Improved clinical trial race/ethnicity reporting and updated inclusion profile, 2017-2022: A New Jersey snapshot.

Background: Diverse representation in clinical trials is an important goal in the testing of a medical, diagnostic, or therapeutic intervention. To date, the desired level of trial equity and inclusivity has been unevenly achieved. Methods: Employing the US National Library of Medicine's Clinicaltrials.gov registry, we examined 481 clinical trials conducted - at least in part - in the state of New Jersey. These trials were initiated after the FDA-mandated Common Rule changes, i.e., between January 2017 and October 2022, were enacted, and had their results posted. We analyzed sex/race/ethnicity reporting as well as applicable enrollment. Using meta-analysis, we estimated group participation proportions of a subset of the 481 identified trials; specifically, the 229 studies that were conducted solely within the US (i.e., without international sites) and compared them to US census data. Findings: Within the 481 clinical trials analyzed, over 97% reported on the race and/or ethnicity of their enrollees; all included information on sex. Reporting was not affected by funding source or therapeutic area. Based on the 229 solely US-based studies, the participants overall were 76.7% White; 14.1% Black; 2.7% Asian; and 15% Hispanic. Inclusion of Black participants did not differ from the 2020 US census data; in contrast, the levels of Asian and Hispanic participation were below the corresponding census percentages. Interpretation: The past five years have seen an overall uptick in the equity of race/ethnicity reporting and inclusivity of clinical trials, as compared to previously reported data, presaging the potential acquisition of ever more powerful and meaningful results of such interventional studies going forward. Funding: Support for this study comes from the Hackensack Meridian Health Research Institute and the Hackensack Meridian School of Medicine. Research in context: Evidence before this studyClinical trials are a critical part of determining whether or not a medical (drug/device/biologic) or socio-behavioral intervention is safe and truly effective. Through their use, scientific understanding is advanced and, ideally, human health is improved. To gain the most impactful information from a clinical trial, it should be sufficiently representative, that is, should enroll an adequate number of participants, and include a diverse population. Without such inclusion, the study is of only limited generalizability. Efforts are underway by funders, sites, and other stakeholders, to enhance reporting and promote inclusive enrollment. The extent to which such attempts are yielding results - at least for clinical trials in the state of New Jersey - is the focus of this data-driven analysis. The ClinicalTrials.gov registry database was carefully mined for the information contained in this report.Added value of this studyOur analysis of clinical trials initiated in the state of New Jersey and conducted there or elsewhere in the US reveals several positive trends. Our 5-year snapshot reveals that a very large percentage of trials report on race/ethnicity - and inclusivity is improving. While there is still some way to go to have the demographic numbers in these trials match US census values, our results suggest that recent efforts are having an effect.Implications of all the available evidenceFor myriad reasons, clinical trials have not enjoyed the public's universal trust over the years. In many ways, medicine moves at the speed of trust - without it, the promise of modern healthcare is brought into question. Clinical trials must include a commitment to diverse enrollment pools and equitable reporting under the law. Creating a legacy of trust - through greater inclusivity in clinical trials and more transparent reporting of results - will begin to heal the divide and engender faith in modern medicine and today's healthcare system. It would also allow for the desired far-reaching generalizability of results across patient populations. To better appreciate what needs to be done going forward, we must truly understand the state of clinical trials reporting and demographic inclusion. This report initiates such an analysis, by carefully documenting how New Jersey's clinical trials are performing. By virtue of its location (e.g., proximity to the cities of New York and Philadelphia) the state is part of a large biopharma cluster and healthcare nexus; it is critical that it performs well with respect to adopting/adhering to updated clinical trial guideline mandates. This report provides a glimpse - an important first look - into the state of clinical trials in New Jersey - from 2017 through 2022.

An explorative assessment of ChatGPT as an aid in medical education: Use it with caution.

OBJECTIVE: To explore the use of ChatGPT by educators and students in a medical school setting. METHOD: This study used the public version of ChatGPT launched by OpenAI on November 30, 2022 (https://openai.com/blog/chatgpt/). We employed prompts to ask ChatGPT to 1) generate a content outline for a session on the topics of cholesterol, lipoproteins, and hyperlipidemia for medical students; 2) produce a list of learning objectives for the session; and 3) write assessment questions with and without clinical vignettes related to the identified learning objectives. We assessed the responses by ChatGPT for accuracy and reliability to determine the potential of the chatbot as an aid to educators and as a "know-it-all" medical information provider for students. RESULTS: ChatGPT can function as an aid to educators, but it is not yet suitable as a reliable information resource for educators and medical students. CONCLUSION: ChatGPT can be a useful tool to assist medical educators in drafting course and session content outlines and create assessment questions. At the same time, caution must be taken as ChatGPT is prone to providing incorrect information; expert oversight and caution are necessary to ensure the information generated is accurate and beneficial to students. Therefore, it is premature for medical students to use the current version of ChatGPT as a "know-it-all" information provider. In the future, medical educators should work with programming experts to explore and grow the full potential of AI in medical education.

