Abstract
BackgroundEdema in nephrotic syndrome results from renal retention of sodium and alteration of the permeability properties of capillaries. Nephrotic syndrome induced by puromycin aminonucleoside (PAN) in rats reproduces the biological and clinical signs of the human disease, and has been widely used to identify the cellular mechanisms of sodium retention. Unfortunately, mice do not develop nephrotic syndrome in response to PAN, and we still lack a good mouse model of the disease in which the genetic tools necessary for further characterizing the pathophysiological pathway could be used. Mouse resistance to PAN has been attributed to a defect in glomerular adenosine deaminase (ADA), which metabolizes PAN. We therefore attempted to develop a mouse line sensitive to PAN through induction of normal adenosine metabolism in their podocytes.MethodsA mouse line expressing functional ADA under the control of the podocyte-specific podocin promoter was generated by transgenesis. The effect of PAN on urinary excretion of sodium and proteins was compared in rats and in mice over-expressing ADA and in littermates.ResultsWe confirmed that expression of ADA mRNAs was much lower in wild type mouse than in rat glomerulus. Transgenic mice expressed ADA specifically in the glomerulus, and their ADA activity was of the same order of magnitude as in rats. Nonetheless, ADA transgenic mice remained insensitive to PAN treatment in terms of both proteinuria and sodium retention.ConclusionsAlong with previous results, this study shows that adenosine deaminase is necessary but not sufficient to confer PAN sensitivity to podocytes. ADA transgenic mice could be used as a background strain for further transgenesis.
Highlights
Edema in nephrotic syndrome results from renal retention of sodium and alteration of the permeability properties of capillaries
In a final experimental series, we investigated whether a second administration of puromycin aminonucleoside (PAN) might amplify its transient effect on sodium excretion and induce proteinuria in ADAtg mice
Experiments in which a unilateral nephrotic syndrome was induced by transient infusion of PAN in one kidney while preventing its access to the general circulation have demonstrated that proteinuria results from a rapid and direct effect of PAN on the kidney
Summary
Edema in nephrotic syndrome results from renal retention of sodium and alteration of the permeability properties of capillaries. Nephrotic syndrome induced by puromycin aminonucleoside (PAN) in rats reproduces the biological and clinical signs of the human disease, and has been widely used to identify the cellular mechanisms of sodium retention. Mice do not develop nephrotic syndrome in response to PAN, and we still lack a good mouse model of the disease in which the genetic tools necessary for further characterizing the pathophysiological pathway could be used. Nephrotic syndrome is defined by abnormal urinary excretion of proteins leading to hypoalbuminemia. These biological signs are secondary to alterations of the glomerular filtration barrier. Mice do not develop nephrotic syndrome in response to PAN, and no mouse model of nephrotic syndrome featuring the signs of the human disease exists yet
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