Paxillin increases as retinoic acid or vitamin D3 induce HL-60 cell differentiation

Enhancement of synthesis of extracellular matrix proteins on retinoic acid loaded electrospun scaffolds

Electrospinning is a renowned technique for the generation of ultrafine, micro- and nanoscale fibres due to its simplicity, versatility and tunability. Owing to its adaptability to a wide selection of materials and scaffold architectures, electrospun meshes have been developed as biocompatible scaffolds and drug delivery systems for tissue engineering. Here, we developed a drug delivery scaffold by electrospinning poly(ε-caprolactone) (PCL) directly blended with a therapeutic agent, retinoic acid (RA), at different concentrations. The release profile, DNA, and elastin analysis of direct and transwell seeded RA-loaded PCL electrospun scaffolds showed desirable controlled release at 15 kV fabrication, with 0.01% RA as the optimum concentration. The selected 0.01% (w/v) RA-loaded PCL meshes were further analysed using five different seeding cultures to investigate and extensively distinguish the effects of RA release with or without cell contact to the PCL electrospun meshes for cell morphology, proliferation and extracellular matrix (ECM) protein secretion of collagen and elastin. Upon exposure to RA-loaded PCL scaffolds, an increase of human dermal fibroblast (HDF) proliferation was observed. In contrast, human mesenchymal stromal cell (hMSC) cultures showed a decrease in cell proliferation. For both hMSC and HDF cultures, exposure to RA-loaded PCL scaffolds provided a significant increase in elastin production per cell. For collagen expression, a slight increase was measured and was outperformed by the 3D geometry stimulation from PCL scaffolds. In contrast to hMSCs, HDFs showed enhanced stress actin fibres in cultures with RA-loaded PCL scaffolds. Both cell types exhibited more vinculin expression when seeded to RA-loaded PCL scaffolds. Hence, electrospun scaffolds releasing RA in a controlled manner were able to regulate cell proliferation, morphology and ECM secretion, and present an attractive approach for optimizing tissue regeneration.

RARα2 and PML-RAR similarities in the control of basal and retinoic acid induced myeloid maturation of acute myeloid leukemia cells

Treatment of acute promyelocytic leukemia (APL) with all-trans retinoic acid (ATRA) is the first example of targeted therapy. In fact, the oncogenic fusion-protein (PML-RAR) typical of this leukemia contains the retinoid-nuclear-receptor RARα. PML-RAR is responsible for the differentiation block of the leukemic blast. Besides PML-RAR, two endogenous RARα proteins are present in APL blasts, i.e. RARα1 and RARα2. We developed different cell populations characterized by PML-RAR, RARα2 and RARα1 knock-down in the APL-derived NB4 cell-line. Unexpectedly, silencing of PML-RAR and RARα2 results in similar increases in the constitutive expression of several granulocytic differentiation markers. This is accompanied by enhanced expression of the same granulocytic markers upon exposure of the NB4 blasts to ATRA. Silencing of PML-RAR and RARα2 causes also similar perturbations in the whole genome gene-expression profiles of vehicle and ATRA treated NB4 cells. Unlike PML-RAR and RARα2, RARα1 knock-down blocks ATRA-dependent induction of several granulocytic differentiation markers. Many of the effects on myeloid differentiation are confirmed by over-expression of RARα2 in NB4 cells. RARα2 action on myeloid differentiation does not require the presence of PML-RAR, as it is recapitulated also upon knock-down in PML-RAR-negative HL-60 cells. Thus, relative to RARα1, PML-RAR and RARα2 exert opposite effects on APL-cell differentiation. These contrasting actions may be related to the fact that both PML-RAR and RARα2 interact with and inhibit the transcriptional activity of RARα1. The interaction surface is located in the carboxy-terminal domain containing the D/E/F regions and it is influenced by phosphorylation of Ser-369 of RARα1.

Quality indicators increase the reliability of microarray data

Large-scale gene expression profiling with DNA microarrays opens new dimensions to molecular biology but still lacks the overall precision of traditional low-scale techniques. We developed a novel strategy of data processing linking search stringency to quality indicators for efficient detection of low-level, regulated genes. Using retinoid-induced differentiation of NB-4 promyelocytic cells, the variation of expression profiles between biological duplicates was studied and compared with the changes induced by all-trans retinoic acid (atRA) treatment. An analysis of 4320 genes showed that retinoic acid has mainly geneactivating function in NB-4 cells. Treatment with atRA for 18 hours induced metabolic genes that may be associated with cell differentiation and signaling factors triggering later events leading to apoptosis; cytokine genes were among the highest stimulated by atRA. Notably, we identified a regulatory loop inhibiting MYC action: as MYC was downregulated, a cognate repressor of MYC was upregulated.

Enhanced recovery of injury-caused downregulation of paxillin protein by eNOS gene expression in rat carotid artery. Mechanism of NO inhibition of intimal hyperplasia?

Injury-caused dedifferentiation accompanied by proliferation and migration of smooth muscle cells (SMCs) is an important process in the development of the neointima. Nitric oxide (NO) stimulates differentiation and inhibits proliferation and migration of SMCs. Paxillin has been found to play an important role in cell differentiation, and its phosphorylation is regulated by NO in cultured SMCs. However, the regulation of paxillin by NO in the injured artery has not been investigated. Therefore, the aim of this study was to study the effects of in vivo endothelial NO synthase (eNOS) gene transfection on paxillin expression and intimal hyperplasia. A catheter balloon-denuded rat carotid artery was transfected in vivo with the replication-deficient adenovirus Ad5/RSVeNOS or with Ad5/RSVLacZ as the control. Transfected eNOS gene expression was determined by immunostaining, Western blot analysis, and citrulline assay. The expression of paxillin and its associated proteins was determined in injured arteries by Western blot analysis. The area of the intima and the ratio of intima to media were examined on cross sections by morphometry. The data showed that the expression of paxillin was significantly downregulated after injury. eNOS gene transfer showed no effect on paxillin downregulation 2 days after injury but significantly enhanced the recovery of paxillin protein 5 days and 2 weeks after injury. Vinculin, a paxillin-binding protein, was not altered by vascular injury or by eNOS gene transfer. eNOS gene transfer significantly inhibited intimal hyperplasia for up to 4 weeks. These results suggest that NO inhibition of intimal hyperplasia may be mediated by enhancing the recovery of injury-caused downregulation of paxillin.

Polyoma middle T antigen in HL-60 cells accelerates hematopoietic myeloid and monocytic cell differentiation

Expression of the polyoma virus middle T antigen in HL-60 cells accelerates their differentiation in response to both monocytic and granulocytic differentiation-inducing agents. Middle T-expressing cells treated with the granulocytic inducer retinoic acid or the monocytic inducer 1,25-dihydroxy vitamin D3 differentiated 24 h earlier than parental, mock-electroporated, or vector control cell lines. The rapid onset of differentiation correlated with an increase in the cellular level of the middle T protein as well as two known retinoic-acid-inducible markers in HL-60 cells: the paxillin and transglutaminase gene products. The accelerated functional differentiation response and expression of retinoic-acid-inducible markers indicate that middle T played a causal role in differentiation. Thus, expression of the polyoma middle T antigen in HL-60 cells enhanced a variety of molecular changes associated with cellular differentiation.