Neonatal murine macrophages show enhanced chemotactic capacity upon toll-like receptor stimulation

BACKGROUND

The neonatal surgical patient is threatened by exuberant inflammatory reactions. Neonatal macrophages are key players in this process. We investigated the ability of neonatal macrophages to initiate a local inflammatory reaction upon exposure to different bacterial or viral ligands to toll-like receptors (TLRs).

METHODS

Peritoneal wash outs from neonatal (<24 h) and adult (42 days) C57BL/6J mice were gained by peritoneal lavages. In a first set of experiments, macrophages were purified and stimulated for 6 h by four different TLR ligands. mRNA was extracted for transcriptome analysis. In a second set of experiments, lipopolysaccharide was applied into peritoneal cavities. After 6 h of incubation, the cellular composition of the inflamed cavities was evaluated by cytological staining as well as chipcytometry.

RESULTS

Neonatal murine peritoneal macrophages differed significantly in the expression of pro- and anti-chemotactic genes. Functional assignment of these genes revealed enhanced chemotactic potential of neonatal macrophages and was confirmed by a higher influx of pro-inflammatory cells into neonatal peritoneal cavities.

CONCLUSION

Neonatal peritoneal macrophages demonstrated an enhanced chemotactic potential upon stimulation with four TLR ligands. This was associated with an increased influx of inflammatory cells to the peritoneal cavity. This might contribute to the strong inflammatory responses of neonates and preterms.

CO2 modulates the inflammatory cytokine release of primary human pleural macrophages

BACKGROUND

It is well known that CO (2) used during laparoscopy affects the peritoneal surface and local inflammatory response, including the inflammatory reactivity of peritoneal macrophages. However, little is known about the local effects of CO (2) during thoracoscopy. In a previous study we have shown that in healthy adolescents, macrophages are the dominant cell population on the pleural surface. Therefore, we examined the effects of CO (2) on the inflammatory response of primary human pleural macrophages.

METHODS

Human primary macrophages were harvested lavage from healthy adolescents undergoing elective surgery for pectus bar correction (n=8). After purification and 24 h resting, cells were incubated for 2 h in 100% CO (2), 5% CO (2) or 95% inert helium with 5% CO (2) as hypoxic control. After incubation cells were stimulated with LPS for 4 h and 24 h. The release of TNF-alpha, IL-8, IL-6, IL-10 and IL-1 beta were determined by ELISA.

RESULTS

CO (2), but not hypoxia, induced a significant reduction in the release of TNF-alpha and IL-8 as well as a significant increase in the release of IL-10 and IL-1 beta within the first 4 h after incubation. The levels of IL-6 and the release of cytokines at 24 h after incubation were not significantly affected.

CONCLUSIONS

CO (2) directly modulates the immediate inflammatory response of pleural macrophages. Therefore, CO (2) insufflation during thoracoscopy could lower the local stress response, but does not appear to have a lasting effect.

Endoloop closure of the urinary bladder is safe and efficient in female piglets undergoing transurethral NOTES nephrectomy

INTRODUCTION

Recently, we showed that various procedures for rigid Natural Orifice Transluminal Endoscopic Surgery (NOTES) can be successfully performed in piglets. However, the safety and effectiveness of endoscopic closure of the urinary bladder remains to be determined before introducing transurethral NOTES in children. Our study was designed to investigate the safety and impermeability of the urinary bladder after endoscopic closure in transurethrally assisted nephrouretectomy in piglets.

MATERIAL AND METHODS

Five female piglets (mean weight 14.5 kg; range: 14-15) underwent right-sided transurethral nephroureterectomy using a hybrid technique with one 15 mm trocar placed umbilically and one 3 mm trocar placed transvesically. Hilar dissection was performed with a 5 mm Endoligasure vessel sealing device. After umbilical retrieval of the resected kidney, the urinary bladder was closed by an Endoloop via an umbilical "two in one system" with the assistance of a 2 mm transurethrally placed endoscopic clamp. Endpoints of the study were total operation time, duration of cystoscopy and transurethral trocar positioning, duration of nephrectomy, duration of bladder closure and determination of bladder impermeability. Intraoperatively, bladder filling was performed with normal saline (ml), while bursting pressure (mmHg) was measured by filling the harvested bladder with air.

