Tocotrienols induce apoptosis and autophagy in rat pancreatic stellate cells through the mitochondrial death pathway

γ-Tocotrienol enhances autophagy of gastric cancer cells by the regulation of GSK3β/β-Catenin pathway

γ-Tocotrienol (γ-T3) is a major subtype of vitamin E, mainly extracted from palm trees, barley, walnuts, and other plants. γ-T3 has effects on anti-inflammation, anti-oxidation, and potential chemoprevention against malignancies. It is still uncompleted to understand the effect of γ-T3 on the inhibitory mechanism of cancer. This study aimed to investigate whether γ-T3 enhanced autophagy in gastric cancer and the underlying molecular mechanism. The results showed that γ-T3 (0-90 μmol/L) inhibited the proliferation of gastric cancer MKN45 cells and AGS cells, and arrested the cell cycle at the G0/G1 phase in a dose-dependent manner. Autophagy was increased in MKN45 cells treated with γ-T3 (0-45 μmol/L), especially at a dose of 30 μmol/L for 24 h. These effects were reversed by 3-methyladenine pretreatment. Furthermore, γ-T3 (30 μmol/L) also significantly downregulated the expression of pGSK-3β (ser9) and β-catenin protein in MKN45 cells, and γ-T3 (20 mg/kg b.w.) effectively decreased the growth of MKN45 cell xenografts in BABL/c mice. GSK-3β inhibitor-CHIR-99021 reversed the negative regulation of GSK-3β/β-Catenin signaling and autophagy. Our findings indicated that γ-T3 enhances autophagy in gastric cancer cells mediated by GSK-3β/β-Catenin signaling, which provides new insights into the role of γ-T3 enhancing autophagy in gastric cancer.

Metabolism and bioenergetics in the pathophysiology of organ fibrosis

Fibrosis is the tissue scarring characterized by excess deposition of extracellular matrix (ECM) proteins, mainly collagens. A fibrotic response can take place in any tissue of the body and is the result of an imbalanced reaction to inflammation and wound healing. Metabolism has emerged as a major driver of fibrotic diseases. While glycolytic shifts appear to be a key metabolic switch in activated stromal ECM-producing cells, several other cell types such as immune cells, whose functions are intricately connected to their metabolic characteristics, form a complex network of pro-fibrotic cellular crosstalk. This review purports to clarify shared and particular cellular responses and mechanisms across organs and etiologies. We discuss the impact of the cell-type specific metabolic reprogramming in fibrotic diseases in both experimental and human pathology settings, providing a rationale for new therapeutic interventions based on metabolism-targeted antifibrotic agents.

Fibroblast subtypes in pancreatic cancer and pancreatitis: from mechanisms to therapeutic strategies

Excessive fibrosis is a predominant feature of pancreatic stroma and plays a crucial role in the development and progression of pancreatic ductal adenocarcinoma (PDAC) and chronic pancreatitis (CP). Emerging evidence showed diversity and heterogeneity of fibroblasts play crucial and somewhat contradictory roles, the interactions between fibroblasts and pancreatic cells or infiltrating immune cells are of great importance during PDAC and CP progression, with some promising therapeutic strategies being tested. Therefore, in this review, we describe the classification of fibroblasts and their functions in PDAC and pancreatitis, the mechanisms by which fibroblasts mediate the development and progression of PDAC and CP through direct or indirect interaction between fibroblast and pancreatic parenchymal cells, or by remodeling the pancreatic immune microenvironment mediates the development and progression of PDAC and CP. Finally, we summarized the current therapeutic strategies and agents that directly target subtypes of fibroblasts or interfere with their essential functions.

Vitamin A, D, E, and K as Matrix Metalloproteinase-2/9 Regulators That Affect Expression and Enzymatic Activity

Fat-soluble vitamins (vitamin A, D, E, and K) assume a pivotal role in maintaining human homeostasis by virtue of their enzymatic functions. The daily inclusion of these vitamins is imperative to the upkeep of various physiological processes including vision, bone health, immunity, and protection against oxidative stress. Current research highlights fat-soluble vitamins as potential therapeutics for human diseases, especially cancer. Fat-soluble vitamins exert their therapeutic effects through multiple pathways, including regulation of matrix metalloproteinases' (MMPs) expression and enzymatic activity. As MMPs have been reported to be involved in the pathology of various diseases, such as cancers, cardiovascular diseases, and neurological disorders, regulating the expression and/or activity of MMPs could be considered as a potent therapeutic strategy. Here, we summarize the properties of fat-soluble vitamins and their potential as promising candidates capable of effectively modulating MMPs through multiple pathways to treat human diseases.

Pancreatic Acinar Cells-Derived Sphingosine-1-Phosphate Contributes to Fibrosis of Chronic Pancreatitis via Inducing Autophagy and Activation of Pancreatic Stellate Cells

BACKGROUND & AIMS

Studies have demonstrated that activated pancreatic stellate cells (PSCs) play a crucial role in pancreatic fibrogenesis in chronic pancreatitis (CP); however, the precise mechanism for PSCs activation has not been fully elucidated. We analyzed the role of injured pancreatic acinar cells (iPACs) in the activation of PSCs of CP.

METHODS

Sphingosine kinase 1 (SPHK1)/sphingosine-1-phosphate (S1P) signaling was evaluated in experimental CP induced by cerulein injection or pancreatic duct ligation, as well as in PACs injured by cholecystokinin. The activation of PSCs and pancreatic fibrosis in CP samples was evaluated by immunohistochemical and immunofluorescence analyses. In vitro coculture assay of iPACs and PSCs was created to evaluate the effect of the SPHK1/S1P pathway and S1P receptor 2 (SIPR2) on autophagy and activation of PSCs. The pathogenesis of CP was assessed in SPHK1-/- mice or PACs-specific SPHK1-knockdown mice with recombinant adeno-associated virus serotypes 9-SPHK1-knockdown, as well as in mice treated with inhibitor of SPHK1 and S1P receptor 2 (S1PR2).

RESULTS

SPHK1/S1P was remarkably increased in iPACs and acinar cells in pancreatic tissues of CP mice. Meanwhile, the pathogenesis, fibrosis, and PSCs activation of CP was significantly prevented in SPHK1-/- mice and recombinant adeno-associated virus serotypes 9-SPHK1-knockdown mice. Meanwhile, iPACs obviously activated PSCs, which was prevented by SPHK1 knockdown in iPACs. Moreover, iPACs-derived S1P specifically combined to S1PR2 of PSCs, by which modulated 5' adenosine monophosphate-activated protein kinase/mechanistic target of rapamycin pathway and consequently induced autophagy and activation of PSCs. Furthermore, hypoxia-inducible factor 1-α and -2α promoted SPHK1 transcription of PACs under hypoxia conditions, which is a distinct characteristic of the CP microenvironment. Coincidently, inhibition of SPHK1 and S1PR2 activity with inhibitor PF-543 and JTE-013 obviously impeded pancreatic fibrogenesis of CP mice.

CONCLUSIONS

The activated SPHK1/S1P pathway in iPACs induces autophagy and activation of PSCs by regulating the S1PR2/5' adenosine monophosphate-activated protein kinase/mammalian target of rapamycin pathway, which promotes fibrogenesis of CP. The hypoxia microenvironment might contribute to the cross talk between PACs and PSCs in pathogenesis of CP.

Fibrosis in Liver and Pancreas: a Review on Pathogenic Significance, Diagnostic Options, and Current Management Strategies

Inflammation is one of the most natural ways of the body's biological response against invading foreign pathogens or injured cells which eventually can lead to a chronic or acute productive response. Fibrosis is an end-stage event associated with an inflammatory response addressed with tissue hardening, discoloration, and most importantly overgrowth of associated tissue. Various organs at different diseased conditions are affected by fibrosis including the liver, pancreas, brain, kidney, and lung. Etiological factors including internal like inflammatory cytokines, growth factors, and oxidative stress and external like alcohol and viruses contribute to the development of fibrosis in both the liver and pancreas. More frequently, these organs are associated with pathogenic progression towards fibrosis from acute and chronic conditions and eventually fail in their functions. The pathogenesis of the organ-fibrotic events mainly depends on the activation of residential stellate cells; these cells help to accumulate collagen in respective organs. Various diagnostic options have been developed recently, and various therapeutic options are in trial to tackle fibrosis. In this review, an overview on fibrosis, the pathogenesis of fibrosis in the liver and pancreas, various diagnostic options developed in recent years, and possible present therapeutic measures to overcome options of fibrosis in the liver and pancreas; thus, restoring the functional status of organs is discussed.

