Air pollution may directly cause those year-round runny noses, according to a mouse study

April 18, 2017
Sinuses of mice that inhaled filtered air. The sinus surface is an intact barrier as seen by the presence of proteins that hold the cells together such as E-cadherin (red). Credit: Ramanathan lab

Although human population studies have linked air pollution to chronic inflammation of nasal and sinus tissues, direct biological and molecular evidence for cause and effect has been scant. Now, Johns Hopkins researchers report that experiments in mice continually exposed to dirty air have revealed that direct biological effect.

Researchers have long known that smog, ash and other particulates from industrial smokestacks and other sources that pollute air quality exacerbate and raise rates of asthma symptoms, but had little evidence of similar damage from those pollutants to the upper respiratory system.

The new findings, published in the American Journal of Respiratory Cell and Molecular Biology, have broad implications for the health and well-being of people who live in large cities and industrial areas with , particularly in the developing world.

"In the U.S., regulations have kept a lot of in check, but in places like New Delhi, Cairo or Beijing, where people heat their houses with wood-burning stoves, and factories release pollutants into the air, our study suggests people are at higher risk of developing chronic sinus problems," says Murray Ramanathan, M.D., associate professor of otolaryngology - head and neck surgery at the Johns Hopkins University School of Medicine.

According to the Centers for Disease Control and Prevention, more than 29 million people in the U.S. or more than 12 percent of adults have a diagnosis. Chronic sinusitis can cause congestion, pain and pressure in the face, and a stuffy, drippy nose.

Numerous studies have reported significant social implications of chronic sinonasal disease, including depression, lost productivity and chronic fatigue.

To see how pollution may directly affect the biology of the upper airways, the researchers exposed 38 eight-week-old male mice to either filtered air or concentrated Baltimore air with particles measuring 2.5 micrometers or less, which excludes most allergens, like dust and pollen. The aerosolized particles, although concentrated, were 30 to 60 percent lower than the average concentrations of particles of a similar size in cities like New Delhi, Cairo and Beijing.

Nineteen mice breathed in filtered air, and 19 breathed polluted air for 6 hours per day, 5 days a week for 16 weeks.

The researchers used water to flush out the noses and sinuses of the mice, and then looked at the inflammatory and other cells in the flushed-out fluid under a microscope.

Sinuses of mice that inhaled polluted air. The sinus surface is breached as seen by the reduction in proteins that hold the cells together, such as E-cadherin (red). Credit: Ramanathan lab

They saw many more that signal inflammation, including macrophages, neutrophils and eosinophils, in the mice that breathed in the polluted air compared with those that breathed in filtered air. For example, the mice that breathed in the polluted air had almost four times as many macrophages than mice that breathed filtered air.

To see if the cells flushed out of the nasal and sinus passages had turned on a generalized inflammatory response, the researchers compared specific genes used by immune system cells from the mice that breathed polluted air with the cells of those that breathed filtered air. They found higher levels of messenger RNA—the blueprints of DNA needed to make proteins—in the genes for interleukin 1b, interleukin 13, oncostatin M and eotaxin-1 in the nasal fluid of mice that breathed the polluted air. All those proteins are considered direct biomarkers for inflammation.

The investigators measured the protein levels of interleukin 1b, interleukin 13 and eotaxin-1, which are chemical messengers called cytokines that cause an immune response. They found five to 10 times higher concentrations of the cytokines involved in inflammation in the mice that breathed the polluted air than in those that breathed filtered air. Interleukin 1b is a chemical messenger that promotes inflammation, and both interleukin 13 and eotaxin-1 are chemical messengers that attract eosinophils.

"Inflammation that attracts eosinophils is what happens in the lungs of people with asthma, so essentially the chronic exposure to air pollution in mice is leading to a kind of asthma of the nose," says Ramanathan.

Next, the researchers examined layers of cells along the nasal passages and sinuses under a microscope and found that the surface layer - or epithelium - was, notably, 30 to 40 percent thicker in mice that breathed in polluted air than in those that breathed filtered air. Ramanathan says that a thicker epithelium is another sign of inflammation in humans and other animals.

The researchers next used glowing antibodies that bind to the proteins claudin-1 and E-cadherin found in between the cells of the epithelium to help hold them together. They report observing far less of both proteins but up to 80 percent less E-cadherin from mice that breathed in the polluted air compared with the mice that breathed filtered air.

