Levels Of Receptor-interacting Protein Kinase 3 Research Articles

Receptor-interacting protein kinase-3 (RIPK3): a new biomarker for necrotising enterocolitis in preterm infants

ObjectiveThis study aimed to evaluate the role of receptor-interacting protein kinase-3 (RIPK3) in the diagnosis, estimation of disease severity, and prognosis of premature infants with necrotising enterocolitis (NEC).MethodsRIPK3, lactic acid (LA), and C-reactive protein (CRP) levels were measured in the peripheral blood of 108 premature infants between 2019 and 2023, including 24 with stage II NEC, 18 with stage III NEC and 66 controls. Diagnostic values of the indicators for NEC were evaluated via receiver operating characteristic (ROC) curve analysis.ResultsPlasma RIPK3 and LA levels upon NEC suspicion in neonates with stage III NEC were 32.37 ± 16.20 ng/mL. The ROC curve for the combination of RIPK3, LA, CRP for NEC diagnosis were 0.925. The time to full enteral feeding (FEFt) after recovery from NEC was different between two expression groups of plasma RIPK3 (RIPK3 < 20.06 ng/mL and RIPK3 ≥ 20.06 ng/mL).ConclusionPlasma RIPK3 can be used as a promising marker for the diagnosis and estimation of disease severity of premature infants with NEC and for the guidance on proper feeding strategies after recovery from NEC.

Analysis of the serum levels of RIP3 and Drp1 in patients with heart failure.

As necroptosis involving receptor-interacting protein kinase 3 (RIP3) and dynamin-related protein 1 (Drp1)-mediated signalling is a crucial mechanism of cell loss in heart failure (HF), we aimed to determine the potential diagnostic use of these molecules. The serum samples of the healthy subjects (n=8) and patients with HF with reduced ejection fraction (n=31), being subdivided according to the aetiology and New York Heart Association (NYHA) class, were used to measure RIP3 and Drp1 levels by enzyme-linked immunosorbent assay. Although the serum levels of Drp1 in the patients with HF were comparable with those seen in healthy individuals, we found a trend of increase in the levels of RIP3 (P=0.0697) in the diseased group. These changes were unlikely dependent on the HF aetiology or NYHA class. The circulating RIP3 correlated with neither the main parameters assessing cardiac function (left ventricular ejection fraction, left ventricular end-diastolic diameter, and N-terminal pro-brain natriuretic peptide) nor the marker of inflammation (C-reactive protein). In this pilot study, findings on serum RIP3 supported the importance of necroptosis in HF pathomechanisms. The potential diagnostic use of circulating RIP3, unlike Drp1, as an additional biomarker of HF has also been indicated; however, further large studies are needed to prove this concept.

Potential of circulating receptor-interacting protein kinase 3 levels as a marker of acute liver injury

The pathogenesis of acute liver failure (ALF) involves cell death. Necroptosis is a newly suggested programmed cell death, and receptor-interacting protein kinase 3 (RIPK3) has been reported as a marker for necroptosis. However, there are few reports on necroptosis in ALF. Therefore, we evaluated the role of cell death markers such as cytokeratin (CK) 18, cleaved CK (cCK) 18, and RIPK3 in ALF, as well as cytokines and hepatocyte growth factor (HGF). Seventy-one hospitalized patients with acute liver injury (38 nonsevere hepatitis [non-SH]/22 severe hepatitis [SH]/11 ALF) were studied. No significant difference was found for cytokines, but a substantial increase in HGF levels was found following the severity of hepatitis. The non-SH group had lower levels of CK18 and cCK18 than the SH/ALF group. RIPK3 was significantly lower in the non-SH/SH group than in the ALF group. HGF, RIPK3, and albumin levels were found to be important predictive variables. The present study suggests that cCK18, CK18, and RIPK3 are associated with the severity of hepatitis. RIPK3 and other markers related cell death may be useful for understanding the pathogenesis of ALF and as a prognostic marker of acute liver injury.

Oral ellagic acid attenuated LPS-induced neuroinflammation in rat brain: MEK1 interaction and M2 microglial polarization.

