Regulation of RIP1 kinase signalling at the crossroads of inflammation and cell death

Non-coding RNAs in cancer therapy-induced cardiotoxicity: Mechanisms, biomarkers, and treatments

As a result of ongoing breakthroughs in cancer therapy, cancer patients' survival rates have grown considerably. However, cardiotoxicity has emerged as the most dangerous toxic side effect of cancer treatment, negatively impacting cancer patients' prognosis. In recent years, the link between non-coding RNAs (ncRNAs) and cancer therapy-induced cardiotoxicity has received much attention and investigation. NcRNAs are non-protein-coding RNAs that impact gene expression post-transcriptionally. They include microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). In several cancer treatments, such as chemotherapy, radiotherapy, and targeted therapy-induced cardiotoxicity, ncRNAs play a significant role in the onset and progression of cardiotoxicity. This review focuses on the mechanisms of ncRNAs in cancer therapy-induced cardiotoxicity, including apoptosis, mitochondrial damage, oxidative stress, DNA damage, inflammation, autophagy, aging, calcium homeostasis, vascular homeostasis, and fibrosis. In addition, this review explores potential ncRNAs-based biomarkers and therapeutic strategies, which may help to convert ncRNAs research into clinical practice in the future for early detection and improvement of cancer therapy-induced cardiotoxicity.

Regulated cell death (RCD) in cancer: key pathways and targeted therapies

Regulated cell death (RCD), also well-known as programmed cell death (PCD), refers to the form of cell death that can be regulated by a variety of biomacromolecules, which is distinctive from accidental cell death (ACD). Accumulating evidence has revealed that RCD subroutines are the key features of tumorigenesis, which may ultimately lead to the establishment of different potential therapeutic strategies. Hitherto, targeting the subroutines of RCD with pharmacological small-molecule compounds has been emerging as a promising therapeutic avenue, which has rapidly progressed in many types of human cancers. Thus, in this review, we focus on summarizing not only the key apoptotic and autophagy-dependent cell death signaling pathways, but the crucial pathways of other RCD subroutines, including necroptosis, pyroptosis, ferroptosis, parthanatos, entosis, NETosis and lysosome-dependent cell death (LCD) in cancer. Moreover, we further discuss the current situation of several small-molecule compounds targeting the different RCD subroutines to improve cancer treatment, such as single-target, dual or multiple-target small-molecule compounds, drug combinations, and some new emerging therapeutic strategies that would together shed new light on future directions to attack cancer cell vulnerabilities with small-molecule drugs targeting RCD for therapeutic purposes.

Cardiomyocyte death in sepsis: Mechanisms and regulation (Review)

Sepsis‑induced cardiac dysfunction is one of the most common types of organ dysfunction in sepsis; its pathogenesis is highly complex and not yet fully understood. Cardiomyocytes serve a key role in the pathophysiology of cardiac function; due to the limited ability of cardiomyocytes to regenerate, their loss contributes to decreased cardiac function. The activation of inflammatory signalling pathways affects cardiomyocyte function and modes of cardiomyocyte death in sepsis. Prevention of cardiomyocyte death is an important therapeutic strategy for sepsis‑induced cardiac dysfunction. Thus, understanding the signalling pathways that activate cardiomyocyte death and cross‑regulation between death modes are key to finding therapeutic targets. The present review focused on advances in understanding of sepsis‑induced cardiomyocyte death pathways, including apoptosis, necroptosis, mitochondria‑mediated necrosis, pyroptosis, ferroptosis and autophagy. The present review summarizes the effect of inflammatory activation on cardiomyocyte death mechanisms, the diversity of regulatory mechanisms and cross‑regulation between death modes and the effect on cardiac function in sepsis to provide a theoretical basis for treatment of sepsis‑induced cardiac dysfunction.

Necroptosis and Neuroinflammation in Retinal Degeneration

Necroptosis mediates the chronic inflammatory phenotype in neurodegeneration. Receptor-interacting protein kinase (RIPK) plays a pivotal role in the induction of necroptosis in various cell types, including microglia, and it is implicated in diverse neurodegenerative diseases in the central nervous system and the retina. Targeting RIPK has been proven beneficial for alleviating both neuroinflammation and degeneration in basic/preclinical studies. In this review, we discuss the role of necroptosis in retinal degeneration, including (1) the molecular pathways involving RIPK, (2) RIPK-dependent microglial activation and necroptosis, and (3) the interactions between necroptosis and retinal neuroinflammation/degeneration. This review will contribute to a renewed focus on neuroinflammation induced by necroptosis and to the development of anti-RIPK drugs against retinal degeneration.

RIPK1 in Liver Parenchymal Cells Limits Murine Hepatitis during Acute CCl4-Induced Liver Injury

Some life-threatening acute hepatitis originates from drug-induced liver injury (DILI). Carbon tetrachloride (CCl₄)-induced acute liver injury in mice is the widely used model of choice to study acute DILI, which pathogenesis involves a complex interplay of oxidative stress, necrosis, and apoptosis. Since the receptor interacting protein kinase-1 (RIPK1) is able to direct cell fate towards survival or death, it may potentially affect the pathological process of xenobiotic-induced liver damage. Two different mouse lines, either deficient for Ripk1 specifically in liver parenchymal cells (Ripk1^LPC-KO) or for the kinase activity of RIPK1 (Ripk1^K45A, kinase dead), plus their respective wild-type littermates (Ripk1^fl/fl, Ripk1^wt/wt), were exposed to single toxic doses of CCl₄. This exposure led in similar injury in Ripk1^K45A mice and their littermate controls. However, Ripk1^LPC-KO mice developed more severe symptoms with massive hepatocyte apoptosis as compared to their littermate controls. A pretreatment with a TNF-α receptor decoy exacerbated liver apoptosis in both Ripk1^fl/fl and Ripk1^LPC-KO mice. Besides, a FasL antagonist promoted hepatocyte apoptosis in Ripk1^fl/fl mice but reduced it in Ripk1^LPC-KO mice. Thus, the scaffolding properties of RIPK1 protect hepatocytes from apoptosis during CCl₄ intoxication. TNF-α and FasL emerged as factors promoting hepatocyte survival. These protective effects appeared to be independent of RIPK1, at least in part, for TNF-α, but dependent on RIPK1 for FasL. These new data complete the deciphering of the molecular mechanisms involved in DILI in the context of research on their prevention or cure.

Lymphotoxin-alpha expression in the meninges causes lymphoid tissue formation and neurodegeneration

Organised meningeal immune cell infiltrates are suggested to play an important role in cortical grey matter pathology in the multiple sclerosis brain, but the mechanisms involved are as yet unresolved. Lymphotoxin-alpha plays a key role in lymphoid organ development and cellular cytotoxicity in the immune system and its expression is increased in the cerebrospinal fluid of naïve and progressive multiple sclerosis patients and post-mortem meningeal tissue. Here we show that persistently increased levels of lymphotoxin alpha in the cerebral meninges can give rise to lymphoid-like structures and underlying multiple sclerosis-like cortical pathology. Stereotaxic injections of recombinant lymphotoxin-alpha into the rat meninges led to acute meningeal inflammation and subpial demyelination that resolved after 28 days, with demyelination being dependent on prior sub-clinical immunisation with myelin oligodendrocyte glycoprotein. Injection of a lymphotoxin-alpha lentiviral vector into the cortical meningeal space, to produce chronic localised over-expression of the cytokine, induced extensive lymphoid-like immune cell aggregates, maintained over 3 months, including T-cell rich zones containing podoplanin+ fibroblastic reticular stromal cells and B-cell rich zones with a network of follicular dendritic cells, together with expression of lymphoid chemokines and their receptors. Extensive microglial and astroglial activation, subpial demyelination and marked neuronal loss occurred in the underlying cortical parenchyma. Whereas subpial demyelination was partially dependent on prior myelin oligodendrocyte glycoprotein immunisation, the neuronal loss was present irrespective of immunisation. Conditioned medium from LTα treated microglia was able to induce a reactive phenotype in astrocytes. Our results show that chronic lymphotoxin-alpha overexpression alone is sufficient to induce formation of meningeal lymphoid-like structures and subsequent neurodegeneration, similar to that seen in the progressive multiple sclerosis brain.

