Role of activating transcription factor 3 （ATF3） in sublytic C5b-9-induced glomerular mesangial cell apoptosis

Sublytic complement C5b-9 complexes can cause cell apoptosis, but the mechanism of glomerular mesangial cell （GMC） apoptosis mediated by these complexes has not been well defined. The activating transcription factor 3 （ATF3） gene is an immediate early gene for the cell to cope with a variety of stress signals and can promote apoptosis of some cells. In this study, ATF3 expression and cell apoptosis in GMCs induced by sublytic C5b-9 were measured, and then the effects of ATF3 gene over-expression or knockdown on GMC apoptosis induced by sublytic C5b-9 were examined at a fixed time. The results showed that both ATF3 expression and GMC apoptosis were markedly increased and ATF3 over-expression obviously increased sublytic C5b-9-induced GMC apoptosis, whereas ATF3 gene silencing had a significant opposite effect. Collectively, these findings indicate that upregulation of ATF3 gene expression is involved in regulating GMC apoptosis induced by sublytic C5b-9 complexes.

Cardiac Fibroblast-Specific Activating Transcription Factor 3 Promotes Myocardial Repair after Myocardial Infarction

Background：Myocardial ischemia injury is one of the leading causes of death and disability worldwide.Cardiac fibroblasts （CFs） have central roles in modulating cardiac function under pathophysiological conditions.Activating transcription factor 3 （ATF3） plays a self-protective role in counteracting CF dysfunction.However,the precise function of CF-specific ATF3 during myocardial infarction （MI） injury/repair remains incompletely understood.The aim of this study was to determine whether CF-specific ATF3 affected cardiac repair after MI.Methods：Fifteen male C57BL/6 wild-type mice were performed with MI operation to observe the expression of ATF3 at 0,0.5,1.0,3.0,and 7.0 days postoperation.Model for MI was constructed in ATF3TGfl/flColla2-Cre＋ （CF-specific ATF3 overexpression group,n =5） and ATF3TGfl/flColla2-Cre-male mice （without CF-specific ATF3 overexpression group,n =5）.In addition,five mice of ATF3TGfl/flCol1a2-Cre＋ and ATF3TGfl/flCol 1 a2-Cre-were subjected to sham MI operation.Heart function was detected by ultrasound and left ventricular remodeling was observed by Masson staining （myocardial fibrosis area was detected by blue collagen deposition area） at the 28th day after MI surgery in ATF3TGfl/flColla2-Cre＋ and ATF3TGfl/flColla2-Cre-mice received sham or MI operation.Quantitative real-time polymerase chain reaction （qRT-PCR） was used to detect cell proliferation/cell cycle-related gene expression in cardiac tissue.BrdU staining was used to detect fibroblast proliferation.Results：After establishment of an MI model,we found that ATF3 proteins were increased in the heart of mice after MI surgery and dominantly expressed in CFs.Genetic overexpression of ATF3 in CFs （ATF3TGfl/flCol1a2-Cre＋ group） resulted in an improvement in the heart function as indicated by increased cardiac ejection fraction （41.0% vs.30.5%,t =8.610,P =0.001） and increased fractional shortening （26.8% vs.18.1%,t =7.173,P =0.002）,which was accompanied by a decrease in cardiac scar area （23.1% vs.11.0%,t =8.610,P =0.001）.qRT-PCR analysis of CFs isolated from ATF3TGfl/flCol1a2-Cre＋ and ATF3TGfl/flCol1a2-Cre-ischemic hearts revealed a distinct transcriptional profile in ATF3-overexpressing CFs,displaying pro-proliferation properties.BrdU-positive cells significantly increased in ATF3-overexpressing CFs than control CFs under angiotensin Ⅱ stimuli （11.5% vs.6.8%,t =31.599,P =0.001） or serum stimuli （31.6% vs.20.1%,t =31.599,P =0.001）.The 5（6）-carboxyfluorescein N-hydroxysuccinimidyl ester assay showed that the cell numbers of the P2 and P3 generations were higher in the ATF3-overexpressing CFs at 24 h （P2：91.6% vs.71.8%,t =8.465,P=0.015） and 48 h （P3：81.6% vs.51.1%,t =9.029,P =0.012） after semm stimulation.Notably,ATF3 overexpression-induced CF proliferation was clearly increased in the heart after MI injury.Conclusions：We identify that CF-specific ATF3 might contribute to be MI repair through upregulating the expression of cell cycle/proliferation-related genes and enhancing cell proliferation.

Activating transcription factor 3 in immune response and metabolic regulation

Activating transcription factor 3(ATF3)is a member of the ATF/cyclic adenosine monophosphate(cAMP)-response element binding protein(CREB)family of transcription factors.In response to stress stimuli,ATF3 forms dimers to activate or repress gene expression.Further,ATF3 modulates the immune response,atherogenesis,cell cycle,apoptosis,and glucose homeostasis.Recent studies have shown that ATF3 may also be involved in pathogenesis of other diseases.However,more studies are needed to determine the role of ATF3 in metabolic regulation.

Knockdown of STAT3 by iRNA Inhibiting Migration and Invasion of Epithelial Ovarian Cancer Cells

Signal transducer and activator of transcription 3（STAT3） is a dual functional transcription factor with the functions of signal transduction and transcription regulation. It is reported that the expression of STAT3 in ovarian cancer is significantly higher and STAT3 can facilitate ovarian cancer growth and metastasis. To clarify the definite effect and molecular mechanism of STAT3 involved in ovarian cancer growth and metastasis, STAT3 expression was significantly downregulated by transfecting ovarian cancer model SK-OV-3 cells with the plasmid vector which express specific RNAi that targets human STAT3. The downregulated STAT3 not only decreased the invasion and migration but also inhibited the proliferation of SK-OV-3 cells. Western blot assay shows that the expression of vascular endothelial growth factor（VEGF） and that of Survivin were reduced in the cells with the plasma vector expressing specific RNAi that targets human STAT3. These results demonstrate that STAT3 involved in the invasion and migration of SK-OV-3 regulates the expression of VEGF and Survivin. In addition, VEGF and Survivin could play an important role in ovarian cancer growth and metastasis.

Edaravone protects against oxygen-glucose-serum deprivation/restoration-induced apoptosis in spinal cord astrocytes by inhibiting integrated stress response

We previously found that oxygen-glucose-serum deprivation/restoration（OGSD/R） induces apoptosis of spinal cord astrocytes, possibly via caspase-12 and the integrated stress response, which involves protein kinase R-like endoplasmic reticulum kinase（PERK）, eukaryotic initiation factor 2-alpha（eIF2α） and activating transcription factor 4（ATF4）. We hypothesized that edaravone, a low molecular weight, lipophilic free radical scavenger, would reduce OGSD/R-induced apoptosis of spinal cord astrocytes. To test this, we established primary cultures of rat astrocytes, and exposed them to 8 hours/6 hours of OGSD/R with or without edaravone（0.1, 1, 10, 100 μM） treatment. We found that 100 μM of edaravone significantly suppressed astrocyte apoptosis and inhibited the release of reactive oxygen species. It also inhibited the activation of caspase-12 and caspase-3, and reduced the expression of homologous CCAAT/enhancer binding protein, phosphorylated（p）-PERK, p-eIF2α, and ATF4. These results point to a new use of an established drug in the prevention of OGSD/R-mediated spinal cord astrocyte apoptosis via the integrated stress response.