[Influences and mechanism of verapamil on ischemia/reperfusion injury in cardiomyocytes of streptozotocin-induced diabetes mellitus rats].

OBJECTIVE: To investigate the effects and mechanism of verapamil preventing ischemia/reperfusion (I/R) injury by cardiac performance intracellular free [Ca(2+)](i) and L-type calcium current (I(Ca-L)) in cardiomyocytes of diabetes mellitus rats. METHODS: Diabetic rats were streptozotocin-induced and received verapamil (8 mg×kg(-1)×d(-1)) from 6 - 14 weeks old. The in vitro heart models of I/R rats were randomly divided into normal control group diabetes group, verapamil control group. the changes of heart functions were observed through a Langendorff-perfusion system. The fluorescence intensity of intracellular Ca(2+) was detected with Fluo-3/AM loading by laser scanning confocal microscope. I(Ca-L) was recorded by the whole-cell technique of patch clamp in enzymatically dissociated single rat ventricular myocytes. RESULTS: (1) In verapamil diabetes group, the values of left ventricular developed pressure [(91.3 ± 4.6) mm Hg], diastolic end pressure [(1535 ± 280) mm Hg], the maximum rising rates of left ventricular pressure [(5833 ± 256) mm Hg/s] and coronary arterial flow [(13.7 ± 0.9) ml/min] were all significantly increased, and the maximum dropping rates of left ventricular pressure [(3504 ± 319) mm Hg/s] was obviously decreased (compared with diabetes group, P < 0.01, respectively). (2) The fluorescence intensities of intracellular free Ca(2+)[(155.6 ± 10.9) nmol/L] in verapamil diabetes group were significantly reduced compared with diabetes group (245.2 ± 17.5 nmol/L, P < 0.01). (3) When clamp voltage was -20mV, I(Ca-L) was (-6.81 ± 0.76) pA/pF in verapamil diabetes group (compared with normal group (-8.17 ± 2.07) pA/pF, P < 0.05, and with diabetes group (-3.21 ± 0.54) pA/pF, P < 0.01, and with verapamil control group (-7.14 ± 2.17) pA/pF, P > 0.05). The current-voltage curve was changed to the lower position with -20mV of peak clamp potential in verapamil diabetes group compared with diabetes group. CONCLUSION: A poor heart function is closely correlated with a rising [Ca(2+)]i and a declining I(Ca-L) associated with I/R injury in diabetic rats hearts. Along-term verapamil therapy may significantly improve the severe cardiac impairment. The mechanism is probably attributed to the fact that verapamil can adjust I(Ca-L) influx, normalize the balance of intercellular [Ca(2+)]i, and block the Ca(2+) overload trigger by the effects of Ca(2+)-induced Ca(2+) release in diabetic cardiomyocytes.

Dexamethasone attenuated endotoxin-induced acute lung injury through inhibiting expression of inducible nitric oxide synthase.

Application of glucocorticoids in sepsis or severe infection is disputable in clinic. In this experiment, we studied the effect of dexamethasone on nitric oxide synthases and whether dexamethasone could attenuate endotoxin-induced acute lung injury (ALI). SD rats received 5 mg/kg lipopolisaccharide (LPS) injection. Then arterial oxygen partial pressure (PaO2), lung histology, lung tissue nitric oxide (NO) production and expression of nitric oxide synthases (NOS) were detected at 0.5, 1, 2, 3 or 4 h after LPS injection. PaO2 and lung injury deteriorated upon time. Production of NO in lung tissue increased significantly particularly in the first two hours, and this change was mainly due to the over-expression of inducible NOS (iNOS), but not endothelial NOS (eNOS). Furthermore, a tight positive correlation was observed between lung injury score (LIS) and NO production level in lung tissue. Dexamethasone could ameliorate PaO2 and lung damage evidently, which were paralleled by significant decreases in the production of NO and in the expression of iNOS mRNA. In conclusion, dexamethasone could effectively attenuate endotoxin-induced lung injury through inhibiting iNOS expression and activation in the very early stage of ALI.

[Protective effect of tert-butylhydroquinone on bone marrow cells in rats from cytotoxicity induced by benzene in vitro].

