C. Percy

Renal ageing: Changes in the cellular mechanism of energy metabolism and oxidant handling (Review Article)

SUMMARY:  The age‐dependent changes in the kidney are often debilitating, can be life‐threatening and are a significant cause of increasing health costs worldwide. Excessive fibrosis, a general lack of regenerative ability and an increase in apoptosis in cells that determine healthy renal function work together to cause chronic kidney disease. This review provides information on the molecules and mechanisms that determine the age‐dependent effects in the kidney, and in particular, the effects of cellular metabolism and oxidant handling on the ageing kidney. With a better understanding of the influence of ageing on the structural and functional alterations that occur, new targeted therapies may be developed to minimize renal damage and promote health in the elderly.

Obesity and hypertension have differing oxidant handling molecular pathways in age-related chronic kidney disease.

Chronic kidney disease (CKD) in ageing is a burden on health systems worldwide. Rat models of age-related CKD linked with obesity and hypertension were used to investigate alterations in oxidant handling and energy metabolism to identify gene targets or markers for age-related CKD. Young adult (3 months) and old (21-24 months) spontaneously-hypertensive (SHR), normotensive Wistar-Kyoto (WKY) and Wistar rats (normotensive, obese in ageing) were compared for renal functional and physiological parameters, renal fibrosis and inflammation, oxidative stress (hemeoxygenase-1/HO-1), apoptosis and cell injury (including Bax:Bcl-2), phosphorylated and non-phosphorylated forms of oxidant and energy sensing proteins (p66Shc, AMPK), signal transduction proteins (ERK1/2, PKB), and transcription factors (NF-kappaB, FoxO1). All old rats were normoglycemic. Renal fibrosis, tubular epithelial apoptosis, interstitial macrophages and myofibroblasts (all p<0.05), p66Shc/phospho-p66 (p<0.05), Bax/Bcl-2 ratio (p<0.05) and NF-kappaB expression (p<0.01) were highest in old obese Wistars. Expression of phospho-FoxO/FoxO was elevated in old Wistars (p<0.001) and WKYs (p<0.01). SHRs had high levels in young and old rats. Expression of PKB, phospho-PKB, ERK1/2 and phospho-ERK1/2 were significantly elevated in all aged animals. These results suggest that obesity and hypertension have differing oxidant handling and signalling pathways that act in the pathogenesis of age-related CKD.

Comparative Analysis of Caspase Activation and Apoptosis in Renal Tubular Epithelial Cells and Renal Cell Carcinomas

Background/Aims: Treatment of renal cell carcinoma (RCC) is limited by its resistance to conventional chemotherapies. This may occur, in part, from resistance to apoptosis. The role of caspase activation in apoptosis resistance in treated RCCs was investigated. Methods: Two human RCC cell lines (ACHN and SN12K1) and renal tubular epithelial cells (HK2) were treated with 5-fluorouracil (0.2–20 µg/ml) or cisplatin (1–100 µM). Activation of caspase-3 and -2 was analysed and compared with levels of apoptosis. Caspase function was analysed using pan-caspase inhibition (z-VAD-fmk) and caspase-2 inhibition (z-VDVAD-fmk). Results: RCC apoptosis was significantly lower (p < 0.05) than in HK2s after treatment, confirming their chemoresistance. Pro-caspase-3 (32 kDa) was detected in all cell lines. Cleaved caspase-3 (19 kDa) was not detected by Western immunoblots in treated RCCs and only minimal activated caspase-3 was detected in treated RCCs using immunohistochemistry. All cells had pro-caspase-2 (48 kDa) and the activated form (33 kDa) appeared in all treated cells. Caspase inhibition caused a reduction in, but not negation of, therapy-induced apoptosis in HK2s and RCCs (p < 0.05 for HK2s and ACHN cells), indicating that a caspase activation pathway must occur in RCC apoptosis but this pathway does not act via caspase-3 cleavage. Inhibition of caspase-2 reduced apoptosis only in HK2s, indicating that the activated caspase-2, identified in treated RCCs, was not responsible for their apoptosis induction. Conclusion: Specific differences in caspase-3 and -2 activation were identified in renal tubular epithelium and RCCs after chemotherapy. Identification of RCC-specific caspase inactivation or redundancy may explain, in part, the resistance of RCCs to cancer therapies and may be useful in targeting apoptotic pathways to overcome RCC resistance to treatment.

Caveolins in the repair phase of acute renal failure after oxidative stress

SUMMARY:  Ischaemia‐reperfusion and toxic injury are leading causes of acute renal failure (ARF). Both of these injury initiators use secondary mediators of damage in oxygen‐derived free radicals. Several recent publications about ischaemia‐reperfusion and toxin‐induced ARF have indicated that plasma membrane structures called caveolae, and their proteins, the caveolins, are potential participants in protecting or repairing renal tissues. Caveolae and caveolins have previously been ascribed many functions, a number of which may mediate cell death or survival of injured renal cells. This review proposes possible pathophysiological mechanisms by which altered caveolin‐1 expression and localization may affect renal cell survival following oxidative stress.

