SOCS3 deficiency in cardiomyocytes elevates sensitivity of ischemic preconditioning that synergistically ameliorates myocardial ischemia reperfusion injury.

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.

High urinary glucose is associated with improved renal prognosis in patients with diabetes mellitus.

AIMS/INTRODUCTION: The relationship between renal function and urinary glucose is poorly understood in diabetes patients who are not using sodium-glucose cotransporter 2 inhibitors. This study aimed to investigate the association of urinary glucose excretion with renal function prognosis in such patients. MATERIALS AND METHODS: This retrospective cohort study included 1,172 patients with type 1 or 2 diabetes mellitus. Patients were recruited and data were collected between 1 January 2007 and 31 December 2011; follow-up data were collected until 30 June 2015. The primary outcome was set as a 30% decline in estimated glomerular filtration rate relative to baseline. The relationship between this outcome and urinary glucose was investigated using Cox proportional hazards model. For analysis, patients were categorized into two groups: urinary glucose <5 g/day or ≥5 g/day. Interaction terms were analyzed. RESULTS: Multivariate analysis showed that the prognosis of renal function was significantly better in patients with high urinary glucose (≥5 g/day; adjusted hazard ratio 0.58, 95% confidence interval 0.35-0.96; P = 0.034). Significant interactions were observed between high urinary glucose and male sex (hazard ratio 0.33, 95% confidence interval 0.14-0.74; P = 0.007), and between high urinary glucose and longer duration of diabetes (≥10 years; hazard ratio 0.25, 95% confidence interval 0.11-0.58; P = 0.001). CONCLUSIONS: The present study suggests that high urinary glucose is associated with prognosis in diabetes patients not taking sodium-glucose cotransporter 2 inhibitors. Measurement of 24-h urinary glucose excretion might have clinical utility for predicting renal prognosis.

Interleukin-22 Directly Activates Myocardial STAT3 (Signal Transducer and Activator of Transcription-3) Signaling Pathway and Prevents Myocardial Ischemia Reperfusion Injury.

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 STAT3 (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 STAT3 activation after IL-22 injection by Western blot analysis and immunostaining for phosphorylated STAT3 in the heart and found that STAT3 activation in heart tissue rapidly peaked after IL-22 injection. Coimmunostaining of phosphorylated STAT3 and α-actinin revealed that STAT3 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 STAT3, 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-STAT3 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 STAT3 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 STAT3 signaling pathway and acted as a cardioprotective cytokine to ameliorate acute myocardial infarction after ischemia reperfusion.

Prevalence of hypothyroidism in patients with hyponatremia: A retrospective cross-sectional study.

OBJECTIVE: Hypothyroidism has been suggested to be an uncommon cause of hyponatremia. However, little is known about the prevalence of hypothyroidism in patients with different levels of hyponatremia. The objective of this study was to investigate the prevalence of hypothyroidism among patients with hyponatremia of varying severity while taking into consideration potential confounders associated with thyroid function. METHODS: All data on thyrotropin (TSH), free thyroxine (T4), and serum sodium (Na) levels were retrospectively collected from medical records at two Japanese tertiary hospitals. The main outcome measure was overt hypothyroidism, defined as TSH > 10.0 µIU/mL and free T4 < 1.01 ng/dL. RESULTS: Of 71,817 patients, 964 patients (1.3%) had overt hypothyroidism. The prevalence of overt hypothyroidism in each category of hyponatremia (Na ≥136, 130-135, and ≤129 mEq/L) was 1.2% (787/65,051), 2.4% (124/5,254) and 3.5% (53/1,512), respectively. A significant increase in prevalence was observed as the severity of hyponatremia increased (P < 0.001 for trend). Multivariate logistic regression with adjustment for age, sex, kidney function, and serum albumin level showed that the odds ratios for overt hypothyroidism increased with increasing severity of hyponatremia when compared with Na ≥ 136 mEq/L (130-135 mEq/L: 1.43, 95% confidence interval [CI], 1.15 to 1.78, P = 0.001; ≤129 mEq/L: 1.87, 95% CI, 1.32 to 2.63, P < 0.001; P< 0.001 for trend). CONCLUSION: The prevalence of overt hypothyroidism was significantly higher as the severity of hyponatremia progressed, even after adjusting for potential confounders. Hypothyroidism should be differentiated in patients with hyponatremia.

