Parasympathetic nervous system dysfunction in primary Sjögren's syndrome

Rab27a Contributes to Cathepsin S Secretion in Lacrimal Gland Acinar Cells

Altered lacrimal gland (LG) secretion is a feature of autoimmune dacryoadenitis in Sjögren's syndrome (SS). Cathepsin S (CTSS) is increased in tears of SS patients, which may contribute to disease. Rab3D and Rab27a/b isoforms are effectors of exocytosis in LG, but Rab27a is poorly studied. To investigate whether Rab27a mediates CTSS secretion, we utilized quantitative confocal fluorescence microscopy of LG from SS-model male NOD and control male BALB/c mice, showing that Rab27a-enriched vesicles containing CTSS were increased in NOD mouse LG. Live-cell imaging of cultured lacrimal gland acinar cells (LGAC) transduced with adenovirus encoding wild-type (WT) mCFP-Rab27a revealed carbachol-stimulated fusion and depletion of mCFP-Rab27a-enriched vesicles. LGAC transduced with dominant-negative (DN) mCFP-Rab27a exhibited significantly reduced carbachol-stimulated CTSS secretion by 0.5-fold and β-hexosaminidase by 0.3-fold, relative to stimulated LGAC transduced with WT mCFP-Rab27a. Colocalization of Rab27a and endolysosomal markers (Rab7, Lamp2) with the apical membrane was increased in both stimulated BALB/c and NOD mouse LG, but the extent of colocalization was much greater in NOD mouse LG. Following stimulation, Rab27a colocalization with endolysosomal membranes was decreased. In conclusion, Rab27a participates in CTSS secretion in LGAC though the major regulated pathway, and through a novel endolysosomal pathway that is increased in SS.

Proton pump inhibitors act with unprecedented potencies as inhibitors of the acetylcholine biosynthesizing enzyme-A plausible missing link for their association with incidence of dementia

INTRODUCTION

Several pharmacoepidemiological studies indicate that proton pump inhibitors (PPIs) significantly increase the risk of dementia. Yet, the underlying mechanism is not known. Here, we report the discovery of an unprecedented mode of action of PPIs that explains how PPIs may increase the risk of dementia.

METHODS

Advanced in silico docking analyses and detailed enzymological assessments were performed on PPIs against the core-cholinergic enzyme, choline-acetyltransferase (ChAT), responsible for biosynthesis of acetylcholine (ACh).

RESULTS

This report shows compelling evidence that PPIs act as inhibitors of ChAT, with high selectivity and unprecedented potencies that lie far below their in vivo plasma and brain concentrations.

DISCUSSION

Given that accumulating evidence points at cholinergic dysfunction as a driving force of major dementia disorders, our findings mechanistically explain how prolonged use of PPIs may increase incidence of dementia. This call for restrictions for prolonged use of PPIs in elderly, and in patients with dementia or amyotrophic lateral sclerosis.

Peripheral nervous system manifestations of Sjögren syndrome: clinical patterns, diagnostic paradigms, etiopathogenesis, and therapeutic strategies

Sjögren syndrome is among the most common autoimmune diseases affecting adults in the United States, and is frequently regarded as an immune-mediated exocrinopathy exclusively causing dry eyes and dry mouth. However, as a systemic rheumatic disease, there can be various "extraglandular" complications. The eclectic permutation of peripheral nervous system (PNS) syndromes which occur in Sjögren patients are among the most common and severe extraglandular complications. This review article highlights the evaluation, differential diagnosis, immunopathogenic mechanisms, and potential treatment options of these PNS complications encountered by neurologists. The sensory neuropathies constitute the most frequent PNS complication. Sjögren patients can suffer from severe neuropathic pain, with small-fiber neuropathy causing lancinating or burning pain which can disproportionately affect the proximal torso or extremities, and the face (ie, in a "non-length-dependent distribution"). The technique of skin biopsy, assessing for the intraepidermal nerve fiber density of unmyelinated nerves, provides a useful technique for neurologists to diagnose small-fiber neuropathies, especially when there is such a non-length-dependent distribution. Other diagnostic techniques (ie, electromyography/nerve-conduction studies, evoked potentials, nerve and muscle biopsy) may be useful in specific subtypes of neuropathies. A rational approach to treatment requires a careful appraisal of the clinical subtype of the neuropathy, as well as a familiarity with such discriminating immunopathogenic mechanisms. The application of the traditional armamentarium used for neuropathic pain can be especially challenging. Sjögren patients can suffer from debilitating fatigue, sicca symptoms, and autonomic findings; as such manifestations can be complications of various neuropathic agents, neurologists should understand how to minimize such iatrogenic complications. Therefore, this article will empower neurologists to more effectively collaborate with rheumatologists, in the diagnosis and treatment of Sjögren patients with PNS complications.

