Expression of apoptosis-related genes and proteins in experimental chronic renal scarring

Evaluation of Bcl-2 as a marker for chronic kidney disease prediction in cats

Chronic kidney disease (CKD) is a frequent condition in elderly cats. Bcl-2 is linked to kidney disease through the processes of apoptosis and fibrosis. The purpose of this study is to examine Bcl-2 levels in CKD and clinically healthy age-matched cats in order to evaluate the relationship between Bcl-2 levels, signalment, and blood parameters in cats with CKD. The circulating levels of Bcl-2 were determined using an immunoassay in twenty-four CKD cats and eleven clinically healthy age-matched cats by the utilization of the general linear model (GLM), Pearson correlation, principal component analysis (PCA), ROC curves, the Cox hazard model, and Kaplan-Meier survival analysis. These were all conducted in order to explore Bcl-2 levels and their connection with other variables. The Bcl-2 immunohistochemical intensity was graded in each glomerulus and tubulointerstitium. McNemar's test was performed in order to compare the expression of Bcl-2 in the two renal tissue sites. The circulating Bcl-2 of CKD cats was significantly lower than those of clinically healthy age-matched cats (P = 0.034). The presence of circulating Bcl-2 (P < 0.01) and the severity of CKD (P = 0.02) were both linked with the survival time of cats with CKD. The area under the curve (AUC) of Bcl-2 for detection of CKD was 0.723. In cats, decreased circulating Bcl-2 was associated with increased blood BUN, creatinine levels, and CKD severity. Bcl-2 protein expression was reduced in the renal tissues of CKD cats as the disease progressed, resulting in a decrease in their survival time. This study demonstrated that Bcl-2 may be effective in diagnosing feline CKD.

Reduced nicotinamide mononucleotide is a new and potent NAD+ precursor in mammalian cells and mice

Nicotinamide adenine dinucleotide (NAD⁺ ) homeostasis is constantly compromised due to degradation by NAD⁺ -dependent enzymes. NAD⁺ replenishment by supplementation with the NAD⁺ precursors nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) can alleviate this imbalance. However, NMN and NR are limited by their mild effect on the cellular NAD⁺ pool and the need of high doses. Here, we report a synthesis method of a reduced form of NMN (NMNH), and identify this molecule as a new NAD⁺ precursor for the first time. We show that NMNH increases NAD⁺ levels to a much higher extent and faster than NMN or NR, and that it is metabolized through a different, NRK and NAMPT-independent, pathway. We also demonstrate that NMNH reduces damage and accelerates repair in renal tubular epithelial cells upon hypoxia/reoxygenation injury. Finally, we find that NMNH administration in mice causes a rapid and sustained NAD⁺ surge in whole blood, which is accompanied by increased NAD⁺ levels in liver, kidney, muscle, brain, brown adipose tissue, and heart, but not in white adipose tissue. Together, our data highlight NMNH as a new NAD⁺ precursor with therapeutic potential for acute kidney injury, confirm the existence of a novel pathway for the recycling of reduced NAD⁺ precursors and establish NMNH as a member of the new family of reduced NAD⁺ precursors.

The potential renal toxicity of silver nanoparticles after repeated oral exposure and its underlying mechanisms

BACKGROUND

Silver nanoparticles (AgNPs) can accumulate in various organs after oral exposure. The main objective of the current study is to evaluate the renal toxicity induced by AgNPs after repeated oral exposure and to determine the relevant molecular mechanisms.

METHODS

In this study, 40 male Wistar rats were treated with solutions containing 30, 125, 300, and 700 mg/kg of AgNPs. After 28 days of exposure, histopathological changes were assessed using hematoxylin-eosin (H&E), Masson's trichrome, and periodic acid-Schiff (PAS) staining. Apoptosis was quantified by TUNEL and immunohistochemistry of caspase-3, and the level of expression of the mRNAs of growth factors was determined using RT-PCR.

RESULTS

Histopathologic examination revealed degenerative changes in the glomeruli, loss of tubular architecture, loss of brush border, and interrupted tubular basal laminae. These changes were more noticeable in groups treated with 30 and 125 mg/kg. The collagen intensity increased in the group treated with 30 mg/kg in both the cortex and the medulla. Apoptosis was much more evident in middle-dose groups (i.e., 125 and 300 mg/kg). The results of RT-PCR indicated that Bcl-2 and Bax mRNAs upregulated in the treated groups (p < 0.05). Moreover, the data related to EGF, TNF-α, and TGF-β1 revealed that AgNPs induced significant changes in gene expression in the groups treated with 30 and 700 mg/kg compared to the control group.

CONCLUSION

Our observations showed that AgNPs played a critical role in in vivo renal toxicity.

Effects of nitrite graded doses on hepatotoxicity and nephrotoxicity, histopathological alterations, and activation of apoptosis in adult rats

Nitrites are found in several forms; they are widely found in water resources and used as additives and preservatives for food and as a color source. We investigated the hazardous effects of exposing rats to different doses of nitrites. Moreover, we examined such impacts, after acute ingestion, on liver and renal tissues in rats and to what extent this affects the organs' functions. Animals were divided into five groups: one control group 1 (group C) and four sodium nitrite (NaNO₂)-treated group (8 rats per group). The four NaNO₂-treated groups include group 2 (N20), group 3 (N40), group 4 (N60), and group 5 (N75). NaNO₂ was dissolved in distilled water, and single acute dose was orally given by gavage at 20, 40, 60, and 75 mg/kg body weight, respectively. Our results revealed significant increase of liver enzymes activity-aspartate transaminase (AST), alanine aminotransferase (ALT), and creatinine between different groups with increasing doses of nitrite ingestion. The results of hepatic and renal oxidative stress showed significant increase in the malondialdehyde (MDA) levels and significant decrease in the antioxidant parameters, such as reduced glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT), as the dose of nitrite increases. Further, the methemoglobin percent showed significant increase with increasing nitrite doses. Abnormal morphological alterations in the liver and kidney tissues were obviously proportional to the administered nitrite doses. The expression of caspase 3 and Bax level showed enhanced induction of immunoexpression, especially in the high doses of nitrites. On the other hand, the maximal immunoexpression level of anti-apoptotic marker Bcl₂ was found in lower doses of nitrites, whereas marked decrease of Bcl₂ levels was observed in the higher doses. In conclusion, administration of sodium nitrite in a dose-dependent manner is capable of inducing cellular and genetic toxicities and causes disturbance in biochemical analysis, oxidative and anti-oxidative balance, and methemoglobinemia. It also makes histopathological alterations and leads to the activation of apoptosis-related Bax, Bcl₂, and caspase 3 genes of liver and kidney tissues in rats.

Cell Death in the Kidney

Apoptotic cell death is usually a response to the cell's microenvironment. In the kidney, apoptosis contributes to parenchymal cell loss in the course of acute and chronic renal injury, but does not trigger an inflammatory response. What distinguishes necrosis from apoptosis is the rupture of the plasma membrane, so necrotic cell death is accompanied by the release of unprocessed intracellular content, including cellular organelles, which are highly immunogenic proteins. The relative contribution of apoptosis and necrosis to injury varies, depending on the severity of the insult. Regulated cell death may result from immunologically silent apoptosis or from immunogenic necrosis. Recent advances have enhanced the most revolutionary concept of regulated necrosis. Several modalities of regulated necrosis have been described, such as necroptosis, ferroptosis, pyroptosis, and mitochondrial permeability transition-dependent regulated necrosis. We review the different modalities of apoptosis, necrosis, and regulated necrosis in kidney injury, focusing particularly on evidence implicating cell death in ectopic renal calcification. We also review the evidence for the role of cell death in kidney injury, which may pave the way for new therapeutic opportunities.

Alleviative effect of fucoxanthin-containing extract from brown seaweed Laminaria japonica on renal tubular cell apoptosis through upregulating Na+/H+ exchanger NHE1 in chronic kidney disease mice

ETHNOPHARMACOLOGICAL RELEVANCE

Brown seaweed is a common food for Asians, and the bioactive ingredient fucoxanthin exerts anti-apoptotic activities in several cell types. Renal tubular cell apoptosis is one of the common cellular events leading to renal fibrosis and chronic kidney disease (CKD). However, the influence of fucoxanthin-containing brown seaweed extract on CKD is still unknown. We intended to evaluate the inhibitory effect of fucoxanthin-containing extract from brown seaweed on renal apoptosis under CKD condition and its molecular mechanism.

