Curcumin-induced autophagy contributes to the decreased survival of oral cancer cells

Natural products and diet for the prevention of oral cancer: Research from south and southeast Asia

Medicinal plants are of prime importance in the discovery of drugs. They are an inherent source of naturally available phytochemicals that can help in the prevention and treatment of several diseases including cancer. This article reviews the experimental and clinical evidence of phytochemicals available in natural dietary products that are used in everyday life across South Asia and South-East Asia for their perceived effectiveness in the management of Potentially Malignant Disorders and prevention of Oral Cancer. The review also highlights the active phytometabolites, their in vitro anti-proliferative properties and targeted signalling pathways, biological activities in in vivo models and translative potential for clinical trials in humans.

Advances in β-Diketocyclisation of Curcumin Derivatives and their Antitumor Activity

Curcumin, derived from the popular spice turmeric, is a pharmacologically active polyphenol. Curcumin's therapeutic activity has been extensively studied in recent decades, with reports implicating curcumin in many biological activities, particularly, its significant anticancer activity. However, its potential as an oral administration product is hampered by poor bioavailability, which is associated with a variety of factors, including low water solubility, poor intestinal permeability, instability, and degradation at alkaline pH. To improve its bioavailability, modifying β-diketone curcumin with heterocycles, such as pyrazole, isoxazole and triazole is a powerful strategy. Derivatives are synthesized while maintaining the basic skeleton of curcumin. The β-diketone cyclized curcumin derivatives are regulators of multiple molecular targets, which play vital roles in a variety of cellular pathways. In some literatures, structurally modified curcumin derivatives have been compared with curcumin, and the former has enhanced biological activity, improved water solubility and stability. Therefore, the scope of this review is to report the most recently synthesized heterocyclic derivatives and to classify them according to their chemical structures. Several of the most important and effective compounds are reviewed by introducing different active groups into the β-diketone position to achieve better therapeutic efficacy and bioavailability.

Tumor microenvironment remodeling in oral cancer: Application of plant derived-natural products and nanomaterials

Oral cancers consist of squamous cell carcinoma (SCC) and other malignancies in the mouth with varying degrees of invasion and differentiation. For many years, different modalities such as surgery, radiation therapy, and classical chemotherapy drugs have been used to control the growth of oral tumors. Nowadays, studies have confirmed the remarkable effects of the tumor microenvironment (TME) on the development, invasion, and therapeutic resistance of tumors like oral cancers. Therefore, several studies have been conducted to modulate the TME in various types of tumors in favor of cancer suppression. Natural products are intriguing agents for targeting cancers and TME. Flavonoids, non-flavonoid herbal-derived molecules, and other natural products have shown promising effects on cancers and TME. These agents, such as curcumin, resveratrol, melatonin, quercetin and naringinin have demonstrated potency in suppressing oral cancers. In this paper, we will review and discuss about the potential efficacy of natural adjuvants on oral cancer cells. Furthermore, we will review the possible therapeutic effects of these agents on the TME and oral cancer cells. Moreover, the potential of nanoparticles-loaded natural products for targeting oral cancers and TME will be reviewed. The potentials, gaps, and future perspectives for targeting TME by nanoparticles-loaded natural products will also be discussed.

The role of curcumin on apoptosis and NLRP3 inflammasome-dependent pyroptosis on colorectal cancer in vitro

BACKGROUND

Colorectal cancer (CRC) is one of the most common cancers worldwide. Many factors such as stress, lifestyle, and dietary habits are known to play a role in the initiation and progression of the disease. Herbal therapeutic agents including curcumin can hold a great potential against cancer treatment; however, their efficacy on CRC is still under investigation. Herein, we evaluated the anticancer mechanism of curcumin on four different CRC cell lines.

METHODS

Cells were treated with curcumin for 24, 48 and 72 h, and IC50 doses for each cell line were calculated. Mechanistic studies were conducted with the lowest IC50 dose determined for each cell line by evaluating apoptosis and necrosis, cell division, and NLRP3-mediated pyroptosis.

RESULTS

Curcumin treatment significantly decreased viability while increasing the SubG1 phase in all cell lines tested, indicating apoptosis is the main programmed cell death pathway activated upon curcumin treatment in CRC. In terms of pyroptosis, components of NLRP3 inflammasome were found to be elevated in SW480 and HCT116 cell lines, although to a lesser extent in the latter, and NLRP3 inflammasome activation was not observed in LoVo and HT29 cells.

DISCUSSION

Our results reveal that while curcumin effectively induces apoptosis, its effects on NLRP3-inflammasome mediated pyroptosis vary. Our results underline the need for further research focusing on the other inflammasome complexes to confirm the differential effects of curcumin on CRC.

Macrophage targeted polymeric curcumin nanoparticles limit intracellular survival of Mycobacterium tuberculosis through induction of autophagy and augment anti-TB activity of isoniazid in RAW 264.7 macrophages

Rapid emergence of antibiotic resistance in tuberculosis has left us with limited resources to treat and manage multi drug resistant (MDR) cases of tuberculosis, prompting the development of novel therapeutics. Mycobacterium tuberculosis (MTB) perturbs the host protective pathways for its survival, therefore host directed therapeutic (HDT) interventions offer an attractive alternative strategy. Curcumin (CMN), the principle curcuminoid from Curcuma longa is known to have anti-TB activity against MDR strains of MTB in macrophages. We discovered that treatment of CMN induced autophagy in uninfected and MTB infected macrophages which was evident by conversion of LC3-I to LC3-II and degradation of p62. Inhibition of autophagy by a pharmacological inhibitor 3-MA resulted in significant inhibition of intracellular killing activity of CMN, suggesting the involvement of autophagy in intracellular clearance of MTB. Moreover, annexin v-FITC/PI staining data suggested induction of apoptosis in uninfected and MTB infected macrophages post CMN treatment. This finding was further corroborated by up-regulated expression of pro-apoptotic proteins, Bax, cleaved caspase-3 and PARP and diminished expression of anti-apoptotic protein Bcl-2 as evaluated by immunoblotting. Using GFP-MTB H37Rv and Lysotracker Red staining we demonstrated co-localization of GFP-MTB H37Rv containing phagosome to lysosome after CMN treatment, indicating enhanced phagosome lysosome fusion. Due to poor bioavailability of CMN, its clinical use is limited, therefore to overcome this issue, CMN was encapsulated in Poly(lactic-co-glycolic) acid (PLGA) shell, resulting in polymeric CMN nano particles (ISCurNP). Flow cytometric evaluation suggested >99% uptake of ISCurNP after 3h of treatment. In BALB/c mice, oral dose of ISCurNP resulted in 6.7-fold increase in the bioavailability compared to free CMN. Moreover, ISCurNP treatment resulted in significant decrease in the intracellular survival of MTB H37Rv through induction of autophagy. Adjunct action of ISCurNP and CMN in combination with isoniazid (INH) revealed >99% decrease in intracellular survival of MTB in macrophage as compared to ISCurNP, CMN or INH alone. In conclusion, our findings suggest the role of ISCurNP as novel host directed formulation to combat both sensitive and MDR strains of MTB by induction of autophagy.

