Biomedical subjects

C Huang

Publications and source records attributed to C Huang.

At least 19 recordsLinked to original sources

PubMed2003

Neural-cadherin expression associated with angiogenesis in non-small-cell lung cancer patients.

An immunohistochemical analysis for E(epithelial)-cadherin and N(neural)-cadherin expression in relation to tumour angiogenesis was performed in 150 patients with nonsmall cell lung cancer (NSCLC). In all, 71 carcinomas (47.3%) were E-cadherin-negative. Epithelial-cadherin-negative tumours had lymph node metastases significantly more frequently than E-cadherin-positive tumours (P=0.0100). On the other hand, 46 carcinomas (30.7%) were N-cadherin-positive. Regarding tumour vascularity, there was no significant correlation between E-cadherin expression and tumour vascular. In contrast, the frequency of hypervascular tumours was significantly higher for N-cadherin-positive carcinomas than for N-cadherin-negative carcinomas (P=0.0373). Regarding prognosis, the 5-year survival rate of patients with E-cadherin-negative NSCLCs was significantly lower than that of patients with E-cadherin-positive NSCLCs (P=0.0146). In contrast, of the patients with large cell carcinomas, the 5-year survival rate of patients with N-cadherin-positive tumours was significantly lower than that of patients with N-cadherin-negative tumours (P=0.0013). A multivariate analysis demonstrated that E-cadherin status (P=0.0339) and tumour vascularity (P=0.0295) were significant indicators for survival. In conclusion, E-cadherin expression and tumour vascularity are significant prognostic factors of NSCLC patients. Furthermore, N-cadherin expression is associated with tumour angiogenesis, and its expression is one of prognostic factors of patients with large cell carcinomas. Thus, N-cadherin also might play a specific role in undifferentiated large cell carcinomas.

Antigens, CD34↗

PubMed2003

Plasma-wakefield acceleration of an intense positron beam.

Plasma wakefields are both excited and probed by propagating an intense 28.5 GeV positron beam through a 1.4 m long lithium plasma. The main body of the beam loses energy in exciting this wakefield while positrons in the back of the same beam can be accelerated by the same wakefield as it changes sign. The scaling of energy loss with plasma density as well as the energy gain seen at the highest plasma density is in excellent agreement with simulations.

Journal Article↗

PubMed2003

Ultrarelativistic-positron-beam transport through meter-scale plasmas.

We report on the first study of the dynamic transverse forces imparted to an ultrarelativistic positron beam by a long plasma in the underdense regime. Focusing of the 28.5 GeV beam is observed from time-resolved beam profiles after the 1.4 m plasma. The strength of the imparted force varies along the approximately 12 ps full length of the bunch as well as with plasma density. Computer simulations substantiate the longitudinal aberration seen in the data and reveal mechanisms for emittance degradation.

Journal Article↗

PubMed2003

Indinavir uncovers different contributions of GLUT4 and GLUT1 towards glucose uptake in muscle and fat cells and tissues.

AIMS/HYPOTHESIS: Insulin-dependent glucose influx in skeletal muscle and adipocytes is believed to rely largely on GLUT4, but this has not been confirmed directly. We assessed the relative functional contribution of GLUT4 in experimental models of skeletal muscle and adipocytes using the HIV-1 protease inhibitor indinavir. METHODS: Indinavir (up to 100 micro mol/l) was added to the glucose transport solution after insulin stimulation of wild-type L6 muscle cells, L6 cells over-expressing either GLUT4myc or GLUT1myc, 3T3-L1 adipocytes, isolated mouse brown or white adipocytes, and isolated mouse muscle preparations. RESULTS: 100 micro mol/l indinavir inhibited 80% of both basal and insulin-stimulated 2-deoxyglucose uptake in L6GLUT4myc myotubes and myoblasts, but only 25% in L6GLUT1myc cells. Cell-surface density of glucose transporters was not affected. In isolated soleus and extensor digitorum longus muscles, primary white and brown adipocytes, insulin-stimulated glucose uptake was inhibited 70 to 80% by indinavir. The effect of indinavir on glucose uptake was variable in 3T3-L1 adipocytes, averaging 45% and 67% inhibition of basal and maximally insulin-stimulated glucose uptake, respectively. In this cell, fractional inhibition of glucose uptake by indinavir correlated positively with the fold-stimulation of glucose uptake by insulin, and was higher with sub-maximal insulin concentrations. The latter finding coincided with an increase only in GLUT4, but not GLUT1, in plasma membrane lawns. CONCLUSION/INTERPRETATION: Indinavir is a useful tool to assess different functional contributions of GLUT4 to glucose uptake in common models of skeletal muscle and adipocytes.

