Effective blockage of both the extrinsic and intrinsic pathways of apoptosis in mice by TAT-crmA

Revenge unraveling the fortress: Exploring anticancer drug resistance mechanisms in BC for enhanced therapeutic strategies

Breast cancer (BC) is the most prevalent form of cancer in women worldwide and the main cause of cancer-related fatalities in females. BC can be classified into various types based on where cancer has begun to grow or spread, specific characteristics that influence how cancer behaves, and treatment choices. BC is multifaceted, and due to its diverse nature, the mechanisms involved are complex and have not yet been understood. Overexpression and expression of various factors involved in the functioning of mechanisms lead to abnormal changes, providing an environment supporting cancer cell growth. Understanding BC risk factors and early diagnosis through screening techniques like mammography and diagnostic techniques such as imaging and biopsies has advanced significantly. A wide range of treatment options, including surgery, radiation, chemotherapy, targeted treatments, and hormonal therapies, are now available. Daily advancements are being made in the clinical treatment of BC. Still, BC drug resistance cases remain highly prevalent and are currently one of the biggest problems faced by medical science. To increase response rates and possibly lengthen survival, there is a critical requirement for novel medicines with minimal sensitivity to overcome drug resistance. This review classifies different mechanisms that are involved in the development of BC and workable pharmacological targets and explains how they relate to the development of BC drug resistance. By concentrating on the mechanisms covered in this review, we can have a deep understanding of different mechanisms and learn innovative ways to develop novel therapeutics for the disease to combat medication resistance.

2,3,5,4'-Tetrahydroxystilbene-2-O-beta-D-glucopyranoside promotes skin flap survival by promoting mitophagy through the PINK1/Parkin pathway

ETHNOPHARMACOLOGICAL RELEVANCE

2,3,5,4'-Tetrahydroxystilbene-2-O-beta-D-glucopyranoside (THSG), the active compound in Polygonum multiflorum (PM), exhibits potential therapeutic effects, including combating oxidative stress, possessing anti-tumor properties, and protecting against ischemia-reperfusion injury. However, the influence and mechanisms by which THSG affects skin flap survival remain unclear.

AIM OF STUDY

To investigate the effects and underlying mechanisms of THSG to promote the survival rate of skin flap.

METHODS

McFarlane skin flap models were created in 24 Sprague-Dawley rats, which were randomly divided into four groups: control group, low-dose THSG group (30 mg/kg/day), medium-dose THSG group (60 mg/kg/day), and high-dose THSG group (120 mg/kg/day). Seven days after postoperative administration, blood perfusion was assessed using laser Doppler, and the survival rate was calculated. Anti-tumor necrosis factor (TNF)-α was analyzed via immunofluorescence. Interleukin (IL)-6 and IL-1β were explored by enzyme-linked immunosorbent assay (ELISA). SOD activity and MDA contents in skin flap tissue were detected to evaluate oxidative stress level, while Western blotting was employed to assess proteins of the PINK1/Parkin signaling axis, apoptosis-related proteins, and vascular endothelial growth factor (VEGF).

RESULTS

THSG upregulated VEGF expression, improved blood flow, and protected flap tissue by reducing inflammation, mitigating oxidative stress, and inhibiting apoptosis. Increased expression of Parkin and PINK1, along with decreased levels of COX IV, suggested that THSG mediates mitophagy via the PINK1/Parkin signaling pathway.

CONCLUSIONS

THSG enhances the survival rate of skin flap by promoting PINK1/Parkin-mediated mitophagy.

Cellular and molecular mechanisms of cell damage and cell death in ischemia-reperfusion injury in organ transplantation

Ischemia-reperfusion injury (IRI) is a critical pathological condition in which cell death plays a major contributory role, and negatively impacts post-transplant outcomes. At the cellular level, hypoxia due to ischemia disturbs cellular metabolism and decreases cellular bioenergetics through dysfunction of mitochondrial electron transport chain, causing a switch from cellular respiration to anaerobic metabolism, and subsequent cascades of events that lead to increased intracellular concentrations of Na+, H+ and Ca2+ and consequently cellular edema. Restoration of blood supply after ischemia provides oxygen to the ischemic tissue in excess of its requirement, resulting in over-production of reactive oxygen species (ROS), which overwhelms the cells' antioxidant defence system, and thereby causing oxidative damage in addition to activating pro-inflammatory pathways to cause cell death. Moderate ischemia and reperfusion may result in cell dysfunction, which may not lead to cell death due to activation of recovery systems to control ROS production and to ensure cell survival. However, prolonged and severe ischemia and reperfusion induce cell death by apoptosis, mitoptosis, necrosis, necroptosis, autophagy, mitophagy, mitochondrial permeability transition (MPT)-driven necrosis, ferroptosis, pyroptosis, cuproptosis and parthanoptosis. This review discusses cellular and molecular mechanisms of these various forms of cell death in the context of organ transplantation, and their inhibition, which holds clinical promise in the quest to prevent IRI and improve allograft quality and function for a long-term success of organ transplantation.

Intranasal Delivery of Anti-Apoptotic siRNA Complexed with Fas-Signaling Blocking Peptides Attenuates Cellular Apoptosis in Brain Ischemia

Ischemic stroke-induced neuronal cell death leads to the permanent impairment of brain function. The Fas-mediating extrinsic apoptosis pathway and the cytochrome c-mediating intrinsic apoptosis pathway are two major molecular mechanisms contributing to neuronal injury in ischemic stroke. In this study, we employed a Fas-blocking peptide (FBP) coupled with a positively charged nona-arginine peptide (9R) to form a complex with negatively charged siRNA targeting Bax (FBP9R/siBax). This complex is specifically designed to deliver siRNA to Fas-expressing ischemic brain cells. This complex enables the targeted inhibition of Fas-mediating extrinsic apoptosis pathways and cytochrome c-mediating intrinsic apoptosis pathways. Specifically, the FBP targets the Fas/Fas ligand signaling, while siBax targets Bax involved in mitochondria disruption in the intrinsic pathway. The FBP9R carrier system enables the delivery of functional siRNA to hypoxic cells expressing the Fas receptor on their surface-a finding validated through qPCR and confocal microscopy analyses. Through intranasal (IN) administration of FBP9R/siCy5 to middle cerebral artery occlusion (MCAO) ischemic rat models, brain imaging revealed the complex specifically localized to the Fas-expressing infarcted region but did not localize in the non-infarcted region of the brain. A single IN administration of FBP9R/siBax demonstrated a significant reduction in neuronal cell death by effectively inhibiting Fas signaling and preventing the release of cytochrome c. The targeted delivery of FBP9R/siBax represents a promising alternative strategy for the treatment of brain ischemia.

