Potentiation by thyroxine of interferon-gamma-induced antiviral state requires PKA and PKC activities

Actions of Thyroid Hormones on Thyroid Cancers

L-Thyroxine (T4) is the principal ligand of the thyroid hormone analogue receptor on the extracellular domain of integrin αvβ3. The integrin is overexpressed and activated in cancer cells, rapidly dividing endothelial cells, and platelets. The biologic result is that T4 at physiological concentration and without conversion to 3,3',5-triiodo-L-thyronine (T3) may stimulate cancer cell proliferation and cancer-relevant angiogenesis and platelet coagulation. Pro-thrombotic activity of T4 on platelets is postulated to support cancer-linked blood clotting and to contribute to tumor cell metastasis. We examine some of these findings as they may relate to cancers of the thyroid. Differentiated thyroid cancer cells respond to physiological levels of T4 with increased proliferation. Thus, the possibility exists that in patients with differentiated thyroid carcinomas in whom T4 administration and consequent endogenous thyrotropin suppression have failed to arrest the disease, T4 treatment may be stimulating tumor cell proliferation. In vitro studies have shown that tetraiodothyroacetic acid (tetrac), a derivative of T4, acts via the integrin to block T4 support of thyroid cancer and other solid tumor cells. Actions of T4 and tetrac or chemically modified tetrac modulate gene expression in thyroid cancer cells. T4 induces radioresistance via induction of a conformational change in the integrin in various cancer cells, although not yet established in thyroid cancer cells. The thyroid hormone receptor on integrin αvβ3 mediates a number of actions of T4 on differentiated thyroid cancer cells that support the biology of the cancer. Additional studies are required to determine whether T4 acts on thyroid cancer cells.

Therapeutics targeting the fibrinolytic system

The function of the fibrinolytic system was first identified to dissolve fibrin to maintain vascular patency. Connections between the fibrinolytic system and many other physiological and pathological processes have been well established. Dysregulation of the fibrinolytic system is closely associated with multiple pathological conditions, including thrombosis, inflammation, cancer progression, and neuropathies. Thus, molecules in the fibrinolytic system are potent therapeutic and diagnostic targets. This review summarizes the currently used agents targeting this system and the development of novel therapeutic strategies in experimental studies. Future directions for the development of modulators of the fibrinolytic system are also discussed.

The fibrinolytic system was originally identified to dissolve blood clots, and is shown to have important roles in other pathological processes, including cancer progression, inflammation, and thrombosis. Molecules or therapeutics targeting fibrinolytic system have been successfully used in the clinical treatments of cancer and thrombotic diseases. The clinical studies and experimental models targeting fibrinolytic system are reviewed by Haili Lin at Sanming First Hosipital, Mingdong Huang at Fuzhou University in China, and Peng Xu at A*STAR in Singapore to demonstrate fibrinolytic system as novel therapeutic targets. As an example, the inhibition of fibrinolytic system protein can be used to suppress cancer prolifieration and metastasis. This review also discusses the potential therapeutic effects of inhibitiors of fibrinolytic system on inflammatory disorders.

Early Glycated Albumin, but Not Advanced Glycated Albumin, Methylglyoxal, or 3-Deoxyglucosone Increases the Expression of Pai-1 in Human Peritoneal Mesothelial Cells

Objective

The continuous contact of glucose-containing peritoneal dialysis (PD) fluids with the peritoneum results in the intraperitoneal formation of early and advanced glycation end-products. This nonenzymatic glycation of proteins may cause morphological and functional alterations to the peritoneum, which may contribute to patient dropout from PD therapy. Because fibrinolytic system components have been demonstrated to play an important role in the balance of intraperitoneal generation and degradation of fibrin, we studied the effect of early and advanced glycated human serum albumin, methylglyoxal, and 3-deoxyglucosone on the synthesis of tissue-type plasminogen activator (tPA), as well as its specific inhibitor (PAI-1), in human peritoneal mesothelial cells (HPMC).

Methods

Antigen concentrations in the supernatants of cultured HPMC were measured by ELISA. Northern blot analysis was conducted for mRNA expression. Electrophoretic mobility shift assays were applied to demonstrate the involvement of the transcription factors nuclear factor kappa B (NF-κB) and activator protein-1 (AP-1) in signal transduction.

Results

Incubation of HPMC with early glycated albumin (GHSA) resulted in a time- and concentration-dependent increase in PAI-1 mRNA expression and antigen secretion. In contrast, no changes in PAI-1 synthesis occurred after stimulation with either the 1,2-dicarbonyl compounds methylglyoxal and 3-deoxyglucosone, or with late advanced glycation end-products. tPA synthesis was not affected by any of the tested components. Furthermore, HPMC exposed to GHSA induced NF-κB and AP-1 DNA binding activity, suggesting that GHSA-induced over-expression of PAI-1 is transcriptionally regulated by both transcription factors.

Conclusions

We conclude that Amadori modified glycated albumin upregulates PAI-1 synthesis in HPMC, possibly mediated through the activation of the transcription factors NF-κB and AP-1. The present data support the clinical relevance of the formation of glycated proteins and their involvement in pathological processes in PD patients. Thus, glycated albumin may contribute to an imbalance between intraperitoneal formation and degradation of fibrin that causes peritoneal structural alterations, with subsequent membrane failure.

Modulation of Fibrinolytic System Components in Mesothelial Cells by Hyaluronan

← Objective

Hyaluronan (HA) is an important extracellular matrix component and is involved in fluid homeostasis, tissue repair, and response to infections. Previous studies have shown that supplementation of dialysis fluid with high molecular weight HA may have a positive impact on peritoneal solute and fluid transport characteristics. In the present study, we investigated the impact of HA on the synthesis of tissue-type plasminogen activator (t-PA) and its inhibitor, plasminogen activator inhibitor type 1 (PAI-1) in cultured human peritoneal mesothelial cells (MC).

← Methods

Cultured human peritoneal MC isolated from omental tissue were used for the experiments. Concentrations of t-PA and PAI-1 antigens were measured in conditioned media of confluent MC using ELISA. Northern blot analysis was performed to investigate mRNA expression of t-PA, PAI-1, and low-density lipoprotein receptor-related protein.

← Results

Hyaluronan in a concentration as suggested for supplementation of dialysis fluid (10 mg/dL) did not have a significant impact on the synthesis of t-PA or PAI-1 in human MC. However, incubation of MC with higher concentrations of HA (30 – 1000 mg/dL) resulted in a concentration- and time- (8 – 48 hours) dependent decrease in t-PA antigen release and mRNA expression. In contrast, PAI-1 antigen secretion was distinctly but not significantly increased in the presence of HA.

← Conclusion

The expression of t-PA and PAI-1 in MC was not affected by low concentrations of HA. Therefore, it is reasonable to assume that supplementation of dialysis fluid with HA (10 mg/dL) will not decrease mesothelial fibrinolytic activity. Only high concentrations (> 50 mg/dL) may disturb the balance between intraperitoneal generation and degradation of fibrin by decreasing t-PA synthesis.

Is Normal Saline Harmful to the Peritoneum?

♦ Background

Normal saline (0.9% NaCl) is used during various abdominal surgical interventions and during peritoneal dialysis to rinse the peritoneal cavity. Although no clear clinical evidence exists for the bioincompatibility of normal saline, various experimental studies have suggested that 0.9% NaCl solution can initiate fibrosis of peritoneum.

♦ Material and Methods

We review the data derived from in vitro and in vivo experimental studies demonstrating the cytotoxic effect of 0.9% NaCl and its ability to initiate peritoneal adhesions.

♦ Results

Normal saline reduces the viability and fibrinolytic activity of peritoneal mesothelial cells. Use of normal saline to wash the peritoneal cavity during abdominal operations or after chronic peritoneal dialysis is more likely to produce adhesions than is no irrigation at all. Chronic exposure of the peritoneum to normal saline causes overgrowth of the connective tissue and formation of new blood vessels within that tissue.

Conclusion

♦ Normal saline is a bioincompatible solution that predisposes to the formation of peritoneal adhesions and fibrosis of the peritoneum. A 0.9% NaCl solution should therefore not be used to rinse the peritoneal cavity after interruption of peritoneal dialysis.