Leveraging the COVID-19 Research Spike to Provide Medical Students with Practical Experience in Data Appraisal and Grant Review.

In April and May 2020, a group of students and professors from the Hackensack Meridian School of Medicine (HMSOM) created an elective to review pre-selected, de-identified COVID-19-related research proposals by physicians and researchers within the Hackensack Meridian Health (HMH) network. Students discussed and rated each proposal's significance, innovation, and approach using grading criteria that paralleled the National Institute of Health's (NIH) study section-based grant review process. In discussing these topics under the guidance of faculty with experience in writing and reviewing research grants, students gained a better understanding of what constitutes a quality research study and a compelling grant proposal.

Microglial Inflammation and Cognitive Dysfunction in Comorbid Rat Models of Striatal Ischemic Stroke and Alzheimer's Disease: Effects of Antioxidant Catalase-SKL on Behavioral and Cellular Pathology.

Ischemic stroke often co-occurs with Alzheimer's disease (AD) leading to a worsened clinical outcome. Neuroinflammation is a critical process implicated in AD and ischemic pathology, associated with cognitive decline. We sought to investigate the combined effects of ischemic stroke induced by endothelin-1 injection in two AD rat models, using motor function, memory and microglial inflammation in the basal forebrain and striatum as readouts. In addition, we sought to determine the effectiveness of the antioxidant biologic CAT-SKL in one of the models. The early AD model employed the bilateral intracerebroventricular injections of the toxic ß-amyloid peptide Aß25-35, the prodromal AD model used the transgenic Fischer 344 rat overexpressing a pathological mutant human amyloid precursor protein. Motor function was assessed using a cylinder, modified sticky tape and beam-walk tasks; learning and memory were tested in the Morris water maze. Microglial activation was examined using immunohistochemistry. Aß25-35 toxicity and stroke combination greatly increased microglial inflammation in the basal forebrain. Prodromal AD-pathology coupled with ischemia in the transgenic rat resulted in a greater microgliosis in the striatum. Combined transgenic rats showed balance alterations, comorbid Aß25-35 rats showed a transient sensorimotor deficit, and both demonstrated spatial reference memory deficit. CAT-SKL treatment ameliorated memory impairment and basal forebrain microgliosis in Aß25-35 rats with stroke. Our results suggest that neuroinflammation could be one of the early processes underlying the interaction of AD with stroke and contributing to the cognitive impairment, and that therapies such as antioxidant CAT-SKL could be a potential therapeutic strategy.

Discharged COVID-19 patients testing positive again for SARS-CoV-2 RNA: A minireview of published studies from China.

In the ongoing coronavirus disease 2019 (COVID-19) pandemic, one potential cause of concern is that some discharged COVID-19 patients are testing positive again for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. To better understand what is happening and to provide public health policy planners and clinicians timely information, we have searched and reviewed published studies about discharged patients testing positive again for the SARS-CoV-2 RNA. Our search found 12 reports, all of which described patients in China. Our review of these reports indicates the presence of discharged patients who remain asymptomatic but test positive. However, it is unclear whether they are contagious because a positive reverse transcriptase - polymerase chain reaction (RT- PCR) test does not necessarily indicate the presence of replicating and transmissible virus. Our review suggests the need for timely, parallel testing of different samples, including, for example, fecal specimens, from COVID-19 patients before and after they are discharged from hospitals.

Clinical Outcomes of COVID-19 Patients with Pre-existing, Compromised Immune Systems: A Review of Case Reports.

