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Superoxide dismutase 3 suppresses hyaluronic acid fragments mediated skin inflammation by inhibition of toll-like receptor 4 signaling pathway: superoxide dismutase 3 inhibits reactive oxygen species-induced trafficking of toll-like receptor 4 to lipid rafts.

AIMS
Hyaluronic acid (HA) is a component of the extracellular matrix and has been extensively applied for cosmetic, therapeutic, and antiaging purposes. However, HA fragments (HAFs) cause adverse effects. Considering that UV-exposure produces HAF that accumulated on the skin, the role of HAF in skin inflammation and its precise mechanism needs to be clarified, and strategies for the prevention of skin inflammation are necessary.


RESULTS
We found that extracellular superoxide dismutase (SOD), SOD3, suppresses HAF-mediated skin inflammation, while HAF mediated skin inflammation, macrophages and dendritic cells (DCs) dominantly infiltrate, up-regulating inflammatory cytokines and chemokines receptors. However, keratinocytes indirectly responded to HAF. Instead, epidermis containing keratinocytes were stimulated by secreted molecules from HAF-treated macrophages or DC and produced inflammatory molecules including chemokines, which, in turn, led to skin inflammation. This orchestrated inflammatory response was inhibited by SOD3. In addition, SOD3 inhibited DC maturation by suppressing the expression of major histocompatibility complex II, CD80, and CD86. Interestingly, these responses did not occur in Toll-like receptor 4 (TLR4) deficient mice. Similar to lipopolysaccharide (LPS), HAF promoted TLR4 translocation into the lipid rafts to initiate signaling. This trafficking was mediated, at least in part, by NAPDH oxidase-dependent reactive oxygen species (ROS) generation. Subsequently, nuclear factor kappa B (NFκB) subunit, p65, was recruited the promoters of genes encoding inflammatory molecules. This inflammatory machinery was blocked by SOD3.


INNOVATION AND CONCLUSION
Thus, we propose that SOD3 might provide an effective strategy for the treatment of HAF-mediated skin inflammation.