Molecular Vision 2006; 12:1380-1385 <http://www.molvis.org/molvis/v12/a155/> Received 24 August 2006 | Accepted 7 November 2006 | Published 15 November 2006

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Polymorphism in the IL-1α (-889) locus associated with elevated risk of primary open angle glaucoma

Chun-Yuan Wang,^1,3 Ying-Cheng Shen,^1,4 Fai-Yun Lo,² Chien-Hui Su,² Shi-Huang Lee,¹ Keng-Hung Lin,¹ Hin-Yeung Tsai,¹ Ni-Wen Kuo,⁵ Seng-Sheen Fan²
 
 

¹Department of Ophthalmology, Taichung Veterans General Hospital, National Yang-Ming University, Taichung, Taiwan, Republic of China; ²Department of Life Science and Life Science Research Center, Tunghai University; ³Hung Kuang University, Taichung, Taiwan, Republic of China; ⁴Overseas Chinese Institute of Technology, Taichung, Taiwan, Republic of China; ⁵Department of Ophthalmology, Kaohsiung Veterans General Hospital, National Yang-Ming University, Kaohsiung, Taiwan, Republic of China

Correspondence to: Chun-Yuan Wang, Department of Ophthalmology, Taichung Veterans General Hospital, No. 160, Sec. 3, Taichung Harbor Rd., Taichung, 407, Taiwan, R.O.C.; Phone: 886-4-23592525 ext. 4207; FAX: 886-4-23591607; email: cywangtw@yahoo.com

Abstract

Purpose: Recent laboratory evidence indicates that the inflammatory cytokine, interleukin-1 (IL-1), has either protective or adverse effects on primary open angle glaucoma (POAG). Inheritance of the IL-1α (-889) polymorphism (the T allele), previously shown to increase IL-1 production, has been associated with an elevated risk of Alzheimer's disease. The neuronal injuries associated with Alzheimer's disease have a number of similarities with the optic nerve changes often seen with POAG. In this report we have explored the possible association between the IL-1α (-889) polymorphism and the development of POAG.

Methods: Chinese patients with POAG (156) were recruited and compared with 167 healthy chinese controls. Genomic DNA was amplified by polymerase chain reaction, followed by enzymatic restriction fragment length polymorphism technique (PCR-RFLP). Patients and controls were genotyped for the C/T polymorphism at position -889 of the IL-1α gene promoter region.

Results: The frequency of the IL-1α (-889) T allele (21% versus 13%, respectively; p=0.007) and the carriers of the IL-1α (-889) T allele (37% versus 25%; p=0.019, OR 1.76, 95%CI 1.1-2.83) were greater in POAG patients compared with controls. There is a higher risk of POAG associated with homozygosity for the IL-1α (-889) T allele (TT genotype) compared with the control population (CC genotype; 5% versus 1%, respectively, p=0.04; OR 5.1, 95% CI 1.19-21.66).

Conclusions: The IL-1α (-889) T allele polymorphism, previously shown to increase IL-1 gene expression, may be a risk factor in the development of POAG.

Introduction

Glaucoma is characterized by cupping of the optic nerve head and irreversible loss of retinal ganglion cells. Glaucoma affects over 60 million people worldwide and constitutes the second largest cause of bilateral blindness in the world [1]. Primary open angle glaucoma (POAG) is a multifactorial neurodegenerative disease. The etiology of POAG is poorly understood, but both genetic and environmental factors are thought to contribute to the pathophysiology of the disease.

POAG is genetically heterogeneous, with at least eight loci found to be associated with the disease. Mutations in genes such as MYOC, OPTN, and WDR36 have been implicated in POAG. [2-4]. Heterozygous CYP1B1 mutations are more frequent in POAG subjects than in normal controls [5,6]. Genetic data shows that the incidence of POAG in first-degree relatives of affected individuals is 7-10 times higher than the general population [7]. Family studies have mapped disease-causing mutations to a number of different loci [2,8-10]. Susceptibility to POAG in most cases, however, is likely to be inherited as a complex trait involving multiple genes, modified by other factors such as environment, nutritional status, or aging [11,12]. POAG usually presents later in life, and diagnosis is often delayed until visual field loss has already occurred. However, genetic factors may also cause early disease onset [13]. Early diagnosis of this disease can be facilitated by a genetic approach that identified those at risk of developing the disease.

