Effects of organoselenium compounds on early and late brain biochemical alterations in sepsis-survivor rats

Toxicology and pharmacology of synthetic organoselenium compounds: an update

Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.

Gold nanoparticles potentiates N-acetylcysteine effects on neurochemicals alterations in rats after polymicrobial sepsis

Herein, we report the effect of gold nanoparticles (AuNP) and n-acetylcysteine (NAC) isolated or in association as important anti-inflammatory and antioxidant compounds on brain dysfunction in septic rats. Male Wistar rats after sham operation or caecal ligation and perforation (CLP) were treated with subcutaneously injection of AuNP (50 mg/kg) and/or NAC (20 mg/kg) or saline immediately and 12 h after surgery. Twenty-four hours after CLP, hippocampus and prefrontal cortex were obtained and assayed for myeloperoxidase (MPO) activity, cytokines, lipid peroxidation, protein carbonyls formation, mitochondrial respiratory chain, and CK activity. AuNP + NAC association decreased MPO activity and pro-inflammatory cytokines production, being more effective than NAC or AuNP isolated treatment. AuNP + NAC association and NAC isolated treatment decreased oxidative stress to lipids in both brain structures, while protein oxidation decreased only in the hippocampus of AuNP + NAC association-treated animals. Complex I activity was increased with AuNP + NAC association and NAC isolated in the hippocampus. Regarding CK activity, AuNP and AuNP + NAC association increased this marker in both brain structures after CLP. Our data provide the first experimental demonstration that AuNP and NAC association was able to reduce sepsis-induced brain dysfunction in rats by decreasing neuroinflammation, oxidative stress parameters, mitochondrial dysfunction and CK activity.

Diphenyl diselenide subcutaneous supplementation of dairy sheep: effects on oxidant and antioxidant status, inflammatory response and milk composition

Diphenyl diselenide ((PhSe)2) is a organoselenium compound with potent antioxidant properties. Therefore, the aim of the present study was to evaluate whether subcutaneous supplementation of (PhSe)2 in dairy sheep has positive effects on milk composition, as well as on the prevention of oxidative stress and exacerbated inflammatory response. For this, 16 primiparous recently calved sheep were divided into the following two groups, with eight animals in each: Group A, the control group; and Group B, the group subcutaneously supplemented with five doses of (PhSe)2 of 3.0µmol/kg each every 7 days. Blood samples from supplemented animals showed increased concentration of antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase and glutathione-S-transferase), and reduced reactive oxygen species and lipid peroxidation, which prevented oxidative damage in the lactation period, as well as increased seric interleukin-10, an anti-inflammatory cytokine. In the sera, supplemented animals showed increased total antioxidant capacity and ferric-reducing ability of plasma compared with the control group. As a consequence, supplemented animals showed increased antioxidant variables, as well as reduced protein oxidation in milk samples. Moreover, milk from supplemented sheep showed a higher fat content, and lower total protein and lactose contents in some periods in the study, than did not-supplemented ewes. Seric concentrations of interleukin-1 were lower on Days 30 and 45 in supplemented animals, as well as the concentrations of tumour necrosis factor α in all periods, than were those in the control group, whereas the interleukin-10 concentrations were higher. Thus, dairy sheep supplementation of (PhSe)2 activated antioxidant and anti-inflammatory responses, and increased milk fat content. Moreover, this protocol increased the antioxidant and, consequently, reduced the oxidant concentration in milk, which is desirable for product quality.

Fructose-1,6-bisphosphate preserves glucose metabolism integrity and reduces reactive oxygen species in the brain during experimental sepsis

Sepsis is one of the main causes of hospitalization and mortality in Intensive Care Units. One of the first manifestations of sepsis is encephalopathy, reported in up to 70% of patients, being associated with higher mortality and morbidity. The factors that cause sepsis-associated encephalopathy (SAE) are still not well known, and may be multifactorial, as perfusion changes, neuroinflammation, oxidative stress and glycolytic metabolism alterations. Fructose-1,6-bisphosphate (FBP), a metabolite of the glycolytic route, has been reported as neuroprotective agent. The present study used an experimental sepsis model in C57BL/6 mice. We used in vivo brain imaging to evaluate glycolytic metabolism through microPET scans and the radiopharmaceutical ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG). Brain images were obtained before and 12 h after the induction of sepsis in animals with and without FBP treatment. We also evaluated the treatment effects in the brain oxidative stress by measuring the production of reactive oxygen species (ROS), the activity of catalase (CAT) and glutathione peroxidase (GPx), and the levels of fluorescent marker 2'7'-dichlorofluorescein diacetate (DCF). There was a significant decrease in brain glucose metabolism due to experimental sepsis. A significant protective effect of FBP treatment was observed in the cerebral metabolic outcomes. FBP also modulated the production of ROS, evidenced by reduced CAT activity and lower levels of DCF. Our results suggest that FBP may be a possible candidate in the treatment of SAE.

