Leukemia inhibitory factor reduces contractile function and induces alterations in energy metabolism in isolated cardiomyocytes

Interleukin (IL)-6 related cytokines may be involved in the pathophysiology of heart failure. Leukemia inhibitory factor (LIF) is an IL-6 related cytokine, and elevated levels of LIF have been found in failing hearts. The aim of our study was to investigate how LIF may influence isolated cardiomyocytes. Adult cardiomyocytes were isolated from male Wistar rat hearts and treated with 1 nM LIF for 48 h. Contractile function was measured using a video-edge detection system. Fractional shortening was reduced at 0.25 Hz in LIF treated cells (7.4% ± 0.5%) compared to control cells (9.0% ± 0.7%). Gene expression analysis showed that expression of the mitochondrial ATP-synthase F1 α subunit was reduced in cells exposed to LIF. The activity of the enzyme was also reduced in these cells (0.10 ± 0.05 μmol/min per mg protein) compared to controls (1.23 ± 0.40 μmol/min per mg protein). The levels of ATP and creatine phosphate were reduced by 15.0% ± 3.0% and 11.2% ± 2.7% in LIF treated cells. LIF increased both 3H-deoxyglucose uptake and lactate levels, suggesting an increase in anaerobic energy metabolism. Beta-oxidation of 14C-oleic acid was increased by 51.2% ± 14.1% following LIF treatment, but no changes were found in cellular uptake or oxidation of 14C-oleic acid to CO2. In conclusion, LIF induces contractile dysfunction and changes in energy metabolism in isolated cardiomyocytes.