Hyperbaric oxygen preconditioning alleviates myocardial ischemic injury in rats

Recent advances in the application of gasotransmitters in spinal cord injury

Spinal Cord Injury (SCI) is a condition characterized by complete or incomplete motor and sensory impairment, as well as dysfunction of the autonomic nervous system, caused by factors such as trauma, tumors, or inflammation. Current treatment methods primarily include traditional approaches like spinal canal decompression and internal fixation surgery, steroid pulse therapy, as well as newer techniques such as stem cell transplantation and brain-spinal cord interfaces. However, the above methods have limited efficacy in promoting axonal and neuronal regeneration. The challenge in medical research today lies in promoting spinal cord neuron regeneration and regulating the disrupted microenvironment of the spinal cord. Studies have shown that gas molecular therapy is increasingly used in medical research, with gasotransmitters such as hydrogen sulfide, nitric oxide, carbon monoxide, oxygen, and hydrogen exhibiting neuroprotective effects in central nervous system diseases. The gas molecular protect against neuronal death and reshape the microenvironment of spinal cord injuries by regulating oxidative, inflammatory and apoptotic processes. At present, gas therapy mainly relies on inhalation for systemic administration, which cannot effectively enrich and release gas in the spinal cord injury area, making it difficult to achieve the expected effects. With the rapid development of nanotechnology, the use of nanocarriers to achieve targeted enrichment and precise control release of gas at Sites of injury has become one of the emerging research directions in SCI. It has shown promising therapeutic effects in preclinical studies and is expected to bring new hope and opportunities for the treatment of SCI. In this review, we will briefly outline the therapeutic effects and research progress of gasotransmitters and nanogas in the treatment of SCI.

Hyperbaric Oxygen Upregulates Mst1 to Activate Keap1/Nrf2/HO-1 Pathway Resisting Oxidative Stress in a Rat Model of Acute Myocardial Infarction

This study aimed to investigate the protective effects and mechanisms of hyperbaric oxygen (HBO) preconditioning in a rat model of acute myocardial infarction (MI) established by ligation of the left anterior descending (LAD) coronary artery. Microarray, real-time PCR, and western blotting (WB) results demonstrated that the Mst1 gene was downregulated in the heart tissue of the MI rat model. HBO preconditioning significantly increased Mst1 expression in cardiac tissues of rats after MI modeling. Lentiviral infection was used to silence the Mst1 gene in rats treated with HBO to probe the effect of Mst1 on HBO cardioprotection. HBO preconditioning decreased heart infarct size and ameliorated cardiac function in MI rats, whereas Mst1 silencing reversed the effect of HBO administration, as indicated after heat infarct size determination via TTC staining, histological examination via HE staining, and measurements of cardiac function. HBO preconditioning reduced oxidative stress and inflammation in cardiac tissue of MI rat model, evidenced by alteration of malondialdehyde (MDA), 8-hydroxy-2-deoxyguanosine (8-OHdG), and protein carbonyl contents, as well as production of inflammation-associated myeloperoxidase (MPO), IL-1β, and TNF-α. These findings provide a new signaling mechanism through which HBO preconditioning can protect against acute MI injury through the Mst1-mediating Keap1/Nrf2/HO-1-dependent antioxidant defense system.

Hyperbaric Oxygen Therapy Following Percutaneous Coronary Intervention for ST-Segment Elevation Myocardial Infarction

INTRODUCTION

Hyperbaric oxygen therapy (HBOT) is a promising treatment modality for ischemic heart disease including myocardial infarction where outcomes are frequently poor despite early revascularization.

OBJECTIVE

To compare single-photon emission computed tomography (SPECT) findings in patients undergoing primary percutaneous coronary intervention (PPCI) for ST-elevation myocardial infarction (STEMI) treated with HBOT vs. control at 6 weeks.

METHODS

In this pilot study, 24 patients were randomly allocated to HBOT (n = 13) and control groups (n = 11). Both groups underwent PPCI and were treated following the guidelines for STEMI management. The HBOT group received additional 15 and 90-minute HBOT sessions. All participants underwent SPECT at initial presentation (within 48 h of PPCI) and at follow up.

