endothelin-1 and Retinal-Degeneration

To study the long-term effects of endothelin-1 (ET-1)-induced retinal pathologies in mouse, using clinically relevant tools.. Adult C57BL/6 mice (7-9 weeks old) were intravitreally injected with PBS (n = 10) or 0.25 (n = 8), 0.5 (n = 8), or 1 nmol ET-1 (n = 9) and examined using electroretinogram, optical coherence tomography (OCT), and Doppler OCT at baseline and postinjection days 10, 28, and 56. Retinal ganglion cell (RGC) survival in retinal whole mount was quantified at days 28 and 56.. ET-1 induced immediate retinal arterial constriction. The significantly reduced total blood flow and positive scotopic threshold response in the 0.5- and 1-nmol ET-1 groups at day 10 were recovered at day 28. A-wave magnitude was also significantly reduced at days 10 and 28. While a comparable and significant reduction in retinal nerve fiber layer thickness was detected in all ET-1 groups at day 56, the 1-nmol group was the earliest to develop such change at day 28. All ET-1 groups showed a transient inner retinal layer thinning at days 10 and 28 and a plateaued outer layer thickness at days 10 to 56. The 1-nmol group showed a significant RGC loss over all retinal locations examined at day 28 as compared with PBS control. As for the lower-dosage groups, significant RGC density loss at central and midperipheral retina was detected at day 56 when compared with day 28.. ET-1 injection in mice resulted in a transient vascular constriction and reduction in retinal functions, as well as a gradual loss of retinal nerve fiber layer and RGC in a dose-dependent manner.

Topics: Animals; Disease Models, Animal; Endothelin-1; Mice; Mice, Inbred C57BL; Retina; Retinal Degeneration; Retinal Ganglion Cells; Tomography, Optical Coherence

The goal of this study was to determine whether JNK2 played a causative role in endothelin-mediated loss of RGCs in mice.. JNK2-/- and wild type (C57BL/6) mice were intravitreally injected in one eye with 1 nmole of ET-1, whereas the contralateral eye was injected with the vehicle. At two time points (two hours and 24 hours) after the intravitreal injections, mice were euthanized, and phosphorylated c-Jun was assessed in retinal sections. In a separate set of experiments, JNK2-/- and wild type mice were intravitreally injected with either 1 nmole of ET-1 or its vehicle and euthanized seven days after injection. Retinal flat mounts were stained with antibodies to the RGC marker, Brn3a, and surviving RGCs were quantified. Axonal degeneration was assessed in paraphenylenediamine stained optic nerve sections.. Intravitreal ET-1 administration produced a significant increase in immunostaining for phospho c-Jun in wild type mice, which was appreciably lower in the JNK2 -/- mice. A significant (P < 0.05) 26% loss of RGCs was found in wild type mice, seven days after injection with ET-1. JNK2-/- mice showed a significant protection from RGC loss following ET-1 administration, compared to wild type mice injected with ET-1. A significant decrease in axonal counts and an increase in the collapsed axons was found in ET-1 injected wild type mice eyes.. JNK2 appears to play a major role in ET-1 mediated loss of RGCs in mice. Neuroprotective effects in JNK2-/- mice following ET-1 administration occur mainly in the soma and not in the axons of RGCs.

Topics: Animals; Axons; Biomarkers; Cell Survival; Endothelin-1; Female; Immunohistochemistry; Intravitreal Injections; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mitogen-Activated Protein Kinase 9; Optic Nerve; Phosphorylation; Retinal Degeneration; Retinal Ganglion Cells; Transcription Factor Brn-3A

Endothelin-1 (ET-1), synthesized in vascular endothelial cells, is a potent vasoconstrictor. ET-1-related vascular abnormality has been known to be important in the pathogenesis of glaucoma, especially in normal tension glaucoma. However, the long-term effect of increased vascular ET-1 on the retinal tissue is still unclear.. The mice with overexpression of ET-1 in vascular endothelial cells (TET-1 mice) were examined with the profile of intraocular pressure (IOP), retinal layer thickness, numbers of retinal ganglion cells (RGCs), and axonal changes associated with blood vessel changes.. The TET-1 mice exhibited a significant progressive loss of RGCs and decrease of retinal thickness in the inner nuclear layer (INL) and outer nuclear layer (ONL) as early as around 10-12 months. At 24 months, the retinal degeneration became more severe, with around 30% RGC loss associated with thinning of the retinal nerve fiber layer and there was an increase in neuronal loss and thinning of the INL and ONL. In the 24-month-old TET-1 mice, IgG leakage in the blood vessels and decrease in the occludin protein were observed. There was increased glial fibrillary acidic protein expression in the Müller cells. In addition, the astrocytic end-feet on blood vessels were enlarged. The IOP level was normal in all ages (1-24 months) of TET-1 mice.. These data suggested that TET-1 mice may be a useful model to address endothelial ET-1-related mechanisms in vascular-associated retinal degenerative diseases.

