Impairments in deeply-saturated optical parametric amplifiers for amplitude- and phase-modulated signals

We measure impairment of on-off-keyed and differential-phase-shift-keyed signals imposed by gain saturation in a fiber parametric amplifier. Phase modulation is observed to be more robust, particularly for deep (15 dB) saturation.

Preparation and Properties of Poly(lactide-co-glycolide) (PLGA)/ Nano-Hydroxyapatite (NHA) Scaffolds by Thermally Induced Phase Separation and Rabbit MSCs Culture on Scaffolds

Biodegradable polymer/bioceramic composites scaffold can overcome the limitation of conventional ceramic bone substitutes such as brittleness and difficulty in shaping. To better mimic the mineral component and the microstructure of natural bone, novel nano-hydroxyapatite (NHA)/polymer composite scaffolds with high porosity and well-controlled pore architectures as well as high exposure of the bioactive ceramics to the scaffold surface is developed for efficient bone tissue engineering. In this article, regular and highly interconnected porous poly(lactide-co-glycolide) (PLGA)/NHA scaffolds are fabricated by thermally induced phase separation technique. The effects of solvent composition, polymer concentration, coarsening temperature, and coarsening time as well as NHA content on the micro-morphology, mechanical properties of the PLGA/NHA scaffolds are investigated. The results show that pore size of the PLGA/NHA scaffolds decrease with the increase of PLGA concentration and NHA content. The introduction of NHA greatly increase the mechanical properties and water absorption ability which greatly increase with the increase of NHA content. Mesenchymal stem cells are seeded and cultured in three-dimensional (3D) PLGA/NHA scaffolds to fabricate in vitro tissue engineering bone, which is investigated by adhesion rate, cell morphology, cell numbers, and alkaline phosphatase assay. The results display that the PLGA/NHA scaffolds exhibit significantly higher cell growth, alkaline phosphatase activity than PLGA scaffolds, especially the PLGA/NHA scaffolds with 10 wt.% NHA. The results suggest that the newly developed PLGA/NHA composite scaffolds may serve as an excellent 3D substrate for cell attachment and migration in bone tissue engineering.

Blockage of intermediate-conductance-Ca(2+) -activated K(+) channels inhibits progression of human endometrial cancer

Potassium (K(+)) channels have been implicated in proliferation of some tumor cells. However, whether K(+) channels are important to the pathogenesis of endometrial cancer (EC) remains unknown. In the present study, we report that intermediate-conductance Ca(2+)-activated K(+) (IKCa1) channels play a critical role in the development of EC. The expression of IKCa1 at both mRNA and protein levels in EC tissues was greatly increased than that in atypical hyperplasia and normal tissues. Treatment of EC cells with clotrimazole and TRAM-34, two agents known to inhibit IKCa1 channels, suppressed the proliferation of EC cells and blocked EC cell cycle at G(0)/G(1) phase. Similarly, downregulation of IKCa1 by siRNA against IKCa1 inhibited EC cell proliferation and arrested its cell cycle at G(0)/G(1) phase. A clotrimazole-sensitive K(+) current was induced in EC cells in response to the increased Ca(2+). The current density induced by Ca(2+) was greatly reduced by clotrimazole, TRAM-34, charybdotoxin or downregulation of IKCa1 by the siRNA against IKCa1. Furthermore, TRAM-34 and clotrimazole slowed the formation in nude mice of tumor generated by injection of EC cells. Our results suggest that increased activity of IKCa1 channel is necessary for the development of EC.

Biological activities of a novel selective oestrogen receptor modulator derived from raloxifene (Y134)

BACKGROUND AND PURPOSE

Selective oestrogen receptor (ER) modulators (SERMs) are of great value in the treatment of breast cancer and osteoporosis. The aim of this study was to characterize pharmacologically a new class of SERMs synthesized based on the core structure of raloxifene.

EXPERIMENTAL APPROACH

Competitive receptor binding and luciferase-based reporter methods were used to study the bioactivities of raloxifene analogues, followed by efficacy determination in breast cancer cell proliferation assay. ER antagonist effects were investigated in female rats by measuring uterine and mammary gland growth, using wet weight, BrdU incorporation and terminal end bud (TEB) as indicators.

