Host cystathionine-γ lyase derived hydrogen sulfide protects against Pseudomonas aeruginosa sepsis

Hydrogen sulfide (H2S) has recently been recognized as a novel gaseous transmitter with several anti-inflammatory properties. The role of host- derived H2S in infections by Pseudomonas aeruginosa was investigated in clinical and mouse models. H2S concentrations and survival was assessed in septic patients with lung infection. Animal experiments using a model of severe systemic multidrug-resistant P. aeruginosa infection were performed using mice with a constitutive knock-out of cystathionine-γ lyase (Cse) gene (Cse-/-) and wild-type mice with a physiological expression (Cse+/+). Experiments were repeated in mice after a) treatment with cyclophosphamide; b) bone marrow transplantation (BMT) from a Cse+/+ donor; c) treatment with H2S synthesis inhibitor aminooxyacetic acid (ΑΟΑΑ) or propargylglycine (PAG) and d) H2S donor sodium thiosulfate (STS) or GYY3147. Bacterial loads and myeloperoxidase activity were measured in tissue samples. The expression of quorum sensing genes (QS) was determined in vivo and in vitro. Cytokine concentration was measured in serum and incubated splenocytes. Patients survivors at day 28 had significantly higher serum H2S compared to non-survivors. A cut- off point of 5.3 μΜ discriminated survivors with sensitivity 92.3%. Mortality after 28 days was 30.9% and 93.7% in patients with H2S higher and less than 5.3 μΜ (p = 7 x 10-6). In mice expression of Cse and application of STS afforded protection against infection with multidrug-resistant P. aeruginosa. Cyclophosphamide pretreatment eliminated the survival benefit of Cse+/+ mice, whereas BMT increased the survival of Cse-/- mice. Cse-/- mice had increased pathogen loads compared to Cse+/+ mice. Phagocytic activity of leukocytes from Cse-/- mice was reduced but was restored after H2S supplementation. An H2S dependent down- regulation of quorum sensing genes of P.aeruginosa could be demonstrated in vivo and in vitro. Endogenous H2S is a potential independent parameter correlating with the outcome of P. aeruginosa. H2S provides resistance to infection by MDR bacterial pathogens.

Association of modulation of pro-inflammatory responses by dectin-2 with preterm delivery: An experimental model

PROBLEM

Pro-inflammatory responses of pathogen recognition receptors (PRR) are implicated in preterm delivery (PTD). Dectin-2 is one PRR recognizing unselective carbohydrate structures; its participation in PTD has never been studied before.

METHOD OF STUDY

In an experimental model, PTD was induced in female pregnant wild-type (WT) mice and mice with homologous deficiency for dectin-2 by the intraperitoneal injection of bacterial lipopolysaccharide (LPS) on day 14 of pregnancy. Time to delivery and fetal mortality were recorded. Challenged mice were killed for tissue collection and splenocyte isolation 6 hours later. Concentrations of tumour necrosis factor-alpha (TNFα), interleukin (IL)-1α, and IL-1β were measured.

RESULTS

Delivery was induced significantly earlier in WT than dectin-2^-/- mice; however, fetal mortality was higher among dectin-2^-/- mice. Candida albicans challenge could not lead to these changes. Sacrifice experiments showed that LPS challenge led to significant increase of TNFα, IL-1α, and IL-1β in maternal tissues of WT; this was further enhanced for TNFα and IL-1β in dectin-2^-/- mice. Pre-treatment with the prostaglandin inhibitor diclofenac delayed time to delivery of WT mice, but not of dectin2^-/- mice. TNFα stimulation of splenocytes of dectin2^-/- mice was enhanced with the addition of anti-TLR4 and decreased in the presence of lipid A.

CONCLUSIONS

Dectin-2 delays LPS-induced PTD by enhancing the production of pro-inflammatory cytokines.

Early increase of VEGF-A is associated with resolution of ventilator-associated pneumonia: Clinical and experimental evidence

BACKGROUND AND OBJECTIVE

The role of vascular endothelial growth factor (VEGF)-A in the resolution of ventilator-associated pneumonia (VAP) was investigated in clinical and mouse pneumonia models.

