The Potential Effect Of Bazedoxifene On Cardiac Remodeling And Dysfunction Caused By Transverse Aortic Constriction

Part ? Bazedoxifene ameliorates cardiac remodeling induced by transverse aortic constriction in C57BL/6J miceObjective: As one of the inflammatory cytokines,IL-6 serves as a mediator in the pathogenesis of cardiac remodeling and the subsequent heart failure,but the role of IL-6/gp130/STAT3 signalling pathway in PO-induced cardiac remodeling keeps controversial.Our group previously demonstrated that bazedoxifene(BAZ),a selective estrogen receptor modulator approved for the prevention of osteoporosis in postmenopausal women,targeted IL-6/gp130 interface and suppressed its downstream signalling in cancer cells.Therefore,BAZ might potentially effect in setting the trajectory of cardiac remodeling.We aim to determine whether BAZ could benefit in cardiac remodeling and dysfunction caused by transverse aortic constriction(TAC)in C57BL/6J mice.Methods: H9c2 myoblasts were used to explore the effect of IL-6 and BAZ on cell hypertrophy.C57BL/6J mice(8-week-old,25 g)were randomized into three groups(sham,TAC,TAC + BAZ).BAZ was gavaged to mice in one group with surgery,and placebo was administrated in the other two groups.Cardiac function,body weight,tibia length,and heart weight were assessed at 4 and 8 weeks post TAC.Histologic staining of Masson and picrosirius red cooperated with PCR assays was to estimate cardiac remodeling.Results: In H9c2 cells IL-6 promoted cellular hypertrophy with elevated levels of ANP and BNP m RNA,which could be suppressed by BAZ.TAC increased heart weight,heart weight/body weight,heart weight/tibia length,and led to cardiac remodeling at 4 weeks post surgery without prominent cardiac dysfunction.BAZ attenuated cardiac hypertrophy and fibrosis in part,but had no significant effect on cardiac function after 4-week TAC.8-week TAC resulted in severe cardiac dysfunction accompanied by overt cardiac remodeling,with an increase in the m RNA expression of BNP,Col1A1,Col3A1 and periostin.BAZ alleviated cardiac remodeling,improved cardiac function,and downregulated the transcripts of hypertrophic or fibrotic markers in myocardium.Conclusions: Bazedoxifene ameliorated the hypertrophic response to IL-6 trigger in H9c2 cells,and could protect the myocardium from the cardiac insult induced by PO in TAC mice.Part ? The potential effect on IL-6/gp130/STAT3 signaling and autophagy in the mitigated cardiac remodeling by bazedoxifeneObjective: BAZ inhibits IL-6 signaling in cancer cells and benefits in TAC-induced myocardial disturbance,but it remains unclear whether BAZ could suppress IL-6/gp130/STAT3 signaling pathway in H9c2 cells and the hearts of TAC mice.Moreover,the effect of BAZ on autophagy is unknown.The study is performed to detect the potential effect on IL-6/gp130/STAT3 signaling and autophagy in the mitigated cardiac remodeling by bazedoxifene in TAC mice.Methods: Immunohistochemistry,western blot and PCR assays were used for detection of IL-6 signaling and autophagy in mice.C57BL/6J mice(8-week-old,25 g)were randomized into three groups(sham,TAC,TAC + BAZ).Mice were treated with BAZ or placebo as referenced in Part ?.Heart tissues were collected 3 hours after surgery to explore the markers of IL-6 signaling and autophagy in the acute window.In H9c2 cells,the effect of IL-6 and BAZ on autophagy was assessed,and western blot was utilized for determining the role of IL-6 in the response to Ang?.RFP-GFP-LC3 adenovirus and chloroquine was used for further study in the autophagic flux.Results: Ang? induced robust STAT3 phosphorylation,which could be inhibited by s IL-6R,indicating the presence of a mediator served by IL-6 in this process.IL-6/gp130/STAT3 signaling pathway was activated at both 3 hours and 8 weeks after TAC.The myocardial expression of LC3-? was reduced in the acute window but increased at 8 weeks post TAC.BAZ treatment inactivated IL-6 signaling as evidenced by reduced IL-6 infiltration,STAT3 phosphorylation,and decreased transcripts of MMP2 and IL-6 in myocardium.Moreover,BAZ reversed LC3-? expression changed by TAC at both time points.In H9c2 cells,IL-6 trigger decreased LC3-? expression,which could be upregulated by BAZ and stattic(a STAT3 inhibitor).Furthermore,in H9c2 cells the additional increased expression of LC3-? by chloroquine was abandoned by IL-6 in part.Finally,IL-6 accelerated the degradation of GFP in RFP-GFP-LC3 adenovirus assays,which was inhibited by BAZ and stattic.Conclusions: Ang?,the canonical effector in RAS activation,induced STAT3 phosphorylation in H9c2 cells,which was mediated by IL-6.TAC led to sustained activation of IL-6/gp130/STAT3 signaling pathway and BAZ suppressed this overactivation throughout the disease progression.IL-6 signaling might promote the formation of autolysosome and the subsequent inner acidation,while inhibition of STAT3 by BAZ or stattic could impede this procedure in autophagic flux.TAC exhibited different characteristics of autophagic markers(LC3-?)in the acute window and in the long term,which might be due to the endogenous kinetics of IL-6 signaling and autophagy in the heart.We speculated that BAZ inhibited IL-6/gp130/STAT3 signaling pathway,thus alleviated the chronic inflammation and modulated disrupted autophagy,all of which contributed to the improved outcomes of PO trigger in mice.