Absent In Melanoma 2 Inflammasome Research Articles

The Anti-Inflammatory Effect of SDF-1 Derived Peptide on Porphyromonas gingivalis Infection via Regulation of NLRP3 and AIM2 Inflammasome.

(1) Background: Peptides are appealing as pharmacological materials because they are easily produced, safe, and tolerable. Despite increasing gum-care awareness, periodontitis is still prevalent and is influenced by factors like high sugar consumption, smoking, and aging. Porphyromonas gingivalis is considered a major etiologic agent of periodontitis and activates the NLR family pyrin domain containing 3 (NLRP3) but is absent in melanoma 2 (AIM2) inflammasomes, resulting in pro-inflammatory cytokine release. (2) Methods: We examined the anti-inflammatory effects of 18 peptides derived from human stromal cell-derived factor-1 (SDF-1) on THP-1 macrophages. Inflammation was induced by P. gingivalis, and the anti-inflammatory effects were analyzed using molecular biological techniques. In a mouse periodontitis model, alveolar bone resorption was assessed using micro-CT. (3) Results: Of the 18 SDF-1-derived peptides, S10 notably reduced IL-1β and TNF-α secretion. S10 also diminished the P. gingivalis-induced expression of NLRP3, AIM2, ASC (apoptosis-associated speck-like protein), caspase-1, and IL-1β. Furthermore, S10 attenuated the enhanced TLR (toll-like receptor) signaling pathway and decreased the phosphorylation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs). In addition, S10 mitigated alveolar bone loss in our P. gingivalis-induced mouse model of periodontitis. (4) Conclusions: S10 suppressed TLR/NF-κB/NLRP3 inflammasome signaling and the AIM2 inflammasome in our P. gingivalis-induced murine periodontitis model, which suggests that it has potential use as a therapeutic treatment for periodontitis.

The effect of the AIM2 inflammasome in noise-induced cognitive dysfunction in rats

Objective: To explore the effect of the absent in melanoma 2 (AIM2) -mediated neuroinflammation in noise-induced cognitive dysfunction in rats. Methods: In April 2023, sixteen male Wistar rats were randomly divided into control group and noise group, with 8 rats in each group. The rats in the noise group were placed in 50 cm×50 cm×40 cm transparent boxes and exposed to 100 dB (A) white noise with a sound pressure level of 100 dB (A) (4 h/d for 30 d) . At the same time, rats in the control group were kept in similar boxes with environmental noise less than 60 dB (A) . After 30 days of noise exposure, the Morris water maze experiment was applied to test the learning and memory abilities of the rats; the pathological morphology of hippocampal tissues was observed by Hematoxylin-Eosin (HE) staining. Western blot was used to detect the protein expression levels of AIM2, cysteinyl aspartate specific proteinase-1 (caspase-1) , apoptosis-associated speck-like protein (ASC) , interleukin-1β (IL-1β) , IL-18, ionic calcium-binding articulation molecule-1 (Iba-1) , and glial fibrillary acidic protein (GFAP) . The expression of both Iba-1 and GFAP in hippocampal tissue was assessed by immunohistochemical staining. The co-localization of AIM2 with Iba-1 or GFAP was determined by immunofluorescence double staining. Results: Compared with the control group, the escape latency of rats in the noise group was increased by 16.29 s, 17.71 s, and 20.26 s on days 3, 4, and 5, respectively. On day 6, the noise-exposed rats spent shorter time in the target quadrant and had fewer times in crossing the platform[ (7.25±2.27) s and (1.13±0.64) times] than the control group[ (15.64±3.99) s and (4.25±2.12) times] (P<0.05) . After noise exposure, hippocampal neurons of rats displayed marked nuclear hyperchromatic and pyknosis phenomenon. The noise-exposed rats had higher numbers of both microglia and astrocytes (27.00±2.65 and 43.33±5.51) in the DG area of the hippocampus relative to the control group (14.67±3.06 and 20.00±4.58) (P<0.05) . Moreover, the glial cells in the noise group had larger cell cytosol with more and thicker branches. The protein expression levels of inflammatory cytokines Cleaved-IL-1β and Cleaved-IL-18 in the hippocampus of rats in the noise group (1.55±0.19 and 1.74±0.12) were significantly higher than the control group (1.00±0.11 and 1.00±0.13) (P<0.05) . After noise exposure, the protein expression levels of AIM2, Cleaved-Caspase-1 and ASC (1.19±0.09, 1.34±0.07 and 1.14±0.01) were higher than the control group (1.00±0.07, 1.00±0.14 and 1.00±0.06) and differences between the two groups were statistically significant (P<0.05) . A significant increase in the number of cells co-localizing AIM2 with Iba-1 or GFAP in the noise group (28.67±4.04 and 40.67±5.13) compared with the control group (15.67±4.04 and 17.67±3.79) , and statistically significant differences were observed between the two groups (P<0.05) . Conclusion: Noise exposure may activate the AIM2 inflammasome in hippocampal glial cells of rats, releasing excessive inflammatory cytokines and causing neuroinflammation that damages neurons.

