Spatiotemporal patterns of postsynaptic density (PSD)-95 expression after rat spinal cord injury

PSD-95 Protein: A Promising Therapeutic Target in Chronic Pain

Chronic pain, as a social public health problem, has a serious impact on the quality of patients' life. Currently, the main drugs used to treat chronic pain are opioids, antipyretic, and nonsteroidal anti-inflammatory drugs (NSAIDs). But the obvious side effects limit their use, so it is urgent to find new therapeutic targets. Postsynaptic density (PSD)-95 protein plays an important role in the occurrence and development of chronic pain. The over-expression of the PSD-95 protein and its interaction with other proteins are closely related to the chronic pain. Besides, the PSD-95-related drugs that inhibit the expression of PSD-95 as well as the interaction with other protein have been proved to treat chronic pain significantly. In conclusion, although more deep studies are needed in the future, these studies indicate that PSD-95 and the related proteins, such as NMDA receptor (NMDAR) subunit 2B (GluN2B), AMPA receptor (AMPAR), calmodulin-dependent protein kinase II (CaMKII), 5-hydroxytryptamine 2A receptor (5-HT2AR), and neuronal nitric oxide synthase (nNOS), are the promising therapeutic targets for chronic pain.

Construction and validation of a risk model based on the key SNARE proteins to predict the prognosis and immune microenvironment of gliomas

Background

Synaptic transmission between neurons and glioma cells can promote glioma progression. The soluble N-ethylmaleimide-sensitive fusion factor attachment protein receptors (SNARE) play a key role in synaptic functions. We aimed to construct and validate a novel model based on the SNARE proteins to predict the prognosis and immune microenvironment of glioma.

Methods

Differential expression analysis and COX regression analysis were used to identify key SRGs in glioma datasets, and we constructed a prognostic risk model based on the key SRGs. The prognostic value and predictive performance of the model were assessed in The Cancer Genome Atlas (TCGA) and Chinese glioma Genome Atlas (CGGA) datasets. Functional enrichment analysis and immune-related evaluation were employed to reveal the association of risk scores with tumor progression and microenvironment. A prognostic nomogram containing the risk score was established and assessed by calibration curves and time-dependent receiver operating characteristic curves. We verified the changes of the key SRGs in glioma specimens and cells by real-time quantitative PCR and Western blot analyses.

Results

Vesicle-associated membrane protein 2 (VAMP2) and vesicle-associated membrane protein 5 (VAMP5) were identified as two SRGs affecting the prognoses of glioma patients. High-risk patients characterized by higher VAMP5 and lower VAMP2 expression had a worse prognosis. Higher risk scores were associated with older age, higher tumor grades, IDH wild-type, and 1p19q non-codeletion. The SRGs risk model showed an excellent predictive performance in predicting the prognosis in TCGA and CGGA datasets. Differentially expressed genes between low- and high-risk groups were mainly enriched in the pathways related to immune infiltration, tumor metastasis, and neuronal activity. Immune score, stromal score, estimate score, tumor mutational burden, and expression of checkpoint genes were positively correlated with risk scores. The nomogram containing the risk score showed good performance in predicting the prognosis of glioma. Low VAMP2 and high VAMP5 were found in different grades of glioma specimens and cell lines.

Conclusion

We constructed and validated a novel risk model based on the expression of VAMP2 and VAMP5 by bioinformatics analysis and experimental confirmation. This model might be helpful for clinically predicting the prognosis and response to immunotherapy of glioma patients.

Effects of the m6Am methyltransferase PCIF1 on cell proliferation and survival in gliomas

BACKGROUND

Previous studies have suggested an important role for N6-methyladenosine (m6A) modification in the proliferation of glioma cells. N6, 2'-O-dimethyladenosine (m6Am) is another methylated form affecting the fate and function of most RNA. PCIF1 has recently been identified as the sole m6Am methyltransferase in mammalian mRNA. However, it remains unknown about the role of PCIF1 in the growth and survival of glioma cells.

METHODS

We constructed glioma cell lines that stably downregulated/upregulated PCIF1, established intracranial xenograft models using these cell lines, and employed the following methods for investigations: CCK-8, EdU, colony formation, flow cytometry, qRT-PCR, Western blot, and immunohistochemistry.