KEY RESULTS

Five analogues, belonging to two different structural series and display higher binding affinities for ERalpha than ERbeta were functionally evaluated. One such analogue, Y134, exhibited potent antagonist activity at ERs in CV-1 cells cotransfected with plasmids containing ERalpha or ERbeta and oestrogen-response element-driven luciferase. The estimated IC(50) value was 0.52 nM for ERalpha and 2.94 nM for ERbeta, comparable to that of raloxifene. Little cytotoxicity was observed at Y134 concentrations below 10 microM. Y134 suppressed oestrogen-stimulated proliferation of ER-positive human breast cancer MCF-7 and T47D cells. At an identical dose, administered to ovariectomized rats, Y134 was more effective than raloxifene at arresting oestrogen-induced outgrowth of TEB and mammary gland DNA synthesis, but their inhibitory effects on the uterus were comparable.

CONCLUSIONS AND IMPLICATIONS

Y134 is a potent ER antagonist with better mammary gland selectivity than raloxifene and shows potential for development as a new SERM for therapeutic use.

A pilot study of weekly versus 3-week docetaxel in combination with capecitabine in patients with anthracycline-pretreated metastatic breast cancer

10771

Background: Capecitabine in combination with docetaxel given every 3 weeks has shown a high degree of activity in anthracycline-pretreated metastatic breast cancer (MBC), but with high toxicities. To improve the therapeutic index, we performed a clinical pilot trial to evaluate the efficacy and safety of weekly or 3-week docetaxel in combination with capecitabine given for 14 days every 21 days. Methods: Patients with at least one measurable lesion were randomized to receive the treatment arms: docetaxel 75mg/m2 on days 1, oral capecitabine 950 mg/m2 twice daily on days 1–14 (Arm A); docetaxel 37.5mg/m2 on days 1 and 8, oral capecitabine 950 mg/m2 twice daily on days 1–14 (arm B). Each cycle was repeated every 3 weeks. Patients remained on study for a maximum 6 cycles or until tumor progression or unacceptable toxicity occurred, response assessments were scheduled every two cycles. Results: 64 pts were enrolled, 62 eligible for safety and tumor assessment. Key baseline variables were well balanced. Dominant site of disease was visceral in 66.1%; 24.2% had ≥3 organ sites of disease; all patients had previously received anthracyclines, 24.2% for MBC. 43. 6% were ER negative and 46.8% were HER-2 overexpress. The overall clinical response rate of all groups was 59.7% (37/62). There was no progressive disease (PD) after two cycles. Efficacy outcomes were similar in the two arms. The response rate of group A and B were 60% (18/30) and 59.4% (19/32) respectively. There were no drug-related deaths observed. Neutropenia was the most common toxicity. In all, the frequence of Grade 3/4 neutropenia were similar in two arm, but Grade 4 neutropenia of Group A 66.7% (20/30) was higher than Group B 34.4% (11/32), P = 0.021. Conclusions: The study confirmed the superior activity of docetaxe-capecitabine combination therapy in anthracycline resistant MBC, and comparing with 3-week schedule, weekly docetaxel plus capecitabine has same high efficacy with a favourable safety profile.

No significant financial relationships to disclose.

Study of brain and whole blood PK/PD of bortezomib in rat models

12036

Background: Bortezomib (Btz) is the first in class proteasome inhibitor and has been approved for treatment of multiple myeloma patients who have received at least 1 prior therapy. The potential for Btz to penetrate the CNS was examined in the rat under two conditions: intact blood brain barrier (BBB) and compromised BBB induced by middle cerebral artery occlusion (MCAO). Methods: Intact BBB: healthy rats received an iv bolus followed by a constant infusion of Btz to steady-state (SS). The blood and brain samples were collected for determination of concentration (Conc) of Btz (PK) and of 20S proteasome activity (PD). The brain samples were collected after a perfusion with saline. Inulin was included in the study in order to determine blood contamination in brain tissues. Compromised BBB: rats underwent MCAO surgery and 1 h later were administered Btz via an iv bolus of 0, 0.1, 0.2 or 0.35 mg/kg. The blood and brain samples were collected through 24 h postdose. Conc of Btz was determined by an LC/MS/MS method. The 20S proteasome activity was measured using an ex vivo assay. Results: 1) Intact BBB: at SS the mean blood Conc of Btz was 140 ng/mL, and proteasome activity in the blood was inhibited by ∼80% compared to the vehicle group (p < 0.0001). In contrast, the brain Conc of Btz was extremely low (∼3 ng/g) with the brain-to-blood ratio of ∼0.02. No difference was observed in brain proteasome activity between the vehicle and Btz-treated groups. 2)The MCAO rat: the PK/PD relationship in the blood was best described by a sigmoid Emax model with an EC50 of 110 ng/mL and gamma factor of 3.8. The model also suggests that there is no proteasome inhibition (PI) when the blood Conc is <40 ng/mL (no effective blood Conc, NOEBC). In the brain, the Cmax of Btz was 22.0 ng/g from the highest dose group, in contrast to the blood Cmax of 164 ng/mL. The increased exposure in the brain of a MCAO rat relative to a normal rat was anticipated as its BBB is impaired. However, the brain Concs were all below the NOEBC. No significant PI was observed in all brain tissues (P>0.1). Conclusion: Very poor brain penetration was observed for Btz in rats. Btz showed PI in whole blood but not in the brain either of normal or MCAO rats following administration of Btz.

