Electrical Stimulation to Enhance Wound Healing

Electrical stimulation (ES) can serve as a therapeutic modality accelerating the healing of wounds, particularly chronic wounds which have impaired healing due to complications from underlying pathology. This review explores how ES affects the cellular mechanisms of wound healing, and its effectiveness in treating acute and chronic wounds. Literature searches with no publication date restrictions were conducted using the Cochrane Library, Medline, Web of Science, Google Scholar and PubMed databases, and 30 full-text articles met the inclusion criteria. In vitro and in vivo experiments investigating the effect of ES on the general mechanisms of healing demonstrated increased epithelialization, fibroblast migration, and vascularity around wounds. Six in vitro studies demonstrated bactericidal effects upon exposure to alternating and pulsed current. Twelve randomized controlled trials (RCTs) investigated the effect of pulsed current on chronic wound healing. All reviewed RCTs demonstrated a larger reduction in wound size and increased healing rate when compared to control groups. In conclusion, ES therapy can contribute to improved chronic wound healing and potentially reduce the financial burden associated with wound management. However, the variations in the wound characteristics, patient demographics, and ES parameters used across studies present opportunities for systematic RCT studies in the future.

Endocannabinoids and endocannabinoid-like compounds modulate hypoxia-induced permeability in CaCo-2 cells via CB1, TRPV1, and PPARα

BACKGROUND AND PURPOSE

We have previously reported that endocannabinoids modulate permeability in Caco-2 cells under inflammatory conditions and hypothesised in the present study that endocannabinoids could also modulate permeability in ischemia/reperfusion.

EXPERIMENTAL APPROACH

Caco-2 cells were grown on cell culture inserts to confluence. Trans-epithelial electrical resistance (TEER) was used to measure permeability. To generate hypoxia (0% O2), a GasPak™ EZ anaerobe pouch system was used. Endocannabinoids were applied to the apical or basolateral membrane in the presence or absence of receptor antagonists.

KEY RESULTS

Complete hypoxia decreased TEER (increased permeability) by ~35% after 4 h (recoverable) and ~50% after 6 h (non-recoverable). When applied either pre- or post-hypoxia, apical application of N-arachidonoyl-dopamine (NADA, via TRPV1), oleamide (OA, via TRPV1) and oleoylethanolamine (OEA, via TRPV1) inhibited the increase in permeability. Apical administration of anandamide (AEA) and 2-arachidonoylglycerol (2-AG) worsened the permeability effect of hypoxia (both via CB1). Basolateral application of NADA (via TRPV1), OA (via CB1 and TRPV1), noladin ether (NE, via PPARα), and palmitoylethanolamine (PEA, via PPARα) restored permeability after 4 h hypoxia, whereas OEA increased permeability (via PPARα). After 6 h hypoxia, where permeability does not recover, only basolateral application PEA sustainably decreased permeability, and NE decreased permeability.

CONCLUSIONS AND IMPLICATIONS

A variety of endocannabinoids and endocannabinoid-like compounds modulate Caco-2 permeability in hypoxia/reoxygenation, which involves multiple targets, depending on whether the compounds are applied to the basolateral or apical membrane. CB1 antagonism and TRPV1 or PPARα agonism may represent novel therapeutic targets against several intestinal disorders associated with increased permeability.

The role of CB1 in intestinal permeability and inflammation

The endocannabinoid system has previously been shown to play a role in the permeability and inflammatory response of the human gut. The goal of our study was to determine the effects of endogenous anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) on the permeability and inflammatory response of intestinal epithelium under normal, inflammatory, and hypoxic conditions. Human intestinal mucosa was modeled using Caco-2 cells. Human tissue was collected from planned colorectal resections. Accumulation of AEA and 2-AG was achieved by inhibiting their metabolizing enzymes URB597 (a fatty acid amide hydrolase inhibitor) and JZL184 (a monoacylglycerol lipase inhibitor). Inflammation and ischemia were simulated with TNF-α and IFN-γ and oxygen deprivation. Permeability changes were measured by transepithelial electrical resistance. The role of the CB₁ receptor was explored using CB₁-knockdown (CB₁Kd) intestinal epithelial cells. Endocannabinoid levels were measured using liquid chromatography-mass spectrometry. Cytokine secretion was measured using multiplex and ELISA. URB597 and JZL184 caused a concentration-dependent increase in permeability via CB₁ (P < 0.0001) and decreased cytokine production. Basolateral application of JZL184 decreased permeability via CB₁ (P < 0.0001). URB597 and JZL184 increased the enhanced (worsened) permeability caused by inflammation and hypoxia (P < 0.0001 and P < 0.05). CB₁Kd cells showed reduced permeability response to inflammation (P < 0.01) but not hypoxia. 2-AG levels were increased in response to inflammation and hypoxia in Caco-2 cells. In human mucosal tissue, inflammation increased the secretion of granulocyte macrophage-colony stimulating factor, IL-12, -13, and -15, which was prevented with ex vivo treatment with URB597 and JZL184, and was inhibited by a CB₁ antagonist. The results of this study show that endogenous AEA and 2-AG production and CB₁ activation play a key modulatory roles in normal intestinal mucosa permeability and in inflammatory and hypoxic conditions.-Karwad, M. A., Couch, D. G., Theophilidou, E., Sarmad, S., Barrett, D. A., Larvin, M., Wright, K. L., Lund, J. N., O'Sullivan, S. E. The role of CB₁ in intestinal permeability and inflammation.

Cannabidiol Reduces Leukemic Cell Size - But Is It Important?

The anti-cancer effect of the plant-derived cannabinoid, cannabidiol, has been widely demonstrated both in vivo and in vitro. However, this body of preclinical work has not been translated into clinical use. Key issues around this failure can be related to narrow dose effects, the cell model used and incomplete efficacy. A model of acute lymphoblastic disease, the Jurkat T cell line, has been used extensively to study the cannabinoid system in the immune system and cannabinoid-induced apoptosis. Using these cells, this study sought to investigate the outcome of those remaining viable cells post-treatment with cannabidiol, both in terms of cell size and tracking any subsequent recovery. The phosphorylation status of the mammalian Target of Rapamycin (mTOR) signaling pathway and the downstream target ribosomal protein S6, were measured. The ability of cannabidiol to exert its effect on cell viability was also evaluated in physiological oxygen conditions. Cannabidiol reduced cell viability incompletely, and slowed the cell cycle with fewer cells in the G2/M phase of the cell cycle. Cannabidiol reduced phosphorylation of mTOR, PKB and S6 pathways related to survival and cell size. The remaining population of viable cells that were cultured in nutrient rich conditions post-treatment were able to proliferate, but did not recover to control cell numbers. However, the proportion of viable cells that were gated as small, increased in response to cannabidiol and normally sized cells decreased. This proportion of small cells persisted in the recovery period and did not return to basal levels. Finally, cells grown in 12% oxygen (physiological normoxia) were more resistant to cannabidiol. In conclusion, these results indicate that cannabidiol causes a reduction in cell size, which persists post-treatment. However, resistance to cannabidiol under physiological normoxia for these cells would imply that cannabidiol may not be useful in the clinic as an anti-leukemic agent.