Renoprotective effects of topiroxostat for Hyperuricaemic patients with overt diabetic nephropathy study (ETUDE study): A prospective, randomized, multicentre clinical trial.

AIM: We aimed to evaluate the anti-albuminuric effects of topiroxostat in Japanese hyperuricaemic patients with diabetic nephropathy. METHODS: In this 24-week, multicentre, open-label, randomized (1 : 1) trial, we assigned hyperuricaemic patients with diabetic nephropathy (estimated glomerular filtration rate ≥ 20 mL/min per 1.73m2 ) and overt proteinuria (0.3 ≤ urine protein to creatinine ratio (UPCR) <3.5 g/g Cr) to either high dose (160 mg daily) or low dose (40 mg daily) topiroxostat. The primary endpoint was the change in albuminuria indicated by urine albumin-to-creatinine ratio (UACR) from the baseline at the final time point. RESULTS: A total of 80 patients underwent randomization. The changes in UACR after 24 weeks of treatment (or at the final time point if patients failed to reach 24 weeks) relative to the baseline were -122 mg/gCr (95% CI: -5.1 to -240.1, P = 0.041) in patients treated with high dose, while treatment with low dose topiroxostat could not show significant reduction (P = 0.067). In the linear mixed model including baseline albuminuria, eGFR, age, and sex as covariates, the decreases in UACR were still significant from baseline to 12 weeks by 228.7 ± 83.2 mg/gCr (P = 0.0075) in the high dose group. The adverse-event profile during this study was not different between the groups. CONCLUSION: Topiroxostat 160 mg daily reduced albuminuria in patients with diabetic nephropathy. (Funded by Sanwa Kagaku Kenkyusho; Trial registration, UMIN000015403).

The Japanese Histologic Classification and T-score in the Oxford Classification system could predict renal outcome in Japanese IgA nephropathy patients.

BACKGROUND: The Oxford Classification is utilized globally, but has not been fully validated. In this study, we conducted a comparative analysis between the Oxford Classification and Japanese Histologic Classification (JHC) to predict renal outcome in Japanese patients with IgA nephropathy (IgAN). METHODS: A retrospective cohort study including 86 adult IgAN patients was conducted. The Oxford Classification and the JHC were evaluated by 7 independent specialists. The JHC, MEST score in the Oxford Classification, and crescents were analyzed in association with renal outcome, defined as a 50% increase in serum creatinine. RESULTS: In multivariate analysis without the JHC, only the T score was significantly associated with renal outcome. While, a significant association was revealed only in the JHC on multivariate analysis with JHC. CONCLUSIONS: The JHC and T score in the Oxford Classification were associated with renal outcome among Japanese patients with IgAN. Superiority of the JHC as a predictive index should be validated with larger study population and cohort studies in different ethnicities.

Unstable Angina Pectoris in a 22-year-old Female Patient.

Because of the protective effect of estrogen for atherosclerosis, the prevalence of acute coronary syndrome in women before menopause is low. We report a rare case of unstable angina in a young Japanese female who had a history of cigarette smoking and contraceptive use. Her coronary stenosis was successfully treated by percutaneous coronary intervention.

Randomized control trial for the assessment of the anti-albuminuric effects of topiroxostat in hyperuricemic patients with diabetic nephropathy (the ETUDE study).

Proteinuria is an established risk factor for diabetic nephropathy. Recent studies indicate that some xanthine oxidase inhibitors have a renoprotective effect. The aim of this study was to assess whether topiroxostat reduces albuminuria in hyperuricemic patients with diabetic nephropathy and overt proteinuria. The ETUDE study is an ongoing 24-week, multicenter, open-label, randomized (1:1), parallel group study involving hyperuricemic patients with diabetic nephropathy (estimated glomerular filtration rate [eGFR] ≥ 20 mL/min/1.73 m(2)) and overt proteinuria (0.3 ≤ urine protein to creatinine ratio (UPCR) < 3.5 g/g Cr). Patients are randomly assigned to high dose (topiroxostat 160 mg daily) or low dose (topiroxostat 40 mg daily) on top of standard of care. The primary endpoint is the change in albuminuria indicated by urine albumin-to-creatinine ratio after 24 treated weeks relative to the baseline values. This trial was registered at the Japanese University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR: UMIN 000015403). The background, rationale, and study design of this trial are presented here. Seventy-six patients from four registered facilities have already been enrolled and received at least one dose of topiroxostat. This trial will end in 2017. The ETUDE trial is the first randomized controlled study of topiroxostat in hyperuricemic patients with diabetic nephropathy and overt proteinuria. We will clarify the pleiotropic function of topiroxostat including an anti-albumiuric effect as well as its effects on safely decreasing serum uric acid levels.

