Fluoride exposure induces mitochondrial damage and mitophagy via activation of the IL-17A pathway in hepatocytes

Golm1 facilitates the CaO2-DOPC-DSPE200-PEI -CsPbBr3 QDs -induced apoptotic death of hepatocytes through the stimulation of mitochondrial autophagy and mitochondrial reactive oxygen species production through interactions with P53/Beclin-1/Bcl-2

Mitophagy is a distinct physiological process that can have beneficial or deleterious effects in particular tissues. Prior research suggests that mitophagic activity can be triggered by CaO2-PM-CsPbBr3 QDs, yet the specific role that mitophagy plays in hepatic injury induced by CaO2-PM-CsPbBr3 QDs has yet to be established. Accordingly, in this study a series of mouse model- and cell-based experiments were performed that revealed the ability of CaO2-PM-CsPbBr3 QDs to activate mitophagic activity. Golm1 was upregulated in response to CaO2-PM-CsPbBr3 QDs treatment, and overexpressing Golm1 induced autophagic flux in the murine liver and hepatocytes, whereas knocking down Golm1 had the opposite effect. CaO2-PM-CsPbBr3 QDs were also able to Golm1 expression, in turn promoting the degradation of P53 and decreasing the half-life of this protein. Overexpressing Golm1 was sufficient to suppress the apoptotic death of hepatocytes in vitro and in vivo, whereas the knockdown of Golm1 had the opposite effect. The ability of Golm1 to promote p53-mediated autophagy was found to be associated with the disruption of Beclin-1 binding to Bcl-2, and the Golm1 N-terminal domain was determined to be required for p53 interactions, inducing autophagic activity in a manner independent of helicase activity or RNA binding. Together, these results indicate that inhibiting Golm1 can promote p53-dependent autophagy via disrupting Beclin-1 binding to Bcl-2, highlighting a novel approach to mitigating liver injury induced by CaO2-PM-CsPbBr3 QDs.

MiRNA-seq and mRNA-seq revealed the mechanism of fluoride-induced cauda epididymal injury

The widespread presence of fluoride in water, food, and the environment continues to exacerbate the impact of fluoride on the male reproductive health. However, as a critical component of the male reproductive system, the intrinsic mechanism of fluoride-induced cauda epididymis damage and the role of miRNAs in this process are still unclear. This study established a mouse fluorosis model and employed miRNA and mRNA sequencing; Evans blue staining, Oil Red O staining, TEM, immunofluorescence, western blotting, and other technologies to investigate the mechanism of miRNA in fluoride-induced cauda epididymal damage. The results showed that fluoride exposure increased the fluoride concentration in the hard tissue and cauda epididymis, altered the morphology and ultrastructure of the cauda epididymis, and reduced the motility rate, normal morphology rate, and hypo-osmotic swelling index of the sperm in the cauda epididymis. Furthermore, sequencing results revealed that fluoride exposure resulted in differential expression of 17 miRNAs and 4725 mRNAs, which were primarily enriched in the biological processes of tight junctions, inflammatory response, and lipid metabolism, with miR-742-3p, miR-141-5p, miR-878-3p, and miR-143-5p serving as key regulators. Further verification found that fluoride damaged tight junctions, raised oxidative stress, induced an inflammatory response, increased lipid synthesis, and reduced lipid decomposition and transport in the cauda epididymis. This study provided a theoretical basis for developing miRNA as potential diagnostic markers and therapeutic target drugs for this injury.

Reactive Oxygen Species-Mediated Mitophagy and Cell Apoptosis are Involved in the Toxicity of Aluminum Chloride Exposure in GC-2spd

Aluminum chloride is an inorganic polymeric coagulant commonly found in daily life and various materials. Although male reproductive toxicity has been associated with AlCl3 exposure, the underlying mechanism remains unclear. This study aimed to examine the impact of AlCl3 exposure on mitophagy and mitochondrial apoptosis in testicular tissue and mouse spermatocytes. Reactive oxygen species (ROS) and ATP levels were measured in GC-2spd after AlCl3 exposure using a multifunctional enzyme labeler. The changes in mitochondrial membrane potential (MMP) and TUNEL were observed through confocal laser microscopy, and the expression of proteins associated with mitophagy and apoptosis was analyzed using Western blot. Our results demonstrated that AlCl3 exposure disrupted mitophagy and increased apoptosis-related protein expression in testicular tissues. In the in vitro experiments, AlCl3 exposure induced ROS production, suppressed cell viability and ATP production, and caused a decrease in MMP, leading to mitophagy and cell apoptosis in GC-2spd cells. Intervention with N-acetylcysteine (NAC) reduced ROS production and partially restored mitochondrial function, thereby reversing the resulting mitophagy and cell apoptosis. Our findings provide evidence that ROS-mediated mitophagy and cell apoptosis play a crucial role in the toxicity of AlCl3 exposure in GC-2spd. These results contribute to the understanding of male reproductive toxicity caused by AlCl3 exposure and offer a foundation for future research in this area.