Vitamin E in Cancer Treatment: A Review of Clinical Applications in Randomized Control Trials

Vitamin E, along with other vitamins and micronutrients play a range of physiologic roles in the homeostasis of the body. Moreover, they also have postulated therapeutic roles that are often incompletely studied and understood. In this scoping review, we explored the recent randomized control trials (RCTs) of Vitamin E in the context of cancer, to investigate whether Vitamin E has a therapeutic role. We searched major bibliographic electronic databases to identify sixteen RCTs studying the role of Vitamin E in cancer management that have been published in the last ten years. These studies had different methodological qualities, including some that used Vitamin E in combination with other treatments. Furthermore, due to the heterogenous results, it is difficult to make a consensus statement on the effectiveness of Vitamin E in cancer therapeutics. In some cases, there were even suggestion of detriment with Vitamin E supplementation. Therefore, well designed, large, prospective RCTs are needed studying pure isoforms of Vitamin E to establish the safety and efficacy of this dietary supplement.

Nutraceuticals as Modulators of Autophagy: Relevance in Parkinson’s Disease

Dietary supplements and nutraceuticals have entered the mainstream. Especially in the media, they are strongly advertised as safe and even recommended for certain diseases. Although they may support conventional therapy, sometimes these substances can have unexpected side effects. This review is particularly focused on the modulation of autophagy by selected vitamins and nutraceuticals, and their relevance in the treatment of neurodegenerative diseases, especially Parkinson’s disease (PD). Autophagy is crucial in PD; thus, the induction of autophagy may alleviate the course of the disease by reducing the so-called Lewy bodies. Hence, we believe that those substances could be used in prevention and support of conventional therapy of neurodegenerative diseases. This review will shed some light on their ability to modulate the autophagy.

Regulation and function of autophagy in pancreatic cancer

Oncogenic KRAS mutation-driven pancreatic ductal adenocarcinoma is currently the fourth-leading cause of cancer-related deaths in the United States. Macroautophagy (hereafter "autophagy") is one of the lysosome-dependent degradation systems that can remove abnormal proteins, damaged organelles, or invading pathogens by activating dynamic membrane structures (e.g., phagophores, autophagosomes, and autolysosomes). Impaired autophagy (including excessive activation and defects) is a pathological feature of human diseases, including pancreatic cancer. However, dysfunctional autophagy has many types and plays a complex role in pancreatic tumor biology, depending on various factors, such as tumor stage, microenvironment, immunometabolic state, and death signals. As a modulator connecting various cellular events, pharmacological targeting of nonselective autophagy may lead to both good and bad therapeutic effects. In contrast, targeting selective autophagy could reduce potential side effects of the drugs used. In this review, we describe the advances and challenges of autophagy in the development and therapy of pancreatic cancer.Abbreviations: AMPK: AMP-activated protein kinase; CQ: chloroquine; csc: cancer stem cells; DAMP: danger/damage-associated molecular pattern; EMT: epithelial-mesenchymal transition; lncRNA: long noncoding RNA; MIR: microRNA; PanIN: pancreatic intraepithelial neoplasia; PDAC: pancreatic ductal adenocarcinoma; PtdIns3K: phosphatidylinositol 3-kinase; SNARE: soluble NSF attachment protein receptor; UPS: ubiquitin-proteasome system.

Mitochondrial dysfunction in fibrotic diseases

Although fibrosis is a common pathological feature of most end-stage organ diseases, its pathogenesis remains unclear. There is growing evidence that mitochondrial dysfunction contributes to the development and progression of fibrosis. The heart, liver, kidney and lung are highly oxygen-consuming organs that are sensitive to mitochondrial dysfunction. Moreover, the fibrotic process of skin and islet is closely related to mitochondrial dysfunction as well. This review summarized emerging mechanisms related to mitochondrial dysfunction in different fibrotic organs and tissues above. First, it highlighted the important elucidation of mitochondria morphological changes, mitochondrial membrane potential and structural damage, mitochondrial DNA (mtDNA) damage and reactive oxidative species (ROS) production, etc. Second, it introduced the abnormality of mitophagy and mitochondrial transfer also contributed to the fibrotic process. Therefore, with gaining the increasing knowledge of mitochondrial structure, function, and origin, we could kindle a new era for the diagnostic and therapeutic strategies of many fibrotic diseases based on mitochondrial dysfunction.

Alcohol and Smoking Mediated Modulations in Adaptive Immunity in Pancreatitis

Pancreatitis is a condition of pancreatic inflammation driven by injury to the pancreatic parenchyma. The extent of acinar insult, intensity, and type of immune response determines the severity of the disease. Smoking, alcohol and autoimmune pancreatitis are some of the predominant risk factors that increase the risk of pancreatitis by differentially influencing the adaptive immune system. The overall decrease in peripheral lymphocyte (T-, B- and (natural killer T-) NKT-cell) count and increased infiltration into the damaged pancreatic tissue highlight the contribution of adaptive immunity in the disease pathology. Smoking and alcohol modulate the responsiveness and apoptosis of T- and B-cells during pancreatic insult. Acute pancreatitis worsens with smoking and alcohol, leading to the development of systemic inflammatory response syndrome and compensatory anti-inflammatory response syndrome, suggesting the critical role of adaptive immunity in fatal outcomes such as multiple organ dysfunction. The presence of CD4⁺ and CD8⁺ T-lymphocytes and perforin-expressing cells in the fibrotic tissue in chronic pancreatitis modulate the severity of the disease. Due to their important role in altering the severity of the disease, attempts to target adaptive immune mediators will be critical for the development of novel therapeutic interventions.

Pancreatic stellate cells in the islets as a novel target to preserve the pancreatic β-cell mass and function

There are numerous lines of clinical evidence that inhibition of the renin-angiotensin system (RAS) can prevent and delay the development of diabetes. Also, the role of RAS in the pathogenesis of diabetes, including insulin resistance and β-cell dysfunction, has been extensively investigated. Nevertheless, this role had not yet been fully shown. A variety of possible protective mechanisms for RAS blockers in the regulation of glucose homeostasis have been suggested. However, the direct effect on pancreatic islet fibrosis has only recently been spotlighted. Various degrees of islet fibrosis are often observed in the islets of patients with type 2 diabetes mellitus, which can be associated with a decrease in β-cell mass and function in these patients. Pancreatic stellate cells are thought to be deeply involved in this islet fibrosis. In this process, the activation of RAS in islets is shown to transform quiescent pancreatic stellate cells into the activated form, stimulates their proliferation and consequently leads to islet fibrotic destruction. In this article, we introduce existing clinical and experimental evidence for diabetes prevention through inhibition of RAS, and review the responsible local RAS signaling pathways in pancreatic stellate cells. Finally, we propose possible targets for the prevention of islet fibrosis.

The Vitamin E Derivative Gamma Tocotrienol Promotes Anti-Tumor Effects in Acute Myeloid Leukemia Cell Lines

Acute myeloid leukemia (AML) is a blood cancer characterized by the formation of faulty defective myelogenous cells with morphological heterogeneity and cytogenic aberrations leading to a loss of their function. In an attempt to find an effective and safe AML treatment, vitamin E derivatives, including tocopherols were considered as potential anti-tumor compounds. Recently, other isoforms of vitamin E, namely tocotrienols have been proposed as potential potent anti-cancerous agents, displaying promising therapeutic effects in different cancer types. In this study we evaluated the anti-cancerous effects of γ-tocotrienol, on AML cell lines in vitro. For this purpose, AML cell lines incubated with γ-tocotrienol were examined for their viability, cell cycle status, apoptotic cell death, DNA fragmentation, production of reactive oxygen species and expression of proapoptotic proteins. Our results showed that γ-tocotrienol exhibits time and dose-dependent anti-proliferative, pro-apoptotic and antioxidant effects on U937 and KG-1 cell lines, through the upregulation of proteins involved in the intrinsic apoptotic pathway.

