Steroid hormones modulate many physiological processes. The effects of steroids that are mediated by the modulation of gene expression are known to occur with a time lag of hours or even days. Research that has been carried out mainly in the past decade has identified other responses to steroids that are much more rapid and take place in seconds or minutes. These responses follow nongenomic pathways, and they are not rare.

Traditionally, steroid hormone action has been described as the modulation of nuclear transcription, thus triggering genomic events that are responsible for physiological effects. Despite early observations of rapid steroid effects that were incompatible with this theory, nongenomic steroid action has been widely recognized only recently. Evidence for these rapid effects is available for steroids of all clones and for a multitude of species and tissues. Examples of nongenomic steroid action include rapid aldosterone effects in lymphocytes and vascular smooth muscle cells, vitamin D3 effects in epithelial cells, progesterone action in human sperm, neurosteroid effects on neuronal function, and vascular effects of estrogens. Mechanisms of action are being studied with regard to signal perception and transduction, and researchers have developed a patchy sketch of a membrane receptor-second messenger cascade similar to those involved in catecholamine and peptide hormone action. Many of these effects appear to involve phospholipase C, phosphoinositide turnover, intracellular pH and calcium, protein kinase C, and tyrosine kinases. The physiological and pathophysiological relevance of these effects is unclear, but rapid steroid effects on cardiovascular, central nervous, and reproductive functions may occur in vivo. The cloning of the cDNA for the first membrane receptor for steroids should be achieved in the near future, and the physiological and clinical relevance of these rapid steroid effects can then be established.

Lösel, Ralf M., Elisabeth Falkenstein, Martin Feuring, Armin Schultz, Hanns-Christian Tillmann, Karin Rossol-Haseroth, and Martin Wehling. Nongenomic Steroid Action: Controversies, Questions, and Answers. Physiol Rev 83: 965–1016, 2003; 10.1152/physrev.00003.2003.—Steroids may exert their action in living cells by several ways: 1) the well-known genomic pathway, involving hormone binding to cytosolic (classic) receptors and subsequent modulation of gene expression followed by protein synthesis. 2) Alternatively, pathways are operating that do not act on the genome, therefore indicating nongenomic action. Although it is comparatively easy to confirm the nongenomic nature of a particular phenomenon observed, e.g., by using inhibitors of transcription or translation, considerable controversy exists about the identity of receptors that mediate these responses. Many different approaches have been employed to answer this question, including pharmacology, knock-out animals, and numerous biochemical studies. Evidence is presented for and against both the participation of classic receptors, or proteins closely related to them, as well as for the involvement of yet poorly understood, novel membrane steroid receptors. In addition, clinical implications for a wide array of nongenomic steroid actions are outlined.

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Progesterone receptor membrane component-1 (PGRMC1) interacts with plasminogen activator inhibitor RNA binding protein-1 (PAIRBP1), a membrane-associated protein involved in the antiapoptotic action of progesterone (P4). In this paper, the first studies were designed to assess the ovarian expression pattern of PGRMC1 and PAIRBP1. Western blot analysis revealed that spontaneously immortalized granulosa cells (SIGCs) as well as granulosa and luteal cells express both proteins. Luteal cells were shown to express more PGRMC1 than granulosa cells. Immunohistochemical studies confirmed this and demonstrated that PGRMC1 was present in thecal/stromal cells, ovarian surface epithelial cells, and oocytes. PAIRBP1 was also expressed in thecal/stromal cells and ovarian surface epithelial cells but not oocytes. Furthermore, PAIRBP1 and PGRMC1 were detected among the biotinylated surface proteins that were isolated by avidin affinity purification, indicating that they localized to the extracellular surface of the plasma membrane. Confocal microscopy revealed that both of these proteins colocalize to the plasma membrane as well as the cytoplasm. The second studies were designed to assess PGRMC1's role in P4's antiapoptotic actions. These studies showed that overexpression of PGRMC1 increased 3H-P4 binding and P4 responsiveness. Conversely, treatment with a PGRMC1 antibody blocked P4's antiapoptotic action. Taken together, the present findings indicate that both PAIRBP1 and PGRMC1 show a similar expression pattern within the ovary and colocalize to the extracellular surface of the plasma membrane. At the plasma membrane, these two proteins interact to form a complex that is required for P4 to transduce its antiapoptotic action.

High-affinity progesterone-binding sites have been identified, characterized in and purified from porcine liver membranes. They were functionally solubilized by the non-denaturing zwitterionic detergent 3-[(3-~holamidopropyl)dimethylammonio]-l -propanesulfonic acid (Chaps, 20 mM, detergent/protein mass ratio 4 : l ) at a yield of 75-80%. Using [3H]progesterone as radioligand, binding studies showed high-affinity and low-affinity binding sites in microsomal preparations with an apparent Kdl of 11 nM and an apparent Kd2 of 286 nM. In solubilized fractions the high-affinity binding sites were present at an apparent Kd of 69 nM. In both preparations, progesterone binding was time-dependent, saturable, reversible, and showed a similar hierachy of affinities for related steroids. A purification scheme was developed based on anion-exchanger procedures. The purified fraction as identified by maximum specific progesterone-binding activity contained two major polypeptides of apparent molecular masses (SDS/PAGE) of 28 kDa and 56 kDa, respectively. Sequencing of both polypeptides showed an identical amino terminus without significant identity in the amino acid sequence to any known protein primary structure.Keywords: progesterone ; membrane-binding site ; liver; amino acid sequence.For the past decade, nonclassical actions of steroid hormones and related signal transduction pathways have gained increasing scientific interest. Evidence for nongenomic steroid effects are provided for all classes of steroid hormones including the secosteroid vitamin D3 and triiodothyronine (for review see [I, 21).As an example, the sex hormone progesterone has been found to act on oocyte maturation in a nontranscriptional manner in Xenopus laevis 131. An important instant effect of progesterone is the rapid stimulation of ion fluxes in human sperm. Blackmore et al. [4, 51 showed a rapid Ca2+ and Turner and Meizel [6] demonstrated CI-effluxes during the acrosome reaction induced by Progesterone. Moreover, in hepatocytes a rapid progesterone-induced increase of cytosolic CaZ+ was seen resulting from Caz+ influx [7].Another prominent example for a nongenomic steroid effect is the rapid stimulation of Na+/H ' -exchanger in human mononu- So far, none of these membrane steroid-binding proteins has been purified in sufficient amounts to allow molecular analysis and cloning; it appears that the lack of a satisfactory solubilization procedure for these labile proteins is one of the major obstacles in this regard. Here, progesterone-specific binding proteins are identified and characterized in porcine liver microsomes, solubilized, purified and partially sequenced from the N-terminus. Materials and Methods

Management of pain and inflammation must consider those risks and find alternative drugs or approaches to limit the negative impact of NSAIDs on mortality and morbidity. Alternative drugs, low-dose/short-term use, but especially non-pharmacologic approaches, such as physiotherapy, exercise, neurophysiologic measures, and local therapies, need to be further utilized. The appalling equation "less pain-more deaths/morbidity" ultimately necessitates treatment optimization in the individual patient.

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