AIR POLLUTION – MONITORING MODELLING AND HEALTH

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322 Air Pollution – Monitoring, Modelling and Health renders the organism more susceptible to cardio-vascular as well as respiratory effects of air pollution. The resulting adverse health effects include generation of oxidative stress, inflammation as well as morbidity. (Bollati & Baccarelli, 2010) It was possible to demonstrate that the underlying mechanism regards methylation of the promoter region of the iNOS (inducible nitric-oxide synthase) – found to be suppressed in foundery workers who were exposed to UFPs. (Tarantini et al., 2009) The same authors also reported demethylation effects induced by longterm exposure to particle mass (PM 10 ) exposure in younger individuals individuals. These effects resemble demethylation patterns that are typically observed in old age. Histone modifications have been observed in workers who experienced long-term exposure to nanosized aerosols at smelters. Both acetylation of the histone H3K9 and demethylation of H3K4 increased by about 15% after a >21 year exposure near the smelter. (Cantone et al., 2011) Another key concept for the developmental origin of diseases comprises a transfer of the acquired predisposition onto subsequent generations without further environmental impacts (see Figure 10). Such trans-generational epigenetic inheritance is responsible for wider effects, such as a fast-track pathway of adaptation to environmental stress. This improves survival until either more stable genetic changes can provide better adaptations or the environment reverts to the previous status. (Finnegan, 2002) Fig. 10. Epigenotype model of developmental origins of disease. Environmental factors acting in early life (from conception to early infancy) have consequences, which become manifest as an altered risk for diseases in later life. The mother conveys a forecast of the post-natal environment to the genome of the unborn. This includes modifications to its metabolism, whole body physiology and growth trajectory to maximize its chances of postnatal survival. These adaptations become detrimental if the environmental conditions after birth differ from those of the fetal stage. Ac - Histone acetylation/active genes; CH 3 - DNA methylation/silent genes. (modified after Sandovici et al., 2008)
Exposure to Nano-Sized Particles and the Emergence of Contemporary Diseases with a Focus on Epigenetics 323 2.3 Embryonic epigenome Paramutation in comparison to bookmarking, regards the quasi “inheritance” of genecharacteristics (allelic interactions) that are "remembered" and expressed in later generations (e.g. via the germ cell linage). Paramutation occurs when certain control alleles impose an epigenetic imprint on susceptible (paramutable) inferior alleles. The epigenetic imprint is inherited through meiosis and persists even after the interacting alleles have segregated. The observation of heritable but reversible changes in gene expression, is evidence for non- Mendelian genetics, and apparently also in mammalian systems. (Chanlder & Stam, 2004) Paramutation fulfils the criteria for a parental identity mark or "imprint" because it can be established either in the sperm or the oocyte by de novo methyl-transferases that act only in one gamete. Once established, it can be stably propagated at each embryonic cell division by a maintenance methyl-transferase, and it can also be erased in the germ line to reset the imprint in the next generation, either by passive demethylation or possibly through the action of a demethylase. (Barlow & Bartolomei, 2008) . The newly fertilized egg or zygote is unique since no other cell has the potential to develop into an entire organism. In order to achieve that, epigenetic marks of both oocyte (female) and sperm (male) are usually efficiently reprogrammed at fertilization, so that upon fertilization the embryonic genome becomes totipotent – an essential property of the zygote. (Surani & Reik, 2007) At the first mitosis after fertilization, most histone marks are quite similar on the maternal and paternal chromosomes. (Santos et al, 2005) To yield the totipotent zygote, dramatic DNA demethylation of the parental genome must be induced by "active demethylation". (Morgan et al., 2005) Hence, gene expression depends on the origin of inheritance. This implies that at an imprinted diploid locus, there is unequal expression of the maternal and paternal alleles. So much so, that in each generation, the parent-specific imprinting marks have to be erased, reset, and maintained. It is obvious that imprinted loci are somewhat prone to errors that may occur during these processes. Indeed, at such an early stage of development, erroneous imprinting in genes, which encode proteins involved in DNA methylation, binding to methylated DNA, and histone modifications may contribute to the fast-growing class of human disorders affecting the epigenome. (Zoghbi & Beaudet, 2007) After further cell divisions, the embryonic stem cells differentiate into roughly 200 different cell lineages, whereby totipotency is gradually downregulated to pluripotency. (Tada et al., 1997; Tada et al., 2001; Cowan et al., 2005) The latter give rise to adult stem cells that generate tissue specific cells. (Surani & Reik, 2007). Tissue-specific stem cells are responsible for the development and regeneration of entire organs, such as skin, gut, and blood system throughout life. To comply with this task, stem cells encompass two unique properties: (i) an extensive selfrenewal potential that enables them to propagate in their uncommitted state; (ii) pluripotency that gives rise to all cell types of an organ by differentiation to multipotent progenitors with gradually restricted developmental potential. These progenitors subsequently undergo commitment to one of several cell lineages and then differentiate along the selected pathway into a functionally specialized cell type of the organ. (Fisher, 2002) Transcription factors reprogram the expression of large sets of genes. They act indirectly by (i) affecting gene expression programs (antagonizing other transcription factors through protein-protein interaction) and directly by (ii) the control of gene transcription (recruiting coactivators or corepressors with histone-modifying or chromatin-remodeling activities to regulatory DNA elements). Hence, the activity of a gene is influenced by the local DNA
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AIR POLLUTION - MONITORING, MODELLI
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Contents Preface IX Chapter 1 Urban
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Preface This book provides a compre
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AIR POLLUTION – MONITORING MODELLING AND HEALTH

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