Featured Research

from universities, journals, and other organizations

Scientists find new mechanism underlying depression

Date:
January 8, 2014
Source:
The Hebrew University of Jerusalem
Summary:
Researchers have shown that changes in a type of brain cells called microglia underlie the depressive symptoms brought on by exposure to chronic stress. In animal experiments, the researchers were able to demonstrate that microglia-stimulating drugs served as effective and fast-acting antidepressants, producing complete recovery of the depressive-like behavioral symptoms and increasing neurogenesis to normal levels within days. This suggests new avenues for drug research, using microglia stimulators as antidepressants.

The World health Organization calls depression "the leading cause of disability worldwide," causing more years of disability than cancer, HIV/AIDS, and cardiovascular and respiratory diseases combined. In any given year, 5-7% of the world's population experiences a major depressive episode, and one in six people will at some point suffer from the disease.

Despite recent progress in understanding depression, scientists still don't understand the biological mechanisms behind it well enough to deliver effective prevention and therapy. One possible reason is that almost all research focuses on the brain's neurons, while the involvement of other brain cells has not been thoroughly examined.

Now researchers at the Hebrew University of Jerusalem have shown that changes in one type of non-neuronal brain cells, called microglia, underlie the depressive symptoms brought on by exposure to chronic stress. In experiments with animals, the researchers were able to demonstrate that compounds that alter the functioning of microglia can serve as novel and efficient antidepressant drugs.

The findings were published in Molecular Psychiatry.

The research was conducted by Prof. Raz Yirmiya, director of the Hebrew University's Psychoneuroimmunology Laboratory, and his doctoral student Tirzah Kreisel, together with researchers at Prof. Yirmiya's laboratory and at the University of Colorado in Boulder, USA.

The researchers examined the involvement of microglia brain cells in the development of depression following chronic exposure to stress. Comprising roughly 10% of brain cells, microglia are the representatives of the immune system in the brain; but recent studies have shown that these cells are also involved in physiological processes not directly related to infection and injury, including the response to stress.

The researchers mimicked chronic unpredictable stress in humans -- a leading causes of depression -- by exposing mice to repeated, unpredictable stressful conditions over a period of 5 weeks. The mice developed behavioral and neurological symptoms mirroring those seen in depressed humans, including a reduction in pleasurable activity and in social interaction, as well as reduced generation of new brain cells (neurogenesis) -- an important biological marker of depression.

The researchers found that during the first week of stress exposure, microglia cells undergo a phase of proliferation and activation, reflected by increased size and production of specific inflammatory molecules, after which some microglia begin to die. Following the 5 weeks of stress exposure, this phenomenon led to a reduction in the number of microglia, and to a degenerated appearance of some microglia cells, particularly in a specific region of the brain involved in responding to stress.

When the researchers blocked the initial stress-induced activation of microglia with drugs or genetic manipulation, they were able to stop the subsequent microglia cell death and decline, as well as the depressive symptoms and suppressed neurogenesis. However, these treatments were not effective in "depressed" mice, which were already exposed to the 5-weeks stress period and therefore had lower number of microglia. Based on these findings, the investigators treated the "depressed" mice with drugs that stimulated the microglia and increased their number to a normal level.

Prof. Yirmiya said, "We were able to demonstrate that such microglia-stimulating drugs served as effective and fast-acting antidepressants, producing complete recovery of the depressive-like behavioral symptoms, as well as increasing the neurogenesis to normal levels within a few days of treatment. In addition to the clinical importance of these results, our findings provide the first direct evidence that in addition to neurons, disturbances in the functioning of brain microglia cells have a role in causing psychopathology in general, and depression in particular. This suggests new avenues for drug research, in which microglia stimulators could serve as fast-acting antidepressants in some forms of depressive and stress-related conditions."


Story Source:

The above story is based on materials provided by The Hebrew University of Jerusalem. Note: Materials may be edited for content and length.


Journal Reference:

  1. T Kreisel, M G Frank, T Licht, R Reshef, O Ben-Menachem-Zidon, M V Baratta, S F Maier, R Yirmiya. Dynamic microglial alterations underlie stress-induced depressive-like behavior and suppressed neurogenesis. Molecular Psychiatry, 2013; DOI: 10.1038/mp.2013.155

Cite This Page:

The Hebrew University of Jerusalem. "Scientists find new mechanism underlying depression." ScienceDaily. ScienceDaily, 8 January 2014. <www.sciencedaily.com/releases/2014/01/140108102451.htm>.
The Hebrew University of Jerusalem. (2014, January 8). Scientists find new mechanism underlying depression. ScienceDaily. Retrieved August 21, 2014 from www.sciencedaily.com/releases/2014/01/140108102451.htm
The Hebrew University of Jerusalem. "Scientists find new mechanism underlying depression." ScienceDaily. www.sciencedaily.com/releases/2014/01/140108102451.htm (accessed August 21, 2014).

Share This




More Mind & Brain News

Thursday, August 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Do More Wedding Guests Make A Happier Marriage?

Do More Wedding Guests Make A Happier Marriage?

Newsy (Aug. 20, 2014) — A new study found couples who had at least 150 guests at their weddings were more likely to report being happy in their marriages. Video provided by Newsy
Powered by NewsLook.com
Charter Schools Alter Post-Katrina Landscape

Charter Schools Alter Post-Katrina Landscape

AP (Aug. 20, 2014) — Nine years after Hurricane Katrina, charter schools are the new reality of public education in New Orleans. The state of Louisiana took over most of the city's public schools after the killer storm in 2005. (Aug. 20) Video provided by AP
Powered by NewsLook.com
Researcher Testing on-Field Concussion Scanners

Researcher Testing on-Field Concussion Scanners

AP (Aug. 19, 2014) — Four Texas high school football programs are trying out an experimental system designed to diagnose concussions on the field. The technology is in response to growing concern over head trauma in America's most watched sport. (Aug. 19) Video provided by AP
Powered by NewsLook.com
Kids' Drawings At Age 4 Linked To Intelligence At Age 14

Kids' Drawings At Age 4 Linked To Intelligence At Age 14

Newsy (Aug. 19, 2014) — A study by King's College London says there's a link between how well kids draw at age 4 and how intelligent they are later in life. 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