Effect of hyperbaric oxygen on liver regeneration in a rat model

Prophylactic Use of Laser Light and Methylene Blue on Ischemia and Liver Reperfusion Injury

OBJECTIVE

This study aimed to evaluate the effect of hepatic preconditioning with laser light in the presence of methylene blue (MB) in the liver ischemia-reperfusion injury process.

METHOD

Forty male Wistar rats were divided into 8 experimental groups (n = 5). Saline (.5 mL) or MB (15 mg/kg) was injected intravenously (inferior vena cava). After 2 minutes, 660 nm laser light was applied at a dose of 112.5 DE. Fifteen minutes after the application of saline or MB, 1 hour partial ischemia followed by 15 minutes of reperfusion was applied when the rats were sacrificed. The mitochondrial function parameters (O₂ consumption rates in states 3 and 4 and the respiratory control ratio), osmotic swelling, and determination of malondialdehyde were evaluated. Hepatic function was studied using the serum determination of the alanine aminotransferase and aspartate aminotransferase enzymes.

RESULTS AND CONCLUSIONS

MB therapy alone showed the capacity of preserving the rate of oxygen consumption in the mitochondrial respiratory state of the group submitted to ischemia compared to the sham group. However, when combined with low-intensity laser therapy, it failed to replicate the relevant protective effects in relation to oxidative phosphorylation or the mitochondrial membrane ischemia/reperfusion injury. Whether or not MB was combined with laser treatment, it was shown to be efficient in reducing oxidative stress. In relation to alanine aminotransferase enzymes, whether or not laser treatment was combined with MB had a protective effect on the hepatic lesion, whereas in relation to aspartate aminotransferase enzymes only laser treatment was able to provide this protection.

Repeated exposure to hyperbaric hyperoxia affects mitochondrial functions of the lung fibroblasts

Hyperbaric oxygen (HBO) therapy, i.e. breathing pure oxygen under increased environmental pressures serves as a treatment for diverse medical conditions. However, elevated oxygen concentration can be detrimental to central nervous system or lungs. Our study aimed to evaluate the effects of repeated exposure to HBO on mitochondrial respiration assessed by high-resolution respirometry (HRR), cell viability estimated by PrestoBlue® reaction, morphology analyzed by routine phase contrast and fluorescent microscopy, and superoxide dismutase (SOD) and citrate synthase (CS) activities using human lung fibroblasts. The cells were exposed to HBO for 2 h per day for 5 consecutive days. One day after the last exposure, HBO cells displayed significantly smaller area and perimeter, compromised viability and elevated SOD activity. No changes were detected in CS activity or quality of mitochondrial network. HRR revealed impaired mitochondrial oxygen consumption manifested by increased leak respiration, decreased activity of complex II and compromised ATP-related oxygen consumption when fatty acids were oxidized. Our findings document that in conditions mimicking chronic intermittent exposure to HBO, lung fibroblasts suffer from compromised mitochondrial respiration linked to complex II and impaired cellular growth in spite of increased antioxidant defense. Underlying mechanism of this HBO-induced mitochondrial dysfunction should be further explored.

Prophylactic application of laser light restores L-FABP expression in the livers of rats submitted to partial ischemia

OBJECTIVES

The objective of the present study was to evaluate the protective effect of pre-conditioning treatment with laser light on hepatic injury in rats submitted to partial ischemia using mitochondrial function and liver fatty acid binding protein as markers.

METHODS

Rats were divided into four groups (n=5): 1) Control, 2) Control + Laser, 3) Partial Ischemia and 4) Partial Ischemia + Laser. Ischemia was induced by clamping the hepatic pedicle of the left and middle lobes of the liver for 60 minutes. Laser light at 660 nm was applied to the liver immediately prior to the induction of ischemia at 22.5 J/cm2, with 30 seconds of illumination at five individual points. The animals were sacrificed after 30 minutes of reperfusion. Blood and liver tissues were collected for analysis of mitochondrial function, determination of malondialdehyde and analysis of fatty acid binding protein expression by Western blot.

RESULTS

Mitochondrial function decreased in the Partial Ischemia group, especially during adenosine diphosphate-activated respiration (state 3), and the expression of fatty acid binding protein was also reduced. The application of laser light prevented bioenergetic changes and restored the expression of fatty acid binding protein.

CONCLUSION

Prophylactic application of laser light to the livers of rats submitted to partial ischemia was found to have a protective effect in the liver, with normalization of both mitochondrial function and fatty acid binding protein tissue expression.