[Table: see text]

Cardiac health and diabetes mellitus in women: problems and prospects

Cardiovascular disease is the leading cause of morbidity and mortality in both genders. Although premenopausal women display a lower prevalence in cardiovascular diseases compared with age-matched men, they lose this ''female advantage'' following menopause. There are significant gender differences in a wide spectrum of cardiovascular incidence, ranging from delayed disease onset to higher prevalence of comorbid diseases for females. Several factors have been suggested to contribute to such difference in cardiovascular incidence including sex hormones, gender-specific intrinsic organ function, difference in body size and cardiovascular risk factor profiles (e.g., use of tobacco and alcohol, hypertension, diabetes mellitus, dyslipidemia, obesity, sedentary lifestyle and atherogenic diet). A gender difference also exists for diabetes and diabetic complications. Heart diseases exhibits a 2-fold and a 5-fold increase in men and women with diabetes, respectively. Although female hearts are usually more tolerable to stress insults than their male counterparts, female sex hormone such as estrogen interacts with diabetic risk factors to precipitate cardiomyopathy. This review aims at recaping our knowledge on gender difference in diabetic heart disease with an emphasis on disease pathogenesis. Deficits and obstacles to optimal risk factor management in diabetic women are also discussed in an effort to improve the overall cardiovascular health of diabetic women.

Cardiac overexpression of catalase rescues cardiac contractile dysfunction induced by insulin resistance: Role of oxidative stress, protein carbonyl formation and insulin sensitivity

AIMS/HYPOTHESIS

Insulin resistance leads to oxidative stress and cardiac dysfunction. This study examined the impact of catalase on insulin-resistance-induced cardiac dysfunction, oxidative damage and insulin sensitivity.

METHODS

Insulin resistance was initiated in FVB and catalase-transgenic mice by 12 weeks of sucrose feeding. Contractile and intracellular Ca2+ properties were evaluated in cardiomyocytes including peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR90), half-width duration (HWD), maximal velocity of shortening/relengthening (+/-dL/dt), fura-fluorescence intensity change (DeltaFFI) and intracellular Ca2+ clearance rate (tau). Reactive oxygen species (ROS) and protein damage were evaluated with dichlorodihydrofluorescein and protein carbonyl formation.

RESULTS

Sucrose-fed mice displayed hyperinsulinaemia, impaired glucose tolerance and normal body weight. Myocytes from FVB sucrose-fed mice exhibited depressed PS and +/-dL/dt, prolonged TR90 and tau, and reduced DeltaFFI associated with normal TPS and HWD compared with those from starch-fed control mice. ROS and protein carbonyl formation were elevated in FVB sucrose-fed mice. Insulin sensitivity was reduced, evidenced by impaired insulin-stimulated 2-deoxy-D: -[3H]glucose uptake. Western blot analysis indicated that sucrose feeding: (1) inhibited insulin-stimulated phosphorylation of insulin receptor and Akt; (2) enhanced protein-tyrosine phosphatase 1B (PTP1B) expression; and (3) suppressed endothelial nitric oxide synthase (eNOS) and Na+-Ca2+ exchanger expression without affecting peroxisome proliferator-activated receptor gamma (PPARgamma), sarco(endo)plasmic reticulum Ca2+-ATPase isozyme 2a and phospholamban. Catalase ablated insulin-resistance-induced mechanical dysfunction, ROS production and protein damage, and reduced eNOS, but not insulin insensitivity. Catalase itself decreased resting FFI and enhanced expression of PTP1B and PPARgamma.