There is evidence to support the hypothesis that the immune system plays a potential pathogenic role in glaucomatous optic nerve degeneration [14,15]. Balancing the benefit of protective immunity and the risk of inducing an autoimmune neurodegenerative disease is critical as the effect of such immuneregulation may be either neuroprotective or neurodestructive [16]. For example, increased autoantibodies were found in the serum of glaucoma patients. These autoantibodies include those with specificities to heat shock proteins (hsp) such as hsp60 and hsp27, and alpha-crystallins [17,18]. Interleukin-1 (IL-1) plays an important role in mediating ischemic and excitotoxic damage in the retina [19]. The association between the degree of immune responses and the development of glaucomatous optic nerve degeneration may be fluid, and in certain cases, may result in retinal ganglion cell death through an aberrant immune signaling process.

A C/T polymorphism at position -889 of the IL-1α gene promoter region has been reported to be associated with Alzheimer's disease, with the IL-1α (-889) T allele polymorphism found to increase the risk for developing Alzheimer's disease [20-22]. In the IL-1α gene, the IL-1α (-889)T allele has also been shown to increase the IL-1α protein level with respect to the IL-1α (-889)C allele [23]. There is evidence that the IL-1α protein may act to promote the development of β-amyloid deposits [24-27]. Similar evidence also indicates that there are β-amyloid build-up in retinal ganglion cells in rats with experimental glaucoma [28,29]. Tamura et al. have shown a high frequency of POAG in patients with Alzheimer's disease [30]. In this regard, glaucoma may be viewed as a chronic neurodegenerative disease similar to Alzheimer's disease, and a slow build up of β-amyloid in ganglion cell may eventually trigger cell death and optic nerve axon loss.

Given the potential similarities in cellular events leading to neurodegeneration between Alzheimer's disease and glaucoma, we hypothesized that the IL-1α (-889) polymorphism may be a genetic factor predisposing affected individuals to glaucoma due to its effect on IL-1 protein expression. Thus we investigated the distribution of the IL-1α (-889) polymorphism in patients with POAG and compared them with a healthy control population.

Methods

Study subjects

Subjects were recruited from the outpatient clinic in the Department of Ophthalmology at the Veterans General Hospital, Taichung, Taiwan from January 2004 to January 2006. POAG patients were approached as they visited the clinic for appointments, and were enrolled after consenting to participate in the study. Normal control subjects were recruited when they visited the outpatient clinic for other reasons.

All participants received comprehensive ophthalmologic examinations including visual acuity testing with refraction, intraocular pressure (IOP) measurement, Humphrey 30-2, slit lamp examination, and dilated slit lamp stereo biomicroscopy. Comprehensive ophthalmologic history and longitudinal follow-up data were also obtained for each individual. The definition for POAG included characteristic arcuate, Bjerrum, Seidel, paracentral scotoma as well as nasal step on Humphrey 30-2 with reference to Anderson's criteria for minimal abnormality in glaucoma [31], and corresponding cupping of optic nerve heads as well as nerve fiber layer defects on stereobiomicroscopy. Open drainage angles on gonioscopy; and the absence of a secondary cause for glaucomatous optic neuropathy, such as previous trauma, a period of steroid administration, or uveitis were required. The POAG cases had an elevated IOP of >21 mmHg on diurnal testing. Cases with a history of inflammation, ocular hypertension, congenital glaucoma, or normal tension glaucoma were excluded.

Unrelated control subjects were recruited from those attending the clinic for conditions such as senile cataract, floaters, refractive errors, or itchy eye. All normal control subjects had no systemic disease and no family history of glaucoma. They were excluded from the glaucoma grasp using the same criteria of diagnosis as the POAG patients after relieving the same ophthalmic examination procedure. The study was carried out with the approval of the Human Study Committee of the Veterans General Hospital. Written informed consent was obtained from all study subjects prior to enrollment.

