Selective targeting of microglia by quantum dots

Background

Microglia, the resident immune cells of the brain, have been implicated in brain injury and various neurological disorders. However, their precise roles in different pathophysiological situations remain enigmatic and may range from detrimental to protective. Targeting the delivery of biologically active compounds to microglia could help elucidate these roles and facilitate the therapeutic modulation of microglial functions in neurological diseases.

Methods

Here we employ primary cell cultures and stereotaxic injections into mouse brain to investigate the cell type specific localization of semiconductor quantum dots (QDs) in vitro and in vivo. Two potential receptors for QDs are identified using pharmacological inhibitors and neutralizing antibodies.

Results

In mixed primary cortical cultures, QDs were selectively taken up by microglia; this uptake was decreased by inhibitors of clathrin-dependent endocytosis, implicating the endosomal pathway as the major route of entry for QDs into microglia. Furthermore, inhibiting mannose receptors and macrophage scavenger receptors blocked the uptake of QDs by microglia, indicating that QD uptake occurs through microglia-specific receptor endocytosis. When injected into the brain, QDs were taken up primarily by microglia and with high efficiency. In primary cortical cultures, QDs conjugated to the toxin saporin depleted microglia in mixed primary cortical cultures, protecting neurons in these cultures against amyloid beta-induced neurotoxicity.

Conclusions

These findings demonstrate that QDs can be used to specifically label and modulate microglia in primary cortical cultures and in brain and may allow for the selective delivery of therapeutic agents to these cells.

Role of phosphoinositide 3-kinase {alpha}, protein kinase C, and L-type Ca2+ channels in mediating the complex actions of angiotensin II on mouse cardiac contractility

Although angiotensin II (Ang II) plays an important role in heart disease associated with pump dysfunction, its direct effects on cardiac pump function remain controversial. We found that after Ang II infusion, the developed pressure and +dP/dt(max) in isolated Langendorff-perfused mouse hearts showed a complex temporal response, with a rapid transient decrease followed by an increase above baseline. Similar time-dependent changes in cell shortening and L-type Ca(2+) currents were observed in isolated ventricular myocytes. Previous studies have established that Ang II signaling involves phosphoinositide 3-kinases (PI3K). Dominant-negative inhibition of PI3Kalpha in the myocardium selectively eliminated the rapid negative inotropic action of Ang II (inhibited by approximately 90%), whereas the loss of PI3Kgamma had no effect on the response to Ang II. Consistent with a link between PI3Kalpha and protein kinase C (PKC), PKC inhibition (with GF 109203X) reduced the negative inotropic effects of Ang II by approximately 50%. Although PI3Kalpha and PKC activities are associated with glycogen synthase kinase-3beta and NADPH oxidase, genetic ablation of either glycogen synthase kinase-3beta or p47(phox) (an essential subunit of NOX2-NADPH oxidase) had no effect on the inotropic actions of Ang II. Our results establish that Ang II has complex temporal effects on contractility and L-type Ca(2+) channels in normal mouse myocardium, with the negative inotropic effects requiring PI3Kalpha and PKC activities.

Enhanced translation of heme oxygenase-2 preserves human endothelial cell viability during hypoxia

Heme oxygenases (HOs) -1 and -2 catalyze the breakdown of heme to release carbon monoxide, biliverdin, and ferrous iron, which may preserve cell function during oxidative stress. HO-1 levels decrease in endothelial cells exposed to hypoxia, whereas the effect of hypoxia on HO-2 expression is unknown. The current study was carried out to determine if hypoxia alters HO-2 protein levels in human endothelial cells and whether this enzyme plays a role in preserving their viability during hypoxic stress. Human umbilical vein endothelial cells (HUVECs), human aortic endothelial cells (HAECs), and human blood outgrowth endothelial cells were exposed to 21% or 1% O(2) for 48 or 16 h in the presence or absence of tumor necrosis factor-alpha (10 ng/ml) or H(2)O(2) (100 microm). In all three endothelial cell types HO-1 mRNA and protein levels were decreased following hypoxic incubation, whereas HO-2 protein levels were unaltered. In HUVECs HO-2 levels were maintained during hypoxia despite a 57% reduction in steady-state HO-2 mRNA level and a 43% reduction in total protein synthesis. Polysome profiling revealed increased HO-2 transcript association with polysomes during hypoxia consistent with enhanced translation of these transcripts. Importantly, inhibition of HO-2 expression by small interference RNA increased oxidative stress, exacerbated mitochondrial membrane depolarization, and enhanced caspase activation and apoptotic cell death in cells incubated under hypoxic but not normoxic conditions. These data indicate that HO-2 is important in maintaining endothelial viability and may preserve local regulation of vascular tone, thrombosis, and inflammatory responses during reductions in systemic oxygen delivery.

