In vivo studies of aquaporins 3 and 10 in human stratum corneum

Abstract

Aquaporins (AQPs) constitute one family of transmembrane proteins facilitating transport of water across cell membranes. Due to their specificity, AQPs have a broad spectrum of physiological functions, and for keratinocytes there are indications that these channel proteins are involved in cell migration and proliferation with consequences for the antimicrobial defense of the skin. AQP3 and AQP10 are aqua-glyceroporins, known to transport glycerol as well as water. AQP3 is the predominant AQP in human skin and has previously been demonstrated in the basal layer of epidermis in normal human skin, but not in stratum corneum (SC). AQP10 has not previously been identified in human skin. Previous studies have demonstrated the presence of AQP3 and AQP10 mRNA in keratinocytes. In this study, our aim was to investigate if these aquaporin proteins were actually present in human SC cells. This can be seen as a first step toward elucidating the possible functional role of AQP3 and AQP10 in SC hydration. Specifically we investigate the presence of AQP3 and AQP10 in vivo in human SC using "minimal-invasive" technique for obtaining SC samples. SC samples were obtained from six healthy volunteers. Western blotting and immunohistochemistry were used to demonstrate the presence of AQP3 as well as AQP10. The presence of AQP3 and AQP10 was verified by Western blotting, allowing for detection of proteins by specific antibodies. Applying immunohistochemistry, cell-like structures in the shape of corneocytes were identified in all samples by AQP3 and AQP10 antibodies. In conclusion, identification of AQP3 and AQP10 protein in SC in an in vivo model is new. Together with the new "minimal-invasive" method for SC collection presented, this opens for new possibilities to study the role of AQPs in relation to function of the skin barrier.

Aquaporin-3 Re-Expression Induces Differentiation in a Phospholipase D2-Dependent Manner in Aquaporin-3-Knockout Mouse Keratinocytes

“…Aquaporin 3 (AQP3) not only transports water but also allows movement of small solutes like glycerol across the plasma membrane (Hara and Verkman, 2003;Hara-Chikuma and Verkman, 2005). In mammalian skin, AQP3 is expressed in the basal layer as well as in the suprabasal layers of the epidermis (Verkman and Mitra, 2000;Hara-Chikuma and Verkman, 2008;Lee et al, 2012;Guo et al, 2013), whereas its presence in the stratum corneum is controversial (Sougrat et al, 2002;Jungersted et al, 2013). Studies characterizing AQP3-knockout mice suggest that this aquaglyceroporin is required for maintaining normal stratum corneum hydration, skin elasticity, wound healing, epidermal biosynthesis, and barrier recovery (Ma et al, 2002;Hara-Chikuma and Verkman, 2008).…”

N-Acetylglutaminoyl-S-farnesyl-l-cysteine (SIG-1191): an anti-inflammatory molecule that increases the expression of the aquaglyceroporin, aquaporin-3, in human keratinocytes

“…AQP3 is mostly expressed at the basal layer of the epidermis [46] and its expression is downregulated by UVB irradiation [26, 46]. It is present in both viable and stratum corneum layers of the epidermis [28], thus suggesting the functional role in water transport. Interestingly, the water loss prevention of the stratum corneum is linked to the specific expression of AQP3 between the dermis and basal layers of the epidermis, thus operating as a “water-clamp” to prevent water loss gradient from the dermis to the stratum corneum [47].…”

“…Thirteen mammalian AQPs have been identified over the last 23 years with differing functions dependent on localization [23]. To date, AQP3, AQP9 and AQP10, called aqua-glycoporins because they transport water, glycerol and possibly other small solutes, have been found in skin [28, 42]. AQP3, the most abundant AQP found in skin, is located in the basal, suprabasal and stratum corneum layers [2, 18, 28, 33, 51] of the epidermis at the cell periphery [47].…”

Epidermal aquaporin‐3 downexpression in symmetrical acrokeratoderma

“…Although most reports including this report found that AQP3 is expressed only in strata basale and spinosum in human epidermis, 2,5,6 it was detected in stratum corneum using minimal-invasive technique. 7 Both water and glycerol permeability are remarkably decreased in the epidermis of AQP3-knockout mice, and glycerol transport impairment mainly contribute to reduced stratum corneum hydration and increased TEWL. 2,3 AQP3 overexpression contributes to epidermal hyperplasia, barrier disruption and incremental proinflammatory cytokines in atopic dermatitis.…”

“…Using immunohistochemical technique with anti-AQP3 monoclonal antibody (clone EPR19932, ab215853; 1:500 dilution; Abcam, Cambridge, MA, USA), AQP3 protein expression was detected in lesional and perilesional normal-appearing skin on the wrists of 12 SAK patients (10 males and two females; 20.83 AE 7.69 years, range 7-39) and control skin on the forearms of 14 healthy subjects (seven males and seven females; 26.86 AE 5.95 years, range 15-35). AQP3 expression was assessed by addition of positive percentage of stained cells (<10% = 1; 11-33% = 2; 34-66% = 3; >67% = 4) and staining intensity (weak = 1; moderate = 2; strong = 3) and scored as 1+ (2-3), 2+ (4-5) and 3+ (6)(7). Results were analysed using Kruskal-Wallis and Mann-Whitney tests.…”