The role of cell signalling in the crosstalk between autophagy and apoptosis

Mitofusin2, as a Protective Target in the Liver, Controls the Balance of Apoptosis and Autophagy in Acute-on-Chronic Liver Failure

Aim: Acute-on-chronic liver failure (ACLF) is closely related to mitochondrial dysfunction. Previous studies showed the vital role of mitofusin2 (Mfn2) in the regulation of mitochondrial function. However, the effect of Mfn2 on ACLF remains unknown. As one of mitochondrial-related pathways, BNIP3-mediated pathway controls the balance between apoptosis and autophagy. However, the relationship between Mfn2 and BNIP3-mediated pathway in ACLF is still obscure. The aim of our study is to clarify the effect of Mfn2 and potential molecular mechanisms in ACLF.

Methods: We collected liver tissue from ACLF patients and constructed an ACLF animal model and a hepatocyte autophagy injury model, using adenovirus and lentivirus to deliver Mfn2 and Mfn2-siRNA to liver cells, in order to assess the effect of Mfn2 on autophagy and apoptosis in ACLF. We explored the biological mechanisms of Mfn2-induced autophagy and apoptosis of ACLF through Western blotting, Quantitative Real-Time PCR (RT-PCR), transmission electron microscopy, immunofluorescence, immunohistochemical staining, and hematoxylin–eosin staining.

Results: Compared with the normal liver tissue, the expressions of Mfn2, Atg5, Beclin1, and LC3-II/I were significantly decreased and the expression of P62 was much higher in patients with ACLF. Mfn2 significantly attenuated ACLF, characterized via microscopic histopathology and reduced serum AST and ALT levels. Mfn2 promoted the expressions of ATP synthase β, Atg5, Beclin1, LC3-II/I, and Bcl2 and reduced the expressions of P62, Bax, and BNIP3.

Conclusions: Mfn2 plays a protective role in the progression of ACLF. BNIP3-mediated signaling pathway is not the only factor associated with Mfn2 controlling the balance of apoptosis and autophagy in ACLF. Mfn2 will provide a promising therapeutic target for patients with ACLF.

Sevoflurane induces cognitive impairment in young mice via autophagy

Background

Anesthesia may induce neurotoxicity and neurocognitive impairment in young mice. However, the underlying mechanism remains largely to be determined. Meanwhile, autophagy is involved in brain development and contributes to neurodegenerative diseases. We, therefore, set out to determine the effects of sevoflurane on autophagy in the hippocampus of young mice and on cognitive function in the mice.

Methods

Six day-old mice received 3% sevoflurane, for two hours daily, on postnatal days (P) 6, 7 and 8. We then decapitated the mice and harvested the hippocampus of the young mice at P8. The level of LC3, the ratio of LC3-II to LC3-I, and SQSTM1/p62 level associated with the autophagy in the hippocampus of the mice were assessed by using Western blotting. We used different groups of mice for behavioral testing via the Morris Water Maze from P31 to P37.

Results

The anesthetic sevoflurane increased the level of LC3-II and ratio of LC3-II/LC3-I, decreased the p62 level in the hippocampus of the young mice, and induced cognitive impairment in the mice. 3-Methyladenine, the inhibitor of autophagy, attenuated the activation of autophagy and ameliorated the cognitive impairment induced by sevoflurane in the young mice.

Conclusion

These data showed that sevoflurane anesthesia might induce cognitive impairment in the young mice via activation of autophagy in the hippocampus of the young mice. These findings from the proof of concept studies have established a system and suggest the role of autophagy in anesthesia neurotoxicity and cognitive impairment in the young mice, pending further investigation.

The ginsenoside Rk3 exerts anti-esophageal cancer activity in vitro and in vivo by mediating apoptosis and autophagy through regulation of the PI3K/Akt/mTOR pathway

The rare ginsenoside Rk3 is a bioactive component derived from ginseng and Panax notoginseng that has been proven to possess anti-lung cancer activity. However, the effect of Rk3 on human esophageal cancer has not yet been reported. In this study, we aimed to explore its anticancer curative effect and potential molecular mechanisms in the Eca109 and KYSE150 cell lines. We found that Rk3 was able to significantly repress cell proliferation and colony formation in both Eca109 and KYSE150 cells in vitro. In the KYSE150 xenograft model, Rk3 obviously inhibited tumor growth and exhibited little toxicity in organs. Moreover, Rk3 could trigger G1 phase arrest and induce apoptosis and autophagy. Interestingly, apoptosis induced by Rk3 could be partly abrogated by 3-MA (an autophagy inhibitor), implying that autophagy could enhance apoptosis. Further studies indicated that pretreatment with the Akt inhibitor GSK690693 or the mTOR inhibitor rapamycin promoted Rk3-induced apoptosis and autophagy, demonstrating that the PI3K/Akt/mTOR pathway is related to Rk3-induced apoptosis and autophagy. In conclusion, the present study is the first to clarify that Rk3 can inhibit Eca109 and KYSE150 cell proliferation through activating apoptosis and autophagy by blocking the PI3K/Akt/mTOR pathway, suggesting that Rk3 may be a promising antitumor agent for esophageal cancer. In addition, this study provides ideas and an experimental basis for further research on the anti-esophageal cancer effects of the ginsenoside Rk3 and its mechanism.

A Hopeful Natural Product, Pristimerin, Induces Apoptosis, Cell Cycle Arrest, and Autophagy in Esophageal Cancer Cells

Esophageal cancer is one of the most common malignant digestive diseases worldwide. Although many approaches have been established for the treatment of esophageal cancer, the survival outcome has not improved. Pristimerin is a quinone methide triterpenoid with anticancer, antiangiogenic, anti-inflammatory, and antiprotozoal activities. However, the role of pristimerin in cancers such as esophageal cancer is unclear. In this study, we investigated the role and mechanisms of action of pristimerin in esophageal cancer. First, we found that pristimerin can induce apoptosis in esophageal cancer in vivo and in vitro. CCK-8 and clonogenic assays showed that pristimerin decreased the growth of Eca109 cells. In addition, we found that pristimerin decreased the protein expression of CDK2, CDK4, cyclin E, and BCL-2 and increased the expression of CDKN1B. Meanwhile, pristimerin elevated the ratio of LC3-II/LC3-I. Otherwise, downregulation of CDKN1B can reduce the esophageal cancer tumor growth induced by pristimerin. In conclusion, our findings revealed an important role of pristimerin in esophageal cancer and suggest that pristimerin might be a potential therapeutic agent for this cancer.

Trifluoperazine as an alternative strategy for the inhibition of tumor growth of colorectal cancer

The development of cancer in patients with schizophrenia is affected by genetic and environmental factors and antipsychotic medication. Several studies found that schizophrenia was associated with decreased risk of some cancers, and the neuroleptic medication might help to reduce the risk of colorectal cancer (CRC). Phenothiazine drugs including trifluoperazine (TFP) are widely used antipsychotic drugs and showed some antitumor effects, we here investigated the potential application of TFP in the treatment of colon cancer. A series doses of TFP were treated to the colon cancer cell line HCT116 and the inhibitory concentration (IC₅₀ ) of TFP for HCT116 was determined by cell counting kit-8. The results indicated that the treatment of TFP impaired the cell vitality of HCT116 in a dose- and time-dependent manner. Meanwhile, the Edu assay demonstrated that the proliferation was also inhibited by TFP, which was accompanied with the induction of apoptosis and autophagy. The expression of CCNE1, CDK4, and antiapoptosis factor BCL-2 was downregulated but the proapoptosis factor BAX was upregulated. The autophagy inhibitor chloroquine could significantly reverse the TFP-induced apoptosis. Moreover, the ability of migration and invasion of HCT116 was found to be suppressed by TFP, which was associated with the inhibition of epithelial-mesenchymal transition (EMT). The function of TFP in vivo was further confirmed. The results showed that the administration of TFP remarkably abrogated the tumor growth with decreased tumor volume and proliferation index Ki-67 level in tumor tissues. The EMT phenotype was also confirmed to be inhibited by TFP in vivo, suggesting the promising antitumor effects of TFP in CRC.

