Assessment of skin absorption and irritation potential of arachidonic acid and glyceryl arachidonate using in vitro diffusion cell techniques

Abstract

Arachidonic acid (AA), a precursor of pro-inflammatory mediators, and its glycerin ester, glyceryl arachidonate (GA), are reportedly used in cosmetic products. In vitro skin penetration of AA and GA and GA's ester hydrolysis was determined in flow-through diffusion cells. AA penetration with human and rat skin was 19.5% and 52.3% of the applied dose respectively, a substantial amount of which remained in the skin at 24h. Similar penetration results were obtained with GA in human skin. However, GA penetration through cultured skin (EpiDerm) was 51% of the applied dose, almost all of which appeared in the receptor fluid. At least 27.8% of GA penetrating skin was hydrolyzed to AA. In vitro methods were used to assess skin irritation in diffusion cells. Skin irritation of AA, sodium lauryl sulfate (SLS), and Tween 80 was determined by changes in transepidermal water loss (TEWL), skin viability (3-(4,5-dimethylthiaxol-2-yl)-2,5-diphenyltetrazolium bromide, MTT, formation), and cytokine release (IL-1alpha). SLS irritation was much less pronounced in an emulsion versus an aqueous vehicle. No significant irritation was observed in vitro from AA in an emulsion. This work predicts that AA would penetrate human skin in vivo and that it could be formed in skin from topically applied GA.

In VitroSkin Permeation Methodology

“…A major potential variant in the design of in vitro skin permeation experiments is the nature of the skin membrane. Animal skin has been widely used as a substitute for human skin (see e.g., Bronaugh et al 17 ) but, although some animal models are still occasionally promoted (e.g., Barbero and Frasch 18 ), such models are generally believed to give unreliable results (see Eppler et al 19 ). On the basis that the most reliable model for human skin penetration and permeation in vivo is human skin in vitro , this membrane will be the subject of the following discussion.…”

Methods for in vitro skin metabolism studies

“…The skin absorption and metabolism of arachidonic acid (AA) and glyceryl arachidonate (GA) were assessed in diffusion cells following application in an emulsion vehicle (8). The skin absorption of AA was 19.5% and 52.3% of the applied dose in human and rat skin, respectively, with most of the absorbed material remaining in the skin at the end of the studies.…”

“…Many esters are hydrolyzed by esterase to their parent alcohol and acid molecules (6)(7)(8)(9). Primary amines are frequently acetylated during absorption through skin (10)(11)(12).…”

Antioxidant capacity of 3D human skin EpiDermTM model: effects of skin moisturizers

“…In the recent years, reconstructed human skin models have been developed and used to test phototoxicity, irritancy, corrosivity, substance transport and the effects of numerous chemical groups [13][14][15][16][17][18][19][20][21]. In fact, the reconstructed human skin models have been proven to be efficient alternatives to animal testing [20], thus, these models are currently widely used.…”