Transient hypothermia and hyperphagia induced by selenium and tellurium compounds in mice

Facilitation of long-term object recognition memory by pretraining administration of diphenyl diselenide in mice

Selenium compounds display antioxidant and neuroprotective properties. Diphenyl diselenide (PhSe)(2) is an organic selenium compound that affects a number of neuronal processes. The aim of the present study was to evaluate the effects of the systemic administration of (PhSe)(2) on novel object recognition memory in mice. Adult male CF1 mice were given an i.p. injection of (PhSe)(2) (0.2, 1.0, 5.0, or 25.0 micromol/kg) 30 min before training in an object recognition task. (PhSe)(2) did not affect short-term memory or the total time exploring both objects, but induced a facilitation of retention measured 24 h after training. The present findings show that systemic administration of (PhSe)(2) induces a facilitation of formation of long-term object recognition memory.

Methamphetamine-induced dopaminergic neurotoxicity: role of peroxynitrite and neuroprotective role of antioxidants and peroxynitrite decomposition catalysts

Oxidative stress, reactive oxygen (ROS), and nitrogen (RNS) species have been known to be involved in a multitude of neurodegenerative disorders such as Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS). Both ROS and RNS have very short half-lives, thereby making their identification very difficult as a specific cause of neurodegeneration. Recently, we have developed a high performance liquid chromatography/electrochemical detection (HPLC/EC) method to identify 3-nitrotyrosine (3-NT), an in vitro and in vivo biomarker of peroxynitrite production, in cell cultures and brain to evaluate if an agent-driven neurotoxicity is produced by the generation of peroxynitrite. We show that a single or multiple injections of methamphetamine (METH) produced a significant increase in the formation of 3-NT in the striatum. This formation of 3-NT correlated with the striatal dopamine depletion caused by METH administration. We also show that PC12 cells treated with METH has significantly increased formation of 3-NT and dopamine depletion. Furthermore, we report that pretreatment with antioxidants such as selenium and melatonin can completely protect against the formation of 3-NT and depletion of striatal dopamine. We also report that pretreatment with peroxynitrite decomposition catalysts such as 5, 10,15,20-tetrakis(N-methyl-4'-pyridyl)porphyrinato iron III (FeTMPyP) and 5, 10, 15, 20-tetrakis (2,4,6-trimethyl-3,5-sulfonatophenyl) porphinato iron III (FETPPS) significantly protect against METH-induced 3-NT formation and striatal dopamine depletion. We used two different approaches, pharmacological manipulation and transgenic animal models, in order to further investigate the role of peroxynitrite. We show that a selective neuronal nitric oxide synthase (nNOS) inhibitor, 7-nitroindazole (7-NI), significantly protect against the formation of 3-NT as well as striatal dopamine depletion. Similar results were observed with nNOS knockout and copper zinc superoxide dismutase (CuZnSOD)-overexpressed transgenic mice models. Finally, using the protein data bank crystal structure of tyrosine hydroxylase, we postulate the possible nitration of specific tyrosine moiety in the enzyme that can be responsible for dopaminergic neurotoxicity. Together, these data clearly support the hypothesis that the reactive nitrogen species, peroxynitrite, plays a major role in METH-induced dopaminergic neurotoxicity and that selective antioxidants and peroxynitrite decomposition catalysts can protect against METH-induced neurotoxicity. These antioxidants and decomposition catalysts may have therapeutic potential in the treatment of psychostimulant addictions.

Selenium, an antioxidant, attenuates methamphetamine-induced dopaminergic toxicity and peroxynitrite generation

Methamphetamine (METH) has been known to produce neurotoxicity via generation of reactive oxygen and nitrogen species. Selenium, an antioxidant, was reported to protect against METH-induced dopaminergic neurotoxicity in mouse caudate nucleus. In the present study, the in vitro and in vivo efficacy of the supplementation of selenium was studied in METH-induced generation of peroxynitrite. PC12 cell cultures were exposed to 200 microM METH either with or without 10 microM and 20 microM selenium (30 min prior to METH exposure). After 24 h, METH exposure resulted in the significant depletion of dopamine, and its metabolites DOPAC and HVA, as well as the significant formation of 3-nitrotyrosine (3-NT), a marker of peroxynitrite generation, in PC12 cell cultures. Selenium supplementation attenuated the depletion of dopamine and its metabolites, DOPAC and HVA and the formation of 3-NT in PC12 cells. For in vivo studies, adult male mice were supplemented with selenium in drinking water, 1 week before and 1 week after the multiple injections of METH (4x10 mg/kg, i.p. at 2-h interval) or an equivalent volume of saline. The supplementation of Se attenuated the formation of 3-NT in the striatum resulting from METH treatment. These data suggest that METH-induced neurotoxicity is mediated by the production of peroxynitrite, and selenium plays a protective role in METH-induced neurotoxicity.

Radioprotection by metals: selenium

The need exists for compounds that will protect individuals from high-dose acute radiation exposure in space and the agents that might be less protective but less toxic and longer acting. Metals and metal derivatives provide a small degree of radioprotection (dose reduction factor < or = 1.2 for animal survival after whole-body irradiation). Emphasis is placed here on the radioprotective potential of selenium (Se). Both the inorganic salt, sodium selenite, and the organic Se compound, selenomethionine, enhance the survival of irradiated mice (60Co, 0.2 Gy/min) when injected IP either before (-24 hr and -1 hr) or shortly after (+15 min) radiation exposure. When administered at equitoxic doses (one-fourth LD10; selenomethionine = 4.0 mg/kg Se, sodium selenite = 0.8 mg/kg Se), both drugs enhanced the 30-day survival of mice irradiated at 9 Gy. Survival after 10-Gy exposure was significantly increased only after selenomethionine treatment. An advantage of selenomethionine is lower lethal and behavioral toxicity (locomotor activity depression) compared to sodium selenite, when they are administered at equivalent doses of Se. Sodium selenite administered in combination with WR-2721, S-2-(3-aminopropylamino)ethylphosphorothioic acid, enhances the radioprotective effect and reduces the lethal toxicity, but not the behavioral toxicity, of WR-2721. Other studies on radioprotection and protection against chemical carcinogens by different forms of Se are reviewed. As additional animal data and results from human chemoprevention trials become available, consideration also can be given to prolonged administration of Se compounds for protection against long-term radiation effects in space.