CD28/B7 Deficiency Attenuates Systolic Overload-Induced Congestive Heart Failure, Myocardial and Pulmonary Inflammation, and Activated T Cell Accumulation in the Heart and Lungs

Abstract

The inflammatory response regulates congestive heart failure (CHF) development. T cell activation plays an important role in tissue inflammation. We postulate that CD28 or B7 deficiency inhibits T cell activation and attenuates CHF development by reducing systemic, cardiac, and pulmonary inflammation. We demonstrated that chronic pressure overload-induced end-stage CHF in mice is characterized by profound accumulation of activated effector T cells (CD3(+)CD44(high) cells) in the lungs and a mild but significant increase of these cells in the heart. In knockout mice lacking either CD28 or B7, there was a dramatic reduction in the accumulation of activated effector T cells in both hearts and lungs of mice under control conditions and after transverse aortic constriction. CD28 or B7 knockout significantly attenuated transverse aortic constriction-induced CHF development, as indicated by less increase of heart and lung weight and less reduction of left ventricle contractility. CD28 or B7 knockout also significantly reduced transverse aortic constriction-induced CD45(+) leukocyte, T cell, and macrophage infiltration in hearts and lungs, lowered proinflammatory cytokine expression (such as tumor necrosis factor-α and interleukin-1β) in lungs. Furthermore, CD28/B7 blockade by CTLA4-Ig treatment (250 μg/mouse every 3 days) attenuated transverse aortic constriction-induced T cell activation, left ventricle hypertrophy, and left ventricle dysfunction. Our data indicate that CD28/B7 deficiency inhibits activated effector T cell accumulation, reduces myocardial and pulmonary inflammation, and attenuates the development of CHF. Our findings suggest that strategies targeting T cell activation may be useful in treating CHF.

Keywords: T-cell activation; congestive heart failure; heart; inflammation; leukocytes; lung.

Figure 1. CD28 deficiency attenuates transverse aortic constriction (TAC)-induced cardiac dysfunction and pulmonary congestion

Data were collected from wild-type (WT) and CD28 knockout (CD28 KO) mice under control conditions (Ctr) or 8 weeks after TAC. A to C, The ratio of left ventricle (LV), left atria (LA) and lung weight to body weight of mice. D to F, Echocardiographic measurements of LV ejection fraction, LV end-systolic diameter and LV end-diastolic diameter from hearts. G to I, Hemodynamics of LV end-diastolic pressure, LV maximum rate of rise of pressure (dP/dt_max) and LV maximum rate of decline of pressure (dP/dt_min) from hearts. J to L, Western blot of ANP, β-MHC and vinculin (loading control) in LV lysates of mice. *P<0.05 vs control group; ^#P<0.05 vs TAC group of WT mice.

Figure 2. B7 deficiency attenuates transverse aortic constriction (TAC)-induced cardiac dysfunction and pulmonary congestion

Data were collected from wild-type (WT) and B7 knockout (B7 KO) mice under control conditions (Ctr) or 8 weeks after TAC. A to C, The ratio of left ventricle (LV), left atria (LA) and lung weight to body weight of mice. D to F, Echocardiographic measurements of LV ejection fraction, LV end-systolic diameter and LV end-diastolic diameter from hearts. G to I, Hemodynamics of LV end-diastolic pressure, LV maximum rate of rise of pressure (dP/dt_max) and LV maximum rate of decline of pressure (dP/dt_min) from hearts. J to L, Western blot of ANP, β-MHC and vinculin (loading control) in LV lysates of mice. *P<0.05 vs control group; ^#P<0.05 vs TAC group of WT mice.

Figure 3. CD28 or B7 deficiency inhibits CD3⁺ T-cell activation and leukocyte accumulation in the left ventricle (LV) and lungs after transverse aortic constriction (TAC)

Flow cytometry data were collected from wild-type (WT) and CD28 or B7 knockout (KO) mice under control conditions (Ctr) or 8 weeks after TAC. A to C, Flow cytometry plots and quantitative data represent the percentage of CD3⁺CD44^high T cells (activated effector T cells) in LV tissues and lungs. D to F, Quantitative data represent total numbers of CD3⁺CD44^high T cells, CD3⁺ T cells and CD45⁺ cells in LV tissues and lungs. n=5–6 per group. *P<0.05 vs control group; ^#P<0.05 vs TAC group of WT mice.

Figure 4. CD28 or B7 deficiency inhibits transverse aortic constriction (TAC)-induced CD4⁺ and CD8⁺ T-cell activation and accumulation in the lung

Flow cytometry data of lungs were collected from wild-type (WT) and CD28 or B7 knockout (KO) mice under control conditions (Ctr) or 8 weeks after TAC. A and C, Flow cytometry plots and quantitative data represent the percentage of CD44^highCD62L^low T cells (effector memory T cells, TEM) within the CD4⁺ population of lungs. D, Total numbers of CD4⁺CD44^highCD62L^low T cells in lungs. B and E, Flow cytometry plots and quantitative data represent the percentage of CD44^highCD62L^low T cells within the CD8⁺ population of lungs. F, Total numbers of CD8⁺CD44^highCD62L^low T cells in lungs. n=5–6 per group. *P<0.05 vs control group; ^#P<0.05 vs TAC group of WT mice.

Figure 5. CD28 or B7 deficiency attenuates transverse aortic constriction (TAC)-induced lung macrophage infiltration and pro-inflammatory cytokine expression

Data were collected from lungs of wild-type (WT) and CD28 or B7 knockout (KO) mice under control conditions (Ctr) or 8 weeks after TAC. A, Flow cytometry plots and quantitative data represent the percentage of macrophages (F4/80⁺) in the lung. B, Quantitative data of flow cytometry represent the total number of macrophages in the lung. C to E, Quantitative RT-PCR results of IL-1β, TNF-α and MCP-1 mRNA levels in lung lysates. n=5–6 per group. *P<0.05 vs control group; ^#P<0.05 vs TAC group of WT mice.

Figure 6. CD28/B7 blockade attenuates transverse aortic constriction (TAC)-induced cardiac hypertrophy and dysfunction

Data were collected from mice under basal conditions (Ctr), or treated with human-Ig (vehicle) or CTLA4-Ig under TAC conditions. A to C, The ratio of left ventricle (LV), left atria (LA) and lung weight to body weight of mice. D to F, Echocardiographic measurements of LV ejection fraction, LV end-systolic diameter and LV end-diastolic diameter from hearts. *P<0.05 vs control group; ^#P<0.05 vs TAC group of vehicle mice.