OBJECTIVE: To investigate the protective effect of tert-butylhydroquinone on bone marrow cells in rats from cytotoxicity induced by benzene in vitro. METHODS: The bone marrow cells in rats were divided into two groups randomizedly. Cells of the control group were stimulated by 0, 5, 10, 15, 20 mmol/L benzene for 2, 4, 6 hours respectively. Cells of the tBHQ-pretreated group were treated by 100 micromol/L tBHQ for 12 hours followed by the same conditions as the control group. The DNA damage was detected by single cell gel electrophoresis assay (SCGE) and cell apoptosis was examined by flow cytometry. The activities of NAD (P) H: quinone oxidoreductase (NQO1) in bone marrow cells of rats were also measured before benzene treatment in two groups. RESULTS: In control group, the DNA damage and the apoptosis of bone marrow cells was increased with the growing concentration and time of benzene treatment. The DNA migration and the lengths of DNA migration of the bone marrow cells in the rats under 5, 10, 15, 20 mmol/L benzene treatment in the tBHQ-pretreated group were significantly lower than those in control group at the same time point (P < 0.05). The apoptosis of the bone marrow cells in the rats stimulated by 15, 20 mmol/L benzene for 2 hours and 10, 15, 20 mmol/L benzene for 4 hours as well as 5, 10, 15, 20 mmol/L benzene for 6 hours were also significantly lower than those in control group (P < 0.05). The activities of NQO1 in the bone marrow cells in the rats were increased after tBHQ treatment (P < 0.01) (1.62 +/- 0.16 min(-1).mg(-1) vs. the control group: 0.95 +/- 0.08 min(-1).mg(-1)). CONCLUSION: The benzene can induce the DNA damage and the apoptosis of bone marrow cells in rats in a time dependent and dose dependent manner to some extent. The tBHQ can protect the bone marrow cells in rats from the cytotoxicity induced by benzene, which can be partly explained by the increase of the NQO1 activity induced by tBHQ.

Rosiglitazone ameliorates abnormal expression and activity of protein tyrosine phosphatase 1B in the skeletal muscle of fat-fed, streptozotocin-treated diabetic rats.

Protein tyrosine phosphatase 1B (PTP1B) acts as a physiological negative regulator of insulin signaling by dephosphorylating the activated insulin receptor (IR). Here we examine the role of PTP1B in the insulin-sensitizing action of rosiglitazone (RSG) in skeletal muscle and liver. Fat-fed, streptozotocin-treated rats (10-week-old), an animal model of type II diabetes, and age-matched, nondiabetic controls were treated with RSG (10 micromol kg(-1) day(-1)) for 2 weeks. After RSG treatment, the diabetic rats showed a significant decrease in blood glucose and improved insulin sensitivity. Diabetic rats showed significantly increased levels and activities of PTP1B in the skeletal muscle (1.6- and 2-fold, respectively) and liver (1.7- and 1.8-fold, respectively), thus diminishing insulin signaling in the target tissues. We found that the decreases in insulin-stimulated glucose uptake (55%), tyrosine phosphorylation of IRbeta-subunits (48%), and IR substrate-1 (IRS-1) (39%) in muscles of diabetic rats were normalized after RSG treatment. These effects were associated with 34 and 30% decreases in increased PTP1B levels and activities, respectively, in skeletal muscles of diabetic rats. In contrast, RSG did not affect the increased PTP1B levels and activities or the already reduced insulin-stimulated glycogen synthesis and tyrosine phosphorylation of IRbeta-subunits and IRS-2 in livers of diabetic rats. RSG treatment in normal rats did not significantly change PTP1B activities and levels or protein levels of IRbeta, IRS-1, and -2 in diabetic rats. These data suggest that RSG enhances insulin activity in skeletal muscle of diabetic rats possibly by ameliorating abnormal levels and activities of PTP1B.

The effects of Chinese herb Angelica in focal cerebral ischemia injury in the rat.

