Complement inhibition prevents gut ischemia and endothelial cell dysfunction after hemorrhage/resuscitation

Identification and analysis of differential miRNA-mRNA interactions in coronary heart disease: an experimental screening approach

Objective

This aim of this study is to screen the differential molecules of kidney deficiency and blood stasis (KDBS) syndrome in coronary heart disease by high-throughput sequencing. In addition, the study aims to verify the alterations in the expression levels of miR-4685-3p and its regulated downstream, namely, C1QC, C4, and C5, using quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA), and to determine whether the complement and coagulation cascade pathway is the specific pathogenic pathway.

Methods

Patients diagnosed with unstable angina pectoris with KDBS syndrome, patients with non-kidney deficiency blood stasis (NKDBS) syndrome, and a Normal group were recruited. The clinical symptoms of each group were further analyzed. Illumina's NextSeq 2000 sequencing platform and FastQC software were used for RNA sequencing and quality control. DESeq software was used for differential gene expression (DGE) analysis. qPCR and ELISA verification were performed on DGE analysis.

Results

The DGE profiles of 77 miRNA and 331 mRNA were selected. The GO enrichment analysis comprised 43 biological processes, 49 cell components, and 42 molecular functions. The KEGG enrichment results included 40 KEGG pathways. The PCR results showed that, compared with the Normal group, the miR-4685-3p levels decreased in the CHD_KDBS group (P = 0.001), and were found to be lower than those observed in the CHD_NKDBS group. The downstream mRNA C1 regulated by miR-4685-3p showed an increasing trend in the CHD_KDBS group, which was higher than that in the Normal group (P = 0.0019). The mRNA C4 and C5 in the CHD_KDBS group showed an upward trend, but the difference was not statistically significant. ELISA was utilized for the detection of proteins associated with the complement and coagulation cascade pathway. It was found that the expression level of C1 was significantly upregulated in the CHD_KDBS group compared with the Normal group (P < 0.0001), which was seen to be higher than that in the CHD_NKDBS group (P < 0.0001). The expression levels of C4 and C5 in the CHD_KDBS group were significantly lower than the Normal group, and were lower than that in the CHD_NKDBS group (P < 0.0001).

Conclusion

The occurrence of CHD_KDBS might be related to the activation of the complement and coagulation cascade pathway, which is demonstrated by the observed decrease in miR-4685-3p and the subsequent upregulation of its downstream C1QC. In addition, the expression levels of complement C4 and C5 were found to be decreased, which provided a research basis for the prevention and treatment of this disease.

The Antioxidant and Anti-Complementary Activities of Crude Polysaccharides from Trifoliate Orange (Poncirus trifoliate) Seeds

In this study, I extracted the crude polysaccharides from trifoliate orange (Poncirus trifoliate) seeds, known as TSCP, using water extraction and ethanol precipitation. The monosaccharide composition of TSCP was in the following order: arabinose (28.28 mol%)> galactose (16.76 mol%)> galacturonic acid+glucuronic acid (13.6 mol%)> glucose (12.45 mol%)> rhamnose (4.18 mol%)> mannose (0.57 mol%)> fucose (0.32 mol%). Its total polyphenol contents were 28.66 and 70.96 μg/mL at 1 and 10 mg/mL, respectively (P<0.01). Further, the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity of 10 mg/mL TSCP (31.67%) was higher than that of 1 mg/mL TSCP (8.07%; P<0.01) and also higher than its 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (11.97%) at the same concentration (10 mg/mL; P<0.01). The anti-complementary property of TSCP increased in a concentration-dependent manner (P<0.001), and at 1,000 μg/mL, it was comparable (61.36%) to the positive control (60%) consisting of polysaccharide-K. In conclusion, TSCP might be a potential immune modulator.

Plant polysaccharides with anti-lung injury effects as a potential therapeutic strategy for COVID-19

When coronavirus disease 2019 (COVID-19) develops into the severe phase, lung injury, acute respiratory distress syndrome, and/or respiratory failure could develop within a few days. As a result of pulmonary tissue injury, pathomorphological changes usually present endothelial dysfunction, inflammatory cell infiltration of the lung interstitium, defective gas exchange, and wall leakage. Consequently, COVID-19 may progress to tremendous lung injury, ongoing lung failure, and death. Exploring the treatment drugs has important implications. Recently, the application of traditional Chinese medicine had better performance in reducing fatalities, relieving symptoms, and curtailing hospitalization. Through constant research and study, plant polysaccharides may emerge as a crucial resource against lung injury with high potency and low side effects. However, the absence of a comprehensive understanding of lung-protective mechanisms impedes further investigation of polysaccharides. In the present article, a comprehensive review of research into plant polysaccharides in the past 5 years was performed. In total, 30 types of polysaccharides from 19 kinds of plants have shown lung-protective effects through the pathological processes of inflammation, oxidative stress, apoptosis, autophagy, epithelial–mesenchymal transition, and immunomodulation by mediating mucin and aquaporins, macrophage, endoplasmic reticulum stress, neutrophil, TGF-β1 pathways, Nrf2 pathway, and other mechanisms. Moreover, the deficiencies of the current studies and the future research direction are also tentatively discussed. This research provides a comprehensive perspective for better understanding the mechanism and development of polysaccharides against lung injury for the treatment of COVID-19.

Role of the C5a-C5a receptor axis in the inflammatory responses of the lungs after experimental polytrauma and hemorrhagic shock

Singular blockade of C5a in experimental models of sepsis is known to confer protection by rescuing lethality and decreasing pro-inflammatory responses. However, the role of inhibiting C5a has not been evaluated in the context of sterile systemic inflammatory responses, like polytrauma and hemorrhagic shock (PT + HS). In our presented study, a novel and highly specific C5a L-aptamer, NoxD21, was used to block C5a activity in an experimental murine model of PT + HS. The aim of the study was to assess early modulation of inflammatory responses and lung damage 4 h after PT + HS induction. NoxD21-treated PT + HS mice displayed greater polymorphonuclear cell recruitment in the lung, increased pro-inflammatory cytokine levels in the bronchoalveolar lavage fluids (BALF) and reduced myeloperoxidase levels within the lung tissue. An in vitro model of the alveolar-capillary barrier was established to confirm these in vivo observations. Treatment with a polytrauma cocktail induced barrier damage only after 16 h, and NoxD21 treatment in vitro did not rescue this effect. Furthermore, to test the exact role of both the cognate receptors of C5a (C5aR1 and C5aR2), experimental PT + HS was induced in C5aR1 knockout (C5aR1 KO) and C5aR2 KO mice. Following 4 h of PT + HS, C5aR2 KO mice had significantly reduced IL-6 and IL-17 levels in the BALF without significant lung damage, and both, C5aR1 KO and C5aR2 KO PT + HS animals displayed reduced MPO levels within the lungs. In conclusion, the C5aR2 could be a putative driver of early local inflammatory responses in the lung after PT + HS.

Therapeutic interventions to restore microcirculatory perfusion following experimental hemorrhagic shock and fluid resuscitation: A systematic review

Objective

Microcirculatory perfusion disturbances following hemorrhagic shock and fluid resuscitation contribute to multiple organ dysfunction and mortality. Standard fluid resuscitation is insufficient to restore microcirculatory perfusion; however, additional therapies are lacking. We conducted a systematic search to provide an overview of potential non‐fluid‐based therapeutic interventions to restore microcirculatory perfusion following hemorrhagic shock.

Methods

A structured search of PubMed, EMBASE, and Cochrane Library was performed in March 2020. Animal studies needed to report at least one parameter of microcirculatory flow (perfusion, red blood cell velocity, functional capillary density).

Results

The search identified 1269 records of which 48 fulfilled all eligibility criteria. In total, 62 drugs were tested of which 29 were able to restore microcirculatory perfusion. Particularly, complement inhibitors (75% of drugs tested successfully restored blood flow), endothelial barrier modulators (100% successful), antioxidants (66% successful), drugs targeting cell metabolism (83% successful), and sex hormones (75% successful) restored microcirculatory perfusion. Other drugs consisted of attenuation of inflammation (100% not successful), vasoactive agents (68% not successful), and steroid hormones (75% not successful).

Conclusion

Improving mitochondrial function, inhibition of complement inhibition, and reducing microvascular leakage via restoration of endothelial barrier function seem beneficial to restore microcirculatory perfusion following hemorrhagic shock and fluid resuscitation.

Protective Effects of the Complement Inhibitor Compstatin CP40 in Hemorrhagic Shock

Trauma-induced hemorrhagic shock (HS) plays a decisive role in the development of immune, coagulation, and organ dysfunction often resulting in a poor clinical outcome. Imbalanced complement activation is intricately associated with the molecular danger response and organ damage after HS. Thus, inhibition of the central complement component C3 as turnstile of both inflammation and coagulation is hypothesized as a rational strategy to improve the clinical course after HS.Applying intensive care conditions, anaesthetized, monitored, and protectively ventilated nonhuman primates (NHP; cynomolgus monkeys) received a pressure-controlled severe HS (60 min at mean arterial pressure 30 mmHg) with subsequent volume resuscitation. Thirty minutes after HS, animals were randomly treated with either an analog of the C3 inhibitor compstatin (i.e., Cp40) in saline (n = 4) or with saline alone (n = 4). The observation period lasted 300 min after induction of HS.We observed improved kidney function in compstatin Cp40-treated animals after HS as determined by improved urine output, reduced damage markers and a tendency of less histopathological signs of acute kidney injury. Sham-treated animals revealed classical signs of mucosal edema, especially in the ileum and colon reflected by worsened microscopic intestinal injury scores. In contrast, Cp40-treated HS animals exhibited only minor signs of organ edema and significantly less intestinal damage. Furthermore, early systemic inflammation and coagulation dysfunction were both ameliorated by Cp40.The data suggest that therapeutic inhibition of C3 is capable to significantly improve immune, coagulation, and organ function and to preserve organ-barrier integrity early after traumatic HS. C3-targeted complement inhibition may therefore reflect a promising therapeutic strategy in fighting fatal consequences of HS.

