RESUMO
In diabetes mellitus (DM), podocyte apoptosis leads to albuminuria and nephropathy progression. Low-density lipoprotein receptor-related protein 6 (LRP6) is WNT pathway receptor that is involved in podocyte death, adhesion and motility. Glycogen synthase kinase 3 (GSK3) interaction with p53 (GSK3-p53) promotes apoptosis in carcinoma cells. It is unknown if GSK3-p53 contributes to podocyte apoptosis in DM. In experimental DM, green tea (GT) reduces albuminuria by an unknown mechanism. In the present study, we assessed the role of the GSK3ß-p53 in podocyte apoptosis and the effects of GT on these abnormalities. In diabetic spontaneously hypertensive rats (SHRs), GT prevents podocyte's p-LRP6 expression reduction, increased GSK3ß-p53 and high p53 levels. In diabetic SHR rats, GT reduces podocyte apoptosis, foot process effacement and albuminuria. In immortalized mouse podocytes (iMPs), high glucose (HG), silencing RNA (siRNA) or blocking LRP6 (DKK-1) reduced p-LRP6 expression, leading to high GSK3ß-p53, p53 expression, apoptosis and increased albumin influx. GSK3ß blockade by BIO reduced GSK3ß-p53 and podocyte apoptosis. In iMPs under HG, GT reduced apoptosis and the albumin influx by blocking GSK3ß-p53 following the rise in p-LRP6 expression. These effects of GT were prevented by LRP6 siRNA or DKK-1. In conclusion, in DM, WNT inhibition, via LRP6, increases GSK3ß-p53 and podocyte apoptosis. Maneuvers that inactivate GSK3ß-p53, such as GT, may be renoprotective in DM.
Assuntos
Apoptose , Diabetes Mellitus Experimental/prevenção & controle , Quinase 3 da Glicogênio Sintase/metabolismo , Proteína-6 Relacionada a Receptor de Lipoproteína de Baixa Densidade/metabolismo , Podócitos/citologia , Chá , Proteína Supressora de Tumor p53/metabolismo , Albuminúria/prevenção & controle , Animais , Biópsia , Caspase 3/genética , Caspase 3/metabolismo , Nefropatias Diabéticas/patologia , Nefropatias Diabéticas/terapia , Regulação para Baixo , Quinase 3 da Glicogênio Sintase/genética , Glicogênio Sintase Quinase 3 beta , Humanos , Marcação In Situ das Extremidades Cortadas , Rim/metabolismo , Rim/patologia , Proteína-6 Relacionada a Receptor de Lipoproteína de Baixa Densidade/genética , Masculino , Camundongos , Microscopia Eletrônica de Transmissão , Ratos , Ratos Endogâmicos SHR , Proteína Supressora de Tumor p53/genética , Via de Sinalização WntRESUMO
Histochemical study of the proventriculus from stingless bee Melipona quadrifasciata anthidioides revealed for the first time the presence of cysteine-rich proteins in the cuticle that covers the bulb of the proventriculus and its associated hair-like process. The presence of tyrosine-rich proteins was observed in the same structure, but not in hair-like projections. The cuticle of the crop and a small portion of the proventriculus contained no acid carbohydrates or fats and small amounts of neutral carbohydrates. These results are discussed in relation to different composition of insect cuticle depending on its different functions.
Assuntos
Abelhas , Epiderme/química , Azul Alciano , Animais , Carboidratos/análise , Corantes , Cisteína/análise , Epiderme/ultraestrutura , Ferricianetos , Histocitoquímica , Microscopia Eletrônica de Varredura , Reação do Ácido Periódico de Schiff , Proteínas/análise , Cloreto de Tolônio , Tirosina/análiseRESUMO
Glucocorticoids and prolactin (PRL) have a direct effect on the formation and maintenance of tight junctions (TJs) in cultured endothelial and mammary gland epithelial cells. In this work, we investigated the effect of a synthetic glucocorticoid dexamethasone (DEX) and PRL on the paracellular barrier function in MDCK renal epithelial cells. DEX (4 microM)+PRL (2 microg/ml) and DEX alone increased significantly the transepithelial electrical resistance after chronic treatment (4 days) of confluent MDCK monolayers or after 24 h treatment of subconfluent monolayers. Immunoblotting and immunocytochemistry revealed no changes in the expression and distribution of TJ-associated proteins occludin, ZO-1 and claudin-1 in confluent monolayers after hormone addition. However, a marked increase in junctional content for occludin and ZO-1 with no changes in their total expression was observed in subconfluent MDCK monolayers 24 h exposed to DEX or DEX+PRL. No change in cell proliferation/growth was detected at subconfluent conditions following hormone treatment. An increase in the total number of viable cells was observed only in confluent MDCK monolayers after exposure to DEX+PRL suggesting that the main effect of these hormones on already established barrier may be associated with the inhibition of cell death. In conclusion, our data suggest that these hormones (specially dexamethasone) have an effect on TJ structure and function only during the formation of MDCK epithelial barrier by probably modulating the localization, stability or assembly of TJ proteins to membrane sites of intercellular contact.