Project description:Background Acute myocardial infarction (AMI) is one of the leading causes of cardiovascular morbidity and mortality worldwide. Pyroptosis is a form of inflammatory cell death that plays a major role in the development and progression of cardiac injury in AMI. However, the underlying mechanisms for the activation of pyroptosis during AMI are not fully elucidated. Methods and Results Here we show that RBP4 (retinol-binding protein 4), a previous identified proinflammatory adipokine, was increased both in the myocardium of left anterior descending artery ligation-induced AMI mouse model and in ischemia-hypoxia‒induced cardiomyocyte injury model. The upregulated RBP4 may contribute to the activation of cardiomyocyte pyroptosis in AMI because overexpression of RBP4 activated NLRP3 (nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3) inflammasome, promoted the precursor cleavage of Caspase-1, and subsequently induced GSDMD (gasdermin-D)-dependent pyroptosis. In contrast, knockdown of RBP4 alleviated ischemia-hypoxia‒induced activation of NLRP3 inflammasome signaling and pyroptosis in cardiomyocytes. Mechanistically, coimmunoprecipitation assay showed that RBP4 interacted directly with NLRP3 in cardiomyocyte, while genetic knockdown or pharmacological inhibition of NLRP3 attenuated RBP4-induced pyroptosis in cardiomyocytes. Finally, knockdown of RBP4 in heart decreased infarct size and protected against AMI-induced pyroptosis and cardiac dysfunction in mice. Conclusions Taken together, these findings reveal RBP4 as a novel modulator promoting cardiomyocyte pyroptosis via interaction with NLRP3 in AMI. Therefore, targeting cardiac RBP4 might represent a viable strategy for the prevention of cardiac injury in patients with AMI.
Project description:BackgroundNeuroinflammation-induced secondary injury is an important cause of sustained progression of spinal cord injury. Inflammatory programmed cell death pyroptosis executed by the pore-forming protein gasdermin D (GSDMD) is an essential step of neuroinflammation. However, it is unclear whether CD73, a widely accepted immunosuppressive molecule, can inhibit pyroptosis via mediating GSDMD.MethodsC57BL/6J CD73 deficient mice and wild-type mice, Lipopolysaccharide (LPS)-induced primary microglia and BV2 cells were respectively used to illustrate the effect of CD73 on microglia pyroptosis in vivo and in vitro. A combination of molecular and histological methods was performed to assess pyroptosis and explore the mechanism both in vivo and in vitro.ResultsWe have shown molecular evidence for CD73 suppresses the activation of NLRP3 inflammasome complexes to reduce the maturation of GSDMD, leading to decreased pyroptosis in microglia. Further analysis reveals that adenosine-A2B adenosine receptor-PI3K-AKT-Foxo1 cascade is a possible mechanism of CD73 regulation. Importantly, we determine that CD73 inhibits the expression of GSDMD at the transcriptional level through Foxo1. What's more, we confirm the accumulation of HIF-1α promotes the overexpression of CD73 after spinal cord injury (SCI), and the increased CD73 in turn upregulates the expression of HIF-1α, eventually forming a positive feedback regulatory loop.ConclusionOur data reveal a novel function of CD73 on microglia pyroptosis, suggesting a unique therapeutic opportunity for mitigating the disease process in SCI.
Project description:The precise control of cardiomyocyte viability is imperative to combat myocardial ischemia-reperfusion injury (I/R), in which apoptosis and pyroptosis putatively contribute to the process. Recent researches indicated that GSDMD is involved in I/R as an executive protein of pyroptosis. However, its effect on other forms of cell death is unclear. We identified that GSDMD and GSDMD-N levels were significantly upregulated in the I/R myocardium of mice. Knockout of GSDMD conferred the resistance of the hearts to reperfusion injury in the acute phase of I/R but aggravated reperfusion injury in the chronic phase of I/R. Mechanistically, GSDMD deficiency induced the activation of PARylation and the consumption of NAD+ and ATP, leading to cardiomyocyte apoptosis. Moreover, PJ34, a putative PARP-1 inhibitor, reduced the myocardial injury caused by GSDMD deficiency. Our results reveal a novel action modality of GSDMD in the regulation of cardiomyocyte death; inhibition of GSDMD activates PARylation, suggesting the multidirectional role of GSDMD in I/R and providing a new theory for clinical treatment.
Project description:Emerging evidence suggests that astrocyte loss is one of the most important pathological features in the hippocampus of patients with major depressive disorder (MDD) and depressive mice. Pyroptosis is a recently discovered form of programmed cell death depending on Caspase-gasdermin D (Casp-GSDMD), which is involved in multiple neuropsychiatric diseases. However, the involvement of pyroptosis in the onset of MDD and glial pathological injury remains obscure. Here, we observed that depressive mice showed astrocytic pyroptosis, which was responsible for astrocyte loss, and selective serotonin reuptake inhibitor (SSRI) treatment could attenuate the pyroptosis induced by the chronic mild stress (CMS) model. Genetic KO of GSDMD, Casp-1, and astrocytic NOD-like receptor protein 3 (NLRP3) inflammasome in mice alleviated depression-like behaviors and inhibited the pyroptosis-associated protein expression. In contrast, overexpression of astrocytic GSDMD-N-terminal domain (GSDMD-N) in the hippocampus could abolish the improvement of behavioral alterations in GSDMD-deficient mice. This work illustrates that targeting the NLRP3/Casp-1/GSDMD-mediated pyroptosis may provide potential therapeutic benefits to stress-related astrocyte loss in the pathogenesis of depression.