The RELT Family of Proteins: An Increasing Awareness of Their Importance for Cancer, the Immune System, and Development

This review highlights Receptor Expressed in Lymphoid Tissues (RELT), a Tumor Necrosis Factor Superfamily member, and its two paralogs, RELL1 and RELL2. Collectively, these three proteins are referred to as RELTfms and have gained much interest in recent years due to their association with cancer and other human diseases. A thorough knowledge of their physiological functions, including the ligand for RELT, is lacking, yet emerging evidence implicates RELTfms in a variety of processes including cytokine signaling and pathways that either promote cell death or survival. T cells from mice lacking RELT exhibit increased responses against tumors and increased inflammatory cytokine production, and multiple lines of evidence indicate that RELT may promote an immunosuppressive environment for tumors. The relationship of individual RELTfms in different cancers is not universal however, as evidence indicates that individual RELTfms may be risk factors in certain cancers yet appear to be protective in other cancers. RELTfms are important for a variety of additional processes related to human health including microbial pathogenesis, inflammation, behavior, reproduction, and development. All three proteins have been strongly conserved in all vertebrates, and this review aims to provide a clearer understanding of the current knowledge regarding these interesting proteins.

Viral SERPINS-A Family of Highly Potent Immune-Modulating Therapeutic Proteins

Serine protease inhibitors, SERPINS, are a highly conserved family of proteins that regulate serine proteases in the central coagulation and immune pathways, representing 2-10% of circulating proteins in the blood. Serine proteases form cascades of sequentially activated enzymes that direct thrombosis (clot formation) and thrombolysis (clot dissolution), complement activation in immune responses and also programmed cell death (apoptosis). Virus-derived serpins have co-evolved with mammalian proteases and serpins, developing into highly effective inhibitors of mammalian proteolytic pathways. Through interacting with extracellular and intracellular serine and cysteine proteases, viral serpins provide a new class of highly active virus-derived coagulation-, immune-, and apoptosis-modulating drug candidates. Viral serpins have unique characteristics: (1) function at micrograms per kilogram doses; (2) selectivity in targeting sites of protease activation; (3) minimal side effects at active concentrations; and (4) the demonstrated capacity to be modified, or fine-tuned, for altered protease targeting. To date, the virus-derived serpin class of biologics has proven effective in a wide range of animal models and in one clinical trial in patients with unstable coronary disease. Here, we outline the known viral serpins and review prior studies with viral serpins, considering their potential for application as new sources for immune-, coagulation-, and apoptosis-modulating therapeutics.

Sensitization of GSH synthesis by curcumin curtails acrolein-induced alveolar epithelial apoptosis via Keap1 cysteine conjugation: A randomized controlled trial and experimental animal model of pneumonitis

INTRODUCTION

Epidemiological studies have reported an association between exposures to ambient air pollution and respiratory diseases, including chronic obstructive pulmonary disease (COPD). Pneumonitis is a critical driving factor of COPD and exposure to air pollutants (e.g., acrolein) is associated with increased incidence of pneumonitis.

OBJECTIVES

Currently available anti-inflammatory therapies provide little benefit against respiratory diseases. To this end, we investigated the preventive role of curcumin against air pollutant-associated pneumonitis and its underlying mechanism.

METHODS

A total of 40 subjects was recruited from Chengdu, China which is among the top three cities in terms of respiratory mortality related to air pollution. The participants were randomly provided either placebo or curcumin supplements for 2 weeks and blood samples were collected at the baseline and at the end of the intervention to monitor systemic markers. In our follow up mechanistic study, C57BL/6 mice (n = 40) were randomly allocated into 4 groups: Control group (saline + no acrolein), Curcumin only group (curcumin + no acrolein), Acrolein only group (saline + acrolein), and Acrolein + Curcumin group (curcumin + acrolein). Curcumin was orally administered at 100 mg/kg body weight once a day for 10 days, and then the mice were subjected to nasal instillation of acrolein (5 mg/kg body weight). Twelve hours after single acrolein exposure, all mice were euthanized.

RESULTS

Curcumin supplementation, with no noticeable adverse responses, reduced circulating pro-inflammatory cytokines in association with clinical pneumonitis as positive predictive while improving those of anti-inflammatory cytokines. In the pre-clinical study, curcumin reduced pneumonitis manifestations by suppression of intrinsic and extrinsic apoptotic signaling, which is attributed to enhanced redox sensing of Nrf2 and thus sensitized synthesis and restoration of GSH, at least in part, through curcumin-Keap1 conjugation.

CONCLUSIONS

Our study collectively suggests that curcumin could provide an effective preventive measure against air pollutant-enhanced pneumonitis and thus COPD.

Role of Caspase Family in Intervertebral Disc Degeneration and Its Therapeutic Prospects

Intervertebral disc degeneration (IVDD) is a common musculoskeletal degenerative disease worldwide, of which the main clinical manifestation is low back pain (LBP); approximately, 80% of people suffer from it in their lifetime. Currently, the pathogenesis of IVDD is unclear, and modern treatments can only alleviate its symptoms but cannot inhibit or reverse its progression. However, in recent years, targeted therapy has led to new therapeutic strategies. Cysteine-containing aspartate proteolytic enzymes (caspases) are a family of proteases present in the cytoplasm. They are evolutionarily conserved and are involved in cell growth, differentiation, and apoptotic death of eukaryotic cells. In recent years, it has been confirmed to be involved in the pathogenesis of various diseases, mainly by regulating cell apoptosis and inflammatory response. With continuous research on the pathogenesis and pathological process of IVDD, an increasing number of studies have shown that caspases are closely related to the IVDD process, especially in the intervertebral disc (IVD) cell apoptosis and inflammatory response. Therefore, herein we study the role of caspases in IVDD with respect to the structure of caspases and the related signaling pathways involved. This would help explore the strategy of regulating the activity of the caspases involved and develop caspase inhibitors to prevent and treat IVDD. The aim of this review was to identify the caspases involved in IVDD which could be potential targets for the treatment of IVDD.

