Caffeic acid phenethyl ester attenuates Enterococcus faecalis infection in vivo: antioxidants and NF-κB have a protective role against stomach damage

Abstract

The mammalian gastrointestinal tract hosts a significant microbial symbiont community, an intriguing feature of this complex organ system. This study aimed to investigate the anti-inflammatory, antioxidant, and protective effects of caffeic acid phenethyl ester (CAPE) against Enterococcus faecalis infection in the stomach at a dose of 10⁶ CFU in Swiss mice. A total of 30 mice were randomly assigned to three groups of ten mice each. Group I was the negative control, Group II was infected orally with E. faecalis for 18 days, and Group III was infected with E. faecalis and treated with CAPE orally at a daily dose of 4 mg/kg for 18 days. We assessed the antioxidant activities of stomach homogenate and the immunohistochemical expressions of the transcription factor nuclear factor kappa B (NF-κB) and proliferating cell nuclear antigen (PCNA). Histopathological examination was performed on the stomachs of all mice. Group II had decreased levels of antioxidant activity and positive expressions of NF-κB and PCNA. Histological observations revealed an increase in mucosal and glandular thickness compared with Group I. Group III, treated with CAPE, showed a significant increase in antioxidant activities and a significant decrease in NF-κB and PCNA immunoreactivities compared with Group II. In addition, Group III showed restoration of the normal thickness of the non-glandular and glandular parts of the stomach. Our results revealed that E. faecalis infection has damaging effects on the stomach and proved that CAPE has promising protective, anti-inflammatory, and antioxidant effects against E. faecalis. Further studies may investigate the potential therapeutic effects of CAPE against E. faecalis infection.

Keywords: CAPE; Enterococcus faecalis; NF-κB; PCNA; antioxidant.

Figure 1

Immunohistochemical staining of NF-κB among mice in different study groups, in the non-glandular forestomach (upper row) and glandular stomach (lower row). The control group shows minimal to no NF-κB immune reactivity in the non-glandular and glandular parts. Group II, infected with Enterococcus faecalis at a dose of 10⁶ CFU shows increased NF-κB immune reactivity in both stomach parts. Group III, treated with CAPE, shows a marked reduction in NF-κB immune reactivity in the non-glandular and glandular parts of the stomach. Original magnification 100×.

Figure 2

Immunohistochemical staining of PCNA among mice in different study groups, in the non-glandular forestomach (upper row) and glandular stomach (lower row). The control group shows minimal to no PCNA immune reactivity in the non-glandular and glandular parts. Group II, infected with Enterococcus faecalis at a dose of 10⁶ CFU shows increased PCNA immune reactivity in both stomach parts. Group III, treated with CAPE, shows a marked reduction in PCNA immune reactivity in the non-glandular and glandular parts of the stomach. Original magnification 100×.

Figure 3

Comparison of NF-κB and PCNA immunohistochemical staining among mice in different groups. A, NF-κB IHC staining area percentage. B, PCNA IHC staining area percentage.

Figure 4

Histopathological examination (H&E staining) among mice in different study groups, in the non-glandular forestomach (upper row) and glandular stomach (lower row). The control group shows normal histological structure of stratified squamous keratinized epithelium with underlying submucosa and muscularis in the non-glandular part, and the fundus shows normal histological structure of gastric glands in the glandular part. Group II, infected with Enterococcus faecalis at a dose of 10⁶ CFU, shows increased mucosal and glandular thickness. Group III, treated with CAPE, shows almost complete restoration of the normal thickness of the non-glandular and glandular parts of the stomach. Black arrow, epithelium; red arrow, submucosa; blue arrow, muscles; green arrow, gastric glands. Original magnification 100×.