Induction of hemeoxygenase-1 reduces glomerular injury and apoptosis in diabetic spontaneously hypertensive rats

Diabetic Nephropathy and Gaseous Modulators

Diabetic nephropathy (DN) remains the leading cause of vascular morbidity and mortality in diabetes patients. Despite the progress in understanding the diabetic disease process and advanced management of nephropathy, a number of patients still progress to end-stage renal disease (ESRD). The underlying mechanism still needs to be clarified. Gaseous signaling molecules, so-called gasotransmitters, such as nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S), have been shown to play an essential role in the development, progression, and ramification of DN depending on their availability and physiological actions. Although the studies on gasotransmitter regulations of DN are still emerging, the evidence revealed an aberrant level of gasotransmitters in patients with diabetes. In studies, different gasotransmitter donors have been implicated in ameliorating diabetic renal dysfunction. In this perspective, we summarized an overview of the recent advances in the physiological relevance of the gaseous molecules and their multifaceted interaction with other potential factors, such as extracellular matrix (ECM), in the severity modulation of DN. Moreover, the perspective of the present review highlights the possible therapeutic interventions of gasotransmitters in ameliorating this dreaded disease.

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.

RhoA/ROCK inhibition attenuates endothelin-1-induced elevated glomerular permeability to albumin, inflammation, and fibrosis

Endothelin-1 (ET-1) contributes to the development of kidney diseases. However, the underlying molecular mechanism is largely undefined. Here we sought to investigate the potential role of ET-1 receptors, ET_A and ET_B in the regulation of increased glomerular permeability and underlying signaling pathways post-ET-1 infusion. Male Sprague-Dawley rats were infused with ET-1 (2 pmol/kg per minute, i.v.) for four weeks, and the effect on glomerular permeability to albumin (P_alb) and albuminuria was measured. The selective ROCK-1/2 inhibitor, Y-27632, was administered to a separate group of rats to determine its effect on ET-1-induced P_alb and albuminuria. The role of ET_A and ET_B receptors in regulating RhoA/ROCK activity was determined by incubating isolated glomeruli from normal rats with ET-1 and with selective ET_A and ET_B receptor antagonists. ET-1 infusion for four weeks significantly elevated P_alb and albuminuria. Y-27632 significantly reduced the elevation of P_alb and albuminuria. The activities of both RhoA and ROCK-1/2 were increased by ET-1 infusion. Selective ET_B receptor antagonism had no effect on the elevated activity of both RhoA and ROCK-1/2 enzymes. Selective ET_A receptor and combined ET_A/ET_B receptors blockade restored the activity of RhoA and ROCK-1/2 to normal levels. In addition, chronic ET-1 infusion increased the levels of glomerular inflammatory and fibrotic markers. These effects were all attenuated in rats following ROCK-1/2 inhibition. These observations suggest that ET-1 contributes to increased albuminuria, inflammation, and fibrosis by modulating the activity of the ET_A-RhoA/ROCK-1/2 pathway. Selective ET_A receptor blockade may represent a potential therapeutic strategy to limit glomerular injury and albuminuria in kidney disease.

The efficacy of PDE5 inhibitors in diabetic patients

BACKGROUND

Phosphodiesterase 5 inhibitors (PDE5i), since their introduction in the late 1990s, have proven their efficacy in treating several conditions, predominantly pulmonary hypertension and erectile dysfunction where they remain the first-line therapeutic option. However, in the recent years, growing evidence from both animal and human studies has emerged to suggest the additional benefits of PDE5i in cardiovascular and metabolic disorders. This is of specific interest to the diabetes population where prevalent cardiovascular disease and metabolic dysregulation significantly contribute to the increased morbidity and mortality.

OBJECTIVES

To examine the available data on the non-standard, pleiotropic effects of PDE5i in patients with diabetes mellitus.

MATERIALS AND METHODS

The review of the published background research, preclinical studies and clinical trials.

RESULTS

In human studies, PDE5 inhibition appeared to be associated with reduced cardiovascular mortality and overall improved clinical outcomes in those with established cardiovascular disease. PDE5i were also consistently found to reduce albuminuria in subjects with diabetic nephropathy. Furthermore, animal data suggest a plausible effect of this group of medication on sensory function and neuropathic symptoms in diabetic neuropathy as well as improved wound healing. A decrease in insulin resistance and augmentation of beta cell function seen in preclinical studies has not been consistently demonstrated in human trials.

DISCUSSION AND CONCLUSION

In animal models, PDE5 inhibition appears to decrease oxidative stress and reduce some of the micro- and macrovascular complications associated with diabetes. However, data from human trials are limited and largely inconsistent, highlighting the need for adequately powered, randomised-controlled trials in diabetic cohorts in order to fully assess the benefits of PDE5i in this group of patients.

Sexual dimorphism in renal heme oxygenase-1 and arachidonic acid metabolizing enzymes in spontaneously hypertensive rats versus normotensive Wistar Kyoto rats

Numerous studies have demonstrated a sexual dimorphism in blood pressure (BP) control in spontaneously hypertensive rats (SHR), however the mechanisms remain to be further elucidated. Based on the established role of arachidonic acid metabolites and heme oxygenase (HO) in BP control, we hypothesize that higher BP in male SHR is associated with differential expression in renal HO and arachidonic acid metabolizing enzymes vs. female SHR. Higher BP in male SHR coincided with significant increases in renal cortical superoxide production and thiobarbituric acid reactive substances (TBARs) levels as measures of oxidative stress compared to normotensive female WKY and female SHR. The elevations in BP and oxidative stress in male SHR were also associated with a decrease in cortical heme oxygenase-1 (HO-1) expression when compared to normotensive female WKY. Although there was no sex or strain differences in cortical expression of the epoxyeicosatrienoic acids (EETs) producing enzyme, cytochrome P450 epoxygenase (CYP2C23), in male and female SHR and WKY, SHR had greater expression of the EETs metabolizing enzyme, soluble epoxide hydrolase (sEH) vs. WKY. Cortical expression of the 20-hydroxyeicosatetraenoic acid (20-HETE) producing enzyme, cytochrome P450 hydroxylase (CYP4A), was less in female WKY and SHR compared to strain-matched males and cortical 20-HETE levels were also less in female SHR vs. male SHR. Cortical cyclooxygenase-2 (COX-2) expression was significantly greater in female SHR and WKY vs. males and cortical prostaglandin E2 (PGE2) levels in female SHR was significantly greater than male WKY. In conclusion, our data suggest that sex differences in renal oxidative stress, HO-1 and arachidonic acid metabolizing enzymes could contribute to sexual dimorphism in hypertension in young SHR.

