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Biomedical subjects

L He

Publications and source records attributed to L He.

At least 163 records · Page 9Linked to original sources
PubMed2000

Induction of IkappaBalpha mRNA expression in the brain by glucocorticoids: a negative feedback mechanism for immune-to-brain signaling.

Peripheral injection of bacterial endotoxin lipopolysaccharide (LPS) induces brain mRNA expression of the proinflammatory cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha and the cytokine-responsive immediate-early gene IkappaBalpha. Peripheral LPS also increases levels of plasma glucocorticoids. Whether the induction of IkappaBalpha mRNA in the brain after peripheral LPS injection is caused by the feedback action of glucocorticoids has not been determined. In this study, we examined the mRNA expression of IkappaBalpha and IL-1beta in the rat brain by in situ hybridization histochemistry. Injection of the glucocorticoid agonist dexamethasone induced IkappaBalpha mRNA expression in the brain in a pattern identical to that of LPS injection. LPS but not dexamethasone also induced IL-1beta mRNA expression. Pretreatment with dexamethasone 30 min before LPS injection enhanced the expression of IkappaBalpha mRNA in the brain in a dose-dependent manner. Immobilization of rats for 2 hr (which raises glucocorticoid levels) also induced IkappaBalpha mRNA expression without inducing the expression of IL-1beta. Brain IkappaBalpha expression induced by peripheral LPS injection was attenuated by pretreatment of rats with the glucocorticoid antagonist RU-486. Finally, increased expression of IL-1beta mRNA in the brain was observed at 4 hr after peripheral LPS injection in adrenalectomized rats compared with sham-operated rats. These results reveal that in the brain glucocorticoids selectively induce IkappaBalpha mRNA expression, which serves as a negative feedback mechanism for peripheral LPS-induced synthesis of proinflammatory cytokines. Such an inhibitory control mechanism may be important for preventing prolonged expression of proinflammatory cytokines in the brain after peripheral immune challenge.

Animals↗
PubMed2000

Cloning of DPK, a novel dendritic cell-derived protein kinase activating the ERK1/ERK2 and JNK/SAPK pathways.

Mitogen-activated protein kinase (MAPK) cascades are the major signaling systems transducing extracellular signals into intracellular responses, which mainly include the extracellular signal-regulated kinase (ERK) pathway, the c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) pathway, and the p38 pathway. From dendritic cell cDNA library, we isolated a full-length cDNA encoding a potentially novel 898-residue kinase, which was designated DPK. The protein contained a potential kinase domain at the N-terminal exhibiting homology with MEKK1-, MEKK2-, MEKK3-, MEKK4-, MEKK5-, Tpl-2-, and p21-activated kinases (PAKs), but no GTPase-binding domain which is characteristic of PAKs. Northern blotting analysis showed that DPK was ubiquitously expressed in normal tissues, with abundant expression in kidney, skeletal muscle, heart, and liver. When overexpressed in transfected NIH3T3 cells, it could activate both the ERK1/ERK2 pathway and the SAPK pathway in a dose-dependent manner, but not affect the p38 pathway. These findings suggested that DPK might be a novel candidate MAPKKK.

Amino Acid Sequence↗
PubMed2000

Activation of mitogen-activated protein kinases is required for alpha1-adrenergic agonist-induced cell scattering in transfected HepG2 cells.

