Methylmercury (MeHg) reacts with nucleophilic sulfur species to form sulfur adducts, such as the low-toxic metabolite bismethylmercury sulfide [(MeHg)2S]. We found that protein-bound persulfides interact with MeHg to form (MeHg)2S and identified glutathione S-transferase pi 1 as a S-sulfhydrated protein involved in (MeHg)2S formation. Although glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a house-keeping protein abundantly expressed in various tissues, has been reported to undergo S-sulfhydration in the presence of sulfur donors or cystathionine γ-lyase, the biological significance of this post-translational modification is poorly understood. In this study, we investigated the possible interaction between GAPDH and MeHg to form (MeHg)2S. High-performance liquid chromatography/atomic absorption spectrophotometry revealed that (MeHg)2S was formed during the reaction of MeHg with a model of cysteine persulfide and GAPDH following incubation of the protein with NaHS. After reacting with NaHS, GAPDH C152S and C156S mutants transformed MeHg into (MeHg)2S, whereas formation of the sulfur adduct was not observed for the C247S mutant, suggesting that Cys247 is critical for conversion of MeHg to (MeHg)2S. These results suggest that the sulfane sulfur on Cys247 of GAPDH plays a protective role in reducing MeHg toxicity.
The present study was conducted to survey the influence of canola oil (CAN) ingestion on the steroid hormone production in stroke-prone spontaneously hypertensive rats (SHRSP). Male SHRSP were fed a diet containing 10 wt/wt% soybean oil (SOY, the control) or CAN as the sole dietary fat for 8 weeks. Plasma concentration of luteinizing hormone (LH) was similar in the 2 dietary groups. However, the plasma testosterone level in the CAN group, 1.36 ± 0.271 ng/mL, was lower than in the SOY group, 2.79 ± 0.514 ng/mL (p < 0.05, unpaired t-test; n = 10), and plasma concentration of aldosterone in the CAN group, 345 ± 79.6 pg/mL, was higher than in the SOY group, 159 ± 33.7 pg/mL (p < 0.05, unpaired t-test; n = 10). In the testis, the expressions of mRNA for StAR, CYP11A1, CYP17, 3βHSD and 17βHSD and the amounts of the corresponding proteins were significantly decreased. However, in the adrenal gland, the expressions of mRNA for StAR, CYP11A1, 3βHSD and CYP11B1 in the CAN group were not different from those in the SOY group, but the expression of mRNA and the amount of the corresponding protein for CYP11B2 were increased significantly in the CAN group. These findings are indicative of a peripheral, testicular toxicity of CAN. The decreased testosterone and the concomitantly increased aldosterone may play a role in the aggravation by CAN of the genetic diseases (i.e., metabolic syndrome-like complications) in male SHRSP.
Carbon-nanotube yarn (CNT-Y) made from high-purity, highly crystalized, double-walled carbon nanotubes is an advanced material with excellent electrical conductivity and flexibility; hence, it could potentially be used as a novel electrode for biopotential measurements. To our knowledge, the present study is the first in which CNT-Y electrodes were used to conduct electrocardiography (ECG) and electroencephalography (EEG) on experimental animals. All procedures and biopotential measurements were performed under isoflurane anesthesia. The CNT-Y electrodes were attached to the animals by creating a single interrupting suture on the skin. The lead II electrode configuration was used for ECG recording, i.e., the positive, negative, and body-earth electrodes were placed on the left apex of the auricular surface, the interscapular region, and the cervical region, respectively. The bipolar lead was used for EEG recording, with the exploring and reference electrodes on the bregma and base of the right auricular surface, respectively. Using CNT-Y electrodes, we obtained a clear ECG waveform from rats and a guinea pig; the QRS amplitude was ~1.4 mV. In rats, we obtained an EEG waveform with an amplitude of ~150 µV; the peak frequency was 0.8 Hz and the range was ~3 Hz according to power spectral density analysis. In the guinea pig, we obtained an EEG waveform with an amplitude of ~500 µV; the first peak was 0.1 Hz, the second peak was 1 Hz, and the range was ~3 Hz. These results show that CNT-Y could be used in toxicology studies to easily and inexpensively obtain high-resolution biological signals.