Heme oxygenase-1 attenuates ischemia/reperfusion-induced apoptosis and improves survival in rat renal allografts

Artesunate alleviates intestinal ischemia/reperfusion induced acute lung injury via up-regulating AKT and HO-1 signal pathway in mice

Acute Lung injury (ALI) is a common complication following intestinal ischemia/reperfusion (II/R) injury that can lead to acute respiratory distress syndrome (ARDS) a fatal illness for there is no specific therapy. The semisynthetic artemisinin Artesunate (Art) extracted from Artemisia annua has been found lots of pharmaceutical effects such as anti-malaria, anti-inflammatory, and anti-apoptosis. This study aimed to investigate the effect of Artesunate on intestinal ischemia/reperfusion and the mechanism of how Artesunate works in mice. To establish the II/R model, the C57BL/c mice were subjected to occlude superior mesenteric artery (SMA) for 45 min and 120 min reperfusion, and the lung tissue was collected for examination. Severe lung injury occurred during the II/R, meanwhile Art pretreatment decreased the lung injury score, wet/dry ratio, the level of MDA, MPO, IL-1β, TNFα, CXCL1, MCP-1, the TUNEL-positive cells, Bax and Cleaved-Caspase3 protein expression obviously, and increased the activity of SOD and the expression of Bcl-2. In addition, the protein of P-AKT and HO-1 were upregulated during the Art pretreatment. Then the AKT inhibitor Triciribin and HO-1 inhibitor Tin-protoporphyrin IX were administered which reversed the protein expression of apoptosis, AKT and HO-1. Our study suggests that Art mitigated the II/R induced acute lung injury by targeting the oxidative stress, inflammatory response and apoptosis which is associated with the activating of AKT and HO-1, providing novel insights into the therapeutic candidate for the treatment of II/R induced acute lung injury.

The roles of heme oxygenase-1 in renal disease

Heme oxygenase (HO), a heat shock protein containing hemoglobin, is an important enzyme in heme catabolism. It is involved in cell homeostasis and has anti-inflammatory, antioxidant, anti-apoptosis, immunomodulation, and other functions. It is expressed at a modest level in most normal tissues. When the body suffers from ischemia hypoxia, injury, toxins, and other nociceptive stimuli, the expression increases, which can transform the oxidative microenvironment into an antioxidant environment to promote tissue recovery from damage. In recent years, research has continued to verify its value in a variety of human bodily systems. It is also regarded as a key target for the treatment of numerous disorders. With the advancement of studies, its significance in renal disease has gained increasing attention. It is thought to have a significant protective function in preventing acute kidney injury and delaying the progression of chronic renal diseases. Its protective mechanisms include anti-inflammatory, antioxidant, cell cycle regulation, apoptosis inhibition, hemodynamic regulation, and other aspects, which have been demonstrated in diverse animal models. Furthermore, as a protective factor, its potential therapeutic efficacy in renal disease has recently become a hot area of research. Although a large number of preclinical trials have confirmed its therapeutic potential in reducing kidney injury, due to the problems and side effects of HO-1 induction therapy, its efficacy and safety in clinical application need to be further explored. In this review, we summarize the current state of research on the mechanism, location, and treatment of HO and its relationship with various renal diseases.

Expression Dynamics of Heme Oxygenase-1 in Tumor Cells and the Host Contributes to the Progression of Tumors

Heme oxygenase (HO-1) plays an important role in cellular protection against various stresses. The induction of HO-1 is an effective strategy for reactive oxygen species-related diseases, inflammatory diseases, as well as suppressing carcinogenesis. On the other hand, the high expression of HO-1 is now well known in many tumors. In this study, we investigated the dynamics of HO-1 expression in the host and the tumor. In the mouse sarcoma S180 solid tumor model and the rat hepatoma AH136B ascitic tumor model, HO-1 expression in the tumor, as indicated by the end product of HO-1 activation, i.e., carbon monoxide, gradually increased along with tumor growth. Over-expression of HO-1 expression in mouse colon cancer C26 tumor cells significantly promoted tumor growth as well as lung metastasis, whereas opposite results were found when the HO-1 expression was reduced in the cells. On the other hand, upregulating HO-1 levels in the host by using an HO-1 inducer protected the progression of the xenograft tumor in mice, whereas lowering HO-1 expression in the host with an HO-1 inhibitor showed accelerated tumor growth and lung metastasis after subcutaneous tumor xenograft inoculation. These findings strongly suggest that the balance of HO-1 levels in the host and the tumor cells is essential for the occurrence, progression, and prognosis of cancer. Maintenance of appropriately high HO-1 levels in the host is favorable for cancer prevention, whereas suppression of HO-1 in the tumor cells may thus become a therapeutic strategy for cancer.

Application of carbon monoxide in kidney and heart transplantation: A novel pharmacological strategy for a broader use of suboptimal renal and cardiac grafts

Carbon monoxide (CO) was historically regarded solely as a poisonous gas that binds to hemoglobin and reduces oxygen-carrying capacity of blood at high concentrations. However, recent findings show that it is endogenously produced in mammalian cells as a by-product of heme degradation by heme oxygenase, and has received a significant attention as a medical gas that influences a myriad of physiological and pathological processes. At low physiological concentrations, CO exhibits several therapeutic properties including antioxidant, anti-inflammatory, anti-apoptotic, anti-fibrotic, anti-thrombotic, anti-proliferative and vasodilatory properties, making it a candidate molecule that could protect organs in various pathological conditions including cold ischemia-reperfusion injury (IRI) in kidney and heart transplantation. Cold IRI is a well-recognized and complicated cascade of interconnected pathological pathways that poses a significant barrier to successful outcomes after kidney and heart transplantation. A substantial body of preclinical evidence demonstrates that CO gas and CO-releasing molecules (CO-RMs) prevent cold IRI in renal and cardiac grafts through several molecular and cellular mechanisms. In this review, we discuss recent advances in research involving the use of CO as a novel pharmacological strategy to attenuate cold IRI in preclinical models of kidney and heart transplantation through its administration to the organ donor prior to organ procurement or delivery into organ preservation solution during cold storage and to the organ recipient during reperfusion and after transplantation. We also discuss the underlying molecular mechanisms of cyto- and organ protection by CO during transplantation, and suggest its clinical use in the near future to improve long-term transplantation outcomes.

Immunomodulatory Effects of Heme Oxygenase-1 in Kidney Disease

Kidney disease is a general term for heterogeneous damage that affects the function and the structure of the kidneys. The rising incidence of kidney diseases represents a considerable burden on the healthcare system, so the development of new drugs and the identification of novel therapeutic targets are urgently needed. The pathophysiology of kidney diseases is complex and involves multiple processes, including inflammation, autophagy, cell-cycle progression, and oxidative stress. Heme oxygenase-1 (HO-1), an enzyme involved in the process of heme degradation, has attracted widespread attention in recent years due to its cytoprotective properties. As an enzyme with known anti-oxidative functions, HO-1 plays an indispensable role in the regulation of oxidative stress and is involved in the pathogenesis of several kidney diseases. Moreover, current studies have revealed that HO-1 can affect cell proliferation, cell maturation, and other metabolic processes, thereby altering the function of immune cells. Many strategies, such as the administration of HO-1-overexpressing macrophages, use of phytochemicals, and carbon monoxide-based therapies, have been developed to target HO-1 in a variety of nephropathological animal models, indicating that HO-1 is a promising protein for the treatment of kidney diseases. Here, we briefly review the effects of HO-1 induction on specific immune cell populations with the aim of exploring the potential therapeutic roles of HO-1 and designing HO-1-based therapeutic strategies for the treatment of kidney diseases.