Beneficial effects of Houttuynia cordata polysaccharides on "two-hit" acute lung injury and endotoxic fever in rats associated with anti-complementary activities

Houttuynia cordata Thunb. is a traditional herb used for clearing heat and eliminating toxins, and has also been used for the treatment of severe acute respiratory syndrome (SARS). In vitro, the crude H. cordata polysaccharides (CHCP) exhibited potent anti-complementary activity through both the classical and alternative pathways by acting on components C3 and C4 of the complement system without interfering with the coagulation system. This study was to investigate the preventive effects of CHCP on acute lung injury (ALI) induced by hemorrhagic shock plus lipopolysaccharide (LPS) instillation (two-hit) and LPS-induced fever in rats. CHCP significantly attenuated pulmonary injury in the “two-hit” ALI model by reducing pulmonary edema and protein exudation in bronchoalveolar lavage fluid (BALF). In addition, it reduced the deposit of complement activation products in the lung and improved oxidant-antioxidant imbalance. Moreover, CHCP administration inhibited fever in rats, reduced the number of leukocytes and restored serum complement levels. The inhibition on the inappropriate activation of complement system by CHCP may play an important role in its beneficial effects on inflammatory diseases. The anti-complementary polysaccharides are likely to be among the key substances for the heat-clearing function of H. cordata.

Generation of complement molecular complex C5b-9 (C5b-9) in response to poly-traumatic hemorrhagic shock and evaluation of C5 cleavage inhibitors in non-human primates

Severe trauma initiates a systemic inflammatory cascade and that involves early activation of complement and cleavage of C5 into C5a (anaphylatoxin) and C5b (C5b-9 membrane attack complex). We examined activation of C5 in non-human primate (NHP) models of hemorrhagic shock. Blood plasma concentrations of C5b-9 were significantly increased in NHPs in response to hemorrhage alone and were further increased with the addition of tissue trauma. The onset of increased C5 cleavage was accelerated in NHPs that experienced decompensated poly-traumatic hemorrhagic shock. Next, to identify an effective inhibitor of NHP C5 cleavage in vitro, as a first step in the development of a potential therapy, three inhibitors of human C5 cleavage and hemolysis were tested in vitro. NHP C5 cleavage and complement-mediated hemolysis were successfully inhibited by pre-treatment of serum samples with a small, inhibitory peptide RA101348. Commercially-available C5 inhibitory antibodies were found to exhibit species-specific efficacy in vitro. Quidel's A217 antibody demonstrated dose-dependent inhibition of C5 cleavage and hemolysis in NHP samples, whereas LGM-Eculizumab only inhibited complement-mediated hemolysis in human samples. This study shows that complement activation in NHPs following experimental poly-traumatic hemorrhagic shock is consistent with clinical reports, and that cleavage of C5 and complement-mediated hemolysis can be effectively inhibited in vitro using a small peptide inhibitor. Taken together, these findings offer a clinically-relevant vehicle and a potential strategy for treatment of hemorrhagic shock with poly-traumatic injury.

TLR2 Regulates Complement-Mediated Inflammation Induced by Blood Loss During Hemorrhage

Hemorrhagic shock resulting from blood loss directs the majority of the blood to the vital organs, dramatically reducing blood flow to the intestines and resulting in damage and inflammation. The excessive intestinal inflammatory response includes pro-inflammatory cytokines and complement activation, although the mechanism is not clear. Toll-like receptors play a vital role in the innate immune response and toll-like receptor 2 (TLR2) is required for intestinal ischemia/reperfusion-induced injury. We hypothesized that TLR2 plays an integral role in the intestinal inflammatory response after hemorrhage and subjected C57Bl/6 wild-type and Tlr2(-/-) mice to atraumatic loss of ∼30% total blood volume. Two hours after blood removal, the intestinal injury and inflammation were assessed. We demonstrate that compared with wild-type control mice, Tlr2(-/-) mice sustain less intestinal damage and inflammation. Importantly, TLR2 regulated eicosanoid and complement activation and IL-12 and TNFα secretions, indicating interactions between TLR2 and complement in response to significant blood loss.

Norepinephrine Decreases Fluid Requirements and Blood Loss While Preserving Intestinal Villi Microcirculation during Fluid Resuscitation of Uncontrolled Hemorrhagic Shock in Mice

Background:

Norepinephrine administration is controversial during hemorrhagic shock resuscitation to stabilize mean arterial pressure (MAP) level because it could have deleterious effects on local circulations. The authors investigated the effect of norepinephrine on intestinal microcirculation during fluid resuscitation in uncontrolled hemorrhagic shock.

Methods:

Mice (n = 6 per group) submitted to an uncontrolled hemorrhagic shock by tail section were randomly assigned to a resuscitation with fluid but without norepinephrine to target a MAP level of 50 mmHg (FR50) or 60 mmHg (FR60) or a resuscitation with fluid and norepinephrine to target a MAP level of 50 mmHg (FRNE50) or 60 mmHg (FRNE60). Intestinal microcirculation was observed by intravital microscopy.

Results:

Fluid requirements were lower in groups resuscitated with fluid and norepinephrine than in groups resuscitated with fluid without norepinephrine (74.6 ± 45.1 in FR50vs. 28.1 ± 10.0 µl/g in FRNE50; P = 0.004 and 161.9 ± 90.4 in FR60vs. 44.5 ± 24.0 µl/g in FRNE60; P = 0.041). Blood loss was not statistically different between FR50 and FRNE50 (14.8 ± 8.3 vs. 8.5 ± 2.9 µl/g; P = 0.180) but was significantly lower in FRNE60 than in FR60 (10.1 ± 4.2 vs. 22.6 ± 9.6 µl/g; P = 0.015). This beneficial effect was associated with the restoration of intestinal microcirculation to the same extent in fluid resuscitated groups without norepinephrine (FR50 and FR60) and fluid resuscitated groups with norepinephrine (FRNE50 and FRNE60).

Conclusions:

During MAP-directed resuscitation of uncontrolled hemorrhagic shock, the administration of norepinephrine decreased blood loss and fluid requirements while preserving intestinal villi microcirculation.

Synergistic deleterious effect of hypoxemia and hypovolemia on microcirculation in intestinal villi*

OBJECTIVE

To investigate the effect of hypoxemia, hemorrhagic shock, and the association of both of these on intestinal microcirculation (microcirculatory perfusion and leukocytes-endothelium interactions in postcapillary venules), as it can be encountered in hemorrhagic shock following trauma.

DESIGN

Prospective controlled experimental study.

SETTING

University research laboratory.

SUBJECTS

Forty-eight anesthetized and mechanically ventilated Balb/c mice.

INTERVENTION

Mice were randomly assigned to hypoxemia group in which we decreased inspired oxygen fraction during 60 minutes to reach a PaO2 of 40 mm Hg, hemorrhagic shock group in which animals were exsanguinated to a mean arterial pressure level of 40 mm Hg during 30 minutes, hypoxemia-hemorrhagic shock group in which PaO2 was decreased to 40 mm Hg during 60 minutes with exsanguination from the 30th to the 60th minute to a mean arterial pressure level of 40 mm Hg; or control group.

MEASUREMENTS AND MAIN RESULTS

Hypoxemia decreased RBCs velocity in intestinal villi but did not alter the fraction of perfused villi. Hypoxemia also triggered leukocytes adhesion to the venular endothelium. Hemorrhagic shock not only decreased RBCs velocity in villi but also slightly altered the fraction of perfused villi (94% ± 2% in hemorrhagic shock group vs 100% ± 0% in control group, p < 0.005). Furthermore, hemorrhagic shock triggered leukocytes adhesion to the venular endothelium to the same extent as hypoxemia. When hypoxemia was associated to hemorrhagic shock, it decreased villous RBCs velocity in an additive manner and the fraction of perfused villi dropped in a synergistic manner (69% ± 3% in hypoxemia-hemorrhagic shock group vs 94 ± 2 in hemorrhagic shock group, p < 0.005). The association of hypoxemia and hemorrhagic shock did not further amplify leukocytes adhesion to intestinal venules compared with either hypoxemia or hemorrhagic shock alone.

CONCLUSIONS

During hemorrhagic shock, the occurrence of hypoxemia considerably alters villous intestinal perfusion as it decreases the fraction of perfused villi in a synergistic manner, thereby increasing the risk of villous ischemia. The association of hypoxemia and hemorrhagic shock did not amplify leukocytes adhesion to the endothelium further than either hemorrhagic shock or hypoxemia alone did. As hypoxemia frequently occurs simultaneously with hemorrhagic shock in traumatic conditions, it can worsen gut ischemia leading to the exacerbation of multiple organ failure syndrome.

The complement system in ischemia-reperfusion injuries

Tissue injury and inflammation following ischemia and reperfusion of various organs have been recognized for many years. Many reviews have been written over the last several decades outlining the role of complement in ischemia/reperfusion injury. This short review provides a current state of the art knowledge on the complement pathways activated, complement components involved and a review of the clinical biologics/inhibitors used in the clinical setting of ischemia/reperfusion. This is not a complete review of the complement system in ischemia and reperfusion injury but will give the reader an updated view point of the field, potential clinical use of complement inhibitors, and the future studies needed to advance the field.

