Abstract 1413: Interleukin 13 Exerts Anti-appoptotic Effects On Hypoxic Cardiomyocytes Through Pi3 Kinase In The Absence Of Hypertrophic Effects
Objectives: Recent research has focussed on anti-inflammatory cytokines (a-ICs) as cardio-protective agents. A-ICs were mainly considered in the context of inhibition of secretion of pro-ICs such as tumour necrosis factor-α and with the exception of transforming growth factor β little is known about direct effects of a-ICs on cardiomyocytes (CMC).
Methods: To clarify a direct functional relationship of a-ICs we evaluated effects of interleukin-4, -10 and -13 on cultured CMC by planimetry, confocal microscopy (CF), protein synthesis determination (PS), 2DE-analysis (2DE), mass spectrometry and Western blotting. Intracellular pathways were analysed with specific chemical inhibitors. Anti-appoptotic effects were evaluated by determinating the cell number, cleaved caspase 3 (cC3) and PARP (cP) under 2% O2. Untreated cell lines (unCO) or leukemia inhibitory factor (LIF) treated CMC served as controls.
Findings: In contrast to Il-13 we did not detect effects of Il-4 and Il-10 on CMC. Il-13 treated CMC showed a 40% (p<0.01) increased viability over unCO under normoxic and 65% (p<0.01) under hypoxic conditions after 4d and 12h, respectively. Under hypoxia antiapoptotic effects were visible in 60% reduction of cC3 (60%; p<0.05) and cP (40%; p<0.05). Using a battery of more than 300 phospho-specific antibodies we found that phosphorylation of Akt (5-fold, p<0.01) was the predominant activated pathway but we found also mild increases in P-MEK1/2 (1.7-fold). The antiapoptotic effects and Akt activation were abolished in the presence of the PI3 kinase inhibitor (20μM) LY294002 (p<0.01) but not in the presence of the MEK1/2 inhibitor (5μM) UO126. In contrast we did not find any significant morphological changes of CMC in the presence of Il-13 neither in the protein composition of structural proteins (2DE, CF), nor increases in PS nor changes in cell surface area, width and length opposing hypertrophic responses visible after LIF treatment.
Conclusions: These findings indicate that Il-13 can directly support myocyte function in addition to its inactivation of immune cells. Our results and the existence of a Il-13 receptor in the heart altogether throws light on Il-13 as a promising therapeutical target.