Hypertension produced by reduced uterine perfusion in pregnant rats is associated with increased soluble fms-like tyrosine kinase-1 expression

The balance between proangiogenic and antiangiogenic factors, such as vascular endothelial growth factor, placental growth factor, and soluble fms-like tyrosine kinase-1 (sFlt-1), is altered in preeclampsia, and this dysregulation of angiogenic factors may be important in the pathogenesis of preeclampsia. Although sFlt-1 is elevated in preeclampsia, the mechanisms responsible for increasing this antiangiogenic factor remain unclear. We hypothesized that the hypertension produced by reduced uterine perfusion pressure (RUPP) is associated with increased sFlt-1 expression and decreased plasma vascular endothelial growth factor and placental growth factor concentrations in the pregnant rat. Arterial pressure was increased (130+/-3 versus 100+/-2 mm Hg; P<0.01) in the RUPP rats compared with the normal pregnant control rats. Plasma sFlt-1 concentration (660+/-270 versus 82+/-26 pg/mL; P<0.05) was increased, whereas plasma free placental growth factor (0.28+/-0.05 versus 1.7+/-0.5 pg/mL; P<0.01) and vascular endothelial growth factor (594+/-34 versus 830+/-33 pg/mL; P<0.01) concentrations were decreased in the RUPP rats compared with normal pregnant rats. Plasma sFlt-1:placental growth factor (37.2+/-7.8 versus 8.9+/-1.6; P<0.02) and sFlt-1:vascular endothelial growth factor (0.86+/-0.22 versus 0.28+/-0.06; P<0.05) ratios were increased in the RUPP rats compared with normal pregnant rats. Immunoreactive placental sFlt-1 was increased (1.1+/-0.1 versus 0.3+/-0.1; P<0.01) in RUPP rats contrasted with the normal pregnant rats. These findings support our hypothesis that RUPP increases the expression of sFlt-1 and alters the balance of angiogenic factors in the maternal circulation. These data also indicate that the RUPP model of pregnancy-induced hypertension may provide an invaluable model for mechanistic studies into the role of sFlt-1 in the pathogenesis preeclampsia.

Hypertension in response to chronic reductions in uterine perfusion in pregnant rats: effect of tumor necrosis factor-alpha blockade

Reductions in uterine perfusion pressure (RUPP) in pregnant rats is associated with increased tumor necrosis factor-alpha (TNF-alpha). This study was designed to determine the role of endogenous TNF-alpha in mediating changes in arterial pressure and endothelin-1 (ET-1) in RUPP rats. To achieve this goal we examined the effect of RUPP in the presence and absence of a TNF-alpha-soluble receptor, etanerecept (0.4 mg/kg). Mean arterial pressure increased from 102+/-1 mm Hg in normal pregnant (NP) rats to 134+/-3 mm Hg (P<0.05) in RUPP rats. Serum TNF-alpha increased to 40+/-7.6 pg/mL in RUPP rats (n=24) versus 14.8+/-3.3 pg/mL (n=16; P<0.05) in NP rats. Administration of etanerecept decreased TNF-alpha in RUPP rats (n=20) to 17.2+/-3 pg/mL and mean arterial pressure to 118+/-2 mm Hg (P<0.05). Tissue ET-1 decreased in etanerecept-treated RUPP rats compared with control RUPP rats. The direct effect of TNF-alpha blockade on endothelial activation in response to placental ischemia was examined in human umbilical vein endothelial cells. ET-1 secreted from human umbilical vein endothelial cells treated with RUPP serum was 59.2+16 pg/mg and decreased when etanerecept was added to the medium with RUPP serum (7.60+/-0.77 pg/mg), as well as in response to serum from etanerecept-treated RUPP rats (7.30+/-0.55 pg/mg; P<0.001). ET-1 secreted from human umbilical vein endothelial cells was 15.6+/-2 pg/mg when treated with NP serum. These data support the hypothesis that endogenous TNF-alpha is an important stimulus for ET-1 in response to placental ischemia and is important in mediating endothelial cell activation and hypertension during pregnancy.