Therapeutic potential of curcumin and its nanoformulations for treating oral cancer

The global incidence of oral cancer has steadily increased in recent years and is associated with high morbidity and mortality. Oral cancer is the most common cancer in the head and neck region, and is predominantly of epithelial origin (i.e. squamous cell carcinoma). Oral cancer treatment modalities mainly include surgery with or without radiotherapy and chemotherapy. Though proven effective, chemotherapy has significant adverse effects with possibilities of tumor resistance to anticancer drugs and recurrence. Thus, there is an imperative need to identify suitable anticancer therapies that are highly precise with minimal side effects and to make oral cancer treatment effective and safer. Among the available adjuvant therapies is curcumin, a plant polyphenol isolated from the rhizome of the turmeric plant Curcuma longa. Curcumin has been demonstrated to have anti-infectious, antioxidant, anti-inflammatory, and anticarcinogenic properties. Curcumin has poor bioavailability, which has been overcome by its various analogues and nanoformulations, such as nanoparticles, liposome complexes, micelles, and phospholipid complexes. Studies have shown that the anticancer effects of curcumin are mediated by its action on multiple molecular targets, including activator protein 1, protein kinase B (Akt), nuclear factor κ-light-chain-enhancer of activated B cells, mitogen-activated protein kinase, epidermal growth factor receptor (EGFR) expression, and EGFR downstream signaling pathways. These targets play important roles in oral cancer pathogenesis, thereby making curcumin a promising adjuvant treatment modality. This review aims to summarize the different novel formulations of curcumin and their role in the treatment of oral cancer.

Autophagic mechanisms in longevity intervention: role of natural active compounds

The term 'autophagy' literally translates to 'self-eating' and alterations to autophagy have been identified as one of the several molecular changes that occur with aging in a variety of species. Autophagy and aging, have a complicated and multifaceted relationship that has recently come to light thanks to breakthroughs in our understanding of the various substrates of autophagy on tissue homoeostasis. Several studies have been conducted to reveal the relationship between autophagy and age-related diseases. The present review looks at a few new aspects of autophagy and speculates on how they might be connected to both aging and the onset and progression of disease. Additionally, we go over the most recent preclinical data supporting the use of autophagy modulators as age-related illnesses including cancer, cardiovascular and neurodegenerative diseases, and metabolic dysfunction. It is crucial to discover important targets in the autophagy pathway in order to create innovative therapies that effectively target autophagy. Natural products have pharmacological properties that can be therapeutically advantageous for the treatment of several diseases and they also serve as valuable sources of inspiration for the development of possible new small-molecule drugs. Indeed, recent scientific studies have shown that several natural products including alkaloids, terpenoids, steroids, and phenolics, have the ability to alter a number of important autophagic signalling pathways and exert therapeutic effects, thus, a wide range of potential targets in various stages of autophagy have been discovered. In this review, we summarised the naturally occurring active compounds that may control the autophagic signalling pathways.

Effects of curcumin on oral cancer at molecular level: A systematic review

This systematic review mainly focuses on the effects of curcumin on oral cancer cells at the molecular level and summarizes the results of the studies. We searched and analyzed various databases such as Pub Med, ProQuest, Google Scholar, Science Direct, and Scopus. Searches were conducted from 2006 to 2021. This systematic review evaluated various effects of curcumin on oral cancer at the molecular level. All the studies related to the effects of curcumin on oral cancer, both in-vivo and in-vitro, were included. After abstract and text screening a total of 13 articles were finally selected for the study based on the inclusion and exclusion criteria. All most all the included studies reported that after treating the cell lines with curcumin there is a reduction in cell proliferation and cell growth, analyzed using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Curcumin also induces S phase cell cycle arrest and also prevents Tregs migration. The curcumin reverses the process of epithelial mesenchymal transition (EMT) back to mesenchymal epithelial transition (MET). From this review, it is concluded that curcumin inhibited proliferation, migration, invasion, and metastasis, and induced apoptosis via modulating multiple signaling pathways in oral cancer cell lines. But further clinical trials are needed for a detailed evaluation of the effects of curcumin on patients with oral cancer.

New Visions on Natural Products and Cancer Therapy: Autophagy and Related Regulatory Pathways

Macroautophagy (autophagy) has been a highly conserved process throughout evolution and allows cells to degrade aggregated/misfolded proteins, dysfunctional or superfluous organelles and damaged macromolecules, in order to recycle them for biosynthetic and/or energetic purposes to preserve cellular homeostasis and health. Changes in autophagy are indeed correlated with several pathological disorders such as neurodegenerative and cardiovascular diseases, infections, cancer and inflammatory diseases. Conversely, autophagy controls both apoptosis and the unfolded protein response (UPR) in the cells. Therefore, any changes in the autophagy pathway will affect both the UPR and apoptosis. Recent evidence has shown that several natural products can modulate (induce or inhibit) the autophagy pathway. Natural products may target different regulatory components of the autophagy pathway, including specific kinases or phosphatases. In this review, we evaluated ~100 natural compounds and plant species and their impact on different types of cancers via the autophagy pathway. We also discuss the impact of these compounds on the UPR and apoptosis via the autophagy pathway. A multitude of preclinical findings have shown the function of botanicals in regulating cell autophagy and its potential impact on cancer therapy; however, the number of related clinical trials to date remains low. In this regard, further pre-clinical and clinical studies are warranted to better clarify the utility of natural compounds and their modulatory effects on autophagy, as fine-tuning of autophagy could be translated into therapeutic applications for several cancers.

Effect of Curcumin-Loaded Mesoporous Silica Nanoparticles on the Head and Neck Cancer Cell Line, HN5

Curcumin is an active ingredient isolated from Curcuma longa. It has several pharmacological effects, including anticancer, anti-inflammatory, and antioxidant effects. Due to its low bioavailability, chemical structure instability, and easy oxidation, the application of curcumin has been limited. In this study, to overcome these limitations, curcumin-loaded mesoporous silica nanoparticles (Cur-MSN) were prepared, and the anticancerous effect of Cur-MSNs on head and neck cancer cells, HN5, was investigated. Transmission electron microscopy (TEM) revealed rod-shaped mesoporous nanoparticles with average particle size smaller than 100 nm. Higher cytotoxicity of Cur-MSNs was seen in treated cancer cells compared with free curcumin. The expression of Bcl-2 was significantly reduced in the presence of Cur-MSNs compared to the control (untreated HN5 cells) (p < 0.05). A 3.43-fold increase in the Bax/Bcl-2 ratio was seen in Cur-MSNs treated HN5 cells at the IC50. Cur-MSNs increased intracellular reactive oxygen species (ROS) production. Based on these novel results, we suggest that Cur-MSNs offer efficacy for cancer treatment and future studies should further characterize their properties in various experimental cancer models.

A renewed concept on the MAPK signaling pathway in cancers: Polyphenols as a choice of therapeutics

Abnormalities in the mitogen-activated protein kinase (MAPK) signaling pathway are a key contributor to the carcinogenesis process and have therefore been implicated in several aspects of tumorigenesis, including cell differentiation, proliferation, invasion, angiogenesis, apoptosis, and metastasis. This pathway offers multiple molecular targets that may be modulated for anticancer activity and is of great interest for several malignancies. Polyphenols from various dietary sources have been observed to interfere with certain aspects of this pathway and consequently play a substantial role in the development and progression of cancer by suppressing cell growth, inactivating carcinogens, blocking angiogenesis, causing cell death, and changing immunity. A good number of polyphenolic compounds have shown promising outcomes in numerous pieces of research and are currently being investigated clinically to treat cancer patients. The current study concentrates on the role of the MAPK pathway in the development and metastasis of cancer, with particular emphasis on dietary polyphenolic compounds that influence the different MAPK sub-pathways to obtain an anticancer effect. This study aims to convey an overview of the various aspects of the MAPK pathway in cancer development and invasion, as well as a review of the advances achieved in the development of polyphenols to modulate the MAPK signaling pathway for better treatment of cancer.

