Vascular Endothelial Growth Factor (VEGF)

0 downloads 0 Views 660KB Size Report
1Pharmacobiology Department, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional. (Cinvestav) ... Correspondence: Félix Gil Carrasco, M.D., Glaucoma ... ies report VEGF presence in the aqueous humor and.

Current Eye Research, 35(4), 287–294, 2010 Copyright © 2010 Informa Healthcare USA, Inc. ISSN: 0271-3683 print/ 1460-2202 online DOI: 10.3109/02713680903545315

ORIGINAL ARTICLE

Aqueous Humor Endothelin-1 (Et-1),­Vascular Endothelial Growth Factor (VEGF) and Cyclooxygenase-2 (COX-2) levels in Mexican Glaucomatous Patients Simone Iwabe1, Mónica Lamas1, Carlos G. Vásquez Pélaez2, and Félix Gil Carrasco3 Pharmacobiology Department, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (Cinvestav), Mexico City, Mexico 2 Bioestatistic Department, Veterinary Medicine School, Universidad Nacional Autónoma de México, Mexico City, Mexico 3 Glaucoma Department, Asociación Para Evitar la Ceguera en México, Hospital Dr. Luis Sánchez Bulnes, IAP, Mexico City, Mexico

Curr Eye Res Downloaded from informahealthcare.com by Cinvestav on 07/27/11 For personal use only.

1

ABSTRACT Purpose: To evaluate the concentration of endothelin-1, vascular endothelial growth factor, and cyclooxygenase-2 in aqueous humor from normal and glaucomatous human patients. Material and Methods: Concentrations of these proteins were measured using ELISA kits in 83 patients (30 presenting for cataract surgery and 53 with glaucoma). Results: Endothelin-1, vascular endothelial growth factor, and cyclooxygenase-2 were detected in all samples. The ages of the patients with glaucoma (64.51 ± 17.51 years) and cataracts subjects (59.30 ± 19.15 years) were similar. The endothelin-1 concentration in cataracts patients (48.55 ± 9.50 pg/ml) was statistically different when compared to endothelin-1 concentration in aqueous humor from primary open-angle glaucoma (107.94 ± 12.20 pg/ml) and neovascular glaucoma (114.68 ± 25.50 pg/ml) (p  0.05). Vascular endothelial growth factor concentration was higher in neovascular glaucoma (81.84 ± 6.40 pg/ml), being the difference statistically significant when compared with the other groups (p  0.05). No effect of age, gender, or previously medication of aqueous humor concentration of these proteins could be detected (p > 0.05). Conclusion: In this study we observed increased levels of endothelin-1 in aqueous humor from patients with primary open-angle glaucoma and neovascular glaucoma, and increased levels of vascular endothelial growth factor only in neovascular glaucoma patients, raising a possible connection between endothelin-1 and vascular endothelial growth factor in the role of some types of glaucoma. Regarding cyclooxygenase-2 levels detected, perhaps indicate that low values of cyclooxygenase-2 are necessary for normal functions of the eye. KEYWORDS:  Aqueous humor; Endothelin-1;VEGF; COX-2; Glaucoma

Received 28 September 2009; accepted 03 December 2009

INTRODUCTION

Correspondence: Félix Gil Carrasco, M.D., Glaucoma ­Department, Asociación Para Evitar la Ceguera en México, ­Hospital Dr. Luis Sánchez Bulnes, IAP, Mexico City, Mexico. E-mail: [email protected]

Glaucoma is a neuropathy of the optic nerve head that courses with abundant loss of retinal ganglion 287

Curr Eye Res Downloaded from informahealthcare.com by Cinvestav on 07/27/11 For personal use only.

