Diphenyl diselenide and streptozotocin did not alter cerebral glutamatergic and cholinergic systems but modulate antioxidant status and sodium pump in diabetic rats

Diphenyl diselenide modulate antioxidant status, inflammatory and redox-sensitive genes in diesel exhaust particle-induced neurotoxicity

This study seeks to determine the influence of diphenyl diselenide (DPDSe) on redox status, inflammatory and redox-sensitive genes in diesel exhaust particle (DEP)-induced neurotoxicity in male albino rats. Male Wistar albino rats were administered nasally with DEP (30 and 60 μg/kg) and treated with intraperitoneal administration of 10 mg/kg DPDSe. Non-enzymatic (lipid peroxidation and conjugated diene concentrations) and enzymatic (catalase, superoxide dismutase, glutathione peroxidase) antioxidant indices and activity of acetylcholinesterase enzyme were evaluated in brain tissues of the rats. Furthermore, the expression of genes linked to oxidative stress (HO-1, Nrf2), pro-inflammatory (NF-KB, IL-8, TNF-α) anti-inflammatory (IL-10) and brain-specific (GFAP, ENO-2) genes were also determined. The results indicated that DPDSe caused a notable reduction in the high levels of thiobarbituric acid reactive substances and conjugated diene observed in the brain of DEP-administered rats. DPDSe also reversed the observed reduction in catalase, superoxide dismutase and glutathione peroxidase enzyme activities in the brain of DEP-administered rats. Lastly, the downregulation of genes associated with redox homeostasis, anti-inflammatory and brain-specific genes and upregulation of pro-inflammatory genes observed in the DEP-treated groups were ameliorated by DPDSe. The immediate restoration of altered biochemical conditions and molecular expression in the brain of DEP-treated rats by DPDSe further validates its use as a promising therapeutic candidate for restoring neurotoxicity linked with DEP-induced oxidative stress.

Liver Proteome in Diabetes Type 1 Rat Model: Insulin-Dependent and -Independent Changes

Diabetes mellitus type 1 (DM1) is a major public health problem that continues to burden the healthcare systems worldwide, costing exponentially more as the epidemic grows. Innovative strategies and omics system diagnostics for earlier diagnosis or prognostication of DM1 are essential to prevent secondary complications and alleviate the associated economic burden. In a preclinical study design that involved streptozotocin (STZ)-induced DM1, insulin-treated STZ-induced DM1, and control rats, we characterized the insulin-dependent and -independent changes in protein profiles in liver samples. Digested proteins were subjected to LC-MS^E for proteomic data. Progenesis QI data processing and analysis of variance were utilized for statistical analyses. We found 305 proteins with significantly altered abundance among the control, DM1, and insulin-treated DM1 groups (p < 0.05). These differentially regulated proteins were related to enzymes that function in key metabolic pathways and stress responses. For example, gluconeogenesis appeared to return to control levels in the DM1 group after insulin treatment, with the restoration of gluconeogenesis regulatory enzyme, FBP1. Insulin administration to DM1 rats also restored the blood glucose levels and enzymes of general stress and antioxidant response systems. These observations are crucial for insights on DM1 pathophysiology and new molecular targets for future clinical biomarkers, drug discovery, and development. Additionally, we underscore that proteomics offers much potential in preclinical biomarker discovery for diabetes as well as common complex diseases such as cancer, dementia, and infectious disorders.

Influence of gallic acid on oxidative stress-linked streptozotocin-induced pancreatic dysfunction in diabetic rats

BACKGROUND

Recent advances in diabetic research involve the evaluation of agents that can regenerate or reverse pancreatic dysfunction. Although gallic acid (GA) has been reported as an antidiabetic agent, its ability to directly reverse altered biochemical parameters in diabetic pancreas has not been demonstrated.

METHODS

Male albino rats with diabetes induced by the administration of streptozotocin (STZ) (50 mg/kg, intraperitoneally) were treated with oral administration of GA. Antioxidants (enzymatic and non-enzymatic), purinergic enzymes, δ-aminolevulinic acid dehydratase and lactate dehydrogenase were evaluated in the pancreas of both diabetic and nondiabetic animals.

