Involvement of apoptosis in patients with diabetic nephropathy: A study on plasma soluble Fas levels and pathological findings

Serum Fas levels during first week of sepsis are associated with severity and mortality

INTRODUCTION

The aim of our study was to explore whether there is an association of serum sFas (cell death apoptosis receptor) concentrations during the first week of sepsis with sepsis severity and sepsis mortality.

METHODS

In this observational study, septic patients were recruited. Serum sFas concentrations were determined on days 1, 4, and 8 of sepsis diagnosis. Thirty-day mortality was the outcome variable.

RESULTS

Surviving patients (n = 181) compared to non-survivors (n = 101) presented lower serum sFas levels on day 1 (p < 0.001), day 4 (p < 0.001) and day 8 (p < 0.001), and lower SOFA on day 1 (p < 0.001), day 4 (p < 0.001) and day 8 (p < 0.001). Logistic regression analyses showed associations between 30-day mortality and serum sFas levels controlling for SOFA on day 1 (OR = 1.005; 95% CI = 1.003-1.007; p < 0.001), day 4 (OR = 1.044; 95% CI = 1.029-1.060; p < 0.001) and day 8 (OR = 1.012; 95% CI = 1.002-1.022; p = 0.02).

CONCLUSIONS

The association of serum sFas concentrations during the first week of sepsis with sepsis severity and sepsis mortality were our new findings.

Pentosan polysulfate ameliorates apoptosis and inflammation by suppressing activation of the p38 MAPK pathway in high glucose‑treated HK‑2 cells

The apoptosis of tubular epithelial cells in diabetic nephropathy (DN) is commonly observed in human renal biopsies. Inflammation plays a key role in DN, and pentosan polysulfate (PPS) has been shown to largely attenuate the inflammation of nephropathy in aging diabetic mice. p38 mitogen-activated protein kinase (p38 MAPK) plays a crucial role in tissue inflammation and cell apoptosis, and it is activated by hyperglycemia. In the present study, high glucose (HG)-treated human renal proximal tubular epithelial cells (HK-2) were used to examine the protective effects of PPS against HG-stimulated apoptosis and inflammation. The results of the study revealed that PPS markedly suppressed the HG-induced reduction in cell viability. Incubation of HK-2 cells with HG activated the p38 MAPK pathway and, subsequently, as confirmed by western blot analysis and flow cytometry, increased cell apoptosis, which was blocked by PPS. In addition, PPS treatment significantly inhibited HG-stimulated p38 MAPK and nuclear factor-κB activation, and reduced the production of pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-1β and IL-6. In conclusion, PPS ameliorates p38 MAPK-mediated renal cell apoptosis and inflammation. The anti-apoptotic actions and anti-inflammatory effects of PPS prompt further investigation of this compound as a promising therapeutic agent against DN.

Alteration of oxidative stress and inflammatory cytokines induces apoptosis in diabetic nephropathy

Diabetic nephropathy (DN) is one of the most significant long‑term complications in terms of morbidity and mortality for diabetic patients; however, the exact cause remains unknown. To address this, the DN model was established, and oxidative stress indexes, including malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH‑Px), and inflammatory cytokines, includinginterleukin‑6 (IL‑6), tumor necrosis factor‑alpha (TNF‑α) and transforming growth factor‑beta (TGF‑β), were examined by ELISA. Renal pathological alterations and cell apoptosis was examined by hematoxylin and eosin and terminal deoxynucleotidyl transferase mediated dUTP nick‑end labeling staining, respectively. The expression levels of B‑cell lymphoma‑2 (Bcl‑2), Bcl‑2 associated X (Bax) and caspase‑3 wereexamined by immunohistochemistry and western blotting. The DN model was correctly established, with lower body weight and the higher blood glucose in the diabetes model group. The expression levels of SOD and GSH‑Px were significantly decreased in the diabetes model group; however, MDA, IL‑6, TNF‑α and TGF‑β were significantly increased. The kidney was severely damaged in the diabetes model group, with inflammatory cell invasion, increasing amount of interstitial matrix and hypertrophy with vacuolar degeneration of renal tubular cells. Cell apoptosis levels were significantly increased, and Bcl‑2 was significantly decreased in the diabetes model group in contrast with that of the sham group; however, Bax and caspase‑3 were significantly increased. It suggested that increased oxidative stress and inflammatory cytokines may enhance the apoptosis levels in DN, and may provide a significant diagnostic reference for DN in diabetes patients.

