Oxidative Stress

Enzymatic Defenses#

#### Superoxide Dismutases (SODs)

SODs catalyze the dismutation of superoxide to hydrogen peroxide and oxygen (2 O2.- + 2H+ --> H2O2 + O2). Three isoforms exist in mammals. copper/zinc superoxide dismutase (Cu/Zn-SOD) (SOD1): Cytoplasmic; requires Copper and Zinc as cofactors.

The most abundant intracellular SOD.

manganese (Mn)-SOD (SOD2): Mitochondrial; requires Manganese as cofactor. The primary defense against superoxide generated by the electron transport chain. manganese-SOD is essential for life—homozygous knockout is lethal in mice.^{[4]Metal Ion Acquisition in Staphylococcus aureus: Overcoming Nutritional ImmunityJames E. Cassat, Eric P. Skaar · 2012Open reference 4 ↓}

EC-SOD (SOD3): Extracellular; copper/zinc-dependent.

nickel (Ni)-SOD: Found in Streptomyces spp. and some other prokaryotes; uses Nickel as cofactor. Important for oxidative stress defense in plant-colonizing bacteria.^{[5]Role of Nickel in Microbial PathogenesisRobert J. Maier, Stéphane L. Benoit · 2019Open reference 5 ↓}

In Nickel toxicology, UNi shows an inverse U-shaped relationship with SOD activity in humans, and nickel exposure increases SOD activity in liver while reducing catalase in heart and kidneys.^{[6]Cardio-Metabolic Effects of Nickel: A Narrative ReviewYucheng Liu, Xiaomin Luo, Yongde Peng et al. · 2025Open reference 6 ↓}

#### Catalase (CAT)

Catalase decomposes hydrogen peroxide to water and oxygen (2 H2O2 --> 2 H2O + O2).

It contains an iron-heme prosthetic group and is concentrated in peroxisomes. Lead inhibits catalase activity along with other antioxidant enzymes; PbA (500 mg/L) reduces CAT in liver and kidney.^{[7]Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and ArsenicBalali-Mood M, Naseri K, Tahergorabi Z et al. · 2021Open reference 7 ↓}

#### Glutathione Peroxidases (GPX)

GPX enzymes reduce hydrogen peroxide and organic hydroperoxides using glutathione (GSH) as a co-substrate. Most GPX isoforms are selenoproteins, directly linking Selenium status to antioxidant capacity. GPX1-3: Reduce H2O2 and small organic hydroperoxides.

GPX4: The only enzyme capable of reducing lipid hydroperoxides within membranes; its loss triggers Ferroptosis.^{[3]Microbial Metallomics and Parkinson's Disease: A Unified Metal-Driven Framework Linking Ferroptosis, Dysbiosis, and alpha-Synuclein PathologyKaren Pendergrass · 2025Open reference 3 ↓[8]Molecular Mechanisms of Cellular Injury and Role of Toxic Heavy Metals in Chronic Kidney DiseaseManish Mishra, Larry Nichols, Aditi A. Dave et al. · 2022Open reference 8 ↓}

selenium (Se) supplementation increases GPx and thioredoxin reductase (TR) activity and decreases oxidative stress markers in Hashimoto's Thyroiditis patients.^{[9]Kravchenko 2023 — Thyroid hormones and minerals in immunocorrection of disorders in autoimmune thyroid diseasesKravchenko V, Zakharchenko T · 2023Open reference 9 ↓[10]McGregor Brock 2015 — The Role of Selenium in Thyroid Autoimmunity: A ReviewMcGregor Brock · 2015Open reference 10 ↓}

Non-Enzymatic Defenses#

#### Glutathione (GSH)

Glutathione (gamma-glutamyl-cysteinyl-glycine) is the most abundant intracellular thiol and the primary non-enzymatic antioxidant. It serves as. A direct scavenger of ROS via its sulfhydryl group.

The essential co-substrate for GPX enzymes. A conjugation agent for electrophilic xenobiotics (via glutathione S-transferases).

