Role of bifidobacteria in the activation of the lignan secoisolariciresinol diglucoside

Lignans are ubiquitous plant polyphenols, which have relevant health properties being the major phytoestrogens occurring in Western diets. Secoisolariciresinol (SECO) is the major dietary lignan mostly found in plants as secoisolariciresinol diglucoside (SDG). To exert biological activity, SDG requires being deglycosylated to SECO and transformed to enterodiol (ED) and enterolactone (EL) by the intestinal microbes. The involvement of bifidobacteria in the transformation of lignans glucosides has been investigated for the first time in this study. Twenty-eight strains were assayed for SDG and SECO activation. They all failed to transform SECO into reduced metabolites, excluding any role in ED and EL production. Ten Bifidobacterium cultures partially hydrolyzed SDG, giving both SECO and the monoglucoside with yields < 25%. When the cell-free extracts were assayed in SDG transformation, seven additional strains were active in the hydrolysis. Cellobiose induced β-glucosidase activity and caused the enhancement of both the rate of SDG hydrolysis and the final yield of SECO only in the strains capable of SDG bioconversion. The highest SDG conversion to SECO was achieved by Bifidobacterium pseudocatenulatum WC 401, which exhibited 75% yield in cellobiose-based medium after 48 h. These results indicate that SDG hydrolysis is not a common feature in Bifidobacterium genus, but selected probiotic strains can be combined to β-glucoside-based prebiotics to enhance the release of SECO, thus improving its bioavailability for absorption by colonic mucosa and/or the biotransformation to ED and EL by other intestinal microorganisms.     

Gene expression profiling identifies eleven DNA repair genes down-regulated during mouse neural crest cell migration

Neural Crest Cells (NCCs) are transient multipotent migratory cells that derive from the embryonic neural crest which is itself derived from the margin of the neural tube. DNA repair genes are expressed in the early stages of mammalian development to reduce possible replication errors and genotoxic damage. Some birth defects and cancers are due to inappropriate or defective DNA repair machinery, indicating that the proper functioning of DNA repair genes in the early stages of fetal development is essential for maintaining DNA integrity. We performed a genome-wide expression analysis combining laser capture microdissection (LCM) and high-density oligo-microarray of murine NCCs at pre-migratory embryonic days 8.5 (E8.5), and at E13.5, as well as on neural crest-derived cells from the adrenal medulla at postnatal day 90. We found 11 genes involved in DNA repair activity (response to DNA damage stimulus, DNA damage checkpoint, base-excision repair, mismatch repair), over-expressed in the early stages of mouse embryo development. Expression of these 11 genes was very low or undetectable in the differentiated adrenal medulla of the adult mouse. Amongst the 11 genes, 6 had not been previously reported as being over-expressed during mouse embryonic development. High expression of DNA repair genes in enriched NCCs during early embryonic development may contribute to maintaining DNA integrity whilst failure of some of these genes may be associated with the onset of genetic disease and cancer. Our model of enriched murine NCCs and neural crest-derived cells can be used to elucidate the key roles of genes during normal embryonic development and in cancer pathogenesis.     

Many facets of chromosome 3p cytogenetic findings in clear cell renal carcinoma: the need for agreement in assessment FISH analysis to avoid diagnostic errors

Abnormalities of the locus chromosome 3p and the entire chromosome 3 are involved in the cancerogenesis of clear cell renal carcinoma and may be detected by interphase fluorescence in situ hybridization (interphase FISH). We observed a variable detection rate of chromosome 3p/3 abnormalities in different series of clear cell renal carcinoma. Therefore, we focused on problematic issues when performing analysis on routinely available formalin-fixed and paraffin embedded tissue. A group of studies encountered a single approach to chromosome 3p detection, by using probe/s to map different codes of the short arm 3p without a control of the entire chromosome 3. Deletion of chromosome 3p and monosomy of chromosome 3 ranged from 38% to 100% in clear cell renal carcinoma. Cut-off values for the threshold were chosen randomly or obtained by calculation of the mean value plus 1 or 2 or 3 standard deviations. Loss of chromosome 3p was assessed either as the percentage of single signals on the total number of nuclei, or applying a double approach with corrections of control chromosome 3. Moreover, cut off values were sometimes arbitrarily corrected with the findings from normal adjacent renal parenchyma. A consensus of experts in the field is needed in order to define the best methodological approach and the appropriate threshold in assessment 3p deletion when interphase FISH is performed in clear cell renal carcinoma. This harbours relevant diagnostic and therapeutic implications, at light also of targeted therapies recently available to clear cell renal carcinoma.     

