A Vicious Cycle: Heart Disease And The Immune System
When I first started my career as a scientist, I had no idea how much impact the immune system has on cardiovascular disease. I was under this naïve idea that disease progression was dependent on blood cholesterol levels, stress or genetics only, never realizing how much the immune system influenced cardiovascular disease. Now that I have been studying the influence of heart disease on the immune system for a few years, I am still amazed by how intertwined these two systems are.
There is a lot of published research, both in patients as well as in experimental animal models, showing that the immune system plays a role in multiple heart conditions. Atherosclerosis is a prime example. The process of hardening of blood vessels due to cholesterol and lipid deposits is an immune system mediated disease. The inflammation triggered by the immune system is the root cause of the process of plaque formation and blood vessels blockage. Viral myocarditis, which can cause sudden death, occurs as a result of a hyper reactive immune response to viral infections. In congestive heart failure, the immune system contributes to disease by releasing inflammatory molecules that further increase the heart size. The influence of the immune system also extends to other disease that can trigger heart disease such as diabetes and obesity.
If you think the interaction between cardiovascular disease and the immune system stops there, think again. Recently, it has become evident that the cardiovascular and the immune systems live in this vicious cycle of constantly influencing each other to worsen disease outcome. For instance, the increase in lipids accumulated during coronary artery disease or obesity affects how the cells of the immune system consume fuel resources such as glucose and fats, a process known as immunometabolism. Changes in immunometabolism influence how immune cells respond to injury triggered by the increased lipids, further worsening disease. Not only that, but by virtue of overall changes in how immune cells function, heart and metabolic disease can affect how the immune system as a whole responds to other conditions such as infections and cancer.
This field of immunometabolism is still at its infancy. It will be interesting to see how much it will advance in the next few years and how much relationship scientists will find between immunometabolism and heart disease. If therapeutic approaches are found that can break this vicious cycle, patients with heart disease and other metabolic disease will gain tremendously. I would expect that the impact of such therapeutic approaches would extend to other ailments that hit those patients beyond the scope of cardiovascular disease.
Dalia Gaddis is a postdoctoral fellow at the La Jolla Institute for Allergy and Immunology. She has a Ph.D. in microbiology and immunology. She is currently working on understanding the interactions between the immune system and atherosclerosis development.