[Effect and mechanism of thymosin beta 4 on spinal cord-derived neural stem /progenitor cell injury induced by oxidative stress]

Abstract

Objective: To investigate the role and mechanism of thymosin beta 4 (Tβ4) in oxidative stress injury of spinal cord-derived neural stem/progenitor cells (NSPCs) induced by hydrogen peroxide (H₂O₂).

Methods: NSPCs were isolated from Sprague-Dawley (SD) adult male rats, and divided into control group (untreated NSPCs cells), H₂O₂ group (NSPCs cells damaged by 500 μM H₂O₂), Tβ4 -3 groups (NSPCs were treated with 1, 2.5, 5 μg/ml Tβ4 on the basis of H₂O₂ treatment) and TAK-242 group [NSPCs were treated with 5 μg/ml Tβ4 and Toll-like receptor 4(TLR4) inhibitor TAK-242 on the basis of H₂O₂ treatment]. NSPCs were transfected with lentivirus vector of myeloid differentiation factor 88(MyD88) to construct MyD88-overexpressing cell lines, which were treated with H₂O₂ and Tβ4. The expression of Tβ4, TLR4, MyD88 were detected by qRT-PCR and Western blot. Cell viability was detected by MTT assay and lactate dehydrogenase(LDH) assay kit. Ca2+ concentration was detected by Fluo-3/AM probe method. The apoptosis of NSPCs was detected by flow cytometry and Caspase-3 and Caspase-9 kits;reactive oxygen species (ROS), superoxi dedismu-tase dismutase(SOD) activity and glutathione (GSH) content were detected by corresponding kits. Interleukin(IL)-6 and IL-1β were detected by enzyme-linked immunosorbent assay.

Results: The expression of Tβ4 was decreased in H₂O₂ injured NSPCs(P<0.05). Compared with H₂O₂ group, the cell viability and Ca2+ concentration was significantly increased, release of LDH and apoptosis were significantly decreased, production of ROS and pro-inflammatory cytokines were significantly decreased, and the expression levels of TLR4 and MyD88 protein were significantly decreased in Tβ4-3 groups and TAK-242 group (P<0.05). After overexpression of MyD88, cell viability, SOD activity and GSH content of NSPCs decreased, LDH release and apoptosis increased significantly (P<0.05), while after treatment with Tβ4, cell viability, SOD activity and GSH content increased, LDH release and apoptosis decreased (P<0.05).

Conclusion: Tβ4 attenuates H₂O₂-induced NSPCs oxidative stress, apoptosis and inflammation in NSPCs via inhibiting TLR4 and MyD88 pathways.

Keywords: Myeloid differentiation factor 88; Neural stem cells; Oxidative stress injury; Progenitor cells; Thymosin β4.