Lin Heng, Cheng Ching-Feng, Hou Hsin-Han, Lian Wei-Shiung, Chao Ying-Chi, Ciou Yi-Yun, Djoko Bambang, Tsai Ming-Tzu, Cheng Chien-Jui, Yang Ruey-Bing
Institute of Pharmacology and Toxicology, School of Medicine, Tzu Chi University, Hualien, Taiwan.
J Am Soc Nephrol. 2008 Feb;19(2):339-48. doi: 10.1681/ASN.2007050550. Epub 2008 Jan 16.
The membrane forms of guanylyl cyclase (GC) serve as cell-surface receptors that synthesize the second messenger cGMP, which mediates diverse cellular processes. Rat kidney contains mRNA for the GC-G isoform, but the role of this receptor in health and disease has not been characterized. It was found that mouse kidney also contains GC-G mRNA, and immunohistochemistry identified GC-G protein in the epithelial cells of the proximal tubule and collecting ducts. Six hours after ischemia-reperfusion (I/R) injury, GC-G mRNA and protein expression increased three-fold and remained upregulated at 24 h. For determination of whether GC-G mediates I/R injury, a mutant mouse with a targeted disruption of the GC-G gene (Gucy2g) was created. At baseline, no histologic abnormalities were observed in GC-G(-/-) mice. After I/R injury, elevations in serum creatinine and urea were attenuated in GC-G(-/-) mice compared with wild-type controls, and this correlated with less tubular disruption, less tubular cell apoptosis, and less caspase-3 activation. Measures of inflammation (number of infiltrating neutrophils, myeloperoxidase activity, and induction of IL-6 and P-selectin) and activation of NF-kappaB were lower in GC-G(-/-) mice compared with wild-type mice. Direct transfer of a GC-G expression plasmid to the kidneys of GC-G(-/-) mice resulted in a dramatically higher mortality after renal I/R injury, further supporting a role for GC-G in mediating injury. In summary, GC-G may act as an early signaling molecule that promotes apoptotic and inflammatory responses in I/R-induced acute renal injury.
鸟苷酸环化酶（GC）的膜形式作为细胞表面受体，可合成第二信使环磷酸鸟苷（cGMP），后者介导多种细胞过程。大鼠肾脏含有GC-G亚型的信使核糖核酸（mRNA），但该受体在健康和疾病中的作用尚未明确。研究发现，小鼠肾脏也含有GC-G mRNA，免疫组织化学鉴定出近端小管和集合管上皮细胞中有GC-G蛋白。缺血再灌注（I/R）损伤6小时后，GC-G mRNA和蛋白表达增加了两倍，并在24小时时仍保持上调。为了确定GC-G是否介导I/R损伤，构建了一种靶向破坏GC-G基因（Gucy2g）的突变小鼠。在基线时，未在GC-G（-/-）小鼠中观察到组织学异常。I/R损伤后，与野生型对照相比，GC-G（-/-）小鼠血清肌酐和尿素的升高有所减轻，这与肾小管破坏减少、肾小管细胞凋亡减少以及半胱天冬酶-3激活减少相关。与野生型小鼠相比，GC-G（-/-）小鼠的炎症指标（浸润中性粒细胞数量、髓过氧化物酶活性以及白细胞介素-6和P-选择素的诱导）和核因子κB的激活较低。将GC-G表达质粒直接导入GC-G（-/-）小鼠的肾脏，导致肾I/R损伤后死亡率显著升高，进一步支持了GC-G在介导损伤中的作用。总之，GC-G可能作为一种早期信号分子，在I/R诱导的急性肾损伤中促进凋亡和炎症反应。
