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Taku Yamamoto, Atsuhiro Kanda, Miyuki Murata, Satoru Kase, Susumu Ishida; Hypoxia-inducible factor-1α is a key regulator of galectin-1/LGALS1 expression in human retinal pigment epithelial cells. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1551.
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Galectin-1/LGALS1, one of galactoside-binding lectin family proteins, is an angiogenic and fibrogenic factor associated with cancer and age-related macular degeneration (AMD). Recently, we reported that galectin-1/LGALS1 expression in retinal pigment epithelium (RPE) contributed to the formation of choroidal neovascularization (CNV) (Wu D et al., FASEB J. 2019); however, its molecular mechanism still remains largely unknown. In the CNV tissues from AMD patients and the rodent model, activation of the hypoxia-inducible factor (HIF)-1α pathway in RPE cells was shown to promote the inflammatory and angiogenic responses. In this study, we demonstrate the regulatory mechanism of galectin-1 expression in RPE cells.
Real-time quantitative PCR and immunoblot analyses were performed to measure mRNA and protein levels in human RPE (hTERT-RPE1) cells. Chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) and reporter assays were performed to determine the DNA-binding and transcription-activating functions. Human surgical samples were examined by immunofluorescence.
RPE cells demonstrated time-dependent responsiveness to hypoxia in LGALS1 transcripts (fold change; 24 hours = 1.7, 48 hours = 2.3, p < 0.01) and products. Reporter activity of LGALS1 promoter containing hypoxia response elements (HREs) was significantly augmented by hypoxia (fold change = 1.8), which was abolished in the HREs-mutated promoter (fold change = 0.7, p < 0.05). Additionally, ChIP-qPCR revealed that binding of HIF-1α to the HREs in LGALS1 promoter was significantly upregulated under hypoxia (fold change = 10, p < 0.01). Supporting these in vitro findings, AMD patient specimens demonstrated co-localization of galectin-1 with HIF-1α in RPE cells in the CNV tissue.
Our data indicate that interaction between HIF-1α and the HREs in LGALS1 promoter plays a critical role in galectin-1/LGALS1 expression in RPE cells under hypoxia.
This is a 2020 ARVO Annual Meeting abstract.
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