Salivary Gland Derived BDNF Overexpression in Mice Exerts an Anxiolytic Effect

Is serum BDNF level relıable parameter ın detectıng of dental anxıety before ımpacted thırd molar surgery?

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a factor that implicate in the pathophysiology and treatment of depression and anxiety. The aim of this study was to determine the relationship between dental anxiety and BDNF serum level through impacted third molar surgery.

MATERIAL AND METHODS

In this randomized, double-blind, cross-sectional study, the sample included patients who had been admitted for the impacted third molar extraction under local anesthesia between January to November 2020. The primary predictor variable was serum BDNF level and the second predictor variable was dental anxiety scores before and after operation in patients. The primary outcome variable was the correlation between anxiety scores (APAIS, MDAS, STAI, VAS) and serum BDNF level. The sample included 55 patients (22 Male, 33 Female) aged 18 to 42 (24,2+5,55).

RESULTS

Comparison of pre-operative scores (APAIS, MDAS, STAI, VAS and BDNF) and post-operative scores were statistically significant (P < .05). Post-operatively, MDAS and VAS scores decreased, while BDNF levels and STAI scores increased compared to the preoperative scores. BDNF was not correlated with APAIS, MDAS, STAI, and VAS preoperatively and postoperatively.

CONCLUSIONS

There may be a relationship between serum BDNF level and dental anxiety scale, but, no correlation was found between them.

Transcriptomic analysis of the submandibular gland under psychological stress condition

BACKGROUND

Psychological stress is associated with changes in salivary flow and composition. However, studies to show the effect of psychological stress on the transcriptome of the salivary gland are limited. This study aims to perform a transcriptomic analysis of the submandibular gland under psychological stress using a chronic restraint stress model of rats.

METHODS

Sprague-Dawley rats were divided into stress groups and control groups. Psychological stress was induced in the stress group rats by enclosing them in a plastic tube for 4 h daily over 6 weeks. RNA sequencing was performed on RNA extracted from the submandibular gland. The differentially expressed genes were identified, and the genes of interest were further validated using qRT-PCR, immunofluorescence, and western blot.

RESULTS

A comparison between control and stress groups showed 45 differentially expressed genes. The top five altered genes in RNA sequencing data showed similar gene expression in qRT-PCR validation. The most downregulated gene in the stress group, FosB, was a gene of interest and was further validated for its protein-level expression using immunofluorescence and western blot. The genesets for gene ontology cellular component, molecular function, and KEGG showed that pathways related to ribosome biosynthesis and function were downregulated in the stress group compared to the control.

CONCLUSION

Psychological stress showed transcriptomic alteration in the submandibular gland. The findings may be important in understanding stress-related oral diseases.

Neurotoxic stimulation alters prosaposin levels in the salivary systems of rats

Prosaposin (PSAP), a potent neurotrophic factor, is found in neuronal and non-neuronal tissues and various biological fluids. Neuropathological conditions often alter PSAP production in neural tissues. However, little is known about its alterations in non-neural tissues, particularly in the salivary glands, which are natural reservoirs of various neurotrophic factors. In this study, we explored whether neurotoxic stimulation by kainic acid (KA), a glutamate analog, altered PSAP levels in the salivary system of rats. The results revealed that KA injection did not alter total saliva production. However, KA-induced neurotoxic stimulation significantly increased the PSAP level in the secreted saliva but decreased it in the serum. In addition, KA-induced elevated immunoreactivities of PSAP and its receptors have been observed in the granular convoluted tubule (GCT) cells of the submandibular gland (SMG), a major salivary secretory organ. Indeed, a large number of PSAP-expressing immunogold particles were observed in the secretory granules of the SMG. Furthermore, KA-induced overexpression of PSAP was co-localized with secretogranin in secretory acini (mostly in GCT cells) and the ductal system of the SMG, suggesting the release of excess PSAP from the salivary glands into the oral cavity. In conclusion, the salivary system produces more PSAP during neurotoxic conditions, which may play a protective role in maintaining the secretory function of the salivary glands and may work in distant organs.