Upregulation of hemeoxygenase enzymes HO-1 and HO-2 following ischemia-reperfusion injury in connection with experimental cardiac arrest and cardiopulmonary resuscitation: Neuroprotective effects of methylene blue

Oxidative stress plays an important role in neuronal injuries after cardiac arrest. Increased production of carbon monoxide (CO) by the enzyme hemeoxygenase (HO) in the brain is induced by the oxidative stress. HO is present in the CNS in two isoforms, namely the inducible HO-1 and the constitutive HO-2. Elevated levels of serum HO-1 occurs in cardiac arrest patients and upregulation of HO-1 in cardiac arrest is seen in the neurons. However, the role of HO-2 in cardiac arrest is not well known. In this review involvement of HO-1 and HO-2 enzymes in the porcine brain following cardiac arrest and resuscitation is discussed based on our own observations. In addition, neuroprotective role of methylene blue- an antioxidant dye on alterations in HO under in cardiac arrest is also presented. The biochemical findings of HO-1 and HO-2 enzymes using ELISA were further confirmed by immunocytochemical approach to localize selective regional alterations in cardiac arrest. Our observations are the first to show that cardiac arrest followed by successful cardiopulmonary resuscitation results in significant alteration in cerebral concentrations of HO-1 and HO-2 levels indicating a prominent role of CO in brain pathology and methylene blue during CPR followed by induced hypothermia leading to superior neuroprotection after return of spontaneous circulation (ROSC), not reported earlier.

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.

Heme Oxygenase-1 Upregulation: A Novel Approach in the Treatment of Cardiovascular Disease

Significance: Heme oxygenase (HO) plays a pivotal role in both vascular and metabolic functions and is involved in many physiological and pathophysiological processes in vascular endothelial cells (ECs) and adipocytes. Recent Advances: From the regulation of adipogenesis in adipose tissue to the adaptive response of vascular tissue in the ECs, HO plays a critical role in the capability of the vascular system to respond and adjust to insults in homeostasis. Recent studies show that HO-1 through regulation of adipocyte and adipose tissue functions ultimately aid not only in local but also in systemic maintenance of homeostasis. Critical Issues: Recent advances have revealed the existence of a cross talk between vascular ECs and adipocytes in adipose tissue. In the pathological state of obesity, this cross talk contributes to the condition's adverse chronic effects, and we propose that specific targeting of the HO-1 gene can restore signaling pathways and improve both vascular and adipose functions. Future Directions: A complete understanding of the role of HO-1 in regulation of cardiovascular homeostasis is important to comprehend the homeostatic regulation as well as in cardiovascular disease. Efforts are required to highlight the effects and the ability to target the HO-1 gene in models of obesity with an emphasis on the role of pericardial fat on cardiovascular health.

Studies on characteristics and anti-diabetic and -nephritic effects of polysaccharides isolated from Paecilomyces hepiali fermentation mycelium in db/db mice

Type 2 diabetes mellitus plagues many people in China and the world, and its nephritis complication is the leading cause of death for patients. Paecilomyces hepiali contained various functional components, especially polysaccharides, which possesses well pharmacological activities. In this study, polysaccharide purified from Paecilomyces hepiali fermented mycelium entitled PHEA was obtained, and its structure was systemically characterized using fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR). In C57BL/KsJ (BKS).Cg-Dock7^m +/+ Lepr^db/JNju mice (db/db mice), via detecting the alternations on biochemical criterions, pathological indicators and protein expressions related to nuclear factor-E2-related factor 2 (Nrf2) and nuclear factor-κB (NF-κB) signaling in serum and/or tissues including muscle, liver and kidney after 8-week PHEA administration, the hypoglycemic, hypolipidemic, and anti-diabetic nephropathic activities of PHEA were confirmed. The purified P. Hepiali polysaccharide with the anti-diabetic and -nephritic properties was first reported in this study via regulating Nrf2-meadited NF-κB signaling in db/db mice.

HO-1 overexpression and underexpression: Clinical implications

In this review we examine the effects of both over- and under-production of heme oxygenase-1 (HO-1) and HO activity on a broad spectrum of biological systems and on vascular disease. In a few instances e.g., neonatal jaundice, overproduction of HO-1 and increased HO activity results in elevated levels of bilirubin requiring clinical intervention with inhibitors of HO activity. In contrast HO-1 levels and HO activity are low in obesity and the HO system responds to mitigate the deleterious effects of oxidative stress through increased levels of bilirubin (anti-inflammatory) and CO (anti-apoptotic) and decreased levels of heme (pro-oxidant). Site specific HO-1 overexpression diminishes adipocyte terminal differentiation and lipid accumulation of obesity mediated release of inflammatory molecules. A series of diverse strategies have been implemented that focus on increasing HO-1 and HO activity that are central to reversing the clinical complications associated with diseases including, obesity, metabolic syndrome and vascular disease.

5-Aminolevulinic acid with ferrous iron improves early renal damage and hepatic steatosis in high fat diet-induced obese mice

5-Aminolevulinic acid, a natural amino acid, activates mitochondrial respiration and induces heme oxygenase-1 expression. Obesity and type 2 diabetes mellitus are associated with age-related mitochondrial respiration defect, oxidative stress and inflammation. The aim of this study is to investigate the effects of 5-aminolevulinic acid with sodium ferrous citrate on early renal damage and hepatic steatosis. 7-Month-old C57BL/6 mice were fed with a standard diet or high fat diet for 9 weeks, which were orally administered 300 mg/kg 5-aminolevulinic acid combined with 47 mg/kg sodium ferrous citrate (5-aminolevulinic acid/sodium ferrous citrate) or vehicle for the last 5 weeks. We observed that 5-aminolevulinic acid/sodium ferrous citrate significantly decreased body weight, fat weight, hepatic lipid deposits and improved levels of blood glucose and oral glucose tolerance test. In addition, 5-aminolevulinic acid/sodium ferrous citrate suppressed increased glomerular tuft area in high fat diet-fed mice, which was associated with increased heme oxygenase-1 protein expression. Our findings demonstrate additional evidence that 5-aminolevulinic acid/sodium ferrous citrate could improve glucose and lipid metabolism in diabetic mice. 5-Aminolevulinic acid/sodium ferrous citrate has potential application in obesity or type 2 diabetes mellitus-associated disease such as diabetic nephropathy and nonalcoholic fatty liver disease.

