The adverse health effects of elevated exposures to PM10 (particulate matter collected through a size selective inlet with an efficiency of 50% for particles with an aerodynamic diameter of 10 μm) in relation to morbidity and mortality, especially in susceptible individuals, are now well recognised. PM10 consists of a variable cocktail of components differing in chemical composition and size. Epidemiological and toxicological data suggest that transition metals and ultrafine particles are both able to drive the cellular and molecular changes that underlie PM10-induced inflammation and so worsen disease status. Toxicological evidence also suggest roles for the biological components of PM10 including volatile organic compounds (VOC’s), allergens and bacterial-derived endotoxin. Many of these components, in particular transition metals, ultrafine particles, endotoxin and VOC’s induce a cellular oxidative stress which initiates an intracellular signaling cascade involving the activation of phosphatase and kinase enzymes as well as transcription factors such as nuclear factor kappa B. Activation of these signaling mechanisms results in an increase in the expression of pro-inflammatory mediators, and hence enhanced inflammation. Given that many of the components of PM10 stimulate similar or even identical intracellular signaling pathways, it is conceivable that this will result in synergistic or additive interactions so that the biological response induced by PM10 exposure is a response to the composition rather than the mass alone. A small number of studies suggest that synergistic interactions occur between ultrafine particles and transition metals, between particles and allergens, and between particles and VOC’s. Elucidation of the consequences of interaction between the components of PM10 in relation to their biological activity implies huge consequences for the methods used to monitor and to legislate pollution exposure in the future, and may drive a move from mass based measurements to composition.
seconds ; Transition Elements ; SIZES ; Drug Interactions ; Cellular biology

Hypoxia-inducible factor-1 (HIF-1) is composed of HIF-1alpha and HIF-1beta, and is a master regulator of oxygen homeostasis, playing critical roles in physiological and pathological processes. Normally, the formation and transcriptional activity of HIF-1 depend on the amount of HIF-1alpha, and the expression of HIF-1alpha is tightly controlled by the cellular oxygen tension. Recent progress in the study of its regulation mechanism provided clues as to how HIF-1alpha is regulated by oxygen. It appears that HIF-1alpha is not regulated only by the oxygen tension, but also by various other stimuli, such as transition metals, nitric oxide, reactive oxygen species, growth factors, and mechanical stresses. In this review, we summarize the oxygen-dependent and -independent regulation of HIF-1alpha, and the respective physiological and pathological meanings.
Animals ; Growth Substances/metabolism ; Humans ; Hypoxia-Inducible Factor 1, alpha Subunit ; Molecular Structure ; Nitric Oxide/metabolism ; Oxygen/*metabolism ; Reactive Oxygen Species/metabolism ; Stress, Mechanical ; Transcription Factors/chemistry/genetics/*metabolism ; Transition Elements/metabolism

A hypoxic microenvironment leads to cancer progression and increases the metastatic potential of cancer cells within tumors via epithelial-mesenchymal transition (EMT) and cancer stemness acquisition. The hypoxic response pathway can occur under oxygen tensions of < 40 mmHg through hypoxia-inducible factors (HIFs), which are considered key mediators in the adaptation to hypoxia. Previous studies have shown that cellular responses to hypoxia are required for EMT and cancer stemness maintenance through HIF-1α and HIF-2α. The principal transcription factors of EMT include Twist, Snail, Slug, Sip1 (Smad interacting protein 1), and ZEB1 (zinc finger E-box-binding homeobox 1). HIFs bind to hypoxia response elements within the promoter region of these genes and also target cancer stem cell-associated genes and mediate transcriptional responses to hypoxia during stem cell differentiation. Acquisition of stemness characteristics in epithelial cells can be induced by activation of the EMT process. The mechanism of these phenotypic changes includes epigenetic alterations, such as DNA methylation, histone modification, chromatin remodeling, and microRNAs. Increased expression of EMT and pluripotent genes also play a role through demethylation of their promoters. In this review, we summarize the role of hypoxia on the acquisition of EMT and cancer stemness and the possible association with epigenetic regulation, as well as their therapeutic applications.
Anoxia* ; Chromatin Assembly and Disassembly ; DNA Methylation ; Epigenomics* ; Epithelial Cells ; Epithelial-Mesenchymal Transition* ; Fingers ; Gastropoda ; Genes, Homeobox ; Histones ; MicroRNAs ; Oxygen ; Promoter Regions, Genetic ; Response Elements ; Snails ; Stem Cells ; Transcription Factors