Mechanical ventilation with high tidal volumes attenuates myocardial dysfunction by decreasing cardiac edema in a rat model of LPS-induced peritonitis

H2 Protects Against Lipopolysaccharide-Induced Cardiac Dysfunction via Blocking TLR4-Mediated Cytokines Expression

Background and Purpose: Septic cardiomyopathy, which is one of the features of multi-organ dysfunction in sepsis, is characterized by ventricular dilatation, reduced ventricular contractility, and reduction in ejection fraction and, if severe, can lead to death. To date, there is no specific therapy that exists, and its treatment represents a large unmet clinical need. Herein, we investigated the effects and underlying anti-inflammatory mechanisms of hydrogen gas in the setting of lipopolysaccharide (LPS)-induced cardiomyocytes injury.

Experimental Approach: Hydrogen gas was intraperitoneally injected to mice in LPS plus hydrogen group and hydrogen group for 4 days. On fourth, LPS was given by intraperitoneal injection to mice in LPS group and to mice in LPS plus hydrogen group. In addition, H9c2 cardiomyocytes were treated with hydrogen-rich medium for 30 min before LPS. The transthoracic echocardiography was performed at 6 h post‐LPS to assess left ventricular end-systolic diameter (LVESD), left ventricular end-diastolic diameter (LVEDD), left ventricular ejection fraction (EF%), fractional shortening (FS%), left ventricular mass average weight (LV mass AW), and LV mass AW (Corrected). The histological and morphological analyses of left ventricular were performed by hematoxylin and eosin (H&E) staining and Masson’s trichrome staining. The mRNA levels of ANP and BNP were examined by PCR in vitro. The expression of cytokines were assayed by Enzyme Linked Immunosorbent Assay (ELISA) and PCR. Moreover, Western blotting was performed to examine the expression of TLR4, the activation of ERK1/2, p38, JNK, and the expression of NF-κB in nucleus after 6 h of LPS challenge in vivo and in vitro.

Key Results: LPS induced cardiac dysfunction; hydrogen therapy improved cardiac function after LPS challenge. Furthermore, pretreatment with hydrogen resulted in cardioprotection during septic cardiomyopathy via inhibiting the expression of pro-inflammatory cytokines TNFα, IL-1β, and IL-18; suppressing the phosphorylation of ERK1/2, p38, and JNK; and reducing the nuclear translocation of NF-κB and the expression of TLR4 by LPS.

Conclusion and Implications: Hydrogen therapy prevents LPS-induced cardiac dysfunction in part via downregulation of TLR4-mediated pro-inflammatory cytokines expression.

Anti-exudation effects of sodium ferulate and oxymatrine combination via modulation of aquaporin 1

The present study aimed to investigate the anti-exudative effects of sodium ferulate combined with oxymatrine in a mouse model of acetic acid-induced peritonitis. Furthermore, the underlying mechanisms were explored by determining the effects of these drugs on the volume and aquaporin 1 (AQP1) expression in vascular endothelial cells on omentum majus and human umbilical vein endothelial cells (HUVEC). Treatment with sodium ferulate combined with oxymatrine was shown to significantly inhibit acetic acid-induced vascular permeability in the peritonitis model mice and furthermore to significantly decrease the optical density of Evans blue, the leukocyte number and the levels of interleukin-6, C-reactive protein and interferon-γ in peritoneal lavage fluid. Pathological analysis of the omentum majus revealed that sodium ferulate and oxymatrine combination treatment significantly alleviated vascular endothelial cell edema and capillary loss. In vitro, flow cytometry revealed that the volume of HUVECs was significantly reduced in the drug treatment groups, as reflected in the forward scatter value. The optical density of AQP1 on the membrane of the vascular endothelial cells on omentum majus and HUVECs were significantly increased in the drug treatment groups compared with the model group. These results indicated that sodium ferulate and oxymatrine combination treatment possessed prominent anti-exudative effects and that the underlying mechanisms are likely to include the improvement of vascular endothelial cellular edema, possibly by upregulation of AQP1 expression on their membrane, which requires further exploration.

