Morusin induces paraptosis-like cell death through mitochondrial calcium overload and dysfunction in epithelial ovarian cancer

Saikosaponin D potentiates the antineoplastic effects of doxorubicin in drug-resistant breast cancer through perturbing NQO1-mediated intracellular redox balance

BACKGROUND

Drug resistance to doxorubicin (DOX) significantly limits its therapeutic efficacy in breast cancer (BC) patients. Saikosaponin D (SSD), a triterpene saponin derived from the traditional herb Radix Bupleuri, has shown promise as a chemotherapeutic sensitizer in preclinical studies due to its notable antitumor activity. However, the role and mechanism of SSD in DOX-resistant BC cells remain largely unexplored.

PURPOSE

This study aimed to investigate the chemosensitizing effect of SSD on DOX-resistant BC and the underlying molecular mechanisms both in vitro and in vivo.

METHODS

In vitro assays, including cell viability, clone formation, three-dimensional tumor spheroid growth, and apoptosis analysis, were conducted to evaluate the synergistic effect of SSD and DOX on resistant BC cells. Reactive oxygen species (ROS), GSH/GSSG, NADPH/NADP+, and NADH/NAD+ detections were employed to assess the impact of SSD on cellular redox homeostasis. Western blotting, cell cycle distribution assay, and DOX uptake assay were performed to further elucidate the possible antineoplastic mechanism of SSD. Finally, a subcutaneous MCF7/DOX cell xenografted model in nude mice was established to identify the in vivo anticarcinogenic effect of SSD combined with DOX.

RESULTS

SSD significantly inhibited cell viability, proliferation, and clone formation, enhancing DOX's anticancer efficacy in vitro and in vivo. Mechanistically, SSD reduced STAT1, NQO1, and PGC-1α protein levels, leading to cellular redox imbalance, excessive ROS generation, and depletion of GSH, NADPH, and NADH. SSD induced DNA damage by disrupting redox homeostasis, resulting in G0/G1 phase cell cycle arrest. Additionally, SSD increased DOX accumulation in BC cells via inhibiting P-gp protein expression and efflux activity.

CONCLUSION

We demonstrated for the first time that SSD enhances the sensitivity of chemoresistant BC cells to DOX by disrupting cellular redox homeostasis through inactivation of the STAT1/NQO1/PGC-1α signaling pathway. This study provides evidence for SSD as an adjuvant agent in drug-resistant BC treatment.

Endoplasmic reticulum stress response pathway-mediated cell death in ovarian cancer

The endoplasmic reticulum (ER) is one of the largest organelles, and Endoplasmic Reticulum Stress Response Pathway is a series of responses triggered by the homeostatic imbalance of the ER and the state in which unfolded or misfolded proteins accumulate in the ER, which can trigger cell death. Cell death plays a crucial role in the development of diseases such as gynecological oncology. Herein, we review the current research on the response and ovarian cancer, discussing the key sensors (IRE1, PERK, ATF6), and the conditions under which it occurs (Ca2+ homeostasis disruption, hypoxia, others). Using the response as a starting point, provide a comprehensive overview of the relationship with the four types of cell death (apoptosis, autophagy, immunogenic cell death, paraptosis) in an attempt to provide new targeted therapeutic strategies for the organelle-Endoplasmic Reticulum Stress Response Pathway-cell death in ovarian cancer therapy.

Induction of Paraptotic Cell Death in Cancer Cells by Triptycene-Peptide Hybrids and the Revised Mechanism of Paraptosis II

In previous work, we reported on iridium(III) (Ir(III)) complex-peptide hybrids as amphiphilic conjugates (IPH-ACs) and triptycene-peptide hybrids as amphiphilic conjugates (TPH-ACs) and found that these hybrid compounds containing three cationic KK(K)GG peptide units through C6-C8 alkyl linkers induce paraptosis II, which is one of the nonapoptotic programmed cell death (PCD) types in Jurkat cells and different from previously reported paraptosis. The details of that study revealed that the paraptosis II induced by IPH-ACs (and TPH-ACs) proceeds via a membrane fusion or tethering of the endoplasmic reticulum (ER) and mitochondria, and Ca2+ transfer from the ER to mitochondria, which results in a loss of mitochondrial membrane potential (ΔΨm) in Jurkat cells. However, the detailed mechanistic studies of paraptosis II have been conducted only in Jurkat cells. In the present work, we decided to conduct mechanistic studies of paraptosis II in HeLa-S3 and A549 cells as well as in Jurkat cells to study the general mechanism of paraptosis II. Simultaneously, we designed and synthesized new TPH-ACs functionalized with peptides that contain cyclohexylalanine, which had been reported to enhance the localization of peptides to mitochondria. We found that TPH-ACs containing cyclohexylalanine promote paraptosis II processes in Jurkat, HeLa-S3 and A549 cells. The results of the experiments using fluorescence Ca2+ probes in mitochondria and cytosol, fluorescence staining agents of mitochondria and the ER, and inhibitors of paraptosis II suggest that TPH-ACs induce Ca2+ increase in mitochondria and the membrane fusion between the ER and mitochondria almost simultaneously, suggesting that our previous hypothesis on the mechanism of paraptosis II should be revised.

Mitochondrial mechanisms in the pathogenesis of chronic inflammatory musculoskeletal disorders

Chronic inflammatory musculoskeletal disorders characterized by prolonged muscle inflammation, resulting in enduring pain and diminished functionality, pose significant challenges for the patients. Emerging scientific evidence points to mitochondrial malfunction as a pivotal factor contributing to these ailments. Mitochondria play a critical role in powering skeletal muscle activity, but in the context of persistent inflammation, disruptions in their quantity, configuration, and performance have been well-documented. Various disturbances, encompassing alterations in mitochondrial dynamics (such as fission and fusion), calcium regulation, oxidative stress, biogenesis, and the process of mitophagy, are believed to play a central role in the progression of these disorders. Additionally, unfolded protein responses and the accumulation of fatty acids within muscle cells may adversely affect the internal milieu, impairing the equilibrium of mitochondrial functioning. The structural discrepancies between different mitochondrial subsets namely, intramyofibrillar and subsarcolemmal mitochondria likely impact their metabolic capabilities and susceptibility to inflammatory influences. The release of signals from damaged mitochondria is known to incite inflammatory responses. Intriguingly, migrasomes and extracellular vesicles serve as vehicles for intercellular transfer of mitochondria, aiding in the removal of impaired mitochondria and regulation of inflammation. Viral infections have been implicated in inducing stress on mitochondria. Prolonged dysfunction of these vital organelles sustains oxidative harm, metabolic irregularities, and heightened cytokine release, impeding the body's ability to repair tissues. This review provides a comprehensive analysis of advancements in understanding changes in the intracellular environment, mitochondrial architecture and distribution, biogenesis, dynamics, autophagy, oxidative stress, cytokines associated with mitochondria, vesicular structures, and associated membranes in the context of chronic inflammatory musculoskeletal disorders. Strategies targeting key elements regulating mitochondrial quality exhibit promise in the restoration of mitochondrial function, alleviation of inflammation, and enhancement of overall outcomes.

Morusin-Cu(II)-indocyanine green nanoassembly ignites mitochondrial dysfunction for chemo-photothermal tumor therapy

Nanoscale drug delivery systems derived from natural bioactive materials accelerate the innovation and evolution of cancer treatment modalities. Morusin (Mor) is a prenylated flavonoid compound with high cancer chemoprevention activity, however, the poor water solubility, low active pharmaceutical ingredient (API) loading content, and instability compromise its bioavailability and therapeutic effectiveness. Herein, a full-API carrier-free nanoparticle is developed based on the self-assembly of indocyanine green (ICG), copper ions (Cu2+) and Mor, termed as IMCNs, via coordination-driven and π-π stacking for synergistic tumor therapy. The IMCNs exhibits a desirable loading content of Mor (58.7 %) and pH/glutathione (GSH)-responsive motif. Moreover, the photothermal stability and photo-heat conversion efficiency (42.8 %) of IMCNs are improved after coordination with Cu2+ and help to achieve photothermal therapy. Afterward, the released Cu2+ depletes intracellular overexpressed GSH and mediates Fenton-like reactions, and further synergizes with ICG at high temperatures to expand oxidative damage. Furthermore, the released Mor elicits cytoplasmic vacuolation, expedites mitochondrial dysfunction, and exerts chemo-photothermal therapy after being combined with ICG to suppress the migration of residual live tumor cells. In vivo experiments demonstrate that IMCNs under laser irradiation could excellently inhibit tumor growth (89.6 %) through the multi-modal therapeutic performance of self-enhanced chemotherapy/coordinated-drugs/ photothermal therapy (PTT), presenting a great potential for cancer therapy.