Bruceine A alleviates alcoholic liver disease by inhibiting AIM2 inflammasome activation via activating FXR

BackgroundAlcoholic liver disease (ALD), a public health challenge worldwide caused by long-term persistent drinking, is life-threatening with minimal approved therapies. Hepatic steatosis accompanied by inflammation is an initial and inevitable stage in the complex progression of simple alcoholic liver injury to more severe liver diseases such as hepatitis, liver fibrosis, cirrhosis and liver cancer. PurposeWe aimed to identify the therapeutic role of Bruceine A (BA) in ALD whilst attempting to explore whether its protective effects depend specifically on the farnesoid X receptor (FXR). MethodsAutodock was applied to detect the affinity between BA and FXR. Lieber-DeCarli liquid diet with 5 % ethanol (v/v) was adopted to establish the mouse ALD model. The lentivirus mediating FXR (LV-FXR) was injected into mice via the tail vein to establish FXR-overexpressed mice. FXR silencing or overexpression plasmids were transfected into AML-12 cells prior to ethanol stimulation. Quantitative real-time PCR, Western blotting and immunofluorescence assays were employed to determine the expression of related genes. We subjected liver sections to H&E and Oil Red O staining to evaluate the liver histological injury and the deposition of lipid droplets. ResultsBA significantly reduced body weight and liver-to-body weight ratios as well as biochemical indexes in mice. Ethanol-induced liver damage and lipid accumulation could be alleviated by BA treatment. BA bound to FXR by two hydrogen bonds. There was a positive correlation between BA administration and FXR expression. BA inhibited the expression of lipid synthesis genes and enhanced the expression of lipid metabolism genes by activating FXR, thus alleviating steatosis in ALD. Moreover, BA exerted an ameliorative effect against inflammation by inhibiting the activation of absent in melanoma 2 (AIM2) inflammasome by activating FXR. FXR overexpression possessed the ability to counter the accumulation of lipid and the activation of AIM2 inflammasome caused by ethanol. FXR deficiency exacerbated ethanol-induced liver steatosis and inflammation. The hepatoprotective effect of BA could be disrupted by FXR antagonist guggulsterone (GS) in vivo and FXR siRNA in vitro. ConclusionBA alleviated alcoholic liver disease by inhibiting AIM2 inflammasome activation through an FXR-dependent mechanism. This study may potentially represent a new therapeutic approach for ALD.

Disrupted mitochondrial transcription factor A expression promotes mitochondrial dysfunction and enhances ocular surface inflammation by activating the absent in melanoma 2 inflammasome

PurposeSevere dry eye disease causes ocular surface damage, which is highly associated with mitochondrial dysfunction. Mitochondrial transcription factor A (TFAM) is essential for packaging mitochondrial DNA (mtDNA) and is crucial for maintaining mitochondrial function. Herein, we aimed to explore the effect of a decreased TFAM expression on ocular surface damage. MethodsFemale C57BL/6 mice were induced ocular surface injury by topical administrating benzalkonium chloride (BAC). Immortalized human corneal epithelial cells (HCECs) were stimulated by tert-butyl hydroperoxide (t-BHP) to create oxidative stress damage. HCECs with TFAM knockdown were established. RNA sequencing was employed to analyze the whole-genome expression. Mitochondrial changes were measured by transmission electron microscopy, Seahorse metabolic flux analysis, mitochondrial membrane potential, and mtDNA copy number. TFAM expression and inflammatory cytokines were determined using RT-qPCR, immunohistochemistry, immunofluorescence, and immunoblotting. ResultsIn both the corneas of BAC-treated mice and t-BHP-induced HCECs, we observed impaired TFAM expression, accompanied by mitochondrial structure and function defects. TFAM downregulation in HCECs suppressed mitochondrial respiratory capacity, reduced mtDNA content, induced mtDNA leakage into the cytoplasm, and led to inflammation. RNA sequencing revealed the absent in melanoma 2 (AIM2) inflammasome was activated in the corneas of BAC-treated mice. The AIM2 inflammasome activation was confirmed in TFAM knockdown HCECs. TFAM knockdown in t-BHP-stimulated HCECs aggravated mitochondrial dysfunction and the AIM2 inflammasome activation, thereby further triggering the secretion of inflammatory factors such as interleukin (IL) -1β and IL-18. ConclusionsTFAM reduction impaired mitochondrial function, activated AIM2 inflammasome and promoted ocular surface inflammation, revealing an underlying molecular mechanism for ocular surface disorders.

