Role of nitric oxide in Sjögren's syndrome

The human major sublingual gland and its neuropeptidergic and nitrergic innervations

BACKGROUND

What textbooks usually call the sublingual gland in humans is in reality a tissue mass of two types of salivary glands, the anteriorly located consisting of a cluster of minor sublingual glands and the posteriorly located major sublingual gland with its outlet via Bartholin's duct. Only recently, the adrenergic and cholinergic innervations of the major sublingual gland was reported, while information regarding the neuropeptidergic and nitrergic innervations is still lacking.

METHODS

Bioptic and autoptic specimens of the human major sublingual gland were examined by means of immunohistochemistry for the presence of vasoactive intestinal peptide (VIP)-, neuropeptide Y (NPY)-, substance P (SP)-, calcitonin gene related-peptide (CGRP)-, and neuronal nitric oxide synthase (nNOS)-labeled neuronal structures.

RESULTS

As to the neuropeptidergic innervation of secretory cells (here in the form of mucous tubular and seromucous cells), the findings showed many VIP-containing nerves, few NPY- and SP-containing nerves and a lack of CGRP-labeled nerves. As to the neuropeptidergic innervation of vessels, the number of VIP-containing nerves was modest, while, of the other neuropeptide-containing nerves under study, only few (SP and CGRP) to very few (NPY) nerves were observed. As to the nitrergic innervation, nNOS-containing nerves were very few close to secretory cells and even absent around vessels.

CONCLUSION

The various innervation patterns may suggest potential transmission mechanisms involved in secretory and vascular responses of the major sublingual gland.

Primary Sjögren's syndrome: new perspectives on salivary gland epithelial cells

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease primarily affecting exocrine glands such as the salivary glands, leading to impaired secretion and sicca symptoms. As the mainstay of salivation, salivary gland epithelial cells (SGECs) have an important role in the pathology of pSS. Emerging evidence suggests that the interplay between immunological factors and SGECs may not be the initial trigger or the sole mechanism responsible for xerostomia in pSS, challenging conventional perceptions. To deepen our understanding, current research regarding SGECs in pSS was reviewed. Among the extensive aberrations in cellular architecture and function, this review highlighted certain alterations of SGECs that were identified to occur independently of or in absence of lymphocytic infiltration. In particular, some of these alterations may serve as upstream factors of immuno-inflammatory responses. These findings underscore the significance of introspecting the pathogenesis of pSS and developing interventions targeting SGECs in the early stages of the disease.

Adropin Serum Levels in Patients with Primary Sjögren's Syndrome

Primary Sjögren’s syndrome (pSS) patients have higher prevalence of endothelial dysfunction and premature atherosclerosis. Recent studies investigated adropin, a secretory protein that can regulate lipid metabolism and insulin resistance and protect endothelial cells’ function and that has an anti-inflammatory effect. The aim of this study was to determine adropin levels in pSS patients compared to healthy controls. Additional goals were exploring the correlation between adropin and several metabolic and immunological parameters in pSS, including disease specific antibodies, EULAR Sjögren’s Syndrome Disease Activity Index (ESSDAI), and Sjögren’s Syndrome Disease Damage Index (SSDDI). This research included 52 pSS patients and 52 healthy controls. pSS patients have significantly higher adropin levels compared to the control group (3.76 ± 0.68 vs. 3.14 ± 0.69 ng/mL, p < 0.001). Correlation analysis showed that adropin levels in pSS patients have positive correlation with high-density lipoprotein (HDL) (r = 0.290, p = 0.036) and anti SSA/Ro52 antibodies (r = 0.307, p = 0.026) and negative correlation with SSDDI (r = −0.401, p = 0.003). Multivariant linear regression showed that adropin levels are independently associated with HDL (β ± SE, 0.903 ± 0.283, p = 0.002) and SSDDI (β ± SE, −0.202 ± 0.073, p = 0.008). Our findings imply that adropin could be involved in the pathophysiology of pSS, yet it remains to be elucidated in future studies whether adropin has a protective or detrimental role in this setting.

Association between increased Bcl-2, Fas and FasL levels and inflammation extent in labial salivary glands during primary Sjögren's syndrome

BACKGROUND

Primary Sjögren syndrome (pSS) is a chronic autoimmune disease characterized by epithelial atrophy, mononuclear infiltration in exocrine glands resulting in defective function of these glands. In pSS, atrophy of the epithelium is caused by an increased amount of apoptosis.

OBJECTIVE

The main aim of this study is to investigate the role of the apoptosis-related factors by studying Bcl-2, Fas and FasL expression in relation to the extent of inflammation as well as the effect of therapy on the expression of these mediators.

METHODS

In pSS patients (n=62) documented for their serological and clinical features, Fas, FasL and Bcl-2 plasma levels were assessed using enzyme-linked immunosorbent assays. In the same context, we investigated their expression by immunohistochemistry analysis in the labial salivary glands samples in association with the extent of inflammation.

RESULTS

Interestingly, our results indicated that in pSS patients, the plasmatic Bcl-2, Fas and FasL levels, which appear to be associated with the severity of inflammation and were significantly elevated in comparison to the healthy controls. Moreover, a significant decrease in all these factors was observed in patients after combined corticosteroids-hydroxychloroquine therapy. Importantly, we report a strong positive correlation between Bcl-2 and NO levels. The immunohistochemical staining reveals a strong Bcl-2 expression in infiltrating mononuclear cells and a total absence in the acinar cells. The Bcl-2 level varies according to the severity of the pathology. However, the expression of Fas and FasL was less important and predominantly localized in infiltrating mononuclear cells.

CONCLUSION

Our current study highlights the involvement of Bcl-2, Fas and FasL in pSS glands injury. These factors may act as useful predictor markers of a clinical course in pSS suggesting a novel approach in the pSS patients monitoring.

Nitric Oxide in Macrophage Immunometabolism: Hiding in Plain Sight

Nitric Oxide (NO) is a soluble endogenous gas with various biological functions like signaling, and working as an effector molecule or metabolic regulator. In response to inflammatory signals, immune myeloid cells, like macrophages, increase production of cytokines and NO, which is important for pathogen killing. Under these proinflammatory circumstances, called “M1”, macrophages undergo a series of metabolic changes including rewiring of their tricarboxylic acid (TCA) cycle. Here, we review findings indicating that NO, through its interaction with heme and non-heme metal containing proteins, together with components of the electron transport chain, functions not only as a regulator of cell respiration, but also a modulator of intracellular cell metabolism. Moreover, diverse effects of NO and NO-derived reactive nitrogen species (RNS) involve precise interactions with different targets depending on concentration, temporal, and spatial restrictions. Although the role of NO in macrophage reprogramming has been in evidence for some time, current models have largely minimized its importance. It has, therefore, been hiding in plain sight. A review of the chemical properties of NO, past biochemical studies, and recent publications, necessitates that mechanisms of macrophage TCA reprogramming during stimulation must be re-imagined and re-interpreted as mechanistic results of NO exposure. The revised model of metabolic rewiring we describe here incorporates many early findings regarding NO biochemistry and brings NO out of hiding and to the forefront of macrophages immunometabolism.

