Biomedical subjects

B C Kim

Publications and source records attributed to B C Kim.

At least 19 recordsLinked to original sources

PubMed2006

Application of a multi-channel system for continuous monitoring and an early warning system.

A multi-channel continuous toxicity monitoring system developed in our laboratory, based on two-stage mini-bioreactors, was successfully implemented in the form of computer-based data acquisition. The multi-channel system consists of a series of a two-stage minibioreactor systems connected by a fiber optic probe to a luminometer, and uses genetically engineered bioluminescent bacteria for the detection of the potential toxicity from the soluble chemicals. This system can be stably and continuously operated due to the separation of the culture reactor from the test reactor and accomplish easy and long-term monitoring without system shut down by abrupt inflows of severe polluting chemicals. Four different recombinant bioluminescent bacteria were used in different channels so that the modes of the samples toxicities can be reasonably identified and evaluated based upon the response signature of each channel. The bioluminescent signatures were delivered from four channels by switching one at once, while the data is automatically logged to an IBM compatible computer. We also achieved the enhancement of the system through the manipulation of the dilution rate and the use of thermo-lux fusion strains. Finally, this system is now being implemented to a drinking water reservoir and river for remote sensing as an early warning system.

Bacteria↗

PubMed2006

Comparison of histochemical characteristics in various pork groups categorized by postmortem metabolic rate and pork quality.

The purpose of the present study was to investigate the variations in histochemical characteristics of muscle samples segregated according to metabolic rates (MR) and pork quality attributes. A total of 231 crossbred Duroc x (Yorkshire x Landrace) pigs was evaluated. Samples of the LM were taken to evaluate histochemical characteristics, postmortem MR, and meat quality. Samples were classified into fast, normal, and slow MR groups based on muscle pH at 45 min and R-value. Drip loss and lightness (L*) were used to assign samples to 1 of 4 quality classes. Pale, soft, and exudative pork belonging in the fast group had the greatest (P < 0.05) percentage of type IIb fibers, and RSE (reddish-pink, soft, and exudative) pork belonging in the fast group had a similar tendency. Additionally, RFN (reddish-pink, firm, and nonexudative) pork belonging in the normal group showed a lower (P < 0.05) percentage of type IIb fibers than PSE or RSE, regardless of MR, and DFD pork had the lowest (P < 0.05) percentage of type IIb fibers. In general, the fast-glycolyzing PSE pork with the lowest pH at both 45 min and 24 h had greater percentages of type IIb fibers than the fast-glycolyzing RFN pork. There were more fiber-type composition differences between quality classes in pork undergoing a fast rate of metabolism compared with pork undergoing a normal rate of metabolism. It can be concluded that muscle histochemical characteristics are associated with early postmortem MR, the extent of glycolysis, and, thereby, pork quality; however, these effects are limited to the pigs exhibiting a fast glycolytic rate.

Animals↗

PubMed2005

Effects of different levels of dietary supplemental selenium on performance, lipid oxidation, and color stability of broiler chicks.

This study examined the effects of supplemental dietary selenium on growth performance, lipid oxidation, and color stability of broiler chicks. Male broiler chicks (Arbor Acres, 1 d old, total 900 chicks) were randomly assigned to 6 pens containing 30 chicks each, corresponding to each of 6 dietary treatments. Six different diets were supplied to the chicks from 3 to 6 wk of age. After 42 d of feeding, all the broilers were slaughtered conventionally at a slaughtering plant. The carcasses were packed in polyethylene bags in a manner similar to that used for retail trade and stored for 12 d at 4 degrees C. Body weight and feed efficiency were not affected by dietary selenium levels, and no adverse effect on growth was observed during the experimental period. The dietary selenium and alpha-tocopherol levels did not affect surface meat color or level of metmyoglobin accumulation. Lipid stability was improved by supplementation with 100 IU of alpha-tocopherol (P < 0.05). Dietary selenium supplementation at 8 ppm in combination with 100 IU of alpha-tocopherol, however, was more effective in reducing lipid oxidation compared with 100 IU of alpha-tocopherol/kg feed only (P < 0.05). Supplementation with 100 IU of alpha-tocopherol affected cholesterol oxidation product levels on d 7 and 12, but selenium supplementation did not have an additional effect on the reduction of cholesterol oxidation products. Therefore, an increase in the dietary selenium from 1 to 8 ppm revealed only minor improvements in the oxidative stability of chicken meat during refrigerated storage.

