Nucleus pulposus (NP) degeneration plays pivotal roles in intervertebral disc degeneration. The effect and mechanism of oxidative stress and epigenetics in NP degeneration is still unclear. We performed this study to evaluate the function of oxidative stress in NP and to explore the potential mechanism of ROS induced expression of matrix metalloproteinases (MMPs). We tested four methyltransferases, KMT2A, KMT2B, KMT2C and KMT2D in human NP samples, only KMT2D was significantly up-regulated in the severe degeneration samples. Knockdown of Kmt2d by siRNA significantly down-regulated the expression levels of catabolic enzymes including Mmp3, Mmp9 and Mmp13. Moreover, an interaction between KMT2D and ubiquitination was confirmed, and the application of H₂O₂ abrogated this process. Co-IP assay confirmed that H₂O₂ induced the phosphorylation of KMT2D to block the ubiquitination degradation, which was mainly mediated by phosphorylation of p38/MAPK. Further investigation suggested that ROS induced the alteration in levels of methylation is linked to H3K4me1 and H3K4me2, but not me3. However, usage of OICR-9429 (OICR) also suppressed the expression levels of Mmp3, Mmp9 and Mmp13. In an ex vivo model, application of OICR-9429 (OICR) also attenuated the degeneration of NP according to the H&E and Safranin-O/Fast Green staining assay, and the protein levels of MMP3, MMP9 and MMP13 were down-regulated, as well. In conclusion, we approved that oxidative stress induced ROS production promote the process of NP degeneration by enhancing KMT2D mediated transcriptional regulation of matrix degeneration related genes during NP degeneration.

髓核（NP）变性在椎间盘变性中起关键作用。氧化应激和表观遗传学在NP变性中的作用和机制尚不清楚。我们进行了这项研究，以评估氧化应激在NP中的功能，并探讨ROS诱导基质金属蛋白酶（MMPs）表达的潜在机制。我们在人NP样品中测试了四种甲基转移酶KMT2A，KMT2B，KMT2C和KMT2D，在严重的变性样品中只有KMT2D显着上调。siRNA敲低Kmt2d显着下调了分解代谢酶（包括Mmp3，Mmp9和Mmp13）的表达水平。此外，证实了KMT2D和泛素化之间的相互作用，以及H ₂ O ₂的应用取消了此过程。Co-IP分析证实了H ₂ O ₂诱导KMT2D磷酸化以阻断泛素化降解，这主要是由p38 / MAPK磷酸化介导的。进一步的研究表明，ROS诱导甲基化水平的改变与H3K4me1和H3K4me2有关，但与me3不相关。但是，使用OICR-9429（OICR）也可以抑制Mmp3，Mmp9和Mmp13的表达水平。在离体模型中，根据H＆E和Safranin-O / Fast Green染色法，应用OICR-9429（OICR）还可以减轻NP的变性，并且MMP3，MMP9和MMP13的蛋白质水平下调，因为好。总之，我们批准了氧化应激诱导的ROS产生通过增强NP变性过程中KMT2D介导的基质变性相关基因的转录调控来促进NP变性的过程。