Differential behavior of NF-κB, IκBα and EGFR during the renal carcinogenic process in an experimental model in vivo.

Renal cell carcinoma (RCC) is the most common type of cancer of the adult kidney. It is generally asymptomatic even at advanced stages, so opportune diagnosis is rare, making it almost impossible to study this cancer at its early stages. RCC tumors induced by ferric nitrilotriacetate (FeNTA) in rats histologically correspond to the human clear cell RCC subtype (ccRCC) and the exposure to this carcinogen during either one or two months leads to different early stages of neoplastic development. High levels of nuclear factor kappa B (NF-κB) and epidermal growth factor receptor (EGFR) as well as low levels of NF-κB inhibitor alpha (IκBα) are frequent in human RCC, but their status in FeNTA-induced tumors and their evolution along renal carcinogenesis is unclear. On this basis, in the present study NF-κB, IκBα and EGFR behavior was analyzed at different stages of the experimental renal carcinogenesis model. Similar to patients with RCC, neoplastic tissue showed high levels of p65, one of the predominant subunits of NF-κB in ccRCC and of EGFR (protein and mRNA), as well as a decrease in the levels of NF-κB's main inhibitor, IκBα, resulting in a classic oncogenic combination. Conversely, different responses were observed at early stages of carcinogenesis. After one month of FeNTA-exposure, NF-κB activity and EGFR levels augmented; but unexpectedly, IκBα also did. While after two months, NF-κB activity diminished, but EGFR and IκBα levels remained elevated. In conclusion, FeNTA-induced tumors and RCC human neoplasms are analogues regarding to the classic NF-κB, IκBα and EGFR behavior, and distinctive non-conventional combination of changes is developed at each early stage studied. The results obtained suggest that the dysregulation of the analyzed molecules could be related to different signaling pathways and therefore, to particular effects depending on the phase of the carcinogenic process.

Differential expression of estrogen receptors in two hippocampal regions during the estrous cycle of the rat.

In the hippocampus, estrogens increase dendritic arborization, long-term potentiation, neuroprotection, and participate in many functions related with learning, memory, and affective behaviors. The presence of both estrogen receptors alpha (ERα) and beta (ERß) isoforms has been described in the hippocampus where they play different physiological roles. The aim of this study was to investigate, by using both techniques immunohistochemistry and Western Blot, the expression pattern of ERα and ERß in the hippocampus of the rat along the estrous cycle. Western blot analysis was used to confirm the specificity of the antibodies used against ERα and ERß and its relative content in the hippocampus. Results from immunohistochemical studies indicate that ERß expression increased more than the ERα in CA1 and CA3 regions during all phases of the estrous cycle. ERß immunoreactivity was mainly located in the nucleus and predominantly expressed in CA1 during estrous and metestrus, and in CA3 during diestrus. ERα was more abundant during estrous in comparison to other phases of the cycle in CA1 region, while it was more abundant during metestrus in CA3. Interestingly, the immunolocalization of ERα subtype was both cytoplasmic and nuclear. The overall results indicate that there is a differential expression, cellular localization, and distribution of both ER subtypes in CA1 and CA3 regions, suggesting different roles for these two receptors in the hippocampus along the estrous cycle.

The protective effect of testosterone on streptozotocin-induced apoptosis in beta cells is sex specific.

OBJECTIVES: To investigate the protective role of steroid hormones on streptozotocin (STZ)-induced apoptosis in rat pancreatic beta cells. METHODS: Two sets of experiments were performed. In the first, male rats were orchidectomized and substituted 72 hours later with testosterone, estradiol, or progesterone, and 24 hours later, administered with STZ. Subjects were killed 6 hours later, and apoptosis was determined in sections of the pancreas. In the second experiment, male or female rats were gonadectomized, were further substituted with testosterone, and then administered STZ. Six hours later, the animals were killed, and apoptosis, as well as immunoreactive expression of insulin, catalase, or Cu/Zn superoxide dismutase, was determined in sections of the pancreas. In addition, gonadectomized male or female subjects were substituted with testosterone and administered STZ, and 24 hours later, serum glucose and insulin were measured. RESULTS: It was found that the cytoprotective effect was only shown in testosterone-treated male rats but not progesterone- or estradiol-treated male rats. In addition, the effect was seen in male rats but not in female rats, and there was an inverse correlation between apoptotic index and antioxidant enzyme immunoreactivity. CONCLUSIONS: The cytoprotective effect of testosterone is sex specific and is related to the induction of antioxidant enzyme activities in pancreatic beta cells.

Progesterone receptor mRNA expression and distribution in the female rabbit brain.

