Regulation of necroptosis signaling and cell death by reactive oxygen species

The protective role of Cordyceps cicadae and its active ingredient myriocin against sodium iodate-induced age-related macular degeneration via an anti-necroptotic TNF-RIPK1/3 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps cicadae (C.cicadae), named "Chan Hua", an anamorph of Isaria cicadae Miquel, is an entomogenous complex formed by fungi parasitizing on the larvae of cicadas and belongs to the Claviciptaceae family and the genus Codyceps, which traditionally holds a significant place in Chinese ethnopharmacology, specifically for eye clarity and as a remedy for age-related ocular conditions. The underlying mechanisms contributing to its eyesight enhancement and potential effectiveness against Age-related macular degeneration (AMD) remain unexplored.

AIM OF THE STUDY

This study aims to elucidate the protective role of C.cicadae and its active ingredient, Myriocin (Myr), against AMD.

MATERIALS AND METHODS

A chemical inducer was employed to make retinal pigment epithelium (RPE) damage in vitro and in vivo. The key ingredients of C.cicadae and their related mechanisms for anti-AMD were studied through bioinformatic analysis and molecular biological approaches.

RESULTS

Myr was identified through high-performance liquid chromatography (HPLC) as an active ingredient in C.cicadae, and demonstrated a protective effect on RPE cells, reducing the structural damage and cell death induced by sodium iodate (SI). Further, Myr reduced eyelid secretions in AMD mice and restored their retinal structure and function. The differentially expressed genes (DEGs) in Myr treatment are primarily associated with TNF and Necroptosis signaling pathways. Molecular docking indicated a strong affinity between TNF and Myr. Myr inhibited the TNF signaling pathway thereby reducing the expression of inflammatory factors in ARPE-19 cells. Additionally, Myr had consistent action with the necroptosis inhibitor Necrostatin-1 (Nec-1), inhibited the RIPK1/RIPK3/MLKL pathway thereby protecting ARPE-19 cells.

CONCLUSION

The findings present Myr, as a potent protector against SI-induced AMD, predominantly through modulation of the TNF-RIPK1/RIPK3/MLKL signaling pathway, offering the insights of therapeutic C.cicadae as viable candidates for AMD treatment.

TBBPS caused necroptosis and inflammation in hepatocytes by blocking PINK1-PARKIN-mediated mitochondrial autophagy

The widespread use of Tetrabromobisphenol S (TBBPS), as an alternative to tetrabromobisphenol A (TBBPA), has been detected at high frequency in environmental media in recent years, TBBPS can enter the body via the digestive tract and other routes, thus long-term TBBPS exposure may cause adverse health effects. Therefore, it is necessary to evaluate the toxicological effects of TBBPS. In the current work, two cell models of the liver were used (a human-derived cell line THLE-2 and a murine-derived AML12). The liver cells were then exposed to different concentrations of TBBPS. The results of cell proliferation assays showed that TBBPS resulted in a significant attenuation of the proliferative capacity of liver cells. Further results from ELISA and Western-blot assays showed that TBBPS induced an inflammatory response in liver cells by detecting the levels of inflammatory factors, such as TNFα, IL-1β and IL-6. We also found that TBBPS promoted the necroptosis in liver cells by evaluating the levels of RIP3 and pMLKL, and the use of inhibitors of necroptosis confirmed that the type of cell death induced by TBBPS belongs to necroptosis. Molecular mechanistic studies showed that TBBPS suppressed mitochondrial autophagy mediated by the PINK1-PARKIN signaling pathway, which led to accumulation of damaged mitochondria in THLE-2 and AML12 cells. Subsequently, accumulated ROS activated necroptosis of liver cells. Current toxicological studies suggest that we need to better control and regulate the production and use of TBBPS, the current work provide a reference for studying the toxicology of TBBPS.

Neurotoxic β-amyloid oligomers cause mitochondrial dysfunction-the trigger for PANoptosis in neurons

As the global population ages, the incidence of elderly patients with dementia, represented by Alzheimer's disease (AD), will continue to increase. Previous studies have suggested that β-amyloid protein (Aβ) deposition is a key factor leading to AD. However, the clinical efficacy of treating AD with anti-Aβ protein antibodies is not satisfactory, suggesting that Aβ amyloidosis may be a pathological change rather than a key factor leading to AD. Identification of the causes of AD and development of corresponding prevention and treatment strategies is an important goal of current research. Following the discovery of soluble oligomeric forms of Aβ (AβO) in 1998, scientists began to focus on the neurotoxicity of AβOs. As an endogenous neurotoxin, the active growth of AβOs can lead to neuronal death, which is believed to occur before plaque formation, suggesting that AβOs are the key factors leading to AD. PANoptosis, a newly proposed concept of cell death that includes known modes of pyroptosis, apoptosis, and necroptosis, is a form of cell death regulated by the PANoptosome complex. Neuronal survival depends on proper mitochondrial function. Under conditions of AβO interference, mitochondrial dysfunction occurs, releasing lethal contents as potential upstream effectors of the PANoptosome. Considering the critical role of neurons in cognitive function and the development of AD as well as the regulatory role of mitochondrial function in neuronal survival, investigation of the potential mechanisms leading to neuronal PANoptosis is crucial. This review describes the disruption of neuronal mitochondrial function by AβOs and elucidates how AβOs may activate neuronal PANoptosis by causing mitochondrial dysfunction during the development of AD, providing guidance for the development of targeted neuronal treatment strategies.

The role of programmed cell death in osteosarcoma: From pathogenesis to therapy

Osteosarcoma (OS) is a prevalent bone solid malignancy that primarily affects adolescents, particularly boys aged 14-19. This aggressive form of cancer often leads to deadly lung cancer due to its high migration ability. Experimental evidence suggests that programmed cell death (PCD) plays a crucial role in the development of osteosarcoma. Various forms of PCD, including apoptosis, ferroptosis, autophagy, necroptosis, and pyroptosis, contribute significantly to the progression of osteosarcoma. Additionally, different signaling pathways such as STAT3/c-Myc signal pathway, JNK signl pathway, PI3k/AKT/mTOR signal pathway, WNT/β-catenin signal pathway, and RhoA signal pathway can influence the development of osteosarcoma by regulating PCD in osteosarcoma cell. Therefore, targeting PCD and the associated signaling pathways could offer a promising therapeutic approach for treating osteosarcoma.

Endoplasmic reticulum stress-induced necroptosis promotes cochlear inflammation: Implications for age-related hearing loss

Age-related hearing loss (ARHL) is the most common sensory disorder associated with human aging. Chronic inflammation is supposed to be an important contributor to ARHL. Yet, the underlying mechanisms of developing cochlear inflammation are still not well understood. In this study, we found that the inflammation, endoplasmic reticulum (ER) stress and necroptosis signalings are activated in the cochlea of aged C57BL/6 mice. ER stress activator tunicamycin (TM) induced necroptosis in cochlear HEI-OC1 cells and cochlear explants, while necroptosis inhibitors protected cochlear cells from ER stress-induced cell death. The antioxidants inhibited necroptosis and protected HEI-OC1 cells from TM insults. Necroptotic HEI-OC1 cells promoted the activation of the co-cultured macrophages via Myd88 signaling. Moreover, necroptosis inhibitor protected from TM-induced hearing loss, and inhibited inflammation in C57BL/6 mice. These findings suggest that ER stress-induced necroptosis promotes cochlear inflammation and hearing loss. Targeting necroptosis serves as a potential approach for the treatment of cochlear inflammation and ARHL.

