Crotoxin induces apoptosis and autophagy in human lung carcinoma cells in vitro via activation of the p38MAPK signaling pathway

Cytotoxic effects of crotoxin from Crotalus durissus terrificus snake in canine mammary tumor cell lines

Background

Mammary gland tumors are the most prevalent neoplasm in intact female dogs, and they are good natural models to study comparative oncology. Most canine mammary malignancies, as in women, are commonly refractory to conventional therapies and demand continuous new therapeutic approaches. Crotalus durissus terrificus, also called rattlesnake, has more than 60 different proteins in its venom with multiple pharmaceutical uses, such as antitumor, antiviral, and antimicrobial action. Crotoxin, a potent β-neurotoxin formed by the junction of two subunits, a basic subunit (CB-PLA2) and an acidic subunit (crotapotin), has already been reported to have anticancer properties in different types of cancers.

Methods

In this work, we describe the cytotoxic potential of crotoxin and its subunits compared to doxorubicin (drug of choice) in two canine mammary carcinoma cell lines.

Results

Crotoxin, CB-PLA2, crotalic venom, and doxorubicin decreased cell viability and the ability to migrate in a dose-dependent manner, and crotapotin did not present an antitumoral effect. For all compounds, the predominant cell death mechanism was apoptosis. In addition, crotoxin did not show toxicity in normal canine mammary gland cells.

Conclusion

Therefore, this work showed that crotoxin and CB-PLA2 had cytotoxic activity, migration inhibition, and pro-apoptotic potential in canine mammary gland carcinoma cell lines, making their possible use in cancer research.

Cytotoxic effect of crotoxin on cancer cells and its antitumoral effects correlated to tumor microenvironment: A review

Cancer is the second leading cause of death worldwide, and despite the effort of standard treatments, the search for new tools against this disease is necessary. Importantly, it is known that the tumor microenvironment plays a crucial role in tumor initiation, progression, and response to therapies. Therefore, studies of potential drugs that act on these components are as critical as studies regarding antiproliferative substances. Through the years, studies of several natural products, including animal toxins, have been conducted to guide the development of medical compounds. In this review, we present the remarkable antitumor activities of crotoxin, a toxin from the rattlesnake Crotalus durissus terrificus, highlighting its effects on cancer cells and in the modulation of relevant elements in the tumor microenvironment as well as the clinical trials conducted with this compound. In summary, crotoxin acts through several mechanisms of action, such as activation of apoptosis, induction of cell cycle arrest, inhibition of metastasis, and decrease of tumor growth, in different tumor types. Crotoxin also modulates tumor-associated fibroblasts, endothelial cells, and immune cells, which contribute to its antitumoral effects. In addition, preliminary clinical studies confirm the promising results of crotoxin and support its potential future use as an anticancer drug.

Neurotoxins Acting at Synaptic Sites: A Brief Review on Mechanisms and Clinical Applications

Neurotoxins generally inhibit or promote the release of neurotransmitters or bind to receptors that are located in the pre- or post-synaptic membranes, thereby affecting physiological functions of synapses and affecting biological processes. With more and more research on the toxins of various origins, many neurotoxins are now widely used in clinical treatment and have demonstrated good therapeutic outcomes. This review summarizes the structural properties and potential pharmacological effects of neurotoxins acting on different components of the synapse, as well as their important clinical applications, thus could be a useful reference for researchers and clinicians in the study of neurotoxins.

Antineoplastic properties and pharmacological applications of Crotalus durissus terrificus snake venom

Snake toxins are widely studied owing to their importance in snakebite accidents, a serious public health issue in tropical countries, and their broad therapeutic potential. Isolated fractions from venom produced by snakes of the genus Crotalus sp. present a wide variety of pharmacological uses such as antifungal, antiviral, antibacterial, and antitumor properties, among other therapeutic potentialities. Given the direct effect of this venom on tumor cells, isolation of its compounds is important for the characterization of its anticarcinogenic actions. Crotalus durissus terrificus venom and its toxins have been widely evaluated as potential candidates for the development of new antineoplastic therapies that are efficient against different tumor lines and cellular targets. This review highlights the venom toxins of this species, with a focus on their antineoplastic properties.