RESULTS

All nephroureterectomies were successfully performed with negligible blood loss. Mean total operation time was 46 min (range: 35-69). Cystoscopy and transurethral trocar positioning took 14 min (range: 9-23), and nephrectomy took 28 min (range: 18-48). Mean duration of bladder closure was 4 min (range: 2-6). Mean volume of intraoperative bladder filling was 94 ml (range: 80-100), indicating adequate capacity after closure with Endoloops. Post-mortem bladder impermeability was confirmed by a mean air filling bursting pressure of 88 mmHg (range: 70-140) indicating sufficient bladder closure.

CONCLUSION

A safe urinary bladder closure is mandatory for transurethral rigid NOTES procedures and can be adequately achieved with Endoloops.

CO2 pneumoperitoneum increases survival in mice with polymicrobial peritonitis

PURPOSE

Laparoscopic techniques are commonly used in patients with bacterial peritonitis. CO2 is known to suppress local and systemic inflammatory responses. Nonetheless, an active immune system is needed to contain bacterial contamination of the abdominal cavity. Therefore, we investigated the early and late effects of CO2 pneumoperitoneum on the ability of mice to overcome polymicrobial peritonitis.

MATERIAL AND METHODS

Male C57/B6 mice were subjected to pneumoperitoneum with CO2 or helium, or underwent a midline laparotomy. In a first set, changes of arterial blood gases were monitored. In further experiments, polymicrobial peritonitis was induced after 1 h of pneumoperitoneum/laparotomy by cecal ligation and puncture. In a second set of experiments polymicrobial peritonitis was induced 4 h prior to exposure to pneumoperitoneum/laparotomy. After the interventions, survival rates (early survival: 6 to 48 h; late survival > 48 h) were monitored for 7 days.

RESULTS

There was no significant effect of pneumoperitoneum or laparotomy on arterial blood gas parameters. CO2 pneumoperitoneum significantly reduced the early (6 to 48 h) mortality of subsequent peritonitis after CO2 pneumoperitoneum compared to laparotomy (2/20 vs. 9/25; p < 0.05). The protective effect did not reach significance after 7 days (late mortality). The application of a helium peritoneum did not show any beneficial effect. Application of a CO2 pneumoperitoneum during polymicrobial peritonitis significantly reduced overall mortality (p < 0.05) compared to laparotomy.

CONCLUSIONS

The modulation of immune responses by CO2, but not helium pneumoperitoneum, has a significant positive impact on survival during abdominal sepsis in a mouse model. Thus, application of a CO2 pneumoperitoneum may be beneficial in conditions with bacterial contamination of the abdominal cavity.

Carbon dioxide differentially affects the cytokine release of macrophage subpopulations exclusively via alteration of extracellular pH

BACKGROUND

The improved outcome after endoscopic surgery has been attributed to less surgical trauma. However, the underlying mechanisms are not fully understood, and direct effects of CO2 used for pneumoperitoneum, cellular acidification, and/or the lack of air contamination have been postulated to additionally modulate immune functions during endoscopic surgery. We investigated the effects of CO2 incubation, extracellular acidification, and air contamination on the inflammatory response of two distinct macrophage populations.

METHODS

R2 and NR 8383 rat macrophage cell lines were used. Interleukin-6 (IL-6) and nitric oxide after lipopolysaccharide (LPS) stimulation were determined in these sets of experiments: incubation in 100% CO2, 5% CO2, and room air for 2h; incubation at pH 7.4, 6.5, and 5.5 for 2 h in 5% CO2; and incubation in 100% CO2, 5% CO2 and room air in fixed pH 6.3. The extracellular pH was monitored during incubation. We determined the alteration of intracellular pH in cells subjected to extracellular acidification by fluorescence microscopy.

RESULTS

Extracellular pH decreased to 6.3 during 100% CO2 incubation. IL-6 release was reduced after CO2 incubation in NR 8383 cells and increased in R2 cells (p < 0.05). It was not altered by air incubation. Decreasing the extracellular pH to 6.5 mimicked the effects of CO2 and a decrease to 5.5 suppressed IL-6 release in both cell lines. In fixed pH at 6.3, CO2 and air incubation had no effect. CO2 and pH had no impact on nitric oxide release and vitality. Intracellular pH decreased with extracellular acidification without significant difference between the two cell lines.

