Catalase Deficiency Research Articles

BackgroundCurrent therapies for AD using traditional theories have been insufficiency. Of note, other mechanisms, such as oxidative stress, contribute to the pathogenesis of AD (1). Importantly, there are sex-related differences in oxidative stress during the cognitive modulation and neurodegenerative process. Previous studies found that sodium benzoate was capable of improving cognitive function of patients with mild AD (Lin et al., Biol Psychiatry 2014) or schizophrenia (Lane et al., JAMA Psychiatry 2013). Of interest, benzoate showed efficacy for female patients but not for male patients with dementia (2). Catalase is a crucial endogenous antioxidant that alleviates oxidative stress; and deficiency of catalase is regarded to be related to the pathogenesis of age-related neurodegenerative diseases like AD (3) and schizophrenia (Lin et al., Int J Neuropsychopharmacol 2023). Earlier, sodium benzoate’ s treatment response for schizophrenia was observed to be related with its effect on catalase activity assayed in peripheral blood (Lin et al., Biol Psychiatry 2018). Recently, a randomized, double- blind, dose-comparison (500 mg/day, 750 mg/day, and 1000 mg/day), placebo-controlled trial showed that sodium benzoate performed best at 1000 mg/day in improving cognitive function of the patients with mild AD (4). While both sex and benzoate doses influenced cognitive outcome in patients with dementia, and clinical improvement after benzoate treatment was positively correlated with catalase change in the blood of schizophrenia patients (Lin et al., Biol Psychiatry 2018), whether sex or benzoate doses also affect catalase activity in the benzoate-treated AD patients remain unknown.Aims & ObjectivesThe current study aimed to examine the roles of sex and benzoate dosage in the alteration of catalase activity and the clinical impact in the patients with mild AD who received benzoate treatment.MethodsThis secondary analysis used data from a double-blind trial (4), in which 149 AD patients were randomized to receive placebo or one of three benzoate doses (500, 750, or 1000 mg/day) and measured with Alzheimer's disease assessment scale-cognitive subscale. Blood levels of catalase and another two endogenous antioxidants, superoxide dismutase (SOD) (Lin et al., Neuropsychiatr Dis Treat 2020) and glutathione (Lin &Lane, Antioxidants 2021), were assayed before and after treatment. While sodium benzoate is also an inhibitor of D-amino acid oxidase (DAAO) (Lin &Lane, Schizophr Res 2023), blood levels of DAAO were also measured (Lin &Lane, Int J Neuropsychopharmacol 2022).ResultsHigher baseline catalase activity was associated with more cognitive improvement after benzoate treatment among both female and male patients. Benzoate treatment, particularly at 1000 mg/day, increased catalase among female patients, but not among male. The increases in the catalase activity among the benzoate-treated women were correlated with their cognitive improvements. SOD, Glutathione, and DAAO didn’ t affect the cognitive outcome after benzoate or placebo treatment.Discussion & ConclusionSupporting the oxidative stress theory and sex difference in AD, the finding suggest that sex (female) and benzoate dose co-determine catalase increase in benzoate-treated AD patients and the catalase increment contributes to cognitive improvement of benzoate-treated women.

In previous studies, titanium peroxide nanoparticles (PAA-TiOx NPs) with surfaces functionalized using polyacrylic acid (PAA) and hydrogen peroxide (H2O2) demonstrated a synergistic effect when combined with X-ray irradiation. The combination generated H2O2 and reactive oxygen species (ROS) that enhanced the irradiation efficacy. In the present study, we examined the relationship between catalase and PAA-TiOx NPs sensitization to X-ray radiation because catalase is the primary antioxidant enzyme that converts H2O2 to water and oxygen. Catalase-knockout PANC-1 (dCAT) cells were generated using the CRISPR/Cas9 system, which was confirmed by the suppression of catalase expression in mRNA and protein levels that resulted in an 81.7% decrease in catalase activity compared with levels in wild-type cells. Catalase deficiency was found to increase the production of ROS, particularly in hypoxia. Also, the combination of PAA-TiOx NPs and X-ray 5 Gy resulted in a 7-fold decrease in the survival fraction (SF; p < 0.01) of dCAT cells compared with rates documented in wild-type cells. Interestingly, the combination treatment with X-ray 3 Gy in dCAT cells resulted in an SF similar to that observed in wild-type cells treated with the same combination but at a higher radiation dose (5 Gy). These results suggest that a strategy of catalase inhibition could be used to establish an advanced combination treatment of PAA-TiOx NPs and X-ray irradiation for pancreatic cancer cells.

