EPO, VEGF, chronic hypoxia adaptations and metabolism in the heart

Transcription

1 EPO, VEGF, chronic hypoxia adaptations and metabolism in the heart BSc Catherine Privat M. Laboratorio de Transporte de Oxígeno Instituto de Investigaciones de Altura Dpto de Ciencias Biológicas y Fisiológicas Facultad de Ciencias y Filosofía Universidad Peruana Cayetano Heredia

2 PROJECT TITLE: VEGF expression in the heart of anemic transgenic mice exposed to 24 hours and 14 days of hypoxia: Impact on myocardium capillarization PROJECT AUTHORS: F. Favret a, T. Launay a, A. Pichon a, R. El Hasnaoui a, JL Macarlupu b, C. Privat b, F. Leon-Velarde b, J.P. Richalet a. a Université Paris 13, Laboratoire Réponses cellulaires et fonctionnelles à l hypoxie, Bobigny, France b Laboratorio de Transporte de Oxígeno/IIA, Instituto de Investigación de Altura, Universitad Peruana Cayetano Heredia, Lima 100, Perú

3 Angiogenic Factors in myocardium acidic Fibroblast Growth Factor (afgf) Erythropoietin (EPO) Vascular Endothelial Growth Factor (VEGF) Angiotensin 1 (Ang1) Platelet Derived Growth Factor (PDGF) Folkman, J., and Klagsbrun, M. (1987). Angiogenic factors. Science 235, Jaquet K. et al. Erythropoietin and VEGF exhibit equal angiogenic potential. Microvascular research :

4 HYPOXIA Metabolic stress HIF-1 Mecanic stress (stretch) EPO VEGF Vascularization Kertesz N et. al. The Role of Erythropoietin in regulating angiogenesis. Dev biology :

5 Angiogenic factors in myocardium under Hypoxia Angiogenic requirement Epo VEGF Ang 1 VEGF Jaquet K. et al. Erythropoietin and VEGF exhibit equal angiogenic potential. Microvascular research : Lenz T. et.al. Role of Erythropoietin for angiogenesis and vasculogenesis-from embryonic development through adulthood. Am J Physiol :184

6 O 2 delivery Blood flow O 2 carrying capacity of the blood O 2 extraction Anemia Cardiac Output EPO 2,3 DPG Metevier F. et. al. Pathophysiology of anaemia: Focus on the Heart and blood vessels. Nephrol Dial Transplant (3): 14-18

7 Epo TAg h Mouse Transgenic model* Disruption in EPO gene that reduces Epo expression Anemia - Hct 24 %, Hb 4-6 g/dl. Cardiac Hypertrophy Greater Cardiac Output Allows the study of hypoxia without polycythemia. *Maxwell P. et.al. Identification of the renal erythropoietin-producing cells using transgenic mice. Kidney Int. 1993; 44(5):

8 Aims Determinate if VEGF levels in myocardium presents significant changes under anemia, with EPO gene partially blocked. Analyze vascular remodeling under anemia, with EPO gene partially blocked. Determinate the relationship between VEGF levels and vascular remodeling Define if vascularization is the other protective mechanism developed by the Epo-Tag h to compensate anemia.

9 Methods We will use Epo TAg h mice and their WT littermates to analize: Vascular density (Inmunohistochemistry) Measurement of Angiogenic factors, like VEGF A (ELISA and RT-PCR).

10 ELISA Assay The Enzyme-Linked Immunosorbent Assay (ELISA) is a method employed to detect if a certain substance is present in a sample. It utilizes antibodies specific to the substance; these antibodies are linked to an enzyme which causes a chromogenic substrate to produce a signal.

11 Technique Incubate microplate s wells with a capture antibody to fix it to the surface. Add standard, control or sample to the wells to be reconized by the Ab. Add a detection antibody to mark the protein reconized by the capture Ab. Add the reagent to generate a color sign in the wells The ELISA reader must give an absorbance that represents the amount of the protein of interest present in the sample.

12 Expected results According to unpublished data (Favret F, Richalet JP,Launay T.), there is no change in VEGF expression in skeletal muscle, however there is a fall in its capillarization, probably due to the lack of Epo. It is expected to find higher levels of VEGF in myocardium due to a more protective response from the organism in this tissue.

13 VEGF Left ventricule * WT Nx Epo TAg Nx WT Hx Epo TAg Hx & VEGF (pg/ml) There is a significant increase in the amounts of VEGF under chronic anemia in the left ventricule, and a normalization of this value after 14 days of barometric hypoxia.

14 VEGF Right Ventricule # VEGF (pg/ml) & 0.00 WT Nx Epo TAg Nx WT Hx Epo TAg Hx The Right ventricule of Epo TAg under Normoxia and Chronic Hypoxia displays high levels of VEGF while the WT reduces its after Hypoxia.

15 Epo TAg h VS TG6 Epo TAg h Disruption in EPO gene that reduces Epo expression Anemia Hct 24 % RV and LV Hypertrophy Greater cardiac output. Allows the study of hypoxia without polycythemia. TG6 Systemic overexpression of Human Epo Polycythemia Hct 80-90% RV Hypertrophy Without variations in heart rate, cardiac output and blood pressure Allows the study of polycythemia without hypoxia Vogel J. et. al. Transgenic mice overexpressing erythropoietin adapt to excessive erythrocytosis bu regulating blood viscosity. Blood. 2003;102(6): Maxwell P. et.al. Identification of the renal erythropoietin-producing cells using transgenic mice. Kidney Int. 1993; 44(5):

16 Future studies Analyze: - VEGF expression, activity and amount. -Vascularization. In cardiac tissue of TG6 mice, the transgenic model for excessive erythrocytosis.

17 Aims: Analyze VEGF levels and their impact on vascular density under Excessive Erythrocytosis (EE). Determinate if these modifications can be ranked as additional O 2 delivery strategies under EE, but be triggered by Erythrocytosis instead of Hypoxia.

18 Acknowledgments HAPPOM - ALFA Program. Laboratoire Réponses cellulaires et fonctionnelles à l hypoxie, Université Paris 13, Bobigny, France Laboratorio de Transporte de Oxígeno, Instituto de Investigación de Altura, Universitad Peruana Cayetano Heredia, Lima, Perú