Influence of systemic inflammatory response syndrome on host resistance against bacterial infections*

The effect of leptin gene polymorphisms (LEP rs7799039 and LEPR rs1137101) on febrile neutropenia

Background and aim

Leptin is mainly produced in adipose tissue and released into systemic circulation. Leptin and its receptor LEPR activate the Janus kinase/signal transducers and activators of transcription signaling cascade and increase cytokine discharge. In our study, we aimed to examine the role of leptin gene (LEP) rs7799039 and LEPR rs1137101 polymorphisms on the susceptibility for febrile neutropenia (FEN) attacks and their relationship with clinical findings during the course of FEN.

Methods

This study included pediatric patients with a diagnosis of malignancy who applied to the pediatric emergency department between December 2019 and June 2022 and healthy controls. The genotypes of the LEP rs7799039 and LEPR rs1137101 genes were statistically compared between patients and healthy controls. In addition, the relationship between the genotype distribution of LEP rs7799039 and LEPR rs1137101 polymorphisms and clinical features during the course of FEN was investigated.

Results

In the statistical analysis in terms of LEP rs7799039 and LEPR rs1137101 genotype distributions between the patient and healthy groups, there was no significant difference. Patients with the AA genotype of LEPR rs1137101 polymorphism had significantly more commonly a body mass index (BMI) value of <25, and all the patients with the AG/GG genotype had a BMI value of 25 and above. LEP rs7799039 and LEPR rs1137101 genotype distributions were not statistically significant with other clinical features.

Conclusions

It was revealed that leptin gene polymorphisms did not have a significant effect during the course of FEN.

Serum leptin level as a diagnostic and prognostic marker in infectious diseases and sepsis: A comprehensive literature review

BACKGROUND

Infections and sepsis are common causes of morbidity and mortality, with an increasing incidence worldwide. Leptin is involved in the inflammatory process and may modulate the cytokine production, immune cell proliferation and endothelial function. There are conflicting results regarding alterations of leptin levels in infectious diseases and the outcome from sepsis.The aim of the current article is to provide an overview of the medical literature on the correlations between variations of leptin levels and infectious diseases and sepsis.

METHODS

We performed an extensive literature search in PubMed and Google Scholar databases, using keywords to identify articles related to leptin in infectious diseases and sepsis. Searches were referenced using medical subject headings that included "leptin," "adipokines," "sepsis," "infectious diseases," "leptin deficiency," "leptin resistance" or "hyperleptinemia." The language of publication, journal, or country were not included as limitation criteria.Articles or abstracts containing adequate information, such as age, sex, anthropometric indices, clinical presentation, comorbidities, and management were included in the study, whereas articles with insufficient clinical and demographic data were excluded. We assessed the quality of the studies selected.The final review of all databases was conducted on June 18, 2020.

RESULTS

We find the results from the current review to be of great importance due to the possible therapeutic role of leptin analogs in states of leptin deficiency associated with infectious diseases or sepsis.In hyperleptinemia, a therapeutic plan for obtaining leptin neutralization also needs further investigations. This could lead to the reduction of proinflammatory responses.There is a need for further studies to demonstrate the specificity and sensitivity of leptin in the early diagnosis of sepsis and the need to measure serum leptin levels in routine evaluation of the critical patient.

CONCLUSION

The multiple effects of leptin are of growing interest, but further studies are needed to elucidate the role of leptin signalling in infectious diseases and sepsis. Because very few human studies are reported, we recommend the need for further research.Better understanding of the pathophysiology of sepsis and the implication of circulating total leptin in this process could help physicians in managing this life-threatening condition.

Sepsis and Nosocomial Infection: Patient Characteristics, Mechanisms, and Modulation

Sepsis is a leading cause of death worldwide. After initial trials modulating the hyperinflammatory phase of sepsis failed, generations of researchers have focused on evaluating hypo-inflammatory immune phenotypes. The main goal has been to develop prognostic biomarkers and therapies to reduce organ dysfunction, nosocomial infection, and death. The depressed host defense in sepsis has been characterized by broad cellular reprogramming including lymphocyte exhaustion, apoptosis, and depressed cytokine responses. Despite major advances in this field, our understanding of the dynamics of the septic host response and the balance of inflammatory and anti-inflammatory cellular programs remains limited. This review aims to summarize the epidemiology of nosocomial infections and characteristic immune responses associated with sepsis, as well as immunostimulatory therapies currently under clinical investigation.

Emergence of Leptin in Infection and Immunity: Scope and Challenges in Vaccines Formulation

Deficiency of leptin (ob/ob) and/or desensitization of leptin signaling (db/db) and elevated expression of suppressor of cytokine signaling-3 (SOCS3) reported in obesity are also reported in a variety of pathologies including hypertriglyceridemia, insulin resistance, and malnutrition as the risk factors in host defense system. Viral infections cause the elevated SOCS3 expression, which inhibits leptin signaling. It results in immunosuppression by T-regulatory cells (Tregs). The host immunity becomes incompetent to manage pathogens' attack and invasion, which results in the accelerated infections and diminished vaccine-specific antibody response. Leptin was successfully used as mucosal vaccine adjuvant against Rhodococcus equi. Leptin induced the antibody response to Helicobacter pylori vaccination in mice. An integral leptin signaling in mucosal gut epithelial cells offered resistance against Clostridium difficile and Entameoba histolytica infections. We present in this review, the intervention of leptin in lethal diseases caused by microbial infections and propose the possible scope and challenges of leptin as an adjuvant tool in the development of effective vaccines.

