Effect of acupoint injection on olfactory dysfunction and apoptosis of olfactory mucosal cells in rats with allergic rhinitis

To observe the effect of acupoint injection on olfactory function, olfactory mucosa structure, olfactory mucosa apoptosis and apoptosis-related protein expression in rats with olfactory dysfunction of allergic rhinitis (AR), so as to explore its mechanisms underlying improvement of AR olfactory dysfunction.

Thirty-six SD rats were used in the present study. Nine of them were randomly selected to be used as the normal group, and the rest of the rats were used to prepare the AR olfactory dysfunction model by ovalbumin sensitization. After successful modeling, the AR model rats were allocated to the model, non-meridian non-acupoint injection, and acupoint injection groups, with 9 rats in each group. For rats of the acupoint injection group, an isotonic mixture (0.05 mL/point) of dexamethasone and lidocaine was injected into the bilateral ”Yingxiang” (LI20) once every 3 days, for a total of 4 times. For rats of the non-meridian non-acupoint injection group, the same mixture solution (0.05 mL/point) was injected into the midpoint of the line connecting “Houhai” (GV1) and “Huantiao” (GB30) on both sides. The frequency and course of treatment were the same as those of the acupoint injection group. The rats’ nasal symptoms were observed and scored, the olfactory function was evaluated by buried food pellet test (BFPT). The histopathological changes and ultrastructure of the olfactory mucosa were observed by H. E. staining and transmission electron microscopy. The contents of serum interleukin (IL) 4, IL-5, IL-13 and IL-17 were detected by ELISA. The expression of olfactory marker protein (OMP) in the olfactory mucosa was detected by immunofluorescence method, and apoptosis of olfactory mucosal cells was detected by TUNEL method. The expression levels of cysteine aspartate protease-3 (Caspase-3), B lymphoblastoma-2 related gene X protein (Bax), and B lymphoblastoma-2 gene (Bcl-2) proteins of the nasal mucosa were detected by Western blot.

The histopathological and ultrastructural observations showed that in the model group, the olfactory mucosal epithelium was severely shed, and the intrinsic layer cells were degenerated and necrotic with inflammatory infiltration; the outer mitochondrial membrane was blurred and broken, and the cristae structure dissolved and disappeared. But compared with the model group, the acupoint injection group had an apparent improvement in the structure of the olfactory mucosa, and a relatively complete and unambiguous structure in the outer mitochondrial membrane and cristae of the inner membrane. Compared with the normal group, the model group had a significant increase in the nasal symptom score, search time for food goblet, apoptosis rate of olfactory mucosal cells, contents of serum IL-4, IL-5, IL-13 and IL-17, and expression of Caspase-3 and Bax proteins in the nasal mucosa (P<0.01), and a notable decrease in the immunofluorescence density of OMP and expression of Bcl-2 in the olfactory mucosa tissue (P<0.01). After non-meridian non-acupoint injection and acupoint injection, both the increase and decrease of the indexes mentioned above were all reversed (P<0.05, P<0.01). Comparison between the two injection groups showed that the effects of the acupoint injection group were significantly superior to those of the non-meridian non-acupoint injection group in all indexes (P<0.01).

Acupoint injection can significantly improve olfactory function and olfactory mucosal damage in rats with AR olfactory dysfunction, which may be related to its functions in inhibiting the inflammatory damage and reducing cell apoptosis of the olfactory mucosa.