Abstract
Only a few types of inflammasomes have been described in central nervous system cells. Among these, the absent in melanoma 2 (AIM2) inflammasome is primarily found in neurons, is highly specific and can be activated only by double-stranded DNA. Although it has been demonstrated that the AIM2 inflammasome is activated by poly(deoxyadenylic-deoxythymidylic) acid sodium salt and leads to pyroptotic neuronal cell death, the role of AIM2 inflammasome-mediated pyroptosis in early brain injury (EBI) after subarachnoid haemorrhage (SAH) has rarely been studied. Thus, we designed this study to explore the mechanism of gasdermin D(GSDMD)-induced pyroptosis mediated by the AIM2 inflammasome in EBI after SAH. The level of AIM2 from the cerebrospinal fluid (CSF) of patients with SAH was detected. The pathway of AIM2 inflammasome-mediated pyroptosis, the AIM2/Caspase-1/GSDMD pathway, was explored after experimental SAH in vivo and in primary cortical neurons stimulated by oxyhaemoglobin (oxyHb) in vitro. Then, we evaluated GSDMD-induced pyroptosis mediated by the AIM2 inflammasome in AIM2 and caspase-1- deficient mice and primary cortical neurons generated through lentivirus (LV) knockdown. Compared with that of the control samples, the AIM2 level in the CSF of the patients with SAH was significantly increased. Pyroptosis-associated proteins mediated by the AIM2 inflammasome were significantly increased in vivo and in vitro following experimentally induced SAH. After AIM2 and caspase-1 were knocked down by an LV, GSDMD-induced pyroptosis mediated by the AIM2 inflammasome was alleviated in EBI after SAH. Intriguingly, when caspase-1 was knocked down, apoptosis was significantly suppressed via impeding the activation of caspase-3. GSDMD-induced pyroptosis mediated by the AIM2 inflammasome may be involved in EBI following SAH. The inhibition of AIM2 inflammasome activation caused by knocking down AIM2 and caspase-1 alleviates GSDMD-induced pyroptosis in EBI after SAH.
Highlights
Aneurysmal subarachnoid haemorrhage (SAH) is a lifethreatening disease with high mortality and morbidity
(see figure on previous page) Fig. 3 The Absent in melanoma 2 (AIM2) inflammasome-mediated pyroptosis pathway was measured in primary cortical neurons exposed to oxyHb. a Representative images of cultured primary cortical neurons, scale bars (NeuN) = 50 μm, scale bars (MAP2) = 200 μm; b Western blot assay for the expression of AIM2, gasdermin D (GSDMD), GSDMD N-terminus (GSDMD-N), caspase-1, caspase-1 p20 and ASC in all groups; c Quantification of AIM2, GSDMD, GSDMD-N, caspase-1, caspase-1 p20 and ASC; d, e Quantitative analysis of IL-1β and IL-18 secreted in the supernatant; f Flow cytometry analysis of neurons in all groups; g Quantification of caspase-1 and propidium iodide (PI)-positive neurons in all groups
In the present study, we studied the possible role of GSDMD-induced pyroptosis mediated by the AIM2 inflammasome in the pathogenesis of early brain injury (EBI) after SAH
Summary
Aneurysmal subarachnoid haemorrhage (SAH) is a lifethreatening disease with high mortality and morbidity. Absent in melanoma 2 (AIM2), a member of the haemopoietic interferon-inducible nuclear 200 family of proteins, induces the formation of a highly specific type of inflammasome in the neurons that can recognise aberrant double-stranded DNA (dsDNA). AIM2 triggers the formation of inflammasomes that contain the apoptosisassociated speck-like protein containing a CARD (ASC) and caspase-1 and that induce the cleavage of caspase-1, the maturation of interleukin-1β (IL-1β) and interleukin[18] (IL-18) and pyroptosis. The AIM2 inflammasome mediates pyroptotic neuronal cell death, as has been shown in vivo by incubating cortical neurons with poly (deoxyadenylic-deoxythymidylic) acid sodium salt, a synthetic dsDNA5. The role of gasdermin D (GSDMD)-induced pyroptosis mediated by the AIM2 inflammasome in the pathogenesis of EBI after SAH has not been clearly elucidated
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