by Dan Roberts
(Updated November 10, 2008)
Concentration of two cytokines, interleukin-6 and interleukin-8, have been found in two different studies to be potential biomarkers for incidence of dry AMD. Cytokines are signaling compounds in the cells that are involved in a variety of immunological, inflammatory, and infectious diseases.
Janice C. Law, MD, and her colleagues at the Vanderbilt Eye Institute reported to the November 2008 annual AAO meeting that interleukin 6 (IL-6), was found to be significantly higher in a group of 57 AMD patients when compared to an age-matched control group.
IL-6 levels also correlated with oxidative stress measurements in these patients. According to the researchers, the results suggest that IL-6 is a good candidate for further study as a potential AMD 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. These findings are in line with numerous other studies that have confirmed the role of oxidative stress in AMD development and progression.
A report in the February 28, 2008 online British Journal of Ophthalmology revealed that at least some cases of age-related macular degeneration may stem from genetically driven production of another cytokine, interleukin-8. The gene variant is found more commonly in patients with age-related macular degeneration.
The -251AA genotype of the interleukin-8 promoter gene has previously been found to promote release of interleukin-8, an inflammatory cytokine. This latest study has shown that the -251AA genotype is often found in people with AMD. Other inflammatory diseases, cancers, and even smoking behaviors have been linked to the gene, and it may also promote angiogenesis, as in wet AMD.
The results came from a case-control study involving 478 patients with macular degeneration and 555 people with healthy eyes. 35% of the patients and 27% of controls had the -251AA genotype. If follow-up studies confirm the findings, researchers think it may be worthwhile to test patients for the -251AA genotype and treat them with anti-inflammatory therapies.
Source: Goverdhan S, et al “Interleukin-8 promoter polymorphism -251A/T is a risk factor for age-related macular degeneration” BJO 2008; DOI: 10.1136/bjo.2007.123190.