Article
Angiotensin II type 1, type 2, and MAS receptors are present in Human Nucleus Pulposus Cells and associated with inflammatory processes
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Authors
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Babak Saravi
- AO Research Institute, Davos, Switzerland, University Medical Center Freiburg, Germany, Freiburg, Germany
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Valentina Basoli
- AO Research Institute Davos, Davos, Switzerland, Davos, Switzerland
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Mauro Alini
- AO Research Institute Davos, Davos, Switzerland, Davos, Switzerland
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Sibylle Grad
- AO Research Institute Davos, Davos, Switzerland, Davos, Switzerland
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Norbert Südkamp
- Albert-Ludwigs-Universität Freiburg, Klinik für Orthopädie- und Unfallchirurgie, Freiburg, Germany
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Hagen Schmal
- University Medical Center Freiburg, Freiburg, Germany
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Zhen Li
- AO Research Institute Davos, Davos, Switzerland
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Gernot Lang
- University Medical Center Freiburg, Freiburg, Germany
| Published: | October 26, 2021 |
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Outline
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Objectives: Low back pain is the main reason for disability worldwide, and degeneration of the intervertebral disc (IDD) is a major cause. Numerous recent studies have described local renin-angiotensin systems in human tissues and indicated that they contain pathological and protective components involved in balancing the cells' inflammatory state. Our previous work demonstrated the existence of local angiotensin II in the human intervertebral disc. Here, we sought to prove the existence and evaluate the role of renin-angiotensin system receptors, namely the angiotensin II type 1 (AGTR1), type 2 (AGTR2), and the MAS receptor (MasR) in human nucleus pulposus (NP) cells.
Methods: Human NP tissue was obtained from four donors. NP cells were isolated and expanded. The cytocompatibility of angiotensin II (0.1 µM-10 µM) was assessed via cell viability analysis after 24, 48, and 72 hours, respectively. The distribution of AGTR1, AGTR2, and MasR in human NP cells was validated with immunofluorescent staining. TNF-alpha (10 ng/mL) was used to induce degeneration and inflammation. Angiotensin II was supplemented in two different concentrations (0.1µM and 10 µM), and gene expression of tissue renin-angiotensin system (tRAS) molecules and inflammatory markers were measured. Secreted nitric oxide (NO), an inflammatory and cell stress marker, was assessed in the conditioned medium.
Results and Conclusion: No cytotoxic effects of angiotensin II were observed in the cell viability analysis. AGTR1, AGTR2, and MAS receptors were identified in human NP cells. The addition of angiotensin II, did not show significant effects on gene expression of inflammatory (TNF-alpha, IL-6, IL-8, TLR4), anti-inflammatory (IL-10), regenerative/ degenerative (ACAN, COL1, MMP1, MMP3) or tRAS markers (AGTR1, ACE, AGTR2, MAS1) in human NP cells. However, there was a significant increase of NO secreted by the cells in the angiotensin II exposed groups compared to the control (p<0.05) or TNF-alpha (p<0.01) only group. The gene expression ratios of pro-inflammatory/anti-inflammatory cytokines IL-6/-10, IL-8/IL-10, and TNF-alpha/IL-10 were positively correlated with the AGTR1/AGTR2 and AGTR1/MAS1 ratios, respectively (Figure 1 [Fig. 1]).
The current data showed that AGTR1, AGTR2, and MAS receptors are expressed within human NP cells. In addition, the relative expression levels of these receptors may play an important role in the inflammatory processes. The correlation of the AGTR1/AGTR2 and the AGTR1/MAS1 ratio with the classical inflammatory markers supports the theory of pathological (AGTR1) and protective (AGTR2, MAS1) tRAS components in humans. The modulation of this system might become of importance in counteracting the detrimental setting present in IDD.
