Culture of human peritoneum--a new method to measure the local cytokine response and the effect of immunomodulators

Disruption of Dense Granular Protein 2 (GRA2) Decreases the Virulence of Neospora caninum

Neospora caninum causes abortions in cattle and nervous system dysfunction in dogs. Dense granular proteins (GRAs) play important roles in virulence; however, studies on NcGRA functions are limited. In the present study, multiple methods, including site-directed mutagenesis; CRISPR/Cas9 gene editing; Western blotting; quantitative polymerase chain reaction; confocal microscopy; plaque, invasion, egress, and replication assays; animal assays of survival rate and parasite burden; and hematoxylin-eosin staining, were used to characterize the NcGRA2 protein, construct an NcGRA2 gene disruption (ΔNcGRA2) strain, and explore its virulence in vivo and vitro. The results showed that NcGRA2 shared 31.31% homology with TgGRA2 and was colocalized with NcGRA6 at the posterior end of tachyzoites and the intravacuolar network of parasitophorous vacuoles (PVs). Cell fractionation analysis showed that NcGRA2 behaved as a transmembrane and membrane-coupled protein. The ΔNcGRA2 strain was constructed by coelectroporation of the NcGRA2-targeting CRISPR plasmid (pNc-SAG1-Cas9:U6-SgGRA2) and DHFR-TS DNA donor and verified at the protein, genome, and transcriptional levels and by immunofluorescence localization analysis. The in vitro virulence results showed that the ΔNcGRA2 strain displayed smaller plaques, similar invasion and egress abilities, and slower intracellular growth. The in vivo virulence results showed a prolonged survival time, lower parasite burden, and mild histopathological changes. Overall, the present study indicates that NcGRA2, as a dense granular protein, forms the intravacuolar network structure of PVs and weakens N. caninum virulence by slowing proliferation. These data highlight the roles of NcGRA2 and provide a foundation for research on other protein functions in N. caninum.

Regulation of Peritoneal Inflammatory Response to Implant Material Using an Ex Vivo Model System

BACKGROUND

Implants used in abdominal wall reconstruction are associated with intra-abdominal inflammation that can cause complications such as adhesions, fistulae, or failure of the implant. This study analyzed the inflammatory response of human peritoneum explants when exposed to different implant materials including synthetic and biological (cross-linked and non-cross-linked).

MATERIALS AND METHODS

Human peritoneum explants (parietal and visceral) were incubated in culture with implants used for abdominal wall reconstruction. Implants included Permacol (biological implant with chemical cross-linking); Biodesign and Strattice (biological implants without chemical cross-linking); Prolene (synthetic nonabsorbable); and Vicryl (synthetic absorbable). Control peritoneum samples were incubated without implant. Cytokine concentrations and corresponding gene expression were measured by enzyme-linked immunosorbent assay and quantitative polymerase chain reaction, respectively. Further evaluation included assessment of tissue viability and implant-cytokine adsorption.

RESULTS

Incubation of human peritoneal explants with Biodesign or Strattice was associated with a significant reduction in interleukin-6, interleukin-1β, and tumour necrosis factor alpha protein and gene expression compared with control. These could not be explained by reduced cell viability or implant-cytokine adsorption. Incubation of explants in Biodesign-conditioned media displayed a similar effect to incubation of explants with Biodesign itself.

CONCLUSIONS

Human peritoneal explants cultured with different mesh implant materials show an altered inflammatory cytokine response suggesting a tissue-specific response. Downregulation of key inflammatory cytokines by the peritoneum exposed to non-cross-linked biological implants may be mediated by the release of soluble factors from these implants inhibiting cytokine gene expression. This ex vivo human peritoneal system provides a novel preclinical model to investigate peritoneum-implant interactions.

A peritonitis model with low mortality and persisting intra-abdominal abscesses

Intra-abdominal abscesses are a potential source of recurrent or residual infection after surgical intervention for secondary peritonitis. The development of therapies requires a model which combines low mortality with the formation of persisting abscesses and which is also suitable to study the local inflammatory response. Male Wistar rats were injected intraperitoneally with a mixture of sterile rat faeces, increasing doses of E. coli (10(4)-10(8) cfu/ml) and a fixed dose of B. Fragilis (10(4) cfu/ml). After one h a laparotomy was performed and the peritoneal cavity was debrided. Blood samples were taken under anaesthesia after 6 and 24 h. Abdominal fluid samples were collected (by laparotomy) after 24 and 72 h. The rats were killed after 5 days and the abdomen was inspected for abscesses. Mortality was 90% in the two groups with the highest doses of E. coli and 30% in those with the two lowest doses. In the latter groups all surviving rats but one showed intraabdominal abscesses and bacteremia was encountered frequently, especially after 24 h in the 10(5) cfu E. coli group. The groups receiving 10(4)-10(6) cfu E. coli showed similar plasma IL-6 concentrations after 6 h which were lowered significantly after 24 h. No circulating TNF-alpha was found. Considerable concentrations of TNF-alpha, IL-6, IL-1beta, and IL-10, were found in the peritoneal fluid after 24 h but no differences were observed between the contro groups and those receiving 10(4)-10(6) cfu E. coli. At 72 h cytokine levels were reduced significantly and remained the highest in the animals dosed with 10(6) cfu E. coli. The present model is suitable to study the mechanisms involved in, and prevention of, intra-abdominal abscess formation after surgical treatment of generalized peritonitis.

Laparoscopic-type environment enhances mesothelial cell fibrinolytic activity in vitro via a down-regulation of plasminogen activator inhibitor-1 activity

BACKGROUND

Fewer intraperitoneal adhesions have been observed after laparoscopic surgery compared with conventional techniques. The aim of this study is to assess the effect of the pneumoperitoneum on mesothelial cell fibrinolytic activity by use of an in vitro model.

