Diphenyl diselenide reduces temporarily hyperglycemia: Possible relationship with oxidative stress

Diphenyl diselenide in its selenol form has dehydroascorbate reductase and glutathione S-transferase-like activity dependent on the glutathione content

Objectives

The antioxidant action of diphenyl diselenide ((PhSe)2) is attributed to the mechanism by which (PhSe)2 has pharmacological activity. Although (PhSe)2 has glutathione peroxidase mimetic activity, the exact mechanism involved in its antioxidant effect has not yet been completely elucidated. In the present study, mechanisms involved in the antioxidant property of (PhSe)2 (1–50 µm) were investigated.

Methods

Dehydroascorbate (DHA) reductase- and glutathione S-transferase (GST)-like activity, 2,2′-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical-scavenging activity and the protection against the oxidation of Fe2+ were evaluated.

Key findings

(PhSe)2 at concentrations equal to, or greater than, 5 µm showed DHA reductase- and GST-like activity. (PhSe)2 was not a scavenger of DPPH or ABTS radicals and did not protect against the oxidation of Fe2+.

Conclusions

These results clearly indicated that DHA reductase- and GST-like activity are the mechanisms involved in the antioxidant effect of (PhSe)2.

Acute exposure of rabbits to diphenyl diselenide: a toxicological evaluation

The simple organoselenium compound diphenyl diselenide (PhSe)(2) is a promising new pharmacological agent. However, few toxicological evaluations of this molecule have been reported. We evaluated the effects of acute administration of (PhSe)(2) on toxicological parameters in rabbits. Adult New Zealand rabbits were exposed to (PhSe)(2) (5-500 micromol kg(-1) , intraperitoneally) once a day for 5 days. Exposure to 500 micromol kg(-1) caused 85% mortality. Exposure to 50 micromol kg(-1) of (PhSe)(2) increased the glutathione levels in the hippocampus, kidney, heart, muscle and blood, whereas lipoperoxidation (TBARS) decreased in the cerebellum and kidney after exposure to 5 micromol kg(-1) . The activity of glutathione peroxidase increased in the heart and muscle of rabbits treated with 50 micromol kg(-1) of (PhSe)(2) and glutathione reductase activity was reduced in the cerebellum, cerebral cortex and kidney. Treatment with (PhSe)(2) reduced the activity of δ-aminolevulinate dehydratase in the hippocampus and increased this activity in the heart, but did not alter the activity of complexes I and II of the respiratory chain in the liver and brain. Hepatic and renal biochemical and histological parameters were not modified by (PhSe)(2) and apoptosis was not detected in these tissues; however, the hepatic cells tended to accumulate fat vacuoles. These results indicated that acute toxicology to (PhSe)(2) in rabbit is dependent on the dose, which should motivate further experiments on the therapeutic properties of this compound.

Diphenyl diselenide protects against glycerol-induced renal damage in rats

In this study we evaluated the effect of diphenyl diselenide (PhSe)(2) on glycerol-induced acute renal failure in rats. Rats were pre-treated by gavage every day with (PhSe)(2 )(7.14 mg kg(-1)) for 7 days. On the eighth day, rats received an intramuscular injection of glycerol (8 mL kg(-1)). Twenty-four hours afterwards, rats were euthanized and the levels of urea and creatinine were measured in plasma. Catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), delta-aminolevulinate dehydratase (delta-ALA-D) and Na(+), K(+)-ATPase activities and ascorbic acid levels were evaluated in renal homogenates. Histopathological evaluations were also performed. The results demonstrated that (PhSe)(2) was able to protect against the increase in urea and creatinine levels and histological alterations in kidney induced by glycerol. (PhSe)(2) protected against the inhibition in delta-ALA-D, CAT and GPx activities and the reduction in ascorbic acid levels induced by glycerol in kidneys of rats. In conclusion, the present results indicate that (PhSe)(2) was effective in protecting against acute renal failure induced by glycerol.

