The protective effect of hyperbaric oxygenation on the small intestine in ischemia-reperfusion injury

Potential Advances of Adjunctive Hyperbaric Oxygen Therapy in Infective Endocarditis

Patients with infective endocarditis (IE) form a heterogeneous group by age, co-morbidities and severity ranging from stable patients to patients with life-threatening complications with need for intensive care. A large proportion need surgical intervention. In-hospital mortality is 15-20%. The concept of using hyperbaric oxygen therapy (HBOT) in other severe bacterial infections has been used for many decades supported by various preclinical and clinical studies. However, the availability and capacity of HBOT may be limited for clinical practice and we still lack well-designed studies documenting clinical efficacy. In the present review we highlight the potential beneficial aspects of adjunctive HBOT in patients with IE. Based on the pathogenesis and pathophysiological conditions of IE, we here summarize some of the important mechanisms and effects by HBOT in relation to infection and inflammation in general. In details, we elaborate on the aspects and impact of HBOT in relation to the host response, tissue hypoxia, biofilm, antibiotics and pathogens. Two preclinical (animal) studies have shown beneficial effect of HBOT in IE, but so far, no clinical study has evaluated the feasibility of HBOT in IE. New therapeutic options in IE are much needed and adjunctive HBOT might be a therapeutic option in certain IE patients to decrease morbidity and mortality and improve the long-term outcome of this severe disease.

Integrin-mediated adhesive properties of neutrophils are reduced by hyperbaric oxygen therapy in patients with chronic non-healing wound

In recent years, several studies suggested that the ability of hyperbaric oxygen therapy (HBOT) to promote healing in patients with diabetic ulcers and chronic wounds is due to the reduction of inflammatory cytokines and to a significant decrease in neutrophils recruitment to the damaged area. α4 and β2 integrins are receptors mediating the neutrophil adhesion to the endothelium and the comprehension of the effects of hyperbaric oxygenation on their expression and functions in neutrophils could be of great importance for the design of novel therapeutic protocols focused on anti-inflammatory agents. In this study, the α4 and β2 integrins' expression and functions have been evaluated in human primary neutrophils obtained from patients with chronic non-healing wounds and undergoing a prolonged HBOT (150 kPa per 90 minutes). The effect of a peptidomimetic α4β1 integrin antagonist has been also analyzed under these conditions. A statistically significant decrease (68%) in β2 integrin expression on neutrophils was observed during the treatment with HBO and maintained one month after the last treatment, while α4 integrin levels remained unchanged. However, cell adhesion function of both neutrophilic integrins α4β1 and β2 was significantly reduced 70 and 67%, respectively), but α4β1 integrin was still sensitive to antagonist inhibition in the presence of fibronectin, suggesting that a combined therapy between HBOT and integrin antagonists could have greater antinflammatory efficacy.

Heat Shock Protein 70 (HSP70) Reduces Hepatic Inflammatory and Oxidative Damage in a Rat Model of Liver Ischemia/Reperfusion Injury with Hyperbaric Oxygen Preconditioning

Background

Several clinical conditions can cause hepatic ischemia/reperfusion (I/R) injury. This study aimed to determine the mechanism of the protective effect of hyperbaric oxygen preconditioning (HBO₂P) on hepatic ischemia/reperfusion (I/R) injury in a rat model, and to investigate the effects on HBO₂P and I/R injury of blocking HSP70 using antibody (Ab) pretreatment.

Material/Methods

Male Sprague-Dawley rats underwent HBO₂P for 60 min at 2.0 atmosphere absolute (ATA) pressure for five consecutive days before surgical hepatic I/R injury, performed by clamping the portal vein and hepatic lobe. Four groups studied included: the non-HBO₂P+ non-I/R group, which underwent sham surgery (N=10); the non-HBO₂P + I/R group (N=10); the HBO₂P + I/R group (N=10); and the HBO₂P + HSP70-Ab + I/R group (N=10) received one dose of HSP70 antibody one day before hepatic I/R injury. Serum lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and hepatic malondialdehyde (MDA) and myeloperoxidase (MPO) were measured biochemically. Rat liver tissues were examined histologically.

Results

In rats with hepatic I/R injury without HSP70 antibody pre-treatment, HBO₂P significantly reduced hepatic injury and levels of LDH, AST, ALT, TNF-α, IL-6, MDA, and MPO levels; in comparison, the group pre-treated with an antibody to inhibit HSP70 (the HBO₂P + HSP70-Ab + I/R group) showed significant reversal of the beneficial effects of HBO₂P on hepatic I/R injury (p<0.05).

