Functional and molecular characterizations of chloride channels in rat pleural mesothelial cells

Pleural effusions induced by human herpesviruses in the immunocompetent host

METHODS

A computer-based search of the English literature for articles relative to Human Herpesviruses (HHVs) infection and pleural effusions (PEs) in the immunocompetent host was performed in PubMed and Scopus. The reference lists of the retrieved articles were also reviewed for relevant articles.

RESULTS

A total of 20 articles satisfied the selection criteria and were included in the study. In the majority of the articles, PEs were reported as clinical complications of systemic HHV-induced infection. The frequency of HHVs within the reported cases was five for HHV-1/2, one for HHV-3, six for HHV-4, six for HHV-5 and one for HHV-6. One case involved HHV-4 and HHV-5 co-infection. No case of HHV-7 or HHV-8 related PE in the immunocompetent host was retrieved.

CONCLUSIONS

Pleural effusions in the immunocompetent host occur in severe viral infections and can be due to comorbidities (or septic complications) or due to the direct HHV pathogenicity although research relative to the susceptibility of pleural mesothelial cells to HHV infection is lacking. HHV pathogenicity needs to be studied further as it could explain undiagnosed PEs.

ClC-3 Chloride Channel Proteins Regulate the Cell Cycle by Up-regulating cyclin D1-CDK4/6 through Suppressing p21/p27 Expression in Nasopharyngeal Carcinoma Cells

It was shown in this study that knockdown of ClC-3 expression by ClC-3 siRNA prevented the activation of hypotonicity-induced chloride currents, and arrested cells at the G0/G1 phase in nasopharyngeal carcinoma CNE-2Z cells. Reconstitution of ClC-3 expression with ClC-3 expression plasmids could rescue the cells from the cell cycle arrest caused by ClC-3 siRNA treatments. Transfection of cells with ClC-3 siRNA decreased the expression of cyclin D1, cyclin dependent kinase 4 and 6, and increased the expression of cyclin dependent kinase inhibitors (CDKIs), p21 and p27. Pretreatments of cells with p21 and p27 siRNAs depleted the inhibitory effects of ClC-3 siRNA on the expression of CDK4 and CDK6, but not on that of cyclin D1, indicating the requirement of p21 and p27 for the inhibitory effects of ClC-3 siRNA on CDK4 and CDK6 expression. ClC-3 siRNA inhibited cells to progress from the G1 phase to the S phase, but pretreatments of cells with p21 and p27 siRNAs abolished the inhibitory effects of ClC-3 siRNA on the cell cycle progress. Our data suggest that ClC-3 may regulate cell cycle transition between G0/G1 and S phases by up-regulation of the expression of CDK4 and CDK6 through suppression of p21 and p27 expression.

Discovery of bufadienolides as a novel class of ClC-3 chloride channel activators with antitumor activities

ClC-3 chloride (Cl(-)) channel has been shown to be involved in cell proliferation, cell cycle, and cell migration processes. Herein, we found that a series of bufadienolides isolated from toad venom were a novel class of ClC-3 Cl(-) channel activators with antitumor activities. Bufalin, which has the most potent antitumor activity, and 15β-acetyloxybufalin, which has no antitumor activity, were chosen as representative compounds to investigate the role of the ClC-3 Cl(-) channel. It was found that bufalin rapidly elicited activation of the ClC-3 Cl(-) channel and subsequently induced apoptosis through inhibition of the PI3K/Akt/mTOR pathway. The PI3K/Akt/mTOR pathway was attenuated by pretreatment with Cl(-) channel blockers [tamoxifen and 5-nitro-2-(3-phenylpropylamino)benzoic acid, NPPB] or ClC-3 small interfereing RNA. In summary, we discovered that activation of the ClC-3 Cl(-) channel, which subsequently induced inhibition of the PI3K/Akt/mTOR signaling pathway, was involved in the antitumor activities of bufadienolides.

ClC-3 is a main component of background chloride channels activated under isotonic conditions by autocrine ATP in nasopharyngeal carcinoma cells

In this study, the activation mechanisms of the background chloride current and the role of the current in maintaining of basal cell volume were investigated in human nasopharyngeal carcinoma CNE-2Z cells. Under isotonic conditions, a background chloride current was recorded by the patch clamp technique. The current presented the properties similar to those of the volume-activated chloride current in the same cell line and was inhibited by chloride channel blockers or by cell shrinkage induced by hypertonic challenges. Extracellular applications of reactive blue 2, a purinergic receptor antagonist, suppressed the background chloride current in a concentration-dependent manner under isotonic conditions. Depletion of extracellular ATP with apyrase or inhibition of ATP release from cells by gadolinium chloride decreased the background current. Extracellular applications of micromolar concentrations of ATP activated a chloride current which was inhibited by chloride channel blockers and hypertonic solutions. Extracellular ATP could also reverse the action of gadolinium chloride. Transfection of CNE-2Z cells with ClC-3 siRNA knocked down expression of ClC-3 proteins, attenuated the background chloride current and prevented activation of the ATP-induced current. Furthermore, knockdown of ClC-3 expression or exposures of cells to ATP (10 mM), the chloride channel blockers 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and tamoxifen, or reactive blue 2 increased cell volume under isotonic conditions. The results suggest that ClC-3 protein may be a main component of background chloride channels which can be activated under isotonic conditions by autocrine/paracrine ATP through purinergic receptor pathways; the background current is involved in maintenance of basal cell volume.