RESULTS

Baseline characteristics were similar in both groups. The number of affected SPECT segments in the HBOT group at baseline and 6 weeks were 47.1 ± 14.6% vs. 33.7 ± 16.2%, respectively, with p = 0.039, and in the control group, the number of affected segment at these times were 55.5 ± 19.5% vs. 45.9 ± 17.9%, respectively, with p = 0.090. At follow-up, a decrease in the summed rest score was noted in both groups (HBOT: 20 ± 6.0 vs. 12.7 ± 8.1; p = 0.0017; control: 23 ± 8.2 vs. 16.7 ± 6.6; p = 0.031). The left ventricular ejection fraction in the HBOT group improved from 44 ± 22.1% to 57.2 ± 15.4% (p = 0.011) and in the control group from 45.9 ± 18.2% to 55 ± 12.1% (p = 0.044).

CONCLUSIONS

HBOT use in STEMI patients was associated with an improvement in perfusion and an increase in ejection fraction following PPCI. These observations warrant a larger randomized clinical trial.

Hyperbaric Oxygen Inhibits Reperfusion-Induced Neutrophil Polarization and Adhesion Via Plasmin-Mediated VEGF Release

Background:

Ischemia-reperfusion (IR) injury is seen in many settings such as free flap salvage and limb replantation/revascularization. The consequences—partial/total flap loss, functional muscle loss, or amputation—can be devastating. Of the treatment options available for IR injury, hyperbaric oxygen (HBO) is the most beneficial. HBO inhibits neutrophil-endothelial adhesion through interference of CD18 neutrophil polarization in IR, a process mediated by nitric oxide. The purposes of this study were to examine the involvement of vascular endothelial growth factor (VEGF) in the beneficial HBO effect on CD18 polarization and neutrophil adhesion and investigate the effect of plasmin on VEGF expression in skeletal muscle following IR injury.

Methods:

A rat gracilis muscle model of IR injury was used to evaluate the effect of VEGF in IR, with and without HBO, on neutrophil CD18 polarization and adhesion in vivo and ex vivo. Furthermore, we investigated the effects that plasmin has on VEGF expression in gracilis muscle and pulmonary tissue by blocking its activation with alpha-2-antiplasmin.

Results:

HBO treatment following IR injury significantly decreased neutrophil polarization and adhesion ex vivo compared with the IR group. Anti-VEGF reversed the beneficial HBO effect after IR with polarization and adhesion. In vivo adhesion was also increased by anti-VEGF. HBO treatment of IR significantly increased the VEGF protein in both gracilis and pulmonary vasculature. Alpha-2-antiplasmin significantly reversed the HBO-induced increase of VEGF in gracilis muscle.

Conclusions:

These results suggest that HBO inhibits CD18 polarization and neutrophil adhesion in IR injury through a VEGF-mediated pathway involving the extracellular matrix plasminogen system.

Hyperbaric Oxygen Preconditioning Provides Preliminary Protection Against Doxorubicin Cardiotoxicity

BACKGROUND

Doxorubicin (DOX) is generally recognized to have important cardiotoxic side effects. Studies are contradictory about the interaction between hyperbaric oxygen (HBO₂) therapy and doxorubicin-induced cardiomyotoxicity. Recent data suggests that HBO₂ therapy can lead to preconditioning of myocardium while generating oxidative stress. Herein we have investigated the effect of HBO₂ therapy in a DOX-induced cardiomyocyte injury animal model.

METHODS

Twenty-one rats were divided into three equal groups as follows: 1) Group 1 is a control group (without any intervention), used for evaluating the basal cardiac structures and determining the normal value of cardiacs and serum oxidative markers; 2) Group 2 is the doxorubicin group (single dose i.p. 20 mg/kg doxorubicin) for detecting the cardiotoxic and systemic effects of doxorubicin; 3) Group 3 is the doxorubicin and HBO₂ group (100% oxygen at 2.5 atmospheric for 90 minutes, daily), for evaluating the effect of HBO₂ in doxorubicin induced cardiotoxicity. At the end of the protocols, the hearts were harvested and blood samples (2 ml) were obtained.