High-fat diet and hydrochlorothiazide increase oxidative stress in brain of rats

This study evaluated the effect of possible synergic interaction between high fat diet (HF) and hydrochlorothiazide (HCTZ) on biochemical parameters of oxidative stress in brain. Rats were fed for 16 weeks with a control diet or with an HF, both supplemented with different doses of HCTZ (0.4, 1.0, and 4.0 g kg(-1) of diet). HF associated with HCTZ caused a significant increase in lipid peroxidation and blood glucose levels. In addition, HF ingestion was associated with an increase in cerebral lipid peroxidation, vitamin C and non-protein thiol groups (NPSH) levels. There was an increase in vitamin C as well as NPSH levels in HCTZ (1.0 and 4.0 g kg(-1) of diet) and HF plus HCTZ groups. Na(+)-K(+)-ATPase activity of HCTZ (4.0 g kg(-1) of diet) and HCTZ plus HF-fed animals was significantly inhibited. Our data indicate that chronic intake of a high dose of HCTZ (4 g kg(-1) of diet) or HF change biochemical indexes of oxidative stress in rat brain. Furthermore, high-fat diets consumption and HCTZ treatment have interactive effects on brain, showing that a long-term intake of high-fat diets can aggravate the toxicity of HCTZ.

Acute diphenyl diselenide treatment reduces hyperglycemia but does not change delta-aminolevulinate dehydratase activity in alloxan-induced diabetes in rats

This study was designed to evaluate the effect of diphenyl diselenide in a classical model of alloxan-induced diabetes in rats. Oxidative stress is involved in alloxan toxic effects and we have hypothesized that diphenyl diselenide via its antioxidant properties could confer protection against alloxan pancreatic toxicity. Diabetes was induced by administration of alloxan (150 mg/kg, intravenously). Diphenyl diselenide (10 mg/kg, subcutaneously) was administered for 6 d before (prevention group) or for 6 d after (remediation group) diabetes induction. Diphenyl diselenide treatment reduced the blood glucose and fructosamine levels, which were increased in alloxan-treated rats. However, the delta-aminolevulinate dehydratase (delta-ALA-D) activity inhibited by alloxan was not restored by diphenyl diselenide. Moreover, diphenyl diselenide caused by itself an inhibition in hepatic and renal delta-ALA-D activity. Our findings suggest that the acute treatment with diphenyl diselenide reduces the hyperglycemia but does not improve delta-ALA-D activity decreased by alloxan. Although the dose of diphenyl diselenide used here for treating diabetic animals has been relatively high and produced toxic effects, the compound or analogous molecules might not be rejected as a promising anti-hyperglycemic agent.

Diphenyl diselenide exerts anxiolytic-like effect in Wistar rats: putative roles of GABAA and 5HT receptors

Diphenyl diselenide [(PhSe)2] is an organoselenium compound which presents pharmacological antioxidant, anti-inflammatory, antinociceptive and antidepressant properties. The present study was designed to investigate the anxiolytic effect of (PhSe)2 in rats, employing the elevated plus maze task. The involvement of 5HT and GABA receptors in the anxiolytic-like effect was also evaluated. (PhSe)2 (5, 25 and 50 micromol/kg, i.p.) did not affect locomotor activity as evaluated in the open open-field test, and learning and memory when assessed in the inhibitory foot-shock avoidance task. However, (PhSe)2 at the 50 micromol/kg dose produced signs of an anxiolytic action, namely a decreased number of fecal boli in the open-field arena and an increased time spent in as well as an increased number of entries to the open arms of the elevated plus maze test. To evaluate the role of GABA and 5HT receptors in the anxiolytic-like effect of (PhSe)2, a selective GABAA receptor antagonist bicuculline, (0.75 mg/kg, i.p.), a non-selective 5HT2A/2C receptor antagonist, ritanserin (2 mg/kg, i.p.), a selective 5HT2A receptor antagonist, ketanserin (1 mg/kg, i.p.), and a selective 5HT1A receptor antagonist, WAY100635 (0.1 mg/kg, i.p.) were used. All the antagonists used were able to abolish the anxiolytic effect of (PhSe)2 suggesting that GABAA and 5HT receptors may play a role in the pharmacological property of this selenocompound in the central nervous system.