The cytoplasmic sensor, the AIM2 inflammasome: A precise therapeutic target in vascular and metabolic diseases.

Cardio-cerebrovascular diseases encompass pathological changes in the heart, brain and vascular system, which pose a great threat to health and well-being worldwide. Moreover, metabolic diseases contribute to and exacerbate the impact of vascular diseases. Inflammation is a complex process that protects against noxious stimuli but is also dysregulated in numerous so-called inflammatory diseases, one of which is atherosclerosis. Inflammation involves multiple organ systems and a complex cascade of molecular and cellular events. Numerous studies have shown that inflammation plays a vital role in cardio-cerebrovascular diseases and metabolic diseases. The absent in melanoma 2 (AIM2) inflammasome detects and is subsequently activated by double-stranded DNA in damaged cells and pathogens. With the assistance of the mature effector molecule caspase-1, the AIM2 inflammasome performs crucial biological functions that underpin its involvement in cardio-cerebrovascular diseases and related metabolic diseases: The production of interleukin-1 beta (IL-1β), interleukin-18 (IL-18) and N-terminal pore-forming Gasdermin D fragment (GSDMD-N) mediates a series of inflammatory responses and programmed cell death (pyroptosis and PANoptosis). Currently, several agents have been reported to inhibit the activity of the AIM2 inflammasome and have the potential to be evaluated for use in clinical settings. In this review, we systemically elucidate the assembly, biological functions, regulation and mechanisms of the AIM2 inflammasome in cardio-cerebrovascular diseases and related metabolic diseases and outline the inhibitory agents of the AIM2 inflammasome as potential therapeutic drugs.

Mitochondrial damage and clearance in retinal pigment epithelial cells.

Age-related macular degeneration (AMD) is a devastating eye disease that causes permanent vision loss in the central part of the retina, known as the macula. Patients with such severe visual loss face a reduced quality of life and are at a 1.5 times greater risk of death compared to the general population. Currently, there is no cure for or effective treatment for dry AMD. There are several mechanisms thought to underlie the disease, for example, ageing-associated chronic oxidative stress, mitochondrial damage, harmful protein aggregation and inflammation. As a way of gaining a better understanding of the molecular mechanisms behind AMD and thus developing new therapies, we have created a peroxisome proliferator-activated receptor gamma coactivator 1-alpha and nuclear factor erythroid 2-related factor 2 (PGC1α/NFE2L2) double-knockout (dKO) mouse model that mimics many of the clinical features of dry AMD, including elevated levels of oxidative stress markers, damaged mitochondria, accumulating lysosomal lipofuscin and extracellular drusen-like structures in retinal pigment epithelial cells (RPE). In addition, a human RPE cell-based model was established to examine the impact of non-functional intracellular clearance systems on inflammasome activation. In this study, we found that there was a disturbance in the autolysosomal machinery responsible for clearing mitochondria in the RPE cells of one-year-old PGC1α/NFE2L2-deficient mice. The confocal immunohistochemical analysis revealed an increase in autophagosome marker microtubule-associated proteins 1A/1B light chain 3B (LC3B) as well as multiple mitophagy markers such as PTE-induced putative kinase 1 (PINK1) and E3 ubiquitin ligase (PARKIN), along with signs of damaged mitochondria. However, no increase in autolysosome formation was detected, nor was there a colocalization of the lysosomal marker LAMP2 or the mitochondrial marker, ATP synthase β. There was an upregulation of late autolysosomal fusion Ras-related protein (Rab7) in the perinuclear space of RPE cells, together with autofluorescent aggregates. Additionally, we observed an increase in the numbers of Toll-like receptors 3 and 9, while those of NOD-like receptor 3 were decreased in PGC1α/NFE2L2 dKO retinal specimens compared to wild-type animals. There was a trend towards increased complement component C5a and increased involvement of the serine protease enzyme, thrombin, in enhancing the terminal pathway producing C5a, independent of C3. The levels of primary acute phase C-reactive protein and receptor for advanced glycation end products were also increased in the PGC1α/NFE2L2 dKO retina. Furthermore, selective proteasome inhibition with epoxomicin promoted both nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and mitochondrial-mediated oxidative stress, leading to the release of mitochondrial DNA to the cytosol, resulting in potassium efflux-dependent activation of the absent in melanoma 2 (AIM2) inflammasome and the subsequent secretion of interleukin-1β in ARPE-19 cells. In conclusion, the data suggest that there is at least a relative decrease in mitophagy, increases in the amounts of C5 and thrombin and decreased C3 levels in this dry AMD-like model. Moreover, selective proteasome inhibition evoked mitochondrial damage and AIM2 inflammasome activation in ARPE-19 cells.

