The intracellular 52-kd Ro/SSA autoantigen in keratinocytes is up-regulated by tumor necrosis factor alpha via tumor necrosis factor receptor I.
OBJECTIVE
Previous studies have shown that the nuclear Ro/SSA autoantigens involved in photosensitive cutaneous lupus manifestations are regulated by ultraviolet B (UVB) irradiation. UVB exposure triggers the release of tumor necrosis factor alpha (TNFalpha) from keratinocytes in the epidermis and from mast cells in the dermis. The present study aimed to characterize the effect of TNFalpha on messenger RNA (mRNA) and protein expression of the intracellular 52-kd Ro/SSA autoantigen in primary human keratinocytes and to elucidate the TNFalpha receptor (TNFR) signaling pathways mediating this effect.


METHODS
Expression of 52-kd Ro/SSA mRNA in primary human keratinocytes was investigated by quantitative real-time polymerase chain reaction (LightCycler system) using GAPDH as the housekeeping gene. Expression of 52-kd Ro/SSA protein was studied by flow cytometry after staining intracellular protein with IgG purified from an anti-52-kd Ro/SSA-positive serum. TNFR function was assessed by culturing cells in the presence and absence of neutralizing antibodies directed against the TNFR subunits TNFRI and TNFRII.


RESULTS
TNFalpha-induced up-regulation of 52-kd Ro/SSA mRNA expression peaked at 4 hours, followed by up-regulation of intracellular 52-kd Ro/SSA protein expression at 24 hours, independently of apoptosis. Between different donors, a high variability of both constitutive expression levels and TNFalpha-induced changes in 52-kd Ro/SSA mRNA and protein expression was observed. The up-regulatory effect of TNFalpha on 52-kd Ro/SSA mRNA and protein expression was inhibited by anti-TNFRI antibodies but enhanced by anti-TNFRII antibodies.


CONCLUSIONS
The finding that TNFalpha up-regulates 52-kd Ro/SSA expression in keratinocytes via TNFRI suggests that it may play a role in the pathogenesis of anti-Ro/SSA-associated cutaneous lupus erythematosus.
Gerl
Velia
V
Charité Hospital, Center for University Medicine in Berlin, and German Rheumatism Research Center, Berlin, Germany.
Hostmann
Björn
B
Johnen
Christa
C
Waka
Aderajew
A
Gerl
Markus
M
Schumann
Frank
F
Klein
Rolf
R
Radbruch
Andreas
A
Hiepe
Falk
F
D017209:Apoptosis; D001324:Autoantigens / Q000276:immunology*; D002478:Cells, Cultured; D015870:Gene Expression; D006801:Humans; D015603:Keratinocytes / Q000276:immunology*; D008178:Lupus Erythematosus, Cutaneous / Q000276:immunology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor / Q000502:physiology*; D012261:Ribonucleoproteins / Q000032:analysis*; D015398:Signal Transduction / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D015854:Up-Regulation; D000099207:SS-A Antigen
D001324:Autoantigens; D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor; D012261:Ribonucleoproteins; D014409:Tumor Necrosis Factor-alpha; D000099207:SS-A Antigen