Laminin-5 mediates vascular smooth muscle cell response to growth factors

The development and normal function of cells in the body depend upon interactions with other molecules. One such group of molecules, referred to as the extracellular matrix (ECM), is secreted by subsets of epithelial, endothelial, and mesenchymal cells within multicellular organisms. The laminin families comprise a set of soluble ECM glycoproteins that are required for structural integrity and development in many epithelial tissues. Ln-5 is a laminin isoform composed of three subunits: alpha3, beta3, and gamma2. In this study, I sought to determine temporal and spatial patterns of ln-5 expression in non epithelial tissues. Using an enzyme-linked immunofluorescence amplification system and newly developed photobleaching treatment, I observed ln-5 expression in previously undocumented sites including vascular smooth muscle cells (VSMC) of the aorta, pulmonary arteries, and also in bone and cartilage. In adult animals, VSMC are terminally differentiated and control blood flow and contraction in response to various chemical and mechanical stimuLi However, during the formation of atherosclerotic and restenotic lesions, VSMCs revert to a synthetic a phenotype characterized by a secretory-, proliferative-, and migratory-active state. I analyzed the functional significance of ln-5 expression, which is upregulated by growth factors induced following arterial injury. I found that ln-5 significantly altered the proliferation of VSMC in response to platelet-derived growth factor (PDGF-BB), a potent mitogen and chemoattractant for VSMC. I demonstrated that the alpha6beta1 and the alpha6beta4 integrin complex may be responsible for the initial VSMC adhesion to ln-5. I also demonstrated that ln-5 does not support haptotactic VSMC migration, however PDGF-BB-stimulation greatly enhanced VSMC migration on ln-5. I therefore postulated that PDGF-BB-stimulated MAPK activation is responsible for the increased migratory phenotype of VSMC on ln-5 and found stimulation of VSMC with PDGF-BB reduced VSMC adhesion to ln-5 and concomitantly increased VSMC migration on ln-5 while revealing detectable increases in ERK1/2 activation. As ln-5 is involved in the enhanced migration of various cell types, the increased production and decreased adhesion of VSMC on ln-5 may provide a mechanism for the design of novel and interesting targets in the prevention of pathological processes associated with the arterial vasculature, such as restenosis following angioplasty

Platelet-derived growth factor modulates rat vascular smooth muscle cell responses on laminin-5 via mitogen-activated protein kinase-sensitive pathways

BACKGROUND: A treatment to remove vascular blockages, angioplasty, can cause damage to the vessel wall and a subsequent abnormal wound healing response, known as restenosis. Vascular smooth muscle cells (VSMC) lining the vessel wall respond to growth factors and other stimuli released by injured cells. However, the extracellular matrix (ECM) may differentially modulate VSMC responses to these growth factors, such as proliferation, migration and adhesion. Our previous reports of low-level expression of one ECM molecule, laminin-5, in normal and injured vessels suggest that laminin-5, in addition to growth factors, may mediate VSMC response following vascular injury. To elucidate VSMC response on laminin-5 we investigated-the role of platelet-derived growth factor (PDGF-BB) in activating the mitogen-activated protein kinase (MAPK) signaling cascade as a possible link between growth-factor initiated phenotypic changes in vitro and the ECM. RESULTS: Using a system of in vitro assays we assessed rat vascular smooth muscle cell (rVSMC) responses plated on laminin-5 to the addition of exogenous, soluble PDGF-BB. Our results indicate that although laminin-5 induces haptotactic migration of rVSMC, the addition of PDGF-BB significantly increases rVSMC migration on laminin-5, which is inhibited in a dose-dependent manner by the MAPK inhibitor, PD98059, and transforming growth factor (TGF-β1). In addition, PDGF-BB greatly reduces rVSMC adhesion to laminin-5, an effect that is reversible by MAPK inhibition or the addition of TGF-β1. In addition, this reduction in adhesion is less significant on another ECM substrate, fibronectin and is reversible using TGF-β1 but not MAPK inhibition. PDGF-BB also strongly increased rVSMC proliferation on laminin-5, but had no effect on rVSMC plated on fibronectin. Finally, plating rVSMC on laminin-5 did not induce an increase in MAPK activation, while plating on fibronectin or the addition of soluble PDGF-BB did. CONCLUSION: These results suggest that rVSMC binding to laminin-5 activates integrin-dependent intracellular signaling cascades that are different from those of fibronectin or PDGF-BB, causing rVSMC to respond more acutely to the inhibition of MAPK. In contrast, our results suggest that fibronectin and PDGF-BB may activate parallel, reinforcing intracellular signaling cascades that converge in the activation of MAPK and are therefore less sensitive to MAPK inhibition. These results suggest a partial mechanism to explain the regulation of rVSMC behaviors, including migration, adhesion, and proliferation that may be responsible for the progression of restenosis

