Can raising your body temperature guard against infection? [abstract]
Abstract
Each year approximately 30,000 premature babies are delivered in the United States. Ten percent of
these babies will develop pulmonary hypertension in the first couple days of their lives due to
incomplete development of their hearts. Some of them will live to a young age; others will die only
weeks after their birth. Our laboratory is devoted to the study of pulmonary hypertension. To develop
our study we looked to help our body enhance its own response to such a problem. What could that
response be we asked? Well, what is the first thing you check when you think your sick? Your
temperature of course. Most people do not realize that your body intentionally increases its
temperature to help ward of sicknesses and injuries. Increasing an animal's body temperature above
normal for a short period is known as heat shocking. Heat shocking causes cells in the body to produce
heat shock proteins that act to protect cells from damage caused by various inflammatory agents. This
kind of stress preconditioning with heat shock has been shown to increase survivorship during certain
types of lethal forms of infection in animals. Endotoxin, an extract of bacterial cell coats, can cause
infection-like symptoms in animals. Administration of this drug is an excellent model of pulmonary
hypertension. Endotoxin causes cells in the lungs to overproduce the gas, nitric oxide, which causes
lung injury and inflammation. These symptoms are, according to scientist today, the mediators of
pulmonary hypertension pathology. Recently, studies from our laboratory and others have shown that
nitric oxide itself formed within the lungs is a cause of lung injury. Furthermore, measurement of the
amount of nitric oxide exhaled by the lungs is an easy and noninvasive method of evaluating the
severity of this injury. In this experiment, our laboratory showed that stress preconditioning with heat
shock twenty hours prior to infection with endotoxin can protect against lung injury. Also, results
indicated that a level of nitric oxide produced in the lungs was raised to abnormally high in
endotoxemic animals. However, in rats that were heat shock preconditioned showed only a low
increase in nitric oxide due to endotoxin. With this data along with other results, we determined that
heat shock preconditioning can protect against lung injury.