Multi-Elemental Analysis of Human Optic Chiasm—A New Perspective to Reveal the Pathomechanism of Nerve Fibers’ Degeneration

Abstract

The effect of metals on the functioning of the human eye is multifactorial and includes enzyme activity modulation, trace metal metabolic pathways changes, and cytotoxic activity. Functional dysfunctions appear mostly as a result of the accumulation of toxic xenobiotic metals or disturbances of micronutrients’ homeostasis. So far, the affinity of selected metals to eye tissues, i.e., the cornea, choroid, lens, and anterior chamber fluid, has been most studied. However, it is known that many eye symptoms are related to damage to the optic nerve. In order to fill this gap, the aim of the study is to perform a multi-element analysis of tissue collected postmortem from optic chiasm and optic nerves. A total of 178 samples from 107 subjects were tested. The concentrations of 51 elements were quantified by inductively coupled plasma mass spectrometry (ICP-MS) after the wet-mineralization step. In terms of elemental composition, the optic chiasm is dominated by two trace elements, i.e., iron (Fe) and zinc (Zn), besides macro-elements Ca, K, Na, P, and Mg. The subjects formed a homogeneous cluster (over 70% subjects) with the highest accumulation of aluminum (Al). The remaining two departing clusters were characterized by an increased content of most of the elements, including toxic elements such as bismuth (Bi), uranium (U), lead (Pb), chromium (Cr), and cadmium (Cd). Changes in elemental composition with age were analyzed statistically for the selected groups, i.e., females, males, and subjects with alcohol use disorder (AUD) and without AUD. A tendency of women to lose Se, Cu, Zn, Fe with age was observed, and a disturbed Ca/Mg, Na/K ratio in subjects with AUD. Although the observed trends were not statistically significant, they shed new light on the risks and possible pathologies associated with metal neurotoxicity in the visual tract.

Assessment of the Concentration of 51 Elements in the Liver and in Various Parts of the Human Brain—Profiling of the Mineral Status

“…There was also no significant correlation between brain and liver Al levels. A similar result was obtained in the previous study, which was a multi-element analysis of post-mortem tissue from the optic chiasm and optic nerves [33]. It should be noted that the presence and importance of Al in the brain is mainly analyzed in relation to neurological disorders, i.e., amyotrophic lateral sclerosis, senile dementia, Parkinson's disease, and, to some extent, Alzheimer's disease and autism spectrum disorder (ASD) [56][57][58].…”

“…The procedure of the human tissues pre-treatment was proposed previously [ 30 , 31 , 32 , 33 ]. In brief, wet mineralization of each 0.3–0.5 g sample was performed via the addition of 7 mL of 69% HNO 3 ultrapure for trace metal analysis (Baker, Radnor, PA, USA), followed by heating to 190 °C in closed Teflon containers in the microwave mineralization system Multiwave 5000 (Anton Paar, Graz, Austria).…”

“…Our previous work in the field of metallomics has investigated the accumulation of seven trace elements, including Ca, Co, Cr, Cu, Fe, K and Mg, Mn, Na, Zn, and Se in the liver of people with alcohol use disorder (AUD) [ 30 , 31 ], the elemental composition of the meninges, i.e., dura mater and arachnoid [ 32 ], the optic chiasm by ICP-MS [ 33 ] and the aqueous humor of cataract patients [ 34 , 35 , 36 ]. Other authors have also used ICP-MS to analyze selected metals.…”

Linking Metallic Micronutrients and Toxic Xenobiotics to Atherosclerosis and Fatty Liver Disease—Postmortem ICP-MS Analysis of Selected Human Tissues

“…The sample preparation procedure was the same as previously published [51][52][53]. In brief, 7 mL of 69% suprapur nitric acid HNO 3 (Baker, Radnor, PA, USA) was added to approximately 0.3-0.5 g of tissue sample, followed by heating to 190 • C in closed Teflon containers in the microwave mineralisation system Multiwave 5000 (Anton Paar, Graz, Austria).…”

Particulate matter constituents trigger the formation of extracellular amyloid β and Tau-containing plaques and neurite shorteningin vitro

“…Another group showed that �tanium content in mouse hippocampus a�er 90 days of con�nuous intranasal exposure to TiO2 nanopar�cles was 0.6 mg/g �ssue at the highest administered dose of 10 mg/kg body weight (Ze et al, 2014), much higher than the levels observed in humans. Titanium can be found in human �ssue at lower average concentra�ons ranging from 1 μg/g (Peters et al, 2020) up to 80 μg/g (Baj et al, 2023) in the human brain. Thus, neuroinflamma�on and impairment of spa�al memory observed in mice occur at more than ten �mes higher brain content than observed in humans.…”