How UV Causes Skin Damage
When skin is exposed to ultraviolet (UV) light, especially UVA (315–400 nm), the rays penetrate deep into the dermis. This leads to:
Collagen breakdown – UV activates enzymes called MMPs (matrix metalloproteinases) that degrade collagen fibers.
AP-1 activation – A stress-response protein complex that increases MMP activity while reducing collagen production.
Visible changes – Wrinkles, sagging, loss of elasticity, and uneven tone are classic signs of UV-driven photoaging.
How COS Interacts With UV
The 3–5 kDa chito-oligosaccharide (COS) fraction shows strong activity against these processes:
UV Absorption – COS absorbs light across UVA and UVB ranges, lowering the amount of harmful energy that reaches dermal cells.
Cellular Protection – In fibroblast studies, COS improved cell survival under UVA exposure in a dose-dependent manner.
Enzyme Regulation
MMP Inhibition: COS reduced levels of MMP-1, MMP-8, and MMP-13, which normally break down collagen.
TIMP Support: At the same time, COS boosted TIMP-1 and TIMP-2, the natural inhibitors of MMPs.
→ This combination helps slow collagen degradation.
AP-1 Pathway Down-Regulation
COS was shown to down-regulate AP-1 signaling, the transcription factor that drives MMP activity.
By calming AP-1, COS prevents the stress loop that accelerates collagen loss under UV.
Boosting Collagen Synthesis
COS increased markers of collagen I, III, and IV, the structural proteins that maintain skin’s firmness and resilience.
It also restored procollagen levels reduced by UVA, indicating better support for new collagen production.
Plain-English Takeaway
3–5 kDa COS acts like a dual shield:
Blocks and absorbs UV light to reduce damage at the surface.
Regulates enzymes and signaling pathways inside fibroblasts, leading to less collagen breakdown and more collagen synthesis.
This makes COS a promising cosmetic active for photo-exposed skin — not as a sunscreen, but as an ingredient that supports skin structure and resilience when used alongside approved UV filters.