Abstract
Background and Aims
Activating Transcription Factor 3 (ATF3) is a stress-adaptive transcription factor, which has been suggested to be involved in maintaining glucose homeostasis. ATF3 respond rapidly to various stimuli like high glucose, fatty acids and oxidative stress, and is observed to either protective or detrimental effects in diabetic condition. Therefore to elucidate the exact role in diabetic nephropathy of ATF3, we investigated the role of ATF3 by inhibition with Raf-inhibitor GW5047 on diabetic mice model.
Method
ATF3 level was examined in the mouse podocytes and NRK cells with either overexpression or downregulation with ATF3. 8 week db/m and db/db mice as the model of diabetic mice were examined for the expression of ATF3 and were treated with GW5074, a Raf1 kinase inhibitor targeting the ATF3 intraperitoneally with a dose of 0.5mg/kg for 12 weeks.
Results
In cultured mouse podocytes and NRK cells, high glucose and angiotensin II markedly increased ATF3 expression. Gene Expressions of NOX4, MCP-1 and NF-kB were augmented by ATF3, and were attenuated by ATF3 siRNA. In db/db mice, plasma ATF3 level was not different from control db/m, however the urinary ATF3 excretion was significantly higher. Treatment of GW5074 decreased urinary ATF3 excretion. After 12 week treatment, serum creatinine level was significantly lower in the treatment db/db group, with less systemic oxidative stress. There were no significant differences in body weight, whereas the food intake was decreased in GW5047 group. Overall lipid profile or HOMA-IR, HbA1c level was not different from each group. Serum adiponectin were otherwise increased in GW5074 group. Urinary excretion of albumin at 2 month of treatment decreased with urinary nephrin excretion. Trend of increased gene expression of JNK, p-38, smad2, ERK which was downregulated by GW5074 was noted.
Conclusion
These findings suggest that in diabetic condition, the activation of ATF3 is associated pathogenesis of diabetic nephropathy and targeting ATF3 may have a protective role in the disease progression.
An aquaporin gene as a direct target of the Zic1 transcription factor