|M.Sc Student||Yaccob Afif|
|Subject||Alterations in Glomerular Slit Diaphragm Proteins in|
Experimental Nephrotic Syndrome: Effects of
Different Anti-Proteinuric Therapies
|Department||Department of Medicine||Supervisor||PROF. Zaid A. Abassi|
Proteinuria is the consequence of various pathological processes affecting glomerular ultrafiltration, resulting in extensive leakage of plasma albumin and other large proteins. Massive proteinuria can lead to nephrotic syndrome (NS), a syndrome characterized by hypoalbuminemia, hyperlipidemia and edema formation. During the last decade, there has been an exponential increase in our knowledge of the structure and function of the filtration barrier, especially with the discovery of two proteins in the slit diaphragm: nephrin and podocin.
Despite the considerable advances in unraveling the pathogenesis of proteinuria, the molecular mechanisms underlying therapeutic responses of antiproteinuric regimens remain poorly elucidated. The present study was designed to study the efficacy of early and late treatment with various inhibitors of the renin angiotensin aldosterone system (RAAS), i.e., enalapril (Angiotensin converting enzyme inhibitor - ACEI) and losartan (Angiotensin receptor blocker ARB); given as monotherapy or combined, Eplerenone (Aldosterone blocker), Omapatrilat (mixed NEP and ACE inhibitor) and immunomodulatory treatment with mycophenolate mofetil (Cellcept) on the development of proteinuria in Adriamycin-induced nephropathy in rats. In addition, we examined whether antiproteinuric effects of these agents correlated with alterations in the glomerular abundance of nephrin and podocin. Injection of adriamycin (ADR) caused a significant increase in daily (from 26.96± 3.43 mg/day to 958.57±56.7 mg/day, P<0.01) and cumulative protein excretion during 6 weeks (from 900.33 ±135.50 mg to 22490.62 ±931.26 mg, P<0.001). Early treatment with enalapril significantly decreased the daily proteinuria (from 958.57±56.69 to 600.31±65.13 mg/day, P<0.001) and cumulative proteinuria (from 22490.62 ±931.26 mg to 12843.37±1798.17 mg P<0.001). Similarly, early treatment with eplerenone reduced daily proteinuria from 958.57±56.69 mg to 593.38±21.83 mg/day and cumulative proteinuria from 22490.62±931.2 mg to 16601.84±1334.3 mg; P< 0.0001. Additive effect was obtained when enalapril and eplerenone were given early to NS rats: daily urinary protein decreased from 958.57±56.69 mg to 424.17±38.54 mg/day, P<0.0001 and cumulative protein was reduced from 22490.62±931.26 mg to 10252.88±1011 mg/ day, P<0.05. A similar effect, although to a lesser extent, was obtained after omapatrilat or mycophenolate mofetil treatment. In contrast, losartan treatment did not significantly influence the cumulative proteinuria which remained comparable (20351 ± 1360 mg, P>0.05) to that observed in untreated NS rats. Nephrotic rats exhibited severe disruption of slit diaphragm structure as seen by rapid and profound loss of nephrin and podocin. Beneficial effects of enalapril, eplerenone omapatrilat, and mycophenolate mofetil paralleled the preservation of nephrin, as determined immunohistochemically, and enabled prediction of significant anti-proteinuric responses. Enalapril alone or in combination with losartan resulted in significant preservation of podocin.