The role of Ca2+/calmodulin-dependent protein kinase II and calcineurin in TNF-α-induced myocardial hypertrophy

We investigated whether Ca²⁺/calmodulin-dependent kinase II (CaMKII) and calcineurin (CaN) are involved in myocardial hypertrophy induced by tumor necrosis factor α (TNF-α). The cardiomyocytes of neonatal Wistar rats (1-2 days old) were cultured and stimulated by TNF-α (100 µg/L), and Ca²⁺ signal transduction was blocked by several antagonists, including BAPTA (4 µM), KN-93 (0.2 µM) and cyclosporin A (CsA, 0.2 µM). Protein content, protein synthesis, cardiomyocyte volumes, [Ca²⁺]_i transients, CaMKIIδ_B and CaN were evaluated by the Lowry method, [³H]-leucine incorporation, a computerized image analysis system, a Till imaging system, and Western blot analysis, respectively. TNF-α induced a significant increase in protein content in a dose-dependent manner from 10 µg/L (53.56 µg protein/well) to 100 µg/L (72.18 µg protein/well), and in a time-dependent manner from 12 h (37.42 µg protein/well) to 72 h (42.81 µg protein/well). TNF-α (100 µg/L) significantly increased the amplitude of spontaneous [Ca²⁺]_i transients, the total protein content, cell size, and [³H]-leucine incorporation in cultured cardiomyocytes, which was abolished by 4 µM BAPTA, an intracellular Ca²⁺ chelator. The increases in protein content, cell size and [³H]-leucine incorporation were abolished by 0.2 µM KN-93 or 0.2 µM CsA. TNF-α increased the expression of CaMKIIδ_B by 35.21% and that of CaN by 22.22% compared to control. These effects were abolished by 4 µM BAPTA, which itself had no effect. These results suggest that TNF-α induces increases in [Ca²⁺]_i, CaMKIIδ_B and CaN and promotes cardiac hypertrophy. Therefore, we hypothesize that the Ca²⁺/CaMKII- and CaN-dependent signaling pathways are involved in myocardial hypertrophy induced by TNF-α.     

Aldosterone and TGF-β1 synergistically increase PAI-1 expression in hepatic stellate cells of rats

Objective: Aldosterone is related to the fibrosis of several organs, but the specific mechanism underlying the aldosterone induced hepatic fibrosis is still unclear. Methods: Separation, culture and identification of primary hepatic stellate cells (HSCs): The fluids and digestives used in the present study were able to completely remove blood cells, digest hepatocytes and matrix, and effectively separate HSCs. The in situ perfusion was performed at 2 steps: in situ perfusion with pre-perfusion fluid and ex vivo perfusion with enzyme-containing perfusion fluid. Influence of Ald on PAI-1 and Smad expressions in HSCs: cells were divided into control group, Ald group (10^-6 M), spironolactone (SPI) group and Ald+SPI group, and the mRNA and protein expressions of PAI-1 and Smad were detected. Ald induced type I collagen expression in HSCs: Immunohistochemistry was performed to detect type I collagen expression in the supernatant of control group, Ald group (10^-6 M), TGF-β₁ group, and Ald+TGF-β₁ group. Influence of Ald and TGF-β₁ on PAI-1 expression in HSCs: cells were divided into control group, Ald group (10^-6 M), TGF-β₁ group, and Ald+TGF-β₁ group, and the mRNA and protein expressions of PAI-1 were determined by RT-PCR and Western blot assay, respectively. Synergistic effect of Ald and TGF-β₁ on PAI-1 expression in HSCs: cells were divided into control group, Ald group (10^-6), TGF-β₁ group, Ald (10^-6 M)+TGF-β₁ group, Ald (10^-7 M)+TGF-β₁ group and Ald (10^-8 M)+TGF-β₁ group, and the mRNA and protein expressions of PAI-1 were detected by RT-PCR and Western blot assay, respectively. Results: The survival rate, purity, markers and activation of HSCs were determined after separation. Influence of Ald on PAI-1 expression in HSCs: PAI-1 expression increased in HSCs of Ald group, SPI group and Ald+API group, and the PAI-1 expression in Ald group and Ald+SPI group was significantly higher than in control group (P<0.01). Influence of Ald on Smad expression in HSCs: Smad expression in Ald group, TGF-β₁ group and ALD+TGF-β₁ group was markedly higher than in control group (P<0.05). Smad expression in ALD+TGF-β₁ group increased significantly when compared with Ald group (P<0.01). Ald induced type I collagen expression in HSCs: type I collagen expression in Ald group, TGF-β₁ group and ALd+TGF-β₁ group was dramatically higher than in control group (P<0.05), and it in ALd+TGF-β₁ group was also significantly different from that in Ald group and TGF-β₁ group (P<0.01). Synergistic effects of Ald and TGF-β₁ on PAI expression in HSCs: PAI-1 expression in treated cells was markedly higher than in control group (P<0.01). PAI-1 expression in 10^-6 M Ald+5 ng/ml TGF-β₁ group increased dramatically as compared to Ald group and TGF-β₁ group (P<0.01), but the increased PAI-1 expression reduced after SPI treatment. Ald at different concentrations exerts synergistic effect with TGF-β₁ to increase PAI-1 expression in HSCs: PAI-1 expression in HSCs after different treatments increased markedly as compared to control group (P<0.01). Significant difference in PAI-1 expression was observed in 10^-6 M Ald+50 pg/ml TGF-β₁ group and 10^-6 M Ald group (P<0.01), PAI-1 expression in 10^-7 M Ald+50 pg/ml TGF-β₁ group was significantly higher than in 50 pg/ml TGF-β₁ group (P<0.01), but the PAI-1 expression in 10^-7 M Ald+50 pg/ml TGF-β₁ group was similar to that in 10^-6 M Ald group (P>0.05). Conclusion: Aldosterone is able to activate HSCs and increase PAI-1 expression during hepatic fibrosis, which may be inhibited by spironolactone. Aldosterone and TGF-β₁ may synergistically act on HSCs to increase PAI-1 expression as compared to treatment with aldosterone or TGF-β₁ alone. Aldosterone or TGF-β₁ alone may slightly increase PAI-1 expression in HSCs, which can be inhibited by spironolactone.     