Conclusions

In a rat model of hepatic I/R injury with HBO₂P, HSP70 reduced hepatic inflammatory and oxidative damage.

The effects of scalpel, harmonic scalpel and monopolar electrocautery on the healing of colonic anastomosis after colonic resection

Purpose

In our study, the effects of harmonic scalpel, scalpel, and monopolar electrocautery usage on the health and healing of colon anastomosis after resection was investigated.

Methods

In this study, 120 female albino Wistar rats were divided into 3 groups each containing 40 rats. Group A, resection with scalpel; group B, resection with monopolar electrocautery; group C, resection with harmonic scalpel. The groups were divided into 4 subgroups consisting of 10 rats and analysed in the postoperative 1st, 3rd, 5th, and 7th days. Anastomotic bursting pressures, hydroxyproline levels and histopathological parameters were surrogate parameters for evaluating wound healing.

Results

The tissue hydroxyproline levels did not show any significant difference between the groups and subgroups. The mean bursting pressure of group A on the 5th day was significantly higher than groups B and C (P < 0.001). When the fibroblast and fibrosis scores were evaluated, scores of group C on the 5th day were significantly higher than the other groups, but the results of bursting pressures and biochemical parameters did not support the fibroblast and fibrosis scores. There were not any significant differences between the groups in other histopathologic parameters.

Conclusion

The use of monopolar electrocautery needs more attention since the device causes tissue destruction. The obliterating effect of harmonic scalpel on luminal organs is an important problem, especially if an anastomosis is planned. Despite the disadvantages of scalpel, its efficacy on early wound healing is better than the other devices.

Effects of hyperbaric oxygen on intestinal mucosa apoptosis caused by ischemia-reperfusion injury in rats

BACKGROUND

Hyperbaric oxygen (HBO) is an effective adjuvant therapy for ischemia- reperfusion (I/R) injury of the brain, small intestine and testis in addition to crushing injury. Studies have shown that HBO increases the activity of villi of the ileum 30 minutes after I/R injury. The present study aimed to observe the effect of HBO on apoptosis of epithelial cells in the small intestine during different periods of I/R and to elucidate the potential mechanisms.

METHODS

Rats were subjected to 60-minute ischemia by clamping the superior mesenteric artery and 60-minute reperfusion by removal of clamping. The rats were randomly divided into four groups: I/R group, HBO precondition or HBO treatment before ischemia (HBO-P), HBO treatment during ischemia period (HBO-I), and HBO treatment during reperfusion (HBO-R). After 60-minute reperfusion, samples of the small intestine were prepared to measure the level of ATP by using the colorimetric method and immunochemical expression of caspase-3. The levels of TNF-α in intestinal tissue were measured using the enzyme-linked immunosorbent assay method (Elisa).

RESULTS

TNF-α levels were significantly lower in the HBO-I group than in the HBO-P (P<0.05), HBO-R and I/R groups; there was no significant difference between the HBO-R and I/R groups (P>0.05). The expression of caspas-3 was significantly lower in the HBO-I group than in the HBO-P group (P<0.05); it was also significantly lower in the HBO-P group than in the I/R and HBO-R groups (P<0.05). ATP level was significantly lower in the HBO-I group than in the HBO-P group (P<0.05), and also it was significantly lower in the HBO-P group than in the I/R and HBO-R groups (P<0.05).

CONCLUSIONS

There is an association between HBO, small intestinal I/R injury, and mucosa apoptosis. HBO maintains ATP and aerobic metabolism, inhibites TNF-α production, and thus prevents intestinal mucosa from apoptosis. Best results can be obtained when HBO is administered to patients in the period of ischemia, and no side effects are produced when HBO is given during the period of reperfusion.

Preconditioned hyperbaric oxygenation protects skin flap grafts in rats against ischemia/reperfusion injury

