As a new type of cell death, necroptosis is initiated by tumor necrosis factor receptor 1(TNFR1), and then activated receptor-interacting protein kinase 1(RIP1) and receptor-interacting protein kinase 3 (RIP3), following by the activation of mixed lineage kinase domain-like protein(MLKL) to deliver cell death signal. When necroptosis happens, damage associated molecular patterns (DAMPs) enter into extracellular area through the ruptured cytomembrane, followed by the disordered tissue hemeostasis. In recent years, many researches showed that necroptosis playimportant roles in a few bone related diseases, such as osteoporosis, osteonecrosis, osteosarcoma, etc. Thus, we try to briefly review the researches in this field.
Apoptosis ; Necroptosis ; Protein Kinases

Necroptosis is one of the regulated cell death, which involves receptor interacting protein kinase (RIPK) 1/RIPK3/mixed lineage kinase domain like protein (MLKL) signaling pathway. Among them, MLKL is the final execution of necroptosis. The formation of RIPK1/RIPK3/MLKL necrosome induces the phosphorylated MLKL, and the activated MLKL penetrates into the membrane bilayer to form membrane pores, which damages the integrity of the membrane and leads to cell death. In addition to participating in necroptosis, MLKL is also closely related to other cell death, such as NETosis, pyroptosis, and autophagy. Therefore, MLKL is involved in the pathological processes of various diseases related to abnormal cell death pathways (such as cardiovascular diseases, neurodegenerative diseases and cancer), and may be a therapeutic target of multiple diseases. Understanding the role of MLKL in different cell death can lay a foundation for seeking various MLKL-related disease targets, and also guide the development and application of MLKL inhibitors.
Protein Kinases/metabolism* ; Necroptosis/physiology* ; Receptor-Interacting Protein Serine-Threonine Kinases ; Signal Transduction ; Pyroptosis ; Apoptosis

Acute kidney injury (AKI) refers to a clinical syndrome in which renal function declines rapidly in a short period of time caused by various pathological factors. During the development of AKI, renal tubules with the functions of reabsorption and excretion are prone to cell death due to external pathological stimuli, which is an important cause of impaired renal function. In recent years, a variety of new cell death pathways have been gradually recognized. Researchers have now found that regulated cell death (RCD), such as necroptosis, pyroptosis and ferroptosis, are important regulatory mechanisms of AKI. This article will summarize the research advances of various types of RCD involved in the process of AKI, aiming to deepen the understanding of AKI and provide innovative thoughts for the clinical treatment of AKI.
Acute Kidney Injury/metabolism* ; Cell Death ; Humans ; Kidney/metabolism* ; Necroptosis ; Necrosis/pathology* ; Regulated Cell Death

Renal ischemia-reperfusion injury (IRI) is histologically characterized by tubular cell death. Diverse pathways of regulated cell death (RCD) have been reported to contribute to renal IRI in recent studies. In this review, we discuss the signaling pathways, regulators and crosstalk of RCD, including necroptosis, ferroptosis and pyroptosis, and their role in renal IRI in order to pave the way for new therapeutic opportunities.
Apoptosis ; Ferroptosis ; Humans ; Kidney/metabolism* ; Necroptosis ; Regulated Cell Death ; Reperfusion Injury/drug therapy*

