Effects of Diabetes and Voluntary Exercise on IgA Concentration and Polymeric Immunoglobulin Receptor Expression in the Submandibular Gland of Rats.

Background and Objectives: Patients with diabetes are more susceptible to upper respiratory tract infections (URTIs) because they are easily infected. Salivary IgA (sali-IgA) levels play a major role in transmitting URTIs. Sali-IgA levels are determined by salivary gland IgA production and polymeric immunoglobulin receptor (poly-IgR) expression. However, it is unknown whether salivary gland IgA production and poly-IgR expression are decreased in patients with diabetes. While exercise is reported to increase or decrease the sali-IgA levels, it is unclear how exercise affects the salivary glands of patients with diabetes. This study aimed to determine the effects of diabetes and voluntary exercise on IgA production and poly-IgR expression in the salivary glands of diabetic rats. Materials and Methods: Ten spontaneously diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats (eight-week-old) were divided into two groups of five rats each: a non-exercise group (OLETF-C) and a voluntary wheel-running group (OLETF-E). Five Long-Evans Tokushima Otsuka (LETO) rats without diabetes were bred under the same conditions as the OLETF-C. Sixteen weeks after the study began, the submandibular glands (SGs) were collected and analyzed for IgA and poly-IgR expression levels. Results: IgA concentrations and poly-IgR expression levels in SGs were lower in OLETF-C and OLETF-E than in LETO (p < 0.05). These values did not differ between the OLETF-C and OLETF-E. Conclusions: Diabetes decreases IgA production and poly-IgR expression in the salivary glands of rats. Moreover, voluntary exercise increases sali-IgA levels but does not increase IgA production and poly-IgR expression in the salivary glands of diabetic rats. Increasing IgA production and poly-IgR expression in the salivary glands, which is reduced in diabetes, might require slightly higher-intensity exercise than voluntary exercise under the supervision of a doctor.

Effect of ingesting yogurt fermented with Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 on influenza virus-bound salivary IgA in elderly residents of nursing homes: a randomized controlled trial.

Objective: The purpose of this study was to clarify the influence of consuming yogurt fermented with Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 (1073R-1-yogurt) on influenza virus-bound salivary immunoglobulin A (IgA) levels, in the elderly residents of nursing homes. Methods: A double-blind, parallel-group, randomized controlled trial was conducted with 96 elderly volunteers residing in 2 nursing homes. During the trial, participants consumed 100 g of 1073R-1-yogurt every morning for 12 weeks, whereas the control participants consumed yogurt fermented with a different Lactobacillus strain (control yogurt). Saliva was collected before the trial and after 4, 8 and 12 weeks of yogurt ingestion. Results: Our data indicated that consumption of 1073R-1-yogurt affected influenza A virus subtype H3N2-bound IgA levels in saliva (p = .001). In addition, saliva flow rate and total IgA levels increased in response to the yogurt intake period in both the 1073R-1 and control yogurt groups (p = .04). Conclusions: Our study suggests that continuous daily ingestion of 1073R-1-yogurt may help prevent infection with influenza A virus subtype H3N2 in elderly subjects with weakened immunity, by increasing the production of influenza A virus subtype of H3N2-bound salivary IgA.

Human ß-defensin-2 and interleukin-1ß expression in response to Porphyromonas gingivalis challenge in mice transplanted with periodontitic human gingiva.

