Anal fissure

Anal fissures are present in about 10-15% of proctological patients. The cause of the illness is unknown, but is probably multifactorial. Cardinal symptoms are pain during and after defecation, as well as persistent sphincter spasm. In most cases an acute anal fissure heals spontaneously or with adequate conservative therapy. Chronic anal fissures can be cured in some cases by conservative treatment. Where there is treatment resistance, surgical cleansing is necessary.

O3 uptake and drought stress effects on carbon acquisition of ponderosa pine in natural stands

• The effect of O₃ exposure or uptake on carbon acquisition (net assimilation (A) or gross photosynthesis (P_g )), with and without drought stress, is reported here in 40-yr-old-ponderosa pine (Pinus ponderosa) trees. • Maximum daily gas exchange was measured monthly for 12 trees at four sites differing in pollutant exposure over two growing seasons with above- and below-average annual precipitation. Gas exchange measures were estimated between sampling periods using a generalized additive regression model. • Both A and P_g generally declined with cumulative O₃ exposure or uptake at all sites. As a response variable, P_g was slightly more sensitive than A to cumulative O₃ exposure. As a metric, O₃ uptake vs exposure permitted slightly better statistical resolution of seasonal response between sites. • The effect of late summer drought stress was statistically significant only at the moderate pollution site, and combined synergistically with O₃ exposure or uptake to reduce P_g . The general additive model allows the user to define a deleterious level of cumulative O₃ exposure or uptake, and to quantitatively assess biological response.

Diversity and phylogeny of gephyrin: tissue-specific splice variants, gene structure, and sequence similarities to molybdenum cofactor-synthesizing and cytoskeleton-associated proteins

Gephyrin is essential for both the postsynaptic localization of inhibitory neurotransmitter receptors in the central nervous system and the biosynthesis of the molybdenum cofactor (Moco) in different peripheral organs. Several alternatively spliced gephyrin transcripts have been identified in rat brain that differ in their 5' coding regions. Here, we describe gephyrin splice variants that are differentially expressed in non-neuronal tissues and different regions of the adult mouse brain. Analysis of the murine gephyrin gene indicates a highly mosaic organization, with eight of its 29 exons corresponding to the alternatively spliced regions identified by cDNA sequencing. The N- and C-terminal domains of gephyrin encoded by exons 3-7 and 16-29, respectively, display sequence similarities to bacterial, invertebrate, and plant proteins involved in Moco biosynthesis, whereas the central exons 8, 13, and 14 encode motifs that may mediate oligomerization and tubulin binding. Our data are consistent with gephyrin having evolved from a Moco biosynthetic protein by insertion of protein interaction sequences.

Distribution of the receptor-anchoring protein gephyrin in the rat dentate gyrus and changes following entorhinal cortex lesion

We analyzed the distribution of the receptor-anchoring protein gephyrin in the normal and deafferented rat dentate gyrus to investigate whether the expression of this postsynaptic protein is altered in response to the formation of new synaptic contacts. Confocal microscopy and digital image analysis revealed that in normal dentate gyrus immunolabeling was most prominent in the outer molecular layer and decreased successively in the direction of the granule cell layer. Simultaneous immunolabeling for gephyrin and cell-specific markers showed that granule cells and parvalbumin-positive interneurons express gephyrin. Large, intensely stained, gephyrin-positive clusters were distributed along distinct dendrites, and most of them were positive for parvalbumin. Calbindin-immunostained dendrites were associated with smaller, gephyrin-positive clusters. Lesion of the medial entorhinal cortex leads to deafferentiation of the middle molecular layer which resulted in an increased gephyrin immunoreactivity. These changes were due to a significantly increased concentration of the very small gephyrin-positive clusters. Parvalbumin-positive dendrites did not display any increase in co-localizing gephyrin-positive structures. The altered immunolabeling pattern persisted until 12 weeks after lesion, a time when the process of synaptic reorganization is complete. Our findings suggest that synaptogenesis following deafferentiation results in a cell-specific redistribution of gephyrin immunoreactivity at specific inhibitory synapses.

Establishing health state valuations for disease specific states: an example from heart disease

This study considers the feasibility of defining a QALY from disease-specific data using the New York Heart Association (NYHA) classification of heart failure. The study derives health state values for the four different NYHA classifications of disease progression using the time trade-off (TTO) instrument associated with the five dimensional (EQ-5D) health state valuation method. Consistent mappings between the disease classification and the chosen QALY instrument are found. With this being the case, the assumption of constant proportionality, which is necessary to define the QALY as an acceptable measure of health related preferences, is considered. It is found that constant proportionality does not hold across the more severe health states, thus questioning the use of QALYs as representing cardinal preference structures.