The conserved factor DE-ETIOLATED 1 cooperates with CUL4-DDB1DDB2 to maintain genome integrity upon UV stress

Plants and many other eukaryotes can make use of two major pathways to cope with mutagenic effects of light, photoreactivation and nucleotide excision repair (NER). While photoreactivation allows direct repair by photolyase enzymes using light energy, NER requires a stepwise mechanism with several protein complexes acting at the levels of lesion detection, DNA incision and resynthesis. Here we investigated the involvement in NER of DE-ETIOLATED 1 (DET1), an evolutionarily conserved factor that associates with components of the ubiquitylation machinery in plants and mammals and acts as a negative repressor of light-driven photomorphogenic development in Arabidopsis. Evidence is provided that plant DET1 acts with CULLIN4-based ubiquitin E3 ligase, and that appropriate dosage of DET1 protein is necessary for efficient removal of UV photoproducts through the NER pathway. Moreover, DET1 is required for CULLIN4-dependent targeted degradation of the UV-lesion recognition factor DDB2. Finally, DET1 protein is degraded concomitantly with DDB2 upon UV irradiation in a CUL4-dependent mechanism. Altogether, these data suggest that DET1 and DDB2 cooperate during the excision repair process.     

Differential regulation of the postsynaptic clustering of γ-aminobutyric acid type A (GABAA) receptors by collybistin isoforms

Collybistin promotes submembrane clustering of gephyrin and is essential for the postsynaptic localization of gephyrin and γ-aminobutyric acid type A (GABA(A)) receptors at GABAergic synapses in hippocampus and amygdala. Four collybistin isoforms are expressed in brain neurons; CB2 and CB3 differ in the C terminus and occur with and without the Src homology 3 (SH3) domain. We have found that in transfected hippocampal neurons, all collybistin isoforms (CB2(SH3+), CB2(SH3-), CB3(SH3+), and CB3(SH3-)) target to and concentrate at GABAergic postsynapses. Moreover, in non-transfected neurons, collybistin concentrates at GABAergic synapses. Hippocampal neurons co-transfected with CB2(SH3-) and gephyrin developed very large postsynaptic gephyrin and GABA(A) receptor clusters (superclusters). This effect was accompanied by a significant increase in the amplitude of miniature inhibitory postsynaptic currents. Co-transfection with CB2(SH3+) and gephyrin induced the formation of many (supernumerary) non-synaptic clusters. Transfection with gephyrin alone did not affect cluster number or size, but gephyrin potentiated the clustering effect of CB2(SH3-) or CB2(SH3+). Co-transfection with CB2(SH3-) or CB2(SH3+) and gephyrin did not affect the density of presynaptic GABAergic terminals contacting the transfected cells, indicating that collybistin is not synaptogenic. Nevertheless, the synaptic superclusters induced by CB2(SH3-) and gephyrin were accompanied by enlarged presynaptic GABAergic terminals. The enhanced clustering of gephyrin and GABA(A) receptors induced by collybistin isoforms was not accompanied by enhanced clustering of neuroligin 2. Moreover, during the development of GABAergic synapses, the clustering of gephyrin and GABA(A) receptors preceded the clustering of neuroligin 2. We propose a model in which the SH3- isoforms play a major role in the postsynaptic accumulation of GABA(A) receptors and in GABAergic synaptic strength.     