NLS-RARα Inhibits the Effects of All-trans Retinoic Acid on NB4 Cells by Interacting with P38α MAPK

Nuclear localization signal retinoic acid receptor alpha(NLS-RARα), which forms from the cleavage of promyelocytic leukemia-retinoic acid receptor alpha(PML-RARα) protein by neutrophil elastase(NE), possesses an important role in the occurrence and development of acute promyelocytic leukemia(APL). However, the potential mechanism underlying the effects of NLS-RARα on APL is still not entirely clear. Here, we investigated the effects of NLS-RARα on APL NB4 cells and its mechanism. We found that all-trans retinoic acid(ATRA) could promote differentiation while inhibit proliferation of APL NB4 cells via upregulating the expression of phosphorylated p38α mitogen-activated protein kinase(p-p38α MAPK). We also found that NLS-RARα could inhibit differentiation while accelerate proliferation of NB4 cells via downregulating the expression of p-p38α protein in the presence of ATRA. Furthermore, immunofluorescence and co-immunoprecipitation assays confirmed NLS-RARα interacted with p38α protein directly. Finally, application of PD169316, an inhibitor of p38α protein, suggested that recruitment p38α-combinded NLS-RARα by ATRA eventually caused activation of p38α protein. In summary, our study demonstrated that ATRA cound promote differentiation while inhibit proliferation of APL NB4 cells via activating p38α protein after recruiting p38α-combinded NLS-RARα, while NLS-RARα could inhibit the effects of ATRA in the process.     

Effects of interferon-alpha (IFN-α) administration on leucocytes in healthy humans

Plasma concentrations of IFN-α are increased in several inflammatory conditions. Several lines of evidence indicate that IFN-α has anti-inflammatory properties. To study the effects of IFN-α on leucocyte subsets and activation and on cytokines, we administered IFN-α (rhIFN-α2b; 5 × 10⁶ U/m²) to eight healthy human subjects in a randomized controlled cross-over study and analysed changes in circulating leucocytes and parameters for neutrophil and monocyte activation. After administration of IFN-α, neutrophil counts increased, monocyte counts decreased transiently, whereas the number of lymphocytes, basophils and eosinophils showed a sustained decrease. IFN-α administration was also associated with neutrophil activation, reflected in an increase in the plasma concentrations of elastase–α₁-antitrypsin complexes and lactoferrin. Serum neopterin, a marker for monocyte activation, was significantly increased 10 h after administration of IFN-α. IFN-α significantly increased plasma concentrations of IL-6, IL-8 and IL-10. Although IL-1 and tumour necrosis factor (TNF) remained undetectable, plasma concentrations of soluble TNF receptors p55 and p75 increased after IFN-α administration. We conclude that IFN-α induces multiple alterations in the distribution and functional properties of leucocytes. IFN-α exerts pro- as well as anti-inflammatory effects within the cytokine network.     

