Expression and localization of brain-derived neurotrophic factor (BDNF) mRNA and protein in human submandibular gland

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.

Association between salivary mature brain-derived neurotrophic factor and psychological distress in healthcare workers

INTRODUCTION

Previous studies have suggested association between brain-derived neurotrophic factor (BDNF) and the stress level of workers. However, no studies have investigated the potential of salivary mature BDNF (mBDNF) level as a noninvasive biomarker for psychological distress. This study aimed to explore the reliability of salivary mBDNF as a biomarker for psychological distress in healthcare workers. Furthermore, we examined the relationship between salivary and plasma mBDNF levels and their correlation with age, sex, body mass index (BMI), and exercise habits.

METHODS

Fifty-one healthy healthcare workers (26 men) from the University of Occupational and Environmental Health, Japan, participated in this study. In this cross-sectional study, participants provided demographic information. Psychological distress was assessed using the Kessler 6 (K6). Saliva and blood samples were collected, and mBDNF was measured by ELISA. Spearman's rank correlation coefficient was performed to analyze the relationship between mBDNF (saliva and plasma) and K6. Statistical analyses were conducted using Stata 17.0, and a significance level of p < .05 was applied.

RESULTS

The median K6 score was 1 (interquartile range [IQR]: 0-3). The median (IQR) salivary mBDNF was 1.36 (1.12-1.96) pg/mL, whereas the mean (standard deviation) plasma mBDNF was 1261.11 (242.98) pg/mL. No correlation was observed between salivary and plasma mBDNF concentrations or with the K6 score. Additionally, there were no associations between salivary or plasma mBDNF concentrations and age, sex, or exercise habits. Finally, an association between plasma mBDNF concentration and BMI was found only in univariate analysis.

CONCLUSION

Our findings indicate that salivary mBDNF can be accurately measured noninvasively in healthcare workers. Within our study sample, salivary mBDNF did not demonstrate any correlation with K6 and plasma mBDNF. Future studies with a larger study sample and a diverse study population consisting of healthy participants and patients with psychiatric disorders are warranted.

Targeted Gene Candidates for Treatment and Early Diagnosis of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is an eye disease that impairs the sharp and central vision need for daily activities. Recent advances in molecular biology research not only lead to a better understanding of the genetics and pathophysiology of AMD but also to the development of applications based on targeted gene expressions to treat the disease. Clarification of molecular pathways that causing to development and progression in dry and wet types of AMD needs comprehensive and comparative investigations in particular precious biopsies involving peripheral blood samples from the patients. Therefore, in this investigation, dry and wet types of AMD patients and healthy individuals were aimed at investigating in regard to targeted gene candidates by using gene expression analysis for the first time. 13 most potent candidate genes involved in neurodegeneration were selected via in silico approach and investigated through gene expression analysis to suggest new targets for disease therapy. For the analyses, 30 individuals (10 dry and 10 wet types AMD patients and 10 healthy people) were involved in the study. SYBR-Green based Real-Time PCR analysis was performed on isolated peripheral blood mononuclear cells (PBMCs) to analyze differentially expressed genes related to these cases. According to the investigations, only the CRP gene was found to be upregulated for both dry and wet disease types. When the downregulated genes were analyzed, it was found that 11 genes were commonly decreased for both dry and wet types in the aspect of expression pattern. From these genes, CFH, CX3CR1, FLT1, and TIMP3 were found to have the most downregulated gene expression properties for both diseases. From these results, it might be concluded that these common upregulated and downregulated genes could be used as targets for early diagnosis and treatment for AMD.