Polymorphisms affecting micro-RNA regulation and associated with the risk of dietary-related cancers: a review from the literature and new evidence for a functional role of rs17281995 (CD86) and rs1051690 (INSR), previously associated with colorectal cancer

In this review, we focus on the genetic variations (single nucleotide polymorphisms, SNPs) known to occur in microRNAs and in their binding sites and the susceptibility to cancers of the gastro-intestinal (GI) tract in humans. Since the sequence complementarity and the thermodynamics of binding play an essential role in the interaction of miRNA with its target mRNA, sequence variations in the miRNA-binding seed regions or in miRNA genes (either within pre-, pri-, or mature miRNA regions) should reinforce, weaken, or disrupt the miRNA-mRNA interaction and affect the expression of mRNA targets. Indirect evidences supporting these hypotheses are reported in the literature, essentially coming from case-control association studies. Several studies have been published on the association between miR-SNPs or SNPs within their binding sites and the risk of oesophageal, gastric, or colorectal cancer. Unfortunately, functional studies are lacking. Besides reviewing the available literature, we present here for the first time two SNPs (rs17281995 in CD86 and rs1051690 in INSR) previously associated with the risk of CRC in a Czech population are also associated with the risk in a Spanish population. Moreover, we show for the first time that both these alleles regulate differentially the amount of a reporter gene (luciferase) in an in vitro assay on HeLa cells. These findings suggest that both these SNPs may have a functional role in regulating the expression of CD-86 and INSR proteins acting at the level of the 3'UTR. More functional studies are needed in order to better understand the role of polymorphic regulatory sequences at the 3'UTR of genes.     

Molecular bases of cyclic and specific disulfide interchange between human ERO1alpha protein and protein-disulfide isomerase (PDI)

In the endoplasmic reticulum (ER) of human cells, ERO1α and protein-disulfide isomerase (PDI) constitute one of the major electron flow pathways that catalyze oxidative folding of secretory proteins. Specific and limited PDI oxidation by ERO1α is essential to avoid ER hyperoxidation. To investigate how ERO1α oxidizes PDI selectively among more than 20 ER-resident PDI family member proteins, we performed docking simulations and systematic biochemical analyses. Our findings reveal that a protruding β-hairpin of ERO1α specifically interacts with the hydrophobic pocket present in the redox-inactive PDI b'-domain through the stacks between their aromatic residues, leading to preferred oxidation of the C-terminal PDI a'-domain. ERO1α associated preferentially with reduced PDI, explaining the stepwise disulfide shuttle mechanism, first from ERO1α to PDI and then from oxidized PDI to an unfolded polypeptide bound to its hydrophobic pocket. The interaction of ERO1α with ERp44, another PDI family member protein, was also analyzed. Notably, ERO1α-dependent PDI oxidation was inhibited by a hyperactive ERp44 mutant that lacks the C-terminal tail concealing the substrate-binding hydrophobic regions. The potential ability of ERp44 to inhibit ERO1α activity may suggest its physiological role in ER redox and protein homeostasis.     

Urotensin II receptor predicts the clinical outcome of prostate cancer patients and is involved in the regulation of motility of prostate adenocarcinoma cells

Urotensin II (UT-II) is a potent vasoconstrictor peptide and its receptor (UTR) was correlated with human cortico-adrenal carcinoma proliferation. In this study, we have evaluated the correlation between UTR expression and prognosis of human prostate adenocarcinoma and the involvement of this receptor in the regulation of biological properties on both in vivo and in vitro models. UTR mRNA and protein, evaluated by real-time PCR and Western blotting, respectively, were expressed at high levels only in androgen-dependent LNCaP cells. In order to investigate UTR changes occurring in human prostate tumorigenesis, we have also evaluated the expression of UTR in vivo in 195 human prostate tissue samples. UTR was always expressed at low intensity in hyperplastic tissues and at high intensity in well-differentiated carcinomas (Gleason 2-3). Moreover, we have evaluated the effects of an antagonist of UTR, urantide on migration and invasion of LNCaP cells. Urantide induced a dose-dependent decrease of motility and invasion of LNCaP cells whose characteristic ameboid movement seems to be advantageous for their malignancy. These effects were paralleled by down-regulating the autophosphorylation of focal adhesion kinase and the integrin surface expression on LNCaP cells. The effects on cell motility and invasion were likely due to the inhibition of RhoA activity induced by both urantide and shRNA UTR. These data suggest that UTR can be considered a prognostic marker in human prostate adenocarcinoma patients.