MUC1 downregulation promotes TNF-α-induced necroptosis in human bronchial epithelial cells via regulation of the RIPK1/RIPK3 pathway

Targeting necroptosis: a promising avenue for respiratory disease treatment

Respiratory diseases are a growing concern in public health because of their potential to endanger the global community. Cell death contributes critically to the pathophysiology of respiratory diseases. Recent evidence indicates that necroptosis, a unique form of programmed cell death (PCD), plays a vital role in the molecular mechanisms underlying respiratory diseases, distinguishing it from apoptosis and conventional necrosis. Necroptosis is a type of inflammatory cell death governed by receptor-interacting serine/threonine protein kinase 1 (RIPK1), RIPK3, and mixed-lineage kinase domain-like protein (MLKL), resulting in the release of intracellular contents and inflammatory factors capable of initiating an inflammatory response in adjacent tissues. These necroinflammatory conditions can result in significant organ dysfunction and long-lasting tissue damage within the lungs. Despite evidence linking necroptosis to various respiratory diseases, there are currently no specific alternative treatments that target this mechanism. This review provides a comprehensive overview of the most recent advancements in understanding the significance and mechanisms of necroptosis. Specifically, this review emphasizes the intricate association between necroptosis and respiratory diseases, highlighting the potential use of necroptosis as an innovative therapeutic approach for treating these conditions.

Cell type-specific molecular mechanisms and implications of necroptosis in inflammatory respiratory diseases

Necroptosis is generally considered as an inflammatory cell death form. The core regulators of necroptotic signaling are receptor-interacting serine-threonine protein kinases 1 (RIPK1) and RIPK3, and the executioner, mixed lineage kinase domain-like pseudokinase (MLKL). Evidence demonstrates that necroptosis contributes profoundly to inflammatory respiratory diseases that are common public health problem. Necroptosis occurs in nearly all pulmonary cell types in the settings of inflammatory respiratory diseases. The influence of necroptosis on cells varies depending upon the type of cells, tissues, organs, etc., which is an important factor to consider. Thus, in this review, we briefly summarize the current state of knowledge regarding the biology of necroptosis, and focus on the key molecular mechanisms that define the necroptosis status of specific cell types in inflammatory respiratory diseases. We also discuss the clinical potential of small molecular inhibitors of necroptosis in treating inflammatory respiratory diseases, and describe the pathological processes that engage cross talk between necroptosis and other cell death pathways in the context of respiratory inflammation. The rapid advancement of single-cell technologies will help understand the key mechanisms underlying cell type-specific necroptosis that are critical to effectively treat pathogenic lung infections and inflammatory respiratory diseases.

MUC1 attenuates neutrophilic airway inflammation in asthma by reducing NLRP3 inflammasome-mediated pyroptosis through the inhibition of the TLR4/MyD88/NF-κB pathway

BACKGROUND

Neutrophilic airway inflammation is a challenge in asthma management and is associated with poor patient prognosis. Mucin 1 (MUC1), which contains a cytoplasmic tail (MUC1-CT), has been found to mediate glucocorticoid sensitivity in asthma; however, its role in modulating neutrophilic airway inflammation in asthma remains unknown.

METHODS

Human-induced sputum cells were collected from healthy participants (n = 12), patients with mild-to-moderate asthma (n = 34), and those with severe asthma (n = 18). In vitro human lung bronchial 1 epithelial cell line (BEAS-2B) was transfected with small interfering RNA against MUC1 (MUC1-siRNA) and then stimulated by lipopolysaccharide (LPS), where some cells were pretreated with a TLR4 inhibitor (TAK-242). In vivo mouse model of asthmatic neutrophil airway inflammation was induced by ovalbumin (OVA)/LPS. Some groups were intraperitoneally injected with MUC1-CT inhibitor (GO-203) and/or TAK-242 .