TrkB-Targeted Therapy for Mucoepidermoid Carcinoma

The brain-derived neurotrophic factor (BDNF)/tyrosine receptor kinase B (TrkB) pathway was previously associated with key oncogenic outcomes in a number of adenocarcinomas. The aim of our study was to determine the role of this pathway in mucoepidermoid carcinoma (MEC). Three MEC cell lines (UM-HMC-2, H253 and H292) were exposed to Cisplatin, the TrkB inhibitor, ANA-12 and a combination of these drugs. Ultrastructural changes were assessed through transmission electron microscopy; scratch and Transwell assays were used to assess migration and invasion; and a clonogenic assay and spheroid-forming assay allowed assessment of survival and percentage of cancer stem cells (CSC). Changes in cell ultrastructure demonstrated Cisplatin cytotoxicity, while the effects of ANA-12 were less pronounced. Both drugs, used individually and in combination, delayed MEC cell migration, invasion and survival. ANA-12 significantly reduced the number of CSC, but the Cisplatin effect was greater, almost eliminating this cell population in all MEC cell lines. Interestingly, the spheroid forming capacity recovered, following the combination therapy, as compared to Cisplatin alone. Our studies allowed us to conclude that the TrkB inhibition, efficiently impaired MEC cell migration, invasion and survival in vitro, however, the decrease in CSC number, following the combined treatment of ANA-12 and Cisplatin, was less than that seen with Cisplatin alone; this represents a limiting factor.

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.

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.

Elevated levels of serum, but not salivary, brain-derived neurotrophic factor following mild traumatic brain injury in collegiate athletes post return-to-play

Brain-derived neurotrophic factor (BDNF) helps restore neuronal function following mild traumatic brain injury. BDNF levels can be obtained in blood serum and more recently in saliva. However, the relationship between serum and salivary BDNF is poorly understood—especially in relation to alterations in BDNF levels following mild traumatic brain injury. In this study, serum and salivary BDNF were collected from a sample of 42 collegiate student athletes. Half of the participants were recently cleared by a physician and/or an athletic trainer to return-to-play after experiencing a sports-related concussion. The other half had not experienced a concussion within the past year and were matched by age, sex, sport, and time of sample. Results suggest that incidences of depression, anxiety, and stress were all elevated in the concussion group, relative to the control participants. When controlling for stress-related negative affect, serum BDNF was elevated in the concussion group. However, there was no difference in salivary BDNF. Serum and salivary BDNF were uncorrelated across the entire sample. Yet, these measures of BDNF were correlated in the concussion group, but not the control group. In sum, serum BDNF is elevated in concussion post return-to-play; however, further research is needed to explore the utility of salivary BDNF following concussion.

Detection of anti-citrullinated protein antibody (ACPA) in saliva for rheumatoid arthritis using DBA mice infected with Porphyromonas gingivalis

OBJECTIVE

The anti-citrullinated protein antibody (ACPA), an autoantibody of rheumatoid arthritis (RA), is very specific in the diagnosis of RA and has been detected in early cases and several years before the onset of the disease. In this study, we focused on ACPA and examined whether it could be detected in saliva whether it is associated with periodontal disease.

DESIGN

Porphyromonas gingivalis (Pg) or Escherichia coli (Ec) was administered into the oral cavity of DBA/1JJmsSlc mice. The arthritis index was measured in foot bones, and collected saliva and serum. The amount of ACPA in serum and saliva was measured using ELISA, and antibodies in serum, saliva, and foot bones were detected and analysed by western blotting.

RESULT

Histopathological analysis of foot bones of the Pg/RA group detected greater inflammatory cell infiltration than in the RA group, and bone resorption was evident. Furthermore, ELISA results show that the amount of ACPA in serum was significantly higher in the Pg/RA group (P < 0.05), with a tendency to also increase in the saliva. In addition, western blotting results show a 55 kDa citrullinated protein in the serum and saliva of the RA and Pg/RA groups.

CONCLUSIONS

We conclude that Pg infection increases ACPA in the serum and is reflected in the saliva, and may be involved in the inflammatory progression of RA.

