Melatonin improves cerebrovascular function and decreases oxidative stress in chronically hypoxic lambs

Abstract

Chronic hypoxia during gestation and delivery results in oxidative stress and cerebrovascular dysfunction in the neonate. We assessed whether melatonin, a potent antioxidant and potential vasodilator, improves the cerebral vascular function in chronically hypoxic neonatal lambs gestated and born in the highlands (3600 m). Six lambs received melatonin (1 mg/kg per day oral) and six received vehicle, once a day for 8 days. During treatment, biometry and hemodynamic variables were recorded. After treatment, lambs were submitted to a graded FiO2 protocol to assess cardiovascular responses to oxygenation changes. At 12 days old, middle cerebral arteries (MCA) were collected for vascular reactivity, morphostructural, and immunostaining evaluation. Melatonin increased fractional growth at the beginning and improved carotid blood flow at all arterial PO2 levels by the end of the treatment (P < 0.05). Further, melatonin treatment improved vascular responses to potassium, serotonin, methacholine, and melatonin itself (P < 0.05). In addition, melatonin enhanced the endothelial response via nitric oxide-independent mechanisms in isolated arteries (162 ± 26 versus 266 ± 34 AUC, P < 0.05). Finally, nitrotyrosine staining as an oxidative stress marker decreased in the MCA media layer of melatonin-treated animals (0.01357 ± 0.00089 versus 0.00837 ± 0.00164 pixels/μm2 , P < 0.05). All the melatonin-induced changes were associated with no systemic cardiovascular alterations in vivo. In conclusion, oral treatment with melatonin modulates cerebral vascular function, resulting in a better cerebral perfusion and reduced oxidative stress in the neonatal period in chronically hypoxic lambs. Melatonin is a potential therapeutic agent for treating cerebrovascular dysfunction associated with oxidative stress and developmental hypoxia in neonates.

Melatonin reduces oxidative stress and improves vascular function in pulmonary hypertensive newborn sheep

“…At birth, all animals showed similar biometric variables as previously reported . Further, blood gases were similar between groups at 3 days old (data not shown), and these values were preserved until the end of the experimental protocol (Table ).…”

Pharmacological approaches in either intermittent or permanent hypoxia: A tale of two exposures

“…Recently, we have shown that melatonin increases the enzymatic antioxidants mechanisms and improves pulmonary endothelial function associated with a slight increase of the luminal radius of pulmonary arteries [70]. Interestingly, the same treatment also improved vascular function and decreased oxidative stress in the neonatal brain [95].…”

Effects of Antenatal Melatonin Treatment on the Cerebral Vasculature in an Ovine Model of Fetal Growth Restriction

“…Indeed there is evidence that MLT acts directly on vasculature to mediate blood flow to various vascular beds including the brain, to stabilize blood brain barrier integrity [33] , prevent endothelial cell dysfunction [34] , decrease nitric oxide and VEGF production, and suppress ischemia-induced cerebral edema [35] . Furthermore, neonatal treatment with oral MLT improves cerebral vascular function in chronically hypoxic newborn lambs by increasing cerebral blood flow and improving vascular function [36] . In this study, we have further characterized the role of MLT by showing that it protects the structural integrity of the cerebral vasculature via antiapoptotic actions, and by maintaining the normal cell contact of astrocytes and pericytes with the microvessel wall in the white matter of the FGR brain.…”