RESULTS

The pharmacological effect of GA was accompanied by a restoration of the observed decreased levels of vitamin C and reduced glutathione in the pancreas of STZ-treated rats. GA also caused a marked reduction in the high levels of thiobarbituric acid reactive substances observed in the STZ-induced diabetic group. Furthermore, GA also improves the free radical scavenging property, Fe2+ chelating ability and Fe3+ reducing property of the pancreas of diabetic animals. Finally, the inhibition of pancreatic catalase, glutathione S-transferase, δ-aminolevulinic acid dehydratase and lactate dehydrogenase and increased activity of purinergic enzymes accompanied by hyperglycemia were prevented by GA in the pancreas.

CONCLUSIONS

The direct influence and consequent restoration of altered biochemical conditions in the pancreatic tissue of diabetic animal models by GA makes it a promising antidiabetic candidate especially in pancreatic cell regeneration.

Possible involvement of membrane lipids peroxidation and oxidation of catalytically essential thiols of the cerebral transmembrane sodium pump as component mechanisms of iron-mediated oxidative stress-linked dysfunction of the pump's activity

The precise molecular events defining the complex role of oxidative stress in the inactivation of the cerebral sodium pump in radical-induced neurodegenerative diseases is yet to be fully clarified and thus still open. Herein we investigated the modulation of the activity of the cerebral transmembrane electrogenic enzyme in Fe²⁺-mediated in vitro oxidative stress model. The results show that Fe²⁺ inhibited the transmembrane enzyme in a concentration dependent manner and this effect was accompanied by a biphasic generation of aldehydic product of lipid peroxidation. While dithiothreitol prevented both Fe²⁺ inhibitory effect on the pump and lipid peroxidation, vitamin E prevented only lipid peroxidation but not inhibition of the pump. Besides, malondialdehyde (MDA) inhibited the pump by a mechanism not related to oxidation of its critical thiols. Apparently, the low activity of the pump in degenerative diseases mediated by Fe²⁺ may involve complex multi-component mechanisms which may partly involve an initial oxidation of the critical thiols of the enzyme directly mediated by Fe²⁺ and during severe progression of such diseases; aldehydic products of lipid peroxidation such as MDA may further exacerbate this inhibitory effect by a mechanism that is likely not related to the oxidation of the catalytically essential thiols of the ouabain-sensitive cerebral electrogenic pump.

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Fe²⁺ evoked lipid peroxidation (LPO) and inhibition of sodium pump (SP) in rat brain.

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However, dithiothreitol prevented both Fe²⁺-mediated LPO and inhibition of SP.

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Conversely, vitamin E prevented only Fe²⁺-mediated LPO but not inhibition of SP.

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Thus Fe²⁺ mediated inactivation of SP likely by oxidizing the essential thiol on SP.

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However, malondialdehyde inhibited SP by a mechanism not related to thiol oxidation.

Melatonin synthesis impairment as a new deleterious outcome of diabetes-derived hyperglycemia

Melatonin is a neurohormone that works as a nighttime signal for circadian integrity and health maintenance. It is crucial for energy metabolism regulation, and the diabetes effects on its synthesis are unresolved. Using diverse techniques that included pineal microdialysis and ultrahigh-performance liquid chromatography, the present data show a clear acute and sustained melatonin synthesis reduction in diabetic rats as a result of pineal metabolism impairment that is unrelated to cell death. Hyperglycemia is the main cause of several diabetic complications, and its consequences in terms of melatonin production were assessed. Here, we show that local high glucose (HG) concentration is acutely detrimental to pineal melatonin synthesis in rats both in vivo and in vitro. The clinically depressive action of high blood glucose concentration in melatonin levels was also observed in type 1 diabetes patients who presented a negative correlation between hyperglycemia and 6-sulfatoxymelatonin excretion. Additionally, high-mean-glycemia type 1 diabetes patients presented lower 6-sulfatoxymelatonin levels when compared to control subjects. Although further studies are needed to fully clarify the mechanisms, the present results provide evidence that high circulating glucose levels interfere with pineal melatonin production. Given the essential role played by melatonin as a powerful antioxidant and in the control of energy homeostasis, sleep and biological rhythms and knowing that optimal glycemic control is usually an issue for patients with diabetes, melatonin supplementation may be considered as an additional tool to the current treatment.

