Biomedical subjects

Lan Ma

Publications and source records attributed to Lan Ma.

At least 19 recordsLinked to original sources

PubMed2007

Beta-arrestin signaling and regulation of transcription.

Beta-arrestin 1 and beta-arrestin 2 are well-known negative regulators of G-protein-coupled receptor (GPCR) signaling. Upon GPCR activation, beta-arrestins translocate to the cell membrane and bind to the agonist-occupied receptors. This uncouples these receptors from G proteins and promotes their internalization, thus causing desensitization. However, accumulating evidence indicates that beta-arrestins also function as scaffold proteins that interact with several cytoplasmic proteins and link GPCRs to intracellular signaling pathways such as MAPK cascades. Recent work has also revealed that, in response to activation of certain GPCRs, beta-arrestins translocate from the cytoplasm to the nucleus and associate with transcription cofactors such as p300 and cAMP-response element-binding protein (CREB) at the promoters of target genes to promote transcription. They also interact with regulators of transcription factors, such as IkappaBalpha and MDM2, in the cytoplasm and regulate transcription indirectly. This beta-arrestin-mediated regulation of transcription appears to play important roles in cell growth, apoptosis and modulation of immune functions.

Animals↗

PubMed2006

The effect of L-stepholidine, a novel extract of Chinese herb, on the acquisition, expression, maintenance, and re-acquisition of morphine conditioned place preference in rats.

The effect of L-stepholidine (SPD), a novel alkaloid extract of the Chinese herb Stephania with partial dopamine D1 receptor agonistic and D2 receptor antagonistic dual actions, on morphine conditioned place preference (CPP) was studied. Daily injection of morphine (10 mg/kg, i.p.) for 6 days induced CPP in rats, and daily treatment with SPD at 10 or 20 mg/kg before morphine injection dose-dependently attenuated morphine-induced CPP. On the day following acquisition of morphine CPP, a single administration of SPD at 10 or 20 mg/kg failed to block the expression of CPP. However, daily administration of SPD at 20 mg/kg for 7 days attenuated the maintenance of CPP. Morphine-induced CPP extinguished after a 21-day saline training and then a single injection of morphine (3 mg/kg, i.p.) induced re-acquisition of morphine CPP; however, pretreatment with SPD at 10 or 20 mg/kg 30 min before morphine injection dose-dependently blocked morphine (3 mg/kg, i.p.)-induced re-acquisition of morphine CPP. Furthermore, our data indicate that SPD had no effect on food-induced CPP or state-dependent learning, suggesting that the observed effect of SPD does not result from an inhibition of general learning ability. These results demonstrate that SPD can inhibit acquisition, maintenance, and re-acquisition of morphine conditioned place preference and suggest its potential for treatment of opioid addiction.

Analgesics, Opioid↗

PubMed2006

Different roles of dopamine receptor subtypes in footshock stress-induced enhancement of morphine conditioned place preference.

The present study investigated the involvement of dopamine mechanism in the effect of intermittent footshock stress on the morphine-induced place preference. A single intermittent footshock session significantly enhanced the place preference induced by 3.0mg/kg morphine. This enhancing effect was inhibited by selective D(1) receptor antagonist SCH23390 and selective D(2) receptor antagonist sulpiride pretreatment 20min before footshock session, suggesting dopamine D(1) and D(2) receptors are required for the development of intermittent footshock stress-induced enhancement of morphine-associated place preference. However, different from D(1) and D(2) receptors this enhancing effect was blocked by stimulation of dopamine D(3) receptor with selective D(3) receptor agonist 7-OH-DPAT pretreatment 20min before footshock session which suggest dopamine D(3) receptor play a negative mediation effect on the intermittent footshock stress-induced this enhancement. These results indicate that dopamine D(1), D(2), and D(3) receptor subtypes play different roles in footshock stress-induced enhancement of morphine conditioned place preference.

Animals↗

PubMed2006

Inhibition of transforming growth factor beta-enhanced serum response factor-dependent transcription by SMAD7.

