Heme oxygenase-1 protects against radiocontrast-induced acute kidney injury by regulating anti-apoptotic proteins

Radiocontrast agents are thought to induce acute kidney injury in part through increased production of reactive oxygen species and increased cellular apoptosis. In this study we determined whether heme oxygenase-1 could prevent or reduce radiocontrast-induced acute kidney injury and, if so, what were the mechanisms by which this can occur. Sodium iothalamate was administered to uninephrectomized, salt-depleted male Sabra rats to initiate acute kidney injury. Heme oxygenase-1 was induced with cobalt protoporphyrin or inhibited with stannous mesoporphyrin. Inhibition of heme oxygenase exacerbated kidney injury as measured by an increase in plasma creatinine and in superoxide production. Heme oxygenase-1 induction prevented the increase in plasma creatinine and in superoxide in both the cortex and medulla compared to untreated rats with acute kidney injury. This protective effect of heme oxygenase-1 was associated with increased anti-apoptotic proteins Bcl-2 and Bcl-xl and a decrease of pro-apoptotic caspase-3 and caspase-9 along with increased expression of inactive BAX. Our study suggests that increased levels of heme oxygenase-1 are protective against acute kidney injury due to radiocontrast exposure.

Induction of heme oxygenase-1 in renovascular hypertension is associated with inhibition of apoptosis

The goal of this study was to characterize the impact of induction or inhibition of the heme-HO system on renal apoptosis in clipped and non-clipped kidneys from 2K1C hypertensive rats. Male Sprague-Dawley rats had a 0.25 mm silver clip placed around the left renal artery. Four groups of rats were studied: sham operated animals, 2K1C control rats, 2K1C rats received weekly injections of CoPP (5 mg/100 g body wt, administered subcutaneously), and 2K1C rats pretreated with SnMP (5 mg/ 100g body wt, administered intraperitoneally three times a week). The animals were sacrificed three weeks after surgery. We measured systolic blood pressure, plasma renin activity, non-clipped and clipped kidney HO-1 and HO-2 protein expression, HO activity, heme content, nitrotyrosine levels, and activation of selected pro- and anti-apoptotic proteins. Systolic blood pressure and plasma renin activity were significantly higher in 2K1C rats compared to sham rats. Compared to kidneys from sham animals, clipped kidneys from 2K1C rats showed a significant increase in HO-1 expression with increases in HO activity (26%), heme content (47%) and nitrotyrosine levels (49%), accompanied by an increase in caspase-3 and caspase-9 activity. In contrast, non-clipped kidneys from 2K1C rats showed no differences in HO-1 expression, HO activity, heme content, nitrotyrosine levels and caspase activity compared to sham rats. In clipped kidneys from 2K1C rats, inhibition of HO activity by SnMP augmented caspase-3 and caspase-9 activity and decreased expression of the anti-apoptotic Bcl-2 protein, while induction of HO-1 with CoPP strongly inhibited the activity of both caspases and increased the induction of Bcl-2 and Bcl-xl proteins. These findings demonstrate that the clipped kidneys responded to decreased renal perfusion pressure and increased oxidative stress by activation of the heme-HO system, which exerts antiapoptotic action via mechanisms involving decreased caspase-3 and caspase-9 activity, and increased expression of antiapoptotic molecules.

Up-regulation of heme oxygenase provides vascular protection in an animal model of diabetes through its antioxidant and antiapoptotic effects

Heme oxygenase (HO) plays a critical role in the regulation of cellular oxidative stress. The effects of the reactive oxygen species scavenger ebselen and the HO inducers cobalt protoporphyrin and stannous chloride (SnCl(2)) on HO protein levels and activity, indices of oxidative stress, and the progression of diabetes were examined in the Zucker rat model of type 2 diabetes. The onset of diabetes coincided with an increase in HO-1 protein levels and a paradoxical decrease in HO activity, which was restored by administration of ebselen. Up-regulation of HO-1 expressed in the early development of diabetes produced a decrease in oxidative/nitrosative stress as manifested by decreased levels of 3-nitrotyrosine, superoxide, and cellular heme content. This was accompanied by a decrease in endothelial cell sloughing and reduced blood pressure. Increased HO activity was also associated with a significant increase in the antiapoptotic signaling molecules Bcl-xl and phosphorylation of p38-mitogen-activated protein kinase but no significant increases in Bcl-2 or BAD proteins. In conclusion, 3-nitrotyrosine, cellular heme, and superoxide, promoters of vascular damage, are reduced by HO-1 induction, thereby preserving vascular integrity and protecting cardiac function involving an increase in antiapoptotic proteins.

Genetic suppression of HO-1 exacerbates renal damage: reversed by an increase in the antiapoptotic signaling pathway

Apoptosis has been shown to contribute to the development of acute and chronic renal failure. The antiapoptotic action of the heme oxygenase (HO) system may represent an important protective mechanism in kidney pathology. We examined whether the lack of HO-1 would influence apoptosis in clipped kidneys of two-kidney, one-clip (2K1C) rats. Five-day-old Sprague-Dawley rats were injected in the left ventricle with approximately 5 x 10(9) colony-forming units/ml of retrovirus containing rat HO-1 antisense (LSN-RHO-1-AS) or control retrovirus (LXSN). After 3 mo, a 0.25-mm U-shaped silver clip was placed around the left renal artery. Animals were killed 3 wk later. Clipping the renal artery in LSN-RHO-1-AS rats did not result in increased HO-1 expression. In contrast to LXSN animals, 2K1C LSN-RHO-1-AS rats showed increased expression of cyclooxygenase 2 (COX-2) and higher 3-nitrotyrosine (3-NT) content as well as increased expression of the proapoptotic protein Apaf-1 and caspase-3 activity. Clipping the renal artery in LXSN rats resulted in increased expression of the antiapoptotic proteins Bcl-2 and Bcl-xl, while clipping the renal artery in LSN-RHO-1-AS rats did not change Bcl-2 levels and decreased the levels of Bcl-xl. Treatment of LSN-RHO-1-AS rats with cobalt protoporphyrin resulted in induction of renal HO-1, which was accompanied by decreases in blood pressure, COX-2, 3-NT, and caspase-3 activity, and increased expression of anti-apoptotic molecules (Bcl-2, Bcl-xl, Akt and p-Akt) in the clipped kidneys. These findings underscore the prominent role of HO-1 in counteracting apoptosis in this 2K1C renovascular hypertension model.

