Lab review: Molecular dissection of the signal transduction pathways associated with PTEN deletion-induced optic nerve regeneration

Entrectinib can induce nerve cell damage by inhibiting PI3K-AKT and TGF-β signaling pathways

Background

The tyrosine receptor kinase inhibitor (TRKi) entrectinib is used to treat neurotrophic tyrosine receptor kinase (NTRK) fusion-positive solid tumors and ROS1-positive patients. Despite its impressive efficacy against cancer, the clinical application is still limited by the central nervous system (CNS)-related toxicities. However, the precise mechanism of such CNS-related toxicities remains elusive.

Methods

The effect of entrectinib-induced nerve cell damage was evaluated by the nerve cells (PC12, HT22 and SK-N-SH) based in vitro models. Various assays, including CCK-8, colony formation and EdU incorporation assays were utilized to estimate the cellular viability and proliferation ability. Cell apoptosis was measured by flow cytometry. Next, transcriptome sequencing technology was performed to identify differentially expressed genes (DEGs). Gene ontology (GO), kyoto encyclopedia of genes and genomes (KEGG) analysis and gene set enrichment analysis (GSEA) were applied to predict the potential functions of DEGs. Quantitative real time polymerase chain reaction (qRT-PCR) and Western blotting assays were performed to measure the expressions of thrombospondin-1 (THBS1), TGF-β1, PI3K, AKT and phosphorylated AKT (p-AKT) in the entrectinib-treated nerve cells. Additionally, we Preliminary observed and validated whether THBS1 overexpression could rescue nerve cell damage and the abnormalities in PI3K-AKT and TGF-β signaling pathways.

Results

Entrectinib significantly inhibited the nerve cells proliferation and colony formation, and induced nerve cells apoptosis. Transcriptome sequencing analysis and qRT-PCR revealed that THBS1 was downregulated within entrectinib treatment. KEGG and GSEA analysis also suggested that entrectinib directly caused the abnormalities in proliferation-related signaling pathway like PI3K-AKT pathway, and apoptosis-related signaling pathway including TGF-β pathway. We further demonstrated that THBS1, TGF-β1, PI3K, AKT and p-AKT were downregulated by entrectinib. Meanwhile, pretreatment with THBS1 overexpression plasmids significantly rescued nerve cells (PC12, HT22 and SK-N-SH) from cell death and the abnormalities in PI3K-AKT and TGF-β signaling pathways.

Conclusion

These results identified a critical role of entrectinib in promoting nerve cell damage by downregulating the expression of THBS1 while also inhibiting PI3K-AKT and TGF-β signaling pathways. Our findings will provide potential therapeutic targets for CNS-related toxicities.

Role and Interplay of Different Signaling Pathways Involved in Sciatic Nerve Regeneration

Regeneration of the sciatic nerve is a sophisticated process that involves the interplay of several signaling pathways that orchestrate the cellular responses critical to regeneration. Among the key pathways are the mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K)/AKT, cyclic adenosine monophosphate (cAMP), and Janus kinase/signal transducers and transcription activators (JAK/STAT) pathways. In particular, the cAMP pathway modulates neuronal survival and axonal regrowth. It influences various cellular behaviors and gene expression that are essential for nerve regeneration. MAPK is indispensable for Schwann cell differentiation and myelination, whereas PI3K/AKT is integral to the transcription, translation, and cell survival processes that are vital for nerve regeneration. Furthermore, GTP-binding proteins, including those of the Ras homolog gene family (Rho), regulate neural cell adhesion, migration, and survival. Notch signaling also appears to be effective in the early stages of nerve regeneration and in preventing skeletal muscle fibrosis after injury. Understanding the intricate mechanisms and interactions of these pathways is vital for the development of effective therapeutic strategies for sciatic nerve injuries. This review underscores the need for further research to fill existing knowledge gaps and improve therapeutic outcomes.

Reversibility of visual field defects through induction of brain plasticity: vision restoration, recovery and rehabilitation using alternating current stimulation

For decades visual field defects were considered irreversible because it was thought that in the visual system the regeneration potential of the neuronal tissues is low. Nevertheless, there is always some potential for partial recovery of the visual field defect that can be achieved through induction of neuroplasticity. Neuroplasticity refers to the ability of the brain to change its own functional architecture by modulating synaptic efficacy. It is maintained throughout life and just as neurological rehabilitation can improve motor coordination, visual field defects in glaucoma, diabetic retinopathy or optic neuropathy can be improved by inducing neuroplasticity. In ophthalmology many new treatment paradigms have been tested that can induce neuroplastic changes, including non-invasive alternating current stimulation. Treatment with alternating current stimulation (e.g., 30 minutes, daily for 10 days using transorbital electrodes and ~10 Hz) activates the entire retina and parts of the brain. Electroencephalography and functional magnetic resonance imaging studies revealed local activation of the visual cortex, global reorganization of functional brain networks, and enhanced blood flow, which together activate neurons and their networks. The future of low vision is optimistic because vision loss is indeed, partially reversible.