Protective effect of NLRP12 knockdown on retinal damage in rats with ocular hypertension and its mechanism of inhibiting cell pyroptosis

Objective

To investigate the effect and mechanism of NOD-like receptor family pyrin domain containing 12 (NLRP12) knockdown on inflammatory factor levels and retinal injury in retinal ganglion cells (RGCs) of rats with high intraocular pressure.

Methods

Seventy SPF adult male SD rats were selected and randomized into control group, high intraocular pressure (IOP) group, high IOP+ small interfering RNA negative control (siNC) group, high IOP+ siNLRP12 group and high IOP+ siNLRP12+ recombinant rat caspase-1 (rrcaspase-1) group, with 14 rats in each group.Rats in the control group were only treated with conjunctival incision in the right eye, and ocular hypertension model was established in the other four groups with external scleral vein cauterization.High IOP+ siNC group, high IOP+ siNLRP12 group and high IOP+ siNLRP12+ rrcaspase-1 group were injected with siNC, siNLRP12 and siNLRP12+ rrcaspase-1 reagent via the tail vein, respectively.The IOP of the right eye was measured at 1 day, 1, 2 and 3 weeks after the operation.Three weeks after the operation, the retinal structure was observed by hematoxylin-eosin staining, and the number of RGCs in each group was counted.RGCs were divided into control group, rrcaspase-1 group, siNC+ rrcaspase-1 group, siNLRP12+ rrcaspase-1 group.The cells in rrcaspase-1 group, siNC+ rrcaspase-1 group and siNLRP12+ rrcaspase-1 group were treated with rrcaspase-1, siNC+ rrcaspase-1 and siNLRP12+ rrcaspase-1 reagent for 24 hours, respectively.No treatment was given to the control group.The expression levels of NLRP12, caspase-1 and cleaved-caspase-1 proteins in RGCs and retinal tissue were detected by Western blot.The concentrations of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in rat serum or cell culture supernatant were detected by enzyme-linked immunosorbent assay.The study protocol was approved by the Animal Ethics Committee of the First People’s Hospital of Chenzhou (No.2020086).

Results

Compared with control group, the IOP was higher in high IOP group at 1, 2 and 3 weeks after cauterization, and the differences were statistically significant (all at P<0.05). The retinal tissue was clear with the RGCs in a single layer arrangement in the control group.In the high IOP group and the high IOP+ siNC group, the RGCs layer was loose and the inner plexiform layer was thin.The inner plexiform layer was thickened in high IOP+ siNLRP12 group compared with high IOP group, and the RGCs layer was loose in the high IOP+ siNLRP12 group and the high IOP+ siNLRP12+ rrcaspase-1 group.The number of RGCs in control group, high IOP group, high IOP+ siNC group, high IOP+ siNLRP12 group and high IOP+ siNLRP12+ rrcaspase-1 group was 119.31±23.25, 89.19±16.98, 88.87±13.92, 109.33±10.25 and 92.89±12.58, respectively, showing a statistically significant overall difference (F=201.932, P<0.001). The number of RGCs was lower in the high IOP group, high IOP+ siNC group, high IOP+ siNLRP12 group and high IOP+ siNLRP12+ rrcaspase-1 group than the control group, higher in the high IOP+ siNLRP12 group than the high IOP+ siNC group, and lower in the high IOP+ siNLRP12+ rrcaspase-1 group than the high IOP+ siNLRP12 group, and the differences were statistically significant (all at P<0.05). The relative expressions of caspase-1 and cleaved-caspase-1 proteins and the concentrations of TNF-α and IL-1β in the retinal tissue were higher in high IOP group, high IOP+ siNC group, high IOP+ siNLRP12 group and high IOP+ siNLRP12+ rrcaspase-1 group than control group, higher in high IOP+ siNLRP12 group than high IOP+ siNC group, and higher in high IOP+ siNLRP12+ rrcaspase-1 group than high IOP+ siNLRP12 group (all at P<0.05). Relative expression levels of caspase-1 and cleaved-caspase-1 protein were increased in rrcaspase-1 group and siNC+ rrcaspase-1 group compared with control group, and relative expression levels of NLRP12, caspase-1 and cleaved-caspase-1 protein were decreased in siNLRP12+ rrcaspase-1 group compared with control group (all at P<0.05). The relative mass concentrations of TNF-α and IL-1β were increased in rrcaspase-1 group, siNC+ rrcaspase-1 group and siNLRP12+ rrcaspase-1 group compared with the control group (all at P<0.05). Relative expression levels of NLRP12, caspase-1 and cleaved-caspase-1 proteins and relative mass concentrations of TNF-α and IL-1β in siNLRP12+ rrcaspase-1 group were lower than those in siNC+ rrcaspase-1 group (all at P<0.05).

Conclusions

Knockdown of NLRP12 can reduce the inflammatory response and retinal injury induced by high IOP by inhibiting the activation of caspase-1.

Glaucoma; Ocular hypertension; Retinal ganglion cells; NLRP12 protein; Caspase-1; Pyroptosis