Regulation of proliferation and membrane potential by chloride currents in rat pulmonary artery smooth muscle cells

Pulmonary artery smooth muscle cell (PASMC) proliferation contributes to increased pulmonary vascular resistance and pulmonary hypertension. Because proliferation depends on membrane potential (V(m)) and because V(m) is, in part, determined by Cl(-) currents (I(Cl)), we examined the effects of I(Cl) inhibition with 4,4;-diisothiocyanatostilbene-2,2;-disulfonic acid (DIDS) on cultured rat PASMCs. DIDS (30 mumol/L) reduced cell numbers, decreased 5-bromodeoxyuridine incorporation and delayed cell cycle progression. I(Cl) inhibition with 5-Nitro-2-(3-phenylpropylamino) benzoic acid (100 mumol/L) also reduced cell numbers of cultured rat PASMCs. To test the possible involvement of I(Cl) in the regulation of PASMC proliferation, we measured V(m) and I(Cl) in both cultured (proliferating) and acutely dissociated (nonproliferating) rat PASMCs. V(m) (-39.3+/-1.4 mV) was close to the equilibrium potential of Cl(-) (-39 mV) in proliferating PASMCs but differed from equilibrium potential of Cl(-) in acutely dissociated cells (-45.3+/-0.9 mV). DIDS and substitution of extracellular Cl(-) with I(-) induced V(m) hyperpolarization in proliferating but not nonproliferating PASMCs. Consistent with V(m) recordings, DIDS-sensitive baseline and swelling-activated (Ca(2+)-independent) I(Cl)s, recorded with low Ca(2+) (<1 nmol/L) pipette solutions, were approximately 5-fold greater in proliferating than in nonproliferating PASMCs. By contrast, Ca(2+)-activated I(Cl) did not differ between proliferating and nonproliferating PASMCs. Ca(2+)-independent I(Cl)s were also increased in proliferating PASMCs acutely dissociated from rats exposed to hypoxia (10% O(2); 7 days). These findings are consistent with the conclusion that I(Cl)s regulate proliferation of PASMCs and suggest that selective I(Cl) inhibition may be useful in treating pulmonary hypertension.

The natural history of trachoma infection and disease in a Gambian cohort with frequent follow-up

Background

The natural history of ocular Chlamydia trachomatis infections in endemic communities has not been well characterised and is an important determinant of the effectiveness of different mass treatment strategies to prevent blindness due to trachoma.

Methodology/Principal Findings

A multistate hidden Markov model was fitted to data on infection and active disease from 256 untreated villagers in The Gambia who were examined every 2 weeks over a 6-month period. Parameters defining the natural history of trachoma were estimated, and associations between these parameters, demographic and baseline immune measurements examined. The median incubation period following infection was estimated at 17 days (95% confidence interval: 11–28). Disease persisted for longer than infection (median 21 (15–32) weeks) versus 17 (12–24) weeks), with an estimated median duration of post-infection inflammation of 5 (3–8) weeks. The duration of active disease showed a significant decline with age even after accounting for lower rates of re-infection and disease at older ages (p = 0.004). Measurements of levels of baseline IgA to epitopes in the major outer membrane protein of Chlamydia trachomatis were not significantly correlated with protection or more rapid clearance of infection.

Conclusions

The average duration of infection with Chlamydia trachomatis especially at younger ages is long. This contributes to the persistence and gradual return of trachoma after community-wide treatment with antibiotics.

Trachoma is an infectious disease of the eye that causes blindness in many of the poorest parts of the world. In this paper, we use a novel statistical approach to estimate the characteristics of this disease among people living in The Gambia who were examined every 2 weeks over a 6-month period. We found that the typical duration of infection with Chlamydia trachomatis and of clinically active disease were significantly longer than previously estimated. We tested different hypotheses about the natural history of trachoma that explain the relationship between infection and disease observed in the field. We also confirmed that disease lasts significantly longer among young children under 5 years old compared with older children and adults, even after accounting for high rates of re-infection in this age group, consistent with the development of immunity with age. The long duration of infection, especially among younger children, contributes to the persistence and gradual return of trachoma after community-wide treatment with azithromycin. This implies the need for high treatment coverage if infection is to be eliminated from a community, even where the return of infection after treatment is seen to be slow.