Ellagic acid, the marker component of peels of Punica granatum L., is known traditionally to treat traumatic hemorrhage. In this study, the cellular mechanism underlying ellagic acid-induced anti-inflammation was investigated using lipopolysaccharides (LPSs) as a neuroinflammation inducer. Our in vitro data showed that LPS (1 μg/mL) consistently phosphorylated ERK and induced neuroinflammation, such as elevation in tumor necrosis factor-α (TNF-α) and nitric oxide production in treated BV-2 cells. Incubation of ellagic acid significantly inhibited LPS-induced ERK phosphorylation and subsequent neuroinflammation in treated BV-2 cells. Furthermore, our in vivo study of neuroinflammation employed an intranigral infusion of LPS that resulted in a time-dependent elevation in phosphorylated ERK levels in the infused substantia nigra (SN). Oral administration of ellagic acid (100 mg/kg) significantly attenuated LPS-induced ERK phosphorylation. A four-day treatment of ellagic acid did not alter LPS-induced ED-1 elevation but ameliorated LPS-induced reduction in CD206 and arginase-1 (two biomarkers of M2 microglia). A seven-day treatment of ellagic acid abolished LPS-induced increases in heme-oxygenase-1, cyclo-oxygenase 2, and α-synuclein trimer levels (a pathological hallmark) in the infused SN. At the same time, ellagic acid attenuated LPS-induced increases in active caspase 3 and receptor-interacting protein kinase-3 levels (respective biomarkers of apoptosis and necroptosis) as well as reduction in tyrosine hydroxylase-positive cells in the infused SN. In silico analysis showed that ellagic acid binds to the catalytic site of MEK1. Our data suggest that ellagic acid is capable of inhibiting MEK1-ERK signaling and then attenuated LPS-induced neuroinflammation, protein aggregation, and programmed cell deaths. Moreover, M2 microglial polarization is suggested as a novel antineuroinflammatory mechanism in the ellagic acid-induced neuroprotection.

Z-DNA/RNA Binding Protein 1 Senses Mitochondrial DNA to Induce Receptor-Interacting Protein Kinase-3/Mixed Lineage Kinase Domain-Like-Driven Necroptosis in Developmental Sevoflurane Neurotoxicity

Developmental sevoflurane exposure leads to widespread neuronal cell death known as sevoflurane-induced neurotoxicity (SIN). Receptor-interacting protein kinase-3 (RIPK3) and mixed lineage kinase domain-like (MLKL)-driven necroptosis plays an important role in cell fate. Previous research has shown that inhibition of RIPK1 activity alone did not attenuate SIN. Since RIPK3/MLKL signaling could also be activated by Z-DNA/RNA binding protein 1 (ZBP1), the present study was designed to investigate whether ZBP1-mediated and RIPK3/MLKL-driven necroptosis is involved in SIN through in vitro and in vivo experiments. We found that sevoflurane priming triggers neuronal cell death and LDH release in a time-dependent manner. The expression levels of RIPK1, RIPK3, ZBP1 and membrane phosphorylated MLKL were also dramatically enhanced in SIN. Intriguingly, knockdown of RIPK3, but not RIPK1, abolished MLKL-mediated neuronal necroptosis in SIN. Additionally, inhibition of RIPK3-mediated necroptosis with GSK’872, rather than inhibition of apoptosis with zVAD, significantly ameliorated SIN. Further investigation showed that sevoflurane treatment causes mitochondrial DNA (mtDNA) release into the cytosol. Accordingly, ZBP1 senses cytosolic mtDNA and consequently activates RIPK3/MLKL signaling. This conclusion was reinforced by the evidence that knockdown of ZBP1 or depleting mtDNA with ethidium bromide remarkably improved SIN. Finally, the administration of the RIPK3 inhibitor GSK'872 relieved sevoflurane-induced spatial and emotional disorders without influence on locomotor activity. Altogether, these results illustrate that ZBP1 senses cytosolic mtDNA to induce RIPK3/MLKL-driven necroptosis in SIN. Elucidating the role of necroptosis in SIN will provide new insights into understanding the mechanism of anesthetic exposure in the developing brain.

RIPK3 dampens mitochondrial bioenergetics and lipid droplet dynamics in metabolic liver disease.

Receptor-interacting protein kinase 3 (RIPK3) mediates NAFLD progression, but its metabolic function is unclear. Here, we aimed to investigate the role of RIPK3 in modulating mitochondria function, coupled with lipid droplet (LD) architecture in NAFLD. Functional studies evaluating mitochondria and LD biology were performed in wild-type (WT) and Ripk3-/- mice fed a choline-deficient, amino acid-defined (CDAA) diet for 32 and 66 weeks and in CRISPR-Cas9 Ripk3 -null fat-loaded immortalized hepatocytes. The association between hepatic perilipin (PLIN) 1 and 5, RIPK3, and disease severity was also addressed in a cohort of patients with NAFLD and in PLIN1 -associated familial partial lipodystrophy. Ripk3 deficiency rescued impairment in mitochondrial biogenesis, bioenergetics, and function in CDAA diet-fed mice and fat-loaded hepatocytes. Ripk3 deficiency was accompanied by a strong upregulation of antioxidant systems, leading to diminished oxidative stress upon fat loading both in vivo and in vitro. Strikingly, Ripk3-/- hepatocytes displayed smaller size LD in higher numbers than WT cells after incubation with free fatty acids. Ripk3 deficiency upregulated adipocyte and hepatic levels of LD-associated proteins PLIN1 and PLIN5. PLIN1 upregulation controlled LD structure and diminished mitochondrial stress upon free fatty acid overload in Ripk3-/- hepatocytes and was associated with diminished human NAFLD severity. Conversely, a pathogenic PLIN1 frameshift variant was associated with NAFLD and fibrosis, as well as with increased hepatic RIPK3 levels in familial partial lipodystrophy. Ripk3 deficiency restores mitochondria bioenergetics and impacts LD dynamics. RIPK3 inhibition is promising in ameliorating NAFLD.

