Induction of heme oxygenase-1 and dilatation of hepatic sinusoids by an administration of pyrrolidine dithiocarbamate in rat livers

Hepatic Stellate Cells Play a Functional Role in Exacerbating Ischemia-Reperfusion Injury in Rat Liver

PURPOSE

The involvement of hepatic stellate cells (HSCs) with ischemia-reperfusion (I/R) injury in rat liver was examined using gliotoxin, which is known to induce HSC apoptosis.

METHODS

Male Sprague-Dawley rats were used. HSC was represented by a glial fibrillary acidic protein (GFAP)-positive cell. Liver ischemia was produced by cross-clamping the hepatoduodenal ligament. The degree of I/R injury was evaluated by a release of aminotransferases. Sinusoidal diameter and sinusoidal perfusion rates were examined using intravital fluorescence microscopy.

RESULTS

Gliotoxin significantly decreased the number of GFAP-positive cells 48 h after dosing (2.50 ± 0.19% [mean ± SD] in the nontreated group vs. 1.91 ± 0.46% in the gliotoxin-treated group). Liver damage was significantly suppressed by the pretreatment with gliotoxin. Sinusoidal diameters in zone 3 were wider in the gliotoxin group (10.25 ± 0.35 µm) than in the nontreated group (8.21 ± 0.50 µm). The sinusoidal perfusion rate was maintained as well in the gliotoxin group as in normal livers, even after I/R.

CONCLUSIONS

Pretreatment with gliotoxin significantly reduced the number of HSCs in the liver and further suppressed liver injury following I/R. It is strongly suggested that HSCs play a functional role in exacerbating the degree of I/R injury of the liver.

Haemoxygenase modulates cytokine induced neutrophil chemoattractant in hepatic ischemia reperfusion injury

AIM

To investigate the hepatic microcirculatory changes due to Haemoxygenase (HO), effect of HO inhibition on remote ischemic preconditioning (RIPC) and modulation of CINC.

METHODS

Eight groups of animals were studied - Sham, ischemia reperfusion injury (IRI) the animals were subjected to 45 min of hepatic ischemia followed by three hours of reperfusion, RIPC (remote ischemic preconditioning) + IRI group, remote ischemic preconditioning in sham (RIPC + Sham), PDTC + IR (Pyridodithiocarbamate, HO donor), ZnPP + RIPC + IRI (Zinc protoporphyrin prior to preconditioning), IR-24 (45 min of ischemia followed by 24 h of reperfusion), RIPC + IR-24 (preconditioning prior to IR). After 3 and 24 h of reperfusion the animals were killed by exsanguination and samples were taken.

RESULTS

Velocity of flow (160.83 ± 12.24 μm/s), sinusoidal flow (8.42 ± 1.19) and sinusoidal perfusion index (42.12 ± 7.28) in hepatic IR were lower (P < 0.05) in comparison to RIPC and PDTC (HO inducer). RIPC increased velocity of flow (328.04 ± 19.13 μm/s), sinusoidal flow (17.75 ± 2.59) and the sinusoidal perfusion index (67.28 ± 1.82) (P < 0.05). PDTC (HO induction) reproduced the effects of RIPC in hepatic IR. PDTC restored RBC velocity (300.88 ± 22.109 μm/s), sinusoidal flow (17.66 ± 3.71) and sinusoidal perfusion (82.33 ± 3.5) to near sham levels. ZnPP (HO inhibition) reduced velocity of flow of RBC in the RIPC group (170.74 ± 13.43 μm/s and sinusoidal flow in the RIPC group (9.46 ± 1.34). ZnPP in RIPC (60.29 ± 1.82) showed a fall in perfusion only at 180 min of reperfusion. Neutrophil adhesion in IR injury is seen in both postsinusoidal venules (769.05 ± 87.48) and sinusoids (97.4 ± 7.49). Neutrophil adhesion in RIPC + IR injury is reduced in both postsinusoidal venules (219.66 ± 93.79) and sinusoids (25.69 ± 9.08) (P < 0.05). PDTC reduced neutrophil adhesion in both postsinusoidal venules (89.58 ± 58.32) and sinusoids (17.98 ± 11.01) (P < 0.05) reproducing the effects of RIPC. ZnPP (HO inhibition) increased venular (589.04 ± 144.36) and sinusoidal neutrophil adhesion in preconditioned animals (121.39 ± 30.65) (P < 0.05). IR after 24 h of reperfusion increased venular and sinusoidal neutrophil adhesion in comparison to the early phase and was significantly reduced by RIPC. Hepatocellular cell death in IRI (80.83 ± 13.03), RIPC + IR (17.35 ± 2.47), and PTDC + IR (11.66 ± 1.17) reduced hepatocellular death. ZnPP + RIPC + IR (41.33 ± 3.07) significantly increased hepatocellular death (P < 0.05 PTDC/RIPC vs ZnPP and IR). The CINC cytokine levels in sham (101.32 ± 6.42). RIPC + sham (412.18 ± 65.24) as compared to sham (P < 0.05). CINC levels in hepatic IR were (644.08 ± 181.24). PDTC and RIPC CINC levels were significantly lower than hepatic IR (P < 0.05). HO inhibition in preconditioned animals with Zinc protoporphyrin increased serum CINC levels (521.81 ± 74.9) (P < 0.05). The serum CINC levels were high in the late phase of hepatic IR (15306 ± 1222.04). RIPC reduced CINC levels in the late phase of IR (467.46 ± 26.06), P < 0.05.