Low-Dose Chemotherapy Preferentially Shapes the Ileal Microbiome and Augments the Response to Immune Checkpoint Blockade by Activating AIM2 Inflammasome in Ileal Epithelial Cells.

Intervention of the gut microbiome is a promising adjuvant strategy in cancer immunotherapy. Chemotherapeutic agents are recognized for their substantial impacts on the gut microbiome, yet their therapeutic potential as microbiome modulators remains uncertain, due to the complexity of microbiome-host-drug interactions. Here, it is showed that low-dose chemotherapy preferentially shapes the ileal microbiome to augment the extraintestinal immune response to anti-programmed death-1 (anti-PD-1) therapy without causing intestinal toxicity. Mechanistically, low-dose chemotherapy causes DNA damage restricted to highly-proliferative ileal epithelial cells, resulting in the accumulation of cytosolic dsDNA and the activation of the absent in melanoma 2 (AIM2) inflammasome. AIM2-dependent IL-18 secretion triggers the interplay between proximal Th1 cells and Paneth cells in ileal crypts, impairing the local antimicrobial host defense and resulting in ileal microbiome change. Intestinal epithelium-specific knockout of AIM2 in mice significantly attenuates CPT-11-caused IL-18 secretion, Paneth cell dysfunction, and ileal microbiome alteration. Moreover, AIM2 deficiency in mice or antibiotic microbial depletion attenuates chemotherapy-augmented antitumor responses to anti-PD1 therapy. Collectively, these findings provide mechanistic insights into how chemotherapy-induced genomic stress is transduced to gut microbiome change and support the rationale of applying low-dose chemotherapy as a promising adjuvant strategy in cancer immunotherapy with minimal toxicity.

FXR overexpression prevents hepatic steatosis through inhibiting AIM2 inflammasome activation in alcoholic liver disease.

Alcoholic liver disease (ALD), a metabolic liver disease caused by excessive alcohol consumption, has attracted increasing attention due to its high prevalence and mortality. Up to date, there is no effective and feasible treatment method for ALD. This study was to investigate whether Farnesoid X receptor (FXR, NR1H4) can alleviate ALD and whether this effect is mediated by inhibiting absent in melanoma 2 (AIM2) inflammasome activation. The difference in FXR expression between normal subjects and ALD patients was analyzed using the Gene Expression Omnibus (GEO) database. Lieber-DeCarli liquid diet with 5% ethanol (v/v) (EtOH) was adopted to establish the mouse ALD model. Liver histopathological changes and the accumulation of lipid droplets were assessed by H&E and Oil Red O staining. Quantitative real-time PCR, Western blotting analysis and immunofluorescence staining were utilized to evaluate the expression levels of related genes and proteins. DCFH-DA staining was adopted to visualize reactive oxidative species (ROS). FXR was distinctly downregulated in liver tissues of patients with steatosis compared to normal livers using the GEO database, and in ethanol-induced AML-12 cellular steatosis model. FXR overexpression ameliorated hepatic lipid metabolism disorder and steatosis induced by ethanol by inhibiting the expression of genes involved in lipid synthesis and inducing the expression of genes responsible for lipid metabolism. Besides, FXR overexpression inhibited ethanol-induced AIM2 inflammasome activation and alleviated oxidative stress and ROS production during ethanol-induced hepatic steatosis. However, when FXR was knocked down, the results were completely opposite. FXR attenuated lipid metabolism disorders and lipid degeneration in alcohol-caused liver injury and alleviated oxidative stress and inflammation by inhibiting AIM2 inflammasome activation.

