Suppressed T-cell growth lymphokine production and proliferation have been demonstrated in patients with severe trauma, burn, and sepsis, as well as in experimental animals with comparable injuries. Such a cell- mediated immunosuppression in conjunction with the hyperactivation of the macrophage/monocyte proinflammatory mediator response can evidently exacerbate the systemic inflammatory response syndrome in the injured hosts. The mechanisms of T-cell suppression are not well understood. We hypothesize that the inhibitory mediators such as TGF-beta, IL4, IL-10, PGE and glucocorticoid, that are collectively released by macrophage/monocyte, certain T-cells and adrenal cortex, interfere with the T-cell receptor (TCR)-associated early signal transduction pathways involving protein tyrosine kinases (PTK), protein kinase C (PKC), and intracellular Ca2+ (Ca2+i) mobilization, to cause T-cell deactivation. We will test this hypothesis in models of early and late stages of intraabdominal sepsis in rats and mice, and in rat or mouse splenic macrophage and T-cell co-cultures exposed to LPS. T-cell responses IL-2 secretion and IL-2 receptor expression, and cell signaling pathways will be assessed in primary T-lymphocyte cultures. The first specific aim is to determine the time course the release of the inhibitory mediators and changes in T-cell responses in septic rats and mice. Systemic release of the inhibitory mediators, and splenic tissue generation of inhibitory cytokines and their mRNAs will be quantified. The second specific aim is to define the changes in T-cell signaling pathways (PTK, PKC, Ca2+ mobilization) in septic animals. Ca2+ will be quantified in cell suspensions by means of Fura-2 photofluorometry, and in single cells using the Ca2+ imaging technique. The third specific aim is to determine through in vitro studies the direct effects of the inhibitory mediators, individually and in some combinations as warranted by previous studies, on the T-cells' signaling pathways, and to demonstrate that inhibitors/antibodies of the inhibitory mediators can abrogate the T-cell signaling alterations, and suppression of IL-2 production and proliferation in the LPS exposed co-cultures of splenic macrophages and T-lymphocytes from rats or mice. The fourth specific aim is to examine the putative effects of the blockers of PTK, PKC, and Ca2+i mobilization on T-cells' responses and to ascertain that agonist of PKC and Ca2+ mobilization can restore T-cell responses in rat splenic macrophage and T-lymphocyte co-cultures exposed to LPS. Through these in vivo and in vitro studies we will evaluate correlations and causal relationships between the inhibitory mediators and T-cell signaling and responses during the septic injury process. The proposed studies will allow for the development of rational immunomodulant therapies against suppressed cell- mediated immunity in sepsis.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM053235-04
Application #
2750060
Study Section
Special Emphasis Panel (ZRG7-SB (01))
Project Start
1995-08-01
Project End
1999-07-31
Budget Start
1998-08-01
Budget End
1999-07-31
Support Year
4
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Loyola University Chicago
Department
Physiology
Type
Schools of Medicine
DUNS #
791277940
City
Maywood
State
IL
Country
United States
Zip Code
60153
Sayeed, Mohammed M (2005) Inflammatory/cardiovascular-metabolic responses in a rat model of burn injury with superimposed infection. Shock 24 Suppl 1:40-4
Al-Ghoul, Walid M; Khan, Mehdi; Fazal, Nadeem et al. (2004) Mechanisms of postburn intestinal barrier dysfunction in the rat: roles of epithelial cell renewal, E-cadherin, and neutrophil extravasation. Crit Care Med 32:1730-9
Choudhry, Mashkoor A; Mao, Haihong; Haque, Farah et al. (2002) Role of NFAT and AP-1 in PGE2-mediated T cell suppression in burn injury. Shock 18:212-6
Fazal, N; Al-Ghoul, W M; Choudhry, M A et al. (2001) PAF receptor antagonist modulates neutrophil responses with thermal injury in vivo. Am J Physiol Cell Physiol 281:C1310-7
Choudhry, M A; Sir, O; Sayeed, M M (2001) TGF-beta abrogates TCR-mediated signaling by upregulating tyrosine phosphatases in T cells. Shock 15:193-9
Sayeed, M M (2000) Signaling mechanisms of altered cellular responses in trauma, burn, and sepsis: role of Ca2+. Arch Surg 135:1432-42
Fazal, N; Shamim, M; Khan, S S et al. (2000) Neutrophil depletion in rats reduces burn-injury induced intestinal bacterial translocation. Crit Care Med 28:1550-5
Fazal, N; Shamim, M; Zagorski, J et al. (2000) CINC blockade prevents neutrophil Ca(2+) signaling upregulation and gut bacterial translocation in thermal injury. Biochim Biophys Acta 1535:50-9
Fazal, N; Knaus, U G; Sabeh, F et al. (1999) Enhanced expression of neutrophil NADPH oxidase components in intestine of rats after burn injury. Shock 12:438-42
Choudhry, M A; Ahmed, Z; Sayeed, M M (1999) PGE(2)-mediated inhibition of T cell p59(fyn) is independent of cAMP. Am J Physiol 277:C302-9

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