Inhibitory regulation of amylase release in rat parotid acinar cells by benzodiazepine receptors

Effect of propofol on salivary secretion from the submandibular, sublingual, and labial glands during intravenous sedation

Background

Recent animal studies have suggested the role of GABA type A (GABA-_A) receptors in salivation, showing that GABA-_A receptor agonists inhibit salivary secretion. This study aimed to evaluate the effects of propofol (a GABA-_A agonist) on salivary secretions from the submandibular, sublingual, and labial glands during intravenous sedation in healthy volunteers.

Methods

Twenty healthy male volunteers participated in the study. They received a loading dose of propofol 6 mg/kg/h for 10 min, followed by 3 mg/kg/h for 15 min. Salivary flow rates in the submandibular, sublingual, and labial glands were measured before, during, and after propofol infusion, and amylase activity was measured in the saliva from the submandibular and sublingual glands.

Results

We found that the salivary flow rates in the submandibular, sublingual, and labial glands significantly decreased during intravenous sedation with propofol (P < 0.01). Similarly, amylase activity in the saliva from the submandibular and sublingual glands was significantly decreased (P < 0.01).

Conclusion

It can be concluded that intravenous sedation with propofol decreases salivary secretion in the submandibular, sublingual, and labial glands via the GABA-_A receptor. These results may be useful for dental treatment when desalivation is necessary.

Hypnotics and infections: disproportionality analysis of the U.S. Food & Drug Administration adverse event reporting system database

STUDY OBJECTIVES

There is no consensus information on infections associated with nonbenzodiazepines. Knowledge about infections related to newly marketed hypnotics (orexin receptor antagonists and melatonin receptor agonists) is scarce. The study aimed to detect infection signals for nonbenzodiazepines, orexin receptor antagonists, and melatonin receptor agonists by analyzing data from the U.S. Food & Drug Administration adverse event reporting system.

METHODS

A disproportionality analysis was performed to quantitatively detect infection signals for hypnotics by calculating the reporting odds ratio and the 95% confidence interval. Data registered in the U.S. Food & Drug Administration adverse event reporting system from 2010-2020 were retrieved.

RESULTS

A total of 3,092 patients with infection were extracted for the 3 classes of hypnotic drugs. Nonbenzodiazepines were associated with a higher disproportionality of infections (reporting odds ratio: 1.10; 95% confidence interval, 1.06-1.14). The association of infections was not present for melatonin receptor agonists (reporting odds ratio: 0.86; 95% confidence interval, 0.74-1.00) and orexin receptor antagonists (reporting odds ratio: 0.19; 95% confidence interval, 0.15-0.25). Significant reporting associations were identified for nonbenzodiazepines concerning the categories of bone and joint infections, dental and oral soft tissue infections, upper respiratory tract infections, and urinary tract infections.

CONCLUSIONS

Nonbenzodiazepines had a positive signal for infections, while orexin receptor antagonists and melatonin receptor agonists had a negative signal. More research needs to be conducted to confirm this relationship.

CITATION

Meng L, Huang J, He Q, et al. Hypnotics and infections: disproportionality analysis of the U.S. Food & Drug Administration adverse event reporting system database. J Clin Sleep Med. 2022;18(9):2229-2235.

Different expression and subcellular localization of vesicular inhibitory amino acid transporter in ducts of major salivary glands: An in situ study in mice

OBJECTIVE

The aim of this study was to clarify the mechanism of GABA (□-amino butyric acid)-signaling in the salivary glands by localization of vesicular inhibitory amino acid transporter, a key molecule in GABA-synthesis.

DESIGN

Parotid, sublingual and submandibular glands of mice at various postnatal stages were examined in immuno-light and electron microscopy as well as immuno-blotting.

RESULTS

Expression for vesicular inhibitory amino acid transporter was detected in parotid and sublingual glands of both sexes and female submandibular gland throughout postnatal development, while it was negligible in male submandibular glands at and after puberty. The expression in female submandibular glands attenuated after testosterone injection. The immunoreactivity was localized in striated ductal cells, but not acinar cells, in the salivary glands, and it occurred in association with intracellular and plasma membranes of the cells. It also occurred in myoepithelial and vascular smooth muscle cells.

CONCLUSIONS

GABA-signaling was suggested to be a significant signaling pathway in salivary ductal cells, which was suppressed in male submandibular glands at and after puberty. The suppression in the submandibular duct was by testosterone. In addition, the participation of vesicular inhibitory amino acid transporter in GABA signaling through plasma membranes of the ductal cells was suggested. The significance of occurrence of the immunoreactivity in myoepithelial and smooth muscle cells remains to be further elucidated in terms of implication in GABA signaling.