A Comparison of Phenomenologic Growth Laws for Myocardial Hypertrophy

The heart grows in response to changes in hemodynamic loading during normal development and in response to valve disease, hypertension, and other pathologies. In general, a left ventricle subjected to increased afterload (pressure overloading) exhibits concentric growth characterized by thickening of individual myocytes and the heart wall, while one experiencing increased preload (volume overloading) exhibits eccentric growth characterized by lengthening of myocytes and dilation of the cavity. Predictive models of cardiac growth could be important tools in evaluating treatments, guiding clinical decision making, and designing novel therapies for a range of diseases. Thus, in the past 20 years there has been considerable effort to simulate growth within the left ventricle. While a number of published equations or systems of equations (often termed "growth laws") can capture some aspects of experimentally observed growth patterns, no direct comparisons of the various published models have been performed. Here we examine eight of these laws and compare them in a simple test-bed in which we imposed stretches measured during in vivo pressure and volume overload. Laws were compared based on their ability to predict experimentally measured patterns of growth in the myocardial fiber and radial directions as well as the ratio of fiber-to-radial growth. Three of the eight laws were able to reproduce most key aspects of growth following both pressure and volume overload. Although these three growth laws utilized different approaches to predict hypertrophy, they all employed multiple inputs that were weakly correlated during in vivo overload and therefore provided independent information about mechanics.

Role of thyroid hormones in the neoplastic process: an overview

Thyroid hormones (TH) are critical regulators of several physiological processes, which include development, differentiation and growth in virtually all tissues. In past decades, several studies have shown that changes in TH levels caused by thyroid dysfunction, disruption of deiodinases and/or thyroid hormone receptor (TR) expression in tumor cells, influence cell proliferation, differentiation, survival and invasion in a variety of neoplasms in a cell type-specific manner. The function of THs and TRs in neoplastic cell proliferation involves complex mechanisms that seem to be cell specific, exerting effects via genomic and nongenomic pathways, repressing or stimulating transcription factors, influencing angiogenesis and promoting invasiveness. Taken together, these observations indicate an important role of TH status in the pathogenesis and/or development of human neoplasia. Here, we aim to present an updated and comprehensive picture of the accumulated knowledge and the current understanding of the potential role of TH status on the different hallmarks of the neoplastic process.

H89 enhances the sensitivity of cancer cells to glyceryl trinitrate through a purinergic receptor-dependent pathway

High doses of the organic nitrate glyceryl trinitrate (GTN), a nitric oxide (NO) donor, are known to trigger apoptosis in human cancer cells. Here, we show that such a cytotoxic effect can be obtained with subtoxic concentrations of GTN when combined with H89, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulphonamide.2HCl. This synergistic effect requires the generation of reactive oxygen species (ROS) from H89 and NO from GTN treatment that causes cGMP production and PKG activation. Furthermore, the GTN/H89 synergy was attenuated by inhibition of P2-purinergic receptors with suramin and competition with ATP/UDP. By down-regulating genes with antisense oligonucleotides, P2-purinergic receptors P2X3, P2Y1, and P2Y6 were found to have a role in creating this cytotoxic effect. Thus, H89 likely acts as an ATP mimetic synergizing with GTN to trigger apoptosis in aggressive cancer cells.

Thrombin down-regulates tissue factor pathway inhibitor expression in a PI3K/nuclear factor-κB-dependent manner in human pleural mesothelial cells

Tissue factor pathway inhibitor (TFPI) is the primary inhibitor of the extrinsic coagulation cascade, and its expression is reported to be relatively stable. Various pathophysiologic agents have been shown to influence TFPI activity by regulating its expression or by modifying the protein. It is not clear how TFPI activity is regulated in normal physiology or in injury. Because thrombin and TFPI are locally elaborated in pleural injury, we sought to determine if thrombin could regulate TFPI in human pleural mesothelial cells (HPMCs). Thrombin significantly decreased TFPI mRNA and protein levels by > 70%. Thrombin-mediated down-regulation of TFPI promoted factor X activation by HPMCs. The ability of thrombin to significantly decrease TFPI mRNA and protein levels was maintained at nanomolar concentrations. Protease-activated receptor (PAR)-1, a mediator of thrombin signaling, is detectable in the mesothelium in human and murine pleural injury. PAR-1 silencing blocked thrombin-mediated decrements of TFPI in HPMCs. Thrombin activates PI3K/Akt and nuclear factor κB (NF-κB) signaling in HPMCs. Inhibition of PI3K (by PX-866) and NF-κB (by SN50) prevented thrombin-mediated TFPI mRNA and protein down-regulation. These are the first studies to demonstrate that thrombin decreases TFPI expression in HPMCs. Our findings demonstrate a novel mechanism by which thrombin regulates TFPI expression in HPMCs and promotes an unrestricted procoagulant response, and suggest that interactions between PI3K and NF-κB signaling pathways are linked in HPMCs and control TFPI expression. These findings raise the possibility that targeting this pathway could limit the ability of the mesothelium to support extravascular fibrin deposition and organization associated with pleural injury.

In vivo epicardial force and strain characterisation in normal and MLP-knockout murine hearts

The study's objective is to quantify in vivo epicardial force and strain in the normal and transgenic myocardium using microsensors.Male mice (n = 39), including C57BL/6 (n = 26), 129/Sv (n = 5), wild-type (WT) C57  ×  129Sv (n = 5), and muscle LIM protein (MLP) knock-out (n = 3), were studied under 1.5% isoflurane anaesthesia. Microsurgery allowed the placement of two piezoelectric crystals at longitudinal epicardial loci at the basal, middle, and apical LV regions, and the independent (and/or concurrent) placement of a cantilever force sensor. The findings demonstrate longitudinal contractile and relaxation strains that ranged between 4.8-9.3% in the basal, middle, and apical regions of C57BL/6 mice, and in the mid-ventricular regions of 129/Sv, WT, and MLP mice. Measured forces ranged between 3.1-8.9 mN. The technique's feasibility is also demonstrated in normal mice following afterload, occlusion-reperfusion challenges.Furthermore, the total mid-ventricular forces developed in MLP mice were significantly reduced compared to the WT controls (5.9  ±  0.4 versus 8.9  ±  0.2 mN, p < 0.0001), possibly owing to the fibrotic and stiffer myocardium. No significant strain differences were noted between WT and MLP mice.The possibility of quantifying in vivo force and strain from the normal murine heart is demonstrated with a potential usefulness in the characterisation of transgenic and diseased mice, where regional myocardial function may be significantly altered.

Thyroid hormone inhibition in L6 myoblasts of IGF-I-mediated glucose uptake and proliferation: new roles for integrin αvβ3

Thyroid hormones L-thyroxine (T4) and 3,3',5-triiodo-L-thyronine (T3) have been shown to initiate short- and long-term effects via a plasma membrane receptor site located on integrin αvβ3. Also insulin-like growth factor type I (IGF-I) activity is known to be subject to regulation by this integrin. To investigate the possible cross-talk between T4 and IGF-I in rat L6 myoblasts, we have examined integrin αvβ3-mediated modulatory actions of T4 on glucose uptake, measured through carrier-mediated 2-deoxy-[3H]-D-glucose uptake, and on cell proliferation stimulated by IGF-I, assessed by cell counting, [3H]-thymidine incorporation, and fluorescence-activated cell sorting analysis. IGF-I stimulated glucose transport and cell proliferation via the cell surface IGF-I receptor (IGFIR) and, downstream of the receptor, by the phosphatidylinositol 3-kinase signal transduction pathway. Addition of 0.1 nM free T4 caused little or no cell proliferation but prevented both glucose uptake and proliferative actions of IGF-I. These actions of T4 were mediated by an Arg-Gly-Asp (RGD)-sensitive pathway, suggesting the existence of crosstalk between IGFIR and the T4 receptor located near the RGD recognition site on the integrin. An RGD-sequence-containing integrin inhibitor, a monoclonal antibody to αvβ3, and the T4 metabolite tetraiodothyroacetic acid all blocked the inhibition by T4 of IGF-I-stimulated glucose uptake and cell proliferation. Western blotting confirmed roles for activated phosphatidylinositol 3-kinase and extracellular regulated kinase 1/2 (ERK1/2) in the effects of IGF-I and also showed a role for ERK1/2 in the actions of T4 that modified the effects of IGF-I. We conclude that thyroid hormone inhibits IGF-I-stimulated glucose uptake and cell proliferation in L6 myoblasts.

Human tissue-type plasminogen activator

Tissue-type plasminogen activator (t-PA ) plays an important role in the removal of intravascular fibrin deposits and has several physiological roles and pathological activities in the brain. Its production by many other cell types suggests that t-PA has additional functions outside the vascular and central nervous system. Activity of t-PA is regulated at the level of its gene transcription, its mRNA stability and translation, its storage and regulated release, its interaction with cofactors that enhance its activity, its inhibition by inhibitors such as plasminogen activator inhibitor type 1 or neuroserpin, and its removal by clearance receptors. Gene transcription of t-PA is modulated by a large number of hormones, growth factors, cytokines or drugs and t-PA gene responses may be tissue-specific. The aim of this review is to summarise current knowledge on t-PA function and regulation of its pericellular activity, with an emphasis on regulation of its gene expression.