RESULTS

The doxorubicin treated animals (Group 2) had increased oxidative stress markers (both cardiac and serum) and severe cardiac injury as compared to the basal findings in the control group. Nevertheless, the highest cardiac oxidative stress index was detected in Group 3 (control vs. Group 3, p = 0.01). However, histological examination revealed that cardiac structures were well preserved in Group 3 when compared with Group 2.

CONCLUSIONS

Our results suggest that HBO₂ preconditioning appears to be protective in the doxorubicin-induced cardiotoxicity model. Future studies are required to better elucidate the basis of this preconditioning effect of HBO₂.

Hyperbaric oxygen therapy (HBOT) suppresses biomarkers of cell stress and kidney injury in diabetic mice

The disease burden from diabetic kidney disease is large and growing. Effective therapies are lacking, despite an urgent need. Hyperbaric oxygen therapy (HBOT) activates Nrf2 and cellular antioxidant defenses; therefore, it may be generally useful for treating conditions that feature chronic oxidative tissue damage. Herein, we determined how periodic exposure to oxygen at elevated pressure affected type 2 diabetes mellitus-related changes in the kidneys of db/db mice. Two groups of db/db mice, designated 2.4 ATA and 1.5 ATA, were treated four times per week with 100 % oxygen at either 1.5 or 2.4 ATA (atmospheres absolute) followed by tests to assess kidney damage and function. The sham group of db/db mice and the Hets group of db/+ mice were handled but did not receive HBOT. Several markers of kidney damage were reduced significantly in the HBOT groups including urinary biomarkers neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C (CyC) along with significantly lower levels of caspase-3 activity in kidney tissue extracts. Other stress biomarkers also showed trends to improvement in the HBOT groups, including urinary albumin levels. Expressions of the stress response genes NRF2, HMOX1, MT1, and HSPA1A were reduced in the HBOT groups at the end of the experiment, consistent with reduced kidney damage in treated mice. Urinary albumin/creatinine ratio (ACR), a measure of albuminuria, was significantly reduced in the db/db mice receiving HBOT. All of the db/db mouse groups had qualitatively similar changes in renal histopathology. Glycogenated nuclei, not previously reported in db/db mice, were observed in these three experimental groups but not in the control group of nondiabetic mice. Overall, our findings are consistent with therapeutic HBOT alleviating stress and damage in the diabetic kidney through cytoprotective responses. These findings support an emerging paradigm in which tissue oxygenation and cellular defenses effectively limit damage from chronic oxidative stress more effectively than chemical antioxidants.

Hyperbaric Oxygen Preconditioning Attenuates Myocardium Ischemia-Reperfusion Injury Through Upregulation of Heme Oxygenase 1 Expression: PI3K/Akt/Nrf2 Pathway Involved

BACKGROUND

With the rise of the burden of ischemic heart disease, both clinical and economic evidence show a desperate need to protect the heart against myocardium ischemia-reperfusion injury-related complications following cardiac surgery or percutaneous coronary intervention. However, there is no effective intervention for myocardium ischemia-reperfusion injury as yet.

METHODS

We pretreated mice with 4 daily 2.0 absolute atmosphere (ATA) hyperbaric oxygen, then observed its effects on heart function parameters and infarct size following in situ ischemia-reperfusion. Multiple oxidative and inflammation products were measured in the myocardium. Next, we investigated the expression of heme oxygenase 1 (HO-1), phosphatidylinositol 3-kinase (PI3K)/serine/threonine protein kinase (Akt) pathway, and NF-E2-related factor 2 (Nrf2) in the presence of myocardium ischemia-reperfusion injury, hyperbaric oxygen preconditioning, and their inhibitors and their effects on heart function parameters.

