Can the Cecal Ligation and Puncture Model Be Repurposed To Better Inform Therapy in Human Sepsis?

A recent report by the National Institutes of Health on sepsis research has implied there is a trend to move away from mouse models of sepsis. The most commonly used animal model to study the pathogenesis of human sepsis is cecal ligation and puncture (CLP) in mice. The model has been the mainstay of sepsis research for decades and continues to be considered the gold standard to inform novel pathways of sepsis physiology and its therapeutic direction. As there have been many criticisms of the model, particularly regarding its relevance to human disease, how this model might be repurposed to be more reflective of the human condition begs discussion. In this piece, we compare and contrast the mouse microbiome of the CLP model to the emerging science of the microbiome of human sepsis and discuss the relevance for mice to harbor the specific pathogens present in the human microbiome during sepsis, as well as an underlying disease process to mimic the characteristics of those patients with undesirable outcomes. How to repurpose this model to incorporate these "human factors" is discussed in detail and suggestions offered.

The uroS and yifB Genes Conserved among Tetrapyrrole Synthesizing-Deficient Bacteroidales Are Involved in Bacteroides fragilis Heme Assimilation and Survival in Experimental Intra-abdominal Infection and Intestinal Colonization.

The human intestinal anaerobic commensal and opportunistic pathogen Bacteroides fragilis does not synthesize the tetrapyrrole protoporphyrin IX in order to form heme that is required for growth stimulation and survival in vivo Consequently, B. fragilis acquires essential heme from host tissues during extraintestinal infection. The absence of several genes necessary for de novo heme biosynthesis is a common characteristic of many anaerobic bacteria; however, the uroS gene, encoding a uroporphyrinogen III synthase for an early step of heme biosynthesis, is conserved among the heme-requiring Bacteroidales that inhabit the mammalian gastrointestinal tract. In this study, we show that the ability of B. fragilis to utilize heme or protoporphyrin IX for growth was greatly reduced in a ΔuroS mutant. This growth defect appears to be linked to the suppression of reverse chelatase and ferrochelatase activities in the absence of uroS In addition, this ΔuroS suppressive effect was enhanced by the deletion of the yifB gene, which encodes an Mg2+-chelatase protein belonging to the ATPases associated with various cellular activities (AAA+) superfamily of proteins. Furthermore, the ΔuroS mutant and the ΔuroS ΔyifB double mutant had a severe survival defect compared to the parent strain in competitive infection assays using animal models of intra-abdominal infection and intestinal colonization. This shows that the presence of the uroS and yifB genes in B. fragilis seems to be linked to pathophysiological and nutritional competitive fitness for survival in host tissues. Genetic complementation studies and enzyme kinetics assays indicate that B. fragilis UroS is functionally different from canonical bacterial UroS proteins. Taken together, these findings show that heme assimilation and metabolism in the anaerobe B. fragilis have diverged from those of aerobic and facultative anaerobic pathogenic bacteria.

Poor Outcome Could Be Predicted by Lower Monocyte Human Leukocyte Antigen-DR Expression in Patients with Complicated Intra-Abdominal Infections: A Review.

Complicated intra-abdominal infections (cIAIs) are still associated with high morbidity and mortality levels. Early prognostic evaluation is a great challenge, and a serious amount of resources have been used to find the perfect mortality predictor. Monocyte human leukocyte antigen-DR (mHLA-DR) expression has been studied as a biomarker in patients with sepsis and other infections. Our aim was to evaluate the potential prognostic performance of mHLA-DR in patients with cIAIs. Methods: We performed an electronic search of Google Scholar and PubMed databases for articles published before January 2019. The search terms were "HLA-DR," "monocyte HLA-DR," "intra-abdominal infections," "sepsis," "outcome," and "mortality." Results: A total of 12 studies with 761 patients met our inclusion criteria. In 10 studies, poor outcome was predicted by lower mHLA-DR expression, and two studies showed no prognostic value. Conclusion: This review found association between lower mHLA-DR expression and mortality. We concluded that mHLA-DR could be a reliable and meaningful predictor of poor outcome in patients with cIAIs. Nevertheless, more large prospective studies with surgical patients exclusively are needed before using this biomarker in a clinical setting.

