Endothelin protein expression in tear glands of the rabbit

[The role of endothelin-1 in the pathogenesis of familial exudative vitreoretinopathy]

Familial exudative vitreoretinopathy (FEVR) is a rare hereditary disease characterized by pathological retinal vascularization with a progressive and variable course. The mechanisms of disease progression remain unclear. One substance that plays an important role in the pathogenesis of retinal vascular diseases is endothelin (ET). It was found that tissue hypoxia enhances the expression of the gene encoding ET-1, and ET-1 can be locally produced in the eye.

PURPOSE

The study evaluates the possible role of endothelin-1 in the pathogenesis of FEVR.

MATERIAL AND METHODS

The study included 85 patients with FEVR aged from 1 months to 17 years who were examined in Helmholtz National Medical Research Center of Eye Diseases. The concentration of ET-1 was evaluated in 19 patients with FEVR in the blood serum (n=17), lacrimal fluid (n=18) and 16 patients from the control group.

RESULTS

The median of ET-1 in the lacrimal fluid in patients with FEVR was 13.74 pg/mL, respectively, which exceeded the same indicator of the control group 4.66 pg/mL by 2.5 times (p<0.001). The median of ET-1 in the blood serum exceeded the control group by 2.4 times (21.61 pg/mL and 9.21 pg/mL, respectively, p<0.001).

CONCLUSIONS

An increase in the concentration of ET-1 in the lacrimal fluid and blood serum of patients with FEVR in comparison with the control group indicates its involvement in the pathogenesis of the disease.

Changes of a2-macroglobulin activity and endothelin-1 concentration in tears of rabbits after transplantation of retinal pigment epithelium cells derived from the induced pluripotent stem cells

Retinal diseases accompanied with the dysfunction or death of the retinal pigment epithelial (RPE) cells are widespread, hard to treat, and appear to be a leading case of visual loss and blindness among the persons older than 55 years. Transplantation of RPE cells derived from the induced pluripotent stem cells (IPSC-RPE) is a promising method of therapy for these diseases. To ensure the transplant survival instant follow-up is required. It can be based on biochemical analyses of tear fluid that can be easily non-invasively collected. For the post-transplantation process monitoring we have choosen such polyfunctional bioregulators as α2-macroglobulin (α2-MG) and endothelin-1 (ET-1). RPE atrophy in New Zealand Albino rabbits was modeled via the subretinal injection of bevacizumab. IPSC-RPE in suspension or as a monolayer on the scaffold were transplanted subretinally 1 month after the injection. α2-MG activity and ET-1 concentration in tears were estimated during the first month and after 2, 3 and 7 months after transplantation. On the 7-14 days after transplantation α2-MG activity increased in tears of the both operated and controlateral eye probably as a reaction on the corticosteroid therapy. In 50% rabbits there was one more increase after 2-3 months that could be due to the immune inflammation. Concentration of ET-1 in tears decreased dramatically on the 7-14 days and 7 months after transplantation, and it could have an influence upon the retinal vassal tone. The data obtained show that estimation of bioregulators in tears can help monitoring local metabolic processes after RPE transplantation that is necessary for the opportune, reasonable and focused medicamental correction of post-transplantation process.

The effect of endothelin receptor antagonists in the endotoxin-induced uveitis rabbit model. Cutan Ocul Toxicol 2017;37:133-138. [PMID: 28707522 DOI: 10.1080/15569527.2017.1355317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

PURPOSE

To investigate the effect of Bosentan (non-selective endothelin receptor antagonist) and BQ123 (ET_A receptor antagonist) on intraocular inflammation in an endotoxin-induced uveitis (EIU) rabbit model.

METHODS

Uveitis was induced by intravitreal injection of lipopolysaccharide (LPS). The animals were divided into 7 groups and there were six rabbits in each group (saline, saline and ethanol, bosentan, BQ123, lipopolysaccharide (LPS), bosentan and LPS, BQ123 and LPS-injected groups). Bosentan and BQ123 were applied before LPS injection. Aqueous humour was collected at 24th hour post-injections and enucleation was performed for the evaluation of histopathological changes.

