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.

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.

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.

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.

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).

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.

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.

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.

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.

Automated oxyhemoglobin dissociation curve construction to assess sickle cell anemia therapy

Oxyhemoglobin dissociation curves measure the most important function of red blood cells - the affinity for oxygen and its delivery to the tissues. This function may be deranged in sickle cell anemia and some other hemoglobinopathies. An automated oxyhemoglobin dissociation curve analyzer constructed dissociation curves in 55 patients with hemoglobinopathies and in 24 control subjects while maintaining constant temperature and pH. Sigmoid curves were converted to rectilinear ones using the Hill equation. Oxygen affinity of red cells was assessed by calculation of P50 (the PO2 at which hemoglobin is half saturated). Results revealed separation of oxyhemoglobin dissociation Hill plots according to phenotype but with wide variability. Mean oxygen affinity of fetal hemoglobin was greatest, whereas that of sickle hemoglobin was least. Other hemoglobins were intermediate. A positive correlation between decreased oxygen affinity and carboxyhemoglobin confirmed the decreased oxygen affinity of sickle hemoglobin and decreased oxygen affinity and increased diphosphoglycerate in red cells. Hill plots are less sensitive discriminators of oxygen affinity than traditional sigmoid dissociation curves and offer no particular advantage. Serial studies in a subset of three sickle cell anemia patients treated conservatively suggest automated oxyhemoglobin dissociation curves may be useful in assessment of effectiveness of newer therapies of sickle cell anemia after refinement of the method and studies of larger populations.

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.

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.

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.

LDL stimulates collagen mRNA synthesis in mesangial cells through induction of PKC and TGF-beta expression

Abnormal lipid accumulation in glomeruli could be implicated in the pathogenesis of glomerulosclerosis. Low-density lipoprotein (LDL) stimulates collagen mRNA expression in cultured human mesangial cells (HMC). To explore the possible molecular mechanisms by which LDL promotes collagen gene expression, we examined the effects of LDL on protein kinase C (PKC) activity and transforming growth factor-beta (TGF-beta) expression in relation to collagen gene regulation in HMC. LDL (200 microg/ml) induced an acute increase in PKC activity, particularly PKC-alpha and -delta, within 15 min, which decreased to control value at 2 h. LDL stimulated TGF-beta1, and alpha1(I) and alpha1(IV) collagen mRNA expression within 30 min of incubation with HMC, and levels remained elevated until hour 4. LDL induced the secretion of TGF-beta by HMC. This TGF-beta was shown by CCL-64 mink lung cell assay to be, in part, bioactive. The stimulatory effects of LDL on collagen gene regulation in HMC were blocked by the inhibition of PKC using GF-109203X (GFX) or the downregulation of PKC using phorbol myristate acetate. Neutralizing antibody to TGF-beta inhibited the increased collagen mRNA expression by HMC exposed to LDL. The downregulation or inhibition of PKC did not affect the stimulatory effect of LDL on TGF-beta mRNA or protein expression. These results suggest that in HMC, LDL stimulates collagen mRNA expression through the rapid activation of PKC-alpha and -delta and transcriptional upregulation of TGF-beta. Thus PKC and TGF-beta may function as independent key signaling intermediaries in the pathway by which LDL upregulates collagen gene expression in HMC.

Roles of phosphatidylinositol 3-kinase and Rac in the nuclear signaling by tumor necrosis factor-alpha in rat-2 fibroblasts

We investigated the extent to which phosphatidylinositol 3-kinase (PI 3-kinase) and Rac, a member of the Rho family of small GTPases, are involved in the signaling cascade triggered by tumor necrosis factor (TNF)-alpha leading to activation of c-fos serum response element (SRE) and c-Jun amino-terminal kinase (JNK) in Rat-2 fibroblasts. Inhibition of PI 3-kinase by LY294002 or wortmannin, two specific PI 3-kinase antagonists, or co-transfection with a dominant negative mutant of PI 3-kinase dose-dependently blocked stimulation of c-fos SRE by TNF-alpha. Similarly, LY294002 significantly diminished TNF-alpha-induced activation of JNK, suggesting that nuclear signaling triggered by TNF-alpha is dependent on PI 3-kinase-mediated activation of both c-fos SRE and JNK. We also found nuclear signaling by TNF-alpha to be Rac-dependent, as demonstrated by the inhibitory effect of transient co-transfection with a dominant negative Rac mutant, RacN17. Our findings suggest that Rac is situated downstream of PI 3-kinase in the TNF-alpha signaling pathway to the nucleus, and we conclude that PI 3-kinase and Rac each plays a pivotal role in the nuclear signaling cascade triggered by TNF-alpha.