Stilbene Glucoside, a Putative Sleep Promoting Constituent from Polygonum multiflorum Affects Sleep Homeostasis by Affecting the Activities of Lactate Dehydrogenase and Salivary Alpha Amylase

Chinese herbal medicine (CHM) has been used for treating insomnia for centuries. The most used CHM for insomnia was Polygonum multiflorum. However, the molecular mechanism for CHM preventing insomnia is unknown. Stilbene glucoside (THSG), an important active component of P. multiflorum, may play an important role for treating insomnia. To test the hypothesis, Kunming mice were treated with different dosages of THSG. To examine the sleep duration, a computer-controlled sleep-wake detection system was implemented. Electroencephalogram (EEG) and electromyogram (EMG) electrodes were implanted to determine sleep-wake state. RT-PCR and Western blot was used to measure the levels of lactate dehydrogenase (LDH) and saliva alpha amylase. Spearman's rank correlation coefficient was used to identify the strength of correlation between the variables. The results showed that THSG significantly prolonged the sleep time of the mice (p<0.01). THSG changed sleep profile by reducing wake and rapid eye movement (REM) period, and increasing non-REM period. RT-PCR and Western blot analysis showed that THSG could down-regulate the levels of LDH and saliva alpha amylase (p<0.05). The level of lactate and glucose was positively related with the activity of LDH and saliva alpha amylase (p<0.05), respectively. On the other hand, the activities of LDH and amylase were negatively associated with sleep duration (p<0.05). The levels of lactate and glucose affect sleep homeostasis. Thus, THSG may prevent insomnia by regulating sleep duration via LDH and salivary alpha amylase.

Rebamipide, an anti-ulcerative drug, inhibits induction of salivary dysfunction by benzodiazepines

OBJECTIVES

The purpose of this study was to determine whether rebamipide, an antistomach ulcer agent, ameliorated benzodiazepine-induced hyposalivation in rat parotid gland (PG) and submandibular gland (SMG).

METHODS

Saliva was collected from PG and SMG through a capillary cannula inserted into the parotid duct and sublingual papillae, respectively, every 15 min for 1 h after stimulation with pilocarpine dissolved in physiological saline and intraperitoneally administered at 1 mg kg^-1 . Diazepam (DZP) was administered intraperitoneally at a dose of 0.2 mg kg^-1 twice daily for 7 days. Rebamipide was administered at 10, 20, 30, or 100 mg kg^-1 concomitantly with DZP to determine its effect on hyposalivation. The effect of rebamipide on movement of intracellular calcium ([Ca²⁺ ]i) in isolated parotid acinar cells was analyzed using Fluo4, a fluorescent dye used to detect Ca²⁺ .

RESULTS

Repetitive administration of DZP decreased salivary secretion in PG and SMG. This inhibitory effect was weakened by administration of rebamipide. Prior administration of DZP (10^-6 M) significantly suppressed carbachol (10^-7 M)-induced increase in [Ca²⁺ ]i. This inhibitory effect was ameliorated by combined use with rebamipide (5 × 10^-4 M).

CONCLUSION

This findings suggest that rebamipide weakens the downregulatory effect of DZP on salivary secretion by preventing DZP-induced suppression of increase in [Ca²⁺ ]i.

Effects of Benzodiazepines on Acinar and Myoepithelial Cells

Background: Benzodiazepines (BZDs), the most commonly prescribed psychotropic drugs with anxiolytic action, may cause hyposalivation. It has been previously shown that BZDs can cause hypertrophy and decrease the acini cell number. In this study, we investigated the effects of BZDs and pilocarpine on rat parotid glands, specifically on acinar, ductal, and myoepithelial cells.

Methods: Ninety male Wistar rats were divided into nine groups. Control groups received a saline solution for 30 days (C30) and 60 days (C60), and pilocarpine (PILO) for 60 days. Experimental groups received lorazepam (L30) and midazolam (M30) for 30 days. Another group (LS60 or MS60) received lorazepam or midazolam for 30 days, respectively, and saline for additional 30 days. Finally, other groups (LP60 or MP60) received either lorazepam or midazolam for 30 days, respectively, and pilocarpine for additional 30 days. The expression of calponin in myoepithelial cells and the proliferating cell nuclear antigen (PCNA) in acinar and ductal cells were evaluated.

Results: Animals treated with lorazepam showed an increase in the number of positive staining cells for calponin as compared to control animals (p < 0.05). Midazolam administered with pilocarpine (MP60) induced an increase in the proliferation of acinar and ductal cells and a decrease in the positive staining cells for calponin as compared to midazolam administered with saline (MS60).

Conclusion: We found that myoepithelial cells might be more sensitive to the effects of BZD than acinar and ductal cells in rat parotid glands.