Oleoylethanolamine and palmitoylethanolamine modulate intestinal permeability in vitro via TRPV1 and PPARα

Cannabinoids modulate intestinal permeability through cannabinoid receptor 1 (CB₁). The endocannabinoid-like compounds oleoylethanolamine (OEA) and palmitoylethanolamine (PEA) play an important role in digestive regulation, and we hypothesized they would also modulate intestinal permeability. Transepithelial electrical resistance (TEER) was measured in human Caco-2 cells to assess permeability after application of OEA and PEA and relevant antagonists. Cells treated with OEA and PEA were stained for cytoskeletal F-actin changes and lysed for immunoassay. OEA and PEA were measured by liquid chromatography-tandem mass spectrometry. OEA (applied apically, logEC₅₀ -5.4) and PEA (basolaterally, logEC₅₀ -4.9; apically logEC₅₀ -5.3) increased Caco-2 resistance by 20-30% via transient receptor potential vanilloid (TRPV)-1 and peroxisome proliferator-activated receptor (PPAR)-α. Preventing their degradation (by inhibiting fatty acid amide hydrolase) enhanced the effects of OEA and PEA. OEA and PEA induced cytoskeletal changes and activated focal adhesion kinase and ERKs 1/2, and decreased Src kinases and aquaporins 3 and 4. In Caco-2 cells treated with IFNγ and TNFα, OEA (via TRPV1) and PEA (via PPARα) prevented or reversed the cytokine-induced increased permeability compared to vehicle (0.1% ethanol). PEA (basolateral) also reversed increased permeability when added 48 or 72 h after cytokines (P < 0.001, via PPARα). Cellular and secreted levels of OEA and PEA (P < 0.001-0.001) were increased in response to inflammatory mediators. OEA and PEA have endogenous roles and potential therapeutic applications in conditions of intestinal hyperpermeability and inflammation.-Karwad, M. A., Macpherson, T., Wang, B., Theophilidou, E., Sarmad, S., Barrett, D. A., Larvin, M., Wright, K. L., Lund, J. N., O'Sullivan, S. E. Oleoylethanolamine and palmitoylethanolamine modulate intestinal permeability in vitro via TRPV1 and PPARα.

Raman spectroscopy: an evolving technique for live cell studies

One of the most exciting developments in Raman spectroscopy in the last decade has been its application to cells and tissues for diagnostic and pharmaceutical applications, and in particular its use in the analysis of cellular dynamics. Raman spectroscopy is rapidly advancing as a cell imaging method that overcomes many of the limitations of current techniques and is earning its place as a routine tool in cell biology. In this review we focus on important developments in Raman spectroscopy that have evolved into the exciting technique of live-cell Raman microscopy and highlight some of the most recent and significant applications to cell biology.

Cannabinoid-induced autophagy regulates suppressor of cytokine signaling-3 in intestinal epithelium

Autophagy is a catabolic process involved in homeostatic and regulated cellular protein recycling and degradation via the lysosomal degradation pathway. Emerging data associate impaired autophagy, increased activity in the endocannabinoid system, and upregulation of suppressor of cytokine signaling-3 (SOCS3) protein expression during intestinal inflammation. We have investigated whether these three processes are linked. By assessing the impact of the phytocannabinoid cannabidiol (CBD), the synthetic cannabinoid arachidonyl-2'-chloroethylamide (ACEA), and the endocannabinoid N-arachidonoylethanolamine (AEA) on autophagosome formation, we explored whether these actions were responsible for cyclic SOCS3 protein levels. Our findings show that all three cannabinoids induce autophagy in a dose-dependent manner in fully differentiated Caco-2 cells, a model of mature intestinal epithelium. ACEA and AEA induced canonical autophagy, which was cannabinoid type 1 receptor-mediated. In contrast, CBD was able to bypass the cannabinoid type 1 receptor and the canonical pathway to induce autophagy, albeit to a lesser extent. Functionally, all three cannabinoids reduced SOCS3 protein expression, which was reversed by blocking early and late autophagy. In conclusion, the regulatory protein SOCS3 is regulated by autophagy, and cannabinoids play a role in this process, which could be important when therapeutic applications for the cannabinoids in inflammatory conditions are considered.

Physiological intestinal oxygen modulates the Caco-2 cell model and increases sensitivity to the phytocannabinoid cannabidiol

The Caco-2 cell model is widely used as a model of colon cancer and small intestinal epithelium but, like most cell models, is cultured in atmospheric oxygen conditions (∼21%). This does not reflect the physiological oxygen range found in the colon. In this study, we investigated the effect of adapting the Caco-2 cell line to routine culturing in a physiological oxygen (5%) environment. Under these conditions, cells maintain a number of key characteristics of the Caco-2 model, such as increased formation of tight junctions and alkaline phosphatase expression over the differentiation period and maintenance of barrier function. However, these cells exhibit differential oxidative metabolism, proliferate less and become larger during differentiation. In addition, these cells were more sensitive to cannabidiol-induced antiproliferative actions through changes in cellular energetics: from a drop of oxygen consumption rate and loss of mitochondrial membrane integrity in cells treated under atmospheric conditions to an increase in reactive oxygen species in intact mitochondria in cells treated under low-oxygen conditions. Inclusion of an additional physiological parameter, sodium butyrate, into the medium revealed a cannabidiol-induced proliferative response at low doses. These effects could impact on its development as an anticancer therapeutic, but overall, the data supports the principle that culturing cells in microenvironments that more closely mimic the in vivo conditions is important for drug screening and mechanism of action studies.

Cannabinoids mediate opposing effects on inflammation-induced intestinal permeability

BACKGROUND AND PURPOSE

Activation of cannabinoid receptors decreases emesis, inflammation, gastric acid secretion and intestinal motility. The ability to modulate intestinal permeability in inflammation may be important in therapy aimed at maintaining epithelial barrier integrity. The aim of the present study was to determine whether cannabinoids modulate the increased permeability associated with inflammation in vitro.

EXPERIMENTAL APPROACH

Confluent Caco-2 cell monolayers were treated for 24 h with IFNγ and TNFα (10 ng·mL(-1) ). Monolayer permeability was measured using transepithelial electrical resistance and flux measurements. Cannabinoids were applied either apically or basolaterally after inflammation was established. Potential mechanisms of action were investigated using antagonists for CB(1) , CB(2) , TRPV1, PPARγ and PPARα. A role for the endocannabinoid system was established using inhibitors of the synthesis and degradation of endocannabinoids.

KEY RESULTS

Δ(9) -Tetrahydrocannabinol (THC) and cannabidiol accelerated the recovery from cytokine-induced increased permeability; an effect sensitive to CB(1) receptor antagonism. Anandamide and 2-arachidonylglycerol further increased permeability in the presence of cytokines; this effect was also sensitive to CB(1) antagonism. No role for the CB(2) receptor was identified in these studies. Co-application of THC, cannabidiol or a CB(1) antagonist with the cytokines ameliorated their effect on permeability. Inhibiting the breakdown of endocannabinoids worsened, whereas inhibiting the synthesis of endocannabinoids attenuated, the increased permeability associated with inflammation.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that locally produced endocannabinoids, acting via CB(1) receptors play a role in mediating changes in permeability with inflammation, and that phytocannabinoids have therapeutic potential for reversing the disordered intestinal permeability associated with inflammation.

LINKED ARTICLES

This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of Cannabinoids in Biology and Medicine visit http://dx.doi.org/10.1111/bph.2011.163.issue-7.