CONCLUSIONS

A decrease in extracellular pH during incubation in CO2 differentially affects IL-6 release in macrophage subpopulations. This may explain contradictory results in the literature. Moreover, we demonstrated that air contamination does not affect macrophage cytokine release. The decrease in extracellular pH is the primary underlying mechanism of the alteration of macrophage cytokine release after CO2 incubation, and it appears that the ability to maintain intracellular pH is not determined by the effects of CO2 or extracellular acidification.

Mini-laparotomy and full laparotomy, but not laparoscopy, alter hepatic macrophage populations in a rat model

BACKGROUND

Immune function is better preserved by laparoscopic versus conventional surgery. Numerous mediators of the systemic trauma response are synthesized and/or regulated by the liver. However, it has been stated that the advantages of laparoscopic surgery are no more obvious when conventional operations are performed via mini-laparotomy. We set out to compare the impact of laparoscopy and mini- and full laparotomy on the hepatic macrophage populations.

METHODS

Male Lewis rats were subjected to anesthesia alone (control), mini-laparotomy (1 cm), full laparotomy (7 cm), or laparoscopy for 60 min. Endpoints were the total protein in the peritoneal lavage fluid, hepatic ED-1 cells (recruited monocytes), hepatic ED-2 cells (Kupffer cells), the expression of OX-6 in the liver, and C-reactive protein (CRP) in plasma.

RESULTS

Protein in the peritoneal lavage fluid increased significantly after all interventions. Full laparotomy was accompanied by an enhancement in ED-1-positive monocytes in the liver parenchyma compared to all other groups (p < 0.001). Mini- and full laparotomy led to an increase in ED-2-positive Kupffer cells (p < 0.001). Laparoscopy did not affect the number of monocytes/macrophages. There was no significant alteration of OX-6 expression in either group. No change in the cellular composition in the periportal fields was observed. The CRP plasma levels did not significantly differ between groups.

CONCLUSIONS

Laparoscopy completely prevents hepatic macrophage populations from expansion and normal cell disposition is preserved. Laparotomy, irrespective of incision size, increases the number of Kupffer cells. Moreover, full laparotomy, but not mini-laparotomy or laparoscopy, causes an increase in hepatic monocyte recruitment. The regulating pathways after surgery differ from other immunologic challenges, such as sepsis, in which immunocompetent cells accumulate and are stimulated in the periportal fields.

Pulmonary surfactant in birds: coping with surface tension in a tubular lung

As birds have tubular lungs that do not contain alveoli, avian surfactant predominantly functions to maintain airflow in tubes rather than to prevent alveolar collapse. Consequently, we have evaluated structural, biochemical, and functional parameters of avian surfactant as a model for airway surfactant in the mammalian lung. Surfactant was isolated from duck, chicken, and pig lung lavage fluid by differential centrifugation. Electron microscopy revealed a uniform surfactant layer within the air capillaries of the bird lungs, and there was no tubular myelin in purified avian surfactants. Phosphatidylcholine molecular species of the various surfactants were measured by HPLC. Compared with pig surfactant, both bird surfactants were enriched in dipalmitoylphosphatidylcholine, the principle surface tension-lowering agent in surfactant, and depleted in palmitoylmyristoylphosphatidylcholine, the other disaturated phosphatidylcholine of mammalian surfactant. Surfactant protein (SP)-A was determined by immunoblot analysis, and SP-B and SP-C were determined by gel-filtration HPLC. Neither SP-A nor SP-C was detectable in either bird surfactant, but both preparations of surfactant contained SP-B. Surface tension function was determined using both the pulsating bubble surfactometer (PBS) and capillary surfactometer (CS). Under dynamic cycling conditions, where pig surfactant readily reached minimal surface tension values below 5 mN/m, neither avian surfactant reached values below 15 mN/m within 10 pulsations. However, maximal surface tension of avian surfactant was lower than that of porcine surfactant, and all surfactants were equally efficient in the CS. We conclude that a surfactant composed primarily of dipalmitoylphosphatidylcholine and SP-B is adequate to maintain patency of the air capillaries of the bird lung.

