RIPK3 Expression Research Articles

The Trend of ripk1/ripk3 and mlkl Mediated Necroptosis Pathway in Patients with Different Stages of Prostate Cancer as Promising Progression Biomarkers.

Programmed cell death is critical to maintain tissue homeostasis. Necroptosis, as well as apoptosis, has been considered as another form of regulated cell death which can be used as an effective way to overcome apoptosis-resistant tumor tissue growth. The aim of present study was to test whether or not ripk1, ripk3, or mlkl expression levels, as the key necroptotic modulators in different stages of prostate tumor growth. Sixty-seven prostate tissues representing histologically confirmed cancer were selected. The cancer samples were categorized into 4 different stages based on cellular differentiation, tumor growth rate, and extra tissue expansion to regional lymph nodes, average PSA levels, and tumor volume. RNA extraction, cDNA synthesis and quantitative real time PCR were done based on standard guidelines. No statistically significant changes in ripk1 expression showed in all three stages (stage II to IV). The expression pattern of ripk3 represented a remarkable elevation in early stage, while, predominantly repressed in final cancer stage (IV). Also, there has been a significant negative correlation between ripk3 gene expression and tumor size and PSA levels. We cannot exclude the importance of the key regulator proteins in development and progression of prevalent lethal disease like prostate cancer. The ripk1/ripk3 mediated necroptosis pathway is more activated in early stages of prostate cancer via induced ripk3 expression, while repressed during prostate cancer final stages. Also, the repression of ripk3 is related to elevation of both PSA levels and tumor volume which represented the tumor progression in final stages.

A dominant autoinflammatory disease caused by non-cleavable variants of RIPK1.

Activation of RIPK1 controls TNF-mediated apoptosis, necroptosis and inflammatory pathways1. Cleavage of human and mouse RIPK1 after residues D324 and D325, respectively, by caspase-8 separates the RIPK1 kinase domain from the intermediate and death domains. The D325A mutation in mouse RIPK1 leads to embryonic lethality during mouse development2,3. However, the functional importance of blocking caspase-8-mediated cleavage of RIPK1 on RIPK1 activation in humans is unknown. Here we identify two families with variants in RIPK1 (D324V and D324H) that lead to distinct symptoms of recurrent fevers and lymphadenopathy in an autosomal-dominant manner. Impaired cleavage of RIPK1 D324 variants by caspase-8 sensitized patients' peripheral blood mononuclear cells to RIPK1 activation, apoptosis and necroptosis induced by TNF. The patients showed strong RIPK1-dependent activation of inflammatory signalling pathways and overproduction of inflammatory cytokines and chemokines compared with unaffected controls. Furthermore, we show that expression of the RIPK1 mutants D325V or D325H in mouse embryonic fibroblasts confers not only increased sensitivity to RIPK1 activation-mediated apoptosis and necroptosis, but also induction of pro-inflammatory cytokines such as IL-6 and TNF. By contrast, patient-derived fibroblasts showed reduced expression of RIPK1 and downregulated production of reactive oxygen species, resulting in resistance to necroptosis and ferroptosis. Together, these data suggest that human non-cleavable RIPK1 variants promote activation of RIPK1, and lead to an autoinflammatory disease characterized by hypersensitivity to apoptosis and necroptosis and increased inflammatory response in peripheral blood mononuclear cells, as well as a compensatory mechanism to protect against several pro-death stimuli in fibroblasts.

ΜicroRNA‑421 participates in vitiligo development through regulating human melanocyte survival by targeting receptor‑interacting serine/threonine kinase 1.

Vitiligo is a common localized or generalized skin pigmentation disorder. Endoplasmic reticulum (ER) stress may be implicated in the development of vitiligo. microRNA-421 (miR-421) has been reported to be dysregulated in various human tumors. However, there is no report to date on the role of miR-421 in vitiligo development. The present study demonstrated that 3 µM tunicamycin (TM) increased the expression of the ER stress-related proteins protein kinase RNA-like endoplasmic reticulum kinase (PERK), α subunit of eukaryotic translation initiation factor 2 (eIF2α) and C/EBP homologous protein (CHOP) in human primary epidermal melanocytes. Moreover, TM suppressed melanocyte viability and induced apoptosis. Reverse transcription-quantitative PCR analysis demonstrated that TM promoted miR-421 expression in human melanocytes. Next, TargetScan and dual luciferase reporter gene assay indicated that receptor-interacting serine/threonine kinase 1 (RIPK1) was a direct target of miR-421. RIPK1 expression was significantly downregulated in TM-induced human melanocytes. Subsequently, the effect of miR-421 downregulation on the damage of human melanocytes induced by ER stress was investigated. Human melanocytes were transfected with inhibitor control, miR-421 inhibitor, miR-421 inhibitor + control-short hairpin (sh)RNA, or miR-421 inhibitor + RIPK1-shRNA for 24 h and then treated with TM (3 µM) for 48 h. TM was found to upregulate PERK, eIF2α and CHOP protein expression in human melanocytes, which was reduced by an miR-421 inhibitor. In addition, the miR-421 inhibitor increased viability and reduced apoptosis in TM-treated melanocytes. Furthermore, all these effects of the miR-421 inhibitor on TM-induced human melanocytes were reversed by RIPK1-shRNA. Further analyses revealed that the miR-421 inhibitor activated the phosphoinositide 3 kinase/protein kinase B/mammalian target of rapamycin signaling pathway in TM-induced human melanocytes. These data collectively suggest that miR-421 may serve as a new treatment target in vitiligo development.