Collybistin, a newly identified brain-specific GEF, induces submembrane clustering of gephyrin

The formation of postsynaptic GABAA and glycine receptor clusters requires the receptor-associated peripheral membrane protein gephyrin. Here we describe two splice variants of a novel gephyrin-binding protein, termed collybistin I and II, which belong to the family of dbl-like GDP/GTP exchange factors (GEFs). Co-expression of collybistin II with gephyrin induced the formation of submembrane gephyrin aggregates that accumulate hetero-oligomeric glycine receptors. Our data suggest that collybistin II regulates the membrane deposition of gephyrin by activating a GTPase of the Rho/Rac family. Therefore, this protein may be an important determinant of inhibitory postsynaptic membrane formation and plasticity.

Assembly of signaling machinery at the postsynaptic membrane

The postsynaptic membrane and the subsynaptic cell compartment are specialized for inter- and intracellular signaling. Recent work has focused on the role of synaptic activity in regulating the surface distribution of neurotransmitter receptors. In addition, several components of secondary signaling pathways involved in the long-term regulation of synaptic efficacy have been identified.

Interaction of RAFT1 with gephyrin required for rapamycin-sensitive signaling

RAFT1 (rapamycin and FKBP12 target 1; also called FRAP or mTOR) is a member of the ATM (ataxia telangiectasia mutated)-related family of proteins and functions as the in vivo mediator of the effects of the immunosuppressant rapamycin and as an important regulator of messenger RNA translation. In mammalian cells RAFT1 interacted with gephyrin, a widely expressed protein necessary for the clustering of glycine receptors at the cell membrane of neurons. RAFT1 mutants that could not associate with gephyrin failed to signal to downstream molecules, including the p70 ribosomal S6 kinase and the eIF-4E binding protein, 4E-BP1. The interaction with gephyrin ascribes a function to the large amino-terminal region of an ATM-related protein and reveals a role in signal transduction for the clustering protein gephyrin.

Structure and functions of inhibitory and excitatory glycine receptors

The strychnine-sensitive glycine receptor (GlyR) is a pentameric chloride channel protein that exists in several developmentally and regionally regulated isoforms in the CNS. These result from the differential expression of four genes encoding different variants (alpha 1-alpha 4) of the ligand-binding subunit of the GlyR. Their assembly with the structural beta subunit is governed by "assembly cassettes" within the extracellular domains of these proteins and creates chloride channels of distinct conductance properties. GlyR gating is potentiated by Zn2+, a metal ion co-released with different neurotransmitters. Site-directed mutagenesis has unraveled major determinants of agonist binding and Zn2+ potentiation. During development, glycine receptors mediate excitation that results in Ca2+ influx and neurotransmitter release. Ca2+ influx triggered by the activation of embryonic GlyRs is required for the synaptic localization of the GlyR and its anchoring protein gepyhrin. In the adult, mutations in GlyR-subunit genes result in motor disorders. The spastic and spasmodic phenotypes in mouse as well as human hereditary startle disease will be discussed.

Hydrophobic interactions mediate binding of the glycine receptor beta-subunit to gephyrin

Glycine receptors (GlyRs) are ligand-gated chloride channel proteins composed of alpha- and beta-subunits. GlyRs are located to and anchored at postsynaptic sites by the receptor-associated protein gephyrin. Previous work from our laboratory has identified a core motif for gephyrin binding in the cytoplasmic loop of the GlyR beta-subunit. Here, we localized amino acid residues implicated in gephyrin binding by site-directed mutagenesis. In a novel transfection assay, a green fluorescent protein-gephyrin binding motif fusion protein was used to monitor the consequences of amino acid substitutions for beta-subunit interaction with gephyrin. Only multiple, but not single, replacements of hydrophobic side chains abolished the interaction between the two proteins. Our data are consistent with gephyrin binding being mediated by the hydrophobic side of an imperfect amphipathic helix.

