Endothelial connexin32 enhances angiogenesis by positively regulating tube formation and cell migration

The gap junction proteins connexin32 (Cx32), Cx37, Cx40, and Cx43 are expressed in endothelial cells, and regulate vascular functions involving inflammation, vasculogenesis and vascular remodeling. Aberrant Cxs expression promotes the development of atherosclerosis which is modulated by angiogenesis; however the role played by endothelial Cxs in angiogenesis remains unclear. In this study, we determined the effects of endothelial Cxs, particularly Cx32, on angiogenesis. EA.hy926 cells that had been transfected to overexpress Cx32 significantly increased capillary length and the number on branches compared to Cx-transfectant cells over-expressing Cx37, Cx40, and Cx43 or mock-treated cells. Treatment via intracellular transfer of anti-Cx32 antibody suppressed tube formation of human umbilical vein endothelial cells (HUVECs) compared to controls. In vitro wound healing assays revealed that Cx32-transfectant cells significantly increased the repaired area while anti-Cx32 antibody-treated HUVECs reduced it. Ex vivo aorta ring assays and in vivo matrigel plaque assays showed that Cx32-deficient mice impaired both vascular sprouting from the aorta and cell migration into the implanted matrigel. Therefore endothelial Cx32 facilitates tube formation, wound healing, vascular sprouting, and cell migration. Our results suggest that endothelial Cx32 positively regulates angiogenesis by enhancing endothelial cell tube formation and cell migration.     

RhoA/rho kinase signaling reduces connexin43 expression in high glucose-treated glomerular mesangial cells with zonula occludens-1 involvement

RhoA/Rho kinase (ROCK) signaling has been suggested to be involved in diabetic nephropathy (DN) pathogenesis. Altered expression of connexin43 (Cx43) has been found in kidneys of diabetic animals. Both of them have been found to regulate nuclear factor kappa-B (NF-κB) activation in high glucose-treated glomerular mesangial cells (GMCs). The aim of this study was to investigate the relationship between RhoA/ROCK signaling and Cx43 in the DN pathogenesis. We found that upregulation of Cx43 expression inhibited NF-κB p65 nuclear translocation induced by RhoA/ROCK signaling in GMCs. Inhibition of RhoA/ROCK signaling attenuated the high glucose-induced decrease in Cx43. F-actin accumulation and an enhanced interaction between zonula occludens-1 (ZO-1) and Cx43 were observed in high glucose-treated GMCs. ZO-1 depletion or disruption of F-actin formation also inhibited the reduction in Cx43 protein levels induced by high glucose. In conclusion, activated RhoA/ROCK signaling induces Cx43 degradation in GMCs cultured in high glucose, depending on F-actin regulation. Increased F-actin induced by RhoA/ROCK signaling promotes the association between ZO-1 and Cx43, which possibly triggered Cx43 endocytosis, a mechanism of NF-κB activation in high glucose-treated GMCs.     

Arginase inhibition restores endothelial function in diet-induced obesity

Arginase may play a major role in the regulation of vascular function in various cardiovascular disorders by impairing nitric oxide (NO) production. In the current study, we investigated whether supplementation of the arginase inhibitor N^ω-hydroxy-nor-l-arginine (nor-NOHA) could restore endothelial function in an animal model of diet-induced obesity. Arginase 1 expression was significantly lower in the aorta of C57BL/6J mice fed a high-fat diet (HFD) supplemented with nor-NOHA (40 mg kg^-1/day) than in mice fed HFD without nor-NOHA. Arginase inhibition led to considerable increases in eNOS expression and NO levels and significant decreases in the levels of circulating ICAM-1. These findings were further confirmed by the results of siRNA-mediated knockdown of Arg in human umbilical vein endothelial cells. In conclusion, arginase inhibition can help restore dysregulated endothelial function by increasing the eNOS-dependent NO production in the endothelium, indicating that arginase could be a therapeutic target for correcting obesity-induced vascular endothelial dysfunction.     

