Featured Research

from universities, journals, and other organizations

Smoking Mice Lead To Emphysema Breakthrough

Date:
September 26, 1997
Source:
Washington University School Of Medicine
Summary:
With the help of some heavy-smoking mice, researchers at Washington University School of Medicine in St. Louis have discovered that lungs lacking a certain enzyme are apparently immune to emphysema.

St. Louis, Sept. 26, 1997 -- With the help of some heavy-smoking mice, researchers at Washington University School of Medicine in St. Louis have discovered that lungs lacking a certain enzyme are apparently immune to emphysema. The discovery, described in the Sept. 26, 1997, issue of Science, throws serious doubt on conventional theories of the disease, and researchers are already using the finding to search for potential new drugs.

Steven D. Shapiro, M.D., associate professor of medicine and of cell biology and physiology at the School of Medicine, and colleagues found that mice genetically engineered to lack an enzyme called macrophage elastase showed no signs of emphysema even after inhaling the smoke of two unfiltered cigarettes a day, six days a week for six months. Such heavy smoking invariably causes emphysema-like symptoms in normal mice. "There hasn't been a new drug for emphysema in 20 years, and that was oxygen," Shapiro says. "Blocking this enzyme or related enzymes might give us a way to halt the disease."

Emphysema, almost always caused by smoking, robs lungs of their elasticity and leaves patients gasping for air. The lungs actually become overinflated, leaving no room for deep breaths. About 2 million Americans suffer from the disease.

Before this study, most researchers assumed that emphysema was caused by neutrophils, white blood cells that destroy foreign invaders and, occasionally, cause inflammation. According to the most widely-accepted scenario, neutrophils mount a counter-attack against smoke by congregating in the lungs and releasing inflammatory enzymes. The enzymes eventually break down elastic fibers in the lungs, causing a new case of emphysema.

But the prevailing theory had a shortcoming: lungs with emphysema don't have many neutrophils. Instead, they are full of macrophages, immune-system cells that eat bacteria and other intruders. Few thought macrophages played a role in emphysema because the cells seemed incapable of destroying sturdy lung tissue. But recent experiments by Shapiro and others showed that macrophages did indeed produce an enzyme -- macrophage elastase -- that could be up to the task.

To find out if macrophage elastase causes emphysema, Shapiro and others created a strain of mice that lacked the enzyme. He calls them "mighty mice" and estimates their value at tens of thousands of dollars apiece. "We could speculate for years about the function of this enzyme," he says. "These mice helped us pin it down."

Researchers put both the mighty mice and normal mice into smoking chambers twice a day, six days a week. The mice didn't actually have cigarettes in their mouths, but they got enough passive smoke to become quite fond of their routine. "After a while, they just started running into the chambers," Shapiro says. "They loved it." To Shapiro's knowledge, his is the first smoking chamber ever designed for mice.

Six months later, all of the normal mice had inflamed, over-inflated lungs ? the hallmarks of emphysema. The mighty mice, however, appeared completely healthy. "This enzyme clearly plays a primary role in the development of the disease in mice and probably in humans," Shapiro says.

Macrophage elastase is a member of a family of enzymes that is currently attracting intense scientific interest. Many researchers believe that members of this family, called metalloproteinases, play a major role in a host of disorders including tooth decay, atherosclerosis, arthritis ? and, now, emphysema. Pharmaceutical companies are now trying to develop metalloproteinase inhibitors that may be able to effectively prevent many of these disorders. Shapiro is currently determining whether a metalloproteinase inhibitor can block emphysema in normal, heavy-smoking mice.

Shapiro notes that a drug that blocks macrophage elastase would, at best, only prevent damage caused by emphysema. Such a drug could not repair already-damaged lungs. There is still no "cure" for emphysema on the horizon, and the best way to avoid the disease is to not smoke, he says.

One important question remains largely unanswered: What are metalloproteinases good for? They apparently help remodel tissues during growth and wound healing, but their role in healthy adults is unclear, Shapiro says. "Before we give people drugs to block these enzymes, we really need to know what the enzymes do," he explains. Other strains of "mighty mice" will undoubtedly be the stars of future experiments to answer these questions, he says.


Story Source:

The above story is based on materials provided by Washington University School Of Medicine. Note: Materials may be edited for content and length.


Cite This Page:

Washington University School Of Medicine. "Smoking Mice Lead To Emphysema Breakthrough." ScienceDaily. ScienceDaily, 26 September 1997. <www.sciencedaily.com/releases/1997/09/970926050405.htm>.
Washington University School Of Medicine. (1997, September 26). Smoking Mice Lead To Emphysema Breakthrough. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/1997/09/970926050405.htm
Washington University School Of Medicine. "Smoking Mice Lead To Emphysema Breakthrough." ScienceDaily. www.sciencedaily.com/releases/1997/09/970926050405.htm (accessed July 31, 2014).

Share This




More Health & Medicine News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Health Insurers' Profits Slide

Health Insurers' Profits Slide

Reuters - Business Video Online (July 30, 2014) Obamacare-related costs were said to be behind the profit plunge at Wellpoint and Humana, but Wellpoint sees the new exchanges boosting its earnings for the full year. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Xtreme Eating: Your Daily Caloric Intake All On One Plate

Xtreme Eating: Your Daily Caloric Intake All On One Plate

Newsy (July 30, 2014) The Center for Science in the Public Interest released its 2014 list of single meals with whopping calorie counts. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins