Cytokine Regulation in Sepsis and
Inflammation
(R37 GM40586)
Proinflammatory cytokines in general, and tumor necrosis factor (TNF)
in particular, play pivotal roles in the host response to acute and
chronic inflammation. Although much of the interest in TNF has focused
on its proinflammatory properties, TNF and other members of its
superfamily, including Fas ligand (FasL), induce programmed cell death
(apoptosis) in selected cell populations. Elucidation of the TNF
receptors involved, well as the intracellular signaling pathways for
TNF and FasL which lead to apoptosis and/or inflammation is essential
for an in vivo understanding of how TNF (and FasL) mediate their
actions during acute inflammation and sepsis, as well as for the
rational development of therapies to prevent their undesirable
actions.
Therefore, the specific aims of the current application are: l) to
determine the relative contributions of p55 and p75 TNF receptor
activation to TNF mediated inflammation and apoptosis, 2) to examine
intracellular signal-transduction pathways responsible for TNF
mediated inflammation and apoptotic cell death, 3) to explore FasL
synthesis in acute inflammation and to dissect the role that FasL
plays in the induction of TNF, and vice versa, and, 4) to determine
the contribution of TNF and FasL to the apoptotic injury during acute
inflammation.
Two approaches are proposed. In murine studies, proinflammatory and
apoptotic responses to either lipopolysaccharide (with
D-galactosamine), concanavalin A, or a cecal ligation and puncture
will be evaluated in transgenic mice expressing null forms of p55,
p75, Fas, caspase-l, acid-sphingomyelinase, or the p50 component of
NF-KB to identify key pathways involved in TNF and FasL signaling. In
addition, proinflammatory and apoptotic processes will be evaluated in
both healthy nonhuman primates (Papio) receiving novel TNF muteins
with specificity for the p55 or p75 TNF receptor, or E. coli
bacteremic animals receiving novel inhibitors of TNF and FasL. Using
an whole blood model, intracellular signaling pathways for LPS or
TNF-mediated cytokine production an ptosis will be determined using
these TNF muteins and inhibitors of caspase activity. Therefore, the
overall goals of this application are to identify the importance of
TNF and FasL to proinflammatory and apoptotic responses in
well-described murine and primate models of inflammation, to identify
critical intracellular signaling pathways responsible for both the
proinflammatory and apoptotic actions of TNF and FasL, and to
determine which TNF receptors (p55 or p75) contribute to inflammation
and apoptosis.
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