The neurotransmitter receptor-anchoring protein gephyrin reconstitutes molybdenum cofactor biosynthesis in bacteria, plants, and mammalian cells

The molybdenum cofactor (Moco), a highly conserved pterin compound complexing molybdenum, is required for the enzymatic activities of all molybdenum enzymes except nitrogenase. Moco is synthesized by a unique and evolutionarily old pathway that requires the activities of at least six gene products. Some of the proteins involved in bacterial, plant, and invertebrate Moco biosynthesis show striking homologies to the primary structure of gephyrin, a polypeptide required for the clustering of inhibitory glycine receptors in postsynaptic membranes in the rat central nervous system. Here, we show that gephyrin binds with high affinity to molybdopterin, the metabolic precursor of Moco. Furthermore, gephyrin expression can reconstitute Moco biosynthesis in Moco-deficient bacteria, a molybdenum-dependent mouse cell line, and a Moco-deficient plant mutant. Conversely, inhibition of gephyrin expression by antisense RNA expression in cultured murine cells reduces their Moco content significantly. These data indicate that in addition to clustering glycine receptors, gephyrin also is involved in Moco biosynthesis and illustrate the remarkable conservation of its function in Moco biosynthesis throughout phylogeny.

Incorporation of a gephyrin-binding motif targets NMDA receptors to gephyrin-rich domains in HEK 293 cells

The peripheral membrane protein gephyrin is essential for the postsynaptic localization of inhibitory glycine receptors (GlyRs). Binding of gephyrin to the GlyR beta subunit is mediated by a sequence motif located in the intracellular loop region connecting transmembrane segments 3 and 4. Here, insertion of this binding motif is shown to alter the subcellular distribution of an excitatory neurotransmitter receptor in transfected mammalian cells. Upon coexpression with gephyrin, a mutant N-methyl-D-aspartate (NMDA) receptor containing NMDA receptor 1 (NR1) subunits which harboured a gephyrin-binding motif within its cytoplasmic tail region, was targeted to intracellular gephyrin-rich domains, as previously observed for the GlyR beta subunit. Our data indicate that a gephyrin-binding motif located in a cytoplasmic domain of an integral membrane protein suffices for routing to gephyrin-rich domains.

The M-cadherin catenin complex interacts with microtubules in skeletal muscle cells: implications for the fusion of myoblasts

M-cadherin, a calcium-dependent intercellular adhesion molecule, is expressed in skeletal muscle cells. Its pattern of expression, both in vivo and in cell culture as well as functional studies, have implied that M-cadherin is important for skeletal muscle development, in particular the fusion of myoblasts into myotubes. M-cadherin formed complexes with the catenins in skeletal muscle cells similar to E-cadherin in epithelial cells. This suggested that the muscle-specific function of the M-cadherin catenin complex might be mediated by additional interactions with yet unidentified cellular components, especially cytoskeletal elements. These include the microtubules which also have been implicated in the fusion process of myoblasts. Here we present evidence that the M-cadherin catenin complex interacts with microtubules in myogenic cells by using three independent experimental approaches. (1) Analysis by laser scan microscopy revealed that the destruction of microtubules by nocodazole leads to an altered cell surface distribution of M-cadherin in differentiating myogenic cells. In contrast, disruption of actin filaments had little effect on the surface distribution of M-cadherin. (2) M-cadherin antibodies coimmunoprecipitated tubulin from extracts of nocodazole-treated myogenic cells but not of nocodazole-treated epithelial cells ectopically expressing M-cadherin. Vice versa, tubulin antibodies coimmunoprecipitated M-cadherin from extracts of nocodazole-treated myogenic cells but not of nocodazole-treated M-cadherin-expressing epithelial cells. (3) M-cadherin and the catenins, but not a panel of control proteins, were copolymerized with tubulin from myogenic cell extracts even after repeated cycles of assembly and disassemly of tubulin. Moreover, neither M-cadherin nor E-cadherin could be found in a complex with microtubules in epithelial cells ectopically expressing M-cadherin. Our data are consistent with the idea that the interaction of M-cadherin with microtubules might be essential to keep the myoblasts aligned during fusion, a process in which both M-cadherin and microtubules have been implicated.

Dual requirement for gephyrin in glycine receptor clustering and molybdoenzyme activity

Glycine receptors are anchored at inhibitory chemical synapses by a cytoplasmic protein, gephyrin. Molecular cloning revealed the similarity of gephyrin to prokaryotic and invertebrate proteins essential for synthesizing a cofactor required for activity of molybdoenzymes. Gene targeting in mice showed that gephyrin is required both for synaptic clustering of glycine receptors in spinal cord and for molybdoenzyme activity in nonneural tissues. The mutant phenotype resembled that of humans with hereditary molybdenum cofactor deficiency and hyperekplexia (a failure of inhibitory neurotransmission), suggesting that gephyrin function may be impaired in both diseases.