Association between 24h Urinary Sodium and Potassium Excretion and Estimated Glomerular Filtration Rate (eGFR) Decline or Death in Patients with Diabetes Mellitus and eGFR More than 30 ml/min/1.73m2.

BACKGROUND: Data regarding the association between 24h urinary sodium and potassium excretion with kidney outcomes in patients with diabetes mellitus is currently scarce. METHODS: We conducted a single-center, retrospective cohort study in which 1230 patients with diabetes who had undergone a 24h urinary sodium and potassium excretion test were analyzed. Patients with incomplete urine collection were excluded based on 24h urinary creatinine excretion. Outcomes were the composite of a 30% decline in eGFR or death. Multivariate cox regression analysis was used to investigate the association between urinary sodium and potassium excretion and outcomes. RESULTS: With a mean follow up period of 5.47 years, 130 patients reached the outcomes (30% decline in eGFR: 124, death: 6). Mean (SD) eGFR and 24h urinary sodium and potassium excretion at baseline were 78.6 (19.5) ml/min/1.73m2, 4.50 (1.64) g/day, and 2.14 (0.77) g/day. Compared with sodium excretion < 3.0 g/day, no significant change in risk of outcomes was observed with increased increments of 1.0 g/day. Compared with potassium excretion of < 1.5 g/day, 2.0-2.5 g/day, and 2.5-3.0 g/day were significantly associated with a lower risk of outcomes (hazard ratio [HR], 0.49 and 0.44; 95% confidence interval [CI], 0.28 to 0.84 and 0.22 to 0.87). CONCLUSIONS: 24h urinary sodium excretion was not significantly associated with a risk of 30% decline in eGFR or death in patients with diabetes. However, an increased risk of 30% decline in eGFR or death was significantly associated with 24h urinary potassium excretion < 1.5 g/day than with 2.0-2.5 g/day and 2.5-3.0 g/day.

Clinical impact of kidney function on presepsin levels.

OBJECTIVE: Presepsin is highlighted as a diagnostic and prognostic marker of sepsis. Little information is available regarding the accurate association between presepsin levels and the degree of kidney function. We analyzed presepsin levels in patients with a glomerular filtration rate (GFR) in the categories G1 to G5, evaluated via inulin renal clearance test, and receiving hemodialysis (HD). METHODS: Patients who were not receiving HD were included if they had undergone inulin renal clearance measurements for the accurate measurement of GFR (measured GFR), and patients who were receiving hemodialysis (HD) were included if they had anuria. Exclusion criteria were infection, cancer, liver disease, autoimmune disorders, or steroid or immunosuppressant use. GFR category was defined as follows; G1: GFR ≥ 90 ml/min/1.73 m2, G2: GFR = 60 to 90 ml/min/1.73 m2, G3: GFR = 30 to 60 ml/min/1.73 m2, G4: GFR = 15 to 30 ml/min/1.73 m2, G5: GFR ≤ 15 ml/min/1.73 m2. RESULTS: Seventy-one patients were included. The median (IQR) presepsin values of patients in each GFR category were as follows: G1 + G2: 69.8 (60.8-85.9) pg/ml; G3: 107.0 (68.7-150.0) pg/ml; G4: 171.0 (117.0-200.0) pg/ml; G5: 251.0 (213.0-297.5) pg/ml; and HD: 1160.0 (1070.0-1400.0) pg/ml. The log-transformed presepsin values, excluding patients receiving HD, inversely correlated with the measured GFR (Pearson's correlation coefficient = -0.687, P < 0.001). The multivariate analysis revealed that measured GFR and hemoglobin levels significantly correlated with elevated presepsin levels. CONCLUSION: Presepsin levels were markedly high in patients receiving HD, similar to values seen in patients with severe sepsis or septic shock. In patients who were not receiving HD, presepsin levels increased as GFR decreased. Thus, the evaluation of presepsin levels in patients with chronic kidney disease requires further consideration, and a different cutoff value is needed for diagnosing sepsis in such patients.