Decay-accelerating factor limits hemorrhage-instigated tissue injury and improves resuscitation clinical parameters

BACKGROUND

Complement is invariably activated during trauma and contributes to tissue injury. Recombinant human decay-accelerating factor (DAF), a complement regulatory protein that inhibits both classical and alternative pathways, improves survival and reduces tissue damage in animal models of tissue injury. The extent to which DAF may facilitate resuscitation in hemorrhaged large animals is not known.

METHODS

Male Yorkshire swine assigned to one of six groups were subjected to controlled, isobaric hemorrhage over 15 min to a target mean arterial pressure (MAP) of 35 mm Hg. Hypotension was maintained for 20 min followed by a bolus intravenous injection of DAF or vehicle followed by Hextend resuscitation. Animals were observed for 3 h after hypotensive Hextend resuscitation. Survival, blood chemistry, and physiological parameters were recorded. Additionally, tissue from lung, small intestine, liver, and kidney were subjected to histopathologic evaluation and tissue deposition of complement proteins was determined by immunohistochemistry, dot-blot, and Western blot analyses.

RESULTS

Administration of DAF (25 μg/kg) to animals subjected to hemorrhage prior to Hextend infusion significantly improved survival (73% versus 27%); protected gut, lung, liver, and kidney tissue from damage; and resulted in reduced resuscitation fluid requirements when compared with animals subjected to hemorrhage and resuscitation with Hextend alone. Animals treated with a higher dose of DAF (50 μg/kg) followed by Hextend fluid resuscitation did not experience the same benefit, suggesting a narrow therapeutic range for use of DAF as adjunct to Hextend fluid.

CONCLUSION

DAF improved survival and reduced early Hextend fluid resuscitation requirements in swine subjected to hemorrhagic shock. These benefits are attributed to decreased complement deposition and limited organ damage.

Human β2-glycoprotein I attenuates mouse intestinal ischemia/reperfusion induced injury and inflammation

Intestinal ischemia-reperfusion (IR)-induced injury results from a complex cascade of inflammatory components. In the mouse model of intestinal IR, the serum protein, β2-glycoprotein I (β2-GPI) binds to the cell surface early in the cascade. The bound β2-GPI undergoes a conformational change which exposes a neoantigen recognized by naturally occurring antibodies and initiates the complement cascade. We hypothesized that providing additional antigen with exogenous β2-GPI would alter IR-induced tissue injury. Administration of human but not mouse β2-GPI attenuated IR-induced tissue damage and prostaglandin E(2) production indicating a physiological difference between β2-GPI isolated from the two species. To investigate whether structural features were responsible for this physiological difference, we compared the chemical, physical and biochemical properties of the two proteins. Despite possessing 76% amino acid identity and 86% sequence homology, we found that mouse β2-GPI differs from the human protein in size, carbohydrate chain location, heterogeneity and secondary structural content. These data suggest that the structural differences result in mouse Ab recognition of soluble human but not mouse β2-GPI and attenuated IR-induced injury. We conclude that caution should be exercised in interpreting results obtained by using human β2-GPI in a mouse model.

Macrophage-produced IL-12p70 mediates hemorrhage-induced damage in a complement-dependent manner

Hemorrhage and hemorrhagic shock instigate intestinal damage and inflammation. Multiple components of the innate immune response, including complement and neutrophil infiltration, are implicated in this pathology. To investigate the interaction of complement activation and other components of the innate immune response during hemorrhage, we treated mice after hemorrhage with CR2-fH, a targeted inhibitor of the alternative complement pathway and assessed intestinal damage and inflammation 2 h after hemorrhage. In wild-type mice, CR2-fH attenuated hemorrhage-induced, midjejunal damage and inflammation as determined by decreased mucosal damage, macrophage infiltration, leukotriene B4, IL-12p40, and TNF-[alpha] production. The critical nature of intestinal macrophage infiltration and activation in the response to hemorrhage was further determined using mice pretreated with clodronate-containing liposomes. The absence of either macrophages or IL-12p70 attenuated intestinal damage. These data suggest that complement activation and macrophage infiltration with IL-12p70 production are critical to hemorrhage-induced midjejunal damage and inflammation.

[Diagnosis and management of acute mesenteric ischemia]

The prevalence of significant splanchnic arterial stenoses is increasing, but remains mostly asymptomatic due to abundant collateral circulation. Acute insufficiency of mesenteric arterial blood flow accounts for 60 to 70% of cases of mesenteric ischemia and results mostly from a superior mesenteric embolus. Despite major advances have been achieved in understanding the pathogenic mechanisms of bowel ischemia, its prognosis remains dismal with mortality rates about 60%. The diagnosis of acute mesenteric ischemia depends upon a high clinical suspicion, especially in patients with known risk factors. Rapid diagnosis is essential to prevent intestinal infarction. However, early signs and symptoms of mesenteric ischemia are non specific, and definitive diagnosis often requires radiologic examinations. Early and liberal implementation of angiography has been the major advance over the past 30 years which allowed increasing diagnostic accuracy of acute mesenteric ischemia. CT and MR-based angiographic techniques have emerged as alternatives less invasive and more accurate to analyse splanchnic vessels and evaluate bowel infarction. The goal of treatment of patients with acute mesenteric ischemia is to restore intestinal oxygenation as quickly as possible after initial management that includes rapid hemodynamic monitoring and support. Surgery should not be delayed in patients suspected of having intestinal necrosis.

CR2+ marginal zone B cell production of pathogenic natural antibodies is C3 independent

Intestinal ischemia-reperfusion (IR)-induced damage requires complement receptor 2 (CR2) for generation of the appropriate natural Ab repertoire. Pathogenic Abs recognize neoantigens on the ischemic tissue, activate complement, and induce intestinal damage. Because C3 cleavage products act as ligands for CR2, we hypothesized that CR2(hi) marginal zone B cells (MZBs) require C3 for generation of the pathogenic Abs. To explore the ability of splenic CR2(+) B cells to generate the damaging Ab repertoire, we adoptively transferred either MZBs or follicular B cells (FOBs) from C57BL/6 or Cr2(-/-) mice into Rag-1(-/-) mice. Adoptive transfer of wild type CR2(hi) MZBs but not CR2(lo) FOBs induced significant damage, C3 deposition, and inflammation in response to IR. In contrast, similarly treated Rag-1(-/-) mice reconstituted with either Cr2(-/-) MZB/B1 B cells (B1Bs) or FOBs lacked significant intestinal damage and displayed limited complement activation. To determine whether C3 cleavage products are critical in CR2-dependent Ab production, we evaluated the ability of the natural Ab repertoire of C3(-/-) mice to induce damage in response to IR. Infusion of C3(-/-) serum into Cr2(-/-) mice restored IR-induced tissue damage. Furthermore, Rag-1(-/-) mice sustained significant damage after infusion of Abs from C3(-/-) but not Cr2(-/-) mice. Finally, adoptive transfer of MZBs from C3(-/-) mice into Rag-1(-/-) mice resulted in significant tissue damage and inflammation. These data indicate that CR2 expression on MZBs is sufficient to induce the appropriate Abs required for IR-induced tissue damage and that C3 is not critical for generation of the pathogenic Abs.

Hemorrhage-induced intestinal damage is complement-independent in Helicobacter hepaticus-infected mice

With more than half of the world population infected, Helicobacter infection is an important public health issue associated with gastrointestinal cancers and inflammatory bowel disease. Animal studies indicate that complement and oxidative stress play a role in Helicobacter infections. Hemorrhage (HS) induces tissue damage that is attenuated by blockade of either complement activation or oxidative stress products. Therefore, we hypothesized that chronic Helicobacter hepaticus infection would modulate HS-induced intestinal damage and inflammation. To test this hypothesis, we examined HS-induced jejunal damage and inflammation in uninfected and H. hepaticus-infected mice. Helicobacter hepaticus infection increased HS-induced midjejunal mucosal damage despite attenuating complement activation. In addition, infection alone increased chemokine secretion, changing the HS-induced neutrophil infiltration to a macrophage-mediated inflammatory response. The HS-induced macrophage infiltration correlated with increased secretion of tumor necrosis factor-α and nitric oxide in the infected mice. Together, these data indicate that Helicobacter infection modulates the mechanism of HS-induced intestinal damage and inflammation from a complement-mediated response to a macrophage response with elevated tumor necrosis factor-α and nitric oxide. These data indicate that chronic low-level infections change the response to trauma and should be considered when designing and administering therapeutics.