RESULTS

The mRNA expression of MUC1 was downregulated in the induced sputum of patients with asthma and correlated with asthmatic neutrophilic airway inflammation. The mRNA expressions of TLR4, MyD88, nucleotide-binding oligomerization domain-like pyrin domain-containing protein 3 (NLRP3), caspase-1, interleukin (IL)-18, and IL-1β in induced sputum cells of patients with asthma were upregulated and related to the mRNA expression of MUC1. LPS activated the TLR4 pathway and NLRP3-mediated pyroptosis in BEAS-2B cells in vitro, which were significantly aggravated after MUC1-siRNA transfection. Furthermore, MUCl-CT interacted with TLR4, and the interaction between TLR4 and MyD88 was significantly increased after MUCl-siRNA transfection. Moreover, TAK-242 ameliorated TLR4/MyD88/nuclear factor kappa B (NF-κB) pathway activation, NLRP3 inflammasome-mediated pyroptosis, and neutrophilic inflammation exacerbated by MUC1 downregulation. GO-203 exacerbated TLR4/MyD88/NF-κB pathway activation in vivo, and NLRP3 inflammasome-mediated pyroptosis reduced in a mouse model of asthmatic neutrophil airway inflammation induced by OVA/LPS; these pathological changes were partially alleviated after TAK-242 application.

CONCLUSION

This study revealed that MUC1 downregulation plays an important role in asthmatic neutrophilic airway inflammation. MUC1-CT reduces NLRP3 inflammasome-mediated pyroptosis by inhibiting the activation of the TLR4/MyD88/NF-κB pathway, thereby attenuating neutrophil airway inflammation in patients with asthma.

Programmed Cell Death in Asthma: Apoptosis, Autophagy, Pyroptosis, Ferroptosis, and Necroptosis

Bronchial asthma is a complex heterogeneous airway disease, which has emerged as a global health issue. A comprehensive understanding of the different molecular mechanisms of bronchial asthma may be an efficient means to improve its clinical efficacy in the future. Increasing research evidence indicates that some types of programmed cell death (PCD), including apoptosis, autophagy, pyroptosis, ferroptosis, and necroptosis, contributed to asthma pathogenesis, and may become new targets for future asthma treatment. This review briefly discusses the molecular mechanism and signaling pathway of these forms of PCD focuses on summarizing their roles in the pathogenesis and treatment strategies of asthma and offers some efficient means to improve clinical efficacy of therapeutics for asthma in the near future.

miR-210/NF-κB axis: A new direction for regulating cadmium-induced pig artery inflammatory injury

Cadmium (Cd) is a toxic metal pollutant that still exists in the environment. The microRNA (miRNA) is a type of noncoding RNA that plays an important role in gene posttranscriptional regulation and disease development. Although the toxic effects of Cd have been extensively studied, studies on the mechanism of Cd from the perspective of miRNA are still limited. So, we established a Cd-exposure pig model, which confirmed that Cd exposure would cause pig artery damage. The miR-210 with the most reduced expression and the nuclear factor kappa B (NF-κB) that had a targeting relationship with miR-210 were screened. The effect of miR-210/NF-κB on the artery damage induced by Cd exposure was investigated by acridine orange/ethidium bromide staining, reactive oxygen species (ROS) staining, quantitative PCR, and western blotting. The results showed that miR-210 inhibitor, pcDNA-NF-κB could induce ROS overproduction in pig hip artery endothelial cells, thus inducing Th1/Th2 imbalance and necroptosis, leading to increased inflammation, while small interfering RNA-NF-κB played a mitigating role. In conclusion, Cd can induce artery necroptosis and Th1/Th2 imbalance by regulating the miR-210/NF-κB axis, so as to lead to artery inflammatory damage. In this study, we explored the way in which Cd exposure causes artery damage in pig, providing a new perspective on the regulatory damage of miR-210/NF-κB axis.

