metallothionein and Sepsis

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.. 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.. 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.. MT overexpression improved cardiac function and ablated oxidative stress in LPS treated mice.

Topics: Animals; Calcium; Lipopolysaccharides; Male; Metallothionein; Mice; Mice, Inbred Strains; Mice, Transgenic; Myocardial Contraction; Myocytes, Cardiac; Oxidative Stress; Reactive Oxygen Species; Sepsis

Sepsis is characterized by systematic inflammation where oxidative damage plays a key role in organ failure. This study was designed to examine the impact of the antioxidant metallothionein (MT) on lipopolysaccharide (LPS)-induced cardiac contractile and intracellular Ca(2+) dysfunction, oxidative stress, endoplasmic reticulum (ER) stress and autophagy. Mechanical and intracellular Ca(2+) properties were examined in hearts from FVB and cardiac-specific MT overexpression mice treated with LPS. Oxidative stress, activation of mitogen-activated protein kinase pathways (ERK, JNK and p38), ER stress, autophagy and inflammatory markers iNOS and TNFalpha were evaluated. Our data revealed enlarged end systolic diameter, decreased fractional shortening, myocyte peak shortening and maximal velocity of shortening/relengthening as well as prolonged duration of relengthening in LPS-treated FVB mice associated with reduced intracellular Ca(2+) release and decay. LPS treatment promoted oxidative stress (reduced glutathione/glutathione disulfide ratio and ROS generation). Western blot analysis revealed greater iNOS and TNFalpha, activation of ERK, JNK and p38, upregulation of ER stress markers GRP78, Gadd153, PERK and IRE1alpha, as well as the autophagy markers Beclin-1, LCB3 and Atg7 in LPS-treated mouse hearts without any change in total ERK, JNK and p38. Interestingly, these LPS-induced changes in echocardiographic, cardiomyocyte mechanical and intracellular Ca(2+) properties, ROS, stress signaling and ER stress (but not autophagy, iNOS and TNFalpha) were ablated by MT. Antioxidant N-acetylcysteine and the ER stress inhibitor tauroursodeoxycholic acid reversed LPS-elicited depression in cardiomyocyte contractile function. LPS activated AMPK and its downstream signaling ACC in conjunction with an elevated AMP/ATP ratio, which was unaffected by MT. Taken together, our data favor a beneficial effect of MT in the management of cardiac dysfunction in sepsis.

Topics: Adenylate Kinase; Animals; Autophagy; Biomechanical Phenomena; Calcium; Endoplasmic Reticulum; Endoplasmic Reticulum Chaperone BiP; Enzyme Activation; Feeding Behavior; Inflammation; Intracellular Membranes; Intracellular Space; Lethal Dose 50; Lipopolysaccharides; Lysosomes; Metallothionein; Mice; Myocardial Contraction; Myocardium; Myocytes, Cardiac; Oxidative Stress; Reactive Oxygen Species; Sepsis; Signal Transduction

The response to injury is dependent on several factors, including the type and extent of the injury, genetics, and the environment. In the present study, the genetic contribution to sepsis was evaluated in a mouse model. Sepsis was induced in two inbred mouse strains, C57BL/6J (B6) and A/J, by cecal ligation and single puncture (CLP). Frequency of mortality was significantly higher in B6 than A/J mice from 36 to 132 h after CLP. Plasma TNF-alpha, IL-1beta, and IL-6 levels were similar in both strains after CLP. IL-10 plasma levels were significantly higher in B6 mice as opposed to A/J mice after 24 h of CLP. Similarly, hepatic myeloperoxidase activity, an index of polymorphonuclear leukocytes, was elevated in B6 mice as compared with A/J mice after 24 h of CLP. On the contrary, metallothionein mRNA levels were higher in A/J mice compared with B6 mice. Finally, leptin levels were also higher in A/J than B6 mice within 19 h of CLP. This study demonstrates a genetic contribution in the response to sepsis.

Topics: Animals; Disease Models, Animal; Fibrinogen; Interleukin-1; Interleukin-10; Interleukin-6; Leptin; Liver; Male; Metallothionein; Mice; Mice, Inbred C57BL; Mice, Inbred Strains; Peroxidase; Sepsis; Species Specificity; Survival Rate; Tumor Necrosis Factor-alpha