A High-Protein Diet Promotes Atrial Arrhythmogenesis via Absent-in-Melanoma 2 Inflammasome.

High-protein diets (HPDs) offer health benefits, such as weight management and improved metabolic profiles. The effects of HPD on cardiac arrhythmogenesis remain unclear. Atrial fibrillation (AF), the most common arrhythmia, is associated with inflammasome activation. The role of the Absent-in-Melanoma 2 (AIM2) inflammasome in AF pathogenesis remains unexplored. In this study, we discovered that HPD increased susceptibility to AF. To demonstrate the involvement of AIM2 signaling in the pathogenesis of HPD-induced AF, wildtype (WT) and Aim2-/- mice were fed normal-chow (NC) and HPD, respectively. Four weeks later, inflammasome activity was upregulated in the atria of WT-HPD mice, but not in the Aim2-/--HPD mice. The increased AF vulnerability in WT-HPD mice was associated with abnormal sarcoplasmic reticulum (SR) Ca2+-release events in atrial myocytes. HPD increased the cytoplasmic double-strand (ds) DNA level, causing AIM2 activation. Genetic inhibition of AIM2 in Aim2-/- mice reduced susceptibility to AF, cytoplasmic dsDNA level, mitochondrial ROS production, and abnormal SR Ca2+-release in atrial myocytes. These data suggest that HPD creates a substrate conducive to AF development by activating the AIM2-inflammasome, which is associated with mitochondrial oxidative stress along with proarrhythmic SR Ca2+-release. Our data imply that targeting the AIM2 inflammasome might constitute a novel anti-AF strategy in certain patient subpopulations.

The Comparative Effects of Schwann Cells and Wharton's Jelly Mesenchymal Stem Cells on the AIM2 Inflammasome Activity in an Experimental Model of Spinal Cord Injury

Inflammasome activation and the consequent release of pro-inflammatory cytokines play a crucial role in the development of sensory/motor deficits following spinal cord injury (SCI). Immunomodulatory activities are exhibited by Schwann cells (SCs) and Wharton's jelly mesenchymal stem cells (WJ-MSCs). In this study, we aimed to compare the effectiveness of these two cell sources in modulating the absent in melanoma 2 (AIM2) inflammasome complex in rats with SCI. The Basso, Beattie, Bresnahan (BBB) test, Nissl staining, and Luxol fast blue (LFB) staining were performed to evaluate locomotor function, neuronal survival, and myelination, respectively. Real-time polymerase chain reaction (RT-PCR), Western blotting, and enzyme-linked immunosorbent assay (ELISA) were employed to analyze the gene and protein expressions of inflammasome components, including AIM2, ASC, caspase-1, interleukin-1β (IL-1β), and IL-18. Both gene and protein expressions of all evaluated factors were decreased after SC or WJ-MSC treatment, with a more pronounced effect observed in the SCs group (P < 0.05). Additionally, SCs promoted neuronal survival and myelination. Moreover, the administration of 3 × 105 cells resulted in motor recovery improvement in both treatment groups (P < 0.05). Although not statistically significant, these effects were more prominent in the SC-treated animals. In conclusion, SC therapy demonstrated greater efficacy in targeting AIM2 inflammasome activation and the associated inflammatory pathway in SCI experiments compared to WJ-MSCs.

Tangeretin Attenuates Cerebral Ischemia-Reperfusion-Induced Neuronal Pyroptosis by Inhibiting AIM2 Inflammasome Activation via Regulating NRF2.

Pyroptosis is closely involved in the pathopoiesis of cerebral ischemia and reperfusion (I/R) injury which seriously dangers human's life. Studies report that tangeretin (TANG), which is enriched in the peel of Citrus reticulata, has neuroprotective effects. Here, we explored whether absent in melanoma 2 (AIM2) inflammasome-mediated pyroptosis is involved in the cerebral I/R injury and the protective mechanism of TANG against cerebral I/R injury. In this study, we found that TANG treatment effectively alleviated I/R-induced brain injury and inhibited neuronal pyroptosis in anin vivomice model with middle cerebral artery occlusion/reperfusion (MCAO/R) injury andin an in vitro hippocampal HT22 cell model with oxygen-glucose deprivation and reoxygenation (OGD/R) injury. Furthermore, we found TANG inhibited cerebral I/R-induced neuronal AIM2 inflammasome activation in vivo and in vitro via regulating nuclear factor E2-related factor 2 (NRF2). Moreover, administration of ML385, a chemical inhibitor of NRF2, notably blocked the neuroprotective effects of TANG against cerebral I/R injury. In conclusion, TANG attenuates cerebral I/R-induced neuronal pyroptosis by inhibiting AIM2 inflammasome activation via regulating NRF2. These findings indicate TANG is a potential therapeutic agent for cerebral I/R injury.

