A role for microsomal glutathione transferase 1 in melanin biosynthesis and melanoma progression.

Recent advancements in the treatment of melanoma are encouraging, but there remains a need to identify additional therapeutic targets. We identify a role for microsomal glutathione transferase 1 (MGST1) in biosynthetic pathways for melanin and as a determinant of tumor progression. Knockdown (KD) of MGST1 depleted midline-localized, pigmented melanocytes in zebrafish embryos, while in both mouse and human melanoma cells, loss of MGST1 resulted in a catalytically dependent, quantitative, and linear depigmentation, associated with diminished conversion of L-dopa to dopachrome (eumelanin precursor). Melanin, especially eumelanin, has antioxidant properties, and MGST1 KD melanoma cells are under higher oxidative stress, with increased reactive oxygen species, decreased antioxidant capacities, reduced energy metabolism and ATP production, and lower proliferation rates in 3D culture. In mice, when compared to nontarget control, Mgst1 KD B16 cells had less melanin, more active CD8+ T cell infiltration, slower growing tumors, and enhanced animal survival. Thus, MGST1 is an integral enzyme in melanin synthesis and its inhibition adversely influences tumor growth.

Research progress on carotenoid production by Rhodosporidium toruloides.

Carotenoids are natural lipophilic pigments, which have been proven to provide significant health benefits to humans, relying on their capacity to efficiently scavenge singlet oxygen and peroxyl radicals as antioxidants. Strains belonging to the genus Rhodosporidium represent a heterogeneous group known for a number of phenotypic traits including accumulation of carotenoids and lipids and tolerance to heavy metals and oxidative stress. As a representative of these yeasts, Rhodosporidium toruloides naturally produces carotenoids with high antioxidant activity and grows on a wide variety of carbon sources. As a result, R. toruloides is a promising host for the efficient production of more value-added lipophilic compound carotenoids, e.g., torulene and torularhodin. This review provides a comprehensive summary of the research progress on carotenoid biosynthesis in R. toruloides, focusing on the understanding of biosynthetic pathways and the regulation of key enzymes and genes involved in the process. Moreover, the relationship between the accumulation of carotenoids and lipid biosynthesis, as well as the stress from diverse abiotic factors, has also been discussed for the first time. Finally, several feasible strategies have been proposed to promote carotenoid production by R. toruloides. It is possible that R. toruloides may become a critical strain in the production of carotenoids or high-value terpenoids by genetic technologies and optimal fermentation processes. KEY POINTS: • Biosynthetic pathway and its regulation of carotenoids in Rhodosporidium toruloides were concluded • Stimulation of abiotic factors for carotenoid biosynthesis in R. toruloides was summarized • Feasible strategies for increasing carotenoid production by R. toruloides were proposed.

Microsomal glutathione transferase 1 controls metastasis and therapeutic response in melanoma.

While recent targeted and immunotherapies in malignant melanoma are encouraging, most patients acquire resistance, implicating a need to identify additional drug targets to improve outcomes. Recently, attention has been given to pathways that regulate redox homeostasis, especially the lipid peroxidase pathway that protects cells against ferroptosis. Here we identify microsomal glutathione S-transferase 1 (MGST1), a non-selenium-dependent glutathione peroxidase, as highly expressed in malignant and drug resistant melanomas and as a specific determinant of metastatic spread and therapeutic sensitivity. Loss of MGST1 in mouse and human melanoma enhanced cellular oxidative stress, and diminished glycolysis, oxidative phosphorylation, and pentose phosphate pathway. Gp100 activated pmel-1 T cells killed more Mgst1 KD than control melanoma cells and KD cells were more sensitive to cytotoxic anticancer drugs and ferroptotic cell death. When compared to control, mice bearing Mgst1 KD B16 tumors had more CD8+ T cell infiltration with reduced expression of inhibitory receptors and increased cytokine response, large reduction of lung metastases and enhanced survival. Targeting MGST1 alters the redox balance and limits metastases in melanoma, enhancing the therapeutic index for chemo- and immunotherapies.