METHODS

VEGF-A was measured for seven consecutive days by an immunosorbent assay in sera of 82 patients with VAP and changes from baseline were correlated with the resolution of VAP. Experimental animals were challenged intratracheally with Pseudomonas aeruginosa. Mouse bronchoalveolar lavage (BAL) samples and segments of lung tissue were obtained at 24, 48 and 124 h after bacterial challenge. Levels of VEGF-A, tumour Necrosis Factor alpha (TNF-α), interleukin (IL)-1β, interferon-gamma (IFNγ) and myeloperoxidase (MPO) activity were measured in these samples.

RESULTS

VAP resolved in 36.1% of patients with a less than 45% increase of VEGF-A on day 5 compared to 65.2% of patients with a more than 45% increase (P = 0.014). This was also accompanied by an earlier resolution of VAP (log-rank: 7.99; P = 0.005) and it was not pathogen-specific. The increase of VEGF-A was an independent variable associated with VAP resolution in forward logistic regression analysis where Acute Physiology and Chronic Health Evaluation (APACHE) II and Sequential Organ Failure Assessment (SOFA) scores were included as independent variables. VEGF-A in mouse BAL and lung tissue increased significantly at 124 h but not with the other mediators. In mice pre-treated with bevacizumab, VEGF-A concentrations decreased while TNF-α and MPO significantly increased.

CONCLUSION

In patients, an association between increased levels of circulating VEGF-A and VAP resolution was observed. The mouse study suggests that elevated VEGF-A levels may be associated with lung inflammation resolution.

CLINICAL TRIAL REGISTRATION

NCT00297674 at www.clinicaltrials.gov.

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.

Immunomodulatory effect of three-day continuous administration of clarithromycin for experimental sepsis due to multidrug-resistant Pseudomonas aeruginosa

Based on former animal studies showing the effect of clarithromycin in experimental sepsis by multidrug-resistant Pseudomonas aeruginosa following administration of single doses, the significance of its administration for three consecutive days was evaluated. Acute pyelonephritis was induced in 20 rabbits after inoculation of the test isolate in the renal pelvis. Therapy was administered upon signs of sepsis in group B; A served as control. Survival was recorded; monocytes were isolated for determination of ex vivo TNFalpha secretion. Quantitative cultures of organs were performed after death. Mean survival of groups A and B was 2.65 and 7.95 days respectively. At 24 hours, serum malondialdehyde of group B, which is an index of the oxidant status in serum, was lower than A. Ex vivo release of TNFalpha by the isolated monocytes of group B was lower than A at 3.5 and 48 hours. Tissue bacterial load was similar in two groups after animal death. It is concluded that clarithromycin possessed considerable immunomodulatory effects restraining release of TNFalpha from blood monocytes.

Early apoptosis of blood monocytes is a determinant of survival in experimental sepsis by multi-drug-resistant Pseudomonas aeruginosa

Apoptosis of blood monocytes was studied in experimental sepsis by multi-drug-resistant Pseudomonas aeruginosa. Thirty-six rabbits were used, divided into the following groups: A (n = 6), sham; B (n = 6), administered anaesthetics; and C (n = 24), acute pyelonephritis induced after inoculation of the test isolate in the renal pelvis. Blood was sampled at standard time intervals for estimation of tumour necrosis factor (TNF)-alpha and isolation of monocytes. Half the monocytes were incubated and the other half was lysed for estimation of the cytoplasmic activity of caspase-3 by a kinetic chromogenic assay. No animal in groups A and B died; those in group C were divided into two subgroups, CI (n = 8) with present activity of caspase-3 of blood monocytes at 3.5 h and CII (n = 16) with absent activity. Their median survival was 2.0 and 3.5 days, respectively (P = 0.0089). Ex vivo secretion of TNF-alpha from monocytes was higher by monocytes of subgroup CII than subgroup CI at 3.5 h (P = 0.039) and of group A than CII at 48 h (P = 0.010). Median change of caspase-3 activity between 3.5 and 24 h of sampling was 56.1 and -5.8 pmol/min per 10(4) cells for subgroups CI and CII (P = 0.040), respectively. Respective changes between 3.5 and 48 h were 28 981.0 and 0 pmol/min per 10(4) cells (P = 0.036). Early induction of apoptosis in blood monocytes is of prime importance for the survival of the septic host and might be connected to changes of monocyte potential for the secretion of TNF-alpha.