Dual immuno-renal targeting of 7-benzylidenenaltrexone alleviates lupus nephritis via FcγRIIB and HO-1

Known as a selective δ1 opioid receptor (DOR1) antagonist, the 7-benzylidenenaltrexone (BNTX) is also a DOR1-independent immunosuppressant with unknown mechanisms. Here we investigated if BNTX could be beneficial for diseased MRL/lpr lupus mice. We treated mice with 0.5, 2, 5 or 10 mg/kg/day of BNTX for 2 weeks. At as low as 2 mg/kg/day, BNTX significantly improved splenomegaly and lymphadenopathy. Notably, B cell numbers, particularly autoreactive plasma cells, were preferentially reduced; moreover, BNTX enhanced surface expression of FcγRIIB, an immune complex (IC)-dependent apoptotic trigger of B cells. Consequently, serum autoantibody concentrations were significantly decreased, leading to diminished glomerular IC deposition and renal fibrosis, thereby improving proteinuria. Microarray and pathway analyses revealed heme oxygenase-1 (HO-1) and p38 MAPK as key mediators of BNTX-induced upregulation of FcγRIIB. Moreover, HO-1 expression was also induced by BNTX via p38 MAPK at renal proximal tubules to further cytoprotection. Taken together, we demonstrate that BNTX can alleviate lupus nephritis by reducing autoreactive B cells via FcγRIIB and by augmenting renal protection via HO-1. Accordingly, we propose a new strategy to treat lupus nephritis via such a dual immuno-renal targeting using either a single agent or combined agents to simultaneously deplete B cells and enhance renal protection.

KEY MESSAGES

7-Benzylidenenaltrexone (BNTX) alleviates lupus nephritis in diseased MRL/lpr mice. BNTX reduces autoreactive plasma cell numbers and serum autoantibody titers. BNTX upregulates FcγRIIB levels via p38 MAPK and HO-1 to reduce B cell numbers. Reduction of immune complex deposition and fibrosis by BNTX improves proteinuria. BNTX induces HO-1 via p38 MAPK to enhance protection of renal proximal tubules.

Association of serum bilirubin with renal outcomes in Han Chinese patients with chronic kidney disease

BACKGROUND

Oxidative stress and inflammation play pivotal roles in chronic kidney disease (CKD). Bilirubin is an endogenous anti-inflammatory antioxidant. However, the relationship between serum bilirubin and renal outcomes in CKD is controversial. We explored the association of serum bilirubin levels with renal outcomes in Han Chinese patients with CKD.

METHODS

Clinical and laboratory data were collected from 316 patients with CKD. The primary clinical endpoint was renal replacement therapy or death. The association between serum bilirubin and clinical parameters was assessed by correlation analysis. Multiple Cox regression analysis was used to explore the relationship between serum bilirubin and renal outcomes in patients with CKD.

RESULTS

Serum total and indirect bilirubin were positively correlated with estimated glomerular filtration rate, but negatively correlated with 24-h urine protein in patients with CKD. Serum total and indirect bilirubin were inversely associated with CKD stages in patients with CKD stages 1-5. Multiple Cox regression analysis demonstrated that the higher concentration of serum total bilirubin was independently associated with better renal outcomes in CKD.

CONCLUSIONS

Our results suggest that serum total bilirubin may have protective effects on kidneys.

Diabetes-Related Induction of the Heme Oxygenase System and Enhanced Colocalization of Heme Oxygenase 1 and 2 with Neuronal Nitric Oxide Synthase in Myenteric Neurons of Different Intestinal Segments

Increase in hyperglycaemia-induced oxidative stress and decreased effectiveness of endogenous defense mechanisms plays an essential role in the initiation of diabetes-related neuropathy. We demonstrated that nitrergic myenteric neurons display different susceptibilities to diabetic damage in different gut segments. Therefore, we aim to reveal the gut segment-specific differences in the expression of heme oxygenase (HO) isoforms and the colocalization of these antioxidants with neuronal nitric oxide synthase (nNOS) in myenteric neurons. After ten weeks, samples from the duodenum, ileum, and colon of control and streptozotocin-induced diabetic rats were processed for double-labelling fluorescent immunohistochemistry and ELISA. The number of both HO-immunoreactive and nNOS/HO-immunoreactive myenteric neurons was the lowest in the ileal and the highest in the colonic ganglia of controls; it increased the most extensively in the ileum and was also elevated in the colon of diabetics. Although the total number of nitrergic neurons decreased in all segments, the proportion of nNOS-immunoreactive neurons colocalizing with HOs was enhanced robustly in the ileum and colon of diabetics. We presume that those nitrergic neurons which do not colocalize with HOs are the most seriously affected by diabetic damage. Therefore, the regional induction of the HO system is strongly correlated with diabetes-related region-specific nitrergic neuropathy.

Targeting heme oxygenase-1 in early diabetic nephropathy in streptozotocin-induced diabetic rats

Diabetic nephropathy (DN) is one of the most common microvascular diabetic complications. This study was designed to evaluate the possible protective effect and underlying mechanisms of HO-1 induction in streptozotocin (STZ)-induced early DN in rats. The diabetic rats were divided into three groups: STZ-diabetic, cobalt protoporphyrin (CoPP)-treated diabetic, and zinc protoporphyrin IX (ZnPP)-treated diabetic groups. Compared to the STZ-diabetic group, CoPP-induced HO-1 upregulation improved the diabetic state and renal functional parameters, suppressed the renal proinflammatory marker, NF-κB, abrogated the elevated renal hydroxyprolin, and decreased the enhanced renal nicotinamide adenine dinucleotide phosphate oxidase activity with parallel reduction of urinary oxidative stress markers. On the contrary, treatment with ZnPP abrogated HO-1 levels, aggravated the diabetic condition with further increases in renal oxidative stress, fibrotic and inflammatory markers, and exacerbated renal dysfunction in diabetic animals. These findings suggest that the reduced diabetic renal injury upon HO-1 induction implicates the role of HO-1 induction as a potential treatment for DN.

Euterpe oleracea Mart. seed extract protects against renal injury in diabetic and spontaneously hypertensive rats: role of inflammation and oxidative stress

PURPOSE

Euterpe oleracea Mart. (açaí) seed extract (ASE), through its anti-hypertensive, antioxidant and anti-inflammatory properties, may be useful to treat or prevent human diseases. Several evidences suggest that oxidative stress and inflammation contribute to the pathogenesis of diabetic nephropathy; therefore, we tested the hypothesis that ASE (200 mg/kg^-1day^-1) prevents diabetes and hypertension-related oxidative stress and inflammation, attenuating renal injury.

