Habermann H, Chang W Y, Birch L, Mehta P, Prins G S
Department of Urology, University of Illinois, Chicago, Illinois 60612, USA.
Endocrinology. 2001 Jan;142(1):359-69. doi: 10.1210/endo.142.1.7893.
Brief exposure to estrogens during the neonatal period interrupts rat prostatic development by reducing branching morphogenesis and by blocking epithelial cells from entering a normal differentiation pathway. Upon aging, ventral prostates exhibit extensive hyperplasia and dysplasia suggesting that neonatal estrogens may predispose the prostate gland to preneoplastic lesions. To determine whether these prostatic lesions may be manifested through aberrant cell-to-cell communications, the present study examined specific gap junction proteins, Connexins (Cx) 32, and Cx 43, and the cell adhesion molecule, E-cadherin, in the developing, adult and aged rat prostate gland. Male rat pups were given 25 microgram estradiol benzoate or oil on days 1, 3, and 5 of life. Prostates were removed on days 1, 4, 5, 6, 10, 15, 30, or 90 or at 16 months, and frozen sections were immunostained for E-cadherin, Cx 43, and Cx 32. Colocalization studies were performed with immunofluorescence using specific antibodies for cell markers. Gap junctions in undifferentiated epithelial cells at days 1-10 of life were composed of Cx 43, which always colocalized with basal cell cytokeratins (CK 5/15). Cx 32 expression was first observed between days 10-15 and colocalized to differentiated luminal cells (CK 8/18). Cx 43 and Cx 32 never colocalized to the same cell indicating that gap junction intercellular communication differs between basal and luminal prostatic cells. While epithelial connexin expression was not initially altered in the developing prostates following estrogen exposure, adult prostates of neonatally estrogenized rats exhibited a marked decrease in Cx 32 staining and an increased proportion of Cx 43 expressing cells. In the developing prostate, E-cadherin was localized to lateral surfaces of undifferentiated epithelial cells and staining intensity increased as the cells differentiated into luminal cells. By day 30, estrogenized prostates had small foci of epithelial cells that did not immunostain for E-cadherins. In the adult and aged prostates of estrogenized rats, larger foci with differentiation defects and dysplasia were associated with a decrease or loss in E-cadherin staining. The present findings suggest that estrogen-induced changes in the expression of E-cadherin, Cx32 and Cx43 may result in impaired cell-cell adhesion and defective cell-cell communication and may be one of the key mechanisms through which changes toward a dysplastic state are mediated. These findings are significant in light of the data on human prostate cancers where carcinogenesis and progression are associated with loss of E-cadherin and a switch from Cx32 to Cx43 expression in the epithelium.
新生期短暂接触雌激素会通过减少分支形态发生以及阻止上皮细胞进入正常分化途径来干扰大鼠前列腺发育。随着年龄增长，腹侧前列腺会出现广泛的增生和发育异常，这表明新生期雌激素可能使前列腺易患癌前病变。为了确定这些前列腺病变是否可能通过异常的细胞间通讯表现出来，本研究检测了发育中的、成年和老年大鼠前列腺中特定的间隙连接蛋白，即连接蛋白（Cx）32和Cx 43，以及细胞粘附分子E-钙粘蛋白。在出生后第1、3和5天，给雄性大鼠幼崽注射25微克苯甲酸雌二醇或油。在出生后第1、4、5、6、10、15、30或90天或16个月时取出前列腺，冰冻切片进行E-钙粘蛋白、Cx 43和Cx 32的免疫染色。使用细胞标志物的特异性抗体通过免疫荧光进行共定位研究。出生后1 - 10天未分化上皮细胞中的间隙连接由Cx 43组成，其总是与基底细胞角蛋白（CK 5/15）共定位。Cx 32表达在第10 - 15天首次观察到，并与分化的腔面细胞（CK 8/18）共定位。Cx 43和Cx 32从未在同一细胞中共定位，表明基底和腔面前列腺细胞之间的间隙连接细胞间通讯不同。虽然雌激素暴露后发育中的前列腺上皮连接蛋白表达最初未改变，但新生期经雌激素处理的大鼠成年前列腺中Cx 32染色明显减少，表达Cx 43的细胞比例增加。在发育中的前列腺中，E-钙粘蛋白定位于未分化上皮细胞的侧面，随着细胞分化为腔面细胞，染色强度增加。到第30天，经雌激素处理的前列腺中有一小群上皮细胞对E-钙粘蛋白不进行免疫染色。在经雌激素处理的大鼠成年和老年前列腺中，具有分化缺陷和发育异常的较大病灶与E-钙粘蛋白染色减少或缺失有关。本研究结果表明，雌激素诱导的E-钙粘蛋白、Cx32和Cx43表达变化可能导致细胞间粘附受损和细胞间通讯缺陷，可能是介导向发育异常状态转变的关键机制之一。鉴于人类前列腺癌的数据，这些发现具有重要意义，在人类前列腺癌中，致癌作用和进展与E-钙粘蛋白的丧失以及上皮细胞中从Cx32表达向Cx43表达的转变有关。
