Exercise Ameliorates Fluoride-induced Anxiety- and Depression-like Behavior in Mice: Role of GABA

Association between fluoride exposure and psychiatric disorders in adults

To explore the association between fluoride exposure and depression / anxiety in adults, the 1,169 participants were recruited. The demographic information of participants was obtained through questionnaire survey and physical measurements. Morning urine samples were collected, and urinary fluoride (UF) level was determined. Changes in depression and anxiety levels were evaluated using the Patient Health Questionnaire-2 and General Anxiety Disorder-2 scales. The association between psychiatric disorders and UF levels was analyzed. In the total population, the prevalence of depression and anxiety were 3.17% and 4.19%, respectively. These results showed no significant association between depression / anxiety scale scores and UF levels. Logistic regression suggested no significant association between depression / anxiety levels, and UF levels, but there was an interaction between UF and income on depression. Our findings highlighted the interaction between fluoride exposure and monthly income, which may affect depression in adults.

Aerobic Exercise Improves the Overall Outcome of Type 2 Diabetes Mellitus Among People With Mental Disorders

The escalating global prevalence of type 2 diabetes mellitus (T2DM) and mental disorder (MD) including schizophrenia, bipolar disorder, major depressive disorder, and anxiety highlights the urgency for comprehensive therapeutic strategies. Aerobic exercise (AE) is a viable adjunct therapy, providing significant benefits for individuals dealing with both T2DM and MD. This review consolidates evidence on AE's role in alleviating the physiological and psychological effects of these comorbid conditions. It delves into the pathophysiological connections between T2DM and various MD, including depression, schizophrenia, anxiety, and bipolar disorder-emphasizing their reciprocal exacerbation. Key neurophysiological mechanisms through which AE confers benefits are explored, including neuroinflammation modulation, brain structure and neuroplasticity enhancement, growth factor expression regulation, and hypothalamic-pituitary-adrenal (HPA)/microbiota-gut-brain (MGB) axis normalization. Clinical results indicate that AE significantly improves both metabolic and psychological parameters in patients with T2DM and MD, providing a substantial argument for integrating AE into comprehensive treatment plans. Future research should aim to establish detailed, personalized exercise prescriptions and explore the long-term benefits of AE in this population. This review underscores the potential of AE to complement existing therapeutic modalities and enhance the management of patients with T2DM and MD.

An in vivo and in silico probing of the protective potential of betaine against sodium fluoride-induced neurotoxicity

Excessive fluoride exposure beyond the tolerable limit may adversely impacts brain functionality. Betaine (BET), a trimethyl glycine, possesses antioxidant, anti-inflammatory and anti-apoptotic functions, although the underlying mechanisms of the role of BET on fluoride-induced neurotoxicity remain unelucidated. To assess the mechanism involved in the neuro-restorative role of BET on behavioural, neurochemical, and histological changes, we employed a rat model of sodium fluoride (NaF) exposure. Animals were treated with NaF (9 mg/kg) body weight (bw) only or co-treated with BET (50 and 100 mg/kg bw) orally uninterrupted for 28 days. We obtained behavioural phenotypes in an open field, performed negative geotaxis, and a forelimb grip test, followed by oxido-inflammatory, apoptotic, and histological assessment. Behavioural endpoints indicated lessened locomotive and motor and heightened anxiety-like performance and upregulated oxidative, inflammatory, and apoptotic biomarkers in NaF-exposed rats. Co-treatment with BET significantly enhanced locomotive, motor, and anxiolytic performance, increased the antioxidant signalling mechanisms and demurred oxidative, inflammatory, and apoptotic biomarkers and histoarchitectural damage in the cerebrum and cerebellum cortices mediated by NaF. The in-silico analysis suggests that multiple hydrogen bonds and hydrophobic interactions of BET with critical amino acid residues, including arginine (ARG380 and ARG415) in the Keap1 Kelch domain, which may disrupt Keap1-Nrf2 complex and activate Nrf2. This may account for the observed increased in the Nrf2 levels, elevated antioxidant response and enhanced anti-inflammatory response. The BET-Keap1 complex was also observed to exhibit structural stability and conformational flexibility in solvated biomolecular systems, as indicated by the thermodynamic parameters computed from the trajectories obtained from a 100 ns full atomistic molecular dynamics simulation. Therefore, BET mediates neuroprotection against NaF-induced cerebro-cerebellar damage through rats' antioxidant, anti-inflammatory, and anti-apoptotic activity, which molecular interactions with Keap1-Nrf2 may drive.

