C HUANG, L ZHANG, H YI, Y SHI, XM CHEN, C POLLOCK
Renal Laboratory, Sydney Medical School, The University of Sydney, Kolling Institute, Royal North Shore Hospital, St Leonards, New South Wales
Aim: This study aimed to investigate the therapeutic effect of KCa3.1 inhibi- tor TRAM34 in a mouse model of established diabetic nephropathy.
Background: Existing treatments of established diabetic nephropathy have not been proven to have long term efﬁcacy. Hence it is urgent to discover novel therapeutic targets to retard diabetic nephropathy. KCa3.1, a calcium activated potassium channel, is known to regulate calcium entry into cells and thereby modulate calcium-signalling processes. We have previously demonstrated in murine models of diabetes mellitus that gene silencing or pharmacological blockade of KCa3.1, prevented the subsequent development of diabetic induced interstitial ﬁbrosis through inhibition of TGF-β1 signalling pathway.
Methods: Diabetic eNOS-/- mice with established nephropathy (24 weeks after induction of type 1 diabetes induced by streptozotocin) were administrated with TRAM34 or DMSO (vehicle control) for a further 14 weeks. After termination, renal function and structure were assessed as well as inﬂammatory, ﬁbrotic markers and the TGF-β1 signalling pathway.
Results: The 24h urinary albumin was signiﬁcantly increased in the diabetic animals compared to the non-diabetic controls (P< 0.01). Albuminuria was signiﬁcantly reduced in TRAM34 treated diabetic animals compared to the diabetic group (P<0.05). Immunohistochemistry demonstrated increased CD68 and F4/80 expression, indicating increased macrophage inﬁltration in the diabetic animals (P< 0.05), which was reversed by treatment with TRAM34 (P< 0.05). Similarly, TRAM34 reversed the increased mRNA and protein expression of type I and type III collagen and ﬁbronectin observed in the diabetic animals (P< 0.05). Furthermore, blocking the KCa3.1 channel by TRAM34 led to the reduction of TGF-β1 signalling through inhibiting phosphorylation of Smad2/3 (P< 0.05).
Conclusions: Blockade of KCa3.1 by TRAM34 is a promising therapeutic intervention in established diabetic nephropathy.