Endothelial cell cytotoxicity induced by nephrotic serum : role of oxidant and antioxidant imbalance and its therapeutic implication

Abstract

Background A glomerular endothelial dysfunction expressed as a reduction in renal perfusion has been substantiated in variety of chronic renal diseases in particular in the severe form of idiopathic nephritic syndrome. The specific information concerning the plausible cause of glomerular endothelial dysfunction remains to be further elucidated. The progressive reduction in renal perfusion as the disease severity progresses provides a hint that certain toxic factor in the serum of such patient is suspected. That the nature of such toxic substance remains to be specifically addressed. In this regard, reactive oxygen species know to be substance that is not only derived from various sources in all cell types but also is upregulated in various renal diseases, appears to be important candidate that is likely to induce glomerular endothelial dysfunction. The excessive reactive oxygen species are noted to incriminate in the pathogenesis of progressive renal injury in both clinical and experimental settings of acute and chronic glomerular disease. Thus the preceding concerns form the main objectives of this study. Objectives The study is aimed to determine (1) the induction of endothelial cell cytotoxicity (ECC) by nephrotic serum in vitro (2) oxidant and antioxidant status in relation to endothelial cell cytotoxicity : effect of oxidative stress (3) the effect of antioxidant and vasodilator therapy in relevant to the endothelial cell function and to the prevention of renal disease progression (by determining the renal functions) Results 1. Sera from nephritic patients were capable of inducing ECC in vitro which is in accord with the clinical severity. Sera from the mild form (mesangial proliferative nephrosis) induced 16.5± 5.8% ECC whereas sera from the severe form (focal segmental glumerulosclerosis) induced 35.3± 9.3% ECC. 2. The oxidant and antioxidant study revealed an oxidant and antioxidant imbalanced state in both mild and severe forms of nephrosis. The initial values of plasma malondialdehyde (MDA) in mild and severe forms of nephrosis were 3.58± 0.7 µ M and 3.71±0.68 µ M respectively; versus 2.48±1 µ M of control. The initial values of GSH in mild and severe forms of nephrosis were 7.35±1.18µ mol/g Hb and 6.19±0.8µ mol/g Hb respectively; versus 9.09±0.66 µ mol/g Hb of control. The initial values of vitamin C in mild and severe forms of nephrosis were 1.64±1.43 mg/L and 0.57±0.74 mg/L respectively; versus 4.79±2.5 mg/L of control. The initial values of vitamin E in mild and severe forms of nephrosis were 0.11±0.03 n M respectively; versus 0.19±0.05 m M of control. Following the treatment with vitamin C (1,000 – 3,000 mg), vitamin E (400-800 U) and vasodilator (enalapril 5-20 mg/day), there had been a significant improvement in oxidant and antioxidant status. The plasma and erythrocyte MDA declined to normal level and the GSH, vitamin C and vitamin E were normalized. Such an improvement in oxidant and antioxidant status also correlated with the suppression of ECC observed in nephrosis following the therapy 3. The initial study of renal function revealed a significant impairment in both mild and severe forms of nephrosis. Of the mild form of nephrosis, the initial creatinine clearance (CCr) was 88±28ml/1.73m² (normal value 120 ml/1.73m²) and the FEMg was 2.9± 1%(normal 2.2%) Of the severe form, the initial CCr was 44.8±24 ml/min/1.73m² and the FEMg was 5.6±2.6%. The initial glomerular filtration rate (GFR) in mild and severe lorms of nephrosis were 76.5±14.8 ml/min/1.73m² and 34±13 ml/min/1.73m² respectively. The intrarenal hemodynamic study in mild form of nephrosis revealed a mild impairment.The renal plasma flow (RPF) was 538±146 ml/min/1.73m²), the peritubular capillary flow (PTCF) was 436±142 ml/min/1.73m²(normal 480 ml/min/1.73m²), the efferent arteriolar resistance (RE) was 3701±1233 dyne.s.cm⁻⁵ (normal 3000 dyne.s.cm-5 ). The intraglomerular hydrostatic pressure (PG) was 52±1.9 mm Hg (normal 53 mm Hg). Of the severe form of nephrosis, the RPF was 178±73 ml/min/1.73m², the 15648± 8538 dynes.cm⁻⁵ and the PG 55±2 mm Hg. Following the therapy with antioxidant and vasodilator, there was a significant improvement in renal function in both forms of nephrosis. Of the mild form, the CCr increased to 128± 68 ml/min/1.73m and FEMg declined to 1.8± 0.6%. Of the severe form nephrosis, the CCr rose to 60±34 ml/min/1.73m² and the FEMg declined to 4.1±2.3%. The intrarenal hemodynamics revealed a significant improvement: the RPF rose to 347±75 ml/min/1.73m, the PTCF rose to 284±63 ml/min/1.73m², the RE declined to 5302±161 dyne.s.cm⁻⁵ and the PG declined to 51±1 mm Hg. Conclusion The study renders a supportive view that the oxidant and antioxidant imbalance is likely to induce the glomerular endothelial cytotoxicity and dysfunction wit subsequent hemodynamic maladjustment in severe nephrosis by which the correction of such disorders by antioxidant therapy and vasodilators (a new therapeutic strategy, can improve the renal function and prevent the renal disease progression.