Ph.D. afhandling, Roskilde universitetscenter 2000.

<p>Many blood cell mechanisms in the human body are working all the time to maintain haemostasis in the blood vessels. Once a wound arises platelets are alerted via different substances to cover the wound and prevent loss of blood. Most of the times these mechanisms do stop the blood, and further heal the wound. During other circumstances the platelet-covering continues to form a thrombus, preventing the blood to flow and instead causes myocardial infarction or stroke. There are several risk factors triggering development of circulatory diseases such as obesity, lack of exercise, smoking, infection and stress.</p><p>This thesis describes the interaction between the two platelet thrombin receptors PAR1 and PAR4, together with the interaction of the oral pathogen <em>Porphyromonas gingivalis</em> (with thrombin-like gingipains), and the cross talk with the stress hormone epinephrine and its α_2A adrenergic receptor. Until now PAR1 is thought to be the most important thrombin receptor due to its high affinity for thrombin. From a phylogenetical and patophysiological point of view there must be a reason why platelets express two different thrombin receptors. Today PAR4 is considered less important, but this thesis implies that PAR4 plays an important role in platelet signaling and haemostasis.</p><p>The results show that bacteria pre-stimulated platelets, followed by epinephrine gives a strong and full aggregation and calcium mobilization, in both aspirinated and non-aspirinated human platelets. The amount of bacteria does not itself, or epinephrine alone give aggregation or calcium mobilization. This mechanism is dependent on both Rgp type gingipain released from <em>P. gingivalis</em>, and PARs in an interaction with the α_2A adrenergic receptor.</p><p>Further, results reveal that PAR4 interacts and cross talks with the platelet α_2A-adrenergic receptor in <em>aspirinated </em>platelets. Neither of the two platelet purinergic P2Y-receptors (P2Y₁₂ and P2Y₁) contribute to this action, but the purinergic P2X₁ does. In aggregation studies a low dose of PAR4 activating peptide (AP), but not PAR1-AP, followed by epinephrine results in a strong aggregation and in a calcium mobilization. ATP secretion measurements did reveal that ATP was released during epinephrine stimulation, which indicate that ATP and P2X₁ have a key role in this event. By blocking P2X₁ both aggregation and calcium mobilization were abolished, but not by blocking P2Y₁₂ and P2Y₁. Inhibition of PI3-kinase, both epinephrine-induced calcium mobilization and aggregation were significant reduced. In <em>non-aspirinated</em> platelets PAR1 synergizes with the α_2A adrenergic receptor and P2X₁.</p><p>In conclusion, this thesis suggests that PAR4 plays an intriguing and important role in platelets with inactived cyclooxygenase 1.  The results described in this thesis contribute to an increased knowledge of the platelet thrombin receptors.</p>

The G protein-coupled receptors (GPCRs) and solute carriers (SLC) are two large families of membrane-bound proteins. The aim of this study was to characterize these two families in terms of evolution and function. The melanocortin (MC) receptors belong to the Rhodopsin family of GPCRs and we cloned the MC4 and MC5 receptors from the rainbow trout, MC3 and MC5 from the spiny dogfish and MCa and MCb from the river lamprey. Pharmacological characterization of the cloned MC receptors demonstrated higher affinity for adrenocorticotropic hormone (ACTH) compared to melanocyte stimulating hormone (MSH) peptides (alpha-, beta- and gamma-MSH). We performed expression analysis with reverse transcription PCR, which showed that the MC4 and MC5 receptors in the rainbow trout are expressed centrally as well as in peripheral tissues. The dogfish MC3 and MC5 receptors were expressed in the brain, while the lamprey MCa and MCb receptors were expressed in the periphery. An extensive tissue localization analysis was performed for the entire family of Adhesion GPCRs in the rat and mouse. Using quantitative real-time PCR (qRT-PCR) we discovered that the majority of GPCRs were expressed either specifically in the CNS or ubiquitously in the CNS and peripheral tissues. We identified all non-olfactory GPCRs in the dog and classified them into Adhesion, Frizzled, Glutamate, Rhodopsin and Secretin families. The dog GPCR repertoire seemed to be more similar to the human repertoire than to the repertoires in rodents. Solute carrier family 25 includes mitochondrial membrane transporters. Using bioinformatics techniques we identified 14 novel members of the SLC25 family, which now has 46 members. We identified orthologs of the novel SLC25 family members in yeast and performed expression analysis of 9 of them with qRT-PCR on a panel containing 30 central and peripheral tissues from the rat. To conclude, this study has expanded our knowledge of the repertoire of genes coding for membrane-bound proteins and provided information about their functional roles.

