Immunorecognition of Streptococcus mutans secreted proteins protects against caries by limiting tooth adhesion

INTRODUCTION

Childhood caries, a prevalent chronic disease, affects 60-90 % of children in industrialized regions, leading to lesions in both primary and permanent teeth. This condition precipitates hospital admissions, emergency room visits, elevated treatment costs, and missed school days, thereby impeding the child's academic engagement and increasing the likelihood of caries into adulthood. Despite multiple identified risk factors, significant interpersonal variability remains unexplained. The immune system generates a unique antibody repertoire, essential for maintaining a balanced and healthy oral microbiome. Streptococcus mutans is a primary contributor to the development of caries.

METHODS

Employing mass spectrometry, we investigated the S. mutans proteins targeted by antibodies in children both with and without caries, delineating a fundamental suite of proteins discernible by the immune systems of a majority of individuals. Notably, this suite was enriched with proteins pivotal for bacterial adhesion. To ascertain the physiological implications of these discoveries, we evaluated the efficacy of saliva in thwarting S. mutans adherence to dental surfaces.

RESULTS

Antibodies in most children recognized a core set of ten S. mutans proteins, with additional proteins identified in some individuals. There was no significant difference in the proteins identified by children with or without caries, but there was variation in antibody binding intensity to some proteins. Functionally, saliva from caries-free individuals, but not children with caries, was found to hinder the binding of S. mutans to teeth. These findings delineate the S. mutans proteome targeted by the immune system and suggest that the inhibition of bacterial adherence to teeth is a primary mechanism employed by the immune system to maintain oral balance and prevent caries formation.

CONCLUSIONS

These findings enhance our knowledge of the immune system's function in oral health maintenance and caries prevention, shedding light on how immunoglobulins interact with S. mutans proteins.

CLINICAL SIGNIFICANCE

Targeting S. mutans proteins implicated in bacterial adhesion could be a promising strategy for preventing childhood caries.

MC3R links nutritional state to childhood growth and the timing of puberty

The state of somatic energy stores in metazoans is communicated to the brain, which regulates key aspects of behaviour, growth, nutrient partitioning and development1. The central melanocortin system acts through melanocortin 4 receptor (MC4R) to control appetite, food intake and energy expenditure2. Here we present evidence that MC3R regulates the timing of sexual maturation, the rate of linear growth and the accrual of lean mass, which are all energy-sensitive processes. We found that humans who carry loss-of-function mutations in MC3R, including a rare homozygote individual, have a later onset of puberty. Consistent with previous findings in mice, they also had reduced linear growth, lean mass and circulating levels of IGF1. Mice lacking Mc3r had delayed sexual maturation and an insensitivity of reproductive cycle length to nutritional perturbation. The expression of Mc3r is enriched in hypothalamic neurons that control reproduction and growth, and expression increases during postnatal development in a manner that is consistent with a role in the regulation of sexual maturation. These findings suggest a bifurcating model of nutrient sensing by the central melanocortin pathway with signalling through MC4R controlling the acquisition and retention of calories, whereas signalling through MC3R primarily regulates the disposition of calories into growth, lean mass and the timing of sexual maturation.

Maternal obesity causes fetal hypothalamic insulin resistance and disrupts development of hypothalamic feeding pathways

Objective

Perinatal exposure to maternal obesity results in predisposition of offspring to develop obesity later in life. Increased weight gain in offspring exposed to maternal obesity is usually associated with hyperphagia, implicating altered central regulation of food intake as a cause. We aimed to define how maternal obesity impacts early development of the hypothalamus to program lasting dysfunction in feeding regulatory pathways.

Methods

Mice offspring of diet-induced obese mothers were compared to the offspring of lean control mothers. We analysed gene expression in the fetal hypothalamus, alongside neurosphere assays to investigate the effects of maternal obesity on neural progenitor cell proliferation in vitro. Western blotting was used to investigate the insulin signalling pathway in the fetal hypothalamus. Characterisation of cell type and neuropeptide profile in adulthood was linked with analyses of feeding behaviour.

