Effect of inhalation of different-concentrations of moxa smoke on apoptosis and regeneration of olfactory epithelial cells in rats

Abstract

To observe the effect of long-term inhalation of moxa-smoke on olfactory epithelial cells in rats, in order to explore the safety of moxa-smoke inhalation (MSI). A total of 32 SD rats (half male and half female) were randomly divided into 4 groups: normal, low concentration (LCMSI), medium concentration (MCMSI) and high concentration (HCMSI), with 8 rats in each group. Rats of the LCMSI, MCMSI and HCMSI groups were put into closed boxes which were filled with ignited moxa stick-released smoke at concentrations of (0.11±0.05)mg/m3, (0.23±0.05) mg/m3 and (0.53±0.05)mg/m3, respectively. The treatment was given 4 h each time, twice a day for 90 days. Rats of the normal group were fed routinely. The rats' general state and behavior (including fur appearance, activities in cage, response to external stimuli, spirit, stool, diet and water drinking) were recorded, and the olfactory function was assessed by using latency of finding the buried food pellet (BFP) test. The number of apoptotic olfactory epithelial cells was counted after terminal labeling (TUNEL), and the proliferation of basal cells of the nasal mucosa was detected by BrdU incorporation immunohistochemical technique. The latency of BFP was significantly longer in the MCMSI and HCMSI groups than in the normal and LCMSI groups (P<0.01), and had no significant differences between the LCMSI and normal groups, and between the MCMSI and HCMSI groups (P>0.05). The numbers of the apoptotic olfactory epithelial cells and proliferative basal cell in the nasal mucus tissue were markedly more in the LCMSI, MCMSI and HCMSI groups than in the normal group (P<0.01, P<0.05), and obviously more in the MCMSI and HCMSI groups than in the LMCMSI group (P<0.01), and apparently more in the HCMSI group than in the MCMSI group (P<0.01). The general state observation showed that in the first 45 days, only yellowish fur and water intake increase were seen in rats of the 3 moxa smoke inhalation groups, while no obvious changes in rats of the LCMSI group, and decrease in activities, being sensitive to external stimulation and fiddle-footed, and lower spirit in rats of the MCMSI and HCMSI groups in comparison with rats of the normal group after 90 day's MSI. Long-term inhalation of medium and high concentrations of moxa smoke may cause a reduction of the olfactory sensitivity and an increase of apoptosis of olfactory epithelial cells and proliferation of basal cells.