Advanced glycation endproduct (AGE) accumulation and AGE receptor (RAGE) up-regulation contribute to the onset of diabetic cardiomyopathy

Diabetic cardiomyopathy is manifested by compromised systolic and diastolic function. This study was designed to examine the role of advanced glycation endproduct (AGE) and AGE receptor (RAGE) in diabetic cardiomyopathy. Heart function was assessed in isolated control and streptozotocin-induced diabetic hearts following in vivo RAGE gene knockdown using RNA interference. Cardiomyocyte mechanical properties were evaluated including peak shortening (PS), time-to-PS (TPS) and time-to-90% relengthening (TR(90)). RAGE was assayed by RT-PCR and immunoblot. Diabetes significantly enhanced cardiac MG, AGE and RAGE levels accompanied with colocalization of AGE and RAGE in cardiomyocytes. Diabetes-elicited increase in RAGE was inhibited by in vivo siRNA interference. The AGE formation inhibitor benfotiamine significantly attenuated diabetes-induced elevation in MG, AGE, RAGE and collagen cross-linking without affecting hypertriglyceridaemia and hypercholesterolaemia in diabetes. Diabetes markedly decreased LV contractility, as evidenced by reduced +/-dP/dt and LV developed pressure (LVDP), which were protected by RAGE gene knockdown. In addition, MG-derived AGE (MG-AGE) up-regulated cardiac RAGE mRNA and triggered cardiomyocyte contractile dysfunction reminiscent of diabetic cardiomyopathy. The MG-AGE-elicited prolongation of TPS and TR(90) was ablated by an anti-RAGE antibody in cardiomyocytes. Interestingly, MG-AGE-induced cardiomyocyte dysfunction was associated with mitochondrial membrane potential (MMP) depolarization and reduced GSK-3beta inactivation in control cardiomyocytes, similar to those from in vivo diabetes. Treatment with siRNA-RAGE ablated diabetes-induced MMP depolarization and GSK-3beta inactivation. Collectively, our result implicated a role of AGE-RAGE in the pathogenesis of diabetic cardiomyopathy.

Mitochondrial aldehyde dehydrogenase (ALDH2) protects against streptozotocin-induced diabetic cardiomyopathy: role of GSK3β and mitochondrial function

BACKGROUND

Mitochondrial aldehyde dehydrogenase (ALDH2) displays some promise in the protection against cardiovascular diseases although its role in diabetes has not been elucidated.

METHODS

This study was designed to evaluate the impact of ALDH2 on streptozotocin-induced diabetic cardiomyopathy. Friendly virus B(FVB) and ALDH2 transgenic mice were treated with streptozotocin (intraperitoneal injection of 200 mg/kg) to induce diabetes.

RESULTS

Echocardiographic evaluation revealed reduced fractional shortening, increased end-systolic and -diastolic diameter, and decreased wall thickness in streptozotocin-treated FVB mice. Streptozotocin led to a reduced respiratory exchange ratio; myocardial apoptosis and mitochondrial damage; cardiomyocyte contractile and intracellular Ca2+ defects, including depressed peak shortening and maximal velocity of shortening and relengthening; prolonged duration of shortening and relengthening; and dampened intracellular Ca2+ rise and clearance. Western blot analysis revealed disrupted phosphorylation of Akt, glycogen synthase kinase-3β and Foxo3a (but not mammalian target of rapamycin), elevated PTEN phosphorylation and downregulated expression of mitochondrial proteins, peroxisome proliferator-activated receptor γ coactivator 1α and UCP-2. Intriguingly, ALDH2 attenuated or ablated streptozotocin-induced echocardiographic, mitochondrial, apoptotic and myocardial contractile and intracellular Ca2+ anomalies as well as changes in the phosphorylation of Akt, glycogen synthase kinase-3β, Foxo3a and phosphatase and tensin homologue on chromosome ten, despite persistent hyperglycemia and a low respiratory exchange ratio. In vitro data revealed that the ALDH2 activator Alda-1 and glycogen synthase kinase-3β inhibition protected against high glucose-induced mitochondrial and mechanical anomalies, the effect of which was cancelled by mitochondrial uncoupling.

CONCLUSIONS

In summary, our data revealed that ALDH2 acted against diabetes-induced cardiac contractile and intracellular Ca2+ dysregulation, possibly through regulation of apoptosis, glycogen synthase kinase-3β activation and mitochondrial function independent of the global metabolic profile.