Added value of inflammatory markers to vital signs to predict mortality in patients suspected of severe infection.

OBJECTIVE: To evaluate the added value of inflammatory markers to vital signs to predict mortality in patients suspected of severe infection. METHODS: This study was conducted at an acute care hospital (471-bed capacity). Consecutive adult patients suspected of severe infection who presented to either ambulatory care or the emergency department from April 2015 to March 2017 were retrospectively evaluated. A prognostic model for predicting 30-day in-hospital mortality based on previously established vital signs (systolic blood pressure, respiratory rate, and mental status) was compared with an extended model that also included four inflammatory markers (C-reactive protein, neutrophil-lymphocyte ratio, mean platelet volume, and red cell distribution width). Measures of interest were model fit, discrimination, and the net percentage of correctly reclassified individuals at the pre-specified threshold of 10% risk. RESULTS: Of the 1015 patients included, 66 (6.5%) died. The extended model including inflammatory markers performed significantly better than the vital sign model (likelihood ratio test: p < 0.001), and the c-index increased from 0.69 (range 0.67-0.70) to 0.76 (range 0.75-0.77) (p = 0.01). All included markers except C-reactive protein showed significant contribution to the model improvement. Among those who died, 9.1% (95% CI -2.8-21.8) were correctly reclassified by the extended model at the 10% threshold. CONCLUSIONS: The inflammatory markers except C-reactive protein showed added predictive value to vital signs. Future studies should focus on developing and validating prediction models for use in individualized predictions including both vital signs and the significant markers.

The Association Between Intra-abdominal View and Systemic Cytokine Response in Complicated Intra-abdominal Infections.

BACKGROUND: There is a wide variety of disease severity in patients with complicated intraabdominal infection (cIAI). The prognostic role of intraabdominal view (IAV) was recently studied, and an IAV score was introduced. The aim of this study was to analyze the associations between the preoperative levels of eight relevant circulating cytokines and IAV components, the IAV score, as well as outcome. MATERIALS AND METHODS: This was a single-center prospective study. The study cohort consisted of operatively managed adult patients with a cIAI. Preoperative plasma levels of eight cytokines were determined. The operating surgeon filled a form describing IAV. Outcomes analyzed were 30-day mortality and the development of organ dysfunctions requiring intensive care unit admission. RESULTS: A total of 131 patients with cIAI were analyzed, 30-day mortality was 9.9% (n = 13), and 28 (21.4%) patients had postoperative organ dysfunctions. All components of IAV, the IAV score, and outcomes were associated with various cytokine levels. Interleukin-8 was the most competent marker associating with all the variables assessed in this study: diffuse peritonitis (P < 0.001), substantial diffuse redness (P = 0.012), substantial diffuse fibrin (P = 0.003), fecal or bile as exudate (P = 0.001), nonappendiceal source of infection (P < 0.001), IAV Score groups (P < 0.001), organ dysfunctions (P < 0.001), and 30-day mortality (P = 0.035). CONCLUSIONS: Various cytokines associate with the IAV and outcome. IL-8 showed the best overall performance. The results emphasize the role of the surgeons' perception of the IAV. IAV provides an approximation of the magnitude of the systemic inflammatory response.

Diversity of Saccharomyces boulardii CNCM I-745 mechanisms of action against intestinal infections.

The yeast Saccharomyces boulardii CNCM I-745 is one of the probiotics recommended for the prevention of antibiotic-associated diarrhea. Studies conducted in vivo and in vitro demonstrated that in the case of infectious diseases there are two potential sites of action of Saccharomyces boulardii CNCM I-745: (1) An action on enteropathogenic microorganisms (adhesion of bacteria and their elimination or an effect on their virulence factors: Toxins, lipopolysaccharide, etc.); and (2) a direct action on the intestinal mucosa (trophic effects, effects on epithelial reconstitution, anti-secretory effects, anti-inflammatory, immunomodulators). Oral administration of Saccharomyces boulardii CNCM I-745 to healthy subjects does not alter their microbiota. However, in the case of diseases associated with the use of antibiotics or chronic diarrhea, Saccharomyces boulardii CNCM I-745 can restore the intestinal microbiota faster. The interaction of Saccharomyces boulardii CNCM I-745 with the innate immune system have been recently demonstrated thus opening up a new therapeutic potential of this yeast in the case of diseases associated with intestinal infections but also other pathologies associated with dysbiosis such as inflammatory diseases.