Exercise Alleviates Fluoride-Induced Learning and Memory Impairment in Mice: Role of miR-206-3p and PREG

Fluorosis decreases the learning and memory ability in humans and animals, while exercise can reduce the risk of cognitive decline. However, the effect of exercise on learning and memory in fluoride-exposed mice is unclear. For this purpose, in this study, mice were randomly allotted into four groups (16 mice per group, half male and half female): control group (group C), fluoride group (group F, 100 mg/L sodium fluoride (NaF)), exercise group (group E, treadmill exercise), and E plus F group (group EF, treadmill exercise, and 100 mg/L NaF). During 6 months of exposure, exercise alleviated the NaF-induced decline in memory and learning. In addition, NaF induced injuries in mitochondria and myelin sheath ultrastructure and reduced the neurons number, while exercise restored them. Metabolomics results showed that phosphatidylethanolamine, pregnenolone (PREG), and lysophosphatidic acid (LysoPA) were altered among groups C, F, and EF. Combined with previous studies, it can be suggested that PREG might be a biomarker in response to exercise-relieving fluorine neurotoxicity. The miRNA sequencing results indicated that in the differently expressed miRNAs (DEmiRNAs), miR-206-3p, miR-96-5p, and miR-144-3p were shared in groups C, F, and EF. After the QRT-PCR validation and in vitro experiments, it was proved that miR-206-3p could reduce cell death and regulate AP-1 transcription factor subunit (JunD) and histone deacetylase 4 (HDAC4) to alleviate fluoride neurotoxicity. To sum up, the current study reveals that exercise could alleviate NaF-induced neurotoxicity by targeting miR-206-3p or PREG, which will contribute to revealing the pathogenesis and therapeutic method of fluoride neurotoxicity.

Effect of Voluntary Wheel Running on Anxiety- and Depression-Like Behaviors in Fluoride-Exposed Mice

Fluoride, an environmental toxicant, could induce endoplasmic reticulum stress (ERS) in neuronal cells ultimately leading to apoptosis and emotional dysfunction. Meanwhile, voluntary wheel running contributes to mitigate anxiety and depression. Our investigation aimed to study the effect of voluntary wheel running on anxiety- and depression-like behaviors in fluoride-exposure mice. The results showed that exposure to 100 mg/L sodium fluoride (NaF) for 6 months can induce anxiety- and depression-like behavior in mice. Fluorosis mice subjected to voluntary wheel running have less anxiety- and depression-like behaviors. Nissl and TUNEL staining demonstrated that fluoride led to a reduced proportion of Nissl body area in the cerebral cortex and an increased apoptotic ratio of nerve cells in the cerebral cortex. In contrast, these pathologic damages were improved in voluntary wheel running mice exposed to NaF. Moreover, the expressions of mRNA in the cerebral cortex GABA, GAD65, GAD67, DR, vGLU, 5-HT1A, BDNF, NMDAR1, and Bcl2 were downregulated and the levels of c-fos, GRP78, PERK, eIF2α, CHOP, Caspase-12, and Caspase-3 mRNA were upregulated in mice exposed to fluoride. NaF treatment had increased the PERK, ATF6, IRE1, p-eIF2α, and Caspase-3 protein levels and reduced the expressions of proteins, including GAD67, VGAT, BDNF, NMDAR1, PSD95, and SYN. By contrast, fluorosis mice subjected to voluntary wheel running enhanced the expression of GAD65, GAD67, VGAT, and neuroplasticity-related proteins in mice and inhibited the PERK-CHOP pathway. It is worth noting that the correlation between the amount of exercise and the behavioral indicators as well as neurotransmitter levels was found. In conclusion, voluntary wheel running inhibits the fluoride-induced ERS and GRP78 expression through the PERK-CHOP pathway and plays an anti-apoptotic role, ultimately ameliorating emotional dysfunction in NaF-exposed mice.

