Song Liu

Background: Peripheral nerve injury (PNI) presents a significant clinical challenge due to limited endogenous regenerative capacity. The translocator protein (TSPO) ligand etifoxine (ETX) has shown promise in promoting nerve repair, but the underlying cellular and molecular mechanisms remain incompletely understood. Methods: Utilizing in vitro co-culture systems with human Schwann cells (HSCs) and THP-1-derived macrophages, TSPO-knockdown HSCs, conditioned medium experiments, and an in vivo rat sciatic nerve crush injury model, we investigated the effects of ETX on cellular crosstalk and macrophage polarization. Molecular analyses included RNA sequencing, western blotting, fatty acid oxidation (FAO) assays, and a Mito-QC reporter system to assess mitophagy. Functional recovery was evaluated through behavioral tests (hindlimb grip strength, mechanical pain threshold), immunofluorescence, and retrograde tracing. Results: ETX specifically activated TSPO on Schwann cells, stimulating progesterone synthesis and secretion. This Schwann cell-derived progesterone acted as a paracrine signal on macrophages, activating the PPARγ–PGC1α axis. This activation triggered dual reprogramming in macrophages: a metabolic shift toward FAO and induction of BNIP3L-mediated mitophagy, both essential for sustaining a pro-regenerative M2 phenotype. These effects were significantly attenuated by the progesterone receptor antagonist RU486 or the PPARγ antagonist GW9662. In vivo, ETX treatment accelerated functional recovery, enhanced axonal regeneration, and increased infiltration of M2 macrophages at the injury site, effects that were partially reversed by RU486 or GW9662 co-administration. Conclusion: ETX facilitates peripheral nerve repair by promoting Schwann cell-derived progesterone, which drives macrophage PPARγ pathway activation, orchestrating metabolic-autophagic reprogramming necessary for sustained M2 polarization. These findings identify a novel Schwann cell–macrophage metabolic crosstalk mechanism and support the therapeutic potential of targeting this axis in PNI.

Malignant peripheral nerve sheath tumors (MPNSTs) represent the most severe complication of neurofibromatosis type 1 (NF1), with limited therapeutic option

Background: Malignant peripheral nerve sheath tumor (MPNST) is an aggressive soft tissue sarcoma characterized by high recurrence and poor prognosis, necessitating the search for novel therapeutic targets and strategies. This study investigated the expression of mitochondrial translocator protein (TSPO) in MPNST and its role in regulating ferroptosis.Methods: TSPO expression was analyzed in adjacent non-tumor tissues, benign neurofibromas, and malignant tissues using real-time PCR, western blotting, immunohistochemistry staining. Expression levels of classic ferroptosis markers, including AKR1C1 and FTH1 were assessed. Ferroptosis was evaluated by measuring cell viability, ferroptosis marker levels, and intracellular Fe²⁺ and reactive oxygen species (ROS) levels. Oxidized phospholipid profiles of wild-types and TSPO knockdown MPNST cells were determined using liquid chromatography-mass spectrometry. The potential role of GPX4 in mediating TSPO’s effect on ferroptosis was investigated in vitro.Results: Compared with adjacent non-tumor tissues and benign neurofibromas, TSPO expression was significantly lower in MPNST specimens. Notably, TSPO expression positively correlated with the classic ferroptosis markers AKR1C1 and FTH1. TSPO-knockdown MPNST cells exhibited significant resistance to ferroptotic cell death. Additionally, biochemical characterization indicated that TSPO deficiency decreased intracellular Fe²⁺ and ROS. Furthermore, oxidized phospholipids were remarkably reduced in TSPO-knockdown cells. TSPO enriches cellular oxidized phospholipids by downregulating GPX4-GSH antioxidant pathway. Furthermore, GPX4 is elevated in malignant tumors compared to benign specimens and negatively correlated with TSPO expression in clinical tumor specimens.Conclusion: Our findings revealed that TSPO deficiency inhibited ferroptosis in MPNST cells by upregulating GPX4 antioxidant pathway, suggesting that mitochondrial TSPO-GPX4-ferroptosis axis may be a promising therapeutic target for improving the outcomes of patients with MPNST.

Malignant peripheral nerve sheath tumor (MPNST) is a highly aggressive sarcoma, often arising in patients with neurofibromatosis type I (NF1), and has a poor prognosis with a 5-year survival rate of only 8–13%. Current treatments are largely ineffective, underscoring the need for new therapeutic targets. Dysregulation of the cell cycle is a key contributor to cancer development, making cyclin-dependent kinases (CDKs) promising targets for cancer therapy. However, single-agent therapies often face rapid resistance, suggesting that combinatorial approaches may offer greater therapeutic efficacy. Notably, TSPO deficiency modulates the cell cycle in MPNSTs via CDK1, presenting a potential molecular target for both prognosis and treatment.

