Protective effects of intermedin on cardiovascular, pulmonary and renal diseases: comparison with adrenomedullin and CGRP.

Intermedin/adrenomedullin-2 (IMD/AM2) belongs to the calcitonin gene-related peptide (CGRP) / adrenomedullin (AM) family. The biological actions of this family are attributed to their actions at three receptor subtypes comprising the calcitonin receptor-like receptor (CLR) complexed with one of three receptor activity modifying proteins. In contrast to AM and CGRP, IMD binds non-selectively to all three receptor subtypes: CGRP, AM1, AM2. The peptide displays an overlapping but differential and more restricted distribution across the healthy systemic and pulmonary vasculature, heart and kidney relative to CGRP and AM. This, combined with tissue, regional and cell-type specific receptor expression, underpins differences in regard to magnitude, potency and duration of haemodynamic, cardiac and renal effects of IMD relative to those of AM and CGRP, and receptor-subtype involvement. In common with other family members, IMD protects the mammalian vasculature, myocardium and kidney from acute ischaemia-reperfusion injury, chronic oxidative stress and pressure-loading; IMD inhibits apoptosis, attenuates maladaptive tissue remodelling and preserves cardiac and renal function. Robust upregulation of IMD expression in rodent models of cardiovascular and renal disease argues strongly for the pathophysiological relevance of this particular counter-regulatory peptide. Such findings are likely to translate well to the clinic: early reports indicate that IMD is expressed in and protects cultured human vascular and cardiac non-vascular cells from simulated ischaemia-reperfusion injury, primarily via the AM1 receptor, and may have utility as a plasma biomarker in cardiovascular disease. These observations should provide the rationale for short-term administration of the peptide in acute disease, including myocardial infarction, cerebrovascular insult, cardiac and renal failure.