In a study published yesterday in the Proceedings of the National Academy of Sciences, researchers found that social status determined how macaques responded to a key stress hormone.
“The goal is to understand the mechanisms through which social experiences or environment ‘get under the skin,’ so to speak, to affect health and survival,” says first author Noah Snyder-Mackler, a UW assistant professor of psychology.
The team’s first step was to mix up the existing social groupings of nearly four-dozen macaques. According to the authors, organizing the macaques into nine new groups created a new social hierarchy, and the order in which each monkey was introduced helped determine its status. The first in the group became the most dominant and held the highest rank, while the last to join the group typically held the lowest status.
After each group’s hierarchy was established, the team observed the macaques’ behavior and then took blood samples. They treated the samples with a synthetic glucocorticoid that mimicked the macaques’ natural primary stress hormone to simulate acute stress. In doing so, the researchers could determine whether a macaque responded productively to the stress hormone, or whether it had already been worn down by the hormone and no longer responded appropriately.
In this experiment, the cells of the lower-status macaques were less able than those of the higher-status animals to respond productively to the glucocorticoid. One explanation for this lack of a response had to do with chromatin accessibility, or how the DNA is packaged in the cell. The researchers found that the immune cells in low-status females were less accessible to receive the signal from the glucocorticoids than immune cells from higher-status macaques.
Glucocorticoid resistance is the physical toll at the cellular level that stress plays on the body. In humans, it seems to be linked to stressful situations, such as losing a job, caring for a chronically ill child, or grieving the death of a loved one.
“We know that social adversity early in life can have far-reaching effects that extend into adulthood,” says Snyder-Mackler. “The questions are, when do these events have to occur, how severe do they have to be, and are they reversible or even preventable?”