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Published on: March 18, 2022
mTORC2 inhibition by JR-AB2-011 improves IL-1β-induced inflammation, catabolic response, and apoptosis in human
Meryem Temiz-Resitoglu1, Zainab Sabrie2, Rukiye Nalan Tiftik3
1Department of Pharmacology, Faculty of Pharmacy, Mersin University, Mersin, Turkey. meryemtemiz88@gmail.com.
Abstract:
Osteoarthritis (OA) is a very common chronic joint condition marked by inflammation and cartilage loss. mTOR is a well-known mediator of inflammation, cell survival, and aging; however, its role in OA has not been determined. To explore the role of mTORC2 in OA-and associated pathological changes, we examined the contribution of mTORC2-mediated Akt, rictor and IκB-α/NF-κB p65 pathway in interleukin (IL)-1β-treated human chondrocytes. We focused on the protein expression of proinflammatory cytokines and catabolic and apoptotic factors, including TNF-α, IL-6, iNOS, MMP13, Bax, and caspase3, which may occur through this signalling pathway in IL-1β-treated chondrocytes. Chondrocytes were cultured and treated with either 2 ng/mL IL‑1β alone or in combination with increasing concentrations of JR-AB2-011 (50, 100, or 250 µM), a selective mTORC2 inhibitor. The protein levels of phosphorylated (p)‑Akt, Akt, rictor, p-NF-κB p65, NF-κB p65, IκB-α, p-IκB-α, iNOS, MMP13, Bax, and caspase3 were evaluated by Western blotting. In IL-1β-stimulated chondrocytes, mTORC2 activity was increased with increased phosphorylation of Akt and expression of rictor. IL-1β increased the expression of p-IκBα, p-NF-κB p65, NF-κB p65, IL-6, TNF-α, iNOS, Bax, and caspase3 proteins and decreased the expression of IκB-α. All of these IL-1β-induced alterations were prevented by JR-AB2-011. The main novel finding in the present study is that selective mTORC2 inhibition by JR-AB2-011 prevents the inflammatory, catabolic, and apoptotic responses induced by IL-1β via modulation of IκB-α/NF-κB activity. Therefore, we demonstrated a previously unknown function of mTORC2 inhibition that seems to be a potential therapeutic target for OA.
Insights
Selective inhibition of mTORC2 prevents inflammation and cartilage breakdown in osteoarthritis (OA). This study shows mTORC2 inhibition is a potential therapeutic strategy for OA by blocking key inflammatory pathways.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Osteoarthritis (OA) is a prevalent chronic joint disease characterized by inflammation and cartilage degradation.
- The role of the mechanistic target of rapamycin (mTOR) pathway, specifically mTORC2, in OA pathogenesis is not well understood.
- mTOR is implicated in inflammation, cell survival, and aging processes.
Purpose of the Study:
- To investigate the role of mTORC2 in interleukin (IL)-1β-induced inflammatory, catabolic, and apoptotic responses in human chondrocytes.
- To examine the involvement of the Akt/rictor and IκB-α/NF-κB p65 signaling pathways in OA pathogenesis.
- To evaluate the therapeutic potential of a selective mTORC2 inhibitor, JR-AB2-011, in an in vitro OA model.
Main Methods:
- Human chondrocytes were treated with IL-1β alone or in combination with the mTORC2 inhibitor JR-AB2-011.
- Protein expression levels of key signaling molecules (p-Akt, Akt, rictor, p-NF-κB p65, NF-κB p65, IκB-α, p-IκB-α) and pathological factors (TNF-α, IL-6, iNOS, MMP13, Bax, caspase3) were assessed using Western blotting.
- mTORC2 activity was inferred from Akt phosphorylation and rictor expression.
Main Results:
- IL-1β stimulation increased mTORC2 activity, evidenced by elevated p-Akt and rictor levels.
- IL-1β upregulated pro-inflammatory (IL-6, TNF-α, iNOS), catabolic (MMP13), and apoptotic (Bax, caspase3) factors, alongside increased p-IκBα and p-NF-κB p65, while decreasing IκB-α.
- Treatment with JR-AB2-011 effectively reversed all IL-1β-induced changes, inhibiting inflammatory, catabolic, and apoptotic responses by modulating IκB-α/NF-κB signaling.
Conclusions:
- mTORC2 plays a significant role in mediating IL-1β-induced inflammatory, catabolic, and apoptotic processes in human chondrocytes.
- Selective inhibition of mTORC2 by JR-AB2-011 effectively suppresses these OA-associated pathological responses.
- mTORC2 inhibition represents a promising therapeutic target for osteoarthritis treatment.
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