Upregulation of Beclin-1 expression and phosphorylation of Bcl-2 and p53 are involved in the JNK-mediated autophagic cell death

Identification and In Vivo Validation of Unique Anti-Oncogenic Mechanisms Involving Protein Kinase Signaling and Autophagy Mediated by the Investigational Agent PV-10

PV-10 is a 10% formulation of rose bengal sodium that has potent immunotherapeutic and anti-cancer activity against various tumors, including metastatic melanoma and refractory neuroblastoma. Currently, PV-10 is undergoing clinical testing for refractory metastatic neuroendocrine cancer and melanomas. However, preclinical investigation of PV-10 activity and its mechanisms against phenotypically and molecularly diverse adult solid tumors had not been conducted. In a panel of human cell lines derived from breast, colorectal, head and neck, and testicular cancers, we demonstrated that PV-10 induces cytotoxicity by apoptotic and autophagic pathways involving caspase-mediated PARP cleavage, downregulation of SQSTM1/p62, and upregulation of beclin-1. Treatment with PV-10 also consistently reduced phosphorylation of WNK1, which has been implicated in cancer cell migration and autophagy inhibition. By wound healing assay, PV-10 treatment inhibited the migration of cancer cells. Finally, significant inhibition of tumor growth was also noted in tumor-bearing mice treated with PV-10 by intralesional or systemic administration. In addition to known PV-10-mediated tumor-specific cytotoxic effects, we identified the mechanisms of PV-10 and provide new insights into its effect on autophagy and metastasis. Our data provide essential mechanism-based evidence and biomarkers of activity to formulate clinical studies of PV-10 in the future.

Targeting autophagy drug discovery: Targets, indications and development trends

Autophagy plays a vital role in sustaining cellular homeostasis and its alterations have been implicated in the etiology of many diseases. Drugs development targeting autophagy began decades ago and hundreds of agents were developed, some of which are licensed for the clinical usage. However, no existing intervention specifically aimed at modulating autophagy is available. The obstacles that prevent drug developments come from the complexity of the actual impact of autophagy regulators in disease scenarios. With the development and application of new technologies, several promising categories of compounds for autophagy-based therapy have emerged in recent years. In this paper, the autophagy-targeted drugs based on their targets at various hierarchical sites of the autophagic signaling network, e.g., the upstream and downstream of the autophagosome and the autophagic components with enzyme activities are reviewed and analyzed respectively, with special attention paid to those at preclinical or clinical trials. The drugs tailored to specific autophagy alone and combination with drugs/adjuvant therapies widely used in clinical for various diseases treatments are also emphasized. The emerging drug design and development targeting selective autophagy receptors (SARs) and their related proteins, which would be expected to arrest or reverse the progression of disease in various cancers, inflammation, neurodegeneration, and metabolic disorders, are critically reviewed. And the challenges and perspective in clinically developing autophagy-targeted drugs and possible combinations with other medicine are considered in the review.

DUSP4 maintains the survival and LSD1 protein stability in esophageal squamous cell carcinoma cells by inhibiting JNK signaling-dependent autophagy

DUSP4 is a biomarker of esophageal squamous cell carcinoma (ESCC), which is responsible for the prognosis in ESCC. However, the underlying mechanism of DUSP4-regulated ESCC carcinogenesis is unknown. As a negative regulator of JNK, DUSP4 can inhibit autophagy, which contributes to tumorigenesis. This study aimed to explore the role of autophagy in DUSP4-regulated ESCC carcinogenesis. Our results showed that DUSP4 overexpression inhibited autophagy and promoted LSD1 protein expression in ESCC cells, while DUSP4 silencing showed the opposite effects. However, DUSP4 overexpression and silencing did not affect LSD1 mRNA expression. But the regulatory ability of DUSP4 overexpression on autophagy, death level, and LSD1 protein was reversed by rapamycin. In addition, DUSP4 overexpression inhibited JNK and Bcl2 phosphorylation and the dissociation of Bcl2-Beclin1 complex, while DUSP4 silencing promoted JNK and Bcl2 phosphorylation. Moreover, the regulatory ability of DUSP4 overexpression on autophagy, death, and LSD1 protein was reversed by JNK activator anisomycin. The xenograft assays also showed that DUSP4 overexpression-promoted ESCC tumor growth in vivo and LC3II and LSD1 protein expression in tumor tissues were reversed by rapamycin or anisomycin. Overall, DUSP4 inhibits Bcl2-Beclin1-autophagy signal transduction through the negative regulation of JNK, thus suppressing autophagic death and the autophagic degradation of LSD1 in ESCC, by which DUSP4 promotes ESCC carcinogenesis.

Potential benefits of medium chain fatty acids in aging and neurodegenerative disease

Neurodegenerative diseases are a large class of neurological disorders characterized by progressive dysfunction and death of neurones. Examples include Alzheimer's disease, Parkinson's disease, frontotemporal dementia, and amyotrophic lateral sclerosis. Aging is the primary risk factor for neurodegeneration; individuals over 65 are more likely to suffer from a neurodegenerative disease, with prevalence increasing with age. As the population ages, the social and economic burden caused by these diseases will increase. Therefore, new therapies that address both aging and neurodegeneration are imperative. Ketogenic diets (KDs) are low carbohydrate, high-fat diets developed initially as an alternative treatment for epilepsy. The classic ketogenic diet provides energy via long-chain fatty acids (LCFAs); naturally occurring medium chain fatty acids (MCFAs), on the other hand, are the main components of the medium-chain triglyceride (MCT) ketogenic diet. MCT-based diets are more efficient at generating the ketone bodies that are used as a secondary energy source for neurones and astrocytes. However, ketone levels alone do not closely correlate with improved clinical symptoms. Recent findings suggest an alternative mode of action for the MCFAs, e.g., via improving mitochondrial biogenesis and glutamate receptor inhibition. MCFAs have been linked to the treatment of both aging and neurodegenerative disease via their effects on metabolism. Through action on multiple disease-related pathways, MCFAs are emerging as compounds with notable potential to promote healthy aging and ameliorate neurodegeneration. MCFAs have been shown to stimulate autophagy and restore mitochondrial function, which are found to be disrupted in aging and neurodegeneration. This review aims to provide insight into the metabolic benefits of MCFAs in neurodegenerative disease and healthy aging. We will discuss the use of MCFAs to combat dysregulation of autophagy and mitochondrial function in the context of "normal" aging, Parkinson's disease, amyotrophic lateral sclerosis and Alzheimer's disease.

CopA3 peptide inhibits MDM2-p53 complex stability in colorectal cancers and activates p53 mediated cell death machinery

The diverse expression patterns of the tumor suppressor p53 in cancer cells reflect the regulatory efficiency of multiple cellular pathways. By contrast, many human tumors are reported to develop in the presence of wild-type p53. Recently, several oncogene inhibitors have been used clinically to suppress tumor development by functionally reactivating other oncoproteins. On the other hand, p53 reactivation therapies have not been well established, as few of the p53-MDM2 complex inhibitors such as Nutlin-3 induces mutation in p53 gene upon prolonged usage. Therefore, in this study CopA3, a 9-mer dimeric D-type peptide with anticancer activity against the human colorectal cancer cells, was used to explore the efficacy of p53 reactivation in-vitro and in-vivo. The anticancer activity of CopA3 was more selective towards the wild-type p53 expressing cells than the p53 deficient or mutant colorectal cancer cells. In response to this, this study investigated the signaling pathway in vitro and validated its anti-tumor activity in-vivo. The protein-peptide interaction and molecular docking efficiently provided insight into the specific binding affinity of CopA3 to the p53-binding pocket of the MDM2 protein, which efficiently blocked the p53 and MDM2 interaction. CopA3 plays a crucial role in the binding with MDM2 and enhanced the nuclear translocation of the p53 protein, which sequentially activated the downstream targets to trigger the autophagic mediated cell death machinery through the JNK/Beclin-1 mediated pathway. Collectively, CopA3 affected the MDM2-p53 interaction, which suppressed tumor development. This study may provide a novel inhibitor candidate for the MDM2-p53 complex, which could ultimately suppress the growth of colorectal cancer cells without being cytotoxic to the healthy neighboring cells present around the tumor microenvironment.