Animals↗

PubMed2003

Release of ciprofloxacin from poloxamer-graft-hyaluronic acid hydrogels in vitro.

Recently, in situ gel formation has extensively been studied to enhance ocular bioavailability and duration of the drug activity. In this study, we report grafting of poloxamer onto the hyaluronic acid for application of tissue engineering oriented ophthalmic drug delivery system. Graft copolymers were prepared by coupling mono amine-terminated poloxamer (MATP) with hyaluronic acid (HA) backbone using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxylsuccinimide (NHS) as coupling agents. The coupling of MATP with HA was clarified by 1H NMR and FT-IR spectroscopy. The gelation temperature of graft copolymers was dependent on the content of HA and the concentration of poloxamer. From drug release studies in vitro, ciprofloxacin was sustainedly released from the poloxamer-g-hyaluronic acid hydrogel due to the in situ gel formation of the copolymer and viscous properties of HA.

Ciprofloxacin↗

PubMed2003

Degradation of polyvinyl alcohol by Sphingomonas sp. SA3 and its symbiote.

A total of 800 samples was taken from Taegu province, Korea, where many textile factories provide a source of polyvinyl alcohol (PVA) waste. These samples were screened for PVA-degrading bacteria. A new strain, SA3, was discovered which formed yellow colonies and used PVA as the sole carbon and energy source. Strain SA3 was identified as a Sphingomonas sp., based on the partial nucleotide sequence analysis of 16S ribosomal RNA, the presence of 2-hydroxymyristic acid (14:O 2-OH) and sphingolipids with d-17:0, d-18:0, d-19:1, and d-20:1 as the main dihydrosphingosines. This genus has not previously been reported as a PVA-degrading bacterium. Sphingomonas sp. SA3 needs a symbiote strain, SA2, for PVA degradation as a growth factor producer. In mixed cultures of these strains, the optimum temperature for PVA biodegradation ranged from 30 degrees C to 35 degrees C. The optimum pH was 8.0 and the most effective nitrogen source was NH(4)(+).

Biodegradation, Environmental↗

PubMed2003

A fatal case of Vibrio vulnificus meningoencephalitis.

The objective of this paper is to report a rare case of Vibrio vulnificus presenting as meningoencephalitis without a wound infection. Vibrio vulnificus is capable of causing severe and often fatal infections in susceptible individuals. It commonly causes necrotizing wound infections, primary septicemia, and gastroenteritis. A 69-year-old man had meningoencephalitis with lesion on the red nucleus, substantia nigra, basal ganglia, and dentate nucleus as the initial clinical manifestation of a V. vulnificus infection. This is the first case of V. vulnificus infection in which MRI demonstrated the involvement of deep nuclei of the brain.

Aged↗

PubMed2002

HLA class II allele and haplotype frequencies in Koreans based on 107 families.