Effect of the Sirtuin Inhibitor MC2494 on RIPK1 Expression

Laura Della Torre1, Angelita Poziello1, Federica Sarno1, Alessandro Paiardini2, Antonello Mai2, Dante Rotili2, Angela Nebbioso1*, Lucia Altucci1*° and Vincenzo Carafa1*° Author Affiliations 1Department of Precision Medicine, Italy 2Department of the Chemistry and Technology, Italy Received: November 26, 2019 | Published: December 04, 2019 Corresponding author: Angela Nebbioso, Lucia Altucci and Vincenzo Carafa, Department of Precision Medicine, University of Campania “Luigi Vanvitelli”, 80138 Napoli, Italy °Co-last authors DOI: 10.26717/BJSTR.2019.23.003920

Retinal Ganglion Cells Die by Necroptotic Mechanisms in a Site-Specific Manner in a Rat Blunt Ocular Injury Model.

Closed-globe injury can cause visual loss in military and civilian populations, with retinal cell death, including retinal ganglion cell (RGC) degeneration, leading to irreversible blindness. RGC and optic nerve (ON) degeneration after eye or head injury is termed traumatic optic neuropathy (TON). There are currently no treatments for RGC loss, therefore novel therapeutics to prevent RGC death or promote axonal regeneration are a priority. We investigated necroptotic signaling mechanisms in a rat blunt ocular injury model. After bilateral blunt trauma, protein expression and retinal localization of necroptosis pathway members (receptor interacting protein kinase 1, RIPK1; receptor interacting protein kinase 3, RIPK3; and mixed lineage kinase domain like pseudokinase, MLKL) were assessed by Western blot and immunohistochemistry (IHC), and potent necroptosis inhibitor Necrostatin-1s (Nec-1s) was delivered by intravitreal injection to one eye and vehicle to the contralateral eye. RGC and photoreceptor survival were assessed by cell counting and outer nuclear layer (ONL) thickness measurements on histology. The neuroprotective effects of Nec-1s were assessed in primary retinal culture by βIII-tubulin+ RGC cell counts. MLKL protein expression were upregulated at 48 h after injury and MLKL immunolocalised to retinal binding protein with multiple splice (RBPMS)+ RGC, inner nuclear cells and ONL cells, specifically at the retinal injury site. RIPK3 expression did not increase but RIPK3 co-immunolocalised with RBPMS+ RGC in intact and injured retinae. In vitro, a Nec-1s concentration of 0.01 pg/µL was RGC neuroprotective. In the blunt ocular injury rat model, Nec-1s prevented RGC death at the center of the impact site but did not protect against ONL thinning or provide functional restitution. RGC degeneration in our blunt ocular injury model is site-specific, with necroptosis driving death at the center of the focal impact site.

Effects of prostaglandin F2\u03b1 (PGF2\u03b1) on cell-death pathways in the bovine corpus luteum (CL)

BackgroundProstaglandin F2α (PGF2α) may differentially affect viability of luteal cells by inducing either proliferation or cell death (via apoptosis or necroptosis). The diverse effects of PGF2α may depend on its local vs. systemic actions. In our study, we determined changes in expression of genes related to: (i) apoptosis: caspase (CASP) 3, CASP8, BCL2 associated X (BAX), B-cell lymphoma 2 (BCL2) and (ii) necroptosis: receptor-interacting protein kinase (RIPK) 1, RIPK3, cylindromatosis (CYLD), and mixed lineage kinase domain-like (MLKL) in the early and mid-stage corpus luteum (CL) that accompany local (intra-CL) vs. systemic (i.m.) analogue of PGF2α (aPGF2α) actions. Cows at day 4 (n = 24) or day 10 (n = 24) of the estrous cycle were treated by injections as follows: (1) systemic saline, (2) systemic aPGF2α (25 mg; Dinoprost), (3) local saline, (4) local aPGF2α (2.5 mg; Dinoprost). After 4 h, CLs were collected by ovariectomy. Expression levels of mRNA and protein were investigated by RT-q PCR, Western blotting and immunohistochemistry, respectively.ResultsWe found that local and systemic administration of aPGF2α in the early-stage CL resulted in decreased expression of CASP3 (P < 0.01), but CASP8 mRNA expression was up-regulated (P < 0.05). However, the expression of CASP3 was up-regulated after local aPGF2α treatment in the middle-stage CL, whereas systemic aPGF2α administration increased both CASP3 and CASP8 expression (P < 0.01). Moreover, we observed that both local and systemic aPGF2α injections increased RIPK1, RIPK3 and MLKL expression in the middle-stage CL (P < 0.05) while CYLD expression was markedly higher after i.m. aPGF2α injections (P < 0.001). Moreover, we investigated the localization of necroptotic factors (RIPK1, RIPK3, CYLD and MLKL) in bovine CL tissue after local and systemic aPGF2α injections in the bovine CL.ConclusionOur results demonstrated for the first time that genes related to cell death pathways exhibit stage-specific responses to PGF2α administration depending on its local or systemic actions. Locally-acting PGF2α plays a luteoprotective role by inhibiting apoptosis and necroptosis in the early CL. Necroptosis is a potent mechanism responsible for structural CL regression during PGF2α-induced luteolysis in cattle.