TAT-Beclin 1 represses the carcinogenesis of DUSP4-positive PTC by enhancing autophagy

BACKGROUND

DUSP4 is a pro-tumorigenic molecule of papillary thyroid carcinoma (PTC). DUSP4 also exists as an autophagic regulator. Moreover, DUSP4, as a negative regulator of MAPK, can prevent Beclin 1 from participating in autophagic response. This study aimed to explore whether TAT-Beclin 1, a recombinant protein of Beclin 1, could inhibit the tumorigenesis of DUSP4-positive PTC by regulating autophagy.

METHODS

First, we divided PTC tissues into three groups according to DUSP4 expression levels by immunohistochemical analyses, and evaluated the relationship between autophagic molecules (Beclin 1 and LC3II) and DUSP4 using Western blotting assays. After overexpression of DUSP4 by lentiviral transduction, the in vitro and in vivo roles of TAT-Beclin 1 on DUSP4-overexpressed PTC cells were assessed (including autophagic activity, cell survival and function, and tumor growth). The roles of TAT-Beclin 1 in the survival of DUSP4-silenced PTC cells were also evaluated.

RESULTS

Our results showed that the expression levels of autophagic proteins decreased with the increase of DUSP4 expression in PTC tissues. In PTC cells, DUSP4 overexpression-inhibited autophagic activity (including Beclin 1 expression, LC3 conversion rate and LC3-puncta formation) and -promoted cell proliferation and migration were reversed by TAT-Beclin 1 administration. In vivo assays also showed that DUSP4-overexpressed PTC cells had stronger tumorigenic ability and weaker autophagic activity, which was blocked by TAT-Beclin 1 administration.

CONCLUSION

TAT-Beclin 1, as an autophagic promoter, could repress the carcinogenesis of DUSP4-positive PTC, which implies that the use of TAT-Beclin 1 for the PTC patients' treatment might be determined according to the DUSP4 level in their tumors.

DUSP4 inhibits autophagic cell death and apoptosis in colorectal cancer by regulating BCL2-Beclin1/Bax signaling

BACKGROUND

The DUSP4 gene plays an important role in the carcinogenesis of colorectal cancer (CRC). However, the underlying mechanism of DUSP4-regulated colorectal carcinogenesis is unknown. DUSP4 is a negative regulator of the MAP kinase (MAPK) JNK, and JNK-mediated BCL2 phosphorylation is associated with apoptosis and autophagic cell death. Our study aimed to explore the significance of BCL2 phosphorylation-dependent autophagy and apoptosis in DUSP4-promoted colorectal carcinogenesis.

METHODS

We first investigated the roles of DUSP4 in the survival of HCT116 and SW480 CRC cell lines using gene-silencing and -overexpression techniques. Next, we explored the effects of DUSP4 on the BCL2 phosphorylation, autophagy and apoptosis of HCT116 and SW480 cells. Ultimately, with the help of pharmacological inhibitors of Beclin1 and BCL2 (spautin-1 and ABT-737), the relationship between BCL2-Beclin1/Bax signaling and DUSP4-regulated autophagy, apoptosis, survival and migration in HCT116 cells was clarified.

RESULTS

Our results first confirmed the contribution of DUSP4 to the survival of HCT116 and SW480 cells. In addition, DUSP4 silencing resulted in BCL2 phosphorylation and the enhancement in autophagy and apoptosis in HCT116 and SW480 cells, while DUSP4 overexpression showed the opposite effect. Moreover, DUSP4 silencing inhibited the protein interaction between BCL2 and Beclin1 or Bax in HCT116 cells. Moreover, the survival and migration of HCT116 cells inhibited by DUSP4 silencing were blocked by autophagy inhibition with spautin-1. Notably, the survival and migration of HCT116 cells promoted by DUSP4 overexpression were reversed by ABT-737.

CONCLUSIONS

It was indicated that DUSP4 can maintain the survival and function of CRC cells by inhibiting BCL2 phosphorylation-dependent autophagic cell death and apoptosis.

Octanoic acid-rich enteral nutrition prevented lipopolysaccharide-induced acute liver injury through c-Jun N-terminal kinase-dependent autophagy

BACKGROUND

Acute liver injury (ALI) is an essential component of sepsis associated with poor outcomes. Octanoic acid (OA), a medium-chain fatty acid, has a protective effect on sepsis-induced organ damage, and autophagy is an adaptive response to sepsis. However, the underlying mechanism by which OA prevents ALI remains unknown. Therefore, we investigated whether OA-rich enteral nutrition (EN) prevented lipopolysaccharide (LPS)-induced ALI through the c-Jun N-terminal kinase (JNK)-dependent autophagy.

METHODS

Firstly, Sprague Dawley rats were randomly divided into four groups (sham, LPS, LPS + EN, and LPS + EN + OA) to detect the effect of OA-rich EN on LPS-induced ALI. Then, rats were randomly divided into five groups (sham, LPS, LPS + EN + OA, LPS + EN + OA + anisomycin (AN), and LPS + SP600125) to explore the mechanism by which OA-rich EN prevented ALI. EN and OA-rich EN were conducted through gastric tubes for 3 days. The liver protective effects were measured by liver histopathological changes, enzymes, inflammatory cytokines of serum and liver, the levels of autophagy, and JNK activity.

RESULTS

OA-rich EN inhibited JNK activity, up-regulated autophagy and prevented LPS-induced ALI. Inhibition of JNK activity conferred by SP promoted autophagy and prevented LPS-induced ALI. Moreover, the protective effect of autophagy and inhibition of JNK activity conferred by OA-rich EN on ALI was counteracted by AN.

CONCLUSION

OA-rich EN prevented LPS-induced ALI through JNK-dependent autophagy. This result suggested that OA-rich EN may be a therapeutic potential for ALI in patients with sepsis.

At a Crossroads to Cancer: How p53-Induced Cell Fate Decisions Secure Genome Integrity

P53 is known as the most critical tumor suppressor and is often referred to as the guardian of our genome. More than 40 years after its discovery, we are still struggling to understand all molecular details on how this transcription factor prevents oncogenesis or how to leverage current knowledge about its function to improve cancer treatment. Multiple cues, including DNA-damage or mitotic errors, can lead to the stabilization and nuclear translocation of p53, initiating the expression of multiple target genes. These transcriptional programs may be cell-type- and stimulus-specific, as is their outcome that ultimately imposes a barrier to cellular transformation. Cell cycle arrest and cell death are two well-studied consequences of p53 activation, but, while being considered critical, they do not fully explain the consequences of p53 loss-of-function phenotypes in cancer. Here, we discuss how mitotic errors alert the p53 network and give an overview of multiple ways that p53 can trigger cell death. We argue that a comparative analysis of different types of p53 responses, elicited by different triggers in a time-resolved manner in well-defined model systems, is critical to understand the cell-type-specific cell fate induced by p53 upon its activation in order to resolve the remaining mystery of its tumor-suppressive function.

Exopolysaccharides isolated from Rhizopus nigricans induced colon cancer cell apoptosis in vitro and in vivo via activating the AMPK pathway

Colorectal cancer (CRC) is a leading cause of cancer-related human deaths. The exopolysaccharide (EPS1-1), isolated from Rhizopus nigricans, has been described as exhibiting anti-tumor and pro-apoptotic activity against CRC, although the underlying mechanism is poorly understood. Herein, we investigate how EPS1-1 induces apoptosis of CRC cells in vitro and in vivo. Our results show that, in vitro, EPS1-1 suppressed cell growth and facilitated apoptosis in a dose- and time-dependent manner by activating the AMP-activated protein kinase (AMPK) pathway in mouse colon cancer CT26 cells. However, treatment with small interfering RNAs (siRNAs) targeting AMPKα or with compound C, an AMPK inhibitor, interfered with the pro-apoptosis effects of EPS1-1. We also show that EPS1-1 initiated the release of reactive oxygen species (ROS) and liver kinase B1 (LKB1), both of which are necessary signals for AMPK activation. Furthermore, EPS1-1-mediated apoptosis is regulated by inactivation of mammalian target of rapamycin complex 1 (mTORC1) and activation of the jun-NH₂ kinase (JNK)-p53 signaling axis dependent on AMPK activation. In vivo, azoxymethane/dextran sulfate sodium (AOM/DSS)-treated CRC mice, when administered EPS1-1, exhibited activation of the AMPK pathway, inhibition of mTORC1, and accumulation of p53 in tumor tissues. Collectively, these findings suggest that EPS1-1-induced apoptosis relies on the activation of the AMPK pathway. The present study provides evidence suggesting that EPS1-1 may be an effective target for development of novel CRC therapeutic agents.