Emerging role of immunogenic cell death in cancer immunotherapy

Cancer immunotherapy, such as immune checkpoint blockade (ICB), has emerged as a groundbreaking approach for effective cancer treatment. Despite its considerable potential, clinical studies have indicated that the current response rate to cancer immunotherapy is suboptimal, primarily attributed to low immunogenicity in certain types of malignant tumors. Immunogenic cell death (ICD) represents a form of regulated cell death (RCD) capable of enhancing tumor immunogenicity and activating tumor-specific innate and adaptive immune responses in immunocompetent hosts. Therefore, gaining a deeper understanding of ICD and its evolution is crucial for developing more effective cancer therapeutic strategies. This review focuses exclusively on both historical and recent discoveries related to ICD modes and their mechanistic insights, particularly within the context of cancer immunotherapy. Our recent findings are also highlighted, revealing a mode of ICD induction facilitated by atypical interferon (IFN)-stimulated genes (ISGs), including polo-like kinase 2 (PLK2), during hyperactive type I IFN signaling. The review concludes by discussing the therapeutic potential of ICD, with special attention to its relevance in both preclinical and clinical settings within the field of cancer immunotherapy.

New Ca2+ based anticancer nanomaterials trigger multiple cell death targeting Ca2+ homeostasis for cancer therapy

Calcium ion (Ca2+) is a necessary element for human and Ca2+ homeostasis plays important roles in various cellular process and functions. Recent reaches have targeted on inducing Ca2+ overload (both intracellular and transcellular) for tumor therapy. With the development of nanotechnology, nanoplatform-mediated Ca2+ overload has been safe theranostic model for cancer therapy, and defined a special calcium overload-induced tumor cell death as "calcicoptosis". However, the underlying mechanism of calcicoptosis in cancer cells remains further identification. In this review, we summarized multiple cell death types due to Ca2+ overload that induced by novel anticancer nanomaterials in tumor cells, including apoptosis, autophagy, pyroptosis, and ferroptosis. We reviewed the roles of these anticancer nanomaterials on Ca2+ homeostasis, including transcellular Ca2+ influx and efflux, and intracellular Ca2+ change in the cytosolic and organelles, and connection of Ca2+ overload with other metal ions. This review provides the knowledge of these nano-anticancer materials-triggered calcicoptosis accompanied with multiple cell death by regulating Ca2+ homeostasis, which could not only enhance their efficiency and specificity, but also enlighten to design new cancer therapeutic strategies and biomedical applications.

Cannabidiol activates MAPK pathway to induce apoptosis, paraptosis, and autophagy in colorectal cancer cells

Mitogen-activated protein kinase (MAPK) activation by natural compounds is known to be involved in the induction of apoptosis, paraptosis, and autophagy. Cannabidiol (CBD), a bioactive compound found in Cannabis sativa, is endowed with many pharmacological activities. We investigated the cytotoxic effect of CBD in a panel of colorectal cancer (CRC) cells (HT-29, SW480, HCT-116, and HCT-15). CBD induced significant cytotoxicity as evidenced by the results of MTT  assay, live-dead assay, and flow cytometric analysis. Since CBD displayed cytotoxicity against CRC cells, we examined the effect of CBD on apoptosis, paraptosis, and autophagy. CBD decreased the expression of antiapoptotic proteins and increased the Annexin-V-positive as well as TUNEL-positive cells suggesting that CBD induces apoptosis. CBD increased the expression of ATF4 (activating transcription factor 4) and CHOP (CCAAT/enhancer-binding protein homologous protein), elevated endoplasmic reticulum stress, and enhanced reactive oxygen species levels indicating that CBD also promotes paraptosis. CBD also induced the expression of Atg7, phospho-Beclin-1, and LC3 suggesting that CBD also accelerates autophagy. Since, the MAPK pathway is a common cascade that is involved in the regulation of apoptosis, paraptosis, and autophagy, we investigated the effect of CBD on the activation of JNK, p38, and ERK pathways. CBD activated all the forms of MAPK proteins and pharmacological inhibition of these proteins reverted the observed effects. Our findings implied that CBD could induce CRC cell death by activating apoptosis, paraptosis, and autophagy through the activation of the MAPK pathway.

Targeting paraptosis in cancer: opportunities and challenges

Cell death can be classified into two primary categories: accidental cell death and regulated cell death (RCD). Within RCD, there are distinct apoptotic and non-apoptotic cell death pathways. Among the various forms of non-apoptotic RCD, paraptosis stands out as a unique mechanism characterized by distinct morphological changes within cells. These alterations encompass cytoplasmic vacuolization, organelle swelling, notably in the endoplasmic reticulum and mitochondria, and the absence of typical apoptotic features, such as cell shrinkage and DNA fragmentation. Biochemically, paraptosis distinguishes itself by its independence from caspases, which are conventionally associated with apoptotic death. This intriguing cell death pathway can be initiated by various cellular stressors, including oxidative stress, protein misfolding, and specific chemical compounds. Dysregulated paraptosis plays a pivotal role in several critical cancer-related processes, such as autophagic degradation, drug resistance, and angiogenesis. This review provides a comprehensive overview of recent advancements in our understanding of the mechanisms and regulation of paraptosis. Additionally, it delves into the potential of paraptosis-related compounds for targeted cancer treatment, with the aim of enhancing treatment efficacy while minimizing harm to healthy cells.

Paraptosis: a non-classical paradigm of cell death for cancer therapy

Due to the sustained proliferative potential of cancer cells, inducing cell death is a potential strategy for cancer therapy. Paraptosis is a mode of cell death characterized by endoplasmic reticulum (ER) and/or mitochondrial swelling and cytoplasmic vacuolization, which is less investigated. Considerable evidence shows that paraptosis can be triggered by various chemical compounds, particularly in cancer cells, thus highlighting the potential application of this non-classical mode of cell death in cancer therapy. Despite these findings, there remain significant gaps in our understanding of the role of paraptosis in cancer. In this review, we summarize the current knowledge on chemical compound-induced paraptosis. The ER and mitochondria are the two major responding organelles in chemical compound-induced paraptosis, which can be triggered by the reduction of protein degradation, disruption of sulfhydryl homeostasis, overload of mitochondrial Ca2+, and increased generation of reactive oxygen species. We also discuss the stumbling blocks to the development of this field and the direction for further research. The rational use of paraptosis might help us develop a new paradigm for cancer therapy.

Gastrointestinal Cancer Therapeutics via Triggering Unfolded Protein Response and Endoplasmic Reticulum Stress by 2-Arylbenzofuran

Gastrointestinal cancers are a major global health challenge, with high mortality rates. This study investigated the anti-cancer activities of 30 monomers extracted from Morus alba L. (mulberry) against gastrointestinal cancers. Toxicological assessments revealed that most of the compounds, particularly immunotoxicity, exhibit some level of toxicity, but it is generally not life-threatening under normal conditions. Among these components, Sanggenol L, Sanggenon C, Kuwanon H, 3'-Geranyl-3-prenyl-5,7,2',4'-tetrahydroxyflavone, Morusinol, Mulberrin, Moracin P, Kuwanon E, and Kuwanon A demonstrate significant anti-cancer properties against various gastrointestinal cancers, including colon, pancreatic, and gastric cancers. The anti-cancer mechanism of these chemical components was explored in gastric cancer cells, revealing that they inhibit cell cycle and DNA replication-related gene expression, leading to the effective suppression of tumor cell growth. Additionally, they induced unfolded protein response (UPR) and endoplasmic reticulum (ER) stress, potentially resulting in DNA damage, autophagy, and cell death. Moracin P, an active monomer characterized as a 2-arylbenzofuran, was found to induce ER stress and promote apoptosis in gastric cancer cells, confirming its potential to inhibit tumor cell growth in vitro and in vivo. These findings highlight the therapeutic potential of Morus alba L. monomers in gastrointestinal cancers, especially focusing on Moracin P as a potent inducer of ER stress and apoptosis.

