Dokument: Characterization of molecular mechanisms involved in intrinsic and extrinsic skin aging of in situ aged normal human dermal fibroblasts

Titel:	Characterization of molecular mechanisms involved in intrinsic and extrinsic skin aging of in situ aged normal human dermal fibroblasts
URL für Lesezeichen:	https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=57435
URN (NBN):	urn:nbn:de:hbz:061-20210917-112415-6
Kollektion:	Dissertationen
Sprache:	Englisch
Dokumententyp:	Wissenschaftliche Abschlussarbeiten » Dissertation
Medientyp:	Text
Autor:	Schneider, Sabine [Autor]
Dateien:	[Dateien anzeigen] Adobe PDF [Details] 20,49 MB in einer Datei [ZIP-Datei erzeugen] Dateien vom 13.09.2021 / geändert 13.09.2021
Beitragende:	Prof. Dr. Krutmann, Jean [Betreuer/Doktorvater] Prof. Dr. Martin, William [Gutachter]
Dewey Dezimal-Klassifikation:	500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie
Beschreibung:	Aging is principally driven by the combination of intrinsic and extrinsic factors. Whereas intrinsic factors (genetic constitution, somatic capacity, composition) define the scope of possibilities, extrinsic factors such as the individual’s behavior and the resulting exposure to environmental factors determine to what extent this is exploited. The skin is particularly suited for comparing intrinsic versus extrinsic aging, since the entire skin ages intrinsically, but only certain areas (e.g. face, neck) are subjected to environmental influences and thus to extrinsic aging. Textbook knowledge generally assumes that extrinsic skin aging superimposes intrinsic skin aging, but corresponding studies and thus scientific evidence to show that this is indeed the case are scarce. To assess this relationship more closely, we have focused on dermal fibroblasts (NHDF), because aging of this non-proliferating, skin-resident cell population is thought to be of key importance to both intrinsic and extrinsic skin aging. Specifically, we have compared NHDF isolated from buttocks skin, as an example of intrinsically aged skin (NHDFINT), versus neck skin, as a skin area representative for extrinsically aged skin (NHDFEXT). These cells aged in situ in human skin, i.e. they were obtained from human volunteers of three different age groups [young (Y), 20-25 yr.; middle-aged (M), 36-49 yr.; old (O), 60-64 yr.]. Performing proteome analysis via quantitative, label-free mass spectrometry, we found that NHDFINT versus NHDFEXT fundamentally differed in age-dependent trajectories of protein levels. Accordingly, quantitative assessments demonstrated that NHDFINT exhibited gradual, almost linear changes in protein abundances over all three age groups (YM>O). This was in sharp contrast to NHDFEXT, in which alterations of protein quantities showed a non-linear kinetic. Specifically, almost no changes could be detected in cells isolated from Y versus M probands (Y=M), whereas a marked difference was observed between cells derived from M versus O donors (M<>O). These changes were very pronounced and outreached the ones found in NHDFINT. At a qualitative level, it appeared that in NHDFEXT proteins involved in cellular respiration were among the most strongly affected. For example, tricarboxylic acid (TCA) cycle-related proteins were upregulated in NHDFEXT versus NHDFINT of M donors and at the same time, NAD+ levels were reduced and ADP/ATP ratios elevated. These observations indicate for Y and M donors, that NHDFEXT, in contrast to NHDFINT, show a compensatory behavior to cope with a situation characterized by enhanced energy demands and an energy deficit. However, when NHDFEXT of M versus O donors were compared, NHDFEXT of O donors seemed to have passed a “tipping point”, at which compensatory mechanisms failed. Accordingly, we observed a dramatic decline of TCA cycle-associated proteins accompanied by a severe reduction of protein diversity and protein biosynthesis, i.e. two biological processes known to consume vast amounts of ATP. Taken together these findings suggest an energy crisis in NHDFEXT of O donors that seems to cause a collapse of compensatory metabolic processes and protein production. In NHDFEXT versus NHDFINT of M donors, this energy deficit was associated with decreased sirtuin-1 (SIRT1) protein levels and compromised deacetylation of lysine 56 of histone 3 (H3K56) and lysine 16 of histone 4 (H4K16). Also, mitochondrial superoxide levels and ROS-related gene expression were elevated in NHDFEXT versus NHDFINT of M probands. Of note, the mitochondrial phenotype present in NHDFEXT of M donors could be rescued upon treatment of these cells with the NAD+ precursor β-nicotinamide mononucleotide (NMN). Specifically, NAD+ concentration, ADP/ATP ratio, levels of TCA cycle-related proteins, SIRT1 abundance and deacetylation of H3K56 and H4K16 were normalized to levels observed in age group-matched NHDFINT. These studies demonstrate that the relationship between intrinsic and extrinsic skin aging might be more complex than originally thought and different from a simple superimposition, because age-dependent proteomic/metabolic changes in NHDFEXT follow a substantially different kinetic compared to NHDFINT. They identify restricted availability of NAD+ as a factor driving metabolic/epigenetic alterations contributing to extrinsic skin aging. It is thus tempting to speculate that treatment of NHDFEXT with NMN might be efficient to switch NHDFEXT into NHDFINT and thereby protect these cells from reaching the “tipping point”.
Lizenz:	Urheberrechtsschutz
Fachbereich / Einrichtung:	Sonstige Einrichtungen/Externe » An-Institute » Institut für Umweltmedizinische Forschung (IUF) an der HHU
Dokument erstellt am:	17.09.2021
Dateien geändert am:	17.09.2021
Promotionsantrag am:	18.05.2021
Datum der Promotion:	06.09.2021