Hormonelike molecules

The eicosanoids are a diverse group of extremely powerful hormonelike molecules produced in most mammalian tissues. They mediate a wide variety of physiological processes. Examples include smooth muscle contraction, inflammation, pain perception, and blood flow regulation. Eicosanoids are also implicated in several diseases such as myocardial infarct and rheumatoid arthritis. Because they are generally active within the cell in which they are produced, the eicosanoids are called autocrine regulators instead of hormones. Most eicosanoids are derived from arachidonic acid (20 4A5-81114), which is also called 5,8,11,14-eicosatetraenoic acid. (Arachidonic acid is synthesized from linoleic acid by adding a three-carbon unit followed by decarboxylation and desaturation.)... 

Fatty acids are monocarboxylic acids that occur primarily in triacylglycerols, phospholipids, and sphingolipids. The eicosanoids are a group of powerful hormonelike molecules derived from long chain fatty acids. The eicosanoids include the prostaglandins, thromboxanes, and the leukotrienes. 

Some of the unsaturated fatty acids containing more than one double bond cannot be synthesized by the body For many years it has been known that linolenic acid and linoleic acid, called the essential fatty acids, are necessary for specific biochemical functions and must be supplied in the diet (see Table 18.1). The fimction of linoleic acid became clear in the 1960s when it was discovered that linoleic acid is required for the bios)mthesis of arachidonic acid, the precursor of a class of hormonelike molecules known as eicosanoids. The name is derived from the Greek word eikos, meaning "twenty," because they are all derivatives of twenty-carbon fatty acids. The eicosanoids include three groups of structurally related compounds the prostaglandins, the leukotrienes, and the thromboxanes. 

Bromelain is a mixture of cysteine proteases obtained from pineapple stems (Ananas comosus, Bromeliaceae) that has been used therapeutically for the treatment of inflammation and trauma [119]. 7n vitro, it has varied stimulatory effects on leukocyte populations, increases CD2-mediated T cell activation, enhances Ag-independent binding to monocytes, etc. The effects of bromelain have previously been attributed to its degradative action at cell surfaces. However, it also acts independent of the removal of cell surface molecules [120]. In order to investigate the possible hormonelike effects of bromelain on intracellular signalling, its effects on TCR7CD3 signalling and IL-2 production were studied. It was observed that bromelain inhibits ERK-2 activation in ThO cells stimulated via the TCR, or with combined TPA plus calcium ionophore. In addtion, bromelain decreased IL-2, IFN-y, and IL-4 mRNA accumulation in ThO cells stimulated with TPA plus calcium ionophore, while the cytokine mRNA accumulation in cells stimulated via TCR was not affected. It seems that bromelain does not act on ERK-2 directly but also inhibits p2r activation, an effector molecule upstream from ERK-2 in the Raf-1/MEKl/ERK kinase cascade. Since p21 is an effector for multiple MAPK pathways, it is likely that bromelain affects other MAPK signalling cascades, such as the INK pathway or p38 MAPK pathway [121],... 

Some xenobiotic compounds can have hormonelike effects and cause disruption of the endocrine system. A compound that mimics the action of a particular hormone is termed an agonist, whereas one that blocks its activity is an antagonist. Hormone activity is governed by receptors that recognize the shape of the molecule, so potentially other molecules with suitable structural characteristics can interact with these receptors. There are other potential modes of action of endocrine disrupters. To summarize ... 

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