Fetal hypoxia is a common complication of pregnancy. It has been shown to programme cardiac and endothelial dysfunction in the offspring in adult life. However, the mechanisms via which this occurs remain elusive, precluding the identification of potential therapy. Using an integrative approach at the isolated organ, cellular and molecular levels, we tested the hypothesis that oxidative stress in the fetal heart and vasculature underlies the molecular basis via which prenatal hypoxia programmes cardiovascular dysfunction in later life. In a longitudinal study, the effects of maternal treatment of hypoxic (13% O2) pregnancy with an antioxidant on the cardiovascular system of the offspring at the end of gestation and at adulthood were studied. On day 6 of pregnancy, rats (n = 20 per group) were exposed to normoxia or hypoxia ± vitamin C. At gestational day 20, tissues were collected from 1 male fetus per litter per group (n = 10). The remaining 10 litters per group were allowed to deliver. At 4 months, tissues from 1 male adult offspring per litter per group were either perfusion fixed, frozen, or dissected for isolated organ preparations. In the fetus, hypoxic pregnancy promoted aortic thickening with enhanced nitrotyrosine staining and an increase in cardiac HSP70 expression. By adulthood, offspring of hypoxic pregnancy had markedly impaired NO-dependent relaxation in femoral resistance arteries, and increased myocardial contractility with sympathetic dominance. Maternal vitamin C prevented these effects in fetal and adult offspring of hypoxic pregnancy. The data offer insight to mechanism and thereby possible targets for intervention against developmental origins of cardiac and peripheral vascular dysfunction in offspring of risky pregnancy.

Chronic exposure to light at night, as in shift work, alters biological clocks (chronodisruption), negatively impacting pregnancy outcome in humans. Actually the interaction of maternal and fetal circadian systems could be a key factor determining a fitting health in adults. We propose that chronic photoperiod shift (CPS) during pregnancy alter maternal circadian rhythms and impair circadian physiology in the adult offspring, increasing health risks. Pregnant rats were exposed to normal photoperiod (12 h light, 12 h dark) or to CPS until 85% of gestation. The effects of gestational CPS were evaluated on the mother and adult offspring. In the mother we measured rhythms of heart rate, body temperature, and activity through gestation and daily rhythms of plasma variables (melatonin, corticosterone, aldosterone, and markers of renal function) at 18 days of gestation. In adult offspring, we measured rhythms of the clock gene expression in the suprachiasmatic nucleus (SCN), locomotor activity, body temperature, heart rate, blood pressure, plasma variables, glucose tolerance, and corticosterone response to ACTH. CPS altered all maternal circadian rhythms, lengthened gestation, and increased newborn weight. The adult CPS offspring presented normal rhythms of clock gene expression in the SCN, locomotor activity, and body temperature. However, the daily rhythm of plasma melatonin was absent, and corticosterone, aldosterone, renal markers, blood pressure, and heart rate rhythms were altered. Moreover, CPS offspring presented decreased glucose tolerance and an abnormal corticosterone response to ACTH. Altogether these data show that gestational CPS induced long-term effects on the offspring circadian system, wherein a normal SCN coexists with altered endocrine, cardiovascular, and metabolic function.

Melatonin participates in circadian, seasonal and reproductive physiology. Melatonin also acts as a potent endogenous antioxidant by scavenging free radicals and upregulating antioxidant pathways. The placenta expresses melatonin receptors and melatonin protects against oxidative damage induced in rat placenta by ischemia-reperfusion. One of the most common complications in pregnancy is a reduction in fetal nutrient delivery, which is known to promote oxidative stress. However, whether melatonin protects placental function and fetal development in undernourished pregnancy is unknown. Here, we investigated the effects of maternal treatment with melatonin on placental efficiency, fetal growth, birth weight and protein expression of placental oxidative stress markers in undernourished pregnancy. On day 15 of pregnancy, rats were divided into control and undernourished pregnancy (35% reduction in food intake), with and without melatonin treatment (5 microg/mL drinking water). On day 20 of gestation, fetal biometry was carried out, the placenta was weighed and subsequently analyzed by Western blot for xanthine oxidase, heat shock protein (HSP) 27 and 70, catalase, manganese superoxide dismutase (Mn-SOD) and glutathione peroxidase 1 (GPx-1). A separate cohort was allowed to deliver to assess effects on birth weight. Maternal undernutrition led to a fall in placental efficiency, disproportionate intrauterine growth retardation and a reduction in birth weight. Maternal treatment with melatonin in undernourished pregnancy improved placental efficiency and restored birth weight, and it increased the expression of placental Mn-SOD and catalase. The data show that in pregnancy complicated by undernutrition, melatonin may improve placental efficiency and birth weight by upregulating placental antioxidant enzymes.

The pineal hormone melatonin participates in circadian, seasonal, and reproductive physiology. The presence of melatonin binding sites in human brain and peripheral tissues is well documented. However, in the mammalian adrenal gland, low-affinity melatonin binding sites have been detected only in the rat by some but not all authors. Conflicting evidence for a regulatory role of melatonin on adrenal cortisol production, prompted us to investigate this possibility in a New World primate, the capuchin monkey. Expression of melatonin receptors in the adrenal cortex was demonstrated through pharmacological characterization and autoradiographic localization of 2-[125I]iodomelatonin binding sites (dissociation constant = 96.9 +/- 15 pM; maximal binding capacity = 3.8 +/- 0.4 fmol/mg protein). The mt1 identity of these receptors was established by cDNA sequencing. Melatonin treatment of dispersed cells and explants from adrenal gland did not affect basal cortisol production. However, cortisol production stimulated by 100 nM ACTH was significantly inhibited by low melatonin concentrations (0.1-100 nM); this inhibitory effect was reversed by the mt1/MT2 melatonin antagonist luzindole. Melatonin also inhibited dibutyril-cAMP-stimulated cortisol production, suggesting that melatonin acts through a cAMP-independent signaling pathway. The present data demonstrate that the primate adrenal gland cortex expresses functional mt1 melatonin receptors and shows that melatonin inhibits ACTH-stimulated cortisol production.

Surprisingly, in our modern 24/7 society, there is scant information on the impact of developmental chronodisruption like the one experienced by shift worker pregnant women on fetal and postnatal physiology. There are important differences between the maternal and fetal circadian systems; for instance, the suprachiasmatic nucleus is the master clock in the mother but not in the fetus. Despite this, several tissues/organs display circadian oscillations in the fetus. Our hypothesis is that the maternal plasma melatonin rhythm drives the fetal circadian system, which in turn relies this information to other fetal tissues through corticosterone rhythmic signaling. The present data show that suppression of the maternal plasma melatonin circadian rhythm, secondary to exposure of pregnant rats to constant light along the second half of gestation, had several effects on fetal development. First, it induced intrauterine growth retardation. Second, in the fetal adrenal in vivo it markedly affected the mRNA expression level of clock genes and clock-controlled genes as well as it lowered the content and precluded the rhythm of corticosterone. Third, an altered in vitro fetal adrenal response to ACTH of both, corticosterone production and relative expression of clock genes and steroidogenic genes was observed. All these changes were reversed when the mother received a daily dose of melatonin during the subjective night; supporting a role of melatonin on overall fetal development and pointing to it as a ‘time giver’ for the fetal adrenal gland. Thus, the present results collectively support that the maternal circadian rhythm of melatonin is a key signal for the generation and/or synchronization of the circadian rhythms in the fetal adrenal gland. In turn, low levels and lack of a circadian rhythm of fetal corticosterone may be responsible of fetal growth restriction; potentially inducing long term effects in the offspring, possibility that warrants further research.