Carbon monoxide and biliverdin prevent endothelial cell sloughing in rats with type I diabetes

Hyperglycemia has been linked to increased oxidative stress, a resultant endothelial cell dysfunction, and, ultimately, apoptosis. Heme oxygenases (HO-1/HO-2) and the products of their activity, biliverdin/bilirubin and carbon monoxide (CO), play a physiological role in the vascular system. The effects of heme-mediated HO-1 induction, CO, and biliverdin on urinary 8-epi-isoprostane PGF(2alpha) and endothelial cell sloughing were examined in an animal model of streptozotocin (STZ)-induced diabetes. Hyperglycemia itself did not affect HO-1 and HO-2 protein levels, but caused a net decrease in HO activity. Weekly heme administration induced HO-1 protein, as demonstrated by immunohistochemistry and Western blot analyses. Administration of biliverdin or the CO donor, CORM-3, decreased urinary 8-epi-isoprostane PGF(2alpha), P < 0.5 compared to diabetes. Hyperglycemia increased endothelial cell sloughing; 8.2 +/- 0.8 cells/ml blood in control rats vs. 48 +/- 4.8 cells/ml blood in diabetic rats (P < 0.05). Heme administration significantly increased endothelial cell sloughing in diabetic rats (98 +/- 8.1 cells/ml blood, P < 0.0007) whereas biliverdin modestly decreased endothelial cell sloughing (26 +/- 3.5 cells/ml blood, P < 0.003). Administration of CORM-3 to diabetic rats resulted in a significant decrease in endothelial cell sloughing to 21.3 +/- 2.3 (P < 0.001). Administration of SnMP to CORM-3 diabetic rats only partially reversed the protective effects of CORM-3 on endothelial cell sloughing from 21.3 +/- 2.3 to 29 +/- 2.1 cells/ml, thus confirming a direct protective of CO, in addition to the ability of CORM-3 to induce HO-1 protein. These results demonstrate that exogenously administered CO or bilirubin can prevent endothelial cell sloughing in diabetic rats, likely via a decrease in oxidative stress, and thus represents a novel approach to prophylactic vascular protection in diabetes.

Heme oxygenase-1 enhances renal mitochondrial transport carriers and cytochrome C oxidase activity in experimental diabetes

Up-regulation of heme oxygenase (HO-1) by either cobalt protoporphyrin (CoPP) or human gene transfer improves vascular and renal function by several mechanisms, including increases in antioxidant levels and decreases in reactive oxygen species (ROS) in vascular and renal tissue. The purpose of the present study was to determine the effect of HO-1 overexpression on mitochondrial transporters, cytochrome c oxidase, and anti-apoptotic proteins in diabetic rats (streptozotocin, (STZ)-induced type 1 diabetes). Renal mitochondrial carnitine, deoxynucleotide, and ADP/ATP carriers were significantly reduced in diabetic compared with nondiabetic rats (p < 0.05). The citrate carrier was not significantly decreased in diabetic tissue. CoPP administration produced a robust increase in carnitine, citrate, deoxynucleotide, dicarboxylate, and ADP/ATP carriers and no significant change in oxoglutarate and aspartate/glutamate carriers. The increase in mitochondrial carriers (MCs) was associated with a significant increase in cytochrome c oxidase activity. The administration of tin mesoporphyrin (SnMP), an inhibitor of HO-1 activity, prevented the restoration of MCs in diabetic rats. Human HO-1 cDNA transfer into diabetic rats increased both HO-1 protein and activity, and restored mitochondrial ADP/ATP and deoxynucleotide carriers. The increase in HO-1 by CoPP administration was associated with a significant increase in the phosphorylation of AKT and levels of BcL-XL proteins. These observations in experimental diabetes suggest that the cytoprotective mechanism of HO-1 against oxidative stress involves an increase in the levels of MCs and anti-apoptotic proteins as well as in cytochrome c oxidase activity.

Heme oxygenase-2 deficiency contributes to diabetes-mediated increase in superoxide anion and renal dysfunction

Heme oxygenase-1 (HO-1) and -2 play an important role in cytoprotection and are physiologic regulators of heme-dependent protein synthesis in renal tissues. The impact of HO-2 deletion comparing hyperglycemic HO-2 (+/+) mice and HO-2 knockout (-/-) mice was examined. Hyperglycemia was induced by streptozotocin (STZ) injection, and its effect on renal HO-1/HO-2 protein, HO activity, and creatinine levels were assessed. The effect of HO induction using systemic administration of the HO inducers heme or cobalt protoporphyrin and the effect of HO inhibition using systemic administration of the HO inhibitor tin mesoporphyrin also were assessed in STZ-treated mice. In STZ-treated HO-2 (-/-) mice, there was marked renal functional impairment as reflected by an increase in plasma creatinine, associated with acute tubular damage and microvascular pathology as compared with HO-2 (+/+). In these animals, HO activity was decreased with a concomitant increase in superoxide anion. Upregulation of HO-1 in HO-2 (-/-) mice by weekly administration of cobalt protoporphyrin prevented the increase in plasma creatinine levels and tubulointerstitial and microvascular pathology. Inhibition of HO activity by administration of tin mesoporphyrin accentuated superoxide production and increased creatinine levels in hyperglycemic HO-2 (-/-) mice. In conclusion, HO-2 deficiency enhanced STZ-induced renal dysfunction and morphologic injury and HO-1 upregulation in HO-2 (-/-) mouse rescue and prevented the morphologic damage. These observations indicate that HO activity is essential in preserving renal function and morphology in STZ-induced diabetic mice probably via mitigation of concomitant oxidative stress.