Macrophage Tim-3 maintains intestinal homeostasis in DSS-induced colitis by suppressing neutrophil necroptosis

T-cell immunoglobulin domain and mucin domain-3 (Tim-3) is a versatile immunomodulator that protects against intestinal inflammation. Necroptosis is a type of cell death that regulates intestinal homeostasis and inflammation. The mechanism(s) underlying the protective role of macrophage Tim-3 in intestinal inflammation is unclear; thus, we investigated whether specific Tim-3 knockdown in macrophages drives intestinal inflammation via necroptosis. Tim-3 protein and mRNA expression were assessed via double immunofluorescence staining and single-cell RNA sequencing (sc-RNA seq), respectively, in the colonic tissues of patients with inflammatory bowel disease (IBD) and healthy controls. Macrophage-specific Tim3-knockout (Tim-3M-KO) mice were generated to explore the function and mechanism of Tim-3 in dextran sodium sulfate (DSS)-induced colitis. Necroptosis was blocked by pharmacological inhibitors of receptor-interacting protein kinase (RIP)1, RIP3, and reactive oxygen species (ROS). Additionally, in vitro experiments were performed to assess the mechanisms of neutrophil necroptosis induced by Tim-3 knockdown macrophages. Although Tim-3 is relatively inactive in macrophages during colon homeostasis, it is highly active during colitis. Compared to those in controls, Tim-3M-KO mice showed increased susceptibility to colitis, higher colitis scores, and increased pro-inflammatory mediator expression. Following the administration of RIP1/RIP3 or ROS inhibitors, a significant reduction in intestinal inflammation symptoms was observed in DSS-treated Tim-3M-KO mice. Further analysis indicated the TLR4/NF-κB pathway in Tim-3 knockdown macrophages mediates the TNF-α-induced necroptosis pathway in neutrophils. Macrophage Tim-3 regulates neutrophil necroptosis via intracellular ROS signaling. Tim-3 knockdown macrophages can recruit neutrophils and induce neutrophil necroptosis, thereby damaging the intestinal mucosal barrier and triggering a vicious cycle in the development of colitis. Our results demonstrate a protective role of macrophage Tim-3 in maintaining gut homeostasis by inhibiting neutrophil necroptosis and provide novel insights into the pathogenesis of IBD.

Sodium p-perfluorous nonenoxybenzene sulfonate induces ROS-mediated necroptosis by directly targeting catalase in HepG2 cells

Sodium p-perfluorous nonenoxybenzene sulfonate (OBS) has been widely used as a substitute for perfluorooctane sulfonic acid (PFOS) because of its high surface activity and low cost, but the knowledge of its biological effects is still limited. In this study, we compared the toxic effects of OBS and PFOS on human hepatoma cells (HepG2). OBS resulted in lower cell viability, higher ROS levels, and more severe necrosis than PFOS, indicating that OBS caused higher cytotoxicity than PFOS. In this process, OBS induced a burst of ROS and downregulation of catalase (CAT). OBS-induced oxidative stress was recovered after the CAT overexpression, but the CAT levels were not reversed after N-acetylcysteine (NAC) pretreatment. This indicates that the downregulated CAT is an upstream signal of the ROS burst. Moreover, drug affinity targeting assay, spectroscopic analysis and molecular docking were conducted, showing that OBS directly targeted CAT and therefore downregulated CAT. In addition, we found that OBS-induced necrosis is RIP1/RIP3-dependent programmed necroptosis. In summary, OBS directly targets CAT to reduce CAT levels and induces oxidative stress and necroptosis. Our findings are helpful to understand the toxicity of OBS and to evaluate the safety of OBS as a substitute for PFOS.

Genome, Metabolism, or Immunity: Which Is the Primary Decider of Pancreatic Cancer Fate through Non-Apoptotic Cell Death?

Pancreatic ductal adenocarcinoma (PDAC) is a solid tumor characterized by poor prognosis and resistance to treatment. Resistance to apoptosis, a cell death process, and anti-apoptotic mechanisms, are some of the hallmarks of cancer. Exploring non-apoptotic cell death mechanisms provides an opportunity to overcome apoptosis resistance in PDAC. Several recent studies evaluated ferroptosis, necroptosis, and pyroptosis as the non-apoptotic cell death processes in PDAC that play a crucial role in the prognosis and treatment of this disease. Ferroptosis, necroptosis, and pyroptosis play a crucial role in PDAC development via several signaling pathways, gene expression, and immunity regulation. This review summarizes the current understanding of how ferroptosis, necroptosis, and pyroptosis interact with signaling pathways, the genome, the immune system, the metabolism, and other factors in the prognosis and treatment of PDAC.

Modulatory effect of rupatadine on mesenchymal stem cell-derived exosomes in hepatic fibrosis in rats: A potential role for miR-200a

AIMS

Mesenchymal stem cell-derived exosomes (MSC-EXOs) have emerged as a promising approach in regenerative medicine for management of different diseases. However, the maintenance of their efficacy after in vivo transplantation is still a major concern. The present investigation aimed to assess the modulatory effect of rupatadine (RUP) on MSC-EXOs in diethylnitrosamine (DEN)-induced liver fibrosis (LF), and to explore the possible underlying mechanism.

MAIN METHODS

LF was induced in rats by i.p. injection of DEN (100 mg/kg) once per week for 6 successive weeks. Rats were then treated with RUP (4 mg/kg/day, p.o.) for 4 weeks with or without a single i.v. administration of MSC-EXOs. At the end of the experiment, animals were euthanized and serum and liver were separated for biochemical, and histological measurements.

KEY FINDINGS

The combined MSC-EXOs/RUP therapy provided an additional improvement towards inhibition of DEN-induced LF compared to MSC-EXOs group alone. These outcomes could be mediated through antioxidant, anti-inflammatory, and anti-fibrotic effects of RUP which created a more favorable environment for MSC-EXOs homing, and action. This in turn would enhance more effectively miR-200a expression which reduced oxidative stress, inflammation, necroptosis pathway, and subsequently fibrosis as revealed by turning off TGF-β1/α-SMA expression, and hedgehog axis.

SIGNIFICANCE

The present findings reveal that RUP enhanced the anti-fibrotic efficacy of MSC-EXOs when used as a combined therapy. This was revealed through attenuation of PAF/RIPK3/MLKL/HMGB1, and TGF-β1/hedgehog signaling pathways with a significant role for miR-200a.

Current Progress in Gallium-based Liquid Metals for Combinatory Phototherapeutic Anticancer Applications

A variety of therapeutic approaches using liquid metal (LM) have been intensively investigated, due to its unique physico-chemical properties that include high surface tension, fluidity, shape deformability, thermal conductivity, and electrical conductivity. Among a series of LMs, the relatively lower toxicity and minimal volatility of gallium (Ga)-based LMs (GaLMs) enables their usage in a series of potential biomedical applications, especially implantable platforms, to treat multiple diseases. In addition, the highly efficient conversion of light energy into thermal or chemical energy via GaLMs has led to recent developments in photothermal and photodynamic applications for anticancer treatments. As attractive photothermal agents or photosensitizers, a systematic interpretation of the structural characteristics and photo-responsive behaviors of GaLMs is necessary to develop effective anticancer engineering applications. Therefore, the aim of this review is to provide a comprehensive summary of currently suggested GaLM-mediated photo-therapeutic cancer treatments. In particular, the review summarizes (1) surface coating techniques to form stable and multifunctional GaLM particulates, (2) currently investigated GaLM-mediated photothermal and photodynamic anticancer therapies, (3) synergistic efficacies with the aid of additional interventions, and (4) 3D composite gels embedded with GaLMs particles, to convey the potential technological advances of LM in this field.

A fijiviral nonstructural protein triggers cell death in plant and bacterial cells via its transmembrane domain

Southern rice black-streaked dwarf virus (SRBSDV; Fijivirus, Reoviridae) has become a threat to cereal production in East Asia in recent years. Our previous cytopathologic studies have suggested that SRBSDV induces a process resembling programmed cell death in infected tissues that results in distinctive growth abnormalities. The viral product responsible for the cell death, however, remains unknown. Here P9-2 protein, but not its RNA, was shown to induce cell death in Escherichia coli and plant cells when expressed either locally with a transient expression vector or systemically using a heterologous virus. Both computer prediction and fluorescent assays indicated that the viral nonstructural protein was targeted to the plasma membrane (PM) and further modification of its subcellular localization abolished its ability to induce cell death, indicating that its PM localization was required for the cell death induction. P9-2 was predicted to harbour two transmembrane helices within its central hydrophobic domain. A series of mutation assays further showed that its central transmembrane hydrophobic domain was crucial for cell death induction and that its conserved F90, Y101, and L103 amino acid residues could play synergistic roles in maintaining its ability to induce cell death. Its homologues in other fijiviruses also induced cell death in plant and bacterial cells, implying that the fijiviral nonstructural protein may trigger cell death by targeting conserved cellular factors or via a highly conserved mechanism.

