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Review
. 2007 Dec;22(12):1983-90.
doi: 10.1007/s00467-007-0521-3. Epub 2007 Jun 7.

Molecular mechanism of edema formation in nephrotic syndrome: therapeutic implications

Alain Doucet  1 , Guillaume Favre, Georges Deschênes
Affiliations
Review

Molecular mechanism of edema formation in nephrotic syndrome: therapeutic implications

Alain Doucet et al. Pediatr Nephrol. 2007 Dec.

Abstract

Sodium retention and edema are common features of nephrotic syndrome that are classically attributed to hypovolemia and activation of the renin-angiotensin-aldosterone system. However, numbers of clinical and experimental findings argue against this underfill theory. In this review we analyze data from the literature in both nephrotic patients and experimental models of nephrotic syndrome that converge to demonstrate that sodium retention is not related to the renin-angiotensin-aldosterone status and that fluid leakage from capillary to the interstitium does not result from an imbalance of Starling forces, but from changes of the intrinsic properties of the capillary endothelial filtration barrier. We also discuss how most recent findings on the cellular and molecular mechanisms of sodium retention has allowed the development of an efficient treatment of edema in nephrotic patients.

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Figures

Fig. 1
Fig. 1
Cellular mechanism of sodium reabsorption in principal cells of collecting ducts from normal rats and nephrotic rats. Sodium reabsorption in principal cells proceeds along a two-step mechanism that includes active extrusion of intracellular sodium ions by the basolateral Na,K-ATPase and passive apical entry of sodium via the amiloride-sensitive epithelial sodium channel (ENaC). In CCDs from normal rats (top panels), most ENaCs are sequestered in the intracellular compartment of principal cells (left panel), and basolateral expression of Na,K-ATPase in collecting ducts (asterisk) principal cells is very weak, in comparison with that in thick ascending limbs (T) and even proximal tubules (P) (right panel). Accordingly, the rate of sodium reabsorption is very low. In CCDs from PAN nephrotic rats (bottom panels), ENaC is expressed at the apical border of principal cells (left panel), and expression of basolateral Na,K-ATPase is drastically increased in collecting ducts (asterisk). Polarized increases in expression of ENaC and Na,K-ATPase in principal cells account for increased sodium reabsorption in CCDs. In both normal and nephrotic rats expression of Na,K-ATPase is undetectable in the glomerulus (G); in CCDs, unlabeled cells for both ENaC and Na,K-ATPase are intercalated cells (redrawn from [13, 14])
Fig. 2
Fig. 2
Profile of sodium excretion in PAN nephrotic rats. Daily urinary sodium excretion, expressed as a function of urinary creatinine excretion, following administration of puromycin aminonucleoside (150 mg/kg body wt, intravenously) in normal rats (dotted lines) or genetically modified or pharmacologically treated rats (solid lines). Arrows or grey boxes show the time of treatment. Brattleboro rats genetically lack vasopressin secretion. JB1, an inhibitor of IGF-1 receptors, was continuously administered via subcutaneous mini-pumps at a dose of 12 μg/100 g body wt per day, starting on day 3. The antagonist of AT1 receptor, irbesartan, was administered per os at a dose of 2 mg/100g body wt per day. Etanercept, a chimeric antibody directed against TNF receptor, was administered twice (days −1 and 2) at a dose of 0.2 mg/100g body wt. The inhibitor of nitric oxide synthase, L-NAME, was administered twice daily by gavage (0.5 mg/100 g body wt per 12 h) throughout the study. The antagonist of PPARγ, SR202, was given per os at a dose of 20 mg/100 g body wt. All controls were treated in parallel with the vehicle. Values are means ± SE from 4–5 rats
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References

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