Administration of Donor-Derived Nonexpanded Adipose Stromal Vascular Fraction Attenuates Ischemia-Reperfusion Injury in Donation After Cardiac Death Rat Renal Transplantation

Donation after cardiac death (DCD) has become a potential source for transplantation organs. However, ischemia/reperfusion injury (IRI) induced by cardiac arrest has limited the use of DCD organs. Stromal vascular fraction (SVF) without the culturing step has been proposed as a safer and easier source for stem cell therapy, which has emerged as an attractive technology that could facilitate the recovery of renal function and structure from acute kidney injury induced by IRI after DCD renal transplantation. In this study, freshly isolated donor-derived SVF was identified and then delivered intra-arterially into the grafts in DCD rat renal transplantation. Administration of freshly isolated donor-derived SVF could significantly alleviate the IRI of renal grafts and enhance graft reparation by promoting graft cell proliferation and microvascularization in DCD renal transplantation. Moreover, results revealed that the oxidative stress in grafts was significantly alleviated with SVF treatment, and this might be attributed to the overexpression of antioxidative molecules including nuclear factor erythroid-related factor 2, superoxide dismutase-1, and heme oxygenase-1. In conclusion, our study demonstrated that the administration of freshly isolated donor-derived nonexpanded adipose SVF could attenuate IRI and protect the grafts after DCD rat renal transplantation.

15-Deoxy-Δ12,14-prostaglandin J2 Upregulates VEGF Expression via NRF2 and Heme Oxygenase-1 in Human Breast Cancer Cells

There is a plethora of evidence to support that inflammation is causally linked to carcinogenesis. Cyclooxygenase-2 (COX-2), a rate-limiting enzyme in the biosynthesis of prostaglandins, is inappropriately overexpressed in various cancers and hence recognized as one of the hallmarks of chronic inflammation-associated malignancies. However, the mechanistic role of COX-2 as a link between inflammation and cancer remains largely undefined. In this study, we found that 15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂), one of the final products of COX-2, induced upregulation of vascular endothelial growth factor (VEGF) and capillary formation and migration through nuclear factor erythroid 2-related factor 2 (NRF2)-dependent heme oxygenase-1 (HO-1) induction in MCF-7 cells. Analysis of the publicly available TCGA data set showed that high mRNA levels of both COX-2 and NRF2 correlated with the poor clinical outcomes in breast cancer patients. Moreover, human tissue analysis showed that the levels of 15d-PGJ₂ as well the expression of COX-2, NRF2, and HO-1 were found to be increased in human breast cancer tissues. In conclusion, the elevated levels of 15d-PGJ₂ during inflammatory response activate VEGF expression through NRF2-driven induction of HO-1 in human breast cancer cells, proposing a novel mechanism underlying the oncogenic function of 15d-PGJ₂.

Heme Oxygenase 1: A Defensive Mediator in Kidney Diseases

The incidence of kidney disease is rising, constituting a significant burden on the healthcare system and making identification of new therapeutic targets increasingly urgent. The heme oxygenase (HO) system performs an important function in the regulation of oxidative stress and inflammation and, via these mechanisms, is thought to play a role in the prevention of non-specific injuries following acute renal failure or resulting from chronic kidney disease. The expression of HO-1 is strongly inducible by a wide range of stimuli in the kidney, consequent to the kidney's filtration role which means HO-1 is exposed to a wide range of endogenous and exogenous molecules, and it has been shown to be protective in a variety of nephropathological animal models. Interestingly, the positive effect of HO-1 occurs in both hemolysis- and rhabdomyolysis-dominated diseases, where the kidney is extensively exposed to heme (a major HO-1 inducer), as well as in non-heme-dependent diseases such as hypertension, diabetic nephropathy or progression to end-stage renal disease. This highlights the complexity of HO-1's functions, which is also illustrated by the fact that, despite the abundance of preclinical data, no drug targeting HO-1 has so far been translated into clinical use. The objective of this review is to assess current knowledge relating HO-1's role in the kidney and its potential interest as a nephroprotection agent. The potential therapeutic openings will be presented, in particular through the identification of clinical trials targeting this enzyme or its products.

Antioxidative Effects of Thymus quinquecostatus CELAK through Mitochondrial Biogenesis Improvement in RAW 264.7 Macrophages

Oxidative stress plays a key role in the pathogenesis of several diseases, including neurodegenerative diseases. Recent studies have reported that mitochondrial dysfunction is a leading cause of the overproduction of reactive oxygen species and oxidative stress. Mitochondrial changes play an important role in preventing oxidative stress. However, there is a lack of experimental evidence supporting this hypothesis. Thymus quinquecostatus CELAK (TQC) extract is a plant from China belonging to the thymus species, which can mediate the inflammatory response and prevent cell damage through its antioxidant activities. This study examines whether TQC can scavenge excess ROS originating from the mitochondria in RAW 264.7 macrophages. We used lipopolysaccharide (LPS) to induce inflammation and oxidative stress in RAW 264.7 macrophages and performed an immunocytochemistry dot blot of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and real-time PCR to analyze the expression levels of genes involved in mitochondrial biogenesis and oxidative metabolism. TQC was found to significantly reduce the intensity of immunostained MitoSOX and 8-OHdG levels in the total genomic DNA within the mitochondria in RAW 264.7 macrophages. The HO-1 and Nrf2 mRNA levels were also significantly increased in the TQC groups. Therefore, we verified that TQC improves mitochondrial function and attenuates oxidative stress induced by LPS. Our results can provide reference for the effect of TQC to develop new therapeutic strategies for various diseases.

Heme-Oxygenase and Kidney Transplantation: A Potential for Target Therapy?

Kidney transplantation is a well-established therapy for patients with end-stage renal disease. While a significant improvement of short-term results has been achieved in the short-term, similar results were not reported in the long-term. Heme-oxygenase (HO) is the rate-limiting enzyme in heme catabolism, converting heme to iron, carbon monoxide, and biliverdin. Heme-oxygenase overexpression may be observed in all phases of transplant processes, including brain death, recipient management, and acute and chronic rejection. HO induction has been proved to provide a significant reduction of inflammatory response and a reduction of ischemia and reperfusion injury in organ transplantation, as well as providing a reduction of incidence of acute rejection. In this review, we will summarize data on HO and kidney transplantation, suggesting possible clinical applications in the near future to improve the long-term outcomes.

Targeting Mitochondria during Cold Storage to Maintain Proteasome Function and Improve Renal Outcome after Transplantation

Kidney transplantation is the preferred treatment for end-stage kidney disease (ESKD). Compared to maintenance dialysis, kidney transplantation results in improved patient survival and quality of life. Kidneys from living donors perform best; however, many patients with ESKD depend on kidneys from deceased donors. After procurement, donor kidneys are placed in a cold-storage solution until a suitable recipient is located. Sadly, prolonged cold storage times are associated with inferior transplant outcomes; therefore, in most situations when considering donor kidneys, long cold-storage times are avoided. The identification of novel mechanisms of cold-storage-related renal damage will lead to the development of new therapeutic strategies for preserving donor kidneys; to date, these mechanisms remain poorly understood. In this review, we discuss the importance of mitochondrial and proteasome function, protein homeostasis, and renal recovery during stress from cold storage plus transplantation. Additionally, we discuss novel targets for therapeutic intervention to improve renal outcomes.

