4 research outputs found
Salivary epithelial cells from Sjogren's syndrome patients are highly sensitive to anoikis induced by TLR-3 ligation
In certain types of cells, Toll-like receptor-3 (TLR-3) ligation by
viral dsRNA induces apoptotic death, likely engaged into the elimination
of virus-infected cells. We have previously shown that TLR-3 ligation on
cultured non-neoplastic salivary gland epithelial cells (SGEC) with
polyI:C (a synthetic analogue of viral dsRNA) results in the induction
of surface immunoactive molecules, however, the pro-apoptotic effect of
such signaling has not been addressed. In this study, polyI:C-treated
SGEC were found to suffer severe detachment from substratum and
subsequent apoptosis, a phenomenon suggestive of anoikis or anoikia
(detachment-induced apoptosis). PolyI:C-induced anoikis in SGEC was
associated with the upregulation of the pro-apoptotic Bmf, BimEL and Bax
and the down-regulation of the pro-survival Bcl-2 (real-time PCR
analyses). Finally, the comparative analysis of SGEC lines derived from
primary Sjogren’s syndrome (SS) patients (SS-SGEC) and non-SS controls
had revealed that SS-SGEC are particularly susceptible to TLR-3-induced
anoikis, as it was triggered by suboptimally low concentrations of
polyI:C. This finding correlated with significantly higher constitutive
surface TLR-3 expression by SS-SGEC, a feature indicative of their
intrinsic activation status. In conclusion, TLR-3 signaling pathway in
the salivary epithelium appears to extend beyond the induction of innate
immune responses and to involve the activation of programmed-cell death
via anoikis. In the same context, the increased vulnerability of SS-SGEC
to the injurious effect of TLR-3 ligation is likely associated with the
intrinsic activation processes that apparently operate in the epithelia
of SS patients, and a feature of key pathogenetic importance for the
disorder. (C) 2010 Elsevier Ltd. All rights reserved
RNA Interference of Interferon Regulatory Factor-1 Gene Expression in THP-1 Cell Line Leads to Toll-Like Receptor-4 Overexpression/Activation As Well As Up-modulation of Annexin-II1
Interferon regulatory factor-1 (IRF-1) is a candidate transcription factor for the regulation of the Toll-like receptor-4 (TLR-4) gene. Using a small interfering RNA-based (siRNA) process to silence IRF-1 gene expression in the leukemic monocytic cell line THP-1, we investigated whether such a modulation would alter TLR-4 expression and activation status in these cells. The siIRF-1 cells expressed elevated levels of TLR-4 mRNA and protein compared to controls by 90% and 77%, respectively. ICAM.1 protein expression and apoptosis levels were increased by 8.35- and 4.25-fold, respectively. The siIRF-1 cells overexpressed Bax mRNA compared to controls. Proteomic analysis revealed upmodulation of the Annexin-II protein in siIRF-1 THP-1 cells. Myelodysplastic syndrome (MDS) patients with an absence of full-length IRF-1 mRNA also overexpressed Annexin-II. It is plausible that this overexpression may lead to the activation of TLR-4 contributing to the increased apoptosis characterizing MDS