Dietary nitrate does not alter cardiac function, calcium handling proteins, or SERCA activity in the left ventricle of healthy rats.

Dietary nitrate has been shown to increase cytosolic calcium concentrations within the heart, which would necessitate greater calcium sequestration for relaxation. In the present study we demonstrate that while nitrate supplementation reduced blood pressure, calcium-handling protein content, sarco(endo)plasmic reticulum Ca-ATPase 2a (SERCA) enzymatic properties, and left ventricular function were not altered. In addition, nitrite did not alter in vitro SERCA activity. Combined, these data suggest that in healthy rats, dietary nitrate does not increase left ventricle SERCA-related calcium-handling properties. Novelty Dietary nitrate decreases blood pressure but does not alter left ventricular calcium-handling protein content or SERCA activity in healthy rats.

Novel role of Sarco/endoplasmic reticulum calcium ATPase 2 in development of colorectal cancer and its regulation by F36, a curcumin analog.

Sarco/endoplasmic reticulum calcium ATPase (SERCA) enzymes play important roles in several signal transduction pathways that control proliferation, differentiation and apoptosis. Here, we reported that SERCA2 expression was positively correlated with tumor node metastasis (TNM) stages (n=75, P=0.0251) and grades (n=63, P=0.0146) of patients with colorectal cancer. The animal experiments demonstrated that SERCA2 expression was consistent with PCNA staining of intestinal tissues of male C57BL/6J-Apc(Min/)JNju mice. Besides, SERCA2 expression was also increased in undifferentiated HT-29 cells as compared with that in differentiated HT-29gal cells. Moreover, SERCA2 overexpression promoted proliferation and migration of SW480 cells via activating MAPK and AKT signaling pathways, while silence of SERCA2 inhibited the proliferation and migration of SW480 cells. In addition, we identified that a curcumin analog, F36, exhibited more potent inhibitory effect in colorectal cancer cells than curcumin through inhibiting SERCA2 expression. Taken together, our findings indicate that SERCA2 is involved in the malignant progress of colorectal cancer and maybe a therapeutic target for colorectal cancer treatment. Curcumin analog F36 shows enhanced anti-cancer activity in colorectal cancer cells by targeting SERCA2.

ERK/PP1a/PLB/SERCA2a and JNK pathways are involved in luteolin-mediated protection of rat hearts and cardiomyocytes following ischemia/reperfusion.

Luteolin has long been used in traditional Chinese medicine for treatment of various diseases. Recent studies have suggested that administration of luteolin yields cardioprotective effects during ischemia/reperfusion (I/R) in rats. However, the precise mechanisms of this action remain unclear. The aim of this study is to confirm that luteolin-mediated extracellular signal regulated kinase (ERK1/2) and c-Jun N-terminal kinase (JNK) pathways are responsible for their cardioprotective effects during I/R. Wistar rats were divided into the following groups: (i) DMSO group (DMSO); (ii) I/R group (I/R); (iii) luteolin+I/R group (Lut+I/R); (iv) ERK1/2 inhibitor PD98059+I/R group (PD+I/R); (v) PD98059+luteolin+I/R group (PD+Lut+I/R); and (vi) JNK inhibitor SP600125+I/R group (SP+I/R). The following properties were measured: contractile function of isolated heart and cardiomyocytes; infarct size; the release of lactate dehydrogenase (LDH); the percentage of apoptotic cells; the expression levels of Bcl-2 and Bax; and phosphorylation status of ERK1/2, JNK, type 1 protein phosphatase (PP1a), phospholamban (PLB) and sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a). Our data showed that pretreatment with luteolin or SP600125 significantly improved the contraction of the isolated heart and cardiomyocytes, reduced infarct size and LDH activity, decreased the rate of apoptosis and increased the Bcl-2/Bax ratio. However, pretreatment with PD98059 alone before I/R had no effect on the above indexes. Further, these consequences of luteolin pretreatment were abrogated by co-administration of PD98059. We also found that pretreatment with PD98059 caused a significant increase in JNK expression, and SP600125 could cause ERK1/2 activation during I/R. In addition, we are the first to demonstrate that luteolin affects PP1a expression, which results in the up-regulation of the PLB, thereby relieving its inhibition of SERCA2a. These results showed that luteolin improves cardiomyocyte contractile function after I/R injury by an ERK1/2-PP1a-PLB-SERCA2a-mediated mechanism independent of JNK signaling pathway.

Chronic depletion of glutathione exacerbates ventricular remodelling and dysfunction in the pressure-overloaded heart.