Recent advances in natural compounds inducing non-apoptotic cell death for anticancer drug resistance

The induction of cell death is recognized as a potent strategy for cancer treatment. Apoptosis is an extensively studied form of cell death, and multiple anticancer drugs exert their therapeutic effects by inducing it. Nonetheless, apoptosis evasion is a hallmark of cancer, rendering cancer cells resistant to chemotherapy drugs. Consequently, there is a growing interest in exploring novel non-apoptotic forms of cell death, such as ferroptosis, necroptosis, pyroptosis, and paraptosis. Natural compounds with anticancer properties have garnered significant attention due to their advantages, including a reduced risk of drug resistance. Over the past two decades, numerous natural compounds have been discovered to exert anticancer and anti-resistance effects by triggering these four non-apoptotic cell death mechanisms. This review primarily focuses on these four non-apoptotic cell death mechanisms and their recent advancements in overcoming drug resistance in cancer treatment. Meanwhile, it highlights the role of natural compounds in effectively addressing cancer drug resistance through the induction of these forms of non-apoptotic cell death.

Apoptotic and anti-Warburg effect of Morusin via ROS mediated inhibition of FOXM1/c-Myc signaling in prostate cancer cells

Though Morusin is known to induce apoptotic, antiprolifertaive, and autophagic effects through several signaling pathways, the underlying molecular mechanisms of Morusin still remain unclear until now. To elucidate antitumor mechanism of Morusin, cytotoxicity assay, cell cycle analysis, Western blotting, TUNEL assay, RNA interference, immunofluorescense, immunoprecipitation, reactive oxygen species (ROS) measurement, and inhibitor study were applied in this study. Morusin enhanced cytotoxicity, increased the number of TUNEL positive cells, sub-G1 population and induced the cleavages of PARP and caspase3, attenuated the expression of HK2, PKM2, LDH, c-Myc, and Forkhead Box M1 (FOXM1) along with the reduction of glucose, lactate, and ATP in DU145 and PC3 cells. Furthermore, Morusin disrupted the binding of c-Myc and FOXM1 in PC-3 cells, which was supported by String and cBioportal database. Notably, Morusin induced c-Myc degradation mediated by FBW7 and suppressed c-Myc stability in PC3 cells exposed to MG132 and cycloheximide. Also, Morusin generated ROS, while NAC disrupted the capacity of Morusin to reduce the expression of FOXM1, c-Myc, pro-PARP, and pro-caspase3 in PC-3 cells. Taken together, these findings provide scientific evidence that ROS mediated inhibition of FOXM1/c-Myc signaling axis plays a critical role in Morusin induced apoptotic and anti-Warburg effect in prostate cancer cells. Our findings support scientific evidence that ROS mediated inhibition of FOXM1/c-Myc signaling axis is critically involved in apoptotic and anti-Warburg effect of Morusin in prostate cancer cells.

Various concentrations of hesperetin induce different types of programmed cell death in human breast cancerous and normal cell lines in a ROS-dependent manner

The polyphenolic component of citrus fruits, hesperetin (Hst), is a metabolite of hesperidin. In this study, we examined the effect of varying doses and exposure times of hesperetin on MCF-7 and MDA-MB-231 cancer cells, as well as MCF-10A normal cells. By using MTT assay, real-time PCR, western blot, and flow cytometry, we determined the effects of Hst on cell viability, ROS levels, and markers of cell death. Furthermore, molecular docking was used to identify Hst targets that might be involved in ROS-dependent cell death. According to the results, different concentrations of Hst induced different modes of cell death at specific ROS levels. Paraptosis occurred in all cell lines at concentration ranges of IC35 to IC60, and apoptosis occurred at concentrations greater than IC65. In addition, MDA-MB-231 cells were subjected to senescence at sub-toxic doses when treated for a long period of time. When Hst levels were higher, N-acetylcysteine (NAC)'s effect on neutralizing ROS was more pronounced. According to the docking results, Hst may interact with several proteins involved in the regulation of ROS. As an example, the interaction of CCS (Copper chaperone for superoxide dismutase) with Hst might interfere with its chaperone function in folding SOD-1 (superoxide dismutase enzyme), contributing to an increase in cytoplasmic ROS levels. Finally, depending on the ROS level, Hst induces various modes of cell death.

Unveiling the therapeutic potential of natural-based anticancer compounds inducing non-canonical cell death mechanisms

In the Mid-19th century, Rudolf Virchow considered necrosis to be a prominent form of cell death; since then, pathologists have recognized necrosis as both a cause and a consequence of disease. About a century later, the mechanism of apoptosis, another form of cell death, was discovered, and we now know that this process is regulated by several molecular mechanisms that "programme" the cell to die. However, discoveries on cell death mechanisms are not limited to these, and recent studies have allowed the identification of novel cell death pathways that can be molecularly distinguished from necrotic and apoptotic cell death mechanisms. Moreover, the main goal of current cancer therapy is to discover and develop drugs that target apoptosis. However, resistance to chemotherapeutic agents targeting apoptosis is mainly responsible for the failure of clinical therapy and adverse side effects of the chemotherapeutic agents currently in use pose a major threat to the well-being and lives of patients. Therefore, the development of natural-based anticancer drugs with low cellular and organismal side effects is of great interest. In this comprehensive review, we thoroughly examine and discuss natural anticancer compounds that specifically target non-canonical cell death mechanisms.

Morusin shows potent antitumor activity for melanoma through apoptosis induction and proliferation inhibition

BACKGROUND

The discovery of new anti-melanoma drugs with low side effect is urgently required in the clinic. Recent studies showed that morusin, a flavonoid compound isolated from the root bark of Morus Alba, has the potential to treat multiple types of cancers, including breast cancer, gastric cancer, and prostate cancer. However, the anti-cancer effect of morusin on melanoma cells has not been investigated.

METHODS

We analyzed the effects of morusin on the proliferation, cell cycle, apoptosis, cell migration and invasion ability of melanoma cells A375 and MV3, and further explored the effects of morusin on tumor formation of melanoma cell. Finally, the effects of morusin on the proliferation, cycle, apoptosis, migration and invasion of A375 cells after knockdown of p53 were detected.

RESULTS

Morusin effectively inhibits the proliferation of melanoma cells and induces cell cycle arrest in the G2/M phase. Consistently, CyclinB1 and CDK1 that involved in the G2/M phase transition were down-regulated upon morusin treatment, which may be caused by the up-regulation of p53 and p21. In addition, morusin induces cell apoptosis and inhibits migration of melanoma cells, which correlated with the changes in the expression of the associated molecules including PARP, Caspase3, E-Cadherin and Vimentin. Moreover, morusin inhibits tumor growth in vivo with little side effect on the tumor-burden mice. Finally, p53 knockdown partially reversed morusin-mediated cell proliferation inhibition, cell cycle arrest, apoptosis, and metastasis.

CONCLUSION

Collectively, our study expanded the spectrum of the anti-cancer activity of morusin and guaranteed the clinical use of the drug for melanoma treatment.

V. J, Pal S, Nair BG, Kar R, Mishra N. Paraptosis: a unique cell death mode for targeting cancer

Programmed cell death (PCD) is the universal process that maintains cellular homeostasis and regulates all living systems' development, health and disease. Out of all, apoptosis is one of the major PCDs that was found to play a crucial role in many disease conditions, including cancer. The cancer cells acquire the ability to escape apoptotic cell death, thereby increasing their resistance towards current therapies. This issue has led to the need to search for alternate forms of programmed cell death mechanisms. Paraptosis is an alternative cell death pathway characterized by vacuolation and damage to the endoplasmic reticulum and mitochondria. Many natural compounds and metallic complexes have been reported to induce paraptosis in cancer cell lines. Since the morphological and biochemical features of paraptosis are much different from apoptosis and other alternate PCDs, it is crucial to understand the different modulators governing it. In this review, we have highlighted the factors that trigger paraptosis and the role of specific modulators in mediating this alternative cell death pathway. Recent findings include the role of paraptosis in inducing anti-tumour T-cell immunity and other immunogenic responses against cancer. A significant role played by paraptosis in cancer has also scaled its importance in knowing its mechanism. The study of paraptosis in xenograft mice, zebrafish model, 3D cultures, and novel paraptosis-based prognostic model for low-grade glioma patients have led to the broad aspect and its potential involvement in the field of cancer therapy. The co-occurrence of different modes of cell death with photodynamic therapy and other combinatorial treatments in the tumour microenvironment are also summarized here. Finally, the growth, challenges, and future perspectives of paraptosis research in cancer are discussed in this review. Understanding this unique PCD pathway would help to develop potential therapy and combat chemo-resistance in various cancer.