Inter-individual variability in the host response contributes significantly to expression of periodontal disease. Thus, research into the human host response is considered important in the analysis of periodontal disease. Human ß-defensin-2 (hBD-2) is typically produced by epithelial tissues after stimulation with microorganisms and inflammatory mediators, and it contributes to the initial defense in the innate immune response. However, hBD-2 expression in response to infection has not been investigated in human gingival tissue with periodontitis. We examined the response to Porphyromonas gingivalis in an established in vivo model of human gingival grafts with various degrees of periodontitis. We also investigated the expression profile of interleukin-1ß (IL-1ß). Gingival tissues were collected from 40 patients with chronic periodontitis (21 with slight-to-moderate disease, 19 with severe disease) during tooth extraction or periodontal surgery. These tissues were transplanted subcutaneously into nu/nu mice. We used real-time PCR to compare the expression of hBD-2 and IL-1ß. In slight-to-moderate chronic periodontitis, hBD-2 expression was significantly higher in the stimulated group than in the non-stimulated group (p < 0.05), but there was no significant increase in the group with severe chronic periodontitis. IL-1ß expression did not differ between groups. Increased expression of hBD-2 and IL-1ß was associated with slight-to-moderate periodontitis (p < 0.05), and there was a significant relationship between decreased hBD-2 and IL-1ß expression and severe periodontitis (p < 0.05). The initial expression profile of hBD-2 in P. gingivalis infection differs according to the severity of periodontitis. In addition, changes in hBD-2 and IL-1ß expression may be important in the progression of periodontitis.

Salivary lactoferrin is transferred into the brain via the sublingual route.

Lactoferrin (LF) is produced by exocrine glands including salivary gland, and has various functions including infection defense. However, the transfer of LF from peripheral organs into the brain remains unclear. To clarify the kinetics of salivary LF (sLF), we investigated the consequences of sialoadenectomy and bovine LF (bLF) sublingual administration in rats. The salivary glands were removed from male Wistar rats, and we measured rat LF levels in the blood and brain at 1 week post-surgery. We also examined the transfer of LF into the organs of the rats after sublingual administration of bLF. Rat LF levels in the blood and brain were significantly reduced by sialoadenectomy. Sublingual bLF administration significantly increased bLF levels in the brain, which then decreased over time. These results indicate that LF is transferred from the sublingual mucosa to the brain, in which favorable effects of sLF on brain will be expected via the sublingual mucosa.

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.

Effects of yogurt fermented with Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 on the IgA flow rate of saliva in elderly persons residing in a nursing home: A before-after non-randomised intervention study.

OBJECTIVE: The aim of this study was to investigate the alterations in the salivary IgA levels of elderly persons administered yogurt fermented with Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) OLL1073R-1, which has been reported to reduce the risk of colds. BACKGROUND: Salivary immunoglobulin (Ig)A plays an important role in the defence of the oral cavity mucous membrane against foreign antigens and pathogens. Accordingly, low levels of salivary IgA are associated with an increased risk of upper respiratory tract infection. Furthermore, salivary IgA secretion has been reported to decrease with age. Recently, several studies have reported that certain strains of Lactobacillus and their products can modulate the immune response, but there are currently few studies on the effects of on the IgA level in human saliva. MATERIALS AND METHODS: This was a before-after non-randomised intervention study. Thirty-seven elderly persons (mean age, 82.7 years) residing in a single nursing home ingested 112 g of the yogurt every morning for 12 weeks. The participants' saliva was collected before and after 4, 8 and 12 weeks of yogurt intake. RESULTS: Our results showed that yogurt intake affected the concentration of IgA in the saliva (P < .0001). Additionally, yogurt intake and the body weight of the participants affected the IgA flow rate of saliva (P = .0003 and .03, respectively). CONCLUSION: Continuous intake of yogurt fermented with L. bulgaricus OLL1073R-1 may help improve the mucosal immune function in elderly people with weakened immune systems.

Voluntary exercise increases IgA concentration and polymeric Ig receptor expression in the rat submandibular gland.

Salivary IgA-a primary factor in local immunity of the oral cavity-plays an important role in maintaining local immune function in the oral cavity and prevent upper respiratory tract infections. Oral IgA levels are known to fluctuate in an exercise-dependent manner; thus, we investigated the effects of voluntary exercise on salivary IgA secretion in rats to better understand the mechanism by which this occurs. Six-week-old male Wistar rats were placed in individual cages with or without access to exercise wheels for three weeks. Notably, animals who engaged in voluntary exercise demonstrated significant increases in IgA concentration in saliva and submandibular gland tissue, as well as a markedly higher salivary IgA flow rate. Moreover, active rats also exhibited elevated polymeric Ig receptor (pIgR) mRNA expression in submandibular gland tissue. Collectively, these results suggest that voluntary exercise may increase salivary IgA concentration and boost immune function in the oral cavity.

