Suppressor of cytokine signalling (SOCS)-3 protects beta cells against IL-1beta-mediated toxicity through inhibition of multiple nuclear factor-kappaB-regulated proapoptotic pathways.
OBJECTIVE
The proinflammatory cytokine IL-1beta induces apoptosis in pancreatic beta cells via pathways dependent on nuclear factor-kappaB (NF-kappaB), mitogen-activated protein kinase, and protein kinase C. We recently showed suppressor of cytokine signalling (SOCS)-3 to be a natural negative feedback regulator of IL-1beta- and IFN-gamma-mediated signalling in rat islets and beta cell lines, preventing their deleterious effects. However, the mechanisms underlying SOCS-3 inhibition of IL-1beta signalling and prevention against apoptosis remain unknown.


METHODS
The effect of SOCS-3 expression on the global gene-expression profile following IL-1beta exposure was microarray-analysed using a rat beta cell line (INS-1) with inducible SOCS-3 expression. Subsequently, functional analyses were performed.


RESULTS
Eighty-two known genes and several expressed sequence tags (ESTs) changed expression level 2.5-fold or more in response to IL-1beta alone. Following 6 h of IL-1beta exposure, 23 transcripts were up-regulated. Of these, several, including all eight transcripts relating to immune/inflammatory response pathways, were suppressed by SOCS-3. Following 24 h of IL-1beta exposure, secondary response genes were detected, affecting metabolism, energy generation, protein synthesis and degradation, growth arrest, and apoptosis. The majority of these changes were prevented by SOCS-3 expression. Multiple IL-1beta-induced NF-kappaB-dependent proapoptotic early response genes were inhibited by SOCS-3 expression, suggesting that SOCS-3 inhibits NF-kappaB-mediated signalling. These observations were experimentally confirmed in functional analyses.


CONCLUSIONS
This study suggests that there is an unexpected cross-talk between the SOCS/IFN and the IL-1beta pathways of signalling in pancreatic beta cells, which could lead to a novel perspective of blocking two important proapoptotic pathways in pancreatic beta cells by influencing a single signalling molecule, namely SOCS-3.
Karlsen
A E
AE
Steno Diabetes Center, Niels Steensensvej 2, 2820 Gentofte, Denmark. aek@novonordisk.com
Heding
P E
PE
Frobøse
H
H
Rønn
S G
SG
Kruhøffer
M
M
Orntoft
T F
TF
Darville
M
M
Eizirik
D L
DL
Pociot
F
F
Nerup
J
J
Mandrup-Poulsen
T
T
Billestrup
N
N
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D005786:Gene Expression Regulation; D007375:Interleukin-1 / Q000633:toxicity*; D016328:NF-kappa B / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
D017931:DNA Primers; D007375:Interleukin-1; D016328:NF-kappa B; D012097:Repressor Proteins; C491410:Socs3 protein, rat; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors; D009569:Nitric Oxide