288    S. Iwabe et al. cells (RGC) and with progressive degeneration of the optic nerve head (ONH) and vision deterioration leading to blindness. These anomalies are associated with an increase in intraocular pressure (IOP), which is an important risk factor leading to rapid and progressive damage of the optic nerve. At each level of IOP there is a threat of glaucomatous damage, however this threat increases with higher IOP. Alterations of the optic nerve and progressive vision loss persist even when IOP is diminished, which suggests that factors other than IOP are involved in the glaucomatous optic neuropathy.1,2,3 Damage can occur extremely fast as seen in angle-­closure glaucoma, or may progress slowly as observed in primary open-angle glaucoma (POAG).4 Most of the theories concerning to glaucoma pathogenesis can be grouped in two major groups, those mechanical related to IOP elevation and those vasogenic related to proteins involved in the vascular function, such as endothelin-1 and nitric oxide.5 Endothelin-1 (Et-1) is a small peptide and a potent endogenous vasoconstrictor involved in the modulation of ocular blood flow,6 which is synthesized and released from the ciliary process in the eye.7 Et-1 wide distribution indicates complex roles for this peptide in ocular blood vessel physiology, participating in the regulation of IOP by its action on smooth muscles, such as the ciliary body and iris muscles.8 The activity of the Et-1 family peptide (Et-1, Et-2, and Et-3) are mediated via two distinct Et receptor subtypes, the receptor type-A (Et-A) and the receptor type-B (Et-B), which belong to the superfamily of receptors coupled to heterotrimeric G proteins9 and are found on retinal cells and other ocular tissues.7 This protein has been implicated in glaucoma pathogenesis as high levels of aqueous Et-1 were observed in humans8 and other species6 with glaucoma. Other studies report that acute delivery of Et-1 can produce retinal ganglion cell (RGC) specific cell death,10 induce astroglial proliferation in the optic nerve head astrocytes culture,11 and exacerbate neurodegeneration by stimulating efflux of glutamate in ischemia environment.9 In an environment of hypoxia, the ischemic tissue compensates the decrease in oxygen by forming new blood vessels increasing the levels of vascular endothelial growth factor (VEGF).12 VEGF is a potent endothelial cell-specific angiogenic and vasopermeable factor that binds to high-affinity membrane-bound receptors that exhibit tyrosine kinase activity.13 It is one of the most important angiogenic factors that stimulate the growth of vascular endothelial cells enhancing vascular permeability. In the eye, VEGF is expressed and produced by the corneal endothelium, retinal pigment epithelium, iris pigment epithelium, retinal ganglion cells, astrocytes, Müller cells, uveal melanocytes, and ­choroidal fibroblasts.14 VEGF gene

expression is induced by hypoxia or ischemia, and, by alternative mRNA splicing, multiple glycosylated homodimeric isoforms are produced, such as VEGF121, VEGF165, VEGF189, and VEGF206.13,15 Previous studies report VEGF presence in the aqueous humor and its concentration in the eye has shown to be increased in glaucoma13,14 and diabetic retinopathy.16 In human patients, vitreous VEGF levels are elevated in eyes with active neovascularization of the iris, retina, and optic nerve.15 Other studies report a decrease in VEGF levels in the presence of endothelin receptors type A and B antagonists.16,17 In recent years, the evidence of prostaglandin (PG) involvement in the regulation of intraocular pressure has increased. PGs, known to regulate the production of aqueous humor, vascular blood flow, and ciliary body muscle relaxation, also modify the bloodaqueous barrier and the outflow of aqueous humor.18 It is known that prolonged topical administration of glucocorticoids to the eye causes increased IOP and that these glucocorticoids inhibit the expression of cyclooxygenase 2 (COX-2), an important enzyme in the formation of PGs. PGs are related to the regulation of the IOP as the reduction of PGs in the eye by the inhibition of COX-2 expression seems to be the mechanism by which steroids cause secondary glaucoma.19 The cyclooxygenase (COX) participates in the arachidonic acid cycle producing prostaglandins and exists in 2 isoforms, COX-1 and COX-2 encoded by separated genes. COX-1 is a constitutive enzyme that produces prostaglandins required for normal physiological functions and COX-2 is an inducible enzyme that produces prostaglandins that mediate cell growth and inflammation and is not detected under normal conditions. However, COX-2 is induced in a variety of tissues by growth factors, oncogenes, inflammatory stimuli, and tumor promoters.20 Previous studies demonstrated decreased levels of COX-2 in human glaucomatous eyes19 and increased levels of VEGF and COX-2 during tumor angiogenesis.20,21 In the present study, we propose to evaluate the concentration of Et-1, VEGF, and COX-2 in aqueous humor from normal and glaucomatous human patients.

MATERIAL AND METHODS Collection of Aqueous Humor This study protocol was approved by the Ethics Committee of the Asociación Para Evitar la Ceguera en México, Hospital Dr. Luis Sanchez Bulnes, IAP. Samples of aqueous humor were collected in the operating room from 83 human patients (age range 2–97 years; mean 63.14 ± 18.44 years). Thirty normal patients were Current Eye Research

Curr Eye Res Downloaded from informahealthcare.com by Cinvestav on 07/27/11 For personal use only.