Effects of AIM2 and IFI16 on Infectious Diseases and Inflammation.

Both absent in melanoma 2 (AIM2) and interferon-inducible protein 16 (IFI16) are intracellular innate immune receptors that recognize double-stranded DNA released during pathogenic infection, leading to the assembly of the inflammasome. The assembly of the inflammasome results in the secretion of bioactive interleukin (IL)-1β and IL-18 and induces cell death through an inflammatory process called pyroptosis. Although the AIM2 inflammasome is generally harmful in the context of some aseptic inflammatory illnesses, it plays a protective role in infectious diseases. During inflammatory processes, there is competition between IFI16 and AIM2. In this review, we explore the impacts of IFI16 and AIM2 in infectious disease and aseptic inflammation, respectively, and how they compete.

PANoptosome signaling and therapeutic implications in infection: central role for ZBP1 to activate the inflammasome and PANoptosis.

The innate immune response provides the first line of defense against infection and disease. Regulated cell death (RCD) is a key component of innate immune activation, and RCD must be tightly controlled to clear pathogens while preventing excess inflammation. Recent studies have highlighted a central role for the innate immune sensor Z-DNA-binding protein 1 (ZBP1) as an activator of a form of inflammatory RCD called PANoptosis, which is regulated by a multifaceted cell death complex called the PANoptosome. In response to influenza A virus infection, ZBP1 activates the nucleotide-bindingoligomerizationdomain-like receptor family pyrin domain-containing protein 3(NLRP3) inflammasome, which then acts as an integral component of the ZBP1-PANoptosome to drive inflammatory cell death, PANoptosis. In this context, the NLRP3 inflammasome is critical for caspase-1 activation and proinflammatory cytokine interleukin (IL)-1β and IL-18 maturation, but dispensable for cell death due to functional redundancies between PANoptosome molecules. Similarly, ZBP1 is also central to the absent in melanoma 2 (AIM2)-PANoptosome; this PANoptosome forms in response to Francisella novicida and herpes simplex virus 1infection and incorporates the AIM2 inflammasome as an integral component. In this review, we will discuss the critical roles of ZBP1 in mediating innate immune responses through inflammasomes, PANoptosomes, and PANoptosis during infection. An improved understanding of the molecular mechanisms of innate immunity and cell death will be essential for the development of targeted modalities that can improve patient outcomes by mitigating severe disease.

Pre-treatment of rapamycin transformed M2 microglia alleviates traumatic cervical spinal cord injury via AIM2 signaling pathway in vitro and in vivo.

Traumatic spinal cord injury (SCI) is still devastating. It was suggested that the inhibition of mTOR may alleviate neuronal inflammatory injury but its underlying mechanism remained to be elucidated. AIM2 (absent in melanoma 2) recruits ASC (apoptosis-associated speck-like protein containing a CARD) and caspase-1 to form the AIM2 inflammasome, activate caspase-1, and elicit inflammatory responses. We designed this study to elucidate whether pre-treatments of rapamycin could suppress SCI induced neuronal inflammatory injury via AIM2 signaling pathway in vitro and in vivo. We performed oxygen and glucose deprivation / re-oxygenation (OGD) treatment and rats clipping model to mimic neuronal injury after SCI in vitro and in vivo. Morphologic changes of injured spinal cord were detected by hematoxylin and eosin staining. The expression of mTOR, p-mTOR, AIM2, ASC, Caspase-1 and et al were analyzed by fluorescent staining, western blotting or qPCR. The polarization phenotype of microglia was identified by flow cytometry or fluorescent staining. We found BV-2 microglia without any pre-treatment cannot alleviate primary cultured neuronal OGD injury. However, pre-treated rapamycin in BV-2 cells could transform microglia to M2 phenotype and protects against neuronal OGD injury via AIM2 signaling pathway. Similarly, pre-treatment of rapamycin could improve the outcome of cervical SCI rats through AIM2 signaling pathway. It was suggested that resting state microglia pre-treated by rapamycin could protect against neuronal injury via AIM2 signaling pathway in vitro and in vivo. Pre-inhibition of mTOR pathway may improve neuronal protection after SCI.