Generalized immune activation in pulmonary tuberculosis: co-activation with HIV infection

Parameters of immune activation/differentiation were studied in a group of newly diagnosed HIV⁻ and HIV⁺ pulmonary tuberculosis (TB) patients. Compared with controls, HLA-DR expression on both CD4 and CD8 T cells from the HIV⁻ TB patients was approximately doubled; HLA-DR on T cells from the HIV⁺ group was tripled. The monocytes from both groups of patients expressed abnormally high levels of the Fcγ receptors I and III. Serum levels of tumour necrosis factor-alpha (TNF-α), neopterin and β₂-microglobulin were increased in HIV⁻ and even more so in HIV⁺ TB patients. The expression of HLA-DR on T cell subsets and of FcγR on monocytes correlated with each other, but not with serum activation markers. This pattern of non-specific activation during TB infection may be associated with enhanced susceptibility to HIV infection.     

大鼠成纤维细胞生长因子对心肌成纤维细胞增殖和转分化的作用机制

目的 探讨成纤维细胞生长因子（FGF）对心肌成纤维细胞(CFs)在增殖和转分化为肌成纤维细胞（MFs）中的作用。 方法 分离、培养大鼠CFs,利用FGF对其进行诱导培养,CCK-8技术检测细胞活性和增殖状况,免疫荧光和Western blotting技术测定α平滑肌肌动蛋白（α-SMA）和Ⅰ型胶原（ColⅠ）的表达量。 结果 随大鼠CFs培养代数的增加,其α-SMA、ColⅠ的表达和活化为MFs的数量增加。加入FGF诱导培养的大鼠CFs数量没有明显增加;加入FGF1、FGF2诱导的CFs表达α-SMA减少,活化为MFs 数量减少。 结论 FGF家族对大鼠CFs没有促增殖作用,但FGF1和FGF2可以抑制CFs活化,减少其向MFs的分化。     

Inverted Vδ1/Vδ2 ratio within the T cell receptor (TCR)-γδ T cell population in peripheral blood of heart transplant recipients

We investigated the levels of TCR-γδ T cells and their subpopulations Vδ1 and Vδ2 in the peripheral blood lymphocytes (PBL) of 28 heart transplant (HTx) patients. Patients (n = 10) receiving cyclosporin A (CsA) for treatment of a nephrotic syndrome (NS) and 10 healthy individuals served as controls. There was no difference in levels of TCR-γδ T cells between the different groups. However, an elevated proportion of Vδ1⁺γδ T cells was found in the PBL of HTx patients, especially when these cells were present in their graft-infiltrating lymphocyte (GIL) cultures. Vδ1⁺γδ T cells of HTx patients showed normal expression of CD45RO and lacked the activation markers CD25 and HLA-DR. After expanding in IL-2-containing medium, PBL cultures of HTx patients more often were dominated by Vδ1 cells than PBL cultures of controls, in which Vδ2 cells were predominantly grown. The aberrant composition of the TCR-γδ population in HTx patients was not a result of immunosuppressive medication, since the proportion Vδ1⁺γδ T cells was normal in the PBL of the NS patients receiving a similar dose of CsA. It is postulated that long-term antigenic stimulation by the graft, at low level, might be responsible for the altered composition of the γδ pool in the HTx patients. Since no donor HLA-specific γδ T cells have been detected, other ligands, such as heat shock proteins, may be involved.     

Differential Regulation of Mouse B Cell Development by Transforming Growth Factor β1

Transforming growth factor β (TGFβ) can inhibit the in vitro proliferation, survival and differentiation of B cell progenitors, mature B lymphocytes and plasma cells. Here we demonstrate unexpected, age-dependent reductions in the bone marrow (BM) B cell progenitors and immature B cells in TGFβ1^-/- mice. To evaluate TGFβ responsiveness during normal B lineage development, cells were cultured in interleukin 7 (IL7)±TGFβ. Picomolar doses of TGFβ1 reduced pro-B cell recoveries at every timepoint. By contrast, the pre-B cells were initially reduced in number, but subsequently increased compared to IL7 alone, resulting in a 4-fold increase in the growth rate for the pre-B cell population. Analysis of purified BM sub-populations indicated that pro-B cells and the earliest BP1^- pre-B cells were sensitive to the inhibitory effects of TGFβ1. However, the large BP1⁺ pre-B cells, although initially reduced, were increased in number at days 5 and 7 of culture. These results indicate that TGFβ1 is important for normal B cell development in vivo, and that B cell progenitors are differentially affected by the cytokine according to their stage of differentiation.     

