IntroductionCertain chloride channels and H+/Cl− antiporters, such as chloride channel 3 (ClC-3), are expressed at the apical pole of thyrocytes, facilitating iodide (I−) efflux. However, the relationship between ClC-3 and I− uptake remains unclear. Additionally, whether ClC-3 and reactive oxygen species (ROS) regulate sodium-iodide symporter (NIS) expression and localization under excessive I− conditions remain underexplored.MethodsThe expression and localization of ClC-3 in wild-type (WT), ClC-3 overexpression (OE) and ClC-3 knockout (KO) were detected by Western blotting (WB), immunohistochemistry and immunofluorescence, respectively. The 131I uptake of the thyroid was measured by thyroid function instrument. The expression and localization of NIS in normal and high iodide diet were detected, respectively. The role of ROS in the regulation of NIS by ClC-3 was observed.ResultsClC-3 expressions in thyrocytes were primarily localized to the basolateral and lateral membranes, in both ClC-3 OE and WT mice groups under normal I− conditions. I− uptake was significantly higher in WT and ClC-3 OE mice than in the ClC-3 KO mice under normal I− conditions. The ClC-3 OE group exhibited a higher number of thyroid follicles with elevated NIS expression in the basolateral and lateral membranes than the WT and KO groups. In the ClC-3 KO group, the NIS was predominantly localized in the cytoplasm. In the WT group, NIS fluorescence intensity at the basolateral and lateral membranes increased after 48 h of excessive iodide exposure compared to 24 h. In ClC-3 OE mice, NIS, initially localized intracellularly after 24 h of excessive iodide exposure, was almost fully reintegrated into the basolateral and lateral membranes after 48 h. In contrast, in ClC-3 KO mice, NIS remained primarily cytoplasmic, with no significant change between 24 h and 48 h of I− excess. ROS fluorescence intensity was significantly higher in the ClC-3 OE group than those in the WT and KO groups after 24 h of I− excess. Pre-inhibition of ROS showed no significant differences in NIS localization or expression among the three groups after 24 h of I− excess.DiscussionThese findings suggest that ClC-3 may regulate NIS function via ROS signaling under excessive iodide conditions.

Iodide (I−) is crucial to thyroid function, and its regulation in thyrocytes involves ion transporters and reactive oxygen species (ROS). However, the extent of 2Cl−/H+ exchanger (ClC-3) involvement in the iodide (I−) efflux from thyrocytes remains unclear. Therefore, we examined the effects of ClC-3 on I− efflux. ClC-3 expression was found to significantly alter the serum TT3 and TT4 concentrations in mice. We further found that excess I− stimulation affected ClC-3 expression, distribution, and I− efflux in FRTL-5 cells. Immunofluorescence analyses indicated that ClC-3 mainly accumulated in the cell membrane and co-localized with β-tubulins after 24 h of excess I− treatment, and that this process depended on ROS production. Thus, ClC-3 may be involved in I− efflux at the apical pole of thyrocytes via excess I−-induced ROS production and β-tubulin polymerization. Our results reveal novel insights into the role of ClC-3 in I− transport and thyroid function.

Estradiol regulates thyroid function, and chloride channels are involved in the regulation of thyroid function. However, little is known about the role of chloride channels in the regulation of thyroid functions by estrogen. In this study, the effects of estrogen on chloride channel activities in human thyroid Nthy-ori3-1 cells were therefore investigated using the whole cell patch-clamp technique. The results showed that the extracellular application of 17β-estradiol (E2) activated Cl- currents, which reversed at a potential close to Cl- equilibrium potential and showed remarkable outward rectification and an anion permeability of I- > Br- > Cl- > gluconate. The Cl- currents were inhibited by the chloride channel blockers, NPPB and tamoxifen. Quantitative Real-time PCR results demonstrated that ClC-3 expression was highest in ClC family member in Nthy-ori3-1 cells. The down-regulation of ClC-3 expression by ClC-3 siRNA inhibited E2-induced Cl- current. The Cl- current was blocked by the estrogen receptor antagonist, ICI 182780 (fulvestrant). Estrogen receptor alpha (ERα) and not estrogen receptor beta was the protein expressed in Nthy-ori3-1 cells, and the knockdown of ERα expression with ERα siRNA abolished E2-induced Cl- currents. Estradiol can promote the accumulation of ClC-3 in cell membrane. ERα and ClC-3 proteins were partially co-localized in the cell membrane of Nthy-ori3-1 cells after estrogen exposure. The results suggest that estrogen activates chloride channels via ERα in normal human thyroid cells, and ClC-3 proteins play a pivotal role in the activation of E2-induced Cl- current.

目的:探讨ClC-3氯通道在顺铂诱导的鼻咽癌细胞凋亡中的作用及机制.方法:将不同浓度的顺铂作用于人低分化鼻咽癌细胞(CNE-2Z细胞);MTT法检测不同浓度的顺铂处理24h和48h后细胞活力;采用ClC-3-siRNA下调ClC-3的表达,Annexin V-FITC/PI双染法检测细胞凋亡,多功能微孔板检测仪和流式细胞术检测细胞不同状态下的ROS水平.结果:(1)顺铂呈时间和浓度依赖性抑制CNE-2Z细胞生长,氯通道阻断剂DIDS显著抑制顺铂引起的细胞凋亡(P＜0.01);(2)顺铂促进CNE-2Z细胞ClC-3表达,下调ClC-3蛋白表达后,顺铂诱导的细胞凋亡率下降(P＜0.05);(3)顺铂促进CNE-2Z细胞ROS产生,用抗氧化剂抑制细胞产生ROS后,顺铂诱导的ClC-3蛋白表达和凋亡被抑制,而下调ClC-3蛋白表达对ROS水平影响不大.结论:顺铂可通过提升CNE-2Z细胞ROS水平,上调氯通道ClC-3蛋白水平,从而诱导细胞凋亡.