CONCLUSIONS/INTERPRETATION

These data indicate that catalase rescues insulin-resistance-induced cardiac dysfunction related to ROS production and protein oxidation but probably does not improve insulin sensitivity.

Schistosoma japonicum triose-phosphate isomerase plasmid DNA vaccine protects pigs against challenge infection

The protective efficacy of a Schistosoma japonicum, Chinese strain, triose-phosphate isomerase (TPI) plasmid DNA vaccine was examined in naïve pigs. Pigs were vaccinated with the TPI DNA-plasmid alone, or in conjunction with IL-12 as pcDNA3.1-P35, pcDNA3.1-P40 plasmids via intramuscular injection. Control pigs were immunized with equivalent amounts of pcDNA3.1. Pigs were immunized 3 times at 21-day intervals and challenged 30 days after the final boost. Forty-five days post-challenge, pigs were sacrificed and perfused to compare adult worm burdens, female worm burdens, liver egg burdens and granuloma size. We found that pigs vaccinated with SjCTPI DNA alone had adult worm burdens reduced by 48.3% and that a further decrease in adult worm burdens was not seen in the group vaccinated with SjCTPI DNA in conjunction with IL-12 (46.2% reduction). The SjCTPI DNA vaccines had a more pronounced effect on reducing female worm burdens i.e. 53.6% SjCTPI alone and 59.6% for SjCTPI+IL-12. Vaccination with SjCTPI-DNA reduced liver eggs by 49.4% and this response was significantly enhanced by the addition of IL-12 (65.8% reduction in liver eggs). In addition to the dramatic protective effects seen in vaccinated pigs, we also noted that granuloma size was reduced by 42% in both groups. Thus, vaccination of pigs and other large animals in China with SjCTPI DNA vaccine will likely reduce transmission by reducing adult worm burdens and worm egg output and simultaneously reduce hepatic egg-associated pathology.

Cardiac contractile dysfunction in Lep/Lep obesity is accompanied by NADPH oxidase activation, oxidative modification of sarco(endo)plasmic reticulum Ca2+-ATPase and myosin heavy chain isozyme switch

AIMS/HYPOTHESIS

Obesity is an independent risk factor for heart diseases but the underlying mechanism is not clear. This study examined cardiac contraction, oxidative stress, oxidative modification of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) and the myosin heavy chain (MHC) isoform switch in obese mice.

METHODS

Mechanical properties were evaluated in ventricular myocytes from C57BL/6J lean and Lep/Lep obese mice (formerly known as ob/ob mice), including peak shortening (PS), time to 50 or 90% PS, time to 50 or 90% relengthening (TR50, TR90), maximal velocity of shortening/relengthening (+/-dL/dt), intracellular Ca2+ and its decay (tau). Oxidative stress, lipid peroxidation, protein damage and SERCA activity were assessed by glutathione/glutathione disulfide, malondialdehyde, protein carbonyl and 45Ca2+ uptake, respectively. NADPH oxidase was determined by immunoblotting.

RESULTS

Myocytes from Lep/Lep mice displayed depressed PS and +/- dL/dt, prolonged TR50, TR90, elevated resting [Ca2+]i, prolonged tau, reduced contractile capacity at high stimulus frequencies and diminished responsiveness to extracellular Ca2+ compared with lean controls. Cardiac glutathione/glutathione disulfide was decreased whereas malondialdehyde, protein carbonyl, membrane p47(phox) and membrane gp91(phox) were increased in the Lep/Lep group. SERCA isoenzyme 2a was markedly modified by oxidation in Lep/Lep hearts and associated with decreased 45Ca2+ uptake. The MHC isozyme displayed a shift from the alpha to the beta isoform in Lep/Lep hearts. Short-term incubation of angiotensin II with myocytes mimicked the mechanical defects, SERCA oxidation and 45Ca2+ uptake seen in Lep/Lep myocytes. Incubation of the NADPH oxidase inhibitor apocynin with Lep/Lep myocytes alleviated contractile defects without reversing SERCA oxidation or activity.