METHODS

Human peritoneal mesothelial cells were seeded onto 24-well plates and incubated in carbon dioxide or helium at 5 mm Hg for 4 hours or standard culture conditions. Supernatant was removed for analysis at 0, 24, 48, and 72 hours after gas incubation and analyzed for plasminogen activator activity, total tissue plasminogen activator (tPA), and total plasminogen activator inhibitor-1 (PAI-1) concentrations by use of an enzyme-linked immunosorbent assay. The effect of different insufflation pressures (0, 7, and 14 mm Hg) was also examined.

RESULTS

Enhanced plasminogen activator activity was observed at 48 hours and 72 hours from cells exposed to CO(2) (P<.04 each) and helium (P<.05 each) compared with control. This was associated with a decrease in PAI-1 concentrations at 48 and 72 hours in both the CO(2) and helium groups compared with control (P<.03 each, CO(2) vs control; and P<.04 each, helium vs control). No changes in tPA levels were observed. Changes in insufflation pressures did not affect plasminogen activator activity.

CONCLUSIONS

These results suggest that incubation of human mesothelial cells with both CO(2) and helium in the absence of oxygen enhances mesothelial cell fibrinolytic activity because of a reduction in PAI-1 concentrations. These changes may participate in the observed reduction in adhesions after laparoscopic surgery relative to open surgery.

Microdialysis: a new technique to monitor perioperative human peritoneal mediator production

BACKGROUND

Standardized methods to measure peritoneal cytokine production do not exist. This feasibility study examines the use of microdialysis to monitor perioperative peritoneal mediator production in patients following abdominal surgery for infective or non-infective conditions.

MATERIALS AND METHODS

At the beginning of the operation, a microdialysis catheter was placed between the patient's parietal peritoneum and the muscular fascia of the abdominal wall in the connective tissue bed. The device was irrigated (18 microL/h, Ringer's solution/0.05% albumin) for up to 7 days. Samples of the dialysate were collected at least twice a day, and concentrations of interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1 were measured by an ELISA technique. Four of the nine patients included had proved intra-abdominal infections.

RESULTS

In uninfected patients, IL-6 concentrations peaked 8 h after skin incision (mean +/- SEM): 1696 +/- 1292 pg/mL and dropped rapidly to significantly lower concentrations (less than 400 pg/mL) thereafter. MCP-1 concentrations also peaked at 8 h (12787 +/- 6893 pg/mL). In the following days, MCP-1 concentrations were variable between 1000 and 5000 pg/mL. In infected patients, early IL-6 production tended to be higher and that of MCP-1 tended to be lower than in uninfected patients. Catheters were removed between day four and day seven when the system failed or when the patients became mobile without any clinical symptoms of complications.

CONCLUSION

The samples derived from microdialysis were suitable to measure sub-peritoneal mediator profiles during surgery and up to 7 days postoperatively. Microdialysis data should be validated for a potential correlation with the clinical course.

Effect of abdominal infections on peritoneal and systemic production of interleukin 6 and monocyte chemoattractant protein-1

The aim of the study was to compare peritoneal and systemic production of interleukin 6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) in uninfected patients and in patients with peritonitis. Peritoneum was excised at laparotomy for acute peritonitis (n = 22) or noninfectious reasons (n = 61), and was incubated with or without lipopolysaccharide (LPS). Mediator concentrations in the culture-supernatants, in the patients' serum, and in plasmasupernatants of LPS-stimulated whole blood were related to outcome. Spontaneous production of IL-6 by the peritoneum was increased in infected patients compared with uninfected patients. In contrast to IL-6, LPS-stimulated production of MCP-1 was significantly less in infected patients. Serum concentrations of both mediators were higher in infected patients and the highest concentrations of MCP-1 were in patients who died. LPS-stimulated production of IL-6 in whole blood was least, whereas that of MCP-1 was greatest in infected patients who died. These contrasting results for local and systemic production of mediators illustrate the compartmentalized immune response to intra-abdominal infection.

Natural immunity and neuroimmune host defense

Innate resistance is mediated by non-immune defense and by natural immunity. Non-immune defense includes diverse mechanisms (e.g., physico-chemical defense by bile acids). Natural killer (NK) cells, gamma delta T lymphocytes and CD5+ B lymphocytes are key mediators of natural immunity. These cells utilize germ-line coded receptors that recognize highly conserved, homologous epitopes (homotopes). Typically, it is not the antigen, but cytokines and hormones that regulate the level of NK-mediated cytotoxicity. These include interleukin-2, interferons, prolactin and growth hormone. Less is known about gamma delta T lymphocytes. CD5+ B lymphocytes produce germ-line coded antibodies (predominantly IgM) that are polyspecific, and able to recognize a great variety of microorganisms, cancer-cells and self-components. Antigen is not an effective stimulus for natural antibody (NAb), but bacterial lipopolysaccharide (LPS) is. During the acute phase response (febrile illness) the T-cell-regulated adaptive immune response is switched off and natural immune mechanisms are amplified several hundred to a thousand times within 24-48 hours (immunoconversion). This immunoconversion is initiated by immune-derived cytokines, and involves profound neuroendocrine and metabolic changes, all in the interest of host defense. Immune recognition is assured by natural antibodies and by some liver-derived acute phase proteins, such as C-reactive protein or endotoxin-binding protein, the level of which is elevated in the serum. Thus, natural immunity is essential for a first and last line of defense and the neuroendocrine system is an important promoter of this activity.