Ozone priming enhanced low temperature tolerance of wheat (Triticum aestivum L.) based on physiological, biochemical and transcriptional analyses.

Low temperature significantly inhibits the plant growth in wheat (Triticum aestivum L.), prompting the exploration of effective strategies to mitigate low temperature stress. Several priming methods enhance low temperature stress tolerant, however, the role of ozone priming remains unclear in wheat. Here we found ozone priming alleviated low temperature stress in wheat. Transcriptome analysis showed that ozone priming positively modulated 'photosynthesis-antenna proteins' pathway in wheat under low temperature. Which was confirmed by the results of the ozone-primed plants had higher trapped energy flux and electron transport flux per reaction, and less damage to chloroplasts than non-primed plants under low temperature. Ozone priming also mitigated the overstimulation of glutathione metabolism and induced the accumulation of total ascorbic acid and glutathione, maintained redox homeostasis in wheat under low temperature. Moreover, gene expressions and enzyme activities in glycolysis pathways were upregulated in ozone priming comparing with non-priming after the low temperature stress. Furthermore, exogenous antibiotics significantly increased low temperature tolerance, which further proved that the inhibition of ribosome biogenesis by ozone priming was involved in low temperature tolerance in wheat. In conclusion, ozone priming enhanced wheat low temperature tolerance through promoting light-harvesting capacity, redox homeostasis, and carbohydrate metabolism, as well as inhibiting ribosome biogenesis.

Saikosaponin D potentiates the antineoplastic effects of doxorubicin in drug-resistant breast cancer through perturbing NQO1-mediated intracellular redox balance.

BACKGROUND: Drug resistance to doxorubicin (DOX) significantly limits its therapeutic efficacy in breast cancer (BC) patients. Saikosaponin D (SSD), a triterpene saponin derived from the traditional herb Radix Bupleuri, has shown promise as a chemotherapeutic sensitizer in preclinical studies due to its notable antitumor activity. However, the role and mechanism of SSD in DOX-resistant BC cells remain largely unexplored. PURPOSE: This study aimed to investigate the chemosensitizing effect of SSD on DOX-resistant BC and the underlying molecular mechanisms both in vitro and in vivo. METHODS: In vitro assays, including cell viability, clone formation, three-dimensional tumor spheroid growth, and apoptosis analysis, were conducted to evaluate the synergistic effect of SSD and DOX on resistant BC cells. Reactive oxygen species (ROS), GSH/GSSG, NADPH/NADP+, and NADH/NAD+ detections were employed to assess the impact of SSD on cellular redox homeostasis. Western blotting, cell cycle distribution assay, and DOX uptake assay were performed to further elucidate the possible antineoplastic mechanism of SSD. Finally, a subcutaneous MCF7/DOX cell xenografted model in nude mice was established to identify the in vivo anticarcinogenic effect of SSD combined with DOX. RESULTS: SSD significantly inhibited cell viability, proliferation, and clone formation, enhancing DOX's anticancer efficacy in vitro and in vivo. Mechanistically, SSD reduced STAT1, NQO1, and PGC-1α protein levels, leading to cellular redox imbalance, excessive ROS generation, and depletion of GSH, NADPH, and NADH. SSD induced DNA damage by disrupting redox homeostasis, resulting in G0/G1 phase cell cycle arrest. Additionally, SSD increased DOX accumulation in BC cells via inhibiting P-gp protein expression and efflux activity. CONCLUSION: We demonstrated for the first time that SSD enhances the sensitivity of chemoresistant BC cells to DOX by disrupting cellular redox homeostasis through inactivation of the STAT1/NQO1/PGC-1α signaling pathway. This study provides evidence for SSD as an adjuvant agent in drug-resistant BC treatment.

A Nanozyme-Boosted MOF-CRISPR Platform for Treatment of Alzheimer's Disease.

