Tungstate-targeting of BKαβ1 channels tunes ERK phosphorylation and cell proliferation in human vascular smooth muscle

The promoting role of Cx43 on the proliferation and migration of arterial smooth muscle cells for angiotensin II-dependent hypertension

BACKGROUND

Recent studies have shown that endothelin-1 and angiotensin II (AngII) can increase gap junctional intercellular communication (GJIC) by activating Mitogen-activated protein kinases (MAPKs) pathway. However, not only the precise interaction of AngII with Connexin43(Cx43) and the associated functions remain unclear, but also the regulatory role of Cx43 on the AngII-mediated promotion proliferation and migration of VSMCs is poorly understood.

MATERIAL AND METHODS

Our research applicated pressure myography measurements, immunofluorescence and Western blot analyses to investigate the changes in physiological indicators in spontaneously hypertensive rats (SHRs) and AngII-stimulated proliferation and migration of A7r5 SMCs(Rat vascular smooth muscle cells). The aim was to elucidate the role of CX43 in hypertension induced by AngII.

RESULTS

Chronic ramipril (angiotensin converting enzyme inhibitor) management for SHRs significantly attenuated blood pressure and blood vessel wall thickness, also reduced contraction rate in the cerebral artery. The cerebral artery contraction rates, mRNA and protein expression of Cx43, osteopontin (OPN) and proliferating cell nuclear antigen (PCNA) protein expression in the SHR + ramipril and SHR + ramipril + carbenoxolone (CBX, Cx43 specific blocker) groups were significantly lower than those in the SHR group. Cx43 protein expression and Ser368 phosphorylated Cx43 protein levels increased significantly in AngII-stimulated A7r5 cells. However, the levels of phosphorylated Cx43 decreased after pre-treatment with candesartan (AT1 receptor blocker), GF109203X (protein kinase C (PKC) blocker) and U0126 (mitogen-activated protein kinases/extracellular signal-regulated kinase1/2(MEK/ERK1/2)-specific blocker) in AngII-stimulated A7r5 cells. Cx43 was widely distributed in the cell membrane, nucleus, and cytoplasm of the SMCs. Furthermore, pre-treatment of the AngII- stimulated A7r5 cells with Gap26 (Cx43 blocker) significantly inhibited cell migration and decreased the expression levels of MEK1/2, ERK1/2, P-MEK1/2, and P-ERK1/2.

CONCLUSION

Our research confirms that Cx43 plays an important role in the regulation of proliferation and migration of VSMCs via MEK/ERK and PKC signal pathway in AngII-dependent hypertension.

Heavy Metals in the Environment and Thyroid Cancer

In recent decades, the incidence of thyroid cancer has increased more than most other cancers, paralleling the generalized worldwide increase in metal pollution. This review provides an overview of the evidence supporting a possible causative link between the increase in heavy metals in the environment and thyroid cancer. The major novelty is that human thyroid stem/progenitor cells (thyrospheres) chronically exposed to different metals at slightly increased environmentally relevant concentrations show a biphasic increase in proliferation typical of hormesis. The molecular mechanisms include, for all metals investigated, the activation of the extracellular signal-regulated kinase (ERK1/2) pathway. A metal mixture, at the same concentration of individual metals, was more effective. Under the same conditions, mature thyrocytes were unaffected. Preliminary data with tungsten indicate that, after chronic exposure, additional abnormalities may occur and persist in thyrocytes derived from exposed thyrospheres, leading to a progeny population of transformation-prone thyroid cells. In a rat model predisposed to develop thyroid cancer, long-term exposure to low levels of metals accelerated and worsened histological signs of malignancy in the thyroid. These studies provide new insight on metal toxicity and carcinogenicity occurring in thyroid cells at a low stage of differentiation when chronically exposed to metal concentrations that are slightly increased, albeit still in the "normal" range.

