 was lower in HD patients before (0.8-fold) and further diminished after dialysis (0.6-fold). Stimulation of monocytes resulted in diminished responses in HD patients compared to CON. In conclusion, a systematic analysis of the expression of particular surface markers on distinct monocyte subsets may help to distinguish between uremia and/or dialysis induced effects and to evaluate the functionality of monocytes and biocompatibility of HD.

LMP1 signaling pathway activates IRF4 in latent EBV infection and a positive circuit between PI3K and Src is required

Interferon (IFN) regulatory factors (IRFs) have crucial roles in immune regulation and oncogenesis. We have recently shown that IRF4 is activated through c-Src-mediated tyrosine phosphorylation in virus-transformed cells. However, the intracellular signaling pathway triggering Src activation of IRF4 remains unknown. In this study, we provide evidence that Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) promotes IRF4 phosphorylation and markedly stimulates IRF4 transcriptional activity, and that Src mediates LMP1 activation of IRF4. As to more precise mechanism, we show that LMP1 physically interacts with c-Src, and the phosphatidylinositol 3 kinase (PI3K) subunit P85 mediates their interaction. Depletion of P85 by P85-specific short hairpin RNAs disrupts their interaction and diminishes IRF4 phosphorylation in EBV-transformed cells. Furthermore, we show that Src is upstream of PI3K for activation of both IRF4 and Akt. In turn, inhibition of PI3K kinase activity by the PI3K-speicfic inhibitor LY294002 impairs Src activity. Our results show that LMP1 signaling is responsible for IRF4 activation, and further characterize the IRF4 regulatory network that is a promising therapeutic target for specific hematological malignancies.

Enterohemorrhagic Escherichia coli Pathogenesis and the Host Response

Enterohemorrhagic Escherichia coli (EHEC) is a highly pathogenic bacterial strain capable of causing watery or bloody diarrhea, the latter termed hemorrhagic colitis, and hemolytic-uremic syndrome (HUS). HUS is defined as the simultaneous development of non-immune hemolytic anemia, thrombocytopenia, and acute renal failure. The mechanism by which EHEC bacteria colonize and cause severe colitis, followed by renal failure with activated blood cells, as well as neurological symptoms, involves the interaction of bacterial virulence factors and specific pathogen-associated molecular patterns with host cells as well as the host response. The innate immune host response comprises the release of antimicrobial peptides as well as cytokines and chemokines in addition to activation and/or injury to leukocytes, platelets, and erythrocytes and activation of the complement system. Some of the bacterial interactions with the host may be protective in nature, but, when excessive, contribute to extensive tissue injury, inflammation, and thrombosis, effects that may worsen the clinical outcome of EHEC infection. This article describes aspects of the host response occurring during EHEC infection and their effects on specific organs.

Association of haemolytic uraemic syndrome with dysregulation of chemokine receptor expression in circulating monocytes

Haemolytic uraemic syndrome (HUS) is the major complication of Escherichia coli gastrointestinal infections that are Shiga toxin (Stx) producing. Monocytes contribute to HUS evolution by producing cytokines that sensitize endothelial cells to Stx action and migration to the injured kidney. As CC chemokine receptors (CCRs) are involved in monocyte recruitment to injured tissue, we analysed the contribution of these receptors to the pathogenesis of HUS. We analysed CCR1, CCR2 and CCR5 expression in peripheral monocytes from HUS patients during the acute period, with healthy children as controls. We observed an increased expression of CCRs per cell in monocytes from HUS patients, accompanied by an increase in the absolute number of monocytes CCR1+, CCR2+ and CCR5+. It is interesting that prospective analysis confirmed that CCR1 expression positively correlated with HUS severity. The evaluation of chemokine levels in plasma showed that regulated on activation of normal T-cell-expressed and -secreted (RANTES) protein was reduced in plasma from patients with severe HUS, and this decrease correlated with thrombocytopenia. Finally, the expression of the higher CCRs was accompanied by a loss of functionality which could be due to a mechanism for desensitization to compensate for altered receptor expression. The increase in CCR expression correlates with HUS severity, suggesting that the dysregulation of these receptors might contribute to an increased risk of renal damage. Activated monocytes could be recruited by chemokines and then receptors could be dysregulated. The dysregulation of CCRs and their ligands observed during the acute period suggests that a chemokine pathway would participate in HUS development.

