Monocyte apoptosis in dialysis patients is Fas ligand-mediated

Damage-associated molecular patterns derived from mitochondria may contribute to the hemodialysis-associated inflammation

PURPOSE

Inflammation is common in hemodialysis (HD) patients. Mitochondrial damage-associated molecular patterns (DAMPs) are released during cell necrosis or apoptosis and induce inflammation. Cell apoptosis is increased in HD patients. The mitochondrial protein cytochrome c, as a marker of released mitochondrial DAMPs, and interleukin-6 (IL-6), as a marker of inflammation, were evaluated in HD patients.

METHODS

Thirty-four HD patients and 20 controls were enrolled in the study. Serum cytochrome c and IL-6 were measured by means of enzyme-linked immunosorbent assay.

RESULTS

Compared to controls, cytochrome c was markedly increased in HD patients (1392.88 ± 905.24 pg/mL vs. 212.95 ± 91.71 pg/mL). IL-6 was also significantly increased in HD patients (50.32 ± 35.89 pg/mL vs. 14.27 ± 6.83 pg/mL). In HD patients serum IL-6 was positively related to serum cytochrome c (r = 0.458).

CONCLUSION

Both circulating cytochrome c and IL-6 are markedly increased in HD patients. Cytochrome c is positively related to IL-6.

Dialysis Membrane-Induced Oxidative Stress: Role of Heme Oxygenase-1

Dialysis membranes have been reported to induce monocyte apoptosis. We studied the role of oxidative stress in the induction of dialysis membrane-induced monocyte apoptosis. Superoxide dismutase, a superoxide scavenger, prevented dialysis membrane-induced monocyte apoptosis. Similarly, other antioxidants also inhibited dialysis membrane- induced apoptosis. In addition, the interaction of dialysis membranes with monocytes was associated with the generation of molecules leading to oxidative stress such as superoxide and TBARS. Interestingly, pre-induction of heme oxygenase (HO)-1 by hemin prevented dialysis membrane-induced monocyte apoptosis, whereas inhibition of HO-1 activity (treatment with tin protoporphyrin, SN-P) enhanced dialysis membrane-induced monocyte apoptosis. We suggest that oxidative injury associated with dialysis membrane and monocyte interaction plays a role in monocyte injury. Pre-induction of HO-1 may attenuate dialysis membrane-induced monocyte apoptosis.

Hemodialysis modulates gene expression profile in skeletal muscle

BACKGROUND

Uremia alters diverse metabolic pathways involving multiple organ systems, including skeletal muscle. Skeletal muscle has an important role in nutrition, metabolism, oxidative stress, and inflammation. We hypothesized that hemodialysis (HD) will change the genomic fingerprinting associated with uremia and facilitate expression of a distinct set of genes.

METHODS

Five patients with end-stage renal disease (ESRD) were studied. Skeletal muscle biopsy specimens from the vastus lateralis were obtained before (pre-HD) and during the last 10 minutes of HD (post-HD). Oligonucleotide microarray (version 2, GeneChip arrays; Affymetrix U95A, Santa Clara, CA) was used to analyze global transcriptional modification in skeletal muscle by HD. Pre-HD data were compared with data from 3 subjects without renal failure.

RESULTS

In skeletal muscle of patients with ESRD, 83 genes were upregulated and 8 genes were downregulated pre-HD compared with controls. Pathway analysis linked 55 genes to 5 gene networks involved in the regulation of cell cycle, cell proliferation, cellular organization, apoptosis, and inflammation. During HD, expression of 22 genes increased and 1 (TOB1) decreased. Pathway analysis mapped 20 genes to 2 genetic networks involved in: (1) inflammation, cell proliferation, and cell signaling; and (2) apoptosis, cell function, protein synthesis, and tissue morphology. Reverse-transcription polymerase chain reaction confirmed increased expression of GADD45A, BTG2, PDE4B, and CEBPD and downregulation of TOB1 in skeletal muscle intradialysis.

CONCLUSION

In response to the uremic milieu, skeletal muscle goes through very active transcriptional and translational changes. HD activates a diverse, yet biologically linked, network of genes related to inflammation and apoptosis in skeletal muscle.

Kinetic study of adenosine concentrations and the expression of adenosine deaminase in mononuclear cells during hemodialysis

BACKGROUND

We previously showed that high intralymphocytic adenosine (Ado) concentrations are found in hemodialyzed patients due to the reduced activity of mononuclear cell adenosine deaminase (MCADA). These abnormalities contribute to the immune defect observed in HD patients. The kinetics of these abnormalities and the causes of the low MCADA activity, however, have not been investigated. Here, we addressed this question. Since interferon gamma (IFNgamma) partially modulates MCADA, we also evaluated the effect of IFNgamma on MCADA activity in vitro.

METHODS AND RESULTS

The study included 12 patients (eight men and four women) who were observed from the first to the 36th hemodialysis (HD) session, and eight healthy subjects (controls). MCADA activity and Ado concentrations were normal before the first HD session. Ado concentrations progressively increased from the first (10.5 +/- 3.1 pmol/10(7) cells) to the fourth session (26.7 +/- 3 pmol/10(7) cells), before stabilizing at a high level. MCADA activity increased transiently until the second session (2.2 +/- 0.5 IU/10(7) cells before HD vs. 2.8 +/- 0.6 IU/10(7)cells), and then decreased and stabilized at a low level (1.0 +/- 0.5 IU/10(7)cells). The amount of MCADA mRNA transiently increased until the third session (mRNA MCADA/mRNA beta-actin: 0.6 +/- 0.2 vs. 0.8 +/- 0.2), and then decreased to 0.3 +/- 0.1 at the 36th session. MCADA activity underwent a dose-dependent increase after IFNgamma stimulation.

CONCLUSION

HD affects the transcription of the gene encoding MCADA after just three HD sessions, leading to decreased MCADA activity and increased plasma concentration of Ado.