Comparative outcomes of exposing human liver and kidney cell lines to tungstate and molybdate

Tungsten has no known function in humans and is a relatively new contaminant, whereas molybdenum, its congener in the periodic table, is a nutritionally essential element. In addition to early studies on molybdosis in ruminants, their toxic effects in the form of tungstate and molybdate have been addressed primarily in rodents and are predominantly mediated by inducing oxidative stress in various tissues. The purpose of this study was to evaluate the differences between tungstate and molybdate in human liver (HepG2) and kidney (HEK293) cell lines in terms of retention in cells, effect on reactive oxygen species, and activities of xanthine oxidase and phosphatases. The cell lines were exposed to tungstate or molybdate (1 µM to 10 mM) for 24 h, lysed and analyzed for the above biochemical parameters. Despite the chemical similarity of the two anions, cell-specific differential effects were observed. At all concentrations, tungstate was retained more in HEK293 cells while molybdate was retained more in HepG2 cells. HepG2 cells were more sensitive to tungstate than molybdate, showing reduced viability at concentrations as low as 10 µM. Exposure to either anion resulted in the inhibition of protein tyrosine phosphatases at 1 mM and an increased production of reactive oxygen species (ROS) at 100 µM despite their inhibition of the ROS-producing molybdenum enzyme xanthine oxidase. In conclusion, the results indicate that excess of nutritionally essential molybdate or non-essential tungstate causes toxicity by affecting ROS- and phosphorylation-dependent signaling pathways and ensuing gene expression.

Arachidonic acid effect on the allosteric gating mechanism of BK (Slo1) channels associated with the β1 subunit

Arachidonic acid (AA) is a fatty acid involved in the modulation of several ion channels. Previously, we reported that AA activates the high conductance Ca²⁺- and voltage-dependent K⁺ channel (BK) in vascular smooth muscle depending on the expression of the auxiliary β1 subunit. Here, using the patch-clamp technique on BK channel co-expressed with β1 subunit in a heterologous cell expression system, we analyzed whether AA modifies the three functional modules involved in the channel gating: the voltage sensor domain (VSD), the pore domain (PD), and the intracellular calcium sensor domain (CSD). We present evidence that AA activates BK channel in a direct way, inducing VSD stabilization on its active configuration observed as a significant left shift in the Q-V curve obtained from gating currents recordings. Moreover, AA facilitates the channel opening transitions when VSD are at rest, and the CSD are unoccupied. Furthermore, the activation was independent of the intracellular Ca²⁺ concentration and reduced when the BK channel was co-expressed with the Y74A mutant of the β1 subunit. These results allow us to present new insigths in the mechanism by which AA modulates BK channels co-expressed with its auxiliary β1 subunit.

Kv channels and vascular smooth muscle cell proliferation

Kv channels are present in virtually all VSMCs and strongly influence contractile responses. However, they are also instrumental in the proliferative, migratory, and secretory functions of synthetic, dedifferentiated VSMCs upon PM. In fact, Kv channels not only contribute to all these processes but also are active players in the phenotypic switch itself. This review is focused on the role(s) of Kv channels in VSMC proliferation, which is one of the best characterized functions of dedifferentiated VSMCs. VSMC proliferation is a complex process requiring specific Kv channels at specific time and locations. Their identification is further complicated by their large diversity and the differences in expression across vascular beds. Of interest, both conserved changes in some Kv channels and vascular bed-specific regulation of others seem to coexist and participate in VSMC proliferation through complementary mechanisms. Such a system will add flexibility to the process while providing the required robustness to preserve this fundamental cellular response.

Whole Body Vibration Retards Progression of Atherosclerosis via Insulin-Like Growth Factor 1 in Apolipoprotein E-Deficient Mice

Whole body vibration (WBV) has a marked impact on lipid metabolism and the endocrine system, which is related to the progression of atherosclerosis (AS). To investigate the effects of WBV, we measured the atherosclerotic plaque area of apolipoprotein E-knockout (ApoE^−/−) AS mice, which were trained by WBV (15 Hz, 30 min) for 12 weeks. Simultaneously, serum levels of lipids, insulin-like growth factor 1 (IGF-1), insulin-like growth factor 1 receptor (IGF-1R), interleukin 6 (IL-6), and the mRNA and protein levels of the same in the aorta were compared between the control and WBV groups. The results indicated that WBV significantly reduced the atherosclerotic plaque area with lower very low-density lipoprotein (VLDL) and oxidized low-density lipoprotein (ox-LDL) in the blood. Moreover, the levels of IGF-1 in serum and expression of IL-6, IGF-1R, and p-IGF-1R protein in the mice aorta decreased significantly in the WBV group. In addition, we found that serum IGF-1 in mice increased to the highest concentration in 30 min after WBV for 10, 30, 60, and 120 minutes. These results suggested that appropriate WBV may delay the progression of AS, which was associated with acutely elevated serum IGF-1 and lower levels of IGF-1 and IL-6 in the aorta for long-term treatment.