We have investigated the distribution of HLA class II alleles and haplotypes in 107 Korean families (207 parents and 291 children) for the HLA-DRB1, DRB3/B4/B5, DQA1, DQB1 and DPB1 loci. Numbers of alleles observed for each locus were DRB1: 25, DQA1: 14, DQB1: 15, and DPB1: 13. Only two to three alleles were observed for the DRB3 (*0101, *0202, *0301), DRB4 (*0103, * 0103102 N), and DRB5 (*0101, *0102) loci. These alleles showed strong associations with DRB1 alleles: DRB3*0101 with DRB1*1201, *1301 and *1403; DRB3*0301 with DRB1*1202 and *1302; DRB3*0202 with DRB1*0301, *1101, *1401 and *1405; DRB5*0101 and *0102 were exclusively associated with DRB1*1501 and *1502, respectively. The seven most common DRB1-DQB1 haplotypes of frequencies > 0.06 accounted for 52% of the total haplotypes. These haplotypes were exclusively related with the seven most common DRB1-DRB3/B4/B5-DQA1-DQB1 haplotypes: DRB1*1501-DRB5*0101-DQA1*0102-DQB1*0602 (0.085), DRB1*0405-DRB4*0103-DQA1*0303-DQB1*0401 (0.082), DRB1*09012-DRB4*0103-DQA1*0302-DQB1*03032 (0.082), DRB1*0101-DQA1*0101-DQB1*0501 (0.075), DRB1*0701-DRB4*0103-DQA1*0201-DQB1*0202 (0.065), DRB1*0803-DQA1*0103-DQB1*0601 (0.065), and DRB1*1302-DRB3*0301-DQA1*0102-DQB1*0604 (0.065). When these haplotypes were extended to the DPB1 locus, much diversification of haplotypes was observed and only one haplotype remained with a frequency of > 0.06: DRB1*0405-DRB4*0103-DQA1*0303-DQB1*0401-DPB1*0501 (0.062). Such diversification would have resulted from cumulated events of recombination within the HLA class II region, and the actual recombination rate observed between the HLA-DQB1 and DPB1 loci was 2.3% (10/438 informative meioses, including 2 recombinants informative by analysis of TAP genes). Comparison of the distribution of DRB1-DQB1 haplotypes with other populations revealed that Koreans are closest to Japanese people. However, Koreans share a few haplotypes with white people and Africans, which are rare in Japanese: DRB1*0701-DQB1*0202 and DRB1*1302-DQB1*0609. The results obtained in this study will provide useful information for anthropology, organ transplantation and disease association studies.

Alleles↗

PubMed2001

Role of the cytosolic phospholipase A2-linked cascade in signaling by an oncogenic, constitutively active Ha-Ras isoform.

Activation of Ras signaling by growth factors has been associated with gene regulation and cell proliferation. Here we characterize the contributory role of cytosolic phospholipase A(2) in the oncogenic Ha-Ras(V12) signaling pathway leading to activation of c-fos serum response element (SRE) and transformation in Rat-2 fibroblasts. Using a c-fos SRE-luciferase reporter gene, we showed that the transactivation of SRE by Ha-Ras(V12) is mainly via a Rac-linked cascade, although the Raf-mitogen-activated protein kinase cascade is required for full activation. In addition, Ha-Ras(V12)-induced DNA synthesis was significantly attenuated by microinjection of recombinant Rac(N17), a dominant negative mutant of Rac1. To identify the mediators downstream of Rac in the Ha-Ras(V12) signaling, we investigated the involvement of cytosolic phospholipase A(2). Oncogenic Ha-Ras(V12)-induced SRE activation was significantly inhibited by either pretreatment with mepacrine, a phospholipase A(2) inhibitor, or cotransfection with the antisense oligonucleotide of cytosolic phospholipase A(2). We also found cytosolic phospholipase A(2) to be situated downstream of Ha-Ras(V12) in a signal pathway leading to transformation. Together, these results are indicative of mediatory roles of Rac and cytosolic phospholipase A(2) in the signaling pathway by which Ha-Ras(V12) transactivates c-fos SRE and transformation. Our findings point to cytosolic phospholipase A(2) as a novel potential target for suppressing oncogenic Ha-Ras(V12) signaling in the cell.

Animals↗

PubMed2001

Characterization of mutations of the type VII collagen gene (COL7A1) in recessive dystrophic epidermolysis bullosa mitis (M-RDEB) from three Korean patients.