Pretreatment with Cholecalciferol Alleviates Renal Cellular Stress Response during Ischemia/Reperfusion-Induced Acute Kidney Injury

Background

Cellular stress is involved in ischemia/reperfusion- (I/R-) induced acute kidney injury (AKI). This study is aimed at investigating the effects of pretreatment with cholecalciferol on renal oxidative stress and endoplasmic reticulum (ER) stress during I/R-induced AKI.

Methods

I/R-induced AKI was established by cross-clamping renal pedicles for 90 minutes and then reperfusion. In the Chol + I/R group, mice were orally administered with three doses of cholecalciferol (25 μg/kg) at 1, 24, and 48 h before ischemia. Renal cellular stress and kidney injury were measured at different time points after reperfusion.

Results

I/R-induced AKI was alleviated in mice pretreated with cholecalciferol. In addition, I/R-induced renal cell apoptosis, as determined by TUNEL, was suppressed by cholecalciferol. Additional experiment showed that I/R-induced upregulation of renal GRP78 and CHOP was inhibited by cholecalciferol. I/R-induced renal IRE1α and eIF2α phosphorylation was attenuated by cholecalciferol. Moreover, I/R-induced renal GSH depletion, lipid peroxidation, and protein nitration were blocked in mice pretreated with cholecalciferol. I/R-induced upregulation of renal NADPH oxidases, such as p47phox, gp91phox, and nox4, was inhibited by cholecalciferol. I/R-induced upregulation of heme oxygenase- (HO-) 1, gshpx and gshrd, was attenuated in mice pretreated with cholecalciferol.

Conclusions

Pretreatment with cholecalciferol protects against I/R-induced AKI partially through suppressing renal cellular stress response.

Defining the optimal duration for normothermic regional perfusion in the kidney donor: A porcine preclinical study

Kidneys from donation after circulatory death (DCD) are highly sensitive to ischemia-reperfusion injury and thus require careful reconditioning, such as normothermic regional perfusion (NRP). However, the optimal NRP protocol remains to be characterized. NRP was modeled in a DCD porcine model (30 minutes of cardiac arrest) for 2, 4, or 6 hours compared to a control group (No-NRP); kidneys were machine-preserved and allotransplanted. NRP appeared to permit recovery from warm ischemia, possibly due to an increased expression of HIF1α-dependent survival pathway. At 2 hours, blood levels of ischemic injury biomarkers increased: creatinine, lactate/pyruvate ratio, LDH, AST, NGAL, KIM-1, CD40 ligand, and soluble-tissue-factor. All these markers then decreased with time; however, AST, NGAL, and KIM-1 increased again at 6 hours. Hemoglobin and platelets decreased at 6 hours, after which the procedure became difficult to maintain. Regarding inflammation, active tissue-factor, cleaved PAR-2 and MCP-1 increased by 4-6 hours, but not TNF-α and iNOS. Compared to No-NRP, NRP kidneys showed lower resistance during hypothermic machine perfusion (HMP), likely associated with pe-NRP eNOS activation. Kidneys transplanted after 4 and 6 hours of NRP showed better function and outcome, compared to No-NRP. In conclusion, our results confirm the mechanistic benefits of NRP and highlight 4 hours as its optimal duration, after which injury markers appear.

Characterization of Renal Injury and Inflammation in an Experimental Model of Intravascular Hemolysis

Intravascular erythrocyte destruction, accompanied by the release of pro-oxidative and pro-inflammatory components hemoglobin and heme, is a common event in the pathogenesis of numerous diseases with heterogeneous etiology and clinical features. A frequent adverse effect related to massive hemolysis is the renal injury and inflammation. Nevertheless, it is still unclear whether heme––a danger-associated molecular pattern––and ligand for TLR4 or upstream hemolysis-derived products are responsible for these effects. Well-characterized animal models of hemolysis with kidney impairment are needed to investigate how hemolysis drives kidney injury and to test novel therapeutic strategies. Here, we characterized the pathological processes leading to acute kidney injury and inflammation during massive intravascular hemolysis, using a mouse model of phenylhydrazine (PHZ)-triggered erythrocyte destruction. We observed profound changes in mRNA levels for markers of tubular damage (Kim-1, NGAL) and regeneration (indirect marker of tubular injury, Ki-67), and tissue and vascular inflammation (IL-6, E-selectin, P-selectin, ICAM-1) in kidneys of PHZ-treated mice, associated with ultrastructural signs of tubular injury. Moreover, mass spectrometry revealed presence of markers of tubular damage in urine, including meprin-α, cytoskeletal keratins, α-1-antitrypsin, and α-1-microglobulin. Signs of renal injury and inflammation rapidly resolved and the renal function was preserved, despite major changes in metabolic parameters of PHZ-injected animals. Mechanistically, renal alterations were largely heme-independent, since injection of free heme could not reproduce them, and scavenging heme with hemopexin in PHZ-administered mice could not prevent them. Reduced overall health status of the mice suggested multiorgan involvement. We detected amylasemia and amylasuria, two markers of acute pancreatitis. We also provide detailed characterization of renal manifestations associated with acute intravascular hemolysis, which may be mediated by hemolysis-derived products upstream of heme release. This analysis provides a platform for further investigations of hemolytic diseases and associated renal injury and the evaluation of novel therapeutic strategies that target intravascular hemolysis.

Head-to-head comparison of structurally unrelated dipeptidyl peptidase 4 inhibitors in the setting of renal ischemia reperfusion injury

Background and Purpose

Results regarding protective effects of dipeptidyl peptidase 4 (DPP4) inhibitors in renal ischaemia–reperfusion injury (IRI) are conflicting. Here we have compared structurally unrelated DPP4 inhibitors in a model of renal IRI.

Experimental Approach

IRI was induced in uninephrectomized male rats by renal artery clamping for 30 min. The sham group was uninephrectomized but not subjected to IRI. DPP4 inhibitors or vehicle were given p.o. once daily on three consecutive days prior to IRI: linagliptin (1.5 mg·kg⁻¹·day⁻¹), vildagliptin (8 mg·kg⁻¹·day⁻¹) and sitagliptin (30 mg·kg⁻¹·day⁻¹). An additional group received sitagliptin until study end (before IRI: 30 mg·kg⁻¹·day⁻¹; after IRI: 15 mg·kg⁻¹·day⁻¹).

Key Results

Plasma‐active glucagon‐like peptide type 1 (GLP‐1) increased threefold to fourfold in all DPP4 inhibitor groups 24 h after IRI. Plasma cystatin C, a marker of GFR, peaked 48 h after IRI. Compared with the placebo group, DPP4 inhibition did not reduce increased plasma cystatin C levels. DPP4 inhibitors ameliorated histopathologically assessed tubular damage with varying degrees of drug‐specific efficacies. Renal osteopontin expression was uniformly reduced by all DPP4 inhibitors. IRI‐related increased renal cytokine expression was not decreased by DPP4 inhibition. Renal DPP4 activity at study end was significantly inhibited in the linagliptin group, but only numerically reduced in the prolonged/dose‐adjusted sitagliptin group. Active GLP‐1 plasma levels at study end were increased only in the prolonged/dose‐adjusted sitagliptin treatment group.

Conclusions and Implications

In rats with renal IRI, DPP4 inhibition did not alter plasma cystatin C, a marker of glomerular function, but may protect against tubular damage.

Inadequate Antioxidative Responses in Kidneys of Brain-Dead Rats

BACKGROUND

Brain death (BD)-related lipid peroxidation, measured as serum malondialdehyde (MDA) levels, correlates with delayed graft function in renal transplant recipients. How BD affects lipid peroxidation is not known. The extent of BD-induced organ damage is influenced by the speed at which intracranial pressure increases. To determine possible underlying causes of lipid peroxidation, we investigated the renal redox balance by assessing oxidative and antioxidative processes in kidneys of brain-dead rats after fast and slow BD induction.