Transforming growth factor (TGF)-beta is present in large amounts in the airways of patients with asthma and with other diseases of the lung. We show here that TGFbeta treatment increased transcriptional activation of SM22alpha, a smooth muscle-specific promoter, in airway smooth muscle cells, and we demonstrate that this effect stems in part from TGFbeta-induced enhancement of serum response factor (SRF) DNA binding and transcription promoting activity. Overexpression of Smad7 inhibited TGFbeta-induced stimulation of SRF-dependent promoter function, and chromatin immunoprecipitation as well as co-immunoprecipitation assays established that endogenous or recombinant SRF interacts with Smad7 within the nucleus. The SRF binding domain of Smad7 mapped to the C-terminal half of the Smad7 molecule. TGFbeta treatment weakened Smad7 association with SRF, and conversely the Smad7-SRF interaction was increased by inhibition of the TGFbeta pathway through overexpression of a dominant negative mutant of TGFbeta receptor I or of Smad3 phosphorylation-deficient mutant. Our findings thus reveal that SRF-Smad7 interactions in part mediate TGFbeta regulation of gene transcription in airway smooth muscle. This offers potential targets for interventions in treating lung inflammation and asthma.

Animals↗

PubMed2006

Decreased morphine analgesia in rat overexpressing beta-arrestin 2 at periaqueductal gray.

Beta-arrestin 2 plays important physiological roles in regulating the function of the mu opioid receptor (muOR) in vivo. Periaqueductal gray (PAG) is a potential structure where morphine produces its antinociception, but it is unclear whether beta-arrestin 2 plays its regulatory effect on morphine at PAG. In the present study beta-arrestin 2 overexpression was induced by adenovirus at PAG of rats. Morphine was administrated in these rats through PAG microinjection and systemic administration. The antinociceptive effects of morphine were abolished in rats received microinjection of morphine at PAG and partially attenuated in rats received systemic administration of morphine. These findings support the notion that PAG is an important site where beta-arrestin 2 plays its regulatory effects on morphine analgesia.

Adenoviridae↗

PubMed2006

[Effects of RNAi on hypoxia inducible factor-1alpha activity and proliferation of hypoxic pulmonary artery smooth muscle cells in rat].

Pulmonary vascular remodeling is one of the major characteristics of hypoxia-induced pulmonary hypertension, mainly represented by over-proliferation of pulmonary artery smooth muscle cells (PASMCs). Hypoxia inducible factor-1alpha (HIF-1alpha) is a transcription factor which is produced by the cells exposed to hypoxia. HIF-1alpha up-regulates the expression of many hypoxia response genes (HRGs) for the body to adapt to hypoxia and maintain homeostasis. The expression of HIF-1alpha in the PASMCs is remarkably elevated under hypoxic condition and it stimulates the proliferation of PASMCs. In this experiment, we used gene clone technology to design and synthesize two siRNAs based on the sequence of HIF-1alpha mRNA. They were separately subcloned into the plasmid of pGenesil-1 containing U6 promoter. The pGenesil-1 vector of the RNA interference eukaryotic expression vector specific to HIF-1alpha gene was constructed. DNA sequencing of the plasmid verified the successful construction of the HIF-1alpha RNAi. We isolated and cultured the PASMCs of rat. The pGenesil-1 vector was transferred into the PASMCs with METAFECTENE in vitro. The positive cell clones transfected with pGenesil-1 were obtained after being screened with 400 mug/ml G418. These PASMCs were cultured in normoxia and hypoxia. After 48 h, the effects of RNAi on the expression of HIF-1alpha mRNA were detected by RT-PCR. The cellular growth activities were assayed by MTT colorimetry and flow cytometry in vitro. The results showed that for the PASMCs cultured in hypoxia for 48 h, the cell proliferation of blank group and control group were remarkably increased and the HIF-1alpha mRNA expressions were up-regulated, while the cell proliferation of the treatment groups did not increase and the HIF-1alpha mRNA expressions were not up-regulated. In conclusion, we successfully constructed the recombinant plasmid of RNAi and transfected them into the PASMCs in vitro. The RNAi inhibited the expression of HIF-1alpha mRNA in the PASMCs, and subsequently it remarkably suppressed the proliferation of PASMCs in hypoxia. These results indicate that HIF-1alpha plays a pivotal role in PASMC proliferation.