METHODS

Male rats with streptozotocin (STZ)-induced diabetes (D), and spontaneously hypertensive rats with STZ-induced diabetes (DH) were treated daily with tap water or ASE (D + ASE and DH + ASE, respectively) for 45 days. The control (C) and hypertensive (H) animals received water.

RESULTS

The elevated serum levels of urea and creatinine in D and DH, and increased albumin excretion in HD were reduced by ASE. Total glomeruli number in D and DH, were increased by ASE that also reduced renal fibrosis in both groups by decreasing collagen IV and TGF-β1 expression. ASE improved biomarkers of renal filtration barrier (podocin and nephrin) in D and DH groups and prevented the increased expression of caspase-3, IL-6, TNF-α and MCP-1 in both groups. ASE reduced oxidative damage markers (TBARS, carbonyl levels and 8-isoprostane) in D and DH associated with a decrease in Nox 4 and p47 subunit expression and increase in antioxidant enzyme activity in both groups (SOD, catalase and GPx).

CONCLUSION

ASE substantially reduced renal injury and prevented renal dysfunction by reducing inflammation, oxidative stress and improving the renal filtration barrier, providing a nutritional resource for prevention of diabetic and hypertensive-related nephropathy.

Amelioration of high fat diet-induced nephropathy by cilostazol and rosuvastatin

Multiple comorbidities of metabolic disorders are associated with facilitated chronic kidney disease progression. Anti-platelet cilostazol is used for the treatment of peripheral artery disease. In this study, we investigated the potential beneficial effects of cilostazol and rosuvastatin on metabolic disorder-induced renal dysfunctions. C57BL/6 mice that received high fat diet (HFD) for 22 weeks and a low dose of streptozotocin (STZ, 40 mg/kg) developed albuminuria and had increased urinary cystatin C excretion, and cilostazol treatment (13 weeks) improved these markers. Histopathological changes, including glomerular mesangial expansion, tubular vacuolization, apoptosis, and lipid accumulation were ameliorated by cilostazol treatment. Tubulointerstitial fibrosis that was indicated by the increases in collagen and transforming growth factor-β1 subsided by cilostazol. Renoprotective effects were also observed in rosuvastatin-treated mice, and combinatorial treatment with cilostazol and rosuvastatin demonstrated enhanced ameliorative effects in histopathological evaluations. Notably, repressed renal heme oxygenase-1 (Ho-1) level in HFD/STZ mice was restored in cilostazol group. Further, we demonstrated that cilostazol enhanced Nrf2/Ho-1 signaling in cultured proximal tubular epithelial cells. Collectively, these results suggest the potential advantageous use of cilostazol as an adjunctive therapy with statins for the amelioration of metabolic disorder-associated renal injury.

Hmox1 Deficiency Sensitizes Mice to Peroxynitrite Formation and Diabetic Glomerular Microvascular Injuries

OBJECTIVE

Indirect evidence suggests a role for heme oxygenase-1 (HO-1) in limiting diabetic vasculopathy. The goal of this study was to assess the role of HO-1 in the development of microvascular lesions within glomeruli during diabetes mellitus using a mouse model with specific alteration of the Hmox1 gene.

APPROACH AND RESULTS

The effects of Hmox1 haploinsufficiency were studied as a means of assessing the intrinsic contribution of HO-1 in the development of renal microvascular lesions during diabetes. Renal function and histology were analyzed 10 weeks after diabetes induction with streptozotocin. Diabetic Hmox1^+/- mice showed higher levels of albuminuria and blood urea compared to their wild-type diabetic littermates. More severe glomerular microvascular lesions were also observed in the diabetic Hmox1^+/- mice. This was associated with a renal increase in the expression of the oxidative stress marker, nitrotyrosine.

CONCLUSIONS

Genetic Hmox1 partial deficiency is sufficient to sensitize mice to the development of diabetic glomerular microvascular lesions. HO-1 exerts antioxidant effects in the kidney during diabetes mellitus. These have protective effects on the development of glomerular endothelial injury.

Mesenchymal stem cells: a future experimental exploration for recession of diabetic nephropathy

BACKGROUND

The progresses made in stem cell therapy offer an innovative approach and exhibit great potential for the repair of damaged organs and tissues. This study was conducted with a view to find the mechanisms responsible for the effectiveness of bone marrow-derived mesenchymal stem cells (BM-MSCs) in the suppression of diabetes and experimentally-induced diabetic nephropathy.

METHODS

To realize this objective, diabetic and diabetic nephropathy subject groups that underwent MSC treatment were studied through numerous biochemistry and molecular genetics analyses.

RESULTS

The findings show that, relative to the control groups, the rats in the diabetic and diabetic nephropathy groups treated with stem cells infused with BM-MSCs showed a significant reversal in the levels of their insulin, glucose, heme-oxygenase-1 (HO-1) serum, and advanced glycation end product (AGEP). Moreover, BM-MSC therapy was also found to have a definite positive effect on the kidney functions. In addition, it also corresponded with a significant decrease in the availability of certain growth factors, namely the fibroblast growth factor (FGF), the platelet-derived growth factor (PDGF), and the transforming growth factor-β (TGF-β). BM-MSC treatment also improved the levels of expression of monocyte chemoatractant-1 (MCP-1) and interleukin-8 (IL-8) genes within kidney tissues. Lastly, the treatment recovered the organizational structure of the kidney and pancreas, a result demonstrated by a histopathological analysis. These results greatly coincide with those obtained through the biochemistry and molecular genetics analyses.

CONCLUSION

Treatment using BM-MSCs is determined to be definitely effective in cases of diabetes and diabetic nephropathy.