Impaired endothelial function in C-reactive protein overexpressing mice

Increasing evidence suggests that the inflammatory biomarker, C-reactive protein (CRP), may play a causal role in the development and progression of atherothrombosis. Since endothelial dysfunction is an early and integral component of atherosclerosis, we hypothesized that endothelial homeostasis would be impaired in CRP-overexpressing CRP transgenic (CRPtg) mice. Male CRPtg and wild-type mice were injected thrice over 2 weeks with vehicle or turpentine to induce the inflammation-sensitive CRP transgene. Serum human CRP levels in turpentine-treated CRPtg mice was 276.28 +/- 95.7 microg/ml. Human CRP was undetectable in the sera of wild-type mice and present at only low levels (1.41 +/- 0.2 microg/ml) in vehicle-treated CRPtg mice (n=6-8 mice/group). Aortic segments from turpentine-induced CRP-overexpressing CRPtg mice demonstrated impaired endothelium-dependent responses to acetylcholine vs. those from vehicle-treated CRPtg controls (57.1 +/- 9.5% vs. 85.0 +/- 5.0%, P<0.05, n=6). Nitric oxide release as well as phosphorylated eNOS protein expression from isolated aortic segments of CRPtg mice overexpressing CRP were markedly reduced compared to that from vehicle-treated controls. Masson's trichrome staining revealed increased perivascular fibrosis in CRP-overexpressing CRPtg mice. CRP overexpression was also associated with augmented aortic endothelial staining for VCAM-1 and MCP-1 and enhanced macrophage infiltration. Mice overexpressing the human CRP gene exhibit endothelial dysfunction, possibly via reduced NO bioavailability, with resultant changes in vascular structure. These data further support a role for CRP in mediating endothelial dysfunction.

Oxygen regulation of arterial smooth muscle cell proliferation and survival

The purpose of this study was to determine if hypoxia elicits different proliferative and apoptotic responses in systemic arterial smooth muscle cells incubated under conditions that do or do not result in cellular ATP depletion and whether these effects are relevant to vascular remodeling in vivo. Gene expression profiling was used to identify potential regulatory pathways. In human aortic smooth muscle cells (HASMCs) incubated at 3% O(2), proliferation and progression through the G1/S interphase are enhanced. Incubation at 1% O(2) reduced proliferation, delayed G1/S transition, increased apoptotic cell death, and is associated with mitochondrial membrane depolarization and reduced cellular ATP levels. In aorta and mesenteric artery from rats exposed to hypoxia (10% O(2), 48 h), both proliferation and apoptosis are increased, as are medial nuclear density and smooth muscle cell content. Although nuclear levels of hypoxia-inducible factor 1-alpha (HIF-1alpha) are increased to a similar extent in HASMCs incubated at 1 and 3% O(2), expression of tumor protein p53, its transcriptional target p21, as well as their regulatory factors and downstream effectors, are differentially affected under these two conditions, suggesting that the bidirectional effects of hypoxia are mediated by this pathway. We conclude that hypoxia induces a state of enhanced cell turnover through increased rates of both smooth muscle cell proliferation and death. This confers the ability to remodel the vasculature in response to changing tissue metabolic needs while avoiding the accumulation of mutations that may lead to malignant transformation or the formation of abnormal vascular structures.

Induction of matrix metalloproteinase-2 enhances systemic arterial contraction after hypoxia