Diphenyl diselenide, a simple glutathione peroxidase mimetic, inhibits human LDL oxidation in vitro

Oxidative modification of low-density lipoprotein (LDL) represents an important factor in atherogenesis. In the present study, we have investigated the antioxidant capability of diphenyl diselenide (PhSe)(2), a simple organoseleno compound, against copper (Cu2+) and peroxyl radical-induced human LDL oxidation in vitro. In initial studies using human serum, (PhSe)(2) caused a dose-dependent inhibition of Cu(2+)-induced lipid peroxidation, which was correlated to thiol consumption. (PhSe)(2) increased lipid peroxidation lag phase and decreased lipid peroxidation rate in isolated human LDL, evaluated by measuring both conjugated diene (CD) and thiobarbituric acid reactive substances (TBARS) levels. Consistent with these observations, (PhSe)(2) showed a marked inhibitory effect on 2,2-azobis(2-amidinopropane dihydrochloride) (AAPH)-induced oxidation of LDL or parinaric acid (PnA) incorporated into LDL. (PhSe)(2) also displayed a dose-dependent protective effect against Cu(2+)-induced lipid peroxidation in rat aortic slices. Interestingly, besides the antioxidant effects of (PhSe)(2) toward the lipid moieties of LDL, which was related to its thiol-peroxidase activity, protein moieties from human isolated LDL were also protected against Cu(2+)-induced oxidation. The results presented herein are the first to show that (i) (PhSe)(2) inhibits lipid peroxidation in human isolated LDL in vitro, (ii) this phenomenon is related to its thiol-peroxidase activity, and (iii) this chalcogen also prevents the oxidation of protein moieties of human LDL. Taken together, such data render (PhSe)(2) a promising molecule for pharmacological studies with respect to the atherogenic process.

Dietary diphenyl diselenide reduces the STZ-induced toxicity

Oxidative stress is implicated in the pathogenesis of diabetes mellitus. Selenium supplementation has some benefits in experimental models of diabetes mellitus. This study evaluated whether dietary diphenyl diselenide, a simple synthetic organoselenium compound with antioxidant properties, reduces the streptozotocin (STZ)-induced toxicity. STZ-induced diabetic rats were fed with either standard and diphenyl diselenide (10 ppm) supplemented diets. In experimental trials, dietary diphenyl diselenide significantly decreased mortality rate (p<0.05) induced by STZ treatment. No correlation between this effect and glycemic levels were found. Diphenyl diselenide intake also promoted an increase in vitamin C, -SH levels (liver, kidney and blood) and in catalase (liver and kidney) activity, which were decreased in STZ-treated rats. In enzyme assays, diphenyl diselenide supplementation caused a significant improvement in platelets NTPDase and 5'-nucleotidase activities in STZ-induced diabetic rats when compared to the control and diabetic groups (p<0.05). Nevertheless, this supplementation did not modify the inhibition induced by STZ in delta-ALA-D activity. Our findings suggest that diphenyl diselenide compound showed beneficial effects against the development of diabetes by exhibiting antioxidant properties.

