Inhibition of HDAC4 by GSK3β leads to downregulation of KLF5 and ASK1 and prevents the progression of intravertebral disc degeneration

Abstract

Background Intervertebral disc degeneration (IDD) is a major cause of lower back pain. This study aimed at exploring the effects of histone deacetylase 4 (HDAC4) and its upstream and downstream signaling molecules on IDD development. Methods A murine IDD model was established by inducing a needle puncture injury to the vertebrate, whereupon we isolated and transfected of nucleus pulposus (NP) cells. Disc height index (DHI) of the mice was determined by X-ray tomography, while the pain experienced by the IDD mice was evaluated by mechanical and thermal sensitivity tests. Next, the interaction between GSK3β and HDAC4 as well as that between HDAC4 and KLF5 acetylation was assessed by co-immunoprecipitation, while the promoter region binding was assessed identified by chromatin immunoprecipitation. By staining methods with TUNEL, Safranin O fast green, and hematoxylin and eosin, the NP cell apoptosis, degradation of extracellular matrix, and morphology of intervertebral disc tissues were measured. Furthermore, mRNA and protein expressions of GSK3β, HDAC4, KLF5, and ASK1, as well as the extent of HDAC4 phosphorylation, were determined by RT-qPCR and Western blotting. Results GSK3β was identified to be downregulated in the intervertebral disc tissues obtained from IDD mice, while HDAC4, KLF5, and ASK1 were upregulated. HDAC4 silencing alleviated IDD symptoms. It was also found that GSK3β promoted the phosphorylation of HDAC4 to increase its degradation, while HDAC4 promoted ASK1 expression through upregulating the expression of KLF5. In IDD mice, GSK3β overexpression resulted in increased DHI, inhibition of NP cell apoptosis, alleviation of disc degeneration, and promoted mechanical and thermal pain thresholds. However, HDAC4 overexpression reversed these effects by promoting ASK1 expression. Conclusion Based on the key findings of the current study, we conclude that GSK3β can promote degradation of HDAC4, which lead to an overall downregulation of the downstream KLF5/ASK1 axis, thereby alleviating the development of IDD.

HDAC4 in cancer: A multitasking platform to drive not only epigenetic modifications

“…This circuit allows the expansion of cancer stem cells, tumor aggressiveness and metastasis ( Zhang et al, 2020 ). This result is in agreement with the possible involvement of MEF2 family members in EMT ( Su et al, 2016 ; Xiao L et al, 2021 ).…”

ZIP4 upregulation aggravates nucleus pulposus cell degradation by promoting inflammation and oxidative stress by mediating the HDAC4-FoxO3a axis

“…For instance, HDAC4 bolsters morphological alterations in endplate chondrocytes and augments ECM degradation and endplate cartilage degeneration [33]. In an IDD mouse model, GSK3β was downregulated in intervertebral disc tissues, and upregulating GSK3β mitigated NP cell apoptosis and disc degeneration in IDD mice by repressing HDAC4 [13].…”

“…Histone deacetylase 4 (HDAC4), belonging to the HDAC family, functions importantly in transcriptional regulation and cell cycle development [12]. Reportedly, HDAC4 expression is upregulated in the intervertebral disc tissues of IDD mice, while HDAC4 overexpression bolsters NP cell apoptosis and exacerbates IDD in mice [13]. Engaging in a plethora of biological activities, including cell proliferation, apoptosis, oxidative stress, and inflammation [14], FoxO3a, a constituent of the forkhead transcription factor family, demonstrates its multiple functions, such as proliferation, apoptosis, cell cycle regulation, and DNA damage [15].…”