Heme Oxygenase 1 Up-Regulates Glomerular Decay Accelerating Factor Expression and Minimizes Complement Deposition and Injury.

Complement-activation controllers, including decay accelerating factor (DAF), are gaining emphasis as they minimize injury in various dysregulated complement-activation disorders, including glomerulopathies. Heme oxygenase (HO)-1 overexpression or induction has been shown to attenuate injury in complement-dependent models of glomerulonephritis. This study investigated whether up-regulation of DAF by heme oxygenase 1 (HO-1) is an underlying mechanism by using Hmox-1-deficient rats (Hmox1+/-; Hmox1-/-) or rats with HO-1 overexpression targeted to glomerular epithelial cells (GECHO-1), which are particularly vulnerable to complement-mediated injury owing to their terminally differentiated nature. Constitutively expressed DAF was decreased in glomeruli of Hmox1-/- rats and augmented in glomeruli of GECHO-1 rats. In GECHO-1 rats with anti-glomerular basement membrane antibody mediated, complement-dependent injury, complement component C3 fragment b (C3b) deposition was reduced, whereas proteinuria was diminished. In glomeruli of wild-type rats, the natural Hmox substrate, hemin, induced glomerular DAF. This effect was attenuated in glomeruli of Hmox1-/- rats and augmented in glomeruli of GECHO-1 rats. Hemin analogues differing in either metal or porphyrin ring functionalities, acting as competitive Hmox-substrate inhibitors, also increased glomerular DAF and reduced C3b deposition after spontaneous complement activation. In the presence of a DAF-blocking antibody, the reduction in C3b deposition was reversed. These observations establish HO-1 as a physiologic regulator of glomerular DAF and identify hemin analogues as inducers of functional glomerular DAF able to minimize C3b deposition.

Phenotypic characterization of a novel HO-1 depletion model in the rat.

Although the protective role of HO-1 induction in various forms of kidney disease is well established, mechanisms other than heme catabolism to biliverdin, bilirubin and carbon monoxide have recently been identified. Unraveling these mechanisms requires the generation of appropriate animal models. The present study describes the generation of a HO-1 deficient Hmox1 -/- rat model and characterizes its renal and extrarenal phenotype. Hmox1 -/- rats had growth retardation and splenomegaly compared to their Hmox1 +/+ littermates. Focal segmental glomerulosclerosis-type lesions and interstitial inflammatory infiltrates were prominent morphologic findings and were associated with increased blood urea nitrogen, serum creatinine and albuminuria. There was no increase in iron deposition in glomeruli, tubules or interstitium. Iron deposition in spleen and liver was reduced. Electron microscopic examination of glomeruli revealed edematous podocytes with scant areas of foot process effacement but otherwise well preserved processes and slit-diaphragms. Of the filtration barrier proteins examined, ß-catenin expression was markedly reduced both in glomeruli and extrarenal tissues. Since the rat is the preferred laboratory animal in experimental physiology and pathophysiology, the rat model of HO-1 deficiency may provide a novel tool for investigation of the role of this enzyme in renal function and disease.

Effect of Heme Oxygenase-1 Deficiency on Glomerular Proteomics.

BACKGROUND: The cytoprotective effect of heme oxygenase (HO)-1 in various forms of renal glomerular injury is established. However, little is known on the role of HO-1 in preserving glomerular structural/functional integrity in the absence of injury. The present study addressed this question in HO-1-deficient rats. METHODS: HO-1-deficient rats were generated using zinc finger nuclease-mediated HO-1 gene (Hmox1) disruption and studied. Glomeruli were isolated from HO-1-deficient (Hmox1-/-) rats and their wild type (WT) littermates for proteomic analysis. RESULTS: Glomerular lesions were characterized and differentially expressed proteins important for preserving integrity of the glomerular filtration barrier were identified. HO-1-deficient (Hmox1-/-) rats developed albuminuria with decreased glomerular filtration rate. In albuminuric rats, there were lesions resembling focal and segmental glomerulosclerosis (FSGS). Western blot analysis of the integral slit diaphragm proteins, nephrin and podocin revealed a significant decrease in nephrin, with no change in podocin. Proteomic analysis of glomerular protein lysates from Hmox1-/- and WT rats revealed differential expression of proteins previously linked with FSGS pathogenesis. Specifically, α-actinin-4, actin related protein 3, cytokeratins and novel candidates including transgelin-2 and lamins. Bioinformatic analysis predicted the upregulation of pathways implicated in platelet aggregation and fibrin clot formation. CONCLUSION: HO-1 is a putative regulator of proteins important in preserving glomerular structural stability and integrity, and in minimizing the activity of proinflammatory pathways.