Results

There was a reduction in the expression of proliferative genes in the fetal hypothalamus of offspring exposed to maternal obesity. This reduction in proliferation was maintained in vitro when hypothalamic neural progenitor cells were grown as neurospheres. Hypothalamic fetal gene expression and neurosphere growth correlated with maternal body weight and insulin levels. Foetuses of obese mothers showed hypothalamic insulin resistance, which may be causative of reduced proliferation. Furthermore, maternal obesity activated the Notch signalling pathway in neonatal offspring hypothalamus, resulting in decreased neurogenesis. Adult offspring of obese mothers displayed an altered ratio of anorexigenic and orexigenic signals in the arcuate nucleus, associated with an inability to maintain energy homeostasis when metabolically challenged.

Conclusions

These findings show that maternal obesity alters the molecular signature in the developing hypothalamus, which is associated with disrupted growth and development of hypothalamic precursor cells and defective feeding regulation in adulthood. This is the first report of fetal hypothalamic insulin resistance in an obese pregnancy and suggests a mechanism by which maternal obesity causes permanent changes to hypothalamic structure and function.

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Exposure to maternal obesity reduces hypothalamic neural progenitor cell growth.

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Maternal obesity activates hypothalamic Notch signalling and reduces neurogenesis.

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Maternal obesity causes fetal hypothalamic insulin resistance.

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Maternal obesity alters the ratio of anorexigenic/orexigenic signals in ARC.

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Changes in food intake precede increased adiposity in offspring of obese dams.

Preventing stillbirths through improved antenatal recognition of pregnancies at risk due to fetal growth restriction

Most stillbirths used to be categorized as 'unexplained' and were considered, by implication, unavoidable. Recent evidence indicates that they represent a combined challenge for public health and for clinical services. Independent case reviews have found that many deaths are associated with a failure to recognize risk factors and to afford them the appropriate standard of care. The majority of normally formed fetal deaths had preceding, unrecognized intrauterine growth failure. Improved training and adoption of standardized protocols has led to increased antenatal detection of fetal growth restriction, and this in turn has resulted in significant reductions in stillbirths in areas with high uptake of the training programme. A comprehensive, evidence-based growth assessment protocol (GAP) is currently being rolled out across the NHS to implement this strategy for stillbirth prevention.

Bisquaternary dimers of strychnine and brucine. A new class of potent enhancers of antagonist binding to muscarinic M2 receptors

Bisquaternary dimers of strychnine and brucine were synthesized and their allosteric effect on muscarinic acetylcholine M(2) receptors was examined. The compounds retarded the dissociation of the antagonist [(3)H]N-methylscopolamine ([(3)H]NMS) from porcine cardiac cholinoceptors. This action indicated ternary complex formation. All compounds exhibited higher affinity to the allosteric site of [(3)H]NMS-occupied M(2) receptors than the monomeric strychnine and brucine, while the positive cooperativity with NMS was fully maintained. SAR studies revealed the unchanged strychnine ring as an important structural feature for high allosteric potency.

Skilled nursing practice -- a qualitative study of the elements of nursing

An understanding of skilled nursing practice has implications for the identity of nursing in service delivery, and for the learning environment of the developing nurse. Here I report a qualitative study, largely reliant on ethnography, which became a journey of exploration through accounts and descriptions given by nurses in a number of different practice settings. This journey is founded in an understanding of what I have called a phenomenological and psychosocial tradition, recognising the importance of a postmodern influence, which is in tension with a scientific and behavioural tradition. The emergence of four domains of skilled nursing practice in a contextualised narrative would seem to offer justification of assumptions concerning the value of embedded knowledge and intuitive clinical judgement in nursing practice, and lay a foundation for a qualitative study of the developing nurse.

Bisquaternary caracurine V derivatives as allosteric modulators of ligand binding to M2 acetylcholine receptors

The allosteric effect on muscarinic acetylcholine M2 receptors of 11 bisquaternary salts of the Strychnos alkaloid caracurine V was determined. The effect was indicated by the concentration which retarded the rate of dissociation of the antagonist [3H]-N-methylscopolamine from porcine cardiac cholinoceptors by a factor of 2 (EC50). The most potent compounds carry allyl and propargyl substituents, respectively. Introduction of more bulky substituents (e.g., benzyl groups) resulted in a considerably reduced allosteric potency. The wide range of EC50 values (3 nM for R = allyl. 1750 nM for R = 2-naphthyl) suggests a sterically restricted binding pocket. Molecular modeling studies indicated that the caracurine V ring system satisfies the pharmacophore model for the allosteric interaction.