Agonist and antagonist-dependent internalization of the human vasopressin V2 receptor

In this report we demonstrate that in HEK293 cells stably expressing the human V2 vasopressin receptor, ligand-induced internalization of the hormone receptor occurs via the clathrin-dependent pathway. Studies of receptor trafficking either by direct visualization of the V2 receptor by confocal microscopy or binding experiments show a rapid internalization (half-time 6-7 min). Blocking of the clathrin-dependent pathway by hypertonic sucrose increased vasopressin-induced cellular cAMP production and decreased the desensitization of the V2 receptor-adenylyl cyclase system. Thus, internalization appears to be a major regulatory mechanism terminating vasopressin action in HEK293 cells. Two antagonists of the vasopressin V2 receptor exerted different effects on receptor internalization, as determined by confocal fluorescence microscopy. The nonpeptidic antagonist OPC31260 did not induce any visible receptor internalization, whereas the peptidic antagonist d(CH2)5[D-Tyr(Et)2,Val4,Lys8,Tyr-NH29]VP induced a slow but substantial receptor internalization. These results suggest that long-term treatment with peptidic V2 receptor antagonists might lead to desensitization.

Simultaneous in vivo spectral editing and water suppression

Water suppression is typically performed in vivo by exciting the longitudinal magnetization in combination with dephasing, or by using frequency-selective coherence generation. MEGA, a frequency-selective refocusing technique, can be placed into any pulse sequence element designed to generate a Hahn spin-echo or stimulated echo, to dephase transverse water coherences with minimal spectral distortions. Water suppression performance was verified in vivo using stimulated echo acquisition mode (STEAM) localization, which provided water suppression comparable with that achieved with four selective pulses in 3,1-DRYSTEAM. The advantage of the proposed method was exploited for editing J-coupled resonances. Using a double-banded pulse that selectively inverts a J-coupling partner and simultaneously suppresses water, efficient metabolite editing was achieved in the point resolved spectroscopy (PRESS) and STEAM sequences in which MEGA was incorporated. To illustrate the efficiency of the method, the detection of gamma-aminobutyric acid (GABA) was demonstrated, with minimal contributions from macromolecules and overlying singlet peaks at 4 T. The estimated occipital GABA concentration was consistent with previous reports, suggesting that editing for GABA is efficient when based on MEGA at high field strengths.

Simultaneous in vivo spectral editing and water suppression

Water suppression is typically performed in vivo by exciting the longitudinal magnetization in combination with dephasing, or by using frequency-selective coherence generation. MEGA, a frequency-selective refocusing technique, can be placed into any pulse sequence element designed to generate a Hahn spin-echo or stimulated echo, to dephase transverse water coherences with minimal spectral distortions. Water suppression performance was verified in vivo using stimulated echo acquisition mode (STEAM) localization, which provided water suppression comparable with that achieved with four selective pulses in 3,1-DRYSTEAM. The advantage of the proposed method was exploited for editing J-coupled resonances. Using a double-banded pulse that selectively inverts a J-coupling partner and simultaneously suppresses water, efficient metabolite editing was achieved in the point resolved spectroscopy (PRESS) and STEAM sequences in which MEGA was incorporated. To illustrate the efficiency of the method, the detection of gamma-aminobutyric acid (GABA) was demonstrated, with minimal contributions from macromolecules and overlying singlet peaks at 4 T. The estimated occipital GABA concentration was consistent with previous reports, suggesting that editing for GABA is efficient when based on MEGA at high field strengths.

Simultaneous in vivo spectral editing and water suppression

Water suppression is typically performed in vivo by exciting the longitudinal magnetization in combination with dephasing, or by using frequency-selective coherence generation. MEGA, a frequency-selective refocusing technique, can be placed into any pulse sequence element designed to generate a Hahn spin-echo or stimulated echo, to dephase transverse water coherences with minimal spectral distortions. Water suppression performance was verified in vivo using stimulated echo acquisition mode (STEAM) localization, which provided water suppression comparable with that achieved with four selective pulses in 3,1-DRYSTEAM. The advantage of the proposed method was exploited for editing J-coupled resonances. Using a double-banded pulse that selectively inverts a J-coupling partner and simultaneously suppresses water, efficient metabolite editing was achieved in the point resolved spectroscopy (PRESS) and STEAM sequences in which MEGA was incorporated. To illustrate the efficiency of the method, the detection of gamma-aminobutyric acid (GABA) was demonstrated, with minimal contributions from macromolecules and overlying singlet peaks at 4 T. The estimated occipital GABA concentration was consistent with previous reports, suggesting that editing for GABA is efficient when based on MEGA at high field strengths.

