Effect of Cinnamon on Benzo[a]pyrene-Treated Rats Based on Sciatic and Spinal Nerve Protein Expression

This study investigated the effects of cinnamon on benzo[a]pyrene- administered rats within the peripheral and central nerves using behavioral and molecular biological methods. As a result, the benzo[a]pyrene-administered group (Ben-DW) showed a significant decrease in locomotor activity at night compared to the corn oil-administered group (Corn-DW), but this decrease was significantly suppressed in the cinnamon-administered rat groups (Ben-3 mg CNM and Ben-10 mg CNM). In the study of sensory threshold changes using 2000 Hz electrical stimulation, the Ben-DW group showed increased sensory threshold compared with that in the Corn-DW group. However, the administration of cinnamon suppressed this increase in the threshold. In addition, the Ben-DW group experienced more oxidative stress than did the Corn-DW group, and cinnamon administration improved the oxidative stress. To investigate the relationship between behavioral and oxidative stress level changes in rats induced by administrating benzo[a]pyrene and cinnamon and assess changes in the peripheral and central nerves, cytochrome P450 (P450) 1A1 (CYP1A1), myelin-associated glycoprotein (MAG), and myelin basic protein (MBP) proteins were analyzed on the sciatic nerve fibers and spinal cord. Regarding the Aryl hydrocarbon receptor (AHR) target gene CYP1A1, the Ben-DW group had significantly increased CYP1A1 protein expression in both the sciatic and spinal nerves, when compared with that in the Corn-DW group. However, cinnamon administration on both nerves significantly suppressed that increase. For MAG protein, the Ben-DW group had significantly decreased protein expression, in comparison with that in the Corn-DW group, in the sciatic nerve fibers, and its suppression decreased in the cinnamon-treated group. However, there was no significant difference between the groups in the spinal cord. As for MBP protein, there was a slight change between the groups in both sciatic and spinal nerves, but there was no significant difference. According to these results, we can conclude that exposure to benzo[a]pyrene may cause paresthesia due to its toxicity to both the peripheral and central nerves. However, it is hypothesized that the peripheral nerves are more likely to be affected than the central nerves. In addition, herbs and herbal ingredients such as cinnamon, which have antioxidant and AHR activity inhibitory effects, may be effective in benzo[a]pyrene exposure. However, further studies are needed to clarify the action of dioxins, such as benzo[a]pyrene, on the central nervous system.