Advanced glycation endproduct induces ROS accumulation, apoptosis, MAP kinase activation and nuclear O-GlcNAcylation in human cardiac myocytes

Accumulation of advanced glycation endproduct (AGE) has been implicated in the pathogenesis of diabetic complications. However, the precise role and mechanism behind AGE-associated diabetic heart injury are not fully clear. This study was designed to evaluate the effect of AGE on accumulation of reactive oxygen species (ROS), apoptosis, mitogen-activated protein kinase (MAPK) activation and nuclear O-GlcNAcylation in fetal human cardiac myocytes. Myocytes were maintained for 24-72 h in a defined culture medium containing high glucose, the AGE carbon precursor methylglyoxal (MG), and MG-AGE derived from MG and bovine serum albumin (BSA). Generation of ROS was detected by 5-(6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate. Apoptosis was evaluated by caspase-3 activity and quantitative DNA fragmentation. Both high glucose (25.5 mM) and MG (200 microM) significantly enhanced ROS and AGE formation with greater effects elicited by MG. Both high glucose and MG-AGE significantly facilitated apoptosis with a more predominant effect from MG-AGE. In addition, phosphorylation of MAPK cascade [extracellular signal-regulated kinase-1/2 (ERK1/2) and p38] and nuclear O-GlcNAcylation were enhanced in MG-AGE-treated myocytes, similar to those elicited by high glucose. MG-AGE-induced phosphorylation of ERK1/2 and p38 was nullified by neutralizing AGE with specific anti-AGE antibody but not nonspecific antiserum. Collectively, these results indicated that AGE or its precursor MG may trigger ROS generation, apoptosis, MAPK activation and nuclear O-GlcNAcylation in human cardiac myocytes, in a manner reminiscent of high extracellular glucose.

Aldehyde dedydrogenase-2 plays a beneficial role in ameliorating chronic alcohol-induced hepatic steatosis and inflammation through regulation of autophagy

BACKGROUND & AIMS

Mitochondrial aldehyde dehydrogenase (ALDH2) plays a critical role in the detoxification of the ethanol metabolite acetaldehyde. This study was designed to examine the impact of global ALDH2 overexpression on alcohol-induced hepatic steatosis.

METHODS

Wild type Friend virus B (FVB) and ALDH2 transgenic mice were placed on a 4% alcohol or control diet for 12 weeks. Serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), bilirubin and cholesterol, hepatic triglyceride, steatosis, fat metabolism-related proteins, pro-inflammatory cytokines, glutathione (GSH), oxidized glutathione (GSSG), autophagy and autophagy signalling were examined. The role of autophagy was evaluated in alcohol dehydrogenase 1 (ADH1)-transfected human hepatocellular liver carcinoma cells (VA-13) treated with or without the autophagy inducer rapamycin and lysosomal inhibitors.

RESULTS

Chronic alcohol intake led to elevated AST-, ALT-levels, bilirubin, AST/ALT ratio, cholesterol, hepatic triglycerides and hepatic fat deposition as evidenced by H&E and Oil Red O staining. Hepatic fat deposition was associated with disturbed levels of fat metabolism-related proteins (fatty acid synthase, SCD1), upregulated interleukin-6, TNF-α, cyclooxygenase, oxidative stress, and loss of autophagy, effects which were attenuated or ablated by the ALDH2 transgene. Moreover, ethanol (100 mM) and acetaldehyde (100 and 500 μM) increased levels of IL-6 and IFN-γ, and suppressed autophagy in VA-13 cells, effects which were markedly alleviated by rapamycin. In addition, lysosomal inhibitors mimicked ethanol-induced p62 accumulation with little additive effect with ethanol. Ethanol significantly suppressed LC3 conversion in the presence of lysosomal inhibitors.

CONCLUSIONS

In summary, our results revealed that ALDH2 plays a beneficial role in ameliorating chronic alcohol intake-induced hepatic steatosis and inflammation through regulation of autophagy.

