Autonomic Dysfunction, Sympathetic Hyperactivity and the Development of End-Organ Damage in Hypertension: Multiple Benefits of Exercise Training

Abstract

Autonomic dysfunction is closely related to the development of hypertension, which
is characterized by increased sympathetic activity, decreased vagal tonus and baroreflex dysfunction.
The hypertension-induced maladaptive changes progressively lead to heart failure,
myocardial infarction and stroke. Hypertrophic remodeling of brain arterioles, chemoreceptors
activation, blood-brain barrier abnormalities, oxidative stress and pro-inflammatory cytokines
production in autonomic brain areas increase neuronal activity and sympathetic outflow. These
responses, together with increased baroreflex dysfunction-induced pressure variability, reninangiotensin
system hyperactivation and capillary rarefaction, increase blood pressure levels
and act as a positive feedback mechanism to perpetuate hypertension and development of endorgan
damage. Exercise training, a non-pharmacological tool, has been used as an adjuvant
therapy to treat hypertension. Our recent data showed that moderate aerobic training in adult
SHR completely normalizes oxidative stress and inflammation in autonomic brain areas involved
in cardiovascular control and promptly corrects baroreflex dysfunction and increases
cardiac vagal activity. The early (2-weeks) training-induced beneficial responses improve autonomic
control even in the persistence of hypertension, since a partial reduction of pressure levels
was observed after 8 weeks of exercise training, which was related to reversion of arteriolar
hypertrophic remodeling and consequent decrease of peripheral vascular resistance.