Et-1, VEGF, COX-2 in Aqueous Humor    289 considered and underwent elective cataract ­surgery, 23 had primary open-angle glaucoma (POAG), 9 had chronic closed-angle glaucoma (CCAG), 4 had neovascular glaucoma (NVG), 2 had normal tension glaucoma (NTG), 6 had pseudophaquia glaucoma, 3 had postretinal surgery glaucoma, 2 had pseudoexfoliative glaucoma, 1 had pigmentary glaucoma, 1 had Voght-Koyanagy-Harada secondary glaucoma, 1 had traumatic glaucoma, and 1 had congenital glaucoma. Patients with pseudophaquia glaucoma, postretinal surgery glaucoma, pseudoexfoliative glaucoma, pigmentary glaucoma, Voght-Koyanagy-Harada secondary glaucoma, traumatic glaucoma, and congenital glaucoma were joined in the same group as secondary glaucoma. Samples were obtained (100–200 μl) by limbal paracentesis using a 30-gauge needle attached to a syringe without touching the iris, lens, or corneal endothelium. The samples were placed immediately in Eppendorf tubes and stored at −70°C until analysis. The mask method was used to prevent research bias during sample analysis, only the research in charge of getting the samples knew the diagnostics from each patient, information that was open at the end of the process to statistical analysis.

Endothelin-1 Analysis Measurements of ET-1 were made using Human Endothelin-1 ELISA Kit (DRG Internacional Inc, Mountainside, New Jersey, USA). According to manufacturer protocol, 50 μl/well of standard or sample, 25 μl of primary antiserum, and 25 μl of biotinylated peptide were added in the 96 well immunoplate and incubated at room temperature for 2 hr. The plate was washed 4 times with 1X assay buffer, added 100 μl/well of streptavidin-horseradish peroxidase and incubated at room temperature for 1 hr. After 4 washes, 100 μl/well of 3,3',5,5'-tetramethylbenzidine (TMB) was added prior to 1 hr incubation at room temperature with the immunoplate protected from light. The reaction was stopped adding 100 μl/well of 2N HCl and the absorbance was measured at 450 nm within 20 min by using a microplate reader (Sunrise, Tecan Trading AG, Switzerland). Assay range: 0–25 ng/ml.

Vascular Endothelial Growth Factor (VEGF) Analysis VEGF levels were measured using Human VEGF ELISA Kit (Biosource, Invitrogen, Carlsbad, California, USA). Briefly, 50 μl of incubation buffer was added to all wells and 100 μl of standard or 50 μl of sample + 50 μl of standard diluent buffer was added to each © 2010 Informa Healthcare USA, Inc.

well; the immunoplate was covered and incubated at room temperature for 2 hr. The plate was washed 4 times with wash buffer and incubated with 100 μl of biotinylated anti-VEGF for 1 hr. After 4 washes, 100 μl of streptavidin peroxidase working solution was added and incubated for 30 min at room temperature. After 4 washes the plate was incubated with 100 μl of stabilized chromogen for 30 min at room temperature with the plate protected from light. After this period, the reaction was stopped adding 100 μl of stop solution and the absorbance was measured at 450 nm within 2 hrs after adding the stop solution. Minimum detectable dose is  0.05).

225 200 175 150 125 100 75 50 25 0

Endothelin-1 levels

Cat

POAG

CCAG

NVG

Et-1 levels detected in CCAG (74.88 ± 17.70 pg/ml) and Gsec (77.87 ± 14.60 pg/ml) were in the middle range between cataract levels and those detected in POAG and NVG (p = 0.0051). Et-1 concentration found in NTG (69.14 ± 52.80 pg/ml) was within the range observed in the normal control group (Table 2). VEGF was detected in all aqueous humor samples as Et-1 (Figure 2). As expected, aqueous humor levels of VEGF were increased in NVG 3.7 times higher than in the cataract patients. VEGF concentration was higher in NVG (81.84 ± 6.40 pg/ml), being the difference statistically significant when compared with the other groups (p  0.05). CCAG levels (21.76 ± 4.40 pg/ml) were in a middle range between cataracts levels and those detected in the other glaucoma groups (Table 2). COX-2 protein is normally detected in cell lysates because serum, plasma, or other biological fluids have extremely low levels of this protein and sometimes it is not possible to measure it. However, we were able to detect COX-2 in all aqueous humor samples. Nevertheless, no statistical difference was observed between the cataract group (0.459 ± 0.05 ng/ml) and any other glaucoma group: POAG (0.405 ± 0.07 ng/ml), CCAG (0.340 ± 0.11 ng/ml), NVG (0.492 ± 0.14 ng/ml), NTG (0.619 ± 0.29 ng (ml), and Gsec (0.267 ± 0.08 ng/ml) (p > 0.05) (Figure 3 and Table 2). Age and gender had no significant influence on aqueous humor Et-1, VEGF, and COX-2 concentration in all groups (p > 0.05). All glaucoma patients were under different medications, thus no statistical analysis was done regarding to type of treatments.