Choice of NSAID and management strategy in rheumatoid arthritis and osteoarthritis. The impact on costs and outcomes in the UK

OBJECTIVE

Although nonsteroidal anti-inflammatory drugs (NSAIDs) are an effective therapy for rheumatoid arthritis, they are associated with significant adverse effects, the management of which imposes additional costs on the healthcare system. Prescribing NSAIDs which have a lower risk of major adverse effects as the first-line NSAID for patients with rheumatoid arthritis and osteoarthritis may be expected to lead to an improvement in clinical outcomes and reduce overall treatment costs. This analysis examines data from a published randomised controlled trial of 5 NSAIDs to explore these hypotheses.

DESIGN AND SETTING

Data from a clinical trial comparing 5 NSAIDs were combined with published cost data to construct 2 clinical decision models, reflecting alternative approaches to the management of major and minor adverse effects in the UK.

INTERVENTIONS

The 5 NSAIDs evaluated in the analysis were nabumetone, diclofenac, ibuprofen, piroxicam and naproxen, although only the results for ibuprofen and nabumetone are reported.

MAIN OUTCOME MEASURES AND RESULTS

The total cost of care per patient receiving nabumetone was estimated to be between 25 pounds sterling (Pound) and 41 Pounds more expensive than ibuprofen. In a hypothetical cohort of 100,000 patients, there were between 690 and 821 more major adverse effects using ibuprofen than nabumetone. The cost per life-year gained (LYG) from using nabumetone rather than ibuprofen ranged between 1880 Pounds and 2517 Pounds (1995 values), depending upon the management of adverse effects.

CONCLUSIONS

These results indicate that: (i) prescribing the newer, currently more expensive, NSAIDs will not necessarily lead to cost savings; (ii) the management of adverse effects can have a significant impact on costs; and (iii) the additional cost may be justifiable in terms of the mortality and morbidity gains associated with the new lower-risk NSAIDs.

Molecular mechanisms that underlie structural and functional changes at the postsynaptic membrane during synaptic plasticity

The synaptic plasticity that is addressed in this review follows neurodegeneration in the brain and thus has both structural as well as functional components. The model of neurodegeneration that has been selected is the kainic acid lesioned hippocampus. Degeneration of the CA3 pyramidal cells results in a loss of the Schaffer collateral afferents innervating the CA1 pyramidal cells. This is followed by a period of structural plasticity where new synapses are formed. These are associated with changes in the numbers and shapes of spines as well as changes in the morphometry of the dendrites. It is suggested that this synaptogenesis is responsible for an increase in the ratio of NMDA to AMPA receptors mediating excitatory synaptic transmission at these synapses. Changes in the temporal and spatial properties of these synapses resulted in an altered balance between LTP and LTD. These properties together with a reduction in the inhibitory drive increased the excitability of the surviving CA1 pyramidal cells which in turn triggered epileptiform bursting activity. In this review we discuss the insights that may be gained from studies of the underlying molecular machinery. Developments in one of the collections of the cogs in this machinery has been summarized through recent studies characterizing the roles of neural recognition molecules in synaptic plasticity in the adult nervous systems of vertebrates and invertebrates. Such investigations of neural cell adhesion molecules, cadherins and amyloid precursor protein have shown the involvement of these molecules on the morphogenetic level of synaptic changes, on the one hand, and signal transduction effects, on the other. Further complex cogs are found in the forms of the low-density lipoprotein receptor (LDL-R) family of genes and their ligands play pivotal roles in the brain development and in regulating the growth and remodelling of neurones. Evidence is discussed for their role in the maintenance of cognitive function as well as Alzheimer's. The molecular mechanisms responsible for the clustering and maintenance of transmitter receptors at postsynaptic sites are the final cogs in the machinery that we have reviewed. Postsynaptic densities (PSD) from excitatory synapses have yielded many cytoskeletal proteins including actin, spectrin, tubulin, microtubule-associated proteins and calcium/calmodulin-dependent protein kinase II. Isolated PSDs have also been shown to be enriched in AMPA, kainate and NMDA receptors. However, recently, a new family of proteins, the MAGUKs (for membrane-associated guanylate kinase) has emerged. The role of these proteins in clustering different NMDA receptor subunits is discussed. The MAGUK proteins are also thought to play a role in synaptic plasticity mediated by nitric oxide (NO). Both NMDA and non-NMDA receptors are highly clustered at excitatory postsynaptic sites in cortical and hippocampal neurones but have revealed differences in their choice of molecular components. Both GABAA and glycine (Gly) receptors mediate synaptic inhibition in the brain and spinal cord. Whilst little is known about how GABAA receptors are localized in the postsynaptic membrane, considerable progress has been made towards the elucidation of the molecular mechanisms underlying the formation of Gly receptors. It has been shown that the peripheral membrane protein gephyrin plays a pivotal role in the formation of Gly receptor clusters most likely by anchoring the receptor to the subsynaptic cytoskeleton. Evidence for the distribution as well as function of gephyrin and Gly receptors is discussed. Postsynaptic membrane specializations are complex molecular machinery subserving a multitude of functions in the proper communication between neurones. Despite the fact that only a few key players have been identified it will be a fascinating to watch the story as to how they contribute to structural and functional plasticity unfold.

