Noninvasive delivery of siRNA into the epidermis by iontophoresis using an atopic dermatitis-like model rat.

Topical application of siRNA to the skin should be an effective treatment for serious skin disorders, such as atopic dermatitis. However, it is difficult to introduce hydrophilic macromolecules, including siRNA, into the skin by conventional methods. For efficient delivery of siRNA, we examined an iontophoretic technique, since it is suitable for the delivery of charged molecules. Naked siRNA effectively accumulated in the epidermis (and not in the dermis) after iontophoretic delivery. In contrast, siRNA did not penetrate tape-stripped skin by passive diffusion. In a rat model of atopic dermatitis, skin was sensitized with ovalbumin to stimulate IL-10 mRNA expression as observed in skin lesions. Iontophoretic delivery of anti-IL-10 siRNA significantly reduced (73%) the level of IL-10 mRNA. In conclusion, we successfully delivered naked siRNA into the epidermis and concomitantly suppressed the expression of an endogenous immuno-regulatory cytokine.

Effects of Carboxylic Acids on the Crystallization of Calcium Carbonate.

The effects of seven carboxylic acids, i.e., acrylic acid, maleic acid, tartaric acid, malic acid, succinic acid, and citric acid, on CaCO(3) crystallization were studied using the unseeded pH-drift method along with a light-scattering technique. Experiments were started by mixing solutions of CaCl(2) and NaHCO(3) in the presence or absence of additives. The crystallization was studied by recording the decrease in pH resulting from the reaction Ca(2+)+HCO(3)(-)-->CaCO(3)+H(+). A given amount of carboxylic acid was added to the solution of CaCl(2) or NaHCO(3) before mixing the reactants. The pH profiles obtained in the case of the CaCl(2) solution containing an additive were similar to those for the NaHCO(3) solution containing one, and when an additive was added after the onset of crystallization, the growth of CaCO(3) immediately stopped. The light-scattering observations, in all cases, indicated that CaCO(3) nucleation occurred at 10-20 s after mixing of the reactants. The results indicated that the nucleation of CaCO(3) was not influenced by the presence of carboxylic acids, but CaCO(3) crystal growth was reduced by their adsorption to the surface of the CaCO(3) crystals. These phenomena were explained by assuming a stronger affinity of the carboxylic acids for CaCO(3) particles than for the free Ca(2+) ions in solution. The crystallization of CaCO(3) in the presence of additives was divided into three stages: nucleation, growth incubation, and growth periods. Copyright 2001 Academic Press.

Inhibitory effects of aminoglycosides on renal protein phosphorylation by protein kinase C.

Aminoglycosides such as neomycin are commonly prescribed antibiotics; however, there is associated serious damage to the kidney. We examined the effect of aminoglycoside antibiotics on renal protein phosphorylation and found that neomycin selectively inhibited Ca++-activated, phospholipid-dependent phosphorylation of 88-kDa protein in cell lysates of the rabbit kidney. Fifty percent inhibition of phosphorylation of this protein occurred with 5 X 10(-5) to 1 X 10(-4) M neomycin. In living PtK2 cells, neomycin dose-dependently inhibited 12-O-tetradecanoyl-phorbol-13-acetate-induced phosphorylation of 88 K Da protein. This drug also inhibited phosphorylation of exogenous protein catalyzed by protein kinase C, isolated from rabbit kidney in vitro. In contrast, neomycin had little or no inhibitory effect on cyclic GMP-dependent protein kinase, cyclic AMP-dependent protein kinase, casein kinase I, casein kinase II and Ca++-calmodulin-dependent myosin light chain kinase. Whereas activity of protein kinase C was inhibited 65% by neomycin (0.1 mM) at pH 5 to 7, inhibition decreases to 33% at pH 8 and to zero at pH 9. The potencies of a series of aminoglycoside antibiotics to inhibit the kinase agreed well with number of ionizable amino groups of compounds (gamma = 0.99) and this also approximates their known nephrotoxic potential; amikacin less than or equal to kanamycin less than gentamycin less than or equal to tobramycin less than neomycin. As aminoglycoside antibiotics present in the kidney after administration of toxicological doses (10(-2) M) will inhibit the effects of protein kinase C, the aminoglycoside antibiotics-induced nephrotoxicity is discussed in relation to inhibition of intracellular protein kinase C.