Theranostic Potential of Adaptive Cold Atmospheric Plasma with Temozolomide to Checkmate Glioblastoma: An In Vitro Study

Simple Summary

Glioblastoma (GBM) is an aggressive form of brain cancer. Here, we present a combination therapy of cold atmospheric plasma (CAP) and temozolomide (TMZ) to treat GBM in vitro. We analyze the effects of the co-treatment in two GBM (TMZ-resistant and -sensitive) cell lines. The aim of this study is mainly to sensitize these cells using CAP so that they respond well to TMZ. We further found that the removal of cell culture media after CAP treatment does not affect the sensitivity of CAP to cancer cells but enhances the effects of TMZ. However, it was observed in our study that keeping the CAP-treated media for a shorter time did not significantly inhibit T98G cells. Interestingly, keeping the same plasma-treated media for a longer duration resulted in a decrease in cell viability. On the contrary, TMZ-sensitive cell A172 responded well to the co-treatment. This could be a potential reason for the sensitization of the combination therapy.

Abstract

Cold atmospheric plasma (CAP) has been used for the treatment of various cancers. The anti-cancer properties of CAP are mainly due to the reactive species generated from it. Here, we analyze the efficacy of CAP in combination with temozolomide (TMZ) in two different human glioblastoma cell lines, T98G and A172, in vitro using various conditions. We also establish an optimized dose of the co-treatment to study potential sensitization in TMZ-resistant cells. The removal of cell culture media after CAP treatment did not affect the sensitivity of CAP to cancer cells. However, keeping the CAP-treated media for a shorter time helped in the slight proliferation of T98G cells, while keeping the same media for longer durations resulted in a decrease in its survivability. This could be a potential reason for the sensitization of the cells in combination treatment. Co-treatment effectively increased the lactate dehydrogenase (LDH) activity, indicating cytotoxicity. Furthermore, apoptosis and caspase-3 activity also significantly increased in both cell lines, implying the anticancer nature of the combination. The microscopic analysis of the cells post-treatment indicated nuclear fragmentation, and caspase activity demonstrated apoptosis. Therefore, a combination treatment of CAP and TMZ may be a potent therapeutic modality to treat glioblastoma. This could also indicate that a pre-treatment with CAP causes the cells to be more sensitive to chemotherapy treatment.

TAT-RHIM: a more complex issue than expected

Murine cytomegalovirus protein M45 contains a RIP homotypic interaction motif (RHIM) that is sufficient to confer protection of infected cells against necroptotic cell death. Mechanistically, the N-terminal region of M45 drives rapid self-assembly into homo-oligomeric amyloid fibrils, and interacts with the endogenous RHIM domains of receptor-interacting protein kinases (RIPK) 1, RIPK3, Z-DNA binding protein 1, and TIR domain-containing adaptor-inducing interferon-β. Remarkably, all four mammalian proteins harbouring such a RHIM domain are key components of inflammatory signalling and regulated cell death processes. Immunogenic cell death by regulated necrosis causes extensive tissue damage in a wide range of diseases, including ischemia reperfusion injury, myocardial infarction, sepsis, stroke and organ transplantation. To harness the cell death suppression properties of M45 protein in a therapeutically usable manner, we developed a synthetic peptide encompassing only the RHIM domain of M45. To trigger delivery of RHIM into target cells, we fused the transactivator protein transduction domain of human immunodeficiency virus 1 to the N-terminus of the peptide. The fused peptide could efficiently penetrate eukaryotic cells, but unexpectedly it killed all tested cancer cell lines and primary cells irrespective of species without further stimulus through a necrosis-like cell death. Typical inhibitors of different forms of regulated cell death cannot impede this process, which appears to involve a direct disruption of biomembranes. Nevertheless, our finding has potential clinical relevance; reliable induction of a necrotic form of cell death distinct from all known forms of regulated cell death may offer a novel therapeutic approach to combat resistant tumour cells.

BAX-dependent mitochondrial pathway mediates the crosstalk between ferroptosis and apoptosis

Ferroptosis is considered a distinctive form of cell death compared to other types of death such as apoptosis. It is known to result from iron-dependent accumulation of lipid peroxides rather than caspase activation. However, we reported recently that ferroptosis interplays with apoptosis. In this study, we investigated a possible mechanism of this interplay between ferroptosis and apoptosis. Results from our studies reveal that combined treatment of the ferroptotic agent erastin and the apoptotic agent TRAIL effectively disrupted mitochondrial membrane potential (ΔΨm) and subsequently promoted caspase activation. The alterations of mitochondrial membrane potential are probably due to an increase in oligomerization of BAX and its accumulation at the mitochondria during treatment with erastin and TRAIL. Interestingly, the combined treatment-promoted apoptosis was effectively inhibited in BAX-deficient HCT116 cells, but not BAK-deficient cells. These results indicate that the BAX-associated mitochondria-dependent pathway plays a pivotal role in erastin-enhanced TRAIL-induced apoptosis.

Effect of Selenium on Expression of Apoptosis-Related Genes in Cryomedia of Mice Ovary after Vitrification

Introduction

Freezing of ovarian tissue is used for preservation of fertility. The freezing-thawing process is accompanied by oxidative stress and induction of apoptosis. Apoptosis is a complex process that has been studied in animal models. The present study was aimed at investigating the effect of selenium on suppression of apoptosis during vitrification-thawing process of mice ovary via studying expression of apoptosis-related genes, and also, we aimed to design statistical models for the roles of single genes and gene-gene interactions in suppression of apoptosis.

