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BS13 Intravital investigations of the role of IL-36 in mediating age and gender specific changes in the injured beating coronary microcirculation
  1. Juma El-awaisi,
  2. Dean Kavanagh,
  3. Neena Kalia
  1. University of Birmingham, Birmingham, UK

Abstract

Introduction Whilst blood flow restoration is critical following myocardial infarction (MI), ischemia-reperfusion injury (IRI) accounts for ~50% of the final infarct size. We have previously shown intravitally that myocardial IRI induces thromboinflammation and reduces functional capillary density (FCD) in adult mouse beating heart microcirculation in vivo. [1] The newly discovered and inflammatory cytokine, interleukin-36 (IL-36), could potentially mediate these disturbances. However, its role in myocardial IRI is not known. This study aimed to determine whether coronary microcirculatory disturbances and infarct size post-IRI were modified by age and gender. Secondly, we investigated if IL-36 (α/β) and its receptor (IL-36R) were present in the heart, and whether their expression varied in an injury and age-related manner. Lastly, we investigated whether an IL-36 receptor antagonist (IL-36Ra) could confer vasculoprotection and reduce myocardial infarction.

Methods Myocardial IRI was induced in adult (3-months) and aged (>18-months) female mice, with gender differences assessed in adult male and female mice. Beating heart coronary microcirculation was imaged intravitally and also ex vivo using multiphoton microscopy. IL-36R/α/β, and VCAM-1 expression were investigated immunohistochemically or using western blots. In some studies, recombinant mouse IL-36Ra (15ug/mouse) was injected intra-arterially at 5 minutes pre-reperfusion and 60 minutes post-reperfusion. Infarct size was measured using dual TTC/Evans Blue staining.

Results Significantly increased basal (p<0.0001) and IRI-induced (p<0.0001) neutrophil recruitment, and greater decreases in FCD, was observed in aged mice compared to adults. Neutrophils primarily adhered within coronary capillaries although in aged hearts remarkable venular adhesion was also identified. These events were mirrored in deeper myocardial layers when imaged using multiphoton microscopy. Interesting gender-dependent perturbations were noted. Neutrophil recruitment dominated in injured female hearts whilst male hearts demonstrated a greater presence of occlusive platelet microthrombi. IL-36R/α/β were expressed predominantly on vasculature of murine hearts, with cardiomyocyte and intercalated disc expression being observed. Expression of IL-36R/α/β and VCAM-1 significantly increased with injury and age (see table 1). Interestingly, increased injury and age- related vascular expression of IL-36R/α/ß was observed specifically on micro- and not macro-vessels. IL-36Ra significantly reduced inflammation (p<0.0001) and infarct size (p<0.0001) in both adult and aged mice.

Abstract BS13 Table 1

Conclusion Our novel findings of enhanced coronary microcirculatory perturbations associated with age may explain the poorer outcomes in elderly MI patients. Furthermore, the cellular nature of the thromboinflammatory response may explain the gender-related differences in outcome after MI. Importantly, we are the first to demonstrate that targeting IL-36 may be a potential novel therapy for treatment of myocardial IRI.

Conflict of Interest No

  • Novel targets for myocardial infarction
  • IL-36
  • Ageing

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