Sex- and dose-dependent catalase increase and its clinical impact in a benzoate dose-finding, randomized, double-blind, placebo-controlled trial for Alzheimer's disease

Catalase is a key antioxidative enzyme, and a deficiency or malfunction of catalase is hypothesized to be related to various diseases. To investigate catalase activity, it is important to use reliable methods and experimental protocols enabling consistent fallouts. One major problem, however, is that the activity values obtained with different techniques and procedures can vary to a large extent. The aim of this work was to identify experimental conditions that provide similar catalase activity values with two different methods based on either spectrophotometry or chronoamperometry. The investigated parameters include the concentration of catalase and its substrate (H2O2), as well as the effect of deoxygenation of the catalase medium by nitrogen (N2). Within the frame of investigated conditions, we show that spectrophotometry is strongly affected by the catalase concentration, whereas chronoamperometry is shown to be more dependent on the substrate concentration. Deoxygenation leads to elevated catalase activity values in the case of chronoamperometry, whereas it shows no influence on the results obtained with spectrophotometry. In particular, in the case of low substrate concentrations (i.e., low catalase reaction rates), higher and more accurate results are obtained with deoxygenation in the case of chronoamperometry measurements due to minimized oxygen escape. The effect of deoxygenation, giving rise to elevated catalase activity values, however, is not statistically significant at high substrate concentrations, implying that the protocol can be simplified by excluding this step as long as the other parameters are optimized. Finally, by comparing the two methods at different experimental conditions, we identified protocols resulting in similar results, i.e., 10 mM H2O2 and catalase activity of 4–5 U/mL. Based on this work, improved consistency of catalase activity data obtained with different methodologies and in different labs is expected.

BackgroundFatty acids (FA) derived from adipose tissue and liver serve as the main fuel in thermogenesis of brown adipose tissue (BAT). Catalase, a peroxisomal enzyme, plays an important role in maintaining intracellular redox homeostasis by decomposing hydrogen peroxide to either water or oxygen that oxidize and provide fuel for cellular metabolism. Although the antioxidant enzymatic activity of catalase is well known, its role in the metabolism and maintenance of energy homeostasis has not yet been revealed. The present study investigated the role of catalase in lipid metabolism and thermogenesis during nutrient deprivation in catalase-knockout (KO) mice.ResultsWe found that hepatic triglyceride accumulation in KO mice decreased during sustained fasting due to lipolysis through reactive oxygen species (ROS) generation in adipocytes. Furthermore, the free FA released from lipolysis were shuttled to BAT through the activation of CD36 and catabolized by lipoprotein lipase in KO mice during sustained fasting. Although the exact mechanism for the activation of the FA receptor enzyme, CD36 in BAT is still unclear, we found that ROS generation in adipocytes mediated the shuttling of FA to BAT.ConclusionsTaken together, our findings uncover the novel role of catalase in lipid metabolism and thermogenesis in BAT, which may be useful in understanding metabolic dysfunction.Graphical

The increased level of hydrogen peroxide accompanies some modes of macrophage specification and is linked to ROS-based antimicrobial activity of these phagocytes. In this study, we show that activation of toll-like receptors with bacterial components such as LPS is accompanied by the decline in transcription of hydrogen peroxide decomposing enzyme-catalase, suppression of which facilitates the polarization of human macrophages towards the pro-inflammatory phenotype. The chromatin remodeling at the CAT promoter involves LSD1 and HDAC1, but activity of the first enzyme defines abundance of the two proteins on chromatin, histone acetylation status and the CAT transcription. LSD1 inhibition prior to macrophage activation with LPS prevents CAT repression by enhancing the LSD1 and interfering with the HDAC1 recruitment to the gene promoter. The maintenance of catalase level with LSD1 inhibitors during M1 polarization considerably limits LPS-triggered expression of some pro-inflammatory cytokines and markers such as IL1β, TNFα, COX2, CD14, TLR2, and IFNAR, but the effect of LSD1 inhibitors is lost upon catalase deficiency. Summarizing, activity of LSD1 allows for the CAT repression in LPS stimulated macrophages, which negatively controls expression of some key pro-inflammatory markers. LSD1 inhibitors can be considered as possible immunosuppressive drugs capable of limiting macrophage M1 specialization.