Methods

A total of 10 right ovary samples from 10 mice were randomly divided into two groups of selenium treatment (at dose 5 μg/ml sodium selenite, through adding to the media) and control group. Vitrification-thawing process was done according to the existed protocols. Real-time PCR was used for gene expression study. The apoptosis gene profile included P53, Bax, Fas, and Bcl-2. General linear model was applied to study single gene associations and gene-gene interactions.

Results

From the studied genes, P53 showed a significant downregulation in the selenium group in comparison to the control group (∆∆CT = 1.96; P = 0.013; relative expression (RE) = 0.28). Bcl-2 showed a significant upregulation in the selenium group in comparison to the control group (∆∆CT = −2.49; P < 0.001; RE = 3.49). No significant result was found for other genes. According to the multiple models, Bcl-2 showed a protective single gene association (beta = −0.33; P = 0.032), and Fas∗Bcl-2 interaction was significantly positive (beta = 0.19; P = 0.036).

Conclusion

Addition of selenium to cryomedia of vitrification-thawing process could reduce the apoptosis induced by freezing-thawing stress in mice ovary via downregulation of P53 and upregulation of Bcl-2 at transcription level. Multivariable statistical models should be performed in future researches to study biological systems.

Deriving Immune Modulating Drugs from Viruses-A New Class of Biologics

Viruses are widely used as a platform for the production of therapeutics. Vaccines containing live, dead and components of viruses, gene therapy vectors and oncolytic viruses are key examples of clinically-approved therapeutic uses for viruses. Despite this, the use of virus-derived proteins as natural sources for immune modulators remains in the early stages of development. Viruses have evolved complex, highly effective approaches for immune evasion. Originally developed for protection against host immune responses, viral immune-modulating proteins are extraordinarily potent, often functioning at picomolar concentrations. These complex viral intracellular parasites have "performed the R&D", developing highly effective immune evasive strategies over millions of years. These proteins provide a new and natural source for immune-modulating therapeutics, similar in many ways to penicillin being developed from mold or streptokinase from bacteria. Virus-derived serine proteinase inhibitors (serpins), chemokine modulating proteins, complement control, inflammasome inhibition, growth factors (e.g., viral vascular endothelial growth factor) and cytokine mimics (e.g., viral interleukin 10) and/or inhibitors (e.g., tumor necrosis factor) have now been identified that target central immunological response pathways. We review here current development of virus-derived immune-modulating biologics with efficacy demonstrated in pre-clinical or clinical studies, focusing on pox and herpesviruses-derived immune-modulating therapeutics.

Effect of selenium on freezing-thawing damage of mice spermatogonial stem cell: a model to preserve fertility in childhood cancers

Background

During treatment of childhood cancers, fertility of boys may be affected. Therefore, freezing spermatogonial stem cell (SSC) is recommended. However, freezing-thawing process may cause damage to SSCs. This study was conducted to evaluate protective effects of selenium on freezing-thawing damage of mice SSCs using investigation of cell viability and investigation of apoptosis related genes expression including Fas, Caspase3, Bcl2, Bax and P53.

Methods

SSCs were extracted from 80 6-day-old mice. The SSCs were divided into four groups: cryopreservation along with selenium (low and high dose), vitrification along with selenium (low and high dose), cryopreservation control, and vitrification control. Trypan blue staining and real-time polymerase chain reaction (real-time PCR) were used to investigate cell viability and gene expression, respectively.

Result

Comparison of cell viability in the experimental groups did not show a significant association. Expression of Fas and Caspase3 was significantly lower in cryopreservation group with low-dose selenium. Expression of Bcl2 was significantly lower in cryopreservation group with high-dose selenium. Expression of Bax and Caspase3 was significantly lower in vitrification group with low-dose selenium, and expression of P53 was significantly upper. Expression of Bax and Fas was significantly lower in vitrification group with high-dose selenium, and expression of P53 was significantly upper (P<0.001).

Conclusions

Selenium had dose dependent effect on apoptosis related genes profile. The only evident effect was the effect of low-dose selenium in cryopreservation on inhibition of apoptosis via extrinsic pathway.

Molecular Understanding of the Cardiomodulation in Myocardial Infarction and the Mechanism of Vitamin E Protections

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Myocardial infarction is a major cause of deaths globally. Modulation of several molecular mechanisms occurs during the initial stages of myocardial ischemia prior to permanent cardiac tissue damage, which involves both pathogenic as well as survival pathways in the cardiomyocyte. Currently, there is increasing evidence regarding the cardioprotective role of vitamin E in alleviating the disease. This fat-soluble vitamin does not only act as a powerful antioxidant; but it also has the ability to regulate several intracellular signalling pathways including HIF-1, PPAR-γ, Nrf-2, and NF-κB that influence the expression of a number of genes and their protein products. Essentially, it inhibits the molecular progression of tissue damage and preserves myocardial tissue viability. This review aims to summarize the molecular understanding of the cardiomodulation in myocardial infarction as well as the mechanism of vitamin E protection.

Mitochondrial targeting as a novel therapy for stroke

Stroke is a main cause of mortality and morbidity worldwide. Despite the increasing development of innovative treatments for stroke, most are unsuccessful in clinical trials. In recent years, an encouraging strategy for stroke therapy has been identified in stem cells transplantation. In particular, grafting cells and their secretion products are leading with functional recovery in stroke patients by promoting the growth and function of the neurovascular unit – a communication framework between neurons, their supply microvessels along with glial cells – underlying stroke pathology and recovery. Mitochondrial dysfunction has been recently recognized as a hallmark in ischemia/reperfusion neural damage. Emerging evidence of mitochondria transfer from stem cells to ischemic-injured cells points to transfer of healthy mitochondria as a viable novel therapeutic strategy for ischemic diseases. Hence, a more in-depth understanding of the cellular and molecular mechanisms involved in mitochondrial impairment may lead to new tools for stroke treatment. In this review, we focus on the current evidence of mitochondrial dysfunction in stroke, investigating favorable approaches of healthy mitochondria transfer in ischemic neurons, and exploring the potential of mitochondria-based cellular therapy for clinical applications. This paper is a review article. Referred literature in this paper has been listed in the references section. The data sets supporting the conclusions of this article are available online by searching various databases, including PubMed.

