High-fat diet activates pyroptosis of retinal pigment epithelial cells in aged TgAPPswePS1 transgenic mice

Abstract

Purpose: This study assesses the impact of high-fat diet on retinal pigment epithelium (RPE) of aged TgAPPswePS1 transgenic mice, focusing on the involvement of RPE cell pyroptosis.

Methods: Twenty-four TgAPPswePS1 transgenic mice (18 months) was randomly divided into Tg group (n = 12) and Fat group (n = 12). Mice in Fat group were fed with high-fat diet consisting of 81.85% standard chow, supplemented with 1% cholesterol, 015% cholic acid, and 17% hydrogenated vegetable oil. Another 12 wild-type C57BL/6J mice were serve as control group. The fundus was examined through Micron IV. The eyes of mice were removed for paraffin-embedding and sectioning. HE staining was carried out to observe the structure of retina and measure retinal thickness. The expressions of amyloid-beta (Aβ), NOD-like receptor thermal protein domain associated protein 3 (NLRP3), Caspase-1, gasdermin D (GSDMD), IL-1β and IL-18 in RPE, as well as the number of RPE were detected.

Results: The RPE in Fat group showed obvious Aβ accumulation (p < 0.0001). Compared with the Tg group, the thickness of retina in the Fat group was significantly reduced (t = 5, p = 0.0075), and the number of RPE was statistically decreased (t = 4.243, p = 0.0132). In addition, the expressions of pyroptosis-related proteins NLRP3, Caspase-1, GSDMD, IL-1β and IL-18 in RPE were significantly increased in Fat group (p < 0.05).

Conclusions: High-fat diet leads to Aβ accumulation in the RPE of aged TgAPPswePS1 transgenic mice, causes RPE damage, in which RPE cell pyroptosis may play a crucial role.

Keywords: Amyloid-beta; Pyroptosis; Retinal pigment epithelium; TgAPPswePS1 transgenic mice.

Fig. 1

Fundus images of mice obtained using Micron IV imaging. A Representative fundus image of an aged wild-type C57BL/6J mouse. B Representative fundus image of an aged TgAPPswePS1 transgenic mouse. C Representative fundus image of an aged TgAPPswePS1 transgenic mouse fed with high-fat diet. The arrows indicate exudates resembling drusen

Fig. 2

Immunofluorescence analysis of the Aβ expression in RPE cells. Scale bar = 20 μm. A Representative images showing Aβ expression in RPE cells. B Semi-quantitative analysis of Aβ fluorescence intensity in RPE cells. ****p < 0.0001, ns, no significance

Fig. 3

Histological analysis of retinal structure of mice, as assessed by hematoxylin and eosin (H&E) staining. Scale bar = 20 μm. A Representative retinal section of an aged wild-type C57BL/6J mouse. B Representative retinal section of an aged TgAPPswePS1 transgenic mouse. C Representative retinal section of an aged TgAPPswePS1 transgenic mouse fed with high-fat diet. D Retinal thickness measurements of the mice. E Quantification of RPE cell number of the mice. *p < 0.05, ns, no significance. NFL, nerve fiber layer; RGC, retinal ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; IS, inner segment; OS, outer segment; RPE, retinal pigment epithelium; BM, Bruch’s membrane; Ch, choroid

Fig. 4

Immunofluorescence analysis of the pyroptosis-related proteins in RPE cells. Scale bar = 20 μm. A Representative images showing the expressions of NLRP3, caspase-1 and GSDMD in RPE cells. B Representative images showing the expressions of IL-1β and IL-18 in RPE cells. C Semi-quantitative analysis of fluorescence intensity for NLRP3, caspase-1, GSDMD, IL-1β and IL-18 expressions in RPE cells. **p < 0.01, ***p < 0.001, ****p < 0.0001, ns, no significance

Fig. 5

Expression alternations of pyroptosis-related proteins in RPE cells. A NLRP3, caspase-1, GSDMD protein expressions in RPE were detected via western blotting. B IL-1β and IL-18 levels in RPE were tested via ELISA. *p < 0.05, **p < 0.01, ***p < 0.001, ns, no significance