Pharmacology Report: ELA-2, Angiotensin II Generation, and MI Impact

This pharmacology report delves into the role of Elastase-2 (ELA-2) in the context of myocardial infarction (MI). The study by Becari et al. (2017) investigates how ELA-2 contributes to the generation of Angiotensin II (Ang II) in resistance arteries, thereby modulating cardiac function after MI. The research utilizes techniques like genotyping, echocardiography, and histology to analyze the effects of ELA-2 in ELA-KO mice. The results reveal that ELA-2 is responsible for ACE-independent dysregulation of the renin-angiotensin-system (RAS), with significant impacts on left ventricle diameter, cardiac output, and stroke volume. The findings highlight ELA-2's pivotal role in peripheral resistance and basal cardiac function, suggesting its potential as a therapeutic target for cardiovascular diseases and MI. The study also confirms increased RAS activation in vascular beds and provides first evidence where MI did not affect the Ang I contractile responses that increased the generation of Ang-II upon MI. Furthermore, it explores the dysregulation in ELA-2 KO mice along with increased parasympathetic and decreased sympathetic modulation, adding to the existing knowledge of overall systemic or autonomic dysregulation in mesenteric nerves.

Running head: PHARMACOLOGY
Pharmacology
Name of the Student
Name of the University
Author note
Keywords: Elastase-2, myocardial infarction, angiotensin, ELA-KO mice, resistance mesenteric
arteries
Abbreviations- MI, myocardial infarction; ANG II, Angiotensin II; ELA-2, Elastase-2; ACE,
Angiotensin converting enzyme; RAS, renin-angiotensin-system; PCR, Polymerase chain
reaction; LV, Left ventricle

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ELA-2 responsible for Ang II generation
Angiotensin-converting enzyme (ACE) generates the production of Angiotensin II (Ang
II) that mediates the renin-angiotensin-system (RAS) effects in the body (Becari et al., 2011). On
the other hand, Elastase-2 (ELA-2) which is a chymotrypsin-serine protease elastase family
member 2A alternatively generates the production of Ang II in the arteries of rats. RAS
activation is accelerated after myocardial infarction, however the mechanisms are unknown that
lead to Ang II generaton in resistance arteries (Ahmad et al., 2011). Therefore, the paper by
Becari et al., (2017) deals with the study of Elastase-2 (ELA-2) activity contributing to increased
Angiotensin II (Ang II) formation in resistant arteries and modulation of cardiac function after
myocardial infarction (MI). They hypothesized that ELA-2 is responsible for the generation of
Ang II and leads to cardiac damage in mice and MI. The result studies showed the first evidence
for the hypothesis that ELA-2 is responsible for the formation of Ang II in the resistance arteries
that is modulated to cardiac function after MI. This illustrates that ELA-2 is responsible for the
ACE-independent dysregulation of RAS.
Techniques used
Genotyping The tail tissue genomic DNA was obtained and
amplification of the target gene by Polymerase
Chain Reaction (PCR). Myocardial infarction was
induced by ventral midline skin incision. They
were killed by Carbon dioxide (CO2) inhalation
after 4 weeks of MI surgery.
Echocardiography Fractional shortening and ejection fraction was
calculated for the systolic function of left ventricle
(LV).
Histology Mesenteric arterial bed removal was done and heart
was harvested to calculate the infarct size and heart
sections were analysed by video microscopy
software Leica Qwin.
Randomization, group size or blinding Randomization was done to MI or sham surgery in
groups; sham WT, ELA-2 KO and MI ELA-2 KO
through six independent experiments and data was

