From Molecules to Behavior in Long-Term Inorganic Mercury Intoxication: Unraveling Proteomic Features in Cerebellar Neurodegeneration of Rats

Mercury is a severe environmental pollutant with neurotoxic effects, especially when exposed for long periods. Although there are several evidences regarding mercury toxicity, little is known about inorganic mercury (IHg) species and cerebellum, one of the main targets of mercury associated with the neurological symptomatology of mercurial poisoning. Besides that, the global proteomic profile assessment is a valuable tool to screen possible biomarkers and elucidate molecular targets of mercury neurotoxicity; however, the literature is still scarce. Thus, this study aimed to investigate the effects of long-term exposure to IHg in adult rats’ cerebellum and explore the modulation of the cerebellar proteome associated with biochemical and functional outcomes, providing evidence, in a translational perspective, of new mercury toxicity targets and possible biomarkers. Fifty-four adult rats were exposed to 0.375 mg/kg of HgCl2 or distilled water for 45 days using intragastric gavage. Then, the motor functions were evaluated by rotarod and inclined plane. The cerebellum was collected to quantify mercury levels, to assess the antioxidant activity against peroxyl radicals (ACAPs), the lipid peroxidation (LPO), the proteomic profile, the cell death nature by cytotoxicity and apoptosis, and the Purkinje cells density. The IHg exposure increased mercury levels in the cerebellum, reducing ACAP and increasing LPO. The proteomic approach revealed a total 419 proteins with different statuses of regulation, associated with different biological processes, such as synaptic signaling, energy metabolism and nervous system development, e.g., all these molecular changes are associated with increased cytotoxicity and apoptosis, with a neurodegenerative pattern on Purkinje cells layer and poor motor coordination and balance. In conclusion, all these findings feature a neurodegenerative process triggered by IHg in the cerebellum that culminated into motor functions deficits, which are associated with several molecular features and may be related to the clinical outcomes of people exposed to the toxicant.

Changes in fatty acid profile of Holothuria forskali muscle following acute mercury exposure

The present study aimed to document the interaction between mercury (Hg), as a model chemical stressor to an aquatic organism, and Fatty acid (FA) profile in the longitudinal muscle of the sea cucumber Holothuria forskali. To assess the sensitivity of this species to the toxic effects of Hg, young H. forskali were exposed to gradual doses of Hg (40, 80 and160 µg·L-1) for 96 h. The results showed that following Hg exposure, the FA profile of H. forskali corresponded to an increase in the level of saturated fatty acids, and the decrease in the level of monounsaturated and polyunsaturated fatty acids. The most prominent changes in the FA composition were recorded at the lowest dose with noticeable decreases in linoleic, arachidonic and eicosapentaenoic acid levels and an increase of docosahexaenoic acid. The occurrence of a state of oxidative stress induced by Hg contamination was evidenced by the enhanced levels of malondialdehyde, hydrogen peroxide and lipid hydroperoxide. Overall, the low concentration of mercury exerted the most obvious effects on lipid metabolism, suggesting that changes in fatty acid composition may be act as an early biomarker to assess mercury toxicity in this ecologically and economically important species.

Choice of Restorative Materials for Direct Posterior Restorations among Undergraduate Saudi College Students

Background: The most common restorative materials used in dentistry are amalgam and composite. Amalgam is a controversial material owing to its mercury toxicity. With recent advances in the properties of composite materials, there has been a shift towards its use. Objectives: The aim of this study was to understand the perceptions of undergraduate dental students in a northern Saudi Arabian dental school about the choice of restorative materials for restoring posterior teeth. Methodology: The study included undergraduate students studying in 4th and 5th year dental program in College of Dentistry, Jouf University. A four-item questionnaire with 18 close-ended questions was developed by the investigators, which were hand delivered to all the students. Data analysis is presented through tables and descriptive methods. Results: A total of 98 (out of 131) undergraduate students participated in this study. Overall, the students reported a significantly strong influence of the type of restorative materials in relation to the cavity size and margin of the restorations along with the esthetics factor(p<0.05). There was slight influence on the student’s choice because of the instructor's influence, whereas the students felt they were knowledgeable and had appropriate training to use either amalgam or composite. The study also found that patient’s preference had a strong influence on choosing composite material. The students were mostly not influenced while choosing the material as far as the safety of it was concerned. However, the patient’s influence was slight when it came to the choice of the material. A significant difference was noted among the students when it came to pregnancy-related safety concerns where the choice of material was not influenced by either amalgam or composite (p=.002). Conclusion: The undergraduate dental students at College of Dentistry, Jouf University are comfortable in using both amalgam and composite as a posterior restorative material. They are knowledgeable about both the materials and are adequately trained to use either one.