Background: Remote ischemic preconditioning (RIPC) induced by transient limb ischemia is a powerful innate mechanism of cardioprotection against ischemia. Several described mechanisms explain how RIPC may act through neural pathways or humoral factors; however, the mechanistic pathway linking the remote organ to the heart has not yet been fully elucidated. This study aimed to investigate the mechanisms underlying the RIPC-induced production of Janus kinase (JAK)-signal transducer and activator of the transcription (STAT)-activating cytokines and cardioprotection by using mouse and human models of RIPC. Methods and Results:Screened circulating cardioprotective JAK-STAT-activating cytokines in mice unexpectedly revealed increased serum erythropoietin (EPO) levels after RIP induced by transient ischemia. In mice, RIPC rapidly upregulated EPO mRNA and its main transcriptional factor, hypoxia-inducible factor-1α (HIF1α), in the kidney. Laser Doppler blood flowmetry revealed a prompt reduction of renal blood flow (RBF) after RIPC. RIPC activated cardioprotective signaling pathways and the anti-apoptotic Bcl-xL pathway in the heart, and reduced infarct size. In mice, these effects were abolished by administration of an EPO-neutralizing antibody. Renal nerve denervation also abolished RIPC-induced RBF reduction, EPO production, and cardioprotection. In humans, transient limb ischemia of the upper arm reduced RBF and increased serum EPO levels. Conclusions:Based on the present data, we propose a novel RIPC mechanism in which inhibition of infarct size by RIPC is produced through the renal nerve-mediated reduction of RBF associated with activation of the HIF1α-EPO pathway. 1558OBA T et al. Hypoxia Inducible Factor-1α (HIF1α) Immunohistochemical StainingMouse kidneys were harvested 1 h after RIPC. Embedded sections were deparaffinized, and endogenous peroxidase activity was inhibited by treating the sections with 0.3% H2O2 in PBS for 10 min. After several washes with PBS, the sections were incubated for 20 min with blocking solution (Jackson ImmunoResearch) to block non-specific binding, followed by overnight incubation at 4°C with the purified anti-hypoxia inducible factor-1α (HIF1α) antibody (Abcam). Subsequently, the sections were incubated with an alkaline phosphatase-conjugated goat anti-rabbit IgG antibody for 30 min. Signal amplification was achieved by incubating the slides for 30 min with Vectastain Elite Avidin-Biotin Complex solution (Vectastain ABC Kit, Vector), followed by incubation with Vectastain diaminobenzidine solution as the chromagen marker (Dako). 28 For a negative staining control, goat serum was used in place of the HIF1α antibody. Renal Blood Flow (RBF) MonitoringMouse RBF was measured at 0 min and every 2 min during and after RIPC induction, using a laser Doppler blood flow imager (Laser Doppler Perfusion Imager System, moorLDI TMMark 2, Moor Instruments). Before RBF scanning in the right kidney, mice were placed on a heating pad at 37°C to minimize temperature variations. In control mice, a sham...

Myocardial ischemia reperfusion injury (IRI) adversely affects cardiac performance and the prognosis of patients with acute myocardial infarction. Although myocardial signal transducer and activator of transcription (STAT) 3 is potently cardioprotective during IRI, the inhibitory mechanism responsible for its activation is largely unknown. The present study aimed to investigate the role of the myocardial suppressor of cytokine signaling (SOCS)-3, an intrinsic negative feedback regulator of the Janus kinase (JAK)-STAT signaling pathway, in the development of myocardial IRI. Myocardial IRI was induced in mice by ligating the left anterior descending coronary artery for 1 h, followed by different reperfusion times. One hour after reperfusion, the rapid expression of JAK-STAT–activating cytokines was observed. We precisely evaluated the phosphorylation of cardioprotective signaling molecules and the expression of SOCS3 during IRI and then induced myocardial IRI in wild-type and cardiac-specific SOCS3 knockout mice (SOCS3-CKO). The activation of STAT3, AKT, and ERK1/2 rapidly peaked and promptly decreased during IRI. This decrease correlated with the induction of SOCS3 expression up to 24 h after IRI in wild-type mice. The infarct size 24 h after reperfusion was significantly reduced in SOCS3-CKO compared with wild-type mice. In SOCS3-CKO mice, STAT3, AKT, and ERK1/2 phosphorylation was sustained, myocardial apoptosis was prevented, and the expression of anti-apoptotic Bcl-2 family member myeloid cell leukemia-1 (Mcl-1) was augmented. Cardiac-specific SOCS3 deletion led to the sustained activation of cardioprotective signaling molecules including and prevented myocardial apoptosis and injury during IRI. Our findings suggest that SOCS3 may represent a key factor that exacerbates the development of myocardial IRI.