Increase in heme oxygenase-1 levels ameliorates renovascular hypertension

BACKGROUND

The heme oxygenase system (HO-1 and HO-2) catalyzes the conversion of heme to free iron, carbon monoxide (CO), a vasodepressor, and biliverdin, which is further converted to bilirubin, an antioxidant. HO-1 induction has been shown to suppress arachidonic acid metabolism by cytochrome P450 (CYP450) monooxygenases and cyclooxygenases (COX), and to decrease blood pressure in spontaneously hypertensive rats (SHR). The Goldblatt 2K1C model is a model of renovascular hypertension in which there is increased expression of COX-2 in the macula densa and increased renin release from the juxtaglomerular apparatus of the clipped kidney. We examined whether HO-1 overexpression, as a prophylactic approach, would attenuate renovascular hypertension and evaluated potential mechanisms that may account for its effect.

METHODS

2K1C rats were treated with cobalt protoporphyrin (CoPP) or tin mesoporphyrin (SnMP) one day before surgery and weekly for three weeks thereafter. We measured systolic blood pressure, HO activity, HO-1, HO-2, COX-1 and COX-2 protein expression, heme content, and nitrotyrosine levels as indices of oxidative stress. Urinary prostaglandin excretion (PGE2), plasma renin activity (PRA), and plasma aldosterone levels were also measured.

RESULTS

CoPP administration induced renal HO-1 expression by 20-fold and HO activity by 6-fold. This was associated with a reduction in heme content, nitrotyrosine levels, COX-2 expression and urinary PGE2 excretion, and attenuation of the development of hypertension in the 2K1C rats. There was no decrease in plasma renin activity; however, plasma aldosterone levels were significantly lower. In the 2K1C SnMP-treated rats, blood pressure was significantly higher than that of untreated 2K1C rats throughout the study, and the difference in the size of the smaller left clipped kidney compared to the nonclipped right kidney was significantly increased.

CONCLUSION

These findings define an action of prolonged HO-1 induction to interrupt and counteract the influence of the renin-angiotensin-aldosterone system (RAAS) to increase in blood pressure in the 2K1C model of renovascular hypertension. Multiple mechanisms include a decrease in oxidative stress as indicated by the decrease in cellular heme and nitrotyrosine levels, an anti-inflammatory action as evidenced by a decrease in COX-2 and PGE2, interference with the action of angiontensin II (Ang II) as evidenced by an increase in PRA in the face of a decrease in PGE2 and aldosterone, as well as the inhibition of aldosterone synthesis.

Protective Effects of Heme-Oxygenase Expression in Cyclosporine A - Induced Injury

Cyclosporine A (CsA) is the immunosuppressant of first choice in allotransplantation. Its use is associated with side effects of nephrotoxicity and neurotoxicity, which are among the most prominent. This study was undertaken to explore whether expression and activity of heme oxygenase (HO), the rate-limiting enzyme in heme degradation, is altered in a rat model of CsA-induced injury. Male Sprague Dawley rats were divided into four groups and treated for 21 days. Group I (control) was injected with olive oil (vehicle), group II with CsA (15 mg/kg/day), group III with CsA and the HO inhibitor stannous mesoporphyrin (SnMP) (30 micromol/kg/day) and group IV with one dose of the HO inducer cobalt protoporphyrin (CoPP) 5 mg/100 or heme (10 mg/kg body weight), three days after onset of CsA treatment. Renal tissue was processed for light microscopy, and for HO-1 enzyme activity, assay and for Western blot analysis. In CsA-treated rats there was histological evidence of tubulointerstitial scarring. HO-1 was undetectable in CsA-treated rats compared to control while there was no change in HO-2. In animals treated with a combination of CsA and SnMP, HO-1 activity was further reduced. In animals treated with a combination of CsA and CoPP, HO-1 protein levels were partially restored. These observations indicate that downregulation of HO-1 expression by CsA could be one mechanism underlying CsA-induced toxicity. The CsA-induced decrease in HO-1 expression is partial and restorable, and attempts to preserve HO levels may attenuate CsA toxicity.

Expression of human heme oxygenase-1 in the thick ascending limb attenuates angiotensin II-mediated increase in oxidative injury

BACKGROUND

Heme oxygenase-1 (HO-1) catalyzes the conversion of heme to bilirubin, carbon monoxide (CO), and free iron, thus controlling the level of cellular heme. The medullary thick ascending limb of the loop of Henle (TALH) is situated in a site of markedly diminished oxygen tension and, as such, is highly vulnerable to ischemic insult. We hypothesize that selective upregulation of HO-1 in TALH by gene transfer attenuates oxidative stress caused by angiotensin II (Ang II).

METHODS

An adenoviral vector expressing the human HO-1 under the control of the TALH-specific promoter [Na(+)-K(+)-Cl(-) cotransporter (NKCC2 promoter)] was constructed and the cell specific expression of the recombinant adenovirus was examined using several types of cells, including endothelial, vascular smooth muscle, and TALH cells. The effects of HO-1 transduction on HO-1 expression, HO activity and the response to Ang II with respect to cyclooxygenase-2 (COX-2) up-regulation and oxidative injury [growth-stimulating hormone (GSH) levels and cell death] were determined.