Fluoride induces pyroptosis via IL-17A-mediated caspase-1/11-dependent pathways and Bifidobacterium intervention in testis

Fluoride, a ubiquitous environmental pollutant, poses a significant public health threat. Our previous study revealed a correlation between fluoride-induced testicular pyroptosis and male reproductive dysfunction. However, the underlying mechanism remains unclear. Wild-type and interleukin 17A knockout mice were exposed to sodium fluoride (100 mg/L) in deionized drinking water for 18 weeks. Bifidobacterium intervention (1 × 109 CFU/mL, 0.2 mL/day, administered via gavage) commenced in the 10th week. Sperm quality, testicular morphology, key pyroptosis markers, spermatogenesis key genes, IL-17A signaling pathway, and pyroptosis pathway related genes were determined. The results showed that fluoride reduced sperm quality, damaged testicular morphology, affected spermatogenesis, elevated IL-17A levels, and induced testicular pyroptosis. Bifidobacterium intervention alleviated adverse reproductive outcomes. Fluoride-activated testicular pyroptosis through both typical and atypical pathways, with IL-17A involvement. Bifidobacterium supplementation attenuated pyroptosis by downregulating IL-17A, inhibiting NLRP3 and PYRIN-mediated caspase-1 and caspase-11 dependent pathways in testis, thereby alleviating fluoride-induced male reproductive damage. In summary, this study uncovers the mechanism underlying fluorine-induced testicular pyroptosis and illustrates the novel protecting feature of Bifidobacterium against fluoride-induced harm to male reproduction, along with its potential regulatory mechanism. These results provide fresh perspectives on treating male reproductive dysfunction resulting from fluoride or other environmental toxins.

Progress in research on the role of fluoride in immune damage

Excessive fluoride intake from residential environments may affect multiple tissues and organs; however, the specific pathogenic mechanisms are unclear. Researchers have recently focused on the damaging effects of fluoride on the immune system. Damage to immune function seriously affects the quality of life of fluoride-exposed populations and increases the incidence of infections and malignant tumors. Probing the mechanism of damage to immune function caused by fluoride helps identify effective drugs and methods to prevent and treat fluorosis and improve people's living standards in fluorosis-affected areas. Here, the recent literature on the effects of fluoride on the immune system is reviewed, and research on fluoride damage to the immune system is summarized in terms of three perspectives: immune organs, immune cells, and immune-active substances. We reviewed that excessive fluoride can damage immune organs, lead to immune cells dysfunction and interfere with the expression of immune-active substances. This review aimed to provide a potential direction for future fluorosis research from the perspective of fluoride-induced immune function impairment. In order to seek the key regulatory indicators of fluoride on immune homeostasis in the future.

Combined Effects of Fluoride and Dietary Seleno-L-Methionine at Environmentally Relevant Concentrations on Female Zebrafish (Danio rerio) Liver: Histopathological Damages, Oxidative Stress and Inflammation

Fluoride, a global environmental pollutant, is ubiquitous in aquatic environments and coexists with selenium, which can cause complex effects on exposed organisms. However, data on the interaction of fluoride and selenium remain scarce. In this study, female zebrafish (Danio rerio) were exposed to fluoride (80 mg/L sodium fluoride) and/or dietary selenomethionine (Se-Met) for 30, 60 and 90 days, the effects on the liver of zebrafish were investigated. The results indicated that an increase in fluoride burden, inhibited growth and impaired liver morphology were recorded after fluoride exposure. Furthermore, fluoride alone caused oxidative stress and inflammation in the liver, as reflected by the increase in ROS and MDA contents, the reduction of anti-oxidative enzymes, the altered immune related enzymes (ACP, AKP, LZM and MPO) and the expression of IL-6, IL-1β, TNF-α, IL-10 and TGF-β. In contrast, co-exposure to fluoride and Se-Met decreased fluoride burden and restored growth. Furthermore, dietary Se-Met alleviated oxidative stress, inflammation and impaired morphology in liver trigger by fluoride. However, dietary Se-Met alone increased the activities of SOD and CAT. These results demonstrate that the protective effect of dietary Se-Met against chronic fluoride toxicity at a certain level.

Calcium supplementation attenuates fluoride-induced bone injury via PINK1/Parkin-mediated mitophagy and mitochondrial apoptosis in mice

Excessive consumption of fluoride can cause skeletal fluorosis. Mitophagy has been identified as a novel target for bone disorders. Meanwhile, calcium supplementation has shown great potential for mitigating fluoride-related bone damage. Hence, this study aimed to elucidate the association between mitophagy and skeletal fluorosis and the precise mechanisms through which calcium alleviates these injuries. A 100 mg/L sodium fluoride (NaF) exposure model in Parkin knockout (Parkin-/-) mice and a 100 mg/L NaF exposure mouse model with 1% calcium carbonate (CaCO3) intervention were established in the current study. Fluoride exposure caused the impairment of mitochondria and activation of PTEN-induced putative kinase1 (PINK1)/E3 ubiquitin ligase Park2 (Parkin)-mediated mitophagy and mitochondrial apoptosis in the bones, which were restored after blocking Parkin. Additionally, the intervention model showed fluoride-exposed mice exhibited abnormal bone trabecula and mechanical properties. Still, these bone injuries could be effectively attenuated by adding 1% calcium to their diet, which reversed fluoride-activated mitophagy and apoptosis. To summarize, fluoride can activate bone mitophagy through the PINK1/Parkin pathway and mitochondrial apoptosis. Parkin-/- and 1% calcium provide protection against fluoride-induced bone damage. Notably, this study provides theoretical bases for the prevention and therapy of animal and human health and safety caused by environmental fluoride contamination.