Different Ways to Die: Cell Death Pathways and Their Association With Spinal Cord Injury

Cell death is a systematic/nonsystematic process of cessation of normal morphology and functional properties of the cell to replace and recycle old cells with new also promoting inflammation in some cases. It is a complicated process comprising multiple pathways. Some are well-explored, and others have just begun to be. The research on appropriate control of cell death pathways after acute and chronic damage of neuronal cells is being widely researched today due to the lack of regeneration and recovering potential of a neuronal cell after sustaining damage and the inability to control the direction of neuronal growth. In the progression and onset of various neurological diseases, impairments in programmed cell death signaling processes, like necroptosis, apoptosis, ferroptosis, pyroptosis, and pathways directly or indirectly linked, like autophagy as in nonprogrammed necrosis, are observed. Spinal cord injury (SCI) involves the temporary or permanent disruption of motor activities due to the death of a neuronal and glial cell in the spinal cord accompanied by axonal degeneration. Recent years have seen a significant increase in research on the intricate biochemical interactions that occur after a SCI. Different cell death pathways may significantly impact the subsequent damage processes that lead to the eventual neurological deficiency after an injury to the spinal cord. A better knowledge of the molecular basis of the involved cell death pathways might help enhance neuronal and glial survival and neurological deficits, promoting a curative path for SCI.

Phytochemistry and pharmacology of natural prenylated flavonoids

Prenylated flavonoids are a special kind of flavonoid derivative possessing one or more prenyl groups in the parent nucleus of the flavonoid. The presence of the prenyl side chain enriched the structural diversity of flavonoids and increased their bioactivity and bioavailability. Prenylated flavonoids show a wide range of biological activities, such as anti-cancer, anti-inflammatory, neuroprotective, anti-diabetic, anti-obesity, cardioprotective effects, and anti-osteoclastogenic activities. In recent years, many compounds with significant activity have been discovered with the continuous excavation of the medicinal value of prenylated flavonoids, and have attracted the extensive attention of pharmacologists. This review summarizes recent progress on research into natural active prenylated flavonoids to promote new discoveries of their medicinal value.

A Mulberry Diels-Alder-Type Adduct, Kuwanon M, Triggers Apoptosis and Paraptosis of Lung Cancer Cells through Inducing Endoplasmic Reticulum Stress

The mulberry tree (Morus alba) has been cultivated in China for thousands of years. Mulberry Diels-Alder-type adducts (MDAAs) are characteristic constituents of the genus Morus. The unique structure and diverse bioactivities of MDAAs have attracted the attention of researchers. Kuwanon M (KWM) is an MDAA isolated from the root bark of Morus alba. This research reports the growth inhibitory effects of KWM on human lung cancer cells and its possible mechanism. In A549 and NCI-H292 cells, KWM treatment induced suppression of cell proliferation and migration. The appearance of chromatin condensation, phosphatidyl serine exposure and caspase cleavage indicated the arising of apoptosis. The loss of mitochondrial membrane potential (MMP), release of cytochrome c and dysregulation of Bax/Bcl-2 demonstrated that the KWM-induced apoptosis was through the mitochondrial pathway. Paraptosis was simultaneously detected under KWM treatment, as evidenced by the exhibition of cytoplasmic vacuolation, down-regulation of Alix and up-regulation of endoplasmic reticulum (ER) stress-related proteins. Mechanistically, ER stress induced activation of unfolded protein response (UPR) pathways and activation of the MAPK (JNK and ERK) pathway, all of which were critical for KWM-induced apoptosis and paraptosis. These findings suggested the possibility that KWM might be considered as a potential lung cancer therapeutic agent.

Potential of natural flavonols and flavanones in the treatment of ulcerative colitis

Ulcerative colitis (UC) is an inflammatory bowel disease generally characterized by chronic, persistent, recurrent, and non-specific ulcers of the intestine. Its main clinical manifestations include abdominal pain, diarrhea, and bloody stools. This disease is difficult to cure and even carries the risk of canceration. It has been listed as a modern refractory disease by the World Health Organization. Though a large amount of drugs are available for the inhibition of UC, the conventional treatment such as aminosalicylic acids, glucocorticoids, immunosuppressors, and biological agents possess certain limitations and serious side effects. Therefore, it is urgently needed for safe and effective drugs of UC, and natural-derived flavonols and flavanones showed tremendous potential. The present study concentrated on the progress of natural-derived flavonols and flavanones from edible and pharmaceutical plants for the remedy of UC over the last two decades. The potential pharmaceutical of natural-derived flavonols and flavanones against UC were closely connected with the modulation of gut microflora, gut barrier function, inflammatory reactions, oxidative stress, and apoptosis. The excellent efficacy and safety of natural flavonols and flavanones make them prospective drug candidates for UC suppression.

The role of nanomaterials in enhancing natural product translational potential and modulating endoplasmic reticulum stress in the treatment of ovarian cancer

Ovarian cancer, and particularly its most frequent type, epithelial ovarian carcinoma, constitutes one of the most dangerous malignant tumors among females. Substantial evidence has described the potential of phytochemicals against ovarian cancer. The effect of natural compounds on endoplasmic reticulum (ER) stress is of great relevance in this regard. In ovarian cancer, the accumulation of misfolded proteins in the ER lumen results in decompensated ER stress. This leads to deregulation in the physiological processes for the posttranslational modification of proteins, jeopardizes cellular homeostasis, and increases apoptotic signaling. Several metabolites and metabolite extracts of phytochemical origin have been studied in the context of ER stress in ovarian cancer. Resveratrol, quercetin, curcumin, fucosterol, cleistopholine, fucoidan, and epicatechin gallate, among others, have shown inhibitory potential against ER stress. The chemical structure of each compound plays an important role concerning its pharmacodynamics, pharmacokinetics, and overall effectiveness. Studying and cross-comparing the chemical features that render different phytochemicals effective in eliciting particular anti-ER stress actions can help improve drug design or develop multipotent combination regimens. Many studies have also investigated the properties of formulations such as nanoparticles, niosomes, liposomes, and intravenous hydrogel based on curcumin and quercetin along with some other phytomolecules in ovarian cancer. Overall, the potential of phytochemicals in targeting genetic mechanisms of ovarian cancer warrants further translational and clinical investigation.

Epimedokoreanin B inhibits the growth of lung cancer cells through endoplasmic reticulum stress-mediated paraptosis accompanied by autophagosome accumulation

Epimedokoreanin B (EKB) is a prenylated flavonoid isolated from Epimedium koreanum. In this article, we described the anti-cancerous effects of EKB and its underlying mechanism in human non-small cell lung cancer (NSCLC) A549 and NCI-H292 cells. EKB treatment inhibited cell proliferation and migration accompanied by cytoplasmic vacuolation in both cell lines. The cell death induced by EKB lacked the features of apoptosis like chromatin condensation, phosphatidyl serine exposure and caspase cleavage. The vacuoles stimulated by EKB predominantly derived from endoplasmic reticulum (ER) and mitochondria dilation, which are the characteristics of paraptosis. Down-regulation of Alix and up-regulation of ER stress-related proteins after EKB treatment further supported the occurrence of paraptosis. ER stress inhibitor 4-phenylbutyric acid (4-PBA) and protein synthesis inhibitor cycloheximide (CHX) treatment antagonized the vacuoles formation as well as cell death induced by EKB, indicating that ER stress was involved in EKB induced paraptosis. In addition, autophagosome accumulation accompanied with autophagy flux blocking was observed in EKB treated cells, this was consistent with the occurrence of ER stress. Collectively, EKB was demonstrated as a paraptosis-like cell death inducer in A549 and NCI-H292 cells. The inhibitory effect of EKB on lung cancer cell proliferation was further demonstrated in a zebrafish xenograft model. These findings raise the possibility that paraptosis inducers may be considered as alternative choices for lung cancer therapy.

Post-complexation Functionalization of Cyclometalated Iridium(III) Complexes and Applications to Biomedical and Material Sciences

Cyclometalated iridium(III) (Ir(III)) complexes exhibit excellent photophysical properties that include large Stokes shift, high emission quantum yields, and microsecond-order emission lifetimes, due to low-lying metal-to-ligand charge transfer (spin-forbidden singlet-triplet (³MLCT) transition). As a result, analogs have been applied for research not only in the material sciences, such as the development of organic light-emitting diodes (OLEDs), but also for photocatalysts, bioimaging probes, and anticancer reagents. Although a variety of methods for the synthesis and the applications of functionalized cyclometalated iridium complexes have been reported, functional groups are generally introduced to the ligands prior to the complexation with Ir salts. Therefore, it is difficult to introduce thermally unstable functional groups such as peptides and sugars due to the harsh reaction conditions such as the high temperatures used in the complexation with Ir salts. In this review, the functionalization of Ir complexes after the formation of cyclometalated Ir complexes and their biological and material applications are described. These methods are referred to as "post-complexation functionalization (PCF)." In this review, applications of PCF to the design and synthesis of Ir(III) complexes that exhibit blue -red and white color emissions, luminescence pH probes, luminescent probes of cancer cells, compounds that induce cell death in cancer cells, and luminescent complexes that have long emission lifetimes are summarized.