RESULTS

Western blot and reverse transcription-polymerase chain reaction (RT-PCR) revealed that human HO-1 was selectively expressed in primary cultured TALH cells following infection with Ad-NKCC2-HO-1. In TALH cells infected with Ad-NKCC2-HO-1, Ang II-stimulated prostaglandin E(2) (PGE(2)) levels were reduced by 40%. Ang II caused a marked decrease in GSH levels and this decrease was greatly attenuated in TALH cells transduced with Ad-NKCC2-HO-1. Moreover, Ang II-mediated DNA degradation was completely blocked by the site-specific expression of human HO-1 gene.

CONCLUSION

These results indicate that TALH cell survival after exposure to oxidative stress injury may be facilitated by selective upregulation of HO-1, thusly blocking inflammation and apoptosis.

Overexpression of human heme oxygenase-1 attenuates endothelial cell sloughing in experimental diabetes

Heme oxygenase (HO)-1 represents a key defense mechanism against oxidative injury. Hyperglycemia produces oxidative stress and various perturbations of cell physiology. The effect of streptozotocin (STZ)-induced diabetes on aortic HO activity, heme content, the number of circulating endothelial cells, and urinary 8-epi-isoprostane PGF2alpha (8-Epi) levels in control rats and rats overexpressing or underexpressing HO-1 was measured. HO activity was decreased in hyperglycemic rats. Hyperglycemia increased urinary 8-Epi, and this increase was augmented in rats underexpressing HO-1 and diminished in rats overexpressing HO-1. The number of detached endothelial cells and O2- formation increased in diabetic rats and in hyperglycemic animals underexpressing HO-1 and decreased in diabetic animals overexpressing HO-1 compared with controls. These data demonstrate that HO-1 gene transfer in hyperglycemic rats brings about a reduction in O2- production and a decrease in endothelial cell sloughing. Upregulation of HO-1 decreases oxidant production and endothelial cell damage and shedding and may attenuate vascular complications in diabetes.

Heme oxygenase-1 prevents superoxide anion-associated endothelial cell sloughing in diabetic rats

Heme oxygenase-1 (HO-1) represents a key defense mechanism against oxidative injury. Hyperglycemia has been linked to increased oxidative stress, leading to endothelial dysfunction, delayed cell replication, and enhanced apoptosis. The effect of streptozotocin (STZ)-induced diabetes on HO activity, HO-1 promoter activity, superoxide anion (O*-2, and the number of circulating endothelial cells was measured. The expression of HO-1/HO-2 protein was unchanged, but HO activity was decreased in aortas of diabetic rats compared with control (p < 0.05). High glucose decreased HO-1 promoter activity (p < 0.05). Hyperglycemia increased O*-2 and this increase was augmented with HO-1 inhibition and diminished with HO-1 upregulation (p < 0.05). Circulating endothelial cells were significantly higher in diabetic rats and were decreased or increased with administration of the HO-1 inducer (CoPP) or inhibitor (SnMP), respectively (p<0.05). In conclusion, HO-1 upregulation in diabetic rats brings about an increase in serum bilirubin, a reduction in O*-2 production, and a decrease in endothelial cell sloughing.

Functional expression of human heme oxygenase-1 gene in renal structure of spontaneously hypertensive rats

Heme oxygenase (HO), by catabolizing heme to bile pigments, regulates the levels and activity of cellular hemoprotein and HO activity. We examined the effect of delivery of the human HO-1 gene on cellular heme in renal tissue using a retroviral vector. We used a single intracardiac injection of the concentrated infectious viral particles in 5-day-old spontaneously hypertensive rats; 25 were transduced with empty vector and 25 were transduced with the human HO-1 gene. Functional expression of human and rat HO-1 was measured after 2 and 4 weeks. Reverse transcription polymerase chain reaction showed that human HO-1 mRNA was expressed as early as 2 weeks, with the highest levels in the kidney. Western blot analysis showed distribution of human HO-1 protein in rat kidney structures, predominantly in the thick ascending limb of the loop of Henle as well as in proximal tubules and preglomerular arterioles. These areas also demonstrated higher HO activity as measured by increased conversion of heme to bilirubin and carbon monoxide. Functional expression of the human HO-1 gene was associated with a decrease in blood pressure in 4- and 8-week-old spontaneously hypertensive rats. Compared with nontransduced rats, human HO-1 gene overexpression in transduced rats was associated with a 35% decrease in urinary 20-hydroxyeicosatetraenoic acid, a potent vasoconstrictor and an inhibitor of tubular Na(+) transport, which may be related to the decrease in blood pressure.

Differential effect of cobalt protoporphyrin on distributions of heme oxygenase in renal structure and on blood pressure in SHR

Heme oxygenase (HO) is a microsomal enzyme that oxidatively cleaves heme to form biliverdin, releasing iron and carbon monoxide (CO). Thus, HO not only controls the availability of heme for the synthesis of hemeproteins but also generates CO, which binds to the heme moiety of hemoproteins, thereby affecting their enzymatic activity. The present study was undertaken to explore changes in the relative expression of renal HO-1 and HO-2 in response to modulators and the effect on blood pressure regulation in spontaneously hypertensive rats (SHR). Immunohistochemistry confirmed a cobalt protoporphyrin (CoPP)-mediated increase in HO-1 protein. After a single injection of CoPP (5 mg/100 gram body weight) in 7-week-old SHR, blood pressure significantly decreased (p<0.01) while renal HO activity increased 6-fold over controls. CoPP pretreatment deceased the levels of the renal cytochrome P450-derived arachidonic acid metabolite, 20-HETE, a powerful vasoconstrictor, by 65% in renal tissue. Western blot analysis demonstrated that CoPP significantly increased HO-1 protein expression in the cortex and outer medulla and, to a lesser degree, in the inner medulla of the rat kidney. HO-2 was constitutively expressed in all parts of the kidney, and did not significantly change after treatment with CoPP. These results indicate that selective induction of cortical and outer medullary HO-1 is associated with a decrease in 20-HETE and blood pressure, suggesting an important role for HO-1 activity in the regulation of urine volume, electrolyte excretion and blood pressure.