OBJECTIVE: This study investigated how the natural phytophenol and potent SIRT1 activator resveratrol (RSV) regulate necroptosis during Vibrio vulnificus (V. vulnificus)-induced sepsis and the potential mechanism. METHODS: The effect of RSV on V. vulnificus cytolysin (VVC)-induced necroptosis was analyzed in vitro using CCK-8 and Western blot assays. Enzyme-linked immunosorbent assays and quantitative real-time polymerase chain reaction, western blot, and immunohistochemistry and survival analyses were performed to elucidate the effect and mechanism of RSV on necroptosis in a V. vulnificus-induced sepsis mouse model. RESULTS: RSV relieved necroptosis induced by VVC in RAW264.7 and MLE12 cells. RSV also inhibited the inflammatory response, had a protective effect on histopathological changes, and reduced the expression level of the necroptosis indicator pMLKL in peritoneal macrophages, lung, spleen, and liver tissues of V. vulnificus-induced septic mice in vivo. Pretreatment with RSV downregulated the mRNA of the necroptosis indicator and protein expression in peritoneal macrophages and tissues of V. vulnificus-induced septic mice. RSV also improved the survival of V. vulnificus-induced septic mice. CONCLUSION Our findings collectively demonstrate that RSV prevented V. vulnificus-induced sepsis by attenuating necroptosis, highlighting its potency in the clinical management of V. vulnificus-induced sepsis.
Animals ; Mice ; Necroptosis ; Resveratrol/therapeutic use* ; Vibrio vulnificus ; Sepsis/drug therapy* ; Blotting, Western

The aim of the study is to identify the effects and underlying mechanisms of visfatin on inflammation and necroptosis in vascular endothelial cells. Human umbilical vein endothelial cells (HUVECs) were stimulated with visfatin or pretreated with Polyinosinic acid (LOX-1 inhibitor). By using the Western blot, RT-PCR, immunocytochemistry, enzyme-linked immunosorbent assay (ELISA), MTT and flow cytometry technique, the occurrence of inflammation and necroptosis in HUVECs were evaluated. Our results showed that 100 ng/mL visfatin significantly increased the mRNA and protein expression of monocyte chemotactic protein 1 (MCP-1) and LOX-1 after 24 hours' treatment in HUVECs. However, pretreatment with Polyinosinic acid could significantly reduce the expression of MCP-1 compared with visfatin group. Additionally, 100 ng/mL visfatin could induce the production of necrotic features and increase the mRNA expression of BMF (one of the markers of necroptosis), while pretreating with Polyinosinic acid markedly downregulated the mRNA expression of BMF gene and promoted the cell proliferation. These results indicate that visfatin might induce inflammation and necroptosis via LOX-1 in HUVECs, suggesting that visfatin plays a central role in the development of atherosclerosis.
Cells, Cultured ; Human Umbilical Vein Endothelial Cells ; Humans ; Inflammation/chemically induced* ; Necroptosis ; Nicotinamide Phosphoribosyltransferase ; Scavenger Receptors, Class E/genetics*

There remains a significant gap in our quantitative understanding of crosstalk between apoptosis and necroptosis pathways. By employing the SWATH-MS technique, we quantified absolute amounts of up to thousands of proteins in dynamic assembling/de-assembling of TNF signaling complexes. Combining SWATH-MS-based network modeling and experimental validation, we found that when RIP1 level is below ~1000 molecules/cell (mpc), the cell solely undergoes TRADD-dependent apoptosis. When RIP1 is above ~1000 mpc, pro-caspase-8 and RIP3 are recruited to necrosome respectively with linear and nonlinear dependence on RIP1 amount, which well explains the co-occurrence of apoptosis and necroptosis and the paradoxical observations that RIP1 is required for necroptosis but its increase down-regulates necroptosis. Higher amount of RIP1 (>~46,000 mpc) suppresses apoptosis, leading to necroptosis alone. The relation between RIP1 level and occurrence of necroptosis or total cell death is biphasic. Our study provides a resource for encoding the complexity of TNF signaling and a quantitative picture how distinct dynamic interplay among proteins function as basis sets in signaling complexes, enabling RIP1 to play diverse roles in governing cell fate decisions.
Animals ; Apoptosis ; Caspase 8/metabolism* ; GTPase-Activating Proteins/metabolism* ; HEK293 Cells ; Humans ; Mice ; Mice, Knockout ; Necroptosis ; Receptor-Interacting Protein Serine-Threonine Kinases/metabolism*

