Betacellulin Induces Increased Retinal Vascular Permeability in Mice

BACKGROUND: Diabetic maculopathy, the leading cause of vision loss in patients with type 2 diabetes, is characterized by hyper-permeability of retinal blood vessels with subsequent formation of macular edema and hard exudates. The degree of hyperglycemia and duration of diabetes have been suggested to be good predictors of retinal complications. Intervention studies have determined that while intensive treatment of diabetes reduced the development of proliferative diabetic retinopathy it was associated with a two to three-fold increased risk of severe hypoglycemia. Thus we hypothesized the need to identify downstream glycemic targets, which induce retinal vascular permeability that could be targeted therapeutically without the additional risks associated with intensive treatment of the hyperglycemia. Betacellulin is a 32 kD member of the epidermal growth factor family with mitogenic properties for the retinal pigment epithelial cells. This led us to hypothesize a role for betacellulin in the retinal vascular complications associated with diabetes. METHODS AND FINDINGS: In this study, using a mouse model of diabetes, we demonstrate that diabetic mice have accentuated retinal vascular permeability with a concomitant increased expression of a cleaved soluble form of betacellulin (s-Btc) in the retina. Intravitreal injection of soluble betacellulin induced retinal vascular permeability in normoglycemic and hyperglycemic mice. Western blot analysis of retinas from patients with diabetic retinopathy showed an increase in the active soluble form of betacellulin. In addition, an increase in the levels of A disintegrin and metalloproteinase (ADAM)-10 which plays a role in the cleavage of betacellulin was seen in the retinas of diabetic mice and humans. CONCLUSIONS: These results suggest that excessive amounts of betacellulin in the retina may contribute to the pathogenesis of diabetic macular edema

Diabetic retinopathy: current and future methods for early screening from a retinal hemodynamic and geometric approach

Diabetic retinopathy (DR) is a major disease and is the number one cause of blindness in the UK. In England alone, 4200 new cases appear every year and 1280 lead to blindness. DR is a result of diabetes mellitus, which affects the retina of the eye and specifically the vessel structure. Elevated levels of glucose cause a malfunction in the cell structure, which affects the vessel wall and, in severe conditions, leads to their breakage. Much research has been carried out on detecting the different stages of DR but not enough versatile research has been carried out on the detection of early DR before the appearance of any lesions. In this review, the authors approach the topic from the functional side of the human eye and how hemodynamic factors that are impaired by diabetes affect the vascular structur

Ocular Application of the Kinin B1 Receptor Antagonist LF22-0542 Inhibits Retinal Inflammation and Oxidative Stress in Streptozotocin-Diabetic Rats

Purpose: Kinin B1 receptor (B1R) is upregulated in retina of Streptozotocin (STZ)-diabetic rats and contributes to vasodilation of retinal microvessels and breakdown of the blood-retinal barrier. Systemic treatment with B 1R antagonists reversed the increased retinal plasma extravasation in STZ rats. The present study aims at determining whether ocular application of a water soluble B1R antagonist could reverse diabetes-induced retinal inflammation and oxidative stress. Methods: Wistar rats were made diabetic with STZ (65 mg/kg, i.p.) and 7 days later, they received one eye drop application of LF22-0542 (1 % in saline) twice a day for a 7 day-period. The impact was determined on retinal vascular permeability (Evans blue exudation), leukostasis (leukocyte infiltration using Fluorescein-isothiocyanate (FITC)-coupled Concanavalin A lectin), retinal mRNA levels (by qRT-PCR) of inflammatory (B1R, iNOS, COX-2, ICAM-1, VEGF-A, VEGF receptor type 2, IL-1b and HIF-1a) and anti-inflammatory (B2R, eNOS) markers and retinal level of superoxide anion (dihydroethidium staining). Results: Retinal plasma extravasation, leukostasis and mRNA levels of B 1R, iNOS, COX-2, VEGF receptor type 2, IL-1b and HIF-1a were significantly increased in diabetic retinae compared to control rats. All these abnormalities were reversed to control values in diabetic rats treated with LF22-0542. B1R antagonist also significantly inhibited the increased production of superoxide anion in diabetic retinae. Conclusion: B1R displays a pathological role in the early stage of diabetes by increasing oxidative stress and proinflammator