Domain V peptides inhibit beta2-glycoprotein I-mediated mesenteric ischemia/reperfusion-induced tissue damage and inflammation

Reperfusion of ischemic tissue induces significant tissue damage in multiple conditions, including myocardial infarctions, stroke, and transplantation. Although not as common, the mortality rate of mesenteric ischemia/reperfusion (IR) remains >70%. Although complement and naturally occurring Abs are known to mediate significant damage during IR, the target Ags are intracellular molecules. We investigated the role of the serum protein, β2-glycoprotein I as an initiating Ag for Ab recognition and β2-glycoprotein I (β2-GPI) peptides as a therapeutic for mesenteric IR. The time course of β2-GPI binding to the tissue indicated binding and complement activation within 15 min postreperfusion. Treatment of wild-type mice with peptides corresponding to the lipid binding domain V of β2-GPI blocked intestinal injury and inflammation, including cellular influx and cytokine and eicosanoid production. The optimal therapeutic peptide (peptide 296) contained the lysine-rich region of domain V. In addition, damage and most inflammation were also blocked by peptide 305, which overlaps with peptide 296 but does not contain the lysine-rich, phospholipid-binding region. Importantly, peptide 296 retained efficacy after replacement of cysteine residues with serine. In addition, infusion of wild-type serum containing reduced levels of anti-β2-GPI Abs into Rag-1(-/-) mice prevented IR-induced intestinal damage and inflammation. Taken together, these data suggest that the serum protein β2-GPI initiates the IR-induced intestinal damage and inflammatory response and as such is a critical therapeutic target for IR-induced damage and inflammation.

Complement factor 3 deficiency attenuates hemorrhagic shock-related hepatic injury and systemic inflammatory response syndrome

Although complement activation is known to occur in the setting of severe hemorrhagic shock and tissue trauma (HS/T), the extent to which complement drives the initial inflammatory response and end-organ damage is uncertain. In this study, complement factor 3-deficient (C3(-/-)) mice and wild-type control mice were subjected to 1.5-h hemorrhagic shock, bilateral femur fracture, and soft tissue injury, followed by 4.5-h resuscitation (HS/T). C57BL/6 mice were also given 15 U of cobra venom factor (CVF) or phosphate-buffered saline injected intraperitoneally, followed by HS/T 24 h later. The results showed that HS/T resulted in C3 consumption in wild-type mice and C3 deposition in injured livers. C3(-/-) mice had significantly lower serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and circulating DNA levels, together with much lower circulating interleukin (IL)-6, IL-10, and high-mobility group box 1 (HMGB1) levels. Temporary C3 depletion by CVF preconditioning also led to reduced transaminases and a blunted cytokine release. C3(-/-) mice displayed well-preserved hepatic structure. C3(-/-) mice subjected to HS/T had higher levels of heme oxygenase-1, which has been associated with tissue protection in HS models. Our data indicate that complement activation contributes to inflammatory pathways and liver damage in HS/T. This suggests that targeting complement activation in the setting of severe injury could be useful.

Hemorrhage-induced hepatic injury and hypoperfusion can be prevented by direct peritoneal resuscitation

BACKGROUND

Crystalloid fluid resuscitation after hemorrhagic shock (HS) that restores/maintains central hemodynamics often culminates in multi-system organ failure and death due to persistent/progressive splanchnic hypoperfusion and end-organ damage. Adjunctive direct peritoneal resuscitation (DPR) using peritoneal dialysis solution reverses HS-induced splanchnic hypoperfusion and improves survival. We examined HS-mediated hepatic perfusion (galactose clearance), tissue injury (histopathology), and dysfunction (liver enzymes).

METHODS

Anesthetized rats were randomly assigned (n = 8/group): (1) sham (no HS); (2) HS (40% mean arterial pressure for 60 min) plus conventional i.v. fluid resuscitation (CR; shed blood + 2 volumes saline); (3) HS + CR + 30 mL intraperitoneal (IP) DPR; or (4) HS + CR + 30 mL IP saline. Hemodynamics and hepatic blood flow were measured for 2 h after CR completion. In duplicate animals, liver and splanchnic tissues were harvested for histopathology (blinded, graded), hepatocellular function (liver enzymes), and tissue edema (wet-dry ratio).

RESULTS

Group 2 decreased liver blood flow, caused liver injuries (focal to submassive necrosis, zones 2 and 3) and tissue edema, and elevated liver enzymes (alanine aminotransferase (ALT), 149 +/- 28 microg/mL and aspartate aminotransferase (AST), 234 +/- 24 microg/mL; p < 0.05) compared to group 1 (73 +/- 9 and 119 +/- 10 microg/mL, respectively). Minimal/no injuries were observed in group 3; enzymes were normalized (ALT 89 +/- 9 microg/mL and AST 150 +/- 17 microg/mL), and tissue edema was similar to sham.

CONCLUSIONS

CR from HS restored and maintained central hemodynamics but did not restore or maintain liver perfusion and was associated with significant hepatocellular injury and dysfunction. DPR added to conventional resuscitation (blood and crystalloid) restored and maintained liver perfusion, prevented hepatocellular injury and edema, and preserved liver function.

Interaction between the coagulation and complement system

The complement system as a main column of innate immunity and the coagulation system as a main column in hemostasis undergo massive activation early after injury. Interactions between the two cascades have often been proposed but the precise molecular pathways of this interplay are still in the dark. To elucidate the mechanisms involved, the effects of various coagulation factors on complement activation and generation of anaphylatoxins were investigated and summarized in the light of the latest literature. Own in vitro findings suggest, that the coagulation factors FXa, FXIa and plasmin may cleave both C5 and C3, and robustly generate C5a and C3a (as detected by immunoblotting and ELISA). The produced anaphylatoxins were found to be biologically active as shown by a dose-dependent chemotactic response of neutrophils and HMC-1 cells, respectively. Thrombin did not only cleave C5 (Huber-Lang et al. 2006) but also in vitro-generated C3a when incubated with native C3. The plasmin-induced cleavage activity could be dose-dependently blocked by the serine protease inhibitor aprotinin and leupeptine. These findings suggest that various serine proteases belonging to the coagulation system are able to activate the complement cascade independently of the established pathways. Moreover, functional C5a and C3a are generated, both of which are known to be crucially involved in the inflammatory response.

Complement component C5a mediates hemorrhage-induced intestinal damage

BACKGROUND

Complement has been implicated in the pathogenesis of intestinal damage and inflammation in multiple animal models. Although the exact mechanism is unknown, inhibition of complement prevents hemodynamic alterations in hemorrhage.

MATERIALS AND METHODS

C57Bl/6, complement 5 deficient (C5-/-) and sufficient (C5+/+) mice were subjected to 25% blood loss. In some cases, C57Bl/6 mice were treated with C5a receptor antagonist (C5aRa) post-hemorrhage. Intestinal injury, leukotriene B4, and myeloperoxidase production were assessed for each treatment group of mice.

RESULTS

Mice subjected to significant blood loss without major trauma develop intestinal inflammation and tissue damage within 2 hours. We report here that complement 5 (C5) deficient mice are protected from intestinal tissue damage when subjected to hemorrhage (injury score = 0.36 compared with wildtype hemorrhaged animal injury score = 2.89; P < 0.05). We present evidence that C5a represents the effector molecule because C57Bl/6 mice treated with a C5a receptor antagonist displayed limited intestinal injury (injury score = 0.88), leukotriene B4 (13.16 pg/mg tissue), and myeloperoxidase (115.6 pg/mg tissue) production compared with hemorrhaged C57Bl/6 mice (P < 0.05).

CONCLUSIONS

Complement activation is important in the development of hemorrhage-induced tissue injury and C5a generation is critical for tissue inflammation and damage. Thus, therapeutics targeting C5a may be useful therapeutics for hemorrhage-associated injury.

Heparin-binding EGF-like growth factor preserves mesenteric microcirculatory blood flow and protects against intestinal injury in rats subjected to hemorrhagic shock and resuscitation

BACKGROUND

The gut is highly susceptible to injury after hemorrhagic shock and resuscitation (HS/R) because of progressive mesenteric hypoperfusion. The aim of the current study was to evaluate the effect of heparin-binding EGF-like growth factor (HB-EGF) on mesenteric microcirculatory blood flow and intestinal injury in rats subjected to HS/R.

METHODS

HS/R was induced in adult rats, with some rats receiving HB-EGF (600 mug/kg) IV at the onset of resuscitation (HS/R+HB-EGF) and others receiving vehicle only (HS/R). FITC-dextran was administered intra-arterially to evaluate mesenteric microcirculation, and intestinal damage and restitution were evaluated histologically. Data were expressed as mean +/- SE, with P < .05 considered statistically significant.

RESULTS

Microcirculatory blood flow was significantly reduced 1 hour after HS/R. HS/R+HB-EGF rats had significantly increased microcirculatory flow compared with HS/R rats at 1 hour (4.5 +/- 0.43 vs 2.64 +/- 0.46, P < .05) and 3 hours (8.04 +/- 1.58 vs 2.89 +/- 0.63, P < .05) after HS/R. HS/R+HB-EGF rats had significantly less intestinal damage compared with HS/R rats 3 hours after resuscitation (2.04 +/- 0.5 vs 3.08 +/- 0.5, P < .05), along with significantly fewer incompetent (nonresurfaced, nonhealed) villi, which is indicative of improved restitution.

CONCLUSIONS

HB-EGF significantly improved postresuscitation microcirculatory blood flow in rats subjected to HS/R, associated with significantly decreased intestinal damage and increased restitution. These results suggest that HB-EGF may be a useful therapeutic agent that improves intestinal blood flow in patients with intestinal injury secondary to hemorrhagic shock.

Adrenomedullin and adrenomedullin binding protein-1 prevent metabolic acidosis after uncontrolled hemorrhage in rats

OBJECTIVE

Management of trauma victims with uncontrolled hemorrhage remains a major problem in combat casualty care at the far-forward battlefield setting. The neuroendocrine response to hemorrhage is to maintain perfusion to the heart and brain, often at the expense of other organ systems. Decreased organ perfusion after hemorrhagic shock is associated with metabolic acidosis, in which the up-regulated endothelin-1 plays an important role. We have recently shown that vascular responsiveness to adrenomedullin (AM), a newly discovered vasodilator peptide, is depressed after hemorrhage and resuscitation. Down-regulation of AM binding protein (AMBP-1) appears to be responsible for this hyporesponsiveness. We therefore hypothesized that administration of AM/AMBP-1 would prevent metabolic acidosis after uncontrolled hemorrhage via down-regulation of endothelin-1.