Animals↗

PubMed2006

Single and repeated morphine administrations differently regulate expression of N-ethylmaleimide-sensitive factor gene in the rat brain.

The present study investigated the potential effects of single and repeated morphine treatments on gene expression of N-ethylmaleimide-sensitive protein, a key regulatory protein of neurotransmitter release and synaptic plasticity. After a single morphine injection (10 mg/kg), N-ethylmaleimide-sensitive factor gene expression increased significantly in the cortex, hippocampus and periaqueductal gray. In contrast, N-ethylmaleimide-sensitive factor gene expression was not changed after repeated morphine exposures in these brain regions. Sixteen hours after cessation of repeated morphine administration, N-ethylmaleimide-sensitive factor mRNA level increased again to a level approximate to that of the single morphine injection group in the hippocampus, periaqueductal gray and cerebral cortex. These findings suggest that the N-ethylmaleimide-sensitive factor may be involved in the maladaptive changes in the nervous system after opiate treatment.

Analysis of Variance↗

PubMed2006

Enhanced cocaine self-administration in adult rats with adolescent isolation experience.

It is widely accepted that early environmental influences may affect the behavior of adult animals and their responses to psychotropic drugs. Rearing animals in isolation is a relevant paradigm for studying early life stress and for understanding the development of certain neurological and psychiatric diseases. The present study evaluated the effect of adolescent isolation on intravenous cocaine self-administration in adult rats. Male Sprague-Dawley rats were raised from postnatal day 22 to 55 either alone (isolated) or in groups of four per cage (grouped). Then, rats were trained for cocaine self-administration. Our results showed that both isolated and grouped rats acquired stable cocaine self-administration during 5 days of self-administration training. Numbers of both lever presses and cocaine infusions in isolated rats were significantly more than those in grouped rats. Especially, numbers of incorrect lever presses in isolated rats were significantly more than those in grouped rats. In addition, the intervals of inter-reinforcement for cocaine in isolated rats were significantly shorter as compared with grouped rats. These results indicate that rats with adolescent isolation experience have enhanced cocaine self-administration behavior.

Animals↗

PubMed2006

[Signal transduction mechanism of curcumin in inhibiting the proliferation of bovine lens epithelial cell induced by recombinant human epidermal growth factor].

OBJECTIVE: To investigate the signal transduction mechanism of curcumin in inhibiting the proliferation of bovine lens epithelial cell (LEC) induced by recombinant human epidermal growth factor (rhEGF). METHODS: There were three groups in this experiment, which were normal control group, untreated group and curcumin-treated group. Proliferation of LEC was induced by rhEGF (50 microg/L). The concentration of intracellular Ca(2+) ([Ca(2+)](i)) in LEC was measured with Fura-2/AM by spectrofluorimetry. The contents of intracellular cAMP and cGMP were assayed by radioimmunoassay. RESULTS: The [Ca(2+)]i in LEC was obviously increased in the untrated group as compared with that in the normal control group (P<0.01), and the [Ca(2+)](i) in LEC in the curcumin-treated group was highest among three groups (P<0.01). The content of intracellular cAMP in LEC was decreased while the content of intracellular cGMP was obviously increased in the untreated group as compared with those in the normal control group (P<0.01). The content of intracellular cAMP in LEC was higher in the curcumin-treated group than that in the untreated group, while the content of intracellular cGMP was lower than that in the untreated group (P<0.01). CONCLUSION: The antiproliferation effects of curcumin on LEC may relate to the regulations of multiple processes of signal transduction.

Animals↗

PubMed2005

Occupancy of a single anesthetic binding pocket is sufficient to enhance glycine receptor function.

