Modulation of TLR4, hBD-2, and hBD-3 expression and hepatic tissue response by systemic probiotics in experimental apical periodontitis in rats.

OBJECTIVE: To evaluate whether systemic supplementation with L. rhamnosus LR-04 and L. acidophilus LA-14 modulates the expression of TLR4, hBD-2, and hBD-3 in a rat model of experimental apical periodontitis (AP), and to assess potential histopathological alterations in the liver.

METHODOLOGY: Twenty-four male Wistar rats were randomly allocated into three groups (n=8): control (AP + water), AP + L. rhamnosus LR-04, and AP + L. acidophilus LA-14. AP was induced by exposing the pulp chambers of the first mandibular molars for 30 days. From the day of induction, probiotics (109 CFU/day via oral gavage) or water (control) were administered daily. After 30 days, the rats were euthanized. Mandibles were processed for immunohistochemical analysis of hBD-2, hBD-3, and TLR4 expression, which was assessed semi-quantitatively. Liver samples were collected, fixed, and stained with hematoxylin-eosin for histopathological evaluation of lobular inflammation, necrosis, portal inflammation, and fibrosis. Data were analyzed using the nonparametric Kruskal-Wallis test at a 5% significance level.

RESULTS: No hepatic histopathological alterations were observed in any group. Probiotic supplementation resulted in significantly greater hBD-2 immunoreactivity in periapical tissues compared to the control group (P<0.05). hBD-3 expression was significantly higher in the L. acidophilus LA-14 group than in both the control and L. rhamnosus LR-04 groups (P<0.05). TLR4 expression in periapical lesions was increased in both probiotic groups relative to control (P<0.05).

CONCLUSION: Systemic supplementation with L. rhamnosus LR-04 and L. acidophilus LA-14 enhanced the local immune response in apical periodontitis, as evidenced by upregulation of TLR4, hBD-2, and hBD-3, without inducing detectable hepatic histopathological alterations.