Influence of polymorphism in dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin-related (DC-SIGNR) gene on HIV-1 trans-infection

The dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) and DC-SIGN-related (DC-SIGNR) molecules on the cell surface are known to enhance human immunodeficiency virus type 1 (HIV-1) infection by capturing the virions and transmitting them to CD4+ T-cell, a process termed trans-infection. The neck region and carbohydrate recognition domain of the two proteins are important for efficient binding to the HIV-1 envelope protein. DC-SIGNR is polymorphic in Exons 4 and 5 that encode the neck region and carbohydrate recognition domain, respectively; the former contains a variable number of tandem repeats, and the latter the SNP (rs2277998). Since it remains unclear whether the DC-SIGNR polymorphism is related to the risk of HIV-1 infection, we tested possible effects of the polymorphism on HIV-1 trans-infection efficiency, by constructing six kinds of cDNAs encoding DC-SIGNR variants with various numbers of repeat units and various SNP. We were able to express the variants on the surface of Raji cells, a human B cell line. Flow cytometry showed that all the tested DC-SIGNR molecules were efficiently expressed on the cell surface at various levels; the assay for HIV trans-infection efficacy showed that all the tested variants had that activity with different efficacy levels. We found a correlation between the HIV trans-infection efficiency and the mean fluorescent intensity of DC-SIGNR expression (R² = 0.95). Thus, our results suggest that the variation of the tested DC-SIGNR genotypes affects the efficacy of trans-infection by affecting the amounts of the protein expressed on the cell surface.     

Assessment of penetration of quantum dots through in vitro and in vivo human skin using the human skin equivalent model and the tape stripping method

Quantum dots (QDs) are rapidly emerging as an important class of nanoparticles (NPs) with potential applications in medicine. However, little is known about penetration of QDs through human skin. This study investigated skin penetration of QDs in both in vivo and in vitro human skin. Using the tape stripping method, this study demonstrates for the first time that QDs can actually penetrate through the stratum corneum (SC) of human skin. Transmission electron microscope (TEM) and energy diverse X-ray (EDX) analysis showed accumulation of QDs in the SC of a human skin equivalent model (HSEM) after dermal exposure to QDs. These findings suggest possible transdermal absorption of QDs after dermal exposure over a relatively long period of time.     

Long-Lived, High-Strength States of ICAM-1 Bonds to β2 Integrin, I: Lifetimes of Bonds to Recombinant αLβ2 Under Force

Using single-molecule force spectroscopy to probe ICAM-1 interactions with recombinant α_Lβ₂ immobilized on microspheres and β₂ integrin on neutrophils, we quantified an impressive hierarchy of long-lived, high-strength states of the integrin bond, which start from basal levels with integrin activation in solutions of divalent cations and shift dramatically upward to hyperactivated states with cell signaling in leukocytes. Taking advantage of very rare events, we used repeated measurements of bond lifetimes under steady ramps of force to achieve a direct assay for the off-rates of ICAM-1 from β₂ integrin in each experiment. Of fundamental importance, the assay for off-rates does not depend on how the force is applied over time, and remains valid when the rates of dissociation change with different levels of force. In this first article, we present results from tests of a monovalent ICAM-1 probe against immobilized α_Lβ₂ in environments of divalent cations (Ca²⁺, Mg²⁺, and Mn²⁺) and demonstrate in detail the method for assay of off-rates. When extrapolated to zero force, the force-free values for the off-rates are found to be consistent with published solution-based assays of soluble ICAM-1 dissociation from immobilized LFA-1, i.e., ∼10⁻²/s in Mg²⁺ or Mn²⁺ and ∼1/s in Ca²⁺. At the same time, as expected for adhesive function, we find that the β₂ integrin bonds activated in Mn²⁺ or Mg²⁺ possess significant and persistent mechanical strength (e.g., >20 pN for >1 s) even when subjected to slow force ramps (<10 pN/s). As discussed in our companion article, using the same assay, we find that although the rates of dissociation for diICAM-1fc bonds to LFA-1 on neutrophils in Mn²⁺ are similar to those for mICAM-1 bonds to recombinant α_Lβ₂ on microspheres, they appear to represent a dimeric attachment to a pair of tightly clustered integrin heterodimers. The mechanical strengths and lifetimes of the dimeric interactions increase dramatically when the neutrophils are stimulated by the chemokine IL-8 or are bound with an allosterically activating (anti-CD18) monoclonal antibody, demonstrating the major impact of cell signaling on LFA-1.     