Rectifying the aberrant microenvironment of a disease through maintenance of redox homeostasis has emerged as a promising perspective with significant therapeutic potential for Alzheimer's disease (AD). Herein, we design and construct a novel nanozyme-boosted MOF-CRISPR platform (CMOPKP), which can maintain redox homeostasis and rescue the impaired microenvironment of AD. By modifying the targeted peptides KLVFFAED, CMOPKP can traverse the blood-brain barrier and deliver the CRISPR activation system for precise activation of the Nrf2 signaling pathway and downstream redox proteins in regions characterized by oxidative stress, thereby reinstating neuronal antioxidant capacity and preserving redox homeostasis. Furthermore, cerium dioxide possessing catalase enzyme-like activity can synergistically alleviate oxidative stress. Further in vivo studies demonstrate that CMOPKP can effectively alleviate cognitive impairment in 3xTg-AD mouse models. Therefore, our design presents an effective way for regulating redox homeostasis in AD, which shows promise as a therapeutic strategy for mitigating oxidative stress in AD.

The influence of iron nutrition on the development of intestine and immune cell divergency in neonatal pigs.

BACKGROUND: Appropriate iron supplementation is essential for neonatal growth and development. However, there are few reports on the effects of iron overload on neonatal growth and immune homeostasis. Thus, the aim of this study was to investigate the effects of iron nutrition on neonatal growth and intestinal immunity by administering different levels of iron to neonatal pigs. RESULTS: We found that iron deficiency and iron overload resulted in slow growth in neonatal pigs. Iron deficiency and iron overload led to down-regulation of jejunum intestinal barrier and antioxidant marker genes, and promoted CD8+ T cell differentiation in jejunum and mesenteric lymph nodes (MLN) of pigs, disrupting intestinal health. Moreover, iron levels altered serum iron and tissue iron status leading to disturbances in redox state, affecting host innate and adaptive immunity. CONCLUSIONS: These findings emphasized the effect of iron nutrition on host health and elucidated the importance of iron in regulating redox state and immunity development. This study provided valuable insights into the regulation of redox state and immune function by iron metabolism in early life, thus contributing to the development of targeted interventions and nutritional strategies to optimize iron nutrition in neonates.

Astroglial membrane camouflaged Ptbp1 siRNA delivery hinders glutamate homeostasis via SDH/Nrf2 pathway.

Polypyrimidine tract-binding protein 1 (PTBP1) regulates numerous alternative splicing events during tumor progression and neurogenesis. Previously, PTBP1 downregulation was reported to convert astrocytes into functional neurons; however, how PTBP1 regulates astrocytic physiology remains unclear. In this study, we revealed that PTBP1 modulated glutamate uptake via ATP1a2, a member of Na+/K+-ATPases, and glutamate transporters in astrocytes. Ptbp1 knockdown altered mitochondrial function and energy metabolism, which involved PTBP1 regulating mitochondrial redox homeostasis via the succinate dehydrogenase (SDH)/Nrf2 pathway. The malfunction of glutamate transporters following Ptbp1 knockdown resulted in enhanced excitatory synaptic transmission in the cortex. Notably, we developed a biomimetic cationic triblock polypeptide system, i.e., polyethylene glycol44-polylysine30-polyleucine10 (PEG44-PLL30-PLLeu10) with astrocytic membrane coating to deliver Ptbp1 siRNA in vitro and in vivo, which approach allowed Ptbp1 siRNA to efficiently cross the blood-brain barrier and target astrocytes in the brain. Collectively, our findings suggest a framework whereby PTBP1 serves as a modulator in glutamate transport machinery, and indicate that biomimetic methodology is a promising route for in vivo siRNA delivery.

Crosslinked-hybrid nanoparticle embedded in thermogel for sustained co-delivery to inner ear.