Influence of acute high-intensity exercise on salivary nitric oxide levels

This study, employing an exercise versus control crossover design, was conducted to investigate the influence of acute high-intensity exercise on salivary nitric oxide (NO) levels. Nine healthy males (aged 23.8 ± 1.4 years) performed ergometer exercise at 80%VO_2peak for 60 min, whereas controls sat at rest for 60 min. Saliva samples were collected before (Pre: 0800 h) and after (Post 0-h: 0900 h, Post 1-h: 1000 h, Post 2-h: 1100 h, Post 3-h: 1200 h) the interventions. Salivary NO levels were determined by colorimetric assay. It was found that the salivary NO levels in controls were decreased (P < 0.05) at Post 0-h (-94 ± 15), Post 1-h (-80 ± 20), Post 2-h (-92 ± 34) and Post 3-h (-145 ± 39) relative to the Pre values. Under exercise conditions, salivary NO levels did not change after high-intensity ergometer exercise relative to the Pre values. Thus, the response of salivary NO levels appeared to differ between high-intensity ergometer exercise and inactivity, that exercise-related stress induces the production of salivary NO.

Comparison of Oxidative Effects of Two Different Administration Form of Oxybutynin in the Potential Target Tissues

Oxybutynin is an important anticholinergic agent that prevents uncontrolled contractions in the treatment of overactive bladder (OAB). However, drugs containing oxybutynin have significant side effects such as dry eyes, dry mouth, increased heart rate, constipation, blurred vision, and confusion. In recent years, new delivery methods for this agent are being searched. One of them is vaginal delivery. In this study, we aimed to compare the effects of oxybutynin on oxidative parameters in the potential target tissues of the oral and vaginal delivery. Female New Zealand white rabbits (n=12) were divided into two groups: oral delivery and vaginal delivery. The animals were sacrificed 48 h after administration and nitric oxide (NOx), thiobarbituric acid-reactive substances (TBARs), and glutathione (GSH) levels were determined spectrophotometrically in the aorta, salivary gland, and small intestine tissue samples. Vaginal delivery significantly decreased NOx levels in all tissue samples as compared to oral delivery (p < 0.05). Moreover, it reduced TBARs levels in salivary gland and aorta tissue samples (p < 0.05). In the light on these findings, it can be said that vaginal delivery may decrease the oxidant-induced side effects of oxybutynin as compared to oral delivery.

Oxidative stress in autoimmune rheumatic diseases

The management of patients with autoimmune rheumatic diseases such as rheumatoid arthritis (RA) remains a significant challenge. Often the rheumatologist is restricted to treating and relieving the symptoms and consequences and not the underlying cause of the disease. Oxidative stress occurs in many autoimmune diseases, along with the excess production of reactive oxygen species (ROS) and reactive nitrogen species (RNS). The sources of such reactive species include NADPH oxidases (NOXs), the mitochondrial electron transport chain, nitric oxide synthases, nitrite reductases, and the hydrogen sulfide producing enzymes cystathionine-β synthase and cystathionine-γ lyase. Superoxide undergoes a dismutation reaction to generate hydrogen peroxide which, in the presence of transition metal ions (e.g. ferrous ions), forms the hydroxyl radical. The enzyme myeloperoxidase, present in inflammatory cells, produces hypochlorous acid, and in healthy individuals ROS and RNS production by phagocytic cells is important in microbial killing. Both low molecular weight antioxidant molecules and antioxidant enzymes, such as superoxide dismutase, catalase, glutathione peroxidase, and peroxiredoxin remove ROS. However, when ROS production exceeds the antioxidant protection, oxidative stress occurs. Oxidative post-translational modifications of proteins then occur. Sometimes protein modifications may give rise to neoepitopes that are recognized by the immune system as 'non-self' and result in the formation of autoantibodies. The detection of autoantibodies against specific antigens, might improve both early diagnosis and monitoring of disease activity. Promising diagnostic autoantibodies include anti-carbamylated proteins and anti-oxidized type II collagen antibodies. Some of the most promising future strategies for redox-based therapeutic compounds are the activation of endogenous cellular antioxidant systems (e.g. Nrf2-dependent pathways), inhibition of disease-relevant sources of ROS/RNS (e.g. isoform-specific NOX inhibitors), or perhaps specifically scavenging disease-related ROS/RNS via site-specific antioxidants.

Update on Pathogenesis of Sjogren's Syndrome

Sjogren's syndrome is a common autoimmune disease that presents with sicca symptoms and extraglandular features. Sjogren's syndrome is presumably as common as RA; yet it is poorly understood, underdiagnosed and undertreated. From the usual identity as an autoimmune exocrinopathy to its most recent designate as an autoimmune epithelitis - the journey of SS is complex. We herein review some of the most important milestones that have shed light on different aspects of pathogenesis of this enigmatic disease. This includes role of salivary gland epithelial cells, and their interaction with cells of the innate and adaptive immune system. Non-immune factors acting in concert or in parallel with immune factors may also be important. The risk genes identified so far have only weak association, nevertheless advances in genetics have enhanced understanding of disease mechanisms. Role of epigenetic and environmental role factors is also being explored. SS has also some unique features such as congenital heart block and high incidence of lymphoma; disease mechanisms accounting for these manifestations are also reviewed.

Interferon-β inhibits inflammatory responses mediators via suppression of iNOS signaling pathway in PBMCs from patients with primary Sjögren's syndrome

BACKGROUND

Primary Sjögren's syndrome (pSS) represents a chronic, systemic autoimmune disorder, characterized by lymphocytic infiltration of exocrine glands, inducing compromised secretory function and tissue destruction. Increasing evidence had revealed that inflammatory mediators, such as nitric oxide (NO) and pro-inflammatory cytokines, are critical in the development and perpetuation of pSS systemic manifestations. In our current study, we aimed to investigate the ex vivo immunomodulatory effect of interferon (IFN)-β on iNOS expression, as well as on pro-inflammatory (tumor necrosis factor (TNF)-α, interleukin (IL)-6) and immunoregulatory (IL-10) cytokine production. Furthermore, we examined potential associations between the influence of IFN-β treatment on NO production, and pSS clinical and serological manifestations.

METHODS

In 41 pSS patients documented for their clinical and serological features, NO and cytokines levels were measured by the Griess method and enzyme-linked immunosorbent assay, respectively. Inducible nitric oxide synthase expression was analyzed by fluorescence immunostaining assay, using peripheral blood mononuclear cells (PBMCs) isolated from healthy controls and pSS patients.

RESULTS

Our results revealed a strong down-modulating effect of IFN-β in the secretion of pro-inflammatory mediators including TNF-α, IL-6, and NO production. Interestingly, IFN-β exerts an increase in IL-10 levels. The most suppressive effect exerted by IFN-β on NO production was importantly reported for patients with neurological manifestation. This immunomodulatory effect of IFN-β on NO production is highly related to the decrease of inducible nitric oxide synthase (iNOS) expression.