CONCLUSIONS/INTERPRETATION

These data indicate that obesity-related cardiac defects may be related to NADPH oxidase activation, oxidative damage to SERCA and the MHC isozyme switch.

Short courses of low dose dexamethasone delay bleomycin-induced lung fibrosis in rats

After comparing mortality and clinical signs in rats receiving different dexamethasone treatments, we investigated whether 0.5 mg/kg/d dexamethasone could delay pulmonary fibrosis induced by bleomycin and its time course (1, 3, 7, 14, 21 and 28 days). Tissue injury was assessed by apoptosis, lactate dehydrogenase (LDH) release, malondialdehyde content, and protein content; and inflammation was measured in terms of myeloperoxidase (MPO) activity, inflammatory cell count, and the mRNA expression of pro/inflammatory cytokines. Fibrogenic activity was analyzed by measuring the mRNA expression of fibrotic cytokines in tissue, and the promotion of fibroproliferation and synthesis of collagen type I by bronchoalveolar lavage fluids in vitro; and fibrosis was assessed by measuring the hydroxyproline content and collagen-I mRNA expression, and by histology. Bleomycin treatment induced tissue injury, inflammation and fibrogenic activity in lung, and led to fibrosis. Treatment with dexamethasone diminished the extent of fibrosis by strongly reducing inflammation, lung damage, and fibrogenic activity. These results demonstrate that the progression of bleomycin-induced pulmonary fibrosis in rats can be delayed by dexamethasone treatment, which appeared to alleviate not only inflammation but also lung damage and fibrogenic activity, indicating a possible new role for dexamethasone in the treatment of fibrosis.

Paradoxical effects of ginkgolide B on cardiomyocyte contractile function in normal and high-glucose environments

AIM

Ginkgo biloba extract is a natural product used widely for cerebral and cardiovascular diseases. It is mainly composed of terpene lactones (ginkgolide A and B) and flavone glycosides (eg quercetin and kaempferol). To better understand the cardiac electromechanical action of Ginkgo biloba extract in normal and diabetic states, this study was designed to examine the effect of ginkgolide B on cardiomyocyte contractile function under normal and high-glucose environments.

METHODS

Isolated adult rat ventricular myocytes were cultured for 6 h in a serum-free medium containing either normal (NG; 5.5 mmol/L) or high (HG; 25.5 mmol/L) glucose with or without ginkgolide B (0.5-2.0 microg/mL). Mechanical properties were evaluated using the IonOptix MyoCam system. Contractile properties analyzed included peak shortening (PS), maximal velocity of shortening/relengthening (+/-dl/dt), time-to-PS (TPS) and time-to-90% relengthening (TR90). Levels of essential Ca(2+) regulatory proteins sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA2a), phospholamban (PLB) and Na(+)-Ca(2+) exchanger (NCX) were assessed by Western blotting.

RESULTS

Ginkgolide B nullified HG-induced prolongation in TR90. However, ginkgolide B depressed PS, +/-dl/dt and shortened TPS in NG and HG cells. Ginkgolide B also prolonged TR90 in NG cells. Western blot analysis revealed that HG upregulated SERCA2a and downregulated PLB expression without affecting that of NCX. Ginkgolide B disrupted the NG-HG response pattern in SERCA2a and NCX without affecting that of PLB.

CONCLUSION

Ginkgolide B affects cardiomyocyte contractile function under NG or HG environments in a paradoxical manner, which may be attributed to uneven action on Ca(2+) regulatory proteins under NG and HG conditions.

Impaired cardiac contractile function in ventricular myocytes from leptin-deficient ob/ob obese mice