Preparation of the RIPK3 Polyclonal Antibody and Its Application in Immunoassays of Nephropathogenic Infectious Bronchitis Virus-Infected Chickens.

Receptor interacting protein kinase 3 (RIPK3) is a vital serine/threonine kinase in regulating the programmed destruction of infected cells to defend against RNA viruses. Although the role of RIPK3 in viruses in mice is well characterized, it remains unclear where in nephropathogenic infectious bronchitis virus (NIBV) in chickens. Here, we use a self-prepared polyclonal antibody to clarify the abundance of RIPK3 in tissues and define the contributions of RIPK3 in tissue damage caused by NIBV infection in chickens. Western blot analyses showed that RIPK3 polyclonal antibody can specifically recognize RIPK3 in the vital tissues of Hy-Line brown chicks and RIPK3 protein is abundantly expressed in the liver and kidney. Moreover, NIBV significantly upregulated the expression levels of RIPK3 in the trachea and kidney of chicks in a time-dependent manner. In addition, the activation of necroptosis in response to NIBV infection was demonstrated by the coimmunoprecipitation (CoIP) experiments through RIPK3 in the necrosome, which phosphorylates its downstream mixed-spectrum kinase structural domain-like protein (MLKL). Our findings offered preliminary insights into the key role of RIPK3 protein in studying the underlying mechanism of organ failure caused by NIBV infection.

Enterococcus faecalis-Induced Macrophage Necroptosis Promotes Refractory Apical Periodontitis.

ABSTRACTThe persistence of residual bacteria, particularly Enterococcus faecalis, contributes to refractory periapical periodontitis, which still lacks effective therapy. The role of receptor-interacting protein kinase 3 (RIPK3)- and mixed lineage kinase domain-like protein (MLKL)-mediated necroptosis, a highly proinflammatory form of regulated cell death, has recently drawn much attention. However, the role of necroptosis in the pathogenesis of refractory periapical periodontitis remains unclear. We investigated whether the RIPK3/MLKL signaling pathway was activated in periapical lesion specimens obtained from patients diagnosed with refractory periapical periodontitis. RIPK3-deficient mice were then used to determine the role of necroptosis under this condition in vivo. We found that the phosphorylation levels of RIPK3 and MLKL were elevated in periapical lesion specimens of patients with refractory periapical periodontitis. In addition, necroptosis was induced in an E. faecalis-infected refractory periapical periodontitis mouse model, in which inhibition of necroptosis by RIPK3 deficiency could markedly alleviate inflammation and bone destruction. Moreover, double-labeling immunofluorescence suggested that macrophage necroptosis may be involved in the development of refractory periapical periodontitis. Then, we established an in vitro macrophage infection model with E. faecalis. E. faecalis infection was found to induce necroptotic cell death in macrophages through the RIPK3/MLKL signaling pathway, which was markedly alleviated by the RIPK3- or MLKL-specific inhibitor. Our study revealed that RIPK3/MLKL-mediated macrophage necroptosis contributes to the development of refractory periapical periodontitis and suggests that inhibitors or treatments targeting necroptosis represent a plausible strategy for the management of refractory periapical periodontitis.IMPORTANCE Oral infectious diseases represent a major neglected global population health challenge, imposing an increasing burden on public health and economy. Refractory apical periodontitis (RAP), mainly caused by Enterococcus faecalis, is a representative oral infectious disease with considerable therapeutic challenges. The interplay between E. faecalis and the host often leads to the activation of programmed cell death. This study identifies an important role of macrophage necroptosis induced by E. faecalis in the pathogenesis of RAP. Manipulating RIPK3/MLKL-mediated necroptosis may represent novel therapeutic targets, not only for RAP but also for other E. faecalis-associated infectious diseases.

