Different effects of angiotensin II and catecholamine on renal cell apoptosis and proliferation in rats

Cyathus striatus Extract Induces Apoptosis in Human Pancreatic Cancer Cells and Inhibits Xenograft Tumor Growth In Vivo

Simple Summary

The main aim of the present study is to test the effect of Cyathus striatus extract on the cell growth of human pancreatic cancer cells in vitro and in vivo. In addition, the effect of the extract on the gene expression was detected. The results indicated that Cyathus striatus extract significantly inhibited the cell viability and induced apoptosis. The treatment of xenograft mice harboring human pancreatic cancer cells significantly inhibited tumor growth through the induction of apoptosis. RNAseq experiments revealed the involvement of the MAPK and P53 signaling pathways and pointed toward endoplasmic reticulum stress induced apoptosis. These results may suggest that Cyathus striatus extract may contain pro-apoptotic factors that can be identified and used for the treatment of human cancer.

Abstract

Pancreatic cancer is a highly lethal disease with limited options for effective therapy and the lowest survival rate of all cancer forms. Therefore, a new, effective strategy for cancer treatment is in need. Previously, we found that a culture liquid extract of Cyathus striatus (CS) has a potent antitumor activity. In the present study, we aimed to investigate the effects of Cyathus striatus extract (CSE) on the growth of pancreatic cancer cells, both in vitro and in vivo. The proliferation assay (XTT), cell cycle analysis, Annexin/PI staining and TUNEL assay confirmed the inhibition of cell growth and induction of apoptosis by CSE. A Western blot analysis demonstrated the involvement of both the extrinsic and intrinsic apoptosis pathways. In addition, a RNAseq analysis revealed the involvement of the MAPK and P53 signaling pathways and pointed toward endoplasmic reticulum stress induced apoptosis. The anticancer activity of the CSE was also demonstrated in mice harboring pancreatic cancer cell line-derived tumor xenografts when CSE was given for 5 weeks by weekly IV injections. Our findings suggest that CSE could potentially be useful as a new strategy for treating pancreatic cancer.

Influence of Angiotensin II on cell viability and apoptosis in rat renal proximal tubular epithelial cells in in vitro studies

Introduction:

Angiotensin II (Ang II) is multifunctional peptide that plays an important role in blood pressure regulation and maintenance electrolyte homeostasis. It shows biological effects by activating two main receptors: AT₁ and AT₂. The aim of the present work was to investigate the effect of Ang II on NRK-52E cells in in vitro studies. Furthermore, an attempt was made to determine the effectiveness of the AT₁ and AT₂ receptor blocker activity (respectively, losartan and PD123319).

Methods:

The study was carried out using adherent NRK-52E cell line. Immunofluorescence and Western Blot method were used to confirm the presence of AT₁ and AT₂ receptors in the cells. The SRB and MTT tests showed decrease in the viability of NRK-52E cells incubated with Ang II in comparison to the control (without Ang II).

Results:

The blockade of the AT₁ receptor caused an increase in cell viability in comparison to cells incubated with Ang II only. The blockade of AT₂ receptor also triggered statistically significant increase in cell viability in comparison with cells only exposed to Ang II. Combined administration of blockers for both receptors (losartan and PD123319) decreased Ang II cytotoxicity against NRK-52E cell line. The apoptosis was only observed in cells incubated with Ang II in comparison with control cells. However, simultaneous use of both blockers caused statistically significant decrease in apoptosis.

Conclusions:

The result of our study indicates that Ang II causes damaging effect on NRK-52E cells by directing them to programmed cell death. It seems that not only does the AT₂ receptor itself play an important role in the induction of apoptosis, but also its interaction with AT₁ receptor does as well.

Heme oxygenase-1 inhibitor tin-protoporphyrin improves liver regeneration after partial hepatectomy

AIMS

This study investigates the effects of the heme oxygenase-1 (HO-1) inhibitor tin protoporphyrin IX (SnPP), on rat liver regeneration following 2/3 partial hepatectomy (PH) in order to clarify the controversial role of HO-1 in the regulation of cellular growth.

MAIN METHODS

Male Wistar rats received a subcutaneous injection of either SnPP (10 μmoles/kg body weight) or saline 12 h before PH and 0, 12 and 24 h after surgery. Rats were killed from 0.5 to 36 h after PH. Bromodeoxyuridine (BrdU) incorporation was used to analyze cell proliferation. Immunohistochemistry, Western blot analysis and quantitative Real Time-PCR were used to assess molecular and cellular changes after PH.

KEY FINDINGS

Data obtained have shown that administration of SnPP caused an increased entry of hepatocytes into S phase after PH, as demonstrated by labeling (L.I.) and mitotic (M.I.) indexes. Furthermore, enhanced cell cycle entry in PH-animals pre-treated with SnPP was associated with an earlier activation of IL-6 and transcription factors involved in liver regeneration, such as phospho-JNK and phospho-STAT3.

SIGNIFICANCE

Summarizing, data here reported demonstrate that inhibition of HO-1 enhances rat liver regeneration after PH which is associated to a very rapid increase in the levels of inflammatory mediators such as IL-6, phopsho-JNK and phospho-STAT3, suggesting that HO-1 could act as a negative modulator of liver regeneration. Knowledge about the mechanisms of liver regeneration can be applied to clinical problems caused by delayed liver growth, and HO-1 repression may be a mechanism by which cells can faster proliferate in response to tissue damage.

Increased Apoptosis in the Paraventricular Nucleus Mediated by AT1R/Ras/ERK1/2 Signaling Results in Sympathetic Hyperactivity and Renovascular Hypertension in Rats after Kidney Injury

Background: The central nervous system plays a vital role in the development of hypertension, but the molecular regulatory mechanisms are not fully understood. This study aimed to explore signaling in the paraventricular nucleus (PVN) which might contribute to renal hypertension.

Methods: Renal hypertension model was established by five-sixth nephrectomy operation (5/6Nx) in male Sprague Dawley rats. Ten weeks afterwards, they were random assigned to no treatment, or intracerebroventricular injection (ICV) with artificial cerebrospinal fluid, losartan [angiotensin II receptor type 1 (AT1R) antagonist], farnesylthiosalicylic acid (Ras inhibitor), PD98059 (MEK inhibitor), or SB203580 (p38 inhibitor) and Z-DEVD-FMK (caspase-3 inhibitor). Before and after treatment, physiological and biochemical indices were measured. Immunohistochemistry, western blot and RT-PCR were applied to quantify key components of renin-angiotensin system, apoptosis-related proteins, Ras-GTP, and MAPKs in the PVN samples. TUNEL assay was used to measure the situ apoptosis in PVN.

