Fluoride-induced testicular and ovarian toxicity: evidence from animal studies

Fluoride (F), as a natural element found in a wide range of sources such as water and certain foods, has been proven to be beneficial in preventing dental caries, but concerns have been raised regarding its potential deleterious effects on overall health. Sodium fluoride (NaF), another form of F, has the ability to accumulate in reproductive organs and interfere with hormonal regulation and oxidative stress pathways, contributing to reproductive toxicity. While the exact mechanisms of F-induced reproductive toxicity are not fully understood, this review aims to elucidate the mechanisms involved in testicular and ovarian injury. In males, F exposure at different doses has been associated with reduced testis weight, reduced sperm quality in terms of count, motility, and viability, as well as abnormal sperm morphology and disruption of seminiferous tubules by altering hormone levels (especially testosterone), impairing spermatogenesis, and inducing oxidative stress and zinc deficiency. Similarly, administration of F can impact female reproductive health by affecting ovarian function, hormone levels, oocyte quality, and the regularity of the estrous cycle. However, the impact of F exposure on LH, FSH, and GnRH levels is controversial between males and females. In both males and females, F exerts its adverse effects by triggering apoptosis, autophagy, inflammation, mitochondrial dysfunction, reduction in ATP synthesis, and modulation of important genes involved in steroidogenesis. Furthermore, genetic susceptibility and individual variations in F metabolism may contribute to different responses to fluoride exposure.

Novel Aspects of cAMP-Response Element Modulator (CREM) Role in Spermatogenesis and Male Fertility

Spermatogenesis is a very complex process with an intricate transcriptional regulation. The transition from the diploid to the haploid state requires the involvement of specialized genes in meiosis, among other specific functions for the formation of the spermatozoon. The transcription factor cAMP-response element modulator (CREM) is a key modulator that triggers the differentiation of the germ cell into the spermatozoon through the modification of gene expression. CREM has multiple repressor and activator isoforms whose expression is tissue-cell-type specific and tightly regulated by various factors at the transcriptional, post-transcriptional and post-translational level. The activator isoform CREMτ controls the expression of several relevant genes in post-meiotic stages of spermatogenesis. In addition, exposure to xenobiotics negatively affects CREMτ expression, which is linked to male infertility. On the other hand, antioxidants could have a positive effect on CREMτ expression and improve sperm parameters in idiopathically infertile men. Therefore, CREM expression could be used as a biomarker to detect and even counteract male infertility. This review examines the importance of CREM as a transcription factor for sperm production and its relevance in male fertility, infertility and the response to environmental xenobiotics that may affect CREMτ expression and the downstream regulation that alters male fertility. Also, some health disorders in which CREM expression is altered are discussed.

Royal jelly arranges apoptotic and oxidative stress pathways and reduces damage to liver tissues of rats by down-regulation of Bcl-2, GSK3 and NF-κB and up-regulation of caspase and Nrf-2 protein signalling pathways

IntroductionRoyal jelly (RJ) from the honey bee, Apis mellifera, is a traditional product that is widely used as a food supplement to support the medical treatment of various diseases.Material and methodsOur study continued for 8 weeks. 42 Wistar albino (8 weeks old) male rats were used in the study. The study included 6 groups; Group 1: Control group (fed with standard diet), Group 2: RJ (100 mg/kg, bw), Group 3: F-50 (50 mg/kg, bw), group 4: F-100 (100 mg/kg, bw) group 5: F-50 (50 mg/kg, bw) + RJ (100 mg/kg, bw) Group 6: F-100 (100 mg/kg, bw) + RJ (100 mg/kg, bw). Malondialdehyde (MDA), catalase (CAT) and glutathione (GSH) activities in liver tissue were determined by spectrophotometer. Liver tissue samples were examined histopathologically and various protein levels were determined by Western blotting technique.ResultsRJ caused a significant decrease in MDA level, Bcl-2, GSK3 and NF-κB protein expression levels, whereas induced a significant increase in GSH level, CAT activities and Bax, BDNF, caspase-6, caspase-3, Nrf-2 protein expression levels.ConclusionOur findings suggest RJ to be used as a hepatoprotective agent in the clinic to modulate the toxic effects of fluoride and other chemicals in the future.