Processed product (Pinelliae Rhizoma Praeparatum) of Pinellia ternata (Thunb.) Breit. Alleviates the allergic airway inflammation of cold phlegm via regulation of PKC/EGFR/MAPK/PI3K-AKT signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Pinelliae Rhizoma Praeparatum (PRP) is a traditional processed product of Pinellia ternata (Thunb.) Berit., which mainly used for treating cold asthma (CA). However, the mechanism of action of PRP for treating CA have not been fully elucidated.

AIM OF THE STUDY

To investigate the core active constituents and the pharmacological mechanism of PRP against CA.

MATERIALS AND METHODS

Ovalbumin (OVA) and cold water-induced cold asthma model were established in male mice. The effects of water extract from PRP were evaluated by general morphological observation, expectorant activity, airway hyperresponsiveness, mucus hypersecretion, inflammatory cytokines, etc. Additionally, the mRNA and protein expression of mucin 5AC (MUC5AC) and aquaporin 5 (AQP5) in vivo and in vitro were detected by immunohistochemistry (IHC), qRT-PCR, and western blotting. The mechanisms of action were investigated through network pharmacology and transcriptomic, and validated through western blotting and molecular docking.

RESULTS

PRP exhibited a favorable expectorant activity, and significantly reduced the airway inflammation, mucus secretion, and hyperresponsiveness in cold asthma model. It also reduced the levels of IL-4, IL-5, IL-8, and IL-13 in bronchoalveolar lavage fluid (BALF) and IL-4 and total IgE in serum, while obviously increased the levels of IL-10 and IFN-γ in serum for asthmatic mice. Meanwhile, PRP also attenuated the pathological changes and mucus production in cold asthmatic mice. Moreover, the downregulation of MUC5AC and upregulation of AQP 5 were detected by western blotting and qRT-PCR after administration with PRP both in vivo and in vitro. PRP expectedly inhibited the protein expression of PKC-α, SRC, p-EGFR, p-ERK1/2, p-JNK, p-p38, p-PI3K, and p-Akt levels in vivo.

CONCLUSIONS

These combined data showed that PRP suppressed the allergic airway inflammation of CA by regulating the balance of Th1 and Th2 cytokines and the possible involvement of the PKC/EGFR/MAPK/PI3K-Akt signaling pathway. Pentadecanoic acid, licochalcone A, β-sitosterol, etc. were considered as main active ingredients of PRP against CA. This study provides a novel perspective of the classical herbal processed product PRP in the treatment of CA.

Acteoside attenuates RSV-induced lung injury by suppressing necroptosis and regulating metabolism

Background: Necroptosis and inflammation are closely related to the pathogenesis of respiratory syncytial virus (RSV). Acteoside (AC), a natural phenylpropanoid glycoside from Kuding Tea, has significant anti-RSV effect. However, the roles of AC on RSV-induced lung necroptosis and inflammation are yet to be elucidated.

Methods: The effects of AC were investigated in BALB/c mice and A549 cells. Lung histopathology was observed through H&E staining. The viral titer was assessed via plaque assay. The RSV-F expression was determined by RT-qPCR and immunohistochemistry assay. The levels of cytokines were detected by ELISA and RT-qPCR. The necroptosis rate and mitochondrial membrane potential were evaluated via flow cytometry. The expressions of HMGB1/NF-κB and RIP1/RIP3/MLKL/PGAM5/DRP1 were detected by western blot. Additionally, untargeted metabolomics was conducted to investigate the metabolic profiles and related metabolic pathways via Gas Chromatography-Mass Spectrometry.

Results: The results showed that compared with the RSV-infected group, AC treatment significantly attenuated lung pathological damage, virus replication, and cytokines levels. AC also alleviated RSV-induced necroptosis and mitochondrial dysfunction in vitro and in vivo. Moreover, AC treatment down-regulated the expression of HMGB1, p-Iκbα/Iκbα, p-p65/p65, RIP1, RIP3, MLKL, PGAM5, and DRP1. Furthermore, metabolomic analyses suggested that the perturbations in major metabolites of AC therapy were related to variations in amino acid and energy metabolism.

Conclusion: Our findings validated the beneficial effects of AC in suppressing necroptosis and regulating metabolism, suggesting AC may be a new drug candidate for RSV infection.