Oleic acid ameliorates palmitic acid-induced ER stress and inflammation markers in naive and cerulein-treated exocrine pancreas cells

Dietary fat overload (typical to obesity) increases the risk of pancreatic pathologies through mechanisms yet to be defined. We previously showed that saturated dietary fat induces pancreatic acinar lipotoxicity and cellular stress. The endoplasmic reticulum (ER) of exocrine pancreas cells is highly developed and thus predisposed to stress. We studied the combination of saturated and unsaturated FAs in metabolic and pancreatitis like cerulein (CER)-induced stress states on cellular ER stress.

Exocrine pancreas AR42J and rat primary exocrine acinar cells underwent acute (24 h) challenge with different FAs (saturated, monounsaturated) at different concentrations (250 and 500 µM) and in combination with acute CER-induced stress, and were analyzed for fat accumulation, ER stress unfolded protein response (UPR) and immune and enzyme markers. Acute exposure of AR42J and pancreatic acinar cells to different FAs and their combinations increased triglyceride accumulation. Palmitic acid significantly dose-dependently enhanced the UPR, immune factors and pancreatic lipase (PL) levels, as demonstrated by XBP1 splicing and elevation in UPR transcripts and protein levels (Xbp1,Atf6, Atf4, Chop, Tnfα, Tgfβ and Il-6). Exposure to high palmitic levels in a CER-induced stress state synergistically increased ER stress and inflammation marker levels. Exposure to oleic acid did not induce ER stress and PL levels and significantly decreased immune factors in an acute CER-induced stress state. Combination of oleic and palmitic acids significantly reduced the palmitic-induced ER stress, but did not affect the immune factor response. We show that combination of monounsaturated and saturated FAs protects from exocrine pancreatic cellular ER stress in both metabolic and CER-induced stress.

Tocotrienols Modulate a Life or Death Decision in Cancers

Malignancy often arises from sophisticated defects in the intricate molecular mechanisms of cells, rendering a complicated molecular ground to effectively target cancers. Resistance toward cell death and enhancement of cell survival are the common adaptations in cancer due to its infinite proliferative capacity. Existing cancer treatment strategies that target a single molecular pathway or cancer hallmark fail to fully resolve the problem. Hence, multitargeted anticancer agents that can concurrently target cell death and survival pathways are seen as a promising alternative to treat cancer. Tocotrienols, a minor constituent of the vitamin E family that have previously been reported to induce various cell death mechanisms and target several key survival pathways, could be an effective anticancer agent. This review puts forward the potential application of tocotrienols as an anticancer treatment from a perspective of influencing the life or death decision of cancer cells. The cell death mechanisms elicited by tocotrienols, particularly apoptosis and autophagy, are highlighted. The influences of several cell survival signaling pathways in shaping cancer cell death, particularly NF-κB, PI3K/Akt, MAPK, and Wnt, are also reviewed. This review may stimulate further mechanistic researches and foster clinical applications of tocotrienols via rational drug designs.

Natural forms of vitamin E and metabolites-regulation of cancer cell death and underlying mechanisms

The disappointing results from large clinical studies of α-tocopherol (αT), the major form of vitamin E in tissues, for prevention of chronic diseases including cancer have cast doubt on not only αT but also other forms of vitamin E regarding their role in preventing carcinogenesis. However, basic research has shown that specific forms of vitamin E such as γ-tocopherol (γT), δ-tocopherol (δT), γ-tocotrienol (γTE) and δ-tocotrienol (δTE) can inhibit the growth and induce death of many types of cancer cells, and are capable of suppressing cancer development in preclinical cancer models. For these activities, these vitamin E forms are much stronger than αT. Further, recent research revealed novel anti-inflammatory and anticancer effects of vitamin E metabolites including 13'-carboxychromanols. This review focuses on anti-proliferation and induction of death in cancer cells by vitamin E forms and metabolites, and discuss mechanisms underlying these anticancer activities. The existing in vitro and in vivo evidence indicates that γT, δT, tocotrienols and 13'-carboxychromanols have anti-cancer activities via modulating key signaling or mediators that regulate cell death and tumor progression, such as eicosanoids, NF-κB, STAT3, PI3K, and sphingolipid metabolism. These results provide useful scientific rationales and mechanistic understanding for further translation of basic discoveries to the clinic with respect to potential use of these vitamin E forms and metabolites for cancer prevention and therapy. © 2018 IUBMB Life, 71(4):495-506, 2019.

RB1CC1-enhanced autophagy facilitates PSCs activation and pancreatic fibrogenesis in chronic pancreatitis

Chronic pancreatitis (CP) is described as a progressive fibro-inflammatory disorder of the exocrine disease, which eventually leads to damage of the gland. Excessive activation of pancreatic stellate cells (PSCs) is a critical participant in the initiation of CP. Autophagy is involved in multiple degeneration and inflammation in acute pancreatitis and CP. In our study, we report that retinoblastoma coiled coil protein 1 (RB1CC1) expression and the autophagic level are elevated in activated PSCs. RB1CC1 is positively correlated with pancreatic fibrogenesis in tissues and plasma of CP patients. Knockdown of RB1CC1 restrains alpha smooth muscle actin (α-SMA) and collagen expressions, and autophagy in activated PSCs in vitro. Furthermore, we show that RB1CC1 induces PSC activation via binding to ULK1 promoter and the direct interaction with ULK1 protein. These suppress ULK1 expression and its kinase activity. In mice, knockdown of RB1CC1 blocks autophagy and then inhibits the pancreatic duct ligation-induced pancreatic fibrosis. Consequently, our study highlights that RB1CC1-mediated autophagy is a key event for the activation of PSCs. Inhibition of RB1CC1 alleviates autophagy, which plays a critical role in anti-fibrotic activation in PSCs and CP progression. RB1CC1 could be a novel strategy for the treatment of pancreatic fibrosis.

Zeb1 in Stromal Myofibroblasts Promotes Kras-Driven Development of Pancreatic Cancer

The transcription factor Zeb1 has been identified as a crucial player in Kras-dependent oncogenesis. In pancreatic ductal adenocarcinoma (PDAC), Zeb1 is highly expressed in myofibroblasts and correlates with poor prognosis. As Kras mutations are key drivers in PDAC, we aimed here to assess the necessity of Zeb1 for Kras-driven PDAC and to define the role of Zeb1-expressing myofibroblasts in PDAC development. Genetically engineered mice with conditional pancreatic Kras^G12D and Trp53 mutations (KPC) were crossed with Zeb1 haploinsufficient mice (Z^+/-). Extensive PDAC was prominent in all 20-week-old KPC;Z^+/+ mice, whereas only low-grade precursor lesions were detected in age-matched KPC;Z^+/- littermates, with PDAC developing eventually in KPC;Z^+/- aged animals. Zeb1 expression in myofibroblasts occurred early in tumorigenesis and Zeb1 haploinsufficiency retarded native expansion of stromal myofibroblasts during precursor-to-cancer progression. Zeb1 downregulation in mPSC repressed their activated gene profile, impaired their migratory and proliferative activity, and attenuated their tumor-supporting features. Conditioned media from Z^+/+ mouse-activated (myofibroblast-like) pancreatic stellate cells (mPSC) boosted Ras activity in pancreatic cancer cells carrying mutant Kras; this effect was not observed when using conditioned media from Z^+/- mPSC, revealing a paracrinal cooperative axis between Zeb1-expressing PSC and oncogenic Kras-bearing tumor cells. We conclude that Zeb1-expressing stromal myofibroblasts enable a heterotypic collaboration with the Kras-fated epithelial compartment, thus supporting pancreatic malignancy.Significance: Zeb1 expression in stromal myofibroblasts supports PDAC development via collaboration with the epithelial compartment bearing oncogenic Kras mutations. Cancer Res; 78(10); 2624-37. ©2018 AACR.

