Ablation of matrix metalloproteinase-9 increases severity of viral myocarditis in mice.

BACKGROUND: Coxsackievirus B3 (CVB3) causes human myocarditis, which can result in cardiac damage, maladaptive remodeling, and heart failure. Matrix metalloproteinases (MMP)-8 and -9 have been identified in virus-infected myocardium, but their particular roles and underlying mechanisms of effect are unknown. For the first time, we examine the severity of CVB3-induced myocarditis in MMP-8-and MMP-9-deficient mice. METHODS AND RESULTS: CVB3-infected MMP-8 and MMP-9 knockout (KO) mice and corresponding wild-type (WT) mice were euthanized and harvested at 9 days after infection. Expression of MMP-2, -8, -12, and -13 and tissue inhibitors of MMPs was assessed by zymography or immunoblotting on harvested hearts, and in situ hybridization was performed to detect active infection. Infected MMP-9 KO mice had greater myocardial injury and foci of infection than WT mice despite similar pancreatic infection. Increased fibrosis (10.6+/-2.7% versus 7.1+/-2.6%, P=0.04), viral titer, as well as decreased cardiac output, were evident in MMP-9 KO compared with WT mice as assessed by picrosirius red staining, plaque assay, and echocardiography, respectively. Immune infiltration was also greatly increased in MMP-9 KO compared with WT mice (15.2+/-12.6% versus 2.0+/-3.0%, P<0.002). Myocardial interferon-beta1, interferon-gamma, interleukin-6, interleukin-10, and macrophage inflammatory protein-1alpha expression was elevated in MMP-9 KO mice as measured by quantitative real-time polymerase chain reaction and ELISA. In contrast, MMP-8 KO mice had the same degree of cardiac injury, fibrosis, and viral infection as their WT counterparts. CONCLUSIONS: During acute CVB3 infection, MMP-9 appears necessary to halt virus propagation in the heart, promote proper immune infiltration and remodeling, and preserve cardiac output.

A comparison of biologically variable ventilation to recruitment manoeuvres in a porcine model of acute lung injury.

BACKGROUND: Biologically variable ventilation (return of physiological variability in rate and tidal volume using a computer-controller) was compared to control mode ventilation with and without a recruitment manoeuvre - 40 cm H2O for 40 sec performed hourly; in a porcine oleic acid acute lung injury model. METHODS: We compared gas exchange, respiratory mechanics, and measured bronchoalveolar fluid for inflammatory cytokines, cell counts and surfactant function. Lung injury was scored by light microscopy. Pigs received mechanical ventilation (FIO2 = 0.3; PEEP 5 cm H2O) in control mode until PaO2 decreased to 60 mm Hg with oleic acid infusion (PaO2/FIO2 <200 mm Hg). Additional PEEP to 10 cm H2O was added after injury. Animals were randomized to one of the 3 modes of ventilation and followed for 5 hr after injury. RESULTS: PaO2 and respiratory system compliance was significantly greater with biologically variable ventilation compared to the other 2 groups. Mean and mean peak airway pressures were also lower. There were no differences in cell counts in bronchoalveolar fluid by flow cytometry, or interleukin-8 and -10 levels between groups. Lung injury scoring revealed no difference between groups in the regions examined. No differences in surfactant function were seen between groups by capillary surfactometry. CONCLUSIONS: In this porcine model of acute lung injury, various indices to measure injury or inflammation did not differ between the 3 approaches to ventilation. However, when using a low tidal volume strategy with moderate levels of PEEP, sustained improvements in arterial oxygen tension and respiratory system compliance were only seen with BVV when compared to CMV or CMV with a recruitment manoeuvre.

Physiological noise versus white noise to drive a variable ventilator in a porcine model of lung injury.

PURPOSE: Variable ventilation is superior to control mode ventilation in a number of circumstances. The nature of the breathing file used to deliver the variable rate and tidal volume has not been formally examined. METHODS: We compared two different noise files in a randomized prospective trial of variable ventilation. Pigs were anesthetized, intubated, and mechanically ventilated. Oleic acid was infused to introduce lung injury. The animals were ventilated at a tidal volume of 7 mL x kg(-1), in variable mode, with either physiologically-derived noise (variability file - 1,587 breath intervals-obtained from a spontaneously breathing volunteer; n = 10) or a variability file of identical length derived from computer- generated white noise (n = 10). RESULTS: The physiologically-derived noise had a power law alpha-exponent of -0.27 and a Hölder exponent of -0.38, indicative of auto-correlated noise. The computer-generated noise had an alpha-exponent of -0.52 and a Hölder exponent of -0.49, indicative of white noise. Both files showed multifractal characteristics. There were no differences between groups, at any time period, for PaO2, PaCO2, and static or dynamic respiratory system compliance. No differences were observed between groups for wet:dry lung weight ratios or for interleukin-8 in bronchoalveolar lavage fluid. CONCLUSION: This study demonstrates that the nature of the variability files, chosen to drive the variable ventilator, had no effect on indices of gas exchange or respiratory mechanics in this model. A considerable overlap of the multifractal files existed. The potential to drive a variable ventilator using algorithm-derived files with multifractal characteristics, thereby eliminating the requirement to use physiologically-derived signals, is discussed.