A reservoir of cysteine for protein synthesis.

The GSH/GSSG ratio (reduced-to-oxidized glutathione) is a key indicator of cellular redox status. Heavy Metals interact with GSH in multiple ways: Arsenic and Mercury deplete GSH through direct thiol binding and conjugation;^{[7]Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and ArsenicBalali-Mood M, Naseri K, Tahergorabi Z et al. · 2021Open reference 7 ↓} Cadmium forms organo-metallic complexes with GSH sulfhydryl groups;^{[11]Heavy Metals and Essential Elements in Association with Oxidative Stress in Women with Polycystic Ovary Syndrome -- A Systematic ReviewSmovrsnik T, Virant-Klun I, Pinter B · 2023Open reference 11 ↓} Chromium(VI) reduction to chromium (Cr)(III) by GSH generates hydroxyl radicals as intermediates.^{[7]Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and ArsenicBalali-Mood M, Naseri K, Tahergorabi Z et al. · 2021Open reference 7 ↓}

PCOS patients show significantly decreased serum GSH levels (6.24 vs 8.09 mg/ml; P < 0.001) with strong negative correlations between heavy metals (arsenic (As), lead (Pb), mercury (Hg)) and GSH.^{[12]Antioxidant Status in Relation to Heavy Metals Induced Oxidative Stress in Patients with Polycystic Ovarian Syndrome (PCOS)Manal Abudawood, Hajera Tabassum, Atheer H. Alanazi et al. · 2021Open reference 12 ↓}

#### Metallothioneins (MTs)

Metallothioneins are low-molecular-weight (7-8 kDa) cysteine-rich proteins (18-23 cysteines per 61-68 amino acids) that bind divalent metal cations. They serve dual roles as metal storage/detoxification proteins and as antioxidants via thiol-mediated ROS scavenging.

MTs are principally responsible for Cadmium sequestration—the cadmium (Cd)-MT complex has a half-life of 25-30 years in the kidneys.^{[13]The Effects of Cadmium ToxicityGiuseppe Genchi, Maria Stefania Sinicropi, Graziantonio Lauria et al. · 2020Open reference 13 ↓}

Cadmium produces dispositional tolerance by inducing MT synthesis, but MT capacity is finite; once saturated, free cadmium causes oxidative damage.^{[7]Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and ArsenicBalali-Mood M, Naseri K, Tahergorabi Z et al. · 2021Open reference 7 ↓}

#### Ascorbate (Vitamin C) and Tocopherol (Vitamin E)

Ascorbate is a water-soluble antioxidant that scavenges ROS and regenerates vitamin E. Vitamin E (alpha-tocopherol) is the primary lipid-soluble chain-breaking antioxidant in membranes, terminating lipid peroxidation chain reactions. Their roles in metal toxicology are complex—see the ascorbate-chromium paradox below.

Nickel—Indirect/Multifactorial#

Nickel generates oxidative stress through several indirect mechanisms rather than direct Fenton chemistry.

Ascorbate depletion: nickel (Ni)(II) depletes intracellular ascorbate, reducing antioxidant capacity and impairing iron (Fe)-dependent hydroxylases.^{[17]Genetic and Epigenetic Mechanisms in Metal Carcinogenesis and Cocarcinogenesis: Nickel, Arsenic, and ChromiumKonstantin Salnikov, Anatoly Zhitkovich · 2008Open reference 17 ↓} Iron displacement: nickel(II) oxidizes iron in iron-sulfur clusters and iron-containing enzymes, disrupting iron homeostasis (IRP-1/IRP-2, transferrin receptor, ferritin).^{[17]Genetic and Epigenetic Mechanisms in Metal Carcinogenesis and Cocarcinogenesis: Nickel, Arsenic, and ChromiumKonstantin Salnikov, Anatoly Zhitkovich · 2008Open reference 17 ↓}