The critical roles of activated stellate cells-mediated paracrine signaling, metabolism and onco-immunology in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignant diseases worldwide. It is refractory to conventional treatments, and consequently has a documented 5-year survival rate as low as 7%. Increasing evidence indicates that activated pancreatic stellate cells (PSCs), one of the stromal components in tumor microenvironment (TME), play a crucial part in the desmoplasia, carcinogenesis, aggressiveness, metastasis associated with PDAC. Despite the current understanding of PSCs as a "partner in crime" to PDAC, detailed regulatory roles of PSCs and related microenvironment remain obscure. In addition to multiple paracrine signaling pathways, recent research has confirmed that PSCs-mediated tumor microenvironment may influence behaviors of PDAC via diverse mechanisms, such as rewiring metabolic networks, suppressing immune responses. These new activities are closely linked with treatment and prognosis of PDAC. In this review, we discuss the recent advances regarding new functions of activated PSCs, including PSCs-cancer cells interaction, mechanisms involved in immunosuppressive regulation, and metabolic reprogramming. It's clear that these updated experimental or clinical studies of PSCs may provide a promising approach for PDAC treatment in the near future.

Plant Phenols and Autophagy

Many plant phenols (stilbenes, curcumins, catechins, flavonoids, etc.) are effective antioxidants and protect cells during oxidative stress. Extensive clinical studies on the potential of phenolic compounds for treatment of cardiovascular, neurodegenerative, oncological, and inflammatory diseases are now being conducted. In addition to direct antioxidant effect, plant phenols may provide a protective effect via activation of the Keap1/Nrf2/ARE redox-sensitive signaling system and regulation of autophagy. In this review, mechanisms of effects of the most common plant phenols on autophagy are presented.

Hydrogen-rich saline protects against mitochondrial dysfunction and apoptosis in mice with obstructive jaundice

Previous studies have demonstrated that hydrogen-rich saline (HS) protects against bile duct ligation (BDL)-induced liver injury by suppressing oxidative stress and inflammation. Mitochondria, which are targets of excessive reactive oxygen species and central mediators of apoptosis, have a pivotal role in hepatic injury during obstructive jaundice (OJ); however, the implications of HS in the hepatic mitochondria of BDL mice remain unknown. The present study investigated the hypothesis that HS could reduce OJ‑induced liver injury through the protection of mitochondrial structure and function, as well as inhibition of the mitochondrial apoptotic pathway. Male C57BL/6 mice were randomly divided into three experimental groups: Sham operation group, BDL injury with normal saline (NS) treatment group, and BDL‑injury with HS treatment group. Mitochondrial damage and apoptotic parameters were determined 3 days post‑BDL injury and treatment. The results demonstrated that mitochondria isolated from the livers of NS-treated BDL mice exhibited increased mitochondrial swelling, cytochrome c release, and oxidative damage. In addition, liver samples from NS‑treated BDL mice exhibited significant increases in B‑cell lymphoma 2 (Bcl‑2)‑associated X protein expression, caspase activities, and hepatocyte apoptosis compared with livers from sham‑operated controls. Notably, treatment with HS reduced the levels of these markers and alleviated morphological defects in the mitochondria following injury. In addition, HS markedly increased the antioxidant potential of mitochondria, as evidenced by elevated adenosine triphosphate levels, mitochondrial respiratory function, and increased levels of active Bcl‑2. In conclusion, HS attenuates mitochondrial oxidative stress and dysfunction, and inhibits mitochondrial-mediated apoptosis in the livers of BDL mice.

Suppression of NLRP3 inflammasome by γ-tocotrienol ameliorates type 2 diabetes

The Nod-like receptor 3 (NLRP3) inflammasome is an intracellular sensor that sets off the innate immune system in response to microbial-derived and endogenous metabolic danger signals. We previously reported that γ-tocotrienol (γT3) attenuated adipose tissue inflammation and insulin resistance in diet-induced obesity, but the underlying mechanism remained elusive. Here, we investigated the effects of γT3 on NLRP3 inflammasome activation and attendant consequences on type 2 diabetes. γT3 repressed inflammasome activation, caspase-1 cleavage, and interleukin (IL) 1β secretion in murine macrophages, implicating the inhibition of NLRP3 inflammasome in the anti-inflammatory and antipyroptotic properties of γT3. Furthermore, supplementation of leptin-receptor KO mice with γT3 attenuated immune cell infiltration into adipose tissue, decreased circulating IL-18 levels, preserved pancreatic β-cells, and improved insulin sensitivity. Mechanistically, γT3 regulated the NLRP3 inflammasome via a two-pronged mechanism: 1) the induction of A20/TNF-α interacting protein 3 leading to the inhibition of the TNF receptor-associated factor 6/nuclear factor κB pathway and 2) the activation of AMP-activated protein kinase/autophagy axis leading to the attenuation of caspase-1 cleavage. Collectively, we demonstrated, for the first time, that γT3 inhibits the NLRP3 inflammasome thereby delaying the progression of type 2 diabetes. This study also provides an insight into the novel therapeutic values of γT3 for treating NLRP3 inflammasome-associated chronic diseases.

Physiological and clinically attainable concentrations of 1,25-dihydroxyvitamin D3 suppress proliferation and extracellular matrix protein expression in mouse pancreatic stellate cells

BACKGROUND/OBJECTIVES

Vitamin D is an antiproliferative and differentiation-promoting secosteroid hormone with pleiotropic homeostatic functions in bone and extraskeletal tissues. Signaling of vitamin D is mediated via its ubiquitously expressed nuclear receptor, the vitamin D receptor (VDR). Pancreatic stellate cells have recently been identified as targets of vitamin D action. Our aim was to elucidate the effectiveness of the most potent endogenous vitamin D metabolite, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on the proliferation and extracellular matrix (ECM) protein expression in pancreatic stellate cells (PSCs) using concentrations of the compound from the physiological and clinically attainable range in humans.

METHODS

Culture-activated mouse PSCs were exposed to 1,25(OH)2D3 concentrations ranging from 0.1 nM to 10 nM for 7 days and subjected to colorimetric crystal violet assay for cell growth assessment and to Western blot and immunohistochemical analyses of VDR, fibronectin and collagen I using protein-specific antibodies. Immunohistochemical localization of VDR was performed on mouse pancreatic tissue and on a set of human specimens obtained at pancreatic surgery.

RESULTS

A low basal level of VDR was detected in PSCs that was strongly induced in the presence of ligand. Cell growth was suppressed dose-dependently by 1,25(OH)2D3, the mean percentages of inhibition ranging from 24% at the physiological 0.1 nM concentration to around 60% at 10 nM. Significant 48% and 40% reductions in fibronectin expression were seen at 0.5 nM and 1 nM 1,25(OH)2D3. A minor decrease in collagen I expression was detected at 5 nM. VDR was predominantly localized in the islets of Langerhans in mouse and human tissues. In the latter VDR was expressed also in the exocrine tissue showing individual variation in its cellular distribution.

CONCLUSIONS

Mouse PSCs express VDR protein and are sensitive 1,25(OH)2D3 target cells with low levels of 1,25(OH)2D3 exerting antiproliferative and antifibrotic effects on activated PSCs in vitro.

