Womack, T. | bioRxiv Science

bioRxiv2021

Prostacyclin as a Negative Regulator of Angiogenesis in the Neurovasculature

In this study, multiple measures of angiogenic processes were assessed in murine brain endothelial (bEnd.3) cells after exposure to the stable prostacyclin analog, iloprost. Additionally, changes in the {gamma}-secretase enzyme were evaluated after activation of prostacyclin signaling using PGI2 overexpressing mouse brain tissue and immunohistology studies in bEnd.3 cells. A three-dimensional assay of tube formation revealed that iloprost inhibits normal formation by significantly reduced tube lengths and vessel mesh area. The iloprost-mediated inhibition of tube-like structures was ameliorated by a specific IP-receptor antagonist, CAY10449. Reductions in wound healing were observed with iloprost application in a dose-dependent manner and this effect was reversed using CAY10449. Iloprost did not exhibit anti-proliferative effects in the bEnd.3 cells. When subjected to a Transwell assay to evaluate changes in trans-epithelial electrical resistance (TEER), bEnd.3 cells displayed reduced TEER values in the presence of iloprost an effect that lasted over prolonged periods (24 hours). Again, CAY10449 was able to reverse iloprost-mediated reductions in TEER value. Surprisingly, the adenylyl cyclase activator, forskolin, produced higher TEER values in the bEnd.3 cells over the same time. The TEER results suggest that iloprost may not activating the Gs protein of the IP receptor to increase cAMP levels given by the opposing results seen with iloprost and forskolin. In terms of {gamma}-secretase expression, PGI2 overexpression in mice increased the expression of the APH-1 subunit in the hippocampus and cortex. In bEnd.3 cells, iloprost application slightly increased APH-1 subunit expression measured by western blot and interrupted the colocalization of Presenilin 1 and APH-1 subunits using immunohistochemistry. The results suggest that prostacyclin signaling within bEnd.3 cells is anti-angiogenic and further downstream events have effects on the expression and most likely the activity of the A{beta} cleaving enzyme, {gamma}-secretase.

neuroscience↗

bioRxiv2020

Prostacyclin promotes degenerative pathology in a model of Alzheimer's disease

Alzheimers disease (AD) is a progressive neurodegenerative disorder that is the most common cause of dementia in aged populations. A substantial amount of data demonstrates that chronic neuroinflammation can accelerate neurodegenerative pathologies, while epidemiological and experimental evidence suggests that the use of anti-inflammatory agents may be neuroprotective. In AD, chronic neuroinflammation results in the upregulation of cyclooxygenase and increased production of prostaglandin H2, a precursor for many vasoactive prostanoids. While it is well-established that many prostaglandins can modulate the progression of neurodegenerative disorders, the role of prostacyclin (PGI2) in the brain is poorly understood. We have conducted studies to assess the effect of elevated prostacyclin biosynthesis in a mouse model of AD. Upregulated prostacyclin expression significantly worsened multiple measures associated with amyloid disease pathologies. Mice overexpressing both amyloid and PGI2 exhibited impaired learning and memory and increased anxiety-like behavior compared with non-transgenic and PGI2 control mice. PGI2 overexpression accelerated the development of amyloid accumulation in the brain and selectively increased the production of soluble amyloid-{beta} 42. PGI2 damaged the microvasculature through alterations in vascular length and branching; amyloid expression exacerbated these effects. Our findings demonstrate that chronic prostacyclin expression plays a novel and unexpected role that hastens the development of the AD phenotype.

neuroscience↗