Induction, transcription, synthesis, and adsorption of interleukin-1 by dialyzer membranes

Increased intracellular reactive oxygen species in patients with end-stage renal failure: effect of hemodialysis

BACKGROUND

Reactive oxygen species (ROS) have been implicated in various forms of cellular injury. ROS may cause cell damage and are involved in the pathophysiology of several diseases, including atherosclerosis and chronic inflammation.

METHODS

Disturbances of intracellular ROS levels were investigated in 28 patients with end-stage renal failure. The intracellular ROS levels were measured in lymphocytes before and after hemodialysis using biocompatible membranes and were compared with those from 11 patients with end-stage renal failure, not yet on renal replacement therapy, and 27 healthy control subjects. ROS levels were measured spectrophotometrically using the intracellular dye dichlorofluorescin diacetate.

RESULTS

The spontaneous production of ROS was significantly higher in lymphocytes from patients with end-stage renal failure compared with healthy control subjects (P < 0.01). The addition of 100 nmol/L phorbol-myristate-acetate (PMA) produced a significant increase of ROS, both in lymphocytes from patients with end-stage renal failure and healthy control subjects. The PMA-induced ROS increase was significantly higher in lymphocytes from patients with end-stage renal failure compared with healthy control subjects (P < 0.01). In patients with end-stage renal failure, not yet on renal replacement therapy, the PMA-induced ROS was also significantly higher compared with healthy control subjects. The PMA-induced ROS increases were significantly inhibited by catalase, but not by superoxide dismutase or the superoxide dismutase mimetic, tempol. PMA-induced ROS was significantly reduced by tyrphostin A51 in lymphocytes from patients with end-stage renal failure and from healthy control subjects (each P < 0.01), indicating the involvement of a tyrosine kinase-dependent pathway. In patients with end-stage renal failure, the spontaneous and the PMA-induced production of ROS was not significantly different before and after hemodialysis.

CONCLUSIONS

Regular hemodialysis sessions using biocompatible membranes have no effect on the elevated intracellular ROS in patients with end-stage renal failure.

Regulation of beta2-microglobulin expression in different human cell lines by proinflammatory cytokines

BACKGROUND

Proinflammatory monocytic cytokines such as interleukin-1 (IL-1), tumour necrosis factor-alpha (TNF-alpha) and IL-6 have been incriminated in the pathogenesis of elevated beta2-microglobulin (beta2M) serum concentrations in patients undergoing haemodialysis with so-called bioincompatible dialyser membranes. However, neither the source of the elevated serum beta2M nor the precise role of monocytic cytokines in the expression of the beta2M gene have been elucidated conclusively. The aim of the current study was to evaluate whether monocytic cytokines, and in particular IL-6, are regulators of beta2M gene expression in human hepatoma cells, T-lymphocytes and monocytes.

METHODS

HepG2 and HuH7 human hepatoma cells, Jurkat T-cells, monocytic MonoMac6 cells, primary human monocytes and synoviocytes were stimulated with IL-1beta, IL-6, interferon-alpha (IFN-alpha), IFN-gamma or conditioned media from lipopolysaccharide (LPS)-treated monocytes. Expression of beta2M mRNA was analysed by Northern blotting, beta2M protein synthesis was determined by metabolic labelling and immunoprecipitation, and beta2M secretion was measured by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

In all cell types tested, IFN-gamma and, to a lesser extent, IFN-alpha stimulated gene expression of beta2M resulting in an increased synthesis and secretion of beta2M protein. Neither IL-1beta and IL-6 nor supernatants from LPS-treated monocytes were capable of inducing beta2M gene expression, with the exception of a small increase in HuH7 hepatoma cells upon IL-1beta treatment.

CONCLUSIONS

The present study provides evidence that interferons are important regulators of beta2M expression. It also shows that proinflammatory monocytic cytokines do not modulate directly the expression of beta2M in cells of hepatic, monocytic and T-lymphocytic origin. Whether they influence beta2M synthesis and secretion indirectly by modulating interferon synthesis needs to be elucidated.

Role of cytokines in the response to erythropoietin in hemodialysis patients

BACKGROUND

Cytokines are regulatory factors of erythropoiesis, especially in pathologic conditions. Even though a relevant role for a deranged cytokine production in the pathogenesis of dialysis anemia has been suggested, no data are available that analyze the role of cytokines in the key therapeutic issue of the needs of erythropoietin. The aim of the present study in hemodialysis patients was, therefore, to examine the relationship between the dose of recombinant human erythropoietin (EPO) and the production of cytokines by peripheral blood mononuclear cells (PBMC).

METHODS

After the exclusion of subjects with major active causes of EPO resistance, data from 34 hemodialysis patients were available for analysis. Cytokine levels were measured in the supernatants of stimulated [with bacterial lipopolysaccharide and interferon gamma (IFN-gamma)] and unstimulated PBMC. Mean yearly values of hematocrit, hemoglobin, transferrin saturation, ferritin, parathormone (PTH) and aluminum levels and EPO doses (U/kg/week) were calculated. For analysis, the 34 patients were divided according to their cutoff requirements for EPO: patients with requirements of EPO > or = 60 U/kg/week (group A1, 26 subjects) versus EPO < 60 U/kg/week (group B1, 8 subjects) and patients with requirements of EPO > or = 100 U/kg/week (group A2, 18 subjects) versus <100 U/kg/week (group B2, 16 subjects).

RESULTS

A significant direct correlation between interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-a) production values and EPO doses was found (P = 0.039 and P = 0.02 respectively). On the other hand, there was a significantly negative correlation between interleukin-12 (IL-12) production values and EPO doses (P = 0.029). Patients of groups A1 and A2 had spontaneously higher tumor necrosis factor-alpha (TNF-alpha) and lower IL-12 and IFNgamma production compared to patients from groups B1 and B2.

CONCLUSIONS

Our data disclose a previously undescribed pattern of cytokine alteration that is relevant to determine increased needs of EPO in hemodialysis patients. The present results have potential applicability in designing strategies to improve EPO resistance.

Platelet-activating factor and the production of human interferon-gamma

Platelet-activating factor (PAF) was tested for its ability to alter yields of human interferon (IFN) produced from peripheral blood mononuclear cells (PBMC). Using different concentrations of phytohemagglutinin (PHA) we could not demonstrate a consistent effect of PAF at any concentration tested on the yield of IFN-gamma. Similarly, although PAF was associated with a slight enhancement of IFN-gamma yields when PBMC were induced by interleukin-2 (IL-2), the results were not statistically significant. No effect was observed on the accumulation of human IFN-gamma mRNA induced by PHA. Furthermore, PAF did not enhance yields of IFN-gamma when the cells were induced by poly I:poly C. We conclude that although PAF may have a role in sepsis, it is not likely that this is in any way related to its ability to significantly alter the yield of interferons.

Increased met-enkephalin plasma levels in hemodialysis patients with or without pruritus

Met-enkephalin plasma levels were measured in 21 hemodialysis patients with or without pruritus. The mean value was significantly increased in the total of the patients compared with that in ten healthy subjects. There was, however no correlation between met-enkephalin levels and the degree of pruritus. The findings suggest that the opioid system may be activated in this condition, although the relevance of this endogenous opioid peptide to pruritus remains to be determined.