Calcium- and voltage-gated BK channels in vascular smooth muscle

Ion channels in vascular smooth muscle regulate myogenic tone and vessel contractility. In particular, activation of calcium- and voltage-gated potassium channels of large conductance (BK channels) results in outward current that shifts the membrane potential toward more negative values, triggering a negative feed-back loop on depolarization-induced calcium influx and SM contraction. In this short review, we first present the molecular basis of vascular smooth muscle BK channels and the role of subunit composition and trafficking in the regulation of myogenic tone and vascular contractility. BK channel modulation by endogenous signaling molecules, and paracrine and endocrine mediators follows. Lastly, we describe the functional changes in smooth muscle BK channels that contribute to, or are triggered by, common physiological conditions and pathologies, including obesity, diabetes, and systemic hypertension.

Application of radiopaque micro-particle fillers for 3-D imaging of periodontal pocket analogues using cone beam CT

BACKGROUND

Periodontitis is an infectious/inflammatory disease most often diagnosed by deepening of the gingival sulcus, which leads to periodontal pockets (PPs) conventional manual periodontal probing does not provide detailed information on the three-dimensional (3-D) nature of PPs.

OBJECTIVES

To determine whether accurate 3-D analyses of the depths and volumes of calibrated PP analogues (PPAs) can be obtained by conventional cone beam computed tomography (CBCT) coupled with novel radiopaque micro-particle fillers (described in the companion paper) injected into the PPAs.

METHODS

Two PPA models were employed: (1) a human skull model with artificial gingiva applied to teeth with alveolar bone loss and calibrated PPAs, and (2) a pig jaw model with alveolar bone loss and surgically-induced PPAs The PPAs were filled with controlled amounts of radiopaque micro-particle filler using volumetric pipetting Inter-method and intra-method agreement tests were then used to compare the PPA depths and volumes obtained from CBCT images with values obtained by masked examiners using calibrated manual methods.

RESULTS

Significant inter-method agreement (0.938-0.991) and intra-method agreement (0.94-0.99) were obtained when comparing analog manual data to digital CBCT measurements enabled by the radiopaque filler.

SIGNIFICANCE

CBCT imaging with radiopaque micro-particle fillers is a plausible means of visualizing and digitally assessing the depths, volumes, and 3-D shapes of PPs This approach could transform the diagnosis and treatment planning of periodontal disease, with particular initial utility in complex cases Efforts to confirm the clinical practicality of these fillers are currently in progress.

BK Knockout by TALEN-Mediated Gene Targeting in Osteoblasts: KCNMA1 Determines the Proliferation and Differentiation of Osteoblasts

Large conductance calcium-activated potassium (BK) channels participate in many important physiological functions in excitable tissues such as neurons, cardiac and smooth muscles, whereas the knowledge of BK channels in bone tissues and osteoblasts remains elusive. To investigate the role of BK channels in osteoblasts, we used transcription activator-like effector nuclease (TALEN) to establish a BK knockout cell line on rat ROS17/2.8 osteoblast, and detected the proliferation and mineralization of the BK-knockout cells. Our study found that the BK-knockout cells significantly decreased the ability of proliferation and mineralization as osteoblasts, compared to the wild type cells. The overall expression of osteoblast differentiation marker genes in the BK-knockout cells was significantly lower than that in wild type osteoblast cells. The BK-knockout osteoblast cell line in our study displays a phenotype decrease in osteoblast function which can mimic the pathological state of osteoblast and thus provide a working cell line as a tool for study of osteoblast function and bone related diseases.