Focus on cognitive impairment induced by excessive fluoride: An update review

Fluorosis is a global public health concern. Prolonged exposure to excessive fluoride causes fluoride accumulation in the hippocampus, resulting in cognitive dysfunction. Cell death is necessary for maintaining tissue function and morphology, and changes in the external morphology of nerve cells and the function of many internal organelles are typical features of cell death; however, it is also a typical feature of cognitive impairment caused by fluorosis. However, the pathogenesis of cognitive impairment caused by different degrees of fluoride exposure varies. Herein, we provide an overview of cognitive impairment caused by excessive fluoride exposure in different age groups, and the underlying mechanisms for cognitive impairment in various model organisms. The mechanisms underlying these impairments include oxidative stress, synaptic and neurotransmission dysfunction, disruption of mitochondrial and energy metabolism, and calcium channel dysregulation. This study aims to provide potential insights that serve as a reference for subsequent research on the cognitive function caused by excessive fluoride.

Vibration-reduced anxiety-like behavior relies on ameliorating abnormalities of the somatosensory cortex and medial prefrontal cortex

Tibetan singing bowls emit low-frequency sounds and produce perceptible harmonic tones and vibrations through manual tapping. The sounds the singing bowls produce have been shown to enhance relaxation and reduce anxiety. However, the underlying mechanism remains unclear. In this study, we used chronic restraint stress or sleep deprivation to establish mouse models of anxiety that exhibit anxiety-like behaviors. We then supplied treatment with singing bowls in a bottomless cage placed on the top of a cushion. We found that unlike in humans, the combination of harmonic tones and vibrations did not improve anxiety-like behaviors in mice, while individual vibration components did. Additionally, the vibration of singing bowls increased the level of N-methyl-D-aspartate receptor 1 in the somatosensory cortex and prefrontal cortex of the mice, decreased the level of γ-aminobutyric acid A (GABA) receptor α 1 subtype, reduced the level of CaMKII in the prefrontal cortex, and increased the number of GABAergic interneurons. At the same time, electrophysiological tests showed that the vibration of singing bowls significantly reduced the abnormal low-frequency gamma oscillation peak frequency in the medial prefrontal cortex caused by stress restraint pressure and sleep deprivation. Results from this study indicate that the vibration of singing bowls can alleviate anxiety-like behaviors by reducing abnormal molecular and electrophysiological events in somatosensory and medial prefrontal cortex.

Pesticide-Induced Alterations in Locomotor Activity, Anxiety, and Depression-like Behavior Are Mediated through Oxidative Stress-Related Autophagy: A Persistent Developmental Study in Mice

Chlorpyrifos (CPF), dichlorvos (DDV), and cypermethrin (CP), as commonly used pesticides, have been implicated in inducing neuropsychiatric disorders, such as anxiety, depression-like behaviors, and locomotor activity impairment. However, the exact molecular mechanisms of these adverse effects, particularly in both sexes and their next-generation effects, remain unclear. In this study, we conducted behavioral analysis, along with cellular assays (monodansylcadaverine staining) and molecular investigations (qRT-PCR and western blotting of mTOR, P62, and Beclin-1) to clear the potential role of autophagy in pesticide-induced behavioral alterations. For this purpose, 42 adult female and 21 male inbred ICR mice (F0) were distributed into seven groups. Maternal mice (F0) and 112 F1 offspring were exposed to 0.5 and 1 ppm of CPF, DDV, and CP through drinking water. F1 male and female animals were studied to assess the sex-specific effects of pesticides on brain tissue. Our findings revealed pronounced anxiogenic effects and impaired locomotor activity in mice. F1 males exposed to CPF (1 ppm) exhibited significantly elevated depression-like behaviors compared to other groups. Moreover, pesticide exposure reduced mTOR and P62 levels, while enhancing the Beclin-1 gene and protein expression. These changes in autophagy signaling pathways, coupled with oxidative and neurogenic damage in the cerebral cortex and hippocampus, potentially contribute to heightened locomotor activity, anxiety, and depression-like behaviors following pesticide exposure. This study underscores the substantial impact of pesticides on both physiological and behavioral aspects, emphasizing the necessity for comprehensive assessments and regulatory considerations for pesticide use. Additionally, the identification of sex-specific responses presents a crucial dimension for pharmaceutical sciences, highlighting the need for tailored therapeutic interventions and further research in this field.