Upregulation of necroptosis markers RIPK3/MLKL and their crosstalk with autophagy-related protein Beclin-1 in primary immune thrombocytopenia

Necroptosis is a novel form of programmed necrotic cell death involved in various autoimmune diseases. The potential role of necroptosis in primary immune thrombocytopenia (ITP) and the possible interlink with autophagy have not been fully investigated. The gene expression of mixed lineage kinase-like domain (MLKL), receptor-interacting protein kinase 3 (RIPK3) and Beclin-1 were quantified in peripheral blood of 45 ITP patients and 20 healthy controls. Their associations with clinical, laboratory parameters and response to steroid therapy in ITP patients were evaluated. RIPK3, MLKL, and Beclin-1 were significantly upregulated in ITP patients than in healthy controls (P < 0.001). Beclin-1 mRNA levels were positively correlated with both RIPK3 and MLKL mRNA levels in ITP patients (P < 0.0001). In addition, MLKL, RIPK3, and Beclin-1 mRNA levels were inversely correlated with platelet count (r = −0.330, −0.527 and −0.608, respectively). On the hand, positive correlations between MLKL (P = 0.01), RIPK3 (P = 0.005), Beclin-1 (P = 0.002) mRNA levels and severity of bleeding in ITP patients were reported. Steroid responders (n = 18, 40%) had significantly lower MLKL, RIPK3, Beclin-1 mRNA expression levels than their levels in the non-responders (n = 27, 60%). Necroptosis may play a critical role in the pathogenesis of ITP and provide both novel therapeutic targets and promising biomarkers for the prediction of bleeding severity and treatment response in ITP patients. Additionally, this study highlighted the crosstalk between autophagy and necroptosis in ITP patients.Graphical abstract

RIP3 Translocation into Mitochondria Promotes Mitofilin Degradation to Increase Inflammation and Kidney Injury after Renal Ischemia-Reperfusion.

The receptor-interacting protein kinase 3 (RIP3) has been reported to regulate programmed necrosis–necroptosis forms of cell death with important functions in inflammation. We investigated whether RIP3 translocates into mitochondria in response to renal ischemia–reperfusion (I/R) to interact with inner mitochondrial protein (Mitofilin) and promote mtDNA release into the cytosol. We found that release of mtDNA activates the cGAS–STING pathway, leading to increased nuclear transcription of pro-inflammatory markers that exacerbate renal I/R injury. Monolateral C57/6N and RIP3−/− mice kidneys were subjected to 60 min of ischemia followed by either 12, 24, or 48 h of reperfusion. In WT mice, we found that renal I/R injury increased RIP3 levels, as well as its translocation into mitochondria. We observed that RIP3 interacts with Mitofilin, likely promoting its degradation, resulting in increased mitochondria damage and mtDNA release, activation of the cGAS–STING–p65 pathway, and increased transcription of pro-inflammatory markers. All of these effects observed in WT mice were decreased in RIP3−/− mice. In HK-2, RIP3 overexpression or Mitofilin knockdown increased cell death by activating the cGAS–STING–p65 pathway. Together, this study point to an important role of the RIP3–Mitofilin axis in the initiation and development of renal I/R injury.

RIP3 translocation into Mitochondria promotes Mitofilin degradation to increase inflammation and kidney injury after renal ischemia/reperfusion

Background. Acute kidney injury (AKI) is an independent risk factor for mortality and morbidity. Inflammation is now believed to play a major role in the pathophysiology of AKI. Receptor‐interacting protein kinase 3 (RIP3) is a member of the receptor‐interacting protein (RIP) family of serine/threonine protein kinases. RIP3 is a regulator of both programmed necrosis/necroptosis, an inflammatory form of cell death observed in pathogen‐induced and sterile inflammation, and TNFα‐induced apoptosis. In the induction of necroptosis, RIP3 is a major component of the tumor necrosis factor (TNF) receptor‐I signaling complex which through additional interactions with (RIP1) and pseudokinase mixed lineage kinase domain‐like protein (MLKL) forms the necrosome. More recently, RIP3 activity was found to promote sepsis‐induced AKI via mitochondrial dysfunction. Since I/R injury triggers numerous pathological changes, including apoptosis, oxidative stress, and inflammation, suggesting a role of mitochondrial function in RIP3‐dependent I/R injury.ObjectiveWe investigated whether RIP3 translocates into mitochondria in response to ischemia/reperfusion (I/R) to interact with Mitofilin and promote mitochondria damage that facilitates mtDNA release into the cytosol. We postulated that release of mtDNA activates cGAS/STING pathway leading to increased nuclear transcription of pro‐inflammatory markers that exacerbates renal I/R injury.Material and methods. C57/6N and RIP3‐/‐ mice as well as HK2 cells were used. Monolateral kidneys were subjected to 30 min of ischemia followed by either 12, 24, or 48 h of reperfusion. Protein levels of RIP3, Mitofilin, cGAS, STING, and p‐p65 were measured using Western and immunofluorescence analysis, while IL‐6, TNF‐α, and ICAM‐1 expressions as well as mtDNA release were assessed by qRT‐PCR, ELISA. Kidney function was measured by blood urea nitrogen and creatinine kits, and the interaction between RIP3 and Mitofilin was measured by Co‐Immunoprecipitation. In WT,Results. We found that renal I/R increased RIP3 levels, and its translocation into mitochondria. We observed that RIP3 interacts with Mitofilin likely promoting its degradation. While renal I/R associated with mitochondria damage, increased mtDNA release, activation of cGAS/STING/p65 pathway and increased transcription of pro‐inflammatory markers including IL‐6, TNF‐α and ICAM‐1, all these effects were decreased in RIP3‐/‐ mice. In HK‐2, RIP3 overexpression or Mitofilin knockdown increased cell death by activating the cGAS‐STING/p65 pathway.Conclusion. We demonstrated that kidney I/R increases RIP3 levels in the cytosol and it translocates into mitochondria, where it interacts with and promote Mitofilin degradation leading to increased mitochondrial structures damage and dysfunction. The subsequent increase in ROS production in mitochondria is postulated to facilitate mtDNA damage and release into the cytosol where it activates the cGAS/STING/p‐p65 pathway leading to amplified nuclear transcription of pro‐inflammatory markers that subsequently increase renal I/R injury. Together, this study point to an important role of RIP3 in the initiation and development of renal I/R injury.