Compromised glutathione synthesis results in high susceptibility to acetaminophen hepatotoxicity in acatalasemic mice

Peroxisomes are dynamic organelles that participate in a diverse array of cellular processes, including β-oxidation, which produces a considerable amount of reactive oxygen species (ROS). Although we showed that catalase depletion induces ROS-mediated pexophagy in cells, the effect of catalase deficiency during conditions that favor ROS generation remains elusive in mice. In this study, we reported that prolonged fasting in catalase-knockout (KO) mice drastically increased ROS production, which induced liver-specific pexophagy, an autophagic degradation of peroxisomes. In addition, increased ROS generation induced the production of pro-inflammatory cytokines in the liver tissues of catalase-KO mice. Furthermore, there was a significant increase in the levels of aspartate transaminase and alanine transaminase as well as apparent cell death in the liver of catalase-KO mice during prolonged fasting. However, an intra-peritoneal injection of the antioxidant N-acetyl-l-cysteine (NAC) and autophagy inhibitor chloroquine inhibited the inflammatory response, liver damage, and pexophagy in the liver of catalase-KO mice during prolonged fasting. Consistently, genetic ablation of autophagy, Atg5 led to suppression of pexophagy during catalase inhibition by 3-aminotriazole (3AT). Moreover, treatment with chloroquine also ameliorated the inflammatory response and cell death in embryonic fibroblast cells from catalase-KO mice. Taken together, our data suggest that ROS-mediated liver-specific pexophagy observed during prolonged fasting in catalase-KO mice may be responsible for the process associated with hepatic cell death.

Abstract Background: Testicular germ cell tumor (GCT) is the most common cancer in young men between 15 and 35 years of age. Cisplatin-based combination chemotherapy will cure 70% of patients with metastatic GCT. Patients who relapse can still be cured with salvage standard-dose or high-dose chemotherapy. However, about 15% of patients with relapsed/refractory GCT are incurable. NAD(P)H:quinone oxidoreductase 1 (NQO1) is a two-electron oxidoreductase elevated in several tumor types compared to normal tissue. NQO1 detoxifies quinones and reduces oxidative stress. NQO1 bioactivatable drugs induce DNA damage in cells overexpressing NQO1, but not in cells lacking it, hence delivering tumor-selective damage and cell death. Alterations in catalase expression can cause cytoprotection. The ratio of NQO1:catalase activities is presumed to be a predictive marker for therapeutic activity of NQO1 bioactivatable drugs. There is no existing data on NQO1 or catalase expression in GCTs. Methods: Patients with testicular or extra-gonadal GCT who had surgery between January 2016 and December 2018 were identified from the Indiana University Melvin and Bren Simon Cancer Center Tissue Bank database. Patients with non-seminomatous GCT (NSGCT) of testis or primary mediastinal NSGCT were selected and specimens obtained. Immunohistochemistry staining was performed on tumor tissue to determine the quantity and intensity of NQO1 and catalase expression. Results: NQO1 and catalase expression were determined in 16 patients. Thirteen specimens stained moderately to strongly positive for NQO1. Only 1 specimen stained negative. Conversely, no specimen stained strongly positive for catalase, and only 2 stained moderately positive. Fourteen specimens were catalase deficient or only mildly positive for catalase. The details of the immunostaining is summarized in the table below. Immunohistochemistry staining for NQO1 and catalase in GCTImmunostainNegative(0)Mildly positive (&amp;lt;10%)Moderately positive (10-50%)Strongly positive (&amp;gt;50%)NQO1Quantity01114Intensity0547Combined score1267CatalaseQuantity3472Intensity31120Combined score7720 Conclusions: NSGCTs appear to have high levels of NQO1 and deficiency of catalase. NQO1 bioactivatable agents could serve as a potential therapeutic approach in patients with refractory testicular GCTs. Citation Format: Neda Hashemi Sadraei, Nabil Adra, Constance Temm, Kenneth A. Kesler, Muhammad T. Idrees, David A. Boothman, Lawrence Einhorn. Tissue analysis of NAD(P)H: quinone oxidoreductase (NQO1) and catalase expression in patients with germ cell tumors (GCT) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5169.

