Sympathetic nervous system, genes and human essential hypertension.

The sympathetic nervous system (SNS) is the first line of defense in the response to environmental stress through its regulation of second-to-second changes in blood pressure (BP). Both the activity of the SNS and the therapeutic responses to SNS agonists and antagonists are known to be highly variable in the population. "Small" changes caused by single nucleotide polymorphisms (SNPs) of SNS genes may have considerable impact on SNS function and individualized hypertension treatment. In this review, we first describe the physiology of the SNS and its influence on cardiovascular and renal mechanisms of BP regulation. A thorough review of the role of genetic variability of various SNS genes in relation to the development of BP and essential hypertension (EH) follows. Given the vast number of SNS components, evaluations of multiple SNPs from multiple SNS genes are necessary for future association studies of BP and EH. One way to surpass the limitations and inconsistencies of previous association studies is to use a gene-based approach also referred to as indirect association, which takes all common variation within a candidate gene into account. In order to determine how SNS genes are differentially expressed or silenced, activated or inactivated against various environmental backgrounds, it is important to assess not only environmental and lifestyle risk factors such as diet, climate, chronic stress, but also personality characteristics such as hostility and coping styles. Uncovering relevant gene-gene and gene-environment interactions within the SNS cascade will not only enable early detection of EH risk but will also aid in the treatment of hypertensives through both non-pharmacological and pharmacological means.