Sasanquasaponin ΙΙΙ from Schima crenata Korth induces autophagy through Akt/mTOR/p70S6K pathway and promotes apoptosis in human melanoma A375 cells

BACKGROUND

Melanoma is a high fatality skin cancer which lacks effective drugs. Sasanquasaponin, an important sort of constituents in theaceae, has been demonstrated to have potent anti-tumor effect in breast cancer and hepatocellular carcinoma. As a sasanquasaponin, we speculate that Sasanquasaponin III (SQS III) isolated from Schima crenata Korth may also have anti-tumor activity.

PURPOSE

This study aims to investigate whether SQS III has anti-melanoma activity and examine the underlying mechanisms of SQS III against melanoma.

METHODS/STUDY DESIGNS

The anti-proliferative effect of SQS III was assessed by cells viability assay. Annexin V-FITC/PI double staining assay was utilized for detection of apoptosis. Mitochondrial membrane potential and reactive oxygen species (ROS) production were detected using JC-1 and DCFH-DA assay, respectively. Autophagy was monitored using transmission electron microscopy (TEM) and GFP-LC3 transfection fluorescence analysis. Autophagosome-lysosome fusion and lysosomal degradation were determined using a GFP-LC3 & LAMP1 co-localization assay and DQ-BSA staining. Proteins related to apoptosis and autophagy were analyzed by Western blotting.

RESULTS

Our results demonstrated that the SQS III exhibited potent anti-cancer activity in A375 cells by inducing both apoptosis and autophagy. In melanoma cells treated with SQS III, caspases were activated and PARP was cleaved, proving the occurrence of apoptosis. Mechanistic studies indicated that the pro-apoptosis activity of SQS III was mediated by death receptor pathway and mitochondrial dysfunction which was induced by ROS accumulation and reversed by the ROS inhibitor N-acetyl-cysteine (NAC). In addition to triggering apoptosis, SQS III may also cause autophagy in melanoma cells. Our results demonstrated that SQS III induced up-regulated expression of GFP-LC3, autophagosome-lysosomal fusion and lysosomal degradation. Additionally, the ROS accumulation was also involved in the activation of autophagy. Meanwhile, it was also found that after SQS III treatment, the expression of LC3-II was up-regulated and the AKT/mTOR signaling pathway was inhibited. The autophagy inhibitor 3-MA converted cytotoxicity and apoptosis of SQS III in A375 cells, which indicated that autophagy promoted the SQS III-induced apoptosis.

CONCLUSION

SQS III showed potent anti-cancer activity by inducing apoptosis and autophagy, which provides insights into its possible use as a therapy for melanoma.

Acteoside inhibits autophagic apoptosis of retinal ganglion cells to rescue glaucoma-induced optic atrophy

BACKGROUND

Glaucoma is the world's second biggest cause of blindness, and patients progressively lose their eyesight. The current clinical treatment for glaucoma involves controlling intraocular pressure with drugs or surgery; however, some patients still progressively lose their eyesight. This treatment is also similar to the treatment of traumatic optic neuropathy. Thus, saving retinal ganglion cells (RGCs) from apoptosis is essential.

METHODS

The role of Acteoside on autophagy modulation in the 661 W cell line.

RESULTS

In this study, we first find that Acteoside inhibits autophagy, Rapamycin alleviates this inhibition and the PI3K inhibitor, 3-MA or LY294002, synergistically promotes it. In a mechanistic study, we find that Optineurin (OPTN) mediates Acteoside regulation of autophagy. OPTN overexpression or knockdown activates or inhibits autophagy, respectively. OPTN is inhibited by autophagy inhibitors, such as Acteoside and 3-MA and is promoted by the autophagy activator, Rapamycin. Meanwhile, PI3K and AKT are elevated by Acteoside and 3-MA and inhibited by Rapamycin. Finally, we find that Acteoside inhibits apoptosis in parallel to autophagy and that this inhibition is also mediated by OPTN.

CONCLUSION

In summary, we conclude that Acteoside inhibits autophagy-induced apoptosis in RGCs through the OPTN and PI3K/AKT/mTOR pathway, and glaucoma patients may benefit from Acteoside treatment alone or in combination with other autophagy inhibitors.

Inhibition of Autophagy Alleviates Cadmium-Induced Mouse Spleen and Human B Cells Apoptosis

Cadmium (Cd) is a toxic heavy metal that can accumulate and cause severe damage to many organs, such as liver, kidney, lung, etc. Cd also significantly suppresses immunity, however, the underlying mechanism involved in Cd-induced immunnotoxicity is still unclear. The present study indicated that semichronic Cd exposure (7 days) induced apoptotic damage of mouse spleen. In human Ramos B cells, Cd exposure also induced apoptosis, which was dependent on Cd-induced vacuole membrane protein 1 (VMP1) expression and autophagy. Cd-induced autophagy and apoptosis were abated when VMP1 expression was knockdown. In addition, Cd-induced VMP1 expression, autophagy, and apoptosis were dependent on the elevation of Ca2+ and reactive oxygen species (ROS). More important, Cd exposure also induced VMP1 expression and autophagy in mouse spleen tissue, and the intraperitoneal injection of the autophagy inhibitor chloroquine (CQ) into mice effectively reduced Cd-induced spleen apoptotic damage. Taken together, these results indicate Cd-induced autophagy, promotes apoptosis in immune cells, and inhibition of autophagy can alleviate Cd-induced spleen and immune cell apoptosis. This study might provide the groundwork for future studies on Cd-induced immunomodulatory effects and immune diseases.

Trehalose Modulates Autophagy Process to Counteract Gliadin Cytotoxicity in an In Vitro Celiac Disease Model

Celiac disease (CD) is a chronic systemic autoimmune disorder that is triggered by the ingestion of gliadin peptides, the alcohol-soluble fraction of wheat gluten. These peptides, which play a key role in the immune response that underlies CD, spontaneously form aggregates and exert a direct toxic action on cells due to the increase in the reactive oxygen species (ROS) levels. Furthermore, peptic-tryptic digested gliadin peptides (PT-gliadin) lead to an impairment in the autophagy pathway in an in vitro model based on Caco-2 cells. Considering these premises, in this study we have analyzed different mTOR-independent inducers, reporting that the disaccharide trehalose, a mTOR-independent autophagy activator, rescued the autophagy flux in Caco-2 cells treated with digested gliadin, as well as improved cell viability. Moreover, trehalose administration to Caco-2 cells in presence of digested gliadin reduced the intracellular levels of these toxic peptides. Altogether, these results showed the beneficial effects of trehalose in a CD in vitro model as well as underlining autophagy as a molecular pathway whose modulation might be promising in counteracting PT-gliadin cytotoxicity.