In recent years, the molecular basis for the main subtypes of epidermolysis bullosa (EB) has been elucidated with pathogenetic mutations delineated in ten different genes encoding structural components of the dermal-epidermal junction. Both the autosomal dominant and recessive forms of dystrophic EB (DEB) is caused by mutations in the COL7A1 gene. Type VII collagen is a major component of anchoring fibrils, structural elements that stabilize the attachment of the basement membrane to underlying dermis. Recent delineation of the exon-intron organization of the COL7A1 gene provided the basis for the comprehensive design of PCR primer pairs that amplified exons in genomic DNA by placing the primers on the flanking introns. A number of COL7A1 mutations have been reported and some genotype-phenotype correlations are starting to emerge. In this study, we examined mutational analyses from three Korean patients with recessive dystrophic EB (RDEB) mitis. We designed and optimized primers according to the previously reported sequences. Such PCR amplification products can be examined by electrophoretic scanning technique, CSGE heteroduplex analyses. Utilizing heteroduplex analyses, we have identified a number of sequence variants in COL7A1 both in unaffected individuals and in patients with M-RDEB. Mutation detection of the COL7A1 gene revealed six allelic mutations (V6677E, P6685S, Y3749S, P6084S, P6695R and G6697C). We suggest that the full length of type VII collagen polypeptide are synthesized, but those missense mutations, that may affect a critical amino acid, can alter the conformation of the protein and interferes with the assembly and packing of type VII collagen molecules into anchoring fibrils. Immunohistochemical study of skin biopsies by use of anti-type VII collagen antibody showed markedly reduced staining and presence of a dermo/epidermal cleavage. This is the first report of a COL7A1 mutation study in DEB from Korean patients. We hope that these data contribute to the expanding database on COL7A1 mutations in dystrophic epidermolysis bullosa, and further illustrate the extensive diversity of mutational events that led to the RDEB phenotype.

Adolescent↗

PubMed2001

Melatonin reduces X-ray irradiation-induced oxidative damages in cultured human skin fibroblasts.

Melatonin is a hormone with multiple functions in humans, produced by the pineal gland and stimulated by beta-adrenergic receptors. Melatonin has been shown to have radioprotection properties, but there has been little progress toward identifying the specific mechanisms of its action. To clarify the role of melatonin as a radioprotective compound, in response to X-ray irradiation, we investigated the effects of X-ray irradiation and melatonin on cytotoxicity, lipid peroxidation and alteration of the cell cycle in cultured skin fibroblast. An 8 Gy dose of X radiation resulted in cell death in 63% of irradiated cells, i.e. the cell viability was 37%. The damage was associated with lipid peroxidation of the cell membrane, as shown by the accumulation of malondialdehyde (MDA). By pre-incubation with melatonin (10(-5) M), a significant preventive effect was noted on the increase in the absolute number of surviving cells (up to 68% of cells were survived), and the levels of MDA were markedly decreased. These findings suggest a close correlation between an increase of lipid peroxidation and a rate of cell death. Morphological changes associated with apoptotic cell death were demonstrated by TEM. DNA flow-cytometry analysis revealed that X radiation increased pre-G1 apoptotic population by 7.6% compared to a very low level (1.3%) of non-irradiated cells. However, in the presence of melatonin, this apoptotic population decreased up to 4.5% at 10(-5) M. The p53 and p21 protein levels of skin fibroblasts increased 4 h after 8 Gy irradiation, but melatonin pretreatment did not change those levels. This study suggests that melatonin pretreatment inhibits radiation-induced apoptosis, and melatonin exerts its radioprotective effect by inhibition of lipid peroxidation and without any involvement of the p53/p21 pathway.

Cell Survival↗

PubMed2001

The effects of the melatonin on ultraviolet-B irradiated cultured dermal fibroblasts.

It has been reported that reactive oxygen species (ROS) and oxygen-derived free radicals are generated by ultraviolet (UV) radiation and various chemicals and their important roles in cellular damage and apoptosis are being increasingly recognized. Melatonin is a hormone with multiple functions in humans, produced by the pineal gland and stimulated by beta-adrenergic receptors. Melatonin has been shown to have photo protection properties, but there has been little progress toward identifying the specific mechanisms of its action. To clarify the role of melatonin as a free radical scavenger, in response to ultraviolet-B (UVB) irradiation, we investigated the effects of UVB and melatonin on cytotoxicity, lipid peroxidation, terminal deoxynucleotidyl transferase-mediated digoxigenin-dUTP nick end-labeling (TUNEL) assay and alteration of cell cycle in cultured skin fibroblast. Cell survival curves after UVB irradiation showed dose dependent decrement pattern by trypan blue exclusion assay. Only 56% of dermal fibroblasts were survived at 140 mJ/cm2 UVB irradiation. The damage was associated with cell membrane lipid peroxidation, as shown by accumulation malondialdehyde (MDA). By pre-cultivation with melatonin (10(-9) M), a significant preventive effect was noted on the increase in the absolute number of surviving cells (up to 92.5% of cells were survived) and the levels of MDA were markedly decreased. These finding suggest significant correlation between an increase of lipid peroxide and cell viability. Morphological changes associated with apoptotic cell death were easily distinguished by TUNEL stain. Quantitative analysis of DNA content of skin fibroblasts was evaluated by flow cytometric analysis performed after vital staining with propidium iodide. UVB suppresses the G1 progression induced pre-G1 arrest leading to apoptotic changes of dermal fibroblast and those are blocked by melatonin pre-treatment. The results show the photodynamic effects of UVB that supposes the production of ROS and arrest the cell cycle. Melatonin, which have newly accepted as a potential UV protection properties, is effective membrane peroxidation inhibitor and prevent the pre-G1 arrest when present in relevant concentration during UVB irradiation.

