Biomedical subjects

Henning Frenzel

Publications and source records attributed to Henning Frenzel.

7 recordsLinked to original sources

PubMed2006

Inhibition of TRPM2 cation channels by N-(p-amylcinnamoyl)anthranilic acid.

1. TRPM2 is a Ca2+ -permeable nonselective cation channel activated by intracellular ADP-ribose (ADPR) and by hydrogen peroxide (H2O2). We investigated the modulation of TRPM2 activity by N-(p-amylcinnamoyl)anthranilic acid (ACA). ACA has previously been reported to inhibit phospholipase A2 (PLA2). 2. Using patch-clamp and calcium-imaging techniques, we show that extracellular application of 20 microM ACA completely blocked ADPR-induced whole-cell currents and H2O2-induced Ca2+ signals (IC50 = 1.7 microM) in HEK293 cells transfected with human TRPM2. Two other PLA2 inhibitors, p-bromophenacyl bromide (BPB; 100 microM) and arachidonyl trifluoromethyl ketone (20 microM), had no significant effect on ADPR-stimulated TRPM2 activity. 3. Inhibition of TRPM2 whole-cell currents by ACA was voltage independent and accelerated at decreased pH. ACA was ineffective when applied intracellularly. The single-channel conductance was not changed during ACA treatment, suggesting a reduction of TRPM2 open probability by modulating channel gating. 4. ACA (20 microM) also blocked currents through human TRPM8 and TRPC6 expressed in HEK293 cells, while BPB (100 microM) was ineffective. TRPC6-mediated currents (IC50 = 2.3 microM) and TRPM8-induced Ca2+ signals (IC50 = 3.9 microM) were blocked in a concentration-dependent manner. 5. ADPR-induced currents in human U937 cells, endogeneously expressing TRPM2 protein, were fully suppressed by 20 microM ACA. 6. Our data indicate that ACA modulates the activity of different TRP channels independent of PLA2 inhibition. Owing to its high potency and efficacy ACA can serve, in combination with other blockers, as a useful tool for studying the unknown function of TRPM2 in native cells.

Adenosine Diphosphate Ribose↗

PubMed2006

Borderline indications for ear reconstruction.

While the indication for an ear reconstruction with rib cartilage is clear in pediatric patients and patients without previous surgery, there are borderline cases in which neither a reconstruction nor a prosthesis seems to be first choice. Within the last 6 years, approximately 120 patients were treated with a reconstruction with rib cartilage and 20 with a prosthesis at our hospital. Patients without extensively scarred periauricular tissue clearly benefit by a reconstruction with cartilage. The classic indication for an ear prosthesis is status post-malignant tumor resection. In borderline cases presenting with heavy scars, the most favorable repair method has to be decided upon individually. Under these circumstances, one of the main criteria for a reconstruction with rib cartilage is a viable temporoparietal fascia flap. A consideration that is important to note is that an unfavorable ear reconstruction can be converted almost always into a prosthesis repair but very rarely vice versa.

Adolescent↗

PubMed2003

Haplotype structure and association to Crohn's disease of CARD15 mutations in two ethnically divergent populations.

Current debate focuses on the relevance of linkage disequilibrium (LD), ethnicity and underlying haplotype structure to the search for genes involved in complex disorders. The recently described association between single nucleotide polymorphisms (SNPs) of the CARD15 (NOD2) gene and Crohn's disease (CD) in populations of north-European descent provides a test case that we have subjected to detailed SNP haplotype based analyses. We examined 23 SNPs spanning 290 kb, including CARD15, in large North-European and Korean samples of patients with Crohn's disease and normal controls. In Europeans we confirmed that the three disease-associated SNPs occur independently but share a common background haplotype. This suggests a common origin and the possibility of an undiscovered more strongly predisposing mutation. Korean CD patients present a phenotype identical to the European patients and have not previously been screened for CARD15. The three disease-associated SNPs were absent and there was no evidence of association between CARD15 and CD. Consequently, the disease-associated mutations in the Europeans, which are rare, have arisen recently (after the Asian-European split). Our results highlight important issues relevant to mapping the genes that predispose to complex disorders. First, although ethnically divergent populations may present identical phenotypes they do not necessarily share the same set of predisposing genes. Second, although single-locus tests of association showed consistent association with markers throughout the gene, pair-wise LD between markers (r(2) and D') yielded very little information about actual disease-association. Third, a population comparative approach allowed refining of the marker set through the examination of shared polymorphisms and common LD-groups. This approach, in conjunction with the examination of the mutational steps in a haplotype network, allows unambiguous identification of the potentially causative mutations.

Asian People↗

PubMed2002

Mutation detection and physical mapping of the CD11 gene cluster in association with inflammatory bowel disease.

