Antihypertensive and renoprotective effect of the kinin pathway activated by potassium in a model of salt sensitivity following overload proteinuria.

The albumin overload model induces proteinuria and tubulointersitial damage, followed by hypertension when rats are exposed to a hypersodic diet. To understand the effect of kinin system stimulation on salt-sensitive hypertension and to explore its potential renoprotective effects, the model was induced in Sprague-Dawley rats that had previously received a high-potassium diet to enhance activity of the kinin pathway, followed with/without administration of icatibant to block the kinin B₂ receptor (B₂R). A disease control group received albumin but not potassium or icatibant, and all groups were exposed to a hypersodic diet to induce salt-sensitive hypertension. Potassium treatment increased the synthesis and excretion of tissue kallikrein (Klk1/rKLK1) accompanied by a significant reduction in blood pressure and renal fibrosis and with downregulation of renal transforming growth factor-β (TGF-β) mRNA and protein compared with rats that did not receive potassium. Participation of the B₂R was evidenced by the fact that all beneficial effects were lost in the presence of the B₂R antagonist. In vitro experiments using the HK-2 proximal tubule cell line showed that treatment of tubular cells with 10 nM bradykinin reduced the epithelial-mesenchymal transdifferentiation and albumin-induced production of TGF-β, and the effects produced by bradykinin were prevented by pretreatment with the B₂R antagonist. These experiments support not only the pathogenic role of the kinin pathway in salt sensitivity but also sustain its role as a renoprotective, antifibrotic paracrine system that modulates renal levels of TGF-β.