Anti-P-selectin antibody protects against hepatic ichemia-reperfusion injury

Reperfusion Syndrome: Cellular Mechanisms of Microvascular Dysfunction and Potential Therapeutic Strategies

Reperfusion injury is the paradoxical and complex phenomenon of exacerbation of cellular dysfunction and increase in cell death after the restoration of blood flow to previously ischemic tissues. It involves biochemical and cellular changes causing oxidant production and complement activation, which culminates in an inflammatory response, mediated by neutrophil and platelet cell interactions with the endothelium and among the cells themselves. The mounted inflammatory response has both local and systemic manifestations. Despite improvements in imaging, interventional techniques, and pharmacological agents, morbidity from reperfusion remains high. Extensive research has furthered the understanding of the various pathophysiological mechanisms involved and the development of potential therapeutic strategies. Preconditioning has emerged as a powerful method of ameliorating ischemia reperfusion injury to the myocardium and in transplant surgery. More recently, postconditioning has been shown to provide a therapeutic counter to vasoocclusive emergencies. More research and well-designed trials are needed to bridge the gap between experimental evidence and clinical implementation.

Disruption of guanylyl cyclase-G protects against acute renal injury

The membrane forms of guanylyl cyclase (GC) serve as cell-surface receptors that synthesize the second messenger cGMP, which mediates diverse cellular processes. Rat kidney contains mRNA for the GC-G isoform, but the role of this receptor in health and disease has not been characterized. It was found that mouse kidney also contains GC-G mRNA, and immunohistochemistry identified GC-G protein in the epithelial cells of the proximal tubule and collecting ducts. Six hours after ischemia-reperfusion (I/R) injury, GC-G mRNA and protein expression increased three-fold and remained upregulated at 24 h. For determination of whether GC-G mediates I/R injury, a mutant mouse with a targeted disruption of the GC-G gene (Gucy2g) was created. At baseline, no histologic abnormalities were observed in GC-G(-/-) mice. After I/R injury, elevations in serum creatinine and urea were attenuated in GC-G(-/-) mice compared with wild-type controls, and this correlated with less tubular disruption, less tubular cell apoptosis, and less caspase-3 activation. Measures of inflammation (number of infiltrating neutrophils, myeloperoxidase activity, and induction of IL-6 and P-selectin) and activation of NF-kappaB were lower in GC-G(-/-) mice compared with wild-type mice. Direct transfer of a GC-G expression plasmid to the kidneys of GC-G(-/-) mice resulted in a dramatically higher mortality after renal I/R injury, further supporting a role for GC-G in mediating injury. In summary, GC-G may act as an early signaling molecule that promotes apoptotic and inflammatory responses in I/R-induced acute renal injury.

CXC-chemokine regulation and neutrophil trafficking in hepatic ischemia-reperfusion injury in P-selectin/ICAM-1 deficient mice

BACKGROUND

Neutrophil adhesion and migration are critical in hepatic ischemia and reperfusion injury (I/R). P-selectin and the intercellular adhesion molecule (ICAM)-1 can mediate neutrophil-endothelial cell interactions, neutrophil migration, and the interactions of neutrophils with hepatocytes in the liver. Despite very strong preclinical data, recent clinical trials failed to show a protective effect of anti-adhesion therapy in reperfusion injury, indicating that the length of injury might be a critical factor in neutrophil infiltration. Therefore, the aim of this study was to assess the role of P-selectin and ICAM-1 in neutrophil infiltration and liver injury during early and late phases of liver I/R.

METHODS

Adult male wild-type and P-selectin/ICAM-1-deficient (P/I null) mice underwent 90 minutes of partial liver ischemia followed by various periods of reperfusion (6, 15 h, and a survival study). Liver injury was assessed by plasma level of alanine aminotransferase (ALT) and histopathology. The plasma cytokines, TNF-alpha, IL-6, MIP-2 and KC, were measured by ELISA.

RESULTS

Reperfusion caused significant hepatocellular injury in both wild-type and P/I null mice as was determined by plasma ALT levels and liver histopathology. The injury was associated with a marked neutrophil infiltration into the ischemic livers of both wild-type and P/I null mice. Although the levels of ALT and neutrophil infiltration were slightly lower in the P/I null mice compared with the wild-type mice the differences were not statistically significant. The plasma cytokine data of TNF-alpha and IL-6 followed a similar pattern to ALT data, and no significant difference was found between the wild-type and P/I null groups. In contrast, a significant difference in KC and MIP-2 chemokine levels was observed between the wild-type and P/I null mice. Additionally, the survival study showed a trend towards increased survival in the P/I null group.

