Alpha hydroxyacids modulate stratum corneum barrier function

Abstract

Alpha hydroxyacids (AHAs) are used to enhance stratum corneum desquamation and improve skin appearance. The purpose of this study was to evaluate whether some AHAs improve skin barrier function and prevent skin irritation. Eleven healthy subjects (aged 28 +/- 6 years, mean +/- SD) entered the study. Six test sites of 8 x 5 cm (four different AHAs, vehicle only (VE) and untreated control (UNT) were selected and randomly rotated on the volar arm and forearm. The four different AHAs at 8% concentration in base cream were glycolic acid (GA), lactic acid, tartaric acid (TA) and gluconolactone (GLU). The products were applied twice a day for 4 weeks (2 mg/cm2). At week 4, a 5% sodium lauryl sulphate (SLS) challenge patch test was performed under occlusion for 6 h (HillTop chamber, 18 mm wide) on each site. Barrier function and skin irritation were evaluated by means of evaporimetry (Servomed EP-1) and chromametry (a* value, Minolta CR200) weekly, and at 0, 24 and 48 h after SLS patch removal. No significant differences in transepidermal water loss (TEWL) and erythema were observed between the four AHAs at week 4. After SLS challenge, GLU- and TA-treated sites resulted in significantly lower TEWL compared with VE, UNT (P < 0.01) and GA (P < 0.05) both at 24 and 48 h. Similarly, a* values were significantly reduced after irritation in GLU- and TA-treated sites. This study shows that AHAs can modulate stratum corneum barrier function and prevent skin irritation; the effect is not equal for all AHAs, being more marked for the molecules characterized by antioxidant properties.

Extracellular pH Controls NHE1 Expression in Epidermis and Keratinocytes: Implications for Barrier Repair

“…In previous studies, we demonstrated that transient perturbations in SC pH, induced by topical applications of either superbases (Hachem et al, 2003) or polyhydoxyl acids (Berardesca et al, 1997), do not alter basal permeability barrier function, as assessed by transepidermal water loss (TEWL) (see also Ritter et al, 2001). Moreover, prior studies have shown that treatment with agents such as 1,1,3,3-tetramethylguanidine (TMG) (a superbase) also does not produce cell toxicity, as assessed by light or electron microscopy (Berardesca et al, 1997;Hachem et al, 2003). To determine whether SC acidification/ neutralization regulates NHE1 expression independent of barrier status, either TMG (a superbase) or lactobionic acid (LBA) (a polyhydroxyl acid) was applied to the flanks of Acidity at the skin surface decreases after barrier disruption.…”

“…In prior studies, a-hydroxy-acids, such as gluconolactone (GL), another polyhydroxyl acid, were shown to accelerate permeability barrier recovery and prevent skin irritation (Berardesca et al, 1997). This effect was not equal among all ahydroxy-acids.…”

“…This effect was not equal among all ahydroxy-acids. Those characterized by antioxidant properties (i.e., LBA, GL) were superior to glycolic or lactic acid (Berardesca et al, 1997). Additionally, topical treatment with either glycolic and lactic acid appears to enhance UVB-and UVA-induced tanning (Tsai et al, 2000;Kaidbey et al, 2003), which does not seem to occur with GL (Green et al, 1999;Rona et al, 2004).…”

“…The superbase alkalinization model has been previously described to be non-toxic on mouse skin in topical application (Hachem et al, 2003). In addition, LBA is used in cosmetic preparations (Berardesca et al, 1997).…”

Biology of percutaneous penetration

“…Increased percutaneous penetration can result. In contrast, hyperacidification of the stratum corneum in hairless mice using lactobionic acid (LBA) and gluconolactone (GL) can enhance permeability barrier homeostasis and stratum corneum desquamation (32). Drugs usually exist in unionized or ionized forms depending on their pKa (drug dissociation constant) relative to skin pH.…”