Project description:Skeletal muscle atrophy is one of the major side effects of high dose or sustained usage of glucocorticoids. Pyroptosis is a novel form of pro-inflammatory programmed cell death that may contribute to skeletal muscle injury. Trimetazidine, a well-known anti-anginal agent, can improve skeletal muscle performance both in humans and mice. We here showed that dexamethasone-induced atrophy, as evidenced by the increase of muscle atrophy F-box (Atrogin-1) and muscle ring finger 1 (MuRF1) expression, and the decrease of myotube diameter in C2C12 myotubes. Dexamethasone also induced pyroptosis, indicated by upregulated pyroptosis-related protein NLR family pyrin domain containing 3 (NLRP3), Caspase-1, and gasdermin-D (GSDMD). Knockdown of NLRP3 or GSDMD attenuated dexamethasone-induced myotube pyroptosis and atrophy. Trimetazidine treatment ameliorated dexamethasone-induced muscle pyroptosis and atrophy both in vivo and in vitro. Activation of NLRP3 using LPS and ATP not only increased the cleavage and activation of Caspase-1 and GSDMD, but also increased the expression levels of atrophy markers MuRF1 and Atrogin-1 in trimetazidine-treated C2C12 myotubes. Mechanically, dexamethasone inhibited the phosphorylation of PI3K/AKT/FoxO3a, which could be attenuated by trimetazidine. Conversely, co-treatment with a PI3K/AKT inhibitor, picropodophyllin, remarkably increased the expression of NLRP3 and reversed the protective effects of trimetazidine against dexamethasone-induced C2C12 myotube pyroptosis and atrophy. Taken together, our study suggests that NLRP3/GSDMD-mediated pyroptosis might be a novel mechanism for dexamethasone-induced skeletal muscle atrophy. Trimetazidine might be developed as a potential therapeutic agent for the treatment of dexamethasone-induced muscle atrophy.
Project description:The reactive oxygen species- (ROS-) induced nod-like receptor protein-3 (NLRP3) inflammasome triggers sterile inflammatory responses and pyroptosis, which is a proinflammatory form of programmed cell death initiated by the activation of inflammatory caspases. NLRP3 inflammasome activation plays an important role in myocardial ischemia/reperfusion (MI/R) injury. Our present study investigated whether diabetes aggravated MI/R injury through NLRP3 inflammasome-mediated pyroptosis. Type 1 diabetic rat model was established by intraperitoneal injection of streptozotocin (60?mg/kg). MI/R was induced by ligating the left anterior descending artery (LAD) for 30?minutes followed by 2?h reperfusion. H9C2 cardiomyocytes were exposed to high glucose (HG, 30?mM) conditions and hypoxia/reoxygenation (H/R) stimulation. The myocardial infarct size, CK-MB, and LDH release in the diabetic rats subjected to MI/R were significantly higher than those in the nondiabetic rats, accompanied with increased NLRP3 inflammasome activation and increased pyroptosis. Inhibition of inflammasome activation with BAY11-7082 significantly decreased the MI/R injury. In vitro studies showed similar effects, as BAY11-7082 or the ROS scavenger N-acetylcysteine, attenuated HG and H/R-induced H9C2 cell injury. In conclusion, hyperglycaemia-induced NLRP3 inflammasome activation may be a ROS-dependent process in pyroptotic cell death, and NLRP3 inflammasome-induced pyroptosis aggravates MI/R injury in diabetic rats.
Project description:Recent findings have revealed that the protein gasdermin D (GSDMD) plays key roles in cell pyroptosis. GSDMD binds lipids and forms pore structures to induce pyroptosis upon microbial infection and associated danger signals. However, detailed structural information for GSDMD remains unknown. Here, we report the crystal structure of the C-terminal domain of human GSDMD (GSDMD-C) at 2.64-Å resolution. The first loop on GSDMD-C inserts into the N-terminal domain (GSDMD-N), which helps stabilize the conformation of the full-length GSDMD. Substitution of this region by a short linker sequence increased levels of cell death. Mutants F283A and F283R can increase protein heterogeneity in vitro and are capable of undergoing cell pyroptosis in 293T cells. The small-angle X-ray-scattering envelope of human GSDMD is consistent with the modeled GSDMD structure and mouse GSDMA3 structure, which suggests that GSDMD adopts an autoinhibited conformation in solution. The positive potential surface of GSDMD-N covered by GSDMD-C is exposed after being released from the autoinhibition state and can form high-order oligomers via a charge-charge interaction. Furthermore, by mapping different regions of GSDMD, we determined that one short segment is sufficient to kill bacteria in vitro and can efficiently inhibit cell growth in Escherichia coli and Mycobacterium Smegmatis These findings reveal that GSDMD-C acts as an auto-inhibition executor and GSDMD-N could form pore structures via a charge-charge interaction upon cleavage by caspases during cell pyroptosis.
