Apoptotic Caspases: Multiple or Mistaken Identities?

The Caspase-Activated DNase drives inflammation and contributes to defense against viral infection

Mitochondria react to infection with sub-lethal signals in the apoptosis pathway. Mitochondrial signals can be inflammatory but mechanisms are only partially understood. We show that activation of the caspase-activated DNase (CAD) mediates mitochondrial pro-inflammatory functions and substantially contributes to host defense against viral infection. In cells lacking CAD, the pro-inflammatory activity of sub-lethal signals was reduced. Experimental activation of CAD caused transient DNA-damage and a pronounced DNA damage response, involving major kinase signaling pathways, NF-κB and cGAS/STING, driving the production of interferon, cytokines/chemokines and attracting neutrophils. The transcriptional response to CAD-activation was reminiscent of the reaction to microbial infection. CAD-deficient cells had a diminished response to viral infection. Influenza virus infected CAD-deficient mice displayed reduced inflammation in lung tissue, higher viral titers and increased weight loss. Thus, CAD links the mitochondrial apoptosis system and cell death caspases to host defense. CAD-driven DNA damage is a physiological element of the inflammatory response to infection.

Apoptotic and non-apoptotic roles of caspases in placenta physiology and pathology

Caspases, a family of cysteine proteases, are pivotal regulators of apoptosis, the tightly controlled cell death process crucial for eliminating excessive or unnecessary cells during development, including placental development. Collecting research has unveiled the multifaceted roles of caspases in the placenta, extending beyond apoptosis. Apart from their involvement in placental tissue remodeling via apoptosis, caspases actively participate in essential regulatory processes, such as trophoblast fusion and differentiation, significantly influencing placental growth and functionality. In addition, growing evidence indicates an elevation in caspase activity under pathological conditions like pre-eclampsia (PE) and intrauterine growth restriction (IUGR), leading to excessive cell death as well as inflammation. Drawing from advancements in caspase research and placental development under both normal and abnormal conditions, we examine the significance of caspases in both cell death (apoptosis) and non-cell death-related processes within the placenta. We also discuss potential therapeutics targeting caspase-related pathways for placenta disorders.

A Non-Apoptotic Pattern of Caspase-9/Caspase-3 Activation During Differentiation of Human Embryonic Stem Cells into Cardiomyocytes

In vitro studies have demonstrated that the differentiation of embryonic stem cells (ESCs) into cardiomyocytes requires activation of caspases through the mitochondrial pathway. These studies have relied on synthetic substrates for activity measurements, which can be misleading due to potential none-specific hydrolysis of these substrates by proteases other than caspases. Hence, caspase-9 and caspase-3 activation are investigated during the differentiation of human ESCs (hESCs) by directly assessing caspase-9 and -3 cleavage. Western blot reveals the presence of the cleaved caspase-9 prior to and during the differentiation of human ESCs (hESCs) into cardiomyocytes at early stages, which diminishes as the differentiation progresses, without cleavage and activation of endogenous procaspase-3. Activation of exogenous procaspase-3 by endogenous caspase-9 and subsequent cleavage of chromogenic caspase-3 substrate i.e. DEVD-pNA during the course of differentiation confirmes that endogenous caspase-9 has the potency to recognize and activate procaspase-3, but for reasons that are unknown to us fails to do so. These observations suggest the existence of distinct mechanisms of caspase regulation in differentiation as compared to apoptosis. Bioinformatics analysis suggests the presence of caspase-9 regulators, which may influence proteolytic function under specific conditions.

Transient caspase-mediated activation of caspase-activated DNase causes DNA damage required for phagocytic macrophage differentiation

Phagocytic macrophages are crucial for innate immunity and tissue homeostasis. Most tissue-resident macrophages develop from embryonic precursors that populate every organ before birth to lifelong self-renew. However, the mechanisms for versatile macrophage differentiation remain unknown. Here, we use in vivo genetic and cell biological analysis of the Drosophila larval hematopoietic organ, the lymph gland that produces macrophages. We show that the developmentally regulated transient activation of caspase-activated DNase (CAD)-mediated DNA strand breaks in intermediate progenitors is essential for macrophage differentiation. Insulin receptor-mediated PI3K/Akt signaling regulates the apoptosis signal-regulating kinase 1 (Ask1)/c-Jun kinase (JNK) axis to control sublethal levels of caspase activation, causing DNA strand breaks during macrophage development. Furthermore, caspase activity is also required for embryonic-origin macrophage development and efficient phagocytosis. Our study provides insights into developmental signaling and CAD-mediated DNA strand breaks associated with multifunctional and heterogeneous macrophage differentiation.

Immunogenic cell death in cancer: targeting necroptosis to induce antitumour immunity

Most metastatic cancers remain incurable due to the emergence of apoptosis-resistant clones, fuelled by intratumour heterogeneity and tumour evolution. To improve treatment, therapies should not only kill cancer cells but also activate the immune system against the tumour to eliminate any residual cancer cells that survive treatment. While current cancer therapies rely heavily on apoptosis - a largely immunologically silent form of cell death - there is growing interest in harnessing immunogenic forms of cell death such as necroptosis. Unlike apoptosis, necroptosis generates second messengers that act on immune cells in the tumour microenvironment, alerting them of danger. This lytic form of cell death optimizes the provision of antigens and adjuvanticity for immune cells, potentially boosting anticancer treatment approaches by combining cellular suicide and immune response approaches. In this Review, we discuss the mechanisms of necroptosis and how it activates antigen-presenting cells, drives cross-priming of CD8+ T cells and induces antitumour immune responses. We also examine the opportunities and potential drawbacks of such strategies for exposing cancer cells to immunological attacks.

Single-Cell Caspase-3 Measurement Using a Biomimetic Nanochannel

Direct single-cell caspase-3 (Casp-3) analysis has remained challenging. A study of single-cell Casp-3 could contribute to revealing the fundamental pathogenic mechanisms in Casp-3-associated diseases. Here, a biomimetic nanochannel capable of single-cell sampling and ionic detection of intracellular Casp-3 is devised, which is established upon the installment of target-specific organic molecules (luc-DEVD) within the orifice of a glass nanopipette. The specific cleavage of luc-DEVD by Casp-3 could induce changes of inner-surface chemical groups and charge properties, thus altering the ionic response of the biomimetic nanochannel for direct Casp-3 detection. The practical applicability of this biomimetic nanochannel is confirmed by probing intracellular Casp-3 fluctuation upon drug stimulation and quantifying the Casp-3 evolution during induced apoptosis. This work realizes ionic single-cell Casp-3 analysis and provides a different perspective for single-cell protein analysis.

Ionizing radiation induces cells with past caspase activity that contribute to the adult organ in Drosophila and show reduced Loss of Heterozygosity

There is increasing recognition that cells may activate apoptotic caspases but not die, instead displaying various physiologically relevant consequences. Mechanisms that underlie the life-or-death decision in a cell that has activated apoptotic caspases, however, are incompletely understood. By optimizing a published reporter for past caspase activity, we were able to visualize cells that survived caspase activation specifically after exposure to ionizing radiation in Drosophila larval wing discs. We found that cells with X-ray-induced past active caspases (XPAC) did not arise at random but were born at specific locations within the developing wing imaginal discs of Drosophila larvae. Inhibiting key components of the apoptotic pathway decreased XPAC number, suggesting that apoptotic signaling is needed to induce XPAC cells. Yet, XPAC cells appeared in stereotypical patterns that did not follow the pattern of IR-induced apoptosis, suggesting additional controls at play. Functional testing identified the contribution of wingless (Drosophila Wnt1) and Ras signaling to the prevalence of XPAC cells. Furthermore, by following irradiated larvae into adulthood, we found that XPAC cells contribute to the adult wing. To address the relationship between XPAC and genome stability, we combined a reporter for past caspase activity with mwh, an adult marker for Loss of Heterozygosity (LOH). We found a lower incidence of LOH among XPAC compared to cells that did not activate the reporter for past caspase activity. In addition, at time points when wing disc cells are finishing DNA repair, XPAC cells show an anti-correlation with cells with unrepaired IR-induced double-stranded breaks. Our data suggest that non-lethal caspase activity safeguards the genome by facilitating DNA repair and reducing LOH after transient exposure to X-rays. These results identify a physiological role for non-lethal caspase activity during recovery from radiation damage.