DISCUSSION

NTG

Gsec

Figure 1  Endothelin-1 absolute values in aqueous humor from normal and glaucomatous patients showing minimal value, maximum value and mean (▴). POAG: primary openangle glaucoma; CCAG: chronic closed-angle glaucoma; NVG: neovascular glaucoma; NTG: normal tension glaucoma; Gsec: secondary glaucoma.

Glaucoma is a complex disease with the final pathway being a progressive optic neuropathy characterized by decreased retinal ganglion cell (RGC) sensitivity and function, RGC death, optic nerve axons loss, a typical excavated appearance of the optic nerve head (ONH), incremental reduction in visual fields, and eventual blindness.3 The main mechanisms thought to induce this optic nerve damage in primary glaucoma are mechanical effects on an abnormal IOP and probably ischemia combined with vascular ­dysregulation. Regarding to mechanical and vasogenic factors related to glaucoma pathogenesis, endothelin-1 (Et-1) and nitric oxide are two cellular mediators involved in Current Eye Research

Et-1, VEGF, COX-2 in Aqueous Humor    291

VEGF levels

120 100

pg/ml

80 60 40 20 0

Cat

POAG

CCAG

NVG

NTG

Gsec

Figure 2  VEGF absolute values in aqueous humor in normal and glaucomatous patients showing minimal value, maximum value and mean (▴). VEGF: vascular endothelial growth factor; POAG: primary open-angle glaucoma; CCAG: chronic closedangle glaucoma; NVG: neovascular glaucoma; NTG: normal tension glaucoma; Gsec: secondary glaucoma. COX-2 levels

1.2 1 0.8 ng/ml

Curr Eye Res Downloaded from informahealthcare.com by Cinvestav on 07/27/11 For personal use only.

Table 2  Aqueous humor Et-1, VEGF and COX-2 concentrations in cataract and glaucoma patients Et-1 concentration (pg/ml) VEGF concentration (pg/ml) COX-2 concentration (ng/ml) Groups Number of eyes Mean ± SD Mean ± SD Mean ± SD Cataracts 30 48.55 ± 9.50 21.46 ± 2.40 0.459 ± 0.050 Glaucoma 53 93.07 ± 52.31 21.42 ± 19.99 0.415 ± 0.250 POAG 23 107.94 ± 12.20 16.07 ± 2.60 0.405 ± 0.070 CCAG 9 74.88 ± 17.70 21.76 ± 4.40 0.340 ± 0.110 NVG 4 114.68 ± 25.50 81.84 ± 6.40 0.492 ± 0.140 NTG 2 69.14 ± 52.80 1.51 ± 9.90 0.619 ± 0.290 Gsec 15 77.87 ± 14.60 17.31 ± 3.30 0.267 ± 0.080 Et-1, VEGF and COX-2 concentrations were measured in aqueous humor aspirates taken at surgery moment from patients using ELISA kit. Mean and SD were transformed in least-square for statistical analysis. Et-1: endothelin-1; VEGF: vascular endothelial growth factor; COX-2: cyclooxygenase-2; POAG: primary open-angle glaucoma; CCAG: chronic closed-angle glaucoma; NVG: ­neovascular glaucoma; NTG: normal tension glaucoma; Gsec: secondary glaucoma.

0.6 0.4 0.2 0

Cat

POAG

CCAG

NVG

NTG

Gsec

Figure 3  COX-2 absolute values in aqueous humor in normal and glaucomatous patients showing minimal value, maximum value and mean (▴). COX-2: cyclooxygenase-2; POAG: primary open-angle glaucoma; CCAG: chronic closed-angle glaucoma; NVG: neovascular glaucoma; NTG: normal tension glaucoma; Gsec: secondary glaucoma.

the regulation of IOP and local modulation of ­ocular blood flow.22 Another vascular factor that may be implicated is the growth factor named vascular endothelial growth factor (VEGF), a glycoprotein involved in the © 2010 Informa Healthcare USA, Inc.

