Biology subjects

Facundo, H. T.

Publications and source records attributed to Facundo, H. T..

7 recordsLinked to original sources

bioRxiv2026

Caloric Restriction Promotes Ischemia/Reperfusion Cardioprotection Through Increased Mitochondrial Na+/Ca2+ Exchange

Caloric restriction (CR) protects against cardiac ischemia/reperfusion (I/R) injury, but the underlying mechanisms remain incompletely understood. Since mitochondrial Ca2+ overload and redox imbalance is a major driver of cardiac damage during reperfusion, we investigated if enhanced mitochondrial Ca2+ efflux contributes toward CR-induced cardioprotection. Rats were subjected to 16 weeks of ad libitum (AL) feeding or 40% caloric restriction. CR significantly increased mitochondrial Ca2+ retention capacity when Na+ ions were present, reduced H2O2 release, and increased the expression of proteins related to mitochondrial Ca2+ extrusion. In cardiomyocytes exposed to serum from CR rats, Ca2+ retention capacity also markedly increased, as well as Ca2+ efflux and the expression of extrusion proteins NCLX and TMEM65. Following I/R, CR hearts exhibited improved functional recovery accompanied by enhanced retention and increased mitochondrial Ca2+ efflux activity, as well as reduced H2O2 release compared to AL controls. Inhibition of mitochondrial Na+/Ca2+ exchange abolished the mitochondrial adaptive effects of CR, eliminating its protection against damage in cardiomyocytes and perfused hearts. These findings demonstrate that CR protects the heart from I/R injury by enhancing CGP-sensitive Na+-dependent mitochondrial Ca2+ efflux, preserving mitochondrial function, limiting redox imbalance, and improving post-ischemic cardiac recovery.

biochemistry↗

bioRxiv2026

Vitamin D3 Regulates Mitochondrial Function and Redox Homeostasis in the Brain

Mitochondria are essential for metabolic homeostasis and neuronal function, extending beyond ATP production to roles in cell signaling, inflammation, and stress responses. Mitochondrial dysfunction, marked by abnormal morphology, ATP deficiency, and oxidative stress, is a key feature of aging-related diseases and neurodegenerative disorders like Parkinsons. Given the importance of mitochondrial homeostasis to brain function, this study aimed to determine the possible vitamin D (VD3) effects on mitochondrial susceptibility to Ca2+-induced mitochondrial permeability transition pore (mPTP), bioenergetics in brain mitochondria, and redox balance. We demonstrated that VD3 protects isolated brain mitochondria. Male rats were divided into control and VD3-treated groups. Brain mitochondria were isolated for assessments of Ca2+-induced mitochondrial swelling secondary to MPTP opening, oxygen consumption (states 3 - ADP-stimulated and state 4 - in the presence of oligomycin), and the respiratory control ratio (RCR). Oxidative stress parameters (nitrite and lipid peroxidation), superoxide dismutase (SOD) activity, and reduced glutathione (GSH) levels were also evaluated. The results revealed that VD3 treatment blocked Ca2+-induced mitochondrial swelling secondary to MPTP opening. Additionally, VD3 improved mitochondrial RCR compared to controls, in the presence of complex I (malate/glutamate) and complex II (succinate) substrates, reduced mitochondrial succinate-driven H2O2 release, and enhanced SOD activity and GSH levels. These changes occurred in parallel with decreased nitrite and TBARS formation. These results suggest that vitamin D{square} confers mitochondrial neuroprotection, emphasizing its prospective role in maintaining neuronal homeostasis and mitigating neurodegenerative processes.

biochemistry↗

bioRxiv2026

Redoxyme: a lightweight graphical user interface for standardized calculation of antioxidant enzyme activities

