RESUMEN
OBJECTIVE: Our aim was to evaluate the effects of a dietary regimen (suckling or early weaning) and feeding status (fed or fasted) on the distribution of transforming growth factor-beta3 (TGF-beta3) and TGF receptor-I (TbetaRI) in the gastric epithelium of pups. METHODS: Wistar rats were used. At 15 d, half of the pups were separated from dams and fed with hydrated powered chow. On day 17, suckling and early weanling rats were subjected to fasting (17h). Four different conditions were established: suckling fed and fasted and early weanling fed and fasted. At 18 d stomachs were collected under anesthesia and were fixed in 4% formaldehyde for immunohistochemistry. The number of immunostained epithelial cells per microscopic field was determined for TGF-beta3 and TbetaRI in longitudinal sections from the gastric mucosa. RESULTS: We found that during suckling, fasting reduced the number of immunolabeled cells per field of both molecules when compared with the fed group (P<0.05), whereas in early weaning, food restriction increased TGF-beta3 and TbetaRI distributions (P<0.05). We also observed that TGF-beta3 and TbetaRI were more concentrated in parietal cells in the upper gland in suckling pups, whereas after early weaning these were displaced to parietal and chief cells at the bottom of the gland. CONCLUSION: Suckling and early weaning directly influence TGF-beta3 and TbetaRI distributions in the gastric epithelium in response to fasting, such that early weaning anticipates the effects observed in adult rats. Furthermore, the differential concentrations of TGF-beta3 and TbetaRI indicate that they might be important for cell proliferation events in growth control.
Asunto(s)
Células Epiteliales/metabolismo , Ayuno/metabolismo , Mucosa Gástrica/metabolismo , Receptores de Factores de Crecimiento Transformadores beta/metabolismo , Factor de Crecimiento Transformador beta3/metabolismo , Animales , Animales Lactantes , Proliferación Celular , Mucosa Gástrica/citología , Mucosa Gástrica/crecimiento & desarrollo , Ratas , Ratas Wistar , Estómago/citología , Estómago/crecimiento & desarrollo , DesteteRESUMEN
The nutritional status influences gastric growth, and interestingly, whereas cell proliferation is stimulated by fasting in suckling rats, it is inhibited in adult animals. Corticosterone takes part in the mechanisms that govern development, and its effects are regulated in particular by corticosterone-binding globulin (CBG) and glucocorticoid receptor (GR). To investigate whether corticosterone activity responds to fasting and how possible changes might control gastric epithelial cell cycle, we evaluated different parameters during the progression of fasting in 18- and 40-day-old rats. Food restriction induced higher corticosterone plasma concentration at both ages, but only in pups did CBG binding increase after short- and long-term treatments. Fasting also increased gastric GR at transcriptional and protein levels, but the effect was more pronounced in 40-day-old animals. Moreover, in pups, GR was observed in the cytoplasm, whereas, in adults, it accumulated in the nucleus after the onset of fasting. Heat shock protein (HSP) 70 and HSP 90 were differentially regulated and might contribute to the stability of GR and to the high cytoplasmic levels in pups and elevated shuttling in adult rats. As for gastric epithelial cell cycle, whereas cyclin D1 and p21 increased during fasting in pups, in adults, cyclin E slowly decreased, concomitant with higher p27. In summary, we demonstrated that corticosterone function is differentially regulated by fasting in 18- and 40-day-old rats, and such variation might attenuate any possible suppressive effects during postnatal development. We suggest that this mechanism could ultimately increase cell proliferation and allow regular gastric growth during adverse nutritional conditions.
