Targeting Nsun2-Mediated M⁵C Modification Attenuates Chondrocyte Senescence And Nlrp3 Activation In Osteoarthritis

A recent study found that increased levels of the protein NSUN2 and a specific RNA modification called m5C contribute to the aging and inflammation of cartilage cells in osteoarthritis, and targeting NSUN2 could offer a new therapeutic approach.

Osteoarthritis (OA) is a widespread joint disease that causes pain and disability due to the breakdown of cartilage, the flexible tissue cushioning our joints. A key factor in its development is cellular senescence, a process where cells stop dividing and accumulate, contributing to tissue damage and inflammation.

Researchers have been investigating the role of specific molecular changes in OA progression. One such change involves a modification on RNA molecules called 5-methylcytosine (m5C) and the protein, NSUN2, responsible for adding this modification.

This study revealed that both NSUN2 and m5C modifications are significantly elevated in the damaged cartilage of individuals with OA and in aged mice. Further investigation showed that NSUN2 actively promotes the aging of cartilage cells (chondrocyte senescence) and triggers the activation of the NLRP3 inflammasome, a crucial pathway involved in inflammation.

The mechanism behind this involves NSUN2 working with another protein, ALYREF, to stabilize and facilitate the movement of a specific messenger RNA (mRNA) called IP3R3 out of the cell’s nucleus. This leads to an increase in IP3R3 protein, which then causes an overload of calcium within the cells.

Crucially, when the researchers reduced the activity of NSUN2 or blocked IP3R3, they observed a protective effect on mouse cartilage, preventing both cellular aging and inflammation, and ultimately slowing down the progression of OA. These findings suggest that targeting NSUN2 could be a promising new strategy for developing treatments for osteoarthritis.

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Source: link to paper