Progress in biological activities and biosynthesis of edible fungi terpenoids.

The edible fungi have both edible and medicinal functions, in which terpenoids are one of the most important active ingredients. Terpenoids possess a wide range of biological activities and show great potential in the pharmaceutical and healthcare industries. In this review, the diverse biological activities of edible fungi terpenoids were summarized with emphasis on the mechanism of anti-cancer and anti-inflammation. Subsequently, this review focuses on advances in knowledge and understanding of the biosynthesis of terpenoids in edible fungi, especially in the generation of sesquiterpenes, diterpenes, and triterpenes. This paper is aim to provide an overview of biological functions and biosynthesis developed for utilizing the terpenoids in edible fungi.

The beneficial potential of protein hydrolysates as prebiotic for probiotics and its biological activity: a review.

Probiotics are not only a food supplement, but they have shown great potential in their nutritional, health and therapeutic effects. To maximize the beneficial effects of probiotics, it is commonly achieved by adding prebiotics. Prebiotics primarily comprise indigestible carbohydrates, specific peptides, proteins, and lipids, with oligosaccharides being the most extensively studied prebiotics. However, these rapidly fermenting oligosaccharides have many drawbacks and can cause diarrhea and flatulence in the body. Hence, the exploration of new prebiotic is of great interest. Besides oligosaccharides, protein hydrolysates have been demonstrated to enhance the expression of beneficial properties of probiotics. Consequently, this paper outlines the mechanism underlying the action of protein hydrolysates on probiotics, as well as the advantageous impacts of proteins hydrolysates derived from various food sources on probiotics. In addition, this paper also reviews the currently reported biological activities of protein hydrolysates. The aim is a theoretical basis for the development and implementation of novel prebiotics.

Enhancement of ergothioneine production by discovering and regulating its metabolic pathway in Cordyceps militaris.

BACKGROUND: Cordyceps militaris is a traditional medicinal fungus contains a variety of functional ingredients and has been developed as an important mushroom food recently. Ergothioneine, one of the antioxidative compounds in C. militaris, is benefits on aging-related diseases and therefore became a novel functional food nutritive fortifier. Currently, the main diet source of ergothioneine is mushroom food. However, the mushroom farming faces the problems such as rather low ingredient yield and spontaneous degeneration associated fruiting body that restricts large scale production of ergothioneine. RESULTS: In this study, we excavated the ergothioneine synthetases in mushroom and modified the genes in C. militaris to construct a new ergothioneine synthesis pathway. By further introducing this pathway into C. militaris genome, we succeeded to increase the ingredients' production of engineering strain, the highest amount of ergothioneine and cordycepin were up to 2.5 g/kg dry weight and 2 g/L, respectively. Additionally, the expression of ergothioneine synthetase genes in the shape-mutated degenerative C. militaris could recover the ability of degenerative strain to produce high amount of ingredients, suggesting the metabolic regulation of ergothioneine might release the symptom of mushroom degeneration. CONCLUSION: This study reveals a new pathway to fulfill the market needs of functional mushroom food and food fortifier ergothioneine. It implied the mycelium of C. militaris could be engineered as a novel medicinal mushroom food which could produce higher amount of valuable ingredients.

Development of Telintra as an Inhibitor of Glutathione S-Transferase P.

Glutathione S-transferase P (GSTP) is a component of a complex series of pathways that provide cellular redox homeostasis. It is an abundant protein in certain tumors and is over-expressed in cancer drug resistance. It has diverse cellular functions that include, thiolase activities with small electrophilic agents or susceptible cysteine residues on the protein to mediate S-glutathionylation, and chaperone binding with select protein kinases. Preclinical and clinical testing of a nanomolar inhibitor of GSTP, TLK199 (Telintra; Ezatiostat) has indicated a role for the enzyme in hematopoiesis and utility for the drug in the treatment of patients with myelodysplastic syndrome.

S-Glutathionylation of estrogen receptor α affects dendritic cell function.

