Important and novel roles for neuropeptide Y (NPY) signaling in the control of bone homeostasis have recently been identified, with deletion of either the Y1 or Y2 receptors resulting in a ...generalized increase in bone formation. Whereas the Y2 receptor‐mediated anabolic response is mediated by a hypothalamic relay, the Y1‐mediated response is likely mediated by osteoblastic Y1 receptors. The presence of Y1 receptors on osteoblasts and various other peripheral tissues suggests that, in addition to neuronal input, circulating factors may also interact with the Y1‐mediated pathways. The skeletal and adipose tissue (peripheral and marrow) responses to Y1 receptor deficiency were examined after (1) leptin deficiency, (2) gonadectomy, and (3) hypothalamic NPY overexpression. Bone formation was consistently increased in intact Y1−/− mice. However, the hypogonadism of gonadectomy or leptin deficiency blocked this anabolism in male Y1−/− mice, whereas females remained unchanged. The Y1‐mediated bone anabolic pathway thus seems to be dependent on the presence of intact androgen signaling. Y1 deficiency also led to increased body weight and/or adiposity in all experimental models, with the exception of male ob/ob, showing a general adipogenic effect of Y1 deficiency that is not dependent on androgens. Interestingly, marrow adipocytes were regulated differently than general adipose depots in these models. Taken together, this interaction represents a novel mechanism for the integration of endocrine and neural signals initiated in the hypothalamus and provides further insight into the coordination of bone and energy homeostasis.
Abstract only
The attaching and effacing (A/E) pathogens enterohemorrhagic
Escherichia coli
and enteropathogenic
E. coli
cause serious diarrheal diseases. These organisms colonize the apices of the ...intestinal mucosa and inject pathogenic effectors into host cells altering sub‐cellular epithelial cell components. During these infections small molecules are released from the cells into the lumen of intestinal tracts, contributing to diarrhea. We investigate the role of gap junctions, a group of intercellular channels involved in the transport of small molecules and water, during A/E pathogen infection. Gap junctions are composed of paired connexon channels; however single connexon hemichannels also exist. Each connexon is formed by connexin (Cx) monomers. Using
Citrobacter rodentium
, a natural murine A/E pathogen, we show that Cx43 protein levels are increased and re‐localized during infection. Cx43 that normally localizes only to the lateral membrane of colonocytes was also localized at the infected cell apices forming functionally open hemichannels. During
C. rodentium
infection, Cx43 mutant mice had abolished diarrheal phenotypes while maintaining the bacterial colonization levels of wild‐type infections. These results provide the first evidence of connexon hemichannel formation to generate diarrhea and provides a novel target for future therapeutics to prevent bacterially‐induced diarrheal disease.
Grant Funding Source
CIHR and NSERC
Invasive and extracellular bacterial pathogens have developed strategies to usurp the endocytic machinery of their host cells. In my research, I studied the mechanism employed by two bacterial ...pathogens, Enteropathogenic E. coli (EPEC), and Francisella tularensis to usurp the endocytic machinery of the host cells. EPEC were found to control the internalization machinery for non-invasive functions, as they use clathrin to generate actin-rich structures that protrude from the cell surface known as pedestals, To elucidate the relationship between EPEC and the host cell clathrin-mediated endocytic machinery, I used a combination of experimental approaches, including fluorescent microscopy, immunoblotting and RNA interference, to examine the influence of an array of clathrin-associated accessory proteins on pedestal formation. Several key clathrin-associated components including CD2AP, Eps15 and epsin were localized at EPEC pedestals and were found to be necessary for pedestal formation, revealing a unique and differential strategy used by this extracellular pathogen to control clathrin endocytic machinery. Ubiquitylation is a post-translational modification process that regulates a broad spectrum of cellular signalling processes in eukaryotic cells, including endocytosis. Consequently, I also investigated the host cell ubiquitylation status during EPEC infections in vitro. I found that the overall abundance of ubiquitin-conjugated proteins was severely diminished. Suppression of ubiquitylation was attributed to an E. coli adherence factor (EAF) iv plasmid found in EPEC strain 2348/69 and was independent of the EPEC chromosome-encoded locus of enterocyte effacement (LEE) and non-LEE (NLE) effectors. Finally, I studied the invasion mechanisms used by the intracellular pathogen Francisella tularensis, a highly infectious bacterial pathogen that causes tularemia. Using an F. tularensis surrogate ( F. novicida) as a model, I demonstrated that this pathogen exploits both clathrin- and cholesterol- mediated endocytosis to gain entry into non-phagocytic cells. In conclusion, I have conducted a comprehensive analysis on how two different bacterial pathogens induce host subcellular alterations and demonstrated how similar endocytic proteins can function in very different manners when controlled by different bacterial pathogens.
