The present experimental study identified remarkable protect

The present experimental study identified remarkable protective effects for celecoxib against renal toxicity caused by CSA. All aspects of CSA nephrotoxicity, functional, inflammatory, fibrotic, and structural, were improved by celecoxib. Mechanistically, pharmacological and immunostaining protein expression studies implicated the TGF-β1/IL-2/COX-2/ETB receptor pathway, at least partly, in the renoprotective capacity of celecoxib. Understandably, such information is mandatory for the proper design of effective therapeutic regimens to combat nephrotoxicity caused by CSA and probably other similar nephrotoxic modalities. Based on the current findings, the therapeutic prospect of celecoxib for this purpose is recommended.
Conflict of interest statement
Acknowledgments This work was supported in part by the Science and Technology Development Fund (STDF), Egypt, Grant No. 502.
Introduction Cyclosporin A (CsA), an immunosuppressant drug discovered in 1972, is widely used in organ transplantation to prevent rejection. 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 (ETB) in vasculature (Zheng et al., 2013), but the underlying mechanisms were not completely understood. Endothelin-1 (ET-1) has potent vascular effects by binding to transmembrane endothelin A receptor (ETA) and ETB receptor. ETA and ETB receptors in the vascular smooth muscle metalloproteinase (VSMC) mediate vasoconstriction (Seo et al., 1994), whereas ETB receptor in endothelial cells contributes to vasodilatation and ET-1 clearance (Schneider et al., 2007). Although the exact roles of VSMC ETB receptor in the development of cardiovascular diseases remain elusive, upregulation of ETB receptor in VSMC has been observed in stroke (Vikman et al., 2006), coronary ischemic heart disease (Wackenfors et al., 2004), hypertension (Nilsson et al., 2008), and atherosclerotic plaque (Iwasa et al., 1999). Moreover, a growing body of evidence suggests that mitogen-activated protein kinase (MAPK) (Huang et al., 2013, Uddman et al., 2003, Xu et al., 2008) and nuclear factor-kappaB (NF-κB) (Huang et al., 2013, Xu et al., 2008, Zheng et al., 2010) signaling pathways are involved in the transcriptional upregulation of ETB receptor. Given that CsA activates MAPK and NF-κB signaling (Chi et al., 2012, Siedlecki et al., 2010, Wang et al., 2013), the present study aims to investigate if MAPK and NF-κB pathways are involved in CsA-induced upregulation of ETB in VSMC. Our data demonstrates that organ culture with CsA results in further enhanced expression of contractile ETB receptor in VSMC via activation of ERK1/2 and p38 MAPK, as well as the downstream transcription factor NF-κB signaling pathways.
Materials and methods
Results
Discussion CsA is an important risk factor for post-transplant hypertension (Hoorn et al., 2012), and the underlying molecular mechanisms are still under active investigation. Our previous study showed that organ culture with CsA enhanced ETB receptor-mediated vasocontraction in mesenteric artery of rats; but the molecular basis was not clear. The present study has for the first time revealed that CsA enhanced ETB receptor upregulation (at mRNA, protein, and functional levels) in VSMC via activation of intracellular MAPK (ERK1/2 and p38) and the downstream transcriptional factor NF-κB signaling pathways. Organ culture with vehicle (DMSO) significantly increased ETB receptor mRNA expression (Fig. 1), which was consistent with previous studies where organ culture per se upregulated ETB receptor in VSMC (Adner et al., 1996, Zheng et al., 2010). Treatment with CsA further enhanced ETB receptor mRNA (Fig. 1) and protein expression (Fig. 2), and ETB receptor-mediated vasoconstriction (Zheng et al., 2013); and these changes were attenuated by transcription inhibitor AcD (Fig. 3, Fig. 4), suggesting the de novo transcriptional mechanism contributed to upregulation of ETB receptor induced by CsA.