Mitogen-activated protein kinases regulate platelet-activating factor-induced hyperpermeability

Abstract

Objective: The authors tested the hypothesis that p42/44- (ERK-1/2) and/or p38-mitogen-activated protein kinases (MAPK) are in vivo regulatory elements in the platelet-activating factor (PAF) activated signaling cascade that stimulates microvascular hyperpermeability.

Methods: FITC-dextran 70 was used as the macromolecular tracer for microvascular permeability in the mouse mesenteric fat tissue. Interstitial integrated optical intensity (IOI) was used as an index of permeability.

Results: An application of 10(-7) M PAF increased IOI from 23.1 +/- 3.6 to 70.8 +/- 7.4 (mean +/- SEM). Inhibition of ERK-1/2 with 3 microM and 30 microM AG126 reduced IOI to 32.3 +/- 2.5. Similarly, inhibition of p38-MAPK with 6 nM, 60 nM and 600 nM SB203580 lowered IOI to 29.1 +/- 2.4.

Conclusions: The results demonstrate that ERK-1/2 and p38MAPK participate in the signaling cascade that regulates PAF-induced microvascular hyperpermeability in vivo.

Figure 1

PAF (10⁻⁷ M) increases microvascular permeability in mesenteric tissue–fat interphase. The panel shows the time course of microvascular permeability as assessed by changes in net IOI. PAF significantly increased IOI relative to control. Data are means ± SEM (n = 5 for control and PAF experiments; p < .05 at t = 5 min; p < .001 thereafter).

Figure 2

Inhibition of p42/p44 MAPK, with AG126, reduces PAF-induced hyperpermeability. The panel displays the time course of IOI as an index of microvascular permeability to FITC-dextran 70. Inhibitor was applied topically via superfusate, starting 10 min before topical application of 10⁻⁷ M PAF and continued throughout the remainder of the experiment. AG126 significantly inhibited PAF-induced hyperpermeability. Data are means ± SEM (n = 5 for PAF and each AG126 concentration; p < .01 at t ≥ 20 min).

Figure 3

Inhibition of p38-MAPK, with SB203580, reduces PAF-induced hyperpermeability. The panel displays the time course of IOI as an index of microvascular permeability to FITC-dextran 70. Inhibitor was applied topically via superfusate, starting 10 min before topical application of 10⁻⁷ M PAF and continued throughout the remainder of the experiment. SB203580 significantly inhibited PAF-induced hyperpermeability. Data are means ± SEM (n = 5 for PAF and each SB203580 concentration; p < .01 at t ≥ 20 min).