Understanding the Role of Dysfunctional and Healthy Mitochondria in Stroke Pathology and Its Treatment

Stroke remains a major cause of death and disability in the United States and around the world. Solid safety and efficacy profiles of novel stroke therapeutics have been generated in the laboratory, but most failed in clinical trials. Investigations into the pathology and treatment of the disease remain a key research endeavor in advancing scientific understanding and clinical applications. In particular, cell-based regenerative medicine, specifically stem cell transplantation, may hold promise as a stroke therapy, because grafted cells and their components may recapitulate the growth and function of the neurovascular unit, which arguably represents the alpha and omega of stroke brain pathology and recovery. Recent evidence has implicated mitochondria, organelles with a central role in energy metabolism and stress response, in stroke progression. Recognizing that stem cells offer a source of healthy mitochondria—one that is potentially transferrable into ischemic cells—may provide a new therapeutic tool. To this end, deciphering cellular and molecular processes underlying dysfunctional mitochondria may reveal innovative strategies for stroke therapy. Here, we review recent studies capturing the intimate participation of mitochondrial impairment in stroke pathology, and showcase promising methods of healthy mitochondria transfer into ischemic cells to critically evaluate the potential of mitochondria-based stem cell therapy for stroke patients.

Caspase-1 Engagement and TLR-Induced c-FLIP Expression Suppress ASC/Caspase-8-Dependent Apoptosis by Inflammasome Sensors NLRP1b and NLRC4

The caspase activation and recruitment domain (CARD)-based inflammasome sensors NLRP1b and NLRC4 induce caspase-1-dependent pyroptosis independent of the inflammasome adaptor ASC. Here, we show that NLRP1b and NLRC4 trigger caspase-8-mediated apoptosis as an alternative cell death program in caspase-1^-/- macrophages and intestinal epithelial organoids (IECs). The caspase-8 adaptor FADD was recruited to ASC specks, which served as cytosolic platforms for caspase-8 activation and NLRP1b/NLRC4-induced apoptosis. We further found that caspase-1 protease activity dominated over scaffolding functions in suppressing caspase-8 activation and induction of apoptosis of macrophages and IECs. Moreover, TLR-induced c-FLIP expression inhibited caspase-8-mediated apoptosis downstream of ASC speck assembly, but did not affect pyroptosis induction by NLRP1b and NLRC4. Moreover, unlike during pyroptosis, NLRP1b- and NLRC4-elicited apoptosis retained alarmins and the inflammasome-matured cytokines interleukin 1β (IL-1β) and IL-18 intracellularly. This work identifies critical mechanisms regulating apoptosis induction by the inflammasome sensors NLRP1b and NLRC4 and suggests converting pyroptosis into apoptosis as a paradigm for suppressing inflammation.

Naringin Protects Pancreatic β-Cells Against Oxidative Stress-Induced Apoptosis by Inhibiting Both Intrinsic and Extrinsic Pathways in Insulin-Deficient Diabetic Mice

SCOPE

Oxidative stress has been suggested to play a central role in the pathogenesis of diabetes, as well as other metabolic disorders. Naringin, a major flavanone glycoside in citrus species, has been shown to display strong antioxidant potential in in vitro and in vivo models of oxidative stress; however, the underlying protective mechanisms in diabetes are unclear.

METHODS AND RESULTS

To study the protective effects and molecular mechanisms of naringin in preventing islet dysfunction and diabetes, we examined glucose homeostasis, β-cell apoptosis, and inflammatory response in insulin-deficient diabetic mice exposed to acute oxidative stress with streptozotocin (STZ). Naringin dose-dependently ameliorated hyperglycemia and islet dysfunction in insulin-deficient diabetic mice. Naringin counteracted STZ-induced β-cell apoptosis by inhibiting both the intrinsic (mitochondria-mediated) and extrinsic (death receptor-mediated) pathways. Furthermore, these protective effects were associated with suppression of DNA damage response and nuclear factor-kappa B- and mitogen-activated protein kinase-mediated signaling pathways, as well as reduction of reactive oxygen species accumulation and pro-inflammatory cytokine production in the pancreas.

CONCLUSION

Taken together, our study provides insights into the underlying mechanisms through which naringin protects the pancreatic β-cells against oxidative stress-induced apoptosis.

Surfactant protein D regulates caspase-8-mediated cascade of the intrinsic pathway of apoptosis while promoting bleb formation

Surfactant-associated protein D (SP-D) is a soluble innate immune collectin present on many mucosal surfaces. We recently showed that SP-D suppresses the extrinsic pathway of apoptosis by downregulating caspase-8 activation. However, the effects of SP-D on the intrinsic pathway of apoptosis are not clearly understood. In the intrinsic pathway, cytochrome c is released by mitochondria into the cytoplasm. Oxidation of cytochrome c by cytochrome c oxidase activates the apoptosome and caspase-9 cascade. Both caspase-8- and caspase-9-mediated branches are activated in the intrinsic pathway of apoptosis; however, little is known about the relevance of the caspase-8 pathway in this context. Here we studied the effects of SP-D on different branches of the intrinsic pathway of apoptosis using UV-irradiated Jurkat T-cells. We found that SP-D does not inhibit the caspase-9 branch of apoptosis and the relevance of the caspase-8-related branch became apparent when the caspase-9 pathway was inhibited by blocking cytochrome c oxidase. Under these conditions, SP-D reduces the activation of caspase-8, executioner caspase-3 and exposure of phosphatidylserine (PS) on the membranes of dying cells. By contrast, SP-D increases the formation of nuclear and membrane blebs. Inhibition of caspase-8 confirms the effect of SP-D is unique to the caspase-8 pathway. Overall, SP-D suppresses certain aspects of the intrinsic pathway of apoptosis via reduction of caspase-8 activation and PS flipping while at the same time increasing membrane and nuclear bleb formation. This novel regulatory aspect of SP-D could help to regulate intrinsic pathway of apoptosis to promote effective blebbing and breakdown of dying cells.