Natural killer T (NKT) cells accelerate Shiga toxin type 2 (Stx2) pathology in mice

Shiga toxin-producing Escherichia coli (STEC) is a leading cause of childhood renal disease Hemolytic Uremic Syndrome (HUS). The involvement of renal cytokines and chemokines is suspected to play a critical role in disease progression. In current article, we tested the hypothesis that NKT cells are involved in Stx2-induced pathology in vivo. To address this hypothesis we compared Stx2 toxicity in WT and CD1 knockout (KO) mice. In CD1KO mice, which lack natural killer T (NKT) cells, Stx2-induced pathologies such as weight loss, renal failure, and death were delayed. In WT mice, Stx2-specific selective increase in urinary albumin occurs in later time points, and this was also delayed in NKT cell deficient mice. NKT cell-associated cytokines such as IL-2, IL-4, IFN-γ, and IL-17 were detected in kidney lysates of Stx2-injected WT mice with the peak around 36 h after Stx2 injection. In CD1KO, there was a delay in the kinetics, and increases in these cytokines were observed 60 h post Stx2 injection. These data suggest that NKT cells accelerate Stx2-induced pathology in mouse kidneys. To determine the mechanism by which NKT cells promote Stx2-associated disease, in vitro studies were performed using murine renal cells. We found that murine glomerular endothelial cells and podocytes express functional CD1d molecules and can present exogenous antigen to NKT cells. Moreover, we observed the direct interaction between Stx2 and the receptor Gb₃ on the surface of mouse renal cells by 3D STORM-TIRF which provides single molecule imaging. Collectively, these data suggest that Stx2 binds to Gb₃ on renal cells and leads to aberrant CD1d-mediated NKT cell activation. Therefore, strategies targeting NKT cells could have a significant impact on Stx2-associated renal pathology in STEC disease.

Differential expression of the fractalkine chemokine receptor (CX3CR1) in human monocytes during differentiation

Circulating monocytes (Mos) may continuously repopulate macrophage (MAC) or dendritic cell (DC) populations to maintain homeostasis. MACs and DCs are specialized cells that play different and complementary immunological functions. Accordingly, they present distinct migratory properties. Specifically, whereas MACs largely remain in tissues, DCs are capable of migrating from peripheral tissues to lymphoid organs. The aim of this work was to analyze the expression of the fractalkine receptor (CX3CR1) during the monocytic differentiation process. Freshly isolated Mos express high levels of both CX3CR1 mRNA and protein. During the Mo differentiation process, CX3CR1 is downregulated in both DCs and MACs. However, MACs showed significantly higher CX3CR1 expression levels than did DC. We also observed an antagonistic CX3CR1 regulation by interferon (IFN)-γ and interleukin (IL)-4 during MAC activation through the classical and alternative MAC pathways, respectively. IFN-γ inhibited the loss of CX3CR1, but IL-4 induced it. Additionally, we demonstrated an association between CX3CR1 expression and apoptosis prevention by soluble fractalkine (sCX3CL1) in Mos, DCs and MACs. This is the first report demonstrating sequential and differential CX3CR1 modulation during Mo differentiation. Most importantly, we demonstrated a functional link between CX3CR1 expression and cell survival in the presence of sCX3CL1.

Hemolytic uremic syndrome: toxins, vessels, and inflammation

Hemolytic uremic syndrome (HUS) is characterized by thrombotic microangiopathy of the glomerular microcirculation and other vascular beds. Its defining clinical phenotype is acute kidney injury (AKI), microangiopathic anemia, and thrombocytopenia. There are many etiologies of HUS including infection by Shiga toxin-producing bacterial strains, medications, viral infections, malignancy, and mutations of genes coding for proteins involved in the alternative pathway of complement. In the aggregate, although HUS is a rare disease, it is one of the most common causes of AKI in previously healthy children and accounts for a sizable number of pediatric and adult patients who progress to end stage kidney disease. There has been great progress over the past 20 years in understanding the pathophysiology of HUS and its related disorders. There has been intense focus on vascular injury in HUS as the major mechanism of disease and target for effective therapies for this acute illness. In all forms of HUS, there is evidence of both systemic and intra-glomerular inflammation and perturbations in the immune system. Renewed investigation into these aspects of HUS may prove helpful in developing new interventions that can attenuate glomerular and tubular injury and improve clinical outcomes in patients with HUS.