Effects of hypo- and hyperthyroid states on herpes simplex virus infectivity in the rat

OBJECTIVE

Available data from in vitro studies show that thyroid hormones (THs) regulate herpes simplex virus (HSV) gene expression and may modulate latency/reactivation of the virus. Whether infectivity of the virus is also affected by THs is not known. Using animal models (in vivo study) and Vero cell culture (in vitro study), we examined the effects of alterations in THs level on HSV-1 infectivity.

METHODS

Rats were rendered hypo- and hyperthyroid by daily addition of methimazole and l-thyroxine into their drinking water, respectively. Euthyroid animals served as control. All animals were given a single dose of HSV-1 (10(7)TCID50, ip) and sacrificed 3 d later. The spleen of the animals was then removed and viral particles were recovered from the tissue extract through aseptic procedures. Serial dilution of the extracts was prepared and added to Vero cell culture. For the in vitro study, the cultures were pretreated with l-thyroxine and the viral particles were then added. Virus titration was determined by Reed-Muench quantal assay.

RESULTS

The viral load of spleen in hyperthyroid rats was significantly lower (1000-fold) than that of the euthyroid rats. Similarly, in vitro presence of supraphysiologic levels of l-thyroxine in the culture media of Vero cells decreased virus infectivity. Interestingly, hypothyroid animals showed a significant increase (10-fold) in spleen viral load as compared to that of their euthyroid counterparts.

CONCLUSIONS

These data clearly show that the HSV-1 infectivity is affected by THs, and suggest that THs or their analogs may have a potential application in prevention and/or treatment of viral infections.

Hyperthyroid state or in vitro thyroxine treatment modulates TH1/TH2 responses during exposure to HSV-1 antigens

Increasingly in recent years, thyroid hormones (THs) have been considered to be important regulators of the immune system. However, their roles in host defense against viral infections are not clearly established. Therefore, this study was undertaken to examine proliferative activity and cytokine production by lymphocytes isolated from hyperthyroid and euthyroid Balb/c mice in response to herpes simplex virus-1 (HSV-1). Lymphocytes of hyperthyroid animals showed a significantly higher rate of proliferation and interferon (IFN)-γ production when compared with that by lymphocytes from euthyroid mice. In vitro thyroxine (T4) treatment was similarly effective in the potentiation of proliferation, but not IFNγ production, by euthyroid lymphocytes. Furthermore, the hyperthyroid state significantly attenuated ConA-, but not HSV-1-, induced interleukin (IL)-10 release; in vitro T4 treatment synergized this effect. These findings suggest that supra-physiologic TH levels (i.e. as occur in hyper-thyroid states) or in vitro TH treatment modulate T-helper (TH)1/TH2 lymphocyte responses and thereby amplifies host defenses against viral infections. One may also conclude that THs may have a potential application in viral immunization and/or treatment of viral infections.

Thyroid hormones as modulators of immune activities at the cellular level

BACKGROUND

Increasing evidence suggests that thyroid hormones, L-thyroxine (T(4)) and 3,3',5-triiodo-L-thyronine (T(3)), are modulators of the immune response. In monocytes, macrophages, leukocytes, natural killer cells, and lymphocytes, a wide range of immune functions such as chemotaxis, phagocytosis, generation of reactive oxygen species (ROS), and cytokine synthesis and release are altered under hypo- and hyperthyroid conditions.

SUMMARY

Hyperthyroidism decreases the proinflammatory activities of monocytes and macrophages, whereas enhancement of phagocytosis and increased levels of ROS may occur during hypothyroidism. The expression of proinflammatory molecules such as macrophage inflammatory protein-1α and interleukin-1β increases in hypothyroidism. However, in Kupffer cells, proinflammatory activities such as the respiratory burst, nitric oxide synthase activity, and tumor necrosis factor-α expression may result from increased T(3) levels. Thyroid hormones also affect natural killer cell activity and cell-mediated immune responses. Still, for many immune cells no clear correlation has been found so far between abnormally high or low T(3) or T(4) levels and the effects observed on the immune responses.

CONCLUSIONS

In this review we outline the contributions of thyroid hormones to different aspects of innate and adaptive immune responses. The relationship between thyroid hormones and immune cells is complex and T(3) and T(4) may modulate immune responses through both genomic and nongenomic mechanisms. Future studies of the molecular signaling mechanisms involved in this cross-talk between thyroid hormones and the immune system may support development of new strategies to improve clinical immune responses.

Short-term effects of thyroid hormones on Na+-K+-ATPase activity of chick embryo hepatocytes during development: focus on signal transduction

Nongenomic effects of thyroid hormones on Na+-K+-ATPase activity were studied in chick embryo hepatocytes at two different developmental stages, 14 and 19 days of embryonal age, and the signal transduction pathways involved were characterized. Our data showed the following. 1) 3,5,3′-Triiodo-l-thyronine (T3) and 3,5-diiodo-l-thyronine (3,5-T2) rapidly induced a transient inhibitory effect on the Na+-K+-ATPase; the extent and duration depended on the developmental age of the cells. 2) 3,5-T2behaved as a true hormone and fully mimicked the effect of T3. 3) Thyroxine had no effect at any of the developmental stages. 4) The inhibition of Na+-K+-ATPase was mediated by activation of protein kinase A, protein kinase C, and phosphoinositide 3-kinase, suggesting several modes of modulation of ATPase activity through phosphorylation at different sites. 5) The MAPK pathway did not seem to be involved in the early phase of hormone treatment. 6) The nonpermeant analog T3-agarose inhibited Na+-K+-ATPase activity in the same way as T3, confirming that hormone signaling initiated at a receptor on the plasma membrane. From these results, it can be concluded that the cell response mechanisms change rapidly and drastically within the early phase of embryo growth. The differences found at the two stages probably reflect the different roles of thyroid hormones during development and differentiation.

Effect of ileal fat perfusion on satiety and hormone release in healthy volunteers

OBJECTIVE

The ileal brake is a feedback mechanism activated by nutrients, especially fat, with marked effects on satiety. The effects of low doses of ileal fat on satiety are largely unknown. We therefore studied the effect of ileal vs oral delivery of low doses of fat on satiety and gut peptide secretion.

DESIGN

Randomized, single-blind crossover design.

SUBJECTS

Sixteen healthy, normal-weight volunteers (6 male; mean age 26 years, mean body mass index 22.4).

INTERVENTION

Participants were intubated with a 290-cm-long nasoileal tube and consumed, on 3 consecutive days, either a liquid breakfast with 3 g fat followed by an ileal placebo infusion at t=105-150 min (treatment C) or a fat-free liquid breakfast followed by an ileal infusion of either an emulsion of 3 g (treatment 13 g) or 9 g (treatment 19 g) fat (safflower oil).

MEASUREMENTS

Satiety parameters by visual analog scales and plasma concentrations of CCK and PYY.

RESULTS

C significantly increased satiety and CCK secretion compared with the fat-free breakfast. Ileal fat perfusion of both 3 and 9 g 13 g and 19 g) significantly increased satiety during and after fat perfusion, without differences in satiety between 13 g and 19 g. During ileal fat infusion, CCK increased dose dependently, whereas PYY concentrations increased significantly only after 9 g of fat. Secretion of CCK but not of PYY correlated to satiety levels.

CONCLUSION

Postprandial satiety following a liquid breakfast can be effectively and significantly increased by small amounts (as little as 3 g) of fat perfused into the ileum. Ileal fat dose-dependently increased CCK but not PYY secretion. The satiating effect of ileal fat may be partly mediated by CCK.

Experimental Encapsulating Peritoneal Sclerosis Models: Pathogenesis and Treatment

Encapsulating peritoneal sclerosis (EPS) is rare but, with its high morbidity and mortality, it represents one of the most serious complications of long-term peritoneal dialysis. The pathogenesis of EPS has not been elucidated yet; therefore, there has been a growing interest in establishing appropriate animal models for EPS that would explain the pathogenesis of EPS and verify the efficacy of therapeutic agents targeting pathways such as angiogenesis and/ or fibrosis. This brief review provides an update on previously published animal experimental models of EPS. Based on this review, we discuss some aspects of pathogenesis and treatment options in patients with EPS. Experimental models of EPS cannot exactly reproduce human EPS because the latter most likely has a diverse etiology, including the influences of uremia, dialysis, and genetic factors. There is a need for new animal models that would test interventions targeting multiple risk factors while also taking into account putative genetic diversities that most likely are involved in human EPS.