The level of the obese gene product leptin is often positively correlated with body weight, supporting the notion that hyperleptinemia contributes to obesity-associated cardiac dysfunction. However, a link between leptin levels and cardiac function has not been elucidated. This study was designed to examine the role of leptin deficiency (resulting from a point mutation of the leptin gene) in cardiomyocyte contractile function. Mechanical properties and intracellular Ca(2+) transients were evaluated in ventricular myocytes from lean control and leptin-deficient ob/ob obese mice at 12 weeks of age. Cardiac ultrastructure was evaluated using transmission electron microscopy. ob/ob mice were overtly obese, hyperinsulinemic, hypertriglycemic, hypoleptinemic and euglycemic. Ultrastructural examination revealed swelling and disorganization of cristae in mitochondria from ob/ob mouse ventricular tissues. Cardiomyocytes from ob/ob mice displayed reduced expression of the leptin receptor Ob-R, larger cross-sectional area, decreased peak shortening and maximal velocity of shortening/relengthening, and prolonged relengthening but not shortening duration compared with lean counterparts. Consistent with mechanical characteristics, myocytes from ob/ob mice displayed reduced intracellular Ca(2+) release upon electrical stimulus associated with a slowed intracellular Ca(2+) decay rate. Interestingly, the contractile aberrations seen in ob/ob myocytes were significantly improved by in vitro leptin incubation. Contractile dysfunction was not seen in age- and gender-matched high fat-induced obese mice. These results suggested that leptin deficiency contributes to cardiac contractile dysfunction characterized by both systolic and diastolic dysfunction, impaired intracellular Ca(2+) hemostasis and ultrastructural derangement in ventricular myocytes.

Gene expression profile of transgenic mouse kidney reveals pathogenesis of hepatitis B virus associated nephropathy

Hepatitis B virus (HBV)-associated nephritis has been reported worldwide. Immune complex deposition has been accepted as its pathogenesis, although the association between the presence of local HBV DNA and viral antigen and the development of nephritis remains controversial. To understand better the roles played by HBV protein expression in the kidney, the global gene expression profile was studied in the kidney tissue of a lineage of HBV transgenic mouse (#59). The mice expressed HBsAg in serum, and HBsAg and HBcAg in liver and kidney, but without virus replication. Full-length HBV genome (adr subtype, C genotype) isolated from a chronic HBV carrier was used to establish the transgenic mice #59. Similarly manipulated mice that did not express HBV viral antigens served as controls. Southern blotting, hybridization with HBV probe, and immuno-histochemical staining were used to study HBV gene expression. mRNA extracted from the kidney tissue was analyzed using Affymetrix microarrays. HBsAg and HBcAg were located mainly in the cytoplasm of tubular epithelium. Altogether 520 genes were "up-regulated" more than twofold and 76 genes "down-regulated" more than twofold in the kidney. The complement activation, blood coagulation, and acute-phase response genes were markedly "up-regulated". Compared to the controls, the level of serum C3 protein was decreased in #59 mice, while the level of C3 protein from kidney extract was increased. Results indicate that expression of HBsAg and HBcAg in tubular epithelial cells of the kidney per se can up-regulate complement-mediated inflammatory gene pathways, in addition to immune complex formation.

Quantification of quantum dots in HUVECs by confocal laser scanning microscopy

Quantum dots (QDs) are emerged as a new class of fluorescent probes for many biological and biomedical applications. Comparing with conventional fluorescent probes, they have substantial advantages such as bright fluorescence, narrow emission, broad excitation band and high photostability. However, little is known about the toxicity of nanoscale particles to biological systems. In this study, the interaction between 3-Mercaptopropionic acid capped CdTe QDs and HUVECs was studied quantitatively in vitro. Fluorescent intensity of QDs in cells was measured by confocal fluorescence laser scanning microscopy. The results showed that the amount of QDs absorbed by cells is dependent on concentration and incubation time. Further, the viability of cells incubated with QDs was investigated using MTT assay. Dramatic dose-dependent decrease in cellular viability was observed.

Metallothionein alleviates cardiac contractile dysfunction induced by insulin resistance: role of Akt phosphorylation, PTB1B, PPARgamma and c-Jun

AIMS/HYPOTHESIS

Insulin resistance is concomitant with metabolic syndrome, oxidative stress and cardiac contractile dysfunction. However, the causal relationship between oxidative stress and cardiac dysfunction is unknown. This study was designed to determine the impact of overexpression of the cardiac antioxidant metallothionein on cardiac dysfunction induced by insulin resistance in mice.

METHODS

Whole-body insulin resistance was generated in wild-type FVB and metallothionein transgenic mice by feeding them with sucrose for 12 weeks. Contractile and intracellular Ca(2+) properties were evaluated in ventricular myocytes using an IonOptix system. The contractile indices analysed included: peak shortening (PS), time to 90% PS (TPS(90)), time to 90% relengthening (TR(90)), half-width duration, maximal velocity of shortening (+dL/dt) and relengthening (-dL/dt), fura-fluorescence intensity change (DeltaFFI) and decay rate (tau).