Inhibition of advanced glycation endproduct (AGE) rescues against streptozotocin-induced diabetic cardiomyopathy: Role of autophagy and ER stress

Diabetes mellitus leads to oxidative stress and contractile dysfunction in the heart. Although several rationales have been speculated, the precise mechanism behind diabetic cardiomyopathy remains elusive. This study was designed to assess the role of inhibition of advanced glycation endproducts (AGE) in streptozotocin (STZ)-induced diabetic cardiac dysfunction. Cardiac contractile function was assessed in normal C57BL/6 and STZ (200mg/kg, single injection and maintained for 2 wks)-induced diabetic mice treated with or without the AGE inhibitor aminoguanidine (50mg/kg/d in drinking water) for 2 weeks using echocardiography and IonOptix MyoCam techniques. Diabetes compromised cardiac contractile function shown as reduced fractional shortening and ejection fraction, enlarged left ventricular end systolic/diastolic diameters, decreased peak shortening, maximal velocity of shortening/relengthening, prolonged shortening and relengthening duration as well as impaired intracellular Ca²⁺ homeostasis, the effects of which were alleviated or reversed by aminoguanidine treatment. Diabetes also inhibited autophagy, increased ER stress and phosphorylation of pro-hypertrophic signaling molecules Akt and mTOR, the effect of which was reversed by aminoguanidine. In vitro study revealed that methylglyoxal-derived AGE (MG-AGE) incubation in isolated cardiomyocytes promoted oxidation of sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA2a) and production of superoxide, the effects of which were negated by the autophagy inducer rapamycin, the ER stress chaperone TUDCA or the antioxidant N-acetylcysteine. Taken together, these data revealed that inhibition of AGE formation rescues against experimental diabetes-induced cardiac remodeling and contractile dysfunction possible through regulation of autophagy and ER stress.

Cardiac overexpression of antioxidant catalase attenuates aging-induced cardiomyocyte relaxation dysfunction

Catalase, an enzyme which detoxifies H2O2, may interfere with cardiac aging. To test this hypothesis, contractile and intracellular Ca2+ properties were evaluated in cardiomyocytes from young (3-4 months) and old (26-28 months) FVB and transgenic mice with cardiac overexpression of catalase. Contractile indices analyzed included peak shortening (PS), time-to-90% PS (TPS90), time-to-90% relengthening (TR90), half-width duration (HWD), maximal velocity of shortening/relengthening (+/-dL/dt) and intracellular Ca2+ levels or decay rate. Levels of advanced glycation endproduct (AGE), Na+/Ca2+ exchanger (NCX), sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2a), phospholamban (PLB), myosin heavy chain (MHC), membrane Ca2+ and K+ channels were measured by western blot. Catalase transgene prolonged survival while did not alter myocyte function by itself. Aging depressed+/-dL/dt, prolonged HWD, TR90 and intracellular Ca2+ decay without affecting other indices in FVB myocytes. Aged FVB myocytes exhibited a stepper decline in PS in response to elevated stimulus or a dampened rise in PS in response to elevated extracellular Ca2+ levels. Interestingly, aging-induced defects were nullified or significantly attenuated by catalase. AGE level was elevated by 5-fold in aged FVB compared with young FVB mice, which was reduced by catalase. Expression of SERCA2a, NCX and Kv1.2 K+ channel was significantly reduced although levels of PLB, L-type Ca2+ channel dihydropyridine receptor and beta-MHC isozyme remained unchanged in aged FVB hearts. Catalase restored NCX and Kv1.2 K+ channel but not SERCA2a level in aged mice. In summary, our data suggested that catalase protects cardiomyocytes from aging-induced contractile defect possibly via improved intracellular Ca2+ handling.

Nutrient restriction impairs nephrogenesis in a gender-specific manner in the ovine fetus

Inadequate nutrition compromises fetal development and poses long-term health risks for the offspring, even without decreased birth weight. The present study sought to 1) establish the ontogeny of fetal renal glomerulus number (GN) in sheep and 2) evaluate the effects of 50% global nutrient restriction (NR) during early to midgestation on GN and the renin-angiotensin system in the fetal kidney. GN increased from 78 dG (68,560 +/- 3802) to 135 dG (586,118 +/- 25,792). NR increased combined kidney weight (29 +/- 0.6 g versus 23 +/- 1.1 g), whereas decreased GN relative to right kidney weight approached significance in males (26,000 +/- 5300 versus 39,000 +/- 2800 GN/g) compared with control (C) males and females. NR decreased immunoreactive angiotensin II (Ang II) type 1 receptor (AT1) in the NR kidneys at 78 dG and increased renin at 135 dG. Immunoreactive renin decreased from 78 to 135 dG. Female fetuses had more immunoreactive Ang II type 2 receptor (AT2) than male fetuses at 78 dG and males had more AT1 at 135 dG. The present study demonstrates gender-specific differences in fetal growth and development and in fetal kidney development in pregnancies affected by NR.