Receptor-Interacting Protein Kinase 3 Inhibition Relieves Mechanical Allodynia and Suppresses NLRP3 Inflammasome and NF-κB in a Rat Model of Spinal Cord Injury.

BackgroundNeuroinflammation is critical in developing and maintaining neuropathic pain after spinal cord injury (SCI). The receptor-interacting protein kinase 3 (RIPK3) has been shown to promote inflammatory response by exerting its non-necroptotic functions. In this study, we explored the involvement of RIPK3 in neuropathic pain after SCI.MethodsThoracic (T10) SCI rat model was conducted, and the mechanical threshold in rats was measured. The expressions of RIPK3, nod-like receptor family pyrin domain-containing protein 3 (NLRP3), caspase-1, and nuclear factor-κB (NF-κB) were measured with western blotting analysis or quantitative real-time polymerase chain reaction (qRT-PCR). Double immunofluorescence staining was used to explore the colabeled NLRP3 with NeuN, glial fibrillary acidic protein (GFAP), and ionized calcium-binding adapter molecule 1 (IBA1). In addition, enzyme-linked immunosorbent assay (ELISA) was applied to analyze the levels of proinflammatory factors interleukin 1 beta (IL-1β), interleukin 18 (IL-18), and tumor necrosis factor alpha (TNF-α).ResultsThe expression of RIPK3 was elevated from postoperative days 7–21, which was consistent with the development of mechanical allodynia. Intrathecal administration of RIPK3 inhibitor GSK872 could alleviate the mechanical allodynia in SCI rats and reduce the expression levels of RIPK3. The activation of NLRP3 inflammasome and NF-κB was attenuated by GSK872 treatment. Furthermore, immunofluorescence suggested that NLRP3 had colocalization with glial cells and neurons in the L4–L6 spinal dorsal horns. In addition, GSK872 treatment reduced the production of inflammatory cytokines.ConclusionOur findings indicated that RIPK3 was an important facilitated factor for SCI-induced mechanical allodynia. RIPK3 inhibition might relieve mechanical allodynia by inhibiting NLRP3 inflammasome, NF-κB, and the associated inflammation.

Plasma levels of receptor-interacting protein kinase 3 is associated with postoperative acute kidney injury in acute DeBakey type I aortic dissection

BackgroundPostoperative acute kidney injury (AKI) in acute DeBakey type I aortic dissection (ADIAD) is common but has unclear pathogeneses and limited treatments. Receptor-interacting protein kinase 3 (RIP3), a mediator of necroptosis, is associated with human sepsis-induced and posttraumatic AKI, but its role in human postoperative AKI in ADIAD remains unclear. We assumed that RIP3 levels is associated with postoperative AKI in ADIAD.MethodsPlasma samples and the clinical data of continuous patients with ADIAD were collected prospectively. The patients were divided into three groups according to AKI stage postoperatively. The plasma RIP3 levels were compared among the groups, and the relationship between RIP3 and serum creatinine (sCr), inflammatory cytokines as well as clinical results were analyzed.ResultsEighty patients were enrolled. The postoperative and elevated RIP3 levels among the three groups were significantly different (P < 0.0001), both with a positive trend across the AKI stage (P for trend < 0.001), and they were also independent risk factors for postoperative AKI in ADIAD (OR = 1.018 and 1.026, P < 0.05). The postoperative RIP3 levels were positively correlated with the aortic crossclamp time (R = 0.253, P < 0.05); the peak values of sCr, procalcitonin, interleukin-6 and lactate postoperatively; the mechanical ventilation time; and the ICU stay time (R = 0.66, 0.369, 0.409, 0.397, 0.474 and 0.435, respectively; all P < 0.001). Plasma RIP3 level and sCr were comparable in diagnosing postoperative AKI in ADIAD (P = 0.898), and higher postoperative RIP3 level was associated with lower survival rate.ConclusionThe plasma RIP3 levels are associated with postoperative AKI, inflammatory response and clinical outcomes in ADIAD.

