PANoptosis is a newly identified type of regulated cell death that consists of pyroptosis, apoptosis, and necroptosis, which simultaneously occur during the pathophysiological process of infectious ...and inflammatory diseases. Although our previous literature mining study suggested that PANoptosis might occur in neuronal ischemia/reperfusion injury, little experimental research has been reported on the existence of PANoptosis. In this study, we used in vivo and in vitro retinal neuronal models of ischemia/reperfusion injury to investigate whether PANoptosis-like cell death (simultaneous occurrence of pyroptosis, apoptosis, and necroptosis) exists in retinal neuronal ischemia/reperfusion injury. Our results showed that ischemia/reperfusion injury induced changes in morphological features and protein levels that indicate PANoptosis-like cell death in retinal neurons both in vitro and in vivo. Ischemia/reperfusion injury also significantly upregulated caspase-1, caspase-8, and NLRP3 expression, which are important components of the PANoptosome. These results indicate the existence of PANoptosis-like cell death in ischemia/reperfusion injury of retinal neurons and provide preliminary experimental evidence for future study of this new type of regulated cell death.
•Caspases negatively regulate necrosis.•Initiation of necrosis signaling depends on receptor interacting kinase 1/3 (RIP1/RIP3) activation.•Mixed lineage kinase domain-like protein (MLKL) is the core ...machinery of necrosis execution.•Recent successes include the development of necrosis inhibitors and biomarkers.
Classically, there are two major forms of cell death: necrosis, an unregulated digestion of cellular components; and apoptosis, a programmed mechanism that is promoted by caspases. However, another form of cell death has recently been identified that is inhibited by caspases, and yet occurs through a regulated mechanism, termed programmed necrosis or necroptosis. The biochemical basis of this program has begun to emerge, with the discovery of the receptor-interacting kinase RIP3 and its substrate, the pseudokinase mixed lineage kinase domain-like protein (MLKL), as core components. Furthermore, animal models have revealed significant functions for RIP3/MLKL-mediated necrotic cell death in immune responses against microbial infection and in the etiology of diseases involving tissue damage. This review discusses recent advances in our understanding of the mechanistic details and physiological functions of programmed necrosis.
Chronic liver diseases affect over a billion people worldwide and often lead to fibrosis. Nonalcoholic steatohepatitis (NASH), a disease paralleling a worldwide surge in metabolic syndromes, is ...characterized by liver fibrosis, and its pathogenesis remains largely unknown, with no effective treatment available. Necroptosis has been implicated in liver fibrosis pathogenesis. However, there is a lack of research on necroptosis specific to certain cell types, particularly the vascular system, in the context of liver fibrosis and NASH. Here, we employed a mouse model of NASH in combination with inducible gene knockout mice to investigate the role of endothelial necroptosis in NASH progression. We found that endothelial cell (EC)-specific knockout of mixed lineage kinase domain-like protein (MLKL), a critical executioner involved in the disruption of cell membranes during necroptosis, alleviated liver fibrosis in the mouse NASH model. Mechanistically, EC-specific deletion of
mitigated the activation of TGFβ/Smad 2/3 pathway, disrupting the pro-fibrotic crosstalk between endothelial cells and hepatic stellate cells (HSCs). Our findings highlight endothelial MLKL as a promising molecular target for developing therapeutic interventions for NASH.
Pigs infected by pseudorabies virus (PRV) display necrotic pathology in multiple organs. The mechanism by which PRV induces cell death is still unclear. Recently, necroptosis was identified as a ...programmed process dependent on the receptor interacting protein kinase 3 (RIPK3) and mixed lineage kinase-like protein (MLKL). In this study, we demonstrated that PRV induced RIPK3-dependent necroptosis in PK-15 cells. The data showed that PRV infection caused cell death with Propidium Iodide (PI)-positive staining. Transmission electron microscopy analysis indicated plasma membrane disruption in PRV-infected cells. A pan-caspase inhibitor did not prevent PRV-induced necrotic cell death. Western blot analysis indicated that caspase-3 and caspase-8 were not cleaved during PRV infection. Although the transcription of tumor necrosis factor-alpha (TNF-α) was increased by PRV infection, RIPK1 was shown to be not involved in PRV-induced necrotic cell death by use of its specific inhibitor. Further experiments indicated that the phosphorylation of RIPK3 and MLKL was upregulated in PRV-infected cells. Stable shRNA knockdown of RIPK3 or MLKL had a recovery effect on PRV-induced necrotic cell death. Meanwhile, viral titers were enhanced in RIPK3 and MLKL knockdown cells. Hence, we concluded that initiation of necroptosis in host cells plays a limiting role in PRV infection. Considering that necroptosis is an inflammatory form of programmed cell death, our data may be beneficial for understanding the necrotic pathology of pigs infected by PRV.
