Biomedical subjects

P O'Neal

Publications and source records attributed to P O'Neal.

10 recordsLinked to original sources

PubMed1999

Adherence of Borrelia burgdorferi. Identification of critical lysine residues in DbpA required for decorin binding.

Borrelia burgdorferi, the causative agent of Lyme disease, expresses on its surface two decorin binding adhesins, DbpA and DbpB. Previous studies have demonstrated that vaccination of mice with DbpA provided protection against challenge with heterologous Borrelia strains despite considerable sequence variability among DbpA in these strains. We have now examined the importance of individual amino acid residues in DbpA for decorin binding. We demonstrated that chemical modification of lysine residues resulted in loss of ligand binding activity. Of the 27 lysine residues in native DbpA from strain 297, 6 are present in most and 5 are conserved in all 30 DbpA sequences examined so far. Analysis of recombinant DbpA in which individual lysine residues have been mutated to alanine suggested that three of the conserved residues distributed throughout the DbpA sequence are required for decorin binding. These mutants lost their ability to bind decorin in Western ligand blot assay and bound reduced amounts of decorin in an ELISA. Furthermore, these mutant DbpA proteins did not inhibit the adherence of B. burgdorferi to a decorin substrata, and they did not recognize decorin in an extracellular matrix established by human fibroblast cultures. We conclude that the three lysine residues Lys-82, Lys-163, and Lys-170 are crucial for the binding of DbpA to decorin.

Amino Acid Sequence↗

PubMed1998

Eicosanoids in sickle cell disease: potential relevance of 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid to the pathophysiology of vaso-occlusion.

The monohydroxyeicosanoid 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE), which is derived from oxygenation of arachidonic acid by 12-lipoxygenase, is one of the major metabolites in platelets. In a recent study, we have showed that this eicosanoid stimulated basal sickle-red-cell-endothelial-cell adhesion. To understand the pathophysiologic significance of 12-HETE, we measured the levels of this eicosanoid in plasma and urine from children with sickle cell disease. We found that as compared with controls, plasma 12-HETE levels are increased in patients with sickle-cell disease in the steady state, and are increased further during vaso-occlusive crises. Urinary 12-HETE levels were also increased during the steady state. We also assessed plasma levels of soluble P-selectin (another potential marker for platelet activation), and found changes in the levels of this marker similar to those seen with plasma 12-HETE. In additional studies, we found that 12-HETE enhanced hypoxia-induced sickle-red-cell-endothelial adherence, and that this effect was mediated by potentiation of agonist-induced upregulation of the expression of the mRNA for vascular cell adhesion molecule-1 (VCAM-1) in endothelial cells. Because 12-HETE appears to enhance both basal and agonist-induced sickle-red-cell adhesion, this metabolite could potentially play a role in the pathogenesis of the vaso-occlusive crisis (VOC) in sickle-cell disease.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1996

Inhibition of neutrophil elastase suppresses the development of skin tumors in hairless mice.

In this study we investigated whether a reduction in neutrophil elastase activity in mice would alter the development of ultraviolet B or chemically induced skin tumors. A mutant strain of neutrophil elastase-deficient mice was developed by crossing beige mice with SKH 1 hairless mice. Ultraviolet irradiation three times per week for 20 wk developed an average of 10 tumors per normal mouse, whereas elastase-deficient hairless mice receiving the same treatment developed only 0.4 tumors per mouse. Benzopyrene administered topically for 20 wk resulted in an average of seven tumors per control mouse, while similar treatment to elastase-deficient hairless mice reduced the tumor count to 0.2 per mouse. Two small molecular weight elastase inhibitors, which were shown to inhibit mouse neutrophil elastase, were administered subcutaneously to normal SKH-1 mice during 16 wk of ultraviolet B exposure. Both inhibitors significantly reduced the incidence of ultraviolet B-induced tumors. When control and elastase-deficient mice were immunized with 2,4,6-trinitrochlorobenzene and oxazolone, both molecules elicited a significant contact hypersensitivity response. Ultraviolet B irradiation prior to immunization at a nonirradiated site completely suppressed the induction of contact hypersensitivity in both the normal and the deficient mice, suggesting that prevention of systemic immunosuppression was not the reason for the resistance to skin tumors observed in the elastase-deficient mice. The results suggest that neutrophil elastase can be an important factor in squamous cell tumor development.

Animals↗

PubMed1985