Low tidal volume ventilation ameliorates left ventricular dysfunction in mechanically ventilated rats following LPS-induced lung injury

Background

High tidal volume ventilation has shown to cause ventilator-induced lung injury (VILI), possibly contributing to concomitant extrapulmonary organ dysfunction. The present study examined whether left ventricular (LV) function is dependent on tidal volume size and whether this effect is augmented during lipopolysaccharide(LPS)-induced lung injury.

Methods

Twenty male Wistar rats were sedated, paralyzed and then randomized in four groups receiving mechanical ventilation with tidal volumes of 6 ml/kg or 19 ml/kg with or without intrapulmonary administration of LPS. A conductance catheter was placed in the left ventricle to generate pressure-volume loops, which were also obtained within a few seconds of vena cava occlusion to obtain relatively load-independent LV systolic and diastolic function parameters. The end-systolic elastance / effective arterial elastance (Ees/Ea) ratio was used as the primary parameter of LV systolic function with the end-diastolic elastance (Eed) as primary LV diastolic function.

Results

Ees/Ea decreased over time in rats receiving LPS (p = 0.045) and high tidal volume ventilation (p = 0.007), with a lower Ees/Ea in the rats with high tidal volume ventilation plus LPS compared to the other groups (p < 0.001). Eed increased over time in all groups except for the rats receiving low tidal volume ventilation without LPS (p = 0.223). A significant interaction (p < 0.001) was found between tidal ventilation and LPS for Ees/Ea and Eed, and all rats receiving high tidal volume ventilation plus LPS died before the end of the experiment.

Conclusions

Low tidal volume ventilation ameliorated LV systolic and diastolic dysfunction while preventing death following LPS-induced lung injury in mechanically ventilated rats. Our data advocates the use of low tidal volumes, not only to avoid VILI, but to avert ventilator-induced myocardial dysfunction as well.

Pulse pressure variation does not reflect stroke volume variation in mechanically ventilated rats with lipopolysaccharide-induced pneumonia

1. The present study examined the relationship between centrally measured stroke volume variation (SVV) and peripherally derived pulse pressure variation (PPV) in the setting of increased total arterial compliance (CA rt ). 2. Ten male Wistar rats were anaesthetized, paralysed and mechanically ventilated before being randomized to receive intrapulmonary lipopolysaccharide (LPS) or no LPS. Pulse pressure (PP) was derived from the left carotid artery, whereas stroke volume (SV) was measured directly in the left ventricle. Values of SVV and PPV were calculated over three breaths. Balloon inflation of a catheter positioned in the inferior vena cava was used, for a maximum of 30 s, to decrease preload while the SVV and PPV measurements were repeated. Values of CA rt were calculated as SV/PP. 3. Intrapulmonary LPS increased CA rt and SV. Values of SVV and PPV increased in both LPS-treated and untreated rats during balloon inflation. There was a correlation between SVV and PPV in untreated rats before (r = 0.55; P = 0.005) and during (r = 0.69; P < 0.001) occlusion of the vena cava. There was no such correlation in LPS-treated rats either before (r = -0.08; P = 0.70) or during (r = 0.36; P = 0.08) vena cava occlusion. 4. In conclusion, under normovolaemic and hypovolaemic conditions, PPV does not reflect SVV during an increase in CA rt following LPS-induced pneumonia in mechanically ventilated rats. Our data caution against their interchangeability in human sepsis.

Estrogen protects cardiomyocytes against lipopolysaccharide by inhibiting autophagy

Autophagy has a significant role in myocardial injury induced by lipopolysaccharide (LPS). Estrogen (E2) has been demonstrated to protect cardiomyocytes against apoptosis; however, it remains to be determined whether it exhibits anti‑autophagic effects. The aim of the present study was to investigate whether estrogen-regulated autophagy attenuates cardiomyocyte injury induced by LPS. The cardiomyocytes of neonatal rats were randomized to the control (Con), LPS and estrogen + LPS groups. The LPS group was treated with 1 µg LPS for 24 h and the estrogen + LPS group was treated with 10‑8 M estrogen 30 min prior to treatment with LPS. Cardiomyocyte autophagy was quantitated by investigating the mRNA and protein level of autophagy‑related genes (Atgs). The mRNA expression of Atg5 and Beclin1 were measured by quantitative polymerase chain reaction and the microtubule‑associated protein light chain 3 (LC3) protein expression was measured by western blot analysis. To demonstrate the cardiomyocyte protection of estrogen, cell vitality and serum lactate dehydrogenase (LDH) levels were measured following LPS treatment. It was identified that LPS induced cardiomyocyte injury, together with the upregulation of Atg5, Beclin1 mRNA and LC3‑II protein. Furthermore, estrogen attenuated the effect of LPS. The present study provides evidence that estrogen has a myocardial protective role against injury induced by LPS by regulating autophagy.