Glucose-based PD solution, but not icodextrin-based PD solution, induces plasminogen activator inhibitor-1 and tissue-type plasminogen activator in human peritoneal mesothelial cells via ERK1/2

Peritoneal dialysis (PD) solutions containing glucose are considered to cause peritoneal fibrosis. Plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (t-PA) participate in fibrogenesis of various organs, and human peritoneal mesothelial cells (HPMC) can produce PAI-1 and t-PA following glucose stimulation. Icodextrin has been widely used as an alternative osmotic agent. In this study, we investigated whether icodextrin-based PD solution reduced the production of PAI-1 and t-PA by HPMC. We also examined the involvement of extracellular signal-regulated kinase 1/2 (ERK1/2). Glucose-based PD solutions increased the production of PAI-1 and t-PA by HPMC, whereas icodextrin-based PD solution exerted lesser effects. Glucose-based PD solutions activated ERK1/2, and PD98059 inhibited the production of PAI-1 and t-PA-responses not observed with icodextrin-based PD solution. In conclusion, glucose-based PD solutions, unlike icodextrin-based PD solution, induce overproduction of PAI-1 and t-PA via the ERK1/2 pathway.

Histone deacetylase inhibitors suppress TF-kappaB-dependent agonist-driven tissue factor expression in endothelial cells and monocytes

Histone deacetylase inhibitors (HDACi), such as trichostatin A (TSA), can regulate gene expression by promoting acetylation of histones and transcription factors. Human tissue factor (TF) expression is partly governed by a unique, NF-kappaB-related "TF-kappaB" promoter binding site. We find that TSA and four other HDACi (apicidin, MS-275, sodium butyrate, and valproic acid) all inhibit by approximately 90% TF activity and protein level induction in human umbilical vein endothelial cells stimulated by the physiologic agonists tumor necrosis factor (TNF)-alpha, interleukin-1beta, lipopolysaccharide, and HOSCN without affecting expression of the NF-kappaB-regulated adhesion molecules ICAM-1 and E-selectin. TSA and butyrate also blunt TF induction approximately 50% in vitro in peripheral blood mononuclear cells and in vivo in thioglycolate-elicited murine peritoneal macrophages. In human umbilical vein endothelial cells, TSA attenuates by approximately 70% TNF-alpha stimulation of TF mRNA transcription without affecting that of ICAM-1. By electrophoretic mobility shift assay analyses, TNF-alpha and lipopolysaccharide induce strong p65/p50 and p65/c-Rel heterodimer binding to both NF-kappaB and TF-kappaB probes. TSA nearly abolishes TF-kappaB binding without affecting NF-kappaB binding. A chromatin immunoprecipitation assay and a promoter-luciferase reporter system confirm that TSA inhibits TF-kappaB but not NF-kappaB activation. Chromatin immunoprecipitation and small interfering RNA inhibitor studies demonstrate that HDAC3 plays a significant role in TNF-alpha-mediated TF induction. Thus, HDACi transcriptionally inhibit agonist-induced TF expression in endothelial cells and monocytes by a TF-kappaB- and HDAC3-dependent mechanism. We conclude that histone deacetylases, particularly HDAC3, play a hitherto unsuspected role in regulating TF expression and raise the possibility that HDACi might be a novel therapy for thrombotic disorders.

Genomic-independent action of thyroid hormones on NTPDase activities in Sertoli cell cultures from congenital hypothyroid rats

The Sertoli cells play an essential role in the maintenance and control of spermatogenesis. The ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase) and 5'-nucleotidase activities can modulate the extracellular adenine nucleotide levels, controlling nucleotide-mediated signaling events in Sertoli cells. Since thyroid hormones (TH) and adenine nucleotides and nucleosides play important modulatory roles in Sertoli cell proliferation and differentiation, the aim of our study was to investigate the effect of hypothyroidism upon the NTPDase and 5'-nucleotidase activities in Sertoli cell cultures, as well as to verify whether these effects may be reversed by short and long-term supplementation with TH. Congenital hypothyroidism was induced by adding 0.02% methimazole in the drinking water from day 9 of gestation and continually until 18 days of age. Hypothyroidism significantly decreased the extracellular ATP and ADP hydrolysis and this effect was significantly reversed when cell cultures were supplemented with 1 microM T3 or 0.1 microM T4 for 30 min. In contrast, AMP hydrolysis was not altered by hypothyroidism, but was increased by T4 supplementation for 24 h. The presence of the enzymes NTPDase 1, 2 and 3 was detected by RT-PCR in Sertoli cell cultures, however, hypothyroidism was not able to alter the expression of these enzymes. These findings demonstrate that TH modify NTPDase activities in hypothyroid Sertoli cells, probably via nongenomic mechanisms and, consequently, may influence the reproductive function throughout development.

Thyroid hormones increase inducible nitric oxide synthase gene expression downstream from PKC-ζ in murine tumor T lymphocytes

Regulation of cell proliferation by thyroid hormone (TH) has been demonstrated, but the effect of THs and the mechanisms involved in lymphocyte activity have not been elucidated. Differential expression of PKC isoenzymes and high nitric oxide synthase (NOS) activity have been described in tumor T lymphocytes. We have analyzed the direct actions of TH on normal T lymphocytes and BW5147 T lymphoma cells in relation to PKC and NOS activities. THs increased tumor and mitogen-induced normal T lymphocyte proliferation. PKC isoenzyme-selective blockers impaired these effects in both cell types, indicating the participation of Ca2+-dependent and -independent isoenzymes in normal and tumor cells, respectively. TH actions were blunted by extra- and intracellular Ca2+ blockers only in normal T lymphocytes, whereas NOS blockers impaired TH-induced proliferation in T lymphoma cells. Incubation for 24 h with TH induced a rise in total and membrane-associated PKC activities in both cell types and led to a rapid and transient effect only in tumor cells. THs increased atypical PKC-ζ expression in BW5147 cells and classical PKC isoenzymes in mitogen-stimulated normal T cells. TH augmented NOS activity and inducible NOS protein and gene expression only in tumor cells. Blockade of PKC and the atypical PKC-ζ isoform inhibited TH-mediated stimulation of inducible NOS and cell proliferation. These results show, for the first time, that differential intracellular signals are involved in TH modulation of lymphocyte physiology and pathophysiology.

Short-Term Effects of Thyroid Hormones on Cytoskeletal Proteins Are Mediated by GABAergic Mechanisms in Slices of Cerebral Cortex from Young Rats

: Thyroid hormones play important roles in brain function. However, few information is available about the effect of 3,5,3'-triiodo-L-thyronine (T(3)) or thyroxine (T(4)) on the in vitro phosphorylation of intermediate filament (IF) proteins from cerebral cortex of rats. In this study we investigated the involvement of GABAergic mechanisms mediating the effects of T(3) and T(4) on the in vitro incorporation of (32)P into IF proteins from cerebral cortex of 10-day-old male rats. Tissue slices were incubated with or without T(3), T(4), gamma-aminobutiric acid (GABA), kinase inhibitors or specific GABA antagonists and (32)P-orthophosphate for 30 min. The IF-enriched cytoskeletal fraction was extracted in a high salt Triton-containing buffer and the in vitro (32)P incorporation into IF proteins was measured. We first observed that 1 microM T(3) and 0.1 microM T(4) significantly increased the in vitro incorporation of (32)P into the IF proteins studied through the PKA and PKCaMII activities. A similar effect on IF phosphorylation was achieved by incubating cortical slices with GABA. Furthermore, by using specific GABA antagonists, we verified that T(3) induced a stimulatory effect on IF phosphorylation through noncompetitive mechanisms involving GABA(A), beyond GABA(B) receptors. In contrast, T(4) effects were mediated mainly by GABA(B) mechanisms. In conclusion, our results demonstrate a rapid nongenomic action of T(3) and T(4) on the phosphorylating system associated to the IF proteins in slices of cerebral cortex of 10 day-old male rats and point to GABAergic mechanisms mediating such effects.

Measurement of Strain in the Left Ventricle during Diastole with cine-MRI and Deformable Image Registration

The assessment of regional heart wall motion (local strain) can localize ischemic myocardial disease, evaluate myocardial viability, and identify impaired cardiac function due to hypertrophic or dilated cardiomyopathies. The objectives of this research were to develop and validate a technique known as hyperelastic warping for the measurement of local strains in the left ventricle from clinical cine-magnetic resonance imaging (MRI) image datasets. The technique uses differences in image intensities between template (reference) and target (loaded) image datasets to generate a body force that deforms a finite element (FE) representation of the template so that it registers with the target image. To validate the technique, MRI image datasets representing two deformation states of a left ventricle were created such that the deformation map between the states represented in the images was known. A beginning diastolic cine-MRI image dataset from a normal human subject was defined as the template. A second image dataset (target) was created by mapping the template image using the deformation results obtained from a forward FE model of diastolic filling. Fiber stretch and strain predictions from hyperelastic warping showed good agreement with those of the forward solution (R2=0.67 stretch, R2=0.76 circumferential strain, R2=0.75 radial strain, and R2=0.70 in-plane shear). The technique had low sensitivity to changes in material parameters (deltaR2= -0.023 fiber stretch, deltaR2=-0.020 circumferential strain, deltaR2=-0.005 radial strain, and deltaR2=0.0125 shear strain with little or no change in rms error), with the exception of changes in bulk modulus of the material. The use of an isotropic hyperelastic constitutive model in the warping analyses degraded the predictions of fiber stretch. Results were unaffected by simulated noise down to a signal-to-noise ratio (SNR) of 4.0 (deltaR2= -0.032 fiber stretch, deltaR2=-0.023 circumferential strain, deltaR2=-0.04 radial strain, and deltaAR2=0.0211 shear strain with little or no increase in rms error). This study demonstrates that warping in conjunction with cine-MRI imaging can be used to determine local ventricular strains during diastole.