413 Background: NAD(P)H:quinone oxidoreductase 1 (NQO1) is an enzyme which detoxifies quinones and reduces oxidative stress. NQO1 is expressed in multiple tumor types at levels up to 200-fold above normal tissue, including in breast, pancreatic, and non-small cell lung cancers. NQO1 bioactivatable drugs have the potential to deliver tumor-selective DNA damage and cell death by exploiting the elevation of NQO1. Alterations in catalase expression can cause marked cytoprotection. The ratio of NQO1:catalase activities is presumed to be a predictive marker for therapeutic activity of NQO1 bioactivatable drugs. There is no data available on NQO1 and catalase expression in germ cell tumors. Methods: Patients with germ cell tumor who underwent orchiectomy/tumor resection between January 2016 and December 2018 were identified from the Indiana University Melvin and Bren Simon Cancer Center database. Patients with non-seminomatous germ cell tumor of testis or primary mediastinal non-seminomatous germ cell tumor were selected. Immunohistochemistry staining for NQO1 and catalase was performed on tumor tissue. Results: NQO1 and catalase expression were assessed in 16 patients. Fifteen of 16 tumors stained positive for NQO1, 13 of which were moderately to strongly positive. Conversely, the majority of tumors were catalase deficient or only mildly positive for catalase. The details of the Immunostaining is summarized in the table below. Conclusions: Non-seminomatous germ cell tumors appear to have overexpression of NQO1 and deficiency of catalase. NQO1 bioactivatable agents could be beneficial in treating patients with refractory non-seminomatous germ cell tumors.[Table: see text]

Quinolones have been thought to rapidly kill bacteria in two ways: (i) quinolone-topoisomerase-DNA lesions stimulate the accumulation of toxic reactive oxygen species (ROS); and (ii) the lesions directly cause lethal DNA breaks. Traditional killing assays may have underestimated the ROS contribution by overlooking the possibility that ROS continue to accumulate and kill cells on drug-free agar after quinolone removal. Quinolone-induced, ROS-mediated killing of Escherichia coli was measured by plating post-treatment samples on agar with/without anti-ROS agents. When E. coli cultures were treated with ciprofloxacin or moxifloxacin in the presence of chloramphenicol (to accentuate DNA-break-mediated killing), lethal activity, revealed by plating on quinolone-free agar, was inhibited by supplementing agar with ROS-mitigating agents. Moreover, norfloxacin-mediated lethality, observed with cells suspended in saline, was blocked by inhibitors of ROS accumulation and exacerbated by a katG catalase deficiency that impairs peroxide detoxification. Unlike WT cells, the katG mutant was killed by nalidixic acid or norfloxacin with chloramphenicol present and by nalidixic or oxolinic acid with cells suspended in saline. ROS accumulated after quinolone removal with cultures either co-treated with chloramphenicol or suspended in saline. Deficiencies in recA or recB reduced the protective effects of ROS-mitigating agents, supporting the idea that repair of quinolone-mediated DNA lesions suppresses the direct lethal effects of such lesions. ROS are the dominant factor in all modes of quinolone-mediated lethality, as quinolone-mediated primary DNA lesions are insufficient to kill without triggering ROS accumulation. ROS-stimulating adjuvants may enhance the lethality of quinolones and perhaps other antimicrobials.

Reactive species produced in the cell during normal cellular metabolism can chemically react with cellular biomolecules such as nucleic acids, proteins, and lipids, thereby causing their oxidative modifications leading to alterations in their compositions and potential damage to their cellular activities. Fortunately, cells have evolved several antioxidant defense mechanisms (as metabolites, vitamins, and enzymes) to neutralize or mitigate the harmful effect of reactive species and/or their byproducts. Any perturbation in the balance in the level of antioxidants and the reactive species results in a physiological condition called “oxidative stress.” A catalase is one of the crucial antioxidant enzymes that mitigates oxidative stress to a considerable extent by destroying cellular hydrogen peroxide to produce water and oxygen. Deficiency or malfunction of catalase is postulated to be related to the pathogenesis of many age-associated degenerative diseases like diabetes mellitus, hypertension, anemia, vitiligo, Alzheimer's disease, Parkinson's disease, bipolar disorder, cancer, and schizophrenia. Therefore, efforts are being undertaken in many laboratories to explore its use as a potential drug for the treatment of such diseases. This paper describes the direct and indirect involvement of deficiency and/or modification of catalase in the pathogenesis of some important diseases such as diabetes mellitus, Alzheimer's disease, Parkinson's disease, vitiligo, and acatalasemia. Details on the efforts exploring the potential treatment of these diseases using a catalase as a protein therapeutic agent have also been described.