CONCLUSION

While ICAM-1 and P-selectin does not appear to be critical for neutrophil infiltration and I/R injury in the liver, they may regulate CXC-chemokine production. Blockage of these adhesion molecules may improve survival and remote organ injury that often accompanies liver I/R injury, through chemokine regulation.

Molecular characterization of rat leukocyte P-selectin glycoprotein ligand-1 and effect of its blockade: protection from ischemia-reperfusion injury in liver transplantation

P-selectin glycoprotein ligand-1 (PSGL-1) mediates the initial tethering of leukocytes to activated platelets and endothelium. We report molecular cloning and characterization of the rat PSGL-1 gene. A neutralizing Ab was generated, and its binding epitope was mapped to the N-terminal binding region of rat PSGL-1. We examined the effects of early PSGL-1 blockade in rat liver models of cold ischemia, followed by ex vivo reperfusion or transplantation (orthotopic liver transplantation (OLT)) using an anti-PSGL-1 Ab with diminished Fc-mediated effector function. In the ex vivo hepatic cold ischemia and reperfusion model, pretreatment with anti-PSGL-1 Ab improved portal venous flow, increased bile production, and decreased hepatocellular damage. Rat pretreatment with anti-PSGL-1 Ab prevented hepatic insult in a model of cold ischemia, followed by OLT, as assessed by 1) decreased hepatocellular damage (serum glutamic oxaloacetic transaminase/glutamic-pyruvic transaminase levels), and ameliorated histological features of ischemia/reperfusion injury, consistent with extended OLT survival; 2) reduced intrahepatic leukocyte infiltration, as evidenced by decreased expression of P-selectin, ED-1, CD3, and OX-62 cells; 3) inhibited expression of proinflammatory cytokine genes (TNF-alpha, IL-1beta, IL-6, IFN-gamma, and IL-2); and 4) prevented hepatic apoptosis accompanied by up-regulation of antiapoptotic Bcl-2/Bcl-xL protective genes. Thus, targeting PSGL-1 with a blocking Ab that has diminished Fc-mediated effector function is a simple and effective strategy that provides the rationale for novel therapeutic approaches to maximize the organ donor pool through the safer use of liver transplants despite prolonged periods of cold ischemia.

Ischaemic preconditioning in transplantation and major resection of the liver

BACKGROUND

Ischaemia-reperfusion injury (IRI) contributes significantly to the morbidity and mortality of transplantation and major resection of the liver. Its severity is reduced by ischaemic preconditioning (IP), the precise mechanisms of which are not completely understood. This review discusses the pathophysiology and role of IP in this clinical setting.

METHODS

A Medline search was performed using the keywords 'ischaemic preconditioning', 'ischaemia-reperfusion injury', 'transplantation' and 'hepatic resection'. Additional articles were obtained from references within the papers identified by the Medline search.

RESULTS AND CONCLUSION

The mechanisms underlying hepatic IRI are complex, but IP reduces the severity of such injury in several animal models and in recent human trials. Increased understanding of the cellular processes involved in IP is of importance in the development of treatment strategies aimed at improving outcome after liver transplantation and major hepatic resection.

Hepatic reticuloendothelial system dysfunction after ischemia-reperfusion: role of P-selectin-mediated neutrophil accumulation

The relationship between hepatic ischemia-reperfusion (I-R) and subsequent injury through neutrophil accumulation is well described. Although alterations in reticuloendothelial system (RES) function (specifically Kupffer cell function) after I-R have been delineated, the degree to which discrete components of RES function (phagocytosis and killing) are independently modulated under these conditions has not been quantified. A hepatic segmental I-R model was established in mice, in which blood supply to the left lateral lobe of the liver was occluded for 45 minutes, the liver was reperfused, and the laparotomy incision was closed. Experimental animals were pretreated with either vinblastin (1.5 mg/kg) to induce neutropenia or anti-P-selectin monoclonal antibody (mAb; 50 microg/mice) 4 days and 5 minutes before ischemia, respectively. We previously reported that after intravenous injection of chromium 51 ((51)Cr) and iodine 125 ((125)I) double-labeled Escherichia coli, hepatic (51)Cr levels could be used to reliably quantify hepatic phagocytic clearance (HPC) of bacteria from blood, whereas the subsequent release of (125)I from the liver accurately paralleled hepatic bacterial killing efficiency (HKE). Using this double-label bacteria clearance assay, HPC and HKE were depressed after I-R, in association with hepatic neutrophil accumulation. Segmental I-R resulted in decreased HPC and HKE activity in both ischemic and nonischemic hepatic lobes. Depressions in HPC and HKE were attenuated by either vinblastin-induced neutropenia or blocking neutrophil adhesion to the hepatic endothelium with anti-P-selectin mAb. These findings support the hypothesis that I-R induces hepatic RES dysfunction, at least in part, through P-selectin-mediated neutrophil accumulation.

