Biomedical subjects

Feng-Qian Li

Publications and source records attributed to Feng-Qian Li.

12 recordsLinked to original sources

PubMed2006

Development of a gradient reversed-phase HPLC method for the determination of sodium ferulate in beagle dog plasma.

A gradient reversed-phase HPLC assay has been developed to determine sodium ferulate (SF) in beagle dog plasma with tinidazole as an internal standard. Chromatographic separation was made on a C(18) column using 0.5% acetic acid and acetonitrile (80:20, v/v) as mobile phase. UV detection was performed at 320 nm. The calibration curve for SF was linear in the range of 0.05-10 microg/ml, and the achieved limit of quantification (LOQ) was 51.4 ng/ml. The results of linearity, within- and between-day precision, and accuracy demonstrate that this method is reliable, sensitive and sufficient for in vivo beagle dog pharmacokinetic (PK) studies of SF.

Animals↗

PubMed2006

In vitro controlled release of sodium ferulate from Compritol 888 ATO-based matrix tablets.

A controlled release matrix formulation for freely water-soluble drug of sodium ferulate (SF) was designed and developed to achieve a 24h release profile. Using Compritol 888 ATO as an inert matrix-forming agent to control the release of SF, formulation granules containing the physical mixtures or solid dispersions were investigated. The matrix tablets for these formulations were prepared by direct compression and their in vitro release tests were carried out. The solid dispersion based tablets were found to be more effective than those compressed from physical mixtures in retarding the release of SF. Drug release from the matrix tablets containing physical mixtures nearly completed within 12h, while that from the solid dispersion formulations lasted for over 24h. Images of the tablet surface and cross-section were characterized by scanning electron microscopy to show the formed pores and channels in the matrices. These might provide the release pathway for the inner embedded drugs. Drug released fast from the matrix tablets with the release-enhancer of lactose. The addition of surfactants was also found to increase the release rate of SF effectively. Moreover, the co-mixing of polyethylene glycol 6000 (PEG 6000) in the waxy matrices played a meaningful role in controlling the drug release for 24h. The drug release from the novel formulation might be attributed to the diffusion-controlled mechanism.

Chemistry, Pharmaceutical↗

PubMed2005

[Effect of cetirizine hydrochloride on the expression of substance P in IgE-mediated triphasic cutaneous reaction].

AIM: To investigate the effect of cetirizine hydrochloride on the expression of neuropeptide substance P (SP) in IgE-dependent triphasic cutaneous reaction induced by dinitrofluorobenzene (DNFB) in the ears of BALB/c mice. METHODS: BALB/c mice were passively sensitized by intravenous infection of anti-DNP IgE monoclonal antibody 24 h before DNFB challenge. Skin reaction was elicited by applying DNFB to both sides of each ear of sensitized mice. Mice were treated with cetirizine (1 and 10 mg x kg)-1), ig). The ears were removed for pathohistological examination and immunohistochemical staining of SP at different designated times after challenge. The contents of SP in the skin of mouse ear were determined by radioimmunoassay (RIA). RESULTS: The mice exhibited a triphasic cutaneous reaction with an immediate-phase response (IPR) at 1 h, a late-phase response (LPR) at 24 h and a very late-phase response (vLPR) at 7 days after challenge with DNFB. The expression of SP in different phases increased gradually. Cetirizine (1 and 10 mg x kg(-1)) was shown to significantly inhibit the ear swellings induced by the IPR (P < 0.01), while no obvious effect on the vLPR. The SP contents in ear skin of triphasic cutaneous reaction were decreased by cetirizine. CONCLUSION: SP is considered to be involved in the pathogenesis of allergic dermatitis. Cetirizine hydrochloride can inhibit the expression of SP in IgE-dependent triphasic cutaneous reaction. It might be part of the mechanisms of anti-anaphylaxis of cetirizine.

Animals↗

PubMed2004

Paradoxical homozygous expression from heterozygotes and heterozygous expression from homozygotes as a consequence of transcriptional infidelity through a polyadenine tract in the AP3B1 gene responsible for canine cyclic neutropenia.

Canine cyclic neutropenia is an autosomal recessive disease in which the number of neutrophils, the primary blood phagocyte, oscillates between almost zero and normal values with two week frequency. We previously found that the causative mutation is an insertion of an extra adenine residue within a tract of nine A's in exon 21 of the 27 exon canine AP3B1 gene. In the course of identifying the mutation, however, we observed an unusual phenomenon: heterozygous carrier dogs, who have one normal allele and one mutant allele, produce a homogeneous population of normal AP3B1 transcripts (containing nine A's), but homozygous affected dogs, who have two mutant alleles, produce a heterogeneous population of AP3B1 mRNA containing mutant transcripts with ten A's and, unexpectedly, wild-type transcripts with nine A's. By RT-PCR subclone analysis and use of an in vitro reporter assay, we show that there is a high frequency of errors made during the transcription of homopolymeric adenine sequences, such that the A tract in the mRNA is frequently shortened or lengthened by an extra residue. Out of frame transcripts are degraded, accounting for this paradox through the preferential accumulation of normal message from mutant alleles.