[Autoinflammatory diseases associated with RIPK1 mutations: A review of the literature]

Autoinflammatory diseases related to RIPK1 mutations have been recently described. Two distinct clinical phenotypes have been reported and depend on the type and location of the mutation. When the mutation is recessive with loss of function, patients develop a combined phenotype of immune deficiency with recurrent bacterial and fungal infections and signs of early inflammatory bowel disease, non-erosive polyarthritis and growth retardation. On the other hand, when the mutation is dominant, gain of function, the manifestations are only auto-inflammatory with extensive lymphoproliferation, oral lesions such as aphthosis or ulcers, abdominal pain and hepatosplenomegaly. The mutations described for the dominant form affect only the cleavage site of caspase 8 and the clinical phenotype is called CRIA for Cleavage-Resistant RIPK1-Induced Autoinflammatory syndrome. The recessive form is severe and life-threatening requiring hematopoietic stem cell transplantation while the dominant form responds well to interleukin-6 receptor antagonists. Thus, RIPK1 mutations can induce various clinical manifestations with two distinct phenotypes. Although still rare, because of their recent description, these diseases can be suspected by an internist, in front of recurrent digestive features and will be increasingly diagnosed in the future through the integration of this gene in the diagnostic chips dedicated to autoinflammatory diseases and early inflammatory bowel diseases, using next generation sequencing.

Hsa_circ_0010729 regulates H2O2-induced myocardial injury by regulating miR-1184/RIPK1 axis

BACKGROUND

Ischemia-reperfusion (I/R) is an important risk factor for cardiovascular diseases (CVDs) and cardiac transplantation, as I/R can cause myocardial cell hypoxia/reoxygenation (H/R) injury. Recent research has shown that circular RNAs (circRNAs) may affect the progress of H/R-induced myocardial injury, but the mechanism remains unknown. Our work explored the role of circ_0010729 in H2O2-induced myocardial injury.

METHODS

The levels of circ_0010729, microRNA-1184 (miR-1184) and mRNA of receptor interacting serine/threonine kinase 1 (RIPK1) were indicated by quantitative real-time polymerase chain reaction (qRT-PCR) in human cardiac myocytes (HCMs). Meanwhile, the protein level of RIPK1 was quantified by western blot analysis. Besides, the cell functions were examined by 5-Ethynyl-29-deoxyuridine (EdU) assay, flow cytometry assay, western blot and antioxidant indexes analysis. Furthermore, the interplay between miR-1184 and circ_0010729 or RIPK1 was detected by dual-luciferase reporter assay. Eventually, the in vivo experiments were applied to measure the role of circ_0010729.

RESULTS

The levels of circ_0010729 RNA and RIPK1 protein were increased, and the miR-1184 was decreased in HCMs exposed to H₂O₂. In functional analysis, circ_0010729 deficiency restrained cell apoptosis and oxidative stress, whereas promoted cell proliferation in HCMs under H₂O₂ exposure. Moreover, miR-1184 inhibited the H₂O₂-induced myocardial injury by targeting RIPK1. Mechanistically, circ_0010729 acted as a miR-1184 sponge to regulate the level of RIPK1.

CONCLUSION

Circ_0010729 promotes H₂O₂-induced myocardial injury, and thus circ_001729 may be targeted as a potential therapy for H/R-induced myocardial injury.

Immunorthodontics: Role of HIF-1α in the Regulation of (Peptidoglycan-Induced) PD-L1 Expression in Cementoblasts under Compressive Force

Patients with periodontitis undergoing orthodontic therapy may suffer from undesired dental root resorption. The purpose of this in vitro study was to investigate the molecular mechanisms resulting in PD-L1 expression of cementoblasts in response to infection with Porphyromonas gingivalis (P. gingivalis) peptidoglycan (PGN) and compressive force (CF), and its interaction with hypoxia-inducible factor (HIF)-1α molecule: The cementoblast (OCCM-30) cells were kinetically infected with various concentrations of P. gingivalis PGN in the presence and absence of CF. Western blotting and RT-qPCR were performed to examine the protein expression of PD-L1 and HIF-1α as well as their gene expression. Immunofluorescence was applied to visualize the localization of these proteins within cells. An HIF-1α inhibitor was added for further investigation of necroptosis by flow cytometry analysis. Releases of soluble GAS-6 were measured by ELISA. P. gingivalis PGN dose dependently stimulated PD-L1 upregulation in cementoblasts at protein and mRNA levels. CF combined with P. gingivalis PGN had synergistic effects on the induction of PD-L1. Blockade of HIF-1α inhibited the P. gingivalis PGN-inducible PD-L1 protein expression under compression, indicating an HIF-1α dependent regulation of PD-L1 induction. Concomitantly, an HIF-1α inhibitor decreased the GAS-6 release in the presence of CF and P. gingivalis PGN co-stimulation. The data suggest that PGN of P. gingivalis participates in PD-L1 up-regulation in cementoblasts. Additionally, the influence of compressive force on P. gingivalis PGN-induced PD-L1 expression occurs in HIF-1α dependently. In this regard, HIF-1α may play roles in the immune response of cementoblasts via immune-inhibitory PD-L1. Our results underline the importance of molecular mechanisms involved in bacteria-induced periodontics and root resorption.

ZBP1 promotes inflammatory responses downstream of TLR3/TLR4 via timely delivery of RIPK1 to TRIF

While ZBP1 is well documented to drive cell death in response to viruses, its role in the context of Toll-like receptor (TLR)–mediated immune activation remains less defined. Here, we show that ZBP1 promotes inflammation in response to bacterial lipopolysaccharide (LPS) or double-stranded RNA (dsRNA). In a dose dependent manner, ZBP1 promotes the recruitment of RIPK1 to the TLR3/4 adaptor TRIF, activating downstream inflammatory signaling. ZBP1 plays a crucial role in TRIF-dependent responses in vivo, as Zbp1^−/− mice exhibited resistance to LPS-induced hypothermia and attenuated inflammatory responses to dsRNA. Our findings suggest that ZBP1 plays a synergistic role in the immune response by driving inflammation downstream of TLRs in response to bacterial and viral components.

ZBP1 is widely recognized as a mediator of cell death for its role in initiating necroptotic, apoptotic, and pyroptotic cell death pathways in response to diverse pathogenic infection. Herein, we characterize an unanticipated role for ZBP1 in promoting inflammatory responses to bacterial lipopolysaccharide (LPS) or double-stranded RNA (dsRNA). In response to both stimuli, ZBP1 promotes the timely delivery of RIPK1 to the Toll-like receptor (TLR)3/4 adaptor TRIF and M1-ubiquitination of RIPK1, which sustains activation of inflammatory signaling cascades downstream of RIPK1. Strikingly, ZBP1-mediated regulation of these pathways is important in vivo, as Zbp1^−/− mice exhibited resistance to LPS-induced septic shock, revealed by prolonged survival and delayed onset of hypothermia due to decreased inflammatory responses and subsequent cell death. Further findings revealed that ZBP1 promotes sustained inflammatory responses by mediating the kinetics of proinflammatory “TRIFosome” complex formation, thus having a profound impact downstream of TLR activation. Given the well-characterized role of ZBP1 as a viral sensor, our results exemplify previously unappreciated crosstalk between the pathways that regulate host responses to bacteria and viruses, with ZBP1 acting as a crucial bridge between the two.

