Antioxidant Supplementation Research Articles

Dietary Antioxidants and Natural Compounds in Preventing Thrombosis and Cardiovascular Disease

Reactive oxygen species (ROS) contribute to endothelial dysfunction, platelet activation, and coagulation abnormalities, promoting thrombus formation. Given the growing interest in non-pharmacological approaches to modulate oxidative stress, we examine the potential of various dietary interventions and antioxidant supplementation in reducing oxidative damage and preventing thrombotic events. Key dietary patterns, such as the Mediterranean, Dietary Approaches to Stop Hypertension (DASH), and ketogenic diets, as well as antioxidant-rich supplements like curcumin, selenium, and polyphenols, demonstrate promising effects in improving oxidative stress markers, lipid profiles, and inflammatory responses. This review highlights recent advances in the field, drawing from in vitro, ex vivo, and clinical studies, and underscores the importance of integrating dietary strategies into preventive and therapeutic approaches for managing thrombosis and cardiovascular health. Further research is needed to better understand long-term effects and personalize these interventions for optimizing patient outcomes.

Selected Trace Elements and Their Impact on Redox Homeostasis in Eye Health

Oxidative stress plays a crucial role in the pathogenesis of various ocular degenerative diseases, leading to structural and functional changes in eye tissues. This imbalance between reactive oxygen species (ROS) and antioxidants significantly contributes to conditions such as age-related macular degeneration, diabetic retinopathy, cataracts, and glaucoma. Both enzymatic and nonenzymatic antioxidants are vital for maintaining ocular health by neutralizing ROS and restoring cellular redox balance. Essential trace elements, including iron, zinc, copper, and selenium, are fundamental for the proper functioning of these antioxidant systems. Iron is indispensable for enzymatic activity and cellular energy production, zinc supports numerous proteins involved in visual functions and antioxidant defense, copper is essential for various enzymatic reactions preventing oxidative stress, and selenium is critical for the activity of antioxidant enzymes such as glutathione peroxidase (GPX) and thioredoxin reductase (TrxR). This review summarizes current research on the complex interactions between oxidative stress and trace elements in ocular diseases, highlighting the therapeutic potential of antioxidant supplementation to mitigate oxidative damage and improve eye health. By integrating insights from studies on oxidative stress, trace elements, and eye physiology, this article underscores new diagnostic and therapeutic strategies that could lead to more effective prevention and treatment of ocular diseases, aiming to enhance clinical outcomes and guide future research in optimizing therapeutic strategies for eye health.

Environmental Stress-Induced Alterations in Embryo Developmental Morphokinetics.

The association between embryo morphokinetics and its developmental competence is well documented. For instance, early cleaved embryos are more competent in developing to blastocysts, whereas the proportion of abnormally cleaved embryos that further developed to blastocysts is low. Numerous factors, such as the parental age, lifestyle, health, and smoking habits have been reported to affect the embryo morphokinetics and, consequently, its development. However, less is known about the effect of environmental stressors on embryo morphokinetics. The current review discusses the effect of the most concerning environmental stressors on embryo morphokinetics. These stresses include heat stress and human-made chemicals such as phthalates (e.g., bis-(2-ethylhexyl phthalate, dibutyl phthalate, dimethyl phthalate, and their primary metabolites), herbicides (e.g., diaminochlorotriazine, the primary metabolite of atrazine), pharmaceutical compounds (e.g., carbamazepine, nocodazole) and pro-oxidant agents (cumene hydroperoxide, Triton X-100), as well as naturally occurring toxins such as mycotoxin (e.g., aflatoxin B1 and its metabolite, and ochratoxin A). In addition, this review discusses the effect of ionizing or non-ionizing radiation and viral infections (e.g., SARS-CoV-2, papillomavirus). Finally, it points out some potential mechanisms that underlie the impairment of embryo morphokinetics, and it suggests protective compounds, mainly the supplementation of antioxidants to improve the morphokinetics, and consequently, the embryo developmental competence.