Results: The 5/6Nx rats showed significantly elevated systolic blood pressure, urinary protein excretion, serum creatinine, and plasma norepinephrine (p < 0.05) compared to sham rats. The expression of angiotensinogen, Ang II, AT1R, p-ERK1/2, or apoptosis-promoting protein Bax were 1.08-, 2.10-, 0.74-, 0.82-, 0.83-fold higher in the PVN of 5/6Nx rats, than that of sham rats, as indicated by immunohistochemistry. Western blot confirmed the increased levels of AT1R, p-ERK1/2 and Bax; meanwhile, Ras-GTP and p-p38 were also found higher in the PVN of 5/6Nx rats, as well as the apoptosis marker cleaved caspase-3 and TUNEL staining. In 5/6Nx rats, ICV infusion of AT1R antagonist, Ras inhibitor, MEK inhibitor or caspase-3 inhibitor could lower systolic blood pressure (20.8-, 20.8-, 18.9-, 14.3%-fold) together with plasma norepinephrine (53.9-, 57.8-,63.3-, 52.3%-fold). Western blot revealed that blocking the signaling of AT1R, Ras, or MEK/ERK1/2 would significantly reduce PVN apoptosis as indicated by changes of apoptosis-related proteins (p < 0.05). AT1R inhibition would cause reduction in Ras-GTP and p-ERK1/2, but not vice versa; such intervention with corresponding inhibitors also suggested the unidirectional regulation of Ras to ERK1/2.

Conclusion: These findings demonstrated that the activation of renin-angiotensin system in PVN could induce apoptosis through Ras/ERK1/2 pathway, which then led to increased sympathetic nerve activity and renal hypertension in 5/6Nx rats.

Losartan improved antioxidant defense, renal function and structure of postischemic hypertensive kidney

Ischemic acute renal failure (ARF) is a highly complex disorder involving renal vasoconstriction, filtration failure, tubular obstruction, tubular backleak and generation of reactive oxygen species. Due to this complexity, the aim of our study was to explore effects of Angiotensin II type 1 receptor (AT1R) blockade on kidney structure and function, as well as oxidative stress in spontaneously hypertensive rats (SHR) after renal ischemia reperfusion injury. Experiments were performed on anaesthetized adult male SHR in the model of ARF with 40 minutes clamping the left renal artery. The right kidney was removed and 40 minutes renal ischemia was performed. Experimental groups received AT1R antagonist (Losartan) or vehicle (saline) in the femoral vein 5 minutes before, during and 175 minutes after the period of ischemia. Biochemical parameters were measured and kidney specimens were collected 24h after reperfusion. ARF significantly decreased creatinine and urea clearance, increased LDL and lipid peroxidation in plasma. Treatment with losartan induced a significant increase of creatinine and urea clearance, as well as HDL. Lipid peroxidation in plasma was decreased and catalase enzyme activity in erythrocytes was increased after losartan treatment. Losartan reduced cortico-medullary necrosis and tubular dilatation in the kidney. High expression of pro-apoptotic Bax protein in the injured kidney was downregulated after losartan treatment. Our results reveal that angiotensin II (via AT1R) mediates the most postischemic injuries in hypertensive kidney through oxidative stress enhancement. Therefore, blockade of AT1R may have beneficial effects in hypertensive patients who have developed ARF.

Determination of an angiotensin II-regulated proteome in primary human kidney cells by stable isotope labeling of amino acids in cell culture (SILAC)

Angiotensin II (AngII), the major effector of the renin-angiotensin system, mediates kidney disease progression by signaling through the AT-1 receptor (AT-1R), but there are no specific measures of renal AngII activity. Accordingly, we sought to define an AngII-regulated proteome in primary human proximal tubular cells (PTEC) to identify potential AngII activity markers in the kidney. We utilized stable isotope labeling with amino acids (SILAC) in PTECs to compare proteomes of AngII-treated and control cells. Of the 4618 quantified proteins, 83 were differentially regulated. SILAC ratios for 18 candidates were confirmed by a different mass spectrometry technique called selected reaction monitoring. Both SILAC and selected reaction monitoring revealed heme oxygenase-1 (HO-1) as the most significantly up-regulated protein in response to AngII stimulation. AngII-dependent regulation of the HO-1 gene and protein was further verified in PTECs. To extend these in vitro observations, we overlaid a network of significantly enriched gene ontology terms from our AngII-regulated proteins with a dataset of differentially expressed kidney genes from AngII-treated wild type mice and AT-1R knock-out mice. Five gene ontology terms were enriched in both datasets and included HO-1. Furthermore, HO-1 kidney expression and urinary excretion were reduced in AngII-treated mice with PTEC-specific AT-1R deletion compared with AngII-treated wild-type mice, thus confirming AT-1R-mediated regulation of HO-1. Our in vitro approach identified novel molecular markers of AngII activity, and the animal studies demonstrated that these markers are relevant in vivo. These interesting proteins hold promise as specific markers of renal AngII activity in patients and in experimental models.

Blood pressure-renal blood flow relationships in conscious angiotensin II- and phenylephrine-infused rats

Chronic ANG II infusion in rodents is widely used as an experimental model of hypertension, yet very limited data are available describing the resulting blood pressure-renal blood flow (BP-RBF) relationships in conscious rats. Accordingly, male Sprague-Dawley rats (n = 19) were instrumented for chronic measurements of BP (radiotelemetry) and RBF (Transonic Systems, Ithaca, NY). One week later, two or three separate 2-h recordings of BP and RBF were obtained in conscious rats at 24-h intervals, in addition to separate 24-h BP recordings. Rats were then administered either ANG II (n = 11, 125 ng·kg(-1)·min(-1)) or phenylephrine (PE; n = 8, 50 mg·kg(-1)·day(-1)) as a control, ANG II-independent, pressor agent. Three days later the BP-RBF and 24-h BP recordings were repeated over several days. Despite similar increases in BP, PE led to significantly greater BP lability at the heart beat and very low frequency bandwidths. Conversely, ANG II, but not PE, caused significant renal vasoconstriction (a 62% increase in renal vascular resistance and a 21% decrease in RBF) and increased variability in BP-RBF relationships. Transfer function analysis of BP (input) and RBF (output) were consistent with a significant potentiation of the renal myogenic mechanism during ANG II administration, likely contributing, in part, to the exaggerated reductions in RBF during periods of BP elevations. We conclude that relatively equipressor doses of ANG II and PE lead to greatly different ambient BP profiles and effects on the renal vasculature when assessed in conscious rats. These data may have important implications regarding the pathogenesis of hypertension-induced injury in these models of hypertension.