Hyperbaric oxygen (HBO) therapy is an effective therapy for ischemia/reperfusion (I/R) injury of the brain, small intestine, testes and liver. However, the detailed molecular mechanisms underlying the effect of HBO therapy remain undetermined. In the current study, the hypothesis that preconditioning rats with HBO protects grafted skin flaps against subsequent I/R injury was investigated. In addition, the molecular mechanisms underlying HBO therapy were characterized by analyzing the roles of the following important inflammatory factors: High mobility group protein 1 (HMGB1) and nuclear factor-κ B (NF-κB). A total of 40 rats were randomly divided into the following five groups: (i) Sham surgery (SH); (ii) ischemia followed by reperfusion 3 days following surgery (I/R3d); (iii) ischemia followed by reperfusion 5 days following surgery (I/R5d); (iv) HBO preconditioning (HBO-PC) and ischemia followed by reperfusion 3 days following surgery (HBO-PC+3d); and (v) HBO-PC and ischemia followed by reperfusion 5 days following surgery (HBO-PC+5d). For the surgical procedure, all pedicled skin flaps were first measured and elevated (9×6 cm). The feeding vessels of the skin flaps were subsequently clamped for 3 h and released to restore blood flow. The rats in the HBO-PC+3d and HBO-PC+5d groups received 1 h HBO for 3 and 5 consecutive days, respectively, prior to surgery. Following surgery, the rats were euthanized, and grafted tissues were collected for western blotting and immunohistochemistry. HBO-PC increased blood perfusion in epigastric skin flaps and attenuated I/R injury following skin flap graft. Additionally, the elevated expression of HMGB1 and NF-κB proteins during I/R injury was attenuated by HBO-PC treatment. HBO-PC may therefore be applied to reduce I/R injury and improve the survival rate of grafted skin flaps. The molecular mechanisms underlying the effect of HBO therapy are associated with the attenuation of inflammatory responses.

Role of high mobility group box chromosomal protein 1 in ischemia-reperfusion injury in the rat small intestine

BACKGROUND

High mobility group box chromosomal protein 1 (HMGB1) has recently been shown to be an important late mediator of endotoxic shock and sepsis. The purpose of the present study was to investigate the role of HMGB1 in response to ischemia-reperfusion injury.

METHODS

Ischemia-reperfusion injury was induced in male Wistar rats by clamping the superior mesenteric artery for 60 min. Using this model, the serum concentrations and localization of HMGB1 were investigated. The histologic findings from reperfused intestines and the survival rates were compared between the anti-HMGB1 antibody treatment groups (group A treated with 6.0 mg/kg antibody and group B with 0.6 mg/kg antibody) and the control antibody treatment group (control group).

RESULTS

Serum HMGB1 concentrations increased early after reperfusion and peaked at 3 h. Immunohistochemistry for HMGB1 revealed a high degree of positive staining in the epithelial cells of the damaged villi. Anti-HMGB1 antibody treatment significantly reduced this damage (P < 0.05) and improved the 48-h survival rate (90% in group A versus 50% in the controls; P < 0.05).

CONCLUSIONS

These results suggest that HMGB1 plays a key role in small intestinal ischemia-reperfusion injury.

Effect of hyperbaric oxygen therapy on esophagojejunal anastomosis healing in rats

PURPOSE

To evaluate hyperbaric oxygen therapy (HBO) after esophagojejunal anastomosis in a rat experimental model and the effect of HBO on the healing of esophagojejunal anastomosis in gastrectomized rats.

METHODS

Forty adult male Wistar rats, weighing 322 g to 506 g, were divided into two random groups. In group A (control group), 20 rats were subjected to total gastrectomy. In group B, 20 rats were similarly gastrectomized, but also received postoperative HBO treatment for 90 minutes/day for seven days. All rats were sacrificed on the eighth postoperative day and evaluated according to the following study variables: a) presence of anastomotic fistula; b) evaluation of esophagojejunal anastomosis healing by measuring the breaking strength at the suture line as per Hendriks & Mastboom; and c) determining the collagen concentration in the anastomosis, as per Kovács criteria. For the comparative statistical analysis between groups, Student's "t" test was used. A value of p<0.05 was considered significant.

RESULTS

There was a 20% mortality rate. There were five deaths in group A and three in group B (p=N.S.). There was only one anastomotic fistula in each group, and neither caused any morbidity or death. Breaking strength measured at the suture line (p=0.528) and collagen concentration determined at the esophagojejunal anastomosis (p=0.89) were not significantly different between Groups A and B.

CONCLUSION

Hyperbaric oxygen therapy did not affect the healing process of esophagojejunal anastomosis.

Beneficial effects of hyperbaric oxygen pretreatment on massive hepatectomy model in rats

BACKGROUND

The purpose of this study was to investigate the impact of hyperbaric oxygen (HBO) pretreatment in massive hepatectomy model, a surrogate model of small-for-size graft, using rats.