Oxidative stress results from excessive accumulation of reactive oxygen species (ROS) and plays a central role in numerous physiological and pathological processes. Accurate quantification of antioxidant enzyme activities is therefore essential in redox biology research. However, data analysis for commonly used assays, such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), is frequently performed using spreadsheets or manual calculations, which are time-consuming and prone to error. Here, we present Redoxyme, a free, open-source, Python-based graphical user interface designed to standardize and automate the calculation of antioxidant enzyme activities. The software integrates protein normalization, enzyme-specific calculation routines, data visualization, and Excel export within an intuitive interface that does not require programming expertise. Redoxyme was validated using experimental data obtained from animal tissues (rats and mice), demonstrating excellent agreement with manual calculations and established analytical methods. Redoxyme provides a practical solution for improving reproducibility and efficiency in antioxidant enzyme activity analysis. The software is currently distributed as a standalone executable for Windows (locally installed), and an interactive web-based calculator implemented in Streamlit, enabling direct use without local installation. The source code and version-controlled development history are openly accessible via GitHub, promoting transparency, reproducibility, community-driven improvements, and can, in principle, be adapted for other operating systems. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=63 SRC="FIGDIR/small/703993v2_ufig1.gif" ALT="Figure 1"> View larger version (10K): org.highwire.dtl.DTLVardef@120cc68org.highwire.dtl.DTLVardef@4be246org.highwire.dtl.DTLVardef@1f47134org.highwire.dtl.DTLVardef@1341100_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2025

Mitochondrial Electron Transport Chain Disruption and Oxidative Stress in Lipopolysaccharide-Induced Cardiac Dysfunction in rats and mice

Sepsis, characterized by severe systemic inflammation and an excessive immune response to infection, is frequently triggered by bacterial endotoxins like lipopolysaccharide (LPS) from Gram-negative bacteria. Moreover, sepsis-induced cardiac dysfunction remains a leading cause of mortality. This study aims to elucidate the effects of LPS-induced cardiac injury on mitochondrial damage, oxidative stress, and subsequent cardiac dysfunction. LPS injections (in rats and mice) for three days (1.5 mg/kg) impacted the body weight and increased cardiac TNF-. Additionally, it decreased mitochondrial complexes I and II activities while complexes III and IV remained unaffected. Disturbed in mitochondrial electron transport chain leads to an increase in reactive oxygen species (ROS). Indeed, LPS treatment significantly increased mitochondrial hydrogen peroxide production, reduced the activity of antioxidant enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase activity. This was accompanied by decreased mitochondrial and cytosolic sulfhydryl proteins and parallel increased cellular lipid peroxidation in the presence or absence of Fe2+. LPS-treated samples had increased glutathione s-transferase activity, which may be an attempt of the cell to remove toxic lipid peroxidation products. In a more acute Langendorff-perfused rat hearts, LPS infusion (0.5 g/mL) induced a significant elevation in left ventricular end-diastolic pressure and a decrease in left ventricular developed pressure. These findings elucidate the harmful mitochondrial and oxidative effects of LPS in cardiac tissue and could help the development of targeted therapies to mitigate the adverse effects of sepsis-induced cardiac dysfunction.

biochemistry↗

bioRxiv2023

Competitive interaction between ATP and GTP regulates mitochondrial ATP-sensitive potassium channels

Mitochondrial ATP-sensitive K+ channels (mitoKATP) have been recently characterized structurally, and possess a protein through which K+ enters mitochondria (MitoKIR), and a regulatory subunit (mitoSUR). The mitoSUR regulatory subunit is an ATP-binding cassette (ABC) protein isoform 8 (ABCB8). Opening of these channels is known to be cardioprotective, but the molecular and physiological mechanisms that activate them are not fully known. Here, to better understand the molecular and physiological mechanisms of activators (GTP) and inhibitors (ATP) on the activity of mitoKATP, we exposed isolated mitochondria to both nucleotides. We also used molecular docking directed to the nucleotide-binding domain of human ABCB8/mitoSUR to test a comparative model of ATP and GTP effects. As expected, we find that ATP dose-dependently inhibits mitoKATP activity (IC50 = 21.24 {+/-} 1.4 mM). However, simultaneous exposure of mitochondria to GTP dose-dependently (EC50 = 13.19 {+/-} 1.33 mM) reversed ATP inhibition. Pharmacological and computational studies suggest that GTP reverses ATP activity competitively. Docking directed to the site of crystallized ADP reveals that both nucleotides bind to mitoSUR with high affinity, with their phosphates directed to the Mg2+ ion and the walker A motif of the protein (SGGGKTT). These effects, when combined, result in GTP binding, ATP displacement, mitochondrial ATP-sensitive K+ transport, and lower formation of reactive oxygen species. Overall, our findings demonstrate the basis for ATP and GTP binding in mitoSUR using a combination of biochemical, pharmacological, and computational experiments. Future studies may reveal the extent to which the balance between ATP and GTP actions contribute toward cardioprotection against ischemic events.

