HNF4alpha Dysfunction as a Molecular Rational for Cyclosporine Induced Hypertension

Abstract

Induction of tolerance against grafted organs is achieved by the immunosuppressive agent cyclosporine, a prominent member of the calcineurin inhibitors. Unfortunately, its lifetime use is associated with hypertension and nephrotoxicity. Several mechanism for cyclosporine induced hypertension have been proposed, i.e. activation of the sympathetic nervous system, endothelin-mediated systemic vasoconstriction, impaired vasodilatation secondary to reduction in prostaglandin and nitric oxide, altered cytosolic calcium translocation, and activation of the renin-angiotensin system (RAS). In this regard the molecular basis for undue RAS activation and an increased signaling of the vasoactive oligopeptide angiotensin II (AngII) remain elusive. Notably, angiotensinogen (AGT) is the precursor of AngII and transcriptional regulation of AGT is controlled by the hepatic nuclear factor HNF4alpha. To better understand the molecular events associated with cyclosporine induced hypertension, we investigated the effect of cyclosporine on HNF4alpha expression and activity and searched for novel HNF4alpha target genes among members of the RAS cascade. Using bioinformatic algorithm and EMSA bandshift assays we identified angiotensin II receptor type 1 (AGTR1), angiotensin I converting enzyme (ACE), and angiotensin I converting enzyme 2 (ACE2) as genes targeted by HNF4alpha. Notably, cyclosporine represses HNF4alpha gene and protein expression and its DNA-binding activity at consensus sequences to AGT, AGTR1, ACE, and ACE2. Consequently, the gene expression of AGT, AGTR1, and ACE2 was significantly reduced as evidenced by quantitative real-time RT-PCR. While RAS is composed of a sophisticated interplay between multiple factors we propose a decrease of ACE2 to enforce AngII signaling via AGTR1 to ultimately result in vasoconstriction and hypertension. Taken collectively we demonstrate cyclosporine to repress HNF4alpha activity through calcineurin inhibitor mediated inhibition of nuclear factor of activation of T-cells (NFAT) which in turn represses HNF4alpha that leads to a disturbed balance of RAS.

Pathogenesis of calcineurin inhibitor–induced hypertension

“…In smooth muscle cells, cyclosporine caused a twofold increase in the number of angiotensin II type 1 receptors, suggesting that the effects of angiotensin II could be augmented, even when its plasma levels are unchanged (39). More recently, one study suggested that inhibition of NFATc by CNIs represses the hepatic nuclear factor 4 alpha and that this would activate angiotensin II type 1 receptors to cause vasoconstriction (40). …”

Cyclosporin A upregulates ETB receptor in vascular smooth muscle via activation of mitogen-activating protein kinases and NF-κB pathways

“…However, long term treatment with CsA is frequently complicated by systemic and renal vasoconstriction, leading to arterial hypertension (Curtis, 2002). Although numerous factors have been implicated in the development of CsA-induced hypertension (Hoorn et al, 2012;Niehof and Borlak, 2011), the molecular mechanisms remain obscure. Our previous study with organ culture system showed that CsA upregulated both mRNA expression and contractile function of endothelin B receptor (ET B ) in vasculature (Zheng et al, 2013), but the underlying mechanisms were not completely understood.…”

Vasomotor Dysfunction in the Mesenteric Artery after Organ Culture with Cyclosporin A

“…However, the usage of CsA is accompanied by mild to severe side effects, and the clinically most important are nephrotoxicity and hypertension . There is definitive proof for cyclosporine to increase blood pressure in human beings and animals , and the underlying mechanisms by which CsA causes arterial hypertension after kidney transplantation are related to the activation of the sympathetic nervous system , the increased vasoconstriction and the impaired vasodilatation . Although the molecular mechanisms for CsA‐induced hypertension are still under active investigation, it is hampered by the lack of suitable in vitro models to study the roles of specific signalling pathway in CsA‐induced vascular pathogenesis.…”