Activation of alpha1B-adrenergic receptors ((alpha1B)AR) by phenylephrine (PE) induces scattering of HepG2 cells stably transfected with the (alpha1B)AR (TFG2 cells). Scattering was also observed after stimulation of TFG2 cells with phorbol myristate acetate (PMA) but not with hepatocyte growth factor/scatter factor, epidermal growth factor, or insulin. PMA but not phenylephrine rapidly activated PKCalpha in TFG2 cells, and the highly selective PKC inhibitor bisindolylmaleimide (GFX) completely abolished PMA-induced but not PE-induced scattering. PE rapidly activated p44/42 mitogen-activated protein kinase (MAPK), p38 MAPK, c-Jun N-terminal kinase (JNK), and AP1 (c-fos/c-jun). Selective blockade of p42/44 MAPK activity by PD98059 or by transfection of a MEK1 dominant negative adenovirus significantly inhibited the PE-induced scattering of TFG2 cells. Selective inhibition of p38 MAPK by SB203850 or SB202190 also blocked PE-induced scattering, whereas treatment of TFG2 cells with the PI3 kinase inhibitors LY294002 or wortmannin did not inhibit PE-induced scattering. Blocking JNK activation with a dominant negative mutant of JNK or blocking AP1 activation with a dominant negative mutant of c-jun (TAM67) significantly inhibited PE-induced cell scattering. These data indicate that PE-induced scattering of TFG2 cells is mediated by complex mechanisms, including activation of p42/44 MAPK, p38 MAPK, and JNK. Cell spreading has been reported to play important roles in wound repair, tumor invasion, and metastasis. Therefore, catecholamines acting via the (alpha1)AR may modulate these physiological and pathological processes.

Adrenergic alpha-Agonists↗
PubMed2000

Inhibition of the interferon-gamma/signal transducers and activators of transcription (STAT) pathway by hypermethylation at a STAT-binding site in the p21WAF1 promoter region.

Expression of the cyclin-dependent kinase inhibitor p21WAF1 can be up-regulated by activation of signal transducers and activators of transcription (STAT) proteins in response to IFN-gamma. In this study, we examined CpG methylation at the p21WAF1 promoter region in rhabdomyosarcomas (RMSs) using Southern blot analysis with the methylation-sensitive restriction enzyme HpaII. Sis-inducible element (SIE)-1, a STAT-responsive element located upstream of the p21 WAF1 CpG island, was completely methylated at an internal CpG in 13 of 26 (50%) primary RMS tumors and 2 of 5 RMS cell lines. In contrast, all normal tissues examined showed a partial methylation pattern at SIE-1. Complete methylation within SIE-1 strongly correlated with decreased p21WAF1 mRNA expression in RMS. We further studied the effects of SIE-1 hypermethylation on p21WAF1 induction by STAT activation. CpG methylation within SIE-1 significantly inhibited binding of activated STAT1 in electrophoretic mobility shift assays and abrogated STAT-mediated transcription activation in response to IFN-gamma in luciferase reporter gene assays. Activation of STAT1 in response to IFN-gamma resulted in increased p21WAF1 expression and growth suppression in RMS cells containing unmethylated SIE-1 but failed to induce p21WAF1 or growth inhibition in RD and A673 cells, both of which were completely methylated within SIE-1. However, demethylation at SIE-1, induced by a demethylating agent 5-aza-2'-deoxycytidine, reactivated p21WAF1 expression and restored the responsiveness to IFN-gamma in RD cells. Our results indicate a mechanism by which altered DNA methylation in the p21 WAF1 promoter region, by precluding STAT1 binding to SIE-1, directly inhibits the p21WAF1 induction and cell growth regulation through the IFN-gamma/STAT signaling pathway in RMS cells.

Antimetabolites, Antineoplastic↗
PubMed2000

On the total synthesis and preliminary biological evaluations of 15(R) and 15(S) aza-dEpoB: a Mitsunobu inversion at C15 in pre-epothilone fragments.

[reaction-see text] The syntheses of two epothilone analogues, 15(S)-aza-12,13-desoxyepothilone B and the epimeric 15(R)-aza-12,13-desoxyepothilone B, are described. A Mitsunobu inversion was utilized for elaboration of pre-epothilone fragments to the corresponding macrolactam. Tubulin binding and cytotoxicity profiles of these analogues are presented.

Antineoplastic Agents↗
PubMed2000

Lead and calcium produce rod photoreceptor cell apoptosis by opening the mitochondrial permeability transition pore.