Recent advances in the synthesis of natural products containing the phloroglucinol motif

Covering: June 2009 to 2021Natural products containing a phloroglucinol motif include simple and oligomeric phloroglucinols, polycyclic polyprenylated acylphloroglucinols, phloroglucinol-terpenes, xanthones, flavonoids, and coumarins. These compounds represent a major class of secondary metabolites which exhibit a wide range of biological activities such as antimicrobial, anti-inflammatory, antioxidant and hypoglycaemic properties. A number of these compounds have been authorized for therapeutic use or are currently being studied in clinical trials. Their structural diversity and utility in both traditional and conventional medicine have made them popular synthetic targets over the years. In this review, we compile and summarise the recent synthetic approaches to the natural products bearing a phloroglucinol motif. Focus has been given on ingenious strategies to functionalize the phloroglucinol moiety at multiple positions. The isolation and bioactivities of the compounds are also provided.

Engineering Chemotherapeutic-Augmented Calcium Phosphate Nanoparticles for Treatment of Intraperitoneal Disseminated Ovarian Cancer

Ovarian cancer is a common gynecologic malignancy with a high fatality rate. Intraperitoneal chemotherapy has been proved as an efficient clinical treatment for disseminated ovarian cancer. However, there are limitations for conventional small molecule drugs to achieve an ideal therapeutic effect. Herein, a synergistic treatment for intraperitoneally disseminated ovarian cancer was achieved by Arg-Gly-Asp (RGD)-modified amorphous calcium phosphate loading with doxorubicin (designated as RGD-CaPO/DOX). The engineered calcium-involved nanomedicine augmented the therapeutic effect of DOX by aggravating endoplasmic reticulum stress, calcium overload, and mitochondrial dysfunction, ultimately triggering mitochondrial apoptosis in the SKOV3 (human ovarian cancer) cell line. In an intraperitoneally disseminated tumor model, RGD modification and the weak negative surface potential of the NPs were beneficial for intraperitoneal retention and tumor targeting. Moreover, intraperitoneal injection of RGD-CaPO/DOX NPs resulted in a favorable antitumor effect. The mean survival time of SKOV3-bearing mice was significantly extended from 29 to 59 days with negligible toxicity. Therefore, this study has been designed to provide an effective chemotherapeutic-augmented treatment for intraperitoneally disseminated ovarian cancer.

Design, Synthesis, and Anticancer Activity of Triptycene-Peptide Hybrids that Induce Paraptotic Cell Death in Cancer Cells

We report on the design and synthesis of triptycene-peptide hybrids (TPHs), 5, syn-6, and anti-6, which are conjugates of a triptycene core unit with two or three cationic KKKGG peptides (K: lysine and G: glycine) through a C₈ alkyl chain. It was discovered that syn-6 and anti-6 induce paraptosis, a type of programmed cell death (PCD), in Jurkat cells (leukemia T-lymphocytes). Mechanistic studies indicate that these TPHs induce the transfer of Ca²⁺ from the endoplasmic reticulum (ER) to mitochondria, a loss of mitochondrial membrane potential (ΔΨ_m), tethering of the ER and mitochondria, and cytoplasmic vacuolization in the paraptosis processes.

Induction of Paraptosis by Cyclometalated Iridium Complex-Peptide Hybrids and CGP37157 via a Mitochondrial Ca2+ Overload Triggered by Membrane Fusion between Mitochondria and the Endoplasmic Reticulum

We previously reported that a cyclometalated iridium (Ir) complex-peptide hybrid (IPH) 4 functionalized with a cationic KKKGG peptide unit on the 2-phenylpyridine ligand induces paraptosis, a relatively newly found programmed cell death, in cancer cells (Jurkat cells) via the direct transport of calcium (Ca²⁺) from the endoplasmic reticulum (ER) to mitochondria. Here, we describe that CGP37157, an inhibitor of a mitochondrial sodium (Na⁺)/Ca²⁺ exchanger, induces paraptosis in Jurkat cells via intracellular pathways similar to those induced by 4. The findings allow us to suggest that the induction of paraptosis by 4 and CGP37157 is associated with membrane fusion between mitochondria and the ER, subsequent Ca²⁺ influx from the ER to mitochondria, and a decrease in the mitochondrial membrane potential (ΔΨ_m). On the contrary, celastrol, a naturally occurring triterpenoid that had been reported as a paraptosis inducer in cancer cells, negligibly induces mitochondria-ER membrane fusion. Consequently, we conclude that the paraptosis induced by 4 and CGP37157 (termed paraptosis II herein) proceeds via a signaling pathway different from that of the previously known paraptosis induced by celastrol, a process that negligibly involves membrane fusion between mitochondria and the ER (termed paraptosis I herein).

Cinnamaldehyde induces autophagy-mediated cell death through ER stress and epigenetic modification in gastric cancer cells

Previous reports suggested that cinnamaldehyde (CA), the bioactive ingredient in Cinnamomum cassia, can suppress tumor growth, migratory, and invasive abilities. However, the role and molecular mechanisms of CA in GC are not completely understood. In the present study, we found that CA-induced ER stress and cell death via the PERK-CHOP axis and Ca²⁺ release in GC cells. Inhibition of ER stress using specific-siRNA blocked CA-induced cell death. Interestingly, CA treatment resulted in autophagic cell death by inducing Beclin-1, ATG5, and LC3B expression and by inhibiting p62 expression whereas autophagy inhibition suppressed CA-induced cell death. We showed that CA induces the inhibition of G9a and the activation of LC3B. Moreover, CA inhibited G9a binding on Beclin-1 and LC3B promoter. Overall, these results suggested that CA regulates the PERK-CHOP signaling, and G9a inhibition activates autophagic cell death via ER stress in GC cells.

Redox Activity of Flavonoids: Impact on Human Health, Therapeutics, and Chemical Safety

The cost-effectiveness of presently used therapies is a problem in overall redox-based management, which is posing a significant financial burden on communities across the world. As a result, sophisticated treatment models that provide notions of predictive diagnoses followed by targeted preventive therapies adapted to individual patient profiles are gaining global acclaim as being beneficial to patients, the healthcare sector, and society as a whole. In this context, natural flavonoids were considered due to their multifaceted antioxidant, anti-inflammatory, and anticancer effects as well as their low toxicity and ease of availability. The aim of this review is to focus on the capacity of flavonoids to modulate the responsiveness of various diseases and ailments associated with redox toxicity. The review will also focus on the flavonoids' pathway-based redox activity and the advancement of redox-based therapies as well as flavonoids' antioxidant characteristics and their influence on human health, therapeutics, and chemical safety. Research findings indicated that flavonoids significantly exhibit various redox-based therapeutic responses against several diseases such as inflammatory, neurodegenerative, cardiovascular, and hepatic diseases and various types of cancer by activating the Nrf2/Keap1 transcription system, suppressing the nuclear factor κB (NF-κB)/IκB kinase inflammatory pathway, abrogating the function of the Hsp90/Hsf1 complex, inhibiting the PTEN/PI3K/Akt pathway, and preventing mitochondrial dysfunction. Some flavonoids, especially genistein, apigenin, amentoflavone, baicalein, quercetin, licochalcone A, and biochanin A, play a potential role in redox regulation. Conclusions of this review on the antioxidant aspects of flavonoids highlight the medicinal and folk values of these compounds against oxidative stress and various diseases and ailments. In short, treatment with flavonoids could be a novel therapeutic invention in clinical trials, as we hope.

Extract of Ganoderma sinensis spores induces cell cycle arrest of hepatoma cell via endoplasmic reticulum stress

CONTEXT

Ganoderma sinensis Zhao, Xu et Zhang (Ganodermataceae) has been used for the prevention or treatment of a variety of diseases, including cancer.

OBJECTIVE

We investigated the antitumor activity and mechanism of an extract from G. sinensis against hepatocellular carcinoma.

