Abstract
Background
MRL/MpJ-Tnfrsf6 lpr (MRL/lpr) mice, a murine model of systemic lupus erythematosus (SLE), have defective expression of Fas, substantially reducing signaling for apoptosis via this mechanism. However, it is known that MRL//pr mice have increased spontaneous apoptosis of leukocytes. These conflicting observations have stimulated interest in apoptosis in this SLE model. MRL/lpr mice overproduce nitric oxide (NO) as autoimmune disease progresses. In vitro administration of NO may induce or decrease apoptosis depending on the cell type. Therefore, we hypothesized that NO induces MRL/lpr spleen lymphocyte apoptosis independent of Fas receptor engagement.
Methods
Percentages of apoptotic spleen lymphocytes from MRL/lpr and BALB/cJ mice were determined ex vivo after in vivo treatment with NG-monomethyl-
Results
Spleen lymphocytes from MRL/lpr mice with active disease had increased levels of ex vivo apoptosis when compared with BALB/cJ controls. This increase was reduced by pharmacologic inhibition of NOS in MRL/lpr but not in BALB/cJ mice. Exogenous administration of NO in vitro reduced PKC activity and induced apoptosis in MRL/lpr spleen lymphocytes, an effect that could be reduced via coadministration of PMA in vitro.
Conclusion
These results suggest that NO plays a role in spleen lymphocyte apoptosis in MRL/lpr mice, possibly via inhibition of PKC, despite a Fas defect.
Keywords
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