Caveolin-1 promotes glioma proliferation and metastasis by enhancing EMT via mediating PAI-1 activation and its correlation with immune infiltrates.

Glioma is typically characterized by a poor prognosis and is associated with a decline in the quality of life as the disease advances. However, the development of effective therapies for glioma has been inadequate. Caveolin-1 (CAV-1) is a membrane protein that plays a role in caveolae formation and interacts with numerous signaling proteins, compartmentalizing them in caveolae and frequently exerting direct control over their activity through binding to its scaffolding domain. Although CAV-1 is a vital regulator of tumour progression, its role in glioma remains unclear. Our findings indicated that the knockdown of CAV-1 significantly inhibits the proliferation and metastasis of glioma. Subsequent mechanistic investigations demonstrated that CAV-1 promotes proliferation and metastasis by activating the photoshatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway. Furthermore, we demonstrated that CAV-1 overexpression upregulates the expression of serpin peptidase inhibitor, class E, member 1 (SERPINE1, also known as PAI-1), which serves as a marker for the epithelial-mesenchymal transition (EMT) process. Further research showed that PAI-1 knockdown abolished the CAV-1 mediated activation of PI3K/Akt signaling pathway. In glioma tissues, CAV-1 expression exhibited a correlation with unfavorable prognosis and immune infiltration among glioma patients. In summary, our study provided evidence that CAV-1 activates the PI3K/Akt signaling pathway by upregulating PAI-1, thereby promoting the proliferation and metastasis of glioma through enhanced epithelial-mesenchymal transition (EMT) and angiogenesis, and CAV-1 is involved in the immune infiltration.

Exosomes Derived from Hypoxic Glioma Cells Reduce the Sensitivity of Glioma Cells to Temozolomide Through Carrying miR-106a-5p.

Background: Hypoxia is a frequent feature of solid tumors which significantly affects the efficacy of treatments such as chemotherapy. In addition, exosomes from hypoxic cancer cells could contribute to the chemoresistance of tumor cells through carrying miRNAs. It has been shown that miR-106-5p level was upregulated in glioma. However, whether exosomes derived from hypoxic glioma cells could affect temozolomide (TMZ) resistance in glioma through carrying miR-106a-5p remains unexplored. Methods: Exosomes were isolated from glioma cells under normoxia or hypoxia condition. EdU staining and flow cytometry assays were used to assess the cell proliferation and cell apoptosis. The relation between miR-106a-5p and PTEN was investigated by dual luciferase assay. Results: MiR-106a-5p was enriched in exosomes derived from hypoxic glioma cells compared to exosomes from cells under normoxia condition. Additionally, hypoxic glioma cells were able to transfer exosomes to glioma cells, resulting in a significant increase of miR-106a-5p level in cells. TMZ remarkably suppressed glioma cell proliferation and triggered cell apoptosis. However, hypoxic glioma cell-derived exosomes markedly promoted the proliferation and suppressed the apoptosis in TMZ-treated glioma cells, and miR-106a-5p inhibitor was able to abolish these phenomena. Meanwhile, PTEN was verified to be a direct target of miR-106a-5p. Furthermore, TMZ elevated PTEN and Bax level and reduced p-Akt level in glioma cells, whereas these changes were reversed by hypoxia glioma cell-derived exosomes. Furthermore, hypoxia glioma cell-derived exosomes reduced the sensitivity of glioma cells to TMZ in vivo via downregulating PTEN. Conclusion: Collectively, exosomal miR-106a-5p derived from hypoxia glioma cells could reduce the sensitivity of glioma cells to TMZ through downregulating PTEN. Thus, our study might provide new strategies for improving the clinical efficacy of TMZ on glioma.

Up-regulation of FOS-like antigen 1 contributes to neuronal apoptosis in the cortex of rat following traumatic brain injury.

Neuronal apoptosis is an important process of secondary brain injury which is induced by neurochemical signaling cascades after traumatic brain injury (TBI). Present study was designed to investigate whether FOS-like antigen 1 (Fra-1) is involved in the neuronal apoptosis. Western blot analysis and immunohistochemistry in a rat TBI model revealed a significant increase in the expression of Fra-1 in the ipsilateral brain cortex, which was in parallel with increase in the expression of active caspase-3. With immunofluorescence double-labeling, Fra-1 was colocalized with active caspase-3 and with NeuN, a neuronal marker. In an in vitro cell injury model, H2O2 exposure induced cell apoptosis and reduced cell viability and at the same time, a similar increased expression of active caspase-3, p53 and Fra-1 was found in PC12 cells. Down-regulation of Fra-1 through transfection with Fra-1 siRNA remarkably elevated cell viability, reduced the expression of active caspase-3 and p53, and decreased apoptosis of PC12 cells after H2O2 exposure. Taken together, present findings suggest that Fra-1 may be involved in the induction of neuronal apoptosis through up-regulating p53 signaling pathway and that this action may contribute to the secondary neuropathological process after TBI.