Membrane-Tethered Mucin 1 Is Stimulated by Interferon and Virus Infection in Multiple Cell Types and Inhibits Influenza A Virus Infection in Human Airway Epithelium

Influenza A virus (IAV) causes significant morbidity and mortality in the human population. Tethered mucin 1 (MUC1) is highly expressed in airway epithelium, the primary site of IAV replication, and also by other cell types that influence IAV infection, including macrophages. MUC1 has the potential to influence infection dynamics through physical interactions and/or signaling activity, yet MUC1 modulation and its impact during viral pathogenesis remain unclear. Thus, we investigated MUC1-IAV interactions in an in vitro model of human airway epithelium (HAE). Our data indicate that a recombinant IAV hemagglutinin (H3) and H3N2 virus can bind endogenous HAE MUC1. Notably, infection of HAE with H1N1 or H3N2 IAV strains does not trigger MUC1 shedding but instead stimulates an increase in cell-associated MUC1 protein. We observed a similar increase after type I or III interferon (IFN) stimulation; however, inhibition of IFN signaling during H1N1 infection only partially abrogated this increase, indicating that multiple soluble factors contribute to MUC1 upregulation during the antiviral response. In addition to HAE, primary human monocyte-derived macrophages also upregulated MUC1 protein in response to IFN treatment and conditioned media from IAV-infected HAE. Then, to determine the impact of MUC1 on IAV pathogenesis, we developed HAE genetically depleted of MUC1 and found that MUC1 knockout cultures exhibited enhanced viral growth compared to control cultures for several IAV strains. Together, our data support a model whereby MUC1 inhibits productive uptake of IAV in HAE. Infection then stimulates MUC1 expression on multiple cell types through IFN-dependent and -independent mechanisms that further impact infection dynamics.

Necroptosis triggers spatially restricted neutrophil-mediated vascular damage during lung ischemia reperfusion injury

Intravital imaging, oxidative lipidomics, and a transplant model were used to define mechanisms that regulate neutrophil recruitment into lungs during ischemia reperfusion injury, a clinically relevant form of sterile inflammation. We found that early neutrophil-mediated damage is largely confined to the subpleural vasculature, a process that is orchestrated by a spatially restricted distribution of nonclassical monocytes that produce chemokines following necroptosis of pulmonary cells. Neutrophils disrupt the integrity of subpleural capillaries, which is associated with impaired lung function. Neutrophil-mediated vascular leakage is dependent on TLR4 expression on vascular endothelium, NOX4 signaling, and formation of neutrophil extracellular traps. Our research provides insights into mechanisms that regulate neutrophil recruitment during sterile lung inflammation and lays the foundation for developing new therapies.

Ischemia reperfusion injury represents a common pathological condition that is triggered by the release of endogenous ligands. While neutrophils are known to play a critical role in its pathogenesis, the tissue-specific spatiotemporal regulation of ischemia-reperfusion injury is not understood. Here, using oxidative lipidomics and intravital imaging of transplanted mouse lungs that are subjected to severe ischemia reperfusion injury, we discovered that necroptosis, a nonapoptotic form of cell death, triggers the recruitment of neutrophils. During the initial stages of inflammation, neutrophils traffic predominantly to subpleural vessels, where their aggregation is directed by chemoattractants produced by nonclassical monocytes that are spatially restricted in this vascular compartment. Subsequent neutrophilic disruption of capillaries resulting in vascular leakage is associated with impaired graft function. We found that TLR4 signaling in vascular endothelial cells and downstream NADPH oxidase 4 expression mediate the arrest of neutrophils, a step upstream of their extravasation. Neutrophil extracellular traps formed in injured lungs and their disruption with DNase prevented vascular leakage and ameliorated primary graft dysfunction. Thus, we have uncovered mechanisms that regulate the initial recruitment of neutrophils to injured lungs, which result in selective damage to subpleural pulmonary vessels and primary graft dysfunction. Our findings could lead to the development of new therapeutics that protect lungs from ischemia reperfusion injury.