This experiment was designed to study the therapeutic mechanisms of Angelica on the focal cerebral ischemia injury of the rat. The ischemic area was determined by TTC stain. And terminal deoxynucleotidyl transferase (TDT) mediated DUTP-biotin nick end labeling (TUNEL) method was applied to detect neuronal apoptosis. The expressions of Bcl-2 and Bax proteins were observed by immunohistochemical staining methods. Results show that the treatment with angelica reduced the volume of cerebral infarction (p < 0.05), and that the number of neuronal apoptosis cells decreased significantly (p < 0.01). Also the expression level of Bax protein decreased (p < 0.01). These results suggest that Angelica can reduce the number of apoptosis cells by decreasing the expression of Bax protein. This is maybe one of the mechanisms of the therapeutic effect of Angelica on focal cerebral ischemia injury.

[Change of glucose transporter 4 and its influence on glucose and fatty-acid metabolism in type 2 diabetic myocardium].

OBJECTIVE: To investigate the relationship between sarcolemmal content of glucose transporter 4 (GLUT4) and the myocardial glucose and fatty acid utilization in type 2 diabetes. METHODS: Twenty-four Sprague-Dawley rats were randomized into four groups: control, HFD/STZ, control/RSG and HFD/STZ/RSG. Sprague-Dawley rats were fed with high-fat diet (40% of the calories was supplied by fat) for 4 weeks, intraperitoneally injected with 35 mg/kg streptozotocin to establish type 2 diabetes model, and 24 diabetic rats were randomized into four groups: HFD/STZ/RSG group [fed with high fat food and given rosiglitazone (3 mg.kg(-1).d(-1)) for 2 weeks], HFD/STZ group (fed with high fat food and given normal saline), control/RSG [fed with normal food and given rosiglitazone (3 mg.kg(-1).d(-1)) for 2 weeks], and control group (fed with normal food and given normal saline). Then the rats were killed and their hearts were taken out to be mounted onto a Langendorff perfusion apparatus to be perfused with Krebs-Henseleit buffer in the presence of 5 mmol/L glucose and 0.4 mmol/L (3)H labeling palmitate. Glucose uptake and (3)H2O collection were used to evaluate the rate of carbohydrate and fatty acid oxidation. The sarcolemmal content of GLUT4 protein was detected by Western blotting method. RESULTS: Compared with the control group, the diabetic rats had a significantly depression of glucose uptake of the heart [(55 +/- 6) micromol/g dry weight vs (69 +/- 6) micromol/g dry weight, P < 0.01], the oxidation rate of glucose decreased from 25% to 18% and the oxidation rate of palmitate increased from 75% to 82%, and the sarcolemmal GLUT4 content was decreased by 53% after 30 minutes' perfusion. In the HFD/STZ/RSG group the glucose uptake level was (64 +/- 6) micromol/g dry weight, significantly higher than that of the HFD/STZ group (P < 0.05), the proportions of glucose oxidation and fatty acid oxidation were 24% and 76% respectively, and the GLUT4 expression was 92% that of the normal rats, significantly higher than that of the HFD/STZ group (47%, P < 0.01). CONCLUSION: The sarcolemmal GLUT4 content in the type 2 diabetic myocardium is obviously decreased, which may be associated with the decrease of glucose uptake and increase of fatty acid oxygen. Rosiglitazone treatment may exert beneficial effects on the energy substrate utilization by increasing the expression of GLUT4.

Mechanism of improving effect of losartan on insulin sensitivity of non-insulin-dependent diabetes mellitus rats.

The specific inhibition of angiotensin II action at AT(1) receptors by losartan has been shown to decrease peripheral insulin resistance in type 2 diabetic patients and animal models. We examined the effect of losartan on the expression of insulin receptor substrate 1 (IRS-1), protein kinase B (PKB) and glucose transporter 4 (GLUT4), as well as the phosphorylation status of IRS-1 and the association between IRS-1 and phosphatidylinositol (PI) 3-kinase in skeletal muscle from fat-fed and-streptozotocin (STZ)-treated rats, an animal model of type 2 diabetes mellitus. In addition, the effects of losartan on GLUT4 translocation in muscle cells and on insulin sensitivity were also evaluated. Muscle tissues were isolated from male losartan-treated and untreated normal or non-insulin-dependent diabetes mellitus (NIDDM) rats with a dose of 4 mg/kg per day for 6 weeks. Oral administration of losartan improved insulin sensitivity, which was determined by an oral glucose tolerance test (OGTT). In skeletal muscles, the protein levels of IRS-1, PKB and GLUT4 in NIDDM rats were not significantly different from those of the control rats, and they were not affected by losartan. The levels of IRS-1 tyrosine phosphorylation, PI 3-kinase activity associated with IRS-1 and PKB activation after stimulation with insulin in muscle tissue of NIDDM rats were significantly decreased (P<0.01) compared with those in the control rats, while they were not increased by losartan. Losartan had a major effect on GLUT4 translocation in myocytes, as it significantly increased (P<0.05) the insulin-induced amounts of GLUT4 in plasma membrane (PM) and T-tubules (TT) in myocytes from NIDDM rats. Consistent with these results, the plasma glucose level in losartan-treated NIDDM rats was decreased (P<0.05) compared with that in untreated NIDDM rats. Our results suggest that losartan may exert beneficial effects on insulin resistance by increasing the translocation of GLUT4 in muscle tissue, which is probably associated with a non-PI 3-kinase-dependent mechanism.

