Proceedings of The Physiological Society
University of Cambridge (2008) Proc Physiol Soc 11, C28
Melatonin up-regulates placental expression of catalase and manganese superoxide dismutase under maternal undernutrition but not hypoxic conditions
H. G. Richter1, S. Raut1, J. A. Hansell1, D. A. Giussani1
1. Department of Physiology, Development & Neuroscience, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom.
+Mel melatonin. Values are Mean ± SEM (n=7) for the ratios protein/β-actin obtained by digital band densitometry. *P<0.05 (ANOVA and Tukey’s Multiple Comparison Test). Two-tailed Unpaired t-test for control without melatonin versus control with melatonin indicated no action of melatonin per se
The neurohormone melatonin participates in circadian, seasonal and reproductive physiology. Melatonin also acts as a potent endogenous antioxidant by scavenging free radicals and up-regulating endogenous antioxidant pathways (1). The presence of melatonin receptors in the placenta suggests a role in placental function (2) and melatonin protects against oxidative damage induced in rat placenta by ischaemia-reperfusion (3). Complicated pregnancy is often characterised by reductions in oxygen and nutrient delivery, and both hypoxia and undernutrition promote oxidative stress (4). Previously, we reported that melatonin treatment in rats rescued the fall in placental efficiency in undernourished but not hypoxic pregnancy (5). In this study, we have investigated the effects of maternal treatment with melatonin on the expression of placental antioxidant proteins in both hypoxic and undernourished pregnancy. On day 15 of pregnancy, Wistar rats were divided into 6 groups (n=7 per group): control (21% O2), hypoxic (10% O2) and undernourished pregnancy (40% reduced food intake), with and without melatonin treatment (5µg.ml-1 drinking water). Water and food intake were monitored daily. On day 20, the dams underwent euthanasia (0.2 mL, i.p., xylazine and ketamine) and the placentae were snap frozen for subsequent protein isolation. Western blot was used to semi-quantify expression of the antioxidant enzymes catalase, manganese superoxide dismutase (Mn-SOD) and glutathione peroxidase 1 (GPx-1); relative to β-actin levels. Melatonin increased the expression of catalase and Mn-SOD in undernourished pregnancy but had no effect in control or hypoxic pregnancies (Table). The data show that in pregnancy complicated by undernutrition, but not by hypoxia, melatonin may attenuate placental oxidative damage and improve placental efficiency by up-regulating at least two potent antioxidant enzymes.
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