Session Information
Title: B cell Biology and Targets in Autoimmune Disease: Systemic Lupus Erythematosus and Related Diseases
Session Type: Abstract Submissions (ACR)
Background/Purpose:
PTEN regulates normal signaling through the B cell receptor (BCR). In systemic lupus erythematosus(SLE), enhanced BCR signaling contributes to increased B cell activity. We, therefore, examined whether abnormalities in PTEN might contribute to increased B cell activity in SLE.
Methods:
We mainly used B cells from peripheral blood of newly diagnosed untreated SLE patients (vs. HC) to determine whether PTEN plays a critical role in the immunodysregulation in patients with SLE. The expression of PTEN protein, and the phosphorylation of Akt and/or STAT3 were examined by flow cytometry and/or western blotting. Expression of candidate microRNAs that could regulate PTEN was identified by TargetScan prediction, and confirmed using a dual luciferase reporter gene assay with a reporter construct containing the PTEN 3’ UTR. To determine whether the abnormal expression of PTEN and its regulation by these microRNA contribute to B cells function in SLE, we electroporated peripheral B cells with pre-microRNA or an microRNA antagomir in the presence or absence of siPTEN. The levels of PTEN mRNA and microRNAs were assessed by real-time PCR, and the intracellular calcium levels were assessed by Fluo4-AM and then measured by flow cytometry.
Results:
By FACS analysis, we found all SLE B cell sub-sets, except for memory B cells, showed decreased expression of PTEN, and the level was inversely correlated with disease activity. Notably, IL-21 induced PTEN expression and also suppressed Akt phosphorylation induced by anti-IgM and CD40L stimulation in normal but not SLE B cells. However, IL-21-induced STAT3 phosphorylation was intact and IL-21 up-regulated PTEN mRNA in SLE B cells. Therefore, expression of candidate microRNAs that could regulate PTEN was examined and SLE B cells were found to express increased levels of miR-7, 21 and 22. These microRNAs down-regulated expression of PTEN, and IL-21 stimulation increased expression of miR-7 and 22 in both normal and SLE B cells. Decreased expression of PTEN in SLE B cells was associated with augmented calcium signaling induced by BCR engagement as well as increased IL-21-mediated B cell proliferation and plasma cells differentiation, and these abnormalities were corrected by a miR-7 antagomir. Moreover, knockdown of PTEN with siRNA significantly increased the baseline calcium signal, and this increase was not altered by either an miR-7 agomir or antagomir. In addition, IL-21-mediated inhibition of the BCR-induced calcium signal as well as Akt phosphorylation was altered when PTEN was knocked down in a very similar manner to that caused by miR-7.
Conclusion: Defective miR-7 regulation of PTEN contributes to B cell hyperresponsiveness in SLE and could be a new target of therapeutic intervention.
Disclosure:
X. Wu,
None;
Y. Ye,
None;
J. Niu,
None;
Y. Li,
None;
X. Li,
None;
X. You,
None;
H. Chen,
None;
L. Zhao,
None;
X. Zeng,
None;
F. Zhang,
None;
F. Tang,
None;
W. He,
None;
X. Cao,
None;
X. Zhang,
None;
P. E. Lipsky,
None.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/defective-pten-regulation-and-function-contributes-to-b-cell-hyper-responsiveness-in-systemic-lupus-erythematosus/