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.

Role of functional polymorphisms of NRAMP1 gene for the development of Crohn's disease.

BACKGROUND: Crohn's disease (CD) is characterized by chronic activation of macrophages. Natural resistance-associated macrophage protein 1 (NRAMP1) gene exerts many pleiotropic effects on macrophage functions. Hence, NRAMP1 may be also involved in the resistance to intracellular pathogens, and this effector of the innate immunity might be involved in CD pathogenesis. Polymorphic alleles at the NRAMP1 locus have been previously associated with susceptibility both to the putative infectious agents and to autoimmune disorders. Based on these indications, in the present study we investigate its candidacy as a genetic determinant for CD in a Greek population in an association-based study, comparing frequencies of 274 CD patients to these of 200 healthy control subjects. METHODS: The 5'(GT)n promoter polymorphism and 9 either single nucleotide (SNPs) or insertion/deletion type polymorphisms were genotyped across the NRAMP1 gene. Reverse-transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry were performed in order to investigate the NRAMP1 mRNA levels in RNA isolated from biopsies of CD patients as well as protein expression in tissues. RESULTS: Three NRAMP1 polymorphisms [5'(GT)n, D543N, and INT4G/C] were significantly associated with CD. Consistent with previous autoimmune disease studies, allele 3 at the functional 5'(GT)n promoter region repeat polymorphism, was significantly associated with CD when compared to healthy controls (odds ratio 1.50; 95% confidence interval [CI]: 1.16-1.95; P = 0.002). Interestingly, we observed that CD patients homozygous for allele 3 expressed higher NRAMP1 mRNA levels compared to carriers of allele 2. Furthermore, the protein levels of allele 3 carriers in tissues were also elevated compared to those of allele 2 carriers. Based on these data we can speculate that overrepresentation of allele 3 in CD patients could lead to hyperactivation of bowel-wall macrophages that are chronically exposed to lipopolysaccharide and this could subsequently cause the autoimmune-like phenotype characteristic of CD. CONCLUSIONS: Collectively, our data indicate that genetic polymorphisms of NRAMP1 might be associated with susceptibility to CD.

Vascular endothelial growth factor and endoglin (CD-105) in gastric cancer.

BACKGROUND: Vascular endothelial growth factor (VEGF) overexpression has been associated with advanced stage and poor survival in several cancers. Additionally, CD-105 (endoglin) was proposed as a marker of neovascularization in solid malignancies. The aim of the present study was to (1) evaluate the VEGF and CD-105 expression in gastric carcinoma, (2) determine the role of VEGF gene sequence variations in VEGF expression in gastric carcinoma, and (3) correlate the results of VEGF and CD-105 expression with other standard prognostic parameters, such as size, grade, stage of the disease, metastases, and patient survival. METHODS: VEGF and CD-105 expression were evaluated in 100 unrelated gastric cancer patients using immunohistochemistry. For the genotyping, DNA was isolated from the blood of the gastric cancer patients and from 100 healthy individuals. The genotyping was performed by polymerase chain-restriction fragment length polymorphism analysis. RESULTS: VEGF protein was strongly expressed in the cytoplasm of 36% of the gastric carcinoma samples tested. In all cases, high VEGF expression was accompanied with high endoglin expression. Our results revealed no statistical significant association of any VEGF gene polymorphism with the VEGF and endoglin expression. The correlation of VEGF/CD-105 expression with the clinicopathological parameters of gastric cancer showed that the high expression of VEGF/CD015 was correlated only with lymph node metastasis (P = 0.028). The Kaplan-Meier survival curves have shown a clear association of overall survival after diagnosis of gastric cancer with high VEGF, as well as high CD-105 expression. CONCLUSION: Our results support that VEGF and CD-105 are closely relevant to lymph node metastasis and act as two valuable indicators of prognosis.