The 8-oxo-deoxyguanosine glycosylase increases its migration to mitochondria in compensated cardiac hypertrophy

The role of DNA and RNA guanosine oxidation in cardiovascular diseases

Cardiovascular diseases (CVD) persist as a prominent cause of mortality worldwide, with oxidative stress constituting a pivotal contributory element. The oxidative modification of guanosine, specifically 8-oxoguanine, has emerged as a crucial biomarker for oxidative stress, providing novel insights into the molecular underpinnings of CVD. 8-Oxoguanine can be directly generated at the DNA (8-oxo-dG) and RNA (8-oxo-G) levels, as well as at the free nucleotide level (8-oxo-dGTP or 8-oxo-GTP), which are produced and can be integrated through DNA replication or RNA transcription. When exposed to oxidative stress, guanine is more readily produced in RNA than in DNA. A burgeoning body of research surrounds 8-oxoguanine, exhibits its accumulation playing a pivotal role in the development of CVD. Therapeutic approaches targeting oxidative 8-Oxoguanine damage to DNA and RNA, encompassing the modulation of repair enzymes and the development of small molecule inhibitors, are anticipated to enhance CVD management. In conclusion, we explore the noteworthy elevation of 8-oxoguanine levels in patients with various cardiac conditions and deliberate upon the formation and regulation of 8-oxo-dG and 8-oxo-G under oxidative stress, as well as their function in CVD.

Sulforaphane Protects against Unilateral Ureteral Obstruction-Induced Renal Damage in Rats by Alleviating Mitochondrial and Lipid Metabolism Impairment

Unilateral ureteral obstruction (UUO) is an animal rodent model that allows the study of obstructive nephropathy in an accelerated manner. During UUO, tubular damage is induced, and alterations such as oxidative stress, inflammation, lipid metabolism, and mitochondrial impairment favor fibrosis development, leading to chronic kidney disease progression. Sulforaphane (SFN), an isothiocyanate derived from green cruciferous vegetables, might improve mitochondrial functions and lipid metabolism; however, its role in UUO has been poorly explored. Therefore, we aimed to determine the protective effect of SFN related to mitochondria and lipid metabolism in UUO. Our results showed that in UUO SFN decreased renal damage, attributed to increased mitochondrial biogenesis. We showed that SFN augmented peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α) and nuclear respiratory factor 1 (NRF1). The increase in biogenesis augmented the mitochondrial mass marker voltage-dependent anion channel (VDAC) and improved mitochondrial structure, as well as complex III (CIII), aconitase 2 (ACO2) and citrate synthase activities in UUO. In addition, lipid metabolism was improved, observed by the downregulation of cluster of differentiation 36 (CD36), sterol regulatory-element binding protein 1 (SREBP1), fatty acid synthase (FASN), and diacylglycerol O-acyltransferase 1 (DGAT1), which reduces triglyceride (TG) accumulation. Finally, restoring the mitochondrial structure reduced excessive fission by decreasing the fission protein dynamin-related protein-1 (DRP1). Autophagy flux was further restored by reducing beclin and sequestosome (p62) and increasing B-cell lymphoma 2 (Bcl2) and the ratio of microtubule-associated proteins 1A/1B light chain 3 II and I (LC3II/LC3I). These results reveal that SFN confers protection against UUO-induced kidney injury by targeting mitochondrial biogenesis, which also improves lipid metabolism.

8-Oxoguanine DNA Glycosylase (OGG1) Deficiency Exacerbates Doxorubicin-Induced Cardiac Dysfunction