Effect of propofol on H2O2-induced necroptosis in rat cardiomyocytes

Objective To evaluate the effect of propofol on H2O2-induced necroptosis in rat cardiomyocytes. Methods H9C2 cells at the logarithmic growth phase were divided into 4 groups (n= 9 each) using a random number table method: control group (group C), H2O2 group, propofol group (group P) and dimethyl sulfoxide group (group D). Cells were incubated in normal DMEM medium in group C. H2O2 was added to the culture medium with the final concentration of 500 μmol/L in group H2O2.Propofol at the final concentration of 50 μmol/L and the equal volume of dimethyl sulfoxide were added to the cell medium at 30 min before H2O2 exposure in group P and group D, respectively.After 12-h culture or incubation with H2O2, cardiomyocytes necrosis was detected by PI staining, reactive oxygen species (ROS) level was determined by DCFH-DA staining, and the expression of receptor-interacting serine/threonine-protein kinase 1 (RIPK1), RIPK3 and mixed lineage kinase domain-like protein (MLKL) was determined by Western blot. Results Compared with group C, necrosis rate and ROS level were significantly increased, and the expression of RIPK1, RIPK3 and MLKL was up-regulated in H2O2 and D groups (P<0.05). Compared with group H2O2, necrosis rate and ROS level were significantly decreased, and the expression of RIPK1, RIPK3 and MLKL was down-regulated in group P (P<0.05). Conclusion Propofol can attenuate H2O2-induced necroptosis in cardiomyocytes of rats. Key words: Propofol; Hydrogen peroxide; Myocytes, cardiac; Necroptosis

Effect of dexmedetomidine on necroptosis during intestinal injury in rats undergoing autologous orthotopic liver transplantation

Objective To evaluate the effect of dexmedetomidine on necroptosis during intestinal injury in rats undergoing autologous orthotopic liver transplantation (AOLT). Methods Twenty-four SPF adult male Sprague-Dawley rats, aged 8-10 weeks, weighing 250-280 g, were divided into 3 groups (n=8 each) using a random number table method: sham operation group (group S), AOLT group (group T) and dexmedetomidine group (group D). Dexmedetomidine 50 μg/kg was intraperitoneally injected at 30 min before surgery in group D. Blood samples were collected from the inferior vena cava at 6 h after opening the hepatic portal vein (at 6 h after the end of surgery in group S) for determination of serum diamine oxidase (DAO), D-lactic acid (D-LA) and tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10) concentrations.The intestine was removed for examination of the pathological changes (with a light microscope) and for determination of the level of malondialdehyde (MDA) content and superoxide dismutase (SOD) activity (using spectrophotometry) and expression of receptor-interacting protein kinase-1 (RIPK1), RIPK3, and mixed lineage kinase domain-like (MLKL) in intestinal tissues (by Western blot). Intestinal damage was assessed and scored according to Chiu. Results Compared with group S, the serum DAO, D-LA, TNF-α and IL-10 concentrations, intestinal MDA content and Chiu′s score were significantly increased, the SOD activity was decreased, and the expression of RIPK1, RIPK3 and MLKL was up-regulated in group T (P<0.05). Compared with group T, the serum DAO, D-LA and TNF-α concentrations, intestinal MDA content and Chiu′s score were significantly decreased, the SOD activity and serum IL-10 concentration were increased, and the expression of RIPK1, RIPK3 and MLKL was down-regulated in group D (P<0.05). Conclusion The mechanism by which dexmedetomidine attenuates intestinal injury is related to inhibiting necroptosis in rats undergoing AOLT. Key words: Dexmedetomidine; Liver transplantation; Intestine; Necrosis

Necroptosis is dispensable for motor neuron degeneration in a mouse model of ALS.

