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additional production of intrarenal and intratubular angiotensin II, while renin-PRR
interactions could be involved in the development of hypertension and kidney dis-
ease [ 67 ]. Several researches have shown a stimulating effect of the intrarenal
angiotensin II on PRR expression [ 68 ] through a succession of processes which
involves the cyclooxygenase-2-prostaglandin E2 pathway with vasoconstrictor
effects [ 69 ] and the prostaglandin E-prostanoid 4 receptor [ 70 ], therefore leading to
the development of angiotensin II-dependent hypertension [ 71 ].
Therapeutic correlation Even though experimental research has not been yet able
to fully understand the involvement of PRR in each cell and disease context, the
usage of PRR as potential target in RH prevention and treatment is currently being
considered, as it has been shown that neuron-specific PRR knockout hinders the
development of salt-sensitive hypertension [ 72 ]. Therefore, the addition of a renin
inhibitor in the treatment of RH and associated organ damage could increase the
efficiency of RAAS blockade in tissues [ 73 ].
Angiotensin Receptors
The role and interaction of angiotensin receptors have also been investigated within
the context of RH. While the physiological functions of angiotensin type 1 receptor
(AT1R) are well ascertained and described, the involvement of type 2 receptor (AT2R)
is far less investigated. The location of AT2 expression largely in vascular endothelial
cells and muscular media in resistant arteries and in the perivascular nerve fibers as
well indicates its involvement in systemic and neuronal blood pressure regulation
[ 74 ]. Also, experimental studies on insulin-resistant hypertensive rats have shown that
one function of AT2R is to counterbalance the effects of AT1R on blood pressure and
glucose metabolism [ 75 ], while the actions of both receptors are dissociated from
their involvement in glucose metabolism. With respect to AT1R, studies have shown
that various factors are involved in its regulation in salt- sensitive HT such as the renin-
angiotensin system [ 76 ] and estrogenic hormones [ 77 ]. Furthermore, it has been
reported that polymorphism of AT1 A-C1166 gene could be involved in the defective
regulation of blood pressure of RH patients [ 78 ]. Activation of AT1R in cardiac hyper-
trophy appears to be mediated by autocrine and paracrine effects of locally produced
angiotensin II, although there are studies which indicate an angiotensin-independent
activator effect for mechanical stress [ 79 ]. Further studies are required in order to
complete the description of the pathophysiological functions for this receptor.
Chymase
As part of the effort to optimize the effects of RAAS blockade, investigations
regarding production pathways for angiotensin II have introduced chymase as an
essential enzyme involved in this process [ 80 ]. Chymase is synthesized in mast cells
A. Burlacu and A. Covic