Investigation on the expression regulation of RIPK1/RIPK3 in the retinal ganglion cells (RGCs) cultured in high glucose

Diabetic retinopathy (DR) represents the most typical complication of type 2 diabetes mellitus and one of the most primary oculopathy causing blindness. However, the mechanism of DR remains unknown. RIPK1/RIPK3, as homologous serine/threonine kinases, are key elements in mediating necroptosis and may have functions in DR development. To clarify the relationship between DR and RIPK1/RIPK3, this study established a model of apoptosis using high-glucose induced RGCs, which were treated with 7.5, 19.5, and 35 mM D-glucose for 12, 24, and 48 h, respectively. Subsequently, the expression of RIPK1/RIPK3 was determined and the protective effect of necrostatin-1 on RGCs injury induced by high glucose was explored. The results demonstrated that the expression of RIPK1 and RIPK3 in the cells was increased markedly following 12 h treatment with 19.5 mM D-glucose. Additionally, following an addition of 100 μM necrostatin-1 in 19.5 mM D-glucose medium for RGCs treatment 12 h, the protein expression of RIPK1 and RIPK3 was decreased markedly, and the number of Nissl bodies in cells was increased substantially. The findings of the present study indicated that high glucose could induce the expression of RIPK1/RIPK3, and necrostatin-1 could effectively protect RGCs from D-glucose-induced cell necrosis.

Intermittent hypoxia aggravates non-alcoholic fatty liver disease via RIPK3-dependent necroptosis-modulated Nrf2/NFκB signaling pathway

AIMS

Hepatocyte necroptosis is a critical event in the progression of non-alcoholic fatty liver disease (NAFLD). Obstructive sleep apnea hypopnea syndrome (OSAHS) and chronic intermittent hypoxia (CIH) may be linked with the pathogenesis and the severity of NAFLD. However, the potential role of necroptosis in OSAHS-associated NAFLD has not been evaluated. The present study investigated whether IH could affect NAFLD progression through promoting receptor-interacting protein kinase-3 (RIPK3)-dependent necroptosis, oxidative stress, and inflammatory response, and further elucidated the underlying molecular mechanisms.

MAIN METHODS

LO2 cells were treated with palmitic acid (PA) and subjected to IH, and necroptosis, oxidative stress, and inflammation were assessed. The high-fat choline-deficient (HFCD)-fed mouse model was also used to assess the effects of CIH in experimental NAFLD in vivo.

KEY FINDINGS

In this study, we found that RIPK3-mediated necroptosis was activated both in the PA plus IH-treated LO2 cells and liver of HFCD/CIH mice, and which could trigger oxidative stress and inflammatory response by decreasing Nrf2 and increasing p-P65. RIPK3 downregulation significantly reduced hepatocyte necroptosis, and ameliorated oxidative stress and inflammation through modulating Nrf2/NFκB pathway in vitro and vivo. Similarly, pretreatment with TBHQ, an activator of Nrf2, effectively blocked the generation of oxidative productions and inflammatory cytokines. In addition, RIPK3 inhibitor GSK-872 or TBHQ administration obviously alleviated hepatic injury, including histology, transaminase activities, and triglyceride contents in vivo.

SIGNIFICANCE

IH aggravates NAFLD via RIPK3-dependent necroptosis-modulated Nrf2/NFκB signaling pathway, and which should be considered as a potential therapeutic strategy for the treatment of NAFLD with OSASH.