Alcohols and volatile anesthetics enhance the function of inhibitory glycine receptors (GlyRs). This is hypothesized to occur by their binding to a pocket formed between the transmembrane domains of individual alpha1 GlyR subunits. Because GlyRs are pentameric, it follows that each GlyR contains up to five alcohol/anesthetic binding sites, with one in each subunit. We asked how many subunits per pentamer need be bound by drug in order to enhance receptor-mediated currents. A cysteine mutation was introduced at amino acid serine 267 (S267C) in the transmembrane 2 domain as a tool to block GlyR potentiation by some anesthetic drugs and to provide a means for covalent binding by the small, anesthetic-like thiol reagent propyl methanethiosulfonate. Xenopus laevis oocytes were co-injected with various ratios of wild-type (wt) to S267C alpha1 GlyR cDNAs in order to express heteromeric receptors with a range of wt:mutant subunit stoichiometries. The enhancement of GlyR currents by 200 mm ethanol and 1.5 mm chloroform was positively correlated with the number of wt subunits found in heteromeric receptors. Furthermore, currents from oocytes injected with high ratios of wt to S267C cDNAs (up to 200:1) were significantly and irreversibly enhanced following propyl methanethiosulfonate labeling and washout, demonstrating that drug binding to a single subunit in the receptor pentamer is sufficient to induce enhancement of GlyR currents.

Alcohols↗

PubMed2005

A nuclear function of beta-arrestin1 in GPCR signaling: regulation of histone acetylation and gene transcription.

Chromatin modification is considered to be a fundamental mechanism of regulating gene expression to generate coordinated responses to environmental changes, however, whether it could be directly regulated by signals mediated by G protein-coupled receptors (GPCRs), the largest surface receptor family, is not known. Here, we show that stimulation of delta-opioid receptor, a member of the GPCR family, induces nuclear translocation of beta-arrestin 1 (betaarr1), which was previously known as a cytosolic regulator and scaffold of GPCR signaling. In response to receptor activation, betaarr1 translocates to the nucleus and is selectively enriched at specific promoters such as that of p27 and c-fos, where it facilitates the recruitment of histone acetyltransferase p300, resulting in enhanced local histone H4 acetylation and transcription of these genes. Our results reveal a novel function of betaarr1 as a cytoplasm-nucleus messenger in GPCR signaling and elucidate an epigenetic mechanism for direct GPCR signaling from cell membrane to the nucleus through signal-dependent histone modification.

Acetylation↗

PubMed2005

Role of withdrawal in reinstatement of morphine-conditioned place preference.

RATIONALE: Relapse is a major characteristic of drug addiction and the primary problem in treating drug abuse. Based on the negative reinforcement view of addiction, in which the motivation to take drugs is thought to result from the desire to avoid the aversive effect of drug withdrawal, it has been theorized that withdrawal symptoms play a major role in the maintenance of and relapse to drug taking. However, the role of withdrawal in relapse has not yet been systemically investigated in the reinstatement model. OBJECTIVES: Using a conditioned place preference (CPP) paradigm, we examined the role of different morphine withdrawal states (spontaneous withdrawal, naloxone-precipitated withdrawal, and conditioned withdrawal) in relapse to drug seeking. METHODS: Rats alternately received morphine (10 mg/kg, s.c.) and saline for 8 days to acquire the CPP. The morphine CPP disappeared after a 2-week extinction phase of saline-paired training. Rats were then chronically administered morphine to induce physical dependence. The different withdrawal states were induced and their roles in the reinstatement of extinguished CPP were assessed. During conditioned withdrawal, trunk blood samples were taken and the corticosterone level was measured by radioimmunoassay. To examine the role of corticotropin-releasing factor (CRF) receptor antagonist on conditioned-withdrawal-induced reinstatement of CPP, different doses of alpha-helical CRF (0.1 and 1 mug, i.c.v.) were administered 30 min prior to the CPP testing. RESULTS: The results show that morphine spontaneous withdrawal and naloxone-precipitated morphine withdrawal were ineffective in reinstatement morphine CPP. However, the withdrawal cues significantly elicited the reinstatement of CPP and increased corticosterone level. Moreover, pretreatment with the CRF receptor antagonist alpha-helical CRF (1 mug, i.c.v.) significantly attenuated the effects of withdrawal cues on reinstatement of CPP and corticosterone levels. CONCLUSION: These findings demonstrate that the cues associated with previous drug withdrawal play a major role in drug relapse and that activation of the CRF receptor is involved in conditioned-withdrawal-induced reinstatement. The present study suggests that CRF receptor antagonists might be of value in the treatment and prevention of relapse to drug seeking after long-term abstinence.

