MicroRNAs (miRNAs) are known to participate in post-transcriptional regulation of gene expression and are involved in multiple pathogenic processes. Here, we identified miRNA expression changes in the retinas of Akita mice, a genetic model of type 1 diabetes, and investigated the potential role of miRNA in diabetic retinopathy.

Researchers at the Oklahoma Health Sciences Center evaluated visual function of Akita and control mice by electroretinography. MiRNA expression changes in the retinas of Akita mice were identified by miRNA-specific microarray and confirmed by quantitative RT-PCR (qRT-PCR). The potential downstream targets of identified miRNAs were predicted by bioinformatic analysis using web-based applications and confirmed by dual luciferase assay. The mRNA and protein changes of identified downstream targets were examined by qRT-PCR and Western blot analysis.

MiRNA-specific microarray and qRT-PCR showed that miR-200b was upregulated significantly in the Akita mouse retina. Sequence analysis and luciferase assay identified oxidation resistance 1 (Oxr1) as a downstream target gene regulated by miR-200b. In a human Müller cell line, MIO-M1, transfection of a miR-200b mimic downregulated Oxr1 expression. Conversely, transfection of MIO-M1 with a miR-200b inhibitor resulted in upregulated Oxr1. Furthermore, overexpression of recombinant Oxr1 attenuated oxidative stress marker, nitration of cellular proteins, and ameliorated apoptosis induced by 4-hydroxynonenal (4-HNE), an oxidative stressor. Similarly, transfection of a miR-200b inhibitor decreased, whereas transfection of miR-200b mimic increased the number of apoptotic cells following 4-HNE treatment.

These results suggested that miR-200b–regulated Oxr1 potentially has a protective role in diabetic retinopathy.

MicroRNA expression profile in the Akita mouse retina

LC Sciences

(A) Retinal RNA was isolated from three Akita mice and three controls at age nine months: the RNA from each group was pooled and the miRNA-specific microarray was conducted by LC Sciences. The log2 of microarray signal intensities is shown in bar graph for top 10 upregulated (black bars) and top 5 downregulated (white bars) miRNAs in the Akita retinas. (B) The retinal levels of miR-200b in the Akita mice were analyzed by qRT-PCR and expressed as the fold change over that in the age-matched nondiabetic control (mean ± SEM, n = 8 wild type and n = 11 Akita, *P < 0.05).

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Reference

Murray AR, Chen Q, Takahashi Y, Zhou KK, Park K, Ma J. (2013) MicroRNA-200b Downregulates Oxidation Resistance 1 (Oxr1) Expression in the Retina of Type 1 Diabetes Model. Investigative ophthalmology & visual science 54(3), 1689-1697. [article]