Alleviating effects of selenium on fluoride-induced testosterone synthesis disorder and reproduction toxicity in rats

Fluoride (F) exists widely in food, water and other natural resources, and can cause damage to the reproductive system of human and animals. Studies have shown that selenium (Se) is a necessary trace element to maintain the normal male reproductive system. However, it is not clear whether it can alleviate the damage of reproductive system induced by F. Hence, sodium fluoride (NaF) was administered singly in drinking water at 100 mg L^-1 alone and co-administered by drinking with sodium selenite (Na₂SeO₃) at 0.5, 1.0, 2.0 mg L^-1 for 10 consecutive weeks. The results demonstrated that the sperm deformity rate were increased significantly by F, however, it was improved significantly after the addition of 2.0 mg L^-1 Na₂SeO₃. The contents of glutathione peroxidase 4 (GPX-4), selenoprotein P (SePP), pregnenolone (PREG), androstenedione (ASD), and testosterone (T) were reduced obviously in the F group, however, it was increased significantly after adding 0.5, 1.0 and 2.0 mg L^-1 Na₂SeO₃. F decreased noticeably the mRNA and protein expression levels of steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side chain lyase (P450scc), 3β-hydroxysteroid dehydrogenase (3β-HSD), cytochrome P450 17α-hydroxylase (P450c17) and 17β-hydroxysteroid dehydrogenase (17β-HSD), which was increased obviously after the addition of 1.0 and 2.0 mg L^-1 Na₂SeO₃. In summary, 2.0 mg L^-1 Na₂SeO₃ can alleviate testosterone synthesis disorder induced by F via reducing oxidative stress, increasing the level of selenoprotein in testis and regulating the content of related hormones and enzyme activity during testosterone synthesis pathway.

Protective effect of royal jelly on fluoride-induced nephrotoxicity in rats via the some protein biomarkers signaling pathways: A new approach for kidney damage

Introduction: Protective effect of royal jelly (RJ) on fluoride-induced nephrotoxicity was investigated in this study.Methods: 42 healthy male Wistar rats (n = 42, 8 weeks of age) were divided equally into 6 groups with 7 rats in each; (1) Group-1: Controls fed with standard diet; (2) Group-2: RJ [100 mg/kg] bw (body weight), by oral gavage; (3) Group-3: Fluoride [50 mg/kg] bw, in drinking water; (4) Group-4: Fluoride [100 mg/kg] bw, in drinking water; (5) Group-5: RJ [100 mg/kg] bw, by oral gavage + Fluoride [50 mg/kg] bw, in drinking water; (6) Group-6: RJ [100 mg/kg] bw, by oral gavage + Fluoride [100 mg/kg] bw, in drinking water. After 8 weeks, all rats were decapitated and their kidney tissues were removed for further analysis. The protein expression levels of caspase-3, caspase-6, caspase-9, Bcl-2, Bax, VEGF, GSK-3, BDNF, COX-2 and TNF-α proteins in kidney tissue were analysed by western blotting techniqueResults: RJ increased Bcl-2, COX-2, GSK-3, TNF-α and VEGF protein levels and a decreased caspase-3, caspase -6, caspase-9, Bax and BDNF protein levels in fluoride-treated rats.Conclusion: RJ application may have a promising therapeutical potential in the treatment of many diseases in the future by reducing kidney damage.

The expression, function, and utilization of Protamine1: a literature review

Objective

Protamine 1 (PRM1) is specific in sperm and plays essential roles in fertilization, also a member of cancer testis antigen (CTA) family. This study aims to summarize the expression and function of PRM1 in spermatogenesis, and to broaden the current knowledge and inspire future development of PRM1-based therapeutic strategies in cancer treatment and nanomedicine.

Background

The protamine proteins, are characterized by an arginine-rich core and cysteine residues. Humans express two types of protamine: PRM1 and PRM2. The abnormal expression or proportion of PRM1 and PRM2 is known to be associated with subfertility and infertility, especially for PRM1 which is highly evolutionary conserved in mammalians and expressed in all vertebrates. Biological functions of PRM1 have been unveiled in diverse cellular processes, such as tumorigenesis, somatic cell nucleus transfer, and drug delivery systems. Moreover, PRM1 is identified as a CTA in chronic leukemia (CLL) and colorectal cancer (CRC).

