Streptococcal wall component OK432 restores sensitivity of non-obese diabetic (NOD) thymocytes to apoptotic signals.
OBJECTIVE
The streptococcal wall component, OK432, prevents diabetes in NOD mice and BB rats by elimination of effector cells. Based on the knowledge of a link between autoimmunity and resistance of immune cells to elimination by apoptosis, we investigated whether OK432 treatment restored the sensitivity of NOD lymphocytes to apoptotic signals centrally (thymus) or peripherally (spleen) or both and we examined the pathways for the enhanced apoptosis rate.


METHODS
We treated NOD mice with OK432 (0.1 mg/kg i.p. weekly from 21 to 70 days). Apoptosis was measured by TUNEL 16 h after cyclophosphamide (70 mg/kg) and 24 h after dexamethasone (0.2 mg/mouse). Real time quantitative RT-PCR was used to investigate changes in gene expression.


RESULTS
Thymocyte apoptosis levels after cyclophosphamide were restored by OK432 treatment to levels observed in C57BL/6 mice: in NOD males apoptosis increased from 8 +/- 1% to 18 +/- 5% (p < 0.05) compared with 20 +/- 4% in C57BL/6 males, and in NOD females from 6+/- 2% to 11 +/- 2% (p < 0.05) compared with 12 +/- 2% in C57BL/6 females. The dexamethasone-induced thymocyte apoptosis rate was equally restored by OK432 treatment (58 +/- 4% vs 41 +/- 3% in control males (p < 0.0005) and 39 +/- 5% vs 26 +/- 3% in control females (p < 0.05)]. No change in apoptosis levels was on the contrary observed in splenocytes after OK432 treatment. By RT-PCR analysis of a panel of apoptosis-related genes in thymocytes we showed a down-regulation of anti-apoptotic Bcl-xL and c-myc by OK432 treatment.


CONCLUSIONS
Our data suggest that OK432 prevents diabetes in NOD mice by better elimination of effector cells through increased sensitivity to apoptotic signals centrally in the thymus.
Decallonne
B
B
Laboratory for Experimental Medicine and Endocrinology, Catholic University Leuven, Belgium.
Overbergh
L
L
Casteels
K M
KM
Gysemans
C
C
Bouillon
R
R
Mathieu
C
C
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D003520:Cyclophosphamide / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology; D007166:Immunosuppressive Agents / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016688:Mice, Inbred NOD; D010844:Picibanil / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000737:chemistry / Q000166:cytology* / Q000276:immunology*; D013950:Thymus Gland / Q000737:chemistry / Q000166:cytology; D051020:bcl-X Protein
C494812:Bcl2l1 protein, mouse; D005938:Glucocorticoids; D007166:Immunosuppressive Agents; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D051020:bcl-X Protein; D010844:Picibanil; D003907:Dexamethasone; D003520:Cyclophosphamide