Age dependent incorporation of 14C-DHA into rat brain and body tissues after dosing various 14C-DHA-esters.

INTRODUCTION: The omega-3 fatty acid docosahexaenoic acid (DHA) accounts for 10% of fatty acids in human brain and is critical for neuronal function and brain development. Mechanisms of transport, accumulation and conservation of DHA in the brain are unclear. The objective of the study was to quantify the age dependent DHA incorporation into the brain of 2-, 4- or 10-week-old rats after a bolus dose of different DHA-esters. METHODS: Rats were gavaged with (14)C-DHA-TAG, (14)C-DHA-PL or (14)C-DHA-TAG+PL at 2 mg DHA/kg BW. After 24h the distribution of radioactivity in body and brain regions was determined using quantitative whole body autoradiography (QWBA). Radiolabeled compounds were extracted from the brains to determine the identity of the radiolabeled compounds. RESULTS: Accumulation of orally ingested (14)C-DHA in rat brain was less than 1% of the dose and decreased with age. Ester specific differences were seen only in 10-week-old rats, where oral (14)C-DHA-PL delivered a 2-fold higher accretion of radioactivity in the brain. CONCLUSIONS: Less than 1% of a dietary achievable DHA dose reached the rat brain within 24h. Optimal efficacy of DHA-PL may occur in older age groups.

Biphenotypic B/macrophage cells express COX-1 and up-regulate COX-2 expression and prostaglandin E(2) production in response to pro-inflammatory signals.

B/macrophage cells are biphenotypic leukocytes of unknown function that simultaneously express B lymphocyte (IgM, IgD, B220, CD5) and macrophage (phagocytosis, F4/80, Mac-1) characteristics. B/macrophage cells can be generated from purified mouse B lymphocytes incubated in fibroblast-conditioned medium. A potential role for B/macrophage cells in inflammation was shown by their ability to express prostaglandin H synthase-1 (COX-1) and prostaglandin H synthase-2 (COX-2) and by their production of prostaglandin (PG) E(2). COX-1 and COX-2 mRNA expression is not observed in the precursor B lymphocytes and is not known to be a property of B lineage cells. In contrast, COX-2 and the prostanoids PGE(2), PGF(2alpha) and PGD(2) are highly inducible in B/ macrophage cells upon stimulation with lipopolysaccharide, CD40 ligand, or via engagement of surface IgM, supporting a role for these cells in inflammation. PGD(2) and its metabolites are of interest because they activate the nuclear receptor PPARgamma that regulates lipid metabolism. The B/macrophage represents the first instance of a normal B-lineage cell capable of expressing COX-2. Importantly, B/macrophage cells were identified in vivo, providing evidence that they may play a significant role in immune responses. Since PGE(2) blunts IL-12 production, its synthesis by B/macrophage cells may shift the balance of an immune response towards Th2 and humoral immunity.

Transcription regulatory elements of the first intron control human transglutaminase type I gene expression in epidermal keratinocytes.

Expression of the transglutaminase type1 gene (TGM1), which encodes an epithelial cell-specific protein cross-linking enzyme, is limited to particular stages of epidermal development and keratinocyte differentiation. As a result, transglutaminase type 1 (TGase1) enzyme activity in epidermal cells increases with the onset of keratinization in vivo and in vitro. We determined, by functional mapping of deletion mutations in the TGM1 5' untranslated region, that an element in first intron of the human TGM1 gene, in addition to the 5' proximal promoter, initiates transcription and upregulates transcriptional activity. These two transcription control elements function interdependently to regulate the expression of the human TGM1 gene in keratinocytes. We also identified distinct regulatory elements that cooperatively modify the 5' proximal and intron 1 promoter activities in response to environmental variations in retinoic acid and calcium ion concentrations. In conclusion, we report that TGM1 differential gene expression is controlled by two distinct elements, proximal and intronic, which function cooperatively to initiate and modulate TGM1 gene transcription in response to regulatory signals. We propose that in nonexpressing cells these regulatory signals repress a default mechanism that operates in their absence. The specificity of their function is integrated into the default mechanism and consists of the tissue-, developmental-, and differentiation-specific interplay of 5' URR and intron 1 elements tuned to physiological status.