[Immunological characteristics of peritoneal cavity and intra-abdominal infection].

Despite the evolution of aggressive surgical techniques, extensive methods of supportive care and a vast array of anti-microbial options, intra-abdominal infection (IAI) is still a challenging clinical issue. Especially, when progressed IAI with septic complications because of unbalanced immune responses, the prognosis will deteriorated significantly. Recent studies indicate that besides the natural immunological cells, including macrophages and neutrophils, local immunological characteristics of peritoneal cavity should be studied with great attention. Among them, the omentum is considered to be a visceral adipose tissue with unique immune function. The milky spots(MSs) formed by the accumulation of immune cells performs immune surveillance and has a lymph node-like immune function, which is very important for the immune defense of the abdominal cavity. B1 cells and two types of intrinsic lymphocytes(ILC2) in the peritoneal cavity, although belonging to the lymphatic lineage, may play an important role in abdominal infections, especially in the early stages of the disease, due to their rapid responsiveness and acquired immune function. Therefore, paying attention to the immunological characteristics of the peritoneal cavity, and elucidating the changes, functions and regulatory mechanisms of B1 cells and ILC2 around the MSs and their components in the process of IAI, in order to explore the immunomodulation targets of blocking the infection from local to systemic dissemination, may be the key to solving the clinical problem of severe IAI and improving prognosis.

Immune Protection against Lethal Fungal-Bacterial Intra-Abdominal Infections.

Polymicrobial intra-abdominal infections (IAIs) are clinically prevalent and cause significant morbidity and mortality, especially those involving fungi. Our laboratory developed a mouse model of IAI and demonstrated that intraperitoneal inoculation with Candida albicans or other virulent non-albicans Candida (NAC) species plus Staphylococcus aureus resulted in 70 to 80% mortality in 48 to 72 h due to robust local and systemic inflammation (sepsis). Surprisingly, inoculation with Candida dubliniensis or Candida glabrata with S. aureus resulted in minimal mortality, and rechallenge of these mice with lethal C. albicans/S. aureus (i.e., coninfection) resulted in >90% protection. The purpose of this study was to define requirements for C. dubliniensis/S. aureus-mediated protection and interrogate the mechanism of the protective response. Protection was conferred by C. dubliniensis alone or by killed C. dubliniensis plus live S. aureusS. aureus alone was not protective, and killed S. aureus compromised C. dubliniensis-induced protection. C. dubliniensis/S. aureus also protected against lethal challenge by NAC plus S. aureus and could protect for a long-term duration (60 days between primary challenge and C. albicans/S. aureus rechallenge). Unexpectedly, mice deficient in T and B cells (Rag-1 knockouts [KO]) survived both the initial C. dubliniensis/S. aureus challenge and the C. albicans/S. aureus rechallenge, indicating that adaptive immunity did not play a role. Similarly, mice depleted of macrophages prior to rechallenge were also protected. In contrast, protection was associated with high numbers of Gr-1hi polymorphonuclear leukocytes (PMNLs) in peritoneal lavage fluid within 4 h of rechallenge, and in vivo depletion of Gr-1+ cells prior to rechallenge abrogated protection. These results suggest that Candida species can induce protection against a lethal C. albicans/S. aureus IAI that is mediated by PMNLs and postulated to be a unique form of trained innate immunity.IMPORTANCE Polymicrobial intra-abdominal infections are clinically devastating infections with high mortality rates, particularly those involving fungal pathogens, including Candida species. Even in patients receiving aggressive antimicrobial therapy, mortality rates remain unacceptably high. There are no available vaccines against IAI, which is complicated by the polymicrobial nature of the infection. IAI leads to lethal systemic inflammation (sepsis), which is difficult to target pharmacologically, as components of the inflammatory response are also needed to control the infection. Our studies demonstrate that prior inoculation with low-virulence Candida species provides strong protection against subsequent lethal infection with C. albicans and S. aureus Surprisingly, protection is long-lived but not mediated by adaptive (specific) immunity. Instead, protection is dependent on cells of the innate immune system (nonspecific immunity) and provides protection against other virulent Candida species. This discovery implies that a form of trained innate immunity may be clinically effective against polymicrobial IAI.