Effect of hydrogen-rich water on acute peritonitis of rat models

OBJECTIVE

To study the effect of hydrogen-rich water (HRW) on acute peritonitis with three different rat models.

METHODS

Acute peritonitis was induced by three methods including intraperitoneal injection of lipopolysaccharide (LPS), rats' feces or cecal ligation and puncture (CLP) operation. For each model, male Sprague Dawley rats were used and distributed into saline control group, HRW control group, saline plus model group, and HRW plus model group. Saline or HRW (3 ml per rat) was orally administered by gavage for 7 days beforehand and 3 days after modeling. The efficacy was tested by detecting concentrations of white blood cells (WBCs), plasma endotoxin, interleukin (IL)-6 and tumor necrosis factor (TNF)-α. The activities of malondialdehyde (MDA), myeloperoxidase (MPO) and glutathione (GSH) in visceral peritoneum tissues were also evaluated. Meanwhile, histopathology examination of visceral peritoneum was performed using hematoxylin and eosin staining. The expression and location of nuclear factor kappaB (NF-κB) in the visceral peritoneum were detected by immunohistochemistry.

RESULTS

Three models showed the same result that hydrogen-rich water had an efficient protective effect on acute peritonitis. HRW could significantly lower the levels of WBCs, plasma endotoxin and cytokines, enhance GSH activity and reduce MPO and MDA activities in the peritoneum tissue when compared with that of groups with only saline treated. Simultaneously, we found that HRW could also decrease the NF-κB expression in the peritoneum tissues.

CONCLUSION

Hydrogen-rich water could alleviate the severity of acute peritonitis, and it might perform this function by its anti-inflammation, anti-oxidation and anti-bacterial effects and reducing NF-κB expression in the peritoneum tissues.

NOX2 in lung inflammation: quantum dot based in situ imaging of NOX2-mediated expression of vascular cell adhesion molecule-1

Quantum dot (QD) imaging is a powerful tool for studying signaling pathways as they occur. Here we employ this tool to study adhesion molecule expression with lung inflammation in vivo. A key event in pulmonary inflammation is the regulation of vascular endothelial cell adhesion molecule-1 (VCAM), which drives activated immune cell adherence. The induction of VCAM expression is known to be associated with reactive oxygen species (ROS) production, but the exact mechanism or the cellular source of ROS that regulates VCAM in inflamed lungs is not known. NADPH oxidase 2 (NOX2) has been reported to be a major source of ROS with pulmonary inflammation. NOX2 is expressed by both endothelial and immune cells. Here we use VCAM-targeted QDs in a mouse model to show that NOX2, specifically endothelial NOX2, induces VCAM expression with lung inflammation in vivo.

Effects of incrementally increasing tidal volume on the cross-sectional area of the right internal jugular vein

Background

Different tidal volume (TV) settings during mechanical ventilation alter intrathoracic blood volume, and these changes could alter central venous pressure and the cross sectional area (CSA) of the right internal jugular vein (RIJV). The aim of this study was to determine the optimal TV for maximizing the CSA of the RIJV in the supine and Trendelenburg positions in anesthetized patients.

Methods

Forty patients were randomly allocated to a supine group (Group S, n = 20) or a Trendelenburg group (Group T, n = 20) by computer generated randomization. RIJV CSAs were measured repeatedly after increasing the inspiratory volume in 1 ml/kg increments from a TV of 8 ml/kg to 14 ml/kg using ultrasound images.

Results

Peak inspiratory pressure increased significantly on increasing TV from 11 ml/kg to 14 ml/kg and between baseline (TV 8 ml/kg) and 11 ml/kg in both groups (P < 0.05). RIJV CSA was not increased versus baseline even after TV changes in either group and no intergroup difference was found.

Conclusions

TV increases do not increase the CSA of the RIJV within the TV range 8 to 14 ml/kg in the supine or 10° Trendelenburg position.