The protective role of musk on salivary glands of mice exposed to chronic unpredictable mild stress

This study assessed the impact of chronic unpredictable mild stress (CUMS) on the structure of mouse salivary glands and the role of musk in alleviating this impact. Forty male albino mice were distributed equally into four groups; control (untreated), CUMS (exposed to CUMS for 4 weeks), CUMS+fluoxetine (FLU) (exposed to CUMS then treated with FLU, CUMS+musk (exposed to CUMS then treated with musk). Behavioral changes and serum corticosterone levels were assessed at the end of the experiment. The submandibular and parotid glands were dissected out and processed for histopathological and immunohistochemical examination using antibodies against alpha smooth muscle actin (ASMA) and brain-derived neurotropic factor (BDNF). Exposure to CUMS significantly (P < 0.001) increased the serum corticosterone level and induced depression. CUMS also induced vacuolation in acinar cells along with a significant (P < 0.001) reduction of ASMA immunoexpression, indicating an effect on myoepithelial cells, and a significant (P < 0.001) increase of BDNF expression in the gland ductal system. Both FLU and musk alleviated the CUMS-induced behavioral, biochemical and histopathological changes in the salivary glands. In conclusion, musk ameliorates stress-induced structural changes in mouse salivary glands. This effect might be mediated through up-regulation of BDNF secretion by the glands.

Salivary BDNF and Cortisol Responses During High-Intensity Exercise and Official Basketball Matches in Sedentary Individuals and Elite Players

Salivary cortisol increases in response to stressors, including physical exertion and psychological stress associated with sports competition. In addition, stress may induce change in brain-derived neurotrophic factor (BDNF). However, there are still no data available to compare the salivary BDNF level in sedentary male individuals and elite team-sport male athletes, regularly involved in activities that require elevated attention and concentration. This information could contribute to the advance of understanding of the effect of regular exercise on the salivary level of BDNF, the pre-to-post change in salivary BDNF during exercise, and the association between salivary cortisol and salivary BDNF responses to physical exercise. Therefore, this study aimed to compare the concentration of salivary cortisol and BDNF, before and after exercise, in sedentary individuals and elite male basketball players. The sedentary group (23.0 ± 4.2 yrs) performed a high-intensity exercise protocol and the basketball players (18.6 ± 0.5 yrs) participated in three official basketball matches. Saliva samples were tested for cortisol and BDNF using ELISA. A significant increase in salivary cortisol from pre- to post-match was observed only for the basketball players (p < 0.05). Basketball players also presented a higher salivary BDNF concentration for both resting (pre) and post-physical exercise (p < 0.05); however, no change in pre- to post-exercise salivary BDNF was observed for either group (p > 0.05). Elevated BDNF in athletes may be associated to their repeated exposure to stressful competition situations. The current findings also suggest that different mechanisms might be involved in salivary cortisol and BDNF responses during physical exercise.

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.

Prosaposin and its receptors are differentially expressed in the salivary glands of male and female rats

Salivary glands produce various neurotrophins that are thought to regulate salivary function during normal and pathological conditions. Prosaposin (PSAP) is a potent neurotrophin found in several tissues and various biological fluids and may play roles in the regulation of salivary function. However, little is known about PSAP in salivary glands. As the functions of salivary glands are diverse based on age and sex, this study examines whether PSAP and its receptors, G protein-coupled receptor 37 (GPR37) and GPR37L1, are expressed in the salivary glands of rats and whether sex and aging affect their expression. Immunohistochemical analysis revealed that PSAP and its receptors were expressed in the major salivary glands of rats, although their expression varied considerably based on the type of gland, acinar cells, age and sex. In fact, PSAP, GPR37 and GPR37L1 were predominantly expressed in granular convoluted tubule cells of the submandibular gland and the intensity of their immunoreactivity was higher in young adult female rats than age-matched male rats, which was more prominent at older ages (mature adult to menopause). On the other hand, weak PSAP, GPR37 and GPR37L1 immunoreactivity was observed mainly in the basal layer of mucous cells of the sublingual gland. Triple label immunofluorescence analysis revealed that PSAP, GPR37 and GPR37L1 were co-localized in the basal layer of acinar and ductal cells in the major salivary glands. The present findings indicate that PSAP and its receptors, GPR37 and GPR37L1, are expressed in the major salivary glands of rats and their immunoreactivities differ considerably with age and sex.

