Metal deposition and functional neurotoxicity in rats after 3–6 weeks nasal exposure by two physicochemical forms of manganese

Recognition and detection technology for microplastic, its source and health effects

Microplastic (MP) is ubiquitous in the environment which appeared as an immense intimidation to human and animal health. The plastic fragments significantly polluted the ocean, fresh water, food chain, and other food items. Inadequate maintenance, less knowledge of adverse influence along with inappropriate usage in addition throwing away of plastics items revolves present planet in to plastics planet. The present study aims to focus on the recognition and advance detection technologies for MPs and the adverse effects of micro- and nanoplastics on human health. MPs have rigorous adverse effect on human health that leads to condensed growth rates, lessened reproductive capability, ulcer, scrape, and oxidative nervous anxiety, in addition, also disturb circulatory and respiratory mechanism. The detection of MP particles has also placed emphasis on identification technologies such as scanning electron microscopy, Raman spectroscopy, optical detection, Fourier transform infrared spectroscopy, thermo-analytical techniques, flow cytometry, holography, and hyperspectral imaging. It suggests that further research should be explored to understand the source, distribution, and health impacts and evaluate numerous detection methodologies for the MPs along with purification techniques.

The plastic brain: neurotoxicity of micro- and nanoplastics

Given the global abundance and environmental persistence, exposure of humans and (aquatic) animals to micro- and nanoplastics is unavoidable. Current evidence indicates that micro- and nanoplastics can be taken up by aquatic organism as well as by mammals. Upon uptake, micro- and nanoplastics can reach the brain, although there is limited information regarding the number of particles that reaches the brain and the potential neurotoxicity of these small plastic particles.

Earlier studies indicated that metal and metal-oxide nanoparticles, such as gold (Au) and titanium dioxide (TiO₂) nanoparticles, can also reach the brain to exert a range of neurotoxic effects. Given the similarities between these chemically inert metal(oxide) nanoparticles and plastic particles, this review aims to provide an overview of the reported neurotoxic effects of micro- and nanoplastics in different species and in vitro. The combined data, although fragmentary, indicate that exposure to micro- and nanoplastics can induce oxidative stress, potentially resulting in cellular damage and an increased vulnerability to develop neuronal disorders. Additionally, exposure to micro- and nanoplastics can result in inhibition of acetylcholinesterase activity and altered neurotransmitter levels, which both may contribute to the reported behavioral changes.

Currently, a systematic comparison of the neurotoxic effects of different particle types, shapes, sizes at different exposure concentrations and durations is lacking, but urgently needed to further elucidate the neurotoxic hazard and risk of exposure to micro- and nanoplastics.

The effects of nano-sized PbO on biomarkers of membrane disruption and DNA damage in a sub-chronic inhalation study on mice

Although the production of engineered nanoparticles increases our knowledge of toxicity and mechanisms of bioactivity during relevant exposures is lacking. In the present study mice were exposed to PbO nanoparticles (PbONP; 192.5 µg/m³; 1.93 × 10⁶ particles/cm³) for 2, 5 and 13 weeks through continuous inhalation. The analyses addressed Pb and PbONP distribution in organs (lung, liver, kidney, brain) using electrothermal atomic absorption spectrometry and transmission electron microscopy, as well as histopathology and analyses of oxidative stress biomarkers. New LC-MS/MS methods were validated for biomarkers of lipid damage F2-isoprostanes (8-iso-prostaglandins F_2-alpha and E₂) and hydroxylated deoxoguanosine (8-OHdG, marker of DNA oxidation). Commonly studied malondialdehyde was also measured as TBARS by HPLC-DAD. The study revealed fast blood transport and distribution of Pb from the lung to the kidney and liver. A different Pb accumulation trend was observed in the brain, suggesting transfer of NP along the nasal nerve to the olfactory bulbs. Long-term inhalation of PbONP caused lipid peroxidation in animal brains (increased levels of TBARS and both isoprostanes). Membrane lipid damage was also detected in the kidney after shorter exposures, but not in the liver or lung. On the contrary, longer exposures to PbONP increased levels of 8-OHdG in the lung and temporarily increased lung weight after 2 and 5 weeks of exposure. The histopathological changes observed mainly in the lung and liver indicated inflammation and general toxicity responses. The present long-term inhalation study indicates risks of PbONP to both human health and the environment.

Subacute manganese exposure in rats is a neurochemical model of early manganese toxicity

Manganese (Mn) is an essential trace element, but excess exposure leads to accumulation in biological tissues, including the brain. Chronically high Mn levels in the brain are neurotoxic and can result in a progressive, irreversible neurological disorder known as manganism. Manganism has signs and symptoms similar to, but distinguishable from idiopathic Parkinson's disease, which include both psychological and motor disturbances. Evidence suggests that Mn exposure impacts neurotransmitter levels in the brain. However, it remains unclear if subacute, low-level Mn exposure resulted in alterations in neurotransmitter systems with concomitant behavioral deficits. The current study used high performance liquid chromatography to quantify neurotransmitter levels in rat striatum (STR), substantia nigra (SN), and hippocampus (HP). Subacute Mn exposure via i.p. injection of 15mg Mn/kg as MnCl2 caused significantly increased dopamine (DA) levels in the STR. The enhancement was accompanied by significantly elevated levels of the DA metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in the STR. In addition, levels of HVA were significantly increased in the SN and HP. These data indicate that subacute, low-level Mn exposure disrupts multiple neurotransmitter systems in the rat brain which may be responsible, in part, for observed locomotor deficits.