MATERIALS AND METHODS

A G. sinensis extract (GSE) was obtained from sporoderm-broken G. sinensis spores by supercritical fluid carbon dioxide extraction. Hepatoma cells, HepG2 cells, were treated with emulsified sample of GSE at 12.5, 25, 50, 100 and 150 μg/mL for 24 h. The Alamar Blue assay was used to examine growth inhibitory effects. Changes in cell structure and morphology were assessed via transmission electron microscopy and confocal laser scanning microscope. Cell cycle distribution was analysed by flow cytometry.

RESULTS

GSE suppressed the proliferation of HepG2 cells (IC₅₀=70.14 μg/mL). Extensive cytoplasmic vacuolation originating from dilation of the endoplasmic reticulum (ER) was shown in GSE-treated HepG2 cells. GSE treatment also upregulated the expression of ER stress-related proteins in HepG2 cells. Cells tended to be arrested at the G2/M cell cycle stage after GSE treatment (30.8 ± 1.4% and 42.2 ± 2.6% at GSE with 50 μg/mL and 100 μg/mL vs. 21.03 ± 1.10%, control). Pre-treatment with salubrinal, an inhibitor of ER stress, effectively attenuated cell cycle arrest induced by GSE.

DISCUSSION AND CONCLUSIONS

Our findings provide new evidence that GSE suppresses growth of cancer cells in vitro through activating the ER stress pathway. The GSE may be clinically applied in the prevention and/or treatment of cancer.

Cyclometalated Iridium(III) Complex-Cationic Peptide Hybrids Trigger Paraptosis in Cancer Cells via an Intracellular Ca2+ Overload from the Endoplasmic Reticulum and a Decrease in Mitochondrial Membrane Potential

In our previous paper, we reported that amphiphilic Ir complex–peptide hybrids (IPHs) containing basic peptides such as KK(K)GG (K: lysine, G: glycine) (e.g., ASb-2) exhibited potent anticancer activity against Jurkat cells, with the dead cells showing a strong green emission. Our initial mechanistic studies of this cell death suggest that IPHs would bind to the calcium (Ca²⁺)–calmodulin (CaM) complex and induce an overload of intracellular Ca²⁺, resulting in the induction of non-apoptotic programmed cell death. In this work, we conduct a detailed mechanistic study of cell death induced by ASb-2, a typical example of IPHs, and describe how ASb-2 induces paraptotic programmed cell death in a manner similar to that of celastrol, a naturally occurring triterpenoid that is known to function as a paraptosis inducer in cancer cells. It is suggested that ASb-2 (50 µM) induces ER stress and decreases the mitochondrial membrane potential (ΔΨ_m), thus triggering intracellular signaling pathways and resulting in cytoplasmic vacuolization in Jurkat cells (which is a typical phenomenon of paraptosis), while the change in ΔΨ_m values is negligibly induced by celastrol and curcumin. Other experimental data imply that both ASb-2 and celastrol induce paraptotic cell death in Jurkat cells, but this induction occurs via different signaling pathways.

Neochlorogenic acid anchors MCU-based calcium overload for cancer therapy

Cancer is a major threat to human health worldwide, yet the clinical therapies remain unsatisfactory. In this study, we found that a Tetrastigma hemsleyanum leaves flavone (TLF) intervention could achieve tumor inhibition. Besides, neochlorogenic acid (NA), which had the highest absorbance peak in the HPLC profile of TLF, showed superior anti-proliferation ability over TLF, and could effectively trigger apoptosis, restrain migration, and facilitate cytoskeleton collapse, suggesting its key role in TLF's anticancer property. Molecular docking analysis suggested that NA was capable of binding with mitochondrial Ca²⁺ uniporter (MCU), and further experiments confirmed that NA upregulated the MCU level to permit excess calcium ion influx, leading to mitochondrial calcium imbalance, dysfunction, structure alteration, and ROS elevation. Moreover, tumor-bearing mice were applied to further confirm the excellent tumor inhibition ability of NA under Ca²⁺-abundant conditions. Therefore, this study uncovered that NA could effectively trigger robust MCU-mediated calcium overload cancer therapy, which could be utilized in novel strategies for future cancer treatment.

Insights into the Role of Oxidative Stress in Ovarian Cancer

Oxidative stress (OS) arises when the body is subjected to harmful endogenous or exogenous factors that overwhelm the antioxidant system. There is increasing evidence that OS is involved in a number of diseases, including ovarian cancer (OC). OC is the most lethal gynecological malignancy, and risk factors include genetic factors, age, infertility, nulliparity, microbial infections, obesity, smoking, etc. OS can promote the proliferation, metastasis, and therapy resistance of OC, while high levels of OS have cytotoxic effects and induce apoptosis in OC cells. This review focuses on the relationship between OS and the development of OC from four aspects: genetic alterations, signaling pathways, transcription factors, and the tumor microenvironment. Furthermore, strategies to target aberrant OS in OC are summarized and discussed, with a view to providing new ideas for clinical treatment.

The Pro-Health Benefits of Morusin Administration-An Update Review

Prenylflavonoids are widespread in nature. Plants are valuable sources of natural polyphenolic compounds with isoprenyl groups, which include flavones, flavanones, chalcones and aurones. They can be found in flowers, bark and stems. One of the most important compounds found in the bark of white mulberry (Morus alba) is morusin, a prenylated flavone with interesting pro-health properties. The research carried out so far revealed that morusin has antioxidant, antitumor, anti-inflammatory and anti-allergic activity. Moreover, its neuroprotective and antihyperglycemic properties have also been confirmed. Morusin suppresses the growth of different types of tumors, including breast cancer, glioblastoma, pancreatic cancer, hepatocarcinoma, prostate cancer, and gastric cancer. It also inhibits the inflammatory response by suppressing COX activity and iNOS expression. Moreover, an antimicrobial effect against Gram-positive bacteria was observed after treatment with morusin. The objective of this review is to summarize the current knowledge about the positive effects of morusin on human health in order to facilitate future study on the development of plant polyphenolic drugs and nutraceutics in the group of prenylflavones.

Metal-coordinated nanomedicine for combined tumor therapy by inducing paraptosis and apoptosis

Apoptosis resistance of tumor cells often results in chemoresistance and treatment failure in clinic. In this work, a Cu²⁺-coordinated morusin/doxorubicin biological organizer (designated as COMBO) is designed to combat cellular resistance to apoptosis for combined tumor therapy. By virtue of the coordination and π-π stacking effects, the self-assembled COMBO possesses nanometer particle size, narrow and homogenous graininess distribution as well as a good dispersion stability. Moreover, COMBO could be disassembled by glutathione (GSH) with an effective drug release and fluorescence recovery. Morusin-mediated paraptosis could induce extensive vacuolization through the dilation of endoplasmic reticulum (ER) and mitochondria, leading to non-apoptotic programmed cell death (PCD) regardless of the cellular resistance to apoptosis. Furthermore, the released doxorubicin prefers to locate in cell nucleus to cause cell apoptosis for combined chemotherapy. By the joint action of paraptosis and apoptosis, COMBO exhibits a great superiority over monotherapy in tumor inhibition with a low system toxicity. This study may open a window in the development of self-delivery nanomedicine for overcoming apoptosis resistance in tumor therapy.

Celastrol acts synergistically with afatinib to suppress non-small cell lung cancer cell proliferation by inducing paraptosis

Non-small cell lung cancer (NSCLC) with wild-type epidermal growth factor receptor (EGFR) is intrinsic resistance to EGFR-tyrosine kinase inhibitors (TKIs), such as afatinib. Celastrol, a natural compound with antitumor activity, was reported to induce paraptosis in cancer cells. In this study, intrinsic EGFR-TKI-resistant NSCLC cell lines H23 (EGFR wild-type and KRAS mutation) and H292 (EGFR wild-type and overexpression) were used to test whether celastrol could overcome primary afatinib resistance through paraptosis induction. The synergistic effect of celastrol and afatinib on survival inhibition of the NSCLC cells was evaluated by CCK-8 assay and isobologram analysis. The paraptosis and its modulation were assessed by light and electron microscopy, Western blot analysis, and immunofluorescence. Xenografts models were established to investigate the inhibitory effect of celastrol plus afatinib on the growth of the NSCLC tumors in vivo. Results showed that celastrol acted synergistically with afatinib to suppress the survival of H23 and H292 cells by inducing paraptosis characterized by extensive cytoplasmic vacuolation. This process was independent of apoptosis and not associated with autophagy induction. Afatinib plus celastrol-induced cytoplasmic vacuolation was preceded by endoplasmic reticulum stress and unfolded protein response. Accumulation of intracellular reactive oxygen species and mitochondrial Ca2+ overload may be initiating factors of celastrol/afatinib-induced paraptosis and subsequent cell death. Furthermore, Celastrol and afatinib synergistically suppressed the growth of H23 cell xenograft tumors in vivo. The data indicate that a combination of afatinib and celastrol may be a promising therapeutic strategy to surmount intrinsic afatinib resistance in NSCLC cells.

