New Insights on Symptoms Related to Chronic Fluoride Toxicity

Objectives: Gastrointestinal symptoms such as nausea, vomiting, abdominal pain and especially diarrhea are the first signs of toxicity by fluoride (F). In this work, rats chronically exposed to F had the ileum evaluated by proteomics, as well as by morphological analysis.
Methods: Male rats received water containing 0, 10 or 50 mgF / L for 30 days. These F concentrations correspond to ~2 and 10 mgF/L in the drinking water for humans. Immunofluorescence techniques were performed in the myenteric plexus of the ileum to detect HuC/D, neuronal Nitric Oxide (nNOS), Vasoactive Intestinal Peptide (VIP), Calcitonin Gene Related Peptide (CGRP), and Substance P (SP). Proteomic analysis of ileum was performed using nanoAcquity UPLC-Xevo QTof MS system and the ProteinLynx Global Server (PLGS) software. For bioinformatics analysis, the Cytoscape software and the Cluster Marker and Cluego pluggins were used.
Results: Treatment with F, regardless the dose, significantly decreased the density of nHuC/D-IR neurons, whereas the CGRP-IR and SP-IR varicosities were significantly increased compared to the control group. Increased VIP-IR varicosities were significantly observed only in the group treated with the highest concentration of F. In addition, we found a significant increase in ileum tunica muscularis, as well as in the total thickness of the ileum wall. Several proteins were altered in the presence of F, such as different isoforms of myosin, as well as Calmodulin, which are possible justifications for the observed increased in the ileum tunica muscularis and in the total thickness of the ileum wall. Decrease in Gastrotopin may be associated with diarrhea, a common symptom found in cases of intoxication by F.
Conclusions: Morphological alterations as well as changes in protein expression induced by F have similarity with Crohn's disease, which should be investigated in further studies.