NMI and IFP35 serve as proinflammatory DAMPs during cellular infection and injury.

Damage-associated molecular patterns (DAMP) trigger innate immune response and exacerbate inflammation to combat infection and cellular damage. Identifying DAMPs and revealing their functions are thus of crucial importance. Here we report that two molecules, N-myc and STAT interactor (NMI) and interferon-induced protein 35 (IFP35) act as DAMPs and are released by activated macrophages during lipopolysaccharide-induced septic shock or acetaminophen-induced liver injury. We show that extracellular NMI and IFP35 activate macrophages to release proinflammatory cytokines by activating nuclear factor-κB through the Toll-like receptor 4 pathway. In addition, the serum levels of NMI are increased in patients who succumbed to severe inflammation. NMI deficiency reduces inflammatory responses and mortality in mouse models of sepsis and liver injury. We therefore propose that extracellular NMI and IFP35 exacerbate inflammation as DAMPs, making them potential therapeutic targets for clinical intervention.Damage-associated molecular patterns (DAMP) are important mediators of innate immunity. Here the authors show that N-myc and STAT interactor (NMI) and interferon-induced protein 35 (IFP35) act as DAMPs to promote inflammation by activating macrophages via the Toll-like receptor 4 and NF-κB pathways.

[PREDICTORS OF UNFAVORABLE OUTCOME IN PATIENTS WITH ABDOMINAL SEPSIS.]

OBJECTIVE: The study focuses on identifying predictors of treatment outcome in abdominal sepsis (AS) in humans. SUBJECTS AND METHODS: 70 patients underwent determination of blood pressure, heart rate, SpO , the content of leu- kocytes, albumin, C-reactive protein, fibrinogen and TNF-a in arterial (femoral artery) and venous (subclavian vein) blood. Automatic biochemical analyzer Cobas-Integra 400 ('Roche", Switzerland), the test system Microlab STAR ELISA kit reagents "alpha TNF - ELISA - best" were used during the research. System statistical analysis included paired comparison of patients with favorable (n=27) and lethal (n=43) outcome, correlation, cluster; discriminating analysis, multidimensional scaling and plotting ROC curves with sensitivity and specificity indicators predictive value. RESULTS: Identfied predictors of outcome inpatients,from which to form a predictive model of CRP fibrinogen, albumin, and TNF-a arterial blood. It is established that if the basic treatment of the patient CRP <9,8 g/l,fibrinogen >3,43 g/l, albumin <28,9 gl and TNF-a <499,3 ng/ml, the probability of death was statistically significantly higher thanfavorable. CONCLUSION: It is assumed that therapeutic measures should be aimed at correction of the above mentioned indicators.

Association of lectin pathway proteins with intra-abdominal Candida infection in high-risk surgical intensive-care unit patients. A prospective cohort study within the fungal infection network of Switzerland.

