Effects of Manganese on Genomic Integrity in the Multicellular Model Organism Caenorhabditis elegans

Dysfunctional copper homeostasis in Caenorhabditis elegans affects genomic and neuronal stability

While copper (Cu) is an essential trace element for biological systems due to its redox properties, excess levels may lead to adverse effects partly due to overproduction of reactive species. Thus, a tightly regulated Cu homeostasis is crucial for health. Cu dyshomeostasis and elevated labile Cu levels are associated with oxidative stress and neurodegenerative disorders, but the underlying mechanisms have yet to be fully characterized. Here, we used Caenorhabditis elegans loss-of-function mutants of the Cu chaperone ortholog atox-1 and the Cu binding protein ortholog ceruloplasmin to model Cu dyshomeostasis, as they display a shifted ratio of total Cu towards labile Cu. We applied highly selective and sensitive techniques to quantify metabolites associated to oxidative stress with focus on mitochondrial integrity, oxidative DNA damage and neurodegeneration all in the context of a disrupted Cu homeostasis. Our novel data reveal elevated oxidative stress, compromised mitochondria displaying reduced ATP levels and cardiolipin content. Cu dyshomeostasis further induced oxidative DNA damage and impaired DNA damage response as well as neurodegeneration characterized by behavior and neurotransmitter analysis. Our study underscores the essentiality of a tightly regulated Cu homeostasis as well as mitochondrial integrity for both genomic and neuronal stability.

Consequences of Disturbing Manganese Homeostasis

Manganese (Mn) is an essential trace element with unique functions in the body; it acts as a cofactor for many enzymes involved in energy metabolism, the endogenous antioxidant enzyme systems, neurotransmitter production, and the regulation of reproductive hormones. However, overexposure to Mn is toxic, particularly to the central nervous system (CNS) due to it causing the progressive destruction of nerve cells. Exposure to manganese is widespread and occurs by inhalation, ingestion, or dermal contact. Associations have been observed between Mn accumulation and neurodegenerative diseases such as manganism, Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. People with genetic diseases associated with a mutation in the gene associated with impaired Mn excretion, kidney disease, iron deficiency, or a vegetarian diet are at particular risk of excessive exposure to Mn. This review has collected data on the current knowledge of the source of Mn exposure, the experimental data supporting the dispersive accumulation of Mn in the brain, the controversies surrounding the reference values of biomarkers related to Mn status in different matrices, and the competitiveness of Mn with other metals, such as iron (Fe), magnesium (Mg), zinc (Zn), copper (Cu), lead (Pb), calcium (Ca). The disturbed homeostasis of Mn in the body has been connected with susceptibility to neurodegenerative diseases, fertility, and infectious diseases. The current evidence on the involvement of Mn in metabolic diseases, such as type 2 diabetes mellitus/insulin resistance, osteoporosis, obesity, atherosclerosis, and non-alcoholic fatty liver disease, was collected and discussed.

Manganese-Induced Toxicity in C. elegans: What Can We Learn from the Transcriptome?

Manganese (Mn) is an essential ubiquitous transition metal and, when occupationally or environmentally overexposed, a well-known risk factor for several neurological pathologies. However, the molecular mechanisms underlying Mn-induced neurotoxicity are largely unknown. In this study, addressing RNA-Seq analysis, bioavailability and survival assays, key pathways of transcriptional responses to Mn overexposure were investigated in the model organism Caenorhabditis elegans (C. elegans), providing insights into the Mn-induced cellular stress and damage response. Comparative transcriptome analyses identified a large number of differentially expressed genes (DEGs) in nematodes exposed to MnCl₂, and functional annotation suggested oxidative nucleotide damage, unfolded protein response and innate immunity as major damage response pathways. Additionally, a time-dependent increase in the transcriptional response after MnCl₂ exposure was identified by means of increased numbers of DEGs, indicating a time-dependent response and activation of the stress responses in Mn neurotoxicity. The data provided here represent a powerful transcriptomic resource in the field of Mn toxicity, and therefore, this study provides a useful basis for further planning of targeted mechanistic studies of Mn-induced neurotoxicity that are urgently needed in the face of increasing industrially caused environmental pollution with Mn.