Inverse MCP-1/IL-8 ratio in effluents of CAPD patients with peritonitis and in isolated cultured human peritoneal macrophages

Dyslipidemia and Intraperitoneal Inflammation Axis in Peritoneal Dialysis Patients: A Cross-Sectional Pilot Study

Background

We have hypothesized that the problem of dyslipidemia in peritoneal dialysis (PD) patients lies beyond certain levels of plasma lipoprotein and involves cardiovascular risk, but can also influence the development of chronic intraperitoneal inflammation.

Objectives

The aim of our work was to define whether the association of dyslipidemia with intraperitoneal inflammation really exists and if it could it be used in a prospective cohort of PD patients.

Patients and Methods

We performed a cross-sectional, single-center, pilot study involving 40 nondiabetic PD patients (27 men and 13 women with an average age of 49.3 ± 12.2 years). The median time on PD was 29 (18.5-37) months. The parameters dialysis adequacy, blood lipid profile, and the concentrations of tumor necrosis factor (TNF)-α, monocyte chemoattractant protein (MCP)-1, and interleukin (IL)-10 in peritoneal dialysate effluent (PDE) were determined. Cohen's d effect size was computed post hoc to determine the differences between groups in the concentrations of pro- and anti-inflammatory mediators.

Results

PD patients with atherogenic dyslipidemia had significantly high levels of MCP-1 compared with dyslipidemia-free patients (Cohen's d = 1.32). A reduced high-density lipoprotein cholesterol level was associated with a high intraperitoneal production of the proinflammatory mediator TNF-α (p < 0.0001) and anti-inflammatory IL-10 (p < 0.0001). Atherogenic index of plasma was directly correlated with MCP-1 (p < 0.0001) and TNF-α (p < 0.0001). In multiple regression analysis, MCP-1 appeared to predict PD inadequacy (R ² = 0.58; F ratio = 9.4; p = 0.006) independently of age and blood C-reactive protein level. Effect size was 1.38 with α = 0.05, n = 40, and 3 predictors.

Conclusions

Our cross-sectional pilot study first demonstrated a close interaction between the atherogenic lipid profile and a high concentration of MCP-1 in PDE; this might be a prognostic marker for PD inadequacy. The potential significance of our finding is that it provides useful preliminary information necessary for further research into this area.

The aldosterone receptor antagonist spironolactone prevents peritoneal inflammation and fibrosis

Peritoneal fibrosis is a complication of patients with long-term continuous ambulatory peritoneal dialysis (CAPD). Reports have indicated that angiotensin (Ang) II may correlate with the development of peritoneal fibrosis. However, it is unknown whether aldosterone also has a role in the development of peritoneal inflammation and fibrosis. The aim of the present study was to clarify the role of aldosterone in peritoneal inflammation and fibrosis. A rat model of peritoneal inflammation and fibrosis was established by daily intraperitoneal injection of dialysates and lipopolysaccharide in a 4-day interval over a period of 7 days. The animals were randomly assigned to five groups as follows: control (C); peritoneal dialysis (PD); peritoneal dialysis-spironolactone (PD-S); peritoneal dialysis-cilazapril (PD-C); and peritoneal dialysis-spironolactone-cilazapril (PD-SC). After 30 days, the TGF-β1 concentration in dialysates from all treatment groups was determined by ELISA. The histopathology of the parietal peritoneum was examined, and the expression of MCP-1, c-Jun, fibronectin (FN) and TGF-β1 in the abdominal membrane was determined by immunohistochemistry. Mineralocorticoid receptor (MR), 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) and CYP11B2 (aldosterone synthase) were analyzed by real time-PCR. Collagen deposition was significantly higher in PD compared with the other groups. The expression of MR, 11β-HSD2 and CYP11B2 was significantly higher in PD compared with the other groups. Spironolactone and/or cilazapril treatment partially ablated the increase in monocyte chemoattractant protein (MCP)-1, p-c-Jun, transforming growth factor (TGF)-β1, FN, MR, 11β-HSD2 and CYP11B2. Furthermore, treatment with spironolactone and/or cilazapril also reduced the infiltration of CD-4- and ED-1-positive cells in rat peritoneal tissues after peritoneal fibrosis. Exogenous aldosterone may have a key role in the development of peritoneal inflammation and fibrosis. Spironolactone decreased peritoneal inflammation and fibrosis, which was associated with reduced secretion from peritoneal macrophages, inactivation of the c-Jun N-terminal kinase (JNK) pathway and subsequent downregulation of the expression of TGF-β1.

