Does Prorenin Exert Angiotensin-Independent Effects In Vivo?

Renin-angiotensin system in pre-eclampsia: everything old is new again

This review presents an update of the role of the renin-angiotensin system in normal pregnancy and pre-eclampsia. We have known for years that the circulatory renin-angiotensin system in pre-eclampsia is suppressed. We now know that the circulating renin-angiotensin system does not only have a vasoconstrictor arm, but also a vasodilator arm, which is upregulated in normal pregnancy; this balance is probably disturbed in pre-eclampsia. Recent studies show the importance of the local renin-angiotensin system in the uteroplacental unit for early placentation and regulation of placental blood flow. We discuss the possible role of autoantibodies against the AT1-receptor in pre-eclampsia and the suggestion that activation of the AT1-receptor in the placenta may lead to placental dysfunction and the clinical syndrome of pre-eclampsia.

The interaction between prorenin, renin and the (pro)renin receptor: time to rethink the role in hypertension

PURPOSE OF REVIEW

Elevated prorenin levels are seen in diabetics with microvascular disease. The discovery of a receptor capable of binding renin and prorenin [(P)RR] and triggering an intracellular signal in the laboratory setting raised the expectation that prorenin might be directly responsible for these vascular disorders. However, there has been substantial disagreement concerning the signaling properties of renin and prorenin and it has been impossible to inactivate the (P)RR gene in mouse to define its function.

RECENT FINDINGS

Mouse and rat models in which prorenin is highly overexpressed do not demonstrate the glomerulosclerosis typically seen in severe diabetic nephropathy, but do exhibit an increase in blood pressure that is angiotensin II-dependent. (P)RR has been shown to colocalize with other subunits of the vacuolar ATPase in the kidney and heart and to be necessary for Wnt signaling in a renin-independent manner. Although whole-body inactivation of the (P)RR gene is lethal, tissue-specific inactivation results in severe disorders associated with massive cell death.

SUMMARY

These results do not support a role of direct prorenin or renin signaling through (P)RR in vascular disorders. Rather, they suggest that the main role of (P)RR is as a subunit of the vacuolarATPase complex. Whether or not (P)RR is responsible for the ability of prorenin to generate angiotensin II in tissues has not been resolved.