Fig. 1.

The mechanism by which ginseng prevents disease via regulation of the endocrine and immune systems. Ginseng regulates the hypothalamic–pituitary–adrenal (HPA) axis. Ginseng thus prevents various diseases by ameliorating tissue injury and immune cell death, while modulating immune cells in order to limit inflammatory responses. The HPA axis is the major pathway regulating the immune response to stress; this is initiated by hypothalamic secretion of corticotrophin-releasing hormone (CRH) and secretion of arginine vasopressin (AVP) from the pituitary gland. CRH stimulates the pituitary gland to release adrenocorticotropic hormone (ACTH) into the bloodstream. ACTH in turn triggers the release of glucocorticoids, such as cortisol, from the adrenal cortex. In the event of severe stress-induced dysfunction of the HPA axis, endocrine homeostasis is disturbed; this can predispose the patient to a number of diseases. Patients with depression and anxiety exhibit increased production of HPA hormones, including CRH and AVP, as compared to healthy individuals [18]. Additionally, glucocorticoids and norepinephrine modulate proinflammatory cytokine production by immune cells. Consequently, chronic and severe stress causes immune dysfunction, which in turn can lead to various diseases [19]. It is well known that glucocorticoids suppress immune function during acute stress, thus increasing susceptibility to disease. However, should the stress become chronic, receptors become resistant to glucocorticoids and can no longer downregulate inflammatory processes [20]. IL, interleukin; TNF-α, tumor necrosis factor alpha.