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analysed.
Statistical analysis and normalization Log transformation was done to analyse the Ang I
and Ang II concentration effect curves and data
was analysed through nonlinear regression.
Maximum contractile and PD2 values were
obtained and two-way ANOVA was done for the
statistical analysis.
(Table 1- techniques used)
Results:
Echocardiographic analysis
The heart images showed that in WT animals, there was a significantly large LV diameter
than ELA-2 KO mice during the events of diastole and systole (4.1 ± 0.03 vs. 3.7 ± 0.07 mm, P <
0.05, respectively).This reduction of LV diameter was not observed in infracted mice. The
assessment of cardiac function showed that there was decrease in MI and in the ejection fraction
in both the strains of infracted and ELA-KO mice. Sham-ELA-2 KO mice showed a lower stroke
volume and cardiac output as compared to WT mice. There was decreased cardiac output and
stroke volume in WT mice as compared to ELA-2 KO mice. Uehara et al., (2013) also studied
that Ang II is activated by RAS as the final physiological product and strong vasopressor that
promote tissue remodelling in heart. This mechanism for cardiovascular remodelling is not
known that can be helpful in inhibiting the Ang II formation and for the prevention of
cardiovascular remodelling (Groutas, Dou & Alliston, 2011).
ELA-2 is functional in resistance arteries of mice
To confirm the functional analysis of ELA-2 in resistance mice arteries, ELA-2 KP mice
were induced by chymostatin and no responses were obtained. However, there was significant
attenuation of Ang I-induced maximal response in sham-WT mice. There was a rightward-shift
of the concentration curve of Ang I due to chymostatin induction. This data clearly illustrated
that Ang II generation was induced by serine proteases in resistance mesenteric arteries of mice
and in turn, ELA-2 is the major driving reason for the generation of Ang-II enzyme in the
arteries.

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ELA-2 contribution to Ang-I in mesenteric resistance arteries of mice to MI
To confirm the ELA-2 contribution to Ang-I, Ang II and Ang I concentration curves were
subjected to MI or sham-surgery. The concentration response curve shifted to left of Ang I with
maximum effect in WT mice mesenteric arteries. There was also significant increase in the
concentration of Ang I in WT mice as compared sham-Wt mice. This data confirmed that MI is
strongly associated with increased RAS activation. Therefore, this paper provided the first
evidence for the ELA-2 responsible for Ang II increased activity in mesenteric resistance arteries
upon MI.
Ang I conversion to Ang II by ACE subjected to MI
There was rightward-shift in Ang I concentration response curves of mesenteric arteries
when subjected Captopril. In ELA-2 KO mice, there was ACE-independent dysregulation of
RAS in MI and it might be in other cardiovascular diseases. There is RAS hyperactivity
associated with heart failure and there was significant increase in the RAS expression levels due
to MI including myocardium (Santos et al., 2013). In a study conducted by Becari, Oliveira &
Salgado, (2011) showed that cardiac changes in infracted mice was similar to humans that
highlights the importance of ELA-2 as the driving factor for Ang I generation at an increased
level.
The significance of the study is that the mechanism through which Ang II is converted
from Ang I and synthesized in human tissues can be helpful in the pharmacology in inhibiting
local Ang II formation and further MI (Thatcher et al., 2014). Therefore, this elucidation of
ELA-2 being the contributor to the Ang II formation can be a great strategy for the prevention of
cardiovascular diseases and remodelling as in MI.
From the above-obtained results, it can be inferred that ELA-2 is the contributor to
vascular Ang II increased formation. It may also contribute to the cardiac dysfunctioning after
MI. This implies that ELA-2 enzyme is the key player in the ACE-independent RAS
dysregulation. This study confirmed that there is increased RAS activation in vascular beds as
there was augmented Ang-1 induction in resistance arteries of sham-mice to MI. This is the first
evidence provided by this study where MI did not affect the Ang I contractile responses that
increased the generation of Ang-II upon MI. There is also significant cardiac sympathovagal

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balance dysregulation in ELA-2 KO mice along with increased parasympathetic and decreased
sympathetic modulation. There was low cardiac output, heart rate, reduced LV and stroke
volume that are interesting findings of this study adding to the existing knowledge of overall
systemic or autonomic dysregulation in mesenteric nerves. This data indicated that ELA-2 plays
the pivotal role in the peripheral resistance and basal cardiac function.

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References
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Chymase-dependent generation of angiotensin II from angiotensin-(1-12) in human atrial
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