BACKGROUND Interleukin ( IL )‐22, a member of the IL ‐10 cytokine family, is the only known cytokine that is secreted by immune cells but does not target immune cells; it mainly targets epithelial cells. In this study, we aimed to determine whether IL ‐22 administration could activate the myocardial STAT 3 (signal transducer and activator of transcription‐3) signaling pathway, and thus prevent myocardial injury, in a mouse model of ischemia reperfusion injury. METHODS AND RESULTS We evaluated the STAT 3 activation after IL ‐22 injection by Western blot analysis and immunostaining for phosphorylated STAT 3 in the heart and found that STAT 3 activation in heart tissue rapidly peaked after IL ‐22 injection. Coimmunostaining of phosphorylated STAT 3 and α‐actinin revealed that STAT 3 activation occurred in cardiomyocytes after IL ‐22 administration. In heart tissue from intact mice, real‐time PCR demonstrated significant expression of IL ‐22 receptor subunit 1, and coimmunostaining of IL ‐22 receptor subunit 1 and α‐actinin showed IL ‐22 receptor subunit 1 expression in cardiomyocytes. In cultured cardiomyocytes, IL ‐22 activated STAT 3, and we detected IL ‐22 receptor subunit 1 expression. Overall, these results indicated that IL ‐22 directly activated the myocardial IL ‐22‐receptor subunit 1– STAT 3 signaling pathway. Following ischemia reperfusion, compared with PBS ‐treated mice, IL ‐22‐treated mice exhibited a significantly reduced infarct size, significantly reduced myocardial apoptosis, and significantly enhanced phosphorylated STAT 3 expression. Moreover, heart tissue from IL ‐22‐treated mice exhibited a significantly reduced expression ratio of phosphorylated p53 to p53. CONCLUSIONS Our present findings suggest that IL ‐22 directly activated the myocardial STAT 3 signaling pathway and acted as a cardioprotective cytokine to ameliorate acute myocardial infarction after ischemia reperfusion.

Traditionally, patients with end-stage heart failure (HF) have rarely been involved in end-of-life care (EOLC) discussions in Japan. The purpose of this study was to examine the impact of HF-specific palliative care team (HF-PCT) activities on EOLC discussions with patients, HF therapy and care, and food intake at the end of life. We retrospectively analyzed 52 consecutive patients with HF (mean age, 70 ± 15 years; 42% female) who died at our hospital between May 2013 and July 2020 and divided them into two groups: before (Era 1, n = 19) and after (Era 2, n = 33) the initiation of HF-PCT activities in June 2015. Compared to Era 1, Era 2 showed a decrease in invasive procedures, an increase in opioid and non-intubating sedative use for symptom relief, improved quality of meals at the end of life, and an increase in participation in EOLC discussions. The administration of artificial nutrition in the final three days was associated with non-ischemic cardiomyopathy etiology, the number of previous hospitalizations for HF, and multidisciplinary EOLC discussion support. HF-PCT activities may provide an opportunity to discuss EOLC with patients, reduce the burden of physical and psychological symptoms, and shift the goals of end-of-life nutritional intake to ensure comfort and quality of life.

Ischemic preconditioning (IPC) is the most powerful endogenous cardioprotective form of cellular adaptation. However, the inhibitory or augmenting mechanism underlying cardioprotection via IPC remains largely unknown. Suppressor of cytokine signaling-3 (SOCS3) is a cytokine-inducible potent negative feedback regulator of the signal transducer and activator of transcription-3 (STAT3) signaling pathway. Here, we aimed to determine whether cardiac SOCS3 deficiency and IPC would synergistically reduce infarct size after myocardial ischemia reperfusion injury. We evaluated STAT3 activation and SOCS3 induction after ischemic conditioning (IC) using western blot analysis and real-time PCR, and found that myocardial IC alone transiently activated myocardial STAT3 and correspondingly induced SOCS3 expression in wild-type mice. Compared with wild-type mice, cardiac-specific SOCS3 knockout (SOCS3-CKO) mice showed significantly greater and more sustained IC-induced STAT3 activation. Following ischemia reperfusion, IPC substantially reduced myocardial infarct size and significantly enhanced STAT3 phosphorylation in SOCS3-CKO mice compared to in wild-type mice. Real-time PCR array analysis revealed that SOCS3-CKO mice after IC exhibited significantly increased expressions of several anti-apoptotic genes and SAFE pathway-related genes. Moreover, real-time PCR analysis revealed that myocardial IC alone rapidly induced expression of the STAT3-activating cytokine erythropoietin in the kidney at 1 h post-IC. We also found that the circulating erythropoietin level was promptly increased at 1 h after myocardial IC. Myocardial SOCS3 deficiency and IPC exert synergistic effects in the prevention of myocardial injury after ischemia reperfusion. Our present results suggest that myocardial SOCS3 is a potent inhibitor of IPC-induced cardioprotection, and that myocardial SOCS3 inhibition augment IPC-mediated cardioprotection during ischemia reperfusion injury.