In:
Journal of the American Society of Nephrology, Ovid Technologies (Wolters Kluwer Health), Vol. 31, No. 3 ( 2020-3), p. 532-542
Abstract:
Although the effects of angiotensin II (AngII) on glomerular perfusion pressure are well characterized, the relevance of AngII signaling in podocytes remains elusive. The authors’ in vivo study demonstrates that AngII elicits only a limited calcium response in podocytes in healthy mice. In contrast, in mice subjected to chemical injury or genetic deletion of the podocin-encoding gene Nphs2 , the resultant podocyte damage and proteinuria rendered podocytes responsive to pronounced AngII-induced calcium transients. These findings may explain clinical trial results in humans that demonstrated beneficial renal effects of blockade of the renin-angiotensin system in proteinuric patients, but not in patients with nonproteinuric kidney disease. This study also underscores the importance of inhibition of the renin-angiotensin system in patients with podocyte damage and proteinuria. Background Inhibition of angiotensin II (AngII) signaling, a therapeutic mainstay of glomerular kidney diseases, is thought to act primarily through regulating glomerular blood flow and reducing filtration pressure. Although extravascular actions of AngII have been suggested, a direct effect of AngII on podocytes has not been demonstrated in vivo . Methods To study the effects of AngII on podocyte calcium levels in vivo , we used intravital microscopy of the kidney in mice expressing the calcium indicator protein GCaMP3. Results In healthy animals, podocytes displayed limited responsiveness to AngII stimulation. In contrast, in animals subjected to either adriamycin-induced acute chemical injury or genetic deletion of the podocin-encoding gene Nphs2 , the consequent podocyte damage and proteinuria rendered the cells responsive to AngII and resulted in AngII-induced calcium transients in significantly more podocytes. The angiotensin type 1 receptor blocker losartan could fully inhibit this response. Also, responsiveness to AngII was at least partly mediated through the transient receptor potential channel 6, which has been implicated in podocyte calcium handling. Interestingly, loss of a single Nphs2 allele also increased podocytes’ responsiveness to AngII signaling. This direct effect of AngII on injured podocytes results in increased calcium transients, which can further aggravate the underlying kidney disease. Conclusions Our discovery that podocytes become sensitized to AngII-induced calcium signaling upon injury might explain results from large, randomized, controlled trials in which improved renal outcomes occur only in the subgroup of patients with proteinuria, indicating podocyte damage. Our findings also emphasize the need to treat every patient with a glomerular disease with either an angiotensin-converting enzyme inhibitor or an angiotensin type 1 receptor blocker.
Type of Medium:
Online Resource
ISSN:
1046-6673
,
1533-3450
DOI:
10.1681/ASN.2019020109
Language:
English
Publisher:
Ovid Technologies (Wolters Kluwer Health)
Publication Date:
2020
detail.hit.zdb_id:
2029124-3
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