RESULTS

Hyperbaric oxygen preconditioning ameliorated the cardiac function and histological alterations induced by myocardium ischemia-reperfusion injury, decreased oxidative products and proinflammatory cytokine. Hyperbaric oxygen preconditioning increased expression of HO-1, which was suppressed by PI3K inhibitor LY294002, Nrf2 knockout, and Akt inhibitor triciribine. The expression of Nrf2 was enhanced by hyperbaric oxygen preconditioning, but decreased by LY294002 and triciribine. The Akt was also activated by hyperbaric oxygen preconditioning but suppressed by LY294002. The hemodynamic assays showed that cardiac function was suppressed by LY294002, Nrf2 knockout, and triciribine.

CONCLUSION

These data present a novel signaling mechanism by which hyperbaric oxygen preconditioning protects myocardium ischemia-reperfusion injury via PI3K/Akt/Nrf2-dependent antioxidant defensive system.

Normobaric hyperoxia preconditioning ameliorates cisplatin nephrotoxicity

BACKGROUND

Cisplatin is a potent anticancer drug, but its nephrotoxicity limits the clinical use of it. To reduce the Cisplatin-induced nephrotoxicity, various interventions have been implicated. The aim of this study was to examine whether preconditioning with normobaric hyperoxia would prevent Cisplatin-induced nephrotoxicity in patient with solid tumor.

METHODS

In a prospective study, 80 adult patients with solid tumor who were treated with Cisplatin between February 2011 and December 2011 were included. Forty-three patients were exposed to pure oxygen via non-rebreathing reservoir mask which increased the provided oxygen rate to 60% oxygen for 2 hours at 48, 24, and 6 hours before intravenous administration of Cisplatin and 37 patients received only Cisplatin as a control group. Estimated glomerular filtration rate (eGFR) calculated in all patients on day 1 before and on days 1, 3, 6, 30 after Cisplatin exposures.

RESULTS

Patients treated with Cisplatin and 60% oxygen showed a mild improvement in eGFR and mild reduction of serum creatinine after 30 days with statistically mild significant differences (p = 0.048).

CONCLUSION

This study showed that normobaric and intermittent precondition of 60% oxygen prior to Cisplatin treatment had an acute transient adverse effect on renal function; however, the improvement of renal function will be seen after 30 days. Thus, it may help to prevent Cisplatin nephrotoxicity.

Effect of hyperbaric oxygenation on intervertebral disc degeneration: an in vivo study with sprague-dawley rats

STUDY DESIGN

An in vivo study was conducted to test the effect of hyperbaric oxygenation (HBO) on intervertebral disc degeneration in Sprague-Dawley rats.

OBJECTIVE

To observe the changes in intervertebral disc height and levels of glycosaminoglycan, collagen, interleukin-1β (IL-1β), prostaglandin E2 (PGE2), and inducible nitric oxide synthase (iNOS) in degenerated intervertebral discs after HBO therapy.

SUMMARY OF BACKGROUND DATA

Although the involvement of IL-1β, PGE-2, NO, and low O2 concentration has been demonstrated in intervertebral disc degeneration, the actual mechanism is not clear. It has been reported that HBO influences changes in IL-1β, PGE-2, NO, and O2 concentration. Previously, a study demonstrated an in vitro positive effect of HBO on the human nucleus pulposus. Thus, an in vivo study in animals was necessary.

METHODS

Twelve Sprague-Dawley rats were each injected with chondroitinase ABC in 2 proximal intervertebral discs of the tail. After treating with 100% oxygen at 2.5 atmospheres 2 hours per days for 10 days, the change in disc height was determined by radiography. The amounts of PGE-2, iNOS, glycosaminoglycan, and total collagen in the intervertebral disc were quantified by enzyme-linked immunosorbent assay. Tissue morphology and the distribution of glycosaminoglycan, IL-1β, and iNOS in the intervertebral disc were assessed by histology and immunohistochemistry. The area of IL-1β in the intervertebral discs was quantified using image analysis software.

RESULTS

HBO therapy stopped the decrease in intervertebral disc height, caused an increase in the amount of glycosaminoglycan, and inhibited IL-1β, PGE-2, and iNOS production.

