The expression pattern of N-acetyltransferase 1 in healthy human skin

Abstract

Background: N-acetyltransferase 1 (NAT1) is an enzyme expressed among others in keratinocytes in human skin. NAT1 is important in the biotransformation of aromatic amines, an important example being p-phenylenediamine (PPD), a hair dye molecule. Unoxidized PPD penetrates the skin and is N-acetylated by NAT1.

Objectives: To investigate in detail the expression pattern of NAT1 in human skin.

Materials and methods: Cryosections obtained from healthy human skin were stained for NAT1 and expression patterns were observed. NAT1 double stainings were performed with antibodies against different cellular organelles to determine expression patterns.

Result: A speckled, granular expression of NAT1 was seen predominantly in the stratum basale. NAT1 was expressed in a cytoplasmic pattern, perinuclear, and in the nucleus. No co-localisation was seen with the selected cellular organelles. Local differences in NAT1 expression patterns were observed between donors and between different biopsies obtained from the same donor.

Conclusions: NAT1 is expressed predominantly in the stratum basale and can be found in the cytoplasm, nucleus, and perinuclear in human skin. Further studies should be performed to investigate expression of NAT1 in a larger sample size.

Keywords: N-acetyltransferase 1; P-phenylenediamine; contact allergy; human skin; immunofluorescence.

FIGURE 1

N‐acetyltransferase 1 is expressed in different epidermal layers in healthy human skin. (A‐E, G) Skin biopsies of six different donors were included (see Table 1). Two donors provided two biopsies each: donor 5 (E, F) and donor 6 (G, H). (A‐G) Biopsies were incubated with monoclonal rabbit antibody EPR3221 (2) (green). (H) Biopsy included a control staining incubated with polyclonal rabbit antibody ES‐195 (green). (I) Tissue section presents a negative control (omission of first antibody) from biopsy (G). In all skin tissues, a speckled/granular expression located primarily in the stratum basale and, to a lesser extent, in the upper epidermis were observed. In all skin biopsies expression was found in the nuclei (blue). The levels of expression in the cytoplasm varied between donors. White bar is 25 μm

FIGURE 2

N‐acetyltransferase 1 (NAT1) is expressed in the cytoplasm. Double staining for NAT1 (red) and desmoglein 1 (green). Tissue sections were taken from biopsy E (see Table 1). Single focal plane scans at the height of z‐stack (μm) from the glass slide shows NAT1 is present in the cytosol as it does not localize with membrane bound desmoglein 1. NAT1 is present perinuclear and nuclear (arrows) as well. White bar is 5 μm

FIGURE 3

No co‐localization of N‐acetyltransferase (NAT1) and different organelle proteins. (A) mitochondria (Mito; MTCO2) are visible both perinuclear as well as free in the cytoplasm. (B) endosomes (EEA1; clone 14), (C) golgi apparatus (Golgin97) and (D) lysosomes (Lys; H4A3) have a cytoplasmic speckled pattern while (E) negative controls show no fluorescence in the presence of a non‐sense 1st Ab (COL14). NAT1 (green, EPR3221 [2]) does not co‐localize with either of these four organelle proteins (red, A‐D). White bar = 0.5 μm