Cytokine-mediated inflammatory hyperalgesia limited by interleukin-4

Abstract

1. The effect of IL-4 on responses to intraplantar (i.pl.) carrageenin, bradykinin, TNFalpha, IL-1beta, IL-8 and PGE2 was investigated in a model of mechanical hyperalgesia in rats. Also, the cellular source of the IL-4 was investigated. 2. IL-4, 30 min before the stimulus, inhibited responses to carrageenin, bradykinin, and TNFalpha, but not responses to IL-1beta, IL-8 and PGE2. 3. IL-4, 2 h before the injection of IL-1beta, did not affect the response to IL-1beta, whereas IL-4, 12 or 12+2 h before the IL-1beta, inhibited the hyperalgesia (-30%, -74%, respectively). 4. In murine peritoneal macrophages, murine IL-4 for 2 h before stimulation with LPS, inhibited (-40%) the production of IL-1beta but not PGE2. Murine IL-4 (for 16 h before stimulation with LPS) inhibited LPS-stimulated PGE2 but not IL-1beta. 5. Anti-murine IL-4 antibodies potentiated responses to carrageenin, bradykinin and TNFalpha, but not IL-1beta and IL-8, as well as responses to bradykinin in athymic rats but not in rats depleted of mast cells with compound 40/80. 6. These data suggest that IL-4 released by mast cells limits inflammatory hyperalgesia. During the early phase of the inflammatory response the mode of action of the IL-4 appears to be inhibition of the production TNFalpha, IL-1beta and IL-8. In the later phase of the response, in addition to inhibiting the production of pro-inflammatory cytokines, IL-4 also may inhibit the release of PGs.

Figure 1

Effect of IL-4 (2.5–10 ng, 100 μl, i.pl.) on hyperalgesic response to injections (in 100 μl, i.pl.) of carrageenin (Cg, 100 μg), bradykinin (BK, 500 ng), TNFα (2.5 pg), IL-1β (0.5 pg), IL-8 (100 pg), and PGE₂, (100 ng). IL-4 was injected into paws to be injected with a hyperalgesic agent, 30 min before the hyperalgesic agent. The intensity of hyperalgesia was measured 3 h after injection of hyperalgesic agents. Means±s.e.means in groups of five rats are shown.

Figure 2

Effect of IL-4 (10 ng, 100 μl, i.pl.) on hyperalgesic responses to injections (in 100 μl, i.pl.) of IL-1β (0.5 pg, panel A) and IL-8 (100 pg, panel B). IL-4 was injected into paws to be injected with a hyperalgesic agent, 2, 12, or 2+12 h before the hyperalgesic agent. The intensity of hyperalgesia was measured 3 h after injection of hyperalgesic agents. Means±s.e.means in groups of five rats are shown; ^*P<0.001, ^**P<0.0001.

Figure 3

Effect of IL-4 on the production of IL-1β and PGE by murine macrophages stimulated with LPS (3 μg ml⁻¹). The macrophages (10⁶ cells well⁻¹) were cultured with murine IL-4 (1.6 or 16 ng ml⁻¹) in medium (+) or medium alone (−). Two h or 12 h later the macrophages were stimulated with LPS (3 μg ml⁻¹) in medium (+) or with medium alone (−) for a further 16 h. At the end of this period the concentrations of IL-1β (panel A) and PGE₂ (panel B) in the macrophage-conditioned media were measured. Means±s.e.means of triplicate wells are shown; ^*P<0.001, ^**P<0.0001.

Figure 4

Effect of MAbs to IL-4, 11B11 and BVDG (50 μg in 50 μl, i.pl.), a control antibody and saline on hyperalgesic responses to injections (in 100 μl, i.pl.) of carrageenin (Cg, 10 μg), bradykinin (BK, 50 ng), TNFα (0.25 pg), IL-1β (0.05 pg), and IL-8 (10 pg). One of the MAbs or saline was injected into paws to be injected with a hyperalgesic agent, 30 min before the hyperalgesic agent. The intensity of hyperalgesia was measured 3 h after injection of hyperalgesic agents. Means±s.e.means in groups of five rats are shown. ^**P<0.0001.

Figure 5

Effect of a MAb to IL-4, BVDG (50 μg in 50 μl, i.pl., horizontally hatched columns) and a control MAb (open columns) on hyperalgesic responses to injections (in 100 μl, i.pl.) of bradykinin (BK, 50 ng, panel A,B) and dextran (200 μg, panel C) in athymic (nude) rats (panel A), wild type rats (panel C) and wild type rats depleted of mast cells (panel B). The MAbs were injected into paws to be injected with a hyperalgesic agent, 30 min before the hyperalgesic agent. The intensity of hyperalgesia was measured 3 h after injection of hyperalgesic agents. Means±s.e.means in groups of five rats are shown; ^**P<0.0001.