Treatment-induced ototoxicity and accompanying hearing loss are a great concern associated with chemotherapeutic or antibiotic drug regimens. Thus, prophylactic cure or early treatment is desirable by local delivery to the inner ear. In this study, we examined a novel way of intratympanically delivered sustained nanoformulation by using crosslinked hybrid nanoparticle (cHy-NPs) in a thermoresponsive hydrogel i.e. thermogel that can potentially provide a safe and effective treatment towards the treatment-induced or drug-induced ototoxicity. The prophylactic treatment of the ototoxicity can be achieved by using two therapeutic molecules, Flunarizine (FL: T-type calcium channel blocker) and Honokiol (HK: antioxidant) co-encapsulated in the same delivery system. Here we investigated, FL and HK as cytoprotective molecules against cisplatin-induced toxic effects in the House Ear Institute - Organ of Corti 1 (HEI-OC1) cells and in vivo assessments on the neuromast hair cell protection in the zebrafish lateral line. We observed that cytotoxic protective effect can be enhanced by using FL and HK in combination and developing a robust drug delivery formulation. Therefore, FL-and HK-loaded crosslinked hybrid nanoparticles (FL-cHy-NPs and HK-cHy-NPs) were synthesized using a quality-by-design approach (QbD) in which design of experiment-central composite design (DoE-CCD) following the standard least-square model was used for nanoformulation optimization. The physicochemical characterization of FL and HK loaded-NPs suggested the successful synthesis of spherical NPs with polydispersity index < 0.3, drugs encapsulation (> 75%), drugs loading (~ 10%), stability (> 2 months) in the neutral solution, and appropriate cryoprotectant selection. We assessed caspase 3/7 apopototic pathway in vitro that showed significantly reduced signals of caspase 3/7 activation after the FL-cHy-NPs and HK-cHy-NPs (alone or in combination) compared to the CisPt. The final formulation i.e. crosslinked-hybrid-nanoparticle-embedded-in-thermogel was developed by incorporating drug-loaded cHy-NPs in poloxamer-407, poloxamer-188, and carbomer-940-based hydrogel. A combination of artificial intelligence (AI)-based qualitative and quantitative image analysis determined the particle size and distribution throughout the visible segment. The developed formulation was able to release the FL and HK for at least a month. Overall, a highly stable nanoformulation was successfully developed for combating treatment-induced or drug-induced ototoxicity via local administration to the inner ear.

AT-hook motif nuclear localized transcription factors function redundantly in promoting root growth through modulation of redox homeostasis.

Maintaining an optimal redox status is essential for plant growth and development, particularly when the plants are under stress. AT-hook motif nuclear localized (AHL) proteins are evolutionarily conserved transcription factors in plants. Much of our understanding about this gene family has been derived from studies on clade A members. To elucidate the functions of clade B genes, we first analyzed their spatial expression patterns using transgenic plants expressing a nuclear localized GFP under the control of their promoter sequences. AHL1, 2, 6, 7, and 10 were further functionally characterized owing to their high expression in the root apical meristem. Through mutant analyses and transgenic studies, we showed that these genes have the ability to promote root growth. Using yeast one-hybrid and dual luciferase assays, we demonstrated that AHL1, 2, 6, 7, and 10 are transcription regulators and this activity is required for their roles in root growth. Although mutants for these genes did not showed obvious defects in root growth, transgenic plants expressing their fusion proteins with the SRDX repressor motif exhibited a short-root phenotype. Through transcriptome analysis, histochemical staining and molecular genetics experiments, we found that AHL10 maintains redox homeostasis via direct regulation of glutathione transferase (GST) genes. When the transcript level of GSTF2, a top-ranked target of AHL10, was reduced by RNAi, the short-root phenotype in the AHL10-SRDX expressing plant was largely rescued. These results together suggest that AHL genes function redundantly in promoting root growth through direct regulation of redox homeostasis.

Reactive oxygen species of tumor microenvironment: Harnessing for immunogenic cell death.

