TNF-? acts to prevent occurrence of malformed fetuses in diabetic mice

Abstract

Aims/hypothesis. Activation of apoptosis in embryos is thought to be a key event in the pathogenesis of diabetes-induced embryopathies such as early embryonic death and inborn structural anomalies. TNF-α can activate apoptotic and anti-apoptotic signalling cascades, indicating its ability to contribute to and counteract diabetes-induced maldevelopment. To investigate how TNF-α regulates the response of embryos to diabetesinduced embryopathic stress, we used streptozotocininduced diabetic TNF-α knockout mice. Materials. To evaluate the reproductive performance, mated diabetic female mice were examined on days 4 and 8 of pregnancy for the presence of blastocysts or embryos in uterine horns. To evaluate the teratogenic effect, the female mice were killed on day 18 of pregnancy and fetuses were examined for gross external anomalies. In addition, apoptotic nuclei were localised by the TUNEL assay and DNA-binding activity of the transcription factor NF-κB was evaluated by electrophoretic mobility shift assay in 10-and 11-day-old embryos respectively. Results. Severely diabetic TNF-α +/+ female mice had a much greater decrease in pregnancy rate but a lower incidence of malformed fetuses in litters than severely diabetic TNF-α −/− female mice. Also, the intensity of excessive apoptosis was higher, but the amount of active NF-κB complexes was lower in malformed TNF-α −/− embryos than in TNF-α +/+ embryos. Conclusions/interpretation. TNF-α contributes to death of peri-implantation embryos and possibly protects postimplantation embryos exposed to diabetes-induced teratogenic stimuli via activation of NF-κB-mediated anti-apoptotic signalling. It seems that TNF-α prevents the birth of malformed offspring in severely diabetic mice. [Diabetologia (2004) 47:132-139] Keywords Diabetes · teratogenic effect · inborn structural anomalies · apoptosis · TNF-α · NF-κB verse effects on early embryos. Thus the amount of TNF-α released into the culture supernatant by uterine explants dissected from diabetic rats at the time of implantation was four times higher than in uterine explants dissected from non-diabetic rats [3]. Blastocysts incubated in media preconditioned with uterine explants from diabetic rats developed less well than those incubated in control media [4]. Finally various studies [5,6,7] showed that the pregnancy rate of chemically induced diabetic mice is lower than in their non-diabetic counterparts. This decrease in pregnancy rate was accompanied by increased expression of TNF-α in uterine cells from the beginning of implantation onwards [8].Other data suggest that TNF-α could be involved in the formation of teratogen-induced structural anomaTumour necrosis factor-α, a multifunctional cytokine, is expressed by uterine, placental and embryonic cells practically at all stages of development [1,2]. In the last decade convincing evidence has been collected that TNF-α plays a role in mediating diabetes-induced ad-

Double-stranded RNA-dependent Protein Kinase Phosphorylation of the α-Subunit of Eukaryotic Translation Initiation Factor 2 Mediates Apoptosis

“…Although TNF␣ receptor signaling is not required for embryonic apoptosis, there are a number of circumstances where TNF␣-induced apoptosis is physiologically important including lipopolysaccharide-mediated apoptosis in the liver (64), hepatotoxicant-induced apoptosis (65), suppression of acute HSV-1 viral infection (66), limitation of T cell number during chronic LCMV viral infection (67), infarction induced myocardial rupture and ventricular dysfunction (68), and death of malformed embryos (69). Adenovirus delivery of TNF␣ induced apoptosis in esophageal cancer cells in a manner that required PKR (70), suggesting the utility of this approach to promote apoptosis in transformed cells.…”

p53 regulates cyclophosphamide teratogenesis by controlling caspases 3, 8, 9 activation and NF-κB DNA binding

“…There is also considerable evidence demonstrating NF-kB as an inducer of cell proliferation in cells exposed to toxic stimuli (Chen et al 2001, Shishodia & Aggarwal 2004. The involvement of NF-kB in regulating the teratogenic response has been suggested by the results of studies with such teratogens as CP (Torchinsky et al 2002(Torchinsky et al , 2003(Torchinsky et al , 2006, alcohol (Acquaah-Mensah et al 2002), thalidomide (Hansen et al 2002), diabetes (Torchinsky et al 2004), and phenytoin (an anticonvulsant drug; Kennedy et al 2004). Finally, considerable evidence has been presently collected suggesting the existence of the mechanisms by which NF-kB and p53 are able to regulate each other's activity (Webster & Perkins 1999, Ryan et al 2000, Pommier et al 2004.…”

TNFalpha in the Pathogenesis of Diabetes-Induced Embryopathies: Functions and Targets

“…Our study also revealed that the pregnancy rate in STZ-induced diabetic TNFα knockout mice was lower than that in non-diabetic females but far higher than that recorded in their TNFα-positive counterparts [23]. The critical outcome of this observation was that the cytokine may be a central component in the mechanisms underlying diabetes-induced death of early embryos.…”

“…death of the pre-or periimplantation stage embryos. To clarify this question, we evaluated the pregnancy rate in STZ-induced diabetic mice on days 4 (the end of the pre-implantation period) and 8 (the end of the implantation period) of pregnancy [23]. We found that the pregnancy rate was identical in diabetic and non-diabetic females tested on day 4, but not on day 8, of pregnancy.…”

“…If TNFα-induced injures in embryos were responsible for early pregnancy loss, then we would observe a significant decrease in the implantation rate in pregnant diabetic females at any time point after completing the implantation period. Although three studies found lower implantation rates [22,31,32], in most studies the rate did not differ from that observed in nondiabetic females [7,10,20,21,23,[33][34][35][36][37][38][39][40][41][42][43]. When blastocysts were exposed to diabetic environments or TNFα, the cellular deficit in these blastocysts was mostly at the expense of the inner cell mass (ICM) -the cells that form the fetus -but not of the trophectoderm (TE) cells that ensure implantation of the blastocyst into the uterine wall [44].…”