Abstract Manganese (Mn) is an essential trace element required for various physiological processes, but excessive exposure can lead to neurotoxicity and motor impairments. This study investigated the immediate and delayed behavioral effects and potential tissue biomarkers, as well as the immediate oxidative and metabolic alterations, following subacute Mn intoxication in adult male and female Wistar rats. Animals received MnCl₂ (15 mg/kg, intraperitoneally, for 5 days per week over 4 weeks, totaling 30 days of exposure). Following this treatment, animals were allocated into two independent experimental endpoints. The first group was evaluated immediately after the end of the 30-day MnCl 2 exposure period. The second group underwent an additional 30-day Mn-free recovery period before evaluation, resulting in a total experimental duration of 60 days for this group. Corresponding control groups were run in parallel for both endpoints. After the exposure period, no significant motor coordination deficits were observed. However, motor impairments emerged after the recovery period, suggesting delayed neurotoxic effects. Oxidative stress markers revealed decreased non-protein thiol levels in the cortex and hippocampus, indicating Mn-induced antioxidant depletion, while mitochondrial complex activities varied by sex and brain regions. Although Mn concentrations in brain tissues returned to baseline after recovery, elevated Mn levels persisted in nails and teeth, suggesting that these tissues are promising non-invasive biomarkers of cumulative Mn exposure. These findings demonstrate that, within a predefined two-endpoint design, Mn neurotoxicity manifests in a time- and sex-dependent manner, highlighting distinct temporal patterns of functional and biochemical vulnerability. Thus, the identification of nails and teeth as reliable non-invasive biomarkers further underscores the complexity of Mn toxicity and highlights the importance of considering sex-specific responses in toxicological assessments. Graphical Abstract Summary of sex-dependent behavioral, biochemical, and bioaccumulation outcomes following subacute manganese (Mn) exposure in adult Wistar rats. Male and female rats were exposed to MnCl₂ (15 mg/kg/day, intraperitoneally) for 30 consecutive days and evaluated at two predefined experimental endpoints: immediately after the exposure period and after an additional 30-day Mn-free recovery interval. Immediate assessments revealed sex-dependent alterations in anxiety-like behavior and region-specific oxidative and mitochondrial changes. After the recovery period, delayed motor coordination impairments were evident, particularly in males, despite normalization of brain Mn levels. Mn bioaccumulation persisted in peripheral tissues, including hair, nails, and teeth, in both sexes. Overall, the results show that, within this two-endpoint design, Mn induces time-dependent and sex-specific neurotoxic effects, with nails and teeth emerging as reliable non-invasive biomarkers of cumulative Mn exposure.
Eichwald et al. (Thu,) studied this question.