Biological and Medical Aspects Related to South American Rattlesnake Crotalus durissus (Linnaeus, 1758): A View from Colombia

In Colombia, South America, there is a subspecies of the South American rattlesnake Crotalus durissus, C. d. cumanensis, a snake of the Viperidae family, whose presence has been reduced due to the destruction of its habitat. It is an enigmatic snake from the group of pit vipers, venomous, with large articulated front fangs, special designs on its body, and a characteristic rattle on its tail. Unlike in Brazil, the occurrence of human envenomation by C. durisus in Colombia is very rare and contributes to less than 1% of envenomation caused by snakes. Its venom is a complex cocktail of proteins with different biological effects, which evolved with the purpose of paralyzing the prey, killing it, and starting its digestive process, as well as having defense functions. When its venom is injected into humans as the result of a bite, the victim presents with both local tissue damage and with systemic involvement, including a diverse degree of neurotoxic, myotoxic, nephrotoxic, and coagulopathic effects, among others. Its biological effects are being studied for use in human health, including the possible development of analgesic, muscle relaxant, anti-inflammatory, immunosuppressive, anti-infection, and antineoplastic drugs. Several groups of researchers in Brazil are very active in their contributions in this regard. In this work, a review is made of the most relevant biological and medical aspects related to the South American rattlesnake and of what may be of importance for a better understanding of the snake C. d. cumanensis, present in Colombia and Venezuela.

Pennogenin-3-O-α-L-Rhamnopyranosyl-(1→2)-[α-L-Rhamnopyranosyl-(1→3)]-β-D-Glucopyranoside (Spiroconazol A) Isolated from Dioscorea bulbifera L. var. sativa Induces Autophagic Cell Death by p38 MAPK Activation in NSCLC Cells

In our previous study, we reported the isolation of pennogenin-3-O-α-L-rhamnopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→3)]-β-D-glucopyranoside (spiroconazol A), a steroidal saponin, from the flowers of Dioscorea bulbifera L. var. sativa. In the present study, we aimed to investigate the effects of spiroconazol A on autophagy and its underlying mechanisms in A549 and NCI-H358 human non-small cell lung cancer (NSCLC) cells. Spiroconazol A inhibited the proliferation of NSCLC cells in a concentration- and time-dependent manner. To determine the type of programmed cell death induced by spiroconazol A, we performed a characterization of apoptosis in spiroconazol A-treated A549 cells. Our results showed that spiroconazol A significantly suppressed A549 cell viability but did not influence cell apoptosis because phosphatidylserine and caspase activation were not detected. Furthermore, spiroconazol A treatment upregulated the expression of LC3-II and autophagy-related Beclin-1 protein, suggesting that spiroconazol A induces autophagy in A549 cells. Moreover, spiroconazol A activated the phosphorylation of p38 mitogen-activated protein kinase (MAPK) but did not affect the phosphorylation of Janus kinase or ERK1/2. Notably, SB203580, a p38 MAPK inhibitor, had a significant inhibitory effect on spiroconazol A-induced autophagic cell death in A549 cells. Our results indicated that spiroconazol A-induced autophagy is dependent on p38 MAPK signaling and has potential as a therapeutic target in NSCLC.

Discovery of Leptulipin, a New Anticancer Protein from theIranian Scorpion, Hemiscorpius lepturus

Cancer is one of the leading causes of mortality in the world. Unfortunately, the present anticancer chemotherapeutics display high cytotoxicity. Accordingly, the discovery of new anticancer agents with lower side effects is highly necessitated. This study aimed to discover an anticancer compound from Hemiscorpius lepturus scorpion venom. Bioactivity-guided chromatography was performed to isolate an active compound against colon and breast cancer cell lines. 2D electrophoresis and MALDI-TOF were performed to identify the molecule. A partial protein sequence was obtained by mass spectrometry, while the full-length was deciphered using a cDNA library of the venom gland by bioinformatics analyses and was designated as leptulipin. The gene was cloned in pET-26b, expressed, and purified. The anticancer effect and mechanism action of leptulipin were evaluated by MTT, apoptosis, and cell cycle assays, as well as by gene expression analysis of apoptosis-related genes. The treated cells displayed inhibition of cell proliferation, altered morphology, DNA fragmentation, and cell cycle arrest. Furthermore, the treated cells showed a decrease in BCL-2 expression and an increase in Bax and Caspase 9 genes. In this study, we discovered a new anticancer protein from H. lepturus scorpion venom. Leptulipin showed significant anticancer activity against breast and colon cancer cell lines.