Apoptosis↗

PubMed2001

The continuous monitoring of field water samples with a novel multi-channel two-stage mini-bioreactor system.

Toxicity monitoring of field water samples was performed using a novel multi-channel two-stage mini-bioreactor system and genetically engineered bioluminescent bacteria for the continuous monitoring and classification of the toxicity present in the samples. The toxicity of various samples spiked with known endocrine disrupting chemicals and phenol was also investigated for system characterization. The field samples used in this study were obtained from two different sites on a monthly basis--from a drinking water treatment plant, referred to as site N, and from a stream near a dam which is currently being constructed, referred to as site T. These samples were either pumped or injected into the second mini-bioreactors to initiate the toxicity test. Most of the samples did not show any specific toxicity. However, one sample showed to have, based upon the detection results, and was deemed toxic. The samples spiked with phenol showed possible responses in the DPD2540 and TV1061 channels, indicating the occurrence of both membrane and protein damage due to phenol. In the tests using an endocrine disrupting chemical, bisphenol A, DNA damage was detected in the DPD2794 channel with a concentration of 2 ppm. Finally, a simple but novel early warning protocol that can be used in a drinking water reservoir and a suspected place where effluents of toxic materials enter the water sourse was suggested with a schematic diagram. In conclusion, this system showed good feasibility for use as a toxicity monitoring system in the field and as an early warning system, indicating if effluents are toxic.

Bacteria↗

PubMed2001

Advanced glycosylation end products stimulate collagen mRNA synthesis in mesangial cells mediated by protein kinase C and transforming growth factor-beta.

Advanced glycosylation end products (AGE) seem to be implicated in the pathogenesis of diabetic nephropathy. The present study has examined the effects of AGE on protein kinase C (PKC) activity and transforming growth factor-beta1 (TGF-beta1) in relation to collagen gene regulation in cultured human mesangial cells (HMCs). Quiescent HMCs were exposed to serum-free media containing bovine serum albumin (BSA), AGE-modified BSA (AGE-BSA), or glycated BSA in which AGE formation was prevented by the use of aminoguanidine (BSA-AM). AGE-BSA (200 microg/mL) induced a peak membrane-associated PKC activity, particularly PKC-a, at 4 hours. AGE-BSA stimulated alpha1(I) and alpha1(IV) collagen mRNA expression after 24-hour incubation with HMCs, which remained elevated until hour 60. HMCs incubated with AGE-BSA induced a significant inhibition of cell proliferation compared with cells incubated with BSA. AGE-BSA stimulated TGF-beta mRNA and protein expression in HMCs. The TGF-beta secreted by HMCs was shown by CCL-64 mink lung cell assay to be bioactive. In contrast, BSA-AM did not affect either collagen or TGF-beta mRNA or protein expression in HMCs. The stimulatory effects of AGE-BSA on collagen gene regulation in HMCs could be negated by the pretreatment of HMCs with GF 109203X for 30 minutes or with phorbol myristate acetate for 24 hours before AGE-BSA administration. Neutralizing antibody to TGF-beta inhibited increased collagen mRNA expression by HMCs exposed to AGE-BSA. These results suggest that AGE-BSA stimulates collagen mRNA expression by activating PKC and the transcriptional upregulation of TGF-beta1 in HMCs. Thus, PKC and TGF-beta may function as key signaling intermediaries in the AGE-up-regulated collagen gene expression pathway in HMCs.

