Browsing by Author "Dr. Kenneth B. Adler, Committee Member"

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    Contribution of Bacterial Lipopolysaccharide to Carbon Nanotube- and Vanadium Pentoxide-Induced Pulmonary Fibrosis in Rats
    (2010-04-20) Cesta, Mark Francis; Dr. James C. Bonner, Committee Co-Chair; Dr. David E. Malarkey, Committee Member; Dr. Kenneth B. Adler, Committee Member; Dr. Philip L. Sannes, Committee Chair
    Pulmonary fibrosis is typically accompanied by inflammation, which is thought to play a role in its pathogenesis, and occurs with occupational exposure to particulates and metals, such as asbestos and vanadium pentoxide (V2O5). Lipopolysaccharide (LPS), a model of acute lung injury and inflammation, chronic bronchitis, and pulmonary fibrosis, upregulates platelet-derived growth factor receptor (PDGF-Rα) in rat lung fibroblasts (RLF). PDGF, a potent mitogen and chemoattractant for mesenchymal cells, is an important mediator in fibrotic lung diseases. This dissertation examines the effects of pre-existing inflammation, induced by LPS, on carbon nanotube (CNT)- and V2O5-induced pulmonary fibrosis in rats and the involvement of PDGF signaling. Rats were pretreated with 2.5 mg/kg LPS by intranasal aspiration, followed 24 hr later by 4 mg /kg CNT, carbon black (CB), or V2O5 administered by intratracheal instillation. Total and differential cell counts, lactate dehydrogenase (LDH), total protein, and PDGF and transforming growth factor-β (TGF-β) protein levels (by ELISA) were examined in bronchoalveolar lavage (BAL) fluid of control and CB- and MWCNT –exposed rats. Lungs from all animals were collected for histopathological analysis, immunohistochemistry, and qPCR of the Pdgf-a, Pdgf-c, Pdgf-rα, and Tgf-β genes. Pdgf-a, Pdgf-c, Pdgf-rα, Tgf-β, and Col1a2 gene expression was also measured in vitro in RLF and NR8383 rat alveolar macrophages in response to CNT or CB with and without LPS. In vivo, CNT and CB caused fibroproliferative, granulomatous lesions, which were located primarily in the alveolar ducts and alveoli. Pretreatment with LPS significantly increased collagen deposition associated with these lesions. In the BAL fluid, LPS pretreatment lead to increases in LDH, total protein, and PDGF-AA protein in rats exposed to MWCNT, and an increase in inflammatory cells in CB-exposed rats compared to controls. In vitro, LPS stimulated Pdgf-rα gene expression in RLF, and LPS and nanoparticles synergistically increased Pdgf-a expression in NR8383 cells. Combined LPS/V2O5 exposure augmented V2O5-induced pulmonary inflammation, airway epithelial necrosis, and fibrosis and amplified in vivo collagen gene expression. The airway lesions were of particular interest because LPS pretreatment increased the incidence of bronchiolitis obliterans-like lesions, including subepithelial fibrosis and intraluminal fibrotic polyps. These data confirm that LPS pretreatment augments the fibrotic effects of CNT and V2O5 in rats, which likely involves enhanced PDGF signaling. This dissertation provides evidence that pre-existing pulmonary inflammation, as occurs with chronic obstructive pulmonary diseases or cigarette smoking, can enhance pulmonary fibrotic responses to environmental agents. Furthermore, exposure to environmental LPS may play a role in the pathogenesis of some fibrotic lung diseases.
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    The Effects of PM2.5 on Allergic Inflammation in Mast Cell Deficient Mice
    (2002-08-19) Madison, Sharon L.; Dr. Bruce Hammerberg, Committee Chair; Dr. Susan L. Tonkonogy, Committee Member; Dr. Stephen H. Gavett, Committee Member; Dr. Kenneth B. Adler, Committee Member
    Animal models of asthma have confirmed epidemiological findings that exposure to fine particulate matter (PM2.5) can enhance asthmatic symptoms, including eosinophilic inflammation and airway hyperresponsiveness. Critics have dismissed the possibility that these studies utilizing artificial exposure scenarios, like intratracheal instillation (i.t.), can be legitimately extrapolated to human risk largely due to the fact that the doses required for this type of model exceed the normal ambient concentrations of PM2.5. In order to improve the credibility of the findings from previous animal studies utilizing the i.t. method for delivery of aqueous particle suspensions to the lung, and to determine the biological mechanisms responsible for the observed enhancement of allergic inflammation following PM2.5 exposure, large-scale air samplers have been developed making it possible to directly expose wild type (WT) and genetically altered mice to fine, concentrated ambient particles (CAPs). In this study allergic asthma was modeled in both WT and mast cell deficient (MCD) mice by local (L) or systemic (S) sensitization to ovalbumin (OVA). Two weeks later mice were challenged with OVA (day 0) and then exposed to CAPs (day 0 & 1) with numerous endpoints collected (day 0-2). Overall, there was a temporal difference in the bronchoalveolar lavage cell profile between L and S sensitized mice, and the contribution of mast cells (MC) to this differential response was best observed for neutrophils at day 0 and day 1. Compared to air exposed mice, CAPs depressed total inflammatory cell infiltrates in the bronchoalveolar lavage fluid at day 0 and day 1 after OVA challenge for all groups. This overwhelming difference of limited cellular infiltration of monocytes and neutrophils in the bronchoalveolar lavage fluid following CAPs exposure, and the significant difference between the L and S sensitization protocols, confound interpretation for all of the factors examined. However, the specific finding that CAPs can enhance eosinophil recruitment by day 2 after OVA challenge indicates that the results from previous animal studies utilizing i.t. PM2.5 exposures do in fact support the epidemiological associations linking PM2.5 exposures with the enhancement of allergic inflammation indicative of the asthmatic phenotype. Given the strict regulation of immunological tolerance at mucosal surfaces like the lung, the genetic variability of different mouse strains, and the daily changes in ambient PM2.5 composition, the findings of this study prompt many unique questions. However, the bottom line is that this study demonstrates that ambient PM2.5 does alter Th2-like responses in mice by enhancing pulmonary BAL eosinophils in the late phase response (day 2), and that mast cells are critical to their recruitment.