Modulation of cGMP by human HO-1 retrovirus gene transfer in pulmonary microvessel endothelial cells

Carbon monoxide (CO) stimulates guanylate cyclase (GC) and increases guanosine 3',5'-cyclic monophosphate (cGMP) levels. We transfected rat-lung pulmonary endothelial cells with a retrovirus-mediated human heme oxygenase (hHO)-1 gene. Pulmonary cells that expressed hHO-1 exhibited a fourfold increase in HO activity associated with decreases in the steady-state levels of heme and cGMP without changes in soluble GC (sGC) and endothelial nitric oxide synthase (NOS) proteins or basal nitrite production. Heme elicited significant increases in CO production and intracellular cGMP levels in both pulmonary endothelial and pulmonary hHO-1-expressing cells. N(omega)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NOS, significantly decreased cGMP levels in heme-treated pulmonary endothelial cells but not heme-treated hHO-1-expressing cells. In the presence of exogenous heme, CO and cGMP levels in hHO-1-expressing cells exceeded the corresponding levels in pulmonary endothelial cells. Acute exposure of endothelial cells to SnCl2, which is an inducer of HO-1, increased cGMP levels, whereas chronic exposure decreased heme and cGMP levels. These results indicate that prolonged overexpression of HO-1 ultimately decreases sGC activity by limiting the availability of cellular heme. Heme activates sGC and enhances cGMP levels via a mechanism that is largely insensitive to NOS inhibition.

Overexpression of the heme oxygenase gene in renal cell carcinoma

Heme oxygenase (HO) activity has been implicated in the regulation of renal function and cell growth in normal and disease states. Expression of HO genes has been shown to regulate important hemoprotein(s) such as cytochrome P450. In the present study, HO activity was measured in samples of human adenocarcinoma, juxtatumor, and normal renal tissues. The samples were histologically examined to verify the malignant and normal nature. HO activity was 4-fold higher in the adenocarcinoma than in either normal or juxtatumor tissues. We designed a reverse transcriptase-polymerase chain reaction (RT-PCR) method to assess the presence of HO-1 and HO-2 mRNA in biopsy samples of various human renal tissues. Total RNA from renal samples was reverse transcribed and amplified simultaneously by PCR using specific primers for HO-1 and HO-2. Results show that both HO-1 and HO-2 mRNAs were expressed in all renal tissues examined and that HO-1 appeared to be amplified more than HO-2. Northern blot analysis revealed that HO-1 mRNA was elevated by several-fold in adenocarcinoma compared with juxtatumor or normal tissues. In contrast, no differences in HO-2 mRNA levels were observed using either RT-PCR or Northern blot. Cytochrome P450 arachidonic acid epoxygenase and omega-hydroxylase activities were markedly reduced in the tumor tissues, whereas, in the juxtatumor tissue, cytochrome P450 omega-hydroxylase activity was significantly increased. Northern blot analysis using cytochrome P450 cDNA probe 4A2 cDNA for the omega-hydroxylase gene family revealed that mRNA levels for omega-hydroxylase transcripts were significantly decreased in the adenocarcinoma compared with juxtatumor. The decrease in cytochrome P450 4All mRNA levels correlated with a decrease in the arachidonic acid omega-hydroxylation metabolite, 20-HETE. The production of 20-HETE was significantly higher in juxtatumor in agreement with omega-hydroxylase mRNA. Higher levels of HO-1 may be a contributing factor for the undetectable levels of cytochrome P450 arachidonic acid metabolites, 20-HETE, in the adenocarcinoma. Our results suggest that increased generation of mitogenic activities by omega-hydroxylase and 20-HETE in the juxtatumor may be a contributing factor in the development and growth of neoplastic tissues, and the induction of HO in the tumor tissue may be an attempt to limit oxidative injury caused by the cytochrome P450 metabolites and other oxidative stress.

Quantitative measurement of heme oxygenase-1 in the human renal adenocarcinoma

Heme oxygenase (HO-1) is the rate-limiting enzyme in heme catabolism. HO-1, a stress protein, has been suggested to be involved in defense mechanisms against agents that may induce oxidative stress. It has been proposed that renal HO gene expression regulates important hemoprotein(s) such as cytochrome P450 and may be essential to maintain homeostasis in the kidney. Because accurate assessment of HO-1 mRNA in normal and disease states in kidney were not available due to the limited number of cells, we developed a system to quantitate human HO-1 mRNA in samples limited in cell number and/or mRNA copies. Total RNA from human kidney was used to establish this technique; it was reverse-transcribed and then amplified by polymerase chain reaction (PCR) in a tube also containing an internal standard obtained by deleting 50 bp from the original human HO-1 gene. This allowed us to use the same primers for both the sample and internal standard. After amplification, templates were resolved by acrylamide gel electrophoresis and quantitated either by densitometry or radioactivity counted from the bands excised from the gel. When the internal standard is present in the reaction mixture, the ratio of amplified sample vs. the standard template is proportional to the amount of sample RNA, and it is therefore possible to calculate the number of specific mRNA molecules. We have used this approach to quantitate the number of HO-1 mRNA molecules in adenocarcinoma cells. Results show that reverse transcription (RT)/PCR methods were able to determine the number of HO-1 mRNA copies in biopsy samples of human adenocarcinoma cells.