Progesterone regulates diverse functions in the rabbit brain through the interaction with its nuclear receptor (PR). Although PR protein has been detected in some regions of the rabbit forebrain, PR mRNA expression and distribution in the rabbit brain are unknown. Hence, we investigated these issues by in situ hybridization. New Zealand adult female rabbits were ovariectomized and treated with vehicle or estradiol (5 microg/(kg day)) for 3 days. The results show an extended distribution of PR mRNA expression in the rabbit brain. The highest expression was detected in preoptic area and hypothalamic anterior nuclei such as paraventricular, periventricular and arcuate nuclei. A high expression was also detected in thalamic and telencephalic areas, including hippocampus and cerebral cortex. Estradiol treatment induced an increase in PR mRNA expression in many brain areas, particularly in the hippocampus and the hypothalamic and preoptic area regions. The wide distribution of PR mRNA in the rabbit brain suggests that progesterone through PR activation is involved in several functions apart from reproductive behavior in rabbits, and that PR expression is up-regulated by estradiol in the rabbit brain.

Expression of p53 in luminal and glandular epithelium during the growth and regression of rat uterus during the estrous cycle.

It has been well recognized that epithelial cells of the rat endometrium cyclically proliferate and die during the estrous cycle. The aim of the present study was to determine p53 expression pattern and correlate it with the the apoptotic pattern of epithelial cells of the rat uterus during the estrous cycle. The p53 mRNA and protein expression pattern was assessed by in situ hybridization and immunohistochemistry. The apoptotic index was determined by using terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) and electron microscopy. The highest p53 mRNA content, detected by in situ hybridization, was observed on the metestrus day both in the luminal and the glandular epithelia. During this period both epithelia presented high proliferation. The content of p53 mRNA markedly decreased in the following days, presenting its minimal values on the estrus day. The highest number of p53 immunopositive nuclei, in both the luminal and the glandular epithelia, was also detected on the metestrus day, while the lowest one was found on estrus day. On the proestrus day, p53 protein was predominantly detected in the glandular epithelium. However, on the estrus day, p53 protein was detected both in the nuclei and in the cytoplasm of luminal epithelial cells, predominantly in the cytoplasm. The highest apoptotic index in both the luminal and the glandular epithelia was observed on the estrus day whereas the lowest one was observed on the proestrus day. The apoptotic index values were higher in the luminal than in the glandular epithelia. The overall results indicate that p53 expression at both mRNA and protein levels is higher on the metestrus day when the apoptotic index is low. This suggests that p53 should play an important physiological role during proliferative phases of the estrous cycle in the rat uterus.

El gen supresor de tumores p53: mecanismos de acción en la proliferación y muerte celular / The tumor suppressor p53: mechanism of action in proliferation and cell death

El desarrollo normal es un proceso equilibrado que incluye la proliferación y la muerte celular. Los procesos de proliferación y muerte celular por apoptosis son muy complejos e involucran la participación de muchos genes. En ambos procesos, el gen supresor p53 es uno de los genes más importantes y estudiados. Este factor de transcripción activa una variedad de genes que resulta en la inhibición de la progresión del ciclo celular y la reparación celular o en apoptosis. Las señales que activan la función de p53 incluyen: daño al ADN por agentes químicos o radiación g y ultravioleta e hipoxia, entre otros. Cuando p53 es activado induce la expresión de p21 (Waf1, Cip-1), el cual participa en la inhibición de la progresión del ciclo celular durante la fase G1, o la expresión de bax, PIGs, IGF-BP3, Fas, FasL y DR5. Estos últimos participan en la cascada de eventos que inducen apoptosis. Cuando una célula es dañada, dependen de la intensidad del daño el que se detenga el ciclo o se induzca apoptosis. El resultado final de los diferentes mecanismos de acción de p53 es mantener la estabilidad genómica de las células. Por lo tanto, la deficiencia de esta proteína contribuye a la inestabilidad genómica, a la acumulación de mutaciones y la aceleración de la tumorogénesis. p53 se encuentra mutado en el 50-55 por ciento de todos los tipos de cáncer en humanos. Estas mutaciones se encuentran localizadas principalmente en el dominio de unión al ADN, lo que resulta en la pérdida de su actividad biológica. Se ha demostrado que algunos tipos tumorales que responden bien a la quimio y radioterapia presentan p53 tipo silvestre, a diferencia de los que presentan p53 mutado. Este trabajo describe la estructura y función de p53 y sus alteraciones durante el cáncer. El conocimiento de la participación de p53 en el desarrollo de esta enfermedad puede dar un nuevo enfoque en el diseño de nuevas estrategias en el tratamiento del cáncer, incluyendo la terapia génica.