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

Studies have consistently reported the participation of oxidative stress, energetic metabolism impairment, and creatine kinase (CK) activity alterations in rat brain in early times in an animal model of sepsis and persist for up to 10 days. We have assessed the antioxidant effects of administration of Ebselen (Eb) e diphenyl diselenide (PhSe)2 two organoselenium compounds on brain oxidative stress, energetic metabolism, and CK activity 12, 24 h, and 10 days after sepsis by cecal ligation and perforation (CLP) in rats. Male Wistar rats underwent either sham operation or CLP and were treated with oral injection of Eb (50 mg/kg) or (PhSe)2 (50 mg/kg) or vehicle. 12, 24 h, and 10 days after CLP, the rats were sacrificed, and samples from brain (hippocampus, striatum, cerebellum, prefrontal cortex, and cortex) were obtained and assayed for thiobarbituric acid reactive species and protein carbonyls formation, mitochondrial respiratory chain, and CK activity. We observed in the results a reduction of oxidative damage to lipids and proteins in the different cerebral structures studied and times with the administration of (PhSe)2; however, Eb seems to exert the same effect. Such changes are reflected in the assessment of mitochondrial respiratory chain complexes by reversing the decreased activity of the complex caused by the model of CLP and CK activity. Our data provide the first experimental demonstration that (PhSe)2 was able to reduce the brain dysfunction associated with CLP-induced sepsis in rats, by decreasing oxidative stress parameters mitochondrial dysfunction and CK activity in early times and in late time.

Mercury toxicity on sodium pump and organoseleniums intervention: a paradox

Mercury is an environmental poison, and the damage to living system is generally severe. The severity of mercury poisoning is consequent from the fact that it targets the thiol-containing enzymes, irreversibly oxidizing their critical thiol groups, consequently leading to an inactivation of the enzyme. The Na⁺/K⁺-ATPase is a sulfhydryl protein that is sensitive to Hg²⁺ assault. On the other hand, organoseleniums are a class of pharmacologically promising compounds with potent antioxidant effects. While Hg²⁺ oxidizes sulfhydryl groups of Na⁺/K⁺-ATPase under in vitro and in vivo conditions, the organoselenium compounds inhibit Na⁺/K⁺-ATPase in vitro but enhance its activities under in vivo conditions with concomitant increase in the level of endogenous thiols. Paradoxically, it appears that these two thiol oxidants can be used to counteract one another under in vivo conditions, and this hypothesis serves as the basis for this paper.

Comparative study on the influence of subcutaneous administration of diphenyl and dicholesteroyl diselenides on sulphydryl proteins and antioxidant parameters in mice

Although in vitro data from our previous studies show that the antioxidant effect and reactions of both diphenyl diselenide (DPDS) and dicholesteroyl diselenide (DCDS) towards thiol-containing proteins differ considerably, the present study sought to evaluate the interaction of both organodiselenides with thiol-containing proteins in vivo. Mice were injected subcutaneously with DPDS or DCDS previously dissolved in soya bean oil at doses of 0.5 mmol kg⁻¹ body weight for four consecutive days. The activities of delta aminolevulinic acid dehydratase (ALA-D), Na+/K+-ATPase, and isoforms of lactate dehydrogenase (LDH) and catalase were investigated. In addition, the antioxidant status of the mice was determined by measuring the levels of glutathione (GSH), vitamin C (Vit C) and thiobarbituric acid reactive substances. The results show that both diselenides significantly increased the levels of GSH and Vit C but did not markedly alter other antioxidant indices. With respect to the thiol-containing enzymes that were evaluated, DPDS and not DCDS caused a marked reduction in the activities of hepatic ALA-D; however, both diselenides inhibited all isoforms of LDH evaluated. In addition, the activities of cerebral Na+/K+-ATPase were not markedly inhibited by both diselenides, suggesting that this cerebral enzyme may not be a molecular target of organodiselenides toxicity. Taken together, the pharmacological and toxicological chemistry of organoselenium compounds is complex and multifactorial and is dependent on delicate equations which include vehicle solution, animal species and mode of delivery.