Objective: To explore the new mechanism of liver fibrosis through D-galactosamine/lipopolysaccharide (D-GalN/LPS)-induced necroptosis as an entry point to inhibit lethal injury. Methods: The carbon tetrachloride (CCl4)-induced mouse model of liver fibrosis was established. At 6 weeks of fibrosis, the mice were challenged with a lethal dose of D-GalN/LPS, and the normal mice treated with the same treatment were used as the control. The experiment was divided into four groups: control group (Control), acute injury group (D-GalN/LPS), liver fibrosis group (Fib), and liver fibrosis + acute challenge group (Fib + D-GalN/LPS). Quantitative PCR and immunofluorescence were used to analyze the expression of necroptosis key signal molecules RIPK1, RIPK3, MLKL and/or P-MLKL in each group. Normal mice were treated with inhibitors targeting key signaling molecules of necroptosis, and then given an acute challenge. The inhibitory effect of D-GalN/LPS-induced-necroptosis on acute liver injury was evaluated according to the changes in transaminase levels and liver histology. Liver fibrosis spontaneous ablation model was established, and then acute challenge was given. Necroptosis key signal molecules expression was analyzed in liver tissue of mice in each group and compared by immunohistochemistry. The differences between groups were compared with t-test or analysis of variance. Results: Quantitative PCR and immunofluorescence assays result showed that D-GalN/LPS-induced significant upregulation of RIPK1, RIPK3, MLKL and/or P-MLKL. Necroptosis key signal molecules inhibition had significantly reduced D-GalN/LPS-induced liver injury, as manifested by markedly reduced serum ALT and AST levels with improvement in liver histology. Necroptosis signaling molecules expression was significantly inhibited in fibrotic livers even under acute challenge conditions. Additionally, liver fibrosis with gradual attenuation of fibrotic ablation had inhibited D-GalN/LPS-induced necroptosis. Conclusion: Liver fibrosis may protect mice from acute lethal challenge injury by inhibiting D-GalN/LPS-induced necroptosis.
Animals ; Chemical and Drug Induced Liver Injury/pathology* ; Galactosamine/adverse effects* ; Lipopolysaccharides/adverse effects* ; Liver/pathology* ; Liver Cirrhosis/pathology* ; Liver Failure, Acute/chemically induced* ; Mice ; Necroptosis

To explore the effect and mechanism of Dahuang Zhechong Pills(DHZCP), a classical prescription, in improving testicular aging(TA) in vivo, the authors randomly divided 24 male rats into four groups: the normal, model, DHZCP and vitamin E(VE) groups. The TA rat model was established by continuous gavage of D-galactose(D-gal). During the experiment, the rats in the DHZCP and VE groups were given DHZCP suspension and VE suspension, respectively by gavage, while those in the normal and model groups were gavaged saline separately every day. After the co-administration of D-gal and various drugs for 60 days, all rats were sacrificed, and their blood and testis were collected. Further, various indexes related to TA and necroptosis of testicular cells in the model rats were examined and investigated, which included the aging phenotype, total testicular weight, testicular index, histopathological features of testis, number of spermatogenic cells, sex hormone level, expression characteristics of reactive oxygen species(ROS) in testis, expression levels and characteristics of cyclins in testis, and protein expression levels of the key molecules in receptor-interacting serine/threonine-protein kinase 1(RIPK1)/receptor-interacting serine/threonine-protein kinase 3(RIPK3)/mixed lineage kinase domain like pseudokinase(MLKL) signaling pathway in each group. The results showed that, for the TA model rats, both DHZCP and VE improved their aging phenotype, total testicular weight, testicular index, pathological features of testis, number of spermatogenic cells, serum testosterone and follicle stimulating hormone levels, expression characteristics of ROS and protein expression levels and characteristics of P21 and P53 in testis. In addition, DHZCP and VE improved the protein expression levels of the key molecules in RIPK1/RIPK3/MLKL signaling pathway in testis of the model rats. Specifically, DHZCP was better than VE in the improvement of RIPK3. In conclusion, in this study, the authors found that DHZCP, similar to VE, ameliorated D-gal-induced TA in model rats in vivo, and its mechanism was related to reducing necroptosis of testicular cells by inhibiting the activation of RIPK1/RIPK3/MLKL signaling pathway. This study provided preliminary pharmacological evidence for the development and application of classical prescriptions in the field of men's health.
Aging ; Animals ; Drugs, Chinese Herbal ; Male ; Necroptosis ; Protein Kinases/genetics* ; Rats ; Reactive Oxygen Species/metabolism* ; Receptor-Interacting Protein Serine-Threonine Kinases/pharmacology* ; Serine/pharmacology* ; Signal Transduction ; Testis ; Threonine/pharmacology*

