Manabu Kitazawa

Antioxidants modulate acute solar ultraviolet radiation-induced NF-kappa-B activation in a human keratinocyte cell line

Exposure of the human skin to ultraviolet radiation (UVR) leads to depletion of cutaneous antioxidants, regulation of gene expression and ultimately to the development of skin diseases. Although exogenous supplementation of antioxidants prevents UVR-induced photooxidative damage, their effects on components of cell signalling pathways leading to gene expression has not been clearly established. In the present study, the effects of the antioxidants alpha-lipoic acid, N-acetyl-L-cysteine (NAC) and the flavonoid extract silymarin were investigated for their ability to modulate the activation of the transcription factors nuclear factor kappa B (NF-kappaB) and activator protein-1 (AP-1) in HaCaT keratinocytes after exposure to a solar UV simulator. The activation of NF-kappaB and AP-1 showed a similar temporal pattern: activation was detected 2 h after UV exposure and maintained for up to 8 h. To determine the capacity of activated NF-kappaB to stimulate transcription, NF-kappaB-dependent gene expression was measured using a reporter gene assay. The effects of the antioxidants on NF-kappaB and AP-1 activation were evaluated 3 h after exposure. While a high concentration of NAC could achieve a complete inhibition, low concentrations of alpha-lipoic acid and silymarin were shown to significantly inhibit NF-kappaB activation. In contrast, AP-1 activation was only partially inhibited by NAC, and not at all by alpha-lipoic acid or silymarin. These results indicate that antioxidants such as alpha-lipoic acid and silymarin can efficiently modulate the cellular response to UVR through their selective action on NF-kappaB activation.

Ultraviolet generation at 266 nm in a novel organic nonlinear optical crystal: l‐pyrrolidone‐2‐carboxylic acid

A novel organic nonlinear optical crystal, l‐pyrrolidone‐2‐carboxylic acid (l‐PCA), has been found to be phase matchable for second‐harmonic generation (SHG) and sum‐frequency mixing down to the UV range at room temperature. Tunable radiation down to 266 nm was obtained. The nonlinear coefficient d14 of l‐PCA for the fundamental wavelength of 532 nm was determined to be 0.32 pm/V. The angular acceptance (the full width at half‐maximum) of the type II phase‐matched SHG has also been measured to be 3.03 mrad cm which agreed with the calculated value. This value is much larger than that of the type I phase‐matched SHG in β‐BBO.

Reduction of ultraviolet light-induced oxidative stress by amino acid-based iron chelators.

The generation of free radicals by ultraviolet (UV) light accelerates skin aging, which is known as photoaging. Cutaneous iron catalyzes the generation of free radicals. We designed novel antioxidants that suppressed the iron-catalyzed free radical generation and the ensuing UV-induced damage by mimicking the binding site of iron sequestering proteins. These antioxidants, N-(2-hydroxybenzyl)amino acids, were prepared by condensation of amino acids such as glycine and L-serine with salicylaldehyde and followed by catalytic reduction. The compounds formed a 2:1 complex to iron ion. These amino acid derivatives inhibited the iron-induced hydroxyl radical generation (the Fenton reaction). The compounds also suppressed UV-induced lipid peroxidation in murine dermal fibroblast homogenates. In addition, N-(2-hydroxybenzyl)-L-serine showed protective activity against UV-induced cytotoxicity in murine dermal fibroblasts. Desferrioxamine, a strong iron sequestering compound, was effective in inhibiting the Fenton reaction and the lipid peroxidation, but it was ineffective in protecting against UV-induced cytotoxicity. The results suggest that UV-induced oxidative stress can be reduced by these amino acid derivatives.

Iron chelators may help prevent photoaging.

For years, cosmetic ingredients for anti‐aging treatments have attracted consumers. Skin aging is accelerated by reactive oxygen species (ROS), generated by exposure to solar ultraviolet radiation (UVR), in a process known as photoaging. Because cutaneous iron catalyses ROS generation, it is thought to play a key role in photoaging. Iron is essential to almost all forms of life. However, excess iron is potentially toxic as its catalytic activity induces the generation of ROS. Iron‐catalysed ROS generation is involved in numerous pathological conditions, including cutaneous damage.

