Lack of linkage and association of adrenomedullin and its receptor genes in French Caucasian rheumatoid arthritis trio families.

OBJECTIVE: Rheumatoid arthritis (RA) is characterized by hyperplasia of fibro-blast-like synoviocytes (FLSs), in part due to apoptosis resistance. Adrenomedullin, an anti-apoptotic peptide, is secreted more by RA than osteoarthritis FLSs. Adrenomedullin binds to a heterodimeric functional receptor, of calcitonin receptor-like receptor (CRLR) coupled with a receptor activity-modifying protein-2 (RAMP-2), which is also overexpressed by rheumatoid synoviocytes. Since adrenomedullin decreases RA FLS apoptosis, possibly contributing to the development of pannus, study of adrenomedullin and its receptor genes might reveal a linkage and association in French Caucasian RA trio families. METHODS: Within each of 100 families, one RA-affected patient and both parents underwent genotyping for polymorphisms of adrenomedullin, CRLR and RAMP-2, by PCR-restricted fragment-length polymorphism (RFLP) or Taqman 5' allelic discrimination assay. Statistical analysis relied on the transmission disequilibrium test, the affected family-based controls and the genotype relative risk. Haplotypes of CRLR were inferred, and linkage and association studies were performed. RESULTS: No significant transmission disequilibrium or association between the three genes and RA was observed. CRLR haplotypes revealed two major haplotypes, but no significant linkage with RA. CONCLUSION: Our findings provided no significant linkage or association of adrenomedullin and CRLR-RAMP-2 genes with RA in the studied trio families. The two CRLR polymorphisms rs3771076 and rs3771084 should be investigated in larger samples.

Estradiol inhibits adhesion and promotes apoptosis in murine osteoclasts in vitro.

Osteoporosis caused by estrogen deficiency is characterized by enhanced bone resorption mediated by osteoclasts. Adhesion to bone matrix and survival of differentiated osteoclasts is necessary to resorb bone. The aim of our study was to investigate the in vitro effects of estradiol on murine osteoclasts. RAW 264.7 cells treated with 30 ng/ml RANK-L were used as a model for osteoclastogenesis. Estradiol (10(-8)M) for 5 days induced an inhibition of osteoclast differentiation and beta3 expression. Estradiol inhibited significantly the adhesion of mature osteoclasts by 30%. Furthermore estradiol-induced apoptosis shown by with nuclear condensation and Bax/Bcl2 ratio. In addition, estradiol enhanced caspase-3, -8 and -9 activities. This effect completely disappeared using specific caspase-8 inhibitor. However, increased caspase-3 activity by estradiol was observed in the presence of caspase-9 inhibitor, indicating the preferential involvement of caspase-8 pathway. Fas and FasL mRNA expression was not regulated by estradiol. However, estradiol enhanced caspase-3 activity in Fas-induced apoptosis on mature osteoclasts, suggesting that this might interact with the Fas-signaling pathway. These data suggest that estradiol decreases bone resorption by several mechanisms including adhesion and apoptosis of osteoclasts.

SPRED1, a RAS MAPK pathway inhibitor that causes Legius syndrome, is a tumour suppressor downregulated in paediatric acute myeloblastic leukaemia.

Constitutional dominant loss-of-function mutations in the SPRED1 gene cause a rare phenotype referred as neurofibromatosis type 1 (NF1)-like syndrome or Legius syndrome, consisted of multiple café-au-lait macules, axillary freckling, learning disabilities and macrocephaly. SPRED1 is a negative regulator of the RAS MAPK pathway and can interact with neurofibromin, the NF1 gene product. Individuals with NF1 have a higher risk of haematological malignancies. SPRED1 is highly expressed in haematopoietic cells and negatively regulates haematopoiesis. SPRED1 seemed to be a good candidate for leukaemia predisposition or transformation. We performed SPRED1 mutation screening and expression status in 230 paediatric lymphoblastic and acute myeloblastic leukaemias (AMLs). We found a loss-of-function frameshift SPRED1 mutation in a patient with Legius syndrome. In this patient, the leukaemia blasts karyotype showed a SPRED1 loss of heterozygosity, confirming SPRED1 as a tumour suppressor. Our observation confirmed that acute leukaemias are rare complications of the Legius syndrome. Moreover, SPRED1 was significantly decreased at RNA and protein levels in the majority of AMLs at diagnosis compared with normal or paired complete remission bone marrows. SPRED1 decreased expression correlated with genetic features of AML. Our study reveals a new mechanism which contributes to deregulate RAS MAPK pathway in the vast majority of paediatric AMLs.

Removal of dissolved O2 by a fluid membrane of Fomblin Y (perfluoro polyether): fluorescence of diphenylhexatriene in Fomblin Y.

O2 can be gently removed from solutions by contact with a "bulk fluid membrane" of the viscous and nearly inert perfluoro polyether Fomblin Y. A volume of Fomblin dissolves approximately 20 times more O2 than an equal volume of water. Hence, when a volume of aqueous solution which was in equilibrium with air is enclosed with an equal volume of Fomblin which had been flushed with argon, oxygen would diffuse into the Fomblin, leaving in the water only 5% of the oxygen that was there. When the Fomblin is stirred, diffusion is rather rapid. The residue can be removed either by placing an oxygen scavenger on the other side of the Fomblin or by flowing a trickle of deoxygenated Fomblin through the sample. Diphenylhexatriene, a fluorescent probe of cell membranes, can be dissolved in Fomblin Y and has a fluorescence lifetimes extending from 12 ns in O2 saturation to 30 ns (!) in the absence of oxygen. Stern-Volmer plots calibrated against a Clark electrode validate this system for oximetry. A general purpose anaerobic cuvette for fluorescence spectroscopy, containing the sample solution, a Fomblin compartment and the oxygen scavenger Na-dithionite is demonstrated.

Novel fluorescence-photochrome labeling method in the study of biomembrane dynamics.

A novel photochrome-fluorescence method (PFLM) based on monitoring fluorescence parameters and kinetics of photochrome photoisomerization of para-substituted stilbenes (PSS) has been proposed. It was shown that PSS exhibits fluorescence characteristics which are similar to ones of typical membrane fluorescence probes such as diphenylhexatriene (DPH). A study of kinetics of PSS trans-cis and cis-trans photoisomerization makes it possible to estimate, under certain conditions, the rotational correlation time of the stilbene fragments in the excited state of PSS for the fixed angle 180 degrees. In viscous media this process is a rate-determining stage. Taken together, the both techniques, fluorescence and photochrome, make it possible to establish a detailed mechanism and measure quantitative parameters of stilbene probe (PSS) mobility in a membrane. The PFLM was applied to the study of E. coli membrane dynamics.