Calcium overload is suggested to play a fundamental role in the process of rod apoptosis in chemical-induced and inherited retinal degenerations. However, this hypothesis has not been tested directly. We developed an in vitro model utilizing isolated rat retinas to determine the mechanisms underlying Ca(2+)- and/or Pb(2+)-induced retinal degeneration. Confocal microscopy, histological, and biochemical studies established that the elevated [Ca(2+)] and/or [Pb(2+)] were localized to photoreceptors and produced rod-selective apoptosis. Ca(2+) and/or Pb(2+) induced mitochondrial depolarization, swelling, and cytochrome c release. Subsequently caspase-9 and caspase-3 were sequentially activated. Caspase-7 and caspase-8 were not activated. The effects of Ca(2+) and Pb(2+) were additive and blocked completely by the mitochondrial permeability transition pore (PTP) inhibitor cyclosporin A, whereas the calcineurin inhibitor FK506 had no effect. The caspase inhibitors carbobenzoxy-Leu-Glu-His-Asp-CH(2)F and carbobenzoxy-Asp-Glu-Val-Asp-CH(2)F, but not carbobenzoxy-Ile-Glu-Thr-Asp-CH(2)F, differentially blocked post-mitochondrial events. The levels of reduced and oxidized glutathione and pyridine nucleotides in rods were unchanged. Our results demonstrate that rod mitochondria are the target site for Ca(2+) and Pb(2+). Moreover, they suggest that Ca(2+) and Pb(2+) bind to the internal metal (Me(2+)) binding site of the PTP and subsequently open the PTP, which initiates the cytochrome c-caspase cascade of apoptosis in rods.

Animals↗
PubMed2000

A common pharmacophore for Taxol and the epothilones based on the biological activity of a taxane molecule lacking a C-13 side chain.

Extensive structure-activity studies done with Taxol have identified the side chain at C-13 as one of the requirements for biological activity. Baccatin III, an analogue of Taxol lacking the C-13 side chain, has none of the biological characteristics of Taxol. Since 2-m-azido Taxol, a Taxol derivative with a m-azido substituent in the C-2 benzoyl ring, has greater activity than Taxol, we questioned whether 2-m-azido baccatin III might be active. 2-m-Azido baccatin III inhibited the proliferation of human cancer cells at nanomolar concentrations, blocked cells at mitosis, and reorganized the interphase microtubules into distinct bundles, a typical morphological change induced by Taxol. In contrast to 2-m-azido baccatin III, 2-p-azido baccatin III was similar to baccatin III, having no Taxol-like activity, further indicating the specificity and significance of the 2-meta position substituent. Molecular modeling studies done with the C-2 benzoyl ring of Taxol indicated that it fits into a pocket formed by His227 and Asp224 on beta-tubulin and that the 2-m-azido, in contrast to the 2-p-azido substituent, is capable of enhancing the interaction between the benzoyl group and the side chain of Asp224. The observation that the C-13 side chain is not an absolute requirement for biological activity in a taxane molecule has enabled the development of a new common pharmacophore model between Taxol and the epothilones.

Antineoplastic Agents, Phytogenic↗
PubMed2000

Interleukin 18 and interleukin 1beta production is decreased in HIV type 1-seropositive hemophiliacs but not in HIV type 1-seropositive nonhemophiliacs.