The tumor microenvironment (TME) is a dynamic and complex system that undergoes continuous changes in its network architecture, notably affecting redox homeostasis. These alterations collectively shape a diverse ecosystem actively supporting tumor progression by influencing the cellular and molecular components of the TME. Despite the remarkable clinical advancements in cancer immunotherapy, its spectrum of clinical utility is limited by the altered TME and inadequate tumor immunogenicity. Recent studies have revealed that some conventional and targeted therapy strategies can augment the efficacy of immunotherapy even in patients with less immunogenic solid tumors. These strategies provoke immunogenic cell death (ICD) through the ROS-dependent liberation of damage-associated molecular patterns (DAMPs). These DAMPs recognize and bind with Pattern Recognition Receptors (PRRs) on immune cells, activating and maturing defense cells, ultimately leading to a robust antitumor immune response. The present review underscores the pivotal role of redox homeostasis in orchestrating the transition of TME from a cold to a hot phenotype and the ROS-ICD axis in immune response induction. Additionally, it provides up-to-date insights into strategies that leverage ROS generation to induce ICD. The comprehensive analysis aims to develop ROS-based effective cancer immunotherapies for less immunogenic tumors.

SLC7A11: the Achilles heel of tumor?

The non-natriuretic-dependent glutamate/cystine inverse transporter-system Xc- is composed of two protein subunits, SLC7A11 and SLC3A2, with SLC7A11 serving as the primary functional component responsible for cystine uptake and glutathione biosynthesis. SLC7A11 is implicated in tumor development through its regulation of redox homeostasis, amino acid metabolism, modulation of immune function, and induction of programmed cell death, among other processes relevant to tumorigenesis. In this paper, we summarize the structure and biological functions of SLC7A11, and discuss its potential role in tumor therapy, which provides a new direction for precision and personalized treatment of tumors.

The Interplay between Endogenous and Foodborne Pro-Oxidants and Antioxidants in Shaping Redox Homeostasis.

Oxidative stress has been known about in biological sciences for several decades; however, the understanding of this concept has evolved greatly since its foundation. Over the past years, reactive oxygen species, once viewed as solely deleterious, have become recognized as intrinsic components of life. In contrast, antioxidants, initially believed to be cure-all remedies, have failed to prove their efficacy in clinical trials. Fortunately, research on the health-promoting properties of antioxidants has been ongoing. Subsequent years showed that the former assumption that all antioxidants acted similarly was greatly oversimplified. Redox-active compounds differ in their chemical structures, electrochemical properties, mechanisms of action, and bioavailability; therefore, their efficacy in protecting against oxidative stress also varies. In this review, we discuss the changing perception of oxidative stress and its sources, emphasizing everyday-life exposures, particularly those of dietary origin. Finally, we posit that a better understanding of the physicochemical properties and biological outcomes of antioxidants is crucial to fully utilize their beneficial impact on health.

Regulation of nitro-oxidative homeostasis: an effective approach to enhance salinity tolerance in plants.

Soil salinity is a major constraint for sustainable agricultural productivity, which together with the incessant climate change may be transformed into a severe threat to the global food security. It is, therefore, a serious concern that needs to be addressed expeditiously. The overproduction and accumulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are the key events occurring during salt stress, consequently employing nitro-oxidative stress and programmed cell death in plants. However, very sporadic studies have been performed concerning different aspects of nitro-oxidative stress in plants under salinity stress. The ability of plants to tolerate salinity is associated with their ability to maintain the cellular redox equilibrium mediated by both non-enzymatic and enzymatic antioxidant defense mechanisms. The present review emphasizes the mechanisms of ROS and RNS generation in plants, providing a detailed evaluation of how redox homeostasis is conserved through their effective removal. The uniqueness of this article stems from its incorporation of expression analyses of candidate genes for different antioxidant enzymes involved in ROS and RNS detoxification across various developmental stages and tissues of rice, utilizing publicly available microarray data. It underscores the utilization of modern biotechnological methods to improve salinity tolerance in crops, employing different antioxidants as markers. The review also explores how various transcription factors contribute to plants' ability to tolerate salinity by either activating or repressing the expression of stress-responsive genes. In summary, the review offers a thorough insight into the nitro-oxidative homeostasis strategy for extenuating salinity stress in plants.

Cadmium exposure induced light/dark- and time-dependent redox changes at subcellular level in Arabidopsis plants.