Metabolic profiles of saliva in male mouse models of chronic sleep disorders induced by psychophysiological stress

Disordered sleep is a global social problem and an established significant risk factor for psychological and metabolic diseases. We profiled non-targeted metabolites in saliva from mouse models of chronic sleep disorder (CSD). We identified 288 and 55 metabolites using CE-FTMS and LC-TOFMS, respectively, among which concentrations of 58 (CE-FTMS) and three (LC-TOFMS) were significantly changed by CSD. Pathway analysis revealed that CSD significantly suppressed glycine, serine and threonine metabolism. Arginine and proline metabolic pathways were among those that were both upregulated and downregulated. Pathways of alanine, aspartate and glutamate metabolism, genetic information processing, and the TCA cycle tended to be downregulated, whereas histidine metabolism tended to be upregulated in mice with CSD. Pyruvate, lactate, malate, succinate and the glycemic amino acids alanine, glycine, methionine, proline, and threonine were significantly decreased, whereas 3-hydroxybutyric and 2-hydroxybutyric acids associated with ketosis were significantly increased, suggesting abnormal glucose metabolism in mice with CSD. Increases in the metabolites histamine and kynurenic acid that are associated with the central nervous system- and decreased glycine, might be associated with sleep dysregulation and impaired cognitive dysfunction in mice with CSD. Our findings suggested that profiling salivary metabolites could be a useful strategy for diagnosing CSD.

Lactobacillus rhamnosus zz-1 exerts preventive effects on chronic unpredictable mild stress-induced depression in mice via regulating the intestinal microenvironment

Depression remains one of the most prevalent psychiatric disorders, and it has been confirmed that it is related to the dysfunction of the microbiota-gut-brain axis. Manipulation of the gut microenvironment by probiotics might improve mental health and prevent stress-related psychiatric disorders. The present study aimed to determine whether Lactobacillus rhamnosus (L. rhamnosus) zz-1 could prevent the occurrence of depression and its potential mechanisms using a mouse model with chronic unpredictable mild stress (CUMS). The results indicated that L. rhamnosus zz-1 intervention ameliorated CUMS-induced depression-like behaviors of mice with reduced body growth rate, lowered sucrose preference, increased immobility time, as well as decreased curiosity and mobility. Moreover, L. rhamnosus zz-1 significantly inhibited hormones released due to hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, alleviated CUMS-induced deficits of monoamine neurotransmitters, and increased the expression of brain-derived neurotrophic factor (BDNF) and tyrosine kinase receptor B (TrkB). These benefits were partially linked to the regulation of the intestinal microenvironment. L. rhamnosus zz-1 alleviated intestinal damage and reduced intestinal inflammation of the depressed mice. Meanwhile, L. rhamnosus zz-1 effectively adjusted the dysbiosis of mouse gut microbiota induced by CUMS, such as changes in the abundance of the Lachnospiraceae NK4A136 group, Bacteroides, and Muribaculum. Taken together, these results demonstrated that L. rhamnosus zz-1 was effective in preventing depression from chronic stress, adding new evidence to support the mental benefits of probiotics.

Perturbation of monoamine metabolism and enhanced fear responses in mice defective in the regeneration of tetrahydrobiopterin