Hepatic Ischemia/Reperfusion Injury in P-Selectin and Intercellular Adhesion Molecule-1 Double-Mutant Mice

Neutrophil adhesion and recruitment represents one of the early cellular events that occur during hepatic ischemia/reperfusion (IR) injury and plays a critical role in determining the extent of tissue damage. The adhesion molecules, such as selectins and intercellular adhesion molecules (ICAM), are important in mediating neutrophil-endothelial cell interactions and neutrophil emigration. The goal of this study was to evaluate the role of P-selectin and ICAM-1 in hepatic IR injury. Male wild-type and P-selectin/ICAM-1-deficient (P/I null) mice underwent 90 minutes of partial hepatic ischemia followed by reperfusion at various time points (0, 1.5, 3, and 6 hours). Reperfusion caused a time-dependent hepatocellular injury in both wild-type and P/I null mice as judged by plasma alanine aminotransferase (ALT) levels and liver histopathology examination. Although ALT levels were slightly lower in the P/I null mice compared with the wild-type mice the differences were not statistically significant. Neutrophil infiltration to the ischemic liver was observed in both mouse groups after 6 hours of reperfusion; however, the infiltration to the midzonal region of the ischemic liver was more pronounced in the wild-type group. This study suggests that hepatocellular injury induced after hepatic IR was independent of P-selectin and ICAM-1 in this model of acute inflammatory tissue injury.

Persantine Attenuates Hemorrhagic Shock-Induced P-Selectin Expression

Ischemia/reperfusion (I/R), a phenomenon that is associated with conditions such as organ transplantation, trauma, vascular disease, and stroke, involves the recruitment of activated and adherent leukocytes that subsequently mediate tissue injury. Endothelial cell adhesion molecules such as P-selectin mediate I/R-induced leukocyte recruitment and allow the adherent leukocytes to damage the vascular wall and parenchymal cells. This study examines the influence of dypiridamole (persantine) on hemorrhagic shock (H/S)-induced P-selectin expression. H/S was induced in C57BL/6 mice by withdrawing blood to drop the mean arterial blood pressure to 30 to 35 mm Hg for 45 minutes. The mice were resuscitated by infusing the shed blood and Ringer's lactate (50% shed blood volume). In vivo P-selectin expression was determined using a dual monoclonal antibody technique in the heart, lung, liver, kidneys, stomach, small bowel, and colon of a control group, a hemorrhagic shock group, and a hemorrhagic shock group that was pretreated with Persantine (Boehringer, Ingelheim, Ingelheim, Germany). H/S significantly ( P < 0.01) increased P-selectin expression in all regional vascular beds of untreated mice. Persantine treatment largely prevented the H/S-induced P-selectin expression in the same vascular beds. Persantine significantly attenuates the upregulation of P-selectin in the hemorrhagic shock model.

Plasma-soluble E-selectin after cardiopulmonary bypass in children: is it a marker of the postoperative course?

OBJECTIVE

To investigate the relationship and possible role of soluble adhesion molecule E-selectin in the postoperative course in children undergoing cardiopulmonary bypass (CPB).

DESIGN

Prospective cohort study.

SETTING

Pediatric intensive care unit of a university hospital.

