New Delhi: Psychological stress can alter the gut microbiome and accelerate ageing-like changes in blood-forming stem cells, potentially increasing the risk of diseases such as heart ailments and diabetes, according to a study conducted in mice.

The findings, published in the journal Cell Stem Cell, describe how psychological stress affects hematopoietic stem cells in the bone marrow by disrupting the intestinal microbiota, providing fresh insights into the biological link between stress and immune function.

"Our research shows how stress-responsive brain regions regulate the balance of the intestinal microbiota, which ultimately affects the function of hematopoietic stem cells," senior author Meng Zhao of Sun Yat-sen University said.

Previous studies have shown that chronic stress can influence immune function and the formation of immune cells in the bone marrow through inflammatory pathways and adrenergic receptors involved in the body's "fight-or-flight" response. However, the mechanism by which stress signals travel from the brain to the bone marrow had remained unclear.

The researchers analysed four mouse models of psychological stress to investigate interactions among the brain, intestine and bone marrow.

They found that chronic stress reduced activity in the medial prefrontal cortex, which processes emotional and cognitive information, and the periaqueductal gray, a brain region involved in pain modulation.

The reduced brain activity triggered several physiological changes, including depletion of hematopoietic stem cells and reduced production of lymphocytes, a type of immune cell.

The team also observed significant alterations in the gut microbiome. Stressed mice showed a decline in Lactobacillus reuteri, a beneficial bacterial species that helps maintain gut health, along with lower levels of spermidine, a naturally occurring compound involved in removing damaged cells.

Co-author Linjia Jiang said one of the study's key findings was that suppressing just two specific brain regions was sufficient to reproduce many of the blood-forming stem cell defects associated with psychological stress.

The researchers said future studies would examine whether similar mechanisms operate in humans and whether interventions could help improve bone marrow function during ageing or prolonged stress.

The findings provide a framework for developing new strategies to counter immune ageing and stress-related immune dysfunction, Zhao said.

Jiang added that managing psychological stress could not only improve mental well-being but also help preserve immune function and promote healthy ageing.