Various forms of mercury possess different rates of absorption, metabolism and excretion, and consequently, toxicity. Methylmercury (MeHg) is a highly neurotoxic organic mercurial. Human exposure is mostly due to ingestion of contaminated fish. Ethylmercury (EtHg), another organic mercury compound, has received significant toxicological attention due to its presence in thimerosal-containing vaccines. This study was designed to compare the toxicities induced by MeHg and EtHg, as well as by their complexes with cysteine (MeHg-S-Cys and EtHg-S-Cys) in the C6 rat glioma cell line. MeHg and EtHg caused significant (p < 0.0001) decreases in cellular viability when cells were treated during 30 min with each mercurial following by a washing period of 24 h (EC50 values of 4.83 and 5.05 μM, respectively). Significant cytotoxicity (p < 0.0001) was also observed when cells were treated under the same conditions with MeHg-S-Cys and EtHg-S-Cys, but the respective EC50 values were significantly increased (11.2 and 9.37 μM). L-Methionine, a substrate for the L-type neutral amino acid carrier transport (LAT) system, significantly protected against the toxicities induced by both complexes (MeHg-S-Cys and EtHg-S-Cys). However, no protective effects of L-methionine were observed against MeHg and EtHg toxicities. Corroborating these findings, L-methionine significantly decreased mercurial uptake when cells were exposed to MeHg-S-Cys (p = 0.028) and EtHg-S-Cys (p = 0.023), but not to MeHg and EtHg. These results indicate that the uptake of MeHg-S-Cys and EtHg-S-Cys into C6 cells is mediated, at least in part, through the LAT system, but MeHg and EtHg enter C6 cells by mechanisms other than LAT system.

Trypanosomatids cause many diseases in and on animals (including humans) and plants. Altogether, about 37 million people are infected with Trypanosoma brucei (African sleeping sickness), Trypanosoma cruzi (Chagas disease) and Leishmania species (distinct forms of leishmaniasis worldwide). The class Kinetoplastea is divided into the subclasses Prokinetoplastina (order Prokinetoplastida) and Metakinetoplastina (orders Eubodonida, Parabodonida, Neobodonida and Trypanosomatida) [1,2]. The Prokinetoplastida, Eubodonida, Parabodonida and Neobodonida can be free-living, commensalic or parasitic; however, all members of theTrypanosomatida are parasitic. Although they seem like typical protists under the microscope the kinetoplastids have some unique features. In this review we will give an overview of the family Trypanosomatidae, with particular emphasis on some of its "peculiarities" (a single ramified mitochondrion; unusual mitochondrial DNA, the kinetoplast; a complex form of mitochondrial RNA editing; transcription of all protein-encoding genes polycistronically; trans-splicing of all mRNA transcripts; the glycolytic pathway within glycosomes; T. brucei variable surface glycoproteins and T. cruzi ability to escape from the phagocytic vacuoles), as well as the major diseases caused by members of this family. However, the present review does not cover all trypanosomatids; for example, the insect trypanosomatids are underrepresented here. On the other hand, reviews on this particular group of parasites have been written by experts in the field [3-12].

Huntington’s disease (HD) is an autosomal dominantly inherited neurodegenerative disease characterized by symptoms attributable to the death of striatal and cortical neurons. The molecular mechanisms mediating neuronal death in HD involve oxidative stress and mitochondrial dysfunction. Administration of 3-nitropropionic acid (3-NP), an irreversible inhibitor of the mitochondrial enzyme succinate dehydrogenase, in rodents has been proposed as a useful experimental model of HD. This study evaluated the effects of probucol, a lipid-lowering agent with anti-inflammatory and antioxidant properties, on the biochemical parameters related to oxidative stress, as well as on the behavioral parameters related to motor function in an in vivo HD model based on 3-NP intoxication in rats. Animals were treated with 3.5 mg/kg of probucol in drinking water daily for 2 months and, subsequently, received 3-NP (25 mg/kg i.p.) once a day for 6 days. At the end of the treatments, 3-NP-treated animals showed a significant decrease in body weight, which corresponded with impairment on motor ability, inhibition of mitochondrial complex II activity and oxidative stress in the striatum. Probucol, which did not rescue complex II inhibition, protected against behavioral and striatal biochemical changes induced by 3-NP, attenuating 3-NP-induced motor impairments and striatal oxidative stress. Importantly, probucol was able to increase activity of glutathione peroxidase (GPx), an enzyme important in mediating the detoxification of peroxides in the central nervous system. The major finding of this study was that probucol protected against 3-NP-induced behavioral and striatal biochemical changes without affecting 3-NP-induced mitochondrial complex II inhibition, indicating that long-term probucol treatment resulted in an increased resistance against neurotoxic events (i.e., increased oxidative damage) secondary to mitochondrial dysfunction. These data appeared to be of great relevance when extrapolated to human neurodegenerative processes involving mitochondrial dysfunction and indicates that GPx is an important molecular target involved in the beneficial effects of probucol.

Targeted extrahepatic delivery of siRNA remains a challenging task in the field of nucleic acid therapeutics. An ideal delivery tool must internalize siRNA exclusively into the cells of interest without affecting the silencing activity of siRNA. Here, we report the use of anti-EGFR Nanobodies (trademark of Ablynx N.V.) as tools for targeted siRNA delivery. A straightforward procedure for site-specific conjugation of siRNA to an engineered C-terminal cysteine residue on the Nanobody (trademark of Ablynx N.V.) is described. We show that siRNA-conjugated Nanobodies (Nb−siRNA) retain their binding to EGFR and enter EGFR-positive cells via receptor-mediated endocytosis. The activity of Nb−siRNAs was assessed by measuring the knockdown of a housekeeping gene (AHSA1) in EGFR-positive and EGFR-negative cells. We demonstrate that Nb− siRNAs are active in vitro and induce mRNA cleavage in the targeted cell line. In addition, we discuss the silencing activity of siRNA conjugated to fused Nbs with various combinations of EGFR-binding building blocks. Finally, we compare the performance of Nb−siRNA joined by four different linkers and discuss the advantages and limitations of using cleavable and noncleavable linkers in the context of Nanobody-mediated siRNA delivery.

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