Curcumin and o-Vanillin Exhibit Evidence of Senolytic Activity in Human IVD Cells In Vitro

Hosni Cherif,Peter Jarzem,Daniel Bisson,Jean Ouellet,Lisbet Haglund,Michael Weber

doi:10.3390/jcm8040433

Abstract

Curcumin and o-Vanillin cleared senescent intervertebral disc (IVD) cells and reduced the senescence-associated secretory phenotype (SASP) associated with inflammation and back pain. Cells from degenerate and non-mildly-degenerate human IVD were obtained from organ donors and from patients undergoing surgery for low back pain. Gene expression of senescence and SASP markers was evaluated by RT-qPCR in isolated cells, and protein expression of senescence, proliferation, and apoptotic markers was evaluated by immunocytochemistry (ICC). The expression levels of SASP factors were evaluated by enzyme-linked immunosorbent assay (ELISA). Matrix synthesis was verified with safranin-O staining and the Dimethyl-Methylene Blue Assay for proteoglycan content. Western blotting and ICC were used to determine the molecular pathways targeted by the drugs. We found a 40% higher level of senescent cells in degenerate compared to non-mildly-degenerate discs from unrelated individuals and a 10% higher level in degenerate compared to non-mildly-degenerate discs from the same individual. Higher levels of senescence were associated with increased SASP. Both drugs cleared senescent cells, and treatment increased the number of proliferating as well as apoptotic cells in cultures from degenerate IVDs. The expression of SASP factors was decreased, and matrix synthesis increased following treatment. These effects were mediated through the Nrf2 and NFkB pathways.

Highlights

Back pain is a leading cause of disability and loss of workplace productivity in otherwise healthy young and middle-aged individuals
To investigate the contribution of degeneration in human intervertebral disc (IVD) cell senescence, Nucleus pulposus (NP) and annulus fibrosis (AF) cells were obtained from patients undergoing spinal fusion or disc replacement surgery for chronic LBP, or from organ donors
Regardless of the differences in the exact numbers of cells determined as senescent, both methods showed a 40% higher number of senescent cells in degenerate AF and NP tissue when compared to the corresponding non-degenerate tissues (p < 0.05) (Figure 1E)

Summary

Introduction

Back pain is a leading cause of disability and loss of workplace productivity in otherwise healthy young and middle-aged individuals. The degenerating IVD constitutes an inflammatory environment, with the accumulation of senescent cells. Stress-induced premature senescence can be triggered by DNA damage, oxidative stress, adverse load, and inflammation [3]. Permanently non-dividing, remain metabolically active and secrete a range of pro-inflammatory cytokines, chemokines, proteases, and growth factors, called the SASP. The SASP influences the tissue microenvironment, accelerates aging, and contributes to local and systemic dysfunction in diseases such as osteoarthritis [4,5]. It can, in a paracrine manner, induce senescence, which further intensifies tissue deterioration [6]. More specific molecular biomarkers, such as the cyclin-dependent kinase inhibitor 2A ( known as p16INK4a), are used [7]

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Conclusion