Innate Immune Cell Death in Neuroinflammation and Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder molecularly characterized by the formation of amyloid β (Aβ) plaques and type 2 microtubule-associated protein (Tau) abnormalities. Multiple studies have shown that many of the brain's immunological cells, specifically microglia and astrocytes, are involved in AD pathogenesis. Cells of the innate immune system play an essential role in eliminating pathogens but also regulate brain homeostasis and AD. When activated, innate immune cells can cause programmed cell death through multiple pathways, including pyroptosis, apoptosis, necroptosis, and PANoptosis. The cell death often results in the release of proinflammatory cytokines that propagate the innate immune response and can eliminate Aβ plaques and aggregated Tau proteins. However, chronic neuroinflammation, which can result from cell death, has been linked to neurodegenerative diseases and can worsen AD. Therefore, the innate immune response must be tightly balanced to appropriately clear these AD-related structural abnormalities without inducing chronic neuroinflammation. In this review, we discuss neuroinflammation, innate immune responses, inflammatory cell death pathways, and cytokine secretion as they relate to AD. Therapeutic strategies targeting these innate immune cell death mechanisms will be critical to consider for future preventive or palliative treatments for AD.

Safety, pharmacokinetics and target engagement of novel RIPK1 inhibitor SAR443060 (DNL747) for neurodegenerative disorders: Randomized, placebo-controlled, double-blind phase I/Ib studies in healthy subjects and patients

RIPK1 is a master regulator of inflammatory signaling and cell death and increased RIPK1 activity is observed in human diseases, including Alzheimer’s disease (AD) and amyotrophic lateral sclerosis (ALS). RIPK1 inhibition has been shown to protect against cell death in a range of preclinical cellular and animal models of diseases. SAR443060 (previously DNL747) is a selective, orally bioavailable, central nervous system (CNS)–penetrant, small‐molecule, reversible inhibitor of RIPK1. In three early‐stage clinical trials in healthy subjects and patients with AD or ALS (NCT03757325 and NCT03757351), SAR443060 distributed into the cerebrospinal fluid (CSF) after oral administration and demonstrated robust peripheral target engagement as measured by a reduction in phosphorylation of RIPK1 at serine 166 (pRIPK1) in human peripheral blood mononuclear cells compared to baseline. RIPK1 inhibition was generally safe and well‐tolerated in healthy volunteers and patients with AD or ALS. Taken together, the distribution into the CSF after oral administration, the peripheral proof‐of‐mechanism, and the safety profile of RIPK1 inhibition to date, suggest that therapeutic modulation of RIPK1 in the CNS is possible, conferring potential therapeutic promise for AD and ALS, as well as other neurodegenerative conditions. However, SAR443060 development was discontinued due to long‐term nonclinical toxicology findings, although these nonclinical toxicology signals were not observed in the short duration dosing in any of the three early‐stage clinical trials. The dose‐limiting toxicities observed for SAR443060 preclinically have not been reported for other RIPK1‐inhibitors, suggesting that these toxicities are compound‐specific (related to SAR443060) rather than RIPK1 pathway‐specific.

Targeting Necroptosis as a Promising Therapy for Alzheimer's Disease

Alzheimer's disease (AD) is an irreversible and progressive neurodegenerative disorder featured by memory loss and cognitive default. However, there has been no effective therapeutic approach to prevent the development of AD and the available therapies are only to alleviate some symptoms with limited efficacy and severe side effects. Necroptosis is a new kind of cell death, being regarded as a genetically programmed and regulated pattern of necrosis. Increasing evidence reveals that necroptosis is tightly related to the occurrence and development of AD. This review aims to summarize the potential role of necroptosis in AD progression and the therapeutic capacity of targeting necroptosis for AD patients.

Salidroside alleviates cadmium-induced toxicity in mice by restoring the notch/HES-1 and RIP1-driven inflammatory signaling axis

OBJECTIVE

Salidroside (SAL) is a marker glycoside of Rhodiola rosea with significant antioxidant, anti-inflammatory, and other health benefits. In this study, we determined its neuroprotective effects against Cd-induced toxicity in cultured cells and mice.

MATERIALS AND METHODS

GL261 cell and Cd-intoxicated mouse model were used. ICP-MS and MWM were performed to measure Cd content and Cd-induced cognitive impairment in mice, respectively.

RESULTS

SAL attenuated Cd toxicity in GL261 cells as well as protected mice from substantial organic damage and cognitive deficits. SAL treatment alleviated Cd-induced oxidative stress, glial cell activation, and elevation of pro-inflammatory factors including TNF-α, IL-1β, and IL-6. Cd-induced cognitive deficits observed in the Morris water maze in mice were rescued by SAL. At the mechanistic level, SAL maintained the activity of antioxidant enzymes such as SOD and GSH-Px in the serum and brain, and scavenged the peroxidation product MDA, thereby restoring redox homeostasis in vivo, attenuating neuronal damage, and ultimately antagonized Cd-induced toxicity. Furthermore, Cd activated the RIP1-driven inflammatory signaling pathway and Notch/HES-1 signaling axis in the brain, leading to inflammation and neuronal loss, which could be attenuated by SAL.

CONCLUSION

SAL is a natural product with good anti-Cd effects, indicating that Rhodiola rosea is promising plant that is worthy of cultivation for health and economic benefits.

A novel small molecule Hsp90 inhibitor, C-316-1, attenuates acute kidney injury by suppressing RIPK1-mediated inflammation and necroptosis

Acute kidney injury (AKI) is marked by a fast deterioration of the kidney function that may be caused by a variety of factors. Recently, although our group found that PPBICA alleviated programmed cell death in AKI, poor water solubility limited its bioavailability. In this research, we screened a series of derivatives and found that C-316-1 had the best suppressive effect on preventing necroptosis and inflammation in cisplatin- and ischemia/reperfusion-induced AKI in vitro and in vivo with lower toxicity and better water solubility. Mass spectrometry results showed that C-316-1 bound to heat shock protein 90 (Hsp90), which was further confirmed by molecular docking and surface plasmon resonance. Additionally, the Hsp90 expression was upregulated in the blood and tissues of AKI patients. We discovered that C-316-1 decreased the RIPK1 protein level without affecting its mRNA expression. The proteasome inhibitor, MG132 restored the level of RIPK1 reduced by C-316-1, suggesting that C-316-1 limits necroptosis by promoting the degradation of RIPK1 rather than by reducing its production. Immunoprecipitation further showed that pretreatment with C-316-1 disrupted the Hsp90-Cdc37 protein-protein Interactions (PPIs). Thereby, C-316-1 inhibited the Hsp90-Cdc37 complex formation and led to a significant decrease in RIPK1, which in turn reduced necroptosis. Moreover, C-316-1 treatment did not protect against kidney injury in vivo and in vitro when Hsp90 was knocked down and R46, E47, and S50 in Cdc37 binding site of Hsp90 might form an important active pocket with C-316-1. These findings suggest that C-316-1 is a potential therapeutic agent against RIPK1-Mediated Necroptosis in AKI.

DAPT Attenuates Cadmium-Induced Toxicity in Mice by Inhibiting Inflammation and the Notch/HES-1 Signaling Axis

The small molecule DAPT inhibits the Notch signaling pathway by blocking γ-secretase mediated Notch cleavage. Given the critical role of the Notch signaling axis in inflammation, we asked whether DAPT could block Notch-mediated inflammation and thus exert neuronal protection. We established a mouse model of chronic exposure to cadmium (Cd)-induced toxicity and treated it with DAPT. DAPT was effective in ameliorating Cd-induced multi-organ damage and cognitive impairment in mice, as DAPT restored abnormal performance in the Y-maze, forced swimming and Morris water maze (MWM) tests. DAPT also reversed Cd-induced neuronal loss and glial cell activation to normal as observed by immunofluorescence and immunohistochemistry of brain tissue sections. In addition, Cd-intoxicated mice showed significantly increased levels of the Notch/HES-1 signaling axis and NF-κB, as well as decreased levels of the inflammatory inhibitors C/EBPβ and COP1. However, DAPT down regulated the elevated Notch/HES-1 signaling axis to normal, eliminating inflammation and thus protecting the nervous system. Thus, DAPT effectively eliminated the neurotoxicity of Cd, and blocking γ-secretase as well as Notch signaling axis may be a potential target for the development of neuronal protective drugs.