The in vitro effective antiviral action of povidone-iodine (PVP-I) may also have therapeutic potential by its intravenous administration diluted with Ringer's solution

The use of povidone-iodine (PVP-I) is well known in clinical medical practice. In vitro studies of cell cultures infected by HIV and H5N1 virus have shown that PVP-I has an antiviral action, while the cell hosts were not affected and survived. It is therefore worth investigating whether PVP-I, diluted with Ringer's solution, may have a therapeutic effect by parenteral administration. Specifically, the question is whether small concentrations of intravenous PVP-I could be well tolerated by the human organism, and in addition, if it would be possible to detect a beneficial activity. Its intravenous use may have a potential value against infections (by microbes, viruses, fungi and parasites), as well as an anti-inflammatory activity, especially in cases where antibiotics are ineffective. It could be used as a blood disinfectant, for treating burns, for the prevention of cancer, for the therapy of H5N1 influenza after its mutation, and other potential applications.

OLEUROPEIN

Oleuropein, a novel immunomodulator derived from olive tree, was assessed in vitro and in experimental sepsis by Pseudomonas aeruginosa. After addition in monocyte and neutrophil cultures, malondialdehyde, TNF-alpha, IL-6, and bacterial counts were estimated in supernatants. Acute pyelonephritis was induced in 70 rabbits after inoculation of pathogen in the renal pelvis. Intravenous therapy was administered in four groups postchallenge by one multidrug-resistant isolate (A, controls; B, oleuropein; C, amikacin; D, both agents) and in three groups postchallenge by one susceptible isolate (E, controls; F, oleuropein; G, amikacin). Survival was recorded; bacterial growth in blood and organs was counted; endotoxins (LPS), malondialdehyde, total antioxidant status, and TNF-alpha in serum were estimated. TNF-alpha and IL-6 of cell supernatants were not increased compared with controls when triggered by LPS and P. aeruginosa. Counts of multidrug-resistant P. aeruginosa were decreased in monocyte supernatants. Median survival of groups A, B, C, D, E, F, and G were 3.00, 6.00, 2.00, 10.00, 1.00, 5.00, and 1.00 days, respectively. Bacteria in blood were lower at 48 h in groups B and D compared with A and in groups F and G compared with E. Total antioxidant status decreased steadily over time in groups A, C, D, and G, but not in groups B and F. TNF-alpha of groups B, C, and D was lower than A at 48 h. Tissue bacteria decreased in group F compared with E. Oleuropein prolonged survival in experimental sepsis probably by promoting phagocytosis or inhibiting biosynthesis of proinflammatory cytokines.

Clarithromycin is an effective immunomodulator in experimental pyelonephritis caused by pan-resistant Klebsiella pneumoniae

OBJECTIVES

To apply clarithromycin as an immunomodulatory treatment in experimental infection caused by pan-resistant Klebsiella pneumoniae.

METHODS

Acute pyelonephritis was induced in 80 rabbits after inoculation of the test isolate in the renal pelvis. Rabbits were divided into eight groups, with 10 animals in each group. In groups A-D, therapy was administered simultaneously with bacterial challenge as follows: A, controls; B, intravenous clarithromycin; C, amikacin; and D, both agents. In groups E-H, therapy was administered 24 h after bacterial challenge as follows: E, controls; F, intravenous clarithromycin; G, amikacin; and H, both agents. Blood was sampled for estimation of tumour necrosis factor-alpha (TNF-alpha) and malondialdehyde (MDA); monocytes were isolated for determination of intracellular activity of caspase-3 and ex vivo TNF-alpha secretion. Four days after bacterial challenge, animals were sacrificed for quantitative cultures and biopsies of organs.

RESULTS

Serum TNF-alpha at 48 h was lower in groups B, C and D compared with group A. Activity of caspase-3 of monocytes was lower at 48 h in group D compared with group A. Bacterial loads of liver and spleen were decreased in group D compared with those of group A. The numbers of inflammatory cells of spleen of group B were lower compared with those of group A; those of kidney and mesenteric lymph nodes of group D were lower than those of group A. Serum MDA of group H was lower than that of group E and serum TNF-alpha of group F was lower compared with that of group E. TNF-alpha of monocyte supernatants and activity of caspase-3 of monocytes of group F were lower than those of group E. Bacterial tissue loads did not differ among groups E, F, G and H. The numbers of inflammatory cells of liver of groups F and H were lower compared with those of group E; those of kidney of groups F, G and H were lower compared with those of group E.

CONCLUSIONS

Clarithromycin administered intravenously in experimental infection caused by pan-resistant K. pneumoniae attenuated systemic inflammatory response and local tissue damage. This effect is probably attributed to immunomodulatory intervention on blood monocytes.