Background/Objectives: The cerebral cortex is critical for neurological functions that are strongly affected by the aging process. Astrocytes play a central role in maintaining neurotransmitter balance and regulating antioxidant and anti-inflammatory responses, but these physiological functions may also decline with age. This study aimed to investigate the effects of melatonin, a molecule with known antioxidant, anti-inflammatory and neuroprotective properties, on astrocytes of mature cortical tissue obtained from adult Wistar rats. Methods: Primary cortical astrocyte cultures were obtained from neonatal and 90-day-old Wistar rats and treated with melatonin (300 µM for 24 h). We assessed cell viability and metabolism (MTT and extracellular lactate levels), glutamine synthetase (GS) activity, glutathione (GSH) content, release of cytokines, and the expression of genes and proteins associated with oxidative stress and inflammation by RT-qPCR and Western blotting. Results: Melatonin did not affect cell viability or lactate production. Moreover, there were no changes in GS activity, a key enzyme in glutamate metabolism, or in GSH levels, an antioxidant defense molecule synthesized by astrocytes. However, melatonin significantly reduced the expression of the nuclear factor NFκB, cyclooxygenase 2 (COX-2), and inducible nitric oxide synthase (iNOS), while increasing interleukin 6 and 10 levels. Melatonin also upregulated the gene expression of the transcriptional factors Nrf2 and sirtuin 1 (SIRT1) and downregulated AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), while PGC-1α protein levels remained unchanged. A complementary analysis of astrocytes obtained from neonatal rats showed that melatonin did not change metabolic or redox parameters under basal conditions. Conclusions: Melatonin exerted anti-inflammatory effects on adult astrocyte cultures, likely through modulation of protective signaling pathways, such as Nrf2/SIRT1. These findings highlight the potential role of melatonin in preserving astrocytic function and mitigating age-related neuroinflammatory processes.

Background: In the sporadic model of Alzheimer's disease (AD), induced by intracerebroventricular streptozotocin (STZ) administration, cognitive impairment is accompanied by specific astrocytic changes in the hippocampus prior to amyloid deposition. Objective: Hypothesizing that the synthesis of GABA, via MAO-B, contributes to ammonia elevation, thereby compromising antioxidant defense and ATP synthesis, and possibly contributing to cognitive damage, we determined the hippocampal levels of glutamine synthetase (GS), monoamine oxidase B (MAO-B) and other enzymes related to GABA metabolism. Methods: Immunoblotting and RT-PCR assays were carried out in hippocampal samples of Wistar rats, at 4 and 16 weeks post-STZ, in the sporadic STZ-induced AD model, corresponding to the pre-amyloid and amyloid phases, respectively. Results: We observed a reduction in GS activity and increased MAO-B content, both in 4 weeks and in 16 weeks, reinforcing the idea that astroglial dysfunction precedes the amyloid phase. These alterations were accompanied by an increase in the content of ornithine decarboxylase 1 (ODC1), which catalyzes the synthesis of putrescine (substrate for GABA synthesis, via MAO-B), and a reduction in the gene expression of arginine-glycine amidinotransferase (AGAT), an enzyme involved in the synthesis of creatine, and in the generation of GABA agonists. These changes were only seen in the amyloid phase of the AD model. Conclusions: Our findings contribute to explain the greater damage that occurs in energy metabolism at this stage, in addition to the greater GABAergic loss. The changes reinforce the importance of the STZ model and further our understanding of the changes in both AD phases.

Background: Advanced glycation end products (AGEs) and receptors for AGEs (RAGE) have been extensively implicated in metabolic and neurodegenerative disorders due to their capacity to alter protein structure and function through non-enzymatic glycation. More recently, methylglyoxal (MG), a highly reactive glycolytic byproduct, has gained attention as a critical mediator of AGE formation and an independent contributor to cellular distress, particularly in the context of diabetes mellitus and Alzheimer’s disease. Objectives: This review synthesizes evidence from experimental and clinical studies addressing MG generation and metabolism in brain tissue, emphasizing the glyoxalase system as the primary detoxification mechanism, the functional contribution of astrocytes, and the downstream consequences of MG accumulation. In addition, we examined the interplay between MG, RAGE signaling, unfolded protein response, and regulatory mechanisms involving the hexosamine biosynthesis pathway and O-GlcNAcylation of key proteins in glucose metabolism and insulin signaling. Results and Conclusions: Brain glucose hypometabolism is a consequence of insulin resistance and results in a metabolic rearrangement that expands the glycolytic pathway and generates more MG, which, in turn, can affect insulin signaling, further compromising the molecular basis of insulin resistance and creating a vicious cycle. Astrocytes are key cells in the generation and detoxification of MG in the brain, making them a therapeutic target.

