Reverse kinetics of angiopoietin-2 and endotoxins in acute pyelonephritis: Implications for anti-inflammatory treatment?

Based on former studies showing an antagonism between angiopoietin-2 (Ang-2) and bacterial endotoxins (LPS), we investigated the role of Ang-2 as immunomodulatory treatment. At first, kinetics of circulating LPS in Gram-negative pyelonephritis developing after urinary obstruction was studied. Serum LPS, interleukin (IL)-6 and Ang-2 were measured in 25 patients with acute pyelonephritis and sepsis before and after removal of the obstruction performed either with insertion of a pigtail catheter (n=12) or percutaneous drainage (n=13). At a second stage, Ang-2 was given as anti-inflammatory treatment in 40 rabbits one hour after induction of acute pyelonephritis by ligation of the ureter at the level of pelvo-ureteral junction and upstream bacterial inoculation. Survival was recorded; blood mononuclear cells were isolated and stimulated for the production of tumour necrosis factor-alpha (TNFα). The decrease in circulating LPS was significantly greater among patients undergoing drainage than pigtail insertion. This was accompanied by reciprocal changes of Ang-2 and IL-6. Treatment with Ang-2 prolonged survival from Escherichia coli pyelonephritis despite high levels of circulating LPS. When Ang-2 was given as treatment of Pseudomonas aeruginosa pyelonephritis, sepsis-induced decrease of TNFα production by circulating mononuclear cells was reversed without an effect on tissue bacterial overgrowth. It is concluded that Ang-2 and LPS follow reverse kinetics in acute pyelonephritis. When given as experimental treatment, Ang-2 prolongs survival through an effect on mononuclear cells.

Immunomodulatory intervention with interferon-γ in Escherichia coli pyelonephritis.

PURPOSE: We investigated the efficacy of recombinant human interferon-γ in experimental pyelonephritis due to Escherichia coli. MATERIALS AND METHODS: Pyelonephritis was induced by intrapelvic inoculation of bacteria after ureteral ligation in 38 rabbits assigned to 1 of 3 groups, including group 1-16 controls, group 2-14 rabbits treated with intravenous recombinant human interferon-γ and group 3-8 rabbits treated with intravenous recombinant human interferon-γ plus amikacin. Bacterial counts, cytokines and malondialdehyde were measured in blood. Peripheral blood mononuclear cells were isolated to measure TNFα transcripts, cytokine stimulation and apoptosis. Survival was recorded, and the tissue bacterial load and myeloperoxidase activity were measured after sacrifice. RESULTS: The mortality rate in groups 1, 2 and 3 was 66.7%, 25% and 12.5%, respectively. The circulating bacterial count and tissue bacterial load were less in group 2 than in group 1. Circulating malondialdehyde negatively correlated with the bacterial load of the spleen. Although the number of TNFα transcripts in circulating peripheral blood mononuclear cells did not differ, peripheral blood mononuclear cells isolated from group 2 at 48 hours produced much greater concentrations of tumor necrosis factor-α after stimulation with Pam3Cys. In parallel, the apoptosis rate of circulating monocytes was increased in group 2 at 48 hours. Lung myeloperoxidase activity at 24 hours, serving as indirect evidence of neutrophil infiltration, was decreased in group 2. CONCLUSIONS: Recombinant human interferon-γ administration prolonged survival in rabbits with experimental E. coli urosepsis. Its action was probably related to increased bacterial phagocytosis after modulation of oxidant status and reversal of monocyte immunoparalysis.

Efficacy of tigecycline alone and in combination with gentamicin in the treatment of experimental endocarditis due to linezolid-resistant Enterococcus faecium.

We evaluated the efficacy of tigecycline in a rabbit model of experimental endocarditis caused by a linezolid-resistant clinical strain of Enterococcus faecium. Tigecycline-treated animals had a 2.8-log10-CFU/g reduction in microbial counts in excised vegetations compared with controls. Addition of gentamicin caused a further arithmetical reduction in colony counts. The therapeutic effect was sustained 5 days after completion of treatment, as shown by relapse studies performed in treatment groups.

Pre-treatment with low-dose endotoxin prolongs survival from experimental lethal endotoxic shock: Benefit for lethal peritonitis by Escherichia coli.