Magnolia officinalis Bark Extract Prevents Enterocyte Death in a Colitis Mouse Model by Inhibiting ROS-Mediated Necroptosis

Necroptosis is a form of programmed cell death with features of necrosis and apoptosis that occurs in the intestinal epithelium of patients with inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease. In addition, necroptosis has also been observed in enterocytes in animal models of dextran sulfate sodium (DSS)-induced colitis. Thus, the discovery of natural products for regulating necroptosis may represent an important therapeutic strategy for improving IBD. We found that Magnolia officinalis bark extract (MBE) prevented weight loss and suppressed the activation of the proinflammatory cytokine IL6 in DSS-induced colitis. Furthermore, MBE restored the length of the damaged colon and decreased the expression of necroptosis markers in mice with DSS-induced colitis. In vitro, necroptosis-induced reactive oxygen species (ROS) production was reduced by MBE, and the expression of COX2, a target protein of ROS, was simultaneously suppressed. Both magnolol and honokiol, the two major bioactive compounds in MBE, inhibited necroptosis in human primary intestinal epithelial cells and colorectal adenocarcinoma cells. Our findings highlight the effectiveness of MBE in modulating enterocyte necroptosis and suggest that MBE may be developed as a natural, disease-targeting drug for the treatment of colitis.

Fetuin-A alleviates neuroinflammation against traumatic brain injury-induced microglial necroptosis by regulating Nrf-2/HO-1 pathway

BACKGROUND

The microglia-mediated inflammatory response is a vital mechanism of secondary damage following traumatic brain injury (TBI), but the underlying mechanism of microglial activation is unclear.

METHODS

Controlled cortical impact (CCI) was induced in adult male C57BL/6J mice, and glutamate was used to construct a classical in vitro injury model in the primary microglia. Microglial activation was determined by western blot and immunostaining. The inflammatory factors were measured by enzyme-linked immunosorbent assay. The oxidative stress marker and mitochondrial reactive oxygen species (ROS) were measured by immunoblotting and MitoSox Red staining. Transmission electron microscopy was used to observe the typical morphology of necroptotic cells.

RESULTS

Our quantitative proteomics identified 2499 proteins; 157 were significantly differentially expressed in brain tissue between the 6 h after CCI (CCI6h) group and sham group, and 109 were significantly differentially expressed between the CCI24h and sham groups. Moreover, compared with the sham group, the terms "acute-phase response", "inflammation", and "protein binding" were significantly enriched in CCI groups. Fetuin-A, a liver-secreted acute-phase glycoprotein, was involved in these biological processes. Using an experimental TBI model, we found that the Fetuin-A level peaked at 6 h and then decreased gradually. Importantly, we showed that administration of Fetuin-A reduced the cortical lesion volume and edema area and inhibited the inflammatory response, which was associated with suppressing microglial necroptosis, thus decreasing microglial activation. Furthermore, administration of Fetuin-A attenuated mitochondrial oxidative stress in glutamate-treated microglial cells, which is a critical mechanism of necroptosis suppression. In addition, we demonstrated that Fetuin-A treatment promoted translocation of nuclear factor erythroid 2-related factor 2 (Nrf-2) from the cytoplasm to the nucleus in vivo; however, the Nrf-2 inhibitor ML385 and si-heme oxygenase-1 (si-HO-1) disrupted the regulation of oxidative stress by Fetuin-A and induced increased ROS levels and necroptosis in glutamate-treated microglial cells. Fetuin-A also protected neurons from adverse factors in vivo and in vitro.

CONCLUSIONS

Our results demonstrated that Fetuin-A activated Nrf-2/HO-1, suppressed oxidative stress and necroptosis levels, and thereby attenuates the abnormal inflammatory response following TBI. The findings suggest a potential therapeutic strategy for TBI treatment.

Exploring the underlying mechanism of oleanolic acid treating glioma by transcriptome and molecular docking

OBJECTIVE

Oleanolic acid is a promising drug for treating gliomas, but its underlying mechanism is unclear. This study aimed to determine the potential effect of oleanolic acid on glioma and its mechanism.

METHODS

Firstly, the effects of oleanolic acid on the proliferation, invasion, and apoptosis of glioma U251 cells were detected by in vitro experiments such as MTT assay, cell cloning, and flow cytometry. The transcriptome data of U251 cells treated with oleanolic acid and untreated were sequenced by mRNA, and then the differentially expressed genes were analyzed by gene ontology (GO), genomic encyclopedia (KEGG) pathway enrichment analysis, and protein interaction topology analysis. The underlying mechanism of oleanolic acid was predicted, and the related protein interaction network was constructed. Finally, Western blotting and molecular docking techniques verified the mRNA sequencing results.

RESULTS

Oleanolic acid could effectively inhibit the proliferation, colony formation, and invasion of U251 cells and induce apoptosis. A total of 446 differentially expressed genes were detected by mRNA sequencing, of which 96 genes were up-regulated and 350 down-regulated. Oleanolic acid induces the TNF signal pathway and NOD-like receptor signal pathway at the intracellular level. In addition, OAS2, OASL, IFIT3, RSAD2, and IRF1 may be the core targets of oleanolic acid in treating glioma.

CONCLUSION

Transcriptome combined with molecular docking technique is used to predict the possible mechanism of oleanolic acid in the treatment of glioma, which provides new ideas and insights for developing and researching antitumor drugs.

Mitochondrial ROS promotes susceptibility to infection via gasdermin D-mediated necroptosis

Although mutations in mitochondrial-associated genes are linked to inflammation and susceptibility to infection, their mechanistic contributions to immune outcomes remain ill-defined. We discovered that the disease-associated gain-of-function allele Lrrk2G2019S (leucine-rich repeat kinase 2) perturbs mitochondrial homeostasis and reprograms cell death pathways in macrophages. When the inflammasome is activated in Lrrk2G2019S macrophages, elevated mitochondrial ROS (mtROS) directs association of the pore-forming protein gasdermin D (GSDMD) to mitochondrial membranes. Mitochondrial GSDMD pore formation then releases mtROS, promoting a switch to RIPK1/RIPK3/MLKL-dependent necroptosis. Consistent with enhanced necroptosis, infection of Lrrk2G2019S mice with Mycobacterium tuberculosis elicits hyperinflammation and severe immunopathology. Our findings suggest a pivotal role for GSDMD as an executer of multiple cell death pathways and demonstrate that mitochondrial dysfunction can direct immune outcomes via cell death modality switching. This work provides insights into how LRRK2 mutations manifest or exacerbate human diseases and identifies GSDMD-dependent necroptosis as a potential target to limit Lrrk2G2019S-mediated immunopathology.

Piperlongumine increases the sensitivity of bladder cancer to cisplatin by mitochondrial ROS

BACKGROUND

The development of cisplatin resistance often results in cisplatin inefficacy in advanced or recurrent bladder cancer. However, effective treatment strategies for cisplatin resistance have not been well established.

METHODS

Gene expression was measured by qRT-PCR and Western blotting. CCK-8 assay was performed to detect cell survival. The number of apoptotic cells was determined using the Annexin V-PI double-staining assay. The level of reactive oxygen species (ROS) was measured using 2',7'-dichlorodihydrofluorescein diacetate fluorescent dye, and the ATP level was detected using an ATP measurement kit.

RESULTS

The expression of receptor-interacting protein kinase 1 (RIPK1), a key regulator of necroptosis, gradually decreased during cisplatin resistance. We first used piperlongumine (PL) in combination with cisplatin to act on cisplatin-resistant BC cells and found that PL-induced activation of RIPK1 increased the sensitivity of T24 resistant cells to cisplatin treatment. Furthermore, we revealed that PL killed T24 cisplatin-resistant cells by triggering necroptosis, because cell death could be rescued by the mixed lineage kinase domain-like (MLKL) protein inhibitor necrotic sulfonamide or MLKL siRNA, but could not be suppressed by the apoptosis inhibitor z-VAD. We further explored the specific mechanism and found that PL activated RIPK1 to induce necroptosis in cisplatin-resistant cells by stimulating mitochondrial fission to produce excessive ROS.