MATERIALS AND METHODS

The fucoxanthin-containing brown seaweed extract (LJE) was prepared from Laminaria japonica. We investigated how LJE influences on both doxorubicin-treated rat renal tubular cells (NRK-52E) and the renal symptoms of nephrectomy-induced CKD mice.

RESULTS

LJE inhibited doxorubicin-induced apoptosis and upregulated Na+/H+ exchanger isoform 1 (NHE1) expression in NRK-52E cells, which were blocked by the NHE1 inhibitor cariporide. LJE also upregulated peroxisome proliferator-activated receptor alpha (PPARα). PPARα siRNA transfection inhibited LJE-induced NHE1 expression and anti-apoptotic effect. In CKD mice, LJE increased NHE1 expression in renal tubules and reduced apoptotic renal tubular cells, but not in PPARα knockout mice. The inhibitory effect of LJE on apoptosis also reduced renal tubulointerstitial fibrosis and improved renal function in CKD mice.

CONCLUSION

We demonstrated that LJE inhibits renal apoptosis via NHE1 upregulation. The anti-apoptotic effect of LJE also improves renal function in CKD mice. Therefore, fucoxanthin-containing brown seaweed may have a therapeutic potential for CKD patients.

A Putative Role of Apolipoprotein L1 Polymorphism in Renal Parenchymal Scarring Following Febrile Urinary Tract Infection in Nigerian Under-Five Children: Proposal for a Case-Control Association Study

Background

Although urinary tract infection (UTI) resolves with prompt treatment in a majority of children, some children, especially those aged less than 5 years, also develop renal parenchymal scarring (RPS). RPS causes high blood pressure that may lead to severe chronic kidney disease and end-stage renal disease (ESRD). Although the risk of UTI is higher in white children than in black children, it is unknown whether RPS is more common in white children than in black children as data are scarce in this regard. A common genetic predisposition to kidney disease in African Americans and the sub-Saharan African blacks is the possession of apolipoprotein L1 (APOL1). APOL1 risk variants regulate the production of APOL1. APOL1 circulates in the blood, and it is also found in the kidney tissue. While circulating, APOL1 kills the trypanosome parasites; an increased APOL1 in kidney tissues, under the right environmental conditions, can also result in the death of kidney tissue (vascular endothelium, the podocytes, proximal tubules, and arterial cells), which, ultimately, is replaced by fibrous tissue. APOL1 may influence the development of RPS, as evidence affirms that its expression is increased in kidney tissue following UTI caused by bacteria. Thus, UTI may be a putative environmental risk factor responsible for APOL1-induced kidney injury.

Objective

The aim of this proposal was to outline a study that seeks to determine if the possession of two copies of either G1 or G2 APOL1 variant increases the risk of having RPS, 6 months following a febrile UTI among Nigerian under-five children.

Methods

This case-control association study seeks to determine whether the risk of RPS from febrile UTI is conditional on having 2 APOL1 risk alleles (either G1 or G2). Cases will be children with a confirmed RPS following a febrile UTI. Controls will be age-, gender-, and ethnic-matched children with a febrile UTI but without RPS. Children with vesicoureteral reflux and other congenital anomalies of the urinary tract are to be excluded. Association between predictor variables (ethnicity, APOL1 G1 or G2, and others) and RPS will be tested at bivariate logistic regression analyses. Predictors that attained significance at a P value of ˂.05 will be considered for multiple logistic regressions. Likelihood-based tests will be used for hypothesis testing. Estimation will be done for the effect size for each of the APOL1 haplotypes using a generalized linear model.

Results

The study is expected to last for 3 years.

Conclusions

The study is contingent on having a platform for undergoing a research-based PhD program in any willing university in Europe or elsewhere. The findings of this study will be used to improve the care of African children who may develop RPS following febrile UTI.

Registered Report Identifier

RR1-10.2196/9514

Indoxyl Sulfate Induces Apoptosis and Hypertrophy in Human Kidney Proximal Tubular Cells

Indoxyl sulfate (IS) is a protein-bound uremic toxin that accumulates in patients with declining kidney function. Although generally thought of as a consequence of declining kidney function, emerging evidence demonstrates direct cytotoxic role of IS on endothelial cells and cardiomyocytes, largely through the expression of pro-inflammatory and pro-fibrotic factors. The direct toxicity of IS on human kidney proximal tubular epithelial cells (PTECs) remains a matter of debate. The current study explored the effect of IS on primary cultures of human PTECs and HK-2, an immortalized human PTEC line. Pathologically relevant concentrations of IS induced apoptosis and increased the expression of the proapoptotic molecule Bax in both cell types. IS impaired mitochondrial metabolic activity and induced cellular hypertrophy. Furthermore, statistically significant upregulation of pro-fibrotic (transforming growth factor-β, fibronectin) and pro-inflammatory molecules (interleukin-6, interleukin-8, and tumor necrosis factor-α) in response to IS was observed. Albumin had no influence on the toxicity of IS. The results of this study suggest that IS directly induced a pro-inflammatory and pro-fibrotic phenotype in proximal tubular cells. In light of the associated apoptosis, hypertrophy, and metabolic dysfunction, this study demonstrates that IS may play a role in the progression of chronic kidney disease.

Regulation of the Ku70 and apoptosis-related proteins in experimental diabetic nephropathy

BACKGROUND

Apoptosis contributes nephropathy pathogenesis in diabetes. However, its mechanisms still remain unclear. We examined the extent to which the angiotensin-II type 1 receptor blocker (AT1RB) irbesartan and the angiotensin converting enzyme inhibitor (ACEI) perindopril affected the apoptosis-related proteins Bcl-2, Bax, caspase-3, cytochrome-c and Ku70 in streptozotocin (STZ)-diabetic rats.

MATERIALS AND METHODS

Animals were divided into five groups of eight each, four of which received STZ (60mg/kg in a single dose, i.p.) to induce diabetes. The groups were performed as untreated diabetic; non-diabetic control; daily irbesartan (15mg/kg/day) or perindopril (6mg/kg/day) and also combined irbesartan and perindopril (respectively, 5mg/kg/day, 3mg/kg/day) were applied by gavage for 30days to STZ-diabetic rats. The kidney tissue analysis was performed by using immunohistochemical staining with Bcl-2, Bax, caspase-3, cytochrome-c and Ku70 antibodies and by using Western blot analysis with caspase-3 and cytochrome-c antibodies.

RESULTS

Immunoreactivity of Bax, caspase-3, cytochrome-c and Ku70 was increased in the tubuli and glomeruli of the untreated diabetic group, but decreased in all treated diabetic groups. In the irbesartan and perindopril treated diabetic groups Bcl-2 immunoreactivity was higher than that of the untreated diabetic group. Caspase-3 and cytoplasmic cytochrome-c protein levels increased in the untreated diabetic group.

CONCLUSIONS

We conclude that the increased expression of Bax and caspase-3, and the increased level of cytoplasmic cytochrome-c relate to renal tissue injury. This case is also seen in the early stages of diabetes as a result of the damage caused by local increased expression of renin angiotensin system (RAS) in the renal tissue, which is induced by hyperglycemia. The increase of the cytosolic cytochrome-c, caspase-3 and Ku70 expression in the tubuli is suggestive of apoptosis. Overall, our results show that treatments of irbesartan and perindopril are effective and efficient in preventing renal tissue injury and apoptosis by blocking the RAS in experimental diabetic nephropathy and reducing the expression of proteins associated with apoptosis.

RIPK3-Mediated Necroptosis and Apoptosis Contributes to Renal Tubular Cell Progressive Loss and Chronic Kidney Disease Progression in Rats

Tubulointerstitial fibrosis (TIF) is caused by the progressive loss of renal tubular cells and the consequent replacement of the extracellular matrix. The progressive depletion of renal tubular cells results from apoptosis and necroptosis; however, the relative significance of each of these cell death mechanisms at different stages during the progression of chronic kidney disease (CKD) remains unclear. We sought to explore the mechanisms of renal tubular cell death during the early and intermediate stages of chronic renal damage of subtotal nephrectomied (SNx) rats. The results of tissue histological assays indicated that the numbers of necrotic dying cells and apoptotic cells were significantly higher in kidney tissues derived from a rat model of CKD. In addition, there was a significant increase in necroptosis observed by transmission electron microscopy (TEM) and an increase in the proportion of TUNEL-positive cells in kidney tissues from SNx rats compared with control rats, and necrostatin-1 (Nec-1) could inhibit necroptosis and reduce the proportion of TUNEL-positive cells. More importantly, we observed a significant increase in the incidence of necroptosis compared with apoptosis by TEM in vivo and in vitro and a significant increase in the proportion of TUNEL-positive tubular epithelial cells that did not express caspase-3 compared with those expressing cleaved caspase-3 in vitro. Furthermore, treatment with Nec-1 and zVAD strongly reduced necroptosis- and apoptosis-mediated renal tubular cell death and decreased the levels of blood urea nitrogen and serum creatinine and tubular damage scores of SNx rats. These results suggest that necroptotic cell death plays a more significant role than apoptosis in mediating the loss of renal tubular cells in SNx rats and that effectively blocking both necroptosis and apoptosis improves renal function and tubular damage at early and intermediate stages of CKD.

