Selectin Inhibition Modulates NF-κ B and AP-1 Signaling After Liver Ischemia/Reperfusion

Nanotheranostics for the Management of Hepatic Ischemia-Reperfusion Injury

Hepatic ischemia-reperfusion injury (IRI), in which an insufficient oxygen supply followed by reperfusion leads to an inflammatory network and oxidative stress in disease tissue to cause cell death, always occurs after liver transplantations and sections. Although pharmacological treatments favorably prevent or protect the liver against experimental IRI, there have been few successes in clinical applications for patient benefits because of the incomprehension of complicated IRI-induced signaling events as well as short blood circulation time, poor solubility, and severe side reactions of most antioxidants and anti-inflammatory drugs. Nanomaterials can achieve targeted delivery and controllable release of contrast agents and therapeutic drugs in desired hepatic IRI regions for enhanced imaging sensitivity and improved therapeutic effects, emerging as novel alternative approaches for hepatic IRI diagnosis and therapy. In this review, the application of nanotechnology is summarized in the management of hepatic IRI, including nanomaterial-assisted hepatic IRI diagnosis, nanoparticulate systems-mediated remission of reactive oxygen species-induced tissue injury, and nanoparticle-based targeted drug delivery systems for the alleviation of IRI-related inflammation. The current challenges and future perspectives of these nanoenabled strategies for hepatic IRI treatment are also discussed.

Loss of L-selectin-guided CD8+ , but not CD4+ , cells protects against ischemia reperfusion injury in a steatotic liver

Steatotic liver responds with increased hepatocellular injury when exposed to an ischemic-reperfusion insult. Increasing evidence supports the role of immune cells as key mediators of this injury in a normal (lean) state, but data about their role in a steatotic liver are practically nonexistent. The objective of the current study was to delineate the contribution of specific phenotypes of T cells and adhesion molecules in exacerbated cell death in steatotic liver injury. RNA sequencing was performed on isolated steatotic primary hepatocytes, and T-cell markers were assessed in hepatic lymphocytes after ischemia reperfusion injury (IRI) in high-fat diet (HFD)-fed mice. Cluster of differentiation 8 knockout (CD8^-/- ) and CD4^-/- mice along with CD8 and L-selectin antibody-treated mice were fed an HFD, and hepatocellular injury was assessed by histology, propidium iodide injection, and alanine aminotransferase after IRI. RNA sequencing demonstrated a strikingly differential gene profile in steatotic hepatocytes versus lean hepatocytes. After injury, the HFD liver showed increased necrosis, infiltrating CD8⁺ cells, alanine aminotransferase, and proinflammatory cytokines. Hepatic lymphocytes demonstrated increased CD8⁺ /CD62L⁺ (L-selectin) cells in HFD-fed mice after IRI. CD8^-/- mice and CD8-depleted C57BL/6 mice demonstrated significant protection from injury, which was not seen in CD4^-/- mice. L-selectin blockade also demonstrated significant hepatoprotection from IRI. L-selectin ligand MECA-79 was increased in HFD-fed mice undergoing IRI.

CONCLUSION

Blockade of CD8 and L-selectin, but not CD4, ameliorated hepatocellular injury, confirming that CD8⁺ cells are critical drivers of injury in a steatotic liver; this represents a therapeutic target in steatotic liver injury, underlining the importance of development of therapies specific to a steatotic liver. (Hepatology 2017;66:1258-1274).

Cyclopamine attenuates acute warm ischemia reperfusion injury in cholestatic rat liver: hope for marginal livers

Cholestasis is a significant risk factor for immediate hepatic failure due to ischemia reperfusion (I/R) injury in patients undergoing liver surgery or transplantation. We recently demonstrated that inhibition of Hedgehog (Hh) signaling with cyclopamine (CYA) before I/R prevents liver injury. In this study we hypothesized that Hh signaling may modulate I/R injury in cholestatic rat liver. Cholestasis was induced by bile duct ligation (BDL). Seven days after BDL, rats were exposed to either CYA or vehicle for 7 days daily before being subjected to 30 min of ischemia and 4 h of reperfusion. Expression of Hh ligands (Sonic Hedgehog, Patched-1 and Glioblastoma-1), assessment of liver injury, neutrophil infiltration, cytokines, lipid peroxidation, cell proliferation and apoptosis were determined. Significant upregulation of Hh ligands was seen in vehicle treated BDL rats. I/R injury superimposed on these animals resulted in markedly elevated serum alanine transaminase (ALT), aspartate transaminase (AST), total bilirubin accompanied with increased neutrophil recruitment and lipid peroxidation. Preconditioning with CYA reduced the histological damage and serum liver injury markers. CYA also reduced neutrophil infiltration, proinflammatory cytokines such as TNF-α and IL-1β expression of α-smooth muscle actin and type 1 collagen resulting in reduced fibrosis. Furthermore CYA treated animals showed reduced cholangiocyte proliferation, and apoptosis. Hepatoprotection by CYA was conferred by reduced activation of protein kinase B (Akt) and extracellular signal regulated kinase (ERK). Endogenous Hh signaling in cholestasis exacerbates inflammatory injury during liver I/R. Blockade of Hh pathway represents a clinically relevant novel approach to limit I/R injury in cholestatic marginal liver.

