Inhibitory effect of long non-coding RNA Neat1 on ultraviolet B-induced pyroptosis of human lens epithelial cells and its mechanism

Objective

To investigate the role of long non-coding RNA nuclear paraspeckle assembly transcript 1 (Neat1) in pyroptosis of ultraviolet B (UVB)-induced human lens epithelial cells (LECs) and to explore the possible mechanism.

Methods

The human lens epithelial cell line HLE-B3 was cultured in vitro, and cells at log phase were exposed to ultraviolet B for 0, 2, 4 and 8 hours, respectively.The expression of cysteine aspartic acid-specific protease-1 (caspase-1), a protein related to pyroptosis, was detected by Western blot.The relative expression level of Neat1 in cells after different irradiation durations was determined by real-time quantitative PCR.Cell viability was determined by the cell counting kit-8 (CCK-8) method to screen the optimal irradiation duration for UVB-induced LECs pyroptosis, which was finally determined to be 4 hours.HLE-B3 cells were divided into negative siRNA transfection group, siRNA Neat1 transfection group, negative siRNA transfection+ irradiation group and siRNA Neat1 transfection+ irradiation group, and were transfected with corresponding reagents for 24 hours.The negative siRNA transfection+ irradiation group and siRNA Neat1 transfection+ irradiation group were irradiated with UVB for 4 hours after transfection.The cell viability was detected by the CCK-8 method.The pyroptosis rate was detected by flow cytometry.The expression levels of caspase-1, gasdermin D (GSDMD) and nod-like receptor protein 3 (NLRP3) proteins were detected by Western blot.The concentration of interleukin (IL)-1β was detected by enzyme-linked immunosorbent assay (ELISA). Ultrastructural changes in HLE-B3 cells were observed under a transmission electron microscope.

Results

The grayscale of caspase-1 protein bands increased with the extension of irradiation duration.The relative expression levels of caspase-1 protein at 0, 2, 4 and 8 hours of irradiation were 0.05±0.01, 0.25±0.07, 0.51±0.04 and 0.74±0.02, respectively, with a statistically significant overall difference (F=168.223, P<0.001), and significant differences were found in paired comparisons (all at P<0.05). With prolonged irradiation, the relative expression level of Neat1 mRNA increased and the cell viability decreased, with statistically significant differences in paired comparisons (all at P<0.05). Compared with negative siRNA transfection group, the cell viability was increased in siRNA Neat1 transfection group and decreased in negative siRNA transfection+ irradiation group, with statistically significant differences (both at P<0.01). Compared with negative siRNA transfection+ irradiation group, the cell viability was increased in siRNA Neat1 transfection+ irradiation group, showing a statistically significant difference (P<0.05). The pyroptosis rate was significantly lower in negative siRNA transfection group and siRNA Neat1 transfection+ irradiation group than in negative siRNA transfection+ irradiation group, and the differences were statistically significant (both at P<0.01). The relative expression levels of caspase-1, NLRP3 and GSDMD proteins in negative siRNA transfection+ irradiation group were higher than those in negative siRNA transfection group and siRNA Neat1 transfection+ irradiation group and the differences were statistically significant (all at P<0.01). The concentration of IL-1β was significantly higher in negative siRNA transfection+ irradiation group than in negative siRNA transfection group and siRNA Neat1 transfection+ irradiation group, and the differences were statistically significant (all at P<0.05). Cell swelling, formed cell membrane pores, vacuolated cells and fuzzy mitochondrial cristae were seen in negative siRNA transfection+ irradiation group and siRNA Neat1 transfection+ irradiation group by transmission electron microscopy.Compared with negative siRNA transfection+ irradiation group, slighter cell swelling, fewer cell membrane pores and lighter mitochondrial swelling were seen in siRNA Neat1 transfection+ irradiation group.

Conclusions

Neat1 is involved in human LECs pyroptosis induced by UVB through the classic pyroptosis pathway mediated by caspase-1.Knockdown of Neat1 can inhibit the pyroptosis of human LECs.

Cataract; Lens, crystalline; Epithelial cells; Pyroptosis; Ultraviolet B; LncRNA Neat1