Biology Reference
In-Depth Information
response to LPS is exemplified in Fig. 6.19, where peritoneal exudate
cells (PEC's) from both normal mice (C3H/OuJ) and TLR4-inactive
mice (C3H/HeJ) were treated with LPS. The normal mouse PEC's
responded as expected, with high levels of TNFα secretion observed at
24 hours within the context of a standard dose-response curve. However,
the TLR4-defective HeJ mouse PEC's exhibited no discernable TNFα-
generating capability upon LPS stimulation. The identical experiment
with the gallotannin/ellagitannin hybrid
81
provided some insight into
the role that the TLR4 receptor might play in tannin-mediated secretion
of TNFα. There appeared to be a relatively small (compared to the LPS
data, see Fig. 6.19) but consistent decrease of TNFα release with the
TLR4-inactive HeJ mice compared to the OuJ mice controls (Fig. 6.20).
800
700
600
500
TNF
α
(pg/mL)
400
300
HeJ w/ LPS
OuJ w/ LPS
200
100
0
0
10
20
30
40
LPS conc (ng/mL)
Fig. 6.19 The TNFα secretion response upon treating normal OuJ mice and TLR4-
inactive HeJ mice with LPS.
The difference between these two mouse strains was much less
dramatic than in the LPS challenge experiment, with TNFα
concentrations hovering around 50-60% less in the HeJ series throughout
the concentration range. Nevertheless, as with the CD14 competitive
binding experiments, there is an unmistakably diminished response with
the TLR4-inactive mice, suggesting that at least some of the tannins'
effects require a functioning TLR4 receptor. Taken together, these
mechanistic experiments provide preliminary data that is entirely
consistent with a model whereby the tannin stimulant utilizes, at least in