SOD/catalase imbalance: Nickel increases SOD activity in liver but reduces catalase in heart and kidneys, creating an H2O2 surplus that cannot be adequately detoxified.^{[6]Cardio-Metabolic Effects of Nickel: A Narrative ReviewYucheng Liu, Xiaomin Luo, Yongde Peng et al. · 2025Open reference 6 ↓}

Elevated MDA in multiple organs confirms lipid peroxidation as a downstream consequence.^{[6]Cardio-Metabolic Effects of Nickel: A Narrative ReviewYucheng Liu, Xiaomin Luo, Yongde Peng et al. · 2025Open reference 6 ↓} In carcinogenesis, oxidative stress plays a secondary role to Epigenetic Modifications and Hypoxic Signaling (HIF-1α Pathway).^{[17]Genetic and Epigenetic Mechanisms in Metal Carcinogenesis and Cocarcinogenesis: Nickel, Arsenic, and ChromiumKonstantin Salnikov, Anatoly Zhitkovich · 2008Open reference 17 ↓}

Arsenic—GSH Depletion and Reactive Methylated Intermediates#

Arsenic generates ROS through multiple routes, though its role as a primary carcinogenic mechanism is debated.^{[17]Genetic and Epigenetic Mechanisms in Metal Carcinogenesis and Cocarcinogenesis: Nickel, Arsenic, and ChromiumKonstantin Salnikov, Anatoly Zhitkovich · 2008Open reference 17 ↓}

Inhibits pyruvate dehydrogenase (blocking the Krebs cycle) and uncouples oxidative phosphorylation.^{[7]Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and ArsenicBalali-Mood M, Naseri K, Tahergorabi Z et al. · 2021Open reference 7 ↓} Biomethylation produces reactive intermediates: DMA(III) is highly reactive and causes oxidative damage. Activates MAPK/NF-kB pathways, enhances myeloperoxidase activity.^{[8]Molecular Mechanisms of Cellular Injury and Role of Toxic Heavy Metals in Chronic Kidney DiseaseManish Mishra, Larry Nichols, Aditi A. Dave et al. · 2022Open reference 8 ↓}

Arsenic-induced ROS may be more relevant to acute toxicity than to carcinogenesis.^{[17]Genetic and Epigenetic Mechanisms in Metal Carcinogenesis and Cocarcinogenesis: Nickel, Arsenic, and ChromiumKonstantin Salnikov, Anatoly Zhitkovich · 2008Open reference 17 ↓} DNA adduct 8-OHdG is elevated in exposed populations.^{[7]Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and ArsenicBalali-Mood M, Naseri K, Tahergorabi Z et al. · 2021Open reference 7 ↓}

Lead—ALAD Inhibition and Antioxidant Depletion#

Lead generates oxidative stress through. ALAD (aminolevulinic acid dehydratase) inhibition: Disrupts heme biosynthesis, causing accumulation of aminolevulinic acid (ALA), which auto-oxidizes to generate superoxide and hydrogen peroxide.^{[7]Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and ArsenicBalali-Mood M, Naseri K, Tahergorabi Z et al. · 2021Open reference 7 ↓}

Ferrochelatase inhibition: Further disrupts heme synthesis, reducing heme available for catalase and other heme-dependent antioxidant enzymes. Direct antioxidant depletion: Reduces GSH, SOD, CAT, GPx; increases lipid peroxidation (MDA) and H2O2.^{[7]Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and ArsenicBalali-Mood M, Naseri K, Tahergorabi Z et al. · 2021Open reference 7 ↓}

lead (Pb) follows ionic mechanisms similar to calcium(II) (Ca2+), magnesium(II) (Mg2+), iron(II) (Fe2+), displacing essential metals from binding sites.^{[1]Toxicity, Mechanism and Health Effects of Some Heavy MetalsMonisha Jaishankar, Tenzin Tseten, Naresh Anbalagan et al. · 2014Open reference 1 ↓}

In children, blood lead levels >10 ug/dL affect IQ; lead is taken up by oligodendrocytes, reducing CNPase activity and causing demyelination.^{[21]Metal Profiles in Autism Spectrum Disorders: A Crosstalk between Toxic and Essential MetalsBlazewicz A, Grabrucker AM · 2023Open reference 21 ↓}