LXR agonist T0901317 upregulates thrombomodulin expression in glomerular endothelial cells by inhibition of nuclear factor‑κB

Dysfunction of glomerular endothelial cells (GECs) induces a variety of symptoms, including proteinuria, inflammation, vascular diseases, fibrosis and thrombosis. Thrombomodulin (TM) acts as a vasoprotective molecule on the surface of the vascular endothelial cells to maintain the homeostasis of the endothelial microenvironment by suppressing cellular proliferation, adhesion and inflammatory responses. Liver X receptor (LXR), a nuclear receptor (NR) and a bile acid‑activated transcription factor, regulates metabolism and cholesterol transport, vascular tension and inflammation. Previous studies indicated that TM expression is upregulated by various NRs; however, it is unclear whether pharmacological modulation of LXR may affect TM expression and GEC function. The current study revealed that LXR activation by its agonist, T0901317, upregulates the expression and activity of TM. This effect was mediated specifically through LXR‑α, and not through LXR‑β. Additionally, T0901317 treatment inhibited nuclear factor‑κB (NF‑κB) signaling and the secretion of high glucose‑induced proinflammatory mediators, including tumor necrosis factor‑α and interleukin‑1β in GECs. Co‑immunoprecipitation experiments determined that treatment with T0901317 enhances the interaction between LXR‑α and the transcriptional coactivator, p300, in GEC extracts. The present findings suggest that NF‑κB may be a negative regulator of TM expression, and its removal may contribute to TM gene expression, particularly when in competition with the T0901317‑enhanced formation of the LXR/p300 complex. Therefore, LXR may be a novel molecular target for manipulating TM in GECs, which may advance the treatment of endothelial cell‑associated diseases.

Targeting Mitochondria and Reactive Oxygen Species-Driven Pathogenesis in Diabetic Nephropathy

Diabetic kidney disease is one of the major microvascular complications of both type 1 and type 2 diabetes mellitus. Approximately 30% of patients with diabetes experience renal complications. Current clinical therapies can only mitigate the symptoms and delay the progression to end-stage renal disease, but not prevent or reverse it. Oxidative stress is an important player in the pathogenesis of diabetic nephropathy. The activity of reactive oxygen and nitrogen species (ROS/NS), which are by-products of the diabetic milieu, has been found to correlate with pathological changes observed in the diabetic kidney. However, many clinical studies have failed to establish that antioxidant therapy is renoprotective. The discovery that increased ROS/NS activity is linked to mitochondrial dysfunction, endoplasmic reticulum stress, inflammation, cellular senescence, and cell death calls for a refined approach to antioxidant therapy. It is becoming clear that mitochondria play a key role in the generation of ROS/NS and their consequences on the cellular pathways involved in apoptotic cell death in the diabetic kidney. Oxidative stress has also been associated with necrosis via induction of mitochondrial permeability transition. This review highlights the importance of mitochondria in regulating redox balance, modulating cellular responses to oxidative stress, and influencing cell death pathways in diabetic kidney disease. ROS/NS-mediated cellular dysfunction corresponds with progressive disease in the diabetic kidney, and consequently represents an important clinical target. Based on this consideration, this review also examines current therapeutic interventions to prevent ROS/NS-derived injury in the diabetic kidney. These interventions, mainly aimed at reducing or preventing mitochondrial-generated oxidative stress, improving mitochondrial antioxidant defense, and maintaining mitochondrial integrity, may deliver alternative approaches to halt or prevent diabetic kidney disease.