Natural Polyphyllins (I, II, D, VI, VII) Reverses Cancer Through Apoptosis, Autophagy, Mitophagy, Inflammation, and Necroptosis

Cancer is the second leading cause of mortality worldwide. Conventional therapies, including surgery, radiation, and chemotherapy, have limited success because of secondary resistance. Therefore, safe, non-resistant, less toxic, and convenient drugs are urgently required. Natural products (NPs), primarily sourced from medicinal plants, are ideal for cancer treatment because of their low toxicity and high success. NPs cure cancer by regulating different pathways, such as PI3K/AKT/mTOR, ER stress, JNK, Wnt, STAT3, MAPKs, NF-kB, MEK-ERK, inflammation, oxidative stress, apoptosis, autophagy, mitophagy, and necroptosis. Among the NPs, steroid saponins, including polyphyllins (I, II, D, VI, and VII), have potent pharmacological, analgesic, and anticancer activities for the induction of cytotoxicity. Recent research has demonstrated that polyphyllins (PPs) possess potent effects against different cancers through apoptosis, autophagy, inflammation, and necroptosis. This review summarizes the available studies on PPs against cancer to provide a basis for future research.

DUSP4 inhibits autophagic cell death in PTC by inhibiting JNK-BCL2-Beclin1 signaling

Dual specificity phosphatase 4 (DUSP4) is a prognostic marker and potential target of papillary thyroid carcinoma (PTC); however, the molecular mechanism underlying DUSP4-regulated PTC carcinogenesis is unknown. DUSP4 is a negative regulator of the autophagy promoter, JNK. This study explored the relationship between DUSP4 and JNK-mediated autophagic cell death in PTC, and the roles of DUSP4 in PTC using gain-of-function and loss-of-function assays. In addition, we further identified the significance of the JNK-BCL2-Beclin1-autophagy signaling pathway on DUSP4-regulated PTC carcinogenesis by combining knockdown of DUSP4 with a JNK-specific inhibitor (SP600125). We found that knockdown of DUSP4 promoted the phosphorylation of JNK and BCL2 in PTC cells, and enhanced the release of Beclin1 from the BCL2-Beclin1 complex. Knockdown of DUSP4 promoted autophagy and the death of PTC cells. The death and autophagy enhanced by knockdown of DUSP4 was reversed by the JNK inhibitor. We further extended the in-vitro experiments by subcutaneously injecting nude mice with K1 cells transfected with DUSP4-silencing vector. In-vivo assays showed that knockdown of DUSP4 not only inhibited tumor growth, but also promoted the phosphorylation of JNK and BCL2 and the expression of LC3II. In conclusion, DUSP4 inhibits BCL2-Beclin1-autophagy signaling by negatively regulating JNK activity, thus inhibiting PTC oncogenesis. The data from this study contribute to the prevention and cure of PTC.

LncRNA NBR2 inhibits tumorigenesis by regulating autophagy in hepatocellular carcinoma

Long noncoding RNAs (lncRNAs) have been identified to play increasingly important roles in tumorigenesis, and they may serve as novel biomarkers for cancer therapy. LncRNA NBR2 (neighbor of BRCA1 gene 2), a novel identified lncRNA, is demonstrated to decrease in several cancers. However, it is still unknown whether lncRNA NBR2 is involved in hepatocellular carcinoma and autophagy. We found that HCC cases with lower NBR2 expression had significantly worse overall survival than those with higher NBR2 expression in advanced patients. And the expression of NBR2 was negatively correlated with the degree of malignancy of HCC cell lines and differentiation of hepatocellular carcinoma. Besides, NBR2 inhibited the proliferation, invasion, and migration of liver cancer cells. We further found that NBR2 repressed cytoprotective autophagy to restrain HCC cell proliferation. Moreover, NBR2 inhibited Beclin 1-dependent autophagy through ERK and JNK pathways. Taken together, NBR2 suppressed autophagy-induced cell proliferation at least partly through ERK and JNK pathways. These data indicated that NBR2 served as a tumor suppressor gene in hepatocellular carcinoma. The current study provides a novel insight and treatment strategy for hepatocellular carcinoma.

IRE1 and CaMKKβ pathways to reveal the mechanism involved in microcystin-LR-induced autophagy in mouse ovarian cells

Microcystin-LR (MC-LR) is an emerging water pollutant produced by blooming cyanobacteria. It could be absorbed into human body via contaminated food and drinking water causing severe reproductive toxicity. Previous studies showed that MC-LR could regulate autophagy by inducing endoplasmic reticulum (ER) stress thereby causing female reproductive toxicity. However, the molecular mechanisms of MC-LR-induced autophagy remain to be elucidated. It is known that IRE1 and CaMKKβ pathways are two important pathways involved in autophagy induced by ER stress. Hence, this study investigated the roles of both pathways in MC-LR-induced autophagy in mouse ovarian cells. The results showed that MC-LR significantly up-regulated the expression of autophagy marker proteins LC3Ⅱ and BECLIN1 and down-regulated the expression of P62 in vivo and in vitro. MC-LR-caused increase of autophagosomes could be observed in KK-1 cells by MDC staining. MC-LR induced the formation of autolysosomes as indicated by the overlap of LAMP1 and LC3. Meanwhile, MC-LR significantly activated the proteins in IRE1 pathway (IRE1, XBP1 and JNK) and in CaMKKβ pathway (CaMKKβ, AMPK, mTOR). Furthermore, MC-LR caused weight loss and ovarian histopathological damage in mice. In contrast, after the expression and function of IRE1 and CaMKKβ were inhibited with siRNA in vitro and by inhibitors (4μ8C and STO-609, respectively) in vivo, the up-regulation of LC3Ⅱ and BECLIN1 and the degradation of P62 induced by MC-LR were significantly suppressed. MC-LR-induced autophagosomes in KK-1 cells and autolysosomes in mouse ovarian cells were also decreased. Moreover, the knockdown of IRE1 and CaMKKβ relieved MC-LR-induced histopathological injury to mouse ovaries. These results indicated that MC-LR induced ovarian cell autophagy and ovarian injury via IRE1 and CaMKKβ pathways. This study is the first study revealing the molecular mechanisms of MC-LR-induced autophagy of ovarian cells and providing new insights into the female reproductive toxicity of MC-LR.

The Remedial Potential of Lycopene in Pancreatitis through Regulation of Autophagy

Autophagy is an evolutionarily conserved process that degrades damaged organelles and recycles macromolecules to support cell survival. However, in certain disease states, dysregulated autophagy can play an important role in cell death. In pancreatitis, the accumulation of autophagic vacuoles and damaged mitochondria and premature activation of trypsinogen are shown in pancreatic acinar cells (PACs), which are the hallmarks of impaired autophagy. Oxidative stress mediates inflammatory signaling and cytokine expression in PACs, and it also causes mitochondrial dysfunction and dysregulated autophagy. Thus, oxidative stress may be a mediator for autophagic impairment in pancreatitis. Lycopene is a natural pigment that contributes to the red color of fruits and vegetables. Due to its antioxidant activity, it inhibited oxidative stress-induced expression of cytokines in experimental models of acute pancreatitis. Lycopene reduces cell death through the activation of 5′-AMP-activated protein kinase-dependent autophagy in certain cells. Therefore, lycopene may ameliorate pancreatitis by preventing oxidative stress-induced impairment of autophagy and/or by directly activating autophagy in PACs.