DESIGN

Prospective, controlled, and randomized animal study.

SETTING

A research institute laboratory.

SUBJECTS

Male Sprague-Dawley rats (275-325 g).

INTERVENTIONS

A rat model of uncontrolled hemorrhage with an extremely low volume of fluid resuscitation was used to mimic the combat situation.

MEASUREMENTS AND MAIN RESULTS

Both lumbar veins of male adult rats were isolated and severed at the junction to the vena cava. The abdomen was kept open but covered with a saline wet gauze for 45 mins and then closed in layers. The animals received 1 mL of normal saline (vehicle) with or without AM (12 microg/kg of body weight) and AMBP-1 (40 microg/kg of body weight) over 45 mins. Various variables were measured at 4 hrs after resuscitation. The bleed-out volumes in the vehicle group and the AM/ AMBP-1 treatment group were 6.78 +/- 0.19 and 6.81 +/- 0.25 mL/rat, respectively. The results indicate that AM/AMBP-1 administration prevented metabolic acidosis, mitigated organ injury, down-regulated preproendothelin-1 gene expression, and decreased plasma levels of endothelin-1 after hemorrhage.

CONCLUSIONS

AM/AMBP-1 may provide a novel approach for the treatment of uncontrolled hemorrhage. The beneficial effect of AM/AMBP-1 is associated with down-regulation of endothelin-1.

C5-blocking antibody reduces fluid requirements and improves responsiveness to fluid infusion in hemorrhagic shock managed with hypotensive resuscitation

Hypotensive resuscitation strategies and inhibition of complement may both be of benefit in hemorrhagic shock. We asked if C5-blocking antibody (anti-C5) could diminish the amount of fluid required and improve responsiveness to resuscitation from hemorrhage. Awake, male Sprague-Dawley rats underwent controlled hemorrhage followed by prolonged (3 h) hypotensive resuscitation with lactated Ringer’s or Hextend, with or without anti-C5. Anti-C5 treatment led to an estimated 62.3 and 58.5% reduction in the volume of Hextend and lactated Ringer’s, respectively. In the subgroup of animals with a positive mean arterial pressure (MAP) response to fluid infusion following prolonged hypotension, anti-C5 treatment led to an estimated 4.7- and 4.1-fold increase in mean arterial pressure response per unit Hextend and lactated Ringer’s infused, respectively. We observed no significant postresuscitation metabolic differences between the anti-C5 groups and controls. Whether anti-C5 could serve as a volume-sparing adjunct that improves responsiveness to fluid administration in humans deserves further study.

Clinical peritoneal dialysis solutions modulate white blood cell-intestinal vascular endothelium interaction

BACKGROUND

Hemorrhagic shock (HS) with conventional resuscitation (CR) (HSCR) primes neutrophils and modulates leukocyte (WBC)-endothelium interaction as part of an exaggerated systemic inflammatory response. We hypothesize that topical application of clinical peritoneal dialysis solutions (PD) modulates such interaction.

METHODS

Intestinal intravital microscopy was used to measure WBC rolling in terminal ileum post capillary venules (V2 and V3) in sham-operated animals, and in animals that underwent fixed pressure hemorrhage (50% mean arterial pressure for 60 minutes), followed by conventional resuscitation with the return of the shed blood and 2 vol of saline. Number of rolling WBCs per thirty seconds in selected V2 and V3, bathed in either Kreb's solution or a 2.5% clinical peritoneal dialysis solution (PD) was quantified. Diameters were measured for the in-flow arterioles (A1), and out-flow venules (V1), for calculation of local blood flow with optical Doppler velocimetry.

RESULTS

The PD solution significantly (P < .05, n = 11) attenuated WBC-endothelium interaction in sham-operated animals while no significant difference was elicited in HSCR (P > .05, n = 9 Kreb's, n = 7 PD). In addition, the PD solution produced an instantaneous dilation at all levels of the intestinal arterioles in both sham and HSCR. While intestinal venular blood outflow was increased by the PD solution, venular diameters changed very little.

CONCLUSION

Superfusion of the gut with glucose-based peritoneal dialysis solutions decreases the concentration of rolling leukocytes along the venular vascular endothelium by a vasodilation-mediated increase in arteriolar inflow and venous outflow mechanism. Hemorrhagic shock and conventional resuscitation enhance the concentration of rolling leukocytes presumably by mechanisms related to upregulation of the adhesion molecules and the low-flow state. Hemorrhage and resuscitation-enhanced leukocytes rolling was not reversed by adjunctive DPR despite the associated marked increase in arterial inflow and venous outflow. The status of the endothelium and the level of leukocyte priming in low-flow states are stronger predictors of leukocyte-endothelium interaction than rheology factors.

Strategies of therapeutic complement inhibition

The involvement of complement in the pathogenesis of a great number of partly life threatening diseases defines the importance to develop inhibitors which specifically interfere with its deleterious action. Endogenous soluble complement-inhibitors, antibodies or low molecular weight antagonists, either blocking key proteins of the cascade reaction or neutralizing the action of the complement-derived anaphylatoxins have successfully been tested in various animal models over the past years. Promising results consequently led to first clinical trials. This review is focused on different approaches for the development of inhibitors, on their site of action in the cascade, on possible indications for complement inhibition based on experimental animal data, and on potential side effects of such treatment.

APT070 (Mirococept), a membrane-localised complement inhibitor, inhibits inflammatory responses that follow intestinal ischaemia and reperfusion injury

Activation of the complement system has been shown to play a major role in the mediation of reperfusion injury. Here, we assessed the effects of APT070 (Mirococept), a novel membrane-localised complement inhibitor based on a recombinant fragment of soluble CR1, on the local, remote and systemic injuries following intestinal ischaemia and reperfusion (I/R) in the rat. In a model of mild I/R injury (30 min of ischaemia and 30 min of reperfusion), APT070 dose-dependently (1-10 mg kg(-1)) inhibited the increase in vascular permeability of and neutrophil influx into intestine and lungs. Maximal inhibition occurred at 10 mg kg(-1). Following severe I/R injury (120 min of ischaemia and 120 min of reperfusion), APT070 (10 mg kg(-1)) markedly prevented neutrophil influx and the increase in vascular permeability both in the intestine and the lungs.APT070 also effectively suppressed the increase of tissue (intestine and lungs) and serum concentrations of TNF-alpha and IL-6, but not those of IL-1beta or IL-10. There was no significant reduction of mortality in the APT070 group. In conclusion, treatment with the membrane-targeted complement inhibitor APT070 significantly reduced the hyperinflammatory response after mild and severe ischaemia and reperfusion injury (I/RI) in rats. APT070 may be effective in therapeutic indications involving gut I/RI.

Vascular dysfunction in ischemia-reperfusion injury

Microvascular dysfunction mediates many of the local and systemic consequences of ischemic-reperfusion (I/R) injury, with a spectrum of changes specific to arterioles, capillaries, and venules. This review discusses the specific changes in the endothelium during I/R injury; describes the differential responses of the various levels of the vasculature including arterioles, capillaries, and venules; and explores mechanisms for remote organ injury. Vascular dysfunction is largely a consequence of changes in the endothelial cells themselves, affecting the integrity of barrier function, cytokine and adhesion molecule expression, and vascular tone. The bioavailability of nitric oxide, an important mediator of vasodilation, is profoundly decreased during the reperfusion period, resulting in impaired vasodilation of arterioles. Release of inflammatory mediators and increased expression of adhesion molecules initiate inflammatory and coagulation cascades that culminate in the occlusion of capillaries, known as the "no-reflow''" phenomenon. In postcapillary venules, the recruitment and transmigration of leukocytes further compromise the integrity of the endothelial barrier and increase the oxidative burden, resulting in leakage and tissue edema. I/R injury can have significant and untoward consequences beyond the affected tissue, with such conditions as systemic inflammatory response syndrome. This review highlights recent progress in understanding of the varied phenomena of vascular dysfunction in I/R injury and some promising advances in the understanding and application of ischemic preconditioning and other potential therapies.

Direct energy delivery improves tissue perfusion after resuscitated shock

BACKGROUND

Conventional resuscitation (CR) from hemorrhagic shock (HS) does not restore intestinal blood flow. Indicators of anaerobic metabolism suggest that cellular energy production also is compromised. We hypothesize that the direct intravenous delivery of lipid-encapsulated high-energy phosphates to cells improves intestinal perfusion during HS and resuscitation (RES).

METHODS

MAP (MAP) was monitored in male rats (200 g), terminal ileum microvessel diameters were measured by in vivo videomicroscopy, and blood flow (Doppler velocimetry) was calculated. Cellular energy delivery was accomplished by intravenous infusion during RES of fusogenic unilamellar lipid vesicles that contain adenosine triphosphate (ATP; VitaSol). Our protocol was HS to 50% baseline MAP for 60 minutes, 30 minutes of RES, and continued microscopy observation for 120 minutes. Experimental groups (n=8 each) were HS+CR (group I); HS+CR+ VitaSol (group II); HS+CR+Vehicle, Vehicle is the phospholipid vesicles without magnesium ATP, (group III); HS+ VitaSol (group IV); sham-operated control+VitaSol (group V); and a time-matched sham-operated control (group VI). The survival outcome and total tissue water from wet weight/dry weight ratio as a function of adjunct VitaSol resuscitation were evaluated in separate intact animal experiments.