This study was carried out to determine the role of increased vascular matrix metalloproteinase-2 (MMP-2) expression in the changes in systemic arterial contraction after prolonged hypoxia. Rats and mice were exposed to hypoxia (10% and 8% O(2), respectively) or normoxia (21% O(2)) for 16 h, 48 h, or 7 days. Aortae and mesenteric arteries were either mounted in organ bath myographs or frozen in liquid nitrogen. MMP-2 inhibition with cyclic CTTHWGFTLC (CTT) reduced contraction to phenylephrine (PE) in aortae and mesenteric arteries from rats exposed to hypoxia for 7 days but not in vessels from normoxic rats. Similarly, CTT reduced contraction to Big endothelin-1 (Big ET-1) in aortae from rats exposed to hypoxia for 7 days. Responses to PE were reduced in hypoxic MMP-2(-/-) mice compared with MMP-2(+/+) mice. Increased contraction to Big ET-1 after hypoxia was observed in MMP-2(+/+) mice but not in MMP-2(-/-) mice. Rat aortic MMP-2 and membrane type 1 (MT1)-MMP protein levels and MMP activity were increased after 7 days of hypoxia. Rat aortic MMP-2 and MT1-MMP mRNA levels were increased in the deep medial vascular smooth muscle. We conclude that hypoxic induction of MMP-2 expression potentiates contraction in systemic conduit and resistance arteries. This may preserve the capacity to regulate the systemic circulation in the transition between the alterations in vascular tone and structural remodeling that occurs during prolonged hypoxic epochs.

Endothelium-independent flow-induced dilation in the mouse carotid artery

BACKGROUND

We investigated the locus of flow regulation of vascular tone in carotid arteries of C57 Bl/6 and eNOS(-/-) mice.

METHODS

Arterial segments (2-3 mm) were mounted in a perfusion myograph and preconstricted with 1 muM phenylephrine before monitoring flow-induced changes in lumen diameter.

RESULTS

Both control and eNOS(-/-) mice demonstrated flow-dependent relaxation. This response was not attenuated by the NO synthase antagonist L-NAME, the cyclooxygenase inhibitor indomethacin, the selective guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ), the adenylate cyclase inhibitor Rp-8-Br-cAMPs, integrin-binding RGD peptides, or by removal of the endothelium. Hypoxia, a physiological stimulus known to alter endothelium-dependent flow regulation of vascular tone, also failed to attenuate the observed flow-mediated dilation.

CONCLUSIONS

These findings indicate the existence of a previously unidentified endothelium-independent mechanism of flow-induced dilation in the carotid artery. Further investigations to identify the mechanisms that underlie this response may provide novel therapeutic directions in the treatment of disorders characterized by abnormal flow regulation of vascular tone.

Hypoxia induces a functionally significant and translationally efficient neuronal NO synthase mRNA variant

We tested the hypothesis that induction of neuronal NO synthase (nNOS) impairs vascular smooth muscle contractility after hypoxia. nNOS protein was increased in aorta, mesenteric arterioles, pulmonary arteries, brain, and diaphragm from rats exposed to 8% O2 for 48 hours and in human aortic SMCs after hypoxic incubation (1% O2). Ca-dependent NO synthase activity was increased in endothelium-denuded aortic segments from hypoxia-exposed rats. N-nitro-L-arginine methyl ester enhanced the contractile responses of endothelium-denuded aortic rings and mesenteric arterioles from hypoxia-exposed but not normoxic rats (P < 0.05). The hypoxia-inducible mRNA transcript expressed by human cells was found to contain a novel 5'-untranslated region, consistent with activation of transcription in the genomic region contiguous with exon 2. Translational efficiency of this transcript is markedly increased compared with previously described human nNOS mRNAs. Transgenic mice possessing a lacZ reporter construct under control of these genomic sequences demonstrated expression of the construct after exposure to hypoxia (8% O2, 48 hours) in the aorta, mesenteric arterioles, renal papilla, and brain. These results reveal a novel human nNOS promoter that confers the ability to rapidly upregulate nNOS expression in response to hypoxia with a functionally significant effect on vascular smooth muscle contraction.

Effect of medium type, age and aeration on the MICs of tigecycline and classical tetracyclines

BACKGROUND

Tigecycline is a minocycline derivative, belonging to a chemical class prone to oxidation and to medium-related effects on susceptibility. We therefore studied the effect of medium type and age on the tigecycline MICs found in broth and on agar by the Clinical Laboratory Standards Institute and British Society for Applied Chemotherapy methods.

METHODS

MICs of tigecycline, minocycline and tetracycline were determined for 96 non-fastidious bacteria and 20 streptococci using Mueller-Hinton broth (MHB), Mueller-Hinton agar (MHA), Iso-Sensitest broth (ISB) and Iso-Sensitest agar (ISA) as: (i) freshly-prepared media; (ii) fresh media but with the antibiotic added 1 day before inoculation and (iii) media stored for 7 days before antibiotic addition and use.