Adult↗

PubMed2001

Thermoanaerobacter yonseiensis sp. nov., a novel extremely thermophilic, xylose-utilizing bacterium that grows at up to 85 degrees C.

A novel strictly anaerobic, extremely thermophilic, spore-forming and xylose-utilizing bacterium, designated strain KB-1TP (type and patent strain), was isolated from a geothermal hot stream at Sileri on Java island, Indonesia. The cells were rod-shaped, motile and had terminal spores. The newly isolated strain stained gram-positive and the cells occurred singly or in pairs during the exponential growth phase. The temperature optimum for growth was 75 degrees C and growth occurred in the range 50-85 degrees C. The pH range for growth was 4.5-9.0, with an optimum at pH 6.5. Strain KB-1TP grew chemo-organotrophically by fermenting a wide range of substrates such as glucose, fructose, D-xylose, lactose, maltose, sucrose, mannose, galactose, cellobiose, pullulan and soluble starch. Arabinose, xylan, cellulose, olive oil and Tween 80 were not fermented. The predominant fermentation end products after growth on glucose were lactate, acetate, ethanol, CO2 and small amounts of isovaleric acid, butyric acid, propionic acid, 1-pentanol and 2-propanol. Thiosulfate was reduced to H2S. Strain KB-1TP was sensitive to tetracycline, chloramphenicol, penicillin G, neomycin, kanamycin, vancomycin and rifampicin at concentrations of 100 microg ml(-1). No effect was observed with chloramphenicol and neomycin at concentrations of 10 microg ml(-1). This indicates that strain KB-1TP belongs to the bacterial domain. The G+C content of the DNA was 37 mol%. The comparison of the 165 rDNA sequence to that of closely related strains revealed that strain KB-1TP belonged to clostridial cluster V, showing highest sequence identities (92.7%) to members of the genus Thermoanaerobacter. Taking into account the physiological and molecular properties of the new isolate, it is proposed that strain KB-1TP should be classified as a new species of the genus Thermoanaerobacter, designated Thermoanaerobacter yonseiensis. The type strain, KB-1TP, has been deposited in the Korean Federation of Culture Collections (KFCC 11116P) as a patent strain and in the Deutsche Sammlung von Mikroorganismen und Zellkulturen as a type strain (= DSM 13777T).

Bacillaceae↗

PubMed2001

5-fluorouracil-induced leukoencephalopathy in patients with breast cancer.

The purpose of this study is to determine the characteristic clinical features, radiologic findings, and precipitating and prognostic factors in the patients with breast cancer and with 5-Fluorouracil (5-FU)-induced leukoencephalopathy. We reviewed the medical records of six breast cancer patients who developed leukoencephalopathy after chemotherapy which included 5-FU and also evaluated thorough neurological examinations including mini-mental status examination, cerebrospinal fluid studies, brain images and brain biopsies. Six patients exhibited slowly progressing neurologic symptoms characterized by the impairment of cognitive function, abulia, ataxic gait, and/or akinetic mutism. None of the patients had any specific causes or etiologic factors for leukoencephalopathy. Brain MRI in all patients showed diffuse periventricular white matter changes in the T2-weighted MR image. Brain biopsy in Patient 1 showed fragmented axonal fiber and minimally deprived myelination with many scattered macrophages. Five patients who treated with steroids at the onset of neurological symptoms showed clinical improvement, regardless of their age, sex, the pathology and stage of breast cancer, or the total dosage of chemotherapeutic agents. We conclude that leukoencephalopathy in these cases could be attributable to 5-FU neurotoxicity and suggest that the administration of steroids might be the treatment of choice.

Adenocarcinoma, Mucinous↗

PubMed2000

Involvement of cytosolic phospholipase A2, and the subsequent release of arachidonic acid, in signalling by rac for the generation of intracellular reactive oxygen species in rat-2 fibroblasts.