The effect of myo-inositol antioxidant activity on human sperm parameters and DNA damage in ultra-rapid and conventional freezing methods

Male fertility preservation is still challenged by cell damage induced during sperm cryopreservation and impaired sperm structure and function. Sperm ultra-rapid freezing, despite a higher protective effect compared to conventional freezing method, is still associated with suboptimal sperm cryosurvival and needs to be modified to increase its efficiency in sperm protection. Sperm freezing media supplemented with antioxidants can improve sperm parameters following freezing-warming process. In this study, we aimed to investigate the effect of employing ultra-rapid freezing and myo-inositol on sperm cryosurvival. Thirty semen samples with normal sperm parameters were collected and each one was divided into four portions to cryopreserve by conventional freezing, ultra-rapid freezing, conventional freezing + myo-inositol 2 mg/ml, and ultra-rapid freezing + myo-inositol 2 mg/ml. Sperm samples warmed after at least 24 h of freezing and sperm cryosurvival were analyzed by evaluation of sperm motility, viability, morphology and DNA fragmentation index (DFI). Freezing method had a significant influence on post-thaw sperm DFI and morphology (p < 0.05) and the interaction between freezing method and antioxidant supplementation significantly affected sperm morphology (p < 0.05). The highest percentage of sperm normal morphology and minimal DFI was achieved using ultra-rapid freezing supplemented by myo-inositol antioxidant compared to other groups (P < 0.05). The highest sperm DNA damage after freezing-warming was observed following the conventional freezing method. In conclusion, sperm freezing method was identified as factor strongly influencing sperm DFI and morphology after thawing/warming. Sperm samples can be rapidly frozen using the modified freezing media supplemented by myo-inositol without impacting sperm DNA and morphology.

Profiling oxidative stress markers and cardiovascular complications in chronic kidney disease patients supplemented with vitamin E

IntroductionCardiovascular diseases are common complications in chronic kidney disease (CKD). Oxidative stress associated with renal and metabolic dysfunctions is one of the cardiovascular complications (CVC) in haemodialysis patients. The aim of the present study is to analyse the oxidative stress markers in CDK patients supplemented with antioxidants and vitamin E, with monitoring of CVC.Material and methodsThis was a cross-sectional study conducted on 99 subjects. CKD patients received oral supplementation of vitamin E (300 mg/day) for 2 years. Oxidative stress markers, nitric oxide (NO); myeloperoxidase (MPO); oxidized low-density lipoprotein (LDLox); malondialdehyde (MDA) and glutathione were measured before and after the vitamin treatment.ResultsNO (62.62 ±2.80 µmol/l), LDLox (10.55 ±4.62 µmol/l), MDA (6.11 ±2.83 µmol/l) and MPO (53.35 ±3.82 UI/ml) were overconcentrated, while glutathione (62.09 ±4.15 UI/ml) was less concentrated in CKD patients with cardiovascular complications, compared to those without cardiovascular complications (67.08 ±1.90 µmol/l, 31.18 ±5.25 µmol/l, 16 ±6.47 µmol/l, 57.00 ±7.24 UI/ml, 43.09 ±3.33 UI/ml, respectively). After 2 years of vitamin E treatment, the overall cardiovascular complications were not significantly decreased.ConclusionsThese results showed that oral complementation with vitamin E did not affect the occurrence of cardiovascular complications associated with CKD. These findings may pave the way for future innovative strategies for antioxidant supplementation in CKD patients.

Effects of Supplementation of Different Antioxidants to Cryopreservation Extender on the Post-Thaw Quality of Rooster Semen-A Meta-Analysis.