STEAP4 modulates cell proliferation and oxidative stress in benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a quite common chronic disease plagued elderly men and its etiology remains unclear. It was reported that the six-transmembrane epithelial antigen of prostate 4 (STEAP4) could modulate cell proliferation/apoptosis ratio and oxidative stress in cancers. Our current study aimed to explore the expression, biological function, and underlying mechanism of STEAP4 in BPH progress. Human prostate tissues and cell lines were utilized. qRT-PCR and immunofluorescence staining were employed. STEAP4 knockdown (STEAP4-KD) or STEAP4 overexpression (STEAP4-OE) cell models were established. Cell proliferation, cell cycle, apoptosis, and reactive oxygen species (ROS) were determined by cell counting kit-8 (CCK-8) assay and flow cytometry. Apoptosis-related proteins and antioxidant enzymes were identified by Western Blot. In addition, the epithelial-mesenchymal transition (EMT) process and fibrosis biomarker (collagen I and α-SMA) were analyzed. It was indicated that STEAP4 was mainly located in the prostate epithelium and upregulated in BPH tissues. STEAP4 deficiency induced apoptosis and inhibited cell survival, but had no effect on the cell cycle, fibrosis, and EMT process. In addition, ROS changes were observed in the STEAP4-KD model. Consistently, overproduction of STEAP4 suppressed apoptosis and promoted cell proliferation, as well as facilitated ROS production. We further examined AKT / mTOR, p38MAPK / p-p38MAPK, and WNT/ β-Catenin signaling pathway and demonstrated that STEAP4 regulated the proliferation and apoptosis of prostate cells through AKT / mTOR signaling, rather than p38MAPK / p-p38MAPK and WNT/ β-Catenin pathways. Furthermore, activating AKT / mTOR signaling with SC79 significantly reversed apoptosis triggered by STEAP4 deficiency, whereas suppressing AKT / mTOR signaling with MK2206 reduced the increase of cell viability triggered by STEAP4 overproduction. Our original data demonstrated that STEAP4 is crucial in the onset and progression of prostate hyperplasia and may become a new target for the treatment of BPH.

Apoptosis in mesenchymal stromal cells activates an immunosuppressive secretome predicting clinical response in Crohn's disease

In vivo apoptosis of human mesenchymal stromal cells (MSCs) plays a critical role in delivering immunomodulation. Yet, caspase activity not only mediates the dying process but also death-independent functions that may shape the immunogenicity of apoptotic cells. Therefore, a better characterization of the immunological profile of apoptotic MSCs (ApoMSCs) could shed light on their mechanistic action and therapeutic applications. We analyzed the transcriptomes of MSCs undergoing apoptosis and identified several immunomodulatory factors and chemokines dependent on caspase activation following Fas stimulation. The ApoMSC secretome inhibited human T cell proliferation and activation, and chemoattracted monocytes in vitro. Both immunomodulatory activities were dependent on the cyclooxygenase2 (COX2)/prostaglandin E2 (PGE2) axis. To assess the clinical relevance of ApoMSC signature, we used the peripheral blood mononuclear cells (PBMCs) from a cohort of fistulizing Crohn's disease (CD) patients who had undergone MSC treatment (ADMIRE-CD). Compared with healthy donors, MSCs exposed to patients' PBMCs underwent apoptosis and released PGE2 in a caspase-dependent manner. Both PGE2 and apoptosis were significantly associated with clinical responses to MSCs. Our findings identify a new mechanism whereby caspase activation delivers ApoMSC immunosuppression. Remarkably, such molecular signatures could implicate translational tools for predicting patients' clinical responses to MSC therapy in CD.

How does caspases regulation play role in cell decisions? apoptosis and beyond

Caspases are a family of cysteine proteases, and the key factors behind the cellular events which occur during apoptosis and inflammation. However, increasing evidence shows the non-conventional pro-survival action of apoptotic caspases in crucial processes. These cellular events include cell proliferation, differentiation, and migration, which may appear in the form of metastasis, and chemotherapy resistance in cancerous situations. Therefore, there should be a precise and strict control of caspases activity, perhaps through maintaining the threshold below the required levels for apoptosis. Thus, understanding the regulators of caspase activities that render apoptotic caspases as non-apoptotic is of paramount importance both mechanistically and clinically. Furthermore, the functions of apoptotic caspases are affected by numerous post-translational modifications. In the present mini-review, we highlight the various mechanisms that directly impact caspases with respect to their anti- or non-apoptotic functions. In this regard, post-translational modifications (PTMs), isoforms, subcellular localization, transient activity, substrate availability, substrate selection, and interaction-mediated regulations are discussed.

Impact of ferroptosis on preeclampsia: A review

Preeclampsia (PE) is usually associated with the accumulation of reactive oxygen species (ROS) resulting from heightened oxidative stress (OS). Ferroptosis is a unique type of lipid peroxidation-induced iron-dependent cell death distinct from traditional apoptosis, necroptosis, and pyroptosis and most likely contributes considerable to PE pathogenesis. At approximately 10-12 weeks of gestation, trophoblasts create an environment rich in oxygen and iron. In patients with PE, ferroptosis-related genes such as HIF1 and MAPK8 are downregulated, whereas PLIN2 is upregulated. Furthermore, miR-30b-5p overexpression inhibits solute carrier family 11 member 2, resulting in a decrease in glutathione levels and an increase in the labile iron pool. At the maternal-fetal interface, physiological hypoxia/reperfusion and excessive iron result in lipid peroxidation and ROS production. Owing to the high expression of Fpn and polyunsaturated fatty acid-containing phospholipid-related enzymes, including acyl-CoA synthetase long-chain family member 4, lysophosphatidylcholine acyl-transferase 3, and spermidine/spermine N1-acetyltransferase 1, trophoblasts become more susceptible to OS and ROS damage. In stage 1, the injured trophoblasts exhibit poor invasion and incomplete uterine spiral artery remodeling caused by ferroptosis, leading to placental ischemia and hypoxia. Subsequently, ferroptosis marked by OS occurs in stage 2, eventually causing PE. We aimed to explore the new therapeutic target of PE through OS in ferroptosis.

Roles of RIPK1 as a stress sentinel coordinating cell survival and immunogenic cell death

Cell death and inflammation are closely linked arms of the innate immune response to combat infection and tissue malfunction. Recent advancements in our understanding of the intricate signals originating from dying cells have revealed that cell death serves as more than just an end point. It facilitates the exchange of information between the dying cell and cells of the tissue microenvironment, particularly immune cells, alerting and recruiting them to the site of disturbance. Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is emerging as a critical stress sentinel that functions as a molecular switch, governing cellular survival, inflammatory responses and immunogenic cell death signalling. Its tight regulation involves multiple layers of post-translational modifications. In this Review, we discuss the molecular mechanisms that regulate RIPK1 to maintain homeostasis and cellular survival in healthy cells, yet drive cell death in a context-dependent manner. We address how RIPK1 mutations or aberrant regulation is associated with inflammatory and autoimmune disorders and cancer. Moreover, we tease apart what is known about catalytic and non-catalytic roles of RIPK1 and discuss the successes and pitfalls of current strategies that aim to target RIPK1 in the clinic.

Chalcone/1,3,4-Oxadiazole/Benzimidazole hybrids as novel anti-proliferative agents inducing apoptosis and inhibiting EGFR & BRAFV600E

INTRODUCTION

One of the most robust global challenges and difficulties in the 21st century is cancer. Treating cancer is a goal which continues to motivate researchers to innovate in design and development of new treatments to help battle the disease.

OBJECTIVES

Our objective was developing new antiapoptotic hybrids based on biologically active heterocyclic motifs "benzimidazole?oxadiazole-chalcone hybrids'' that had shown promising ability to inhibit EGFR and induce apoptosis. We expected these scaffolds to display anticancer activity via inhibition of BRAF, EGFR, and Bcl-2 and induction of apoptosis through activation of caspases.

METHODS

The new hybrids 7a-x were evaluated for their anti-proliferative, EGFR & BRAFV600E inhibitory, and apoptosis induction activities were detected. Docking study & dynamic stimulation into EGFR and BRAFV600E were studied.

RESULTS

All hybrids exhibited remarkable cell growth inhibition on the four tested cell lines with IC50 ranging from 0.95 μM to 12.50 μM. which was comparable to Doxorubicin. Compounds 7k-m had the most potent EGFR inhibitory activity. While, compounds 7e, 7g, 7k and 7l showed good inhibitory activities against BRAFV600E. Furthermore, Compounds 7k, 7l, and 7m increased Caspases 3,8 & 9, Cytochrome C and Bax levels and decreased Bcl-2 protein levels. Compounds 7k-m received the best binding scores and showed binding modes that were almost identical to each other and comparable with that of the co-crystalized Erlotinib in EGFR and BRAF active sites.