Modes of action of acarbose hydrolysis and transglycosylation catalyzed by a thermostable maltogenic amylase, the gene for which was cloned from a Thermus strain

A maltogenic amylase gene was cloned in Escherichia coli from a gram-negative thermophilic bacterium, Thermus strain IM6501. The gene encoded an enzyme (ThMA) with a molecular mass of 68 kDa which was expressed by the expression vector p6xHis119. The optimal temperature of ThMA was 60 degrees C, which was higher than those of other maltogenic amylases reported so far. Thermal inactivation kinetic analysis of ThMA indicated that it was stabilized in the presence of 10 mM EDTA. ThMA harbored both hydrolysis and transglycosylation activities. It hydrolyzed beta-cyclodextrin and starch mainly to maltose and pullulan to panose. ThMA not only hydrolyzed acarbose, an amylase inhibitor, to glucose and pseudotrisaccharide (PTS) but also transferred PTS to 17 sugar acceptors, including glucose, fructose, maltose, cellobiose, etc. Structural analysis of acarbose transfer products by using methylation, thin-layer chromatography, high-performance ion chromatography, and nuclear magnetic resonance indicated that PTS was transferred primarily to the C-6 of the acceptors and at lower degrees to the C-3 and/or C-4. The transglycosylation of sugar to methyl-alpha-D-glucopyranoside by forming an alpha-(1,3)-glycosidic linkage was demonstrated for the first time by using acarbose and ThMA. Kinetic analysis of the acarbose transfer products showed that the C-4 transfer product formed most rapidly but readily hydrolyzed, while the C-6 transfer product was stable and accumulated in the reaction mixture as the main product.

UV-B-induced photomorphogenesis in Arabidopsis thaliana

Relatively little is known about the types of photomorphogenic responses and signal transduction pathways that plants employ in response to ultraviolet-B (UV-B, 290-320 nm) radiation. In wild-type Arabidopsis seedlings, hypocotyl growth inhibition and cotyledon expansion were both reproducibly promoted by continuous UV-B. The fluence rate response of hypocotyl elongation was examined and showed a biphasic response. Whereas photomorphogenic responses were observed at low doses, higher fluences resulted in damage symptoms. In support of our theory that photomorphogenesis, but not damage, occurs at low doses of UV-B, photomorphogenic responses of UV-B sensitive mutants were indistinguishable from wild-type plants at the low dose. This allowed us to examine UV-B-induced photomorphogenesis in photoreceptor deficient plants and constitutive photomorphogenic mutants. The cry1 cryptochrome structural gene mutant, and phytochrome deficient hy1, phyA and phyB mutant seedlings resembled wild-type seedlings, while phyA/phyB double mutants were less sensitive to the photomorphogenic effects of UV-B. These results suggest that either phyA or phyB is required for UV-B-induced photomorphogenesis. The constitutive photomorphogenic mutants cop1 and det1 did not show significant inhibition of hypocotyl growth in response to UV-B, while det2 was strongly affected by UV-B irradiation. This suggests that COP1 and DET1 work downstream of the UV-B signaling pathway.

All-trans-retinoic acid down-regulates elastin promoter activity elevated by ultraviolet B irradiation in cultured skin fibroblasts

Topical tretinoin therapy produces clinical improvements in the fine wrinkling of photodamaged skin, possibly by enhancement of collagen synthesis. A major biochemically and histologically detectable change in photodamaged skin is the accumulation of abnormal elastic fibers (elastotic material). However, little is known about the effects of retinoic acid and ultraviolet B (UVB) on elastin gene expression. Consequently, we examined the effects of all-trans-retinoic acid (t-RA) and UVB on elastin gene expression in cultured human skin fibroblasts in vitro. Elastin mRNA gene expression was up-regulated in response to UVB by approximately equal to 3-fold, in a dose dependent manner, between 3 and 10 mJ/cm2 doses. Similar results were obtained by chloramphenicol acetyltransferase assay, in which a maximal promoter activation more than 5.4-fold that in nonirradiated controls occurred after a single dose of 20 mJ/cm2. Also t-RA inhibited the increase in elastin mRNA level following a single exposure to UVB by approximately 16%, and the increase in promotor activity by about 65%. The inhibitory effect of t-RA on elastin induced by UVB was also demonstrated by indirect immunofluorescence studies. Taken together, t-RA down-regulated human elastin gene expression elevated by a single exposure to UVB at transcriptional and possibly protein levels. These results suggest that the anti-photoaging effect of t-RA may be related, at least in part, to down-regulation of elastin gene expression elevated by UVB.