Falcarindiol Stimulates Apoptotic and Autophagic Cell Death to Attenuate Cell Proliferation, Cell Division, and Metastasis through the PI3K/AKT/mTOR/p70S6K Pathway in Human Oral Squamous Cell Carcinomas

Human oral squamous cell carcinomas (OSCCs) have high cancer mortality and a 5-year survival rate lower than that of most other carcinomas. New therapeutic strategies are required for the treatment and prevention against OSCCs. An approach to cancer therapy using plant-derived natural compounds has been actively in progress as a trend. Falcarindiol (FALC), or its isolated form Ostericum koreanum Kitagawa (O. koreanum), is present in many food and dietary plants, especially in carrots, and this compound has a variety of beneficial effects. However, biological activity of FALC has not been reported in OSCCs yet. This study aimed to demonstrate the antitumor effects of FALC against OSCCs, YD-10B cells. In this study, FALC was selected as a result of screening for compounds isolated from various natural products in YD-10B cells. FALC suppressed cell growth, and FALC-induced apoptotic cell death was mainly accompanied by the dephosphorylation of PI3K, AKT, mTOR, and p70S6K. The apoptotic cell death was also associated with autophagy as evidenced by the expression of Beclin-1, the conversion of LC3-II, and the formation of autophagosome. FALC-induced autophagy was accompanied by MAPKs including ERK1/2 and p38. Furthermore, FALC caused the antimetastatic effects by inhibiting the migration and invasion of YD-10B cells. Taken together, the findings suggest the potential value of FALC as a novel candidate for therapeutic strategy against OSCCs.

A New Approach to Inhibiting Triple-Negative Breast Cancer: In Vitro, Ex Vivo and In Vivo Antiangiogenic Effect of BthTx-II, a PLA2-Asp-49 from Bothrops jararacussu Venom

Phospholipases A2 (PLA2) represent a superfamily of enzymes widely distributed in living organisms, with a broad spectrum of pharmacological activities and therapeutic potential. Anti-angiogenic strategies have become one of the main tools in fighting cancer. In this sense, the present work reports the inhibition of tumor angiogenesis induced by Asp-49 BthTX-II using in vitro, ex vivo and in vivo approaches. We demonstrate that BthTx-II inhibited cell adhesion, proliferation, and migration of human umbilical vein endothelial cells (HUVEC), as well as caused a reduction in the levels of endothelial growth factor (VEGF) during in vitro angiogenesis assays. BthTx-II was also able to inhibit the sprouting angiogenic process, by the ex vivo germination assay of the aortic ring; in addition, this toxin inhibited the migration and proliferation of HUVEC in co-culture with triple-negative breast cancer cells (e.g., MDA-MB-231 cells). Finally, in vivo tumor suppression and anti-angiogenic activities were analyzed using MDA-MB-231 cells with Matrigel injected into the chorioallantoic membrane of chicken embryo (CAM) for 7 days treatment with BthTx-II, showing a considerable reduction in vessel caliber, on the size and weight of tumors. Together, these results suggest an important antiangiogenic and antitumor role for BthTx-II, as a potential prototype for the development of new tools and antitumor drugs in cancer therapy.

Revisiting the potential of South American rattlesnake Crotalus durissus terrificus toxins as therapeutic, theranostic and/or biotechnological agents

The potential biotechnological and biomedical applications of the animal venom components are widely recognized. Indeed, many components have been used either as drugs or as templates/prototypes for the development of innovative pharmaceutical drugs, among which many are still used for the treatment of human diseases. A specific South American rattlesnake, named Crotalus durissus terrificus, shows a venom composition relatively simpler compared to any viper or other snake species belonging to the Crotalus genus, although presenting a set of toxins with high potential for the treatment of several still unmet human therapeutic needs, as reviewed in this work. In addition to the main toxin named crotoxin, which is under clinical trials studies for antitumoral therapy and which has also anti-inflammatory and immunosuppressive activities, other toxins from the C. d. terrificus venom are also being studied, aiming for a wide variety of therapeutic applications, including as antinociceptive, anti-inflammatory, antimicrobial, antifungal, antitumoral or antiparasitic agent, or as modulator of animal metabolism, fibrin sealant (fibrin glue), gene carrier or theranostic agent. Among these rattlesnake toxins, the most relevant, considering the potential clinical applications, are crotamine, crotalphine and gyroxin. In this narrative revision, we propose to organize and present briefly the updates in the accumulated knowledge on potential therapeutic applications of toxins collectively found exclusively in the venom of this specific South American rattlesnake, with the objective of contributing to increase the chances of success in the discovery of drugs based on toxins.