DNA preparation and genotyping

Blood samples were collected from each subject (5 ml) and genomic DNA was isolated using the Qiagen QiaAmp Blood mini kit (Qiagen, Valencia, CA). Interleukin-1α C(-889)T genotyping of genomic DNA was determined with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique on blood samples obtained for routine clinical work according to standard procedures [32]. RCR fragments of the IL-1α promoter region (-889) were amplified using the following primers: 5'-GCA TGC CAT CAC ACC TAG TT-3' and 5'-TTA CAT ATG AGC CTT CCA TG-3' as upstream and downstream primers, respectively. These primers amplified the region of IL-1α from -1062 to -869 (194 base pairs [bp]) [33]. The PCR products were digested with Nco I (New England Biolabs, Inc, Beverly, MA) overnight at 37 °C and were run on ethidium bromide-stained 6% polyacrylamide gels for 45 min at 200 V and detected under ultraviolet (UV) light. The IL-1α (-889) C allele showed two fragments of 178 bp and 16 bp, and the IL-1α (-889) T allele showed an intact fragment of 194 bp. To ensure accuracy, each test was performed three times for each sample.

Statistical analysis

Genotype and allele frequencies between the control and POAG groups were compared using the chi-square test. Fisher's exact test was used if any expected frequency was lower than 5. Age and gender were compared between the control and POAG groups using the Mann-Whitney U test and chi-square test, respectively. Odds ratios were computed to assess the strength of association between the presence of each genotype and the clinical diagnosis of POAG. A p-value of less than 0.05 was defined to be of statistical significance. All statistical analyses were performed using SPSS 10.0 (SPSS Inc., Chicago, IL).

Results

Subject characteristics

In our study, 156 Chinese patients with POAG and 167 normal Chinese controls were enrolled. The mean age was 72 years for the POAG patients (range 35-87) and 70 years for the controls (range 30-85). There was no difference between the control and POAG groups in age (p>0.05). There was no difference between the POAG (75 males and 81 females) and control (80 males and 87 females) groups in terms of gender (p>0.05).Patients were followed up for between 1-9 years (with a mean of 5 years). Eighteen patients had received trabeculectomy and four of the 18 patients had received trabeculectomy twice from different sites. Of the POAG patients, 140 were prescribed antiglaucoma eyedrops. All medical treatment included primarily topical beta-blockers and prostaglandin. Each patient used an average of 1.4 types of antiglaucoma drugs. Sixteen patients did not need medication to control IOP after trabeculectomy.

IL-1α (-889) T association with elevated risk of primary open angle glaucoma

The distribution of IL-1α (-889) genotypes and alleles is shown in Table 1. In POAG patients, the genotype IL-1α (-889) T/T was more frequent than in controls (5% versus 1%; p=0.04). In addition, the C/T genotype was also slightly overrepresented in the POAG group compared with controls (32% versus 24%; p=0.08). The frequency of the IL-1α (-889) T allele was significantly increased in POAG group (21% versus13%, p= 0.007). In comparison with controls there were significantly more carriers of the IL-1α (-889) T allele among patients with POAG (37% versus 25%; p=0.019), with the odds ratio of 1.76 (95% CI: 1.2-2.8; Table 2). The distribution of genotypes in the population of patients controls was consistent with Hardy-Weinberg equilibrium, with no significant detectable differences between the expected and the observed numbers.

Discussion

Glaucoma is a complex clinical trait, and its inheritance has been shown to follow both Mendelian and non-Mendelian models [34]. In addition to identified genes with an autosomal dominant pattern of inheritance (myocillin, optineurin) [2,3], there may be many gene variations that may elevate the risk of the retinal degeneration characteristic of glaucoma (OPA1, apolipoprotein E) [35,36]. Many more important gene variants have recently been associated with glaucoma risk (CYP1B1, DWR36, E-cadherin [E-CDH]) [4,6,37]. Given the prevalence of POAG and that this disease is amenable to treatment when detected early, a genetic predisposition screening could potentially reduce the overall morbidity of the disease. In addition, genetic association studies aimed at defining susceptibility to POAG may provide important insights into the pathogenesis of POAG.