Modulation of benzodiazepine receptor, adrenoceptor and muscarinic receptor by diazepam in rat parotid gland

This study investigated the influence of diazepam on the binding characteristics of adrenoceptor, muscarinic and benzodiazepine receptors in rat parotid gland membrane using a radioligand binding assay. At a concentration of >10(-6)M, diazepam competed with [(3)H]dihydroalprenolol for β-adrenoceptor, but not [(3)H]prazosin for α-adrenoceptor or [(3)H]quinuclidinyl benzilate for muscarinic receptor. Continuous administration of diazepam at doses of 0.4mg/kg/day, i.p. for 7days in rat significantly decreased pilocarpine (4.0mg/kg, i.p.)-induced parotid salivary flow. Diazepam also produced a significant increase in the dissociation constant (Kd) value for [(3)H]dihydroalprenolol binding, but no change in the maximal binding capacity (Bmax) value, and a decrease in the Kd value for [(3)H]diazepam binding to benzodiazepine receptors, but no change in the Kd or Bmax values for [(3)H]prazosin or [(3)H]quinuclidinyl benzilate binding. These results suggest that continuous administration of diazepam modifies affinity for β-adrenoceptor and benzodiazepine receptor binding sites in parotid gland membrane and that changes in these binding sites may be closely related to diazepam-induced suppression of salivary secretion.

Diazepam enhances production of diazepam-binding inhibitor (DBI), a negative saliva secretion regulator, localized in rat salivary gland

Peripheral-type benzodiazepine receptor (PBR) and central-type benzodiazepine receptor (CBR) in salivary gland play a role in the inhibitory regulation of salivary secretion in rodents. Diazepam-binding inhibitor (DBI), an endogenous ligand for PBR, produces neurosteroids, which modulate CBR activity. In this study, we investigated the effect of repetitive administration of diazepam (DZP) on salivary secretion and expression of DBI mRNA and peptide. Moreover, mRNA expression of PBR and pituitary adenylate cyclase-activating polypeptide (PACAP), a transcriptional regulator for DBI promoter, was evaluated after repetitive administration of DZP. Repetitive administration, but not single administration, of 0.4 mg/kg DZP caused inhibition of salivary secretion and enhanced expression of DBI, PACAP, and PBR mRNA in rat salivary gland, with an increase in production of DBI peptide. These results suggest that repetitive administration of DZP stimulates DBI production, which may result in an increase in the suppressive effect of DZP on salivary secretion.

Immunohistochemical study on GABAergic system in salivary glands

Gamma-aminobutyric acid (GABA) and its receptors are found in the central nervous system and several peripheral tissues. The purpose of this study was to determine the expression and distribution of GABA and glutamate decarboxylase (GAD), a GABA biosynthetic enzyme, in rat salivary gland. Western blot and real time quantitative RT-PCR revealed that GAD67 was the major isoform of GAD in the salivary glands. Furthermore, both GABA and GAD were detected around the acinar cells in the submandibular glands by immunohistochemical analysis. When both sympathetic and parasympathetic nerves related to the submandibular glands were denervated, the immunoreactivities of GABA and GAD were dramatically depressed, and levels of GAD67 and GABA significantly decreased. However, no morphological changes in the glands were observed after denervation. These results indicate that GAD67 is present around acinar cells in the salivary glands, and suggest that the GABAergic system in the glands is closely related to the autonomic nervous system.

Effect of translocator protein (18 kDa)-ligand binding on neurotransmitter-induced salivary secretion in rat submandibular glands

BACKGROUND INFORMATION

TSPO (translocator protein), previously known as PBR (peripheral-type benzodiazepine receptor), is a ubiquitous 18 kDa transmembrane protein that participates in diverse cell functions. High-affinity TSPO ligands are best known for their ability to stimulate cholesterol transport in organs synthesizing steroids and bile salts, although they modulate other physiological functions, including cell proliferation, apoptosis and calcium-dependent transepithelial ion secretion. In present study, we investigated the localization and function of TSPO in salivary glands.

RESULTS

Immunohistochemical analysis of TSPO in rat salivary glands revealed that TSPO and its endogenous ligand, DBI (diazepam-binding inhibitor), were present in duct and mucous acinar cells. TSPO was localized to the mitochondria of these cells, whereas DBI was cytosolic. As expected, mitochondrial membrane preparations, which were enriched in TSPO, exhibited a high affinity for the TSPO drug ligand, (3)H-labelled PK 11195, as shown by B(max) and K(d) values of 10.0+/-0.5 pmol/mg and 4.0+/-1.0 nM respectively. Intravenous perfusion of PK 11195 increased the salivary flow rate that was induced by muscarinic and alpha-adrenergic agonists, whereas it had no effect when administered alone. Addition of PK 11195 also increased the K(+), Na(+), Cl(-) and protein content of saliva, indicating that this ligand modulated secretion by acini and duct cells.

CONCLUSIONS

High-affinity ligand binding to mitochondrial TSPO modulates neurotransmitter-induced salivary secretion by duct and mucous acinar cells of rat submandibular glands.

