The human proteome is exponentially derived from a limited number of genes via alternative splicing, where one gene gives rise to multiple proteins. Alternatively spliced gene products, although crucial for normal physiology, are also linked to an increasing number of pathologies. Consequently, a growing focus is currently being placed on elucidating the extrinsic cues and ensuing signaling mechanisms which direct changes in gene splicing to yield functionally distinct proteins. Of note is the dysregulation of the vascular endothelial growth factor (VEGF) receptor, Flt1 and its soluble splice variants, sFlt1_v1 and sFlt1_v2, in the pregnancy-related disorder, preeclampsia. Preeclampsia is characterized by proteinuria and hypertension and is responsible for almost 600,000 maternal and fetal yearly deaths, worldwide. Here, we examined the impact of endothelial mitogens VEGF and FGF2 (fibroblast growth factor 2), both of which are upregulated in preeclampsia, on Flt1 transcript variants in umbilical vein endothelial cells. We tested the hypothesis that VEGF modulates the expression of Flt1 variants via the signaling kinase Akt and its impact on SR proteins. VEGF was observed to induce expression of overall Flt1 mRNA, principally as variants Flt1 and sFlt1_v1. Conversely, FGF2 induced a shift in splicing toward sFlt1_v2 without significant increase in overall Flt1. Based on inhibitor studies, the VEGF and FGF2 signals were transduced via ERK, but with the involvement of different upstream components. We mapped predicted SR protein binding to Flt1 pre-mRNA and identified two candidate proteins, SRSF2 and SRSF3, that may be involved in VEGF- or FGF2-induced Flt1 pre-mRNA splicing. Examination of SRSF2 and SRSF3 relative mRNA expression levels, following inhibition of VEGF- and FGF2-activated kinases, indicates that FGF2 significantly downregulates SRSF3 mRNA levels via PKC-independent activation of ERK. Additionally, our data suggest that FGF2 may impact Flt1 and sFlt1_v1 via SR protein kinases Akt and SRPK, while conversely regulating sFlt1_v2 levels via Clk. We did not find evidence of VEGF-induced Flt1 variant splicing via SR protein kinase activation or SRSF2 and SRSF3 mRNA levels. Thus, VEGF and FGF2 signals were tranduced via related but distinct mechanisms to differentially influence Flt1 pre-mRNA splicing. These findings implicate VEGF and FGF2 and their related intracellular signaling mechanisms in soluble Flt1 regulation. / Ph. D.

Submitted by (edna.saturno@ufrpe.br) on 2016-07-25T12:46:12Z No. of bitstreams: 1 Natalie Emanuelle Ribeiro e Silva.pdf: 562491 bytes, checksum: e2fc3bb4739adc151a9f70d9d8e255e1 (MD5) / Made available in DSpace on 2016-07-25T12:46:12Z (GMT). No. of bitstreams: 1 Natalie Emanuelle Ribeiro e Silva.pdf: 562491 bytes, checksum: e2fc3bb4739adc151a9f70d9d8e255e1 (MD5) Previous issue date: 2013-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Intrauterine programmed cardiovascular disease may be linked to placental oxidative stress. It was investigated whether NaCl supplement, during pregnancy, affects placental oxidative stress and angiogenesis and imprints increased levels of oxidative stress in fetal liver. Dams were treated with 1.8% NaCl in drinking water from 20 days before and along pregnancy. Along pregnancy α-tocopherol, tempol or both were administered. Angiogenesis was evaluated throughout the expression of flt-1, the type 1 receptor for VEGF, in the villous bundles/labirinth. NaCl diminished flt-1 expression, as well as, reduced malonyldialdehide and augmented reduced gluthatione in placenta and fetal liver. α-Tocopherol led to an additional reduction in MDA levels in these organs, but diminished GSH. Otherwise, tempol increased MDA and diminished GSH in both placenta and fetal liver. No antioxidant changed the expression of flt-1. The reduced levels of MDA in placenta and fetal liver of dams under NaCl supplement might be due to reduced angiogenesis, that reduced oxygen supply, and also to the increased GSH levels. However the paradoxical pro-oxidant action of tempol indicates that the antioxidant reservoir in dams under sodium overload is limited. Furthermore, the parallel between the pattern of placental and fetal liver oxidative stress suggests that superoxide anions transferred from mothers may be important in programming cardiovascular diseases. / Doenças cardiovaculares programadas intrauterinamente podem está ligadas ao estresse oxidativo placentário. Neste trabalho, investigamos se a sobrecarga de NaCl, durante a gravidez, afeta o estresse oxidativo e angiogênese placentária, bem como se afeta os níveis de estresse oxidativo no fígado do feto. Mães foram tratadas com NaCl, 1,8%, na água de beber, 20 dias antes e ao longo da gravidez. α-Tocoferol, tempol ou ambos foram administrados ao longo da gravidez. A angiogênese foi avaliada por meio da expressão do flt-1, o receptor tipo 1 para o VEGF, nos feixes vilosos do labrinto. A suplementação com NaCl diminuiu a expressão de flt-1, bem como, reduziu os níveis de malonildialdeido e aumentou os níveis de glutationa reduzida na placenta e no fígado fetal. O α-tocoferol levou a uma redução adicional nos níveis de MDA nesses órgãos, mas diminuiu os níveis de GSH. De maneira diferente, o tempol aumentou os níveis de MDA e diminuiu os níveis de na placenta e no fígado fetal. O tratamento com os antioxidantes não alterou a expressão do flt-1. Os níveis reduzidos de MDA na placenta e no fígado do feto de mães submetidas a sobrecarga de NaCl podem ser devidos à angiogênese diminuida, o que reduziu o suprimento de oxigênio, ou aos os níveis aumentados de GSH. Entretanto, a ação paradoxal, pro-oxidante, do tempol indica que a reserva antioxidante nas mães submetidas a sobrecarga de sódio é limitada. Além disso, o paralelo entre o padrão de estresse oxidativo placentário e do fígado fetal sugere que ânions superóxidos transferidos a partir das mães podem ser importantes na programação das doenças cardiovaculares.