The development of glaucoma involves tissues in both the trabecular meshwork and the retina of the eye. IL-1 has been broadly implicated in protective responses and glaucoma disease pathogenesis in both tissue locations [38-41]. This study investigated the association between POAG and the IL-1α (-889) polymorphism that has already been implicated in diseases involving diverse organ systems. Here we report an association between the IL-1α (-889) polymorphism and the susceptibility to POAG, with a significant overrepresentation of the IL-1α (-889) T allele carriers among POAG patients. Patients with IL-1α (-889) T/T genotype have an increased relative risk of developing POAG compared to healthy controls.

In this study we showed that IL-1α (-889) polymorphism, one of the genetic factors leading to aberrant immune responses, is tightly associated with retinal ganglion degeneration in POAG and thus is a possible predisposing factor to the development of POAG in Chinese population. Further studies with POAG cohort of different ethnic background are required to further define this association. The possibility that linkage disequilibrium between IL-1α polymorphisms and other genes on chromosome 2 cause the increasing POAG risk cannot be excluded.

Published evidence suggests an autoimmune component to the pathophysiology seen at the optic nerve head of POAG, which could include cytokines involved in the immune response such as IL-1 [42-44]. The mechanisms by which IL-1 contributes to retinal ganglion cell degeneration remain unknown. In the optic nerve ligation model (which may mimic some aspects of glaucoma), IL-1 is induced locally and promotes optic nerve damage, at least in part, by increasing synthesis of matrix metalloproteinase-9 (MMP-9) [45,46]. IL-1 can also induce nitric oxide synthesis, another mediator of optic nerve head damage in experimental models [47,48]. The IL-1α (-889) T allele could potentially alter the risk of POAG by increasing the levels of IL-1 protein produced in response to stress [23]. An increased production of IL-1 in response to stressful stimuli could act on either the outflow pathways or retinal ganglion cells. Such an increase in IL-1 production may confer greater cytodestructive properties toward the trabecular meshwork cells of the outflow pathways and the retinal ganglion cells. Additionally, inheritance of the IL-1α (-889) T allele has been associated with an elevated risk of developing Alzheimer's disease [20-22]. There is evidence that the IL-1α protein may act to promote the development of β-amyloid deposits in Alzheimer's patients [24-27], and McKinnon and colleagues have demonstrated evidence of buildup of β-amyloid in retinal ganglion cells in the rat glaucoma model [28,29]. The death of retinal ganglion cells in glaucoma involving chronic β-amyloid neurotoxicity may mimic Alzheimer's disease at the molecular level. These data point to a potential overlap between the degenerative pathways underlying POAG and Alzheimer's disease.

In our study, we noted that the IL-1α (-889) T allele polymorphism may be a risk factor in the development of POAG. Besides the IL-1α gene, previous studies have noted other cytokine genes (IL-1β, TNF-α) and growth factor gene (insulin-like growth factor-II) polymorphisms are associated with an elevated risk of POAG [49-52]. Lin et al. found that the IL-1β (+3953) T allele was significantly more common in POAG patients than in control [49]. The IL-1β (+3953) C/T polymorphisms, in exon 5 of the IL-1β gene, do not alter the encoded amino acid sequence. The previous work showed the homozygosity for the IL-1β (+3953T) allele has been associated with a fourfold increase in the production of IL-1β when compared to homozygosity for IL-1β (+3953C) allele [53]. Shinji et al. [54] found IL-1β plays an important role in mediating ischemic and excitotoxic damage in the retina in glaucoma. Pro-inflammatory cytokines such as IL-1, as well as other indicators of microglial activation, have been suggested as drivers of neuropathological changes in several neurodegenerative conditions. Taken together, these results suggest that IL-1α and IL-1β are common inflammatory components associated with POAG, and genetic variants in the IL-1α and IL-1β genes may play a role in susceptibility to POAG. Genes coding for the two isoforms of IL-1 (IL-1α and IL-1β) and for the IL-1 receptor antagonist (IL-1RA) are located within the IL-1 gene cluster at chromosomal locus 2q13. The possibility that linkage disequilibrium between IL-1α, IL-1β gene polymorphisms and other genes on chromosome 2 cause an increased POAG risk should be further investigated. The exact roles of IL-1α and IL-1β genes may need to be determined by proteomics in the future.

