163suggest a novel cardioprotective role for CST, which appears mainly due to a direct
reduction of post-ischemic myocardial damages and dysfunction, rather than to an
involvement of adrenergic terminals and/or endothelium. These different results
may be tentatively explained on the basis of the different models investigated
(regional vs global ischemia) and the modality and the dose of administration of
CST (the entire reperfusion period or the first 20 min of reperfusion).
It must be remembered, however, that the protective effect of CST already
observed on the isolated rat heart, has been confirmed on isolated rat cardiomyo-
cytes exposed to a protocol of simulated I/R injury (Penna et al. 2010 ). Interestingly,
the cardioprotective effect of CST in isolated cardiomyocytes was attained a very
low concentration, in comparison with that needed in the isolated heart (5 nM vs
75 nM), that is comparable to the circulating concentrations of this peptide found in
healthy humans (O’Connor et al. 2002 ). Although our results do not rule out an
additional role for the anti-adrenergic and/or endothelium-dependent mechanisms
in the in situ heart, they strongly suggest that CST is able to attain such protection
also via a direct effect on cardiomyocytes, independent from the presence of cate-
cholamine in the extracellular milieu or of endothelial cells.
Recent experiments were performed in our laboratory to define the cardioprotec-
tive signalling pathways activated by CST on isolated adult rat cardiomyocytes
(Bassino et al. 2015 ). To this purpose, besides cell viability rate, we also evaluated
mitochondrial membrane potential (MMP). The involvement of Akt, glycogen syn-
thase kinase 3β (GSK3β) and phospholamban (PLN) cascade was studied by immu-
nofluorescence, while the role of PI3K-Akt pathway was investigated by using the
pharmacological blocker Wm. We observed that in isolated cardiomyocytes under-
going simulated I/R, CST increased cell viability rate by 65%. The protective effect
of CST was related to its ability to maintain mitochondrial membrane potential
(MMP) and to increase Akt, PLN and GSK3β phosphorylation. The cardioprotective
effect of CST was abolished by Wm. These results give new insights into the molecu-
lar mechanisms involved in the protective role of CST, suggesting that the cardiopro-
tective effect of CST depends on PI3K-Akt-GSK3β cascade activation and is related
to MMP stabilization. Moreover, as suggested by PLN phosphorylation, CST may
enhance calcium recovery in sarcoplasmatic reticulum, thus reducing calcium over-
load in cardiomyocytes. Interestingly, similarly to cardiomyocytes, anti-apoptotic
properties on endothelial cells were described for CST (Teurl et al. 2010 ).
6 Conclusions and Perspectives
Accumulating evidences point to a significant role for the CgA-derived peptides
VS-1 and CST in the protective modulation of the cardiovascular activity, mainly
because of their ability to counteract the adrenergic signal. Indeed, these peptides
are able to control catecholamine release from chromaffin cells and noradrenergic
neurons, to exert in vivo and in vitro vasodilatory effects, and to limit the inotropic
and lusitropic responses to β-adrenergic stimulation of the heart. The
Signalling Pathways of CgA-Derived Peptides in Cardiac and endothelial cells