Ellagic acid prevents submandibular gland inflammation in a rat model of hypertension with nitric oxide deficiency

P. Prachaney¹, R. Samrid¹, P. Boonprom¹, T. Berkban², P. Pakdeechote³, K. Chaisiwamongkol¹, P. Chaiyarit⁴. ¹Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand, ²Anatomy, Faculty of Medicine, Mahasarakham University, Mahasarakham, Thailand, ³Physiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand, ⁴Oral Diagnosis, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand.

Introduction: It has well established that administration of N^ω-nitro-L-arginine methyl ester (L-NAME) results in systemic hypertension¹ and vascular inflammation². Recently, biological differences of submandibular gland between control and hypertensive rats which induced by L-NAME have been reported³. Ellagic acid (EA) is a natural polyphenolic compound (Fig. 1) present in fruits, such as strawberries, grapes, pomegranates, and nuts⁴, and possesses anti-inflammatory activities⁵. The aim of this study was to investigate whether EA can prevent submandibular gland inflammation in hypertensive condition. 

Method: Hypertension was induced in male Sprague-Dawley rats by administration of L-NAME (40 mg/kg) in drinking water and simultaneously treated with EA (15 mg/kg/day, p.o.) for three weeks (n= 6/each group). Systolic blood pressure (SBP) was measured once a week using a tail cuff method. Submandibular glands weight was recorded and histomorphology was investigated by Hematoxylin and Eosin (H&E) staining. The Western blot analysis was used to determine an iNOS protein expression. Data were expressed as mean±S.E.M. Statistical analysis was tested by one-way analysis of variance (ANOVA) and followed by Student Newman-Keul's test. 

Results: L-NAME treated rats has higher SBP than the values in control and L-NAME + EA group (p<0.05, Fig. 2). Submandibular gland weight in L-NAME rats was higher than that in control (0.43 g ± 0.01 vs 0.34 g ± 0.01, n=6, p<0.05) and this was prevented by EA (0.36 g ± 0.01, n=6, p<0.05). Although histomorphology by H&E did not show the difference among groups, the expression of iNOS protein in submandibular glands from L-NAME rats was significantly upregulated when compared to the control (p<0.05). Preventive treatment of EA significantly alleviated iNOS protein overexpression (p<0.05, Fig. 3). 

Conclusion: These results indicate that EA can effectively prevent submandibular inflammation of rats with hypertensive condition.

References:

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