3T3 Cells↗

PubMed2003

A protein kinase from Colletotrichum trifolii is induced by plant cutin and is required for appressorium formation.

When certain phytopathogenic fungi contact plant surfaces, specialized infection structures (appressoria) are produced that facilitate penetration of the plant external barrier; the cuticle. Recognition of this hydrophobic host surface must be sensed by the fungus, initiating the appropriate signaling pathway or pathways for pathogenic development. Using polymerase chain reaction and primers designed from mammalian protein kinase C sequences (PKC), we have isolated, cloned, and characterized a protein kinase from Colletotrichum trifolii, causal agent of alfalfa anthracnose. Though sequence analysis indicated conserved sequences in mammalian PKC genes, we were unable to induce activity of the fungal protein using known activators of PKC. Instead, we show that the C. trifolii gene, designated LIPK (lipid-induced protein kinase) is induced specifically by purified plant cutin or long-chain fatty acids which are monomeric constituents of cutin. PKC inhibitors prevented appressorium formation and, to a lesser extent, spore germination. Overexpression of LIPK resulted in multiple, abnormally shaped appressoria. Gene replacement of lipk yielded strains which were unable to develop appressoria and were unable to infect intact host plant tissue. However, these mutants were able to colonize host tissue following artificial wounding, resulting in typical anthracnose lesions. Taken together, these data indicate a central role in triggering infection structure formation for this protein kinase, which is induced specifically by components of the plant cuticle. Thus, the fungus is able to sense and use host surface chemistry to induce a protein kinase-mediated pathway that is required for pathogenic development.

Amino Acid Sequence↗

PubMed2003

Observations of blanket characteristics in full-scale floc blanket clarifiers.

We monitored the changes in concentrations, zeta potentials, sizes and capillary suction times of the solids flocs in the clarified water from eight floc blanket clarifiers of PingTsan Water Works of Taiwan Water Supply Company with low (< 10 NTU) and high (> 100 NTU) turbidity raw water. For the former, one-stage coagulation-sedimentation treatment was adopted which yielded a rather unstable blanket. Complete washout was noticeable when the PACl dosage was insufficient. On the treatment of high-turbidity raw water, on the other hand, the Works adopted the combined treatment process, that is, the raw water was first coagulated and settled in a pre-sedimentation tank, afterwards, its effluent was coagulated again and clarified in the clarifiers. The resulting flocs could form a networked blanket that was relatively stable to the shock load in raw water turbidity.

Bioreactors↗

PubMed2002

Hygroscopic expansion of a compomer and a composite on artificial gap reduction.

