Plasma Interleukin 6 as a Potential Biomarker of Age-related Macular Degeneration (AMD)
In its advanced stages, Age-related Macular Degeneration destroys the detailed, central vision we need to read, drive, recognize faces, and enjoy daily life, and is a major cause of vision loss in the U.S. Ophthalmic researchers are making rapid progress in understanding how genetics, immune system factors, nutrition choices, and other variables interact to produce or prevent Age-related Macular Degeneration. These discoveries will enable ophthalmologists (Eye M.D.s) to more precisely identify those who are likely to develop AMD, to select optimal, individualized treatments, and to monitor the disease.
Janice C. Law, MD, and her colleagues at the Vanderbilt Eye Institute, looked for plasma (blood) biochemical markers, or biomarkers, that would indicate systemic oxidative stress and an inflammatory response in 57 patients with Age-related Macular Degeneration and in an age-matched control group. Oxidative stress occurs in the body when there is an imbalance between cells' production of reactive oxygen (such as superoxide and hydrogen peroxide) and cells' ability to detoxify byproducts of reactive oxygen, such as free radicals, which can damage protein, DNA and other cell components. In an inflammatory response, the body's vascular and immune systems work in concert to remove disease-causing agents, damaged cells, or other irritants, and to initiate tissue healing. If immune system regulation goes awry, an overly strong inflammatory response--such as hay fever or atherosclerosis--can result.
In Dr. Law's study an inflammation-promoting biochemical, interleukin 6 (IL-6), was found to be significantly higher in the AMD patients, and IL-6 levels also correlated with oxidative stress measurements in these patients. This suggests that IL-6 is a good candidate for further study as a potential Age-related Macular Degeneration biomarker. It also indicates that common biological signaling mechanisms may be involved in both oxidative stress and inflammation and may contribute to AMD development as well as general aging.
Other recent research has established that Age-related Macular Degeneration is closely associated with certain genetic variations that control aspects of the immune system, especially the inflammatory response. Numerous studies have also confirmed the role of oxidative stress in AMD development and progression. Dr. Law's study focused on plasma-based biomarkers because blood sample screening is a relatively simple yet accurate diagnostic tool.
This preliminary cohort study did not attempt to determine whether IL-6 levels varied with AMD types--"wet" Age-related Macular Degeneration, characterized by rapid growth of abnormal blood vessels and heightened risk of vision loss, or the more common "dry" type--or with disease severity.