NLRP12 collaborates with NLRP3 and NLRC4 to promote pyroptosis inducing ganglion cell death of acute glaucoma

Abstract

Background: Acute glaucoma, characterized by a sudden elevation in intraocular pressure (IOP) and retinal ganglion cells (RGCs) death, is a major cause of irreversible blindness worldwide that lacks approved effective therapies, validated treatment targets and clear molecular mechanisms. We sought to explore the potential molecular mechanisms underlying the causal link between high IOP and glaucomatous RGCs death.Methods: A murine retinal ischemia/ reperfusion (RIR) model and an in vitro oxygen and glucose deprivation/ reoxygenation (OGDR) model were used to investigate the pathogenic mechanisms of acute glaucoma.Results: Our findings reveal a novel mechanism of microglia-induced pyroptosis-mediated RGCs death associated with glaucomatous vision loss. Genetic deletion of gasdermin D (GSDMD), the effector of pyroptosis, markedly ameliorated the RGCs death and retinal tissue damage in acute glaucoma. Moreover, GSDMD cleavage of microglial cells was dependent on caspase-8 (CASP8)-hypoxia-inducible factor-1α (HIF-1α) signaling. Mechanistically, the newly identified nucleotide-binding leucine-rich repeat-containing receptor (NLR) family pyrin domain-containing 12 (NLRP12) collaborated with NLR family pyrin domain-containing 3 (NLRP3) and NLR family CARD domain-containing protein 4 (NLRC4) downstream of the CASP8-HIF-1α axis, to elicit pyroptotic processes and interleukin-1β (IL-1β) maturation through caspase-1 activation, facilitating pyroptosis and neuroinflammation in acute glaucoma. Interestingly, processing of IL-1β in turn magnified the CASP8-HIF-1α-NLRP12/ NLRP3/NLRC4-pyroptosis circuit to accelerate inflammatory cascades.Conclusions: These data not only indicate that the collaborative effects of NLRP12, NLRP3 and NLRC4 on pyroptosis are responsible for RGCs death, but also shed novel mechanistic insights into microglial pyroptosis, paving novel therapeutic avenues for the treatment of glaucoma-induced irreversible vision loss through simultaneously targeting of pyroptosis.

The Regulatory NOD-Like Receptor NLRC5 Promotes Ganglion Cell Death in Ischemic Retinopathy by Inducing Microglial Pyroptosis

“…These cleaved N-terminal GSDMD proteins accumulate in the plasma membrane and form pores, eventually leading to plasma membrane rupture and release of cytosolic contents (Kovacs and Miao, 2017). This study, together with our recently published study, provide compelling evidence that pyroptosis of activated microglia contributes to retinal ischemic injury, including the death of RGCs (Chen et al, 2020). We also found that both apoptosis and pyroptosis pathways were activated in OGDRstimulated microglia, and that the expression of pyroptotic marker proteins increased more rapidly than apoptotic marker proteins.…”

“…Mounting evidence implicates inflammasome-forming NLRs such as NLRP3, NLRP1, and NLRP6 in RIR injury (Chi et al, 2014;Wan et al, 2019), but the potential roles of regulatory NLRs have not been explored. By analyzing transcriptome sequencing data obtained from our recently published study (Chen et al, 2020), we discovered that the mRNA expression level of regulatory NLRC5 was significantly upregulated in the retina of RIR injury model mice, and this upregulation was further confirmed by RT-qPCR (Figures 1D,E). Both western blot and immunohistochemical staining also demonstrated significantly upregulated expression of NLRC5 in the retina at different times during reperfusion (Figures 1F-H).…”

“…While inflammasome-forming NLRs are well described, regulatory NLRs such as NOD1, NOD2, NLRX1, NLRC3, and NLRC5 are less studied and mainly refer to function as either positive or negative regulators of inflammatory signaling cascades ( Coutermarsh-Ott et al, 2016 ; Fekete et al, 2018 ). In the past several years, accumulated evidence from in vitro and in vivo studies has clearly shown that inflammasome-forming NLRs, such as NLRP3, NLRP1, NLRP6, and NLRC4, play an important role in RIR injury ( Chi et al, 2014 ; Wan et al, 2019 ; Chen et al, 2020 ). However, the contributions of regulatory NLRs to RIR injury are still unknown.…”

“…Programmed cell death (PCD), such as apoptosis, pyroptosis and necroptosis, is a fundamental cellular process essential for the homeostasis and development of multicellular organisms ( Man et al, 2017 ). Our recent studies revealed that a NLRP12/NLRP3/NLRC4 inflammasome-initiated pyroptosis pathway contributes to RGCs death in elevated intraocular pressure (IOP)-induced retinal ischemia ( Chen et al, 2020 ). Recent breakthroughs reveal that the different types of PCD are highly interconnected and could be regarded as a single, coordinated cell death system that allows for flexible mutual compensation, just like in some conditions inflammatory caspases can trigger apoptosis while apoptotic triggers can induce pyroptosis ( Bedoui et al, 2020 ).…”

Interleukin-35 Suppresses Pyroptosis and Protects Neuronal Death in Retinal Ischemia/Reperfusion Injury

“…The N-terminal domain of cleaved GSDMD translocates to the cell membrane, forming the transmembrane pores that facilitate the release of cleaved IL-1β and IL-18, to stimulate in ammatory responses 23 . Accumulating evidence has shown that pyroptosis occurs in virous in ammatory diseases 24,25 , and our previous studies also found that pyroptosis participates in the pathological process of retina injuries following high IOP 18,26 . This study, for the rst time, found that IL-35 can lower the expression of in ammatory molecules and attenuate pyroptosis in vivo.…”