Elevated Level of PINK1/Parkin-Mediated Mitophagy Pathway Involved to the Inhibited Activity of Mitochondrial Superoxide Dismutase in Rat Brains and Primary Hippocampal Neurons Exposed to High Level of Fluoride

To reveal the molecular mechanism of brain damage induced by chronic fluorosis, expression of PTEN-induced kinase 1 (PINK1)/parkin RBR E3 ubiquitin-protein ligase (Parkin)-mediated mitophagy pathway and activity of mitochondrial superoxide dismutase (SOD) were investigated in rat brains and primary cultured neurons exposed to high level of fluoride. Sprague-Dawley (SD) rats were treated with fluoride (0, 5, 50, and 100 ppm) for 3 and 6 months. The primary neurons were exposed to 0.4 mM (7.6 ppm) fluoride and thereafter treated with 100 nM rapamycin (a stimulator of mitophagy) or 50 μM 3-methyladenine (3-MA, an inhibitor of mitophagy) for 24 h. The expressions of PINK1/Parkin at the protein level and the activity of SOD in mitochondria of rat brains and cultured neurons were determined by Western blotting and biochemical method, respectively. The results showed that the rats exposed to fluoride exhibited different degrees of dental fluorosis. In comparison to controls, the expressions of PINK1 and Parkin were significantly higher in the rat brains and primary neurons exposed to high fluoride. In addition, a declined activity of mitochondrial SOD was determined. Interestingly, rapamycin treatment enhanced but 3-MA inhibited the changes of PINK1/Parkin pathway and SOD activity, and the correlations between the inhibited SOD activity and the elevated PINK1/Parkin proteins were observed. The results suggest that the inhibition of mitochondrial SOD activity induced by fluorosis may stimulate the expressions of mitophagy (PINK1/ Parkin) pathway to maintain the mitochondrial homeostasis.

Fluoride exposure confers NRF2 activation in hepatocyte through both canonical and non-canonical signaling pathways

Due to the high abundance in the Earth's crust and industrial application, fluoride is widely present in our living environment. However, excessive fluoride exposure causes toxicity in different organs. As the most important detoxification and excretion organ, liver is more easily involved in fluoride toxicity than other organs, and oxidative stress is considered as the key mechanism related with fluoride hepatotoxicity. In this study, we mainly investigated the role of nuclear factor erythroid-derived 2-like 2 (NRF2, a core transcription factor in oxidative stress) in fluoride exposure-induced hepatotoxicity as well as the related mechanism. Herein, liver cells (BNL CL.2) were treated with fluoride in different concentrations. The hepatotoxicity and NRF2 signaling pathway were analyzed respectively. Our results indicated that excessive fluoride (over 1 mM) resulted in obvious toxicity in hepatocyte and activated NRF2 and NRF2 target genes. The increased ROS generation after fluoride exposure suppressed KEAP1-induced NRF2 ubiquitylation and degradation. Meanwhile, fluoride exposure also led to blockage of autophagic flux and upregulation of p62, which contributed to activation of NRF2 via competitive binding with KEAP1. Both pharmaceutical activation and genetic activation of NRF2 accelerated fluoride exposure-induced hepatotoxicity. Thus, the upregulation of NRF2 in hepatocyte after fluoride exposure can be regarded as a cellular self-defense, and NRF2-KEAP1 system could be a novel molecular target against fluoride exposure-induced hepatotoxicity.

Hexafluoropropylene oxide trimer acid exposure triggers necroptosis and inflammation through the Wnt/β-catenin/NF-κB axis in the liver

Hexafluoropropylene oxide trimer acid (HFPO-TA), an emerging alternative to perfluorooctanoic acid (PFOA), has recently been identified as a significant environmental pollutant. Nevertheless, there is a scarcity of studies regarding the hepatotoxic effects of HFPO-TA. Here, we investigated the types and potential mechanisms of liver damage caused by HFPO-TA. Initially, we validated that the introduction of HFPO-TA resulted in the Wnt/β-catenin signaling (W/β signaling) activation, as well as the induction of necroptosis and inflammation, both in the liver of mice and in HepG2 cells. Subsequently, we established that the W/β signaling mediated the necroptosis and inflammation observed in the liver and HepG2 cells exposed to HFPO-TA. Finally, we demonstrated that the phosphorylated form of NF-κB p65 (p-NF-κB p65) played a role in mediating the necroptosis and inflammation, and its activity could be regulated by the W/β signaling pathway in the liver of mice and HepG2 cells exposed to HFPO-TA. In conclusion, our investigation elucidates the role of HFPO-TA in inducing necroptosis and inflammation in the liver, which is facilitated through the activation of the W/β/NF-κB axis.

