Bai Shao

Peroxisome proliferator-activated receptor γ agonist pioglitazone inhibits β-catenin-mediated glioma cell growth and invasion.

Gliomas are the most common primary tumors of the central nervous system. Rapid proliferation and diffuse brain invasion of these tumors are likely to determine the unfavorable prognosis. Recent studies have shown that ligand activation of peroxisome proliferator-activated receptor γ (PPARγ) can induce differentiation and inhibit proliferation of several cancer cells. In this study, we identified pioglitazone, one PPARγ ligand in particular, suppressed human glioma cells proliferation, migration, and induced glioma cells apoptosis. Concomitantly, expression level of β-catenin protein, a key molecule in carcinogenesis, was decreased in glioma cells treated with pioglitazone. Noteworthy, knockdown of β-catenin expression using siRNA technology mimicked the anti-neoplastic potency of pioglitazone. These results indicate that β-catenin is one of the mediators for pioglitazone to suppress glioma cells growth and invasion. Due to its capacity to counteract β-catenin and glioma cell proliferation and migration, pioglitazone represents a promising drug for adjuvant therapy of glioma and other highly migratory tumor entities.

Involvement of CLEC16A in activation of astrocytes after LPS treated.

CLEC16A, C-type lectin domain family 16, member A was recently found to be associated with inflation process in the autoimmune diseases. In this study, we elucidated the dynamic expression changes and localization of CLEC16A in lipopolysaccharide (LPS)-induced neuroinflammatory processes in adult rats. CLEC16A expression was strongly induced in active astrocytes in inflamed cerebral cortex. In vitro studies indicated that the up-regulation of CLEC16A may be involved in the subsequent astrocyte activation following LPS challenge. And Knock-down of CLEC16A in cultured primary astrocytes by siRNA showed that CLEC16A was required for the activation of astrocytes induced by LPS. Collectively, these results suggested CLEC16A may be important in host defense in astrocyte-mediated immune response. Understanding the cell signal pathway may provide a novel strategy against inflammatory and immune reaction in neuroinflammtion in CNS.

Increased expression of transcription initiation factor IIB after rat traumatic brain injury

The protein TFIIB is a general transcription initiation factor that plays a pivotal role in the preinitiation complex (PIC) and selects the transcription initiation site. However, its distribution and function in the central nervous system (CNS) remains unclear. In the present study, we mainly investigated the expression and cellular localization of TFIIB during traumatic brain injury (TBI). Western blot analysis revealed that TFIIB was present in normal rat brain cortex. It gradually increased, reached a peak at the 5th day after TBI, and then decreased. Importantly, more TFIIB was colocalized with astrocytes and microglia, which are largely proliferated. In addition, Western blot detection showed that the 5th day post injury was also the proliferation peak indicated by the elevated expression of PCNA. Importantly, injury-induced expression of TFIIB was colabelled by proliferating cell nuclear antigen (proliferating cells marker). These data suggested that TFIIB may be implicated in the proliferation of astrocytes and microglia and the recovery of neurological outcomes. But the inherent mechanisms remained unknown. Further studies are needed to confirm the exact role of TFIIB after brain injury.

Upregulation of p21-activated Kinase 6 in rat brain cortex after traumatic brain injury

Abstractp21-activated Kinase 6 (PAK6) is a serine/threonine kinase belonging to the p21-activated kinase (PAK) family. PAK kinases are well-known regulators of a wide variety of cellular functions, including regulation of cytoskeleton rearrangement, cell survival, apoptosis and the mitogen-activated protein kinase signaling pathway. To elucidate the expressions and possible functions of PAK6 in central nervous system (CNS) lesion and repair, we performed a traumatic brain injury (TBI) model in adult rats. Western blot analysis revealed that PAK6 level significantly increased at day 3 after damage, and then declined during the following days. Besides, double immunofluorescence staining showed PAK6 was primarily expressed in the neurons and a few of glial cells in the normal group. While after injury, the expression of PAK6 was increased significantly in the astrocytes and neurons, and the astrocytes had largely proliferated. We also examined the expression of proliferating cell nuclear antigen (PCNA) whose change was correlated with the expression of PAK6. Importantly, double immunofluorescence staining revealed that cell proliferation evaluated by PCNA appeared in many PAK6-expressing cells at day 3 after injury. In addition, injury-induced expression of PAK6 was co-labeled by active caspase-3 during neuronal apoptosis after injury. Collectively, we hypothesized PAK6 may play important roles in CNS pathophysiology after TBI and further research is needed to have a good understanding of its function and mechanism.

