Practical application of cellular bioenergetics to the care of aged skin.

In human skin fibroblasts in vitro, procollagen-1 and NAD(+)/NADH were reduced in three strains of adult fibroblasts compared with neonatal fibroblasts. The levels of both procollagen-1 and NAD(+)/NADH were increased in the adult fibroblasts by treatment for 24 (NAD energy) or 48 h (procollagen-1) with a complex containing niacinamide, Pal-KTTKS peptide and an olive oil fatty acid derivative (Olivem(®)), especially in combination with a natural extract from dill (Lys'lastine V(®)). In one of the adult fibroblast strains evaluated, these changes in procollagen-1 and NAD(+)/NADH in response to the complex of bioactives were in parallel with increased expression of mRNA biomarkers related primarily to dermal matrix and basement membrane structure, including COL1A1, COL3A1, COL5A1, COL14A1, ELN and LOXL2, in addition to SOD2, NAMPT and TGFBR3; MMP1 was decreased in expression. In general, these mRNA biomarker effects were maintained or boosted by the addition of Lys'lastine V, particularly at 1%, and were similar to the fold changes in mRNA expression in neonatal compared with adult fibroblasts. These results indicate that the complex of niacinamide, Pal-KTTKS and Olivem, especially with addition of Lys'lastine V, increases the NAD(+)/NADH bioenergy level of adult skin fibroblasts in parallel with increased expression of skin structure biomarkers in vitro to levels similar to those in younger fibroblasts. Thus, niacinamide, Pal-KTTKS, Olivem and Lys'lastine V are promising bioactive candidates for inclusion in cosmetic formulations.

Hepatic expression of ErbB3 is repressed by insulin in a pathway sensitive to PI-3 kinase inhibitors.

ErbB3 is an epidermal growth factor receptor-related type I tyrosine kinase receptor capable, in conjunction with ErbB2 or epidermal growth factor receptor, of transmitting proliferative and differentiative signals in a variety of cell types. We previously showed that ErbB3 messenger RNA and protein increase in cultured hepatocytes during the first 12 h in culture, as does the binding of heregulin beta1, a ligand for ErbB3. Insulin inhibits the increase in heregulin beta1 binding, as well as the increase in ErbB3 messenger RNA and protein. Two models of insulin deficiency in vivo (diabetes and fasting) demonstrated elevated levels of hepatic ErbB3 protein, strengthening the relevance of our observations in vitro. Using chemical activators or antagonists, we sought to identify the signaling pathways that link insulin to ErbB3 expression. The PI-3 kinase inhibitors, wortmannin and LY294002, completely blocked the inhibition of ErbB3 protein expression by insulin, suggesting a role for PI-3 kinase in the regulation of this growth factor receptor. Rapamycin, an inhibitor of p70 S6 kinase, an enzyme downstream of PI-3 kinase, failed to block the effect of insulin on ErbB3 expression. These results suggest a complex regulatory paradign for ErbB3 that includes PI-3 kinase and may be linked, via insulin, to the metabolic status of the animal.

Insulin regulates heregulin binding and ErbB3 expression in rat hepatocytes.

The heregulin-ErbB system of ligands and receptors are newly described epidermal growth factor (EGF) and EGF receptor-related proteins that regulate growth, differentiation, and gene expression in numerous cell types. This study describes a receptor for heregulin beta-1 (HRGbeta1) on cultured rat hepatocytes and an inhibitory influence of insulin on HRGbeta1 binding. HRGbeta1 (30 nM) stimulated DNA synthesis 2-fold and was not augmented by insulin as is the case with EGF receptor ligands. A labeled peptide corresponding to the EGF domain of HRGbeta1 bound to a single population of 19,600 +/- 1,800 binding sites/cell with a Kd of 360 +/- 22 pM. Cross-linking experiments showed binding of HRGbeta1 to ErbB3 but not ErbB2 or ErbB4. HRGbeta1 induced phosphorylation of ErbB3 and decreased ErbB3 protein levels, suggesting that HRGbeta1 activates signaling through the ErbB3 receptor and influences receptor trafficking. Following plating, [125I]HRGbeta1 binding and ErbB3 protein levels increased 8- and 3-fold, respectively, over the first 12 h in culture. These increases required de novo protein synthesis and were inhibited with 50 nM insulin resulting in 3500 binding sites with a Kd of 265 pM. These data suggest that the heregulin-ErbB system can regulate liver functions and may be linked to the metabolic and nutritional status of the animal.

Effects of nimodipine and dexamethasone on low-level CO2 laser-induced release of 51chromium from canine 2C5 gliosarcoma cells.

Low-energy penumbral irradiation of surgical lasers may produce undesirable effects on surrounding tissues. This study used a 51Cr cell labeling technique to determine if gliosarcoma cells could be therapeutically protected prior to their exposure to low-power laser irradiation. Canine 2C5 gliosarcoma cells with intracellular 51Cr were treated with nimodipine and/or dexamethasone and then exposed to low-power levels of CO2 laser. The 51Cr was released from the cells in a dose-dependent fashion following exposure to laser energy. Correlative analysis of the data indicated that a strong direct relationship between laser fluence and 51Cr release did exist for controls and drug-treated groups with coefficients of correlation r > or = +0.90 and coefficients of determination r2 > or = 0.82. However, comparison of the data from the drug-treated and control groups found that there was no significant difference between them (P > .05). Therefore, no protective or detrimental effects were observed with the use of nimodipine and/or dexamethasone on the gliosarcoma cells as tested in this system. Further investigation is necessary in order to define the mechanisms by which low-power level lasers affect these cells. These effects do not appear to be mediated through localization of mechanisms to the cell membranes or their constituent Ca2+ channels.

Low-level CO2 laser-induced release of 51chromium from canine 2C5 gliosarcoma cells.

Recently, interest has grown in the area of low-power laser effects upon tissues. We used a 51Cr cell labeling technique with glioma tissue to better understand these effects. Canine 2C5 gliosarcoma cells with intracellular 51Cr were exposed to CO2 laser in the range of 0.2 to 3.0 J/cm2. Correlative analysis of the data indicated that there is a strong direct relationship between laser fluence and the percent of total intracellular 51Cr released from the glioma cells with a coefficient of correlation (r) of +0.93. The calculated standard error of the correlation coefficient was +/- 0.06 and the coefficient of determination (r2) was 0.86. These results indicate that the 51Cr cell labeling technique is a useful method for quantifying the low-power laser effects on the integrity of the cell membrane of gliosarcoma cells in vitro. However, further investigation is needed to clarify the specific mechanisms by which the CO2 laser induces changes upon these cells.