Reduction of diphenyl diselenide and analogs by mammalian thioredoxin reductase is independent of their gluthathione peroxidase-like activity: a possible novel pathway for their antioxidant activity

Since the successful use of the organoselenium drug ebselen in clinical trials for the treatment of neuropathological conditions associated with oxidative stress, there have been concerted efforts geared towards understanding the precise mechanism of action of ebselen and other organoselenium compounds, especially the diorganyl diselenides such as diphenyl diselenide, and its analogs. Although the mechanism of action of ebselen and other organoselenium compounds has been shown to be related to their ability to generally mimic native glutathione peroxidase (GPx), only ebselen however has been shown to serve as a substrate for the mammalian thioredoxin reductase (TrxR), demonstrating another component of its pharmacological mechanisms. In fact, there is a dearth of information on the ability of other organoselenium compounds, especially diphenyl diselenide and its analogs, to serve as substrates for the mammalian enzyme thioredoxin reductase. Interestingly, diphenyl diselenide shares several antioxidant and neuroprotective properties with ebselen. Hence in the present study, we tested the hypothesis that diphenyl diselenide and some of its analogs (4,4'-bistrifluoromethyldiphenyl diselenide, 4,4'-bismethoxy-diphenyl diselenide, 4.4'-biscarboxydiphenyl diselenide, 4,4'-bischlorodiphenyl diselenide, 2,4,6,2',4',6'-hexamethyldiphenyl diselenide) could also be substrates for rat hepatic TrxR. Here we show for the first time that diselenides are good substrates for mammalian TrxR, but not necessarily good mimetics of GPx, and vice versa. For instance, bis-methoxydiphenyl diselenide had no GPx activity, whereas it was a good substrate for reduction by TrxR. Our experimental observations indicate a possible dissociation between the two pathways for peroxide degradation (either via substrate for TrxR or as a mimic of GPx). Consequently, the antioxidant activity of diphenyl diselenide and analogs can be attributed to their capacity to be substrates for mammalian TrxR and we therefore conclude that subtle changes in the aryl moiety of diselenides can be used as tool for dissociation of GPx or TrxR pathways as mechanism triggering their antioxidant activities.

Reduction of diphenyl diselenide and analogs by mammalian thioredoxin reductase is independent of their gluthathione peroxidase-like activity: a possible novel pathway for their antioxidant activity

Since the successful use of the organoselenium drug ebselen in clinical trials for the treatment of neuropathological conditions associated with oxidative stress, there have been concerted efforts geared towards understanding the precise mechanism of action of ebselen and other organoselenium compounds, especially the diorganyl diselenides such as diphenyl diselenide, and its analogs. Although the mechanism of action of ebselen and other organoselenium compounds has been shown to be related to their ability to generally mimic native glutathione peroxidase (GPx), only ebselen however has been shown to serve as a substrate for the mammalian thioredoxin reductase (TrxR), demonstrating another component of its pharmacological mechanisms. In fact, there is a dearth of information on the ability of other organoselenium compounds, especially diphenyl diselenide and its analogs, to serve as substrates for the mammalian enzyme thioredoxin reductase. Interestingly, diphenyl diselenide shares several antioxidant and neuroprotective properties with ebselen. Hence in the present study, we tested the hypothesis that diphenyl diselenide and some of its analogs (4,4'-bistrifluoromethyldiphenyl diselenide, 4,4'-bismethoxy-diphenyl diselenide, 4.4'-biscarboxydiphenyl diselenide, 4,4'-bischlorodiphenyl diselenide, 2,4,6,2',4',6'-hexamethyldiphenyl diselenide) could also be substrates for rat hepatic TrxR. Here we show for the first time that diselenides are good substrates for mammalian TrxR, but not necessarily good mimetics of GPx, and vice versa. For instance, bis-methoxydiphenyl diselenide had no GPx activity, whereas it was a good substrate for reduction by TrxR. Our experimental observations indicate a possible dissociation between the two pathways for peroxide degradation (either via substrate for TrxR or as a mimic of GPx). Consequently, the antioxidant activity of diphenyl diselenide and analogs can be attributed to their capacity to be substrates for mammalian TrxR and we therefore conclude that subtle changes in the aryl moiety of diselenides can be used as tool for dissociation of GPx or TrxR pathways as mechanism triggering their antioxidant activities.