Additive toxicity of limonene and 50% oxygen and the role of glutathione in detoxification in human lung cells

Therapeutic potential of d-limonene in rheumatoid arthritis: Modulation of inflammatory, anti-inflammatory cytokines, and prostaglandin E2

Rheumatoid arthritis (RA) is a persistent autoimmune disorder predominantly affecting the joint structures, eliciting inflammatory responses, and ultimately leading to degenerative changes without proper medical intervention. Ultimately, this can severely impair joint function and impact the patient's quality of life. Current treatment approaches include disease-modifying anti-rheumatic drugs, non-steroidal anti-inflammatory drug, corticosteroids, and biologic therapies for RA management. The current study contributes to the ongoing advancements in RA treatment. d-Limonene is a monocyclic monoterpene. It is present in essential oils of various aromatic plants, such as Lippia alba and Artemisia dracunculus, and in citrus fruits such as lemon and orange. It has reported anti-inflammatory and anti-nociceptive properties and was selected for the current study as a potential anti-arthritic candidate. It was administered at three dosages (25, 50, 100 mg/kg, b.w., p.o) in Complete Freund's adjuvant-induced arthritic rats over 28 days. The efficacy of the compound was compared to piroxicam, a widely used standard drug for treating RA. The anti-arthritic activity of the compound was assessed by measuring arthritic scoring and plethysmometry at both baseline and post-intervention stages. Additional confirmation of the investigation was sought by performing biochemical and hematological activities. Moreover, quantitative polymerase chain reaction was employed to determine the levels of messenger RNA expression for transcription factors such as tumor necrosis factor-α, interleukin (IL)-1β, nuclear factor-κB, matrix metalloproteinase-3, IL-6, and IL-4 in the blood. The levels of PGE2 were evaluated by enzyme-linked immunosorbent assay. The histopathological and radiographic studies were also carried out for further confirmation. The results of these findings supported our assertion regarding the anti-arthritic potential of the compound.

Evaluation of Lippia scaberrima Sond. and Aspalathus linearis (Burm.f.) R. Dahlgren extracts on human CYP enzymes and gold nanoparticle synthesis: implications for drug metabolism and cytotoxicity

BACKGROUND

Metabolism is an important component of the kinetic characteristics of herbal constituents, and it often determines the internal dose and concentration of these effective constituents at the target site. The metabolic profile of plant extracts and pure compounds need to be determined for any possible herb-drug metabolic interactions that might occur.

METHODS

Various concentrations of the essential oil of Lippia scaberrima, the ethanolic extract of Lippia scaberrima alone and their combinations with fermented and unfermented Aspalathus linearis extract were used to determine the inhibitory potential on placental, microsomal and recombinant human hepatic Cytochrome P450 enzymes. Furthermore, the study investigated the synthesis and characterization of gold nanoparticles from the ethanolic extract of Lippia scaberrima as a lead sample. Confirmation and characterization of the synthesized gold nanoparticles were conducted through various methods. Additionally, the cytotoxic properties of the ethanolic extract of Lippia scaberrima were compared with the gold nanoparticles synthesized from Lippia scaberrima using gum arabic as a capping agent.

RESULTS

All the samples showed varying levels of CYP inhibition. The most potent inhibition took place for CYP2C19 and CYP1B1 with 50% inhibitory concentration (IC50) values of less than 0.05 µg/L for the essential oil tested and IC50-values between 0.05 µg/L-1 µg/L for all the other combinations and extracts tested, respectively. For both CYP1A2 and CYP2D6 the IC50-values for the essential oil, the extracts and combinations were found in the range of 1 - 10 µg/L. The majority of the IC50 values found were higher than 10 µg/L and, therefore, were found to have no inhibition against the CYP enzymes tested.

CONCLUSION

Therefore, the essential oil of Lippia scaberrima, the ethanolic extract of Lippia scaberrima alone and their combinations with Aspalathus linearis do not possess any clinically significant CYP interaction potential and may be further investigated for their adjuvant potential for use in the tuberculosis treatment regimen. Furthermore, it was shown that the cytotoxic potential of the Lippia scaberrima gold nanoparticles was reduced by twofold when compared to the ethanolic extract of Lippia scaberrima.

