Name: MICHELLE HORTELAN
Publication date: 14/04/2023
Examining board:
Name |
Role |
|---|---|
| NAZARE SOUZA BISSOLI | Examinador Interno |
| PRISCILA DE BATISTA | Examinador Externo |
Summary: High blood pressure is one of the main causes of cardiovascular diseases. In the
hypertension animal model, SHR, vascular dysfunction has been described as
dependent on oxidative inactivation of nitric oxide (NO) due to higher vascular
production of reactive oxygen species (ROS) dependent on NADPH oxidase (NOX).
NOX's redox signaling pathways involve regulatory mechanisms, depending on
second-mediated pathways messengers and intra- and extracellular signalers.
Recently, importance has been given to the signaling pathway dependent on PKD1,
an enzyme that belongs to the protein-kinase-dependent Ca2+-calmodulin
superfamily. PKD1 has been related to vascular smooth muscle contraction and thus
to the modulation of vascular reactivity. The hypothesis of this study is that the PKD1
pathway is involved in the regulation of vascular tone, in the SHR model, via NOXdependent
oxidative stress. We used isolated aortic rings from Wistar and SHR rats to
evaluate vascular reactivity mediated by 1 receptors and for angiotensin II (ATII). We
performed concentration-response curves to phenylephrine (1010 to 104 M) and
angiotensin II (1010 to 105 M) cumulatively, in the presence and absence of CID 3,2
M, a selective inhibitor of PKD1, and Apokinin 30 M, a NOX inhibitor. Vascular
oxidative stress was analyzed by the thiobarbituric acid reactive species (TBARS)
measurement technique, which allows us to evaluate lipid peroxidation and oxidative
fluorescence of DHE in situ. Systolic blood pressure (SBP, mmHg) was measured by
tail plethysmography 48 hours before the experiments. The results are described as
mean ± SEM and were analyzed using: Student's t-test, one- or two-way ANOVA and
Tukey's post-hoc test. The SHR group had lower body mass (Wistar (n=10) 313 ± 5.5
g vs SHR (n=10), 260 ± 8.5*g, *p<0.01) and higher SBP (Wistar: 130.0 ± 1.7 vs SHR:
(n=10), 197.3 ± 2.5* mmHg, *p<0.01). There was no difference in HR values between
the groups. The results collected so far demonstrated that the inhibition of PKD1, with
ICD, did not modify the reactivity to phenylephrine in the Wistar group (Wistar Rmax:
114.4 ± 7.54 x Wistar-CID= 96.11 ± 13.7 % KCl). However, the incubation of aortic
rings with CID reduced aortic reactivity to phenylephrine in the SHR group (SHR Rmax:
129.9 ± 8.28 x SHR-CID= 83.74 ± 9.3* % KCl, *p<0.01). The vasoconstrictor response
to Angiotensin II was reduced in the presence of CID only in the Wistar group (Wistar
Rmax: 52.5 ± 3.7 x Wistar-CID= 38.8 ± 6.4 % KCl, *p<0.01). There was no difference
in Rmax responses between the CID and CID-Apokinin groups in the Wistar and SHR groups. The vascular oxidative stress was not different between the groups, in the
presence and absence of CID after incubation with Angiotensin II. However, the coincubation
of CID and Apokinin, reduced the production of MDA in the SHR group.
Based on the results found, we can accept our hypothesis that the PKD1 pathway
participates in the regulation of aortic ring reactivity in the SHR and Wistar groups. We
conclude that, while the PKD1 pathway seems to play a key role in the contraction of
the aortic rings of the SHR group mediated by phenylephrine, the same pathway
seems to be involved only in the response to angiotensin II in the Wistar group. Our
hypothesis of the participation of oxidative stress in CID-mediated responses was
rejected, since co-perfusation with Apokinin did not modify the CID-mediated
response. This information is relevant to the understanding of the mechanisms
involved in the regulation of blood pressure and may have important implications for
the development of targeted therapies for the treatment of arterial hypertension.