METHODS

Brain death was induced in 64 ventilated male Fisher rats by inflating a 4.0F Fogarty catheter in the epidural space. Fast and slow inductions were achieved by an inflation speed of 0.45 and 0.015 mL/min, respectively, until BD confirmation. Healthy non-brain-dead rats served as reference values. Brain-dead rats were monitored for 0.5, 1, 2, or 4 hours, after which organs and blood were collected.

RESULTS

Increased MDA levels became evident at 2 hours of slow BD induction at which increased superoxide levels, decreased glutathione peroxidase (GPx) activity, decreased glutathione levels, increased inducible nitric oxide synthase and heme-oxygenase 1 expression, and increased plasma creatinine levels were evident. At 4 hours after slow BD induction, superoxide, MDA, and plasma creatinine levels increased further, whereas GPx activity remained decreased. Increased MDA and plasma creatinine levels also became evident after 4 hours fast BD induction.

CONCLUSION

Brain death leads to increased superoxide production, decreased GPx activity, decreased glutathione levels, increased inducible nitric oxide synthase and heme-oxygenase 1 expression, and increased MDA and plasma creatinine levels. These effects were more pronounced after slow BD induction. Modulation of these processes could lead to decreased incidence of delayed graft function.

Heme Oxygenase-1 in Kidney Health and Disease

SIGNIFICANCE

Acute kidney injury (AKI) and chronic kidney disease (CKD) represent a considerable burden in healthcare. The heme oxygenase (HO) system plays an important role in regulating oxidative stress and is protective in a variety of human and animal models of kidney disease. Preclinical studies of the HO system have led to the development of several clinical trials targeting the enzyme or its products.

RECENT ADVANCES

Connection of HO, ferritin, and other proteins involved in iron regulation has provided important insight into mechanisms of damage in AKI. Also, HO-1 expression is important in the pathogenesis of hypertension, diabetic kidney disease, and progression to end-stage renal disease.

CRITICAL ISSUES

Despite intriguing discoveries, no drugs targeting the HO system have been translated to the clinic. Meanwhile, treatments for AKI and CKD are urgently needed. Many factors have likely contributed to challenges in clinical translation, including variation in animal models, difficulties in obtaining human tissue, and complexity of the disease processes being studied.

FUTURE DIRECTIONS

The HO system represents a promising avenue of investigation that may lead to targeted therapeutics. Tissue-specific gene modulation, widening the scope of animal studies, and continued clinical research will provide valuable insight into the role HO plays in kidney homeostasis and disease. Antioxid. Redox Signal. 25, 165-183.

Heme oxygenase‑1 protects H2O2‑insulted glomerular mesangial cells from excessive autophagy

Increasing evidence has demonstrated that the activation of heme oxygenase (HO)‑1 reduces autophagy stimulated by oxidative stress injury, in which the supraphysiological production of reactive oxygen species (ROS) is detected. However, the potential mechanism underlying this effect remains unclear. The present study aimed to investigate the function of HO‑1 activation in the regulation of autophagy in glomerular mesangial cells subjected to H2O2‑induced oxidative stress injury. The results demonstrated that the HO‑1 agonist, hemin, reduces the LC3 protein level, which was enhanced by H2O2 treatment. Furthermore, hemin‑activated HO‑1 may function as a regulator of oxidative stress‑induced autophagy in a dose‑dependent manner. Pharmacological activation of c‑Jun N‑terminal kinase (JNK) inhibited the effect of hemin, indicating that the JNK signaling pathway is associated with the mechanism of HO‑1 in impeding excessive autophagy. In addition to successfully alleviating H2O2‑induced oxidative stress and cellular apoptosis, hemin‑activated HO‑1 may provide cytoprotection against rapamycin, a specific autophagy agonist. The present result suggested the inhibitory action of HO‑1 in the avoidance of a potentially enhanced linkage between autophagy and apoptosis, particularly in the setting of excessive ROS. Therefore, enhancing the intracellular activity of HO‑1 may assist the crosstalk between oxidative stress, autophagy and apoptosis, and represent a novel therapeutic strategy for renal ischemic disease.

Targeting HO-1 by Epigallocatechin-3-Gallate Reduces Contrast-Induced Renal Injury via Anti-Oxidative Stress and Anti-Inflammation Pathways

Both oxidative stress and inflammation are involved in the pathogenesis of contrast-induced nephropathy (CIN). Epigallocatechin-3-gallate (EGCG), a purified catechin from green tea, has antioxidant and anti-inflammatory effects. However, it is unknown whether or not EGCG is effective in treating CIN. Our present study found that intravenous administration of EGCG, either before or just after the establishment of CIN, had a protective effect, determined by normalization of serum creatinine and blood urea nitrogen levels, improvement in renal histopathological scoring and alleviation of apoptosis, accompanied by decreased oxidative stress and inflammation. Because EGCG is a potent inducer of the antioxidant heme oxygenase-1 (HO-1), we studied HO-1 signaling in CIN. HO-1 levels were increased in CIN; treatment with EGCG further increased HO-1 levels, accompanied by an increase in Nrf2, a regulator of antioxidant proteins. Interestingly, blockade of HO-1 with protoporphyrin IX zinc(II) (ZnPP) prevented the protective effect of EGCG on CIN. ZnPP also blocked the ability of EGCG to increase the activity of an antioxidant (superoxide dismutase), and decrease markers of oxidative stress (myeloperoxidase and malondialdehyde) and inflammation (myeloperoxidase and IL-1β), indicating that HO-1 is the upstream molecule that regulates the EGCG-mediated protection. To determine further the role of HO-1 on the EGCG-mediated inhibition of inflammation, we studied the effect of EGCG on the NLRP3 inflammasome, an upstream signaling of IL-1β. EGCG down-regulated NLRP3 expression, which was blocked by ZnPP, indicating that HO-1 links EGCG with NLRP3. Therefore, EGCG, via up-regulation of HO-1, protects against CIN by amelioration of oxidative stress and inflammation.

Cobalt protoporphyrin protects the liver against apoptosis in rats of brain death

Brain death (BD) leads to a marked increase in apoptosis, which influences the viability of donor organs. Induction of heme oxygenase 1 (HO-1) has been shown to exert beneficial effects in different liver injury models. Therefore, we examined the effect of pretreating rats with cobalt protoporphyrin (CoPP), an HO-1 inducer, on apoptosis in liver during BD and elucidated the mechanisms involved. First, rats were killed at 0, 1, 2, 4 and 6 h after BD induction to examine the expression of hepatic HO-1. Second, rats were randomly divided into four groups (n=6): (S group) rats undergoing sham operation, (CS group) rats pretreated with CoPP for 24 h before the sham operation, (B group) rats undergoing BD for 6 h, (CB group) rats pretreated with CoPP for 24 h before BD induction. The expression levels of hepatic HO-1 mRNA and protein in rats increased at 0, 1, 2, 4 and 6h after BD induction, compared with sham operated rats. In the CB group compared with the B group, the increased hepatic expression of HO-1 correlated with a significant decrease in serum ALT/AST levels, fewer apoptotic cells in liver, increased hepatic expression of Mcl-1 and Bcl-2, and decreased hepatic expression of Bax, cytosolic cytochrome c and cleaved caspase-3. CoPP inhibits apoptosis in liver of BD rats in part via modulating the mitochondrial apoptosis pathway. HO-1 may serve as a potential target for improving the quality of organs from BD donors.