Alpha-lipoic acid attenuates p-cresyl sulfate-induced renal tubular injury through suppression of apoptosis and autophagy in human proximal tubular epithelial cells

The p-cresyl sulfate accumulates in kidney disease and may be involved in renal injury. α-Lipoic acid (α-LA) acts as an antioxidant in cell injury. We investigated the effects of α-LA treatment on p-cresyl sulfate-induced renal tubular injury. p-Cresyl sulfate induced cell death, and increased Bax/Bcl-2, cleaved caspase-3, Beclin-1, and LC3BII/LC3BI in human renal proximal tubular epithelial (HK-2) cells, which was counteracted by α-LA treatment. p-Cresyl sulfate-induced apoptosis was reduced by autophagy inhibitor 3-methyladenine, and p-cresyl sulfate induced autophagy was reduced by pan-caspase inhibitor Z-VAD-FMK. Moreover, p-cresyl sulfate treatment increased the expression of ER stress proteins and decreased the expression of baculoviral IAP repeat-containing proteins 6; these effects were prevented by α-LA treatment. Apoptosis and autophagy were associated with the phosphorylation of mitogen-activated protein kinase and nuclear translocation of the nuclear factor-κB p65 subunit. Pretreatment inhibitors of p38 and JNK, and knockdown of ATF4 gene reduced apoptosis- and autophagy-related protein expressions in p-cresyl sulfate treated HK-2 cells. These results demonstrate that α-lipoic acid attenuated p-cresyl sulfate-induced cell death by suppression of apoptosis and autophagy via regulation of ER stress in HK-2 cells.

Copper-Mediated Mitochondrial Fission/Fusion Is Associated with Intrinsic Apoptosis and Autophagy in the Testis Tissues of Chicken

The aim of this study is to investigate whether copper (Cu) could induce testicular poisoning and influence the mitochondrial dynamics, apoptosis, and autophagy in chickens. For this purpose, thirty-six 1-day-old male Hy-line chickens were divided into control group (C group) and test group (Cu group). The chickens were exposed to 0 (C group) or 300 mg/kg (Cu group) of copper sulfate (CuSO₄) for 30, 60, and 90 days. CuSO₄ was added into the basal diet to make supplements. Testis tissues were subjected to observation of ultrastructure and detection of testis-related indexes. The results indicated that in the test group, the levels of the pro-apoptotic genes were up-regulated and the levels of the anti-apoptotic genes were down-regulated; the levels of mitochondrial fission-related genes markedly increased, and the levels of mitochondrial fusion-related genes were highly decreased; autophagy-related gene (autophagy-associated gene 4B (ATG4B), dynein, microtubule-associated protein 1 light chain 3 beta (LC3-II), ATG5, and beclin-1) levels were increased, while mammalian target of rapamycin (mTOR) and LC3-I levels were declined. The results of transmission electron microscopy (TEM) demonstrated that Cu induced mitochondrial fragmentation, which induced autophagy and apoptosis in chicken testes. In conclusion, CuSO₄ exposure can influence the mitochondrial dynamics balance and lead to mitochondria-initiated intrinsic pathway of apoptosis and autophagy, which triggers the testicular poisoning in chickens. What is more, there is a correlation among mitochondrial dynamics, apoptosis, and autophagy.

Dioscin Alleviates Crystalline Silica-Induced Pulmonary Inflammation and Fibrosis through Promoting Alveolar Macrophage Autophagy

Occupational exposure to crystalline silica (CS) particles leads to silicosis, which is characterized by chronic inflammation and abnormal tissue repair. Alveolar macrophages (AMs) play a crucial role in the process of silicosis. Previously, we demonstrated positive effect of dioscin on silicosis through modulating macrophage-elicited innate immune response. However, the concrete molecular mechanism remains to be discovered.

Methods: We established experimental model of silicosis with wildtype and Atg5^flox/floxDppa3^Cre/+ mice and oral administrated dioscin daily to explore the effects of dioscin on macrophages and pulmonary fibrosis. AM cell line MH-S with Atg5 silence was used to explore specific function of dioscin on macrophage-derived inflammation and the underlying molecular mechanism.

Results: Dioscin could promote autophagy in macrophages. Dioscin-triggered AMs autophagy limited mitochondrial reactive oxygen species (mtROS) mass stimulated by CS, reduced mitochondria-dependent apoptosis pathway activation and facilitated cell survival. Relieved oxidative stress resulted in decreased secretion of inflammatory factors and chemokines. Dioscin treatment alleviated macrophage-derived inflammation and subsequent abnormal collagen repair. All the dioscin's protective effects were diminished in Atg5^flox/floxDppa3^Cre/+ mice.

Conclusion: Dioscin promoting autophagy leads to reduced CS-induced mitochondria-dependent apoptosis and cytokine production in AMs, which may provide concrete molecular mechanism for the therapy of silicosis.

ROS generation and autophagosome accumulation contribute to the DMAMCL-induced inhibition of glioma cell proliferation by regulating the ROS/MAPK signaling pathway and suppressing the Akt/mTOR signaling pathway

Purpose

Chemotherapy after surgery can prolong the survival of patients with gliomas. Dimethylaminomicheliolide (DMAMCL), a novel chemotherapeutic agent, exhibited antitumor properties in acute myeloid leukemia stem cells and showed an increased drug concentration in the brain. This study aims to investigate the specific anticancer activities and mechanisms of DMAMCL in glioma cells.

Materials and methods

In this study, the effects of DMAMCL were evaluated and characterized in U87-MG and U251 glioma cells. Cell viability was assessed by Cell Counting Kit-8. Apoptosis, mitochondrial membrane potential, and intracellular reactive oxygen species (ROS) generation were assessed by fluorescence microscopy. Autophagosome formation was observed with transmission electron microscopy, and the autophagy flux was measured by transfecting cells with mRFP-GFP-LC3 adenoviral vectors. Immunofluorescence and Western blot analyses were used to determine the expression of proteins.

Results

In the present study, treatment with DMAMCL decreased cell viability and induced apoptosis in U87-MG and U251 glioma cells. Additionally, DMAMCL activated autophagy-mediated cell death as evidenced by the formation of autophagosomes, accumulation of LC3B-II, inhibition of autophagy flux, and increase in cell viability after cotreatment with an autophagy inhibitor. Subsequent experiments showed that the DMAMCL-induced apoptosis and autophagy were possibly mediated by ROS generation and Akt/mTOR signaling pathway inhibition. On the other hand, the ROS scavenger N-acetyl-L-cysteine and the Akt activator insulin-like growth factor-1 attenuated the DMAMCL-induced autophagy and cell death.

Conclusion

Our findings revealed that DMAMCL induced apoptosis and autophagic cell death by regulating the ROS/mitogen-activated protein kinase signaling pathway and suppressing the Akt/mTOR signaling pathway in human glioma cells. DMAMCL may be a novel effective anticancer agent, which can target gliomas.

Licochalcone A Inhibits Cellular Motility by Suppressing E-cadherin and MAPK Signaling in Breast Cancer

A compound isolated from Glycyrrhiza uralensis, licochalcone A (LA) exhibits anti-inflammatory and anti-tumor properties in various cell lines. LA has been found to promote autophagy and suppress specificity protein 1, inducing apoptosis in breast cancer cells. However, the regulation of breast cancer cell invasion and migration by LA is elusive. Thus, the present study investigated whether LA induces apoptosis and cellular motility in MDA-MB-231 breast cells, and investigated the underlying molecular mechanisms. MDA-MB-231 cells treated with LA and cell viability measured by cell counting kit-8 assay. Apoptotic signal proteins checked by flow cytometry, fluorescent staining, and Western blot. LA effectively suppressed cell migration, and modulated E-cadherin and vimentin expression by blocking MAPK and AKT signaling. LA inhibited cell proliferation and cell cycle, modulated mitochondrial membrane potential and DNA damage, and reduced oxidative stress in MDA-MB-231 cells. LA also activated cleaved-caspase 3 and 9, significantly decreased Bcl-2 expression, ultimately causing the release of cytochrome c from the mitochondria into the cytoplasm. Overall, our findings suggest that LA decreases cell proliferation and increases reactive oxygen species production for induced apoptosis, and regulates E-cadherin and vimentin by reducing MAPK and AKT signaling, resulting in suppressed MDA-MB-231 cell migration and invasion.