RIPK3-Dependent Necroptosis Activates MCP-1-Mediated Inflammation in Mice after Intracerebral Hemorrhage

BackgroundRecent studies have reported that receptor-interacting protein kinase 3 (RIPK3)-dependent necroptosis is related to the pathological process of intracerebral hemorrhage (ICH). Some studies support the view that inhibiting necroptosis is a key mechanism preventing inflammation. Inflammation is a crucial factor contributing to neurological injuries and unfavorable outcomes after ICH. The aim of this study was to clarify the association between necroptosis and monocyte chemoattractant protein-1 (MCP-1)-mediated inflammation and identify a new target for the treatment of ICH. Methods: An ICH model was established in C57BL/6 mice by injecting collagenase IV into the right basal ganglia. The RIPK3 inhibitor GSK872 was administered through intraventricular injection. Then, we assessed brain edema and neurobehavioral function. Western blotting was employed to detect changes in RIPK3, phospho-mixed lineage kinase domain-like protein (p-MLKL), MCP-1, phospho-c-Jun N-terminal kinase (p-JNK) and interleukin 6 (IL-6) levels in the brain tissue. The localization of RIPK3 and MCP-1 was observed using immunofluorescence staining. Co-immunoprecipitation was performed to determine the interaction between RIPK3 and MCP-1. Results: Compared with the sham group, the levels of RIPK3, p-MLKL, MCP-1, p-JNK and IL-6 were increased post-ICH. GSK872 pretreatment significantly reduced RIPK3, p-MLKL, MCP-1, p-JNK and IL-6 expression, accompanied by mitigated cerebral edema and neurobehavioral defects. RIPK3 and MCP-1 colocalized in the perinuclear region after ICH. We detected the formation of the RIPK3-MCP-1 complex in ICH brain tissue. Conclusions: There exerted an association between RIPK3 and MCP-1. The inhibition of RIPK3 alleviated MCP-1-mediated inflammation following ICH.

Quyu Shengxin Decoction Alleviates DSS-Induced Ulcerative Colitis in Mice by Suppressing RIP1/RIP3/NLRP3 Signalling.

Purpose To study the therapeutic effect of Quyu (QY) Shengxin (SX) decoction (QYSXD) in mice with dextran sulfate sodium- (DSS-) induced ulcerative colitis and to investigate the effects of QYSXD on the regulation of the receptor-interacting protein kinase 1 (RIP1)/receptor-interacting protein kinase 3 (RIP3)/nucleotide-binding oligomerization domain-like receptor family pyrin domain protein 3 (NLRP3) signaling pathway. Method Thirty-six mice were randomly divided into the following 6 groups: the experimental group (QYSX group), the model group (DSS group), the positive control group (5-aminosalicylic acid (5-ASA) group), the control group, the first component group (QY group), and the second component group (SX group). Each group included 6 mice. Ulcerative colitis (UC) was induced in the mice by providing 3.5% DSS in drinking water. The mice were weighed every day to evaluate the disease activity index (DAI). After 7 days, the mice were sacrificed, and colonic tissues were obtained for colon length measurement. The morphological changes in the colon and the pathological scores of the mice in each group were observed by hematoxylin-eosin (HE) staining. The messenger ribonucleic acid (mRNA) and protein expression levels of RIP1, RIP3, dynamin-related protein 1 (Drp1), NLRP3, cysteinyl aspartate specific proteinase-1 (caspase-1), interleukin (IL)-1β, and IL-18 in the colon tissues of the mice in each group were detected and compared by real-time quantitative reverse transcription PCR (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA). The levels of RIP1, RIP3, NLRP3, IL-1β, and IL-8 in the colonic mucosa were detected by ELISA. Western blotting was used to compare the protein expression of Drp1, caspase-1, mitochondrial fission protein 1 (FIS1), and mitophagy-associated protein light chain 3a/b (LC3a/b) among groups. The levels of reactive oxygen species (ROS) in the colonic mucosal cells were compared by immunofluorescence. Results Compared with those in the DSS group, the mice with DSS-induced colitis in the QYSX group exhibited clearly higher body weights (P < 0.05) and DAI scores (P < 0.05). The colon lengths of the mice in the QYSX group were longer than those in the DSS group (P < 0.05), and the pathological score of the QYSX group was lower than that of the DSS group (P < 0.05). The RIP1, RIP3, Drp1, IL-1β, IL-18, and caspase-1 mRNA levels in the QYSX, 5-ASA, SX, and QY groups were significantly lower than those in the DSS group (P < 0.05), but there were no differences between the QYSX group and the 5-ASA group. The levels of RIP1, RIP3, NLRP3, IL-1β, and IL-18 in the QYSX group were lower than those in the DSS group (P < 0.01). The levels of Drp1, caspase-1, FIS1, and LC3a/b in the QYSX group and the 5-ASA group were lower than those in the DSS group (P < 0.05). The levels of ROS in the colonic mucosal cells in the QYSX, 5-ASA, and QY groups were lower than those in the DSS group (P < 0.05). Conclusion QYSXD has certain therapeutic effects on DSS-induced colitis in mice and may be as effective as 5-ASA. QY and SX decoctions also have certain effects on colitis; however, these decoctions are not as beneficial as QYSXD. QYSXD may ameliorate colitis by inhibiting the expression of RIP1/RIP3/NLRP3 pathway-related proteins and reversing mitochondrial dysfunction to control inflammation.

