The glycolipid sulfatide protects insulin-producing cells against cytokine-induced apoptosis, a possible role in diabetes.
OBJECTIVE
Cytokine-induced apoptosis is recognised as a major cause of the decline in β-cell mass that ultimately leads to type 1 diabetes mellitus. Interleukin-1β, interferon-γ and tumour necrosis factor-α in conjunction initiate a series of events that lead to β-cell apoptosis; important among these is NO production. The glycosphingolipid sulfatide is present in β-cells in the secretory granules in varying amounts and is secreted together with insulin. We now investigate whether sulfatide is able to protect insulin-producing cells against the pro-apoptotic effect of interleukin-1β, interferon-γ and tumour necrosis factor-α.


METHODS
INS-1E cells and genuine rat islets were incubated for 24 h exposed to interleukin-1β, interferon-γ and tumour necrosis factor-α with or without sulfatide. The production of NO was monitored and the number of apoptotic cells was determined using terminal deoxynucleotidyl transferase-mediated dUTP Nick-End labelling and caspase-3/7 activity assays. In addition, the amount of iNOS mRNA was determined using real-time quantitative polymerase chain reaction.


RESULTS
Cytokine-induced apoptosis was reduced to 27% of cytokine-treated controls with 30 µmol/L sulfatide treatment (p < 0.01). Likewise, sulfatide in concentrations of 3-30 µmol/L decreased NO production in a dose-dependent manner to 19-40% of cytokine-treated controls (overall p = 0.0007). The level of iNOS mRNA after cytokine exposure was reduced to 55% of cytokine-treated controls with 30 µmol/L of sulfatide.


CONCLUSIONS
In the present study, we report the ability of sulfatide to significantly reduce apoptosis, cellular leakage and NO production in insulin-producing cells. Data suggest this is not due to induction of β-cell rest. Our findings indicate a possible implication for sulfatide in the pathogenesis of diabetes.
Roeske-Nielsen
A
A
Bartholin Institute, Rigshospitalet, Blegdamsvej 9, Copenhagen, Denmark. allan@roeske.dk
Dalgaard
L T
LT
Månsson
J-E
JE
Buschard
K
K
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics; D016207:Cytokines / Q000494:pharmacology*; D003924:Diabetes Mellitus, Type 2 / Q000209:etiology*; D005947:Glucose / Q000494:pharmacology; D050417:Insulin-Secreting Cells / Q000187:drug effects*; D007371:Interferon-gamma / Q000037:antagonists & inhibitors / Q000494:pharmacology; D053583:Interleukin-1beta / Q000037:antagonists & inhibitors / Q000494:pharmacology; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D013433:Sulfoglycosphingolipids / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000494:pharmacology
C491766:Ccl2 protein, rat; D018932:Chemokine CCL2; D016207:Cytokines; D053583:Interleukin-1beta; D012333:RNA, Messenger; D013433:Sulfoglycosphingolipids; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D007371:Interferon-gamma; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D005947:Glucose