Motor neuron degeneration in amyotrophic lateral sclerosis (ALS) is proposed to occur by necroptosis, an inflammatory form of regulated cell death. Prior studies implicated necroptosis in ALS based on accumulation of necroptotic markers in affected tissues of patients and mouse models, and amelioration of disease in mutant superoxide dismutase 1 (SOD1G93A) mice with inhibition of the upstream necroptotic mediators, receptor interacting protein kinase 1 (RIPK1), and RIPK3. To definitively address the pathogenic role of necroptosis in ALS, we genetically ablated the critical terminal executioner of necroptosis, mixed lineage kinase domain-like protein (MLKL), in SOD1G93A mice. Disease onset, progression, and survival were not affected in SOD1G93A mice lacking MLKL. Motor neuron degeneration and activation of neuroinflammatory cells, astrocytes, and microglia, were independent of MLKL expression in SOD1G93A mice. While RIPK1 accumulation occurred in spinal cords of SOD1G93A mice in late stage disease, RIPK3 and MLKL expression levels were not detected in central nervous system tissues from normal or SOD1G93A mice at any disease stage. These findings demonstrate that necroptosis does not play an important role in motor neuron death in ALS, which may limit the potential of therapeutic targeting of necroptosis in the treatment of neurological disorders.

Di-(2-ethyl hexyl) phthalate induces necroptosis in chicken cardiomyocytes by triggering calcium overload

Di-(2-ethyl hexyl)phthalate (DEHP) is a kind of plasticizer that can cause cardiovascular disorders in animals, but its specific mechanism of action has not been determined. We aimed to investigate whether taxifolin (TAX) can antagonize the cytotoxicity of DEHP on cardiomyocytes. Chicken cardiomyocytes were treated with DEHP (500 μM) and/or TAX (0.5 μM) for 24 h. Ca2+ staining showed that the concentration of Ca2+ in the cytoplasm of cardiomyocytes was significantly increased under DEHP stimulation. However, in the DEHP + TAX group, the Ca2+ concentration was largely restored. In addition, the results of necroptosis--fluorescent and flow cytometry analysis showed that the DEHP group had severe necroptosis compared with the control group. The necrotic rate in the DEHP + TAX group was significantly lower than that in the DEHP group. At the mRNA and protein levels, the expression of the necrotic-calcium pathway genes RIPK1, RIPK3, MLKL, FAS, Caspase-8, CAMKII, and SERCA in the DEHP group increased to varying degrees relative to the control group. However, TAX improved this injury. Compared with the DEHP group, the expression of these genes was significantly decreased in the DEHP + TAX group. The present study indicate that DEHP could trigger cardiomyocyte necroptosis through Ca2+ overload, which could be alleviated by TAX.

Transcriptomic Analysis Implicates Necroptosis in Disease Progression and Prognosis in Myelodysplastic Syndromes

INTRODUCTION: Myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis and cytopenias due to uncontrolled programmed cell death. The presence of pro-inflammatory cytokines and constitutive activation of innate immunity signals in MDS cells suggest inflammatory cell death, such as necroptosis, may be responsible for disease phenotype. There is no data evaluating the association of RIPK1, RIPK3 and MLKL with response and prognosis in MDS. METHODS: We evaluated 64 bone marrow samples from 55 patients with MDS or chronic myelomonocytic leukemia (CMML) obtained prior to (n=46) or after (n=18) therapy with hypomethylating agents (HMAs). RNA from sorted bone marrow CD34+ cells was isolated and subject to amplification and RNA-seq. Gene co-expression was evaluated using Spearman correlation. Pathway enrichment analysis was performed using gene set enrichment analysis, with the fgsea library in R. Sequencing data was obtained by use of a 81-gene targeted PCR-based next generation sequencing (NGS) platform. Previously described somatic mutations registered at the Catalogue of Somatic Mutations in Cancer (COSMIC: http://cancer.sanger.ac.uk/cosmic) were considered as potential driver mutations. RESULTS: Compared to healthy controls, MLKL (CMML vs controls: 2.09 log2FC, p=0.0013; MDS vs control: 1.89 log2FC, p=0.003), but not RIPK1 or RIPK3, were significantly upregulated in patients with MDS and CMML (Figure 1A-C). No differences in the level of expression of RIPK1, MLKL or RIPK3 were observed based on the mutation context or burden. No significant difference in RIPK1, RIPK3 or MLKL expression levels was observed based on presence of cytogenetic abnormalities (RIPK1: 0.10 log2FC, p=0.6; RIPK3: -0.39 log2FC, p=0.40; MLKL: 0.34 log2FC, p=0.30). Higher expression levels of MLKL were associated with lower hemoglobin levels at the time of diagnosis (-0.19 log2FC per 1g/dL increase of Hgb, p=0.03) (Figure 1D). Exposure to HMA therapy was associated with a trend to decreased expression of MLKL (-0.52 log2FC, p=0.08) when all post-HMA therapy samples were evaluated. Among patient matched samples, significant reduction in MLKL levels was observed after HMA therapy (-1.06 log2FC, p=0.05). The degree of reduction in expression levels was greater among non-responders (-2.89 log2FC, p=0.06) compared to responders (-0.78, log2FC, p=0.06). Expression levels of RIPK1 at the time of diagnosis predicted for shorter survival for patients with high RIPK1 levels, defined as a log expression higher than median mRNA expression values, (median OS 10.7 vs 24.2 months, HR 1.92, 95% CI 1.00-3.67, p=0.049 by Cox proportional hazards) (Figure 1E). A multivariate analysis for overall survival using both IPSS-R risk and RIPK1 expression levels demonstrated that high RIPK1 expression was an independent adverse prognostic factor in MDS patients (HR 6.83, 95% CI 1.74-26.8, p=0.006). A total of 359 genes were significantly correlated with RIPK1 levels in MDS CD34+ cells (Spearman's method q&lt;0.2). Among these, 21 genes were positively correlated with RIPK1 expression, while 17 genes were negative correlated (Spearman's correlation, q&lt;0.1). Gene set enrichment analysis identified 373 gene sets that significantly correlated with RIPK1 expression. Upregulated genes were associated with molecular signals associated with innate immunity and inflammatory signaling including TNF-α signaling via NFkB, NFkB signaling, the IFN-g pathway, and RIG-I-like receptor (RLRs) signaling genes (Figure 1F). CONCLUSIONS: This data provides further support for a role of necroptosis in MDS, and potentially response to HMAs and prognosis. This data also indicates that RIPK1/RIPK3/MLKL are potential therapeutic targets in MDS. Figure 1 Disclosures Sasaki: Otsuka: Honoraria; Pfizer: Consultancy. Bueso-Ramos:Incyte: Consultancy. Kantarjian:Cyclacel: Research Funding; Jazz Pharma: Research Funding; AbbVie: Honoraria, Research Funding; Astex: Research Funding; Amgen: Honoraria, Research Funding; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Research Funding; Immunogen: Research Funding; Daiichi-Sankyo: Research Funding; Pfizer: Honoraria, Research Funding; Novartis: Research Funding; Ariad: Research Funding; Agios: Honoraria, Research Funding; Takeda: Honoraria. Garcia-Manero:Amphivena: Consultancy, Research Funding; Helsinn: Research Funding; Novartis: Research Funding; AbbVie: Research Funding; Celgene: Consultancy, Research Funding; Astex: Consultancy, Research Funding; Onconova: Research Funding; H3 Biomedicine: Research Funding; Merck: Research Funding.

