Modulation of estrogen action during preimplantation period and in immature estradiol-primed rat uterus by anti-implantation agent, ormeloxifene

Ormeloxifene, a selective estrogen receptor modulator, protects against pulmonary hypertension

PURPOSE

Protective effect of 17β-estradiol is well-known in pulmonary hypertension. However, estrogen-based therapy may potentially increase the risk of breast cancer, necessitating a search for novel drugs. This study, therefore, investigated the ameliorative effects of a selective estrogen receptor modulator, ormeloxifene, in pulmonary hypertension.

METHODS

Cardiomyocytes (H9C2) and human pulmonary arterial smooth muscle cells (HPASMCs) were exposed to hypoxia (1% O₂) for 42 and 96 h, respectively, with or without ormeloxifene pre-treatment (1 μM). Also, female (ovary-intact or ovariectomized) and male Sprague-Dawley rats received monocrotaline (60 mg/kg, once, subcutaneously), with or without ormeloxifene treatment (2.5 mg/kg, orally) for four weeks.

RESULTS

Hypoxia dysregulated 17β-hydroxysteroid dehydrogenase (17βHSD) 1 & 2 expressions, reducing 17β-estradiol production and estrogen receptors α and β in HPASMC but increasing estrone, proliferation, inflammation, oxidative stress, and mitochondrial dysfunction. Similarly, monocrotaline decreased plasma 17β-estradiol and uterine weight in ovary-intact rats. Further, monocrotaline altered 17βHSD1 & 2 expressions and reduced estrogen receptors α and β, increasing right ventricular pressure, proliferation, inflammation, oxidative stress, endothelial dysfunction, mitochondrial dysfunction, and vascular remodeling in female and male rats, with worsened conditions in ovariectomized rats. Ormeloxifene was less uterotrophic; however, it attenuated both hypoxia and monocrotaline effects by improving pulmonary 17β-estradiol synthesis. Furthermore, ormeloxifene decreased cardiac hypertrophy and right ventricular remodeling induced by hypoxia and monocrotaline.

CONCLUSION

This study demonstrates that ormeloxifene promoted pulmonary 17β-estradiol synthesis, alleviated inflammation, improved the NOX4/HO1/Nrf/PPARγ/PGC-1α axis, and attenuated pulmonary hypertension. It is evidently safe at tested concentrations and may be effectively repurposed for pulmonary hypertension treatment.

Anti-cancer potential of a novel SERM ormeloxifene

Ormeloxifene is a non-steroidal Selective Estrogen Receptor Modulator (SERM) that is used as an oral contraceptive. Recent studies have shown its potent anti-cancer activities in breast, head and neck, and chronic myeloid leukemia cells. Several in vivo and clinical studies have reported that ormeloxifene possesses an excellent therapeutic index and has been well-tolerated, without any haematological, biochemical or histopathological toxicity, even with chronic administration. A reasonably long period of time and an enormous financial commitment are required to develop a lead compound into a clinically approved anti-cancer drug. For these reasons and to circumvent these obstacles, ormeloxifene is a promising candidate on a fast track for the development or repurposing established drugs as anti-cancer agents for cancer treatment. The current review summarizes recent findings on ormeloxifene as an anti-cancer agent and future prospects of this clinically safe pharmacophore.

Clinical pharmacokinetics and interaction of centchroman--a mini review

This article provides a brief review of the information available regarding the published pharmacokinetics data for the nonsteroidal, once-a-week oral contraceptive, centchroman (INN: ormeloxifene). This agent is a unique need-oriented contraceptive agent which is included in the National Family Welfare Programme of India. Since 1991, centchroman has been used as a need-oriented contraceptive and is being given for treating dysfunctional bleeding of the uterus. Information regarding absorption, tissue distribution, elimination and kinetic interactions is discussed.

Expression of estrogen receptor co-regulators SRC-1, RIP140 and NCoR and their interaction with estrogen receptor in rat uterus, under the influence of ormeloxifene

Ormeloxifene binds competitively to ERs and antagonizes estrogen-induced gene expression in the uterus. However its detailed molecular mechanisms are not well understood. Present study was aimed to examine the changes in expression pattern of co-regulatory proteins SRC-1 (co-activator), RIP140 and NCoR (co-repressors) and their interaction with ERalpha in rat uterus under the influence of ormeloxifene (Orm) and tamoxifen (Tam). Adult ovariectomized rats were treated with estradiol (E(2)) (5 microg/100g), or Orm or Tam (200 microg/100g, s.c.) alone or along with E(2), for 3 days. RT-PCR analysis of uterine RNA and immunoblotting of uterine extracts revealed that expression of SRC-1, RIP140 and NCoR was insensitive to E(2) or Orm or Tam treatment. Direct protein-protein interaction experiments using co-immunoprecipitation revealed that E(2)-induced the interaction of ERalpha with co-activator SRC-1. In rats given Orm alone or along with E(2), there was a significant reduction in E(2)-induced effect on ERalpha-SRC-1 interaction. In case of ERbeta and SRC-1, Orm reduced interaction only in the absence of E(2). Interaction of RIP140 or NCoR with ERalpha was found to be more in rats treated with Orm along with E(2) as compared to that in E(2)-treated rats whereas no such recruitment was found in Tam treated rats. Interaction of RIP140 with ERbeta was insensitive to Orm or Tam treatment whereas the interaction of NCoR with ERalpha and ERbeta was increased in Orm treated rats. Ormeloxifene also showed inhibitory effects on uterine ER-ERE binding and estrogen-induced expression of progesterone receptor. Taken together, these findings demonstrate that ormeloxifene antagonizes ERalpha-mediated transcription by inhibiting the recruitment of SRC-1 and inducing the recruitment of RIP140 and NCoR.