RESULTS

BQ123 decreased clinical score, cell counts and protein amount more than bosentan and it was significant for cell counts (p = 0.018). Bosentan significantly diminished inflammatory reactions more than BQ123 as shown in histopathological specimens (p = 0.002).

CONCLUSIONS

ET_A receptor blockage is effective on uveitis treatment by its protective effect on blood aqueous barrier.

Endothelin-1 role in human eye: a review

Endothelin is a potent vasoactive peptide occurring in three isotypes, ET-1, ET-2, and ET-3. Through its two main receptors, endothelin A and endothelin B, it is responsible for a variety of physiological functions, primarily blood flow control. Recent evidence from both human and animal models shows involvement of endothelin in diabetes, retinal circulation, and optic neuropathies. Increased circulating levels of endothelin-1 (ET-1) have been found in patients with diabetes, and a positive correlation between plasma ET-1 levels and microangiopathy in patients with type-2 diabetes has been demonstrated. In addition to its direct vasoconstrictor effects, enhanced levels of ET-1 may contribute to endothelial dysfunction through inhibitory effects on nitric oxide (NO) production. Experimental studies have shown that chronic ET-1 administration to the optic nerve immediately behind the globe causes neuronal damage, activation of astrocytes, the major glial cell in the anterior optic nerve, and upregulation of endothelin B receptors. This paper outlines the ubiquitous role of endothelin and its potential involvement in ophthalmology.

Duct system of the rabbit lacrimal gland: structural characteristics and role in lacrimal secretion

PURPOSE

To develop a nomenclature for the lacrimal duct system in the rabbit, based on the anatomic and structural characteristics of each duct segment, and to provide RT-PCR and immunofluorescence data to support the notion that the duct system plays important roles in lacrimal function.

METHODS

Paraffin-embedded lacrimal glands (LGs) were stained with hematoxylin and eosin (H&E) and evaluated with a stereomicroscope. Cryosections of LG were stained with cresyl violet, and acinar cells and ductal epithelial cells were isolated from each duct segment by laser capture microdissection (LCM). mRNA levels from these cells were analyzed by real-time RT-PCR. Standard protocol was followed for immunofluorescence detection of ionic transporters.

RESULTS

The lacrimal duct system was divided into six segments on the basis of morphologic characteristics: the intercalated, intralobular, interlobular, intralobar, interlobar, and main excretory ducts. Although the morphologic features change incrementally along the entire duct system, the gene expression of ionic transporters and aquaporins, including AE3, AQP4, AQP5, CFTR, ClC2gamma, KCC1, NHE1, NKAalpha1, NKAbeta1, NKAbeta2, NKAbeta3, and NKCC1 varied greatly among duct segments. Immunofluorescence results were generally in accordance with the abundance of mRNAs along the acinus-duct axis.

CONCLUSIONS

Most LG research has focused on the acinar cells, with relatively little attention being paid to the lacrimal ducts. The lack of knowledge regarding the lacrimal ducts was so profound that a precise nomenclature had not been established for the duct system. The present data establish a nomenclature for each segment of the lacrimal duct system and provide evidence that ducts play critical roles in lacrimal secretion.

A novel, local technique for studying rabbit lacrimal gland secretion in situ

AIM

To develop a local approach to study rabbit lacrimal secretion in situ by administering specific secretagogues directly onto the lacrimal gland (LG).

METHODS

After the rabbit has been anesthetized, the inferior bulbar conjunctiva and underlying connective tissue are blunt dissected. A polyethylene tube, for drug delivery, is inserted through the fibrous membrane overlying the inferior surface of the orbital cavity beneath which the LG resides. Lacrimal fluid is collected by cannulating the lacrimal duct.

RESULTS

Pilocarpine induced robust lacrimal fluid secretion from the LG that had been bathed with either pilocarpine or phenylephrine, with no detectable effect on the contralateral LG and salivary secretion. By next giving pilocarpine or phenylephrine to the control LG while the experimental gland used before served as control, we duplicated the results exactly.