Methods

Literature was obtained using PubMed and the keywords protamine 1, PRM1, or P1, from January 1, 1980, through July 20, 2021. We also collect the additional evidence through screening references of articles identified through the PubMed searches.

Conclusions

PRM1 is well-studied in male infertility, and further researches and attempts to develop PRM1 as novel tumor marker, as well as drug delivery vector, will be of important clinical significance.

The inducing of caspase and Bcl-2 pathway with royal jelly decreases the muscle tissue damage exposed with fluoride in rats

In this study, 42 Wistar albino male rats (n = 42, 8 weeks old) were used. Rats were divided into 6 groups and 7 rats included each group. Groups: (i) Control group: Standard diet; (ii) RJ (royal jelly) group: Standard diet + royal jelly; (iii) F50 group: Standard diet + 50 mg/kg fluoride; (iv): F100 group: Standard diet + 100 mg/kg fluoride; (v) F50+RJ group: Standard diet + 50 mg/kg fluoride + royal jelly; (vi): F100+RJ group: Standard diet + 100 mg/kg fluoride + royal jelly. After 8 weeks, the rats were decapitated, and their muscle tissues were removed. Expression levels of Caspase-3, Caspase-6, Bax, tumor necrosis factor-α (TNF-α), interleukin 1 alpha (IL1-α) and Bcl-2 proteins in muscle tissue were determined by western blotting method. Histopathological analyses were also performed on the muscle tissue. Malondialdehyde (MDA), glutathione (GSH) and catalase (CAT) analyses were determined by a spectrophotometer. According to the obtained results, Bcl-2, TNF-α and IL1-α protein expression was increased in damage groups compared to the control and royal jelly groups, while Caspase-3, Caspase-6 and Bax protein expression levels decreased in damage groups. MDA level increased in damage groups compared to the control and royal jelly groups, while CAT and GSH levels increased with royal jelly application in royal jelly-given group in comparison to the flouride-exposed group. According to histopathological analysis results, edema and inflammatory cell formations were found in the injury groups, a tendency to decrease in these injuries was observed in the treatment groups. Based on these results, we can say that royal jelly has protective effects on muscle tissue against fluoride damage.

Royal jelly abrogates flouride-induced oxidative damage in rat heart tissue by activating of the nrf-2/NF-κB and bcl-2/bax pathway

Royal jelly is known to strengthen memory, provide antioxidative, antidiabetic, antitumor, anticancer, antibacterial, antiinflammatory, antihypertensive. In this study, 42 rats (n = 42) were used, and these rats were divided into 6 groups of 7 rats each. Groups: (i) Control Group: Group fed with standard diet; (ii) Royal Jelly (RJ) Group: RJ (100 mg/kg bw, gavage); (iii) F50 Group: Fluoride (50 mg/kg bw, drinking water); (iv) F100 Group: F (100 mg/kg bw, drinking water); (v) F50 + RJ Group: F (50 mg/kg bw, drinking water) + RJ (100 mg/kg bw, gavage); (vi) F100 + RJ Group: F (100 mg/kg bw, drinking water) + RJ (100 mg/kg bw, gavage). The rats were decapitated after 8 weeks, and their heart tissues were taken and examined. Lipid peroxidation by MDA (malondialdehyde) analyzes, GSH (glutathione) level and catalase activity were determined by spectrophotometer. Protein expression levels of caspase-3, caspase-6, caspase-9, Bcl-2, Bax, BDNF, Gsk-3, Nrf-2 and NF-κB proteins in heart tissue were determined by western blotting technique and hearth tissue evaluated by histopathologically. As a result, MDA levels, Bcl-2, Gsk-3 and NF-κB protein expression levels were reduced, whereas GSH levels, caspase-3, caspase-9, caspase-6, Bax, BDNF and Nrf-2 protein levels were increased in the F50 + RJ and F100 + RJ groups compared to the F50 and F100 groups. According to the results of this study, it has been concluded that Royal jelly has the potential to be developed in to a drug for treatment of heart diseases in addition to providing protection against heart damage.

