Effects of verapamil and elgodipine on isoprenaline-induced metabolic responses in rabbits

Etiology of the membrane potential of rat white fat adipocytes

The plasma membrane potential (Vm) is key to many physiological processes; however, its ionic etiology in white fat adipocytes is poorly characterized. To address this question, we employed the perforated patch current clamp and cell-attached patch clamp methods in isolated primary white fat adipocytes and their cellular model 3T3-L1. The resting Vm of primary and 3T3-L1 adipocytes were -32.1 ± 1.2 mV (n = 95) and -28.8 ± 1.2 mV (n = 87), respectively. Vm was independent of cell size and fat content. Elevation of extracellular K(+) to 50 mM by equimolar substitution of bath Na(+) did not affect Vm, whereas substitution of bath Na(+) with the membrane-impermeant cation N-methyl-D-glucamine(+)-hyperpolarized Vm by 16 mV, data indicative of a nonselective cation permeability. Substitution of 133 mM extracellular Cl(-) with gluconate-depolarized Vm by 25 mV, whereas Cl(-) substitution with I(-) caused a -9 mV hyperpolarization. Isoprenaline (10 μM), but not insulin (100 nM), significantly depolarized Vm. Single-channel ion activity was voltage independent; currents were indicative for Cl(-) with an inward slope conductance of 16 ± 1.3 pS (n = 11) and a reversal potential close to the Cl(-) equilibrium potential, -29 ± 1.6 mV. Although the reduction of extracellular Cl(-) elevated the intracellular Ca(2+) of adipocytes, this was not as large as that produced by elevation of extracellular K(+). In conclusion, the Vm of white fat adipocytes is well described by the Goldman-Hodgkin-Katz equation with a predominant permeability to Cl(-), where its biophysical and single-channel properties suggest a volume-sensitive anion channel identity. Consequently, changes in serum Cl(-) homeostasis or the adipocyte's permeability to this anion via drugs will affect its Vm, intracellular Ca(2+), and ultimately its function and its role in metabolic control.

SOX2 gene regulates the transcriptional network of oncogenes and affects tumorigenesis of human lung cancer cells

Recent studies demonstrated that cancer stem cells (CSCs) have higher tumorigenesis properties than those of differentiated cancer cells and that transcriptional factor-SOX2 plays a vital role in maintaining the unique properties of CSCs; however, the function and underlying mechanism of SOX2 in carcinogenesis of lung cancer are still elusive. This study applied immunohistochemistry to analyze the expression of SOX2 in human lung tissues of normal individuals as well as patients with adenocarcinoma, squamous cell carcinoma, and large cell and small cell carcinoma and demonstrated specific overexpression of SOX2 in all types of lung cancer tissues. This finding supports the notion that SOX2 contributes to the tumorigenesis of lung cancer cells and can be used as a diagnostic probe. In addition, obviously higher expression of oncogenes c-MYC, WNT1, WNT2, and NOTCH1 was detected in side population (SP) cells than in non-side population (NSP) cells of human lung adenocarcinoma cell line-A549, revealing a possible mechanism for the tenacious tumorigenic potential of CSCs. To further elucidate the function of SOX2 in tumorigenesis of cancer cells, A549 cells were established with expression of luciferase and doxycycline-inducible shRNA targeting SOX2. We found silencing of SOX2 gene reduces the tumorigenic property of A549 cells with attenuated expression of c-MYC, WNT1, WNT2, and NOTCH1 in xenografted NOD/SCID mice. By using the RNA-Seq method, an additional 246 target cancer genes of SOX2 were revealed. These results present evidence that SOX2 may regulate the expression of oncogenes in CSCs to promote the development of human lung cancer.

SOX2 promotes tumorigenesis and increases the anti-apoptotic property of human prostate cancer cell

SRY-related HMG-box gene 2 (SOX2) is one of the key regulatory genes that maintain the pluripotency and self-renewal properties in embryonic stem cells. Here we used immunohistochemistry to analyze the expression of SOX2 in human prostate tissues and found it contributed to tumorigenesis and correlated with histologic grade and Gleason score. We further investigated SOX2's function in cell growth and apoptosis process by using a human prostate cancer cell line DU145 with SOX2 overexpression or down-regulation. Cell cycle assay revealed that SOX2 promoted cell growth and increased the percentage of cells in S phase. In vitro and in vivo xenograft experiments in NOD/SCID mice further demonstrated that SOX2 increased the apoptosis-resistant properties of DU145 cells with decreased function of store-operated Ca(2+) entry and reduced expression of Orai1 at both mRNA and protein levels, suggesting a potential mechanism that contributes to the anti-apoptotic property of SOX2. To our knowledge, this study is the first to investigate SOX2's function in tumorigenesis and apoptosis of human prostate cancer and to elucidate its regulatory effect on the activity of store-operated Ca(2+) channels. Our results support the concept that SOX2 has the potential to be a significant marker to evaluate the progression of prostate cancer and serve as a potentially useful target for prostate cancer therapy.

Benzylamine exhibits insulin-like effects on glucose disposal, glucose transport, and fat cell lipolysis in rabbits and diabetic mice

Benzylamine, a substrate of semicarbazide-sensitive amine oxidase (SSAO), stimulates glucose transport in rat adipocytes and improves glucose disposal in diabetic rats only in the presence of vanadate. These effects have been described to result from a synergism between the hydrogen peroxide formed during amine oxidation and vanadate, via the generation of pervanadate, a powerful insulin mimicker. However, it has also been reported that benzylamine alone can stimulate glucose uptake and inhibit lipolysis in human fat cells. In this work, we therefore investigated whether benzylamine on its own was able to induce both in vivo and in vitro insulin-like responses in animal models other than rat. In rabbits, the i.v. infusion of 7 micromol/kg benzylamine before a glucose tolerance test resulted in a net reduction of the hyperglycemic response without a change in insulin secretion. Benzylamine also improved glucose tolerance and reduced lipid mobilization in hyperglycemic/obese mice. In vitro, 0.1 mM benzylamine stimulated glucose transport and inhibited lipolysis in mouse and rabbit adipocytes. These effects were blocked by previous treatments with semicarbazide, a SSAO inhibitor. Levels of benzylamine oxidation were more elevated in mouse than in rabbit adipose tissues, whereas the reverse was observed for skeletal muscles. Finally, benzylamine was unable to stimulate insulin secretion by isolated pancreatic islets from both species and SSAO activity was hardly detectable in pancreas. Together, our results bring evidence that benzylamine on its own can improve glucose tolerance in rabbit and mouse, likely by stimulating glucose uptake via amine oxidase activation in insulin-sensitive tissues.