FINDINGS

Downregulating PCIF1 promoted glioma cell proliferation, while overexpressing PCIF1 showed the opposite effects. Overexpression of PCIF1 blocked cell cycle progression and induced apoptosis in glioma cells, which was further confirmed by alterations in the expression of cell checkpoint proteins and apoptotic markers. Interestingly, disruption of PCIF1 methyltransferase activity slightly reversed the effect of PCIF1 overexpression on cell proliferation, but had no significant reversal effects on cell cycle progression or apoptosis. Knockdown of PCIF1 promoted the growth of gliomas, while overexpressing PCIF1 inhibited tumor growth and prolonged the survival time of tumor-bearing mice. In addition, the mRNA and protein levels of PCIF1 were gradually decreased with the increase of WHO grade in glioma tissues, but there was no significant correlation with patient survival.

INTERPRETATION

These results indicated that PCIF1 played a suppressing role in glioma growth and survival, which may not entirely depend on its methyltransferase activity.

The Expression of VHL (Von Hippel-Lindau) After Traumatic Spinal Cord Injury and Its Role in Neuronal Apoptosis

The VHL (Von Hippel-Lindau) gene is a tumor suppressor gene, which is best known as an E3 ubiquitin ligase that negatively regulates the hypoxia inducible factor. The inactivation of VHL gene could result in the abnormal synthesis of VHL protein, which is in contact with the development and occurrence of renal clear cell carcinoma. However, the expression and possible function of VHL in central nervous system (CNS) is still unclear. To examine the function of VHL in CNS injury and repair, we used an acute spinal cord injury (SCI) model in adult rats. Western blot analysis showed an important upregulation of VHL protein, reaching a peak at day 3 and then declined during the following days. Double immunofluorescence staining showed that VHL was co-expressed with neurons, but not with astrocytes and microglia. Moreover, we detected that active caspase-3 had co-localized with VHL in neurons after SCI. Additionally in vitro, VHL depletion, by short interfering RNA, significantly reduced neuronal apoptosis. In conclusion, these data suggested that the change of VHL protein expression was related to neuronal apoptosis after SCI.

Expression of CDc6 after acute spinal cord injury in adult rats

The cell division cycle 6 (CDc6) protein has been primarily investigated as a component of the pre-replicative complex for the initiation of DNA replication. Some studies have shown that CDc6 played a critical role in the development of human carcinoma. However, the expression and roles of CDc6 in the central nervous system remain unknown. We have performed an acute spinal cord injury (SCI) model in adult rats and investigated the dynamic changes of CDc6 expression in spinal cord. Western blot have found that CDc6 protein levels first significantly increase, reach a peak at day 3, and then gradually return to normal level at day 14 after SCI. Double immunofluorescence staining showed that CDc6 immunoreactivity was found in neurons, astrocytes, and microglia. Additionally, colocalization of CDc6/active caspase-3 has been detected in neurons and colocalization of CDc6/proliferating cell nuclear antigen has been detected in astrocytes and microglial. In vitro, CDc6 depletion by short interfering RNA inhibits astrocyte proliferation and reduces cyclin A and cyclin D1 protein levels. CDc6 knockdown also decreases neuronal apoptosis. We speculate that CDc6 might play crucial roles in CNS pathophysiology after SCI.

An Up-regulation of IRF-1 After a Spinal Cord Injury: Implications for Neuronal Apoptosis

IRF-1, a kind of transcription factor, is expressed in many cell types, except in early embryonal cells. IRF-1 has played an essential role in various physiological and pathological processes, including tumor immune surveillance, viral infection, development of immunity system and pro-inflammatory injury. However, the expression and function of IRF-1 in spinal cord injury (SCI) are still unknown. In this study, we have performed an acute SCI model in adult rats and investigated the dynamic changes of IRF-1 expression in the spinal cord. Western blot have shown that IRF-1 protein levels gradually increased, reaching a peak at day 3 and then gradually declined to a normal level at day 14 after SCI. Double immunofluorescence staining showed that IRF-1 immunoreactivity was found in neurons, but not in astrocytes and microglia. Additionally, colocalization of IRF-1/active caspase-3 was detected in neurons. In vitro, IRF-1 depletion, by short interfering RNA, obviously decreases neuronal apoptosis. In conclusion, this is the first description of IRF-1 expression in spinal cord injury. Our results suggested that IRF-1 might play crucial roles in CNS pathophysiology after SCI.

