IQUIFIB   02644
INSTITUTO DE QUIMICA Y FISICOQUIMICA BIOLOGICAS "PROF. ALEJANDRO C. PALADINI"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Angiotensin-(1-7) regulates tyrosine hydroxylase and norepinephrine transporter expression in neuronal cultures from spontaneously hypertensive rats
Autor/es:
LOPEZ VERRILLI M. A.; GIRONACCI M.
Lugar:
Berlin
Reunión:
Congreso; 22nd Scientific Meeting of the International Society of Hypertension; 2008
Resumen:
Angiotensin-(1-7)
regulates tyrosine hydroxylase and norepinephrine transporter expression in
neuronal cultures from spontaneously hypertensive rats
M. A. Lopez Verrilli, M. M.
Gironacci. Instituto de Química y Físicoquímica Biológicas, Facultad de Farmacia y
Bioquímica, Universidad de Buenos Aires.
Objectives: Angiotensin
(Ang) (1-7) is an antihypertensive peptide of the renin-angiotensin system that
exerts opposite effects to Ang II on central sympathetic activity. Since
Ang-(1-7) decreases hypothalamic norepinephrine (NE) release (Hypertension
2004;44:783-7) we hypothesize that Ang-(1-7) may decrease NE biosynthesis
modulating tyrosine hydroxylase (TH), the rate-limiting step enzyme in NE
biosynthesis, or stimulate NE uptake through NE transporter (NET). Our aim was
to investigate the effect of Ang-(1-7) on NET and TH expression at the central
level in spontaneously hypertensive rats (SHR). Methods: Neuronal cells
in primary culture from hypothalamus-brainstem of SHR were used to determine TH
and NET expression by western blot. One-way ANOVA was used to perform
statistical analysis. Results: Endogenous TH levels were 1.7-fold
greater in neuronal cultures from SHR than in those from normotensive
Wistar-Kyoto (WKY) rats. Treatment of SHR neuronal cultures with 100 nM
Ang-(1-7) during 30 min caused a decrease in TH endogenous expression of 31±3%,
and this effect was blocked by an AT2 receptor antagonist. No change
was observed with longer time exposure. Since the ubiquitin-proteasome system
is the major pathway for protein degradation, we examined the involvement of
the proteasomal pathway in the Ang-(1-7)-induced decrease in TH expression. MG132,
a selective proteasome inhibitor, blocked the Ang-(1-7)-mediated TH
downregulation, suggesting a proteasome-dependent TH degradation. Basal NET
expression was 3-fold higher in neuronal cultures from SHR than in WKY.
Incubation of SHR neuronal cultures with 10 or 100 nM Ang-(1-7) during 3 h
caused an increase in NET endogenous levels of 70±18% and 60±11%, respectively.
Conclusion: Together with the fact that the peptide induces a decrease
in NE release, our study supports a negative neuromodulator role for Ang-(1-7)
on NE central sympathetic nervous activity.