Steroids immune system

L-Tyrosine metabohsm and catecholamine biosynthesis occur largely in the brain, central nervous tissue, and endocrine system, which have large pools of L-ascorbic acid (128). Catecholamine, a neurotransmitter, is the precursor in the formation of dopamine, which is converted to noradrenaline and adrenaline. The precise role of ascorbic acid has not been completely understood. Ascorbic acid has important biochemical functions with various hydroxylase enzymes in steroid, dmg, andhpid metabohsm. The cytochrome P-450 oxidase catalyzes the conversion of cholesterol to bUe acids and the detoxification process of aromatic dmgs and other xenobiotics, eg, carcinogens, poUutants, and pesticides, in the body (129). The effects of L-ascorbic acid on histamine metabohsm related to scurvy and anaphylactic shock have been investigated (130). Another ceUular reaction involving ascorbic acid is the conversion of folate to tetrahydrofolate. Ascorbic acid has many biochemical functions which affect the immune system of the body (131). 

Among vertebrate species, the neuro-endocrine-immime system is responsible for many complex, inter-related physiological processes including neuronal, homeostatic, reproductive and immune functions. There are four main types of hormone polypeptides, eicosanoids, steroids and thyroid hormones. Reflecting the inter-dependency of the neiiro-endocrine and immune systems, hormones, neuropeptides and other neiirotransmitters are known to be produced by some immune cells and play a role in the regulation of the immune system, while endocrine and nervous tissues express receptors for many substances produced by the immune system. The major focus of interest in endocrine disruption has... 

The mammalian and avian immune systems function similarly both incorporate humoral and cell-mediated cytotoxic mechanisms, " and are thought to share a 160m year old relationship with the reptilian immune system. The immune system of mammals shows sexual dimorphism " a greater immune response is normally observed in females, which has been attributed to differences in steroid hormone concentration. In the toad Bufo regularis, sexual dimorphism of the immune system is also apparent. ... 

So far there are no satisfactory treatments for multiple organ failure, although steroids are sometimes used to inhibit the activity of the immune system. Provision of antibodies to one or more of the proinflammatory cytokines is one novel approach. 

Lipophilic hormones, which include steroid hormones, iodothyronines, and retinoic acid, are relatively small molecules (300-800 Da) that are poorly soluble in aqueous media. With the exception of the iodothyronines, they are not stored by hormone-forming cells, but are released immediately after being synthesized. During transport in the blood, they are bound to specific carriers. Via intracellular receptors, they mainly act on transcription (see p. 358). Other effects of steroid hormones—e.g., on the immune system—are not based on transcriptional control. Their details have not yet been explained. 

The most important clinical application of glucocorticoids and their semisynthetic analogs is their anti-inflammatory activity, discovered in 1949 by Hench and co-workers. The profound anti-inflammatory effects of glucocorticoids arise from the combined effects of these steroids on both the cellular and molecular mediators of inflammation these effects are separate from the metabolic effects described above and further indication of the widespread diversity of macromolecules to which steroids can bind. Glucocorticoids suppress inflammation at the cellular level by downregulating the concentration, distribution, and function of leukocytes (white blood cells) that profoundly influence inflammation and response to infection within the body (In this way, steroids help to mediate the overlap between the endocrine systems [chapter 5] and the immune systems [chapter 6]). Glucocorticoids also suppress inflammation at the molecule level by suppressing inflammatory cytokines, chemokines, and other molecular mediators of inflammation. 

Conditions which can affect the immune system and cause it to malfunction are Cushing s disease (caused by excess steroid production or treatment - T and B cell lysis), Hodgkin s disease (cancer of the lymph nodes - whole body T cell deficiency), Bruton s disease (B cell deficiency -susceptibility to infection), and, of course, AIDS (Acquired Immune Deficiency Syndrome). 

The two principal groups of adrenal steroids are the glucocorticoids and mineralocorticoids. These hormones are synthesized from cholesterol within cells of the adrenal cortex. The primary glucocorticoid produced in humans is cortisol (hydrocortisone), and the primary mineralocorticoid is aldosterone. Glucocorticoids exert a number of effects such as regulation of glucose metabolism, attenuation of the inflammatory response, and suppression of the immune system. Mineralocorticoids are involved primarily in the control of fluid and electrolyte balance. 

Glucocorticoid The general class of steroid agents that affect glucose metabolism and are used pharmacologically to decrease inflammation and suppress the immune system. Principle examples include cortisol and corticosterone. 

TCDD on the immune system." One potentially important indirect mechanism operates through effects on the endocrine system. Glucocorticoids, sex steroids, T4, growth hormone, and prolactin have been shown to regulate immune responses, and 2,3,7,8-TCDD has been shown to alter the activity of all of them (see also sections on endocrine and reproductive effects). 

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