环孢素A对神经肽Y刺激的大鼠血管平滑肌细胞增殖的影响

目的:观察环孢素A(CsA)对神经肽Y(NPY)诱导的大鼠主动脉平滑肌细胞增殖的影响,以探讨钙调神经磷酸酶(CaN)信号通路在血管平滑肌细胞增殖中的作用。方法:体外培养的大鼠主动脉平滑肌细胞分为3组:(1)NPY组,(2)CsA+NPY组,(3)对照组。检测CaN活性(定磷法)、细胞增殖活度(MTT法)的变化,观察增殖细胞核抗原(PCNA)的表达水平(免疫组化定量技术)。结果:NPY组CaN活性、血管平滑肌细胞增殖活度(吸光度表示),PCNA表达水平(光密度值表示)明显高于对照组(P＜0.01或P＜0.05),CsA+NPY组各项指标明显低于NPY组(P＜0.01或P＜0.05)。结论:环孢素A可显著阻滞神经肽Y刺激的血管平滑肌细胞增殖,这种作用可能通过抑制CaN信号通路所致。     

β2 Integrin deficiency yields unconventional double-negative T cells distinct from mature classical natural killer T cells in mice

Expressed on leucocytes, β₂ integrins (CD11/CD18) are specifically involved in leucocyte function. Using a CD18-deficient (CD18^−/−) mouse model, we here report on their physiological role in lymphocyte differentiation and trafficking. CD18^−/− mice present with a defect in the distribution of lymphocytes with highly reduced numbers of naïve B and T lymphocytes in inguinal and axillary lymph nodes. In contrast, cervical lymph nodes were fourfold enlarged harbouring unconventional T-cell receptor-αβ (TCR-αβ) and TCR-γδ CD3⁺ CD4⁻ CD8⁻ (double-negative; DN) T cells that expanded in situ. Using adoptive transfer experiments, we found that these cells did not home to peripheral lymph nodes of CD18^wt recipients but, like antigen-experienced T or natural killer (NK) T cells, recirculated through non-lymphoid organs. Lacking regulatory functions in vitro, CD18^−/− TCR-αβ DN T cells did not suppress the proliferation of polyclonally activated CD4⁺ or CD8⁺ (single-positive; SP) T cells. Most interestingly, CD18^−/− TCR-αβ DN T cells showed intermediate TCR expression levels, an absent activation through allogeneic major histocompatibility complex and a strong proliferative dependence on interleukin-2, hence, closely resembling NKT cells. However, our data oppose former reports, clearly showing that, because of an absent reactivity with CD1d-αGalCer dimers, these cells are not mature classical NKT cells. Our data indicate that CD18^−/− TCR-αβ DN T cells, like NKT and TCR-γδ T cells, share characteristics of both adaptive and innate immune cells, and may accumulate as a compensatory mechanism to the functional defect of adaptive immunity in CD18^−/− mice.     

The role of integrin-β/FAK in cyclic mechanical stimulation in MG-63 cells

Objective: This study aims to explore the function of Integrin-β/FAK in the mechanical signal transduction and the connection with downstream ERK signal pathways. Methods: Human osteosarcoma MG63 cell lines were used in this study. The effects of mechanical strain on the Integrin-β₁ expression, FAK and ERK signal pathway in Human osteosarcoma MG63 cells were detected using RT-PCR and Western-blotting methods. The localization of FAK in Human osteosarcoma MG63 cells were determined using immunofluorescent method. The interaction between Integrin-β₁ and FAK were detected by using co-immunoprecipitation method. Results: The expression of Integrin-β₁ shows a notable bimodel distribution, mechanical strain stimulation can promote Integrin-β₁ expression and the phosphorylation of FAK and ERK, mechanical strain activated FAK and ERK mediated by Integrin-β₁. Conclusion: Integrin-β₁ may play an important role in osteoblast proliferation differentiation process, it might feel external strain stimulation through ECM composition and makes FAK phosphated through the interaction with FAK, thus causing a series of activation of signal molecules. Finally it reduces MAPK (ERK) activation and cellular responses to finish mechanical signal transduction.     