RIP3/MLKL pathway-regulated necroptosis: A new mechanism of paclitaxel-induced peripheral neuropathy.

Paclitaxel (PTX) chemotherapy treatment often leads to neuropathic pain, which is resistant to available analgesic treatments. Death of cells and neuroinflammatory response are associated with PTX-induced peripheral neuropathy (PIPN). Necroptosis is a form of regulated necrotic cell death that accompanies strong inflammatory response. It is mediated by receptor-interacting protein kinase 3 (RIP3) and mixed-lineage kinase domain-like protein (MLKL), which contribute to the pathogenesis of several neurodegenerative diseases. Nevertheless, the role of necroptosis in PIPN remains unexplored. The aim of this study was to investigate the role of necroptosis in PIPN using its antagonists (necrostatin-1 and Nec-1). The quartic PTX administration (accumulated dose: 8 mg/kg, ip) in rats induced robust hyperalgesia and allodynia with significant cell necrosis and an increase in proinflammatory cytokines in the dorsal root ganglion (DRG). PTX application also increased RIP3 and MLKL protein levels in DRG, which were primarily in neurons. Moreover, it also promoted satellite glial cells (SGCs) activation, as assayed by glial fibrillary acidic protein (GFAP) upregulation. All these PTX-induced changes were prevented by the Nec-1 treatment. When taken together, the present study indicated that RIP3/MLKL pathway-regulated neuronal necroptosis, which promoted an inflammatory cascade reaction in DRG, might be a new mechanism of PIPN.

Enhanced RIPK3 kinase activity-dependent lytic cell death in M1 but not M2 macrophages

Macrophages play a crucial role in host innate immune defense against infection and tissue injury. Macrophages are highly plastic cells and their subtypes have been characterized as M1 (also termed classically activated) and M2 (alternatively activated). Although the M1/M2 paradigm has been well documented, less is known regarding the role of macrophage activation/polarization in inflammation-associated necrotic cell death. To address this gap in current knowledge, we prepared bone marrow-derived macrophages, induced them to M1 or M2 subtypes, and then investigated the expression of necroptosis signaling molecules and macrophage subtype-dependent responses to different necroptosis inducers. We found that necroptosis effector mixed lineage kinase domain-like protein (MLKL) and the key necroptosis regulator Z-DNA/RNA binding protein 1 were predominantly induced in M1 but not M2 macrophages. Interestingly, the protein but not mRNA levels of receptor-interacting protein kinase-3 (RIPK3) were also upregulated in M1 macrophages. We further found that macrophage necrotic cell death, the releases of lactate dehydrogenase and dead cell proteases as well as MLKL phosphorylation at Ser345 in response to various necroptosis inducers were greatly augmented in M1 but not M2 macrophages, and the accelerated effects were blocked by two structurally distinct specific RIPK3 inhibitors GSK872 or GSK843. Thus, our findings demonstrate that M1 but not M2 subtypes of macrophages are more susceptible to inflammation-related lytic cell death in an RIPK3 kinase activity-dependent manner.

RAGE interacts with the necroptotic protein RIPK3 and mediates transfusion-induced danger signal release.

