Up-regulation of ski-interacting protein in rat brain cortex after traumatic brain injury

Regeneration in the nervous system with erythropoietin

Globally, greater than 30 million individuals are afflicted with disorders of the nervous system accompanied by tens of thousands of new cases annually with limited, if any, treatment options. Erythropoietin (EPO) offers an exciting and novel therapeutic strategy to address both acute and chronic neurodegenerative disorders. EPO governs a number of critical protective and regenerative mechanisms that can impact apoptotic and autophagic programmed cell death pathways through protein kinase B (Akt), sirtuins, mammalian forkhead transcription factors, and wingless signaling. Translation of the cytoprotective pathways of EPO into clinically effective treatments for some neurodegenerative disorders has been promising, but additional work is necessary. In particular, development of new treatments with erythropoiesis-stimulating agents such as EPO brings several important challenges that involve detrimental vascular outcomes and tumorigenesis. Future work that can effectively and safely harness the complexity of the signaling pathways of EPO will be vital for the fruitful treatment of disorders of the nervous system.

Up-regulation of SKIP relates to retinal ganglion cells apoptosis after optic nerve crush in vivo

Cell cycle re-entry is one of the key processes in neuronal apoptosis. Previous studies have shown that Ski-interacting protein (SKIP) played an important role in cell cycle re-entry. However, its expression and function in optic nerve injury are still with limited acquaintance. To investigate whether SKIP is involved in retinal ganglion cells (RGCs) death, we performed an optic nerve crush (ONC) model in adult rats. Western blot analysis revealed that up-regulation of SKIP was present in retina at 5 days after ONC. Immunofluorescent labeling indicated that up-regulated SKIP was found mainly in RGCs. We also investigated co-localization of SKIP with active-caspase-3 and TUNEL (apoptotic markers) -positive cells in the retina after ONC. In addition, the expression of SKIP was increased in parallel with P53 and P21 in retina after ONC. All these results suggested that up-regulation of SKIP in the retina was associated with RGCs death after ONC.

Expression and prognostic role of SKIP in human breast carcinoma

Ski-interacting protein (SKIP) is a nuclear hormone receptor-interacting cofactor, interactions with the proto-oncogene Ski, appears to modulate a number of signalling pathways involved in control of cell proliferation and differentiation, and may play a critical role in oncogenesis. In the present study, to investigate the potential roles of SKIP in breast cancer, expression patterns, interaction and the correlation with clinical/prognostic factors of SKIP and Ki-67 were examined among patients with breast cancer. Immunohistochemistry and Western blot analysis were performed for SKIP in 85 breast carcinoma samples. The data were correlated with clinicopathological features. The univariate and multivariate survival analyses were also performed to determine their prognostic significance. We found that SKIP was over expressed in breast carcinoma as compared with the adjacent normal tissues. High expression of SKIP was positively associated with histological grade (P = 0.01) and Ki-67 (P = 0.004). Univariate analysis showed that SKIP expression was associated with a poor prognosis (P = 0.006). While in vitro, following release of breast cancer cell lines from serum starvation, the expression of SKIP was up-regulated, whereas p27 was down-regulated. In addition, we employed small interfering RNA (siRNA) technique to knock down SKIP expression and observed it effects on MDA-MB-231 cells growth. SKIP depletion by siRNA inhibited cell proliferation, blocked S phase and decreased cyclin A and cyclin B levels. On the basis of these results, we suggested that SKIP overexpression was involved in the pathogenesis of breast cancer, which might serve as a future target for breast cancer.

Phosphorylated retinoblastoma protein (p-Rb) is involved in neuronal apoptosis after traumatic brain injury in adult rats

Phosphorylated retinoblastoma protein (p-Rb), a well identified cell cycle related protein, is involved in regulating the biological functions of various cell types including neurons. One attractive biological function of p-Rb is releasing E2F transcription factor to induce S-phase entry and cellular proliferation of mitotic cells. However, some studies point out that the role of p-Rb in post-mitotic cells such as mature neurons is unique; it may induce cellular apoptosis rather than proliferation via regulating cell cycle reactivation. Up to now, the knowledge of p-Rb function in CNS is still limited. To investigate whether p-Rb is involved in CNS injury and repair, we performed a traumatic brain injury model in adult rats. Up-regulation of p-Rb was observed in the injured brain cortex by western blot analysis and immunohistochemistry staining. Terminal deoxynucleotidyl transferase deoxy-UTP-nick end labeling (TUNEL) and 4',6-diamidino-2-phenylindole (DAPI) staining suggested that p-Rb was relevant to neuronal apoptosis after brain injury. In addition, glutamate excitotoxic model of primary cortex neurons was introduced to further investigate the role of p-Rb in neuronal apoptosis; the result implied p-Rb was associated with cell cycle activation in the apoptotic neurons. Based on our data, we suggested that p-Rb might play an important role in neuronal apoptosis after traumatic brain injury in rat; which might also provide a basis for the further study on its role in regulating cell cycle re-entry in apoptotic neurons, and might gain a novel strategy for the clinical therapy for traumatic brain injury.