Nonapoptotic cell death in acute kidney injury and transplantation

Acute tubular necrosis causes a loss of renal function, which clinically presents as acute kidney failure (AKI). The biochemical signaling pathways that trigger necrosis have been investigated in detail over the past 5 years. It is now clear that necrosis (regulated necrosis, RN) represents a genetically driven process that contributes to the pathophysiology of AKI. RN pathways such as necroptosis, ferroptosis, parthanatos, and mitochondrial permeability transition-induced regulated necrosis (MPT-RN) may be mechanistically distinct, and the relative contributions to overall organ damage during AKI in living organisms largely remain elusive. In a synchronized manner, some necrotic programs induce the breakdown of tubular segments and multicellular functional units, whereas others are limited to killing single cells in the tubular compartment. Importantly, the means by which a renal cell dies may have implications for the subsequent inflammatory response. In this review, the recent advances in the field of renal cell death in AKI and key enzymes that might serve as novel therapeutic targets will be discussed. As a consequence of the interference with RN, the immunogenicity of dying cells in AKI in renal transplants will be diminished, rendering inhibitors of RN indirect immunosuppressive agents.

CPP-Assisted Intracellular Drug Delivery, What Is Next?

For the past 20 years, we have witnessed an unprecedented and, indeed, rather miraculous event of how cell-penetrating peptides (CPPs), the naturally originated penetrating enhancers, help overcome the membrane barrier that has hindered the access of bio-macromolecular compounds such as genes and proteins into cells, thereby denying their clinical potential to become potent anti-cancer drugs. By taking the advantage of the unique cell-translocation property of these short peptides, various payloads of proteins, nucleic acids, or even nanoparticle-based carriers were delivered into all cell types with unparalleled efficiency. However, non-specific CPP-mediated cell penetration into normal tissues can lead to widespread organ distribution of the payloads, thereby reducing the therapeutic efficacy of the drug and at the same time increasing the drug-induced toxic effects. In view of these challenges, we present herein a review of the new designs of CPP-linked vehicles and strategies to achieve highly effective yet less toxic chemotherapy in combating tumor oncology.

Inhibition of regulated cell death by cell-penetrating peptides

Development of the means to efficiently and continuously renew missing and non-functional proteins in diseased cells remains a major goal in modern molecular medicine. While gene therapy has the potential to achieve this, substantial obstacles must be overcome before clinical application can be considered. A promising alternative approach is the direct delivery of non-permeant active biomolecules, such as oligonucleotides, peptides and proteins, to the affected cells with the purpose of ameliorating an advanced disease process. In addition to receptor-mediated endocytosis, cell-penetrating peptides are widely used as vectors for rapid translocation of conjugated molecules across cell membranes into intracellular compartments and the delivery of these therapeutic molecules is generally referred to as novel prospective protein therapy. As a broad coverage of the enormous amount of published data in this field is unrewarding, this review will provide a brief, focused overview of the technology and a summary of recent studies of the most commonly used protein transduction domains and their potential as therapeutic agents for the treatment of cellular damage and the prevention of regulated cell death.

Cell-Permeable Peptide Targeting the Nrf2-Keap1 Interaction: A Potential Novel Therapy for Global Cerebral Ischemia

The current study examined efficacy of a small Tat (trans-activator of transcription)-conjugated peptide activator of the Nrf2 (nuclear factor-E2-related factor-2) antioxidant/cell-defense pathway as a potential injury-specific, novel neuroprotectant against global cerebral ischemia (GCI). A competitive peptide, DEETGE-CAL-Tat, was designed to facilitate Nrf2 activation by disrupting interaction of Nrf2 with Keap1 (kelch-like ECH-associated protein 1), a protein that sequesters Nrf2 in the cytoplasm and thereby inactivates it. The DEETGE-CAL-Tat peptide contained the critical sequence DEETGE for the Nrf2-Keap1 interaction, the cell transduction domain of the HIV-Tat protein, and the cleavage sequence of calpain, which is sensitive to Ca(2+) increase and allows injury-specific activation of Nrf2. Using an animal model of GCI, we demonstrated that pretreatment with the DEETGE-CAL-Tat peptide markedly decreased Nrf2 interaction with Keap1 in the rat hippocampal CA1 region after GCI, and enhanced Nrf2 nuclear translocation and DNA binding. The DEETGE-CAL-Tat peptide also induced Nrf2 antioxidant/cytoprotective target genes, reduced oxidative stress, and induced strong neuroprotection and marked preservation of hippocampal-dependent cognitive function after GCI. These effects were specific as control peptides lacked neuroprotective ability. Intriguingly, the DEETGE-CAL-Tat peptide effects were also injury specific, as it had no effect upon neuronal survival or cognitive performance in sham nonischemic animals. Of significant interest, peripheral, postischemia administration of the DEETGE-CAL-Tat peptide from days 1-9 after GCI also induced robust neuroprotection and strongly preserved hippocampal-dependent cognitive function. Based on its robust neuroprotective and cognitive-preserving effects, and its unique injury-specific activation properties, the DEETGE-CAL-Tat peptide represents a novel, and potentially promising new therapeutic modality for the treatment of GCI.

SIGNIFICANCE STATEMENT

The current study demonstrates that DEETGE-CAL-Tat, a novel peptide activator of a key antioxidant gene transcription pathway in the hippocampus after global cerebral ischemia, can exert robust neuroprotection and preservation of cognitive function. A unique feature of the peptide is that its beneficial effects are injury specific. This feature is attractive as it targets drug activation specifically in the site of injury, and likely would lead to a reduction of undesirable side effects if translatable to the clinic. Due to its injury-specific activation, robust neuroprotection, and cognitive-preserving effects, this novel peptide may represent a much-needed therapeutic advance that could have efficacy in the treatment of global cerebral ischemia.