Senescence determines the fate of activated rat pancreatic stellate cells

In chronic pancreatitis (CP), persistent activation of pancreatic stellate cells (PSC) converts wound healing into a pathological process resulting in organ fibrosis. Here, we have analysed senescence as a novel mechanism involved in the termination of PSC activation and tissue repair. PSC senescence was first studied in vitro by establishing long-term cultures and by applying chemical triggers, using senescence-associated β-Galactosidase (SA β-Gal) as a surrogate marker. Subsequently, susceptibility of PSC to immune cell-mediated cytolysis was investigated employing cocultures. Using the model of dibutyltin dichloride-induced CP in rats, appearance of senescent cells was monitored by immunohistochemistry and immunofluorescence, and correlated with the progression of tissue damage and repair, immune cell infiltration and fibrosis. The results indicated that long-term culture and exposure of PSC to stressors (doxorubicin, H₂O₂ and staurosporine) induced senescence. Senescent PSC highly expressed CDKN1A/p21, mdm2 and interleukin (IL)-6, but displayed low levels of α-smooth muscle actin. Senescence increased the susceptibility of PSC to cytolysis. In CP, the number of senescent cells correlated with the severity of inflammation and the extension of fibrosis. Areas staining positive for SA β-Gal overlapped with regions of fibrosis and dense infiltrates of immune cells. Furthermore, a close physical proximity of immune cells and activated PSC was observed. We conclude that inflammation, PSC activation and cellular senescence are timely coupled processes which take place in the same microenvironment of the inflamed pancreas. Lymphocytes may play a dual-specific role in pancreatic fibrogenesis, triggering both the initiation of wound healing by activating PSC, and its completion by killing senescent stellate cells.

γ-Tocotrienol-induced autophagy in malignant mammary cancer cells

γ-Tocotrienol, a member of the vitamin E family of compounds, displays potent antiproliferative and cytotoxic effects in a variety of cancer cell types at treatment doses that have little or no effect on normal cell viability or growth. Autophagy is a tightly regulated lysosomal self-digested process that can either promote cell survival or programmed cell death, but the role of autophagy in mediating γ-tocotrienol-induced cytotoxicity in breast cancer is not presently completely understood. Mouse (+SA) and human (MCF-7 and MDA-MD-231) mammary tumor cells lines were exposed to 0-40 µmol/L γ-tocotrienol for a 24 h treatment period. γ-Tocotrienol treatment caused a relatively large increase in the accumulation of monodansylcadaverine (MDC)-labeled vacuoles, a marker of autophagosome formation, in all tumor cell lines. Results also showed that γ-tocotrienol treatment induced an increased conversion of microtubule-associated protein, 1A/1B-light chain 3, from its cytosolic form (LC3B-I) to its lipidated form (LC3B-II), increased Beclin-1 levels, and increased acridine orange staining as determined by flow cytometry analysis, providing further evidence of γ-tocotrienol-induced autophagy in these mammary cancer cell lines. In contrast, similar treatment with γ-tocotrienol was not found to increase autophagy marker expression in immortalized mouse (CL-S1) and human (MCF-10 A) normal mammary epithelial cell lines. Treatment with γ-tocotrienol also caused a reduction in PI3K/Akt/mTOR signaling and a corresponding increase in the Bax/Bcl-2 ratio, cleaved caspase-3, and cleaved poly (ADP-ribose) polymerase (PARP) levels in these cancer cell lines, suggesting that γ-tocotrienol-induced autophagy may be involved in the initiation of apoptosis. In summary, these findings demonstrate that the cytotoxic effects of γ-tocotrienol are associated with the induction of autophagy in a mouse and human mammary cancer cells.

High expression of tocochromanol biosynthesis genes increases the vitamin E level in a new line of giant embryo rice

'Shangshida No. 5' is a new variety of giant embryo rice derived from a single-point mutation of the giant embryo gene (ge) in 'Chao2-10' rice. This study quantified the levels of eight vitamin E homologues (α-, β-, γ-, and δ-tocopherol and α-, β-, γ-, and δ-tocotrienol) in brown rice, embryos, endosperm, and developing seeds of giant embryo and normal embryo rice using a normal phase high-performance liquid chromatographic method. Quantitative RT-PCR analysis was conducted to reveal the different expression patterns of the ge gene and tocochromanol biosynthesis genes in developing giant and normal embryo seeds. The total vitamin E content in 'Shangshida No. 5' brown rice was 52.54 mg α-tocopherol equivalent (α-TE)/kg, of which α-tocopherol constituted 49.14 mg/kg, which was approximately 2.2-fold greater than that in 'Chao2-10' brown rice. In giant embryo seeds, the expression level of the ge gene was higher than that in normal embryo seeds during early developmental stages. These results are the first to indicate that coup-regulated expression of the OsHPPD, OsHPT, and OsMPBQ MT2 genes might be the primary reason for the large accumulation of α-tocopherol in giant embryo rice seeds. The different transcription pattern of the tocochromanol biosynthesis genes in 'Shangshida No. 5' rice seeds compared with 'Chao2-10' rice seeds is attributable to the ge mutation and the different expression level of the ge gene in giant embryo seeds.

Antioxidative and antigenotoxic effect of vitamin E against patulin cytotoxicity and genotoxicity in HepG2 cells

Patulin (PAT) is a mycotoxin produced in fruits, mainly in apples, by certain species of Penicillium, Aspergillus, and Byssochlamys. It has been shown that PAT is cytotoxic, genotoxic, and mutagenic in different cell types. Several studies incriminate the oxidative stress as a mechanism of PAT-mediated toxicity. In this context, our aim was to investigate the protective role of Vitamin E (Vit E), an antioxidant agent, against PAT induced cytotoxicity and genotoxicity in cultured HepG2 cells. The obtained results showed that addition of Vit E in cells treated with PAT significantly reduce cell mortality induced by this toxin. In the same conditions, Vit E decreased the intracellular level of ROS, reduced PAT induced p53 expression, and reversed PAT induced DNA damage. In addition, Vit E prevented significantly the percentage of chromosome aberrations induced by PAT in HepG2 cells in a concentration dependant manner. These results suggest that Vit E, an exogenous antioxidant agent, plays an important role in defense against PAT-induced cytotoxicity and genotoxicity, which confirms the involvement of oxidative stress in the induction of DNA damage by PAT in HepG2 cells.

Cdkn1a is a key mediator of rat pancreatic stellate cell senescence

BACKGROUND/OBJECTIVES

Completion of pancreatic wound healing requires termination of pancreatic stellate cell (PSC) activation to prevent fibrosis. Besides induction of apoptosis and return to a quiescent phenotype, senescence of PSC followed by immune cell-mediated cytolysis represents a potential mechanism. Here, we have studied if the cell cycle inhibitor cyclin-dependent kinase inhibitor 1A (Cdkn1a, p21/Waf1), expression of which is increased in senescent rat PSC, plays a causative role in the senescence process.

METHODS

Senescence was induced by doxorubicin treatment. The functions of Cdkn1a were analyzed using two approaches, treatment of primary rat PSC with siRNA and tetracycline-regulated overexpression of Cdkn1a in immortalized rat cells. Expression of senescence-associated β-galactosidase (SA β-Gal) was used as a surrogate marker of senescence.

RESULTS

The knockdown of Cdkn1a significantly attenuated the growth-inhibitory effect of doxorubicin and strongly diminished the portion of SA β-Gal-positive cells. Overexpression of Cdkn1a enhanced both the antiproliferative effect of doxorubicin and induction of senescence. In primary PSC, doxorubicin treatment was associated with increased expression of interleukin-6 (IL-6) and matrix metalloproteinase (MMP)-9, while expression of the activation marker α-smooth muscle actin (α-SMA), p53, Cdk1 and Rad54 was diminished. The application of Cdkn1a siRNA specifically antagonized the effects of doxorubicin on the expression of p53, Cdk1 and Rad54 but not IL-6 and α-SMA, while MMP-9 expression and also activity were even enhanced.

CONCLUSIONS

Cdkn1a plays a direct role in the process of rat PSC senescence. Additional Cdkn1a-independent pathways may contribute to the partial maintenance of a gene expression profile typical of senescent PSC.

