Featured Research

from universities, journals, and other organizations

Why People Often Get Sicker When They Are Stressed

Date:
March 10, 2009
Source:
UT Southwestern Medical Center
Summary:
A newly discovered receptor in a strain of Escherichia coli might help explain why people often get sicker when they're stressed.

Dr. Vanessa Sperandio.
Credit: Image courtesy of UT Southwestern Medical Center

A newly discovered receptor in a strain of Escherichia coli might help explain why people often get sicker when they're stressed.

Related Articles


Researchers at UT Southwestern Medical Center are the first to identify the receptor, known as QseE, which resides in a diarrhea-causing strain of E coli. The receptor senses stress cues from the bacterium's host and helps the pathogen make the host ill. A receptor is a molecule on the surface of a cell that docks with other molecules, often signaling the cell to carry out a specific function.

The study is available online and in a future issue of the Proceedings of the National Academy of Sciences. Dr. Vanessa Sperandio, associate professor of microbiology at UT Southwestern and the study's senior author, said QseE is an important player in disease development because the stress cues it senses from a host, chiefly epinephrine and phosphate, are generally associated with blood poisoning, or sepsis.

"Patients with high levels of phosphate in the intestine have a much higher probability of developing sepsis due to systemic infection by intestinal bacteria," Dr. Sperandio said. "If we can find out how bacteria sense these cues, then we can try to interfere in the process and prevent infection."

Millions of potentially harmful bacteria exist in the human body, awaiting a signal from their host that it's time to release their toxins. Without those signals, the bacteria pass through the digestive tract without infecting cells. What hasn't been identified is how to prevent the release of those toxins.

"There's obviously a lot of chemical signaling between host and bacteria going on, and we have very little information about which bacteria receptors recognize the host and vice versa," Dr. Sperandio said. "We're scratching at the tip of the iceberg on our knowledge of this."

In 2006, Dr. Sperandio's lab was the first to identify the receptor QseC sensor kinase, a molecule found in the membrane of a diarrhea-causing strain of E coli known as enterohemorrhagic Escherichia coli, or EHEC. Prior research by Dr. Sperandio found that when a person ingests EHEC – which is usually transmitted through contaminated food such as raw meat – it travels peacefully through the digestive tract until reaching the intestine. There, chemicals produced by the friendly gastrointestinal microbial flora and the human hormones epinephrine and norepinephrine alert the bacteria to its location.

Once QseC recognizes the stress hormones, it initiates a cascade of genetic activations in which EHEC colonizes the intestine and moves toxins into human cells, altering the makeup of the cells and robbing the body of nutrients.

"The bacteria get what they want – nourishment – and the person ends up getting diarrhea," Dr. Sperandio said.

The new study identifies QseE, a receptor only found in intestinal bacteria, as the receptor that ends this QseC-initiated cascade. It also provides the timing for the bacterium's actions, including the regulation of the genes necessary for EHEC to cause diarrhea.

"EHEC needs both receptors to be fully virulent and express its toxins," Dr. Sperandio said. "When people are stressed they have more epinephrine and norepinephrine being released. Both of these human hormones activate the receptors QseC and QseE, which in turn trigger virulence. Hence, if you are stressed, you activate bacterial virulence."

Dr. Sperandio said the findings also suggest that there may be more going on at the genetic level in stress-induced illness than previously thought.

"The problem may not only be that the stress signals are weakening your immune system, but that you're also priming some pathogens at the same time," she said. "Then it's a double-edged sword. You have a weakened immune system and pathogens exploiting it."

Previous research by Dr. Sperandio found that phentolamine, an alpha blocker drug used to treat hypertension, and a new drug called LED209 prevent QseC from expressing its virulence genes in cells.

The next step is to test whether phentolamine has the same effect on QseE.

Nicola Reading, former graduate student at UT Southwestern, was the study's lead author. Dr. David Rasko, former assistant professor of microbiology at UT Southwestern and now at the University of Maryland, and Dr. Alfredo Torres from UT Medical Branch in Galveston also contributed to the work.

The research was funded by the National Institutes of Health, the Ellison Medical Foundation and the Burroughs Wellcome Fund.


Story Source:

The above story is based on materials provided by UT Southwestern Medical Center. Note: Materials may be edited for content and length.


Cite This Page:

UT Southwestern Medical Center. "Why People Often Get Sicker When They Are Stressed." ScienceDaily. ScienceDaily, 10 March 2009. <www.sciencedaily.com/releases/2009/03/090309191507.htm>.
UT Southwestern Medical Center. (2009, March 10). Why People Often Get Sicker When They Are Stressed. ScienceDaily. Retrieved October 30, 2014 from www.sciencedaily.com/releases/2009/03/090309191507.htm
UT Southwestern Medical Center. "Why People Often Get Sicker When They Are Stressed." ScienceDaily. www.sciencedaily.com/releases/2009/03/090309191507.htm (accessed October 30, 2014).

Share This



More Health & Medicine News

Thursday, October 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Mind-Controlled Prosthetic Arm Restores Amputee Dexterity

Mind-Controlled Prosthetic Arm Restores Amputee Dexterity

Reuters - Innovations Video Online (Oct. 29, 2014) A Swedish amputee who became the first person to ever receive a brain controlled prosthetic arm is able to manipulate and handle delicate objects with an unprecedented level of dexterity. The device is connected directly to his bone, nerves and muscles, giving him the ability to control it with his thoughts. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Google To Use Nanoparticles, Wearables To Detect Disease

Google To Use Nanoparticles, Wearables To Detect Disease

Newsy (Oct. 29, 2014) Google X wants to improve modern medicine with nanoparticles and a wearable device. It's all an attempt to tackle disease detection and prevention. Video provided by Newsy
Powered by NewsLook.com
Can Drinking Milk Lead To Early Death?

Can Drinking Milk Lead To Early Death?

Newsy (Oct. 29, 2014) Researchers in Sweden released a study showing heavy milk drinkers face an increased mortality risk from a variety of causes. Video provided by Newsy
Powered by NewsLook.com
Obama: The US Will Not 'run and Hide' From Ebola

Obama: The US Will Not 'run and Hide' From Ebola

AP (Oct. 29, 2014) Surrounded by health care workers in the White House East Room, President Barack Obama said the U.S. will likely see additional Ebola cases in the weeks ahead. But he said the nation can't seal itself off in the fight against the disease. (Oct. 29) Video provided by AP
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:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

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