Extracellular acidification, playing a promoting role in the process of acute pancreatitis, has been reported to activate Cl- channels in several types of cells. However, whether extracellular acidification aggravates acute pancreatitis via activating Cl- channels remains unclear. Here, we investigated the effects of extracellular acidification on Cl- channels in rat pancreatic acinar AR42J cells using whole-cell patch-clamp recordings. We found that extracellular acidification induced a moderately outward-rectified Cl- current, with a selectivity sequence of I- > Br- >= Cl- > gluconate(-), while intracellular acidification failed to induce the currents. The acid-sensitive currents were inhibited by Cl- channel blockers, 4,4'-Diisothiocyanatostilbene-2,2'-disulfonic acid disodium salt hydrate and 5-Nitro 2 (3-phenylpropylamino) benzoic acid. After ClC-3 was silenced by ClC-3 shRNA, the acid-sensitive Cl- currents were attenuated significantly, indicating that ClC-3 plays a vital role in the induction of acid-sensitive Cl- currents. Extracellular acid elevated the intracellular level of reactive oxygen species (ROS) significantly, prior to inducing Cl- currents. When ROS production was scavenged, the acid-sensitive Cl(-)currents were abolished. Whereas, the level of acid-induced ROS was unaffected with silence of ClC-3. Our findings above demonstrate that extracellular acidification induces a Cl- current in pancreatic acinar cells via promoting ROS generation, implying an underlying mechanism that extra-cellular acidification might aggravate acute pancreatitis through Cl- channels. (C) 2020 Elsevier Inc. All rights reserved.

Nutrient deficiency develops frequently in nasopharyngeal carcinoma cell (CNE-2Z) due to the characteristics of aggregation and uncontrolled proliferation. Therefore, starvation can induce autophagy in these cells. Chloride channel 3 (ClC-3), a member of the chloride channel family, is involved in various biological processes. However, whether ClC-3 plays an important role in starvation-induced autophagy is unclear. In this study, Earle's balanced salt solution (EBSS) was used to induce autophagy in CNE-2Z cells. We found that autophagy and the chloride current induced by EBSS were inhibited by chloride channel blockers. ClC-3 knockdown inhibited the degradation of LC3-II and P62. Furthermore, when reactive oxygen species (ROS) generation was suppressed by antioxidant N-acetyl-l-cysteine (L-NAC) pretreatment, EBSS-induced autophagy was inhibited, and the chloride current was unable to be activated. Nevertheless, ClC-3 knockdown had little effect on ROS levels, indicating that ROS acted upstream of ClC-3 and that both ROS and ClC-3 participated in EBSS-induced autophagy regulation in CNE-2Z.

AIM:To study the effect of ClC-3 gene over-expression on thyroid structure and function in mice. METHODS:Three-months-old FVB mice were used to study the difference of thyroid structure and function between wild-type(WT)mouse and ClC-3 transgene mice.The expression and distribution of ClC-3 in the thyroid of mice were deter-mined by the methods of qPCR,Western blot and immunofluorescence.Behavioral monitoring was performed on the daily activities of mice.Serum concentrations of total triiodothyronine(TT3), total thyroxine(TT4)and thyrotropin(TSH) were measured by ELISA.RESULTS:Compared with the WT group,the expression of ClC-3 in the thyroid of ClC-3 trans-gene group was significantly increased(P<0.05).The thyroid gland showed obvious hyperplasia and the folliculi glandu-lae thyreoideae was significantly bigger in ClC-3 transgene mice(P<0.05).The weight loss was increased in ClC-3 trans-gene mice(P<0.05).The expression of TT3 and TT4 were significantly higher than that of WT group(P<0.05),but the change of TSH was not obvious.CONCLUSION:ClC-3 over-expression results in thyroid hyperplasia and thyroid hor-mone secretion.This study suggests that ClC-3 is likely to be involved in the synthesis of thyroid hormones.

Recently, many potential prognostic biomarkers for gastric cancer (GC) have been identified, but the prognosis of advanced GC patients remains poor. Chloride channels are promising cancer biomarkers, and their family member chloride channel-3 (CLC-3) is involved in multiple biological behaviors. However, whether CLC-3 is a prognostic biomarker for GC patients is rarely reported. The molecular mechanisms by which CLC-3 is regulated in GC are unclear.

Zoledronic acid (ZA), a third-generation bisphosphonate, has been applied for treatment of bone metastases caused by malignant tumors. Recent studies have found its anti-cancer effects on various tumor cells. One of the mechanisms of anti-cancer effects of ZA is induction of apoptosis. However, the mechanisms of ZA-induced apoptosis in tumor cells have not been clarified clearly. In this study, we investigated the roles of chloride channels in ZA-induced apoptosis in nasopharyngeal carcinoma CNE-2Z cells. Apoptosis and chloride current were induced by ZA and suppressed by chloride channel blockers. After the knockdown of ClC-3 expression by ClC-3 siRNA, ZA-induced chloride current and apoptosis were significantly suppressed, indicating that the chloride channel participated in ZA-induced apoptosis may be ClC-3. When reactive oxygen species (ROS) generation was inhibited by the antioxidant N-acetyl-L-cysteine (L-NAC), ZA-induced apoptosis and chloride current were blocked accordingly, suggesting that ZA induces apoptosis through promoting ROS production and subsequently activating chloride channel.