CONCLUSION

Compounds 7k-m could be used as potential apoptotic anti-proliferative agents upon further optimization.

Copper deprivation enhances the chemosensitivity of pancreatic cancer to rapamycin by mTORC1/2 inhibition

Cuproplasia, or copper-dependent cell proliferation, has been observed in varieties of solid tumors along with aberrant copper homeostasis. Several studies reported good response of patients to copper chelator assisted neoadjuvant chemotherapy, however, the internal target molecules are still undetermined. Unravel copper-associated tumor signaling would be valuable to forge new links to translate biology of copper into clinical cancer therapies. We evaluated the significance of high-affinity copper transporter-1 (CTR1) by bioinformatic analysis, and in 19 pairs of clinical specimens. Then, with the help of gene interference and chelating agent, enriched signaling pathways were identified by KEGG analysis and immunoblotting. Accompanying biological capability of pancreatic carcinoma-associated proliferation, cell cycle, apoptosis, and angiogenesis were investigated. Furthermore, a combination of mTOR inhibitor and CTR1 suppressor has been assessed in xenografted tumor mouse models. Hyperactive CTR1 was investigated in pancreatic cancer tissues and proven to as the key point of cancer copper homeostasis. Intracellular copper deprivation induced by CTR1 gene knock-down or systematic copper chelation by tetrathiomolybdate suppressed proliferation and angiogenesis of pancreatic cancer cell. PI3K/AKT/mTOR signaling pathway was suppressed by inhibiting the activation of p70(S6)K and p-AKT, and finally inhibited mTORC1 and mTORC2 after copper deprivation. Additionally, CTR1 gene silencing successfully improved the anti-cancer effect of mTOR inhibitor rapamycin. Our study reveals that CTR1 contributes to pancreatic tumorigenesis and progression, by up-regulating the phosphorylation of AKT/mTOR signaling molecules. Recovering copper balance by copper deprivation addresses as promising strategy for improved cancer chemotherapy.

Effects of photodynamic therapy using Red LED-light combined with hypocrellin B on apoptotic signaling in cutaneous squamous cell carcinoma A431 cells

BACKGROUND

The incidence of cutaneous squamous cell carcinoma (cSCC) has been demonstrating yearly increases. cSCC is a malignant cancer and exerts a major impact on patients' health and quality of life. Thus, the development and use of novel therapies in the treatment of cSCC are needed. It has been reported that LED photodynamic therapy (LED PDT) mediated by Hypocrellin B and its derivatives, a second-generation photosensitizer, can induce apoptosis in a variety of tumor cells, However, its potential pro-apoptotic effects on cSCC have yet to be investigated.

OBJECTIVE

This study aims to investigate the pro-apoptotic effects and molecular mechanisms of HB-LED PDT in cutaneous squamous cell carcinoma A431 cells (Subsequent abbreviation A431 cells). Such information can provide an important theoretical foundation for the clinical translation of HB-LED PDT in the treatment of cSCC.

METHODS

1. Effects of HB on A431 cells were determined using a Cell Counting Kit-8 assay, which method can indirectly reflect the number of living cells. In this way, this assay can then provide a means to identify the optimal concentrations of HB required for the induction of apoptosis in A431 cells. 2. The effects of HB-LED PDT on the morphology of A431 cells and changes in the nuclei after Hoechst33342 staining as determined using inverted fluorescent microscopy. 3. Use of the Annexin V-FITC test kit to detect levels of apoptosis in A431 cells in response to treatment with HB. Changes in reactive oxygen species and mitochondrial membrane potential following HB-LED PDT treatment in A431 cells were determined using fluorescence activated cell sorting (FACS). 4. Real-time quantitative PCR and Western Blot were applied to assess changes in several key factors involved in apoptosis including Bax, Bcl-2, and Caspase-3, at both transcription and translation levels. With these assays, it was possible to investigate the apoptotic signaling pathway in A431 cells in response to HB-LED PDT.

RESULTS

HB-LED PDT inhibited proliferation activity and promoted nuclear fragmentation within these A431 cells. HB-LED PDT inhibited mitochondrial activity, increased reactive oxygen species production, and promoted apoptosis of A431 cells. In addition, several key factors in the apoptotic signaling pathway were increased at both the transcriptional and translational levels in A431 cells in response to the HB-LED PDT, indicating that the apoptotic signaling pathway was activated by HB-LED PDT.

CONCLUSION

HB-LED PDT induces apoptosis in A431 cells through a mitochondria-mediated apoptotic pathway. Such findings serve as an important foundation for the development of new approaches in the treatment of cSCC.

IMT504 protects beta cells against apoptosis and maintains beta cell identity, without modifying proliferation

We have demonstrated that oligodeoxynucleotide IMT504 promotes significant improvement in the diabetic condition in diverse animal models. Based on these results, here we evaluated whether these effects observed in vivo could be due to direct effects on β-cells. We demonstrate by immunofluorescence that IMT504 enters the cell and locates in cytoplasm where it induces GSK-3β phosphorylation that inactivates this kinase. As GSK-3β tags Pdx1 for proteasomal degradation, by inactivating GSK-3β, IMT504 induces an increase in Pdx1 protein levels, demonstrated by Western blotting. Concomitantly, an increase in Ins2 and Pdx1 gene transcription was observed, with no significant increase in insulin content or secretion. Enhanced Pdx1 is promising since it is a key transcription factor for insulin synthesis and is also described as an essential factor for the maintenance β-cell phenotype and function. Dose-dependent inhibition of H2 O2 -induced apoptosis determined by ELISA as well as decreased expression of Bax was also observed. These results were confirmed in another β-cell line, beta-TC-6 cells, in which a cytokine mix induced apoptosis that was reversed by IMT504. In addition, an inhibitor of IMT504 entrance into cells abrogated the effect IMT504. Based on these results we conclude that the β-cell recovery observed in vivo may include direct effects of IMT504 on β-cells, by maintaining their identity/phenotype and protecting them from oxidative stress and cytokine-induced apoptosis. Thus, this work positions IMT504 as a promising option in the framework of the search of new therapies for type I diabetes treatment.

Apoptosis in Alzheimer's disease: insight into the signaling pathways and therapeutic avenues

Alzheimer's disease (AD) is characterized by the accumulation of hyperphosphorylated tau and amyloid-β (Aβ) protein resulting in synaptic loss and apoptosis. Aβ and tau deposition trigger apoptotic pathways that result in neuronal death. Apoptosis is considered to be responsible for manifestations associated with AD under pathological conditions. It regulates via extrinsic and intrinsic pathways. It activates various proteins including Bcl-2 family proteins like Bax, Bad, Bid, Bcl-XS, Bcl-XL and caspases comprising of initiator, effector and inflammatory caspases carried out through a cascade of events that finally lead to cell disintegration. The apoptotic elements interact with trophic factors, signaling molecules including Ras-ERK, JNK, GSK-3β, BDNF/TrkB/CREB and PI3K/AKT/mTOR. Ras-ERK signaling is involved in the progression of cell cycle and apoptosis. JNK pathway is also upregulated in AD which results in decreased expression of anti-apoptotic proteins. JAK-STAT triggers caspase-3 mediated apoptosis leading to neurodegeneration. The imbalance between autophagy and apoptosis is regulated by PI3K/Akt/mTOR pathway. GSK-3β is involved in the stimulation of pro-apoptotic factors resulting in dysregulation of apoptosis. Drugs like filgrastim, epigallocatechin gallate, curcumin, nicergoline and minocycline are under development which target these pathways and modulate the disease condition. This study sheds light on apoptotic pathways that are cardinal for neuronal survival and perform crucial role in the occurrence of AD along with the trends in therapeutics targeting apoptosis induced AD. To develop prospective treatments for AD, it is desirable to elucidate potential targets including restoration apoptotic balance, regulation of caspases, Bcl-2 and other crucial proteins involved in apoptosis mediated AD.