Metabolic engineering of the L-serine biosynthetic pathway improves glutathione production in Saccharomyces cerevisiae

Background

Glutathione is a valuable tri-peptide that is industrially produced by fermentation using the yeast Saccharomyces cerevisiae, and is widely used in the pharmaceutical, food, and cosmetic industries. It has been reported that addition of l-serine (l-Ser) is effective at increasing the intracellular glutathione content because l-Ser is the common precursor of l-cysteine (l-Cys) and glycine (Gly) which are substrates for glutathione biosynthesis. Therefore, we tried to enhance the l-Ser biosynthetic pathway in S. cerevisiae for improved glutathione production.

Results

The volumetric glutathione production of recombinant strains individually overexpressing SER2, SER1, SER3, and SER33 involved in l-Ser biosynthesis at 48 h cultivation was increased 1.3, 1.4, 1.9, and 1.9-fold, respectively, compared with that of the host GCI strain, which overexpresses genes involved in glutathione biosynthesis. We further examined simultaneous overexpression of SHM2 and/or CYS4 genes involved in Gly and l-Cys biosynthesis, respectively, using recombinant GCI strain overexpressing SER3 and SER33 as hosts. As a result, GCI overexpressing SER3, SHM2, and CYS4 showed the highest volumetric glutathione production (64.0 ± 4.9 mg/L) at 48 h cultivation, and this value is about 2.5-fold higher than that of the control strain.

Conclusions

This study first revealed that engineering of l-Ser and Gly biosynthetic pathway are useful strategies for fermentative glutathione production by S. cerevisiase.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01880-8.

Toxicity of Selected Monoterpenes and Essential Oils Rich in These Compounds

Monoterpenes make up the largest group of plant secondary metabolites. They can be found in numerous plants, among others, the Lamiaceae family. The compounds demonstrate antioxidative, antibacterial, sedative and anti-inflammatory activity, hence, they are often employed in medicine and pharmaceuticals. Additionally, their fragrant character is often made use of, notably in the food and cosmetic industries. Nevertheless, long-lasting studies have revealed their toxic properties. This fact has led to a detailed analysis of the compounds towards their side effects on the human organism. Although most are safe for human food and medical applications, there are monoterpene compounds that, in certain amounts or under particular circumstances (e.g., pregnancy), can cause serious disorders. The presented review characterises in vitro and in vivo, the toxic character of selected monoterpenes (α-terpinene, camphor, citral, limonene, pulegone, thujone), as well as that of their original plant sources and their essential oils. The selected monoterpenes reveal various toxic properties among which are embryotoxic, neurotoxic, allergenic and genotoxic. It is also known that the essential oils of popular plants can also reveal toxic characteristics that many people are unaware of.

D-limonene: A multifunctional compound with potent therapeutic effects

D-limonene or 4-isopropenyl-1-methylcyclohexene (C₁₀ H₁₆ ) is a monocyclic monoterpene abundant in citrus plants like lemon, orange, and grape. The application of D-limonene in the form of flavor and fragrance additive in perfumes, soaps, foods, and beverages is consistently increased due to its high-quality fragrance property. This review is intended to analyze and delineate every possible available evidence and details about D-limonene with the special focus on its therapeutic efficacy. Many studies have reported that D-limonene effectively plays a valuable role in the prevention of several chronic and degenerative diseases. This review provides worthy information about the beneficial effects of D-limonene such as antioxidant, antidiabetic, anticancer, anti-inflammatory, cardioprotective, gastroprotective, hepatoprotective, immune modulatory, anti-fibrotic, anti-genotoxic etc. This could in turn help in the application of D-limonene for clinical studies. PRACTICAL IMPLICATIONS: Various plant families contain Terpenes as their secondary metabolites. Monoterpenes constitute an important part of these secondary metabolites. D-limonene is a well-identified monoterpene that is commonly applied as a fragrance ingredient in essential oils. D-limonene is known to possess remarkable biological activities. It can be effectively used for treating various ailments and diseases. Due to its diverse functions, it can be efficiently utilized for human health.