Mild systemic thermal therapy ameliorates renal dysfunction in a rodent model of chronic kidney disease

Thermal therapy has become a nonpharmacological therapy in clinical settings, especially for cardiovascular diseases. However, the practical role of thermal therapy on chronic kidney disease remains elusive. We performed the present study to investigate whether a modified thermal protocol, repeated mild thermal stimulation (MTS), could affect renal damages in chronic kidney disease using a mouse renal ablation model. Mice were subjected to MTS or room temperature (RT) treatment once daily for 4 wk after subtotal nephrectomy (Nx) or sham operation (Sh). We revealed that MTS alleviated renal impairment as indicated by serum creatinine and albuminuria in Nx groups. In addition, the Nx + MTS group showed attenuated tubular histological changes and reduced urinary neutrophil gelatinase-associated lipocalin excretion approximately by half compared with the Nx + RT group. Increased apoptotic signaling, such as TUNEL-positive cell count and cleavage of caspase 3, as well as enhanced oxidative stress were significantly reduced in the Nx + MTS group compared with the Nx + RT group. These changes were accompanied with the restoration of kidney Mn-SOD levels by MTS. Heat shock protein 27, a key molecular chaperone, was phosphorylated by MTS only in Nx kidneys rather than in Sh kidneys. MTS also tended to increase the phosphorylation of p38 MAPK and Akt in Nx kidneys, possibly associated with the activation of heat shock protein 27. Taken together, these results suggest that modified MTS can protect against renal injury in a rodent model of chronic kidney disease.

Dipeptidyl peptidase-4 inhibitor improves cardiac function by attenuating adverse cardiac remodelling in rats with chronic myocardial infarction

NEW FINDINGS

What is the central question of this study? Although cardioprotective effects of dipeptidyl peptidase-4 (DPP-4) inhibitors have been demonstrated, their cardiac effects in chronic myocardial infarction (MI) are unclear. We determined the effects of a DPP-4 inhibitor on cardiac function and remodelling in rats with chronic MI. What is the main finding and its importance? We demonstrated, for the first time, that DPP-4 inhibitor, but not metformin, exerted similar efficacy in improving cardiac function and attenuating cardiac fibrosis compared with enalapril in rats with chronic MI. These findings reveal benefits additional to the glycaemic control by the DPP-4 inhibitor in chronic MI, and it might become the new drug of choice for MI in patients with diabetes mellitus. Adverse cardiac remodelling after myocardial infarction (MI) leads to progressive heart failure. Dipeptidyl peptidase-4 (DPP-4) inhibitors are new antidiabetic drugs that exert cardioprotection. However, their role in cardiac function and remodelling in chronic MI is unclear. We hypothesized that the DPP-4 inhibitor vildagliptin reduces adverse cardiac remodelling and improves cardiac function in rats with chronic MI. These effects were also compared with enalapril and metformin. Male Wistar rats (n = 36) with chronic MI induced by ligation of the left anterior descending coronary artery were divided into six groups to receive vehicle, vildagliptin (3 mg kg(-1)  day(-1) ), metformin (30 mg kg(-1)  day(-1) ), enalapril (10 mg kg(-1)  day(-1) ), combined metformin and enalapril or combined vildagliptin and enalapril for 8 weeks. At the end of the study, plasma malondialdehyde (MDA), heart rate variability (HRV), left ventricular (LV) function, pathological and biochemical studies of cardiac remodelling were investigated. Our study demonstrated that rats with chronic MI had increased oxidative stress levels, depressed HRV, adverse cardiac remodelling, indicated by cardiac fibrosis, and LV dysfunction. Treatment with vildagliptin or enalapril significantly decreased oxidative stress, attenuated cardiac fibrosis and improved HRV and LV function. We conclude that vildagliptin exerts similar cardioprotective effects to enalapril in attenuating oxidative stress and cardiac fibrosis and improving cardiac function in rats with chronic MI. Metformin does not provide these benefits in this model. Moreover, addition of either metformin or vildagliptin to enalapril does not provide additional benefit in attenuating cardiac remodelling or improving LV function compared with enalapril alone.

Histological, molecular and biochemical detection of renal injury after Echis pyramidum snake envenomation in rats

Nephrotoxicity is a common sign of snake envenomation. The present work aimed to clarify the effect of intraperitoneal injection of 1/8 LD50 and 1/4 LD50 doses of Echis pyramidum snake venom on the renal tissue of rats after 2, 4 and 6 h from envenomation. Histopathological examination showed intense dose and time dependent abnormalities, including swelling glomerulus and tubular necrosis and damage as well as signs of intertubular medullary hemorrhage at early stages of envenomation. However, at late stages of envenomation by any of the doses under investigation, no intact renal corpuscles were recorded and complete lysis in renal corpuscles with ruptured Bowman's capsules was observed. Immunohistochemistry by immunohistochemical staining was used to test the protein expression of Bax in renal tissue of rats. The result showed that the expression of Bax in renal tissue sections of envenomated rats was increased according to dose and time-dependant manner. The isolation of DNA from the renal cells of envenomed rats pointed out to the occurrence of DNA fragmentation, which is another indicator for renal tissue injury especially after 6 h of 1/4 LD50 of E. pyramidum envenomation. Oxidative stress biomarkers malondialdehyde and nitrite/nitrate levels, antioxidant parameters; glutathione, total antioxidant capacity and catalase were assayed in renal tissue homogenates. The venom induced significant increase in the levels of malondialdehyde and nitrite/nitrate while the levels of glutathione, total antioxidant capacity and catalase were significantly decreased, especially after 6 h of envenomation. The results revealed that the E. pyramidum induced dose and time-dependant significant disturbances in the physiological parameters in the kidney. We conclude that the use of the immunohistochemical techniques, the detection of DNA integrity and oxidative stress marker estimations are more specific tools that can clarify cellular injury and could point out to the defense activity of the renal tissue at envenomation.

Inhibition of heat-induced apoptosis in rat small intestine and IEC-6 cells through the AKT signaling pathway

Background

As the world warms up, heat stress is becoming a major cause of economic loss in the livestock industry. Long-time exposure of animals to hyperthermia causes extensive cell apoptosis, which is harmful to them. AKT and AKT-related serine–threonine kinases are known to be involved in signaling cascades that regulate cell survival, but the mechanism remains elusive. In the present study, we demonstrate that phosphoinositide 3-kinase (PI3K) /AKT signal pathway provides protection against apoptosis induced by heat stress to ascertain the key point for treatment.

Results

Under heat stress, rats showed increased shedding of intestinal epithelial cells. These rats also had elevated levels of serum cortisol and improved expression of heat shock proteins (Hsp27, Hsp70 and Hsp90) in response to heat stress. Apoptosis analysis by TUNEL assay revealed a higher number of villi epithelial cells that were undergoing apoptosis in heat-treated rats than in the normal control. This is supported by gene expression analysis, which showed an increased ratio of Bax/Bcl-2 (p < 0.05), an important indicator of apoptosis. During heat-induced apoptosis, more AKTs were activated, showing increased phosphorylation. An increase of BAD phosphorylation, which is an inhibitory modification, ensued. In rat IEC-6 cell line, a significant higher level of AKT phosphorylation was observed at 2 h after heat exposure. This coincided with a marked reduction of apoptosis.

Conclusion

Together, these results suggest that heat stress caused damages to rat jejunum and induced apoptosis to a greater degree. HSPs and pro-survival factors were involved in response to heat stress. Among them, AKT played a key role in inhibiting heat-induced apoptosis.