CONCLUSION

RIPC protects hepatic microcirculation by induction of HO and modulation of CINC in hepatic IR.

Intestinal ischemic preconditioning ameliorates hepatic ischemia/reperfusion injury in rats: role of heme oxygenase 1 in the second window of protection

Preconditioning by brief ischemia protects not only the concerned organ but also other distant organs against subsequent lethal damage; this is called remote ischemic preconditioning (RIPC). This study was designed to investigate the impact of intestinal RIPC on hepatic ischemia/reperfusion injury (IRI) with a special interest in heme oxygenase 1 (HO-1) induction in the second window of protection (SWOP). Male Wistar rats were randomly assigned to 1 of 2 groups: an RIPC group or a sham group. Before hepatic IRI, either intestinal RIPC, consisting of 2 cycles of 4-minute superior mesenteric artery clamping separated by 11 minutes of declamping (RIPC group), or a sham procedure (sham group) was performed. After 48 hours of recovery, the rats were exposed to 30 minutes of total hepatic IRI. Transaminase releases and proinflammatory cytokines were determined at several time points after reperfusion. Histopathological analysis and animal survival were also investigated. Intestinal RIPC significantly lowered transaminase release (alanine aminotransferase at 2 hours: 873.3 ± 176.4 IU/L for the RIPC group versus 3378.7 ± 871.1 IU/L for the sham group, P < .001) as well as proinflammatory cytokine production (tumor necrosis factor α at 2 hours: 930 ± 42 versus 387 ± 17 pg/μL, P < .001). The morphological integrity of the liver and the ileum was maintained significantly better with intestinal RIPC; this reached statistical significance not only in Suzuki's liver injury score (3.5 ± 0.2 versus 0.7 ± 0.5, P = .007) but also in Park's score for intestinal damage (4.0 ± 0.4 versus 2.0 ± 0.2, P = .007). Animal survival was also markedly improved (83.1% versus 15.4%, P < .001). As a mechanism underlying this protection, HO-1 was substantially induced in liver tissue, especially in hepatocytes, with remarkable up-regulation of bradykinin in the portal blood, whereas HO-1 protein induction in enterocytes was not significant. In conclusion, intestinal RIPC remarkably attenuates hepatic IRI in the SWOP, presumably by HO-1 induction in hepatocytes.

Protective effect of heme oxygenase-1 on hepatic ischemia-reperfusion injury through inhibition of platelet adhesion to the sinusoids

BACKGROUND AND AIM

Heme oxygenase-1 (HO-1) acts as a protector against hepatic inflammatory injury. HO-1 catalyzes the conversion of heme protein to biliverdin, free iron, and carbon monoxide. Pro-inflammatory responses play critical roles in hepatic ischemia-reperfusion (I/R) injury, and carbon monoxide effectively downregulates I/R injury. The aim of this study was to evaluate the mechanism by which HO-1 reduces warm I/R injury.