Meloxicam fails to augment the reno-protective effects of soluble epoxide hydrolase inhibition in streptozotocin-induced diabetic rats via increased 20-HETE levels

The pro-inflammatory cyclooxygenase (COX)-derived prostaglandins and the anti-inflammatory cytochrome P450 epoxygenase-derived epoxyeicosatrienoic acids (EETs) play an important role in the regulation of renal injury. The current study examined whether COX inhibition augments the reno-protective effects of increased EETs levels via inhibiting EETs degradation by soluble epoxide hydrolase (sEH) in diabetic rats. Streptozotocin (50mg/kg, i.v) was used to induce diabetes in male Sprague Dawley rats. Rats were then divided into 5 groups (n=6-8); control non diabetic, diabetic, diabetic treated with the sEH inhibitor trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB), diabetic treated with the COX inhibitor meloxicam and diabetic treated with meloxicam plus t-AUCB for 2 months. Glomerular albumin permeability and urinary albumin and nephrin excretion levels were significantly elevated in diabetic rats together with decreased glomerular α3 integrin and nephrin expression levels. Inhibition of sEH reduced glomerular albumin permeability, albumin and nephrin excretion levels and restored the decrease in glomerular α3 integrin and nephrin expression in diabetic rats. Meloxicam failed to reduce renal injury or even to synergize the reno-protective effects of sEH inhibition in diabetic rats. Furthermore, inhibition of sEH reduced the elevation in renal collagen deposition and urinary MCP-1 excretion levels together with a reduction in the number of renal TUNEL positive cells in diabetic vs. control rats (P<0.05). Meloxicam did not reduce renal inflammation or apoptosis in diabetic rats or even exacerbate the anti-inflammatory and anti-apoptotic effects of sEH inhibition. Renal 20-hydroxyeicosatetranoic acid (20-HETE) levels were elevated in diabetic rats and meloxicam further exacerbated this elevation. In conclusion, our study suggests that inhibition of COX failed to provide renal protection or to augment the reno-protective effects of sEH inhibition in diabetic rats, at least in part, via increased inflammatory 20-HETE levels.

Glomerular Epithelial Cells-Targeted Heme Oxygenase-1 Over Expression in the Rat: Attenuation of Proteinuria in Secondary But Not Primary Injury

BACKGROUND/AIMS

Induction of heme oxygenase 1 (HO-1) in glomerular epithelial cells (GEC) in response to injury is poor and this may be a disadvantage. We, therefore, explored whether HO-1 overexpression in GEC can reduce proteinuria induced by puromycin aminonucleoside (PAN) or in anti-glomerular basement membrane (GBM) antibody (Ab)-mediated glomerulonephritis (GN).

METHODS

HO-1 overexpression in GEC (GECHO-1) of Sprague-Dawley rats was achieved by targeting a FLAG-human (h) HO-1 using transposon-mediated transgenesis. Direct GEC injury was induced by a single injection of PAN. GN was induced by administration of an anti-rat GBM Ab and macrophage infiltration in glomeruli was assessed by immunohistochemistry and western blot analysis, which was also used to assess glomerular nephrin expression.

RESULTS

In GECHO-1 rats, FLAG-hHO-1 transprotein was co-immunolocalized with nephrin. Baseline glomerular HO-1 protein levels were higher in GECHO-1 compared to wild type (WT) rats. Administration of either PAN or anti-GBM Ab to WT rats increased glomerular HO-1 levels. Nephrin expression markedly decreased in glomeruli of WT or GECHO-1 rats treated with PAN. In anti-GBM Ab-treated WT rats, nephrin expression also decreased. In contrast, it was preserved in anti-GBM Ab-treated GECHO-1 rats. In these, macrophage infiltration in glomeruli and the ratio of urine albumin to urine creatinine (Ualb/Ucreat) were markedly reduced. There was no difference in Ualb/Ucreat between WT and GECHO-1 rats treated with PAN.

CONCLUSION

Depending on the type of injury, HO-1 overexpression in GEC may or may not reduce proteinuria. Reduced macrophage infiltration and preservation of nephrin expression are putative mechanisms underlying the protective effect of HO-1 overexpression following immune injury.

Hypoxia: The Force that Drives Chronic Kidney Disease

In the United States the prevalence of end-stage renal disease (ESRD) reached epidemic proportions in 2012 with over 600,000 patients being treated. The rates of ESRD among the elderly are disproportionally high. Consequently, as life expectancy increases and the baby-boom generation reaches retirement age, the already heavy burden imposed by ESRD on the US health care system is set to increase dramatically. ESRD represents the terminal stage of chronic kidney disease (CKD). A large body of evidence indicating that CKD is driven by renal tissue hypoxia has led to the development of therapeutic strategies that increase kidney oxygenation and the contention that chronic hypoxia is the final common pathway to end-stage renal failure. Numerous studies have demonstrated that one of the most potent means by which hypoxic conditions within the kidney produce CKD is by inducing a sustained inflammatory attack by infiltrating leukocytes. Indispensable to this attack is the acquisition by leukocytes of an adhesive phenotype. It was thought that this process resulted exclusively from leukocytes responding to cytokines released from ischemic renal endothelium. However, recently it has been demonstrated that leukocytes also become activated independent of the hypoxic response of endothelial cells. It was found that this endothelium-independent mechanism involves leukocytes directly sensing hypoxia and responding by transcriptional induction of the genes that encode the β2-integrin family of adhesion molecules. This induction likely maintains the long-term inflammation by which hypoxia drives the pathogenesis of CKD. Consequently, targeting these transcriptional mechanisms would appear to represent a promising new therapeutic strategy.

Gasotransmitters in Vascular Complications of Diabetes

In the past decades three gaseous signaling molecules-so-called gasotransmitters-have been identified: nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S). These gasotransmitters are endogenously produced by different enzymes in various cell types and play an important role in physiology and disease. Despite their specific functions, all gasotransmitters share the capacity to reduce oxidative stress, induce angiogenesis, and promote vasorelaxation. In patients with diabetes, a lower bioavailability of the different gasotransmitters is observed when compared with healthy individuals. As yet, it is unknown whether this reduction precedes or results from diabetes. The increased risk for vascular disease in patients with diabetes, in combination with the extensive clinical, financial, and societal burden, calls for action to either prevent or improve the treatment of vascular complications. In this Perspective, we present a concise overview of the current data on the bioavailability of gasotransmitters in diabetes and their potential role in the development and progression of diabetes-associated microvascular (retinopathy, neuropathy, and nephropathy) and macrovascular (cerebrovascular, coronary artery, and peripheral arterial diseases) complications. Gasotransmitters appear to have both inhibitory and stimulatory effects in the course of vascular disease development. This Perspective concludes with a discussion on gasotransmitter-based interventions as a therapeutic option.