Temperature dependences of carbon assimilation processes in four dominant species from mountain grassland ecosystem

Temperature responses of carbon assimilation processes were studied in four dominant species from mountain grassland ecosystem, i.e. Holcus mollis (L.), Hypericum maculatum (Cr.), Festuca rubra (L.), and Nardus stricta (L.), using the gas exchange technique. Leaf temperature (T _L) of all species was adjusted within the range 13–30 °C using the Peltier thermoelectric cooler. The temperature responses of metabolic processes were subsequently modelled using the Arrhenius exponential function involving the temperature coefficient Q ₁₀. The expected increase of global temperature led to a significant increase of dark respiration rate (R _D; Q ₁₀ = 2.0±0.5), maximum carboxylation rate (V _Cmax; Q ₁₀ = 2.2±0.6), and maximum electron transport rate (J _max; Q ₁₀ = 1.6±0.4) in dominant species of mountain grassland ecosystems. Contrariwise, the ratio between J _max and V _Cmax linearly decreased with T _L [y = −0.884 T _L + 5.24; r ² = 0.78]. Hence temperature did not control the ratio between intercellular and ambient CO₂ concentration, apparent quantum efficiency, and photon-saturated CO₂ assimilation rate (P _max). P _max primarily correlated with maximum stomatal conductance irrespective of T _L. Water use efficiency tended to decrease with T _L [y = −0.21 T _L + 8.1; r ² = 0.87].     

Up-regulation of connexin 43 and gap junctional intercellular communication by Coleusin Factor is associated with growth inhibition in rat osteosarcoma UMR106 cells

Gap junctions, formed by connexin (Cx) family proteins, permit direct exchange of regulatory ions and small signal molecules between neighbouring cells. Gap junctional intercellular communication (GJIC) plays an important role in maintaining the homeostasis and preventing cell transformation. Most of the tumour cells feature deficient or aberrant connexin expression and GJIC level, and restoration of connexin expression and GJIC is correlated with cell growth control. Numerous researches has suggested the possibility of connexins as potential anti-tumour targets for chemoprevention and chemotherapy. We investigated the ability of Coleusin Factor (CF, also named FSK88) to regulate the Cx43 expression and GJIC level in rat osteosarcoma UMR106 cells. The results have demonstrated that CF increased the mRNA and protein expression of Cx43 in both in a dose- and timedependent manner, and concomitant with up-regulation of Cx43, CF treatment up-regulated the diminished GJIC level in UMR106 cells as assayed by dye transfer experiments. In addition, Cx43 distribution at the plasma membrane was also enhanced dramatically by CF treatment. Furthermore, we discovered that CF was potent to inhibit the growth and proliferation of UMR106 cells. These results provide the first evidence that CF can regulate connexin and GJIC, indicating that Cx43 may be a target of CF to exert its anti-tumour effects.     

Hitch-hiking between cells on lipoprotein particles

Cell surface proteins containing covalently linked lipids associate with specialized membrane domains. Morphogens like Hedgehog and Wnt use their lipid anchors to bind to lipoprotein particles and employ lipoproteins to travel through tissues. Removal of their lipid anchors or decreasing lipoprotein levels give rise to adverse Hedgehog and Wnt signaling. Some parasites can also transfer their glycosylphosphatidylinositol-anchored surface proteins to host lipoprotein particles. These antigen-loaded lipoproteins spread throughout the circulation, and probably hamper an adequate immune response by killing neutrophils. Together, these findings imply a widespread role for lipoproteins in intercellular transfer of lipid-anchored surface proteins, and may have various physiological consequences. Here, we discuss how lipid-modified proteins may be transferred to and from lipoproteins at the cellular level.