Thrombin-induced vimentin phosphorylation in cultured human umbilical vein endothelial cells

Depression and monocyte dysfunction: a follow-up study

Several studies have reported immune cellular and humoral dysfunction during depression. We specifically focused on the study of the monocyte as it has a key role in the activation of the immune response. To examine the association between severity of depressive symptoms and values of monocyte parameters (HLA-DR, CD35, phagocytic activity and vimentin filaments), we used a longitudinal design and assessed monocyte markers at intake and at follow-up 12 weeks after discharge from the hospital in 49 depressed patients. Seventy percent of patients showed pretreatment a marked monocyte dysfunction (82.5% had at least one parameter altered). After treatment, alterations in immunological variables were significantly associated (P< 0.05) with depression scores higher than 15. The findings indicate that the monocyte dysfunction is temporally associated with the state of depression. Before and after treatment the immunoreactive vimentin filaments significantly increased (P< 0.01) after incubation of monocytes with naloxone, suggesting that an increased opioid activity might account for the monocyte dysfunction.

Epithelial-mesenchymal transition occurs after epidermal development in mouse skin

In the present study, we studied epithelial-mesenchymal transition (EMT) with fetal and postnatal serial skin sections. E-cadherin, occludin and zonula occludens 1 (ZO-1)-expressing cells appear in the dermal area from E18.5 to postnatal day 9 (P9), with highest expression from P2 to P5. The co-expression of mesenchymal marker alpha-smooth muscle (alpha-SMA), fibronectin and vimentin with E-cadherin in these dermal cells was further examined. Almost no dermal cells express alpha-SMA before P0. From P2 to P6, cells expressing both E-cadherin and alpha-SMA appear in the dermis. In contrast, fibronectin-releasing cells were detected in the dermis as early as on E15.5, although on P5, some dermal cells was found weakly expressing both fibronectin and E-cadherin, most cells strongly expressing fibronectin did not express E-cadherin. Vimentin was mainly expressed in both endothelial and blood-derived cells and did not show co-expression with E-cadherin. Confocal microscopy studies further found that during EMT, E-cadherin appears intracellularly, while the expression of alpha-SMA starts from the membrane area and moves to the cytosol of the cells. Our data are the first in vivo evidence that EMT occurs during mouse skin development. Dermal cells are derived from EMT and other origins, including blood, during skin development.

Signaling Mechanisms Regulating Endothelial Permeability

The microvascular endothelial cell monolayer localized at the critical interface between the blood and vessel wall has the vital functions of regulating tissue fluid balance and supplying the essential nutrients needed for the survival of the organism. The endothelial cell is an exquisite “sensor” that responds to diverse signals generated in the blood, subendothelium, and interacting cells. The endothelial cell is able to dynamically regulate its paracellular and transcellular pathways for transport of plasma proteins, solutes, and liquid. The semipermeable characteristic of the endothelium (which distinguishes it from the epithelium) is crucial for establishing the transendothelial protein gradient (the colloid osmotic gradient) required for tissue fluid homeostasis. Interendothelial junctions comprise a complex array of proteins in series with the extracellular matrix constituents and serve to limit the transport of albumin and other plasma proteins by the paracellular pathway. This pathway is highly regulated by the activation of specific extrinsic and intrinsic signaling pathways. Recent evidence has also highlighted the importance of the heretofore enigmatic transcellular pathway in mediating albumin transport via transcytosis. Caveolae, the vesicular carriers filled with receptor-bound and unbound free solutes, have been shown to shuttle between the vascular and extravascular spaces depositing their contents outside the cell. This review summarizes and analyzes the recent data from genetic, physiological, cellular, and morphological studies that have addressed the signaling mechanisms involved in the regulation of both the paracellular and transcellular transport pathways.