Mercury—GSH Depletion and Enzyme Inhibition#

Mercury generates oxidative stress primarily through. Thiol binding: High affinity for sulfhydryl groups leads to GSH conjugation and depletion.^{[7]Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and ArsenicBalali-Mood M, Naseri K, Tahergorabi Z et al. · 2021Open reference 7 ↓} Enzyme inhibition: Inhibits glutathione peroxidase, reducing capacity to detoxify H2O2 and lipid peroxides.^{[7]Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and ArsenicBalali-Mood M, Naseri K, Tahergorabi Z et al. · 2021Open reference 7 ↓}

Aquaporin disruption: Reduces aquaporin mRNA, affecting cellular water and solute homeostasis.

methylmercury (MeHg) and ethylHg are more toxic than inorganic mercury; methylmercury crosses the BBB and is 95-100% absorbed in the intestinal tract.^{[1]Toxicity, Mechanism and Health Effects of Some Heavy MetalsMonisha Jaishankar, Tenzin Tseten, Naresh Anbalagan et al. · 2014Open reference 1 ↓}

In ASD, mercury inhibits GSH and increases ROS, contributing to mitochondrial dysfunction.^{[21]Metal Profiles in Autism Spectrum Disorders: A Crosstalk between Toxic and Essential MetalsBlazewicz A, Grabrucker AM · 2023Open reference 21 ↓}

Manganese—Mitochondrial Dysfunction#

Manganese paradoxically serves as the cofactor for the mitochondrial antioxidant manganese (Mn)-SOD (SOD2) but is neurotoxic at elevated levels.

Excess manganese disrupts mitochondrial function, inducing cytochrome C release and caspase activation in dopaminergic neurons.^{[3]Microbial Metallomics and Parkinson's Disease: A Unified Metal-Driven Framework Linking Ferroptosis, Dysbiosis, and alpha-Synuclein PathologyKaren Pendergrass · 2025Open reference 3 ↓} manganese accumulates preferentially in the globus pallidus and striatum, causing parkinsonism distinct from idiopathic Parkinson's disease.

Metal-driven gut Dysbiosis by manganese (and iron (Fe), nickel (Ni)) initiates a cascade: loss of barrier integrity, bacterial translocation, systemic Metal-Driven Inflammation, and Neuroinflammation converging on dopaminergic neuron vulnerability.^{[3]Microbial Metallomics and Parkinson's Disease: A Unified Metal-Driven Framework Linking Ferroptosis, Dysbiosis, and alpha-Synuclein PathologyKaren Pendergrass · 2025Open reference 3 ↓}

Lipid Peroxidation#

MDA/TBARS (Malondialdehyde / Thiobarbituric acid reactive substances): The most widely used biomarker of lipid peroxidation. UNi shows a positive linear correlation with MDA in humans.^{[6]Cardio-Metabolic Effects of Nickel: A Narrative ReviewYucheng Liu, Xiaomin Luo, Yongde Peng et al. · 2025Open reference 6 ↓} MDA is elevated in PCOS women alongside elevated heavy metals.^{[11]Heavy Metals and Essential Elements in Association with Oxidative Stress in Women with Polycystic Ovary Syndrome -- A Systematic ReviewSmovrsnik T, Virant-Klun I, Pinter B · 2023Open reference 11 ↓}

selenium (Se) supplementation in hypothyroid patients decreased MDA levels.^{[9]Kravchenko 2023 — Thyroid hormones and minerals in immunocorrection of disorders in autoimmune thyroid diseasesKravchenko V, Zakharchenko T · 2023Open reference 9 ↓}

4-HNE (4-Hydroxynonenal): A reactive aldehyde product of omega-6 PUFA oxidation; both a biomarker and a mediator of oxidative damage.

