Decreased Interleukin-6 (IL-6) Synthesis in Sciatic Nerve Axotomy on Streptozotocin-Induced Diabetic Rats

Abstract

It is well-known that impaired nerve fiber regeneration is one of the major pathogens in diabetic neuropathy. In other hand, it has also been suggested that IL-6, one of the inflammatory cytokines, has an essential role in eliciting the nerve fiber regeneration.
We examined interleukin-6 (IL-6) levels and myelinated fiber regeneration in axotomized sciatic nerve in streptozotocin-induced diabetic rats. In non-axotomized nerve, using bioassay analysis, IL-6 was found to be expressed at low levels. However, a rapid but transient increase in IL-6 synthesis occurred in axotomized nerves, peak levels being reached less than three days after nerve injury. At 35 days after axotomy, myelinated fiber regeneration was quantitated using light microscopic morphometry. Regenerated fiber density was significantly reduced in a diabetic rat, to 32% of thatin a control, rat, and fiber size also decreased. Although both sections demonstrated some remnant of fiber degeneration, such as macrophage invasion and a destructive myelin, regeneration cluster was much more noticeable in the control rat.
The study we present here demonstrates decreased IL-6 synthesis in experimental diabetic neuropathy in vivo, but the mechanism of IL-6 suppression is still unknown. Further evaluation of the dynamics of recruited macrophage and functional deficits of Schwann cells on the nerve injury are required.