Biomarkers, oxidative stress and autophagy in skin aging

Aging is a major cause of many degenerative diseases. The most intuitive consequence of aging is mainly manifested on the skin, resulting in cumulative changes in skin structure, function and appearance, such as increased wrinkles, laxity, elastosis, telangiectasia, and aberrant pigmentation of the skin. Unlike other organs of the human body, skin is not only inevitably affected by the intrinsic aging process, but also affected by various extrinsic environmental factors to accelerate aging, especially ultraviolet (UV) radiation. Skin aging is a highly complex and not fully understood process, and the lack of universal biomarkers for the definitive detection and evaluation of aging is also a major research challenge. Oxidative stress induced by the accumulation of reactive oxygen species (ROS) can lead to lipid, protein, nucleic acid and organelle damage, thus leading to the occurrence of cellular senescence, which is one of the core mechanisms mediating skin aging. Autophagy can maintain cellular homeostasis when faced with different stress conditions and is one of the survival mechanisms of cell resistance to intrinsic and extrinsic stress. Autophagy and aging have many features in common and may be associated with skin aging mediated by different factors. Here, we summarize the changes and biomarkers of skin aging, and discuss the effects of oxidative stress and autophagy on skin aging.

Autophagy: A Promising Target for Age-related Osteoporosis

Autophagy is a process the primary role of which is to clear up damaged cellular components such as long-lived proteins and organelles, thus participating in the conservation of different cells. Osteoporosis associated with aging is characterized by consistent changes in bone metabolism with suppression of bone formation as well as increased bone resorption. In advanced age, not only bone mass but also bone strength decrease in both sexes, resulting in an increased incidence of fractures. Clinical and animal experiments reveal that age-related bone loss is associated with many factors such as accumulation of autophagy, increased levels of reactive oxygen species, sex hormone deficiency, and high levels of endogenous glucocorticoids. Available basic and clinical studies indicate that age-associated factors can regulate autophagy. Those factors play important roles in bone remodeling and contribute to decreased bone mass and bone strength with aging. In this review, we summarize the mechanisms involved in bone metabolism related to aging and autophagy, supplying a theory for therapeutic targets to rescue bone mass and bone strength in older people.

BAG2 ameliorates endoplasmic reticulum stress-induced cell apoptosis in Mycobacterium tuberculosis-infected macrophages through selective autophagy

BAG2 (BCL2 associated athanogene 2) is associated with cell fate determination in response to various pathological conditions. However, the effects of BAG2 on M. tuberculosis-induced endoplasmic reticulum (ER) stress remain elusive. Herein, we report that M. tuberculosis infection of macrophages triggered ER stress and downregulated BAG2 expression. Overexpression of BAG2 enhanced autophagic flux and activated macroautophagy/autophagy targeted to the ER (reticulophagy). In addition, through increasingly localizing SQSTM1 to the ER in BAG2-overexpressing macrophages, we found that the autophagy receptor protein SQSTM1/p62 (sequestosome 1) is associated with the BAG2-induced reticulophagy. Our data also confirmed that BAG2 could render cells resistant to M. tuberculosis-induced cellular damage, and the anti-apoptotic effects of BAG2 in M. tuberculosis-treated macrophages were partially abolished by the autophagic flux inhibitor bafilomycin A₁. Furthermore, the dissociation of BECN1 and BCL2 mediated by activation of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) was responsible for BAG2-activated autophagy. In addition, XBP1 downstream of the ERN1/IRE1 signaling pathway was bound to the Bag2 promoter region and transcriptionally inhibited BAG2 expression. Collectively, these results indicated that BAG2 has anti-apoptotic effects on M. tuberculosis-induced ER stress, which is dependent on the promotion of autophagic flux and the induction of selective autophagy. We revealed a potential host defense mechanism that links BAG2 to ER stress and autophagy during M. tuberculosis infection.

ABBREVIATIONS

ATF6: activating transcription factor 6; BECN1: beclin 1; Baf A1: bafilomycin A₁; CASP3: caspase 3; DDIT3/CHOP/GADD153: DNA damage inducible transcript 3; DAPI: 4',6-diamidino-2-phenylindole; EIF2AK3/PERK: eukaryotic translation initiation factor 2 alpha kinase 3; ER: endoplasmic reticulum; ERN1/IRE1: endoplasmic reticulum to nucleus signaling 1; HSPA5/GRP78/BiP: heat shock protein 5; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAPK/ERK: mitogen-activated protein kinase; SQSTM1/p62: sequestosome 1; UPR: unfolded protein response; XBP1: x-box binding protein 1.

Probiotic Bacillus Attenuates Oxidative Stress- Induced Intestinal Injury via p38-Mediated Autophagy

Probiotics have been widely used in maintaining intestinal health and one of their benefits is to enhance host antioxidant capacity. However, the involved molecular mechanisms require further investigated. Autophagy is a self-protection process in response to diverse stresses. We hypothesized that probiotics could modulate intestinal autophagy to alleviate oxidative stress. Sprague-Dawley (SD) rats were orally administered Bacillus SC06 or SC08 daily for 24 days and thereafter received an intraperitoneal injection of diquat (DQ) to induce oxidative stress. We found that rats administered Bacillus SC06 showed more significant intestinal tissue repair and antioxidant properties than those administered SC08, which suggests a strain-specific effect of probiotics. Moreover, SC06 alleviated apoptosis by regulating the expression of Bcl2, Bax and cleaved caspase-3. Further investigations revealed that SC06 triggered autophagy, indicated by the upregulation of LC3 and Beclin1 and the degradation of p62 in rat jejunum and IEC-6 cells. Preincubation with autophagy inhibitor 3-methyladenine (3-MA) significantly aggravated reactive oxygen species (ROS) production and apoptotic cell formation. Furthermore, we demonstrated that p38 MAPK (mitogen-activated protein kinase), not AKT (alpha serine/threonine kinase)/mTOR (mammalian target of rapamycin), was involved in SC06-induced autophagy. Taken together, Bacillus SC06 can alleviate oxidative stress-induced disorders and apoptosis via p38-mediated autophagy. The above findings highlight a novel mechanism underlying the beneficial effects of probiotics as functional food and provide a new perspective on the prevention and treatment of oxidative damages.

Pathophysiological roles of autophagy and aldo-keto reductases in development of doxorubicin resistance in gastrointestinal cancer cells

Here, we show that incubation of three human gastrointestinal cancer cell lines (HCT15, LoVo and MKN45) with doxorubicin (DOX) provokes autophagy through facilitating production of reactive oxygen species (ROS). HCT15 cell treatment with DOX resulted in up-regulation of Beclin1, down-regulation of Bcl2, activation of AMPK and JNK, and Akt inactivation, all of which were restored by pretreating with an antioxidant N-acetyl-l-cysteine. These data suggest that all the autophagy-related alterations evoked by DOX result from the ROS production. In the DOX-resistant cancer cells, degree of autophagy elicited by DOX was milder than the parental cells, and DOX treatment hardly activated the ROS-dependent apoptotic signals [formation of 4-hydroxy-2-nonenal (HNE), cytochrome-c release into cytosol, and activation of JNK and caspase-3], inferring an inverse correlation between cellular antioxidant capacity and autophagy induction by DOX. Monitoring of expression levels of aldo-keto reductases (AKRs) in the parental and DOX-resistant cells revealed an up-regulation of AKR1B10 and/or AKR1C3 with acquiring the DOX resistance. Knockdown and inhibition of AKR1B10 or AKR1C3 in these cells enhanced DOX-elicited autophagy. Measurement of DOX-reductase activity and HNE-sensitivity assay also suggested that both AKR1B10 (via high HNE-reductase activity) and AKR1C3 (via low HNE-reductase and DOX-reductase activities) are involved in the development of DOX resistance. Combination of inhibitors of autophagy and the two AKRs overcame DOX resistance and cross-resistance of gastrointestinal cancer cells with resistance development to DOX or cis-diamminedichloroplatinum. Therefore, concomitant treatment with the inhibitors may be effective as an adjuvant therapy for elevating DOX sensitivity of gastrointestinal cancer cells.