CONCLUSION

HBO provides a potential treatment modality for intervertebral disc degeneration.

Effects of alpha lipoic acid and its R+ enantiomer supplemented to hyperbaric oxygen therapy on interleukin-6, TNF-α and EGF production in chronic leg wound healing

CONTEXT

Lipoic acid (LA) and hyperbaric oxygenation therapy (HBOT) improve chronic wound healing.

OBJECTIVE

We compared the effects of LA or its enantiomer R-(+)-lipoic acid (RLA) on wound healing.

MATERIALS AND METHODS

Groups LA + HBOT (L), RLA + HBOT (R) and placebo + HBOT (P). Lesion areas measured before treatment and on 20th and 40th day. The biopsies and plasma were harvested before treatment and on 7th and 14th (measurements of VEGF, vascular endothelial growth factor; EGF, epidermal growth factor, TNF-α and IL-6).

RESULTS

Ulcers improved more on RLA. In both L and R groups, EGF and VEFG increased in time. RLA decreased IL-6 on T7 and T14, which did not happen with LA. TNF-α levels decreased on T14 in both LA and RLA.

DISCUSSION

The improved wound healing is associated with increased EGF and VEGF and reduced plasma TNF-α and IL-6.

CONCLUSION

RLA may be more effective than LA in improving chronic wound healing in patients undergoing HBO therapy.

Hyperbaric oxygen preconditioning protects skin from UV-A damage

Hyperbaric oxygen therapy (HBOT) is used for a number of applications, including the treatment of diabetic foot ulcers and CO poisoning. However, we and others have shown that HBOT can mobilize cellular antioxidant defenses, suggesting that it may also be useful under circumstances in which tissue protection from oxidative damage is desired. To test the protective properties of hyperbaric oxygen (HBO) on a tissue level, we evaluated the ability of a preconditioning treatment regimen to protect cutaneous tissue from UV-A-induced oxidative damage. Three groups of hairless SKH1-E mice were exposed to UV-A 3 days per week for 22 weeks, with two of these groups receiving an HBO pretreatment either two or four times per week. UV-A exposure increased apoptosis and proliferation of the skin tissue, indicating elevated levels of epithelial damage and repair. Pretreatment with HBO significantly reduced UV-A-induced apoptosis and proliferation. A morphometric analysis of microscopic tissue folds also showed a significant increase in skin creasing following UV-A exposure, which was prevented by HBO pretreatment. Likewise, skin elasticity was found to be greatest in the group treated with HBO four times per week. The effects of HBO were also apparent systemically as reductions in caspase-3 activity and expression were observed in the liver. Our findings support a protective function of HBO pretreatment from a direct oxidative challenge of UV-A to skin tissue. Similar protection of other tissues may likewise be achievable.

Cardiac tissue injury resistance during myocardial infarction at adulthood by developmental exposure to cadmium

It has been suggested that prenatal exposure to cadmium may alter the cardiovascular function during adulthood. Using the left coronary artery ligation model of acute myocardial infarction, we studied the cardiac function of female adult offspring rats exposed to cadmium (30 ppm) during gestation. The cardiac ischemic zone in the control and cadmium-exposed groups was measured 72 h post-ligation using the TPT staining technique. Offspring from cadmium-treated dams showed a significantly smaller infarcted area compared with the control group (7.1 ± 1.5 vs. 19.6 ± 2.8%, P ≤ 0.05). We also performed echocardiographic and biochemical studies, which positively correlated with the differences observed previously. To evaluate whether the effects were associated to pre-infarct tissue damage and/or angiogenic molecules, we performed histological studies and measured the expression of vascular endothelial growth factor (VEGF), and platelet endothelial cellular adhesion molecule-1 (PECAM-1). Results revealed a higher heart vascularization in the exposed offspring that was associated with an increase in PECAM and a decrease in VEGF expression. We conclude that prenatal exposure to cadmium induces fetal adaptive responses involving changes in the expression of some cardiac angiogenic molecules resulting in long-term resistance to infarction.

