Metabolism of E1 and E2 in Ishikawa endometrium carcinoma cells: influence of TNF alpha

The Relevance of Aquaporins for the Physiology, Pathology, and Aging of the Female Reproductive System in Mammals

Aquaporins constitute a group of water channel proteins located in numerous cell types. These are pore-forming transmembrane proteins, which mediate the specific passage of water molecules through membranes. It is well-known that water homeostasis plays a crucial role in different reproductive processes, e.g., oocyte transport, hormonal secretion, completion of successful fertilization, blastocyst formation, pregnancy, and birth. Further, aquaporins are involved in the process of spermatogenesis, and they have been reported to be involved during the storage of spermatozoa. It is noteworthy that aquaporins are relevant for the physiological function of specific parts in the female reproductive system, which will be presented in detail in the first section of this review. Moreover, they are relevant in different pathologies in the female reproductive system. The contribution of aquaporins in selected reproductive disorders and aging will be summarized in the second section of this review, followed by a section dedicated to aquaporin-related proteins. Since the relevance of aquaporins for the male reproductive system has been reviewed several times in the recent past, this review aims to provide an update on the distribution and impact of aquaporins only in the female reproductive system. Therefore, this paper seeks to determine the physiological and patho-physiological relevance of aquaporins on female reproduction, and female reproductive aging.

Reduced migration of Ishikawa cells associated with downregulation of aquaporin-5

Aquaporin (AQP)-dependent cell migration has broad implications in angiogenesis, tumor metastasis, wound healing, glial scarring and other events requiring cell movement. There are 13 isoforms of AQP (0-12) that have been identified in mammals. It is unclear whether AQP5 plays a role in the development of endometrial cancer. We recently demonstrated that ovarian steroids may affect the expression of AQP5 in the female genital tract. In this study, we considered whether AQP5 may affect cell migration in Ishikawa cells, an adenocarcinoma cell line derived from the endometrium. The results showed that the downregulation of AQP5 results in reduced Ishikawa cell migration. The estrogen (E2) receptor in the promoter of AQP5 mediated the regulation of AQP5 expression in the normal endometrium and endometrial cancer. By contrast, the upregulation of AQP5 by E2 increased cell migration, invasion and adhesion through increased annexin-2, which is responsible for F-actin remodeling and rearrangement. E2 regulates Ishikawa cell migration by regulating the AQP5 expression.

X-linked inhibitor of apoptosis protein levels and protein kinase C activity regulate the sensitivity of human endometrial carcinoma cells to tumor necrosis factor alpha-induced apoptosis

Endometrial carcinomas are often chemoresistant. TNFalpha shows potent antitumor activity against various cancers, and if it demonstrates good antitumor activity against endometrial cancer, the cytokine could represent a valuable alternative therapeutic approach. We have tested the ability of TNFalpha to induce apoptosis in endometrial carcinoma cells, and examined a putative role for X-linked inhibitor of apoptosis protein (XIAP) in regulating cellular sensitivity to the cytokine. Exposure to TNFalpha triggered TNF-R1-dependent activation of caspases-8, -9, and -3, down-regulated Akt and XIAP proteins and induced dose-dependent and time-dependent apoptosis in Ishikawa cells. On the opposite, TNFalpha up-regulated XIAP in Hec-1A cells; in these cells, the cytokine induced delayed TNF-R1-dependent activation of caspase-8, and failed to activate caspases -9 and -3 and to induce apoptosis. However, XIAP small interfering RNA restored TNFalpha-induced caspase signaling and apoptosis in Hec-1A cells; XIAP small interfering RNA also increased TNFalpha-induced apoptosis in Ishikawa cells. In addition, inhibition of protein kinase C activity enhanced TNFalpha-induced down-regulation of XIAP and potentiated apoptosis induction, in both Ishikawa and Hec-1A cells. Finally, we found XIAP immunoreactivity in epithelial cells from a large number of human endometrial tumor tissue samples, indicating that XIAP is produced by endometrial tumor cells in vivo. This could allow XIAP to play a putative in vivo role in counteracting TNFalpha-induced apoptosis in endometrial tumor cells; in this case, direct or indirect targeting of XIAP should potentiate the antitumor effect of TNFalpha.