Pharmacological effects of cannabinoids on the Caco-2 cell culture model of intestinal permeability

Activation of cannabinoid receptors decreases emesis, inflammation, gastric acid secretion, and intestinal motility. However, the effects of cannabinoids on intestinal permeability have not yet been established. The aim of the present study is to examine the effects of cannabinoids on intestinal permeability in an in vitro model. Caco-2 cells were grown until fully confluent on inserts in 12-well plates. Transepithelial electrical resistance (TEER) measurements were made as a measure of permeability. EDTA (50 μM) was applied to reversibly increase permeability (reduce TEER). The effects of cannabinoids on permeability in combination with EDTA, or alone, were assessed. Potential target sites of action were investigated using antagonists of the cannabinoid (CB)(1) receptor, CB(2) receptor, transient receptor potential vanilloid subtype 1 (TRPV1), peroxisome proliferator-activated receptor (PPAR)γ, PPARα, and a proposed cannabinoid receptor. When applied to the apical or basolateral membrane of Caco-2 cells, Δ(9)-tetrahydrocannabinol (THC) and cannabidiol (CBD) enhanced the speed of recovery of EDTA-induced increased permeability. This effect was sensitive to cannabinoid CB(1) receptor antagonism only. Apical application of endocannabinoids caused increased permeability, sensitive to cannabinoid CB(1) receptor antagonism. By contrast, when endocannabinoids were applied basolaterally, they enhanced the recovery of EDTA-induced increased permeability, and this involved additional activation of TRPV1. All cannabinoids tested increased the mRNA of the tight junction protein zona occludens-1, but only endocannabinoids also decreased the mRNA of claudin-1. These findings suggest that endocannabinoids may play a role in modulating intestinal permeability and that plant-derived cannabinoids, such as THC and CBD, may have therapeutic potential in conditions associated with abnormally permeable intestinal epithelium.

Cannabinoid CB2 receptors in the gastrointestinal tract: a regulatory system in states of inflammation

The emerging potential for the cannabinoid (CB) system in modulating gastrointestinal inflammation has gained momentum over the last few years. Traditional and anecdotal use of marijuana for gastrointestinal disorders, such as diarrhoea and abdominal cramps is recognized, but the therapeutic benefit of cannabinoids in the 21st century is overshadowed by the psychoactive problems associated with CB1 receptor activation. However, the presence and function of the CB2 receptor in the GI tract, whilst not yet well characterized, holds great promise due to its immunomodulatory roles in inflammatory systems and its lack of psychotropic effects. This review of our current knowledge of CB2 receptors in the gastrointestinal tract highlights its role in regulating abnormal motility, modulating intestinal inflammation and limiting visceral sensitivity and pain. CB2 receptors represent a braking system and a pathophysiological mechanism for the resolution of inflammation and many of its symptoms. CB2 receptor activation therefore represents a very promising therapeutic target in gastrointestinal inflammatory states where there is immune activation and motility dysfunction.

Temporal variation in CB2R levels following T lymphocyte activation: Evidence that cannabinoids modulate CXCL12-induced chemotaxis

Cannabinoids have long been proposed to affect the immune system, especially as one of the cannabinoid receptors, the cannabinoid receptor-2 (CB(2)R) has been found almost exclusively on immune cells. Here, using human in vitro activated peripheral blood-derived T lymphocytes we investigated the long-term changes in cannabinoid receptor protein expression following cellular activation and the effects of cannabinoids on migration. We report that resting T lymphocytes do not detectably express either the cannabinoid receptor-1 (CB(1)R) or CB(2)R at the protein level. However, CB(2)R protein expression is upregulated in a biphasic manner in T lymphocytes following activation by superantigen. The cannabinoids 2-AG and JWH-133 were found to elicit activation of downstream biochemical effectors (as assessed by the phosphorylation of the ERK1/2 MAP kinases). Neither 2-AG nor JWH-133 induced chemotaxis in day 5 activated T lymphocytes, when receptor expression was at its highest. Interestingly, both 2-AG and JWH-133 inhibited CXCL12-induced chemotaxis, suggesting a modulatory role for cannabinoids in activated T lymphocytes.

The chemokines CXCL9, CXCL10, and CXCL11 differentially stimulate G alpha i-independent signaling and actin responses in human intestinal myofibroblasts

Intestinal myofibroblasts have been implicated in the pathogenesis of chronic inflammatory conditions such as Crohn's disease via interactions with an elaborate network of cytokines, growth factors, and other inflammatory mediators. CXCR3 is a Galpha(i) protein-coupled receptor that binds the proinflammatory chemokines CXCL9, CXCL10, and CXCL11, which are released from the intestinal epithelium. The three CXCR3 ligands shared the ability to activate biochemical (e.g., PI3K and MAPK activation) and functional events (actin reorganization) in intestinal myofibroblasts. However, CXCL11 is unique in its ability to elevate intracellular calcium. Surprisingly, although CXCR3 mRNA is detectable in these myofibroblasts, there is no detectable surface expression of CXCR3. Furthermore, the biochemical responses and actin reorganization stimulated by the CXCR3 ligands in intestinal myofibroblasts are insensitive to the Galpha(i) inhibitor, pertussis toxin. This suggests either the existence of differential receptor coupling mechanisms in myofibroblasts for CXCR3 that are distinct from those observed in PBLs and/or that these cells express a modified or variant CXCR3 compared with the CXCR3 expressed on PBLs.

Differential modulation of COX-2 expression in A549 airway epithelial cells by structurally distinct PPARγ agonists: evidence for disparate functional effects which are independent of NF-κB and PPARγ

Ligands of peroxisome proliferator-activated receptor-gamma (PPAR(gamma)) are thought to possess anti-inflammatory properties mediated via both PPAR(gamma) dependent and independent mechanisms. This work investigates the effects of PPAR(gamma) ligands on the regulation of cyclooxygenase-2 (COX-2) in the human lung epithelial cell line, A549. The synthetic ligand troglitazone activated the phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase pathway (MAPK), whereas the endogenous ligand, 15-deoxy-Delta(12,14)-prostaglandin J2 (15d-PGJ2), only activated the PI3K pathway. 15d-PGJ2 had no detectable effects on COX-2, mPGES expression, or PGE2 production. However, troglitazone induced time-dependent COX-2 expression, which was insensitive to PPAR(gamma) antagonists, but was abrogated by inhibitors of PI3K and the ERK MAP kinase pathway. Furthermore, troglitazone induced mPGES expression and PGE2 production. Neither troglitazone nor 15d-PGJ2 was able to convincingly activate NF-kappaB in A549 cells. Further heterogeneity in the responses to troglitazone and 15d-PGJ2 was observed in the regulation of gene expression as assessed by microarray analysis. In summary, this study provides compelling evidence that troglitazone (like 15d-PGJ2) can exert functional effects independently of actions via PPAR(gamma). Moreover, we have identified unique biochemical and functional actions of troglitazone that are not shared by 15d-PGJ2, which may influence the therapeutic potential of this compound in inflammatory settings.

Differential regulation of prostaglandin E biosynthesis by interferon-gamma in colonic epithelial cells

1. Cyclooxygenase (COX)-2 expression and activity in response to pro-inflammatory cytokines TNF alpha and IFN gamma was evaluated in the colonic epithelial cell line HT29 and the airway epithelial cell line A549. 2. TNF alpha induced concentration- and time-dependent upregulation of COX-2 mRNA, protein and prostaglandin (PG)E(2) synthesis. 3. Co-stimulation of TNF alpha with IFN gamma resulted in reduced COX-2 mRNA and protein expression. 4. IFN gamma had no effect on the stability of TNF alpha-induced COX-2 mRNA. 5. TNF alpha-induced PGE(2) biosynthesis was significantly enhanced by the simultaneous addition of IFN gamma and was COX-2 dependent. 6. The combination of IFN gamma and TNF alpha induced the microsomal prostaglandin E synthase (mPGES), comensurate with the enhanced PGE(2) synthesis. 7. These results suggest that, in terms of PGE(2) biosynthesis, IFN gamma plays a negative regulatory role at the level of COX-2 expression and a positive regulatory role at the level of mPGES expression. This may have important implications for the clinical use of IFN gamma in inflammatory diseases.