In the ongoing COVID-19 pandemic, all COVID-19 patients are naïve patients as it is the first-time humans have been exposed to the SARS-CoV-2 virus. As with exposure to many viruses, individuals with pre-existing, compromised immune systems may be at increased risk of developing severe symptoms and/or dying because of (SARS-CoV-2) infection. To learn more about such individuals, we conducted a search and review of published reports on the clinical characteristics and outcomes of COVID-19 patients with pre-existing, compromised immune systems. Here we present our review of patients who possess pre-existing primary antibody deficiency (PAD) and those who are organ transplant recipients on maintenance immunosuppressants. Our review indicates different clinical outcomes for the patients with pre-existing PAD, depending on the underlying causes. For organ transplant recipients, drug-induced immune suppression alone does not appear to enhance COVID-19 mortality risk - rather, advanced age, comorbidities, and the development of secondary complications appears required.

Treating triple negative breast cancer cells with erlotinib plus a select antioxidant overcomes drug resistance by targeting cancer cell heterogeneity.

Among breast cancer patients, those diagnosed with the triple-negative breast cancer (TNBC) subtype have the worst prog-nosis. TNBC does not express estrogen receptor-alpha, progesterone receptor, or the HER2 oncogene; therefore, TNBC lacks targets for molecularly-guided therapies. The concept that EGFR oncogene inhibitor drugs could be used as targeted treatment against TNBC has been put forth based on estimates that 30-60% of TNBC express high levels of EGFR. However, results from clinical trials testing EGFR inhibitors, alone or in combination with cytotoxic chemotherapy, did not improve patient outcomes. Results herein offer an explanation as to why EGFR inhibitors failed TNBC patients and support how combining a select antioxidant and an EGFR-specific small molecule kinase inhibitor (SMKI) could be an effective, novel therapeutic strategy. Treatment with CAT-SKL-a re-engineered protein form of the antioxidant enzyme catalase-inhibited cancer stem-like cells (CSCs), and treatment with the EGFR-specific SMKI erlotinib inhibited non-CSCs. Thus, combining the antioxidant CAT-SKL with erlotinib targeted both CSCs and bulk cancer cells in cultures of EGFR-expressing TNBC-derived cells. We also report evidence that the mechanism for CAT-SKL inhibition of CSCs may depend on antioxidant-induced downregulation of a short alternative mRNA splicing variant of the methyl-CpG binding domain 2 gene, isoform MBD2c.

Targeted Antioxidant, Catalase-SKL, Reduces Beta-Amyloid Toxicity in the Rat Brain.

Accumulation of beta-amyloid (Aß) in the brain has been implicated as a major contributor to the cellular pathology and cognitive impairment observed in Alzheimer's disease. Beta-amyloid may exert its toxic effects by increasing reactive oxygen species and neuroinflammation in the brain. This study set out to investigate whether a genetically engineered derivative of the peroxisomal antioxidant enzyme catalase (CAT-SKL), is able to reduce the toxicity induced by intracerebroventricular injection of Aß25-35 in the mature rat brain. Histopathological and immunohistochemical analyses were used to evaluate neuroinflammation, and neuronal loss. Spatial learning and reference memory was assessed using the Morris water maze. CAT-SKL treatment was able to reduce the pathology induced by Aß25-35 toxicity by significantly decreasing microglia activation in the basal forebrain and thalamus, and reducing cholinergic loss in the basal forebrain. Aß25-35 animals showed deficits in long-term reference memory in the Morris water maze, while Aß25-35 animals treated with CAT-SKL did not demonstrate long-term memory impairments. This preclinical data provides support for the use of CAT-SKL in reducing neuroinflammation and long-term reference memory deficits induced by Aß25-35.

Peroxisome biogenesis in mammalian cells: The impact of genes and environment.

The initiation and progression of many human diseases are mediated by a complex interplay of genetic, epigenetic, and environmental factors. As all diseases begin with an imbalance at the cellular level, it is essential to understand how various types of molecular aberrations, metabolic changes, and environmental stressors function as switching points in essential communication networks. In recent years, peroxisomes have emerged as important intracellular hubs for redox-, lipid-, inflammatory-, and nucleic acid-mediated signaling pathways. In this review, we focus on how nature and nurture modulate peroxisome biogenesis and function in mammalian cells. First, we review emerging evidence that changes in peroxisome activity can be linked to the epigenetic regulation of cell function. Next, we outline how defects in peroxisome biogenesis may directly impact cellular pathways involved in the development of disease. In addition, we discuss how changes in the cellular microenvironment can modulate peroxisome biogenesis and function. Finally, given the importance of peroxisome function in multiple aspects of health, disease, and aging, we highlight the need for more research in this still understudied field.

Catalase therapy corrects oxidative stress-induced pathophysiology in incipient diabetic retinopathy.

