Proposal is designed to elucidate pharmacologic mechanisms whereby endotoxin alters vascular reactivity. Endotoxin exposure in vivo or in vitro impairs contractile responses in isolated aorta principally by inducing the expression of an (abnormal) nitric oxide (NO) synthase activity. It acts separately on endothelium to inhibit the elaboration of endothelium-derived relaxing factor (EDRF) in response to vasorelaxant agonists. Proposed studies, performed in cultured endothelial and vascular smooth muscle cells, isolated conduit and resistance size arteries, will determine cellular mechanisms mediating these vascular effects of endotoxin. Protocols will use measures of isometric contraction and relaxation, superfusion bioassay of EDRF production, fluorescence measurement of cytosolic calcium, responses of permeabilized arteries, and of microvascular tissue to explore the hypotheses that: 1) Endotoxin exposure modulates the activity of specific endothelial signal-transduction systems impairing EDRF synthesis by limiting the rise in endothelial cytosolic free calcium in response to vasorelaxant agonists, 2) Endotoxin impairs vascular smooth muscle contractile responses, principally via an NO-dependent mechanism, both by limiting the availability of cytosolic calcium as well as by impairing the calcium sensitivity of the contractile apparatus, 3) Endotoxin induces similar changes in microvascular endothelial and smooth muscle function, contributing to its systemic hemodynamic effect. Sepsis, or endotoxin administration, often results in pressor-refractory hypotension due primarily to low systemic vascular resistance and to organ failure which may be related to an impairment in tissue oxygen utilization by disordered regulation of blood flow distribution. Results of these studies will clarify mechanisms responsible for endotoxin-induced changes in both vasoconstriction and vasodilation, providing insights into pathophysiology of hemodynamic changes in sepsis which may be exploited therapeutically.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29HL048302-04
Application #
2224375
Study Section
Pharmacology A Study Section (PHRA)
Project Start
1992-04-17
Project End
1997-03-31
Budget Start
1995-04-01
Budget End
1996-03-31
Support Year
4
Fiscal Year
1995
Total Cost
Indirect Cost
Name
University of Chicago
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
225410919
City
Chicago
State
IL
Country
United States
Zip Code
60637
Wylam, M E; Metkus, A P; Umans, J G (2001) Nitric oxide dependent and independent effects of in vitro incubation or endotoxin on vascular reactivity in rat aorta. Life Sci 69:455-67
Davidson-Garcia, C A; Nalbantian-Brandt, C; Umans, J G (2000) Possible role of P-450-derived metabolites in endothelium-dependent relaxation of rat small mesenteric arteries. Life Sci 66:1097-104
Pascoal, I F; Lindheimer, M D; Nalbantian-Brandt, C et al. (1998) Preeclampsia selectively impairs endothelium-dependent relaxation and leads to oscillatory activity in small omental arteries. J Clin Invest 101:464-70
Umans, J G; Salvi, D; Murray, P T et al. (1998) Selectivity of endotoxin-induced defect in endothelial calcium mobilization. Kidney Int 54:1063-9
Wylam, M E; Gungor, N; Mitchell, R W et al. (1998) Eosinophils, major basic protein, and polycationic peptides augment bovine airway myocyte Ca2+ mobilization. Am J Physiol 274:L997-L1005
Murray, P T; Wylam, M E; Umans, J G (1998) Endotoxin impairs agonist-induced calcium mobilization in bovine aortic myocytes by a nitric oxide-independent mechanism. J Lab Clin Med 131:336-43
Murray, P T; Wylam, M E; Umans, J G (1997) Endotoxin impairs agonist-induced calcium mobilization in rat mesangial cells. Am J Respir Crit Care Med 156:1846-54
Pascoal, I F; Umans, J G (1996) Effect of pregnancy on mechanisms of relaxation in human omental microvessels. Hypertension 28:183-7
Yamasaki, M; Lindheimer, M D; Umans, J G (1996) Effects of pregnancy on femoral microvascular responses in the rat. Am J Obstet Gynecol 175:730-6
Schumacker, P T; Kazaglis, J; Connolly, H V et al. (1995) Systemic and gut O2 extraction during endotoxemia. Role of nitric oxide synthesis. Am J Respir Crit Care Med 151:107-15

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