Adaptor Protein Complex 3↗

PubMed2004

Hereditary neutropenia: dogs explain human neutrophil elastase mutations.

Mutations in ELA2, the gene encoding neutrophil elastase (NE), cause the human diseases cyclic neutropenia (CN) and severe congenital neutropenia (SCN). Numerous mutations are known, but their lack of consistent biochemical effect has proven puzzling. The recent finding that mutation of AP3B1, which encodes the beta subunit of adaptor protein complex 3 (AP3), is the cause of canine CN suggests a model for the molecular basis of hereditary neutropenias, involving the mistrafficking of NE: AP3 recognizes NE as a cargo protein, and their interaction implies that NE is a transmembrane protein. Computerized algorithms predict two NE transmembrane domains. Most CN mutations fall within predicted transmembrane domains and lead to excessive deposition of NE in granules, whereas SCN mutations usually disrupt the AP3 recognition sequence, resulting in excessive transport to the plasma membrane.

Adaptor Protein Complex 3↗

PubMed2004

A novel notch protein, N2N, targeted by neutrophil elastase and implicated in hereditary neutropenia.

Mutations in ELA2, encoding the human serine protease neutrophil elastase, cause cyclic and severe congenital neutropenia, and recent evidence indicates that the mutations alter the membrane trafficking of neutrophil elastase. These disorders feature impaired bone marrow production of neutrophils along with excess monocytes-terminally differentiated lineages corresponding to the two alternative fates of myeloid progenitor cells. We utilized a modified yeast two-hybrid system and identified a new, widely expressed gene, N2N, whose product is homologous to Notch2, that interacts with neutrophil elastase. N2N is a 36-kDa protein distributed throughout the cell and secreted. Its amino-terminal sequence consists of several EGF repeats identical to those of the extracellular region of Notch2, and its carboxyl terminus contains a unique 24-residue domain required for interaction with neutrophil elastase. Neutrophil elastase cleaves N2N within EGF repeats in vitro and in living cells, but the C-terminal domain retards proteolysis. In vitro, N2N represses transcriptional activities of Notch proteins. Disease-causing mutations of neutrophil elastase disrupt the interaction with N2N, impair proteolysis of N2N and Notch2, and interfere with Notch2 signaling, suggesting defective proteolysis of an inhibitory form of Notch as an explanation for the alternate switching of cell fates characteristic of hereditary neutropenia.

Cloning, Molecular↗

PubMed2004

Improvement of the dissolution rate of silymarin by means of solid dispersions.

Solid dispersions of silymarin were prepared by the fusion method with the intention of improving the dissolution properties of silymarin. Polyethylene glycol 6000 (PEG 6000) was used as the inert hydrophilic matrix. The dissolution studies of the solid dispersions were performed in vitro. And the results obtained showed that the dissolution rate of silymarin was considerably improved when formulated in solid dispersions with PEG 6000 as compared to original drug, and the increased dissolution rate might be favorable for further oral absorption.

Absorption↗

PubMed2003

Lymphoid enhancer factor-1 links two hereditary leukemia syndromes through core-binding factor alpha regulation of ELA2.

Two hereditary human leukemia syndromes are severe congenital neutropenia (SCN), caused by mutations in the gene ELA2, encoding the protease neutrophil elastase, and familial platelet disorder with acute myelogenous leukemia (AML), caused by mutations in the gene AML1, encoding the transcription factor core-binding factor alpha (CBFalpha). In mice, CBFalpha regulates the expression of ELA2, suggesting a common link for both diseases. However, gene-targeted mouse models have failed to reproduce either human disease, thus prohibiting further in vivo studies in mice. Here we investigate CBFalpha regulation of the human ELA2 promoter, taking advantage of bone marrow obtained from patients with either illness. In particular, we have identified novel ELA2 promoter substitutions (-199 C to A) within a potential motif for lymphoid enhancer factor-1 (LEF-1), a transcriptional mediator of Wnt/beta-catenin signaling, in SCN patients. The LEF-1 motif lies adjacent to a potential CBFalpha binding site that is in a different position in human compared with mouse ELA2. We find that LEF-1 and CBFalpha co-activate ELA2 expression. In vitro, the high mobility group domain of LEF-1 interacts with the runt DNA binding and proline-, serine-, threonine-rich activation domains of CBFalpha. ELA2 transcript levels are up-regulated in bone marrow of an SCN patient with the -199 C to A substitution. Conversely, a mutation of the CBFalpha activation domain, found in a patient with familial platelet disorder with AML, fails to stimulate the ELA2 promoter in vitro, and bone marrow correspondingly demonstrates reduced ELA2 transcript. Observations in these complementary patients indicate that LEF-1 cooperates with CBFalpha to activate ELA2 in vivo and also suggest the possibility that up-regulating promoter mutations can contribute to SCN. Two hereditary AML predisposition syndromes may therefore intersect via LEF-1, potentially linking them to more generalized cancer mechanisms.

