Abstract
Purpose :
The S100 proteins are the most abundant family of small Ca2+-binding EF-hand proteins (~25 members) with high structural homology and pleiotropic functions, including cell growth and differentiation, cytoskeleton regulation, inflammation, and innate immune responses. As a critical damage-associated molecular patterns (DAMPs) molecule, S100A9 has gained much interest in various systemic diseases. In the eye, S100A9 protein was upregulated in vitreous of patients with proliferative diabetic retinopathy (DR) and was localized in the retinal microglia. However, the interplay between S100A9 protein and Müller cells has not been reported. Since Müller cells are the primary macroglia cells responsible for maintaining retinal integrity and homeostasis, any changes to Müller glial cells will disrupt the retinal microenvironment, affecting visual function.
Methods :
Müller cells were prompted via oxidative and inflammatory stress in a time- (4H, 24H, and 72H) and dose-dependent manner (5, 10, & 20ng/ml). The cells were also analyzed for S100A9 production using real-time PCR, ELISA, immunoblots, and immunocytochemistry. In addition, Müller cells were exposed to S100A9 to study its role in gliosis.
Results :
Müller cells did not produce S100A9 under oxidative and inflammatory stress, but exogenous exposure to recombinant human (rH)S100A9 increased reactive oxygen species and superoxide radicals in a time-dependent manner, revealing oxidative stress in Müller cells. Additionally, reactive oxygen species (ROS)-related genes (GCLC, catalase, Txnrd-1, MN-SOD, GPx-1, and GR) were significantly upregulated in a time-dependent manner, along with elevated proinflammatory markers like TNFα and IL-1β expression. Immunocytochemistry confirmed Müller cell gliosis in a time-dependent manner with increased expression of apoptotic genes.
Conclusions :
Müller cells do not produce S100A9, but exposure to S100A9 triggered reactive oxygen species, causing an imbalance in the oxidative stress-related genes, leading to proinflammatory and apoptotic responses, instigating Müller cell gliosis.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.