PARTICIPANTS

Thirteen children who were candidates for cardiac surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Serial blood samples of 13 CPB patients were collected from the arterial catheter or from the bypass circuits preoperatively; on initiation of CPB; on termination of CPB; and 1, 2, 4, 8, 12, 18, 24, and 48 hours postoperatively. Plasma was recovered immediately, aliquoted, and frozen at -70 degrees C until use. Circulating soluble selectin molecules were measured with a sandwich enzyme-linked immunosorbent assay technique. There were significant changes in plasma levels of soluble E-selectins in patients after CPB, and these levels were associated with patient characteristics, operative variables, and postoperative course. Soluble E-selectin correlated significantly with inotropic support and the use of anti-inflammatory drugs. There was a significant association between the development of postoperative sepsis and soluble E-selectin levels. No correlation was found between soluble E-selectins and duration of CPB, aortic cross-clamping, or hemodynamic variables, including heart rate and mean systemic arterial pressure.

CONCLUSION

These results suggest a relationship between CPB-induced mediators and early and late clinical effects. Although the mechanism for the increase of soluble E-selectin remains to be elucidated, the upregulation of soluble E-selectin indicates neutrophil activation, and its inhibition may represent a target for reducing the inflammatory response associated with CPB.

Murine response to DNA encoding herpes simplex virus type-1 glycoprotein D targeted to the liver

Plasmid DNA encoding herpes simplex virus type-1 glycoprotein D (gD-1) was complexed with asialoorosomucoid conjugated to poly-L-lysine. Following its intravenous injection into BALB/c mice, this complex was targeted to the liver. Liver cells expressing gD-1 were detected immunohistochemically through day 6 post-immunization, while gD-1 DNA was detectable through 14 days post-immunization. Decline of gD-1 expression and detectable gD-1 DNA in the liver correlated with influx of T cells, predominantly CD4(+). The ASOR-poly-L-lysine DNA carrier system promotes hepatic expression of gD-1 and may be useful in vaccination against herpes simplex virus type-1.

Both ischemic and pharmacological preconditioning decrease hepatic leukocyte/endothelial cell interactions

BACKGROUND

Ischemic preconditioning has been shown to protect some tissues from ischemia/reperfusion (I/R) injury. Adenosine is believed to play an important role by attenuating leukocyte-endothelial cell adhesive interactions. Dipyridamole increases adenosine bioavailability. The purpose of this study was to evaluate the effects of mechanical (MPC) and pharmacological preconditioning (PPC) on leukocyte endothelial cell interaction in hepatic I/R injury.

METHODS

C57BL6 mice were subjected to 30 min of ischemia to the left lobe of the liver. Groups tested at 30 min, 2, 5, 12, and 24 hr of reperfusion had 1) sham laparotomy (n = 10, 2) I/R (n = 25), 3) ischemic preconditioning with 5 min of ischemia and 10 min reperfusion before I/R (n = 25), and 4) (PPC) with dipyridamole (n = 25). Intravital microscopic examination was used to assess leukocyte/endothelial cell adhesion. Blood was drawn for leukocyte counts and liver function tests.

RESULTS

A significant decrease in leukocyte rolling was observed at 30-min and 5-hr reperfusion intervals in the PPC and ischemic preconditioning groups compared with the I/R group. A significant decrease in leukocyte saltation was also observed in the PPC and MPC groups at 2, 5, and 12 hr of reperfusion when compared with the I/R group. aspartate aminotransferase was significantly decreased in the 5-hr preconditioning groups. There was not a significant decrease in the white blood cell count because of PPC or MPC vs. I/R CONCLUSIONS: Preconditioning decreases endothelial/ leukocyte interaction and reduces liver damage as measured by aspartate aminotransferase. These data prove that IPC and PPC provide some degree of hepatic protection in I/R injury.

Blocking P-selectin protects from ischemia/reperfusion-induced acute renal failure

Acute renal failure (ARF) in response to ischemia-reperfusion is thought to be associated with neutrophil infiltration. Neutrophil recruitment depends on adhesion molecules, including P-selectin. Our study sought to characterize the role of P-selectin in ischemia-reperfusion (I/R) -induced acute renal failure (ARF). In wild-type (wt) and P-selectin-deficient (P-/-) mice (both C57BL/6), ARF was induced by 32 min bilateral renal ischemia, followed by reperfusion (I/R). Wt showed a 12- and 20-fold increase in creatinine at 24 and 48 h after I/R, respectively. Similar changes were seen in blood urea nitrogen (BUN). By contrast, in P-/- creatinine and BUN increased only moderately (fourfold over sham). In wt, renal myeloperoxidase activity, indicating neutrophil infiltration, peaked after 24 h (19-fold over sham). This was significantly attenuated in P-/- (fivefold over sham). Western blot analysis revealed maximum P-selectin expression 12 h after I/R in wt. Immunostaining detected P-selectin in glomerular endothelium and in platelets adherent in glomerular and peritubular vessels. Postischemic injection of P-selectin antibody at 10 min after reperfusion, but not isotype control antibody, protected wt from ARF similar to the protection seen in P-/-. We conclude that blocking P-selectin even after onset of reperfusion protects mice from I/R-induced ARF, suggesting potential therapeutic strategies aimed at blocking P-selectin.

