Cyclooxygenases (COXs) are of important therapeutic value as they are the target site of aspirin-like drugs. Here I report nine new COX-1 splice variants in chapter 1, which I characterized with regard to heme-binding and other properties. Inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) are co-inducible in many tissues following mitogenic and proinflammatory stimulation. In chapter 2, I investigate the physical and enzymatic properties of human COX-2 and iNOS and demonstrate that, despite reports to the contrary by another laboratory, they do not interact. The only reported COX-1 splice variant to exhibit cyclooxygenase activity has been isolated from dog brain and is termed COX-3. It contains an in-frame insertion of intron 1. However the existence of human COX-3 remains questionable since intron 1 is out of frame. Two putative in-frame human COX-3 isozymes, COX-1b2 and COX-1b3, (herein designated as COX-3-72 and COX-3-50) have been reported in the literature, but only one of them, COX-3-72, has been characterized. In chapter 3, COX-3-50 and COX-3-72 are reported to be over-expressed and determined to be active cyclooxygenases. COX-3-72 and, to a greater extent, COX-3-50, were stimulated by rofecoxib at physiological concentrations. A similar rofecoxib-stimulated COX activity is observed in quiescent A549 cells. Immunoblot and immunoprecipitation analysis suggest that human platelet and potentially A549 cells, contain a COX-3-50 like protein. Lonicera japonica is used as an anti-inflammatory treatment in traditional Chinese medicine. Its working mechanism is not well known. In chapter 4, I report that extracts from this herb inhibit COX-2 by three mechanisms: direct inhibition, transcriptional and post-transcriptional down regulation. COX-1 and COX-2 are similar to each other in their crystallographic structures. One of the most striking differences is that there are eight amino acids immediately following the signal peptide in COX-1 which are not found in COX-2. The function of this sequence is unknown. In chapter 5, I found that deletion of these amino acids decreased COX-1 Vmax by approximately 4-fold, but had little effect on other properties of the enzyme. Selecting bacteria transformed with recombinant plasmids is a laborious step in gene cloning experiments. This selection process is even more tedious when large numbers of clones need to be screened. In appendix I, I describe an ultra fast plasmid screening method. This new method was frequently used in the experiments performed in chapters 2-6.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 203-238).

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Kimberly Kline and Bob G. Sanders. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

published_or_final_version / abstract / Surgery / Doctoral / Doctor of Philosophy

The objectives of this research were to elucidate the involvement of constrictor prostanoids in the vascular reactivity to vasopressin (VP) and the role of estrogen in the regulation of the constrictor prostanoid mechanism in the female rat. Aortas obtained from male, intact (InT)-, ovariectomized (OvX)- and OvX + estrogen-replaced (OvX+Est)-female rats were studied. Contractile responses to VP were examined in the presence of nonselective and selective cyclooxygenase (COX) inhibitors. Basal and VP-stimulated release of thromboxane A2 (TxA2) and prostacyclin (PGI2) from the aortic wall were measured. Concentration-response curves to exogenous TxA2 were also obtained. To elucidate the regulatory effects of estrogen on the constrictor prostanoid pathway, the expression of COX-1, COX-2, thromboxane synthase (TxS) and thromboxane receptor (TP) mRNA were detected by reverse transcription-polymerase chain reaction (RT-PCR). Further, immunohistochemistry was employed to determine COX-1, COX-2 and TxS protein expression in aortic endothelium and vascular smooth muscle. The major findings of this research are that: 1) The contractile responses of the female rat aorta to VP were enhanced by COX-2-mediated production of constrictor prostanoids (PGH2/TxA2), and this mechanism is potentiated by estrogen; 2) Vascular reactivity to exogenous TxA2 was higher in the female than in the male rat aorta, and OvX attenuated and estrogen replacement therapy restored vascular reactivity to TxA2 in the female aorta; 3) VP-stimulated release of endogenous TxA2 and PGI2 were higher in the female than in the male rat aorta, and OvX attenuated and estrogen replacement therapy restored VP-stimulated release of these endogenous prostanoids by the female aorta; and 4) The expression of COX-2 and TxS mRNA and protein, and the expression of TP mRNA were higher in InT-female than in male, and were reduced by OvX and restored by estrogen replacement therapy. In conclusion, estrogen potentiated contractile responses of the female rat aorta to VP by upregulating the expression of COX-2, TxS and TP; thereby enhancing VP-induced release of TxA2, as well as the vascular reactivity to endogenous TxA2.