Topics: Aging; Animals; Axons; Blotting, Western; Endothelial Cells; Endothelin-1; Immunoglobulin G; Intraocular Pressure; Mice; Mice, Transgenic; Retina; Retinal Degeneration; Retinal Ganglion Cells

The purpose of this study was to examine the effects of endothelin-1 (ET-1) on retrograde axonal transport in the rat optic nerve. Vehicle or ET-1 (0.2, 1, or 5 pmol/eye) were injected into the vitreous body in Sprague-Dawley rats. Retinal vessels were observed, using a fundus camera, before, and at 10 min, 3 days and 7 days after a single intravitreous injection. Two days after the injection, a neuronal tracer, fluoro gold, was administered via the superior colliculi to retrogradely label active retinal ganglion cells (RGCs). Five days after the tracer administration, retrogradely labeled RGCs were evaluated in the flat-mounted retina, and cross sections from each optic nerve were graded for injury by four independent, masked observers. ET-1 at 5 pmol/eye caused a significant constriction of retinal vessels (versus the vehicle-treated group) at 10 min after the injection. Intravitreous injection of ET-1 caused a dose-related decrease in the number of retrogradely labeled RGCs. Injection of 5 pmol/eye ET-1 led to a statistically significant decrease in the number of retrogradely labeled RGCs (versus the vehicle-treated group). ET-1 at 1 and 5 pmol/eye caused histological optic nerve damage (evaluated using a graded scale). The histological optic nerve damage correlated with the number of retrogradely labeled RGCs. In conclusion, a single intravitreous injection of ET-1 impaired retrograde axonal transport in the rat optic nerve and this impairment correlated with the histological optic nerve damage.

Topics: Animals; Axonal Transport; Axons; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin-1; Glaucoma, Open-Angle; Male; Optic Disk; Optic Neuropathy, Ischemic; Rats; Rats, Sprague-Dawley; Retinal Artery; Retinal Degeneration; Retinal Ganglion Cells; Stilbamidines; Vasoconstriction; Wallerian Degeneration

We have studied the distribution of endothelinergic molecules: prepro-endothelin-1 (PPET-1), endothelin-1 (ET-1), and receptors A and B (ET-A) and (ET-B) in the retina of mice. The localization of these molecules in normal mice was compared to their localization in retinas from animals submitted to continuous illumination during 1, 6, 9 or 18 days. We also evaluated the distribution of smooth muscle actin (SMA) and glial markers, glial fibrillary acidic protein (GFAP) and glutamine synthase (GS). PPET-1 immunoreactivity mainly appeared in retinal pigment epithelium (RPE) and cells of the ganglion cell layer (GCL), whereas ET-1 immunoreactivity was present in the RPE, outer plexiform layer (OPL) and astrocytes. Astrocytes exhibited the strongest immunostaining in the retina. ET-A immunoreactivity was observed in endothelium, RPE, OPL and cells of the GCL. By contrast, ET-B immunoreactivity could be detected in endothelial cells, horizontal cells and astrocytes. Astrocytes of the optic nerve also exhibited ET-1, ET-A, and ET-B immunoreactivities. After light-induced degeneration, there was an increase of RPE immunostaining. Degeneration of photoreceptors was accompanied by disappearance of immunoreactivity in the OPL. However, ET-A immunoreactivity appeared in the amacrine sublayer of the INL. There was an enormous increase in astrocytes and its cell processes. The increase of astrocytic immunoreactivities for ET-1 and ET-B was confirmed by quantitative image analysis. Growth of astrocytic cell processes was most marked around retinal blood vessels. Our findings indicate that there are at least three endothelinergic pathways in the normal retina: (1) between the RPE and choriocapillaris, (2) at the OPL, and (3) between blood vessels, astrocytes and cells of the GCL. After light-induced degeneration of photoreceptors, endothelinergic molecules were overexpressed at the RPE and astrocytes, but mostly disappeared from the OPL.

Topics: Animals; Astrocytes; Endothelin-1; Light; Male; Mice; Mice, Inbred BALB C; Optic Nerve; Pigment Epithelium of Eye; Radiation Injuries; Receptors, Endothelin; Retina; Retinal Degeneration