The high toxicity of clostridial neurotoxins primarily results from their specific binding and uptake into neurons. At motor neurons, the seven botulinum neurotoxin serotypes A–G (BoNT/A–G) inhibit acetylcholine release, leading to flaccid paralysis, while tetanus neurotoxin blocks neurotransmitter release in inhibitory neurons, resulting in spastic paralysis. Uptake of BoNT/A, B, E and G requires a dual interaction with gangliosides and the synaptic vesicle (SV) proteins synaptotagmin or SV2, whereas little is known about the entry mechanisms of the remaining serotypes. Here, we demonstrate that BoNT/F as wells depends on the presence of gangliosides, by employing phrenic nerve hemidiaphragm preparations derived from mice expressing GM3, GM2, GM1 and GD1a or only GM3. Subsequent site‐directed mutagenesis based on homology models identified the ganglioside binding site at a conserved location in BoNT/E and F. Using the mice phrenic nerve hemidiaphragm assay as a physiological model system, cross‐competition of full‐length neurotoxin binding by recombinant binding fragments, plus accelerated neurotoxin uptake upon increased electrical stimulation, indicate that BoNT/F employs SV2 as protein receptor, whereas BoNT/C and D utilise different SV receptor structures. The co‐precipitation of SV2A, B and C from Triton‐solubilised SVs by BoNT/F underlines this conclusion.

The main pathogenic feature of preeclampsia is maternal endothelial dysfunction that results from impaired angiogenesis and reduced endothelial repair capacity. In addition, preeclampsia risk is associated with vitamin D deficiency. We hypothesized that vitamin D3 stimulates proangiogenic properties of endothelial colony-forming cells (ECFCs). ECFCs were obtained and cultured from cord blood and characterized by immunocytochemistry and flow cytometry. Proliferation, total length of tubule formation on Matrigel, expression of VEGF mRNA, and pro-matrix metalloproteinases (MMP)-2 activity were assessed after treatment of ECFCs with vitamin D 3. Specificity of the observed effects was tested by blocking the vitamin D receptor (VDR) or the VEGF signaling pathway. ECFCs treated with 10 nM vitamin D3 showed a 1.27 times higher tubule formation compared with vehicle-treated controls (1.27 Ϯ 0.19) as well as a 1.36 times higher proliferation rate (1.36 Ϯ 0.06). Vitamin D3 induced pro-MMP-2 activity (1.29 Ϯ 0.17) and VEGF mRNA levels (1.74 Ϯ 0.73) in ECFCs. VDR blocking by pyridoxal-5-phosphate (0.73 Ϯ 0.19) or small interfering RNA (0.75 Ϯ 0.17) and VEGF inhibition by Su5416 (0.56 Ϯ 0.16) or soluble fms-like tyrosine kinase-1 (0.7 Ϯ 0.14) reduced tubule formation and pro-MMP-2 activity (pyridoxal-5-phosphate: 0.84 Ϯ 0.09; Su5416: 0.79 Ϯ 0.11; or sFlt: 0.88 Ϯ 0.13). This effect was neutralized by vitamin D3. Consequently, vitamin D3 significantly promoted angiogenesis in ECFCs in vitro possibly due to an increase in VEGF expression and pro-MMP-2 activity. Since angiogenesis is a crucial feature in the pathophysiology of preeclampsia these findings could explain the positive influence of vitamin D3 in reducing preeclampsia risk. vitamin D; preeclampsia; ECFC; angiogenesis; VEGF VITAMIN D, PRIMARILY KNOWN for its important role in calcium homeostasis and bone metabolism, influences the cardiovascular system through unclear mechanisms (33). Vitamin D deficiency is associated with increased all-cause and cardiovascular disease mortality, coronary heart disease, and various cardiovascular risk factors (33).Preeclampsia, a pregnancy-specific disorder that affects 3-7% of all pregnancies, is a major cause of maternal and fetal morbidity and mortality (43) and is associated with an increased risk for cardiovascular events later in life (6). Endothelial dysfunction underlies the hypertension, proteinuria, and multiorgan damage that occur during preeclampsia. The mechanisms that contribute to the disturbed endothelial homeostasis in the pathophysiology of preeclampsia remain unclear (41,46). Compared with normal pregnancies, preeclampsia is characterized by marked changes in vitamin D and calcium metabolism (3). Epidemiological studies have demonstrated an association between low maternal vitamin D levels and the incidence of preeclampsia (23, 27) and suggest vitamin D deficiency to be an independent risk factor for the development of preeclampsia (7). Moreover, vitamin D supplementation studies also showed protective effects on pr...

BackgroundPlacental hypoxia is a result of abnormal and shallow trophoblast invasion and involved in the pathophysiology of preeclampsia. Hypoxia increases extracellular adenosine levels and plays an important role in the regulation of angiogenesis, proliferation, vascular tone, endothelial permeability and inflammation. It was shown that adenosine concentrations are higher in preeclamptic patients. We tested the hypothesis that hypoxia and A2B adenosine receptor activation influence cyclic adenosine monophosphate (cAMP) production, proliferation, invasion and cAMP-PKA-CREB signaling in trophoblast cells (HTR-8/SVneo).MethodsHTR-8/SVneo and human uterine microvascular endothelial cells (HUtMVEC) were used as model for experiments. We employed a cAMP assay, invasion assay, proliferation, RT-PCR and Western Blot. Statistical analyses were performed with ANOVA, Kruskal-Wallis-, Wilcoxon signed rank- or Mann–Whitney Test, as appropriate.ResultsHypoxia (2% O2) in comparison to normoxia (21% O2) led to increased A2B mRNA levels (1.21 ± 0.06 fold, 1 h 2% O2; 1.66 ± 0.2 fold, 4 h 2% O2 and 1.2 ± 0.04 fold, 24 h 2% O2). A2B adenosine receptor activation (NECA) stimulated trophoblast proliferation at 2% O2 (1.27 ± 0.06 fold) and 8% O2 (1.17 ± 0.07 fold) after 24 h and at 2% O2 (1.22 ± 0.05 fold), 8% O2 (1.23 ± 0.09 fold) and 21% O2 (1.15 ± 0.04 fold) after 48 h of incubation. Trophoblast invasion into an endothelial monolayer was significantly expanded by activation of the receptor (NECA) at 8% O2 (1.20 ± 0.07 fold) and 21% O2 (1.22 ± 0.006 fold). A2B adenosine receptor stimulation (NECA) additionally led to increased CREB phosphorylation in trophoblast cells at 2% O2 (2.13 ± 0.45 fold), 8% O2 (1.55 ± 0.13 fold) and 21% O2 (1.71 ± 0.34 fold). Blocking of CREB signaling resulted in reduced proliferation and CREB phosphorylation.ConclusionThese data expand the recent knowledge regarding the role of adenosine receptor A2B in human placental development, and may provide insight in mechanisms associated with pregnancy complications linked to impaired trophoblast invasion such as preeclampsia.

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