Alerted microglia and the sympathetic nervous system: A novel form of microglia in the development of hypertension

• Microglia are ubiquitously expressed in sympathetic nervous system.
• Microglia are capable of modulating sympathetic nerve activity.
• Microglial dysfunction in cardiorespiratory sites may be involved in hypertension.

Microglia, commonly known as the tissue resident macrophages of the central nervous system (CNS), are ubiquitously expressed in the CNS. Microglia, in their resting, or surveilling, stage, play a critical role in the maintenance of normal neuronal physiology and homeostasis. On activation, microglia can acquire either a neurotoxic (M1) or a neuroprotective (M2) phenotype. Prior to development of the M1 or M2 phenotype, little was known about changes in microglial activity, when subjected to stimuli. It is postulated, that an inability of microglia to maintain neuronal physiology within a normal working range can contribute to the development of cardiovascular disorders (CVDs) such as hypertension, but clear evidence supporting this hypothesis is missing. Even though our understanding of microglial function in a state of CNS injury/inflammation is extensive, the literature concerning role of microglia in the healthy CNS, is limited. Involvement of microglia in the pathophysiology of CVDs, in a neuroprotective/neurotoxic manner, is a key area that requires further investigation.