Astaxanthin Modulation of Signaling Pathways That Regulate Autophagy

Autophagy is a lysosomal pathway that degrades and recycles unused or dysfunctional cell components as well as toxic cytosolic materials. Basal autophagy favors cell survival. However, the aberrant regulation of autophagy can promote pathological conditions. The autophagy pathway is regulated by several cell-stress and cell-survival signaling pathways that can be targeted for the purpose of disease control. In experimental models of disease, the carotenoid astaxanthin has been shown to modulate autophagy by regulating signaling pathways, including the AMP-activated protein kinase (AMPK), cellular homolog of murine thymoma virus akt8 oncogene (Akt), and mitogen-activated protein kinase (MAPK), such as c-Jun N-terminal kinase (JNK) and p38. Astaxanthin is a promising therapeutic agent for the treatment of a wide variety of diseases by regulating autophagy.

[Pt(O,O'-acac)(γ-acac)(DMS)] Induces Autophagy in Caki-1 Renal Cancer Cells

We have demonstrated the cytotoxic effects of [Pt(O,O′-acac)(γ-acac)(dimethyl sulfide (DMS))] on various immortalized cell lines, in primary cultures, and in murine xenograft models in vivo. Recently, we also showed that [Pt(O,O′-acac)(γ-acac)(DMS)] is able to kill Caki-1 renal cells both in vivo and in vitro. In the present paper, apoptotic and autophagic effects of [Pt(O,O′-acac)(γ-acac)(DMS)] and cisplatin were studied and compared using Caki-1 cancerous renal cells. The effects of cisplatin include activation of caspases, proteolysis of enzyme poly ADP ribose polymerase (PARP), control of apoptosis modulators B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and BH3-interacting domain death agonist (Bid), and cell cycle arrest in G2/M phase. Conversely, [Pt(O,O′-acac)(γ-acac)(DMS)] did not induce caspase activation, nor chromatin condensation or DNA fragmentation. The effects of [Pt(O,O′-acac)(γ-acac)(DMS)] include microtubule-associated proteins 1A/1B light chain 3B (LC3)-I to LC3-II conversion, Beclin-1 and Atg-3, -4, and -5 increase, Bcl-2 decrease, and monodansylcadaverine accumulation in autophagic vacuoles. [Pt(O,O′-acac)(γ-acac)(DMS)] also modulated various kinases involved in intracellular transduction regulating cell fate. [Pt(O,O′-acac)(γ-acac)(DMS)] inhibited the phosphorylation of mammalian target of rapmycin (mTOR), p70S6K, and AKT, and increased the phosphorylation of c-Jun N-terminal kinase (JNK1/2), a kinase activity pattern consistent with autophagy induction. In conclusion, while in past reports the high cytotoxicity of [Pt(O,O′-acac)(γ-acac)(DMS)] was always attributed to its ability to trigger an apoptotic process, in this paper we show that Caki-1 cells die as a result of the induction of a strong autophagic process.

Autophagy in Human Health and Disease: Novel Therapeutic Opportunities

SIGNIFICANCE

In eukaryotes, autophagy represents a highly evolutionary conserved process, through which macromolecules and cytoplasmic material are degraded into lysosomes and recycled for biosynthetic or energetic purposes. Dysfunction of the autophagic process has been associated with the onset and development of many human chronic pathologies, such as cardiovascular, metabolic, and neurodegenerative diseases as well as cancer. Recent Advances: Currently, comprehensive research is being carried out to discover new therapeutic agents that are able to modulate the autophagic process in vivo. Recent evidence has shown that a large number of natural bioactive compounds are involved in the regulation of autophagy by modulating several transcriptional factors and signaling pathways.

CRITICAL ISSUES

Critical issues that deserve particular attention are the inadequate understanding of the complex role of autophagy in disease pathogenesis, the limited availability of therapeutic drugs, and the lack of clinical trials. In this context, the effects that natural bioactive compounds exert on autophagic modulation should be clearly highlighted, since they depend on the type and stage of the pathological conditions of diseases.

FUTURE DIRECTIONS

Research efforts should now focus on understanding the survival-supporting and death-promoting roles of autophagy, how natural compounds interact exactly with the autophagic targets so as to induce or inhibit autophagy and on the evaluation of their pharmacological effects in a more in-depth and mechanistic way. In addition, clinical studies on autophagy-inducing natural products are strongly encouraged, also to highlight some fundamental aspects, such as the dose, the duration, and the possible synergistic action of these compounds with conventional therapy.

Is Fat Mass Cross-Sectionally Associated with Cortical Aβ Load in the Human Brain?

OBJECTIVES

The objective of this study was to examine the relationship of fat mass (FM) with brain amyloid (Aβ) load in older adults.

METHODS

Data from the Multidomain Alzheimer's Preventive Trial (MAPT) for Positron emission tomography and dual-energy X-ray absorptiometry (DXA) were used. Linear regressions controlling for appendicular muscle, age, education, clinical dementia rating scale and Apolipoprotein-E were performed to explore the relationships between FM, trunk FM and Aβ-load.

RESULTS

Thirty-nine participants (75.7 ± 4.2 years old) with an average BMI of 27.5 ± 4.0 kg/m2 were analyzed in this study. There were significant and positive associations of both total and trunk FM with Aβ load [0.01 (0.002-0.02) and 0.02 (0.001-0.04), respectively]; however, when adding ApoE-ε4 as a confounder, associations were no longer significant.

CONCLUSIONS

This study has found associations between FM as measured by DXA and cerebral Aβ load, suggesting that excessive FM might be involved in AD pathology.

Inhibition of ERK-Drp1 signaling and mitochondria fragmentation alleviates IGF-IIR-induced mitochondria dysfunction during heart failure

Mitochondrial dysfunction is a major contributor to myocyte loss and the development of heart failure. Myocytes have quality control mechanisms to retain functional mitochondria by removing damaged mitochondria via specialized autophagy, i.e., mitophagy. The underlying mechanisms of fission affect the survival of cardiomyocytes, and left ventricular function in the heart is poorly understood. Here, we demonstrated the direct effect and potential mechanisms of mitochondrial functional defects associated with abnormal mitochondrial dynamics in heart failure. We observed that IGF-IIR signaling produced significant changes in mitochondrial morphology and function; such changes were associated with the altered expression and distribution of dynamin-related protein (Drp1) and mitofusin (Mfn2). IGF-IIR signaled extracellular signal-regulated kinase (ERK) activation to promote Drp1 phosphorylation and translocation to mitochondria for mitochondrial fission and mitochondrial dysfunction. Moreover, IGF-IIR signaling triggered Rab9-dependent autophagosome formation by the JNK-mediated phosphorylation of Bcl-2 at serine 87 and promoted ULK1/Beclin 1-dependent autophagic membrane formation. Excessive mitochondrial fission by Drp1 enhanced the Rab9-dependent autophagosome recognition and engulfing of damaged mitochondria and eventually decreased cardiomyocyte viability. Therefore, these results demonstrated the connection between Rab9-dependent autophagosomes and mitochondrial fission in cardiac myocytes, which provides a potential therapeutic strategy for treating heart disease.

Mechanisms of autophagy and relevant small-molecule compounds for targeted cancer therapy

Autophagy is an evolutionarily conserved, multi-step lysosomal degradation process for the clearance of damaged or superfluous proteins and organelles. Accumulating studies have recently revealed that autophagy is closely related to a variety of types of cancer; however, elucidation of its Janus role of either tumor-suppressive or tumor-promoting still remains to be discovered. In this review, we focus on summarizing the context-dependent role of autophagy and its complicated molecular mechanisms in different types of cancer. Moreover, we discuss a series of small-molecule compounds targeting autophagy-related proteins or the autophagic process for potential cancer therapy. Taken together, these findings would shed new light on exploiting the intricate mechanisms of autophagy and relevant small-molecule compounds as potential anti-cancer drugs to improve targeted cancer therapy.