A genetic component in the etiology of inflammatory bowel disease (IBD) has clearly been demonstrated by epidemiological and genetic linkage studies. Linkage to IBD on proximal Chromosome (Chr) 16p is well established and replicated. A stratification experiment showed that the recent identification of a disease gene on the q arm does not interfere with the approach on the p arm, and the linkage peak is still significant. Here we present a candidate gene study of the alpha integrins (CD11A-D) on Chr 16. The alpha integrins play a key role in inflammatory processes, including leukocyte adhesion and migration. Their genes are located on the p arm of Chr 16, and therefore represent excellent positional and functional candidates. Since the assignment of the CD11 genes in the genome was not clear, we performed physical, radiation hybrid, and fluorescent in situ hybridization mapping of the gene family. All CD11 genes map on Chr 16p11-12. CD11B-D are arranged in a gene cluster within 300 kb and CD11A is located about 2.5 Mb telomeric. Thirteen new single nucleotide polymorphisms (SNPs) and eight SNPs from databases were identified through full-length sequencing. Case-control statistics demonstrated an association lead in the CD11 gene cluster, which was not confirmed in further family based association/linkage analyses using single markers and haplotypes. It is unlikely that the CD11 genes play an important role in the pathogenesis of IBD. The marginally significant results could indicate a disease gene in the vicinity of the gene cluster.

CD11 Antigens↗

PubMed2001

Evidence for a NOD2-independent susceptibility locus for inflammatory bowel disease on chromosome 16p.

Heritable predisposition to inflammatory bowel disease (IBD) has been demonstrated by epidemiological and genetic analysis. Linkage of IBD to broad regions of chromosome 16 has been established by analysis of multiple populations. NOD2, located on proximal 16q, was recently identified as an IBD gene. As the linkage regions on chromosome 16 are large, we have investigated the possibility that NOD2 is not the only IBD gene located on this chromosome. A high-density experiment using 39 microsatellite markers was performed to identify additional regions of association, and to indicate areas of interest for further investigation. A triple-peaked configuration of the linkage curve with peak logarithm of odds (lod) scores of 2.7, 3.2, and 3.1 was observed on proximal 16p, proximal 16q, and central 16q, respectively. The cohort was stratified by coding individuals carrying the NOD2 single nucleotide polymorphism (SNP)8 and SNP13 "unknown." Significance at the central peak, corresponding to the genomic location of NOD2, then decreased from 3.2 to 1.2. The maximal lod scores on the proximal p-arm (lod = 2.1) and central q-arm (lod = 2.6) changed only moderately. An exploratory association analysis (TRANSMIT) yielded a strong lead at D16S3068 (P = 0.00028). The region around this marker was further investigated by using anonymous SNPs. An associated haplotype containing three SNPs was identified (peak significance P = 0.00027, IBD phenotype). On stratification based on NOD2 genotype, this significance increased to P = 0.0001. These results confirm the importance of NOD2 and provide evidence for a second IBD gene located on chromosome 16p.

Carrier Proteins↗

PubMedDate not supplied

Isolation of human myeloid dendritic cells from tumor tissue and peripheral blood.

BACKGROUND: Human myeloid dendritic cells (MDC) have been identified in human solid tumor tissue of head and neck squamous cell carcinoma (HNSCC), their cellular functions being strongly affected in this environment. The characterization of MDC differentiation and functions requires the establishment of highly efficient isolation procedures. MATERIALS AND METHODS: Human MDC were isolated from peripheral blood and solid HNSCC using density gradient centrifugation or preparation of single cell suspensions, respectively. The cells were isolated by "magnetic bead separation" using magnetically-labelled antibodies and were analyzed by flow cytometry. RESULTS: The isolation of human MDC from peripheral blood or solid HNSCC tissue resulted in highly enriched cell populations and revealed cell purities of about 90%. CONCLUSION: The scale of molecular investigations on human myeloid dendritic cells is restricted by the limited proportion of this cell type. Thus, highly efficient and gentle MDC isolation procedures are essential to characterize in vivo matured MDC.

Adolescent↗

PubMedDate not supplied

Toll-like receptor interference in myeloid dendritic cells through head and neck cancer.

BACKGROUND: In head and neck squamous cell carcinoma (HNSCC) the secretion of various immunosuppressive mediators contributes to large-scale effects on the immune functions. The influence of HNSCC on the Toll-like receptor (TLR) expression profiles of human myeloid dendritic cells (MDCs), which have been identified in human solid tumor tissue of the head and neck, was analysed. MATERIALS AND METHODS: MDCs were isolated from peripheral blood by 'magnetic bead separation' and subsequently incubated with supernatants of HNSCC permanent cell lines. TLR expression profiles were investigated using Af cytometry and SDS-PAGE. RESULTS: Human MDC from peripheral blood were found to express all human TLRs except TLR4 and TLR9. Incubation of MDC with supernatants of HNSCC resulted in an increased expression of TLR7. CONCLUSION: The data suggest an interference of TLR7 expression through HNSCC and provide novel evidence of TLR alterations as a potential tumor promoting event in head and neck cancer.

Adolescent↗