Neutral Sphingomyelinase Modulation in the Protective/Preventive Role of rMnSOD from Radiation-Induced Damage in the Brain

The structure-function relationships and physiological roles of MnSOD mutants

In this review, we focus on understanding the structure–function relationships of numerous manganese superoxide dismutase (MnSOD) mutants to investigate the role that various amino acids play to maintain enzyme quaternary structure or the active site structure, catalytic potential and metal homeostasis in MnSOD, which is essential to maintain enzyme activity. We also observe how polymorphisms of MnSOD are linked to pathologies and how post-translational modifications affect the antioxidant properties of MnSOD. Understanding how modified forms of MnSOD may act as tumor promoters or suppressors by altering the redox status in the body, ultimately aid in generating novel therapies that exploit the therapeutic potential of mutant MnSODs or pave the way for the development of synthetic SOD mimics.

α-Lipoic Acid Reduces Ceramide Synthesis and Neuroinflammation in the Hypothalamus of Insulin-Resistant Rats, While in the Cerebral Cortex Diminishes the β-Amyloid Accumulation

Background

Oxidative stress underlies metabolic diseases and cognitive impairment; thus, the use of antioxidants may improve brain function in insulin-resistant conditions. We are the first to evaluate the effects of α-lipoic acid (ALA) on redox homeostasis, sphingolipid metabolism, neuroinflammation, apoptosis, and β-amyloid accumulation in the cerebral cortex and hypothalamus of insulin-resistant rats.

Methods

The experiment was conducted on male cmdb/outbred Wistar rats fed a high-fat diet (HFD) for 10 weeks with intragastric administration of ALA (30 mg/kg body weight) for 4 weeks. Pro-oxidant and pro-inflammatory enzymes, oxidative stress, sphingolipid metabolism, neuroinflammation, apoptosis, and β-amyloid level were assessed in the hypothalamus and cerebral cortex using colorimetric, fluorimetric, ELISA, and HPLC methods. Statistical analysis was performed using three-way ANOVA followed by the Tukey HSD test.

Results

ALA normalizes body weight, food intake, glycemia, insulinemia, and systemic insulin sensitivity in HFD-fed rats. ALA treatment reduces nicotinamide adenine dinucleotide phosphate (NADPH) and xanthine oxidase activity, increases ferric-reducing antioxidant power (FRAP) and thiol levels in the hypothalamus of insulin-resistant rats. In addition, it decreases myeloperoxidase, glucuronidase, and metalloproteinase-2 activity and pro-inflammatory cytokines (IL-1β, IL-6) levels, while in the cerebral cortex ALA reduces β-amyloid accumulation. In both brain structures, ALA diminishes ceramide synthesis and caspase-3 activity. ALA improves systemic oxidative status and reduces insulin-resistant rats’ serum cytokines, chemokines, and growth factors.

Conclusion

ALA normalizes lipid and carbohydrate metabolism in insulin-resistant rats. At the brain level, ALA primarily affects hypothalamic metabolism. ALA improves redox homeostasis by decreasing the activity of pro-oxidant enzymes, enhancing total antioxidant potential, and reducing protein and lipid oxidative damage in the hypothalamus of HFD-fed rats. ALA also reduces hypothalamic inflammation and metalloproteinases activity, and cortical β-amyloid accumulation. In both brain structures, ALA diminishes ceramide synthesis and neuronal apoptosis. Although further study is needed, ALA may be a potential treatment for patients with cerebral complications of insulin resistance.

Irradiated cell-derived exosomes transmit essential molecules inducing radiotherapy resistance

Radio-resistance has always been a major obstacle in radiation therapy (RT) progress. Radiotherapy (RT) leads to changes in the contents of released exosomes. The researches have shown that irradiated cell-derived exosomes influence recipient cell proliferation, migration, cell cycle arrest and apoptosis. All evidence indicates that exosomes play a significant role in radio-resistance. In this review, we describe the potential role of exosomes in cancer. We summarize that the irradiated cell-derived exosomes influence radio-resistance in recipient cells by three main mechanisms: 1) enhancing DNA repair, 2) regulating cell death signalling pathways, 3) inducing cancer cells to exhibit stem cell properties. We also discuss that the origin of the phenomenon might be the changes of molecular mechanisms of irradiated cell-derived exosomes formation affected by RT. Further, targeting exosomes as an adjuvant therapy might be a promising way for cancer treatments.

Role of Glutathione Peroxidases and Peroxiredoxins in Free Radical-Induced Pathologies

In this review, we discuss the pathogenesis of some socially significant diseases associated with the development of oxidative stress, such as atherosclerosis, diabetes, and radiation sickness, as well as the possibilities of the therapeutic application of low-molecular-weight natural and synthetic antioxidants for the correction of free radical-induced pathologies. The main focus of this review is the role of two phylogenetically close families of hydroperoxide-reducing antioxidant enzymes peroxiredoxins and glutathione peroxidases - in counteracting oxidative stress. We also present examples of the application of exogenous recombinant antioxidant enzymes as therapeutic agents in the treatment of pathologies associated with free-radical processes and discuss the prospects of the therapeutic use of exogenous antioxidant enzymes, as well as the ways to improve their therapeutic properties.

Acid and Neutral Sphingomyelinase Behavior in Radiation-Induced Liver Pyroptosis and in the Protective/Preventive Role of rMnSOD

Sphingomyelins (SMs) are a class of relevant bioactive molecules that act as key modulators of different cellular processes, such as growth arrest, exosome formation, and the inflammatory response influenced by many environmental conditions, leading to pyroptosis, a form of programmed cell death due to Caspase-1 involvement. To study liver pyroptosis and hepatic SM metabolism via both lysosomal acid SMase (aSMase) and endoplasmic reticulum/nucleus neutral SMase (nSMase) during the exposure of mice to radiation and to ascertain if this process can be modulated by protective molecules, we used an experimental design (previously used by us) to evaluate the effects of both ionizing radiation and a specific protective molecule (rMnSOD) in the brain in collaboration with the Joint Institute for Nuclear Research, Dubna (Russia). As shown by the Caspase-1 immunostaining of the liver sections, the radiation resulted in the loss of the normal cell structure alongside a progressive and dose-dependent increase of the labelling, treatment, and pretreatment with rMnSOD, which had a significant protective effect on the livers. SM metabolic analyses, performed on aSMase and nSMase gene expression, as well as protein content and activity, proved that rMnSOD was able to significantly reduce radiation-induced damage by playing both a protective role via aSMase and a preventive role via nSMase.