CONCLUSIONS

Our results demonstrated the role of RIPK1 in cisplatin-resistant cells and the sensitization effect of the natural drug PL on bladder cancer. These may provide a new treatment strategy for overcoming cisplatin resistance in bladder cancer.

Diet-derived ergothioneine induces necroptosis in colorectal cancer cells by activating the SIRT3/MLKL pathway

Ergothioneine (Egt) is a dietary amino acid which acts as an antioxidant to protect against aging-related diseases. We investigated the anticancer properties of Egt in colorectal cancer cells (CRC). Egt treatment exerted cytotoxicity in a dose-dependent manner, induced reactive oxygen species accumulation, loss of mitochondrial membrane potential, and upregulation of the histone deacetylase SIRT3. Immunoblotting analysis indicated that the cell death occurred via necroptosis through activation of the RIP1/RIP3/MLKL pathway. An immunoprecipitation assay unveiled that the interaction between the terminal effector in necroptotic signaling MLKL and SIRT3 increased during the Egt treatment. SIRT3 gene silencing blocked the upregulation of MLKL and abolished the ability of Egt to induce necroptosis. The SIRT3-MLKL interaction may mediate the necroptotic effects of Egt in CRC, suggesting the potential of this dietary amino-thione in the prevention of CRC.

Natural Products as the Modulators of Oxidative Stress: An Herbal Approach in the Management of Prostate Cancer

Prostate cancer is the most commonly diagnosed and frequently occurred cancer in the males globally. The current treatment strategies available to treat prostate cancer are not much effective and express various adverse effects. Hence, there is an urgent need to identify novel treatment that can improve patient outcome. From times immemorial, natural products are highly recognized for novel drug development for various diseases including cancer. Cancer cells generally maintain higher basal levels of reactive oxygen species (ROS) when compared to normal cells due to its high metabolic rate. However, initiation of excess intracellular ROS production can not be tolerated by the cancer cells and induce several cell death signals which are in contrast to normal cells. Therefore, small molecules of natural origin that induce ROS can potentially kill cancer cells in specific and provide a better opportunity to develop a novel drug therapy. In this review, we elaborated various classes of medicinal compounds and their mechanism of killing prostate cancer cells through direct or indirect ROS generation. This can generate a novel thought to develop promising drug candidate to treat prostate cancer patients.

Zinc finger protein 91 mediates necroptosis by initiating RIPK1-RIPK3-MLKL signal transduction in response to TNF receptor 1 ligation

Necroptosis is a form of regulated programmed cell death that is mediated by receptor-interacting protein kinase 1 (RIPK1), receptor-interacting serine/threonine protein kinase-3 (RIPK3), and mixed lineage kinase domain-like protein (MLKL); however, it is not known whether zinc finger protein 91 (ZFP91) is involved in this process. Here, we investigated ZFP91 as a potential mediator of necroptosis. Our mechanistic study demonstrates that ZFP91 promotes RIPK1-RIPK3 interaction, thereby stabilizing the RIPK1 and RIPK3 proteins and facilitating necroptosis. ZFP91 stabilized RIPK1 to promote cell death by inducing RIPK1 de-ubiquitination. ZFP91 also significantly increased production of mitochondrial reactive oxygen species (ROS). Accumulation of ROS promoted RIPK3-independent necroptosis triggered by tumor necrosis factor (TNF). in vivo, ZFP91 knockdown alleviated TNFα-induced systemic inflammatory response syndrome (SIRS). These results provide direct evidence that ZFP91 plays an important role in the initiation of RIPK1/RIPK3-dependent necroptosis in vitro and in vivo. We discussed the potential of ZFP91 as a novel therapeutic target for necroptosis-associated diseases.

Reactive Oxygen Species: Do They Play a Role in Adaptive Immunity?

The immune system protects the host from a plethora of microorganisms and toxins through its unique ability to distinguish self from non-self. To perform this delicate but essential task, the immune system relies on two lines of defense. The innate immune system, which is by nature fast acting, represents the first line of defense. It involves anatomical barriers, physiological factors as well as a subset of haematopoietically-derived cells generically call leukocytes. Activation of the innate immune response leads to a state of inflammation that serves to both warn about and combat the ongoing infection and delivers the antigenic information of the invading pathogens to initiate the slower but highly potent and specific second line of defense, the adaptive immune system. The adaptive immune response calls on T lymphocytes as well as the B lymphocytes essential for the elimination of pathogens and the establishment of the immunological memory. Reactive oxygen species (ROS) have been implicated in many aspects of the immune responses to pathogens, mostly in innate immune functions, such as the respiratory burst and inflammasome activation. Here in this mini review, we focus on the role of ROS in adaptive immunity. We examine how ROS contribute to T-cell biology and discuss whether this activity can be extrapolated to B cells.

Upregulation of RIP3 promotes necroptosis via a ROS‑dependent NF‑κB pathway to induce chronic inflammation in HK‑2 cells

Tubular atrophy/interstitial fibrosis (TA/IF) is a major cause of late allograft loss, and inflammation within areas of TA/IF is associated with adverse outcomes in kidney transplantation. However, there is currently no satisfactory method to suppress this inflammation to improve TA/IF. The present study aimed to determine the proinflammatory role of receptor-interacting protein 3 (RIP3) in TA/IF to discover a novel therapeutic target. Reverse transcription-quantitative PCR and western blotting were performed to detect the expression of RIP3 and inflammation-associated factors. Lactate dehydrogenase release assay was used to determine necroptosis. Fluorescent 2,7-dichlorodihydrofluorescein diacetate was used to detect the levels of reactive oxygen species (ROS). The results demonstrated that patients with chronic TA/IF exhibited upregulated receptor-interacting protein 3 (RIP3) expression compared with the patients who had a favorable recovery after renal transplant. Therefore, the current study used normal renal tubular epithelial cells HK-2 to establish a cellular model with a high expression level of RIP3 in order to investigate the effect of RIP3 on renal epithelial cells after transplantation. The western blotting results demonstrated that overexpression of RIP3 could significantly increase the phosphorylation level of the necroptosis executive molecule mixed lineage kinase domain-like protein. Lactate dehydrogenase release, a key feature of necroptosis, was also markedly improved by RIP3 overexpression. Moreover, a higher inflammatory response was detected in HK-2 cells with RIP3 overexpression, and this elevated inflammation could be restored by the necroptosis inhibitor necrosulfonamide. Of note, it was found that overexpression of RIP3 activated the NF-κB signaling pathway via the excessive accumulation of ROS to induce necroptosis, which ultimately led to inflammation. Collectively, these findings indicated that overexpression of RIP3 promoted necroptosis via a ROS-dependent NF-κB pathway to induce chronic inflammation, suggesting that RIP3 may have the potential to be a therapeutic target against inflammation in TA/IF.

Combined Anticancer Effect of Plasma-Activated Infusion and Salinomycin by Targeting Autophagy and Mitochondrial Morphology

Non-thermal atmospheric pressure plasma (NTAPP)-activated liquids have emerged as new promising anticancer agents because they preferentially injure malignant cells. Here, we report plasma-activated infusion (PAI) as a novel NTAPP-based anti-neoplastic agent. PAI was prepared by irradiating helium NTAP to form a clinically approved infusion fluid. PAI dose-dependently killed malignant melanoma and osteosarcoma cell lines while showing much lower cytotoxic effects on dermal and lung fibroblasts. We found that PAI and salinomycin (Sal), an emerging anticancer stem cell agent, mutually operated as adjuvants. The combined administration of PAI and Sal was much more effective than single-agent application in reducing the growth and lung metastasis of osteosarcoma allografts with minimal adverse effects. Mechanistically, PAI explicitly induced necroptosis and increased the phosphorylation of receptor-interacting protein 1/3 rapidly and transiently. PAI also suppressed the ambient autophagic flux by activating the mammalian target of the rapamycin pathway. PAI increased the phosphorylation of Raptor, Rictor, and p70-S6 kinase, along with decreased LC3-I/II expression. In contrast, Sal promoted autophagy. Moreover, Sal exacerbated the mitochondrial network collapse caused by PAI, resulting in aberrant clustering of fragmented mitochondrial in a tumor-specific manner. Our findings suggest that combined administration of PAI and Sal is a promising approach for treating these apoptosis-resistant cancers.

