Encapsulating peritoneal sclerosis is associated with T-cell activation

BACKGROUND

Encapsulating peritoneal sclerosis (EPS) is an excessive fibrotic response of the peritoneum that may occur after long-term peritoneal dialysis (PD). The underlying pathophysiology is poorly understood, but involvement of peritoneal inflammatory T helper 1 cells may be pivotal.

METHODS

Soluble interleukin-2 receptor alpha (sCD25) concentration was measured as a marker for T-cell activation in serum and ascites from EPS patients and various control patient groups. Peritoneal biopsies were stained for the presence of T cells, and T cells isolated from ascites of EPS patients were characterized in detail for differentiation status and cytokine expression.

RESULTS

Serum sCD25 concentrations are significantly and specifically increased in EPS patients compared with haemodialysis, PD and predialysis patients. Peritoneal effluent of stable PD patients contains very low levels of sCD25, while sCD25 levels in ascites of EPS patients are high and indicative of local production. In the years preceding the diagnosis of EPS, the serum sCD25 concentrations increased while remaining at stable levels in control PD patients. The peritoneum and ascites of EPS patients showed a significant influx of T cells with relatively increased numbers of CD4(+) T cells. These T cells were fully differentiated and displayed a T helper 1 cell type with a pro-inflammatory cytokine profile.

CONCLUSIONS

Increased serum sCD25 concentrations and peritoneal lymphocytosis in EPS patients indicate the involvement of activated T cells in the pathophysiology of excessive fibrosis.

Alternative activation of macrophages in human peritoneum: implications for peritoneal fibrosis

BACKGROUND

Depending on the cytokine microenvironment, macrophages (Mϕ) can adopt a proinflammatory (M1) or a profibrotic (M2) phenotype characterized by the expression of cell surface proteins such as CD206 and CD163 and soluble factors such as CC chemokine ligand 18 (CCL18). A key role for Mϕ in fibrosis has been observed in diverse organ settings. We studied the Mϕ population in a human model of peritoneal dialysis in which continuous stress due to dialysis fluids and recurrent peritonitis represent a risk for peritoneal membrane dysfunction reflected as ultrafiltration failure (UFF) and peritoneal fibrosis.

METHODS

We used flow cytometry and quantitative reverse transcription-polymerase chain reaction to analyse the phenotype of peritoneal effluent Mϕ and tested their ability to stimulate the proliferation of human fibroblasts. Mϕ from non-infected patients were compared with those from patients with active peritonitis. Cytokine production was evaluated by enzyme-linked immunosorbent assay (ELISA) in spent dialysates and cell culture supernatants.

RESULTS

CD206(+) and CD163(+) M2 were found within peritoneal effluents by flow cytometry analysis, with increased frequencies of CD163(+) cells during peritonitis (P = 0.003). TGFB1, MMP9 and CCL18 messenger RNA (mRNA) levels in peritoneal macrophages (pMϕ) were similar to those found in M2 cells differentiated in vitro. The ability of pMϕ to stimulate fibroblast proliferation correlated with CCL18 mRNA levels (r = 0.924, P = 0.016). CCL18 production by pMϕ was confirmed by immunostaining of cytospin samples and ELISA. Moreover, CCL18 effluent concentrations correlated with decreased peritoneal function, which was evaluated as dialysate to plasma ratio of creatinine (r = 0.724, P < 0.0001), and were significantly higher in patients with UFF (P = 0.0025) and in those who later developed sclerosing peritonitis (P = 0.024).

CONCLUSIONS

M2 may participate in human peritoneal fibrosis through the stimulation of fibroblast cell growth and CCL18 production as high concentrations of CCL18 are associated with functional deficiency and fibrosis of the peritoneal membrane.

CD4/CD8 T-cell ratio in peritoneal dialysis effluents predicts the outcome of peritonitis in patients undergoing continuous ambulatory peritoneal dialysis

This study aimed to clarify the role of peritoneal T-lymphocytes in peritoneal immune defense mechanisms. This study was designed to examine the changes in T-cell subpopulations during peritonitis in patients treated with continuous ambulatory peritoneal dialysis (CAPD). Our observations were correlated to responses to treatment and with outcomes. The present study was carried out in 20 patients (8 males, 12 females) under CAPD. Peritonitis was diagnosed according to the criteria defined by the Ad Hoc Advisory Committee on Peritonitis Management. Peritoneal dialysate effluent (PDE) samples were collected from our patients, and lymphocyte subsets (CD2+, CD3+, CD3+/4+, CD3+/8+, CD3-/16+56+, CD4/CD8 ratio) were quantitated by using monoclonal antibodies. CD4/CD8 ratio was measured every day during peritonitis until the patients had completely recovered. The serial measurements of the CD4/CD8 ratio made in the PDE during peritonitis followed two patterns: the first pattern was characterized by a progressive increase in the CD4/CD8 ratio. The CD4/CD8 ratios on days 5, 6, and 7 were significantly higher than those on day 1 (P < 0.05). Overall, the patients who exhibited pattern 1 had favorable clinical courses. The second pattern was characterized by high initial CD4/CD8 ratios, which progressively decreased significantly (P < 0.05). This second pattern was associated with a delayed clinical response to treatment. Symptoms and signs of peritonitis persisted beyond 72 h. The pattern of the CD4/CD8 ratio in PDE may determine the outcome of peritonitis in CAPD patients.