Relationship between salivary immunoglobulin a, lactoferrin and lysozyme flow rates and lifestyle factors in Japanese children: a cross-sectional study.

OBJECTIVE: The antimicrobial substances in saliva contribute to the maintenance of both oral health and overall health of the body. Therefore, the associations among immunoglobulin A (IgA), lactoferrin and lysozyme flow rates in the saliva of children, and their relationships with the physical attributes and lifestyle factors of children, were examined. MATERIALS AND METHODS: Saliva was collected from 90 children who visited the Kanagawa Dental University Hospital Pediatric Dentistry, and questionnaires were completed by guardians. IgA, lactoferrin and lysozyme concentrations were measured in the saliva samples using enzyme-linked immunosorbent assays (ELISAs). RESULTS: The IgA flow rate in saliva increased as age, height and weight increased. A correlation was found between lactoferrin and lysozyme flow rates. When the antimicrobial substance flow rates in the saliva were divided into two groups of 22 children each based on the highest and lowest quartiles, children with either a low or high IgA flow rate also had a high or low lactoferrin flow rate, respectively. The same pattern was observed for lactoferrin and lysozyme flow rates. CONCLUSIONS: There is a high probability that the IgA flow rate in the saliva of children reflects and corresponds to the developmental status of immune function as the child ages and increases in height and weight. The flow rates of lactoferrin and lysozyme were correlated in children. In addition, regarding lifestyle factors, the duration of sleep and lactoferrin flow rate were also related.

Intake of indigestible carbohydrates influences IgA response and polymeric Ig receptor expression in the rat submandibular gland.

Secretory IgA in the saliva is essential for protection from mucosally transmitted pathogens and maintaining homeostasis at mucosal surfaces of the oral cavity. Expression of submandibular gland polymeric Ig receptor (pIgR) is essential for IgA secretion. In the present study, we investigated the influence of indigestible carbohydrates on IgA production in the salivary gland and saliva. Five-week-old rats were fed a fibre-free diet (control), or a diet with 5 % (w/w) fructo-oligosaccharide (FOS) or a combination of 2·5 % (w/w) polydextrose (PDX) and 2·5 % (w/w) lactitol for 21-d. IgA concentrations in the caecal digesta, submandibular gland tissue, and saliva in the FOS and PDX+lactitol diet groups were significantly higher than those in the control group (P< 0·05). The increase in IgA in the submandibular gland tissue was confirmed using immunohistochemical analysis. However, the IgA concentrations of serum did not differ between the FOS or PDX+lactitol groups and the control group (P= 0·5). In the FOS and PDX+lactitol groups, the pIgR mRNA (pIgR/ß-actin) expression level in the submandibular gland tissue was significantly higher than that in the control group (P< 0·05). The present study suggests that indigestible carbohydrates play an important role in the increase in IgA concentrations in the submandibular gland tissue, saliva, and caecal digesta.

Associations between brain-derived neurotrophic factor and estradiol in women's saliva.

OBJECTIVE: The aim of this study was to assess the relationship between brain-derived neurotrophic factor (BDNF) and sex hormones (estradiol [E2] and progesterone), using saliva samples obtained from healthy women. METHODS: Forty female dental hygienist students were divided into groups according to being in the follicular phase or luteal phase. Saliva BDNF, E2, and progesterone levels were measured using a sandwich ELISA system. The correlation between these factors was analyzed using Spearman's index, and fluctuations of these levels in the whole menstrual cycle were investigated classifying the subjects by every 4 days according to the phase of their menstrual cycle. RESULTS: Saliva BDNF variations strongly correlated with saliva E2 levels in the follicular phase (r = 0.721, p = 0.000) and luteal phase (r = 0.770, p = 0.000). The correlation coefficient showing the relationship between progesterone and BDNF levels in the luteal phase (r = 0.371, p = 0.157) was lower than that in the follicular phase (r = 0.631, p = 0.001). Moreover, the fluctuation of BDNF levels in the menstrual cycle followed a similar pattern to that of E2. CONCLUSIONS: We found that saliva BDNF and E2 levels were closely related in healthy young women. In particular, for first time, that correlation was investigated throughout the menstrual cycle. Monitoring of saliva BDNF may yield insight into women's reproductive and mental health.