Foam Cells in Atherosclerosis: Novel Insights Into Its Origins, Consequences, and Molecular Mechanisms

Foam cells play a vital role in the initiation and development of atherosclerosis. This review aims to summarize the novel insights into the origins, consequences, and molecular mechanisms of foam cells in atherosclerotic plaques. Foam cells are originated from monocytes as well as from vascular smooth muscle cells (VSMC), stem/progenitor cells, and endothelium cells. Novel technologies including lineage tracing and single-cell RNA sequencing (scRNA-seq) have revolutionized our understanding of subtypes of monocyte- and VSMC-derived foam cells. By using scRNA-seq, three main clusters including resident-like, inflammatory, and triggering receptor expressed on myeloid cells-2 (Trem2 hi ) are identified as the major subtypes of monocyte-derived foam cells in atherosclerotic plaques. Foam cells undergo diverse pathways of programmed cell death including apoptosis, autophagy, necroptosis, and pyroptosis, contributing to the necrotic cores of atherosclerotic plaques. The formation of foam cells is affected by cholesterol uptake, efflux, and esterification. Novel mechanisms including nuclear receptors, non-coding RNAs, and gut microbiota have been discovered and investigated. Although the heterogeneity of monocytes and the complexity of non-coding RNAs make obstacles for targeting foam cells, further in-depth research and therapeutic exploration are needed for the better management of atherosclerosis.

LncRNA HABON promoted liver cancer cells survival under hypoxia by inhibiting mPTP opening

Hypoxia is an important feature of the tumor microenvironment (TME). While targeting hypoxic TME is emerging as a potential strategy for treating solid tumors including liver cancer. Recent studies have shown that hypoxia can regulate tumor adaptation to hypoxic TME through long non-coding RNA (lncRNA). In the previous study, we identify a novel hypoxia-activated lncRNA and termed it as HABON. Here, we demonstrated that knockdown of HABON caused necroptosis of tumor tissue and inhibited the subcutaneous tumor growth of SMMC-7721 cells in nude mice. Moreover, knockdown of HABON increased RIPK1 and MLKL expression as well as their phosphorylation level in SMMC-7721 and Huh7 liver cancer cells. Meanwhile, Necrostatin-1 and GSK872 could restore cell death of liver cancer cells caused by knockdown of HABON under hypoxia. The above results suggested that HABON could inhibit hypoxia-induced necroptosis of liver cancer cells. Mechanically, knockdown of HABON in liver cancer cells aggravated mitochondrial dysfunction caused by hypoxia. Furthermore, the RNA pull-down combined with mass spectrometry analysis identified HABON can interact with mitochondria-related protein VDAC1 and the RNA immunoprecipitation (RIP) analysis proved the interaction. In addition, we proved that VDAC1 mediated the mitochondrial permeability transition pore (mPTP) opening, mitochondrial dysfunction, as well as necroptosis caused by knockdown of HABON. Overall, our work demonstrates HABON can reduce hypoxia-induced necroptosis of liver cancer cells and suggests that inhibition of HABON in the hypoxic TME is a potential therapeutic strategy for treating liver cancer.

Investigation on the chemical space of the substituted triazole thio-benzoxazepinone RIPK1 inhibitors

As a key upstream kinase involved in the activation of necroptosis, receptor-interacting protein kinase 1 (RIPK1) plays a vital role in the treatment of relevant inflammatory diseases. Recently, we described the thio-benzoxazepinones as RIPK1 necroptosis inhibitors. On this basis, we further explored the chemical space of the thio-benzoxazepinones by introducing substitutions on the triazole group and evaluated their anti-necroptotic activity. The structure-activity relationship (SAR) was extended for this series of new derivatives. The best compound 2 with methyl and compound 10 with fluoroethyl were obtained and both specifically inhibited necroptosis rather than apoptosis with EC₅₀ values of 2.5 and 8.9 nM, respectively. They blocked the downstream necroptotic pathway to prevent cell lysis and prevent in vivo inflammation in a dose-dependent manner. This work provides that substituted thio-benzoxazepines can better occupy the hydrophobic cavity and enhance the hydrophobic interaction as promising lead compounds to enhance the in vivo activity of this class of compounds.

Inhibition of RIPK1 by ZJU-37 promotes oligodendrocyte progenitor proliferation and remyelination via NF-κB pathway

Receptor interacting serine/threonine protein kinase 1 (RIPK1) activation and necroptosis have been genetically and mechanistically linked with human multiple sclerosis and neurodegenerative diseases for which demyelination is a common key pathology. Demyelination can be healed through remyelination which is mediated by new oligodendrocytes derived from the adult oligodendrocyte progenitor cells (OPCs). Unfortunately, the efficiency of remyelination declines with progressive aging partially due to the depletion of OPCs following chronic or repeated demyelination. However, to our knowledge, so far there is no drug which enhances proliferation of OPCs, and it is unknown whether inhibiting RIPK1 activity directly affect OPCs, the central player of remyelination. Using TNFα induced RIPK1-dependent necroptosis in Jurkat FADD^−/− cells as a cell death assay, we screened from 2112 FDA-approved drugs and the drug candidates of new RIPK1 inhibitors selected by ourselves, and identified ZJU-37, a small molecule modified by introducing an amide bond to Nec-1s, is a new RIPK1 kinase inhibitor with higher potency than Nec-1s which has the best reported potency. We unveil in addition to protecting myelin from demyelination and axons from degeneration, ZJU-37 exhibits a new role on promoting proliferation of OPCs and enhancing remyelination by inhibiting RIPK1 kinase activity with higher potency than Nec-1s. Mechanistically, ZJU-37 promotes proliferation of OPCs by enhancing the transcription of platelet derived growth factor receptor alpha via NF-κB pathway. This work identifies ZJU-37 as a new drug candidate which enhances remyelination by promoting proliferation of OPCs, paving the way for a potential drug to enhance myelin repair.

Role of Induced Programmed Cell Death in the Chemopreventive Potential of Apigenin

The flavonoid apigenin (4′,5,7-trihydroxyflavone), which is one of the most widely distributed phytochemicals in the plant kingdom, is one of the most thoroughly investigated phenolic components. Previous studies have attributed the physiological effects of apigenin to its anti-allergic, antibacterial, antidiabetic, anti-inflammatory, antioxidant, antiviral, and blood-pressure-lowering properties, and its documented anticancer properties have been attributed to the induction of apoptosis and autophagy, the inhibition of inflammation, angiogenesis, and cell proliferation, and the regulation of cellular responses to oxidative stress and DNA damage. The most well-known mechanism for the compound’s anticancer effects in human cancer cell lines is apoptosis, followed by autophagy, and studies have also reported that apigenin induces novel cell death mechanisms, such as necroptosis and ferroptosis. Therefore, the aim of this paper is to review the therapeutic potential of apigenin as a chemopreventive agent, as well as the roles of programmed cell death mechanisms in the compound’s chemopreventive properties.

Pan-cancer analysis of necroptosis-related gene signature for the identification of prognosis and immune significance

BACKGROUND

Necroptosis is a novel programmed cell death mode independent on caspase. A number of studies have revealed that the induction of necroptosis could act as an alternative therapeutic strategy for drug-resistant tumors as well as affect tumor immune microenvironment.

