Discussion
At present, the mechanism of immunity and allergy in OME pathogenesis is
still controversial. Yellon et al. [11] first detected IL-1, IL-2,
TNF-, INF-and IL-6 in middle ear exudate of children with chronic OME
and found the incidence was 51%, 54%, 63%, 19% and 36%,
respectively. Doyle W J [12] found that Ⅰ type such as allergy, Th2
cytokines and cell infiltration is likely to be the main cause of OME
persist. Sobol et al. [13] found that Th2 cytokines IL-4, IL-5 and
eosinophils were significantly higher than those with negative skin
tests in the OME middle ear effusion with positive allergens.
Treg cell transcription factor is Foxp3, which mainly secretes cytokines
such as TGF- and IL-10, and Treg cells participate in immune
pathogenesis [14-16]. Th17 transcription factor is ROR T, mainly
secreting IL-17A-F and IL-6 series cytokines, which plays a
physiological role in allergic and autoimmune diseases. IL-17 levels
were significantly increased in rheumatoid arthritis, asthma and other
immune diseases [15-16]. We found increased level of Th17 and
inflammatory factor IL - 6 and reduced Treg cells factor TGF – beta and
IL - 10 in OME.
In addition, ROR T/Foxp3 equilibrium also determines the direction of
initial T cell differentiation toward Th17 or Treg cells [17]. In
this study, the expression of ROR T was increased in PC group and
decreased in NC group. However, Foxp3 expression was decreased in PC
group and increased in NC group. In OME model group in middle ear
mucosa, ROR gamma t has a strong positive expression and Foxp3
expression has a weak positivity, suggesting ROR gamma t/Foxp3
imbalance, further illustrating the whole body and middle ear local
Treg/th17 balance in the process of occurrence and development of OME.
Like other autoimmune diseases, middle ear mucosa as an extension of the
upper respiratory tract mucous membrane, membrane layer of epithelium
contains a lot of mucus glands, middle ear mucosa by antigen stimulation
and called out ditto mucous membrane, organs become immune activity.
Middle ear effuents in patients with OME with allergenic factors do not
clear normally and may not be caused by initial viral/bacterial
infection, but by circulating mast cells, eosinophil, etc., migrating to
the site of inflammation to act on them and trigger a programmed immune
response - ”local allergic immune response” - to allergen stimulation
[18].
HE staining of OME animal models showed that middle ear mucosa local
buoyed by allergen, middle ear mucosa thickening, local hyperemia,
tissue edema, glands expansion, plasma cells, eosinophil gathering, and
the upper and lower respiratory tract after the allergen stimulation
have the same immune response, middle ear organs become an immune
activity. Regarding this, in the experiment of animal model of
peripheral blood flow OME cytology, OME were also found in the rat model
of spleen lymphocytes with negative correlation Treg and Th17 cells, so
we speculated that the body state of sensitization may be easy to
stimulate the important factors that cause middle ear mucosa, among
them, the IL - 6 is a motivating factor with many biological activities.
In the absence of IL-6, TGF- induces FOXP3 expression, which binds to
ROR T and blocks its function, leading to the transformation of naive T
cells into Treg. However, in the presence of IL-6, it eliminates the
inhibition of FOXP3 on ROR t, leading to the conversion of naive t cells
into Th17 cells [19]. This explains, on the one hand, the increased
levels of IL-6 in middle ear effusion and peripheral blood in OME
patients.
There are more and more evidence that on allergy treatment applied to
OME aspects, this is different from the traditional upper respiratory
tract (nose, sinuses, nasopharyngeal), located at the side of the
respiratory tract (eustachian tube and middle ear tympanic cavity)
allergic inflammation and also there are links, such as OME and the
relationship between the AR epidemiology, anatomy, immunization and
pathophysiology [20]
In addition, we verified the presence of PI3K/Akt/mTOR signaling pathway
in OME, which affects T cell differentiation. Mammalian Target of
rapamycin (mTOR) is a highly conserved serine/THR kinase that is
activated and participates in the regulation of T cell growth,
proliferation and differentiation under the action of glucocorticoids,
nutrients (glucose, fatty acids, etc.) and various stressors [21].
An increasing number of studies have found that mTOR plays an important
role in the development of a variety of autoimmune diseases by breaking
the Thl7 / Treg balance, such as Systemic Lupus erythematosus (SLE) and
rheumatoid Arthritis (RA). In the experimental autoimmune
encephalomyelitis (EAE) mouse model, rapamycin was shown to inhibit Thl7
cell differentiation by blocking the mTOR/STAT3 signaling pathway
[22].The Mtorc1 inhibitor rapamycin inhibits IL-17 and promotes
Foxp3 expression, thereby selectively amplifying Treg cells and
enhancing their stability and anti-inflammatory ability [23-24].
Compared with CON, OME middle ear mucosa had increased expression of
PI3K/Akt/mTOR pathway marks, indicating activation of this signaling
pathway, leading to inhibition of Treg cells differentiation and
amplification, Treg/Th17 imbalance, and subsequent middle ear local
immune response. However, the specific mechanism of Treg reduction in
OME and its interaction with the TPI3K/Akt/mTOR signaling pathway
remains to be further studied. These results indicate that the
activation of PI3K/Akt/mTOR signaling pathway may partially inhibit the
differentiation of Tregs, thus changing the Thl7 / Treg ratio.
This study has some limitations because of ethical limitations in
obtaining middle ear mucosa and spleen tissue in OME patients and
healthy individuals. Therefore, we established the OME rat model to
compensate for local tissue detection and T cell detection in the
spleen.