OBJECTIVES: Human studies on the role of mannose-binding lectin (MBL) in patients with invasive candidiasis have yielded conflicting results. We investigated the influence of MBL and other lectin pathway proteins on Candida colonization and intra-abdominal candidiasis (IAC) in a cohort of high-risk patients. METHODS: Prospective observational cohort study of 89 high-risk intensive-care unit (ICU) patients. Levels of lectin pathway proteins at study entry and six MBL2 single-nucleotide polymorphisms were analyzed by sandwich-type immunoassays and genotyping, respectively, and correlated with development of heavy Candida colonization (corrected colonization index (CCI) ≥0.4) and occurrence of IAC during a 4-week period. RESULTS: Within 4 weeks after inclusion a CCI ≥0.4 and IAC was observed in 47% and 38% of patients respectively. Neither serum levels of MBL, ficolin-1, -2, -3, MASP-2 or collectin liver 1 nor MBL2 genotypes were associated with a CCI ≥0.4. Similarly, none of the analyzed proteins was found to be associated with IAC with the exception of lower MBL levels (HR 0.74, p = 0.02) at study entry. However, there was no association of MBL deficiency (<0.5 µg/ml), MBL2 haplo- or genotypes with IAC. CONCLUSION: Lectin pathway protein levels and MBL2 genotype investigated in this study were not associated with heavy Candida colonization or IAC in a cohort of high-risk ICU patients.

Toll-like Receptor 4 Signaling on Dendritic Cells Suppresses Polymorphonuclear Leukocyte CXCR2 Expression and Trafficking via Interleukin 10 During Intra-abdominal Sepsis.

BACKGROUND: Toll-like receptor 4 (TLR4) is a critical receptor involved in the sensing of gram-negative bacterial infection. However, the roles of TLR4 in sepsis are cell-type specific. Dendritic cells (DCs) are known to play a central role in microbial detection, alerting the immune system to the presence of infection and coordinating adaptive immune response. The goal of this study was to investigate the impact of DC-specific TLR4 signaling on host defense against intra-abdominal polymicrobial sepsis. METHODS: C57BL/6, global Tlr4 knockout, cell-specific knockout control, and CD11c-specific Tlr4(-/-) mice underwent cecal ligation and puncture (CLP). RESULTS: Specific deletion of TLR4 on DCs in mice improved survival and enhanced bacterial clearance. Deletion of TLR4 on DCs was associated with lower levels of circulating interleukin 10 (IL-10), higher polymorphonuclear leukocyte (PMN) accumulation in the peritoneal cavity, and higher expression of chemokine (C-X-C motif) receptor 2 (CXCR2) on PMNs after CLP. In vitro studies of DC and neutrophil cocultures confirmed that TLR4-dependent secretion of IL-10 from DCs regulated neutrophil CXCR2 expression. CONCLUSIONS: Our data shed light on a previously unrecognized role for TLR4 signaling on DCs in driving IL-10 secretion during sepsis and, through this pathway, regulates PMN recruitment via suppression of CXCR2 expression.

Divergent invariant natural killer T-cell response to sepsis of abdominal vs. non-abdominal origin in human beings.

BACKGROUND: The etiology of sepsis is broad. The peritoneal cavity displays compartmentalization with respect to inflammatory responses, so peripheral blood responses to sepsis of abdominal vs. non-abdominal origin are expected to be divergent. Lymphocytes and invariant natural killer T (iNKT) cells play important roles in survival from sepsis, as they dampen the neutrophil and macrophage responses. We assessed whether circulating iNKT cells display distinct phenotypic profiles depending on the presence of abdominal vs. non-abdominal infection with sepsis. METHODS: Patients with sepsis, defined as infection confirmed microbiologically with a systemic inflammatory response syndrome (SIRS), were enrolled prospectively. They were categorized as having either exclusively sepsis of abdominal or exclusively non-abdominal origin. The white blood cell (WBC) count was recorded. Whole-blood staining with monoclonal antibodies to CD3, V-alpha-24 (to identify iNKT cells), and CD69 (marker of early activation) was applied. RESULTS: Of the 53 enrolled patients, 18 had abdominal infection. Pneumonia was the most common non-abdominal type. There was no difference in gender, age, Acute Physiology and Chronic Health Evaluation (APACHE) II score, WBC count, or CD3(+) T cells (7.1%±1.6% vs. 6.5%±0.9%; p=0.75) in the two groups. Patients with abdominal infection had a higher proportion of iNKT cells (2.7%±1.1% vs. 0.89%±0.14%; p=0.032). Correcting for WBC count, this translated into a higher absolute number of iNKT cells (3.4±1.8×10(7)/L vs. 0.74±0.15×10(7)/L; p=0.03). Patients with sepsis of abdominal origin had a lower percentage of CD69(+) iNKT cells (9.1%±3.1% vs. 27.2%±5.8%; p=0.028). In patients in shock vs. those who were not, patients with non-abdominal infection exhibited a greater number of iNKT cells (1.47±0.3 v. 0.62±0.1×10(7)/L; p=0.022) and percentage of activated iNKT cells (53±14.5% vs. 17.9±4.8%; p=0.04). Patients with non-abdominal infection who died had a lower absolute number of activated iNKT cells (0.8±1.2×10(7)/L vs. 0.34±0.1×10(7)/L; p=0.023); however, no such shock or death correlation was noted in patients with sepsis of abdominal origin. CONCLUSIONS: Divergent sepsis etiologies display distinct blood iNKT cell population changes. In non-abdominal infection, this difference was associated with septic shock and death. Elucidating the importance and basis for these changes relative to the response to sources of infection will help clarify appropriate diagnosis and management of the patient with sepsis.