In Japan, the proportion of hemophiliacs infected with human immunodeficiency virus type 1 (HIV-1) is 40%, whereas more than 90% are infected with hepatitis C virus (HCV). To evaluate the immunological status of hemophiliacs infected with HIV-1, we investigated the pattern of cytokine production in peripheral blood mononuclear cells (PBMCs) of HIV-1-seropositive and -seronegative hemophiliacs, HIV-1-seropositive non-hemophiliacs, and healthy individuals. The production of IL-18 and IL-1beta from PBMCs stimulated with Staphylococcus aureus Cowan strain 1 (SAC) in the HIV-1-seropositive hemophiliacs was significantly decreased in comparison with the other groups. On the other hand, IL-12 production in both HIV-1-seropositive groups was significantly lower than in HIV-1-seronegative groups. TNF-alpha and IL-6 production was similar among the four groups. In contrast, plasma levels of TGF-beta1 were increased in HIV-1-seropositive hemophiliacs, HIV-1-seropositive nonhemophiliacs, and HIV-1-seronegative hemophiliacs, with the highest levels being in HIV-1-seropositive hemophiliacs, suggesting that coinfection with HIV-1 and HCV increases the level of plasma TGF-beta in HIV-1-seropositive hemophiliacs. Treatment of PBMCs from healthy individuals with TGF-beta1 inhibited IL-18 and IL-1beta production without affecting IL-6, IL-10, or TNF-alpha production. Suppression of the expression of caspase 1 mRNA, which is known to be an IL-1beta-converting enzyme and which also cleaves the precursor of IL-18, was observed in the SAC-stimulated PBMCs from healthy individuals after treatment with TGF-beta1 and in the SAC-stimulated PBMCs from HIV-1-seropositive hemophiliacs, suggesting that the decreased production of IL-18 and IL-1beta in HIV-1-seropositive hemophiliacs may be related to the downregulation of caspase 1 mRNA induced by high levels of TGF-beta1 in plasma.

Adolescent↗
PubMed2000

Loss of FBP function arrests cellular proliferation and extinguishes c-myc expression.

The c-myc regulatory region includes binding sites for a large set of transcription factors. The present studies demonstrate that in the absence of FBP [far upstream element (FUSE)-binding protein], which binds to the single-stranded FUSE, the remainder of the set fails to sustain endogenous c-myc expression. A dominant-negative FBP DNA-binding domain lacking effector activity or an antisense FBP RNA, expressed via replication-defective adenovirus vectors, arrested cellular proliferation and extinguished native c-myc transcription from the P1 and P2 promoters. The dominant-negative FBP initially augmented the single-stranded character of FUSE; however, once c-myc expression was abolished, melting at FUSE could no longer be supported. In contrast, with antisense FBP RNA, the single-stranded character of FUSE decreased monotonically as the transcription of endogenous c-myc declined. Because transcription is the major source of super-coiling in vivo, we propose that by binding torsionally strained DNA, FBP measures promoter activity directly. We also show that FUSE is predicted to behave as a torsion-regulated switch poised to regulate c-myc and to confer a higher order regulation on a large repertoire of factors.

Animals↗
PubMed2000

4-(1,3-Dimethoxyprop-2-ylamino)-2,7-dimethyl-8-(2, 4-dichlorophenyl)pyrazolo[1,5-a]-1,3,5-triazine: a potent, orally bioavailable CRF(1) receptor antagonist.

Structure-activity studies in the pyrazolo[1,5-a]-1,3,5-triazine series led to the discovery that compound 11i (DMP696) is a potent hCRF(1) receptor antagonist (K(i) = 1.7 nM vs 7.5 nM for alpha-hel-CRF(9-41), hCRF(1) adenylate cyclase IC(50) = 82 nM vs 286 nM for alpha-hel-CRF(9-41)). Compound 11i has excellent oral pharmacokinetic profiles in rats and dogs (37% and 50% oral bioavailabilities, respectively). This compound displays good activity in the rat situational anxiety model (MED = 3 mg/kg (po)), whereas a literature standard 1 (CP154526-1) was inactive (MED > 30 mg/kg (po)). Analogue 11i reduced stereotypical mouth movements in rhesus monkeys by 50% at 21 mg/kg (po) using the human intruder paradigm. Overall, the profile of pyrazolotriazine 11i indicates that hCRF(1) receptor antagonists may be anxiolytic agents, which have reduced motor side effect profiles.

Administration, Oral↗
PubMed2000

Congenital absence of permanent teeth in a six-generation Chinese kindred.