Photomorphogenic development of the Arabidopsis shy2-1D mutation and its interaction with phytochromes in darkness

We previously reported a photomorphogenic mutation of Arabidopsis thaliana, shy2-1D, as a dominant suppressor of a hy2 mutation. Here, we report that shy2-1D confers various photo-responsive phenotypes in darkness and the dark phenotypes of the mutant are affected by phytochrome deficiency. Dark-grown seedlings of the mutant developed several photomorphogenic characteristics such as short hypocotyls, cotyledon expansion and opening, and partial differentiation of plastids. When grown further in darkness, the mutant plant underwent most of the developmental stages of a light-grown wild-type plant, including development of foliar leaves, an inflorescence stem with cauline leaves, and floral organs. In addition, two light-inducible genes, the nuclear-encoded CAB and the plastid-encoded PSBA genes, were highly expressed in the dark-grown mutant seedlings. Furthermore, reduced gravitropism, a phytochrome-modulated response, was observed in the mutant hypocotyl in darkness. Thus, shy2-1D is one of the most pleiotropic photomorphogenic mutations identified so far. The results indicate that SHY2 may be a key component regulating photomorphogenesis in Arabidopsis. Surprisingly, double mutants of the shy2-1D mutant with the phytochrome-deficient mutants hy2, hy3(phyB-1) and fre1-1(phyA-201) showed reduced photomorphogenic response in darkness with a longer hypocotyl, a longer inflorescence stem, and a lower level expression of the CAB gene than the shy2-1D single mutant. These results showed that phytochromes function in darkness in the shy2-1D mutant background. The implications of these results are discussed.

Evidence for role of phospholipase A2 in phosphatidic acid-induced signaling to c-fos serum response element activation

The activity of exogenous phosphatidic acid (PA) to transactivate c-fos serum response element (SRE) was investigated by transient transfection analysis. Incubation of Rat-2 fibroblast cells with exogenous PA caused a stimulation of c-fos SRE-linked luciferase activity in a dose- and time-dependent manner. The SRE stimulation by PA was dramatically reduced by either pre-treatment with mepacrine, an inhibitor of phospholipase A2 (PLA2), or co-transfection with antisense cytosolic phospholipase A2 (cPLA2) oligonucleotide, whereas lysophosphatidic acid (LPA)-induced SRE activation was not affected. Consistent with this specific requirement for PLA2 by PA, the translocation of cPLA2 protein was rapidly induced followed by PA treatment. Together, these results suggest that PLA2, especially cPLA2, plays a critical role in the nuclear signaling cascade of PA in Rat-2 fibroblast cells.

Phosphatidic acid-induced elevation of intracellular Ca2+ is mediated by RhoA and H2O2 in Rat-2 fibroblasts

We have investigated possible roles of RhoA and H2O2 in the elevation of intracellular Ca2+ ([Ca2+]i) by phosphatidic acid (PA) in Rat-2 fibroblasts. PA induced a transient elevation of [Ca2+]i in the presence or absence of EGTA. Lysophosphatidic acid (LPA) also increased [Ca2+]i, but the sustained Ca2+ response was inhibited by EGTA. LPA stimulated the production of inositol phosphates, but PA did not. In the presence of EGTA, preincubation with LPA completely blocked the subsequent elevation of [Ca2+]i by PA, but not vice versa. PA stimulated the translocation of RhoA to the particulate fraction as did LPA. Scrape loading of C3 transferase inhibited the transient Ca2+ response to PA, but not to LPA, suggesting an essential role of RhoA in the elevation of [Ca2+]i by PA. H2O2 also induced a transient increase of [Ca2+]i as did PA. H2O2 scavengers, catalase and N-acetyl-L-cysteine, completely blocked the rise of [Ca2+]i stimulated by PA, but not by LPA. Furthermore, preincubation with PA blocked the subsequent Ca2+ response to H2O2, and the incubation with H2O2 also blocked the PA-induced rise of [Ca2+]i. Thus, it was suggested that PA stimulated Ca2+ release from PA-sensitive, but not inositol 1,4,5-trisphosphate-sensitive, Ca2+ stores by the activation of RhoA and intracellular H2O2.

Intracellular hemoglobin S polymerization and the clinical severity of sickle cell anemia