Early antagonism of cerebral high mobility group box-1 protein is benefit for sepsis induced brain injury

Sepsis induced brain injury acts as an acute complication and accounts for deterioration and high mortality rate of septic condition. HMGB1 is a late inflammatory mediator that plays a critical role in brain dysfunction and diseases. However, the role of HMGB1 in sepsis induced brain dysfunction remains intricate. The current study investigated the effect of HMGB1 on brain injury in septic mice model with intracerebroventricular injection of BoxA (a specific antagonist of HMGB1). The expression of HMGB1, morphological changes of brain tissues, apoptosis of brain cells, and alteration of behavior were determined. The expressions of HMGB1 in cortex, hippocampus, and striatum were significantly enhanced in the sepsis group when compared with the sham group. In septic conditions, brain tissues showed significant abnormalities in tissue structure, and increased apoptosis of brain cells which was caspase-3 dependent. Septic mice showed suppression of locomotor activity and impairment of memory and learning. Neutralizing brain HMGB1 significantly improved brain injury and apoptosis of brain cells, and further ameliorated disturbed locomotor activities and damaged memory and learning. However, no significant improvement of survival rate was seen after inhibiting central HMGB1. These results reveal that HMGB1 is a potential target for ameliorating sepsis induced brain injury with early antagonizing.

Vitamin B6 Reduces Neurochemical and Long-Term Cognitive Alterations After Polymicrobial Sepsis: Involvement of the Kynurenine Pathway Modulation

Neurological dysfunction as a result of neuroinflammation has been reported in sepsis and cause high mortality. High levels of cytokines stimulate the formation of neurotoxic metabolites by kynurenine (KYN) pathway. Vitamin B₆ (vit B₆) has anti-inflammatory and antioxidant properties and also acts as a cofactor for enzymes of the KYN pathway. Thus, by using a relevant animal model of polymicrobial sepsis, we studied the effect of vit B₆ on the KYN pathway, acute neurochemical and neuroinflammatory parameters, and cognitive dysfunction in rats. Male Wistar rats (250-300 g) were submitted to cecal ligation and perforation (CLP) and divided into sham + saline, sham + vit B₆, CLP + saline, and CLP + vit B₆ (600 mg/kg, s.c.) groups. Twenty-four hours later, the prefrontal cortex and hippocampus were removed for neurochemical and neuroinflammatory analyses. Animals were followed for 10 days to determine survival rate, when cognitive function was assessed by behavioral tests. Vitamin B₆ interfered in the activation of kynurenine pathway, which led to an improvement in neurochemical and neuroinflammatory parameters and, consequently, in the cognitive functions of septic animals. Thus, the results indicate that vit B₆ exerts neuroprotective effects in acute and late consequences after sepsis.

Induction of reactive oxygen species by diphenyl diselenide is preceded by changes in cell morphology and permeability in Saccharomyces cerevisiae

Organoselenium compounds, such as diphenyl diselenide (PhSe)₂ and phenylselenium zinc chloride (PhSeZnCl), show protective activities related to their thiol peroxidase activity. However, depending on experimental conditions, organoselenium compounds can cause toxicity by oxidising thiol groups of proteins and induce the production of reactive oxygen species (ROS). Here, we analysed the toxicity of (PhSe)₂ and PhSeZnCl in yeast Saccharomyces cerevisiae. Cell growth of S. cerevisiae after 1, 2, 3, 4, 6, and 16 h of treatment with 2, 4, 6, and 10 μM of (PhSe)₂ was evaluated. For comparative purpose, PhSeZnCl was analysed only at 16 h of incubation at equivalent concentrations of selenium (i.e. 4, 8, 12, and 20 μM). ROS production (DCFH-DA), size, granularity, and cell membrane permeability (propidium iodide) were determined by flow cytometry. (PhSe)₂ inhibited cell growth at 2 h (10 μM) of incubation, followed by increase in cell size. The increase of cell membrane permeability and granularity (10 μM) was observed after 3 h of incubation, however, ROS production occurs only at 16 h of incubation (10 μM) with (PhSe)₂, indicating that ROS overproduction is a more likely consequence of (PhSe)₂ toxicity and not its determinant. All tested parameters showed that only concentration of 20 μM induced toxicity in samples incubated with PhSeZnCl. In summary, the results suggest that (PhSe)₂ toxicity in S. cerevisiae is time and concentration dependent, presenting more toxicity when compared with PhSeZnCl.