Curcumin attenuates Cr (VI)-induced cell growth and migration by targeting autophagy-dependent reprogrammed metabolism

Hexavalent chromium [Cr (VI)] is a well-established carcinogen. Cr (VI)-treated cells are phenotypically characterized by aberrant levels of growth and migration. Curcumin, a polyphenolic compound from the plant turmeric, has been found to possess antiproliferation, anti-inflammation, and antioxidant properties. In this study, the effect of curcumin on Cr (VI)-induced cell survival and migration and the underlying mechanism were investigated. Cell viability assay on A549 and human embryonic lung fibroblast cells showed that curcumin at the concentration of 10 µM could significantly attenuate Cr (VI)-induced viability in both cell lines. Following Western blot assay and metabolomics assays, cotreatment with curcumin and Cr (VI) resulted in the suppression of Cr (VI)-induced glycolysis-, autophagy-, and migration-related proteins. Meanwhile, curcumin increased Cr (VI)-reduced oxidative phosphorylation (OXPHOS)-related proteins, COXIV and ND1. Moreover, curcumin suppressed Cr (VI)-induced mitochondrial dysfunction, mitochondrial mass decrease, and mitochondrial membrane potential loss. Treatment with curcumin for 24 h significantly attenuated pcATG4B-induced autophagy and the subsequent expression of glucose transporter 1, hexokinase II, and pyruvate kinase M2. Wound healing and transwell assay demonstrated that curcumin reduced Cr (VI)-induced cell migration. Taken together, these results showed that curcumin was able to attenuate Cr (VI)-induced cell viability and migration by targeting autophagy-dependent reprogrammed metabolism from OXPHOS to glycolysis.

A Comprehensive Review on the Benefits and Problems of Curcumin with Respect to Human Health

Curcumin is the most important active component in turmeric extracts. Curcumin, a natural monomer from plants has received a considerable attention as a dietary supplement, exhibiting evident activity in a wide range of human pathological conditions. In general, curcumin is beneficial to human health, demonstrating pharmacological activities of anti-inflammation and antioxidation, as well as antitumor and immune regulation activities. Curcumin also presents therapeutic potential in neurodegenerative, cardiovascular and cerebrovascular diseases. In this review article, we summarize the advancements made in recent years with respect to curcumin as a biologically active agent in malignant tumors, Alzheimer’s disease (AD), hematological diseases and viral infectious diseases. We also focus on problems associated with curcumin from basic research to clinical translation, such as its low solubility, leading to poor bioavailability, as well as the controversy surrounding the association between curcumin purity and effect. Through a review and summary of the clinical research on curcumin and case reports of adverse effects, we found that the clinical transformation of curcumin is not successful, and excessive intake of curcumin may have adverse effects on the kidneys, heart, liver, blood and immune system, which leads us to warn that curcumin has a long way to go from basic research to application transformation.

Curcumin analog HO-3867 triggers apoptotic pathways through activating JNK1/2 signalling in human oral squamous cell carcinoma cells

Human oral squamous cell carcinoma (OSCC) is the common head and neck malignancy in the world. While surgery, radiotherapy and chemotherapy are emerging as the standard treatment for OSCC patients, the outcome is limited to the recurrence and side effects. Therefore, patients with OSCC require alternative strategies for treatment. In this study, we aimed to explore the therapeutic effect and the mode of action of the novel curcumin analog, HO-3867, against human OSCC cells. We analysed the cytotoxicity of HO-3867 using MTT assay. In vitro mechanic studies were performed to determine whether MAPK pathway is involved in HO-3867 induced cell apoptosis. As the results, we found HO-3867 suppressed OSCC cells growth effectively. The flow cytometry data indicate that HO-3867 induce the sub-G1 phase. Moreover, we found that HO-3867 induced cell apoptosis by triggering formation of activated caspase 3, caspase 8, caspase 9 and PARP. After dissecting MAPK pathway, we found HO-3867 induced cell apoptosis via the c-Jun N-terminal kinase (JNK)1/2 pathway. Our results suggest that HO-3867 is an effective anticancer agent as its induction of cell apoptosis through JNK1/2 pathway in human oral cancer cells.

Emerging Role of Autophagy in the Development and Progression of Oral Squamous Cell Carcinoma

Autophagy is a cellular catabolic process, which is characterized by degradation of damaged proteins and organelles needed to supply the cell with essential nutrients. At basal levels, autophagy is important to maintain cellular homeostasis and development. It is also a stress responsive process that allows the cells to survive when subjected to stressful conditions such as nutrient deprivation. Autophagy has been implicated in many pathologies including cancer. It is well established that autophagy plays a dual role in different cancer types. There is emerging role of autophagy in oral squamous cell carcinoma (OSCC) development and progression. This review will focus on the role played by autophagy in relation to different aspects of cancer progression and discuss recent studies exploring the role of autophagy in OSCC. It will further discuss potential therapeutic approaches to target autophagy in OSCC.

Anti-glioblastoma effects of nanomicelle-curcumin plus erlotinib

Glioblastoma (GBM), one of the most significant brain neoplasms, is characterized by high metastasis and recurrence. Crossing the blood-brain barrier is one of the main therapeutic obstacles, seriously hampering therapeutic agents entering the brain. This research investigated the co-delivery of erlotinib and curcumin via nanomicelles for enhancing anti-GBM treatment in vitro. For this purpose, curcumin and nanomicelle-curcumin (50 μM) were investigated alone and also with erlotinib (50 μM) in U87 glioblastoma cells. The cell viability of U87 cells after exposure to curcumin/nanomicelle curcumin/erlotinib and their combinations was measured by CCK-8 assay. The expression of the Wnt signaling-related genes was measured by qRT-PCR assay. The altered expression of NF-kB and proteins associated with angiogenesis, apoptosis, and autophagy were investigated by western blot assay. Compared with the control, all treatments reduced the viability of U87 glioblastoma cells. Furthermore, the level of proteins related to angiogenesis and Wnt pathway-associated genes in the nanomicelle-curcumin + erlotinib group were significantly decreased compared to the curcumin, erlotinib, and control groups. Each treatment regulated autophagy and apoptosis-associated proteins. Total phospho-NF-κB (p65) and total NF-κB (p65) declined in each treatment at the protein levels. Overall, nanomicelle-curcumin alone or combined with erlotinib showed anti-GBM activity in the U87 cell line by regulating the signaling pathways in GBM pathogenesis and thus may be a promising nanodrug candidate for application in the field of GBM therapy.

Targeting Drug Chemo-Resistance in Cancer Using Natural Products

Cancer is one of the leading causes of death globally. The development of drug resistance is the main contributor to cancer-related mortality. Cancer cells exploit multiple mechanisms to reduce the therapeutic effects of anticancer drugs, thereby causing chemotherapy failure. Natural products are accessible, inexpensive, and less toxic sources of chemotherapeutic agents. Additionally, they have multiple mechanisms of action to inhibit various targets involved in the development of drug resistance. In this review, we have summarized the basic research and clinical applications of natural products as possible inhibitors for drug resistance in cancer. The molecular targets and the mechanisms of action of each natural product are also explained. Diverse drug resistance biomarkers were sensitive to natural products. P-glycoprotein and breast cancer resistance protein can be targeted by a large number of natural products. On the other hand, protein kinase C and topoisomerases were less sensitive to most of the studied natural products. The studies discussed in this review will provide a solid ground for scientists to explore the possible use of natural products in combination anticancer therapies to overcome drug resistance by targeting multiple drug resistance mechanisms.

Molecular Mechanisms Responsible for In Vitro Cytotoxic Attributes of Conyza bonariensis Extract against Lymphoblastic Leukaemia Jurkat Cells

BACKGROUND

Conyza bonariensis is known to have anti-cancer properties.

OBJECTIVE

The study investigated the in vitro pro-apoptotic properties of Conyza bonariensis (C. bonariensis) towards human lymphoblastic leukemia Jurkat cells.

METHODS

C. bonariensis are extracted with non-polar solvent by maceration. MTS cell viability assay was employed to determine the cytotoxic activity of the extract towards human leukemia Jurket cells and normal Peripheral Blood Mononuclear Cells (PBMCs) cells. The phytochemical composition of the extract was chemically characterized using HPLC. Flow cytometric studies (FACS) were conducted to explore the pro-apoptotic potential of the extract. Western blot studies were employed to identify the molecular targets involved in the induction of apoptosis.