The objectives of this research were to elucidate the involvement of constrictor prostanoids in the vascular reactivity to vasopressin (VP) and the role of estrogen in the regulation of the constrictor prostanoid mechanism in the female rat. Aortas obtained from male, intact (InT)-, ovariectomized (OvX)- and OvX + estrogen-replaced (OvX+Est)-female rats were studied. Contractile responses to VP were examined in the presence of nonselective and selective cyclooxygenase (COX) inhibitors. Basal and VP-stimulated release of thromboxane A2 (TxA2) and prostacyclin (PGI2) from the aortic wall were measured. Concentration-response curves to exogenous TxA2 were also obtained. To elucidate the regulatory effects of estrogen on the constrictor prostanoid pathway, the expression of COX-1, COX-2, thromboxane synthase (TxS) and thromboxane receptor (TP) mRNA were detected by reverse transcription-polymerase chain reaction (RT-PCR). Further, immunohistochemistry was employed to determine COX-1, COX-2 and TxS protein expression in aortic endothelium and vascular smooth muscle. The major findings of this research are that: 1) The contractile responses of the female rat aorta to VP were enhanced by COX-2-mediated production of constrictor prostanoids (PGH2/TxA2), and this mechanism is potentiated by estrogen; 2) Vascular reactivity to exogenous TxA2 was higher in the female than in the male rat aorta, and OvX attenuated and estrogen replacement therapy restored vascular reactivity to TxA2 in the female aorta; 3) VP-stimulated release of endogenous TxA2 and PGI2 were higher in the female than in the male rat aorta, and OvX attenuated and estrogen replacement therapy restored VP-stimulated release of these endogenous prostanoids by the female aorta; and 4) The expression of COX-2 and TxS mRNA and protein, and the expression of TP mRNA were higher in InT-female than in male, and were reduced by OvX and restored by estrogen replacement therapy. In conclusion, estrogen potentiated contractile responses of the female rat aorta to VP by upregulating the expression of COX-2, TxS and TP; thereby enhancing VP-induced release of TxA2, as well as the vascular reactivity to endogenous TxA2.

Thesis (Ph. D. in Cancer Biology)--Vanderbilt University, May 2008. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--Michigan State University. Dept. of Biochemistry and Molecular Biology, 2007. / Title from PDF t.p. (viewed Aug. 17, 2009). Includes bibliographical references (p. 114-125). Also issued in print.

Immune-mediated hemolytic anemia (IMHA) is one of the most common causes of anemia in dogs. Despite aggressive therapy, there is a 50% mortality rate in IMHA patients, and the most common cause of death is thromboembolic disease, particularly pulmonary thromboembolism. With the high thromboembolism rate in dogs with IMHA, anti-platelet therapy with aspirin can be a life-saving preventative therapy. Along with anti-platelet therapy, immunosuppressive therapy is needed to decrease erythrocyte destruction. Cyclosporine has become a popular medication for immunosuppression in IMHA patients. Unfortunately, recent human reports have suggested that cyclosporine could activate platelets and contribute to a hypercoagulable state. With the goal of improving therapy, these studies investigated the role aspirin plays in inhibiting platelet function and cyclooxygenase expression, an enzyme that enhances platelet reactivity. The effect of cyclosporine on platelet reactivity and hypercoagulablity was investigated to determine if this medication would create activated platelets and a prothrombotic state.