South American snake venoms with abundant neurotoxic components. Composition and toxicological properties. A literature review

In South America there are three snake genera with predominantly neurotoxic venoms: Crotalus, Micrurus and Hydrophis, which include nine species/subspecies, 97 species and a single marine species, respectively. Although accidents with neurotoxic venoms are less frequent than those with anticoagulant, cytotoxic or necrotic venoms (e.g. from Bothrops), they are of major public health importance. Venoms from genus Crotalus have been extensively studied, while data on the venoms from the other two genera are very limited, especially for Hydrophis. The venoms of North and South American Crotalus species show biochemical and physiopathological differences. The former species cause bothrops-like envenomation symptoms, while the latter mainly have neurotoxic and myotoxic effects, leading to respiratory paralysis and, occasionally, renal failure by myoglobinuria and death, often with no local lesions. Micrurus and Hydrophis also cause neurotoxic envenomations. Many studies have isolated, identified and characterized new enzymes and toxins, thus expanding the knowledge of snake venom composition. The present review summarizes the currently available information on neurotoxic venoms from South American snakes, with a focus on protein composition and toxicological properties. It also includes some comments concerning potential medical applications of elapid and crotalic toxins.

Proliferation of Lung Epithelial Cells Is Regulated by the Mechanisms of Autophagy Upon Exposure of Soots

Background

Soots are known to cause many diseases in humans, but their underlying mechanisms of toxicity are still not known. Here, we report that soots induce cell proliferation of lung epithelial cells via modulating autophagy pathways.

Results

Fullerene soot and diesel exhaust particles (DEP) induced cell proliferation of lung epithelial, A549 cells via distinct autophagic mechanisms and did not cause cell death. Exposure of fullerene soot protected the cell death of A549 cells, caused by hydrogen peroxide, and inhibited LPS-induced autophagy. Fullerene soot co-localized with the autophagic proteins and inhibited starvation-induced autophagy (downregulated ATG-5, beclin-1, p62, and LC3 expressions) independent of its antioxidant properties. Similarly, it decreased the expression profile of autophagic genes and upregulated the proliferation-responsive gene, Ki-67, in mice. We observed that expressions of fullerene soot-responsive genes (Beclin-1, ATG-5, and p62) were reverted by Akt Inhibitor X, indicating an important role of the Akt pathway. At an elemental level, we found that elemental carbon of fullerene soot may be converted into organic carbon, as measured by OCEC, which may point fullerene soot as a source of carbon. On the other hand, DEP upregulated the expressions of autophagy genes. Akt Inhibitor X did not attenuate DEP-induced cell proliferation and autophagic response. However, an autophagic inhibitor, chloroquine, and significantly inhibited DEP-induced cell proliferation.

Conclusion

It can be said that distinct autophagic mechanisms are operational in cell proliferation of lung epithelial cells due to soots, which may be responsible for different diseases. Understanding the mechanism of these pathways provides some important targets, which can be utilized for the development of future therapeutics.

The anti-cancer potential of crotoxin in estrogen receptor-positive breast cancer: Its effects and mechanism of action

Estrogen receptor-positive (ER⁺) breast cancer is the most diagnosed subtype of breast cancer. Currently, aromatase inhibitors (AIs) are used as first-line treatment option in this type of tumors, however they cause several side effects, which is why new therapeutic approaches are demanding. The South American rattlesnake Crotalus durissus terrificus produces a venom enriched in several bioactive substances, like phospholipases A₂ (PLA₂). One of those is crotoxin, a β-neurotoxin, that has already been reported for its anti-cancer properties in different cancers. Recently, its clinical interest has emerged and, in fact, a clinical trial in patients with advanced cancer is underway. Considering this, in this work, we studied the biological mechanisms behind the anti-cancer effects of crotoxin B (CTX) in an ER⁺ aromatase-overexpressing breast cancer cell line (MCF-7aro cells). Results revealed that CTX impairs MCF-7aro cells growth, through a cell cycle arrest at G₂/M phase, inhibition of ERK1/2 pathway and by apoptosis through activation of caspase-8. In addition, it can be considered a safe natural compound as did not affect non-cancerous cells and only showed anti-growth effects in breast cancer cells. Therefore, this study represents an important landmark to better understand the effects and mechanisms of action of crotoxin in ER⁺ breast cancer.

