Education

Biochemist, University of Havana, Cuba, 1973
Ph.D. INSA, Toulouse, France/ University of Havana, Cuba, 1985

Research Interests

Leptin signaling in the endometrium.

Several hormones, cytokines and growth factors regulate embryo-maternal molecular cross talk and are also involved in several disease states of the reproductive system. Leptin, a pleiotropic and ubiquitous cytokine, known primarily for its effects on food intake, also plays a critical role in reproductive function. Much research has been directed toward understanding and exploiting the effects of leptin on the control of body weight. Our research over the past several years, however, has focused on the role of leptin in human reproduction, specifically in the regulation of embryo implantation and placentation (Fig 1). Leptin and its receptor (OB-R) are expressed by both the embryo and endometrium (Fig 2). Leptin enhances endometrial receptivity and the trophoblast invasive phenotype. Mice deficient in leptin, OB-R or leukemia inhibitory factor (LIF) are infertile. We have found that leptin increases the levels of the IL-1 and LIF systems (ligand and receptor) in human, rabbit and mouse endometrial cells. Leptin also increases b3-integrin (a marker of endometrial receptivity) levels and p-STAT3 (signal transducer and activator of transcription-3) suggesting that leptin signals through OB-R and Janus kinase 2 (JAK2)/STAT3 pathways. In addition to the JAK-STAT signaling pathway, other pathways, including the mitogen-activated protein kinase (MAPK), protein kinase C (PKC), and phosphoinositol 3-kinase pathways, are also activated by leptin and LIF. We are currently investigating if leptin/OB-R also signal in the endometrium through above potential signaling pathways. We also found that IL-1 increases LIF-R expression. IL-1 also induces vascular endothelial growth factor (VEGF) and colony stimulator growth factor?1 (CSF-1) expression in different cell types. Inhibition of IL-1R tI partially prevents leptin-induced effects on LIF/LIFR suggesting that IL-1 may mediate in part some of leptin's effects on endometrial cells. In order to produce inhibitors of OB-R signaling we developed a structural model of leptin binding to OB-R by superimposing the four-helix bundle structure of leptin on that of a homologous protein, granulocyte-colony stimulator factor (G-CSF) complexed to its receptor G-CSFR. Analysis of this model suggested that leptin sequences corresponding to helices I and III formed the interacting surfaces. These helices correspond to amino acids 3-34 and 70-95, respectively, of the leptin sequence. Consequently, we hypothesized that peptides [leptin peptide antagonists (LPA-1, LPA-2 and LPA-3) derived from these putative leptin binding sequences will compete with leptin for binding to OB-R and block leptin/OB-R signaling (Fig 3). In fact a single intrauterine injection of LPA-1, LPA-2 or LPA-3 at Day 3 of pregnancy significantly impaired mouse embryo implantation (19-20 % versus 77- 81 % of horns injected with scrambled peptides, LPA-1/2Sc) (Fig 4 and Fig 5). The intra-uterine injection of LPAs also decreases the expression of LIF-R, VEGF-R2 (KDR), IL-1R tI and b3 integrin by mouse endometrium. OB-R staining disappears from mouse luminal epithelium post-implantation in contrast to glandular epithelium suggesting the expression of OB-R in uterine lining is turned-off after the embryo has successfully implanted (Fig 6). Therefore, the timely and local expression of OB-R by the luminal epithelium could represent a mechanism to allow an active molecular communication between the preimplantation embryo and the endometrium. In consequence, shortly after mouse embryo implantation occurs the leptin actions in the endometrium could mainly involve leptin/OB-R signaling in the glandular epithelium. The role of LIF in regulating endometrial cell biology and establishing pregnancy is not completely understood. Interestingly, abnormal endometrial expression of LIF and b3-integrin has been associated with human infertility. Since leptin has profound effects on the expression of cytokines fundamental to endometrial receptivity it is likely that leptin itself has profound effects on implantation. Our data suggest that leptin is one of the primary signals that initiates a wave of regulation of several important molecules during implantation (IL-1, LIF and b3 integrin, and probably CSF-1 and VEGF (Fig 7). Leptin may also be involved in endometrial inflammatory disorders and cancer. Endometriosis is a painful, chronic disease that affects millions of girls and women worldwide. This disorder is characterized by the ectopic growth of endometrial tissue in the peritoneum and several organs. The disease still remains under diagnosed and under treated. The abnormal production of leptin by ectopic endometrium may be casually linked to endometriosis and its progression. Consequently, we hypothesize that the blockade of OB-R might provide a new strategy for the treatment of endometriosis. Currently, we are investigating if inhibition OB-R signaling with LPAs could affect the development of endometriosis in mouse models. Our results are very promising. LPAs might be useful as drugs for fertility control and might shed light on disease states such as endometriosis, endometrial cancer, preeclampsia, diabetes mellitus and obesity, all conditions associated with abnormalities in leptin function (Fig 8). Our work is supported in part by a CONRAD/CICCR grant (CIG -02 87)