Pathological Role and Diagnostic Value of Endogenous Host Defense Peptides in Adult and Neonatal Sepsis: A Systematic Review

BACKGROUND

Sepsis is a systemic host response to an infection leading to organ failure. This is associated with dynamic expression of endogenous host defense peptides. Dysregulation of these peptides is associated with septic morbidity and mortality.

METHODS

We performed a systematic search of articles indexed in PubMed, ISI Web of Knowledge, EmBase, and Scopus database from inception to October 2016. Both preclinical and clinical studies investigating the role of host defense peptides in pathogenesis and as biomarkers for sepsis were included.

RESULTS

Of the available literature, cathelicidin, defensin, and hepcidin are among the best-characterized peptides. These regulate immune response, and crosstalk with pyroptosis and coagulation cascades. The applicability of these peptides as septic biomarkers has been investigated in vitro and in vivo studies. However, numerous studies were based on endotoxemia without an infection, jeopardizing interpretation of the outcomes. Cathelicidin and defensin were frequently reported in adult sepsis while hepcidin in neonatal sepsis. The expression level of these peptides is significantly associated with septic condition. Most of the studies employed a cross-sectional design, precluding the establishment of a temporal relationship between candidate peptide biomarkers and sepsis.

CONCLUSIONS

Innate defense peptides have been insufficiently evaluated as either diagnostic or prognostic biomarkers. In the future, evaluation of host defense peptides as septic biomarkers may employ a longitudinal design and consider a panel of multiple peptides.

Predictive Value of IL-8 for Sepsis and Severe Infections After Burn Injury: A Clinical Study

The inflammatory response induced by burn injury contributes to increased incidence of infections, sepsis, organ failure, and mortality. Thus, monitoring postburn inflammation is of paramount importance but, so far, there are no reliable biomarkers available to monitor and/or predict infectious complications after burn. As interleukin 8 (IL-8) is a major mediator for inflammatory responses, the aim of our study was to determine whether IL-8 expression can be used to predict postburn sepsis, infections, and mortality. Plasma cytokines, acute-phase proteins, constitutive proteins, and hormones were analyzed during the first 60 days after injury from 468 pediatric burn patients. Demographics and clinical outcome variables (length of stay, infection, sepsis, multiorgan failure [MOF], and mortality) were recorded. A cutoff level for IL-8 was determined using receiver operating characteristic analysis. Statistical significance is set at P < 0.05. Receiver operating characteristic analysis identified a cutoff level of 234 pg/mL for IL-8 for survival. Patients were grouped according to their average IL-8 levels relative to this cutoff and stratified into high (H) (n = 133) and low (L) (n = 335) groups. In the L group, regression analysis revealed a significant predictive value of IL-8 to percent of total body surface area burned and incidence of MOF (P < 0.001). In the H group, IL-8 levels were able to predict sepsis (P < 0.002). In the H group, elevated IL-8 was associated with increased inflammatory and acute-phase responses compared with the L group (P < 0.05). High levels of IL-8 correlated with increased MOF, sepsis, and mortality. These data suggest that serum levels of IL-8 may be a valid biomarker for monitoring sepsis, infections, and mortality in burn patients.

Post-Sepsis State Induces Tumor-Associated Macrophage Accumulation through CXCR4/CXCL12 and Favors Tumor Progression in Mice

Survivors from sepsis are in an immunosuppressed state that is associated with higher long-term mortality and risk of opportunistic infections. Whether these factors contribute to neoplastic proliferation, however, remains unclear. Tumor-associated macrophages (TAM) can support malignant cell proliferation, survival, and angiogenesis. We addressed the relationship between the post-sepsis state, tumor progression and TAM accumulation, and phenotypic and genetic profile, using a mouse model of sepsis resolution and then B16 melanoma in mice. In addition, we measured the serum concentrations of TNFα, TGFβ, CCL2, and CXCL12 and determined the effect of in vivo CXCR4/CXCL12 inhibition in this context. Mice that survived sepsis showed increased tumor progression both in the short and long term, and survival times were shorter. TAM accumulation, TAM local proliferation, and serum concentrations of TGFβ, CXCL12, and TNFα were increased. Naïve mice inoculated with B16 together with macrophages from post-sepsis mice also had faster tumor progression and shorter survival. Post-sepsis TAMs had less expression of MHC-II and leukocyte activation-related genes. Inhibition of CXCR4/CXCL12 prevented the post-sepsis-induced tumor progression, TAM accumulation, and TAM in situ proliferation. Collectively, our data show that the post-sepsis state was associated with TAM accumulation through CXCR4/CXCL12, which contributed to B16 melanoma progression.

Is boosting the immune system in sepsis appropriate?

A relative immunosuppression is observed in patients after sepsis, trauma, burns, or any severe insults. It is currently proposed that selected patients will benefit from treatment aimed at boosting their immune systems. However, the host immune response needs to be considered in context with pathogen-type, timing, and mainly tissue specificity. Indeed, the immune status of leukocytes is not universally decreased and their activated status in tissues contributes to organ failure. Accordingly, any new immune-stimulatory therapeutic intervention should take into consideration potentially deleterious effects in some situations.

Bacterial respiratory tract infections are promoted by systemic hyperglycemia after severe burn injury in pediatric patients

BACKGROUND

Burns are associated with hyperglycemia leading to increased incidence of infections with pneumonia being one of the most prominent and adverse complications. Recently, various studies in critically ill patients indicated that increased pulmonary glucose levels with airway/blood glucose threshold over 150 mg/dl lead to an overwhelming growth of bacteria in the broncho-pulmonary system, subsequently resulting in an increased risk of pulmonary infections. The aim of the present study was to determine whether a similar cutoff value exists for severely burned pediatric patients.