Treatment and prevention of enterohemorrhagicEscherichia coliinfection and hemolytic uremic syndrome

Over a quarter century after the discovery of verocytotoxin and the first report by Karmali and colleagues of cases of postdiarrheal hemolytic uremic syndrome (HUS) caused by verotoxigenic Escherichia coli (VTEC), otherwise known as Shiga-toxigenic E. coli (STEC), successful treatment of these infections has remained elusive. This is because the pathological insult producing the clinical picture of HUS occurs early in the disease process and curtails quickly, making treatment intervention a largely vain hope. Nevertheless, understanding of the pathogenesis of HUS has expanded and, as a result, we can expect a future breakthrough in the treatment of this life-threatening condition. This review examines the pathogenesis of HUS and explores targets for treatment, including the reasons why certain therapies have failed and why future therapies could be successful. This review also examines the status of vaccine development in prevention of VTEC/STEC disease.

Advances in pathogenesis and therapy of hemolytic uremic syndrome caused by Shiga toxin-2

Shiga toxin (Stx) producing Escherichia coli (STEC) is responsible to bloody diarrhea (hemorrhagic colitis) and the hemolytic uremic syndrome (HUS). STEC strains carry inducible lambda phages integrated into their genomes that encode Stx 1 and/or 2, with several allelic variants each one. O157:H7 is the serotype that was documented in the vast majority of HUS cases although non-O157 serotypes have been increasingly reported to account for HUS cases. However, the outbreak that occurred in central Europe during late spring of 2011 showed that the pathogen was E. coli O104:H4. More than 4,000 persons were infected mainly in Germany, and it produced more than 900 cases of HUS resulting in 54 deaths. E. coli O104:H4 is a hybrid organism that combines some of the virulence genes of STEC and enteroaggregative E. coli specially production of Stx2 and the adherence mechanisms to intestinal epithelium. The differences in the epidemiology and presentation of E. coli pathogen meant a challenge for public health and scientific research to increase the knowledge of HUS-pathophysiology and to improve available therapies to treat HUS.

Cytokine production is altered in monocytes from children with hemolytic uremic syndrome

PURPOSE

The interaction of Shiga toxin (Stx) and/or lipopolysaccharide (LPS) with monocytes (Mo) may be central to the pathogenesis of hemolytic uremic syndrome (HUS), providing the cytokines necessary to sensitize endothelial cells to Stx action. We have previously demonstrated phenotypical alterations in Mo from HUS patients, including increased number of CD16+ Mo. Our aim was to investigate cytokine production in Mo from HUS patients.

METHODS

We evaluated TNF-α and IL-10 intracellular contents and secretion in the different Mo subsets in mild (HUS 1) and moderate/severe (HUS 2 + 3) patients. As controls, we studied healthy (HC) and infected children (IC). We also studied Mo responsive capacity towards LPS, measuring the modulation of Mo surface molecules and cytokine production.

RESULTS

In basal conditions, the intracellular measurement of TNF-α and IL-10 revealed that the highest number of cytokine-producing Mo was found in HUS 2 + 3 and IC, whereas LPS caused a similar increase in TNF-α and IL-10-producing Mo for all groups. However, when evaluating the release of TNF-α and IL-10, we found a diminished secretion capacity in the entire HUS group and IC compared to HC in basal and LPS conditions. Similarly, a lower Mo response to LPS in HUS 2 + 3 and IC groups was observed when surface markers were studied.

CONCLUSION

These results indicate that Mo from severe cases of HUS, similar to IC but different to mild HUS cases, present functional changes in Mo subpopulations and abnormal responses to LPS.