Biliary tract external drainage alleviates kidney injury in shock

BACKGROUND

Kidney injury is common in hemorrhagic shock (HS). Kidney injury leads to a systemic increase in serum chemokines and cytokines and causes injuries to other vital organs. Our previous studies showed that vitamin C led to organ protection and inflammation inhibitory effects in rat models of HS via induction heme oxygenase-1 (HO-1). We also found that biliary tract external drainage (BTED) increased the expression levels of HO-1 in rat livers. We investigated roles of BTED in kidney injury and its relationship with the HO-1 pathway in HS in this research.

METHODS

Rat models of HS were induced by drawing blood from the femoral artery. BTED was performed by inserting a catheter into the bile duct. Thirty-six Sprague-Dawley rats were randomized to sham group; HS group; zinc protoporphyrin IX (Znpp) group; BTED group; BTED + Znpp group, and BTED + bile infusion group. The expression levels of HO-1 in the kidney were analyzed by Western blotting. The expression levels of occludin messenger RNA in the kidney were analyzed by real-time reverse transcription-polymerase chain reaction. The expression levels of occludin in the kidney were analyzed by immunohistochemistry. Histology of renal was performed by hematoxylin and eosin staining.

RESULTS

Occludin messenger RNA and protein levels in the kidney increased markedly after BTED under HS conditions. Renal histopathologic scores decreased significantly after BTED under HS conditions. Znpp significantly inhibited all mentioned effects.

CONCLUSIONS

BTED alleviates kidney injury in rats of HS via the HO-1 pathway.

Targeting stress responses for regenerative medicine

Some internal and external stimuli elicit stress responses on the cellular level and at the level of the organism. When the stimulus is brief and its intensity mild to moderate, it triggers adaptation changes that improve the cell's or organism's survival. This adaptation is achieved through a variety of cellular mechanisms such as induction of repair mechanisms, improved removal of damaged macromolecules, upregulation of endogenous antioxidant defenses, and prevention of apoptosis triggering by moderate stressors. The key intracellular signaling pathways involved in stress adaptation are the mTORC1 and SIRT1. Manipulating these stress adaptation signaling pathways with a variety of agents, improves the cellular adaptation to stress, prolongs cell survival, and improves the transplantation outcome in animal models and in clinical trials. The challenge for the future is to fine-tune the numerous experimental techniques to suit the needs of transplantation and regenerative medicine.

Adipose tissue-derived stem cells suppress acute cellular rejection by TSG-6 and CD44 interaction in rat kidney transplantation

BACKGROUND

In addition to its abundance and easy accessibility, adipose tissue yields more potent immunoregulatory stem cells (adipose tissue-derived stem cells, ADSCs) than does bone marrow. However, the beneficial effects of ADSCs on alloreactivity are scarcely known. This study evaluated the beneficial effects of ADSCs in rat kidney transplantation and analyzed the underlying molecular mechanism.

METHODS

Dark Agouti rat kidneys were transplanted into Lewis rats. Autologous ADSCs (2×10) were injected through the left renal artery of the donors before the nephrectomy (ADSCs group). Graft survival, histologic changes, and the expression of several cytokines and proteins were assessed. In an in vitro experiment, the immunosuppressive capacity of ADSCs was tested in a mixed lymphocyte reaction.

RESULTS

Histologic findings of the ADSCs group revealed a reduced rejection grade, whereas the number of infiltrated CD4/CD8 T cells was also significantly decreased as compared to the control. Relative to these findings, injection of ADSCs led to a significantly prolonged mean graft survival compared with the control. In vitro, autologous ADSCs dose-dependently suppressed alloreactive lymphocytes. Moreover, ADSCs increased the level of tumor necrosis factor-inducible gene 6 protein (TSG-6) in mixed lymphocyte reaction, which has an anti-inflammatory capacity. Recombinant TSG-6 markedly suppressed alloreactive T cells through downregulating CD44, which may lead to the suppression of T-cell activation and infiltration into allografts.

CONCLUSION

Our findings clearly showed that ADSCs attenuated acute rejection by secreting TSG-6 as well as through direct cell interaction. These findings contribute to the clinical application of these cells in solid organ transplantation.

A comparison of inflammatory, cytoprotective and injury gene expression profiles in kidneys from brain death and cardiac death donors

BACKGROUND

The superior long-term survival of kidneys from living donors (LDs) compared with kidneys from donation-after-brain-death (DBD) and donation-after-cardiac-death (DCD) donors is now well established. However, comparative studies on transcriptional changes that occur at organ retrieval and during and after cold ischemia (CI) are sparse.

METHODS

Using a rat model, we used qRT-PCR to examine expression levels of inflammatory, cytoprotective, and injury genes at different time points after organ retrieval. Cleaved caspase-3 was used to evaluate early apoptosis in DCD and DBD kidneys.

RESULTS

Immediately after retrieval, we found massive up-regulation of proinflammatory genes interleukin-1β, interleukin-6, tumor necrosis factor-α, monocyte chemotactic protein-1, P-selectin, and E-selectin in DBD compared with LD and DCD kidneys. A significant increase in the expression of injury markers Kim-1, p21, and the cytoprotective gene heme oxygenase-1 accompanied this. Bax was increased in DCD kidneys, and Bcl-2 was decreased in DBD kidneys. After 2 hr of CI in the LD group and 18 hr in the DBD and DCD groups, gene expression levels were similar to those found after retrieval. During 18 hr of cold storage, expression levels of these genes did not change. In DCD and DBD kidneys, early apoptosis increased after CI.

DISCUSSION/CONCLUSION

The gene expression profile in DBD kidneys represents an inflammatory and injury response to brain death. In contrast, DCD kidneys show only mild up-regulation of inflammatory and injury genes. These results may imply why delayed graft function in DCD kidneys does not have the deleterious effect it has on DBD kidneys.

Osteoblast-secreted factors promote proliferation and osteogenic differentiation of bone marrow stromal cells via VEGF/heme-oxygenase-1 pathway

The hypoxia-inducible factors (HIFα) are the critical factors that couple angiogenesis and osteogenesis by activating transcription of VEGF in osteoblasts. Mice lacking von Hippel-Lindau gene (Vhl), thus overexpressing HIFα in osteoblasts develop extremely dense and highly vascularized long bones. Here we provide evidence that osteoblasts lacking Vhl overexpress and secrete high levels of VEGF, which subsequently promotes the proliferation and osteogenic differentiation of bone marrow stromal cells (BMSC) by promoting expression of Heme oxygenase-1 (HO-1) in BMSC. Conditioned medium from osteoblasts Vhl (CM-CRE) promoted the proliferation and osteogenic differentiation of BMSC, in comparison with conditioned medium derived from normal osteoblasts (CM-GFP). Recombinant VEGF stimulated the proliferation and osteogenic differentiation of BMSC culturing in CM-GFP. By contrast, VEGF-neutralizing antibody inhibited the proliferation and osteogenic differentiation of BMSC culturing in CM-CRE. Treatment with a HO-1 inhibitor, SnPP, significantly inhibited VEGF-induced BMSC proliferation and osteogenic differentiation. On the contrary, activation of HO-1 with CoPP reversed the suppressing of VEGF-antibody on the proliferation and osteogesis of BMSC culturing in CM-CRE. These studies suggest that osteoblasts promote the proliferation and osteogenic differentiation of BMCS by VEGF/HO-1 pathway.