Neural regulation of lacrimal gland secretory processes: relevance in dry eye diseases

The lacrimal gland is the major contributor to the aqueous layer of the tear film which consists of water, electrolytes and proteins. The amount and composition of this layer is critical for the health, maintenance, and protection of the cells of the cornea and conjunctiva (the ocular surface). Small changes in the concentration of tear electrolytes have been correlated with dry eye syndrome. While the mechanisms of secretion of water, electrolytes and proteins from the lacrimal gland differ, all three are under tight neural control. This allows for a rapid response to meet the needs of the cells of the ocular surface in response to environmental conditions. The neural response consists of the activation of the afferent sensory nerves in the cornea and conjunctiva to stimulate efferent parasympathetic and sympathetic nerves that innervate the lacrimal gland. Neurotransmitters are released from the stimulated parasympathetic and sympathetic nerves that cause secretion of water, electrolytes, and proteins from the lacrimal gland and onto the ocular surface. This review focuses on the neural regulation of lacrimal gland secretion under normal and dry eye conditions.

Dysfunctional neural regulation of lacrimal gland secretion and its role in the pathogenesis of dry eye syndromes

Tears are a complex fluid consisting of three layers, each of which is secreted by a different set of tissues or glands. The aqueous portion of the tear film is produced predominantly by the lacrimal gland. Dry eye syndromes are diseases in which the amount and composition of tears are altered, which can lead to ocular surface damage. There are many causes for dry eye syndromes. One such cause is the alteration in the functions of nerves innervating the lacrimal gland and the ocular surface. The autoimmune disease Sjogren syndrome can deleteriously affect the innervation of the lacrimal gland. Damage to the sensory nerves in the ocular surface, specifically the cornea, as a result of refractive surgery and normal aging, prevents the normal reflex arc to the lacrimal gland. Both defects can result in decreased tear secretion and dry eye syndromes. This review will discuss the current information regarding neurally-stimulated protein, water, and electrolyte secretion from the lacrimal gland and delineate how nerve dysfunction resulting from a variety of causes decreases secretion from this gland.

Experience with experimental biological treatment and local gene therapy in Sjogren's syndrome: implications for exocrine pathogenesis and treatment

Sjögren's syndrome is an autoimmune exocrinopathy, mainly affecting the lacrimal and salivary glands, and resulting in ocular and oral dryness (keratoconjunctivitis sicca and xerostomia). The aetiology and pathogenesis are largely unknown, and only palliative treatment is currently available. Data obtained from experimental animal and human studies using biological agents or gene therapeutics can offer insight into the disease process of Sjögren's syndrome. This article reviews the current literature on these approaches and assesses the lessons learnt about the pathogenesis of Sjögren's syndrome.

Neutralization of muscarinic receptor autoantibodies by intravenous immunoglobulin in Sjögren syndrome

Autoantibodies that inhibit M3 muscarinic receptor (M3R)-mediated neurotransmission and cause bladder and bowel dysfunction have been reported in patients with Sjögren syndrome and belong to a family of functional autoantibodies that includes the thyroid-stimulating hormone receptor antibody present in Graves disease. We have recently reported that antiidiotypic antibodies present in pooled immunoglobulin (Ig) G or IgG from healthy individuals neutralize anti-M3R antibody-mediated inhibition of smooth muscle contraction in vitro. Here we extend these studies to the clinic by examining whether therapeutic doses of intravenous immunoglobulin (IVIG) provided to patients with autoimmune diseases neutralize anti-M3R activity in vivo and improve bladder and bowel symptoms. Three patients with primary Sjögren syndrome, dermatomyositis, and celiac disease, respectively, all of whom had anti-M3R activity on a functional bladder contractile assay, were provided a single course of IVIG at a dose of 400 mg/kg per day for 5 days. Anti-M3R activity was neutralized at 4 weeks after IVIG infusion, whereas levels of specific autoantibodies (anti-La, anti-Jo-1, and anti-tissue transglutaminase) were unchanged. Bladder and bowel scores revealed variable improvement after IVIG. Neutralization of anti-M3R activity by IVIG in vivo, presumably as a result of antiidiotypic antibodies directed specifically against anti-M3R autoantibodies, provides a clinical correlate of our in vitro findings. This offers a rationale for IVIG as a treatment for parasympathetic dysfunction in patients with autoantibodies inhibiting postganglionic cholinergic neurotransmission. We suggest the presence of a network of naturally occurring antiidiotypic antibodies that regulate the expression of functional autoantibodies against neuronal receptors and ion channels.