Chemokine receptor CCR1 disruption limits renal damage in a murine model of hemolytic uremic syndrome

Shiga toxin (Stx)-producing Escherichia coli is the main etiological agent that causes hemolytic uremic syndrome (HUS), a microangiopathic disease characterized by hemolytic anemia, thrombocytopenia, and acute renal failure. Although direct cytotoxic effects on endothelial cells by Stx are the primary pathogenic event, there is evidence that indicates the inflammatory response mediated by polymorphonuclear neutrophils and monocytes as the key event during HUS development. Because the chemokine receptor CCR1 participates in the pathogenesis of several renal diseases by orchestrating myeloid cell kidney infiltration, we specifically addressed the contribution of CCR1 in a murine model of HUS. We showed that Stx type 2-treated CCR1(-/-) mice have an increased survival rate associated with less functional and histological renal damage compared with control mice. Stx type 2-triggered neutrophilia and monocytosis and polymorphonuclear neutrophil and monocyte renal infiltration were significantly reduced and delayed in CCR1(-/-) mice compared with control mice. In addition, the increase of the inflammatory cytokines (tumor necrosis factor-α and IL-6) in plasma was delayed in CCR1(-/-) mice compared with control mice. These data demonstrate that CCR1 participates in cell recruitment to the kidney and amplification of the inflammatory response that contributes to HUS development. Blockade of CCR1 could be important to the design of future therapies to restrain the inflammatory response involved in the development of HUS.

Newly emerging therapies targeting viral-related lymphomas

Gamma-(γ)-herpes virus lymphomas comprise a heterogenous group of B-cell and T-cell neoplasms most commonly associated with Epstein-Barr virus and rarely human herpes virus-8 infection. Adult T-cell leukemia/lymphoma (ATLL) is a unique disease entity caused by the human T-cell lymphotrophic virus, type 1 (HTLV-I), the only retrovirus known to cause cancer in humans. Viral lymphomas behave aggressively and disproportionally affect immunocompromised individuals and those living in underdeveloped regions. These diseases are often difficult to treat with conventional approaches. Despite recent advancements using cytotoxic, lymphoma-specific, and adoptive therapies, the long-term outcome of patients with γ-herpesvirus lymphomas occurring in severely immunocompromised patients and ATLL continues to be poor. Lytic-inducing therapies targeting NF-κB, and viral and tumor cell epigenetic mechanisms afford the advantage of exploiting the intrinsic presence of oncogenic viruses to eradicate infected tumor cells. In this review, viral-related lymphomas and newly emerging clinical approaches targeting viral latency are discussed.

Newer developments in adult T-cell leukemia/lymphoma therapeutics

INTRODUCTION

Adult T-cell leukemia/lymphoma (ATL) is a rare disease with a unique geographic distribution. Conducting controlled randomized trials to assess the effective therapeutic strategies has therefore been a significant challenge to date.

AREAS COVERED

This review explores the natural history and diagnostic evaluation of ATL, followed by a focused review of existing studies on the most potent individual pharmaceutical agents and combinations used in the therapy of this malignancy. Readers will acquire considerable insights about the clinical subsets, diagnosis and the most effective therapies used in various ATL types.

EXPERT OPINION

International, multicenter, randomized clinical trials are essential to design optimal therapeutic strategies for various ATL subsets. It appears that patients with acute ATL type benefit considerably from the first-line combined antiviral therapy with zidovudine and interferon alpha, whereas patients with ATL of the lymphoma type may experience a better outcome with intensive chemotherapy. The role of therapy in smoldering and chronic disease types remains to be clarified. In addition, the results of allogeneic stem-cell transplantation in ATL appear promising, as up to 40% of patients who achieve remission and have suitable donors can now become long-term survivors. Prospective evaluation of novel effective agents and their incorporation into various therapeutic algorithms is stringently needed.

Cytokine and chemokine levels in tears from healthy subjects

PURPOSE

There is growing evidence for the existence of an 'immune tone' in normal tears. The aim of this study was to determine the levels of a large panel of cytokines and chemokines in tears obtained from healthy subjects. These levels can then serve as baseline values for comparison with patients suffering from ocular surface diseases.