Effects of dextran and pentoxifylline on hemorrhagic shock-induced P-selectin expression

BACKGROUND

Dextran and pentoxifylline have been shown to prevent leukocyte-endothelium adherence encountered after hemorrhagic shock. P-Selectin is the first endothelial cell adhesion molecule to be upregulated after an ischemic insult. We investigated the effects of resuscitation with dextran 70 and administration of pentoxifylline during resuscitation on hemorrhagic shock-induced P-selectin expression.

MATERIAL AND METHODS

Hemorrhagic shock was induced in C57BL/6 mice by withdrawing blood to reduce mean arterial blood pressure to 30 mm Hg for 45 min. Animals were resuscitated by infusing one of the following solutions (each n:5): (1) Ringer's lactate, (2) 6% dextran 70, (3) Ringer's lactate plus 50 mg/kg pentoxifylline, (4) 5% human albumin. Afterward shed blood was infused. In vivo P-selectin expression was determined using dual-radiolabeled monoclonal antibody technique in lung, heart, liver, kidney, mesentery, stomach, small bowel, and colon 5 h after resuscitation.

RESULTS

P-Selectin was significantly upregulated in all of the organs studied in the Ringer's lactate resuscitation group (P < 0.001). Resuscitation with dextran 70 and administration of pentoxifylline during resuscitation prevented P-selectin upregulation. Resuscitation with human albumin caused significant attenuation but could not prevent P-selectin upregulation (p < 0.01).

CONCLUSION

Our study implies that the prevention of hemorrhagic shock-induced leukocyte-endothelium adherence by dextran 70 and pentoxifylline observed in other studies may be mediated by prevention of P-selectin expression by these agents.

The role of ischemic preconditioning in the recruitment of rolling and adherent leukocytes in hepatic venules after ischemia/reperfusion

BACKGROUND

We have recently shown that hepatic ischemia/reperfusion (I/R) results in rolling and adherence of leukocytes in terminal hepatic venules (THV) followed by hepatic enzyme elevation and tissue destruction. The objective of this study was to determine the effect of ischemic preconditioning on the recruitment of leukocytes in THV after liver I/R.

METHODS

Left hepatic lobe ischemia was induced for 5 min (preconditioning) in anesthetized C57B1/6 mice followed by reperfusion for 10 min and then prolonged ischemia for 30 min. The number of rolling, saltating, and adherent leukocytes in THV was measured at 0.5, 2, 5, 12, and 24 h after reperfusion using intravital video microscopy. Matching sham groups were evaluated after 30 min of ischemia.

RESULTS

Hepatic I/R elicited significant increases in the number of rolling, saltating, and adherent leukocytes, with peak values observed at 30 min and 5 h after reperfusion. All of these responses were significantly attenuated in mice undergoing ischemic preconditioning. Rolling leukocytes in THV following I/R without preconditioning reached peak levels of 25.2 +/- 1.4 leuk/2 min (leukocytes/2 min) at 30 min reperfusion and 31.4 +/- 1.5 leuk/2 min at 5 h reperfusion. With ischemic preconditioning these values fell to 12.3 +/- 0.9 leuk/2 min and 14.4 +/- 1.0 leuk/2 min, respectively (P < 0.001). Similarly, adherent leukocytes in nonpreconditioned mice reached peak values of 4.8 +/- 1.3 leuk/2 min at 30 min reperfusion and 8.3 +/- 1.2 leuk/2 min at 5 h reperfusion compared with 2.0 +/- 1.5 leuk/2 min and 1.6 +/- 1.1 leuk/2 min in preconditioned mice, respectively (P < 0.001).

CONCLUSION

Ischemic preconditioning attenuates the initial events leading to leukocyte-mediated hepatic destruction following I/R injury. Delineating these mechanisms may play an important role in hepatic transplantation, resection, shock, and sepsis.