Metabolism of surfactant phosphatidylcholine molecular species in cftr(tm1HGU/tm1HGU) mice compared to MF-1 mice

In cftr(tmIHGU/m1HGU) mice, an animal model designed to study pathophysiologic alterations due to the CFTR defect found in cysticfibrosis, surfactant phospholipids of bronchoalveolar lavage fluid (BALF) are increased. To study the metabolical basis of such increases, we intraperitoneally injected cft(tm1HGU/tm1HGU) mice [methyl-3H]choline and measured [methyl-3H]choline incorporation into phosphatidylcholine (PC) molecular species of lung tissue and BALF after 1.5 to 24 hours. MF1 and MF1 x cftr(tm1HGU/tm1HGU) hybrid mice served as controls. In tissue [methyl-3H]choline incorporation into total PC was constant for 24 hours and identical in control and cftr(tmIHGU/m1HGU) mice. However, from 7.5 to 24 hours there was a shift of [methyl-3H]choline incorporation from palmitoyloleoyl-PC and palmitoyllinoleoyl-PC towards PC species enriched in surfactant, dipalmitoyl-PC, palmitoylmyristoyl-PC, and palmitoylpalmitoleoyl-PC. The relative and absolute 3H-labels of PC species were identical for cftr(tmIHGU/m1HGU) compared to control mice. In BALF [methyl-3H]choline of total PC increased from 1.5 to 24 hours (R2 > .98), mainly due to [methyl-3H]choline-labelled dipalmitoyl-PC, in all experimental groups. In BALF from cftr(tmIHGU/m1HGU) mice, the [methyl-3H]choline label of total PC and individual PC species was significantly increased over control values after 24 hours, but not after 1.5 to 6 hours. Numbers and composition of BALF cells were not different between controls and cftr(tmIHGU/m1HGU) mice. We, conclude that increased alveolar phospholipid in cftr(tmIHGU/m1HGU) mice is likely due to decreased reuptake of surfactant.

Examination of the mononuclear phagocyte system in lupus-prone male BXSB mice

During the course of lupus-like autoimmune disease male BXSB mice develop an increasing monocytosis in the peripheral blood. As we demonstrated previously, this monocytosis is parallelled by an expansion of a strain-specific high number of macrophage precursor cells (CFU-M) in the bone marrow of male mice. To test the hypothesis that the expanded mononuclear phagocyte system (MPS) may promote autoimmune disease in these mice the organ-associated macrophage system was examined. Our latest data show that an unusual expansion of CFU-M also appears in spleen and liver of male mice 2 weeks after birth. In addition to a morphological alteration of the organs during the course of the disease there is a change in number and distribution of organ-resident macrophages. Considering these results the possible contribution of the expanded MPS in promoting autoimmune disease is discussed.

Expanded macrophage precursor populations in BXSB mice: possible reason for the increasing monocytosis in male mice

The BXSB mouse spontaneously develops an autoimmune disease that resembles human systemic lupus erythematosus (SLE). During their lifetime, male BXSB mice show an increasing monocytosis in the peripheral blood as opposed to their female littermates. This monocytosis is unique among autoimmune-prone mice. To test the hypothesis that alterations at the stem cell level may be responsible for this monocytosis, myeloid bone marrow precursor cells were examined in both male and female BXSB mice from 4 to 40 weeks of age. The number of M-CSF responding stem cells (CFU-M) and the number of GM-CSF responding stem cells (CFU-GM) were higher than in all other inbred mouse strains tested. In addition, male BXSB mice developed a progressive increase of CFU-M and CFU-GM in the bone marrow during their lifetime, which paralleled the peripheral blood monocytosis. The monocytosis in male BXSB mice is the result of a further expansion of the strain-specific high number of macrophage precursors by intrinsic factors, which may be attributed to the influence of the Yaa factor. The sex-specific expanded mononuclear phagocyte system may promote the autoimmune process and may be one reason for the dramatic course of murine SLE in male BXSB mice.