SUBJECTS AND METHODS

Nine healthy subjects participated in this study, and normal ocular surface health was documented by the results of a dry eye questionnaire, Schirmer strip wetting, and vital staining of the cornea. Four microliters of tears were collected from each eye and analysed separately with multiplex bead-based assays for the concentration of 30 cytokines and chemokines.

RESULTS

Twenty-five cytokines/chemokines were detected. CCL11/Eotaxin1, GM-CSF, G-CSF, IFN-γ, IL-2, IL-3, IL-4, IL-5, IL-10, IL-13, IL-12p70, IL-15, CX3CL1/Fractalkine, TNF-α, epidermal growth factor, and CCL4/MIP-1β were present at 5-100 pg/ml. IL-1β, IL-6, IL-7A, CXCL8/IL-8, and CCL2/MCP-1 were present at 100-400 pg/ml. IL-1Ra, CXCL10/IP-10 and vascular endothelial growth factor were present at more than 1000 pg/ml.

CONCLUSION

Multiplex bead-based assays are convenient for cytokine/chemokine detection in tears. Fracktalkine has been detected in human healthy tears for the first time. The knowledge of cytokine/chemokine concentrations in tears from normal subjects is an important reference for further comparison with patients suffering from ocular surface diseases. Variability in their levels can reflect a phenomenon of potential importance for the understanding of the ocular surface cytokine pattern.

Shiga toxin-associated hemolytic uremic syndrome: pathophysiology of endothelial dysfunction

Shiga toxin (Stx)-producing enterohemorrhagic Escherichia coli O157:H7 has become a global threat to public health, as a primary cause of a worldwide spread of hemorrhagic colitis complicated by diarrhea-associated hemolytic uremic syndrome (HUS), a disorder of thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure that mainly affects early childhood. Endothelial dysfunction has been recognized as the trigger event in the development of microangiopathic processes. Endothelial cells, mainly those located in the renal microvasculature, are primary targets of the toxic effects of Stx1 and 2. Stxs bound to their specific globotriaosylceramide (Gb3Cer) receptor on the cell surface trigger a cascade of signaling events, involving NF-κB activation, that induce expression of genes encoding for adhesion molecules and chemokines, and culminate in the adhesion of leukocytes to endothelial cells, thereby increasing the endothelial susceptibility to leukocyte-mediated injury. Activated endothelial cells in response to Stxs lose the normal thromboresistance phenotype and become thrombogenic, initiating microvascular thrombus formation. Evidence is emerging that complement activation in response to Stxs favors platelet thrombus formation on endothelial cells, which may play a role in amplifying the inflammation-thrombosis circuit in Stx-associated HUS.

Exploration of disease mechanism in acute kidney injury using a multiplex bead array assay: a nested case-control pilot study

BACKGROUND

Acute kidney injury (AKI) following cardiac surgery with cardiopulmonary bypass (CPB) causes increased morbidity and mortality.

OBJECTIVE

To evaluate the plasma profile of biomarkers potentially involved in AKI development following CPB.

METHODS

In a nested case-control study, plasma levels of 27 biomarkers in 11 AKI cases were compared with 25 controls.

RESULTS

Pre-CPB, plasma levels of epidermal growth factor and macrophage inflammatory protein-1beta, 2 h following CPB, soluble vascular cell adhesion molecule-1 (sVCAM-1), fractalkine and macrophage inflammatory protein-1alpha, and at later time points, sVCAM-1 and interleukin-6 were associated with AKI.

CONCLUSION

Biomarkers associated with AKI following CPB may merit further study.