Background: Elevated levels of methylmalonic acid (MMA) are observed in the bodily fluids and tissues of patients with methylmalonic aciduria, a metabolic disorder characterized by manifestations such as vomiting, lethargy, muscle weakness, seizures, and coma. Objectives and Methods: To better understand the neuropathological mechanisms underlying this condition, we investigated the effects of intraperitoneal (i.p.) and intracerebroventricular (i.c.v.) administration of MMA on antioxidant defenses, citric acid cycle functioning, and glial reactivity in the cerebral cortex and striatum of Wistar rats. Amino acid levels were also quantified. Results: i.p. and i.c.v. administration of MMA decreased reduced glutathione levels and altered the activities of different antioxidant enzymes in the cortex and striatum. The activity of the citric acid cycle enzyme succinate dehydrogenase was diminished in both brain regions by i.p. and i.c.v. administration. Citrate synthase, isocitrate dehydrogenase, and malate dehydrogenase activities were further inhibited in the striatum. Furthermore, the i.p. administration increased glial fibrillary acidic protein (GFAP) and glucose transporter 1 (GLUT1) levels, whereas i.c.v. administration elevated GFAP and ionized calcium-binding adaptor molecule 1 (IBA1) levels in the striatum, suggesting glial activation. In contrast, no significant changes in glial markers were detected in the cortex. Moreover, synaptophysin levels remained unaltered in both regions. Finally, i.p. administration increased glutamate, glycine, and serine levels and reduced tyrosine concentrations in the striatum. Conclusions: Our findings indicate that oxidative stress, bioenergetic dysfunction, and glial reactivity induced by MMA may contribute to the neurological deficits observed in methylmalonic aciduria.

Doxorubicin (DOX) is a highly effective chemotherapeutic agent whose clinical use is limited by dose-dependent cardiotoxicity associated with oxidative stress, inflammation, and cellular stress responses. Here, we investigated whether preventive aerobic training could protect against DOX-induced cardiac injury in Wistar rats. Animals were assigned to sedentary control (C), sedentary DOX (D), trained control (CT), and trained DOX (DT) groups. The moderate-intensity (~50–80% maximal exercise test) treadmill protocol (40 min/day, 4 days/week for 4 weeks) was performed before intraperitoneal administration of DOX (4 mg/kg, weekly for 4 weeks) or saline. Preventive training markedly improved exercise capacity (p < 0.001) and attenuated oxidative damage, maintaining antioxidant enzyme activity (GR, SOD) at control levels (p > 0.05). DOX significantly upregulated cardiac IL-6 and IL-1β expression (p < 0.01), while trained animals preserved IL-1β expression similar to controls (p > 0.99). In parallel, DOX increased cardiac HIF-1 expression (p < 0.05), indicating activation of hypoxia- and stress-related signaling pathways, an effect that was attenuated by preventive training (p > 0.99). DOX-induced cardiac atrophy was evidenced by reduced left ventricular mass (p < 0.001), which was partially prevented by training (p < 0.05). Although hematological toxicity persisted, preventive aerobic exercise effectively counteracted DOX cardiotoxicity by restoring redox homeostasis, dampening inflammation, and limiting apoptotic signaling. Collectively, these findings highlight exercise preconditioning as a promising non-pharmacological strategy in cardio-oncology to mitigate chemotherapy-associated cardiac injury.

Alzheimer’s disease (AD) is the most prevalent form of dementia, with aging as its primary risk factor. Among experimental models of sporadic AD, intracerebroventricular (ICV) administration of streptozotocin (STZ) in rodents is widely used. We hypothesized that STZ accelerates the process of cellular senescence, which in astrocytes can be assessed using classic markers, including p16, β-galactosidase, Lamin B1, and the senescence-associated secretory phenotype (SASP). To explore this, we cultured hypothalamic astrocytes from adult male Wistar rats at four weeks after STZ-ICV model induction to investigate whether the astroglial changes observed in vivo were maintained under in vitro conditions, and whether markers of senescence were more evident in astrocytes from STZ animals. As in the STZ dementia model, astrocyte cultures exhibited reduced levels of glutamine synthetase and glutathione. Furthermore, elevations in the transcription factors, FOXO3a, Nrf2, and NF-κB, were observed. Markers of unfolded protein response (CHOP and sorcin) were also increased in astrocytes from STZ animals. When evaluating senescence parameters, increases in p53, p21, and p16 were observed, while Lamin B1 levels remained unchanged. With regard to SASP, modulations in TNFα and extracellular HMGB1 and S100B levels also suggested the induction of a senescent profile. Taken together, these findings demonstrate that cultured astrocytes retain key alterations observed in the in vivo model of STZ-induced dementia, highlighting its usefulness for studying AD and therapeutic strategies. Observations in cultures suggest that STZ indeed induces astrocyte senescence and that S100B may be included as a component of the astroglial SASP.