The impact of ammonia and microcystin-LR on neurobehavior and glutamate/gamma-aminobutyric acid balance in female zebrafish (Danio rerio): ROS and inflammation as key pathways

Ammonia and microcystin-LR (MC-LR) are both toxins that can be in eutrophic waters during cyanobacterial blooms. While previous studies have focused on the effects of ammonia exposure on fish neurobehavioral toxicity, little attention has been given to the effects of MC-LR and combined exposures to both. This study exposed adult female zebrafish to ammonia (30 mg/L) and MC-LR (10 μg/L) alone and in combination for 30 days to investigate their neurotoxic effects and underlying mechanisms. Behavioral results showed that exposure to ammonia and MC-LR, both alone and in combination, led to decreased locomotor activity and increased anxiety in fish. Histomorphological analysis revealed the formation of thrombi and vacuolization in the brain across all exposure groups. Exposure to ammonia and MC-LR resulted in significant increases in MDA contents, decreases in Mn-SOD activities, and alterations in GSH contents compared to the control. Single and combined exposure to ammonia and MC-LR also induced the release of inflammatory factors (IL-1β and TNF-α) by activating the NOD/NF-κB signaling pathway. Furthermore, both ammonia and MC-LR significantly changed the expression of genes related to the glutamatergic and GABAergic systems, elevated Glu and GABA contents, as well as increased the Glu/GABA ratio, indicating that a shift towards increased Glu levels. Overall, these findings suggested that exposure to MC-LR and ammonia, individually and in combination, could decrease locomotor activity and increase anxiety of female zebrafish. This was likely due to brain damage from over-activated ROS and the release of pro-inflammatory cytokines, which led to a disruption in the balance of glutamatergic and GABAergic systems. However, there was no significant interaction between MC-LR and ammonia in fish neurobehavioral toxicity.

The therapeutic effects of saikosaponins on depression through the modulation of neuroplasticity: From molecular mechanisms to potential clinical applications

Depression is a major global health issue that urgently requires innovative and precise treatment options. In this context, saikosaponin has emerged as a promising candidate, offering a variety of therapeutic benefits that may be effective in combating depression. This review delves into the multifaceted potential of saikosaponins in alleviating depressive symptoms. We summarized the effects of saikosaponins on structural and functional neuroplasticity, elaborated the regulatory mechanism of saikosaponins in modulating key factors that affect neuroplasticity, such as inflammation, the hypothalamic-pituitary-adrenal (HPA) axis, oxidative stress, and the brain-gut axis. Moreover, this paper highlights existing gaps in current researches and outlines directions for future studies. A detailed plan is provided for the future clinical application of saikosaponins, advocating for more targeted researches to speed up its transition from preclinical trials to clinical practice.

Arsenic exposure induced anxiety-like behaviors in male mice via influencing the GABAergic Signaling in the prefrontal cortex