METHODS

(Experiment I) Rats were divided into the following four groups: HBO (-), HBO-1D (day), HBO-3D, and HBO-5D. Samples were taken after the completion of HBO pretreatment, and the following parameters were evaluated: reverse transcription polymerase chain reaction and immunohistochemical staining for HSP 70 and HO-1; biochemical parameters; and liver weight to body weight ratio (Lw/Bw ratio). (Experiment II) Rats were divided into four groups as follows; 70% hepatectomy (Hx), 70% Hx-HBO, 90% Hx, and 90% Hx-HBO group. Samples were taken 12, 24, 48, and 72 hr after hepatectomy and the following parameters were investigated: biochemical analysis; Lw/Bw ratio; PCNA labeling index; and survival.

RESULTS

(Experiment I) The expression of HSP70 mRNA was significantly increased in the HBO-3D group compared with the HBO (-) group (P<0.05). HSP70- and HO-1-positive hepatocytes were significantly increased in the HBO-3D group compared with the HBO (-) group (P<0.05). (Experiment II) Transaminases were significantly decreased in both 70% and 90% Hx-HBO groups compared with Hx alone group (P<0.05). The Lw/Bw ratio and PCNA labeling index of the 90% Hx-HBO group were significantly increased compared with the 90% Hx group, 24, 48 and 72 hr after hepatectomy (P<0.05). The survival rate in the 90% Hx-HBO group was significantly higher than that in the 90% Hx group (P=0.01).

CONCLUSIONS

HBO pretreatment had beneficial effects in a massive hepatectomy model in rats via the induction of HSP70 and HO-1.

Hyperbaric oxygenation attenuates renal ischemia-reperfusion injury in rats

BACKGROUND

Oxygen-derived free radicals play an important role in ischemia-reperfusion injury (IR). Hyperbaric oxygenation (HO) decreases free radical production. The aim of this study was to determine the effect of HO treatment on renal ischemia-reperfusion injury in rats.

METHODS

Rats were divided into four groups. All groups underwent right nephrectomy. Group I served as the control group; group II had left renal ischemia-reperfusion; group III was pretreated with HO; and group IV, ischemia-reperfusion and HO pretreatment. Tissue malondialdehyde (MDA) and glutathione (GSH) levels were measured, and histopathologic damage scored.

RESULTS

HO pretreatment significantly decreased tissue MDA levels and histopathologic scores among rats with IR. There was an increased GSH in HO-pretreated rats with IR; however, the difference was not significant.

CONCLUSION

HO prior to ischemia displayed a beneficial effect on renal IR by reducing oxygen radical peroxidation of lipid membranes.

Fasciotomy closure using simultaneous vacuum-assisted closure and hyperbaric oxygen

Fasciotomies performed for compartment syndrome and ischemic vascular disease often requires closure in 2 to 4 weeks by skin graft. This leaves the patient with an unsightly scar and a limb with reduced strength. The use of vacuum-assisted closure (VAC) and hyperbaric oxygen therapy (HBOT) quickly reduce the edema and permit earlier closure with adjacent skin. A study of three trauma patients with compartment syndrome, fasciotomies, and the use of the VAC and HBOT to close the fasciotomy wounds with adjacent skin is presented. The pathophysiology of compartment syndrome and ischemia-reperfusion syndrome is discussed. These patients had closure of the fasciotomy wounds in 3 to 18 days. The simultaneous use of HBOT and VAC accelerates the reduction of edema in a synergistic fashion, permitting early closure of fasciotomy wounds.

Hyperbaric Oxygen Therapy Attenuates Renal Ischemia/Reperfusion Injury in Rats

OBJECTIVE

Renal ischemia/reperfusion (I/R) injury occurs in both native and transplanted kidneys. Hyperbaric oxygen (HBO) has been shown to prevent I/R injury in different tissues. The aim of this study was to evaluate the effect of HBO on renal I/R injury in rats.

MATERIALS AND METHODS

Sprague-Dawley rats were randomly assigned to one of three groups. The Control group (n = 6) received right nephrectomy. The I/R (n = 6) and I/R+HBO groups (n = 6) received 30 min left renal ischemia followed by 24 h of reperfusion after right nephrectomy. The I/R+HBO group (n = 6) received additional HBO therapy for 60 min at 2.5 absolute atmospheres starting at the initial 15th minute of reperfusion.

RESULTS

In the I/R group, blood urea nitrogen (BUN) and creatinine levels increased significantly compared with the Control and I/R+HBO groups (p < 0.05). BUN and creatinine levels were similar in the Control and I/R+HBO groups. Kidney samples from I/R group rats revealed severe tubular damage and neutrophil infiltration at histopathological examination. The animals treated with HBO showed markedly improved lesions and less neutrophil infiltration compared with the I/R group (p < 0.05).