Animals↗

PubMed2005

A plausible model for the digital response of p53 to DNA damage.

Recent observations show that the single-cell response of p53 to ionizing radiation (IR) is "digital" in that it is the number of oscillations rather than the amplitude of p53 that shows dependence on the radiation dose. We present a model of this phenomenon. In our model, double-strand break (DSB) sites induced by IR interact with a limiting pool of DNA repair proteins, forming DSB-protein complexes at DNA damage foci. The persisting complexes are sensed by ataxia telangiectasia mutated (ATM), a protein kinase that activates p53 once it is phosphorylated by DNA damage. The ATM-sensing module switches on or off the downstream p53 oscillator, consisting of a feedback loop formed by p53 and its negative regulator, Mdm2. In agreement with experiments, our simulations show that by assuming stochasticity in the initial number of DSBs and the DNA repair process, p53 and Mdm2 exhibit a coordinated oscillatory dynamics upon IR stimulation in single cells, with a stochastic number of oscillations whose mean increases with IR dose. The damped oscillations previously observed in cell populations can be explained as the aggregate behavior of single cells.

Ataxia Telangiectasia Mutated Proteins↗

PubMed2005

Prototype of immunochromatographic assay strips using colloidal CdTe nanocrystals as biological luminescent label.

Colloidal semiconductor nanocrystals have attracted considerable attention as a novel biological luminescent label. The bioinorganic conjugates of luminescent CdTe nanocrystals and protein, including CdTe/BSA (bovine serum albumin) and CdTe/MAB (mouse monoclonal antibody against hepatitis B surface antigen), were formed via electrostatic/coordination self-assembly. Pure CdTe nanocrystals, CdTe/BSA and CdTe/MAB were used in the immunochromatographic assay experiments, respectively. And the results indicated that CdTe nanocrystals could be used and developed as a novel label with good stability, high sensitivity and facile determination of several analytes in immunochromatographic assay strips.

Animals↗

PubMed2005

Preparation of gold colloid monolayer by immunological identification.

The design and initial characterization of the self-assembled gold colloid monolayer by a sandwich structure via the immunological identification are reported. The 13 nm gold colloid nanoparticles and the silicon or quartz substrates have been modified with the mouse polyclonal antibody against hepatitis B virus surface antigen (PAb) and the mouse monoclonal antibody against hepatitis B virus surface antigen (MAb), respectively. They can be linked by a special reaction with their corresponding hepatitis B virus surface antigen (Antigen) as a sandwich structure. Thus, the density of gold nanoparticles self-assembled on the substrate can be readily controlled by the amount of the antigen added. The resulting substrates have been characterized by atomic force microscopy (AFM) and surface-enhanced Raman scattering (SERS) spectroscopy when the gold nanoparticles were modified with SERS-active probe molecules of 4-mercaptobenzoic acid (MBA) after silver enhancement. These data show that the gold nanoparticles are separately fixed onto the substrate and form a uniform monolayer, which possess a set of features that make them very attractive for both basic and applied uses, including roughness, high stability, and biocompatibility.

Animals↗

PubMed2005

Activation of tyrosine kinase of EGFR induces Gbetagamma-dependent GRK-EGFR complex formation.

This study demonstrated that activation of tyrosine kinase of epidermal growth factor receptor (EGFR) induces its association with G protein-coupled receptor kinase 2 (GRK2). Immunoprecipitation experiments showed that EGF stimulation increased GRK2 binding to EGFR complex in HEK293 cells coexpressing EGFR and GRK2. The EGF-induced GRK2-EGFR complex formation was greatly reduced by perturbation of EGFR and Src tyrosine kinase activity. Furthermore, studies with GRK2 mutants showed that neither catalytic activity nor the N-terminal domain of GRK2 was required for EGF-induced GRK2-EGFR complex formation. However, overexpression of Gbetagamma scavengers blocked EGF-induced formation of GRK2-EGFR complex.