The role of quantitative changes in the epxression of insulin receptor substrate-1 and nuclear ubiquitin in abnormal glycometabolism in the livers of KKay mice and the relative therapeutic mechanisms of Astragalus polysaccharide.

Ubiquitin and the ubiquitination pathway are important regulators of insulin signaling. The insulin receptor substrate­1 (IRS-1), an ubiquitin-interacting adaptor protein, serves as the key docking protein in insulin signaling. The effects of this dynamic interaction and the changes in ubiquitin expression on hepatic insulin signaling, as well as the relative therapeutic effects of Astragalus polysaccharide (APS) have not yet been elucidated. In this study, we aimed to investigate the abnormal changes which occur in the levels of IRS-1 and ubiquitin in the livers of mice (mice with insulin resistance and diabetes), and to elucidate the possible mechanisms responsible for these changes. A control group (CG), an insulin resistance group (IG) and a diabetes group (DG) were respectively composed of 12-week-old C57BL/6J mice fed a normal diet, C57BL/6J mice fed a high­fat diet and KKay mice fed a high­fat diet, and treatment groups were composed of corresponding groups treated with APS (CG + A, IG + A, DG + A). All the mice were age-matched and grouped at random. After eight weeks, the mouse models were successfully established and the related physiological or biochemical indexes were detected using corresponding methods. Ubiquitin expression in the liver was detected by immunohistochemisty, and western blot analysis was used to detect the expression of IRS-1 and ubiquitin. The results revealed that the expression of IRS-1 in the DG was significantly lower compared to that in the CG and IG; however, the nuclear expression of ubiquitin and the ubiquitination levels of IRS-1, including body weight and blood glucose and triglyceride levels in the DG were significantly higher compared to those in the CG or IG (P<0.05). There was a significant improvement in the ubiquitination levels in DG + A, including the blood glucose and triglyceride levels compared with the DG (P<0.05). From the stage of insulin resistance to the stage of diabetes, the reduced expression of IRS-1 and its enhanced ubiquitination levels combined with the overexpression of nuclear ubiquitin contributed to the abnormal glycometabolism and the disruption of insulin signaling. APS showed beneficial effects, such as lowering body weight, as well as blood glucose and triglyceride levels, and these effects correlated with the downregulation of the ubiquitination levels of IRS-1 and the nuclear expression of ubiquitin.

Differential expression and function of the caveolin-1 gene in non-small cell lung carcinoma.

This study was designed to clarify the function of caveolin-1 (Cav-1) in the development of lung cancer by investigating the mutation and protein expression of the Cav-1 gene in non-small cell lung carcinoma (NSCLC). Quantum dot immunofluorescence histochemistry was used to evaluate Cav-1 protein expression and subcellular localization in the lung cancer tissue microarray including 140 cases of lung cancer and 20 cases of non-cancerous lung tissue. Mutation of the Cav-1 gene in exon 1 and exon 3 was detected by polymerase chain reaction-single strand conformation polymorphism and sequencing. The positive rates of Cav-1 expression were 49.3% (69/140) in NSCLC group, significantly lower than the 100% (20/20) rate in the control group. Adenocarcinomas (16.7%), adenosquamous carcinomas (38.4%), squamous cell carcinomas (67.1%) and large cell lung cancers (66.7%) displayed Cav-1 positive staining, suggesting a gradient of Cav-1 expression according to tumor histotype-related aggressiveness. High-expression of Cav-1 protein was statistically correlated with pathologic TNM stage and lymph node metastasis. No mutation could be detected in exon 1 and exon 3 from all Cav-1 protein negative expression of NSCLC samples. Cav-1 immunoreactivity in lung cancer is histotype-dependent, increased Cav-1 expression indicates the malignant progression and high invasion features of NSCLCs. Deregulation of Cav-1 expression in NSCLCs may not correlate with mutation.

