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- Carlsson, Stina K., 1982-
(författare)
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Effects of adenosine and acetylcholine on the lacrimal gland
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A balanced tear film is essential for a healthy ocular surface. Insufficient tear production may result in dry eye, a common disorder in the elderly population. Dry eye causes significant discomfort in the patients and may lead to visual impairment and ocular infections. The lacrimal gland secretes water, proteins and electrolytes to the aqueous layer of the tear film. Lacrimal gland secretion is tightly regulated by e.g. neuronally released acetylcholine. The effect of acetylcholine on lacrimal gland secretion was recently found to be potentiated by adenosine. Adenosine is an important signaling molecule acting upon the adenosine receptors: A1, A2A, A2B and A3.The aim of this thesis was to study effects of adenosine and acetylcholine on intracellular signaling pathways and lacrimal gland secretion. Cholinergic stimulation of secretion was shown to be regulated by the mitogen activated protein kinase p38, a protein previously not known to be involved in exocrine secretion. p38 was activated in response to cholinergic stimulation and inhibition of p38 significantly diminished cholinergic secretion.When investigating adenosine effects, potentiation of cholinergic secretion was observed by activation of the A2B receptor in addition to the previously studied A1 receptor. An A2 receptor agonist increased cholinergic rabbit lacrimal gland protein secretion at several concentrations. The increase was inhibited by antagonism of the A2B receptor, but not the A2A receptor. When investigating the intracellular signaling pathways following adenosine and acetylcholine receptor activation, adenosine was shown to increase of cAMP levels. An additional increase in cAMP levels was observed after parallel adenosine and cholinergic receptor activation. Inhibition of Ca2+ release from the endoplasmic reticulum had inhibitory effects of cholinergic stimulation of secretion. In addition, the expression of adenosine receptors in a mouse model of autoimmune dry eye was investigated. The results showed a lymphocyte dependent upregulation of A2A receptors in diseased mice compared to controls.In conclusion, the results in this thesis provide significant contributions in the search of dry eye therapeutics through studies of adenosine and acetylcholine receptor activation.
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- Edman, Maria C, et al.
(författare)
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Functional expression of the adenosine A1 receptor in rabbit lacrimal gland.
- 2008
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Ingår i: Experimental eye research. - : Elsevier BV. - 0014-4835. ; 86:1, s. 110-7
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Tidskriftsartikel (refereegranskat)abstract
- It has become increasingly clear that purine compounds play a mediator role in exocrine secretion. Therefore, the present study was aimed at examining the presence of the adenosine A1 receptor in rabbit lacrimal gland and to evaluate the role of the A1 receptor in regulated secretion. The expression of the A1 receptor was investigated with reverse transcriptase PCR, cyto- and histochemistry as well as with pharmacological methods. Acinar cells were isolated, cultured in a serum-free medium for 2 days and thereafter treated with purinergic agonists/antagonists and/or carbachol and VIP. Secretory response was assessed by measuring secreted beta-hexosaminidase enzymatic activity. Microscopical evaluation of the immunocyto- and histochemistry specimens indicated that the adenosine A1 receptor is expressed in the rabbit lacrimal gland, which was also supported by reverse transcriptase PCR resulting in a sequence 100% identical with the previously published sequence for the rabbit A1 receptor gene. Incubation of acinar cells with adenosine and the A1 specific agonist N6-cyclopentyladenosine (CPA) resulted in a fourfold increase of secretion at the determined optimal concentrations. Incubation with carbachol alone resulted in a 10- to 15-fold increase. Carbachol combined with either adenosine or CPA increased the secretion 20-fold or more, demonstrating a synergistic effect. Our data provides evidence for the presence of adenosine A1 receptors in both tissue and cultured cells. Even though adenosine and CPA alone had only a moderate effect on secretion, the observed synergistic effect with carbachol suggests a modulatory role for the adenosine A1 receptor in the lacrimal gland.
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- Ekblad, Lars, et al.
(författare)
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Purification of rabbit lacrimal gland plasma membranes by aqueous two-phase affinity partitioning
- 2000
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Ingår i: Journal of Chromatography. B. - 1387-2273. ; 743:1-2, s. 397-401
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Tidskriftsartikel (refereegranskat)abstract
- We describe the purification of lacrimal gland plasma membranes by affinity partitioning using a two-phase system containing polyethylene glycol and dextran in which wheat germ agglutinin conjugated to dextran is used as affinity ligand. When partitioning a microsomal fraction, the plasma membrane marker 5'-nucleotidase was obtained in the affinity ligand-containing bottom phase, whereas the endoplasmic reticulum marker NADH-ferricyanide reductase remained in the top phase. The affinity partitioning behaviour of components involved in exocytosis and cellular signalling was also examined.
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