Soluble VCAM-1 Induces Chemotaxis of Jurkat and Synovial Fluid T Cells Bearing High Affinity Very Late Antigen-4

It has been shown that cells with high affinity very late Ag (VLA)-integrins have up-regulated expression of a β1-subunit epitope, which is detected by 15/7 mAb. In this study, we demonstrate that soluble VCAM-1 (sVCAM-1) exhibits chemotactic activity of T cells with high affinity VLA-4 against VCAM-1, such as Jurkat T cells and IL-2-dependent T cells. Moreover, we found that T cells in the synovial fluid show high basal migration in the absence of sVCAM-1, compared with peripheral blood T cells in patients with rheumatoid arthritis. Among T cells in the synovial fluid, CD45RO+ memory T cells, in response to sVCAM-1, showed a much higher than basal migratory response when compared with CD45RA+ naive cells, while no significant difference was observed between CD4+ and CD8+ T cells. The chemotactic activity of sVCAM-1 is inhibited in the presence of anti-VCAM-1 and anti-VLA-4, which interfered with the binding between VCAM-1 and VLA-4. Inhibition studies using various kinase inhibitors (C3 exoenzyme, KN62, and H7) show that Rho, Ca2+/calmodulin-dependent kinase II, and protein kinase C are involved in signal transduction in sVCAM-1-induced chemotaxis, respectively, whereas tyrosine kinase seems to play a lesser role, since genistein showed only partial inhibition of T cell chemotaxis. Western blot analysis using an anti-phospho-serine mAb (MO82) reveals that Ser82 in the vimentin is phosphorylated specifically by Ca2+/calmodulin-dependent kinase II through sVCAM-1 activation in the IL-2 dependent T cells. Collectively, by inducing migration and recruitment of T cells through several kinase activations, sVCAM-1 contributes to the development of the inflammation of synovial lesion.

Neuroendocrine and immunological functions in depressed patients: a follow-up study

The development, evaluation and use of biological markers with a diagnostic purpose in psychiatry is extremely important. However, with certain exceptions, truly sensitive and specific markers have not yet emerged. In order to investigate the relationship between the immune apparatus and the hypothalamic-pituitary activity on the one hand, and the psychopathological state of the patients on the other, we used a longitudinal design and assessed monocyte parameters (HLA-DR, CD 35, vimentin filaments, and phagocytosis index) and neuroendocrine tests (dexamethasone suppression test [DST] and thyrotropin-releasing hormone [TRH] stimulation test) at intake and at follow-up in 49 depressed patients. Immunological parameters were compared with neuroendocrine tests in both phases of the study. The combined use of both immunological and neuroendocrine tests did not add sensitivity to the immunological identification of depressed patients. The findings lead us to consider the role of the monocyte parameters as sensitive depressive state markers, while the combined use of both neuroendocrine and immunological tests in current clinical practice would be debatable.

Bacterial lipopolysaccharide induces actin reorganization, intercellular gap formation, and endothelial barrier dysfunction in pulmonary vascular endothelial cells: concurrent F-actin depolymerization and new actin synthesis

Bacterial lipopolysaccharide (LPS) influences pulmonary vascular endothelial barrier function in vitro. We studied whether LPS regulates endothelial barrier function through actin reorganization. Postconfluent bovine pulmonary artery endothelial cell monolayers were exposed to Escherichia coli 0111:B4 LPS 10 ng/ml or media for up to 6 h and evaluated for: 1) transendothelial 14C-albumin flux, 2) F-actin organization with fluorescence microscopy, 3) F-actin quantitation by spectrofluorometry, and 4) monomeric G-actin levels by the DNAse 1 inhibition assay. LPS induced increments in 14C-albumin flux (P < 0.001) and intercellular gap formation at > or = 2-6 h. During this same time period the endothelial F-actin pool was not significantly changed compared to simultaneous media controls. Mean (+/- SE) G-actin (micrograms/mg total protein) was significantly (P < 0.002) increased compared to simultaneous media controls at 2, 4, and 6 h but not at 0.5 or 1 h. Prior F-actin stabilization with phallicidin protected against the LPS-induced increments in G-actin (P = 0.040) as well as changes in barrier function (P < 0.0001). Prior protein synthesis inhibition unmasked an LPS-induced decrement in F-actin (P = 0.0044), blunted the G-actin increment (P = 0.010), and increased LPS-induced changes in endothelial barrier function (P < 0.0001). Therefore, LPS induces pulmonary vascular endothelial F-actin depolymerization, intercellular gap formation, and barrier dysfunction. Over the same time period, LPS increased total actin (P < 0.0001) and new actin synthesis (P = 0.0063) which may be a compensatory endothelial cell response to LPS-induced F-actin depolymerization.

