title: [Cardiac metallothionein overexpression improves cardiac contractile function and attenuates oxidative stress in lipopolysaccharide-treated mice].
abstract: OBJECTIVE
  This study was designed to examine the impact of the antioxidant metallothionein (MT) on cardiac contractile, intracellular Ca(2+) function and oxidative stress in lipopolysaccharide (LPS)-treated mice.
  
  
  METHODS
  Weight and age matched adult male FVB and cardiac-specific MT-overexpressing transgenic mice were injected intraperitoneally with 4 mg/kg Escherichia Coli LPS dissolved in sterile saline or an equivalent volume of pathogen-free saline (control groups). Six hours following LPS or saline injection, cardiac geometry and function were evaluated in anesthetized mice using the 2-D guided M-mode echocardiography. Mechanical and intracellular Ca(2+) properties were examined in hearts. Cell shortening and relengthening were assessed using the following indices: peak shortening (PS)-indicative of the amplitude a cell can shorten during contraction; maximal velocities of cell shortening and relengthening (± dl/dt)-indicative of peak ventricular contractility; time-to-PS (TPS)-indicative of systolic duration; time-to-90% relengthening (TR(90))-indicative of diastolic duration (90% rather 100% relengthening was used to avoid noisy signal at baseline concentration). The 360 nm excitation scan was repeated at the end of the protocol and qualitative changes in intracellular Ca(2+) concentration were inferred from the ratio of fura-2 fluorescence intensity (FFI) at two wavelengths (360/380). Fluorescence decay time was measured as an indicator of the intracellular Ca(2+) clearing rate. Glutathione/glutathione disulfide ratio and ROS generation were detected as the markers of oxidative stress.
  
  
  RESULTS
  Heart rate was increased while EF was reduced in LPS-FVB mice and heart rate was reduced and EF increased in MT-LPS transgenic mice [(528 ± 72) beats/min vs (557 ± 69) beats/min, (66 ± 14)% vs (42 ± 10)%, P < 0.05]. Cardiomyocytes from the LPS treated FVB mice displayed significantly reduced peak shortening (PS) and maximal velocity of shortening/relengthening (±dl/dt) associated with prolonged time-to-90% relengthening (TR(90)), these effects were attenuated in cardiomyocytes from the MT-LPS mice [PS(5 ± 1.1)% vs (7.2 ± 0.8)%, dl/dt(160 ± 15) µm/s vs (212 ± 36) µm/s, -dl/dt (175 ± 32) µm/s vs (208 ± 29) µm/s, TR(90) (0.24 ± 0.03)s vs (0.19 ± 0.02)s, P < 0.05]. LPS treated mice showed significantly reduced peak intracellular Ca(2+) and electrically-stimulated rise in intracellular Ca(2+) as well as prolonged intracellular Ca(2+) decay rate without affecting the basal intracellular Ca(2+) levels, again, these effects were significantly attenuated in MT-LPS transgenic mice. Metallothionein overexpression also ablated oxidative stress [reduced ROS generation and increased glutathione/glutathione disulfide ratio, ROS (0.35 ± 0.08) A/µg protein vs (0.24 ± 0.03) A/µg protein]. GSH/GSSG 2.1 ± 0.2 vs 2.6 ± 0.4, P < 0.05.
  
  
  CONCLUSIONS
  MT overexpression improved cardiac function and ablated oxidative stress in LPS treated mice.
authors.affiliation: Department of Cardiology, Provincial Hospital Affiliated to Shandong University, Jinan 250021, China. pengalfie@yahoo.com.cn
authors.forename: Peng
authors.initials: P
authors.lastname: Zhao
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Xi
authors.initials: X
authors.lastname: Chu
authors.forename: Hai-tao
authors.initials: HT
authors.lastname: Yuan
authors.forename: Lian-qun
authors.initials: LQ
authors.lastname: Cui
authors.forename: Xing-lei
authors.initials: XL
authors.lastname: Zhu
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D008070:Lipopolysaccharides; D008297:Male; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000502:physiology; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism; D018805:Sepsis / Q000378:metabolism / Q000503:physiopathology
chemical_list: D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D008668:Metallothionein; D002118:Calcium