A Review of the Role of Endo/Sarcoplasmic Reticulum-Mitochondria Ca2+ Transport in Diseases and Skeletal Muscle Function

The physical contact site between a mitochondrion and endoplasmic reticulum (ER), named the mitochondria-associated membrane (MAM), has emerged as a fundamental platform for regulating the functions of the two organelles and several cellular processes. This includes Ca²⁺ transport from the ER to mitochondria, mitochondrial dynamics, autophagy, apoptosis signalling, ER stress signalling, redox reaction, and membrane structure maintenance. Consequently, the MAM is suggested to be involved in, and as a possible therapeutic target for, some common diseases and impairment in skeletal muscle function, such as insulin resistance and diabetes, obesity, neurodegenerative diseases, Duchenne muscular dystrophy, age-related muscle atrophy, and exercise-induced muscle damage. In the past decade, evidence suggests that alterations in Ca²⁺ transport from the ER to mitochondria, mediated by the macromolecular complex formed by IP₃R, Grp75, and VDAC1, may be a universal mechanism for how ER-mitochondria cross-talk is involved in different physiological/pathological conditions mentioned above. A better understanding of the ER (or sarcoplasmic reticulum in muscle)-mitochondria Ca²⁺ transport system may provide a new perspective for exploring the mechanism of how the MAM is involved in the pathology of diseases and skeletal muscle dysfunction. This review provides a summary of recent research findings in this area.

Ca2+ overload- and ROS-associated mitochondrial dysfunction contributes to δ-tocotrienol-mediated paraptosis in melanoma cells

Melanoma is an aggressive tumor with still poor therapy outcomes. δ-tocotrienol (δ-TT) is a vitamin E derivative displaying potent anti-cancer properties. Previously, we demonstrated that δ-TT triggers apoptosis in human melanoma cells. Here, we investigated whether it might also activate paraptosis, a non-canonical programmed cell death. In accordance with the main paraptotic features, δ-TT was shown to promote cytoplasmic vacuolization, associated with endoplasmic reticulum/mitochondrial dilation and protein synthesis, as well as MAPK activation in A375 and BLM cell lines. Moreover, treated cells exhibited a significant reduced expression of OXPHOS complex I and a marked decrease in oxygen consumption and mitochondrial membrane potential, culminating in decreased ATP synthesis and AMPK phosphorylation. This mitochondrial dysfunction resulted in ROS overproduction, found to be responsible for paraptosis induction. Additionally, δ-TT caused Ca²⁺ homeostasis disruption, with endoplasmic reticulum-derived ions accumulating in mitochondria and activating the paraptotic signaling. Interestingly, by using both IP3R and VDAC inhibitors, a close cause-effect relationship between mitochondrial Ca²⁺ overload and ROS generation was evidenced. Collectively, these results provide novel insights into δ-TT anti-melanoma activity, highlighting its ability to induce mitochondrial dysfunction-mediated paraptosis. δ-tocotrienol induces paraptotic cell death in human melanoma cells, causing endoplasmic reticulum dilation and mitochondrial swelling. These alterations induce an impairment of mitochondrial function, ROS production and calcium overload.

Honokiol induces paraptosis-like cell death of acute promyelocytic leukemia via mTOR & MAPK signaling pathways activation

Acute promyelocytic leukemia (APL) is a blood system disease caused by the accumulation of a large number of immature blood cells in bone marrow. Although the introduction of all-trans retinoic acid (ATRA) and arsenic has reached a high level of complete remission rate and 5-year disease-free survival rate, the occurrence of various adverse reactions still severely affects the quality of life of patients. As a natural product, honokiol (HNK) has the advantages of low toxicity and high efficiency, and it is a potential drug for the treatment of cancer. Since cancer cells can escape apoptotic cell death through multiple adaptive mechanisms, HNK, a drug that induces cancer cell death in a nonapoptotic way, has attracted much interest. We found that HNK reduced the viability of human APL cell line (NB4 cells) by inducing paraptosis-like cell death. The process was accompanied by excessive reactive oxygen species (ROS), mitochondrial damage, endoplasmic reticulum stress, and increased microtubule-associated protein 1 light chain 3 (LC3) processing. The inactivation of proteasome activity was the main cause of misfolded and unfolded protein accumulation in endoplasmic reticulum, such as LC3II/I and p62. This phenomenon could be alleviated by adding cycloheximide (CHX), a protein synthesis inhibitor. We found that mTOR signaling pathway participated in paraptosis-like cell death induced by HNK in an autophagy-independent process. Moreover, the mitogen-activated protein kinase (MAPK) signaling pathway induced paraptosis of NB4 cells by promoting endoplasmic reticulum stress. In summary, these findings indicate that paraptosis may be a new way to treat APL, and provide novel insights into the potential mechanism of paraptosis-like cell death.

Synergistic killing effect of paclitaxel and honokiol in non-small cell lung cancer cells through paraptosis induction

PURPOSE

Paclitaxel is an anticancer drug for the treatment of non-small cell lung cancer (NSCLC). However, drug-resistance remains a major problem. Honokiol is a natural component which has been found to exhibit anti-tumor activity. Paclitaxel and honokiol have been reported to be able to induce paraptosis. The aim of this study was to investigate whether honokiol can reverse paclitaxel resistance by inducing paraptosis in NSCLC cells.

METHODS

NSCLC cell lines H1650 (paclitaxel-sensitive), H1299 and H1650/PTX (intrinsic and acquired paclitaxel-resistant, respectively) were used to assess the cytotoxic effects of paclitaxel and honokiol. Light and transmission electron microscopy were performed to detect cytoplasmic vacuolation. In vitro cell viability and clonogenic survival assays, as well as in vivo xenograft assays were conducted to test synergistic killing effects of paclitaxel and honokiol on NSCLC cells. Western blotting, flow cytometry and immunofluorescence were performed to evaluate paraptosis-regulating mechanisms.

RESULTS

We found that combination treatment with paclitaxel and honokiol synergistically killed H1650, H1299 and H1650/PTX cells by inducing paraptosis, which is characterized by cytoplasmic vacuolation. Moreover, paclitaxel/honokiol treatment resulted in a significant growth delay in H1299 xenograft tumors that showed extensive cytoplasmic vacuolation. Mechanistically, proteasomal inhibition-mediated endoplasmic reticulum (ER) stress and unfolded protein responses leading to ER dilation, and the disruption of intracellular Ca2+ homeostasis and mitochondrial Ca2+ overload resulting in mitochondrial disfunction, were found to be involved in paclitaxel/honokiol-induced paraptosis. Cellular protein light chain 3 (LC3) may play an important role in paclitaxel/honokiol induced cytoplasmic vacuolation and NSCLC cell death.

CONCLUSIONS

Combination of honokiol and paclitaxel may represent a novel strategy for the treatment of paclitaxel-resistant NSCLC.

Programmed cell death in spinal cord injury pathogenesis and therapy

Spinal cord injury (SCI) always leads to functional deterioration due to a series of processes including cell death. In recent years, programmed cell death (PCD) is considered to be a critical process after SCI, and various forms of PCD were discovered in recent years, including apoptosis, necroptosis, autophagy, ferroptosis, pyroptosis and paraptosis. Unlike necrosis, PCD is known as an active cell death mediated by a cascade of gene expression events, and it is crucial for elimination unnecessary and damaged cells, as well as a defence mechanism. Therefore, it would be meaningful to characterize the roles of PCD to not only enhance our understanding of the pathophysiological processes, but also improve functional recovery after SCI. This review will summarize and explore the most recent advances on how apoptosis, necroptosis, autophagy, ferroptosis, pyroptosis and paraptosis are involved in SCI. This review can help us to understand the various functions of PCD in the pathological processes of SCI, and contribute to our novel understanding of SCI of unknown aetiology in the near future.