α-Lipoic acid improves mitochondrial biogenesis and dynamics by enhancing antioxidant and inhibiting Wnt/Ca2+ pathway to relieve fluoride-induced hepatotoxic injury

Fluoride (F), widely present in water and food, poses a serious threat to liver health, and oxidative damage and mitochondrial damage are its main causes. As a natural mitochondrial protector and antioxidant, α-lipoic acid (ALA)'s alleviating effect on fluorosis liver injury and its underlying mechanism are still unclear. Therefore, this study established a fluorosis ALA intervention mice model to explore the mechanism of mitochondrial biogenesis, mitochondrial dynamics, and Wnt/Ca2+ pathway in ALA attenuating fluorosis liver injury. The results showed that ALA mitigated F-induced weight loss, hepatic structural and functional damage, hepatocytes mitochondrial damage, and decreased antioxidant levels. However, ALA did not reduce F accumulation in the femur. Further mRNA and protein detection results showed that F increased the expression levels of key genes in the mitochondrial fission (Drp1, Mff, and Fis1), mitophagy (Parkin, Pink1, and Prdx3), Wnt/Ca2+ pathway (Wnt5a and CaMK2), and rised the number and intensity of fluorescent spots of Drp1, but decreased the expression levels of key genes in the mitochondrial biogenesis (Sirt1, Sirt3, and PGC-1α) and fusion (OPA1, Mfn2, and Mfn1), and reduced the number and intensity of fluorescent spots of PGC-1α in the liver. However, the intervention of ALA relieved the F-induced changes in the expressions of the above genes. In conclusion, ALA mitigated F-induced hepatic injury through enhancing antioxidant capacity and inhibiting Wnt/Ca2+ pathway to improve mitochondrial biogenesis and dynamics disturbance. This study further reveals the hepatotoxic mechanism of F and the protective mechanism of ALA, and provides a theoretical basis for ALA as a potential preventive and palliative agent for F-induced hepatotoxic injury.

Fluoride-induced osteoporosis via interfering with the RANKL/RANK/OPG pathway in ovariectomized rats: Oophorectomy shifted skeletal fluorosis from osteosclerosis to osteoporosis

Osteosclerosis and osteoporosis are the two main clinical manifestations of skeletal fluorosis. However, the reasons for the different clinical manifestations are unclear. In this study, we established the fluoride (F) -exposed ovariectomized (OVX) and non-OVX rat models to assess the potential role of ovarian function loss in osteosclerosis and osteoporosis. Micro-CT scanning showed that excessive F significantly induced a high bone mass in non-OVX rats. In contrast, a low bone mass manifestation was presented in OVX F-exposed rats. Also, a prominent feature of increasing trabecular connectivity, collagen area, growth plate thickness, and reduced trabecular space was found by histopathological morphology in non-OVX F-exposed rats; an opposite result was observed in OVX F-exposed. These alterations indicated ovariectomy was a vital factor leading to osteosclerosis or osteoporosis in skeletal fluorosis. Furthermore, levels of bone alkaline phosphatase (BALP) and tartrate-resistant acid phosphatase (TRAP) increased, combined with the increasing osteoclasts number, showing a sign of high bone turnover in both OVX and non-OVX F-exposed rats. Mechanistically, oophorectomy considerably activated the RANKL/RANK/OPG signaling pathway. Meanwhile, it was discovered that upregulated NF-κB positively facilitated the accumulation of nuclear factor of activated T-cells 1 (NFATC1), significantly promoting osteoclast differentiation. To sum up, this study greatly enriched the causes of clinical skeletal fluorosis and provided a new perspective for studying the pathogenesis of skeletal fluorosis.

Combined Effects of Fluoride and Dietary Seleno-L-methionine at Environmentally Relevant Concentrations on Female Zebrafish (Danio rerio) Liver: Histopathological Damages, Oxidative Stress and Inflammation

Fluoride, a global environmental pollutant, is ubiquitous in aquatic environments and coexists with selenium, which can cause complex effects on exposed organisms. However, data on the interaction of fluoride and selenium remain scarce. In this study, female zebrafish (Danio rerio) were exposed to fluoride (80 mg/L sodium fluoride) and/or dietary selenomethionine for 30, 60 and 90 days, the effects on the liver of zebrafish were investigated. The results indicated that an increase in fluoride burden, inhibited growth and impaired liver morphology were recorded after fluoride exposure. Furthermore, fluoride alone caused oxidative stress and inflammation in the liver, as reflected by the increase in ROS and MDA contents, the reduction of anti-oxidative enzymes, the altered immune related enzymes (ACP, AKP, LZM and MPO) and the expression of IL-6, IL-1β, TNF-α, IL-10 and TGF-β. In contrast, co-exposure to fluoride and Se-Met decreased fluoride burden and restored growth. Furthermore, dietary Se-Met alleviated oxidative stress, inflammation and impaired morphology in liver trigger by fluoride. However, dietary Se-Met alone increased the activities of SOD and CAT. These results demonstrate that the protective effect of dietary Se-Met against chronic fluoride toxicity at a certain level.