Asunto(s)
Ayuno/metabolismo , Mucosa Gástrica/citología , Mucosa Gástrica/metabolismo , Receptores de Glucocorticoides/metabolismo , Transcortina/metabolismo , Factores de Edad , Animales , Animales Lactantes , Ciclo Celular/fisiología , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , División Celular/fisiología , Corticosterona/metabolismo , Proteínas HSP70 de Choque Térmico/metabolismo , Proteínas HSP90 de Choque Térmico/metabolismo , ARN Mensajero/metabolismo , Ratas , Ratas Wistar , Receptores de Glucocorticoides/genéticaRESUMEN
As the content of Transforming Growth Factor-beta (TGFbeta) wanes in the milk of lactating rat, an increase in TGFbeta is observed in the gastric epithelia concomitant with differentiation of the glands upon weaning. Whereas TGFbeta has been shown to inhibit the proliferation of gastrointestinal cells in vitro, its functional significance and mechanisms of action have not been studied in vivo. Therefore, we administered TGFbeta1 (1 ng/g body wt.) to 14-day-old rats in which the gastric epithelium was induced to proliferate by fasting, and determined the involvement of signaling through Smads and the impact on epithelial cell proliferation and apoptosis. After the gavage, we observed the progressive increase of active TGFbeta1 while TbetaRII-receptor remained constant in the gastric mucosa. By immunohistochemistry, we showed Smad2/3 increase at 60 min (p<0.05) and Smad2 phosphorylation/activation and translocation to the nucleus most prominently between 0 and 30 min after treatment (p<0.05). Importantly, TGFbeta1 inhibited cell proliferation (p<0.05), which was estimated by BrDU pulse-labeling 12 h after gavage. Lower proliferation was reflected by increased p27(kip1) at 2 h (p<0.05). Also, TGFbeta1 increased apoptosis as measured by M30 labeling at 60 and 180 min (p<0.001), and by morphological features at 12 h (p<0.05). In addition, we observed higher levels of activated caspase 3 (17 kDa) from 0 to 30 min. Altogether, these data indicate a direct effect of TGFbeta1 signaling through Smads on both inhibiting proliferation, through alteration of cycle proteins, and inducing apoptosis of gastric epithelial cells in vivo. Further, the studies suggest a potential role for both milk and tissue-expressed TGFbeta1 in gastric growth during postnatal development.
Asunto(s)
Proliferación Celular/efectos de los fármacos , Mucosa Gástrica/efectos de los fármacos , Mucosa Gástrica/crecimiento & desarrollo , Factor de Crecimiento Transformador beta1/farmacología , Animales , Animales Lactantes , Apoptosis/efectos de los fármacos , Western Blotting , Mucosa Gástrica/citología , Antígeno Nuclear de Célula en Proliferación/efectos de los fármacos , Antígeno Nuclear de Célula en Proliferación/metabolismo , Ratas , Ratas Wistar , Transducción de Señal/efectos de los fármacos , Proteínas Smad/efectos de los fármacos , Proteínas Smad/metabolismoRESUMEN
The stomach of the rat undergoes extensive changes during the formation and maturation of gastric glands. The presence of transforming growth factor beta (TGFbeta) in rat milk and in the gastrointestinal tract of pups may suggest its role in this process. The current study evaluated the in vivo dynamic expression and distribution of TGFbeta1, beta2, beta3 and their receptors TbetaRI and TbetaRII in the gastric epithelium of 20-day fetal rats and 1-, 14-, 21-, and 30-day-old pups. Immunohistochemistry was used to detect the proteins, and staining was classified according to intensity and cell type. The results showed that the gastric epithelium expresses TGFbeta isoforms and receptors throughout development. We found that immunoreactivity paralleled the appearance of differentiated cells, such that surface mucous cells were the first to be immunostained and chief cells were the last. The intensity of reactions followed this same pattern, showing that the expression of TGFbeta isoforms spread along the gland with growth. Of interest, the highest apparent activity of TGFbeta was observed from 21 days onward, a period that is concomitant with weaning and maturation of most gastric cell types. In addition, surface mucous cells were strongly labeled at the basal cytoplasm at 14 days, suggesting an interaction with the connective tissue. In conclusion, the dynamic expression of TGFbeta1, beta2, beta3, and TbetaRI and TbetaRII through stomach development suggests significant paracrine and autocrine roles for this growth factor. We propose that temporal and spatial differences may be regulated by dietary changes, which in turn control cell proliferation and differentiation in the gastric epithelium.