The Lung Microbiome: Key to Respiratory problems
Dysbiosis is a disassociation of the equilibrium in a microbiome. We’re really talking about the collapse of an ecosystem. The factors involved might range from antibiotics, which would obviously cause a significant disruption, to immune disorders, since the immune system is the interface between the bacterial populations, the microbiome, and the human body.
When the immune system is disrupted it can cause chaos in the microbiome. Diet can affect the microbiome. Differential exposures early in life that could determine what kind of microbes colonize you can affect it, as well as medications and treatments that can have an impact upon the structure and the function of that microbial community. In the lungs, Veillonella, Prevotella, Neisseria, and Acinetobacter and some types of Streptococcus are completely normal and sit in our airways all the time. Then there are organisms we think of as being pathogens just by virtue of being there. Like we’ve found that the bacterium Pseuduomonas, which is clearly a pathogen in many contexts, is more prevalent in people who have severe asthma, but we see it hardly at all in normal lungs.
It has long been thought that asthma is a disease of inflammation, but never understood what initiated it. More and more, we’re understanding that certain bacteria, fungi, and viruses have a role. And these pathogens can sustain the inflammation in adults. Over time, that’s going to cause the airways to become fibrotic and now you have the reversible obstruction of airways that you see in early asthma. A study published last summer examined why Amish children have a dramatically lower rate of asthma and allergies than Hutterite kids, even though they belong to communities that are almost exactly alike culturally and genetically.
In the Amish communities the young children are fully exposed to farm life at an early age. To animals and all the dust that goes with that. The Hutterites, for whatever reasons, do not want their young children exposed to the barns and farm life. And so not only are the barns located some distance away from their homes, but the young children weren’t going out into the barns to work as do Amish youngsters.
So, exposure to farm pathogens at a very early age seems to train the Amish youngsters’ immune systems, so that they don’t develop allergies later on. The basic principle is again, that the disruption of microbiota during a critical window in the development of the immune system, say due to antibiotic therapy and vaccines, leads to a long-term chronic problem. Many specific disease states are being linked to that early window, everything from obesity and metabolic ills to neurological disorders such as autism and these more chronic inflammatory conditions, such as asthma, related to immune function. We see that there are stages in a child’s development soon after birth when microbial exposure is interrupted and can cause a problem. A lot of that work is in the gut microbiome. When we alter that, we affect immunity throughout the body. The gut microbiome isn’t just affecting the gut. It has very distal effects altering immune responses in other organs, such as the heart, liver, and kidneys. It’s highly likely that the same is true for the lung. This communication between different microbiomes may well be a 2-way street. We’ve got some data in animals and a bit in humans suggesting the gut microbiome may influence inflammation in the airways in asthma and cystic fibrosis. An interesting question is whether the airway microbiome then sends signals back to the gut that will be changing the gut over time.
Source Lyon J. The Lung Microbiome: Key to Respiratory Ills. JAMA. Published online April 12, 2017. doi:10.1001/jama.2017.3023 – courtesy of Daniel Weber, Panaxea