Carnosine prevents apoptosis of glomerular cells and podocyte loss in STZ diabetic rats

BACKGROUND/AIMS

We identified carnosinase-1 (CN-1) as risk-factor for diabetic nephropathy (DN). Carnosine, the substrate for CN-1, supposedly is a protective factor regarding diabetic complications. In this study, we hypothesized that carnosine administration to diabetic rats might protect the kidneys from glomerular apoptosis and podocyte loss.

METHODS

We examined the effect of oral L-carnosine administration (1g/kg BW per day) on apoptosis, podocyte loss, oxidative stress, AGEs and hexosamine pathway in kidneys of streptozotocin-induced diabetic Wistar rats after 3 months of diabetes and treatment.

RESULTS

Hyperglycemia significantly reduced endogenous kidney carnosine levels. In parallel, podocyte numbers significantly decreased (-21% compared to non-diabetics, p<0.05), apoptotic glomerular cells numbers increased (32%, compared to non-diabetic, p<0.05) and protein levels of bax and cytochrome c increased (175% and 117%). Carnosine treatment restored carnosine kidney levels, prevented podocytes loss (+23% compared to diabetic, p<0.05), restrained glomerular apoptosis (-34% compared to diabetic; p<0.05) and reduced expression of bax and cytochrome c (-63% and -54% compared to diabetics, both p<0.05). In kidneys of all diabetic animals, levels of ROS, AGEs and GlcNAc-modified proteins were increased.

CONCLUSION

By inhibition of pro-apoptotic signaling and independent of biochemical abnormalities, carnosine protects diabetic rat kidneys from apoptosis and podocyte loss.

Moderate exercise attenuates caspase-3 activity, oxidative stress, and inhibits progression of diabetic renal disease in db/db mice

Diabetic nephropathy, the leading cause of end-stage renal disease, is characterized by a proapoptotic and prooxidative environment. The mechanisms by which lifestyle interventions, such as exercise, benefit diabetic nephropathy are unknown. We hypothesized that exercise inhibits early diabetic nephropathy via attenuation of the mitochondrial apoptotic pathway and oxidative damage. Type 2 diabetic db/db and normoglycemic wild-type mice were exercised for an hour everyday at a moderate intensity for 7 wk, following which renal function, morphology, apoptotic signaling, and oxidative stress were evaluated. Exercise reduced body weight, albuminuria, and pathological glomerular expansion in db/db mice independent of hyperglycemic status. Changes in renal morphology were also related to reduced caspase-3 (main effector caspase in renal apoptosis), caspase-8 (main initiator caspase of the "extrinsic" pathway) activities, and TNF-alpha expression. A role for the mitochondrial apoptotic pathway was unlikely as both caspase-9 activity (initiator caspase of this pathway) and expression of regulatory proteins such as Bax and Bcl-2 were unchanged. Kidneys from db/db mice also produced higher levels of superoxides and had greater oxidative damage concurrent with downregulation of superoxide dismutase (SOD) 1 and 3. Interestingly, although exercise also increased superoxides, there was also upregulation of multiple SODs that likely inhibited lipid (hydroperoxides) and protein (carbonyls and nitrotyrosine) oxidation in db/db kidneys. In conclusion, exercise can inhibit progression of early diabetic nephropathy independent of hyperglycemia. Reductions in caspase-3 and caspase-8 activities, with parallel improvements in SOD expression and reduced oxidative damage, could underlie the beneficial effects of exercise in diabetic kidney disease.

Serum concentrations of markers of TNFalpha and Fas-mediated pathways and renal function in nonproteinuric patients with type 1 diabetes

BACKGROUND AND OBJECTIVES

The aim of our study was to examine serum markers of the TNF and Fas pathways for association with cystatin-C based estimated glomerular filtration rate (cC-GFR) in subjects with type 1 diabetes (T1DM) and no proteinuria.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The study group (the 2nd Joslin Kidney Study) comprised patients with T1DM and normoalbuminuria (NA) (n = 363) or microalbuminuria (MA) (n = 304). Impaired renal function (cC-GFR <90 ml/min) was present in only 10% of patients with NA and 36% of those with MA. We measured markers of the tumor necrosis factor alpha (TNFalpha) pathway [TNFalpha, soluble TNF receptor 1 (sTNFR1), and 2 (sTNFR2)], its downstream effectors [soluble intercellular and soluble vascular adhesion molecules (sICAM-1 and sVCAM-1), interleukin 8 (IL8/CXCL8), monocytes chemoattractant protein-1 (MCP1), and IFNgamma inducible protein-10 (IP10/CXCL10)], the Fas pathway [soluble Fas (sFas) and Fas ligand (sFasL)], CRP, and IL6.

