Changes in the BAG1 expression of Schwann cells after sciatic nerve crush

Chaperone Proteins in the Central Nervous System and Peripheral Nervous System after Nerve Injury

Injury to axons of the central nervous system (CNS) and the peripheral nervous system (PNS) is accompanied by the upregulation and downregulation of numerous molecules that are involved in mediating nerve repair, or in augmentation of the original damage. Promoting the functions of beneficial factors while reducing the properties of injurious agents determines whether regeneration and functional recovery ensues. A number of chaperone proteins display reduced or increased expression following CNS and PNS damage (crush, transection, contusion) where their roles have generally been found to be protective. For example, chaperones are involved in mediating survival of damaged neurons, promoting axon regeneration and remyelination and, improving behavioral outcomes. We review here the various chaperone proteins that are involved after nervous system axonal damage, the functions that they impact in the CNS and PNS, and the possible mechanisms by which they act.

Pathway-focused PCR array profiling of enriched populations of laser capture microdissected hippocampal cells after traumatic brain injury

Cognitive deficits in survivors of traumatic brain injury (TBI) are associated with irreversible neurodegeneration in brain regions such as the hippocampus. Comparative gene expression analysis of dying and surviving neurons could provide insight into potential therapeutic targets. We used two pathway-specific PCR arrays (RT2 Profiler Apoptosis and Neurotrophins & Receptors PCR arrays) to identify and validate TBI-induced gene expression in dying (Fluoro-Jade-positive) or surviving (Fluoro-Jade- negative) pyramidal neurons obtained by laser capture microdissection (LCM). In the Apoptosis PCR array, dying neurons showed significant increases in expression of genes associated with cell death, inflammation, and endoplasmic reticulum (ER) stress compared with adjacent, surviving neurons. Pro-survival genes with pleiotropic functions were also significantly increased in dying neurons compared to surviving neurons, suggesting that even irreversibly injured neurons are able to mount a protective response. In the Neurotrophins & Receptors PCR array, which consists of genes that are normally expected to be expressed in both groups of hippocampal neurons, only a few genes were expressed at significantly different levels between dying and surviving neurons. Immunohistochemical analysis of selected, differentially expressed proteins supported the gene expression data. This is the first demonstration of pathway-focused PCR array profiling of identified populations of dying and surviving neurons in the brain after TBI. Combining precise laser microdissection of identifiable cells with pathway-focused PCR array analysis is a practical, low-cost alternative to microarrays that provided insight into neuroprotective signals that could be therapeutically targeted to ameliorate TBI-induced neurodegeneration.

Up-regulation of HDAC4 is associated with Schwann cell proliferation after sciatic nerve crush

Histone deacetylase 4 (HDAC4), a member of the class IIa HDACs subfamily, has emerged as a critical regulator of cell growth, differentiation, and migration in various cell types. It was reported that HDAC4 stimulated colon cell proliferation via repression of p21. Also, HDAC4 contributes to platelet-derived growth factor-BB-induced proliferation and migration of vascular smooth muscle cells. Furthermore, HDAC4 may play an important role in the regulation of neuronal differentiation and survival. However, the role of HDAC4 in the process of peripheral nervous system regeneration after injury remains virtually unknown. Herein, we investigated the spatiotemporal expression of HDAC4 in a rat sciatic nerve crush model. We found that sciatic nerve crush induced up-regulated expression of HDAC4 in Schwann cells. Moreover, the expression of the proliferation marker Ki-67 exhibited a similar tendency with that of HDAC4. In cell cultures, we observed increased expression of HDAC4 during the process of TNF-α-induced Schwann cell proliferation, whereas the protein level of p21 was down-regulated. Interference of HDAC4 led to enhanced expression of p21 and impaired proliferation of Schwan cells. Taken together, our findings implicated that HDAC4 was up-regulated in the sciatic nerve after crush, which was associated with proliferation of Schwann cells.

Upregulated expression of ebp1 contributes to schwann cell differentiation and migration after sciatic nerve crush

Ebp1, an ErbB3-binding protein, is the human homologue of the cell cycle-regulated mouse protein p38-2G4. Ebp1 was reported to inhibit the proliferation and induce the differentiation of human cancer cells. Its p48 isoform contributes to neuronal differentiation and growth factor specificity. However, the expression and role of Ebp1 in peripheral system lesions and repair are still unknown. Herein, we investigated the spatiotemporal pattern of Ebp1 expression following sciatic nerve crush. After crush, the level of Ebp1 protein was elevated gradually, peaked at day 5, and then declined to the normal at 4 weeks, which was similar to the expression of Oct-6. Furthermore, using double immunofluorescent staining, we found Ebp1 had a colocalization with S100 and Oct-6 in 5-day injured tissues. In vitro, we observed enhanced expression of Ebp1 during the process of cyclic adenosine monophosphate (cAMP)-induced Schwann cells differentiation. Interestingly, Ebp1-depleted SCs did not show significant morphologic change after the treatment of cAMP. Also, we observed a colocalization between Ebp1 and Cyclin D1 and that Ebp1-specific siRNA-transfected SCs had a decreased migration. Taken together, we speculated that Ebp1 was upregulated in the sciatic nerve after crush, which was involved in the differentiation and migration of Schwann cells.