The investigators also said they found much higher levels of the protein serum albumin in the mice that breathed in the polluted air. High levels of serum albumin indicate that barriers to the nasal passages and sinuses were breached.

"We've identified a lot of evidence that breathing in dirty air directly causes a breakdown in the integrity of the sinus and nasal air passages in ," says Ramanathan. "Keeping this barrier intact is essential for protecting the cells in the tissues from irritation or infection from other sources, including pollen or germs."

Ramanathan says his team will continue to study the specific molecular changes that occur when the sinus and nasal barriers are breached because of air pollution, as well as investigate possible ways to repair them.

Explore further: Air pollution linked to learning and memory problems, depression

More information: Murugappan Ramanathan, Jr. et al. Airborne Particulate Matter Induces Non-allergic Eosinophilic Sinonasal Inflammation in Mice, American Journal of Respiratory Cell and Molecular Biology (2017). DOI: 10.1165/rcmb.2016-0351OC

Related Stories

Air pollution linked to learning and memory problems, depression

July 5, 2011
Long-term exposure to air pollution can lead to physical changes in the brain, as well as learning and memory problems and even depression, new research in mice suggests.

Immune system blood cell a potential marker for sinus polyp regrowth

June 8, 2016
In an effort to identify a simple, reliable way to track the course of nasal polyps in chronic sinus disease, Johns Hopkins Medicine researchers say they've linked rising levels of immune system white blood cells, called ...

Serum periostin IDs comorbid chronic rhinosinusitis in asthma

March 21, 2017
(HealthDay)—For patients with asthma, serum periostin is useful for detecting chronic rhinosinusitis with nasal polyps, according to a study published online March 1 in the Annals of the American Thoracic Society.

Exposure to air pollution increases the risk of obesity

February 19, 2016
Laboratory rats who breathed Beijing's highly polluted air gained weight and experienced cardio-respiratory and metabolic dysfunctions after three to eight weeks of exposure.

Interleukin-1α causes people to choke on air

December 22, 2016
Scientists at the Immunology Frontier Research Center (IFReC) at Osaka University, Japan, have pinpointed specific molecular events that could explain allergic reactions to air pollution. These findings provide a new therapeutic ...

Immune cell drives heart failure in mice

March 16, 2017
A new study in mice reveals that eosinophils, a type of disease-fighting white blood cell, appear to be at least partly responsible for the progression of heart muscle inflammation to heart failure in mice.

Recommended for you

Gene immunotherapy protects against multiple sclerosis in mice

September 21, 2017
A potent and long-lasting gene immunotherapy approach prevents and reverses symptoms of multiple sclerosis in mice, according to a study published September 21st in the journal Molecular Therapy. Multiple sclerosis is an ...

New academic study reveals true extent of the link between hard water and eczema

September 21, 2017
Hard water damages our protective skin barrier and could contribute to the development of eczema, a new study has shown.

Exposure to pet and pest allergens during infancy linked to reduced asthma risk

September 19, 2017
Children exposed to high indoor levels of pet or pest allergens during infancy have a lower risk of developing asthma by 7 years of age, new research supported by the National Institutes of Health reveals. The findings, published ...

Cholesterol-like molecules switch off the engine in cancer-targeting 'Natural Killer' cells

September 18, 2017
Scientists have just discovered how the engine that powers cancer-killing cells functions. Crucially, their research also highlights how that engine is fuelled and that cholesterol-like molecules, called oxysterols, act as ...

MicroRNA helps cancer evade immune system

September 18, 2017
The immune system automatically destroys dysfunctional cells such as cancer cells, but cancerous tumors often survive nonetheless. A new study by Salk scientists shows one method by which fast-growing tumors evade anti-tumor ...

'Exciting' discovery on path to develop new type of vaccine to treat global viruses

September 15, 2017
Scientists at the University of Southampton have made a significant discovery in efforts to develop a vaccine against Zika, dengue and Hepatitis C viruses that affect millions of people around the world.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

gkam
1 / 5 (4) Apr 18, 2017
Bad year for allergies in California. All the seeds which had no water have sprouted, and the pollen covered my PV panels.

We started sneezing the day after the air cleaner went bad.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.