Anne-Marie Koop

4 169 ( figure 4a ) and GDF-15 ( figure 4b ) increased after 2 weeks. IL-6 was increased at two weeks only, albeit with a large interindividual variation ( suppl. table 2 ). Expression of other cytokines (IL-1β (with fold changes in control versus PAB of 1:0.94, 0.33:0.47 and 0.55:0.38 at two, five, and twelve weeks respectively) and IL-33 ( suppl. table 2 ) did not change in response to pressure load. To assess whether the upregulated gene expression of CD68 resulted in increased macrophage infiltration, CD68 staining was performed. CD68 staining revealed positive trend of increased infiltration of macrophages in the pressure loaded RV at all time points, yet the increase was not statistically significant ( figure 4c,d ). RV pressue load did induce a transient increase in cardiac expression of NADPH oxidases 2 and 4 ( figure 4e,f resp. ), both of which are known to induce oxidative stress. Actual measurement of oxidative stress, by using advanced oxidation protein products (AOPP) assay, showed a positieve trend at all time points compared to controls, however, statistical significance was not met ( figure 4g ). No decreases in anti-oxidative capacity were observed, possibly due to the relatively low levels of oxidative stress ( figure 4h ). Expression of superoxide dismutase was unaffected ( suppl. table 2 ). Levels of AOPP and GDF-15 in blood plasma, showed no differenceswhen compared to controls at all time points ( figure 4i,j resp. ). DISCUSSION With this study in chronic experimental RV pressure load, we aimed to characterize the alterations in RV lipid content during chronic pressure load and to assess its correlation with RV-function, -remodelling and -metabolism over time. The main finding of this study is that chronic pressure load of the RV induces a decrease of myocardial lipid content, that is associated with the development of RV dysfunction. The decrease of intracardiac lipids was mostly expressed in the lipid major classes diglycerides and cardiolipins, driven by (poly)unsaturated forms. This included tetralinoleoyl-cardiolipin, themost abundant formof cardiolipin. The decrease in fatty acids was not accompanied by an impairment of mitochondrial fatty acid oxidation, whereas the mitochondrial respiratory capacity for glucose oxidation increased. RV pressure overload induced early expression of inflammatory and oxidative stress markers, that gradually faded again in the following weeks. This pattern corresponds to the pattern of the expression of pro-fibrotic genes, that preceded the occurrence of fibrosis in the RV. Decrease of cardiolipin levels, predominantly tetralinoleoyl-cardiolipin, has been described in different forms of heart failure, including pediatric heart failure. 35-39 Cardiolipin in the tetralinoleoyl-form (noted as CL18:2 4 , L 4 or more generally CL(72:8)) is the most abundant cardiolipin in the mitochondrial membrane of most tissues and