Optimal chemotactic responses of leukemic T cells to stromal cell-derived factor-1 requires the activation of both class IA and IB phosphoinositide 3-kinases

Stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 are a multifunctional chemokine/receptor system with essential roles in the development of the immune system and other aspects of embryogenesis, including vascularization and organ development. SDF-1 is also a potent chemoattractant for T cells and has roles in both inflammation and immune homeostasis. Our group has previously demonstrated that phosphoinositide 3-kinase (PI 3-kinase) is activated in SDF-1-stimulated T cells and is indeed required for SDF-1-mediated chemotaxis. In this study Jurkat clones were established, stably expressing dominant negative constructs of class IA and class IB PI 3-kinases under the control of the tetracycline off inducible gene system, to determine the relative roles of these PI 3-kinases in SDF-1 signaling. Our results show that expression of either kinase-dead PI3Kgamma (KD-PI3Kgamma) or Deltap85 (a construct unable to bind class I(A) p110alpha, -beta, or -delta) leads to a partial inhibition of SDF-1-stimulated protein kinase B phosphorylation, but had no effect on SDF-1-induced phosphorylation of the mitogen-activated protein kinase ERK1/2. Functional studies demonstrated that expression of KD-PI3Kgamma markedly inhibited SDF-1-mediated chemotaxis, typically eliciting 40-60% inhibition. Interestingly, the expression of Deltap85 also leads to inhibition of the SDF-1-mediated chemotactic response, albeit to a much lesser extent than achieved with the KD-PI3Kgamma mutant, typically in the range of 20-40% inhibition. Furthermore, the inhibition of chemotaxis by the expression of dominant negative class IA or class IB PI 3-kinases could be enhanced by the presence of the PI 3-kinase inhibitor LY294002. Together, these results demonstrate that optimal chemotactic response of leukemic T cells to SDF-1 requires the activation of both class IA and class IB PI 3-kinases.

Evidence that SHIP-1 contributes to phosphatidylinositol 3,4,5-trisphosphate metabolism in T lymphocytes and can regulate novel phosphoinositide 3-kinase effectors

The leukemic T cell line Jurkat is deficient in protein expression of the lipid phosphatases Src homology 2 domain containing inositol polyphosphate phosphatase (SHIP) and phosphatase and tensin homolog deleted on chromosome ten (PTEN). We examined whether the lack of expression of SHIP-1 and PTEN is shared by other leukemic T cell lines and PBLs. Analysis of a range of cell lines and PBLs revealed that unlike Jurkat cells, two other well-characterized T cell lines, namely CEM and MOLT-4 cells, expressed the 5'-phosphatase SHIP at the protein level. However, the 3-phosphatase PTEN was not expressed by CEM or MOLT-4 cells or Jurkat cells. The HUT78 cell line and PBLs expressed both SHIP and PTEN. Jurkat cells exhibited high basal levels of phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P(3); the lipid substrate for both SHIP and PTEN) as well as saturated protein kinase B (PKB) phosphorylation. Lower levels of PI(3,4,5)P(3) and higher levels of phosphatidylinositol 3,4-bisphosphate (PI(3,4)P(2)) as well as unsaturated constitutive phosphorylation of PKB were observed in CEM and MOLT-4 cells compared with Jurkat cells. In PBLs and HUT78 cells which express both PTEN and SHIP-1, there was no constitutive PI(3,4,5)P(3) or PKB phosphorylation, and receptor stimuli were able to elicit robust phosphorylation of PKB. Expression of a constitutively active SHIP-1 protein in Jurkat cells was sufficient to reduce both constitutive PKB membrane localization and PKB phosphorylation. Together, these data indicate important differences between T leukemic cells as well as PBLs, regarding expression of key lipid phosphatases. This study provides the first evidence that SHIP-1 can influence the constitutive levels of PI(3,4,5)P(3) and the activity of downstream phosphoinositide 3-kinase effectors in T lymphocytes.

Regulation of the human transforming growth factor beta type II receptor gene promoter by novel Sp1 sites

The transforming growth factor-beta (TGF beta) type II receptor (T beta R-II) is responsible for transducing the growth inhibitory signals of TGF beta. The T beta R-II gene promoter lacks both a TATA box and a CAAT box near the transcription initiation site, and has been shown to contain binding sequences for several transcription factors (Sp1, AP1, NF-Y, Cut and ERT) which are important for T beta R-II gene promoter activity in vitro. However, it is still not clear which interactions are important for the regulation of T beta R-II gene promoter activity in vivo. Using in vivo genomic DNA footprinting of normal human epithelial cells (HaCaT), we have identified two novel identical and strongly protected sites (ggggctgg) at positions -59 and -102 of the T beta R-II gene promoter. Mutation of either site significantly reduced promoter activity in transient transfections. Protein binding to these sites, as determined by electrophoretic mobility shift assays (EMSA), was specifically competed with consensus Sp1 oligonucleotides. Furthermore, anti-Sp1/3 antibodies produced band shifts when incubated with the T beta R-II -59 and -102 DNA probes. Importantly, Sp1 protein binding was influenced by the presence of an intact NF-Y binding site at position -83. Our data suggests that both Sp1 and NF-Y may play an important role in regulating T beta R-II gene promoter basal activity in vivo.

Studies in Neotropical Paleobotany. XV. A Mio-Pliocene palynoflora from the Eastern Cordillera, Bolivia: implications for the uplift history of the Central Andes

An assemblage of 33 fossil pollen and spores, recovered from the 3600-m high Pislepampa locality of E. W. Berry, Eastern Cordillera, Bolivia, adds considerably to our knowledge of three aspects of the region in late Neogene time: (1) the paleovegetation, (2) the paleoclimate, and (3) the paleoelevation of the Central Andes. The plant microfossils recognized are Isoetes, Lycopodium (three types), Cnemidaria, Cyathea (three types), Grammitis, Hymenophyllum, Pteris, trilete fern spores (two types), Danaea, monolete fern spores (four types), Podocarpus, Gramineae, Palmae, Ilex, cf. Oreopanax, Cavanillesia, cf. Pereskia, Compositae (three types), Ericaceae, Tetrorchidium, and unknowns (three types). The diversity of the Compositae suggest that this flora has a maximum age around the Miocene-Pliocene boundary, that is, 6-7 million years. All members of the paleocommunity presently grow in the bosque montano húmedo (cloud forest) along the eastern slope of the Central Andes of Bolivia, which occurs between MATs (mean annual temperatures) of ∼10° and 20°C. The Pislepampa flora probably represents the lower limits of this forest because the fossil leaves collected by Berry from the same locality all have entire margins, suggesting that the flora grew near the cloud forest-tropical forest transition. Presently, the lower limit of the cloud forest forest has MATs of ∼20°C, a mean annual precipitation between 1000 and 1500 mm, and that part containing most of the identified genera of fossil pollen is found at elevations ∼1200-1400 m. These conditions are thus inferred for the Pislepampa flora; however, because of the uncertainty of the magnitude of global climate change and of possible changes in the ecological range of plant genera, we estimate an error of at least ±1000 m for the paleoelevation estimate. When the total uplift is corrected for probable amounts of erosionally driven isostatic rebound, the paleoelevation estimate suggests that from one-third to one-half of the uplift of the Eastern Cordillera had occurred by the beginning of the Pliocene. This estimate is consistent with other paleoelevation estimates from the Central Andes.

Varying functions of specific major histocompatibility class II transactivator promoter III and IV elements in melanoma cell lines

Melanoma cells commonly express MHC class II molecules constitutively. This is a rare, or possibly unique, phenotype for a nonprofessional antigen-presenting cell, where MHC class II expression ordinarily occurs only after IFN-gamma treatment. Despite the fact that constitutive expression of MHC class II on melanoma cells has been observed for decades and that the regulation of the MHC class II genes is well understood for many different cell types, there is no data regarding the basis for constitutive MHC class II expression in melanoma cells. Here we report that MHC class II expression in melanoma cells can be traced to constitutive expression of the class II transactivator protein (CIITA), which mediates both IFN-gamma-inducible and -constitutive MHC class II expression in all other cell types. In addition, we determined that constitutive CIITA expression is the result of the activation of both the B cell-specific CIITA promoter III and the IFN-gamma-inducible CIITA promoter IV, the latter of which previously has never been known to function as a constitutive promoter in any cell type. The recently described B cell-related ARE-1 activity is important for promoter III activation in the melanoma cells. Constitutive promoter IV activation involves the IFN regulatory factor element (IRF-E), which binds members of the IRF family of proteins, although the major, IFN-gamma inducible member of this family, IRF-1, is not constitutively expressed in these cells. In cells with constitutively active promoter IV, the promoter IV IRF-E is most likely activated by IRF-2. The relevance of these results to the pathway of melanoma development is discussed.

