Inflammasome facilitates ganglion cell loss via pyroptosis and apoptosis in ocular hypertension injury

Abstract

Purpose : Our results show a complex spatio-temporal pattern of innate immune responses in the retina. Acute inflammasome induction results in early pyroptotic and apoptotic cell death, the key contributor to RGC loss. These results implicate neuronal and glial inflammasomes in pathophysiology of the OHT injury and provide feasibility of inflammasome modulation for neuroprotection in acute glaucoma.

Methods : A transient unilateral ocular hypertension (OHT) was used as RGC injury model. IL-1β cytokine production was assessed with sandwich ELISA, RGC loss was assessed by direct counts in retinal flat mounts. Inflammasome activation was examined by RNAscope, Western blot and immunohistochemistry. Wild type and an ASC-citrin bioindicator mouse strain were used to detect and map active inflammasomes. Cell-permeable fluorescent FLICA substrates were injected to detect caspases -1 and -3/7 activities

Results : Fluorescent ASC specks of active inflammasomes localized to astroglia, RGCs and Mueller glia, but much less to microglial cells in the OHT-injured retina. Acute activation of NLRP1, NLRP3 and Aim2 inflammasomes complexes was detected by immunostaining and RNAscope. NLRP1 was detected in RGCs and other neurons, NLRP3 in astrocytes and Aim2 in Muller glia. The activation of caspases-1 and 11, and the release of IL-1β in the retina were detected at 6-24 h post-injury. Consistently, the induction and cleavage of the pyroptotic pore protein gasdermin D was detected in the ganglion cell layer neurons at 6-12h, in the astrocytes at 12-24h post-injury. Unexpectedly, we detected cross-activation of pyroptotic and apoptotic pathways in the inner retina, as evidenced by co-activation of caspases 1 and 3/7 in the same cells. The release of cytokines, Casp3 activity and RGC death were completely blocked in Casp1^- and in the wild type eyes treated with Casp1 and gasderminD inhibitors. RGC death was significantly decreased in Panx1^-/- and in wild-type mice treated with the Panx1 inhibitors.

Conclusions : Our results show a complex spatio-temporal pattern of innate immune responses in the retina. Acute inflammasome induction results in early pyroptotic and apoptotic cell death, the key contributor to RGC loss. These results implicate neuronal and glial inflammasomes in pathophysiology of the OHT injury and provide feasibility of inflammasome modulation for neuroprotection.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Inflammasome-induced cell death in the retina