Effects of carbon dioxide pneumoperitoneum on the inflammatory response and bacterial translocation in intraabdominal infection.

BACKGROUND: This study evaluated the effect of CO2 pneumoperitoneum on intraabdominal infection and bacterial translocation in intraabdominal infection. MATERIALS AND METHODS: Escherichia coli and Bacteroides fragilis were injected separately into the abdominal cavities of 30 New Zealand white rabbits to establish two animal models of intraabdominal infection. Each model was divided into a laparotomy group, a pneumoperitoneum group, and a control group. Before and 1, 2, 4, and 7 days after surgery, blood and peritoneal fluids were obtained to determine bacterial culture and serum interleukin-6, tumor necrosis factor-α, and C-reactive protein levels by enzyme-linked immunosorbent assay. The total number of white blood cells (WBCs) was measured. Seven days after surgery, the animals were sacrificed and dissected, and liver, kidney, and spleen tissues were obtained for bacterial culture. RESULTS: In the two bacterial models, incidence rates of bacteremia were higher in the laparotomy and pneumoperitoneum groups than in the control group. However, there were no significant differences between the laparotomy and pneumoperitoneum groups. Visceral bacterial translocation was detected in each group with no significant difference among the three groups. The change of inflammatory factors in the E. coli group and the B. fragilis group was nearly the same: the inflammatory factor levels and WBC counts in the laparotomy group were significantly higher than in the pneumoperitoneum group. The inflammatory factor levels and WBC counts in the pneumoperitoneum group increased slowly and were restored to normal quickly. CONCLUSIONS: In the intraabdominal infection animal model of the pneumoperitoneum group, the inflammatory response was weaker and the immune function was less affected and restored to normal more quickly than in the laparotomy group. The incidence rate of visceral bacterial translocation was not higher than that in the laparotomy group.

Genetic variations in toll-like receptor 4 in Mexican-Mestizo patients with intra-abdominal infection and/or pneumonia.

Sepsis is a leading cause of death around the world, and 73-83% of all sepsis cases requiring attention in intensive care units are linked to intra-abdominal infection (IAI) or pneumonia. The activation of innate immunity is central to the manifestation of sepsis, and toll-like receptor (TLR) 4 plays an important role in this activation process. The 299G and 399I alleles of TLR4 have been linked with an increased risk of Gram-negative bacteria (GNB) infections and septic shock in some populations. This case-control study evaluated the prevalence of D299G/T399I polymorphisms in Mexican patients with IAI and/or pneumonia and in healthy controls. Genotyping revealed that 1 in 44 patients (2.3%; CI 95%: 0.05-12.0%) and 4 in 126 controls (3.2%; CI 95%: 0.9-7.9%) were heterozygous for both the D299G and T399l polymorphisms (OR: 0.71, CI 95%: 0.01-7.44, p = NS), confirming the co-segregation of these alleles in this population. Furthermore, the patients with a GNB infection and severe sepsis were not carriers of the risk alleles. In summary, this report shows that the frequency of the D299G and T399I polymorphisms in Mexican-Mestizos is lower than anticipated in comparison with other ethnic groups, emphasizing the variable distribution of TLR4 polymorphisms among different populations. Consequently, this study was not able to detect associations between TLR4 polymorphisms and sepsis in this population.