Resveratrol inhibits necroptosis by mediating the TNF-α/RIP1/RIP3/MLKL pathway in myocardial hypoxia/reoxygenation injury

Resveratrol (RES) protects myocardial cells from hypoxia/reoxygenation (H/R)-caused injury. However, the mechanism of this effect has not been clarified. Thus, in this study, we aimed to determine whether RES attenuates H/R-induced cell necroptosis by inhibiting the tumor necrosis factor-alpha (TNF-α)/receptor-interacting protein kinase 1 (RIP1)/RIP3/mixed-lineage kinase domain-like (MLKL) signaling pathway. Rat myocardial ischemia/reperfusion (I/R) models and H/R-injured cell models were constructed. Our study showed that myocardial H/R injury significantly increased the levels of TNF-α, RIP1, RIP3, and p-MLKL/MLKL by western blot analysis. Cell viability assay and 4,6-dianmidino-2-phenylindole (DAPI)-propidium iodide staining showed that the cell viability was decreased, and necroptosis was increased after myocardial H/R injury. The expressions of TNF-α, RIP1, RIP3, and p-MLKL/MLKL in H/R myocardial cells treated with different concentrations of RES were significantly downregulated. In addition, we also found that the cell viability was increased and necroptosis was decreased in dose-dependent manners when H/R-injured cells were treated with RES. In addition, the enhanced effect of TNF-α on necroptosis in myocardial H/R-injured cells was improved by RES, and the effect of RES was confirmed in vivo in I/R rats. This study also showed that RES suppresses necroptosis in H9c2 cells, which may occur through the inhibition of the TNF-α/RIP1/RIP3/MLKL signaling pathway. Our data suggest that necroptosis is a promising therapeutic target and may be a promising therapeutic target for the treatment of myocardial I/R injury.

Cadmium exposure induces TNF-α-mediated necroptosis via FPR2/TGF-β/NF-κB pathway in swine myocardium

Cadmium (Cd) is one common environmental pollutant with systemic toxicity. Lipoxin A4 (LXA4) can regulate transforming growth factor-β (TGF-β) pathway and alleviate tissue injury via binding to formyl peptide receptor 2 (FPR2). The activation of nuclear factor-κB (NF-κB) pathway can promote the occurence of necroptosis. However, whether Cd exposure induces necroptosis in swine myocardium and the role of FPR2/TGF-β/NF-κB pathway in this process are unclear. Hence, we established Cd-exposed swine myocardial injury model by feeding a CdCl₂ added diet (20 mg Cd/kg diet). Hematoxylin-eosin (H&E) staining was used to observe the morphological changes, and inductively coupled plasma mass spectrometry (ICP-MS) was performed to detect the levels of ion elements in myocardium. We further detected LXA4 and its receptor FPR2, TGF-β, Nrf2, NF-κB pathway and necroptosis related-genes expressions by RT-PCR and western blot. The results showed that Cd exposure induced necrotic cell death and ion homeostasis imbalance in swine myocardium. Moreover, Cd exposure increased the LXA4 content, inhibited the FPR2 expression, activated TGF-β pathway and suppressed Nrf2 pathway, activating the NF-κB pathway. In addition, Cd exposure increased the expressions of necroptosis related-genes TNF-α, TNFR1, RIP1, RIP3 and MLKL. It indicated Cd exposure induced necroptosis via FPR2/TGF-β/NF-κB pathway, revealing the potential mechanism of Cd-induced cardiotoxicity in swine myocardium.

Tetrachlorobenzoquinone exposure triggers ferroptosis contributing to its neurotoxicity

Halogenated quinones are representative metabolites of persistent organic pollutants. Tetrachlorobenzoquinone (TCBQ) is a reactive metabolite of the widely used fungicide hexachlorobenzene (HCB) and wood preservative pentachlorophenol (PCP). Our previous studies have demonstrated that TCBQ induced neuron-like cell apoptosis in a reactive oxygen species (ROS)-dependent manner. Here, we found that TCBQ caused lipid peroxidation and cellular morphological changes including shrinked mitochondrial size, suggesting the involvement of a recently uncovered form of programmed cell death (PCD), ferroptosis. Indeed, we then identified that ferroptosis is a novel PCD driven by TCBQ, which was correlated with a decrease in glutathione peroxidase 4 (GPX4) level and iron accumulation by altering iron metabolism. Notably, nuclear factor erythroid-derived 2-like 2 (Nrf2) is a negative regulator in modulating the outcomes of ferroptosis as an adaptive cellular defense response. Nrf2 activation enhanced iron storage capacity and GPX4 activity by elevating ferritin heavy chain 1 (FTH1) expression and glutathione (GSH) level, respectively. On the contrary, Nfe2l2 (Nrf2) deficiency enhanced PC12 cells susceptibility to ferroptosis.

Emodin Induced Necroptosis and Inhibited Glycolysis in the Renal Cancer Cells by Enhancing ROS

Renal cell carcinoma (RCC) is a tumor with unpredictable presentation and poor clinical outcome. RCC is always resistant to chemotherapy and radiation, and weakly sensitive to immunotherapeutic agents. Therefore, novel agents and approaches are urgently needed for the treatment of RCC. Emodin, an anthraquinone compound extracted from rhubarb and other traditional Chinese herbs, has been implicated in a wide variety of pharmacological effects, such as anti-inflammatory, antiviral, and antitumor activities. However, its role in RCC remains unknown. In this study, we found that emodin effectively killed renal cancer cells without significant toxicity to noncancerous cell HK-2. Flow cytometry assay with Annexin V-FITC and PI demonstrated that emodin induces necroptosis, but not apoptosis, in renal cancer cells. Meanwhile, the phosphorylation levels of RIP1 and MLKL, the key necroptosis-related proteins, were significantly increased. To explore how emodin inhibits kidney tumor growth, we tested reactive oxygen species (ROS) levels and found that the levels of ROS increased upon emodin treatment in a dose-dependent manner. Further studies demonstrated that emodin induces necroptosis through ROS-mediated activation of JNK signaling pathway and also inhibits glycolysis by downregulation of GLUT1 through ROS-mediated inactivation of the PI3K/AKT signaling pathway. Our findings revealed the potential mechanisms by which emodin suppresses renal cancer cell growth and will help develop novel therapeutic approaches for patients with JNK- or PI3K/AKT-dysregulated renal cancer.

CB1R Promotes Chronic Alcohol-Induced Neuronal Necroptosis in Mice Prefrontal Cortex

AIMS

Alcohol abuse induces multiple neuropathology and causes global burden to human health. Prefrontal cortex (PFC) is one of the most susceptible regions to alcohol-induced neuropathology. However, precise mechanisms underlying these effects on PFC remain to be elucidated. Herein, we investigated whether RIP1/RIP3/MLKL-mediated necroptosis was involved in the alcohol-induced PFC injury, and explored the effect that cannabinoid receptors (CBRs) exerted on the neurotoxicity of alcohol.

METHODS

In this study, dynamic development of neuronal necroptosis in the PFC region was monitored after 95% (v/v) alcohol vapor administration for 15 and 30 days, respectively. Selective CBRs agonists or inverse agonists were pretreated according to the experimental design. All the PFC tissues were isolated and further examined by biochemical and histopathological analyses.

RESULTS

It was found that chronic alcohol exposure increased the protein level of MLKL and also the phosphorylated levels of RIP1, RIP3 and MLKL in a time-dependent manner, all of which indicated the activation of necroptosis signaling. Particularly, compared to astrocytes, neurons from the PFC showed more prototypical necrotic morphology in response to alcohol insults. In parallel, an increased protein level of CB1R was also found after 15 and 30 days alcohol exposure. Administration of specific inverse agonists of CB1R (AM251 and AM281), but not its agonists or CB2R modulators, significantly alleviated the RIP1/RIP3/MLKL-mediated neuronal necroptosis.

CONCLUSION

We reported the involvement of RIP1/RIP3/MLKL-mediated necroptosis in alcohol-induced PFC neurotoxicity, and identified CB1R as a critical regulator of neuronal necroptosis that enhanced our understanding of alcohol-induced neuropathology in the PFC.

