Hyperbaric oxygenation attenuates renal ischemia-reperfusion injury in rats

Hyperbaric Oxygenation: Can It Be a Novel Supportive Method in Acute Kidney Injury? Data Obtained from Experimental Studies

Despite constant achievements in treatment, acute kidney injury (AKI) remains a significant public health problem and a cause of mortality in the human population. In developed countries, AKI is a significant and frequent hospital complication, especially among patients admitted to intensive care units, where mortality rates can reach up to 50%. In addition, AKI has been implicated as an independent risk factor for the development of chronic kidney disease. Hyperbaric oxygenation (HBO) has been used as a primary or adjunctive therapy for the past 50 years, both in experimental and clinical studies. HBO is a treatment in which the patient is occasionally exposed to 100% oxygen at a pressure greater than atmospheric pressure at sea level. However, despite decades of extensive research, the potentially beneficial effects of this therapeutic approach are still not fully understood, although many potential mechanisms have been proposed, such as antioxidative, anti-inflammatory, anti-apoptotic, etc. Furthermore, the low cost and insignificant adverse events make HBO a potentially important strategy in the prevention and treatment of different diseases. Considering all of this, this review highlights the potential role of HBO in maintaining cellular homeostasis disrupted due to AKI, caused in different experimental models.

Non-invasive physical therapy as salvage measure for ischemic skin flap: A literature review

This review focuses on the available evidence regarding the molecular mechanisms and treatment potential of several non-surgical physical therapies for managing flap ischemia to propose a non-invasive, economical, and simple treatment to improve flap survival. A review of the literature was conducted on the topics of various non-invasive methods for the treatment of ischemic necrosis of the distal end of the flap between 1988 and 2019. A total of 52 published studies were reviewed on the applications of hyperbaric oxygen therapy, electrical stimulation therapy, heat stress pretreatment, phototherapy, and vibration therapy to manage skin flap necrosis. The underlying molecular mechanisms of these physical therapies on revitalizing the dying skin flaps were discussed and preliminary clinical uses of these therapies to salvage the necrotic skin flaps were pooled and summarized for clarifying the safety and feasibility of these methods. Various physical therapy regimens have been ushered to manage necrotic development in cutaneous flaps. With the refinement of these new technologies and enhancement of related basic science research on vascular revitalization, the prevention and treatment of flap ischemia will enter a new era.

Hyperbaric Oxygen Preconditioning Upregulates Heme OxyGenase-1 and Anti-Apoptotic Bcl-2 Protein Expression in Spontaneously Hypertensive Rats with Induced Postischemic Acute Kidney Injury

Renal ischemia and reperfusion (I/R) injury is the most common cause of acute kidney injury (AKI). Pathogenesis of postischemic AKI involves hemodynamic changes, oxidative stress, inflammation process, calcium ion overloading, apoptosis and necrosis. Up to date, therapeutic approaches to treat AKI are extremely limited. Thus, the aim of this study was to evaluate the effects of hyperbaric oxygen (HBO) preconditioning on citoprotective enzyme, heme oxygenase-1 (HO-1), pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins expression, in postischemic AKI induced in normotensive Wistar and spontaneously hypertensive rats (SHR). The animals were randomly divided into six experimental groups: SHAM-operated Wistar rats (W-SHAM), Wistar rats with induced postischemic AKI (W-AKI) and Wistar group with HBO preconditioning before AKI induction (W-AKI + HBO). On the other hand, SHR rats were also divided into same three groups: SHR-SHAM, SHR-AKI and SHR-AKI + HBO. We demonstrated that HBO preconditioning upregulated HO-1 and anti-apoptotic Bcl-2 protein expression, in both Wistar and SH rats. In addition, HBO preconditioning improved glomerular filtration rate, supporting by significant increase in creatinine, urea and phosphate clearances in both rat strains. Considering our results, we can also say that even in hypertensive conditions, we can expect protective effects of HBO preconditioning in experimental model of AKI.