METHODS

One-hundred six severely burned pediatric patients were enrolled in the study. Patients were divided in two groups: high (H) defined as daily average glucose levels >75% of LOS >150 mg/dl), and low (L) with daily average glucose levels >75% of the LOS <150 mg/dl). Incidences of pneumonia, atelectasis, and acute respiratory distress syndrome (ARDS) were assessed. Incidence of infections, sepsis, and respiratory parameters were recorded. Blood was analyzed for glucose and insulin levels. Statistical analysis was performed using Student's t-test and chi-square test. Significance was set at p<0.05.

RESULTS

Patient groups were similar in demographics and injury characteristics. Pneumonia in patients on the mechanical ventilation (L: 21%, H: 32%) and off mechanical ventilation (L: 5%, H: 15%), as well as ARDS were significantly higher in the high group (L: 3%, H: 19%), p<0.05, while atelectasis was not different. Patients in the high group required significantly longer ventilation compared to low patients (p<0.05). Furthermore, incidence of infection and sepsis were significantly higher in the high group, p<0.05.

CONCLUSION

Our results indicate that systemic glucose levels over 150 mg/dl are associated with a higher incidence of pneumonia confirming the previous studies in critically ill patients.

Acute lung injury induced by the intravenous administration of cigarette smoke extract

OBJECTIVE

To investigate the acute effects of intravenous administration of cigarette smoke extract (CSE) on histological, inflammatory, and respiratory function parameters in rats, as well as to compare this potential acute lung injury (ALI) model with that with the use of oleic acid (OA).

METHODS

We studied 72 Wistar rats, divided into four groups: control (those injected intravenously with saline); CSE (those injected intravenously with CSE and saline); OA (those injected intravenously with saline and OA); and CSE/OA (those injected intravenously with CSE and OA).

RESULTS

Mean lung compliance was significantly lower in the OA and CSE/OA groups (2.12 ± 1.13 mL/cmH2O and 1.82 ± 0.77 mL/cmH2O, respectively) than in the control group (3.67 ± 1.38 mL/cmH2O). In bronchoalveolar lavage fluid, the proportion of neutrophils was significantly higher in the OA and CSE/OA groups than in the control group, as was the activity of metalloproteinases 2 and 9. Pulmonary involvement, as assessed by morphometry, was significantly more severe in the OA and CSE/OA groups (72.9 ± 13.8% and 77.6 ± 18.0%, respectively) than in the control and CSE groups (8.7 ± 4.1% and 32.7 ± 13.1%, respectively), and that involvement was significantly more severe in the CSE group than in the control group.

CONCLUSIONS

The intravenous administration of CSE, at the doses and timing employed in this study, was associated with minimal ALI. The use of CSE did not potentiate OA-induced ALI. Additional studies are needed in order to clarify the potential role of this model as a method for studying the mechanisms of smoking-induced lung injury.

Effect of CCL2 antisense oligodeoxynucleotides on bacterial translocation and subsequent sepsis in severely burned mice orally infected with Enterococcus faecalis

Severely burned mice are susceptible to sepsis stemming from Enterococcus faecalis translocation due to the impaired generation of M1 macrophages (M1MΦs) in local translocation sites. In our previous studies, CCL2 has been characterized as a major effector molecule on the burn-associated generation of M2MΦs, an inhibitor cell type for resident MΦ conversion into M1MΦs. In this study, we tried to protect burned mice orally infected with E. faecalis utilizing CCL2 antisense oligodeoxynucleotides (ODNs). We show that M2MΦs in mesenteric lymph nodes (MLNs) were not demonstrated in burned mice treated with CCL2 antisense ODNs. M1MΦs were not induced by heat-killed E. faecalis from resident MΦs transwell-cultured with mesenteric lymph node macrophages (MLN-MΦs) from burned mice, while M1MΦs were induced by the same antigen from resident MΦs transwell-cultured with MΦs which were isolated from burned mice treated with CCL2 antisense ODNs. Bacterial growth in MLNs was shown in burned mice orally infected with a lethal dose of E. faecalis. However, after the same infection, sepsis did not develop in burned mice treated with CCL2 antisense ODNs. These results indicate that bacterial translocation and subsequent sepsis are controlled in burned mice orally infected with a lethal dose of E. faecalis by gene therapy utilizing CCL2 antisense ODNs.

The novel antibacterial drug XF-70 is a potent inhibitor of Staphylococcus aureus infection of the burn wound

The authors report the findings of in vivo studies of XF-70 (a novel, dicationic porphyrin) against Staphylococcus aureus in a murine model of a burn wound infection. Mice received a 15% total body scald burn wound, which were inoculated with S. aureus (1.8 x 10 CFU). After 24 hours, escharectomies were performed and groups (n = 8) received single or two doses (6 hours apart) of XF-70* (100 microg/wound) or silver sulfadiazine, Acticoat, or saline applied topically. Viable bacteria were quantified from homogenized burn tissue biopsies and the spleen by plating dilutions onto agar plates and CFU determination. A single dose of XF-70 reduced bacterial burden by 98.77% (untreated: 2.78 +/- 2.96 x 10 CFU/g vs XF-70 treated: 3.4 +/- 0.19 x 10 CFU/g, P < .01). Two XF-70 doses reduced the growth of S. aureus by 99.96% (1.2 +/- 0.6 x 10 CFU/g, P < .01). These results were similar to the results obtained from commonly used topical antibacterials silver sulfadiazine and Acticoat. The spleens of mice treated with saline had a robust growth of S. aureus (7.0 +/- 1.97 x 10 CFU/g) whereas those treated with one or two XF-70 doses grew only 3.5 +/- 0.002 x 10 CFU/g and 5.7 +/- 0.002 x 10 CFU/g, respectively, a significant (P < .001) reduction in S. aureus dissemination. Single and multiple doses of XF-70 were effective in controlling S. aureus growth in burn wounds and inhibited systemic dissemination of S. aureus. Early treatment of burn wounds with XF-70 may be effective in slowing bacterial dissemination to other tissues.