Increasing evidence suggests the involvement of peripheral amino acid metabolism in the pathophysiology of neuropsychiatric disorders, whereas the molecular mechanisms are largely unknown. Tetrahydrobiopterin (BH4) is a cofactor for enzymes that catalyze phenylalanine metabolism, monoamine synthesis, nitric oxide production, and lipid metabolism. BH4 is synthesized from guanosine triphosphate and regenerated by quinonoid dihydropteridine reductase (QDPR), which catalyzes the reduction of quinonoid dihydrobiopterin. We analyzed Qdpr-/- mice to elucidate the physiological significance of the regeneration of BH4. We found that the Qdpr-/- mice exhibited mild hyperphenylalaninemia and monoamine deficiency in the brain, despite the presence of substantial amounts of BH4 in the liver and brain. Hyperphenylalaninemia was ameliorated by exogenously administered BH4, and dietary phenylalanine restriction was effective for restoring the decreased monoamine contents in the brain of the Qdpr-/- mice, suggesting that monoamine deficiency was caused by the secondary effect of hyperphenylalaninemia. Immunohistochemical analysis showed that QDPR was primarily distributed in oligodendrocytes but hardly detectable in monoaminergic neurons in the brain. Finally, we performed a behavioral assessment using a test battery. The Qdpr-/- mice exhibited enhanced fear responses after electrical foot shock. Taken together, our data suggest that the perturbation of BH4 metabolism should affect brain monoamine levels through alterations in peripheral amino acid metabolism, and might contribute to the development of anxiety-related psychiatric disorders. Cover Image for this issue: https://doi.org/10.1111/jnc.15398.

Cognitive Dysfunction in a Mouse Model of Cerebral Ischemia Influences Salivary Metabolomics

Vascular dementia, caused by cerebrovascular disease, is associated with cognitive impairment and reduced hippocampal metabolite levels. Specifically, cognitive impairment can be induced by decreased hippocampal brain-derived neurotrophic factor (BDNF) expression. The development of low or non-invasive biomarkers to characterize these diseases is an urgent task. Disturbance of metabolic pathways has been frequently observed in cognitive impairment, and salivary molecules also showed the potentials to reflect cognitive impairment. Therefore, we evaluated salivary metabolic profiles associated with altered hippocampal BDNF expression levels in a cerebral ischemia mouse model using metabolomic analyses. The effect of tacrine (a cholinesterase inhibitor) administration was also examined. The arteries of ICR mice were occluded with aneurysm clips to generate the cerebral ischemia model. Learning and memory performance was assessed using the elevated plus maze (EPM) test. Hippocampal and blood BDNF levels were quantified using an enzyme-linked immunosorbent assay. Glutamate decarboxylase 1 (GAD1) mRNA expression, is associated with cognitive impairment, was quantified by a real-time polymerase chain reaction. The EPM test revealed impaired spatial working memory in the cerebral ischemia mouse model; tacrine administration ameliorated this memory impairment. Cerebral ischemia suppressed GAD1 expression by decreasing hippocampal BDNF expression. In total, seven salivary metabolites, such as trimethylamine N-oxide and putrescine, were changed by cognitive impairment and tacrine administration. Our data suggest that salivary metabolite patterns were associated with cognitive function.

Pathology of salivary gland dysfunction and restoration of function

In this review, the author shows that simultaneous multiple disorders caused by reactivation of Epstein-Barr virus can lead to salivary gland disorders as part of Sjogren's syndrome (SS). Therefore, clinicians must differentiate SS from other diseases when diagnosing and treating salivary gland disorders. In particular, the author explains how microbial infection in SS overcomes immunological tolerance, leading to pathological changes, and how cytokine overexpression and endocrine disrupters contribute to glandular tissue injury. Also, the author suggests that involvement of reactive oxygen species is a common pathogenesis of salivary gland disorders and SS, so regulation of oxidative stress is an effective treatment for both. The results of clinical studies on restoring salivary gland function and regenerating salivary glands with tissue stem cells may provide clues on elucidating the cause of SS.

