Immunomodulation by exogenous surfactant: effect on TNF-alpha secretion and luminol-enhanced chemiluminescence activity by murine macrophages stimulated with group B streptococci

Combination therapy with ampicillin and azithromycin improved outcomes in a mouse model of group B streptococcal sepsis

BACKGROUND

Evidence suggests that β-lactam monotherapy of streptococcal infections may incite stronger inflammation and is inferior to combination therapy with macrolides. We hypothesized that use of macrolides alone or in combination with a β-lactam for group B streptococcal (GBS) sepsis would improve outcomes by reducing inflammation.

METHODS

TNF-α was measured from supernatants of RAW 264.7 cells stimulated with GBS isolates, in presence of four treatment regimens: ampicillin alone, azithromycin alone, or combination of azithromycin plus ampicillin. Mouse model of GBS sepsis was developed and treated with same four regimens. Clinical sepsis scores were monitored; serum cytokines (TNF-α, IL-6, IL-10) and chemokines (MIP-1α) were measured at the end.

RESULTS

GBS isolates exposed to azithromycin or combination (compared to ampicillin alone) stimulated less TNF production in vitro. In the murine sepsis model, mortality was lower along with decreased sepsis scores in mice treated with combination therapy. Mean serum IL-6 was lower in mice treated with azithromycin alone (66±52 pg/ml) or combination of ampicillin plus azithromycin (52±22 pg/ml) compared to ampicillin alone (260±160 pg/ml) (p<0.005).

CONCLUSIONS

Combination therapy of ampicillin+azithromycin improved outcomes in a murine GBS sepsis model; this therapeutic approach deserves additional study.

In Vivo and In Vitro Anti-inflammatory Activities of Neoandrographolide

Neoandrographolide, one of the principal diterpene lactones, isolated from a medicinal herb Andrographis paniculata Nees, was tested in vivo and in vitro for its anti-inflammatory activities and mechanism. Oral administration of neoandrographolide (150 mg/kg) significantly suppressed ear edema induced by dimethyl benzene in mice. Oral administration of neoandrographolide (100–150 mg/kg) also reduced the increase in vascular permeability induced by acetic acid in mice. In vitro studies were performed using the macrophage cell line RAW264.7 to study the effect of neoandrographolide on suppressing phorbol-12-myristate-13-acetate (PMA)-stimulated respiratory bursts and lipopolysaccharide (LPS)-induced production of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-α). Respiratory bursts were quantified by chemiluminescence (CL) measurements.Results showed that neoandrographolide suppressed PMA-stimulated respiratory bursts dose-dependently from 30 μM to 150 μM. Neoandrographolide also inhibited NO and TNF-α production in LPS-induced macrophages, contributing to the anti-inflammatory activity of A. paniculata. These results indicate that neoandrographolide possesses significant anti-inflammatory effects, which implies that it would be one of the major contributing components to participate in the anti-inflammatory effect of A. paniculata. and a potential candidate for further clinical trial.

Surfactant for bacterial pneumonia in late preterm and term infants

BACKGROUND

Pulmonary surfactant is an important part of the host defence against respiratory infections. Bacterial pneumonia in late preterm or term newborn infants often leads to surfactant deficiency or dysfunction, as surfactant is either inactivated or peroxidated. Studies of animal models of pneumonia and clinical case reports suggest that exogenous surfactant might be beneficial to infants with bacterial pneumonia.

OBJECTIVES

To assess the effect of exogenous surfactant treatment on mortality and pulmonary complications in infants with bacterial pneumonia.

SEARCH METHODS

We used standard Cochrane Collaboration methodology to conduct our search of databases. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 6); MEDLINE (accessed via Ovid SP June 2011); EMBASE (via Ovid SP 1980 to June 2011); and CINAHL Plus (accessed via EBSCOHost June 2011).

SELECTION CRITERIA

We limited our search to randomised and quasi-randomised trials of surfactant replacement therapy in infants > 35 weeks gestation with bacterial pneumonia in the first 28 days of life. The primary outcome measures were death, time to resolution of pneumonia, incidence of chronic lung disease, pneumothoraces and pulmonary haemorrhage.

DATA COLLECTION AND ANALYSIS

We assessed all studies with predefined criteria as to whether they were eligible for inclusion. We extracted data using RevMan 5 (RevMan 2011). We used the standard Cochrane Collaboration methodology for data collection and analysis to assess risk of bias, heterogeneity, treatment effect, missing data and reporting bias where appropriate.

MAIN RESULTS

We did not identify any studies that met our inclusion criteria.