Necroptosis in Pulmonary Diseases: A New Therapeutic Target

In the past decades, apoptosis has been the most well-studied regulated cell death (RCD) that has essential functions in tissue homeostasis throughout life. However, a novel form of RCD called necroptosis, which requires receptor-interacting protein kinase-3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL), has recently been receiving increasing scientific attention. The phosphorylation of RIPK3 enables the recruitment and phosphorylation of MLKL, which oligomerizes and translocates to the plasma membranes, ultimately leading to plasma membrane rupture and cell death. Although apoptosis elicits no inflammatory responses, necroptosis triggers inflammation or causes an innate immune response to protect the body through the release of damage-associated molecular patterns (DAMPs). Increasing evidence now suggests that necroptosis is implicated in the pathogenesis of several human diseases such as systemic inflammation, respiratory diseases, cardiovascular diseases, neurodegenerative diseases, neurological diseases, and cancer. This review summarizes the emerging insights of necroptosis and its contribution toward the pathogenesis of lung diseases.

NF‑κB/IκBα signaling pathways are essential for resistance to heat stress‑induced ROS production in pulmonary microvascular endothelial cells

The results of a previous study demonstrated that heat stress (HS) triggered oxidative stress, which in turn induced the apoptosis of epithelial cells. These results uncovered a novel mechanism underlying the activation of NF-κB in primary human umbilical vein endothelial cells. The present study aimed to further investigate the role of NF-κB/IκBα signaling pathways in the inhibition of HS-induced reactive oxygen species (ROS) generation and cytotoxicity in endothelial cells. The results of the present study demonstrated that HS triggered a significant amount of NF-κB and IκBα nuclear translocation without IκBα degradation in a time-dependent manner. Mutant constructs of IκBα phosphorylation sites (Ser32, Ser36) were employed in rat pulmonary microvascular endothelial cells (PMVECs). Cell Counting Kit-8 assays demonstrated that both the small interfering (si)RNA-mediated knockdown of p65 and IκBα mutant constructs significantly decreased cell viability and aggravated ROS accumulation in HS-induced rat PMVECs compared with the control. Additionally, western blot analysis revealed that p65 siRNA attenuated the protein expression of IκBα. However, IκBα mutant constructs failed to attenuate NF-κB activation and nuclear translocation, indicating that IκBα-independent pathways contributed to NF-κB activity and nucleus translocation in a time-dependent manner following HS. Collectively, the results of the present study suggested that the NF-κB/IκBα pathway was essential for resistance to HS-induced ROS production and cytotoxicity in rat PMVECs, and that it could be a potential therapeutic target to reduce the mortality and morbidity of heat stroke.

The latest information on the RIPK1 post-translational modifications and functions

RIPK1 is a protein kinase that simultaneously regulates inflammation, apoptosis, and necroptosis. It is thought that RIPK1 has separate functions through its scaffold structure and kinase domains. Moreover, different post-translational modifications in RIPK1 play distinct or even opposing roles. Under different conditions, in different cells and species, and/or upon exposure to different stimuli, infections, and substrates, RIPK1 activation can lead to diverse results. Despite continuous research, many of the conclusions that have been drawn regarding the complex interactions of RIPK1 are controversial. This review is based on an examination and analysis of recent studies on the RIPK1 structure, post-translational modifications, and activation conditions, which can affect its functions. Finally, because of the diverse functions of RIPK1 and their relevance to the pathogenesis of many diseases, we briefly introduce the roles of RIPK1 in inflammatory and autoimmune diseases and the prospects of its use in future diagnostics and treatments.

Membrane-associated mucins of the human ocular surface in health and disease

Mucins are a family of high molecular weight, heavily-glycosylated proteins produced by wet epithelial tissues, including the ocular surface epithelia. Densely-packed O-linked glycan chains added post-translationally confer the biophysical properties of hydration, lubrication, anti-adhesion and repulsion. Membrane-associated mucins (MAMs) are the distinguishing components of the mucosal glycocalyx. At the ocular surface, MAMs maintain wetness, lubricate the blink, stabilize the tear film, and create a physical barrier to the outside world. In addition, it is increasingly appreciated that MAMs function as cell surface receptors that transduce information from the outside to the inside of the cell. Recently, our team published a comprehensive review/perspectives article for molecular scientists on ocular surface MAMs, including previously unpublished data and analyses on two new genes MUC21 and MUC22, as well as new MAM functions and biological roles, comparing human and mouse (PMID: 31493487). The current article is a refocus for the audience of The Ocular Surface. First, we update the gene and protein information in a more concise form, and include a new section on glycosylation. Next, we discuss biological roles, with some new sections and further updating from our previous review. Finally, we provide a new chapter on MAM involvement in ocular surface disease. We end this with discussion of an emerging mechanism responsible for damage to the epithelia and their mucosal glycocalyces: the unfolded protein response (UPR). The UPR offers a novel target for therapeutic intervention.

