The top picture shows normal ether lipid production in mice, alongside an abundance of neutrophils. The bottom picture shows reduced neutrophils in mice with impaired ether lipid production.
Image credit: Washington University School of Medicine
The researchers, including senior investigator Dr. Clay F. Semenkovich of the Division of Endocrinology, Metabolism and Lipid Research, reveal that enzymes that play a role in converting carbohydrates to a certain type of fatty acid - called an ether lipid - play a role in the health of neutrophils.
Neutrophils are a type of white blood cell that helps ward off infections in the body, especially those caused by bacteria or fungi.
However, an abnormally high number of neutrophils present in the blood - referred to as neutrophilia - can be a sign of acute inflammation and is associated with rheumatoid arthritis. Neutrophilia is also common among individuals with leukemia.
Without ether lipids, neutrophils die
For their study, published in the journal Cell Metabolism, Dr. Semenkovich and colleagues analyzed genetically engineered mice. These mice were unable to create the enzymes that produce ether lipids.
They found that without ether lipids, the mice rapidly lost weight and their white blood cell count became very low. In particular, the mice displayed extremely low levels of neutrophils; they found that lack of ether lipids appeared to kill neutrophils.
Around 52.5 million adults in the US have some form of arthritis, and it is estimated that there were around 52,380 new cases of leukemia diagnosed last year, with 24,090 deaths from the disease.
But Dr. Semenkovich and colleagues believe their findings could open the door to new treatments for both of these conditions:
"This may be a pathway to limit inflammation. If we could reduce the activity of these enzymes without eliminating them entirely, it could lower the levels of ether lipids and potentially help patients with leukemia and inflammatory diseases, such as arthritis."
Defective enzymes only killed mature neutrophils
In addition, the researchers found that the enzymes that were unable to produce ether lipids solely targeted neutrophils and avoided killing other white blood cells. What is more, the enzymes only killed mature neutrophils, avoiding their precursors.
According to the team, this means that reducing production of ether lipids would only lower neutrophil levels temporarily, meaning a patient's neutrophil count would increase - normalizing the immune system - once treatment ceases.
"We had never thought about treating rheumatoid arthritis or leukemia by targeting enzymes that produce fatty acids," comments first author Irfan J. Lodhi, also of the Division of Endocrinology, Metabolism and Lipid Research, "but this work supports that line of thinking."
In September last year, Medical News Today reported on a study published in the journal Arthritis Research & Therapy, which details a promising new targeted treatment for rheumatoid arthritis.
The researchers of that study, led by Dr. Ahuva Nissim of Queen Mary University of London in the UK, suggest that biologic drugs that block inflammatory signals could be delivered directly to arthritic joints, reducing the occurrence of side effects triggered by similar drugs that circulate the whole body.