METHODS

Gene expression profiles and clinical data were downloaded from XENA-UCSC (including The Cancer Genome Atlas and Genotype-Tissue Expression), Gene Expression Omnibus, International Cancer Genome Consortium and Chinese Glioma Genome Atlas. We used non-negative matrix factorization method to conduct tumor classification. The least absolute shrinkage and selection operator regression was applied to establish risk models, whose prognostic effectiveness was examined in both training and testing sets with Kaplan-Meier analysis, time-dependent receiver operating characteristic curves as well as uni- and multi-variate survival analysis. Principal Component Analysis, t-distributed Stochastic Neighbor Embedding and Uniform Manifold Approximation and Projection were conducted to check the risk group distribution. Gene Set Enrichment Analyses, immune infiltration analysis based on CIBERSORT, EPIC, MCPcounter, ssGSEA and ESTIMATE, gene mutation and drug sensitivity between the risk groups were also taken into consideration.

RESULTS

There were eight types of cancer with at least ten differentially expressed necroptosis-related genes which could influence patients' prognosis, namely, adrenocortical carcinoma (ACC), cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC), acute myeloid leukemia (LAML), brain lower grade glioma (LGG), pancreatic adenocarcinoma (PAAD), liver hepatocellular carcinoma (LIHC), skin cutaneous melanoma (SKCM) and thymoma (THYM). Patients could be divided into different clusters with distinct overall survival in all cancers above except for LIHC. The risk models could efficiently predict prognosis of ACC, LAML, LGG, LIHC, SKCM and THYM patients. LGG patients from high-risk group had a higher infiltration level of M2 macrophages and cancer-associated fibroblasts. There were more CD8+ T cells, Th1 cells and M1 macrophages in low-risk SKCM patients' tumor microenvironment. Gene mutation status and drug sensitivity are also different between low- and high-risk groups in the six cancers.

CONCLUSIONS

Necroptosis-related genes can predict clinical outcomes of ACC, LAML, LGG, LIHC, SKCM and THYM patients and help to distinguish immune infiltration status for LGG and SKCM.

Suppression of RIP1 activity via S415 dephosphorylation ameliorates obesity-related hepatic insulin resistance

OBJECTIVE

Receptor-interacting serine/threonine-protein kinase 1 (RIP1) is a well-documented key regulator of TNFα-mediated inflammation, apoptosis, and necroptosis, which contribute to the development of obesity-related metabolic diseases such as nonalcoholic steatohepatitis. However, the mechanism regarding how RIP1 influences obesity-related insulin resistance remains elusive.

METHODS

Primary hepatocytes with necrostatin 1 treatment or RIP1 expression were exposed to palmitic acid (PA), prior to the examination of cellular insulin signaling. Phosphorylation sites of RIP1 were detected by liquid chromatography with tandem mass spectrometry, and RIP1 variants with mutated phosphorylation sites were overexpressed in hepatocytes to identify the specific residue that influenced the RIP1-mediated insulin resistance. Adenovirus expressing RIP1 (S415A) mutant were administered into diet-induced obese mice to assess the effects on insulin sensitivity.

RESULTS

This study uncovered an aberrant increase in RIP1 activity during the development of obesity-induced insulin resistance. Inhibition of RIP1 activity with necrostatin 1 ameliorated PA- or high-fat diet-caused hepatic insulin resistance. With liquid chromatography with tandem mass spectrometry analysis and mutagenesis screening, S415, a novel phosphorylation site of RIP1, was identified to be responsible for RIP1-mediated insulin resistance. Loss-of-function mutation of S415 efficiently blunted RIP1-evoked insulin resistance in PA-treated hepatocytes or diet-induced obese mice.

CONCLUSIONS

These findings highlight the diabetogenic role of RIP1 S415 and propose RIP1 as a promising therapeutic target for type 2 diabetes.

Synthesis and characterization of potent RIPK3 inhibitors based on a tricyclic scaffold

Background: Necroptosis is an important form of regulated cell death involved in inflammatory diseases, degenerative diseases and cancer. RIPK3 is an interesting target for intervention of necroptosis-associated diseases. Methodology: Herein the authors report the synthesis of a series RIPK3 inhibitors under the guidance of structure-based drug design which leads to the identification of compound 37. Results: Compound 37 potently rescued human and mouse cells from necroptotic stimuli TNFα, Smac mimetic, z-VAD and LPS + z-VAD, displayed high affinity to RIPK3 (Kd = 14 nM) but no observable affinity to RIPK1 and inhibited RIPK3 kinase function. Importantly, compound 37 significantly alleviated TNF-induced systemic inflammatory response syndrome in the mouse model. Conclusion: These results support compound 37 as a prototype RIPK3 inhibitor for lead optimization.

The megakaryocytic transcription factor ARID3A suppresses leukemia pathogenesis

Given the plasticity of hematopoietic stem and progenitor cells, multiple routes of differentiation must be blocked in the the pathogenesis of acute myeloid leukemia, the molecular basis of which is incompletely understood. We report that posttranscriptional repression of the transcription factor ARID3A by miR-125b is a key event in the pathogenesis of acute megakaryoblastic leukemia (AMKL). AMKL is frequently associated with trisomy 21 and GATA1 mutations (GATA1s), and children with Down syndrome are at a high risk of developing the disease. The results of our study showed that chromosome 21-encoded miR-125b synergizes with Gata1s to drive leukemogenesis in this context. Leveraging forward and reverse genetics, we uncovered Arid3a as the main miR-125b target behind this synergy. We demonstrated that, during normal hematopoiesis, this transcription factor promotes megakaryocytic differentiation in concert with GATA1 and mediates TGFβ-induced apoptosis and cell cycle arrest in complex with SMAD2/3. Although Gata1s mutations perturb erythroid differentiation and induce hyperproliferation of megakaryocytic progenitors, intact ARID3A expression assures their megakaryocytic differentiation and growth restriction. Upon knockdown, these tumor suppressive functions are revoked, causing a blockade of dual megakaryocytic/erythroid differentiation and subsequently of AMKL. Inversely, restoring ARID3A expression relieves the arrest of megakaryocytic differentiation in AMKL patient-derived xenografts. This work illustrates how mutations in lineage-determining transcription factors and perturbation of posttranscriptional gene regulation can interact to block multiple routes of hematopoietic differentiation and cause leukemia. In AMKL, surmounting this differentiation blockade through restoration of the tumor suppressor ARID3A represents a promising strategy for treating this lethal pediatric disease.

Diverse and precision therapies open new horizons for patients with advanced pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a common cause of cancer-related death, and most patients are with advanced disease when diagnosed. At present, despite a variety of treatments have been developed for PDAC, few effective treatment options are available; on the other hand, PDAC shows significant resistance to chemoradiotherapy, targeted therapy, and immunotherapy due to its heterogeneous genetic profile, molecular signaling pathways, and complex tumor immune microenvironment. Nevertheless, over the past decades, there have been many new advances in the key theory and understanding of the intrinsic mechanisms and complexity of molecular biology and molecular immunology in pancreatic cancer, based on which more and more diverse new means and reasonable combination strategies for PDAC treatment have been developed and preliminary breakthroughs have been made. With the continuous exploration, from surgical local treatment to comprehensive medical management, the research-diagnosis-management system of pancreatic cancer is improving. This review focused on the variety of treatments for advanced PDAC, including traditional chemotherapy, targeted therapy, immunotherapy, microenvironment matrix regulation as well as the treatment targeting epigenetics, metabolism and cancer stem cells. We pointed out the current research bottlenecks and future exploration directions.