PURPOSE: Preclinical studies have highlighted retinal oxidative stress in the pathogenesis of diabetic retinopathy. We evaluated whether a treatment designed to enhance cellular catalase reduces oxidative stress in retinal cells cultured in high glucose and in diabetic mice corrects an imaging biomarker responsive to antioxidant therapy (manganese-enhanced magnetic resonance imaging [MEMRI]). METHODS: Human retinal Müller and pigment epithelial cells were chronically exposed to normal or high glucose levels and treated with a cell-penetrating derivative of the peroxisomal enzyme catalase (called CAT-SKL). Hydrogen peroxide (H2O2) levels were measured using a quantitative fluorescence-based assay. For in vivo studies, streptozotocin (STZ)-induced diabetic C57Bl/6 mice were treated subcutaneously once a week for 3 to 4 months with CAT-SKL; untreated age-matched nondiabetic controls and untreated diabetic mice also were studied. MEMRI was used to analytically assess the efficacy of CAT-SKL treatment on diabetes-evoked oxidative stress-related pathophysiology in vivo. Similar analyses were performed with difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase. RESULTS: After catalase transduction, high glucose-induced peroxide production was significantly lowered in both human retinal cell lines. In diabetic mice in vivo, subnormal intraretinal uptake of manganese was significantly improved by catalase supplementation. In addition, in the peroxisome-rich liver of treated mice catalase enzyme activity increased and oxidative damage (as measured by lipid peroxidation) declined. On the other hand, DFMO was largely without effect in these in vitro or in vivo assays. CONCLUSIONS: This proof-of-concept study raises the possibility that augmentation of catalase is a therapy for treating the retinal oxidative stress associated with diabetic retinopathy.

Amyloid-beta neuroprotection mediated by a targeted antioxidant.

Amyloid-beta (Aß)-induced neurotoxicity is a major contributor to the pathologies associated with Alzheimer's disease (AD). The formation of reactive oxygen species (ROS), an early response induced by the peptide and oligomeric derivatives of Aß, plays a significant role in effecting cellular pathogenesis. Here we employ particularly toxic forms of Aß with cultured primary cortical/hippocampal neurons to elicit ROS and drive cellular dysfunction. To prevent and even reverse such effects, we utilized a cell-penetrating, peroxisome-targeted, protein biologic--called CAT-SKL. We show the recombinant enzyme enters neurons, reverses Aß-induced oxidative stress, and increases cell viability. Dramatic restorative effects on damaged neuronal processes were also observed. In addition, we used DNA microarrays to determine Aß's effects on gene expression in neurons, as well as the ability of CAT-SKL to modify such Aß-induced expression profiles. Our results suggest that CAT-SKL, a targeted antioxidant, may represent a new therapeutic approach for treatment of disorders, like Alzheimer's disease, that are driven through oxidative stress. Preclinical testing is ongoing.

A targeted enzyme approach to sensitization of tyrosine kinase inhibitor-resistant breast cancer cells.

Gefitinib is an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) of potential use in patients with breast cancer. Unfortunately, in clinical studies, gefitinib is often ineffective indicating that resistance to EGFR inhibitors may be a common occurrence in cancer of the breast. EGFR has been shown to be overexpressed in breast cancer, and in particular remains hyperphosphorylated in cell lines such as MDA-MB-468 that are resistant to EGFR inhibitors. Here, we investigate the cause of this sustained phosphorylation and the molecular basis for the ineffectiveness of gefitinib. We show that reactive oxygen species (ROS), known to damage cellular macromolecules and to modulate signaling cascades in a variety of human diseases including cancers, appear to play a critical role in mediating EGFR TKI-resistance. Furthermore, elimination of these ROS through use of a cell-penetrating catalase derivative sensitizes the cells to gefitinib. These results suggest a new approach for the treatment of TKI-resistant breast cancer patients specifically, the targeting of ROS and attendant downstream oxidative stress and their effects on signaling cascades.

Peroxisomes, oxidative stress, and inflammation.

Peroxisomes are intracellular organelles mediating a wide variety of biosynthetic and biodegradative reactions. Included among these are the metabolism of hydrogen peroxide and other reactive species, molecules whose levels help define the oxidative state of cells. Loss of oxidative equilibrium in cells of tissues and organs potentiates inflammatory responses which can ultimately trigger human disease. The goal of this article is to review evidence for connections between peroxisome function, oxidative stress, and inflammation in the context of human health and degenerative disease. Dysregulated points in this nexus are identified and potential remedial approaches are presented.