Oxidative Stress and Antioxidant Treatments in Cardiovascular Diseases

Oxidative stress plays a key role in many physiological and pathological conditions. The intracellular oxidative homeostasis is tightly regulated by the reactive oxygen species production and the intracellular defense mechanisms. Increased oxidative stress could alter lipid, DNA, and protein, resulting in cellular inflammation and programmed cell death. Evidences show that oxidative stress plays an important role in the progression of various cardiovascular diseases, such as atherosclerosis, heart failure, cardiac arrhythmia, and ischemia-reperfusion injury. There are a number of therapeutic options to treat oxidative stress-associated cardiovascular diseases. Well known antioxidants, such as nutritional supplements, as well as more novel antioxidants have been studied. In addition, novel therapeutic strategies using miRNA and nanomedicine are also being developed to treat various cardiovascular diseases. In this article, we provide a detailed description of oxidative stress. Then, we will introduce the relationship between oxidative stress and several cardiovascular diseases. Finally, we will focus on the clinical implications of oxidative stress in cardiovascular diseases.

Mitochondrial ROS prime the hyperglycemic shift from apoptosis to necroptosis

We have previously identified a shift from TNF-α-induced apoptosis to necroptosis that occurs under hyperglycemic conditions. This shift involves the downregulation or silencing of caspases and concurrent upregulation of necroptotic proteins leading to activation of the necrosome. In addition, under hyperglycemic conditions in vivo, this shift in cell death mechanisms exacerbates neonatal hypoxia-ischemia (HI) brain injury. Here, we identify two major factors that drive the hyperglycemic shift to necroptosis: (1) reactive oxygen species (ROS) and (2) receptor-interacting protein kinase 1 (RIP1). ROS, including mitochondrial superoxide, led to the oxidation of RIP1, as well as formation and activation of the necrosome. Concurrently, ROS mediate a decrease in the levels and activation of executioner caspases-3, -6, and -7. Importantly, hyperglycemia and mitochondrial ROS result in the oxidation of RIP1 and loss of executioner caspases prior to death receptor engagement by TNF-α. Moreover, RIP1 partially controlled levels of mitochondrial ROS in the context of hyperglycemia. As a result of its regulation of ROS, RIP1 also regulated necrosome activation and caspase loss. Mitochondrial ROS exacerbated neonatal HI-brain injury in hyperglycemic mice, as a result of the shift from apoptosis to necroptosis.

Mechanisms and pathogenesis underlying environmental chemical-induced necroptosis

Necroptosis is a regulated cell death that is governed by mixed lineage kinase domain-like, receptor-interacting serine-threonine kinase 3 and commonly displays with necrosis morphological characteristics. This study examined the molecular mechanisms involved in the chemical-induced necroptosis where a systematic evaluation of experimental studies addressing this issue is missing. We strictly reviewed all scientific reports related to our search terms including "necroptosis" or "programmed necrosis", "environmental chemicals" or "air pollutants" or "pesticides" or "nanoparticles" and "Medicines" from 2009 to 2019. Manuscripts that met the objective of this study were included for further evaluations. Studies showed that several pathological contexts like cancer, neurodegenerative disorders, and inflammatory diseases were related to necroptosis. Furthermore, multiple chemical-induced cytotoxic effects, such as DNA damage, mitochondrial dysregulation, oxidative damage, lipid peroxidation, endoplasmic reticulum disruption, and inflammation are also associated with necroptosis. The main environmental exposures that are related to necroptosis are air pollutants (airborne particulate matter, cadmium, and hydrogen sulfide), nanoparticles (gold, silver, and silica), pesticides (endosulfan, cypermethrin, chlorpyrifos, and paraquat), and tobacco smoke. To sum up, air pollutants, pesticides, and nanoparticles could potentially affect human health via disruption of cell growth and induction of necroptosis. Understanding the exact molecular pathogenesis of these environmental chemicals needs further comprehensive research to provide innovative concepts for the prevention approaches and introduce novel targets for the amelioration of a range of human health problems.

Systemic deficiency of mouse arachidonate 15-lipoxygenase induces defective erythropoiesis and transgenic expression of the human enzyme rescues this phenotype

Arachidonic acid 15-lipoxygenases (ALOX15) are lipid peroxidizing enzymes, which has previously been implicated in the maturational breakdown of intracellular organelles and plasma membrane remodeling during reticulocyte-erythrocyte transition. Conventional Alox15^-/- mice are viable, develop normally but do not exhibit a major defective erythropoietic phenotype. To characterize the putative in vivo relevance of Alox15 for red blood cell development, we explored the impact of systemic inactivation of the Alox15 gene on mouse erythropoiesis. We found that Alox15^-/- mice exhibited reduced erythrocyte counts, elevated reticulocyte counts and red cell hyperchromia. The structure of the plasma membrane of Alox15^-/- erythrocytes is altered and a significant share of the red cells was present as echinocytes and/or acanthocytes. An increased share of the Alox15^-/- erythrocytes cells were annexin V positive, which indicates a loss of plasma membrane asymmetry. Erythrocytes of Alox15^-/- mice were more susceptible to osmotic hemolysis and exhibited a reduced ex vivo life span. When we transgenically expressed human ALOX15 in Alox15^-/- mice under the control of the aP2 promoter the defective erythropoietic system was rescued and the impaired osmotic resistance was normalized. Together these data suggest the involvement Alox15 in the maturational remodeling of the plasma membrane during red cell development.

Targeting necroptosis in anticancer therapy: mechanisms and modulators

Necroptosis, a genetically programmed form of necrotic cell death, serves as an important pathway in human diseases. As a critical cell-killing mechanism, necroptosis is associated with cancer progression, metastasis, and immunosurveillance. Targeting necroptosis pathway by small molecule modulators is emerging as an effective approach in cancer therapy, which has the advantage to bypass the apoptosis-resistance and maintain antitumor immunity. Therefore, a better understanding of the mechanism of necroptosis and necroptosis modulators is necessary to develop novel strategies for cancer therapy. This review will summarize recent progress of the mechanisms and detecting methods of necroptosis. In particular, the relationship between necroptosis and cancer therapy and medicinal chemistry of necroptosis modulators will be focused on.

Turkish Propolis and Its Nano Form Can Ameliorate the Side Effects of Cisplatin, Which Is a Widely Used Drug in the Treatment of Cancer

This study was performed to determine the effects of chitosan-coated nano-propolis (NP), which is synthesized via a green sonochemical method, and propolis on the side effects of cisplatin (CP), which is a widely used drug in the treatment of cancer. For this aim, 56 rats were divided into seven groups, balancing their body weights (BW). The study was designed as Control, CP (3 mg/kg BW at single dose of CP as intraperitoneal, ip), Propolis (100 mg/kg BW per day of propolis by gavage), NP-10 (10 mg/kg BW of NP per day by gavage), CP + Propolis (3 mg/kg BW of CP and 100 mg/kg BW of propolis), CP + NP-10 (3 mg/kg CP and 10 mg/kg BW of NP), and CP + NP-30 (3 mg/kg BW of CP and 30 mg/kg BW of NP). Propolis and NP (especially NP-30) were preserved via biochemical parameters, oxidative stress, and activation of apoptotic pathways (anti-apoptotic protein: Bcl-2 and pro-apoptotic protein: Bax) in liver and kidney tissues in the toxicity induced by CP. The NP were more effective than propolis at a dose of 30 mg/kg BW and had the potential to ameliorate CP's negative effects while overcoming serious side effects such as liver and kidney damage.

Structure-tuned membrane active Ir-complexed oligoarginine overcomes cancer cell drug resistance and triggers immune responses in mice

The development of chemotherapy, an important cancer treatment modality, is hindered by the frequently found drug-resistance phenomenon. Meanwhile, researchers have been enthused lately by the synergistic use of chemotherapy with emerging immunotherapeutic treatments. In an effort to address both of the two unmet needs, reported herein is a study on a series of membrane active iridium(iii) complexed oligoarginine peptides with a new cell death mechanism capable of overcoming drug resistance as well as stimulating immunological responses. A systematic structure-activity relationship study elucidated the interdependent effects of three structural factors, i.e., hydrophobicity, topology and cationicity, on the regulation of the cytotoxicity of the Ir(iii)-oligoarginine peptides. With the most prominent toxicities, Ir-complexed octaarginines (R8) were found to display a progressive oncotic cell death featuring cell membrane-penetration and eruptive cytoplasmic content release. Consequently, this membrane-centric death mechanism showed promising potential in overcoming multiple chemical drug-resistance of cancer cells. More interestingly, the eruptive mode of cell death proved to be immunogenic by stimulating the dendritic cell maturation and inflammatory factor accumulation in mice tumours. Taking these mechanisms together, this work demonstrates that membrane active compounds may become the next generation chemotherapeutics because of their combined advantages.

