12/15-Lipoxygenase and Diabetic Neuropathy

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DESCRIPTION (provided by applicant): Evidence for the important role of arachidonic acid metabolism in diabetes complications is emerging. Recent in vivo and cell culture studies including those from our group revealed that 12/15-lipoxygenase (12/15-LO) 1) contributes to impaired cell signaling and inflammatory response; and 2) is implicated in the pathogenesis of endothelial dysfunction, nephropathy and retinopathy, associated with diabetes. The objective of this proposal is to evaluate the role of 12/15-LO in peripheral diabetic neuropathy (PDN) using animal models of Type 1 and Type 2 diabetes and high glucose-exposed co-cultures of mouse Schwann cells and DRG neurons and cultures of human Schwann cells (HSC). Our preliminary data indicate that 1) 12/15-LO is abundantly expressed in the peripheral nerve and its expression and activity increase in diabetic conditions; 2) 12/15-LO-/- mice develop less severe PDN than wild-type mice; 3) some manifestations of PDN in STZ-diabetic mice are reversed by a short-term 12/15-LO inhibitor treatment; 4) 12/15-LO overexpression is manifest after a short-term (24h) exposure of HSC to high glucose; and 5) a 12/15-LO inhibitor treatment counteracts high glucose-induced mitogen-activated protein kinase (MAPK) phosphorylation in HSC. The SPECIFIC AIMS are 1) evaluate two structurally unrelated 12/15-LO inhibitors on functional, biochemical and structural indices of PDN in mouse models of Type 1 and Type 2 diabetes, i.e., STZ-diabetic and high-fat diet fed mice; 2) compare severity of PDN in 12/15-LO-/- mice and wild-type mice with Type 1 and Type 2 diabetes; 3) assess the role for the most important, "upstream", mechanism of PDN, i.e. increased aldose reductase activity, in 12/15-LO upregulation, and 4) examine the contribution of 12/15-LO to MAPK activation, in peripheral nerve, spinal cord and DRG neurons in the afore-mentioned animal and cell culture models. The project will combine physiological, behavioral, biochemical, immunohistochemical and structural studies in animals with biochemical (HPLC, Western blotting, spectrofluorometric enzymatic assays) and molecular (real-time PCR, siRNA transfections) approaches in cell culture models. The findings will generate new information on the role for 12/15-LO in PDN of Type 1 and Type 2 diabetes, and may provide rationale for development of 12/15-LO inhibitors for its prevention and treatment.