Antioxidant Enzyme Activity#

SOD activity: Decreased in PCOS patients (9.30 vs 17.39 IU/ml; P < 0.001).^{[12]Antioxidant Status in Relation to Heavy Metals Induced Oxidative Stress in Patients with Polycystic Ovarian Syndrome (PCOS)Manal Abudawood, Hajera Tabassum, Atheer H. Alanazi et al. · 2021Open reference 12 ↓} In nickel exposure, shows an inverse U-shaped relationship with urinary nickel.^{[6]Cardio-Metabolic Effects of Nickel: A Narrative ReviewYucheng Liu, Xiaomin Luo, Yongde Peng et al. · 2025Open reference 6 ↓}

CAT activity: Reduced by lead, nickel, and cadmium exposure in multiple organ systems. GPx activity: Inhibited by mercury (direct enzyme inhibition) and decreased in PCOS.^{[12]Antioxidant Status in Relation to Heavy Metals Induced Oxidative Stress in Patients with Polycystic Ovarian Syndrome (PCOS)Manal Abudawood, Hajera Tabassum, Atheer H. Alanazi et al. · 2021Open reference 12 ↓}

Redox Status Markers#

GSH/GSSG ratio: Reflects overall cellular redox balance. Decreased GSH in PCOS patients negatively correlates with arsenic (As), lead (Pb), mercury (Hg) levels.^{[12]Antioxidant Status in Relation to Heavy Metals Induced Oxidative Stress in Patients with Polycystic Ovarian Syndrome (PCOS)Manal Abudawood, Hajera Tabassum, Atheer H. Alanazi et al. · 2021Open reference 12 ↓}

TOS (Total Oxidant Status) / TAS (Total Antioxidant Status): Composite markers. PCOS women show lower TAS and higher TOS.^{[11]Heavy Metals and Essential Elements in Association with Oxidative Stress in Women with Polycystic Ovary Syndrome -- A Systematic ReviewSmovrsnik T, Virant-Klun I, Pinter B · 2023Open reference 11 ↓}

hs-CRP and TNF-alpha: Inflammatory markers elevated alongside oxidative stress markers in PCOS.^{[11]Heavy Metals and Essential Elements in Association with Oxidative Stress in Women with Polycystic Ovary Syndrome -- A Systematic ReviewSmovrsnik T, Virant-Klun I, Pinter B · 2023Open reference 11 ↓}

Carcinogenesis#

Oxidative stress contributes to cancer through DNA damage, genomic instability, and activation of proliferative signaling, but its importance as a primary mechanism varies by metal.

Chromium: Oxidative DNA damage is secondary to chromium (Cr)-DNA adducts; 8-oxo-dG occurs mainly at supraphysiological doses.^{[17]Genetic and Epigenetic Mechanisms in Metal Carcinogenesis and Cocarcinogenesis: Nickel, Arsenic, and ChromiumKonstantin Salnikov, Anatoly Zhitkovich · 2008Open reference 17 ↓} Nickel: Oxidative stress is secondary to epigenetic modifications and HIF-1alpha stabilization.^{[17]Genetic and Epigenetic Mechanisms in Metal Carcinogenesis and Cocarcinogenesis: Nickel, Arsenic, and ChromiumKonstantin Salnikov, Anatoly Zhitkovich · 2008Open reference 17 ↓}

Arsenic: ROS debated as primary vs. secondary mechanism; arsenic primarily acts through cellular proliferation, NF-kB signaling, and epigenetic changes.^{[17]Genetic and Epigenetic Mechanisms in Metal Carcinogenesis and Cocarcinogenesis: Nickel, Arsenic, and ChromiumKonstantin Salnikov, Anatoly Zhitkovich · 2008Open reference 17 ↓}

Cadmium: Induces ROS, inhibits DNA repair, and acts as a metalloestrogen binding ERalpha; carcinogenicity likely involves epigenetic pathways.^{[19]Cadmium and breast cancer - Current state and research gaps in the underlying mechanismsTarhonska K, Lesicka M, Janasik B et al. · 2022Open reference 19 ↓[13]The Effects of Cadmium ToxicityGiuseppe Genchi, Maria Stefania Sinicropi, Graziantonio Lauria et al. · 2020Open reference 13 ↓}

