Efficacy/mechanisms of curcumin in diabetic nephropathy

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Diabetic (DM) nephropathy (DN) is the commonest cause of end stage renal disease. Albuminuria (Ualb) exacerbates DN by ill-defined mechanisms. Podocytes (podo) modulate Ualb via actin cytoskeleton (Actskn) chnages mediated by signaling events. We showed that phospho-p38MAPK induces biphosphorylation (p2) of podo heat shock protein 25 (HSP25, rodents; HSP27, humans) in response to acute glycemic stress, in an adaptation to maintain podo Actskn and prevent Ualb. Adaptation fails later. We also showed that the 12/15 lipoxygenase (LO) pathway of arachidonate metabolism mediates glucose, angiotensin II, PDGF, and TGF- beta actions in podo and mesangial cells, all underlying DN. 12/15LO knockout DM mice exhibit inhibition of renal cortical TGF-beta and CTGF mRNAs, TGF-beta expression, Smad 2/3 signaling, and proteinuria. Thus, our data implicate HSP25 and 12/15LO pathways in DN. Evidence relates the pathways: chemical LO inhibition stimulates HSP27, providing a key pathogenetic link between the benefits conferred by each. The biologic actions of the dietary spice curcumin simulate HSP25 and 12/15LO actions. It increases HSP27 and inhibits LO and TGF-beta. In rats with short-term DM, curcumin inhibited proteinuria and improved renal histology. After preliminary experiments to optimize curcumin product, dose, and route of administration, we will test the hypothesis that curcumin will: 1) Ameliorate DN in mice with long-term DM; 2) Preserve Actskn and inhibit extracellular matrix synthesis by enhancing HSP25 and inhibiting 12/15LO and TGF-beta; 3) Exhibit multiple salutary effects, making it comparable or superior to either HSP27 overexpression or 12/15LO inhibition alone as therapy; and 4) Induce interactions linking HSP27 and 12/15LO. Using novel HSP27 gain of function and 12/15LO loss of function mouse mdoels and state of the art molecular techniques, these studies assess efficacy and define underlying mechanisms of curcumin action. HSP27, TGF-beta, and 12/15LO are not now modifiable directly be medications. In Phase 1trials, humans tolerated curcumin well in doses up to 8 gm/day. A Phase 2 trial for Alzheimer disease is in progress. Efficacy in experimental DN could translate rapidly into a testable therapy for patients.