METHODS

Sprague-Dawley rats were divided into two groups: the 20-min ischemia group (control group; n = 6) and the 20-min ischemia with cobalt protoporphyrin (CoPP group; n = 6). CoPP is an inducer of HO-1 in the sinusoids. Kupffer cells were labeled using the liposome entrapment method, and platelets were labeled with rhodamine-6G. The adherent platelets were observed for up to 120 min after reperfusion by intravital microscopy.

RESULTS

In the control group, the number of adherent platelets significantly increased than in the CoPP group. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were observed after 120 min of reperfusion in the control group. They were not observed in the CoPP group. In the CoPP group, serum alanine transaminase and interleukin-6 levels reduced after reperfusion. Moreover, the flow velocity of platelets in the hepatic sinusoid markedly increased.

CONCLUSIONS

This study suggests that HO-1 inhibits platelet adhesion to sinusoids. Such inhibition leads to the prevention of hepatic I/R injury.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

The in-vivo effect of pyrrolidine dithiocarbamate on hepatic parenchymal microcirculation and oxygenation of the rat liver

OBJECTIVE

Pyrrolidine dithiocarbamate has been shown to be a potent inducer of haemeoxygenase-1. This study investigated its in-vivo effects on systemic and hepatic microcirculatory perfusion.

METHODS

Male Sprague-Dawley rats (n=12) were administered intravenously with pyrrolidine dithiocarbamate (10, 20 and 50 mg/kg body weight) or vehicle (0.2 ml physiological saline) served as control. Systemic and hepatic haemodynamics including arterial oxygen saturation, heart rate, mean arterial blood pressure and portal blood flow were monitored. Microcirculation in skeletal muscle and liver was measured by laser Doppler flowmetry and intravital fluorescence microscopy, whereas hepatic tissue oxyhaemoglobin and cytochrome oxidase CuA redox state, which is an indicative of extracellular and intracellular oxygenation were measured by near infrared spectroscopy.

RESULTS

Pyrrolidine dithiocarbamate induced a dose-dependent increase in mean arterial blood pressure and skeletal muscle microcirculation. The hepatic parenchymal microcirculation was significantly improved and an increase in sinusoidal diameter and reduction in RBC velocity were observed. Pyrrolidine dithiocarbamate also showed beneficial effect on hepatic tissue oxygenation showed by an increase in oxyhaemoglobin and cytochrome oxidase CuA redox state as well.

CONCLUSION

Pyrrolidine dithiocarbamate improves hepatic parenchymal microcirculation and tissue oxygenation, suggesting that it may be used as a potential agent in pharmacological preconditioning in the liver.

Protective effects of pyrrolidine dithiocarbamate against airway inflammation in the ovalbumin-induced mouse model

Pyrrolidine dithiocarbamate (PDTC) is known to exert anti-tumor and anti-inflammatory effects. However, the effects of PDTC against airway inflammation and its underlying mechanisms have not been reported. In the present study, we examined the protective effects of PDTC in a murine model of asthma induced by ovalbumin. PDTC reduced the number of infiltrating inflammatory cells in concert with reduced eosinophil peroxidase (EPO) activity in bronchoalveolar lavage fluid. In parallel, PDTC decreased airway hyperresponsiveness in a dose dependent manner. All these effects were correlated with heme oxygenase-1 (HO-1) mRNA and protein induction, and reversed by ZnPP, a HO-1 inhibitor. In addition, PDTC reduced the secretion of Th(2) cytokines such as IL-4 and IL-5, whereas ZnPP blocked the inhibitory effects of PDTC on Th(2) cytokine secretion. These results suggest that PDTC protects against airway inflammation at least in part via HO-1 induction, and that inhibitory action on Th(2) cytokines may be associated with the protective mechanism of PDTC.

