Recent studies suggest that exogenously administered CO is beneficial for the resolution of acute inflammation. In this study, we assessed the role of CO liberated from a systemically administered tricarbonyldichlororuthenium-(II)-dimer (CORM-2) on modulation of liver inflammation during sepsis. Polymicrobial sepsis in mice was induced by cecal ligation and perforation (CLP). CORM-2 (8 mg/kg iv) was administered immediately after CLP induction, and neutrophil [polymorphonuclear leukocyte (PMN)] tissue accumulation, activation of transcription factor, NF-kappaB, and changes in adhesion molecule ICAM-1 expression (inflammation-relevant markers) were assessed in murine liver 24 h later. In addition, the effects and potential mechanisms of CORM-2-released CO in modulation of vascular endothelial cell proinflammatory responses were assessed in vitro. To this end, human umbilical vein endothelial cells (HUVEC) were stimulated with LPS (1 microg/ml) in the presence or absence of CORM-2 (10-100 microM) and production of intracellular reactive oxygen species (ROS), (DHR123 oxidation) and NO (DAF-FM nitrosation) and subsequent activation of NF-kappaB were assessed 4 h later. In parallel, expression of ICAM-1 and inducible NO synthase (iNOS) proteins along with PMN adhesion to LPS-challenged HUVEC were also assessed. Induction of CLP resulted in increased PMN accumulation, ICAM-1 expression, and activation of NF-kappaB in the liver of septic mice. These effects were significantly attenuated by systemic administration of CORM-2. In in vitro experiments, CORM-2-released CO attenuated LPS-induced production of ROS and NO, activation of NF-kappaB, increase in ICAM-1 and iNOS protein expression and PMN adhesion to LPS-stimulated HUVEC. Taken together, these findings indicate that CO released from systemically administered CORM-2 provides anti-inflammatory effects by interfering with NF-kappaB activation and subsequent downregulation of proadhesive vascular endothelial cell phenotype in the liver of septic mice.

Storage of rat red blood cells for 28 days in citrate phosphate dextrose adenine-1 impaired their ability to improve tissue oxygenation when transfused into either control or septic rats placed into supply dependency of systemic VO2.

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Heme Oxygenase is the rate-limiting enzyme in the degradation of heme into carbon monoxide (CO), iron and bilirubin. To date, three heme oxygenase isozymes have been identified: HO-1, HO-2 and HO-3. While HO-1 is structurally different from its counterparts, HO-2 and HO-3 are very similar (90% homology), with HO-3 being a poor heme catalyst. Of the three isozymes, HO-1 is believed to be the only inducible form. Constitutively expressed HO-2 has been identified in several organs including kidney and vascular smooth muscle, with the most abundant sources (and activity) being in the liver, brain, spleen and testes. Within the normal liver, HO-2 is constitutively expressed within hepatocytes, Kupffer cells, endothelial cells and Ito cells. Until recently, products of the HO reaction were regarded as potentially toxic waste destined only for excretion. However, this view is changing as evidence suggests that HO activity plays an important protective role against cellular stress during inflammatory diseases. Biliverdin is reduced to bilirubin, which has been shown to possess potent antioxidative properties. CO, which is produced in equimolar concentrations to biliverdin and ferrous iron during heme oxidation by HO, may function as a second messenger stimulating soluble guanylate cyclase (sGC) and regulating vascular tone in combination with the free radical gas NO. CO may also possess anti-inflammatory properties such as the capacity to inhibit platelet aggregation, or the expression of pro-inflammatory cytokines. Recently, it has been shown that CO regulates bile formation and bile flow. We review the functional role of HO in liver and the potential application of HO-1 in therapeutic approaches to the treatment of inflammation.

Lung ischemia-reperfusion (I-R) is an important model of oxidant-mediated acute lung and vascular injury. Heme oxygenase-1 (HO-1) is a cytoprotective gene that is markedly induced by lung I-R injury. HO-1 mRNA is increased in mouse lung after 30 min of lung hilar clamping (ischemia) followed by 2-6 h of unclamping (reperfusion) compared with control mice. In a variety of vascular cell types, HO-1 mRNA is induced after 24 h of anoxia followed by 30 min-1 h of reoxygenation (A-R). Transfection studies reveal that the promoter and 5'-distal enhancer E1 are necessary and sufficient for increased HO-1 gene transcription after A-R. Immunoblotting studies show all three subfamilies of MAPKs (ERK, JNK, and p38) are activated by 15 min of reperfusion. We also demonstrate that HO-1 gene transcription after A-R involves ERK, JNK, and p38 MAPK pathways. Together, our data show that I-R not only induces HO-1 gene expression in mouse lungs and vascular cells but that gene transcription occurs via the promoter and E1 enhancer and involves upstream MAPK pathways.

The aim of this study was to confirm that microvascular perfusion was abnormal during the early phases of normotensive sepsis and to determine whether these changes were due to the development of tissue edema. Skeletal muscle red blood cell (RBC) flow was studied in rats made septic by cecal ligation and perforation (CLP). After anesthesia with halothane, arterial and venous cannulae were inserted and, in the treatment group, a CLP performed. At 6, 24, and 48 h after entry into the study, the incidence of microcirculatory absence of flow in the extensor digitorum longus muscle (EDL) was examined with intravital microscopy. The number of capillaries containing RBCs were counted over a 60-s interval, and the flow status of each capillary was recorded. A significant increase in the number of stopped-flow capillaries was observed in the CLP group (p < 0.01) as compared with time-matched controls. In both groups the number of capillaries with stopped flow was greater than in naive animals. The severity of absence of flow was negatively correlated with the systemic hemoglobin concentration. These changes were not associated with an increase in tissue wet/dry weight ratio or albumin flux. This study shows that sepsis was associated with increased RBC flow heterogeneity. These changes, which occur within 24 h of the septic insult, are a persistent feature of the evolving septic process in the absence of tissue edema. These observations support the view that extrinsic compression of the microcirculation by tissue edema is not the primary cause of alterations in microcirculatory flow in sepsis.

It is known that a substantial amount of capillary tortuosity is found in shortened muscles. However, the increased capillary length and surface area contributed by tortuosity and branching are seldom taken into account when capillarity is estimated and/or blood-tissue exchange is modeled in muscles. In this paper, we sought morphometric estimates of capillarity in transverse sections that incorporated data on capillary geometry. We derived equations to estimate capillary perimeter per fiber perimeter (i.e., capillary-to-fiber perimeter ratio) in transverse sections. We show how capillary-to-fiber perimeter ratio is related to capillary surface per fiber surface, i.e., to the amount of capillary surface available for exchange per muscle fiber surface area, and how it can be obtained by morphometry. Because capillary tortuosity and fiber perimeter are both a function of sarcomere length, the degree of extension or shortening of muscle samples obviously needs to be taken into account when capillary-to-fiber perimeter ratio is compared between muscles and/or samples. Using data currently available on capillary length and diameter with fiber shortening and extension, we show that it is a feature of capillary-to-fiber perimeter ratio to change relatively little with sarcomere length. As sarcomere length decreases from 2.80 to 1.58 microns in perfusion-fixed hindlimb muscles of rats, capillary and fiber perimeters in transverse sections increase substantially, whereas the ratio between the two variables, capillary-to-fiber perimeter ratio, changes only less than or equal to 10-15%.(ABSTRACT TRUNCATED AT 250 WORDS)