Investigation of the changes in hepatic 5-hydroxytryptamine 2A receptor levels caused by lipopolysaccharide of Porphyromonas gingivalis and the effect of Thymoquinone on these changes.

Background: The present study aimed to assess the effect of Porphyromonas gingivalis-Lipopolysaccharide (P.gingivalis-LPS) on hepatic disorder mediated by 5-hydroxytryptamine receptor 2A (HT2AR) and whether there is any impact of Thymoquinone (TQ) administration. Methods: 10 µl P. gingivalis-LPS (1mg/ml) injected 6 times at 48-hour intervals into the palatal gingiva of rats. TQ was given by oral gavage (10 mg/kg per day) for two weeks. HT2AR and pro-caspase-3 levels were measured by the enzyme-linked immunosorbent assay (ELISA). Morphological changes in the liver were identified by hematoxylin and eosin staining. Results: In the P.gingivalis-LPS injected group, the hepatic HT2AR levels increased while pro-caspase-3 levels decreased, disturbing the liver morphological structure. TQ administration increased pro-caspase-3 levels and improved morphological structure despite increased HT2AR levels. Conclusion: Our results suggest that oral application of P. gingivalis-LPS decreased pro-caspase 3, an inactive form of caspase-3 by HT2AR, probably due to increased cleaved caspase-3 levels, and TQ administration increased pro-caspase-3 levels, leading to improved liver morphological structure. Therephore, our study indicated that oral pathogen P. gingivalis might impact the liver HT2AR-mediated, and TQ may have a beneficial effect.