Using the rat hypoxia model, the imbalanced work of antiradical defense enzymes with insufficient dismutase activity in blood leading to the development of oxidative stress, which was more pronounced in animals receiving a natural drinking diet, has been confirmed on the basis of the comparative analysis of the antiradical defense enzyme functioning index. It has been observed that acute hypoxia in the brain tissues is characterized by the development of catalase deficiency and the risk of excessive hydrogen peroxide production. It has been demonstrated that a decrease in the D/H (deuterium/protium) ratio in the blood and brain reduces the severity of the impairment of antioxidant enzyme work in hypoxia.

Oxidative stress has been considered to contribute to the development of obesity-related metabolic disorders including insulin resistance. To the contrary, deficiency of an anti-oxidizing enzyme, glutathione peroxidase (GPx)-1, was reported to enhance insulin signaling, suggesting that oxidative stress may inhibit the development of type 2 diabetes. However, the beneficial effects of the absence of GPx-1 in metabolic homeostasis, including body weight control, have not yet been clearly manifested. To clarify the relationship between oxidative stress and obesity-related metabolic disorders, we investigated another mouse deficient with both GPx-1 and catalase (Cat). C57BL/6J wild-type and GPx-1-/- × Cat-/- mice were fed with a high-fat diet (60% fat) or a normal chow diet for 16weeks and were investigated for metabolic and histological studies. Body weight gain was significantly reduced, and glucose metabolism as well as hepatic steatosis was obviously improved in the GPx-1-/- × Cat-/- mice. The serum levels of insulin and total cholesterol were also significantly lowered. For the underlying mechanism, inflammation was attenuated and expression of markers for fat browning was enhanced in the visceral white adipose tissues. Oxidative stress due to deficiency of GPx-1 and Cat may improve obesity-related metabolic disorders through attenuation of inflammation and fat browning.

Abstract The primary site for the development of T lymphocytes is the thymus, where cross-talk between thymic stromal cells (TSCs) and T cell progenitors mediates the development and maintenance of both populations. However, the thymus begins to atrophy relatively early in life, resulting in diminished T cell output, and corresponding immunodeficiencies in aged individuals. Our previous studies revealed that thymic stromal cells express conspicuously low levels of the peroxide quenching enzyme catalase (CAT), which results in high reactive oxygen species (ROS) levels and accumulated oxidative damage in thymic stromal cells, ultimately promoting thymic atrophy. In our current studies, we find that when catalase deficiency is complemented by overexpression targeted to mitochondria in transgenic mice (mCAT Tg), stromal function declines in young mice relative to non-transgenic littermates. TSC transcriptome analysis reveals decreased expression of tissue-restricted antigen (TRA) genes in young mCat Tg mice relative to controls. Stromal TRA expression is required for self-antigen presentation, and therefore promotes negative selection of potentially auto-reactive T cells. We propose that oxidative stress generated by low catalase levels in stromal cells promotes this key physiological function in the young, steady state thymus; in contrast however, the resulting accumulated oxidative damage ultimately impairs function in the aged thymus.

For epithelial ovarian cancer cells to survive during the metastatic cascade, cells must be able to evade anoikis, a caspase-dependent cell death mechanism initiated by extracellular matrix (ECM) detachment. However, many of the details behind this phenomenon have yet to be unveiled. Here, we examined the role of the antioxidant enzyme, catalase, in the survival and proliferation of anchorage-independent SKOV3 ovarian cancer cells. Catalase deficiency severely compromises cell viability and anchorage-independent growth in ECM-detached SKOV3 cells. Notably, cellviability and proliferation were unaffected in ECM-attached catalase-deficient SKOV3 cells. In aggregate, we discovered that catalase plays a prominent role in protection from ECM-detachment-induced cell death in SKOV3 cells. Furthermore, these findings imply that catalase may be an effective therapeutic target for epithelial ovarian cancer cells that survive the ECM-bereft metastatic cascade.