The standardization of the semen cryopreservation technique could be an effective tool in poultry for the conservation of genetic resources. During this process, the production of reactive oxygen species increases, leading to oxidative stress that causes damage to the spermatozoa. To reduce this effect, the addition of exogenous antioxidants in the cryopreservation diluent has been reported to be effective. Multiple antioxidants such as catalase, vitamin E, cysteamine, ergothioneine, and serine have been studied in roosters. Therefore, the present investigation aims to perform a meta-analysis to determine if the use of the aforementioned antioxidants added to the cryopreservation extender produces an improvement in semen quality parameters in roosters after thawing. After collecting the data, a discriminant canonical analysis was performed to determine which of the selected semen quality traits provided the most information, with hypo-osmotic swelling test (HOST), viability, and total motility variables showing the highest discriminatory power. However, according to the descriptive statistics, catalase and serine are the antioxidants that improve a greater number of seminal quality parameters, and since catalase gives the most favorable results for most of the discriminating variables, it could be the antioxidant of choice.

Antioxidant intake and its relationship with generalized anxiety disorder among adults

ABSTRACT Antioxidant intake may contribute to the prevention of numerous diseases, particularly those related to stress-induced psychiatric and stress disorders. The current study aimed to assess the relationship between daily antioxidant intake (DAI) and Generalized Anxiety Disorder (GAD) in adults. It also sought to investigate the correlation between the type of diet in conjunction with DAI and the scores on GAD 7-Item Scale in adults. A cross-sectional design was used to examine if DAI was lower in individuals with GAD; followed by an interventional study of 40 adults with severe GAD, who were exposed to higher DAI for a period of 6 weeks. The results indicated that participants with severe GAD had significantly lower levels of DAI compared to healthy controls (p < 0.001). After 6 weeks of antioxidant supplementation, a significant decrease in GAD-7 scores of participants was observed (p < 0.001). The study found a significant negative relationship between DAI and GAD.

Evaluation of zinc oxide nanocomposites and L-ascorbic acid on meat quality during transport induced stress in birds of Sonali breed

The study assessed the efficacy of phytofabricated zinc oxide nanoparticles (CF-ZnONPs) and L-ascorbic acid in alleviating pre-slaughter transport induced stress in birds of Sonali breed (Cross bred of Rhode Island Red cocks and Fayoumi hens). A total of 120 birds were divided into four groups: negative control (T1) which were loaded in vehicle but not transported, Positive control (T2) birds were transported without any prior supplementation, T3 and T4 birds were transported with prior supplementation (a day before transportation) of CF-ZnONPs @100 µg/ml and L-ascorbic acid @82 µg/ml in drinking water. Results obtained observed significant reduction in live weight, meat colour and pH but increased drip loss percentage in T2 group. Significantly elevated H/L ratio was recorded in all transported groups. Increased cortisol and TSH levels and decreased thyroid hormones, Triiodothyronine and thyroxin (T3 and T4) levels were recorded in T2 group. However, supplementation with CF-ZnONPs and L-ascorbic acid notably reversed these adverse effects, restoring meat quality and other metabolic profiles. Notably, ascorbic acid exhibited greater efficacy, suggesting its superior role in mitigating transportation-induced stress. Overall, these findings highlight the importance of antioxidant supplementation in alleviating transport induced stress in birds.

In vitro maturation of bovine oocytes: the role of ROS, oxidative stress, and the impact of natural antioxidant supplementation

According to available data in the literature, Brazil has one of the largest cattle herds in the world and is one of the leading embryo producers, with a clear predominance of embryos produced in vitro. These data influence the ongoing pursuit of optimizing the results obtained in IVEP (in vitro embryo production). In this technique, in vitro maturation (IVM) is such a crucial stage that it justifies studies involving components that, when added to the media, can lead to improved cleavage rates and blastocyst development. It is well known that oocyte quality is influenced by oxidative stress, and in this context, the inclusion of antioxidants in the IVM medium may enhance these outcomes. Thus, the present study aimed to review oocyte maturation, the impact of oxidative stress, and the addition of antioxidants, such as Moringa oleifera, to the IVM media.