OBJECTIVE: This study compared the effect of water sorption on the extent of marginal gap reduction in a compomer (Dyract AP, Dentsply) and a composite (Spectrum, Dentsply) over a 12-week storage period. MATERIALS AND METHODS: Artificial gaps were created in 40 borosilicate glass cylinders, each 5mm deep and with an internal diameter of 5.5mm. Half of the internal bonding surface of each cylinder was sandblasted, silanised and coated with a dentine adhesive (Prime&Bond NT, Dentsply). Twenty partially bonded cylinders were incrementally filled with Dyract AP (AP) and the rest with Spectrum (S). For each material, 10 specimens were stored in de-ionised water (W), and 10 (control) in non-aqueous silicone fluid (O) at 37 degrees C. The dimension of the same maximum gap created in each specimen was repeatedly measured at 0, 1, 2, 4, 6, 8, 10 and 12 weeks, using a light microscope under incident light at 570x magnification. Gap widths in each of the four groups (n=10) were statistically compared. Correlations between mean gap width reduction and storage time were also examined. RESULTS: Friedman repeated measures ANOVA on ranks revealed significant differences (p<0.001) among the gap widths measured at different time intervals in groups AP-W and S-W. No significant differences (p>0.05) were found in groups AP-O and S-O. Tukey's multiple comparison test indicated that no significant differences (p>0.05) were detectable beyond the sixth week in AP-W and the fourth week in S-W. Linear regression analyses showed that mean gap widths decreased exponentially with time for AP-W (r=0.97) and S-W (r=0.90). From the slopes of the regression lines, the rate of marginal gap reduction in AP-W was 4.6 times faster than S-W. CONCLUSION: Marginal gap reduction in both the materials are directly attributed to water sorption and that the reduction is larger and more rapid in Dyract AP.

Absorption↗

PubMed2002

Up-regulation of cystatin C expression in the murine hippocampus following perforant path transections.

Cystatins are endogenous cysteine protease inhibitors that modulate the turnover of intracellular and extracellular proteins. These inhibitors are strongly implicated in a variety of pathological processes such as tumor metastasis and many degenerating CNS disorders. Here we report the expression of cystatin C, a major cysteine protease inhibitor of mammalian animals, in the murine hippocampus at 3, 7, 15 and 30 days following perforant path transections. Northern blot analysis showed that cystatin C transcripts were up-regulated in a transient manner with a significant increase at 7 and 15 days post-lesion (219% and 185% of control, respectively) in the rat hippocampus after entorhinal deafferentation. In situ hybridization and immunohistochemistry confirmed the time-dependent up-regulation of both cystatin C mRNA and protein expressions in a mouse model which initiated at 3 days post-lesion, reached maximal levels 7-15 days post-lesion, and remained slightly elevated by day 30 post-lesion. The modulation of cystatin C expression was observed to occur specifically in the entorhinally denervated zones: the stratum lacunosum-moleculare of the hippocampus and the outer molecular layer of the dentate gyrus. Double labeling by either a combination of in situ hybridization for cystatin C with immunohistochemistry for glial fibrillary acidic protein or double immunofluorescence staining for both proteins in mouse hippocampus at 7 and 15 days post-lesion revealed that most cystatin C-expressing cells are astrocytes. From these results we suggest that the spatiotemporal up-regulation of cystatin C in the hippocampus is induced by entorhinal deafferentation and that cystatin C may be involved in the astroglia-mediated neural plasticity events in the hippocampus following perforant path transections.

Animals↗

PubMed2002

Mental health of primary family caregivers with children with intellectual disability who receive a home care programme.

BACKGROUND: The aims of the present study were to describe the change in mental health over time in a group of family caregivers with a child with intellectual disability (ID) and to explore the effect of a home care service on the psychological well-being of the caregiver. METHODS: The authors identified children with ID who received home care services in the southern part of Taiwan. A total of 46 primary family caregivers (age range = 21-65 years) were recruited for the present study. The study design was a quasi-experimental follow-up analysis. The children with ID and their families regularly received home-based care. The 12-item version of the Chinese Health Questionnaire (CHQ) was used to evaluate the subjects' mental health at three time points: (1) baseline, (2) 3 months and (3) 9 months. The validity and reliability of the CHQ have been tested in Taiwan. The Generalized Estimating Equation was used to conduct longitudinal data analyses. RESULTS: The authors found that the family caregivers showed a significant improvement in their mental health by month 9. CONCLUSIONS: The preliminary findings of this study accredit the effect of home care services and suggest that home care services are necessary for family caregivers.