The antimicrobial peptide, epinecidin-1, mediates secretion of cytokines in the immune response to bacterial infection in mice.

Epinecidin-1, an antimicrobial peptide which encodes 21 amino acids, was isolated from a marine grouper (Epinephelus coioides). In this study, we investigated its immunomodulatory functions in mice co-injected with Pseudomonas aeruginosa. In vivo results showed that the synthetic epinecidin-1 peptide induced significant secretion of immunoglobulin G1 (IgG1) in mice co-injected with P. aeruginosa. Moreover, after injection of 40, 100, 200, or 500 µg epinecidin-1/mouse, we detected IgM, IgG, IgG1, and IgG2a in mice treated for 1, 2, 3, 7, 14, 21, and 28 days. Results showed that there were no significant differences in IgM, IgG, or IgG2a between mice injected with epinecidin-1 alone. IgG1 increased to a peak at 24 h, 7 days, and 28 days after an epinecidin-1 (40 µg/mouse) injection. Injection of 500 µg epinecidin-1/mouse increased IgG1 to peaks at 2 and 3 days; injection of 100 µg epinecidin-1/mouse increased IgG1 to a peak at 21 days. This supports epinecidin-1 being able to activate the Th2 cell response (enhance IgG1 production) against P. aeruginosa infection. Treatment with different concentrations of epinecidin-1 in mice elevated plasma interleukin (IL)-10 to initial peaks at 24 and 48 h, and it showed a second peak at 16 days. In RAW264.7 cells, treatment with epinecidin-1 alone did not produce significant changes in tumor necrosis factor (TNF)-α protein secretion at 1, 6, or 24h after treatment with 3.75, 7.5, or 15 µg/ml epinecidin-1 compared to the lipopolysaccharide group.

Peritoneal fluid: a potential mechanism of systemic neutrophil priming in experimental intra-abdominal sepsis.

BACKGROUND: Recent studies suggest that peritoneal fluid (PF) may be an important mediator of inflammation. The aim of this study was to test the hypothesis that PF may drive systemic inflammation in intra-abdominal sepsis by representing a priming agent for neutrophils. METHODS: PF was collected 12 hours after the initiation of intra-abdominal sepsis in swine. Naive human neutrophils were primed with PF before treatment with N-formyl-Met-Leu-Phe or phorbol 12-myristate 13-acetate to elucidate receptor-dependent and receptor-independent mechanisms of neutrophil activation. Flow cytometry was used to quantify neutrophil surface adhesion marker expression of integrins and selectins and superoxide anion production. Additionally, proinflammatory cytokines were quantified in PF. RESULTS: PF primed neutrophils via receptor-dependent and receptor-independent mechanisms. There were significant increases in the proinflammatory cytokines interleukin-6 and tumor necrosis factor-α in PF correlating with the development of intra-abdominal sepsis. CONCLUSIONS: PF represents a priming agent for naive polymorphonuclear cells in intra-abdominal sepsis. This may be secondary to increased levels of proinflammatory cytokines. Strategies to reduce the amount of PF may decrease the systemic inflammatory response by reducing a priming agent for neutrophils.

Regulation of lymphocyte trafficking by CXC chemokine receptor 3 during septic shock.

