M C S Armelin

The interaction of small cationic vesicles composed of dioctadecyldimethylammonium bromide (DODAB) with normal versus transformed mouse fibroblasts is described using cell microelectrophoresis, turbidimetry, and cell viability assays over a wide range of DODAB concentrations (10-7−10-3 M). Normal and transformed cells (104 cells/mL) attain a point of zero charge at, respectively, 18.0 and 1.6 μM DODAB. Further increasing DODAB concentration (C) generates positively charged cells. At 105 cells/mL and C ≥ 50 μM, DODAB induces cell−cell adhesion. For transformed and normal cells, peak adhesion occurs at 100 and 1000 μM DODAB, respectively. Upon 0.5 h interaction time with 100 μM DODAB, at 104 cells/mL, 20% of cell death is obtained for normal cells whereas transformed cells remain unaffected. Transformed cells have a higher affinity for DODAB vesicles than their normal counterparts but are more resistant to DODAB-induced cell death. The results indicate that DODAB vesicles interact with cells with very high affinity at low ionic strength and are not toxic below 1 mM, suggesting that they might successfully deliver oppositely charged proteins or DNA strands to cells. These results may be of importance for liposome-mediated processes currently being used for drug or gene delivery to cells.

We report the results of an extensive kinetic analysis of the effects of ACTH, cAMP derivatives (dibutyryl cAMP and 8-bromo-cAMP) and phorbol ester (phorbol-12-myristate-13-acetate) on the expression of fos and jun gene family members at the mRNA (Northern hybridization) and protein levels (immunoprecipitation and indirect immunofluorescence) in the mouse Y-1 adrenocortical cell line. FOS and JUN proteins are induced by ACTH independently of cell cycle stage. c-Fos, fos-B, fra-1, fra-2, c-jun, and jun-B genes are induced by ACTH, the kinetic profiles for mRNAs and respective protein products being similar, except for a 1-h protein delay. Jun-D mRNA is an exception, being constitutively expressed. However, JUN D protein is induced by ACTH. phorbol-12-myristate-13-acetate closely mimics these inductive effects of ACTH. On the other hand, cAMP derivatives are not effective in inducing the fos and jun genes, except for fra-2 mRNA, JUN D protein, and to some extent JUN B protein. Clearly, ACTH is endowed with the versatile capability of modulating fos and jun gene expression, suggesting that AP-1 transcription factors play a role in ACTH mechanisms of action. ACTH receptors are likely to activate signaling routes other than the classical cAMP/protein kinase A in order to induce FOS and JUN proteins.

We have shown that glucocorticoids reversibly change the growth control of rat C6 glioma cells from a transformed to a normal pattern. Here we report that the glucocorticoid hormone hydrocortisone (Hy) modulates structure and function of cell surface and cytoskeleton. The hormone is shown to cause: (a) increased flattening and adhesion to solid substrates and to fibrin layers, (b) inhibition of the cell shape change triggered by catecholamines and cAMP, (c) extensive fibronectin deposition on normally fibronectinless cells' surface, and (d) microtubule rearrangement. Comparison of Hy-hypersensitive and Hy-resistant variants showed that microtubule rearrangements correlate with the growth control change induced by Hy, whereas fibronectin deposition does not.