Effect of Hyperbaric Oxygen on Tissue Damage and Expression of Adhesion Molecules and C3 in a Rat Model of Renal Ischemia-Reperfusion Injury After Kidney Transplantation

BACKGROUND The aim of this study was to investigate the protective effect and mechanism of hyperbaric oxygen (HBO) in a rat model of renal ischemia-reperfusion injury following kidney transplantation. MATERIAL AND METHODS Sprague Dawley rats were randomly divided into 3 groups (n=18): sham group, kidney transplantation group, and HBO treatment group. Six rats in each group were sacrificed at 1, 3, and 5 hours after reperfusion, and serum and renal tissue were then collected. The serum creatinine levels and histopathological changes of the renal tissue were detected. ICAM-1, VCAM-1, and C3 expression levels were also detected by immunohistochemical staining or real-time polymerase chain reaction. RESULTS Renal function was damaged in the kidney transplantation group and the HBO treatment group compared with sham group (P<0.05). Renal histopathological changes, including tubular cell swelling, tubular dilatation, and hyaline casts, were remarkably reduced in the HBO treatment group compared to the kidney transplantation group. In the immunohistochemical examination, the expression levels of ICAM-1, VCAM-1, and C3 were obviously increased in the kidney transplantation group and the HBO treatment group; moreover, the levels in the HBO treatment group were significantly lower than in the kidney transplantation group (P<0.05). In addition, the ICAM-1 and C3 mRNA levels were increased in the kidney transplantation group and HBO treatment group, but the levels of in the HBO treatment group them were significantly decreased compared to the kidney transplantation group that at 3 and 5 hours after reperfusion (P<0.05). CONCLUSIONS HBO treatment exerted a protective effect on renal function through inhibition of adhesion molecule overexpression and complement system activation in a rat model of renal ischemia-reperfusion injury after kidney transplantation.

Attenuation of partial unilateral ureteral obstruction - induced renal damage with hyperbaric oxygen therapy in a rat model

OBJECTIVE

The objective of the present study was to evaluate the effectiveness of HBO therapy on biochemical parameters, renal morphology and renal scintigraphy in rats undergoing chronic unilateral partial ureteral obstruction (UPUO).

MATERIAL AND METHODS

Thirty-five rats were divided into five equal groups: Control group; Sham group; HBO group; UPUO group and UPUO/HBO group. The effects of HBO therapy were examined using biochemical parameters and histopathological changes. After calculating the score for each histopathological change, the total histopathological score was obtained by adding all the scores. In addition, dynamic renal scintigraphy findings were evaluated.

RESULTS

Serum parameters indicating inflammation, serum tumor necrosis factoralpha, ischemia modified-albumin, IMA/albumin ratio and Pentraxin-3 levels, were observed to be high in the UPUO group and low in the UPUO/HBO treatment group. Similarly, in the treatment group, the reduction in malondialdehyde, total oxidant status and oxidative stress index levels and increase in total antioxidant capacity values were observed to be statistically significant compared to the UPUO group (p<0.001, p=0.007, p<0.001, p=0.001, respectively). The total score and apoptosis index significantly decreased after administration of HBO treatment. Dynamic 99mTc-MAG3 renal scintigraphy also showed convincing evidence regarding the protective nature of HBO against kidney injury. In the UPUO/HBO therapy group, the percentage contribution of each operated kidney increased significantly compared to the UPUO group (41.73% versus 32.72%).

CONCLUSION

The findings of this study indicate that HBO therapy had a reno-protective effect by reducing inflammation and oxidative stress, and preserving renal function after renal tissue damage due to induction of UPUO.

Ischaemia-reperfusion injury and hyperbaric oxygen pathways: a review of cellular mechanisms

Ischaemia-induced tissue injury has wide-ranging clinical implications including myocardial infarction, stroke, compartment syndrome, ischaemic renal failure and replantation and revascularization. However, the restoration of blood flow produces a 'second hit' phenomenon, the effect of which is greater than the initial ischaemic event and characterizes ischaemia-reperfusion (IR) injury. Some examples of potential settings of IR injury include: following thrombolytic therapy for stroke, invasive cardiovascular procedures, solid organ transplantation, and major trauma resuscitation. Pathophysiological events of IR injury are the result of reactive oxygen species (ROS) production, microvascular vasoconstriction, and ultimately endothelial cell-neutrophil adhesion with subsequent neutrophil infiltration of the affected tissue. Initially thought to increase the amount of free radical oxygen in the system, hyperbaric oxygen (HBO) has demonstrated a protective effect on tissues by influencing the same mechanisms responsible for IR injury. Consequently, HBO has tremendous therapeutic value. We review the biochemical mechanisms of ischaemia-reperfusion injury and the effects of HBO following ischaemia-reperfusion.