Malignant peripheral nerve sheath tumors (MPNSTs) are highly aggressive Schwann cell-derived sarcomas that are sporadic or associated with Neurofibromatosis 1 (NF1) gene mutations. Traditional therapies are usually ineffective for treating MPNSTs, so new targets need to be identified for the treatment of MPNSTs. In the present study, the role of the mitochondrial translocator protein (TSPO) in the regulation of cell proliferation and the cell cycle in MPNSTs was investigated. TSPO expression was lower in MPNSTs than in NFs. Loss-of-function experiments revealed that TSPO deficiency promoted MPNST cell growth, migration, and invasion and influenced the cell cycle in vitro and in vivo. In addition, TSPO depletion suppressed cell apoptosis by downregulating the expression of caspase-3, caspase-8, HSP60, p27, p53, and BCL-2 and suppressed the cell cycle by upregulating CDK1, CDK2, CCNB1 and CCNA2. Furthermore, CDK1 was determined to be an upstream target of TSPO-mediated regulation via RNA-seq, qPCR, and Western blotting. Specifically, depletion of CDK1 weakened the effect of TSPO deficiency on cell proliferation and migration. More importantly, CDK1 knockdown induced significant cell cycle arrest in the G2/M phase. In summary, TSPO deficiency regulates the cell cycle in MPNSTs by targeting CDK1, which may be an effective molecular target for prognosis evaluation and treatment.

Objective To provide useful information for selecting the most appropriate peripheral nerve injury model for different research purposes in nerve injury and repair studies, and to compare nerve regeneration capacity and characteristics between them.Methods Sixty adult SD rats were randomly divided into two groups and underwent crush injury alone (group A, n = 30) or transection injury followed by surgical repair (group B, n = 30) of the right hind paw. Each group was subjected to the CatWalk test, gastrocnemius muscle evaluation, pain threshold measurement, electrophysiological examination, retrograde neuronal labeling, and quantification of nerve regeneration before and 7, 14, 21, and 28 days after injury.Results Gait analysis showed that the recovery speed in group A was significantly faster than that in group B at 14 days. At 21 days, the compound muscle action potential of the gastrocnemius muscle in group A was significantly higher than that in group B, and the number of labeled motor neurons in group B was lower than that in group A. The number of new myelin sheaths and the g-ratio were higher in group A than in group B. There was a 7-day time difference in the regeneration rate between the two injury groups.Conclusion The regeneration of nerve fibers was rapid after crush nerve injury, whereas the transection injury was relatively slow, which provides some ideas for the selection of clinical research models.

Patients with germline neurofibromatosis type 1 (NF1) microdeletions frequently exhibit hereditary syndromes such as cardiovascular anomalies and have an increased risk of malignant peripheral nerve sheath tumors (MPNSTs). This study aimed to identify the genes codeleted with SUZ12 that are related to MPNST. We used differential gene expression and enrichment analyses to analyze the SUZ12-mutant and SUZ12-wild-type gene expression profiles in the GSE118186 and GSE66743 datasets in Gene Expression Omnibus (GEO). PPI network analysis combined with MPNST patient survival analysis was used to identify ADCY1, which catalyzes the conversion of ATP to cAMP, as a key gene. Moreover, chromatin immunoprecipitation sequencing (ChIP-Seq) showed that the distribution of H3K27me3 in the ADCY1 promoter region and gene body was significantly reduced in SUZ12-mutant cells. To verify the role of ADCY1 in SUZ12 mutation, we used RNA interference and plasmid transfection to interfere with SUZ12 expression in plexiform neurofibroma (pNF) and MPNST cell lines and then treated the cells with forskolin, IBMX and H89. ERK phosphorylation was accelerated and prolonged after siRNA transfection, especially in ipNF05.5 cells, and the intensity and duration of ERK activation were reduced after SUZ12 overexpression. Importantly, the level of p-ERK was consistent with that of Rap1-GTP. Moreover, H89 completely blocked Rap1 activation and the changes in the p-ERK level after SUZ12 siRNA transfection. In conclusion, our findings suggested that SUZ12 loss potentiates the effects of NF1 mutations by amplifying Ras signaling through the ADCY1/cAMP/Rap1/ERK pathway and that SUZ12 may serve as a therapeutic and prognostic biomarker in NF1-associated neurofibromas.