Blockade of NFkappaB activation and renal inflammation by ultrasound-mediated gene transfer of Smad7 in rat remnant kidney.
BACKGROUND
Transforming growth factor-beta (TGF-beta) in renal fibrosis has been well studied, but little attention has been paid to the potential role of TGF-beta in the resolution of renal inflammation. We hypothesize that TGF-beta exerts its anti-inflammation properties by stimulating its negative signaling pathway involving Smad7.


METHODS
A rat remnant kidney model was treated with a doxycycline-regulated Smad7 gene or control empty vector using an ultrasound-microbubble (Optison)-mediated system. Smad7 transgene expression within the kidney was tightly controlled by the addition of doxycycline in the daily drinking water. All animals were euthanized at week 4 for examination of inflammatory responses.


RESULTS
Real-time polymerase chain reaction (PCR) and immunohistochemistry revealed that gene transfer of Smad7 resulted in a substantial inhibition of interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha) expression (all P < 0.01 vs. control). This was associated with the attenuation of histology damage, proteinuria, serum creatinine, and an increase in creatinine clearance (all P < 0.05). In addition, overexpression of Smad7 significantly inhibited renal inflammation, including ICAM-1, iNOS, and accumulation of macrophages and T cells in both glomeruli and tubulointerstitium. Furthermore, gene transfer of Smad7 also substantially blocked nuclear factor kappa B (NFkappaB) activation in the rat remnant kidney (P < 0.01).


CONCLUSIONS
TGF-beta/Smad7 signaling plays a critical role in the resolution of renal inflammation in rat remnant kidney model. Inhibition of NFkappaB activation is a key mechanism by which Smad7 suppresses renal inflammation, which suggests a crosstalk pathway between NFkappaB and Smad7. The ability of Smad7 to inhibit renal inflammation indicates that ultrasound-microbubble-mediated Smad7 gene therapy may represents a new therapeutic strategy for glomerulonephritis.
Ng
Yee-Yung
YY
Section of Nephrology, Department of Medicine, Taipei Veterans General Hospital, Institute of Clinical Medicine, National Yang Ming University, Taipei, Taiwan.
Hou
Chun-Cheng
CC
Wang
Wansheng
W
Huang
Xiao R
XR
Lan
Hui Y
HY
D000818:Animals; D001794:Blood Pressure; D004268:DNA-Binding Proteins / Q000235:genetics*; D015316:Genetic Therapy / Q000379:methods*; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics; D007375:Interleukin-1 / Q000235:genetics; D007677:Kidney Function Tests; D007962:Leukocytes / Q000473:pathology; D008297:Male; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D009392:Nephrectomy; D009393:Nephritis / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy*; D019001:Nitric Oxide Synthase / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D051906:Smad7 Protein; D015534:Trans-Activators / Q000235:genetics*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics; D018084:Ultrasonography, Interventional
D004268:DNA-Binding Proteins; D007375:Interleukin-1; D016328:NF-kappa B; D051906:Smad7 Protein; C497808:Smad7 protein, rat; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat