Stress-triggered changes in peripheral catecholaminergic systems | JoVE Visualize

Area of Science:

Neuroendocrinology
Stress Physiology
Autonomic Nervous System Research

Background:

The sympathetic nervous system (SNS) regulates crucial physiological responses to stress, including cardiovascular and metabolic adjustments.
Stressors differentially impact the sympathoneural and sympathoadrenomedullary systems via distinct metabolic pathways and temporal responses.
Nonneuronal catecholamine enzymes are induced by stress, primarily mediated by corticosteroids.

Purpose of the Study:

To elucidate how short- and long-term stressors differentially affect catecholamine synthetic enzyme pathways in the sympathetic nervous system.
To investigate the role of transcription factors and glucocorticoids in mediating stress-induced alterations in sympathetic activity.
To examine the presence and regulation of nonneuronal catecholamine enzymes, such as phenylethanolamine N-methyltransferase (PNMT), in response to stress and glucocorticoids.

Main Methods:

Analysis of tyrosine hydroxylase gene transcription following immobilization stress.
Investigation of transcription factors (CREB, Egr-1, Fra-2) involved in short- and long-lived stress responses.
Assessment of glucocorticoid and ACTH induction of sympathoneural enzymes.
Examination of nonneuronal PNMT expression in cardiac and other tissues.
Correlation of human stressors (e.g., caregiving, sleep apnea) with physiological markers (norepinephrine, blood pressure, receptor downregulation).

Main Results:

Short-term immobilization rapidly increases tyrosine hydroxylase gene transcription via CREB, but this effect is transient.
Repeated or long-term stress engages transcription factors like Egr-1 and Fra-2 for sustained sympathetic nervous system activation.
Glucocorticoids and ACTH induce sympathoneural enzymes, leading to distinct short-term and long-lived SNS activation patterns.
Nonneuronal PNMT is present in the adult organism, increases with glucocorticoid exposure, and is linked to fetal PNMT induction and hypertension.
Human stressors are associated with persistent increases in blood norepinephrine, elevated blood pressure, and downregulated catecholamine receptors, mirroring animal models.

Conclusions:

Stress-induced alterations in the sympathetic nervous system are complex, involving differential regulation of catecholamine synthesis and enzyme activity.
Both neuronal and nonneuronal pathways, influenced by corticosteroids and specific transcription factors, contribute to the adaptive and maladaptive responses to chronic stress.
Findings in experimental animals translate to humans, where stressors like caregiving and sleep apnea induce sustained sympathetic activation, hypertension, and altered receptor function.