Enzymatic improvement of mitochondrial thiol oxidase Erv1 for oxidized glutathione fermentation by Saccharomyces cerevisiae

Background

Oxidized glutathione (GSSG) is the preferred form for industrial mass production of glutathione due to its high stability compared with reduced glutathione (GSH). In our previous study, over-expression of the mitochondrial thiol oxidase ERV1 gene was the most effective for high GSSG production in Saccharomyces cerevisiae cells among three types of different thiol oxidase genes.

Results

We improved Erv1 enzyme activity for oxidation of GSH and revealed that S32 and N34 residues are critical for the oxidation. Five engineered Erv1 variant proteins containing S32 and/or N34 replacements exhibited 1.7- to 2.4-fold higher in vitro GSH oxidation activity than that of parental Erv1, whereas the oxidation activities of these variants for γ-glutamylcysteine were comparable. According to three-dimensional structures of Erv1 and protein stability assays, S32 and N34 residues interact with nearby residues through hydrogen bonding and greatly contribute to protein stability. These results suggest that increased flexibility by amino acid replacements around the active center decrease inhibitory effects on GSH oxidation. Over-expressions of mutant genes coding these Erv1 variants also increased GSSG and consequently total glutathione production in S. cerevisiae cells. Over-expression of the ERV1^S32A gene was the most effective for GSSG production in S. cerevisiae cells among the parent and other mutant genes, and it increased GSSG production about 1.5-fold compared to that of the parental ERV1 gene.

Conclusions

This is the first study demonstrating the pivotal effects of S32 and N34 residues to high GSH oxidation activity of Erv1. Furthermore, in vivo validity of Erv1 variants containing these S32 and N34 replacements were also demonstrated. This study indicates potentials of Erv1 for high GSSG production.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-017-0658-0) contains supplementary material, which is available to authorized users.

A novel and sensitive fluorescence sensor for glutathione detection by controlling the surface passivation degree of carbon quantum dots

A novel fluorescence sensor based on controlling the surface passivation degree of carbon quantum dots (CQDs) was developed for glutathione (GSH) detection. First, we found that the fluorescence intensity of the CQDs which was obtained by directly pyrolyzing citric acid would increased largely after the surface passivation treatment by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). In the light of this phenomenon, we designed a simple, rapid and selective fluorescence sensor based on the surface passivated CQDs. A certain and excess amount of EDC were mixed with GSH, part of EDC would form a stable complex with GSH owing to the exposed sulfhydryl group of GSH. As the synthesized CQDs were added into the above mixture solution, the fluorescence intensity of the (EDC/GSH)/CQDs mixture solution could be directly related to the amount of GSH. Compared to other fluorescence analytical methods, the fluorescence sensor we design is neither the traditional fluorescent "turn on" probes nor "turn off" probes. It is a new fluorescence analytical method that target object indirectly control the surface passivation degree of CQDs so that it can realize the detection of the target object. Moreover, the proposed method manifested great advantages including short analysis time, low cost and ease of operation.

Mint Flavorings from Candies Inhibit the Infectivity of Chlamydia pneumoniae

The impact of solvent extracts from the distillation water (flavoring extracts) isolated from mint flavored candies on the infectivity of the intracellular bacterium Chlamydia pneumoniae was evaluated by an in vitro model of epithelial cell infections. The mint flavoring extracts were isolated from the candies by simultaneous hydrodistillation and their chemical composition, established by GC-MS, demonstrated menthol and limonene as the most abundant components. Results obtained by treating C. pneumoniae elementary bodies (EBs) with the flavoring extracts or pure reference compounds showed a significant decrease in EB infectivity, achieved with most of the extracts. This antichlamydial activity could be related to the relatively high menthol content of the extracts. Overall, the obtained data indicates that the flavorings present in the candies are able to target the metabolically quiet, non-replicating form of the bacterium and to suppress the spread of this respiratory pathogen from one cell to another.

