Protein secretion from rat submandibular acini and granular ducts: effects of exogenous VIP and substance P during parasympathetic nerve stimulation

Salivary and serum biomarkers of inflammation in a man with metastatic medullary thyroid carcinoma and hyperreactive gingiva: a fourteen year odyssey

A peripheral (gingival) fibroma, a gingival cyst and hyperplastic gingivitis occurred simultaneously in a man with metastatic medullary thyroid carcinoma (MCT). The gingival growths and hyperplasia appeared to be related to poor oral hygiene rather than to the MTC. Despite the patient's improved oral hygiene, the hyperplastic gingivitis and peripheral fibroma recurred, and a new peripheral fibroma and gingival cyst developed, which prompted reconsideration of a link with the MTC. MTC cells secrete calcitonin (CT), procalcitonin (ProCT) and growth factors; the patient's serum CT and ProCT were several fold higher than normal. The patient's salivary CT and ProCT also were elevated, but α-amylase and epidermal growth factor (EGF) were not, compared to three healthy controls. A possible link between the MTC and gingival hyper-reactivity due to CT and/or ProCT promoting inflammatory cytokines, and the utility of salivary ProCT as an indicator of periodontitis in this patient were explored further. Unstimulated whole saliva and serum were collected from the patient followed by a standard periodontal examination before periodontal treatment, and 3 weeks and 3 months after treatment. This cycle was repeated 7 months after the previous periodontal treatment. The saliva was assayed for ProCT and the serum was assayed for ProCT, high sensitivity C-reactive protein (CRP), interleukin-6 (IL-6) and proadrenomedullin (ProADM). The results were analyzed for correlations among the severity of periodontitis and the biomarkers/cytokines. Only the salivary ProCT was correlated with the severity of periodontitis, i.e. it was higher just before and lower at 3 weeks and 3 months after each periodontal treatment. The patient's salivary ProCT content also was much higher than reported elsewhere. The other biomarkers/cytokines were within normal ranges. Our findings indicate that salivary ProCT is independent of serum ProCT and therefore may be a useful marker for moderate to severe periodontitis in patients with MTC. The greatly elevated salivary and serum CT and ProCT, and a trend toward correlation between the serum CRP and ProCT suggest a pro-inflammatory link between the MTC and the hyperreactive gingiva in this patient. Further studies are warranted to determine whether hyperplastic gingivitis and gingival growths, such as cysts and fibromas, occur with unusual frequency in patients with MTC.

Tri-phasic modulation of ACh- and NA-maintained calcium plateau by high potassium in isolated mouse submandibular granular convoluted tubular cells

OBJECTIVES

The fact that submandibular glands secrete a large amount of potassium ion upon nerve stimulation has long been recognized, but a physiological role for such high potassium in the saliva has never been systematically investigated. In the present work, high potassium effect has been investigated in the freshly isolated mouse submandibular granular convoluted tubules.

DESIGN

Isolated intact mouse submandibular granular convoluted tubules were loaded with Fura-2, and cytosolic calcium concentration in individual tubular cells was measured by microscopic fluorospectrometry.

RESULTS

It was found that high potassium had no effect on basal cytosolic calcium concentration, but had a tri-phasic modulation of the calcium plateau maintained by continued stimulation by acetylcholine (ACh) or noradrenaline (NA): a minor initial transient depression, followed by steady increase, completed by a robust calcium rebound spike upon removal of high potassium. The phase of steady increase was blocked without major effect on the plateau by KB-R 7943, a sodium/calcium exchange (NCX) inhibitor.

CONCLUSION

These data together suggest that high potassium in saliva bathing the mouse submandibular granular convoluted tubular cells has a potent feedback effect on ACh and NA stimulation, and sodium/calcium exchange is likely to play a major role in this process. Such positive feedback actions of high potassium may suggest a role for enhancing ACh- or NA-stimulated protein factor secretion from the granulated convoluted tubular cells.

Tight junctions in salivary epithelium

Epithelial cell tight junctions (TJs) consist of a narrow belt-like structure in the apical region of the lateral plasma membrane that circumferentially binds each cell to its neighbor. TJs are found in tissues that are involved in polarized secretions, absorption functions, and maintaining barriers between blood and interstitial fluids. The morphology, permeability, and ion selectivity of TJ vary among different types of tissues and species. TJs are very dynamic structures that assemble, grow, reorganize, and disassemble during physiological or pathological events. Several studies have indicated the active role of TJ in intestinal, renal, and airway epithelial function; however, the functional significance of TJ in salivary gland epithelium is poorly understood. Interactions between different combinations of the TJ family (each with their own unique regulatory proteins) define tissue specificity and functions during physiopathological processes; however, these interaction patterns have not been studied in salivary glands. The purpose of this review is to analyze some of the current data regarding the regulatory components of the TJ that could potentially affect cellular functions of the salivary epithelium.