Susceptibility to clinically manifest cyclosporine A (CsA)-induced autoimmune disease is associated with interferon-gamma (IFN-γ)-producing CD45RC+RT6− T helper cells

Lethally irradiated Lewis (LEW) rats reconstituted with syngeneic bone marrow and given CsA for a 4-week period, develop, upon withdrawal of CsA, a graft-versus-host-like disease, so-called CsA-induced autoimmunity (CsA-AI). This T cell-mediated autoimmune disease is thymus-dependent; it is generally held that this disease is a consequence of aberrant T cell recovery brought about by CsA. In this study we determined mononuclear cell subsets phenotypically by tri-colour flow cytometry. A strong decrease in recent thymic emigrants (Thy1.1⁺, TCR αβ⁺) was observed as a consequence of CsA treatment, eventually resulting in decreased absolute peripheral T cell numbers. In these rats no altered CD4:CD8 T cell ratio was observed before onset of CsA-AI; CD4⁺ and CD8⁺ cells consisted predominantly of monocytes (CD4^dim+, TCR αβ⁻) and natural killer cells (CD8⁺, TCR αβ⁻), respectively. LEW rats, x-irradiated, syngeneic bone marrow-reconstituted and treated with CsA, showed a marked and persistent, relative expansion of mature CD45RC⁺, RT6⁻ Th cells. In contrast, Brown-Norway rats treated in a similar fashion, or LEW rats subjected to either CsA treatment or x-irradiation, did not show a comparable expansion of mature CD45RC⁺, RT6⁻ Th cells, nor did these animals develop CsA-AI. The CD45RC⁺, RT6⁻ Th cells produced IL-2, and moreover constituted the only Th subset producing IFN-γ upon stimulation, and therefore were considered as Th1-like effector cells. These results are consistent with the view that a persistent preponderance of Th1 cells and not the mere presence of autoreactive cells determines whether or not clinically manifest CsA-AI will occur.     

Mast cell chymase in keloid induces profibrotic response via transforming growth factor-β1/Smad activation in keloid fibroblasts

This study was to examine whether mast cell chymase exists in human keloids and exerts its profibrotic effect via transforming growth factor-β₁/Smad signaling pathway. The number of mast cells and the expression levels of chymase in keloids and normal skin were examined by immunohistochemistry assays. The mRNA expression and activity changes of chymase in keloids and normal skin were determined by real-time quantitative PCR and radioimmunoassay. After keloid fibroblasts were treated with different concentrations of chymase (0, 15, 30, 60, and 120 ng/mL) for various time periods, the proliferation of keloid fibroblasts, collagen synthesis, mRNA and protein expression of TGF-β₁, and the protein expression of phosphorylated Smad2/3, Smad2/3 and Smad7 were investigated using MTT assay, ELISA and Western blotting. Mast cells and chymase exist in keloid. Gene expression and activity of mast cell chymase in keloid are significantly higher than those in normal skin. Chymase promotes keloid fibroblast proliferation and collagen synthesis by activating TGF-β₁. The activation of Smad protein signaling pathway by chymase is related to the elevated P-Smad protein expression in keloid fibroblasts. Our data demonstrated that mast cell chymase plays an important role in keloid formation through TGF-β₁/Smad signaling pathway.     

The influence of β-adrenergic activation on noradrenergic α1 activation of rabbit afferent arterioles