Nilotinib induces apoptosis and autophagic cell death of activated hepatic stellate cells via inhibition of histone deacetylases

Increasing hepatic stellate cell (HSC) death is a very attractive approach for limiting liver fibrosis. Tyrosine kinase inhibitors have been shown to have anti-fibrotic properties, but the mechanisms are poorly understood. Here, we identified the mechanism of action of the second-generation tyrosine kinase inhibitor nilotinib in inducing HSC death. Human HSC line (LX-2) and rat HSCs were treated with nilotinib and its predecessor, imatinib, in the absence or presence of various blockers, known to interfere with death signaling pathways. Nilotinib, but not imatinib, induced progressive cell death of activated, but not quiescent, HSCs in a dose-dependent manner. Activated HSCs died through apoptosis, as denoted by increased DNA fragmentation and caspase activation, and through autophagy, as indicated by the accumulation of autophagic markers, light chain (LC)3A-II and LC3B-II. Although inhibition of caspases with Z-VAD-FMK suppressed nilotinib-induced HSCs' apoptosis, there was no increase in HSCs' survival, because autophagy was exacerbated. However, blocking the mitochondrial permeability transition pore (mPTP) opening with cyclosporin A completely abolished both apoptosis and autophagy due to nilotinib. Moreover, nilotinib treatment decreased the protein expression of histone deacetylases 1, 2 and 4. Interestingly, pretreament with C646, a selective p300/CBP histone acetyl transferase inhibitor, resulted in diverting nilotinib-induced apoptosis and autophagy towards necrosis. In conclusion, the identification of mPTP as a target of nilotinib in activated HSCs suggests coordination with histone deacetylases inhibition to induce apoptosis and autophagy. Thus, our study provides novel insights into the anti-fibrotic effects of nilotinib.

γ-Tocotrienol induces paraptosis-like cell death in human colon carcinoma SW620 cells

Colorectal cancer is one of the most serious illnesses among diagnosed cancer. As a new type of anti-cancer composition from tocotrienol-rich fraction of palm oil, γ-tocotrienol is widely used in anti-cancer research. The objectives of this study were to investigate the effects of γ-tocotrienol on human colon cancer SW620 and HCT-8 cells. We showed that treatment with different concentrations of γ-tocotrienol resulted in a dose dependent inhibition of cell growth. Cell death induced by γ-tocotrienol was mediated by a paraptosis-like cell death in SW620 and HCT-8 cells. Real-time RT-PCR and western blot analyses showed that γ-tocotrienol inhibited the expression level of β-catenin, cyclin D1 and c-jun. These data suggest that a paraptosis-like cell death induced by γ-tocotrienol in SW620 cells is associated with the suppression of the Wnt signaling pathway, which offers a novel tool for treating apoptosis-resistance colon cancer.

Subcellular fractionation enhances proteome coverage of pancreatic duct cells

OBJECTIVES

Subcellular fractionation of whole cell lysates offers a means of simplifying protein mixtures, potentially permitting greater depth of proteomic analysis. Here we compare proteins identified from pancreatic duct cells (PaDC) following organelle enrichment to those identified from PaDC whole cell lysates to determine if the additional procedures of subcellular fractionation increase proteome coverage.

METHODS

We used differential centrifugation to enrich for nuclear, mitochondrial, membrane, and cytosolic proteins. We then compared - via mass spectrometry-based analysis - the number of proteins identified from these four fractions with four biological replicates of PaDC whole cell lysates.

RESULTS

We identified similar numbers of proteins among all samples investigated. In total, 1658 non-redundant proteins were identified in the replicate samples, while 2196 were identified in the subcellular fractionation samples, corresponding to a 30% increase. Additionally, we noted that each organelle fraction was in fact enriched with proteins specific to the targeted organelle.

CONCLUSIONS

Subcellular fractionation of PaDC resulted in greater proteome coverage compared to PaDC whole cell lysate analysis. Although more labor intensive and time consuming, subcellular fractionation provides greater proteome coverage, and enriches for compartmentalized sub-populations of proteins. Application of this subcellular fractionation strategy allows for a greater depth of proteomic analysis and thus a better understanding of the cellular mechanisms of pancreatic disease.

Autophagy and pancreatitis

Acute pancreatitis is an inflammatory disease of the exocrine pancreas that carries considerable morbidity and mortality; its pathophysiology remains poorly understood. Recent findings from experimental models and genetically altered mice summarized in this review reveal that autophagy, the principal cellular degradative pathway, is impaired in pancreatitis and that one cause of autophagy impairment is defective function of lysosomes. We propose that the lysosomal/autophagic dysfunction is a key initiating event in pancreatitis and a converging point of multiple deranged pathways. There is strong evidence supporting this hypothesis. Investigation of autophagy in pancreatitis has just started, and many questions about the "upstream" mechanisms mediating the lysosomal/autophagic dysfunction and the "downstream" links to pancreatitis pathologies need to be explored. Answers to these questions should provide insight into novel molecular targets and therapeutic strategies for treatment of pancreatitis.

The role of stroma in pancreatic cancer: diagnostic and therapeutic implications

Pancreatic ductal adenocarcinoma (PDAC) is one of the five most lethal malignancies worldwide and survival has not improved substantially in the past 30 years. Desmoplasia (abundant fibrotic stroma) is a typical feature of PDAC in humans, and stromal activation commonly starts around precancerous lesions. It is becoming clear that this stromal tissue is not a bystander in disease progression. Cancer-stroma interactions effect tumorigenesis, angiogenesis, therapy resistance and possibly the metastatic spread of tumour cells. Therefore, targeting the tumour stroma, in combination with chemotherapy, is a promising new option for the treatment of PDAC. In this Review, we focus on four issues. First, how can stromal activity be used to detect early steps of pancreatic carcinogenesis? Second, what is the effect of perpetual pancreatic stellate cell activity on angiogenesis and tissue perfusion? Third, what are the (experimental) antifibrotic therapy options in PDAC? Fourth, what lessons can be learned from Langton's Ant (a simple mathematical model) regarding the unpredictability of genetically engineered mouse models?

The role of stroma in pancreatic cancer: diagnostic and therapeutic implications

Pancreatic ductal adenocarcinoma (PDAC) is one of the five most lethal malignancies worldwide and survival has not improved substantially in the past 30 years. Desmoplasia (abundant fibrotic stroma) is a typical feature of PDAC in humans, and stromal activation commonly starts around precancerous lesions. It is becoming clear that this stromal tissue is not a bystander in disease progression. Cancer-stroma interactions effect tumorigenesis, angiogenesis, therapy resistance and possibly the metastatic spread of tumour cells. Therefore, targeting the tumour stroma, in combination with chemotherapy, is a promising new option for the treatment of PDAC. In this Review, we focus on four issues. First, how can stromal activity be used to detect early steps of pancreatic carcinogenesis? Second, what is the effect of perpetual pancreatic stellate cell activity on angiogenesis and tissue perfusion? Third, what are the (experimental) antifibrotic therapy options in PDAC? Fourth, what lessons can be learned from Langton's Ant (a simple mathematical model) regarding the unpredictability of genetically engineered mouse models?

Inhibition of mitochondria- and endoplasmic reticulum stress-mediated autophagy augments temozolomide-induced apoptosis in glioma cells

Autophagy is a crucial process for cells to maintain homeostasis and survival through degradation of cellular proteins and organelles, including mitochondria and endoplasmic reticula (ER). We previously demonstrated that temozolomide (TMZ), an alkylating agent for brain tumor chemotherapy, induced reactive oxygen species (ROS)/extracellular signal-regulated kinase (ERK)-mediated autophagy to protect glioma cells from apoptosis. In this study, we investigated the role of mitochondrial damage and ER stress in TMZ-induced cytotoxicity. Mitochondrial depolarization and mitochondrial permeability transition pore (MPTP) opening were observed as a prelude to TMZ-induced autophagy, and these were followed by the loss of mitochondrial mass. Electron transport chain (ETC) inhibitors, such as rotenone (a complex I inhibitor), sodium azide (a complex IV inhibitor), and oligomycin (a complex V inhibitor), or the MPTP inhibitor, cyclosporine A, decreased mitochondrial damage-mediated autophagy, and therefore increased TMZ-induced apoptosis. TMZ treatment triggered ER stress with increased expression of GADD153 and GRP78 proteins, and deceased pro-caspase 12 protein. ER stress consequently induced autophagy through c-Jun N-terminal kinases (JNK) and Ca²⁺ signaling pathways. Combination of TMZ with 4-phenylbutyrate (4-PBA), an ER stress inhibitor, augmented TMZ-induced cytotoxicity by inhibiting autophagy. Taken together, our data indicate that TMZ induced autophagy through mitochondrial damage- and ER stress-dependent mechanisms to protect glioma cells. This study provides evidence that agents targeting mitochondria or ER may be potential anticancer strategies.