Pathophysiological role of different tubular epithelial cell death modes in acute kidney injury

The histological substrate of many forms of intrinsic acute kidney injury (AKI) has been classically attributed to tubular necrosis. However, more recent studies indicate that necrosis is not the main form of cell death in AKI and that other forms such as apoptosis, regulated necrosis (i.e. necroptosis and parthanatos), autophagic cell death and mitotic catastrophe, also participate in AKI and that their contribution depends on the cause and stage of AKI. Herein, we briefly summarize the main characteristics of the major types of cell death and we also critically review the existing evidence on the occurrence of different types of cell death reported in the most common experimental models of AKI and human specimens. We also discuss the pathophysiological mechanisms linking tubule epithelial cell death with reduced glomerular filtration, azotaemia and hydroelectrolytic imbalance. For instance, special relevance is given to the analysis of the inflammatory component of some forms of cell death over that of others, as an important and differential pathophysiological determinant. Finally, known molecular mechanisms and signalling pathways involved in each cell death type pose appropriate targets to specifically prevent or reverse AKI, provided that further knowledge of their participation and repercussion in each AKI syndrome is progressively increased in the near future.

Regulated cell death in AKI

AKI is pathologically characterized by sublethal and lethal damage of renal tubules. Under these conditions, renal tubular cell death may occur by regulated necrosis (RN) or apoptosis. In the last two decades, tubular apoptosis has been shown in preclinical models and some clinical samples from patients with AKI. Mechanistically, apoptotic cell death in AKI may result from well described extrinsic and intrinsic pathways as well as ER stress. Central converging nodes of these pathways are mitochondria, which become fragmented and sensitized to membrane permeabilization in response to cellular stress, resulting in the release of cell death-inducing factors. Whereas apoptosis is known to be regulated, tubular necrosis was thought to occur by accident until recent work unveiled several RN subroutines, most prominently receptor-interacting protein kinase-dependent necroptosis and RN induced by mitochondrial permeability transition. Additionally, other cell death pathways, like pyroptosis and ferroptosis, may also be of pathophysiologic relevance in AKI. Combination therapy targeting multiple cell-death pathways may, therefore, provide maximal therapeutic benefits.

Modulation of Fas-Fas Ligand Interaction Rehabilitates Hypoxia-Induced Apoptosis of Mesenchymal Stem Cells in Ischemic Myocardium Niche

Mesenchymal stem cells (MSCs) have the potential to repair and regenerate ischemic heart tissue; however, the poor viability of transplanted MSCs in the ischemic region is a major obstacle to their therapeutic use. This cell death is caused by Fas and Fas ligand (FasL) interactions under harsh conditions. To investigate improving the survival and therapeutic effects of MSCs, we focused our research on Fas-FasL-mediated cell death. In this study, we found that the poor viability of transplanted MSCs was caused by Fas-FasL interactions between host ischemic myocardial cells and implanted MSCs. In addition, we found that increased Fas expression and the corresponding decrease of cell survival were in close relation to hypoxic MSCs treated with FasL and H2O2. When MSCs were treated with a recombinant Fas/Fc chimera (Fas/Fc) inhibiting Fas-FasL interactions, the expressions of proapoptotic proteins including caspase-8, caspase-3, Bax, and cytochrome-c were attenuated, and the survival of MSCs was recovered. In ischemia-reperfusion injury models, the interaction between FasL in ischemic heart and Fas in implanted MSCs caused a loss of transplanted MSCs, whereas the inhibition of this interaction by Fas/Fc treatment improved cell survival and restored heart function. Thus, our study suggests that Fas-FasL interactions are responsible for activating cell death signaling in implanted stem cells and could be a potential target for improving therapeutic efficacy of stem cells in treating ischemic heart diseases.

Programmed necrosis in acute kidney injury

Programmed cell death (PCD) had been widely used synonymously to caspase-mediated apoptosis until caspase-independent cell death was described. Identification of necrosis as a regulated process in ischaemic conditions has recently changed our understanding of PCD. At least three pathways of programmed necrosis (PN) have been identified. First, receptor-interacting protein kinase 3 (RIP3)-dependent necroptosis causes organ failure following stroke, myocardial infarction and renal ischaemia/reperfusion injury. Necroptosis can be mediated either by a large intracellular caspase-8-containing signalling complex called the ripoptosome or by the RIP1-/RIP3-containing necroptosome and is controlled by a caspase-8/FLICE inhibitory protein(long) heterodimer at least in the latter case. Second, mitochondrial permeability transition mediates apoptotic or necrotic stimuli and depends on the mitochondrial protein cyclophilin D. The third PN pathway involves the poly(ADP-ribose) polymerase-calpain axis that contributes to acute kidney injury (AKI). Preclinical interference with the PN pathways therefore raises expectations for the future treatment of ischaemic conditions. In this brief review, we aim to summarize the clinically relevant PCD pathways and to transfer the basic science data to settings of AKI. We conclude that pathologists were quite right to refer to ischaemic kidney injury as 'acute tubular necrosis'.

The RIP1-kinase inhibitor necrostatin-1 prevents osmotic nephrosis and contrast-induced AKI in mice

The pathophysiology of contrast-induced AKI (CIAKI) is incompletely understood due to the lack of an appropriate in vivo model that demonstrates reduced kidney function before administration of radiocontrast media (RCM). Here, we examine the effects of CIAKI in vitro and introduce a murine ischemia/reperfusion injury (IRI)-based approach that allows induction of CIAKI by a single intravenous application of standard RCM after injury for in vivo studies. Whereas murine renal tubular cells and freshly isolated renal tubules rapidly absorbed RCM, plasma membrane integrity and cell viability remained preserved in vitro and ex vivo, indicating that RCM do not induce apoptosis or regulated necrosis of renal tubular cells. In vivo, the IRI-based CIAKI model exhibited typical features of clinical CIAKI, including RCM-induced osmotic nephrosis and increased serum levels of urea and creatinine that were not altered by inhibition of apoptosis. Direct evaluation of renal morphology by intravital microscopy revealed dilation of renal tubules and peritubular capillaries within 20 minutes of RCM application in uninjured mice and similar, but less dramatic, responses after IRI pretreatment. Necrostatin-1 (Nec-1), a specific inhibitor of the receptor-interacting protein 1 (RIP1) kinase domain, prevented osmotic nephrosis and CIAKI, whereas an inactive Nec-1 derivate (Nec-1i) or the pan-caspase inhibitor zVAD did not. In addition, Nec-1 prevented RCM-induced dilation of peritubular capillaries, suggesting a novel role unrelated to cell death for the RIP1 kinase domain in the regulation of microvascular hemodynamics and pathophysiology of CIAKI.