RESULTS

MICs of tigecycline in fresh MHB were up to two doubling dilutions higher than on or in MHA, ISA or ISB. Media with tigecycline or classical tetracyclines added a day before use gave raised MICs, though rarely by more than one dilution. MICs of tigecycline (less so classical tetracyclines) were increased in 7-day-old MHB or ISB, even though the antibiotic was freshly added. This latter effect was greatest for the most susceptible strains and was absent or much reduced for organisms with MICs > or = 8 mg/L; it did not occur in the corresponding agar dilution tests. Addition of blood to MHB largely abrogated the effect, as did steaming the broth before adding the antibiotic.

CONCLUSIONS

The raised MICs of tigecycline in aged broth probably reflect inactivation by dissolved oxygen. This accords with the lack of any MIC increase in newly-steamed (i.e. degassed) MHB or on aged agar (which is melted at 100 degrees C before use). Blood, which also abrogated the effect, may increase reducing capacity, protecting the tigecycline. At a practical level, broth MIC determinations for tigecycline should always employ fresh media.

Regulated formation and selection of neuronal processes underlie directional guidance of neuronal migration

Axon guidance and neuronal migration are critical features of neural development, and it is believed that extracellular gradients of secreted guidance cues play important roles in pathfinding. It has been well documented that the growth cones of extending axons respond to such extracellular gradients by growing toward or away from the source of the secreted cue via asymmetrical extension of a single growth cone. However, it is unclear whether migrating neurons change direction in response to guidance molecules using the same mode of turning as extending axons. In this study, we demonstrate that migrating neurons turn away from the chemo-repellent Slit through repeated rounds of process extension and retraction and do not turn through the reorientation of a single growth cone. We further show that Slit increases the rate of somal process formation and that these processes form preferentially on the side of the cell body furthest away from the Slit source. In addition, Slit causes cell turning through asymmetric process selection. Finally, we show that multiple types of migrating neurons employ this mode of cell turning in response to a variety of guidance cues. These results show that migrating neurons employ a unique type of turning when faced with secreted guidance cues that is distinct from the type employed by axons.

Investigations of neuronal migration in the central nervous system

The migration of neuronal precursor cells is essential for the formation of the embryonic nervous system and for the maintenance of the adult nervous system. Modern approaches have greatly facilitated molecular and cellular studies of mechanisms underlying neuronal migration. Here we use the cells migrating from the anterior subventricular zone to the olfactory bulb as a model to discuss in some detail how neuronal migration can be studied. These methods can be adapted to other models of neuronal (or somatic cell) migration.

Factors involved in the incidence of post-dural puncture headache with the 25 gauge Whitacre needle for obstetric anesthesia

Parturients have the greatest risk of postdural puncture headache. use of a pencil-point needle, such as the 25 gauge Whitacre, has been associated with a lower incidence of PDPH. This observational study of 1009 obstetrical patients assessed possible factors related to the incidence of PDPH and other complications associated with spinal anesthesia using the 25 gauge Whitacre needle. The independent variables included procedure, maternal position at insertion, ease of insertion, intraoperative i.v. analgesia supplementation, use of intrathecal narcotics, parity and type of local anesthetic. Patients were followed daily during their hospitalization and questioned specifically about the presence of headache, its nature, onset and treatment. Two hundred and twenty-nine patients developed a headache postperatively but only 25 had postdural puncture headaches (overall incidence 2.5%). The PDPH typically presented on day 2 (median), range 1-4). Six patients (0.59%) required epidural blood patch. There were eight (0.8%) failed finals which were converted to general anesthesia. None of the factors evaluated were significant in predicting the occurrence of PDPH.

Interaction between endothelial heme oxygenase-2 and endothelin-1 in altered aortic reactivity after hypoxia in rats