Senescence-associated changes in human primary proximal tubular epithelial cells

Disease Jeff S Coombes, Amanda Crawford, Robert G Fassett, 3 Dale A Kunde, Iain K Robertson, Madeleine J Ball, Dominic P Geraghty School of Human Movement Studies, University of Queensland, Brisbane, Queensland, AUSTRALIA School of Human Life Sciences, University of Tasmania, Launceston, Tasmania, AUSTRALIA 3 Royal Brisbane and Womens Hospital, Brisbane, Queensland, AUSTRALIA Project funded by the Clifford Craig Medical Research Trust (C Prosser Green Endowment)

Renal age-related chronic disease is associated with key cellular and molecular changes that are modulated by hypertension and obesity

Coexistence of anti-glomerular basement membrane (anti-GBM) antibody and antineutrophil cytoplasmic antibody (ANCA) with myeloperoxidase specificity (MPO-ANCA) exists in a substantial proportion of patients with rapidly progressive glomerulonephritis (RPGN). There is sparse literature on these ‘double positive’ RPGN, without consensus on the different approaches for optimal preservation of renal function and prevention of pulmonary hemorrhages. A previously healthy 71 year old female presented with persistent peripheral edema and general malaise. Serum creatinine level of 8.5 mg/dl and serum potassium level of 6.8 mEq/l prompted emergent hemodialysis. Antibody panels revealed both antiGBM antibodies (142 EU, normal range 0.0–9.0 EU) and MPO-ANCA (13.3 U/ ml, normal range 0.0–8.9 U/ml). Indirect immunofluorescent assay using patient’s sera showed perinuclear staining, confirming the P-ANCA. Renal biopsy revealed histologic features of cellular crescents and global sclerosis, but absence of immunoglobulin deposition in the glomerulus. Typical IgG linear deposition was illustrated in normal human glomeruli using patient’s sera. We started her on steroid and plasma exchange therapy based on the recent findings that ANCA is responsible for pulmonary hemorrhage. Her serum anti-GBM antibody and MPOANCA decreased to subclinical levels after one month of therapy. She was free of pulmonary complication, although persistently dialysis dependent. More work is needed to define the clinical approach for patients with simultaneous ANCA and anti-GBM.

Immunotherapy and radiation increase apoptosis in renal cell carcinoma: Identification of potential diagnostic markers

Coexistence of anti-glomerular basement membrane (anti-GBM) antibody and antineutrophil cytoplasmic antibody (ANCA) with myeloperoxidase specificity (MPO-ANCA) exists in a substantial proportion of patients with rapidly progressive glomerulonephritis (RPGN). There is sparse literature on these ‘double positive’ RPGN, without consensus on the different approaches for optimal preservation of renal function and prevention of pulmonary hemorrhages. A previously healthy 71 year old female presented with persistent peripheral edema and general malaise. Serum creatinine level of 8.5 mg/dl and serum potassium level of 6.8 mEq/l prompted emergent hemodialysis. Antibody panels revealed both antiGBM antibodies (142 EU, normal range 0.0–9.0 EU) and MPO-ANCA (13.3 U/ ml, normal range 0.0–8.9 U/ml). Indirect immunofluorescent assay using patient’s sera showed perinuclear staining, confirming the P-ANCA. Renal biopsy revealed histologic features of cellular crescents and global sclerosis, but absence of immunoglobulin deposition in the glomerulus. Typical IgG linear deposition was illustrated in normal human glomeruli using patient’s sera. We started her on steroid and plasma exchange therapy based on the recent findings that ANCA is responsible for pulmonary hemorrhage. Her serum anti-GBM antibody and MPOANCA decreased to subclinical levels after one month of therapy. She was free of pulmonary complication, although persistently dialysis dependent. More work is needed to define the clinical approach for patients with simultaneous ANCA and anti-GBM.

Mitochondrial dysfunction in senescing renal tubular epithelial and vascular endothelial cells

Aim: To identify whether the macrophage CSF-1 receptor promotes macrophage accumulation and the progression of nephropathy in type 2 diabetic mice. Background: Macrophages are the key inflammatory cells associated with the development and progression of diabetic nephropathy. CSF-1, which is up-regulated in diabetic kidneys, is required for the proliferation, differentiation and activation of monocyte-macrophages and exerts its effects through its receptor tyrosine kinase encoded by the c-fms proto-oncogene. Blockade of c-fms in acute renal disease has proved beneficial in an animal model of renal allograft rejection but the role of c-fms in diabetic nephropathy has not been examined. Methods: Obese, diabetic db/db BL/KS mice with established albuminuria were treated with intraperitoneal injections of neutralizing anti-c-fms mAb (AFS98, 50 mg/kg/twice weekly) or isotype matched control IgG (50 mg/kg/twice weekly) from 12 to 18 weeks of age. Results: Administration of AFS98 mAb did not affect obesity, hyperglycaemia, circulating monocyte levels or the established albuminuria of db/db mice. However, treatment with AFS98 suppressed renal inflammation by reducing kidney macrophages (accumulation, activation and proliferation), MCP-1 levels (mRNA and urine protein), kidney activation of proinflammatory pathways (JNK and ATF-2), and TNF-a mRNA. In addition, AFS98 treatment decreased tubular injury (apoptosis and hypertrophy), interstitial damage (cell proliferation and myofibroblast accrual) and renal fibrosis (TGF-b and collagen IV mRNA), indicating that c-fms antibody can also inhibit the damage caused by inflammation in diabetic kidneys. Conclusions: Treatment with a neutralizing c-fms antibody demonstrates that macrophage activation through the CSF-1 receptor induces renal inflammation and injury in type 2 diabetic mice, supporting the concept that macrophages promote diabetic nephropathy.