CONCLUSION

Our findings highlight a consistent ex vivo inhibitory effect of IFN-β on pro-inflammatory cytokine production and NO pathway in pSS patients. Our data suggest that IFN-β could represent a potential candidate for targeting inflammation during pSS.

Cardamonin inhibits pro-inflammatory cytokine production and suppresses NO pathway in PBMCs from patients with primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disorder with a complex pathophysiology primarily affecting exocrine glands, leading to compromised secretory function. Recent studies imply that many inflammatory mediators, such as pro-inflammatory cytokines and nitric oxide, are critical in the development and perpetuation of pSS systemic manifestations. In the current study, we aimed to investigate the ex vivo immunomodulatory effect of cardamonin (C₁₆H₁₄O₄), on pro-inflammatory cytokines, TNF-α, IL-6 and inducible nitric oxide synthase (iNOS) expression during pSS. For this purpose, peripheral blood mononuclear cells isolated from pSS patients and healthy controls were cultured with different concentrations of cardamonin. Cytokine levels were measured by ELISA and NO production was assessed using the Griess method. Inducible nitric oxide synthase expression and NF-κB activity were analyzed by immunofluorescence staining. Our results suggest that cardamonin inhibits TNF-α, IL-6 and NO production and downregulates iNOS expression and NF-κB activation. Collectively, our results highlight the ex vivo immunomodulatory effects of cardamonin on pro-inflammatory cytokine production and NO pathway in pSS patients. Therefore, cardamonin is a potential candidate for controlling inflammation during pSS.

Activation of plasmacytoid dendritic cells by apoptotic particles - mechanism for the loss of immunological tolerance in Sjögren's syndrome

Sjögren's syndrome (SS) is a common autoimmune disease targeting salivary and lacrimal glands. It is strongly female-dominant, characterized by low oestrogen levels combined with a local intracrine dihydrotestosterone defect. We hypothesized that these hormonal deficits lead to increased apoptosis of the epithelial cells and plasmacytoid dendritic cell (pDC)-mediated proinflammatory host responses. Expression of Toll-like receptors (TLRs)-7 and -9 and cytokine profiles was studied in pDCs treated with apoptotic particles collected in consecutive centrifugation steps of media from apoptotic cells. Expression and localization of SS autoantigens in these particles was also analysed. Furthermore, the effects of sex steroids were studied in pDCs cultured with several concentrations of dihydrotestosterone and 17-β-oestradiol, and in saliva of patient treated with dehydroepiandrosterone. Apoptosis of the epithelial cells led to cleavage and translocation of SS-autoantigens, α-fodrin and SS-A, into apoptotic particles. The apoptosis-induced apoptotic particles also contained another SS-autoantigen, hy1-RNA. These particles were internalized by pDCs in a size-dependent manner and affected TLR-7 and -9 expression and the production of proinflammatory cytokines. The analysed androgens protected cells from apoptosis, influenced redistribution of autoantigens and diminished the apoptotic particle-stimulated increase of the TLRs in pDCs. Our findings suggest that the formation of apoptotic particles may play a role in loss of immune tolerance, manifested by production of autoantibodies and the onset of autoinflammation in SS.

A case for IL-6, IL-17A, and nitric oxide in the pathophysiology of Sjögren's syndrome

Sjögren's syndrome (SS) is an autoimmune epithelitis characterized by mononuclear cell (MNC) infiltration of the lacrimal and salivary glands (SG), as well as the presence of serum autoantibodies. This condition is a growing public health concern in Algeria. Herein, we sought to determine if the levels of interleukin (IL)-6, IL-17A, and nitric oxide (NO), were correlated with the extent of MNC infiltration. The expression of inducible NO synthase (NOS2) and CD68 was measured in the SG of all patients, but not in those of the normal controls (NCs). We included 44 primary Sjögren's syndrome (pSS) patients and 15 NCs in this study; we found that the expression of NOS2 and CD68 was elevated in all of the SG of SS patients. Additionally, the serum and saliva levels of IL-6, IL-17A, and NO were higher in the pSS patients, compared with the NCs. Furthermore, the NOS2-induced excess NO was associated with the extent of the MNC infiltration, and thereby with tissue injury. It is also important to note that there were correlations between the levels of IL-6, IL-17A, and NO. Such findings indicate that through the effects of NO, IL-17A participates in the pathophysiology of the disease. With the purpose of improving both the diagnosis and prognosis, IL-6, IL-17A, and NO should be assayed in the serum and saliva of patients suspected of SS.

Hydrogen sulfide: a novel gaseous signaling molecule and intracellular Ca2+ regulator in rat parotid acinar cells

In addition to nitric oxide (NO), hydrogen sulfide (H2S) is recognized as a crucial gaseous messenger that exerts many biological actions in various tissues. An attempt was made to assess the roles and underlying mechanisms of both gases in isolated rat parotid acinar cells. Ductal cells and some acinar cells were found to express NO and H2S synthases. Cevimeline, a muscarinic receptor agonist upregulated endothelial NO synthase in parotid tissue. NO and H2S donors increased the intracellular Ca2+ concentration ([Ca2+]i). This was not affected by inhibitors of phospholipase C and inositol 1,4,5-trisphosphate receptors, but was decreased by blockers of ryanodine receptors (RyRs), soluble guanylyl cyclase, and protein kinase G. The H2S donor evoked NO production, which was decreased by blockade of NO synthases or phosphoinositide 3-kinase or by hypotaurine, an H2S scavenger. The H2S donor-induced [Ca2+]i increase was diminished by a NO scavenger or the NO synthases blocker. These results suggest that NO and H2S play important roles in regulating [Ca2+]i via soluble guanylyl cyclase-cGMP-protein kinase G-RyRs, but not via inositol 1,4,5-trisphosphate receptors. The effect of H2S may be partially through NO produced via phosphoinositide 3-kinase-Akt-endothelial NO synthase. It was concluded that both gases regulate [Ca2+]i in a synergistic way, mainly via RyRs in rat parotid acinar cells.

Production and physiological role of NO in the oral cavity

Nitric oxide (NO) is a free radical which is produced from a wide variety of cells and tissues in the human body. NO is involved in the regulation of many physiological processes, such as vascular relaxation, neurotransmission, immune regulation, and cell death. NO is generated by nitric oxide synthase (NOS), which has three identified isoforms: neuronal type NOS (nNOS), endothelial type NOS (eNOS), and inducible type NOS (iNOS). Different isoforms are expressed depending on the organs, tissues, and cells, and investigation of the types and functions of enzymes expressed in various tissues is underway. The oral cavity is a space in which marked changes have been detected in NO levels, and each tissue is constantly influenced by NO. NO is a component of saliva and is produced by oral bacteria in the oral cavity and released by NOS expressed in oral mucosa. NOS isoforms expressed under normal conditions differ among the oral organs. In addition, the overexpression of NOS was involved in carcinogenesis and tumor growth progression. This review summarized the expression of NOS and functions of NO in oral cavity organs, and their roles in diseases and the influences of treatments.