The potent inhibitory role of suppressing TBK1 in RIPK1 associated cerebral ischemia-reperfusion injury

The pathological mechanism of cell death features in cerebral ischemia-reperfusion injury (CIRI) was complicated. The occurrence of various cell death pathways during the progression of ischemia/reperfusion injury promoted complex further neuroinflammation. RIPK1, receptor interacting protein kinase 1, was convinced to be involved in both necroptosis and apoptosis, which is a special RIPK1-dependent apoptosis. More evidences indicated the physiological role of RIPK1 in necroptosis, apoptosis and also autophagy. In this study, we elucidated the RIPK1 exhibited characterization in various cell death pathways in time-course dependent feature. The necroptosis occupied dominant neuron death within 24 hours after ischemia/reperfusion injury. However, the neuronal death feature seemed turned to apoptosis 24 hours after reperfusion. In this study, it was also found that TBK1 (TANK binding kinase 1) played as suppressor in the regulation of kinase activity of RIPK1. This result might provide a potential approach in mediating the kinase activity of RIPK1 in clinic.

The lncRNA CASC2 Modulates Hepatocellular Carcinoma Cell Sensitivity and Resistance to TRAIL Through Apoptotic and Non-Apoptotic Signaling

The immune cytokine tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been widely concerned as a tumor therapy because of its ability of selective triggering cancer cell apoptosis; nevertheless, hepatocellular carcinoma (HCC) exhibits acquired resistance to TRAIL-induced apoptosis. In the present study, tumor-suppressive lncRNA cancer susceptibility candidate 2 (CASC2) was downregulated in HCC tissues and cell lines; HCC patients with lower CASC2 expression predicted a shorter overall survival rate. In vitro, CASC2 overexpression dramatically repressed HCC cell proliferation and inhibited cell apoptosis; in vivo, CASC2 overexpression inhibited subcutaneous xenotransplant tumor growth. CASC2 affected the caspase cascades and NF-κB signaling in TRAIL-sensitive [Huh-7 (S) and HCCLM3 (S)] or TRAIL-resistant cell lines [Huh-7 (R) and HCCLM3 (R)] in different ways. In Huh-7 (S) and HCCLM3 (S) cells, CASC2 affected cell apoptosis through the miR-24/caspase-8 and miR-221/caspase-3 axes and the caspase cascades. miR-18a directly targeted CASC2 and RIPK1. In Huh-7 (R) and HCCLM3 (R) cells, CASC2 affected cell proliferation through the miR-18a/RIPK1 axis and the NF-κB signaling. RELA bound to CASC2 promoter region and inhibited CASC2 transcription. In conclusion, CASC2 affects cell growth mainly via the miR-24/caspase-8 and miR-221/caspase-3 axes in TRAIL-sensitive HCC cells; while in TRAIL-resistant HCC cells, CASC2 affects cell growth mainly via miR-18a/RIPK1 axis and the NF-κB signaling. These outcomes foreboded that CASC2 could be a novel therapeutic target for further study of HCC-related diseases.

Design, synthesis, and evaluation of potent RIPK1 inhibitors with in vivo anti-inflammatory activity

RIPK1 plays a key role in the necroptosis pathway that regulates inflammatory signaling and cell death in various diseases, including inflammatory and neurodegenerative diseases. Herein, we report a series of potent RIPK1 inhibitors, represented by compound 70. Compound 70 efficiently blocks necroptosis induced by TNFα in both human and mouse cells (EC₅₀ = 17-30 nM). Biophysical assay demonstrates that compound 70 potently binds to RIPK1 (K_d = 9.2 nM), but not RIPK3 (K_d > 10,000 nM). Importantly, compound 70 exhibits greatly improved metabolic stability in human and rat liver microsomes compared to compound 6 (PK68), a RIPK1 inhibitor reported in our previous work. In addition, compound 70 displays high permeability in Caco-2 cells and excellent in vitro safety profiles in hERG and CYP assays. Moreover, pre-treatment of 70 significantly ameliorates hypothermia and lethal shock in SIRS mice model. Lastly, compound 70 possesses favorable pharmacokinetic parameters with moderate clearance and good oral bioavailability in SD rat. Taken together, our work supports 70 as a potent RIPK1 inhibitor and highlights its potential as a prototypical lead for further development in necroptosis-associated inflammatory disorders.

A survey of the clinical pipeline in neuroscience

Many new first-in-class drugs for neuroscience indications have been introduced in the past decade including new treatments for migraine, amyotrophic lateral sclerosis, depression, and multiple sclerosis. However, significant unmet patient needs remain in areas such as chronic pain, neurodegeneration, psychiatric diseases, and epilepsy. This review summarizes some of the advanced clinical compounds for these indications. Additionally, current opportunities and challenges that remain with respect to genetic validation, biomarkers, and translational models are discussed.

Inhibition of Neuronal Necroptosis Mediated by RIPK1 Provides Neuroprotective Effects on Hypoxia and Ischemia In Vitro and In Vivo

Ischemic brain injury is a widespread pathological condition, the main components of which are a deficiency of oxygen and energy substrates. In recent years, a number of new forms of cell death, including necroptosis, have been described. In necroptosis, a cascade of interactions between the kinases RIPK1 and RIPK3 and the MLKL protein leads to the formation of a specialized death complex called the necrosome, which triggers MLKL-mediated destruction of the cell membrane and necroptotic cell death. Necroptosis probably plays an important role in the development of ischemia/reperfusion injury and can be considered as a potential target for finding methods to correct the disruption of neural networks in ischemic damage. In the present study, we demonstrated that blockade of RIPK1 kinase by Necrostatin-1 preserved the viability of cells in primary hippocampal cultures in an in vitro model of glucose deprivation. The effect of RIPK1 blockade on the bioelectrical and metabolic calcium activity of neuron-glial networks in vitro using calcium imaging and multi-electrode arrays was assessed for the first time. RIPK1 blockade was shown to partially preserve both calcium and bioelectric activity of neuron-glial networks under ischemic factors. However, it should be noted that RIPK1 blockade does not preserve the network parameters of the collective calcium dynamics of neuron-glial networks, despite the maintenance of network bioelectrical activity (the number of bursts and the number of spikes in the bursts). To confirm the data obtained in vitro, we studied the effect of RIPK1 blockade on the resistance of small laboratory animals to in vivo modeling of hypoxia and cerebral ischemia. The use of Necrostatin-1 increases the survival rate of C57BL mice in modeling both acute hypobaric hypoxia and ischemic brain damage.

Bclaf1 regulates c-FLIP expression and protects cells from TNF-induced apoptosis and tissue injury

TNF stimulation generates pro-survival signals through activation of NF-κB that restrict the build-in death signaling triggered by TNF. The competition between TNF-induced survival and death signals ultimately determines the fate of a cell. Here, we report the identification of Bclaf1 as a novel component of the anti-apoptotic program of TNF. Bclaf1 depletion in multiple cells sensitizes cells to TNF-induced apoptosis but not to necroptosis. Bclaf1 exerts its anti-apoptotic function by promoting the transcription of CFLAR, a caspase 8 antagonist, downstream of NF-κB activation. Bclaf1 binds to the p50 subunit of NF-κB, which is required for Bclaf1 to stimulate CFLAR transcription. Finally, in Bclaf1 siRNA administered mice, TNF-induced small intestine injury is much more severe than in control mice with aggravated signs of apoptosis and pyroptosis. These results suggest Bclaf1 is a key regulator in TNF-induced apoptosis, both in vitro and in vivo.

Development of a Once-Daily Modified-Release Formulation for the Short Half-Life RIPK1 Inhibitor GSK2982772 using DiffCORE Technology

Purpose

GSK2982772 is a selective inhibitor of receptor-interacting protein kinase-1 (RIPK1) with a short 2- to 3-h half-life. In a previous modified-release (MR) study, a matrix monolithic formulation (80% GSK2982772 released over 12 h) provided a once-daily (QD) pharmacokinetic (PK) profile in the fasted state; however, it was susceptible to food effects. The current study evaluated the safety and PK of MR formulations using GSK proprietary DiffCORE™ technology.