The Modulatory Role of Heme Oxygenase on Subpressor Angiotensin II-Induced Hypertension and Renal Injury

Angiotensin II (AngII) causes hypertension (HTN) and promotes renal injury while simultaneously inducing reno-protective enzymes like heme oxygenase-1 (HO-1). We examined the modulatory role of HO on sub-pressor angiotensin II (SP-AngII) induced renal inflammation and injury. We first tested whether the SP-AngII-induced renal dysfunction, inflammation and injury are exacerbated by either preventing (chronic HO-1 inhibition) or reversing (late HO-1 inhibition) SP-AngII-induced HO (using tin protoporphyrin; SnPP). We next examined whether additional chronic or late induction of SP-AngII-induced HO (using cobalt protoporphyrin; CoPP), prevents or ameliorates renal damage. We found that neither chronic nor late SnPP altered blood pressure. Chronic SnPP worsened SP-AngII-induced renal dysfunction, inflammation, injury and fibrosis, whereas late SnPP worsened renal dysfunction but not inflammation. Chronic CoPP prevented HTN, renal dysfunction, inflammation and fibrosis, but surprisingly, not the NGAL levels (renal injury marker). Late CoPP did not significantly alter SP-AngII-induced HTN, renal inflammation or injury, but improved renal function. Thus, we conclude (a) endogenous HO may be an essential determining factor in SP-AngII induced renal inflammation, injury and fibrosis, (b) part of HO's renoprotection may be independent of blood pressure changes; and (c) further induction of HO-1 protects against renal injury, suggesting a possible therapeutic target.

Fluorofenidone inhibits Ang II-induced apoptosis of renal tubular cells through blockage of the Fas/FasL pathway

OBJECTIVES

The present study was designed to investigate the inhibitory effects of fluorofenidone on Ang II-induced apoptosis in renal tubular cells and the related signaling pathway.

METHODS

Rat proximal tubular epithelial cells (NRK-52E) were used to examine the anti-apoptosis effects of fluorofenidone. Cell proliferation was assessed by methyl thiazolyl tetrazolium assay. Apoptosis was examined by AO/EB staining and TUNEL assay. The expression of Fas/FasL pathway members, including Fas, FasL, Bax, Bcl-2, Caspase-8, and Caspase-3 was detected by real-time RT-PCR and/or Western blot, respectively. The activity of Caspase-8 and Caspase-3 was detected by spectrophotometry.

RESULTS

Fluorofenidone didn't affect the proliferation of NRK-52E cells, but significantly inhibited the apoptosis of NRK-52E cells induced by Ang II. Fluorofenidone significantly reduced Ang II-induced increases in Fas, FasL, Bax, Caspase-8 and Caspase-3 at the mRNA level. Consistent with these observations, fluorofenidone also prevented Ang II-mediated up-regulation of FasL and Bax at the protein level. Additionally, Ang II-induced activation of Caspase-8 and Caspase-3 as well as Ang II-initiated downregulation of Bcl-2 at both mRNA and protein levels was all prevented by fluorofenidone.

CONCLUSIONS

Fluorofenidone can inhibit Ang II-induced apoptosis of renal tubular cells through blockage of the Fas/FasL pathway.

Heme oxygenase activity as a determinant of the renal hemodynamic response to low-dose ANG II

ANG II causes renal injury through hemodynamic and other effects, and pressor doses of ANG II induce heme oxygenase-1 (HO-1) as a protective response. The present studies examined the hemodynamic effects of more clinically relevant, lower doses of ANG II and the role of HO activity in influencing these effects. Under euvolemic conditions, ANG II increased arterial pressure and renal vascular resistance. ANG II did not induce oxidative stress, inflammation/injury-related gene expression, or proteinuria and did not alter extrarenal vascular reactivity. At these doses, ANG II failed to increase HO-1 or HO-2 mRNA expression or HO activity. Inhibiting HO activity in ANG II-treated rats by tin mesoporphyrin further increased renal vascular resistances, decreased renal blood flow, and blunted the rise in arterial pressure without inducing oxidative stress or altering expression of selected vasoactive/injury/inflammation-related genes; tin mesoporphyrin did not alter vasorelaxation of mesenteric resistor vessels. We conclude that in this model renal vasoconstriction occurs without the recognized adverse effects of ANG II on glomerular filtration rate, renal blood flow, oxidative stress, vascular reactivity, proteinuria, and injury-related gene expression; renal HO activity is essential in preserving perfusion of the ANG II-exposed kidney. These findings represent an uncommon example wherein function of a stressed organ (by ANG II), but not that of the unstressed organ, requires intact renal HO activity, even when the imposed stress neither induces HO-1 nor HO activity. These findings may be germane to conditions attended by heightened ANG II levels, ineffective renal perfusion, and susceptibility to acute kidney injury.

NADPH oxidase in the kidney: a Janus in determining cell fate

NADPH oxidase-derived reactive oxygen species are implicated in apoptosis in certain kidney cells. On the other hand, NADPH oxidase is also involved in promoting cell proliferation in the kidney. The two faces of NADPH oxidase in these situations prompt us to argue that the role of this enzyme in various kidney diseases needs to be addressed in a cell-specific manner.

Heme oxygenase-1 suppresses hepatitis C virus replication and increases resistance of hepatocytes to oxidant injury

Oxidative injury to hepatocytes occurs as a result of hepatitis C virus (HCV) infection and replication. Modulation of host cell antioxidant enzymes such as heme oxygenase-1 (HO-1) may be useful therapeutically to minimize cellular injury, reduce viral replication, and attenuate liver disease. In this report, we evaluated the effects of HO-1 overexpression on HCV replication and hepatocellular injury. Full-length (FL) (Con1) or nonstructural (NS) replicons (I 389 NS3-3') were transfected with complete human HO-1 sequences or empty vector for control. Cell lines overexpressing HO-1 (twofold to sixfold above basal values) or empty vector were isolated, and their HCV RNA synthesis, pro-oxidant levels, and resistance to oxidative injury were assessed. HO-1 overexpression decreased HCV RNA replication in both FL and NS replicons without affecting cellular growth or DNA synthesis. The attenuation of HCV replication was significantly reversed in both replicon systems with HO-1 small interfering RNA (siRNA) knockdown. Both FL and NS replicons that overexpress HO-1 showed reduced prooxidant levels at baseline and increased resistance to oxidant-induced cytotoxicity. HO-1 induction with hemin also markedly decreased HCV replication in both parental FL and NS replicon cell lines. Conversely, knockdown of HO-1 messenger RNA (mRNA) by siRNA in parental FL or NS replicons did not significantly affect HCV replication, suggesting that less than basal levels of HO-1 had minimal effect on HCV replication.

CONCLUSION

Overexpression or induction of HO-1 results in decreased HCV replication as well as protection from oxidative damage. These findings suggest a potential role for HO-1 in antiviral therapy and therapeutic protection against hepatocellular injury in HCV infection.