Hepatic ischemia-reperfusion injury and therapeutic strategies to alleviate cellular damage

Warm hepatic ischemia-reperfusion injury is a significant medical problem in many clinical conditions such as liver transplantation, hepatic surgery for tumor excision, trauma and hepatic failure after hemorrhagic shock. Partial or, mostly, total interruption of hepatic blood flow is often necessary when liver surgery is performed. This interruption of blood flow is termed "warm ischemia" and upon revascularization, when molecular oxygen is reintroduced, the organ undergoes a process called "reperfusion injury" that causes deterioration of organ function. Ischemia reperfusion results in cellular damage and tissue injury associated with a complex series of events. Pathophysiological mechanisms leading to tissue injury following ischemia-reperfusion will be discussed and therapies targeted to reduce liver damage will be summarized within this review.

Neutrophil phenotype and function in partial hepatectomy in man

PURPOSE

Hepatic resections are still associated with considerable morbidity mainly because of postoperative infection. Adequate function of neutrophils is a crucial element in host defense. The aim of the study was to characterize neutrophils during partial hepatectomy.

METHODS

Fourteen patients undergoing partial liver resection were enrolled. Twenty-four hours pre-, intra- (after induction of anesthesia, after preparation of the liver, and 15 min after release of the Pringle maneuver), as well as postoperatively (3 h after Pringle; 24, 48, and 120 h after surgery), blood samples were obtained. In addition, healthy volunteers (n = 5) were investigated. Adhesion molecules (CD 62, CD 18), Fcy receptors (CD 16, CD 32), and phagocytosis by neutrophils were characterized by fluorescence-activated cell sorter analysis. Spontaneous and stimulated (formyl-methionyl-leucyl-phenylalanine) oxygen radical generation was measured by lucigenin-enhanced chemiluminescence.

RESULTS

Numeric upregulation of CD 62 and CD 18 on neutrophils was seen before the use of Pringle maneuver and persisted thereafter (p < 0.05). Spontaneous numeric expression of Fcy receptors (CD16 and CD 32) was unchanged during liver dissection but downregulated after Pringle maneuver was opened (p < 0.05). Although numeric Fcy receptors were downregulated, phagocytosis of heterologous opsonized Escherichia coli bacteria by neutrophils was unaffected. Spontaneous oxygen radical production peaked sharply 15 min after release of the Pringle maneuver (p < 0.05), contrary to stimulated oxygen radical production, which was depressed 3 h after the release of the Pringle maneuver (ns).

CONCLUSIONS

Uneventful partial hepatectomy in man resulted already in a significant change in the phenotype but in less significant changes in the functions of neutrophils.

Selectin inhibitors and their proposed role in ischemia and reperfusion

The selectin family of cellular adhesion molecules plays an important role in the cellular infiltration and molecular signaling associated with ischemia/reperfusion (I/R). Selectins are essential in the recruitment and infiltration of leukocytes to sites of inflammation, and consequently, selectin blockade represents an important area of current research in the potential alleviation of the cell-mediated injury associated with I/R. Previously, treatments targeted at only a single selectin have proven ineffective, due to compensation by uninhibited cell-adhesion molecules. However, pan-selectin antagonists - those inhibitors capable of blocking the actions of all three selectins - have demonstrated great potential in blocking the initial events in the leukocyte-endothelium adhesion cascade. A number of therapeutics have been developed, with the most promising results demonstrated by a class of non-oligosaccharide, small-molecule selectin antagonists. TB-1269 and OC-229 are two of the most promising of inhibitors in this class - they are capable of binding all three selectins, they have been demonstrated to reduce neutrophil infiltration following ischemia/reperfusion, and they have been associated with reduced tissue damage in experimental animal models of ischemia/reperfusion involving the liver, the heart, the kidneys, and the whole body. Furthermore, TBC-1269 has recently undergone successful phase I and phase IIa clinical trials for asthma and psoriasis. Though the timing of selectin inhibition is essential in attenuating leukocyte infiltration and cell-mediated injury, the transient blockade of selectin function, in a well-controlled setting, could be an extremely beneficial intervention in ischemia/reperfusion injury.

Effect of notoginsenoside R1 on hepatic microcirculation disturbance induced by gut ischemia and reperfusion

AIM: To assess the effect of notoginsenoside R1 on hepatic microcirculatory disturbance induced by gut ischemia/reperfusion (I/R) in mice.

METHODS: The superior mesenteric artery (SMA) of C57/BL mice was ligated for 15 min to induce gut ischemia followed by 30-min reperfusion. In another set of experiments, R1 was continuously infused (10 mg/kg per hour) from 10 min before I/R until the end of the investigation to study the influence of R1 on hepatic microcirculatory disturbance induced by gut I/R. Hepatic microcirculation was observed by inverted microscopy, and the vascular diameter, red blood cell (RBC) velocity and sinusoid perfusion were estimated. Leukocyte rolling and adhesion were observed under a laser confocal microscope. Thirty and 60 min after reperfusion, lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate transaminase (AST) in peripheral blood were determined. The expression of adhesion molecules CD11b/CD18 in neutrophils and tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and monocyte chemotactic protein-1 (MCP-1) in plasma were evaluated by flow cytometry. E-selectin and intercellular adhesion molecule-1 (ICAM-1) in hepatic tissue were examined by immunofluorescence.

RESULTS: After gut I/R, the diameters of terminal portal venules and central veins, RBC velocity and the number of perfused sinusoids were decreased, while the leukocyte rolling and adhesion, the expression of E-selectin in hepatic vessels and CD18 in neutrophils, IL-6, MCP-1, LDH, ALT and AST were increased. R1 treatment attenuated these alterations except for IL-6 and MCP-1.

CONCLUSION: R1 prevents I/R-induced hepatic microcirculation disturbance and hepatocyte injury. The effect of R1 is related to its inhibition of leukocyte rolling and adhesion by inhibiting the expression of E-selectin in endothelium and CD18 in neutrophils.