Hemin and L-arginine regulation of blood pressure in spontaneous hypertensive rats

Perturbation in heme metabolism is known to affect the level and activity of hemoproteins, including cytochrome P450-dependent arachidonic acid metabolism. The latter has been associated with elevation in blood pressure seen in spontaneously hypertensive rats. The effect of heme arginate and its components, arginine and heme, on cytochrome P450 levels and blood pressure in spontaneously hypertensive rats were studied. Administration of heme arginate or heme alone at doses of 9 to 30 mg/kg body wt/day for 4 days resulted in a marked decrease of blood pressure in spontaneously hypertensive rats, whereas blood pressure in rats receiving the vehicle control was not affected. Similarly, L-arginine, but not D-arginine, in a dose-dependent manner decreased blood pressure in spontaneously hypertensive rats. The maximal change in blood pressure was achieved at 100 mg/kg body wt of arginine and was associated with a significant increase in heme oxygenase activity. A higher concentration (500 mg/kg) did not cause an additional decrease in blood pressure but further increased heme oxygenase activity. The arginine-induced heme oxygenase activity was suppressed by Sn-protoporphyrin. Administration of heme to spontaneously hypertensive rats resulted in an accumulation of heme oxygenase mRNA, which was accompanied by an increase in enzyme activity. The increase in heme oxygenase activity was also prevented by Sn-protoporphyrin. It is postulated that heme treatment resulted in an increase in heme oxygenase mRNA, which consequently led to a diminution of cellular heme and depletion of hemoproteins, such as the cytochrome P450 arachidonate metabolizing enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytochrome P450-dependent arachidonic acid metabolism in human kidney

Cytochrome P450-dependent arachidonic acid metabolism in human kidney cortex from several postmortem subjects has been characterized. Using HPLC and GC/MS, four cytochrome P450-arachidonic acid metabolites were tentatively but not unequivocally identified as epoxyeicosatrienoic acid (EET), dihydroxyeicosatrienoic acid (DHT) and 19- and 20-hydroxyeicosatetraenoic acids, suggesting the involvement of two major cytochrome P450 enzymes, epoxygenase and omega/omega-1 hydroxylases. This pattern of metabolism was similar to that found in rabbit and rat kidneys. The formation of these metabolites was dependent on the presence of NADPH and inhibited by IgG of NADPH-cytochrome P450 (c) reductase. Immunologic studies of renal cytochrome P450 epoxygenase demonstrated that antibodies prepared against human-purified hepatic cytochrome P450 epoxygenase recognized renal enzyme protein and inhibited the enzyme activity by 92%. In contrast, control immunoglobulin did not inhibit renal cytochrome P450 epoxygenase. Antibody inhibition of renal cytochrome P450 epoxygenase demonstrated a degree of conservation of both enzyme proteins between liver and kidney. Antibodies against lauric acid omega/omega-1 hydroxylases (P450 omega) inhibited the formation of omega/omega-1 hydroxylase products, 19- and 20-HETEs. Identical qualitative patterns of arachidonic acid metabolites were observed in all cortical microsomes studied. Interindividual variations were observed in the cytochrome P450-dependent arachidonic acid metabolism, and the activities ranged from 0.031 to 5.027 nmol arachidonic acid converted/mg protein/30 min. which is about a 150-fold difference. However, when the specific activities for total cytochrome P450-dependent arachidonic acid metabolism were calculated, two separate groups could be distinguished, high and low metabolizers of arachidonic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptive myocardial hypertrophy in the renal ablation model

We have previously reported downregulation of the vascular alpha 1-receptor in the 5/6 renal ablation model. In this investigation we have examined the adaptive response of the heart following 5/6 renal ablation. Renal ablated and sham rats were maintained under identical conditions for 6 weeks. Despite the presence of systemic hypertension in renal ablated rats (185 +/- 10 mm Hg, P less than .01), heart weight did not differ from sham. [125I] +/- CYP binding was performed and myocardial norepinephrine (NE) content determined to evaluate myocardial sympathetic neuroeffector mechanisms. Scatchard analysis and 1-isoproterenol competition curves did not reveal a difference in the binding properties of the myocardial beta-receptor. No difference in myocardial NE was found in renal ablated and sham rats. Unexpectedly, 1-isoproterenol stimulation of adenylate cyclase was impaired in renal ablated rats (32.6 +/- 6 v 58.6 +/- 5 pmol/mg/min, P less than .01) and the dose response curve shifted to the right. We conclude that despite systemic hypertension an adaptive hypertrophic response was not present in hearts of renal ablated rats; myocardial sympathetic neuroeffector mechanisms are not altered in this model; and impaired stimulation of adenylate cyclase appears to be the result of a post-receptor defect.

Properties of human kidney heme oxygenase: inhibition by synthetic heme analogues and metalloporphyrins

Heme oxygenase activities in human kidney microsomes were found to be from 0.238 to 0.620 nmol of bilirubin/mg/hr (mean 0.375, SD 0.134), which represent approximately 30% of activities determined for human adult liver. There was interindividual variation in heme oxygenase activity of a 2-5-fold difference. Rabbits were immunized with purified human liver heme oxygenase and the resulting antibody preparation was used to examine the species specificity of the enzyme. Microsomal protein with a molecular weight of 32,000 from human kidney was identified on Western blots by its reaction with the anti-heme oxygenase liver antibody similar to the purified enzyme protein. Thus, a homology exists between human hepatic and kidney heme oxygenase. The enzyme activity was sensitive to inhibition by metalloporphyrins, such as tin-protoporphyrin IX and, to a lesser degree, by zinc and cobalt protoporphyrin IX. In a study of different synthetic heme analogues for in vitro inhibition of heme oxygenase, we found that replacement of iron by zinc in deuteroporphyrin IX 2,4 bis glycol dramatically potentiated the inhibition of heme oxygenase activity. This finding demonstrated that zinc deuteroporphyrin IX 2,4 bis glycol is a most potent inhibitor of heme oxygenase activity.