Hyperbaric Oxygen Therapy for the Compromised Graft or Flap

Significance: Tissue grafts and flaps are used to reconstruct wounds from trauma, chronic disease, tumor extirpation, burns, and infection. Despite careful surgical planning and execution, reconstructive failure can occur due to poor wound beds, radiation, random flap necrosis, vascular insufficiency, or ischemia-reperfusion (IR). Traumatic avulsions and amputated composite tissues-compromised tissue-may fail from crush injury and excessively large sizes. While never intended, these complications result in tissue loss, additional surgery, accrued costs, and negative psychosocial patient effects. Recent Advances: Hyperbaric oxygen (HBO) has demonstrated utility in the salvage of compromised grafts/flaps. It can increase the likelihood and effective size of composite graft survival, improve skin graft outcomes, and enhance flap survival. Mechanisms underlying these beneficial effects include increased oxygenation, improved fibroblast function, neovascularization, and amelioration of IR injury. Critical Issues: Common strategies for the compromised graft or flap include local wound care, surgical debridement, and repeated reconstruction. These modalities are associated with added costs, time, need for reoperation, morbidity, and psychosocial effects. Preservation of the amputated/avulsed tissues minimizes morbidity and maximizes the reconstructive outcome by salvaging the compromised tissue and obviating additional surgery. HBO is often overlooked as a potential tool that can limit these issues. Future Directions: Animal studies demonstrate a benefit of HBO in the treatment of compromised tissues. Clinical studies support these findings, but are limited to case reports and series. Further research is needed to provide multicenter prospective clinical studies and cost analyses comparing HBO to other adjunctive therapies in the treatment of compromised grafts/flaps.

Hyperbaric oxygen therapy induces kidney protection in an ischemia/reperfusion model in rats

Ischemia/reperfusion (I/R) injury remains a major cause of graft dysfunction, which impacts short- and long-term follow-up. Hyperbaric oxygen therapy (HBO), through plasma oxygen transport, has been currently used as an alternative treatment for ischemic tissues. The aim of this study was to analyze the effects of HBO on kidney I/R injury model in rats, in reducing the harmful effect of I/R. The renal I/R model was obtained by occluding bilateral renal pedicles with nontraumatic vascular clamps for 45 minutes, followed by 48 hours of reperfusion. HBO therapy was delivered an hypebaric chamber (2.5 atmospheres absolute). Animals underwent two sessions of 60 minutes each at 6 hours and 20 hours after initiation of reperfusion. Male Wistar rats (n = 38) were randomized into four groups: sham, sham operated rats; Sham+HBO, sham operated rats exposed to HBO; I/R, animals submitted to I/R; and I/R+HBO, I/R rats exposed to HBO. Blood, urine, and kidney tissue were collected for biochemical, histologic, and immunohistochemical analyses. The histopathological evaluation of the ischemic injury used a grading scale of 0 to 4. HBO attenuated renal dysfunction after ischemia characterized by a significant decrease in blood urea nitrogen (BUN), serum creatinine, and proteinuria in the I/R+HBO group compared with I/R alone. In parallel, tubular function was improved resulting in significantly lower fractional excretions of sodium and potassium. Kidney sections from the I/R plus HBO group showed significantly lower acute kidney injury scores compared with the I/R group. HBO treatment significantly diminished proliferative activity in I/R (P < .05). There was no significant difference in macrophage infiltration or hemoxygenase-1 expression. In conclusion, HBO attenuated renal dysfunction in a kidney I/R injury model with a decrease in BUN, serum creatinine, proteinuria, and fractional excretion of sodium and potassium, associated with reduced histological damage.