Epigenetic regulation of immune cell functions during post-septic immunosuppression

Studies in humans and animal models indicate that profound immunosuppression is one of the chronic consequences of severe sepsis. This immune dysfunction encompasses deficiencies in activation of cells in both the myeloid and lymphoid cell lineages. As a result, survivors of severe sepsis are at risk of succumbing to infections perpetrated by opportunistic pathogens that are normally controlled by a fully functioning immune system. Recent studies have indicated that epigenetic mechanisms may be one driving force behind this immunosuppression, through suppression of proinflammatory gene production and subsequent immune cell activation, proliferation and effector function. A better understanding of epigenetics and post-septic immunosuppression can improve our diagnostic tools and may be an important potential source of novel molecular targets for new therapies. This review will discuss important pathways of immune cell activation affected by severe sepsis, and highlight pathways of epigenetic regulation that may be involved in post-septic immunosuppression.

The protective effects of Lipoxin A4 during the early phase of severe acute pancreatitis in rats

OBJECTIVE

Our aim was to investigate the protective effects of a Lipoxin A(4) analogue (LXA4) in the early phase of acute pancreatitis in rats.

MATERIALS AND METHODS

Severe acute pancreatitis (SAP) was induced by injection of 5% sodium taurocholate into the pancreatic duct. Rats with SAP were treated with LXA4 (0.1 mg/kg), 10 min after the 5% sodium taurocholate injection, after which LXA4 was administrated every 8 hours, three times (LXA4 group). The sham group was only given the vehicle after operation. Plasma amylase activity, serum levels of interleukin-1 (IL-1), IL-6, and tumor necrosis factor-α (TNF-α) were measured at 4, 12, and 24 h after induction of SAP. The pancreatic index and histopathologic observations were evaluated and the expression of intercellular adhesion molecule-1 (ICAM-1) and NF-κB p65 in the pancreas, and the expression of ICAM-1 in the lungs were detected by immunohistochemistry.

RESULTS

LXA4 treated rats had lower serum levels of TNF-α, IL-1, and IL-6 at all time points measured (p < 0.05), but significantly differed in plasma amylase activity only at 24 h as compared with the SAP group. The pancreatic index and the scores of pancreatitic histopathologic evaluations were lower in the LXA4 group as compared to the SAP group. Immunohistochemistry showed that LXA4 attenuated the expression of ICAM-1 and NF-κB p65 in the pancreas, as well as the expression of ICAM-1 in the lungs in animals with pancreatitis (p < 0.05).

CONCLUSIONS

We demonstrate that LXA4 has protective effects in experimental SAP, which may be achieved by inhibiting the NF-κB signalling pathway, thereby reducing the production of proinflammatory cytokines.

Role of natural killer dendritic cells in host resistance against Pseudomonas aeruginosa infection after thermal injury in mice

The contributions of dendritic cells (DCs) and natural killer dendritic cells (NKDCs) on host antibacterial innate immunities have been described. We have previously reported that mice with partial-thickness burn injuries (PT-burn mice) are resistant to burn wound infections, whereas mice with full-thickness burn injuries (FT-burn mice) are susceptible. In this study, the effect of burn stress on the appearance and properties of DCs and NKDCs was investigated in two different murine models of thermal injury. Dendritic cells isolated from PT-burn mice produced CCL3 and IL-12, whereas these soluble factors were not produced by DCs from FT-burn mice. As compared with unburned mouse controls, a large number of NKDCs were isolated from the DC preparations from PT-burn mice, whereas fewer NKDCs were detected in the DC preparations from FT-burn mice. Nonobese diabetic severe combined immunodeficiency mice inoculated with NKDCs were shown to be resistant against a lethal s.c. Pseudomonas aeruginosa infection. These results strongly suggest that NKDCs influenced by partial-thickness burn injury play a role on the resistance of PT-burn mice to P. aeruginosa s.c. infection.

CNS leptin action modulates immune response and survival in sepsis

Sepsis describes a complex clinical syndrome that results from an infection, setting off a cascade of systemic inflammatory responses that can lead to multiple organ failure and death. Leptin is a 16 kDa adipokine that, among its multiple known effects, is involved in regulating immune function. Here we demonstrate that leptin deficiency in ob/ob mice leads to higher mortality and more severe organ damage in a standard model of sepsis in mice [cecal ligation and puncture (CLP)]. Moreover, systemic leptin replacement improved the immune response to CLP. Based on the molecular mechanisms of leptin regulation of energy metabolism and reproductive function, we hypothesized that leptin acts in the CNS to efficiently coordinate peripheral immune defense in sepsis. We now report that leptin signaling in the brain increases survival during sepsis in leptin-deficient as well as in wild-type mice and that endogenous CNS leptin action is required for an adequate systemic immune response. These findings reveal the existence of a relevant neuroendocrine control of systemic immune defense and suggest a possible therapeutic potential for leptin analogs in infectious disease.

