8-Oxoguanine DNA glycosylase 1 selectively modulates ROS-responsive NF-κB targets through recruitment of MSK1 and phosphorylation of RelA/p65 at Ser276

Reassessing the roles of oxidative DNA base lesion 8-oxoGua and repair enzyme OGG1 in tumorigenesis

ROS cause multiple forms of DNA damage, and among them, 8-oxoguanine (8-oxoGua), an oxidized product of guanine, is one of the most abundant. If left unrepaired, 8-oxoGua may pair with A instead of C, leading to a mutation of G: C to T: A during DNA replication. 8-Oxoguanine DNA glycosylase 1 (OGG1) is a tailored repair enzyme that recognizes 8-oxoGua in DNA duplex and initiates the base excision repair (BER) pathway to remove the lesion and ensure the fidelity of the genome. The accumulation of genomic 8-oxoGua and the dysfunction of OGG1 is readily linked to mutagenesis, and subsequently aging-related diseases and tumorigenesis; however, the direct experimental evidence has long been lacking. Recently, a series of studies have shown that guanine oxidation in the genome has a conservative bias, with the tendency to occur in the regulatory regions, thus, 8-oxoGua is not only a lesion to be repaired, but also an epigenetic modification. In this regard, OGG1 is a specific reader of this base modification. Substrate recognition and/or excision by OGG1 can cause DNA conformation changes, affect chromatin modifications, thereby modulating the transcription of genes involved in a variety of cellular processes, including inflammation, cell proliferation, differentiation, and apoptosis. Thus, in addition to the potential mutagenicity, 8-oxoGua may contribute to tumor development and progression through the altered gene expression stemming from its epigenetic effects.

OGG1: An emerging multifunctional therapeutic target for the treatment of diseases caused by oxidative DNA damage

Oxidative DNA damage-related diseases, such as incurable inflammation, malignant tumors, and age-related disorders, present significant challenges in modern medicine due to their complex molecular mechanisms and limitations in identifying effective treatment targets. Recently, 8-oxoguanine DNA glycosylase 1 (OGG1) has emerged as a promising multifunctional therapeutic target for the treatment of these challenging diseases. In this review, we systematically summarize the multiple functions and mechanisms of OGG1, including pro-inflammatory, tumorigenic, and aging regulatory mechanisms. We also highlight the potential of OGG1 inhibitors and activators as potent therapeutic agents for the aforementioned life-limiting diseases. We conclude that OGG1 serves as a multifunctional hub; the inhibition of OGG1 may provide a novel approach for preventing and treating inflammation and cancer, and the activation of OGG1 could be a strategy for preventing age-related disorders. Furthermore, we provide an extensive overview of successful applications of OGG1 regulation in treating inflammatory, cancerous, and aging-related diseases. Finally, we discuss the current challenges and future directions of OGG1 as an emerging multifunctional therapeutic marker for the aforementioned challenging diseases. The aim of this review is to provide a robust reference for scientific researchers and clinical drug developers in the development of novel clinical targeted drugs for life-limiting diseases, especially for incurable inflammation, malignant tumors, and age-related disorders.

Post-translational modifications of p65: state of the art

P65, a protein subunit of NF-κB, is a widely distributed transcription factor in eukaryotic cells and exerts diverse regulatory functions. Post-translational modifications such as phosphorylation, acetylation, methylation and ubiquitination modulate p65 transcriptional activity and function, impacting various physiological and pathological processes including inflammation, immune response, cell death, proliferation, differentiation and tumorigenesis. The intricate interplay between these modifications can be antagonistic or synergistic. Understanding p65 post-translational modifications not only elucidates NF-κB pathway regulation but also facilitates the identification of therapeutic targets and diagnostic markers for associated clinical conditions.

OGG1 as an Epigenetic Reader Affects NFκB: What This Means for Cancer

8-oxoguanine glycosylase 1 (OGG1), which was initially identified as the enzyme that catalyzes the first step in the DNA base excision repair pathway, is now also recognized as a modulator of gene expression. What is important for cancer is that OGG1 acts as a modulator of NFκB-driven gene expression. Specifically, oxidant stress in the cell transiently halts enzymatic activity of substrate-bound OGG1. The stalled OGG1 facilitates DNA binding of transactivators, such as NFκB to their cognate sites, enabling the expression of cytokines and chemokines, with ensuing recruitment of inflammatory cells. Recently, we highlighted chief aspects of OGG1 involvement in regulation of gene expression, which hold significance in lung cancer development. However, OGG1 has also been implicated in the molecular underpinning of acute myeloid leukemia. This review analyzes and discusses how these cells adapt through redox-modulated intricate connections, via interaction of OGG1 with NFκB, which provides malignant cells with alternative molecular pathways to transform their microenvironment, enabling adjustment, promoting cell proliferation, metastasis, and evading killing by therapeutic agents.

Sinomenine Ameliorates IL-1β-Induced Intervertebral Disc Degeneration in Rats Through Suppressing Inflammation and Oxidative Stress via Keap1/Nrf2/NF-κB Signaling Pathways

Purpose

To investigate the molecular mechanism underlying the inhibitory effect of sinomenine (SN) on interleukin-1β (IL-1β)-induced apoptosis in nucleus pulposus cells (NPCs), and to evaluate the potential role of SN in preventing intervertebral disk degeneration (IDD).

Methods

The Rat NPCs were cultured in vitro and identified using Hematoxylin-Eosin (HE) staining, toluidine blue staining, and immunofluorescence analysis. NPCs were pretreated with or without SN, then induced with IL-1β to assess cell viability, ROS levels, apoptotic rates, and wound healing ability. Relevant protein expression was detected using Elisa, qPCR and Western Blot techniques. NPCs were pretreated with SN, either alone or in combination with Nrf2-IN-1 or SC, before being induced to undergo apoptosis by IL-1β. Apoptosis was detected using Hoechst staining, while qPCR and Western Blot techniques assessed protein expression. Rat caudal intervertebral discs were induced with IDD, with or without SN injection, and then co-injected with IL-1β. The levels of IDD were evaluated using HE staining and modified saffron-O-fix green cartilage staining. Relevant protein expression was detected using Elisa, qPCR, and Western Blot techniques.

Results

IL-1β significantly reduced NPC activity, induced ROS accumulation and apoptosis, decreased cell healing rate, promoted the expression and secretion of inflammatory factors, and inhibited extracellular matrix synthesis. However, pretreatment with SN effectively reversed these effects. Inhibition of the Keap1/Nrf2 signaling pathway or activation of the NF-κB signaling pathway significantly attenuated the cytoprotective effects of SN and increased apoptosis. Acupuncture combined with IL-1β injection markedly induced intervertebral disc degeneration in rat caudal spine, upregulated inflammatory factors expression and secretion, and downregulated extracellular matrix synthesis. SN intervention notably enhanced antioxidant enzyme expression and reversed these outcomes.

Conclusion

SN can prevent IL-1β-induced apoptosis of NPCs and ameliorate IDD by activating the Keap1/Nrf2 pathway and inhibiting the NF-κB signaling pathway.