Traumatic Brain Injury Induces an Up-Regulation of Hs1-Associated Protein X-1 (Hax-1) in Rat Brain Cortex

HS1-associated protein X-1 (Hax-1) is an intracellular protein with anti-apoptotic properties that, in addition to suppressing cell death by inhibiting the activation of initiator caspase-9 and death caspase-3, is involved in an increasing number of signaling cascades. However, its expression and function in the central nervous system lesion are still unclear. In this study, we performed a traumatic brain injury (TBI) model in adult rats and investigated the dynamic changes of Hax-1 expression in the brain cortex. Western blot and immunohistochemistry analysis revealed that Hax-1 was present in normal brain. It gradually increased, reached a peak at day 3 after TBI, and then declined during the following days. Double immunofluorescence staining showed that Hax-1 immunoreactivity (IR) was found in neurons, but not astrocytes and microglia. Moreover, the 3rd day post injury was the apoptotic peak implied by the alteration of caspase-3, Bcl-2 and TUNEL. All these results suggested that Hax-1 may be involved in the pathophysiology of TBI and further research is needed to have a good understanding of its function and mechanism.

The Relationship Between Src-Suppressed C Kinase Substrate and β-1,4 Galactosyltransferase-I in the Process of Lipopolysaccharide-Induced TNF-α Secretion in Rat Primary Astrocytes

Src-suppressed C kinase substrate (SSeCKS), a protein kinase C substrate, is a major lipopolysaccharide (LPS) response protein. In addition, β-1,4 Galactosyltransferase-I (β-1,4-GalT-I) also plays an important role in the inflammation reactions of nervous system. It was reported that both SSeCKS and β-1,4-GalT-I were involved in the LPS-induced tumor necrosis factor-alpha (TNF-α) expression in rat primary astrocytes. However, the functional interaction between SSeCKS and β-1,4-GalT-I in the LPS-induced TNF-α secretion remains unclear. Therefore, in this study, using the inflammation model of astrocytes treated by LPS in vitro, we found that the changed expressions of SSeCKS and β-1,4-GalT-I participated in LPS-induced TNF-α secretion through p38, JNK, and ERK signal transduction pathways in rat primary astrocytes. Knockdown by small-interfering RNAs (siRNAs) or overexpression of SSeCKS and β-1,4-GalT-I could influence Mitogen-activated protein kinases (MAPKs) signaling pathways activation and TNF-α secretion. Besides, we confirmed that knockdown of SSeCKS could prevent the induction of β-1,4-GalT-I in this process. Inversely, β-1,4-GalT-I had no significant effect on SSeCKS expression in the same way. In summary, our data indicated that SSeCKS could regulate LPS-induced TNF-α secretion through β-1,4-GalT-I in rat primary astrocytes.

The nuclear localization of CAPON in hippocampus and cerebral cortex neurons after lipopolysaccharide stimulation.

