Assessment of Spontaneous NF-B Activation in Circulating Monocytes (Protocol A)

(A) Electrophoresis mobility shift assay (EMSA). In each patient, freshly isolated peripheral blood monocytes (5 x 10⁵) were analyzed for the spontaneous presence of activated nuclear factor (NF)-B complexes in their nuclei by EMSA in the presence of anti-p50 subunit monoclonal antibodies or isotype-matched control IgG antibodies. As a positive control (Pos) nuclear extracts were generated from 5 x 10⁵ monocytes incubated for 30 min with 10 ng/ml lipopolysaccharide (LPS), and as a negative control (Neg) nuclear extracts were generated from 5 x 10⁵ monocytes incubated for 30 min with phosphate-buffered solution only. NF-B heterodimers containing the p50 subunit were detected in 82% of group 1 patients, 14% of group 2 patients, and 21% of group 3 patients (p < 0.001; group 1 vs. group 2 and group 3). The figure shows the assessment of NF-B activation in 3 patients (Pt) of group 1 and in 3 patients of group 2. (B) Enzyme-linked immunosorbent assay (ELISA) for active NF-B p65. The amount of activated NF-B p65 subunit in nuclear extract (5 µg), prepared from 5 x 10⁵ monocytes was assessed by a sensitive ELISA assay for active NF-B. The activated NF-B p65 subunit was significantly higher in group 1 than in the other groups. ANOVA = analysis of variance; OD = optical density.

Inflammatory Response According to the NF-B Activation Status (Protocol A)

Serum levels of CRP (A), and production of IL-6 (B) and TNF- (C) in response to in vitro LPS challenge were significantly higher in patients with (NF-B+) than in those without (NF-B–) NF-B activation. (B and C) Monocytes (5 x 10⁵) were stimulated with a low dose of LPS (1 ng/ml); after 4 h of incubation, the culture supernatant was removed and stored at –80°C for IL-6 and TNF- measurements by ELISA. CRP = C-reactive protein; IL = interleukin; TNF = tumor necrosis factor; other abbreviations as in Figure 1.

CRP Induction of NF-B Activation in Circulating Monocytes as Assessed by EMSA (Protocol B)

In 8 healthy volunteers, aliquots of 5 x 10⁵ cells were incubated at 37°C in PBS and stimulated with increasing doses of recombinant human (rh) CRP (5 to 10 to 25 µg/ml) for 30 min to assess the effects on NF-B activation. A cell aliquot was incubated with the NF-B inhibitor pyrrolidine dithiocarbamate (PDTC) (50 mmol/l) for 1 h before CRP stimulation (25 µg/ml), and another cell aliquot was stimulated with CRP (25 µg/ml) denatured by incubation in boiling water bath for 1 h (25den). As a positive control (Pos) nuclear extracts were generated from 5 x 10⁵ monocytes incubated for 30 min with 10 ng/ml LPS, and as a negative control (Neg) nuclear extracts were generated from 5 x 10⁵ monocytes incubated for 30 min with PBS only. As shown in this representative EMSA, NF-B activation in circulating monocytes was induced by stimulation with increasing doses of rhCRP and inhibited by preincubation with PDTC (50 mmol/l) and by the use of denatured rhCRP (A); coincubation of both rhCRP and LPS had a greater-than-additive effect (B). Gel supershift experiments with monoclonal antibodies to the p50 subunit indicated that complexes consisted of heterodimers containing the p50 subunit. Other abbreviations as in Figures 1 and 2.

CRP Amplified the Effect of LPS on NF-B Activation (Protocol B)

Quantification of the nuclear expression of the activated NF-B p65 subunit was performed by ELISA and expressed as OD at 450 nm. The experimental conditions are as described in Figure 3. Purified CRP, used for the ELISA at the increasing doses of 5 to 10 to 25 µg/ml, induced a slight but significant increase in NF-B p65 expression (p = 0.002) up to a mean ± SD value of 0.174 ± 0.164 OD with the dose of 25 µg/ml, 75% over the basal value (0.099 ± 0.081 OD). Pretreatment with the NF-B inhibitor PDTC prevented the NF-B activation induced by purified CRP, as well as the use of denatured CRP (25den) (A); *p < 0.05, purified CRP 25 µg/ml versus the basal value; **p < 0.01, purified CRP 25 µg/ml versus PDTC inhibition and denatured CRP (25den). LPS alone, at the low dose of 10 ng/ml, induced a mean ± SD increase in NF-B p65 expression of 0.133 ± 0.126 OD (35% over the basal value; p = 0.042). Coincubation of purified CRP with LPS induced a further increase in NF-B expression, particularly evident with 25 µg/ml of CRP, up to a mean ± SD value of 0.257 ± 0.162 OD (159% over the basal value), which was significantly greater than that observed with LPS alone (p = 0.001) or CRP alone (p = 0.003) (B). Abbreviations as in Figures 1 and 2.

Confocal Microscopy Assessment of NF-B Activation (Protocol B)

In 3 healthy volunteers, the nuclear accumulation of p65 in the presence of purified CRP (25 µg/ml), LPS (10 ng/ml), or both was assessed by confocal microscopy of monocytes (MO) stained with FITC-labeled antibody against p65. To identify the nucleus, monocytes were stained with 4-,6-diamidino-2-phenylindole dihydrochloride (DAPI). (A) In nonstimulated monocytes, p65 was distributed throughout the cytosol. After stimulation with purified CRP and LPS, p65 consistently disappeared from the cytosol and accumulated in the nucleus, especially after costimulation with both. After treatment of monocytes with denatured CRP, the pattern of the p65 subcellular distribution was similar to that in the nonstimulated cells. (B) Cells were scored as either positive or negative for nuclear p65, and the percentage of cells positive for nuclear p65 was calculated from at least 100 DAPI nuclei (counted for each of the 3 regions analyzed from each stained slide). The percentage of cells positive for nuclear p65 was 12% at baseline (unstimulated cells), 22% after stimulation with purified CRP alone, 30% after stimulation with LPS alone, and close to 50% after treatment with both CRP and LPS, and it was reduced to 16% when denatured CRP was used (25den) (p < 0.001). *p < 0.01, stimulation with LPS alone versus baseline; **p < 0.01, treatment with both CRP and LPS versus baseline, CRP alone, and LPS alone. Other abbreviations as in Figures 1 and 2.