The hypothalamic-pituitary-adrenal axis in the pathogenesis of rheumatic diseases

Is fibromyalgia an autoimmune disorder of endogenous vasoactive neuropeptides?

Fibromyalgia (FM) is a disorder characterised by soft tissue pain, disturbance of function an often prolonged course and variable fatigue and debility. A clearly defined aetiology has not been described. This paper proposes that immunological aberration is likely and this may prove to be associated with an expanding group of novel vasoactive neuropeptides. Vasoactive neuropeptides act as hormones, neurotransmitters, immune modulators and neurotrophes. They are readily catalysed to small peptide fragments. They and their binding sites are immunogenic and are known to be associated with a range of autoimmune conditions. They have a vital role in maintaining vascular flow in organs, and in thermoregulation, memory and concentration. They are co-transmitters for acetylcholine, are potent immune regulators with primarily anti-inflammatory activity, and have a significant role in protection of the nervous system to toxic assault and the maintenance of homeostasis. Failure of these substances has adverse consequences for homeostasis. This paper describes a biologically plausible mechanism for the development of FM based on loss of immunological tolerance to the vasoactive neuropeptides. The proposed mechanism of action is that inflammatory cytokines are provoked by tissue injury from unaccustomed exercise or physical injury. This may trigger a response by certain vasoactive neuropeptides which then undergo autoimmune dysfunction as well as affecting their receptor binding sites. The condition may potentially arise de novo perhaps in genetically susceptible individuals. FM is postulated to be an autoimmune disorder and may include dysfunction of purine nucleotide metabolism and nociception.

Novel repression of the glucocorticoid receptor by anthrax lethal toxin

Death from anthrax has been reported to occur from systemic shock. The lethal toxin (LeTx) is the major effector of anthrax mortality. Although the mechanism of entry of this toxin into cells is well understood, its actions once inside the cell are not as well understood. LeTx is known to cleave and inactivate MAPKKs. We have recently shown that LeTx represses the glucocorticoid receptor (GR) both in vitro and in vivo. This repression is partial and specific, repressing the glucocorticoid, progesterone, and estrogen receptor alpha, but not the mineralocorticoid or estrogen receptor beta. This toxin does not affect GR ligand or DNA binding, and we have suggested that it may function by removing/inactivating one or more of the many cofactors involved in nuclear hormone receptor signaling. Although the precise involvement of this nuclear hormone receptor repression in LeTx toxicity is unknown, examples of blunted HPA axis and glucocorticoid signaling in numerous autoimmune/inflammatory diseases suggest that such repression of critically important receptors could have deleterious effects on health.

Circadian rhythms on hypothalamic–pituitary–adrenal axis hormones and cytokines of collagen induced arthritis in rats

This study is designed to identify whether circadian rhythms of the hormones of the hypothalamic-pituitary-adrenal (HPA) axis are associated with corresponding circadian fluctuations in cytokines in a rat model of collagen-induced arthritis (CIA). CIA is induced in Wistar rats by an intradermal injection of bovine type II collagen emulsified with complete adjuvant at the left foot. On day 33, in both the CIA and the control rats, circulating adrenocorticotropin hormone (ACTH) and corticosterone, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and IL-1beta were evaluated at 6 h intervals from 00:00 to 24:00, and analyzed by statistics and cosinor-rhythmometry. The results showed that plasma corticosterone in CIA rats had a trough at 18:00 and reached a peak at 06:00 significantly. While peak values were presented in TNF-alpha at 24:00 and in IL-6 from 06:00 and 18:00 to 24:00. CIA rats exhibit abnormal circadian rhythms, with degrading amplitudes of corticosterone and IL-6, elevating amplitude of TNF-alpha, and marked phase shifts in corticosterone and IL-6. Our investigation suggests that the disorders of HPA axis in CIA rats may be related to the influence of inflammation mediators on hypothalamic centers. The circadian rhythms of hormones and cytokines in CIA rats may be reset due to the defective function of the HPA axis.

Involvement and role of the hypothalamo-pituitary-adrenal (HPA) stress axis in animal models of chronic pain and inflammation

Hypothalamo-pituitary-adrenal (HPA) axis changes have been reported in several disease states, including major depressive disorder, rheumatoid arthritis, multiple sclerosis and various other conditions associated with chronic pain. These observations suggest that stress and the HPA axis may play important roles in the pathology of these diseases. In order to contribute to a better understanding of the role that chronic stress may play in human pathology, this review article explores the involvement of the HPA axis in those animal models of chronic pain and inflammation that entail persistent rather than intermittent stress.

Neural immune pathways and their connection to inflammatory diseases

Inflammation and inflammatory responses are modulated by a bidirectional communication between the neuroendocrine and immune system. Many lines of research have established the numerous routes by which the immune system and the central nervous system (CNS) communicate. The CNS signals the immune system through hormonal pathways, including the hypothalamic-pituitary-adrenal axis and the hormones of the neuroendocrine stress response, and through neuronal pathways, including the autonomic nervous system. The hypothalamic-pituitary-gonadal axis and sex hormones also have an important immunoregulatory role. The immune system signals the CNS through immune mediators and cytokines that can cross the blood-brain barrier, or signal indirectly through the vagus nerve or second messengers. Neuroendocrine regulation of immune function is essential for survival during stress or infection and to modulate immune responses in inflammatory disease. This review discusses neuroimmune interactions and evidence for the role of such neural immune regulation of inflammation, rather than a discussion of the individual inflammatory mediators, in rheumatoid arthritis.

Cognitive impairment in patients with chronic pain: the significance of stress

This review article examines the role of emotional distress and other aspects of suffering in the cognitive impairment that often is apparent in patients with chronic pain. Research suggests that pain-related negative emotions and stress potentially impact cognitive functioning independent of the effects of pain intensity. The anterior cingulate cortex is likely an integral component of the neural system that mediates the impact of pain-related distress on cognitive functions, such as the allocation of attentional resources. A maladaptive physiologic stress response is another plausible cause of cognitive impairment in patients with chronic pain, but a direct role for dysregulation of the hypothalamic-pituitary-adrenocortical axis has not been systematically investigated.