R-2HG/KDM2B/RIPK1 Signaling Mediates Necroptosis in Myelodysplastic Syndromes

Introduction: Myelodysplastic syndromes (MDS) are a group of heterogeneous hematopoietic stem cell disorders and manifested as ineffective hematopoiesis, refractory cytopenia and a propensity to evolve into acute myeloid leukemia (AML). Isocitrate dehydrogenase 1/2 (IDH1/2) mutations are common in both MDS and AML. Mutated IDH produces R-2-hydroxyglutarate (R-2HG) which inhibits multiple α-ketoglutarate/α-KG-dependent dioxygenases by competing against α-KG binding. Recent studies have demonstrated that R-2-HG can abrogates leukemic growth and induce leukemia cell death. Several nonapoptotic cell death have been identified, including phosphoribosyl pyrophosphate (PPRP)-1 mediated necrosis, pyroptosis, ferroptosis and necroptosis. By now, the specific type of cell death by which R-2-HG exerts anti-tumor effects is still unknown. Results: (1) (2R)-Octyl-2-HG exhibited anti-tumor effect on SKM-1, THP-1, Molm-13, HL-60 cell lines and bone marrow mononuclear cells from MDS and AML patients in a dose- and time-dependent manner. The overexpression of IDH2 mutation induced by doxycycline significantly decreased the viability of AML cell lines, and the inhibition rate was related to the dose of doxycycline. (2R)-Octyl-2-HG promotes apoptosis and causes G0/G1 phase arrest. (2) R-2-HG leads to increased expression of RIPK1 in high-risk MDS cells. The results of gene enrichment analysis indicated that the apoptotic pathway was enriched in (2R)-Octyl-2-HG groups, and the expression of RIPK1 gene was increased in all three (SKM-1, NOMO-1 and MA9.3ITD) (2R)-Octyl-2-HG groups. After treatment with (2R)-Octyl-2-HG, the mRNA and protein expression levels of RIPK1 gene were increased. (3) R-2-HG triggers RIPK1-dependent necroptosis and occurs earlier than apoptosis. Within 10 hours after treatment with (2R)-Octyl-2-HG, cell membrane permeability was disrupted, interactions between RIPK1 and caspase 8 increased, as well as phosphorylated MLKL level. However, caspase activity did not increase significantly, suggesting that necroptosis occurs earlier than apoptosis. With RIPK1 inhibitor Necrostatin-1 and (2R)-Octyl-2-HG co-treating cells, proliferation inhibition was reduced, cell membrane permeability was more stable and RIPK1-caspase8 complex was difficult to form. The same phenomenon occurs in SKM-1 cells stably transfected with RIPK1 shRNA virus, suggesting that RIPK1-dependent necroptosis is involved in cell death caused by (2R)-Octyl-2-HG. (4) In vivo experiments demonstrated that necroptosis by R-2-HG is dependent on the expression of RIPK. In RIPK1 shRNA MDS mice, the tumor burden showed a decreasing trend, but did not show a significant change in the R-2-HG treatment group. Treatment of scramble shRNA MDS mice with R-2-HG resulted in significantly smaller tumors in the spleen and less engrafment of CD45+ cells in bone marrow. (5) Low RIPK1 expression predicts poor prognosis in MDS patients. Data from the TCGA and GEO public databases indicate that RIPK1 expression is reduced in MDS and AML patients compared to healthy controls. Survival analysis showed that patients with lower RIPK1 expression levels had significantly shorter overall survival (OS) than patients with higher RIPK1 expression levels. MDS patients with lower RIPK1 expression levels progress to leukemia more frequently. (6) Inhibition of KDM2B induces necroptosis independently. Western blot assay shows the knockdown of KDM2B, upregulation of RIPK1 and increased levels of p-MLKL. Analysis of cell numbers showed that proliferation ceased from 4 days after doxycycline treatment onwards in shKDM2B cells. Co-IP assay shows the formation of RIPK1-caspase8 complex. Conclusion: This study confirmed that R-2-HG inhibited the viability of MDS and AML cells. R-2-HG increased the expression of RIPK1 in MDS cells, inducing necroptosis. Necroptosis occurred earlier than apoptosis. Inhibition of RIPK1 can alleviate the inhibitory effect of R-2-HG on MDS and AML cells. Clinical studies have shown that low expression of the RIPK1 gene is associated with poor prognosis in patients with MDS and AML. MDS patients with low expression of RIPK1 was more likely to progress to leukemia. Inhibition of KDM2B can induce necroptosis independently. Disclosures No relevant conflicts of interest to declare.