The aim of this thesis was to determine the role of nucleoside analog activating and deactivating enzymes in nucleoside analog metabolism and resistance development. Nucleoside analogs are anti-cancer drogs and are often used to treat different leukemias, attributably to presence of high levels of nucleoside analog activating enzymes in hematopoietic cells. More recently some of the newer analogs have been used  successfully to treat solid tumors as well. We have used human leukemic cell lines, and isolated cells from patients with leukemia, to investigate the nucleoside analog activating enzymes deoxycytidine kinase (dCK) and deoxyguanosine kinase (dGK) and some of the deactivating enzymes called 5'nucleotidases (5'-NTs). We have measured mRNA expressions and enzymatic activities and correlated them with the cytotoxic response to nuc1eoside analogs and changes in cell cycle progression. We optimized and evaluated a siRNA-transfection method and decreased the activities of dCK and dGK in two different cell lines in order to find out more about their respective contribution to activation of these drogs. An expression microarray analysis of a nucleoside analog resistant cell line was also performed in order to clarify which genes are involved in development of resistance. We found that expressions and activities of dCK and dGK were not correlated. The enzyme activities of activating and deactivating enzymes changed during cell cycle progression, giving actively proliferating cells a more favorable enzymatic profile with regard to nucleoside analog cytotoxicity. The activities of dCK and dGK could be reduced transiently in leukemic and solid tumor cell lines, thereby confer either resistance or increased sensitivity to nucleoside analogs to variable degrees. Expression microarray analysis was used to evaluate the effect of the transfection method and the specificity of siRNA. We concluded that cells tolerated the transfection weIl without major effects on gene expression, and considered the siRNA used to be specific to its target. An expression microarray experiment on a nucleoside analog-induced resistant cell line revealed a hypomethylating capacity of the drog and induction of fetal hemoglobin and a multidrog resistance efflux pump as a result of the hypomethylation. This pump should not be affected by nucleoside analoges since they are not a substrate of it, and upregulation of the pump unfortunately renders the cells highly cross-resistant to different types of drogs. Our preliminary data supports our theory that it may be upregulated in order to help excrete hemoglobin that otherwise would be toxic to the cells.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2001. / Härtill 6 uppsatser.

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 6 uppsatser.

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2001. / Härtill 5 uppsatser.

Mental disorders, like anxiety and depression, are a major health problem and can appear early in life. Developing new compounds for anxiety and other mental disorders is desirable and requires good animal models. Two widely used tests to evaluate fear and anxious behavior in rodents are the open field (OF) and elevated plus maze (EPM) tests. The models are simple and it has been argued that different environments give different behavior profiles and measure different kind of behavior. The multivariate concentric square fieldTM (MCSF) is a new test that gives the rodent opportunity to visit different environments and to evaluate more parameters in one test. Validation of the tests is mainly done with adult animals. The aim with this study is to study adolescent rat behavior in the OF, OF with start box, EPM and MCSF tests and to see if there is any difference in running trials in the morning or in the afternoon. A total of 48 adolescent male Wistar rats were divided into 12 rats per group. The groups were OF and MCSF, OF with start box and MCSF, EPM and MCSF, and repeated testing in MCSF. Each session was 20 minutes and there was one week between the two tests. Three rats where run in the morning and three in the afternoon. Statistical analysis did show significant difference in some parameters in the comparison between running trials in the morning or in the afternoon. Repeated testing in the MCSF yielded differences in trial two compared to trial one. No significant difference was found in the trend analysis. The results show individual differences and with larger groups results may have been more liable. In this study some differences were found between morning and afternoon groups. Lots of data have been generated and there are many opportunities to use the same data for additional analyses.

Many blood cell mechanisms in the human body are working all the time to maintain haemostasis in the blood vessels. Once a wound arises platelets are alerted via different substances to cover the wound and prevent loss of blood. Most of the times these mechanisms do stop the blood, and further heal the wound. During other circumstances the platelet-covering continues to form a thrombus, preventing the blood to flow and instead causes myocardial infarction or stroke. There are several risk factors triggering development of circulatory diseases such as obesity, lack of exercise, smoking, infection and stress. This thesis describes the interaction between the two platelet thrombin receptors PAR1 and PAR4, together with the interaction of the oral pathogen Porphyromonas gingivalis (with thrombin-like gingipains), and the cross talk with the stress hormone epinephrine and its α2A adrenergic receptor. Until now PAR1 is thought to be the most important thrombin receptor due to its high affinity for thrombin. From a phylogenetical and patophysiological point of view there must be a reason why platelets express two different thrombin receptors. Today PAR4 is considered less important, but this thesis implies that PAR4 plays an important role in platelet signaling and haemostasis. The results show that bacteria pre-stimulated platelets, followed by epinephrine gives a strong and full aggregation and calcium mobilization, in both aspirinated and non-aspirinated human platelets. The amount of bacteria does not itself, or epinephrine alone give aggregation or calcium mobilization. This mechanism is dependent on both Rgp type gingipain released from P. gingivalis, and PARs in an interaction with the α2A adrenergic receptor. Further, results reveal that PAR4 interacts and cross talks with the platelet α2A-adrenergic receptor in aspirinated platelets. Neither of the two platelet purinergic P2Y-receptors (P2Y12 and P2Y1) contribute to this action, but the purinergic P2X1 does. In aggregation studies a low dose of PAR4 activating peptide (AP), but not PAR1-AP, followed by epinephrine results in a strong aggregation and in a calcium mobilization. ATP secretion measurements did reveal that ATP was released during epinephrine stimulation, which indicate that ATP and P2X1 have a key role in this event. By blocking P2X1 both aggregation and calcium mobilization were abolished, but not by blocking P2Y12 and P2Y1. Inhibition of PI3-kinase, both epinephrine-induced calcium mobilization and aggregation were significant reduced. In non-aspirinated platelets PAR1 synergizes with the α2A adrenergic receptor and P2X1. In conclusion, this thesis suggests that PAR4 plays an intriguing and important role in platelets with inactived cyclooxygenase 1.  The results described in this thesis contribute to an increased knowledge of the platelet thrombin receptors.