RESULTS

HS caused a selective vasoconstriction of the intestinal inflow arterioles (100 microm), which was not seen in the smaller intestinal premucosal arterioles (7-15 microm). CR, which restored baseline hemodynamics, resulted in an initial restoration of intestinal microvascular diameters at all arteriolar levels. However, this was followed by a progressive vasoconstriction and hypoperfusion in premucosal vessels at 120 minutes after RES (-20.48% +/- 2.95% from baseline diameters). In contrast, VitaSol with CR caused enhanced premucosal dilation (+34.27% +/- 4.62%) and augmented flow (+20.50% +/- 10.70%) above prehemorrhage baseline. Vesicles alone had no effect, and VitaSol alone caused only a modest dilation. CR of moderate HS (40% of baseline MAP for 60 minutes, n=10) caused 20% mortality, whereas adjunct VitaSol resuscitation had a 100% survival and less tissue water content.

CONCLUSIONS

Our data confirms that CR causes progressive intestinal hypoperfusion. Cellular resuscitation with direct intravenous energy delivery improves intestinal perfusion after CR and results in improved survival and less tissue edema.

Mechanisms responsible for vascular hyporesponsiveness to adrenomedullin after hemorrhage: the central role of adrenomedullin binding protein-1

OBJECTIVE

Irreversible hypovolemia remains a major clinical problem. Preliminary studies indicate that administration of adrenomedullin and adrenomedullin binding protein-1 in combination (AM/AMBP-1) after hemorrhage, improves cardiovascular function despite the increased levels of AM. Our aim was to determine whether vascular responsiveness to AM is reduced after hemorrhage and, if so, to elucidate the possible mechanism responsible for such hyporesponsiveness.

METHODS

Male rats were bled to and maintained at a mean arterial pressure of 40 mm Hg for 90 minutes. The animals were then resuscitated with 4 times the volume of shed blood with lactated Ringer's solution over 60 minutes. At 1.5 hours postresuscitation, vascular responses to AM and AMBP-1, plasma levels of AM and AMBP-1, AMBP-1 and AM receptor gene expression were measured. In additional animals, AM and AMBP-1 were administered intravenously at 15 minutes after resuscitation over 45 minutes. Serum levels of liver enzymes, lactate, creatinine, TNF-alpha, IL-6, and IL-10 were measured at 1.5 hours postresuscitation.

RESULTS

AM-induced vascular relaxation decreased significantly after hemorrhage and resuscitation, which was markedly improved by AMBP-1. However, AM receptor gene expression did not change under such conditions. Hemorrhage-induced AM hyporesponsiveness was accompanied by the decreased expression and release of AMBP-1. Moreover, AM/AMBP-1 treatment down-regulated TNF-alpha and IL-6, up-regulated IL-10, and attenuated organ injury.

CONCLUSIONS

The decreased AMBP-1 levels rather than alterations in AM receptors are responsible for producing AM hyporesponsiveness after hemorrhage. Thus, administration of AMBP-1 in combination with AM can be useful to reduce organ injury after severe hypovolemia.

A new hypothesis for microvascular inflammation in shock and multiorgan failure: self-digestion by pancreatic enzymes

Shock is accompanied by a severe inflammatory cascade in the microcirculation, the origin of which has been hypothesized in the past to be associated with specific mediators such as endotoxin, oxygen free radicals, nitric oxide, cytokines, and lipid products. But no intervention with clinical effectiveness has been derived from these ideas to date. The authors propose here a new hypothesis suggesting that degradative enzymes, synthesized in the pancreas as part of normal digestion, may play a central role in shock and multiorgan failure. These powerful enzymes have the ability to digest almost every biological material. Self-digestion (i.e. autodegradation) is prevented by compartmentalizing the fully activated degradative enzymes in the intestinal lumen by the mucosal barrier. In shock, maintenance of the mucosal barrier is impaired and it becomes permeable to pancreatic enzymes. Digestive enzymes thereby gain access to the wall of the intestine and initiate self-digestion of submucosal extracellular matrix proteins and interstitial cells. The process leads to generation and release of a host of strong inflammatory mediators. The authors hypothesize that inhibition of pancreatic enzymes in the lumen of tile intestine can serve to attenuate formation of these inflammatory mediators in ischemic tissues following hemorrhagic shock, and consequently prevent cell and tissue injury as well as multiorgan failure.

PERITONEAL LAVAGE WITH OXYGENATED PERFLUOROCHEMICAL IMPROVES HEMODYNAMICS, INTESTINAL INJURY, AND SURVIVAL IN A RAT MODEL OF SEVERE HEMORRHAGIC SHOCK AND RESUSCITATION

Perfluorochemicals (PFC) are chemical substances that have a high solubility for oxygen. This study investigated the effect of peritoneal lavage with oxygenated PFC (O2-PFC) against hemorrhagic shock and resuscitation (HS/R). Male Sprague-Dawley rats were anesthetized and bled to a mean arterial pressure (MAP) of 30 to 35 mmHg for 120 min. The animals then were resuscitated over 20 min with an infusion of shed blood. Peritoneal lavage was performed by inflow and outflow of the PFC solution at 80 mL/h during the shock-resuscitation period. Rats were divided into four groups. Group I, HS without peritoneal lavage; Group II, HS with nitrogenated PFC (N2-PFC) lavage; Group III, HS with O2-PFC lavage; and Group IV, sham-operated rats. Seven of seven (100%) rats in Group IV and six of seven (85.7%) rats in Group III survived for 48 h, and one of seven (14.3%) rats in Group I and zero of seven rats in Group II survived (P < 0.01). In Group III rats, metabolic acidosis (assessed by blood gas analysis) and depression of intestinal blood flow (assessed by laser Doppler flowmetry) during HS were markedly ameliorated in comparison with those in Group I or Group II rats. The elevation of plasma TNF-alpha and IL-6 after HS/R were also attenuated in Group III. Histological study showed that O2-PFC lavage significantly decreased the degree of intestinal mucosal damage. We conclude that treatment with O2-PFC lavage ameliorated HS/R-induced metabolic acidosis and intestinal damage, which was associated with better mortality, possibly by preserving microvascular perfusion and maintaining oxygen metabolism.

Effects of heparin on bacterial translocation and gut epithelial apoptosis after burn injury in the rat: Dose-dependent inhibition of the complement cascade

This study investigated levels of complement inhibition, apoptosis of gut epithelium, and bacterial translocation (BT) associated with different doses of heparin in rats with severe burns. After burn injury, the animals in Groups 1, 2, 3, and 4 received intravenous tail-vein bolus heparin doses of 150, 300, 600, and 1200 U/kg, respectively. Group 5 received no heparin after burn injury. Group 6 served as control group. According to the results, Group 2 had the highest rate of positive staining for C3, and Group 4 had the lowest rate. There were significant differences between these two groups with respect to distribution of immunoflouresein scores for C3 (p=0.01). Group 5 had the highest mean TUNEL index of all the groups (258/10) (p=0.01). On electron microscopy, the connective tissue cells in the ileal submucosa from Groups 4 and 5 showed more significant apoptotic changes than the corresponding cells in the other groups. The total BT values in Group 4 (129 x 10(4) CFU) and Group 5 (100 x 10(4) CFU) were both significantly higher than those in the other groups (p=0.01). Group 1 had the lowest total BT value (6.1 x 10(2) CFU) (p=0.001). In summary, our results confirm that heparin administration after significant burn injury in rats can reduce BT, and that the effect is related to dose. The findings also indicate that levels of BT after burn injury increase in parallel with the extent of gut epithelial cell apoptosis.

Peritoneal resuscitation

BACKGROUND

After resuscitation from hemorrhagic shock, intestinal microvessels constrict leading to impaired mucosal blood flow. This occurs despite restoration of central hemodynamics. We review studies on the use of peritoneal dialysis fluid as an adjunct treatment in amelioration of this gut hypoperfusion.

METHODS

Using in vivo microscopy of the intestinal microcirculation, the effects of topically applied dextrose-based peritoneal dialysis fluid was measured. In other words, animal experiments, the survival benefits, the morbidity, blood flow distribution, and the postresuscitation inflammatory response to direct peritoneal resuscitation (DPR) were determined.

RESULTS

Simulated DPR caused a dramatic vasodilation compared with a progressive vasoconstriction when used during conventional resuscitation (CR) from hemorrhagic shock. It also reversed established vasoconstriction 2 and 4 hours after CR. In CR animals, there was a 40% mortality compared with 100% survival in DPR animals. DPR resulted in a downregulation of the gut-associated proinflammatory response noted after CR and similarly prevented edema formation.

CONCLUSION

DPR enhances organ blood flow to organs incited in the pathogenesis of multiple organ failure and improves survival after severe hemorrhage and CR.