Although LPS tolerance is well-characterized, it remains unknown if it is achieved even with single doses of lipopolysaccharide (LPS) and if it offers protection against lethal bacterial infections. To this end, C57B6 mice were assigned to groups A (sham); B (saline i.p followed after 24h by i.p 30mg/kg LPS); and C (3mg/kg LPS i.p followed after 24h by i.p 30mg/kg LPS). Survival was monitored and animals were sacrificed early after lethal challenge for measurement of tumour necrosis factor-alpha (TNFα) in serum; isolation of splenocytes and cytokine stimulation; and flow-cytometry for apoptosis and TREM-1. Experiments were repeated with mice infected i.p by Escherichia coli after challenging with saline or LPS. Mortality of group B was 72.2% compared with 38.9% of group C (p: 0.020). Serum TNFα of group C was lower than group B. Expression of TREM-1 of group C on monocytes/neutrophils was greater than group B. Release of TNFα, of IFNγ and of IL-17 from splenocytes of group C was lower than group B and the opposite happened for IL-10 showing evidence of cellular reprogramming. In parallel, apoptosis of circulating lymphocytes and of splenocytes of group C was greater compared with group B. Pre-treatment of mice challenged by E. coli with low dose LPS led to 0% mortality compared with 90% of saline pre-treated mice; in these mice, splenocytes improved over-time their capacity for release of IFNγ. It is concluded that single low doses of LPS lead to early reprogramming of the innate immune response and prolong survival after lethal E. coli challenge.

Bacterial translocation in an experimental model of multiple organ dysfunctions.

BACKGROUND: In order to investigate the hypothesis that bacterial translocation from the intestine contributes to death after multiple organ dysfunction syndrome (MODS), a sterile MODS model was studied. METHODS: MODS was induced in 139 male C57BL/6 mice by lipopolysaccharide (LPS) (endotoxin) infusion followed by zymozan infusion in four groups: Α, sham-operation; Β, LPS; C, LPS + 0.8 g/kg zymozan; and D, LPS + 1.2 g/kg zymozan. Mice were sacrificed at 24 and 48 h for quantitative tissue cultures, isolation, and stimulation of splenocytes, measurement of apoptosis of lymphocytes and macrophages, and of serum LPS and survival. Some mice with MODS were treated with the antibiotic ertapenem. RESULTS: Enterobacteriaceae and Enterococcus spp were isolated from tissues. Group D had the highest bacterial load and the shortest survival. Release of interleukin-10, of interleukin-17, and of intgerferon-γ by splenocytes and the rate of apoptosis did not concur with immune paralysis. Serum LPS concentrations were higher in mice with MODS versus controls. Ertapenem prolonged survival and decreased the bacterial load. CONCLUSIONS: Bacterial translocation seems to be an important contributor leading from MODS to death and suggests a change in therapy towards adaptation of antimicrobial treatment upon early signs of MODS.

Compartmentalization of lipid peroxidation in sepsis by multidrug-resistant gram-negative bacteria: experimental and clinical evidence.

INTRODUCTION: Recent evidence suggests a link between excess lipid peroxidation and specific organ failures in sepsis. No study has been performed in sepsis by multidrug-resistant (MDR) Gram-negative bacteria. METHODS: Lethal sepsis was induced in rats by the intraperitoneal injection of one MDR isolate of Pseudomonas aeruginosa. Produced malondialdehyde (MDA) was measured in tissues 5 hours after bacterial challenge with the thiobarbiturate assay followed by high-performance liquid chromatography (HPLC) analysis. Results were compared with those from a cohort of patients with ventilator-associated pneumonia (VAP) and sepsis by MDR Gram-negative bacteria. More precisely, serum MDA was measured on 7 consecutive days, and it was correlated with clinical characteristics. RESULTS: MDA of septic rats was greater in the liver, spleen, and aortic wall, and it was lower in the right kidney compared with sham operated-on animals. Findings were confirmed by the studied cohort. Circulating MDA was greater in patients with hepatic dysfunction and acute respiratory distress syndrome (ARDS) compared with patients without any organ failures. The opposite was found for patients with acute renal dysfunction. No differences were found between patients with ARDS without or with cardiovascular (CV) failure and patients without any organ failure. Serial measurements of MDA in serum of patients indicated that levels of MDA were greater in survivors of hepatic dysfunction and ARDS and lower in survivors of acute renal dysfunction. CONCLUSIONS: Animal findings and results of human sepsis are complementary, and they suggest a compartmentalization of lipid peroxidation in systemic infections by MDR gram-negative bacteria.