RATIONALE: Lymphocytes have been shown to facilitate systemic inflammation and physiologic dysfunction in experimental models of severe sepsis. Our previous studies show that natural killer (NK) cells migrate into the peritoneal cavity during intraabdominal sepsis, but the trafficking of NKT and T lymphocytes has not been determined. The factors that regulate lymphocyte trafficking during sepsis are currently unknown. OBJECTIVES: To ascertain the importance of CXC chemokine receptor 3 (CXCR3) as a regulator of lymphocyte trafficking during sepsis and determine the contribution of CXCR3-mediated lymphocyte trafficking to the pathogenesis of septic shock. METHODS: Lymphocyte trafficking was evaluated in control and CXCR3-deficient mice using flow cytometry during sepsis caused by cecal ligation and puncture (CLP). Survival, core temperature, cytokine production, and bacterial clearance were measured as pathobiological endpoints. MEASUREMENTS AND MAIN RESULTS: This study shows that concentrations of the CXCR3 ligands CXCL9 (monokine induced by interferon γ, MIG) and CXCL10 (interferon γ-induced protein 10, IP-10) increase in plasma and the peritoneal cavity after CLP, peak at 8 hours after infection, and are higher in the peritoneal cavity than in plasma. The numbers of CXCR3(+) NK cells progressively decreased in spleen after CLP with a concomitant increase within the peritoneal cavity, a pattern that was ablated in CXCR3-deficient mice. CXCR3-dependent recruitment of T cells was also evident at 16 hours after CLP. Treatment of mice with anti-CXCR3 significantly attenuated CLP-induced hypothermia, decreased systemic cytokine production, and improved survival. CONCLUSIONS: CXCR3 regulates NK- and T-cell trafficking during sepsis and blockade of CXCR3 attenuates the pathogenesis of septic shock.

[Relation of mesenteric lymph node and innate immune function in septic rats].

OBJECTIVE: To investigate the changes in T helper cells (Th1 and Th2) of mesenteric lymph node (MLN) and blood Th1 and Th2 cells in septic rats. METHODS: Ninety-six male Wistar rats were randomly divided into two groups according to random number table method: sham operation group and model group. Intra-abdominal infection with sepsis was induced by cecal ligation and puncture (CLP). Eight rats in each group were sacrificed after collection of blood samples and MLN samples at 0, 6, 12, 24, 48 and 72 hours after CLP. The ratio of Th1/Th2 and the percentage of regulatory T cell (Treg) in CD4+ T cells in blood and MLN were respectively determined by flow cytometry. RESULTS: In model group, the ratio of Th1/Th2 in abdominal aorta blood increased significantly at 6 hours and reached summit at 12 hours, then it decreased persistently, and when compared with sham group, the ratio of Th1/Th2 was significantly higher at 6, 12, 24 hours (0.82±0.15 vs. 0.60±0.22, 1.23±0.44 vs. 0.76±0.31, 0.85±0.25 vs. 0.66±0.32) and lower at 72 hours (0.41±0.16 vs. 0.59±0.13, P<0.05 or P<0.01). The ratio of Th1/Th2 in MLN of model group reached summit at 6 hours, then decreased significantly, and when compared with sham group, the ratio of Th1/Th2 was significantly higher at 6 hours (1.01±0.16 vs. 0.52±0.13) and lower at 12, 24, 48 and 72 hours (0.34±0.11 vs. 0.53±0.09, 0.23±0.08 vs. 0.51±0.09, 0.17±0.07 vs. 0.47±0.15, 0.16±0.06 vs. 0.53±0.11, P<0.05 or P<0.01). Compared with sham group, the percentage of Treg in MLN of model group was increased at 12, 24, 48 and 72 hours after CLP (9.62±0.69 vs. 7.65±0.67, 9.84±0.74 vs. 8.08±1.06, 10.95±2.09 vs. 7.83±1.15, 10.81±1.34 vs. 8.35±1.12, P<0.05 or P<0.01). There was a negative correlation between the ratio of Th1/Th2 and the percentage of Treg in MLN (r=-0.882, P<0.05). CONCLUSION: Cellular immune function of MLN is suppressed during severe intra-abdominal infection, which induces translocation of gut-derived endotoxin to mesenteric lymphatics, resulting in corporal immuno-suppression, with manifestation of Th1/Th2 cell shift. Immuno-suppression of MLN is related to a higher percentage of Treg due to the effect of endotoxin.