Macrophages: important players in primary Sjögren's syndrome?

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disorder characterized by immune-mediated destruction of the salivary and lacrimal glands with unknown etiology. Due to recent research utilizing human subjects as well as laboratory animal models, our understanding of the pathophysiological and immunological mechanisms of pSS has made great strides. As a consequence, targeted, immune-based therapies are gaining increased attention as the ideal way to conquer autoimmune diseases like pSS. Currently, however, there is no effective treatment to target specific immunological events or effector immune cells in the pathogenesis of pSS (discussed in other reviews of the current issue). Here, we summarize our current understanding and knowledge of the roles of monocytes/macrophages in the pathogenesis of pSS. Human studies, especially utilizing salivary gland biopsies, demonstrate the infiltration of macrophages and its correlation with disease severity. Moreover, animal model studies have shown the functional involvement of macrophages in promoting the ocular component of pSS.

[Assessment of endothelial function in autoimmune diseases]

Numerous autoimmune-inflammatory rheumatic diseases have been associated with accelerated atherosclerosis or other types of vasculopathy leading to an increase in cardiovascular disease incidence. In addition to traditional cardiovascular risk factors, endothelial dysfunction is an important early event in the pathogenesis of atherosclerosis, contributing to plaque initiation and progression. Endothelial dysfunction is characterized by a shift of the actions of the endothelium toward reduced vasodilation, a proinflammatory and a proadhesive state, and prothrombic properties. Therefore, assessment of endothelial dysfunction targets this vascular phenotype using several biological markers as indicators of endothelial dysfunction. Measurements of soluble adhesion molecules (ICAM-1, VCAM-1, E-selectin), pro-thrombotic factors (thrombomodulin, von Willebrand factor, plasminogen activator inhibitor-1) and inflammatory cytokines are most often performed. Regarding the functional assessment of the endothelium, the flow-mediated dilatation of conduit arteries is a non-invasive method widely used in pathophysiological and interventional studies. In this review, we will briefly review the most relevant information upon endothelial dysfunction mechanisms and explorations. We will summarize the similarities and differences in the biological and functional assessments of the endothelium in different autoimmune diseases.

Muscarinic receptor agonists and antagonists: effects on ocular function

Muscarinic agonists act mainly via muscarinic M₃ cholinoceptors to cause contraction of the iris sphincter, ciliary muscle and trabecular meshwork as well as increase outflow facility of aqueous humour. In the iris dilator, the effect of muscarinic agonists is species dependent but is predominantly relaxation via muscarinic M₃ receptors. In the conjunctiva, muscarinic agonists stimulate goblet cell secretion which contributes to the protective tear film. Muscarinic M₂ and M₃ receptors appear mainly involved. In the lens muscarinic agonists act via muscarinic M₁ receptors to produce depolarization and increase [Ca(2+)](i). All five subtypes of muscarinic receptor are present in the retina. In the developing retina, acetylcholine appears to limit purinergic stimulation of retinal development and decrease cell proliferation. In the adult retina acetylcholine and other muscarinic agonists may have complex effects, for example, enhancing light-evoked neuronal firing in transient ON retinal ganglion cells and inhibiting firing in OFF retinal ganglion cells. In the lacrimal gland, muscarinic agonists activate M₃ receptors on secretory globular acinar cells to stimulate tear secretion and also cause contraction of myoepithelial cells. In Sjögren's syndrome, antibodies to the muscarinic M₃ receptor disrupt normal gland function leading to xerophthalmia although the mechanism of action of the antibody is still not clear. Atropine and pirenzepine are useful in limiting the development of myopia in children probably by an action on muscarinic receptors in the sclera, although many other muscarinic receptor antagonists are not effective.

Salivary 8-OHdG Induction by Physical Exercise Training Under Food Restriction

Objective:

We previously reported that physical exercise under food restriction induced alterations in saliva secretion, including a decrease in salivary kallikrein activity, while exercise training alone did not affect the overall saliva content. The objective of the present study was to examine the involvement of oxidative stress in alterations of salivary secretion due to physical exercise under food restriction.

Methods:

Male ICR mice at 32 weeks of age weighing from 39 to 50 g were divided into three groups: an exercise group with food restriction (EXP), an exercise group without food restriction (EXA) and a control group (CTL). The EXP group was fed the same amount of diet as the CTL group (pair-feeding). The EXP and EXA groups had access to a “voluntary running wheel” for exercise. The pilocarpine-stimulated whole saliva was collected from the oral cavity by micro-pipette over 15 min for 12 weeks after the beginning of the experiment. The salivary and serum 8-Hydroxy-2’-deoxyguanosine (8-OHdG) were determined.

Results:

The salivary 8-OHdG levels in the EXP group were significantly higher than in the CTL and EXA groups (p<0.01).

Conclusion:

The alterations of salivary secretion in mice undergoing chronic exercise training under a food-restricted diet may occur as a result of oxidative stress.

Reduced methacholine-induced submandibular salivary secretion in rats with experimental periodontitis

OBJECTIVE

Saliva is the first barrier to the entry of bacteria and viruses into the body and is considered a necessary instrument in oral health. Intraperitoneal injection of lipopolysaccharide endotoxins results in submandibular gland (SMG) hyposalivation. The objective of present studies was to assess if periodontitis, a chronic inflammatory disease caused by oral bacteria, alters cholinergic-induced SMG salivary secretion.

DESIGN

An experimental periodontitis model (EP) (cotton thread ligature around the neck of the first lower molars) was used. Male Wistar rats (300-380g) were randomly divided into 3 groups: control, 7 days-bilateral EP and 7 days-unilateral EP (to study if there were different effects at the ipsilateral and contralateral side). The following determinations were performed in SMG: (1) dose-response curves to the cholinergic agonist methacholine, (2) prostaglandin E (PGE) content, (3) inducible nitric oxide synthase (iNOS) activity and (4) histology of gland sections.

RESULTS

The molars with EP, no matter the group, exhibited significant and similar bone loss (p<0.001). Bilateral EP reduced methacholine-induced salivary secretion (p<0.05, dose 1μg/kg; p<0.001, dose 3-30μg/kg), increased PGE content (p<0.01), stimulated iNOS activity (p<0.05). Ipsilateral glands of unilateral EP animals presented lower methacholine-induced salivary secretion (p<0.05, dose 3μg/kg; p<0.001, dose 10-30μg/kg), and higher PGE content than contralaterals (p<0.001). In turn, at 3 and 10μg/kg of methacholine, contralateral glands showed significantly lower secretion than control animals (p<0.001). Histological studies of glands revealed partial loss of secretor granular material and periductal oedema in the bilateral and unilateral EP groups as compared to controls.

CONCLUSIONS

As far as we know, the present results demonstrate for the first time that EP reduces methacholine-induced SMG salivary secretion.

Altered Salivary Redox Homeostasis in Patients with Systemic Sclerosis

Objective.

