Trends in Neurosciences
Volume 32, Issue 9, September 2009, Pages 506-516
Journal home page for Trends in Neurosciences

Review
Air pollution: mechanisms of neuroinflammation and CNS disease

https://doi.org/10.1016/j.tins.2009.05.009Get rights and content

Air pollution has been implicated as a chronic source of neuroinflammation and reactive oxygen species (ROS) that produce neuropathology and central nervous system (CNS) disease. Stroke incidence and Alzheimer's and Parkinson's disease pathology are linked to air pollution. Recent reports reveal that air pollution components reach the brain; systemic effects that impact lung and cardiovascular disease also impinge upon CNS health. While mechanisms driving air pollution-induced CNS pathology are poorly understood, new evidence suggests that microglial activation and changes in the blood–brain barrier are key components. Here we summarize recent findings detailing the mechanisms through which air pollution reaches the brain and activates the resident innate immune response to become a chronic source of pro-inflammatory factors and ROS, culminating in CNS disease.

Section snippets

Air pollution defined

Air pollution is comprised of a diverse mixture of particulate matter (PM), gases (e.g. ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides), organic compounds (e.g. polycyclic aromatic hydrocarbons and endotoxins) and metals (e.g. vanadium, nickel, and manganese) present in outdoor and indoor air [5]. Of these components, PM and ground-level ozone are the most widespread health threats and have been heavily implicated in disease 2, 4. In fact, millions of people in the USA and

Ischemic stroke

While it is well-known that air pollution affects human health through cardiovascular and respiratory morbidity and mortality, it has only recently been shown that these deleterious effects extend to the brain. The impact of air pollution upon the brain was first noted as an increase in ischemic stroke in individuals exposed to indoor coal fumes [16]. In the United States, stroke is the number one cause of adult disability and the third most common cause of death, behind only cancer and heart

Route of CNS effects

Recent advances have provided key insights into how air pollution exerts deleterious effects on the brain. Specifically, cerebral vascular damage, neuroinflammation, and neurodegeneration in response to air pollution are believed to occur through four major pathways (Figure 1).

Cellular mechanisms of neuroinflammation

In addition to understanding how the effects of air pollution reach the brain, recent studies have begun to address the cell types that mediate air pollution-induced CNS pathology.

Summary and conclusions

In summary, air pollution is a complex mixture of environmental toxicants that assault the CNS through several cellular and molecular pathways to cause disease. CNS effects are chronic, beginning in childhood, and may take time (years) to accumulate pathology. Specifically, air pollution causes neuroinflammation, oxidative stress, cerebrovascular damage, and neurodegenerative pathology. The effects of air pollution cross from the periphery to the brain through systemic inflammation and

Acknowledgements

This work was supported by the NIEHS/NIH Pathway to Independence Award R00ES01549.

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