CONCLUSION

This novel approach avoids the unwanted systemic effects of intravenous injection and is a promising technique to study rabbit LG secretion in situ.

Sjogrens syndrome as failed local immunohomeostasis: prospects for cell-based therapy

Sjogrens syndrome has been estimated to affect between 0.2% and 2% or more of the population. It is an autoimmune disease with the hallmark histopathology of focal, periductal, and perivascular CD4(+) cell infiltration of the lacrimal and salivary glands. The immunohistopathology is typically associated with severe lacrimal and salivary dysfunctions, which contribute to debilitating ocular surface and oral symptoms. The quality of life of patients with Sjogrens syndrome often is degraded further by serious, multisystemic manifestations, and they are subject to a forty-fold increased risk of developing B cell lymphomas. In normal lacrimal glands, secretory epithelial cells, autoimmune effector lymphocytes, and regulatory lymphocytes can be seen as collaborating to maintain a local immunohomeostasis. The epithelium contributes by secreting immunomodulatory paracrine factors and also by continuously exposing autoantigens, which thereby become available for uptake by professional antigen presenting cells (APCs). Local or systemic perturbations may initiate autoimmune pathophysiology by impairing the replacement of normally-turning-over regulatory cells, by altering epithelial production of immunomodulatory paracrine factors, by inducing intact epithelial cells to begin secreting previously cryptic epitopes (epitopes that previously were not available to bind to major histocompatibility complex (MHC) molecules and so could not be recognized by T cell antigen receptors), and by inducing epithelial cells to begin expressing MHC Class II molecules and presenting formerly cryptic epitopes directly to CD4(+) cells. This process has been modeled ex vivo with mixed cell reactions comprised of isolated epithelial cells and autologous lymphocytes. This development has occurred as studies of anterior chamber-associated immune deviation (ACAID) and other immunoregulatory phenomena have elucidated the origins and functions of several different kinds of regulatory lymphocytes and shown that regulatory lymphocytes can be generated ex vivo. It now is possible to envision strategies for exploiting each possible mode of epithelial autoantigen exposure to produce therapeutic regulatory cells that might be capable of re-establishing normal immunohomeostasis. Consideration of the hypothetical therapies identifies a number of basic questions that warrant investigation.

Effects of a dual endothelin-1 receptor antagonist on airway obstruction and acute lung injury in sheep following smoke inhalation and burn injury

Studies have suggested that ET-1 (endothelin-1) is associated with lung injury, airway inflammation and increased vascular permeability. In the present study we have tested the hypothesis that treatment with a dual ET-1 receptor antagonist will decrease airway obstruction and improve pulmonary function in sheep with combined S+B (smoke inhalation and burn) injury. Twelve sheep received S+B injury using the following protocol: six sheep were treated with tezosentan, an ETA and ETB receptor antagonist, and six sheep received an equivalent volume of vehicle. Physiological and morphological variables were assessed during the 48 h study period and at the end of the study. There was no statistically significant difference in the PaO2/FiO2 (partial pressure of O2 in arterial blood/fraction of O2 in the inspired gas) ratio of the tezosentan-treated animals compared with controls; however, lung lymph flow was significantly higher (P<0.05) in the treated animals. PVRI (pulmonary vascular resistance index) was significantly reduced (P<0.05) in the tezosentan-treated animals. Assessment of NOx (nitric oxide metabolite) levels in plasma and lymph showed significantly elevated (P<0.05) levels in the tezosentan-treated animals compared with levels in untreated sheep. The degree of bronchial obstruction was similar in both treated and control sheep; however, bronchiolar obstruction was reduced in sheep treated with tezosentan. Histopathologically, no difference in the degree of parenchymal injury was detected. In conclusion, administration of a dual ET-1 receptor antagonist prevented an increase in PVRI after injury and reduced the degree of bronchiolar obstruction in sheep with S+B; however, treated sheep showed higher levels of NOx and increased lung lymph flow. Tezosentan treatment was ineffective in protecting against acute lung injury in this model.