Positive regulatory domain I binding factor 1 silences class II transactivator expression in multiple myeloma cells

The major histocompatibility complex (MHC) class II transactivator (CIITA) acts as a master switch to activate expression of the genes required for MHC-II antigen presentation. During B-cell to plasma cell differentiation, MHC-II expression is actively silenced, but the mechanism has been unknown. In plasma cell tumors such as multiple myeloma the repression of MHC-II is associated with the loss of CIITA. We have identified that positive regulatory domain I binding factor 1 (PRDI-BF1), a transcriptional repressor, inhibits CIITA expression in multiple myeloma cell lines. Repression of CIITA depends on the DNA binding activity of PRDI-BF1 and its specific binding site in the CIITA promoter. Deletion of a histone deacetylase recruitment domain in PRDI-BF1 does not inhibit repression of CIITA nor does blocking histone deacetylase activity. This is in contrast to PRDI-BF1 repression of the c-myc promoter. Repression of CIITA requires either the N-terminal acidic and conserved PR motif or the proline-rich domain. PRDI-BF1 has been shown to be a key regulator of B-cell and macrophage differentiation. These findings now indicate that PRDI-BF1 has at least two mechanisms of repression whose function is dependent on the nature of the target promoter. Importantly, PRDI-BF1 is defined as the key molecule in silencing CIITA and thus MHC-II in multiple myeloma cells.

Regulatory role of phosphatidylinositol 3-kinase on TNF-alpha-induced cyclooxygenase 2 expression in colonic epithelial cells

BACKGROUND AND AIMS

Cyclooxygenase (COX)-2 is up-regulated in most colonic cancers and in inflammatory bowel disease in which tumor necrosis factor (TNF)-alpha is believed to play a central role. There has been recent speculation on the activation of phosphatidylinositol 3-kinase (PI 3-kinase) by TNF-alpha and its role in the regulation of genes controlled by NF-kappaB. We investigated the regulatory role of PI 3-kinase on COX-2 expression in colonic epithelial cells.

METHODS

In HT-29 and Caco-2 colonic epithelial cells, COX-2 expression was induced by either TNF-alpha or interleukin (IL)-1alpha as observed by Northern and Western analyses. COX-2 activity was assessed by measuring prostaglandin E(2) (PGE2) production by enzyme-linked immunosorbent assay. NF-kappaB binding activity was assessed by electrophoretic mobility shift assay. PI 3-kinase activity was measured by quantifying the accumulation of PI 3-kinase-dependent D-3 lipid products by high-performance liquid chromatography.

RESULTS

The PI 3-kinase inhibitor wortmannin up-regulated induced COX-2 expression in a concentration-dependent manner in both HT-29 and Caco-2 cells. An alternative PI 3-kinase inhibitor, LY294002, caused up-regulation of induced COX-2 messenger RNA (mRNA) in HT-29 cells at concentrations of < or =1 micromol/L. IL-4 and IL-13, which are known to activate PI 3-kinase, down-regulated HT-29 COX-2 mRNA, protein, and PGE2 production. NF-kappaB binding activity was unaltered by PI 3-kinase inhibition in HT-29 cells, in which TNF-alpha was shown to activate PI 3-kinase directly.

CONCLUSIONS

COX-2 is negatively regulated by PI 3-kinase; we propose that the inhibitory effect of IL-4 and IL-13 is mediated via a PI 3-kinase-dependent pathway. This mechanism does not appear to involve NF-kappaB because PI 3-kinase inhibition did not alter NF-kappaB binding activity. TNF-alpha can activate PI 3-kinase directly in addition to inducing COX-2.

Loss of interferon-gamma inducibility of TAP1 and LMP2 in a renal cell carcinoma cell line

The inadequate ability of cancer cells to present antigen on the cell surface via MHC class I molecules is one mechanism by which tumor cells evade antitumor-associated antigen immunity. In many cases, such as in renal cell carcinoma (RCC), the lack of MHC class I antigen presentation can be attributed to the down-regulation of genes needed for antigen processing, such as the transporters associated with antigen processing (TAP)1 and TAP2, and the proteasomal components low molecular weight proteins (LMP)2 and LMP7. The TAP1 and LMP2 genes are transcribed from a shared bidirectional promoter containing an IFN response factor element that confers IFN-gamma inducibility. Here, we investigate the differential responsiveness to IFN-gamma of RCC cell lines, Caki-1 and Caki-2, which have been reported to have abnormally low expressions of TAP1 and LMP2. We now demonstrate that the Caki-2 cell line is defective in the IFN-gamma signaling pathway. The effects of IFN-gamma on TAP1 and LMP2 expression revealed a loss of up-regulation in Caki-2 cells, but not in Caki-1 cells. In vivo DNA footprinting shows a specific loss of occupancy at the IFN response factor element site in Caki-2 cells, whereas Caki-1 cells show full promoter occupancy. Furthermore, in vitro DNA-binding studies indicated that Caki-2 cells do not have IFN-regulatory factor 1- or signal transducer and activator of transcription 1 (Stat1)-binding activity after IFN-gamma stimulation. Examination of Stat1, Jak1, and Jak2 proteins demonstrated that the proteins were expressed, however, not phosphorylated, upon IFN-gamma treatment in Caki-2 cells. Also, this cell line expressed both IFN-gamma receptor chains. IFN-gamma inducibility could not be rescued by introduction of normal Jak1 and/or Jak2 proteins. However, overexpression of Jak1 did increase TAP1 and LMP2 expression independent of IFN-gamma, indicating that the Stat1 and IFN-regulatory factor 1 proteins present in Caki-2 can be activated. These findings suggest that the loss of TAP1 and LMP2 induction is a defect in the earliest steps of the IFN-gamma signaling pathway resulting in the inability of Caki-2 cells to up-regulate the MHC class I antigen-processing pathway. Because immunotherapy may be one of the most promising approaches for treating RCC, understanding the mechanisms by which these tumors circumvent cytokine signaling, thereby evading antitumor-specific-antigen immunity, would greatly aid the efficacy of such therapy.

Interactions between phosphatidylinositol 3-kinase and nitric oxide: explaining the paradox

Nitric oxide (NO) and the many derivatives and reactive oxygen intermediates thereof are all molecules that are utilised by mammalian cells in the war against microbial pathogens and tumours. They are potentially toxic molecules and, with damage control being crucial, the production and metabolism of nitric oxide is a tightly regulated process. The duality of NO is well documented. On the one hand, beneficial effects include normal healing in the skin and intestinal mucosa, killing of certain bacteria, regulating T cell proliferation and differentiation (Th1 vs Th2), and regulating leukocyte recruitment, by affecting adhesion molecule expression. On the other hand, persistent high levels of NO can lead to the production of toxic metabolites (peroxynitrite and hydroxyls), which can have detrimental effects, such as increased microvascular and epithelial permeability, increased oxidative stress (which can damage DNA), and damage to iron-sulphur proteins in mitochondria. NO has been reported to modulate its own production and the mechanisms involved in this self-regulation are being hotly pursued. The purpose of this review is to update recent intriguing advances in our understanding of the interaction of the phosphatidylinositol (PI) 3-kinase-dependent signal transduction pathway in regulating the activity of the enzymes that generate NO, namely, the nitric oxide synthases.