Recent developments in animal venom peptide nanotherapeutics with improved selectivity for cancer cells

Animal venoms are a rich source of bioactive peptides that efficiently modulate key receptors and ion channels involved in cellular excitability to rapidly neutralize their prey or predators. As such, they have been a wellspring of highly useful pharmacological tools for decades. Besides targeting ion channels, some venom peptides exhibit strong cytotoxic activity and preferentially affect cancer over healthy cells. This is unlikely to be driven by an evolutionary impetus, and differences in tumor cells and the tumor microenvironment are probably behind the serendipitous selectivity shown by some venom peptides. However, strategies such as bioconjugation and nanotechnologies are showing potential to improve their selectivity and potency, thereby paving the way to efficiently harness new anticancer mechanisms offered by venom peptides. This review aims to highlight advances in nano- and chemotherapeutic tools and prospective anti-cancer drug leads derived from animal venom peptides.

Zearalenone Induces Apoptosis and Cytoprotective Autophagy in Chicken Granulosa Cells by PI3K-AKT-mTOR and MAPK Signaling Pathways

Zearalenone (ZEA) is a nonsteroidal estrogenic mycotoxin found in several food commodities worldwide. ZEA causes reproductive disorders, genotoxicity, and testicular toxicity in animals. However, little is known about the functions of apoptosis and autophagy after exposure to ZEA in granulosa cells. This study investigated the effects of ZEA on chicken granulosa cells. The results show that ZEA at different doses significantly inhibited the growth of chicken granulosa cells by inducing apoptosis. ZEA treatment up-regulated Bax and downregulated Bcl-2 expression, promoted cytochrome c release into the cytosol, and triggered mitochondria-mediated apoptosis. Consequently, caspase-9 and downstream effector caspase-3 were activated, resulting in chicken granulosa cells apoptosis. ZEA treatment also upregulated LC3-II and Beclin-1 expression, suggesting that ZEA induced a high level of autophagy. Pretreatment with chloroquine (an autophagy inhibitor) and rapamycin (an autophagy inducer) increased and decreased the rate of apoptosis, respectively, in contrast with other ZEA-treated groups. Autophagy delayed apoptosis in the ZEA-treated cells. Therefore, autophagy may prevent cells from undergoing apoptosis by reducing ZEA-induced cytotoxicity. In addition, our results further show that the autophagy was stimulated by ZEA through PI3K-AKT-mTOR and MAPK signaling pathways in chicken granulosa cells.

Antiangiogenic effects of phospholipase A2 Lys49 BnSP-7 from Bothrops pauloensis snake venom on endothelial cells: An in vitro and ex vivo approach

Antiangiogenic strategies are promising tools for cancer treatment and several other disorders. In this sense, phospholipases A₂ (PLA₂s) from snake venom have been described to possess antiangiogenic properties. In this study, we evaluated both in vitro and ex vivo antiangiogenic effects induced by BnSP-7, a Lys49 PLA₂ isolated from Bothrops pauloensis snake venom. BnSP-7 was able to inhibit endothelial cell (HUVEC) proliferation, which was indeed confirmed by a modulation of cell cycle progression. Interestingly, BnSP-7 also inhibited the adhesion and migration of HUVECs and blocked in vitro angiogenesis in a VEGF-dependent manner, an important proangiogenic factor. Finally, BnSP-7 was capable of inhibiting sprouting angiogenic process through an ex vivo aortic ring assay. Taken together, these results indicate that BnSP-7 has potent in vitro and ex vivo antiangiogenic effect.