RESULTS

Of these, TNFalpha, sTNFRs, sFas, sICAM-1, and sIP10 were associated with cC-GFR. However, only the TNF receptors and sFas were associated with cC-GFR in multivariate analysis. Variation in the concentration of the TNF receptors had a much stronger impact on GFR than clinical covariates such as age and albumin excretion.

CONCLUSIONS

Elevated concentrations of serum markers of the TNFalpha and Fas-pathways are strongly associated with decreased renal function in nonproteinuric type 1 diabetic patients. These effects are independent of those of urinary albumin excretion. Follow-up studies are needed to characterize the role of these markers in early progressive renal function decline.

The death ligand TRAIL in diabetic nephropathy

Apoptotic cell death contributes to diabetic nephropathy (DN), but its role is not well understood. The tubulointerstitium from DN biopsy specimens was microdissected, and expression profiles of genes related to apoptosis were analyzed. A total of 112 (25%) of 455 cell death-related genes were found to be significantly differentially regulated. Among those that showed the greatest changes in regulation were two death receptors, OPG (the gene encoding osteoprotegerin) and Fas, and the death ligand TRAIL. Glomerular and proximal tubular TRAIL expression, assessed by immunohistochemistry, was higher in DN kidneys than controls and was associated with clinical and histologic severity of disease. In vitro, proinflammatory cytokines but not glucose alone regulated TRAIL expression in the human proximal tubular cell line HK-2. TRAIL induced tubular cell apoptosis in a dosage-dependant manner, an effect that was more marked in the presence of high levels of glucose and proinflammatory cytokines. TRAIL also activated NF-kappaB, and inhibition of NF-kappaB sensitized cells to TRAIL-induced apoptosis. It is proposed that TRAIL-induced cell death could play an important role in the progression of human DN.

The death ligand TRAIL in diabetic nephropathy

Apoptotic cell death contributes to diabetic nephropathy (DN), but its role is not well understood. The tubulointerstitium from DN biopsy specimens was microdissected, and expression profiles of genes related to apoptosis were analyzed. A total of 112 (25%) of 455 cell death-related genes were found to be significantly differentially regulated. Among those that showed the greatest changes in regulation were two death receptors, OPG (the gene encoding osteoprotegerin) and Fas, and the death ligand TRAIL. Glomerular and proximal tubular TRAIL expression, assessed by immunohistochemistry, was higher in DN kidneys than controls and was associated with clinical and histologic severity of disease. In vitro, proinflammatory cytokines but not glucose alone regulated TRAIL expression in the human proximal tubular cell line HK-2. TRAIL induced tubular cell apoptosis in a dosage-dependant manner, an effect that was more marked in the presence of high levels of glucose and proinflammatory cytokines. TRAIL also activated NF-kappaB, and inhibition of NF-kappaB sensitized cells to TRAIL-induced apoptosis. It is proposed that TRAIL-induced cell death could play an important role in the progression of human DN.

Activated protein C protects against diabetic nephropathy by inhibiting endothelial and podocyte apoptosis

Data providing direct evidence for a causative link between endothelial dysfunction, microvascular disease and diabetic end-organ damage are scarce. Here we show that activated protein C (APC) formation, which is regulated by endothelial thrombomodulin, is reduced in diabetic mice and causally linked to nephropathy. Thrombomodulin-dependent APC formation mediates cytoprotection in diabetic nephropathy by inhibiting glomerular apoptosis. APC prevents glucose-induced apoptosis in endothelial cells and podocytes, the cellular components of the glomerular filtration barrier. APC modulates the mitochondrial apoptosis pathway via the protease-activated receptor PAR-1 and the endothelial protein C receptor EPCR in glucose-stressed cells. These experiments establish a new pathway, in which hyperglycemia impairs endothelial thrombomodulin-dependent APC formation. Loss of thrombomodulin-dependent APC formation interrupts cross-talk between the vascular compartment and podocytes, causing glomerular apoptosis and diabetic nephropathy. Conversely, maintaining high APC levels during long-term diabetes protects against diabetic nephropathy.

