Effects of Smad7 overexpression on peritoneal inflammation in a rat peritoneal dialysis model.
OBJECTIVE
Transforming growth factor-beta (TGF-beta) has been shown to play a role in peritoneal complications due to long-term peritoneal dialysis (PD). In this study, we examined the effects of the TGF-beta signaling pathway on peritoneal inflammation associated with PD in rats by over-expressing Smad7, an inhibitor of TGF-beta/Smad signaling.


METHODS
Peritoneal inflammation was induced in male Sprague-Dawley rats by intraperitoneal injections of 4.25% glucose dialysate (100 mg/kg body weight) daily for 4 weeks, with the addition of lipopolysaccharides (0.6 mg/kg body weight) on days 8, 10, 12, 22, 24, and 26. Peritoneal Smad7 gene transfer was achieved using an ultrasound microbubble mediated, doxycycline regulated, Smad7-expressing plasmid on day 0 and day 14 after initiation of PD. An empty vector was used as control. All rats were sacrificed after 4 weeks of PD. Peritoneal inflammatory response, including infiltration of total leukocytes (OX-1 positive) and macrophages (ED-1 positive) and expression of interleukin (IL)-1beta and tumor necrosis factor-alpha (TNF-alpha), was examined by immunofluorescence and RT-PCR.


RESULTS
After PD, peritoneal inflammation developed in control animals, as demonstrated by an increase in the number of OX-1-positive and ED-1-positive cells and upregulation of IL-1beta and TNF-alpha mRNA and protein expression. In contrast, in animals treated with Smad7 gene transfer, IL-1beta and TNF-alpha expression and OX-1-positive and ED-1-positive cell infiltration were significantly inhibited. Furthermore, prevention of peritoneal inflammation by overexpression of Smad7 was associated with inhibition of phosphorylation of Smad2/3, a downstream of the TGF-beta signaling pathway, as well as TGF-beta1 expression.


CONCLUSIONS
Overexpression of Smad7 suppresses peritoneal inflammation induced by high glucose and lipopolysaccharides. The ability of Smad7 gene transfer to inhibit peritoneal inflammation indicates that targeting TGF-beta/Smad signaling may represent a new therapeutic strategy for the treatment of peritoneal complications associated with PD.
Nie
Jing
J
Department of Nephrology, First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China.
Hao
Wenke
W
Dou
Xianrui
X
Wang
Xin
X
Luo
Ning
N
Lan
Hui Y
HY
Yu
Xueqing
X
D000818:Animals; D004195:Disease Models, Animal; D018014:Gene Transfer Techniques; D018836:Inflammation Mediators / Q000008:administration & dosage / Q000378:metabolism / Q000502:physiology*; D008070:Lipopolysaccharides / Q000008:administration & dosage; D008297:Male; D010530:Peritoneal Dialysis; D010538:Peritonitis / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000517:prevention & control*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000235:genetics; D051906:Smad7 Protein / Q000008:administration & dosage / Q000096:biosynthesis* / Q000235:genetics*; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics
D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D051906:Smad7 Protein; C497808:Smad7 protein, rat; D016212:Transforming Growth Factor beta