Pharmacological blockade of the Interleukin-1 receptor suppressed E. coli lipopolysaccharide-induced neuroinflammation in preterm fetal sheep.

BACKGROUND: Intraamniotic inflammation is associated with preterm birth, especially in cases occurring before 32 weeks' gestation, and is causally-linked with increased risk of neonatal mortality and morbidity. Targeted anti-inflammatory interventions may assist in improving outcomes for pregnancies impacted by intrauterine inflammation. Interleukin (IL)-1 is a central upstream mediator of inflammation. Accordingly, IL-1 is a promising candidate target for intervention therapies, and has previously been targeted using the IL-1 receptor antagonist, anakinra. Recent studies have shown that the novel non-competitive allosteric IL-1 receptor inhibitor, rytvela, partially resolved inflammation associated with preterm birth and fetal injury. In the present study, we used a preterm sheep model of chorioamnionitis to investigate the anti-inflammatory efficacy of rytvela and anakinra, administered to the amniotic fluid in the setting of intraamniotic E. coli lipopolysaccharides (LPS) exposure.

OBJECTIVE: We hypothesized that both rytvela and anakinra would reduce LPS-induced intrauterine inflammation and protect the fetal brain.

STUDY DESIGN: Ewes with a singleton fetus at 105 days of gestation (GA; term is ∼150 days) were randomized to one of the following groups: i) Intraamniotic (IA) injections of 2 ml saline at time = 0 and time = 24 hours as a negative control group (Saline Group, n=12); ii) IA injection of 10 mg E.coli LPS in 2 ml saline and IA injections of 2 ml saline at time = 0 hours and time = 24 hours as an inflammation positive control group (LPS Group, n=11); iii) IA injection of E.coli LPS in 2 ml saline and IA injections of 2.5 mg rytvela at time = 0 hours and time = 24 hours to test the anti-inflammatory efficacy of rytvela (LPS + rytvela Group, n=10); or iv) IA injection of E.coli LPS in 2 ml saline and IA injections of 100 mg anakinra at time = 0 hours and time = 24 hours to test the anti-inflammatory efficacy of anakinra (LPS + anakinra Group, n=12). Amniotic fluid was sampled at time = 0, 24 and 48 hours (i.e. at each intervention and at delivery). Fetal cord blood was collected at delivery for differential blood counts and chemical studies. Inflammation was characterized by the analysis of fetal tissue cytokine/chemokine levels using quantitative polymerase chain reaction (qPCR), enzyme-linked inmmunosorbent assay (ELISA), and histology. The primary study outcome of interest was the assessment of anakinra and rytvela brain-protective effects in the setting of E.coli LPS-induced intrauterine inflammation. Secondary outcomes of interest were to assess protection from fetal and intrauterine (i.e. amniotic fluid, chorioamnion) inflammation.

RESULTS: IA administration of LPS caused inflammation of the fetal lung, brain and chorioamnionitis in preterm fetal sheep. Relative to treatment with saline only in the setting of LPS exposure, IA administration of both rytvela and anakinra both significantly prevented periventricular white matter injury, microglial activation, and histologic chorioamnionitis. anakinra showed additional efficacy in inhibiting fetal lung MPO activity, but its use was associated with metabolic acidaemia and reduced fetal plasma IGF-1 levels at delivery.

CONCLUSION: IA administration of rytvela or anakinra significantly inhibited fetal brain inflammation and chorioamnionitis in preterm fetal sheep exposed to intraamniotic LPS animals. Additionally, anakinra treatment was associated with potential negative impacts on the developing fetus.