Programmed necrosis: backup to and competitor with apoptosis in the immune system

Programmed cell death is essential for the development and maintenance of the immune system and its responses to exogenous and endogenous stimuli. Studies have demonstrated that in addition to caspase-dependent apoptosis, necrosis dependent on the kinases RIP1 and RIP3 (also called necroptosis) is a major programmed cell-death pathway in development and immunity. These two programmed cell-death pathways may suppress each other, and necroptosis also serves as an alternative when caspase-dependent apoptosis is inhibited or absent. Here we summarize recent advancements that have identified the molecular mechanisms that underlie necroptosis and explore the mechanisms that regulate the interplay between apoptosis and necroptosis.     

Targeting death receptor induced apoptosis and necroptosis: a novel therapeutic strategy to prevent neuronal damage in retinal detachment

Retinal detachment (RD) is a common cause of human visual impairment. Detachment of photoreceptors from the retinal pigment epithelium causes photoreceptor loss and subsequent vision decline. Death receptor (DR)-induced apoptosis play critical role in activating apoptosis in photoreceptor cells. Z-VAD-FMK inhibits the DR-induced retinal neuronal apoptosis but promotes neuronal death through necroptosis pathway, an alternative programmed cell death, which can be inhibited by Nec-1. Thus, we may achieve a better result by simultaneous inhibition of DR-induced apoptosis and necroptosis, which provides us with a new direction in the treatment of RD.     

Caspase-8: regulating life and death

Roles for cell death in development, homeostasis, and the control of infections and cancer have long been recognized. Although excessive cell damage results in passive necrosis, cells can be triggered to engage molecular programs that result in cell death. Such triggers include cellular stress, oncogenic signals that engage tumor suppressor mechanisms, pathogen insults, and immune mechanisms. The best-known forms of programmed cell death are apoptosis and a recently recognized regulated necrosis termed necroptosis. Of the two best understood pathways of apoptosis, the extrinsic and intrinsic (mitochondrial) pathways, the former is induced by the ligation of death receptors, a subset of the TNF receptor (TNFR) superfamily. Ligation of these death receptors can also induce necroptosis. The extrinsic apoptosis and necroptosis pathways regulate each other and their balance determines whether cells live. Integral in the regulation and initiation of death receptor-mediated activation of programmed cell death is the aspartate-specific cysteine protease (caspase)-8. This review describes the role of caspase-8 in the initiation of extrinsic apoptosis execution and the mechanism by which caspase-8 inhibits necroptosis. The importance of caspase-8 in the development and homeostasis and the way that dysfunctional caspase-8 may contribute to the development of malignancies in mice and humans are also explored.     

Necroptosis: a novel therapeutic target for glioblastoma

Glioblastoma or glioblastoma multiforme (GBM) is the most encountered and malignant form of brain tumors in clinical practice. In spite of optimal and early treatment, the life expectancy of patients with GBM remains poor. It is believed that dysfunction of apoptosis underlies GBM tumorigenesis, proliferation and resistance to chemotherapy and radiotherapy. Although GBM is defective in apoptotic process, pathologic and radiologic observations almost always reveal obvious necrosis foci within GBM. Necrosis seems to be related with GBM proliferation, angiogenesis and invasion. However, tumor cell necrosis induced by various therapies has a potential therapeutic value. Just recently, necrotic cell death is considered as a regulated and controlled process, like apoptosis, termed necroptosis or programmed necrosis. Induction of apoptosis has not made any significant achievements in the treatment of GBM mainly because the tumor cells are apoptosis-resistant. We may achieve a better result by modulating the necroptosis of GBM thus circumvent the apoptosis resistance. Albeit specific molecular pathways involved in GBM necroptosis is not clear and much more studies are needed to confirm the effects of therapy-induced necroptosis on GBM, it provides us with a new direction in the treatment of GBM.     

