Elevated levels of mitochonrial respiratory complexes activities and ATP production in 17-β-estradiol-induced prolactin-secretory tumor cells in male rats are inhibited by melatonin in vivo and in vitro / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Our earlier studies indicate that melatonin inhibits the proliferation of prolactinoma and induces apoptosis of pituitary prolactin-secreting tumor in rats. Melatonin has also been shown to induce apoptosis and to reduce the production of ATP in breast tumor cells. This study analyzed the levels of the four mitochondrial respiratory complexes and the production of ATP and also the effects of melatonin treatment of prolactinoma.</p><p><b>METHODS</b>In the in vivo study, mitochondria were harvested from control pituitaries or prolactinoma collected from the pituitaries of melatonin- and 17-β-estradiol (E2)-treated male rats. In the in vitro study, prolactinoma cells mitochondria were harvested. Activities of the four mitochondrial respiratory complexes were assayed using fluorometer. ATP production of prolactinoma cells was estimated using bioluminescent methods.</p><p><b>RESULTS</b>Elevated levels of four mitochondrial respiratory complexes activities and ATP production were recorded in prolactinoma cells. Moreover, in both in vivo and in vitro studies, melatonin inhibited the activities of mitochondrial respiratory complexes and the production of ATP in prolactinoma cells.</p><p><b>CONCLUSIONS</b>There is a link between mitochondrial function increase and tumorigenesis. Melatonin induces apoptosis of pituitary prolactin-secreting tumor of rats via the induction of mitochondrial dysfunction and inhibition of energy metabolism.</p>

Melatonin suppressing the proliferation of E2-induced pituitary prolactin-secreting tumor in rat involves the effects of estrogen receptor / 中国应用生理学杂志

<p><b>AIM</b>To investigate effects of melatonin on estrogen receptor at the primary stage of melatonin (MLT) inhibiting the proliferation of 17-beta-estradiol (E2)-induced pituitary prolactin-secreting tumor (prolactinoma) and its mechanisms in the rat.</p><p><b>METHODS</b>MLT inhibiting the proliferation of 17-beta-E2-induced prolactinoma was created by administrating different concentration of melatonin subcutaneously at 18:00 in every group of SD rat in vivo. We also examined the expression of MLT receptor in prolactinoma cells and the effects of MLT on the expression of estrogen receptor (ER) by in situ hybridization and the effects of MLT on the binding of ER to estrogen response element (ERE) by electrophoretic mobility shift assay (EMSA)in primary culture cells iv vitro.</p><p><b>RESULTS</b>The results showed that the weights of prolactinomas in MLT groups, in which 0.25 mg or 0.50 mg/day/rat melatonin was administrated subcutaneously at 18:00, were decreased significantly (P < 0.01 and P < 0.05). The expression of MLT1a and MLT1b were shown in pituitary prolactinoma cells. Compared with the prolactinoma, the expression of ER and the bind of ER to ERE in prolactinoma treated with 0.25 mg/day/rat or 0.50 mg/day/rat MLT was decreased (P < 0.01 and P < 0.01).</p><p><b>CONCLUSION</b>These data indicate that some dosage of MLT inhibit the development of E2-induced prolactinoma in SD rat. One of the mechanisms is involved in suppressing the expression of estrogen receptor and partly inhibiting the bind of ER to ERE.</p>

Analysis of different mutations in regulatory sequence of prolactin gene during the formation of 17 beta-estradiol-induced prolactinoma in eutopic and ectopic pituitary of rats / 中国医学科学院学报

<p><b>OBJECTIVE</b>To analyze different mutations in regulatory sequence of prolactin (PRL) gene during the formation of 17 beta-estradiol (E2 ) -induced prolactinoma in eutopic and ectopic pituitary of rats.</p><p><b>METHODS</b>Male Sprague-Dawley rats transplanted with an isologaus pituitary under renal capsule were treated with subcutaneous implantation of an empty or E2-laden silastic capsule. Reverse transcription-polymerase chain reaction was employed to evaluate the expression of PRL mRNA in pituitary glands, and DNA sequencing was used to analyze the mutation in regulatory sequence of PRL gene.</p><p><b>RESULTS</b>After treated with E2 for 120 days, both the eutopic and ectopic pituitaries were three times more heavier than those from control group (P < 0. 01) , and the body weight of rats was decreased to 42. 90% of the control group (P < 0 01 ). The PRL mRNA expressions in glands from the eutopic and ectopic pituitaries 120 days after treated with E2 were much more than those in untreated pituitary glands (P <0. 01). DNA sequencing showed seven mutations in the regulatory sequence of PRL gene in the eutopic pituitaries 120 days after treated with E2 , while the mutation in the ectopic pituitaries was decreased.</p><p><b>CONCLUSIONS</b>Prolactinomas can be induced by chronic treatment with E2 in both the eutopic and the ectopic pituitaries transplanted under renal capsule distant from the hypothalamus. Different mechanisms exist in the formation of eutopic and ectopic prolactinomas.</p>

Melatonin inhibits the proliferation of pituitary prolactin-secreting tumor by suppressing the enhancer elements mutation of PRL gene in the rat / 生理学报

In order to investigate the molecular mechanisms of the inhibition of the proliferation of 17-beta-estradiol (E(2))-induced pituitary prolactin-secreting tumor (prolactinoma) by melatonin (MLT) in the rat, we examined the inhibitory effects of MLT on the proliferation of E(2)-induced prolactinoma of the rat and the suppressing effects of MLT on the enhancer elements mutation of PRL gene in vivo and in vitro. The results showed that the weights of prolactinomas in MLT groups, in which 0.25 mg or 0.50 mg per day per rat of MLT was administered subcutaneously at 18:00, were decreased significantly. Out of the dosage of MLT, such as 0.05, 1.00 mg and 2.00 mg per day per rat, the antitumor action of MLT is less or disappointing. Polymerase chain reaction (PCR) and DNA sequencing showed five mutations in the enhancer elements of PRL gene in prolactinoma, such as -1885 point mutation (C --> G), -1857 - -1855 substitution (ACA --> G), -1792 - -1791 insertion G, -1383 - -1382 insertion (GGTGTGTG), -1265 - -1250 deletion (GTGTGTGTGTGTGTGT). Excluding of -1885 point mutation (C --> G), the mutation in the prolactinoma treated with 0.25 mg per day per rat MLT was decreased, such as -1792 - -1791 without insertion of G, -1856 - -1855 deletion AC, -1385 - -1384 deletion TG, -1250 - -1253 deletion GTGT. Firefly luciferase reporter gene systems showed that the luminosity of enhancer elements-luciferase reporter fusion gene in normal pituitary, prolactinoma treated without or with 0.25 mg per day per rat MLT were (13448.17+/-3012.74), (161831.67+/-60996.01), and (10212.17+/-634.71) OD units. Compared with the normal pituitary, the activity of PRL gene enhancer elements in prolactinoma was increased by 11 times (P<0.001). Compared with the prolactinoma, the activity of PRL gene enhancer elements in prolactinoma treated with MLT was decreased by 93.69% (P<0.001). Analysis of the space structure of PRL gene enhancer elements showed that the bending index in prolactinoma was higher than that in prolactinoma treated with MLT, which was higher than that in the normal pituitary. These results demonstrate that one of the important molecular mechanisms of MLT inhibiting the proliferation of prolactinoma is related to the reduction of enhancer elements mutation of PRL gene. These data also suggest that MLT-induced attenuation of enhancer elements mutation of PRL gene is involved in decreasing the bending index and attenuating the higher expression of PRL gene.