Mechanistic studies on percutaneous penetration enhancement by N-(4-halobenzoyl)-S,S-dimethyliminosulfuranes.

Halogen-substituted iminosulfuranes are transdermal penetration enhancers (TPEs) in permeation studies using hairless mouse or human cadaver skin. The interaction of N--(4--R-benzoyl)-S,S-dimethyliminosulfuranes 1--4, where R=H, Cl, Br, and I, with l-alpha-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) has been studied using differential scanning calorimetry, isothermal titration calorimetry, nuclear Overhauser effect spectroscopy (NOESY), and NMR spectroscopy, and by calculation of the iminosulfurane polarizabilities in order to elucidate the molecular basis of the TPE activity. The active compounds reduce the melting temperature of the gel-to-liquid-crystal phase transition and induce multiple components in the transition excess heat capacity profile. The partitioning of the bromo derivative 3, the most active compound, into DMPC is unique in that 3 may be trapped in the bilayer, affording an enhanced residence time and a reason for its high TPE activity. The entropy decrease associated with the transfer of 3 to the bilayer is much lower than that for the other compounds, indicating that 3 occupies or induces sites that afford it considerable local motional freedom. Correlations between the iminosulfurane TPE activities, the partition coefficients, and NOESY crosspeak volume were observed. Molecular polarizabilities are not consistent with a TPE mode of action involving interaction of these agents with protein side chains.

Lovastatin induces apoptosis in a primitive neuroectodermal tumor cell line in association with RB down-regulation and loss of the G1 checkpoint.

To develop a new approach to the treatment of primitive neuroectodermal tumors we evaluated the effect of the HMG-CoA reductase inhibitor lovastatin on the Ewing's sarcoma cell line CHP-100. Lovastatin induced neural morphology and markers including neuron-specific enolase and neurofilament protein. The acquisition of neural morphology required new mRNA synthesis, and cDNA microarray analysis confirmed that lovastatin altered the program of gene expression. After morphologic differentiation the cells underwent rapidly progressive apoptosis. In normal development of neuronal progenitors, differentiation signals trigger p21WAF1 accumulation, RB hypophosphorylation, enhanced RB-E2F-1 association, and G1 arrest, and these events have been shown to protect from apoptosis. In contrast, in the Ewing's sarcoma cells lovastatin triggered differentiation without causing cell cycle arrest: p21WAF1 was not induced, RB remained hyperphosphorylated, and RB protein expression and RB-E2F-1 association were markedly downregulated, suggesting that loss of an RB-regulated G1 checkpoint promoted apoptosis. Consistent with this hypothesis, adenoviral p21WAF1 decreased DNA synthesis and partially protected from lovastatin-induced cytotoxicity. The data demonstrate a new model for examining the genetic regulation of cell fate in a neural progenitor tumor and suggest a new approach to the treatment of this neoplasm.

Posttranslational regulation of the retinoblastoma gene family member p107 by calpain protease.

The retinoblastoma protein plays a critical role in regulating the G1/S transition. Less is known about the function and regulation of the homologous pocket protein p107. Here we present evidence for the posttranslational regulation of p107 by the Ca2+-activated protease calpain. Three negative growth regulators, the HMG-CoA reductase inhibitor lovastatin, the antimetabolite 5-fluorouracil, and the cyclic nucleotide dibutyryl cAMP were found to induce cell type-specific loss of p107 protein which was reversible by the calpain inhibitor leucyl-leucyl-norleucinal but not by the serine protease inhibitor phenylmethylsulfonylfluoride, caspase inhibitors, or lactacystin, a specific inhibitor of the 26S proteasome. Purified calpain induced Ca2+-dependent p107 degradation in cell lysates. Transient expression of the specific calpain inhibitor calpastatin blocked the loss of p107 protein in lovastatin-treated cells, and the half-life of p107 was markedly lengthened in lovastatian-treated cells stably transfected with a calpastatin expression vector versus cells transfected with vector alone. The data presented here demonstrate down-regulation of p107 protein in response to various antiproliferative signals, and implicate calpain in p107 posttranslational regulation.

Determinants of diet glycemic index calculated retrospectively from diet records of 342 individuals with non-insulin-dependent diabetes mellitus.

Controlled trials have shown that a diet with a low glycemic index improves blood glucose and lipid control in patients with diabetes. To study the distribution and determinants of diet glycemic index, we obtained two 3-d diet records from 342 free-living subjects with non-insulin-dependent diabetes. Mean +/- SD 24-h intakes were as follows: energy, 7170 +/- 1890 kJ; fat, 33.6 +/- 6.5% of energy; protein, 20.1 +/- 3.2% of energy; available carbohydrate, 45.3 +/- 7.2% of energy; and dietary fiber, 17.2 +/- 6.4 g. Diet glycemic index values (85.4 +/- 4.55, range, 70-97.8) were normally distributed. Diet glycemic index was inversely associated with intake of simple sugars, whether expressed in grams (r = -0.426), percent of energy (r = -0.446), or percent of carbohydrate (r = -0.453, P < 0.001). By step-wise-multiple-linear regression, grams carbohydrate and percent protein were also independently related to diet glycemic index. Differences in diet glycemic index between men and women, and between subjects on different types of diabetes therapy were explained by differences in intake of simple sugars.