Lactate-Driven Histone Modification Accelerates Spinal Disc Degeneration by Suppressing Protective CD248

A newly published laboratory investigation has revealed a detailed molecular cascade showing how the metabolic byproduct lactic acid actively accelerates spinal pathology by modifying chromatin architecture and silencing protective cellular programs. The study demonstrates that intervertebral disc degeneration involves excessive accumulation of lactate within the nucleus pulposus of the disc. Rather than acting solely as an inert metabolic waste product or an acidic stressor, elevated lactate was found to trigger a specific post-translational chromatin alteration termed histone H3 lysine 18 lactylation, abbreviated as H3K18la. This epigenetic mark systematically suppresses the expression of CD248, a transmembrane glycoprotein essential for cellular viability and structural maintenance, through both nuclear transcriptional repression and accelerated cytosolic protein breakdown. When CD248 levels fall, nucleus pulposus cells undergo widespread programmed cell death and degrade their surrounding structural scaffolding. By tracing this pathway from surgical patient tissues to engineered molecular mutants and live animal models, the research team established that preventing or counteracting this epigenetic shutoff can significantly preserve disc integrity.

Intervertebral disc degeneration is one of the core pathological processes of spinal degenerative diseases. Structurally, the intervertebral disc primarily consists of the annulus fibrosus, cartilage endplate, and nucleus pulposus. The nucleus pulposus serves as the primary shock-absorbing component of the disc. Because the adult intervertebral disc is the largest avascular organ in the human body, its resident cells reside within a harsh, permanently hypoxic microenvironment where oxygen cannot freely diffuse. To survive and meet baseline energetic demands, nucleus pulposus cells depend almost exclusively on anaerobic glycolysis for adenosine triphosphate generation.

To investigate metabolic differences during degeneration, the authors collected human nucleus pulposus specimens from surgical patients treated at the First Affiliated Hospital of Harbin Medical University between 2022 and 2024. Using magnetic resonance imaging, the discs were classified according to the Pfirrmann grading scale, with Grade 3 or lower designated as mild degeneration and Grades 4 and 5 as severe degeneration. Untargeted liquid chromatography-tandem mass spectrometry metabolomics confirmed that lactate metabolism was substantially elevated in severely degenerated human nucleus pulposus primary cells compared to milder cohorts. Direct biochemical tissue assays established that lactate concentrations were significantly higher in severely degenerated discs. Drawing on recent discoveries demonstrating that lactate can covalently attach to lysine residues on histone tails to generate functional lactyl-lysine modifications, the investigators probed whether this metabolic surge altered nuclear chromatin. Western blot and immunofluorescence analyses revealed that while five distinct candidate histone sites were examined, including H3K9la, H3K14la, H4K12la, and H2BK15la, the specific mark H3K18la demonstrated the most robust elevation in degenerated human disc tissue.

Building on these baseline patient observations, the researchers exposed cultured human nucleus pulposus cells to escalating exogenous lactate concentrations of zero, three, six, and ten millimolar to mirror the severe acidic microenvironment seen in clinical specimens. The experimental addition of lactate induced a striking, concentration-dependent increase in both total cellular lactylation and specific H3K18la modification levels. Functionally, elevated lactate severely compromised cellular homeostasis: cell counting kit-8 and thymidine analogue incorporation assays revealed a sharp inhibition of cell proliferation, while scratch wound-healing assays demonstrated a marked impairment of cell migration capacity. To determine whether reducing glycolytic byproduct flux could rescue these degenerative phenotypes, the authors introduced 2-deoxy-D-glucose, a pharmacological inhibitor of glycolysis. Treatment with 2-deoxy-D-glucose systematically diminished overall histone lactylation and H3K18la abundance, while restoring cellular proliferation, restoring migratory capacity, decreasing apoptosis rates, and reviving matrix synthesis under high-lactate conditions.

To establish direct causality and verify that these pathological outcomes were specifically mediated by lactylation occurring at the eighteenth lysine residue of histone H3 rather than non-specific cellular acidification, the research group constructed a site-directed genetic point mutant. Crucially, the H3K18R mutation abrogated lactate-induced nucleus pulposus cell apoptosis and extracellular matrix degradation. This targeted molecular substitution demonstrated that the lysine-18 site on histone H3 operates as an indispensable epigenetic switch through which metabolic lactate actively dictates disc cell death and extracellular matrix destruction.

To uncover the downstream target genes governed by this histone modification, the investigators performed comprehensive messenger RNA sequencing on nucleus pulposus cells exposed to external lactate alongside comparative transcriptomic profiling of wild-type versus H3K18R mutant cells. The addition of lactate upregulated 718 genes and downregulated 559 genes, whereas the protective H3K18R mutant upregulated 1168 genes and downregulated 379 genes. Cross-referencing these two vast sequencing datasets yielded an overlapping intersection of fifty-six differentially expressed genes, among which CD248 emerged as the sole candidate exhibiting robust, reciprocal regulation with a absolute log2 fold-change exceeding 1.5 in both datasets. Bioinformatic Gene Ontology analysis linked CD248 directly to extracellular matrix protein binding. Quantitative polymerase chain reaction and Western blotting confirmed that CD248 expression was suppressed by lactate but rescued by the H3K18R mutation, a trend corroborated by human surgical samples where severely degenerated nucleus pulposus tissues displayed marked depletion of CD248 mRNA and protein.