CONCLUSIONS

HBO exhibited marked protection against I/R injury in this study as measured using BUN and creatinine levels and renal histopathology. However, further studies are needed to clarify the renoprotective effect of HBO on I/R injury.

Can hyperbaric oxygen be used as adjunctive heart failure therapy through the induction of endogenous heat shock proteins?

Heart failure (HF) is a chronic condition that is expected to increase in incidence along with increased life expectancy and an aging population. As the incidence of HF increases, the cost to national healthcare budgets is expected to run into the billions. The costs of lost productivity and increased social reliance on state support must also be considered. Recently, acute myocardial infarction (AMI) has come to be seen as the major contributing factor to HF. Although thrombolysis may restore coronary perfusion after an AMI, it may also introduce ischemic reperfusion injury (IRI). In an attempt to ameliorate sustained protein damage caused by IRI, endogenous chaperone proteins known as heat shock proteins (HSPs) are induced as a consequence of the stress of IRI. Recently, hyperbaric oxygen has been shown to induce the production of HSPs in noncardiac tissue, with a resultant protective effect. This current opinion review article suggests a possible role for hyperbaric oxygen, as a technologically modern drug, in augmenting the induction of endogenous HSPs to repair and improve the function of failing hearts that have been damaged by AMI and IRI. In addition, this simple, safe, noninvasive drug may prove useful in easing the economic burden of HF on already overextended health resources.

Hyperbaric oxygen: a novel technology for modulating myocardial schemia-reperfusion via a single drug

Over the years, the anecdotal medical use of oxygen has demonstrated, in a non-evidence-based manner, that it may have wide-ranging clinical consequences. Although oxygen is a critical substrate in the alleviation of hypoxia, anoxia, and ischemia, paradoxically, it also functions as a deleterious metabolite during the reperfusion of previously ischemic tissues. In adding to this controversy, a spate of new pioneering work has identified hyperoxygenation (hyperoxia) and its metabolites as solely and purposefully demonstrating cellular and clinical benefit,particularly in the field of ischemic reperfusion injury (IRI). Furthermore, the beneficial effects of oxygen have been technologically augmented by administration at doses above atmospheric pressure and at higher concentrations. The novel technology that involves oxygen treatment at supra-atmospheric pressures in high concentrations is known as hyperbaric oxygen (HBO). Although the concept of hyperbaric oxygen has been around since the mid 20th century, it is only during the past decade or so that its therapeutic potential as a new technology-based drug has been exploited for the purposes of cellular tolerance and protection. HBO has recently been shown to be a useful adjunct in several models of IRI, including myocardial infarction. How it does this remains to be elucidated. This article attempts to bring into the spotlight some pertinent developments regarding HBO and myocardial IRI, while simultaneously stimulating intellect, thought, and discussion as to whether this novel technology--HBO--which consists of only a singular drug--oxygen--is a therapy that warrants further laboratory and clinical investigation as a therapeutic modality that may be safe and cost-effective, without producing significant adverse effects.

Hyperbaric oxygen: a new drug in myocardial revascularization and protection?

Ischemia-reperfusion injury (IRI) occurs following coronary artery revascularization. Reactive oxygen species (ROS) were initially thought to play a role in the pathogenesis of this injury. However, the evidence for this is inconclusive. Recent studies involving ischemic preconditioning have identified ROS as potential mediators for the cardioprotective effects observed following this technique. Furthermore, cardiac studies involving IRI and the use of hyperbaric oxygen (HBO) have demonstrated the ability of HBO to induce cardioprotection and to attenuate IRI. This review suggests the possible role for HBO as a new drug in the arena of myocardial revascularization and cellular protection. While there is mounting clinical evidence for this, a methodological understanding of HBO's cellular mechanisms of actions appears to be lacking. As such, this article attempts to draw the similarity between HBO and other protective oxidative stress mechanisms and then to speculate in an evidence-based manner its possible cellular mechanistic role as a drug via the generation of ROS.