Role of TrkB expression in rat adrenal gland during acute immobilization stress.

Expression of tyrosine receptor kinase B (TrkB), a receptor for brain-derived neurotrophic factor (BDNF), is markedly elevated in the adrenal medulla during immobilization stress. Catecholamine release was confirmed in vitro by stimulating chromaffin cells with recombinant BDNF. We investigated the role of TrkB and the localization of BDNF in the adrenal gland during immobilization stress for 60 min. Blood catecholamine levels increased after stimulation with TrkB expressed in the adrenal medulla during 60-min stress; however, blood catecholamine levels did not increase in adrenalectomized rats. Furthermore, expression of BDNF mRNA and protein was detected in the adrenal medulla during 60-min stress. Similarly, in rats undergoing sympathetic nerve block with propranolol, BDNF mRNA and protein were detected in the adrenal medulla during 60-min stress. These results suggest that signal transduction of TrkB in the adrenal medulla evokes catecholamine release. In addition, catecholamine release was evoked by both the hypothalamic-pituitary-adrenal axis and autocrine signaling by BDNF in the adrenal gland. BDNF-TrkB interaction may play a role in a positive feedback loop in the adrenal medulla during immobilization stress.

Regeneration processes of alveolar bone and microvascular changes after the application of platelet-rich fibrin.

OBJECTIVES: Platelet-rich fibrin (PRF) is a promising agent for bone regeneration (BR). Platelets contain several growth factors that promote angiogenesis and BR. In this study, we observed the morphology of alveolar BR. METHODS: PRF (Advanced PRF: A-PRF) was prepared by extracting 10 mL of blood from each dog in a collection tube before tooth extraction. The samples were centrifuged at 200 × g for 8 min and incubated for 10 min to allow clotting. The alveolar socket on the dentition's right side was densely filled with PRF. The opposite side, which did not receive PRF, served as the control group. Different methods were used for specimen preparation and observation. Sections stained with hematoxylin and eosin were observed under a light microscope. Bone specimens were observed using stereoscopic microscopy. The resin cast models were examined using a scanning electron microscope. Moreover, bone formation ratio and height were measured. RESULTS: Fourteen days postoperatively, angiogenesis and bone deposition were more advanced in the PRF group than in the control group. Thirty days postoperatively, both groups developed porous bone. In the PRF group, new bone trabeculae (BT) and a network of blood vessels were formed in the bone marrow. Ninety days postoperatively, the resin cast showed a normal bone structure with BT and bone marrow. Thick BT were observed in the PRF group. CONCLUSIONS: Growth factors in PRF stimulate microcirculation and promote angiogenesis and bone deposition. The benefits of PRF include safety and increased bone formation.

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

Brain-derived neurotrophic factor (BDNF) promotes cell survival and differentiation in the central and peripheral nervous systems. Previously, we reported that BDNF is produced by salivary glands under acute immobilization stress in rats. However, expression of BDNF is poorly understood in humans, although salivary gland localization of BDNF in rodents has been demonstrated. In the present study, we investigated the expression and localization of BDNF in the human submandibular gland (HSG) using reverse transcription-polymerase chain reaction, western blot analysis, in situ hybridization (ISH), immunohistochemistry (IHC), and ELISA. BDNF was consistently localized in HSG serous and ductal cells, as detected by ISH and IHC, with reactivity being stronger in serous cells. In addition, immunoreactivity for BDNF was observed in the saliva matrix of ductal cavities. Western blotting detected one significant immunoreactive 14 kDa band in the HSG and saliva. Immunoreactivities for salivary BDNF measured by ELISA in humans were 40.76±4.83 pg/mL and 52.64±8.42 pg/mL, in men and women, respectively. Although salivary BDNF concentrations in females tended to be higher than in males, the concentrations were not significantly different. In conclusion, human salivary BDNF may originate from salivary glands, as the HSG appears to produce BDNF.

