Monomeric CRP regulates inflammatory responses in human intervertebral disc cells

Abstract

AimsCRP is an acute-phase protein that is used as a biomarker to follow severity and progression in infectious and inflammatory diseases. Its pathophysiological mechanisms of action are still poorly defined. CRP in its pentameric form exhibits weak anti-inflammatory activity. The monomeric isoform (mCRP) exerts potent proinflammatory properties in chondrocytes, endothelial cells, and leucocytes. No data exist regarding mCRP effects in human intervertebral disc (IVD) cells. This work aimed to verify the pathophysiological relevance of mCRP in the aetiology and/or progression of IVD degeneration.MethodsWe investigated the effects of mCRP and the signalling pathways that are involved in cultured human primary annulus fibrosus (AF) cells and in the human nucleus pulposus (NP) immortalized cell line HNPSV-1. We determined messenger RNA (mRNA) and protein levels of relevant factors involved in inflammatory responses, by quantitative real-time polymerase chain reaction (RT-qPCR) and western blot. We also studied the presence of mCRP in human AF and NP tissues by immunohistochemistry.ResultsWe demonstrated that mCRP increases nitric oxide synthase 2 (NOS2), cyclooxygenase 2 (COX2), matrix metalloproteinase 13 (MMP13), vascular cell adhesion molecule 1 (VCAM1), interleukin (IL)-6, IL-8, and Lipocalin 2 (LCN2) expression in human AF and NP cells. We also showed that nuclear factor-κβ (NF-κβ), extracellular signal-regulated kinase 1/2 (ERK1/2), and phosphoinositide 3-kinase (PI3K) are at play in the intracellular signalling of mCRP. Finally, we demonstrated the presence of mCRP in human AF and NP tissues.ConclusionOur results indicate, for the first time, that mCRP can be localized in IVD tissues, where it triggers a proinflammatory and catabolic state in degenerative and healthy IVD cells, and that NF-κβ signalling may be implicated in the mediation of this mCRP-induced state.Cite this article: Bone Joint Res 2023;12(3):189–198.

Assessing the causal relationship between CRP,IL-1α, IL-1β, and IL-6 levels and intervertebral discdegeneration: a two-sample Mendelianrandomization study

“…In vitro experiments found that CRP had a significant pathogenic effect in the intervertebral disc. CRP can also cause a sharp increase in the expression of inflammatory mediators in normal IVD cells 36 . It had been revealed by in vitro experiments that there was a balance between IL-1 (IL-1α and IL-1β ) and its inhibitor IL-1Ra in normal IVD cells, which can maintain local homeostasis 37 .…”

“…These inflammatory factors can induce each other, leading to a step-by-step expansion of the inflammatory response. For example, CRP can increase IL-6 and IL-8 expression in IVD AF cells 36 , IL-1β stimulation significantly enhances IL-6 and IL-8 expression in human IVD cells 10,11 . In vivo experiments, degenerative changes including NP ECM degradation and AF rupture can be observed after IVD injection of inflammatory factors 6 .…”

Benefit of sunlight and melatonin on back pain and inflammation

“…In this month’s edition of Bone & Joint Research, two studies present the role of inflammation on human IVD cells. Ruiz-Fernández et al 6 demonstrated that monomeric CRP (mCRP) increases nitric oxide synthase 2 (NOS2), cyclooxygenase-2 (COX2), matrix metalloproteinase 13 (MMP13), vascular cell adhesion protein 1 (VCAM1), interleukin 6 (IL-6), interleukin 8 (IL-8), and lipocalin 2 (LCN2) expression in annulus fibrosus (AF) cells and in the human nucleus pulposus (NP) immortalized cell lines, revealing for the first time functional activity of mCRP in healthy and degenerative human AF and NP disc cells. The authors highlight that mCRP induces sustained multigenic inflammatory responses in healthy tissues without previous exposure to a pro-inflammatory micro-environment.…”

“…The authors highlight that mCRP induces sustained multigenic inflammatory responses in healthy tissues without previous exposure to a pro-inflammatory micro-environment. The study by Ruiz-Fernández et al 6 shows that the effect of mCRP in healthy and degenerative AF cells is mediated by phosphoinositide 3-kinase (PI3K), extracellular signal-regulated kinase 1/2 (ERK 1/2), and Nuclear Factor-kappaB (NF-κβ) p65 signalling pathways. Another important aspect of this research is that mCRP has multiple cell targets and that the above mCRP mediators are activated in a similar manner both in healthy and degenerative AF disc cells, confirming that mCRP action does not depend on a previous inflammatory state.…”

“…10 Nevertheless, both techniques are expensive, and their application in the wider general public to decrease IVD degeneration is unrealistic and still poses many risks associated with side effects of the therapy. In this line of research, the anti-inflammatory and protective properties of melatonin on nucleus pulposus cells (NPCs) were described by Ruiz-Fernández et al 6 in this month’s edition of Bone & Joint Research .…”