Abstract 3474: Cardiac -Specific SOCS3 Dificient Mice Shows Resistance to Lipopolysaccharide-Induced Cardiac Dysfunction
Background: Lypopolysaccharide (LPS)-induced left ventricular (LV) dysfunction is a well-established model for sepsis-induced acute heart failure. STAT3 signaling in the heart has been shown to promote cardiomyocyte survival during LPS-induced LV dysfunction. Little is known, however, about the role of negative regulation of STAT3 signaling during LPS-induced LV dysfunction. Suppressor of cytokine signaling 3 (SOCS3) is an intrinsic negative regulator of gp130 cytokine-induced STAT3 signaling that plays an important role in cardiomyocyte survival. In this study, we determined whether STAT3 signaling and its negative regulator SOCS3 would play a role in LPS-induced LV dysfunction.
Methods and Results: We examined the activation of STAT3 and inductions of gp130 cytokines and SOCS3 in the wild-type (WT) mice hearts after LPS injection by western blot and real-time PCR (RT-PCR). RT-PCR revealed that gp130 cytokines were markedly increased after AMI. Western blot revealed that STAT3 was markedly phosphorylated and SOCS3 was induced in WT mice hearts after LPS injection. To investigate the role of STAT3 signaling and SOCS3 in LPS-induced LV dysfunction, we generated cardiac-specific SOCS3 knockout mice (SOCS3-CKO). Left ventricular ejection fraction (LVEF) of SOCS3-CKO mice was similar to that of WT mice at baseline (64.2 ± 6.1 vs. 62.4 ± 4.4%). LPS (30mg/kg) elicited a significant and robust reduction of LVEF in both SOCS3-CKO mice and WT mice 3 hr after LPS injection (18 ± 4.5 vs. 16 ± 5.2%, p<0.01). LVEF in WT mice was further reduced 6 hr after LPS injection. On the other hand, interestingly, LVEF was restored to the baseline in SOCS3-CKO mice 6 hr after LPS injection (10.4 ± 3.9 vs. 62.2 ± 8.1%, p<0.01). Also the duration and intensity of STAT3 phosphorylation after LPS injection was greater in SOCS3-CKO mice than WT mice. Furthermore, SOCS3-CKO mice showed greater survival rate than WT mice after LPS injection (p<0.01).
Conclusion: Our data show that the deletion of SOCS3 in cardiomyocytes prevents the LPS-induced LV dysfunction in mice, possibly by augmenting the STAT3-mediated gp130 cytokine signaling.