First one in, last one out: the role of gabaergic transmission in generation and degeneration

This paper is the result of discussions between scientists working in widely separated areas, united by an interest in the hippocampus. The discussions focused on the possible role of GABA in the development and maturation of the hippocampus and in neurodegeneration in Alzheimer's disease (AD). GABA neurons are among the first to differentiate in the hippocampus and the properties of GABA neurotransmission in the developing hippocampus are distinct from those in the adult. GABAergic transmission may play a role in the clustering and maturation of GABA receptors, as well as of receptors for other neurotransmitters. The development and maturation of synaptic connections involves changes in the organization of the cytoskeleton, and mechanical force generation is probably required to establish appropriate points of contact. This generation of force may require coupling of specific receptors to the cytoskeleton through specialized proteins. In AD, much of the developmental process is progressively unraveled in the hippocampus, as afferent fibers, most notably from entorhinal excitatory neurons and from basal forebrain cholinergic cells, degenerate. This denervation undoubtedly has consequences for receptor systems, dendritic morphology and the underlying cytoskeleton. GABA neurons remain in the AD hippocampus, and may actually contribute to abnormal firing and degeneration of remaining pyramidal neurons. This attempt to bring together data from different areas of research has allowed the development of a scheme which identifies significant specific gaps in our knowledge, which could be readily filled by focused experimental work.

Localization of the clustering protein gephyrin at GABAergic synapses in the main olfactory bulb of the rat

The tubulin-binding protein gephyrin is essential for the formation of postsynaptic glycine-receptor clusters in cultured spinal neurons. In addition, there is increasing evidence that gephyrin can also be present at nonglycinergic synapses. Here we analyzed immunocytochemically the subcellular localization of gephyrin in the main olfactory bulb of the rat and compared its distribution with that of gamma-aminobutyric acid (GABA) and of two major GABA(A)-receptor subunits. Gephyrin was selectively localized to the postsynaptic side of symmetric synaptic junctions, where the presynaptic terminals contained GABA. Moreover, gephyrin colocalized extensively with the alpha1 and gamma2 subunits of the GABA(A) receptor. In contrast, gephyrin was not detected at presumed glutamatergic synapses. These results indicate that gephyrin is not uniquely associated with glycine receptors, but can also be found at distinct GABAergic synapses. Thus, they raise the possibility that gephyrin is involved in anchoring certain GABA(A)-receptor subtypes in the postsynaptic membrane.

CpG motifs in bacterial DNA activate leukocytes through the pH-dependent generation of reactive oxygen species

B cells and monocytes endocytose DNA into an acidified intracellular compartment. If this DNA contains unmethylated CpG dinucleotides in particular base contexts (CpG motifs), these leukocytes are rapidly activated. We now show that both B cell and monocyte-like cell line responses to DNA containing CpG motifs (CpG DNA) are sensitive to endosomal acidification inhibitors; they are completely blocked by bafilomycin A, chloroquine, and monensin. The specificity of these inhibitors is demonstrated by their failure to prevent responses to LPS, PMA, or ligation of CD40 or IgM. Acidification of endosomal CpG DNA is coupled to the rapid generation of intracellular reactive oxygen species. The CpG DNA-induced reactive oxygen species burst is linked to the degradation of IkappaB and the activation of NFkappaB, which induces leukocyte gene transcription and cytokine secretion. These studies demonstrate a novel pathway of leukocyte activation triggered by CpG motifs.