No abstract

Radiotherapy is one of the most effective treatments for head and neck tumors. However, delayed radiation‐induced brain necrosis (RN) remains a serious issue due to the lack of satisfying prevention and effective treatment. The pathological role of radiation in the delayed onset of brain necrosis is still largely unknown, and the traditional animal model of whole brain irradiation, although being widely used, does not produce reliable and localized brain necrosis mimicking clinical features of RN. In this study, we demonstrated a successful RN mouse model using optimized gamma knife irradiation in male C57BL/6 mice. On the premise that brain necrosis started to appear at 6 weeks postirradiation in our RN model, as confirmed by both MRI and histopathological examinations, we systematically examined different time points before the onset of RN for the histopathological changes and biochemical indicators. Our initial results demonstrated that in the ipsilateral hemisphere of the irradiated brains, a significant decrease in neuronal numbers that occurred at 4 weeks and a sustained increase in TNF‐α, iNOS, and other inflammatory cytokines beginning at 1‐week postirradiation. Changes of cell morphology and cell numbers of both microglia and astrocytes occurred as early as 1‐week postirradiation, and intervention by bevacizumab administration resulted in reduced microglia activation and reduction of radiation‐induced lesion volume, indicating that chronic glial activation may result in subsequent elevation of inflammatory factors, which led to the delayed onset of neuronal loss and brain necrosis. Since C57BL/6 is the most widely used strain of genetic engineered mouse model, our data provide an invaluable platform for the mechanistic study of RN pathogenesis, identification of potential imaging and biological biomarkers, and the development of therapeutic treatment for the disease.

No abstract

The robust proliferation of cancer cells requires vastly elevated levels of protein synthesis, which relies on a steady supply of aminoacylated tRNAs. Delivery of tRNAs to the cytoplasm is a highly regulated process, but the machinery for tRNA nuclear export is not fully elucidated. In this study, using a live cell imaging strategy that visualizes nascent transcripts from a specific tRNA gene in yeast, we identified the nuclear basket proteins Mlp1 and Mlp2, two homologs of the human TPR protein, as regulators of tRNA export. TPR expression is significantly increased in lung cancer tissues and correlated with poor prognosis. Consistently, knockdown of TPR inhibits tRNA nuclear export, protein synthesis and cell growth in lung cancer cell lines. We further show that NXF1, a well-known mRNA nuclear export factor, associates with tRNAs and mediates their transport through nuclear pores. Collectively, our findings uncover a conserved mechanism that regulates nuclear export of tRNAs, which is a limiting step in protein synthesis in eukaryotes.

Background Radiation-induced brain injury (RIBI) is the most serious complication of radiotherapy in patients with head and neck tumors, which seriously affects the quality of life. Currently, there is no effective treatment for patients with RIBI, and identifying new treatment that targets the pathological mechanisms of RIBI is urgently needed. Methods Immunofluorescence staining, western blotting, quantitative real-time polymerase chain reaction (Q-PCR), co-culture of primary neurons and microglia, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay, enzyme-linked immunosorbent assay (ELISA), and CRISPR–Cas9-mediated gene editing techniques were employed to investigate the protective effects and underlying mechanisms of pregabalin that ameliorate microglial activation and neuronal injury in the RIBI mouse model. Results Our findings showed that pregabalin effectively repressed microglial activation, thereby reducing neuronal damage in the RIBI mouse model. Pregabalin mitigated inflammatory responses by directly inhibiting cytoplasmic translocation of high-mobility group box 1 (HMGB1), a pivotal protein released by irradiated neurons which induced subsequent activation of microglia and inflammatory cytokine expression. Knocking out neuronal HMGB1 or microglial TLR2/TLR4/RAGE by CRISPR/Cas9 technique significantly inhibited radiation-induced NF-κB activation and pro-inflammatory transition of microglia. Conclusions Our findings indicate the protective mechanism of pregabalin in mitigating microglial activation and neuronal injury in RIBI. It also provides a therapeutic strategy by targeting HMGB1-TLR2/TLR4/RAGE signaling pathway in the microglia for the treatment of RIBI.