Midkine regulation of the renin-angiotensin system.

Hypertension and chronic kidney disease are often associated. The pathogenesis of these diseases involves the renin-angiotensin system. We have recently reported that the growth factor midkine is a novel regulator of the renin-angiotensin system. Midkine is a heparin-binding growth factor so far implicated in neuronal differentiation, neuroprotection, cardioprotection, inflammation, and cancer development. In a mouse model of chronic kidney disease induced by 5/6 nephrectomy, midkine is produced in the lung and in turn upregulates angiotensin-converting enzyme expression. Hypertension associated with 5/6 nephrectomy is not observed in midkine-deficient mice. Conversely, supplemental administration of midkine to the deficient mice induces hypertension. This review describes the molecular characteristics of midkine and its significance in the renin-angiotensin system and the kidney-lung interaction.