The aim of the present investigation was to examine the effect of beta-adrenergic stimulation on smooth muscle calcium concentration ([Ca2+]i) in resting conditions and after administration of norepinephrine (NE) to stimulate alpha-adrenoceptors in isolated rabbit afferent arterioles loaded with the calcium-sensitive fluorescent probe fura-2. [Ca2+]i was evaluated in the proximal and distal parts of the arterioles. NE (4x10(-7) M) increased [Ca2+]i in both these regions. The alpha1-adrenoceptor antagonist prazosin (10(-7) M) totally abolished the NE-induced increase in [Ca2+]i, while the alpha2-adrenoceptor antagonist yohimbine (5x10(-7) M) had no influence on the response to NE. When beta-adrenoceptors were stimulated, using isoproterenol (10(-7) M), the NE-induced increase in [Ca2+]i was significantly lower in both regions. Activation of beta-adrenoceptors with isoproterenol did not affect the [Ca2+]i increase in response to depolarization with K+. Since beta-adrenoceptor stimulation raises the smooth muscle cell levels of cAMP, an adenylate cyclase stimulator, forskolin (10(-5) M) was administered prior to NE application. This maneuver also blunted the increase in [Ca2+]i in both regions. We conclude that the calcium response to NE in the isolated rabbit afferent arteriole is mediated by an alpha1-adrenoceptor. beta-Adrenoceptor stimulation and forskolin blunt the increase in [Ca2+]i induced by NE stimulation, indicating that cAMP counteracts the NE-induced activation of alpha1-adrenoceptors.     

Protective roles of pulmonary rehabilitation mixture in experimental pulmonary fibrosis in vitro and in vivo

Abnormal high mobility group protein B1 (HMGB1) activation is involved in the pathogenesis of pulmonary fibrosis. Pulmonary rehabilitation mixture (PRM), which combines extracts from eight traditional Chinese medicines, has very good lung protection in clinical use. However, it is not known if PRM has anti-fibrotic activity. In this study, we investigated the effects of PRM on transforming growth factor-β1 (TGF-β1)-mediated and bleomycin (BLM)-induced pulmonary fibrosis in vitro and in vivo. The effects of PRM on TGF-β1-mediated epithelial-mesenchymal transition (EMT) in A549 cells, on the proliferation of human lung fibroblasts (HLF-1) in vitro, and on BLM-induced pulmonary fibrosis in vivo were investigated. PRM treatment resulted in a reduction of EMT in A549 cells that was associated with attenuating an increase of vimentin and a decrease of E-cadherin. PRM inhibited the proliferation of HLF-1 at an IC₅₀ of 0.51 µg/mL. PRM ameliorated BLM-induced pulmonary fibrosis in rats, with reduction of histopathological scores and collagen deposition, and a decrease in α-smooth muscle actin (α-SMA) and HMGB1 expression. An increase in receptor for advanced glycation end-product (RAGE) expression was found in BLM-instilled lungs. PRM significantly decreased EMT and prevented pulmonary fibrosis through decreasing HMGB1 and regulating RAGE in vitro and in vivo. PRM inhibited TGF-β1-induced EMT via decreased HMGB1 and vimentin and increased RAGE and E-cadherin levels. In summary, PRM prevented experimental pulmonary fibrosis by modulating the HMGB1/RAGE pathway.     

Protein Kinase CK1αLS Promotes Vascular Cell Proliferation and Intimal Hyperplasia

