RESUMO
Stanniocalcin 1 (STC1), originally described as an antihypercalcemic hormone in fish, is highly expressed in differentiated mammalian neurons. Mild hypoxic treatment and focal cerebral ischemia induce upregulation of STC1 in the brain. These findings prompted us to investigate whether STC1 contributes to neuroprotection after ischemia and whether STC1 is required for development of ischemic tolerance. We induced 60 minutes of temporary middle cerebral artery occlusion in wild type (WT) and STC1-deficient mice (STC1(-/-)) with or without prior hypoxic preconditioning (HPC, 8% oxygen for 6 hours followed by reoxygenation for 24 hours). Infarct sizes, neurological scores, and Stc1, Stc2, and Il-6 mRNA brain levels were measured 24 hours after ischemia. Additionally, we examined blood-brain barrier (BBB) integrity (Evans Blue fluorescence) under normal conditions and 0 and 24 hours after hypoxia. STC1(-/-) and WT mice developed brain infarcts of similar size. In both strains, HPC triggered ischemic tolerance with similar reduction in infarct size. However, STC1(-/-) mice had worse neurological scores in both scenarios. HPC induced upregulation of STC1 and STC2 in WT mice and of STC2 in STC1(-/-) mice. Ischemic STC1(-/-) mice showed significantly lower Il-6 mRNA expression than ischemic WT mice. Evans Blue fluorescence levels showed no difference in between WT and STC1(-/-) mice under evaluated conditions, thus BBB integrity is preserved despite STC1 deficiency. STC1 was not crucial for the development of ischemic tolerance triggered by HPC or for preserving BBB integrity but may be involved in functional recovery after stroke.
Assuntos
Isquemia Encefálica/metabolismo , Encéfalo/metabolismo , Glicoproteínas/metabolismo , Infarto da Artéria Cerebral Média/metabolismo , Precondicionamento Isquêmico , Recuperação de Função Fisiológica/fisiologia , Animais , Barreira Hematoencefálica/metabolismo , Barreira Hematoencefálica/fisiopatologia , Encéfalo/fisiopatologia , Isquemia Encefálica/genética , Glicoproteínas/genética , Infarto da Artéria Cerebral Média/genética , Infarto da Artéria Cerebral Média/fisiopatologia , Peptídeos e Proteínas de Sinalização Intercelular , Interleucina-6/genética , Interleucina-6/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular , Camundongos , Camundongos Knockout , Permeabilidade , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
Mammalian Stanniocalcin-1 (STC1) is a glycoprotein that has been implicated in various biological processes including angiogenesis. Aberrant STC1 expression has been reported in breast, ovarian and prostate cancers, but the significance of this is not well understood. Here, we report that oxidative stress caused a 40-fold increase in STC1 levels in mouse embryo fibroblasts (MEFs). STC1-/- MEFs were resistant to growth inhibition and cell death induced by H(2)O(2) or by 20% O(2) (which is hyperoxic for most mammalian cells); this is the first phenotype reported for STC1-null cells. STC1-/- cells had higher levels of activated MEK and ERK1/2 than their wild-type (WT) counterparts, and these levels were all reduced by stable expression of exogenous STC1 in STC1-/- cells. Furthermore, pharmacological inhibition by PD98059 or UO126 of MEK and therefore of ERK1/2 activation restored sensitivity of STC1-/- cells to oxidative stress. We also found that H(2)O(2)-induced STC1 expression in WT cells was abolished by inhibition of ERK1/2 activation. Thus, the ERK1/2 signaling pathway upregulates STC1 expression, which in turn downregulates the level of activated MEK and consequently ERK1/2 in a novel negative feedback loop. Therefore, STC1 expression downregulates prosurvival ERK1/2 signaling and reduces survival under conditions of oxidative stress.
Assuntos
Retroalimentação Fisiológica , Glicoproteínas/fisiologia , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Estresse Oxidativo/fisiologia , Transdução de Sinais , Animais , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Embrião de Mamíferos , Fibroblastos/efeitos dos fármacos , Fibroblastos/enzimologia , Fibroblastos/fisiologia , Peróxido de Hidrogênio/farmacologia , Camundongos , Camundongos Knockout , Estresse Oxidativo/efeitos dos fármacosRESUMO
Stanniocalcin (STC) is a glycoprotein hormone that is secreted by the corpuscle of Stannius, an endocrine gland of bony fish, and is involved in calcium and phosphate homeostasis. The related mammalian proteins, STC1 and STC2, are expressed in a wide variety of tissues. The ovaries have the highest level of STC1, and this increases during pregnancy and lactation. STC1 is present in breast ductal epithelium, and its expression is induced by BRCA1, a tumor suppressor gene that has an important role in breast and ovarian cancer. The expression of STC2 is induced by estrogen, and there is a positive correlation between the level of expression of estrogen receptor and expression of both STC1 and STC2 in breast cancer. This article reviews the data currently available regarding the mammalian STCs, and discusses the roles they may play in normal physiology and in breast and other cancers.