7-Geranyloxycinnamic Acid Isolated from Melicope lunu-ankenda Leaves Perturbs Colon Cancer and Breast Cancer Cell Lines' Growth via Induction of Apoptotic Pathway

Globally, breast cancer is the most prevalent form of cancer in women and there is a need for alternative therapies such as plant-derived compounds with low systemic toxicity and selective toxicity to cancer cells. The aim of this study is to assess the cytotoxicity effects of 7-geranyloxycinnamic acid isolated from leaves of Melicope lunu-ankenda, a traditional medicinal plant, on the human breast cancer cell lines. Dried leaf powder was used for the preparation of different crude extracts using different solvents of increasing order of polarity. The structure of the isolated compound from the petroleum ether extract was elucidated by ¹H and ¹³C NMR, LC-MS, and DIP-MS spectroscopy. The cytotoxic activity of the crude extract and 7-geranyloxycinnamic acid analyzed using MTT assay. Apoptotic analysis was evaluated using Annexin V-PI staining, AO/PI staining, intracellular ROS measurement, and measurement of activities of caspases 3/7, 8, and 9. Crude extracts and the isolated pure compound showed significant cytotoxicity against tested cancer cell lines. 7-geranyloxycinnamic acid was found to exert significant cytotoxic effects against breast cancer cell lines such as the MCF-7 and MDA-MB-231 cell lines. The cytotoxic effects are attributed to its ability to induce apoptosis via accumulation of ROS and activation of caspases in both breast cancer cell lines. The pure compound, 7-geranyloxycinnamic acid isolated from the leaves of M. lunu-ankenda, can exert significant cytotoxic effects against breast cancer cell lines without affecting the normal cells.

Inflammation, Mitochondria and Natural Compounds Together in the Circle of Trust

Human diseases are characterized by the perpetuation of an inflammatory condition in which the levels of Reactive Oxygen Species (ROS) are quite high. Excessive ROS production leads to DNA damage, protein carbonylation and lipid peroxidation, conditions that lead to a worsening of inflammatory disorders. In particular, compromised mitochondria sustain a stressful condition in the cell, such that mitochondrial dysfunctions become pathogenic, causing human disorders related to inflammatory reactions. Indeed, the triggered inflammation loses its beneficial properties and turns harmful if dysregulation and dysfunctions are not addressed. Thus, reducing oxidative stress with ROS scavenger compounds has proven to be a successful approach to reducing inflammation. Among these, natural compounds, in particular, polyphenols, alkaloids and coenzyme Q₁₀, thanks to their antioxidant properties, are capable of inhibiting the activation of NF-κB and the expression of target genes, including those involved in inflammation. Even more, clinical trials, and in vivo and in vitro studies have demonstrated the antioxidant and anti-inflammatory effects of phytosomes, which are capable of increasing the bioavailability and effectiveness of natural compounds, and have long been considered an effective non-pharmacological therapy. Therefore, in this review, we wanted to highlight the relationship between inflammation, altered mitochondrial oxidative activity in pathological conditions, and the beneficial effects of phytosomes. To this end, a PubMed literature search was conducted with a focus on various in vitro and in vivo studies and clinical trials from 2014 to 2022.

Executioner caspases restrict mitochondrial RNA-driven Type I IFN induction during chemotherapy-induced apoptosis

During apoptosis, mitochondrial outer membrane permeabilization (MOMP) enables certain mitochondrial matrix macromolecules to escape into the cytosol. However, the fate of mitochondrial RNA (mtRNA) during apoptosis is unknown. Here, we demonstrate that MOMP results in the cytoplasmic release of mtRNA and that executioner caspases-3 and -7 (casp3/7) prevent cytoplasmic mtRNA from triggering inflammatory signaling. In the setting of genetic or pharmacological casp3/7 inhibition, apoptotic insults result in mtRNA activation of the MDA5/MAVS/IRF3 pathway to drive Type I interferon (IFN) signaling. This pathway is sufficient to activate tumor-intrinsic Type I IFN signaling in immunologically cold cancer models that lack an intact cGAS/STING signaling pathway, promote CD8+ T-cell-dependent anti-tumor immunity, and overcome anti-PD1 refractoriness in vivo. Thus, a key function of casp3/7 is to inhibit inflammation caused by the cytoplasmic release of mtRNA, and pharmacological modulation of this pathway increases the immunogenicity of chemotherapy-induced apoptosis.

Proteome integral solubility alteration high-throughput proteomics assay identifies Collectin-12 as a non-apoptotic microglial caspase-3 substrate

Caspases are a family of proteins mostly known for their role in the activation of the apoptotic pathway leading to cell death. In the last decade, caspases have been found to fulfill other tasks regulating the cell phenotype independently to cell death. Microglia are the immune cells of the brain responsible for the maintenance of physiological brain functions but can also be involved in disease progression when overactivated. We have previously described non-apoptotic roles of caspase-3 (CASP3) in the regulation of the inflammatory phenotype of microglial cells or pro-tumoral activation in the context of brain tumors. CASP3 can regulate protein functions by cleavage of their target and therefore could have multiple substrates. So far, identification of CASP3 substrates has been performed mostly in apoptotic conditions where CASP3 activity is highly upregulated and these approaches do not have the capacity to uncover CASP3 substrates at the physiological level. In our study, we aim at discovering novel substrates of CASP3 involved in the normal regulation of the cell. We used an unconventional approach by chemically reducing the basal level CASP3-like activity (by DEVD-fmk treatment) coupled to a Mass Spectrometry screen (PISA) to identify proteins with different soluble amounts, and consequently, non-cleaved proteins in microglia cells. PISA assay identified several proteins with significant change in their solubility after DEVD-fmk treatment, including a few already known CASP3 substrates which validated our approach. Among them, we focused on the Collectin-12 (COLEC12 or CL-P1) transmembrane receptor and uncovered a potential role for CASP3 cleavage of COLEC12 in the regulation of the phagocytic capacity of microglial cells. Taken together, these findings suggest a new way to uncover non-apoptotic substrates of CASP3 important for the modulation of microglia cell physiology.

Role of mitochondrial outer membrane permeabilization during bacterial infection

Beyond the initial 'powerhouse' view, mitochondria have numerous functions in their mammalian cell and contribute to many physiological processes, and many of these we understand only partially. The control of apoptosis by mitochondria is firmly established. Many questions remain however how this function is embedded into physiology, and how other signaling pathways regulate mitochondrial apoptosis; the interplay of bacteria with the mitochondrial apoptosis pathway is one such example. The outer mitochondrial membrane regulates both import into mitochondria and the release of intermembrane, and in some situations also matrix components from mitochondria, and these mitochondrial components can have signaling function in the cytosol. One function is the induction of apoptotic cell death. An exciting, more recently discovered function is the regulation of inflammation. Mitochondrial molecules, both proteins and nucleic acids, have inflammatory activity when released from mitochondria, an activity whose regulation is intertwined with the activation of apoptotic caspases. Bacterial infection can have more general effects on mitochondrial apoptosis-regulation, through effects on host transcription and other pathways, such as signals controlled by pattern recognition. Some specialized bacteria have products that more specifically regulate signaling to the outer mitochondrial membrane, and to apoptosis; both pro- and anti-apoptotic mechanisms have been reported. Among the intriguing recent findings in this area are signaling contributions of porins and the sub-lethal release of intermembrane constituents. We will here review the literature and place the new developments into the established context of mitochondrial signaling during the contact of bacterial pathogens with human cells.

Mitochondrial control of inflammation

Numerous mitochondrial constituents and metabolic products can function as damage-associated molecular patterns (DAMPs) and promote inflammation when released into the cytosol or extracellular milieu. Several safeguards are normally in place to prevent mitochondria from eliciting detrimental inflammatory reactions, including the autophagic disposal of permeabilized mitochondria. However, when the homeostatic capacity of such systems is exceeded or when such systems are defective, inflammatory reactions elicited by mitochondria can become pathogenic and contribute to the aetiology of human disorders linked to autoreactivity. In addition, inefficient inflammatory pathways induced by mitochondrial DAMPs can be pathogenic as they enable the establishment or progression of infectious and neoplastic disorders. Here we discuss the molecular mechanisms through which mitochondria control inflammatory responses, the cellular pathways that are in place to control mitochondria-driven inflammation and the pathological consequences of dysregulated inflammatory reactions elicited by mitochondrial DAMPs.

