Perineurium inflammation and altered connexin isoform expression in a rat model of diabetes related peripheral neuropathy

Diabetes related peripheral neuropathy involves both somatic and autonomic nerves and leads to an array of debilitating abnormalities. Mechanisms may include decreased neuronal conductance, reactive oxygen species, and decreased performance of the perineurium blood-nerve barrier. Here we studied the perineurium characteristics of the dorsal penile nerve in a rat model of diabetes related peripheral neuropathy. Immunohistochemistry showed extensive and perineurial cell-specific nitric oxide synthase2 staining in diabetic animals as compared to age matched controls (P < 0.05); however no apparent difference in immunostaining pattern was observed for 3-nitrotyrosine (a stable biomarker of peroxynitrite formation). Significant reductions in connexins 32 and 26 were seen in the diabetic perineurium with no detectable levels of connexin 43 in either control or diabetic dorsal nerve. These data provide new evidence of perineurial cell inflammatory responses and altered gap junction protein expression during diabetes related neuropathies and suggests that strategies to protect this cell type may have therapeutic value.