Glutathione S-transferase Pi (GSTP) is a thiolase that catalyzes the addition of glutathione (GSH) to receptive cysteines in target proteins, producing an S-glutathionylated residue. Accordingly, previous studies have reported that S-glutathionylation is constitutively decreased in cells from mice lacking GSTP (Gstp1/p2-/-). Here, we found that bone marrow-derived dendritic cells (BMDDCs) from Gstp1/p2-/- mice have proliferation rates that are greater than those in their WT counterparts (Gstp1/p2+/+). Moreover, Gstp1/p2-/- BMDDCs had increased reactive oxygen species (ROS) levels and decreased GSH:glutathione disulfide (GSSG) ratios. Estrogen receptor α (ERα) is linked to myeloproliferation and differentiation, and we observed that its steady-state levels are elevated in Gstp1/p2-/- BMDDCs, indicating a link between GSTP and ERα activities. BMDDCs differentiated by granulocyte-macrophage colony-stimulating factor had elevated ERα levels, which were more pronounced in Gstp1/p2-/- than WT mice. When stimulated with lipopolysaccharide for maturation, Gstp1/p2-/- BMDDCs exhibited augmented endocytosis, maturation rate, cytokine secretion, and T-cell activation; heightened glucose uptake and glycolysis; increased Akt signaling (in the mTOR pathway); and decreased AMPK-mediated phosphorylation of proteins. Of note, GSTP formed a complex with ERα, stimulating ERα S-glutathionylation at cysteines 221, 245, 417, and 447; altering ERα's binding affinity for estradiol; and reducing overall binding potential (receptor density and affinity) 3-fold. Moreover, in Gstp1/p2-/- BMDDCs, ERα S-glutathionylation was constitutively decreased. Taken together, these findings suggest that GSTP-mediated S-glutathionylation of ERα controls BMDDC differentiation and affects metabolic function in dendritic cells.

Musa basjoo regulates the gut microbiota in mice by rebalancing the abundance of probiotic and pathogen.

Musa basjoo is a kind of popular slimming fruit in southern China. However, even though the trophic component and physiological effect are well studied, its internal mechanism in reconstructing gut microbiota remains unclear. In this study, maturity of M. basjoo were divided into four levels. Results indicated that M. basjoo in level Ⅱ (with 35% maturity) represented the greatest increase in the growth in vitro of probiotics, Lactobacillus plantarum FMNP01 and Lactobacillus casei FMNP02. After feeding M. basjoo with the middle dose (2.67 g/kg·BW) to mice for 21 days, gut microbiota from mice feces was isolated and sequenced. Results of 16SrDNA sequencing showed that the scattered genera of gut microbiota were significantly gathered. The amounts of different pathogens were decreased, while probiotics such as genera Bacteroides and Roseburia were significantly increased (p < 0.05). Results of function prediction indicated that the reconstruction of gut microbiota may due to the change in carbohydrate transportation, biosynthesis of cell wall, cell membrane, and cell envelope. This study has drawn a basic mechanism in reconstructing gut microbiota by feeding M. basjoo and lay out a foundation for further reach on the interaction between human as diner and M. basjoo as food.

Adverse Outcomes Associated with Cigarette Smoke Radicals Related to Damage to Protein-disulfide Isomerase.

Identification of factors contributing to the development of chronic obstructive pulmonary disease (COPD) is crucial for developing new treatments. An increase in the levels of protein-disulfide isomerase (PDI), a multifaceted endoplasmic reticulum resident chaperone, has been demonstrated in human smokers, presumably as a protective adaptation to cigarette smoke (CS) exposure. We found a similar increase in the levels of PDI in the murine model of COPD. We also found abnormally high levels (4-6 times) of oxidized and sulfenilated forms of PDI in the lungs of murine smokers compared with non-smokers. PDI oxidation progressively increases with age. We begin to delineate the possible role of an increased ratio of oxidized PDI in the age-related onset of COPD by investigating the impact of exposure to CS radicals, such as acrolein (AC), hydroxyquinones (HQ), peroxynitrites (PN), and hydrogen peroxide, on their ability to induce unfolded protein response (UPR) and their effects on the structure and function of PDIs. Exposure to AC, HQ, PN, and CS resulted in cysteine and tyrosine nitrosylation leading to an altered three-dimensional structure of the PDI due to a decrease in helical content and formation of a more random coil structure, resulting in protein unfolding, inhibition of PDI reductase and isomerase activity in vitro and in vivo, and subsequent induction of endoplasmic reticulum stress response. Addition of glutathione prevented the induction of UPR, and AC and HQ induced structural changes in PDI. Exposure to PN and glutathione resulted in conjugation of PDI possibly at active site tyrosine residues. The findings presented here propose a new role of PDI in the pathogenesis of COPD and its age-dependent onset.

