Regulatory role of heat shock transcription factor 1 in antioxidant and anti-aging function of the retinal pigment epithelial cells

Objective

To investigate the anti-aging and antioxidant effect of the heat shock transcription factor 1 (HSF1) on human retinal pigment epithelial cells.

Methods

Two HSF1-deficient ARPE cells (ARPE/Hsf1^-/-) were constructed by using the clustered regularly interspaced short palindromic repeat and associated protein 9 (CRISPR/Cas9) gene editing system and named H8, H9 konckout cell strains.Experiments were operated on the 3 cell strains: wild-type, H8 and H9 cells.The content of reactive oxygen species in ARPE-19 cell was measured by DHE probe staining combined with flow cytometry technology, and the cell cycle was measured by flow cytometry technology.The cell viability at different time points was measured using cell counting kit-8 (CCK-8).Crystal violet staining assay was used to measure the relative ratio of cell survival.SA-β-gal staining assay was used to detect the ratio of ARPE-19 senescent cells.The expressions of HSP70, HSP27, clusterin (CLU), p53, p21 and interleukin (IL)-1β proteins were measured by Western blot technology.The expressions of p53, p21, IL-6, IL-8, IL-1β and monocyte chemoattractant protein 1 (MCP1) mRNA were measured by quantitative real-time PCR technology.Relative expression of heat shock response protein under different heat shock treatment conditions and HSP90 inhibitor IPI504, relative survival with different concentrations of H₂O₂, relative expression of p21 protein after treatment with or without ROS scavenger N-acetylcysteine (NAC) were compared in each cell strain.

Results

Gene sequencing showed that H8 and H9 cell strains successfully carried mutated genes.Western blot experiment results showed that H8 and H9 cell strains did not express HSF1 protein, and HSF1 was successfully knocked out in ARPE-19 cells.Compared with wild-type cell, the expression levels of HSP70, HSP27 and CLU proteins in H8 and H9 cell strains significantly decreased, with statistically significant differences (all at P<0.05), and no significant difference was found in the relative HSP90 protein expression level (F=0.29, P>0.05).Under different heat shock stimulation and IPI504 induction, the HSP70, HSP27, and CLU protein levels significantly increased in wild-type cells compared with before treatment, and the HSP70, HSP27, and CLU protein levels were significantly lower in H8 and H9 cell strains than in corresponding treated wild-type cells (all at P<0.05).Compared with wild-type cell strains, cell viability significantly decreased in H8 and H9 cell strains at 24, 48, 72, and 96 hours (all at P<0.05).Compared with wild-type cell strains, the percentage of cells in G1 phase was significantly higher and the mRNA and protein levels of the cell cycle inhibitors p53 and p21 significantly increased in H8 and H9 strains, showing statistically significant differences (all at P<0.05), and the ratio of positive cells for SA-β-gal staining significantly increased, showing statistically significant differences (all at P<0.001).The relative expression of aging-related inflammatory factors IL-6, IL-8, IL-1β, and MCP1 mRNA decreased, and the differences were statistically significant (all at P<0.001).In addition, compared with wild-type cell strains, the content of reactive oxygen species (ROS) was higher in H8 and H9 cell strains, and the differences were statistically significant (all at P<0.001).The expression of p21 protein in H8 and H9 cell strains wtih NAC treatment decreased significantly compared with non-NAC treatment cells (both at P<0.05).Compared with wild-type cell strains, H8 and H9 cell viability decreased at 200, 400, 600, and 800 μmol/L H₂O₂ treatment conditions, and the differences were statistically significant (all at P<0.05).

Conclusions

Knockdown of HSF1 can downregulate the expression of heat shock proteins, activate the ROS/P53/P21 pathway, induce senescence in RPE cells, and increase the sensitivity of RPE to oxidative stress stimuli.HSF1 may have anti-senescence and anti-oxidant regulatory effects in RPE cells.

Heat shock transcription factor 1; Age-related macular degeneration; Cellular senescence; Retinal pigment epithelium; Senotherapy; Oxidative stress