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Selected Publications

Gonzalez RR, Rueda BR, Ramos MP, Littell RD, Glasser S, Leavis PC. Leptin induced increase in leukemia inhibitory factor and its receptor by human endometrium is partially mediated by interleukin 1 receptor signaling. Endocrinology. 2004 May 13 [Epub ahead of print].

Gonzalez, R. R., Leavis, P. C. (2003) A peptide derived from the human leptin molecule is a potent inhibitor of the leptin receptor function in rabbit endometrial cells. Endocrine 21(2), 185-95.

Gonzalez, R. R., Leary, K., Petrozza, J. C. & P. C. Leavis. (2003) Leptin regulation of interleukin-1 (IL-1) system in endometrial cells. Mol Hum Reprod 9(3), 151-8.

Devoto, L., Kohen, P., Vega, M., Castro, O., Gonzalez, R. R., Retamales, I., Carvallo, P., Christenson, L. K. & J. F. Strauss. (2002) Control of human luteal steroidogenesis. Mol Cell Endocrinol 186, 137-41.

Gonzalez, R. R. & P. Leavis. (2001) Leptin upregulates beta3-integrin expression and interleukin-1beta, upregulates leptin and leptin receptor expression in human endometrial epithelial cell cultures. Endocrine 16, 21-8.

Gonzalez, R. R., Devoto, L., Campana, A. & P. Bischof. (2001) Effects of leptin, interleukin-1alpha, interleukin-6, and transforming growth factor-beta on markers of trophoblast invasive phenotype: integrins and metalloproteinases. Endocrine 15, 157-64.

Gonzalez, R. R., Palomino, A., Vantman, D., Gabler, F. & L. Devoto. (2001) Abnormal pattern of integrin expression at the implantation window in endometrium from fertile women treated with clomiphene citrate and users of intrauterine device. Early Pregnancy 5, 132-43.

Devoto, L., Kohen, P., Gonzalez, R. R., Castro, O., Retamales, I., Vega, M., Carvallo, P., Christenson, L. K. & J. F. Strauss 3rd. (2001) Expression of steroidogenic acute regulatory protein in the human corpus luteum throughout the luteal phase. J Clin Endocrinol Metab 86, 5633-9.

Gonzalez, R. R., Caballero-Campo, P., Jasper, M., Mercader, A., Devoto, L., Bischof, P. & C. Simon. (2000) Leptin: a new regulatory factor of human implantation. Rev IberoAmericana Fertil XVII 4, 59-74.

Gonzalez, R. R., Caballero-Campo, P., Jasper, M., Mercader, A., Devoto, L., Pellicer, A. & C. Simon. (2000) Leptin and leptin receptor are expressed in the human endometrium and endometrial leptin secretion is regulated by the human blastocyst. J Clin Endocrinol Metab 85, 4883-8.

Gonzalez, R.R., Simon, C., Caballero-Campo, P., Norman, R., Chardonnens, D., Devoto, L. & P. Bischof. (1999) Leptin and reproduction. Hum Reprod Update 6, 290-300.

Gonzalez, R. R., Palomino, A., Boric, A., Vega, M. & L. Devoto. (1999) A quantitative evaluation of alpha1, alpha4, alphaV and beta3 endometrial integrins of fertile and unexplained infertile women during the menstrual cycle. A flow cytometric appraisal. Hum Reprod 14, 2485-92.