Calcineurin-inhibition Results in Upregulation of Local Renin and Subsequent Vascular Endothelial Growth Factor Production in Renal Collecting Ducts

Abstract

Background Tacrolimus (Tac) and Cyclosporine A (CyA) calcineurin inhibitors (CNIs) are 2 effective immunosuppressants which are essential to prevent allograft rejection. Calcineurin inhibitors are known to be nephrotoxic. However, the precise mechanism of nephrotoxicity is not fully understood. In this study, we investigated the in vivo effects of CNIs on the local renal renin-angiotensin system in the collecting duct (CD). Methods Three-week-old mice were treated with either vehicle, CyA (2 mg/kg per day), Tac (0.075 mg/kg per day), CyA + Aliskiren (25 mg/kg per day), or Tac + Aliskiren for 3 weeks. Serum creatinine was measured. Renin and vascular endothelial growth factor (VEGF) contents in CD were evaluated with flow cytometry and multiphoton microscopy. The diameter of vessels was assessed with multiphoton microscopy, and the amount of renal collagen was determined by real-time polymerase chain reaction and Masson staining. Results The elevated level of serum creatinine in CNI groups was abolished by Aliskiren. Flow cytometric analysis found elevated renin content in principal cells, which was prevented by Aliskiren. This result was further confirmed with multiphoton microscopy. The VEGF content in CD correlated with reduced capillary diameter and with the formation of fibrotic islands. Conclusions Calcineurin inhibitors induce production of renin in the CD that may contribute to decreased renal blood flow. In turn, CD responds with increased VEGF production, resulting in disproportional vessel growth, further worsening the local hypoxia and striped fibrosis surrounding the CDs. Aliskiren, a direct renin inhibitor blocks these effects and improves CNI-induced nephropathy by decreasing renin production in the CDs. Our data suggest that Aliskiren may be used for the prevention of CNI nephrotoxicity.

Acute Kidney Injury in Hematopoietic Stem Cell Transplantation: A Review

“…Recently, a study demonstrated that calcineurin inhibitors such as tacrolimus and CsA augment production of renin and vascular endothelial growth factor (VEGF) in renal collecting ducts that causes renal ischemia and periductal fibrosis resulting in calcineurin-induced nephropathy. Furthermore, this process was attenuated by aliskiren, a direct renin inhibitor that may have clinical uses in the prevention of calcineurin-induced nephrotoxicity [40]. Another recent study showed that angiotensin receptor blocker, valsartan, has beneficial effects in preventing CsA related nephrotoxicity.…”

The role of RAAS blockade in kidney transplantation

“…In addition, although the dose response of blood pressure to ACE inhibition is relatively flat, the antiproteinuric effect is dose dependent, particularly in populations administered calcineurin inhibitors. 9,10 It is unfortunate that Knoll et al . did not use a higher dose of ramipril in their study, as it could have important effects on the study outcome.…”

Surgical preparation of rats and mice for intravital microscopic imaging of abdominal organs

“…Other investigators have utilized similar surgical approaches to externalize the left kidney, via left flank incision, in mice [33, 34, 35, 36, 37] and rats [35, 38, 40]. Anesthetic agent of choice for mice in some studies was intraperitoneal injection of ketamine cocktail (ketamine 100mg/kg + Xylazine 8–10mg/kg) [33, 34, 35] and Inactin, 110–130mg/kg intraperitoneal injection, was utilized for rats that underwent non-survival imaging [35, 38, 39].…”

“…Anesthetic agent of choice for mice in some studies was intraperitoneal injection of ketamine cocktail (ketamine 100mg/kg + Xylazine 8–10mg/kg) [33, 34, 35] and Inactin, 110–130mg/kg intraperitoneal injection, was utilized for rats that underwent non-survival imaging [35, 38, 39]. Of note, in Rosivall’s study, for visualization of the juxtaglomerular apparatus in the mouse, a 1-mm cortical slice was removed to create a parenchymal window to expose the most superficial afferent arterioles and glomeruli [35].…”

“…Investigators tend to utilize inverted microscopes to study abdominal organs of interest [1, 5, 9, 32, 33, 34, 45, 46, 50, 51]. However, approaches have been developed for imaging on upright microscope stands, which may be useful to investigators without access to an inverted microscope system.…”