Emerging Roles of p53 Family Members in Glucose Metabolism

Glucose is the key source for most organisms to provide energy, as well as the key source for metabolites to generate building blocks in cells. The deregulation of glucose homeostasis occurs in various diseases, including the enhanced aerobic glycolysis that is observed in cancers, and insulin resistance in diabetes. Although p53 is thought to suppress tumorigenesis primarily by inducing cell cycle arrest, apoptosis, and senescence in response to stress, the non-canonical functions of p53 in cellular energy homeostasis and metabolism are also emerging as critical factors for tumor suppression. Increasing evidence suggests that p53 plays a significant role in regulating glucose homeostasis. Furthermore, the p53 family members p63 and p73, as well as gain-of-function p53 mutants, are also involved in glucose metabolism. Indeed, how this protein family regulates cellular energy levels is complicated and difficult to disentangle. This review discusses the roles of the p53 family in multiple metabolic processes, such as glycolysis, gluconeogenesis, aerobic respiration, and autophagy. We also discuss how the dysregulation of the p53 family in these processes leads to diseases such as cancer and diabetes. Elucidating the complexities of the p53 family members in glucose homeostasis will improve our understanding of these diseases.

Melatonin reduces oxidative damage in mouse granulosa cells via restraining JNK-dependent autophagy

Oxidative stress-induced granulosa cell (GCs) injury is believed to be a common trigger for follicular atresia. Emerging evidence indicates that excessive autophagy occurs in mammalian cells with oxidative damage. N-acetyl-5-methoxytrypamine (melatonin) has been shown to prevent GCs from oxidative injury, although the exact mechanism remains to be elucidated. Here, we first demonstrated that the suppression of autophagy through the JNK/BCL-2/BECN1 signaling is engaged in melatonin-mediated GCs protection against oxidative damage. Melatonin inhibited the loss of GCs viability, formation of GFP-MAP1LC3B puncta, accumulation of MAP1LC3B-II blots, degradation of SQSTM1 and the expression of BECN1, which was correlated with impaired activation of JNK during oxidative stress. On the other hand, blocking of autophagy and/or JNK also reduced the level of H2O2-induced GCs death, but failed to further restore GCs viability in the presence of melatonin. Particularly, the suppression of autophagy provided no additional protective effects when GCs were pretreated with JNK inhibitor and/or melatonin. Importantly, we found that the enhanced interaction between BCL-2 and BECN1 might be a responsive mechanism for autophagy suppression via the melatonin/JNK pathway. Moreover, blocking the downstream antioxidant system of melatonin using specific inhibitors further confirmed a direct role of melatonin/JNK/autophagy axis in preserving GCs survival without scavenging reactive oxygen species (ROS). Taken together, our findings uncover a novel function of melatonin in preventing GCs from oxidative damage by targeting JNK-mediated autophagy, which might contribute to develop therapeutic strategies for patients with ovulation failure-related disorders.

Molecular characterization of autophagic and apoptotic signaling induced by sorafenib in liver cancer cells

Sorafenib is the unique accepted molecular targeted drug for the treatment of patients in advanced stage of hepatocellular carcinoma. The current study evaluated cell signaling regulation of endoplasmic reticulum (ER) stress, c-Jun-N-terminal kinase (JNK), Akt, and 5'AMP-activated protein kinase (AMPK) leading to autophagy and apoptosis induced by sorafenib. Sorafenib induced early (3-12 hr) ER stress characterized by an increase of Ser51 P-eIF2α/eIF2α, C/EBP homologous protein (CHOP), IRE1α, and sXBP1, but a decrease of activating transcription factor 6 expression, overall temporally associated with the increase of Thr183,Tyr185 P-JNK1/2/JNK1/2, Thr172 P-AMPKα, Ser413 P-Foxo3a, Thr308 P-AKt/AKt and Thr32 P-Foxo3a/Foxo3a ratios, and reduction of Ser2481 P-mammalian target of rapamycin (mTOR)/mTOR and protein translation. This pattern was related to a transient increase of tBid, Bim EL , Beclin-1, Bcl-xL, Bcl-2, autophagy markers, and reduction of myeloid cell leukemia-1 (Mcl-1) expression. The progressive increase of CHOP expression, and reduction of Thr308 P-AKt/AKt and Ser473 P-AKt/AKt ratios were associated with the reduction of autophagic flux and an additional upregulation of Bim EL expression and caspase-3 activity (24 hr). Small interfering-RNA (si-RNA) assays showed that Bim, but not Bak and Bax, was involved in the induction of caspase-3 in sorafenib-treated HepG2 cells. Sorafenib increased autophagic and apoptotic markers in tumor-derived xenograft model. In conclusion, the early sorafenib-induced ER stress and regulation of JNK and AMPK-dependent signaling were related to the induction of survival autophagic process. The sustained drug treatment induced a progressive increase of ER stress and PERK-CHOP-dependent rise of Bim EL , which was associated with the shift from autophagy to apoptosis. The kinetic of Bim EL expression profile might also be related to the tight balance between AKt- and AMPK-related signaling leading to Foxo3a-dependent BIM EL upregulation.

PDK2 promotes chondrogenic differentiation of mesenchymal stem cells by upregulation of Sox6 and activation of JNK/MAPK/ERK pathway

This study was undertaken to clarify the role and mechanism of pyruvate dehydrogenase kinase isoform 2 (PDK2) in chondrogenic differentiation of mesenchymal stem cells (MSCs). MSCs were isolated from femurs and tibias of Sprague-Dawley rats, weighing 300-400 g (5 females and 5 males). Overexpression and knockdown of PDK2 were transfected into MSCs and then cell viability, adhesion and migration were assessed. Additionally, the roles of aberrant PDK2 in chondrogenesis markers SRY-related high mobility group-box 6 (Sox6), type ΙΙ procollagen gene (COL2A1), cartilage oligomeric matrix protein (COMP), aggrecan (AGC1), type ΙX procollagen gene (COL9A2) and collagen type 1 alpha 1 (COL1A1) were measured by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The expressions of c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK) and extracellular regulated protein kinase (ERK) were measured. Overexpressing PDK2 promoted cell viability, adhesion and inhibited cell migration in MSCs (all P<0.05). qRT-PCR assay showed a potent increase in the mRNA expressions of all chondrogenesis markers in response to overexpressing PDK2 (P<0.01 or P<0.05). PDK2 overexpression also induced a significant accumulation in mRNA and protein expressions of JNK, p38MAPK and ERK in MSCs compared to the control (P<0.01 or P<0.05). Meanwhile, silencing PDK2 exerted the opposite effects on MSCs. This study shows a preliminary positive role and potential mechanisms of PDK2 in chondrogenic differentiation of MSCs. It lays the theoretical groundwork for uncovering the functions of PDK2 and provides a promising basis for repairing cartilage lesions in osteoarthritis.

microRNA-130a Promotes Human Keratinocyte Viability and Migration and Inhibits Apoptosis Through Direct Regulation of STK40-Mediated NF-κB Pathway and Indirect Regulation of SOX9-Meditated JNK/MAPK Pathway: A Potential Role in Psoriasis

Psoriasis is a chronic inflammatory skin disorder. The aim of this study was to determine a potential role of microRNA (miR)-130a in psoriasis, and underlying mechanism. Expression levels of miR-130a in psoriasis specimens and normal skin tissues were analyzed. MiR-130a mimic, inhibitor, miR-control, small interfering RNA (siRNA) specific serine/threonine kinase 40 (STK40), or sex-determining region Y chromosome-box 9 (SOX9) were transfected to human keratinocyte HaCaT cells, respectively. After transfection, the cell viability, apoptosis, and migration were determined. Luciferase reporter assay, quantitative reverse transcription-polymerase chain reaction, and western blot were performed to explore whether STK40 was a target of miR-130a. The effects of aberrant expressions of miR-130a, STK40, or SOX9 on key proteins of NF-κB and c-Jun N-terminal kinase (JNK)/mitogen-activated protein kinase (MAPK) pathway were assessed. The miR-130a levels were significantly higher in patients with psoriasis compared to the healthy controls (p < 0.01). Overexpressing miR-130a strikingly promoted HaCaT cell viability and migration and inhibited apoptosis (p < 0.01 or p < 0.05). We confirmed that STK40 was a direct target of miR-130a, and STK40 was involved in miR-130a-induced cell functions. Overexpressing miR-130a significantly upregulated NF-κB p65, SOX9, p-c-Jun, p-JNK, and p-p38MAPK proteins and silencing miR-130a downregulated them. In addition, silencing STK40 alleviated the effects of anti-miR-130a on SOX9 expression. Furthermore, silencing SOX9 also decreased levels of p-c-Jun, p-JNK, and p-p38MAPK proteins. MiR-130a regulates human keratinocyte HaCaT viability, migration and apoptosis might be by direct regulation of STK40-mediated NF-κB pathway and by indirect regulation of SOX9-mediated downstream JNK/MAPK signaling pathway.