Inflammasomes and Atherosclerosis: a Mixed Picture.

The CANTOS (Canakinumab Anti-inflammatory Thrombosis Outcome Study) and colchicine trials suggest an important role of inflammasomes and their major product IL-1β (interleukin 1β) in human atherosclerotic cardiovascular disease. Moreover, studies in mouse models indicate a causal role of inflammasomes and IL-1β in atherosclerosis. However, recent studies have led to a more granular view of the role of inflammasomes in atherosclerosis. Studies in hyperlipidemic mouse models suggest that prominent activation of the NLRP3 inflammasome requires a second hit such as defective cholesterol efflux, defective DNA repair, clonal hematopoiesis or diabetes. Similarly in humans some mutations promoting clonal hematopoiesis increase coronary artery disease risk in part by promoting inflammasome activation. Recent studies in mice and humans point to a wider role of the AIM2 (absent in melanoma 2) inflammasome in promoting cardiovascular disease including in some forms of clonal hematopoiesis and diabetes. These developments suggest a precision medicine approach in which treatments targeting inflammasomes or IL-1β might be best employed in clinical settings involving increased inflammasome activation.

The role of AIM2 in human hepatocellular carcinoma and its clinical significance.

AIM2 (absent in melanoma 2) was first discovered as the gene which was not expressed in melanoma cells. It is established that the AIM2 inflammasome function as the double-stranded DNA (dsDNA) sensor, and it plays a crucial role in infectious disorders and cancer. Little is known about the AIM2 expression pattern and its clinical significance in human hepatocellular carcinoma (HCC), understating how AIM2 altered the HCC cells is of high clinical interest. Immunohistochemistry was performed to investigate the AIM2 expression in HCC tissues. Then we constructed the ectopic AIM2-expressed HCC cell line by lentiviral transduction. Biological functional assays were used to analyze the clinical significance of AIM2. AIM2 expression was significantly decreased in human HCC tissues compared with adjacent normal tissues, and the overall survival of HCC patients with higher AIM2 expression was significantly better. Ectopic expression of AIM2 in HCC cells significantly inhibited migration and promoted apoptosis. Furthermore, our study revealed that the notch signaling pathway could be involved in the regulation of AIM2 in the cellular network in HCC cells. AIM2 delayed the tumor progression and correlated with immune cell infiltration. In this study, we suggested AIM2 played an inhibitory role in regulating the growth and metastasis of HCC, which supported the notion that AIM2 could serve as a potential therapeutic target for HCC.

Hematopoietic NLRP3 and AIM2 Inflammasomes Promote Diabetes-Accelerated Atherosclerosis, but Increased Necrosis Is Independent of Pyroptosis.

The contribution of hematopoietic cell inflammasome activation to atherosclerosis associated with type 1 diabetes is unknown. The goal of this study was to address whether hematopoietic NOD, LRR, and pyrin domain-containing protein 3 (NLRP3), absent in melanoma 2 (AIM2) inflammasomes, or the pyroptosis executioner gasdermin D (GSDMD) contributes to atherosclerosis in mouse models of type 1 diabetes. Diabetic mice exhibited increased inflammasome activation, with hematopoietic deletions of NLRP3, AIM2, or GSDMD causing smaller atherosclerotic lesions in diabetic mice, but the increased lesion necrotic core size in diabetic mice was independent of macrophage pyroptosis. Further studies on whether inflammasome activation contributes to cardiovascular complications in people with type 1 diabetes are warranted.

The cytosolic DNA sensor AIM2 promotes Helicobacter-induced gastric pathology via the inflammasome.