Mn-Induced Neurocytes Injury and Autophagy Dysfunction in Alpha-Synuclein Wild-Type and Knock-Out Mice: Highlighting the Role of Alpha-Synuclein

Overexposure to manganese (Mn) is an important environmental risk factor for Parkinsonian-like symptoms referred to as manganism. Alpha-synuclein (α-Syn) oligomerization is a major cause in Mn-induced neurotoxicity. Autophagy, as an adjust response to control intracellular protein homeostasis, is involved in the degradation of α-Syn monomers or oligomers. Furthermore, autophagy dysregulation is also related to development of neurodegenerative disorders. Hence, we speculated that there was an interaction effect between α-Syn oligomerization and autophagy upon Mn exposure. In this study, we applied α-Syn gene knockout mice (α-Syn^-/-) and wild-type mice (α-Syn^+/+) treated with three different concentrations of MnCl₂ (50, 100, and 200 μmol/kg) to elucidate the physiological role of α-Syn in Mn-induced autophagy dysregulation and neurocytes injury. We found that activation of chaperone-mediated autophagy (CMA) pathway by Mn was independent of α-Syn. Additionally, α-Syn could ameliorate excessive autophagy induced by high dose Mn (200 μmol/kg). Next, we used 5 mg/kg Rapamycin (Rap) or 3-methyladenine (3-MA) to regulate autophagy. The study revealed that autophagy is involved in Mn-induced α-Syn oligomerization and neurocytes injury. Taken together, these findings indicated that α-Syn oligomerization might be the major responsible for the Mn-induced autophagy dysregulation and neurocytes injury.

Two distinct cellular pathways leading to endothelial cell cytotoxicity by silica nanoparticle size

Background

Silica nanoparticles (SiNPs) are widely used for biosensing and diagnostics, and for the targeted delivery of therapeutic agents. Safety concerns about the biomedical and clinical applications of SiNPs have been raised, necessitating analysis of the effects of their intrinsic properties, such as sizes, shapes, and surface physicochemical characteristics, on human health to minimize risk in biomedical applications. In particular, SiNP size-associated toxicological effects, and the underlying molecular mechanisms in the vascular endothelium remain unclear. This study aimed to elucidate the detailed mechanisms underlying the cellular response to exposure to trace amounts of SiNPs and to determine applicable size criteria for biomedical application.

Methods

To clarify whether these SiNP-mediated cytotoxicity due to induction of apoptosis or necrosis, human ECs were treated with SiNPs of four different non-overlapping sizes under low serum-containing condition, stained with annexin V and propidium iodide (PI), and subjected to flow cytometric analysis (FACS). Two types of cell death mechanisms were assessed in terms of production of reactive oxygen species (ROS), endoplasmic reticulum (ER) stress induction, and autophagy activity.

Results

Spherical SiNPs had a diameter of 21.8 nm; this was further increased to 31.4, 42.9, and 56.7 nm. Hence, we investigated these effects in human endothelial cells (ECs) treated with these nanoparticles under overlap- or agglomerate-free conditions. The 20-nm SiNPs, but not SiNPs of other sizes, significantly induced apoptosis and necrosis. Surprisingly, the two types of cell death occurred independently and through different mechanisms. Apoptotic cell death resulted from ROS-mediated ER stress. Furthermore, autophagy-mediated necrotic cell death was induced through the PI3K/AKT/eNOS signaling axis. Together, the present results indicate that SiNPs within a diameter of < 20-nm pose greater risks to cells in terms of cytotoxic effects.

Conclusion

These data provide novel insights into the size-dependence of the cytotoxic effects of silica nanoparticles and the underlying molecular mechanisms. The findings are expected to inform the applicable size range of SiNPs to ensure their safety in biomedical and clinical applications.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0456-4) contains supplementary material, which is available to authorized users.

Autophagy: Dual Response in the Development of Hepatocellular Carcinoma

Autophagy is an evolutionary conserved intracellular mechanism which helps eukaryotic cells in maintaining their metabolic state to afford high-efficiency energy requirements. In the physiology of a normal liver and the pathogenesis of liver diseases, autophagy plays a crucial role. Autophagy has been found to be both upregulated and downregulated in different cancers providing the evidence that autophagy plays a dual role in suppressing and promoting cell survival. Hepatocellular carcinoma (HCC) is the most common primary liver cancer and the major leading cause of cancer mortality worldwide. In light of its high complexity and poor prognosis, it is essential to improve our understanding of autophagy’s role in HCC. In this review, we summarize the dual mechanism of autophagy in the development of HCC and elucidate the currently used therapeutic strategies for anti-HCC therapy.

Complementary and distinct roles of autophagy, apoptosis and senescence during early inner ear development

The development of the inner ear complex cytoarchitecture and functional geometry requires the exquisite coordination of a variety of cellular processes in a temporal manner. At early stages of inner ear development several rounds of cell proliferation in the otocyst promote the growth of the structure. The apoptotic program is initiated in exceeding cells to adjust cell type numbers. Apoptotic cells are cleared by phagocytic cells that recognize the phosphatidylserine residues exposed in the cell membrane thanks to the energy supplied by autophagy. Specific molecular programs determine hair and supporting cell fate, these populations are responsible for the functions of the adult sensory organ: detection of sound, position and acceleration. The neurons that transmit auditory and balance information to the brain are also born at the otocyst by neurogenesis facilitated by autophagy. Cellular senescence participates in tissue repair, cancer and aging, situations in which cells enter a permanent cell cycle arrest and acquire a highly secretory phenotype that modulates their microenvironment. More recently, senescence has also been proposed to take place during vertebrate development in a limited number of transitory structures and organs; among the later, the endolymphatic duct in the inner ear. Here, we review these cellular processes during the early development of the inner ear, focusing on how the most recently described cellular senescence participates and cooperates with proliferation, apoptosis and autophagy to achieve otic morphogenesis and differentiation.

Is Autophagy Involved in the Diverse Effects of Antidepressants?

Autophagy has received increased attention as a conserved process governing cellular energy and protein homeostasis that is thus relevant in a range of physiological and pathophysiological conditions. Recently, autophagy has also been linked to depression, mainly through its involvement in the action of antidepressants. Some antidepressant drugs and psychotropic medication have been reported to exert beneficial effects in other diseases, for example, in cancer and neurodegenerative diseases. This review collates the evidence for the hypothesis that autophagy contributes to the effects of antidepressants beyond depression treatment.

Is There a Role of Autophagy in Depression and Antidepressant Action?

Autophagy has been recognized as evolutionary conserved intracellular pathway that ensures energy, organelle, and protein homeostasis through lysosomal degradation of damaged macromolecules and organelles. It is activated under various stress situations, e.g., food deprivation or proteotoxic conditions. Autophagy has been linked to several diseases, more recently also including stress-related diseases such as depression. A growing number of publications report on the role of autophagy in neurons, also referred to as "neuronal autophagy" on the one hand, and several studies describe effects of antidepressants-or of compounds that exert antidepressant-like actions-on autophagy on the other hand. This minireview highlights the emerging evidence for the involvement of autophagy in the pathology and treatment of depression and discusses current limitations as well as potential avenues for future research.