Cardiac-Specific SOCS3 Deletion Prevents In Vivo Myocardial Ischemia Reperfusion Injury through Sustained Activation of Cardioprotective Signaling Molecules.

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.

Renal Nerve-Mediated Erythropoietin Release Confers Cardioprotection During Remote Ischemic Preconditioning.

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.

Omentin prevents myocardial ischemic injury through AMP-activated protein kinase- and Akt-dependent mechanisms.

OBJECTIVES: This study examined the impact of omentin on myocardial injury in a mouse model of ischemia/reperfusion (I/R) and explored its underlying mechanisms. BACKGROUND: Obesity is a major risk factor for ischemic heart disease. Omentin is a circulating adipokine that is down-regulated by obesity. METHODS: In patients who underwent successful reperfusion treatment after acute myocardial infarction, cardiac function and perfusion defect were assessed by using scintigraphic images. Mice were subjected to myocardial ischemia followed by reperfusion. RESULTS: This study found that high levels of plasma omentin were associated with improvement of heart damage and function after reperfusion therapy in patients with acute myocardial infarction. Systemic administration of human omentin to mice led to a reduction in myocardial infarct size and apoptosis after I/R, which was accompanied by enhanced phosphorylation of AMP-activated protein kinase (AMPK) and Akt in the ischemic heart. Fat-specific overexpression of human omentin also resulted in reduction of infarct size after I/R. Blockade of AMPK or Akt activity reversed omentin-induced inhibition of myocardial ischemic damage and apoptosis in mice. In cultured cardiomyocytes, omentin suppressed hypoxia/reoxygenation-induced apoptosis, which was blocked by inactivation of AMPK or Akt. CONCLUSIONS: Our data indicate that omentin functions as an adipokine that ameliorates acute ischemic injury in the heart by suppressing myocyte apoptosis through both AMPK- and Akt-dependent mechanisms.

Cardiomyocyte-specific transgenic expression of lysyl oxidase-like protein-1 induces cardiac hypertrophy in mice.

Lysyl oxidase (LOX) and LOX-like protein-1 (LOXL-1) are extracellular matrix-embedded amine oxidases that have critical roles in the cross-linking of collagen and elastin. LOX family proteins are abundantly expressed in the remodeled heart of animals and humans and are implicated in cardiac fibrosis; however, their role in cardiac hypertrophy is unknown. In this study, in vitro stimulation with hypertrophic agonists significantly increased LOXL-1 expression, LOX enzyme activity and [(3)H] leucine incorporation in neonatal rat cardiomyocytes. A LOX inhibitor, beta-aminopropionitrile (BAPN), inhibited agonist-induced leucine incorporation in cardiomyocytes in vitro, suggesting the involvement of LOXL-1 in cardiomyocyte hypertrophy. Abdominal aortic constriction in rats produced left ventricular hypertrophy in parallel with LOXL-1 mRNA upregulation. And BAPN administration significantly inhibited angiotensin II-induced cardiac hypertrophy in vivo. These results suggest a role of LOXL-1 in cardiac hypertrophy in vivo. We generated transgenic mice with cardiomyocyte-specific expression of LOXL-1. LOXL-1 transgenic mice pups were born normally and grew to adulthood without increased mortality; these mice exhibited a greater left ventricle to body weight ratio, larger myocyte diameter, and more brain natriuretic peptide expression than their wild-type littermates. Echocardiography revealed that the LOXL-1 transgenic mice also had greater wall thickness with preserved cardiac contraction. Our results indicate a possible fundamental role of LOXL-1 in cardiac hypertrophy.

Transient reduction and activation of circulating dendritic cells in patients with acute myocardial infarction.

