University, Diss., 2006--Frankfurt (Main). / Zsfassung in engl. und dt. Sprache.

Lic.-avh. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 2 uppsatser.

Univ., Diss., 2005--Frankfurt (Main) / Zsfassung in engl. und dt. Sprache

Type II diabetes is one of the leading cause of morbidity in the U.S. and other parts of the world. Insulin resistance which precedes Type II diabetes is a complex state of the body where the body fails to respond to insulin. Its complexity lies in its multifactorial origin that is to say various environmental and polygenic components come into play. Here we try to dissect one of these components - `Alox8' in transgenic mice and try to see if it affects blood glucose homeostasis. Comparison of glucose tolerance and insulin sensitivity among sixteen mice comprising of six wild type, five heterozygous and five knockout mice with respect to Alox8 gene showed that wild type mice had relatively more glucose tolerance than knockout mice and this corresponded with relatively more insulin sensitiveness of wild type mice with respect to the knock out. However, these findings were not significant statistically at p=0.05. In search of any relevant biological significance, periodic acid schiff staining of the liver sections from these mice in three independent repeated experiments revealed that the knockout phenotype led to accumulation of glycogen deposits as compared to the wild type mice, an indication of insulin resistance. Taken together, our data suggests that these findings when extrapolated to human which carries ALOX15B instead of mice orthologue Alox8, could lead to a benefit of administration of lower doses of insulin in the wild type phenotype as compared to its polymorphic alleles carrying individuals.

No description available.

Morphogenesis, or the development of tissues, structures, and organs, is at the heart of embryonic development. Morphogenesis is a complex, multi-tissue process that requires coordinated cellular communication, migration, and differentiation; due to this complexity, the mechanisms that underlie morphogenesis remain poorly understood. The sea urchin embryo is morphologically and genetically more simple than most other developmental model organisms, and is optically transparent, making it a highly tractable system in which to study morphogenetic processes. The sea urchin larval endoskeleton is a biomineral that is secreted by primary mesenchyme cells (PMCs). The PMCs ingress into the embryo and remain individual, mesenchymal cells that migrate into a stereotypic three-dimensional (3-D) pattern within the blastocoel, prefiguring the form of the ensuing skeleton, which they subsequently secrete. PMC positioning is directed by cues originating in the overlying ectoderm; however, the molecular identity of those cues has remained unknown. The work described in this dissertation combines systems-level approaches with in vivo 3-D spatial analysis to identify novel skeletal patterning genes and to define their functional roles in skeletal patterning. A transcriptomics-based screen identified numerous novel candidate skeletal patterning cues. Of those cues, two were further pursued for detailed functional studies. First, the sulfate transporter SLC26a2/7 (SLC) was found to promote ventral accumulation of sulfated proteoglycans that is both necessary and sufficient to attract PMCs to the ventral territory for ventral skeleton formation. Second, the enzyme 5-lipoxygenase (LOX) was found to be required for ventral and rotational skeletal patterning, and its product, 5(S)-HETE was found to be a chemoattractant for PMCs, thereby identifying a novel role for lipoxygenase enzymes in embryonic patterning and morphogenesis. Recent work from other groups has demonstrated that PMCs diversify their gene expression profiles during skeletal patterning, implying that PMC diversification is involved in skeletal patterning, likely as a response to locally distinct spatial cues. The studies herein identify Tbx2/3 and Pks2 as important PMC subset-specific genes whose spatial expression is modulated by SLC and LOX, respectively. Together, these results provide new mechanistic insights that define our molecular understanding of the regulation of sea urchin ventral skeletal patterning.

No / Acute exposure of human skin to the ultraviolet radiation (UVR) in sunlight results in the sunburn response. This is mediated in part by pro-inflammatory eicosanoids and other bioactive lipids, which are in turn produced via mechanisms including UVR-induction of oxidative stress, cell signalling and gene expression. Sunburn is a self-limiting inflammation offering a convenient and accessible system for the study of human cutaneous lipid metabolism. Recent lipidomic applications have revealed that a wider diversity of eicosanoids may be involved in the sunburn response than previously appreciated. This article reviews the effects of UVR on cutaneous lipids and examines the contribution of bioactive lipid mediators in the development of sunburn. Since human skin is an active site of polyunsaturated fatty acid (PUFA) metabolism, and these macronutrients can influence the production of eicosanoids/bioactive lipids, as well as modulate cell signalling, gene expression and oxidative stress, the application of PUFA as potential photoprotective agents is also considered.

Ferroptosis is a recently characterized cell death pathway associated with the iron-dependent accumulation of lipid hydroperoxides in phospholipid bilayers. The origin of these hydroperoxides has been an ongoing topic of debate and many researchers argue for a lipoxygenase (LOX) enzyme-controlled mechanism of initiation, given their known role as dioxygenases of polyunsaturated fatty acids (PUFAs). In response to this, our lab investigated the induction and inhibition of ferroptosis in human embryonic kidney (HEK-293) cells transfected to overexpress the three most prevalent LOX isoforms, 5-LOX, p12-LOX, and 15-LOX-1. These studies did not support a role for LOX in the execution of ferroptosis; LOX inhibition was not associated with ferroptosis suppression and in fact, anti-ferroptotic activity was directly tied to purported LOX inhibitors’ ability to act as radical-trapping antioxidants (RTAs). We have investigated the effects of LOX inhibitors on ferroptosis in human fibrosarcoma (HT-1080) cells, the cell line in which ferroptosis was initially characterized, and mouse hippocampal neuronal (HT-22) cells, the cell line in which the closely related cell death modality oxytosis was characterized. In sum, our findings mirror those obtained in HEK-293 cells, and the effectiveness of an inhibitor is tied to its off-target RTA activity, not inhibition of LOX. Moreover, we observed suppression of ferroptosis via necrostatin-1 (Nec-1), a known receptor-interacting serine/threonine-protein kinase 1 (RIPK1) (and necroptosis) inhibitor. Herein, we show that Nec-1 is not an RTA and exerts its effects by a yet unknown mechanism which we investigate in a series of exploratory experiments. Conjugated fatty acids – particularly α-ESA – have recently been reported to induce ferroptosis by an unclear mechanism. Theorizing this phenomenon was tied to the autoxidation of α-ESA’s conjugated trienic unit, we aimed to investigate the kinetic and biological properties of natural α-ESA alongside a deuterated isotopologue. Herein, we report preliminary work to derive biologically relevant rate constants for addition and hydrogen-atom transfer (HAT) of α-ESA. Moreover, we report our progress towards the synthesis of a deuterated α-ESA which will facilitate future study alongside its natural counterpart.

No description available.

No description available.