Systematic manipulation of glutathione metabolism in Escherichia coli for improved glutathione production

BACKGROUND

L-glutathione (GSH) is a non-protein thiol compound with important biological properties and is widely used in pharmaceutical, food, cosmetic and health products. The cellular GSH is determined by the activity and characteristic of GSH-synthesizing enzymes, energy and precursor supply, and degradation of formed GSH.

RESULTS

In this study, genes encoding enzymes related to the precursor amino acid degradation and glycogen formation as well as GSH degradation were systematically manipulated in Escherichia coli strains over-expressing gshF from Actinobacillus succinogenes. The manipulation included disrupting the precursor degradation pathways (tnaA and sdaA), eliminating L-glutathione degradation (ggt and pepT), and manipulating the intracellular ATP level (disruption of glgB). However the constructed mutants showed lower levels of GshF expression. 2-D electrophoresis was performed to elucidate the reasons for this discrepancy, and the results indicated obvious changes in central metabolism and amino acid metabolism in the penta-mutant. Fed-batch culture of the penta-mutant ZJ12345 was performed where the GshF expression level was enhanced, and both the GSH production (19.10 mM) and the yield based on added L-cysteine (0.76 mmol/mmol) were significantly increased.

CONCLUSION

By interrupting the degradation pathways of L-cysteine, serine and GSH and blocking glycogen formation, the GSH production efficiency was significantly improved.

Differential mechanism of Escherichia coli Inactivation by (+)-limonene as a function of cell physiological state and drug's concentration

(+)-limonene is a lipophilic antimicrobial compound, extracted from citrus fruits' essential oils, that is used as a flavouring agent and organic solvent by the food industry. A recent study has proposed a common and controversial mechanism of cell death for bactericidal antibiotics, in which hydroxyl radicals ultimately inactivated cells. Our objective was to determine whether the mechanism of Escherichia coli MG1655 inactivation by (+)-limonene follows that of bactericidal antibiotics. A treatment with 2,000 μL/L (+)-limonene inactivated 4 log₁₀ cycles of exponentially growing E. coli cells in 3 hours. On one hand, an increase of cell survival in the ΔacnB mutant (deficient in a TCA cycle enzyme), or in the presence of 2,2′-dipyridyl (inhibitor of Fenton reaction by iron chelation), thiourea, or cysteamine (hydroxyl radical scavengers) was observed. Moreover, the ΔrecA mutant (deficient in an enzyme involved in SOS response to DNA damage) was more sensitive to (+)-limonene. Thus, this indirect evidence indicates that the mechanism of exponentially growing E. coli cells inactivation by 2,000 μL/L (+)-limonene is due to the TCA cycle and Fenton-mediated hydroxyl radical formation that caused oxidative DNA damage, as observed for bactericidal drugs. However, several differences have been observed between the proposed mechanism for bactericidal drugs and for (+)-limonene. In this regard, our results demonstrated that E. coli inactivation was influenced by its physiological state and the drug's concentration: experiments with stationary-phase cells or 4,000 μL/L (+)-limonene uncovered a different mechanism of cell death, likely unrelated to hydroxyl radicals. Our research has also shown that drug's concentration is an important factor influencing the mechanism of bacterial inactivation by antibiotics, such as kanamycin. These results might help in improving and spreading the use of (+)-limonene as an antimicrobial compound, and in clarifying the controversy about the mechanism of inactivation by bactericidal antibiotics.