vascular permeability and ­vasodilator.23 ­Currently the most effective treatment to reduce IOP are ­prostaglandin F2α (PGF2α) analogs.24 As COX-2 is a key enzyme in the formation of PGs we decide to ­analyze if these exogenous PGs may alter COX-2 levels. About Et-1, we detected increased levels in the aqueous humor of some glaucomatous patients. As previously reported, we also found higher concentrations of Et-1 in POAG patients, nevertheless our results were more than four times higher than the previous study.8 The high levels of Et-1 found in the aqueous humor of POAG patients and the potential for local Et-1 production in anterior uveal tract,25 astrocytes,11 or retinal pigment epithelial cells26 suggest that the contribution of Et-1 to POAG pathogenesis may be local. Our result corroborates the relevant importance of Et-1 in aqueous humor dynamic in these patients and its role in POAG needs further investigations. We also found ET-1 elevated levels in NVG patients. It has been demonstrated that intravitreal injections of Et-1 induce chronic hypoperfusion in the ONH and retina,27 which presumably stimulate VEGF that already has been shown to be increased in hypoxic conditions.28 Other studies demonstrated that Et-1 intravitreal injection produces retinal ganglion cellsspecific death via apoptosis in a mechanism of cell death similar to axotomy and glaucoma models.10,29 Our result makes us hypothesize a possible connection between endothelin-1 and vascular endothelial growth factor in the role of some types of glaucoma. In an attempt to explain the link between systemic levels of endothelin and glaucoma pathology, some studies report elevated Et-1 levels in plasma of POAG30 and NTG31 compared to normal patients, but these findings have not been confirmed by other reports.32,33 Although in this study we did not measure plasma Et-1, we found neither difference in the aqueous humor Et-1 levels in NTG or in CCAG and secondary glaucoma groups compared to the cataract group. One study reported a significant high concentration of Et-1 in the

Curr Eye Res Downloaded from informahealthcare.com by Cinvestav on 07/27/11 For personal use only.

292    S. Iwabe et al. aqueous humor of patients with exfoliation syndrome (XFS) and normal IOP compared with control patients without XFS. This is an age-related disorder, which often leads to the development of exfoliative glaucoma (XFG).34 In the present study, patients presenting XFG were joined in the group of secondary glaucoma and our results were almost ten times higher than in the previous study; nevertheless, we did not observe any statistical difference compared to the cataract group. Our results suggest that the high levels of Et-1 found in the other study may play an important role in early stages of the disease, before the development of XFG. VEGF protein was detected in aqueous humor from all samples as Et-1, nevertheless our results showed statistical difference in VEGF concentration only in NVG patients. This finding supports previous observations and sustains the concept that VEGF is probably the most important factor in the initiation and control of ocular neovascular response.35–37 We can speculate that, in NVG, the hypoxic and ischemic mechanisms may be more severe when compared to the other types of glaucoma. Our results differ from previous studies where increased levels of VEGF were also observed in aqueous humor from some patients presenting POAG besides in NVG.13,14 Considering our hypothesis of a possible connection existence between Et-1 and VEGF, perhaps these patients were in different stages of the disease explaining why some patients had elevated levels of VEGF and Et-1 and others could have only elevated levels of Et-1 but not yet VEGF, this possible relation needs further investigation. Vascular endothelial growth factor has been detected in vitreous samples from patients presenting proliferative diabetic retinopathy, suggesting an intraretinal production of VEGF and that this elevated level in vitreous may also participate in the iris neovascularization and NVG development.38,39 Some reasons that could lead to an increase in aqueous humor VEGF concentration may be related to the ischemia,40 hypoxia,28,41 or elevated reactive oxygen intermediates caused by glaucomatous damage.42 In glaucoma it is known that retina and optic nerve suffer ischemia and hypoxia; conditions that upregulate VEGF mRNA, present in ganglion cells, astrocytes, choroidal fibroblasts,13 Müller cells,43 retinal pigment epithelium,44 and photoreceptor cells.45 However, one important factor was shown in a recent study where VEGF was upregulated in tissues of retina and optic nerve before retinal hypoxia occurred, indicating that ischemia and hypoxia are not the only factors that may stimulate the production of VEGF.46 As far as we know, this is the first time that COX-2 levels have been measured in aqueous humor from human patients. Taking into account the assay range

