FGF-1-dependent proliferative and migratory responses are impaired in senescent human umbilical vein endothelial cells and correlate with the inability to signal tyrosine phosphorylation of fibroblast growth factor receptor-1 substrates

Regulation of astroglial-derived dopaminergic neurotrophic factors by interleukin-1 beta in the striatum of young and middle-aged mice

Interleukin-1 beta (IL-1 beta) can induce dopaminergic axonal sprouting in the denervated striatum of parkinsonian animals. In order to determine whether IL-1 beta effects on dopaminergic axonal sprouting are mediated by the induction of astroglial-derived dopaminergic neurotrophic factors, effects of IL-1 beta treatment on acidic and basic fibroblast growth factor (aFGF and bFGF) and glial cell line-derived growth factor (GDNF) gene expression were examined in primary striatal astrocyte cultures and after in vivo administration. We found a selective induction of bFGF mRNA synthesis but not aFGF or GDNF mRNA after IL-1 beta treatment both in vitro and in vivo. This suggests that bFGF may be the putative endogenous dopaminergic neurotrophic factor mediating lesion-induced plasticity of dopamine neurons. In addition, to determine why recovery from injury becomes reduced with age, we examined whether there was an aging-associated decline in the ability of IL-1 beta to induce the synthesis of neurotrophic factors in middle-aged animals compared to young mice. Interestingly, IL-1 beta stimulated a greater induction in bFGF mRNA levels in the middle-aged mice compared to young mice. These results suggest that the regulation of bFGF and possibly its receptor signaling efficacy may vary as the brain ages.

Activation of pp60c-src is necessary for human vascular smooth muscle cell migration

BACKGROUND

The most widely distributed nonreceptor tyrosine kinase is pp60c-src (src), yet the role of this intracellular signaling protein in cell migration has not been defined. Given that smooth muscle cell (SMC) migration is essential for the development of intimal hyperplasia, we investigated the importance of src in locomotion of human vascular SMC.

METHODS

SMC migration was evaluated using a microchemotaxis chamber assay and videomicroscopy. Src kinase activity was determined by measuring phosphorylation of a synthetic derivative of p34cdc2, a specific substrate for src. Blocking antibodies to src were introduced using a cytoplasmic microinjection technique.

RESULTS

Stimulation of SMC with platelet-derived growth factor (PDGF)-BB and AB resulted in an increase in src activation, whereas PDGF-AA did not consistently enhance src activity. These findings correlated with the ability of the PDGF isotypes to stimulate SMC chemotaxis; PDGF-BB and AB produced 7.4 +/- 0.3- and 5.3 +/- 0.5-fold increases in SMC chemotaxis, whereas PDGF-AA inhibited chemotaxis. SMC migration in response to PDGF-BB and serum was significantly inhibited by intracellular injection of a blocking antibody.

CONCLUSIONS

Our findings reveal an association between agonist-induced src activation and chemotaxis. Moreover, an antibody that inhibits src activation dramatically inhibits migration of individual SMC. We conclude that activation of src is necessary for SMC migration. Because of its importance in SMC migration, either molecular or pharmacologic inhibitors of src may be useful in the control of intimal hyperplasia.

Heterogeneity of endothelial cells. Specific markers

During embryonic development, endothelial cells differentiate from a common precursor called angioblast and acquire organ-specific properties. One of the important determinants of endothelial cell differentiation is the local environment, and especially the interaction with surrounding cells. This interaction may occur through the release of soluble cytokines, cell-to-cell adhesion and communication, and the synthesis of matrix proteins on which the endothelium adheres and grows. The acquisition and maintenance of specialized properties by endothelial cells is important in the functional homeostasis of the different organs. For instance, in the brain, alteration of the blood-brain barrier properties may have important consequences on brain functional integrity. One of the major limitations to the study of endothelial cell heterogeneity is the fact that these cells are still difficult to isolate and culture from the microcirculation of different organs, and once in culture, they tend to lose their specialized properties. This finding suggests that we have to develop new culture systems, which possibly include coculture with other cell types. An important issue is to develop tools that can help in recognizing endothelial cells and their differentiated phenotype both in vivo and in tissue culture. In this review we give a short overview of the differentiated properties of the endothelium, considering a few examples of highly specialized endothelial cells, such as the brain or bone marrow microcirculation or high endothelial venules. We made a particular effort to list the most common markers of endothelial cell phenotypes. These molecules and related antibodies may be valuable tools for endothelial cell isolation and characterization.

Integrin beta4 is involved in apoptotic signal transduction in endothelial cells

To clarify the signal transduction in vascular endothelial cells (VEC) apoptosis induced by deprivation of FGF and serum, we investigated the function of integrin beta4 by using the monoclonal antibody (mAb) of this integrin. We added anti-beta 4 integrin mAb at the concentration of 5 microg/ml to the cells deprived of FGF and serum, apoptosis of these cells were completely inhibited 24 h after the treatment. Furthermore we plated the cells onto untreated bacterial culture plates on which the cells cannot adhere and spread in MCDB medium without FGF and serum; however, when anti-beta 4 integrin mAb was present at 5 microg/ml in the seeding medium, the cells rapidly adhered and spread. Our results first demonstrated that integrin beta4 participated in apoptotic signaling in VEC, and our findings indicate that hemidesmosome structures and keratin filament system might be important in regulation of apoptotic signaling.