Experimental Induction of Local and Systemic Food Allergy Using Ovalbumin in Rats: Pathology and Treatment by Glucocorticoids and Omega-3 Fatty Acids

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Immunologically mediated enteropathies consist of a group of different disease that is characterized by varying degree of villous destruction in the small intestine. Examples of these diseases are celiac disease and food allergy (Marsh, 1996 and Westerholm -Ormio, 2004). Food allergy is treated in human and experimental animals by using either omega-3 (Nagafuchi, et al., 2000; Nagura, et al., 2002; and Takano et al., 2004 ) or dexamethasone (Krishnaswamy, et al., 2001; Sampson, 2003 and Kamingawa and Nanno, 2004).
The aim of this work is to induce OVA food allergy and to study their pathogenesis, gross and microscopic changes and try to treat the induced condition by using omega-3 fatty acids and dexamethasone.
1-Experimental design (A)- Local anaphylaxis protocol The animals were divided into 4 groups.
All rats except the control group were exposed to chicken egg albumin by daily gavages dosing for 44 days without the use of an adjuvant. The dexamethasone treated group received single intraperitoneal injection of 1 mg of dexamethasone per week and the omega-3 treated group received daily gavage dosing with 0.1 ml of code liver oil (that provide 6.8mg eicosapentaenoic acid (EPA) and 4.9mg docosa-hexaenoic acid (DHA).

-Systemic anaphylaxis protocol The animals were divided into 4 groups. These animals except the control group received the sensitization dose which consisted of intra-peritoneal injection of 10 μg of chicken egg albumin protein and 10 mg of aluminum hydroxide [Al
(OH) 3] as adjuvant in 0.9 % saline. After 15 day sensitization, the rats exposed to 1 mg chicken egg albumin protein / ml tap water, 1 ml per animal by daily gavages dosing for 44 days. The dexamethasone treated group received single intra-peritoneal injection of 1 mg of dexamethasone per week and the omega-3 treated group received daily gavage dosing with 0.1 ml of code liver oil.

2-Histopathological analysis
Tissue samples were taken from duodenum, jejunum and ileum and were prepared for morphometric analysis, IELs and morpho-pathological examination.
The statistical analysis was performed by using Students t-test using GraphPad Prism version 5.01 Program by Graph Pad software Inc. The results were considered significant if P < 0.05.
In both local and systemic food allergic experiments, administration of ovalbumin (OVA) induced allergic enteritis in the duodenum, jejunum and ileum. This inflammation could be classified into: A-Acute serous enteritis. BSubacute sero-catarrhal enteritis-Chronic catarrhal enteritis. The components of inflammation were: Degenerative and necrobiotic changes in the lining epithelium of villi and crypts, non significant in the acute phase and prominent in the
subacute and chronic phases. Thrombosis in the blood vessels in the three phases.
Intraepithelial lymphocytosis in both villi and crypts. Inflammatory exudates were infiltrating villi cores and lamina propria. Vasculitis. Villi and crypts hyperplasia and goblet cell metaplasia of the lining epithelium in the subacute phase.
Fibrocytic cells proliferation was infiltrating villi cores and lamina propria in the subacute and chronic phases. Germination of submucosal lymphoid follicles.
These inflammatory reactions lead to changes in the shapes of villi and crypts and decrease of villi heights and crypts depths.
Omega-3 was better than dexamethasone in the correction of: 1-IELs of the villi and crypts in local allergic duodenitis and jejunitis and in systemic allergic ileitis. 2-The villi heights in the three small intestinal segments in both local and systemic food allergy.

3-The crypts depths in the duodenum and ileum in local food allergy and in the three small intestinal segments in systemic food allergy.

4- In normalizing the atypical regeneration in the three small intestinal segments in systemic food allergy.5-In transforming the submucosal lymphoid follicles to diffuse mature lymphocytes in the three small intestinal segments in both local and systemic food allergy, vise versa to dexamethasone which caused lymphoid exhaustion.

Dexamethasone was better in the correction of:
1-Crypts depths in local allergic jejunitis.
2- IELs in both villi and crypts in systemic allergic duodenitis and jejunitis.
3- In normalizing the atypical regeneration in the jejunum and ileum in local food allergy.

The two drugs had similar effects in the following:
1- In preventing vasculitis and thrombosis in the three small intestinal segments in both local and systemic food allergy.
2- In preventing the IELs in both ileal villi and crypts in local food allergy. 3- In normalizing the villi shape in the three small intestinal segments in both local and systemic food allergy.

Finally, we suggest the use of daily course of omega-3 treatment together with dexamethasone injection weekly for 45 days

Experimental Induction of Local and Systemic Food Allergy Using Ovalbumin in Rats: Pathology and Treatment by Glucocorticoids and Omega-3 Fatty Acids

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