Oxidative stress has been implicated in the pathogenesis of systemic sclerosis (SSc). Our objective was to determine whether SSc is associated with altered redox homeostasis in human saliva.

Methods.

Study participants were 70 women with SSc and 120 female controls. 8-hydroxy-2’-deoxyguanosine (8-OHdG), 8-epi-prostaglandin F 2α (8-epi-PGF2α), and total protein carbonyls were assayed by ELISA to quantify oxidative damage to nucleic acids, lipids, and proteins, respectively, in whole nonstimulated saliva.

Results.

We observed a significantly positive association between salivary log protein carbonyls and SSc in a crude statistic (OR 9.06, p < 0.0001), and multivariable model adjusted for log 8-OHdG, log 8-epi-PGF2α, and antioxidant exposure (OR 9.26, p < 0.0001). No significant association was noted between SSc and salivary log 8-epi-PGF2α or log 8-OHdG.

Conclusion.

Salivary redox homeostasis is perturbed in patients with SSc and may inform on the pathophysiology and presence of the disease (biomarkers) and efficacy of therapeutic interventions.

Inducible nitric oxide synthase increases secretion from inflamed salivary glands

Objective. Salivary gland secretion is dependent on cholinergic stimulation via autonomic nerves and calcium signalling in acinar cells. Secretory dysfunction associated with SS may be partly caused by the damaging effects of increased glandular concentrations of nitric oxide (NO) derived from up-regulation of inducible NO synthase (iNOS) that accompanies glandular inflammation. The present study examines the effects of increased iNOS expression on salivary gland secretory function.

Methods. The inflammogen lipopolysaccharide (LPS) was introduced intraductally into rat submandibular glands, and glandular responsiveness to cholinergic stimulation was determined.

Results. LPS provoked a rapid, long-lasting inflammation, increasing gland weight (by almost 20%) and inflammatory cell infiltration at 3 and 24 h. Immunoblotting of glandular homogenates indicated that iNOS expression was increased ∼4-fold, and immunohistochemistry of frozen tissue sections showed increased iNOS expression in acinar cells. Salivary secretion from inflamed glands was significantly increased in response to low doses of methacholine and accompanied by increased acinar cell calcium signalling in vitro. Prior administration of the iNOS inhibitors, aminoguanidine or l-NIL [l-N6-(1-iminoethyl)-lysine dihydrochloride] abolished increased secretion and acinar cell calcium signalling.

Conclusions. Up-regulation of glandular iNOS expression can increase cholinergically evoked salivary secretion and appears to offset any secretory hypofunction linked with glandular inflammation. It seems unlikely that increased glandular levels of NO are responsible for the secretory hypofunction that accompanies SS.

A role for nitric oxide-mediated glandular hypofunction in a non-apoptotic model for Sjogren's syndrome

OBJECTIVE

To investigate a role for the inflammatory mediator, nitric oxide (NO) in SS, an autoimmune condition characterized by salivary and lacrimal gland hypofunction resulting from failure of acinar cells to secrete.

METHODS

FURA-2 microfluorimetry was used to measure agonist-evoked changes of [Ca(2+)](i) in isolated mouse and human salivary acinar cells following exposure to NO donors.

RESULTS

NO had a biphasic effect on salivary acinar function. Acute exposure to NO (2 min) caused a cyclic guanosine monophosphate (GMP)-dependent, 1-H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-sensitive increase in the Ca(2+) signal elicited in response to acetylcholine (ACh) stimulation, consistent with stimulation of ryanodine receptors by cyclic adenosine diphosphate ribose. Prolonged exposure to NO (>40 min) significantly reduced the ACh-evoked Ca(2+) signal by a mechanism independent of cyclic GMP. We found no differences between the responses of human and mouse acinar cells.

CONCLUSION

Our data show that chronic exposure to NO, which is known to be elevated in SS, could have a role in salivary gland hypofunction. We note a similarity in the response to stimulation of salivary acinar exposed to NO and that which we have previously reported in salivary acinar cells isolated from patients with SS. We speculate that NO-mediated nitrosylation of one or more elements of the signal transduction pathway could underlie down-regulation of salivary function in SS.

Different role of isoproterenol and NOS inhibitors on salivary ducts of rats

OBJECTIVES

Nitric oxide (NO) is a diffusible intracellular messenger that is present in saliva. Chronic treatment with isoproterenol, a beta receptor agonist, stimulates the release of NO from acinar cells and induces salivary gland hypertrophy. The aim of this study was to investigate the effect of NO synthesis inhibitors and isoproterenol on rat salivary glands. We analyzed salivary gland weight and the number of ducts per unit area (0.5mm(2)) by NADPH-diaphorase histochemistry (to identify the presence of the enzyme NO synthase-NOS) and haematoxylin-and-eosin (HE).

METHODS

For 8 days male Wistar rats received daily single intraperitoneal injections of saline or a NOS inhibitor (40mg/kg N(omega)-nitro-L-arginine L-NOARG or N(omega)-nitro-l-arginine methyl ester L-NAME). This was followed, 30min later, by subcutaneous injection of isoproterenol (2 or 5mg/kg) or saline.

RESULTS

Isoproterenol increased parotid and submandibular gland weights. Isoproterenol (2mg/kg) induced a decrease of ducts per unit area inversely correlated to the weight of the parotid gland. This effect was augmented by L-NAME. In the submandibular gland L-NAME attenuated isoproterenol (2mg/kg) weight increase. In the submandibular gland isoproterenol and NOS inhibitors induced an increase in ducts per unit area (HE and NADPH-diaphorase). No effect was observed in the sublingual gland.

CONCLUSION

To our knowledge this is the first description of isoproterenol and NOS inhibitors increasing duct density in the submandibular gland. Our results corroborate the hypothesis that NO plays different roles in parotid and submandibular glands.

The influence of estrogen and progesterone on parasympathetic vasodilatation in the rat submandibular gland

Previous studies suggest that NO- and PGI(2)-independent pathways play a greater role in parasympathetic vasodilatation in the submandibular glands (SMG) of female than of male rats. Thus, the purpose of this study was to determine whether estrogen and progesterone influence the relative contributions of NO and PGI(2) to parasympathetic vasodilatation in the SMG. Vascular responses to chorda-lingual nerve stimulation were examined in sham-operated (SHAM) and ovariectomized (OVX) female rats and in OVX rats treated with either 17beta-estradiol alone or a combination of 17beta-estradiol and progesterone. Compared with SHAM animals, increases in vascular conductance in OVX rats were reduced at 1, 2 and 5 Hz (p<0.05). Blood flow responses in OVX+17beta-estradiol and OVX+17beta-estradiol+progesterone rats were indistinguishable from those observed in SHAM animals. Indomethacin had no effect on vasodilatation in SHAM and OVX+17beta-estradiol rats, but increased vascular responses in OVX animals (p<0.02). The addition of L-NAME resulted in a significant reduction in vasodilatation at all frequencies. In OVX rats treated with both estrogen and progesterone, indomethacin caused a reduction in vasodilatation and L-NAME further diminished the remaining responses. Under all conditions, vasodilatation was due largely, if not exclusively, to direct parasympathetic rather than antidromic sensory nerve activation. Finally, both neuronally-derived and endothelium-derived NO appeared to be responsible for the NO-dependent vasodilatation, but endothelium-derived NO became increasingly important as the frequency of stimulation increased. We conclude that estrogen and progesterone influence parasympathetic vasodilatation through combined effects on NO-, PGI(2)- and non-NO/PGI(2)-mediated pathways.