The Impact of Exercise on DNA Damage in Athletes: Causes, Mechanisms, and Case Studies

Although physical activity is important for the athlete’s health and performance, it may also lead to Deoxyribonucleic Acid (DNA) damage, which may have long-term health consequences and affect performance. This article summarizes different types of DNA damage that may occur in athletes, including their potential risk causes, such as mechanical stress, heat stress, and oxidative stress. Furthermore, several mechanisms by which physical activity might lead to DNA damage and affect health and performance are also discussed. Various strategies such as diet and nutrition, antioxidant supplements, cooling strategies, and recovery modalities are also presented to mitigate, prevent, and minimize the potential DNA damage upon physical activities. This article also highlights case studies of athletes who have experienced DNA damage and the effects on their performance and health. In summary, this article offers valuable perspectives on the intricate relationship between physical activity and DNA damage as well as the importance of addressing this issue in the context of athletic performance and health. Keywords: athlete, DNA damage, exercise, RONS

Status of sperm mitochondrial functions and DNA methylation in infertile men with clinical varicocele before and after treatment.

Varicocele has been associated with reduced male fertility potential. Treatment modalities for varicocele improve semen parameters, yet more than 50% of cases remain infertile. Varicocele-induced heat and hypoxia stress may affect sperm mitochondrial functions, possibly leading to aberrant epigenetic modifications. This study includes 30 fertile men and 40 infertile men with clinical varicocele. The effect of varicocele treatment (antioxidant supplementation and or varicocelectomy) was evaluated after 3 months of treatment. Mitochondrial membrane potential (MMP) and intracellular reactive oxygen species (iROS) were measured by flow cytometry using JC-1 and DCFDA, respectively. mtDNA copy number and deletions were determined by PCR. DNA methylation was analysed by pyrosequencing. Present investigations suggest that infertile men with varicocele have abnormal semen parameters; significantly low MMP, high iROS, and high mtDNA copy number. Semen parameters were improved in a subset of men of both the treatment modalities; however, it was noted that varicocelectomy helped better in improving sperm parameters compared to antioxidant treatment. Both treatment modalities helped in reducing iROS and mtDNA copy number significantly; however, they were non effective in improving MMP. Altered DNA methylation at mitochondria D loop and mitochondrial structure and function genes UQCRC2, MIC60, TOM22, and LETM1 (promoter region) were observed in varicocele group. The DNA methylation levels were restored after varicocele treatment; however, the restoration was not consistent at all CpG sites. Both the treatment modalities helped in restoring the altered DNA methylation levels of mitochondrial genes but the restoration is nonhomogeneous across the studied CpG sites.

Seaweed Milk Food Supplement Produced from Hydropuntia eucheumatoides (Harvey)

Objective / Background Hydropuntia eucheumatoides (HE) seaweed is widely distributed in tropical seas and is a common food for coastal people. Our objectives were to prepare seaweed milk from HE, and test is possible utility as a food supplement and source of antioxidants that has an appropriate sensory profile. Methods We used an enzyme from Lactobacillus strains for polysaccharide hydrolysis into HE seaweed milk food supplements. We cultured five Lactobacillus strains with appropriate agarase, cellulase, and amylase enzyme activities. Results We optimized the enzyme concentration (mass of seaweed HE: 40 g/L), substrate concentration (2 mL enzyme/g seaweed), temperature (50 °C), pH (5), and hydrolysis time (96 h). The hydrolyzate included oligosaccharides, monosaccharides, amino acids, and minerals. The product exhibited excellent sensory details and is likely to be safe for consumption. Conclusions We completed our objectives. Our product is ready for initial consumer sensory testing.

Alleviating heat stress on broiler breeder hens: effect of dietary antioxidant supplementation on reproductive performance, egg quality, offspring growth, and antioxidant capacity

Alleviating heat stress on broiler breeder hens: effect of dietary antioxidant supplementation on reproductive performance, egg quality, offspring growth, and antioxidant capacity

Electrostatically self-assembled magnetized MXene/copper ferrite nanospheres hybrids: Evaluation of molecularly imprinted electrochemical sensor for the quercetin antioxidant supplement