Multiple hemodynamic effects of endogenous hydrogen sulfide on central nervous system in rats.

BACKGROUND: Endogenous hydrogen sulfide is a new neuromodulator which takes part in the regulation of central nervous system physiology and diseases. Whether endogenous hydrogen sulfide in the central nervous system regulates cardiovascular activity is not known. In the present study, we observed the hemodynamic changes of hydrogen sulfide or its precursor by intracerebroventricular injection, and investigate the possible roles of endogenous digitalis like factors and sympathetic activity in the regulation. METHODS: Ninety-four Sprague-Dawley rats underwent a right cerebroventricular puncture, then the hydrogen sulfide saturation buffer or its precursor injected by intrcerebroventricular catheter. A heperin-filled catheter was inserted into the right femoral artery or into the left ventricle, and changes of blood pressure or cardiac function recorded by a Powerlab/4S instrument. Phentolamine or metoprolol were pre-injected to observe the possible role in autonomic nerve activity. After rats were sacrificed, plasma was collected and endogenous digitalis-like factors were measured with a commercial radioimmunoassay kit. The aortic, cardiac sarcolemmal vesicles were isolated and the activity of Na(+)-K(+)-ATPase was measured as ouabain-sensitive ATP hydrolysis under maximal velocity conditions by measuring the release of inorganic phosphate from ATP. Unpaired Student's t test for two groups or analysis of variances (ANOVA) for multiple groups were used to compare the differences of the changes. RESULTS: Intracerebroventricular injection of hydrogen sulfide induced a transient hypotension, then dramatic hypertenive effects in a dose-dependent manner. Bolus injection of L-cysteine or beta- mercaptopyruvate also increased mean arterial pressure (P < 0.01), whereas hydroxylamine-a cystathionine beta synthase inhibitor decreased the arterial pressure (P < 0.01). Hydrogen sulfide and L-cysteine increased mean arterial pressure, left ventricular develop pressure and left-ventricle maximal rate of systolic and diastolic pressure; these functions were decreased by hydroxylamine (P < 0.01). Glibenclamide (a K(ATP) channel blocker) blocked the transient hypotensive effect, phentolamine (an alpha-adrenergic receptor blocker) blocked the hypertensive effect, and metoprolol (a selective beta 1 receptor blocker) blocked the positive inoptropic effect of central nervous system hydrogen sulfide. The endogenous digitalis-like factors in plasma were elevated (P < 0.01) after treatment with L-cysteine, association with decreasing Na(+)-K(+)-ATPase activity in cardiac or aortic sarcolemmal vesicles (P < 0.01). Hydroxylamine injection reduced the endogenous digitalis-like factors level in plasma association with increasing Na(+)-K(+)-ATPase activity in cardiac and aortic sarcolemmal vesicles. CONCLUSION: Central nervous system endogenous hydrogen sulfide upregulated mean arterial pressure and cardiac systolic function by activation of sympathetic nerves or release of endogenous digitalis-like factors.

Hypoglycemic effect of polysaccharide enriched extract of Astragalus membranaceus in diet induced insulin resistant C57BL/6J mice and its potential mechanism.