程序性坏死研究进展

程序性坏死是近年来发现的一种由死亡受体介导的caspases非依赖性细胞死亡模式,通常在凋亡被抑制的情况下发生,具有坏死细胞的形态学特征。研究发现程序性坏死同细胞凋亡一样受细胞内信号因子的周密调节,激酶受体相互作用蛋白激酶1和受体相互作用蛋白激酶3是其关键的调控因子。程序性坏死在炎症性病变、缺血性心脑血管病、神经退行性疾病等多种疾病的发生发展及肿瘤细胞的耐药方面具有重要意义。     

程序性细胞坏死及细胞焦亡信号通路研究进展概述

细胞死亡是生命活动中一个非常重要的事件,真核生物可因物理损伤刺激导致细胞死亡,因特异信号通路介导的程序性细胞死亡近年来得到越来越多的关注。目前程序性细胞死亡主要存在以下3种方式:凋亡(apoptosis)、程序性坏死(necroptosis)、细胞焦亡(pyroptosis)。程序性坏死和细胞焦亡是近年来才发现的新的细胞程序性死亡方式,在细菌或病毒感染宿主细胞过程中起着关键作用。这两种细胞死亡都是细胞裂解型死亡,但其信号通路存在明显差异。本文就这两种程序性细胞死亡的形态学特征、信号转导通路及其在病原体感染过程中的作用等方面的研究进展作一综述。     

坏死性凋亡与肿瘤

坏死性凋亡是不依赖于caspase激活的一种细胞程序性死亡方式,其激活主要依赖于坏死性小体的形成。坏死性凋亡的调控受到多种因素响,RIPK1既可启动坏死性凋亡,也可抑制坏死性凋亡;caspase-8是坏死性凋亡的重要负反馈调节蛋白;CHIP是新发现的坏死性凋亡调控蛋白。坏死性凋亡的触发为对经典凋亡途径抵抗的肿瘤提供了新的治疗策略。     

RIPK3-driven cell death during virus infections

The programmed self-destruction of infected cells is a powerful antimicrobial strategy in metazoans. For decades, apoptosis represented the dominant mechanism by which the virus-infected cell was thought to undergo programmed cell death. More recently, however, new mechanisms of cell death have been described that are also key to host defense. One such mechanism in vertebrates is programmed necrosis, or “necroptosis”, driven by receptor-interacting protein kinase 3 (RIPK3). Once activated by innate immune stimuli, including virus infections, RIPK3 phosphorylates the mixed lineage kinase domain-like protein (MLKL), which then disrupts cellular membranes to effect necroptosis. Emerging evidence demonstrates that RIPK3 can also mediate apoptosis and regulate inflammasomes. Here, we review studies on the mechanisms by which viruses activate RIPK3 and the pathways engaged by RIPK3 that drive cell death.     

Caspase-6 is a key regulator of cross-talk signal way in PANoptosis in cancer

Cysteinyl aspartate specific proteinase (caspase)-6 belongs to the caspase family and plays a vital role in mediating cell death. Under certain conditions, three pathways of programmed cell death (PCD), including apoptosis, necroptosis and pyroptosis (PANoptosis), transform one way into another, with enormous therapeutic potential. Initially, scholars reported that caspase-6 is a caspase executor that mediates apoptosis. With the ceaseless exploration of the PCD types, studies have demonstrated that caspase-6 mediates pyroptosis by regulating gasdermin D and mediates necroptosis by regulating mixed lineage kinase domain-like. By regulating PANoptosis, caspase-6 plays a crucial role in tumorigenesis in humans and mediates anti-tumour immunity. Therefore, a comprehensive understanding of caspase-6 function in cancer via PANoptosis is important for the prevention and therapy of tumours. This article summarized the function of caspase-6 in PANoptosis and its impact on cancer development, providing targets and strategies for tumour treatment.     