RESULTS

The n-hexane extract showed selective cytotoxic activity towards Jurkat cells. FACS analysis indicated that the extract induced early and late apoptosis in Jurkat cells. Western blot studies revealed that the extract down-regulated the expression of DNMT1, SIRT1, and UHRF1 with a simultaneous up-regulation of the expression of p73 and caspases-3 proteins. HPLC characterization of the extract revealed the presence of phenolic compounds.

CONCLUSION

Overall these findings demonstrate that the anticancer effects of a Conyza bonariensis extract towards human lymphoblastic leukemiais due to the modulation of the activity of multiple oncogenic and tumor suppressor proteins and that its phenolic content is involved are proposed to be responsible for these activities.

Melatonin Induces Autophagy via Reactive Oxygen Species-Mediated Endoplasmic Reticulum Stress Pathway in Colorectal Cancer Cells

Even though an increasing number of anticancer treatments have been discovered, the mortality rates of colorectal cancer (CRC) have still been high in the past few years. It has been discovered that melatonin has pro-apoptotic properties and counteracts inflammation, proliferation, angiogenesis, cell invasion, and cell migration. In previous studies, melatonin has been shown to have an anticancer effect in multiple tumors, including CRC, but the underlying mechanisms of melatonin action on CRC have not been fully explored. Thus, in this study, we investigated the role of autophagy pathways in CRC cells treated with melatonin. In vitro CRC cell models, HT-29, SW48, and Caco-2, were treated with melatonin. CRC cell death, oxidative stress, and autophagic vacuoles formation were induced by melatonin in a dose-dependent manner. Several autophagy pathways were examined, including the endoplasmic reticulum (ER) stress, 5′–adenosine monophosphate-activated protein kinase (AMPK), phosphoinositide 3-kinase (PI3K), serine/threonine-specific protein kinase (Akt), and mammalian target of rapamycin (mTOR) signaling pathways. Our results showed that melatonin significantly induced autophagy via the ER stress pathway in CRC cells. In conclusion, melatonin demonstrated a potential as an anticancer drug for CRC.

Autophagy Modulators From Chinese Herbal Medicines: Mechanisms and Therapeutic Potentials for Asthma

Asthma has become a global health issue, suffering more than 300 million people in the world, which is a heterogeneous disease, usually characterized by chronic airway inflammation and airway hyperreactivity. Combination of inhaled corticosteroids (ICS) and long acting β-agonists (LABA) can relieve asthma symptoms and reduce the frequency of exacerbations, especially for patients with refractory asthma, but there are limited treatment options for people who do not gain control on combination ICS/LABA. The increase in ICS dose generally provides little additional benefit, and there is an increased risk of side effects. Therefore, therapeutic interventions integrating the use of different agents that focus on different targets are needed to overcome this set of diseases. Some findings suggest autophagy is closely correlated with the severity of asthma through eosinophilic inflammation, and its modulation may provide novel therapeutic approaches for severe allergic asthma. The chinese herbal medicine (CHM) have been demonstrated clinically as potent therapeutic interventions for asthma. Moreover some reports have found that the bioactive components isolated from CHM could modulate autophagy, and exhibit potent Anti-inflammatory activity. These findings have implied the potential for CHMs in asthma or allergic inflammation therapy via the modulation of autophagy. In this review, we discuss the basic pathomechanisms underpinning asthma, and the potential role of CHMs in treating asthma with modulating autophagy.

Therapeutic effect of curcumin on oral diseases: A literature review

Curcumin (diferuloylmethane) is a polyphenol compound extracted from the rhizome of the plant Curcuma longa. It has the feature of being a yellow or orange pigment with a variety of biological properties, including anti-inflammation, antioxidation, anti-tumor, anti-bacteria, anti-fungus, and wound healing. Previous studies have reported the role of curcumin in treating different inflammatory diseases and tumors in vitro and in vivo. Recently, it has been demonstrated that curcumin has therapeutic benefits in oral mucosal diseases, periodontal diseases, and mouth neoplasms. In this review, we will focus on the therapeutic effects of curcumin on oral diseases.

From Simple Mouth Cavities to Complex Oral Mucosal Disorders-Curcuminoids as a Promising Therapeutic Approach

Oral diseases are among the most common encountered health issues worldwide, which are usually associated with anomalies of the oral cavity, jaws, and salivary glands. Despite the availability of numerous treatment modalities for oral disorders, a limited clinical response has been observed because of the inefficacy of the drugs and countless adverse side effects. Therefore, the development of safe, efficacious, and wide-spectrum therapeutics is imperative in the battle against oral diseases. Curcumin, extracted from the golden spice turmeric, is a well-known natural polyphenol that has been extensively studied for its broad pleiotropic attributes and its ability to modulate multiple biological processes. It is well-documented to target pro-inflammatory mediators like NF-κB, ROS, COX-2, IL-1, IL-2, TGF-β, growth factors, apoptotic proteins, receptors, and various kinases. These properties make curcumin a promising nutraceutical in the treatment of many oral diseases like oral submucous fibrosis, oral mucositis, oral leukoplakia, oral erythroplakia, oral candidiasis, aphthous stomatitis, oral lichen planus, dental caries, periodontitis, and gingivitis. Numerous in vitro and in vivo studies have shown that curcumin alleviates the symptoms of most of the oral complications, including the inhibition of the progression of oral cancer. In this regard, many clinical trials have been completed, and many are ongoing to investigate the "curcumin effect" in oral maladies. Therefore, the current review delineates the mechanistic framework of curcumin's propensity in curbing oral diseases and present outcomes of the clinical trials of curcumin-based therapeutics that can provide a breakthrough in the clinical management of these diseases.

Curcumin Ameliorates Palmitic Acid-Induced Saos-2 Cell Apoptosis Via Inhibiting Oxidative Stress and Autophagy

Objectives

We aimed to determine the effects of curcumin on palmitic acid- (PA-) induced human osteoblast-like Saos-2 cell apoptosis and to explore the potential molecular mechanisms in vitro level.

Methods

Saos-2 cell were cultured with PA with or without curcumin, N-acetylcysteine (NAC, anti-oxidant), 3-methyladenine (3-MA, autophagy inhibitor) AY-22989 (autophagy agonist) or H₂O₂. Then, the effects of PA alone or combined with curcumin on viability, apoptosis, oxidative stress, and autophagy in were detected by CCK-8, flow cytometry assay and western blot.

Results

We found that autophagy was induced, oxidative stress was activated, and apoptosis was promoted in PA-induced Saos-2 cells. Curcumin inhibited PA-induced oxidative stress, autophagy, and apoptosis in Saos-2 cells. NAC successfully attenuated oxidative stress and apoptosis, and 3-MA attenuated oxidative stress and apoptosis in palmitate-induced Saos-2 cells. Interestingly, NAC inhibited PA-induced autophagy, but 3-MA had no obvious effects on oxidative stress in PA-treated Saos-2 cells. In addition, curcumin inhibited H₂O₂ (oxidative stress agonist)-induced oxidative stress, autophagy, and apoptosis, but curcumin had no obvious effect on AY-22989 (autophagy agonist)-induced autophagy and apoptosis.

Conclusion

The present study demonstrated that oxidative stress is an inducer of autophagy and that curcumin can attenuate excess autophagy and cell apoptosis by inhibiting oxidative stress in PA-induced Saos-2 cells.