PKB/Akt partners with Dab2 in albumin endocytosis

Albumin in the glomerular filtrate is normally retrieved by concerted efforts of clathrin, LDL-type receptor megalin- and clathrin-associated sorting proteins. In glomerular diseases, albumin overload triggers a proapoptotic and inflammatory response contributing to tubulointerstitial fibrosis and tubular atrophy. The relationship between albumin overload-induced proximal tubule injury and albumin endocytosis remains to be discovered. We investigated presence of a possible overlap between endocytosis and cell survival. We showed a novel interaction between prosurvival protein, protein kinase B (PKB/Akt), and adaptor protein, disabled 2 (Dab2), with coimmunoprecipitation. Further delineation of this interaction by GST pull-down experiments utilizing different Dab2 constructs identified proline-rich domain as the interacting partner. Expression of Dab2 and PKB/Akt was downregulated at high concentrations of albumin associated with apoptosis. We then examined the physiological relevance of this interaction with functional studies. Overexpression of PKB/Akt increased albumin uptake in human proximal tubule cells. Conversely, inhibition of PKB/Akt with a nonselective Akt/PKB signaling inhibitor-2 and a dominant negative construct of PKB/Akt resulted in a decrease in albumin uptake. Inhibition of Dab2 by silencing RNA abolished PKB/Akt-induced albumin uptake demonstrating the physiological importance of this novel interaction. We concluded that PKB/Akt is part of an endocytic machinery and it mediates albumin uptake through its interaction with Dab2. The role that PKB/Akt plays in the endocytic cascade may dictate its decreased expression in proteinuric states in an attempt to limit albumin endocytosis that may tilt the balance between cell survival and apoptosis toward cell death.

The effects of angiotensin-II receptor blockers on podocyte damage and glomerular apoptosis in a rat model of experimental streptozotocin-induced diabetic nephropathy

The aim of the study was to determine in a rat model of streptozotocin-induced diabetic nephropathy the expression of: WT-1 (for podocyte loss in the glomerulus), TGF-beta 1 (for tissue damage), caspase-3 and bax (for glomerular apoptosis) and the possible protective effects of an angiotensin II type 1 receptor blocker. Three groups of male Wistar albino rats were used. The first group consisted of non-diabetic control rats. The second group was the untreated diabetic rats. The third group consisted of diabetic rats treated with Irbesartan, which is an angiotensin II receptor antagonist, widely used in treatment for hypertension. Immunohistochemical stainings for TGF-beta 1, bax, caspase-3 and WT-1 were performed. The microalbuminuria levels of the Irbesartan-treated diabetic group were lower than those of the untreated diabetic group (P<0.01). The immunostaining of TGF-beta 1, bax and caspase-3 was decreased in glomeruli of the Irbesartan-treated diabetic group compared to the untreated diabetic group. WT-1 immunopositive podocyte numbers were found to be significantly lower in the untreated diabetic group than in the other groups (P<0.01). In the Irbesartan-treated diabetic group, the WT-1 immunopositive cell numbers were higher compared to the untreated diabetic group (P<0.01). We conclude that the decrease in the number of podocytes is an early marker of diabetic nephropathy, AT1 receptor blocker has renoprotective effects on the regulation of renal hemodynamics and on the control of tissue damage by preventing podocyte loss, which leads to decrease of bax and caspase-3 expressions of apoptosis related proteins, and may prevent glomerular cell apoptosis via angiotensin II.

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.

Effects of low protein intake on the development of the remaining kidney in subtotally nephrectomized immature rats: expression of inducible and endothelial NO synthase

We examined the effects of low protein intake on the development of the remaining kidney in subtotally (5/6) nephrectomized immature rats. Three-week-old rats were kept on a diet containing either 12% protein (Lp rats) or 18% protein (Np rats) for 4 or 8 weeks after subtotal nephrectomy (SUNx). In Western blot analysis, the endothelial NO synthase (eNOS) protein expression of the Lp rats was significantly higher than that of the Np rats at 4 weeks after SUNx. Immunohistochemically, more inducible NO synthase (iNOS)-positive cells were observed in the Np rats than in the Lp rats 4 weeks after SUNx in the distal tubules. In semiquantitative RT-PCR, the expression of renin mRNA was significantly lower in the Lp rats than in the Np rats at 4 and 8 weeks after SUNx. These findings reveal that protein restriction is effective in preventing renal failure of immature rats and that the changes in the expression levels of renin, eNOS, and iNOS is involved in the process of this prevention.

HSP72 attenuates renal tubular cell apoptosis and interstitial fibrosis in obstructive nephropathy

Although heat shock protein 72 kDa (HSP72) protects tubular epithelium from a variety of acute insults, its role in chronic renal injury and fibrosis is poorly characterized. In this study, we tested the hypothesis that HSP72 reduces apoptosis and epithelial-to-mesenchymal transition (EMT), important contributors to tubular cell injury in vitro and in vivo. In rats, orally administered geranylgeranylacetone (GGA), an agent that selectively induces HSP72, markedly reduced both apoptosis and cell proliferation in tubular epithelium and decreased both interstitial fibroblast accumulation and collagen I deposition after unilateral ureteric obstruction, a model of chronic renal tubulointerstitial fibrosis and dysfunction. In cultured renal NRK52E cells, exposure to TGF-beta1 induced EMT and apoptosis, major causes of renal fibrosis and tubular atrophy, respectively. Exposure to a pan-caspase inhibitor (ZVAD-FMK) prevented TGF-beta1-induced apoptosis but did not reduce EMT. In contrast, selective HSP72 expression in vitro inhibited EMT caused by TGF-beta1 as indicated by preserving the E-cadherin expression level and alpha-smooth muscle actin induction. Small interfering RNA directed against HSP72 blocked the cytoprotective effects of HSP72 overexpression on EMT in TGF-beta1-exposed cells. Taken together, our data indicate that HSP72 ameliorates renal tubulointerstitial fibrosis in obstructive nephropathy by inhibiting both renal tubular epithelial cell apoptosis and EMT.

Wnt/beta-catenin signaling modulates survival of high glucose-stressed mesangial cells

Glomerulosclerosis and diabetic nephropathy are attributable to high glucose induction of mesangial cell apoptosis. Whereas Wnt signaling has been found to regulate renal morphogenesis and pathogenesis, the biologic role of Wnt/beta-catenin signaling in controlling high glucose-induced mesangial cell apoptosis is not well defined. Herein is reported that Wnt/beta-catenin signaling is required for protecting glomerular mesangial cells from high glucose-mediated cell apoptosis. High glucose downregulated Wnt4 and Wnt5a expression and the subsequent nuclear translocation of beta-catenin, whereas it increased glycogen synthase kinase-3beta (GSK-3beta) and caspase-3 activities and apoptosis of glomerular mesangial cells. Suppression of GSK-3beta activation or increase in nuclear beta-catenin by transfection of Wnt4 or Wnt5a or stable beta-catenin (S33Y) reversed Akt activation and reduced the high glucose-mediated caspase-3 cleavage and cell apoptosis. Pharmacologic inhibition of GSK-3beta by recombinant Wnt5a or bromoindirubin-3'-oxime or LiCl increased Akt phosphorylation and beta-catenin translocation and abrogated high glucose-mediated proapoptotic activities. Exogenous bromoindirubin-3'-oxime treatment reduced phospho-Ser(9)-GSK-3beta and beta-catenin expression and apoptosis of cells adjacent to glomeruli in diabetic kidneys and attenuated urinary protein secretion in diabetic rats. Taken together, mesangial cells responded to high glucose by impairing that canonical Wnt pathway to increase proapoptotic activities. Sustaining Wnt/beta-catenin signaling is beneficial for promoting survival of mesangial cells that are exposed to high glucose stress.

Apoptosis and Caspase-3 in Long-Term Renal Ischemia/Reperfusion Injury in Rats and Divergent Effects of Immunosuppressants

BACKGROUND

Caspase-3 plays a key role in apoptosis, but the involvement of apoptosis and caspase-3 in mediating long-term ischemia/reperfusion (I/R) and immunosuppressive injury are not fully defined. The present study was undertaken to investigate apoptosis and caspase-3 in a renal I/R injury rat model with or without immunosuppression.

METHODS

The right renal pedicle was clamped for 45 minutes and left nephrectomy was induced. Cyclosporin A (CsA), tacrolimus (Tac), rapamycin (Rap), or mycophenolate mofetil (MMF) were administered daily. Animals were killed at 16 weeks, and the levels of apoptosis (with in situ end-labeling fragmented DNA), caspase-3 protein (with immunohistochemistry, Western blotting, and activity assay), and messenger RNA (mRNA; with quantitative reverse-transcriptase polymerase chain reaction) were evaluated.