Long-term exposition to a high fat diet favors the appearance of β-amyloid depositions in the brain of C57BL/6J mice. A potential model of sporadic Alzheimer's disease

AIMS

The sporadic and late-onset form of Alzheimer's disease (AD) constitutes the most common form of dementia. This non-familiar form could be a consequence of metabolic syndrome, characterized by obesity and the development of a brain-specific insulin resistance known as type III diabetes. This work demonstrates the development of a significant AD-like neuropathology due to these metabolic alterations.

METHODS

C57BL/6J mice strain were divided into two groups, one fed with a diet rich in palmitic acid (high-fat diet, HFD) since their weaning until 16 months of age, and another group used as a control with a regular diet. The analyses were carried out in the dentate gyrus area of the hippocampus using a Thioflavin-S stain and immunofluorescence assays.

RESULTS

The most significant finding of the present research was that HFD induced the deposition of the βA peptide. Moreover, the diet also caused alterations in different cell processes, such as increased inflammatory reactions that lead to a decrease in the neuronal precursor cells. In addition, the results show that there were also dysregulations in normal autophagy and apoptosis, mechanisms related to βA formation.

CONCLUSIONS

The present findings confirm that HFD favors the formation of βA depositions in the brain, a key feature of AD, supporting the metabolic hypothesis of sporadic AD.

Social isolation induces autophagy in the mouse mammary gland: link to increased mammary cancer risk

Social isolation is a strong predictor of early all-cause mortality and consistently increases breast cancer risk in both women and animal models. Because social isolation increases body weight, we compared its effects to those caused by a consumption of obesity-inducing diet (OID) in C57BL/6 mice. Social isolation and OID impaired insulin and glucose sensitivity. In socially isolated, OID-fed mice (I-OID), insulin resistance was linked to reduced Pparg expression and increased neuropeptide Y levels, but in group-housed OID fed mice (G-OID), it was linked to increased leptin and reduced adiponectin levels, indicating that the pathways leading to insulin resistance are different. Carcinogen-induced mammary tumorigenesis was significantly higher in I-OID mice than in the other groups, but cancer risk was also increased in socially isolated, control diet-fed mice (I-C) and G-OID mice compared with that in controls. Unfolded protein response (UPR) signaling (GRP78; IRE1) was upregulated in the mammary glands of OID-fed mice, but not in control diet-fed, socially isolated I-C mice. In contrast, expression of BECLIN1, ATG7 and LC3II were increased, and p62 was downregulated by social isolation, indicating increased autophagy. In the mammary glands of socially isolated mice, but not in G-OID mice, mRNA expressions of p53 and the p53-regulated autophagy inducer Dram1 were upregulated, and nuclear p53 staining was strong. Our findings further indicated that autophagy and tumorigenesis were not increased in Atg7(+/-) mice kept in social isolation and fed OID. Thus, social isolation may increase breast cancer risk by inducing autophagy, independent of changes in body weight.

WT1 is involved in the Akt-JNK pathway dependent autophagy through directly regulating Gas1 expression in human osteosarcoma cells

Macroautophagy (herein termed autophagy) works as a protective mechanism in tumorigenesis and development under metabolic stress condition. Multitudes of genes have been found involved in this process during past decades. In the present study, we report that Wilm's tumor suppressor1 (WT1) is involved in autophagy in osteosarcoma (OS) cells. WT1, a transcription factor with multitude of target genes, expresses in a majority of cancer types. Though wide-ranging effect of WT1 is now well documented, the function of WT1 in tumors remains poorly defined. In this chapter, it is found that high expression of WT1 positively correlates with active autophagy in human osteosarcoma cells. And further study on cell signaling pathway illustrates that Akt/JNK pathway acts as a positive regulator of autophagy induced by WT1. Here, we present evidence that WT1 modulates Akt/JNK signaling pathway mediated autophagy by controlling the expression of growth arrest-specific 1 (Gas1). We show that WT1 is required for Gas1 transcription in osteosarcoma cells. And Gas1 is upregulated followed WT1 overexpression in a time-dependent manner. Loss of Gas1 results in a reduction of WT1-induced autophagy.

MiR-449a regulates autophagy to inhibit silica-induced pulmonary fibrosis through targeting Bcl2

Silicosis is a fatal pulmonary fibrotic disorder characterized by accumulation of fibroblasts and myofibroblasts and deposition of extracellular matrix proteins. MiR-449a is a potential mediator of many cellular processes, including cell proliferation, differentiation, and apoptosis. We hypothesized that miR-449a may play a crucial role in the progression of pulmonary fibrogenesis. Here, we described miR-449a as a new autophagy-regulated miRNA. Importantly, miR-449a expression was significantly decreased in lung tissues of mice with silica treatment, and it was similarly expressed in NIH-3T3 and MRC-5 cells stimulated with TGF-β1. The activity of autophagy was inhibited in fibrotic lung tissues and TGF-β1-treated fibroblasts. To investigate the potential effect of miR-449a, we overexpressed miR-449a in mouse models and found that miR-449a significantly reduced both the distribution and severity of lung lesions induced by silica. In addition, miR-449a was observed to induce the activity of autophagy in vivo and in vitro. Notably, Bcl2 was identified as a target of miR-449a. Bcl2 levels were decreased in NIH-3T3 cells upon miR-449a overexpression. Indeed, the Bcl2 3' UTR contained functional miR-449a responsive sequences. Furthermore, TGF-β1 was observed to increase the expression of Bcl2 via the MAPK/ERK pathway. These results suggest that miR-449a is an important regulator of autophagy, as well as a novel endogenous suppressor of pulmonary fibrosis.

KEY MESSAGE

MiR-449a expression was decreased in fibrotic lungs and activated fibroblasts. Autophagy was inhibited in fibrotic lung tissues and TGF-β1-treated fibroblasts. MiR-449a had an antifibrotic effect in silica-induced lung fibrosis. MiR-449a upregulated autophagic activity in vitro. Bcl2 is the autophagy-related target of miR-449a.

Polyphyllin VII Induces an Autophagic Cell Death by Activation of the JNK Pathway and Inhibition of PI3K/AKT/mTOR Pathway in HepG2 Cells

Polyphyllin VII (PP7), a pennogenyl saponin isolated from Rhizoma Paridis, exhibited strong anticancer activities in various cancer types. Previous studies found that PP7 induced apoptotic cell death in human hepatoblastoma cancer (HepG2) cells. In the present study, we investigated whether PP7 could induce autophagy and its role in PP7-induced cell death, and elucidated its mechanisms. PP7 induced a robust autophagy in HepG2 cells as demonstrated by the conversion of LC3B-I to LC3B-II, degradation of P62, formation of punctate LC3-positive structures, and autophagic vacuoles tested by western blot analysis or InCell 2000 confocal microscope. Inhibition of autophagy by treating cells with autophagy inhibitor (chloroquine) abolished the cell death caused by PP7, indicating that PP7 induced an autophagic cell death in HepG2 cells. C-Jun N-terminal kinase (JNK) was activated after treatment with PP7 and pretreatment with SP600125, a JNK inhibitor, reversed PP7-induced autophagy and cell death, suggesting that JNK plays a critical role in autophagy caused by PP7. Furthermore, our study demonstrated that PP7 increased the phosphorylation of AMPK and Bcl-2, and inhibited the phosphorylation of PI3K, AKT and mTOR, suggesting their roles in the PP7-induced autophagy. This is the first report that PP7 induces an autophagic cell death in HepG2 cells via inhibition of PI3K/AKT/mTOR, and activation of JNK pathway, which induces phosphorylation of Bcl-2 and dissociation of Beclin-1 from Beclin-1/Bcl-2 complex, leading to induction of autophagy.