Mitochondrial ROS promote macrophage pyroptosis by inducing GSDMD oxidation

Disrupted mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) generation are often associated with macrophage pyroptosis. It remains unclear how these forms of mitochondrial dysfunction relate to inflammasome activation and gasdermin-D (Gsdmd) cleavage, two central steps of the pyroptotic process. Here, we also found MMP collapse and ROS generation induced by Nlrp3 inflammasome activation as previous studies reported. The elimination of ROS alleviated the cleavage of Gsdmd, suggesting that Gsdmd cleavage occurs downstream of ROS release. Consistent with this result, hydrogen peroxide treatment augmented the cleavage of Gsdmd by caspase-1. Indeed, four amino acid residues of Gsdmd were oxidized under oxidative stress in macrophages. The efficiency of Gsdmd cleavage by inflammatory caspase-1 was dramatically reduced when oxidative modification was blocked by mutation of these amino acid residues. These results demonstrate that Gsdmd oxidation serves as a de novo mechanism by which mitochondrial ROS promote Nlrp3 inflammasome-dependent pyroptotic cell death.

Raman micro-spectroscopy monitoring of cytochrome c redox state in Candida utilis during cell death under low-temperature plasma-induced oxidative stress

Oxidative stress may result in different modes of cell death, such as necrosis, apoptosis and necroptosis. Currently, researchers are still striving to develop efficient tools/methods to distinguish the cell death modes in direct and label-free ways. In this study, we attempted to employ Raman micro-spectroscopy to observe the molecular changes in Candida utilis cells under oxidative stress induced by low-temperature plasma (LTP) and explore the spectroscopic biomarkers for the modes of cell death under oxidative stress. In this research, we confirmed that LTP could impose oxidative stress on the yeast cells, and recorded the changes of Raman signals of cytochrome c in the cells under LTP oxidative stress. Subsequently, we identified the biochemical and morphological characteristic features corresponding to different modes of cell death. Interestingly, we found that LTP under certain conditions could induce oxidative stress which caused the yeast cell death mainly by means of necroptosis, which was verified by Annexin V/PI, HMGB1 location assay and immunoprecipitation assay of the RIP1/RIP3 necrosome. Correspondingly, we also showed that the LTP induced necroptosis, associated with the increase of cytoplasmic Ca²⁺ and mitochondrial ROS, the decrease of mitochondrial membrane potential, the release of oxidized cytochrome c from the mitochondrion to the cytoplasm, and the destruction of mitochondria in yeast cells. This work has therefore demonstrated that monitoring the redox state of cytochrome c using Raman micro-spectroscopy is very useful for distinguishing the modes of cell death and particularly may unveil the unique necroptosis process of cells under extrinsic oxidative stress.

SIRT3 deficiency delays diabetic skin wound healing via oxidative stress and necroptosis enhancement

Sirtuin 3 (SIRT3) plays a vital role in several dermatological diseases. However, the role and detailed mechanism of SIRT3 in diabetic wound healing are unknown well yet. To explore possible involvement of SIRT3 and necroptosis in diabetic skin wound healing, SIRT3 knockout (KO) mice and 129S1/SvImJ wild‐type (WT) mice were injected with streptozotocin (STZ), and mice skin fibroblasts were exposed to high glucose (HG). It was found that SIRT3 expression decreased in the skin of diabetic patients. SIRT3 deficiency delayed healing rate, reduced blood supply and vascular endothelial growth factor expression, promoted superoxide production, increased malondialdehyde (MDA) levels, decreased total antioxidant capacity (T‐AOC), reduced superoxide dismutase (SOD) activity and aggravated ultrastructure disorder in skin wound of diabetic mice. SIRT3 deficiency inhibited mice skin fibroblasts migration with HG stimulation, which was restored by SIRT3 overexpression. SIRT3 deficiency also suppressed α‐smooth muscle actin (α‐SMA) expression, enhanced superoxide production but decreased mitochondrial membrane potential with HG stimulation after scratch. SIRT3 deficiency further elevated receptor‐interacting protein kinase 3 (RIPK3), RIPK1 and caspase 3 expression both in vitro and in vivo. Collectively, SIRT3 deficiency delayed skin wound healing in diabetes, the mechanism might be related to impaired mitochondria function, enhanced oxidative stress and increased necroptosis. This may provide a novel therapeutic target to accelerate diabetic skin wound healing.

RIPK1 inhibitor Cpd-71 attenuates renal dysfunction in cisplatin-treated mice via attenuating necroptosis, inflammation and oxidative stress

Acute kidney injury (AKI) is a destructive clinical condition induced by multiple insults including ischemic reperfusion, nephrotoxic drugs and sepsis. It is characterized by a sudden decline in renal function, in addition to excessive inflammation, oxidative stress and programmed cell death of renal tubular epithelial cells. RIPK1-mediated necroptosis plays an important role in AKI. In the present study, we evaluated the treatment effects of Compound-71 (Cpd-71), a novel RIPK1 inhibitor, by comparing with Necrostatin-1 (Nec-1), a classic RIPK1 inhibitor, which has several drawbacks like the narrow structure–activity relationship (SAR) profile, moderate potency and non-ideal pharmacokinetic properties, in vivo and in vitro. Our results showed that pretreatment of Cpd-71 attenuated cisplatin-induced renal injury, restored renal function and suppressed renal inflammation, oxidative stress and cell necroptosis. In addition, Cpd-71 inhibited renal damage while reducing the up-regulated serum creatinine (Cr) and blood urea nitrogen (BUN) levels in established AKI mice model. Consistently, we confirmed that Cpd-71 exhibited more effectively suppressive effect on cisplatin-induced renal tubular cell necroptosis than Nec-1, by physically binding to the allosteric type III ligand binding site of RIPK1, thereby reduced RIPK1 kinase activity, RIPK1/RIPK3 complex formation and phosphor-MLKL membrane translocation by molecular docking, Western blot, co-immunoprecipitation and cellular thermal shift assay (CETSA). Taken together, we currently showed that targeting RIPK1 with Cpd-71 may serve as a promising clinical candidate for AKI treatment.

TNFR1 and TNFR2 in the Control of the Life and Death Balance of Macrophages

Macrophages stand in the first line of defense against a variety of pathogens but are also involved in the maintenance of tissue homeostasis. To fulfill their functions macrophages sense a broad range of pathogen- and damage-associated molecular patterns (PAMPs/DAMPs) by plasma membrane and intracellular pattern recognition receptors (PRRs). Intriguingly, the overwhelming majority of PPRs trigger the production of the pleiotropic cytokine tumor necrosis factor-alpha (TNF). TNF affects almost any type of cell including macrophages themselves. TNF promotes the inflammatory activity of macrophages but also controls macrophage survival and death. TNF exerts its activities by stimulation of two different types of receptors, TNF receptor-1 (TNFR1) and TNFR2, which are both expressed by macrophages. The two TNF receptor types trigger distinct and common signaling pathways that can work in an interconnected manner. Based on a brief general description of major TNF receptor-associated signaling pathways, we focus in this review on research of recent years that revealed insights into the molecular mechanisms how the TNFR1-TNFR2 signaling network controls the life and death balance of macrophages. In particular, we discuss how the TNFR1-TNFR2 signaling network is integrated into PRR signaling.