Dual effect of methylprednsolone pulses on apoptosis of peripheral leukocytes in patients with renal diseases

It is well known that change in apoptosis may modulate the natural story of illness, and that many drugs may act through modulation of apoptosis, but the role of steroids in acting through apoptosis in different settings, including renal diseases, has still to be elucidated. We studied the in vivo effects of steroids by oral assumption (10 to 25 mg/deltacortene) or by intravenous pulses (300 to 1000 mg/dose) on apoptosis and cellular subsets of peripheral lymphocytes, by evaluating DNA-fragmentation and lymphocyte subsets in 79 subjects: 22 controls and 57 patients with various renal diseases (25 Lupus-GN, 19 membranous-GN (MGN), 6 rapidly progressive-GN (RPGN), 2 acute interstitial nephritis (AIN), 5 on chronic dialysis. Baseline apoptosis was present in 1/22 (4.5%) of controls, 3/25 (12%) SLE, 2/6 (33.3%) RPGN and 10/19 (52.6%) MGN. A significant decrease in CD3+CD8+ cell count and a significant increase of the CD3+CD4/CD3+CD8+ ratio were found in apoptosis-positive subjects. DNA fragmentation did not change after oral steroids, paralleling a 22 to 32% decrease in total lymphocytes. Following intravenous methylprednisolone pulses, a deeper drop of all lymphocyte subsets was observed, while DNA fragmentation turned from present to absent in 2 MGN, but not in 2 RPGN, and from absent to present in 1 ARF and 1 SLE, independently of the dosage. We demonstrated that the presence of apoptosis in renal diseases is associated with decreased CD3+CD8+ cell count. Furthermore, steroid intravenous pulses, besides inducing a profound decrease in lymphocyte subsets, do exert a dual effect on baseline leukocyte apoptosis, eventually leading to a reversal of baseline patterns, either turning from negative to positive or from positive to negative. Oral steroid therapy did not influence baseline apoptosis.

Fas/Fas-Ligand pathway is impaired in patients with type 2 diabetes. Influence of hypertension and insulin resistance

OBJECTIVES

In type 2 diabetic patients with no cardiac history or symptoms, 1) to evaluate whether the soluble forms of Fas (sFas) and Fas-ligand (sFasL), involved in apoptosis, may be markers of silent coronary disease or related to hypertension or microangiopathic complications; 2) to examine the effect of short-term glycemic control on sFas and sFasL.

METHODS

(1) sFas and sFasL were measured with the ELISA method in 44 asymptomatic diabetic patients, 33 with hypertension, and with a normal myocardial scintigraphy (n=14), with silent myocardial ischemia (SMI) and without (n=15) or with (n=15) significant coronary stenoses; and in 14 controls; (2) sFas and sFasL were measured in 15 poorly controlled diabetic patients before and after 7 days of CSII treatment.

RESULTS

(1) sFas and sFasL differed in the four groups of patients (p=0.003 each). sFas was significantly higher in the patients with SMI without (p=0.035) and with coronary stenoses (p=0.002) than in the control group. sFasL was lower in the three groups of diabetic patients (p<0.05 each) than in control group. In the diabetic population, sFas correlated positively with hypertension (p=0.021), and sFasL negatively with hypertension (p=0.027) and HOMA index in the non-insulin treated patients (p=0.049); (2) sFas did not differ before or after CSII, and there was a marginal decrease in sFasL.

CONCLUSION

Fas-mediated apoptosis is involved in type 2 diabetes and might be associated with hypertension and/or its vascular consequences. sFasL might be affected by insulin resistance. sFas and sFasL are not effective markers of SMI.