Adaptation, Psychological↗

PubMed2001

The intratumoral expression of vascular endothelial growth factor and interleukin-8 associated with angiogenesis in nonsmall cell lung carcinoma patients.

BACKGROUND: Angiogenesis has important effects on tumor growth and metastasis. It is regulated by a variety of angiogenic and angiostatic factors. METHODS: To evaluate the effects of tumor cell-derived angiogenic factors, we performed an immunohistochemic study to evaluate the intratumoral expression of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) in relation to intratumoral microvessel density (IMD) in tumors from 104 nonsmall cell lung carcinoma (NSCLC)patients. RESULTS: Fifty-four carcinomas were VEGF-positive, 47 carcinomas were IL-8-positive, and 53 carcinomas were hypervascular tumors. There was no significant correlation between the percentages of positive VEGF-staining and positive IL-8-staining in NSCLCs (rho = 0.174, P = 0.080). The IMD of VEGF-positive carcinomas was significantly greater than that of VEGF-negative carcinomas (P = 0.023). In addition, the IMD of IL-8-positive carcinomas was significantly greater than that of IL-8-negative carcinomas (P =0.013). The overall survival rate of patients with hypervascular tumors was significantly lower than that of patients with hypovascular tumors (41.0% versus 67.0%, P = 0.004). Cox proportional-hazards regression model also demonstrated that angiogenesis was one of the significant factors in predicting the survival of NSCLC patients (relative risk = 1.944, P = 0.041). CONCLUSIONS: Intratumoral expression of VEGF and IL-8 was associated with angiogenesis in NSCLCs. Tumor angiogenesis significantly affected the prognosis of NSCLC patients.

Adult↗

PubMed2001

Cannabinoid-receptor-independent cell signalling by N-acylethanolamines.

Anandamide and other polyunsaturated N-acylethanolamines (NAEs) exert biological activity by binding to cannabinoid receptors. These receptors are linked to G(i/o) proteins and their activation leads to extracellular-signal-regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAP kinase) activation, inhibition of cAMP-dependent signalling and complex changes in the expression of various genes. Saturated and monounsaturated NAEs cannot bind to cannabinoid receptors and may thus mediate cell signalling through other targets. Here we report that both saturated/monounsaturated NAEs and anandamide (20:4(n-6) NAE) stimulate cannabinoid-receptor-independent ERK phosphorylation and activator protein-1 (AP-1)-dependent transcriptional activity in mouse epidermal JB6 cells. Using a clone of JB6 P(+) cells with an AP-1 collagen-luciferase reporter construct, we found that 16:0, 18:1(n-9), 18:1(n-7), 18:2(n-6) and 20:4(n-6) NAEs stimulated AP-1-dependent transcriptional activity up to 2-fold, with maximal stimulation at approx. 10-15 microM. Higher NAE concentrations had toxic effects mediated by alterations in mitochondrial energy metabolism. The AP-1 stimulation appeared to be mediated by ERK but not JNK or p38 signalling pathways, because all NAEs stimulated ERK1/ERK2 phosphorylation without having any effect on JNK or p38 kinases. Also, overexpression of dominant negative ERK1/ERK2 kinases completely abolished NAE-induced AP-1 activation. In contrast with 18:1(n-9) NAE and anandamide, the cannabinoid receptor agonist WIN 55,212-2 did not stimulate AP-1 activity and inhibited ERK phosphorylation. The NAE-mediated effects were not attenuated by pertussis toxin and appeared to be NAE-specific, as a close structural analogue, oleyl alcohol, failed to induce ERK phosphorylation. The data support our hypothesis that the major saturated and monounsaturated NAEs are signalling molecules acting through intracellular targets without participation of cannabinoid receptors.

Analgesics↗

PubMed2001

Hydrogen peroxide mediates activation of nuclear factor of activated T cells (NFAT) by nickel subsulfide.