Protein kinase CK1α regulates several fundamental cellular processes including proliferation and differentiation. Up to four forms of this kinase are expressed in vertebrates resulting from alternative splicing of exons; these exons encode either the L-insert located within the catalytic domain or the S-insert located at the C terminus of the protein. Whereas the L-insert is known to target the kinase to the nucleus, the functional significance of nuclear CK1αLS has been unclear. Here we demonstrate that selective L-insert-targeted short hairpin small interfering RNA-mediated knockdown of CK1αLS in human vascular endothelial cells and vascular smooth muscle cells impairs proliferation and abolishes hydrogen peroxide-stimulated proliferation of vascular smooth muscle cells, with the cells accumulating in G₀/G₁. In addition, selective knockdown of CK1αLS in cultured human arteries inhibits vascular activation, preventing smooth muscle cell proliferation, intimal hyperplasia, and proteoglycan deposition. Knockdown of CK1αLS results in the harmonious down-regulation of its target substrate heterogeneous nuclear ribonucleoprotein C and results in the altered expression or alternative splicing of key genes involved in cellular activation including CXCR4, MMP3, CSF2, and SMURF1. Our results indicate that the nuclear form of CK1α in humans, CK1αLS, plays a critical role in vascular cell proliferation, cellular activation, and hydrogen peroxide-mediated mitogenic signal transduction.A key morphological distinction between vertebrates and invertebrates is the presence of a closed endothelial-lined vascular system in the vertebrates.¹ Activation of the cells comprising the vertebrate vasculature results in cellular proliferation, enhanced proteoglycan deposition, and secretion of growth factors and cytokines.^2,3,4 Such vascular activation is an important process in both vascular development and in vascular diseases such as atherosclerosis and postangioplasty restenosis. Thus, an understanding of the vertebrate-specific signaling pathways regulating vascular cell activation is of high importance.Protein kinase CK1α regulates several fundamental cellular processes including proliferation and differentiation.⁵ Up to four different forms of the kinase exist owing to the alternative splicing of exons encoding either the L-insert located within the catalytic domain or the S-insert located at the C terminus of the protein.^6,7,8,9 Protein kinase CK1α itself is highly conserved among all metazoans. However, the exon encoding the nuclear localizing L-insert is restricted to vertebrates.¹⁰ Whereas vertebrates may contain up to four different splice forms of CK1α, humans are thought to only express three forms: CK1α, CK1αS, and CK1αLS, which are also referred to as CK1α1, CK1α2, and CK1α3, respectively. In the nucleus, CK1αLS probably plays a role in pre-mRNA processing and alternative splicing based on its ability to phosphorylate the highly abundant vertebrate-specific pre-mRNA binding protein heterogeneous nuclear ribonucleoprotein C (hnRNP-C)^10,11,12 and its localization to nuclear speckles,⁶ sites of accumulation of pre-mRNA processing factors.Within the vessel wall, hydrogen peroxide (H₂O₂) plays important roles in mediating vascular activation resulting from diverse stimuli including altered flow, growth factors, cytokines, and vascular injury.^13,14 In fact, vertebrate cells are known to proliferate in response to low concentrations of H₂O₂.¹⁵ Low levels of H₂O₂ are generated by vertebrate cells in response to growth factor-mediated signaling, and this mitogenic H₂O₂ activates CK1αLS, which then phosphorylates hnRNP-C.^10,11 It is known that hnRNP-C modulates the expression of several genes regulating cell growth and survival, including platelet-derived growth factor B chain (PDGF-B),¹⁶ c-myc,¹⁷ p53,¹⁸ the X-chromosome-linked inhibitor of apoptosis,¹⁹ and the urokinase plasminogen activator receptor.²⁰ Thus, CK1αLS phosphorylation of hnRNP-C may promote H₂O₂-stimulated vertebrate cell growth. However, in the cytoplasm, cytosolic forms of CK1α (CK1α and CK1αS) play important roles inhibiting key proliferative signaling pathways involving both wnt/β-catenin and the nuclear factor of activated T-cells.^21,22 Thus, it has been unclear whether H₂O₂-activated CK1αLS in the nucleus is promoting H₂O₂-stimulated growth or is, in fact, a compensatory counter-regulatory pathway. Here we demonstrate by selective and stable knockdown of CK1αLS that the kinase is, in fact, an important positive regulator of vascular activation and H₂O₂ mitogenic signaling.     

Contribution of Hepatic Parenchymal and Nonparenchymal Cells to Hepatic Fibrogenesis in Biliary Atresia

Extrahepatic biliary atresia is a severe neonatal liver disease resulting from a sclerosing cholangiopathy of unknown etiology. Although biliary obstruction may be surgically corrected by a “Kasai” hepatoportoenterostomy, most patients still develop progressive hepatic fibrosis, although the source of increased collagen deposition is unclear. This study examined the role of hepatic stellate cells (HSCs) and assessed the source of transforming growth factor-β (TGF-β) production in hepatic fibrogenesis in patients with biliary atresia. Liver biopsies from 18 biliary atresia patients (including 5 pre- and post-Kasai) were subjected to immunohistochemistry for α-smooth muscle actin and in situ hybridization for either procollagen α₁ (I) mRNA or TGF-β₁ mRNA. Sections were also subjected to immunohistochemistry for active TGF-β₁ protein. The role of Kupffer cells in TGF-β₁ production was assessed by immunohistochemistry for CD68. Procollagen α₁ (I) mRNA was colocalized to α-smooth muscle actin-positive HSCs within the region of increased collagen protein deposition in fibrotic septa and surrounding hyperplastic bile ducts. The number of activated HSCs was decreased in only one post-Kasai biopsy. TGF-β₁ mRNA expression was demonstrated in bile duct epithelial cells and activated HSCs and in hepatocytes in close proximity to fibrotic septa. Active TGF-β₁ protein was demonstrated in bile duct epithelial cells and activated HSCs. This study provides evidence that activated HSCs are responsible for increased collagen production in patients with biliary atresia and therefore play a definitive role in the fibrogenic process. We have also shown that bile duct epithelial cells, HSCs, and hepatocytes are all involved in the production of the profibrogenic cytokine, TGF-β₁.     