High Expression of Pirh2 is Associated with Poor Prognosis in Glioma.

p53-induced protein with a RING-H2 domain (Pirh2), also known as Rchy1, is an ubiquitin E3 ligase that regulates the turnover and functionality of several proteins involved in cell proliferation and differentiation, cell cycle checkpoints, and cell death. However, it remains unclear whether aberrant expression of Pirh2 is involved in the development of glioma, a major type of primary brain tumor in adults. Western blot and immunohistochemical analyses showed that Pirh2 was highly expressed in glioma specimens, compared with normal brain tissues. High Pirh2 expression was positively correlated with higher tumor grade, as well as Ki-67 expression. Kaplan-Meier analysis revealed that patients with high Pirh2 expression had worsened prognosis, compared with those with low Pirh2 expression. Moreover, to determine whether Pirh2 could regulate malignant behavior of glioma cells, we transfected glioma cells with interfering RNA targeting Pirh2 to specifically silence Pirh2 expression. Mechanistically, our results indicated that knockdown of Pirh2 induced the apoptosis of glioma cells. In addition, depletion of Pirh2 diminished the expression of PCNA and cyclin D1 and led to cell cycle arrest at G1 phase. Taken together, these findings for the first time suggest that Pirh2 might play an important role in the regulation of glioma proliferation and apoptosis and thus serve as a promising therapeutic target in the treatment of glioma.

Up-regulation of Vps4A promotes neuronal apoptosis after intracerebral hemorrhage in adult rats.

Vps4, vacuolar protein sorting 4, belongs to ATPases Associated with diverse cellular Activities (AAA) protein family which is made up of Vps4A and Vps4B. Previous studies demonstrated that Vps4A plays vital roles in diverse aspects such as virus budding, the efficient transport of H-Ras to the PM (plasma membrane) and the involvement in the MVB (multivesiculate bodies) pathway. Interestingly, Vps4A is also expressed in the brain. However, the distribution and function of Vps4A in ICH diseases remain unclear. In this study, we show that Vps4A may be involved in neuronal apoptosis during pathophysiological processes of intracerebral hemorrhage (ICH). Based on the results of Western blot and immunohistochemistry, we found a remarkable up-regulation of Vps4A expression surrounding the hematoma after ICH. Double labeled immunofluorescence showed that Vps4A was co-expressed with NeuN but rarely with astrocytes and microglia. Morever, we detected that neuronal apoptosis marker active caspase-3 had co-localizations with Vps4A. Additionaly, Vps4A knockdown in vitro specifically leads to decreasing neuronal apoptosis coupled with increased Akt phosphorylation. All datas suggested that Vps4A was involved in promoting neuronal apoptosis via inhibiting Akt phosphorylation after ICH.

OTUB1 attenuates neuronal apoptosis after intracerebral hemorrhage.

OTUB1 is a member of deubiquitinating enzymes, which was shown as a proteasome-associated DUB to be involved in the proteins Ub-dependent degradation. Previous studies have indicated that OTUB1 was expressed in brain. But its distribution and function in the brain remain unclear. In this study, we explored the roles of OTUB1 protein in the pathophysiology of intracerebral hemorrhage (ICH). From the results of Western blot, immunohistochemistry, and immunofluorescence, we found an obvious up-regulation of OTUB1 in neurons adjacent to the hematoma after ICH. Furthermore, we also found that the increase of OTUB1 expression was accompanied by the enhanced expression of Bax and active caspase-3, and decreased expression of Bcl-2 in the pathological process of rat ICH. What's more, our in vitro study, using OTUB1 RNA interference in PC12 cells, suggested that OTUB1 might exert its anti-apoptotic function in neuronal apoptosis. Therefore, OTUB1 may play a role in protecting the brain from secondary damage following ICH.

SMAD4 is Involved in the Development of Endotoxin Tolerance in Microglia.

Initial exposure of macrophages to LPS induces hyporesponsiveness to a second challenge with LPS, a phenomenon termed LPS tolerance. Smad4 plays important roles in the induction of LPS tolerance. However, the function of Smad4 in microglia remains unknown. Here we show that expression of Smad4 was highly up-regulated in LPS-tolerized mouse cerebral cortex. Smad4 was mostly colocalized with microglia, rarely with neurons. Using a microglia cell line, BV2, we find that LPS activates endogenous Smad4, inducing its migration into the nucleus and increasing its expression. Smad4 significantly suppressed TLR-triggered production of proinflammatory cytokines (IL-6), increased anti-inflammatory cytokine in LPS-tolerized microglia. Moreover, IL-6 concentrations in culture supernatants after second LPS challenge are higher in SMAD4 small interfering RNA (siRNA) BV2 cells than control siRNA BV2 cells, indicating failure to induce tolerance in absence of Smad4 signaling. In our study, we conclude that both in vivo and in vitro, Smad4 signaling is required for maximal induction of endotoxin tolerance.