Spatiotemporal expression of KHSRP modulates Schwann cells and neuronal differentiation after sciatic nerve injury

KHSRP has oncogenic functions and regulates the expression and alternative splicing of DNA repair genes in breast cancer MDA-MB-231 cells

Breast cancer has become the most common type of cancers worldwide. Its high prevalence and malignant features are associated with various environmental factors and molecules. The KH-type splicing regulatory protein (KHSRP) participates in the development of breast cancer, while the underlying mechanisms are largely unknown. In this study, we silenced KHSRP expression in MDA-MB-231 cells by small interfering RNA (siKHSRP), and then assessed its effects on cellular features. Finally, we performed whole transcriptome sequencing (RNA-seq) experiments to explore the downstream targets of KHSRP, and validated their changed pattern using quantitative polymerase chain reaction. We found KHSRP showed higher expression level and was associated with worse prognosis in breast cancer patients. In siKHSRP samples, the proliferation, invasion, and migration abilities were significantly repressed compared with negative control (NC) samples, while the apoptosis level was increased. By investigating the RNA-seq data, we found KHSRP globally regulates the expression and alternative splicing profiles of MDA-MB-231 cells by identifying 1632 differentially expressed genes (DEGs) and 1630 HKSRP-regulated AS events (RASEs). Functional enriched analysis of DEGs demonstrated that cilium assembly and movement and extracellular matrix organization pathways were specifically enriched in up DEGs, consistent with the repressed migration and invasion abilities in siKHSRP cells. Interestingly, the cell cycle and DNA damage and repair associated pathways were enriched in both down DEGs and RASE genes, suggesting that KHSRP may modulate cell proliferation by regulating genes in these pathways. Finally, we validated the changed expression and AS patterns of genes in cell cycle and DNA damage/repair pathways. Expression levels of BIRC5, CCNA2, CDK1, FEN1, FOXM1, PTTG1, and UHRF1 were downregulated in siKHSRP samples. The AS patterns of PARK7, ERCC1, CENPX, and UBE2A were also dysregulated in siKHSRP samples and confirmed PCR experiments. In summary, our study comprehensively explored the downstream targets and their functions of KHSRP in breast cancer cells, highlighting the molecular mechanisms of KHSRP on the oncogenic features of breast cancer. The identified molecular targets could be served as potential therapeutic targets for breast cancer in future.

LncRNA LINC01305 promotes cervical cancer progression through KHSRP and exosome-mediated transfer

Cervical cancer (CC) is one of the deadliest female malignancies worldwide. Long non-coding RNAs (lncRNAs) are essential regulators for cancer progression. This study aimed to elucidate the role of lncRNA LINC01305 in the progression of CC. We found where LINC01305 was expressed in CC tissues and its correlation with the survival rate of CC patients. Functional experiments were performed to elucidate the effect of LINC01305 on CC. The results showed that LINC01305 was increased in CC tumor tissues and was correlated with a lower survival rate. The overexpression and knockdown of LINC01305 enhanced and inhibited the progression of CC, respectively. Additionally, the upregulation of LINC01305 promoted tumor growth in xenograft mice. Moreover, the effect of LINC01305 on CC was mediated through interacting with the RNA-binding protein, KHSRP. Furthermore, LINC01305 was mainly distributed in exosomes and was transferred to recipient cells to enhance CC progression. Lastly, LINC01305 may participate in the regulation of the stemness of CC. Taken together, the results suggest that LINC01305 promotes the progression of CC through KHSRP and that LINC01305 is released through exosomes and is involved in the stemness of CC. This study sheds light on the molecular mechanism underlying the progression of CC.