Updated Review on the Role of Curcumin in Gastrointestinal Cancers

Malignant conditions of the gastrointestinal tract and accessory organs of digestion, including the oral cavity, esophagus, stomach, biliary system, pancreas, small intestine, large intestine, rectum and anus, are referred to as gastrointestinal cancers. Curcumin is a natural compound derived from turmeric with a wide range of biological activities. Several in vitro and in vivo studies have investigated the effects of curcumin on gastrointestinal cancers. In the current review, we aimed to provide an updated summary on the recent findings regarding the beneficial effects of curcumin on different gastrointestinal cancers in the recent decade. For this purpose, ScienceDirect," "Google Scholar," "PubMed," "ISI Web of Knowledge," and "Wiley Online Library" databases were searched using "curcumin", "cancer", and "gastrointestinal organs" as keywords. In vitro studies performed on different gastrointestinal cancerous cell lines have shown that curcumin can inhibit cell growth through cycle arrest at the G2/M and G1 phases, as well as stimulated apoptosis and autophagy by interacting with multiple molecular targets. In vivo studies performed in various animal models have confirmed mainly the chemopreventive effects of curcumin. Several nano-formulations have been proposed to improve the bioavailability of curcumin and increase its absorption. Moreover, curcumin has been used in combinations with many anti-tumor drugs to increase their anticarcinogenic properties. Taken together, curcumin falls within the category of plant-derived substances capable of preventing or treating gastrointestinal cancers. Further studies, particularly clinical trials, on the efficacy and safety of curcumin are suggested in this regard.

Antiproliferative effect and autophagy induction of curcumin derivative ZYX02-Na on the human lung cancer cells A549

At present, a large number of curcumin derivatives had been produced and identified aiming to replace the curcumin in view of its low bioavailability and stability. Here, a novel curcumin derivative ZYX02-Na was first used to reduce the cell viability of human non-small cell lung cells A549, which was confirmed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Flow cytometry and Western blot analysis showed that ZYX02-Na could lead to cell cycle arrest in G0/G1 phase, which demonstrated that ZYX02-Na inhibited the proliferation of A549 cells. Furthermore, the AMPK/mTOR/4E-BP1 signaling pathway was activated in ZYX02-Na-treated A549 cells. Besides, wounding healing and transwell experiments showed that ZYX02-Na could also inhibited the migration ability of A549 cells. Moreover, we also found that ZYX02-Na could induce autophagy of A549 cells by acridine orange staining, GFP-LC3 subcellular localization observation and Western blotting analysis, respectively. In short, our current studies indicated that ZYX02-Na possessed the antiproliferation effect and autophagy induction on A549 cells, while in vivo anticancer study of ZYX02-Na needs to be done in future.

Curcumin-Loaded Bacterial Cellulose/Alginate/Gelatin as A Multifunctional Biopolymer Composite Film

Multifunctional biopolymer composites comprising mechanically-disintegrated bacterial cellulose, alginate, gelatin and curcumin plasticized with glycerol were successfully fabricated through a simple, facile, cost-effective mechanical blending and casting method. SEM images indicate a well-distributed structure of the composites. The water contact angles existed in the range of 50-70°. Measured water vapor permeability values were 300-800 g/m2/24 h, which were comparable with those of commercial dressing products. No release of curcumin from the films was observed during the immersion in PBS and artificial saliva, and the fluid uptakes were in the range of 100-700%. Films were stretchable and provided appropriate stiffness and enduring deformation. Hydrated films adhered firmly onto the skin. In vitro mucoadhesion time was found in the range of 0.5-6 h with porcine mucosa as model membrane under artificial saliva medium. The curcumin-loaded films had substantial antibacterial activity against E. coli and S. aureus. The films showed non-cytotoxicity to human keratinocytes and human gingival fibroblasts but exhibited potent anticancer activity in oral cancer cells. Therefore, these curcumin-loaded films showed their potential for use as leave-on skin applications. These versatile films can be further developed to achieve desirable characteristics for local topical patches for wound care, periodontitis and oral cancer treatment.

The Curcumin Analogue, EF-24, Triggers p38 MAPK-Mediated Apoptotic Cell Death via Inducing PP2A-Modulated ERK Deactivation in Human Acute Myeloid Leukemia Cells

Curcumin (CUR) has a range of therapeutic benefits against cancers, but its poor solubility and low bioavailability limit its clinical use. Demethoxycurcumin (DMC) and diphenyl difluoroketone (EF-24) are natural and synthetic curcumin analogues, respectively, with better solubilities and higher anti-carcinogenic activities in various solid tumors than CUR. However, the efficacy of these analogues against non-solid tumors, particularly in acute myeloid leukemia (AML), has not been fully investigated. Herein, we observed that both DMC and EF-24 significantly decrease the proportion of viable AML cells including HL-60, U937, and MV4-11, harboring different NRAS and Fms-like tyrosine kinase 3 (FLT3) statuses, and that EF-24 has a lower half maximal inhibitory concentration (IC₅₀) than DMC. We found that EF-24 treatment induces several features of apoptosis, including an increase in the sub-G₁ population, phosphatidylserine (PS) externalization, and significant activation of extrinsic proapoptotic signaling such as caspase-8 and -3 activation. Mechanistically, p38 mitogen-activated protein kinase (MAPK) activation is critical for EF-24-triggered apoptosis via activating protein phosphatase 2A (PP2A) to attenuate extracellular-regulated protein kinase (ERK) activities in HL-60 AML cells. In the clinic, patients with AML expressing high level of PP2A have the most favorable prognoses compared to various solid tumors. Taken together, our results indicate that EF-24 is a potential therapeutic agent for treating AML, especially for cancer types that lose the function of the PP2A tumor suppressor.

Mucoadhesive emulgel systems containing curcumin for oral squamous cell carcinoma treatment: From pre-formulation to cytotoxicity in tissue-engineering oral mucosa

Current oral squamous cell carcinoma chemotherapies demonstrate off-target toxicity, which could be reduced by local delivery. Curcumin acts via many cellular targets to give anti-cancer properties; however the bioavailability is hindered by its physicochemical characteristics. The incorporation of curcumin into emulgel systems could be a promising approach for its solubilization and delivery. The aim of this work was to develop emulgel systems containing curcumin for the treatment of oral cancer. The emulgels containing curcumin were prepared with poloxamer 407, acrylic acid derivatives, oil phase (sesame oil or isopropyl myristate). The more stable system was evaluated for mechanical and rheological properties, as well as, the in vitro drug release profile, permeation and cytotoxic potential to oral mucosa models. The flow-throw system evidenced that the formulations could keep 5 min over porcine oral mucosa. Emulgel showed pseudoplastic behavior and a gelation temperature of 33 °C, which ensure their higher consistency. In addition, 70% of the incorporated curcumin was released within 24 h in an in vitro drug release study and could permeate porcine oral mucosa. Monolayers cultures and tissue-engineered models showed the selectivity of the drug and systems for tumor cells. The physicochemical properties, subsequent release and permeation of curcumin to selectivity kill cancer cells could be improved by the incorporation into emulgel systems.

The pivotal role of SUMO-1-JNK-Tau axis in an in vitro model of oxidative stress counteracted by the protective effect of curcumin

Oxidative stress is a toxic cellular condition, strictly related to inflammation and known to be a common feature of many neurodegenerative diseases. The imbalanced redox state modifies several molecular processes including protein SUMOylation, JNK and Tau protein activation, important actors in Alzheimer's disease. In this study, we showed a strong interaction among SUMO-1-JNK-Tau proteins and their molecular targets in an in vitro model (SHSY5Y cell line) of oxidative stress in which a significant reduction of cell viability and an augmented cell death was induced by increased doses of H2O2. The evoked oxidative stress led to a deficiency in the degradation system showing altered levels of Caspase-3, LC3BII/I and Ubiquitin. Curcumin, a natural compound with anti-oxidant and anti-inflammatory effects, demonstrated to tackle oxidative stress re-equilibrating SUMO-1, JNK and Tau functions. Importantly, 5 μM of curcumin induced an efficient recovery of cell viability, a reduction of cell death and a normalization of altered protein degradation marker levels. Interestingly, we found that H2O2 treatment induced a strong co-localization of SUMO-1-p-JNK-Tau proteins in nuclear bodies (NBs) and that curcumin was able to reduce these nuclear aggregates. These results highlight the SUMO-1-JNK-Tau axis key role in oxidative stress and the protective effect of curcumin against this pathological event, focusing on the importance of SUMO/deSUMOylation balance to regulate essential cellular processes.