Helicobacter pylori (H. pylori) infection can trigger chronic gastric inflammation perpetuated by overactivation of the innate immune system, leading to a cascade of precancerous lesions culminating in gastric cancer. However, key regulators of innate immunity that promote H. pylori-induced gastric pathology remain ill-defined. The innate immune cytosolic DNA sensor absent in melanoma 2 (AIM2) contributes to the pathogenesis of numerous autoimmune and chronic inflammatory diseases, as well as cancers including gastric cancer. We therefore investigated whether AIM2 contributed to the pathogenesis of Helicobacter-induced gastric disease. Here, we reveal that AIM2 messenger RNA and protein expression levels are elevated in H. pylori-positive versus H. pylori-negative human gastric biopsies. Similarly, chronic Helicobacter felis infection in wild-type mice augmented Aim2 gene expression levels compared with uninfected controls. Notably, gastric inflammation and hyperplasia were less severe in H. felis-infected Aim2-/- versus wild-type mice, evidenced by reductions in gastric immune cell infiltrates, mucosal thickness and proinflammatory cytokine and chemokine release. In addition, H. felis-driven proliferation and apoptosis in both gastric epithelial and immune cells were largely attenuated in Aim2-/- stomachs. These observations in Aim2-/- mouse stomachs correlated with decreased levels of inflammasome activity (caspase-1 cleavage) and the mature inflammasome effector cytokine, interleukin-1β. Taken together, this work uncovers a pathogenic role for the AIM2 inflammasome in Helicobacter-induced gastric disease, and furthers our understanding of the host immune response to a common pathogen and the complex and varying roles of AIM2 at different stages of cancerous and precancerous gastric disease.

Selective proteasome inhibition activates AIM2 inflammasome in human retinal pigment epithelium cells

AbstractPurpose: Dysfunctional intracellular clearance is associated with various diseases, including age‐related macular degeneration (AMD). Previously, we reported the inhibition of intracellular clearance by the non‐selective proteasome inhibitor MG‐132 resulted in oxidative stress‐mediated NLR family pyrin domain containing 3 (NLRP3) inflammasome activation and subsequent interleukin‐1β (IL‐1β) secretion in human ARPE‐19 cells. In this study, we used the selective proteasome inhibitor epoxomicin and examined its effect on the inflammasome activation and IL‐1β production.Methods: IL‐1α‐primed human‐derived ARPE‐19 cells were exposed either to MG‐132 or epoxomicin and the autophagy inhibitor bafilomycin A (BafA) and studied using enzyme‐linked immunosorbent assay and cytotoxicity tests.Results: Our data reveal epoxomicin‐induced proteasome inhibition led to NADPH oxidase and mitochondria‐mediated oxidative stress‐related release of mitochondrial DNA to the cytosol, which then resulted in potassium efflux‐dependent absent in melanoma 2 (AIM2) inflammasome activation and subsequent release of inflammatory cytokine IL‐1β in ARPE‐19 cells.Conclusions: Our study emphasizes the role of AIM2 inflammasome in RPE cell degeneration along with the well‐known NLRP3 inflammasome and may represent a novel therapy target.

Roxadustat (FG-4592) protects against ischaemia-induced acute kidney injury via improving CD73 and decreasing AIM2 inflammasome activation.

Hypoxia-mediated inflammation plays a crucial role in renal ischaemia-reperfusion (IR)-induced acute kidney injury (AKI) and may influence renal graft survival, with no available pharmacological treatments. Here we investigate the protective effects and mechanism of roxadustat (FG-4592), a hypoxia-inducible factor stabilizer, against renal IR injury. The protein expression levels of CD73 and AIM2 inflammasome complex were examined in kidney biopsy specimens of AKI and post-renal transplantation (PRT) patients. The effects of FG-4592 on CD73 and absent in melanoma 2 (AIM2) inflammasome components were examined in IR mice (right nephrectomy, followed by 30min of unilateral renal ischaemia and reperfusion for 24h), and some of the model mice received intraperitoneal administrations of adenosine 5'-(α,β-methylene)diphosphate sodium salt, which is an inhibitor of CD73. The function of FG-4592 was also investigated in vitro with HK-2 cells. In the AKI and PRT patients, the protein expression of AIM2 complex [AIM2-apoptosis-associated speck-like protein (ASC)-cleaved caspase-1) increased and the activation of CD73 signalling pathway was detected as well. The pretreatment of FG-4592 improved the creatinine elevation and renal tubular injuries induced by ischaemia. What's more, the administration of FG-4592 significantly enhanced CD73 synthesis in mouse kidney but suppressed the activation of the AIM2 inflammasome [decreased AIM2, ASC, caspase-1, interleukin (IL)-1β and IL-18 levels]. Notably, the renoprotection of FG-4592 and the inhibition of AIM2 were abolished by the CD73 inhibitor. FG-4592-conveyed protection against AKI might be mediated by the induction of CD73 and the suppression of the AIM2 inflammasome, which may provide a novel therapeutic method for the treatment of AKI.