Mechanism of radioprotection by δ-tocotrienol: pharmacokinetics, pharmacodynamics and modulation of signalling pathways

OBJECTIVE

The objective of this study was to investigate the correlation between in vivo δ-tocotrienol (DT3) pharmacokinetics, pharmacodynamics and radiation protection, and to evaluate the effect of DT3 pre-treatment on radiation-induced alterations in apoptotic and autophagic pathways.

METHODS

We evaluated pharmacokinetics (plasma, 0.5 to 12 h) and pharmacodynamics (peripheral blood indices; day 3, 7, 10 and 14) after a single subcutaneous injection of 300 mg kg(-1) DT3 in unirradiated CD2F1 mice. Next, we monitored 30-day post-irradiation survival (9.25 Gy) and haematopoietic recovery of DT3-treated mice (7 Gy) exposed to cobalt-60 γ-irradiation. The effects of DT3 on irradiated bone marrow apoptosis and autophagy were determined by analyses of key caspases (3, 7, 9 and 8), beclin-1 and light chain 3 conversion.

RESULTS

Plasma concentration of DT3 reached ∼195 µM (Cmax) 1 h after injection (Tmax), and DT3 was eliminated from plasma 12 h later. In unirradiated mice, DT3 significantly increased white blood cells (WBCs), neutrophils, lymphocytes (day 3 post DT3 injection) and platelets (day 7) by 1.5- to 2-fold, over vehicle-treated control. DT3 pre-treatment improved 30-day survival to 100% (∼15% in control) and accelerated recovery of reticulocytes, platelets, WBCs, neutrophils, lymphocytes and monocytes in peripheral blood. DT3 reduced activation of caspase-8, caspase-3 and caspase-7, inherent to apoptosis, while increasing autophagy-related beclin-1 expression in irradiated bone marrow.

CONCLUSION

These data indicate that DT3 stimulates multilineage haematopoiesis, protects against radiation-induced apoptosis downstream of the mitochondria and stimulates cytoprotective autophagy. Apart from a potent antioxidant activity, DT3 may elicit survival advantage following irradiation by enhancing haematopoiesis and modulating signalling pathways.

γ-Tocotrienol does not substantially protect DS neurons from hydrogen peroxide-induced oxidative injury

Background

Down syndrome (DS) neurons are more susceptible to oxidative stress and previous studies have shown that vitamin E was able to reduce oxidative stress and improve DS neurons' viability. Therefore, this study was done to investigate the protective role of γ-tocotrienol (γT3) in DS neurons from hydrogen peroxide (H₂O₂) -induced oxidative stress. The pro-apoptosis tendency of γT3 was compared to α-tocopherol (αT) in non-stress condition as well.

Methods

Primary culture of DS and euploid neurons were divided into six groups of treatment: control, H₂O₂, γT3 pre-treatment with H₂O₂, γT3 only, αT pre-treatment with H₂O₂ and αT only. The treatments were assessed by MTS assay and apoptosis assay by single-stranded DNA (ssDNA) apoptosis ELISA assay, Hoechst and Neu-N immunofluorescence staining. The cellular uptake of γT3 and αT was determined by HPLC while protein expressions were determined by Western blot. Comparison between groups was made by the Student's t test, one-way ANOVA and Bonferroni adjustment as well as two-way ANOVA for multiple comparisons.

Results

One day incubation of γT3 was able to reduced apoptosis of DS neurons by 10%, however γT3 was cytotoxic at longer incubation period (14 days) and at concentrations ≥ 100 μM. Pre-treatment of αT and γT3 only attenuate apoptosis and increase cell viability in H₂O₂-treated DS and euploid neurons by 10% in which the effects were minimal to maintain most of the DS cells' morphology. γT3 act as a free radical scavenger by reducing ROS generated by H₂O₂. In untreated controls, DS neurons showed lower Bcl-2/Bax ratio and p53 expression compared to normal neurons, while cPKC and PKC-δ expressions were higher in DS neurons. On the other hand, pre-treatment of γT3 in H₂O₂-treated DS neurons have reduced Bcl-2/Bax ratio, which was not shown in euploid neurons. This suggests that pre-treatment of γT3 did not promote DS cell survival. Meanwhile γT3 and αT treatments without H₂O₂ as well as pre-treatment of γT3 and αT induced changes in cPKC and PKC-δ expression in DS neurons suggesting interaction of γT3 and αT with PKC activity.

Conclusion

Our study suggests that γT3 pre-treatment are not sufficient to protect DS neurons from H₂O₂-induced oxidative assault, instead induced the apoptosis process.

Assessment of the protective effects of oral tocotrienols in arginine chronic-like pancreatitis

Tocotrienols exhibit anti-inflammatory properties over macrophages and promote cytotoxicity in activated pancreatic stellate cells, suggesting that they may limit chronic pancreatitis progression. We aimed to quantitate the effect of oral tocotrienols on a rat model of chronic pancreatic injury. Chronic-like pancreatitis was induced by repeated arginine pancreatitis. Palm oil tocotrienol-rich fraction (TRF) was given by gavage before and after pancreatitis inductions. Amylase and hydroxyproline were determined in pancreatic homogenates; collagen, fibronectin, α-smooth muscle actin (SMA), glial fibrillary acidic protein (GFAP), and phosphorylated Smad3 were assessed by Western blotting. Transforming growth factor (TGF)-β1 was measured in plasma. Morphological assessment included light microscopy, fibrosis area fraction, and collagen network fractal analysis. Arginine pancreatitis induced pancreatic atrophy and increased hydroxyproline that ameliorated after TRF. Arginine increased TGF-β1 (185 ± 40 vs. 15 ± 2 ng/ml; P <0.01) that was blunted by TRF (53 ± 19; P < 0.01). TRF reduced protease and Smad3 activation, collagen, and fibronectin. α-SMA increased and GFAP diminished in arginine pancreatitis, consistent with long-term stellate cell activation, and TRF reverted these changes to basal. Arginine pancreatitis increased fibrosis area fraction (4.5 ± 0.3% vs. 0.2 ± 0.2%), collagen network complexity (fractal dimension 1.52 ± 0.03 vs. 1.42 ± 0.01; P < 0.001), and inhomogeneity (lacunarity 0.63 ± 0.03 vs. 0.40 ± 0.02; P < 0.001), which were all reduced by TRF (1.3 ± 0.4%, 1.43 ± 0.02%, and 0.51 ± 0.03%, respectively; P < 0.01). Best correlation coefficients were obtained when comparing fibrosis area fraction with lacunarity (r = 0.88) and both parameters with pancreatic weight (r = -0.91 and -0.79, respectively). TRF administered only before pancreatitis best, but not fully, recapitulated the beneficial effects of TRF. Tocotrienols improve quantitative measures of chronic pancreatic damage. They may be of benefit in human chronic pancreatitis.

Comparison of antioxidative and antifibrotic effects of α-tocopherol with those of tocotrienol-rich fraction in a rat model of chronic pancreatitis

OBJECTIVES

The α-tocopherol and tocotrienol-rich fraction (TRF) are considered effective antioxidants. This study aimed to compare the antioxidative and antifibrotic effects of α-tocopherol and TFR in dibutylin dichloride (DBTC)-induced chronic pancreatitis (CP) rats.

METHODS

Oral administration of α-tocopherol and TFR (both 800 mg/kg per day) started the next day after DBTC (8 mg/kg) infusion into the tail vein for 4 weeks. Histological examination, Sirius red staining, and measurement of the contents of hydroxyproline and malondialdehyde of the pancreas were performed to evaluate pancreatic damage and fibrosis. Immunohistochemical analysis of α-smooth muscle actin and real-time reverse transcription polymerase chain reaction for transforming growth factor-β1 (TGF-β1) and collagen-α1(I) were performed to evaluate the activation of pancreatic stellate cells and the mRNA levels of fibrosis-related genes, respectively.