Quercetin, a bioflavonoid with significant biological activities, is beneficial for health. Herein, a pioneering molecularly imprinted electrochemical sensor utilizing an MXene/CuFe2O4 magnetic nanosphere hybrid was developed for the first time to detect quercetin ultra-sensitively. CuFe2O4 nanospheres (average 189 nm) were synthesized and combined with MXene sheets, then electrostatically deposited onto a magnetic carbon paste electrode. A functional monomer was then electropolymerized onto this hybrid-modified electrode to form an imprinted polymeric layer, tailored for quercetin binding. Characterizations confirmed the morphological and magnetic properties of the materials. The sensor’s response factors were optimized, achieving a low detection limit of 1.6 nM and two linear ranges (0.005–0.7 μM and 0.7–10 μM). The sensor showed excellent stability, repeatability, reproducibility, and selectivity, and was successfully used to quantify quercetin in dietary supplements.

Vitiligo: From mechanisms of disease to treatable pathways

AbstractVitiligo is a chronic autoimmune‐mediated disease characterised by the loss of pigmentary melanocytes in the epidermis. Vitiligo is associated with loss of functional epithelium and significant reductions in quality of life with limited long‐term treatment options, highlighting a continued unmet clinical need. A comprehensive understanding of the pathophysiology and newly investigated treatment pathways may guide multimodal treatment strategies and identify future drug targets. The pathology of vitiligo is multifactorial; however, environmental insults in genetically susceptible populations may lead to disease development. Autoreactive CD8+ T‐cells that target melanocytes and release inflammatory mediators, including interferon‐γ and interleukins 2, 6, 15, 17 and 33 among others, have been identified in vitiligo pathogenesis. Treatment modalities for vitiligo revolve around six broad disease concepts, including procedural modalities (tissue and cellular grafting), phototherapy, stem cells, anti‐inflammatories, genetic polymorphisms and antioxidants/vitamins/herbals. Genetic polymorphisms, such as catalase gene variations and toll‐like receptor polymorphisms, along with stem cell targets such as melanocytes derived from stem cells, have been implicated in vitiligo onset and possible treatment. Novel JAK‐STAT inhibitors have been recently investigated for vitiligo, whereas topical corticosteroids and calcineurin inhibitors continue to be used. Vitamin D, vitamin E, zinc, copper, piperine, pseudo catalase and other vitamins/herbals may improve vitiligo outcomes primarily through antioxidant supplementation pathways. Future studies should investigate alternative drug pathways and targets implicated in vitiligo in large patient cohorts, as well as treatments that target suspected causative immune cells, including memory T‐cells, which may provide long‐lasting disease‐free remission.

CARotenoid and Parkinson’s Disease Severity study (CARPS) – Preliminary results from a Pilot Study

Abstract Background Carotenoids are naturally occurring anti-oxidants that give fruit and vegetables their bright colour. Skin carotenoid score (SCS) gives total carotenoid-levels in the body and corresponds well to blood carotenoid-levels. Studies have shown blood carotenoid-levels are low in individuals with Alzheimer’s disease compared with controls. CARPS exams the relationship between carotenoids and Idiopathic Parkinson’s Disease (IPD) by measuring carotenoids in the skin and blood of individuals with IPD vs. controls. Methods Cross-sectional, case-control study with age-matched controls. Recruitment commenced January 2024. Case-subjects must have IPD and attend the hospital movement-disorder clinic. Control-subjects are spouse/care-partners of IPD-patients. Exclusion criteria: other forms of PD, Dementia, taking anti-oxidant supplements. Data collected: demographic information, medical history, BMI, frailty assessment. IPD severity assessed using UPDRS. Carotenoid-specific food frequency questionnaire (FFQ) to assess dietary intake. Data was inputted to excel and exported to SPSS. Results 41 IPD-cases (23 Men, 16 Women) and 12 controls (8 Men, 4 Women) have been recruited to-date. 9/12 controls are spouses of an IPD-participant. Mean age of IPD-cases vs control: 76.1 vs. 74.5. Mean UPDRS score for IPD-cases: 28.02. The skin carotenoid score (SCS) was low in both groups, with a score &amp;gt;400 being within normal range. Mean SCS was lower in the IPD-cases compared to controls: 282.61 vs. 320.58. The IPD cohort are slightly frailer compared to the controls, with higher median-CFS: 3 vs. 1. Mean BMI was similar in both groups. Analysis of blood samples and FFQ is due to take place at a later date. Conclusion Early results suggest a trend towards lower SCS scores in the IPD cohort, with an interesting trend towards higher SCS scores in spouse-controls vs. their IPD partners, despite similar food intake. CARPS recruitment is ongoing with further analysis of blood-carotenoids and FFQ required to determine if the link between IPD severity and reduced carotenoid-levels is statistically significant.