Cadmium (Cd) is one of the most toxic heavy metals for plants and humans. Reactive oxygen species (ROS) are some of the primary signaling molecules produced after Cd treatment in plants but the contribution of different organelles and specific cell types, together with the impact of light is unknown. We used Arabidopsis lines expressing GRX1-roGFP2 (glutaredoxin1-roGFP) targeted to different cell compartments and analysed changes in redox state over 24 h light/dark cycle in Cd-treated leaf discs. We imaged redox state changes in peroxisomes and chloroplasts in leaf tissue. Chloroplasts and peroxisomes were the most affected organelles in the dark and blocking the photosynthetic electron transport chain (pETC) by DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) promotes higher Cd-dependent oxidation in all organelles. Peroxisomes underwent the most rapid changes in redox state in response to Cd and DCMU and silencing chloroplastic NTRC (NADPH thioredoxin reductase C) considerably increases peroxisome oxidation. Total NAD(P)H and cytosolic NADH decreased during exposure to Cd, while Ca+2 content in chloroplasts and cytosol increased in the dark period. Our results demonstrate a Cd-, time- and light-dependent increase of oxidation of all organelles analysed, that could be in part triggered by disturbances in pETC and photorespiration, the decrease of NAD(P)H availability, and differential antioxidants expression at subcellular level.

NIR-II-Responsive Versatile Nanozyme Based on H2O2 Cycling and Disrupting Cellular Redox Homeostasis for Enhanced Synergistic Cancer Therapy.

Disturbing cellular redox homeostasis within malignant cells, particularly improving reactive oxygen species (ROS), is one of the effective strategies for cancer therapy. The ROS generation based on nanozymes presents a promising strategy for cancer treatment. However, the therapeutic efficacy is limited due to the insufficient catalytic activity of nanozymes or their high dependence on hydrogen peroxide (H2O2) or oxygen. Herein, we reported a nanozyme (CSA) based on well-defined CuSe hollow nanocubes (CS) uniformly covered with Ag nanoparticles (AgNPs) to disturb cellular redox homeostasis and catalyze a cascade of intracellular biochemical reactions to produce ROS for the synergistic therapy of breast cancer. In this system, CSA could interact with the thioredoxin reductase (TrxR) and deplete the tumor microenvironment-activated glutathione (GSH), disrupting the cellular antioxidant defense system and augmenting ROS generation. Besides, CSA possessed high peroxidase-mimicking activity toward H2O2, leading to the generation of various ROS including hydroxyl radical (•OH), superoxide radicals (•O2-), and singlet oxygen (1O2), facilitated by the Cu(II)/Cu(I) redox and H2O2 cycling, and plentiful catalytically active metal sites. Additionally, due to the absorption and charge separation performance of AgNPs, the CSA exhibited excellent photothermal performance in the second near-infrared (NIR-II, 1064 nm) region and enhanced the photocatalytic ROS level in cancer cells. Owing to the inhibition of TrxR activity, GSH depletion, high peroxidase-mimicking activity of CSA, and abundant ROS generation, CSA displays remarkable and specific inhibition of tumor growth.

Synthetic lethal CRISPR screen identifies a cancer cell-intrinsic role of PD-L1 in regulation of vulnerability to ferroptosis.

Despite the success of programmed cell death 1 (PD-1)/programmed death ligand 1 (PD-L1) inhibition in tumor therapy, many patients do not benefit. This failure may be attributed to the intrinsic functions of PD-L1. We perform a genome-wide CRISPR synthetic lethality screen to systematically explore the intrinsic functions of PD-L1 in head and neck squamous cell carcinoma (HNSCC) cells, identifying ferroptosis-related genes as essential for the viability of PD-L1-deficient cells. Genetic and pharmacological induction of ferroptosis accelerates cell death in PD-L1 knockout cells, which are also more susceptible to immunogenic ferroptosis. Mechanistically, nuclear PD-L1 transcriptionally activates SOD2 to maintain redox homeostasis. Lower reactive oxygen species (ROS) and ferroptosis are observed in patients with HNSCC who have higher PD-L1 expression. Our study illustrates that PD-L1 confers ferroptosis resistance in HNSCC cells by activating the SOD2-mediated antioxidant pathway, suggesting that targeting the intrinsic functions of PD-L1 could enhance therapeutic efficacy.

