Assessment of Translocation of Lacticaseibacillus rhamnosus CGMCC 1.3724 Radiolabeled with Technetium-99 m Isotope in an Experimental Model of Immunosuppression

Immunosuppressant medications disrupt intestinal homeostasis. Probiotics may help restore intestinal balance; however, the safety of their use in immunocompromised individuals is questionable. To investigate the translocation of Lacticaseibacillus rhamnosus radiolabeled with technetium-99m (99mTc) in an experimental model of immunosuppression. Mice were divided into four groups: control (CTL), 5-fluorouracil (5-FU), dexamethasone (DEX), and DEX + 5-FU. Mice in the CTL group received saline (0.1 mL/intraperitoneal [IP]) for seven days; those in the 5-FU group received a single dose of 5-fluorouracil (300 mg/kg/IP) on day 5; those in the DEX group received dexamethasone (5 mg/kg/IP) daily; and those in the DEX + 5-FU group received a single dose of 5-fluorouracil (300 mg/kg/IP) on day 5 and dexamethasone (5 mg/kg/IP) daily. On day 8, the animals received radiolabeled L. rhamnosus (99mTc-L. rhamnosus) by oral gavage. Four hours later, the mice were anesthetized and euthanized for blood and tissue collection. The 5-FU group exhibited leukopenia, whereas the DEX and DEX + 5-FU groups showed granulocytosis and lymphopenia. Radiolabeling demonstrated high stability. Significant probiotic translocation occurred in the 5-FU group, whereas no translocation was observed in the DEXgroup. Intermediate levels of translocation were detected in the DEX + 5-FU group. As expected, 5-FU treatment induced pronounced epithelialinjury, characterized by increased intestinal permeability, oxidative stress, histological damage, and inflammatory infiltration. In the DEX + 5-FUgroup, although histological and morphometric alterations were similar to those observed in the 5-FU group, and peroxidase activity wasincreased with an intermediate reduction in superoxide dismutase levels, intestinal permeability remained unchanged.