Medical treatment included primarily topical beta-blockers and prostaglandin in our study. The production of IL-1 depends on a variety of clinical factors. Published evidence reported that antiglaucoma eyedrops with preservatives may induce expression of cytokines (IL-1α, IL-1β, and IL-6) [55-57]. Goto et al. [55] reported that both timolol maleate and latanoprost can stimulate expression of IL-1α in human lens epithelial cells. Benzalkonium chloride, the most frequently used preservative in antiglaucoma eyedrops, is the damages lens epithelial cells and strongly stimulates the expression of IL-1α in these cells. Antiglaucoma eyedrops can lower IOP, but increase the level of IL-1α protein. Increased IL-1α protein may play a role in retinal ganglion cell death. These findings may explain why POAG progresses, despite IOP well controlled with the use of antiglaucoma eyedrops. Thus, the use of preservative-free antiglaucoma eyedrops should be preferable for hypotensive therapy due to lesser expression of IL-1α.

Controversy exists regarding whether or not there is an absolute increased level of IL-1α protein in the vitreous or plasma that coincides with an increased level in the retinal ganglion tissue of patients with POAG. The genotyping data from this work now allows us to identify potential subpopulations within POAG patients, namely carriers of the IL-1α (-889) T allele, who we predict may have an elevated level of circulating cytokines in the vitreous fluid. Such data will also further strengthen the current hypothesis that neuro-inflammation is a contributing component in the pathogenesis of POAG.

In conclusion, we found an increased risk for individuals carrying (-889) T allele in a Chinese population of POAG patients. Detection of this predisposing gene polymorphism in POAG may lead to early intervention and new strategies for prevention of POAG. Importantly, proper control of inflammation may become an additional therapeutic adjuvant in the treatment of POAG.

Acknowledgements

This work was supported by grants (TCVGH-T-947802) from the Taichung Veteran General hospital and Tunghai university Taichung, Taiwan, Republic of China, to Dr. Chun-Yuan Wang. We express our sincere thanks to Dr. M. Elizabeth Fini at Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, for helpful comments during the preparation of this manuscript, and Dr. A.Y. Huang at Laboratory of Immunology, National Institutes of Health, Bethesda, for his contribution in correcting the English language of this paper.

References

1. Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol 2006; 90:262-7.

2. Rezaie T, Child A, Hitchings R, Brice G, Miller L, Coca-Prados M, Heon E, Krupin T, Ritch R, Kreutzer D, Crick RP, Sarfarazi M. Adult-onset primary open-angle glaucoma caused by mutations in optineurin. Science 2002; 295:1077-9.

3. Stone EM, Fingert JH, Alward WL, Nguyen TD, Polansky JR, Sunden SL, Nishimura D, Clark AF, Nystuen A, Nichols BE, Mackey DA, Ritch R, Kalenak JW, Craven ER, Sheffield VC. Identification of a gene that causes primary open angle glaucoma. Science 1997; 275:668-70.

4. Hauser MA, Allingham RR, Linkroum K, Wang J, LaRocque-Abramson K, Figueiredo D, Santiago-Turla C, del Bono EA, Haines JL, Pericak-Vance MA, Wiggs JL. Distribution of WDR36 DNA sequence variants in patients with primary open-angle glaucoma. Invest Ophthalmol Vis Sci 2006; 47:2542-6.

5. Stoilov I, Akarsu AN, Sarfarazi M. Identification of three different truncating mutations in cytochrome P4501B1 (CYP1B1) as the principal cause of primary congenital glaucoma (Buphthalmos) in families linked to the GLC3A locus on chromosome 2p21. Hum Mol Genet 1997; 6:641-7.

6. Lopez-Garrido MP, Sanchez-Sanchez F, Lopez-Martinez F, Aroca-Aguilar JD, Blanco-Marchite C, Coca-Prados M, Escribano J. Heterozygous CYP1B1 gene mutations in Spanish patients with primary open-angle glaucoma. Mol Vis 2006; 12:748-55 <http://www.molvis.org/molvis/v12/a84/>.

7. Wolfs RC, Klaver CC, Ramrattan RS, van Duijn CM, Hofman A, de Jong PT. Genetic risk of primary open-angle glaucoma. Population-based familial aggregation study. Arch Ophthalmol 1998; 116:1640-5.