Effects of peripheral benzodiazepine receptor ligands on proliferation and differentiation of human mesenchymal stem cells

The peripheral benzodiazepine receptor (PBR) has been known to have many functions such as a role in cell proliferation, cell differentiation, steroidogenesis, calcium flow, cellular respiration, cellular immunity, malignancy, and apoptosis. However, the presence of PBR has not been examined in mesenchymal stem cells. In this study, we demonstrated the expression of PBR in human bone marrow stromal cells (hBMSCs) and human adipose stromal cells (hATSCs) by RT-PCR and immunocytochemistry. To determine the roles of PBR in cellular functions of human mesenchymal stem cells (hMSCs), effects of diazepam, PK11195, and Ro5-4864 were examined. Adipose differentiation of hMSCs was decreased by high concentration of PBR ligands (50 microM), whereas it was increased by low concentrations of PBR ligands (<10 microM). PBR ligands showed a biphasic effect on glycerol-3-phosphate dehydrogenase (GPDH) activity. High concentration of PBR ligands (from 25 to 75 microM) inhibited proliferation of hMSCs. However, clonazepam, which does not have an affinity to PBR, did not affect adipose differentiation and proliferation of hMSCs. The PBR ligands did not induce cell death in hMSCs. PK11195 (50 microM) and Ro5-5864 (50 microM) induced cell cycle arrest in the G(2)/M phase. These results indicate that PBR ligands play roles in adipose differentiation and proliferation of hMSCs.

Inhibitory effect of diazepam on muscarinic receptor-stimulated inositol 1,4,5-trisphosphate production in rat parotid acinar cells

1. This study examined the effect of diazepam (DZP) on phosphoinositide turnover, which plays an important role in the regulation of salivary secretion, in rat parotid acinar cells. 2. DZP (10(-9) M to 10(-5) M), a potent agonist of both central- and peripheral-type benzodiazepine receptors, dose-dependently decreased inositol 1,4,5-trisphosphate IP3 production stimulated by carbachol, a muscarinic receptor agonist, in the cells. 3. DZP produced a maximum inhibitory response at a concentration of 10(-5) M, with IP3 production decreased to 63% of maximal levels. The concentration inducing half maximal inhibition of IP3 production was approximately 3.5 x 10 (-8) M. 4. An inhibitory response to DZP was produced by a short-term pretreatment (<3 min) of the cells and prevented by antagonist and competing ligand for the central- and peripheral-type benzodiazepine receptors, flumazenil and PK 11195, respectively. 5. DZP showed a non-competitive inhibition of carbachol-stimulated IP3 production. It did not directly inhibit the activities of GTP-binding regulatory proteins and phosphatidylinositol 4,5-bisphosphate-specific phospholipase C (PLC) in the parotid gland membranes, though choline chloride inhibited PLC activity. 6. DZP (10(-5) M) attenuated the increase in the intracellular Ca2+ concentration ([Ca(2+)](i)) in the cells following stimulation of the muscarinic and alpha(1)-adrenoceptors. 7. These results suggest that in the parotid acinar cells, DZP inhibits muscarinic receptor-stimulated IP3 production through benzodiazepine receptors and that PLC activity which produces IP3 is inhibited by chloride. The decreases in IP3 and [Ca(2+)](i) in the cells may be connected with the suppression of salivary secretion induced by DZP.

Pharmacological characterization of an 18-kDa protein associated with the peripheral-type benzodiazepine receptor in salivary glands

Pharmacological characterization of peripheral type benzodiazepine receptors in rat, rabbit, mouse and human salivary glands was determined by receptor binding and photoaffinity labeling analysis using [3H]PK14105 (1-(2-fluoro-5-nitrophenyl)-3-isoquinolinecarboxylic acid). [3H]PK14105 bound to the membranes of salivary glands in rats, rabbits, mice and humans with high affinity at the nanomolar level. The rank order of receptor density in submandibular glands among several species was as follows: human > or = rat > or = mouse > rabbit. Competitive potency of receptor ligands against [3H]PK14105 was as follows: PK1195 > or = Ro5-4864 > diazepam > clonazepam > Ro15-1788. The rank order of potency against calcium channel ligands and co-transport inhibitors was as follows: nitrendipine > BAY K 8644 > bumetanide > furosemide. Pretreatment with nitrendipine or BAY K 8644 decreased the affinity of [3H]PK14105 binding to rat parotid gland membranes, without changing the density. The photoaffinity labeling with [3H]PK14105 indicated the presence of the 18-kDa protein in all salivary glands of our experiment. The inhibition of photolabeling by some receptor ligands was the same results as the receptor binding assay. In conclusion, the peripheral type benzodiazepine receptors include the 18-kDa protein photolabeled with [3H]PK14105 in salivary glands of rat, mouse, rabbit and human.