Oral cancer in Nevada: A Public health perspective

Cancer is the second leading cause of death in the United States, and oral cancer remains the eighth leading cause of cancer death among US males. Although previous epidemiologic studies have found that overall rates of cancer, including oral cancer, have declined in the US in recent decades – these declines are neither uniform nor consistent within this population. Anecdotal evidence has suggested that rates of oral cancer in Nevada are relatively high, although no evidence was available to support these assertions. Oral Cancer Epidemiology: Based upon this information, a detailed and thorough epidemiologic examination of oral cancer rates in Nevada was undertaken. Chapter 1 describes a landmark publication in the journal BMC Public Health, which clearly demonstrated that oral cancer rates are, in fact, rising in specific geographic areas. Moreover, the state with the highest documented sustained increases was Nevada. In addition, although previous research has demonstrated increasing oral cancer rates among women and minorities, due to increased wealth, status and access over these past few decades – the observed increases in Nevada’s oral cancer rates were overwhelmingly within the white male population. Risk Factor Analysis: In a follow-up study to determine the factors responsible for the rising rates of oral cancer in Nevada, an in-depth analysis of the primary risk factor for oral cancer development (tobacco usage) was performed. Chapter 2 outlines this study, submitted for publication in the journal Tobacco-Induced Diseases. These results demonstrated that the increased incidence and mortality of oral cancer in Nevada was a state-specific phenomenon and not part of a larger, regional increase. Moreover, trend analysis revealed that tobacco usage rates, although historically higher and linked to other factors, such as lower pricing, taxes and fewer workplace smoking bans, were recently found to be declining. These findings are the first to provide evidence that suggests that rates of oral cancer within this specific geographic area may soon begin to decline. Environmental Factors: In addition to tobacco usage (smoking), many other risk factors may play a role in the development of oral cancers. These additional risk factors include environmental factors, such as nutrition and diet, which are examined in Chapter 3. For example, the recent adoption for required folate fortification in some food products, which has been shown to reduce negative health outcomes related to folate deficiency, has also been demonstrated to increase the rate of growth in undiagnosed (but pre-existing) colorectal cancers. This raises the question of whether folate may play a similar and significant role in the accelerated growth of other slow developing cancers, such as oral cancers. The timing of folate fortification in the US parallels the increased incidence of oral cancer in Nevada, suggesting that this environmental influence may also play an important role in the development and progression of this disease

Interactive Effects of 1, 25-dihydroxyvitamin D3 and Soy Protein Extract (SPE) on Oral Cancer Growth In Vitro: Evidence for Potential Functional Relationships