NOVEL AMINO ACID CRYSTALS FOR PHASE-MATCHED SECOND-HARMONIC GENERATION : L-PYRROLIDONE-2-CARBOXYLIC ACID

A novel nonlinear optical amino acid derivative, L‐pyrrolidone‐2‐carboxylic acid (L‐PCA), has been studied for the application of UV generation by frequency upconversion of laser radiation. L‐PCA is relatively easy to grow from solution to a large size, typically ∼40×20×20 mm3, by a slow cooling method. This crystal is chemically stable because the crystal lattice is composed of a network of hydrogen‐bonded molecules. L‐PCA has a wide transparency extending to the UV region (the cutoff wavelength is 260 nm) and is therefore a good candidate for the second‐harmonic generation (SHG) of Nd:YAG laser radiation (1064 nm). The nonlinear‐optical coefficient d14 was measured to be 0.22 pm/V, and the measured phase‐matching angles agreed with values calculated using refractive index data. The effective nonlinear optical coefficient deff of the type‐I phase‐matched SHG has also been measured to be 0.20 pm/V. UV generation down to 266 nm was achieved by phase‐matched SHG in L‐PCA crystals.

Protective Effects of an Antioxidant Derived from Serine and Vitamin B6 on Skin Photoaging in Hairless Mice

The generation of reactive oxygen species (ROS) by ultraviolet radiation (UVR) accelerates skin aging, which is known as photoaging. Because cutaneous iron catalyzes ROS generation, sequestering iron by chelating agents is thought to be an effective approach toward preventing photoaging. Previously, N‐(4‐pyridoxylmethylene)‐L‐serine (PYSer) was designed as an antioxidant to suppress iron‐catalyzed ROS generation by its iron‐sequestering activity. In this study, PYSer showed protective effects against skin damage in hairless mice irradiated with ultraviolet B (UV‐B). Topical application of PYSer to the skin significantly delayed and/or decreased the visible wrinkle formation induced by chronic UV‐B irradiation. A histological study indicated that UV‐B‐induced epidermal hypertrophy and lymphocytic infiltration were suppressed by PYSer. Moreover, PYSer showed suppressive activity against the UV‐B‐induced increase in glycosaminoglycans (GAG). These results indicate that PYSer is a promising antioxidant for the prevention of chronic skin photoaging by its iron‐sequestering activity.

Intracellular redox regulation by a cystine derivative suppresses UV-induced NF-κB activation

Nuclear factor (NF)‐κB pathways are influenced by the intracellular reduction–oxidation (redox) balance. While NF‐κB is activated through inhibitor (I)‐κB degradation by oxidative stress, its DNA binding is accelerated in the reduced state. We found that N,N′‐diacetyl‐L‐cystine dimethylester (DACDM) suppressed the UVB‐induced NF‐κB binding activity at a much lower concentration (50–100 μM) than N‐acetyl‐L‐cysteine (NAC, 10–30 mM). While NAC suppressed the I‐κB degradation but not the DNA binding, DACDM prevented the activated NF‐κB from binding DNA, without influencing the I‐κB degradation. These properties of DACDM make it possible to effectively regulate the intracellular redox balance.

Growth behavior of L-pyrrolidone-2-carboxylic acid (L-PCA) single crystals

Abstract Growth conditions to prepare large single crystals of L-pyrrolidone-2-carboxylic acid (L-PCA), a novel nonlinear optical organic material, have been intensively studied with an attempt for fabrication in optical devices. L-PCA single crystals of good optical quality having dimensions of typically ~ 2.5 × 1.5 ×1.5 cm 3 were grown from aqueous solutions with seed crystals by a slow cooling method. They are chemically stable because molecules are hydrogen bonded to form three-dimensional networks in the crystal state. Further growth conditions to obtain large single crystals in a shorter time have been investigated by considering both mass balance equations and the kinetics for crystal growth. It was found that increasing the cooling rate in the later periods of crystal growth is advantageous for the purpose. The largest crystal was 17.5 g in weight, which was prepared in 6 days.

Zinc l-pyrrolidone carboxylate inhibits the UVA-induced production of matrix metalloproteinase-1 by in vitro cultured skin fibroblasts, whereas it enhances their collagen synthesis

Reduced collagen matrix in the dermis constitutes one of the characteristic features of chronologically aged skin, which is further enhanced on the sun‐exposed portions of the body by chronic ultraviolet light (UV) irradiation, inducing the unique changes associated with skin photoageing. The zinc salt of l‐pyrrolidone carboxylate (Zinc PCA) has long been used as a cosmetic ingredient, because of its astringent and anti‐microbial properties. In the present study, by employing cultured normal human dermal fibroblasts, we found that Zinc PCA suppressed UVA‐induced activation of activator protein‐1 (AP‐1) and reduced matrix metalloproteinase‐1 production in these cells, which is thought to be involved in collagen degradation in photoaged skin. Moreover, Zinc PCA treatment of the cells increased the expression of an ascorbic acid transporter mRNA, SVCT2, but not SVCT1, resulting in the enhanced production of type I collagen. Based on these in vitro findings, we consider Zinc PCA to be a promising candidate for an anti‐skin ageing agent.