How Stat1 mediates constitutive gene expression: a complex of unphosphorylated Stat1 and IRF1 supports transcription of the LMP2 gene

Analysis of mRNA levels in cells that express or lack signal transducers and activators of transcription 1 (Stat1) reveals that Stat1 mediates the constitutive transcription of many genes. Expression of the low molecular mass polypeptide 2 (LMP2), which requires Stat1, has been studied in detail. The overlapping interferon consensus sequence 2/gamma-interferon-activated sequence (ICS-2/GAS) elements in the LMP2 promoter bind to interferon regulatory factor 1 (IRF1) and Stat1 and are occupied constitutively in vivo. The point mutant of Stat1, Y701F, which does not form dimers involving SH2-phosphotyrosine interactions, binds to the GAS element and supports LMP2 expression. Unphosphorylated Stat1 binds to IRF1 directly and we conclude that this complex uses the ICS-2/GAS element to mediate constitutive LMP2 transcription in vivo. The promoter of the IRF1 gene, which also contains a GAS site but not an adjacent ICS-2 site, is not activated by Stat1 Y701F. The promoters of other genes whose constitutive expression requires Stat1 may also utilize complexes of unphosphorylated Stat1 with IRF1 or other transcription factors.

Interleukin-13 inhibits nitric oxide production in human colonic mucosa

BACKGROUND/AIMS

Nitric oxide synthesis is increased in rectal biopsies from patients with ulcerative colitis and colonic epithelial cells are considered to be a major source of nitric oxide in intestinal inflammation.

METHODOLOGY

Human colonic biopsies from normal bowel mucosa and colonic epithelial cell line HT-29 were cultured in the presence of the inflammatory cytokines IL-1 alpha + TNF-alpha + IFN-alpha added after 1 hour pretreatment with vehicle or Interleukin-13. Nitrite levels were determined at 30 hours in culture supernatants by a fluorometric assay.

RESULTS

Unstimulated human colonic biopsies and HT-29 cells produced a basal amount of nitrite. Stimulation with IL-1 alpha + TNF-alpha + IFN-alpha induced a significant (P < 0.001) increase of nitrite generation by both human colonic biopsies and HT-29 cells. The presence of Interleukin-13 produced a significant (P < 0.001) suppression of the cytokine-induced nitrite generation from both colonic biopsies and HT-29 cells.

CONCLUSIONS

Nitric oxide generation in human colonic mucosa is susceptible to manipulation by proinflammatory cytokines. Interleukin-13 has an inhibitory effect on cytokine induced nitrite production in colonic mucosa and could play an anti-inflammatory role in intestinal inflammation.

Pulmonary arteriovenous malformations after cavopulmonary connection

We report the case of a child with hypoplastic left heart syndrome who developed pulmonary arteriovenous (AV) malformations after superior cavopulmonary anastomoses. Resolution of the pulmonary AV malformations occurred following a completion Fontan procedure. This phenomenon has been reported previously, but only in patients with heterotaxy and polysplenia.

Analysis of the defect in IFN-gamma induction of MHC class II genes in G1B cells: identification of a novel and functionally critical leucine-rich motif (62-LYLYLQL-68) in the regulatory factor X 5 transcription factor

MHC class II deficiency found in bare lymphocyte syndrome patients results from the absence or dysfunction of MHC class II transcriptional regulators, such as regulatory factor X (RFX) and class II transactivator (CIITA). Understanding the roles of these factors has been greatly facilitated by the study of genetic defects in cell lines of bare lymphocyte syndrome patients, as well as in cell lines that have been generated by chemical mutagenesis in vitro. The latter group includes MHC class II-deficient lines that are no longer responsive to induction by IFN-gamma. Here, we show that the defect in G1B, one such cell line, is attributed to the lack of functional RFX5, the largest subunit of RFX. The RFX5 gene isolated from G1B cells contains two separate single-base pair mutations. One alteration does not exhibit a phenotype, whereas a leucine-to-histidine mutation eliminates DNA-binding and transactivating functions. This mutation lies outside of previously defined functional domains of RFX5 but within an unusual, leucine-rich region (62-LYLYLQL-68). To further investigate the significance of the leucine-rich region, we targeted all neighboring leucine residues for mutagenesis. These mutants were also unable to transactivate a MHC class II reporter gene, confirming that these leucine residues play an essential role in RFX activity and characterize a novel leucine-rich motif.

Human cut-like repressor protein binds TGFbeta type II receptor gene promoter

Resistance to the growth inhibitory effects of transforming growth factor beta (TGFbeta) has been associated with decreased levels of the TGFbeta type II receptor (TbetaR-II) and has been correlated with tumorigenicity. Previously, we reported an A --> G mutation at position -364 in the TbetaR-II promoter in A431 tumor cells which results in reduced TbetaR-II promoter activity. In this study, we show that the CDP/Cut (CCAAT displacement protein) transcription factor, a transcriptional repressor, binds both the wild type and the mutant TbetaR-II promoter. We also demonstrate that the A --> G mutation increases CDP/Cut binding affinity, and that overexpression of CDP/Cut reduces transcription from TbetaR-II promoter reporter constructs. Increased binding of the CDP/Cut repressor protein, as a result of a mutation at position -364, represents a novel mechanism of regulation in a neoplastic cell of the promoter of a tumor suppressor gene, TbetaR-II.

A novel element and a TEF-2-like element activate the major histocompatibility complex class II transactivator in B-lymphocytes

Major histocompatibility complex (MHC) class II molecules play a central role in immune responses, and transcription of this family of genes requires the MHC class II transactivator (CIITA). CIITA has four promoters, which are transcribed in a tissue-specific manner. CIITA promoter III is constitutively active in mature B-lymphocytes. This report now describes the minimal 319-base pair promoter region necessary for maximal transcriptional activity in B-lymphocytes. Ultraviolet light and dimethylsulfate in vivo genomic footprinting analyses reveal five occupied DNA sequence elements present in intact B-lymphocytes. Functional analysis of these elements using promoter deletions and site-specific mutations demonstrates that at least two of the sites occupied in vivo are critical for transcriptional activity. In vitro protein/DNA analysis suggests that one of the sites is a TEF-2-like element and the other is occupied by a novel transcription activator. In addition, nuclear factor-1 associates with the promoter both in vivo and in vitro. In myeloma cell lines, loss of CIITA transcription correlates with a completely unoccupied CIITA promoter III. These findings suggest that CIITA transcription in B-lymphocytes is activated through at least two strong promoter elements, while loss of expression in myeloma cells is mediated through changes in promoter assembly.

Co-occupancy of the interferon regulatory element of the class II transactivator (CIITA) type IV promoter by interferon regulatory factors 1 and 2

Class II transactivator (CIITA) activates the expression of major histocompatibility class II genes, which encode antigen-presenting molecules recognized by the T-cell receptor of CD4+ T cells. IFN-gamma induced CIITA transcription in many cell types is directed by the CIITA Type IV promoter. Here we report that the human CIITA Type IV promoter IRF-E binds IRF-1 and can be activated by exogenous expression of IRF-1. Surprisingly, the CIITA Type IV promoter IRF-E is also activated by IRF-2, another member of the IRF family that generally acts as a transcriptional repressor. In addition, we found that IRF-1 and IRF-2 synergistically activate the CIITA Type IV promoter. Electrophoretic mobility shift assays revealed that IRF-1 and IRF-2 can simultaneously occupy the IRF-E of the CIITA Type IV promoter, suggesting a novel mechanism for the role of these two proteins in promoter activation. Our results also indicate that IRF-1 and IRF-2 can cooperatively activate and co-occupy the IRF-E of the guanylate binding protein (GBP) promoter. Finally, CIITA induction by IFN-gamma does not occur in a pancreatic tumor cell line that expresses a mutated IRF-2, representing the first IRF-2 mutation identified in a human tumor cell line.