Heme oxygenase-1 and the vascular bed: from molecular mechanisms to therapeutic opportunities

Heme oxygenase-1, an enzyme degrading heme to carbon monoxide, iron, and biliverdin, has been recognized as playing a crucial role in cellular defense against stressful conditions, not only related to heme release. HO-1 protects endothelial cells from apoptosis, is involved in blood-vessel relaxation regulating vascular tone, attenuates inflammatory response in the vessel wall, and participates in blood-vessel formation by means of angiogenesis and vasculogenesis. The latter functions link HO-1 not only to cardiovascular ischemia but also to many other conditions that, like development, wound healing, or cancer, are dependent on neovascularization. The aim of this comprehensive review is to address the mechanisms of HO-1 regulation and function in cardiovascular physiology and pathology and to demonstrate some possible applications of the vast knowledge generated so far. Recent data provide powerful evidence for the involvement of HO-1 in the therapeutic effect of drugs used in cardiovascular diseases. Novel studies open the possibilities of application of HO-1 for gene and cell therapy. Therefore, research in forthcoming years should help to elucidate both the real role of HO-1 in the effect of drugs and the clinical feasibility of HO-1-based cell and gene therapy, creating the effective therapeutic avenues for this refined antioxidant system.

Aldosterone induces mesangial cell apoptosis both in vivo and in vitro

Both clinical and experimental reports indicate that aldosterone contributes to the progression of renal failure independent of its hemodynamic effects. In the present study, we evaluated effect of aldosterone on human mesangial cell (MC) growth. Aldosterone induced apoptotic and mitogenic effects on MCs. Aldosterone promoted MC apoptosis in a dose- and time-dependent manner. Spironolactone, a mineralocorticoid receptor antagonist, inhibited aldosterone-induced MC apoptosis. Similarly, antioxidants and free radical scavengers partially attenuated proapoaptotic effects of aldosterone. Aldosterone also enhanced dephosphorylation of phospho-Bad and accumulation of cytosolic cytochrome c in MCs. In in vivo studies, rats were randomly assigned to receive normal saline, aldosterone, or eplerenone + aldosterone for 28 days. Systolic blood pressure, urinary albumin excretion rate, serum creatinine, and aldosterone were measured. Aldosterone-infused rats developed elevated systolic blood pressure and albuminuria when compared with control rats. Aldosterone-treated rats also showed greater numbers of apoptosed MCs. This proapoptotic effect of aldosterone was inhibited by eplerenone, a selective aldosterone antagonist. These findings suggest that aldosterone, besides its hemodynamic effects, may also directly contribute to the occurrence of MC apoptosis.

Heme oxygenase-1 in tumors: is it a false friend?

Heme oxygenase-1 (HO-1) catalyzes the oxidation of heme to biologically active products: carbon monoxide (CO), biliverdin, and ferrous iron. It participates in maintaining cellular homeostasis and plays an important protective role in the tissues by reducing oxidative injury, attenuating the inflammatory response, inhibiting cell apoptosis, and regulating cell proliferation. HO-1 is also an important proangiogenic mediator. Most studies have focused on the role of HO-1 in cardiovascular diseases, in which its significant, beneficial activity is well recognized. A growing body of evidence indicates, however, that HO-1 activation may play a role in carcinogenesis and can potently influence the growth and metastasis of tumors. HO-1 is very often upregulated in tumor tissues, and its expression is further increased in response to therapies. Although the exact effect can be tissue specific, HO-1 can be regarded as an enzyme facilitating tumor progression. Accordingly, inhibition of HO-1 can be suggested as a potential therapeutic approach sensitizing tumors to radiation, chemotherapy, or photodynamic therapy.

Hepatitis C core protein inhibits induction of heme oxygenase-1 and sensitizes hepatocytes to cytotoxicity

Hepatitis C virus (HCV) core protein is a transcriptional modifier whose expression is associated with increased levels of prooxidants in hepatocytes in vivo and in vitro. We previously reported that HCV-infected liver biopsies and core protein-expressing hepatocytes show diminished levels of heme oxygenase-1 (HO-1), which is an important oxidative defense enzyme. The objective of these studies was to test the hypothesis that the expression of core protein sensitizes hepatocytes to toxic injury and inhibits the induction of HO-1 in response to stress. The effects of core protein were tested in two different human hepatocyte cell lines, HepG2 and Huh7, which show increased prooxidative activity and cytotoxicity after treatment with heme, heavy metals, and peroxides compared to control cells. HO-1 is upregulated in response to these treatments in control cells, while the induction is attenuated in core protein-expressing cells. The effects of core protein on HO-1 expression are not accounted for by differences in HO-1 mRNA turnover or by the known effects of core protein on cellular proliferation. Collectively, these data suggest that HCV core protein may contribute to hepatocellular injury by increasing both steady-state levels of prooxidants and the susceptibility of hepatocytes to damage by impairing their response to other sources of oxidative stress.

Renal vascular and tubulointerstitial inflammation and proliferation in Cyp1a1-Ren2 transgenic rats with inducible ANG II-dependent malignant hypertension

Transgenic rats with inducible ANG II-dependent malignant hypertension [TGR(Cyp1a1Ren2)] were generated by inserting the mouse Ren2 renin gene into the genome of the rat. The present study was performed to assess renal morphological changes occurring during the development of ANG II-dependent malignant hypertension in these rats. Male Cyp1a1-Ren2 rats (n = 10) were fed normal rat food containing indole-3-carbinol (I3C; 0.3%) for 10 days to induce malignant hypertension. Rats induced with I3C had higher mean arterial pressures (173 +/- 9 vs. 112 +/- 11 mmHg, P < 0.01) than noninduced normotensive rats (n = 9). Glomerular damage was evaluated by determination of the glomerulosclerosis index (GSI) in tissue sections stained with periodic acid-Schiff. Kidneys of hypertensive rats had a higher GSI than normotensive rats (21.3 +/- 5.6 vs. 3.5 +/- 1.31 units). Quantitative analysis of macrophage ED-1-positive cells and proliferating cell nuclear antigen using immunohistochemistry demonstrated increased macrophage numbers in the renal interstitium (106.4 +/- 11.4 vs. 58.7 +/- 5.0 cells/mm(2)) and increased proliferating cell number in cortical tubules (37.8 +/- 5.7 vs. 24.2 +/- 2.1 cells/mm(2)), renal cortical vessels (2.2 +/- 0.5 vs. 0.13 +/- 0.07 cells/vessel), and the cortical interstitium (33.6 +/- 5.7 vs. 4.2 +/- 1.4 cells/mm(2)) of hypertensive rat kidneys. These findings demonstrate that the renal pathological changes that occur during the development of malignant hypertension in Cyp1a1-Ren2 rats are characterized by inflammation and cellular proliferation in cortical vessels and tubulointerstitium.