Cell Line↗

PubMed2005

Development and characterization of a novel Cremophor EL free liposome-based paclitaxel (LEP-ETU) formulation.

Taxol is a marketed product for the treatment of ovarian, breast, non-small cell lung cancer and AIDS-related Kaposi's Sarcoma. It is thus far one of the most effective anticancer drugs available on the market. However, paclitaxel is only sparingly soluble in water and therefore, intravenous administration depends on the use of the non-ionic surfactant Cremophor EL (polyethoxylated castor oil) to achieve a clinically relevant concentrated solution. Unfortunately, Cremophor EL increases toxicity and leads to hypersensitivity reactions in certain individuals. We have developed a well characterized novel lyophilized liposome-based paclitaxel (LEP-ETU) formulation that is sterile, stable and easy-to-use. The mean particle size of the liposomes is about 150 nm before and after lyophilization, and the drug entrapment efficiency is greater than 90%. Stability data indicated that the lyophilized LEP-ETU was physically and chemically stable for at least 12 months at 2-8 and 25 degrees C. Moreover, the formulation can be diluted to about 0.25mg/ml without drug precipitation or change in particle size. In vitro drug release study in phosphate-buffered saline (PBS, pH 7.4) showed that less than 6% of the entrapped paclitaxel was released after 120 h, indicating that the drug is highly stable in an entrapped form at physiologic temperature.

Chemistry, Pharmaceutical↗

PubMed2005

Beta-arrestin1 and beta-arrestin2 are differentially required for phosphorylation-dependent and -independent internalization of delta-opioid receptors.

Beta-arrestins are key negative regulators and scaffolds of G protein-coupled receptor (GPCR) signalling. Beta-arrestin1 and beta-arrestin2 preferentially bind to the phosphorylated GPCRs in response to agonist stimulation, resulting in receptor internalization and desensitization. The critical roles of GPCR kinases (GRKs)-catalyzed receptor phosphorylation and interaction of beta-arrestins with the phosphorylated receptor in receptor internalization are well established. However, emerging evidence suggests that an agonist-stimulated internalization mechanism that is independent of receptor phosphorylation may also be employed in some cases, although the molecular mechanism for the phosphorylation-independent GPCR internalization is not clear. The current study investigated the role of receptor phosphorylation and the involvement of different beta-arrestin subtypes in agonist-induced delta-opioid receptor (DOR) internalization in HEK293 cells. Results from flow cytometry, fluorescence microscopy, and surface biotin labelling experiments showed that elimination of agonist-induced DOR phosphorylation by mutation GRK binding or phosphorylation sites only partially blocked agonist-induced receptor internalization, indicating the presence of an agonist-induced, GRK-independent mechanism for DOR internalization. Fluorescence and co-immunoprecipitation studies indicated that both the wild-type DOR and the phosphorylation-deficient mutant receptor could bind and recruit beta-arrestin1 and beta-arrestin2 to the plasma membrane in an agonist-stimulated manner. Furthermore, internalization of both the wild-type and phosphorylation-deficient receptors was increased by overexpression of either type of beta-arrestins and blocked by dominant-negative mutants of beta-arrestin-mediated internalization, demonstrating that both phosphorylation-dependent and -independent internalization require beta-arrestin. Moreover, double-stranded RNA-mediated interference experiments showed that either beta-arrestin1 or beta-arrestin2 subtype-specific RNAi only partially inhibited agonist-induced internalization of the wild-type DOR. However, agonist-induced internalization of the phosphorylation-deficient DOR was not affected by beta-arrestin1-specific RNAi but was blocked by RNAi against beta-arrestin2 subtype. These data indicate that endogenous beta-arrestin1 functions exclusively in the phosphorylation-dependent receptor internalization, whereas endogenous beta-arrestin2, but not beta-arrestin1, is required for the phosphorylation-independent receptor internalization. These results thus provide the first evidence of different requirement for beta-arrestin isoforms in the agonist induced phosphorylation-dependent and -independent GPCR internalization.

Arrestins↗