Immune cells block the movement of brain fluid
The researchers show that immune cells entering the brain’s membrane, create a net that traps bacteria but also blocks the movement of cerebrospinal fluid. The brain is constantly cleaned by the cerebrospinal fluid that enters the tissue along blood vessels and is responsible for clearing out waste products made by the active brain cells.
This fluid transport system was named the glymphatic system by Maiken Nedergaard, and its function has been shown to be critical for avoiding the accumulation of protein plaques that accumulate in patients with Alzheimer's disease. Glymphatic transport of cerebrospinal fluid is also important for avoiding brain swelling in acute diseases such as stroke.
Brain swelling, also called edema, is a life-threatening condition because the brain is contained within the skull. The swelling compresses blood vessels resulting in loss of brain tissue, which is fatal when the brain regions that control breathing stop working.
That brain swelling in meningitis is caused by blockage of the glymphatic system is now shown for the first time in collaboration between Maiken Nedergaards group at the University of Copenhagen and Iben Lundgaard at MultiPark at Lund University.
“When the immune cells enter the brain, they eat the bacteria, but while doing so the immune cells also produce inflammatory components, including nets that cause swelling,” the research team says.
“The most important aspects of our study is that it suggests that meningitis can be treated by administration of an enzyme that degrades the neutrophil nets. Enzymatic removal of nets eliminated the often fatal accumulation of fluid in the brain in rats with bacterial meningitis. This novel treatment can be combined with antibiotics if needed,” explains Iben Lundgaard.
Hope for an international clinical study
The researchers theorized that if the nets were dissolved, leaving just the immune cells without their nets in the meninges, it would allow the cerebrospinal fluid to pass the brain freely.
The net-like structures consist mainly of DNA, so the research team applied drugs for cutting up DNA, so-called DNase. They gave DNase to the rats infected with pneumococcus bacteria, which causes bacterial meningitis.
“We administered DNase to rats infected with the bacteria, and we were able to show that the nets dissolved. The treatment reduced brain swelling and helped in removing metabolic waste production from the infected brain. In contrast, antibiotic treatment did not have an effect on brain swelling or waste clearance,” says Maiken Nedergaard.
Based on their results, the research team now hopes to set up an international clinical study to investigate DNase in the treatment of patients with bacterial meningitis. Antibiotic resistance is increasing at an alarming rate and the drug the researchers use here is a promising alternative, and has already been approved for human use in other neurological diseases.
“We would also like to investigate how metabolic waste products removal is impaired in other diseases of the brain such as multiple sclerosis or viral meningitis,” says Iben Lundgaard.
This news article was originally published at the Faculty of Health and Medical Sciences, University of Copenhagen.
Read the full paper ‘DNase Treatment Prevents Cerebrospinal Fluid Block in Early Experimental Pneumococcal Meningitis’.