Brain-derived neurotrophic factor is related to stress and chewing in saliva and salivary glands

Chewing is one of the most important orofacial functions. During this process, food is reduced in size, while saliva moistens the food and binds it into a bolus that can be easily swallowed. Characteristics of the oral system, including the number of teeth, bite force, and salivary flow, influence the masticatory process. In addition, salivary glands produce several cell growth factors and play an important role in human health. The nerve growth factor (NGF) family consists of NGF, brain-derived neurotrophic factor (BDNF), and neurotrophins-3 to 7. BDNF is a well-studied neurotrophin involved in the neurogenesis, differentiation, and maintenance of select peripheral and central neuronal cell populations during development and adulthood. However, there has been no detailed description of the expression of neurotrophins other than NGF in the salivary gland. We previously studied the effect of immobilization stress + chewing on BDNF secretion and its receptor, tyrosine receptor kinase B, in rat submandibular glands and found increased BDNF expression in duct cells under these conditions. In this review, we describe recent advances in understanding the role of stress and chewing-related BDNF in the saliva and salivary glands.

Hypertriglyceridemia-induced brain-derived neurotrophic factor in rat submandibular glands

OBJECTIVES

Salivary glands produce brain-derived neurotrophic factor (BDNF), which increases plasma BDNF content. Salivary BDNF influences the hippocampus and enhances anxiety-like behaviors. Dyslipidemia affects the brain, promoting depression and anxiety-like behaviors. This study was performed to investigate whether hypertriglyceridemia influences salivary BDNF expression.

METHODS

Hypertriglyceridemia was induced in rats by high-fat diet intake for 10 weeks. BDNF protein levels in the saliva and submandibular glands were measured using enzyme-linked immunosorbent assay (ELISA). Bdnf mRNA levels in the submandibular gland were determined using real-time polymerase chain reaction.

RESULTS

A hypertriglyceridemia rat model was established. Body weight did not differ between the control and hypertriglyceridemia groups. Bdnf mRNA and protein expression was increased in the submandibular gland in the hypertriglyceridemia group compared to the control group. BDNF expression was also significantly increased in the saliva of the hypertriglyceridemia group.

CONCLUSIONS

This is first study to show that hypertriglyceridemia induces BDNF expression in the rat submandibular gland and suggests that salivary BDNF is associated with lipid metabolism.

UV-Photofunctionalization of Titanium Promotes Mechanical Anchorage in A Rat Osteoporosis Model

Effects of UV-photofunctionalization on bone-to-titanium integration under challenging systemic conditions remain unclear. We examined the behavior and response of osteoblasts from sham-operated and ovariectomized (OVX) rats on titanium surfaces with or without UV light pre-treatment and the strength of bone-implant integration. Osteoblasts from OVX rats showed significantly lower alkaline phosphatase, osteogenic gene expression, and mineralization activities than those from sham rats. Bone density variables in the spine were consistently lower in OVX rats. UV-treated titanium was superhydrophilic and the contact angle of ddH₂O was ≤5°. Titanium without UV treatment was hydrophobic with a contact angle of ≥80°. Initial attachment to titanium, proliferation, alkaline phosphatase activity, and gene expression were significantly increased on UV-treated titanium compared to that on control titanium in osteoblasts from sham and OVX rats. Osteoblastic functions compromised by OVX were elevated to levels equivalent to or higher than those of sham-operated osteoblasts following culture on UV-treated titanium. The strength of in vivo bone-implant integration for UV-treated titanium was 80% higher than that of control titanium in OVX rats and even higher than that of control implants in sham-operated rats. Thus, UV-photofunctionalization effectively enhanced bone-implant integration in OVX rats to overcome post-menopausal osteoporosis-like conditions.

A Newly Created Meso-, Micro-, and Nano-Scale Rough Titanium Surface Promotes Bone-Implant Integration