Salivary Gland Derived BDNF Overexpression in Mice Exerts an Anxiolytic Effect

Brain-derived neurotrophic factor (BDNF) is abundant in the hippocampus and plays critical roles in memory and synapse formation, as well as exerting antidepressant-like effects in psychiatric disorders. We previously reported that BDNF is expressed in salivary glands and affects blood BDNF content. However, the function of salivary BDNF remains unclear. The aim of this study was to generate transgenic mice overexpressing BDNF in the salivary glands. Hence, we used the Lama construct (hemagglutinin (HA)-tagged mouse Bdnf cDNA) to specifically express BDNF in mouse salivary glands. Compared with control mice, Bdnf-HA transgenic mice showed increased blood BDNF and expressed salivary BDNF-HA. Molecular analysis revealed enhanced hippocampal BDNF levels and activation of the BDNF receptor, tyrosine kinase B (TrkB), in transgenic mice. In both the open field and elevated-plus maze tests, transgenic mice showed anxiolytic-like behavioral effects compared with control or sialoadenectomized mice. Among downstream components of the BDNF-TrkB signaling pathway, metabolic activation of the γ-aminobutyric acid (GABA) synthetic pathway was found, including higher levels of the GABA synthetic enzyme, glutamate decarboxylase 1 (GAD1). Thus, we have established a transgenic mouse expressing BDNF in the parotid gland that may be useful to examine the hippocampal effects of salivary BDNF.

Measuring BDNF in saliva using commercial ELISA: Results from a small pilot study

Brain-derived neurotrophic factor (BDNF) is a protein often studied in psychiatric populations. Commercial ELISA kits have been validated for measuring BDNF in blood plasma and serum, but blood collection is an invasive method which cannot always be used. The aim of this pilot study was to explore the noninvasive alternative of measuring BDNF in saliva. Three different commercial ELISA kits were used to analyze parallel plasma and saliva samples from six healthy adults. In total 33 plasma and 33 saliva samples were analyzed according to manufacturers' standard protocols. BDNF was successfully measured in plasma in two of the three kits, of which the results correlated highly (r_s =.88). BDNF could not be measured reliably in saliva. The results of this pilot study suggest that techniques of commercial BDNF kits may not be ready for noninvasive saliva measurements, which limits the sampling frequency and settings.

BDNF mediated TrkB activation contributes to the EMT progression and the poor prognosis in human salivary adenoid cystic carcinoma

BACKGROUND

The aim of the present study was to investigate whether the expression of Brain-Derived Neurotrophic Factor (BDNF) and its receptor Tropomyosin-related kinase B (TrkB) is correlated with the clinical progression of salivary adenoid cystic carcinoma (SACC) and whether the BDNF/TrkB axis is associated with the induction of epithelial-mesenchymal transition (EMT) in SACC cells.

METHOD

The expression of BDNF, TrkB, and E-cadherin (an EMT biomarker) in 76 primary SACC specimens and 20 normal salivary gland tissues was analyzed by immunohistochemistry. Additionally, the expression of BDNF, TrkB, and E-cadherin in SACC cell lines (SACC-83 and SACC-LM) was analyzed by RT-PCR and Western blotting. The biological role of the BDNF/TrkB axis in the EMT progression of SACC was evaluated after treatment with increased levels of BDNF and by inhibiting TrkB activity in SACC-83 cell line. The progression of SACC cells through EMT was assessed by RT-PCR, Western blotting, photography, migration and invasion assays.