RBC transfusion is associated with increased morbidity and mortality in critically ill patients. Endothelial cell necroptosis and subsequent damage-associated molecular pattern (DAMP) release has been identified as a mechanism of injury following RBC transfusion. Mounting evidence implicates the pro-inflammatory pattern recognition receptor, Receptor for Advanced Glycation End Products (RAGE), in initiating cell death programmes such as necroptosis. Here, we demonstrate the role of RAGE in endothelial necroptosis, as deletion of RAGE attenuates necroptotic cell death in response to TNFα, LPS or CpG-DNA. We show direct interaction of RAGE with the critical mediator of necroptosis, Receptor Interacting Protein Kinase 3 (RIPK3), during necroptosis. Furthermore, we observe decreased plasma High Mobility Group Box 1 (HMGB1) and RIPK3 levels in RAGE deficient mice compared to WT mice post-transfusion, substantiating the role for RAGE in transfusion-induced DAMP release in vivo. Collectively, these findings underscore RAGE as an essential mediator of regulated necrosis and post-transfusion DAMP release. Further studies to understand the role of RAGE and the necroptotic pathway in transfusion-induced organ injury may offer key targets to mitigate transfusion-related risks, including the risk of ARDS, in susceptible hosts.

Association of Plasma Level of TNF-Related Apoptosis-Inducing Ligand with Severity and Outcome of Sepsis.

Recent studies have suggested that TNF-related apoptosis-inducing ligand (TRAIL) is associated with mortality in sepsis, possibly through necroptosis. The objective of this study was to analyze the association between the plasma level of TRAIL and sepsis severity and outcomes. Furthermore, the plasma level of TRAIL was compared to that of receptor-interacting protein kinase-3 (RIPK3), a key executor of necroptosis, to identify any correlation between TRAIL and necroptosis. Plasma levels of TRAIL and RIPK3 from consecutively enrolled critically ill patients were measured by ELISA. Of 190 study patients, 59 (31.1%) and 84 (44.2%) patients were diagnosed with sepsis and septic shock, respectively. There was a trend of decreased plasma level of TRAIL across the control, sepsis, and septic shock groups. For 143 patients with sepsis, patients with low plasma TRAIL were more likely to have septic shock and higher SAPS3 and SOFA scores. However, no difference in 28-day and 90-day mortalities was observed between the two groups. The plasma level of TRAIL was inversely associated with RIPK3 in patients with sepsis. Plasma levels of TRAIL increased over time on days three and seven, and were inversely associated with sepsis severity and RIPK3 level, but not with mortality.

Changes in plasma levels of RIPK1, RIPK3, and MLKL in patients with coronary atherosclerotic heart disease and its clinical predictive value.

Coronary atherosclerotic heart disease (CHD) is caused by coronary atherosclerosis, which leads to stenosis and even occlusion of the lumen, resulting in myocardial ischemia, and necrosis subsequently. Its prevalence has been high for a long time. The prevention and treatment of CHD are important. The study aimed to investigate the role of plasma levels of receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3), and mixed-lineage kinase domain-like protein (MLKL) in patients with CHD and its clinical predictive value. A total of 190 patients with CHD who were diagnosed by coronary angiography and 70 healthy subjects in cardiovascular department from September 2015 to May 2017 were enrolled in this study. Patients with CHD were assigned into 4 groups: Patients with stable angina pectoris (SAP, n=46), patients with unstable angina pectoris (UAP, n=56), patients with non-ST-segment elevation myocardial infarction (NSTEMI, n=42), and patients with ST-segment elevation myocardial infarction (STEMI, n=46). Patients with CHD were assigned into a single-vessel lesion group, a double-vessel lesion group, and a multi-vessel lesion group according to the results of coronary angiography, and the severity of coronary artery stenosis was determined by Gensini score. Plasma levels of RIPK1, RIPK3, and MLKL were measured by enzyme-linked immunosorbent assay (ELISA). The plasma levels of RIPK1, RIPK3, and MLKL in patients with CHD were significantly higher than those in the controls (P<0.05). The plasma levels of RIPK1, RIPK3, and MLKL in the UAP group were significantly higher than those in the SAP group (P<0.05). The plasma levels of RIPK1, RIPK3, and MLKL in NSTEMI and STEMI group were significantly higher than those in the UAP group (P<0.05). There was no significant difference between the NSTEMI group and STEMI group (P>0.05). The plasma levels of RIPK1, RIPK3 and MLKL were significantly increased with numbers of coronary artery lesions (P<0.05), which were positively correlated with Gensini scores. The multivariate logistic regression analysis showed that plasma levels of RIPK1, RIPK3, and MLKL were independent risk factors for severe coronary artery stenosis.The average period of follow-up was 24 months after hospital discharge. The patients were divided into 2 groups according to whether they had major adverse cardiovascular events (MACE). Compared with patient without MACE, patient with MACE had higher levels of RIPK1, RIPK3, and MLKL (P<0.05). Receiver operator characteristic (ROC) curve analysis showed that the area under curve of RIPK1 was 0.72 (P<0.001), the area under curve of RIPK3 was 0.83 (P<0.001), and the area under curve of MLKL was 0.75 (P<0.001). Plasma levels of RIPK1, RIPK3, and MLKL are closely related to CHD, and they have predictive value for the prognosis evaluation for patients with CHD.