Corynoxine B ameliorates HMGB1-dependent autophagy dysfunction during manganese exposure in SH-SY5Y human neuroblastoma cells

Manganese (Mn) has recently come into the limelight as an important environmental risk factor for neurodegenerative disorders. Although multiple neurotoxicity of Mn have been extensively studied, the exact mechanism of Mn-induced autophagic dysregulation is still poorly understood. The main aim of this study was to explore the role of cytosolic high-mobility group box 1 (HMGB1)-dependent autophagy in Mn-induced autophagic dysregulation and neurotoxicity. SH-SY5Y cells were treated with culture solution (control) and three different concentrations of Mn (50, 100, and 200 μM) for 24 h to detect the effect of Mn on HMGB1-dependent autophagy. We found Mn could increase the HMGB1 mRNA level and its cytosolic translocation and dysregulate autophagy, and Mn-induced alpha-synuclein overexpression interfered with the interaction of HMGB1 and Beclin1, to subsequently promote Beclin1 binding to Bcl2. Another important finding was the neuroprotective role of corynoxine B (Cory B) in Mn-induced autophagic dysregulation and neurotoxicity. We set up six experimental groups: control (culture solution); 200 μM Mn treatment; 100 μM Cory B-alone treatment; and three different pretreated concentrations of Cory B (25, 50, and 100 μM). Our results showed that Cory B ameliorated Mn-induced autophagic dysregulation and neurotoxicity partly by dissociating HMGB1 from alpha-synuclein and inhibiting mTOR signaling.

ERK-mediated autophagy promotes inactivated Sendai virus (HVJ-E)-induced apoptosis in HeLa cells in an Atg3-dependent manner

Background

Apoptosis and autophagy are known to play important roles in cancer development. It has been reported that HVJ-E induces apoptosis in cancer cells, thereby inhibiting the development of tumors. To define the mechanism by which HVJ-E induces cell death, we examined whether HVJ-E activates autophagic and apoptotic signaling pathways in HeLa cells.

Methods

Cells were treated with chloroquine (CQ) and rapamycin to determine whether autophagy is involved in HVJ-E-induced apoptosis. Treatment with the ERK inhibitor, U0126, was used to determine whether autophagy and apoptosis are mediated by the ERK pathway. Activators of the PI3K/Akt/mTOR/p70S6K pathway, 740 Y-P and SC79, were used to characterize its role in HVJ-E-induced autophagy. siRNA against Atg3 was used to knock down the protein and determine whether it plays a role in HVJ-E-induced apoptosis in HeLa cells.

Results

We found that HVJ-E infection inhibited cell viability and induced apoptosis through the mitochondrial pathway, as evidenced by the expression of caspase proteins. This process was promoted by rapamycin treatment and inhibited by CQ treatment. HVJ-E-induced autophagy was further blocked by 740 Y-P, SC79, and U0126, indicating that both the ERK- and the PI3K/Akt/mTOR/p70S6K-pathways were involved. Finally, autophagy-mediated apoptosis induced by HVJ-E was inhibited by siRNA-mediated Atg3 knockdown.

Conclusion

In HeLa cells, HVJ-E infection triggered autophagy through the PI3K/Akt/mTOR/p70S6K pathway in an ERK1/2-dependent manner, and the induction of autophagy promoted apoptosis in an Atg3-dependent manner.

Inhibition of EZH2 and EGFR produces a synergistic effect on cell apoptosis by increasing autophagy in gastric cancer cells

Background

Numerous reports have shown that a combination of two or more drugs leads to better cancer treatment. Inhibitors of zeste homology 2 and epidermal growth factor receptor have been widely used in cancer treatments. However, the mechanisms of the combined use of these two drugs remain elusive.

Methods

Sulforhodamine B assays and Alexa Fluor^®-488 Annexin V/Dead Cell Apoptosis Kit were used to detect the cell proliferation and cell apoptosis in vitro, respectively. Western blotting analysis was used to detect the relative protein expression, and xenografted tumor was generated in nude mice to evaluate the effect in vivo.

Results

Treatment with either Gefitinib ranging from 0 to 12.5 µM or GSK126 ranging from 0 to 8.3 µM caused a dose-dependent decrease in the cell survival fraction, and the combination of Gefitinib at 12.5 µM and GSK126 at 8.3 µM caused further significant decrease. The combination indexes were 0.061, 0.591, 0.713, and 0.371 for MGC803, A549, PC-3, and MDB-MA-231, respectively. In MGC803 cells, the combination of GSK126 and Gefitinib synergistically induced cell apoptosis (56.2%), which was markedly higher as compared to either drug alone (7.6% and 10.6%, P<0.05). Treatment with either Gefitinib or GSK126 alone induced a significant increase in cell apoptosis in LC3-II and p-ULK, whereas the combination of the two induced a further increase. Pretreatment with an autophagy inhibitor, 3-methyladenine, prevented the apoptosis induced by the combined use of Gefitinib and GSK126. In addition, the combined use of Gefitinib and GSK126 also inhibited the activation of mammalian target of rapamycin signaling pathway. Furthermore, the combined use of GSK126 and Gefitinib synergistically inhibited xenografted tumor proliferation.

Conclusion

The combined use of GSK126 and Gefitinib exerts a synergic effect on tumor growth inhibition both in vitro and in vivo through inducing autophagy and promoting apoptosis. Therefore, GSK126 and Gefitinib in combination may be considered as a potential strategy in treating solid tumor clinically.

Patulin Induces Autophagy-Dependent Apoptosis through Lysosomal-Mitochondrial Axis and Impaired Mitophagy in HepG2 Cells

Patulin (PAT) is a compound produced by fungi including those of the Aspergillus, Penicillium, and Byssochlamys species. PAT has been linked with negative outcomes in certain microorganisms and animal species, but how it causes hepatotoxicity is poorly understood. In this study, we determined that, by treating HepG2 cells using PAT, these cells could be induced to rapidly undergo autophagy, and this was followed within 12 h of treatment by lysosomal membrane permeabilization (LMP) and cathepsin B release. We were able to block these outcomes if cells were treated with 3-methyladenine (3MA), an inhibitor of autophagy, prior to PAT treatment. Moreover, PAT-induced collapse of mitochondrial membrane potential (ΔΨm) depended both on cathepsin B and autophagy. 3MA was further able to reduce the induction of apoptosis in response to PAT, suggesting that autophagy is a driving mechanism for this apoptotic induction. Inhibiting cathepsin B using CA-074 Me further reduced PAT-induced collapses of ΔΨm, mitochondiral cytochrome c release, and apoptosis. We also found that extended treatment of HepG2 cells using PAT over a period of 24 h led to the impairment of mitophagy such that morphologically swollen mitochondria accumulated within cells, and PINK1 failed to colocalize with LC3. Together these data reveal that PAT treatment can promote the induction of apoptosis in HepG2 cells in a manner dependent upon autophagy that progresses via the lysosomal-mitochondrial axis. This study thereby affords new insights into the mechanisms by which PAT drives hepatotoxicity.

The functional role of Bax/Bak in palmitate-induced lipoapoptosis

Induction of programmed cell death, mainly apoptosis (lipoapoptosis) is a major cellular consequence of the lipotoxicity, a harmful effect resulting from the overload of lipids. Both Endoplasmic reticulum (ER) stress and autophagy have been suggested to play important role in the regulation of lipoapoptosis. However, the exact mechanisms underlying lipoapoptosis remain unclear. In the present study, we aimed to investigate the functional role of Bax/Bak in lipoapoptosis using mouse embryonic fibroblasts (MEFs) cell culture model. Results showed that palmitate induced caspase-dependent apoptosis in wild-type Bax/Bak MEF cells, whereas a caspase-independent cell death was induced by palmitate in Bax/Bak knockout MEF cells, suggesting requirement of Bax/Bak in palmitate-induced caspase activation. More importantly, we found that the status of Bax/Bak is a determinant that governs the decision between the pro-survival or pro-death function of autophagy in response to palmitate exposure, and Bax/Bak is required for palmitate-induced activation of endoplasmic reticulum (ER) stress and subsequently ER stress-mediated apoptosis. The findings of the present study provided novel insights into understanding the mechanisms involved in the regulation of palmitate-induced lipoapoptosis.

