Rigin

Rigin (GQPR tetrapeptide core) is derived from the IgG Fc region sequence that naturally modulates immune activity. In skin cells, it reduces IL-6 production by inhibiting NF-kB-mediated transcription in fibroblasts and keratinocytes. IL-6 is a pro-inflammatory cytokine that drives matrix metalloproteinase (MMP) upregulation, collagen degradation, and inflammatory signaling cascades in skin. Chronic elevation of IL-6 in aging skin (inflammaging) contributes to structural degradation. The palmitoyl group enhances skin penetration through the stratum corneum.

The GQPR sequence mimics a fragment of the IgG Fc CH2-CH3 interface that interacts with complement receptors. By competing with IgG Fc for complement C3b binding, rigin may reduce complement-mediated inflammatory amplification in skin. This mechanism is distinct from most cosmetic peptides and provides an immune-modulating component relevant to inflammatory skin conditions and photoaged skin with elevated complement activation.

Rigin reduces IL-6 and TNF-alpha secretion from lipopolysaccharide-stimulated fibroblast cultures at concentrations of 10-100 ug/mL. In skin explant models, rigin reduces prostaglandin E2 levels and reduces post-UV inflammatory response markers. These studies are conducted by Sederma (the developer) and provide the mechanistic basis for anti-inflammatory claims in product literature.

In a 4-week consumer study using 3D optical imaging, rigin at 0.01% in eye cream reduced periorbital puffiness area by approximately 20% compared to vehicle. This is attributed to reduction in inflammatory mediator-driven vascular permeability and lymphatic fluid retention in the periorbital zone. The methodology is cosmetic claims research rather than pharmaceutical trial standard.