Methods

Part A evaluated PK following single-dose (240 mg) fasted and fed (high-fat meal) administration of three DiffCORE MR formulations within pre-defined in vitro extremes of 80% GSK2982772 released over 12 h (MR-12 h) to 80% GSK2982772 released over 18 h (MR-18 h) versus an immediate-release formulation. Part B evaluated MR-16 h (120–960 mg) in different prandial states.

Results

Pharmacokinetic profiles for all MR formulations and doses tested in the fasted and fed states were consistent with QD dosing.

Conclusions

The DiffCORE technology overcame the food effect vulnerability observed with the matrix monolithic formulation. The MR-16 h formulation was selected for further clinical development as a QD dosing regimen (NCT03649412 September 26, 2018).

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-021-03124-7.

TNF-α-Mediated RIPK1 Pathway Participates in the Development of Trigeminal Neuropathic Pain in Rats

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) participates in the regulation of cellular stress and inflammatory responses, but its function in neuropathic pain remains poorly understood. This study evaluated the role of RIPK1 in neuropathic pain following inferior alveolar nerve injury. We developed a model using malpositioned dental implants in male Sprague Dawley rats. This model resulted in significant mechanical allodynia and upregulated RIPK1 expression in the trigeminal subnucleus caudalis (TSC). The intracisternal administration of Necrosatin-1 (Nec-1), an RIPK1 inhibitor, blocked the mechanical allodynia produced by inferior alveolar nerve injury The intracisternal administration of recombinant rat tumor necrosis factor-α (rrTNF-α) protein in naive rats produced mechanical allodynia and upregulated RIPK1 expression in the TSC. Moreover, an intracisternal pretreatment with Nec-1 inhibited the mechanical allodynia produced by rrTNF-α protein. Nerve injury caused elevated TNF-α concentration in the TSC and a TNF-α block had anti-allodynic effects, thereby attenuating RIPK1 expression in the TSC. Finally, double immunofluorescence analyses revealed the colocalization of TNF receptor and RIPK1 with astrocytes. Hence, we have identified that astroglial RIPK1, activated by the TNF-α pathway, is a central driver of neuropathic pain and that the TNF-α-mediated RIPK1 pathway is a potential therapeutic target for reducing neuropathic pain following nerve injury.

GSDMD-mediated pyroptosis: a critical mechanism of diabetic nephropathy

Pyroptosis is a recently identified mechanism of programmed cell death related to Caspase-1 that triggers a series of inflammatory reactions by releasing several proinflammatory factors such as IL-1β and IL-18. The process is characterised by the rupture of cell membranes and the release of cell contents through the mediation of gasdermin (GSDM) proteins. GSDMD is an important member of the GSDM family and plays a critical role in the two pathways of pyroptosis. Diabetic nephropathy (DN) is a microvascular complication of diabetes and a major cause of end-stage renal disease. Recently, it was revealed that GSDMD-mediated pyroptosis plays an important role in the occurrence and development of DN. In this review, we focus on two types of kidney cells, tubular epithelial cells and renal podocytes, to illustrate the mechanism of pyroptosis in DN and provide new ideas for the prevention, early diagnosis and molecular therapy of DN.

Controlled decompression attenuates brain damage in a rat model of epidural extreme intracranial hypertension: Partially via inhibiting necroptosis and inflammatory response

Intracranial hypertension (IH) remains a common symptom of neurological diseases, and requires stepwise treatments to release intracranial pressure (ICP). In the present study, we built a rat model of epidural extreme intracranial hypertension (EEIH) and verified the effectiveness of a surgery method called controlled decompression on attenuating brain injury induced by EEIH. For the model part, we determined the level of EEIH of rats via recording ICP and cerebral perfusion pressure (CPP) and the variation tendency of survival rates, mean blood artery pressure and mean velocity (Vm) of left middle cerebral artery (LMCA) as ICP ascending. SD rats were assigned into 4 groups: Sham group, Controlled decompression group (Con group), Rapid decompression group (Rap group) and Rapid decompression + Necrostatin-1 (Nec-1) group (Rap+Nec-1 group). The results suggested that controlled decompression lowered cerebral water content, improved neurological function, and attenuated EEIH-induced inflammation response and ROS generation to a greater extent than rapid decompression. Meanwhile, controlled decompression functioned to preserve more Nissl bodies, indicating alleviated neuron injury after EEIH. Additionally, the permeability of blood brain barrier (BBB) was also safeguarded in the Con group. Western blotting (WB) and Real-time Polymerase Chain Reaction (rt-PCR) assays consistently determined lower protein and mRNA levels of necroptosis-related molecules receptor interacting protein kinase 1 (RIPK1), interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like protein (MLKL) (WB only) in the Con and Rap+Nec-1 group. Double immunofluorescent staining found weaker fluorescence intensity of RIPK3 in the compressed cortex of the Con and Rap+Nec-1 group.

Biologic and pathologic aspects of osteocytes in the setting of medication-related osteonecrosis of the jaw (MRONJ)

Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe, debilitating condition affecting patients with cancer and patients with osteoporosis who have been treated with powerful antiresorptives (pARs) or angiogenesis inhibitors (AgIs). Oral risk factors associated with the development of MRONJ include tooth extraction and inflammatory dental disease (e.g., periodontitis, periapical infection). In bone tissues, osteocytes play a bidirectional role in which they not only act as the "receiver" of systemic signals from blood vessels, such as hormones and drugs, or local signals from the mineralized matrix as it is deformed, but they also play a critical role as "transmitter" of signals to the cells that execute bone modeling and remodeling (osteoclasts, osteoblasts and lining cells). When the survival capacity of osteocytes is overwhelmed, they can die. Osteocyte death has been associated with several pathological conditions. Whereas the causes and mechanisms of osteocyte death have been studied in conditions like osteonecrosis of the femoral head (ONFH), few studies of the causes and mechanisms of osteocyte death have been done in MRONJ. The three forms of cell death that affect most of the different cells in the body (apoptosis, autophagy, and necrosis) have been recognized in osteocytes. Notably, necroptosis, a form of regulated cell death with "a necrotic cell death phenotype," has also been identified as a form of cell death in osteocytes under certain pathologic conditions. Improving the understanding of osteocyte death in MRONJ may be critical for preventing disease and developing treatment approaches. In this review, we intend to provide insight into the biology of osteocytes, cell death, in general, and osteocyte death, in particular, and discuss hypothetical mechanisms involved in osteocyte death associated with MRONJ.

The role of necroptosis in disease and treatment

Necroptosis, a distinctive type of programmed cell death different from apoptosis or necrosis, triggered by a series of death receptors such as tumor necrosis factor receptor 1 (TNFR1), TNFR2, and Fas. In case that apoptosis process is blocked, necroptosis pathway is initiated with the activation of three key downstream mediators which are receptor-interacting serine/threonine protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like protein (MLKL). The whole process eventually leads to destruction of the cell membrane integrity, swelling of organelles, and severe inflammation. Over the past decade, necroptosis has been found widely involved in life process of human beings and animals. In this review, we attempt to explore the therapeutic prospects of necroptosis regulators by describing its molecular mechanism and the role it played in pathological condition and tissue homeostasis, and to summarize the research and clinical applications of corresponding regulators including small molecule inhibitors, chemicals, Chinese herbal extracts, and biological agents in the treatment of various diseases.