Hyperbaric Oxygen Therapy in Liver Diseases

Hyperbaric oxygen therapy (HBOT) is an efficient therapeutic option to improve progress of lots of diseases especially hypoxia-related injuries, and has been clinically established as a wide-used therapy for patients with carbon monoxide poisoning, decompression sickness, arterial gas embolism, problematic wound, and so on. In the liver, most studies positively evaluated HBOT as a potential therapeutic option for liver transplantation, acute liver injury, nonalcoholic steatohepatitis, fibrosis and cancer, especially for hepatic artery thrombosis. This might mainly attribute to the anti-oxidation and anti-inflammation of HBOT. However, some controversies are existed, possibly due to hyperbaric oxygen toxicity. This review summarizes the current understandings of the role of HBOT in liver diseases and hepatic regeneration. Future understanding of HBOT in clinical trials and its in-depth mechanisms may contribute to the development of this novel adjuvant strategy for clinical therapy of liver diseases.

Application of hyperbaric oxygen in liver transplantation

In recent years, hyperbaric oxygen (HBO) has been used in the treatment of a lot of diseases such as decompression sickness, arterial gas embolism, carbon dioxide poisoning, soft tissue infection, refractory osteomyelitis, and problematic wound, but little is known about its application in liver transplantation. Although several studies have been conducted to investigate the protective effects of HBO on liver transplantation and liver preservation, there are still some controversies on this issue, especially its immunomodulatory effect. In this short review, we briefly summarize the findings supporting the application of HBO during liver transplantation (including donors and recipients).

Effect of hyperbaric hepatic hyperoxia on the liver of rats submitted to intermittent ischemia/reperfusion injury

PURPOSE

To determine the effect of hyperbaric hyperoxia as hepatic preconditioning on hepatocellular integrity in rats submitted to intermittent hepatic ischemia/reperfusion injury.

METHODS

Twenty male Wistar rats were divided into 4 groups (SHAM, I/R, HBO-I/R and CONTROL). The surgical technique consisted of total clamping of the hepatic pedicle for 15 min, followed by reperfusion for 5 min, performed twice. The application of hyperbaric oxygen (HBO) was carried out in a collective chamber (simultaneous exposure of 4 rats) pressurized directly with oxygen at 2 ATA for 60 min. Tissue malondialdehyde (MDA) levels were determined and blood samples were collected for the determination of serum AST and ALT levels. Data were analyzed statistically by the Mann-Whitney test, with the level of significance set at p < 0.05.

RESULTS

A statistically significant difference in MDA (p< 0.05) was observed between control and HBO-I/R, but not between control and I/R. Regarding AST, there was a difference between control and I/R and HBO-I/R. Analysis of ALT revealed a significant difference between control and I/R (p<0.05) and between I/R and HBO-I/R, with no difference between control and HBO-IR.

CONCLUSION

Hyperoxic preconditioning proved to be favorable regarding alanine transaminase, but not aspartate aminotranserase or malondialdehyde levels.

Hyperoxic preconditioning in partial liver ischemia

PURPOSE

To evaluate the effect of the hyperbaric oxygen (HBO) treatment as a pre-conditioning for I/R effects in the liver ischemia.

METHODS

Fifty-seven male Wistar rats (260-300g) were submitted to the following procedures: SHAM; I/R, rats submitted to I/R, consisting of partial ischemia of 70% of the liver for 90 minutes followed by 15 minutes of reperfusion; HBO I/R 1 ATA, 30 minutes of HBO treatment at the pressure of 1 absolute atmosphere (ATA) during the ischemia time. HBO I/R 2 ATA, 30 minutes of HBO (2 ATA) during the ischemia time. Pre HBO I/R 30', rats submitted to 30 minutes of HBO (2 ATA) immediately before the I/R time. Pre HBO I/R 90', rats submitted to 90 minutes of HBO (2 ATA) immediately before the I/R time.

RESULTS

There was a significant worsening of all the parameters of mitochondrial energy production (state 3, 4, RCR and Swelling) in the I/R group, when compared to the Sham group (I/R <Sham, p<0.05). There was also a significant worsening in state 4, RCR and mitochondrial edema in the Pre HBO I/R 90' group compared to the I/R group. Hepatic enzyme concentrations were significantly higher in the I/R group.

CONCLUSION

The use of hyperbaric oxygen before and during I/R did not improve the production of hepatocellular energy reduced by I/R, nor did it prevent the installation of mitochondrial edema induced by Iischemia/reperfusion.

