Attenuated neuroprotective effect of riboflavin under UV-B irradiation via miR-203/c-Jun signaling pathway in vivo and in vitro

Background

Riboflavin (RF) or vitamin B2 is known to have neuroprotective effects. In the present study, we report the attenuation of the neuroprotective effects of RF under UV-B irradiation. Preconditioning of UV-B irradiated riboflavin (UV-B-RF) showed attenuated neuroprotective effects compared to that of RF in SH-SY5Y neuroblostoma cell line and primary cortical neurons in vitro and a rat model of cerebral ischemia in vivo.

Results

Results indicated that RF pretreatment significantly inhibited cell death and reduced LDH secretion compared to that of the UV-B-RF pretreatment in primary cortical neuron cultures subjected to oxygen glucose deprivation in vitro and cortical brain tissue subjected to ischemic injury in vivo. Further mechanistic studies using cortical neuron cultures revealed that RF treatment induced increased miR-203 expression which in turn inhibited c-Jun expression and increased neuronal cell survival. Functional assays clearly demonstrated that the UV-B-RF preconditioning failed to sustain the increased expression of miR-203 and the decreased levels of c-Jun, mediating the neuroprotective effects of RF. UV-B irradiation attenuated the neuroprotective effects of RF through modulation of the miR-203/c-Jun signaling pathway.

Conclusion

Thus, the ability of UV-B to serve as a modulator of this neuroprotective signaling pathway warrants further studies into its role as a regulator of other cytoprotective/neuroprotective signaling pathways.     

An IP-10 (CXCL10)-derived peptide inhibits angiogenesis

Angiogenesis plays a critical role in processes such as organ development, wound healing, and tumor growth. It requires well-orchestrated integration of soluble and matrix factors and timely recognition of such signals to regulate this process. Previous work has shown that newly forming vessels express the chemokine receptor CXC receptor 3 (CXCR3) and, activation by its ligand IP-10 (CXCL10), both inhibits development of new vasculature and causes regression of newly formed vessels. To identify and develop new therapeutic agents to limit or reverse pathological angiogenesis, we identified a 21 amino acid fragment of IP-10, spanning the α-helical domain residues 77-98, that mimic the actions of the whole IP-10 molecule on endothelial cells. Treatment of the endothelial cells with the 22 amino acid fragment referred to as IP-10p significantly inhibited VEGF-induced endothelial motility and tube formation in vitro, properties critical for angiogenesis. Using a Matrigel plug assay in vivo, we demonstrate that IP-10p both prevented vessel formation and induced involution of nascent vessels. CXCR3 neutralizing antibody was able to block the inhibitory effects of the IP-10p, demonstrating specificity of the peptide. Inhibition of endothelial function by IP-10p was similar to that described for IP-10, secondary to CXCR3-mediated increase in cAMP production, activation of PKA inhibiting cell migration, and inhibition of VEGF-mediated m-calpain activation. IP-10p provides a novel therapeutic agent that inhibits endothelial cell function thus, allowing for the modulation of angiogenesis.     

The interaction of DIAP1 with dOmi/HtrA2 regulates cell death in Drosophila

Mitochondrial proteins such as cytochrome c, Smac/DIABLO and Omi/HtrA2 play important roles in the cell death pathways of mammalian cells. In Drosophila, the role of mitochondria in cell death is less clear. Here, we report the identification and characterization of the Drosophila ortholog of human Omi/HtrA2. We show that Drosophila Omi/HtrA2 is imported into the mitochondria where it undergoes proteolytic maturation to yield two isoforms, dOmi-L and dOmi-S. dOmi-L contains a canonical N-terminal IAP-binding motif (AVVS), whereas dOmi-S contains a distinct N-terminal motif (SKMT). DIAP1 was able to bind to both isoforms via its BIR1 and BIR2 domains. This resulted in cleavage of the linker region of DIAP1 between the BIR1 and BIR2 domains and further degradation of the BIR1 domain by the proteolytic activity of dOmi. The binding of DIAP1 to dOmi also resulted in DIAP1-mediated polyubiquitination of dOmi, suggesting that DIAP1 could target dOmi for proteasomal degradation. Consistent with this, expression of DIAP1 in Drosophila eye discs protected them from dOmi-induced eye ablation, indicating that DIAP1 plays an important role in protecting cells from the potentially lethal effects of dOmi. The ability of IAPs to bind to and ubiquitinate mitochondrial proteins such as dOmi may be a key conserved function to counterbalance the lethal effects of these proteins if accidentally released into the cytosol.     

Drosophila SAP18, a member of the Sin3/Rpd3 histone deacetylase complex, interacts with Bicoid and inhibits its activity

Bicoid directs anterior development in Drosophila embryos by activating different genes along the anterior-posterior axis. However, its activity is down-regulated at the anterior tip of the embryo, in a process known as retraction. Retraction is under the control of the terminal polarity system, and results in localized repression of Bicoid target genes. Here, we describe a Drosophila homolog of human SAP18, a member of the Sin3A/Rpd3 histone deacetylase complex. dSAP18 interacts with Bicoid in yeast and in vitro, and is expressed early in development coincident with Bicoid. In tissue culture cells, dSAP18 inhibits the ability of Bicoid to activate reporter genes. These results suggest a model in which dSAP18 interacts with Bicoid to silence expression of Bicoid target genes in the anterior tip of the embryo.     

On the structure of proteoglycan core

Core protein from bovine nasal proteoglycan has been obtained by cyanogen bromide cleavage and by removal of most of the glycosaminoglycan side chains by hydrogen fluoride treatment. Amino acid analysis of the cyanogen bromide fragment shows it to consist mainly of proline, serine, glycine and glutamic acid (glutamine). End-group analyses of the fragment and HF stripped core reveal and N-terminal residue to be valine in each case. The stripped core has been subjected to sequencing and some sequential information is presented. Based upon the amino acid analysis, sequence information and other properties, conformation analysis indicates that the most likely conformation is that of a flexible extended chain containing β-turns. The existence of a common N-terminal residue indicates that it is the C-terminal region which lies in the region of the hyaluronic acid backbone in intact proteoglycan. Furthermore, enzymatic cleavage of core protein which occurs in proteoglycan turnover, aging and degenerative diseases, probably does not occur by a stepwise cleavage from the N terminus of proteoglycan but by a more drastic degradation process.