Pursuing the Elixir of Life: In Vivo Antioxidative Effects of Manganosalen Complexes

Real-time visualization of epileptic seizures using photoacoustic imaging with a peroxynitrite-responsive manganese(ii) texaphyrin

Real-time visualization and tracking of epileptic seizures are important for studying epilepsy pathogenesis and treating epilepsy; however, the requisite sensing is extremely challenging, primarily due to the transient and intricate nature of neural activity associated with epilepsy. The onset of epilepsy is closely correlated with increases in peroxynitrite (ONOO-) levels, a reactive nitrogen species that can serve as a biomarker for epilepsy. However, the fleeting biological half-life and high reactivity of ONOO- has historically impeded its direct visualization within the epileptic brain. This study explores the efficacy of manganese(ii) texaphyrin (MMn), a water-soluble and stable expanded porphyrin, in dynamically sensing ONOO- and providing real-time tracking of epileptic seizures using a custom-built photoacoustic imaging (PAI) setup. UV-vis spectral analyses established the preferential sensitivity of MMn to ONOO- over other reactive oxygen species (ROS), as well as its effectiveness through multiple usage cycles when rejuvenated via reaction with suitable reducing agents. This selectivity was recapitulated in vitro as determined through PAI experiments. In vivo application of this technique revealed that MMn administered intravenously crosses the blood-brain barrier (BBB) in a pentylenetetrazole (PTZ)-induced epilepsy mouse model and provides an observable 14.1 ± 3.7% reduction in photoacoustic (PA) signal intensity within the hippocampal region during epileptic seizures. Multiple decreasing-increasing cycles of PA signal intensity could be detected in the hippocampal region in this model; the observed effect thus mirrors closely the course of epileptic seizures inferred from mouse tail curling. Similar cyclical patterns were also seen in the motor cortex, a finding consistent with the extensive spread of epileptic activity throughout the brain. To the best of our knowledge, the present investigation represents the first real-time visualization and tracking of epileptic seizures using a peroxynitrite-specific sensing probe in combination with photoacoustic imaging (PAI). This approach enables deeper brain imaging while simultaneously capturing dynamic ONOO- fluctuations, offering biochemical insights into epilepsy pathogenesis. By integrating deep-tissue imaging with neurochemical monitoring, this method lays the foundation for potential advances in epilepsy management and treatment.

Antioxidant Microgels Support Peroxide-Challenged Hepatic Cells

Access to therapeutic strategies that counter cellular stress induced by reactive oxygen species (ROS) is an important, long-standing challenge. Here, the assembly of antioxidant artificial cells is based on alginate hydrogels equipped with non-native catalysts, namely platinum nanoparticles and an EUK compound. These artificial cells are able to preserve the viability and lower the intracellular ROS levels of challenged hepatic cells by removing peroxides from the extracellular environment. Conceptually, this strategy illustrates the potential use of artificial cells with a synthetic catalyst toward long-term support of hepatic cells and potentially other mammalian cells.

Scavenging of reactive species probed by EPR and ex-vivo nanomolar reduction of lipid peroxidation of manganese complexes

Antioxidant activity toward H₂O₂, anion radical superoxide, hydroxyl and DPPH (2,2-diphenyl-1-picrylhydrazyl) of two manganese complexes [Mn(III)(bpa)₂]Cl.H₂O (1) and [(Cl)Mn(μ-hbpclnol)(μ-bpclnol)Mn](ClO₄).3H₂O (2) (hbpa = (2-hydroxybenzyl-2-pyridylmethyl)amine and h₂bpclnol = (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)]propylamine) are presented. X-ray diffraction studies were performed for complex (1). Both complexes presented similar or better activities than reference complex [Mn(salen)Cl], when the interaction between them and ROS (H₂O₂, O₂^•- and ^•OH), was monitored, by EPR (Electron Paramagnetic Resonance), in PBS, DMSO and water. The antioxidant activity rank of complexes toward ^•OH, generated by Fenton reaction and monitored by EPR, is (2) > (1) > [Mn(salen)Cl], in water (0.1% of DMSO for each complex), with the values of the IC₅₀ of 7.2 (±1.6), 15.5 (±1.8) and 29.1 (±2.01) μM respectively. EPR data presented herein suggest that complex (2) presents the better scavenging activity toward hydroxyl, being in good agreement with TBARS assay results, in which complex (2) presented the best inhibitory activity toward lipid peroxidation, employing Swiss mice liver homogenate tissue model. IC₅₀ values obtained from the interaction between these complexes and hydroxyl, using TBARS method, were: 0.88 (± 0.029); 0.73 (± 0.01) and 42.7 (± 3.5) nM, respectively for (1), (2) and [Mn(salen)Cl]. Complexes (1) and (2) are regulating the lipid homeostasis, protecting the tissue from the lipid peroxidation, in nanomolar scale, motivating in vivo studies. Redox properties and radical scavenging activity of complexes toward DPPH are non-linear and solvent dependent. Furthermore, the monitoring of antioxidant activity probed by EPR could be a fair and appropriate study to guide more advanced investigations.

