Chymase is an alternative pathway for
angiotensin-converting enzyme in
angiotensin II (Ang II) formation, and its expression is increased in human diabetic kidneys and in human mesangial cells (MCs) stimulated with high
glucose. In addition,
chymase activates
transforming growth factor (TGF-β1) via an Ang II-independent pathway. The aim of this study was to evaluate the role of
chymase on TGF-β1 activation in diabetic rats and in rat MCs (RMCs) stimulated with high
glucose (HG). Diabetes was induced in male Wistar rats by
streptozotocin (60 mg/kg, intravenous). After 30 (D30) or 60 (D60) days,
chymase activity and the expression of profibrotic markers were evaluated. RMCs were stimulated with HG in the presence or absence of 50 μmol/L
chymostatin, a
chymase inhibitor, or 100 nmol/L of
losartan, an Ang II antagonist.
Chymase activity and expression increased in D60 kidneys, with increased expression of
fibronectin, type I and III
collagen, TGF-β1 and Smad 3 and with no change in Smad 7 expression. RMCs exposed to HG presented increases in
chymase activity and expression, together with upregulation in
fibrosis markers and in the TGF-β1 signaling pathway. All these effects were reversed by
chymostatin and by
losartan, but type 1
angiotensin II receptor blockade did not interfere with the Smad 3 and 7 pathway. Similar to HG-stimulated RMCs, control RMCs treated with
chymase responded with increased expression of TGF-β1, Smad 3 and
fibrosis markers. These effects were reversed by
chymostatin but not by
losartan. The results indicate an important role for
chymase in inducing
fibrosis through TGF-β1 activation, parallel with Ang II effects.