RESULTS

Kidneys with I/R injury showed increased apoptosis in tubular and interstitial areas compared with control kidneys. Tacrolimus, Rap, and MMF significantly reduced apoptosis, but CsA did not. Distribution of full-length caspase-3 widened in I/R-injured kidneys from normal distal tubules and collecting ducts to dilated proximal tubules and expanded interstitium, whereas active caspase-3 was mainly scattered in damaged tubules and interstitium. Active caspase-3 staining and 24-kDa active caspase-3 protein was enhanced in I/R-injured and CsA-treated kidneys, but decreased by Tac, Rap, and MMF. These results were also consistent with changes in caspase-3 activity. Although caspase-3 mRNA levels were significantly increased in uninephrectomy and I/R-injured kidneys, they were not significantly affected by the immunosuppressants. In addition, all changes detected were positively correlated with renal structure and function.

CONCLUSION

Apoptosis and caspase-3 are not only involved in the long-term renal I/R injury, but also mediate the divergent effects of immunosuppression in this model.

Chronic hepatitis B serum promotes apoptotic damage in human renal tubular cells

AIM: To investigate the effect of the serum of patients with chronic hepatitis B (CHB) on apoptosis of renal tubular epithelial cells in vitro and to study the role of hepatitis B virus (HBV) and transforming growth factor-β1 (TGF-β1) in the pathogenesis of hepatitis B virus associated glomerulonephritis (HBV-GN).

METHODS: The levels of serum TGF-β₁ were measured by specific enzyme linked immunosorbent assay (ELISA) and HBV DNA was tested by polymerase chain reaction (PCR) in 44 patients with CHB ,and 20 healthy persons as the control. The normal human kidney proximal tubular cell (HK-2) was cultured together with the sera of healthy persons, CHB patients with HBV-DNA negative(20 cases) and HBV-DNA positive (24 cases) for up to 72 h. Apoptosis and Fas expression of the HK-2 were detected by flow cytometer.

RESULTS: The apoptosis rate and Fas expression of HK-2 cells were significantly higher in HBV DNA positive serum group 19.01±5.85% and 17.58±8.35%, HBV DNA negative serum group 8.12±2.80% and 6.96 ± 2.76% than those in control group 4.25±0.65% and 2.33 ±1.09%, respectively (P < 0.01). The apoptosis rate and Fas expression of HK-2 in HBV DNA positive serum group was significantly higher than those in HBV DNA negative serum (P < 0.01). Apoptosis rate of HK-2 cells in HBV DNA positive serum group was positively correlated with the level of HBV-DNA (r = 0.657). The level of serum TGF-β₁ in CHB group was 163.05 ± 91.35 µg/L, significantly higher as compared with 81.40 ± 40.75 µg/L in the control group (P < 0.01).

CONCLUSION: The serum of patients with chronic hepatitis B promotes apoptotic damage in human renal tubular cells by triggering a pathway of Fas up-regulation. HBV and TGF-β₁ may play important roles in the mechanism of hepatitis B virus associated glomerulonephritis.

Carbon monoxide prevents apoptosis induced by uropathogenic Escherichia coli toxins

Urinary tract infections (UTIs) are often caused by Escherichia coli (E. coli). Previous studies have demonstrated that up-regulation of heme oxygenase-1 (HO-1) may trigger a survival mechanism against renal cell death induced by E. coli toxins. The present study analyses the role of carbon monoxide (CO), an end product of HO-1, in the survival mechanism. Moreover, we identified hemolysin as a putative pro-apoptotic toxin in the E. coli supernatant. Tubular cells were incubated with CO in the presence or absence of E. coli toxins. Uropathogenic or transformants of non-pathogenic strains expressing hemolysin were used. We found that the survival pathway during E. coli infection might be activated by HO-1-derived production of CO. The protection by CO was also associated with up-regulation of p21 protein expression. Furthermore, we found that in children with pyelonephritis, all the E. coli strains expressing hemolysin induced apoptosis. In E. coli strains not expressing hemolysin, only 45% of the strains could induce apoptosis. In conclusion, generation of CO elicited by HO-1 could promote survival signaling in renal cells. Hemolysin is one of the secreted toxins that are involved in inducing apoptosis during UTI.

Progression in chronic kidney disease

The pathogenic mechanisms that lead to chronic kidney disease (CKD) converge on a common pathway that results in progressive interstitial fibrosis, peritubular capillary loss with hypoxia, and destruction of functioning nephrons because of tubular atrophy. Interstitial recruitment of inflammatory leukocytes and myofibroblasts occurs early in kidneys destined to develop fibrosis. Circulating monocytes are recruited by locally secreted chemoattractant molecules, facilitated by leukocyte adhesion molecules. Functionally heterogeneous macrophages secrete many fibrosis-promoting molecules, but under some circumstances they may also serve a protective scavenging role. Excessive extracellular matrix production occurs primarily within interstitial myofibroblasts, a population of cells that appears to have more than 1 origin, including the resident interstitial fibroblasts, trans-differentiated tubular epithelial cells, and bone marrow-derived cells. Impaired activity of the endogenous renal matrix-degrading proteases may enhance interstitial matrix accumulation, but the specific pathways that are involved remain unclear. Tubules, inflammatory cells, and myofibroblasts synthesize the molecules that activate the fibrogenic cascades, the most important of which is transforming growth factor beta (TGF-beta). TGF-beta may direct cells to assume a pro-fibrotic phenotype or it may do so indirectly after stimulating synthesis of other fibrogenic molecules such as connective tissue growth factor and plasminogen activator inhibitor-1. Reduced levels of antifibrotic factors that are normally produced in the kidney such as hepatocyte growth factor and bone morphogenic protein-7 may accelerate fibrosis and its destructive consequences. Development of new therapeutic agents for CKD looks promising, but several agents that target different components of the fibrogenic cascade will almost certainly be necessary.

Can renal fibrosis be reversed?

New therapeutic approaches are needed to address the current epidemic of chronic kidney disease. Beyond delaying the inevitable onset of end-stage kidney disease the ultimate dream of clinical therapy is disease regression. Degradation of the interstitial matrix proteins is potentially feasible, especially before the interstitial "scar" becomes highly organized. Currently the specific matrix-degrading proteases that perform this function in vivo have not been clearly identified although several candidates have been suggested. Reversing renal fibrosis will also mandate removal of interstitial myofibroblasts that are the major source of the fibrosis-associated interstitial matrix proteins. However, the greater therapeutic challenge pertains to the current inability to regenerate intact functional nephrons in a site where they have been destroyed. In chronic tubulointerstitial damage that typifies all progressive kidney diseases, it is not interstitial matrix accumulation per se that leads to renal functional decline but rather its destructive effects on neighboring cells. In particular, loss of peritubular capillaries and tubules are the morphological features that underlie declining renal function. Recent advances in several basic scientific fields of investigation such as matrix biology, developmental biology, angiogenesis, and stem cell biology have identified new candidate therapeutic targets. A powerful new molecular tool-box is at our disposal that can be used to begin to translate recent discoveries into the clinical research arena with the goal of reversing renal fibrosis in a functionally meaningful way.

Expression of apoptosis-related proteins bcl-2 and bax along with transforming growth factor (TGF-beta1) in the kidney of patients with glomerulonephritides

BACKGROUND

Apoptosis, a gene-directed form of cell death, has been involved in the resolution of renal injury but also in the development of scarring. Bcl-2 and bax are proteins related to apoptotic process that either provides a survival advantage to rapidly proliferating cells (bcl-2) or promote cell death by apoptosis (bax). Various cytokines and growth factors are involved in this process. This study investigates the expression of bcl-2 and bax and the presence of apoptotic bodies in relation to the TGF-beta1 expression at the time of diagnosis in the renal biopsies of patients with glomerulonephritis (GN).

METHODS

Fifty patients with various types of GN and ten controls were included in the study. Bcl-2, bax and Transforming Growth Factor (TGF-beta1) positive cells were detected in kidney biopsies by immunohistochemistry, while apoptotic cells were detected by in situ end labeling of fragmented DNA (ISEL). Morphometric analysis was used for quantitation of immunostaining.

