Dose and time-course evaluation of a redox-based estradiol-chemical delivery system for the brain. II. Pharmacodynamic responses

Estrogens may reduce mortality and ischemic damage caused by middle cerebral artery occlusion in the female rat

The present study was undertaken to determine if estrogens protect female rats from the neurodegenerative effects of middle cerebral artery (MCA) occlusion. The rats were ovariectomized and 7 or 8 days later various estrogen preparations were administered before or after MCA occlusion. Pretreatment with 17beta-estradiol (17beta-E2) or a brain-targeted 17beta-E2 chemical delivery system (CDS) decreased mortality from 65% in ovariectomized rats to 22% in 17beta-E2-treated and 16% in 17beta-E2 CDS-treated rats. This marked reduction in mortality was accompanied by a reduction in the ischemic area of the brain from 25.6+/-5.7% in the ovariectomized rats to 9.8+/-4% and 9.1+/-4.2% in the 17beta-E2-implanted and the 17beta-E2 CDS-treated rats, respectively. Similarly, pretreatment with the presumed inactive estrogen, 17alpha-estradiol, reduced mortality from 36 to 0% and reduced the ischemic area by 55 to 81%. When administered 40 or 90 minutes after MCA occlusion, 17beta-E2 CDS reduced the area of ischemia by 45 to 90% or 31%, respectively. In summary, the present study provides the first evidence that estrogens exert neuroprotective effects in an animal model of ischemia and suggests that estrogens may be a useful therapy to protect neurons against the neurodegenerative effects of stroke.

Suppression of plasma testosterone and prostate carcinoma size by a redox-based, brain-targeted estrogen delivery system in the rat

Studies were undertaken to examine the effects of an estradiol-chemical delivery system (E2-CDS) or castration (CAST) on plasma testosterone (T) and growth of the Segaloff 11095 carcinoma. Fischer 344 rats were implanted subcutaneously with the Segaloff 11095 tumor and tumor growth was monitored thereafter. After optimal tumor growth, when the average tumor size was approximately 25 x 15 mm (length x width; 4-5 g wet weight), rats were randomized into (1) testis-intact controls; (2) CAST; (3) intact+E2-CDS groups (rats received weekly injection of the E2-CDS at 0.5 mg/kg). Animals were killed 7 or 14 days after the initiation of treatments. Blood and tissue samples were collected for subsequent analysis. Plasma T levels were suppressed by 98% and 97% through 14 days after CAST or E2-CDS treatment. CAST increased plasma gonadotropin (LH) concentrations, while E2-CDS reduced LH compared to intact control levels. E2-CDS treatment increased plasma E2 levels to 24 (one injection) or 75 pg/ml (two injections) at 7 or 14 days, respectively. E2-CDS, given once a week for 2 consecutive weeks, resulted in a decreased growth of the prostate tumor by 61%, while CAST reduced the weights of these tumors by only 20%. In response to E2-CDS (one or two injections), weights of the in situ ventral prostate and seminal vesicles were significantly reduced by 70% and 50%, respectively, in tumor-bearing rats. Similarly, CAST reduced the weights of these tissues by 80% (prostate) or 52% (seminal vesicle) at 7 or 14 days after treatment. Pituitary weight increased, while testes weight decreased by 20% with two injections of E2-CDS, compared with intact control rats. Collectively, these data indicate that E2-CDS is effective in reducing the growth rate of prostatic tumors in the rat.

Effects of a brain-enhanced estrogen delivery system on tail-skin temperature of the rat: implications for menopausal hot flush

The menopause results from the decreasing production of ovarian estrogens/progestins. This loss of ovarian hormones in 75-85% of women leads to a number of brain-mediated steroid-withdrawal symptoms, the most frequent being hot flushes. Thus, replacement therapy with a brain-enhanced estrogen delivery system (E2-CDS) with sustained release of estradiol (E2) in the brain may be more effective in the treatment of menopausal symptoms than currently used estrogens. The present study was designed to evaluate the effects of E2-CDS vs. E2, on the tail-skin temperature (TST) surge associated with administration of naloxone to morphine-dependent rats, an animal model for menopausal hot flush. Ovariectomized rats received a single or multiple doses of E2-CDS at 1.0 mg/kg body weight or E2 (0.5 mg pellet) weekly for 1 or 3 weeks before temperature recording. The mean maximal elevation in TST of the control animals was 6.4 +/- 0.2 degrees C. A single injection of E2-CDS attenuated the naloxone-induced rise in TST by 25%, while multiple injections resulted in significant attenuation of the rise in TST (3.4 +/- 0.6). By contrast, multiple implants of E2 pellet (3 pellets over 3 weeks) did not affect the surge of TST. Plasma E2 levels in animals treated with E2-CDS were slightly increased to 13 pg/ml for single-injected and to 44 pg/ml for multiple-injected rats. However, the E2-pellet treatment produced plasma E2 levels that were 2-fold greater than the E2 levels produced by multiple injections of E2-CDS. Plasma gonadotropins (LH and FSH) were significantly suppressed with the E2-pellet as well as the single and multiple E2-CDS treatment. Plasma prolactin levels were significantly elevated by E2 pellet and multiple injections of E2-CDS. The kinetic profiles of E2-CDS metabolites in plasma indicated an apparent t1/2 = 8 h for E2-Q+ and 3 h for E2. Collectively, these data support the view that E2-CDS may be potentially useful in the treatment of vasomotor hot flushes.

Dose and time-course evaluation of a redox-based estradiol-chemical delivery system for the brain. I. Tissue distribution

Brain-enhanced delivery and sustained release of estradiol (E2) may be potentially useful in the treatments of vasomotor hot flushes and prostatic adenocarcinoma and for fertility regulation. Therefore, we have evaluated a redox-based estradiol-chemical delivery system (E2-CDS) for the brain. The mechanism of this drug delivery is based on an interconvertible dihydropyridine in equilibrium pyridinium salt redox reaction. In this study, we investigated the dose- and time-dependent effects of E2-CDS on the tissue distribution of E2-Q+ and E2, the inactive (intermediate) and active metabolites, respectively, of the E2-CDS. Ovariectomized rats received a single iv injection of E2-CDS at 0.01, 0.1, or 1.0 mg/kg or an E2 dose of 0.7 mg/kg or the drug's vehicle, 2-hydroxypropyl-beta-cyclodextrin (HPCD), on day 0. Tissue samples including brain and peripheral tissues were then analyzed for both E2-Q+ and E2 at 1, 7, 14, 21, or 28 days following the E2-CDS administration. Initially, both E2-Q+ and E2 were detected in all tissues analyzed. The dose-distribution and time-course study demonstrates that (1) at 24 hr (1 day) after administration of E2-CDS, all tissues showed a dose-proportional increase in concentrations of E2-Q+ and E2; (2) the enzymatic oxidation of E2-CDS to E2-Q+ was dose dependent over the 100-fold dose range examined; and (3) the disappearance of E2-Q+ as well as E2 was slow in whole brain and hypothalamus, with an apparent t1/2 = 8-9 days, while both of these metabolites were rapidly cleared from plasma, liver, fat, anterior pituitary, kidney, lung, heart, and uterus.(ABSTRACT TRUNCATED AT 250 WORDS)