Genetic Regulation of RIPK1 and Necroptosis

The receptor-interacting protein kinase 1 (RIPK1) is recognized as a master upstream regulator that controls cell survival and inflammatory signaling as well as multiple cell death pathways, including apoptosis and necroptosis. The activation of RIPK1 kinase is extensively modulated by ubiquitination and phosphorylation, which are mediated by multiple factors that also control the activation of the NF-κB pathway. We discuss current findings regarding the genetic modulation of RIPK1 that controls its activation and interaction with downstream mediators, such as caspase-8 and RIPK3, to promote apoptosis and necroptosis. We also address genetic autoinflammatory human conditions that involve abnormal activation of RIPK1. Leveraging these new genetic and mechanistic insights, we postulate how an improved understanding of RIPK1 biology may support the development of therapeutics that target RIPK1 for the treatment of human inflammatory and neurodegenerative diseases.

Target-Based Small Molecule Drug Discovery Towards Novel Therapeutics for Inflammatory Bowel Diseases

Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), is a class of severe and chronic diseases of the gastrointestinal (GI) tract with recurrent symptoms and significant morbidity. Long-term persistence of chronic inflammation in IBD is a major contributing factor to neoplastic transformation and the development of colitis-associated colorectal cancer. Conversely, persistence of transmural inflammation in CD is associated with formation of fibrosing strictures, resulting in substantial morbidity. The recent introduction of biological response modifiers as IBD therapies, such as antibodies neutralizing tumor necrosis factor (TNF)-α, have replaced nonselective anti-inflammatory corticosteroids in disease management. However, a large proportion (~40%) of patients with the treatment of anti-TNF-α antibodies are discontinued or withdrawn from therapy because of (1) primary nonresponse, (2) secondary loss of response, (3) opportunistic infection, or (4) onset of cancer. Therefore, the development of novel and effective therapeutics targeting specific signaling pathways in the pathogenesis of IBD is urgently needed. In this comprehensive review, we summarize the recent advances in drug discovery of new small molecules in preclinical or clinical development for treating IBD that target biologically relevant pathways in mucosal inflammation. These include intracellular enzymes (Janus kinases, receptor interacting protein, phosphodiesterase 4, IκB kinase), integrins, G protein-coupled receptors (S1P, CCR9, CXCR4, CB2) and inflammasome mediators (NLRP3), etc. We will also discuss emerging evidence of a distinct mechanism of action, bromodomain-containing protein 4, an epigenetic regulator of pathways involved in the activation, communication, and trafficking of immune cells. We highlight their chemotypes, mode of actions, structure-activity relationships, characterizations, and their in vitro/in vivo activities and therapeutic potential. The perspectives on the relevant challenges, new opportunities, and future directions in this field are also discussed.

Defining (and blocking) neuronal death in Parkinson's disease: Does it matter what we call it?

Parkinson's disease (PD) is the second most common neurodegenerative disease, comprised of both familial and idiopathic forms, behind only Alzheimer's disease (AD). The disease is characterized, regardless of the pathogenesis, primarily by a loss of DA neurons in the ventral midbrain as well as noradrenergic neurons of the locus coeruleus; however, by the time symptoms manifest, considerable neuronal loss in both areas has occurred. Neuroprotective strategies thus have to be paired with more sensitive and specific biomarker assays that can identify early at-risk patients in order to initiate disease-modifying therapies at an earlier stage in the disease. Complicating this is the fact that multiple forms of cell death mediate the neuronal loss; however, with a common underlying element that the cell death is considered a "regulated" form of cell death, in contrast to an un-controlled necrotic cell death process. In this review we focus our discussion on several categories of regulated cell death in the context of PD: apoptosis, necroptosis, pyroptosis, and autophagic cell death. In clinical studies as well as experimental in vivo models of PD, there is evidence for a role of each of these forms of cell death in the loss of midbrain DA neurons, and specific therapeutic strategies have been proposed and tested. What remains unclear however is the relative contributions of these distinct forms of cell death to the overall loss of DA neurons, whether they occur at different stages of the disease, or whether specific sub-regions within the midbrain are more susceptible to specific death triggers and pathways.

TAK1: A Molecular Link Between Liver Inflammation, Fibrosis, Steatosis, and Carcinogenesis

Chronic insult and persistent injury can cause liver inflammation, fibrosis, and carcinogenesis; it can also be associated with metabolic disorders. Identification of critical molecules that link the process of inflammation and carcinogenesis will provide prospective therapeutic targets for liver diseases. Rapid advancements in gene engineering technology have allowed the elucidation of the underlying mechanism of transformation, from inflammation and metabolic disorders to carcinogenesis. Transforming growth factor-β-activated kinase 1 (TAK1) is an upstream intracellular protein kinase of nuclear factor kappa-B (NF-κB) and c-Jun N-terminal kinases, which are activated by numerous cytokines, growth factors, and microbial products. In this study, we highlighted the functional roles of TAK1 and its interaction with transforming growth factor-β, WNT, AMP-activated protein kinase, and NF-κB signaling pathways in liver inflammation, steatosis, fibrosis, and carcinogenesis based on previously published articles.

Quantitative analysis of phosphoproteome in necroptosis reveals a role of TRIM28 phosphorylation in promoting necroptosis-induced cytokine production

Necroptosis is a form of regulated necrotic cell death that promotes inflammation. In cells undergoing necroptosis, activated RIPK1 kinase mediates the formation of RIPK1/RIPK3/MLKL complex to promote MLKL oligomerization and execution of necroptosis. RIPK1 kinase activity also promotes cell-autonomous activation of proinflammatory cytokine production in necroptosis. However, the signaling pathways downstream of RIPK1 kinase in necroptosis and how RIPK1 kinase activation controls inflammatory response induced by necroptosis are still largely unknown. Here, we quantitatively measured the temporal dynamics of over 7000 confident phosphorylation-sites during necroptosis using mass spectrometry. Our study defined a RIPK1-dependent phosphorylation pattern in late necroptosis that is associated with a proinflammatory component marked by p-S473 TRIM28. We show that the activation of p38 MAPK mediated by oligomerized MLKL promotes the phosphorylation of S473 TRIM28, which in turn mediates inflammation during late necroptosis. Taken together, our study illustrates a mechanism by which p38 MAPK may be activated by oligomerized MLKL to promote inflammation in necroptosis.

4-Hydroxy-2-Nonenal Promotes Cardiomyocyte Necroptosis via Stabilizing Receptor-Interacting Serine/Threonine-Protein Kinase 1

Background: Necroptosis is a vital regulator of myocardial ischemia/reperfusion (MI/R) injury. Meanwhile, 4-hydroxy-2-nonenal (4-HNE) is abundantly increased during MI/R injury. However, whether 4-HNE induces cardiomyocyte necroptosis during MI/R remains unknown. Methods: To observe the relationship between 4-HNE and necroptosis during MI/R, C57BL/6 mice and aldehyde dehydrogenase 2-transgenic (ALDH2-Tg) mice were both exposed to left anterior descending artery ligation surgery to establish MI/R injury models. For further study, isolated mouse hearts and H9c2 cells were both treated with 4-HNE to elucidate the underlying mechanisms. Results: Necroptosis and 4-HNE were both upregulated in I/R-injured hearts. Cardiomyocyte necroptosis was significantly decreased in I/R-injured hearts from ALDH2-Tg mice as compared with that of wild-type mice. In vitro studies showed that necroptosis was enhanced by 4-HNE perfusion in a time- and concentration-dependent manner. Knockdown of receptor-interacting serine/threonine-protein kinase 1 (RIP1) using small interfering RNA (siRNA) prevented 4-HNE-induced cardiomyocyte necroptosis, manifesting that RIP1 played a key role in the upregulation of cell necroptosis by 4-HNE. Further studies found that 4-HNE reduced the protein degradation of RIP1 by preventing K48-polyubiquitination of RIP1. Conclusion: 4-HNE contributes to cardiomyocyte necroptosis by regulating ubiquitin-mediated proteasome degradation of RIP1.