Targeting Autophagic Pathways by Plant Natural Compounds in Cancer Treatment

Nowadays, natural compounds of plant origin with anticancer effects have gained more attention because of their clinical safety and broad efficacy profiles. Autophagy is a multistep lysosomal degradation pathway that may have a unique potential for clinical benefit in the setting of cancer treatment. To retrieve articles related to the study, the databases of Google Scholar, Web of sciences, Medline and Scopus, using the following keywords: Autophagic pathways; herbal medicine, oncogenic autophagic pathways, tumor-suppressive autophagic pathways, and cancer were searched. Although natural plant compounds such as resveratrol, curcumin, oridonin, gossypol, and paclitaxel have proven anticancer potential via autophagic signaling pathways, there is still a great need to find new natural compounds and investigate the underlying mechanisms, to facilitate their clinical use as potential anticancer agents through autophagic induction.

Iridoids of Valeriana fauriei contribute to alleviating hepatic steatosis in obese mice by lipophagy

Nonalcoholic fatty liver disease (NAFLD) is a common risk factor for metabolic syndrome that increases the risk of future cardiovascular disease, stroke, and diabetes. Recently, autophagy has been proposed as a means to prevent NAFLD. We investigated whether substances with autophagy-inducing activity alleviate NAFLD. The Valeriana fauriei (V. fauriei) was selected as a potential autophagy inducer among various natural materials using a Cyto-ID autophagy detection kit. V. fauriei 70 % ethanol extract (VFE) increased LC3II levels in the presence of the lysosomal inhibitor and reduced the GFP/mCherry puncta ratio, suggesting that VFE enhanced autophagy. VFE reduced oleic acid (OA)-induced lipid accumulation and increased the number of autophagosome in hepatocytes. Autophagy induction by VFE is due to inhibition of mTORC1 activity. VFE supplementation reduced fatty liver by downregulating lipogenesis-related genes and increased the autophagy, as revealed by TEM and IHC analysis in the fatty liver. We identified iridoids as main compounds of VFE; didrovaltrate (DI), valeriotriate B (VAL B), valeriotetrate C (VAL C), valtrate (VAL), and valechlorine (VC) were shown to enhance autophagy. These compounds also reduced OA-induced lipid accumulation in an Atg5-dependent manner. Taken together, VFE and its iridoids might be effective in alleviating fatty liver by acting as autophagy enhancers to break down LDs.

Anti-Cancer Effects of Traditional Medicinal Herbs on Oral Squamous Cell Carcinoma

BACKGROUNDS

Oral squamous cell carcinoma (OSCC) is among the most frequent oral cancers in individuals under 40. Documents have endorsed that a diet enriched with fruit and vegetables can banish the risk of developing major cancers. This study aimed to evaluate the effects of different concentrations of four medicinal herbs including saffron, ginger, cinnamon and curcumin on OSCC cell line.

METHODS

Having obtained the aqueous extract of the four herbs, they were administered on OSCC cell lines per se and in dual, triple, and quadruple combinations. Their effects were measured in different concentrations and in 24 and 48 hours by using MTT assay.

RESULTS

The minimum and maximum effective concentrations were respectively 108 and 217 mg/ml for curcumin with IC30 of 77mg/ml, 108 and 270 mg/ml for ginger with IC30 of 58 mg/ml, 2 and 10 mg/ml for saffron with IC30 of 1.9 mg/ml, and 5 and 40 mg/ml for cinnamon with IC30 of 3.3 mg/ml. The best effect of the combinations was seen for cinnamon-saffron after both 24 and 48 hours and the four herbs combination after 48 hours.

CONCLUSION

Although all the four herbs were effective on OSCC cell line, the strongest extract was saffron, followed by cinnamon. Combination of cinnamon-saffron and combination of the four herbs showed maximum effects. These findings suggest that traditional medicinal herbs may potentially contribute to oral cancer treatment; providing new windows for the development of new therapeutic strategies for OSCC.

Curcumin analog CUR5-8 ameliorates nonalcoholic fatty liver disease in mice with high-fat diet-induced obesity

OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) occurs when excess fat storage in the liver and it is strongly linked with metabolic syndrome including obesity, insulin resistance, dyslipidemia and hypertension. Curcumin5-8 (CUR5-8) is a synthetic derivative of naturally active curcumin (CUR) that has anti-oxidative and anti-inflammatory properties. In the present study, we investigated the effects of CUR5-8, a novel CUR analog, on hepatic steatosis in mice with high-fat diet (HFD)-induced obesity.

METHODS

Based on their diets for 13 weeks, the mice were categorized into the following six groups: regular diet (RD, n = 10), RD with CUR (RD + CUR, 100 mg/kg/day, n = 10), RD with CUR5-8 (RD + CUR5-8, 100 mg/kg/day, n = 10), high-fat diet-induced obese mice (HFD, n = 10), HFD with CUR (HFD + CUR, 100 mg/kg/day, n = 10), and HFD with CUR5-8 (HFD + CUR5-8, 100 mg/kg/day, n = 10) for 13 weeks. Hematoxylin and eosin (H&E) staining of the sections revealed hepatic steatosis.

RESULTS

CUR5-8 administration prevented increase in body and liver weights in mice with HFD-induced obesity. Compared to the HFD group, insulin resistance was significantly improved in the HFD + CUR5-8 group. Serum alanine aminotransferase level, which is an indicator of liver damage, was also decreased after CUR5-8 administration. H&E staining revealed that CUR5-8 treatment decreased hepatic steatosis in mice with HFD-induced obesity. Interestingly, CUR5-8, and not CUR, decreased the elevated liver triglyceride level induced by the HFD.

CONCLUSIONS

These findings suggest that CUR5-8 ameliorates insulin resistance and hepatic steatosis in mice with HFD-induced obesity.

Enhanced sciatic nerve regeneration by poly-L-lactic acid/multi-wall carbon nanotube neural guidance conduit containing Schwann cells and curcumin encapsulated chitosan nanoparticles in rat

The main aim of this study was to improve the efficacy of peripheral nerve regeneration by an artificial neural guidance conduit (NGC) as a carrier to transplant allogeneic Schwann cells (SCs) and curcumin encapsulated chitosan nanoparticles (nanocurcumin). The conduit was prepared by poly-L-lactic acid (PLLA) and surface-modified multi-wall carbon nanotubes (mMWCNT) and filled with SCs and nanocurcumin. SCs play an important role in the regeneration of injured peripheral nerve and controlled curcumin release can decrease SCs apoptosis, and enhance the regeneration and functional recovery of injured peripheral nerves. The mechanical properties, contact angle, and cell biocompatibility experiments showed that the optimized concentration of mMWCNT inside PLLA wall of conduits was 0.15 wt%. The drug release experiments showed slower release of curcumin from nanocurcumin samples compared to nanocurcumin encapsulated inside NGC wrapped fibrin gel sample. It was found that simultaneous using of both SCs and curcumin inside NGC had a significant role in sciatic nerve regeneration in vivo. Histological examination revealed a significant increase in the number of axons in injured sciatic nerve following treatment by SCs and nanocurcumin compared to negative control group. Histological evaluation also revealed a significant decrease in the number of vessels in fibrin groups compared to positive control group. The results showed that there was no significant difference between the reaction time and sciatic functional index (SFI) values of rats with injured sciatic nerve treated by NGC/SCs/nanocurcumin sample and autograft sample. In conclusion, our results strongly showed that PLLA/mMWCNT nanofibrous conduit filled with fibrin gel containing SCs and nanocurcumin is a proper strategy for improving nerve regeneration after a nerve transaction in the rat.