11-O-Galloyl Bergenin from Corylopsis coreanas Leaves Induces Autophagy and Apoptosis in Human Osteosarcoma

Osteosarcoma is the most common malignant bone-forming tumor, wherein most patients with high grade osteosarcomas are treated with chemotherapy. Despite this, survival for metastatic or relapsed osteosarcoma patients has remained at an overall 5-year survival rate of 20%. In particular, the extracts of Corylopsis coreana (Korean winter hazel), a cultivated woody plant in South Korea, have shown beneficial anti-inflammatory, anti-oxidative, anti-osteoclastic, and antihyperuricemic properties. Therefore, this study aimed to demonstrate the antitumor activities and underlying mechanism of 11-O-Galloyl bergenin (OGAL) isolated from Corylopsis coreanas leaves in human osteosarcoma cells. Herein, we found that OGAL inhibited MG63 cell proliferation and induced cellular apoptosis as evidenced by cleaved-PARP, cleaved-caspase 3, TUNEL-positive cells, and Annexin V-positive cells. Specifically, OGAL-induced apoptosis was accompanied by p53 and p21 upregulation, BAX expression, and decreased Bcl-2 and cdk2. Moreover, OGAL induced autophagy via AKT inactivation, LC3II upregulation, and MG63 cell autophagosome formation. OGAL-induced autophagy was also accompanied by increased p38 phosphorylation, whereas JNK and ERK1/2 activities were found to be unaffected upon examining the MAPK signaling pathway. Furthermore, wound healing and Boyden chamber assays showed that OGAL suppressed MG63 cell migration and invasion. Given these findings, this study provided evidence that OGAL has antitumor effects by apoptosis and autophagy enhancement through increased p53, AKT, and p38 signaling, suggesting that OGAL may be a potential therapeutic strategy for osteosarcoma treatment.

Targeting PI3K/AKT/mTOR-mediated autophagy for tumor therapy

Autophagy is a highly conserved catabolic process and participates in a variety of cellular biological activities. The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway, as a critical regulator of autophagy, is involved in the initiation and promotion of a series of pathological disorders including various tumors. Autophagy also participates in regulating the balance between the tumor and the tumor microenvironment. Natural products have been considered a treasure of new drug discoveries and are of great value to medicine. Mounting evidence has suggested that numerous natural products are targeting PI3K/AKT/mTOR-mediated autophagy, thereby suppressing tumor growth. Furthermore, autophagy plays a "double-edged sword" role in different tumors. Targeting PI3K/AKT/mTOR-mediated autophagy is an important therapeutic strategy for a variety of tumors, and plays important roles in enhancing the chemosensitivity of tumor cells and avoiding drug resistance. Therefore, we summarized the roles of PI3K/AKT/mTOR-mediated autophagy in tumorigenesis, progression, and drug resistance of tumors, which may be utilized to design preferably therapeutic strategies for various tumors.

Activation of the p38/MAPK pathway regulates autophagy in response to the CYPOR-dependent oxidative stress induced by zearalenone in porcine intestinal epithelial cells

Zearalenone (ZEA) can widely contaminate crops and agricultural products. The ingestion of ZEA-contaminated food or feed affects the integrity and functions of the intestines. In this study, we aimed to find the potential protective mechanism against ZEA ingestion. We found that ZEA induced cell death in IPEC-J2 cells. Meanwhile, the cytoprotective autophagy was activated in ZEA-treated cells. Further studies demonstrated that a p38/MAPK inhibitor down-regulated autophagy and increased cell death compared to those of the controls. Furthermore, ZEA could induce the accumulation of ROS, and eliminating ROS with NAC resulted in a decline in cell death, p38/MAPK phosphorylation, and the expression of LC3-II compared to those of ZEA-group. In addition, cytochrome P450 reductase (CYPOR) was significantly increased in ZEA-treated cells compared to that in the controls, and an inhibitor of CYPOR decreased ROS levels and mitigated cell death compared to those of the ZEA-group. More importantly, we found that blocking both p38/MAPK signalling and autophagy could enhance CYPOR expression and elevate ROS levels. Overall, our study indicated that the p38/MAPK pathway could activate protective autophagy in response to the CYPOR-dependent oxidative stress that was induced by ZEA in IPEC-J2 cells.