High caspase 3 and vulnerability to dual BCL2 family inhibition define ETO2::GLIS2 pediatric leukemia

Pediatric acute myeloid leukemia expressing the ETO2::GLIS2 fusion oncogene is associated with dismal prognosis. Previous studies have shown that ETO2::GLIS2 can efficiently induce leukemia development associated with strong transcriptional changes but those amenable to pharmacological targeting remained to be identified. By studying an inducible ETO2::GLIS2 cellular model, we uncovered that de novo ETO2::GLIS2 expression in human cells led to increased CASP3 transcription, CASP3 activation, and cell death. Patient-derived ETO2::GLIS2+ leukemic cells expressed both high CASP3 and high BCL2. While BCL2 inhibition partly inhibited ETO2::GLIS2+ leukemic cell proliferation, BH3 profiling revealed that it also sensitized these cells to MCL1 inhibition indicating a functional redundancy between BCL2 and MCL1. We further show that combined inhibition of BCL2 and MCL1 is mandatory to abrogate disease progression using in vivo patient-derived xenograft models. These data reveal that a transcriptional consequence of ETO2::GLIS2 expression includes a positive regulation of the pro-apoptotic CASP3 and associates with a vulnerability to combined targeting of two BCL2 family members providing a novel therapeutic perspective for this aggressive pediatric AML subgroup.

Santin (5,7-Dihydroxy-3,6,4'-Trimetoxy-Flavone) Enhances TRAIL-Mediated Apoptosis in Colon Cancer Cells

TRAIL (Tumor necrosis factor-Related Apoptosis-Inducing Ligand) has the ability to selectively kill cancer cells without being toxic to normal cells. This endogenous ligand plays an important role in surveillance and anti-tumor immunity. However, numerous tumor cells are resistant to TRAIL-induced apoptosis. In this study, the apoptotic effect of santin in combination with TRAIL on colon cancer cells was examined. Flow cytometry was used to detect the apoptosis and expression of death receptors (TRAIL-R1/DR4 and TRAIL-R2/DR5). Mitochondrial membrane potential (ΔΨm) was evaluated by DePsipher staining with the use of fluorescence microscopy. We have shown for the first time that flavonoid santin synergizes with TRAIL to induce apoptosis in colon cancer cells. Santin induced TRAIL-mediated apoptosis through increased expression of death receptors TRAIL-R1 and TRAIL-R2 and augmented disruption of the mitochondrial membrane in SW480 and SW620 cancer cells. The obtained data may indicate the potential role of santin in colon cancer chemoprevention through the enhancement of TRAIL-mediated apoptosis.

Sub-lethal signals in the mitochondrial apoptosis apparatus: pernicious by-product or physiological event?

One of the tasks of mitochondria is the rule over life and death: when the outer membrane is permeabilized, the release of intermembrane space proteins causes cell death by apoptosis. For a long time, this mitochondrial outer membrane permeabilization (MOMP) has been accepted as the famous step from which no cell returns. Recent results have however shown that this quite plainly does not have to be the case. A cell can also undergo only a little MOMP, and it can efficiently repair damage it has incurred in the process. There is no doubt now that such low-scale permeabilization occurs. A major unclarified issue is the biological relevance. Is small-scale mitochondrial permeabilization an accident, a leakiness of the apoptosis apparatus, perhaps during restructuring of the mitochondrial network? Is it attempted suicide, where cell death by apoptosis is the real goal but the stimulus failed to reach the threshold? Or, more boldly, is there a true biological meaning behind the event of the release of low amounts of mitochondrial components? We will here explore this last possibility, which we believe is on one hand appealing, on the other hand plausible and supported by some evidence. Recent data are consistent with the view that sub-lethal signals in the mitochondrial apoptosis pathway can drive inflammation, the first step of an immune reaction. The apoptosis apparatus is almost notoriously easy to trigger. Sub-lethal signals may be even easier to set off. We suggest that the apoptosis apparatus is used in this way to sound the call when the first human cell is infected by a pathogen.

New Insights Into the Anticancer Effects of p-Coumaric Acid: Focus on Colorectal Cancer

Colorectal cancer is considered the second most deadly cancer in the world. Studies have indicated that diet can prevent the risk of developing colorectal cancer. Recently, there has been an increasing interest in polyphenols due to their plausible effect on cancer prevention and treatment. p-Coumaric acid (p-CouA), a phenolic compound, is a cinnamic acid derivative found in several fruits, vegetables, and herbs. A growing body of evidence suggests that p-CouA may be an effective agent for preventing and managing colorectal cancer. In this current review, we briefly highlight the bioavailability of p-CouA. We also provide an up-to-date overview of molecular mechanisms underlying its anticancer effects, focusing on anti-inflammatory and antioxidant potentials, apoptosis induction, and cell cycle blockade. Finally, we discuss the impact of p-CouA on clonogenicity and multidrug resistance of colorectal cancer cells.

Hepatoprotective Effect of Kaempferol: A Review of the Dietary Sources, Bioavailability, Mechanisms of Action, and Safety

The liver is the body's most critical organ that performs vital functions. Hepatic disorders can affect the physiological and biochemical functions of the body. Hepatic disorder is a condition that describes the damage to cells, tissues, structures, and functions of the liver, which can cause fibrosis and ultimately result in cirrhosis. These diseases include hepatitis, ALD, NAFLD, liver fibrosis, liver cirrhosis, hepatic failure, and HCC. Hepatic diseases are caused by cell membrane rupture, immune response, altered drug metabolism, accumulation of reactive oxygen species, lipid peroxidation, and cell death. Despite the breakthrough in modern medicine, there is no drug that is effective in stimulating the liver function, offering complete protection, and aiding liver cell regeneration. Furthermore, some drugs can create adverse side effects, and natural medicines are carefully selected as new therapeutic strategies for managing liver disease. Kaempferol is a polyphenol contained in many vegetables, fruits, and herbal remedies. We use it to manage various diseases such as diabetes, cardiovascular disorders, and cancers. Kaempferol is a potent antioxidant and has anti-inflammatory effects, which therefore possesses hepatoprotective properties. The previous research has studied the hepatoprotective effect of kaempferol in various hepatotoxicity protocols, including acetaminophen (APAP)-induced hepatotoxicity, ALD, NAFLD, CCl₄, HCC, and lipopolysaccharide (LPS)-induced acute liver injury. Therefore, this report aims to provide a recent brief overview of the literature concerning the hepatoprotective effect of kaempferol and its possible molecular mechanism of action. It also provides the most recent literature on kaempferol's chemical structure, natural source, bioavailability, and safety.

Apoptosis and Phagocytosis as Antiviral Mechanisms

Viruses are infectious entities that make use of the replication machinery of their hosts to produce more progenies, causing disease and sometimes death. To counter viral infection, metazoan hosts are equipped with various defense mechanisms, from the rapid-evoking innate immune responses to the most advanced adaptive immune responses. Previous research demonstrated that cells in fruit flies and mice infected with Drosophila C virus and influenza, respectively, undergo apoptosis, which triggers the engulfment of apoptotic virus-infected cells by phagocytes. This process involves the recognition of eat-me signals on the surface of virus-infected cells by receptors of specialized phagocytes, such as macrophages and neutrophils in mice and hemocytes in fruit flies, to facilitate the phagocytic elimination of virus-infected cells. Inhibition of phagocytosis led to severe pathologies and death in both species, indicating that apoptosis-dependent phagocytosis of virus-infected cells is a conserved antiviral mechanism in multicellular organisms. Indeed, our understanding of the mechanisms underlying apoptosis-dependent phagocytosis of virus-infected cells has shed a new perspective on how hosts defend themselves against viral infection. This chapter explores the mechanisms of this process and its potential for developing new treatments for viral diseases.

Reduction of miR-133a-3p contributes to apoptosis and gasdermin E-mediated pyroptosis of keratinocytes in skin exposed to ultraviolet B radiation

Engagement of regulated cell death in keratinocytes plays a crucial role in the pathogenesis and development of skin disorders associated with UV radiation. However, it remains unclear how microRNAs (miRNAs) participate in the regulation of UV-caused keratinocyte death. In this study, we found that miR-133a-3p was decreased in the epidermis of UVB-challenged mice and UVB-irradiated keratinocyte cell line HaCaT cells. The intradermal injection of agomir miR-133a-3p ameliorated skin damage of UVB-challenged mice, especially epidermal necrosis. Meanwhile, the injection inhibited apoptosis indicator PARP cleavage and pyroptosis indicator GSDME cleavage in the epidermis. In UVB-challenged HaCaT cells, transfection of miR-133a-3p mimic or inhibitor alleviated or aggravated UVB-induced apoptosis and GSDME-mediated pyroptosis respectively. miR-133a-3p was also involved in the effects of metformin treatment on alleviating skin damage in UVB-challenged mice and on inhibiting apoptosis and GSDME-mediated pyroptosis in UVB-irradiated HaCaT cells. We confirmed that CYLD is a target gene of miR-133a-3p and participates in the protective effects of miR-133a-3p on inhibiting UVB-caused apoptosis and GSDME-mediated pyroptosis in keratinocytes. This study indicates a pivotal role for miR-133a-3p of keratinocytes in UVB-caused skin damage. Alleviating skin photodamage by restoring the decrease of miR-133a-3p can be considered a potential therapeutic approach.