ABSTRACTBackground: Previous studies have found specific soy isoflavones (Genistein, Daidzein, Glycitein) demonstrate anti-tumor properties against several cancer types, including oral cancer. Few studies have evaluated whole soy extract, containing a combination of these isoflavones and other bioreactive compounds, which may function synergistically and more effectively against oral cancers. Preliminary work by this group has now demonstrated whole soy protein extract (SPE) inhibits oral cancer cell growth specifically and selectively, through independent cell-cycle and apoptotic pathways. However, more recent evidence now suggests that ingestion of vitamin D3, either in dietary foods or supplements may potentiate the activity of soy components and their anti-tumor effects.Objective: The primary goal of this study was to investigate the interactive and inter-connected effects of 1, 25-dihydroxyvitamin D3 administration with the anti-proliferative effects of whole soy protein extract (SPE) on oral cancer and normal cell lines in vitro.Methods: Three oral squamous cell carcinoma cell lines (SCC15, SCC25, and CAL27) were treated with 1, 25-dihydroxy Vitamin D3 at physiological concentrations (10-125 nmol). Cell growth was then compared with cell treatment using soy protein extract (SPE) within the normal physiologic range (0 - 10 /L). Interactive effects were then evaluated using co-administration of SPE and 1, 25-dihydroxy Vitamin D3. Quantitative RT-PCR was performed at various time points to determine any changes in mRNA expression for key cell cycle and apoptotic signaling pathway regulators, including p53, c-myc, ornithine decarboxylase (ODC), caspase-2, caspase-8, and bax.Results: Administration of 1, 25-dihydroxy Vitamin D3 induced distinct dose-dependent, growth-inhibitory effects in all three oral cancer cell lines examined. These inhibitory effects were comparable to the overall range of growth inhibition induced by SPE. However, the combined effects of co-administration were far greater, suggesting the presence of synergistic relationships between these components. In addition, these results indicate that either treatment alone appeared to modulate mRNA expression of oral cancer cell-cycle promoters c-myc and ODC, as well as the caspase-dependent apoptosis pathway, while only 1, 25-dihydroxy Vitamin D3 administration appeared to influence the bax pathway.Conclusion: These results suggest that co-administration with 1, 25-dihydroxy Vitamin D3 and SPE may enhance their anti-tumor effects. This study may help to explain, in part, why balanced diets rich in fruits, vegetables, and soy protein, are associated with protection against development and progression of oral cancers, although further study is needed to develop specific public health recommendations for oral cancer treatment and prevention.Key words: vitamin D, soy extract, whole soy protein, oral cancer, growth inhibition

Why not just Google it? An assessment of information literacy skills in a biomedical science curriculum

<p>Abstract</p> <p>Background</p> <p>Few issues in higher education are as fundamental as the ability to search for, evaluate, and synthesize information. The need to develop information literacy, the process of finding, retrieving, organizing, and evaluating the ever-expanding collection of online information, has precipitated the need for training in skill-based competencies in higher education, as well as medical and dental education.</p> <p>Methods</p> <p>The current study evaluated the information literacy skills of first-year dental students, consisting of two, consecutive dental student cohorts (n = 160). An assignment designed to evaluate information literacy skills was conducted. In addition, a survey of student online search engine or database preferences was conducted to identify any significant associations. Subsequently, an intervention was developed, based upon the results of the assessment and survey, to address any deficiencies in information literacy.</p> <p>Results</p> <p>Nearly half of students (n = 70/160 or 43%) missed one or more question components that required finding an evidence-based citation. Analysis of the survey revealed a significantly higher percentage of students who provided incorrect responses (n = 53/70 or 75.7%) reported using Google as their preferred online search method (p < 0.01). In contrast, a significantly higher percentage of students who reported using PubMed (n = 39/45 or 86.7%) were able to provide correct responses (p < 0.01). Following a one-hour intervention by a health science librarian, virtually all students were able to find and retrieve evidence-based materials for subsequent coursework.</p> <p>Conclusions</p> <p>This study confirmed that information literacy among this student population was lacking and that integration of modules within the curriculum can help students to filter and establish the quality of online information, a critical component in the training of new health care professionals. Furthermore, incorporation of these modules early in the curriculum may be of significant value to other dental, medical, health care, and professional schools with similar goals of incorporating the evidence base into teaching and learning activities.</p