The potential role of necroptosis in clinical diseases (Review)

As an important type of programmed cell death in addition to apoptosis, necroptosis occurs in a variety of pathophysiological processes, including infections, liver diseases, kidney injury, neurodegenerative diseases, cardiovascular diseases, and human tumors. It can be triggered by a variety of factors, such as tumor necrosis factor receptor and Toll‑like receptor families, intracellular DNA and RNA sensors, and interferon, and is mainly mediated by receptor‑interacting protein kinase 1 (RIP1), RIP3, and mixed lineage kinase domain‑like protein. A better understanding of the mechanism of necroptosis may be useful in the development of novel drugs for necroptosis‑related diseases. In this review, the focus is on the molecular mechanisms of necroptosis, exploring the role of necroptosis in different pathologies, discussing their potential as a novel therapeutic target for disease therapy, and providing suggestions for further study in this area.

Heat stress induces RIP1/RIP3-dependent necroptosis through the MAPK, NF-κB, and c-Jun signaling pathways in pulmonary vascular endothelial cells

Necroptosis represents a newly defined form of regulated necrosis and participates in various human inflammatory diseases. It remains unclear whether necroptosis is presented in heatstroke-induced lung injury. We show that heat stress(HS) triggered an significant upregulation of receptor-interacting protein 1 (RIP1) and mixed lineage kinase domain-like protein (MLKL) expression in a time-dependent manner, without a significant change of receptor-interacting protein 3 (RIP3). Furthermore, co-immunoprecipitation assays showed that RIP1 binds to RIP3 to form the necrosome in heat stress-induced PMVECs. In vitro, necrostatin-1 (Nec-1) pre-treatment reduced heat stress-induced PMVECs necroptosis, which also inhibited HMGB1 translocation from the nucleus into the cytoplasm. Similarly, inhibition for ERK (PD98059), NF-κB (BAY11-7082) and c-Jun (c-Jun peptide), respectively, also suppressed the HMGB1 cytoplasm translocation. Furthermore, siRNA-mediated RIP1/RIP3 knockdown negatively regulated the release of HMGB1 in HS-induced necroptosis through the ERK, NF-κB, and c-Jun signaling pathways. Our study reveals that HS induces RIP1/RIP3-dependent necroptosis through the MAPK, NF-κB, and c-Jun signaling pathways in PMVECs.

The construction and analysis of tumor-infiltrating immune cell and ceRNA networks in recurrent soft tissue sarcoma

Soft tissue sarcoma (STS) is one of the most challenging tumors for medical oncologists, with a high rate of recurrence after initial resection. In this study, a recurrent STS-specific competitive endogenous RNA (ceRNA) network including seven recurrence and overall survival (OS)-associated genes (LPP-AS2, MUC1, GAB2, hsa-let-7i-5p, hsa-let-7f-5p, hsa-miR-101-3p and hsa-miR-1226-3p) was established based on the gene expression profiling of 259 primary sarcomas and 3 local recurrence samples from the TCGA database. The algorithm "cell type identification by estimating relative subsets of RNA transcripts (CIBERSORT)" was applied to estimate the fraction of immune cells in sarcomas. Based on 5 recurrence and OS-associated immune cells (NK cells activated, dendritic cells resting, mast cells resting, mast cells activated and macrophages M1), we constructed a recurrent STS-specific immune cells network. Both nomograms were identified to have good reliabilities (Area Under Curve (AUC) of 5-year survival is 0.724 and 0.773, respectively). Then the co-expression analysis was performed to identify the potential regulation network among recurrent STS-specific immune cells and ceRNAs. Hsa-miR-1226-3p and MUC1 were significantly correlated and dendritic cells resting was related to hsa-miR-1226-3p. Additionally, the expression of MUC1 and dendritic cell marker CD11c were also verified by immunohistochemistry (IHC) assay and multidimensional databases. In conclusion, this study illustrated the potential mechanism of hsa-miR-1226-3p regulating MUC1 and dendritic cells resting might play an important role in STS recurrence. These findings might provide potential prognostic biomarkers and therapeutic targets for recurrent STS.