Enterococcus faecalis translocation in mice with severe burn injury: a pathogenic role of CCL2 and alternatively activated macrophages (M2aMphi and M2cMphi)

Here, we investigated a role of CCL2 on the increased susceptibility of severely burned mice to Enterococcus faecalis translocation. After inoculation of Mphi from MLMphi of normal mice, 80% of the SCIDbgMN mice orally infected with the lethal dose of E. faecalis survived, and all mice inoculated with MLMphi from thermally injured mice died. At this time, SCIDbgMN mice inoculated with MLMphi from thermally injured CCL2(-/-) mice were shown to be resistant (90% survival). M1Mphi were not induced by E. faecalis antigen in cultures of MLMphi from thermally injured wild-type mice, and MLMphi from thermally injured CCL2(-/-) mice converted to M1Mphi after the antigen stimulation. MLMphi from wild-type mice 2 days postburn injury possessed M2a- and M2cMphi properties, and those from mice 7-21 days postburn injury carried M2bMphi properties. However, MLMphi from thermally injured CCL2(-/-) mice did not show any typical properties for M2a- or M2cMphi. CCL17 and CXCL13 (biomarkers for M2a- and M2cMphi), but not CCL1 (a biomarker of M2bMphi), were produced by MLMphi from thermally injured CCL2(-/-) mice treated with rCCL2. These results indicate that CCL2 converts resident MLMphi to M2a- and M2cMphi, detected early after burn injury, and decreases host antibacterial innate immunity against sepsis stemming from oral E. faecalis infection.

Molecular biology of inflammation and sepsis: a primer

BACKGROUND

Remarkable progress has been made during the last decade in defining the molecular mechanisms that underlie septic shock. This rapidly expanding field is leading to new therapeutic opportunities in the management of severe sepsis.

AIM

To provide the clinician with a timely summary of the molecular biology of sepsis and to better understand recent advances in sepsis research.

DATA SELECTION

Medline search of relevant publications in basic mechanisms of sepsis/severe sepsis/septic shock, and selected literature review of other manuscripts about the signalosome, inflammasome, apoptosis, or mechanisms of shock. DATA SYNTHESIS AND FINDINGS: The identification of the toll-like receptors and the associated concept of innate immunity based upon pathogen- or damage-associated molecular pattern molecules allowed significant advances in our understanding of the pathophysiology of sepsis. The essential elements of the inflammasome and signal transduction networks responsible for activation of the host response have now been characterized. Apoptosis, mitochondrial dysfunction, sepsis-related immunosuppression, late mediators of systemic inflammation, control mechanisms for coagulation, and reprogramming of immune response genes all have critical roles in the development of sepsis.

CONCLUSIONS

Many of these basic discoveries have direct implications for the clinical management of sepsis. The translation of these "bench-to-bedside" findings into new therapeutic strategies is already underway. This brief review provides the clinician with a primer into the basic mechanisms responsible for the molecular biology of sepsis, severe sepsis, and septic shock.

CC chemokine receptor 4 modulates Toll-like receptor 9-mediated innate immunity and signaling

The present study addressed the modulatory role of CC chemokine receptor 4 (CCR4) in Toll-like receptor (TLR) 9-mediated innate immunity and explored the underlying molecular mechanisms. Our results demonstrated that CCR4-deficient mice were resistant to both septic peritonitis induced by cecal ligation and puncture (CLP) and CpG DNA/D-galactosamine-induced shock. In bone marrow-derived macrophages (BMMPhi) from CLP-treated CCR4-deficient mice, TLR9-mediated pathways of MAPK/AP-1, PI3K/Akt, and IkappaB kinase (IKK)/NF-kappaB were impaired compared to wild-type (WT) cells. While TLR9 expression was not altered, the intensity of internalized CpG DNA was increased in CCR4-deficient macrophages when compared to WT macrophages. Pharmacological inhibitor studies revealed that impaired activation of JNK, PI3K/Akt, and/or IKK/NF-kappaB could be responsible for decreased proinflammatory cytokine expression in CCR4-deficient macrophages. Interestingly, the CCR4-deficient BMMPhi exhibited an alternatively activated (M2) phenotype and the impaired TLR9-mediated signal transduction responses in CCR4-deficient cells were similar to the signaling responses observed in WT BMMPhi skewed to an alternatively activated phenotype. These results indicate that macrophages deficient in CCR4 impart a regulatory influence on TLR9-mediated innate immunity.

Role of polymorphonuclear neutrophils on infectious complications stemming from Enterococcus faecalis oral infection in thermally injured mice

Thermally injured mice are susceptible to Enterococcus faecalis translocation. In this study, the role of polymorphonuclear neutrophils (PMN) on the development of sepsis stemming from E. faecalis translocation was studied in SCID-beige (SCIDbg) mice depleted of PMN (SCIDbgN mice) or macrophages (Mphi) and PMN (SCIDbgMN mice). Sepsis was not developed in SCIDbgN mice orally infected with E. faecalis, while the orally infected pathogen spread systemically in the same mice inoculated with PMN from thermally injured mice (TI-PMN). SCIDbgMN mice were shown to be greatly susceptible to sepsis caused by E. faecalis translocation, while orally infected E. faecalis did not spread into sepsis in the same mice that were previously inoculated with Mphi from unburned SCIDbg mice (resident Mphi). In contrast, orally infected E. faecalis spread systemically in SCIDbgMN mice inoculated with resident Mphi and TI-PMN, while all SCIDbgMN mice inoculated in combination with resident Mphi and PMN from unburned SCIDbg mice survived after the infection. After cultivation with TI-PMN in a dual-chamber transwell, resident Mphi converted to alternatively activated Mphi, which are inhibitory on the generation of classically activated Mphi (typical effector cells in host antibacterial innate immunities). TI-PMN were characterized as immunosuppressive PMN (PMN-II) with abilities to produce cc-chemokine ligand-2 and IL-10. These results indicate that PMN-II appearing in response to burn injury impair host antibacterial resistance against sepsis stemming from E. faecalis translocation through the conversion of resident Mphi to alternatively activated Mphi.