Momordin Ic couples apoptosis with autophagy in human hepatoblastoma cancer cells by reactive oxygen species (ROS)-mediated PI3K/Akt and MAPK signaling pathways

Momordin Ic is a principal saponin constituent of Fructus Kochiae, which acts as an edible and pharmaceutical product more than 2000 years in China. Our previous research found momordin Ic induced apoptosis by PI3K/Akt and MAPK signaling pathways in HepG2 cells. While the role of autophagy in momordin Ic induced cell death has not been discussed, and the connection between the apoptosis and autophagy is not clear yet. In this work, we reported momordin Ic promoted the formation of autophagic vacuole and expression of Beclin 1 and LC-3 in a dose- and time-dependent manner. Compared with momordin Ic treatment alone, the autophagy inhibitor 3-methyladenine (3-MA) also can inhibit apoptosis, while autophagy activator rapamycin (RAP) has the opposite effect, and the apoptosis inhibitor ZVAD-fmk also inhibited autophagy induced by momordin Ic. Momordin Ic simultaneously induces autophagy and apoptosis by suppressing the ROS-mediated PI3K/Akt and activating the ROS-related JNK and P38 pathways. Additionally, momordin Ic induces apoptosis by suppressing PI3K/Akt-dependent NF-κB pathways and promotes autophagy by ROS-mediated Erk signaling pathway. Those results suggest that momordin Ic has great potential as a nutritional preventive strategy in cancer therapy.

Epigallocatechin gallate and mitochondria-A story of life and death

Epigallocatechin gallate (EGCG) is a flavonoid belonging to the chemical class of falvan-3-ols (catechins) esterified with gallic acid. It is the main catechin found in green tea (Camellia sinensis L.) accounting for about 50% of its total polyphenols. Extensive research performed in recent years has revealed that green tea demonstrates a wide range of positive biological activities against serious chronic diseases such as cardiovascular and neurodegenerative pathologies, cancer, metabolic syndrome and type 2 diabetes. These protective properties can be traced back to the potent antioxidant and anti-inflammatory activities of EGCG. Recent studies have suggested that it may exert its beneficial effects by modulating mitochondrial functions impacting mitochondrial biogenesis, bioenergetic control (ATP production and anabolism), alteration of the cell cycle, and mitochondria-related apoptosis. This review evaluates recent evidence on the ability of EGCG to exert critical influence on the above mentioned pathways.

MAPK/JNK signalling: a potential autophagy regulation pathway

Autophagy refers to a lysosomal degradative pathway or a process of self-cannibalization. This pathway maintains nutrients levels for vital cellular functions during periods of starvation and it provides cells with survival advantages under various stress situations. However, the mechanisms responsible for the induction and regulation of autophagy are poorly understood. The c-Jun NH2-terminal kinase (JNK) signal transduction pathway functions to induce defence mechanisms that protect organisms against acute oxidative and xenobiotic insults. This pathway has also been repeatedly linked to the molecular events involved in autophagy regulation. The present review will focus on recent advances in understanding of the relationship between mitogen-activated protein kinase (MAPK)/JNK signalling and autophagic cell death.

Cardamonin induces autophagy and an antiproliferative effect through JNK activation in human colorectal carcinoma HCT116 cells

Cardamonin (2',4'-dihydroxy-6'-methoxychalcone) is derived from Alpinia katsumadai Hayata (Zingiberaceae), a plant that has been used in Traditional Chinese Medicine for thousands of years. Several anticancer agents have been reported to induce autophagy, which either protects cells or further sensitizes cells to drug treatment. However, the possible autophagic and antiproliferative effects of cardamonin on the human colorectal carcinoma HCT116 cell line are unclear. In the present study, experiments were conducted to determine the effects of cardamonin on cell proliferation, cell cycle distribution, and stimulation of autophagy in cultures of the HCT116 cell line. The results showed that cardamonin inhibited cell proliferation, induced G2/M phase cell cycle arrest, and enhanced autophagy in HCT116 cells. We found evidence that cardamonin-induced autophagic and antiproliferative effects are regulated by the tumor protein p53. We also found that the enhanced activation of c-Jun N-terminal kinase (JNK) by cardamonin was partially regulated by p53 and was critical for cardamonin-induced autophagic and antiproliferative effects in HCT116 cells. These findings suggest that cardamonin or other anticancer agents that increase p53/JNK-dependent stimulation of autophagy could be used to effectively treat patients with colorectal carcinoma.

p53-mediated autophagic regulation: A prospective strategy for cancer therapy

Autophagy is a major catabolic process that degrades and recycles cytosolic components in autophagosomes, which fuse with lysosomes. This process enables starving cells to sustain their energy requirements and metabolic states, thus facilitating their survival, especially in cancer pathogenesis. The regulation of autophagy is quite intricate. It involves a series of signaling cascades including p53, known as the best-characterized tumor suppressor protein. Recent reports have indicated that p53 plays dual roles in regulating autophagy depending on its subcellular localization. Nuclear p53 facilitates autophagy by transactivating its target genes, whereas cytoplasmic p53 mainly inhibits autophagy through extranuclear, transcription-independent mechanisms. The relationship between autophagy and neoplasia is complicated. It may be intrinsically associated with the functional status of p53, but this is not clearly elucidated. This review focuses on the role of p53 as a master regulator of autophagy. We conclude that the contextual role of autophagy in cancer, which could be switched by p53 status, is expected to be developed into a new anticancer therapeutic approach.

Targeting TNF-related apoptosis-inducing ligand (TRAIL) receptor by natural products as a potential therapeutic approach for cancer therapy

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to selectively induce apoptotic cell death in various tumor cells by engaging its death-inducing receptors (TRAIL-R1 and TRAIL-R2). This property has led to the development of a number of TRAIL-receptor agonists such as the soluble recombinant TRAIL and agonistic antibodies, which have shown promising anticancer activity in preclinical studies. However, besides activating caspase-dependent apoptosis in several cancer cells, TRAIL may also activate nonapoptotic signal transduction pathways such as nuclear factor-kappa B, mitogen-activated protein kinases, AKT, and signal transducers and activators of transcription 3, which may contribute to TRAIL resistance that is being now frequently encountered in various cancers. TRAIL resistance can be overcome by the application of efficient TRAIL-sensitizing pharmacological agents. Natural compounds have shown a great potential in sensitizing cells to TRAIL treatment through suppression of distinct survival pathways. In this review, we have summarized both apoptotic and nonapoptotic pathways activated by TRAIL, as well as recent advances in developing TRAIL-receptor agonists for cancer therapy. We also briefly discuss combination therapies that have shown great potential in overcoming TRAIL resistance in various tumors.

Mechanism of autophagic regulation in carcinogenesis and cancer therapeutics

Autophagy in cancer is an intensely debated concept in the field of translational research. The dual nature of autophagy implies that it can potentially modulate the pro-survival and pro-death mechanisms in tumor initiation and progression. There is a prospective molecular relationship between defective autophagy and tumorigenesis that involves the accumulation of damaged mitochondria and protein aggregates, which leads to the production of reactive oxygen species (ROS) and ultimately causes DNA damage that can lead to genomic instability. Moreover, autophagy regulates necrosis and is followed by inflammation, which limits tumor metastasis. On the other hand, autophagy provides a survival advantage to detached, dormant metastatic cells through nutrient fueling by tumor-associated stromal cells. Manipulating autophagy for induction of cell death, inhibition of protective autophagy at tissue-and context-dependent for apoptosis modulation has therapeutic implications. This review presents a comprehensive overview of the present state of knowledge regarding autophagy as a new approach to treat cancer.