Epithelial Cdc42 Deletion Induced Enamel Organ Defects and Cystogenesis

Cdc42, a Rho family small GTPase, regulates cytoskeleton organization, vesicle trafficking, and other cellular processes in development and homeostasis. However, Cdc42's roles in prenatal tooth development remain elusive. Here, we investigated Cdc42 functions in mouse enamel organ. Cdc42 showed highly dynamic temporospatial patterns in the developing enamel organ, with robust expression in the outer enamel epithelium, stellate reticulum (SR), and stratum intermedium layers. Strikingly, epithelium-specific Cdc42 deletion resulted in cystic lesions in the enamel organ. Cystic lesions were first noted at embryonic day 15.5 and progressively enlarged during gestation. At birth, cystic lesions occupied the bulk of the entire enamel organ, with intracystic erythrocyte accumulation. Ameloblast differentiation was retarded upon epithelial Cdc42 deletion. Apoptosis occurred in the Cdc42 mutant enamel organ prior to and synchronously with cystogenesis. Transmission electron microscopy examination showed disrupted actin assemblies, aberrant desmosomes, and significantly fewer cell junctions in the SR cells of Cdc42 mutants than littermate controls. Autophagosomes were present in the SR cells of Cdc42 mutants relative to the virtual absence of autophagosome in the SR cells of littermate controls. Epithelium-specific Cdc42 deletion attenuated Wnt/β-catenin and Shh signaling in dental epithelium and induced aberrant Sox2 expression in the secondary enamel knot. These findings suggest that excessive cell death and disrupted cell-cell connections may be among multiple factors responsible for the observed cystic lesions in Cdc42 mutant enamel organs. Taken together, Cdc42 exerts multidimensional and pivotal roles in enamel organ development and is particularly required for cell survival and tooth morphogenesis.

The regulatory roles of glycosphingolipid-enriched lipid rafts in immune systems

Lipid rafts formed by glycosphingolipids (GSLs) on cellular membranes play important roles in innate and adaptive immunity. Lactosylceramide (LacCer) forms lipid rafts on plasma and granular membranes of human neutrophils. These LacCer-enriched lipid rafts bind directly to pathogenic components, such as pathogenic fungi-derived β-glucan and Mycobacteria-derived lipoarabinomannan via carbohydrate-carbohydrate interactions, and mediate innate immune responses to these pathogens. In contrast, a-series and o-series gangliosides form distinct rafts on CD4⁺ and CD8⁺ T cell subsets, respectively, contributing to the respective functions of these cells and stimulating adaptive immune responses through T cell receptors. These findings suggest that gangliosides play indispensable roles in T cell selection and activation. This Review introduces the involvement of GSL-enriched lipid rafts in innate and adaptive immunity.

Cr (VI) induces crosstalk between apoptosis and autophagy through endoplasmic reticulum stress in A549 cells

Hexavalent chromium [Cr (VI)], which is widely found in occupational environments, is a recognized human carcinogen. In this study, the role of endoplasmic reticulum (ER) stress in Cr (VI)-induced crosstalk of apoptosis and autophagy was investigated. Cr (VI) resulted in ER stress by upregulating the expression of GRP78 and p-PERK. 4-Phenylbutyric acid (4PBA), an inhibitor of ER stress, reduced both Cr (VI)-induced apoptosis and autophagy, suggesting that ER stress played an important role in Cr (VI)-induced apoptosis and autophagy in A549 cells. Furthermore, Cr (VI)-induced apoptosis preceded autophagy. Z-VAD-FMK, the suppressor of apoptosis, repressed Cr (VI)-induced autophagy. Pretreatment with 3-MA, the inhibitor of autophagy, increased Cr (VI)-induced apoptosis. Exposure to Cr (VI) significantly reduced mitochondrial membrane potential (MMP) during Cr (VI) treatment for 6-12 h. However, Cr (VI)-reduced MMP rescued significantly after treatment with Cr (VI) for 24 h compared with that of 6 h and 12 h groups, suggesting that Cr (VI)-induced autophagy at 24 h might rescue Cr (VI)-induced decrease of MMP through engulfing damaged mitochondria and then inhibit apoptosis in A549 cells. Above all, our results indicated that Cr (VI)-induced ER stress plays an important role in the crosstalk between apoptosis and autophagy. The autophagy might be apoptosis-dependent and subsequently prevents apoptosis cell death to keep A549 cells resistant to Cr (VI)-induced further toxicity. This maybe underlies the mechanism of Cr (VI)-induced carcinogenesis.

The synergistic anticancer effect of formosanin C and polyphyllin VII based on caspase-mediated cleavage of Beclin1 inhibiting autophagy and promoting apoptosis

OBJECTIVES

Drug combination has a promising and potential development prospect in the treatment of various cancers. The objective of this study is to investigate the synergistic mechanisms of polyphyllin VII (PVII) and formosanin C (FC) in lung cancer.

MATERIALS AND METHODS

The combination of FC and PVII influenced on the apoptosis, autophagy, and the relative signalling pathways were analysed in lung cancer cells.

RESULTS

The combination of FC and PVII demonstrated a concentration- dependent growth inhibition in human lung cancer cells. The combination index (CI) obtained from four lung cancer cells was smaller than 1. This synergistic antitumour effect was based on the increase of their single proapoptotic effect but inhibiting FC-induced autophagy in NCI-H460 cells. FC and PVII activated proapoptotic elements like cleaved-caspase-3, -8, and -9 to induce Beclin1 cleaved into Beclin1-C which suppressed FC-triggered autophagy and enhanced apoptosis.

CONCLUSIONS

Formosanin C and PVII showed a synergistic antitumour effect on lung cancer cells. The findings would provide the foundation for the use of combination drugs in the future.

Antitumor effects of arsenic disulfide on the viability, migratory ability, apoptosis and autophagy of breast cancer cells

In the present study, the antitumor effects of arsenic disulfide (As₂S₂) on the proliferative, survival and migratory ability of human breast cancer MCF-7 and MDA-MB-231 cells were investigated, and its potential underlying molecular mechanisms with an emphasis on cell cycle arrest, apoptosis induction, autophagy induction and reactive oxygen species (ROS) generation were determined. The results indicated that As₂S₂ significantly inhibited the viability, survival and migration of breast cancer cells in a dose-dependent manner. In addition, it was identified that As₂S₂ induced cell cycle arrest primarily at G₂/M phase in the two breast cancer cell lines by regulating the expression of associated proteins, including cyclin B1 and cell division cycle protein 2. In addition to cell cycle arrest, As₂S₂ also triggered the induction of apoptosis in cells by activating the expression of pro-apoptotic proteins, including caspase-7 and −8, as well as increasing the B-cell lymphoma 2 (Bcl-2)-associated X protein/Bcl-2 ratio, while decreasing the protein expression of anti-apoptotic B-cell lymphoma extra-large. In addition, As₂S₂ stimulated the accumulation of microtubule-associated protein 1A/1B-light chain 3 (LC3)-II and increased the LC3-II/LC3-I ratio, indicating the occurrence of autophagy. As₂S₂ treatment also inhibited the protein expression of matrix metalloproteinase-9 (MMP-9), but increased the intracellular accumulation of ROS in the two breast cancer cell lines, which may assist in alleviating metastasis and attenuating the progression of breast cancer. Taken together, the results of the present study suggest that As₂S₂ inhibits the progression of human breast cancer cells through the regulation of cell cycle arrest, intrinsic and extrinsic apoptosis, autophagy, MMP-9 signaling and ROS generation.