Objective: In the brain, nitric oxide (NO) is a retrograde signalling molecule that transfers information from post- to pre-synaptic nerve endings. NO has been shown to be an important inflammatory mediator responding to lipopolysaccharide (LPS). It has been stated that the constitutive NO synthase isoforms (nNOS and eNOS) may also contribute to the inflammation. CAPON, a nNOS regulator, helps regulate nNOS stability, localization and possibly expression during synapse formation as well as muscle re-innervation. Recently, it has been reported that CAPON is associated with psychiatric illness. So we speculated that the CAPON expression-induced physiological changes may be mediated by modifications of NOS-NO signalling pathways. But little is known about the role of CAPON during the inflammation in the central nervous system, so we investigated the expression of CAPON in the brain treated with LPS. Methods and Results: Real-time PCR and Western blot showed that the expression of CAPON increased at mRNA and protein levels in the brain after LPS stimulation. Immunocytochemistry staining revealed that CAPON localized in the nuclei of neurons in the brain after peritoneal injection with LPS in vivo. The same phenomenon was also shown in primary cultured neurons in vitro incubated with LPS for 36 h. In addition, we found that CAPON had a colocalization with phosphorylated nNOS Ser847 but not with nNOS in hippocampus and cerebral cortex by double immunofluorescence. Conclusion: CAPON localized in the nuclei of neurons in hippocampus and cerebral cortex after LPS treatment. Because CAPON competed with PSD-95 for binding nNOS in neurons and nNOS was activated to produce NO through the NMDA- NMDAR pathway, we hypothesized that CAPON might play a proactive role in the process of inflammation by transferring from cytoplasm to the nucleus and through the NMDA-nNOS signal pathway. Further studies are required to clarify the mechanism of the nuclear localization of CAPON and the possible relationship with nNOS/NO signalling.

Changes in Pirh2 and p27kip1 expression following traumatic brain injury in adult rats.

Pirh2, a p53-induced ubiquitin-protein ligase, has been reported to promote ubiquitin-dependent degradation of p27kip1, which plays an essential role in mammalian cell cycle regulation and neurogenesis in the developing central nervous system (CNS). However, their distributions and functions in the nervous system lesion and repair remain unclear. In this study, we observed that the up-regulated expression of Pirh2 was concomitant with decreased p27kip1 level after traumatic brain injury by Western blot and immunohistochemistry. Immunofluorescence double-labeling revealed that Pirh2 was mainly co-expressed with GFAP and CD11b. Meanwhile, we also examined the expression profiles of proliferating cell nuclear antigen (PCNA) whose changes were correlated with the expression of Pirh2. In addition, Pirh2 colocalized with p27kip1 and PCNA. Immunoprecipitation further showed that they interacted with each other in the pathophysiology process. In summary, our data indicated Pirh2 might be a negative regulator of p27kip1 and associated with glial proliferation.

Involvement of early growth response-2 (Egr-2) in lipopolysaccharide-induced neuroinflammation.

Early growth response-2 (Egr-2) protein is a transcription factor, which belongs to Egr family which involve in modulating the peripheral immune response, by means of the induction of differentiation of lymphocyte precursors, activation of T and B cells. Egr-2 plays essential roles in peripheral nerve myelination, adipogenesis, tissue repair and fibrosis, immune tolerance; however, its regulation and role in central nervous system (CNS) remain poorly understood. In contrast to Egr-1, which has been extensively investigated, the regulation and function of Egr-2 remains less well characterized. To elaborate whether Egr-2 was involved in CNS injury, we performed a neuroinflammatory model by lipopolysaccharide (LPS) lateral ventral injection in adult rats. Egr-2 expression was strongly induced in active glia cells (astrocytes and microglias) in inflamed brain cortex. In vitro studies indicated that the upregulation of Egr-2 may be involved in the subsequent glia cellular activation following LPS exposure; and knock down of Egr-2 in primary mixed glial cultures (MGC) by siRNA showed that Egr-2 promoted the synthesis of TNF-α. Collectively, these results suggested Egr-2 may be important in host defense in CNS immune response, which might provide a potential target to the treatment of neuroinflammation.

LPS-Stimulating Astrocyte-Conditioned Medium Causes Neuronal Apoptosis Via Increasing CDK11p58 Expression in PC12 Cells Through Downregulating AKT Pathway

Activation of astrocytes in central nervous system inflammation leads to a disturbance of crosstalk between astrocytes and neurons, and that this may contribute to the death of neurons. CDK11p58 is a member of the large family of p34cdc2-related kinases. It specifically expresses in G2/M phase of the cell cycle and is closely related to cell cycle arrest and apoptosis. Here, we show that astrocyte-conditioned medium stimulated by lipopolysaccharide upregulates CDK11p58 expression and meanwhile causes neuronal apoptosis. CDK11p58 knockdown in PC12 cells represses neuronal apoptosis. CDK11p58 overexpression in PC12 cells promotes neuronal apoptosis. AKT signaling pathway is involved in CDK11p58-induced neuronal apoptosis process.