pharmacology and toxicology↗

bioRxiv2022

Effects of calorie restriction on reactive oxygen species production by mitochondrial reverse electron transport, mitochondrial permeability transition pore, and beta-adrenergic stimulation during cardiac hypertrophy

Calorie restriction is a nutritional intervention that reproducibly protects against the maladaptive consequences of cardiovascular diseases. Pathological cardiac hypertrophy leads to cellular growth, dysfunction (with mitochondrial dysregulation), and oxidative stress. The mechanisms behind the cardiovascular protective effects of calorie restriction are still under investigation. In this study, we addressed the impact of calorie restriction on mitochondria, oxidative stress markers, and {beta}-adrenergic signaling during cardiac hypertrophy. This dietetic intervention prevented cardiac protein elevation, decreased atrial natriuretic peptide levels, and blocked the increase in heart weight per tibia length index seen in isoproterenol-induced cardiac hypertrophy. Our data suggest that inhibition of cardiac pathological growth by calorie restriction is accompanied by a lower mitochondrial reactive oxygen species formation and improved mitochondrial content. We also found that superoxide dismutase and glutathione peroxidase activities negatively correlate with cardiac hypertrophy. Calorie restriction also attenuated the opening of the Ca2+-induced mitochondrial permeability transition pore in mitochondria isolated from isoproterenol-treated mice. Isoproterenol (a {beta}-agonist) increases cardiac rate (chronotropic response) and force of contraction (inotropic response). Given the nature of cardiac hypertrophy induction by isoproterenol, we tested whether calorie restriction could change the cardiac {beta}-adrenergic sensitivity. Using isolated rat hearts in a langendorff system, we found that calorie restriction mice (similar to controls) have preserved {beta}-adrenergic signaling. On the flipside, hypertrophic hearts (treated for seven days with isoproterenol) were insensitive to {beta}-adrenergic activation using isoproterenol (50 nM). Despite protecting against cardiac hypertrophy, calorie restriction did not alter the lack of responsiveness to isoproterenol of isolated hearts harvested from isoproterenol-treated rats. These results suggest (through a series of mitochondrial, oxidative stress, and cardiac hemodynamic studies) that calorie restriction possesses beneficial effects against hypertrophic cardiomyopathy. However, it may lack effects on some of the hypertrophic consequences, such as {beta}-adrenergic signaling repression.

biochemistry↗

bioRxiv2021

Calorie Restriction Maintains Mitochondrial Function and Redox Balance Avoiding Lipidomic Reprogramming during Isoproterenol-Induced Cardiac Hypertrophy

Cardiac hypertrophy induces a metabolic shift, leading to a preferential consumption of glucose (over fatty acids) to support the high energetic demand. Typically, health cardiac tissue utilizes more fat than any other organ. Calorie restriction is a dietary procedure that induces health benefits and lifespan extension in many organisms. Given the beneficial effects of calorie restriction and the metabolic dysregulation seen during cardiac hypertrophy, we hypothesized that calorie restriction prevents cardiac hypertrophy, lipid, mitochondrial, and redox dysregulations. Strikingly, calorie restriction reversed isoproterenol-induced cardiac hypertrophy, lowered succinate driven mitochondrial H2O2 production, improved mitochondrial function (indicated as a higher Respiratory Control Ratio - RCR) and avoided mitochondrial superoxide dismutase (MnSOD) and glutathione peroxidase (GPX) repression. To gain insight into how calorie restriction could interfere with the metabolic changes induced by cardiac hypertrophy, we performed lipidomic profiling. Calorie restriction protected against the consumption of several triglycerides (TG) linked to unsaturated fatty acids, and the accumulation of TGs containing saturated fatty acids observed in hypertrophic samples. Cardiac hypertrophy induced an increase in ceramides, phosphoethanolamines and acylcarnitines (12:0, 14:0, 16:0 and 18:0) that were also reversed by calorie restriction. Altogether, our data demonstrate that hypertrophy changes the cardiac lipidome, causes mitochondrial disturbances and oxidative stress. All these changes are prevented by calorie restriction intervention in vivo. This study uncovers calorie restriction as a resource protect cardiac tissue and prevent cardiac hypertrophy-induced lipidomic remodeling.

biochemistry↗