provided in the ELISA kit for COX-2; we found, although low, COX-2 values in all aqueous humor samples. It is significant information considering that COX-2 is not expected to be detected in serum, plasma, or other biological fluids, due to extremely low levels of this protein and not expected to be detected under normal conditions. In our results, patients with Gsec appear to show almost half the concentration compared to cataracts patients. However, no statistical difference was observed in the COX-2 level in aqueous humor from cataracts and glaucomatous patients probably relating to the fact that our control group was formed by patients presenting cataract and not normal eyes. Nowadays, PGs analogs have been largely used in glaucoma treatment. As COX-2 is an important enzyme in the formation of endogenous PGs, our hypothesis was that exogenous PGs used in these treatments could alter COX-2 concentration in aqueous humor from glaucomatous patients. One study reported a specific loss of COX-2 expression in the nonpigmented secretory epithelium of the ciliary body from POAG. Considering that this portion is responsible for aqueous humor production, this may explain the low levels of COX-2 we found.19 In contrast, an upregulation of COX-2 was reported in anterior segment of canine glaucomatous eyes, demonstrating a species specific difference in the involvement of COX-2 derived PGs in the physiologic and pathophysiologic process of glaucoma development.18 Recent results from studies in cornea,47 retina,48 and retinal pigment epithelial cells49 suggest that COX-2 is involved not only in pathological events, such as inflammation, but also in physiological functions contributing to normal physiological and homeostatic functions of the retina. This fact leads us to two possible explanations to our findings; first that COX-2 levels found in all samples show that this protein is necessary to normal functions of the eye; or, second, that the COX-2 levels detected were indicative of some grade of inflammation but had no relationship with glaucoma pathogenesis. In summary, the high level of Et-1 in POAG patients confirms its role in this disorder and raises a possible connection between endothelin-1 and vascular endothelial growth factor in the role of neovascular glaucoma and need further investigations. Concerning to cyclooxygenase-2 levels detected it may be relevant to the normal functions of the eye.

ACKNOWLEDGMENTS The authors wish to thank all doctors from the Glaucoma Department, Asociación Para Evitar la Ceguera en México, Hospital Dr. Luis Sánchez Bulnes, IAP, Current Eye Research

Et-1, VEGF, COX-2 in Aqueous Humor    293 and a special thanks to Dr. Rafael Castañeda Diez for personally helping to get the aqueous humor samples. Also, the authors wish to thank Ms. Vaslly Ayala Ceja for all of her support and patience. Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.

Curr Eye Res Downloaded from informahealthcare.com by Cinvestav on 07/27/11 For personal use only.

REFERENCES [1] Tielsch JM, Katz J, Sommer A, et al. Hypertension, perfusion, perfusion pressure, and primary open-angle glaucoma. A population-based assessment. Arch Ophthalmol. 1995;113:216–221. [2] Collaborative Normal Tension Glaucoma Study Group. The effectiveness of intraocular pressure reduction in the treatment of normal tension glaucoma. Am J Ophthalmol. 1998;126:498–505. [3] Nickels RW. Retinal ganglion cell death in glaucoma: The how, the why and the maybe. J Glaucoma. 1996;5:345–356. [4] Källberg ME, Brooks DE, Gelatt KN, et  al. Endothelin-1, nitric oxide, and glutamate in the normal and glaucomatous dog eye. Vet Ophthalmol. 2007;10(S1):46–52. [5] Fechtner RD, Weinreb RN. Mechanisms of optic nerve damage in primary open angle glaucoma. Surv Ophthalmol. 1994;39–23. [6] Källberg ME, Brooks DE, Garcia-Sanchez GA, et al. Endothelin 1 levels in the aqueous humor of dogs with glaucoma. J Glaucoma. 2002;11:105–109. [7] Wollensak G, Schaefer HE, Ihling C. An immunohistochemical study of endothelin-1 in the human eye. Curr Eye Res. 1998;17:541–545. [8] Tezel G, Kass MA, Kolker AE, et  al. Plasma and aqueous endothelin levels in primary open-angle glaucoma. J ­Glaucoma. 1997;6:83–89. [9] Sasaki Y, Takimoto M, Oda K, et al. Endothelin evokes efflux of glutamate in cultures of rat astrocytes. J Neurochemistry. 1997;68:2194–2200. [10] Lau J, Dang M, Hockmann K, et al. Effects of acute delivery of endothelin-1 on retinal ganglion cell loss in the rat. Exp Eye Res. 2006;82:132–145. [11] Prasanna G, Krishnamoorthy R, Clark AF, et  al. Human optic nerve head astrocytes as a target for endothelin-1. Invest Ophthalmol Vis Sci. 2002;43:2704–2713. [12] Ergorul C, Ray A, Huang W, et  al. Levels of vascular endothelial growth factor-A165b (VEGF-A165b) are elevated in experimental glaucoma. Mol Vis. 2008;14:1517–1524. [13] Tripathi RC, Li J, Tripathi BJ, et al. Increased levels of vascular endothelial growth factor in aqueous humor of patients with neovascular glaucoma. Ophthalmol. 1998;105:232–237. [14] Hu DN, Ritch R, Liebmann J, et  al. Vascular endothelial growth factor is increased in aqueous humor of glaucomatous eyes. J Glaucoma. 2002;11:406–410. [15] Tolentino MJ, Miller JW, Gragoudas ES, et  al. Vascular endothelial growth factor is sufficient to produce iris neovascularization and neovascular glaucoma in a nonhuman primate. Arch Ophthalmol. 1996;114:964–970. [16] Masuzawa K, Jesmin S, Maeda S, et al. Effect of endothelin dual receptor antagonist on VEGF levels in streptozotocin­induced diabetic rat retina. Exp Biol Med. 2006;231:1090–1094. [17] Masuzawa K, Goto K, Jesmin S, et al. An endothelin type A receptor antagonist reverses upregulated VEGF and ICAM-1 © 2010 Informa Healthcare USA, Inc.