Increased levels of urinary nitrite and nitrotyrosine in Yusho victims 40 years after accidental poisoning with polychlorinated biphenyls in Nagasaki, Japan

Forty years have passed since the accidental poisoning with polychlorinated biphenyls (PCB) in Japan in 1968, named Yusho. High concentrations of PCB are still detected in the serum of the Yusho victims. PCB produces superoxide (O(2) (-)) in the metabolic process and we reported high concentrations of serum nitrite, a stable metabolite reflecting nitric oxide (NO), in the Yusho victims. NO reacts with O(2) (-) and immediately produces peroxynitrite (ONOO(-)). ONOO(-) causes nitration of tyrosine residues and produces nitrotyrosine (NT). Therefore, we measured urinary concentrations of nitrite and NT in the victims and age-matched controls. The mean urinary concentrations of nitrite and NT were significantly higher than in the controls. There was a positive correlation between urinary nitrite and NT in the Yusho victims. Furthermore, there was a positive correlation between the ratio of urinary NT to nitrite and serum PCB concentrations in the Yusho victims. It was considered that the emergence of some ailments could be presumed to have been caused by high levels of urinary nitrite and NT in the Yusho victims.

Increased serum levels of macrophage migration inhibitory factor in patients with primary Sjögren's syndrome

The objective of this study was to analyse levels of the proinflammatory cytokine macrophage migration inhibitory factor (MIF) in patients with primary Sjögren's syndrome (pSS) and to examine associations of MIF with clinical, serological and immunological variables. MIF was determined by ELISA in the sera of 76 patients with pSS. Further relevant cytokines (IL-1, IL-6, IL-10, IFN-γ and TNF-α) secreted by peripheral blood mononuclear cells (PBMC) were determined by ELISPOT assay. Lymphocytes and monocytes were examined flow-cytometrically for the expression of activation markers. Results were correlated with clinical and laboratory findings as well as with the HLA-DR genotype. Healthy age- and sex-matched volunteers served as controls. We found that MIF was increased in patients with pSS compared with healthy controls (p < 0.01). In particular, increased levels of MIF were associated with hypergammaglobulinemia. Further, we found a negative correlation of MIF levels with the number of IL-10-secreting PBMC in pSS patients (r = -0.389, p < 0.01). Our data indicate that MIF might participate in the pathogenesis of primary Sjögren's syndrome. MIF may contribute to B-cell hyperactivity indicated by hypergammaglobulinemia. The inverse relationship of IL-10 and MIF suggests that IL-10 works as an antagonist of MIF in pSS.

Low salivary dehydroepiandrosterone and androgen-regulated cysteine-rich secretory protein 3 levels in Sjögren's syndrome

OBJECTIVE

Sjögren's syndrome (SS), an autoimmune disease of exocrine glands, typically starts at the time of adrenopause. We undertook this study to test the hypothesis that SS is characterized by an insufficient androgen effect at the target tissue level.

METHODS

We searched for androgen response elements (AREs) in the cysteine-rich secretory protein 3 (crisp-3) gene. Dehydroepiandrosterone (DHEA) responsiveness was experimentally studied using quantitative reverse transcriptase-polymerase chain reaction and immunofluorescence staining of human submandibular gland-derived acinar cells and labial salivary gland explants with or without DHEA. Finally, glandular and salivary CRISP-3 in healthy controls and SS patients was analyzed using immunohistochemistry, in situ hybridization, and enzyme-linked immunosorbent assay. Serum DHEA sulfate (DHEAS) and salivary DHEA levels were measured using a radioimmunometric method.

RESULTS

Literature analysis and a search for AREs in gene banks suggested androgen dependency of human CRISP-3, and this was verified by studies of human submandibular gland acinar cells cultured with or without DHEA, in which DHEA increased CRISP-3 messenger RNA (mRNA) levels (P = 0.018). This finding was confirmed by the results of DHEA stimulation of labial salivary gland explants. Glandular CRISP-3 mRNA and protein labeling was weak and diffuse, coupled with low secretion in saliva (mean +/- SEM 21.1 +/- 2.7 mug CRISP-3/15 minutes in SS patients versus 97.6 +/- 12.0 mug CRISP-3/15 minutes in healthy controls; P < 0.0001). Compared with healthy controls, SS patients had low serum levels of DHEAS (P = 0.008) and also low salivary levels of DHEA (mean +/- SEM 224 +/- 33 pmoles versus 419 +/- 98 pmoles; P = 0.005).

CONCLUSION

CRISP-3 pathology was seen in acini remote from lymphocyte foci and is apparently not secondary to local inflammation, but may represent some systemic effect in SS. Indeed, androgen deprivation in the salivary glands of SS patients is evidenced both by low salivary levels of DHEA and by low levels of DHEA-regulated CRISP-3. This may explain some of the characteristic features of SS.

Pathophysiology of Sjögren's syndrome

The term Sjögren's syndrome refers to keratoconjunctivitis sicca and xerostomia due to lymphocytic infiltrates of lachrymal and salivary glands. The current used criteria for diagnosis of primary Sjögren's syndrome is the American-European consensus. Primary Sjögren's syndrome is an autoimmune disorder characterized by lymphocytic infiltrates and destruction of the salivary and lachrymal glands and systemic production of autoantibodies to the ribonucleoprotein particles SS-A/Ro and SS-B/La. The infiltrating cells (T- and B-cells, dendritic cells) interfere with glandular function at several points: destruction of glandular elements by cell-mediated mechanisms; secretion of cytokines that activate pathways bearing the signature of type 1 and 2 interferons; production of autoantibodies that interfere with muscarinic receptors; and secretion of metalloproteinases (MMPs) that interfere with the interaction of the glandular cell with its extracellular matrix, which is necessary for efficient glandular function. As the process progresses, the mucosal surfaces become sites of chronic inflammation and the start of a vicious circle. Despite extensive study of the underlying cause of Sjögren's syndrome, the pathogenesis remains obscure. In broad terms, pathogenesis is multifactorial; environmental factors are thought to trigger inflammation in individuals with a genetic predisposition to the disorder.

