Key Role of Pro-inflammatory Cytokines in the Toxic Effect of Fluoride on Hepa1-6 Cells

Underlying Mechanism of Fluoride Inhibits Colonic Gland Cells Proliferation by Inducing an Inflammation Response

The integrity of colonic gland cells is a prerequisite for normal colonic function and maintenance. To evaluate the underlying injury mechanisms in colonic gland cells induced by excessive fluoride (F), forty-eight female Kunming mice were randomly allocated into four groups and treated with different concentrations of NaF (0, 25, 50, and 100 mg F-/L) for 70 days. As a result, the integrity of the colonic mucosa and the cell layer was seriously damaged after F treatment, as manifested by atrophy of the colonic glands, colonic cell surface collapse, breakage of microvilli, and mitochondrial vacuolization. Alcian blue and periodic acid Schiff staining revealed that F decreased the number of goblet cells and glycoprotein secretion. Furthermore, F increased the protein expression of TLR4, NF-κB, and ERK1/2 and decreased IL-6, interfered with NF-κB signaling, following induced colonic gland cells inflammation. The accumulation of F inhibited proliferation via the JAK/STAT signaling pathway, as characterized by decreased mRNA and protein expression of JAK, STAT3, STAT5, PCNA, and Ki67 in colon tissue. Additionally, the expression of CDK4 was up-regulated by increased F concentration. In conclusion, excessive F triggered colonic inflammation and inhibited colonic gland cell proliferation via regulation of the NF-κB and JAK/STAT signaling pathways, leading to histopathology and barrier damage in the colon. The results explain the damaging effect of the F-induced inflammatory response on the colon from the perspective of cell proliferation and provide a new idea for explaining the potential mechanism of F-induced intestinal damage.

The Effect of Prenatal and Neonatal Fluoride Exposure to Morphine-Induced Neuroinflammation

Physical dependence is associated with the formation of neuroadaptive changes in the central nervous system (CNS), both at the molecular and cellular levels. Various studies have demonstrated the immunomodulatory and proinflammatory properties of morphine. The resulting neuroinflammation in drug dependence exacerbates substance abuse-related behaviors and increases morphine tolerance. Studies prove that fluoride exposure may also contribute to the development of neuroinflammation and neurodegenerative changes. Morphine addiction is a major social problem. Neuroinflammation increases tolerance to morphine, and neurodegenerative effects caused by fluoride in structures related to the development of dependence may impair the functioning of neuronal pathways, change the concentration of neurotransmitters, and cause memory and learning disorders, which implies this element influences the development of dependence. Therefore, our study aimed to evaluate the inflammatory state of selected brain structures in morphine-dependent rats pre-exposed to fluoride, including changes in cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) expression as well as microglial and astroglial activity via the evaluation of Iba1 and GFAP expression. We provide evidence that both morphine administration and fluoride exposure have an impact on the inflammatory response by altering the expression of COX-1, COX-2, ionized calcium-binding adapter molecule (Iba1), and glial fibrillary acidic protein (GFAP) in brain structures involved in dependence development, such as the prefrontal cortex, striatum, hippocampus, and cerebellum. We observed that the expression of COX-1 and COX-2 in morphine-dependent rats is influenced by prior fluoride exposure, and these changes vary depending on the specific brain region. Additionally, we observed active astrogliosis, as indicated by increased GFAP expression, in all brain structures of morphine-dependent rats, regardless of fluoride exposure. Furthermore, the effect of morphine on Iba1 expression varied across different brain regions, and fluoride pre-exposure may influence microglial activation. However, it remains unclear whether these changes are a result of the direct or indirect actions of morphine and fluoride on the factors analyzed.