PP-22 promotes autophagy and apoptosis in the nasopharyngeal carcinoma cell line CNE-2 by inducing endoplasmic reticulum stress, downregulating STAT3 signaling, and modulating the MAPK pathway

Paris polyphylla var. yunnanensis, named Chong Lou, is considered an antitumor substance. In this study, we investigated the effect of PP-22, a monomer purified from P. polyphylla var. yunnanensis, on the nasopharyngeal carcinoma cell line CNE-2 in vitro. The results showed that PP-22 could inhibit the proliferation of CNE-2 cells via the induction of apoptosis, with evidence of the characteristic morphological changes in the apoptosis in the nucleus and an increase in Annexin V-positive cells. In addition, we found that PP-22 could activate the p38 mitogen-activated protein kinase (MAPK) pathway and that this activation was reversed by SB203580, a specific inhibitor of the p38 MAPK pathway. In contrast, PP-22 promoted apoptosis via an intrinsic pathway, including the endoplasmic reticulum stress pathway, in a caspase-dependent manner. A further study showed that PP-22 also induced apoptosis by downregulating the signal transducers and activators of transcription 3 (STAT3) pathway, and the inhibitory effect was also confirmed by STAT3 small interfering RNA. In addition, PP-22 could promote autophagy by inhibiting the extracellular regulated protein kinases (ERK) pathway. And autophagy plays a protective role against apoptosis. Together, these data show that PP-22 promotes autophagy and apoptosis in the nasopharyngeal carcinoma CNE-2 cell line.

Gastrodin Attenuates Bilateral Common Carotid Artery Occlusion-Induced Cognitive Deficits via Regulating Aβ-Related Proteins and Reducing Autophagy and Apoptosis in Rats

Gastrodin (GAS), an active constituent extracted from Gastrodia elata Blume, is used to treat ischemic stroke, epilepsy, dizziness, and dementia for centuries in China. This study examined its effects on vascular dementia (VD) and the underlying molecular mechanisms. VD was established by ligation of bilateral common carotid artery occlusion (BCCAO). A total of 7 days after BCCAO surgery, GAS (15, 30, and 60 mg/kg) was orally administered for 28 consecutive days to evaluate therapeutic effects. Cognitive function was tested by the Morris water maze. The neuronal morphological changes were examined via Hematoxylin-Eosin staining. Flow cytometry was used for evaluating apoptosis in the hippocampi. The target protein expression was examined by Western blot. The results showed that BCCAO induced cognitive impairment, hippocampus CA1 and CA3 pyramidal neuron damage, beta-amyloid (Aβ) deposition, excessive autophagy, and apoptosis. GAS treatment significantly improved BCCAO-induced cognitive deficits and hippocampus neuron damage. Molecular analysis revealed that GAS exerted the protective effect via reducing the levels of Aβ1-40/42, APP, and β-site APP-cleaving enzyme 1 expression, and increasing Aβ-related protein, a disintegrin and metalloprotease 10, and insulin degrading enzyme expression. Meanwhile, GAS inhibited excessive autophagy via decreasing Beclin-1, LC3-II, and p62 levels. Furthermore, GAS inhibited apoptosis through the downregulation of Bax and upregulation of Bcl-2. Moreover, P38 MAPK signaling pathway was involved in the process. Our findings demonstrate that GAS was effective in the treatment of BCCAO-induced VD via targeting Aβ-related protein formation and inhibiting autophagy and apoptosis of hippocampus neurons.

In vitro assessment of cytotoxic activities of Lachesis muta muta snake venom

Envenomation by the bushmaster snake Lachesis muta muta is considered severe, characterized by local effects including necrosis, the main cause of permanent disability. However, cellular mechanisms related to cell death and tissue destruction, triggered by snake venoms, are poorly explored. The purpose of this study was to investigate the cytotoxic effect caused by L. m. muta venom in normal human keratinocytes and to identify the cellular processes involved in in cellulo envenomation. In order to investigate venom effect on different cell types, Alamar Blue assay was performed to quantify levels of cellular metabolism as a readout of cell viability. Apoptosis, necrosis and changes in mitochondrial membrane potential were evaluated by flow cytometry, while induction of autophagy was assessed by expression of GFP-LC3 and analyzed using fluorescence microscopy. The cytotoxic potential of the venom is shown by reduced cell viability in a concentration-dependent manner. It was also observed the sequential appearance of cells undergoing autophagy (by 6 hours), apoptosis and necrosis (12 and 24 hours). Morphologically, incubation with L. m. muta venom led to a significant cellular retraction and formation of cellular aggregates. These results indicate that L. m. muta venom is cytotoxic to normal human keratinocytes and other cell lines, and this toxicity involves the integration of distinct modes of cell death. Autophagy as a cell death mechanism, in addition to apoptosis and necrosis, can help to unravel cellular pathways and mechanisms triggered by the venom. Understanding the mechanisms that underlie cellular damage and tissue destruction will be useful in the development of alternative therapies against snakebites.