We report on rare, heritable, permanent tooth agenesis in a large Chinese kindred. The congenital absence of permanent teeth except the first and second accessory teeth was observed in 52 individuals through six successive generations in the kindred comprising 328 members. Clinical assessments were carried out, and inheritance mode and spousal influence of the anomaly on their offspring were analyzed. Consequently, the anomaly was transmitted in an autosomal dominant fashion with incomplete penetrance (P = 0.88), and no significant clinical manifestations other than the oligodontia were found. A geographical or environmental effect on the affected individuals was obviously eliminated, because any who are related to the kindred but live under the same conditions are fully healthy. The disorder we describe, therefore, differs from any previously reported oligodontia/anodontia syndromes. The oligodontia ranged from a few teeth to the whole set of teeth, and usually occurred at a period from age 7 or 8 years, the time when primary teeth are normally replaced by permanent teeth, to the forties. Roentgenography of the affected persons indicated that only the first and/or second accessory teeth with tooth buds developed as permanent teeth. In fact, the diphyodontic germination sometimes occurred in the oral cavity of the affected individuals.

China↗
PubMed2000

Effect of glipizide on dopamine synthesis, release and metabolism in PC12 cells.

Sulfonylureas block ATP-dependent K(+) channels (K/ATP channels) in pancreatic beta cells and brain gamma-aminobutyric acid (GABA) containing neurons causing depolarization-evoked insulin or GABA release. In high concentrations, sulfonylureas also inhibit catecholamine release from bovine adrenal chromaffin cells and isolated guinea pig aorta. In this study, we examined the effect of glipizide, a sulfonylurea, on dopamine release from PC12 cells and found that neither basal nor K(+)-stimulated dopamine release was affected. Although PC12 cells expressed mRNA for the K/ATP channel, functional K/ATP channels could not be demonstrated electrophysiologically, consistent with the lack of effect of glipizide on dopamine release. Glipizide did, however, increase cytoplasmic retention of the acidic dopamine metabolites, 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), indicating blockade of their outward transport. The cellular accumulation of DOPAC was accompanied by reduced tyrosine hydroxylase activity and reduced formation of dopamine and its metabolites presumably by a negative feedback effect of the increased cytoplasmic concentrations of DOPAC.

ATP-Binding Cassette Transporters↗
PubMed2000

Study on the expression of Fas ligand on the surfaces of human cytotrophoblasts in normal pregnancy.

To further study the mechanism of maternal-fetal immune tolerance, the expression of Fas ligand (FasL) on the surfaces of human cytotrophoblasts in normal pregnancy was detected by using immunohistochemical method. High precise color-image measure system for immuno-histochemistry was used to quantitatively analyze the expression of FasL. The results showed that FasL were expressed on the surfaces of placental cytotrophoblasts throughout normal pregnancy. The variance among the first, second and term pregnant stages was also detected. It was suggested that the expression of FasL on the surfaces of placental cytotrophoblasts might play an important role both in the maintenance of pregnancy and in the normal development of fetus. The maternal specific T cell apoptosis induced by Fas/FasL is one of the significant mechanisms of maternal-fetal immune tolerance.

Adult↗
PubMed2000

Melanocortin 1 receptor variation in the domestic dog.

The melanocortin 1 receptor (Mc1r) is encoded by the Extension locus in many different mammals, where a loss-of-function causes exclusive production of red/yellow pheomelanin, and a constitutively activating mutation causes exclusive production of black/brown eumelanin. In the domestic dog, breeds with a wild-type E allele, e. g., the Doberman, can produce either pigment type, whereas breeds with the e allele, e.g., the Golden Retriever, produce exclusively yellow pigment. However, a black coat color in the Newfoundland and similar breeds is thought to be caused by an unusual allele of Agouti, which encodes the physiologic ligand for the Mc1r. Here we report that the predicted dog Mc1r is 317 residues in length and 96% identical to the fox Mc1r. Comparison of the Doberman, Newfoundland, Black Labrador, Yellow Labrador, Flat-coated Retriever, Irish Setter, and Golden Retriever revealed six sequence variants, of which two, S90G and R306ter, partially correlated with a black/brown coat and red/yellow coat, respectively. R306ter was found in the Yellow Labrador, Golden Retriever, and Irish Setter; the latter two had identical haplotypes but differed from the Yellow Labrador at three positions other than R306ter. In a larger survey of 194 dogs and 19 breeds, R306ter and a red/yellow coat were completely concordant except for the Red Chow. These results indicate that the e allele is caused by a common Mc1r loss-of-function mutation that either reoccurred or was subject to gene conversion during recent evolutionary history, and suggest that the allelic and locus relationships for dog coat color genes may be more analogous to those found in other mammals than previously thought.