Gastrointestinal ischemia-reperfusion injury is lectin complement pathway dependent without involving C1q

Complement activation plays an important role in local and remote tissue injury associated with gastrointestinal ischemia-reperfusion (GI/R). The role of the classical and lectin complement pathways in GI/R injury was evaluated using C1q-deficient (C1q KO), MBL-A/C-deficient (MBL-null), complement factor 2- and factor B-deficient (C2/fB KO), and wild-type (WT) mice. Gastrointestinal ischemia (20 min), followed by 3-h reperfusion, induced intestinal and lung injury in C1q KO and WT mice, but not in C2/fB KO mice. Addition of human C2 to C2/fB KO mice significantly restored GI/R injury, demonstrating that GI/R injury is mediated via the lectin and/or classical pathway. Tissue C3 deposition in C1q KO and WT, but not C2/fB KO, mice after GI/R demonstrated that complement was activated in C1q KO mice. GI/R significantly increased serum alanine aminotransferase, gastrointestinal barrier dysfunction, and neutrophil infiltration into the lung and gut in C1q KO and WT, but not C2/fB KO, mice. MBL-null mice displayed little gut injury after GI/R, but lung injury was present. Addition of recombinant human MBL (rhuMBL) to MBL-null mice significantly increased injury compared with MBL-null mice after GI/R and was reversed by anti-MBL mAb treatment. However, MBL-null mice were not protected from secondary lung injury after GI/R. These data demonstrate that C2 and MBL, but not C1q, are necessary for gut injury after GI/R. Lung injury in mice after GI/R is MBL and C1q independent, but C2 dependent, suggesting a potential role for ficolins in this model.

Direct peritoneal resuscitation from hemorrhagic shock: effect of time delay in therapy initiation

BACKGROUND

After conventional resuscitation from hemorrhagic shock, splanchnic microvessels progressively constrict, leading to impairment of blood flow. This occurs despite restoration and maintenance of central hemodynamics. The authors' recent studies have demonstrated that topical and continuous ex vivo exposure of the gut microvasculature to a glucose-based clinical peritoneal dialysis solution (Delflex), as a technique of direct peritoneal resuscitation (DPR), can prevent these postresuscitation events when initiated simultaneously with conventional resuscitation. This study aimed to determine whether DPR applied after conventional resuscitation reverses the established postresuscitation intestinal vasoconstriction and hypoperfusion.

METHODS

Male Sprague-Dawley rats were bled to 50% of baseline mean arterial pressure and resuscitated intravenously over 30 minutes with the shed blood returned plus two times the shed blood volume of saline. Initiation of ex vivo, topical DPR was delayed to 2 hours (group 1, n = 8), or to 4 hours (group 2, n = 8), respectively, after conventional resuscitation. Intravital microscopy and Doppler velocimetry were used to measure terminal ileal microvascular diameters of inflow A1 and premucosal A3 (proximal pA3, distal dA3) arterioles and blood flow in the A1 arteriole, respectively. Maximum arteriolar dilation capacity was obtained from the topical application, in the tissue bath, of the endothelium-independent nitric oxide-donor sodium nitroprusside (10M).

RESULTS

Hemorrhagic shock caused a selective vasoconstriction of A1 (-24.1% +/- 2.15%) arterioles from baseline, which was not seen in A3 vessels. This caused A1 blood flow to drop by -68.6% of the prehemorrhage value. Conventional resuscitation restored and maintained hemodynamics in all the animals without additional fluid therapy. In contrast, there was a generalized and progressive postresuscitation vasoconstriction of A1 (-21.7%), pA3 (-18.5%), and dA3 (-18.7%) vessels. The average postresuscitation A1 blood flow was -49.5% of the prehemorrhage value, indicating a persistent postresuscitation hypoperfusion. Direct peritoneal resuscitation reversed the postresuscitation vasoconstriction by 40.9% and enhanced A1 blood flow by 112.9% of the respective postresuscitation values.

CONCLUSIONS

Delayed DPR reverses the gut postresuscitation vasoconstriction and hypoperfusion regardless of the initiation time. This occurs without adverse effects on hemodynamics. Direct peritoneal resuscitation-mediated enhancement of tissue perfusion results from the local effects from the vasoactive components of the Delflex solution, which are hyperosmolality, lactate buffer anion, and, to a lesser extent, low pH. The molecular mechanism of this vasodilation effect needs further investigation.

A novel approach to maintaining cardiovascular stability after hemorrhagic shock: beneficial effects of adrenomedullin and its binding protein

BACKGROUND

Vascular responsiveness to adrenomedullin (AM), a recently discovered vasodilator peptide, is depressed after hemorrhage and resuscitation. Downregulation of AM binding protein-1 (ie, AMBP-1) appears to be responsible for this hyporesponsiveness. Therefore, we hypothesize that administration of AM/AMBP-1 improves cardiovascular responses after hemorrhagic shock and resuscitation.

METHODS

Male rats were bled to and maintained at a mean blood pressure of 40 mm Hg for 90 minutes. The animals were then resuscitated with 4 times the volume of shed blood with Ringer's lactate over 60 minutes. At 15 minutes after the beginning of resuscitation in hemorrhaged animals, AM alone, AMBP-1 alone, AM in combination with AMBP-1, or vehicle (phosphate-buffered saline solution) was administered intravenously over 45 minutes. At 4-hour postresuscitation, in vivo left ventricular contractility parameters, maximal rates of ventricular pressure increase (+dP/dt max ) and decrease (-dP/dt max ), were determined. Cardiac output and organ blood flow were measured with the use of radioactive microspheres. In an additional group of animals, cardiac tumor necrosis factor-alpha (TNF-alpha) levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

Four hours after resuscitation, +dP/dt max , -dP/dt max , cardiac output, and organ blood flow in the liver, small intestine, and kidneys were decreased while treatment with AM/AMBP-1 increased these parameters ( P < .05). Moreover, cardiac TNF-alpha levels were elevated at 4 hours after hemorrhage and resuscitation, while AM/AMBP-1 treatment reduced them to sham levels ( P < .05).

CONCLUSIONS

Administration of AM/AMBP-1 appears to be a useful approach for restoring and maintaining cardiovascular stability after severe hemorrhagic shock and crystalloid resuscitation.

Anti-phospholipid antibodies restore mesenteric ischemia/reperfusion-induced injury in complement receptor 2/complement receptor 1-deficient mice

Complement receptor 2-deficient (Cr2(-/-)) mice are resistant to mesenteric ischemia/reperfusion (I/R) injury because they lack a component of the natural Ab repertoire. Neither the nature of the Abs that are involved in I/R injury nor the composition of the target Ag, to which recognition is lacking in Cr2(-/-) mice, is known. Because anti-phospholipid Abs have been shown to mediate fetal growth retardation and loss when injected into pregnant mice, we performed experiments to determine whether anti-phospholipid Abs can also reconstitute I/R injury and, therefore, represent members of the injury-inducing repertoire that is missing in Cr2(-/-) mice. We demonstrate that both murine and human monoclonal and polyclonal Abs against negatively charged phospholipids can reconstitute mesenteric I/R-induced intestinal and lung tissue damage in Cr2(-/-) mice. In addition, Abs against beta2 glycoprotein I restore local and remote tissue damage in the Cr2(-/-) mice. Unlike Cr2(-/-) mice, reconstitution of I/R tissue damage in the injury-resistant Rag-1(-/-) mouse required the infusion of both anti-beta2-glycoprotein I and anti-phospholipid Ab. We conclude that anti-phospholipid Abs can bind to tissues subjected to I/R insult and mediate tissue damage.

Intravital intestinal videomicroscopy: Techniques and experiences

Intravital videomicroscopy (IVM) of the gastrointestinal (GI) tract is a sophisticated and powerful technique to directly observe the neurologically intact microvasculature of rats in naive and pathological conditions. We combine IVM with other techniques (i.e., vascular ring tension analysis and colorimetric microsphere determination of whole organ blood flow) to develop a strategy for the systematic analysis of the regulation of GI blood flow in healthy animals and in models of systemic sepsis and resuscitated hemorrhagic shock. We also study the molecular biology of the GI tract (enzyme- or radio-linked immunosorbent assays, fluorescent Greiss assay, and immunoblots) to correlate expression and levels of vascular mediators in tissue and arterial, venous, and portal blood with functional activity of the GI microvascular tree. When combined, these techniques develop a picture of gut pathophysiology at the level of the endothelium, vascular smooth muscle cells, and blood cells in the microcirculation. Our work led us to the general hypothesis that altered microcirculatory function in disease states lies primarily at the level of the interface between vascular and tissue physiology, i.e., the endothelial cell. This review focuses on methods and techniques for studying microvascular function, and concludes with focused reviews of pertinent findings.

Accelerated ischemia/reperfusion-induced injury in autoimmunity-prone mice

Natural Abs have been implicated in initiating mesenteric ischemia/reperfusion (I/R)-induced tissue injury. Autoantibodies have affinity and self-Ag recognition patterns similar to natural Abs. We considered that autoimmunity-prone mice that express high titers of autoantibodies should have enhanced I/R-induced injury. Five-month-old B6.MRL/lpr mice displayed accelerated and enhanced intestinal I/R-induced damage compared with 2-mo-old B6.MRL/lpr and age-matched C57BL/6 mice. Similarly, older autoimmune mice had accelerated remote organ (lung) damage. Infusion of serum IgG derived from 5-mo-old but not 2-mo-old B6.MRL/lpr into I/R resistant Rag-1-/- mice rendered them susceptible to local and remote organ injury. Injection of monoclonal IgG anti-DNA and anti-histone Abs into Rag-1-/- mice effectively reconstituted tissue injury. These data show that like natural Abs, autoantibodies, such as anti-dsDNA and anti-histone Abs, can instigate I/R injury and suggest that they are involved in the development of tissue damage in patients with systemic lupus erythematosus.