Expression profiles of adult T-cell leukemia-lymphoma and associations with clinical responses to zidovudine and interferon alpha

Adult T-cell leukemia-lymphoma (ATLL) is an HTLV-1-associated lymphoproliferative malignancy that is frequently fatal. We compared gene expression profiles (GEPs) of leukemic specimens from nine patients with ATLL at the time of diagnosis and immediately after combination therapy with zidovudine (AZT) and interferon alpha (IFNalpha). GEPs were also related to genetic aberrations determined by comparative genomic hybridization. We identified several genes anomalously over-expressed in the ATLL leukemic cells at the mRNA level, including LYN, CSPG2, and LMO2, and confirmed LMO2 expression in ATLL cells at the protein level. In vivo AZT-IFNalpha therapy evoked a marked induction of interferon-induced genes accompanied by repression of cell-cycle regulated genes, including those encoding ribosomal proteins. Remarkably, patients not responding to AZT-IFNalpha differed most from responding patients in lower expression of these same IFN-responsive genes, as well as components of the antigen processing and presentation apparatus. Demonstration of specific gene expression signatures associated with response to AZT-IFNalpha therapy may provide novel insights into the mechanisms of action in ATLL.

Adult T-cell leukemia/lymphoma and HTLV-1

Human T-cell leukemia/lymphoma virus type 1 (HTLV-1) was the first oncogenic human retrovirus to be discovered, more than 25 years ago. HTLV-1 infects 15 to 20 million individuals worldwide. This oncoretrovirus can be transmitted in three ways: horizontally (sexually), vertically (mother to child), and via blood transfusion. HTLV-1 causes two major diseases: adult T-cell leukemia/lymphoma (ATLL) and tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). ATLL can be classified into four major subtypes: a smoldering type, a chronic type, a lymphoma type, and a leukemic type. Because of intrinsic chemoresistance and severe immunosuppression, the survival rate of ATLL patients, especially those who develop the acute leukemic or lymphoma forms, is very poor, and such clonal malignant CD4 expansion remains one of the most severe lymphoproliferations. This article discusses a number of recent treatments including antiretroviral therapy, aggressive chemotherapy, and allogeneic bone-marrow transplantation, as well as new drugs.

Hemolytic uremic syndrome: pathogenesis and update of interventions

The typical form of hemolytic uremic syndrome (HUS) is the major complication of Shiga toxin-producing Escherichia coli infections. HUS is a critical health problem in Argentina since it is the main cause of acute renal failure in children and the second cause of chronic renal failure, accounting for 20% of renal transplants in children and adolescents in Argentina. Despite extensive research in the field, the mainstay of treatment for patients with HUS is supportive therapy, and there are no specific therapies preventing or ameliorating the disease course. In this review, we present the current knowledge about pathogenic mechanisms and discuss traditional and innovative therapeutic approaches, with special focus in Argentinean contribution. The hope that a better understanding of transmission dynamics and pathogenesis of this disease will produce better therapies to prevent the acute mortality and the long-term morbidity of HUS is the driving force for intensified research.

Interleukin-10 and interferon-gamma modulate surface expression of fractalkine-receptor (CX(3)CR1) via PI3K in monocytes

The membrane-anchored form of the chemokine fractalkine (CX(3)CL1) has been identified as a novel adhesion molecule that interacts with its specific receptor (CX(3)CR1) expressed in monocytes, T cells and natural killer cells to induce adhesion. In addition, CX(3)CL1 can be cleaved from the cell membrane to induce chemotaxis of CX(3)CR1-expressing leucocytes. Recently, marked variations in CX(3)CR1 monocyte expression have been observed during several pathological conditions. Regulation of CX(3)CR1 in monocytes during basal or inflammatory/anti-inflammatory conditions is poorly understood. The aim of this study was therefore to examine CX(3)CR1 expression during monocyte maturation and the effect of soluble mediators on this process. We found that basal expression of CX(3)CR1 in fresh monocytes was reduced during culture, and that lipopolysacchairde accelerated this effect. In contrast, interleukin-10 and interferon-gamma treatment abrogated CX(3)CR1 down-modulation, through a phosphatidylinositol 3 kinase-dependent pathway. Most importantly, CX(3)CR1 membrane expression correlated with monocyte CX(3)CL1-dependent function. Taken together, our data demonstrate that CX(3)CR1 expression in monocytes can be modulated, and suggest that alterations in their environment are able to influence CX(3)CL1-dependent functions, such as chemotaxis and adhesion, leading to changes in the kinetics, composition and/or functional status of the leucocyte infiltrate.