Alleles↗
PubMed2000

Cellular mechanisms involved in rabbit carotid body excitation elicited by endothelin peptides.

The present study evaluated the effects of endothelin (ET) peptides on carotid sinus nerve (CSN) activity, catecholamine (CA) release, and second messenger signaling pathways in rabbit carotid bodies superfused in vitro, and in dissociated chemosensory type I cells. ET-1 (1.0 microM) and ET-3 (1.0 microM) did not alter basal CSN activity and CA release, but they potentiated nerve activity (P<0. 05) and CA release (P<0.05) evoked by hypoxia. Under basal conditions, ET-1 and ET-3 (1.0 microM each) elevated tissue cyclic AMP (cAMP) levels nearly 3-fold (P<0.001, ET-1; P<0.05, ET-3) and inositol phosphate (IP(n)) levels nearly 4-fold (P<0.01, ET-1). Hypoxia evoked an increase in carotid body cAMP, and this response was also potentiated in the presence of 1.0 microM ET-1 (P<0.01) or 1.0 microM ET-3 (P<0.001). Patch-clamp studies of isolated type I cells showed that 100 nM ET-1 elevated the peak amplitude of voltage-sensitive (L-type) Ca(2+)-currents by an average of 37.6% (P<0.001). Fluorescent Ca(2+)-imaging revealed that 100 nM ET-1 did not alter [Ca(2+)](i) under basal conditions, but that [Ca(2+)](i)-responses evoked by hypoxia were potentiated by 87% (P<0. 01). Our data indicate that ET augments chemoreceptor responses by activating second messenger signaling pathways which promote the phosphorylation of Ca(2+)-channel protein, thereby enhancing stimulus-evoked intracellular Ca(2+) levels.

Animals↗
PubMed2000

Expression of D(3) receptor messenger RNA and binding sites in monkey striatum and substantia nigra after nigrostriatal degeneration: effect of levodopa treatment.

D(3) receptors are prominently localized in the primate caudate-putamen, and D(3) receptor agonist properties may offer an advantage in Parkinson's disease therapy. In the present experiments, we investigated the relationship between D(3) receptor mRNA, D(3) receptor sites and the dopamine transporter in monkey basal ganglia by comparing their distribution in the brain of control and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys (Samirai sciureus). In control monkeys, D(3) receptor mRNA appears to be widely expressed throughout the brain, with a distribution similar to that observed in both man and rodent. D(3) receptors are present in areas which express mRNA but also in some which do not, an observation which suggests they may be both pre- and postsynaptic in the monkey brain. Chronic MPTP administration, which selectively destroys the nigrostriatal system, resulted in a 70 to 99% depletion of the dopamine transporter in the basal ganglia. Autoradiographic analysis showed that after MPTP treatment there was a significant decline in D(3) receptors in the caudate, but not putamen, globus pallidus, substantia nigra or other dopaminergic regions. D(3) receptor mRNA expression was not changed in any region after nigrostriatal lesioning. Two weeks of L-3,4-dihydroxyphenylalanine (levodopa, L-DOPA) treatment, which alleviated Parkinsonism but also induced dyskinesias, reversed the MPTP-induced decline in caudate D(3) receptors. These results show that there is a selective decline in D(3) receptors in the caudate after nigrostriatal degeneration, which is reversed by L-DOPA treatment. Since the majority of dopaminergic nerve terminals were destroyed after MPTP lesioning, the reversal in D(3) receptors after L-DOPA treatment may represent an increase in caudate postsynaptic receptors, which could conceivably contribute to an imbalance in striatal circuitry and the development of dyskinesias.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