Effect of hyperbaric oxygen therapy on the intestinal ischemia reperfusion injury

PURPOSE

Adequate tissue oxygenation is essential for healing. Hyperbaric oxygen therapy (HBOT) has potential clinical applications to treat ischemic pathologies, however the exact nature of any protective effects are unclear at present. We therefore investigated the potential role of HBOT in modulating the ischemia/reperfusion (I/R) injury response in intestinal model of I/R injury.

METHODS

Male Wistar rats were subjected to surgery for the induction of intestinal ischemia followed by reperfusion. HBOT was provided before and/or after intestinal ischemia. Cell viability in the intestinal tissue was assessed using the MTT assay and by measuring serum malondealdehyde (MDA). Microvascular density and apoptosis were evaluated by immunohistochemistry.

RESULTS

The results indicate that HBOT treatment pre- and post-ischemia reduces lesion size to the intestinal tissue. This treatment increases cell viability and reduces the activation of caspase-3, which is associated with increased number of tissue CD34 cells and enhanced VEGF expression.

CONCLUSION

The hyperbaric oxygen therapy can limit tissue damage due to ischemia/reperfusion injury, by inducing reparative signaling pathways.

Salusins protect myocardium against ischemic injury by alleviating endoplasmic reticulum stress

Salusins are regulatory peptides that affect cardiovascular function. We previously reported that salusin-α and -β protected cultured cardiomyocytes from serum deprivation-induced cell death through upregulating glucose-regulated protein 78 (GRP78), an endoplasmic reticulum (ER) resident protein whose overexpression acts as a marker and suppressor of ER stress. The present study examined whether salusin-α and -β inhibit ER stress in ischemic myocardium. In a rat model of myocardial infarction created by ligating the left anterior descending coronary artery (LAD), salusin-α or -β was intravenously injected at 5 or 15 nmol kg(-1) 15 min prior to 2 h of LAD occlusion. The high dose of salusin-α and -β significantly improved heart function and hemodynamics in LAD-occluded rats, but had no effects in sham-operated rats. The arrhythmias caused by LAD occlusion were markedly attenuated by salusin-α and -β. The apoptotic rate in ischemic myocardium was reduced from 31.5%±3.7% to 19.8%±2.2% and 12.3%±2.2%, and the infarct size was reduced from 53.4%±4.0% of the risk area to 26.5%±9.7% and 23.7%±8.9% by 15 nmol kg(-1) salusin-α and -β, respectively. Furthermore, salusin-α and -β prevented the activation of GRP78 and ER stress-specific apoptotic effectors caspase-12 and CHOP (C/EBP homologous protein), and attenuated the reduction of an ER stress-associated antiapoptotic protein Bcl-2 in ischemic cardiac tissue. The salusins also inhibited the ER stress induced by tunicamycin in cultured rat H9c2 cardiomyocytes. These results indicate that salusins protect myocardium against ischemic injury by inhibiting ER stress and ER stress-associated apoptosis.

Effect of hyperbaric oxygenation on intervertebral disc degeneration: an in vitro study with human lumbar nucleus pulposus

STUDY DESIGN

An in vitro study with degenerated human lumbar intervertebral disc specimens cultured under hyperbaric oxygenation (HBO).

OBJECTIVE

To observe the changes in interleukin (IL)-1β, prostaglandin (PG)-E2, nitric oxide (NO), cell growth, and apoptosis of the human nucleus pulposus cell (NPC) after HBO.

SUMMARY OF BACKGROUND DATA

Intervertebral disc degeneration has been demonstrated as related to IL-1β, PG-E2, NO, and O2 concentration but the actual mechanism is not clear. HBO also has also been reported in the literature to influence changes in IL-1β, prostaglandin E2, NO, and O2 concentration. However, the direct effect of HBO on the disc cells has not been previously reported.