Transplantation of bone marrow stromal cell-derived neural precursor cells ameliorates deficits in a rat model of complete spinal cord transection

After severe spinal cord injury, spontaneous functional recovery is limited. Numerous studies have demonstrated cell transplantation as a reliable therapeutic approach. However, it remains unknown whether grafted neuronal cells could replace lost neurons and reconstruct neuronal networks in the injured spinal cord. To address this issue, we transplanted bone marrow stromal cell-derived neural progenitor cells (BM-NPCs) in a rat model of complete spinal cord transection 9 days after the injury. BM-NPCs were induced from bone marrow stromal cells (BMSCs) by gene transfer of the Notch-1 intracellular domain followed by culturing in the neurosphere method. As reported previously, BM-NPCs differentiated into neuronal cells in a highly selective manner in vitro. We assessed hind limb movements of the animals weekly for 7 weeks to monitor functional recovery after local injection of BM-NPCs to the transected site. To test the sensory recovery, we performed functional magnetic resonance imaging (fMRI) using electrical stimulation of the hind limbs. In the injured spinal cord, transplanted BM-NPCs were confirmed to express neuronal markers 7 weeks following the transplantation. Grafted cells successfully extended neurites beyond the transected portion of the spinal cord. Adjacent localization of synaptophysin and PSD-95 in the transplanted cells suggested synaptic formations. These results indicated survival and successful differentiation of BM-NPCs in the severely injured spinal cord. Importantly, rats that received BM-NPCs demonstrated significant motor recovery when compared to the vehicle injection group. Volumes of the fMRI signals in somatosensory cortex were larger in the BM-NPC-grafted animals. However, neuronal activity was diverse and not confined to the original hind limb territory in the somatosensory cortex. Therefore, reconstruction of neuronal networks was not clearly confirmed. Our results indicated BM-NPCs as an effective method to deliver neuronal lineage cells in a severely injured spinal cord. However, reestablishment of neuronal networks in completed transected spinal cord was still a challenging task.

An upregulation of SENP3 after spinal cord injury: implications for neuronal apoptosis

SENP3 (SUMO-specific proteases 3), a member of the small ubiquitin-like modifier specific protease family, was identified as a molecule that deconjugates SUMOylation of modified protein substrates and functions as an isopeptidase by disrupting SUMO homeostasis to facilitate cancer development and progression. However, its expression and function in nervous system injury and repair are still unclear. In this study, we employed an acute spinal cord injury (SCI) model in adult rats and investigated the dynamic changes of SENP3 expression in the spinal cord. Western blot analysis indicated a gradual increase in SENP3 expression, which peaked 3 days after SCI, and then declined over the following days. Immunohistochemistry results further confirmed that SENP3 was expressed at low levels in the gray and white matter in the non-injured condition and increased after SCI. Moreover, immunofluorescence double-labeling showed that SENP3 was co-expressed with the neuronal marker, NeuN. Furthermore, the SENP3-positive cells that were co-expressed with NeuN had also expressed active caspase-3 after injury. To investigate whether SENP3 plays a role in neuronal apoptosis, we applied H(2)O(2) to induce neuronal apoptosis in vitro. Western blot analysis showed a significant upregulation of SENP3 and active caspase-3 following H(2)O(2) stimulation. Taken together, these results suggest that SENP3 may play important roles in the pathophysiology of SCI.

Neuronal MHC class I molecules are involved in excitatory synaptic transmission at the hippocampal mossy fiber synapses of marmoset monkeys

Several recent studies suggested a role for neuronal major histocompatibility complex class I (MHCI) molecules in certain forms of synaptic plasticity in the hippocampus of rodents. Here, we report for the first time on the expression pattern and functional properties of MHCI molecules in the hippocampus of a nonhuman primate, the common marmoset monkey (Callithrix jacchus). We detected a presynaptic, mossy fiber-specific localization of MHCI proteins within the marmoset hippocampus. MHCI molecules were present in the large, VGlut1-positive, mossy fiber terminals, which provide input to CA3 pyramidal neurons. Furthermore, whole-cell recordings of CA3 pyramidal neurons in acute hippocampal slices of the common marmoset demonstrated that application of antibodies which specifically block MHCI proteins caused a significant decrease in the frequency, and a transient increase in the amplitude, of spontaneous excitatory postsynaptic currents (sEPSCs) in CA3 pyramidal neurons. These findings add to previous studies on neuronal MHCI molecules by describing their expression and localization in the primate hippocampus and by implicating them in plasticity-related processes at the mossy fiber-CA3 synapses. In addition, our results suggest significant interspecies differences in the localization of neuronal MHCI molecules in the hippocampus of mice and marmosets, as well as in their potential function in these species.