Evaluation of Effects of Melatonin in Reducing Postoperative Pain and Oxidative Stress in Children Undergoing Surgery,. Trought Circulating miR-34 and miR-124a, 4-Hydroxynonenal and Sirtuin 1 (SIRT1) Plasma Concentrations.

Melatonin shows a potential role in protecting neonates undergoing surgery from the deleterious effects of oxidative stress (OS). After administration of exogenous melatonin, a significant reduction in lipid and protein peroxidation in the postoperative period has been reported in neonates. Recently, Song et al. reported that sirtuin 1 (SIRT1) also plays a critical role in the pathogenesis of pain, showing analgesic effects in chronic pain conditions such as neuropathic and inflammatory pain. In this prospective, randomized, double-blind pilot study, we test the hypothesis that melatonin reduces OS and postoperative pain involving the sirtuin pathway in children undergoing surgery.

Melatonin (Dicoson, Dicofarm, Italy, 5 drops = 1 mg) was administered orally. The product is listed in the Register of Dietary Supplements on the website of the Ministry of Health (http://www.ministerosalute.it/alimenti/dietetica) and is classified with the following code: 943314283. This product is subject to the European Directive on Foodstuffs according to DL n. 169 of May 21, 2004, and not to the European Directive on Medicines 2001/20/EC transposed at the Italian level with D.L. n. 211 of June 24, 2003. Melatonin administration has a good safety profile, with no known adverse effects.

Melatonin plasma levels were assessed at each experimental time point (T0, T1, T2) using a competitive enzyme-linked immunosorbent assay (cELISA) kit from Antibodies.com (A87093) according to the manufacturer's instructions. T1 and T2 plasma samples from Mel treated children suspected of containing concentrations higher than the highest standard (500 pg/mL) were diluted 1:100 (v/v) with sample diluent prior to analysis. Color development was monitored at 450 nm in a Thermo Scientific (MultiSkan FC) microplate reader, and a standard curve (range 7.813-500 pg/mL) was generated using a four-parameter logistic (4-PL) curve fit. The sensitivity of the assay was 4.688 pg/mL; the intra- and inter-assay coefficients of variation were <8% and <10%, respectively.

4-Hydroxynonenal (4-HNE) as a marker of lipid peroxidation was measured to evaluate OS by using a cELISA kit from Antibodies.com (A86962). Plasma concentrations were calculated by reading the absorbance at 450 nm and referring to the standard curve (range 31.25-2000 pg/mL). The sensitivity of the assay was 18.75 pg/mL; the intra- and inter-assay coefficients of variation were <8% and <10%, respectively.

SIRT1 was quantified using an ELISA kit from Invitrogen (EH427RB). Plasma samples were diluted 1:2 as indicated by the Manufacturer before analysis. SIRT1 concentrations were calculated by absorbance reading at 450 nm and referring to the standard curve (range 1.23-300 ng/mL). The sensitivity of the assay was 1.23 ng/mL; the intra- and inter-assay coefficients of variation were <10% and <12%, respectively.