Mechanisms of Schwann Cell injury in diabetes : role of the Cytochromes P450 Pathway -

Abstract

Background: Among the microvascular complications associated with diabetes, diabetic neuropathy (DN) is one of most commonly reported affecting 50percent - 70percent of diabetic subjects. Clinically, DN is characterized by reduced electrophysiological recordings, sensorimotor loss, and paresthesia. Research has correlated these observations with nerve fiber injury leading to degeneration, axonal atrophy, demyelination with limited regenerative potential. The pathogenesis of DN remains to be elucidated; however, ROS production is now considered the final common key mediator. Cytochrome P450 (CYPs) enzymes are known to be major sources of ROS and have been shown to mediate other diabetic complications. Yet, no studies have investigated their role in DN. Aim: The following study aims to investigate CYP4A enzymes as a source of ROS in Schwann cells (SCs) and sciatic nerves. Alteration in CYP4A expression is studied in addition to SC apoptosis and myelin protein level alterations. The effects of hyperglycemia and CYP4A inhibition via HET0016 are further investigated in vivo to study behavioral changes, peripheral nerve injury and alterations in AKT signaling, a key pathway involved in myelination. Methods: Mouse Schwann Cells (MSC80) cultured in a hyperglycemic milieu and 10-week Type II Diabetic MKR adult male mice were used to model a diabetic phenotype for this study. Western blot analyses were performed to assess alterations in CYP4A, phosphorylated-AKT and myelin protein levels in SCs and Sciatic nerves. The Cellular DNA Fragmentation Assay was used to assess SC apoptosis. Dihydroethidium (DHE) staining and NADPH oxidase activity assay were used for the detection of intracellular ROS in sciatic nerves. Sensorimotor function was assessed via three behavioral tests: The Raised Beam Walking test, Hind paw Withdrawal test and Grip Strength test. Results: Hyperglycemia resulted in CYP4A upregulation at the level of SCs and Sciatic nerves which correlated with alterations in myelin protein levels, increased SCs apoptosis and ab