Intravenous itraconazole against experimental neutropenic Candida parapsilosis infection: efficacy after suppression of bacterial translocation.

A variety of studies indicate that itraconazole possesses greater intrinsic activity compared to the other azole derivatives against Candida parapsilosis. Efficacy has never been tested in an experimental setting. To this end, C. parapsilosis was used for challenge of 117 rats rendered neutropenic after a course of cyclophosphamide. Rats were assigned to receive intravenous treatment with saline (group A); itraconazole q12h (group B); fluconazole q12h (group C); single dose of ceftriaxone and saline (group D); single dose of ceftriaxone and itraconazole q12h (group E); and single dose of ceftriaxone and fluconazole q12h (group F). Survival was recorded, and yeast outgrowth of liver, spleen, lung, and kidney was measured after sacrifice at serial time intervals. Growth of the test isolate in tissues was significantly lower in group B than in groups A and C after 72 h. However, outgrowth of enterobacteria was found in tissues of groups A, B, and C, implying a phenomenon of bacterial translocation from the gut. When this phenomenon was suppressed with single doses of ceftriaxone, a striking survival benefit of itraconazole-treated animals was found (p = 0.022, group E vs. group F). The present results suggest than in deep infections by C. parapsilosis intravenously administered intraconazole may eradicate the offending agent and provide survival benefit when chemotherapy-induced bacterial translocation from the gut is suppressed. Further clinical evidence is required to support these findings.

Angiopoietin-2 enhances survival in experimental sepsis induced by multidrug-resistant Pseudomonas aeruginosa.

Levels of circulating angiopoietin-2 (Ang-2) increase in sepsis, raising the possibility that Ang-2 acts as a modulator in the sepsis cascade. To investigate this, experimental sepsis was induced in male C57BL6 mice by a multidrug-resistant isolate of Pseudomonas aeruginosa; survival was determined along with neutrophil tissue infiltration and release of proinflammatory cytokines. Survival was significantly increased either by pretreatment with recombinant Ang-2 2 h before or treatment with recombinant Ang-2 30 min after bacterial challenge. Likewise, Ang-2 pretreatment protected against sepsis-related death elicited by Escherichia coli; however, Ang-2 failed to provide protection in lipopolysaccharide (LPS)-challenged mice. The survival advantage of Ang-2 in response to P. aeruginosa challenge was lost in tumor necrosis factor (TNF)-deficient mice or neutropenic mice. Infiltration of the liver by neutrophils was elevated in the Ang-2 group compared with saline-treated animals. Serum TNF-α levels were reduced by Ang-2, whereas those of interleukin (IL)-6 and IL-10 remained unchanged. This was accompanied by lower release of TNF-α by stimulated splenocytes. When applied to U937 cells in vitro, heat-killed P. aeruginosa induced the secretion of IL-6 and TNF-α; low levels of exogenous TNF-α synergized with P. aeruginosa. This synergistic effect was abolished after the addition of Ang-2. These results put in evidence a striking protective role of Ang-2 in experimental sepsis evoked by a multidrug-resistant isolate of P. aeruginosa attributed to modulation of TNF-α production and changes in neutrophil migration. The protective role of Ang-2 is shown when whole microorganisms are used and not LPS, suggesting complex interactions with the host immune response.

In vitro elution of daptomycin by a synthetic crystallic semihydrate form of calcium sulfate, stimulan.

A synthetic crystallic semihydrate form of calcium sulfate, Stimulan, was evaluated as a biodegradable carrier for the daily in vitro elution of daptomycin. Daptomycin and Stimulan were admixed at a ratio of 95:5. Elution lasted for 28 days. Eluted concentrations peaked on days 1 and 11, when the mean values were 1,320.1 and 949.2 microg/ml, respectively. The lowest eluted concentration was detected on day 28. These results support the application of the system described in experimental models of osteomyelitis.

In vitro elution of moxifloxacin and fusidic acid by a synthetic crystallic semihydrate form of calcium sulphate (Stimulan).

Stimulan was evaluated in vitro as a biodegradable carrier for local delivery of moxifloxacin and fusidic acid. Moxifloxacin or fusidic acid was mixed with calcium sulphate at a ratio of 95:5 to prepare five replicas per antibiotic. In vitro elution was estimated daily using a high-performance liquid chromatography (HPLC) system. Elution of moxifloxacin lasted for 31 days. Eluted concentrations reached their peak on Day 13 (mean level 745 microg/mL); the lowest eluted concentration was detected on Day 30 (mean level 367 microg/mL). Elution of fusidic acid lasted for 14 days. Eluted concentrations reached their peak on Day 6 (mean value 249.5 microg/mL); the lowest eluted concentration was detected on Day 13 (mean value 10.9 microg/mL). The presented results revealed that Stimulan may allow adequate in vitro elution of moxifloxacin and fusidic acid. The latter results support the application of this system in experimental models of osteomyelitis.

