Tickling in the nose can contribute to induce a sneeze, removing allergens and germs that cause illness. The cellular mechanisms that govern the sneeze reflex, however, extend well beyond the sinuses and are little known. A team lead by Washington University School of Medicine, St. Louis researchers has now discovered particular cells and proteins that govern the sneeze reflex in mice.
Understanding Sneezing May Guide To Strategies To Stop The Spread Of Infectious Viruses
A better understanding of what causes people to sneeze, specifically how neurons react to allergens and viruses, could lead to treatments capable of slowing the spread of infectious respiratory diseases via sneezes, according to Qin Liu, Ph.D., an associate professor of anesthesiology and the study’s senior investigator.
The observations were reported in the journal Cell on June 15th.
According to Liu, a researcher at the university’s Center for the Investigate of Itch and Sensory Disorders, they study the neurological process underlying sneezing since so many people, including members of their own family, sneeze due to issues such as seasonal allergies and virus infections.
Their objective is to learn more about how neurons react to allergens and viral infections, particularly how they contribute to itchy eyes, sneezing, and other symptoms. Their latest research has discovered connections between nerve cells and other systems, which might aid in the development of therapies for sneeze and contagious respiratory illnesses.
Sneezing is the most powerful and widespread method of transmitting infectious droplets from respiratory diseases. More than 20 years ago, scientists discovered a sneeze-inducing area in the central nervous system, but little is known about how the sneeze reflex operates at the cellular and molecular levels.
In the current study, Liu and her colleagues created a mouse model to determine which nerve cells convey signals that cause mice to sneeze. The mice were given aerosolized droplets containing either histamine or capsaicin, a spicy chemical derived from chili peppers. Both produced sneezes in the mice, much as they do in humans.
Liu’s team was able to discover a class of tiny neurons associated with a capsaicin-induced sneeze by analyzing nerve cells that were already known to react to the chemical. The researchers next sought chemicals called neuropeptides that might send sneeze signals to those nerve cells and discovered that neuromedin B (NMB) was necessary for sneezing.
In contrast, when they removed the NMD-sensitive neurons from the portion of the neurological system that caused the mice to sneeze, they were able to inhibit the sneeze reflex. All of those neurons produce a protein known as the neuromedin B receptor. Sneezing was substantially decreased in animals lacking that receptor.
The researchers also discovered that by exposing a portion of the mouse brain to the NMB peptide, they could trigger the sneeze reflex. Furthermore, even though the animals had not been exposed to any capsaicin, histamine, or other allergens, they began to sneeze.
Because many viruses and other pathogens, including the majority of human rhinoviruses and coronaviruses such as the Middle East respiratory syndrome coronavirus (MERS-CoV) and SARS-CoV-2, the coronavirus that causes COVID-19, are spread in part by aerosolized droplets, Liu believes it may be possible to limit the spread of those pathogens by targeting NMB or its receptor to reduce sneezing in those known to be susceptible.
According to Liu, a sneeze can produce 20,000 virus-containing droplets that can linger in the air for up to 10 minutes. A cough, on the other hand, produces closer to 3,000 droplets, or roughly the same number as a few minutes of talking. It will be critical to understanding the mechanisms that produce sneeze to inhibit them to avoid future virus outbreaks and help cure pathological sneezing caused by allergens.
They found targets that might lead to therapies for pathological sneezing or methods for restricting the spread of infections by identifying neurons that mediate the sneeze reflex, as well as neuropeptides that stimulate these neurons.