Semisynthetic Esters of 17-Hydroxycativic Acid with in Vitro Cytotoxic Activity against Leukemia Cell Lines

A collection of sixteen semisynthetic 17-hydroxycativic acid esters with alcohols containing a tertiary amine group was evaluated for their in vitro cytotoxicity against two human cancer cell lines, THP-1 and U937, and for their effects on the cell cycle and cell death. While 17-hydroxycativic acid itself is not cytotoxic, all the esters displayed cytotoxic activity, with 50% growth inhibition (GI₅₀) values ranging between 3.2 and 23.1 µM. In general, the most potent compounds in both cell lines were esters with four carbon long alcohol residues. There was no clear relationship between the identity of the terminal secondary amine and the activity of the compound. Experiments using the 6-(pyrrolidin-1-yl)pentyl ester, 2c, revealed that this compound activates caspases-3/7 and causes poly(ADP-ribose)polymerase 1 (PARP-1) fragmentation in THP-1 and U937 cells, indicating the induction of apoptotic cell death. These results suggest that further investigation into the anticancer activity of diterpene derivatives and other labdane diterpenes may be fruitful.

Upregulation of p38 pathway accelerates proliferation and migration of MDA-MB-231 breast cancer cells

Tumor cells capture the signaling pathways used by normal tissue to promote their own survival and dissemination and among them, the NF-κB and MAPK pathways (ERK, JNK and p38). MAPK activation has ambiguous effects on tumor cell fate depending on cell type, cancer stage and the engaged MAPK isoforms. A synthetic peptide named LyeTx II, derived from the venom of the Brazilian spider Lycosa erythrognatha, was capable of increasing MDA-MB-231 aggressive breast cancer cell proliferation as indicated by MTT and BrdU (5-bromo-2'-deoxyuridine) incorporation assay and cell migration. A correlation has been established between the accelerated proliferation and migration observed in the presence of LyeTx II and the upregulation of p38 MAPK phosphorylation. The use of the selective inhibitor of p38α/β (SB203580) abrogated the peptide effect in MDA-MB-231 cells. Besides, an augment of the canonical NF-κB pathway activation considered as crucial in cancer progression was noted after cell incubation with LyeTx II. Importantly, activation of p38 and NF-κB pathways was dependent on TAK1 activity. Together, these data suggest that TAK1-p38 pathway may represent an interesting target for treatment of aggressive breast cancers.

Phloretin induces apoptosis of non-small cell lung carcinoma A549 cells via JNK1/2 and p38 MAPK pathways

Phloretin (Ph) existing in apples, pears and various vegetables is known to have antitumor activities in several cancer cell lines. However, little is known about its effect on human lung cancer cells. The aim of the present study was to see whether Ph could induce apoptosis of non-small cell lung cancer (NSCLC) cells, and explore the possible underlying mechanism of action. We found that Ph markedly induced cell apoptosis of NSCLC cell line A549, and inhibited the migration of A549 cells in a dose-dependent manner. The expression level of BAX, cleaved caspase-3 and -9, and degraded form of PARP was increased and Bcl-2 was decreased after Ph treatment. In addition, the phosphorylation of P38 MAPK, ERK1/2 and JNK1/2 was increased in a dose-dependent manner in parallel with Ph treatment. Inhibition of P38 MAPK and JNK1/2 by specific inhibitors significantly abolished the Ph-induced activation of the caspase-3 and -9. In vivo tumor-suppression assay further indicated that Ph (20 mg/kg) displayed a more significant inhibitory effect on A549 xenografts in tumor growth. All these findings indicate that Ph is able to inhibit NSCLC A549 cell growth by inducing apoptosis through P38 MAPK and JNK1/2 pathways, and therefore may prove to be an adjuvant to the treatment of NSCLC.