Iron chelation by curcumin suppresses both curcumin-induced autophagy and cell death together with iron overload neoplastic transformation

Iron overload, notably caused by hereditary hemochromatosis, is an excess storage of iron in various organs that causes tissue damage and may promote tumorigenesis. To manage that disorder, free iron depletion can be induced by iron chelators like deferoxamine that are of increasing interest also in the cancer field since iron stock could be a potent target for managing tumorigenesis. Curcumin, a well-known active substance extracted from the turmeric rhizome, destabilizes endoplasmic reticulum, and secondarily lysosomes, thereby increasing mitophagy/autophagy and subsequent apoptosis. Recent findings show that cells treated with curcumin also exhibit a decrease in ferritin, which is consistent with its chemical structure and iron chelating activity. Here we investigated how curcumin influences the intracellular effects of iron overload via Fe-nitriloacetic acid or ferric ammonium citrate loading in Huh-7 cells and explored the consequences in terms of antioxidant activity, autophagy, and apoptotic signal transduction. In experiments with T51B and RL-34 epithelial cells, we have found evidence that curcumin-iron complexation abolishes both curcumin-induced autophagy and apoptosis, together with the tumorigenic action of iron overload.

Curcumin diethyl disuccinate, a prodrug of curcumin, enhances anti-proliferative effect of curcumin against HepG2 cells via apoptosis induction

Curcumin (Cur) has been reported to have anti-hepatocellular carcinoma activity but its poor oral bioavailability limits its further development as a chemotherapeutic agent. We synthesized previously a succinate ester prodrug of Cur, curcumin diethyl disuccinate (CurDD) with better chemical stability in a buffer solution pH 7.4. Here, we further investigated and compared the cellular transport and anti-proliferative activity against HepG2 cells of CurDD and Cur. Transport of CurDD across the Caco-2 monolayers provided a significantly higher amount of the bioavailable fraction (BF) of Cur with better cytotoxicity against HepG2 cells compared to that of Cur (p < 0.05). Flow cytometric analysis showed that the BF of CurDD shifted the cell fate to early and late apoptosis to a higher extent than that of Cur. The Western blot analysis revealed that CurDD increased Bax protein expression, downregulated Bcl-2 protein, activated caspase-3 and -9 and increased LC3-II protein level in HepG2 cells. Flow cytometric and immunoblotting results suggest that CurDD can induce HepG2 cell death via an apoptotic pathway. We suggest that CurDD can overcome the limitations of Cur in terms of cellular transport with a potential for further extensive in vitro and in vivo studies of anti-hepatocellular carcinoma effects.

Curcumin overcome primary gefitinib resistance in non-small-cell lung cancer cells through inducing autophagy-related cell death

BACKGROUND

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are being wildly used as target therapy in non-small-cell lung cancer (NSCLC). However, NSCLC patients with wild-type EGFR and KRAS mutation are primary resistant to EGFR-TKIs such as gefitinib. Curcumin has been known as a potential therapeutic agent for several major human cancers. In this study, we investigated the effect of curcumin on the reversal of gefitinib resistance in NSCLC cells as well as their molecular bases.

METHODS

H157 (wild-type EGFR and KARS mutation) and H1299 (wild-type EGFR and HRAS mutation) cells were treated with gefitinib or curcumin alone, or the two combination, and then cell viability, EGFR activity, expressions of Sp1 and Sp1-dependent proteins and receptor tyrosine kinases, markers of autophagy and apoptosis were examined by using CCK-8, colony formation, immunoblot, quantitative PCR, immunofluoscence, and flow cytometry assays. Also xenograft experiments were conduced to test the synergism of curcumin to gefitinib.

RESULTS

Our results showed that curcumin significantly enhanced inhibitory effect of gefitinib on primary gefitinib-resistant NSCLC cell lines H157 and H1299. Combination treatment with curcumin and gefitinib markedly downregulated EGFR activity through suppressing Sp1 and blocking interaction of Sp1 and HADC1, and markedly suppressed receptor tyrosine kinases as well as ERK/MEK and AKT/S6K pathways in the resistant NSCLC cells. Meanwhile, combination treatment of curcumin and gefitinib caused dramatic autophagy induction, autophagic cell death and autophagy-mediated apoptosis, compared to curcumin or gefitinib treatment alone, as evidenced by the findings that curcumin and gefitinib combination treatment-produced synergistic growth inhibition and apoptosis activation can be reversed by pharmacological autophagy inhibitors (Baf A1 or 3-MA) or knockdown of Beclin-1 or ATG7, also can be partially returned by pan-caspase inhibitor (Z-VAD-FMK) in H157 and H1299 cells. Xenograft experiments in vivo yielded similar results.

CONCLUSIONS

These data indicate that the synergism of curcumin on gefitinib was autophagy dependent. Curcumin can be used as a sensitizer to enhance the efficacy of EGFR-TKIs and overcome the EGFR-TKI resistance in NSCLC patients with wild-type EGFR and/or KRAS mutation.

Chlorogenic acid prevents paraquat-induced apoptosis via Sirt1-mediated regulation of redox and mitochondrial function

Paraquat (PQ) is a widely used agro-chemical in agriculture and highly toxic to humans. Although the mechanism of PQ poisoning is not clear, it has been well documented that reactive oxygen species (ROS) generation and apoptosis play pivotal roles. Alternatively, chlorogenic acid (CA) is a biologically active dietary polyphenol, playing several therapeutic roles. However, it is not known whether CA has protective effect on PQ-induced apoptosis. Here, we investigated the effect of CA in preventing PQ-induced apoptosis and explored the underlying mechanisms. A549 cells were pretreated with 100 µM CA for 24 h and then exposed to 160 µM PQ for 24 h. We found that CA was effective in preventing PQ-induced apoptotic features, including the release of cytochrome c from the mitochondria to cytoplasm, the cleavages of caspase 3 and caspase 9, and the increases in levels of Bcl-2-associated X protein (Bax) and intracellular calcium ions. CA alleviated ROS production and prevented the reduction of antioxidant capacity in cells exposed to PQ by increasing NF-E2-related factor 2 (Nrf2), superoxide dismutase 2 (SOD2) and glutathione levels. In addition, CA also attenuated PQ-induced alterations of mitochondrial structure and function (such as the decreases in membrane potential and adenosine triphosphate level), and the impaired autophagic flux was improved by CA. Down-regulation of sirtuin 1 (Sirt1) by short hairpin RNA reversed the protective effects of CA. Thus, CA may be viewed as a potential drug to treat PQ-induced lung epithelial cell apoptosis and other disorders with similar pathologic mechanisms.

Paris Polyphylla Inhibits Colorectal Cancer Cells via Inducing Autophagy and Enhancing the Efficacy of Chemotherapeutic Drug Doxorubicin

Colorectal cancer is one of the most common cancers worldwide and chemotherapy is the main approach for the treatment of advanced and recurrent cases. Developing an effective complementary therapy could help to improve tumor suppression efficiency and control adverse effects from chemotherapy. Paris polyphylla is a folk medicine for treating various forms of cancer, but its effect on colorectal cancer is largely unexplored. The aim of the present study is to investigate the tumor suppression efficacy and the mechanism of action of the ethanolic extract from P. polyphylla (EEPP) in DLD-1 human colorectal carcinoma cells and to evaluate its combined effect with chemotherapeutic drug doxorubicin. The data indicated that EEPP induced DLD-1 cell death via the upregulation of the autophagy markers, without triggering p53- and caspase-3-dependent apoptosis. Moreover, EEPP treatment in combination with doxorubicin enhanced cytotoxicity in these tumor cells. Pennogenin 3-O-beta-chacotrioside and polyphyllin VI were isolated from EEPP and identified as the main candidate active components. Our results suggest that EEPP deserves further evaluation for development as complementary chemotherapy for colorectal cancer.

Curcumin induces apoptotic cell death and protective autophagy by inhibiting AKT/mTOR/p70S6K pathway in human ovarian cancer cells

PURPOSE

Curcumin (Cur), a yellow-colored dietary flavor from the plant (Curcuma longa), has been demonstrated to potentially resist diverse diseases, including ovarian cancer, but drug resistance becomes a major limitation of its success clinically. The key molecule or mechanism associated with curcumin resistance in ovarian cancer still remains unclear. The aim of our study was to investigate the effects of curcumin on autophagy in ovarian cancer cells and elucidate the underlying mechanism.

