Hai Kwan Jung

Inhibitory effect of glycolic acid on ultraviolet B-induced c-fos expression, AP-1 activation and p53–p21 response in a human keratinocyte cell line

Glycolic acid, an alpha-hydroxy acid derived from fruit and milk sugars, has been commonly used as a cosmetic ingredient since it was known to have photo-protective and anti-inflammatory effects, and anti-oxidant effect in UV-irradiated skin. However, little has been known about the functional role of glycolic acid on UV-induced skin tumorigenesis. We previously found that glycolic acid inhibited UV-induced skin tumor development in hairless mouse. In this study we investigated anti-tumor promoting mechanism of glycolic acid on the UV-induced skin tumor development. The ability of glycolic acid to inhibit the UVB-induced cytotoxicity, apoptosis and expression of apoptosis-regulatory genes (p53 and p21) was examined. We also investigated whether glycolic acid could inhibit UVB-induced alternation of cell cycle, c-fos expression and activation of transcription factor AP-1 in cultured immortalized human keratinocyte HaCaT cells. Glycolic acid treatment attenuated the UVB-induced cell cytotoxicity as well as apoptosis. Glycolic acid also inhibited the UVB-induced expression of c-fos and the activation of transcription factor AP-1, and inhibited mRNA levels of apoptosis-regulatory gene (p53 and p21). These results suggest that glycolic acid may exert the inhibitory effect on the UVB-induced skin tumor development by blocking the UVB-induced of apoptosis and cytotoxicity through inhibition of c-fos expression and activation of AP-1 in addition to the inhibition of p53-p2l response pathway.

Inhibitory effect of peroxisome proliferator-activated receptor gamma agonist on ochratoxin A-induced cytotoxicity and activation of transcription factors in cultured rat embryonic midbrain cells.

The effects of 15-deoxy- j 12,14 -prostaglandin J 2 (15-deoxy PGJ 2 ) on ochratoxin A (OTA)-induced neurotoxicity and on the activation of transcription factors activator protein-1 (AP-1) and nuclear factor-kappa B (NF- s B) were investigated in cultured rat embryonic midbrain cells. Twelve-day rat embryo midbrain cells were cultured for 48 h. OTA (0.5 or 1 µg/ml) and/or 15-deoxyPGJ 2 (0.5 µ M ) were then added for 48 h. Cell number and neurite outgrowth were determined to assess the neurotoxicity of OTA. AP-1 and NF- s B activation was determined by gel mobility shift assay after 3 h of exposure to OTA and/or 15-deoxy PGJ 2 . OTA caused concentration-dependent reductions in neurite outgrowth and cell number, and induced AP-1 and NF- s B activation. Cotreatment with 15-deoxy PGJ 2 (0.5 µ M ) blocked OTA-induced decrease in neurite outgrowth and cell number and inhibited AP-1 and NF- s B activation. 15-Deoxy PGJ 2 (0.5 µ M ) caused the expression of peroxisome proliferator-activated receptor-gamma (PPAR- n ) in the cells. Results show that 15-deoxy PGJ 2 blocked OTA-induced neurotoxicity by inhibiting AP-1 and NF- s B activation in cultured rat embryonic midbrain cells.

Effect of Glycolic acid on UVB-induced skin damage and inflammation in guinea pigs

