Semiquantitation was performed using the gel documentation system (BioDO, Analyser, Biometra, Germany) supplied by Biometra according to the following amplification procedure: relative expression of studied gene (R) was calculated following the formula: R=Densitometrical Units of each studied gene/Densitometrical Units of β-actin (Table 2).
Data was coded and entered using the statistical package SPSS version 17 (SPSS, Inc., Chicago, Illinois, USA). Data were summarized using mean±standard deviation for quantitative variables and percentage for qualitative variables. Comparisons between groups were made using χ2 tests for qualitative variables and analysis of variance for normally distributed quantitative variables. Correlation was carried out to test the linear relationship between quantitative variables. A P value of less than 0.05 was considered statistically significant.
The study included 20 patients; 12 male (60%) and eight female (40%). Their age ranged from 10–46 years with a mean of 26.7±10.9 years. Fifteen controls were included in the study, seven male (46%) and eight female (53%). Their age ranged from 15 to 42 years with a mean of 27.7±7.6 years. Both patients and controls were age-matched (P=0.737) and sex-matched (P=0.157) (Table 3).
The mean Cx43 mRNA expression in the patients was 1.23±0.1 μg/gm tissue and 0.27±0.05 in the control group. This denotes a significant statistical difference between the groups (P=0.000) revealing higher expression in patients with atopic dermatitis (Fig. 3).
No statistically significant correlation was present between each of sex, age, duration of the disease, and CX43 expression.
This study revealed a significant increase in Cx43 mRNA expression in atopic skin when compared with normal skin (P=0.000). To the best of our knowledge no previous studies have detected any relationship between Cx43 and atopic dermatitis.
Cxs are the structural GJ proteins that form channels for the exchange of small molecules between connected cells. The cells efficiently use these GJs for electrical synapse and sharing of intracellular metabolites that coordinate various metabolic events . Cx43 is located both in the interfollicular epidermis and in adnexal structures . It is expressed by most of the immunocompetent cells including macrophages, neutrophils, mast cells, and lymphocytes . It is also expressed along with Cx40 in polymorphonuclear cells under inflammatory conditions in humans . The increased expression of Cx43 has been shown to increase the levels of various inflammatory and immunomodulatory molecules such as interleukin-1 and interleukin-6, transforming growth factor-β in cocultured endothelial cells, and smooth muscle cells . Cx43 is known to be regulated by various factors such as glucose  and nitric oxide ; and growth factors such as fibroblast growth factors , transforming growth factor-β , Epidermal growth factor , platelet-derived growth factor , nerve growth factor , ATP , and few cytokines such as tumor necrosis factor-α and interferon-γ  though the precise molecular mechanisms by which they regulate Cx43 are not fully understood.
Altogether, and from our results that showed higher expression of Cx43 in atopic patients, we hypothesize that the disease might start by downregulation of the TJ (which can be triggered either by extrinsic or intrinsic factors) leading to decreased binding to Cx43 and hence its upregulation. The increased level of Cx43 then excites an inflammatory response, as Cx43 has been shown to increase the levels of various inflammatory and immunomodulatory molecules . This explains the higher level of the protein in severe cases detected in this study, although the difference was not statistically significant. This could be more evident if we could increase the number of studied groups of patients with atopic dermatitis with different degrees of severity in future studies.
Another explanation, is that increased expression of Cx43 increased expression in the disease could be a primary event, and as it is reported that it actually regulates the expression and function of TJ proteins its increased expression will lead to defective TJ, resulting in an epidermal barrier defect that will contribute to the evolution of atopic dermatitis.
In contrast, some other studies have reported that any cytosolic stress inhibits the dislocation and degradation of different Cxs . Some evidence indicates that allergic and inflammatory skin diseases such as atopic dermatitis, urticaria, and psoriasis are mediated by oxidative stress. Mast cells generate mainly intracellular reactive oxygen species following the aggregation of FceRI; these reactive oxygen species may act as secondary messengers in the induction of several biological responses . This raised another possibility that the disease through inducing this form of oxidative stress on tissues, might lead to decreased degradation of Cx43 hence elevating its level and aggravating the inflammation.
There are no conflict of interest and funding sources declared.
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