Gene Expression of Clusterin, Tissue Inhibitor of Metalloproteinase-1, and Their Receptors in Retinal Pigment Epithelial Cells and Muller Glial Cells Is Modulated by Inflammatory Stresses

Balanced activities of matrix metalloproteinases (MMPs) and their inhibitors are essential for photoreceptor (PR) cell survival. PR rod cell survival in rodent models of inherited retinitis pigmentosa (RP) is prolonged by recombinant tissue inhibitor of metalloproteinase (TIMP)-1 or clusterin (CLU) proteins. Retinal pigment epithelial cells (RPE) and Muller glia (MG) cells support PR cells. In human RPE and MG cell lines, we measured their mRNA levels of the two genes with quantitative real-time PCR (qRT-PCR) with interleukin (IL)-1 beta treatment, a key pathological component in retinal degeneration. Endogenous CLU gene expression was significantly downregulated by IL-1 beta in both cell types, whereas TIMP-1 expression was upregulated in MG cells, suggesting the transcriptional control of CLU is potentially more sensitive to inflammatory conditions. The expression levels of CLU endocytic receptors revealed that the low-density lipoprotein receptor-related protein 2 (LRP2) was upregulated only in MG cells by the treatment with no detectable change in RPE cells. Like LRP2, IL-1 beta upregulated TIMP-1 receptor LRP1 expression in MG cells; however, it was decreased in the expression of RPE cells. These data suggest that the gene expression of CLU and TIMP-1 and their receptors may be dynamically modulated in inflammatory conditions.