Impairment of the host's antibacterial resistance by norepinephrine activated neutrophils

The susceptibility of mice to infectious complications is dramatically increased in an accompaniment with systemic inflammatory response syndrome (SIRS). Polymorphonuclear neutrophils with immunosuppressive ability (PMN-II) that appear in response to SIRS have been classified as one of the cells responsible for the increased susceptibility of mice with SIRS (SIRS mice) to sepsis induced by cecal-ligation and puncture (CLP). Since a high level of norepinephrine (NE) is demonstrated in the plasma of SIRS mice, in the present study, the role of NE on the appearance of PMN-II in SIRS mice was studied. Similar to SIRS mice, normal mice became susceptible to CLP-induced infectious complications after inoculation with NE-treated PMN. CCL2 and IL-10 (biomarkers for PMN-II) were equally produced by PMN-II prepared from SIRS mice and NE-treated PMN. However, CCL3 and IL-12 (biomarkers for immunostimulatory PMN, PMN-I) were not detected in culture fluids from either PMN preparation. These results indicate that NE mass-produced in association with SIRS development plays a role on the generation of PMN-II and the appearing PMN-II are responsible, in part, for increased susceptibility of SIRS mice to CLP-induced infectious complications.

Mitochondrial Superoxide Production Is Related to the Control of Cytokine Release from Peritoneal Macrophage After Antioxidant Treatment in Septic Rats

BACKGROUND

Reactive oxygen species are involved in several intracellular pathways that ultimately lead to the activation of the innate immune system. In addition, oxidized proteins and lipids could stimulate cytokine release from macrophages through the activation of membrane receptors. Thus we here describe the effects of antioxidant administration to septic rats on peritoneal macrophage parameters of oxidative stress and cytokine release.

MATERIALS AND METHODS

Peritoneal macrophages from Wistar rats subjected to cecal ligation and puncture (CLP). The animals were divided into four groups: sham operated, CLP, basic support (saline plus antibiotics), basic support plus N-acetylcysteine, and deferoxamine. Several times after CLP macrophages were cultured to the determination of thiobarbituric acid reactive species (TBARS), protein carbonyls, mitochondrial superoxide production, catalase, superoxide dismutase activities, and released cytokines.

RESULTS

Sepsis increased TBARS, protein carbonyls, and mitochondrial superoxide production in macrophages and this was associated with an increase release of pro-inflammatory cytokines. Basic support reversed TBARS and protein carbonyls content, but not mitochondrial superoxide production. The addition of antioxidants prevented all oxidative parameters in macrophages, and this was associated with lower cytokine release. Catalase and superoxide dismutase were modulated in the basic support group, but not in the antioxidant treated animals.

CONCLUSIONS

Mitochondrial superoxide production seemed to be the differential oxidative parameter associated with antioxidant-induced modulation of cytokine release.

Adipose tissue macrophages

It is now broadly accepted that low-grade chronic inflammation associated with obesity leads to the onset of insulin resistance and type 2 diabetes mellitus. Obesity-associated inflammation is characterized by an increased abundance of macrophages in adipose tissue along with production of inflammatory cytokines. Adipose tissue macrophages (ATMs) are suspected to be the major source of inflammatory mediators such as TNF-alpha and IL-6 that interfere with adipocyte function by inhibiting insulin action. However, ATMs phenotypically resemble alternatively activated (M2) macrophages and are capable of anti-inflammatory mediator production challenging the concept that ATMs are simply the "bad guys" in obese adipose tissue. Triggers promoting ATM recruitment, ATM functions and dysfunctions, and stimuli and molecular mechanisms that drive them into becoming detrimental to their environment are subject to current research. Strategies to interfere with ATM recruitment and adverse activation could give rise to novel options for treatment and prevention of insulin resistance and type 2 diabetes mellitus.

Human adipose tissue macrophages are of an anti-inflammatory phenotype but capable of excessive pro-inflammatory mediator production

OBJECTIVE

Obesity is associated with a chronic low-grade inflammation and an increased abundance of macrophages in adipose tissue. Adipose tissue macrophages (ATMs) are assumed to interfere with adipocyte function leading to insulin resistance, thereby contributing to the pathogenesis of type 2 diabetes mellitus. Macrophages exist in separate types of differentiation, but the nature of ATMs is largely unknown.

DESIGN AND MEASUREMENTS

Stromal vascular cells (SVCs) and ATMs were isolated from human adipose tissues from different locations. We characterized ATMs phenotypically and functionally by flow cytometry, endocytosis assay and determination of secreted cytokines. For comparison, we used macrophages of the 'classical' (M1) and the 'alternative', anti-inflammatory (M2) type differentiated in vitro from peripheral blood monocytes.

RESULTS

Like prototypic M2 macrophages, ATMs expressed considerable amounts of mannose receptor, haemoglobin scavenger receptor CD163 and integrin alphavbeta5. The number of cells expressing these molecules correlated significantly with the donors' body mass indices (BMIs). Notably, SVCs positive for the common monocyte/macrophage marker CD14 contained a considerable fraction of blood monocytes, the abundance of which did not correlate with the BMIs, pointing to the requirement of the surface markers identified here for the identification of ATMs. ATMs showed endocytic activities similar to M2 macrophages and accordingly secreted high amounts of IL-10 and IL-1 receptor antagonist. However, basal and induced secretion of pro-inflammatory mediators TNF-alpha, IL-6, IL-1, MCP-1 and MIP-1alpha was even higher in ATMs than in pro-inflammatory M1 macrophages.