RESULTS

The sucrose-fed mice displayed glucose intolerance, enhanced oxidative stress, hyperinsulinaemia, hypertriglyceridaemia and normal body weight. Compared with myocytes in starch-fed mice, those from sucrose-fed mice exhibited depressed PS, +dL/dt, -dL/dt, prolonged TR(90) and decay rate, and reduced DeltaFFI associated with normal TPS(90) and half-width duration. Western blot analysis revealed enhanced basal, but blunted insulin (15 mU/g)-stimulated Akt phosphorylation. It also showed elevated expression of insulin receptor beta, insulin receptor tyrosine phosphorylation, peroxisome proliferator-activated receptor gamma, protein tyrosine phosphatase 1B and phosphorylation of the transcription factor c-Jun, associated with a reduced fold increase of insulin-stimulated insulin receptor tyrosine phosphorylation in sucrose-fed mice. All western blot findings may be attenuated or ablated by metallothionein.

CONCLUSIONS/INTERPRETATION

These data indicate that oxidative stress may play an important role in cardiac contractile dysfunction associated with glucose intolerance and possibly related to alteration in insulin signalling at the receptor and post-receptor levels.

Angiotensin II promotes smooth muscle cell proliferation and migration through release of heparin-binding epidermal growth factor and activation of EGF-receptor pathway

Transactivation of EGF-receptor (EGFR) by G-protein coupled receptors (GPCRs) is emerging as an important pathway in cell proliferation, which plays a crucial role in the development of atherosclerotic lesion. Angiotensin II (Ang II) has been identified to have a major role in the formation of atherosclerotic lesions, although the underlying mechanisms remain largely unclear. We hypothesize that Ang II promotes the proliferation and migration of smooth muscle cells through the release of heparin-binding epidermal growth factor like growth factor (HB-EGF), transactivation of EGFR and activation of Akt and Erk 1/2, with matrix metalloproteases (MMPs) playing a dispensable role. Primary rat aortic smooth muscle cells were used in this study. Smooth muscle cells rendered quiescent by serum deprivation for 12 h were treated with Ang II (100 nM) in the presence of either GM6001 (20 microM), a specific inhibitor of MMPs or AG1478 (10 microM), an inhibitor of EGFR. The levels of phosphorylation of EGFR, Akt and Erk 1/2 were assessed in the cell lysates. Inhibition of MMPs by GM6001 significantly attenuated Ang II-stimulated phosphorylation of EGFR, suggesting that MMPs may be involved in the transactivation of EGFR by Ang II receptor. Furthermore Ang II-stimulated proliferation and migration of smooth muscle cells were significantly blunted by inhibiting MMPs and EGFR and applying HB-EGF neutralization antibody, indicating that MMPs, HB-EGF and EGFR activation is necessary for Ang-II stimulated migration and proliferation of smooth muscle cells. Our results suggest that inhibition of MMPs may represent one of the strategies to counter the mitogenic and motogenic effects of Ang II on smooth muscle cells and thereby prevent the formation and development of atherosclerotic lesions.

MUC1 oncoprotein is targeted to mitochondria by heregulin-induced activation of c-Src and the molecular chaperone HSP90

The MUC1 heterodimeric transmembrane glycoprotein is aberrantly overexpressed by most human carcinomas. The MUC1 C-terminal subunit localizes to mitochondria and blocks stress-induced activation of the intrinsic apoptotic pathway. How MUC1 is delivered to mitochondria is not known. The present studies demonstrate that MUC1 forms intracellular complexes with HSP70 and HSP90. We show that the MUC1 cytoplasmic domain binds directly to HSP70 in vitro. By contrast, binding of MUC1 to HSP90 in vitro is induced by c-Src-mediated phosphorylation of the MUC1 cytoplasmic domain. c-Src also increases binding of MUC1 to HSP90 in cells. In concert with these results, we show that heregulin (HRG), a ligand for ErbB receptors, activates c-Src and, in turn, stimulates binding of MUC1 to HSP90. We also show that inhibitors of c-Src or HSP90 block HRG-induced targeting of MUC1 to mitochondria and integration of MUC1 into the mitochondrial outer membrane. These findings indicate that MUC1 is delivered to mitochondria by a mechanism involving activation of the ErbB receptor-->c-Src pathway and transport by the molecular chaperone HSP70/HSP90 complex.