Titanium implants are the standard therapeutic option when restoring missing teeth and reconstructing fractured and/or diseased bone. However, in the 30 years since the advent of micro-rough surfaces, titanium’s ability to integrate with bone has not improved significantly. We developed a method to create a unique titanium surface with distinct roughness features at meso-, micro-, and nano-scales. We sought to determine the biological ability of the surface and optimize it for better osseointegration. Commercially pure titanium was acid-etched with sulfuric acid at different temperatures (120, 130, 140, and 150 °C). Although only the typical micro-scale compartmental structure was formed during acid-etching at 120 and 130 °C, meso-scale spikes (20–50 μm wide) and nano-scale polymorphic structures as well as micro-scale compartmental structures formed exclusively at 140 and 150 °C. The average surface roughness (Ra) of the three-scale rough surface was 6–12 times greater than that with micro-roughness only, and did not compromise the initial attachment and spreading of osteoblasts despite its considerably increased surface roughness. The new surface promoted osteoblast differentiation and in vivo osseointegration significantly; regression analysis between osteoconductivity and surface variables revealed these effects were highly correlated with the size and density of meso-scale spikes. The overall strength of osseointegration was the greatest when the acid-etching was performed at 140 °C. Thus, we demonstrated that our meso-, micro-, and nano-scale rough titanium surface generates substantially increased osteoconductive and osseointegrative ability over the well-established micro-rough titanium surface. This novel surface is expected to be utilized in dental and various types of orthopedic surgical implants, as well as titanium-based bone engineering scaffolds.

Disproportionate Effect of Sub-Micron Topography on Osteoconductive Capability of Titanium

Titanium micro-scale topography offers excellent osteoconductivity and bone-implant integration. However, the biological effects of sub-micron topography are unknown. We compared osteoblastic phenotypes and in vivo bone and implant integration abilities between titanium surfaces with micro- (1-5 µm) and sub-micro-scale (0.1-0.5 µm) compartmental structures and machined titanium. The calculated average roughness was 12.5 ± 0.65, 123 ± 6.15, and 24 ± 1.2 nm for machined, micro-rough, and sub-micro-rough surfaces, respectively. In culture studies using bone marrow-derived osteoblasts, the micro-rough surface showed the lowest proliferation and fewest cells attaching during the initial stage. Calcium deposition and expression of osteoblastic genes were highest on the sub-micro-rough surface. The bone-implant integration in the Sprague-Dawley male rat femur model was the strongest on the micro-rough surface. Thus, the biological effects of titanium surfaces are not necessarily proportional to the degree of roughness in osteoblastic cultures or in vivo. Sub-micro-rough titanium ameliorates the disadvantage of micro-rough titanium by restoring cell attachment and proliferation. However, bone integration and the ability to retain cells are compromised due to its lower interfacial mechanical locking. This is the first report on sub-micron topography on a titanium surface promoting osteoblast function with minimal osseointegration.

Increased BDNF methylation in saliva, but not blood, of patients with borderline personality disorder

Background

The importance of epigenetic alterations in psychiatric disorders is increasingly acknowledged and the use of DNA methylation patterns as markers of disease is a topic of ongoing investigation. Recent studies suggest that patients suffering from Borderline Personality Disorder (BPD) display differential DNA methylation of various genes relevant for neuropsychiatric conditions. For example, several studies report differential methylation in the promoter region of the brain-derived neurotrophic factor gene (BDNF) in blood. However, little is known about BDNF methylation in other tissues.

Results

In the present study, we analyzed DNA methylation of the BDNF IV promoter in saliva and blood of 41 BPD patients and 41 matched healthy controls and found significant hypermethylation in the BPD patient’s saliva, but not blood. Further, we report that BDNF methylation in saliva of BPD patients significantly decreased after a 12-week psychotherapeutic intervention.

Conclusions

Providing a direct comparison of BDNF methylation in blood and saliva of the same individuals, our results demonstrate the importance of choice of tissue for the study of DNA methylation. In addition, they indicate a better suitability of saliva for the study of differential BDNF methylation in BPD patients. Further, our data appear to indicate a reversal of disease-specific alterations in BDNF methylation in response to psychotherapy, though further experiments are necessary to validate these results and determine the specificity of the effect.

Electronic supplementary material

The online version of this article (10.1186/s13148-018-0544-6) contains supplementary material, which is available to authorized users.