Nod1/RICK and TLR signaling regulate chemokine and antimicrobial innate immune responses in mesothelial cells

Mesothelial cells that line the serous cavities and outer surface of internal organs are involved in inflammatory responses induced by microbial stimuli and bacterial infection. Upon exposure to bacterial products, mesothelial cells secrete chemokines, but the signaling pathways by which these cells recognize bacteria to mediate innate immune responses remain largely unknown. We report that stimulation of primary peritoneal mesothelial cells via nucleotide-binding oligomerization domain (Nod)1, a member of the intracytoplasmic Nod-like receptor family, induced potent secretion of the chemokines CXCL1 and CCL2 as well as expression of inducible NO synthase and such responses required the kinase RICK. Mesothelial cells also produced chemokines in response to TLR2, TLR3, TLR4, and TLR5 agonists, but unlike that induced by Nod1 stimulation, the TLR-mediated responses were independent of RICK. Yet, Nod1 stimulation of mesothelial cells via RICK enhanced chemokine secretion induced by LPS or IFN-gamma and cooperated with IFN-gamma in the production of NO. The i.p. administration of KF1B, a synthetic Nod1 agonist, elicited chemokine production in the serum and peritoneal fluid as well as the recruitment of neutrophils into the peritoneal cavity of wild-type mice, but not RICK-deficient mice. Finally, infection of mesothelial cells with Listeria monocytogenes induced production of CXCL1 and this response was significantly reduced in Nod1- or RICK-deficient cells. These results define mesothelial cells as microbial sensors through TLRs and Nod-like receptors and identify Nod1 and RICK as important mediators of chemokine and antimicrobial responses in mesothelial cells.

Changes in serum and ascitic monocyte chemotactic protein-1 (MCP-1) and IL-10 levels in cirrhotic patients with spontaneous bacterial peritonitis

Spontaneous bacterial peritonitis (SBP) is a prototypical infectious disease of cirrhotic patients. It has been suggested that cirrhotic patients' response to infection is less effective because of differences in the inflammatory and immune reactions. This study aimed to investigate the expression of the inflammatory cytokines monocyte chemotactic protein-1 (MCP-1) and interleukin-10 (IL-10) in cirrhotic patients with SBP. The MCP1 and IL-10 levels in the sera and ascitic fluids of cirrhotic patients with (n = 40) or without SBP (n=17) were serially analyzed by ELISA. In the non-SBP group, the mean MCP-1 levels in sera and ascites were 53.0 +/- 45.8 pg/mL and 197.5 +/- 109.5 pg/mL, respectively, and the IL-10 levels were 10.9 +/- 9.5 pg/mL and 77.6 +/- 79.7 pg/mL, respectively. In the SBP group, the mean MCP-1 levels in serum and ascites before treatment were 164.7 +/- 126.4 pg/mL and 365.3 +/- 583.0 pg/mL, respectively, and the IL-10 levels were 31.4 +/- 44.1 pg/mL and 188.1 +/- 189.5 pg/mL, respectively. The sera MCP-1 and ascites IL-10 levels differed significantly between the two groups. In the SBP group, sera and ascitic MCP-1 and IL-10 levels fell during treatment. The low MCP-1 and IL-10 levels on the seventh day of treatment were found to have a statistically significant relationship to patient survival. MCP-1 and IL-10 levels in sera and ascites may be related to the clinical course of SBP.

Dialysate Leukocytes, sICAM-1, Hyaluronan and IL-6: Predictors of Outcome of Peritonitis?

BACKGROUND/AIMS

Despite effective antibiotic therapy, peritonitis still remains a major problem in peritoneal dialysis (PD). The aim of the present study was to investigate changes of CRP, dialysate leukocytes and IL-6, hyaluronan (HA) and sICAM-1 in dialysate during and after peritonitis and their association to the outcome of peritonitis.

METHODS

Dialysate IL-6, HA and sICAM-1 were measured at the onset and on day 4, at the end of the treatment and 2 months after onset of peritonitis. Furthermore, CRP and dialysate leukocytes were measured on days 1-4.

