title: Effects of smoking on human telomerase reverse transcriptase expression in the skin.
abstract: BACKGROUND
  Telomeres are DNA-protein complexes that cap chromosomal ends, promoting chromosome stability. Telomerase is a ribonucleoprotein complex with a direct telomere protective function. Telomere shortening represents lifetime exposure to oxidative stress and is negatively correlated with age, smoking, and mortality. Smoking increases oxidative DNA modification and thus may influence telomere dynamics and human telomerase reverse transcriptase (hTERT) activity.
  
  
  OBJECTIVE
  This study investigated the effect of smoking on hTERT expression in the skin of smokers and non-smokers.
  
  
  METHODS
  A cross-sectional study in 20 current smokers and 20 non-smokers was conducted. Three-mm punch skin biopsies were obtained. Biopsies were examined in routine hematoxylin and eosin staining and immunohistochemistry to investigate expression of hTERT.
  
  
  RESULTS
  All skin biopsies from smokers and non-smokers showed cytoplasmic staining in epidermal cells. Sections positive for hTERT expression showed nuclear and some nucleolar staining in cells of the basal and suprabasal layers. In the dermis, hTERT expression was present in some skin appendages. The epidermis of smokers showed positive hTERT in 55% and negative hTERT in 45% of biopsies. The epidermis of non-smokers showed positive hTERT in 70% and negative hTERT in 30% of biopsies (P > 0.05). Among smokers, 20% showed positive and 80% showed negative hTERT expression in the dermis. Among non-smokers, 30% showed positive and 70% showed negative hTERT expression in the dermis. A higher mean pack year value was found in subjects with negative rather than positive hTERT expression (P < 0.01). In addition, pack year was inversely correlated with hTERT expression in the epidermis (P < 0.05): as pack year increased, hTERT expression decreased. Mean pack year values were higher in subjects with negative rather than positive hTERT expression in the dermis (P < 0.01).
  
  
  CONCLUSIONS
  This research focused on smoking as a lifestyle factor that may alter telomere length and subsequently telomerase kinetics in the skin. Findings showed a higher percentage of negative hTERT in the epidermis and dermis among smokers compared with non-smokers and a higher percentage of positive hTERT expression among non-smokers (not significant). The results of this work showed a statistically significant higher mean pack year count among cases with negative rather than positive hTERT expression in the epidermis and dermis. Pack year count was inversely correlated to hTERT scoring in the epidermis (percentage of cells stained) and hTERT expression in the dermis. Thus, smoking may affect telomerase activity in the skin, thereby contributing to skin aging.
authors.affiliation: Department of Dermatology and Venereology, Ain Shams University, Cairo, Egypt.
authors.forename: Ranya A
authors.initials: RA
authors.lastname: Lotfi
authors.forename: Khaled M
authors.initials: KM
authors.lastname: El Zawahry
authors.forename: Zeinab A
authors.initials: ZA
authors.lastname: Kamar
authors.forename: Zamzam
authors.initials: Z
authors.lastname: Hashem
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D006801:Humans; D008297:Male; D012867:Skin / Q000378:metabolism*; D012907:Smoking; D019098:Telomerase / Q000096:biosynthesis* / Q000187:drug effects*
chemical_list: C509186:TERT protein, human; D019098:Telomerase