[SARS-CoV-2 disrupts the blood-retinal barrier via the interaction between Spike protein and PARP-1 in mice: an...

Objective: To investigate the mechanism by which severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) disrupts the blood-retinal barrier and induces retinal inflammatory response in mice, and to observe the intervention effect of poly(ADP-ribose) polymerase 1 (PARP-1) inhibitor. Methods: This experimental study was conducted from September 2022 to December 2024. Six-to eight-week-old hACE2-ALL CDs-B6J transgenic mice were divided into a control group, an infection group and a PARP-1 intervention group, with 3 mice in each group. Mice in the control group received intranasal instillation of phosphate buffered saline (PBS); mice in the infection group were intranasally inoculated with green fluorescent protein-labeled SARS-CoV-2 pseudovirus, and samples were collected at 3, 5 and 7 days after intervention respectively; for the PARP-1 group, mice were intraperitoneally injected with PARP-1 inhibitor for 48 hours after 5 days of intranasal inoculation with the same pseudovirus. The localization and distribution of retinal Spike protein were observed by immunofluorescence staining, and the vascular leakage rate was quantified by fluorescence microscopy after intravenous injection of dextran. The mRNA and protein expression levels of zonula occludens-1 (ZO-1, a blood-retinal barrier-related molecule), as well as inflammatory factors including interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β) were detected by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) and Western blotting. Co-immunoprecipitation was performed to verify the interaction between Spike protein and PARP-1, and the effect of PARP-1 inhibitor on the above indicators was analyzed. One-way analysis of variance and t-test were used for statistical analysis. Results: Compared with the control group (0.21±0.05), the expression of Spike protein in the retina of the infection group increased with the prolongation of infection time (1.51±0.24, 2.60±0.27, 2.74±0.17), and the differences were statistically significant (all P<0.01). With the extension of infection time, the retinal dextran leakage rate increased compared with the control group (0.03±0.18), which was 0.75±0.05, 1.12±0.03 and 1.20±0.09 at 3, 5 and 7 days after infection respectively, with statistically significant differences (all P<0.01). The expression of ZO-1, a key factor of the blood-retinal barrier, in the infection group (0.17±0.05) was lower than that in the control group (0.81±0.11) (P<0.05). The expression levels of inflammatory factors IL-6, TNF-α and TGF-β in the retina of the infection group (1.51±0.12, 1.57±0.21, 1.38±0.17) were higher than those in the control group (0.71±0.28, 0.39±0.13, 0.28±0.1), with statistically significant differences (all P<0.05). In angiotensin-converting enzyme 2-overexpressing photoreceptor cells (661w cell line), the expression levels of Spike and PARP-1 in the infection group (0.52±0.12, 0.77±0.09) were upregulated compared with the control group (0.04±0.09, 0.29±0.15) (both P<0.01). In addition, co-immunoprecipitation results showed that there was an interaction between Spike protein and PARP-1 protein in the retina and photoreceptor cells of infected mice. Compared with the infection group (1.31±0.04), the expression level of Spike protein in the retina of the PARP-1 group (0.38±0.19) was decreased (P<0.01). Compared with the infection group (1.38±0.13, 1.41±0.15, 0.89±0.21), the expression levels of inflammatory factors IL-6, TNF-α and TGF-β in the PARP-1 group (0.52±0.11, 0.45±0.07, 0.42±0.07) were downregulated (all P<0.01). Conclusions: In the hACE2-ALL CDs-B6J mouse model, SARS-CoV-2 infection disrupts the blood-retinal barrier and induces retinal inflammatory response by mediating the interaction between its Spike protein and host PARP-1 protein. Intervention with PARP-1 inhibitor can inhibit the above pathological changes.