Translational Significance of Heme Oxygenase in Obesity and Metabolic Syndrome

The global epidemic of obesity continues unabated with sequelae of diabetes and metabolic syndrome. This review reflects the dramatic increase in research on the role of increased expression of heme oxygenase (HO)-1/HO-2, biliverdin reductase, and HO activity on vascular disease. The HO system engages with other systems to mitigate the deleterious effects of oxidative stress in obesity and cardiovascular disease (CVD). Recent reports indicate that HO-1/HO-2 protein expression and HO activity have several important roles in hemostasis and reactive oxygen species (ROS)-dependent perturbations associated with metabolic syndrome. HO-1 protects tissue during inflammatory stress in obesity through the degradation of pro-oxidant heme and the production of carbon monoxide (CO) and bilirubin, both of which have anti-inflammatory and anti-apoptotic properties. By contrast, repression of HO-1 is associated with increases of cellular heme and inflammatory conditions including hypertension, stroke, and atherosclerosis. HO-1 is a major focus in the development of potential therapeutic strategies to reverse the clinical complications of obesity and metabolic syndrome.

The Number of GT(n) Repeats in the Hemeoxygenase-1 Gene Promoter is Increased in Pediatric Heart Failure but is Unrelated to Renal, Antioxidant and Anti-inflammatory Markers

Products of hemeoxygenase (HO)-1 have anti-inflammatory and antioxidant functions. The HO-1 promoter has a variable number of GT(n) repeats: A low number (n < 23) is associated with high transcriptional activity in response to oxidative stress. We hypothesized that the frequency of GT(n) repeats in pediatric heart failure (HF) reflects plasma biomarkers of different disease processes: the soluble receptor for advance glycation end products (sRAGE, marking cellular activation), oxLDL (oxidative stress), NGAL (impaired renal function), HIF-1α (hypoxia) and hsCRP (inflammation). Sixty HF children [aged 4-14 years, 30 with HF due to idiopathic dilated cardiomyopathy (IDCM), 30 due to chronic renal failure (CRF)] were compared to 20 healthy controls (HC). Leukocyte HO-1 GT(n) repeats were determined by PCR, plasma markers by ELISA or nephelometry. The number of GT(n) repeats in the HF patients was higher than the number of repeats in the controls, with no difference between the patient groups (p < 0.001). sRAGE, oxLDL, HIF-1α, NGAL and hsCRP were higher in both HF groups compared to HC (all p < 0.01). IDCM had higher sRAGEs and HIF-1α compared to CRF patients (p < 0.01). NGAL was higher in CRF compared to IDCM (p < 0.01). None of the plasma/serum markers correlated with the number of GT(n) repeats in any group. The number of HO-1 promoter GT(n) polymorphism is increased in both IDCM and CRF children with HF, but is unrelated to plasma markers of different pathological processes. This casts doubts on the clinical value of the number of GT(n) repeats in pediatric HF.

Renal protective effects of induction of haem oxygenase-1 combined with increased adiponectin on the glomerular vascular endothelial growth factor-nitric oxide axis in obese rats

What is the central question of this study? This study aimed to investigate whether induction of haem oxygenase-1 (HO-1) can protect the kidneys of obese rats by regulating the glomerular vascular endothelial growth factor-nitric oxide (VEGF-NO) axis by increasing the adiponectin concentrations. What is the main finding and its importance? Induction of HO-1 reduces the degree of microalbuminuria and has renal protective effects by improving endothelial function and regulating the uncoupled glomerular VEGF-NO axis in diet-induced obese rats. The mechanism may be related to increased activation of the HO-1-adiponectin axis. The glomerular vascular endothelial growth factor-nitric oxide (VEGF-NO) axis plays a critical role in maintenance of normal kidney function in obesity. Induction of haem oxygenase-1 (HO-1) may result in a parallel increase in adiponectin secretion. The aim of this study was to investigate whether induction of HO-1 could protect the kidneys of obese rats by regulating the glomerular VEGF-NO axis by increasing adiponectin levels. Rats received high-fat diets and were injected with either cobalt protoporphyrin to induce HO-1 or stannous protoporphyrin to inhibit HO-1. Blood and urine samples were collected. Endothelial function was determined by measuring the endothelium-dependent vasodilatation of the aorta. Renal tissues were collected for CD34 immunohistochemistry. The glomerular VEGF-NO axis and the AMP kinase-phosphoinositide 3-kinase (PI3K)/Akt-endothelial nitric oxide synthase pathway were measured. Induction of HO-1 by cobalt protoporphyrin decreased microalbuminuria, plasma free fatty acids, serum high-sensitivity C-reactive protein and malondialdehyde levels and increased serum adiponectin levels compared with the untreated obese rats. Severe impairment of endothelium-dependent vasodilatation was observed in the obese rats, which was improved to some extent by HO-1 induction. Induction of HO-1 reduced glomerular CD34 expression and production of reactive oxygen species in obese rats. Obese rats showed increased glomerular VEGF expression and reduced NO levels. This uncoupling of the glomerular VEGF-NO axis was improved to some extent by induction of HO-1, with enhancement of p-AMP kinase, p-Akt and phospho-endothelial nitric oxide synthase in obese rats. These results indicate that induction of HO-1 with cobalt protoporphyrin reduces the degree of microalbuminuria and has renal protective effects by improving endothelial dysfunction and regulating the glomerular VEGF-NO axis in diet-induced obese rats by increasing adiponectin levels.

Cobalt protoporphyrin represses osteoclastogenesis through blocking multiple signaling pathways

Cobalt protoporphyrin (CoPP) is a metallo-protoporphyrin that works as a powerful inducer of heme oxigenase-1 (HO-1) in various tissues and cells. Our recent studies have demonstrated that induction of HO-1 by several reagents inhibited differentiation and activation of osteoclasts (OCLs), which are multinucleated bone resorbing cells. However, the effects of CoPP on osteoclastogenesis remain to be elucidated. In this study, we report that CoPP inhibits receptor activator of nuclear factor κB ligand (RANKL)-induced OCL formation in a dose dependent manner. Importantly, CoPP had little cytotoxicity, but rather enhanced cell proliferation of OCLs. CoPP suppressed the protein levels of nuclear factor of activated T cells cytoplasmic-1 (NFATc1) as well as those of OCLs markers such as Src and cathepsin K, which are transcriptionally regulated by NFATc1 in mature OCLs. Western blot analyses also showed that CoPP abolished RANKL-stimulated phosphorylation of several major signaling pathways such as IκB, Akt, ERK, JNK and p38 MAPKs in OCL precursor cells. Thus, our results show that CoPP represses osteoclastogenesis through blocking multiple signaling pathways.