Previous studies have shown that high blood glucose-induced chronic microinflammation can cause inflammatory podocyte injury in patients with diabetic kidney disease(DKD). Therein, necroptosis is a new form of podocyte death that is closely associated with renal fibrosis(RF). To explore the effects and mechanisms in vivo of total flavones of Abelmoschus manihot(TFA), an extract from traditional Chinese herbal medicine Abelmoschus manihot for treating kidney diseases, on podocyte necroptosis and RF in DKD, and to further reveal its scientific connotation with multi-pathway and multi-target, the authors randomly divided all rats into four groups: a namely normal group, a model group, a TFA group and a rapamycin(RAP) group. After the modified DKD rat models were successfully established, four group rats were given double-distilled water, TFA suspension and RAP suspension, respectively by gavage every day. At the end of the 4th week of drug treatment, all rats were sacrificed, and the samples of their urine, blood and kidneys were collected. And then, the various indicators related to podocyte necroptosis and RF in the DKD model rats were observed, detected and analyzed, respectively. The results indicated that, general condition, body weight(BW), serum creatinine(Scr), urinary albumin(UAlb), and kidney hypertrophy index(KHI) in these modified DKD model rats were both improved by TFA and RAP. Indicators of RF, including glomerular histomorphological characteristics, fibronectin(FN) and collagen type Ⅰ(collagen Ⅰ) staining extent in glomeruli, as well as the protein expression levels of FN, collagen Ⅰ, transforming growth factor-β1(TGF-β1) and Smad2/3 in the kidneys were improved respectively by TFA and RAP. Podocyte damage, including foot process form and the protein expression levels of podocin and CD2AP in the kidneys was improved by TFA and RAP. In addition, tumor necrosis factor-α(TNF-α)-mediated podocyte necroptosis in the kidneys, including the morphological characteristics of podocyte necroptosis, the extent and levels of the protein expression of TNF-α and phosphorylated mixed lineage kinase domain like pseudokinase(p-MLKL) was improved respectively by TFA and RAP. Among them, RAP had the better effect on p-MLKL. More importantly, the activation of the receptor interacting serine/threonine protein kinase 1(RIPK1)/RIPK3/MLKL signaling axis in the kidneys, including the expression levels of its key signaling molecules, such as phosphorylated receptor interacting serine/threonine protein kinase 1(p-RIPK1), p-RIPK3, p-MLKL and cysteinyl aspartate specific proteinase-8(caspase-8) was improved respectively by TFA and RAP. Among them, the effect of TFA on p-RIPK1 was superior. On the whole, in this study, the authors demonstrated that TFA alleviates podocyte necroptosis and RF in DKD through inhibiting the activation of the TNF-α-mediated RIPK1/RIPK3/MLKL signaling axis in diabetic kidneys. The authors' findings provide new pharmacological evidence to reveal the scientific connotation of TFA in treating RF in DKD in more depth.
Humans ; Rats ; Animals ; Diabetic Nephropathies/drug therapy* ; Abelmoschus ; Flavones/pharmacology* ; Podocytes ; Tumor Necrosis Factor-alpha/metabolism* ; Necroptosis ; Receptor-Interacting Protein Serine-Threonine Kinases/metabolism* ; Fibrosis ; Threonine/pharmacology* ; Collagen/metabolism* ; Serine/pharmacology* ; Diabetes Mellitus/drug therapy*