Transcriptomic analysis implicates necroptosis in disease progression and prognosis in myelodysplastic syndromes.

Myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis and cytopenias due to uncontrolled programmed cell death. The presence of pro-inflammatory cytokines and constitutive activation of innate immunity signals in MDS cells suggest inflammatory cell death, such as necroptosis, may be responsible for disease phenotype. We evaluated 64 bone marrow samples from 55 patients with MDS or chronic myelomonocytic leukemia (CMML) obtained prior to (n=46) or after (n=18) therapy with hypomethylating agents (HMAs). RNA from sorted bone marrow CD34+ cells was isolated and subject to amplification and RNA-Seq. Compared to healthy controls, expression levels of MLKL (CMML: 2.09 log2FC, p=0.0013; MDS: 1.89 log2FC, p=0.003), but not RIPK1 or RIPK3, were significantly upregulated. Higher expression levels of MLKL were associated with lower hemoglobin levels at diagnosis (−0.19 log2FC per 1g/dL increase of Hgb, p=0.03). Significant reduction in MLKL levels was observed after HMA therapy (−1.06 log2FC, p=0.05) particularly among non-responders (−2.89 log2FC, p=0.06). Higher RIPK1 expression was associated with shorter survival (HR 1.92, 95% CI 1.00–3.67, p=0.049 by Cox proportional hazards). This data provides further support for a role of necroptosis in MDS, and potentially response to HMAs and prognosis. This data also indicates that RIPK1/RIPK3/MLKL are potential therapeutic targets in MDS.

Receptor-Interacting Protein Kinase 1 Promotes Cholangiocarcinoma Proliferation And Lymphangiogenesis Through The Activation Protein 1 Pathway.

PurposeReceptor-interacting protein kinase 1 (RIPK1) is an important upstream regulator of multiple cell signaling pathways including inflammatory signals. RIPK1 is reported to be closely associated with the prognostic implications of cancer, especially epithelial tumors. But its role in proliferation and lymphangiogenesis in cholangiocarcinoma (CCA) remains unclear and requires further investigation.Patients and methodsExpression of RIPK1 in human CCA tissues and CCA cell lines (QBC939, HUH28 and CCPL-1) was measured using qPCR, immunoblotting and immunohistochemistry. Silencing of RIPK1 was achieved by transduction of CCA cells via lentiviral plasmids (LV3-H1/GFP&Puro) encapsulating RIPK1 shRNA (LV-shRIPK1) or negative control shRNA (LV-shNC), and puromycin was used to select stable colonies. Proliferation and lymphangiogenesis were assessed in vitro by CCK-8 and matrigel-based tube formation assays, respectively. Activity of the activation protein-1 (AP-1) was evaluated by double-luciferase reporter gene assay. Protein expression of JNK, P38MAPK, ERK1/2, AP-1, P-AP-1, E-cadherin, N-cadherin and vascular endothelial growth factor-C (VEGF-C) was measured by immunoblotting or ELISA. An orthotopic CCA model in null mice was generated by transplanting QBC939 LV-shRIPK1, LV-shNC and control cells to further evaluate the role of RIPK1 on lymphangiogenesis in vivo. Immunohistochemistry was utilized to evaluate the expression of RIPK1 and VEGF-C, and tumor lymphatic vessels in the CCA model mice.ResultsUpregulated expression of RIPK1 in CCA tissues was closely related to tumor size, lymph node metastasis and poor prognosis. RIPK1 promoted proliferation and lymphangiogenesis in CCA cells, and regulated the activation of JNK and P38MAPK-mediated AP-1/VEGF-C pathway. Finally, in vivo animal experiments in the orthotopic CCA mouse model further confirmed the function of RIPK1 in lymphangiogenesis.ConclusionThis is the first report demonstrating the role of RIPK1 in proliferation and lymphangiogenesis through the MAPK (JNK and P38MAPK)- AP-1 pathway in CCA.