Heme oxygenase-1 attenuates acute pulmonary inflammation by decreasing the release of segmented neutrophils from the bone marrow

Recruiting polymorphonuclear neutrophil granulocytes (PMNs) from circulation and bone marrow to the site of inflammation is one of the pivotal mechanisms of the innate immune system. During inflammation, the enzyme heme oxygenase 1 (HO-1) has been shown to reduce PMN migration. Although these effects have been described in various models, underlying mechanisms remain elusive. Recent studies revealed an influence of HO-1 on different cells of the bone marrow. We investigated the particular role of the bone marrow in terms of HO-1-dependent pulmonary inflammation. In a murine model of LPS inhalation, stimulation of HO-1 by cobalt (III) protoporphyrin-IX-chloride (CoPP) resulted in reduced segmented PMN migration into the alveolar space. In the CoPP group, segmented PMNs were also decreased intravascularly, and concordantly, mature and immature PMN populations were higher in the bone marrow. Inhibition of the enzyme by tin protoporphyrin-IX increased segmented and banded PMN migration into the bronchoalveolar lavage fluid with enhanced PMN release from the bone marrow and aggravated parameters of tissue inflammation. Oxidative burst activity was significantly higher in immature compared with mature PMNs. The chemokine stromal-derived factor-1 (SDF-1), which mediates homing of leukocytes into the bone marrow and is decreased in inflammation, was increased by CoPP. When SDF-1 was blocked by the specific antagonist AMD3100, HO-1 activation was no longer effective in curbing PMN trafficking to the inflamed lungs. In conclusion, we show evidence that the anti-inflammatory effects of HO-1 are largely mediated by inhibiting the release of segmented PMNs from the bone marrow rather than direct effects within the lung.

Induction of heme oxygenase I (HMOX1) by HPP-4382: a novel modulator of Bach1 activity

Oxidative stress is generated by reactive oxygen species (ROS) produced in response to metabolic activity and environmental factors. Increased oxidative stress is associated with the pathophysiology of a broad spectrum of inflammatory diseases. Cellular response to excess ROS involves the induction of antioxidant response element (ARE) genes under control of the transcriptional activator Nrf2 and the transcriptional repressor Bach1. The development of synthetic small molecules that activate the protective anti-oxidant response network is of major therapeutic interest. Traditional small molecules targeting ARE-regulated gene activation (e.g., bardoxolone, dimethyl fumarate) function by alkylating numerous proteins including Keap1, the controlling protein of Nrf2. An alternative is to target the repressor Bach1. Bach1 has an endogenous ligand, heme, that inhibits Bach1 binding to ARE, thus allowing Nrf2-mediated gene expression including that of heme-oxygenase-1 (HMOX1), a well described target of Bach1 repression. In this report, normal human lung fibroblasts were used to screen a collection of synthetic small molecules for their ability to induce HMOX1. A class of HMOX1-inducing compounds, represented by HPP-4382, was discovered. These compounds are not reactive electrophiles, are not suppressed by N-acetyl cysteine, and do not perturb either ROS or cellular glutathione. Using RNAi, we further demonstrate that HPP-4382 induces HMOX1 in an Nrf2-dependent manner. Chromatin immunoprecipitation verified that HPP-4382 treatment of NHLF cells reciprocally coordinated a decrease in binding of Bach1 and an increase of Nrf2 binding to the HMOX1 E2 enhancer. Finally we show that HPP-4382 can inhibit Bach1 activity in a reporter assay that measures transcription driven by the human HMOX1 E2 enhancer. Our results suggest that HPP-4382 is a novel activator of the antioxidant response through the modulation of Bach1 binding to the ARE binding site of target genes.

Downregulation of NO and PGE2 in LPS-stimulated BV2 microglial cells by trans-isoferulic acid via suppression of PI3K/Akt-dependent NF-κB and activation of Nrf2-mediated HO-1

Little is known about whether trans-isoferulic acid (TIA) regulates the production of lipopolysaccharide (LPS)-induced proinflammatory mediators. Therefore, we examined the effect of TIA isolated from Clematis mandshurica on LPS-induced nitric oxide (NO) and prostaglandin E2 (PGE2) production in BV2 microglial cells. We found that TIA inhibited the production of LPS-induced NO and PGE2 without accompanying cytotoxicity in BV2 microglial cells. TIA also downregulated the expression levels of specific regulatory genes such as inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) by suppressing LPS-induced NF-κB activity via dephosphorylation of PI3K/Akt. In addition, we demonstrated that a specific NF-κB inhibitor PDTC and a selective PI3K/Akt inhibitor, LY294002 effectively attenuated the expression of LPS-stimulated iNOS and COX-2 mRNA, while LY294002 suppressed LPS-induced NF-κB activity, suggesting that TIA attenuates the expression of these proinflammatory genes by suppressing PI3K/Akt-mediated NF-κB activity. Our results showed that TIA suppressed NO and PGE2 production through the induction of nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent heme oxygenase-1 (HO-1). Taken together, our data indicate that TIA suppresses the production of proinflammatory mediators such as NO and PGE2, as well as their regulatory genes, in LPS-stimulated BV2 microglial cells, by inhibiting PI3K/Akt-dependent NF-κB activity and enhancing Nrf2-mediated HO-1 expression.

Diabetic nephropathy: protective factors and a new therapeutic paradigm

Diabetic nephropathy (DN) is the most common cause of chronic kidney disease (CKD) and its number has been increasing. CKD is a worldwide threat to health but the precise mechanism of this problem is not fully appreciated. It is believed that hyperglycemia is one of the most important metabolic factors in the development of DN. Multiple molecular mechanisms have been proposed to mediate hyperglycemia's adverse effects on kidney. To identify targets for therapeutic intervention, most studies have focused on understanding how abnormal levels of such metabolities cause DN. However, there have been few reports regarding endogenous renal protective factors. Thus, recognition of the importance of this could be providing a new perspective for understanding the development of DN and a new therapeutic paradigm to combat DN.