RESULTS

Elevated expression of TrkB (92.1%) and BDNF (89.5%), and downregulated expression of E-cadherin (47.4%) was found in SACC specimens, which was significantly correlated with the invasion and metastasis in SACC (P<0.05). The high expression of TrkB and the low expression of E-cadherin was significantly correlated with the poor prognosis of SACC patients (P<0.05). The expression of TrkB was inversely correlated with the expression of E-cadherin in both SACC cases and cell lines (P<0.05). Increasing BDNF levels after treatment with exogenous recombinant human BDNF (rhBDNF) at 100 ng/ml significantly promoted the activation of TrKB and the progression of EMT in SACC cells. While obstruction of TrkB by its inhibitor, k252a (100 nM), significantly inhibited the EMT progression of SACC cells.

CONCLUSIONS

These results suggest that BDNF-mediated TrkB activation contributes to the EMT progression and the poor prognosis in SACC. The present study demonstrated that the BDNF/TrkB axis promotes the migration and invasion of SACC cells via EMT in vitro. Targeting the inactivation of the BDNF/TrkB axis may be a potential strategy for the treatment of SACC.

Evaluation of eight plasma proteins as candidate blood-based biomarkers for malignant gliomas

Eight brain-derived proteins were evaluated regarding their potential for further development as a blood-based biomarker for malignant gliomas. Plasma levels for glial fibrillary acidic protein, neurogranin, brain-derived neurotrophic factor, intracellular adhesion molecule 5, metallothionein-3, beta-synuclein, S100 and neuron specific enolase were tested in plasma of 23 patients with high-grade gliomas (WHO grade IV), 11 low-grade gliomas (WHO grade II), and 15 healthy subjects. Compared to the healthy controls, none of the proteins appeared to be specific for glioblastomas. However, the data are suggestive of higher protein levels in gliosarcomas (n = 2), which may deserve further exploration.

Effects of stress on mouse β-defensin-3 expression in the upper digestive mucosa

PURPOSE

Gastrointestinal integrity and immune surveillance are affected by stress. Stress also adversely affects mucosal barrier function. β-defensins constitute an integral component of the innate immune system as antimicrobial peptides, serving as the first line of defense against microbial pathogens at the epithelial surfaces of the upper digestive mucosa. The primary objective of this study was to determine the effects of stress on the expression profile of mouse β-defensin-3 in the upper digestive mucosa of mice with diabetes.

MATERIALS AND METHODS

We established a mouse model of restraint stress by using NSY/Hos mice with type 2 diabetes mellitus. We used real-time polymerase chain reaction, in situ hybridization, and immunohistochemistry to investigate the effects of stress and glucocorticoid administration on mouse β-defensin-3 expression in the upper digestive mucosa of the gingiva, esophagus, and stomach.

RESULTS

Mouse β-defensin-3 mRNA expression was higher in the esophagus than in the gingiva or stomach (p<0.05). In the esophagus, mouse β-defensin-3 mRNA expression was lower in stressed mice than in non-stressed mice (p<0.05). Furthermore, immunoreactivity to mouse β-defensin-3 protein was lower in the esophagus of stressed mice than non-stressed mice, consistent with the results of mRNA expression analysis. Systemic glucocorticoid administration also downregulated esophageal mouse β-defensin-3 mRNA expression.

CONCLUSION

Our novel findings show that stress decreases mouse β-defensin-3 expression in the esophagus of mice with diabetes, possibly due to increased endogenous glucocorticoid production. It appears to be highly likely that stress management may normalize mucosal antimicrobial defenses in patients with diabetes.

Transient activation of hedgehog pathway rescued irradiation-induced hyposalivation by preserving salivary stem/progenitor cells and parasympathetic innervation

PURPOSE

To examine the effects and mechanisms of transient activation of the Hedgehog pathway on rescuing radiotherapy-induced hyposalivation in survivors of head and neck cancer.