Neurodegeneration and Ferroptosis#

Parkinson's disease: Iron accumulation in the substantia nigra catalyzes Fenton reactions; GPX4 downregulation triggers Ferroptosis in dopaminergic neurons; gut dysbiosis mediates metal-to-brain pathology via the gut-brain axis.^{[3]Microbial Metallomics and Parkinson's Disease: A Unified Metal-Driven Framework Linking Ferroptosis, Dysbiosis, and alpha-Synuclein PathologyKaren Pendergrass · 2025Open reference 3 ↓}

Alzheimer's disease: Multiple metals (lead (Pb), mercury (Hg), cadmium (Cd), iron (Fe), copper (Cu), manganese (Mn)) contribute to oxidative damage in AD through ROS generation, mitochondrial dysfunction, and disruption of metal homeostasis in the brain.^{[21]Metal Profiles in Autism Spectrum Disorders: A Crosstalk between Toxic and Essential MetalsBlazewicz A, Grabrucker AM · 2023Open reference 21 ↓}

ASD Autism Spectrum Disorder: mercury inhibits GSH; cadmium disrupts thiol groups; lead affects ALAD—all converging on oxidative stress and mitochondrial dysfunction. Toxic metals compete with Zinc for protein binding sites, effectively creating functional zinc deficiency.^{[21]Metal Profiles in Autism Spectrum Disorders: A Crosstalk between Toxic and Essential MetalsBlazewicz A, Grabrucker AM · 2023Open reference 21 ↓[22]Metal Dyshomeostasis as a Driver of Gut Pathology in Autism Spectrum DisordersO'Grady K, Grabrucker AM · 2025Open reference 22 ↓}

Cardiovascular Disease#

Nickel exposure is associated with CVD; oxidative stress (SOD/MDA changes) is the primary proposed mechanism. Cardiac toxicity is mitigated by melatonin and ascorbic acid and exacerbated in antioxidant-deficient mice.^{[6]Cardio-Metabolic Effects of Nickel: A Narrative ReviewYucheng Liu, Xiaomin Luo, Yongde Peng et al. · 2025Open reference 6 ↓}

Cadmium damages endothelial cells, raises LDL profiles, and increases atherosclerosis risk via lipid aggregation.^{[20]Exposure to Cadmium and Its Impacts on Human Health: A Short ReviewPuthiyavalappil Rasin, Ashwathi A V, Sabeel M Basheer et al. · 2025Open reference 20 ↓}

Chronic Kidney Disease#

CKD pathogenesis involves oxidative stress, mitochondrial dysfunction, ferroptosis, and inflammation in an interconnected network. As CKD progresses, declining GFR reduces the ability to eliminate toxicants, creating a vicious cycle of metal accumulation.^{[8]Molecular Mechanisms of Cellular Injury and Role of Toxic Heavy Metals in Chronic Kidney DiseaseManish Mishra, Larry Nichols, Aditi A. Dave et al. · 2022Open reference 8 ↓}

Arsenic increases ROS via MAPK/NF-kB; cadmium impairs ETC complexes II/III; mercury disrupts mitochondrial membrane potential.^{[8]Molecular Mechanisms of Cellular Injury and Role of Toxic Heavy Metals in Chronic Kidney DiseaseManish Mishra, Larry Nichols, Aditi A. Dave et al. · 2022Open reference 8 ↓}

GPX4 loss of function triggers ferroptosis in renal tubular cells; iron-restricted diet is protective in animal models.^{[8]Molecular Mechanisms of Cellular Injury and Role of Toxic Heavy Metals in Chronic Kidney DiseaseManish Mishra, Larry Nichols, Aditi A. Dave et al. · 2022Open reference 8 ↓}

PCOS#

Oxidative stress is proposed as a central mechanism linking heavy metal exposure to PCOS pathology.

