Adrenomedullin-RAMP2 System Suppresses ER Stress-Induced Tubule Cell Death and Is Involved in Kidney Protection

作者：Uetake Ryuichi; Sakurai Takayuki; Kamiyoshi Akiko; Ichikawa Shindo Yuka; Kawate Hisaka; Iesato Yasuhiro; Yoshizawa Takahiro; Koyama Teruhide; Yang Lei; Toriyama Yuichi; Yamauchi Akihiro; Igarashi Kyoko; Tanaka Megumu; Kuwabara Takashige; Mori Kiyoshi; Yanagita Motoko; Mukoyama Masashi; Shindo Takayuki^*

来源：PLos One, 2014, 9(2): e87667.

DOI：10.1371/journal.pone.0087667

Various bioactive peptides have been implicated in the homeostasis of organs and tissues. Adrenomedullin (AM) is a peptide with various bioactivities. AM-receptor, calcitonin-receptor-like receptor (CLR) associates with one of the subtypes of the accessory proteins, RAMPs. Among the RAMP subisoforms, only RAMP2 knockout mice (-/-) reproduce the phenotype of embryonic lethality of AM-/-, illustrating the importance of the AM-RAMP2-signaling system. Although AM and RAMP2 are abundantly expressed in kidney, their function there remains largely unknown. We used genetically modified mice to assess the pathophysiological functions of the AM-RAMP2 system. RAMP2+/- mice and their wild-type littermates were used in a streptozotocin (STZ)-induced renal injury model. The effect of STZ on glomeruli did not differ between the 2 types of mice. On the other hand, damage to the proximal urinary tubules was greater in RAMP2+/-. Tubular injury in RAMP2+/- was resistant to correction of blood glucose by insulin administration. We examined the effect of STZ on human renal proximal tubule epithelial cells (RPTECs), which express glucose transporter 2 (GLUT2), the glucose transporter that specifically takes up STZ. STZ activated the endoplasmic reticulum (ER) stress sensor protein kinase RNA-like endoplasmic reticulum kinase (PERK). AM suppressed PERK activation, its downstream signaling, and CCAAT/enhancer-binding homologous protein (CHOP)-induced cell death. We confirmed that the tubular damage was caused by ER stress-induced cell death using tunicamycin (TUN), which directly evokes ER stress. In RAMP2+/- kidneys, TUN caused severe injury with enhanced ER stress. In wild-type mice, TUN-induced tubular damage was reversed by AM administration. On the other hand, in RAMP2+/-, the rescue effect of exogenous AM was lost. These results indicate that the AM-RAMP2 system suppresses ER stress-induced tubule cell death, thereby exerting a protective effect on kidney. The AM-RAMP2 system thus has the potential to serve as a therapeutic target in kidney disease.

• 出版日期2014-2-5