Diphenyl diselenide supplementation delays the development of N-nitroso-N-methylurea-induced mammary tumors

The effect of dietary diphenyl diselenide (1 ppm) on N-nitroso-N-methylurea (NMU)-induced mammary carcinogenesis was examined in female Wistar rats. Beginning at 5 weeks of age, the animals were fed with either control or diphenyl-diselenide-supplied diets until the end of the study (210 days). At 50 days of age, mammary tumor was induced by the administration of three doses of NMU (50 mg/kg body wt, intraperitoneally) once a week for 3 weeks. In experimental trials, latency to tumor onset was extended in rats fed with diet supplemented with diphenyl diselenide (P < 0.05). The incidence and frequency of tumors were significantly small in animals supplemented with diphenyl diselenide. However, the multiplicity of tumors was not altered by dietary diphenyl diselenide. Diphenyl diselenide supplementation also restored superoxide dismutase (SOD) activity and vitamin C levels altered in the NMU group (P < 0.05). Our results suggest that diphenyl diselenide can be considered a chemopreventive agent, even when supplemented at a relatively low concentration.

Diphenyl diselenide attenuates acute thermal hyperalgesia and persistent inflammatory and neuropathic pain behavior in mice

Experiments were designed to address whether diphenyl diselenide (PhSe)(2) has antiallodynic and antihyperalgesic properties. The neuropathic pain was caused by a partial tying (2/3) of sciatic nerve and the inflammatory pain was induced by an intraplantar (i.pl.) injection of 20 microl of Freund's Complete Adjuvant (CFA) in mice. Seven days after sciatic nerve constriction and 24 h after CFA intraplantar (i.pl.) injection, mouse pain threshold was evaluated through tactile allodynia, using Von Frey Hair (VHF) filaments. The acute thermal hyperalgesia was induced by intrathecal (i.t.) injection of glutamate, N-methyl-d-aspartate (NMDA), bradykinin (BK) and prostaglandin E(2) (PGE(2)), and the nociceptive response was assessed using hot-plate test. (PhSe)(2) administered by oral route (p.o.) (10 mg/kg) decreased the paw withdrawal response on the ipsilateral side of the partial sciatic nerve ligation 30 min after drug administration (64+/-7%) and this effect was kept for 1 h after treatment. (PhSe)(2) (10 mg/kg, p.o.) produced a reduction in mechanical allodynia induced by CFA started 30 min after (PhSe)(2) administration (71+/-5%) and this effect was maintained for up 4 h. (PhSe)(2) (0.1-50 mg/kg, p.o.) caused a significant inhibition of glutamate-, NMDA- and BK-(PGE(2))-induced acute thermal hyperalgesia in mice. Together, the present results indicate that (PhSe)(2) produces systemic antiallodynic action when assessed in mechanical stimulus (VHF) in the hindpaw and also attenuates acute thermal hyperalgesia. Thus, this compound might be potentially interesting in the development of new clinically relevant drugs for the management of pain.

Involvement of oxidative stress in seizures induced by diphenyl diselenide in rat pups

In the present study the potential neurotoxicity of diphenyl diselenide, as measured by the manifestation of seizures in rat pups (postnatal days, PND, 12-14) was evaluated. The results suggest that the latency for the appearance of tonic-clonic seizures, characterized by rearing and falling of rat pups body, was dependent of the dose tested. Diphenyl diselenide at high doses induced seizure episodes in rat pups. The highest dose of diphenyl diselenide (500 mg/kg) increased the levels of lipid peroxidation and catalase activity as well as decreased delta-ALA-D (delta-aminolevulinate dehydratase) and Na(+), K(+) ATPase activity in the brain of rat pups. Our results indicate the possible involvement of free radical oxygen injury in diphenyl diselenide-induced seizures. The data obtained with the dose of 150 mg/kg in the brain of rats that exhibited seizures are: an increase in lipid peroxidation levels; the lack of effect on catalase activity; an inhibition of delta-ALA-D activity, supporting that the enzyme activity is more sensitive than other parameters analyzed as an indicator of oxidative stress. The lowest dose of diphenyl diselenide emphasizes the relationship between the appearance of seizures and the latency for the onset of the first episode. Taken together, this paper could add to our understanding of diphenyl diselenide neurotoxic effect demonstrated by the appearance of seizures which are, at least in part, related to the oxidative stress.