Proinflammatory
cytokines, in addition to their role in host defence, may be considered mediators of disease; a reduction of
cytokine synthesis or effects is, therefore, becoming a target of many diseases.
IL-6 is a pro-inflammatory
cytokine that may play a role in several clinical problems related to dialysis treatment. An enhanced spontaneous production of
IL-6 by Peripheral Blood Mononuclear Cells (PBMC) harvested from
ESRD patients dialyzed with a poor biocompatible membrane has been first demonstrated by our group. These results were also obtained in patients undergoing continuous
peritoneal dialysis, in absence of
peritonitis. We have also demonstrated that
IL-6 release was inversely correlated with
serum albumin changes.
Biological activities of
IL-6 may be modulated by two soluble circulating receptors, namely sIL-6R and
sgp130. sIL-6R may enhance the inflammatory effects of
IL-6 and is, therefore, an "agonistically" acting molecule. We have recently studied sIL-6R production in
ESRD patients dialyzed with different membranes; the conclusion was that poor biocompatible membranes, via the sIL-6R, might further increase the inflammatory effects of
IL-6. On the contrary,
sgp130 can efficiently bind the IL-6/sIL-6R complex with "antagonistic" effects. We have evaluated plasma levels of
sgp130 in 18
ESRD patients regularly dialyzed with
hemophan membranes (HE) and in 15 patients dialyzed with more biocompatible synthetic membranes (BIO). Our results demonstrate that plasma levels of
sgp130 in HE are 33% higher than in both healthy controls and BIO. Circulating levels of
sgp130 were correlated positively with
C-reactive protein (r: 0.338, p<0.05) and negatively with
serum albumin (r: -0.334, p<0.05). These results suggest that higher circulating levels of
sgp130 are likely associated with higher
IL-6 levels. These higher amounts are probably insufficient to control the activity of
IL-6 and may be considered only as a marker of PBMC activation.