Role of haem oxygenase in the renoprotective effects of soluble epoxide hydrolase inhibition in diabetic spontaneously hypertensive rats

We have shown previously that inhibition of sEH (soluble epoxide hydrolase) increased EETs (epoxyeicosatrienoic acids) levels and reduced renal injury in diabetic mice and these changes were associated with induction of HO (haem oxygenase)-1. The present study determines whether the inhibition of HO negates the renoprotective effect of sEH inhibition in diabetic SHR (spontaneously hypertensive rats). After 6 weeks of induction of diabetes with streptozotocin, SHR were divided into the following groups: untreated, treated with the sEH inhibitor t-AUCB {trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid}, treated with the HO inhibitor SnMP (stannous mesoporphyrin), and treated with both inhibitors for 4 more weeks; non-diabetic SHR served as a control group. Induction of diabetes significantly increased renal sEH expression and decreased the renal EETs/DHETEs (dihydroxyeicosatrienoic acid) ratio without affecting HO-1 activity or expression in SHR. Inhibition of sEH with t-AUCB increased the renal EETs/DHETEs ratio and HO-1 activity in diabetic SHR; however, it did not significantly alter systolic blood pressure. Treatment of diabetic SHR with t-AUCB significantly reduced the elevation in urinary albumin and nephrin excretion, whereas co-administration of the HO inhibitor SnMP with t-AUCB prevented these changes. Immunohistochemical analysis revealed elevations in renal fibrosis as indicated by increased renal TGF-β (transforming growth factor β) levels and fibronectin expression in diabetic SHR and these changes were reduced with sEH inhibition. Co-administration of SnMP with t-AUCB prevented its ability to reduce renal fibrosis in diabetic SHR. In addition, SnMP treatment also prevented t-AUCB-induced decreases in renal macrophage infiltration, IL-17 expression and MCP-1 levels in diabetic SHR. These findings suggest that HO-1 induction is involved in the protective effect of sEH inhibition against diabetic renal injury.

Characterization of the development of renal injury in Type-1 diabetic Dahl salt-sensitive rats

The present study compared the progression of renal injury in Sprague-Dawley (SD) and Dahl salt-sensitive (SS) treated with streptozotocin (STZ). The rats received an injection of STZ (50 mg/kg ip) and an insulin pellet (2 U/day sc) to maintain the blood glucose levels between 400 and 600 mg/dl. Twelve weeks later, arterial pressure (143 ± 6 vs. 107 ± 8 mmHg) and proteinuria (557 ± 85 vs. 81 ± 6 mg/day) were significantly elevated in STZ-SS rats compared with the values observed in STZ-SD rats, respectively. The kidneys from STZ-SS rats exhibited thickening of glomerular basement membrane, mesangial expansion, severe glomerulosclerosis, renal interstitial fibrosis, and occasional glomerular nodule formation. In additional studies, treatment with a therapeutic dose of insulin (4 U/day sc) attenuated the development of proteinuria (212 ± 32 mg/day) and renal injury independent of changes in arterial pressure in STZ-SS rats. Since STZ-SS rats developed severe renal injury, we characterized the time course of changes in renal hemodynamics during the progression of renal injury. Nine weeks after diabetes onset, there was a 42% increase in glomerular filtration rate in STZ-SS rats vs. time-control SS rats with reduced renal blood flow. These results indicate that SS rats treated with STZ develop hyperfiltration and progressive proteinuria and display renal histological lesions characteristic of those seen in patients with diabetic nephropathy. Overall, this model may be useful to study signaling pathways and mechanisms that play a role in the progression of diabetes-induced renal disease and the development of new therapies to slow the progression of diabetic nephropathy.

New targets for treatment of diabetic nephropathy: what we have learned from animal models

PURPOSE OF REVIEW

There has been an advance in our understanding of the mechanisms of diabetic nephropathy over the past few years and much of that has occurred because of studies in animal models of diabetic nephropathy.

RECENT FINDINGS

Studies in animal models of diabetic nephropathy, especially in mice, have underlined the multifactorial nature of the pathogenesis of the disease process and the recognition that these models only partly replicate the changes found in human disease. Despite these limitations, recent animal model studies have identified a number of new, specific molecular abnormalities that point to pathways and specific molecules as potential targets for preventive or therapeutic intervention. These specific targets include the diabetic nephropathy related decreases in endothelial nitric oxide synthase activity and renal dopamine production and the increases in Nrf-2, JAK/STAT, and mammalian target of rapamycin complex 1 signaling. These and other altered signaling pathways are described in this review. We emphasize the use of a unique investigative resource, Nephromine, to utilize a library of mRNA expression data obtained from the kidney biopsies of humans with diabetic nephropathy, to compare and validate findings in mouse models with human disease.

SUMMARY

Several new pathways have been implicated in the progression of diabetic nephropathy through studies of animal models. Some of these appear to be altered in human diabetic nephropathy and may be targets for therapy.

Microarray analysis of altered gene expression and the role of ATF3 in HK-2 cells treated with hemin

OBJECTIVE

To identify gene expression changes and the role of activating transcription factor 3 (ATF3) in hemin toxicity in renal tubular epithelial cells, then elucidate molecular mechanisms of hemin toxicity on renal tubular epithelial cells.

METHODS

An oligo array comprising 35,035 genes was used to compare differential gene expression in hemin-treated and non-treated HK-2 cells (human renal proximal tubular epithelial cells), and the role of ATF3 in hemin toxicity was assessed using siRNA technique.

RESULTS

A total of 128 mRNAs were at least twofold up-regulated and 101 mRNAs were at least twofold down-regulated after hemin treatment. Expression levels of ATF3, heat shock protein 70, c-fos, and c-jun were remarkably increased. Hemin also suppressed nuclear factor-kappa B inhibitor α, β-2 adrenergic receptor, and interleukin-6 mRNA amounts more than twofold. We further demonstrated the protective role of ATF3 in hemin cytotoxicity.

CONCLUSIONS

The data suggest that hemin caused multiple changes of gene expression in HK-2 cells, and ATF3 protects against hemin cytotoxicity.

Stem cell transplantation increases antioxidant effects in diabetic mice

Intra bone marrow-bone marrow transplantation (IBM- BMT) + thymus transplantation (TT) has been shown to reduce the incidence of graft versus host disease (GVHD) and restore donor-derived T cell function. In addition, an increase in insulin sensitivity occurred in db/db mice after IBM-BMT+TT treatment. Heme oxygenase (HO)-1 is a stress inducible enzyme which exert antioxidant, antiapoptotic, and immune-modulating properties. We examined whether IBM-BMT+TT could modulate the expression of HO-1 in the kidneys of db/db mice. Six-week-old db/db mice with blood glucose levels higher than 250 mg/dl were treated with IBM-BMT+TT. Six weeks later, the db/db mice showed decreased body weight, blood glucose levels and insulin, and increased plasma adiponectin levels. The upregulation of HO-1 was associated with significantly (p<0.05) increased levels of peNOS and pAKT, but decreased levels of iNOS in the kidneys of db/db mice. Plasma creatinine levels also decreased (p<0.05), and the expression of type IV collagen was improved. Thus IBM-BMT+TT unregulated the expression of HO-1, peNOS and pAKT, while decreasing iNOS levels in the kidney of db/db mice. This was associated with an improvement in renal function.