EXPERIMENTAL DESIGN

Mouse salivary glands and cultured human salivary epithelial cells were irradiated by a single 15-Gy dose. The Hedgehog pathway was transiently activated in mouse salivary glands, by briefly overexpressing the Sonic hedgehog (Shh) transgene or administrating smoothened agonist, and in human salivary epithelial cells, by infecting with adenovirus encoding Gli1. The activity of Hedgehog signaling was examined by the expression of the Ptch1-lacZ reporter and endogenous Hedgehog target genes. The salivary flow rate was measured following pilocarpine stimulation. Salivary stem/progenitor cells (SSPC), parasympathetic innervation, and expression of related genes were examined by flow cytometry, salisphere assay, immunohistochemistry, quantitative reverse transcription PCR, Western blotting, and ELISA.

RESULTS

Irradiation does not activate Hedgehog signaling in mouse salivary glands. Transient Shh overexpression activated the Hedgehog pathway in ductal epithelia and, after irradiation, rescued salivary function in male mice, which is related with preservation of functional SSPCs and parasympathetic innervation. The preservation of SSPCs was likely mediated by the rescue of signaling activities of the Bmi1 and Chrm1-HB-EGF pathways. The preservation of parasympathetic innervation was associated with the rescue of the expression of neurotrophic factors such as Bdnf and Nrtn. The expression of genes related with maintenance of SSPCs and parasympathetic innervation in female salivary glands and cultured human salivary epithelial cells was similarly affected by irradiation and transient Hedgehog activation.

CONCLUSIONS

These findings suggest that transient activation of the Hedgehog pathway has the potential to restore salivary gland function after irradiation-induced dysfunction.

Induction of β-Defensin Expression by Porphyromonas gingivalis-Infected Human Gingival Graft Transplanted in nu/nu Mouse Subdermis

It is important to understand the onset of periodontal disease in terms of bacterial infection and host factors. Host-bacteria interactions can be elicited in human cultured cells and animal models, but these models provide only limited biological information about human host reactions against bacterial attacks. Development of an in vivo model using human gingival tissue is needed. We established an in vivo model using nu/nu mice and evaluated host defense following bacterial infection in human gingiva. Human gingival samples were collected from periodontitis patients and transplanted in nu/nu mouse subdermis. After 2 weeks, human characteristics were confirmed by positive immunohistochemical reactions for human-specific markers. We used this model to investigate human β-defensin-2 (hBD-2), an antimicrobial peptide that contributes to initial defense against bacterial invasion. Using real-time polymerase chain reaction, in situ hybridization, and immunohistochemistry, we investigated whether hBD-2 expression was induced in human gingiva as a response to Porphyromonas gingivalis as a periodontal pathogen. Two hours after infection with bacteria, we detected increased expression of hBD-2 mRNA, which was localized in the epithelium of human gingiva. Using our in vivo model, we concluded that increased hBD-2 may play an important role in early defense from bacterial infection in human gingival epithelium.

Role of stress-related brain-derived neurotrophic factor (BDNF) in the rat submandibular gland

The nerve growth factor (NGF) family comprises NGF, brain-derived neurotrophic factor (BDNF) and neurotrophins (NTs)-3, -4/5, -6 and -7, all of which are collectively referred to as neurotrophins. However, the expression of neurotrophins other than NGF in the salivary gland has not been described in detail. Through interaction with the TrkB receptor, BDNF plays an important role in long-term potentiation. We found that BDNF expression increased within submandibular gland tissue in response to stress, suggesting that the salivary glands are sensitive to stress. In addition, stress caused increases in plasma BDNF derived from the submandibular gland and in TrkB receptor mRNA in the adrenal medulla. Plasma BDNF might activate TrkB receptors in the adrenal medulla during acute stress. The salivary glands are likely to influence not only oral health, but also systemic organs. This review addressed the relationship between hormone-like effects and stress-related BDNF expression in the rat submandibular gland.