Arsenic contamination in drinking water causes a global public health problem. Emerging evidence suggests that arsenic may act as an environmental risk factor for anxiety disorders. However, the exact mechanism underlying the adverse effects has not been fully elucidated. This study aimed to evaluate the anxiety-like behaviors of mice exposed to arsenic trioxide (As2O3), to observe the neuropathological changes, and to explore the link between the GABAergic system and behavioral manifestations. For this purpose, male C57BL/6 mice were exposed to various doses of As2O3 (0, 0.15, 1.5, and 15 mg/L) through drinking water for 12 weeks. Anxiety-like behaviors were assessed using the open field test (OFT), light/dark choice test, and elevated zero maze (EZM). Neuronal injuries in the cerebral cortex and hippocampus were assessed by light microscopy with H&E and Nissl staining. Ultrastructural alteration in the cerebral cortex was assessed by transmission electron microscope (TEM). The expression levels of GABAergic system-related molecules (i.e., glutamate decarboxylase, GABA transporter, and GABAB receptor subunits) in the prefrontal cortex (PFC) were determined by qRT-PCR and western blotting. Arsenic exposure showed a striking anxiogenic effect on mice, especially in the group exposed to 15 mg/L As2O3. Light microscopy showed neuron necrosis and reduced cell counts. TEM revealed marked ultrastructural changes, including the vacuolated mitochondria, disrupted Nissl bodies, an indentation in the nucleus membrane, and delamination of myelin sheath in the cortex. In addition, As2O3 influenced the GABAergic system in the PFC by decreasing the expression of the glutamate decarboxylase 1 (GAD1) and the GABAB2 receptor subunit, but not the GABAB1 receptor subunit. To sum up, sub-chronic exposure to As2O3 is associated with increased anxiety-like behaviors, which may be mediated by altered GABAergic signaling in the PFC. These findings shed light on the mechanisms responsible for the neurotoxic effects of arsenic and therefore more cautions should be taken.

Fisetin attenuates arsenic and fluoride subacute co-exposure induced neurotoxicity via regulating TNF-α mediated activation of NLRP3 inflammasome

Groundwater is considered safe, however, the occurrence of contaminants like arsenic and fluoride has raised a major healthcare concern. Clinical studies suggested that arsenic and fluoride co-exposure induced neurotoxicity, however efforts to explore safe and effective management of such neurotoxicity are limited. Therefore, we investigated the ameliorative effect of Fisetin against arsenic and fluoride subacute co-exposure-induced neurotoxicity, and associated biochemical and molecular changes. Male BALB/c mice Arsenic (NaAsO₂: 50mg/L) and fluoride (NaF: 50mg/L) were exposed to drinking water and fisetin (5, 10, and 20mg/kg/day) was administered orally for 28 days. The neurobehavioral changes were recorded in the open field, rotarod, grip strength, tail suspension, forced swim, and novel object recognition test. The co-exposure resulted in anxiety-like behaviour, loss of motor coordination, depression-like behaviour, and loss of novelty-based memory, along with enhanced prooxidant, inflammatory markers and loss of cortical and hippocampal neurons. The treatment with fisetin reversed the co-exposure-induced neurobehavioral deficit along with restoration of redox & inflammatory milieu, and cortical and hippocampal neuronal density. Apart from antioxidants, inhibition of TNF-α/ NLRP3 expression has been suggested as one of the plausible neuroprotective mechanisms of Fisetin in this study.

Moderate exercise relieves fluoride-induced liver and kidney inflammatory responses through the IKKβ/NFκB pathway

With the intensification of environmental pollution, the content of fluoride is increasing in human and animal living environments. Long-term fluoride exposure can cause damage to the liver and kidney, which are the main sites for fluoride metabolism, storage and removal. Moreover, exercise often accompanies the entire process of fluoride exposure in humans and animals. However, the mechanism of exercise on fluoride-induced liver and kidney injury remains unclear. Hence, we established a fluoride exposure and/or exercise mouse model to explore the influence of exercise on fluoride-induced liver and kidney inflammation and the potential mechanism. The results showed that fluoride caused obvious structural and functional damage and the notable recruitment of immunocytes in the liver and kidney. In addition, fluoride increased the levels of IL-1β, IL-2, IL-4, IL-6, IL-10, IL-12, IL-13, IL-21, TNF-α, and TGF-β but decreased the ratio of IFN-γ/IL-4 and IL-2/IL-10, which indicated that fluoride disturbed the inflammatory balance and caused hepatonephritis. In addition, the expression levels of IKKβ and NFκB were increased, and the expression of IκBα was decreased after fluoride exposure, indicating that fluoride activated the IKKβ/NFκB pathway. In summary, long-term moderate treadmill exercise relieved fluoride-induced liver and kidney inflammatory responses through the IKKβ/NFκB pathway, and exercise can be used to prevent fluoride-induced liver and kidney damage.