Heme Oxygenase-1 Mediated Cytoprotection Against Liver Ischemia and Reperfusion Injury: Inhibition of Type-1 Interferon Signaling

BACKGROUND

Toll-like receptor (TLR)-4 signaling plays a key role in initiating exogenous antigen-independent innate immunity-dominated liver ischemia/reperfusion injury (IRI). Heme oxygenase (HO)-1, a heat-shock protein 32, exerts potent adaptive anti-oxidant and anti-inflammatory functions. Signal transducers and activator of transcription (STAT)-1 activation triggers interferon (IFN)-inducible protein 10 (CXCL-10), one of major products of type-1 IFN pathway downstream of TLR4. This study focuses on the role of type-1 IFN pathway in the mechanism of HO-1 cytoprotection during liver IRI.

METHODS AND RESULTS

Cobalt protoporphyrin (CoPP)-induced HO-1 overexpression ameliorated liver damage in a well-defined mouse model of liver warm IRI, as evidenced by improved hepatic function (serum alanine aminotransferase levels) and liver histology (Suzuki's scores). HO-1 downregulated phospho-STAT-1 and its key product, CXCL-10. In contrast, TLR4 expression remained elevated regardless of the IRI status. To dissect the mechanism of HO-1 upon CXCL-10, we cultured RW 264.7 (macrophage) cells with exogenous rIFN-beta to stimulate CXCL-10 production via TLR4 pathway in vitro. Indeed, CoPP-induced HO-1 suppressed otherwise highly upregulated rIFN-beta-triggered CXCL-10. Moreover, consistent with our in vitro data, CoPP pretreatment diminished rIFN-beta-induced CXCL-10 production in normal mouse livers.

CONCLUSION

Hepatic IRI activates TLR4 signaling in vivo to elaborate CXCL-10. HO-1 overexpression downregulates activation of STAT1 via type-1 IFN pathway downstream of TLR4, which in turn decreases CXCL-10 production. This study provides evidence for a novel mechanism by which HO-1 exerts adaptive cytoprotective and anti-inflammatory functions in the context of innate TLR4 activation.

Pharmacological Preconditioning of Rat Liver by Up-Regulation of Heme Oxygenase 1

PURPOSE

We investigated whether pharmacologically induced up-regulation of heme oxygenase 1 by pyrrolidine dithiocarbamate (PDTC) conferred protection against subsequent ischemia-reperfusion injury (IRI) to the rat liver after temporary vascular occlusion of 70% of the organ.

METHODS

Female Wistar rats (200 to 250 g body weight) anesthetized with pentobarbitone were cannulated in the carotid artery and jugular vein. After laparotomy, a rubber band was applied around the entire vascular supply to the median and left lateral lobes, enabling vascular occlusion of 70% of the liver. A laser Doppler miniprobe was placed on the left lateral lobe to monitor peripheral liver blood flow (PLBF). Immediately upon completion of the surgery, the rats were administered either PDTC (50 mg/kg intravenously; n = 8) or its solvent (isotonic NaCl; n = 8). After 60 minutes, regional ischemia was induced for 30 minutes. The animals were then monitored for 2 hours of reperfusion. Blood samples for alanine transferase (ALT) estimation (as a measure of parenchymal injury) were drawn immediately prior to ischemia and reperfusion, as well as 60 and 120 minutes after reperfusion; PLBF was calculated at these times.

RESULTS

ALT increased in the course of the experiments but there was no difference between the groups. The reduction in PBLF due to ischemia-reperfusion was significantly lower in the PDTC group: about 16% versus 40%, after 2 hours of reperfusion.

CONCLUSION

Pretreatment with PDTC attenuated the disturbance of hepatic microcirculation, but not parenchymal injury, in the early phase of IRI.

Heme oxygenase-1 is a modulator of inflammation and vaso-occlusion in transgenic sickle mice

