| Summary: | 博士 === 高雄醫學大學 === 醫學研究所 === 97 === 英文摘要
Kidney disease is one of the complications of diabetes. The pathophysiologic changes in diabetic nephropathy including mesangial cells proliferation and tubular cells hypertrophy. Hyperglycemia is the initial trigger of vascular, renal and retinal cells damage associated with diabetes. Renal ANP synthesis has been found to be significantly increased in several disorders, eg. diabetes. ANP synthesized from the kidney produces local function has never been elucidated. Hyperglycemia-induced cell damage can also be modulated by ANP is still unclear.
This dissertation concerning the role and function of renal ANP synthesis in high glucose stimulated in renal tubular epithelial cells. In this study, we have mainly contained three research directions. First, we investigated the function of ANP by high glucose-stimulated in renal tubular epithelial cells. Second, we investigated the role of endogenous ANP in renal tubular epithelial cells. Third, we investigated the regulation of endogenous ANP by glucose-stimulated in renal tubular epithelial cells.
I. The study of ANP on high glucose-activated transforming growth factor-beta1 (TGF-β1), Smad and collagen synthesis in renal proximal tubular cells.
In diabetic rats, ANP synthesis has been found to be significantly increased, particularly in the proximal tubules. It is reasonable to hypothesize that renal ANP synthesis might directly modulate hyperglycemia-induced injure in this cells.
First, we concerned about cytoprotective action in renal tubular cells by addition of ANP. High glucose significantly increased TGF-β1 and collagen type I expression in renal proximal tubular cells. The addition of ANP significantly attenuated high glucose-enhanced TGF-β1 and collagen type I. LY83583 blocked the influence of ANP on high glucose-activated TGF-β1 and collagen synthesis. In addition, ANP significantly attenuated high glucose-enhanced p-Smad 2/3 ratio.
II. The role of endogenous ANP in renal proximal tubular cells.
It is still unclear on endogenous ANP exerts local function in renal proximal tubular cells. Hyperglycemia activates numerous profibrotic and pro-inflammatory mediators, such as TGF-β1 and NF-κB in renal proximal tubular cells. We investigated whether endogenous ANP could modulate high glucose-stimulated TGF-β1 and collagen type I in renal proximal tubular cells using transfection of ANP and ANP small interfering RNA (siRNA).
In this study, the transfection of ANP significantly attenuated high glucose-activated TGF-β1 and NF-κB expression. ANP siRNA knocked-down ANP but significantly increased TGF-β1 and NF-κB under high glucose conditions. In addition, IkB-α expression increased in ANP-transfected cells, and in contrast, IkB-α expression decreased in ANP siRNA-transfected cells. These results imply an inhibitory action of ANP on NF-κB inhibition by up-regulation of IkB-α.
III. The study of high glucose induces ANP-synthesis via intrarenal renin-angiotensin system in renal proximal tubular cells
Renin-angiotensin system play an important role in diabetic nephropathy. High glucose or angiotensin II could stimulate cells hypertrophy and extracellular matrix formation in renal tubular cells. Therefore, we investigated whether intrarenal renin-angiotensin system could modulate renal ANP synthesis in high glucose-stimulation in proximal tubular cells.
Proximal tubular cells were stimulated with high glucose to up-regulate ANP and ANG mRNA and ANG II protein level. These effects of high glucose were attenuated by angiotensin II receptor antagonist ( losartan or PD123319). ANG siRNA silenced ANG expression, and down-regulate ANP expression in high glucose stimulation in renal tubular cells. In this study, high glucose can stimulate angiotensinogen and angiotensin II expression. High glucose induces ANP-synthesis via intrarenal renin-angiotensin system in renal proximal tubular cells.
In conclusion, using proximal tubular cells to investigate local action of endogenous ANP can directly explanation for the function and regulation of renal ANP synthesis on high glucose-activated in proximal tubular cells.
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