Activation of peroxisome proliferator-activated receptor-gamma by glitazones reduces the expression and release of monocyte chemoattractant protein-1 in human mesothelial cells

Human peritoneal mesothelial cells (MC) play an important role in inflammatory processes of the peritoneal cavity by producing various cytokines and chemokines, such as monocyte chemoattractant protein-1 (MCP-1). The present study was designed to assess the effect of the peroxisome proliferator-activated receptor-gamma- (PPARγ-) activator rosiglitazone on the mesothelial MCP-1 expression and release. Primary cultures of MC were obtained from omental tissue. MCP-1 antigen concentrations were measured in the cell supernatant by ELISA and MCP-1 mRNA levels by real-time polymerase chain reaction. The presence of PPARγ on MC was assayed in a Western Blot analysis. MC constitutively express PPARγ. Activation of this receptor via rosiglitazone (0,1–10 μmol/L) resulted in significantly reduced amounts of mesothelial MCP-1 release as well as MCP-1 mRNA. The use of the PPARγ inhibitor GW-9662 could completely prevent the rosiglitazone effects. Rosiglitazone was also effective in reducing TNFα-induced enhanced secretion of MCP-1. Our findings indicate that glitazones are effective in reducing constitutive and TNFα-stimulated mesothelial MCP-1 mRNA expression and release.

Impairment of MCP-1 expression in mesothelial cells exposed to peritoneal dialysis fluid by osmotic stress and acidic stress

BACKGROUND

Bacterial peritonitis is one of the most frequent complications in patients on peritoneal dialysis. In the present study, we investigated effects of peritoneal dialysis fluid (PDF) on mesothelial cell recruitment of macrophages, focusing especially on unphysiological properties of PDF.

METHODS

Human and murine mesothelial cells were exposed to PDF or individual properties of PDF (low pH, high glucose concentration, hyperosmolality, high lactate concentration) in vitro and in vivo, treated with inflammatory stimuli, and subjected to analyses of monocyte chemoattractant protein-1 (MCP-1), nuclear factor-κB (NF-κB), mitogen-activated protein (MAP) kinases, and MAP kinase phosphatase-1 (MKP-1).

RESULTS

We found that intraperitoneal administration of PDF suppressed expression of MCP-1 and infiltration of mononuclear cells in the peritoneum of mice following injection with lipopolysaccharide. Among the unphysiological properties of PDF, low pH and hyperosmolality caused blunted induction of MCP-1 in cytokine-stimulated mesothelial cells. The attenuated response was ascribed to suppression of NF-κB by low pH and inhibition of p38 MAP kinase by hyperosmolality. Furthermore, the attenuated phosphorylation of p38 MAP kinase by osmotic stress was associated with induction of MKP-1.

CONCLUSION

These results suggest a possibility that mesothelial cells exposed to PDF exhibit attenuated MCP-1 expression and consequent impairment of macrophage recruitment through dual mechanisms, that is, inhibition of NF-κB by acidic stress and blunted activation of p38 MAP kinase by osmotic stress. In patients on peritoneal dialysis, blunted expression of chemokines may lead to perturbation of bacterial clearance by macrophages in the peritoneal cavity.

Restoration of the cellular thiol status of peritoneal macrophages from CAPD patients by the flavonoids silibinin and silymarin

During continuous ambulatory peritoneal dialysis (CAPD) the peritoneal immune cells, mainly macrophages, are highly compromised by multiple factors including oxidative stress, resulting in a loss of functional activity. One reason for the increase of inflammatory reactions could be an imbalance in the thiol-disulfide status. Here, the possible protective effects of the antioxidant flavonoid complex silymarin and its major component silibinin on the cellular thiol status were investigated. Peritoneal macrophages from dialysis fluid of 30 CAPD patients were treated with silymarin or silibinin up to 35 days. A time-dependent increase of intracellular thiols was observed with a nearly linear increment up to 2.5-fold after 96 hours, reaching a maximum of 3.5-fold after 20 days of culture. Surface-located thiols were also elevated. The stabilization of the cellular thiol status was followed by an improvement of phagocytosis and the degree of maturation as well as significant changes in the synthesis of IL-6 and IL-1ra. Furthermore, the treatment of peritoneal macrophages with flavonoids in combination with cysteine donors resulted in a shortened and more efficient time course of thiol normalization as well as in a further increased phagocytosis. In addition, GSH-depletion in thiol-deficient media simulating CAPD procedures led to intracellular thiol deficiency similar to the in vivo situation. It is concluded that treatment with milk thistle extracts silymarin and silibinin alone or, more effectively in combination with cysteine donors, provide a benefit for peritoneal macrophages of CAPD-patients due to a normalization and activation of the cellular thiol status followed by a restoration of specific functional capabilities.