Telmisartan attenuates hydrogen peroxide-induced apoptosis in differentiated PC12 cells

The present study investigated the protective actions of telmisartan, an angiotensin II type 1 receptor blocker (ARBs), against the cell apoptosis induced by exposure to hydrogen peroxide (H₂O₂) in differentiated PC12 cells. Preincubation of PC12 cells with telmisartan prevented H₂O₂-induced cytotoxicity as indicated by increased MTT (3,(4,5-dimethylthiazole-2-yl)2,5-diphenyl-tetrazolium bromide) reduction, decreased lactate dehydrogenase (LDH) release, and improved morphological changes. Hoechst 33,258 staining showed that telmisartan markedly reduced shrunken nuclei of the cells, and Western blot analysis indicated that telmisartan significantly attenuated caspase-3 activity, as indicated by decreased ratio of cleaved Caspase-3 to its precursor and increased ratio of Bcl-2/Bax. The present findings showed that telmisartan protected against cellular oxidative damages by inhibiting apoptotic response.

Neurodegenerative effects of azithromycin in differentiated PC12 cells

Azithromycin is a widely used macrolide antibiotic with sustained and high tissue penetration and intracellular accumulation. While short-term exposure to low-dose azithromycin is usually well tolerated, prolonged treatment can lead to unwanted neurological effects like paresthesia and hearing loss. However, the mechanism causing neurodegeneration is still unknown. Here, we show that even low therapeutically relevant azithromycin concentrations like 1µg/ml decreased cell viability by 15% and induced neurite loss of 47% after 96h in differentiated PC12 cells, which are a well-established model system for neuronal cells. When higher concentrations were used, the drug-induced effects occurred earlier and were more pronounced. Thereby, azithromycin altered tropomyosin-related kinase A (TrkA) signaling and attenuated protein kinase B (Akt) activity, which subsequently induced autophagy. Simultaneously, the antibiotic impaired lysosomal functions by blocking the autophagic flux, and this concurrence reduced cell viability. In good agreement with reversible effects observed in patients, PC12 cells could completely recover if azithromycin was removed after 24h. In addition, the detrimental effects of azithromycin were limited to differentiated cells, as confirmed in the human neuronal model cell line SH-SY5Y. Thus, azithromycin alters cell surface receptor signaling and autophagy in neuronal cells, but does not automatically induce irreversible damage when used in low concentrations and for a short time.

SCY1-Like 1-Binding Protein 1 (SCYL1BP1) Suppressed Sciatic Nerve Regeneration by Enhancing the RhoA Pathway

SCY1-like 1-binding protein 1 (SCYL1BP1) is first identified as an interacting protein with SCYL1. Since SCYL1BP1 is a soluble protein with coiled-coil domains known to be relevant with transcriptional regulation, it has been found to activate the transcription of murine double minute 2 (MDM2) and participate in neurite outgrowth and regeneration. However, the role and mechanism of SCYL1BP1 in peripheral nerve system lesion and repair are still unknown. Here in vitro, our work demonstrated that SCYL1BP1 inhibited cAMP-induced primary Schwann cell differentiation and suppressed nerve growth factor-mediated neurite outgrowth in PC12 cells by enhancing the RhoA pathway. Furthermore, we found that pretreatment with a Rho kinase inhibitor Y-27632 resulted in partial rescue of Schwann cell differentiation and neurite outgrowth. In vivo experiments showed that SCYL1BP1 could also suppress nerve fiber regeneration. In conclusion, we speculated that SCYL1BP1 participated in Schwann cell (SC) differentiation and neurite outgrowth in the sciatic nerve after crush by regulating the RhoA pathway.

Hydroalcoholic extract of red propolis promotes functional recovery and axon repair after sciatic nerve injury in rats

CONTEXT

Peripheral axon injury and degeneration are often mediated by oxidative stress and inflammation. The hydroalcoholic extract of the red propolis (HERP) has attracted great attention because of its antioxidant and anti-inflammatory activities.

OBJECTIVE

The objective of this work is to study the effect of HERP on nerve repair and functional recovery after sciatic nerve injury (SNI) in rats.