BACKGROUND: Dendritic cells (DCs) are highly potent professional antigen-presenting cells that play a central role in initiating the primary immune response. Accumulating evidence suggests that immune-mediated inflammation plays an important role in the pathophysiology of AMI, but the mechanism that triggers such immune responses is unknown. METHODS: Using multi-color flow-cytometry, we determined the numbers of circulating myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) in patients with AMI (n = 26) or stable angina pectoris (SAP) (n = 19), and in age-matched control subjects (n = 19). The DC activation markers CD40 and CD83 were also measured. RESULTS: On admission, circulating mDC and pDC counts were significantly lower in AMI patients compared to control subjects and SAP patients (mDC, P < 0.01; pDC, P < 0.05). The activation markers of mDCs in AMI patients were significantly higher and returned to the levels of control subjects or SAP patients 3 days after AMI (mDC, P < 0.05; pDC, P < 0.05). Reductions of circulating mDC and pDC numbers were restored 7 days after the onset of AMI. Furthermore, we found that the recovery of the circulating DC numbers 14 days after AMI was correlated with the alterations of creatine kinase-MB (CK-MB) (mDC, r = 0.48, P < 0.05; pDC, r=0.52, P < 0.01) and brain natriuretic peptide (BNP) (mDC, r = 0.53, P < 0.01; pDC, r = 0.51, P < 0.01). CONCLUSION: Our findings suggest that the transient reduction and activation of circulating DCs may play important roles in the pathophysiology of myocardial injury after AMI.

Cardiac-specific deletion of SOCS-3 prevents development of left ventricular remodeling after acute myocardial infarction.

OBJECTIVES: The study investigated the role of myocardial suppressor of cytokine signaling-3 (SOCS3), an intrinsic negative feedback regulator of the janus kinase and signal transducer and activator of transcription (JAK-STAT) signaling pathway, in the development of left ventricular (LV) remodeling after acute myocardial infarction (AMI). BACKGROUND: LV remodeling after AMI results in poor cardiac performance leading to heart failure. Although it has been shown that JAK-STAT-activating cytokines prevent LV remodeling after AMI in animals, little is known about the role of SOCS3 in this process. METHODS: Cardiac-specific SOCS3 knockout mice (SOCS3-CKO) were generated and subjected to AMI induced by permanent ligation of the left anterior descending coronary artery. RESULTS: Although the initial infarct size after coronary occlusion measured by triphenyltetrazolium chloride staining was comparable between SOCS3-CKO and control mice, the infarct size 14 days after AMI was remarkably inhibited in SOCS3-CKO, indicating that progression of LV remodeling after AMI was prevented in SOCS3-CKO hearts. Prompt and marked up-regulations of multiple JAK-STAT-activating cytokines including leukemia inhibitory factor and granulocyte colony-stimulating factor (G-CSF) were observed within the heart following AMI. Cardiac-specific SOCS3 deletion enhanced multiple cardioprotective signaling pathways including STAT3, AKT, and extracellular signal-regulated kinase (ERK)-1/2, while inhibiting myocardial apoptosis and fibrosis as well as augmenting antioxidant expression. CONCLUSIONS: Enhanced activation of cardioprotective signaling pathways by inhibiting myocardial SOCS3 expression prevented LV remodeling after AMI. Our data suggest that myocardial SOCS3 may be a key molecule in the development of LV remodeling after AMI.

SOCS3: A novel therapeutic target for cardioprotection.

The suppressors of cytokine signaling (SOCS) family of proteins are cytokine-inducible inhibitors of Janus kinase (JAK)-signal transducer and activator of the transcription (STAT) signaling pathways. Among the family, SOCS1 and SOCS3 potently suppress cytokine actions by inhibiting JAK kinase activities. The generation of mice lacking individual SOCS genes has been instrumental in defining the role of individual SOCS proteins in specific cytokine pathways in vivo; SOCS1 is an essential negative regulator of interferon-γ (IFNγ) and SOCS3 is an essential negative regulator of leukemia inhibitory factor (LIF). JAK-STAT3 activating cytokines have exhibited cardioprotective roles in the heart. The cardiac-specific deletion of SOCS3 enhances the activation of cardioprotective signaling pathways, inhibits myocardial apoptosis and fibrosis and results in the inhibition of left ventricular remodeling after myocardial infarction (MI). We propose that myocardial SOCS3 is a key determinant of left ventricular remodeling after MI, and SOCS3 may serve as a novel therapeutic target to prevent left ventricular remodeling after MI. In this review, we discuss the signaling pathways mediated by JAK-STAT and SOCS proteins and their roles in the development of myocardial injury under stress (e.g., pressure overload, viral infection and ischemia).