ABSTRACT
Objective:To study the regulatory effects of transforming growth factor beta-activated kinase 1 (TAK1) on microglia pyroptosis in hypoxic-ischemic brain damage (HIBD).Methods:Primary microglia cells were isolated from fetal mice and randomly assigned into 4 groups: the control group, 5z-7-oxozeaneol (5z-7) group, oxygen-glucose deprivation (OGD) group and OGD+5z-7 group. OGD models of microglia cells were established for the OGD groups and 5z-7 groups received a small molecule TAK1 inhibitor 5z-7. Expression of phosphorylated TAK1(P-TAK1), pyroptosis related proteins including NOD-like receptor pyrin domain containing 3 (NLRP-3), apoptosis-associated speck-like protein containing a CARD (ASC) oligomers, N terminal of Gasdermin D (GSDMD-N) and interleukin 1β (IL-1β) were examined using Western blot at 0 h, 6 h and 24 h after intervention. Lactate dehydrogenase (LDH) test and transmission electron microscope were used for pyroptosis evaluation.Results:(1) Compared with the control group, expressions of all proteins including P-TAK1, NLRP-3, ASC oligomers, GSDMD-N, IL-1β and LDH level showed no significant differences in the OGD group at 0 h ( P>0.05). P-TAK1 levels in OGD group at 6 h and 24 h were lower than the control group and the levels of NLRP-3, ASC oligomers, GSDMD-N, IL-1β and LDH were significantly higher ( P<0.05). Microglia pyroptosis (characterized by disruption of cell membrane, extravasation of cytoplasm and chromatin margin aggregation) was observed under electron microscope. (2) 5z-7 group and OGD+5z-7 group had lower P-TAK1 levels and higher NLRP-3, ASC oligomers, GSDMD-N, IL-1β and LDH levels than the control group and OGD group at 6 h and 24 h. Conclusions:The down-regulation of TAK1 phosphorylation level may promote microglia pyroptosis in HIBD. This regulatory effects is related to the up-regulation of NLRP-3 expression and the oligomerization of ASC.
ABSTRACT
Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that regulates a wide variety of cellular functions, including cell growth, cellular differentiation, apoptosis, and wound healing. TGF-beta1, the prototype member of the TGF-beta superfamily, is well established as a central mediator of renal fibrosis. In chronic kidney disease, dysregulation of expression and activation of TGF-beta1 results in the relentless synthesis and accumulation of extracellular matrix proteins that lead to the development of glomerulosclerosis and tubulointerstitial fibrosis, and ultimately to end-stage renal disease. Therefore, specific targeting of the TGF-beta signaling pathway is seemingly an attractive molecular therapeutic strategy in chronic kidney disease. Accumulating evidence demonstrates that the multifunctionality of TGF-beta1 is connected with the complexity of its cell signaling networks. TGF-beta1 signals through the interaction of type I and type II receptors to activate distinct intracellular pathways. Although the Smad signaling pathway is known as a canonical pathway induced by TGF-beta1, and has been the focus of many previous reviews, importantly TGF-beta1 also induces various Smad-independent signaling pathways. In this review, we describe evidence that supports current insights into the mechanism and function of TGF-beta-activated kinase 1 (TAK1), which has emerged as a critical signaling molecule in TGF-beta-induced Smad-independent signaling pathways. We also discuss the functional role of TAK1 in mediating the profibrotic effects of TGF-beta1.