MATERIALS AND METHODS

The chemical markers in HERP were identified using high-resolution mass spectroscopy. After axonotmesis of sciatic nerve, ibuprofen (IBP) and HERP treatments were orally administered for 28 d. Behavioural tests were performed weekly after SNI. The myelinated axon number was counted using morphometric analysis.

RESULTS

The compounds found in HERP were pinocembrin, formononetin, vestitol, and biochanin A. The animals that underwent SNI showed a significant decrease in motor function based on the Basso, Beattie and Bresnahan scale and sciatic functional index compared with sham animals until 7 d after the surgery (p < 0.05). After 14 and 21 d, the SNI groups treated with either HERP or IBP showed significant improvement (p < 0.01), and the SNI group treated with HERP 10 mg/kg showed accelerated motor recovery compared with the other groups (p < 0.01). SNI caused also a reduction in the myelinated axon counts, and treatment with HERP 10 mg/kg induced a significant increase in the number of myelinated fibres compared with all other groups.

CONCLUSION

HERP promoted regenerative responses and accelerated functional recovery after sciatic nerve crush. Thus, it can be considered to be a new strategy or complementary therapy for treating nerve injuries.

Comparative analysis of selected innate immune-related genes following infection of immortal DF-1 cells with highly pathogenic (H5N1) and low pathogenic (H9N2) avian influenza viruses

H5N1 and H9N2 viruses are important causes of avian influenza in China. H5N1 is typically associated with severe to fatal disease in poultry, while H9N2 is usually associated with mild disease. Differences in viral virulence prompted us to investigate whether innate immune responses would be differentially regulated following infection by H5N1 and H9N2 viruses. To address this hypothesis, expression of a panel of innate immune-related genes including IFN-α, IFN-β, Mx1, OASL, ISG12, IFIT5, IRF7, USP18, SST, and KHSRP in immortal DF-1 cells following H5N1 and H9N2 infection was analyzed and compared by real-time quantitative RT-PCR. Cells infected by either virus overall exhibited a similar expression profile for four ISGs (Mx1, OASL, ISG12, and IFIT5), IFN-α, IFN-β, and SST gene. However, two immune-regulatory genes (IRF7 and KHSRP) were not responsive to highly pathogenic H5N1 infection but were strongly up-regulated in DF-1 cells infected with low pathogenic H9N2 infection. The subtype-dependent host response observed in this study offers new insights into the potential roles of IRF7 and KHSRP in control and modulation of the replication and virulence of different subtypes or strains of avian influenza A virus.

Involvement of upregulated SYF2 in Schwann cell differentiation and migration after sciatic nerve crush

SYF2 is a putative homolog of human p29 in Saccharomyces cerevisiae. It seems to be involved in pre-mRNA splicing and cell cycle progression. Disruption of SYF2 leads to reduced α-tubulin expression and delayed nerve system development in zebrafish. Due to the potential of SYF2 in modulating microtubule dynamics in nervous system, we investigated the spatiotemporal expression of SYF2 in a rat sciatic nerve crush (SNC) model. We found that SNC resulted in a significant upregulation of SYF2 from 3 days to 1 week and subsequently returned to the normal level at 4 weeks. At its peak expression, SYF2 distributed predominantly in Schwann cells. In addition, upregulation of SYF2 was approximately in parallel with Oct-6, and numerous Schwann cells expressing SYF2 were Oct-6 positive. In vitro, we observed enhanced expression of SYF2 during the process of cyclic adenosine monophosphate (cAMP)-induced Schwann cell differentiation. SYF2-specific siRNA-transfected Schwann cells did not show significant morphological change in the process of Schwann cell differentiation. Also, we found shorter and disorganized microtubule structure and a decreased migration in SYF2-specific siRNA-transfected Schwann cells. Together, these findings indicated that the upregulation of SYF2 was associated with Schwann cell differentiation and migration following sciatic nerve crush.