The Heme Catabolic Pathway and its Protective Effects on Oxidative Stress‐Mediated Diseases

Bilirubin, the principal bile pigment, is the end product of heme catabolism. For many years, bilirubin was thought to have no physiological function other than that of a waste product of heme catabolism--useless at best and toxic at worst. Although hyperbilirubinemia in neonates has been shown to be neurotoxic, studies performed during the past decade have found that bilirubin has a number of new and interesting biochemical and biological properties. In addition, there is now a strong body of evidence suggesting that bilirubin may have a beneficial role in preventing oxidative changes in a number of diseases including atherosclerosis and cancer, as well as a number of inflammatory, autoimmune, and degenerative diseases. The results also suggest that activation of the heme oxygenase and heme catabolic pathway may have beneficiary effects on disease prevention either through the action of bilirubin or in conjunction with bilirubin. If so, it may be possible to therapeutically induce heme oxygenase, increase bilirubin concentrations, and lower the risk of oxidative stress-related diseases.

Heme oxygenase-1: a provenance for cytoprotective pathways in the kidney and other tissues

Heme oxygenase (HO) is the rate-limiting enzyme in the degradation of heme, converting heme to biliverdin, during which iron is released and carbon monoxide (CO) is emitted; biliverdin is subsequently converted to bilirubin by biliverdin reductase. At least two isozymes possess HO activity: HO-1 represents the isozyme induced by diverse stressors, including ischemia, nephrotoxins, cytokines, endotoxin, oxidants, and vasoactive substances; HO-2 is the constitutive, glucocorticoid-inducible isozyme. HO-1 is upregulated in the kidney in assorted conditions and diseases. Interest in HO is driven by the capacity of this system to protect the kidney against injury, a capacity likely reflecting, at least in part, the cytoprotective properties of its products: in relatively low concentrations, CO exerts vasorelaxant, antiapoptotic, and anti-inflammatory effects while bile pigments are antioxidant and anti-inflammatory metabolites. This article reviews the HO system and the extent to which it influences the function of the healthy kidney; it summarizes conditions and stimuli that elicit HO-1 in the kidney; and it explores the significance of renal expression of HO-1 as induced by ischemia, nephrotoxins, nephritides, transplantation, angiotensin II, and experimental diabetes. This review also points out the tissue specificity of the HO system, and the capacity of HO-1 to induce renal injury in certain settings. Studies of HO in other tissues are discussed insofar as they aid in elucidating the physiologic and pathophysiologic significance of the HO system in the kidney.

Low-dose carbon monoxide inhalation prevents development of chronic allograft nephropathy

Chronic allograft nephropathy (CAN) is the primary cause for late kidney allograft loss. Carbon monoxide (CO), a product of heme metabolism by heme oxygenases, is known to impart protection against various stresses. We hypothesized that CO could minimize the chronic fibroinflammatory process and protect kidney allografts from CAN. Lewis kidney grafts were orthotopically transplanted into binephrectomized Brown-Norway rats under short-course tacrolimus. Recipients were maintained in room air or exposed to CO at 20 parts/million for 30 days after transplant. Efficacy of inhaled CO was studied at day 30 and day 80. Isografts maintained normal kidney function throughout the experiment with creatinine clearance of approximately 1.5 ml/min. Renal allograft function in air controls progressively deteriorated, and creatinine clearance declined to 0.2 +/- 0.1 ml/min by day 80 with substantial proteinuria. CO-treated animals had significantly better creatinine clearance (1.3 +/- 0.2 ml/min) with minimal proteinuria. Histological examination revealed the development of progressive CAN in air-exposed grafts, whereas CO-treated grafts had minimal tubular atrophy and interstitial fibrosis, with negligible collagen IV deposition. In vitro analyses revealed that CO-treated recipients had significantly less T cell proliferation against donor peptides via the indirect allorecognition pathway and less anti-donor IgG antibodies compared with air controls. Intragraft mRNA levels for chemokines (regulated on activation normal T cell expressed and secreted, macrophage inflammatory protein-1alpha, chemokine receptors (CCR1, CXCR3, CXCR5), IL-2, and intercellular adhesion molecule-1 were significantly decreased in CO-treated than in air-treated allografts. Furthermore, reduction of blood flow in air-treated allografts was prevented with CO. In conclusion, inhaled CO at a low concentration efficiently abrogates chronic fibroinflammatory changes associated with CAN and improves long-term renal allograft function.

Tubular expression of angiotensin II receptors and their regulation in IgA nephropathy

Enhanced renal expression for the renin-angiotensin system (RAS) is detected in IgA nephropathy (IgAN). Previous data showed an altered glomerular expression of angiotensin II type 1 receptor (AT1R), suggesting a regulatory response to high intrarenal angiotensin II (Ang II) concentration in IgAN. In this study, the expression and regulation of Ang II receptors were examined in human proximal tubular epithelial cells (PTEC) in IgAN. Tubular expression of AT1R and Ang II type 2 receptor (AT2R) was increased in IgAN. In vitro culture experiment showed that the upregulation of Ang II receptors was not due to the direct effect of IgA but the indirect effect after IgA deposition on human mesangial cell. When PTEC were cultured with conditioned culture medium from human mesangial cells activated with IgA, Ang II production was upregulated, leading to inflammation and apoptosis via the AT1R and AT2R, respectively. Sequential expression of Ang II receptors determined the injury of PTEC induced by mediators in the conditioned medium. The initial interaction between Ang II and AT1R activated both protein kinase C and mitogen-activated protein kinase pathways, leading to inflammatory responses. This early AT1R-dependent event was followed by upregulation of AT2R expression and continued Ang II release. The interaction between Ang II and AT2R subsequently led to expression of cleaved poly[ADP-ribose] polymerase through downregulation of the mitogen-activated protein kinase pathway. The data suggest that appropriate control of Ang II receptor activities in PTEC may ameliorate tubulointerstitial injury in IgAN.

Angiotensin II stimulates Pax-2 in rat kidney proximal tubular cells: impact on proliferation and apoptosis

BACKGROUND

The intrarenal renin-angiotensin system (RAS) is intimately involved in the tubular cell proliferation, apoptosis and regeneration that occur following renal injury. Though tubular angiotensin II (Ang II) type 2 receptors (AT2R) decrease greatly after birth, their number increases after injury. Notably, during recovery from injury, renal tubular cells display a relatively immature phenotype expressing genes that are involved in nephron development, for example, the paired homeobox-2 gene (Pax-2). The present investigation hypothesized that AT2R activation would stimulate Pax-2 gene expression in immortalized rat renal proximal tubular cells (IRPTC), as we have found in fetal cells.

METHODS

Pax-2 gene expression in IRPTC was evaluated by immunofluorescence, Western blot, reverse transcription-polymerase chain reaction (RT-PCR) with or without Ang II treatment; apoptosis and proliferation were analyzed by terminal transferase-mediated deoxyuridine triphosphate (dUTP) nick end-labeling (TUNEL) assay and bromodeoxyuridine (BrdU) incorporation in stable IRPTC transformants with Pax-2 sense and antisense orientation, respectively.

