P2X7 receptor inhibition attenuated sympathetic nerve sprouting after myocardial infarction via the NLRP3/IL-1β pathway

Mounting evidence supports the hypothesis that inflammation modulates sympathetic sprouting after myocardial infarction (MI). The myeloid P2X(7) signal has been shown to activate the nucleotide-binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, a master regulator of inflammation. We investigated whether P2X(7) signal participated in the pathogenesis of sympathetic reinnervation after MI, and whether NLRP3/interleukin-1 beta (IL-1 beta) axis is involved in the process. We explored the relationship between P2X(7) receptor (P2X(7)R) and IL-1 beta in the heart tissue of lipopolysaccharide (LPS)-primed naive rats. 3'-O-(4-benzoyl) benzoyl adenosine 5'-triphosphate (BzATP), a P2X(7)R agonist, induced caspase-1 activation and mature IL-1 beta release, which was further neutralized by a NLRP3 inhibitor (16673-34-0). MI was induced by coronary artery ligation. Following infarction, a marked increase in P2X(7)R was localized within infiltrated macrophages and observed in parallel with an up-regulation of NLRP3 inflammasome levels and the release of IL-1 beta in the left ventricle. The administration of A-740003 (a P2X(7)R antagonist) significantly prevented the NLRP3/IL-1 beta increase. A-740003 and/or Anakinra (an IL-1 beta receptor antagonist) significantly reduced macrophage infiltration as well as macrophage-based IL-1 beta and NGF (nerve growth factor) production and eventually blunted sympathetic hyperinnervation, as assessed by the immunofluorescence of tyrosine hydroxylase (TH) and growth-associated protein 43 (GAP 43). Moreover, the use of Anakinra partly attenuated sympathetic sprouting. This indicated that the effect of P2X(7) on neural remodelling was mediated at least partially by IL-1 beta. The arrhythmia score of programmed electric stimulation was in accordance with the degree of sympathetic hyperinnervation. In vitro studies showed that BzATP up-regulated secretion of nerve growth factor (NGF) in M1 macrophages via IL-1 beta. Together, these data indicate that P2X(7)R contributes to neural and cardiac remodelling, at least partly mediated by NLRP3/IL-1 beta axis. Therapeutic interventions targeting P2X(7) signal may be a novel approach to ameliorate arrhythmia following MI.