Tacrolimus induces ligand independent TGFβ receptor signaling to promote renal fibrosis

• Published in: The FASEB journal Vol. 36 Suppl 1
• Main Authors: Ume, Adaku, Yesomi-Wenegieme, Tara, Williams, Clintoria
• Format: Journal Article
• Language: English
• Published: United States 01.05.2022
• ISSN: 1530-6860
• DOI: 10.1096/fasebj.2022.36.S1.R3895

Although calcineurin inhibitors (CNIs) such as tacrolimus and cyclosporin have dramatically improved the quality of patient care, long-term therapy causes irreversible damage to the kidneys in the form of renal fibrosis. These morphologic changes ultimately lead to a decline in renal function and can progress to end-stage renal failure. These detrimental outcomes present a critical need to identify the driving mechanisms by which CNIs cause renal damage. It is well established that TGFb is a major contributor to CNI-induced renal fibrosis. However, the underlying mechanisms remain unknown. The objectives of this study are to 1) investigate whether TGFb secretion is required to stimulate TGFb receptor signaling in a model of CNI-induced renal fibrosis and 2) investigate whether calcineurin plays a critical role in regulating TGFb receptor activity. To examine the role of calcineurin inhibition in altered TGFb receptor signaling, wild type mice were treated with either vehicle (0.01% ethanol) or 10 mg/kg tacrolimus for 7 days. To confirm in vivo findings, wild-type mouse renal cortical fibroblasts were treated with either vehicle (0.01% ethanol) or 1nM tacrolimus for 24 hours in the presence and absence of anti-TGFb neutralizing antibodies. TGFb receptor expression and activation, TGFb receptor downstream signaling mediators, profibrotic markers and calcineurin activity were analyzed. Findings demonstrate that tacrolimus-induced loss of calcineurin activity is accompanied with enhanced TGFb receptor activation and signaling. Notably, increasing concentrations of anti-TGFb neutralizing antibodies failed to abolish aberrant TGFb signaling and increased expression of profibrotic markers. Together, these results demonstrate that 1) CNIs promote ligand-independent TGFb signaling and 2) calcineurin plays a functional role in regulating TGFb receptor activity. This study elucidates a direct pharmacological mechanism by which CNIs promote renal fibrosis and provides a physiological role of calcineurin in regulating TGFb receptor activity. Further insight into the role of calcineurin in regulating TGFb receptor activity could improve the long-term outcomes of patients on chronic CNI therapy.