Involvement of calcium-dependent mechanisms in T3-induced phosphorylation of vimentin of immature rat testis

Thyroid hormones have been shown to act at extra nuclear sites, inducing target cell responses by several mechanisms, frequently involving intracellular calcium concentration. It has also been reported that cytoskeletal proteins are a target for thyroid and steroid hormones and cytoskeletal rearrangements are observed during hormone-induced differentiation and development of rat testes. However, little is known about the effect of 3,5,3'-triiodo-L-thyronine (T3) on the intermediate filament (IF) vimentin in rat testes. In this study we investigated the immunocontent and in vitro phosphorylation of vimentin in the cytoskeletal fraction of immature rat testes after a short-term in vitro treatment with T3. Gonads were incubated with or without T3 and 32P orthophosphate for 30 min and the intermediate filament-enriched cytoskeletal fraction was extracted in a high salt Triton-containing buffer. Vimentin immunoreactivity was analyzed by immunoblotting and the in vitro 32P incorporation into this protein was measured. Results showed that 1 microM T3 was able to increase the vimentin immunoreactivity and in vitro phosphorylation in the cytoskeletal fraction without altering total vimentin immunocontent in immature rat testes. Besides, these effects were independent of active protein synthesis. The involvement of Ca2+-mediated mechanisms in vimentin phosphorylation was evident when specific channel blockers (verapamil and nifedipine) or chelating agents (EGTA and BAPTA) were added during pre-incubation and incubation of the testes with T3. The effect of T3 was prevented when Ca2+ influx was blocked or intracellular Ca2+ was chelated. These results demonstrate a rapid nongenomic Ca2+-dependent action of T3 in phosphorylating vimentin in immature rat testes.

Advances in electrical and mechanical cardiac mapping

Cardiac mapping--recording cardiac activity during electrophysiological testing--has evolved into an indispensable tool in studying the cardiac excitation process, analysing activation patterns, and identifying arrhythmogenic tissue. Cardiac mapping is a broad term that is used here to encompass applications that record electrical or mechanical activity of the heart or both. In recent years, simultaneous and sequential electrical mapping methods have been combined with direct mechanical measurements or imaging techniques to acquire information regarding both the electrical and mechanical activity of the heart (electromechanical mapping) during normal and irregular cardiac behavior. This paper reviews the emerging area of electromechanical mapping from the point of view of the applicable technology, including its history and application.

Signaling of short- and long-term regulation of intestinal epithelial type 1 Na+/H+ exchanger by interferon-gamma

The present study evaluated the effect of interferon-gamma (IFN-gamma) on intestinal Na+/H+ exchange (NHE) activity and the intracellular signaling pathways set into motion after IFN-gamma receptor activation. Caco-2 cells express endogenous NHE1, NHE2 and NHE3 proteins, as detected by immunoblotting. Short- (0.5 h) and long- (24 h) term exposure of Caco-2 cells to IFN-gamma resulted in a concentration-dependent decrease in NHE activity. Inhibition of NHE activity by IFN-gamma was absent in cariporide-treated cells, but not in cells treated with S-3226. The long-term exposure to IFN-gamma was accompanied by a 20% increase in surface NHE1 abundance and no changes in total NHE1 abundance. Inhibition of Raf1, mitogen-activated protein kinase kinase (MAPKK/MEK) and p38 MAPK with, respectively, GW 5074, PD 98059 and SB 203580 and downregulation of protein kinase C (PKC) with phorbol-12,13-dibutyrate (100 nM for 24 h) prevented inhibition of NHE activity by IFN-gamma (0.5 and 24 h exposure). The signal transducer and activator transcription factor 1 (STAT1) inhibitor epigallocatechin-3-gallate (EGCG) prevented inhibition of NHE activity by long- but not the short-term treatment with IFN-gamma. Treatment with IFN-gamma activated phospho-p38 MAPK, this effect being detected as early as 1 h, persisting over 3 h and decreasing after 24 h. IFN-gamma produced a sustained action of phospho-STAT1 that was prevented by EGCG and partially attenuated by SB 203580 and insensitive to downregulation of PKC. In conclusion, short- and long-term inhibition of NHE1 activity by IFN-gamma involves a complex signaling pathway that includes PKC activation and STAT1 phosphorylation, respectively, but is not accompanied by downregulation of NHE1.

Intestinal Na+-K+-ATPase activity and molecular events downstream of interferon-gamma receptor stimulation

This study evaluated the effects of human interferon-gamma (IFN-gamma) on Na(+)-K(+)-ATPase activity and the intracellular signaling pathways involved in human intestinal epithelial Caco-2 cells. Na(+)-K(+)-ATPase activity was determined as the difference between total and ouabain-sensitive ATPase. p38 MAP kinase activity was analyzed by Western blotting using the p38 MAP kinase assay kit. Total and phosphorylated STAT1 protein levels were detected using the PhosphoPlus Stat1. IFN-gamma decreased Na(+)-K(+)-ATPase activity in a time- and concentration-dependent manner. The IFN-gamma-induced decrease in Na(+)-K(+)-ATPase activity was accompanied by no changes in the abundance of alpha(1) subunit Na(+)-K(+)-ATPase. Downregulation of protein kinase C (PKC) with phorbol-12,13-dibutyrate (PDBu) prevented the inhibitory effect of IFN-gamma on Na(+)-K(+)-ATPase activity. Inhibition of Raf-1, mitogen-activated protein kinase kinase (MAPKK/MEK), p38 MAPK and STAT1 with, respectively, GW 5074, PD 98059, SB 203580 and epigallocatechin gallate prevented inhibition of Na(+)-K(+)-ATPase activity by IFN-gamma. Treatment with IFN-gamma markedly increased the expression of total and phospho-STAT1, this being accompanied by activation of p38 MAPK. Activation of phospho-STAT1 by IFN-gamma was almost abolished by epigallocatechin gallate and markedly reduced by SB 203580, but insensitive to downregulation of PKC. The increase in short circuit current (I(sc)) by 1.0 and 2.5 micrograms ml(-1) amphotericin B was markedly attenuated in IFN-gamma-treated cells. However, the inhibitory effect of PDBu on the amphotericin B-induced increase in I(sc) was of similar magnitude in vehicle- and IFN-gamma-treated cells. It is concluded that IFN-gamma markedly attenuates Na(+)-K(+)-ATPase activity. The transduction mechanisms set into motion by IFN-gamma involve the activation of PKC downstream STAT1 phosphorylation and Raf-1, MEK, ERK2 and p38 MAPK pathways, in a complex sequence of events.

A neurokinin 1 receptor antagonist decreases postoperative peritoneal adhesion formation and increases peritoneal fibrinolytic activity

Fibrous adhesions remain a major sequela of abdominal surgery. The proinflammatory peptide substance P (SP), known to participate in inflammatory events, may play a key role in adhesion formation. This hypothesis was tested by using an antagonist, CJ-12,255 (Pfizer), that blocks the binding of SP to the neurokinin 1 receptor (NK-1R). Adhesion formation was surgically induced in the peritoneum of rats receiving daily doses of the NK-1R antagonist (NK-1RA; 5.0 or 10.0 mg/kg per day) or saline. On postoperative day 7, both the low and high doses of NK-1RA significantly (P < 0.05) reduced adhesion formation by 45% and 53%, respectively, compared with controls. Subsequently, the effect of NK-1RA administration on peritoneal fibrinolytic activity was investigated to determine a potential mechanism for SP action in the peritoneum. Samples were collected from nonoperated controls and from animals 24 h postsurgery that were administered either NK-1RA or saline. Fibrinolytic activity in peritoneal fluid was assayed by zymography, and expression of tissue plasminogen activator (tPA) and plasminogen activator inhibitor 1, both regulators of fibrinolytic activity, was assessed in peritoneal tissue and fluid by RT-PCR and bioassay, respectively. NK-1RA administration led to a marked (P < 0.05) increase in tPA mRNA levels in peritoneal tissue compared with nonoperated and saline-administered animals. Likewise, NK-1RA administration significantly (P < 0.05) increased tPA in the peritoneal fluid. These data suggest that activation of the NK-1R promotes peritoneal adhesion formation by limiting fibrinolytic activity in the postoperative peritoneum, thus enabling fibrinous adhesions to persist.