RESULTS

The intensity of bcl-2, bax and TGF-beta1 immunostaining in the renal tissue of patients with GN was significantly more to the observed in the control biopsies. Bcl-2 and bax were expressed within the epithelial cells of proximal, distal and collecting tubules and in the renal interstitium. Bax and bcl-2 proteins were also identified within the glomeruli in a few patients but their distribution was not related to the type of GN. TGF-beta1 was expressed in the cytoplasm of tubular epithelial cells and to a lesser extent in the renal interstitium and glomeruli. A positive correlation of TGF-beta1 with the extent of bax immunostaining (r=0.498, p<0.05) and an inverse correlation with that of bcl-2 (r= -0.490, p<0.05) were identified. Apoptotic bodies were identified only in the renal tissue of patients with GN and were mainly localized among tubular epithelial and interstitial cells.

CONCLUSION

The intensity of bcl-2 and bax proteins expression and the presence of apoptotic bodies in the renal tissue of patients with GN suggest that apoptotic process is ongoing during the evolution of renal disease. The correlation of TGF-beta1 expression with that of apoptosis-related proteins might represent an implication of this growth factor with apoptotic process in the human diseased kidney.

Phosphatidylserine receptor in chronic pancreatitis: evidence for a macrophage independent role

OBJECTIVE

This study analyzes the role of phosphatidylserine receptor (PSR) in chronic pancreatitis.

SUMMARY BACKGROUND DATA

In chronic pancreatitis, destruction of parenchyma comes along with infiltration of lymphocytes and macrophages. The phosphatidylserine receptor is expressed on the surface of macrophages and is crucial for the recognition and engulfment of apoptotic cells. In the present study, we investigated the role of this receptor and its relation to apoptosis in chronic pancreatitis.

METHODS

The expression and localization of PSR were analyzed by Northern blot analysis, RT-PCR, Western blot analysis and immunohistochemistry. Apoptosis was detected by the TUNEL method, and the RNA protection assay (RPA) was used to compare activation of apoptosis with PSR mRNA expression levels. In addition, the molecular data were related to clinicopathological parameters.

RESULTS

PSR mRNA expression was low to absent in normal pancreatic tissue samples. In human chronic pancreatitis, increased expression of PSR mRNA was present in 12 of 29 samples (41%). Up-regulation of PSR could be confirmed by Western blot analysis. In chronic pancreatitis tissue, PSR immunoreactivity was present in all islets, in some ductal cells and in macrophages. The RNA protection assay revealed high mRNA levels of the antiapoptotic genes bcl-2 and bfl-1 (P < 0.05) in chronic pancreatitis tissues with high PSR mRNA expression. The TUNEL apoptosis in situ detection method showed positive signals in some redifferentiating acinar cells and focally in acinar cells adjacent to stromal fibroblasts in chronic pancreatitis tissue samples. The distribution pattern of PSR on pancreatic cells in chronic pancreatitis corresponded to a great extent with regions of high apoptotic activity.

CONCLUSIONS

We show for the first time the presence of PSR in chronic pancreatitis on pancreatic cells other than macrophages in regions with high apoptotic activity. The coexpression and colocalization of this gene with other apoptosis mediators suggest its involvement in apoptotic processes. However, in chronic pancreatitis PSR is not only involved in phagocytosis of apoptotic cells by macrophages.

Testosterone promotes apoptotic damage in human renal tubular cells

BACKGROUND

Apoptosis is a mode of cell death that participates in the kidney physiologic remodeling processes and is thought to contribute to cell loss and kidney structural damage in chronic renal diseases. Gender is one factor which contributes to accelerated nephron loss, with progression more rapid in men than in women in diabetic and nondiabetic chronic renal diseases. Mechanisms by which androgens may cause higher rate of progression of chronic renal diseases in men are poorly explored.

METHODS

In this study, to investigate the role of androgens on apoptotic damage and its associated mechanisms, we examined the effects of testosterone (T) (0.1 nmol/L to 1 micromol/L) on apoptosis, and apoptosis-related proteins in a proximal human tubule cell line (HK-2 cells). Additional experiments were performed in primary cultures of proximal tubular epithelial cells (PTECs). Cells were grown to subconfluence in normal growth medium, and apoptotic damage was induced by serum deprivation for 24 to 48 hours. Cycloheximide, flutamide (a T-receptor antagonist), 17-beta estradiol, or caspase inhibitors were added to cultures that were successively processed for terminal deoxynucleotidyl transferase-mediated uridine triphosphate nick end-labeling (TUNEL) analysis, annexin V/propidium iodide staining, immunofluorescence, or immunoblots to identify effects and apoptotic pathways that could be modulating cell survival.

RESULTS

Both morphologic analysis by annexin V/propidium iodide staining and TUNEL showed that physiologic T levels (1 to 10 nmol/L) induced a significant increase in apoptosis both in HK-2 cells and PTECs. In both types of cell lines pretreatment with the androgen receptor antagonist flutamide prevented the T-induced apoptosis. T-induced apoptosis was enhanced by treatment with cycloheximide and prevented by 17beta-estradiol. Fas, Fas ligand (FasL), and Fas-associating death domain containing protein (FADD) were clearly up-regulated within 48 hours of T treatment in HK-2 cells. Also, T significantly increased the expression of Bax protein (P < 0.01 vs. control) (an effect which was blocked by flutamide), and decreased the expression of Bcl-2. Western blot analysis showed that caspase-3 was activated. Moreover, cleavage into an 85-kD poly(ADP-ribose) polymerase-1 (PARP-1) terminal breakdown product was detectable. The changes in cellular morphology induced by T at 48 hours were no longer observed after the addition of caspase-8, caspase-9, and caspase-3 inhibitors to the culture medium.

CONCLUSION

These results indicate that T increases the permissiveness of proximal tubule kidney cells to apoptotic effects by triggering an apoptotic pathway involving caspase activation, Fas up-regulation, and FasL expression, thus potentially interacting with mechanisms of cell loss which have been already shown to be activated in chronic renal diseases. This is consistent with a role for T in promoting renal injury in men.

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.

A combined regimen of gossypol plus methyltestosterone and ethinylestradiol as a contraceptive induces germ cell apoptosis and expression of its related genes in rats

Attempts to develop gossypol and steroidal hormones alone as a male contraceptive have been tested for many years; however, both caused undesirable side effects that have prevented their acceptance. In this study, we formulated a regimen of combined gossypol at a low dose of 12 mg/kg or a high dose of 50 mg/kg plus methyltestosterone 20 mg/kg and ethinylestradiol 100 g/kg daily (12 mg G+H and 50 mg G+H) administered for 6 weeks in adult rats. The possible roles of germ cell apoptosis and related genes expression were studied by techniques of TdT-mediated dUTP nick end-labeling (TUNEL), agarose gel electrophoresis of low-molecular-weight DNA, in situ hybridization and reverse transcription-polymerase chain reaction detection. Results showed that germ cell apoptosis and related genes expression were significantly induced after combined drug administration. The apoptosis index increased 3.86- and 9.65-fold in the 12-mg and 50-mg G+H-treated groups, respectively, as compared to the control group. DNA ladder formation on the agarose gel further validated the findings of TUNEL-stained apoptotic cells. The apoptosis-related genes fas mRNA expression levels increased 0.44- and 1.39-fold, bax mRNA 0.74- and 2.56-fold, caspase-3 mRNA 0.60- and 1.29-fold, and caspase-9 mRNA 2.50- and 4.08-fold, respectively, in the 12-mg and 50-mg G+H-treated groups vs. the control group. These results indicated that our drug regimen applied as a contraceptive could induce rat germ cell apoptosis. The apoptotic process involved fas system, bax and caspase family genes and the apoptotic extent and cell types were gossypol dose-dependent.

[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.

Tissue transglutaminase and the progression of human renal scarring

Experimental renal scarring indicates that tissue transglutaminase (tTg) may be associated with the accumulation of extracellular matrix (ECM), both indirectly via TGF-beta1 activation and directly by the formation of epsilon(gamma-glutamyl) lysine dipeptide bonds within the ECM. The latter potentially accelerates deposition and confers the ECM with resistance to proteolytic digestion. Studied were 136 human renal biopsy samples from a range of chronic renal diseases (CRD) to determine changes in tTg and epsilon(gamma-glutamyl) lysine crosslinking. Immunofluorescence for insoluble tTg showed a 14-fold increase in the kidneys of CRD patients (5.3 +/- 0.5 versus 76 +/- 54 mV/cm(2)), which was shown to be active by a similar 11-fold increase in the epsilon(gamma-glutamyl) lysine crosslink (1.8 +/- 0.2 versus 19.3 +/- 14.2 mV/cm(2)). Correlations were obtained with renal function for tTg and crosslink. In situ hybridization for tTg mRNA showed that tubular epithelial cells were the major source of tTg; however, both mesangial and interstitial cells also contributed to elevated levels in CRD. This mRNA pattern was consistent with immunohistochemistry for soluble tTg. Changes in renal tTg and its product, the epsilon(gamma-glutamyl) lysine crosslink, occur in progressive renal scarring in humans independently of the original etiology and in a similar manner to experimental models. tTg may therefore play a role in the pathogenesis of renal scarring and fibrosis in patients with CRD and can therefore be considered a potential therapeutic target.