Application of multi-directionally forged high-strength titanium to dental implants in beagle dogs.

Pure titanium is widely used as a material in dental implants. However, it possesses inferior mechanical strength. This study aimed to elucidate the efficacy of acid treated multi-directionally forged (MDF) pure titanium in vivo. We verified the temporal changes until osseointegration in beagle dogs. Using two types of experimental materials (conventional pure titanium or MDF pure titanium), new bone formation was assessed using morphological examinations, and the bone-to-implant contact (BIC) value was evaluated at each time point (14, 30, and 90 days after the operation). As such, new bone formation was observed around the acid-etched MDF group, in which the BIC value was highest, followed by that in the acid-etched pure titanium group. MDF pure titanium implants showed early promotion of new bone formation compared to conventional titanium implants. The new acid-treated MDF made of pure titanium could be applied to humans in the future to prove its practicality.

Advanced platelet-rich fibrin (A-PRF) has an impact on the initial healing of gingival regeneration after tooth extraction.

OBJECTIVES: Platelet-rich fibrin (PRF) is widely used in wound healing because it contains several growth factors, including vascular endothelial growth factor (VEGF). In this study, we investigated the effects of advanced PRF (A-PRF) in early-stage gingival regeneration after tooth extraction. METHODS: Blood sample was collected from females beagle dogs (age: 12 months) before tooth extraction for A-PRF preparation. All animals were sacrificed by perfusion-fixation on postoperative days 1, 3, and 7. The upper jaws were prepared for hematoxylin and eosin staining and immunostaining (for CD34 and VEGF). The lower jaw samples were prepared for scanning electron microscope observations. Blood flow in the gingiva before and after surgery was measured using laser Doppler flowmetry. RESULTS: In the A-PRF group, a large number of microvessels were observed in the gingival tissue on postoperative day 1. The microvessels in the control group were fewer and sparse. Regarding the vascular resin cast, a large number of new blood vessels were observed on postoperative day 1 in the A-PRF group. A stronger CD34-positive signal was obtained around the blood vessels in the A-PRF group than in the control group. Further, a strong VEGF-positive signal was observed in the perivascular tissue in the A-PRF group. Gingival blood flow was significantly higher in the A-PRF group after surgery. CONCLUSION: A-PRF had a positive impact on angiogenesis in the gingiva through the induction of VEGF expression. Thus, A-PRF may be beneficial for gingival tissue regeneration.

Changes in the microcirculation in periodontal tissue due to experimental peri-implantitis.

OBJECTIVES: Peri-implantitis causes dislodgement of dental implants due to inflammation in the peri-implant tissue. The microcirculation in the periodontal tissue undergoes morphological and physiological changes due to inflammation. The immune mechanism of peri-implantitis differs from that of periodontitis. In this study, we examined the changes in the microcirculation in the peri-implant tissue with experimentally induced inflammation, using morphological and physiological techniques. METHODS: Six beagle dogs were used in the experiment. After extracting both mandibular premolars, three titanium screw implants were inserted on each side of the mandibular jaw. Dental floss was placed on the right side for 90 days in the study group but not in the control group. Microvascular resin cast models were created, and morphological changes were observed using scanning electron microscopy. Periodontal blood flow was measured using laser Doppler flowmetry. RESULTS: Ninety days after induction of inflammation, bone resorption was observed around the implant body. Osseointegration was impaired, and a gap at the implant-bone interface was observed. The resin cast models showed that inflamed gingival blood vessels had invaded the bone marrow through the resorbed apical margin of the alveolar bone. Analysis of the physiological data obtained using laser Doppler flowmetry showed a significant increase in blood flow around the implants with experimentally induced inflammation. CONCLUSIONS: Significant morphological and physiological changes occur in the gingival microcirculation of peri-implant tissue due to inflammation. Evaluating the vasculature and blood flow in the tissue surrounding the site of peri-implantitis may be helpful for pathologic analysis in clinical settings.