The biological finding that lactate increased H3K18la enrichment at the CD248 promoter presented an intriguing molecular paradox. In canonical epigenetic models, histone lactylation typically opens chromatin architecture and promotes active gene transcription by recruiting co-activators. However, chromatin immunoprecipitation quantitative PCR demonstrated that while lactate significantly enhanced H3K18la physical occupancy at the second promoter region near the transcription start site of CD248, actual CD248 mRNA synthesis was profoundly repressed. To resolve this contradiction, the team hypothesized that H3K18la was recruiting an atypical transcriptional repressor. Co-immunoprecipitation coupled with liquid chromatography-tandem mass spectrometry identified sixty-seven differentially enriched candidate proteins associated with H3K18la. Among these, the ATP-dependent chromatin remodeler SMARCA5 and the tumor suppressor p53 were isolated as potential transcriptional inhibitors. Subsequent chromatin immunoprecipitation Western blotting and sequential ChIP-reChIP-qPCR demonstrated that SMARCA5, but not p53, was selectively recruited to the CD248 promoter alongside H3K18la under high-lactate conditions. Small interfering RNA knockdown of SMARCA5 successfully relieved the transcriptional blockade, significantly restoring CD248 mRNA transcription in lactate-stressed cells.

Although knocking down SMARCA5 restored CD248 messenger RNA transcription, protein immunoblotting revealed that CD248 protein levels failed to recover, indicating that lactate imposes an additional layer of post-translational control over the glycoprotein. Cycloheximide protein synthesis chase assays demonstrated that lactate treatment drastically shortened the intracellular half-life of CD248 protein. When cells were co-treated with specific degradation inhibitors, the selective proteasome blocker MG132 completely halted lactate-driven CD248 depletion, whereas the lysosomal autophagy inhibitor bafilomycin A1 showed no protective effect. Immunoprecipitation assays confirmed that lactate markedly amplified the ubiquitination of CD248, leading to rapid proteasomal clearance, whereas introducing the lactylation-resistant H3K18R mutation substantially attenuated CD248 ubiquitination. These complementary biochemical experiments proved that lactate exerts a coordinated, dual-level repressive mechanism: it engages the chromatin remodeler SMARCA5 to halt CD248 gene transcription in the nucleus while simultaneously activating ubiquitin-proteasome system machinery in the cytoplasm to accelerate the degradation of existing CD248 protein molecules.

Exploring the downstream biological pathways governed by CD248, the investigators performed Kyoto Encyclopedia of Genes and Genomes enrichment analyses, which identified the evolutionary conserved Hedgehog signaling cascade as a key effector pathway. Functional validation experiments demonstrated that targeted CD248 overexpression in nucleus pulposus cells effectively reversed lactate-induced apoptosis, restored proliferative and migratory capacity, and stimulated matrix synthesis by upregulating the core Hedgehog components GLI1, Sonic Hedgehog, and Smoothened. To evaluate the therapeutic potential of this pathway in living organisms, the researchers established an in vivo disc degeneration model in Sprague-Dawley rats using precise 23-gauge needle puncture of the tail vertebrae followed by intradiscal injection of an adeno-associated virus serotype 9 vector overexpressing CD248.

While these experimental discoveries offer compelling mechanistic insights into spinal biology, the authors emphasized key translational considerations and methodological limitations that frame the scope of their findings. The short-term metabolic reversal achieved in culture using the glycolysis inhibitor 2-deoxy-D-glucose was utilized strictly as an analytical tool to verify lactylation pathways rather than a viable therapeutic candidate. Because nucleus pulposus cells depend on anaerobic glycolysis in their hypoxic environment, long-term inhibition of glycolysis could damage their basic energy metabolism and survival ability. Additionally, the researchers noted that logistical constraints limited their initial site screening to five commercial histone antibodies rather than a comprehensive proteome-wide mass spectrometry mapping of every potential lactylation site. Furthermore, the needle puncture model was conducted in adolescent six-to-eight-week-old rats whose discs still harbor a substantial population of embryonic notochordal cells, meaning this acute mechanical model cannot fully replicate the cellular composition or chronic decades-long natural history of adult human intervertebral disc degeneration.

Subject of Research: Epigenetic mechanisms of intervertebral disc degeneration driven by histone lactylation

Article Title: H3K18 Lactylation in Degenerated Nucleus Pulposus Cells Suppresses CD248 Through Transcriptional and Post‐Translational Modifications to Promote Apoptosis and Extracellular Matrix Degradation

Article References: Ma, Y., Shao, T., Gao, Q., Gu, J., Zhan, W., Han, S., Li, S., & Yu, Z. (2026). H3K18 Lactylation in Degenerated Nucleus Pulposus Cells Suppresses CD248 Through Transcriptional and Post‐Translational Modifications to Promote Apoptosis and Extracellular Matrix Degradation. Aging Cell, 25(11), Article e70810. https://doi.org/10.1111/acel.70810

Image Credits: AI Generated

DOI: 10.1111/acel.70810

Keywords: intervertebral disc degeneration, nucleus pulposus, histone lactylation, H3K18la, CD248, SMARCA5, ubiquitin-proteasome pathway, Hedgehog signaling, anaerobic glycolysis, extracellular matrix degradation, cell apoptosis, chromatin remodeling, Pfirrmann grading, 2-deoxy-D-glucose, GANT61, spinal pathology, epigenetic regulation, GLI1