Tumor Necrosis Factor-α Mediates Inflammation-induced Early-Stage Left Ventricular Systolic Dysfunction

Elevated systemic inflammation contributes to pathogenesis of heart failure with preserved ejection fraction (HFpEF), but molecular mechanisms are poorly understood. Although left ventricular (LV) diastolic dysfunction is the main cause of HFpEF, subclinical systolic dysfunction also contributes. We have previously shown that rats with collagen-induced arthritis (CIA) have systemic inflammation, LV diastolic dysfunction, and that increased circulating TNF-alpha contributes to inflammation-induced HFpEF pathogenesis, but does not mediate LV diastolic dysfunction in CIA rats. Contribution of systemic inflammation to dysfunction of the active process of LV diastolic and systolic function are unknown. In the present study, we used the CIA rat model to investigate the effects of systemic inflammation and TNF-alpha blockade on systolic function, and mRNA expression of genes involved in active diastolic relaxation and of myosin heavy chain (MyHC) isoforms. Collagen inoculation and TNF-alpha blockade did not affect LV mRNA expression of genes that mediate active LV diastolic function. Collagen-induced inflammation impaired LV global longitudinal strain (P = 0.03) and velocity (P = 0.04). This impairment of systolic function was prevented by TNF-alpha blockade. Collagen inoculation decreased mRNA expression of alpha-MyHC (Myh6, P = 0.03) and increased expression of beta-MyHC (Myh7, P = 0.0002), a marker, which is upregulated in failing hearts. TNF-alpha blockade prevented this MyHC isoform-switch. These results show that increased circulating TNF-alpha changes the relative expression of MyHC isoforms, favoring beta-MyHC, which may underlie changes in contractile function that impair systolic function. Our results indicate that TNF-alpha initiates early-stage LV systolic, rather than LV diastolic dysfunction.