RESULTS

Both α-tocopherol and TRF reduced oxidative stress, ameliorated inflammation and fibrosis, and down-regulated the mRNA expression of TGF-β1 and collagen-α1(I) in DBTC-induced CP. The TRF was superior to α-tocopherol in alleviating inflammation and fibrosis and down-regulating TGF-β1 mRNA expression.

CONCLUSIONS

Oral administration of α-tocopherol and TRF improves pancreatic inflammation and fibrosis in DBTC-induced CP rats, with TRF being more effective than α-tocopherol. Therefore, TRF may be a novel option for alleviating inflammation and, particularly, the fibrotic process in CP.

Effect of δ-tocotrienol on melanin content and enzymes for melanin synthesis in mouse melanoma cells

In the present study, we investigated the dose-dependent effect of delta-tocotrienol long term (48, 72 h) on the melanin content of cells treated with delta-tocotrienol, and whether cells treated with delta-tocotrienol for long a time show cytotoxicity. We also examined whether other enzymes responsible for melanin biosynthesis, tyrosinase-related protein-1 (TRP-1) and -2 (TRP-2), are involved in the decrease in melanin levels. Protein levels in cells treated with 25 or 50 microM delta-tocotrienol for 48 h or 72 h were similar to those in control cells. Melanin content decreased by 44 (25 microM delta-tocotrienol) to 50% (50 microM) at 48 h, and by 14 to 21% at 72 h, compared to control levels. Tyrosinase activity, amounts of tyrosinase and TRP-1 decreased dependent on dose : by 50 (25 microM delta-tocotrienol) to 75% (50 microM), 20 to 45% and 42 to 82% at 48 h, and by 25 to 50%, 75 to 80% and 78 to 77% at 72 h, respectively. Although the amount of TRP-2 increased by 20% on treatment with 25 microM delta-tocotrienol for 48 h, it decreased by 52% on treatment with 50 microM delta-tocotrienol for 48 h. The amount of TRP-2 dose-dependently decreased by 55% and 75% on 72 h by treatment with 25 and 50 microM delta-tocotrienol, respectively. From these findings, delta-tocotrienol at up to 50 microM dose-dependently caused a reduction in melanin content by the decrease of TRP-1 and TRP-2 as well as tyrosinase, and no cytotoxicity.

Retinoic acid induces autophagosome maturation through redistribution of the cation-independent mannose-6-phosphate receptor

Retinoic acids (RAs) have diverse biologic effects and regulate several cellular functions. Here, we investigated the role of RA on autophagy by studying its effects on autophagosome (AUT) maturation, as well as on upstream regulators of autophagosome biogenesis. Our studies, based on the use of pH-sensitive fluorescent reporter markers, suggested that RA promotes AUT acidification and maturation. By using competitive inhibitors and specific agonists, we demonstrated that this effect is not mediated by the classic RAR and RXR receptors. RA did not affect the levels of upstream regulators of autophagy, such as Beclin-1, phospho-mTOR, and phospho-Akt1, but induced redistribution of both endogenous cation-independent mannose-6-phosphate receptor CIMPR and transiently transfected GFP and RFP full-length CIMPR fusion proteins from the trans-Golgi region to acidified AUT structures. Those structures were found to be amphisomes (acidified AUTs) and not autophagolysosomes. The critical role of CIMPR in AUT maturation was further demonstrated by siRNA-mediated silencing of endogenous CIMPR. Transient CIMPR knockdown resulted in remarkable accumulation of nonacidified AUTs, a process that could not be reversed with RA. Our results suggest that RA induces AUT acidification and maturation, a process critical in the cellular autophagic mechanism.

Metabolism of tocotrienols in animals and synergistic inhibitory actions of tocotrienols with atorvastatin in cancer cells

Tocotrienols (T3s), members of the vitamin E family, exhibit potent anti-cancer, anti-oxidative, anti-inflammatory, and some other biological activities. To better understand the bioavailability and metabolism of T3s, T3s and their metabolites were identified in urine and fecal samples from mice on diet supplemented with mixed T3s using HPLC/electrochemical detection and liquid chromatography electrospray ionisation mass spectrometry (LC-ESI-MS). Whereas the short-chain metabolites carboxyethyl hydroxychromans (CEHCs) and carboxymethylbutyl hydroxychromans (CMBHCs) were the major metabolites of T3s, several new metabolites with double bonds were also identified. Similar to tocopherols, the majority of T3 metabolites were excreted as sulfate/glucuronide conjugates in mouse urine. The distribution of γ- and δ-T3 and γ-T3 metabolites were also determined in different organs as well as in urine and fecal samples from mice on diets supplemented with corresponding T3s. The synergistic anti-cancer actions of γ-T3 and atorvastatin (ATST) were studied in HT29 and HCT116 colon cancer cell lines. The combination greatly potentiated the ability of each individual agent to inhibit cancer cell growth and to induce cell cycle arrest and apoptosis. The triple combination of γ-T3, ATST, and celecoxib exhibited synergistic actions when compared with any double combination plus the third agent. Mechanistic studies revealed that the synergistic actions of γ-T3 and ATST could be attributed to their mediation of 3-hydroxy-3-methyl-glutaryl-CoA reductase, and the subsequent inhibition of protein geranylgeranylation. It remains to be determined whether such a synergy occurs in vivo.

Gamma-tocotrienol induces apoptosis and autophagy in prostate cancer cells by increasing intracellular dihydrosphingosine and dihydroceramide

Although cell-based studies have shown that γ-tocotrienol (γTE) exhibits stronger anticancer activities than other forms of vitamin E including γ-tocopherol (γT), the molecular bases underlying γTE-exerted effects remains to be elucidated. Here we showed that γTE treatment promoted apoptosis, necrosis and autophagy in human prostate PC-3 and LNCaP cancer cells. In search of potential mechanisms of γTE-provoked effects, we found that γTE treatment led to marked increase of intracellular dihydroceramide and dihydrosphingosine, the sphingolipid intermediates in de novo sphingolipid synthesis pathway but had no effects on ceramide or sphingosine. The elevation of these sphingolipids by γTE preceded or coincided with biochemical and morphological signs of cell death and was much more pronounced than that induced by γT, which accompanied with much higher cellular uptake of γTE than γT. The importance of sphingolipid accumulation in γTE-caused fatality was underscored by the observation that dihydrosphingosine and dihydroceramide potently reduced the viability of both prostate cell lines and LNCaP cells, respectively. In addition, myriosin, a specific inhibitor of de novo sphingolipid synthesis, counteracted γTE-induced cell death. In agreement with these cell-based studies, γTE inhibited LNCaP xenograft growth by 53% (p < 0.05), compared to 33% (p = 0.07) by γT, in nude mice. These findings provide a molecular basis of γTE-stimulated cancer cell death and support the notion that elevation of intracellular dihydroceramide and dihydrosphingosine is likely a novel anticancer mechanism.

Mesenchymal cell proliferation and programmed cell death: key players in fibrogenesis and new targets for therapeutic intervention

An exquisite equilibrium between cell proliferation and programmed cell death is required to maintain physiological homeostasis. In inflammatory bowel disease, and especially in Crohn's disease, enhanced proliferation along with defective apoptosis of immune cells are considered key elements of pathogenesis. Despite the relatively limited attention that has been given to research efforts devoted to intestinal fibrosis to date, there is evidence suggesting that enhanced proliferation along with defective programmed cell death of mesenchymal cells can significantly contribute to the development of excessive fibrogenesis in many different tissues. Moreover, some therapies have demonstrated potential antifibrogenic efficacy through the regulation of mesenchymal cell proliferation and programmed cell death. Further understanding of the pathways involved in the regulation of mesenchymal cell proliferation and apoptosis is, however, required.