Hyperbaric oxygen therapy alleviates oxidative stress and tissue injury in renal ischemia/reperfusion injury in rats

Hyperbaric oxygen (HBO) therapy has been shown to attenuate renal ischemia/reperfusion (I/R) injury in rats, when applied in the early reperfusion period. The aim of this study was to elucidate possible beneficial effects of HBO therapy on renal I/R injury, when applied 24 h after ischemia. Rats were randomized into three groups: (1) control group (n = 20), (2) I/R group (n = 20), and (3) I/R + HBO group (n = 20). Renal I/R injury was created by interrupting renal blood flow for 30 min with a non-traumatic vascular clamp. HBO therapy was administered 24 h after I/R injury and continued for 5 days. At the end of the study, rats were sacrificed under anesthesia, blood was drawn, and right kidneys were harvested for analysis. Renal I/R injury increased serum and tissue malondialdehyde (MDA) levels and reduced superoxide dismutase (SOD) and glutathione peroxidase (GPx) levels. HBO therapy attenuated MDA levels by increasing SOD and GPx activities. HBO therapy also prevented neutrophil infiltration and tissue injury in kidneys. Taken together, HBO therapy has been found to be effective in the delayed period of I/R injury.

Heme oxygenase-1 is induced by thyroid hormone and involved in thyroid hormone preconditioning-induced protection against renal warm ischemia in rat

Thyroid hormone pretreatment was indicated to increase tissue tolerance to ischemia-reperfusion injury (IRI) in various organs, but the underlying molecular mechanisms remains largely unknown. Induction of heme oxygenase-1 (HO-1) protects organs against IRI. The present study investigated the effect of thyroid hormone on HO-1 expression and the possible relation between HO-1 and the thyroid hormone induced renal protection. T(3) administration in rat kidneys induced HO-1 expression in a time-dependent and dose-dependent way, and its expression was accompanied with significant depletion of reduced glutathione and increase in malondialdehyde content, showing a moderate oxidative stress that turns to normal level 48 h after drug injection. Thyroid hormone pretreatment (10 μg/100g body weight) 48 h before IR procedure significantly decreased serum creatinine and urea nitrogen and preserved renal histology, with significant reduction of parameters about oxidative stress and over-expression of HO-1 compared with that of IR group. In conclusion, T(3) administration involving oxidative stress in kidney exerts significant enhancement of HO-1 expression which may, at least in part, account for the renal preconditioning induced by T(3).

Remifentanil, isoflurane, and preconditioning attenuate renal ischemia/reperfusion injury in rats

BACKGROUND

The purpose of this investigation was to examine the effect of isoflurane, remifentanil, and preconditioning in renal ischemia/reperfusion injury (IRI).

METHODS

All 52 male Wistar rats were anesthetized with isoflurane, intubated and mechanically ventilated. The animals were randomly divided into: S group (sham; n = 11) that underwent only right nephrectomy; as well as the I group of right nephrectomy and ischemia for 45 minutes by clamping of left renal artery. (n = 11); the IP (n = 9), the R (n = 10), and the RP (n = 11) groups. In addition, the R and RP animals received remifentanil (2 microg.kg(-1).min(-1)) during the entire experiment. The IP and RP group underwent ischemic preconditioning (IPC = three cycles of 5 minutes). Serum creatinine values were determined before and after IRI, as well as 24 hours later. In addition to an Histological study, cells from the left kidney were evaluated for apoptosis by flow cytometry (FCM).

RESULTS

The Creatinine value of 0.8 +/- 0.2 mg/dl in the S group was significantly lower at 24 hours than the I 3.9 +/- 1.5 mg/dl; IP 2.6 +/- 1.7 mg/dl; R 3.3 +/- 2.8 mg/dl; or RP 1.8 +/- 0.5 mg/dl groups. The RP group value was significantly lower than those of the I, IP, and R groups (p < 0.05). The S group showed less proximal tubular cell damage than the I, IP, R, and RP groups (p < 0.05). The percentages of apoptotic cells (FITC(+)/PI(-)) were: S group = 11.6 +/- 6.5; I = 16.7 +/- 7.3; IP = 37.0 +/- 28.4; R = 11.7 +/- 6.6, and RP = 8.8 +/- 1.5. The difference between the IP vs RP group was significant. Similar percentages of necrotic cells (FITC(+)/PI(+)) and intact cells (FITC(-)/PI(-)) were observed among the groups.