Abnormal mitotic spindle assembly and cytokinesis induced by D-Limonene in cultured mammalian cells

D-Limonene is found widely in citrus and many other plant species; it is a major constituent of many essential oils and is used as a solvent for commercial purposes. With the discovery of its chemotherapeutic properties against cancer, it is important to investigate the biological effects of the exposure to D-Limonene and elucidate its, as yet unknown, mechanism of action. We reported here that D-Limonene is toxic in V79 Chinese hamster cells in a dose-dependent manner. Moreover, to determine the cellular target of D-Limonene, we performed morphological observations and immunocytochemical analysis and we showed that this drug has a direct effect on dividing cells preventing assembly of mitotic spindle microtubules. This affects both chromosome segregation and cytokinesis, resulting in aneuploidy that in turn can lead to cell death or genomic instability.

Oxidized glutathione fermentation using Saccharomyces cerevisiae engineered for glutathione metabolism

Glutathione is a valuable tripeptide that is widely used in the pharmaceutical, food, and cosmetic industries. Intracellular glutathione exists in two forms, reduced glutathione (GSH) and oxidized glutathione (GSSG). Most of the glutathione produced by fermentation using yeast is in the GSH form because intracellular GSH concentration is higher than GSSG concentration. However, the stability of GSSG is higher than GSH, which makes GSSG more advantageous for industrial production and storage after extraction. In this study, an oxidized glutathione fermentation method using Saccharomyces cerevisiae was developed by following three metabolic engineering steps. First, over-expression of the glutathione peroxidase 3 (GPX3) gene increased the GSSG content better than over-expression of other identified peroxidase (GPX1 or GPX2) genes. Second, the increase in GSSG brought about by GPX3 over-expression was enhanced by the over-expression of the GSH1/GSH2 genes because of an increase in the total glutathione (GSH + GSSG) content. Finally, after deleting the glutathione reductase (GLR1) gene, the resulting GPX3/GSH1/GSH2 over-expressing ΔGLR1 strain yielded 7.3-fold more GSSG compared with the parental strain without a decrease in cell growth. Furthermore, use of this strain also resulted in an enhancement of up to 1.6-fold of the total glutathione content compared with the GSH1/GSH2 over-expressing strain. These results indicate that the increase in the oxidized glutathione content helps to improve the stability and total productivity of glutathione.

Safety evaluation and risk assessment of d-Limonene

d-Limonene, a major constituent of citrus oils, is a monoterpene widely used as a flavor/fragrance additive in cosmetics, foods, and industrial solvents as it possesses a pleasant lemon-like odor. d-Limonene has been designated as a chemical with low toxicity based upon lethal dose (LD50) and repeated-dose toxicity studies when administered orally to animals. However, skin irritation or sensitizing potential was reported following widespread use of this agent in various consumer products. In experimental animals and humans, oxidation products or metabolites of d-limonene were shown to act as skin irritants. Carcinogenic effects have also been observed in male rats, but the mode of action (MOA) is considered irrelevant for humans as the protein α(2u)-globulin responsible for this effect in rodents is absent in humans. Thus, the liver was identified as a critical target organ following oral administration of d-limonene. Other than the adverse dermal effects noted in humans, other notable toxic effects of d-limonene have not been reported. The reference dose (RfD), the no-observed-adverse-effect level (NOAEL), and the systemic exposure dose (SED) were determined and found to be 2.5 mg/kg/d, 250 mg/kg//d, and 1.48 mg/kg/d, respectively. Consequently, the margin of exposure (MOE = NOAEL/SED) of 169 was derived based upon the data, and the hazard index (HI = SED/RfD) for d-limonene is 0.592. Taking into consideration conservative estimation, d-limonene appears to exert no serious risk for human exposure. Based on adverse effects and risk assessments, d-limonene may be regarded as a safe ingredient. However, the potential occurrence of skin irritation necessitates regulation of this chemical as an ingredient in cosmetics. In conclusion, the use of d-limonene in cosmetics is safe under the current regulatory guidelines for cosmetics.