AUTHORS' CONCLUSIONS

There is no evidence from randomised controlled trials (RCTs) to support or refute the efficacy of surfactant in near-term and term infants with proven or suspected bacterial pneumonia. RCTs are still required to answer this question.

Does surfactant type cause a differential proinflammatory response in preterm infants with respiratory distress syndrome?

INTRODUCTION

The objective of this study was to compare the pulmonary inflammatory response of premature infants with respiratory distress following instillation of one of two commonly available surfactant preparations.

METHODS

This was a prospective, randomized investigation of preterm infants who were less than 30 weeks of gestational age, weighed less than 1 kg at birth, and who qualified to receive surfactant. Infants with multiple congenital anomalies or whose mothers were taking anti-inflammatory medications were ineligible. Tracheal aspirates (TAs) were collected on days 1, 3, 5, and 7 and airway cytokines from TAs were assayed for interleukin (IL)-8 and IL-6.

RESULTS

Infants were evenly matched by gestation (26+/-2 days and 26+/-1 days [mean+/-SD], Surfactant A and B, respectively) and birth weight (730+/-141 g and 732+/-167 g). TA cytokine levels were not different between or within groups. Ventilator requirements and clinical outcomes were similar between the two groups.

CONCLUSION

The postnatal airway inflammatory response observed in preterm infants is not altered by the instillation of either surfactant preparation.

Immunosuppressive activity of buxidin and E-buxenone from Buxus hyrcana

Buxidin (1) and E-Buxenone (2), steroidal alkaloids from Buxus hyrcana, are found to possess potent immunosuppressive properties. The activity was tested in vitro on oxidative burst, chemotaxis, T-cell proliferation, and cytokine production. Both compounds showed a significant immunomodulatory activity with clear suppressive effect on oxidative burst and chemotaxis in a dose-dependent manner. They also exhibited suppressive effect on the phytohemagglutinin-stimulated T-cell proliferation. The immunomodulatory activity was further confirmed by the suppression of IL-2 and IL-4 production. Furthermore, molecular docking studies were performed to investigate the binding mode of Buxidin (1) and E-Buxenone (2) with IL-2. Despite the structural differences between Buxidin (1) and E-Buxenone (2), docking results revealed that they adopt a similar binding pattern at the active site of the IL-2. A good agreement between practical and theoretic results indicates that the current docking study could provide an alternate tool for the structural optimization of recently identified ligand as more potent IL-2 inhibitors.

Group B streptococci exposed to rifampin or clindamycin (versus ampicillin or cefotaxime) stimulate reduced production of inflammatory mediators by murine macrophages

Streptococcus agalactiae (group B Streptococcus, GBS) is an important cause of sepsis and meningitis in neonates, and excessive production of the inflammatory mediators tumor necrosis factor (TNF) and nitric oxide (NO) causes tissue injury during severe infections. We hypothesized that exposure of GBS to different antimicrobial agents would affect the magnitude of the macrophage inflammatory response to this organism. We stimulated RAW 264.7 murine macrophages with a type-Ia GBS isolate in the presence of ampicillin, cefotaxime, rifampin, clindamycin, or gentamicin, singly or in combination. We found that GBS exposed to rifampin or clindamycin (versus beta-lactam antibiotics) stimulated less TNF secretion and inducible nitric oxide synthase (iNOS) protein accumulation in RAW 264.7 cells. Furthermore, GBS exposed to combinations of antibiotics that included a protein synthesis inhibitor stimulated less macrophage TNF and iNOS production than did organisms exposed to beta-lactam antibiotics singly or in combination. We conclude that exposure of GBS to rifampin or clindamycin leads to a less pronounced macrophage inflammatory mediator response than does exposure of the organism to cell wall-active antibiotics.

Streptococcal beta-hemolysins: genetics and role in disease pathogenesis

A zone of beta-hemolysis surrounding colonies on blood-agar media is a hallmark phenotypic feature of the pathogens group A Streptococcus (GAS) and group B Streptococcus (GBS). In each case, lysis of red blood cells reflects the action of a potent protein exotoxin. Although these toxins have been the subjects of numerous investigations over the years, their purification and molecular identification have proven elusive. These difficulties reflect the instability of hemolytic activity, as both toxins function only in the context of the bacterial surface or certain high molecular weight 'stabilizer' molecules. This review highlights the recent discoveries of two markedly distinct genetic loci, necessary and sufficient for the beta-hemolytic phenotypes of GAS and GBS, respectively. The generation of isogenic GAS and GBS beta-hemolysin-deficient mutants and their analysis using in vitro and in vivo model systems has shown that both toxins function as virulence factors in the pathogenesis of invasive infections.