Upregulation of miR-200c-3p induced by NaF promotes endothelial apoptosis by activating Fas pathway

Fluoride has been considered as a risk factor of cardiovascular disease due to its endothelial toxicology. However, the mechanism underlying the endothelial toxicity of fluoride has not been clearly illustrated. MiR-200c-3p was strongly linked with endothelial function and its level is increased in serum of fluorosis patients, but it is unclear the role of miR-200c-3p in the fluoride induced endothelial dysfunction. In this study, we confirmed that fluoride exposure induced the apoptosis of endothelial cells both in established rats model and cultured human umbilical vein endothelial cells (HUVECs). And miR-200c-3p was found to be upregulated in NaF treated HUVECs. Fluoride stimulation increased caspase-dependent apoptosis through miR-200c-3p upregulation, with repressing expression of its target gene Fas-associated phosphatase 1 (Fap-1), which functioned as Fas inhibitor. This resulted in activation of Fas-associated extrinsic apoptosis via interaction with increased Fas, Fadd, Cleaved Caspase-8 and Cleaved Caspase-3. The activation of Fas-associated extrinsic apoptosis was abrogated by miR-200c-3p inhibitor. Furthermore, the antiapoptotic effect of downregulated miR-200c-3p was restored by Fap-1 siRNA. These results suggested a determinant role of the miR-200c-3p/Fap-1 axis in fluoride induced endothelial apoptosis.

Fluoride exposure arrests the acrosome formation during spermatogenesis via down-regulated Zpbp1, Spaca1 and Dpy19l2 expression in rat testes

The exposure and health effects of fluoride are an ongoing topic that has attracted worldwide attention. Fluoride exposure disturbs the testicular development, sexual hormone levels and spermatogenesis. However, as to whether fluoride interferes with acrosome formation which is essential for production of capable spermatozoa during spermatogenesis still remains unclear. The objective was to determine the effects of fluoride on the acrosome formation and to further elucidate the potential mechanism of impaired reproductive function. For this, forty adult rats were assigned into four groups. The control group received distilled water, while the other three groups were treated with 25, 50 and 100 mg NaF/L via drinking water for 56 d, respectively. Testes were processed for total RNA extraction and western blot analysis. Three samples of each group were fixed in 2.5% glutaraldehyde solution for transmission electron microscopy analysis. From the results, we first found that fluoride decreased the expression of mRNA and protein levels of Zpbp1, Spaca1 and Dpy19l2 of seven markers during acrosome biogenesis in testes. Furthermore, fluoride damaged not only the acrosome structure, but also the structure of the nuclear lamina which was observed to be discontinuous and partially missing by transmission electron microscopy. Moreover, the results indicated that the altered structure in nuclear lamina maybe due to reduced LMNB2 expression in testis induced by fluoride. In a nutshell, fluoride exposure could restrain acrosome biogenesis during spermatogenesis and contribute to the elucidation of the underlying mechanisms of fluoride-induced male reproductive toxicity.

Fluoride altered rat's blood testis barrier by affecting the F-actin via IL-1α

Fluoride is known to affect the pro-inflammatory cytokines in the testis. Most of the recent literatures cited that cytokines regulate the blood-testis-barrier (BTB). However, the involvement of cytokines in the fluoride induced toxicity in BTB remains unclear. In order to study this, 60 male Sprague-Dawley (SD) rats were taken and randomly divided into 5 groups which included four fluoride groups exposed to 0, 25, 50, and 100 mg/L NaF in distilled water and one positive control group. On the 29th day of fluoride exposure, the positive control group rats were administered 0.1% CaCl₂ solution. Biotin tracer technology and transmission electron microscopy (TEM) analysis were applied to evaluate the function and ultra-structure of BTB. The expression levels of the BTB associated proteins, actin relative protein 3 (Arp3), interleukin-1 alpha (IL-1α), and transforming growth factor beta-3 (TGF-β3) were determined using Western blotting and Enzyme Linked Immunosorbent Assay (ELISA) respectively, meanwhile the actin filament (F-actin) was detected by fluorescent phalloidin conjugates. Our results revealed that the function and the ultra-structure of BTB in all the fluoride treated groups were damaged with a concomitant significant decreases in basal ectoplasmic specialization (basal ES), associated protein β-catenin, and F-actin. Moreover, Arp3 levels were significantly increased in 50 and 100 mg/L NaF groups. Meanwhile, IL-1α significantly increased in all the fluoride treated groups. In summary, we concluded that an increase in IL-1α induced by NaF significantly decreased the expression of F-actin and the organization of F-actin highly branched, which might facilitate the BTB's functional and ultra-structural variations.