Oxidative stress, redox regulation and diseases of cellular differentiation.

BACKGROUND: Within cells, there is a narrow concentration threshold that governs whether reactive oxygen species (ROS) induce toxicity or act as second messengers. SCOPE OF REVIEW: We discuss current understanding of how ROS arise, facilitate cell signaling, cause toxicities and disease related to abnormal cell differentiation and those (primarily) sulfur based pathways that provide nucleophilicity to offset these effects. PRIMARY CONCLUSIONS: Cellular redox homeostasis mediates a plethora of cellular pathways that determine life and death events. For example, ROS intersect with GSH based enzyme pathways to influence cell differentiation, a process integral to normal hematopoiesis, but also affecting a number of diverse cell differentiation related human diseases. Recent attempts to manage such pathologies have focused on intervening in some of these pathways, with the consequence that differentiation therapy targeting redox homeostasis has provided a platform for drug discovery and development. GENERAL SIGNIFICANCE: The balance between electrophilic oxidative stress and protective biomolecular nucleophiles predisposes the evolution of modern life forms. Imbalances of the two can produce aberrant redox homeostasis with resultant pathologies. Understanding the pathways involved provides opportunities to consider interventional strategies. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation.

Use of autochthonous lactic acid bacteria starters to ferment mango juice for promoting its probiotic roles.

Strains of Leuconostoc mesenteroides, Pediococcus pentosaceus, and Lactobacillus brevis were identified from mango fruits by partial 16S rDNA gene sequence. Based on the ability of producing mannitol and diacetyl, Leuconostoc mesenteroides MPL18 and MPL39 were selected within the lactic acid bacteria isolates, and used as mixed starters to ferment mango juice (MJ). Both the autochthonous strains grew well in fermented mango juice (FMJ) and remained viable at 9.81 log cfu mL(-1) during 30 days of storage at 4°C. The content of total sugar of FMJ was lower than that of MJ, while the concentration of mannitol was higher than that of MJ, and the concentration of diacetyl was 3.29 ± 0.12 mg L(-1). Among detected organic acids including citric acid, gallic acid, lactic acid, and acetic acid, only citric acid and gallic acid were found in MJ, while all detected organic acids were found in FMJ. The concentration of lactic acid of FMJ was the highest (78.62 ± 13.66 mM) among all detected organic acids. The DPPH radical scavenging capacity of FMJ was higher than that of MJ. Total phenolic compounds were better preserved in FMJ. The acidity and sweetness had a noticeable impact on the overall acceptance of the treated sample.

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and PH domain and leucine-rich repeat phosphatase cross-talk (PHLPP) in cancer cells and in transforming growth factor ß-activated stem cells.

Akt kinase controls cell survival, proliferation, and invasive growth and is a critical factor for cancer development. Here we describe a cross-talk between phosphatases that may preserve levels of activated/phosphorylated Akt and confer aggressive growth of cancer cells. In prostatic cancer cells, but not in non-transformed cells or in prostate stem cells, we found that the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) overexpression down-regulated PH domain and leucine-rich repeat phosphatase (PHLPP) and that PHLPP overexpression down-regulated PTEN. We also show that silencing PTEN by siRNA increased the levels of PHLPPs. This cross-talk facilitated invasive migration and was mediated by epigenetic alterations, including activation of miR-190, miR-214, polycomb group of proteins, as well as DNA methylation. A role for the purinergic receptor P2X4, previously associated with wound healing, was indicated. We also show that TGF-ß1 induced cross-talk concomitant with epithelial-mesenchymal transition in stem cells. The cross-talk emerged as an integrated part of epithelial-mesenchymal transition. We conclude that cross-talk between PTEN and PHLPPs is silenced in normal prostate cells but activated in TGF-ß1 transformed prostate stem and cancer cells and facilitates invasive growth.

