The behavioral and cognitive effects of nicotine suggest that nicotinic acetylcholine receptors (nAChRs) participate in central nervous system (CNS) function. Although nAChR subunit messenger RNA (mRNA) and nicotine binding sites are common in the brain, there is little evidence for synapses mediated by nAChRs in the CNS. To test whether, CNS nAChRs might modify rather than mediate transmission, the regulation of excitatory synaptic transmission by these receptors was examined. Nanomolar concentrations of nicotine enhanced both glutamatergic and cholinergic synaptic transmission by activation of presynaptic nAChRs that increased presynaptic [Ca2]i. Pharmacological and subunit deletion experiments reveal that these presynaptic nAChRs include the alpha 7 subunit. These findings reveal that CNS nAChRs enhance fast excitatory transmission, providing a likely mechanism for the complex behavioral effects of nicotine.

Pore-forming toxins are essential to the virulence of a wide variety of pathogenic bacteria. Gardnerella vaginalis is a bacterial species associated with bacterial vaginosis (BV) and its significant adverse sequelae, including preterm birth and acquisition of human immunodeficiency virus. G. vaginalis makes a protein toxin that generates host immune responses and has been hypothesized to be involved in the pathogenesis of BV. We demonstrate that G. vaginalis produces a toxin (vaginolysin [VLY]) that is a member of the cholesteroldependent cytolysin (CDC) family, most closely related to intermedilysin from Streptococcus intermedius. Consistent with this predicted relationship, VLY lyses target cells in a species-specific manner, dependent upon the complement regulatory molecule CD59. In addition to causing erythrocyte lysis, VLY activates the conserved epithelial p38 mitogen-activated protein kinase pathway and induces interleukin-8 production by human epithelial cells. Transfection of human CD59 into nonsusceptible cells renders them sensitive to VLY-mediated lysis. In addition, a single amino acid substitution in the VLY undecapeptide [VLY(P480W)] generates a toxoid that does not form pores, and introduction of the analogous proline residue into another CDC, pneumolysin, significantly decreases its cytolytic activity. Further investigation of the mechanism of action of VLY may improve understanding of the functions of the CDC family as well as diagnosis and therapy for BV.Bacterial vaginosis (BV) is a common and incompletely understood condition associated with adverse outcomes including preterm birth and acquisition of sexually transmitted diseases (10). Alterations of both local host immunity and the genital tract microflora appear to contribute to the pathogenesis of BV (39), and BV can be difficult to eradicate even in the setting of targeted antimicrobial therapy (4). In addition, randomized trials of antibiotics for the prevention of BV-associated preterm birth have not shown consistently beneficial effects, suggesting that host inflammatory responses set in motion early in the course of disease may contribute significantly to the consequences of infection (27).In the 1950s, Leopold (25) and then Gardner and Dukes (14) observed abundant small, pleomorphic gram-variable rods in the genital tract of women with BV. This organism, first called Haemophilus vaginalis (13) and repeatedly renamed as more information about its characteristics became available (reviewed in reference 5), is now classified as Gardnerella vaginalis, the sole member of the genus Gardnerella (16, 30). Phylogenetic analysis based on 16S rRNA places Gardnerella in the gram-positive family Bifidobacteriales. An abundance of G. vaginalis and a paucity of Lactobacillus species are characteristic of a BV-associated microflora, but the relative contribution of G. vaginalis to the pathogenesis of BV is not clear. G. vaginalis is present in essentially all cases of BV but can also be detected in a minority of asymptomatic women (1). Likewise, us...