Doxorubicin is an anthracycline widely used for the treatment of various cancers; however, the drug has a common deleterious side effect, namely a dose-dependent cardiotoxicity. Doxorubicin treatment increases the generation of reactive oxygen species, which leads to oxidative stress in the cardiac cells and ultimately DNA damage and cell death. The most common DNA lesion produced by oxidative stress is 7,8-dihydro-8-oxoguanine (8-oxoguanine), and the enzyme responsible for its repair is the 8-oxoguanine DNA glycosylase (OGG1), a base excision repair enzyme. Here, we show that the OGG1 deficiency has no major effect on cardiac function at baseline or with pressure overload; however, we found an exacerbation of cardiac dysfunction as well as a higher mortality in Ogg1 knockout mice treated with doxorubicin. Our transcriptomic analysis also showed a more extensive dysregulation of genes in the hearts of Ogg1 knockout mice with an enrichment of genes involved in inflammation. These results demonstrate that OGG1 attenuates doxorubicin-induced cardiotoxicity and thus plays a role in modulating drug-induced cardiomyopathy.

Resveratrol Prevents Right Ventricle Dysfunction, Calcium Mishandling, and Energetic Failure via SIRT3 Stimulation in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is characterized by pulmonary vessel remodeling; however, its severity and impact on survival depend on right ventricular (RV) failure. Resveratrol (RES), a polyphenol found in red wine, exhibits cardioprotective effects on RV dysfunction in PAH. However, most literature has focused on RES protective effect on lung vasculature; recent finding indicates that RES has a cardioprotective effect independent of pulmonary arterial pressure on RV dysfunction, although the underlying mechanism in RV has not been determined. Therefore, this study is aimed at evaluating sirtuin-3 (SIRT3) modulation by RES in RV using a monocrotaline- (MC-) induced PAH rat model. Myocyte function was evaluated by confocal microscopy as cell contractility, calcium signaling, and mitochondrial membrane potential (ΔΨm); cell energetics was assessed by high-resolution respirometry, and western blot and immunoprecipitation evaluated posttranslational modifications. PAH significantly affects mitochondrial function in RV; PAH is prone to mitochondrial permeability transition pore (mPTP) opening, thus decreasing the mitochondrial membrane potential. The compromised cellular energetics affects cardiomyocyte function by decreasing sarco-endoplasmic reticulum Ca²⁺-ATPase (SERCA) activity and delaying myofilament unbinding, disrupting cell relaxation. RES partially protects mitochondrial integrity by deacetylating cyclophilin-D, a critical component of the mPTP, increasing SIRT3 expression and activity and preventing mPTP opening. The preserved energetic capability rescues cell relaxation by maintaining SERCA activity. Avoiding Ca²⁺ transient and cell contractility mismatch by preserving mitochondrial function describes, for the first time, impairment in excitation-contraction-energetics coupling in RV failure. These results highlight the importance of mitochondrial energetics and mPTP in PAH.

Metastatic TNBC is closely associated with a fused mitochondrial morphology and a glycolytic and lipogenic metabolism

Mitochondria modify their function and morphology to satisfy the bioenergetic demand of the cells. Cancer cells take advantage of these features to sustain their metabolic, proliferative, metastatic, and survival necessities. Understanding the morphological changes to mitochondria in the different grades of triple-negative breast cancer (TNBC) could help to design new treatments. Consequently, this research explored mitochondrial morphology and the gene expression of some proteins related to mitochondrial dynamics, as well as proteins associated with oxidative and non-oxidative metabolism in metastatic and non-metastatic TNBC. We found that mitochondrial morphology and metabolism are different in metastatic and non-metastatic TNBC. In metastatic TNBC, there is overexpression of genes related to mitochondrial dynamics, fatty-acid metabolism, and glycolysis. These features are accompanied by a fused mitochondrial morphology. By comparison, in non-metastatic TNBC, there is a stress-associated mitochondrial morphology with hyperfragmented mitochondria, accompanied by the upregulated expression of genes associated with the biogenesis of mitochondria; both of which are characteristics related to the higher production of reactive oxygen species observed in this cell line. These differences between metastatic and non-metastatic TNBC should provide a better understanding of metastasis and contribute to the development of improved specific and personalized therapies for TNBC.

