The expression of Mas-receptor of the renin-angiotensin system in the human eye.

PURPOSE: The local renin-angiotensin system has been held to be expressed in many organs, including the eye. It has an important role in the regulation of local fluid homeostasis, cell proliferation, fibrosis, and vascular tone. Mas-receptor (Mas-R) is a potential receptor acting mainly opposite to the well-known angiotensin II receptor type 1. The aim of this study was to determine if Mas-R is expressed in the human eye. METHODS: Seven enucleated human eyes were used in immunohistochemical detection of Mas-R and its endogenous ligand angiotensin (1-7) [Ang(1-7)]. Both light microscopy and immunofluorescent detection methods were used. A human kidney preparation sample was used as control. RESULTS: The Mas-R was found to have nuclear localization, and localized in the retinal nuclear layers and in the structures of the anterior segment of the eye. A cytoplasmic immunostaining pattern of Ang(1-7) was found in the inner and outer nuclear and plexiform layers of the retina and in the ciliary body. CONCLUSION: To the best of our knowledge, this is the first report showing Mas-R expression in the human eye. Its localization suggests that it may have a role in physiological and pathological processes in the anterior part of the eye and in the retina.

Neurodegeneration and cellular stress in the retina and optic nerve in rat cerebral ischemia and hypoperfusion models.

Experimental cerebral ischemia induces a stress response in neuronal and non-neuronal cells. In the present study we aimed to evaluate detailed cellular stress responses and neurodegenerative changes in the retinas in rat focal cerebral ischemia and hypoperfusion models involving invasive vascular manipulations. Independent groups of adult male Wistar rats were subjected to i) transient middle cerebral artery occlusion (tMCAO), ii) permanent middle cerebral artery occlusion (pMCAO), iii) cortical photothrombosis of the sensorimotor cortex using Rose Bengal dye or iv) bilateral common carotid artery occlusion (BCCAO). Rats were killed, and their eyes with the optic nerves enucleated and processed for histology, immunohistochemistry for neuronal nuclei (NeuN), glial fibrillary acidic protein (GFAP), hypoxia-inducible factor 1alpha (HIF-1alpha), c-fos, alphaB-crystallin, heat shock protein (HSP) 27, HSP60 and HSP70, and detection of DNA defragmentation. The total number of the retinal ganglion cell layer (RGCL) neurons and GFAP-immunoreactive astrocytes located in the nerve fiber layer were estimated using unbiased stereological counting. Our findings indicate that although permanent and transient MCAO does not cause detectable morphological alterations in the retina or optic nerve, it evokes ischemic stress as revealed by HIF-1alpha and HSPs expression in the RGCL neurons and reactive gliosis in the Müller cells. Severe neurodegenerative changes in the retina and optic nerve of the BCCAO rats are accompanied by a significant increase in immunoreactivities for the c-fos, HSP27 and HSP70 as compared with the sham-operated animals. The retinas from the ipsilateral side of the Rose Bengal model showed a significant decrease in the total number of NeuN-positive neurons in the RGCL as compared with the contralateral ones. However, these eyes did not differ between each other in the HSPs and HIF-1alpha expression or in the GFAP-immunoreactivity of the Müller cells. In conclusion, our data suggest differential expression of various HSPs in the retina and possibly their distinct roles in the cerebral ischemia-mediated stress response and neurodegeneration.

The expression of heat shock protein 27 in retinal ganglion and glial cells in a rat glaucoma model.

The heat shock protein 27 kDa (HSP27) is a member of proteins that are highly inducible under various forms of cellular stress. This study describes constitutive HSP27 expression in rat retina and stress-associated expression of HSP27 in an experimental rat glaucoma model. Glaucoma was induced unilaterally using laser photocoagulation of the episcleral and limbal veins. Three and seven days after the elevation of intraocular pressure (IOP), groups of rats were killed. The second laser treatment was performed for those rats killed 14 and 21 days after the first laser treatment. The RGCs were labeled with a retrograde tracer 7 days before kill. The expression of HSP27 was analyzed by Western blotting in retinas of rats killed on day 14 after the first laser treatment. Retinal astrocytes, Müller cells and HSP27-positive cells were visualized using immunohistochemical methods both from retinal whole-mounts and paraffin sections. The total number of retrogradely labeled RGCs decreased by 23.2% after 7 days, 28% after 14 days, and 29.3% after 21 days of elevated IOP when compared with controls. A significant decrease of glial fibrillary acidic protein (GFAP)-immunoreactive retinal astrocytes in laser-treated eyes was observed compared with the controls (accounted for 44.9%, 38.2% and 35% of the control values in the 7-day, 14-day and 21-day groups, respectively). The expression of HSP27 in RGCs and retinal astrocytes was also increased in laser-treated eyes when compared with controls in all groups. However, glycinergic and cholinergic cells in the inner nuclear layer and the highest number of RGCs and astrocytes that expressed HSP27 were found in the 14-day group of rats. The constitutive expression of HSP27 was observed only in retinal astrocytes and Müller cells. This study suggests that constitutive HSP27 expression is a cell-type specific phenomenon in the rat retina. However, at the same time, HSP27 might be considered as a marker for neuronal injury in the rat glaucoma model.

Estrogen treatment improves spatial learning in APP + PS1 mice but does not affect beta amyloid accumulation and plaque formation.

We investigated the effects of ovariectomy (OVX) and 17 beta-estradiol (0.18 mg per pellet) treatment on spatial learning and memory, hippocampal beta amyloid (A beta) levels, and amyloid plaque counts in double transgenic mice (A/P) carrying mutated amyloid precursor protein (APPswe) and presenilin-1 (PS1-A246E). After OVX at 3 months of age, the mice received estrogen treatment for the last 3 months of their lifetime before they were killed at 6, 9, or 12 months of age. Estrogen treatment in A/P OVX mice increased the number of correct choices in a position discrimination task in the T-maze, and slightly improved their performance in a win-stay task (1/8 arms baited) in the radial arm maze (RAM). However, estrogen treatment did not reverse the A beta-dependent cognitive deficits of A/P mice in the water maze (WM) spatial navigation task. Furthermore, ovariectomy or estrogen treatment in OVX and sham-operated A/P mice had no effect on hippocampal amyloid accumulation. These results show that the estrogen treatment in a transgenic mouse model of Alzheimer's disease (AD) improves performance in the same learning and memory tasks as in the normal C57BL/6J mice. However, the estrogen effects in these mice appeared to be unrelated to A beta-induced cognitive deficits. Our results do not support the idea that estrogen treatment decreases the risk or alleviates the symptoms of Alzheimer's disease by inhibiting the accumulation of A beta or formation of amyloid plaques.