The Pathophysiological Changes and Clinical Effects of Tetramethylpyrazine in ICR Mice with Fluoride-Induced Hepatopathy

The excessive intake of fluoride, one of the trace elements required to maintain health, leads to liver injury. Tetramethylpyrazine (TMP) is a kind of traditional Chinese medicine monomer with a good antioxidant and hepatoprotective function. The aim of this study was to investigate the effect of TMP on liver injury induced by acute fluorosis. A total of 60 1-month-old male ICR mice were selected. All mice were randomly divided into five groups: a control (K) group, a model (F) group, a low-dose (LT) group, a medium-dose (MT) group, and a high-dose (HT) group. The control and model groups were given distilled water, while 40 mg/kg (LT), 80 mg/kg (MT), or 160 mg/kg (HT) of TMP was fed by gavage for two weeks, with a maximum gavage volume for the mice of 0.2 mL/10 g/d. Except for the control group, all groups were given fluoride (35 mg/kg) by an intraperitoneal injection on the last day of the experiment. The results of this study showed that, compared with the model group, TMP alleviated the pathological changes in the liver induced by the fluoride and improved the ultrastructure of liver cells; TMP significantly decreased the levels of ALT, AST, and MDA (p < 0.05) and increased the levels of T-AOC, T-SOD, and GSH (p < 0.05). The results of mRNA detection showed that TMP significantly increased the mRNA expression levels of Nrf2, HO-1, CAT, GSH-Px, and SOD in the liver compared with the model group (p < 0.05). In conclusion, TMP can inhibit oxidative stress by activating the Nrf2 pathway and alleviate the liver injury induced by fluoride.

Advanced Biomarkers of Hepatotoxicity in Psychiatry: A Narrative Review and Recommendations for New Psychoactive Substances

One of the factors that increase the effectiveness of the pharmacotherapy used in patients abusing various types of new psychoactive substances (NPSs) is the proper functioning of the liver. However, the articles published to date on NPS hepatotoxicity only address non-specific hepatic parameters. The aim of this manuscript was to review three advanced markers of hepatotoxicity in psychiatry, namely, osteopontin (OPN), high-mobility group box 1 protein (HMGB1) and glutathione dehydrogenase (GDH, GLDH), and, on this basis, to identify recommendations that should be included in future studies in patients abusing NPSs. This will make it possible to determine whether NPSs do indeed have a hepatotoxic effect or whether other factors, such as additional substances taken or hepatitis C virus (HCV) infection, are responsible. NPS abusers are at particular risk of HCV infection, and for this reason, it is all the more important to determine what factors actually show a hepatotoxic effect in them.

Interleukin-17A knockout or self-recovery alleviated autoimmune reaction induced by fluoride in mouse testis

Fluoride (F) is usually treated as a hazardous material, and F-caused public health problem has attracted global attention. Previous studies demonstrate that interleukin-17A (IL-17A) plays a crucial role in F-elicited autoimmune orchitis and self-recovery reverses F-induced testicular toxicity to some extent, but these basic mechanisms remain unclear. Thus, we established a 180 d F exposure model of wild type (WT) mice and IL-17A knockout mice (C57BL/6 J background), and 60 d & 120 d self-recovery model based on F exposure model of WT mice, and used various techniques like qRT-PCR, western blot, immunohistochemistry and ELISA to further explore the mechanism of F-induced autoimmune reaction, the role of IL-17A in it and the reversibility of F-caused toxicity in testis. The results indicated that F exposure for 180 d caused the decreased sperm quality, the damaged testis histopathology, the enhanced mRNA and protein expression levels of inflammatory cytokines, the changes of autoantibody such as the appearance and increased content of anti-testicular autoantibodies in sera and the autoantibody deposition in testis, the alterations of autoimmune related genes containing the decreased mRNA and protein expressions of AIRE and FOXP3 with an increase of MHCII, and the reduced protein expressions of CTLA4, and the activation of IL-17A signaling cascade like the elevated mRNA and protein expressions of IL-17A, Act1, NF-κB, AP-1 and CEBPβ, and the increased protein expressions of IL-17RC, with a decrease of IκBα. After IL-17A knockout, 29 of 35 F-induced changes were alleviated. In two self-recovery models, all F-caused differences except fluorine concentration in femur were gradually restored in a time-dependent manner. This study concluded that IL-17A knockout or self-recovery attenuated F-induced testicular injury and decrease of sperm quality through alleviating autoimmune reaction which was involved with the activation of IL-17A pathway, the damage of self-tolerance and the enhancement of antigen presentation.

