Human Vascular Microphysiological System for in vitro Drug Screening

In vitro human tissue engineered human blood vessels (TEBV) that exhibit vasoactivity can be used to test human toxicity of pharmaceutical drug candidates prior to pre-clinical animal studies. TEBVs with 400–800 μM diameters were made by embedding human neonatal dermal fibroblasts or human bone marrow-derived mesenchymal stem cells in dense collagen gel. TEBVs were mechanically strong enough to allow endothelialization and perfusion at physiological shear stresses within 3 hours after fabrication. After 1 week of perfusion, TEBVs exhibited endothelial release of nitric oxide, phenylephrine-induced vasoconstriction, and acetylcholine-induced vasodilation, all of which were maintained up to 5 weeks in culture. Vasodilation was blocked with the addition of the nitric oxide synthase inhibitor L-N^G-Nitroarginine methyl ester (L-NAME). TEBVs elicited reversible activation to acute inflammatory stimulation by TNF-α which had a transient effect upon acetylcholine-induced relaxation, and exhibited dose-dependent vasodilation in response to caffeine and theophylline. Treatment of TEBVs with 1 μM lovastatin for three days prior to addition of Tumor necrosis factor – α (TNF-α) blocked the injury response and maintained vasodilation. These results indicate the potential to develop a rapidly-producible, endothelialized TEBV for microphysiological systems capable of producing physiological responses to both pharmaceutical and immunological stimuli.

Oestrogens as modulators of neuronal signalosomes and brain lipid homeostasis related to protection against neurodegeneration

Oestrogens trigger several pathways at the plasma membrane that exert beneficial actions against neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. Part of these actions takes place in lipid rafts, which are membrane domains with a singular protein and lipid composition. These microdomains also represent a preferential site for signalling protein complexes, or signalosomes. A plausible hypothesis is that the dynamic interaction of signalosomes with different extracellular ligands may be at the basis of neuronal maintenance against different neuropathologies. Oestrogen receptors are localised in neuronal lipid rafts, taking part of macromolecular complexes together with a voltage-dependent anion channel (VDAC), and other molecules. Oestradiol binding to its receptor at this level enhances neuroprotection against amyloid-β degeneration through the activation of different signal transduction pathways, including VDAC gating modulation. Moreover, part of the stability and functionality of signalling platforms lays on the distribution of lipid hallmarks in these microstructures, which modulate membrane physicochemical properties, thus favouring molecular interactions. Interestingly, recent findings indicate a potential role of oestrogens in the preservation of neuronal membrane physiology related to lipid homeostasis. Thus, oestrogens and docosahexaenoic acid may act synergistically to stabilise brain lipid structure by regulating neuronal lipid biosynthetic pathways, suggesting that part of the neuroprotective effects elicited by oestrogens occur through mechanisms aimed at preserving lipid homeostasis. Overall, oestrogen mechanisms of neuroprotection may occur not only by its interaction with neuronal protein targets through nongenomic and genomic mechanisms, but also through its participation in membrane architecture stabilisation via 'lipostatic' mechanisms.

1,25-Dihydroxyvitamin D3 protects HL60 cells against apoptosis but down-regulates the expression of the bcl-2 gene

Exposure of myeloid leukemia cells to analogs of vitamin D results in monocytic-like maturation of several variants of these cells. We report here that brief treatment of HL60 cells with differentiation-inducing concentrations of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) makes these cells resistant to cell death by apoptosis. Resistance was studied by using the calcium inophore A23187 and the cancer chemotherapeutic drugs 1-beta-D-arabinocytosine and etoposide. Apoptosis was detected by the characteristic morphology under light microscopic examination, presence of DNA "ladders" on agarose gel electrophoresis, DNA fragmentation by filter elution assay, and the "apoptotic index" obtained by comparison of damage to mitochondrial and nuclear genes on Southern blots. The protective effect of 1,25(OH)2D3 treatment was apparent before the phenotypic evidence of differentiation and before altered traverse of the cell cycle could be detected. Northern and Western blot analysis showed that the expression of bcl-2 proto-oncogene was rapidly reduced by 1,25(OH)2D3, which excludes the involvement of this gene in the protective effect. The rapidity of the protective effect of 1,25(OH)2D3 is consistent with the hypothesis that the activation of the monocytic differentiation program is sufficient to interfere with programs that lead to cell death by apoptosis.