Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Odor receptors discovered in lungs

03.01.2014
They’re just like those in your nose, but instead of conjuring up a cup of coffee, they might make you cough

Your nose is not the only organ in your body that can sense cigarette smoke wafting through the air. Scientists at Washington University in St. Louis and the University of Iowa have shown that your lungs have odor receptors as well.


Ben-Shahar
“They’re beautiful cells,” said Ben-Shahar, of the pulmonary neuroendocrine cells he has been studying in lung tissues. The flask-like cells that are full of serotonin (stained green here) and other chemicals extend processes up through the epithelial cells (purple) lining the airways to monitor the chemical makeup of each breath. The top part of the image is a plan view of the airway lining and the bottom part is a section through the lining.

Unlike the receptors in your nose, which are located in the membranes of nerve cells, the ones in your lungs are in the membranes of neuroendocrine cells. Instead of sending nerve impulses to your brain that allow it to “perceive” the acrid smell of a burning cigarette somewhere in the vicinity, they trigger the flask-shaped neuroendocrine cells to dump hormones that make your airways constrict.

The newly discovered class of cells expressing olfactory receptors in human airways, called pulmonary neuroendocrine cells, or PNECs, were found by a team led by Yehuda Ben-Shahar, PhD, assistant professor of biology, in Arts & Sciences, and of medicine at Washington University in St. Louis, and including colleagues Steven L. Brody, MD, and Michael J. Holtzman, MD, of the Washington University School of Medicine, and Michel J. Welsh, MD, of the University of Iowa Carver College of Medicine.

“We forget,” said Ben-Shahar, “that our body plan is a tube within a tube, so our lungs and our gut are open to the external environment. Although they’re inside us, they’re actually part of our external layer. So they constantly suffer environmental insults,” he said, “and it makes sense that we evolved mechanisms to protect ourselves.”

In other words, the PNECs, described in the March issue of the American Journal of Respiratory Cell and Molecular Biology, are sentinels, guards whose job it is to exclude irritating or toxic chemicals.

The cells might be responsible for the chemical hypersensitivity that characterizes respiratory diseases, such as chronic obstructive pulmonary disease (COPD) and asthma. Patients with these diseases are told to avoid traffic fumes, pungent odors, perfumes and similar irritants, which can trigger airway constriction and breathing difficulties.

The odor receptors on the cells might be a therapeutic target, Ben-Shahar suggests. By blocking them, it might be possible to prevent some attacks, allowing people to cut down on the use of steroids or bronchodilators.

Every breath you take
When a mammal inhales, volatile chemicals flow over two patches of specialized epithelial tissue high up in the nasal passages. These patches are rich in nerve cells with specialized odorant-binding molecules embedded in their membranes.

If a chemical docks on one of these receptors, the neuron fires, sending impulses along the olfactory nerve to the olfactory bulb in the brain, where the signal is integrated with those from hundreds of other similar cells to conjure the scent of old leather or dried lavender.

Aware that airway diseases are characterized by hypersensitivity to volatile stimuli, Ben-Shahar and his colleagues realized that the lungs, like the nose, must have some means of detecting inhaled chemicals.

Earlier, a team at the University of Iowa, where Ben-Shahar was a postdoctoral research associate, had searched for genes expressed by patches of tissue from lung transplant donors. They found a group of ciliated cells that express bitter taste receptors. When offending substances were detected, the cilia beat more strongly to sweep them out of the airway. This result was featured on the cover of the Aug. 28, 2009, issue of Science.

But since people are sensitive to many inhaled substances, not just bitter ones, Ben-Shahar decided to look again. This time he found that these tissues also express odor receptors, not on ciliated cells but instead on neuroendocrine cells, flask-shaped cells that dump serotonin and various neuropeptides when they are stimulated.

This made sense. “When people with airway disease have pathological responses to odors, they’re usually pretty fast and violent,” said Ben-Shahar. “Patients suddenly shut down and can’t breathe, and these cells may explain why.”

Ben-Shahar stresses the differences between chemosensation in the nose and in the lung. The cells in the nose are neurons, he points out, each with a narrowly tuned receptor, and their signals must be woven together in the brain to interpret our odor environment.

The cells in the airways are secretory, not neuronal, cells, and they may carry more than one receptor, so they are broadly tuned. Instead of sending nerve impulses to the brain, they flood local nerves and muscles with serotonin and neuropeptides. “They are possibly designed,” he said, “to elicit a rapid, physiological response if you inhale something that is bad for you.”

The different mechanisms explain why cognition plays a much stronger role in taste and smell than in coughing in response to an irritant. It is possible, for example, to develop a taste for beer. But nobody learns not to cough; the response is rapid and largely automatic.

The scientists suspect these pulmonary neuroscretory cells contribute to the hypersensitivity of patients with COPD to airborne irritants. COPD is a group of diseases, including emphysema, that is characterized by coughing, wheezing, shortness of breath and chest tightness.

When the scientists looked at the airway tissues from patients with COPD, they discovered that they had more of these neurosecretory cells than airway tissues from healthy donors.

Of mice and men
As a geneticist, Ben-Shahar would like to go farther, knocking out genes to make sure that the derangement of neurosecretory cells isn’t just correlated with airway diseases but instead suffices to produce it.

But there is a problem. “For example, a liver from a mouse and a liver from a human are pretty similar, they express the same types of cells. But the lungs from different mammalian species are often very different; you can see it at a glance,” Ben-Shahar said.

“Clearly, primates have evolved distinct cell lineages and signaling systems for respiratory-specific functions.”

This makes it challenging to unravel the biomolecular mechanisms of respiratory diseases.

Still, he is hopeful that the PNEC pathways will provide targets for drugs that would better control asthma, COPD and other respiratory diseases. They would be welcome. There has been a steep rise in these diseases in the past few decades, treatment options have been limited, and there are no cures.

Diana Lutz | EurekAlert!
Further information:
http://www.wustl.edu
http://news.wustl.edu/news/Pages/26271.aspx

More articles from Health and Medicine:

nachricht One gene closer to regenerative therapy for muscular disorders
01.06.2017 | Cincinnati Children's Hospital Medical Center

nachricht The gut microbiota plays a key role in treatment with classic diabetes medication
01.06.2017 | University of Gothenburg

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

Im Focus: Optoelectronic Inline Measurement – Accurate to the Nanometer

Germany counts high-precision manufacturing processes among its advantages as a location. It’s not just the aerospace and automotive industries that require almost waste-free, high-precision manufacturing to provide an efficient way of testing the shape and orientation tolerances of products. Since current inline measurement technology not yet provides the required accuracy, the Fraunhofer Institute for Laser Technology ILT is collaborating with four renowned industry partners in the INSPIRE project to develop inline sensors with a new accuracy class. Funded by the German Federal Ministry of Education and Research (BMBF), the project is scheduled to run until the end of 2019.

New Manufacturing Technologies for New Products

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

A new technique isolates neuronal activity during memory consolidation

22.06.2017 | Life Sciences

Plant inspiration could lead to flexible electronics

22.06.2017 | Materials Sciences

A rhodium-based catalyst for making organosilicon using less precious metal

22.06.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>