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LncRNA ANRIL knockdown ameliorates retinopathy in diabetic rats by inhibiting the NF-κB pathway.

OBJECTIVE
To evaluate the impacts of long non-coding ribonucleic acid (lncRNA) antisense non-coding RNA in the INK4 locus (ANRIL) on diabetic retinopathy (DR) in rats and the underlying mechanism.


MATERIALS AND METHODS
A total of 60 adult male Sprague Dawley (SD) rats were randomly divided into 3 groups: the Sham group (n=20), DR group (n=20) and DR + lncRNA ANRIL knockdown group [DR + lncRNA ANRIL small interfering RNA (siRNA) group, n=20]. DR model in rats was established by intraperitoneal injection of streptozocin (STZ; 60 mg/kg). Meanwhile, a certain dose of lncRNA ANRIL siRNA was added dropwise into rat eyes of DR + lncRNA ANRIL siRNA group during model induction to downregulate lncRNA ANRIL expression in the retina. 16 weeks later, rat retinal tissues were taken to extract total RNA and protein. Reverse Transcription-Polymerase Chain Reaction (RT-PCR) was applied to detect the expression levels of lncRNA ANRIL, interleukin-1 (IL-1), IL-6 and monocyte chemotactic protein-1 (MCP-1) in each group of the rat retina. Pathological structure of rat retinal tissues in each group was observed via hematoxylin and eosin (H&E) staining. Immunohistochemistry was adopted to measure the expression levels of B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax) and P65 in each group of retinal tissues. In addition, the retinal vascular permeability in each group of rats was detected by fluorescent staining. Finally, Western blotting was utilized to determine the expressions of genes in the P65 signaling pathway.


RESULTS
Compared with rats in the Sham group, lncRNA ANRIL was upregulated in rat retinal tissues harvested from the DR + lncRNA ANRIL siRNA group (p<0.05). After knockdown of lncRNA ANRIL in the retinal tissues of DR rats, pathologic damage was alleviated notably, and the levels of inflammatory markers (IL-1, IL-10 and MCP-1) were lowered markedly (p<0.05). The protein expressions of Bax and P65 decreased evidently, while the protein level of Bcl-2 increased markedly (p<0.05) in DR rats with ANRIL knockdown. Furthermore, Western blotting results revealed that inhibition of lncRNA ANRIL could prominently repress the phosphorylation level of P65 in the retinal tissues of DR rats (p<0.05).


CONCLUSIONS
LncRNA ANRIL knockdown can significantly ameliorate the retinopathy in diabetic rats by blocking the nuclear factor-kappa B (NF-κB) signaling pathway.