TNF-alpha induces endothelial cell F-actin depolymerization, new actin synthesis, and barrier dysfunction

Tumor necrosis factor-alpha (TNF-alpha) influences pulmonary vascular endothelial barrier function in vitro. We studied whether recombinant TNF-alpha (rTNF-alpha) regulates endothelial barrier function through actin reorganization. Postconfluent bovine pulmonary artery endothelial cell monolayers were exposed to human rTNF-alpha (1,000 U/ml) and evaluated for 1) transendothelial [14C]albumin flux, 2) F-actin organization with fluorescence microscopy, 3) F-actin quantitation by spectrofluorometry, and 4) monomeric G-actin levels by the deoxyribonuclease I inhibition assay. rTNF-alpha induced increments in [14C]albumin flux (P < 0.04) and intercellular gap formation at > or = 2-6 h. During this same time, the endothelial F-actin pool decreased (P = 0.0064), with reciprocal increases in the G-actin pool (P < 0.0001). Prior F-actin stabilization with phallicidin protected against the rTNF-alpha-induced increments in G-actin (P < 0.002) as well as changes in barrier function (P < 0.01). Prior protein synthesis inhibition enhanced the rTNF-alpha-induced decrement in F-actin (P < 0.0001), blunted the G-actin increment (P < 0.002), and increased rTNF-alpha-induced changes in endothelial barrier function (P < 0.003). Therefore, rTNF-alpha induces pulmonary vascular endothelial F-actin depolymerization, intercellular gap formation, and barrier dysfunction. rTNF-alpha also increased total actin (P < 0.02) and new actin synthesis (P < 0.002), which may be a compensatory endothelial cell response to rTNF-alpha-induced F-actin depolymerization.

Protein kinase C phosphorylates caldesmon77 and vimentin and enhances albumin permeability across cultured bovine pulmonary artery endothelial cell monolayers

Cytoskeletal protein (CSP) interactions are critical to the contractile response in muscle and non-muscle cells. Current concepts suggest that activation of the contractile apparatus occurs through selective phosphorylation by specific cellular kinase systems. Because the Ca(2+)-phospholipid-dependent protein kinase C (PKC) is involved in the regulation of a number of key endothelial cell responses, the hypothesis that PKC modulates endothelial cell contraction and monolayer permeability was tested. Phorbol myristate acetate (PMA), a direct PKC activator, and alpha-thrombin, a receptor-mediated agonist known to increase endothelial cell permeability, both induced rapid, dose-dependent activation and translocation of PKC in bovine pulmonary artery endothelial cells (BPAEC), as assessed by gamma-[32P]ATP phosphorylation of H1 histone in cellular fractions. This activation was temporally associated with evidence of agonist-mediated endothelial cell contraction as demonstrated by characteristic changes in cellular morphology. Agonist-induced activation of the contractile apparatus was associated with increases in BPAEC monolayer permeability to albumin (approximately 200% increase with 10(-6) MPMA, approximately 400% increase with 10(-8) M alpha-thrombin). To more closely examine the role of PKC in activation of the contractile apparatus, PKC-mediated phosphorylation of two specific CSPs, the actin- and calmodulin-binding protein, caldesmon77, and the intermediate filament protein, vimentin, was assessed. In vitro phosphorylation of both caldesmon and vimentin was demonstrated by addition of exogenous, purified BPAEC PKC to unstimulated BPAEC homogenates, to purified bovine platelet caldesmon77, or to purified smooth muscle caldesmon150. Caldesmon77 and vimentin phosphorylation were observed in intact [32P]-labeled BPAEC monolayers stimulated with either PMA or alpha-thrombin, as detected by immunoprecipitation. In addition, BPAEC pretreatment with the PKC inhibitor, staurosporine, prevented alpha-thrombin- and PMA-induced phosphorylation of both cytoskeletal proteins, attenuated morphologic evidence of contraction, and abolished agonist-induced barrier dysfunction. These results demonstrate that agonist-stimulated PKC activity results in cytoskeletal protein phosphorylation in BPAEC monolayer, an event which occurs in concert with agonist-mediated endothelial cell contraction and resultant barrier dysfunction.