Activation of MKK4 (SEK1), JNK, and c-Jun in labial salivary infiltrating T cells in patients with Sjögren's syndrome

We wanted to determine via immunohistochemistry, whether or not c-Jun NH2-terminal kinase (JNK) cascade is activated in labial salivary infiltrating T cells in patients with Sjögren's syndrome (SS). Six patients with primary SS were selected for this study. Phosphorylation of mitogen-activated protein kinase (MAPK) kinase 4 (MKK4) (SEK1), JNK, and c-Jun in salivary infiltrating T cells was studied using immunohistochemistry assay, including mirror section technique. Phosphorylated forms of MKK4, JNK, and c-Jun were detected in salivary infiltrating mononuclear cells. Expression of phosphorylated JNK was found in both CD4+ T cells and CD8+ T cells. Moreover, co-expression of phosphorylated JNK and c-Jun was demonstrated in the mirror sections. The results of this study suggest that the JNK cascade is activated in salivary infiltrating CD4+ T cells and CD8+ T cells in SS patients, which appears to contribute to the inflammatory salivary microenvironment of SS.

A multifaceted molecule, nitric oxide in oral and periodontal diseases

Nitric oxide (NO) is a molecule with multiple effects on different tissues. NO takes important roles in vasodilatation, bacterial challenge and cytokine stimulation, regulation of mineralized tissue function, neurotransmission, and platelet aggregation, etc. However, under pathological conditions, NO has damaging effects. NO is synthesized by NO synthases (NOS) and inducible isoform of NOS (iNOS) is closely related to the pathophysiological characteristics of inflammatory diseases such as periodontal diseases. The expression of iNOS has been investigated in salivary gland-related diseases, temporomandibular joint disorders and oral cancer as well. The beneficial and damaging effects of NO in diseases related with periodontal, dental and maxillofacial area are discussed in this review. The biological pathways involved with NO and NO inhibitors may be good drug targets to have a role in the future management of patients with diseases in orofacial region.

Significantly reduced salivary nitric oxide synthesis in patients with Parkinson's disease

In order to study concentration of nitric oxide (NO) in the saliva of patients with Parkinson's disease (PD), we measured the concentration of its stable metabolite nitrite (NO(2)-) in the saliva of these patients and healthy subjects. We analyzed saliva flow rate and salivary NO concentrations in 16 subjects with Parkinson's disease and in 16 healthy subjects. Concentration of nitrite was determined by colorimetric method using Griess reaction. Saliva flow rate was significantly lower in patients with Parkinson's disease (0.2+/-0.03 mL/min; X+/-SEM) than in healthy subjects. Salivary NO(2)-concentration was significantly lower (5.02+/-0.64) than in healthy individuals (22.39+/-1.24, p<0.0001).

Nitric oxide levels are not changed in saliva of patients infected with hepatitis C virus

The aim of this investigation was to determine nitric oxide metabolite levels in saliva samples from hepatitis C virus-positive patients in an attempt to test the hypothesis if increased levels of nitric oxide metabolites correlates with the presence of HCV-RNA in saliva. Saliva of 39 HCV-positive patients and 13 HCV-negative patients, without clinical or laboratorial evidence of liver disease were tested for nitric oxide metabolites. HCV-RNA was detected in serum and saliva by a RT-PCR method and nitric oxide level was determined by evaluation of its stable degradation products, nitrate and nitrite. No differences were found between the concentration of nitrite in saliva from HCV patients and controls, in despite of the presence or not of HCV RNA in saliva. Patients with HCV and cirrhosis had higher concentrations of nitrite but not significantly different from the control group or the groups of anti-HCV patients without cirrhosis. Increased levels of nitrite were not detected in anti-HCV positive patients, an indirect indication that chronic sialoadenitis are infrequent in these patients or occurs with low intensity not sufficient to increase nitric oxide metabolite levels in saliva.

Nitric oxide synthase in human salivary glands

The distribution of the three nitric oxide synthase (NOS) isoforms was determined immunohistochemically in the human minor and major salivary glands with comparison to that of rat salivary glands. In contrast to rat glands, which contained a dense plexus of neuronal NOS-immunoreactive nerve fibers, only a minority of the nerve fibers in human glands showed neuronal NOS immunoreactivity. Human labial and submandibular glands contained sparse NOS-immunoreactive fibers, while only occasional nerve fibers in the parotid or sublingual glands were stained. Furthermore, in contrast to the animal glands, most duct epithelial cells in all human salivary glands were immunoreactive for neuronal NOS. No specific immunoreactivity for inducible or endothelial NOS were observed in the nerve fibers or duct epithelium. We provide evidence to suggest that the role of nitric oxide in the regulation of salivary gland function is different in human as compared to experimental animals. Nitricergic innervation in human tissue is very sparse and thus nitric oxide is probably of minor importance as a neural regulator of salivary glands. Instead, NOS localized in duct epithelial cells suggests that nitric oxide might directly regulate saliva secretion and it is a putative source of nitrates previously reportedly secreted into the saliva.

c-Jun NH2-terminal kinase mediates interleukin-1beta-induced inhibition of lacrimal gland secretion

Sjögren's syndrome, an inflammatory disease affecting the lacrimal and salivary glands, is the leading cause of aqueous tear-deficient type of dry eye. We previously showed that interleukin-1beta (IL-1beta) protein is up regulated in the lacrimal gland of a murine model of Sjögren's syndrome and that exogenous addition of this cytokine inhibits neurotransmitter release and lacrimal gland protein secretion. In the present study we investigated the role of c-Jun NH2-terminal kinase (JNK) in IL-1beta-mediated inhibition of lacrimal gland secretion and tear production. In vitro, IL-1beta induced a time-dependent activation of JNK with a maximum 7.5-fold at 30 min. SP600125, a JNK inhibitor, inhibited, in a concentration-dependent manner, IL-1beta-induced activation of JNK with a maximum of 87% at 10(-4) m. In vivo, IL-1beta stimulated JNK and the expression of the inducible isoform of nitric oxide synthase (iNOS). IL-1beta inhibited high KCl and adrenergic agonist induced protein secretion by 85% and 66%, respectively. SP600125 alleviated the inhibitory effect of IL-1beta on KCl- and agonist-induced protein secretion by 79% and 47%, respectively, and completely blocked the expression of iNOS. Treatment for 7 days with SP600125 increased tear production in a murine model of Sjögren's syndrome dry eye. We conclude that JNK plays a pivotal role in IL-1beta-mediated inhibition of lacrimal gland secretion and subsequent dry eye.

Lack of nitric oxide-mediated regulation of amylase secretion stimulated by VIP in parotid glands of NOD mice

The non-obese diabetic (NOD) mouse is chosen among other experimental models to study autoimmune sialadenitis resembling Sjögren's syndrome (SS), because of its unique characteristic of developing salivary dysfunction. Based on the deep loss of nitric oxide synthase (NOS) activity in parotid glands of NOD mice observed from early stages of disease and the inhibitory effect of nitric oxide (NO) donors on amylase secretion in normal salivary glands, our goal was to investigate whether parotid glands from NOD mice lacking NOS activity presented this regulatory mechanism of amylase secretion. We found that parotid glands from NOD mice lack nitric oxide-mediated regulation of amylase secretion in response to VIP stimulation. The lack of regulation might be assigned to the loss of NOS activity as derived from the results with NOS inhibitors and increasing concentrations of VIP. These functional differences observed in NOD vs. BALB/c parotid glands occur in the absence of immune infiltrates in exocrine tissue, and it is not related to cAMP accumulation. NO-mediated regulation of amylase secretion was not observed in BALB/c submandibular glands to the same extent as described in parotid glands and was absent in submandibular glands of NOD mice.

