Endocrine Abstracts

Objectives: Angiotensin II (AngII) induces renal premature senescence by multiple mechanisms including by increasing oxidative stress. Recent study revealed that growth hormone secretagogue ghrelin exerts anti-senescence effects. In this study, we examined whether ghrelin inhibits AngII-induced renal senescence and damages.

Methods: Renal senescence was induced by infusion of Ang II in C57BL/6 mice with osmotic mini-pump. Ghrelin was administered by the daily intraperitoneal injection. Eight weeks after the treatment, kidneys were removed and utilized in the various experiments. In in vitro experiment, cultured human proximal cell line, HK-2 cells were incubated with 1 μM of AngII for 72 h and ghrelin were administered 30 min prior to AngII stimulation.

Results: AngII infusion induces senescence and oxidative stress as accessed by senescence-associated (SA) β-Gal and 4-hydroxy-2-nonenal (4-HNE) staining, respectively. The expressions of markers for senescence, p21 and p53 as well as senescence-associated cytokines, TGF-β and PAI-1 in the kidney were increased by AngII. AngII infusion also induced renal damages as assayed by the urinary excretion of renal tubular marker, N-acetyl-glucosaminide (NAG) and neutrophil gelatinase-associated lipocalin (NGAL) as well as by urinary protein excretion. Finally, AngII infusion provoked interstitial fibrosis as evaluated by Masson-trichrome staining. These changes were attenuated by the treatment with Ghrelin. In HK-2 cells, the receptors for both Ghrelin and AngII were expressed. SA β-Gal assay revealed tubular cell senescence by AngII. AngII also increased the expression of p21 and p53 as well as TGF-β and PAI-1. These changes were attenuated by pretreatment with Ghrelin. In addition, AngII reduced the mitochondria (Mt) number, which was restored by Ghrelin as measured by staining cells with Mt-specific fluorescent dye. Ghrelin treatment increased the expression of Mit-specific uncoupling protein UCP-2 and master regulator of Mit biogenesis, PGC-1α expression. Finally, in HK-2 celsl, Ghrelin reducued Mit-derived ROS levels and Mit membrane potential.

Conclusions: Our data indicated that ghrelin suppressed AngII-induced renal premature senescence and AngII-induced renal damages presumably through reducing the mitochondrial membrane potential and resultant ROS production.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.