Reversible hyperphosphorylation and reorganization of vimentin intermediate filaments by okadaic acid in 9L rat brain tumor cells

Okadaic acid (OA), a protein phosphatase inhibitor, was found to induce hyperphosphorylation and reorganization of vimentin intermediate filaments in 9L rat brain tumor cells. The process was dose dependent. Vimentin phosphorylation was initially enhanced by 400 nM OA in 30 min and reached maximal level (about 26-fold) when cells were treated with 400 nM OA for 90 min. Upon removal of OA, dephosphorylation of the hyperphosphorylated vimentin was observed and the levels of phosphorylation returned to that of the controls after the cells recovered under normal growing conditions for 11 h. The phosphorylation and dephosphorylation of vimentin induced by OA concomitantly resulted in reversible reorganization of vimentin filaments and alteration of cell morphology. Cells rounded up as they were entering mitosis in the presence of OA and returned to normal appearance after 11 h of recovery. Immuno-staining with anti-vimentin antibody revealed that vimentin filaments were disassembled and clustered around the nucleus when the cells were treated with OA but subsequently returned to the filamentous states when OA was removed. Two-dimensional electrophoresis analysis further revealed that hyperphosphorylation of vimentin generated at least seven isoforms having different isoelectric points. Furthermore, the enhanced vimentin phosphorylation was accompanied by changes in the detergent-solubility of the protein. In untreated cells, the detergent-soluble and -insoluble vimentins were of equal amounts but the solubility could be increased when vimentins were hyperphosphorylated in the presence of OA. Taken together, the results indicated that OA could be involved in reversible hyperphosphorylation and reorganization of vimentin intermediate filaments, which may play an important role in the structure-function regulation of cytoskeleton in the cell.

Identification of vimentin in rat peritoneal mast cells and its phosphorylation in association with histamine release

Stimulation of rat peritoneal mast cells with histamine releasers, such as compound 48/80 and substance P, caused a similar pattern of protein phosphorylations: the molecular weights of the two major phosphorylated proteins were 45 kDa and 59 kDa. When rat mast cells permeabilized with beta-escin were exposed to Ca2+ at concentrations higher than 0.6 microM, phosphorylated proteins of identical molecular weight were also detected. By a radioimmunoprecipitation assay using anti-vimentin mouse monoclonal antibody, the 59 kDa protein was identified as vimentin, one of the intermediate cytoskeletal proteins. Moreover, it became apparent that the phosphoamino acid in phosphorylated vimentin was a serine residue. Sequential changes in vimentin phosphorylation were similar to that of histamine release elicited by histamine releasers: phosphorylation took place within 5 s of stimulation and reached a maximum within 10 s. When permeabilized mast cells were treated with calphostin C, a specific protein kinase C inhibitor, phosphorylation was markedly inhibited. Fluorescence images of mast cells stained with FITC-labelled anti-vimentin antibody showed filamentous structures surrounding the granules in the cytoplasm. However, after exposure to compound 48/80, the filamentous structures promptly disappeared and a dim fluorescence was observed homogeneously in the cell indicating that a rapid depolymerization of vimentin had taken place. From the present study, it became clear that when rat peritoneal mast cells were stimulated, vimentin was rapidly phosphorylated by protein kinase C and this phosphorylation process seems to be related to histamine release.

Mercury-arc photolysis: a method for examining second messenger regulation of endothelial cell monolayer integrity

Cell-cell apposition in bovine pulmonary endothelial cell monolayers was modulated by inducing transient increases in intracellular adenosine 3':5'-cyclic monophosphate (cAMP) and 1,4,5-inositol triphosphate (IP3). This was accomplished by mercury-arc flash photolysis of o-nitrobenzyl derivatives of the second messengers (caged compounds). Second messenger release by the mercury-arc lamp was determined by radioimmunoassay of cAMP to have a t1/2 of approximately 8 min. Each second messenger induced the phosphorylation of a distinct subset of cytoskeletal proteins; however, both IP3 and cAMP increased vimentin phosphorylation. Actin isoform patterns were not altered by the second messengers. Intracellular pulses of IP3 in pulmonary endothelial cells caused disruption of endothelial monolayer integrity as determined by phase-contrast microscopy and by visualization of actin stress fibers with rhodamine-phalloidin. Intracellular pulses of cAMP increased cell-cell contact, cell surface area, and apposition. IP3 appeared to have its greatest effect on the actin peripheral band. In silicone rubber contractility assays this agent caused contraction of pulmonary microvascular endothelial cells as visualized by an increase in wrinkles beneath the cells. On the other hand, cAMP appeared to effect both the peripheral band and centralized actin domains. Caged cAMP caused relaxation of endothelial cells as visualized by a disappearance of wrinkles beneath the cells.