Current translational potential and underlying molecular mechanisms of necroptosis

Cell death has a fundamental impact on the evolution of degenerative disorders, autoimmune processes, inflammatory diseases, tumor formation and immune surveillance. Over the past couple of decades extensive studies have uncovered novel cell death pathways, which are independent of apoptosis. Among these is necroptosis, a tightly regulated, inflammatory form of cell death. Necroptosis contribute to the pathogenesis of many diseases and in this review, we will focus exclusively on necroptosis in humans. Necroptosis is considered a backup mechanism of apoptosis, but the in vivo appearance of necroptosis indicates that both caspase-mediated and caspase-independent mechanisms control necroptosis. Necroptosis is regulated on multiple levels, from the transcription, to the stability and posttranslational modifications of the necrosome components, to the availability of molecular interaction partners and the localization of receptor-interacting serine/threonine-protein kinase 1 (RIPK1), receptor-interacting serine/threonine-protein kinase 3 (RIPK3) and mixed lineage kinase domain-like protein (MLKL). Accordingly, we classified the role of more than seventy molecules in necroptotic signaling based on consistent in vitro or in vivo evidence to understand the molecular background of necroptosis and to find opportunities where regulating the intensity and the modality of cell death could be exploited in clinical interventions. Necroptosis specific inhibitors are under development, but >20 drugs, already used in the treatment of various diseases, have the potential to regulate necroptosis. By listing necroptosis-modulated human diseases and cataloging the currently available drug-repertoire to modify necroptosis intensity, we hope to kick-start approaches with immediate translational potential. We also indicate where necroptosis regulating capacity should be considered in the current applications of these drugs.

MUC1 downregulation promotes TNF-α-induced necroptosis in human bronchial epithelial cells via regulation of the RIPK1/RIPK3 pathway

MUC1 (mucin 1), a membrane-tethered mucin glycoprotein, is highly expressed on the surface of respiratory epithelial cells and plays a key role in anti-inflammatory and antiapoptotic responses against infections. However, little is known about the link between MUC1 and necroptosis in asthma. This study aimed to investigate the effects of MUC1 on TNF-α-induced necroptosis in human bronchial epithelial (16HBE) cells and the underlying molecular mechanism. Negative control and MUC1-siRNA cells were treated with TNF-α in the presence or absence of necrostatin-1 (Nec-1). Necroptosis was investigated using flow cytometry analyses, and the protein expression levels of MUC1, receptor-interacting protein kinase-1 (RIPK1), RIPK3, and phosphorylated RIPK1 were detected by western blot analysis. In addition, the interactions between RIPK and MUC1 were analyzed by coimmunoprecipitation. The results demonstrated that TNF-α could induce necroptosis of 16HBE cells, and MUC1 expression was increased upon treatment with TNF-α. The coimmunoprecipitation outcomes showed that MUC1 interacted with RIPK1 but not with RIPK3 in 16HBE cells, and the interaction was augmented by TNF-α. Furthermore, MUC1 downregulation obviously increased the TNF-α-induced necroptosis of 16HBE cells and enhanced the expression of p-RIPK1-Ser166 and RIPK3, whereas these phenomena were partially attenuated by Nec-1. These results may provide a new insight into the mechanism of severe asthma-related necroptosis and lay a foundation for the future development of new anti-inflammatory drugs for asthma.