Anorexia and weight loss are part of the wasting syndrome of late-stage cancer, are a major cause of morbidity and mortality in cancer, and are thought to be cytokine mediated. Macrophage inhibitory ...cytokine-1 (MIC-1) is produced by many cancers. Examination of sera from individuals with advanced prostate cancer showed a direct relationship between MIC-1 abundance and cancer-associated weight loss. In mice with xenografted prostate tumors, elevated MIC-1 levels were also associated with marked weight, fat and lean tissue loss that was mediated by decreased food intake and was reversed by administration of antibody to MIC-1. Additionally, normal mice given systemic MIC-1 and transgenic mice overexpressing MIC-1 showed hypophagia and reduced body weight. MIC-1 mediates its effects by central mechanisms that implicate the hypothalamic transforming growth factor-b receptor II, extracellular signal-regulated kinases 1 and 2, signal transducer and activator of transcription-3, neuropeptide Y and pro-opiomelanocortin. Thus, MIC-1 is a newly defined central regulator of appetite and a potential target for the treatment of both cancer anorexia and weight loss, as well as of obesity.
Anorexia and weight loss are part of the wasting syndrome of late-stage cancer, are a major cause of morbidity and mortality in cancer, and are thought to be cytokine mediated. Macrophage inhibitory ...cytokine-1 (MIC-1) is produced by many cancers. Examination of sera from individuals with advanced prostate cancer showed a direct relationship between MIC-1 abundance and cancer-associated weight loss. In mice with xenografted prostate tumors, elevated MIC-1 levels were also associated with marked weight, fat and lean tissue loss that was mediated by decreased food intake and was reversed by administration of antibody to MIC-1. Additionally, normal mice given systemic MIC-1 and transgenic mice overexpressing MIC-1 showed hypophagia and reduced body weight. MIC-1 mediates its effects by central mechanisms that implicate the hypothalamic transforming growth factor-beta receptor II, extracellular signal-regulated kinases 1 and 2, signal transducer and activator of transcription-3, neuropeptide Y and pro-opiomelanocortin. Thus, MIC-1 is a newly defined central regulator of appetite and a potential target for the treatment of both cancer anorexia and weight loss, as well as of obesity.
Efficient representation of patients is very important in the healthcare domain and can help with many tasks such as medical risk prediction. Many existing methods, such as diagnostic Cost Groups ...(DCG), rely on expert knowledge to build patient representation from medical data, which is resource consuming and non-scalable. Unsupervised machine learning algorithms are a good choice for automating the representation learning process. However, there is very little research focusing on onpatient-level representation learning directly from medical claims. In this paper, weproposed a novel patient vector learning architecture that learns high quality,fixed-length patient representation from claims data. We conducted several experiments to test the quality of our learned representation, and the empirical results show that our learned patient vectors are superior to vectors learned through other methods including a popular commercial model. Lastly, we provide potential clinical interpretation for using our representation on predictive tasks, as interpretability is vital in the healthcare domain
Campylobacter jejuni is a human pathogen that causes severe diarrhea! disease. However,
our understanding of C. jejuni virulence mechanisms and survival during disease and
transmission remains ...limited. Amino acid ATP Binding Cassette (AA-ABC) transporters in C.
jejuni have been proposed as being important for bacterial physiology and pathogenesis. We
have investigated a novel AA-ABC transporter system, encoded by cj0467-9, by generating
targeted deletions of cj0467 (membrane transport component) and cj0469 (ATPase component)
in C. jejuni 81-176. Analyses described herein have led us to designate these genes paqP and
paqQ, respectively pathogenesis-ssociated glutamine (q) ABC transporter permease () and
ATPase (Q). We found that loss of either component resulted in amino acid uptake defects,
most notably diminished glutamine uptake. Both ΔpaqP and ΔpaqQ mutants also exhibited a
surprising but significant increase in short-term intracellular survival in macrophages and
epithelial cells. Levels of resistance to a series of environmental and in vivo stresses were
examined. Both mutants were hyper-resistant to aerobic and oxidative stress, and while ΔpaqP
was also hyper-resistant to heat and osmotic shock, ΔpaqQ was more susceptible than wild-type
to the latter two stresses. Annexin-V staining coupled with fluorescence microscopy revealed
that macrophages infected with the ΔpaqP and ΔpaqQ mutants underwent a lower level of
apoptosis than cells infected with wild-type bacteria. Macrophages infected with the mutant
strains exhibited a transient decrease in ERK activation compared to wild type-infected
macrophages, potentially explaining the reduced apoptosis phenotype. The ΔpaqP mutant did not
exhibit a defect for short or longer term mouse colonization, consistent with its increased stress
survival and diminished host cell damage phenotypes. Collectively, these results demonstrate a
unique correlation between an AA-ABC transporter with bacterial stress tolerance, intracellular
survival, host cell damage, and host signal transduction in response to pathogen infection.
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