Anemia management and the delay of chronic renal failure progression

Interstitial fibrosis plays a key role in the progression of chronic kidney diseases. Analysis of the biologic effects of erythropoietin and of the pathophysiology of interstitial fibrosis suggest that treatment with epoetin may slow the progression of chronic kidney disease, both by decreasing interstitial fibrosis and by protecting against its consequences. The results of two small prospective studies and of a retrospective one also suggest that treatment with epoetin may have such protective effects.

Effects of caspase inhibition on the progression of experimental glomerulonephritis

BACKGROUND

Caspase-3 has a central role in the execution of apoptosis. In a nephrotoxic nephritis (NTN) model, we previously demonstrated an up-regulation of caspase-3 that was associated with inappropriate renal apoptosis, inflammation, tubular atrophy, and renal scarring.

METHODS

We applied a pan caspase inhibitor, Boc-Asp (OMe)-fluoro-methyl-ketone (B-D-FMK), directly to rat NTN kidney using an intrarenal cannula fed from an osmotic pump. Animals were treated either for the first 7 days (acutely) to determine the effects on renal inflammation (ED-1 staining) and apoptosis (in situ end labeling of fragmented DNA), or for 28 days commencing 15 days after NTN (chronically) to observe the effects on cell death and renal fibrosis. Changes of caspase-3 and caspase-1 activity were detected by fluorometric substrate cleavage assay. Changes in caspase-3 and caspase-1, interleukin-1 beta (IL-1 beta), and collagen I, III, and IV proteins and mRNA were detected by Western blotting and Northern blotting, respectively.

RESULTS

In both treated groups, caspase-3 activity was inhibited, and 17 and 24 kD active caspase-3 proteins were reduced significantly. A compensatory increase of caspase-3 mRNA occurred in the acutely treated group, but decreased in the chronically treated group (P < 0.05). Although there were no significant changes in caspase-1 activity and its active protein, the observed decrease in its precursor in the chronic group was increased by treatment (P < 0.05). Further, IL-1 beta precursor and its mRNA were significantly reduced by treatment only in the chronically treated group. Apoptosis was decreased in the glomeruli of acutely treated rats, and in the tubules and interstitium of chronically treated animals (P < 0.05). Glomerular inflammation was decreased only in the acutely treated group, whereas tubulointerstitial inflammation was lowered in both treated groups (P < 0.05). Glomerulosclerosis was reduced in both inhibitor groups, with a reduction in tubulointerstitial fibrosis and collagen I, III, and IV mRNA restricted to chronically treated animals (P < 0.05). Proteinuria was significantly decreased with caspase inhibition in both treated groups, but not serum creatinine level.

CONCLUSION

This study clearly indicates that caspase inhibition reduces renal apoptosis, ameliorates inflammation and fibrosis, and improves proteinuria in experimental glomerulonephritis, which may mainly be related to changes in the caspase enzymatic system.

Anaemia as a risk factor for the progression of chronic kidney disease

PURPOSE OF REVIEW

About a dozen controlled clinical trials examined the effect of anaemia correction on the progression of chronic kidney disease. None of these studies fulfilled the stringent criteria of a randomized controlled trial as suggested by the CONSORT statement, yet evidence emerged that anaemia sustains mitogenic and fibrogenic stimuli by lowering local partial oxygen tension. This review addresses the question of why and how anaemia could possibly enhance the progression of chronic kidney disease, and summarizes relevant clinical trials.

RECENT FINDINGS

The discovery of hypoxia-inducible factor, a transcription factor stabilized under hypoxic conditions, with DNA-binding properties towards about 50 target genes including erythropoietin, has largely encouraged the hypothesis that tissue hypoxia may serve as another common mechanism for the progression of chronic kidney disease besides hypertension or proteinuria. In addition, anaemia-mediated alterations of renal sympathetic nerve activity and anaemia-related increments of oxidative stress may contribute to a progressive nephron loss. Conclusive evidence from clinical trials is scarce.

SUMMARY

Pathophysiological concepts suggest some impact of anaemia on the progression of chronic kidney disease. The urge for more sound clinical intervention trials is met by the ongoing ECAP study (Effect of early Correction of Anaemia on the Progression of chronic kidney disease).

A shift in the Bax/Bcl-2 balance may activate caspase-3 and modulate apoptosis in experimental glomerulonephritis

BACKGROUND

Although apoptosis has been linked to the renal cell deletion and ensuing renal fibrosis, its regulating mechanisms remain obscure. Of the known regulators of apoptosis, the best characterized is the Bax to Bcl-2 ratio. However, its importance in controlling apoptosis in glomerulonephritis is unclear. Here, using the nephrotoxic nephritis (NTN) model, we evaluated Bax/Bcl-2 in relation to changes in the apoptosis co-ordination enzyme, caspase-3.

METHODS

Kidneys were harvested at days 7, 15, 30 and 45 post-injection of anti-glomerular basement membrane antibody into Wistar Kyoto rats. These were analyzed for apoptosis (in situ end labeling of fragmented DNA, light and electron microscopy), Bax/Bcl-2 protein (Western blotting), mRNA (Northern blotting) and distribution (immunohistochemistry), as well as caspase-3 activity (substrate cleavage assay), inflammation (ED1 staining), proliferation (proliferating cell nuclear antigen staining) and fibrosis (Masson's Trichrome staining).

RESULTS

Bax mRNA was significantly increased while that of Bcl-2 was decreased throughout the time course (+265% and -62% by day 45). Increased Bax and decreased Bcl-2 protein were noted, significantly so on day 7 (+177% and -21%) and day 45 (+363% and -17%). Bax protein was observed in dilated and atrophic tubules, sclerotic glomeruli and inflamed interstitium, while Bcl-2 was only visible in atrophic tubules. The ratios of Bax to Bcl-2 mRNA and protein were significantly increased at all time points. These correlated (P < 0.05) with up-regulated caspase-3 activity (r = 0.742 and 0.531), apoptosis (r = 0.712 and 0.540), proliferation (r = 0.611, mRNA only), inflammation (ED1+, r = 0.474 and 0.419) and fibrosis (r = 0.474 and 0.729).

CONCLUSIONS

Our findings suggest that the changes in the ratio of Bax to Bcl-2 may contribute to the caspase-3 activation and the modulation of renal apoptosis associated with renal inflammation, tubular atrophy and renal fibrosis in experimental glomerulonephritis.

Contribution of prostaglandin D2 synthase to progression of renal failure and dialysis dementia

This article reviews the possible role of prostaglandin D(2) synthase (PGD(2)S) in the progression of chronic renal failure and dialysis dementia. Such a proposal is based on our observation that PGD(2)S significantly increases the rate of apoptosis in cultured pig kidney proximal tubule LLC-PK1 and rat neuronal PC12 cells. Apoptosis was caspase mediated and inhibitable by PGE(1), PGE(2), PGF(2alpha), platelet-derived growth factor (PDGF), and by PGD(2)S inhibitors, selenium and anti-PGD(2)S antibody. Apoptosis was restored by the addition of downstream metabolic products, PGD(2) and 15 deoxy PG triangle up (12,14)J(2). The proposal that PGD(2)S contributes to progression of renal failure and dialysis dementia is based on: (1) the progressive creatinine-like increase in PGD(2)S levels in blood as renal function decreases, increased renal cyclooxygenase (COX) 2 in chronic renal failure, and reported increase in apoptosis noted in the remnant kidney model, and (2) a 35- to 150-fold increase in blood levels of PGD(2)S in dialysis patients. Both conditions appear to favor shifting the PG metabolic pathway to downstream apoptotic metabolites, PGD(2) and 15 deoxy PG triangle up (12,14)J(2). The diverse role that PGs, growth factors, and COX play in progression of chronic renal failure, their interactions with PGD(2)S, and the status of COX inhibitors in retarding the progression of renal failure are reviewed. In addition, the need for a more systematic longitudinal assessment of dementia in dialysis patients by standardized neuropsychologic testing, testing blood levels and glycosylated isoforms of PGD(2)S, and the effect of COX inhibition and erythropoietin administration on dialysis dementia are discussed.