The aim of this study was to determine whether increased expression of heme oxygenase (HO) contributes to impairment of aortic contractile responses after hypoxia through effects on reactivity to endothelin-1 (ET-1). Thoracic aortas from normoxic rats and rats exposed to hypoxia (10% O2) for 16 or 48 h were mounted in organ bath myographs for contractile studies, fixed in paraformaldehyde, or frozen in liquid nitrogen for protein extraction. In rings from normoxic rats, the HO inhibitor tin protoporphyrin IX (SnPP IX, 10 microM) did not alter the response to phenylephrine or ET-1. In rings from rats exposed to 16-h hypoxia, maximum tension generated in response to these agonists was higher in endothelium-intact but not -denuded rings in the presence of SnPP IX. In rings from rats exposed to 48-h hypoxia SnPP IX increased contraction in endothelium-intact but not -denuded rings. In endothelium-intact aortic rings from rats exposed to 16-h hypoxia incubated with endothelin A receptor-specific antagonist BQ-123 (10(-7) M), SnPP IX did not alter phenylephrine-induced contraction. Aortic ET-1 protein levels, measured by radioimmunoassay, were increased in rats exposed to hypoxia for 16 and 48 h. Western blotting showed that HO-1 and HO-2 protein were increased after 16 h of hypoxia and returned to near-control levels after 48 h. Increase in HO-1 protein was detected in endothelium-intact and -denuded rings. Removal of endothelium abolished the increase in HO-2 immunoreactivity. Immunohistochemistry localized expression of HO-1 protein to vascular smooth muscle, whereas HO-2 was only detected in endothelium. HO-2 is expressed by aortic endothelial cells early during hypoxic exposure and impairs ET-1-mediated potentiation of contraction to alpha-adrenoceptor stimulation.

Community and hospital spread of Escherichia coli producing CTX-M extended-spectrum β-lactamases in the UK

OBJECTIVES

During 2003, the Health Protection Agency's Antibiotic Resistance Monitoring and Reference Laboratory began to receive isolates of Escherichia coli for confirmation of extended-spectrum beta-lactamase production with a phenotype implying a CTX-M-type beta-lactamase, i.e. MICs of cefotaxime > or = 8-fold higher than MICs of ceftazidime. Many were referred as being from community patients. We examined 291 CTX-M-producing isolates from the UK and investigated the genetic basis of their phenotype.

METHODS

PCR was used to detect alleles encoding CTX-M enzymes and to assign these to their blaCTX-M phylogenetic groups. Selected alleles were sequenced. Producers were compared by analysis of banding patterns generated by pulsed-field gel electrophoresis of XbaI-digested genomic DNA. MICs were determined by an agar dilution method or by Etest.

RESULTS

Of 291 CTX-M-producing E. coli isolates studied from 42 UK centres, 70 (24%) were reportedly from community patients, many of whom had only limited recent hospital contact. Community isolates were referred by 12 centres. Two hundred and seventy-nine (95.9%) producers contained genes encoding group 1 CTX-M enzymes and 12 contained blaCTX-M-9-like alleles. An epidemic CTX-M-15-producing strain was identified, with 110 community and inpatient isolates referred from six centres. Representatives of four other major strains also produced CTX-M-15, as did several sporadic isolates examined. Most producers were multi-resistant to fluoroquinolones, trimethoprim, tetracycline and aminoglycosides as well as to non-carbapenem beta-lactams.

CONCLUSIONS

CTX-M-producing E. coli are a rapidly developing problem in the UK, with CTX-M-15 particularly common. The diversity of producers and geographical scatter of referring laboratories indicates wide dissemination of blaCTX-M genes. Because of the public health implications, including for the treatment of community-acquired urinary tract infections, the spread of these strains--and CTX-M-15 beta-lactamase in particular--merits close monitoring.

The inositol polyphosphate 5-phosphatase Ocrl associates with endosomes that are partially coated with clathrin

The subcellular localization of Ocrl, the inositol polyphosphate 5-phosphatase that is mutated in Lowe syndrome, was investigated by fluorescence microscopy. Ocrl was localized to endosomes and Golgi membranes along with clathrin, giantin, the mannose 6-phosphate receptor, transferrin, and the early endosomal antigen 1 endosomal marker in fixed cells. The endosomal localization of Ocrl was confirmed by live-cell time-lapse microscopy in which we monitored the dynamics of Ocrl on endosomes. GST binding assays show that Ocrl interacts with the clathrin terminal domain and the clathrin adaptor protein AP-2. Our findings suggest a role for Ocrl in endosomal receptor trafficking and sorting.

Characterization of human humoral responses to the major outer membrane protein and OMP2 of Chlamydophila pneumoniae

Chlamydophila pneumoniae infection is associated with a range of diseases including pneumonia, asthma and heart disease. Although an obligate intracellular pathogen, high levels of antigen-specific antibody are induced and serology is frequently used to diagnose these infections. Proteins targeted by the humoral response include the major outer membrane protein (MOMP) and outer membrane protein 2 (OMP2). Using human anti-chlamydial sera we have defined the B cell epitopes recognized on MOMP and OMP2. Peptides from MOMP, unlike OMP2, were not strongly recognized. Two of these epitopes when linked to an inert carrier reacted strongly with high-titer anti-C. pneumoniae sera.