Evaluation of acute toxicity of a natural compound (+)-limonene epoxide and its anxiolytic-like action

The aim of the study is to determine the acute toxicity and anxiolytic-like effects of a mixture of cis and trans of (+)-limonene epoxide in animal models of anxiety. After acute treatment with (+)-limonene epoxide at doses of 25, 50 and 75 mg/kg (i.p.) no mortality was noted during 14 days of observation. In general, behavior, food and water consumption showed no significant changes. In open field test, (+)-limonene epoxide at doses of 25, 50 and 75 mg/kg, after intraperitoneal administration, significantly decreased the number of crossings, grooming and rearing (p<0.001). All these effects were reversed by the pre-treatment with flumazenil (25 mg/kg, i.p.), similar to those observed with diazepam used as a positive standard. In the elevated-plus-maze test, (+)-limonene epoxide increased the time of permanence and the number of entrances in the open arms. All these effects were reversed by flumazenil, an antagonist of benzodiazepine receptors. In addition, (+)-limonene epoxide (75 mg/kg) also produced a significant inhibition of the motor coordination (p<0.01), that was reversed by flumazenil. In conclusion, the present work evidenced sedative and anxiolytic-like effects of (+)-limonene epoxide, which might involve an action on benzodiazepine-type receptors. These results indicate that the properties of (+)-limonene epoxide should be more thoroughly examined in order to achieve newer tools for management and/or treatment of central nervous system diseases and anxiolytic-like effects. The LD50 obtained for the acute toxicity studies using intraperitoneal route of administration was 4.0 g/kg. These findings suggest that acute administration of the (+)-limonene epoxide exerts an anxiolytic-like effect on mice, and it could serve as a new approach for the treatment anxiety, since it practically does not produce toxic effects.

Proposal on limits for chemical exposure in saturation divers' working atmosphere: the case of benzene

Saturation diving is performed under extreme environmental conditions. The divers are confined to a limited space for several weeks under high environmental pressure and elevated oxygen partial pressure. At present, divers are protected against chemical exposure by standard exposure limits only adjusted for the increased exposure length, i.e. from 8 to 24 hours a day and from 5 to 7 days a week. The objective of the present study was to indicate a procedure for derivation of occupational exposure limits for saturation diving, termed hyperbaric exposure limits (HEL). Using benzene as an example, a procedure is described that includes identification of the latest key documents, extensive literature search with defined exclusion criteria for the literature retrieved. Hematotoxicity and leukemia were defined as the critical effects, and exposure limits based upon concentration and cumulative exposure data and corresponding risks of leukemia were calculated. Possible interactions of high pressure, elevated pO₂, and continuous exposure have been assessed, and incorporated in a final suggestion of a HEL for benzene. The procedure should be applicable for other relevant chemicals in the divers' breathing atmosphere. It is emphasized that the lack of interactions from pressure and oxygen indicated for benzene may be completely different for other chemicals.

Improvement of glutathione production by metabolic engineering the sulfate assimilation pathway of Saccharomyces cerevisiae

Glutathione (GSH) is a valuable tri-peptide that is widely used in the pharmaceutical, food, and cosmetic industries. Glutathione is produced industrially by fermentation using Saccharomyces cerevisiae. In this study, we demonstrated that engineering in sulfate assimilation metabolism can significantly improve GSH production. The intracellular GSH content of MET14 and MET16 over-expressing strains increased up to 1.2 and 1.4-fold higher than that of the parental strain, respectively, whereas those of APA1 and MET3 over-expressing strains decreased. Especially, in the MET16 over-expressing strain, the volumetric GSH concentration was up to 1.7-fold higher than that of the parental strain as a result of the synergetic effect of the increases in the cell concentration and the intracellular GSH content. Additionally, combinatorial mutant strains that had been engineered to contain both the sulfur and the GSH synthetic metabolism synergistically increased the GSH production. External addition of cysteine to S. cerevisiae is well known as a way to increase the intracellular GSH content; however, it results a decrease in cell growth. This study showed that the engineering of sulfur metabolism in S. cerevisiae proves more valuable than addition of cysteine as a way to boost GSH production due to the increases in both the intracellular GSH content and the cell growth.