8. Shimizu S, Lichter PR, Johnson AT, Zhou Z, Higashi M, Gottfredsdottir M, Othman M, Moroi SE, Rozsa FW, Schertzer RM, Clarke MS, Schwartz AL, Downs CA, Vollrath D, Richards JE. Age-dependent prevalence of mutations at the GLC1A locus in primary open-angle glaucoma. Am J Ophthalmol 2000; 130:165-77.

9. Wiggs JL, Haines JL, Paglinauan C, Fine A, Sporn C, Lou D. Genetic linkage of autosomal dominant juvenile glaucoma to 1q21-q31 in three affected pedigrees. Genomics 1994; 21:299-303.

10. Wirtz MK, Samples JR, Kramer PL, Rust K, Topinka JR, Yount J, Koler RD, Acott TS. Mapping a gene for adult-onset primary open-angle glaucoma to chromosome 3q. Am J Hum Genet 1997; 60:296-304.

11. Wiggs JL. Complex disorders in ophthalmology. Semin Ophthalmol 1995; 10:323-30.

12. Parrish RK 2nd. When does information become medically useful?: the role of genetic testing in glaucoma. Arch Ophthalmol 2002; 120:1204-5.

13. Craig JE, Mackey DA. Glaucoma genetics: where are we? Where will we go? Curr Opin Ophthalmol 1999; 10:126-34.

14. Wax MB, Yang J, Tezel G. Serum autoantibodies in patients with glaucoma. J Glaucoma 2001; 10:S22-4.

15. Wax M, Yang J, Tezel G. Autoantibodies in glaucoma. Curr Eye Res 2002; 25:113-6.

16. Tezel G, Wax MB. The immune system and glaucoma. Curr Opin Ophthalmol 2004; 15:80-4.

17. Wax MB, Tezel G, Saito I, Gupta RS, Harley JB, Li Z, Romano C. Anti-Ro/SS-A positivity and heat shock protein antibodies in patients with normal-pressure glaucoma. Am J Ophthalmol 1998; 125:145-57.

18. Tezel G, Seigel GM, Wax MB. Autoantibodies to small heat shock proteins in glaucoma. Invest Ophthalmol Vis Sci 1998; 39:2277-87.

19. Yoneda S, Tanihara H, Kido N, Honda Y, Goto W, Hara H, Miyawaki N. Interleukin-1beta mediates ischemic injury in the rat retina. Exp Eye Res 2001; 73:661-7.

20. Du Y, Dodel RC, Eastwood BJ, Bales KR, Gao F, Lohmuller F, Muller U, Kurz A, Zimmer R, Evans RM, Hake A, Gasser T, Oertel WH, Griffin WS, Paul SM, Farlow MR. Association of an interleukin 1 alpha polymorphism with Alzheimer's disease. Neurology 2000; 55:480-3.

21. Grimaldi LM, Casadei VM, Ferri C, Veglia F, Licastro F, Annoni G, Biunno I, De Bellis G, Sorbi S, Mariani C, Canal N, Griffin WS, Franceschi M. Association of early-onset Alzheimer's disease with an interleukin-1alpha gene polymorphism. Ann Neurol 2000; 47:361-5.

22. Nicoll JA, Mrak RE, Graham DI, Stewart J, Wilcock G, MacGowan S, Esiri MM, Murray LS, Dewar D, Love S, Moss T, Griffin WS. Association of interleukin-1 gene polymorphisms with Alzheimer's disease. Ann Neurol 2000; 47:365-8.

23. Dominici R, Cattaneo M, Malferrari G, Archi D, Mariani C, Grimaldi LM, Biunno I. Cloning and functional analysis of the allelic polymorphism in the transcription regulatory region of interleukin-1 alpha. Immunogenetics 2002; 54:82-6.

24. Wisniewski T, Frangione B. Apolipoprotein E: a pathological chaperone protein in patients with cerebral and systemic amyloid. Neurosci Lett 1992; 135:235-8.

25. Rebeck GW, Reiter JS, Strickland DK, Hyman BT. Apolipoprotein E in sporadic Alzheimer's disease: allelic variation and receptor interactions. Neuron 1993; 11:575-80.