Caspase-8, receptor-interacting protein kinase 1 (RIPK1), and RIPK3 regulate retinoic acid-induced cell differentiation and necroptosis

Among caspase family members, Caspase-8 is unique, with associated critical activities to induce and suppress death receptor-mediated apoptosis and necroptosis, respectively. Caspase-8 inhibits necroptosis by suppressing the function of receptor-interacting protein kinase 1 (RIPK1 or RIP1) and RIPK3 to activate mixed lineage kinase domain-like (MLKL). Disruption of Caspase-8 expression causes embryonic lethality in mice, which is rescued by depletion of either Ripk3 or Mlkl, indicating that the embryonic lethality is caused by activation of necroptosis. Here, we show that knockdown of Caspase-8 expression in embryoid bodies derived from ES cells markedly enhances retinoic acid (RA)-induced cell differentiation and necroptosis, both of which are dependent on Ripk1 and Ripk3; however, the enhancement of RA-induced cell differentiation is independent of Mlkl and necrosome formation. RA treatment obviously enhanced the expression of RA-specific target genes having the retinoic acid response element (RARE) in their promoter regions to induce cell differentiation, and induced marked expression of RIPK1, RIPK3, and MLKL to stimulate necroptosis. Caspase-8 knockdown induced RIPK1 and RIPK3 to translocate into the nucleus and to form a complex with RA receptor (RAR), and RAR interacting with RIPK1 and RIPK3 showed much stronger binding activity to RARE than RAR without RIPK1 or RIPK3. In Caspase-8-deficient as well as Caspase-8- and Mlkl-deficient mouse embryos, the expression of RA-specific target genes was obviously enhanced. Thus, Caspase-8, RIPK1, and RIPK3 regulate RA-induced cell differentiation and necroptosis both in vitro and in vivo.

Integrin-Linked Kinase Deficiency in Collecting Duct Principal Cell Promotes Necroptosis of Principal Cell and Contributes to Kidney Inflammation and Fibrosis.

Necroptosis is a newly discovered cell death pathway that plays a critical role in AKI. The involvement of integrin-linked kinase (ILK) in necroptosis has not been studied. We performed experiments in mice with an Ilk deletion in collecting duct (CD) principal cells (PCs), and cultured tubular epithelial cells treated with an ILK inhibitor or ILK siRNA knockdown. Ilk deletion in CD PCs resulted in acute tubular injury and early mortality in mice. Progressive interstitial fibrosis and inflammation associated with the activation of the canonical TGF-β signaling cascade were detected in the kidneys of the mice lacking ILK in the CD PCs. In contrast to the minimal apoptosis detected in the animals' injured CDs, widespread necroptosis was present in ILK-deficient PCs, characterized by cell swelling, deformed mitochondria, and rupture of plasma membrane. In addition, ILK deficiency resulted in increased expression and activation of necroptotic proteins MLKL and RIPK3, and membrane translocation of MLKL in CD PCs. ILK inhibition and siRNA knockdown reduced cell survival in cultured tubular cells, concomitant with increased membrane accumulation of MLKL and/or phospho-MLKL. Administration of a necroptosis inhibitor, necrostatin-1, blocked cell death in vitro and significantly attenuated inflammation, interstitial fibrosis, and renal failure in ILK-deficient mice. The study demonstrates the critical involvement of ILK in necroptosis through modulation of the RIPK3 and MLKL pathway and highlights the contribution of CD PC injury to the development of inflammation and interstitial fibrosis of the kidney.

Fisetin, a phytopolyphenol, targets apoptotic and necroptotic cell death in HepG2 cells.

