A mimetic peptide of α2,6-sialyllactose promotes neuritogenesis.

Oxidative stress contributes to the pathogenesis of neurodegenerative diseases. With the aim to find reagents that reduce oxidative stress, a phage display library was screened for peptides mimicking α2,6-sialyllactose (6'-SL), which is known to beneficially influence neural functions. Using Sambucus nigra lectin, which specifically binds to 6'-SL, we screened a phage display library and found a peptide comprising identical sequences of 12 amino acids. Mimetic peptide, reverse peptide and scrambled peptide were tested for inhibition of 6'-SL binding to the lectin. Indeed, lectin binding to 6'-SL was inhibited by the most frequently identified mimetic peptide, but not by the reverse or scrambled peptides, showing that this peptide mimics 6'-SL. Functionally, mimetic peptide, but not the reverse or scrambled peptides, increased viability and expression of neural cell adhesion molecule L1 in SK-N-SH human neuroblastoma cells, and promoted survival and neurite outgrowth of cultured mouse cerebellar granule neurons challenged by H2O2-induced oxidative stress. The combined results indicate that the 6'-SL mimetic peptide promotes neuronal survival and neuritogenesis, thus raising hopes for the treatment of neurodegenerative diseases. This study was approved by the Medical Ethics Committee of Shantou University Medical College, China (approval No. SUMC 2014-004) on February 20, 2014.

Spinal cord injury induced Neuregulin 1 signaling changes in mouse prefrontal cortex and hippocampus.

Accumulated evidence has recently demonstrated that spinal cord injury (SCI) can lead to chronic damage in a wide range of brain regions. Neuregulin 1 (Nrg1) signaling has been broadly recognized as an important mechanism contributing to neural differentiation and regeneration. We here studied the effect of SCI on Nrg1 signaling in prefrontal cortex (PFC) and hippocampus (HIP) in a mouse model. As was indicated by the increased levels of GFAP and Iba-1, our results demonstrated that SCI significantly induced activation of astrocytes and microglial cells in both PFC and HIP. In addition, both western blot and morphological assay demonstrated that Nrg1 was altered in both regions at 8 weeks post SCI, which was accompanied with decreased phosphorylation levels of its cognitive receptors Neu and ErbB4. Our combined results indicated that SCI can influence Nrg1 signaling, which may contribute to the worsening of pathophysiological changes in major brain regions during SCI. These results also suggested that exogenous Nrg1 treatment may have a therapeutic role in counteracting SCI-induced brain damage.

CHL1 Is Expressed and Functions as a Malignancy Promoter in Glioma Cells.

The cell adhesion molecule with homology to L1CAM (close homolog of L1) (CHL1) is a member of the cell adhesion molecule L1 (L1CAM) gene family. Although CHL1 expression and function have been reported in several tumors, the roles of CHL1 in the development of glioma remain unclear. In the present study, we investigated the effects of CHL1 on proliferation indexes and activation of Akt1 and Erk signaling by siRNA in U-87 MG human glioblastoma and human U251 and SHG-44 glioma cells. We found that siRNA targeting CHL1 significantly down-regulated the expression of CHL1 mRNA and protein accompanied by reduced cell proliferation and transmigration invasion in all three cell lines. Down-regulating CHL1 expression also reduced cell survival, as measured by the Bax/Bcl-2 ratio, and increased activation of caspase-3. In subcutaneous U-87 MG cell xenograft tumors in nude mice, intratumoral administration of siRNA targeting CHL1 treatment significantly down-regulated CHL1 expression in vivo, accompanied by increased levels of activated caspase-3. Our combined results confirmed for the first time that in contrast to findings about CHL1 in most other cancer types, CHL1 functions in promoting cell proliferation, metastasis and migration in human glioma cells both in vitro and in vivo. These results indicate that CHL1 is a therapeutic target in the clinical management of glioma/glioblastoma.

The Adhesion Molecule-Characteristic HNK-1 Carbohydrate Contributes to Functional Recovery After Spinal Cord Injury in Adult Zebrafish.

The human natural killer cell antigen-1 (HNK-1) is functionally important in development, synaptic activity, and regeneration after injury in the nervous system of several mammalian species. It contains a sulfated glucuronic acid which is carried by neural adhesion molecules and expressed in nonmammalian species, including zebrafish, which, as opposed to mammals, spontaneously regenerate after injury in the adult. To evaluate HNK-1's role in recovery of function after spinal cord injury (SCI) of adult zebrafish, we assessed the effects of the two HNK-1 synthesizing enzymes, glucuronyl transferase and HNK-1 sulfotransferase. Expression of these two enzymes was increased at the messenger RNA (mRNA) level 11 days after injury in the brainstem nuclei that are capable of regrowth of severed axons, namely, the nucleus of medial longitudinal fascicle and intermediate reticular formation, but not at earlier time points after SCI. mRNA levels of glucuronyl transferase and sulfotransferase were increased in neurons, not only of these nuclei but also in the spinal cord caudal to the injury site at 11 days. Mauthner neurons which are not capable of regeneration did not show increased levels of enzyme mRNAs after injury. Reducing protein levels of the enzymes by application of anti-sense morpholinos resulted in reduction of locomotor recovery for glucuronyl transferase, but not for HNK-1 sulfotransferase. The combined results indicate that HNK-1 is upregulated in expression only in those neurons that are intrinsically capable of regeneration and contributes to regeneration after spinal cord injury in adult zebrafish in the absence of its sulfate moiety.

Differential changes in Neuregulin-1 signaling in major brain regions in a lipopolysaccharide-induced neuroinflammation mouse model.

Neuregulin 1 (Nrg1) is involved in multiple biological processes in the nervous system. The present study investigated changes in Nrg1 signaling in the major brain regions of mice subjected to lipopolysaccharide (LPS)-induced neuroinflammation. At 24 h post­intraperitoneal injection of LPS, mouse brain tissues, including tissues from the cortex, striatum, hippocampus and hypothalamus, were collected. Reverse transcription­polymerase chain reaction was used to determine the expression of Nrg1 and its receptors, Neu and ErbB4, at the mRNA level. Western blotting was performed to determine the levels of these proteins and the protein levels of phosphorylated extracellular signal-regulated kinases (Erk)1/2 and Akt1. Immunohistochemical staining was utilized to detect the levels of pNeu and pErbB4 in these regions. LPS successfully induced sites of neuroinflammation in these regions, in which changes in Nrg1, Neu and ErbB4 at the mRNA and protein levels were identified compared with controls. LPS induced a reduction in pNeu and pErbB4 in the striatum and hypothalamus, although marginally increased pErbB4 levels were found in the hippocampus. LPS increased the overall phosphorylation of Src but this effect was reduced in the hypothalamus. Moreover, increased phosphorylation of Akt1 was found in the striatum and hippocampus. These data suggest diverse roles for Nrg1 signaling in these regions during the process of neuroinflammation.