METHODS

We collected 12 human lumbar degenerated disc specimens and evaluated the effects of HBO on the cultured NPCs. The amounts of IL-1β, PG-E2, and NO in the conditioned medium were quantified by enzyme-linked immunosorbent assay and high performance liquid chromatography. Cell growth was measured by increase in cell number. Cell viability and proteoglycan content were evaluated by histologic study using safranin O staining. In situ analysis of apoptosis was performed using Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining.

RESULTS

Our data indicated that HBO treatment inhibited IL-1β, PG-E2, and NO production but increased cell number and matrix synthesis of cultured NPCs. TUNEL staining showed that HBO treatment suppressed the apoptosis of cultured NPCs.

CONCLUSION

HBO provides a potential treatment modality for disc degeneration.

Hyperbaric oxygen preconditioning promotes survival of retinal ganglion cells in a rat model of optic nerve crush

In this study we tested the hypothesis that hyperbaric oxygen preconditioning (HBO-PC) reduces retinal neuronal death due to optic nerve crush (ONC). Adult male Sprague-Dawley rats were subjected to ONC accompanied by a contralateral sham operation. HBO-PC was conducted four times by giving 100% oxygen at 2.5 atmospheres absolute (ATA) for 1 h every 12 h for 2 days prior to ONC. The rats were euthanized at 1 or 2 weeks after ONC. Retinal ganglion cell (RGC) density was counted by hematoxylin and eosin (H&E) staining of the retina and retrograde labeling with FluoroGold application to the superior colliculus. Visual function was assessed by flash visual evoked potentials (FVEP). TUNEL straining and caspase-3 and caspase-9 activity in the retinas were assessed. The RGC density in the retinas of ONC HBO-PC-treated rats was significantly higher than that of the corresponding ONC-only rats (the survival rate was 67.2% versus 49.7% by H&E staining, and 60.3% versus 28.9% by retrograde labeling with FluoroGold, respectively; p < 0.01) at 2 weeks after ONC. FVEP measurements indicated a significantly better preserved latency and amplitude of the P1 wave in the ONC HBO-PC-treated rats than the ONC-only rats (92 +/- 7 msec, 21 +/- 3 microv in the sham-operated group, 117 +/- 12 msec, 14 +/- 2 microv in the HBO-PC-treated group, and 169 +/- 15 msec, 7 +/- 1 microv in the corresponding ONC group; p < 0.01). TUNEL assays showed fewer apoptotic cells in the HBO-PC-treated group, accompanied by the suppression of caspase-3 and caspase-9 activity. These results demonstrate that HBO-PC appears to be neuroprotective against ONC insult via inhibition of neuronal apoptosis pathways.

Hyperbaric oxygen preconditioning improves myocardial function, reduces length of intensive care stay, and limits complications post coronary artery bypass graft surgery

OBJECTIVE

The objective of this study was to determine whether preconditioning coronary artery disease (CAD) patients with HBO(2) prior to first-time elective on-pump cardiopulmonary bypass (CPB) coronary artery bypass graft surgery (CABG) leads to improved myocardial left ventricular stroke work (LVSW) post CABG. The primary end point of this study was to demonstrate that preconditioning CAD patients with HBO(2) prior to on-pump CPB CABG leads to a statistically significant (P<.05) improvement in myocardial LVSW 24 h post CABG.

METHODS

This randomised control study consisted of 81 (control group=40; HBO(2) group=41) patients who had CABG using CPB. Only the HBO(2) group received HBO(2) preconditioning for two 30-min intervals separated 5 min apart. HBO(2) treatment consisted of 100% oxygen at 2.4 ATA. Pulmonary artery catheters were used to obtain perioperative hemodynamic measurements. All routine perioperative clinical outcomes were recorded. Venous blood was taken pre HBO(2), post HBO(2) (HBO(2) group only), and during the perioperative period for analysis of troponin T.