Differential effects of partial hepatectomy on hepatic and renal heme and cytochrome P450 metabolism

Partial hepatectomy has been suggested to affect hepatic and renal cytochrome P450 content and the related drug metabolizing enzyme system. In addition, cytochrome P450 and its dependent activities have been shown to be regulated by the availability of cellular heme. We, therefore, studied cytochrome P450 in addition to the level of heme oxygenase, the rate-limiting enzyme of heme catabolism, and delta-aminolevulinic acid (ALA) synthase, the rate-limiting enzyme of heme synthesis, in the remnant liver and intact kidneys of rats after two-thirds hepatectomy. The level of hepatic heme oxygenase was elevated threefold in partially hepatectomized rats as compared to sham-operated rats, while ALA synthase was decreased by 40%. This was reflected in decreased hepatic cytochrome P450 content, ie, from 0.689 +/- 0.175 nmole/mg to 0.505 +/- 0.089 nmole/mg protein and associated decreased drug metabolizing enzymes: aryl hydrocarbon hydroxylase, 7-ethoxycoumarin-O-deethylase, and benzphetamine N-demethylase, by 40%, 40%, and 47%, respectively. In contrast, renal heme oxygenase was not changed after hepatectomy, whereas renal ALA synthase was increased by fourfold. Renal cytochrome P450, aryl hydrocarbon hydroxylase, 7-ethoxycoumarin-O-deethylase, and benzphetamine N-demethylase were increased after partial hepatectomy by 84%, 360%, 165% and 406%, respectively. These data indicate that partial hepatectomy decreases liver cytochrome P450 levels by inducing heme oxygenase and inhibiting ALA synthase activities. In this situation the kidney plays a substitutive role in metabolizing endogenous substrates oxygenated by cytochrome P450 isozymes.

Amelioration of systemic hypertension by converting enzyme inhibition in the renal ablation model

Hypertension associated with a reduction in renal mass has been traditionally thought of as a volume-dependent state. Recent investigations suggest important roles for systemic and glomerular resistance vessels in the pathogenesis of systemic hypertension (SHT) and progression of end-stage renal disease. To examine this relationship, investigations were performed in two groups of rats maintained for 6 weeks following 5/6 renal ablation. Group A received converting enzyme inhibition (CEI) for 6 weeks. Group B received no treatment. Systolic blood pressure and weight of remnant kidney tissue were both increased in group B (P less than 0.01). BUN did not differ in groups A and B; however, renal PGI2 excretion was increased in group A (P less than 0.01). Renal morphology was preserved in group A, with little or no evidence of glomerular sclerosis. CEI prevents SHT and enhances renal PGI2 excretion in this model. The selective increase in PGI2 may mediate systemic and renal effects of this agent.

Myocardial hypertrophy: the effect of sodium and the role of sympathetic nervous system activity

Dietary sodium and the myocardial alpha 1-receptor have been implicated in the hypertrophic response of myocardial tissue. Alterations in sodium homeostasis have been demonstrated to influence sympathetic nervous function, centrally and peripherally. In this investigation, we have examined the effect of dietary sodium on the development of myocardial hypertrophy; and the role of sympathetic neuroeffector mechanisms in the hypertrophic response. Studies were performed in three groups of uninephrectomized rats: A-regular diet; B-1% saline/regular diet; C-1% Saline/doca/regular diet. Groups A and B did not develop systemic hypertension (SHT). Saline treatment increased heart weight and the density of surface alpha 1-receptors; myocardial norepinephrine (NE) was reduced. Group C developed SHT. Heart weight was greatest in Group C; and myocardial NE was severely depleted. Downregulation of myocardial alpha 1-receptors, a finding consistent with the hyperadrenergic state, was observed in Group C. Our results suggest dietary sodium may modulate hypertrophic response in myocardial tissue, by altering sympathetic neuroeffector mechanisms.

Upregulation of the vascular alpha-1 receptor in malignant DOCA-salt hypertension

In this investigation we describe regulation of the vascular alpha-1 receptor and functional properties of resistance vessels in malignant hypertensive DOCA-salt rats (DOCA-salt). Uninephrectomized control and DOCA-salt rats were maintained for 6 weeks; microscopic renal morphology provided an index of vascular injury. Radioligand binding studies indicated a striking increase in the density of mesenteric alpha-1 binding sites in DOCA-salt (542 +/- 44 fm/mg) vs. salt control (206 +/- 4 fm/mg) and water control (223 +31 fm/mg) P less than .01. The affinity of the receptor for the radioligand [125I] (+/-) BE 2254 was reduced in DOCA-salt rats. Electrical nerve stimulation and agonist dose response curves were performed on isolated perfused mesenteric arteries. A singular correlation between increased receptor density and vascular responses in DOCA-salt rats could not be demonstrated. The norepinephrine (NE) content of mesenteric arteries was reduced in DOCA-salt (1001 +/- 32 ng/g) vs. water control (1522 +/- 44 ng/g) and saline control (1538 +/- 30 ng/g) P less than .01. Our results indicate, upregulation of the mesenteric alpha-1 receptor occurs in DOCA-salt rats, however, additional factors participate in the vascular response to adrenergic stimulation in this model.

