Left ventricular dysfunction and Heart Failure (HF) are associated with systemic inflammation with clinical data showing that HF patients have higher levels of circulating pro-inflammatory cytokines. Recruitment of circulating T cells to tissues across the vascular endothelium is a key event in the inflammatory response, but whether it plays a role in the heart in HF is unknown. We hypothesized that pressure overload induced HF activates cardiac endothelial cells resulting in T cell recruitment into the left ventricle (LV). Using transverse aortic constriction (TAC), quantitative flow cytometry, immunohistochemistry, qPCR and real time live cell videomicroscopy, we examined mRNA and protein expression levels of endothelial cell adhesion molecules and the presence of T cell infiltrates in the LV
in vivo
, and also studied the T cell interactions with primary mouse heart endothelial cells (MHEC) under flow conditions
in vitro
, comparing Sham and TAC operated mice (6-10/group) during the course of HF. 48h after TAC, in the pre-hypertrophic state, no differences were observed in the recruitment of T cells in the LV. Interestingly, two and four weeks after TAC, when mice developed LVH and LV dysfunction (Fractional Shortening 25±13%), E-Selectin, VCAM-1 and ICAM-1 mRNA levels were significantly upregulated in the LV as compared to Sham mice (2.3, 2.8 and 4 fold, respectively), with notable enhancement of endothelial ICAM-1 protein levels in the LV intramyocardial vessels, and T cells infiltrated in the LV in response to TAC (P≤0.05 TAC vs Sham). Furthermore, T cells isolated from mice 2 and 4 weeks after TAC adhered to MHEC under flow conditions in significantly higher numbers than T cells from Sham mice (P≤0.01 TAC vs Sham). Systemically, the frequency of three different T cell subsets in the peripheral lymphoid organs was increased in TAC vs Sham mice, indicating activation of the adaptive immune response to pressure overload. Taken together, our studies indicate that activation of the heart vascular endothelium occurs in response to pressure overload resulting in T cell recruitment into the LV. Further studies will be needed to determine in the extent to which T cell recruitment into the heart contributes to the pathogenesis of HF.
Angiotensin II induces apoptosis of human right and left ventricular endocardial endothelial cells by activating the AT2 receptor