26. Schmechel DE, Saunders AM, Strittmatter WJ, Crain BJ, Hulette CM, Joo SH, Pericak-Vance MA, Goldgaber D, Roses AD. Increased amyloid beta-peptide deposition in cerebral cortex as a consequence of apolipoprotein E genotype in late-onset Alzheimer disease. Proc Natl Acad Sci U S A 1993; 90:9649-53.

27. Ma J, Yee A, Brewer HB Jr, Das S, Potter H. Amyloid-associated proteins alpha 1-antichymotrypsin and apolipoprotein E promote assembly of Alzheimer beta-protein into filaments. Nature 1994; 372:92-4.

28. McKinnon SJ, Lehman DM, Kerrigan-Baumrind LA, Merges CA, Pease ME, Kerrigan DF, Ransom NL, Tahzib NG, Reitsamer HA, Levkovitch-Verbin H, Quigley HA, Zack DJ. Caspase activation and amyloid precursor protein cleavage in rat ocular hypertension. Invest Ophthalmol Vis Sci 2002; 43:1077-87.

29. McKinnon SJ. Glaucoma: ocular Alzheimer's disease? Front Biosci 2003; 8:s1140-56.

30. Tamura H, Kawakami H, Kanamoto T, Kato T, Yokoyama T, Sasaki K, Izumi Y, Matsumoto M, Mishima HK. High frequency of open-angle glaucoma in Japanese patients with Alzheimer's disease. J Neurol Sci 2006; 246:79-83.

31. Anderson DR. Automated static perimetry. St. Louis: Mosby-Year Book; 1992: p 12.

32. McDowell TL, Symons JA, Ploski R, Forre O, Duff GW. A genetic association between juvenile rheumatoid arthritis and a novel interleukin-1 alpha polymorphism. Arthritis Rheum 1995; 38:221-8.

33. Furutani Y, Notake M, Fukui T, Ohue M, Nomura H, Yamada M, Nakamura S. Complete nucleotide sequence of the gene for human interleukin 1 alpha. Nucleic Acids Res 1986; 14:3167-79. Erratum in: Nucleic Acids Res 1986; 14:5124.

34. Wiggs JL, Lynch S, Ynagi G, Maselli M, Auguste J, Del Bono EA, Olson LM, Haines JL. A genomewide scan identifies novel early-onset primary open-angle glaucoma loci on 9q22 and 20p12. Am J Hum Genet 2004; 74:1314-20.

35. Vickers JC, Craig JE, Stankovich J, McCormack GH, West AK, Dickinson JL, McCartney PJ, Coote MA, Healey DL, Mackey DA. The apolipoprotein epsilon4 gene is associated with elevated risk of normal tension glaucoma. Mol Vis 2002; 8:389-93 <http://www.molvis.org/molvis/v8/a46/>.

36. Powell BL, Toomes C, Scott S, Yeung A, Marchbank NJ, Spry PG, Lumb R, Inglehearn CF, Churchill AJ. Polymorphisms in OPA1 are associated with normal tension glaucoma. Mol Vis 2003; 9:460-4 <http://www.molvis.org/molvis/v9/a58/>.

37. Lin HJ, Tsai FJ, Hung P, Chen WC, Chen HY, Fan SS, Tsai SW. Association of E-cadherin gene 3'-UTR C/T polymorphism with primary open angle glaucoma. Ophthalmic Res 2006; 38:44-8.

38. Schuman JS, Wang N, Eisenberg DL. Leukemic glaucoma: the effects on outflow facility of chronic lymphocytic leukemia lymphocytes. Exp Eye Res 1995; 61:609-17.

39. Wang N, Chintala SK, Fini ME, Schuman JS. Activation of a tissue-specific stress response in the aqueous outflow pathway of the eye defines the glaucoma disease phenotype. Nat Med 2001; 7:304-9.

40. Wang N, Chintala SK, Fini ME, Schuman JS. Ultrasound activates the TM ELAM-1/IL-1/NF-kappaB response: a potential mechanism for intraocular pressure reduction after phacoemulsification. Invest Ophthalmol Vis Sci 2003; 44:1977-81.