Colchicine decreases apoptotic cell death in chronic cyclosporine nephrotoxicity

Colchicine has been shown to prevent kidney injury in chronic cyclosporine nephrotoxicity; however, the mechanisms of its action are undetermined. The purpose of this study was to clarify whether colchicine prevents cyclosporine-induced kidney injury by decreasing kidney-cell apoptosis. We also sought to determine whether such an antiapoptotic effect was related to Bcl-2/Bax protein and caspase3 activity. Adult male Sprague-Dawley rats kept on a salt-depleted diet (0.05% sodium) were treated daily for 28 days with cyclosporine (15 mg/kg in 1 mL/kg olive-oil vehicle), colchicine (30 microg/kg in 100% ethanol, diluted with sterile saline solution to a final concentration of 30 microg/mL), or both cyclosporine and colchicine. Kidney function, histomorphologic findings, in situ terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate-biotin nick end-labeling assay, expressions of Bcl-2 and Bax proteins, and caspase-3 enzymatic activity were compared for the different treatment groups. Compared with the vehicle-treated rats, rats given cyclosporine showed a decline in creatinine clearance rate, an increase in serum creatinine concentration, tubulointerstitial fibrosis, and an increase in the number of apoptotic cells (all P <.01). Concomitant administration of colchicine significantly reversed all the above parameters (all P <.05). The decreased expression of Bcl-2 and the ratio of Bcl-2 to Bax protein seen in cyclosporine-treated rat kidneys were significantly increased after colchicine treatment, accompanying a suppression of caspase-3 activity (P <.05). Furthermore, the decreased apoptotic cell death was closely correlated with improved renal tubulointerstitial fibrosis (r = 0.583, P <.05). These findings strongly suggest that a renoprotective effect of colchicine on cyclosporine-induced nephrotoxicity is coassociated with a decrease in apoptotic cells.

Caspase-3 and apoptosis in experimental chronic renal scarring

BACKGROUND

Caspase-3 is a member of the caspase enzyme family, having a central role in the execution of apoptosis. However, the significance of Caspase-3 in the inappropriate and excessive apoptosis that contributes to the progression of non-immune-mediated renal scarring has not been established.

METHODS

Kidneys from sham-operated and subtotal nephrectomized (SNx) rats were harvested on days 7, 15, 30, 60, 90 and 120 post-surgery. These were analyzed for apoptosis (in situ end labeling of DNA, light and electron microscopy), Caspase-3 activity (fluorometric substrate cleavage assay), protein and mRNA (Western and Northern blotting), as well as distribution (immunohistochemistry), inflammation (ED-1 immunohistochemistry) and fibrosis (Masson's Trichrome staining).

RESULTS

Apoptosis, inflammation and fibrosis gradually increased in glomeruli, tubules and interstitium of SNx rats. Caspase-3 was mainly located in damaged tubules, but also was found in some glomerular and interstitial cells. Little or no staining was noted in sham-operated kidneys. In SNx kidneys, Caspase-3 activity was significantly increased from day 30 and peaked on day 120 (2.5-fold). This resulted from increases in the 17 and 24 kD active protein subunits. The 32 kD precursor was increased at all time points (1861% on day 120, P < 0.01). Caspase-3 changes were transcription-dependent with the 2.7 kb caspase-3 mRNA significantly increased at all time points (287% on day 120). Caspase-3 activity was a better predictor of apoptosis (Std beta coefficient = 0.347, P < 0.05) than Caspase-3 proteins or mRNA; however, Caspase-3 at all levels correlated with apoptosis, inflammation and fibrosis (all P < 0.01).

CONCLUSIONS

Up-regulation of apoptosis in remnant kidneys is likely to be Caspase-3-dependent as it is associated with increases in Caspase-3 at the activity, protein and mRNA levels. Therefore, Caspase-3 is a potential therapeutic target for the modification of renal cell apoptosis and subsequently renal fibrosis.

Angiotensin-converting enzyme inhibition prevents glomerular-tubule disconnection and atrophy in passive Heymann nephritis, an effect not observed with a calcium antagonist

In proteinuric nephropathies tubular atrophy leads to glomerular-tubule disconnection through an unknown mechanism. Here we studied whether proteinuria promoted glomerular-tubule disconnection in individual nephrons and whether this phenomenon was prevented by an angiotensin-converting enzyme (ACE) inhibitor. Passive Heymann nephritis (PHN) and control rats were studied at 4 and 8 months. Two additional groups of PHN rats received lisinopril (40 mg/L) or a calcium channel blocker (lacidipine, 3 mg/kg) from day 7 after surgery to 8 months. At sacrifice, kidneys were serially sectioned to identify glomerular- tubule abnormalities in individual nephrons and changes in interstitial volume. In PHN rats, the time-dependent increase in proteinuria was paralleled by tubular atrophy leading to glomerular-tubule disconnection and interstitial volume enlargement. Marked apoptosis was invariably found in atrophic tubules in contrast to the absent or very mild terminal dUTP nick-end labeling staining in tubules normally connected to glomeruli in PHN animals. Treatment with an ACE inhibitor prevented hypertension, proteinuria, the formation of atrophic tubuli, glomerular-tubule disconnection and limited the fractional interstitial volume expansion. Although lacidipine limited hypertension, it did not reduce proteinuria or prevent tubular atrophy and disconnection. Multivariate analysis showed that the appearance of atubular glomeruli and the increase in interstitial volume were better predicted by proteinuria than blood pressure. This study suggests that ACE inhibitors effectively prevent glomerular-tubule disconnection possibly by their ability of reducing proteinuria, which in turn favors proximal tubular cell apoptosis. Agents that only reduced hypertension but not proteinuria do not affect tubular behavior.

Involvement of Bcl-2 family genes and Fas signaling system in primary and secondary male germ cell apoptosis induced by 2-bromopropane in rat

Epidemiological surveys and animal experimental studies suggest that exposure to 2-bromopropane (2-BP) could result in reproductive and hematopoietic disorders. The objectives of this study were to investigate the role of apoptosis in 2-BP-induced testicular toxicity and whether this process involves Bcl-2 family genes and the Fas signaling system. Rats were injected percutaneously with 1350 mg/kg 2-BP for 1 to 5 days and then were euthanized at 6 or 12 h after one dose, 6 h after two, three, or five doses, and 2 or 9 days after the final treatment. Light and electron microscopic analyses, TUNEL staining of DNA fragments, agarose gel electrophoresis of low-molecular-weight DNA, and Western blotting analysis of Bcl-2 family proteins and Fas receptor and ligand were conducted. Two-day treatment resulted in selective degeneration of spermatogonia with marked nuclear chromatin condensation. DNA ladder formation on the agarose gel further validated the findings of TUNEL-stained apoptotic cells. The percentage of apoptotic-positive tubules and apoptotic cell index increased time dependently. 2-BP treatment resulted in two distinct morphological changes: an immediate effect on spermatogonia and secondary apoptosis of spermatocytes 9 days after treatment. Downregulation of Bcl-2 after the first or second injection of 2-BP and upregulation of Bax after the first treatment contributed to the initiation of primary apoptosis of spermatogonia. Expression of FasL was inhibited while expression of Fas increased after the 2-BP treatment and remained at levels about two times of the control. However, it increased about sixfold of the control by day 9 after final injection, which contributed to the induction of secondary apoptosis of spermatocytes. Our results indicate that 2-BP resulted in apoptotic death of testicular germ cells and that this process involves the Bcl-2 family genes and the Fas signaling system.

Contribution of apoptotic cell death to renal injury

Cell number abnormalities are frequent in renal diseases, and range from the hypercellularity of postinfectious glomerulonephritis to the cell depletion of chronic renal atrophy. Recent research has shown that apoptosis and its regulatory mechanisms contribute to cell number regulation in the kidney. The role of apoptosis ranges from induction to repair and progression of renal injury. Death ligands and receptors, such as TNF and FasL, proapoptotic and antiapoptotic Bcl-2 family members and caspases have all been shown to participate in apoptosis regulation in the course of renal injury. These proteins represent potential therapeutic targets, which should be further explored.