Redox pathways in melanoma.

Cases of melanoma are doubling every 12 years, and in stages III and IV, the disease is associated with high mortality rates concomitant with unresectable metastases and therapeutic drug resistance. Despite some advances in treatment success, there is a marked need to understand more about the pathology of the disease. The present review provides an overview of how melanoma cells use and modulate redox pathways to facilitate thiol homeostasis and melanin biosynthesis and describes plausible redox targets that may improve therapeutic approaches in managing malignant disease and metastasis. Melanotic melanoma has some unique characteristics. Making melanin requires a considerable dedication of cellular energy resources and utilizes glutathione and glutathione transferases in certain steps in the biosynthetic pathway. Melanin is an antioxidant but is also functionally important in hematopoiesis and influential in various aspects of host immune responses, giving it unique characteristics. Together with other redox traits that are specific to melanoma, a discussion of possible therapeutic approaches is also provided.

Redox and Energy Homeostasis Enabled by Photocatalytic Material-Microbial Interfaces.

Material-microbial interfaces offer a promising future in sustainable and efficient chemical-energy conversions, yet the impacts of these artificial interfaces on microbial metabolisms remain unclear. Here, we conducted detailed proteomic and metabolomic analyses to study the regulations of microbial metabolism induced by the photocatalytic material-microbial interfaces, especially the intracellular redox and energy homeostasis, which are vital for sustaining cell activity. First, we learned that the materials have a heavier weight in perturbing microbial metabolism and inducing distinctive biological pathways, like the expression of the metal-resisting system, than light stimulations. Furthermore, we observed that the materials-microbe interfaces can maintain the delicate redox balance and the energetic status of the microbial cells since the intracellular redox cofactors and energy currencies show stable levels as naturally inoculated microbes. These observations ensure the possibility of energizing microbial activities with artificial materials-microbe interfaces for diverse applications and also provide guides for future designs of materials-microbe hybrids to guard microbial activities.

Phytofabricated gold nanoparticles as modulators of salt stress responses in spinach: implications for redox homeostasis, biochemical and physiological adaptation.

Introduction: The utilization of plant material for synthesizing nanoparticles effectively triggers physiological and biochemical responses in plants to combat abiotic stresses. Salt stress, particularly caused by NaCl, significantly affects plant morphology and physiology, leading to reduced crop yields. Understanding the mechanisms of salt tolerance is crucial for maintaining crop productivity. Methods: In this study, we examined the effects of 150 µM spinach-assisted gold nanoparticles (S-AuNPs) on various parameters related to seed germination, growth attributes, photosynthetic pigments, stomatal traits, ion concentrations, stress markers, antioxidants, metabolites, and nutritional contents of spinach plants irrigated with 50 mM NaCl. Results: Results showed that S-AuNPs enhanced chlorophyll levels, leading to improved light absorption, increased photosynthates production, higher sugar content, and stimulated plant growth under NaCl stress. Stomatal traits were improved, and partially closed stomata were reopened with S-AuNPs treatment, possibly due to K+/Na+ modulation, resulting in enhanced relative water content and stomatal conductance. ABA content decreased under S-AuNPs application, possibly due to K+ ion accumulation. S-AuNPs supplementation increased proline and flavonoid contents while reducing ROS accumulation and lipid peroxidation via activation of both non-enzymatic and enzymatic antioxidants. S-AuNPs also regulated the ionic ratio of K+/Na+, leading to decreased Na+ accumulation and increased levels of essential ions in spinach plants under NaCl irrigation. Discussion: Overall, these findings suggest that S-AuNPs significantly contribute to salt stress endurance in spinach plants by modulating various physiological attributes.

Evaluating the Impact of an Organic Trace Mineral mix on the Redox Homeostasis, Immunity, and Performance of Sows and their Offspring.

