Abstract 589: Activation of Toll-like Receptor Induces Cardiac Remodeling
Introduction: Diastolic heart failure, due to increased ventricular stiffness, is brought about by extracellular matrix (ECM) remodeling. We have previously shown that T-lymphocyte function directly affects cardiac fibroblast function and thereby the ECM composition and diastolic function. Oligodeoxynucleotides (ODN) that selectively stimulate the Toll-like receptor-9 (TLR9) receptor on dendritic cells (DC), induce TH1 immune response.
Hypothesis: Selective stimulation of the DC TLR 9 receptor with ODN CPG1668 activates TH1 lymphocytes resulting in ECM remodeling and diastolic dysfunction.
Methods: Weight matched C57BL/6J female mice were treated either with PBS (n=8) or with CPG1668 (n=8) at a dose of 50 μg/mouse/week (i.p.) for 4 weeks. After 6 weeks, left ventricular mechanics were determined with pressure-volume loop analysis, ECHO, and ventricular tissue harvested for gene expression, collagen content and crosslinking, and the collagen crosslinking enzymatic activity of lysyl oxidase (LOX). Splenic lymphocytes were harvested for the cytokine determination.
Results: CPG1668 administration increased the TH1 cytokine, IFN-γ, from 429±21 to 954±21 (ng/106 T-cells), while TH2 cytokine, IL-4, decreased from 614±79 to 51±19 (pg/106 T-cells). CPG1668 significantly decreased the end-diastolic volume from 18±1 to 14±1μL (P=0.02), and cardiac output from 6.7±0.6 to 4.9±0.6 mL/min (P=0.05) with no change of ejection fraction 71±3 to 73±4 compared with controls. An increase of ventricular stiffness (β), from 0.16±0.01 to 0.23±0.01 mmHg/μL (P=0.0007), was supported by a decreased E deceleration slope of −8.8±0.6 to −4.1±0.4 (P<0.0001). CPG increased total cardiac collagen two-fold (P=0.0004) and collagen crosslinking by 3-fold (P=0.0007) compared with controls. Correspondingly, CPG administration increased cardiac LOX enzymatic activity by 61% (P=0.02). Real time PCR showed that LOXL3 gene expression increased 9.1-fold (P<0.0001) as well as LOX 1.7-fold (P=0.05) when comparing CPG with controls.
Conclusions: This study demonstrates that stimulation of the TH1 lymphocytes via DC TLR 9 receptor induces cardiac ECM remodeling and diastolic dysfunction associated with LOX induced collagen crosslinking.