Polymorphonuclear leucocyte priming in long intermittent nocturnal haemodialysis patients - Is melatonin a player?

Background. The relationships between sleep quality, melatonin circadian rhythm and polymorphonuclear leucocyte (PMNL) priming during the night of dialysis treatment compared with a night without dialysis were studied in a group of nocturnal haemodialysis (HD) patients. Methods. Twenty-eight long intermittent nocturnal HD patients were included. Sleep quality was assessed by a questionnaire and wrist actigraphy. Plasma melatonin levels were assayed every 2h, from 9p.m. to 5a.m. PMNL priming was assessed by the rate of superoxide release from separated PMNLs at 9p.m. and 5a.m., on a night of dialysis and a night with sleepover in the dialysis unit without being dialysed. Results. Melatonin levels increased similarly during a night with and without dialysis, reaching peak level at 5a.m. Most (73%) of the patients had severe sleep disturbances. A significant negative correlation was found between the sleep quality score, the rate of superoxide release from separated PMNLs and melatonin levels. While during a night without dialysis a significant reduction of the rate of superoxide release was found at 5a.m. (compared with 9p.m.), no significant reduction was observed when the patients were dialysed. Patients with flat melatonin curves, with <10pg/ml, showed a faster rate of superoxide release than those with higher levels. Conclusions. The nocturnal HD process does not affect plasma melatonin levels or rhythms, suggesting that melatonin is not dialysed. Higher endogenous melatonin levels are associated with better sleep and lower PMNL priming. The lower PMNL priming in patients with higher plasma melatonin levels suggests that melatonin overrides the oxidative burden induced by the dialysis process.