Vera Silva

Cellular metabolism is crucial for various physiological processes, with folate-dependent one-carbon (1C) metabolism playing a pivotal role. Folate, a B vitamin, is a key cofactor in this pathway, supporting DNA synthesis, methylation processes, and antioxidant defenses. In dividing cells, folate facilitates nucleotide biosynthesis, ensuring genomic stability and preventing carcinogenesis. Additionally, in neurodevelopment, folate is essential for neural tube closure and central nervous system formation. Thus, dysregulation of folate metabolism can contribute to pathologies such as cancer, severe birth defects, and neurodegenerative diseases. Epidemiological evidence highlights folate’s impact on disease risk and its potential as a therapeutic target. In cancer, antifolate drugs that inhibit key enzymes of folate-dependent 1C metabolism and strategies targeting folate receptors are current therapeutic options. However, folate’s impact on cancer risk is complex, varying among cancer types and dietary contexts. In neurodegenerative conditions, including Alzheimer’s and Parkinson’s diseases, folate deficiency exacerbates cognitive decline through elevated homocysteine levels, contributing to neuronal damage. Clinical trials of folic acid supplementation show mixed outcomes, underscoring the complexities of its neuroprotective effects. This review integrates current knowledge on folate metabolism in cancer and neurodegeneration, exploring molecular mechanisms, clinical implications, and therapeutic strategies, which can provide crucial information for advancing treatments.

Ferroptosis is a type of regulated cell death promoted by the appearance of oxidative perturbations in the intracellular microenvironment constitutively controlled by glutathione peroxidase 4 (GPX4). It is characterized by increased production of reactive oxygen species, intracellular iron accumulation, lipid peroxidation, inhibition of system Xc-, glutathione depletion, and decreased GPX4 activity. Several pieces of evidence support the involvement of ferroptosis in distinct neurodegenerative diseases. In vitro and in vivo models allow a reliable transition to clinical studies. Several in vitro models, including differentiated SH-SY5Y and PC12 cells, among others, have been used to investigate the pathophysiological mechanisms of distinct neurodegenerative diseases, including ferroptosis. In addition, they can be useful in the development of potential ferroptosis inhibitors that can be used as disease-modifying drugs for the treatment of such diseases. On the other hand, in vivo models based on the manipulation of rodents and invertebrate animals, such as Drosophila melanogaster, Caenorhabditis elegans, and zebrafish, have been increasingly used for research in neurodegeneration. This work provides an up-to-date review of the main in vitro and in vivo models that can be used to evaluate ferroptosis in the most prevalent neurodegenerative diseases, and to explore potential new drug targets and novel drug candidates for effective disease-modifying therapies.

The long lifespan of the world’s population has been raising interest in the research for new solutions to delay the aging process. With the aim of skin aging prevention, solid lipid nanoparticles (SLNs) were developed in this work for the encapsulation of three lipophilic natural compounds extracted from vine cane—epigallocatechin gallate (EGCG), resveratrol and myricetin. The developed loaded-SLNs proved to be stable, maintaining their adequate physicochemical characteristics for 30 days. In addition, the loaded-SLNs formulations exhibited high encapsulation efficiencies and loading capacities and high intracellular antioxidant activity. The mixture of EGCG-loaded SLNs with resveratrol-loaded SLNs proved to have the highest protection against induced oxidative stress. The in vitro cytotoxicity of the loaded SLNs was also evaluated, showing that the developed formulations are biocompatible for concentrations up to 50 µg/mL and could be safe for use in cosmetics. The encapsulation of EGCG, resveratrol and myricetin in SLNs seems to be a suitable strategy for the delivery of these antioxidants to the skin, improving their bioavailability.

Oxidative stress, triggered by UV radiation, is one of the major causes of free radical-associated disorders, such as skin cancer. The application of natural compounds (NCs) with antioxidant effects can attenuate free radicals’ accumulation and, therefore, provide a strategy for skin care and cancer prevention. In this work, three natural compounds, naringenin, nordihydroguaiaretic acid (NDGA), and kaempferol, were encapsulated into nanostructured lipid carriers (NLCs) aiming for the development of a formulation for cutaneous application with antioxidant properties. For the experiments, different formulation parameters were evaluated to optimize the NLCs that showed a diameter around 200 nm, which is an adequate particle size for incorporation in cosmetics. Transmission electron microscopy (TEM) analysis confirmed the NLCs’ typical spherical morphology. Encapsulation efficiency (EE) and loading capacity (LC) values revealed an effective production process, with EEs over 90% and LCs near the maximum value. The developed NLCs revealed a prolonged in vitro release of the natural compounds. The NLCs were stable under storage conditions, maintaining their psychochemical characteristics for 30 days. Additionally, they did not show any physical instability in accelerated stability studies, which also suggests long-term stability. Finally, the NCs antioxidant activity was evaluated. Interestingly, the NDGA and kaempferol mixture provided an antioxidant synergic effect. The NLC formulations’ cytotoxicity was tested in vitro in immortalized human keratinocytes (HaCaT). In addition, putative antioxidant effects of the developed NLC formulations against tert-butyl hydroperoxide (t-BHP)-induced oxidative stress were studied, and the NDGA-loaded NLC was revealed to be the one with the most protective effect. Therefore, we concluded that the naringenin, NDGA, and kaempferol incorporation into NLCs constitutes a promising strategy to increase their bioavailability and delivery to the skin.

P-glycoprotein (P-gp) is an ATP-binding cassette transporter involved in the efflux of numerous compounds that influences the pharmacokinetics of xenobiotics. It reduces intestinal absorption and exposure of target cells to toxicity. Thioxanthones are compounds able to induce and/or activate P-gp in vitro. Particularly, 1-(propan-2-ylamino)-4-propoxy-9H-thioxanthen-9-one (TX5) behaves as a P-gp inducer and activator in vitro. The aims of this study were: i) to perform a histological characterization, by testing a single high dose of TX5 [30 mg/kg, body weight (b.w.), gavage], administered to Wistar Han rats, 24 hours after administration; and ii) to perform both a complete histological characterization and a preliminary safety evaluation, in distinct target organs, 24 hours after administration of a single lower dose of TX5 (10 mg/kg, b.w., gavage) to Wistar Han rats. The results showed a relevant histological toxicity for the higher dose of TX5 administered (30 mg/kg, b.w.), manifested by extensive hepatic necrosis and splenic toxicity (parenchyma with hyperemia, increased volume of both white and red pulp, increased follicles marginal zone). Moreover, in the kidneys, a slight hyperemia and tubular edema were observed in TX5-treated animals, as well as an inflammation of the small intestine. On the contrary, for the lower tested dose (10 mg/kg, b.w.), we did not observe any relevant histological toxicity in the evaluated organs. Additionally, no significant differences were found in the ATP levels between TX5-exposed and control animals in any of the evaluated organs, with the exception of the intestine, where ATP levels were significantly higher in TX5-treated rats. Similarly, TX5 caused a significant increase in the ratio GSH/GSSG only in the lungs. TX5 (10 mg/kg, b.w.) did not induce any change in any of the hematological and biochemical circulating evaluated parameters. However, TX5 was able to significantly reduce the activated partial thromboplastin time, without affecting the prothrombin time. The urine biochemical analysis revealed a TX5-mediated increase in both creatinine and sodium. Taken together, our results show that TX5, at a dose of 10 mg/kg, does not induce considerable toxicity in the biological matrices studied. Given this adequate safety profile, TX5 becomes a particularly interesting compound for ex vivo and in vivo studies, regarding the potential for induction and activation of P-gp at the intestinal barrier.