The ␣3 subunit of the neuronal nicotinic acetylcholine receptor is widely expressed in autonomic ganglia and in some parts of the brain. The ␣3 subunit can form heteromultimeric ion channels with other ␣ subunits and with ␤2 and ␤4 subunits, but its function in vivo is poorly understood. We prepared a null mutation for the ␣3 gene by deletion of exon 5 and found that homozygous (؊͞؊) mice lacked detectable mRNA on Northern blotting. The ؊͞؊ mice survive to birth but have impaired growth and increased mortality before and after weaning. The ؊͞؊ mice have extreme bladder enlargement, dribbling urination, bladder infection, urinary stones, and widely dilated ocular pupils that do not contract in response to light. Detailed histological studies of ؊͞؊ mice revealed no significant abnormalities in brain or peripheral tissues except urinary bladder, where inf lammation was prominent. Ganglion cells and axons were present in bladder and bowel. Bladder strips from ؊͞؊ mice failed to contract in response to 0.1 mM nicotine, but did contract in response to electrical field stimulation or carbamoylcholine. The number of acetylcholine-activated single-channel currents was severely reduced in the neurons of superior cervical ganglia in ؊͞؊ mice with five physiologically distinguishable nicotinic acetylcholine receptor subtypes with different conductance and kinetic properties in wild-type mice, all of which were reduced in ؊͞؊ mice. The findings in the ␣3-null mice suggest that this subunit is an essential component of the nicotinic receptors mediating normal function of the autonomic nervous system. The phenotype in ؊͞؊ mice may be similar to the rare human genetic disorder of megacystismicrocolon-intestinal hypoperistalsis syndrome.The neuronal nicotinic acetylcholine (ACh) receptor (nAChR) gene family consists of eight ␣ subunits (␣2-␣9) and three ␤ subunits (␤2-␤4), each containing four membranespanning domains (1-4). Expression studies in Xenopus oocytes have shown that any one of the ␣2, ␣3, or ␣4 subunits in combination with either ␤2 or ␤4 can produce functional receptors (2, 4-6). Diverse combinations of subunits occur, and even a single population of neurons can express multiple classes of nAChRs (7-9). The ␣3 subunit is widely expressed in autonomic ganglia and in some parts of the brain in multiple organisms (1, 2, 10-13). Although the role of ␣3-containing nAChRs in synaptic transmission in the central nervous system is not known, presynaptic receptors have been implicated in the modulation of the release of dopamine, norepinephrine, and glutamate (13-16).In the peripheral autonomic nervous system, efferent signals are relayed by both sympathetic and parasympathetic ganglia. The ␣3 subunit is the predominant ␣ gene expressed in these ganglia in the chicken (17). Functional deletion of the ␣3 subunit by antisense oligomers eliminated specific subtypes of channels expressed by chicken sympathetic neurons (8). In rat trigeminal sensory neurons, ␣3␤4 is the principal subtype (18). The ␣3 subunit is expressed...

Transcripts for the beta2 and the beta4 nicotinic acetylcholine receptor (nAChR) subunits are found throughout the CNS and the peripheral nervous system. These two beta subunits can form heteromultimeric channels with any of the alpha2, alpha3, alpha4, or alpha5 subunits in heterologous expression systems. Nonetheless, the subunit composition of native nAChRs and the role of different nAChR subtypes in vivo remain unclear. We prepared null mutations for the beta2 and the beta4 genes and bred beta2-/-beta4-/- mice by mating mice of identical beta2-/-beta4+/- or beta2+/-beta4-/- genotype. The beta2-/- and the beta4-/- single-mutant mice grow to adulthood with no visible phenotypic abnormalities. The beta2-/-beta4-/- double mutants survive to birth but have impaired growth and increased perinatal mortality. They also present enlarged bladders with dribbling urination and develop urinary infection and bladder stones. The ocular pupils are widely dilated and do not constrict in response to light. Histological studies revealed no significant abnormalities of brain or peripheral tissues except for hyperplasia in the bladder mucosa of beta4-/- and beta2-/-beta4-/- mutants. Bladder strips from beta2-/-beta4-/- mice did not respond to nicotine but contracted when stimulated with a muscarinic agonist or electric field stimulation. Bladder strips from beta4 mutants did not respond to nicotine despite the absence of major bladder dysfunction in vivo. Acetylcholine-activated whole-cell currents were absent in superior cervical ganglion neurons from beta2-/-beta4-/- mice and reduced in neurons from beta4-/- mice. Although there is apparent redundancy and a superficially normal phenotype in beta2-/- and beta4-/- mice, physiological studies indicate major deficits in the beta4-/- mice. Our previous description of a similar phenotype in alpha3-/- mice and the current data suggest that the alpha3 and the beta4 subunits are major components in autonomic nAChRs. The phenotype of the beta2-/-beta4-/- and alpha3-/- mice resembles the autosomal recessive megacystis-microcolon-hypoperistalsis syndrome in humans.

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Preterm birth and fetal demise are likely the direct result of toxin-induced damage and inflammation rather than differences in efficiency of ascension into the upper genital tract. These data demonstrate a distinct contribution of βH/C to GBS chorioamnionitis and subsequent fetal infection in vivo and showcase a model for this most proximal step in GBS pathogenesis.

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Defective placentation and subsequent placental insufficiency lead to maternal and fetal adverse pregnancy outcome (APO), but their pathologic mechanisms are unclear, and treatment remains elusive. The mildly hypertensive BPH/5 mouse recapitulates many features of human APO with pregnancies characterized by fetal loss, growth restriction, abnormal placental development, and defects in maternal decidual arteries. Using this model, we show that recruitment of neutrophils triggered by complement activation at the maternal fetal interface leads to elevation in local TNF-α levels, reduction of the essential angiogenic factor VEGF and, ultimately, abnormal placentation and fetal death. Blockade of complement with inhibitors specifically targeted to sites of complement activation, depletion of neutrophils, or blockade of TNF-α improves spiral artery remodeling and rescues pregnancies. These data underscore the importance of innate immune system activation in the pathogenesis of placental insufficiency and identify novel methods for treatment of pregnancy loss mediated by abnormal placentation.