Preconditioned hyperbaric oxygenation protects the liver against ischemia-reperfusion injury in rats

Hyperbaric oxygen (HBO) therapy is an effective adjunct in treating ischemia-reperfusion (I/R) injury of brain, small intestine, testis, and crushing extremities. This study was designed to test the hypotheses that preconditioning the rats with HBO could protect the liver against subsequent I/R injury. Daily treatment with one-dose HBO (90 min, 2.5 ATA) was brought about for male Sprague Dawley rats for 1 to 3 days before an I/R injury of liver. Hepatic expression of heat-shock protein 70 (Hsp70), total concentration of glutathione (GSH), activity of catalase, superoxide dismutase (SOD), and serum AST and ALT were estimated before and after HBO, as well as after I/R injury. The results showed that activity of hepatic catalase was decreased by one dose, but not three doses, of HBO as compared with baseline data. However, hepatic Hsp70 expression fluctuated insignificantly. AST and ALT increase less in rats preconditioned with one-dose HBO as compared with those without HBO or with three-dose HBO. Our results showed preconditioning by one-dose HBO protects rat liver against subsequent ischemia-reperfusion injury.

Beneficial effect of hyperbaric oxygenation on liver regeneration in cirrhosis

BACKGROUND

Underlying hepatic injury and cirrhosis are leading factors that interfere with the post-operative liver regeneration and function. Hyperbaric oxygenation (HBO) has been reported to ameliorate the ischemia-reperfusion injury of the liver, to induce compensatory hypertrophy of the predicted remnant liver in rats after portal vein ligation and to augment liver regeneration after hepatectomy in non-cirrhotic rats. Our aim was to determine the effect of HBO treatment on liver regeneration after partial hepatectomy in normal and cirrhotic mice in this experimental study.

MATERIALS AND METHODS

The effect of HBO on liver regeneration was studied in a mice model combining carbon tetrachloride induced cirrhosis and partial hepatectomy. Mice were divided into four groups: Control, cirrhotic, non-cirrhotic HBO-treated, and cirrhotic HBO-treated. All animals underwent 40% hepatectomy. Liver regeneration was evaluated by the proliferating cell nuclear antigen-labeling index. Serum aspartate aminotransferase and alanine aminotransferase levels were measured to evaluate liver injury.

RESULTS

Serum alanine aminotransferase and aspartate aminotransferase levels were significantly decreased in HBO-treated cirrhotic group compared to cirrhosis group after hepatectomy (P = 0.001 and P = 0.014, respectively). The proliferating cell nuclear antigen labeling index was significantly higher in HBO treated cirrhotic group than in cirrhotic group after hepatectomy (P = 0.022).

CONCLUSIONS

Our results suggest that HBO treatment improves liver functions and augments hepatocyte regeneration in cirrhotic mice after hepatectomy. Post-operative HBO treatment may have a beneficial effect on post-operative liver function and regeneration in cirrhotic patients.

The Effect of Hyperbaric Oxygen on Ischemia–Reperfusion Injury

The effect of hyperbaric oxygen is known to increase survival of ischemic tissue but its mechanism is not fully understood. The purpose of this study was to evaluate the effect of hyperbaric oxygen on a rat musculocutaneous flap versus ischemia-reperfusion injury, focusing on the mechanism involving the expression of adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) of endothelial cells and CD18 of neutrophils. A transverse rectus abdominis musculocutaneous (TRAM) flap (6 x 5 cm) supplied by a single superior epigastric vascular pedicle was elevated in 100 Sprague-Dawley rats. The rats were divided into 4 groups: group 0, sham (n = 10); group I, 4 hours of ischemia followed by reperfusion (n = 30); group II, 4 hours of ischemia and hyperbaric oxygen (100% oxygen, 2.5 atm absolute, during the last 90 minutes of ischemia before reperfusion) followed by reperfusion (n = 30); and group III, 4 hours of ischemia followed by reperfusion and hyperbaric oxygen (100% oxygen, 2.5 atm absolute, after reperfusion for 90 minutes; n = 30). The study consisted of gross examination for flap survival, histology, immunohistochemical staining, myeloperoxidase assay, flow cytometric study of CD18, and Northern blot analysis on ICAM-1 messenger ribonucleic acid expression. Gross measurement of the flap showed increased survival in groups II and III compared with group I (P < 0.05). The leukocytes adherent to the endothelium were counted at 24 hours and on day 5. Group I leukocytes were significantly increased compared with groups II and III (P < 0.05). The myeloperoxidase assay of TRAM flaps at 24 hours revealed a significant increase in group I compared with groups II and III (P < 0.05). The expression of CD18 was similar between groups I, II, and III. Immunohistochemical staining for ICAM-1 and Northern blot analysis on ICAM-1 messenger ribonucleic acid showed decreased expression in groups II and III compared with group I. Throughout the analysis, groups II and III did not show any significant differences. These results suggests that hyperbaric oxygen reduces the accumulation of leukocytes in the TRAM flap, but not enough to prevent adhesion of neutrophils on endothelial cells; ischemia-reperfusion injury increases the expression of CD18 and ICAM-1 and causes increased adhesion of leukocytes on the endothelium; hyperbaric oxygen does not alter the expression of CD18 but decreases the expression of ICAM-1; and the point of application for hyperbaric oxygen, whether applied before or after reperfusion, did not show any differences in outcome. In conclusion, the application of hyperbaric oxygen against ischemia-reperfusion injury increases flap survival and the beneficial effect may be explained by a protective mechanism involving downregulation of ICAM-1 on endothelial cells.