Role of neutrophils on shock/resuscitation-mediated intestinal arteriolar derangements

Adequate resuscitation from hemorrhagic shock that preserves hemodynamics is associated with a generalized and progressive intestinal arteriolar vasoconstriction and hypoperfusion coupled with impairment of the endothelium-dependent dilation response. This study was performed to investigate the role of neutrophils on the postresuscitation intestinal arteriolar derangements. Experiments were performed in anesthetized rats 24 h after neutrophil depletion. Neutropenia was induced with antineutrophil serum by tail vein injection. Rats injected with rabbit serum lacking anti-rat neutrophil antibody served as controls. Hemorrhagic shock was 50% of mean arterial pressure for 60 min. Resuscitation was with the shed blood returned plus 2 volumes of saline. A nonhemorrhage group served as control. Intravital videomicroscopy of the terminal ileum was used to measure microvascular diameter and centerline red cell velocity. Endothelial function was assessed from the response to the endothelium-dependent dilator acetylcholine (10(-9) to 10(-4) M). Regardless of neutrophil count, hemorrhagic shock caused selective vasoconstriction of inflow A1 arterioles (-21.49 +/- 0.67%) from baseline, which was not seen in the premucosal A3 vessels (pA3, dA3). At 2 h postresuscitation, there was a generalized vasoconstriction from baseline diameter in A1 (-21.26 +/- 2.29%), pA3 (-22.66 +/- 5.02%), and dA3 (-17.62 +/- 4.84%). Neutrophil depletion caused a significant reset of baseline A1 blood flow from 701 +/- 90 nL/s to 978 +/- 90 nL/s and attenuated the postresuscitation hypoperfusion. This occurred independently of the A1 diameter change. Hemorrhagic shock/resuscitation caused impairment of the endothelium-dependent dilation response irrespective of neutrophil count. This study demonstrates that neutrophils do not contribute to the hemorrhagic/resuscitation-mediated intestinal arteriolar derangements, but appear to possess a role in the intestinal arteriolar blood flow regulation under normal and low flow states possibly via a rheologic effect.

The attenuation of hepatic microcirculatory alterations by exogenous substitution of nitric oxide by s-nitroso-human albumin after hemorrhagic shock in the rat

Hepatic microcirculatory disorders such as narrowing of sinusoids after hemorrhagic shock play a major role in the pathogenesis of organ failure. It is known that the balance of vasoactive mediators such as endothelin and nitric oxide (NO) regulate microvascular perfusion, including the diameter of hepatic sinusoids. The present study was designed to evaluate the role of exogenous substitution of NO by S-nitroso-albumin (S-NO-HSA) in the prevention of pathophysiological alterations of hepatic microcirculation. Anesthetized Sprague-Dawley rats were instrumented for invasive hemodynamic monitoring. Hemorrhagic shock was induced by bleeding to a mean arterial pressure (MAP) of 40 mmHg and was maintained for 60 min. Thereafter, the animals were resuscitated with shed blood and Ringer's solution. During the first hour of resuscitation, S-NO-HSA or pure HSA was infused continuously (10 micromol/kg/h) and hepatic microcirculation was detected by intravital epifluorescence microscopy either 5 or 24 h after the insult. Results were compared with a sham-treated group (n = 6-8 per group). Shock-induced microcirculatory narrowing of sinusoids was significantly reduced in the S-NO-HSA group compared with the HSA group both at 5 and 24 h (HSA: 9.3 +/- 0.2 microm; S-NO-HSA: 12.1 +/- 0.2 microm, P < 0.05). Sinusoidal perfusion was significantly higher in the S-NO-HSA group than in the HSA group (HSA: 50,934 +/- 1,382 microm3/s; S-NO-HSA: 78,120 +/- 2,348 microm3/s, P < 0.05). Reversible leukocyte adhesion to sinusoidal endothelium, an indicator of the inflammatory response, was significantly reduced in the S-NO-HAS-treated group. The findings of this study in a rat model of hemorrhagic shock suggest that NO substitution by S-NO-HSA during resuscitation attenuates both early and late hepatic microcirculatory disturbances as well as the increase in leukocyte adherence.

Intraperitoneal resuscitation improves intestinal blood flow following hemorrhagic shock

OBJECTIVE

To study the effects of peritoneal resuscitation from hemorrhagic shock.

SUMMARY BACKGROUND DATA

Methods for conventional resuscitation (CR) from hemorrhagic shock (HS) often fail to restore adequate intestinal blood flow, and intestinal ischemia has been implicated in the activation of the inflammatory response. There is clinical evidence that intestinal hypoperfusion is a major factor in progressive organ failure following HS. This study presents a novel technique of peritoneal resuscitation (PR) that improves visceral perfusion.

METHODS

Male Sprague-Dawley rats were bled to 50% of baseline mean arterial pressure (MAP) and resuscitated with shed blood plus 2 equal volumes of saline (CR). Groups were 1) sham, 2) HS + CR, and 3) HS + CR + PR with a hyperosmolar dextrose-based solution (Delflex 2.5%). Groups 1 and 2 had normal saline PR. In vivo videomicroscopy and Doppler velocimetry were used to assess terminal ileal microvascular blood flow. Endothelial cell function was assessed by the endothelium-dependent vasodilator acetylcholine.

RESULTS

Despite restored heart rate and MAP to baseline values, CR animals developed a progressive intestinal vasoconstriction and tissue hypoperfusion compared to baseline flow. PR induced an immediate and sustained vasodilation compared to baseline and a marked increase in average intestinal blood flow during the entire 2-hour post-resuscitation period. Endothelial-dependent dilator function was preserved with PR.

CONCLUSIONS

Despite the restoration of MAP with blood and saline infusions, progressive vasoconstriction and compromised intestinal blood flow occurs following HS/CR. Hyperosmolar PR during CR maintains intestinal blood flow and endothelial function. This is thought to be a direct effect of hyperosmolar solutions on the visceral microvessels. The addition of PR to a CR protocol prevents the splanchnic ischemia that initiates systemic inflammation.

Resuscitation regimens for hemorrhagic shock must contain blood

Endothelial cell dysfunction occurs during hemorrhagic shock (HS) and persists despite adequate resuscitation (RES) that restores and maintains hemodynamics. We hypothesize that RES from HS with crystalloid solutions alone aggravate the endothelial cell dysfunction. To test this hypothesis, anesthetized nonheparinized rats were monitored for hemodynamics, and the terminal ileum was studied with intravital video microscopy. HS was 50% of mean arterial pressure (MAP) for 60 min. Four hemorrhaged groups (10 animals in each group) were randomized for RES: group I with shed blood returned + equal volume of normal saline (NS); group II with shed blood returned + 2x NS; group III with 2x NS only; and group IV with 4x NS only. Two hours post-RES, endothelial cell function was assessed with the endothelial-dependent agonist acetylcholine (ACh, 10(-9)-10(-4) M). Maximum arteriolar diameter was elicited by the endothelial-independent agonist sodium nitroprusside (NTP, 10(-4) M). HS caused a selective vasoconstriction associated with low blood flow in inflow A1 arterioles in all hemorrhaged groups. Post-RES vasoconstriction developed in A1 and premucosal arterioles (pA3 and dA3) In all hemorrhaged groups regardless of the RES regimen. However, A1 vasoconstriction and flow were significantly worst in the animals RES with NS alone (-43% and -75%, respectively) compared with those resuscitated with blood and NS (-27% and -57%). Impaired dilation response to ACh was noted in all hemorrhaged animals. However, a significant shift to the right of the dose-response curve (decreased sensitivity) was observed in the animals resuscitated with NS alone irrespective of the RES volume. These animals required at least two orders of magnitude greater ACh concentration to produce a 20% dilation response. For all vessel types, Group II had the best preservation of endothelial cell function. In conclusion, HS causes a selective vasoconstriction of A1 arterioles, which was not observed in A3 vessels. RES from HS results in progressive vasoconstriction in all intestinal arterioles irrespective of the RES regimen. Crystalloid RES after HS does not restore hemodynamics to baseline and is associated with a marked endothelial cell dysfunction. Blood-containing RES regimens preserve and maintain hemodynamics and are associated with the least microvascular dysfunction. Therefore, regimens for RES from HS must contain blood. Endothelial cell dysfunction is not the sole etiologic factor of post-RES microvascular impairment.

Detrimental effects of complement activation in hemorrhagic shock

The complement system has been implicated in early inflammatory events and a variety of shock states. In rats, we measured complement activation after hemorrhage and examined the hemodynamic and metabolic effects of complement depletion before injury and worsening of complement activation after hemorrhage and resuscitation [with a carboxypeptidase N inhibitor (CPNI), which blocks the clearance of C5a]. Rats were bled to a mean arterial pressure of 30 mmHg for 50 min and were then resuscitated for 2 h. Shock resulted in significant evidence of complement consumption, with serum hemolytic activity being reduced by 33% (P < 0.05). Complement depletion before injury did not affect hemorrhage volume (complement depleted = 28 +/- 1 ml/kg, complement intact = 29 +/- 1 ml/kg, P = 0.74) but improved postresuscitation mean arterial pressure by 37 mmHg (P < 0.05) and serum bicarbonate levels (complement depleted = 22 +/- 3 meq/ml, complement intact = 13 +/- 8 meq/ml, P < 0.05). Pretreatment with CPNI was lethal in 80% of treated animals vs. the untreated hemorrhaged group in which no deaths occurred (P < 0.05). In this model of hemorrhagic shock, complement activation appeared to contribute to progressive hypotension and metabolic acidosis seen after resuscitation. The lethality of CPNI during acute blood loss suggests that the anaphylatoxins are important in the pathophysiological events involved in hemorrhagic shock.