Phosphorylation in vitro of vimentin by protein kinases A and C is restricted to the head domain. Identification of the phosphoserine sites and their influence on filament formation

The in vitro phosphorylation of vimentin, the intermediate filament protein of mesenchymal cells, by kinases A and C is serine-specific and involves only the N-terminal head domain. In oligomeric protofilament units each kinase recognizes five sites, which have been identified by sequence analysis. Kinase C introduces 1.5 mol phosphate/mol vimentin, while kinase A treatment results in 4 mol phosphate/mol. Kinase-A-treated oligomers do not polymerize in standard assays whereas kinase C treatment has no inhibitory effect. Filaments exposed to kinase A remain stable and incorporate only 1.7 mol phosphate/mol vimentin. These phosphates are essentially restricted to two of the five kinase A sites found in protofilament units. Thus the head domain, previously related to in vitro assembly competence and filament stability, changes in accessibility between the oligomeric and polymeric state. We discuss the possibility that in vivo phosphorylation of vimentin filaments by kinase A may not necessarily be accompanied by an extensive depolymerization. It could instead involve a dynamic change of the filament surfaces, which could alter the interaction of the filaments with other cellular structures.

Naloxone-reversible monocyte dysfunction in patients with chronic fatigue syndrome

We studied monocyte function in 35 consecutive patients with chronic fatigue syndrome (CFS) and 25 healthy controls. Eighty-five per cent of the patients showed monocyte dysfunction characterized by marked reduction in the number of monocytes displaying immunoreactive cytoskeletal vimentin filaments, a low phagocytosis index, and a reduced expression of HLA-DR antigens. These values increased dramatically after incubation of the patients' monocytes with the opioid antagonist naloxone. Other immunological abnormalities also noted in the patients were low lymphocyte blastogenesis and diminished numbers of monocytes displaying receptors for Fc of IgG (FcR) and C3b (CR1). These findings suggest that an increased opioid activity acting through a classical receptor mechanism is active on monocytes from a high proportion of patients with CFS and that this represents a novel example of immunomodulation by opioid peptides in human disease. We suggest that endogenous opioids are involved in the pathogenesis of the chronic fatigue syndrome.

Opioid peptides modulate the organization of vimentin filaments, phagocytic activity, and expression of surface molecules in monocytes

It is theorized that intermediate filaments are important in the modulation of membrane activity and cell motility; however, their functions are unknown. The assembly and organization of these filaments are under hormonal regulation. We investigated in human monocytes the in vitro effects of Met-enkephalin, Leu-enkephalin, and beta-endorphin on the expression of immunoreactive cytoskeletal vimentin filaments. We simultaneously examined their effect on the phagocytosis of Candida albicans and on the membrane display of surface molecules. The three opioid peptides markedly reduced the expression of vimentin filaments, the phagocytic activity, and the display of HLA-DR molecules at concentrations of 10(-6), 10(-8), and 10(-10) M. On the other hand, the intravenous administration of fentanyl, a synthetic opiate agonist, to patients undergoing surgery induced similar changes in monocytes. In other experiments, 10(-8) M beta-endorphin also decreased the expression of CR3 but did not influence the display of CD13, a surface protein of unknown function. Expression of vimentin filaments correlated directly with the display of HLA-DR antigens and CR3 and with the phagocytic activity. The results of this paper indicate that opiates and opioids, neuropeptides known to be released during stress, can directly depress several monocyte functions. Furthermore, from these data it may be speculated that intermediate filaments may regulate the membrane expression of some surface molecules and the phagocytic process.