The role of tumor necrosis factor-alpha and interleukin-1beta in ischemia-reperfusion injury of the rat small intestine

BACKGROUND

To determine the role of tumor necrosis factor (TNF) and interleukin (IL)-1 in small-intestinal ischemia-reperfusion (I-R) injury, we investigated the effect of FR 167653, a specific IL-1 and TNF inhibitor, on warm I-R injury of the rat small intestine.

MATERIALS AND METHODS

Male rats treated with either saline (NS group) or FR 167653 (FR group) underwent 150 min of warm small-intestinal ischemia by applying a vascular clip at the origin of the superior mesenteric artery. In addition to the survival analyses, we investigated plasma TNF-alpha and endotoxin levels, intestinal tissue TNF-alpha and IL-1beta levels, hematocrit values and the amount of exudates in the intestinal lumen, glutamic aspartate aminotransferase (AST), and histological findings up to 120 min after reperfusion.

RESULTS

TNF-alpha and IL-1beta levels in the intestinal tissue, and plasma TNF-alpha and endotoxin levels, were significantly (P < 0.05) reduced in the FR group. Severe mucosal damage on histological findings (120 min after reperfusion) and a large amount of intraluminal exudates (60 min after reperfusion) were shown in the NS group, but these findings were significantly (P < 0.05) ameliorated in the FR group. Serum AST levels in the NS group increased 120 min after reperfusion, but this change was significantly (P<0.05) reduced in the FR group. The 30-day survival rate was 80% in the FR group and 30% in the NS group (P<0.05).

CONCLUSIONS

Dual inhibition of TNF and IL-1 effectively alleviated intestinal I-R injury, suggesting the key role of TNF and IL-1 in this pathophysiology.

Moderate hypothermia ameliorates liver energy failure after intestinal ischaemia-reperfusion in anaesthetised rats

BACKGROUND/PURPOSE

Intestinal ischaemia-reperfusion (IR) can cause liver failure. The aims of this work were to study the effects of intestinal IR on liver energy metabolism and to evaluate the effects of moderate hypothermia.

METHODS

Intestinal IR (90-minute intestinal ischaemia plus 60-minute or 240-minute reperfusion) was achieved by clamping and unclamping the superior mesenteric artery in rats. Normothermia or moderate hypothermia (30 degrees to 33 degrees C) was maintained by adjusting the environmental temperature. The ratio of hepatic inorganic phosphate to adenosine triphosphate (ATP) was monitored continuously during intestinal IR using in vivo phosphorus ((31)P) magnetic resonance spectroscopy. Phosphorus metabolites also were measured in extracts prepared from freeze-clamped liver and intestine.

RESULTS

Mortality occurred exclusively during normothermic intestinal IR. A progressive increase in the hepatic inorganic phosphate to ATP ratio after normothermic intestinal IR was observed. Moderate hypothermia delayed this effect. Analysis of liver extracts confirmed above findings. However, there was no difference in intestinal phosphocreatine or ATP between normothermic and hypothermic rats undergoing intestinal IR.

CONCLUSIONS

Intestinal IR at normothermia was associated with liver energy failure and high mortality rate. Moderate hypothermia ameliorated liver energy failure but did not attenuate intestinal energy failure after intestinal IR. Hypothermia may prove to be useful in the management of patients with intestinal IR injuries in the future.

Intestinal metabolism after ischemia-reperfusion

PURPOSE

This study explores the effects of ischemia-reperfusion on various metabolic aspects of the small intestine.

METHODS

Intestinal ischemia-reperfusion was obtained by clamping and unclamping the superior mesenteric artery in adult rats. Four groups of animals were studied: (A) sham operation for 150 minutes, (B) 90-minute intestinal ischemia, (C) 150-minute intestinal ischemia, and (D) 90-minute intestinal ischemia followed by 60-minute reperfusion. Body temperature was maintained at normothermia (36.5 to 37.5 degrees C). Concentrations of intestinal glucose, succinate, lactate, amino acids, phosphocholine (PC), glycerophosphocholine (GPC), choline, and phosphoenergetics were measured using magnetic resonance spectroscopy of freeze-clamped small intestine extracts.