AIMS: Chronic depletion of myocardial glutathione (GSH) may play a role in cardiac remodelling and dysfunction. This study examined the relationship between chronic GSH depletion and cardiac failure induced by pressure overload in mice lacking the modifier subunit (GCLM) of glutamate-cysteine ligase, the rate-limiting enzyme for GSH synthesis. In addition, we examined the association between idiopathic dilated cardiomyopathy (DCM) in humans and -588C/T polymorphism of the GCLM gene, which reduces plasma levels of GSH. METHODS AND RESULTS: Pressure overload in mice was created by transverse aortic constriction (TAC). Myocardial GSH levels after TAC in GCLM(-/-) mice were 31% of those in GCLM(+/+) mice. TAC resulted in greater heart and lung-weight-to-body-weight ratios, greater dilation and dysfunction of left ventricle, more extensive myocardial fibrosis, and worse survival in GCLM(-/-) than GCLM(+/+) mice. Supplementation of GSH diethyl ester reversed the left-ventricular dilation and contractile dysfunction and the increased myocardial fibrosis after TAC in GCLM(-/-) mice. The prevalence of -588T polymorphism of the GCLM gene was significantly higher in DCM patients (n = 205) than in age- and sex-matched control subjects (n = 253) (36 vs. 19%, respectively, P < 0.001). The -588T polymorphism increased the risk of DCM that was independent of age, diabetes, and systolic blood pressure (OR 3.13, 95% CI: 2.28-4.44; P < 0.0001). CONCLUSION: Chronic depletion of GSH exacerbates remodelling and dysfunction in the pressure-overloaded heart. The clinical relevance of this mouse model is supported by a significant association between -588T polymorphism of the GCLM gene and patients with DCM.

Testosterone regulates cardiac contractile activation by modulating SERCA but not NCX activity.

Alterations in intracellular Ca(2+) transients of cardiomyocytes in orchidectomized (ORX) rats could be a cause of cardiac dysfunction in the hypogonadal condition. To investigate the role of male sex hormones in intracellular Ca(2+) homeostasis during relaxation, Ca(2+)-handling activities by sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) and the Na(+)/Ca(2+) exchanger (NCX) were evaluated in the ventricular muscle of 10-wk-old ORX rats with and without testosterone supplementation (2.5 mg/kg testosterone propionate, 2 times/wk). ORX induced a 50% decrease in contraction force accompanied by a prolonged time to achieve 50% relaxation (T(50)) in isolated intact ventricular trabeculae, which was partially corrected by testosterone administration. Maximum active tension was also suppressed in ORX rats without changes in myofilament Ca(2+) sensitivity and passive stiffness of the heart. Using a sarcoplasmic reticulum-enriched membrane preparation, the maximum thapsigargin-sensitive SERCA activity of the ORX rat was 27% lower with an increased Ca(2+) sensitivity, which was prevented by testosterone treatment. However, neither changes in SERCA content nor its modulating components, sarcolipin and heat shock protein 20, were detected in the ORX rat, but there was a significant decrease in the phosphorylated Thr(17) form of phospholamban. Despite a lower level of NCX protein in the heart of ORX rats, prolonged T(50) disappeared after an incubation with thapsigargin (10 µM), implying a lack of effect of male sex hormone deficiency on NCX function. These findings indicate that male sex hormones can regulate cardiac relaxation by acting mainly through SERCA. However, a detailed mechanism of SERCA modulation under male sex hormone deficiency status remains to be explored.

The cardiac force-frequency relationship and frequency-dependent acceleration of relaxation are impaired in lipopolysaccharide-treated rats: is the phospholamban-SERCA axis a therapeutic target?

Sepsis-induced myocardial dysfunction has traditionally been thought of as principally affecting systolic heart function. One of the primary reasons for this concept is that systolic dysfunction is relatively easy to conceptualize, visualize, and measure. With the advent of preload-independent measurements for diastolic function, both measurement and conceptual difficulties are being resolved, and a new realm of evidence is beginning to emerge regarding the aberrations that are found during cardiac relaxation in sepsis. A recent article in Critical Care brings this issue into sharper focus.

Dyslipidaemia in type II diabetic mice does not aggravate contractile impairment but increases ventricular stiffness.

AIMS: Type II diabetes, often associated with abdominal obesity, frequently leads to heart failure. Clinical and epidemiological evidence suggests that supplemental dyslipidaemia and hypertension, as clustered in the metabolic syndrome, aggravate the cardiovascular outcome. The differential impact of type II diabetes and the metabolic syndrome on left ventricular function, however, remains incompletely defined. METHODS AND RESULTS: We studied left ventricular function in vivo using pressure-volume analysis in obese diabetic mice with leptin deficiency (ob/ob) and obese diabetic dyslipidemic mice with combined leptin and low-density lipoprotein-receptor deficiency (DKO). ob/ob and DKO mice developed a diabetic cardiomyopathy, characterized by impaired contractility and relaxation, from the age of 24 weeks onwards. This was-at least partially-explained by increased apoptosis and disturbed Ca(2+) reuptake in the sarcoplasmic reticulum (SR) in both mouse models. DKO, but not ob/ob, developed increased end-diastolic ventricular stiffness, paralleled by increased left ventricular myocardial fibrosis. Cardiac output was preserved in ob/ob mice by favourable loading conditions, whereas it decreased in DKO mice. CONCLUSIONS: Type II diabetes in mice leads to impaired contractility and relaxation due to disturbed Ca(2+) reuptake in the SR, but only when dyslipidaemia and hypertension are superimposed does vascular-ventricular stiffening increase and left ventricular myocardial fibrosis develop.