levels in streptozotocin-induced diabetic rat retina. Curr Eye Res. 2006;31:79–89. [18] Marshall JL, Stanfield KM, Silverman L, et  al. Enhance expression of cyclooxygenase-2 in glaucomatous dog eyes. Vet Ophthalmol. 2004;7:59–62. [19] Maihöfner C, Schlötzer-Schrehardt U, Gühring H, et  al. Expression of cyclooxygenase-1 and -2 in normal and glaucomatous human eyes. Invest Ophthalmol Vis Sci. 2001;42:2616–2624. [20] Jaeckel EC, Raja S, Tan J, et al. Correlation of expression of cyclooxygenase-2, vascular endothelial growth factor, and peroxisome proliferator-activated receptor δ with head and neck squamous cell carcinoma. Arch Otolaryngol Head Neck Surg. 2001;127:1253–1259. [21] Marrogi AJ, Travis WD, Welsh JA, et al. Nitric oxide synthase, cyclooxygenase 2, and vascular endothelial growth factor in the angiogenesis of non-small cell lung carcinoma. Clin Cancer Res. 2000;6:4739–4744. [22] Haefliger IO, Dettmann E, Liu R, et al. Potential role of nitric oxide and endothelin in the pathogenesis of glaucoma. Survey Ophthalmol. 1999;43(S1):51–58. [23] Lip PL, Felmeden DC, Blann AD, et  al. Plasma vascular endothelial growth factor, soluble VEGF receptor FLT-1, and von Willebrand factor in glaucoma. Br J Ophthalmol. 2002;86:1299–1302. [24] Toris CB, Gabet BT, Kaufman PL. Update on the mechanism of the action of topical prostaglandins for intraocular pressure reduction. Survey Ophthalmol. 2008;53:S107–S120. [25] MacCumber MW, Ross CA, Glaser BM, et al. Endothelin: Visualization of mRNAs by in situ hybridization provides evidence for local action. Proc Natl Acad Sci USA. 1989;86:7285–7289. [26] Narayan S, Prasanna G, Krishmoorthy RR, et  al. Endothelin-1 synthesis and secretion in human retinal pigment epithelial cells (ARPE-19): Differential regulation by cholinergics and TNF-α. Invest Ophthalmol Vis Sci. 2003:44:4885–4894. [27] Sasaoka M, Taniguchi T, Shimazawa M, et  al. Intravitreal injection of endothelin-1 caused optic nerve damage ­following to ocular hypoperfusion in rabbits. Exp Eye Res. 2006;83:629–637. [28] Aiello LP, Northrup JM, Keyt BA, et al. Hypoxic regulation of vascular endothelial growth factor in retinal cells. Arch Ophthalmol. 1995;113:1538–1544. [29] Taniguchi T, Shimazawa M, Sasaoka M, et al. Endothelin-1 impairs retrograde axonal transport and leads to axonal injury in rat optic nerve. Curr Neurovasc Res. 2006;3:81–88. [30] Emre M, Orgül S, Haufschild T, et  al. Increased plasma endothelin-1 levels in patients with progressive open angle glaucoma. Br J Ophthalmol. 2005;89:60–63. [31] Sugiyama T, Moriya S, Oku H, et  al. Association of ­endothelin-1 with normal tension glaucoma: Clinical and fundamental studies. Survey Ophthalmol. 1995;39(S1):49–56. [32] Kunimatsu S, Mayama C, Tomidokoro A, et  al. Plasma endothelin-1 level in Japanese normal tension glaucoma patients. Curr Eye Res. 2006;31:727–731. [33] Kaiser HJ, Flammer J, Wenk M, et al. Endothelin-1 plasma levels in normal-tension glaucoma: Abnormal response to postural changes. Graefes Arch Clin Exp Ophthalmol. 1995;233:484–488. [34] Koliakos GG, Konstas AGP, Schlötzer-Schrehardt U, et al. Endothelin-1 concentration is increased in the aqueous humor of patients with exfoliation syndrome. Br J ­Ophthalmol. 2004;88:523–527. [35] Aiello LP, Avery RL, Arrigg PG, et al. Vascular ­endothelial growth factor in ocular fluid of patients with diabetic

