Interleukin-18 mediates interleukin-1-induced cardiac dysfunction

Abstract

Patients with heart failure (HF) have enhanced systemic IL-1 activity, and, in the experimental mouse model, IL-1 induces left ventricular (LV) systolic dysfunction. Whether the effects of IL-1 are direct or mediated by an inducible cytokine, such as IL-18, is unknown. Recombinant human IL-18-binding protein (IL-18BP) or an IL-18-blocking antibody (IL-18AB) was used to neutralize endogenous IL-18 after challenge with the plasma of patients with HF or with recombinant murine IL-1β in adult male mice. Plasma levels of IL-18 and IL-6 (a key mediator of IL-1-induced systemic effects) and LV fractional shortening were measured in mice sedated with pentobarbital sodium (30-50 mg/kg). Mice with genetic deletion of IL-18 or IL-18 receptors were compared with matching wild-type mice. A group of mice received murine IL-18 to evaluate the effects on LV fractional shortening. Plasma from HF patients and IL-1β induced LV systolic dysfunction that was prevented by pretreatment with IL-18AB or IL-18BP. IL-1β failed to induce LV systolic dysfunction in mice with genetic deletion of IL-18 signaling. IL-1β induced a significant increase in plasma IL-18 and IL-6 levels. Genetic or pharmacological inhibition of IL-18 signaling failed to block the induction of IL-6 by IL-1β. In conclusion, IL-1 induces a release of active IL-18 in the mouse that mediates the LV systolic dysfunction but not the induction of IL-6. IL-18 blockade may therefore represent a novel and more targeted therapeutic approach to treat HF.

Keywords: heart failure; inflammation; interleukins; systolic dysfunction.

Fig. 1.

IL-18 blockade prevents heart failure (HF) plasma-induced dysfunction in the mouse. Healthy mice were injected with human plasma from healthy control subjects [control plasma (0.2 ml)] or human plasma from acute decompensated HF (ADHF) patients alone [ADHF plasma (0.2 ml)] or preceded by IL-18-binding protein (IL-18BP) [ADHF + IL-18BP (10 mg/kg)] or ADHF plasma (0.2 ml) preincubated with IL-18BP (ADHF & IL-18BP, 50 μg/ml of ADHF) at 37°C for 30 min before being injected intraperitoneally to the mouse. Echocardiographic measurements were performed at baseline and 4 h after the ADHF plasma injection and are reported as percent changes compared with baseline. Data (in %) are expressed as mean changes ± SE; n = 4–14 mice/group. *P < 0.001 vs. control plasma; #P < 0.001 vs. ADHF plasma; &P < 0.05 vs. ADHF + IL-18BP.

Fig. 2.

IL-1β increases IL-18 serum levels. A: healthy mice received a single intraperitoneal injection of vehicle (0.9% saline) or recombinant murine IL-1β (3 μg/kg) alone or in combination with anakinra. Left venticular fractional shortening (LVFS) changes compared with baseline are expressed (in %) as means ± SE. B: IL-18 levels were measured in vehicle- and IL-1β-treated mice after 4 h. Data (in pg/ml) are reported as means ± SE; n = 6–12 mice/group. *P < 0.001 vs. vehicle; #P < 0.01 vs. IL-1β; &P = 0.02.

Fig. 3.

IL-18 mediates IL-1β-induced systolic dysfunction. A: C57B6 wild-type (WT) mice, IL-18 knockout (KO) mice, and IL-18 receptor (IL-18R) KO mice were challenged with IL-1β (3 μg/kg). n = 6 mice/group. *P < 0.01 vs. WT mice. B: CD-1 WT mice were challenged with vehicle (0.9% NaCl) or IL-1β (3 μg/kg) alone or in combination with two doses of IL-18BP (1 and 10 mg/kg), and LVFS was recorded. The effects on LVFS of IL-18BP alone were recorded as a control. N = 6 mice/group. *P < 0.01 vs. IL-1β alone. C: IL-1β (3 μg/kg) was given alone or in combination with 1L-18-blocking antibody (IL-18AB; 5 mg/kg). n = 6 mice/group. *P < 0.001 vs. IL-1β or control antibody (Ctrl AB). D: a caspase-1 inhibitor (cas-1 inh) and two p38 inhibitors (SD-2012190 and SD-169) were given 30 min before IL-1β, and changes in LVFS were compared with the IL-18-alone group. n = 4–6 mice/group. *P < 0.05 vs. vehicle; #P < 0.01 vs. IL-1β. Data are reported as averages ± SE.

Fig. 4.

IL-18 induces reversible cardiac dysfunction. A: mice injected with a single dose of recombinant murine IL-18 (25 μg/kg) underwent echocardiography at baseline, 1 h, 4 h, 24 h, 7 days, and 14 days. n = 8 mice/time point. *P < 0.05 vs. baseline. B: four groups of mice were challenged with different doses of IL-18 (0.25, 2.5, 25, and 125 μg/kg), and LVFS was measured after 24 h. n = 6–8 mice/group. C: anakinra (10 mg/kg) was given 30 min before IL-18 (25 μg/kg) to detect effects on LVFS. n = 6 mice/group. Data (in %) are reported as average changes ± SE.

Fig. 5.

Blockade of IL-18 signaling does not prevent the IL-6 increase after IL-1β administration. A: plasma levels of IL-6 in C57BL6 WT, IL-18 KO, and IL-18R KO mice 4 h after IL-1β (3 μg/kg) injection. n = 6 mice/group. *P < 0.01 vs. vehicle. B: plasma levels of IL-6 in CD-1 WT mice treated with IL-18BP and the p38 inhibitor SD-169. n = 4–6 mice/group. *P = 0.01 vs. vehicle; #P < 0.05 vs. vehicle.