Oral findings in coeliac disease and Sjögren's syndrome

OBJECTIVE

Both coeliac disease (CD) and Sjogren's syndrome (SS) have an autoimmune background and increased risk of oral mucosal and dental abnormalities. Individuals suffering concomitantly from CD and SS could even be at a higher risk.

STUDY DESIGN

Oral mucosal and dental abnormalities were examined in 20 patients with CD + SS (mean age 61 years) and compared with age- and sex-matched controls with either CD or SS.

RESULTS

Oral mucosal changes were most common in SS (80%), followed by CD + SS (65%) and CD (40%). Coeliac-type dental enamel defects were found in 89% in CD + SS and in 88% in CD compared with only 25% in SS (P < 0.001). The median number of teeth was six in the CD + SS, 24 in the CD and 22 in the SS group. The DMF index was higher (P < 0.005) in the CD + SS than in the CD group. CD + SS was characterized by higher salivary flow rate (P < 0.001) and lower inflammatory focus score in the salivary glands (P < 0.01) than SS.

CONCLUSIONS

The co-occurrence of CD and SS should be recognized because of its effects on dental and oral mucosal health. A lower salivary gland inflammatory focus score and higher salivary flow rate in CD + SS than in SS suggests that a gluten-free diet treatment may alleviate autoimmune inflammation.

The protein kinase C system in focal adenitis of the lacrimal gland in the non-obese diabetic mouse model for Sjögren's syndrome

PURPOSE

Non-obese diabetic (NOD) mice develop an autoimmune exocrinopathy characterized by hyposecretion of saliva and acinar cell atrophy. As the protein kinase C (PKC) system is involved in the signal transduction pathways associated with primary secretion and acinar cell differentiation and growth, the PKC profile was analysed in NOD mice.

METHODS

Lacrimal glands from BALB/c, NOD, NOD scid and transgenic NOD x interferon-gamma (IFN-gamma) mice were analysed for their PKC profiles using antibodies against several conventional (alpha, beta, gamma), novel (delta, epsilon, theta) and atypical (iota, lambda) PKC isoforms using the Streptavidin/HRP (horseradish peroxidase) method.

RESULTS

Acinar cells in BALB/c control mice expressed two conventional (alpha, beta) and two atypical (iota, lambda) PKC isoforms. In NOD and transgenic NOD x IFN-gamma mice the same isoforms were more strongly expressed. NOD scid mice lacked all other PKC isoforms except PKC lambda.

CONCLUSIONS

Co-expression of several PKC isoforms in single cell type may be necessary for transcriptional activation and agonist-induced secretory responses. Hyposecretion in NOD mice was paradoxically associated with up-regulation of the PKC system. This may be associated with a deranged signal transduction per se rather than with the immune-inflammation, as the transgenic NOD x IFN-gamma mice showed similar PKC profiles. The NOD model does not reproduce lack/consumption of PKC II and PKC as in Sjögren's syndrome. This may be because the receptor autoantibodies in mice are directed against the adrenergic, not muscarinic, receptors. Lack and/or low level PKC expression in NOD scid mouse may explain the excessive acinar cell apoptosis in this model.

Inhibition of calcium-calmodulin kinase restores nitric oxide production and signaling in submandibular glands of a mouse model of salivary dysfunction

Nitric oxide is an intracellular and diffusible messenger of neurotransmitters involved in salivary secretion, as well as an inflammatory mediator in salivary gland diseases. It is synthesized by three different isoforms of nitric oxide synthase (NOS), each subject to a fine transcriptional, post-transcriptional and/or post-translational regulation. Our purpose was to study the possible mechanisms leading to NOS downregulation in submandibular glands of normal mice and in the nonobese diabetic (NOD) mouse model of salivary dysfunction with lower NOS activity. NOS activity and cGMP accumulation were determined by radioassays in submandibular glands of both mice in the presence of the protein kinase inhibitors KN-93 and bisindolylmaleimide. NOS I mRNA and protein expression and localization were assessed by RT-PCR, Western blot and immunohistochemistry. A downregulatory effect of calcium-calmodulin kinase II (CaMK II) on NOS activity in submandibular glands of both NOD and BALB/c mice was observed. Our results are consistent with a physiological regulation of NOS activity by this kinase but not by PKC in normal BALB/c mice. They are also supportive of a role for CaMK II in the lack of detectable NOS activity in submandibular glands of NOD mice. KN-93 also restored cGMP accumulation in NOD submandibular glands. The downregulation of NOS in NOD mice seems to be mainly mediated by this kinase rather than the result of a lower expression or different cellular localization of the enzyme. It was not related to different substrate or cofactors availability either.

Nitrite-mediated protection against hypochlorous acid-induced chondrocyte toxicity: a novel cytoprotective role of nitric oxide in the inflamed joint?

OBJECTIVE

To examine the potential consequences of overproduction of nitric oxide (NO) and nitrite (NO(2) (-)) in the inflamed rheumatoid joint.

METHODS

Human articular chondrocytes in culture were exposed to HOCl (hypochlorous acid, a physiologic oxidant formed in increased amounts at sites of chronic inflammation), and assays of cell viability, intracellular ATP and glutathione (GSH), and lactate dehydrogenase (LDH) were performed. HOCl-induced lipid peroxidation and activation of the MAP kinases ERK-1/2, JNK-1/2, and p38 were also measured. The modulatory effects of NO-derived nitrite (NO(2) (-)) and nitrate (NO(3) (-)) on HOCl-mediated chondrocyte toxicity were investigated.

RESULTS

Exposure of human articular chondrocytes to HOCl resulted in a concentration- and time-dependent loss of viability, decrease in ATP and GSH levels, LDH leakage, and cell death. HOCl induced significant lipid peroxidation as well as activation of the MAP kinases ERK-1/2 and p38 but not JNK-1/2. However, the presence of NO(2) (-) but not NO(3) (-) substantially decreased HOCl-dependent cellular toxicity even when NO(2) (-) was added at low (microM) concentrations. In sharp contrast, NO(2) (-) (1 mM) did not inhibit superoxide-, hydroxyl radical-, H(2)O(2)-, or peroxynitrite-mediated cytotoxicity. Furthermore, culture media from cells treated with interleukin-1beta (to generate NO and NO(2) (-)) offered significantly more protection against HOCl-mediated cytotoxicity than culture media from untreated cells.

CONCLUSION

These data suggest that NO(2) (-) accumulation at chronically inflamed sites where both HOCl and NO are overproduced may be cytoprotective against damage induced by HOCl. Accumulation of NO(2) (-) could represent a novel cytoprotective role of NO in inflamed joints. A mechanism for this is suggested.