Peroxisomes, cell senescence, and rates of aging.

The peroxisome is functionally integrated into an exquisitely complex network of communicating endomembranes which is only beginning to be appreciated. Despite great advances in identifying essential components and characterizing molecular mechanisms associated with the organelle's biogenesis and function, there is a large gap in our understanding of how peroxisomes are incorporated into metabolic pathways and subcellular communication networks, how they contribute to cellular aging, and where their influence is manifested on the initiation and progression of degenerative disease. In this review, we summarize recent evidence pointing to the organelle as an important regulator of cellular redox balance with potentially far-reaching effects on cell aging and the genesis of human disease. The roles of the organelle in lipid homeostasis, anaplerotic reactions, and other critical metabolic and biochemical processes are addressed elsewhere in this volume. This article is part of a Special Issue entitled: Metabolic Functions and Biogenesis of Peroxisomes in Health and Disease.

Intraperoxisomal redox balance in mammalian cells: oxidative stress and interorganellar cross-talk.

Reactive oxygen species (ROS) are at once unsought by-products of metabolism and critical regulators of multiple intracellular signaling cascades. In nonphotosynthetic eukaryotic cells, mitochondria are well-investigated major sites of ROS generation and related signal initiation. Peroxisomes are also capable of ROS generation, but their contribution to cellular oxidation-reduction (redox) balance and signaling events are far less well understood. In this study, we use a redox-sensitive variant of enhanced green fluorescent protein (roGFP2-PTS1) to monitor the state of the peroxisomal matrix in mammalian cells. We show that intraperoxisomal redox status is strongly influenced by environmental growth conditions. Furthermore, disturbances in peroxisomal redox balance, although not necessarily correlated with the age of the organelle, may trigger its degradation. We also demonstrate that the mitochondrial redox balance is perturbed in catalase-deficient cells and upon generation of excess ROS inside peroxisomes. Peroxisomes are found to resist oxidative stress generated elsewhere in the cell but are affected when the burden originates within the organelle. These results suggest a potential broader role for the peroxisome in cellular aging and the initiation of age-related degenerative disease.

Targeted intracellular catalase delivery protects neonatal rat myocytes from hypoxia-reoxygenation and ischemia-reperfusion injury.

UNLABELLED: Hypoxia followed by reoxygenation and ischemia reperfusion cause cell death in neonatal rat ventricular myocytes primarily through the generation of oxidative stress. Extracellular catalase has not been effective in reducing or eliminating ischemia reperfusion- or hypoxia-reoxygenation-induced cell death due both to extracellular degradation and to poor cellular uptake. AIMS: (1) To determine whether a cell-penetrating catalase derivative with enhanced peroxisome targeting efficiency (catalase-SKL) increases intracellular levels of the antioxidant enzyme in neonatal rat ventricular myocytes; and (2) to determine whether catalase-SKL protects against both hypoxia-reoxygenation and ischemia reperfusion injury. METHODS: Neonatal rat ventricular myocytes were subjected to 3 or 6 h of hypoxia-reoxygenation or to 1 h of ischemia reperfusion. Extracellular catalase concentration, activity, and subcellular distribution were determined using standard techniques. Reactive oxygen species and related oxidative stress were visualized using 2',7'-dichlorofluorescin diacetate. Cell death was measured using trypan blue exclusion or lactate dehydrogenase release assays. RESULTS: Extracellular catalase activity was higher in (catalase-SKL) transduced myocytes, was concentrated in a membranous cellular fraction, and potently inhibited oxidative stress. In contrast to nontransducible (unmodified) extracellular catalase, catalase-SKL-treated myocytes were protected against both hypoxia-reoxygenation and ischemia reperfusion. CONCLUSIONS: (1) Catalase-SKL increased myocyte extracellular catalase content and activity and dramatically increased resistance to hydrogen peroxide-induced oxidation; (2) catalase-SKL protects against both hypoxia-reoxygenation and ischemia reperfusion; (3) catalase-SKL may represent a new therapeutic approach to protect hearts against myocardial hypoxia-reoxygenation or ischemia reperfusion.

Peroxisome metabolism and cellular aging.