Toluene diisocyanate: Induction of the autotaxin-lysophosphatidic acid axis and its association with airways symptoms.

Diisocyanates are industrial chemicals which have a wide range of applications in developed and developing countries. They are notorious lung toxicants and respiratory sensitizers. However, the mechanisms behind their adverse effects are not adequately characterized. Autotaxin (ATX) is an enzyme producing lysophosphatidic acid (LPA), and the ATX-LPA axis has been implicated in lung related inflammatory conditions and diseases, including allergic asthma, but not to toxicity of environmental low-molecular-weight chemicals. We investigated effects of toluene diisocyanate (TDI) on ATX induction in human lung epithelial cell models, and we correlated LPA-levels in plasma to biomarkers of TDI exposure in urine collected from workers exposed to <5ppb (parts per billion). Information on workers' symptoms was collected through interviews. One nanomolar TDI robustly induced ATX release within 10min in vitro. A P2X7- and P2X4-dependent microvesicle formation was implicated in a rapid ATX release and a subsequent protein synthesis. Co-localization between purinergic receptors and ATX was documented by immunofluorescence and confocal microscopy. The release was modulated by monocyte chemoattractant protein-1 (MCP-1) and by extracellular ATP. In workers, we found a dose-response relationship between TDI exposure biomarkers in urine and LPA levels in plasma. Among symptomatic workers reporting "sneezing", the LPA levels were higher than among non-symptomatic workers. This is the first report indicating induction of the ATX-LPA axis by an environmental low-molecular-weight chemical, and our data suggest a role for the ATX-LPA axis in TDI toxicity.

Bioproduction of baccatin III, an advanced precursor of paclitaxol, with transgenic Flammulina velutipes expressing the 10-deacetylbaccatin III-10-O-acetyl transferase gene.

BACKGROUND: 10-Deacetylbaccatin III (10-DAB) and baccatin III are intermediates in the biosynthesis of Taxol (an anti-cancer drug) and useful precursors for semi-synthesis of the drug. In this study, a bioconversion system was established for the production of baccatin III, an advanced precursor of paclitaxel, in the transgenic mushroom Flammulina velutipes expressing the 10-deacetylbaccatin III-10ß-O-acetyltransferase gene. The expression vector pgFvs-TcDBAT containing the 10-deacetylbaccatin III-10ß-O-acetyltransferase (DBAT) gene was constructed and transformed into the cells of F. velutipes by polyethylene glycol-mediated protoplast transformation. RESULTS: Polymerase chain reaction and Southern blotting analysis verified the successful integration of the exogenous DBAT gene into the genome of F. velutipes. Reverse transcription polymerase chain reaction and enzyme activity analyses confirmed that the DBAT gene was expressed in F. velutipes, and DBAT is able to convert substrate into baccatin III. CONCLUSION: The DBAT gene from the plant Taxus chinensis can be functionally expressed in F. velutipes. Transgenic F. velutipes expressing the DBAT gene is able to produce the target product, baccatin III. This is the first report about the transformation and expression of paclitaxel biosynthetic gene in the edible mushroom F. velutipes. This represents a significant step towards bio-production of paclitaxel and its advanced precursor baccatin III in an edible fungus.

Submerged Culture of Edible and Medicinal Mushroom Mycelia and Their Applications in Food Products: A Review.