Fisetin (3,7,3',4'-tetrahydroxyflavone), a bioactive dietary flavonoid, intrigued scientists for its anticancer potential against various cancer types. We investigated the fisetin-induced inhibition of growth and survival of human hepatocellular carcinoma. Fisetin decreased cell viability and proliferation of HepG2 cells as revealed from MTT and clonogenicity assays. Cell cycle arrest in the G2/M phase was observed. Annexin V/propidium iodide (PI) staining followed by flow cytometry revealed that fisetin induced both apoptosis and necroptosis in HepG2 cells. Apoptotic cells were significantly increased on fisetin treatment as observed in morphological evaluations and 4',6-diamidino-2-phenylindole and Acridine orange staining. Flow cytometry, fluorescence imaging, and 2', 7'-dichlorofluorescein diacetate analyses showed an increase in reactive oxygen species (ROS) generation on fisetin treatment. Pretreatment with N-acetyl cysteine inhibited ROS production and also rescued mitochondrial membrane potential in HepG2 cells. The underlying mechanisms of apoptosis and necroptosis were determined by analysis of their respective signaling molecules using qRT-PCR and Western blotting. Fisetin showed a marked increase in the expression of TNFα and IKκB with a decrease in NF-κB, pNF-κB and pIKκB expression. Fisetin reduced the expression of Bcl2, and elevated levels of Bax, caspase-3, and PARP and thus induced apoptosis in HepG2 cells. zVAD suppressed the fisetin-induced expression of caspase-8, RIPK1, RIPK3, and MLKL as opposed to fisetin treatment. Nec-1 + fisetin could not completely block necroptosis, which warrants further investigation. Taken together, our findings demonstrate that the fisetin exhibited anti-proliferative effects on HepG2 cells through apoptosis and necroptosis via multiple signaling pathways. Fiestin has potential as a therapeutic agent against hepatocellular carcinoma.

Decreased RIPK1 expression in chondrocytes alleviates osteoarthritis via the TRIF/MyD88-RIPK1-TRAF2 negative feedback loop.

Osteoarthritis (OA) is the most common degenerative joint disease and involves the loss of articular cartilage integrity, formation of articular osteophytes, remodeling of subchondral bone, and synovitis. Knockdown of receptor interacting serine/threonine kinase (RIPK) 1 leads to anti-inflammatory and anti-apoptotic effects. However, the involvement of RIPK1 in the pathogenesis of OA is unclear. Here, we evaluated the effect of RIPK1 on chondrocytes and elaborated the underlying molecular mechanism. Knockdown of RIPK1 protected chondrocytes against inflammation and apoptosis induced by interleukin (IL)-1β in vitro and in vivo. RIPK1 was required for myeloid differentiation primary response 88 (MyD88)- and TIR-domain-containing adapter-inducing interferon b (TRIF)-mediated production of matrix metalloproteinases (MMPs) in OA. Moreover, overexpression of RIPK1 promoted the expression of tumor necrosis factor receptor-associated factor 2 (TRAF2), which blocked the expression and phosphorylation of RIPK1. Upregulation of TRAF2 decreased the expression of TRIF, MyD88, and MMPs in chondrocytes. Furthermore, knockdown of RIPK1 blocked activation of the nuclear factor-κB (NF-κB) and c-Jun N-terminal kinase (JNK) signaling pathways. In summary, knockdown of RIPK1 alleviated OA in a manner mediated by the TRIF/MyD88-RIPK1-TRAF2 negative feedback loop and activation of the NF-κB and JNK signaling pathways.

Fragile X mental retardation protein protects against tumour necrosis factor-mediated cell death and liver injury

ObjectiveThe Fragile X mental retardation (FMR) syndrome is a frequently inherited intellectual disability caused by decreased or absent expression of the FMR protein (FMRP). Lack of FMRP is associated with...

Zinc oxide nanoparticles induce necroptosis and inhibit autophagy in MCF-7 human breast cancer cells

Several studies have shown the toxic effect of zinc oxide nanoparticles (NZnO) on various cancer cells. This study aimed to assess the cellular death mechanism of the NZnO in MCF-7 human breast cancer cells. The cells were pretreated with zVAD (apoptosis inhibitor), 3-MA (an autophagy inhibitor), and Nec (a necroptosis inhibitor) for two hours, followed by their exposure to NZnO for 48 h. In the presence of Nec and 3-MA, NZnO significantly reduced proliferation and viability of MCF-7 cells while the apoptotic index and Bax/Bcl-2 ratio was significantly increased, compared to the only NZnO-treated cells. In the only NZnO-treated cells expression of Caspases-3 and Caspase-8 were up-regulated. NZnO with Nec and 3-MA could significantly increase expression of Caspase-3 and Caspase-9, but not Caspase-8 in the MCF-7 cells. NZnO in presence of zVAD and 3-MA significantly increased expression of RIPK1, RIPK3, and MLKL genes, compared to the only NZnO-treated cells. Furthermore, viability and proliferation of MCF-7 cells in NZnO with the apoptosis and autophagy inhbitors were lower than the other experimental groups. NZnO with apoptosis and necroptosis inhibitors could significantly increase cell viability, cell proliferation, and relative expression of autophagy-related genes such as LC3-II, Beclin-1, and ATG5, compared to the only NZnO-treated. According to the results of this study, the high toxicity of NZnO toward breast cancer cells mainly depends on activation of necroptosis and suppression of autophagy processes.