Nickel compounds induce cell transformation in cell culture models and tumor formation in experimental animals. However, the molecular mechanisms by which nickel compounds induce tumors are not yet well understood. The present study found that exposure of cells to either Ni(3)S(2) or NiCl(2) could result in specific transactivation of nuclear factor of activated T cells (NFAT), although it did not show any activation of p53 or AP-1. Furthermore, nickel compounds were also able to cause generation of reactive oxygen species (ROS). The scavenging of nickel-induced H(2)O(2) with N-acety-L-cyteine (a general antioxidant) or catalase, or the chelation of nickel with deferoxamine, resulted in inhibition of NFAT activation. In contrast, pretreatment of cells with sodium formate (an .OH radical scavenger) or superoxide dismutase (an O(-.)(2) radical scavenger) did not show any inhibitory effects. These results demonstrate that nickel compounds are able to induce NFAT activation, and that the mechanism of NFAT activation seems to be mediated by the generation of H(2)O(2) by these metal compounds. This study should help us understand the signal transduction pathways involved in carcinogenic effects of these nickel compounds.

Acetylcysteine↗

PubMed2001

Ablation of Cypher, a PDZ-LIM domain Z-line protein, causes a severe form of congenital myopathy.

Cypher is a member of a recently emerging family of proteins containing a PDZ domain at their NH(2) terminus and one or three LIM domains at their COOH terminus. Cypher knockout mice display a severe form of congenital myopathy and die postnatally from functional failure in multiple striated muscles. Examination of striated muscle from the mutants revealed that Cypher is not required for sarcomerogenesis or Z-line assembly, but rather is required for maintenance of the Z-line during muscle function. In vitro studies demonstrated that individual domains within Cypher localize independently to the Z-line via interactions with alpha-actinin or other Z-line components. These results suggest that Cypher functions as a linker-strut to maintain cytoskeletal structure during contraction.

Actinin↗

PubMed2001

GLUT4 translocation precedes the stimulation of glucose uptake by insulin in muscle cells: potential activation of GLUT4 via p38 mitogen-activated protein kinase.

We previously reported that SB203580, an inhibitor of p38 mitogen-activated protein kinase (p38 MAPK), attenuates insulin-stimulated glucose uptake without altering GLUT4 translocation. These results suggested that insulin might activate GLUT4 via a p38 MAPK-dependent pathway. Here we explore this hypothesis by temporal and kinetic analyses of the stimulation of GLUT4 translocation, glucose uptake and activation of p38 MAPK isoforms by insulin. In L6 myotubes stably expressing GLUT4 with an exofacial Myc epitope, we found that GLUT4 translocation (t(1/2)=2.5 min) preceded the stimulation of 2-deoxyglucose uptake (t(1/2)=6 min). This segregation of glucose uptake from GLUT4 translocation became more apparent when the two parameters were measured at 22 degrees C. Preincubation with the p38 MAPK inhibitors SB202190 and SB203580 reduced insulin-stimulated transport of either 2-deoxyglucose or 3-O-methylglucose by 40-60%. Pretreatment with SB203580 lowered the apparent transport V(max) of insulin-mediated 2-deoxyglucose and 3-O-methylglucose without any significant change in the apparent K(m) for either hexose. The IC(50) values for the partial inhibition of 2-deoxyglucose uptake by SB202190 and SB203580 were 1 and 2 microM respectively, and correlated with the IC(50) for full inhibition of p38 MAPK by the two inhibitors in myotubes (2 and 1.4 microM, respectively). Insulin caused a dose- (EC(50)=15 nM) and time- (t(1/2)=3 min) dependent increase in p38 MAPK phosphorylation, which peaked at 10 min (2.3+/-0.3-fold). In vitro kinase assay of immunoprecipitates from insulin-stimulated myotubes showed activation of p38 alpha (2.6+/-0.3-fold) and p38 beta (2.3+/-0.2-fold) MAPK. These results suggest that activation of GLUT4 follows GLUT4 translocation and that both mechanisms contribute to the full stimulation of glucose uptake by insulin. Furthermore, activation of GLUT4 may occur via an SB203580-sensitive pathway, possibly involving p38 MAPK.