Berberine attenuates apoptosis in rat retinal Müller cells stimulated with high glucose via enhancing autophagy and the AMPK/mTOR signaling

Berberine (BBR) has beneficial effects on diabetes and the multiple complications of diabetes due to its anti-apoptotic activity; however, the effect of BBR on diabetic retinopathy and its mechanism of action have not been clarified. The present study investigated the effect of BBR on Müller cells stimulated with high glucose (HG). Primary retinal Müller cells were incubated with high glucose to induce cell apoptosis; cells were pretreated with the AMPK inhibitor compound C and the AMPK activator AICAR to further explore the role of the AMPK/mTOR signaling pathway in the anti-apoptotic action of BBR. Immunofluorescence was used to measure apoptosis and autophagy. Western blot analysis was employed to determine the levels of p-AMPK and p-mTOR, as well as apoptosis-related proteins and autophagy-related proteins in Müller cells. Our results showed that BBR attenuated apoptosis, up regulated Bcl-2 and down regulated Bax and caspase-3 expression; enhanced the formation of autophagy, elevated the expression of Beclin-1 and LC3II and activated the AMPK/mTOR signaling pathway in Müller cells under high glucose conditions compared with the control group. The effect of BBR was partly blocked by compound C and strengthened by AICAR. BBR may have therapeutic potential to protect Müller cells from high-glucose-inducing apoptosis through enhancing autophagy and activating the AMPK/mTOR signaling pathway.

Ambiguous Effects of Autophagy Activation Following Hypoperfusion/Ischemia

Autophagy primarily works to counteract nutrient deprivation that is strongly engaged during starvation and hypoxia, which happens in hypoperfusion. Nonetheless, autophagy is slightly active even in baseline conditions, when it is useful to remove aged proteins and organelles. This is critical when the mitochondria and/or proteins are damaged by toxic stimuli. In the present review, we discuss to that extent the recruitment of autophagy is beneficial in counteracting brain hypoperfusion or, vice-versa, its overactivity may per se be detrimental for cell survival. While analyzing these opposite effects, it turns out that the autophagy activity is likely not to be simply good or bad for cell survival, but its role varies depending on the timing and amount of autophagy activation. This calls for the need for an appropriate autophagy tuning to guarantee a beneficial effect on cell survival. Therefore, the present article draws a theoretical pattern of autophagy activation, which is hypothesized to define the appropriate timing and intensity, which should mirrors the duration and severity of brain hypoperfusion. The need for a fine tuning of the autophagy activation may explain why confounding outcomes occur when autophagy is studied using a rather simplistic approach.

Citrus peel polymethoxyflavones, sudachitin and nobiletin, induce distinct cellular responses in human keratinocyte HaCaT cells

A variety of polyphenols have been isolated from plants, and their biological activities have been examined. Sudachitin (5,7,4'-trihydroxy-6,8,3'-trimethoxyflavone) is a polymethoxyflavone that is isolated from the peel of Citrus sudachi. Although we previously reported that sudachitin possesses an anti-inflammatory activity, its other biological activities are not yet understood. In this study, we report a novel biological activity of sudachitin, which selectively induced apoptosis in human keratinocyte HaCaT cells. Another polymethoxyflavone, nobiletin (5,6,7,8,3',4'-hexamethoxyflavone), promoted autophagy but not apoptosis in HaCaT cells. On the other hand, 3'-demethoxysudachitin (5,7,4'-trihydroxy-6,8-dimethoxyflavone) failed to induce apoptosis and autophagy. These results show that three polymethoxyflavones have different effects on apoptosis and autophagy in HaCaT cells. Understanding the structure and biological activity of polymethoxyflavones may lead to the discovery of potential candidates for cancer drug development without significant toxic side effects. Abbreviations: ROS: reactive oxygen species; DMSO: dimethyl sulfoxide; MTT: 3-(4, 5-dimethylthiazol-2yl)-2, 5-diphenyltetrazolium bromide; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; PARP: poly(ADP-ribose) polymerase; PI: propidium iodide; MAPK: mitogen-activated protein kinase.

A cell's agony of choice: how to cross the Styx? : From morphological to molecular approaches to disclose its decision

The original “apoptosis–necrosis” concept was based on morphology and (patho)physiological conditions of the occurrence of cell death: (1) apoptosis, with nuclear and cytoplasmic condensation/fragmentation prominent, exclusion of autolysis, considered to result from coordinated self-destruction of a cell; (2) necrosis, with cell lysis prominent, caused by violent environmental perturbation leading to collapse of internal homeostasis. This suggestion initiated a controversial discussion within the scientific community and it soon became clear that the “apoptosis–necrosis dichotomy” was not generally applicable. Nowadays, there is sufficient evidence that cells may activate diverse suicide pathways, thereby allowing a flexible response to environmental changes, either physiological or pathological. The present paper commemorates electron microscopic and cytochemical studies on cell death of cultured human mammary carcinoma cells performed by Adi Ellinger, adding a significant contribution to recognize that autophagy can be involved in regulated cell death, thereby challenging the apoptosis–necrosis dichotomy still predominant in the 1990s.

[Role of cytoplasmic p53-mediated suppression of autophagy in heat stress-induced injury of cultured mouse aortic endothelial cells]

OBJECTIVE

To explore the association of cytoplasmic p53 with autophagy and apoptosis of primary aortic endothelial cells (MAECs) exposed to heat stress.

METHODS

Cultured mouse MAECs were exposed to heat stress induced by incubation at 43 ℃ for 2 h, with the cells in routine culture condition (37 ℃, 5% CO₂) as the control group. All the cells were further incubated for 1, 3, 6 or 9 h at 37 ℃ before treatment with the autophagy inhibitor 3-MA (5 mmol/L), the autophagy inducer rapamycin (20 μmol/L), or the p53 inhibitor PFT (10 μmol/L) for 1 h. After the treatments, the cell viability was measured with CCK8 method, cell apoptosis analyzed by flow cytometry, and the mitochondrial membrane potential detected with flow cytometry with JC-1 staining; the subcellular localization of p53 and the autophagy- associated protein LC3-Ⅱ was detected with immunofluorescence staining, and their protein expressions were analyzed using Western blotting.

RESULTS

Compared with the control cells, MAECs exposed to heat stress showed significantly decreased viability (P < 0.05). At 6 h after the exposure, the cells exhibited significantly decreased mitochondrial membrane potential with increased apoptotic rate (P < 0.05). The cytoplasmic fraction of p53 expression decreased and its mitochondrial fraction increased gradually with time within 6 h after heat stress. Treatment with 3- MA further decreased the mitochondrial membrane potential and significantly increased the apoptotic rate of the exposed cells (P < 0.05), while rapamycin obviously reversed these heat stress-induced cell injuries (P < 0.05). PFT significantly enhanced the expression of LC3-Ⅱ and also inhibited heat stress-induced mitochondrial membrane potential reduction and cell apoptosis (P < 0.05).

CONCLUSIONS

Heat stress induces mitochondrial damage and apoptosis in MAECs possibly in relation with mitochondrial translocation of cytoplasmic p53 to result in autophagy inhibition.

Effect of autophagy on allodynia, hyperalgesia and astrocyte activation in a rat model of neuropathic pain

Primary damage or dysfunction of the nervous system may cause or initiate neuropathic pain. However, it has been difficult to establish an effective treatment for neuropathic pain, as the mechanisms responsible for its pathology remain largely unknown. Autophagy is closely associated with the pathological process of neurodegenerative diseases, neuropathic injury and cancer, among others. The aim of the present study was to examine the changes in the autophagy-lysosomal pathway and discuss the effects of autophagy on allodynia, hyperalgesia and astrocyte activation in neuropathic pain. A neuropathic pain model was induced by chronic constriction injury (CCI) in rats. Inducers and inhibitors of autophagy and lysosomes were used to assess autophagy, allodynia, hyperalgesia and astrocyte activity. Neuropathic pain was found to induce an increase in the levels of the autophagy-related proteins, LC3II and Beclin 1 and, and in those of the lysosomal proteins, lysosomal-associated membrane protein type 2 (LAMP2) and Ras-related protein Rab-7a (RAB7), whereas p62 levels were found to decrease from day 1 to 14 following CCI. The autophagy inducer, rapamycin, further increased the LC3II, Beclin 1, lysosomal-associated membrane protein 2 (LAMP2) and Ras-related protein Rab-7a (RAB7) expression levels, and decreased the p62 expression levels, which were accompanied by alleviation of allodynia, hyperalgesia and astrocyte activation in the rats subjected to CCI; the autophagy inhibitor, 3-methyladenine, reversed these effects. The use of the lysosomal inhibitors, bafilomycin and chloroquine, resulted in the accumulation of LC3II and Beclin 1, a decrease in the levels of LAMP2 and RAB7, and the exacerbation of allodynia, hyperalgesia and astrocyte activation in rats with neuropathic pain. On the whole, the findings of this study indicate that neuropathic pain activates autophagy, which alleviates mechanical and thermal hyperalgesia and suppresses astrocyte activity. Therefore, neuropathic pain induced by CCI in rats appears to be mediated via the autophagy-lysosomal pathway.