Transforming growth factor-beta1 produced by ovarian cancer cell line HRA stimulates attachment and invasion through an up-regulation of plasminogen activator inhibitor type-1 in human peritoneal mesothelial cells

The processes of ovarian cancer dissemination are characterized by altered local proteolysis, cellular proliferation, cell attachment, and invasion, suggesting that the urokinase-type plasminogen activator (uPA) and its specific inhibitor (plasminogen activator inhibitor type-1 (PAI-1)) could be involved in the pathogenesis of peritoneal dissemination. We showed previously that expression of uPA and PAI-1 in the human ovarian cancer cell line HRA can be down-regulated by exogenous bikunin (bik), a Kunitz-type protease inhibitor, via suppression of transforming growth factor-beta1 (TGF-beta1) up-regulation and that overexpression of the bik gene can specifically suppress the in vivo growth and peritoneal dissemination of HRA cells in an animal model. We hypothesize that the plasminogen activator system in mesothelial cells can be modulated by HRA cells. To test this hypothesis, we used complementary techniques in mesothelial cells to determine whether uPA and PAI-1 expression are altered by exposure to culture media conditioned by HRA cells. Here we show the following: 1) that expression of PAI-1, but not uPA, was markedly induced by culture media conditioned by wild-type HRA cells but not by bik transfected clones; 2) that by antibody neutralization the effect appeared to be mediated by HRA cell-derived TGF-beta1; 3) that exogenous TGF-beta1 specifically enhanced PAI-1 up-regulation at the mRNA and protein level in mesothelial cells in a time- and concentration-dependent manner, mainly through MAPK-dependent activation mechanism; and 4) that mesothelial cell-derived PAI-1 may promote tumor invasion possibly by enhancing cell-cell interaction. This represents a novel pathway by which tumor cells can regulate the plasminogen activator system-dependent cellular responses in mesothelial cells that may contribute to formation of peritoneal dissemination of ovarian cancer.

Nongenomic steroid action: controversies, questions, and answers

Steroids may exert their action in living cells by several ways: 1). the well-known genomic pathway, involving hormone binding to cytosolic (classic) receptors and subsequent modulation of gene expression followed by protein synthesis. 2). Alternatively, pathways are operating that do not act on the genome, therefore indicating nongenomic action. Although it is comparatively easy to confirm the nongenomic nature of a particular phenomenon observed, e.g., by using inhibitors of transcription or translation, considerable controversy exists about the identity of receptors that mediate these responses. Many different approaches have been employed to answer this question, including pharmacology, knock-out animals, and numerous biochemical studies. Evidence is presented for and against both the participation of classic receptors, or proteins closely related to them, as well as for the involvement of yet poorly understood, novel membrane steroid receptors. In addition, clinical implications for a wide array of nongenomic steroid actions are outlined.

Nongenomic actions of steroid hormones

Steroid hormones modulate many physiological processes. The effects of steroids that are mediated by the modulation of gene expression are known to occur with a time lag of hours or even days. Research that has been carried out mainly in the past decade has identified other responses to steroids that are much more rapid and take place in seconds or minutes. These responses follow nongenomic pathways, and they are not rare.

Thyroid hormone actions on neural cells

1. In addition to its role in cellular metabolic activity, thyroid hormone (TH) is critically involved in growth, development, and function of the central nervous system. In the brain, as in other structures, TH is described to exert its major action by the binding of L-3,5,3'-triiodothyronine (T3), considered as the bioactive form of the hormone, to nuclear thyroid hormone receptors (TR) that function as ligand-dependent transcription factors. 2. The transcription of numerous brain genes was indeed shown to be positively or negatively regulated by TH, turning these TR-mediated effects one explanation for the physiological effects of TH. In this context, the knowledge from TR-knockout studies provides some surprising results, since neonatal hypothyroidism is associated to more significant abnormalities than is TR deficiency. Some (nonexclusive) hypotheses include a permissive effect of TH, allowing derepression of unliganded-TR effects and non-TR-mediated effects of the hormone, further emphasizing the importance of a controlled accessibility of neural cells to TH. 3. On the other hand, T3 was demonstrated to directly act not only on neuronal but also on glial cells proliferation and differentiation, contributing to the harmonious development of the brain. Interestingly, in addition to these direct actions on neuronal and glial cells, several lines of evidence, notably developped in our laboratory, point out the role of thyroid hormone in neuronal-glial interactions.

Mesothelial cells: their structure, function and role in serosal repair

The mesothelium is composed of an extensive monolayer of specialized cells (mesothelial cells) that line the body's serous cavities and internal organs. Traditionally, this layer was thought to be a simple tissue with the sole function of providing a slippery, non-adhesive and protective surface to facilitate intracoelomic movement. However, with the gradual accumulation of information about serosal tissues over the years, the mesothelium is now recognized as a dynamic cellular membrane with many important functions. These include transport and movement of fluid and particulate matter across the serosal cavities, leucocyte migration in response to inflammatory mediators, synthesis of pro-inflammatory cytokines, growth factors and extracellular matrix proteins to aid in serosal repair, release of factors to promote both the deposition and clearance of fibrin, and antigen presentation. Furthermore, the secretion of molecules, such as glycosaminoglycans and lubricants, not only protects tissues from abrasion, but also from infection and possibly tumour dissemination. Mesothelium is also unlike other epithelial-like surfaces because healing appears diffusely across the denuded surface, whereas in true epithelia, healing occurs solely at the wound edges as sheets of cells. Although controversial, recent studies have begun to shed light on the mechanisms involved in mesothelial regeneration. In the present review, the current understanding of the structure and function of the mesothelium and the biology of mesothelial cells is discussed, together with recent insights into the mechanisms regulating its repair.

Comparison of the mechanisms of nongenomic actions of thyroid hormone and steroid hormones

Steroids and thyroid hormone are thought primarily to act via binding to hormone-specific nuclear receptor superfamily members. The nuclear ligand-receptor complexes then initiate transcriptional activity. Actions of steroids and iodothyronines that are nongenomic or extranuclear in mechanism have been recognized recently and new insights into such mechanisms are available. Despite their distinct structures and biologic effects, the two families of hormones have similarities in the mechanisms of their nongenomic actions. That is, both steroids and thyroid hormone appear to interact with specific cell surface G protein-coupled receptors and to activate signal transducing kinases such as those involved in the mitogen-activated protein kinase (MAPK) pathway. Much is known about the ability of certain steroids such as estrogen and mineralocorticoids to increase [Ca2+]i acutely and stimulation of the MAPK cascade by L-T4 appears to depend upon a hormone-induced increase in [Ca2+]i via phosphoinositide pathway activation. At least in the case of iodothyronines, hormone activation of the MAPK pathway modulates the cellular activities of certain cytokines and growth factors. One of the two cell surface estrogen receptors (ERs) may be an expression of the same transcript as that for nuclear ER, whereas the mineralocorticoid and progesterone-binding proteins in the plasma membrane appear to be products of genes different from those of nuclear receptors. Iodothyronine structure-activity relationships at the plasma membrane binding site for thyroid hormone suggest that the cell surface receptor for T4 that also binds 3,5,3'-triiodo-L-T3 is different from the nuclear T3 receptor (TR). There are interfaces of nongenomic and genomic mechanisms for both steroids and thyroid hormone. For example, by nongenomic mechanisms, estrogen and thyroid hormone can promote serine phosphorylation, respectively, of nuclear ER and TR. Transcriptional activity of the nuclear receptor proteins can be altered by such phosphorylation.

