Ginsenoside Compound K Promotes Proliferation, Migration and Differentiation of Schwann Cells via the Activation of MEK/ERK1/2 and PI3K/AKT Pathways

Oxidized sodium alginate hydrogel-mouse nerve growth factor sustained release system promotes repair of peripheral nerve injury

In recent years, mouse nerve growth factor (mNGF) has emerged as an important biological regulator to repair peripheral nerve injury, but its systemic application is restricted by low efficiency and large dosage requirement. These limitations prompted us to search for biomaterials that can be locally loaded. Oxidized sodium alginate hydrogel (OSA) exhibits good biocompatibility and physicochemical properties, and can be loaded with drugs to construct a sustained-release system that can act locally on nerve injury. Here, we constructed a sustained-release system of OSA-mouse nerve growth factor (mNGF), and investigated the loading and release of the drug through Fourier transform infrared spectroscopy and drug release curves. In vitro and in vivo experiments showed that OSA-mNGF significantly promoted the biological activities of RSC-96 cells and facilitated the recovery from sciatic nerve crush injury in rats. This observation may be attributed to the additive effect of OSA on promoting Schwann cell biological activities or its synergistic effect of cross-activating phosphoinositide 3-kinase (PI3K) through extracellular signal regulated kinase (ERK) signaling. Although the specific mechanism of OSA action needs to be explored in the future, the current results provide a valuable preliminary research basis for the clinical application of the OSA-mNGF sustained-release system for nerve repair.

Ginsenoside compound K reduces ischemia/reperfusion-induced neuronal apoptosis by inhibiting PTP1B-mediated IRS1 tyrosine dephosphorylation

Background

Ginsenoside compound K (CK) stimulated activation of the PI3K-Akt signaling is one of the major mechanisms in promoting cell survival after stroke. However, the underlying mediators remain poorly understood. This study aimed to explore the docking protein of ginsenoside CK mediating the neuroprotective effects.

Materials and methods

Molecular docking, surface plasmon resonance, and cellular thermal shift assay were performed to explore ginsenoside CK interacting proteins. Neuroscreen-1 cells and middle cerebral artery occlusion (MCAO) model in rats were utilized as in-vitro and in-vivo models.

Results

Ginsenoside CK interacted with recombinant human PTP1B protein and impaired its tyrosine phosphatase activity. Pathway and process enrichment analysis confirmed the involvement of PTP1B and its interacting proteins in PI3K-Akt signaling pathway. PTP1B overexpression reduced the tyrosine phosphorylation of insulin receptor substrate 1 (IRS1) after oxygen-glucose deprivation/reoxygenation (OGD/R) in neuroscreen-1 cells. These regulations were confirmed in the ipsilateral ischemic hemisphere of the rat brains after MCAO/R. Ginsenoside CK treatment reversed these alterations and attenuated neuronal apoptosis.

Conclusion

Ginsenoside CK binds to PTP1B with a high affinity and inhibits PTP1B-mediated IRS1 tyrosine dephosphorylation. This novel mechanism helps explain the role of ginsenoside CK in activating the neuronal protective PI3K-Akt signaling pathway after ischemia-reperfusion injury.

Neuroprotective Mechanisms of Ginsenoside Rb1 in Central Nervous System Diseases

Panax ginseng and Panax notoginseng, two well-known herbs with enormous medical value in Asian countries, have a long usage history in China for the therapy of some diseases, such as stroke. Ginsenoside Rb1 is one of most important active ingredients in Panax ginseng and Panax notoginseng. In the last two decades, more attention has focused on ginsenoside Rb1 as an antioxidative, anti-apoptotic and anti-inflammatory agent that can protect the nervous system. In the review, we summarize the neuroprotective roles of ginsenoside Rb1 and its potential mechanisms in central nervous system diseases (CNSDs), including neurodegenerative diseases, cerebral ischemia injury, depression and spinal cord injury. In conclusion, ginsenoside Rb1 has a potential neuroprotection due to its inhibition of oxidative stress, apoptosis, neuroinflammation and autophagy in CNSDs and may be a promising candidate agent for clinical therapy of CNSDs in the future.

SIRT6 Negatively Regulates Schwann Cells Dedifferentiation via Targeting c-Jun During Wallerian Degeneration After Peripheral Nerve Injury

Silent information regulator 6 (SIRT6) is a mammalian homolog of the nicotinamide adenine dinucleotide (NAD)-dependent deacetylase sirtuin family. Previous studies have been reported a pro-regenerative role of SIRT6 in central nervous system injury. However, the role of SIRT6 in peripheral nerve injury is still unknown. Given the importance and necessity of Schwann cell dedifferentiation response to peripheral nerve injury, we aim to investigate the molecular mechanism of SIRT6 steering Schwann cell dedifferentiation during Wallerian degeneration in injured peripheral nerve. Herein, we first examined the expression pattern of SIRT6 after peripheral nerve injury. Using the explants of sciatic nerve, an ex vivo model of nerve degeneration, we provided evidences indicating that SIRT6 inhibitor accelerates Schwann cell dedifferentiation as well as axonal and myelin degeneration, while SIRT6 activator attenuates this process. Moreover, in an in vitro Schwann cell dedifferentiation model, we found SIRT6 inhibitor promotes Schwann cell dedifferentiation through upregulating the expression of c-Jun. In addition, downregulation of c-Jun reverse the effects of SIRT6 inhibition on the Schwann cells dedifferentiation and axonal and myelin degeneration. In summary, we first described SIRT6 acts as a negative regulator for Schwann cells dedifferentiation during Wallerian degeneration and c-Jun worked as a direct downstream partner of SIRT6 in injured peripheral nerve.

Human Umbilical Cord Mesenchymal Stem Cell-Derived Extracellular Vesicles Promote the Proliferation of Schwann Cells by Regulating the PI3K/AKT Signaling Pathway via Transferring miR-21

As an alternative mesenchymal stem cell- (MSC-) based therapy, MSC-derived extracellular vesicles (EVs) have shown promise in the field of regenerative medicine. We previously found that human umbilical cord mesenchymal stem cell-derived EVs (hUCMSC-EVs) improved functional recovery and nerve regeneration in a rat model of sciatic nerve transection. However, the underlying mechanisms are poorly understood. Here, we demonstrated for the first time that hUCMSC-EVs promoted the proliferation of Schwann cells by activating the PI3K/AKT signaling pathway. Furthermore, we showed that hUCMSC-EVs mediated Schwann cell proliferation via transfer of miR-21. Our findings highlight a novel mechanism of hUCMSC-EVs in treating peripheral nerve injury and suggest that hUCMSC-EVs may be an attractive option for clinical application in the treatment of peripheral nerve injury.