Inhibition of AMPK accentuates prolonged caloric restriction-induced change in cardiac contractile function through disruption of compensatory autophagy

Prolonged caloric restriction often results in alteration in heart geometry and function although the underlying mechanism remains poorly defined. Autophagy, a conserved pathway for bulk degradation of intracellular proteins and organelles, preserves energy and nutrient in the face of caloric insufficiency. This study was designed to examine the role of AMPK in prolonged caloric restriction-induced change in cardiac homeostasis and the underlying mechanism(s) involved with a focus on autophagy. Wild-type (WT) and AMPK kinase dead (KD) mice were caloric restricted (by 40%) for 30 weeks. Echocardiographic, cardiomyocyte contractile and intracellular Ca²⁺ properties, autophagy and autophagy regulatory proteins were evaluated. Caloric restriction compromised echocardiographic indices (decreased ventricular mass, left ventricular diameters, and cardiac output), cardiomyocyte contractile and intracellular Ca²⁺ properties associated with upregulated autophagy (Beclin-1, Atg5 and LC3BII-to-LC3BI ratio), increased autophagy adaptor protein p62, elevated phosphorylation of AMPK and TSC1/2, depressed phosphorylation of mTOR and ULK1. Although AMPK inhibition did not affect cardiac mechanical function, autophagy and autophagy signaling proteins, it significantly accentuated caloric restriction-induced changes in myocardial contractile function and intracellular Ca²⁺ handling. Interestingly, AMPK inhibition reversed caloric restriction-induced changes in autophagy and autophagy signaling. AMPK inhibition led to dampened levels of Beclin-1, Atg 5 and LC3B ratio along with suppressed phosphorylation of AMPK and TSC1/2 as well as elevated phosphorylation of mTOR and ULK1. Taken together, these data suggest an indispensible role for AMPK in the maintenance of cardiac homeostasis under prolonged caloric restriction-induced pathological changes possibly through autophagy regulation. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.

Inhibition of protein kinase C βII isoform ameliorates methylglyoxal advanced glycation endproduct-induced cardiomyocyte contractile dysfunction

AIMS

Accumulation of advanced glycation endproduct (AGE) contributes to diabetic complication including diabetic cardiomyopathy although the precise underlying mechanism still remains elusive. Recent evidence depicted a pivotal role of protein kinase C (PKC) in diabetic complications. To this end, this study was designed to examine if PKCβII contributes to AGE-induced cardiomyocyte contractile and intracellular Ca(2+) aberrations.

MAIN METHODS

Adult rat cardiomyocytes were incubated with methylglyoxal-AGE (MG-AGE) in the absence or presence of the PKCβII inhibitor LY333531 for 12h. Contractile and intracellular Ca(2+) properties were assessed using an IonOptix system including peak shortening (PS), maximal velocity of shortening/relengthening (±dL/dt), time-to-PS (TPS), time-to-90% relengthening (TR90), rise in intracellular Ca(2+) Fura-2 fluorescence intensity and intracellular Ca(2+) decay. Oxidative stress, O2(-) production and mitochondrial integrity were examined using TBARS, fluorescence imaging, aconitase activity and Western blotting.

KEY FINDINGS

MG-AGE compromised contractile and intracellular Ca(2+) properties including reduced PS, ±dL/dt, prolonged TPS and TR90, decreased electrically stimulated rise in intracellular Ca(2+) and delayed intracellular Ca(2+) clearance, the effects of which were ablated by the PKCβII inhibitor LY333531. Inhibition of PKCβII rescued MG-AGE-induced oxidative stress, O2(-) generation, cell death, apoptosis and mitochondrial injury (reduced aconitase activity, UCP-2 and PGC-1α). In vitro studies revealed that PKCβII inhibition-induced beneficial effects were replicated by the NADPH oxidase inhibitor apocynin and were mitigated by the mitochondrial uncoupler FCCP.

SIGNIFICANCE

These findings implicated the therapeutic potential of specific inhibition of PKCβII isoform in the management of AGE accumulation-induced myopathic anomalies.

Retraction Note: Mitochondrial aldehyde dehydrogenase (ALDH2) protects against streptozotocin-induced diabetic cardiomyopathy: role of GSK3β and mitochondrial function

This article has been retracted. Please see the Retraction Notice for more detail: https://doi.org/10.1186/1741-7015-10-40.