Intracellular Ca2 + Imbalance Critically Contributes to Paraptosis

Paraptosis is a type of programmed cell death that is characterized by dilation of the endoplasmic reticulum (ER) and/or mitochondria. Since paraptosis is morphologically and biochemically different from apoptosis, understanding its regulatory mechanisms may provide a novel therapeutic strategy in malignant cancer cells that have proven resistant to conventional pro-apoptotic treatments. Relatively little is known about the molecular basis of paraptosis, but perturbations of cellular proteostasis and ion homeostasis appear to critically contribute to the process. Ca²⁺ transport has been shown to be important in the paraptosis induced by several natural products, metal complexes, and co-treatment with proteasome inhibitors and certain Ca²⁺-modulating agents. In particular, the Ca²⁺-mediated communication between the ER and mitochondria plays a crucial role in paraptosis. Mitochondrial Ca²⁺ overload from the intracellular Ca²⁺-flux system located at the ER–mitochondrial axis can induce mitochondrial dilation during paraptosis, while the accumulation of misfolded proteins within the ER lumen is believed to exert an osmotic force and draw water from the cytoplasm to distend the ER lumen. In this process, Ca²⁺ release from the ER also critically contributes to aggravating ER stress and ER dilation. This review focuses on the role of Ca²⁺ transport in paraptosis by summarizing the recent findings related to the actions of Ca²⁺-modulating paraptosis-inducing agents and discussing the potential cancer therapeutic strategies that may effectively induce paraptosis via Ca²⁺ signaling.

Morusin Inhibits Human Osteosarcoma via the PI3K-AKT Signaling Pathway

OBJECTIVE

Osteosarcoma is considered as one of the most common types of bone tumors, which occurs among adolescents and children.

METHODS

Current therapy strategies still have limited effectiveness therefore, the development of new therapies is urgent. Morusin is a compound isolated from Morus australis (Moraceae). Many studies have reported its anti-tumor effect on several tumor types. However, its role in osteosarcoma is still unclear.

RESULTS

In this study, we determined that morusin significantly suppresses the proliferation and promotes the apoptosis of osteosarcoma cells. Furthermore, the migration and invasion of osteosarcoma were reduced after exposure to morusin. The deep mechanism was determined to be the inhibition of the PI3K/AKT signaling pathway.

CONCLUSION

In conclusion, our study indicates morusin as a potential candidate for osteosarcoma therapy.

Mitochondrial functional and structural impairment is involved in the antitumor activity of δ-tocotrienol in prostate cancer cells

The therapeutic options for castration-resistant prostate cancer (CRPC) are still limited. Natural bioactive compounds were shown to possess pro-death properties in different tumors. We previously reported that δ-tocotrienol (δ-TT) induces apoptosis, paraptosis and autophagy in CRPC cells. Here, we investigated whether δ-TT might exert its activity by impairing mitochondrial functions. We demonstrated that, in PC3 and DU145 cells, δ-TT impairs mitochondrial respiration and structural dynamics. In both cell lines, δ-TT triggers mitochondrial Ca²⁺ and ROS overload. In PC3 cells, both Ca²⁺ and ROS mediate the δ-TT-related anticancer activities (decrease of cell viability, apoptosis, paraptosis, autophagy and mitophagy). As expected, in autophagy-defective DU145 cells, Ca²⁺ overload was involved in δ-TT-induced pro-death effects but not in autophagy and mitophagy. In this cell line, we also demonstrated that ROS overload is not involved in the anticancer activities of δ-TT, supporting a low susceptibility of these cells to ROS-related oxidative stress. Taken together, these data demonstrate that, in CRPC cells, δ-TT triggers cell death by inducing mitochondrial functional and structural impairments, providing novel mechanistic insights in its antitumor activity.

Morusin induces apoptosis and autophagy via JNK, ERK and PI3K/Akt signaling in human lung carcinoma cells

Due to drug resistance and side effects, the development of novel therapeutics for the treatment of lung cancer is still in an urgent need. Morusin, a naturally occurring prenylated flavonoid isolated from the root bark of Morus alba, has been reported to be a promising candidate for cancer treatment including lung cancer. This study aimed to validate the anti-cancer effects of morusin in human non-small cell lung cancer (NSCLC) cell lines A549 and NCI-H292. The results indicated that morusin had growth inhibitory, pro-apoptotic and pro-autophagic effects on A549 and NCI-H292 cells. The induction of apoptosis was characterized by chromatin condensation and PARP cleavage. Mitochondrial membrane potential (MMP) loss, cytochrome c release, Bax/Bcl-2 dysregulation, and caspase-3 cleavage were also observed, indicating a mitochondria-dependent apoptosis was induced by morusin. A pro-autophagic effect was demonstrated by the increased level of LC3-Ⅱ and decreased level of SQSTM1/p62. Furthermore, morusin inhibited PI3K/Akt signaling and activated JNK, ERK pathways as indicated by the alteration in the ratio of phosphorylation level over total protein expression level. A PI3K/Akt inhibitor (LY294002), a JNK inhibitor (SP600125) and a MEK/ERK inhibitor (U0126) contributed to the determination that these pathways were involved in both apoptosis and autophagy induced by morusin. Moreover, morusin treatment strikingly enhanced intracellular ROS level, an ROS scavenger NAC blocked cell death and changes of Akt, JNK and ERK induced by morusin.

The Beneficial Effects of Morusin, an Isoprene Flavonoid Isolated from the Root Bark of Morus

The root bark of Morus has long been appreciated as an antiphlogistic, diuretic and expectorant drug in Chinese herbal medicine, albeit with barely known targets and mechanisms of action. In the 1970s, the development of analytic chemistry allowed for the discovery of morusin as one of 7 different isoprene flavonoid derivatives in the root bark of Morus. However, the remarkable antioxidant capacity of morusin with the unexpected potential for health benefits over the other flavonoid derivatives has recently sparked scientific interest in the biochemical identification of target proteins and signaling pathways and further clinical relevance. In this review, we discuss recent advances in the understanding of the functional roles of morusin in multiple biological processes such as inflammation, apoptosis, metabolism and autophagy. We also highlight recent in vivo and in vitro evidence on the clinical potential of morusin treatment for multiple human pathologies including inflammatory diseases, neurological disorders, diabetes, cancer and the underlying mechanisms.

Chlorotoxin modified morusin-PLGA nanoparticles for targeted glioblastoma therapy

Malignant brain tumors remain a major cause of concern and mortality as successful treatment is hindered due to the poor transport and low penetration of chemotherapeutics across the blood-brain barrier (BBB). In this study, a nano formulation composed of chlorotoxin (CTX)-conjugated morusin loaded PLGA nanoparticles (PLGA-MOR-CTX) was devised against Glioblastoma Multiforme (GBM) and its anti-proliferative effects were evaluated in vitro. The synthesized nanoparticles were loaded with morusin, a naturally derived chemotherapeutic drug, and surface conjugated with CTX, a peptide derived from scorpion venom, highly specific for chloride channels (CIC-3) expressed in glioma tumor cells, as well as for matrix metalloproteinase (MMP-2), which is up regulated in the tumor microenvironment. Subsequently, the anti-cancer potential of the NPs was assessed in U87 and GI-1 (human glioblastoma) cells. Antiproliferative, cell apoptosis, and other cell-based assays demonstrated that the PLGA-MOR-CTX NPs resulted in enhanced inhibitory effects on U87 and GI-1 glioma cells. Prominent cytotoxicity parameters such as ROS generation, enhanced caspase activity, cytoskeletal destabilization, and inhibition of MMP-activity were observed in glioblastoma cells upon PLGA-MOR-CTX NP treatment. The cytocompatibility observed with normal human neuronal cells (HCN-1A) and the enhanced lethal effects in glioblastoma cells highlight the potential of PLGA-MOR-CTX nanoparticles as promising therapeutic nanocarriers towards GBM.

Stress Granule Formation Attenuates RACK1-Mediated Apoptotic Cell Death Induced by Morusin

Stress granules are membraneless organelles composed of numerous components including ribonucleoproteins. The stress granules are characterized by a dynamic complex assembly in response to various environmental stressors, which has been implicated in the coordinated regulation of diverse biological pathways, to exert a protective role against stress-induced cell death. Here, we show that stress granule formation is induced by morusin, a novel phytochemical displaying antitumor capacity through barely known mechanisms. Morusin-mediated induction of stress granules requires activation of protein kinase R (PKR) and subsequent eIF2α phosphorylation. Notably, genetic inactivation of stress granule formation mediated by G3BP1 knockout sensitized cancer cells to morusin treatment. This protective function against morusin-mediated cell death can be attributed at least in part to the sequestration of receptors for activated C kinase-1 (RACK1) within the stress granules, which reduces caspase-3 activation. Collectively, our study provides biochemical evidence for the role of stress granules in suppressing the antitumor capacity of morusin, proposing that morusin treatment, together with pharmacological inhibition of stress granules, could be an efficient strategy for targeting cancer.