RESULTS

Ang II up-regulated Pax-2 gene expression via AT2R in IRPTC. The stimulatory effect of both Ang II on Pax-2 gene expression was blocked by PD123319 (AT2R inhibitor), AG 490 (specific Janus kinase 2 (JAK2) inhibitor) and genistein (tyrosine kinase inhibitor), but not by losartan (AT1R inhibitor). Stable transfection of sense Pax-2 cDNA increased, whereas antisense Pax-2 cDNA down-regulated Pax-2 expression.

CONCLUSION

Our studies suggest that Ang II stimulates Pax-2 gene expression in IRPTC via AT2R and the JAK2/signal transducers and activators of transcription (STAT) signaling transduction pathway, which may be important in renal repair following injury. Cells lacking Pax-2 gene expression appear to be prone toward apoptosis rather than proliferation.

Tight blood pressure control decreases apoptosis during renal damage

BACKGROUND

An excess rate of apoptosis could lead to the gradual loss of renal mass. In this study, we investigated the role of apoptosis in the renal damage secondary to hypertension.

METHODS

Spontaneously hypertensive rats with 5/6 renal mass reduction (subtotal nephrectomy) were distributed to receive no-treatment, 200 mg/L quinapril, 360 mg/L losartan, or triple therapy (200 mg/L hydralazine, 4 mg/L reserpine, and 100 mg/L hydrochlorothiazide) for 5 weeks. Sham-operated spontaneously hypertensive rats served as controls. Age-matched Wistar-Kyoto (WKY) rats, with or without subtotal nephrectomy, were also studied.

RESULTS

Nontreated spontaneously hypertensive rats + subtotal nephrectomy developed proteinuria, glomerular sclerosis, and tubulointerstitial lesions. In comparison to spontaneously hypertensive rats, an increment in the number of [proliferating cell nuclear antigen (PCNA)]-positive and apoptotic [terminal deoxynucleotidyl transferase (Tdt)-mediated deoxyuridine triphosphate biotin nick end labeling (TUNEL)]-positive tubular and glomerular cells was observed. By contrast, WKY + subtotal nephrectomy rats showed less severe morphologic lesions, and only the number of proliferating cells increased. By Western blot, an up-regulation of renal Bax (apoptosis inducer) was noted both in spontaneously hypertensive rats + subtotal nephrectomy and WKY + subtotal nephrectomy rats. By contrast, Bcl-xL (apoptosis protector) was up-regulated in WKY + subtotal nephrectomy rats but not in spontaneously hypertensive rats + subtotal nephrectomy. The administration of appropriate doses of quinapril, losartan, or triple therapy to spontaneously hypertensive rats + subtotal nephrectomy normalized systolic blood pressure, partially prevented proteinuria, renal lesions and apoptosis, and decreased Bax, but no changes were noted in Bcl-xL. The Bax/Bcl-xL index was significantly increased in spontaneously hypertensive rats + subtotal nephrectomy compared to sham-operated spontaneously hypertensive rats and decreased in treated groups.

CONCLUSION

The combination of renal mass reduction and hypertension caused severe renal lesions associated to an increment of apoptosis rate, mainly in tubular epithelial cells. Tight blood pressure control decreased the apoptosis rate and morphologic lesions. These studies suggest that changes in the expression of apoptosis-regulatory genes contribute to the progressive damage in hypertensive rats with renal mass reduction.

Causes and consequences of increased sympathetic activity in renal disease

Much evidence indicates increased sympathetic nervous activity (SNA) in renal disease. Renal ischemia is probably a primary event leading to increased SNA. Increased SNA often occurs in association with hypertension. However, the deleterious effect of increased SNA on the diseased kidney is not only caused by hypertension. Another characteristic of renal disease is unbalanced nitric oxide (NO) and angiotensin (Ang) activity. Increased SNA in renal disease may be sustained because a state of NO-Ang II unbalance is also present in the hypothalamus. Very few studies have directly compared the efficacy of adrenergic blockade with other renoprotective measures. Third-generation beta-blockers seem to have more protective effects than traditional beta-blockers, possibly via stimulation of NO release. Although it has been extensively documented that muscle SNA is increased in chronic renal failure, data on renal SNA and cardiac SNA are not available for these patients before end-stage renal disease. It is also unknown whether additional treatment with third-generation beta-blockers can delay the progression of renal injury and prevent cardiac injury in chronic renal failure more efficiently than conventional treatment with angiotensin-converting enzyme inhibitors only.

[Effects of the combined use of benazepril and valsartan on apoptosis in the kidney of rats with adriamycin-induced nephritic glomerulosclerosis]

The effects of the combined use of angiotensin converting enzyme inhibitor (ACEI) benazepril and angiotensin II type 1 receptor antagonist (AT1RA) valsartan on apoptosis and the expression of apoptosis-related proteins Fas and FasL in the kidney of rats with adriamycin-induced nephritic glomerulosclerosis was investigated. Uninephrectomy and the injection of adriamycin induced the rat model of glomerulosclerosis. Benazepril (6 mg/kg), valsantan (20 mg/kg), or benazepril (3 mg/kg) plus valsantan (20 mg/kg) was respectively delivered daily by gavage to the rats in three treatment groups for 12 weeks. Apoptosis was examined by means of terminal-deoxynucleotidyl transferase mediated d-UTP nick end labeling (TUNEL). Immunohistochemistry was adopted to detect the expression of Fas and FasL. Software of pathological analysis quantitated the levels of Fas and FasL. The results showed that as compared with those in the control group, the kidneys in the model group had more severe glomerulosclerosis, much more apoptotic cells and higher levels of expression of Fas and FasL. The degree of glomerulosclerosis, the number of apoptotic cells and the levels of expression of Fas and FasL were reduced by benazepril and valsartan. The combined use of benazepril and valsartan had the best therapeutic effect. It was concluded that benazepril and valsartan could suppress the excessive apoptosis of kidney cells by lowering the expression of the apoptosis-related proteins Fas and FasL, so as to postpone the process of glomerulosclerosis. The combined use of benazepril and valsartan has better therapeutic effect.