Mechanisms of leukocyte migration across the blood–retina barrier

Immune-mediated inflammation in the retina is regulated by a combination of anatomical, physiological and immuno-regulatory mechanisms, referred to as the blood–retina barrier (BRB). The BRB is thought to be part of the specialised ocular microenvironment that confers protection or “immune privilege” by deviating or suppressing destructive inflammation. The barrier between the blood circulation and the retina is maintained at two separate anatomical sites. These are the endothelial cells of the inner retinal vasculature and the retinal pigment epithelial cells on Bruch’s membrane between the fenestrated choroidal vessels and the outer retina. The structure and regulation of the tight junctions forming the physical barrier are described. For leukocyte migration across the BRB to occur, changes are needed in both the leukocytes themselves and the cells forming the barrier. We review how the blood–retina barrier is compromised in various inflammatory diseases and discuss the mechanisms controlling leukocyte subset migration into the retina in uveoretinitis in more detail. In particular, we examine the relative roles of selectins and integrins in leukocyte interactions with the vascular endothelium and the pivotal role of chemokines in selective recruitment of leukocyte subsets, triggering adhesion, diapedesis and migration of inflammatory cells into the retinal tissue

Bloodstream-To-Eye Infections Are Facilitated by Outer Blood-Retinal Barrier Dysfunction

This work was funded by National Institutes of Health (NIH; http://www.nih.gov) Grants R01EY024140 and R21EY022466 (to M.C.C.) and R01EY019494 (to M.H.E.). Our research is also funded in part by NIH Core Grant P30EY021725 (to Robert E. Anderson, OUHSC) and an unrestricted grant from Research to Prevent Blindness Inc. (http://www.rpbusa.org) to the Dean A. McGee Eye Institute. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.We thank Bolanle Adebayo (Cameron University, Lawton OK), Craig Land (Oklahoma State University, Stillwater OK), Nathan Jia (Oklahoma Christian University, Edmond OK), Kobbe Wiafe (Oklahoma School of Science and Mathematics, Oklahoma City OK), and Amanda Roehrkasse and Madhu Parkunan (OUHSC) for intellectual discussions and technical assistance. The authors also acknowledge thank Nanette Wheatley, Dr. Feng Li, and Mark Dittmar (OUHSC Live Animal Imaging Core, P30EY021725) for their invaluable technical assistance.This work was presented in part at the 2014 Association for Research in Vision and Ophthalmology Annual Conference in Orlando FL.The blood-retinal barrier (BRB) functions to maintain the immune privilege of the eye, which is necessary for normal vision. The outer BRB is formed by tightly-associated retinal pigment epithelial (RPE) cells which limit transport within the retinal environment, maintaining retinal function and viability. Retinal microvascular complications and RPE dysfunction resulting from diabetes and diabetic retinopathy cause permeability changes in the BRB that compromise barrier function. Diabetes is the major predisposing condition underlying endogenous bacterial endophthalmitis (EBE), a blinding intraocular infection resulting from bacterial invasion of the eye from the bloodstream. However, significant numbers of EBE cases occur in non-diabetics. In this work, we hypothesized that dysfunction of the outer BRB may be associated with EBE development. To disrupt the RPE component of the outer BRB in vivo, sodium iodate (NaIO3) was administered to C57BL/6J mice. NaIO3-treated and untreated mice were intravenously injected with 108 colony forming units (cfu) of Staphylococcus aureus or Klebsiella pneumoniae. At 4 and 6 days postinfection, EBE was observed in NaIO3-treated mice after infection with K. pneumoniae and S. aureus, although the incidence was higher following S. aureus infection. Invasion of the eye was observed in control mice following S. aureus infection, but not in control mice following K. pneumoniae infection. Immunohistochemistry and FITC-dextran conjugate transmigration assays of human RPE barriers after infection with an exoprotein-deficient agr/sar mutant of S. aureus suggested that S. aureus exoproteins may be required for the loss of the tight junction protein, ZO-1, and for permeability of this in vitro barrier. Our results support the clinical findings that for both pathogens, complications which result in BRB permeability increase the likelihood of bacterial transmigration from the bloodstream into the eye. For S. aureus, however, BRB permeability is not required for the development of EBE, but toxin production may facilitate EBE pathogenesis.Yeshttp://www.plosone.org/static/editorial#pee