Emerging role of gasotransmitters in renal transplantation

Once patients with kidney disease progress to end-stage renal failure, transplantation is the preferred option of treatment resulting in improved quality of life and reduced mortality compared to dialysis. Although 1-year survival has improved considerably, graft and patient survival in the long term have not been concurrent, and therefore new tools to improve long-term graft and patient survival are warranted. Over the past decades, the gasotransmitters nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) have emerged as potent cytoprotective mediators in various diseases. All three gasotransmitters are endogenously produced messenger molecules that possess vasodilatory, anti-apoptotic, anti-inflammatory and anti-oxidant properties by influencing an array of intracellular signaling processes. Although many regulatory functions of gasotransmitters have overlapping actions, differences have also been reported. In addition, crosstalk between NO, CO and H2S results in synergistic regulatory effects. Endogenous and exogenous manipulation of gasotransmitter levels modulates several processes involved in renal transplantation. This review focuses on mechanisms of gas-mediated cytoprotection and complex interactions between gasotransmitters in renal transplantation.

Protective effect of zinc-N-acetylcysteine on the rat kidney during cold storage

Cold storage of kidneys before transplantation is problematic because of the limited survival time of the allografts. In this study, zinc-N-acetylcysteine (ZnNAC) was shown to be a potent endonuclease inhibitor and antioxidant, and it was tested as a potential additive to a cold storage solution for kidney preservation. Exposure of normal rat kidney NRK-52E cells to ZnNAC resulted in zinc delivery to the cells as determined by TFL-Zn fluorophore and partial protection of the cells against injury by cold storage in University of Wisconsin solution (UWS) as measured by propidium iodide assay. Ex vivo, rat kidneys demonstrated time- and temperature-dependent DNA fragmentation as assessed by TUNEL assay, indicating irreversible cell death. DNA fragmentation was faster in the medulla than in the cortex, and tubules were affected more than glomeruli. Perfusion of rat kidneys with cold ZnNAC solution in UWS significantly inhibited cell death both in the cortex and medulla at concentrations of 0.3-30 mM compared with UWS alone, with a maximum effect at 1-10 mM ZnNAC. Cold storage of the kidney significantly increased quantities of cleaved caspase-3 and endonuclease G (EndoG) in the tissue, which were abolished by 10 mM ZnNAC, indicating its ability to suppress both caspase-dependent and -independent cell death. Therefore, supplementation of UWS with ZnNAC can decrease DNA fragmentation and protect kidney allografts from cell death due to cold storage.

Therapeutic angiogenesis for revascularization in peripheral artery disease

Therapeutic angiogenesis for peripheral artery disease (PAD), achieved by gene and cell therapy, has recently raised a great deal of hope for patients who cannot undergo standard revascularizing treatment. Although pre-clinical studies gave very promising data, still clinical trials of gene therapy have not provided satisfactory results. On the other hand, cell therapy approach, despite several limitations, demonstrated more beneficial effects but initial clinical studies must be constantly validated by larger randomized, multi-center, double-blinded, placebo-controlled trials. This review focuses on previous and recent gene and cell therapy studies for limb ischemia, including both experimental and clinical research, and summarizes some important papers published in this field. Moreover, it provides a short comment on combined gene and cell therapy approach on the example of heme oxygenase-1 overexpressing cells with therapeutic properties.

Brain death induces renal expression of heme oxygenase-1 and heat shock protein 70

Background

Kidneys derived from brain dead donors have lower graft survival and higher graft-function loss compared to their living donor counterpart. Heat Shock Proteins (HSP) are a large family of stress proteins involved in maintaining cell homeostasis. We studied the role of stress-inducible genes Heme Oxygenase-1 (HO-1), HSP27, HSP40, and HSP70 in the kidney following a 4 hour period of brain death.

Methods

Brain death was induced in rats (n=6) by inflating a balloon catheter in the epidural space. Kidneys were analysed for HSPs using RT-PCR, Western blotting, and immunohistochemistry.

Results

RT-PCR data showed a significant increase in gene expression for HO-1 and HSP70 in kidneys of brain dead rats. Western blotting revealed a massive increase in HO-1 protein in brain dead rat kidneys. Immunohistochemistry confirmed these findings, showing extensive HO-1 protein expression in the renal cortical tubules of brain dead rats. HSP70 protein was predominantly increased in renal distal tubules of brain dead rats treated for hypotension.

Conclusion

Renal stress caused by brain death induces expression of the cytoprotective genes HO-1 and HSP70, but not of HSP27 and HSP40. The upregulation of these cytoprotective genes indicate that renal damage occurs during brain death, and could be part of a protective or recuperative mechanism induced by brain death-associated stress.

Transcriptome analysis of renal ischemia/reperfusion injury and its modulation by ischemic pre-conditioning or hemin treatment

Ischemia/reperfusion injury (IRI) is a leading cause of acute renal failure. The definition of the molecular mechanisms involved in renal IRI and counter protection promoted by ischemic pre-conditioning (IPC) or Hemin treatment is an important milestone that needs to be accomplished in this research area. We examined, through an oligonucleotide microarray protocol, the renal differential transcriptome profiles of mice submitted to IRI, IPC and Hemin treatment. After identifying the profiles of differentially expressed genes observed for each comparison, we carried out functional enrichment analysis to reveal transcripts putatively involved in potential relevant biological processes and signaling pathways. The most relevant processes found in these comparisons were stress, apoptosis, cell differentiation, angiogenesis, focal adhesion, ECM-receptor interaction, ion transport, angiogenesis, mitosis and cell cycle, inflammatory response, olfactory transduction and regulation of actin cytoskeleton. In addition, the most important overrepresented pathways were MAPK, ErbB, JAK/STAT, Toll and Nod like receptors, Angiotensin II, Arachidonic acid metabolism, Wnt and coagulation cascade. Also, new insights were gained about the underlying protection mechanisms against renal IRI promoted by IPC and Hemin treatment. Venn diagram analysis allowed us to uncover common and exclusively differentially expressed genes between these two protective maneuvers, underscoring potential common and exclusive biological functions regulated in each case. In summary, IPC exclusively regulated the expression of genes belonging to stress, protein modification and apoptosis, highlighting the role of IPC in controlling exacerbated stress response. Treatment with the Hmox1 inducer Hemin, in turn, exclusively regulated the expression of genes associated with cell differentiation, metabolic pathways, cell cycle, mitosis, development, regulation of actin cytoskeleton and arachidonic acid metabolism, suggesting a pleiotropic effect for Hemin. These findings improve the biological understanding of how the kidney behaves after IRI. They also illustrate some possible underlying molecular mechanisms involved in kidney protection observed with IPC or Hemin treatment maneuvers.

The role of heat shock protein 90 in modulating ischemia-reperfusion injury in the kidney

INTRODUCTION

Kidney transplantation is the gold standard treatment for end-stage renal disease. Ischemia-reperfusion injury (IRI) is an unavoidable consequence of the transplantation procedure and is responsible for delayed graft function and poorer long-term outcomes.

AREAS COVERED

Pharmacological induction of heat shock protein (Hsp) expression is an emerging pre-conditioning strategy aimed at reducing IRI following renal transplantation. Hsp90 inhibition up-regulates protective Hsps (especially Hsp70) and potentially down-regulates NF-κB by disruption of the IκB kinase (IKK) complex. However, the clinical application of Hsp90 inhibitors is currently limited by their toxicity profile and the exact mechanism of protection conferred is unknown. Toll-like receptor 4 (TLR4) is a further regulator of NF-κB and recent studies suggest TLR4 plays a dominant role in mediating kidney damage following IRI. The full interaction of Hsps with TLRs is yet to be delineated and whether TLR4 signalling can be targeted by Hsp90 inhibition in IRI remains uncertain.