RESULTS

All measured soluble factors were higher on the first and fourth day than at the end of the treatment. sICAM-1 and HA were lower at the end of the treatment in patients who later had a relapse/re-infection. IL-6 remained higher 2 months after clinically cured peritonitis. CRP and dialysate leukocytes were higher on day 4 in patients with poor outcome.

CONCLUSIONS

Peritonitis causes increased excretion of soluble factors. Low concentrations of sICAM-1 and HA at the end of the treatment were negative prognostic indicators. Higher IL-6 levels after peritonitis could be a sign of ongoing inflammation in the peritoneal membrane. Delayed decrease in CRP and dialysate leukocytes may indicate poor outcome.

Major involvement of CD40 in the regulation of chemokine secretion from human peritoneal mesothelial cells

BACKGROUND

CD40 is a member of the tumor necrosis factor (TNF) family of receptors, whose ligand, CD154, is expressed by activated mononuclear cells. CD40 activation is a major immune regulatory pathway and is important for the regulation of chemokine and cytokine secretion. This study investigates the effect of CD40 ligation on the secretion of chemokines from human peritoneal mesothelial cells (HPMC).

METHODS

We activated CD40 in HPMC along with combinations of TNF-alpha, interleukin-1 (IL-1), and interferon gamma (IFN-gamma), and evaluated the mRNA levels and protein secretion of regulated upon activation, normal T-cell expressed and secreted (RANTES), monocyte chemoattractant protein-1 (MCP-1), and IL-8.

RESULTS

CD40 ligation had a small stimulatory effect on the secretion of all three chemokines, while TNF-alpha, IL-1 and IFN-gamma induced their secretion in a dose-dependent manner. The combination of CD40 ligation with either IL-1 or TNF-alpha increased chemokine secretion additively. IFN-gamma and CD40 ligation acted in synergy to induce the secretion of the mononuclear recruiting chemokines RANTES and MCP-1 (up to approximately 36-fold and approximately threefold, respectively), for which the combination of all three cytokines with CD40 ligation was extremely potent. In contrast, the secretion of the neutrophil chemoattractant IL-8, induced by CD40 ligation or by the combination of IL-1 and TNF-alpha, was reduced in the presence of IFN-gamma.

CONCLUSION

In light of our data, it is reasonable to suggest that in the mononuclear phase of peritonitis, IFN-gamma and CD154, expressed by activated mononuclear cells, diminish IL-8 secretion from HPMC and thus inhibit neutrophil recruitment. At the same time, the two act in synergy to induce the secretion of RANTES and MCP-1 from HPMC. Hence, by regulating chemokine secretion, CD40 may be involved in peritonitis and in the development of late phase mononuclear predominance.

Interplay between IFN-gamma and IL-6 signaling governs neutrophil trafficking and apoptosis during acute inflammation

Regulated recruitment and clearance of neutrophils (PMN) is the hallmark of competent host defense and resolution of inflammation. We now report that IFN-gamma controls PMN infiltration and modulates IL-6 signaling through its soluble receptor (sIL-6R) to promote their apoptosis and clearance. Induction of peritoneal inflammation in IFN-gamma-deficient (IFN-gamma-/-) mice emphasized that the initial rate of PMN recruitment was impaired. This defect in PMN recruitment was also associated with the suppressed intraperitoneal expression of IL-1beta and IL-6. Reconstitution of IFN-gamma signaling restored the rate of PMN infiltration and IL-6 levels and was accompanied by normalization of PMN-activating CXC chemokine expression. To test whether local IL-6 signaling modulated PMN recruitment, inflammation was induced in IFN-gamma-/- and IL-6-/- mice and cytokine signaling adapted by intraperitoneal sIL-6R-IL-6 fusion protein (HYPER-IL-6) or IFN-gamma. Although HYPER-IL-6 attenuated PMN influx in IFN-gamma-/- mice, IFN-gamma had no effect on PMN infiltration in IL-6-/- mice. Examination of the leukocyte infiltrate from IFN-gamma-/-, IL-6-/-, and wild-type mice showed that apoptosis was aberrant in the absence of IFN-gamma and IL-6 as a result of impaired sIL-6R signaling. These data emphasize a pivotal role for IFN-gamma in regulating innate immunity through control of both the recruitment and clearance phases of PMN trafficking.

Patterns of CD4/CD8 T-cell ratio in dialysis effluents predict the long-term outcome of peritonitis in patients undergoing peritoneal dialysis

BACKGROUND

The peritoneal immune compartment is a microenvironment with a particular T-cell repertoire and susceptible to local inflammation. To clarify the role of T lymphocytes in peritoneal immunity, the changes in T-cell subpopulations in peritoneal dialysis effluents (PDEs), and their influence on the response to the treatment of peritonitis and on its prognosis were studied in patients undergoing long-term, continuous ambulatory peritoneal dialysis (CAPD).

