Increased Expression of Serum Amyloid A in Glaucoma and Its Effect on Intraocular Pressure

• Published in: Investigative ophthalmology & visual science Vol. 49; no. 5; pp. 1916 - 1923
• Main Authors: Wang, Wan-Heng, McNatt, Loretta G, Pang, Iok-Hou, Hellberg, Peggy E, Fingert, John H, McCartney, Mitchell D, Clark, Abbot F
• Format: Journal Article
• Language: English
• Published: Rockville, MD ARVO 01.05.2008; Association for Research in Vision and Ophtalmology
• Subjects: Aged; Aged, 80 and over; Biological and medical sciences; Cells, Cultured; Enzyme-Linked Immunosorbent Assay; Eye and associated structures. Visual pathways and centers. Vision; Female; Fundamental and applied biological sciences. Psychology; Gene Expression Profiling; Gene Expression Regulation - physiology; Glaucoma and intraocular pressure; Glaucoma, Open-Angle - genetics; Glaucoma, Open-Angle - metabolism; Humans; Intraocular Pressure - physiology; Male; Medical sciences; Middle Aged; Oligonucleotide Array Sequence Analysis; Ophthalmology; Organ Culture Techniques; Polymerase Chain Reaction; RNA, Messenger - metabolism; Serum Amyloid A Protein - genetics; Serum Amyloid A Protein - metabolism; Trabecular Meshwork - metabolism; Vertebrates: nervous system and sense organs; Glaucoma; Protozoa; Eye disease; Glaucoma (eye); Serum; Ciliata; Ophthalmology; Intraocular pressure
• ISSN: 0146-0404; 1552-5783; 1552-5783
• DOI: 10.1167/iovs.07-1104

To search for and validate potential molecular pathogenic mechanisms in the trabecular meshwork (TM) responsible for the elevated intraocular pressure (IOP) associated with glaucoma. Gene chip arrays were used to identify differential gene expression in glaucomatous TM tissues. Serum amyloid A (SAA) upregulation was subsequently confirmed with quantitative PCR (QPCR) and ELISA. The effect of SAA on gene expression of cultured human TM cells was tested with gene chip arrays and verified with ELISA, and its effect on IOP was evaluated in the human ocular perfusion organ culture. Microarray analysis showed that the expression of SAA2 was increased in TM tissues from donors with glaucoma. This finding was subsequently confirmed by QPCR. The SAA mRNA levels were increased in glaucoma TM tissues by more than 5-fold (P < 0.05) and in cultured TM cells derived from donors with glaucoma by 25-fold (P < 0.05) compared with controls. SAA protein levels in the TM of glaucoma patients were also significantly (P < 0.05) elevated by 2.9-fold. Treatment of cultured human TM cells with recombinant SAA affected gene expression, including a 22-fold up-regulation of interleukin-8 (P < 0.001). SAA increased IOP by approximately 40% (P < 0.05) in the human ocular perfusion organ culture without any observable changes in the morphology of the tissues involved in aqueous outflow. These findings indicate that SAA, which is an acute-phase apolipoprotein that plays important roles in infection, inflammation, and tissue repair, may contribute to the pathogenic changes to the TM in glaucoma.