EXPERT OPINION

Pharmacological pre-conditioning by Hsp90 inhibition involves direct treatment to the kidney donor and/or organ, which aims to reduce injury prior to the onset of ischemia. The major challenges going forward are to establish the exact mechanism of protection offered by these drugs and the investgiation of less toxic analogues that could be safely translated into human studies.

Methanol Extract of Goat's-beard (Aruncus dioicus) Reduces Renal Injury by Inhibiting Apoptosis in a Rat Model of Ischemia-Reperfusion

Interruption or prolonged reduction and subsequent restoration of blood flow into the kidney triggers the generation of a burst of reactive oxygen species (ROS), leading to injury in the tubular epithelial cells. In this study, we determined whether methanol extract of goat's-beard (Aruncus dioicus) (extract) could prevent this ischemia/re-perfusion injury. When in vitro radical scavenging activity of the extract was measured using a DPPH radical quenching assay, the extract displayed slightly lower activity than ascorbic acid. One hour after administration of the extract (400 mg/kg) by intraperitoneal injection in rats, renal ischemia/reperfusion injury was generated by clamping the left renal artery for forty minutes, followed by 24 hr restoration of blood circulation. Prior to clamping the left renal artery, the right renal artery was removed. Compared with the vehicle-treated group, pre-treatment with the extract significantly reduced the tubular epithelial cell injury by 37% in the outer medulla region, and consequently reduced serum creatinine concentration by 39%. Reduction in the cell injury was mediated by attenuation of Bax/Bcl-2 ratio, inhibition of caspase-3 activation from procaspase-3, and subsequent reduction in the number of apoptotic cells. Thus, goat's-beard (Aruncus dioicus) might be developed as a prophylactic agent to prevent acute kidney injury.

Cell damage following carbon monoxide releasing molecule exposure: implications for therapeutic applications

The cytoprotective properties of carbon monoxide (CO) gas and CO-releasing molecules (CORMs) are well established. Despite promising pre-clinical results, little attention has been paid to the toxicological profile of CORMs. The effects of CORM-2 and its CO-depleted molecule (iCORM-2) (20-400 μM) were compared in primary rat cardiomyocytes and two cell lines [human embryonic kidney (HeK) and Madine-Darby canine kidney Cells (MDCK)]. Cells were assessed for cell viability, apoptosis, necrosis, cytology, mitochondrial energetics, oxidative stress and cell cycle arrest markers. In separate experiments, the anti-apoptotic effects of CORM-2 and i-CORM-2 treatment were compared against CO gas treatment in HeK and MDCK lines. H(2)O(2) -induced cellular damage, measured by lactate dehydrogenase (LDH) release from primary cardiomyocytes, was reduced by 20 μM CORM-2; LDH activity, however, was directly inhibited by 400 μM CORM-2. Both CORM-2/iCORM-2 and CO gas decreased cisplatin-induced caspase-3 activity in MDCK and HeK cells suggesting an anti-apoptotic effect. Conversely, both CORM-2 and iCORM-2 induced significant cellular toxicity in the form of decreased cell viability, abnormal cell cytology, increased apoptosis and necrosis, cell cycle arrest and reduced mitochondrial enzyme activity. Comparison of these markers after CO gas administration to MDCK cells found significantly less cellular toxicity than in 100 μM CORM-2/iCORM-2-treated cells. CO gas did not have an adverse effect on mitochondrial energetics and integrity. Release of CO by low concentrations of intact CORM-2 molecules provides cytoprotective effects. These results show, however, that the ruthenium-based CORM by-product, iCORM-2, is cytotoxic and suggest that the accumulation of iCORM-2 would seriously limit any clinical application of the ruthenium-based CORMs.

Activation of hypoxia-inducible factor-1 ameliorates postischemic renal injury via inducible nitric oxide synthase

Hypoxia-inducible factor-1 (HIF-1) could ameliorate renal ischemia reperfusion injury (IRI), but the underlying mechanism remains elusive. In the current study, we aim to investigate the possible role of prolyl hydroxylases inhibitor dimethyloxalylglycine (DMOG) in inducing delayed preconditioning-like effects against IRI. Mice were divided into four groups (n = 6): sham group; IRI group; DMOG group: pretreated with DMOG 24 h before IRI; and GW274150 + DMOG group: pretreated with DMOG followed by iNOS inhibitor GW274150 treatment 24 h before IRI. The results showed that the protein level of HIF-1a and the expression of its targets inducible nitric oxide synthase (iNOS), erythropoietin, and heme oxygenase-1 were obviously increased after administration of DMOG. Histological analysis of renal function showed improvement in tubulointerstitial injury due to ischemia by delayed preconditioning with DMOG. GW274150 antagonized the delayed renal protection afforded by DMOG as reflected by deteriorated renal dysfunction, aggravated histological injury, increased renal cell apoptosis, and increased vimentin expression in the kidney. In conclusion, our data demonstrate that DMOG pretreatment induces delayed renal protection against IRI in mice and the beneficial effects are mitigated by pharmacological inhibition of iNOS, suggesting that the protective effects derived from HIF-1 activation via DMOG in the kidney are partially mediated by iNOS.

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).

Epigallocatechin-3-gallate protects kidneys from ischemia reperfusion injury by HO-1 upregulation and inhibition of macrophage infiltration

Epigallocatechin-3-gallate (EGCG) shows diverse chemical and biological activities. We investigated the effects of EGCG in a rat renal ischemia reperfusion (I/R) injury model. Sprague-Dawley rats received intraperitoneal injection of 50 mg/kg EGCG 48 h, 24 h, and 30 min prior to I/R injury. The animals were subjected to left renal occlusion for 45 min. EGCG treatment suppressed the peak in serum creatinine. EGCG-treated kidneys showed significantly less tubular damage and a decreased number of apoptotic cells. The I/R-induced elevation in the renal MDA level was significantly decreased in the EGCG group. Reverse-transcriptase polymerase chain reaction showed that EGCG significantly decreased the expression of MHC class II, TLR2, TLR4, MCP-1, IL-18, TGF-β1, procollagen Ia1, TIMP-1, and Kim-1. ED-1 staining showed reduced macrophage infiltration and α-SMA staining revealed less interstitial expression. Heme oxygenase-1 (HO-1) expression in I/R kidneys was upregulated in the EGCG group based on the results of both RT-PCR and Western blotting analysis. Blockade of HO-1 gene induction by SnPP increased renal tubular damage and macrophage infiltration. These findings suggest that EGCG protects the kidneys against I/R injury by reducing macrophage infiltration and decreasing renal fibrosis. These beneficial effects may be mediated, in part, by augmentation of the HO-1 gene.

Innate pathways of immune activation in transplantation

Studies of the immune mechanisms of allograft rejection have predominantly focused on the adaptive immune system that includes T cells and B cells. Recent investigations into the innate immune system, which recognizes foreign antigens through more evolutionarily primitive pathways, have demonstrated a critical role of the innate immune system in the regulation of the adaptive immune system. Innate immunity has been extensively studied in its role as the host's first-line defense against microbial pathogens; however, it is becoming increasingly recognized for its ability to also recognize host-derived molecules that result from tissue damage. The capacity of endogenous damage signals acting through the innate immune system to lower immune thresholds and promote immune recognition and rejection of transplant grafts is only beginning to be appreciated. An improved understanding of these pathways may reveal novel therapeutic targets to decrease graft alloreactivity and increase graft longevity.