Development of a glutathione production process from proteinaceous biomass resources using protease-displaying Saccharomyces cerevisiae

Glutathione is a valuable tri-peptide that is widely used in the pharmaceutical, food, and cosmetic industries. Glutathione is produced industrially by fermentation using Saccharomyces cerevisiae, and supplementation of fermentation with several amino acids can increase intracellular GSH content. More recently, however, focus has been given to protein as a resource for biofuel and fine chemical production. We demonstrate that expression of a protease on the cell surface of S. cerevisiae enables the direct use of keratin and soy protein as a source of amino acids and that these substrates enhanced intracellular GSH content. Furthermore, fermentation using soy protein also enhanced cell concentration. GSH fermentation from keratin and to a greater extent from soy protein using protease-displaying yeast yielded greater GSH productivity compared to GSH fermentation with amino acid supplementation. This protease-displaying yeast is potentially applicable to a variety of processes for the bio-production of value-added chemicals from proteinaceous biomass resources.

Enzymatic glutathione production using metabolically engineered Saccharomyces cerevisiae as a whole-cell biocatalyst

We developed a novel enzymatic glutathione (GSH) production system using Saccharomyces cerevisiae as a whole-cell biocatalyst, and improved its GSH productivity by metabolic engineering. We demonstrated that the metabolic engineering of GSH pathway and ATP regeneration can significantly improve GSH productivity by up to 1.7-fold higher compared with the parental strain, respectively. Furthermore, the combination of both improvements in GSH pathway and ATP regeneration is more effective (2.6-fold) than either improvement individually for GSH enzymatic production using yeast. The improved whole-cell biocatalyst indicates its great potential for applications to other kinds of ATP-dependent bioproduction.

Improved glutathione production by gene expression in Pichia pastoris

To utilize Pichia pastoris to produce glutathione, an intracellular expression vector harboring two genes (gsh1 and gsh2) from Saccharomyces cerevisiae encoding enzymes involved in glutathione synthesis and regulated by the glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter was transformed into P. pastoris GS115. Through Zeocin resistance and expression screening, a transformant that had higher glutathione yield (217 mg/L) in flask culture than the host strain was obtained. In fed-batch culture process, this recombinant strain displayed high activity for converting precursor amino acids into glutathione. The glutathione yield and biomass achieved 4.15 g/L and 98.15 g (dry cell weight, DCW)/L, respectively, after 50 h fermentation combined with addition of three amino acids (15 mmol/L glutamic acid, 15 mmol/L cysteine, and 15 mmol/L glycine).

The effects of wood dusts on the redox status and cell death in mouse macrophages (RAW 264.7) and human leukocytes in vitro

Wood dusts are classified as carcinogenic to humans and also produce other toxic, allergic, and acute effects in woodworkers. However, little is known about causative agents in wood dusts and their mechanisms of action. The effects of different tree species and particle size for biological activity were studied. The differences in the production of reactive oxygen species (ROS) and cell death (necrotic and apoptotic) between mouse macrophage (RAW 264.7) cells and human polymorphonuclear leukocytes (PMNL) for pine, birch, and beech dust exposures were investigated in vitro. The pine and birch dust exposure (1-100 microg/ml) produced concentration-dependent ROS production in both the cells, which was one order of magnitude higher with pine dust. The ROS production was faster in human PNML than murine RAW cells. The higher concentrations (500 and/or 1000 microg/ml) decreased ROS formation. With pine and birch dust exposure, this was probably due to the necrotic cell death. The pine dust concentrations of 500 and 1000 microg/ml were cytotoxic to human PMNL. The beech dust exposure activated the ROS production and decreased the cell viability only at the highest concentrations, being least potent of the three dusts. A sign of the apoptotic cell death in the murine RAW cells was observed at the pine dust concentration of 100 microg/ml. The exposure to the birch and beech dusts with a smaller particle size (<5 microm) produced greater ROS production than exposure to the corresponding dust with a wide range of particle sizes. However, changing the particle size did not affect the cell viability. The results indicate that the type of wood dust (tree species and possibly particle size) has a significant impact on the function and viability of phagocytic cells.