Immune responses in relation to the type and time of thermal injury: an experimental study.

BACKGROUND: Thermal injuries are followed by a complex immune response, but the relationship between the severity of burn injury and the time exposure to the thermal injury on the extent of the immune response is still not known. OBJECTIVE: This study focuses on characterising the effect of temperature and time exposure on the post-burn immune response. METHODS: We used 120 C57BL/6 male mice divided equally in 5 burn groups and one sham operated group (groups A-E and sham). Ten mice per group were sacrificed at 24 and 48 h after burn injury and whole blood was collected; specimens of liver, lung, spleen, kidney and bowel were excised. Apoptosis and TREM-1 expression on circulating blood cells were measured. Splenocytes were isolated and stimulated for cytokine production; the rate of apoptosis of splenocytes was also measured. RESULTS: Production of IL-17 from splenocytes of mice group D was enhanced. Considerable effects were shown on the apoptosis of circulating lymphocytes and of spleen cells. The apoptotic rates varied between groups and also evolved after 24 and 48 h. To examine the origin of this differential response, quantitative bacterial cultures of liver, lung and kidney were made but no differences were observed compared with sham-operated animals. LIMITATIONS: This study was based on an experimental murine model. CONCLUSION: There is a unique response for each type of injury depending on the temperature of the thermal source and the exposure time.

Modulation of the release of Ang-2 in experimental endotoxic shock by a species-specific circulating factor.

OBJECTIVES: To study the modulation of the release of angiopoietin-2 (Ang-2) in experimental endotoxic shock. METHODS: Twelve pigs were studied; eight became septic after the intravenous infusion of lipopolysaccharide (LPS) of Escherichia coli O55:B5. The concentrations of LPS, angiopoietin-2 (Ang-2), tumour necrosis factor-alpha (TNFα) and malondialdehyde (MDA) were measured soon after the LPS infusion in the serum samples from the pulmonary and systemic circulation. Peripheral blood mononuclear cells (PBMCs) were isolated from two healthy swine, from two healthy human donors and from four patients with septic shock. The PBMCs were cultured with the serum of the septic animals in the presence or absence of polymyxin B. Concentrations of Ang-2 and TNFα were measured in supernatants. RESULTS: Serum Ang-2 was higher in the systemic circulation than in the pulmonary circulation. Increased Ang-2 release was noted in swine PBMCs in the presence of polymyxin B. A reciprocal decrease in TNFα release was observed, typically after incubation with serum sampled from the pulmonary circulation. CONCLUSION: There is evidence for a circulating factor that primes Ang-2 release from blood monocytes in the event of septic shock. The finding indicates a possible site of interference within the septic shock cascade.

Early changes of procalcitonin may advise about prognosis and appropriateness of antimicrobial therapy in sepsis.

PURPOSE: The objective of this study is to define if early changes of procalcitonin (PCT) may inform about prognosis and appropriateness of administered therapy in sepsis. METHODS: A prospective multicenter observational study was conducted in 289 patients. Blood samples were drawn on day 1, that is, within less than 24 hours from advent of signs of sepsis, and on days 3, 7, and 10. Procalcitonin was estimated in serum by the ultrasensitive Kryptor assay (BRAHMS GmbH, Hennigsdorf, Germany). Patients were divided into the following 2 groups according to the type of change of PCT: group 1, where PCT on day 3 was decreased by more than 30% or was below 0.25 ng/mL, and group 2, where PCT on day 3 was either increased above 0.25 ng/mL or decreased less than 30%. RESULTS: Death occurred in 12.3% of patients of group 1 and in 29.9% of those of group 2 (P < .0001). Odds ratio for death of patients of group 1 was 0.328. Odds ratio for the administration of inappropriate antimicrobials of patients of group 2 was 2.519 (P = .003). CONCLUSIONS: Changes of serum PCT within the first 48 hours reflect the benefit or not of the administered antimicrobial therapy. Serial PCT measurements should be used in clinical practice to guide administration of appropriate antimicrobials.