Mice transgenic for a human amyloid precursor protein promoter-lacZ reporter construct

Transgenic mouse lines were generated that expressed a 2-kb amyloid precursor protein (APP) promoter/beta-galactosidase reporter gene construction. In brain, hippocampal pyramidal neurons, neurons in the deeper layers of cerebral cortex, and neurons in several thalamic nuclei were heavily labeled by beta-galactosidase histochemistry. In general, molecular layers and white matter regions did not express the reporter gene. When compared with in situ hybridization for endogenous murine APP RNA, the striatum and outer layers of cerebral cortex had little reporter expression. Thus, the match between reporter expression and endogenous APP expression in brain was not perfect. A similar mismatch between the relative expression of the reporter gene and endogenous APP RNA distribution was found in homogenates from several organs. Although prior work in transgenic mice found similar mismatches in reporter gene distribution, none had tested the APP promoter construct in response to neuronal injury. Kainic acid injections successfully increased murine APP expression in the transgenic mice, but had no effect on the reporter gene expression. Based on these data and those collected by others, we conclude that the 2-kb region upstream of the APP transcription initiation site contains some elements responsible for the tissue-specific expression of this gene, but does not contain all the cis-acting elements sufficient for either the differential tissue distribution of this gene or the regulation of this gene subsequent to neural damage.

C-X-C and C-C chemokine expression and secretion by the human colonic epithelial cell line, HT-29: differential effect of T lymphocyte-derived cytokines

Differential chemokine production by colonic epithelial cells is thought to contribute to the characteristic increased infiltration of selected population of leukocytes cells in inflammatory bowel disease. We have previously demonstrated that IL-13 enhances IL-1alpha-induced IL-8 secretion by the colonic epithelial cell line HT-29. We have now explored the C-C chemokine expression and modulation in this system. The combination of TNF-alpha and IFN-gamma was the minimal stimulation required for regulated on activation, normal T cell expressed and secreted (RANTES) and monocyte chemoattractant protein (MCP-1) mRNA expression and secretion by HT-29 cells. The same stimulation induced a stronger IL-8 mRNA expression and secretion. Pretreatment with IL-13 or IL-4, reduced significantly the RANTES, and MCP-1, but not IL-8 mRNA expression and secretion. In contrast, IL-10 had no effect on either MCP-1, or RANTES, or IL-8 generation. Pretreatment of HT-29 cells with wortmannin suggested that the IL-13-induced inhibition of C-C chemokine expression is via activation of a wortmannin-sensitive phosphatidylinositol 3-kinase. These data demonstrate that colonic epithelial cell chemokine production can be differentially regulated by T cell-derived cytokines and suggest an interplay between epithelial cells and T lymphocytes potentially important in the intestinal inflammation.

A mutation in human CMP-sialic acid hydroxylase occurred after the Homo-Pan divergence

Sialic acids are important cell-surface molecules of animals in the deuterostome lineage. Although humans do not express easily detectable amounts of N-glycolylneuraminic acid (Neu5Gc, a hydroxylated form of the common sialic acid N-acetylneuraminic acid, Neu5Ac), it is a major component in great ape tissues, except in the brain. This difference correlates with lack of the hydroxylase activity that converts CMP-Neu5Ac to CMP-Neu5Gc. Here we report cloning of human and chimpanzee hydroxylase cDNAs. Although this chimpanzee cDNA is similar to the murine homologue, the human cDNA contains a 92-bp deletion resulting in a frameshift mutation. The isolated human gene also shows evidence for this deletion. Genomic PCR analysis indicates that this deletion does not occur in any of the African great apes. The gene is localized to 6p22-p23 in both humans and great apes, which does not correspond to known chromosomal rearrangements that occurred during hominoid evolution. Thus, the lineage leading to modern humans suffered a mutation sometime after the common ancestor with the chimpanzee and bonobo, potentially affecting recognition by a variety of endogenous and exogenous sialic acid-binding lectins. Also, the expression of Neu5Gc previously reported in human fetuses and tumors as well as the traces detected in some normal adult humans must be mediated by an alternate pathway.

CIITA stimulation of transcription factor binding to major histocompatibility complex class II and associated promoters in vivo

CIITA is a master transactivator of the major histocompatibility complex class II genes, which are involved in antigen presentation. Defects in CIITA result in fatal immunodeficiencies. CIITA activation is also the control point for the induction of major histocompatibility complex class II and associated genes by interferon-gamma, but CIITA does not bind directly to DNA. Expression of CIITA in G3A cells, which lack endogenous CIITA, followed by in vivo genomic footprinting, now reveals that CIITA is required for the assembly of transcription factor complexes on the promoters of this gene family, including DRA, Ii, and DMB. CIITA-dependent promoter assembly occurs in interferon-gamma-inducible cell types, but not in B lymphocytes. Dissection of the CIITA protein indicates that transactivation and promoter loading are inseparable and reveal a requirement for a GTP binding motif. These findings suggest that CIITA may be a new class of transactivator.

The DMB promoter: delineation, in vivo footprint, trans-activation, and trans-dominant suppression

The HLA-DM loci encode the heterodimeric unconventional class II MHC molecules that are coexpressed with conventional class II MHC molecules. DM molecules are essential for the proper formation and function of conventional class II MHC molecules. This report characterizes the DMB promoter both by in vivo footprint and by in vitro functional analysis and reveals a promoter structure similar to that of conventional class II MHC genes. DR-negative mutant cell lines selectively defective in the transcription factor or class II trans-activator (CIITA) were used to reveal a requirement for both these factors in DMB promoter activation. Complementation of defective cell lines with the appropriate transcription factor reconstituted DMB promoter activation. Further analysis with CIITA identified several mutant forms of CIITA that are trans-dominant-negative mutants, i.e., they suppressed DMB promoter activation by transfected and endogenous CIITA. These mutants may be used in abiological setting to down-regulate the function of DM in Ag processing.

The DMB promoter: delineation, in vivo footprint, trans-activation, and trans-dominant suppression

The HLA-DM loci encode the heterodimeric unconventional class II MHC molecules that are coexpressed with conventional class II MHC molecules. DM molecules are essential for the proper formation and function of conventional class II MHC molecules. This report characterizes the DMB promoter both by in vivo footprint and by in vitro functional analysis and reveals a promoter structure similar to that of conventional class II MHC genes. DR-negative mutant cell lines selectively defective in the transcription factor or class II trans-activator (CIITA) were used to reveal a requirement for both these factors in DMB promoter activation. Complementation of defective cell lines with the appropriate transcription factor reconstituted DMB promoter activation. Further analysis with CIITA identified several mutant forms of CIITA that are trans-dominant-negative mutants, i.e., they suppressed DMB promoter activation by transfected and endogenous CIITA. These mutants may be used in abiological setting to down-regulate the function of DM in Ag processing.

Regulation of inosine-5'-monophosphate dehydrogenase type II gene expression in human T cells. Role for a novel 5' palindromic octamer sequence

Expression of the gene encoding human inosine- 5'-monophosphate dehydrogenase (IMPDH) type II, an enzyme catalyzing the rate-limiting step in the generation of guanine nucleotides, is increased more than 10-fold in activated peripheral blood T lymphocytes and is required for T cell activation. We have examined the 5'-regulatory sequences that are important for the transcriptional regulation of this gene in T cells. DNase I mapping of genomic DNA identified a hypersensitive element near the transcription initiation site. Fine mapping by in vivo footprinting demonstrated five transcription factor binding sites that are occupied in both resting and activated peripheral blood T lymphocytes; these are tandem CRE motifs, a Sp1 site, an overlapping Egr-1/Sp1 site, and a novel palindromic octamer sequence (POS). The tandem CRE and POS sites are of major functional importance as judged by mutational and electrophoretic mobility shift analyses. These data provide evidence that expression of the human IMPDH type II gene is predominantly regulated by the nuclear factors ATF-2 and an as yet unidentified POS-binding protein. Additional major protein-DNA interactions do not occur within the promoter region after T lymphocyte activation, indicating a requirement for additional protein-protein interactions and/or post-translational modifications of pre-bound transcription factors to account for the observed increase in IMPDH type II gene expression.