Effects of hyperbaric oxygen (HBO), as pre-conditioning in liver of rats submitted to periodic liver ischemia/reperfusion

PURPOSE

to assess the effect of hyperbaric oxygen (HBO) as pre-conditioning on periodic liver ischemia/reperfusion injury.

METHODS

Thirty-six male Wistar rats were divided into 4 groups (SHAM, I/R , HBO-I/R and CONTROL). The surgical technique consisted of total clamping of the hepatic pedicle for 15 min followed by twice repeated reperfusion for 5 min (unclamping). HBO was applied in a collective chamber (simultaneous exposure of 4 rats) directly pressurized with oxygen at 2 ATA for 60 min. Hepatic mitochondrial function was determined using samples of the median lobe obtained after exactly 5 min of reperfusion for the analysis of mitochondrial respiration based on the determination of states 3 and 4, the respiratory control ratio and the transition of mitochondrial permeability (mitochondrial swelling).Data were analyzed by the Mann-Whitney test and the level of significance was set at p < 0.05.

RESULTS

There was a statistically significant difference (p < 0.05) in state 3 between the CONTROL and I/R and HBO-I/R groups, in state 4 between the CONTROL and I/R and HBO-I/R groups; in respiratory control ratio (RCR) between the CONTROL and I/R and HBO-I/R groups and between the CONTROL and Sham groups, and in mitochondrial swelling between the CONTROL and I/R and HBO-/R groups and between the Sham and I/R and HBO-I/R groups.

CONCLUSION

In this process of periodic ischemia and reperfusion, hyperbaric pre-conditioning did not improve significantly hepatic mitochondrial function.

New method of stent-facilitated arterial reconstruction for orthotopic mouse liver transplantation

BACKGROUND

Arterialized orthotopic liver transplantation (OLT) in the mouse mimics human liver transplantation physiologically and clinically. The present method of sutured anastomosis for reconstruction of the hepatic artery is complex and is associated with high incidence of complications and failure. This makes the endpoint assessment of using this complex model difficult because of the many variables of the technical aspect.

METHODS

A total of 14 pairs of donors and recipients from syngeneic male mice were used for arterialized OLT. The grafts were stored in University of Wisconsin solution at 4°C for less than 4 h, and the recipients underwent OLT using a two-cuff technique. The arterial reconstruction was facilitated by the use of a single stent connecting the donor liver artery segment to the recipient common hepatic artery.

RESULTS

All 14 recipients survived with the time for arterial reconstruction ranging from 4-10 min. Patency of the artery was confirmed by transecting the artery near the graft 2 and 14 d after transplantation. At day 2, five of the six arteries transected were patent and at day 14, seven of the remaining eight were patent for an overall patency rate of 85.7%.

CONCLUSIONS

The stent-facilitated arterial reconstruction can be done quickly with a high patency rate. This model expands the translational research efforts to address marginal livers such as steatotic livers.

Immunoexpression of proliferating cell nuclear antigen (PCNA) in spleen of splenectomized rats with preservation of inferior pole, submitted to hyperbaric oxygenation

PURPOSE

To analyze PCNA immunoexpression on the inferior pole of the spleen of splenectomized rats submitted to hyperbaric oxygenation (HBO).

METHODS

Were analyzed fragments of the inferior pole of the spleen of 20 male Wistar rats submitted to splenectomy with preservation of the inferior pole. The rats were divided in two groups: group A (n=10) without HBO and group B (n=10) submitted to HBO at 2, 5 atmospheres per 120 minutes, twice a day for three days and once a day for seven days. The groups were then subdivided in four subgroups: A15 (n=5), with euthanasia on the 15th day; A45 (n=5), with euthanasia on the 45th day; B15 (n=5) with euthanasia on the 15th day and B45 with euthanasia on the 45th day. Respectively on these days, fragments of the inferior pole of the spleen of all animals were collected and analyzed with the immunohistochemistry technique in order to evaluate PCNA expression.

RESULTS

There was an expressive increase in PCNA immunoreactivity in the group B. The 45 day postoperative period resulted in a higher level of positivity than the 15 day postoperative period (p<0.01).

CONCLUSION

The quantitative analysis of proliferating cell nuclear antigen positive suggests that hyperbaric oxygenation increases cellular proliferation, contributing to splenic regeneration.