Effect of chronic uremia on the cardiovascular alpha 1 receptor

Adrenergic dysfunction in uremia has been well described. Several lines of evidence suggest disorders of blood pressure regulation and myocardial response may occur secondary to adrenergic dysfunction; attenuated pressor response to norepinephrine (NE) in uremia; attenuated chronotropic responses during dialysis induced hypotension. Since the adrenergic receptors are the effector component of the adrenergic nervous system, we have employed the partially nephrectomized uremic rat, to examine the effect of chronic uremia (4-6 weeks) on the binding properties of alpha 1 receptors in rat mesenteric artery and myocardial tissue. The results indicate that moderate levels of uremia alter the binding properties of both the alpha 1 vascular and myocardial receptor.

Pharmacologic toxicity of cimetidine on hepatic and renal drug metabolism

We studied the effect of cimetidine on liver and kidney heme metabolism and on the activity of the cytochrome P-450 drug metabolizing enzyme system. Results show that the induction of a heme biosynthetic enzyme and the activities of two drug metabolizing enzymes are impaired when cimetidine is given in combination with phenobarbital (PB). When rats were given four 33 mg doses of cimetidine IP per day for 2 days and sacrificed, we found no significant effect on kidney or liver delta-aminolevulinic acid (ALA) synthase activity. Heme oxygenase and cytochrome P-450 levels were also unchanged in these tissues. In contrast, when we measured activities of certain liver drug metabolizing enzymes, it was found that cimetidine significantly inhibited aniline hydroxylase and aminopyrine-N-demethylase by 43% and 65%, respectively. The observed changes in the activities of these drug metabolizing enzymes led us to study cimetidine in combination with other drugs. When the porphyric inducing agent allylisoprophyacetamide (AIA) was administered alone, we found a 326% increase in hepatic ALA synthase activity at 16 hours. Cimetidine given together with AIA increases hepatic ALA synthase 291 and 300% at 16 and 20 hour intervals respectively. Cytochrome P-450 levels in AIA treated rats with or without cimetidine were decreased to 52-65% of control values without a significant change in heme oxygenase levels. When PB was given alone, we found an increase in hepatic ALA synthase activity by 223 and 400% at 16 and 20 hour intervals, respectively. Cimetidine in combination with PB at the same time intervals showed a slightly diminished increase of hepatic ALA synthase activity by 146 and 238%, respectively. When PB was given alone, hepatic cytochrome P-450 was increased 96% at 16 hours, whereas when combined with cimetidine a similar increase of hepatic cytochrome P-450 was observed. In conclusion cimetidine does not significantly alter the action of the porphyric agents PB and ALA on cytochrome P-450; however, combined administration of PB plus cimetidine does impair the induction of ALA synthase. Additionally, cimetidine markedly decreased the drug metabolizing enzymes aniline hydroxylase and aminopyrine-N-demethylase in vivo, and subsequently may interfere with the endogenous metabolism of other drugs.

Inhibition of erythropoiesis in chronic renal failure: the role of parathyroid hormone

Sera from 20 anemic patients with chronic renal failure (CFR) were studied for their effect on bone marrow in vitro erythroid colony formation (CFUE) and the observations correlated with parathyroid hormone (PTH) and ionized calcium levels in the patients' sera. Results demonstrated that 17 out of 20 patients' sera significantly inhibited in vitro erythropoiesis by 47% to 97%. No significant elevation in ionized calcium was found in 16 of the patients tested. Furthermore, assay of PTH levels in these patients revealed that 9 out of 20 had elevated levels of PTH. No correlation was found between PTH serum levels and the degree of in vitro inhibition of erythropoiesis (CFUE) by the patients' sera. Addition of up to 2,000 pg/mL (far above the patients' levels) of exogenous N-terminal or C-terminal PTH with in vitro bone marrow cultures resulted in no inhibitory effect on CFUE. It is concluded that the circulating inhibitor of erythropoiesis which has been shown to exist in the sera of this particular group of patients with CRF, is not PTH.

Hearing impairment associated with chronic renal failure

The auditory sensitivity of 67 patients with chronic end-stage renal failure was assessed. In order to determine the incidence of hearing loss and to describe the impairment and possible contributing factors, one group of 39 patients was assessed prior to treatment by hemodialysis. Twelve of these subjects were then followed for 1 year as they are treated by hemodialysis. The remaining 27 patients, not treated by hemodialysis, were also retested in one year. A second group of 28 patients who ad been receiving hemodialysis over periods of 1 1/2, 3, and 6 years was also evaluated. A high incidence of high-frequency impairment was obtained which could not be attributed to age, noise exposure, ototoxicity, or hereditary. An association between this high-frequency impairment and both the renal disease and its treatment was suggested. Clinically significant sensorineural hearing loss did not appear associated with non-genetic kidney disease.

Hepatitis B vaccine: immune responses in haemodialysis patients

Antibody to hepatitis B surface antigen (anti-HBs) developed within six months in 80% of haemodialysis patients given either two or three 40 micrograms doses of hepatitis B vaccine. A total of 89% had anti-HBs after a booster dose given six months later. Anti-HBs titres were higher in patients who received three initial doses than in those who received only two doses, but the proportion of anti-HBs-positive patients was the same in the two groups. Male patients became anti-HBs positive less often than females and their antibody titres were lower.

Presence of creatine phosphokinase brain band in the serum of chronic renal disease patients

The almost universal presence of the isoenzyme creatine phosphokinase brain band (CPK-BB) in the sera of patients with chronic renal insufficiency and serum creatinine above 4.5 mg/dl is noted. It is absent in patients with severe acute renal failure and in transplanted patients with normal renal function. The source of the enzyme may be nerve tissue and may represent neuronal cell damage in uremics over a period of time.