Biologically variable ventilation improves gas exchange and respiratory mechanics in a model of severe bronchospasm.

OBJECTIVE: Mechanical ventilation can be lifesaving for status asthmaticus, but how best to accomplish mechanical ventilation is unclear. Biologically variable ventilation (mechanical ventilation that emulates healthy variation) and conventional control mode ventilation (monotonously regular) were compared in an animal model of bronchospasm to determine which approach yields better gas exchange and respiratory mechanics. DESIGN: A randomized prospective trial of biologically variable ventilation vs. control mode ventilation in swine. SETTING: University research laboratory. SUBJECTS: Eighteen farm-raised pigs. INTERVENTIONS: Methacholine was administered as a nebulized aerosol to initiate bronchospasm, defined as doubling of peak inspiratory pressure and respiratory system resistance, and then randomized (n = 9 each group) to either continue control mode ventilation or switch to biologically variable ventilation at the same minute ventilation. Over the next 4 hrs, hemodynamics, blood gases, respiratory mechanics, and carbon dioxide expirograms were recorded hourly. At end-experiment, tracheobronchial lavage was undertaken to determine interleukin-6 and -10 concentrations. MEASUREMENTS AND MAIN RESULTS: Measurements of physiologic variables and inflammatory cytokines showed that biologically variable ventilation significantly improved gas exchange, with greater arterial oxygen tensions (p = .006; group x time interaction), lower arterial carbon dioxide tensions (p = .0003; group effect), lower peak inspiratory pressures (p = .0001; group x time), greater static compliance (p = .0001; group x time), greater dynamic compliance (p = .0001; group x time), and lower total respiratory system resistance (p = .028; group x time), compared with conventional ventilation. The appearance of inflammatory cytokines in bronchoalveolar lavage fluid (interleukin-6 and -10) was not affected by mode of ventilation. CONCLUSIONS: In this experimental model, biologically variable ventilation was superior to control mode ventilation in terms of gas exchange and respiratory mechanics during severe bronchospasm.

Biologically variable bypass reduces enzymuria after deep hypothermic circulatory arrest.

BACKGROUND: Renal injury is common after open-heart surgery. Cardiopulmonary bypass contributes to the problem. We compared conventional nonpulsatile perfusion (NP) to biologically variable perfusion (BVP), which uses a computer controller to restore physiological beat-to-beat variability to roller pump flow. We hypothesized BVP would decrease renal injury after deep hypothermic circulatory arrest. METHODS: Pigs were randomly assigned to either BVP (n = 9) or NP (n = 9), cooled, arrested at 18 degrees C (1 hour), reperfused, and rewarmed and maintained normothermic (3 hours). Additional pigs had NP for a similar time as above, but without circulatory arrest (n = 3), or were sham-treated without bypass (n = 3). Hemodynamics, acid-base status, temperature, and urine volumes were measured. Urinary enzyme markers of tubular injury were compared post-hoc for gamma glutamyl transpeptidase, alkaline phosphatase, and glutathione S-transferase and by urine proteomics using mass spectrometry. RESULTS: Urine output at 1 hour after arrest was 250 +/- 129 mL with BVP versus 114 +/- 66 mL with NP (p < 0.02). All three renal enzyme markers were higher with NP after arrest compared with BVP. In animals on bypass without arrest or those sham-treated, no elevations were seen in renal enzymes. Urine proteomics revealed abnormal proteins, persisting longer with NP. Biologically variable perfusion decreased cooling to 21.0 +/- 9.0 minutes versus 31.7 +/- 7.5 minutes (p < 0.002), and decreased rewarming to 22.1 +/- 3.9 minutes versus 31.2 +/- 5.1 minutes (p < 0.002). CONCLUSIONS: Biologically variable perfusion improved urine output, decreased enzymuria, and attenuated mass spectrometry urine protein signal with more rapid temperature changes. This strategy could potentially shorten bypass duration and may decrease renal tubular injury with deep hypothermic circulatory arrest.

ABCA1 mRNA and protein distribution patterns predict multiple different roles and levels of regulation.

Mutations in ABCA1 cause the allelic disorders familial hypolipoproteinemia and Tangier Disease. To identify where ABCA1 was likely to have a functional role, we determined the cellular and tissue-specific patterns of murine ABCA1 expression. RT-PCR and Western blot analysis on dissected murine tissues demonstrated broad expression of ABCA1 mRNA and protein in many tissues with prominent protein expression in liver, testis, and adrenal tissue. In situ hybridization and immunohistochemistry experiments demonstrated specific patterns of ABCA1 expression at the cellular level, with hepatocytes, the epithelial lining of the digestive system and bladder, the proximal convoluted tubule of the kidney, and Purkinje and cortical pyramidal neurons containing abundant ABCA1 protein. Significant discordance between relative mRNA and protein expression patterns suggests the possibility of post-transcriptional regulation of ABCA1 expression in selected cells or tissues. We also show that ABCA1 protein levels are up-regulated specifically in the liver after exposure to an atherogenic diet for 7 days, supporting a major role for the liver in dietary modulation of HDL-C levels. Our observations show that ABCA1 is expressed in a pattern consistent with its role in HDL-C metabolism. Additionally, ABCA1 may have important functional roles in other cell types independent of HDL-C regulation.