Neurological impacts from inhalation of pollutants and the nose–brain connection

doi:10.1016/j.neuro.2011.12.001

NeuroToxicology

Volume 33, Issue 4, August 2012, Pages 838-841

https://doi.org/10.1016/j.neuro.2011.12.001 Get rights and content

Abstract

The effects of inhaled particles have focused heavily on the respiratory and cardiovascular systems. Most studies have focused on inhaled metals, whereas less information is available for other particle types regarding the effects on the brain and other extra-pulmonary organs. We review here the key available literature on nanoparticle uptake and transport through the olfactory pathway, the experimental data from animal and in vitro studies, and human epidemiological observations. Nanoparticles (<0.1 μm in one dimension) may easily reach the brain from the respiratory tract via sensory neurons and transport from the distal alveoli into the blood or lymph as free particles or inside phagocytic cells. These mechanisms and subsequent biologic responses may be influenced by the chemical composition of inhaled particles. Animal studies with ambient particulate matter and certain other particles show alterations in neuro-inflammatory markers of oxidative stress and central neurodegeneration. Human observations indicate motor, cognitive, and behavioral changes especially after particulate metal exposure in children. Exposure to co-pollutants and/or underlying disease states could also impact both the biokinetics and effects of airborne particles in the brain. Data are needed from the areas of inhalation, neurology, and metal toxicology in experimental and human studies after inhalation exposure. An increased understanding of the neurotoxicity associated with air pollution exposure is critical to protect susceptible individuals in the workplace and the general population.

Section snippets

Olfactory transport of inhaled particles and metals

The olfactory system originates with specialized olfactory neurons found within the olfactory epithelium that lines a portion of the nasal cavity. Projections from the olfactory neurons form the olfactory nerve (cranial nerve I), which ultimately terminates in the olfactory bulb after the nerve tracts pass through the skull. Transport of xenobiotics – including particles – along the olfactory nerve provides a route (nose-to-brain) for delivery to the central nervous system (CNS) that bypasses

Nanoparticle dosimetry

Air pollution is a complex mixture of gas- and particulate-phase components that has input from natural and anthropogenic sources. The composition of the particulate phase depends on the source(s), aerosol age, and size fraction and can include carbonaceous soot, metals, crustal elements, organics, and biological agents (e.g. pollens). Particles in ambient air exist in four size classes, with the smallest being the ultrafine or nanosized particles (NPs). Nanoparticles are defined as being <0.1

Conclusions

The “nose–brain” interaction as a route of entry for air pollutants is a topic of emerging interest that deserves further research, especially considering the possibility that NP can be transported to target brain areas. The transport of other toxic components of air pollution, such as gases (ozone, carbon monoxide, sulfur oxides, nitrogen oxides), organic compounds (polycyclic aromatic hydrocarbons and endotoxins) and metals (vanadium, nickel, manganese) also need to be considered. In vivo and

Conflict of interest statement

No conflict of interest declared.

Acknowledgments

RL research is supported by funding from the European Union through its Sixth Framework Program for RTD (contract no. FOOD-CT-2006- 016253), and by Award Number R01ES019222 from the National Institute of Environmental Health Sciences (NIEHS). AE is supported by funding from the National Institutes of Health (R01CA134218, RC2ESO18741, and P30ESO1247). The content is solely the responsibility of the authors and does not necessarily represent the official views of the EU, the US Environmental

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View full text

Neurological impacts from inhalation of pollutants and the nose–brain connection

Abstract

Section snippets

Olfactory transport of inhaled particles and metals

Nanoparticle dosimetry

Conclusions

Conflict of interest statement

Acknowledgments

Toxicol Appl Pharmacol

Int J Dev Neurosci

Exp Toxicol Pathol

Neuroimage

J Pharm Sci

Nucl Med Biol

Neurotoxicology

Neurotoxicology

Neurobiol Dis

Environ Res

Am Heart J

Neurotoxicology

Toxicol Appl Pharmacol

Neurotoxicology

Microglia-mediated neurotoxicity: uncovering the molecular mechanisms

Nat Rev Neurosci

DNA damage in nasal and brain tissues of canines exposed to air pollutants is associated with evidence of chronic brain inflammation and neurodegeneration

Toxicol Pathol

Nasal toxicity of manganese sulfate and manganese phosphate in young male rats following subchronic (13-week) inhalation exposure

Inhal Toxicol

Correlation of brain magnetic resonance imaging changes with pallidal manganese concentrations in rhesus monkeys following subchronic manganese inhalation

Toxicol Sci

Transient expression of the conserved zinc finger gene INSM1 in progenitors and nascent neurons throughout embryonic and adult neurogenesis

J Comp Neurol

Translocation of inhaled ultrafine manganese oxide particles to the central nervous system

Environ Health Perspect