Cloaked in ubiquitin,a killer hides in plain sight: the molecular regulation of RIPK1

In the past decade, studies have shown how instrumental programmed cell death (PCD) can be in innate and adaptive immune responses. PCD can be a means to maintain homeostasis, prevent or promote microbial pathogenesis, and drive autoimmune disease and inflammation. The molecular machinery regulating these cell death programs has been examined in detail, although there is still much to be explored. A master regulator of programmed cell death and innate immunity is receptor-interacting protein kinase 1 (RIPK1), which has been implicated in orchestrating various pathologies via the induction of apoptosis, necroptosis, and nuclear factor-κB-driven inflammation. These and other roles for RIPK1 have been reviewed elsewhere. In a reflection of the ability of tumor necrosis factor (TNF) to induce either survival or death response, this molecule in the TNF pathway can transduce either a survival or a death signal. The intrinsic killing capacity of RIPK1 is usually kept in check by the chains of ubiquitin, enabling it to serve in a prosurvival capacity. In this review, the intricate regulatory mechanisms responsible for restraining RIPK1 from killing are discussed primarily in the context of the TNF signaling pathway and how, when these mechanisms are disrupted, RIPK1 is free to unveil its program of cellular demise.     

Chemopreventive agents induce programmed death-1-ligand 1 (PD-L1) surface expression in breast cancer cells and promote PD-L1-mediated T cell apoptosis

Chemotherapy has been widely used in cancer treatment. However, the prognosis of the cancer patients following chemotherapy has not been substantially improved. Alternative strategies such as immunotherapy and their combinations with chemotherapy are now being considered. Yet, the effects of chemotherapy on the immune responses of cancer cells are not clear. Cancer immunoresistance and immune escape are major obstacles in immunotherapy. In the present studies, we examined the effects of chemopreventive agents, paclitaxel, etoposide and 5-fluorouracil, on the surface expression of programmed death-1-ligand 1 (PD-L1), a negative regulator of T cell anti-tumor immunity. Interaction of PD-L1 on cancer cells with programmed death receptor 1 (PD-1) on T cells has been reported to inhibit the proliferation of tumor-reactive cytotoxic T cells and induce T cell apoptosis, which could be an important mechanism in the development of cancer immunoresistance. We demonstrated that those chemopreventive agents were able to induce PD-L1 surface expression in human breast cancer cells, which then promoted PD-L1-mediated T cell apoptosis. Our studies reveal a potential link between chemotherapy and cancer immunoresistance.     

小鼠胚胎肾脏细胞坏死性凋亡的超微结构

目的 观察小鼠胚胎肾脏发育过程中细胞坏死性凋亡的超微结构变化.方法 应用电子显微镜技术对不同胚龄(E12、14、16、18d)胎鼠(各3例)的肾脏的细胞坏死性凋亡进行系统观察.结果 细胞坏死性凋亡确实出现在胚胎肾脏中,它同时具有坏死的细胞质和凋亡的细胞核.细胞肿胀,细胞膜破溃,细胞器也肿胀空泡化.核染色质高密度固缩,边聚,多呈月牙状.细胞凋亡被发现的机会大于坏死性凋亡和细胞胀亡.结论 细胞坏死性凋亡与细胞凋亡及细胞胀亡共同构成了小鼠胚胎肾脏发育过程中的程序性细胞死亡,但坏死性凋亡和胀亡为辅,而以细胞凋亡为主.     

Roscovitine regulates invasive breast cancer cell (MDA-MB231) proliferation and survival through cell cycle regulatory protein cdk5

Roscovitine, a purine analogue, has been considered for the treatment of cancer. Anti-cancer therapeutic efficacy is being evaluated in clinical trials. However, the mechanisms remain unclear. In the present study, cyclic-dependent kinase 5 (cdk5) proved to be a molecular target for roscovitine-triggered apoptosis for highly invasive breast cancer cell death. Because our previous studies have shown a potential role of cdk5 in endothelial cell proliferation/apoptosis [Sharma, M.R., Tuszynski, G.P., Sharma, M.C. (2004). Angiostatin-induced inhibition of endothelial cell proliferation/apoptosis is associated with the down-regulation of cell cycle regulatory protein cdk5. J. Cell Biochem. 91, 398-409], here we not only demonstrate first that Cdk5, p35, and p25 proteins were all expressed in invasive breast cancer cells MDA-MB231 but also showed that cdk5 expression regulates MDA-MB231 cell proliferation. In addition, potent mitogen bFGF up-regulates cdk5 expression. Roscovitine specifically inhibits cdk5 expression/activity in a dose-dependent manner with concomitant inhibition of MDA-MB231 cell proliferation and induction of apoptosis. By contrast, the roscovitine analog olomoucine, a specific inhibitor of cdk4, failed to affect MDA-MB231 cell proliferation and apoptosis which implies the specific involvement of cdk5 in roscovitine-triggered cell death/proliferation. Additionally, roscovitine-mediated inhibition of proliferation is irreversible. These data suggest that cdk5 may have a significant role in the regulation of breast cancer cell proliferation and apoptosis and extend beyond its role in neurogenesis. These results suggest that Cdk5 is a novel player in roscovitine-triggered breast cancer cell apoptosis and inhibition of proliferation, therefore, may be a potential therapeutic target.     