Visualization of spatially and temporally regulated N-WASP activity during cytoskeletal reorganization in living cells

Members of the WASP/WAVE family of proteins are key regulators of cytoskeletal reorganization across a diverse range of cellular processes. Despite a wealth of biochemical data about WASP/WAVE regulation in vitro, our understanding of the in vivo regulation of these proteins is hampered by the inability to monitor subcellular regulation of their activities in living cells. Here we establish a fluorescence resonance energy transfer-based approach to visualize spatial and temporal regulation of neuronal Wiskott-Aldrich syndrome protein (N-WASP) activity in living cells. Using time-lapse microscopy, we characterize the activation of N-WASP in response to growth-factor stimulation, and we reveal that N-WASP is activated inside extending filopodia. Furthermore, we suggest a role of N-WASP in regulating membrane ruffling downstream of phosphatidylinositol 4,5-bisphosphate and Cdc42.

Role of Cl− currents in rat aortic smooth muscle activation by prostaglandin F2α

The aim of this study was to determine the role of Cl(-) channel activation in prostaglandin F(2 alpha)-stimulated aortic contraction and in membrane depolarization during stimulation with prostaglandin F(2 alpha) in an aortic smooth muscle cell line (A7r5). The Cl(-) channel antagonists 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB), indanyloxyacetic acid-94 (IAA-94) and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) were found to decrease (P<0.05) the maximum tension generated by rat thoracic aortic segments during stimulation with prostaglandin F(2 alpha) and to shift the concentration-response relationship to the right. In the presence of Nifedipine and Cesium, rat aorta-derived A7r5 smooth muscle cells demonstrated outwardly rectifying voltage-dependent currents that were inhibited by NPPB, IAA-94 and DIDS. Both inward and outward currents were enhanced (P<0.05) following addition of prostaglandin F(2 alpha) (4 micromol/l, final concentration) to the bath solution and this increase was completely inhibited by NPPB. In the absence of Cesium, the addition of prostaglandin F(2 alpha) (4 micromol/l) to the extracellular bath solution either depolarized or hyperpolarized the cell membrane depending on the equilibrium potential for Cl(-) ions. Our results indicate that altered Cl(-) conductance is an important mechanism mediating membrane depolarization and contraction of aortic smooth muscle cells during stimulation with prostaglandin F(2 alpha). Given the significant role that prostaglandin F(2 alpha) and its biologically active isomers, the F(2) isoprostanes, play in the control of vascular tone during hypoxic and oxidative stress in the systemic circulation, alterations in Cl(-) channel function and expression may represent an important mechanism in the pathogenesis of abnormal blood flow regulation in disease states.

Mucosal and systemic immune responses to plasmid protein pgp3 in patients with genital and ocular Chlamydia trachomatis infection

The circulating and cervical B cell responses to Chlamydia trachomatis plasmid protein pgp3 were characterized in children and adults with ocular or genital chlamydial infection using the enzyme-linked immunospot assay (ELISPOT) and ELISA. No pgp3-specific ASCs were detected in healthy controls, but predominantly IgA ASCs were detected in UK adults with uncomplicated cervicitis or urethritis (P = 0.03, 0.019). In patients with extragenital complications or pelvic inflammatory disease a mixed response with more IgG and IgM ASCs was evident, suggesting a breach of mucosal immune compartmentalization with more extensive infection. In women with chlamydial cervicitis, ASCs secreting predominantly IgA, but also IgG, to pgp3 were present in cervix at presentation, with a frequency 30-50 times higher than blood. Cervical ASC numbers, especially IgG, fell markedly six weeks after antibiotic treatment. We detected principally IgA pgp3-specific antibody secreting cells (ASCs) in children resident in a Gambian endemic area, with a trend towards suppression of IgA responses during intense trachomatous inflammation (P = 0.06), as previously reported for other chlamydial antigens, and in keeping with the findings in genital disease. These data provide a rationale for further studies of immune responses to pgp3 in humans and animal models of chlamydia-induced disease, and its potential use in diagnostic assays and protective immunization strategies.