Effect of hyperbaric oxygen therapy on liver function during intermittent ischemia

PURPOSE: To analyze the effects of hyperbaric oxygen therapy on liver function in rats previously subjected to ischemia and reperfusion. METHODS: A randomly distribution of 23 Wistar rats was conducted into three groups: SHAM, animals subjected to surgical stress without restricting blood flow by clamping the hepatic pedicle, IR, rats underwent hepatic vascular occlusion intermittently for two complete cycles of 15 minutes of ischemia followed by 5 min of reperfusion, IR / HBO, rats underwent hepatic pedicle clamping and thereafter exposed to hyperbaric oxygen pressure of 2 absolute atmospheres for 60 minutes. We evaluated liver function through mitochondrial function, determined by the stages 3 and 4 of respiration, respiratory control ratio (RCR) and mitochondrial permeability transition (Swelling). Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were also quantified . We analyzed the results using the Mann-Whitney test and were considered significant all results with p <0.05. RESULTS: There were significant differences between the results of stage 3 in SHAM vs IR group ; of the stage 4 in the groups IR vs SHAM and SHAM vs IR /HBO; of the Respiratory Control Ratio (RCR) in the group IR vs IR / HBO ; of alanine aminotransferase in the groups IR vs SHAM , SHAM vs IR/HBO and IR vs IR / HBO; aspartate aminotransferase in the groups SHAM vs IR and SHAM vs IR / HBO. CONCLUSION: The whole analysis of the mitochondiral function indicators permits us to conclude that the hyperbaric oxygen therapy acted as a protective agent of the mitochondrial function, minimizing the ischemia-reperfusion injury of the hepatic parenchyma.

Hyperbaric oxygen therapy reduces the severity of ischaemia, preservation and reperfusion injury in a rat model of liver transplantation

BACKGROUND

  Approaches to increase organ availability for orthotopic liver transplantation (OLT) often result in the procurement of marginal livers that are more susceptible to ischaemia, preservation and reperfusion injury (IPRI).

METHODS

  The effects of post-OLT hyperbaric oxygen (HBO) therapy on IPRI in a syngeneic rat OLT model were examined at various time-points. The effects of IPRI and HBO on hepatocyte necrosis, apoptosis, proliferation, and sinusoidal morphology and ultrastructure were assessed.

RESULTS

  Post-OLT HBO therapy significantly reduced the severity of IPRI; both apoptosis [at 12 h: 6.4 ± 0.4% in controls vs. 1.6 ± 0.7% in the HBO treatment group (p < 0.001); at 48 h: 2.4 ± 0.2% in controls vs. 0.4 ± 0.1% in the HBO treatment group (p < 0.001)] and necrosis [at 12 h: 18.7 ± 1.8% in controls vs. 2.4 ± 0.4% in the HBO treatment group (p < 0.001); at 48 h: 8.5 ± 1.3% in controls vs. 3.4 ± 0.9% in the HBO treatment group (P= 0.019)] were decreased. Serum alanine transaminase was reduced [at 12 h: 1068 ± 920 IU/l in controls vs. 370 ± 63 IU/l in the HBO treatment group (P= 0.030); at 48 h: 573 ± 261 IU/l in controls vs. 160 ± 10 IU/l in the HBO treatment group (P= 0.029)]. Treatment with HBO also promoted liver regeneration [proliferation at 12 h: 4.5 ± 0.1% in controls vs. 1.0 ± 0.3% in the HBO treatment group (p < 0.001); at 48 h: 8.6 ± 0.7% in controls vs. 2.9 ± 0.2% in the HBO treatment group (p < 0.01)] and improved sinusoidal diameter and microvascular density index.

CONCLUSIONS

  Hyperbaric oxygen therapy has persistent positive effects post-OLT that may potentially transfer into clinical practice.

Hyperbaric oxygenation promotes regeneration of biliary cells and improves cholestasis in rats

AIM: To investigate the effects of hyperbaric oxygenation (HBO) on regeneration of the biliary ductal system and postoperative cholestasis in hepatectomized rats.

METHODS: HBO was performed in Wistar rats daily starting 12 h after a 70% partial hepatectomy. Regenerated liver weight, serum parameters and the proliferating cell nuclear antigen labeling index of hepatocytes and biliary ductal cells were measured. Hepatocyte growth factor (HGF), c-Met and transforming growth factor (TGF) β-1 mRNA expression levels were analyzed by quantitative reverse transcription polymerase chain reaction.

RESULTS: HBO improved the postoperative serum levels of total bile acid but not transaminase levels. HBO promoted hepatocyte and biliary ductal cell proliferation. The hematoxylin and eosin-stained specimens revealed fewer ballooned hepatocytes and higher cell densities in the HBO group compared to the control group. HBO suppressed c-Met mRNA levels at 15 h but did not modulate HGF or TGF β-1 mRNA expression levels.