Recent work has enabled us to quantitate the four variables (2,3-DPG concentration, pHi, non-S hemoglobin composition, and O2 saturation) that modulate the equilibrium solubility (csat) of Hb S inside sickle erythrocytes (SS RBCs). Using measured values of mean corpuscular hemoglobin concentration (MCHC), 2,3-DPG concentration, and %Hb (F+A2), along with estimates of pHi and the Deltacsat due to partial oxygenation of SS RBCs in the microcirculation, we calculated the mean polymer fraction (fp) in erythrocytes from 46 SS homozygotes. Values of fp derived from the conservation of mass equation ranged from 0.30 to 0.59. MCHC and %Hb F were major determinants of the magnitude of fp; 2,3-DPG concentration and pHi also contributed, but to a lesser extent. A clinical severity score (CSS) was assigned to each patient based on mean hospitalization rate. There was a weak, but statistically significant, negative correlation between fp and steady state hematocrit (P = .017), but none between fp and whole blood hemoglobin concentration (P = .218). Although there was no correlation between fp and mean number of hospitalization days per year, patients with the greatest number of admissions and hospitalization days were found only among those who had an fp > 0.45. All five patients who died during the follow-up period (median, 7 years; range, 3 to 10 years) had fp values >/=0.48. However, patients with few admissions, low hospitalization days, and long survivals occurred at all fp levels. These results suggest that the clinical course of homozygous SS disease cannot be predicted by mean fp calculations, which assume a homogeneous distribution of the five variables that modulate intraerythrocytic polymerization. A heterogeneous distribution is more likely; so the amount of polymerized Hb S could vary considerably among cell populations. Factors such as membrane abnormalities and endothelial cell interactions may also contribute to clinical severity.

Exogenous C2-ceramide activates c-fos serum response element via Rac-dependent signalling pathway

Ceramide is an important regulatory molecule implicated in a variety of biological processes in response to stress and cytokines. To understand the signal transduction pathway of ceramide to the nucleus, in the present study, we examined whether C2-ceramide, a cell permeable ceramide, activates c-fos serum response element (SRE). Treatment of Rat-2 fibroblast cells with C2-ceramide caused the stimulation of c-fos SRE-dependent reporter gene activity in a dose- and time-dependent manner by transient transfection analysis. Next, we examined the role of Rho family GTPases in the ceramide-induced signalling to SRE activation. By reporter gene analysis following transient transfections with various plasmids expressing a dominant negative mutant form of Cdc42, Rac1 or RhoA, C2-ceramide-induced SRE activation was shown to be selectively repressed by pEXV-RacN17 encoding a dominant negative mutant of Rac1, suggesting that Rac activity is essential for the signalling cascade of ceramide to the nucleus. In a further study to analyse the downstream mediator of Rac in the ceramide-signalling pathway, we observed that either pretreatment with mepacrine, a potent and specific inhibitor of phospholipase A2, or co-transfection with antisense cytosolic phospholipase A2 (cPLA2) oligonucleotide repressed the C2-ceramide-induced SRE activation selectively, implying a critical role of cPLA2 in C2-ceramide-induced signalling to nucleus. Consistent with these results, the translocation of cPLA2 protein as well as the release of arachidonic acid, a principal product of phospholipase A2, was rapidly induced by the addition of C2-ceramide in a Rac-dependent manner. Together, our findings suggest the critical role of 'Rac and subsequent activation of phospholipase A2' in ceramide-signalling to nucleus.

Rac GTPase activity is essential for EGF-induced mitogenesis

Rac, a member of the Rho family GTPases, has been implicated in the regulation of a wide range of biological processes including actin remodeling, cell transformation, G1 cell cycle progression, and gene expression. To determine whether Rac GTPase activity is required for epidermal growth factor-induced mitogenesis, Rat-2 stable cells expressing a dominant-negative Rac1 mutant, RacN17, were prepared. Exposure to EGF exhibited a significantly restricted growth response in Rat-2-RacN17 cells compared to Rat-2 parental cells, suggesting an essential role of Rac in EGF-induced mitogenesis. In contrast, addition of lysophosphatidic acid exerted the same level of growth in Rat-2 and Rat-2-RacN17 cells. To gain further evidence for the essential role of Rac in EGF-induced mitogenesis, we performed the microinjection experiment. EGF-induced DNA synthesis was significantly blocked by microinjection of recombinant RacN17 protein, and not control IgG. Our further study to analyze the downstream mediator of Rac in EGF-signaling to mitogenesis demonstrated that Rac-activated phospholipase A2 plays a critical role. Taken together, our results suggest that the "Rac and Rac-activated PLA2" cascade is one of the major mitogenic pathways induced by EGF.

Nucleotide sequence and revised map location of the arn gene from bacteriophage T4

Non-glucosylated (Glu-) T-even phage DNAs are restricted by Escherichia coli RgIA and RgIB endonucleases with different specificities. RgIB endonuclease activity is strongly inhibited by anti-restriction endonuclease (Arn) encoded by the bacteriophage T4 genome. The nucleotide sequence of the arn gene encoding Arn was determined. The product of the cloned arn gene was overexpressed by the T7 RNA polymerase/promoter system, and its molecular size is consistent with that predicted from the open reading frame of the arn gene. The arn gene is located between the asiA gene and motA gene in the region of 161,300-161,578 nucleotides.