Selenium-Modified Chitosan Induces HepG2 Cell Apoptosis and Differential Protein Analysis

INTRODUCTION

Chitosan is the product of the natural polysaccharide chitin removing part of the acetyl group, and exhibits various physiological and bioactive functions. Selenium modification has been proved to further enhance the chitosan bioactivities, and has been a hot topic recently.

METHODS

The present study aimed to investigate the potential inhibitory mechanism of selenium-modified chitosan (SMC) on HepG2 cells through MTT assays, morphological observation, annexin V-FITC/PI double staining, mitochondrial membrane potential determination, cell-cycle detection, Western blotting, and two-dimensional gel electrophoresis (2-DE).

RESULTS

The results indicated that SMC can induce HepG2 cell apoptosis with the cell cycle arrested in the S and G2/M phases and gradual disruption of mitochondrial membrane potential, reduce the expression of Bcl2, and improve the expression of Bax, cytochrome C, cleaved caspase 9, and cleaved caspase 3. Also, 2-DE results showed that tubulin α1 B chain, myosin regulatory light chain 12A, calmodulin, UPF0568 protein chromosome 14 open reading frame 166, and the cytochrome C oxidase subunit 5B of HepG2 cells were downregulated in HepG2 cells after SMC treatment.

DISCUSSION

These data suggested that HepG2 cells induced apoptosis after SMC treatment via blocking the cell cycle in the S and G2/M phases, which might be mediated through the mitochondrial apoptotic pathway. These results could be of benefit to future practical applications of SMC in the food and drug fields.

PANoptosis: A Unique Innate Immune Inflammatory Cell Death Modality

Innate immunity is the first response to protect against pathogens and cellular insults. Pattern recognition receptors sense pathogen- and damage-associated molecular patterns and induce an innate immune response characterized by inflammation and programmed cell death (PCD). In-depth characterization of innate immune PCD pathways has highlighted significant cross-talk. Recent advances led to the identification of a unique inflammatory PCD modality called PANoptosis, which is regulated by multifaceted PANoptosome complexes that are assembled by integrating components from other PCD pathways. The totality of biological effects observed in PANoptosis cannot be accounted for by any other PCD pathway alone. In this review, we briefly describe mechanisms of innate immune cell death, including molecular mechanisms of PANoptosis activation and regulation. We also highlight the PANoptosomes identified to date and provide an overview of the implications of PANoptosis in disease and therapeutic targeting. Improved understanding of innate immune-mediated cell death, PANoptosis, is critical to inform the next generation of treatment strategies.

The endosomal sorting complex required for transport repairs the membrane to delay cell death

The endosomal sorting complex required for transport (ESCRT) machinery plays a key role in the repair of damaged plasma membranes with puncta form and removes pores from the plasma membrane in regulated cell death, apoptosis, necroptosis, pyroptosis, ferroptosis, and autophagy. ESCRT-I overexpression and ESCRT-III-associated charged multivesicular body protein (CHMP) 4B participate in apoptosis, and the ESCRT-1 protein TSG 101 maintains low levels of ALIX and ALG-2 and prevents predisposition to apoptosis. The ESCRT-III components CHMP2A and CHMP4B are recruited to broken membrane bubble sites with the requirement of extracellular Ca2+, remove membrane vesicles from cells, and delay the time required for active MLKL to mediate necroptosis, thus preserving cell survival. CHMP4B disturbed pyroptosis by recruiting around the plasma membrane neck to remove the GSDMD pores and preserve plasma membrane integrity depending on Ca2+ influx. The accumulation of the ESCRT-III subunits CHMP5 and CHMP6 in the plasma membrane is increased by the classical ferroptosis activators erastin-1 and ras-selective lethal small molecule 3 (RSL3) upon cytosolic calcium influx and repairs the ferroptotic plasma membrane. ESCRT-III- and VPS4-induced macroautophagy, ESCRT-0-initiated microautophagy. ESCRT-I, ESCRT-II, ESCRT-III, ALIX, and VPS4A are recruited to damaged lysosomes and precede lysophagy, indicating that ESCRT is a potential target to overcome drug resistance during tumor therapy.

Sennoside A is a novel inhibitor targeting caspase-1

The assembly of inflammasomes drives caspase-1 activation, which further promotes proinflammatory cytokine secretion and downstream pyroptosis. The discovery of novel caspase-1 inhibitors is pivotal to developing new therapeutic means for inflammasome-involved diseases. In our present study, sennoside A (Sen A), a popular ingredient in multiple weight-loss medicines and dietary supplements, is found to potently inhibit the enzymatic activity of caspase-1 in vitro. Sen A considerably decreased IL-1β production in macrophages stimulated by LPS plus ATP, nigericin or MSU as well as poly(dA:dT) transfection, and remedied ROS-involved pyroptosis via caspase-1 inhibition. Mechanistically, Sen A not only suppressed the assembly of both NLRP3 and AIM2 inflammasome but also affected the priming process of NLRP3 inflammasome by blocking NF-κB signaling. Sen A significantly ameliorated the pathophysiological effect in LPS-, MSU- and carrageenan-challenged rodent models by suppressing inflammasome activation. Furthermore, P2X7 was indispensable for Sen A inhibiting NLRP3 inflammasome since it failed to further decrease IL-1β and IL-18 production in LPS plus ATP-stimulated BMDMs that were transfected with P2X7 siRNA. Sen A also restrained the large pore-forming functionalities of the P2X7R as verified by the YO-PRO-1 uptake assay. Taken together, Sen A inactivates caspase-1 to inhibit NLRP3 and AIM2 inflammasome-involved inflammation in a P2X7-dependent manner, making it an attractive candidate as a caspase-1 small-molecular inhibitor.

The conservation of IAP-like proteins in fungi, and their potential role in fungal programmed cell death

Programmed cell death (PCD) is a tightly regulated process which is required for survival and proper development of all cellular life. Despite this ubiquity, the precise molecular underpinnings of PCD have been primarily characterized in animals. Attempts to expand our understanding of this process in fungi have proven difficult as core regulators of animal PCD are apparently absent in fungal genomes, with the notable exception of a class of proteins referred to as inhibitors of apoptosis proteins (IAPs). These proteins are characterized by the conservation of a distinct Baculovirus IAP Repeat (BIR) domain and animal IAPs are known to regulate a number of processes, including cellular death, development, organogenesis, immune system maturation, host-pathogen interactions and more. IAP homologs are broadly conserved throughout the fungal kingdom, but our understanding of both their mechanism and role in fungal development/virulence is still unclear. In this review, we provide a broad and comparative overview of IAP function across taxa, with a particular focus on fungal processes regulated by IAPs. Furthermore, their putative modes of action in the absence of canonical interactors will be discussed.

Evaluation of the Cytotoxicity of Aqueous Extract and Oleo-Essential Oil of Dorema ammoniacum Plant Oleo-Gum Resin in Some Human Cancer Cell Lines

Results

Aqueous extract and essential oil reduced the viability of A549 cancer cells in a concentration-dependent manner. The lowest inhibitory concentrations (IC₅₀) for both samples of D. ammoniacum oleo-gum resin were 10 and 2.5 μg/ml for 24 hours in A549 cell line, respectively. After treatment with extract and essential oil of D. ammoniacum oleo-gum resin, ROS increased significantly compared to the control group. Although changes in caspase-3 did not show a significant increase in extract, the caspase-3 was found to be increased after exposure to essential oil and caspase-9 was downregulated after exposure to essential oil. Also, exposure to essential oil of D. ammoniacum caused a reduction in MMP level.

Conclusion

Based on results, the cytotoxic effect of essential oil of D. ammoniacum can induce apoptosis toward A549 cell line via induction of oxidative stress, MMP depletion, and caspase-3 activation, which is independent to mitochondrial cytochrome c release and caspase-9 function.