Edible mushrooms have rich nutrition (e.g., proteins, dietary fibers, polysaccharides) and they can be potential sources of important ingredients in food processing. However, the cultivation of mushroom fruiting bodies needs a relatively long time, and they can be easily polluted during the growth process. At the same time, a lot of labor and larger planting areas are also required. As we all know, submerged fermentation is a good way to produce edible mushroom mycelia with less environmental pollution and small footprint, which are also rich in nutrition and bioactive components that are used as dietary supplements or health care products in the food industry. Therefore, it can be considered that the replacement of edible mushroom fruiting bodies with edible mushroom mycelia produced through submerged fermentation has great application potential in food production. At present, most of the research about edible mushroom mycelia focuses on the production of bioactive metabolites in fermentation liquid, but there are few reports that concentrate on their applications in food. This paper reviews the research progress of submerged culture of edible mushroom mycelia and their applications in food products.

Adaptive changes in tumor cells in response to reductive stress.

Reductive stress is characterized by an excess of cellular electron donors and can be linked with various human pathologies including cancer. We developed melanoma cell lines resistant to reductive stress agents: rotenone (ROTR), n-acetyl-L-cysteine, (NACR), or dithiothreitol (DTTR). Resistant cells divided more rapidly and had intracellular homeostatic redox-couple ratios that were shifted towards the reduced state. Resistance caused alterations in general cell morphology, but only ROTR cells had significant changes in mitochondrial morphology with higher numbers that were more isolated, fragmented and swollen, with greater membrane depolarization and decreased numbers of networks. These changes were accompanied by lower basal oxygen consumption and maximal respiration rates. Whole cell flux analyses and mitochondrial function assays showed that NACR and DTTR preferentially utilized tricarboxylic acid (TCA) cycle intermediates, while ROTR used ketone body substrates such as D, L-ß-hydroxybutyric acid. NACR and DTTR cells had constitutively decreased levels of reactive oxygen species (ROS), although this was accompanied by activation of nuclear factor erythroid 2-related factor 2 (Nrf2), with concomitant increased expression of the downstream gene products such as glutathione S-transferase P (GSTP). Further adaptations included enhanced expression of endoplasmic reticulum proteins controlling the unfolded protein response (UPR). Although expression patterns of these UPR proteins were distinct between the resistant cells, a trend implied that resistance to reductive stress is accompanied by a constitutively increased UPR phenotype in each line. Overall, tumor cells, although tolerant of oxidative stress, can adapt their energy and survival mechanisms in lethal reductive stress conditions.

Microsomal glutathione transferase 1 in cancer and the regulation of ferroptosis.

Microsomal glutathione transferase 1 (MGST1) is a member of the MAPEG family (membrane associated proteins in eicosanoid and glutathione metabolism), defined according to enzymatic activities, sequence motifs, and structural properties. MGST1 is a homotrimer which can bind three molecules of glutathione (GSH), with one modified to a thiolate anion displaying one-third-of-sites-reactivity. MGST1 has both glutathione transferase and peroxidase activities. Each is based on stabilizing the GSH thiolate in the same active site. MGST1 is abundant in the liver and displays a broad subcellular distribution with high levels in endoplasmic reticulum and mitochondrial membranes, consistent with a physiological role in protection from reactive electrophilic intermediates and oxidative stress. In this review paper, we particularly focus on recent advances made in understanding MGST1 activation, induction, broad subcellular distribution, and the role of MGST1 in apoptosis, ferroptosis, cancer progression, and therapeutic responses.

Protein disulfide isomerase family mediated redox regulation in cancer.

Protein disulfide isomerase (PDI) and its superfamilies are mainly endoplasmic reticulum (ER) resident proteins with essential roles in maintaining cellular homeostasis, via thiol oxidation/reduction cycles, chaperoning, and isomerization of client proteins. Since PDIs play an important role in ER homeostasis, their upregulation supports cell survival and they are found in a variety of cancer types. Despite the fact that the importance of PDI to tumorigenesis remains to be understood, it is emerging as a new therapeutic target in cancer. During the past decade, several PDI inhibitors has been developed and commercialized, but none has been approved for clinical use. In this review, we discuss the properties and redox regulation of PDIs within the ER and provide an overview of the last 5 years of advances regarding PDI inhibitors.