CONCLUSION

ATMs comprise a particular macrophage type that is M2-like by surface marker expression, but they are competent to produce extensive amounts of inflammatory cytokines, which could considerably contribute to the development of insulin resistance.

A novel antibacterial gene transfer treatment for multidrug-resistant Acinetobacter baumannii-induced burn sepsis

Sepsis caused by multidrug-resistant bacterial infections in critically injured patients has become a major clinical problem. Recently, Acinetobacter baumannii (AB) wound infections, especially in our critically injured soldiers fighting in Iraq and Afghanistan, is posing a major clinical problem and an economic burden. ConjuGon, Inc., has developed a novel antibacterial therapeutic technology using bacterial conjugation. The donor cells are attenuated Escherichia coli carrying a conjugative plasmid. The expression of bactericidal genes cloned on the plasmid is tightly repressed in the donor cells but becomes de-repressed once mobilized into a pathogen and disrupts protein synthesis. Here, we tested the efficacy of this novel conjugation technology to control and eradicate a drug-resistant clinical isolate of AB wound infection both in vitro and in a murine burn sepsis model. C57Blk/6J mice were divided into burn (B) and burn sepsis (BS) groups. All animals received a 12% TBSA dorsal scald full-thickness burn. The BS group was inoculated with multidrug-resistant AB (1 x 10(5) colony-forming units [CFU]) at the burn wound site. BS animals were either untreated or treated with increasing concentrations (10(3) - 19(10) CFU) of attenuated donor E. coli encoding bactericidal proteins. The survival rate was monitored for 10 days. The ability of donor cells to significantly diminish AB levels in the burn wound 24 hours after injury was determined by quantitative cultures. Donor cells were highly effective in killing AB in vitro. In the burn sepsis model, 90% B group animals survived, and 40% to 50% BS animals survived with no treatment in 5 to 6 days. Treatment with donor cells at 10(10) to 10(6) provided significant survival advantage (P < .05). Quantitative cultures of burn wounds revealed that AB numbers increased from 3 x 10(4) CFU to 7.8 +/- 4.4 x 10(9) CFU in 24 hours in the untreated group. Single treatment with donor cells (10(10) CFU) significantly reduced AB in the burn wound to less than the levels seeded into the wound (1.23 +/- 0.5 x 10(4) CFU; P < .05). Taken together, these results indicate that this novel technology is an efficient method to control drug-resistant AB burn wound infections and prevent their systemic spread.

New vistas on macrophage differentiation and activation

Plasticity and heterogeneity are hallmarks of myelomonocytic differentiation and polarized activation. Evidence published in this issue of the European Journal of Immunology, together with other recent data, add new elements and perspectives to the current understanding of mononuclear phagocyte differentiation and activation and are discussed in this Commentary.

Glycyrrhizin inhibits the manifestations of anti-inflammatory responses that appear in association with systemic inflammatory response syndrome (SIRS)-like reactions

In association with the systemic inflammatory response syndrome (SIRS), anti-inflammatory response syndrome is commonly manifested in patients with trauma, burn injury, and after major surgery. These patients are increasingly susceptible to infection with various pathogens due to the excessive release of anti-inflammatory cytokines from anti-inflammatory effector cells. Recently, CC-chemokine ligand 2 (CCL2) found in the sera of mice with pancreatitis was identified as an active molecule for SIRS-associated anti-inflammatory response manifestation. Also, the inhibitory activity of glycyrrhizin (GL) on CCL2 production was reported. Therefore, the effect of GL on SIRS-associated anti-inflammatory response manifestation was investigated in a murine SIRS model. Without any stimulation, splenic T cells from mice 5 days after SIRS induction produced cytokines associated with anti-inflammatory response manifestation. However, these cytokines were not produced by splenic T cells from SIRS mice previously treated with GL. In dual-chamber transwells, IL-4-producing cells were generated from normal T cells cultured with peripheral blood polymorphonuclear neutrophils (PMN) from SIRS mice. However, IL-4-producing cells were not generated from normal T cells in transwell cultures performed with PMN from GL-treated SIRS mice. CCL2 was produced by PMN from SIRS mice, while this chemokine was not demonstrated in cultures of PMN from SIRS mice treated with GL. These results indicate that GL has the capacity to suppress SIRS-associated anti-inflammatory response manifestation through the inhibition of CCL2 production by PMN.

Macrophage serum markers in pneumococcal bacteremia: Prediction of survival by soluble CD163

OBJECTIVE

Soluble CD163 (sCD163) is a new macrophage-specific serum marker. This study investigated sCD163 and other markers of macrophage activation (neopterin, ferritin, transcobalamin, and soluble urokinase plasminogen activator receptor [suPAR]) as prognostic factors in patients with pneumococcal bacteremia.

DESIGN

Observational cohort study.

SETTING

Five university hospitals in Denmark.

PATIENTS

A total of 133 patients with Streptococcus pneumoniae bacteremia (positive blood culture) and 133 age- and gender-matched controls.

INTERVENTIONS

Samples were collected for biochemical analyses at the time of first positive blood culture.

