A Review on the Environmental Exposure to Airborne Manganese, Biomonitoring, and Neurological/Neuropsychological Outcomes

Exposure to Manganese Induces Autophagy-Lysosomal Pathway Dysfunction-Mediated Tauopathy by Activating the cGAS-STING Pathway in the Brain

Manganese (Mn) exposure leads to pathological accumulation of Tau-associated neurodegenerative disease and has become a major public health concern. However, the precise mechanism underlying this effect remains unclear. Here, the mechanism by which Mn induces dysfunction of autophagy-lysosomal pathway-mediated tauopathy by activating the cGAS-STING pathway was explored both in vitro and in vivo. Mn exposure induced tauopathy in microglia and in mice while activating the cGAS-STING pathway, inducing type I interferon production, and impairing the degradation function of the autophagy-lysosomal pathway. Importantly, inactivation of the cGAS-STING pathway rescued the degradation activity of the autophagy-lysosomal pathway, while tauopathy was markedly attenuated, as shown in both cGAS-knockout and STING-knockout BV2 microglia and in mice. Moreover, the autophagy inhibitor 3-methyladenine (3-MA) restored the impaired degradation activity of the autophagy-lysosomal pathway by inactivating the cGAS-STING pathway, thereby clearing Tau aggregation. Taken together, these results indicate that Mn exposure induces tauopathy by impairing the function of the autophagy-lysosomal pathway through the activation of the cGAS-STING pathway. Thus, this study identifies a novel mechanism by which Mn exposure induces Tau aggregation, which in turn triggers potential neurotoxicity, providing a foundation for future drug target research.

Heterointerface of Monodispersed Ultrathin-MnO2@Amorphous Carbon to Attain Durable Lattice Oxygen Redox Chemistry through Creation of Dual Lattice Oxygens

Lattice oxygen (OL) redox chemistry is a key to alleviating the energy and environmental crisis, but it faces challenges in activating the OL while ensuring structural stability. We disclosed herein that engineering a heterogeneous interface between ultrathin oxide and amorphous carbon can attain the durable OL redox chemistry without introducing catalytically impure sites. To this end, we proposed a green strategy to grow ∼3.9 nm-thickness wrinkled δ-MnO2 nanosheets that are rich in defects and are vertically aligned on amorphous carbon spheres. Experiments and calculations reveal that the electrons can easily migrate from the amorphous carbon to MnO2 at the δ-MnO2@C heterointerface. The heterogeneous interfaces can not only regulate the Mn-O bond and create oxygen defects in δ-MnO2 but also introduce lattice oxygen with varying reactivities. Specifically, the δ-MnO2@C structure carries more activated lattice oxygen that contributes to the enhanced activity on catalytic oxidation of bioderived 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), with a high FDCA formation rate of 1759 μmol gcat-1 h-1 and a high selectivity of 95%. The heterogeneous interface of MnO2@C also brings inert lattice oxygen, so that it manifests high structural stability during the oxidation reactions. This work deepens the fundamental understandings in the engineering of lattice oxygen for durable lattice oxygen redox chemistry and showcases an effective interface technique in creating advanced catalysts for clean sustainable energy.

Short- and long-term exposure to trace metal(loid)s from the production of ferromanganese alloys by personal sampling and biomarkers

The environmental exposure to trace metal(loid)s (As, Cd, Cu, Fe, Mn, Pb, and Zn) was assessed near a ferromanganese alloy plant using filters from personal particulate matter (PM) samplers (bioaccessible and non-bioaccessible fine and coarse fractions) and whole blood as short-term exposure markers, and scalp hair and fingernails as long-term biomarkers, collected from volunteers (n = 130) living in Santander Bay (northern Spain). Bioaccessible and non-bioaccessible metal(loid) concentrations in coarse and fine PM from personal samplers were determined by ICP-MS after extraction/digestion. Metal(loid) concentration in biomarkers was measured after alkaline dilution (whole blood) and acid digestion (fingernails and scalp hair) by ICP-MS as well. Results were discussed in terms of exposure, considering the distance to the main Mn source, and sex. In terms of exposure, significant differences were found for Mn in all the studied fractions of PM, As in whole blood, Mn and Cu in scalp hair and Mn and Pb in fingernails, with all concentrations being higher for those living closer to the Mn source, with the exception of Cu in scalp hair. Furthermore, the analysis of the correlation between Mn levels in the studied biomarkers and the wind-weighted distance to the main source of Mn allows us to conclude that scalp hair and mainly fingernails are appropriate biomarkers of long-term airborne Mn exposure. This was also confirmed by the significant positive correlations between scalp hair Mn and bioaccessible Mn in coarse and fine fractions, and between fingernails Mn and all PM fractions. This implies that people living closer to a ferromanganese alloy plant are exposed to higher levels of airborne metal(loid)s, mainly Mn, leading to higher levels of this metal in scalp hair and fingernails, which according to the literature, might affect some neurological outcomes. According to sex, significant differences were observed for Fe, Cu and Pb in whole blood, with higher concentrations of Fe and Pb in males, and higher levels of Cu in females; and for Mn, Cu, Zn, Cd and Pb in scalp hair, with higher concentrations in males for all metal(loid)s except Cu.

Impact of Environmental Airborne Manganese Exposure on Cognitive and Motor Functions in Adults: A Systematic Review and Meta-Analysis

Background/Objective: Whether environmental exposure to Manganese (Mn) in adults is associated with poorer results in cognitive and motor function is unclear. We aimed to determine these associations through a meta-analysis of published studies. Methods: A systematic review was conducted to identify epidemiological studies on a population ≥18 years old exposed to environmental airborne Mn, and in which results on specific tests to evaluate cognitive or motor functions were reported. We consulted Medline through PubMed, Web of Science and SCOPUS databases. We also performed a manual search within the list of bibliographic references of the retrieved studies and systematic reviews. To weight Mn effects, a random effects versus fixed effect model was chosen after studying the heterogeneity of each outcome. Results. Eighteen studies met the inclusion criteria. Among them, eleven studies reported data susceptible for meta-analysis through a pooled correlation or a standardized means difference (SMD) approach between exposed and non-exposed groups. Regarding cognitive function, the results of the studies showed heterogeneity among them (I² = 76.49%, p < 0.001). The overall effect was a statistically significant negative correlation in the random effects model (pooled r = −0.165; 95%CI: −0.214 to −0.116; p < 0.001). For SMD, the results showed a lower heterogeneity with a negative SMD that did not reach statistical significance under the fixed effects model (SMD = −0.052; 95%CI −0.108 to 0.004; p = 0.068). Regarding motor function, heterogeneity (I² = 75%) was also observed in the correlation approach with a pooled r (random effect model) = −0.150; 95%CI: −0.219 to −0.079; p < 0.001. Moderate heterogeneity was observed according to the SMD approach (I² = 52.28%), with a pooled SMD = −0.136; 95%CI: −0.188 to−0.084; p < 0.001, indicating worse motor function in those exposed. Conclusions: Correlation approach results support a negative effect on cognitive and motor functions (the higher the Mn levels, the poorer the scores). Regarding the SMD approach, results also support a worse cognitive and motor functions in those exposed, although only for motor function statistical significance was obtained.