Animals↗

PubMed2003

Mutations associated with neutropenia in dogs and humans disrupt intracellular transport of neutrophil elastase.

Cyclic hematopoiesis is a stem cell disease in which the number of neutrophils and other blood cells oscillates in weekly phases. Autosomal dominant mutations of ELA2, encoding the protease neutrophil elastase, found in lysosome-like granules, cause cyclic hematopoiesis and most cases of the pre-leukemic disorder severe congenital neutropenia (SCN; ref. 3) in humans. Over 20 different mutations of neutrophil elastase have been identified, but their consequences are elusive, because they confer no consistent effects on enzymatic activity. The similar autosomal recessive disease of dogs, canine cyclic hematopoiesis, is not caused by mutations in ELA2 (data not shown). Here we show that homozygous mutation of the gene encoding the dog adaptor protein complex 3 (AP3) beta-subunit, directing trans-Golgi export of transmembrane cargo proteins to lysosomes, causes canine cyclic hematopoiesis. C-terminal processing of neutrophil elastase exposes an AP3 interaction signal responsible for redirecting neutrophil elastase trafficking from membranes to granules. Disruption of either neutrophil elastase or AP3 perturbs the intracellular trafficking of neutrophil elastase. Most mutations in ELA2 that cause human cyclic hematopoiesis prevent membrane localization of neutrophil elastase, whereas most mutations in ELA2 that cause SCN lead to exclusive membrane localization.

Adaptor Protein Complex 3↗

PubMed2003

Mutations in proto-oncogene GFI1 cause human neutropenia and target ELA2.

Mice lacking the transcriptional repressor oncoprotein Gfi1 are unexpectedly neutropenic. We therefore screened GFI1 as a candidate for association with neutropenia in affected individuals without mutations in ELA2 (encoding neutrophil elastase), the most common cause of severe congenital neutropenia (SCN; ref. 3). We found dominant negative zinc finger mutations that disable transcriptional repressor activity. The phenotype also includes immunodeficient lymphocytes and production of a circulating population of myeloid cells that appear immature. We show by chromatin immunoprecipitation, gel shift, reporter assays and elevated expression of ELA2 in vivo in neutropenic individuals that GFI1 represses ELA2, linking these two genes in a common pathway involved in myeloid differentiation.

Adult↗

PubMed2003

Leukemia in severe congenital neutropenia: defective proteolysis suggests new pathways to malignancy and opportunities for therapy.

Severe congenital neutropenia (SCN), a heterogeneous disorder that includes Kostmann syndrome, predisposes to myelodysplasia and acute myelogenous leukemia. Recently identified heterozygous mutations in the gene ELA2, encoding neutrophil elastase on human chromosome 19pter, account for the majority of autosomal dominant cases of SCN, including those demonstrating neoplastic progression. The involvement of the serine protease neutrophil elastase, localized to the granules of neutrophils and monocytes, implies an unexpected role for proteolytic regulation of hematopoiesis. Continued elucidation of the clinical features, molecular genetics, and biochemistry is likely to provide insight into novel pathways of leukemia induction with attendant prospects for new avenues of therapy.

Diagnosis, Differential↗

PubMed2003

Role of neutrophil elastase in bone marrow failure syndromes: molecular genetic revival of the chalone hypothesis.

Two forms of inherited deficiency of neutrophil numbers are cyclic hematopoiesis and severe congenital neutropenia. In cyclic hematopoiesis, neutrophil counts oscillate opposite monocytes in a 3-week cycle. Severe congenital neutropenia consists of static neutropenia and a predisposition to myelodysplasia and acute myelogenous leukemia. All cases of cyclic neutropenia and most cases of severe congenital neutropenia result from heterozygous germline mutations in the gene encoding neutrophil elastase, ela2. Recent work extends the list of neutropenia genes to include WASp, Gfi-1, adaptin, and tafazzin. Studies of mosaic patients suggest that ela2 mutations act in a cell-autonomous fashion. A hypothetical feedback circuit potentially interconnects these genes. Genetic dissection of signaling in model organisms along with experimental hematology implicate C/EPBepsilon, RUNX1/AML1, Notch family members, LEF1, and Cdc42 as additional nodes in this pathway. The authors propose that neutrophil elastase acts as an inhibitor of myelopoiesis, substantiating a chalone hypothesis proposed many years ago.

Bone Marrow Diseases↗