Bile salt-stimulated carboxyl ester lipase influences lipoprotein assembly and secretion in intestine: a process mediated via ceramide hydrolysis

Bile salt-stimulated carboxyl ester lipase (CEL), also called cholesterol esterase, is one of the major proteins secreted by the pancreas. The physiological role of CEL was originally thought to be its mediation of dietary cholesterol absorption. However, recent studies showed no difference between wild type and CEL knockout mice in the total amount of cholesterol absorbed in a single meal. The current study tests the hypothesis that CEL in the intestinal lumen may influence the type of lipoproteins produced. A lipid emulsion containing 4 mm phospholipid, 13.33 mm [(3)H]triolein, and 2.6 mm [(14)C]cholesterol in 19 mm taurocholate was infused into the duodenum of lymph fistula CEL(+/+) and CEL(-/-) mice at a rate of 0.3 ml/h. Results showed no difference between CEL(+/+) and CEL(-/-) mice in the rate of cholesterol and triglyceride transport from the intestinal lumen to the lymph. However, CEL(-/-) mice produced predominantly smaller lipoproteins, whereas the CEL(+/+) mice produced primarily large chylomicrons and very low density lipoprotein. The proximal intestine of CEL(-/-) mice was also found to possess significantly less ceramide hydrolytic activity than that present in CEL(+/+) mice. By using Caco2 cells grown on Transwell membranes as a model, sphingomyelinase treatment inhibited the secretion of larger chylomicron-like lipoproteins without affecting total cholesterol secretion. In contrast, the addition of CEL to the apical medium increased the amount of large lipoproteins produced and alleviated the inhibition induced by sphingomyelinase. Taken together, this study identified a novel and physiologically significant role for CEL, namely the promotion of large chylomicron production in the intestine. The mechanism appears to be mediated through CEL hydrolysis of ceramide generated during the lipid absorption process.

Nutritional efficacy of preterm formula with a partially hydrolyzed protein source: a randomized pilot study

BACKGROUND

Decreased nitrogen levels, calcium intestinal absorption rates, and plasma amino acid imbalances were reported for preterm infants who were fed partially hydrolyzed preterm formulas. In this pilot study, we evaluated a new formula with modified nitrogen and calcium sources.

METHODS

During their second week of life, 16 preterm infants were randomly assigned to one of two groups: 9 were fed the new partially hydrolyzed formula and 7 were fed a conventional formula. Nutrient balance was performed at the end of the first month of life. Amino acid concentrations and anthropometric parameters were measured at theoretical term.

RESULTS

Birth weight and gestational age (mean +/- SD) were similar in the two groups (28.9 +/- 7.0 weeks and 1183 +/- 242 g vs. 27.7 +/- 1.0 weeks and 1139 +/- 162 g). Median nitrogen absorption rates (85% vs. 89%; P = 0.03) and biological values (59% vs. 69%; P = 0.13) were lower for infants who were fed the new formula than for those fed the conventional formula. After correction for difference in nitrogen intake, there was no significant difference in nitrogen retained between the two groups (P = 0.11). Plasma amino acid concentrations were also similar in the two groups. Median calcium absorption tended to be higher in the new-formula group than in the conventional-formula group (54% vs. 45%, P = 0.19). At theoretical term, infants fed the conventional formula were heavier than infants fed the new formula (3559 +/- 362 g vs. 3193 +/- 384 g, P = 0.04).

CONCLUSIONS

Because nitrogen content is 10% higher in hydrolyzed-protein formula than in entire-protein formula, appropriate nitrogen retention, plasma amino acid profile, and mineral use can be achieved with the new partially hydrolyzed formula. Further studies with larger groups are needed to evaluate the effect on growth.

Thyroxine signal transduction in liver cells involves phospholipase C and phospholipase D activation. Genomic independent action of thyroid hormone

BACKGROUND

Numerous investigations demonstrate a novel role of thyroid hormone as a modulator of signal transduction. Protein kinase C (PKC) is critical to the mechanism by which thyroid hormones potentiate both the antiviral and immunomodulatory actions of IFNgamma in different cells and regulate the exchange of signalling phospholipids in hepatocytes. Because nothing is known about accumulation of PKC modulator - diacylglycerol in cells treated with T4, we examined the nongenomic effect of thyroid hormones on DAG formation and phospholipase activation in liver cells.

RESULTS

The results obtained provide the first demonstration of phospholipase C, phospholipase D and protein kinase C nongenomic activation and diacylglycerol (DAG) accumulation by L-T4 in liver cells. The experiments were performed in either the [14C]CH3COOH-labeled rat liver slices or isolated hepatocytes pre-labeled by [14C]oleic acid. L-T4 activates the DAG production in a concentration- and time-dependent manner. DAG formation in stimulated cells is biphasic and short-lived event: there is an initial, rapid rise in DAG concentration and then a slower accumulation that can be sustained for a few minutes. The early phase of L-T4 generated DAG only is accompanied by phosphatidylinositol 4,5-bisphosphate level decrease and inositol 1,4,5-trisphosphate formation while the second phase is abolished by PKC inhibitor l,(5-isoquinolinesulphonyl)2methylpiperasine dihydrochloride (H7) and propranolol. The second phase of DAG production is accompanied by free choline release, phosphatidylcholine content drop and phosphatidylethanol (Peth) formation. Inhibitor of phospholipase-C-dependent phosphoinositide hydrolysis, neomycin sulfate, reduced the Peth as well as the DAG response to L-T4.

CONCLUSIONS

The present data have indicated the DAG signaling in thyroid hormone-stimulated liver cells. L-thyroxine activates a dual phospholipase pathway in a sequential and synchronized manner: phospholipase C initiates the DAG formation, and PKC mediates the integration of phospholipase D into the signaling response during the sustained phase of agonist stimulation.

Myocardial mechanics and collagen structure in the osteogenesis imperfecta murine (oim)

Because the amount and structure of type I collagen are thought to affect the mechanics of ventricular myocardium, we investigated myocardial collagen structure and passive mechanical function in the osteogenesis imperfecta murine (oim) model of pro-alpha2(I) collagen deficiency, previously shown to have less collagen and impaired biomechanics in tendon and bone. Compared with wild-type littermates, homozygous oim hearts exhibited 35% lower collagen area fraction (P:<0.05), 38% lower collagen fiber number density (P:<0.05), and 42% smaller collagen fiber diameter (P:<0.05). Compared with wild-type, oim left ventricular (LV) collagen concentration was 45% lower (P:<0.0001) and nonreducible pyridinoline cross-link concentration was 22% higher (P:<0.03). Mean LV volume during passive inflation from 0 to 30 mm Hg in isolated hearts was 1.4-fold larger for oim than wild-type (P:=NS). Uniaxial stress-strain relations in resting right ventricular papillary muscles exhibited 60% greater strains (P:<0.01), 90% higher compliance (P:=0.05), and 64% higher nonlinearity (P:<0.05) in oim. Mean opening angle, after relief of residual stresses in resting LV myocardium, was 121+/-9 degrees in oim compared with 45+/-4 degrees in wild-type (P:<0.0001). Mean myofiber angle in oim was 23+/-8 degrees greater than wild-type (P:<0.02). Decreased myocardial collagen diameter and amount in oim is associated with significantly decreased fiber and chamber stiffness despite modestly increased collagen cross-linking. Altered myofiber angles and residual stress may be beneficial adaptations to these mechanical alterations to maintain uniformity of transmural fiber strain. In addition to supporting and organizing myocytes, myocardial collagen contributes directly to ventricular stiffness at high and low loads and can influence stress-free state and myofiber architecture.

Potential role for protein kinases in regulation of bidirectional endoplasmic reticulum-to-Golgi transport revealed by protein kinase inhibitor H89

Recent evidence suggests a regulatory connection between cell volume, endoplasmic reticulum (ER) export, and stimulated Golgi-to-ER transport. To investigate the potential role of protein kinases we tested a panel of protein kinase inhibitors for their effect on these steps. One inhibitor, H89, an isoquinolinesulfonamide that is commonly used as a selective protein kinase A inhibitor, blocked both ER export and hypo-osmotic-, brefeldin A-, or nocodazole-induced Golgi-to-ER transport. In contrast, H89 did not block the constitutive ER Golgi-intermediate compartment (ERGIC)-to-ER and Golgi-to-ER traffic that underlies redistribution of ERGIC and Golgi proteins into the ER after ER export arrest. Surprisingly, other protein kinase A inhibitors, KT5720 and H8, as well as a set of protein kinase C inhibitors, had no effect on these transport processes. To test whether H89 might act at the level of either the coatomer protein (COP)I or the COPII coat protein complex we examined the localization of betaCOP and Sec13 in H89-treated cells. H89 treatment led to a rapid loss of Sec13-labeled ER export sites but betaCOP localization to the Golgi was unaffected. To further investigate the effect of H89 on COPII we developed a COPII recruitment assay with permeabilized cells and found that H89 potently inhibited binding of exogenous Sec13 to ER export sites. This block occurred in the presence of guanosine-5'-O-(3-thio)triphosphate, suggesting that Sec13 recruitment is inhibited at a step independent of the activation of the GTPase Sar1. These results identify a requirement for an H89-sensitive factor(s), potentially a novel protein kinase, in recruitment of COPII to ER export sites, as well as in stimulated but not constitutive Golgi-to-ER transport.

