DOI: 10.1161/circ.148.suppl_1.12972 ISSN: 0009-7322

Abstract 12972: Trained Innate Immunity Through Toll-Like Receptor 4/Interferon Signaling Establishes Cardioprotection in a Stress-Induced Cardiomyopathy Model

Kenji Rowel Q Lim, Tomohiro Hayashi, Sajal K Tiwary, Attila Kovacs, Abhinav Diwan, Douglas L Mann
  • Physiology (medical)
  • Cardiology and Cardiovascular Medicine

Introduction: Although extensively studied, the mechanisms responsible for the development of cardioprotection following preconditioning stimuli are not known. Our group showed that isoproterenol (ISO) mediated cardiac injury induces potent cardioprotection against a second ISO challenge for up to 5 weeks. The lack of an immune response after the second ISO dose and the durability of protection suggested that trained innate immunity might represent a novel mechanism for cardioprotection.

Hypothesis: We hypothesized that ISO confers cardioprotection through trained immunity via Toll-like receptor 4 (TLR4) signaling that is activated by damage-associated molecular patterns released by ISO-induced cell necrosis.

Methods: Wild-type C57BL/6J mice were intraperitoneally injected with TLR agonists or diluent (saline), and then 300 mg/kg ISO a week later. Mice were assessed before and after receiving ISO via serum cardiac troponin analysis, flow cytometry, and 2-D echocardiography.

Results: The TLR4 agonist lipopolysaccharide (LPS), but not TLR1/2 or TLR3 agonists, induced cardioprotection as shown by decreased troponin I release (p<0.01), reduced cardiac neutrophil influx (p<0.05), and decreased left ventricle wall motion abnormalities (p<0.05) following ISO injury compared to saline treated controls . RNA sequencing identified interferon signaling as commonly upregulated (p<0.05) in mouse hearts a week after LPS or ISO pre-treatment. Blocking type I/II interferon receptors partially abolished LPS-induced cardioprotection, while pre-treatment with recombinant interferon β+γ conferred cardioprotection as shown by decreased troponin I release post-ISO (p<0.01). Given that β-glucan reverses the epigenetic tolerizing effects of LPS in immune cells, we treated mice with β-glucan following LPS pre-treatment and observed that the cardioprotection to ISO was abolished.

Conclusions: Viewed together this study shows for the first time that TLR4/interferon signaling confers cardioprotection against ISO-induced injury. Our findings further suggest that this cardioprotective response may be secondary to TLR4 mediated epigenetic changes that dampen immune responses following tissue injury, consistent with trained innate immunity.

More from our Archive