The objective of the study was to evaluate the effects of trace mineral supplementation in sows during gestation and lactation on the performance and health status of sows and their offspring. Sows (n = 30; Landrace × Yorkshire; avg parity = 3.9) were randomly allocated into two dietary treatments. Sows received a basal diet supplemented with 12 mg/kg Cu, 30 mg/kg Fe, 90 mg/kg Zn, 70 mg/kg Mn, 0.30 mg/kg Se, and 1.5 mg/kg I from an inorganic trace mineral source (ITM) or a blend of hydroxychloride and organic trace mineral source (HOTM) from day 1 of gestation until the end of the lactation period at day 21. Compared to the ITM, the HOTM supplementation increased (P < 0.05) both litter birth weight and individual piglet birth weight. Although not statistically significant, HOTM tended to increase (P = 0.069) the level of lactose in colostrum. HOTM increased (P < 0.05) the concentration of Mn and Se in the colostrum, milk, and serum of sows and/or piglets. Notably, the Zn concentration in the serum of sows was higher in sows supplemented with ITM compared to HOTM. Moreover, HOTM increased (P < 0.05) the activities of GPX and SOD in gestating sows and piglets, as well as increased (P < 0.05) cytokines (IL-1ß, TNF-α, and IL-10) in the serum of sows. The immunoglobulins (IgA, IgG, and IgM) also increased in sows and/or piglets at certain experimental time points. In conclusion, HOTM supplementation positively affected piglet development and improved the health status of sows and piglets potentially by regulating redox homeostasis and immunity.

Subcellular Localization of Thioredoxin/Thioredoxin Reductase System-A Missing Link in Endoplasmic Reticulum Redox Balance.

The lumen of the endoplasmic reticulum (ER) is usually considered an oxidative environment; however, oxidized thiol-disulfides and reduced pyridine nucleotides occur there parallelly, indicating that the ER lumen lacks components which connect the two systems. Here, we investigated the luminal presence of the thioredoxin (Trx)/thioredoxin reductase (TrxR) proteins, capable of linking the protein thiol and pyridine nucleotide pools in different compartments. It was shown that specific activity of TrxR in the ER is undetectable, whereas higher activities were measured in the cytoplasm and mitochondria. None of the Trx/TrxR isoforms were expressed in the ER by Western blot analysis. Co-localization studies of various isoforms of Trx and TrxR with ER marker Grp94 by immunofluorescent analysis further confirmed their absence from the lumen. The probability of luminal localization of each isoform was also predicted to be very low by several in silico analysis tools. ER-targeted transient transfection of HeLa cells with Trx1 and TrxR1 significantly decreased cell viability and induced apoptotic cell death. In conclusion, the absence of this electron transfer chain may explain the uncoupling of the redox systems in the ER lumen, allowing parallel presence of a reduced pyridine nucleotide and a probably oxidized protein pool necessary for cellular viability.

Characterization of antimalarial activity of artemisinin-based hybrid drugs.

In response to the spread of artemisinin (ART) resistance, ART-based hybrid drugs were developed, and their activity profile was characterized against drug-sensitive and drug-resistant Plasmodium falciparum parasites. Two hybrids were found to display parasite growth reduction, stage-specificity, speed of activity, additivity of activity in drug combinations, and stability in hepatic microsomes of similar levels to those displayed by dihydroartemisinin (DHA). Conversely, the rate of chemical homolysis of the peroxide bonds is slower in hybrids than in DHA. From a mechanistic perspective, heme plays a central role in the chemical homolysis of peroxide, inhibiting heme detoxification and disrupting parasite heme redox homeostasis. The hybrid exhibiting slow homolysis of peroxide bonds was more potent in reducing the viability of ART-resistant parasites in a ring-stage survival assay than the hybrid exhibiting fast homolysis. However, both hybrids showed limited activity against ART-induced quiescent parasites in the quiescent-stage survival assay. Our findings are consistent with previous results showing that slow homolysis of peroxide-containing drugs may retain activity against proliferating ART-resistant parasites. However, our data suggest that this property does not overcome the limited activity of peroxides in killing non-proliferating parasites in a quiescent state.