Effects of long-term Tai Chi vs. aerobic exercise on antioxidant activity and cognitive function in individuals with Parkinson’s disease

An imbalance between the generation of reactive oxygen species and the body’s antioxidant defense mechanisms is closely related to the development and progression of Parkinson’s disease (PD). Considering that physical exercise is a potential therapeutic intervention for modulating oxidative stress markers and cognitive function in PD, the primary purpose of this study was to compare the effects of different long-term exercise modalities on antioxidants and cognitive performance in patients with PD. In addition, the secondary purpose was to explore whether changes in the levels of these biochemical markers are associated with alterations in cognitive performance pre- and post-intervention. In all, 61 participants were randomly divided into the aerobic exercise (AE, n=20), Tai Chi exercise (TCE, n=21), or control (n=20) group. Blood samples were collected before and after a 12-week intervention period for the analysis of antioxidant markers [leukocyte 8-hydroxydeoxyguanosine (8-OHdG), catalase (CAT), glutathione (GSH), glutathione peroxidase (GSH-Px), oxidized glutathione (GSSG), superoxide dismutase (SOD), and uric acid (UA)]. Cognitive function was evaluated using the Mini-Mental State Examination (MMSE). Although no significant changes were observed in the activity of 8-OhdG, GSH-Px, GSSG, GSH:GSSG ratio, SOD, and cognitive performance in the AE and TCE groups, the 12-week AE intervention led to a significant increase in CAT and GSH levels, along with a significantly decrease in UA levels among individuals with PD. Conversely, the TCE intervention resulted in a significant increase in GSH levels. However, SOD activity and MMSE scores were significantly decreased after 12 weeks in the control group. The correlations between changes in MMSE scores and changes in the levels of GSH and UA prior to and after the intervention reached significance in the AE group. Thus, long-term AE and TCE might serve as effective strategies for reducing oxidative damage and preserving cognitive function in PD, with AE exhibiting greater benefits compared with TCE. These findings hold potential clinical relevance as complementary measures to standard medical treatments and alternative therapies, such as antioxidant supplements and dietary adjustments, particularly for individuals in the early stages of PD.

Exploring causal associations of antioxidants from supplements and diet with attention deficit/hyperactivity disorder in European populations: a Mendelian randomization analysis.

Antioxidants from both supplements and diet have been suggested to potentially reduce oxidative stress in individuals with ADHD. However, there is a lack of studies utilizing the Mendelian randomization (MR) method to explore the relationship between dietary and supplemental antioxidants with ADHD. This study employed two-sample mendelian randomization. Various specific antioxidant dietary supplements (such as coffee, green tea, herbal tea, standard tea, and red wine intake per week), along with diet-derived circulating antioxidants including Vitamin C (ascorbate), Vitamin E (α-tocopherol), Vitamin E (γ-tocopherol), carotene, Vitamin A (retinol), zinc, and selenium (N = 2,603-428,860), were linked to independent single nucleotide polymorphisms (SNPs). Data on ADHD was gathered from six sources, comprising 246,888 participants. The primary analytical method utilized was inverse variance weighting (IVW), with sensitivity analysis conducted to assess the robustness of the main findings. In different diagnostic periods for ADHD, we found that only green tea intake among the antioxidants was significantly associated with a reduced risk of ADHD in males (OR: 0.977, CI: 0.963-0.990, p < 0.001, FDR = 0.065), with no evidence of pleiotropy or heterogeneity observed in the results. Additionally, a nominal causal association was found between green tea intake and childhood ADHD (OR: 0.989, 95% CI: 0.979-0.998, p = 0.023, FDR = 0.843). No causal relationships were detected between the intake of other antioxidant-rich diets and ADHD. Our study found a significant inverse association between green tea intake and male ADHD, suggesting that higher green tea consumption may reduce ADHD risk in males. Further research is needed to explore optimal doses and underlying mechanisms.

