IMBECU   20882
INSTITUTO DE MEDICINA Y BIOLOGIA EXPERIMENTAL DE CUYO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Asociación de Caveolina 1 y Hsp70 en túbulos proximales de SHR. Efecto de la inhibición
Autor/es:
VICTORIA BOCANEGRA; WALTER MANUCHA; VALERIA CACCIAMANI; PATRICIA G. VALLES
Lugar:
Centro de Congresos y Exposiciones de Mendoza “Gobernador Emilio Civit”
Reunión:
Jornada; XXI Jornadas de Investigación y III Jornadas de Posgrado de la Universidad Nacional de Cuyo; 2008
Institución organizadora:
Secretaría de Ciencia y Técnica UN de Cuyo
Resumen:
Caveolin proteins function to recruit lipids and proteins to caveolae for participation in intracellular trafficking of cellular components and operation in signal transduction. A direct interaction with caveolin is required to traffic the AT1-R through the exocytic pathway. The chaperone HSP70 participates in the translocation and assembly of proteins. In this study, we examined the effect of the Angiotensin II receptor type 1 inhibition on Cav-1 and HSP70 protein association in SHR proximal tubules (PTs). HSP70 involvement on the cytoprotective effect of losartan was also studied. Methods: Four-week-old SHR, were randomized for receiving the Angiotensin II type 1 antagonist losartan (40 mg.kg-1.day) (SHRLos) or no treatment (SHRH2O) during 8 weeks. Wistar-Kyoto rats (WKY) were controls. Western blot analysis of caveolin-1 (Cav-1) and HSP70 was performed in membrane fractions from microdissected PT and from cortex tissue. Interactions between both proteins were determined by coimmunoprecipitation and by immunocytochemical co-localization (confocal microscopy). For apoptosis study, TUNEL, caspase 3 activity and RNA expression of Bax/BcL2 (RT-PCR) were performed. NADPH oxidase was evaluated by luminol enhanced chemiluminescence. Results: Losartan reduced systolic blood pressure in SHR vs. SHRH2O: 139±6 vs. 170±4 mmHg, p<0.01. Blood pressure in SHRLos was similar to controls; WKYLos and WKYH2O. In SHRLos, increased Cav-1 expression was demonstrated in PT membrane fractions related to WKYH2O: 1.5±0.002, p<0.05 n:2 and in cortex membrane fractions; 1.30 ±0.01 p<0.05, n:6 and 1.40±0.001 p<0.05, n:6 compared to SHRH2O and WKYH2O, respectively. Membrane translocation of HSP70 was demonstrated only in SHRLos through out the HSP70 expression in membrane fractions from PT and cortex. In addition, interactions between Cav-1 and HSP70 in cortex membranes by coimmunoprecipitation and by immunofluorescence co-localization in PT cell membranes were present only in SHRLos. The decreased NADPH oxidase activity (RFU/µg prot/min. incubation) near controls demonstrated in PTs from SHRLos vs. SHRH2O: 41±6.1 vs 142±5.2, p<0.01, was reversed by the pre-incubation with anti-HSP70 antibody. No differences in the number of PT apoptotic cells, capase 3 activity and in the proapoptotic rate Bax/BcL2 in cortex membrane fractions were demonstrated among groups. Conclusion: Due to the interaction of Cav-1 and HSP70 after AT1 Angiotensin II inhibition, a role of both proteins in AT1 regulation could be suggested in SHR proximal tubules. Translocation of HSP70 to proximal tubule membranes in SHRLos, might exert a cytoprotective effect by decreasing oxidative stress.