WNT/RYK signaling functions as an antiinflammatory modulator in the lung mesenchyme

WNT/β-catenin signaling is critical for lung development, and homeostasis and it has also been implicated in inflammatory lung diseases. However, the underlying molecular mechanisms, especially those at play during inflammatory conditions, are unclear. Here, we show that loss of the WNT coreceptor Related to receptor tyrosine kinase (RYK) specifically in mesenchymal cells results in lung inflammation. Our data indicate that RYK signaling through β-catenin and Nuclear Factor kappa B (NF-κB) is part of a safeguard mechanism against mesenchymal cell death, excessive inflammatory cytokine production, and inflammatory cell recruitment and accumulation.

A number of inflammatory lung diseases, including chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, and pneumonia, are modulated by WNT/β-catenin signaling. However, the underlying molecular mechanisms remain unclear. Here, starting with a forward genetic screen in mouse, we identify the WNT coreceptor Related to receptor tyrosine kinase (RYK) acting in mesenchymal tissues as a cell survival and antiinflammatory modulator. Ryk mutant mice exhibit lung hypoplasia and inflammation as well as alveolar simplification due to defective secondary septation, and deletion of Ryk specifically in mesenchymal cells also leads to these phenotypes. By analyzing the transcriptome of wild-type and mutant lungs, we observed the up-regulation of proapoptotic and inflammatory genes whose expression can be repressed by WNT/RYK signaling in vitro. Moreover, mesenchymal Ryk deletion at postnatal and adult stages can also lead to lung inflammation, thus indicating a continued role for WNT/RYK signaling in homeostasis. Our results indicate that RYK signaling through β-catenin and Nuclear Factor kappa B (NF-κB) is part of a safeguard mechanism against mesenchymal cell death, excessive inflammatory cytokine production, and inflammatory cell recruitment and accumulation. Notably, RYK expression is down-regulated in the stromal cells of pneumonitis patient lungs. Altogether, our data reveal that RYK signaling plays critical roles as an antiinflammatory modulator during lung development and homeostasis and provide an animal model to further investigate the etiology of, and therapeutic approaches to, inflammatory lung diseases.

Phosphatidylserine externalization by apoptotic cells is dispensable for specific recognition leading to innate apoptotic immune responses

Surface determinants newly expressed by apoptotic cells that are involved in triggering potent immunosuppressive responses, referred to as “innate apoptotic immunity (IAI)” have not been characterized fully. It is widely assumed, often implicitly, that phosphatidylserine, a phospholipid normally cloistered in the inner leaflet of cells and externalized specifically during apoptosis, is involved in triggering IAI, just as it plays an essential role in the phagocytic recognition of apoptotic cells. It is notable, however, that the triggering of IAI in responder cells is not dependent on the engulfment of apoptotic cells by those responders. Contact between the responder and the apoptotic target, on the other hand, is necessary to elicit IAI. Previously, we demonstrated that exposure of protease-sensitive determinants on the apoptotic cell surface are essential for initiating IAI responses; exposed glycolytic enzyme molecules were implicated in particular. Here, we report our analysis of the involvement of externalized phosphatidylserine in triggering IAI. To analyze the role of phosphatidylserine, we employed a panel of target cells that either externalized phosphatidylserine constitutively, independently of apoptosis, or did not, as well as their WT parental cells that externalized the phospholipid in an apoptosis-dependent manner. We found that the externalization of phosphatidylserine, which can be fully uncoupled from apoptosis, is neither sufficient nor necessary to trigger the profound immunomodulatory effects of IAI. These results reinforce the view that apoptotic immunomodulation and phagocytosis are dissociable and further underscore the significance of protein determinants localized to the cell surface during apoptosis in triggering innate apoptotic immunity.

The Antitumoral/Antimetastatic Action of the Flavonoid Brachydin A in Metastatic Prostate Tumor Spheroids In Vitro Is Mediated by (Parthanatos) PARP-Related Cell Death

Metastatic prostate cancer (mPCa) is resistant to several chemotherapeutic agents. Brachydin A (BrA), a glycosylated flavonoid extracted from Fridericia platyphylla, displays a remarkable antitumoral effect against in vitro mPCa cells cultured as bidimensional (2D) monolayers. Considering that three-dimensional (3D) cell cultures provide a more accurate response to chemotherapeutic agents, this study investigated the antiproliferative/antimetastatic effects of BrA and the molecular mechanisms underlying its action in mPCa spheroids (DU145) in vitro. BrA at 60–100 μM was cytotoxic, altered spheroid morphology/volume, and suppressed cell migration and tumor invasiveness. High-content analysis revealed that BrA (60–100 µM) reduced mitochondrial membrane potential and increased apoptosis and necrosis markers, indicating that it triggered cell death mechanisms. Molecular analysis showed that (i) 24-h treatment with BrA (80–100 µM) increased the protein levels of DNA disruption markers (cleaved-PARP and p-γ-H2AX) as well as decreased the protein levels of anti/pro-apoptotic (BCL-2, BAD, and RIP3K) and cell survival markers (p-AKT1 and p-44/42 MAPK); (ii) 72-h treatment with BrA increased the protein levels of effector caspases (CASP3, CASP7, and CASP8) and inflammation markers (NF-kB and TNF-α). Altogether, our results suggest that PARP-mediated cell death (parthanatos) is a potential mechanism of action. In conclusion, BrA confirms its potential as a candidate drug for preclinical studies against mPCa.

Baicalin induces apoptosis and autophagy in human osteosarcoma cells by increasing ROS to inhibit PI3K/Akt/mTOR, ERK1/2 and β-catenin signaling pathways

•

Baicalin causes apoptosis and autophagy through accumulating ROS to suppress PI3K/Akt/mTOR, ERK1/2 and β-catenin pathways in OS cells.

•

Baicalin-induced autophagosome further triggers apoptosis.

•

Baicalin-induced ROS and Ca²⁺ interactions induce apoptosis.

•

Baicalin molecule targets PI3Kγ, inhibiting downstream effectors AKT and mTOR.

Baicalin, a flavonoid derivative, exerts antitumor activity in a variety of neoplasms. However, whether baicalin exerts antitumor effects on osteosarcoma cells remains to be elucidated. In this study, treatment with baicalin reduced the proliferation and invasive potential of osteosarcoma cells and reduced the mitochondrial membrane potential, which eventually caused mitochondrial apoptosis. In addition, baicalin increased intercellular Ca²⁺ and ROS concentrations. Baicalin-induced apoptosis was confirmed by enhanced Bax, cleaved caspase-3, and cleaved PARP levels and decreased Bcl-2 levels. The increase in LC3-II and p62 suggested that baicalin induced autophagosome formation but ultimately inhibited downstream autophagy. Moreover, apoptosis induced by baicalin was attenuated by the addition of 3-MA. Furthermore, we found that baicalin inhibited the PI3K/Akt/mTOR, ERK1/2 and β-catenin signaling pathways. Chelation of free Ca²⁺ by BAPTA-AM also inhibited both apoptosis induction and ROS concentration changes. Finally, NAC pretreatment reversed baicalin treatment outcomes, including the increase in Ca²⁺ concentration, induction of apoptosis and autophagy, and inhibition of the pathways. Molecular docking results indicated that baicalin might interact with the structural domain of PI3Kγ. Thus, baicalin may be considered a potential candidate for osteosarcoma treatment.

Regulating life after death: how mechanical communication mediates the epithelial response to apoptosis

It is increasingly evident that cells in tissues and organs can communicate with one another using mechanical forces. Such mechanical signalling can serve as a basis for the assembly of cellular communities. For this to occur, there must be local instabilities in tissue mechanics that are the source of the signals, and mechanisms for changes in mechanical force to be transmitted and detected within tissues. In this review, we discuss these principles using the example of cell death by apoptosis, when it occurs in epithelia. This elicits the phenomenon of apical extrusion, which can rapidly eliminate apoptotic cells by expelling them from the epithelium. Apoptotic extrusion requires that epithelial cells detect the presence of nearby apoptotic cells, something which can be elicited by the mechanotransduction of tensile instabilities caused by the apoptotic cell. We discuss the central role that adherens junctions can play in the transmission and detection of mechanical signals from apoptotic cells.