CONCLUSIONS

Ischemic preconditioning showed no protective effect in the isoflurane group (IP) but when isoflurane was administered associated with remifentanil (RP), there was a beneficial effect on the kidney, as demonstrated by flow cytometry and serum creatinine values.

Hyperoxia-induced protection against rat's renal ischemic damage: relation to oxygen exposure time

BACKGROUND

Pre-exposure to hyperoxic gas (>or= 95%) has been shown to protect the heart and central nervous system from ischemia-reperfusion injury. In the present study, we investigated whether oxygen pretreatment induces delayed renal protection in rats. The possible role of some renal antioxidant agents was also investigated.

MATERIALS AND METHODS

Adult male Wistar rats were kept in a hyperoxic (HO) (>or= 95% O(2)) environment for 0.5 h, 1 h, 2 h, 3 h, 6 h, and 2 h/day for three consecutive days and 4 h/day for six consecutive days, and control group (IR) animals were kept in the cage with no HO, one day before subjecting their kidney to 40 minutes of ischemia and 24h of reperfusion. Renal function was assessed by comparing plasma creatinine (Cr), blood urea nitrogen (BUN), creatinine clearance (CLCr), and fractional excretion of sodium (FENa%). Histopathological injury score was also determined according to the Jablonski method. To examine the antioxidant system induction by hyperoxia, we measured renal catalase and superoxide dismutase activity, and renal glutathione and malondialdehyde content.

RESULTS

Our data demonstrated that only in 4 h/day HO for six consecutive days, the renal function tests (Cr, CLCr, BUN, and FENa%) and Jablonski histological injury were better than control group (p < 0.05). The beneficial effect of oxygen pretreatment in this group was associated with increased renal catalase activity compared with those obtained from control group (p < 0.05).

CONCLUSION

The present study demonstrates that repeated exposure to hyperoxic (>or= 95% O(2)) environment can reduce subsequent rat's renal ischemia-reperfusion damage. Induction of endogenous antioxidant system may partially explain this beneficial effect of hyperoxic preconditioning.

Hyperbaric oxygen preconditioning protects against traumatic brain injury at high altitude

BACKGROUND

Recent studies have shown that preconditioning with hyperbaric oxygen (HBO) can reduce ischemic and hemorrhagic brain injury. We investigated effects of HBO preconditioning on traumatic brain injury (TBI) at high altitude and examined the role of matrix metalloproteinase-9 (MMP-9) in such protection.

METHODS

Rats were randomly divided into 3 groups: HBO preconditioning group (HBOP; n = 13), high-altitude group (HA; n = 13), and high-altitude sham operation group (HASO; n = 13). All groups were subjected to head trauma by weight-drop device, except for HASO group. HBOP rats received 5 sessions of HBO preconditioning (2.5 ATA, 100% oxygen, 1 h daily) and then were kept in hypobaric chamber at 0.6 ATA (to simulate pressure at 4000m altitude) for 3 days before operation. HA rats received control pretreatment (1 ATA, room air, 1 h daily), then followed the same procedures as HBOP group. HASO rats were subjected to skull opening only without brain injury. Twenty-four hours after TBI, 7 rats from each group were examined for neurological function and brain water content; 6 rats from each group were killed for analysis by H&E staining and immunohistochemistry.

RESULTS

Neurological outcome in HBOP group (0.71 +/- 0.49) was better than HA group (1.57 +/- 0.53; p < 0.05). Preconditioning with HBO significantly reduced percentage of brain water content (86.24 +/- 0.52 vs. 84.60 +/- 0.37; p < 0.01). Brain morphology and structure seen by light microscopy was diminished in HA group, while fewer pathological injuries occurred in HBOP group. Compared to HA group, pretreatment with HBO significantly reduced the number of MMP-9-positive cells (92.25 +/- 8.85 vs. 74.42 +/- 6.27; p < 0.01).

CONCLUSIONS

HBO preconditioning attenuates TBI in rats at high altitude. Decline in MMP-9 expression may contribute to HBO preconditioning-induced protection of brain tissue against TBI.