Investigating Atypical Inflammatory Signaling in Vascular Pericytes as Potential Target for Controlling Blood-Retinal-Barrier (BRB) Inflammation in Diabetic Retinopathy.

Pericytes are master regulators of vascular homeostasis and play key roles in the progression of many vasculopathies, including neurovascular inflammation and diabetic retinopathy. During inflammation, pericytes can be activated by many signals, leading to pericyte induced proinflammatory signaling and pericyte migration away from the vasculature leaving endothelial tubules exposed and fragile. Despite a clear role for G protein-coupled receptors (GPCR) in the regulation of vascular endothelial inflammation, GPCR control of pericytes has been understudied. Furthermore, pericytes represent a promising candidate for blocking inflammatory responses that could mitigate the onset and progression of neurovascular disease. Our prior studies revealed an atypical inflammatory pathway in endothelial cells, regulated by GPCR induced autoactivation of the mitogen-activated protein kinase (MAPK) p38 pathway. This Atypical inflammatory pathway has not been studied in pericytes and is a promising therapeutic target. Our central hypothesis is that neurovascular inflammation in the brain and eye is controlled by atypical p38 signaling in vascular pericytes. To investigate this we are initially using primary human brain pericytes. We show that that thrombin, histamine and prostaglandin E2 (PGE2) can activate p38 via the atypical p38 signaling pathway in primary human pericytes and that a peptide inhibitor of atypical p38 signaling, blocks PGE2 dependent p38 activation, suppressing proinflammatory cytokine expression. Furthermore we are currently using single cell morphometric analysis to characterize heterogeneous pericyte responses to proinflammatory stimuli. This will enable the correlation of morphological variations to proinflammatory roles in T-cell modulation, cytokine regulation, and migration. These studies are revealing novel insights into GPCR dependent control of pericytes and will be extrapolated into studies investigating pericyte-endothelial cell interactions and the dysregulation of the blood-retinal-barrier during diabetic retinopathy. Our current studies focus on defining this role and in understanding how the neurovascular unit in the eye is regulated through atypical signaling, and whether inhibition of atypical signaling can protect the retina from damage. Thus, these studies represent a novel approach to regulate vascular p38 activity and pro-inflammatory signaling in retinal disease.