PCOS patients have elevated serum arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg) with decreased SOD and GSH.^{[12]Antioxidant Status in Relation to Heavy Metals Induced Oxidative Stress in Patients with Polycystic Ovarian Syndrome (PCOS)Manal Abudawood, Hajera Tabassum, Atheer H. Alanazi et al. · 2021Open reference 12 ↓} Positive correlations between antimony (Sb), lead, cadmium and MDA, TNF-alpha, HOMA-IR.^{[11]Heavy Metals and Essential Elements in Association with Oxidative Stress in Women with Polycystic Ovary Syndrome -- A Systematic ReviewSmovrsnik T, Virant-Klun I, Pinter B · 2023Open reference 11 ↓}

Supplementation with zinc (Zn), chromium (Cr), selenium (Se), magnesium (Mg), calcium (Ca) shows potential for reducing OS and improving endocrine parameters.^{[11]Heavy Metals and Essential Elements in Association with Oxidative Stress in Women with Polycystic Ovary Syndrome -- A Systematic ReviewSmovrsnik T, Virant-Klun I, Pinter B · 2023Open reference 11 ↓}

Heavy metals interact with sulfhydryl groups in GSH, forming organo-metallic complexes; they can disrupt insulin gene promoter activity and reproductive hormone levels.^{[11]Heavy Metals and Essential Elements in Association with Oxidative Stress in Women with Polycystic Ovary Syndrome -- A Systematic ReviewSmovrsnik T, Virant-Klun I, Pinter B · 2023Open reference 11 ↓}

Endometriosis#

Vitamins C and E supplementation reduces systemic oxidative stress indicators in endometriosis patients (randomized triple-blind placebo-controlled trial).^{[14]I Am the 1 in 10 -- What Should I Eat? A Research Review of Nutrition in EndometriosisPiecuch M, Garbicz J, Waliczek M et al. · 2022Open reference 14 ↓} Iron overload in peritoneal fluid causes embryotoxicity via ferroptosis.^{[14]I Am the 1 in 10 -- What Should I Eat? A Research Review of Nutrition in EndometriosisPiecuch M, Garbicz J, Waliczek M et al. · 2022Open reference 14 ↓}

PTEs (nickel (Ni), lead (Pb), Bi) elevated in peritoneal fluid of endometriosis patients may impair oocyte maturation and fertilization via excess ROS.^{[23]Elevated Lead, Nickel, and Bismuth Levels in the Peritoneal Fluid of a Peritoneal Endometriosis Patient without Toxic Habits or Occupational Exposure following a Vegetarian DietLopez-Botella A, Gomez-Torres MJ, Sanchez R et al. · 2023Open reference 23 ↓}

Autism Spectrum Disorder#

Toxic metals (mercury (Hg), cadmium (Cd), lead (Pb)) and essential metal deficiency (zinc (Zn)) converge on oxidative stress and mitochondrial dysfunction as shared pathomechanisms in ASD.^{[21]Metal Profiles in Autism Spectrum Disorders: A Crosstalk between Toxic and Essential MetalsBlazewicz A, Grabrucker AM · 2023Open reference 21 ↓}

Gut pathologies from mercury, cadmium, lead exposure and zinc deficiency overlap: intestinal barrier dysfunction, inflammation, and microbiota dysbiosis.^{[22]Metal Dyshomeostasis as a Driver of Gut Pathology in Autism Spectrum DisordersO'Grady K, Grabrucker AM · 2025Open reference 22 ↓}