Pharmacological evidence for the stimulation of NADPH oxidase by P2X(7) receptors in mouse submandibular glands

ATP in the 100 μM-1 mM concentration range provoked a calcium-independent increase of the oxidation of dichlorodihydrofluorescein (DCFH) to dichlorofluorescein (DCF) by mouse submandibular cells. 3′-O-(4-benzoyl)benzoyl adenosine 5′-triphosphate (BzATP), a P2X₇ agonist, but not a muscarinic or an adrenergic agonist, reproduced the effect of ATP. The inhibition of phospholipase C by U73122 or the potentiation of P2X₄ receptor activation with ivermectin did not modify the response to ATP. ATP did not increase the oxidation of DCFH in cells isolated from submandibular glands of P2X₇ knockout mice or in cells pretreated with a P2X₇ antagonist. The inhibition of protein kinase C or of mitogen-activated protein kinase (MAP kinase) or of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase blocked the oxidation of DCFH without affecting the increase of the intracellular concentration of calcium or the uptake of ethidium bromide in response to extracellular ATP. From these results it is concluded that the activation of the P2X₇ receptors from submandibular glands triggers an intracellular signalling cascade involving protein kinase C and MAP kinase leading to the stimulation of NADPH oxidase and the subsequent generation of reactive oxygen species.

Morphological changes in mouse sublingual gland parenchyma subjected to chorda tympani resection

Morphological changes in the mouse sublingual gland parenchyma subjected to parasympathetic nerve block were investigated. Mice were subjected to unilateral resection of the chorda tympani, near its point of joining with the lingual nerve. After 1, 2, 3, 5, 10 or 20 weeks, the mice were killed and their sublingual glands were removed and processed for light and electron microscopy. Two weeks after resection, the space between the adjoining lobules of the glands on the treated side began to be expanded, and by 10 weeks were 10 times the size of the spaces in the glands of the untreated mice. Three weeks after resection, the lobule area decreased to about 72% of the area of glands in the untreated mice and the acinus area to about 52%. However, no significant difference was seen between the numbers of acini in each group. Electron microscopy showed that the glands on the treated side contained fewer secretory granules than the glands in the untreated mice, though there was no difference in size. Neither the lobules of the glands on the treated side nor those of the glands of the untreated mice contained many TUNEL-positive cells. These findings suggest that following parasympathetic nerve resection, mouse sublingual gland acinar cells undergo atrophy with a reduction size rather than cell death.

Reflex secretion of proteins into submandibular saliva in conscious rats, before and after preganglionic sympathectomy

1. An indwelling catheter was placed in the left submandibular duct of rats, under pentobarbitone anaesthesia, and connected to an outflow cannula that emerged above the skull. 2. Saliva was collected from the outflow cannula in conscious rats, the same day after recovery from anaesthesia, under four different reflex conditions: grooming, heat exposure, rejection of a bitter tasting substance and feeding on softened chow, repeated in different orders. 3. Saliva flow was greatest for grooming and least for rejection. Protein concentrations were least with heat but much greater and similar for the other stimulations. Acinar peroxidase activity was high for feeding, intermediate for grooming and rejection, and again lowest with heat. Tubular tissue kallikrein activities were moderately low, being greatest with feeding and least with grooming. Secretory immunoglobulin A (SIgA) concentration was least with heat and similar for the other stimulations. 4. The next day, under pentobarbitone anaesthesia, the left preganglionic sympathetic trunk was sectioned (sympathetic decentralization) and, after recovery, the preceding stimulations were repeated. Flow of saliva showed little change, but protein and peroxidase concentrations and outputs decreased dramatically with grooming, rejection and feeding to levels similar to those with heat, which showed little change. Tissue kallikrein was lowered less dramatically, but the reductions in output were significant except with heat. Patterns of proteins resolved by electrophoresis changed for grooming, rejection and feeding and became similar to saliva from heat, which showed little change. No significant effects on SIgA concentrations occurred. 5. Gland weights from the sympathetically decentralized side were greater than from the intact side at the end of the experiments and histologically showed retention of acinar mucin. 6. Thus reflex sympathetic drive varied with the different stimulations; it was least during heat, but it had pronounced effects on acinar secretion of proteins during the other stimulations. At the same time this sympathetic drive had less impact on tissue kallikrein secretion from tubules and had little influence on flow or the concentration of SIgA secreted.