Complex roles of necroptosis in cancer Zhu, Fang; Zhang, Wei; Yang, Tao ...
Journal of Zhejiang University. B. Science,
05/2019, Volume:
20, Issue:
5
Journal Article
Peer reviewed
Open access
Necroptosis is a tightly regulated form of necrosis that requires the activation of receptor-interacting protein (RIP) kinases RIPK1 and RIPK3, as well as the RIPK3 substrate mixed lineage kinase ...domain-like protein (MLKL). Because of membrane rupture, necroptotic cells release damage-associated molecular patterns (DAMPs) that evoke immune responses. Necroptosis is emerging as an important cellular response in the modulation of cancer initiation, progression, and metastasis. Necroptosis of cancer cells is considered to be an immunogenic cell death capable of activating anti-tumor immunity. Necroptosis also participates in the promotion of myeloid cell-induced adaptive immune suppression and thus contributes to oncogenesis. In addition, necroptosis of endothelial cells and tumor cells is conducive to tumor metastasis. In this review, we summarize the current knowledge of the complex role of necroptosis in cancer and discuss the potential of targeting necroptosis components for cancer therapies.
Ulcerative colitis (UC) is a chronic inflammatory colonic disease strongly associated with intestinal epithelial cell (IEC) death. Necroptosis is characterized by a newly programmed cell death ...through a caspase-independent pathway. Receptor interacting protein 3 (RIP3) and mixed lineage kinase domain-like protein (MLKL) are very important in the pathway of necroptosis. However, their expression in UC remains unelucidated. This study aimed to investigate the expression of RIP3 and MLKL in patients with UC, along with its correlation with disease activity.
Colonic tissue samples were taken from 22 UC patients and 19 healthy controls. RIP3 and MLKL expression levels were evaluated by immunohistochemical staining and western blotting.
RIP3 and MLKL were upregulated in inflamed tissues of UC (P<0.01). No variations were observed in healthy control subjects and non-inflamed colons (P>0.05). RIP3 and MLKL were positively correlated with UC disease activity (P<0.01).
Our results suggest that necroptosis is strongly associated with intestinal inflammation in patients with UC. Further studies of necroptosis may be helpful in future treatments of UC.
Necroptosis is a regulated form of necrosis that depends on receptor-interacting protein kinase (RIPK)3 and mixed lineage kinase domain-like protein (MLKL). While danger-associated molecular pattern ...(DAMP)s are released from dead cells and involved in various pathological conditions, the mechanisms underlying regulation of the release of DAMPs are not fully understood. Apoptosis and pyroptosis can be detected by several types of sensors such as Forster resonance energy transfer (FRET) biosensors, termed SCAT1 (a sensor for caspase 1 activation based on FRET) and SCAT3, respectively. These sensors have provided better understanding of pyroptosis and apoptosis
and
. However, there have been no biosensors to monitor necroptosis. Development of a FRET biosensor that monitors necroptosis and generation of transgenic mice expressing such FRET biosensor might be useful to understand the mechanisms underlying the execution of necroptosis and also the consequences of necroptosis
. In our recent study (Nat Commun, 9(1):4457), we developed a FRET biosensor for necroptosis, termed SMART (a sensor for MLKL activation by RIPK3 based on FRET). SMART is composed of a fragment of MLKL and monitors necroptosis, but not apoptosis or necrosis. Moreover, we recently developed a platform called Live-Cell Imaging for Secretion activity (LCI-S) to monitor protein secretion at the single cell level. This platform has enabled us to monitor the release of HMGB1 (High Mobility Group Box 1), one of the DAMPs, at the single cell level and reveals two different modes of the release of HMGB1 from necroptotic cells.
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