RESULTS

Intestinal ischemia (groups B and C) alone caused a significant drop in glucose and phosphoenergetics but caused an increase in amino acids, succinate, and lactate. Ischemia and ischemia-reperfusion decreased PC and GPC but increased choline. After intestinal reperfusion (group D), no recovery of phosphoenergetics was observed, but there was partial recovery of glucose, succinate, lactate, and amino acids.

CONCLUSIONS

There is no recovery of phosphoenergetics after 90 minutes of intestinal ischemia followed by 60 minutes of reperfusion. Partial recovery of glucose, succinate, lactate, and amino acids may reflect equilibration of these metabolites between damaged cells and extracellular fluid.

Basic mechanisms of hyperbaric oxygen in the treatment of ischemia-reperfusion injury

HBO treatment affects many of the components involved in I/R injury, including PMNL function, endothelial CAM expression, NO production, NOS expression, cellular energetics, lipid peroxidation, and microvascular blood flow. Given the variety of models used to study the individual components involved in I/R injury, it is difficult to determine which is the predominant factor affected by HBO and which generates the observed beneficial outcomes in most systems. Experimental differences in the types of I/R injury, the timing of HBO treatment relative to the I/R injury (before, during, after, or delayed), the duration of HBO treatment pressure and duration, and the time of outcome measurements confound our ability to compare studies and determine the key beneficial factor. Upon review, it is likely that the sum of many of these effects is responsible for the final outcome. We have been presented with many of the pieces of the puzzle with respect to the beneficial effect of HBO in ischemia-reperfusion injury states. Hopefully, future studies will unite them into a clear picture of the basic mechanism(s) responsible for the benefits of hyperbaric oxygen therapy.

Ischaemia-reperfusion injury to the intestine

Ischaemia-reperfusion injury (IRI) is of obvious relevance in situations where there is an interruption of blood supply to the gut, as in vascular surgery, or in the construction of free intestinal grafts. It is now appreciated that IRI also underlies the guy dysfunction that occurs in early shock, sepsis, and trauma. The events that occur during IRI are complex. However, recent advances in cellular biology have started to unravel these underlying processes. The aim of this review is to provide an outline of current knowledge on the mechanisms and consequences of IRI. Initially, IRI appears to be mediated by reactive oxygen metabolites and, at a later stage, by the priming and activation of polymorphonuclear neutrophils (PMN). Ischaemia-reperfusion injury can diminish the barrier function of the gut, and can promote an increase in the leakage of molecules (intestinal permeability) or the passage of microbes across the wall of the bowel (bacterial translocation). Ischaemia-reperfusion injury to the gut can result in the generation of molecules that may also harm distant tissues.

Hyperbaric oxygen pretreatment attenuates hepatic reperfusion injury

Microcirculatory derangement, energy depletion and lipid peroxidation have been related to development of ischemia-reperfusion injury in the liver. This study investigates the effects of hyperbaric oxygen (HBO) on hepatic ischemia-reperfusion injury. Adult, male Sprague-Dawley rats were used. Three groups were evaluated: 1) sham-operated control (laparotomy only, no ischemia, no HBO), n=8; 2) ischemia control (1-h ischemia, 2-h reperfusion, no HBO), n=8; and 3) HBO pretreatment (100%, oxygen, 2.5 atm absolute, 90 min) plus ischemia (1-h ischemia, 2-h reperfusion), n=8. An in vivo microscope was used to investigate hepatic microcirculation. Tissue malondialdehyde (MDA) and adenosine triphosphate (ATP) were determined. In comparison with the ischemia control group, HBO significantly improved harmful insults following ischemia-reperfusion. HBO lessened adherent leukocyte count (6.00+/-1.31 cells/200 microm vs 11.38+/-2.88 cells/200 microm), and improved flow velocity (1.72+/-0.26 mm/s vs 0.83+/-0.19 mm/s) in post-sinusoidal venules. HBO also reduced MDA (1.04+/-0.24 nmol/mg protein vs 2.24+/-0.49 micromol/g protein), and increased ATP (2.03+/-0.17 micromol/g wet wt vs 0.73+/-0.11 micromol/g wet wt) levels. This study demonstrates that HBO before ischemia may ameliorate the ischemia-reperfusion injury of the liver in the rat model.