Application of deproteinized bovine bone mineral as proangiogenic scaffold for alveolar bone formation in beagle dogs.

Alveolar bone repair after tooth extraction is essential after oral surgeries. Various grafting materials are used to promote the regeneration of lost alveolar bone. This study analysed the morphological features of the tissue regeneration process using deproteinized bovine bone mineral (DBBM). DBBM was used to densely fill the extraction sockets in beagle dogs. Following resin casting of the vasculature, stereomicroscopy and scanning electron microscopy were used to observe blood vessels and hard tissues in haematoxylin and eosin-stained sections on postoperative days 14, 30 and 90 in conjunction with vascular endothelial growth factor (VEGF) immunostaining to evaluate alveolar bone vascularization. On day 14 post-operation, the DBBM granules tightly filled the extraction sockets, maintained alveolar margin height and formed a scaffold for aiding angiogenesis and new bone formation. On day 30, new bone formation was observed around the DBBM granules. By day 90, bone tissue regeneration progressed in both groups but was more pronounced in the DBBM group. Alveolar margin height was maintained in the DBBM group throughout the study. Furthermore, VEGF expression in the DBBM group was detected around newly formed bone. We conclude that DBBM acts as a suitable scaffold for new bone generation, as well as angiogenesis around healing alveolar bone, and that it has the potential to play a key role in vascularization and bone formation.

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.

Effect of High Fat and Fructo-Oligosaccharide Consumption on Immunoglobulin A in Saliva and Salivary Glands in Rats.

Consumption of indigestible dietary fiber increases immunoglobulin A (IgA) levels in saliva. The purpose of this study is to clarify the synergistic effect of the intake of a high amount of fats and indigestible dietary fiber on IgA levels in saliva and submandibular glands (SMG). Seven-week-old Wistar rats were fed a low-fat (60 g/kg) fiberless diet, low-fat fructo-oligosaccharide (FOS, 30 g/kg) diet, high-fat (220 g/kg) fiberless diet, or high-fat FOS diet for 70 days. The IgA flow rate of saliva (IgA FR-saliva) was higher in the low-fat FOS group than in the other groups (p < 0.05). Furthermore, the concentration of tyrosine hydroxylase (a marker of sympathetic nerve activation) in the SMG was higher in the low-fat FOS group (p < 0.05) and positively correlated with the IgA FR-saliva (rs = 0.68. p < 0.0001. n = 32) in comparison to that in the other groups. These findings suggest that during low-fat FOS intake, salivary IgA levels may increase through sympathetic nerve activation.

Expression and Role of the BDNF Receptor-TrkB in Rat Adrenal Gland under Acute Immobilization Stress.

We reported that plasma brain-derived neurotrophic factor (BDNF) was maximally elevated following a 60-min period of acute immobilization stress and that salivary glands were the main source of plasma BDNF under this stress condition. However, the expression pattern of the BDNF receptor, Tyrosine receptor kinase B (TrkB), under this condition has yet to be determined. We therefore investigated the effect of this stress on the expression level of TrkB in various rat organs using real-time PCR. No significant differences were found between controls and 60 min-stressed rats with respect to TrkB level in various organs. Only adrenal glands showed significantly increased TrkB mRNA levels after 60 min of stress. TrkB mRNA and protein were observed to localize in chromaffin cells. In addition, we investigated whether BDNF-TrkB interaction influences the release of stress hormones from PC12 cells, derived from chromaffin cells. Truncated receptor, TrkB-T1, was identified in PC12 cells using RT-PCR. Exposure of PC12 cells to BDNF induced the release of catecholamine. This BDNF-evoked release was totally blocked by administration of the K252a in which an inhibitor of Trk receptors. Thus, BDNF-TrkB interactions may modulate catecholamine release from adrenal chromaffin cells under acute stress conditions.