New evidences for fractalkine/CX3CL1 involved in substantia nigral microglial activation and behavioral changes in a rat model of Parkinson's disease

Activated microglia are instrumental to neurodegeneration in Parkinson's disease (PD). Fractalkine, as an exclusive ligand for CX3CR1 expressed on microglia, has recently been reported to be released out by neurons, and induce microglial activation as a neuron-to-glia signal in the spinal cord. However, the role of fractalkine-induced microglial activation in PD remains unknown. In our study, we injected 1-methyl-4-phenylpyridinium (MPP(+)) into unilateral substantia nigra (SN) which induced ipsilateral endogenous fractalkine expression on neuron and observe the increase of CX3CR1 expression in response to MPP(+) by Western blotting analysis. Moreover, pre-administration of anti-CX3CR1 neutralizing antibody which potentially blocked microglial activation can promote rotation behaviors. To further investigate the role of fractalkine in PD, we injected exogenous fractalkine in unilateral SN, and observed microglial activation, dopaminergic cell depletion, and motor dysfunction. All these effects can be totally abolished by cerebroventricular administration of anti-CX3CR1. Intracerebroventricular administration of minocycline, a selective microglia inhibitor, can prevent fractalkine-induced rotation behaviors, and inhibit dopaminergic neurons from degeneration in the way of dose-dependent. Our studies demonstrate that fractalkine-induced microglial activation plays an important role in the development of PD, and provide an evidence of fractalkine and CX3CR1 as new therapeutic targets for PD treatment.

Fractalkine and CX3CR1 mediate leukocyte capture by endothelium in response to Shiga toxin

Shiga toxins (Stx) are the virulence factors of enterohemorrhagic Escherichia coli O157:H7, a worldwide emerging diarrheal pathogen, which precipitates postdiarrheal hemolytic uremic syndrome, the leading cause of acute renal failure in children. In this study, we show that Stx2 triggered expression of fractalkine (FKN), a CX3C transmembrane chemokine, acting as both adhesion counterreceptor on endothelial cells and soluble chemoattractant. Stx2 caused in HUVEC expression of FKN mRNA and protein, which promoted leukocyte capture, ablated by Abs to either endothelial FKN or leukocyte CX3CR1 receptor. Exposure of human glomerular endothelial cells to Stx2 recapitulated its FKN-inducing activity and FKN-mediated leukocyte adhesion. Both processes required phosphorylation of Src-family protein tyrosine kinase and p38 MAPK in endothelial cells. Furthermore, they depended on nuclear import of NF-kappaB and other stress-responsive transcription factors. Inhibition of their nuclear import with the cell-penetrating SN50 peptide reduced FKN mRNA levels and FKN-mediated leukocyte capture by endothelial cells. Adenoviral overexpression of IkappaBalpha inhibited FKN mRNA up-regulation. The FKN-mediated responses to Stx2 were also dependent on AP-1. In mice, both virulence factors of Stx-producing E. coli, Stx and LPS, are required to elicit hemolytic uremic syndrome. In this study, FKN was detected within glomeruli of C57BL/6 mice injected with Stx2, and further increased after Stx2 plus LPS coadministration. This was associated with recruitment of CX3CR1-positive cells. Thus, in response to Stx2, FKN is induced playing an essential role in the promotion of leukocyte-endothelial cell interaction thereby potentially contributing to the renal microvascular dysfunction and thrombotic microangiopathy that underlie hemolytic uremic syndrome due to enterohemorrhagic E. coli O157:H7 infection.

The trafficking of natural killer cells

Natural killer (NK) cells are large granular lymphocytes of the innate immune system that participate in the early control of microbial infections and cancer. NK cells can induce the death of autologous cells undergoing various forms of stress, recognizing and providing non-microbial 'danger' signals to the immune system. NK cells are widely distributed in lymphoid and non-lymphoid organs. NK cell precursors originate from the bone marrow and go through a complex maturation process that leads to the acquisition of their effector functions, to changes in their expression of integrins and chemotactic receptors, and to their redistribution from the bone marrow and lymph nodes to blood, spleen, liver, and lung. Here, we describe the tissue localization of NK cells, using NKp46 as an NK cell marker, and review the current knowledge on the mechanisms that govern their trafficking in humans and in mice.