Selective Endothelin-B Receptor Stimulation Increases Vascular Endothelial Growth Factor in the Rat Brain during Postnatal Development

Abstract

Endothelin, vascular endothelial growth factor and nerve growth factor play important roles in development of the central nervous system. ET(B) receptors have been shown to promote neurovascular remodeling in the adult ischemic brain through an increase in VEGF and NGF. It is possible that ET(B) receptors may be involved in postnatal development of the brain through VEGF and NGF. In the present study, the brains of male rat pups on postnatal days 1, 7, 14 and 28 were analyzed for expression of ET(B) receptors, VEGF and NGF. In order to determine the effect of ET(B) receptor stimulation, a separate group of pups were administered saline or ET(B) receptor agonist, IRL-1620, on day 21, and their brains were analyzed on day 28. The intensity of ET(B) receptor and VEGF staining in the vasculature as well as the number of blood vessels of normal pups increased with age and was significantly higher on postnatal day 14 compared to day 1 and day 7. In contrast, both ET(B) and NGF staining intensity in the cortex and subventricular zones decreased (P<0.01) at postnatal day 14 compared to earlier time points. Stimulation of ET(B) receptors resulted in a significant increase in VEGF and ET(B) intensity both in the vasculature and the brain (P<0.05), however, IRL-1620 did not produce any change in NGF expression. Results indicate that ET(B) receptors appear to play a role in the development of the CNS and selective stimulation of ET(B) receptors enhances VEGF but not NGF in the postnatal rat brain.

Maternal Cannabinoid Use Alters Cannabinoid (CB₁) and Endothelin (ET_B) Receptor Expression in the Brains of Dams but Not Their Offspring

“…Subsequently, by administration of an ET B agonist in an adult rat stroke model, Leonard et al [22] identified a relationship whereby ET B receptor expression and stimulation enhance vascular endothelial growth factor (VEGF) and neuronal growth factor (NGF) supporting neurovascular remodeling. However, pharmacological stimulation of ET B receptors during postnatal development of normal rats produced an increase in only VEGF with no change in NGF expression in the brain [19] . During CNS development, there is a natural process of establishing a complex network of neurons which involves a nonpathological process of neuronal cell death prenatally resulting in loss of about 50% of the neurons and then elimination of about 50% unwarranted connections between neurons postnatally [23,24] .…”

“…β-Tubulin (1: 2,000; Cell Signaling Technology) or β-actin (1: 10,000; SigmaAldrich) were used as loading controls. The dilutions for all antibodies were determined based on previous studies in our laboratory [19,30,31] using the same antibodies as well as literature provided by the manufacturer. The blots were then visualized with SuperSignal West Pico Chemiluminescent Substrate (Thermo Scientific) using the Kodak Gel Logic 1500 Imaging System (Carestream Health Inc., New Haven, CT, USA).…”

“…Animal studies have elucidated an essential role of this system in the postnatal development of rat pups [18,19] . ET receptors are expressed in neurons, glial cells, and cerebral vasculature of the CNS [19] .…”

“…Animal studies have elucidated an essential role of this system in the postnatal development of rat pups [18,19] . ET receptors are expressed in neurons, glial cells, and cerebral vasculature of the CNS [19] . Puppala et al [18] evaluated ET A and ET B receptor expression in various organs, including the brain of developing rat pups, and found a significant decline in brain ET B receptor expression during postnatal development; these findings were later confirmed in a subsequent study [19] .…”

“…ET receptors are expressed in neurons, glial cells, and cerebral vasculature of the CNS [19] . Puppala et al [18] evaluated ET A and ET B receptor expression in various organs, including the brain of developing rat pups, and found a significant decline in brain ET B receptor expression during postnatal development; these findings were later confirmed in a subsequent study [19] . Combined with other investigations demonstrating severe neuronal disabilities in the case of ET B deletion, it has been suggested that ET B is the primary receptor involved in CNS development [18,20,21] .…”