Although there have been a number of recent studies on the role of Rac in the generation of reactive oxygen species (ROS), details of the signalling pathway remain unclear. In the present study we analysed the extent to which the activation of cytosolic phospholipase A(2) and the resultant release of arachidonic acid (AA) are involved in the Rac-mediated generation of ROS. Transfection of Rat-2 cells with RacV12, a constitutively active form of Rac1, induced elevated levels of ROS, as reflected by increased H(2)O(2)-sensitive fluorescence of 2', 7'-dichlorofluorescein. These effects could be blocked by inhibiting phospholipase A(2) or 5-lipoxygenase but not by inhibiting cyclo-oxygenase. The application of exogenous AA increased levels of ROS but the effect was dependent on the further metabolism of AA to leukotrienes C(4)/D(4)/E(4) by 5-lipoxygenase. Indeed, the exogenous application of a mixture of leukotrienes C(4)/D(4)/E(4) elicited transient elevations in the levels of ROS that were blocked by catalase. These findings indicate that phospholipase A(2) and subsequent AA metabolism by 5-lipoxygenase act as downstream mediators in a Rac signalling pathway leading to the generation of ROS.

Animals↗

PubMed2000

Role of cytosolic phospholipase A(2) as a downstream mediator of Rac in the signaling pathway to JNK stimulation.

Rac is an important regulatory molecule implicated in c-jun N-terminal kinase (JNK) activation in response to stress and cytokines. However, the signaling events that mediate the activation of JNK by Rac are not yet well characterized. To broaden our understanding of downstream mediators that link Rac signals to the JNK pathway, we investigated whether cytosolic phospholipase A(2) (cPLA(2)) is involved in Rac activation of JNK. In this report we demonstrate that either co-transfection with antisense cPLA(2) oligonucleotide or pretreatment with arachidonyltrifluoromethyl ketone (AACOCF3), a potent and specific inhibitor of cPLA(2), inhibits Rac-mediated JNK activation, implying a potential role of cPLA(2) in Rac-signaling to JNK activation. In accordance with this observation, we demonstrate that the addition of exogenous arachidonic acid (AA), a principal product of Rac-activated cPLA(2), or leukotrienes, products of 5-lipoxygenase (5-LO) of AA, caused a specific stimulation of JNK. Together, our findings suggest that cPLA(2) mediates, at least partly, the signaling cascade by which Rac stimulates JNK.

Animals↗

PubMed2000

Effects of dehydroepiandrosterone on collagen and collagenase gene expression by skin fibroblasts in culture.

Dehydroepiandrosterone (DHEA) and its sulfate (DHEA-S) are the most abundant steroids in humans whose low levels are related to aging, greater incidence of various cancers, immune dysfunction, atherosclerosis, and osteoporosis. It has been shown that collagen and collagenase gene expression decreases in fibroblasts taken from more aged donors. In this paper, to investigate the relationship between DHEA and skin aging, we examined the effects of DHEA on the regulation of collagen, collegians and stromelysin-1 genes in cultured human skin fibroblasts. In collagen assay, DHEA slightly increased collagen production in a dose-related fashion, its maximal effect occurred at 10(-5) M DHEA (P>0.05). In the presence of DHEA, steady-state levels of alpha1 (I) procollagen mRNA increased to 1. 6-fold of the non-treated group, while those of fibronectin were not. Interestingly, DHEA differently regulated collagenase and stromelysin-1 gene expression. The steady-state levels of collagenase mRNA decreased in response to DHEA by 40%, whereas those of stromelysin-1 mRNA increased up to 2.4-fold, compared to controls. Similar results were obtained for chloramphenicol acetyltransferase assay (CAT); maximal promoter activation of stromelysin-1 gene occurred at 10(-6) M DHEA, 4.5-fold higher than control. CAT assay revealed that treatment with 10(-5) M DHEA resulted in a strong ( approximately 70%) inhibition of the collagenase promoter activity. In our experiments, the effects of DHEA on these gene expressions were higher at pharmacologic concentration (>/=10(-5) M) than those at physiologic concentration (10(-8)-10(-6) M). This study suggests that the level of DHEA may be related to the process of skin aging through the regulation of production and degradation in extracellular matrix.

Adult↗