METHODS

A cohort of 36 patients treated with CAPD and who had histories of peritonitis were divided into a group with rapid and a group with delayed response to antibiotics, and were followed for 3 years. CD4/CD8 T-cell ratios, T-cell cytokine mRNA expression patterns and transforming growth factor-beta1 (TGF-beta1) concentrations were examined in PDE during bouts of peritonitis. The change in 4 h D/P creatinine during the peritoneal equilibration test (PET) between year 0 and year 3 was expressed as deltaD/P creatinine.

RESULTS

The serial changes in T-cell subsets in PDE during peritonitis showed two patterns: (i) pattern 1, manifest as a progressive increase in the CD4/CD8 ratio, and associated with a rapid response to treatment; and (ii) pattern 2, manifest as a progressive decrease in the CD4/CD8 ratio, and associated with a delayed response to treatment. The major T-cell phenotypes in PDE during peritonitis were Th1-CD4(+) and Tc2-CD8(+), determined by cloning techniques, RT-PCR and double immunofluorescence staining. TGF-beta1 in the effluent was undetectable in pattern 1 after 7-8 days, but remained detectable at 2 weeks in pattern 2. Pattern 2 patients had a significantly greater decrease (deltaD/P creatinine: -0.198+/-0.086) in solute transport than pattern 1 patients (deltaD/P creatinine: -0.036+/-0.077, P<0.05).

CONCLUSIONS

These results suggest that a progressive decrease of the CD4/CD8 ratio in PDE correlates with a persistent expression of TGF-beta1, and plays a pathogenetic role in the evolution of peritonitis, PET deterioration and peritoneal fibrosis. Therefore, patterns of CD4/CD8 T-cell ratio in PDE may predict clinical outcomes of peritonitis in CAPD patients.

Differential regulation of chemokine production in human peritoneal mesothelial cells: IFN-gamma controls neutrophil migration across the mesothelium in vitro and in vivo

Leukocyte recruitment into the infected peritoneal cavity consists of an early, predominant polymorphonuclear leukocyte (PMN) influx and subsequent, prolonged mononuclear cell migration phase. Although chemokine secretion by resident peritoneal cells plays a primary role in mediating this migration, the mechanisms involved in controlling the switch in phenotype of cell infiltrate remain unclear. The present study investigates a potential role for the Th1-type cytokine IFN-gamma in the process of leukocyte recruitment into the peritoneal cavity. Stimulation of cultured human peritoneal mesothelial cells with IFN-gamma (1-100 U/ml) alone or in combination with IL-1beta (100 pg/ml) or TNF-alpha (1000 pg/ml) resulted in significant up-regulation of monocyte chemoattractant protein-1 and RANTES protein secretion. In contrast, IFN-gamma inhibited basal and IL-1beta-, and TNF-alpha-induced production of IL-8. The modulating effects of IFN-gamma on chemokine production occurred at the level of gene expression, and the degree of regulation observed was dependent on the doses of IL-1beta and TNF-alpha used. Analysis of the functional effects of IFN-gamma on IL-1beta-induced transmesothelial PMN migration with an in vitro human transmigration system and an in vivo murine model of peritoneal inflammation demonstrated that IFN-gamma was able to down-regulate PMN migration induced by optimal doses of IL-1beta. These effects were mediated in vivo via down-regulation of CXC chemokine synthesis. These findings suggest that IFN-gamma may play a role in controlling the phenotype of infiltrating leukocyte during the course of an inflammatory response, in part via regulation of resident cell chemokine synthesis.

Limits of peritoneal cytokine measurements during abdominal lavage treatment for intraabdominal sepsis

BACKGROUND

Monitoring of peritoneal cytokine concentrations of tumor necrosis factor (TNF)-alpha was recommended for early detection of severe postoperative complications. In the present study the clinical application of cytokine monitoring was examined in the treatment course of severe peritonitis.

METHODS

Nineteen patients with secondary peritonitis were followed up during 75 abdominal lavages. Serum and peritoneal interleukin (IL)-6, IL-8, and IL-10 and TNF-alpha were measured before the surgical intervention, after 1 hour, 3 hours, 6 hours, and 24 hours. Additionally, cardiorespiratory parameters, osmolarity, C-reactive protein, and total leucocyte count were recorded.

RESULTS

Serum and peritoneal cytokine concentrations did not correlate to each other as well as to the observed cardiorespiratory parameters. Peritoneal cytokine concentrations were 10- to 1000-fold higher to serum concentrations and showed an intermittent wash out. There were no differences in determined cytokine concentrations between survivors and nonsurvivors.

CONCLUSIONS

Once elevated, peritoneal cytokine measurements offer no new diagnostic or prognostic tool in abdominal lavage peritonitis treatment.