Curr Eye Res Downloaded from informahealthcare.com by Cinvestav on 07/27/11 For personal use only.

294    S. Iwabe et al. retinopathy and other retinal disorders. N Engl J Med. 1994;331:1480–1487. [36] Adamis AP, Miller JW, Bernal MT, et al. Increased ­vascular endotheial growth factor levels in the vitreous of eyes with proliferative diabetic retinopathy. Am J Ophthalmol. 1994;118:445–450. [37] Adamis AP, Shima DT, Tolentino MJ, et  al. Inhibition of ­vascular endothelial growth factor prevents retinal ­ischemia-associated iris neovascularization in a nonhuman primate. Arch Ophthalmol. 1996;114:66–71. [38] Burgos R, Simo R, Audi L, et  al. Vitreous levels of vascular endothelial growth factor are not influenced by its serum concentrations in diabetic retinopathy. Diabetologica. 1997;40:1107–1109. [39] Itakura H, Kishi S, Kotajima N, et al. Persistent secretion of vascular endothelial growth factor into vitreous cavity in proliferative diabetic retinopathy after vitrectomy. Ophthalmol. 2004;111:1880–1884. [40] Vinores SA, Youssri AI, Luna JD, et  al. Up-regulation of vascular endothelial growth factor in ischemical and nonischemical human and experimental retinal disease. Histol Histopathol. 1997;12:99–109. [41] Shima DT, Gougos A, Miller JW, et al. Cloning and mRNA expression of vascular endothelial growth factor in ischemic retinas of Macaca fascicularis. Invest Ophthalmol Vis Sci. 1996;37:1334–1340.

[42] Kuroki M, Voest EE, Amano S, et al. Reactive oxygen intermediates increase vascular endothelial growth factor expression in vitro and in vivo. J Clin Invest. 1996;98:1667–1675. [43] Pierce EA, Avery RL, Foley ED, et al. Vascular endothelial growth factor/vascular permeability factor expression in a mouse model of retinal neovascularization. Proc Natl Acad Sci USA. 1995;92:905–909. [44] Seko Y, Seko Y, Fujikura H, et  al. Induction of vascular endothelial growth factor after application of mechanical stress to retinal pigment epithelium of the rat in vitro. Invest Ophthalmol Vis Sci. 1999;40:3287–3291. [45] Miller JW. Vascular endothelial growth factor and ocular neovascularization. Am J Pathol. 1997;151:13–23. [46] Amin RH, Frank RN, Kennedy A, et al. Vascular endothelial growth factor is present in glial cells of the retina and optic nerve of human subjects with nonproliferative diabetic retinopathy. Invest Ophthalmol Vis Sci. 1997;38:36–47. [47] Amico C, Yakimov M, Catania MV, et al. Differential expression of cyclooxygenase-1 and cyclooxygenase-2 in the cornea wound healing. Tissue & Cell. 2004;36:1–12. [48] Ju W, Neufeld AH. Cellular localization of cyclooxygenase-1 and cyclooxygenase-2 in the normal mouse, rat, and human retina. J Comp Neurol. 2002;452:392–399. [49] Chin MS, Naginemi CN, Hooper LC, et al. Cyclooxygenase-2 expression and regulation in human retinal pigment epithelial cells. Invest Ophthalmol Vis Sci. 2001;42:2338–2346.

Current Eye Research

Suggest Documents