α7 Nicotinic Acetylcholine Receptor Regulates Airway Epithelium Differentiation by Controlling Basal Cell Proliferation

Airway epithelial basal cells are known to be critical for regenerating injured epithelium and maintaining tissue homeostasis. Recent evidence suggests that the α7 nicotinic acetylcholine receptor (nAChR), which is highly permeable to Ca²⁺, is involved in lung morphogenesis. Here, we have investigated the potential role of the α7 nAChR in the regulation of airway epithelial basal cell proliferation and the differentiation of the human airway epithelium. In vivo during fetal development and in vitro during the regeneration of the human airway epithelium, α7 nAChR expression coincides with epithelium differentiation. Inactivating α7 nAChR function in vitro increases cell proliferation during the initial steps of the epithelium regeneration, leading to epithelial alterations such as basal cell hyperplasia and squamous metaplasia, remodeling observed in many bronchopulmonary diseases. The regeneration of the airway epithelium after injury in α7^−/− mice is delayed and characterized by a transient hyperplasia of basal cells. Moreover, 1-year-old α7^−/− mice more frequently present basal cells hyperplasia. Modulating nAChR function or expression shows that only α7 nAChR, as opposed to heteropentameric α_xβ_y nAChRs, controls the proliferation of human airway epithelial basal cells. These findings suggest that α7 nAChR is a key regulator of the plasticity of the human airway epithelium by controlling basal cell proliferation and differentiation pathway and is involved in airway remodeling during bronchopulmonary diseases.The respiratory epithelium, which is constantly exposed to airborne pollutants, is frequently injured, which results in altered epithelial functions. To restore these functions, the respiratory epithelium must undergo rapid repair via epithelial cell spreading and migration and regenerate its structure via basal cell proliferation and differentiation.¹ These processes are tightly controlled to restore the pseudostratified architecture of the normal mucociliary epithelium. However, in most respiratory diseases, alterations of the regeneration processes induce epithelial remodeling such as hyperplasia, metaplasia, and fibrosis. Understanding the sequence of processes involved in cell proliferation and differentiation is therefore of crucial importance. Both in vivo and in vitro, human airway basal cells are able to proliferate and reconstitute a fully differentiated and functional epithelium.² These cells are such considered as progenitors of the human airway epithelium and important actors of the airway epithelium regeneration.The nonneuronal cholinergic system is thought to be involved in the regulation of cell functions such as cell-cell interaction, apoptosis, and proliferation.³ It is now established that human bronchial epithelial cells contain all of the machinery for the production, storage, secretion, and degradation of acetylcholine, which acts as an autocrine or paracrine hormone.^4,5 Acetylcholine exerts its effects through muscarinic and nicotinic acetylcholine receptors. Nicotinic acetylcholine receptors (nAChRs) are composed of five subunits, arranged as α/β heteromeric or α homomeric nAChRs, and assembled around a central ion channel, mediating the influx of Ca²⁺.⁶ The airway epithelium expresses α3, α4, α5, α7, α9, β2, and β4 subunits for nAChRs.^7,8,9α7 nAChR is characterized by an elevated Ca²⁺ permeability¹⁰ and has been involved in several important biological processes such as cell proliferation, apoptosis, and angiogenesis in cancer.^11,12 Prenatal nicotine exposure significantly increases pulmonary α7 nAChR expression and alters fetal lung development¹³ and subsequently pulmonary function in newborn.¹⁴ In particular, alteration of lung branching morphogenesis induced by nicotine is mediated by α7 nAChR.¹⁵ Altogether, these observations led us to investigate whether the α7 nAChR could be involved in the differentiation of the respiratory epithelium. In the human airway epithelium, we observed α7 nAChR expression in basal cells, which play a critical role in the epithelial regeneration. Both in vivo and in vitro, the α7 nAChR expression is associated with the airway epithelium differentiation. Moreover, in vitro inactivating α7 nAChR or in vivo disrupting genetic α7 nAChR expression induces airway epithelium remodeling by modulating basal cell proliferation. This study thus provides several lines of evidence that α7 nAChR is significant for airway epithelial differentiation and suggests that α7 nAChR is a key regulator of the plasticity of the airway epithelium.