Effects of thyroid hormone on action potential and repolarizing currents in rat ventricular myocytes

Thyroid hormones play an important role in cardiac electrophysiology through both genomic and nongenomic mechanisms of action. The effects of triiodothyronine (T(3)) on the electrophysiological properties of ventricular myocytes isolated from euthyroid and hypothyroid rats were studied using whole cell patch clamp techniques. Hypothyroid ventricular myocytes showed significantly prolonged action potential duration (APD(90)) compared with euthyroid myocytes, APD(90) of 151 +/- 5 vs. 51 +/- 8 ms, respectively. Treatment of hypothyroid ventricular myocytes with T(3) (0.1 microM) for 5 min significantly shortened APD by 24% to 115 +/- 10 ms. T(3) similarly shortened APD in euthyroid ventricular myocytes, but only in the presence of 4-aminopyridine (4-AP), an inhibitor of the transient outward current (I(to)), which prolonged the APD by threefold. Transient outward current (I(to)) was not affected by the acute application of T(3) to either euthyroid or hypothyroid myocytes; however, I(to) density was significantly reduced in hypothyroid compared with euthyroid ventricular myocytes.

Effect of pH and glucose on cultured human peritoneal mesothelial cells

OBJECTIVE

We investigated the effects of various pH and glucose concentrations on the growth of human peritoneal mesothelial cells and on coagulation and fibrinolytic factors.

MATERIALS AND METHODS

Cells were cultured at various pH values in Ham's F-12 medium containing 1.0% foetal calf serum and supplemented with D-glucose or D-mannitol at various concentrations. After 4-48 h, cell proliferation and 3H-thymidine incorporation were determined. Coagulation and fibrinolytic factors were measured after 48 h.

RESULTS

Glucose caused concentration-dependent inhibition of cell growth at all pH values, but the deleterious effect of low pH on cell proliferation was faster and stronger than that of high glucose. At a similar osmolality, mannitol caused less inhibition of cell proliferation than glucose. There was a glucose concentration-dependent increase of thrombin-antithrombin III complex production at all pH values. At pH 5.2, tissue-type plasminogen activator production was far lower than at higher pH values, and production of the plasminogen activator inhibitor showed a glucose concentration-dependent increase. At pH 6.5 or 7.3, however, the plasminogen activator inhibitor production decreased and tissue-type plasminogen activator production increased in a glucose concentration-dependent manner.

CONCLUSIONS

Low pH and/or high glucose culture medium had an inhibitory effect on peritoneal mesothelial cells, with the effect of high glucose being partially related to hyperosmolality. These cells may modulate peritoneal coagulant and fibrinolytic activity, with the balance between coagulation and fibrinolysis being disturbed by low pH and/or high glucose.

Estrogen receptor-alpha detected on the plasma membrane of aldehyde-fixed GH3/B6/F10 rat pituitary tumor cells by enzyme-linked immunocytochemistry

A population of estrogen receptor-alpha (ER alpha) proteins, located at the plasma membrane, is postulated to mediate the rapid, nongenomic responses of GH3/B6/F10 pituitary cells to estrogen. To demonstrate the presence of ER alpha at the plasma membrane and to distinguish this receptor population from that in the nucleus, GH3/B6/F10 cells were first prepared in 2% paraformaldehyde/0.1% glutaraldehyde in PBS (P/G) without detergent, then exposed to one of several antibodies (Abs) raised against nuclear ER alpha. Ab binding was visualized as a fluorescent/chromagenic reaction product catalyzed by avidin-biotin-complexed alkaline phosphatase. With P/G fixation, Abs could only access antigens at the cell surface, as evidenced by the inability of 70K mol wt dextrans to permeate cells and the absence of intracellular staining by Abs to cytoplasmic or nuclear antigens. ER alpha Abs generated membrane, but not nuclear, staining in P/G-fixed cells; nuclear receptor labeling could only be detected in detergent-treated cells. Specificity of staining for ER alpha was confirmed by three approaches: first, treatment with an antisense oligodeoxynucleotide to nuclear ER alpha mRNA reduced immunolabeling of both membrane and nuclear ER alpha; second, labeling by two Abs raised against different ER alpha oligopeptides was neutralized by competing peptide; third, six Abs (ER21, H226, R4, H222, MC20, and C542) that recognize unique epitopes on rodent ER alpha produced immunolabeling, but neither primate-specific ER alpha Ab nor Ab to ER beta caused staining. In addition to demonstrating the plasma membrane ER alpha in GH3/B6/F10 cells, this method should be applicable to other cell types that exhibit nongenomic responses to estrogen or other steroid hormones.

Endothelin-1 enhances plasminogen activator inhibitor-1 production by human brain endothelial cells via protein kinase C-dependent pathway

The effects of endothelin-1 (ET-1) on the production of plasminogen activator inhibitor 1 (PAI-1) and tissue plasminogen activator (t-PA) by human brain-derived endothelial cells in culture were studied. At 100 nmol/L, ET-1 increased PAI-1 production by 88+/-6% within 72 hours, and increased PAI-1 mRNA expression within 1 hour of stimulation; there was no significant effect on t-PA production. PAI-1 activity was also examined and found to increase with ET-1 treatment. Suboptimal concentrations of ET-1 and tumor necrosis factor-alpha (TNF-alpha) acted synergistically to increase PAI-1 production. ET-1 activated protein kinase C and cAMP-dependent protein kinase pathways within 3 to 5 minutes of treatment, with the peak at 10 minutes. Activation of protein kinase C by phorbol-12-myristate-13-acetate (PMA) resulted in increased PAI-1 production, whereas activation of the cAMP-dependent protein kinase by forskolin or dibutyryl cAMP (dBu-cAMP) significantly decreased PAI-1 production. However, simultaneous activation of protein kinase C by PMA and cAMP-dependent protein kinase by dBu-cAMP only slightly attenuated PMA-induced PAI-1 increase. Inhibition of protein kinase C by GF-109213X abolished the effects of ET-1. These results demonstrate that ET-1 and TNF-alpha function synergistically to induce procoagulant activity of brain endothelial cells in a process that involves a protein kinase C-dependent pathway.

RC3/neurogranin, a postsynaptic calpacitin for setting the response threshold to calcium influxes

In this review, we attempt to cover the descriptive, biochemical and molecular biological work that has contributed to our current knowledge about RC3/neurogranin function and its role in dendritic spine development, long-term potentiation, long-term depression, learning, and memory. Based on the data reviewed here, we propose that RC3, GAP-43, and the small cerebellum-enriched peptide, PEP-19, belong to a protein family that we have named the calpacitins. Membership in this family is based on sequence homology and, we believe, a common biochemical function. We propose a model wherein RC3 and GAP-43 regulate calmodulin availability in dendritic spines and axons, respectively, and calmodulin regulates their ability to amplify the mobilization of Ca2+ in response to metabotropic glutamate receptor stimulation. PEP-19 may serve a similar function in the cerebellum, although biochemical characterization of this molecule has lagged behind that of RC3 and GAP-43. We suggest that these molecules release CaM rapidly in response to large influxes of Ca2+ and slowly in response to small increases. This nonlinear response is analogous to the behavior of a capacitor, hence the name calpacitin. Since CaM regulates the ability of RC3 to amplify the effects of metabotropic glutamate receptor agonists, this activity must, necessarily, exhibit nonlinear kinetics as well. The capacitance of the system is regulated by phosphorylation by protein kinase C, which abrogates interactions between calmodulin and RC3 or GAP-43. We further propose that the ratio of phosphorylated to unphosphorylated RC3 determines the sliding LTP/LTD threshold in concept with Ca2+/ calmodulin-dependent kinase II. Finally, we suggest that the close association between RC3 and a subset of mitochondria serves to couple energy production with the synthetic events that accompany dendritic spine development and remodeling.

Protein synthesis-dependent potentiation by thyroxine of antiviral activity of interferon-gamma

We have studied the prenuclear signal transduction pathway by which thyroid hormone potentiates the antiviral activity of human interferon-gamma (IFN-gamma) in HeLa cells, which are deficient in thyroid hormone receptor (TR). The action of thyroid hormone was compared with that of milrinone, which has structural homologies with thyroid hormone. L-Thyroxine (T4), 3,5,3'-L-triiodothyronine (T3), and milrinone enhanced the antiviral activity of IFN-gamma up to 100-fold, a potentiation blocked by cycloheximide. The 5'-deiodinase inhibitor 6-n-propyl-2-thiouracil did not block the T4 effect. 3,3',5,5'-Tetraiodothyroacetic acid prevented the effect of T4 but not of milrinone. The effects of T4 and milrinone were blocked by inhibitors of protein kinases C (PKC) and A (PKA) and restored by PKC and PKA agonists; only the effect of T4 was blocked by genistein, a tyrosine kinase inhibitor. In separate models, milrinone was shown not to interact with nuclear TR-beta. T4 potentiation of the antiviral activity of IFN-gamma requires PKC, PKA, and tyrosine kinase activities but not traditional TR.