Regulation of Developmental Cell Death in the Animal Kingdom: A Critical Analysis of Epigenetic versus Genetic Factors

The present paper proposes a new level of regulation of programmed cell death (PCD) in developing systems based on epigenetics. We argue against the traditional view of PCD as an altruistic “cell suicide” activated by specific gene-encoded signals with the function of favoring the development of their neighboring progenitors to properly form embryonic organs. In contrast, we propose that signals and local tissue interactions responsible for growth and differentiation of the embryonic tissues generate domains where cells retain an epigenetic profile sensitive to DNA damage that results in its subsequent elimination in a fashion reminiscent of what happens with scaffolding at the end of the construction of a building. Canonical death genes, including Bcl-2 family members, caspases, and lysosomal proteases, would reflect the downstream molecular machinery that executes the dying process rather than being master cell death regulatory signals.

Germ cell apoptosis is critical to maintain Caenorhabditis elegans offspring viability in stressful environments

Maintaining reproduction in highly variable, often stressful, environments is an essential challenge for all organisms. Even transient exposure to mild environmental stress may directly damage germ cells or simply tax the physiology of an individual, making it difficult to produce quality gametes. In Caenorhabditis elegans, a large fraction of germ cells acts as nurse cells, supporting developing oocytes before eventually undergoing so-called physiological germ cell apoptosis. Although C. elegans apoptosis has been extensively studied, little is known about how germline apoptosis is influenced by ecologically relevant environmental stress. Moreover, it remains unclear to what extent germline apoptosis contributes to maintaining oocyte quality, and thus offspring viability, in such conditions. Here we show that exposure to diverse environmental stressors, likely occurring in the natural C. elegans habitat (starvation, ethanol, acid, and mild oxidative stress), increases germline apoptosis, consistent with previous reports on stress-induced apoptosis. Using loss-of-function mutant alleles of ced-3 and ced-4, we demonstrate that eliminating the core apoptotic machinery strongly reduces embryonic survival when mothers are exposed to such environmental stressors during early adult life. In contrast, mutations in ced-9 and egl-1 that primarily block apoptosis in the soma but not in the germline, did not exhibit such reduced embryonic survival under environmental stress. Therefore, C. elegans germ cell apoptosis plays an essential role in maintaining offspring fitness in adverse environments. Finally, we show that ced-3 and ced-4 mutants exhibit concomitant decreases in embryo size and changes in embryo shape when mothers are exposed to environmental stress. These observations may indicate inadequate oocyte provisioning due to the absence of germ cell apoptosis. Taken together, our results show that the central genes of the apoptosis pathway play a key role in maintaining gamete quality, and thus offspring fitness, under ecologically relevant environmental conditions.

Research on Mechanism of Superparamagnetic Iron Oxide Nanoparticles in Activating Endoplasmic Reticulum and Prompting Apoptosis of Liver Cells Through Mediation of Tumor Necrosis Factor-α/Tumor Necrosis Factor Receptor 1 (TNF-α/TNFR1) Pathway

The aim of this study was to assess mechanism of superparamagnetic iron oxide nanoparticles (SPIO-NPs) in activating endoplasmic reticulum (ER) and prompting apoptosis of liver cells through mediating the TNF-α/TNFR1 pathway. The SPIO-NPs were prepared and identified, and HegG2 cells were cultivated in vitro, and their apoptosis was detected. The specific pathogen-free (SPF)-grade rats were divided into several groups; which included blank group, low concentration group, high concentration group and control group. The enzymatic activity of Caspase-3 in liver tissue was tested, and expressions of Caspase-3, Bax, Bcl-2, TNF-α, p-TNFR1, IRE1α, and eIF2α were tested. The size of prepared SPIO-NPs was 7.5 nm and there was no coagulation. There was good dispersity and electric potential, and appearance was stable. The apoptotic rate in the high concentration group was notably higher than in the other groups. There was notable inflammatory cell infiltration in the high concentration group, where quantity of apoptosis was highest. The quantity of apoptosis and fluorocyte in the high concentration group were notably higher than in the other groups. Moreover, there were over expressions of Caspase-3, Bax, Caspase-3, p-TNFR1, IRE1α, and eIF2α in the high concentration group while the expression of TNF-α was lowest. The apoptosis of HegG2 cells was prompted by SPIO-NPs, and quantity of apoptosis was increased with increased adopted concentration. The active expression of p-TNFR1, IRE1α, and eIF2α could be prompted to reduce the expression of TNF-α and increase the expression of Caspase-3 and Bax for prompting the apoptosis.

Piperlongumine, a Potent Anticancer Phytotherapeutic, Induces Cell Cycle Arrest and Apoptosis In Vitro and In Vivo through the ROS/Akt Pathway in Human Thyroid Cancer Cells

Simple Summary

There is no effective treatment currently available for patients with anaplastic, recurrent papillary, or follicular thyroid cancers. Reactive oxygen species (ROS) are believed to hold promise as a new therapeutic strategy for multiple human cancers. However, studies on ROS inducers for human thyroid cancer treatment are scarce. This study assesses the anticancer activity and the detailed downstream mechanisms of piperlongumine, a ROS inducer, in human thyroid cancer cells. We demonstrate that piperlongumine inhibits cell proliferation, regulates the cell cycle, and induces cellular apoptosis in various types of human thyroid cancer cells. The antihuman thyroid cancer activity of piperlongumine was through ROS induction, and it further suppressed the downstream Akt signaling pathway to elevate mitochondria-dependent apoptosis. A mouse xenograft study demonstrated that piperlongumine was safe and could inhibit tumorigenesis in vivo. The present study provides strong evidence that piperlongumine can be used as a therapeutic candidate for human thyroid cancers.

Abstract

Thyroid cancer (TC) is the most common endocrine malignancy, and its global incidence has steadily increased over the past 15 years. TC is broadly divided into well-differentiated, poorly differentiated, and undifferentiated types, depending on the histological and clinical parameters. Thus far, there are no effective treatments for undifferentiated thyroid cancers or advanced and recurrent cancer. Therefore, the development of an effective therapeutic is urgently needed for such patients. Piperlongumine (PL) is a naturally occurring small molecule derived from long pepper; it is selectively toxic to cancer cells by generating reactive oxygen species (ROS). In this study, we demonstrate the potential anticancer activity of PL in four TC cell lines. For this purpose, we cultured TC cell lines and analyzed the following parameters: Cell viability, colony formation, cell cycle, apoptosis, and cellular ROS induction. PL modulated the cell cycle, induced apoptosis, and suppressed tumorigenesis in TC cell lines in a dose- and time-dependent manner through ROS induction. Meanwhile, an intrinsic caspase-dependent apoptosis pathway was observed in the TC cells under PL treatment. The activation of Erk and the suppression of the Akt/mTOR pathways through ROS induction were seen in cells treated with PL. PL-mediated apoptosis in TC cells was through the ROS-Akt pathway. Finally, the anticancer effect and safety of PL were also demonstrated in vivo. Our findings indicate that PL exhibits antitumor activity and has the potential for use as a chemotherapeutic agent against TC. This is the first study to show the sensitivity of TC cell lines to PL.

Caspase-3: Structure, function, and biotechnological aspects

Caspase-3, a cysteine-aspartic acid protease, has recently attracted much attention because of its incredible roles in tissue differentiation, regeneration, and neural development. This enzyme is a key zymogen in cell apoptosis and is not activated until it is cleaved by initiator caspases during apoptotic flux. Since caspase-3 has represented valuable capabilities in the field of medical research, biotechnological aspects of this enzyme, including the production of recombinant type, protein engineering, and designing delivery systems, have been considered as emerging therapeutic strategies in treating the apoptosis-related disorders. To date, several advances have been made in the therapeutic use of caspase-3 in the management of some diseases such as cancers, heart failure, and neurodegenerative disorders. In the current review, we intend to discuss the caspase-3's structure, functions, therapeutic applications, as well as its molecular cloning, protein engineering, and relevant delivery systems.

Apoptosis - Fueling the oncogenic fire

Apoptosis, the most extensively studied form of programmed cell death, is essential for organismal homeostasis. Apoptotic cell death has widely been reported as a tumor suppressor mechanism. However, recent studies have shown that apoptosis exerts noncanonical functions and may paradoxically promote tumor growth and metastasis. The hijacking of apoptosis by cancer cells may arise at different levels, either via the interaction of apoptotic cells with their local or distant microenvironment, or through the abnormal pro-oncogenic roles of the main apoptosis effectors, namely caspases and mitochondria, particularly upon failed apoptosis. In this review, we highlight some of the recently described mechanisms by which apoptosis and these effectors may promote cancer aggressiveness. We believe that a better understanding of the noncanonical roles of apoptosis may be crucial for developing more efficient cancer therapies.