The essential role of peroxisomes in fatty acid oxidation, anaplerotic metabolism, and hydrogen peroxide turnover is well established. Recent findings suggest that these and other related biochemical processes governed by the organelle may also play a critical role in regulating cellular aging. The goal of this review is to summarize and integrate into a model the evidence that peroxisome metabolism actually helps define the replicative and chronological age of a eukaryotic cell. In this model, peroxisomal reactive oxygen species (ROS) are seen as altering organelle biogenesis and function, and eliciting changes in the dynamic communication networks that exist between peroxisomes and other cellular compartments. At low levels, peroxisomal ROS activate an anti-aging program in the cell; at concentrations beyond a specific threshold, a pro-aging course is triggered.

Diabetes increases susceptibility of primary cultures of rat proximal tubular cells to chemically induced injury.

Diabetic nephropathy is characterized by increased oxidative stress and mitochondrial dysfunction. In the present study, we prepared primary cultures of proximal tubular (PT) cells from diabetic rats 30 days after an ip injection of streptozotocin and compared their susceptibility to oxidants (tert-butyl hydroperoxide, methyl vinyl ketone) and a mitochondrial toxicant (antimycin A) with that of PT cells isolated from age-matched control rats, to test the hypothesis that PT cells from diabetic rats exhibit more cellular and mitochondrial injury than those from control rats when exposed to these toxicants. PT cells from diabetic rats exhibited higher basal levels of reactive oxygen species (ROS) and higher mitochondrial membrane potential, demonstrating that the PT cells maintain the diabetic phenotype in primary culture. Incubation with either the oxidants or mitochondrial toxicant resulted in greater necrotic and apoptotic cell death, greater evidence of morphological damage, greater increases in ROS, and greater decreases in mitochondrial membrane potential in PT cells from diabetic rats than in those from control rats. Pretreatment with either the antioxidant N-acetyl-l-cysteine or a catalase mimetic provided equivalent protection of PT cells from both diabetic and control rats. Despite the greater susceptibility to oxidative and mitochondrial injury, both cytoplasmic and mitochondrial glutathione concentrations were markedly higher in PT cells from diabetic rats, suggesting an upregulation of antioxidant processes in diabetic kidney. These results support the hypothesis that primary cultures of PT cells from diabetic rats are a valid model in which to study renal cellular function in the diabetic state.

A role for hydrogen peroxide in the pro-apoptotic effects of photodynamic therapy.

Although the first reactive oxygen species (ROS) formed during irradiation of photosensitized cells is almost invariably singlet molecular oxygen (1O2), other ROS have been implicated in the phototoxic effects of photodynamic therapy (PDT). Among these are superoxide anion radical (*O2(-)), hydrogen peroxide (H2O2) and hydroxyl radical (*OH). In this study, we investigated the role of H2O2 in the pro-apoptotic response to PDT in murine leukemia P388 cells. A primary route for detoxification of cellular H2O2 involves the peroxisomal enzyme catalase. Inhibition of catalase activity by 3-amino-1,2,4-triazole led to an increased apoptotic response. PDT-induced apoptosis was impaired by addition of an exogenous recombinant catalase analog (CAT-skl) that was specifically designed to enter cells and more efficiently localize in peroxisomes. A similar effect was observed upon addition of 2,2'-bipyridine, a reagent that can chelate Fe+2, a co-factor in the Fenton reaction that results in the conversion of H2O2 to *OH. These results provide evidence that formation of H2O2 during irradiation of photosensitized cells contributes to PDT efficacy.

Progeric effects of catalase inactivation in human cells.

Peroxisomes generate hydrogen peroxide, a reactive oxygen species, as part of their normal metabolism. A number of pathological situations exist in which the organelle's capacity to degrade the potentially toxic oxidant is compromised. It is the peroxidase, catalase, which largely determines the functional antioxidant capacity of the organelle, and it is this enzyme that is affected in aging, in certain diseases, and in response to exposure to specific chemical agents. To more tightly control the enzymatic activity of peroxisomal catalase and carefully document the effects of its impaired action on human cells, we employed the inhibitor 3-amino-1,2,4-triazole. We show that by chronically reducing catalase activity to approximately 38% of normal, cells respond in a dramatic manner, displaying a cascade of accelerated aging reactions. Hydrogen peroxide and related reactive oxygen species are produced, protein and DNA are oxidatively damaged, import into peroxisomes and organelle biogenesis is corrupted, and matrix metalloproteinases are hyper-secreted from cells. In addition, mitochondria are functionally impaired, losing their ability to maintain a membrane potential and synthesize reactive oxygen species themselves. These latter results suggest an important redox-regulated connection between the two organelle systems, a topic of considerable interest for future study.