Transgenic sickle mice expressing betaS hemoglobin have activated vascular endothelium that exhibits enhanced expression of NF-kappaB and adhesion molecules that promote vascular stasis in sickle, but not in normal, mice in response to hypoxia/reoxygenation. Sickle mice hemolyze rbcs in vivo as demonstrated by increased reticulocyte counts, plasma hemoglobin and bilirubin, and reduced plasma haptoglobin. The heme content is elevated in sickle organs, which promotes vascular inflammation and heme oxygenase-1 expression. Treatment of sickle mice with hemin further increases heme oxygenase-1 expression and inhibits hypoxia/reoxygenation-induced stasis, leukocyte-endothelium interactions, and NF-kappaB, VCAM-1, and ICAM-1 expression. Heme oxygenase inhibition by tin protoporphyrin exacerbates stasis in sickle mice. Furthermore, treatment of sickle mice with the heme oxygenase enzymatic product carbon monoxide or biliverdin inhibits stasis and NF-kappaB, VCAM-1, and ICAM-1 expression. Local administration of heme oxygenase-1 adenovirus to subcutaneous skin increases heme oxygenase-1 and inhibits hypoxia/reoxygenation-induced stasis in the skin of sickle mice. Heme oxygenase-1 plays a vital role in the inhibition of vaso-occlusion in transgenic sickle mice.

Synergistic effects of brain death and liver steatosis on the hepatic microcirculation

BACKGROUND

The routine transplantation of steatotic livers could potentially mitigate the donor shortage, but so far is associated with a high rate of graft dysfunction. Steatosis and brain death have been perceived as independent risk factors, but they may synergistically target the hepatic microcirculation. This study compares the effects of brain death on the microcirculation of steatotic and normal livers.

METHODS

Brain death was induced in obese and lean Zucker rats. Lean and obese sham-operated animals served as controls. Liver microcirculation was investigated using intravital fluorescence microscopy. Serum liver enzyme and reduced glutathione, expression of P-selectin, ICAM-1 and VCAM-1 mRNA in the liver were determined. The ultrastructural alterations were compared by electron microscopy.

RESULTS

In nonbrain-dead animals, liver steatosis was associated with smaller sinusoidal diameters, but did not impair sinusoidal perfusion. During brain death, sinusoidal diameter and perfusion were reduced in normal and, to a greater extent, in steatotic livers. Also, more leukocytes were recruited to the microvasculature of steatotic livers than to normal livers in brain-dead state. The highest liver enzyme activities and the lowest hepatic GSH concentrations were measured in brain-dead animals with steatotic livers; only in these organs was endothelial cell swelling regularly observed. In brain-dead state, only the P-selectin mRNA expression was increased in steatotic livers as compared to normal livers.

CONCLUSIONS

Brain death amplifies the adverse effects of steatosis on the hepatic microcirculation. Our results underline the need for therapeutic intervention in brain-dead state when steatotic livers are to be used for transplantation.

The HIV protease inhibitor ritonavir synergizes with butyrate for induction of apoptotic cell death and mediates expression of heme oxygenase-1 in DLD-1 colon carcinoma cells

The protease inhibitor ritonavir is an integral part of current antiretroviral therapy targeting human immunodeficiency virus. Recent studies demonstrate that ritonavir induces apoptotic cell death with high efficiency in lymphoblastoid cell lines. Moreover, ritonavir can suppress activation of the transcription factor nuclear factor-kappaB and is an inhibitor of interleukin-1beta and tumor necrosis factor-alpha production in peripheral blood mononuclear cells. Thus, ritonavir appears to have anti-inflammatory properties. In the present study, we investigated in DLD-1 colon carcinoma cell effects of ritonavir on apoptotic cell death and expression of heme oxygenase-1 (HO-1), an anti-inflammatory enzyme that may be critically involved in the modulation of colonic inflammation. Compared to unstimulated control, ritonavir resulted in a moderate increase in the rate of apoptotic cell death as observed after 20 h of incubation. Notably, ritonavir potently synergized with the short-chain fatty acid butyrate for induction of caspase-3-dependent apoptosis in DLD-1 cells. Ritonavir enhanced mRNA and protein expression of HO-1 in DLD-1 cells. Ritonavir-induced HO-1 protein was suppressed by SB203580 or SB202190 and preceded by immediate upregulation of cellular c-Fos and c-Jun protein levels. This process was associated with induction of activator protein-1 as detected by electrophoretic mobility shift analysis. The present data suggest that ritonavir has the potential to curb colon carcinogenesis by reducing cell growth via mechanisms that include apoptosis and by simultaneously modulating colonic inflammation via induction of anti-inflammatory HO-1.