Pathogen SODs as Virulence Factors#

Pathogens have evolved antioxidant defenses to survive the oxidative burst. manganese (Mn)-SOD (SodA/SodM) in Staphylococcus aureus: Manganese-dependent SOD is critical for oxidative stress defense; manganese acquisition via MntABC is a virulence requirement. Host calprotectin sequesters manganese and zinc to limit bacterial SOD activity.^{[4]Metal Ion Acquisition in Staphylococcus aureus: Overcoming Nutritional ImmunityJames E. Cassat, Eric P. Skaar · 2012Open reference 4 ↓}

manganese as SOD cofactor in Streptococci: manganese is the primary cofactor for SOD across pathogenic Streptococcus species; cadmium disrupts manganese uptake/efflux in S. pneumoniae, indirectly increasing oxidative stress susceptibility.^{[24]Metal Homeostasis in Pathogenic StreptococciAkbari MS, Doran KS, Burcham LR · 2022Open reference 24 ↓}

nickel (Ni)-SOD in Streptomyces spp.: A nickel-dependent SOD that protects against oxidative stress in plant hosts.^{[5]Role of Nickel in Microbial PathogenesisRobert J. Maier, Stéphane L. Benoit · 2019Open reference 5 ↓}

Hydrogenases and Acid/Oxidative Stress#

Salmonella enterica serovar Typhimurium: Contains 4 [NiFe] hydrogenases (Hya, Hyb, Hyc, Hyd); Hyb is most important for virulence. Triple mutant is completely avirulent.^{[5]Role of Nickel in Microbial PathogenesisRobert J. Maier, Stéphane L. Benoit · 2019Open reference 5 ↓}

Shigella flexneri: H2-uptake hydrogenases combat acid stress in phagolysosomes, partly related to oxidative conditions.^{[5]Role of Nickel in Microbial PathogenesisRobert J. Maier, Stéphane L. Benoit · 2019Open reference 5 ↓}

Antioxidant Supplementation#

Selenium: selenium (Se) supplementation (200 ug/day) increases GPx3 and selenoprotein P, decreases MDA, and reduces anti-TPO antibodies in Hashimoto's thyroiditis.^{[10]McGregor Brock 2015 — The Role of Selenium in Thyroid Autoimmunity: A ReviewMcGregor Brock · 2015Open reference 10 ↓[9]Kravchenko 2023 — Thyroid hormones and minerals in immunocorrection of disorders in autoimmune thyroid diseasesKravchenko V, Zakharchenko T · 2023Open reference 9 ↓} selenium is the backbone of the selenoproteome including GPX4, the central brake on Ferroptosis.

Zinc: Supplementation enhances intestinal barrier function, reduces permeability, exerts anti-inflammatory effects, and promotes beneficial gut bacteria.^{[22]Metal Dyshomeostasis as a Driver of Gut Pathology in Autism Spectrum DisordersO'Grady K, Grabrucker AM · 2025Open reference 22 ↓} Lower zinc (Zn) in PCOS is associated with lower CAT activity and higher MDA.^{[11]Heavy Metals and Essential Elements in Association with Oxidative Stress in Women with Polycystic Ovary Syndrome -- A Systematic ReviewSmovrsnik T, Virant-Klun I, Pinter B · 2023Open reference 11 ↓}

Vitamins C and E: Reduce systemic oxidative stress in endometriosis.^{[14]I Am the 1 in 10 -- What Should I Eat? A Research Review of Nutrition in EndometriosisPiecuch M, Garbicz J, Waliczek M et al. · 2022Open reference 14 ↓} Vitamin E terminates lipid peroxidation chain reactions in membranes.

Melatonin and ascorbic acid: Mitigate nickel-induced cardiac toxicity in animals; mice deficient in endogenous antioxidants show exacerbated nickel toxicity.^{[6]Cardio-Metabolic Effects of Nickel: A Narrative ReviewYucheng Liu, Xiaomin Luo, Yongde Peng et al. · 2025Open reference 6 ↓}

magnesium (Mg), calcium (Ca) supplementation: Reduces TNF-alpha, weight, BMI in PCOS; calcium + vitamin D decreases LH and hs-CRP.^{[11]Heavy Metals and Essential Elements in Association with Oxidative Stress in Women with Polycystic Ovary Syndrome -- A Systematic ReviewSmovrsnik T, Virant-Klun I, Pinter B · 2023Open reference 11 ↓}