Will the antioxidant supplements impact the mitigation of oxidative stress in Parkinson's disease?

Parkinson's disease is a frequent neurodegenerative condition marked by both non-motor and motor symptoms. It is brought on by the selective depletion of dopamine neurons from the substantia nigra region of the midbrain. Numerous variables, including lifestyle, environment, age, smoking, and underlying medical disorders, affect the occurrence of Parkinson's disease. The free radicals created by oxidative stress have an impact on the morphology and function of neuronal cells and are a factor in many neurodegenerative disorders, including Parkinson’s and Alzheimer’s, disorder. Although the pathophysiological mechanism causing neuronal degeneration is still unknown, oxidative stress plays a critical role in the pathogenesis of idiopathic Parkinson's disease. It also has an association with numerous proteins, including α-synuclein, amyloid, DJ-1 protein and several signalling pathways like extracellular regulated protein kinases. Reactive oxygen species also contribute to complex I's mitochondrial respiratory activity. The naturally occurring antioxidants are the phenols, anthocyanins, carotenoids, flavonoids, vitamins, and lignans. These antioxidants retain the reactive oxygen species generation and plays a role in several biological effects. As a result, natural plant antioxidants may have an impact on Parkinson's disease and offer an alternative therapy that minimises oxidative stress and slows down the evolution of the disease.

A conserved two-component system senses intracellular iron levels and regulates redox balance in Mycobacterium spp.

For bacteria, an intricate coordination between sensing and regulating iron levels and managing oxidative stress is required as their levels are tightly interlinked. While various oxidative stress and heme-based redox sensors have been reported for both pathogenic and non-pathogenic bacteria, the mechanisms governing the modulation of intracellular iron levels in response to changes in redox status remain unclear. In this study, a gene-inactivated strain of mycobacterial sensor kinase PdtaS showed dysregulated expression of genes associated with iron metabolism, including Fe-S clusters, NADH dehydrogenases, and iron uptake. The strain showed poor growth in nutrient-limiting conditions, a defect rescuable by heme but not by Fe3+ supplementation. This observation was associated with the PAS domain of the PdtaS sensor kinase. Biochemical and biophysical experiments established heme-binding to the PAS domain and its inhibitory effect on PdtaS auto-kinase activity, suggesting that the absence of heme induces activation of this sensor kinase. Interestingly, despite having an endogenous heme biosynthetic pathway or even external heme supplementation, the ∆pdtaS mutant exhibited persistent low intracellular iron levels concomitant with elevated oxidative stress. Antioxidant supplementation mitigated growth defects, emphasizing the link between oxidative stress, intracellular iron levels, and PdtaS activity. RNA-IP identified key targets associated with redox homeostasis and iron metabolism as targets of the PdtaR response regulator. The study proposes a novel role for the PdtaS-PdtaR TCS in sensing heme, regulation of intracellular iron levels, and redox balance.IMPORTANCEThe research article investigates the intricate interplay between bacteria's ability to take and utilize iron without inducing excess iron's toxic effects, including oxidative stress. The study shows that bacteria achieve this by sensing intracellular iron available as heme through a sensory protein PdtaS, which turns off when heme is in excess and prevents iron uptake and iron efflux. The process shields bacteria from generating Fe-dependent free radicals and allows it to maintain viability. The absence of sensor kinase abrogates all these processes, increasing bacteria susceptibility to ROS and thereby slowing growth. This feature of the sensor kinase PdtaS makes it an attractive co-therapeutic target for tuberculosis therapy, where its inhibition will prevent iron uptake, even in the presence of low iron, thereby halting bacterial proliferation.