RESULTS

Prior to CPB, the HBO(2) group had significantly lower pulmonary vascular resistance (P=.03). Post CPB, the HBO(2) group had increased stroke volume (P=.01) and LVSW (P=.005). Following CABG, there was a smaller rise in troponin T in HBO(2) group suggesting that HBO(2) preconditioning prior to CABG leads to less postoperative myocardial injury. Post CABG, patients in the HBO(2) group had an 18% (P=.05) reduction in length of stay in the intensive care unit (ICU). Intraoperatively, the HBO(2) group had a 57% reduction in intraoperative blood loss (P=.02). Postoperatively, the HBO(2) group had a reduction in blood loss (11.6%), blood transfusion (34%), low cardiac output syndrome (10.4%), inotrope use (8%), atrial fibrillation (11%), pulmonary complications (12.7%), and wound infections (7.6%). Patients in the HBO(2) group saved US$116.49 per ICU hour.

CONCLUSION

This study met its primary end point and demonstrated that preconditioning CAD patients with HBO(2) prior to on-pump CPB CABG was capable of improving LVSW. Additionally, this study also showed that HBO(2) preconditioning prior to CABG reduced myocardial injury, intraoperative blood loss, ICU length of stay, postoperative complications, and saved on cost, post CABG.

Hydrogen-Rich Saline Protects Myocardium Against Ischemia/Reperfusion Injury in Rats

Protective effect of hydrogen (H2) gas on cardiac ischemia-reperfusion (I/R) injury has been demonstrated previously. This study was designed to test the hypothesis that hydrogen-rich saline (saline saturated with molecular hydrogen), which is easy to use, induces cardioprotection against ischemia (30 min) and reperfusion (24 h) injury in rats. Adult male Sprague-Dawley rats underwent 30-min occlusion of the left anterior descending (LAD) coronary artery and 24-h reperfusion. Intraperitoneal injection of hydrogen-rich saline before reperfusion significantly decreased plasma and myocardium malondialdehyde (MDA) concentration, decreased cardiac cell apoptosis, and myocardial 8-hydroxydeoxyguanosine (8-OHdG) in area at risk zones (AAR), suppressed the activity of caspase-3, and reduced infarct size. The heart function parameters including left ventricular systolic pressure (LVSP), left ventricular diastolic pressure (LVDP), +(dP/dt)max and −(dP/dt)max were also significantly improved 24 h after reperfusion. It is concluded that hydrogen-rich saline is a novel, simple, safe, and effective method to attenuate myocardial I/R injury.

Hyperbaric oxygenation enhances transplanted cell graft and functional recovery in the infarct heart

A major limitation to the application of stem-cell therapy to repair ischemic heart damage is the low survival of transplanted cells in the heart, possibly due to poor oxygenation. We hypothesized that hyperbaric oxygenation (HBO) can be used as an adjuvant treatment to augment stem-cell therapy. Therefore, the goal of this study was to evaluate the effect of HBO on the engraftment of rat bone marrow-derived mesenchymal stem cells (MSCs) transplanted in infarct rat hearts. Myocardial infarction (MI) was induced in Fisher-344 rats by permanently ligating the left-anterior-descending coronary artery. MSCs, labeled with fluorescent superparamagnetic iron oxide (SPIO) particles, were transplanted in the infarct and peri-infarct regions of the MI hearts. HBO (100% oxygen at 2 ATA for 90 min) was administered daily for 2 weeks. Four MI groups were used: untreated (MI); HBO; MSC; MSC+HBO. Echocardiography, electro-vectorcardiography, and magnetic resonance imaging were used for functional evaluations. The engraftment of transplanted MSCs in the heart was confirmed by SPIO fluorescence and Prussian-blue staining. Immunohistochemical staining was used to identify key cellular and molecular markers including CD29, troponin-T, connexin-43, VEGF, alpha-smooth-muscle actin, and von Willebrand factor in the tissue. Compared to MI and MSC groups, the MSC+HBO group showed a significantly increased recovery of cardiac function including left-ventricular (LV) ejection fraction, fraction shortening, LV wall thickness, and QRS vector. Further, HBO treatment significantly increased the engraftment of CD29-positive cells, expression of connexin-43, troponin-T and VEGF, and angiogenesis in the infarct tissue. Thus, HBO appears to be a potential and clinically-viable adjuvant treatment for myocardial stem-cell therapy.