Animals↗

PubMed2001

Comparison of soluble and immobilized acetate for removing Pb from contaminated soil.

Five lead (Pb) contaminated soils were used in a laboratory and modeling study to examine the effects of soluble and immobilized acetate on Pb removal from a contaminated soil as a function of pH. Soluble acetate was added as sodium acetate; immobilized acetate was added in the form of a cation exchange resin. For comparative purposes, Pb adsorption with no acetate also was measured as a function of pH. A surface complexation modeling framework was used to interpret experimental data. Experimental results showed the cation exchange resin was much more effective than soluble acetate in removing Pb from soils due to a strong affinity of the resin for Pb. In addition, concentrations of soluble Pb in resin/soil slurry were very low, minimizing the pollution threat if discharged. As deduced from modeling studies, soluble acetate performed poorly compared to the resin, in part, due to adsorption of the soluble PbAc(+) complex. The effectiveness of both soluble and immobilized acetate was diminished below pH 4 as a result of competition by H(+) for acetate. Modeling results based on resin affinity for Pb compare well with experimental data for resin/soil mixtures, suggesting that Pb partitioning in resin/soil mixtures may be predicted reasonably well if soil/Pb and resin/Pb partitioning are known. Thus, the modeling approach may be used as a screening tool to determine the performance of alternative resins.

Acetates↗

PubMed2001

Differential effects of phosphatidylinositol 3-kinase inhibition on intracellular signals regulating GLUT4 translocation and glucose transport.

Phosphatidylinositol (PI) 3-kinase is required for insulin-stimulated translocation of GLUT4 to the surface of muscle and fat cells. Recent evidence suggests that the full stimulation of glucose uptake by insulin also requires activation of GLUT4, possibly via a p38 mitogen-activated protein kinase (p38 MAPK)-dependent pathway. Here we used L6 myotubes expressing Myc-tagged GLUT4 to examine at what level the signals regulating GLUT4 translocation and activation bifurcate. We compared the sensitivity of each process, as well as of signals leading to GLUT4 translocation (Akt and atypical protein kinase C) to PI 3-kinase inhibition. Wortmannin inhibited insulin-stimulated glucose uptake with an IC(50) of 3 nm. In contrast, GLUT4myc appearance at the cell surface was less sensitive to inhibition (IC(50) = 43 nm). This dissociation between insulin-stimulated glucose uptake and GLUT4myc translocation was not observed with LY294002 (IC(50) = 8 and 10 microm, respectively). The sensitivity of insulin-stimulated activation of PKC zeta/lambda, Akt1, Akt2, and Akt3 to wortmannin (IC(50) = 24, 30, 35, and 60 nm, respectively) correlated closely with inhibition of GLUT4 translocation. In contrast, insulin-dependent p38 MAPK phosphorylation was efficiently reduced in cells pretreated with wortmannin, with an IC(50) of 7 nm. Insulin-dependent p38 alpha and p38 beta MAPK activities were also markedly reduced by wortmannin (IC(50) = 6 and 2 nm, respectively). LY294002 or transient expression of a dominant inhibitory PI 3-kinase construct (Delta p85), however, did not affect p38 MAPK phosphorylation. These results uncover a striking correlation between PI 3-kinase, Akt, PKC zeta/lambda, and GLUT4 translocation on one hand and their segregation from glucose uptake and p38 MAPK activation on the other, based on their wortmannin sensitivity. We propose that a distinct, high affinity target of wortmannin, other than PI 3-kinase, may be necessary for activation of p38 MAPK and GLUT4 in response to insulin.

Androstadienes↗

PubMed2001

Vanadate-induced cell growth regulation and the role of reactive oxygen species.