Developmental neurotoxicity of engineered nanomaterials: identifying research needs to support human health risk assessment

Increasing use of engineered nanomaterials (ENM) in consumer products and commercial applications has helped drive a rise in research related to the environmental health and safety (EHS) of these materials. Within the cacophony of information on ENM EHS to date are data indicating that these materials may be neurotoxic in adult animals. Evidence of elevated inflammatory responses, increased oxidative stress levels, alterations in neuronal function, and changes in cell morphology in adult animals suggests that ENM exposure during development could elicit developmental neurotoxicity (DNT), especially considering the greater vulnerability of the developing brain to some toxic insults. In this review, we examine current findings related to developmental neurotoxic effects of ENM in the context of identifying research gaps for future risk assessments. The basic risk assessment paradigm is presented, with an emphasis on problem formulation and assessments of exposure, hazard, and dose response for DNT. Limited evidence suggests that in utero and postpartum exposures are possible, while fewer than 10 animal studies have evaluated DNT, with results indicating changes in synaptic plasticity, gene expression, and neurobehavior. Based on the available information, we use current testing guidelines to highlight research gaps that may inform ENM research efforts to develop data for higher throughput methods and future risk assessments for DNT. Although the available evidence is not strong enough to reach conclusions about DNT risk from ENM exposure, the data indicate that consideration of ENM developmental neurotoxic potential is warranted.

Effect of intranasal manganese administration on neurotransmission and spatial learning in rats

The effect of intranasal manganese chloride (MnCl(2)·4H(2)O) exposure on spatial learning, memory and motor activity was estimated in Morris water maze task in adult rats. Three-month-old male Wistar rats received for 2weeks MnCl(2)·4H(2)O at two doses the following: 0.2mg/kg b.w. (Mn0.2) or 0.8mg/kg b.w. (Mn0.8) per day. Control (Con) and manganese-exposed groups were observed for behavioral performance and learning in water maze. ANOVA for repeated measurements did not show any significant differences in acquisition in the water maze between the groups. However, the results of the probe trial on day 5, exhibited spatial memory deficits following manganese treatment. After completion of the behavioral experiment, the regional brain concentrations of neurotransmitters and their metabolites were determined via HPLC in selected brain regions, i.e. prefrontal cortex, hippocampus and striatum. ANOVA demonstrated significant differences in the content of monoamines and metabolites between the treatment groups compared to the controls. Negative correlations between platform crossings on the previous platform position in Southeast (SE) quadrant during the probe trial and neurotransmitter turnover suggest that impairment of spatial memory and cognitive performance after manganese (Mn) treatment is associated with modulation of the serotonergic, noradrenergic and dopaminergic neurotransmission in the brain. These findings show that intranasally applied Mn can impair spatial memory with significant changes in the tissue level and metabolism of monoamines in several brain regions.

Electrophysiological and biochemical response in rats on intratracheal instillation of manganese

Chronic exposure to excess manganese via inhalation of metal fumes causes central nervous system damage. For modelling Mn aerosol inhalation, male Wistar rats were intratracheally instilled with MnCl2 solution (0.5 mg/kg b.w. MnCl2; n=12) 5 days a week for 5 weeks. At the end of the treatment, somatosensory cortical evoked potentials, elicited by double-pulse stimulation, were recorded from the animals in urethane anaesthesia. Body weight gain, organ weights, and Mn level in brain, lung and blood samples were also measured. In brain samples, gene expression level of MnSOD (Mn superoxide dismutase) was determined. The effect of Mn was mainly seen on the evoked potential amplitudes, and on the second:first ratio of these. Tissue Mn concentration was elevated in brain and lungs, but changed hardly in the blood. Relative weight of heart, thymus, lungs and brain was significantly altered. The level of MnSOD transcript in brain tissue decreased. The observed effects showed that Mn had access to the brain and that somatosensory cortical responses evoked by double-pulse stimulation might be suitable biomarkers of Mn intoxication.

Nervous system effects in rats on subacute exposure by lead-containing nanoparticles via the airways

CONTEXT AND OBJECTIVE

Lead (Pb) is a heavy metal harmful for human health and environment. From leaded gasoline (still used in certain countries), and in Pb processing and reprocessing industries, airborne particles are emitted which can be inhaled. In such exposure, the size of particles entering the airways is crucial. The nervous system is a primary target for Pb, and consequences like occupational neuropathy and delayed mental development of children are well-known. The aim of this work was to investigate the neurotoxicity of Pb nanoparticles (NPs) applied into the airways of rats.

METHODS

Nano-sized lead oxide particles (mean diameter ca. 20 nm) were suspended in distilled water and instilled into the trachea of adult male Wistar rats (in doses equivalent to 2 and 4 mg/kg Pb), 5 times a week for 3 and 6 weeks. At the end, open field motility was tested, then central and peripheral nervous activity was recorded in urethane anesthesia.

RESULTS AND CONCLUSION

The treated rats' body weight gain was significantly lower than that of the controls from the 3rd week onwards, and the weight of their lungs was significantly increased. Horizontal motility increased while vertical motility decreased. Spontaneous cortical activity was shifted to higher frequencies. The somatosensory cortical evoked potential showed increased latency and decreased frequency-following ability, and similar alterations were seen in the tail nerve. Significant Pb deposition was measured in blood, brain, lung and liver samples of the treated rats. The experiments performed seem to constitute an adequate model of the human effects of inhaled Pb NPs.