P2Y-receptors stimulating the proliferation of human mesangial cells through the MAPK42/44 pathway

1. Mesangial cell proliferation is observed in a number of kidney diseases. The sympathetic cotransmitter ATP is suspected to play a major role in proliferative processes. Therefore, the effects of exogenous ATP on human mesangial cells in culture were studied. 2. Fresh human kidney cortex was processed to obtain mesangial cells in culture. Effects of nucleotides on [(3)H]thymidine incorporation, the activation of mitogen-activated protein kinase and the cell number were studied. The involved P2-receptors were characterized pharmacologically. In addition, we searched for mRNA for P2Y- and P2X-receptors by RT-PCR. 3. ATP (0.1-300 micro M) and related nucleotides induced a significant increase in [(3)H]thymidine incorporation up to 220% of control. The adenine nucleotides ATP and ADP were about equally effective. Also ATP-gamma-S, UTP, ADP-beta-S and 2-m-thio-ADP induced a weaker response. UDP and alpha-beta-methylene-ATP failed to induce an effect on [(3)H]thymidine uptake. 4. ATP (100 micro M) induced a fast activation of the MAPK(42/44) pathway. The effects of ATP on MAPK(42/44) activation and [(3)H]thymidine incorporation were reduced by the MAPK inhibitor PD 98059. Platelet-derived growth factor (PDGF 5 ng ml(-1)) increased the cell number to more than 122% of control. ATP (10 micro M) on top of PDGF amplified PDGF induced cell proliferation to 136% of control. 5. RT-PCR products for P2Y(1,2,4,6,11,12)- and P2X(1,2,4,5,6,7)-receptor subtypes were detected in human mesangial cells. 6. ATP has mitogenic effects on human mesangial cells. DNA synthesis is increased by the activation of the MAPK(42/44) pathway. ATP amplifies PDGF-induced cell hyperplasia.

Heme oxygenase-1 in growth control and its clinical application to vascular disease

Heme oxygenase-1 (HO-1) catalyzes the degradation of heme to carbon monoxide (CO), iron, and biliverdin. Biliverdin is subsequently metabolized to bilirubin by the enzyme biliverdin reductase. Although interest in HO-1 originally centered on its heme-degrading function, recent findings indicate that HO-1 exerts other biologically important actions. Emerging evidence suggests that HO-1 plays a critical role in growth regulation. Deletion of the HO-1 gene or inhibition of HO-1 activity results in growth retardation and impaired fetal development, whereas HO-1 overexpression increases body size. Although the mechanisms responsible for the growth promoting properties of HO-1 are not well established, HO-1 can indirectly influence growth by regulating the synthesis of growth factors and by modulating the delivery of oxygen or nutrients to specific target tissues. In addition, HO-1 exerts important effects on critical determinants of tissue size, including cell proliferation, apoptosis, and hypertrophy. However, the actions of HO-1 are highly variable and may reflect a role for HO-1 in maintaining tissue homeostasis. Considerable evidence supports a crucial role for HO-1 in blocking the growth of vascular smooth muscle cells (SMCs). This antiproliferative effect of HO-1 is mediated primarily via the release of CO, which inhibits vascular SMC growth via multiple pathways. Pharmacologic or genetic approaches targeting HO-1 or CO to the blood vessel wall may represent a promising, novel therapeutic approach in treating vascular proliferative disorders.

Angiotensin II induces apoptosis in renal proximal tubular cells

ANG II has been demonstrated to play a role in the progression of tubulointerstial injury. We studied the direct effect of ANG II on apoptosis of cultured rat renal proximal tubular epithelial cells (RPTECs). ANG II promoted RPTEC apoptosis in a dose- and time-dependent manner. This effect of ANG II was attenuated by anti-transforming growth factor (TGF)-beta antibody. Moreover, TGF-beta triggered RPTEC apoptosis in a dose-dependent manner. ANG II also enhanced RPTEC expression of Fas and Fas ligand (FasL); furthermore, anti-FasL antibody attenuated ANG II-induced RPTEC apoptosis. In addition, ANG II increased RPTEC expression of Bax, a cell death protein. Both ANG II type 1 (AT(1)) and type 2 (AT(2)) receptor blockers inhibited ANG II-induced RPTEC apoptosis. SB-202190, an inhibitor of p38 MAPK phosphorylation, and caspase-3 inhibitor also attenuated ANG II-induced RPTEC apoptosis. ANG II enhanced RPTEC heme oxygenase (HO)-1 expression. Interestingly, pretreatment with hemin as well as curcumin (inducers of HO-1) inhibited the ANG II-induced tubular cell apoptosis; conversely, pretreatment with zinc protoporphyrin, an inhibitor of HO-1 expression, promoted the effect of ANG II. These results suggest that ANG II-induced apoptosis is mediated via both AT(1) and AT(2) receptors through the generation of TGF-beta, followed by the transcription of cell death genes such as Fas, FasL, and Bax. Modulation of tubular cell expression of HO-1 has an inverse relationship with the ANG II-induced tubular cell apoptosis.

Evaluation of p53, bcl-2, and interleukin-15 levels in gingival crevicular fluid of cyclosporin A-treated patients

BACKGROUND

Apoptosis plays an important role in the maintenance of tissue homeostasis. Considering that apoptosis mediators may play a role in the pathogenesis of drug-induced gingival overgrowth, this study was conducted to evaluate p53, bcl-2, and interleukin-15 (IL-15) levels in gingival crevicular fluid (GCF) of cyclosporin A (CsA)-treated patients.

METHODS

Twenty renal transplant patients exhibiting CsA-induced gingival overgrowth and 15 systemically healthy gingivitis patients were included in the study; 15 systemically and periodontally healthy volunteer subjects served as the healthy control group. GCF samples were obtained from one interdental site with gingival overgrowth (GO+) and one site without (GO-) from each CsA-treated patient; hyperplasia index, probing depth, papilla bleeding index, and plaque presence were recorded. One site from each gingivitis patient and healthy control was selected, GCF samples were obtained, and the same clinical parameters were recorded. GCF p53, bcl-2, and IL-15 levels were analyzed by enzyme-linked immunosorbent assay. The results were tested statistically.

RESULTS

p53 and bcl-2 levels were below the minimum detectable level in all GCF samples analyzed. CsA GO+ and CsA GO- sites, as well as gingivitis sites, exhibited significantly higher GCF levels of IL-15 compared to healthy controls (P<0.05). The difference between CsA GO+ sites and gingivitis sites was not statistically significant, although the total amount of IL-15 in CsA GO+ sites was lower than gingivitis sites (P>0.05). The total amount of IL-15 in CsA GO- sites was significantly lower than gingivitis sites (P<0.05). No significant correlation was found between the clinical parameters and GCF IL-15 levels (P>0.05).

CONCLUSIONS

The pathogenesis of CsA-induced gingival overgrowth is multifactorial. The findings of the present study indicate that IL-15 may play a role in the pathogenesis of CsA-induced gingival overgrowth due to its interactions with CsA and its role in apoptosis and inflammation.