坏死性凋亡与脑卒中的研究进展*

程序性死亡包括凋亡、焦亡、铁死亡、坏死性凋亡和自噬等。坏死性凋亡可由多种外部刺激触发，不依赖 caspase 途径，是包括神经系统疾病在内的诸多疾病关键致病因素。前期研究显示，卒中时脑内坏死性凋亡相关 途径被激活，与卒中的致病密切相关，而对坏死性凋亡进行基因调节或药理学抑制，对卒中具有一定的神经保护 作用，因此坏死性凋亡有望成为卒中治疗的潜在靶标。现简要总结坏死性凋亡在卒中致病中的作用，并提出了靶 向坏死性凋亡治疗卒中时存在的一些问题。     

RIP1在细胞程序性死亡中作用的研究进展

近期研究发现受体相互作用蛋白（receptor—interacting protein,RIP）是细胞生存和死亡的重要交叉点,在细胞的凋亡与存活、程序性坏死等过程中发挥着关键性的作用。RIP1为RIP家族中的第一个成员,是一种重要的细胞信号转导调控分子。RIP1的结构与生物学功能及在细胞程序性死亡中的作用具有重要意义。     

细胞程序性坏死及其在炎症中的作用

可调节性细胞死亡在组织稳态中发挥至关重要的作用。最新发现：程序性坏死作为一种调节途径,其涉及RIPK3和MLKL蛋白的参与,且由死亡受体、干扰素、Toll样受体、细胞内RNA和DNA感应器体或其他介质诱发。RIPK1具有激酶依赖性支架功能,可抑制或激发细胞坏死和凋亡。小鼠模型研究显示了程序性坏死在炎症中所发挥的重要作用,这对于研究许多人类的炎性疾病发病原理有重要意义。本文讨论了程序性坏死调节机制及其在炎症和疾病中发挥的潜在作用。     

Cross talk between intracellular pathogens and cell death

Infections with bacterial pathogens often results in the initiation of programmed cell death as part of the host innate immune defense, or as a bacterial virulence strategy. Induction of host cell death is controlled by an elaborate network of innate immune and cell death signaling pathways and manifests in different morphologically and functionally distinct forms of death, such as apoptosis, necroptosis, NETosis and pyroptosis. The mechanism by which host cell death restricts bacterial replication is highly cell-type and context depended, but its physiological importance is highlighted the diversity of strategies bacterial pathogens use to avoid induction of cell death or to block cell death signaling pathways. In this review, we discuss the latest insights into how bacterial pathogens elicit and manipulate cell death signaling, how different forms of cell death kill or restrict bacteria and how cell death and innate immune pathway cross talk to guard against pathogen-induced inhibition of host cell death.     

Necroptosis的调控机制及其在组织及细胞缺血损伤中的作用和意义

Necroptosis不同于坏死和凋亡,具有坏死的细胞形态特点和自噬的活化,并且是主动耗能的,是被一系列信号传导通路所调控的细胞死亡机制.Necroptosis的发现和确认为细胞死亡的逆转和治疗开创了一个新的研究和应用途经.RIP1激酶是调控Necroptosis 形成的关键酶,Necrostatins则是一类小分子化合物,它通过特异性地抑制细胞RIP1激酶而抑制Necroptosis 的形成.