Endotoxin and the hypothalamo-pituitary-adrenal (HPA) axis

摘要: Endotoxin is considered to be a systemic (immunological) stressor eliciting prolonged activation of the hypothalamo-pituitary-adrenal (HPA) axis. The HPA-axis response after an endotoxin challenge mainly due released cytokines (IL-1, IL-6 and TNF-alpha) from stimulated peripheral immune cells, which in turn stimulate different levels HPA Controversy exists regarding main locus action on glucocorticoid secretion, since effect this neuro-endocrine axis has been observed intact animals ablation hypothalamus; however, lack LPS described at both pituitary adrenocortical levels. resulting increase adrenal glucocorticoids well-documented inhibitory effects inflammatory process cytokine release. Therefore, gland by thought occur stimulation corticosteroid-releasing hormone (CRH) production median eminence hypothalamus, which, stimulates secretion ACTH pituitary. Acute administration cortisol release CRH vasopressin (AVP) hypophysial portal blood. During repeated endotoxemia, tolerance function develops, with crucial role for modulation A single exposure high dose can induce long-lasting state second LPS, affecting plasma TNF-alpha hormones. Although there are gender differences IL-1, these responses enhanced castration attenuated androgen estrogen replacement. Estrogens attenuate endotoxin-induced IL-6, IL-1ra subsequent postmenopausal women. There appears temporal functional relation between nitric oxide formation suggesting stimulatory modulating challenges.