Therapeutic promise of carotenoids as antioxidants and anti-inflammatory agents in neurodegenerative disorders

Neurodegenerative disorders (NDs) including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis have various disease-specific causal factors and pathological features. A very common characteristic of NDs is oxidative stress (OS), which takes place due to the elevated generation of reactive oxygen species during the progression of NDs. Furthermore, the pathological condition of NDs including an increased level of protein aggregates can further lead to chronic inflammation because of the microglial activation. Carotenoids (CTs) are naturally occurring pigments that play a significant role in averting brain disorders. More than 750 CTs are present in nature, and they are widely available in plants, microorganisms, and animals. CTs are accountable for the red, yellow, and orange pigments in several animals and plants, and these colors usually indicate various types of CTs. CTs exert various bioactive properties because of its characteristic structure, including anti-inflammatory and antioxidant properties. Due to the protective properties of CTs, levels of CTs in the human body have been markedly linked with the prevention and treatment of multiple diseases including NDs. In this review, we have summarized the relationship between OS, neuroinflammation, and NDs. In addition, we have also particularly focused on the antioxidants and anti-inflammatory properties of CTs in the management of NDs.

Neuroprotective effects of fluorophore-labelled manganese complexes: Determination of ROS production, mitochondrial membrane potential and confocal fluorescence microscopy studies in neuroblastoma cells

In this work, four manganese(II) complexes derived from the ligands H₂L¹-H₂L⁴, that incorporate dansyl or tosyl fluorescent dyes, have been investigated in term of their antioxidant properties. Two of the manganese(II) complexes have been newly prepared using the asymmetric half-salen ligand H₂L² and the thiosemicarbazone ligand H₂L³. The four organic strands and the manganese complexes have been characterized by different analytical and spectroscopic techniques. The study of the antioxidant behaviour of these two new complexes and other two fluorophore-labelled analogues was tested in SH-SY5Y neuroblastoma cells. These four model complexes 1-4 were found to protect cells from oxidative damage in this human neuronal model, by reducing the release of reactive oxygen species. Complexes 1-4 significantly improved cell survival, with levels between 79.1 ± 0.8% and 130.9 ± 4.1%. Moreover, complexes 3 and 4 were able to restore the mitochondrial membrane potential at 1 μM, with 4 reaching levels higher than 85%, similar to the percentages obtained by the positive control agent cyclosporin A. The incorporation of the fluorescent label in the complexes allowed the study of their ability to enter the human neuroblastoma cells by confocal microscopy.

Catalytic Antioxidants in the Kidney

Reactive oxygen species and reactive nitrogen species are highly implicated in kidney injuries that include acute kidney injury, chronic kidney disease, hypertensive nephropathy, and diabetic nephropathy. Therefore, antioxidant agents are promising therapeutic strategies for kidney diseases. Catalytic antioxidants are defined as small molecular mimics of antioxidant enzymes, such as superoxide dismutase, catalase, and glutathione peroxidase, and some of them function as potent detoxifiers of lipid peroxides and peroxynitrite. Several catalytic antioxidants have been demonstrated to be effective in a variety of in vitro and in vivo disease models that are associated with oxidative stress, including kidney diseases. This review summarizes the evidence for the role of antioxidant enzymes in kidney diseases, the classifications of catalytic antioxidants, and their current applications to kidney diseases.