While vanadium compounds are known as potent toxicants as well as carcinogens, the mechanisms of their toxic and carcinogenic actions remain to be investigated. It is believed that an improper cell growth regulation leads to cancer development. The present study examines the effects of vanadate on cell cycle control and involvement of reactive oxygen species (ROS) in these vanadate-mediated responses in a human lung epithelial cell line, A549. Under vanadate stimulation, A549 cells generated hydroxyl radical (*OH), as determined by electron spin resonance (ESR), and hydrogen peroxide (H2O2) and superoxide anion (O2*-), as detected by flow cytometry using specific dyes. The mechanism of ROS generation involved the reduction of molecular oxygen to O2*- by both a flavoenzyme-containing NADPH complex and the mitochondria electron transport chain. The O2*- in turn generated H2O2, which reacted with vanadium(IV) to generate *OH radical through a Fenton-type reaction (V(IV) + H2O2 --> V(V) +*OH + OH-). The ROS generated by vanadate induced G2/M phase arrest in a time- and dose-dependent manner as determined by measuring DNA content. Vanadate also increased p21 and Chk1 levels and reduced Cdc25C expression, leading to phosphorylation of Cdc2 and a slight increase in cyclin B1 expression as analyzed by Western blot. Catalase, a specific antioxidant for H2O2, decreased vanadate-induced expression of p21 and Chk1, reduced phosphorylation of Cdc2Tyr15, and decreased cyclin B1 levels. Superoxide dismutase, a scavenger of O2*-, or sodium formate, an inhibitor of *OH, had no significant effects. The results obtained from the present study demonstrate that among ROS, H2O2 is the species responsible for vanadate-induced G2/M phase arrest. Several regulatory pathways are involved: (1) activation of p21, (2) an increase of Chk1 expression and inhibition of Cdc25C, which results in phosphorylation of Cdc2 and possible inactivation of cyclin B1/Cdc2 complex.

Anions↗

PubMed2001

UV Induces phosphorylation of protein kinase B (Akt) at Ser-473 and Thr-308 in mouse epidermal Cl 41 cells through hydrogen peroxide.

The exposure of mammalian cells to UV irradiation leads to the activation of transcription factors and protein kinases, which are believed to be responsible for the carcinogenic effects of excessive sun exposure. The present study investigated the effect of UV exposure on reactive oxygen species (ROS) generation and protein kinase B (Akt) phosphorylation in epidermal cells and determined if a relationship exists between these UV responses. Exposure of mouse epidermal JB6 Cl 41 cells to UV radiation led to specific phosphorylation of Akt at Ser-473 and Thr-308 in a time-dependent manner. This phosphorylation was confirmed by the observation that overexpression of Akt mutant, Akt-T308/S473A, attenuated phosphorylation of Akt at Ser-473 and Thr-308. UV radiation also generated ROS as measured by electron spin resonance (ESR) in JB6 Cl 41 cells. The generation of ROS by UV radiation was measured further by H(2)O(2) and O(-.2) fluorescence staining assays. The mechanism of ROS generation involved reduction of molecular oxygen to O(-.2), which generated H(2)O(2) through dismutation. H(2)O(2) produced .OH via a metal-independent pathway. The scavenging of UV-generated H(2)O(2) by N-acety-l-cyteine (NAC, a general antioxidant) or catalase (a specific H(2)O(2) inhibitor) inhibited Akt phosphorylation at Ser-473 and Thr-308, whereas the pretreatment of cells with sodium formate (an .OH radical scavenger) or superoxide dismutase (an O(-.2) radical scavenger) did not show any inhibitory effects. Furthermore, treatment of cells with H(2)O(2) increased UV-induced phosphorylation of Akt at Ser-473 and Thr-308. These results demonstrate that UV radiation generates a whole spectrum of ROS including O(-.2), .OH, and H(2)O(2) and induces phosphorylation of Akt at Ser-473. Among the various ROS, H(2)O(2) seems most potent in mediating UV-induced phosphorylation of Akt at Ser-473 and Thr-308. It is possible that Akt may play a role in the carcinogenesis effects by UV radiation.

Animals↗