PRKAA1 induces aberrant mitophagy in a PINK1/Parkin-dependent manner, contributing to fluoride-induced developmental neurotoxicity

Chronic fluoride exposure can cause developmental neurotoxicity, however the precise mechanisms remain unclear. To explore the mechanism of mitophagy in fluoride-induced developmental neurotoxicity, specifically focusing on PRKAA1 in regulating the PINK1/Parkin pathway, we established a Sprage Dawley rat model with continuous sodium fluoride (NaF) exposure and an NaF-treated SH-SY5Y cell model. We found that NaF exposure increased the levels of LC3-Ⅱ and p62, impaired autophagic degradation, and subsequently blocked autophagic flux. Additionally, NaF exposure increased the expression of PINK1, Parkin, TOMM-20, and Cyt C and cleaved PARP in vivo and in vitro, indicating NaF promotes mitophagy and neuronal apoptosis. Meanwhile, phosphoproteomics and western blot analysis showed that NaF treatment enhanced PRKAA1 phosphorylation. Remarkably, the application of both 3-methyladenosine (3-MA; autophagy inhibitor) and dorsomorphin (DM; AMPK inhibitor) suppressed NaF-induced neuronal apoptosis by restoring aberrant mitophagy. In addition, 3-MA attenuated an increase in p62 protein levels and NaF-induced autophagic degradation. Collectively, our findings indicated that NaF causes aberrant mitophagy via PRKAA1 in a PINK1/Parkin-dependent manner, which triggers neuronal apoptosis. Thus, regulating PRKAA1-activated PINK1/Parkin-dependent mitophagy may be a potential treatment for NaF-induced developmental neurotoxicity.

Nrf2/PINK1-mediated mitophagy induction alleviates sodium fluoride-induced hepatic injury by improving mitochondrial function, oxidative stress, and inflammation

Mitophagy has distinct functions, which can lead to either protection or damage of tissues. Though current evidence indicated that NaF triggers mitophagy, the role and regulation of mitophagy in sodium fluoride (NaF)-induced liver injury still remain unclear. Therefore, we exployed the cell and mouse models and confirmed that NaF treatment activates mitophagy. Knocking down PTEN-induced putative kinase protein 1 (PINK1) expression attenuated mitophagy and increased the degree of mitochondrial impairment, oxidative stress, and apoptosis in NaF-treated HepG2 cells. In vivo experiments indicated that PINK1 deficiency weakened NaF-induced mitophagy. Moreover, PINK1-deficient mices aggravated NaF-induced hepatic mitochondrial injury, oxidative stress, and inflammation in livers, evidenced by the increased number of abnormal mitochondria, decreased adenosine triphosphate (ATP) and glutathione (GSH) levels, elevated reactive oxygen species (ROS) and malondialdehyde (MDA) content, enhanced hepatic macrophage infiltration and inflammatory cytokine levels. Notably, NaF exposure activated Nrf2 signaling both in vitro and in vivo. Nrf2 siRNA transfection blocked the upregulation of PINK1 expression and the induction of mitophagy in NaF-treated HepG2 cells. Also, ML385 (Nrf2 inhibitor) partially blocked the upregulation of PINK1 expression caused by NaF in mice livers. To sum up, the present study provided the demonstration that Nrf2/PINK1-mediated mitophagy activation offers a hepatoprotective effect by inhibiting NaF-induced mitochondrial dysfunction, oxidative stress, and inflammation.

Choline alleviated perinatal fluoride exposure-induced learning and memory impairment through α4β2 nAChRs and α7 nAChRs in offspring mice

Fluoride pollution is widely present in the living environment. As a critical period of brain development, the perinatal period is extremely vulnerable to fluoride. Studies have found that choline can protect the brain's memory and enhance the ability to focus. However, the effect of choline on perinatal fluoride-induced nerve damage remains unclear. Therefore, 32 Kunming newly conceived female mice and their offspring mice were randomly divided into control, NaF, LC + NaF, and HC + NaF groups, and the HE staining, Y-maze test, RT-PCR, western blotting, immunohistochemistry, etc. were used in this study. The results showed that fluoride decreased the brain organ coefficients and brain protein content (p < 0.05, p < 0.01), and caused histomorphological damage in the hippocampus and cortex, which suggested that fluoride affected the development of the brain and damaged the brain. Moreover, the results of the Y-maze test showed that fluoride increased the number of learning days, error reaction time, and total reaction time, and decreased the AchE activity in the brain (p < 0.05, p < 0.01), which indicated that fluoride reduced the learning and memory ability of the mice. Besides, the results showed that fluoride decreased the mRNA and protein expression levels of α4β2 nAChRs and α7 nAChRs in the hippocampus and cortex (p < 0.05, p < 0.01). However, perinatal choline supplementation reversed the aforementioned fluoride-induced changes. In short, these results demonstrated that choline alleviated perinatal fluoride-induced learning and memory impairment, which will provide a rationale for the mitigation and prevention of fluoride-induced brain damage.