CCAAT-binding factor NF-Y and RFX are required for in vivo assembly of a nucleoprotein complex that spans 250 base pairs: the invariant chain promoter as a model

The events that lead to promoter accessibility within chromatin are not completely understood. The invariant chain (Ii) promoter was used as a model to determine the contribution of different DNA-binding factors in establishing occupancy of a complex promoter. Gamma interferon induction of the Ii promoter requires the cooperation of multiple cis elements including distal S, X, and Y/CCAAT elements along with proximal GC and Y/CCAAT elements. The heteromeric transcription factor NF-Y binds to both Y/CCAAT elements. Genomic footprinting was used to analyze in vivo protein-DNA contacts for integrated Ii promoters bearing mutations in each element. The results reveal a hierarchy of transcription factor loading with NF-Y binding to the distal Y/CCAAT element being required for establishing protein-DNA interactions over the entire 250 bp analyzed. Mutation of the X box disrupts binding primarily at the adjacent Y/CCAAT element along with a lesser effect on GC box binding. Importantly, this finding is verified with a cell line which lacks a functional X-box-binding factor, RFX, providing physiological validity for the strategy described here. Mutation of both the S element and the GC box results in either no or little effect on transcription factor binding. However, mutation of the proximal Y/CCAAT element disrupts binding to the adjacent GC box and partially reduces binding in the distal S/X/Y domain. The crucial role for NF-Y in establishing promoter occupancy may be related to its histone fold motif, the essential component for assembling nucleosome-like structures.

Cyclin-dependent kinase activation and S-phase induction of the cyclin B1 gene are linked through the CCAAT elements

Control of cell proliferation is dependent on the regulated expression of the cyclin genes. Induction of cyclin B1 gene expression in S phase has been shown to require sequences within the first 90 bp of the proximal promoter region. In this study, we defined the cell cycle regulatory elements within this region and explored the mechanism by which the cyclin B1 gene is activated. A CDE-like element that is important in S-phase regulation of other genes was not required for correct cell cycle expression of cyclin B1. Instead, two CCAAT boxes were essential for S-phase induction of cyclin B1 gene in both NIH3T3 and HeLa cells. Induction of cyclin B1 by cyclin/cyclin-dependent kinase (cdk) complexes were examined by cotransfection of the reporter along with appropriate expression vectors. Complexes of cdk4 with cyclin D1 or cdk2 with cyclin E or A can activate the cyclin B1 promoter, and activation is uniquely dependent on the CCAAT elements in both normal and heterologous contexts. This transcription factor NF-Y binds to both CCAAT elements. These findings suggest that S phase-specific induction of the cyclin B1 promoter is dependent upon NF-Y binding to the CCAAT elements and is correlated with activation by cyclin-dependent kinases.

Identification of specific calcium-binding noncollagenous proteins associated with glutaraldehyde-preserved bovine pericardium in the rat subdermal model

Calcification of glutaraldehyde-preserved bioprosthetic heart valves (BHVs) results in their clinical failure. The mechanism of this pathologic calcification is not well defined. Since serum proteins are known to be taken up in mineralized tissue, we hypothesized that serum proteins derived from several calcium-binding noncollagenous proteins (NCPs) of bone and teeth also may be associated with pathologically mineralized BHVs. Using a rat subdermal model of BHV calcification, glutaraldehyde-preserved bovine pericardium (GPBP) was implanted for 1, 3, 14, and 60 days, and then subjected to an extraction procedure designed to isolate only NCPs tightly bound to the mineral phase. Gel electrophoresis and Coomassie Brilliant Blue staining demonstrated that these proteins became associated with GPBP over time, paralleling reported calcium uptake by the tissue. Stains-All staining demonstrated a marked accumulation of highly acidic, phosphorylated NCPs associated with 60-day GPBP extracts. Some of these proteins were detected in rat serum but were absent from extracts of GPBP incubated in rat serum in vitro. Western blotting with antibodies to three NCPs found in bone and teeth-bone acidic glycoprotein 75 (BAG 75), osteopontin, and SPARC-demonstrated that these NCPs were tightly bound to the mineral phase of calcified GPBP. A fourth NCP, bone sialoprotein II (BSP II) was barely detectable. Thus each identified NCP showed a different pattern of GPBP association relative to mineral deposition, suggesting unique roles for each in pathologic calcification. SPARC increased within 3 days of GPBP implantation but decreased by 2 weeks. BAG 75 and osteopontin uptake was detected in the initial mineral deposits and increased mineralization proceeded. BSP II never increased significantly over the entire-period. Further studies, which should include immunohistochemistry, will be important for delineating the source, location, and function of these three NCPs and for identifying others that also may be involved in this pathological process. Most important, the new insights into the mechanism of pathologic calcification described here present exciting opportunities for novel approaches to BHV calcification prevention.

Regulation of LMP2 and TAP1 genes by IRF-1 explains the paucity of CD8+ T cells in IRF-1-/- mice

The TAP1 and LMP2 genes are central for class I MHC function and share a common promoter. Here, we analyze the molecular mechanism of IFN gamma up-regulation of TAP1 and LMP2. In vivo footprinting indicates IFN gamma up-regulates protein-DNA contacts at an IRF-E that is essential for the up-regulation of TAP1 and LMP2 by IFN gamma. Gel shift analysis indicates that this site binds IRF-1. The expression of TAP1 and LMP2 are both greatly reduced in IRF-1-deficient mice. Surface class I MHC as well as CD8+ T cells are reduced in IRF-1-/- mice. The role of IRF-1 in the regulation of TAP1 and LMP2 suggests a mechanism for the antiviral properties of IRF-1 and the unexpected deficiency of CD8+ T cells observed in IRF-1-/- mice.

Major histocompatibility complex class II-associated invariant chain gene expression is up-regulated by cooperative interactions of Sp1 and NF-Y

Expression of the major histocompatibility complex (MHC) class II-associated invariant chain (Ii) is required for efficient and complete presentation of antigens by MHC class II molecules and a normal immune response. The Ii gene is generally co-regulated with the MHC class II molecules at the level of transcription and a shared SXY promoter element has been described. This report defines the proximal promoter region of Ii which may regulate Ii transcription distinct from MHC class II. In vivo genomic footprinting identified an occupied, imperfect CCAAT box and an adjacent GC box in the proximal region. These sites are bound in Ii-ositive cell lines and upon interferon-gamma induction of Ii transcription. In contrast, both sites are unoccupied in Ii-egative cell lines and in inducible cell lines prior to interferon-gamma treatment. Together these two sites synergize to stimulate transcription. Independently, the transcription factor NF-Y binds poorly to the imperfect CCAAT box with a rapid off rate, while Sp1 binds to the GC box. Stabilization of NF-Y binding occurs upon Sp1 binding to DNA. In addition, the half-life of Sp1 binding also increased in the presence of NF-Y binding. These findings suggest a mechanism for the complete functional synergy of the GC and CCAAT elements observed in Ii transcription. Furthermore, this report defines a CCAAT box of imperfect sequence which binds NF-Y and activates transcription only when stabilized by an adjacent factor, Sp1.