Sonodynamic therapy: A potential treatment for atherosclerosis

Atherosclerosis (AS), a chronic arterial disease, is one of the major causes of morbidity and mortality worldwide. Several treatment modalities have been demonstrated to be effective in treating AS; however, the mortality rate due to AS remains high. Sonodynamic therapy (SDT) is a promising new treatment using low-intensity ultrasound in combination with sonosensitizers. Although SDT was developed from photodynamic therapy (PDT), it has a stronger tissue-penetrating capability and exhibits a more focused effect on the target lesional site requiring treatment. Furthermore, SDT has been demonstrated to suppress the formation of atheromatous plaques, and it can increase plaque stability both in vitro and in vivo. In this article, we critically summarize the recent literature on SDT, focusing on its possible mechanism of action as well as the existing and newly discovered sonosensitizers and chemotherapeutic agents for the treatment of AS.

Effect of RFRP-3, the mammalian ortholog of GnIH, on the epididymis of male rats

RFamide-related peptide-3 (RFRP-3) and its receptor (GPR147) play an important role in reproduction regulation in mammals. To understand the role of RFRP-3 in male reproductive function of epididymis, we first investigated the expression changes in RFRP-3 and its receptor at different stages of development, that is, postnatal day 20 (P20), 40 (P40), 60 (P60) and 80 (P80). Our results showed that fluctuations in the expression of GnIH and GPR147 during postnatal development occurred, and the highest epididymal GnIH and GPR147 expression were both detected in P60. Subsequently, we further investigated the effect of RFRP-3 on the histology, apoptosis and autophagy of the epididymis in vivo. For in vivo study, male rats were treated intratesticularly with different doses of RFRP-3 (control, 0.1 μg, 1 μg, and 10 μg per day) for 7 days. Our results show that RFRP-3 caused dose-dependent histological changes in the epididymal duct, such as a decline in the number of spermatozoa and an increase in degenerated and vacuolated epididymal epithelial cells. Rats treated intratesticularly with RFRP-3 also showed dose-dependent effects on caspase-3 activation and the expression of apoptotic markers (whole caspase-3, cleaved caspase-3 and Bcl-2). However, the expression of autophagy markers (Beclin-1 and Atg5) exhibited a bidirectional, dose-dependent effect. It is concluded that RFRP-3 plays a regulatory role in male rat reproduction, possibly because RFRP-3 mediates the apoptosis and autophagy of the epididymis.

Delphinidin induces apoptosis and inhibits epithelial-to-mesenchymal transition via the ERK/p38 MAPK-signaling pathway in human osteosarcoma cell lines

Delphinidin is major anthocyanidin that is extracted from many pigmented fruits and vegetables. This substance has anti-oxidant, anti-inflammatory, anti-angiogenic, and anti-cancer properties. In addition, delphinidin strongly suppresses the migration and invasion of various cancer cells during tumorigenesis. Although delphinidin has anti-cancer effects, little is known about its functional roles in osteosarcoma (OS). For these reasons, we have demonstrated the effects of delphinidin on OS cell lines. The effects of delphinidin on cell viability and growth of OS cells were assessed using the MTT assay and colony formation assays. Hoechst staining indicated that the delphinidin-treated OS cells were undergoing apoptosis. Flow cytometry, confocal microscopy, and a western blot analysis also indicated evidence of apoptosis. Inhibition of cell migration and invasion was found to be associated with epithelial-to-mesenchymal transition (EMT), observed by using a wound healing assay, an invasion assay, and a western blot analysis. Furthermore, delphinidin treatment resulted in a profound reduction of phosphorylated forms of ERK and p38. These findings demonstrate that delphinidin treatment suppressed EMT through the mitogen-activated protein kinase (MAPK) signaling pathway in OS cell lines. Taken together, our results suggest that delphinidin strongly inhibits cell proliferation and induces apoptosis. Delphinidin treatment also suppresses cell migration and prevents EMT via the MAPK-signaling pathway in OS cell lines. For these reasons, delphinidin has anti-cancer effects and can suppress metastasis in OS cell lines, and it might be worth using as an OS therapeutic agent.

Till Death Do Us Part: The Marriage of Autophagy and Apoptosis

Autophagy is a widely conserved catabolic process that is necessary for maintaining cellular homeostasis under normal physiological conditions and driving the cell to switch back to this status quo under times of starvation, hypoxia, and oxidative stress. The potential similarities and differences between basal autophagy and stimulus-induced autophagy are still largely unknown. Both act by clearing aberrant or unnecessary cytoplasmic material, such as misfolded proteins, supernumerary and defective organelles. The relationship between reactive oxygen species (ROS) and autophagy is complex. Cellular ROS is predominantly derived from mitochondria. Autophagy is triggered by this event, and by clearing the defective organelles effectively, it lowers cellular ROS thereby restoring cellular homeostasis. However, if cellular homeostasis cannot be reached, the cells can switch back and choose a regulated cell death response. Intriguingly, the autophagic and cell death machines both respond to the same stresses and share key regulatory proteins, suggesting that the pathways are intricately connected. Here, the intersection between autophagy and apoptosis is discussed with a particular focus on the role ROS plays.

Animal Toxins as Therapeutic Tools to Treat Neurodegenerative Diseases

Neurodegenerative diseases affect millions of individuals worldwide. So far, no disease-modifying drug is available to treat patients, making the search for effective drugs an urgent need. Neurodegeneration is triggered by the activation of several cellular processes, including oxidative stress, mitochondrial impairment, neuroinflammation, aging, aggregate formation, glutamatergic excitotoxicity, and apoptosis. Therefore, many research groups aim to identify drugs that may inhibit one or more of these events leading to neuronal cell death. Venoms are fruitful natural sources of new molecules, which have been relentlessly enhanced by evolution through natural selection. Several studies indicate that venom components can exhibit selectivity and affinity for a wide variety of targets in mammalian systems. For instance, an expressive number of natural peptides identified in venoms from animals, such as snakes, scorpions, bees, and spiders, were shown to lessen inflammation, regulate glutamate release, modify neurotransmitter levels, block ion channel activation, decrease the number of protein aggregates, and increase the levels of neuroprotective factors. Thus, these venom components hold potential as therapeutic tools to slow or even halt neurodegeneration. However, there are many technological issues to overcome, as venom peptides are hard to obtain and characterize and the amount obtained from natural sources is insufficient to perform all the necessary experiments and tests. Fortunately, technological improvements regarding heterologous protein expression, as well as peptide chemical synthesis will help to provide enough quantities and allow chemical and pharmacological enhancements of these natural occurring compounds. Thus, the main focus of this review is to highlight the most promising studies evaluating animal toxins as therapeutic tools to treat a wide variety of neurodegenerative conditions, including Alzheimer's disease, Parkinson's disease, brain ischemia, glaucoma, amyotrophic lateral sclerosis, and multiple sclerosis.