CONCLUSION: HBO promoted regeneration of biliary ductal cells and improved postoperative cholestasis after a partial hepatectomy.

Can hyperbaric oxygenation decrease doxorubicin hepatotoxicity and improve regeneration in the injured liver?

BACKGROUND/PURPOSE

Portal vein embolization is used in the treatment of hepatocellular cancer, with the purpose of enhancing resectability. However, regeneration is restricted due to hepatocellular injury following chemotherapeutics (e.g. doxorubicin). The aim of this study was to investigate whether hyperbaric oxygenation (HBO) can alleviate the hepatotoxicity of chemotherapy and improve regeneration in the injured liver.

METHODS

Rats were allocated to four experimental groups. Group I rats were subjected to right portal vein ligation (RPVL); rats in groups II and III were administered doxorubicin prior to RPVL, with group III rats being additionally exposed to HBO sessions postoperatively; group IV rats was sham-operated. All rats were sacrificed on postoperative day 7, and liver injury was assessed by measuring alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Protein synthetic ability was determined based albumin levels and liver regeneration by the mitotic index (MI).

RESULTS

The AST and ALT values of group II rats were significantly higher than those of group I, but not those of group III. Rats treated with doxorubicin and HBO (groups II and III) showed slightly but not significant differences in albumin levels than those subjected to only RPVL or sham-operated. The MI was significantly increased in groups I, II, and III, with the MI of group III rats significantly higher than those of group I rats.

CONCLUSIONS

Based on our results, we conclude that HBO treatment has the potential to diminish doxorubicin-related hepatotoxicity and improve regeneration in the injured liver.

Nitric oxide reduces organ injury and enhances regeneration of reduced-size livers by increasing hepatic arterial flow

Background

Reduced-size livers suffer from portal hyperperfusion, diminished arterial blood flow and the risk of postoperative liver injury. The aim of this experimental study was to unravel the role of nitric oxide in this setting.

Methods

Rats underwent 85 per cent partial hepatectomy and either substitution of nitric oxide with molsidomine or inhibition of nitric oxide synthase (NOS) with NG-nitro-l-arginine methyl ester. Untreated hepatectomized animals served as controls and unresected animals as the sham group.

Results

Ultrasonic flowmetry following partial hepatectomy revealed a marked increase in portal venous inflow with a concomitant decrease in hepatic arterial inflow. Nitric oxide substitution counteracted the decline in hepatic arterial inflow and caused a significantly greater increase in cell proliferation after partial hepatectomy compared with control or NOS-inhibited animals. Hepatectomized animals further profited from nitric oxide substitution, as indicated by reduced aminotransferase release and improved liver function.

Conclusion

Nitric oxide improves the postoperative course of rats with reduced-size livers by modulating hepatic macrohaemodynamics and mediating regeneration and cytoprotection, but not by reducing hepatic hyperperfusion and the accompanying sinusoidal shear stress.

Strategies for improving the outcomes of small-for-size grafts in adult-to-adult living-donor liver transplantation

Living-donor liver transplantation (LDLT) has been refined and accepted as a valuable treatment for patients with end-stage liver disease in order to overcome the shortage of organs and mortality on the waiting list. However, graft size problems, especially small-for-size (SFS) grafts, remain the greatest limiting factor for the expansion of LDLT, especially in adult-to-adult transplantation. Various attempts have been made to overcome the problems regarding SFS grafts, such as increasing the graft liver volume and/or controlling excessive portal inflow to a small graft, with considerable positive outcomes. Recent innovations in basic studies have also contributed to the treatment of SFS syndrome. Herein, we review the literature and assess our current knowledge of the pathogenesis and treatment strategies for the use of SFS grafts in adult-to-adult LDLT.

Therapeutic Effect of Hyperbaric Oxygen in Hepatic Artery Thrombosis and Functional Cholestasis After Orthotopic Liver Transplantation

Among the postoperative complications, hepatic artery thrombosis can occur in up to 10% of adult orthotopic liver transplants and intervention is indicated when this occurs within 30 days by retransplantation. Primary graft dysfunction, which can occur in up to 30% of the cases and is another potential complication, although reversible, has a relatively high mortality rate. Hyperbaric therapy, an efficient mode of tissue oxygenation, is being used in an increasing number of clinical situations. We report here two cases where hyperbaric oxygen therapy greatly benefited patients with complications after orthotopic liver transplantation: one with hepatic artery thrombosis and the other with primary graft dysfunction. Both patients showed rapid clinical recovery with gradual reduction of liver and canalicular enzymes soon after commencing hyperbaric oxygen therapy.