Our previous studies found that Astragalus polysaccharide (APS) exerts insulin-sensitizing and hypoglycemic activities in type 2 diabetic (T2DM) rats. The present study was designed to further confirm the hypoglycemic effect of APS and to investigate its possible mechanism underlying the improvement of insulin resistance in vivo and in vitro. Diet-induced insulin resistant C57BL/6J mice treated with or without APS (orally, 700 mg/kg/d) for 8 weeks were analyzed and compared. Simultaneously, an insulin resistant C(2)C(12) cell model and an ER stressed HepG2 cell model were established and incubated with or without APS (200 microg/ml) for 24h respectively. Systematic insulin sensitivity was measured with an insulin-tolerance test (ITT) and an homeostasis model assessment (HOMA IR) index. Metabolic stress variation was analyzed for biochemical parameters and pathological variations. The expression and activity of protein tyrosine phosphatase 1B (PTP1B), which plays a very important role in insulin signaling and in the ER stress response, was measured by immunoprecipitation and Western blot. The ER stress response was analyzed through XBP1 transcription and splicing by real-time PCR. APS could alleviate insulin resistance and ER stress induced by high glucose in vivo and in vitro, respectively. The hyperglycemia, hypolipemia, and hyperinsulinemia status were controlled with APS therapy. Insulin action in the liver of insulin resistant mice was restored significantly with APS administration. APS enhanced adaptive capacity of the ER and promoted insulin signaling by the inhibition of the expression and activity of PTP1B. Furthermore, the anti-obesity effect and hypolipidemia effects of APS were probably due partly to decreasing the leptin resistance of mice, which would positively couple with the normalization of plasma insulin levels. We have shown that APS has beneficial effects on insulin resistance and hyperglycemia. The mechanism is related to the alleviation of ER stress and insulin resistance under hyperglycemia conditions.

[Changes of VASP in shear stress induced cytoskeleton reorganization in endothelial cells].

AIM: To investigate the effects of different level of laminar shear stresses on the vasodilator-stimulated phosphoprotein (VASP) location and expression changes associated with actin reorganization and it's mechanism. METHODS: A parallel-plate flow chamber device was used to create laminar shear stress in vitro on cultured human umbilical endothelial cells (HUVECs). The distribution of VASP and microfilament were observed by double immunofluorescence staining. RT-PCR was used to test VASP mRNA level, while VASP parameters were analyzed quantitatively with Western blot. RESULTS: After exposure to a flow of 10 dyn/cm2 flow for 24 h, HUVECs were elongated and oriented gradually to the direction of the flow. The microfilaments were recruited and oriented to the direction of flow with thicker VASP, specially targeted to the ends of stress fibres. RT-PCR result indicated shear could induce VASP mRNA increase. Western blotting data showed a dynamic reversible phosphorylation of VASP during 24 h, and total VASP expression increased rapidly, peaked at 2 h, then recovered at 8h followed by a slow increase again. H89, a cAMP inhibitor could inhibit shear induced VASP expression increase and phosphorylation. CONCLUSION: VASP is an potential important component which participates in the regulation of cell cytoskeleton reorganization and morphology modification induced by shear flow via a cAMP/cAK pathway.

[Effect of thyroid hormone on protein kinase C signal pathway in cardiac myocytes and fibroblasts of rats in vitro].

AIM: To study the effect of thyroid hormone on protein kinase C activity and isoprotein expressions in cardiac myocytes and fibroblasts of rats in vitro. METHODS: Cardiac myocytes and fibroblasts were cultured according to the method of Simpson. Cells were pretreated with 1% newborn calf serum (NCS) or Angiotensin II (Ang II) for 24 hours, then Triiodothyronine (T3) was added to the culture medium and the culture was kept for another 48 hours. The protein kinase C activation were measured by PepTaga non-radioactive PKC assay, and the expressions of PKC alpha and PKC epsilon were detected by Western blot method. RESULTS: At the condition of 1% NCS culture medium, T3 could inhibit PKC activity and PKC epsilon expression in cardiac myocytes significantly, but the expression of PKC alpha in cardiac myocytes was not influenced by T3. In cardiac fibroblasts, neither PKC activity nor PKC alpha and PKC epsilon expressions was influenced by T3. When cells were pretreated with Ang II for 24 hours, PKC activities in cardiac myocytes and fibroblasts were increased significantly, and PKC epsilon expressions in cardiac myocytes were also markedly increased. Following a T3 treatment, PKC activity and PKC epsilon expression in cardiac myocytes were markedly decreased, but PKC activity in cardiac fibroblasts was not changed. CONCLUSION: Whether at the condition of 1% NCS medium or in a pretreatment with Ang II, thyroid hormone could inhibit the PKC activity and PKC epsilon expression in cardiac myocytes. The influence of thyroid hormone on the PKC signal pathway in cardiac myocyte may be involved in many pathophysiological progress of myocardium.