Cross-talk between autophagy and ferroptosis contributes to the liver injury induced by fluoride via the mtROS-dependent pathway

Fluoride can induce hepatotoxicity, but the mechanisms responsible are yet to be investigated. This study sought to investigate the role and mechanism of mitochondrial reactive oxygen species (mtROS), autophagy, and ferroptosis in fluoride-induced hepatic injury with a focus on the role of mtROS-mediated cross-talk between autophagy and ferroptosis. To this end, an in vivo Sprague-Dawley rat model and in vitro BRL3A cells were exposed to sodium fluoride (NaF). The results revealed that NaF exposure diminished the mitochondrial membrane potential, increased mtROS production and TOMM20 expression, and induced autophagic flux blockage and ferroptosis in vivo and in vitro. Furthermore, the autophagy activator (RAPA) enhanced GPX4 expression while inhibiting ACSL4 expression, reduced the accumulation of ferrous ions in BRL3A cells, and restored lipid peroxidation levels, thus inhibiting ferroptosis. Fer-1, a ferritinase inhibitor, downregulated the expression of LC3-II and p62, increased the number of autolysosomes while decreasing the number of autophagosomes, and alleviated the blockage of autophagic flux by improving autophagic degradation. These results suggest the occurrence of a cross-talk between autophagy and ferroptosis. The mtROS inhibitor (Mito-TEMPO) could alleviate autophagic flux blockage and inhibit ferroptosis in NaF-induced liver injury. In addition, the cross-talk between NaF-induced autophagy and ferroptosis was dependent on the mtROS pathway.

Secukinumab alleviates cognitive impairment by attenuating oxidative stress and neuronal apoptosis via the IL-17RA/AKT/ERK1/2 pathway in a rat model of sepsis

BACKGROUND

Septic-associated encephalopathy (SAE) is a critical manifestation of sepsis that leads to long-term cognitive impairment. Interleukin (IL)-17A has been shown to mediate neuronal apoptosis in central nervous system diseases, while oxidative stress has been found to have a detrimental effect in SAE. However, the relationship between IL-17A and oxidative stress in SAE remains unclear. This study aimed to investigate the effects of secukinumab on alleviating cognitive impairment in a rat model of sepsis, as well as examine its underlying molecular mechanism of action.

METHODS

A total of 282 male 8-week-old Sprague-Dawley rats were randomly subjected to cecal ligation and puncture (CLP) or sham treatment followed by volume resuscitation immediately after surgery. Secukinumab was administered intranasally 1 h post-CLP. Rats were given the p-ERK activator ceramide C6 intracerebroventricularly (i.c.v) 24 h before CLP surgery. Recombinant rIL-17A was administered i.c.v. at 0 h in naive rats, followed by intraperitoneal injection of the AKT inhibitor GDC0068 1 h post-rIL-17A injection. Clinical scores, body weight, and survival rate were assessed. In addition, immunofluorescence staining, neurobehavioral tests, Nissl staining, and western blotting were performed. Cognitive function was assessed 15-20 days post-CLP using the Morris water maze test.

RESULTS

IL-17A and IL-17RA protein expression levels in the rat hippocampus increased and peaked 24 h post-CLP. Furthermore, IL-17RA was found to be expressed in neurons. The survival rate after CLP was 50%. Following CLP, an increased clinical score and significant decrease in body weight were observed. However, treatment with secukinumab led to a decrease in the clinical score of rats 24 h post-CLP. CLP resulted in spatial and memory impairment and anxiety-like behaviors in rats, while secukinumab treatment significantly alleviated cognitive impairment compared to the CLP group (p < 0.05). In addition, oxidative stress and neuronal apoptosis were found to be increased in the CLP group, while secukinumab significantly reduced oxidative stress and neuronal apoptosis in the hippocampus following CLP. Furthermore, secukinumab treatment led to a significant decrease in the protein expression levels of p-AKT, p-ERK1/2, Romo1, and Bax, together with increased Bcl-2 protein expression. Finally, treatment with ceramide C6 and GDC0068 abolished the neuroprotective effects of secukinumab post-CLP.

CONCLUSION

Our results demonstrated that secukinumab attenuated oxidative stress and neuronal apoptosis and partially ameliorated cognitive impairment via the IL-17RA/AKT/ERK1/2 pathway in a rat model of sepsis. Thus, secukinumab may be a potential therapeutic strategy for septic patients.