Project description:Intestinal ischemia-reperfusion (I/R) injury is a life-threatening vascular emergency and has long been a disturbing problem for surgeons. Oxidative stress is considered a vital factor in I/R injury. Metformin has anti-oxidative properties and protects against I/R injury. The present study aimed to investigate whether Metformin protects against intestinal I/R injury and reveal the protective mechanism of Metformin. I/R injury was induced in mice by temporary superior mesenteric artery occlusion, and Caco-2 cells were subjected to OGD/R to establish an in vitro model. Different doses of Metformin were administered in vivo and in vitro. We found that I/R injury led to intestinal barrier disruption and cell death by examining histopathological results and the intestinal barrier index, including TER, tight junction proteins and serum biomarkers. We confirmed the existence of pyroptosis in intestinal I/R injury. Moreover, we confirmed the role of pyroptosis in intestinal I/R injury by silencing the gasdermin D (GSDMD). Then, we confirmed that Metformin treatment protected barrier function against intestinal I/R injury and reduced oxidative stress and the inflammatory response. Importantly, Metformin reduced pyroptosis-related proteins, including NLRP3, cleaved caspase-1, and the N-terminus of GSDMD. Knocking down the GSDMD could reversed the protective effects of Metformin, which showed pyroptosis was one of the major cell death pathways controlled by Metformin treatment in setting of intestinal I/R injury. We also discovered that Metformin suppressed the expression of TXNIP and the interaction between TXNIP and NLRP3. We performed siRNA knockdown and found that the protective effects were abolished, which further confirmed our findings. In conclusion, we believe that Metformin protects against intestinal I/R injury in a TXNIP-NLRP3-GSDMD-dependent manner.
Project description:Acute pancreatitis (AP), especially severe acute pancreatitis (SAP), is an extremely dangerous illness with a high mortality rate. Pyroptotic cells release their cellular contents and inflammatory factors, aggravating the inflammatory response. Pyroptosis may be the main mode of acinar cell death during AP. The circular RNA circHIPK3 is expressed in pancreatic tissue and is associated with inflammatory response. In this study, we focused on the role and underlying mechanism of circHIPK3 in AP. We found that the expression of circHIPK3 was significantly elevated in serum of patients with AP and in caerulein-stimulated AR42J cells and was associated with caspase-1 and caspase-11 activation. circHIPK3 silencing ameliorated caerulein-induced cell damage and reduced the release of inflammatory factors IL-1β, IL-6, IL-8, and TNF-α and inhibited the activation of caspase-1 and caspase-11. In addition, circHIPK3 bound to miR-193a-5p and negatively regulated its expression. Inhibition of miR-193a-5p increased the release of IL-1β, IL-6, IL-8, and TNF-α and activated caspase-1 and caspase-11, thereby counteracting the effect of circHIPK3 silencing on caerulein-induced cell damage. Furthermore, we identified GSDMD as a target gene of miR-193a-5p, which is the key gene for pyroptosis. Interfering with the expression of GSDMD can increase cell viability, reduce the secretion of inflammatory cytokines, and suppress the activation of cleaved caspase-1 and caspase-11. Silencing GSDMD reversed the effects of miR-193a-5p inhibitors on caerulein-induced damage. In conclusion, circHIPK3 promotes pyroptosis in acinar cells through regulation of the miR-193a-5p/GSDMD axis, which eventually aggravates AP disease.
Project description:BackgroundEmodin has recently been reported to have a powerful antiinflammatory effect, protecting the myocardium against ischemia/reperfusion (I/R) injury. Pyroptosis is a proinflammatory programmed cell death that is related to many diseases. The present study investigated the effect of emodin on pyroptosis in cardiomyocytes.Materials and methodsSprague Dawley rats were randomly divided into sham, I/R, and I/R+Emodin groups. I/R model was subjected to 30 minutes' ligation of left anterior descending coronary artery, followed by 2 hours of reperfusion. Cardiomyocytes were exposed to hypoxic conditions for 1 hour and normoxic conditions for 2 hours. The level of the pyroptosis was detected by Western blot, real-time PCR analysis, and ELISA.ResultsThe level of gasdermin D-N domains was upregulated in cardiomyocytes during I/R or hypoxia/reoxygenation (H/R) treatment. Moreover, emodin increased the rate of cell survival in vitro and decreased the myocardial infarct size in vivo via suppressing the levels of I/R-induced pyroptosis. Additionally, the expression of TLR4, MyD88, phospho-IκBα, phospho-NF-κB, and the NLRP3 inflammasome was significantly upregulated in cardiomyocytes subjected to H/R treatment, while emodin suppressed the expression of these proteins.ConclusionThis study confirms that emodin treatment was able to alleviate myocardial I/R injury and inhibit pyroptosis in vivo and in vitro. The inhibitory effect of emodin on pyroptosis was mediated by suppressing the TLR4/MyD88/NF-κB/NLRP3 inflammasome pathway. Therefore, emodin may provide an alternative treatment for myocardial I/R injury.