Mitochondrial Entry of Cytotoxic Proteases: A New Insight into the Granzyme B Cell Death Pathway

The mitochondria represent an integration and amplification hub for various death pathways including that mediated by granzyme B (GB), a granule enzyme expressed by cytotoxic lymphocytes. GB activates the proapoptotic B cell CLL/lymphoma 2 (Bcl-2) family member BH3-interacting domain death agonist (BID) to switch on the intrinsic mitochondrial death pathway, leading to Bcl-2-associated X protein (Bax)/Bcl-2 homologous antagonist/killer- (Bak-) dependent mitochondrial outer membrane permeabilization (MOMP), the dissipation of mitochondrial transmembrane potential (ΔΨm), and the production of reactive oxygen species (ROS). GB can also induce mitochondrial damage in the absence of BID, Bax, and Bak, critical for MOMP, indicating that GB targets the mitochondria in other ways. Interestingly, granzyme A (GA), GB, and caspase 3 can all directly target the mitochondrial respiratory chain complex I for ROS-dependent cell death. Studies of ROS biogenesis have revealed that GB must enter the mitochondria for ROS production, making the mitochondrial entry of cytotoxic proteases (MECP) an unexpected critical step in the granzyme death pathway. MECP requires an intact ΔΨm and is mediated though Sam50 and Tim22 channels in a mtHSP70-dependent manner. Preventing MECP severely compromises GB cytotoxicity. In this review, we provide a brief overview of the canonical mitochondrial death pathway in order to put into perspective this new insight into the GB action on the mitochondria to trigger ROS-dependent cell death.

The Roles of Environmental Factors in Regulation of Oxidative Stress in Plant

Exposure to a variety of environmental factors such as salinity, drought, metal toxicity, extreme temperature, air pollutants, ultraviolet-B (UV-B) radiation, pesticides, and pathogen infection leads to subject oxidative stress in plants, which in turn affects multiple biological processes via reactive oxygen species (ROS) generation. ROS include hydroxyl radicals, singlet oxygen, and hydrogen peroxide in the plant cells and activates signaling pathways leading to some changes of physiological, biochemical, and molecular mechanisms in cellular metabolism. Excessive ROS, however, cause oxidative stress, a state of imbalance between the production of ROS and the neutralization of free radicals by antioxidants, resulting in damage of cellular components including lipids, nucleic acids, metabolites, and proteins, which finally leads to the death of cells in plants. Thus, maintaining a physiological level of ROS is crucial for aerobic organisms, which relies on the combined operation of enzymatic and nonenzymatic antioxidants. In order to improve plants' tolerance towards the harsh environment, it is vital to reinforce the comprehension of oxidative stress and antioxidant systems. In this review, recent findings on the metabolism of ROS as well as the antioxidative defense machinery are briefly updated. The latest findings on differential regulation of antioxidants at multiple levels under adverse environment are also discussed here.

Necrosis, apoptosis, necroptosis, three modes of action of dopaminergic neuron neurotoxins

Most of the Parkinson’s disease (PD) cases are sporadic, although several genes are directly related to PD. Several pathways are central in PD pathogenesis: protein aggregation linked to proteasomal impairments, mitochondrial dysfunctions and impairment in dopamine (DA) release. Here we studied the close crossing of mitochondrial dysfunction and aggregation of α-synuclein (α-syn) and in the extension in the dopaminergic neuronal death. Here, using rat primary cultures of mesencephalic neurons, we induced the mitochondrial impairments using “DA-toxins” (MPP⁺, 6OHDA, rotenone). We showed that the DA-Toxins induced dopaminergic cell death through different pathways: caspase-dependent cell death for 6OHDA; MPP⁺ stimulated caspase-independent cell death, and rotenone activated both pathways. In addition, a decrease in energy production and/or a development of oxidative stress were observed and were linked to α-syn aggregation with generation of Lewy body-like inclusions (found inside and outside the dopaminergic neurons). We demonstrated that any of induced mitochondrial disturbances and processes of death led to α-syn protein aggregation and finally to cell death. Our study depicts the cell death mechanisms taking place in in vitro models of Parkinson’s disease and how mitochondrial dysfunctions is at the cross road of the pathologies of this disease.

Redox biology of regulated cell death in cancer: A focus on necroptosis and ferroptosis

Redox changes and generation of reactive oxygen species (ROS) are part of normal cell metabolism. While low ROS levels are implicated in cellular signaling pathways necessary for survival, higher levels play major roles in cancer development as well as cell death signaling and execution. A role for redox changes in apoptosis has been long established; however, several new modalities of regulated cell death have been brought to light, for which the importance of ROS production as well as ROS source and targets are being actively investigated. In this review, we summarize recent findings on the role of ROS and redox changes in the activation and execution of two major forms of regulated cell death, necroptosis and ferroptosis. We also discuss the potential of using modulators of these two forms of cell death to exacerbate ROS as a promising anticancer therapy.

Emodin induced necroptosis in the glioma cell line U251 via the TNF-α/RIP1/RIP3 pathway

Emodin, an anthraquinone compound extracted from rhubarb and other traditional Chinese medicines, has been proven to have a wide range of pharmacological effects, such as anti-inflammatory, antiviral, and antitumor activities. Previous studies have confirmed that emodin has inhibitory effects on various solid tumors, such as osteosarcoma, liver cancer, prostate cancer and glioma. This study aimed to investigate the effects and mechanisms of emodin-induced necroptosis in the glioma cell line U251 by targeting the TNF-α/RIP1/RIP3 signaling pathway. We found that emodin could significantly inhibit U251 cell proliferation, and the viability of U251 cells treated with emodin was reduced in a dose- and time-dependent manner. Flow cytometry assays and Hoechst-PI staining assays showed that emodin induced apoptosis and necroptosis. Real-time PCR and western blot analysis showed that emodin upregulated the levels of TNF-α, RIP1, RIP3 and MLKL. Furthermore, the RIP1 inhibitor Nec-1 and the RIP3 inhibitor GSK872 attenuated the killing effect of emodin on U251 cells. In addition, emodin could increase the levels of TNF-α, RIP1, RIP3 and MLKL in vivo. The results demonstrate that emodin could induce necroptosis in glioma possibly through the activation of the TNF-α/RIP1/RIP3 axis. These studies provide novel insight into the induction of necroptosis by emodin and indicate that emodin might be a potential candidate for treating glioma through the necroptosis pathway.

Early Protection by Resveratrol in Rat Lung Transplantation

BACKGROUND Resveratrol is a multifunctional bioactive substance that has effects in anti-inflammation and prevention of ischemia-reperfusion injury. This study compared the inflammation and expression of related proteins during the early stages after transplantation to explore the effects and mechanisms of resveratrol on transplanted lung. MATERIAL AND METHODS Sprague-Dawley rats were randomized to receive pretreatment of resveratrol suspension (60 mg/kg; RES group), dexamethasone (1 mg/kg; DEM group), or normal saline solution (2 mL/kg; control group) 1 h before lung transplantation. The cytokine concentration in the serum and bronchoalveolar lavage fluid (BALF) of the recipients was determined 24 h after transplantation. Histopathologic evaluation, including lung injury score, and the expression of necroptosis-associated proteins was assessed. RESULTS Histopathologic evaluation showed pneumocyte damage and endothelialitis associated with hemorrhage in the alveoli in the control group, the severity of which was greater than that in the other 2 groups. The levels of interleukin-6 and tumor necrosis factor-a in the serum and BALF of the RES and DEM groups were lower than those in the control group. The expression of necroptosis-associated proteins in the RES group was lower than that in the control group, and was inversely proportional to lung injury. CONCLUSIONS Pretreatment with resveratrol protected rat lung in the early stages after transplantation. We determined a relationship between necroptosis-associated proteins and transplanted lung injury, which suggests that the mechanism of lung transplantation-associated ischemia-reperfusion injury may be related to necroptosis.

Programmed Necrosis and Disease:We interrupt your regular programming to bring you necroinflammation

Compared to the tidy and immunologically silent death during apoptosis, necrosis seems like a chaotic and unorganized demise. However, we now recognize that there is a method to its madness, as many forms of necrotic cell death are indeed programmed and function beyond lytic cell death to support homeostasis and immunity. Inherently more immunogenic than their apoptotic counterpart, programmed necrosis, such as necroptosis, pyroptosis, ferroptosis, and NETosis, releases inflammatory cytokines and danger-associated molecular patterns (DAMPs), skewing the milieu to a pro-inflammatory state. Moreover, impaired clearance of dead cells often leads to inflammation. Importantly, these pathways have all been implicated in inflammatory and autoimmune diseases, therefore careful understanding of their molecular mechanisms can have long lasting effects on how we interpret their role in disease and how we translate these mechanisms into therapy.