Corneal epithelial wound healing

One of the important functions of the cornea is to maintain normal vision by refracting light onto the lens and retina. This property is dependent in part on the ability of the corneal epithelium to undergo continuous renewal. Epithelial renewal is essential because it enables this tissue to act as a barrier that protects the corneal interior from becoming infected by noxious environmental agents. Furthermore, the smooth optical properties of the corneal epithelial surface are sustained through this renewal process. The rate of renewal is dependent on a highly integrated balance between the processes of corneal epithelial proliferation, differentiation, and cell death. One experimental approach to characterize these three aspects of the renewal process has been to study the kinetics and dynamics of corneal re-epithelialization in a wound-healing model. This effort has employed in vivo and in vitro studies. From such studies it is evident that the appropriate integration and coordination of corneal epithelial proliferation, adhesion, migration, and cell demise is dependent on the actions of a myriad of cytokines. Our goal here is to provide an overview into how these mediators and environmental factors elicit control of cellular proliferation, adhesion, migration, and apoptosis. To this end we review the pertinent literature dealing with the receptor and the cell signaling events that are responsible for mediating cytokine control of corneal epithelial renewal. It is our hope that a better appreciation can be obtained about the complexity of the control processes that are responsible for assuring continuous corneal epithelial renewal in health and disease.

Fluid transport by cultured corneal epithelial cell layers

BACKGROUND/AIMS

Fluid transport across the in vitro corneal epithelium is short lived, hence difficult to detect and characterise. Since stable rates of fluid transport across several cultured epithelial cell layers have been demonstrated, the behaviour of confluent SV40 transformed rabbit corneal epithelial cells (tRCEC) grown on permeable supports was examined.

METHODS

Fluid transport was determined with a nanoinjector volume clamp; the specific electrical resistance of the layers was 184 (SEM 9) Omega cm(2). tRCEC layers transported fluid (from basal to apical) against a pressure head of 3 cm H(2)O for 2-3 hours.

RESULTS

In the first hour, the rate of fluid transport was 5.2 (0.5) microl/h/cm(-2) (n=23), which is comparable with that found in other epithelia. Fluid transport was completely inhibited in 15-30 minutes by either 100 microM ouabain (n=6), 50 microM bumetanide (n=6), or 1 microM endothelin-1 (ET-1; n=6). Preincubation with 10 microM BQ123 (an ET(A) receptor antagonist) obviated inhibition by ET-1 (n=6). ET-1 also caused a 22% decrease in specific resistance.

CONCLUSIONS

Fluid transport appears to depend on transepithelial Cl(- )transport since (1) their directions are the same (stroma-->tear), and (2) both bumetanide and ouabain inhibit it with similar time course. tRCEC appear useful to investigate aspects of the physiology and pharmacology of fluid transport across this layer, including receptor mediated control of this process.

An immunohistochemical study of endothelin-1 in the human eye

PURPOSE

Endothelin-1 (ET-1) is a potent vasoconstrictive and neural peptide that has been demonstrated to be present and functionally active and important in the eye. This study was undertaken to examine for the first time the cellular distribution of ET-1 in the whole human eye.

METHODS

Twelve human eyes were examined by immunohistochemical staining of paraffin sections, using an anti-ET-1 primary antibody and an ABC-detection system.

RESULTS

Endothelin-1-immunoreactivity (ET-1-IR) was detected primarily in the fibrovascular stroma of the iris, ciliary body and choroid, in the retinal blood vessels, the ciliary and optic nerves, and in the corneal and the non-pigmented ciliary epithelium.

CONCLUSION

In the eye, ET-1-IR is present in fibrovascular, neural and epithelial structures. Changes in the distribution and concentration of ET-1 may be relevant to a variety of ocular diseases including diabetes mellitus, hypertension, sickle cell disease, optic neuritis, AION, papilledema, corneal ulcer, corneal epithelial dystrophy or after keratoplasty.