α-Lipoic Acid Alleviated Fluoride-Induced Hepatocyte Injury via Inhibiting Ferroptosis

Fluoride is widely used in agricultural production and food packaging. Excessive fluoride in water and food is a serious threat to liver health. α-Lipoic acid, a natural free radical scavenger, has hepatoprotective properties. However, the protective effect of α-lipoic acid on fluorohepatotoxicity is uncertain. The aim of this study was to investigate the mechanism of ferroptosis in α-lipoic acid preventing fluoride-induced hepatotoxicity. Five-week-old ICR mice were treated with sodium fluoride (100 mg/L) and/or α-lipoic acid (200 mg/kg) for 9 weeks. The results showed that α-lipoic acid attenuated fluoride-induced damage to liver morphology and ultrastructure. Moreover, α-lipoic acid alleviated fluoride-induced iron accumulation, increased oxidative stress, and elevated lipid peroxidation in the liver. In addition, the mechanism study found that α-lipoic acid prevented fluoride-induced ferroptosis through the System Xc^-/GPX4 axis, lipid peroxidation axis, and iron metabolism axis, but it was interestingly not regulated by mitochondrial free radical axis in the hepatocytes. Altogether, this study indicated that α-lipoic acid prevents fluoride-induced liver injury by inhibiting ferroptosis, which has potential implications for the prevention and treatment of fluoride-induced liver injury.

Multiomics Analysis Revealed the Molecular Mechanism of miRNAs in Fluoride-Induced Hepatic Glucose and Lipid Metabolism Disorders

Fluoride-induced liver injury seriously endangers human and animal health and animal food safety, but the underlying mechanism remains unclear. This study aims to explore the mechanism of miRNAs in fluoride-induced hepatic glycolipid metabolism disorders. C57 male mice were used to establish the fluorosis model (22.62 mg/L F^-, 12 weeks). The results indicated that fluoride increased fluoride levels, impaired the structure and function, and disrupted the glycolipid metabolism in the liver. Furthermore, the sequencing results showed that fluoride exposure resulted in the differential expression of 35 miRNAs and 480 mRNAs, of which 23 miRNAs were related to glycolipid metabolism. miRNA-mRNA network analyses and RT-PCR revealed that miRNAs mediated fluoride-induced disturbances in the hepatic glycolipid metabolism. Its possible mechanism was to regulate the insulin pathway, PPAR pathway, and FOXO pathway, which in turn affected the bile secretion, the metabolic processes of glucose, the decomposition of lipids, and the synthesis of unsaturated fatty acids in the liver. This study provides a theoretical basis for miRNAs as diagnostic indicators and target drugs for the treatment of fluoride-induced liver injury.

Fluoride Exposure Provokes Mitochondria-Mediated Apoptosis and Increases Mitophagy in Osteocytes via Increasing ROS Production

Fluoride is a persistent environmental pollutant, and its excessive intake causes skeletal and dental fluorosis. However, few studies focused on the effects of fluoride on osteocytes, making up over 95% of all bone cells. This study aimed to investigate the effect of fluoride on osteocytes in vitro, as well as explore the underlying mechanisms. CCK-8, LDH assay, fluorescent probes, flow cytometry, and western blotting were performed to examine cell viability, apoptosis, mitochondria changes, reactive oxygen species (ROS) and mitochondrial ROS (mtROS), and protein expressions. Results showed that sodium fluoride (NaF) exposure (4, 8 mmol/L) for 24 h inhibited the cell viability of osteocytes MLO-Y4 and promoted G0/G1 phase arrest and increased cell apoptosis. NaF treatment remarkably caused mitochondria damage, loss of MMP, ATP decrease, Cyto c release, and Bax/Bcl-2 ratio increase and elevated the activity of caspase-9 and caspase-3. Furthermore, NaF significantly upregulated the expressions of LC-3II, PINK1, and Parkin and increased autophagy flux and the accumulation of acidic vacuoles, while the p62 level was downregulated. In addition, NaF exposure triggered the production of intracellular ROS and mtROS and increased malondialdehyde (MDA); but superoxide dismutase (SOD) activity and glutathione (GSH) content were decreased. The scavenger N-acetyl-L-cysteine (NAC) significantly reversed NaF-induced apoptosis and mitophagy, suggesting that ROS is responsible for the mitochondrial-mediated apoptosis and mitophagy induced by NaF exposure. These findings provide in vitro evidence that apoptosis and mitophagy are cellular mechanisms for the toxic effect of fluoride on osteocytes, thereby suggesting the potential role of osteocytes in skeletal and dental fluorosis.

Effects of fluoride exposure on mitochondrial function: Energy metabolism, dynamics, biogenesis and mitophagy

Fluoride is ubiquitous in the environment. Furthermore, drinking water represents the main source of exposure to fluoride for humans. Interestingly, low fluoride concentrations have beneficial effects on bone and teeth development; however, chronic fluoride exposure has harmful effects on human health. Besides, preclinical studies associate fluoride toxicity with oxidative stress, inflammation, and apoptosis. On the other hand, it is well-known that mitochondria play a key role in reactive oxygen species production. By contrast, fluoride's effect on processes such as mitochondrial dynamics, biogenesis and mitophagy are little known. These processes modulate the size, content, and distribution of mitochondria and their depuration help to counter the reactive oxygen species production and cytochrome c release, thereby allowing cell survival. However, a maladaptive response could enhance fluoride-induced toxicity. The present review gives a brief account of fluoride-induced mitochondrial alterations on soft and hard tissues, including liver, reproductive organs, heart, brain, lung, kidney, bone, and tooth.