Adenovirus-mediated transfer and overexpression of heme oxygenase 1 cDNA in lung prevents bleomycin-induced pulmonary fibrosis via a Fas-Fas ligand-independent pathway

Heme oxygenase 1 (HO-1) is an inducible enzyme that catalyzes heme to generate bilirubin, ferritin, and carbon monoxide. Because enhanced expression of HO-1 confers protection against many types of cell and tissue damage by modulating apoptotic cell death or cytokine expression profiles, we hypothesized that adenovirus-mediated transfer of HO-1 cDNA and subsequent overexpression of the protein in lung would provide therapeutic benefit in a murine model of bleomycin-induced pulmonary fibrosis. In C57BL/6 mice, HO-1 overexpression clearly suppressed the development of fibrotic changes and was associated with enhanced interferon gamma production in lung and reduced numbers of respiratory epithelial cells with damaged DNA. However, HO-1 overexpression did not prevent pulmonary fibrosis induced by agonistic anti-Fas antibody inhalation in C57BL/6 or ICR mice, a strain known to develop pulmonary fibrosis via the Fas-Fas ligand (FasL) pathway. Consistent with the concept that HO-1 overexpression prevents fibrosis via a pathway independent of Fas-FasL interaction, Ad.HO-1 administration prevented bleomycin-induced pulmonary fibrosis in gld/gld mice, which express nonfunctional FasL. These observations suggest that using HO-1 overexpression strategies to treat idiopathic pulmonary fibrosis, or fibrotic disorders of other target organs, by attenuating apoptotic cell death likely would be effective in clinical situations.

Regulation and localization of HSP70 and HSP25 in the kidney of rats undergoing long-term administration of angiotensin II

Various renal insults result in induction of heat shock protein (HSP) expression within the kidney. Some of the HSPs induced in that manner are postulated to have renoprotective effects via either chaperoning actions or antioxidative properties. We have previously reported that long-term angiotensin (Ang) II administration induces the expression of renal HSP32, also known as heme oxygenase-1 (HO-1). Here, we investigated the regulation of expression and localization of other HSPs, including HSP70, HSP25, and alphaB-crystallin, in the kidney of rats undergoing long-term administration of Ang II (0.7 mg. kg(-1). d(-1)). Immunoblot analysis demonstrated that Ang II increased renal expression of HSP70 and HSP25, as well as HO-1, but that expression of alphaB-crystallin was unaffected by this treatment. The Ang II-induced increase in renal HSP70 and HSP25 was dependent on the angiotensin type 1 receptor activation but not on hypertension per se. Immunohistochemistry revealed that HSP70 and HSP25 were expressed in the medullar regions and in the renal arterial wall in the kidney of control rats. After Ang II infusion, signals for HSP70, HSP25, and HO-1 proteins increased in intensity in the endothelium and medial smooth muscle of the renal artery. In addition, all of these HSPs were induced in proximal renal tubular epithelial cells from the same segments, suggesting that similar mechanisms are responsible for upregulating these HSPs. Our data show that Ang II infusion induces renal HSP70 and HSP25, as well as HO-1, and that Ang II can induce expression of these HSPs in renal cells in a pressor-independent manner.

Induction of p27KIP1 after unilateral ureteral obstruction is independent of angiotensin II

BACKGROUND

Unilateral ureteral obstruction (UUO) is characterized by proliferation of tubular and interstitial cells, and infiltration of the renal parenchyma with macrophages/monocytes. These alterations lead ultimately to tubulointerstitial fibrosis and tubular atrophy. Some of these changes are caused by an activated renin-angiotensin system (RAS). We have previously demonstrated that angiotensin II induces the expression of the cell cycle inhibitor p27KIP1 in cultured tubular cells. The current study tested the hypothesis that interference with the RAS may modulate renal expression of p27KIP1 after UUO.

METHODS

The ureter of the left kidney of Sprague-Dawley rats was ligated. Sham-operated animals served as controls. Rats were randomized in four groups and received one of the following: no therapy, enalapril, losartan, or triple therapy (hydralazine, reserpine, hydrochlorothiazide). Kidneys were removed and cortical protein lysates were prepared for the detection of p27KIP1 by Western blotting. Immunohistochemistry was performed for p27KIP1, PCNA, ED-1, and alpha-smooth muscle actin. Apoptosis was quantified by TUNEL-staining.

RESULTS

p27KIP1 expression as detected by Western blotting reached a maximum 10 days after UUO. Tubular and interstitial cells contributed to this increase in p27KIP1 expression whereas the number of glomerular p27KIP1 positive cell did not change. p27KIP1-positive cells were macrophages/monocytes (positive ED-1 staining) or had the characteristics of myofibroblasts (positive alpha-smooth muscle actin staining). Tubular and interstitial proliferation [proliferating cell nuclear antigen (PCNA)-positive staining] and apoptosis [terminal deoxy transferase uridine triphosphate nick end labeling (TUNEL) staining] also was increased after UUO. However, individual cells stained either positive for p27KIP1 or PCNA, but not both. Although enalapril and losartan reduced the number of macrophages/monocytes and attenuated the degree of tubular and interstitial apoptosis, these drugs did not influence p27KIP1 expression. There was no change in the number of p27KIP1-positive cells in the contralateral kidney undergoing hypertrophy.

CONCLUSION

Induction of p27KIP1 in this model represents an endogenous response to likely limit proliferation that is independent of angiotensin II. Since there was no close correlation between apoptosis and p27KIP1 expression, it may be that the overall number of p27KIP1 expressing cells sets a general restriction point for apoptosis rather than defines an individual level of cell fate.

Abnormal iron deposition in renal cells in the rat with chronic angiotensin II administration

Acute experimental iron loading causes iron to accumulate in the renal tissue. The accumulation of iron may play a role in enhancing oxidant-induced tubular injury by producing increased amounts of reactive oxygen species. From findings in cells from heme oxygenase-1 (HO-1)-deficient mice, HO-1 is postulated to prevent abnormal intracellular iron accumulation. Recently, it has been reported that HO-1 is induced in the renal tubular epithelial cells, in which iron is deposited after iron loading, and that this HO-1 induction may be involved in ameliorating iron-induced renal toxicity. We previously showed that chronic administration of angiotensin II to rats induces HO-1 expression in the tubular epithelial cells. These observations led us to investigate whether there is a link between iron deposition and HO-1 induction in renal tubular cells in rats undergoing angiotensin II infusion. In the present study, rats were given angiotensin II for continuously 7 days. Prussian blue staining revealed the distinct deposits of iron in the proximal tubular epithelial cells after angiotensin II administration. Electron microscopy demonstrated that iron particles were present in the lysosomes of these cells. Histologic and immunohistochemical analyses showed that stainable iron and immunoreactive ferritin and HO-1 were colocalized in the tubular epithelial cells. Treatment of angiotensin II-infused rats with an iron chelator, deferoxamine, blocked the abnormal iron deposition in kidneys and also the induced expression of HO-1 and ferritin expression. Furthermore, deferoxamine treatment suppressed the angiotensin II-induced increase in the urinary excretion of protein and N-acetyl-beta-D-glucosaminidase, a marker of tubular injury; however, deferoxamine did not affect the angiotensin II-induced decrease in glomerular filtration rate. These results suggest that angiotensin II causes renal injury, in part, by inducing the deposition of iron in the kidney.