Neurodegenerative diseases are collective diseases that affect different parts of the brain with common or distinct disease phenotype. In almost all of the Prion diseases, motor impairments that are characterized by motor derangement, apathy, ataxia, and myoclonus are documented and again are shared by motor neuron diseases (MND). Proteins such as; B-Cell lymphoma 2 (BCL2), Copper chaperone for superoxide dismutase (CCS), Amyloid beta precursor protein (APP), Amyloid Precursor-Like Protein1/2 (APLP1/2), Catalase (CAT), and Stress induced phosphoprotein 1 (STIP1), are common interactomes of Prion and superoxide dismutase 1 (SOD1). Although there is no strong evidence to show the interaction of SOD1 and Prion, the implicated common interacting proteins indicate the potential bilateral interaction of those proteins in health and disease. For example, down-regulation of Heat shock protein A (HSPA5), a Prion interactome, increases accumulation of misfolded SOD1 leading to MND. Loss of Cu uptake function disturbs normal function of CCS. Over-expressed proteasome subunit alpha 3 (PSMA3) could fatigue its normal function of removing misfolded proteins. Studies showed the increase in CAT and lipid oxidation both in Prion-knocked out animal and in catalase deficiency cases. Up regulation, down regulation or direct interaction with their interactomes are predicted molecular mechanisms by which Prion and SOD exert their effect. The loss of protective function or the gain of a novel toxic property by the principal proteins is shared in Prion and MND. Thus, it might be possible to conclude that the interplay of proteins displayed in both diseases could be a key phenomenon in motor dysfunction development.

Three genes encode catalase in Arabidopsis. Although the role of CAT2 in photorespiration is well established, the importance of the different catalases in other processes is less clear. Analysis of cat1, cat2, cat3, cat1 cat2, and cat2 cat3 T-DNA mutants revealed that cat2 had the largest effect on activity in both roots and leaves. Root growth was inhibited in all cat2-containing lines, but this inhibition was prevented by growing plants at high CO2 , suggesting that it is mainly an indirect effect of stress at the leaf level. Analysis of double mutants suggested some overlap between CAT2 and CAT3 functions in leaves and CAT1 and CAT2 in seeds. When plants had been grown to a similar developmental stage in short days or long days, equal-time exposure to oxidative stress caused by genetic or pharmacological inhibition of catalase produced a much stronger induction of H2 O2 marker genes in short day plants. Together, our data (a) underline the importance of CAT2 in basal H2 O2 processing in Arabidopsis; (b) suggest that CAT1 and CAT3 are mainly "backup" or stress-specific enzymes; and (c) establish that day length-dependent responses to catalase deficiency are independent of the duration of oxidative stress.

L. J. Thénard and J. L. Gay-Lussac discovered hydrogen peroxide in 1818. Later, Thénard noticed that animal and plant tissues decompose hydrogen peroxide. The substance which is responsible for this reaction was named as catalase by O. Loew in 1900. The catalase enzyme was regarded as a diagnostic and a tumour marker in the late years of the 19th century and in the early years of the 20th century. Acatalasemia, an inherited deficiency of enzyme catalase, was studied in Japan, Switzerland and Hungary. The recent findings on catalase are focusing on the effects of reactive oxygen species and on the association of acatalasemia and diabetes mellitus. Orv Hetil. 2018; 159(24): 959-964.

Abstract T lymphocytes develop in the thymus, where mutually inductive signaling between lymphoid progenitors and thymic stromal cells (TSCs) directs progenitors along a well-characterized differentiation program. However, the biology of stromal cells comprising the lymphopoietic thymic microenvironment remains relatively under-characterized because stromal cells are rare and difficult to isolate. Using a deconvolution technique to study gene expression essentially in situ, we previously identified a deficiency in the peroxide quenching enzyme catalase (CAT) in thymic stromal cells, and found that CAT deficiency results in high reactive oxygen species (ROS) levels in this population, eventually leading to thymic atrophy in aged mice. Here, we find that when catalase deficiency is complemented by overexpression targeted to mitochondria in transgenic mice (mCAT Tg), both ROS levels and stromal function decline in young mice relative to non-transgenic littermates. TSC transcriptome analysis reveals decreased expression of tissue-restricted antigen (TRA) and autophagy pathway genes in mCat Tg mice. Analysis of autophagy flux reporter mice ubiquitously expressing the RFP-EGFP-LC3 fusion transgene also indicates diminished autophagic flux in mCAT Tg mice, particularly in TSCs. Stromal TRA expression and autophagic flux are required for self-antigen presentation, and therefore promote negative selection of potentially auto-reactive T cells. We propose that oxidative stress generated by low catalase levels in stromal cells promotes these key physiological functions in the young, steady state thymus; in contrast however, the resulting accumulated oxidative damage ultimately impairs function in the aged thymus.