METHODS

In our study, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), EdU proliferation assay and colony-forming assay were used to assess cell viability. Apoptosis was detected by western blot and flow cytometric analysis of apoptosis. Autophagy was defined by both electron microscopy and immunofluorescence staining markers such as microtubule-associated protein 1 light chain 3 (LC3). Plasmid construction and shRNA transfection helped us to confirm the function of curcumin.

RESULTS

Curcumin reduced cell viability and induced apoptotic cell death by MTT assay in human ovarian cancer cell lines SK-OV-3 and A2780 significantly. Electron microscopy, western blot and immunofluorescence staining proved that curcumin could induce protective autophagy. Moreover, treatment with autophagy-specific inhibitors or stable knockdown of LC3B by shRNA could markedly enhance curcumin-induced apoptosis. Finally, the cells transiently transfected with AKT1 overexpression plasmid demonstrated that autophagy had a direct relationship with the AKT/mTOR/p70S6K pathway.

CONCLUSIONS

Curcumin can induce protective autophagy of human ovarian cancer cells by inhibiting the AKT/mTOR/p70S6K pathway, indicating the synergistic effects of curcumin and autophagy inhibition as a possible strategy to overcome the limits of current therapies in the eradication of epithelial ovarian cancer.

Curcumin Promotes Connexin 43 Degradation and Temozolomide-Induced Apoptosis in Glioblastoma Cells

Glioblastoma (GBM) is the most commonly occurring tumor in the cerebral hemispheres. Currently, temozolomide (TMZ), an alkylating agent that induces DNA strand breaks, is considered the frontline chemotherapeutic agent for GBM. Despite its frontline status, GBM patients commonly exhibit resistance to TMZ treatment. We have recently established and characterized TMZ-resistant human glioma cells. The aim of this study is to investigate whether curcumin modulates cell apoptosis through the alternation of the connexin 43 (Cx43) protein level in TMZ-resistant GBM. Overexpression of Cx43, but not ATP-binding cassette transporters (ABC transporters), was observed (approximately 2.2-fold) in TMZ-resistant GBM cells compared to the Cx43 levels in parental GBM cells. Furthermore, at a concentration of 10 μ M, curcumin significantly reduced Cx43 protein expression by about 40%. In addition, curcumin did not affect the expression of other connexins like Cx26 or epithelial-to-mesenchymal transition (EMT) proteins such as β -catenin or α E-catenin. Curcumin treatment led to an increase in TMZ-induced cell apoptosis from 4% to 8%. Importantly, it did not affect the mRNA expression level of Cx43. Concomitant treatment with the translation inhibitor cycloheximide (CHX) exerted additional effects on Cx43 degradation. Treatment with the autophagy inhibitor 3-MA (methyladenine) did not affect the curcumin-induced Cx43 degradation. Interestingly, treatment with the proteasome inhibitor MG132 (carbobenzoxy-Leu-Leu-leucinal) significantly negated the curcumin-induced Cx43 degradation, which suggests that curcumin-induced Cx43 degradation occurs through the ubiquitin-proteasome pathway.

Inverse Molecular Docking as a Novel Approach to Study Anticarcinogenic and Anti-Neuroinflammatory Effects of Curcumin

Research efforts are placing an ever increasing emphasis on identifying signal transduction pathways related to the chemopreventive activity of curcumin. Its anticarcinogenic effects are presumably mediated by the regulation of signaling cascades, including nuclear factor κB (NF-κB), activator protein 1 (AP-1), and mitogen-activated protein kinases (MAPK). By modulating signal transduction pathways, curcumin induces apoptosis in malignant cells, thus inhibiting cancer development and progression. Due to the lack of mechanistic insight in the scientific literature, we developed a novel inverse molecular docking protocol based on the CANDOCK algorithm. For the first time, we performed inverse molecular docking of curcumin into a collection of 13,553 available human protein structures from the Protein Data Bank resulting in prioritized target proteins of curcumin. Our predictions were in agreement with the scientific literature and confirmed that curcumin binds to folate receptor β, DNA (cytosine-5)-methyltransferase 3A, metalloproteinase-2, mitogen-activated protein kinase 9, epidermal growth factor receptor and apoptosis-inducing factor 1. We also identified new potential protein targets of curcumin, namely deoxycytidine kinase, NAD-dependent protein deacetylase sirtuin-1 and -2, ecto-5'-nucleotidase, core histone macro-H2A.1, tyrosine-protein phosphatase non-receptor type 11, macrophage colony-stimulating factor 1 receptor, GTPase HRas, aflatoxin B1 aldehyde reductase member 3, aldo-keto reductase family 1 member C3, amiloride-sensitive amine oxidase, death-associated protein kinase 2 and tryptophan-tRNA ligase, that may all play a crucial role in its observed anticancer effects. Moreover, our inverse docking results showed that curcumin potentially binds also to the proteins cAMP-specific 3',5'-cyclic phosphodiesterase 4D and 17-β-hydroxysteroid dehydrogenase type 10, which provides a new explanation for its efficiency in the treatment of Alzheimer's disease. We firmly believe that our computational results will complement and direct future experimental studies on curcumin's anticancer activity as well as on its therapeutic effects against Alzheimer's disease.

Curcumin: A naturally occurring autophagy modulator

Autophagy is a self-degradative process that plays a pivotal role in several medical conditions associated with infection, cancer, neurodegeneration, aging, and metabolic disorders. Its interplay with cancer development and treatment resistance is complicated and paramount for drug design since an autophagic response can lead to tumor suppression by enhancing cellular integrity and tumorigenesis by improving tumor cell survival. In addition, autophagy denotes the cellular ability of adapting to stress though it may end up in apoptosis activation when cells are exposed to a very powerful stress. Induction of autophagy is a therapeutic option in cancer and many anticancer drugs have been developed to this aim. Curcumin as a hydrophobic polyphenol compound extracted from the known spice turmeric has different pharmacological effects in both in vitro and in vivo models. Many reports exist reporting that curcumin is capable of triggering autophagy in several cancer cells. In this review, we will focus on how curcumin can target autophagy in different cellular settings that may extend our understanding of new pharmacological agents to overcome relevant diseases.

Transcriptional Activation of Human GD3 Synthase (hST8Sia I) Gene in Curcumin-Induced Autophagy in A549 Human Lung Carcinoma Cells

Curcumin, a natural polyphenolic compound isolated from the plant Curcuma longa, is known to induce autophagy in various cancer cells, including lung cancer. In the present study, we also confirmed by LC3 immunofluorescence and immunoblotting analyses that curcumin triggers autophagy in the human lung adenocarcinoma A549 cell line. In parallel with autophagy induction, the gene expression of human GD3 synthase (hST8Sia I) responsible for ganglioside GD3 synthesis was markedly elevated in response to curcumin in the A549 cells. To investigate the transcriptional activation of hST8Sia I associated with the autophagy formation in curcumin-treated A549 cells, functional characterization of the 5′-flanking region of the hST8Sia I gene was carried out using the luciferase reporter assay system. Deletion analysis demonstrated that the -1146 to -646 region, which includes the putative c-Ets-1, CREB, AP-1, and NF-κB binding sites, functions as the curcumin-responsive promoter of hST8Sia I in A549 cells. The site-directed mutagenesis and chromatin immunoprecipitation assay demonstrated that the NF-κB binding site at -731 to -722 was indispensable for the curcumin-induced hST8Sia I gene expression in A549 cells. Moreover, the transcriptional activation of hST8Sia I by the curcumin A549 cells was strongly inhibited by compound C, an inhibitor of AMP-activated protein kinase (AMPK). These results suggest that curcumin controls hST8Sia I gene expression via AMPK signal pathway in A549 cells.