Dichotomy between RIP1- and RIP3-mediated necroptosis in tumor necrosis factor-α-induced shock

Tumor necrosis factor receptor (TNFR) signaling may result in survival, apoptosis or programmed necrosis. The latter is called necroptosis if the receptor-interacting protein 1 (RIP1) inhibitor necrostatin-1 (Nec-1) or genetic knockout of RIP3 prevents it. In the lethal mouse model of TNFα-mediated shock, addition of the pan-caspase inhibitor zVAD-fmk (zVAD) accelerates time to death. Here, we demonstrate that RIP3-deficient mice are protected markedly from TNFα-mediated shock in the presence and absence of caspase inhibition. We further show that the fusion protein TAT-crmA, previously demonstrated to inhibit apoptosis, also prevents necroptosis in L929, HT29 and FADD-deficient Jurkat cells. In contrast to RIP3-deficient mice, blocking necroptosis by Nec-1 or TAT-crmA did not protect from TNFα/zVAD-mediated shock, but further accelerated time to death. Even in the absence of caspase inhibition, Nec-1 application led to similar kinetics. Depletion of macrophages, natural killer (NK) cells, granulocytes or genetic deficiency for T lymphocytes did not influence this model. Because RIP3-deficient mice are known to be protected from cerulein-induced pancreatitis (CIP), we applied Nec-1 and TAT-crmA in this model and demonstrated the deterioration of pancreatic damage upon addition of these substances. These data highlight the importance of separating genetic RIP3 deficiency from RIP1 inhibition by Nec-1 application in vivo and challenge the current definition of necroptosis.

Rip1 (receptor-interacting protein kinase 1) mediates necroptosis and contributes to renal ischemia/reperfusion injury

Loss of kidney function in renal ischemia/reperfusion injury is due to programmed cell death, but the contribution of necroptosis, a newly discovered form of programmed necrosis, has not been evaluated. Here, we identified the presence of death receptor-mediated but caspase-independent cell death in murine tubular cells and characterized it as necroptosis by the addition of necrostatin-1, a highly specific receptor-interacting protein kinase 1 inhibitor. The detection of receptor-interacting protein kinase 1 and 3 in whole-kidney lysates and freshly isolated murine proximal tubules led us to investigate the contribution of necroptosis in a mouse model of renal ischemia/reperfusion injury. Treatment with necrostatin-1 reduced organ damage and renal failure, even when administered after reperfusion, resulting in a significant survival benefit in a model of lethal renal ischemia/reperfusion injury. Unexpectedly, specific blockade of apoptosis by zVAD, a pan-caspase inhibitor, did not prevent the organ damage or the increase in urea and creatinine in vivo in renal ischemia/reperfusion injury. Thus, necroptosis is present and has functional relevance in the pathophysiological course of ischemic kidney injury and shows the predominance of necroptosis over apoptosis in this setting. Necrostatin-1 may have therapeutic potential to prevent and treat renal ischemia/reperfusion injury.

Effects of kinetin riboside on proliferation and proapoptotic activities in human normal and cancer cell lines

Kinetin riboside (KR) is a N6-substituted derivative of adenosine. It is a natural compound which occurs in the milk of coconuts on the nanomole level. KR was initially shown to selectively inhibit proliferation of cancer cells and induce their apoptosis. We observed that KR inhibited growth (20-80%) of not only human cancer, but also normal cells and that this effect strongly depended on the type of cells. The anti-apoptotic Bcl-2 protein was downregulated, while proapoptotic Bax was upregulated in normal as well as in cancer cell lines, upon exposure to KR. Cytochrome c level increased in the cytosol upon treatment of cells with KR. The activity of caspases (ApoFluor®Green Caspase Activity Assay), as well as caspase-3 (caspase-3 activation assay) were increased mainly in cancer cells. The expression of procaspase 9 and its active form in the nucleus as well as in cytosol of KR-treated cells was elevated. In contrast, no effect of KR on caspase 8 expression was noted. The results indicated that non-malignant cells were less sensitive to KR then their cancer analogs and that KR most likely stimulated apoptosis mechanism of cancer cells through the intrinsic pathway.

Renal tubular Fas ligand mediates fratricide in cisplatin-induced acute kidney failure

Cisplatin, a standard chemotherapeutic agent for many tumors, has an unfortunately common toxicity where almost a third of patients develop renal dysfunction after a single dose. Acute kidney injury caused by cisplatin depends on Fas-mediated apoptosis driven by Fas ligand (FasL) expressed on tubular epithelial and infiltrating immune cells. Since the role of FasL in T cells is known, we investigated whether its presence in primary kidney cells is needed for its toxic effect. We found that all cisplatin-treated wild-type (wt) mice died within 6 days; however, severe combined immunodeficiency (SCID)/beige mice (B-, T-, and natural killer-cell-deficient) displayed a significant survival benefit, with only 55% mortality while exhibiting significant renal failure. Treating SCID/beige mice with MFL3, a FasL-blocking monoclonal antibody, completely restored survival after an otherwise lethal cisplatin dose, suggesting another source of FasL besides immune cells. Freshly isolated primary tubule segments from wt mice were co-incubated with thick ascending limb (TAL) segments freshly isolated from mice expressing the green fluorescent protein (GFP) transgene (same genetic background) to determine whether FasL-mediated killing of tubular cells is an autocrine or paracrine mechanism. Cisplatin-stimulated primary segments induced apoptosis in the GFP-tagged TAL cells, an effect blocked by MFL3. Thus, our study shows that cisplatin-induced nephropathy is mediated through FasL, functionally expressed on tubular cells that are capable of inducing death of cells of adjacent tubules.