Lorri L. Short

Environmental estrogens : Effects on cholesterol lowering and bone in the ovariectomized rat

Representative non-steroidal estrogens, from common environmental sources such as plants, pesticides, surfactants, plastics, and animal health products, demonstrated an ability to lower serum cholesterol and prevent bone loss. Specifically, select environmental estrogens (coumestrol, genistein, methoxychlor, bisphenol A, and zeranol) effectively lowered total serum cholesterol in an estrogen-dependent animal model, the ovariectomized rat. Of these entities, coumestrol, methoxychlor, and zeranol prevented ovariectomy-induced bone loss. In an in vitro environment, these compounds competed with 17beta-estradiol for estrogen receptor binding and stimulated cell proliferation in a human breast cancer cell line (MCF-7). In addition to their well-documented effects on reproductive tissue, various environmental estrogens can dramatically affect non-reproductive parameters such as cholesterol lowering and bone metabolism.

Raloxifene is a Tissue‐Selective Agonist/Antagonist That Functions through the Estrogen Receptor

Raloxifene (LY 139481), previously called keoxifene, is a benzothiophene derivative that binds to the estrogen receptor (ER) with high affinity (kd = 0.54-0.11 nM).’ This compound has tissue-specific activity, acting as an antiestrogen in breast and uterus, but functioning as an estrogen agonist in bone and on lipid metabolism. The molecular mechanisms of this tissue specificity are still under investigation, but preliminary evidence indicates that raloxifene-ER complexes associate with unique response elements, thus indicating that multiple transcriptional pathways may mediate these e f f e ~ t s . ~ ’ ~

Evaluation of the major metabolites of raloxifene as modulators of tissue selectivity

Raloxifene (LY139481 HCl) is a selective estrogen receptor modulator (SERM) which blocks the effects of estrogen on some tissues, such as the breast and uterus, while mimicking estrogen in other tissues, such as bone. To study the origins of this unique pharmacology, we have prepared the major metabolites of raloxifene as chemical probes for examining the estrogen receptor function in vitro and in vivo. In human breast cancer cell (MCF-7) related assays, these glucuronide conjugates show little affinity for the estrogen receptor and are more than two orders of magnitude less potent at inhibiting cell proliferation than raloxifene. In non-traditional estrogen target tissue, such as bone, these metabolites are less effective than the parent at inhibiting cytokine-stimulated bone resorbing activity in rat osteoclasts or producing transforming growth factor beta-3 (TGF-beta3). In animal models, tissue distribution studies with radiolabelled metabolite indicate that conversion to raloxifene occurs readily in a variety of tissues including the liver, lung, spleen, kidney, bone and uterus. Differential conversion of metabolite in target organs, such as bone and the uterus, is not observed indicating that the origin of raloxifenes pharmacology does not result from tissue-selective deconjugation of metabolite to parent.

Estriol: A potent regulator of TNF and IL-6 expression in a murine model of endotoxemia

The increased incidence of autoimmune disease in premenopausal women suggests the involvement of sex steroids in the pathogenesis of these disease processes. The effects of estrogen on autoimmunity and inflammation may involve changes in the secretion of inflammatory mediators by mononuclear phagocytes. Estradiol, for example, has been reported to regulate TNF, IL-6, IL-1 and JE expression. In the present study the effects of the estrogen agonist, estriol, on cytokine expression have been investigated in mice administered a sublethal lipopolysaccharide, LPS, challenge. Pretreatment of mice with pharmacologic doses of estriol, 0.4–2 mg/kg, resulted in a significant increase in serum TNF levels in both control and autoimmune MRL/lpr mice, following LPS challenge. This increase in TNF over the placebo group was blocked by the estrogen antagonist tamoxifen. Estriol treated mice also exhibited a rapid elevation in serum IL-6 levels following LPS challenge with the peak increase occurring 1 hr post LPS. This contrasted with the placebo group in which maximal serum IL-6 levels were detected at 3 hrs post challenge. This shift in the kinetics of IL-6 increase by estriol was inhibited by tamoxifen. The estriol mediated effects on TNF and IL-6 serum levels were consistent with the changes in TNF and IL-6 mRNA observed ex vivo in elicited peritoneal macrophages. Macrophage cultures from estriol treated animals however, did not demonstrate significant differences from the placebo group for TNF or NO secretion following in vitro LPS challenge. These results suggest that the estrogen agonist estriol can have significant quantitative, TNF, and kinetic, IL-6, effects on inflammatory monokines produced in response to an endotoxin challenge.

Versatile raloxifene triflates

Abstract Methodology has been employed that permits the differentiation of the phenols of raloxifene. Transition metal mediated transformations of raloxifene triflates have subsequently provided a number of analogs that were evaluated further in two in vitro models predictive of estrogen receptor mediated biological activity.

Synthesis and pharmacology of 2-alkyl raloxifene analogs

Abstract A series of 2-alkyl and 2-cycloalkyl raloxifene analogs have been prepared and evaluated in both in vitro and in vivo models of estrogen/antiestrogen activity. In particular, the 2-cyclohexyl analogs show promise as potent selective estrogen-receptor modulators (SERMs).

Conversion of the phytoestrogen coumestrol into a selective estrogen receptor modulator (SERM) by attachment of an amine-containing sidechain

Abstract The naturally occurring estrogen mimetic coumestrol has been shown to stimulate proliferation of MCF-7 mammary tumor cells and to cause uterotrophic effects in ovariectomized (OVX) rats. Attachment of a basic amine-containing sidechain to C-6 of coumestrol converts this estrogen agonist into an antagonist in breast and uterine tissue, while maintaining its estrogen-like activity as a hypocholesterolemic agent.