41. Kee C, Seo K. The effect of interleukin-1alpha on outflow facility in rat eyes. J Glaucoma 1997; 6:246-9.

42. Tezel G, Yang J, Wax MB. Heat shock proteins, immunity and glaucoma. Brain Res Bull 2004; 62:473-80.

43. Zhou X, Li F, Kong L, Tomita H, Li C, Cao W. Involvement of inflammation, degradation, and apoptosis in a mouse model of glaucoma. J Biol Chem 2005; 280:31240-8.

44. Yano T, Yamada K, Kimura A, Takeshita T, Minohara M, Kira J, Senju S, Nishimura Y, Tanihara H. Autoimmunity against neurofilament protein and its possible association with HLA-DRB1*1502 allele in glaucoma. Immunol Lett 2005; 100:164-9.

45. Chintala SK, Zhang X, Austin JS, Fini ME. Deficiency in matrix metalloproteinase gelatinase B (MMP-9) protects against retinal ganglion cell death after optic nerve ligation. J Biol Chem 2002; 277:47461-8.

46. Zhang X, Chintala SK. Influence of interleukin-1 beta induction and mitogen-activated protein kinase phosphorylation on optic nerve ligation-induced matrix metalloproteinase-9 activation in the retina. Exp Eye Res 2004; 78:849-60.

47. Neufeld AH, Sawada A, Becker B. Inhibition of nitric-oxide synthase 2 by aminoguanidine provides neuroprotection of retinal ganglion cells in a rat model of chronic glaucoma. Proc Natl Acad Sci U S A 1999; 96:9944-8.

48. Schwartz M. Lessons for glaucoma from other neurodegenerative diseases: can one treatment suit them all? J Glaucoma 2005; 14:321-3.

49. Lin HJ, Tsai SC, Tsai FJ, Chen WC, Tsai JJ, Hsu CD. Association of interleukin 1beta and receptor antagonist gene polymorphisms with primary open-angle glaucoma. Ophthalmologica 2003; 217:358-64.

50. Funayama T, Ishikawa K, Ohtake Y, Tanino T, Kurosaka D, Kimura I, Suzuki K, Ideta H, Nakamoto K, Yasuda N, Fujimaki T, Murakami A, Asaoka R, Hotta Y, Tanihara H, Kanamoto T, Mishima H, Fukuchi T, Abe H, Iwata T, Shimada N, Kudoh J, Shimizu N, Mashima Y. Variants in optineurin gene and their association with tumor necrosis factor-alpha polymorphisms in Japanese patients with glaucoma. Invest Ophthalmol Vis Sci 2004; 45:4359-67.

51. Lin HJ, Tsai FJ, Chen WC, Shi YR, Hsu Y, Tsai SW. Association of tumour necrosis factor alpha -308 gene polymorphism with primary open-angle glaucoma in Chinese. Eye 2003; 17:31-4.

52. Tsai FJ, Lin HJ, Chen WC, Chen HY, Fan SS. Insulin-like growth factor-II gene polymorphism is associated with primary open angle glaucoma. J Clin Lab Anal 2003; 17:259-63.

53. Hall SK, Perregaux DG, Gabel CA, Woodworth T, Durham LK, Huizinga TW, Breedveld FC, Seymour AB. Correlation of polymorphic variation in the promoter region of the interleukin-1 beta gene with secretion of interleukin-1 beta protein. Arthritis Rheum 2004; 50:1976-83.

54. Mrak RE, Griffin WS. Glia and their cytokines in progression of neurodegeneration. Neurobiol Aging 2005; 26:349-54.

55. Goto Y, Ibaraki N, Miyake K. Human lens epithelial cell damage and stimulation of their secretion of chemical mediators by benzalkonium chloride rather than latanoprost and timolol. Arch Ophthalmol 2003; 121:835-9.

56. Manni G, Centofanti M, Oddone F, Parravano M, Bucci MG. Interleukin-1beta tear concentration in glaucomatous and ocular hypertensive patients treated with preservative-free nonselective beta-blockers. Am J Ophthalmol 2005; 139:72-7.

57. Koh SW, Coll TJ, Rose L, Matsumoto Y, Higginbotham EJ. Antiglaucoma eye drop pulses--increased interleukin-6 secretion by Tenon's capsule fibroblast cultures. J Glaucoma 2004; 13:200-9.