A single session of physical activity restores the mitochondrial organization disrupted by obesity in skeletal muscle fibers

BACKGROUND

Several studies have proved that physical activity (PA) regulates energetic metabolism associated with mitochondrial dynamics through AMPK activation in healthy subjects. Obesity, a condition that induces oxidative stress, mitochondrial dysfunction, and low AMPK activity leads to mitochondrial fragmentation. However, few studies describe the effect of PA on mitochondrial dynamics regulation in obesity.

AIM

The present study aimed to evaluate the effect of a single session of PA on mitochondrial dynamics regulation as well as its effect on mitochondrial function and organization in skeletal muscles of obese rats (Zucker fa/fa).

MAIN METHODS

Male Zucker lean and Zucker fa/fa rats aged 12 to 13 weeks were divided into sedentary and subjected-to-PA (single session swimming) groups. Gastrocnemius muscle was dissected into isolated fibers, mitochondria, mRNA, and total proteins for their evaluation.

KEY FINDINGS

The results showed that PA increased the Mfn-2 protein level in the lean and obese groups, whereas Drp1 levels decreased in the obese group. OMA1 protease levels increased in the lean group and decreased in the obese group. Additionally, AMPK analysis parameters (expression, protein level, and activity) did not increase in the obese group. These findings correlated with the partial restoration of mitochondrial function in the obese group, increasing the capacity to maintain the membrane potential after adding calcium as a stressor, and increasing the transversal organization level of the mitochondria analyzed in isolated fibers.

SIGNIFICANCE

These results support the notion that obese rats subjected to PA maintain mitochondrial function through mitochondrial fusion activation by an AMPK-independent mechanism.

Mechanisms of mitochondrial DNA escape and its relationship with different metabolic diseases

It is well-known that mitochondrial DNA (mtDNA) can escape to intracellular or extracellular compartments under different stress conditions, yet understanding their escape mechanisms remains a challenge. Although Bax/Bak pores and VDAC oligomers are the strongest possibilities, other mechanisms may be involved. For example, mitochondria permeability transition, altered mitophagy, and mitochondrial dynamics are associated with intracellular mtDNA escape, while extracellular traps and extracellular vesicles can participate in extracellular mtDNA escape. The evidence suggests that mtDNA escape is a complex event with more than one mechanism involved. In addition, once the mtDNA is outside the mitochondria, the effects can be complex. Different danger signal sensors recognize the mtDNA as a damage-associated molecular pattern, triggering an innate immune inflammatory response that can be observed in multiple metabolic diseases characterized by chronic inflammation, including autoimmune diseases, diabetes, cancer, and cardiovascular disorders. For these reasons, we will review the most recent evidence regarding mtDNA escape mechanisms and their impact on different metabolic diseases.

Protective effects of N-acetyl-cysteine in mitochondria bioenergetics, oxidative stress, dynamics and S-glutathionylation alterations in acute kidney damage induced by folic acid

Folic acid (FA)-induced acute kidney injury (AKI) is a widely used model for studies of the renal damage and its progression to chronic state. However, the molecular mechanisms by which FA induces AKI remain poorly understood. Since renal function depends on mitochondrial homeostasis, it has been suggested that mitochondrial alterations contribute to AKI development. Additionally, N-acetyl-cysteine (NAC) can be a protective agent to prevent mitochondrial and renal dysfunction in this model, given its ability to increase mitochondrial glutathione (GSH) and to control the S-glutathionylation levels, a reversible post-translational modification that has emerged as a mechanism able to link mitochondrial energy metabolism and redox homeostasis. However, this hypothesis has not been explored. The present study demonstrates for the first time that, at 24 h, FA induced mitochondrial bioenergetics, redox state, dynamics and mitophagy alterations, which are involved in the mechanisms responsible for the AKI development. On the other hand, NAC preadministration was able to prevent mitochondrial bioenergetics, redox state and dynamics alterations as well as renal damage. The protective effects of NAC on mitochondria and renal function could be related to its observed capacity to preserve the S-glutathionylation process and GSH levels in mitochondria. Taken together, our results support the idea that these mitochondrial processes can be targets for the prevention of the renal damage and its progression in FA-induced AKI model.