MEASUREMENTS AND MAIN RESULTS

sCD163 was highly correlated with other macrophage markers and was significantly elevated (median [25-75 percentiles], 4.6 mg/L [2.8-8.9]) compared with healthy controls (2.7 mg/L [2.1-3.3], p < .0001). Increased levels were observed in patients who needed intensive care (hemodialysis, p = .0011; hypotension, p = .0014; mechanical ventilation, p = .0019). Significantly lower levels of sCD163, ferritin, transcobalamin, and suPAR (but not C-reactive protein) were measured in patients > or =75 yrs. In patients <75 yrs, all macrophage markers were increased in patients who died from their infection compared with survivors, whereas no change was observed in any of the markers in the very old age. At cutoff levels of 9.5 mg/L (sCD163) and 1650 nmol/L (C-reactive protein), the relative risk for fatal outcome in patients <75 yrs was 10.1 (95% confidence interval 3.4-31.0) and 7.0 (95% confidence interval 2.4-21.6) for sCD163 and C-reactive protein, respectively. In a multivariate logistic regression model for patients <75 yrs, ferritin, transcobalamin, neopterin, and suPAR contained no significant information on the probability of survival when sCD163 and CRP were known (p = .25).

CONCLUSIONS

Macrophage marker response in pneumococcal bacteremia was compromised in old age. In patients <75 yrs old, sCD163 was superior to other markers, including C-reactive protein, in predicting fatal disease outcome.

Immunologic responses to critical injury and sepsis

Almost 2 million patients are admitted to hospitals in the United States each year for treatment of traumatic injuries, and these patients are at increased risk of late infections and complications of systemic inflammation as a result of injury. Host response to injury involves a general activation of multiple systems in defending the organism from hemorrhagic or infectious death. Clinicians have the capability to support the critically injured through their traumatic insult with surgery and improved critical care, but the inflammatory response generated by such injuries creates new challenges in the management of these patients. It has long been known that local tissue injury induces systemic changes in the traumatized patient that are often maladaptive. This article reviews the effects of injury on the function of immune system cells and highlights some of the clinical sequelae of this deranged inflammatory-immune interaction.

Glycyrrhizin inhibits neutrophil-associated generation of alternatively activated macrophages

Patients with severe burn injuries are extremely susceptible to infection, and the host's antibacterial responses are frequently suppressed by alternatively activated macrophages (M2Mphi), commonly demonstrated in these patients. An immunosuppressive subset of neutrophils (PMN-II), demonstrated in the peripheral blood of thermally injured patients, has been described as an inducer of M2Mphi. In the present studies, the inhibitory effect of glycyrrhizin (GL) on M2Mphi generation stimulated by PMN-II was examined. M2Mphi were generated from resident Mphi (R-Mphi, lower chamber) after cultivation with PMN-II (upper chamber) in a dual-chamber transwell. However, M2Mphi were not generated from R-Mphi when the same transwell cultures were performed in the presence of GL. M2Mphi were not generated from R-Mphi after cultivation with PMN-II previously treated with GL, while R-Mphi previously treated with GL converted to M2Mphi after they were cultured with PMN-II in transwells. Interleukin-10 and CCL2 released from PMN-II were shown to be effector molecules responsible for the generation of M2Mphi. However, these soluble factors were not produced by PMN-II treated with GL. These results indicate that GL inhibits PMN-II-stimulated M2Mphi generation through the inhibition of CCL2/interleukin-10 production by PMN-II.

The systemic inflammatory response syndrome

The systemic inflammatory response syndrome (SIRS) is the body's response to an infectious or noninfectious insult. Although the definition of SIRS refers to it as an "inflammatory" response, it actually has pro- and anti-inflammatory components. This review outlines the pathophysiology of SIRS and highlights potential targets for future therapeutic intervention in patients with this complex entity.

Immunological control of methicillin-resistant Staphylococcus aureus (MRSA) infection in an immunodeficient murine model of thermal injuries

Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), is a major cause of sepsis in patients who are immunosuppressed by their burns. In this study, an immunological regulation of MRSA infection was attempted in a mouse model of thermal injury. SCIDbg mice were resistant to MRSA infection, while SCIDbgMN mice (SCIDbg mice depleted of neutrophils and macrophages (Mphi)) were susceptible to the same infection. Also, thermally injured SCIDbg mice were shown to be susceptible to MRSA infection. On the other hand, the resistance of SCIDbgMN mice to the infection was completely recovered after an inoculation with Mphi from normal mice. However, anti-MRSA resistance was not shown in SCIDbgMN mice inoculated with Mphi from thermally injured mice. Mphi from MRSA-infected thermally injured mice were identified as alternatively activated Mphi, and Mphi from MRSA-infected unburned mice were characterized as classically activated Mphi. Mphi from thermally injured SCIDbg mice previously treated with 2-carboxyethylgermanium sesquioxide (Ge-132) protected SCIDbgMN mice against MRSA infection. Ge-132 has been described as an inhibitor of alternatively activated Mphi generation. These results suggest that MRSA infection in thermally injured patients is controlled immunologically through the induction of anti-MRSA effector cells and elimination of burn-associated alternatively activated Mphi, which are cells that inhibit the generation of classically activated Mphi.

SHIP represses the generation of alternatively activated macrophages

We recently reported that SHIP restrains LPS-induced classical (M1) activation of in vitro differentiated, bone marrow-derived macrophages (BMMPhis) and that SHIP upregulation is essential for endotoxin tolerance. Herein, we show that in vivo differentiated SHIP-/- peritoneal (PMPhis) and alveolar (AMPhis) macrophages, unlike their wild-type counterparts, are profoundly M2 skewed (alternatively activated), possessing constitutively high arginase I (ArgI) and Ym1 levels and impaired LPS-induced NO production. Consistent with this, SHIP-/- mice display M2-mediated lung pathology and enhanced tumor implant growth. Interestingly, BMMPhis from SHIP-/- mice do not display this M2 phenotype unless exposed to TGFbeta within normal mouse plasma (MP) during in vitro differentiation. Our results suggest that SHIP functions in vivo to repress M2 skewing and that macrophage polarization can occur during differentiation in response to TGFbeta if progenitors have elevated PIP3.