The role of maternal exercise on placental, behavioral and genetic alterations induced by prenatal stress

The present study aimed to evaluate the effects of treadmill maternal exercise on alterations induced by prenatal stress in neonatal mice. Female and male Balb/c mice were divided into five groups: control (CON), prenatal restraint stress (PNS), prenatal restraint stress and physical exercise before pregnancy (PNS + EX1), prenatal restraint stress and physical exercise during pregnancy (PNS + EX2), and prenatal restraint stress and physical exercise before and during pregnancy (PNS + EX3). Exercise was performed using a treadmill, at a speed of 10 m/min, for 60 minutes, 5 days a week. Maternal behavior was assessed on days 3, 4 and 5 postpartum (PPD). Placental gene expression of glucocorticoid receptor (GR), 11-β-hydroxysteroid dehydrogenase 2 (11β-HSD2), 5-hydroxytryptamine receptor 1A (5HT_1AR), and corticotropin releasing hormone receptor 1 (CRHR1) were analyzed. In neonatal mice, the gene expression of GR, mineralocorticoid receptor (MR), CRHR1, 5HTr1, oxytocin Receptor 1 (OXTr1), tropomyosin related kinase B (TRκB), brain-derived neurotrophic factor exon I (BDNF I), and BDNF IV was analyzed in the brain (PND0) and hippocampus (PND10). Maternal exercise improved (p < 0.05) maternal care. In the placenta, maternal exercise prevented (p < 0.01) the increase in GR expression caused by PNS. In the brain from PND0, exercise before pregnancy prevented (p = 0.002) the decreased CRHR1 expression promoted by PNS. In the hippocampus of PND10 males, PNS decreased (p = 0.0005) GR expression, and exercise before pregnancy prevented (p = 0.003) this effect. In PND10 females, maternal exercise prevented (p < 0.05) the PNS-induced increase in MR expression. PNS + EX2 males showed increased (p < 0.01) BDNF I gene expression and PNS + EX1 females demonstrated increased (p = 0.03) BDNF IV expression. In conclusion, maternal physical exercise may play a role in modulating maternal-fetal health and may contribute to preventing neurodevelopmental changes induced by prenatal stress.

Mitigation Effects of Selenium Nanoparticles on Depression-Like Behavior Induced by Fluoride in Mice via the JAK2-STAT3 Pathway

Depression is a mental health problem with typically high levels of distress and dysfunction, and 150 mg/L fluoride (F) can induce depression-like behavior. The development of depression is correlated with neuronal atrophy, insufficient secretion of monoamine neurotransmitters, extreme deviations from the normal microglial activation status, and immune-inflammatory response. Studies found that Se supplementation was related to the improvement of depression. In this study, we applied selenium nanoparticles (SeNPs) for F-induced depression disease mitigation by regulating the histopathology, metabolic index, genes, and protein expression related to the JAK2-STAT3 signaling pathway in vivo. Results showed that F and 2 mg Se/kg BW/day SeNPs lowered the dopamine (DA) content (P < 0.05), altered the microglial morphology, ramification index as well as solidity, and triggered the microglial neuroinflammatory response by increasing the p-STAT3 nuclear translocation (P < 0.01). Furthermore, F reduced the cortical Se content and the number of surviving neurons (P < 0.05), increasing the protein expressions of p-JAK2/JAK2 and p-STAT3/STAT3 of the cortex (P < 0.01), accompanied by the depression-like behavior. Importantly, 1 mg Se/kg BW/day SeNPs alleviated the microglial ramification index as well as solidity changes and decreased the interleukin-1β secretion induced by F by suppressing the p-STAT3 nuclear translocation (P < 0.01). Likewise, 1 mg Se/kg BW/day SeNPs restored the F-disturbed dopamine and noradrenaline secretion, increased the number of cortical surviving neurons, and reduced the vacuolation area, ultimately suppressing the occurrence of depression-like behavior through inhibiting the JAK2-STAT3 pathway activation. In conclusion, 1 mg Se/kg BW/day SeNPs have mitigation effects on the F-induced depression-like behavior. The mechanism of how SeNPs repair neural functions will benefit depression mitigation. This study also indicates that inhibiting the JAK/STAT pathway can be a promising novel treatment for depressive disorders.