Role of heme oxygenase-1 in transplantation

Heme oxygenase-1 (HO-1) is the rate-limiting enzyme in heme catabolism that converts heme to Fe++, carbon monoxide and biliverdin. HO-1 acts anti-inflammatory and modulates apoptosis in many pathological conditions. In transplantation, HO-1 is overexpressed in organs during brain death, when undergoing ischemic damage and rejection. However, intentionally induced, it ameliorates pathological processes like ischemia reperfusion injury, allograft, xenograft or islet rejection, facilitates donor specific tolerance and alleviates chronic allograft changes. We herein consistently summarize the huge amount of data on HO-1 and transplantation that have been generated in multiple laboratories during the last 15years and suggest possible clinical implications and applications for the near future.

Inhaled carbon monoxide prevents acute kidney injury in pigs after cardiopulmonary bypass by inducing a heat shock response

BACKGROUND

Cardiopulmonary bypass (CPB) may be associated with acute kidney injury (AKI). Inhaled carbon monoxide (CO) is cyto- and organ-protective. We hypothesized that pretreatment with inhaled CO prevents CPB-associated AKI.

METHODS

Pigs (n = 38) were nonrandomly assigned to SHAM, standard CPB, pretreatment with inhaled CO (250 ppm, 1 hour) before SHAM or CPB, to pretreatment with quercetin (an inhibitor of the heat shock response), and to pretreatment with SnPPIX (an inhibitor of endogenously derived CO), before CO inhalation and CPB. The primary outcome variables were markers of AKI (urea, uric acid, creatinine, cystatin C, neutrophil gelatinase-associated lipocalin, interleukin-6, tumor necrosis factor-alpha), which were determined 120 minutes after CPB. Secondary outcome variables were heat shock protein (HSP)-70 and heme oxygenase-1 protein expressions as indicators of CO-mediated heat shock response.

RESULTS

Pretreatment with inhaled CO attenuated (all P < 0.001) CPB-associated, (1) increases in serum concentrations of cystatin C (64 +/- 14 vs 28 +/- 9 ng/mL), neutrophil gelatinase-associated lipocalin (391 +/- 65 vs 183 +/- 56 ng/mL), renal tumor necrosis factor-alpha (450 +/- 73 vs 179 +/- 110 pg/mL), and interleukin-6 (483 +/- 102 vs 125 +/- 67 pg/mL); (2) increase in renal caspase-3 activity (550 +/- 66 vs 259 +/- 52 relative fluorescent units); and (3) histological evidence of AKI. These effects were accompanied by activation of HSP-70 (196 +/- 64 vs 554 +/- 149 ng/mL, P < 0.001). Pretreatment with the heat shock response inhibitor quercetin counteracted the CO-associated biochemical and histological renoprotective effects (all P < 0.001), whereas the heme oxygenase inhibitor SnPPIX only partially counteracted the CO-associated renoprotection and the activation of the heat shock response.

CONCLUSIONS

CO treatment before CPB was associated with evidence of renoprotection, demonstrated by fewer histological injuries and decreased cystatin C concentrations. The findings that the antiinflammatory and antiapoptotic effects of CO were accompanied by activation of HSP-70, which in turn were reversed by quercetin, suggest that renoprotection by pretreatment with inhaled CO before CPB is mediated by activation of the renal heat shock response.

Epoetin delta reduces oxidative stress in primary human renal tubular cells

Erythropoietin (EPO) exerts (renal) tissue protective effects. Since it is unclear whether this is a direct effect of EPO on the kidney or not, we investigated whether EPO is able to protect human renal tubular epithelial cells (hTECs) from oxidative stress and if so which pathways are involved. EPO (epoetin delta) could protect hTECs against oxidative stress by a dose-dependent inhibition of reactive oxygen species formation. This protective effect is possibly related to the membranous expression of the EPO receptor (EPOR) since our data point to the membranous EPOR expression as a prerequisite for this protective effect. Oxidative stress reduction went along with the upregulation of renoprotective genes. Whilst three of these, heme oxygenase-1 (HO-1), aquaporin-1 (AQP-1), and B-cell CLL/lymphoma 2 (Bcl-2) have already been associated with EPO-induced renoprotection, this study for the first time suggests carboxypeptidase M (CPM), dipeptidyl peptidase IV (DPPIV), and cytoglobin (Cygb) to play a role in this process.

Brain death and its influence on the lungs of the donor: how is it prevented?

The need for lung grafts is currently greater than ever. Unfortunately, the availability of grafts is insufficient for this demand. So we are forced to request organs for transplantation in the "waste bin." One possible solution to this problem may be the use of grafts from brain-dead patients. Sadly brain death is followed by devastating hemodynamic, inflammatory, and neurohumoral reactions in the potential donor which not only inflict direct damage, but also induce activation of the immune system which can cause rejection or even graft failure. Therefore, various groups have examined measures to prevent this outcome. In this review, we attempt to reconstruct the events that follow brain death, suggesting an algorithm to prevent a brain-dead patient's lungs from further damage. Finally, we are proposing potential measures of graft's protection of further investigation.

Is Ozone Really a “Wonder Drug”?

Even if the reader has only browsed through the previous chapters, he ought to have received my feeling that ozone has an enormous therapeutic potential that, so far, has been either disregarded, if not obstructed by world medical authorities. Reasons for delaying the use of ozone are multiple: while quacks and inexpert ozonetherapists are at fault for poor work, other aspects such as commercial and pharmaceutical interests, prejudice, lack of knowledge and a myopic medical vision have done their best to block a substantial and rapid progress.

Carbon Monoxide (CO) Protects Renal Tubular Epithelial Cells against Cold-Rewarm Apoptosis

Recent studies have suggested that carbon monoxide (CO) inhalation can reduce ischemia-reperfusion injury of kidneys. The purpose of the present study was to determine whether the direct application of CO using tricarbonylchloro (glycinato) ruthenium II (CORM3) would reduce cold-rewarm-associated apoptosis in renal tubular epithelial (RPTE) cells. RPTE cells were subjected to 48 hours of cold followed by 24 hours of rewarming with increasing concentrations (0-500 microM) of CORM3. CORM3 (100 microM) reduced apoptosis as determined by the TUNEL method from 21.6 +/- 5.2 to 5.8 +/- 1.1 % (untreated vs. treated, n = 5; p < 0.001). We subsequently observed that the incubation of RPTE cells with CORM3 induced heme oxygenase (HO)-1 gene expression. As HO-1 itself can confer protection against cold rewarm injury, we investigated the role of HO-1 in the protective actions of CORM3 using siRNA oligonucleotides directed against HO-1. CORM3 treatment of RPTE cells caused a 4.9- fold increase in HO-1 gene expression as determined by real time PCR. Prior treatment of RPTE cells with siRNAs against HO-1 was able to completely abolish the CORM3 mediated induction of HO-1 mRNA and protein. The abolition of HO-induction with siRNAs did reduce CORM3-mediated protection against cold rewarm-induced apoptosis; however, CORM3 was able to significantly protect RPTE cells against cold-rewarm injury: apoptosis was 33.7 +/- 0.9% vs. 15.4 +/- 0.5% vs. 62.8 +/- 1.5% vs. 23.5 +/- 3.4 in control cold-rewarm vs. cold-rewarm + CORM3 (100 microM) vs. cold-rewarm + HO-1 siRNA vs. cold-rewarm + CORM3 (100 microM) + HO-1 siRNA (n = 4). These results suggest that increased levels of CO alone can protect against cold-rewarm-induced apoptosis.