Brazilian Journal of Medical and Biological Research
On-line version ISSN 1414-431X
SANTOS, B.C. et al. Absence of peripheral blood mononuclear cells priming in hemodialysis patients. Braz J Med Biol Res [online]. 2003, vol.36, n.2, pp. 219-225. ISSN 1414-431X. http://dx.doi.org/10.1590/S0100-879X2003000200009.
As a consequence of the proinflammatory environment occurring in dialytic patients, cytokine overproduction has been implicated in hemodialysis co-morbidity. However, there are discrepancies among the various studies that have analyzed TNF-a synthesis and the presence of peripheral blood mononuclear cell (PBMC) priming in this clinical setting. We measured bioactive cytokine by the L929 cell bioassay, and evaluated PBMC TNF-a production by 32 hemodialysis patients (HP) and 51 controls. No difference in TNF-a secretion was observed between controls and HP (859 ± 141 vs 697 ± 130 U/106 cells). Lipopolysaccharide (5 µg/ml) did not induce any further TNF-a release, showing no PBMC priming. Paraformaldehyde-fixed HP PBMC were not cytotoxic to L929 cells, suggesting the absence of membrane-anchored TNF-a. Cycloheximide inhibited PBMC cytotoxicity in HP and controls, indicating lack of a PBMC TNF-a pool, and dependence on de novo cytokine synthesis. Actinomycin D reduced TNF-a production in HP, but had no effect on controls. Therefore, our data imply that TNF-a production is an intrinsic activity of normal PBMC and is not altered in HP. Moreover, TNF-a is a product of de novo synthesis by PBMC and is not constitutively expressed on HP cell membranes. The effect of actinomycin D suggests a putative tighter control of TNF-a mRNA turnover in HP. This increased dependence on TNF-a RNA transcription in HP may reflect an adaptive response to hemodialysis stimuli.
Keywords : Cytokine; Stress response; Translational control; Transcriptional blockage; Priming; Membrane-anchored tumor necrosis factor.