Modulation of AP-1 mediated estrogenic response by ormeloxifene in rat uterus

Ormeloxifene is a selective estrogen receptor modulator that exerts antiestrogenic effects and thereby inhibits growth in uterus. The present study was undertaken to examine the AP-1 protein interaction with AP-1 enhancer DNA elements in rat uterus in vivo and in vitro with a view to explore the modulation of estrogen action mediated via alternative pathway under the influence of ormeloxifene (Orm). In addition, the changes in expression of c-fos and c-jun transcription factors and mRNA expression of growth factor (IGF-1) were investigated with a view to assess the AP-1 mediated transcription. Ovariectomizedoung adult rats were administered with estradiol-17beta (5 microg/100 g body weight) or Orm (200 microg/100 g body weight) or vehicle for 3 days and sacrificed on fourth day. Electrophoretic mobility shift assay using uterine nuclear fraction from various treatment groups demonstrated that Orm caused a significant reduction in E2 induced AP-1 DNA binding. In vitro study revealed that Orm promotes AP-1 complex formation whereas its 7-hydroxy derivative inhibits it significantly. Uterine expression of c-fos and c-jun was increased significantly in Orm treated rats as compared to vehicle treated rats. However, the expression of c-fos and c-jun was decreased in rats receiving Orm plus E2. Semi-quantitative RT-PCR analysis revealed that mRNA expression of IGF-1 was increased in E2 treated group as compared to control group whereas reduced expression was observed in Orm treated rats as compared to E2 treated rats. The uterine weight and IGF-1 mRNA showed similar pattern, indicating that IGF-1 is involved in regulation of uterine weight. These results indicate that 7-hydroxy ormeloxifene (an active metabolite of Orm) is a potent antagonist at AP-1 sites. It inhibits the function of AP-1 transcription factors rather than their expression as evident by downregulation of mRNA expression of AP-1 regulated gene IGF-1, thereby inhibits proliferation in rat uterus. Study suggested a non-classicalregulation of estrogen action on uterus by ormeloxifene.

Expression of oestrogen receptors alpha and beta during the period of uterine receptivity in rat: effect of ormeloxifene, a selective oestrogen receptor modulator

AIMS

In the present study, we investigated expression, distribution and regulation of oestrogen receptors (ERs) alpha and beta and their modulation by ormeloxifene (Orm) during the period of uterine receptivity in rat uterus in order to determine their role in endometrial sensitization.

METHODS

Uterine tissues of control and Orm-treated (1.25 mg kg(-1), orally) rats were collected on days 3, 4, 5 morning and day 5 evening post-coitum referring to non-receptive, pre-receptive and receptive phases respectively. mRNA and protein expression levels were determined by RT-PCR and Western blot respectively. Immunohistochemical technique was used to localize the receptors.

RESULTS

RT-PCR analysis revealed that ERalpha mRNA reached a peak level on day 5 morning whereas ERbeta mRNA expression was found to be very low. In Orm-treated rats, the ERalpha mRNA was suppressed at day 5. The protein expression of ERalpha increased after day 3 and that of ERbeta remained very low throughout the pre-implantation period; Orm caused a decrease in ERalpha on day 5 morning. In endometrium, ERalpha expression was regulated differentially in luminal epithelium, glandular epithelium and stroma. Orm caused a decrease in the percentage of ERalpha-positive nuclei in all the three endometrial compartments on days 4 and 5, and the magnitude of reduction varied spatio-temporally. In case of ERbeta, immunostaining was not detectable in Orm-treated and control groups.

CONCLUSION

It appears that the complex uterine response to implantation is governed by differential cell-specific ERalpha expression. The study suggested the inhibitory activity of Orm on ERalpha during the period of uterine receptivity.

Modulation of estrogen receptor transactivation and estrogen-induced gene expression by ormeloxifene-a triphenylethylene derivative

The study was aimed to investigate the interaction of D,L-ormeloxifene (Orm), a triphenylethylene and its hydroxy derivative with estrogen receptor subtypes alpha and beta, its influence on ERE-driven transcriptional activation and progesterone receptor expression. In competitive binding experiments using human recombinant ERalpha and ERbeta, Orm showed interaction with both ER subtypes, with more selectivity and higher affinity towards ERalpha (8.8%) as compared to ERbeta (3%). In case of 7-hydroxy derivative, the relative binding affinity for both ERs was enhanced several folds. Orm showed lower Ki, i.e. higher affinity for ERalpha (250 nM) than for ERbeta (750 nM). It was observed that Orm promoted the formation of ER-ERE complexes in uterine tissue extract whereas its hydroxy derivative showed inhibitory effects. Transient co-transfection assay in COS-1 cells using ERE-luciferase reporter construct, revealed that Orm showed estrogenic response whereas its hydroxy-derivative was potent antiestrogen at ERalpha at transcription level. In immature rats, Orm (2 mg/kg) was associated with less increase in uterine weight and in luminal epithelial cell height than E2 or Tam. Orm also induced the expression of PR mRNA but the expression level was significantly less than estradiol treated group. These results suggest that ER-ERE complexes formed under the influence of 7-hydroxy Orm appear to be transcriptionally less effective hence antagonizing the E2-regulated gene expression in this target tissue.