Objective: Disorganization of acinar cell apical microvilli and the presence of stromal collagen in the acinar lumen suggest that the labial salivary gland (LSG) barrier function is impaired in patients with Sjögren's syndrome. Tight junctions define cell polarity and regulate the paracellular flow of ions and water, crucial functions of acinar cells. This study was undertaken to evaluate the expression and localization of tight junction proteins in LSGs from patients with SS and to determine in vitro the effects of tumor necrosis factor α (TNFα) and interferon‐γ (IFNγ) on tight junction integrity of isolated acini from control subjects.Methods: Twenty‐two patients and 15 controls were studied. The messenger RNA and protein levels of tight junction components (claudin‐1, claudin‐3, claudin‐4, occludin, and ZO‐1) were determined by semiquantitative reverse transcriptase–polymerase chain reaction and Western blotting. Tight junction protein localization was determined by immunohistochemistry. Tight junction ultrastructure was examined by transmission electron microscopy. Isolated acini from control subjects were treated with TNFα and IFNγ.Results: Significant differences in tight junction protein levels were detected in patients with SS. ZO‐1 and occludin were strongly down‐regulated, while claudin‐1 and claudin‐4 were overexpressed. Tight junction proteins localized exclusively to apical domains in acini and ducts of LSGs from controls. In SS patients, the ZO‐1 and occludin the apical domain presence of decreased, while claudin‐3 and claudin‐4 was redistributed to the basolateral plasma membrane. Exposure of isolated control acini to TNFα and IFNγ reproduced these alterations in vitro. Ultrastructural analysis associated tight junction disorganization with the presence of endocytic vesicles containing electron‐dense material that may represent tight junction components.Conclusion: Our findings indicate that local cytokine production in LSGs from SS patients may contribute to the secretory gland dysfunction observed in SS patients by altering tight junction integrity of epithelial cells, thereby decreasing the quality and quantity of saliva.

Early in cancer development, tumour cells express vascular endothelial growth factor (VEGF), a secreted molecule that is important in all stages of angiogenesis, an essential process that provides nutrients and oxygen to the nascent tumor and thereby enhances tumor-cell survival and facilitates growth. Survivin, another protein involved in angiogenesis, is strongly expressed in most human cancers, where it promotes tumor survival by reducing apoptosis as well as favoring endothelial cell proliferation and migration. The mechanisms by which cancer cells induce VEGF expression and angiogenesis upon survivin up-regulation remain to be fully established. Since the PI3K/Akt signalling and β-catenin-Tcf/Lef dependent transcription have been implicated in the expression of many cancer-related genes, including survivin and VEGF, we evaluated whether survivin may favor VEGF expression, release from tumor cells and induction of angiogenesis in a PI3K/Akt-β-catenin-Tcf/Lef-dependent manner. Here, we provide evidence linking survivin expression in tumor cells to increased β-catenin protein levels, β-catenin-Tcf/Lef transcriptional activity and expression of several target genes of this pathway, including survivin and VEGF, which accumulates in the culture medium. Alternatively, survivin downregulation reduced β-catenin protein levels and β-catenin-Tcf/Lef transcriptional activity. Also, using inhibitors of PI3K and the expression of dominant negative Akt, we show that survivin acts upstream in an amplification loop to promote VEGF expression. Moreover, survivin knock-down in B16F10 murine melanoma cells diminished the number of blood vessels and reduced VEGF expression in tumors formed in C57BL/6 mice. Finally, in the chick chorioallantoid membrane assay, survivin expression in tumor cells enhanced VEGF liberation and blood vessel formation. Importantly, the presence of neutralizing anti-VEGF antibodies precluded survivin-enhanced angiogenesis in this assay. These findings provide evidence for the existance of a posititve feedback loop connecting survivin expression in tumor cells to PI3K/Akt enhanced β-catenin-Tcf/Lef-dependent transcription followed by secretion of VEGF and angiogenesis.

Oxidative stress in female cancers Oxidative stress in female cancers