Objectives: Recently the use of glycolic-acid-containing cosmetics has received increased public interest in their supposed ability to reduce wrinkles, roughness, age spots and other skin damage. However, the safety of such products when used excessively or chronically, especially by photosensitive people, is being questioned. The purpose of this study was to examine the effects of glycolic acid alone or in combination with UVB on skin damage and inflammatory response. Method: Guinea pigs were treated with glycolic acid (from 1 to 7 mg/cm2) alone or in combination with UVB (0.4 or 3 J/cm2) for 14 days. Skin damage was evaluated by scoring the skin irritation value by the method of Draize and by histopathological observations. Cyclooxygenase 2 (COX-2) expression and prostaglandin E2 (PGE2) production were also assessed. Results: Glycolic acid caused an increase in the level of skin damage in a dose- and time-dependent manner. Lower doses (1 and 3 mg/cm2) of glycolic acid mostly caused erythema and eschar, and these consequently formed scales, whereas higher doses (5 and 7 mg/cm2) of glycolic acid caused redness, edema and necrotic ulceration. Glycolic acid also increased the thickness of the epidermal layer, reduced the organization of the stratum corneum and eventually destroyed some parts of the epidermal layer at 7 mg/cm2. UVB (0.4 and 3 J/cm2) caused redness and edema as well as reduced the integrity of the stratum corneum. Glycolic acid enhanced the UVB-induced skin damage. The magnitude of the damage caused by combined UVB and glycolic acid treatment was much greater than that caused by glycolic acid or UVB alone. Moreover, partial destruction of the epidermal layer was observed in skin treated with 3 J/cm2 UVB and 3 mg/cm2 glycolic acid. However, glycolic acid did not change the basal and UVB-induced PGE2 production and COX-2 protein expression. Conclusion: These results show that glycolic acid causes skin damage in a dose- and time-dependent manner and that it enhances UVB-induced skin damage without accompanying PGE2 production or COX-2 protein expression. Therefore, caution should be exercised by those using glycolic acid on a chronic basis or excessively. Moreover, those with photosensitive skins and those more exposed to the sun should be particularly careful.

Inhibitory effects of ochratoxin A on nerve growth factor-induced neurite extension through downregulation of p38 MAP kinase and AP-1 activation in cultured pheochromocytoma cells.

Ochratoxin A (OTA) induces microcephaly in animals and in vitro cultured whole embryos. Inhibition of neuronal cell differentiation was proposed as underlying mechanisms responsible for OTA-induced microcephaly. Previously it was found that OTA inhibited differentiation of cultured rat embryonic midbrain cells into neurons. In this study, the influence of OTA on differentiation in PC-12 cells, a widely accepted model cells for study of neuronal differentiation was examined. Cell differentiation was assessed by measurement of neurite extension and quantified by the number of neurites extended. OTA decreased serum and nerve growth factor (NGF)-induced neurite extension in a concentration-dependent manner. Since MAP kinase and transcription factors have been implicated in cell differentiation of neuronal cells, and our previous study demonstrated that p38 MAP kinase and AP-1 are activated during PC 12 cell differentiation, the effect of OTA on NGF-induced p38 MAP kinase and transcription factor activation was examined. Co-treatment of OTA with NGF resulted in inhibition of NGF-induced p38 MAP kinase and AP-1 activation. Moreover, SB203580, a specific inhibitor of p38 MAP kinase blocked p38 MAP kinase and AP-1 activation accompanied by further inhibition of neurite extension. The present study shows that OTA inhibited cell differentiation of PC-12 cells, and this inhibitory effect may be related to inhibition of the activation of the p38 MAP kinase in conjunction with transcription factors AP-1. This finding suggests that the inhibitory effect on neuronal cell differentiation by OTA might be a mechanism responsible for OTA-induced microcephaly.Ochratoxin A (OTA) induces microcephaly in animals and in vitro cultured whole embryos. Inhibition of neuronal cell differentiation was proposed as underlying mechanisms responsible for OTA-induced microcephaly. Previously it was found that OTA inhibited differentiation of cultured rat embryonic midbrain cells into neurons. In this study, the influence of OTA on differentiation in PC-12 cells, a widely accepted model cells for study of neuronal differentiation was examined. Cell differentiation was assessed by measurement of neurite extension and quantified by the number of neurites extended. OTA decreased serum and nerve growth factor (NGF)-induced neurite extension in a concentration-dependent manner. Since MAP kinase and transcription factors have been implicated in cell differentiation of neuronal cells, and our previous study demonstrated that p38 MAP kinase and AP-1 are activated during PC 12 cell differentiation, the effect of OTA on NGF-induced p38 MAP kinase and transcription factor activation was examined. Co-treatment of OTA with NGF resulted in inhibition of NGF-induced p38 MAP kinase and AP-1 activation. Moreover, SB203580, a specific inhibitor of p38 MAP kinase blocked p38 MAP kinase and AP-1 activation accompanied by further inhibition of neurite extension. The present study shows that OTA inhibited cell differentiation of PC-12 cells, and this inhibitory effect may be related to inhibition of the activation of the p38 MAP kinase in conjunction with transcription factors AP-1. This finding suggests that the inhibitory effect on neuronal cell differentiation by OTA might be a mechanism responsible for OTA-induced microcephaly.