Lower urinary tract symptoms in female patients with rheumatoid arthritis

OBJECTIVE

Patients with autoimmune diseases such as systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS) are associated with an increased severity of lower urinary tract symptoms (LUTS). Recent surveys also reveal that rheumatoid arthritis (RA) is prevalent in patients with interstitial cystitis (IC). Therefore, we have investigated LUTS in patients with RA.

METHODS

A total of 198 female patients with RA, aged 40 years or older, from the rheumatology outpatient clinic completed this prospective study. The American Urological Association Symptom Index (AUASI) score was used to assess the severity of LUTS and the O'Leary-Sant Symptom Index (ICSI) was used to evaluate IC-like urinary symptoms in these patients, which were compared to those of 679 age-matched controls. The possible associations of clinical parameters with LUTS were also explored.

RESULTS

The Mean AUASI score and the percentage of individuals reporting severe LUTS (AUASI score > or = 20) or IC-like urinary symptoms (ICSI score > or = 12) showed no significant differences between the RA and control groups. However, in the RA group multivariate regression analyses identified patients with secondary SS (n = 21) to be associated with a significantly higher AUASI score (p = 0.007) and a higher percentage of severe LUTS (p = 0.02); these were also significantly higher than those of the control group (p = 0.02 and p = 0.01, respectively).

CONCLUSION

Patients with RA have similar urinary complaints when compared to controls. However, those with secondary SS have a greater severity of LUTS, a finding similar to that observed in patients with primary SS.

Effect of human vasoactive intestinal peptide gene transfer in a murine model of Sjogren's syndrome

BACKGROUND

Sjögren's syndrome (SS), an autoimmune exocrinopathy mainly affecting lachrymal and salivary glands, results in ocular and oral dryness (keratoconjunctivitis sicca and xerostomia). The aetiology and pathogenesis are largely unknown; currently, only palliative treatment is available.

OBJECTIVE

To determine whether gene transfer of vasoactive intestinal peptide (VIP), based on its immunomodulatory properties, might be useful in the management of SS.

METHODS

A recombinant serotype 2 adeno-associated virus encoding the human VIP transgene (rAAV2hVIP) was constructed and its efficacy tested in the female non-obese diabetic (NOD) mouse model for SS after retrograde instillation in submandibular glands (SMGs). 10(10) particles/gland of rAAV2hVIP or rAAV2LacZ (encoding beta-galactosidase; control vector) were administered at 8 weeks of age (before sialadenitis onset). Salivary flow rates were determined before vector delivery and at time of death (16 weeks). After death, saliva, serum, and SMGs were harvested. Salivary output, inflammatory infiltrates (focus scores), VIP protein expression, cytokine profile, and serum anti-VIP antibodies were analysed.

RESULTS

rAAV2hVIP significantly improved the salivary flow, increased SMG and serum expression of VIP, and reduced SMG cytokines interleukin (IL) 2, IL10, IL12 (p70), and tumour necrosis factor alpha, and serum RANTES, compared with the control vector. No difference in focus scores or apoptotic rates was found; neutralising antibodies were not detected.

CONCLUSIONS

Local delivery of rAAV2hVIP can have disease modifying and immunosuppressive effects in SMGs of the NOD mouse model of SS. The new strategy of employing VIP prophylactically may be useful for both understanding and managing the salivary component of SS.

Sjögren's syndrome: the diagnostic potential of early oral manifestations preceding hyposalivation/xerostomia

Sjögren's syndrome (SS) is a systemic autoimmune exocrinopathy that affects mainly the salivary and lacrimal glands, leading to progressive reduction in saliva and tear flow. Although the underlying immuno-mediated glandular destruction is thought to develop slowly over several years, a long delay from the start of the symptoms to final diagnosis has been frequently reported. A limited knowledge concerning SS natural history is among the major causes of the actual diagnostic delay. Although very few studies have been focused on the analysis of SS early clinical onset, a series of oral features preceding xerostomia/hyposalivation development in patients eventually diagnosed as having SS have been reported. Sialochemistry alterations, salivary gland swelling, early dental loss and sialorrhea have been observed before the onset of typical signs and symptoms (namely xerostomia and/or hyposalivation), which usually lead to SS clinical presentation and diagnosis. Here we suggest, after evaluating available data, that the traditional 'untouchable' association between SS and xerostomia/hyposalivation might probably be reconsidered, and that astute clinicians should not underestimate the possible presence or development of SS in patients without xerostomia/hyposalivation and presenting these atypical early oral features.

Passive transfer of Sjögren's syndrome IgG produces the pathophysiology of overactive bladder

OBJECTIVE

The presence, in patients with primary and secondary Sjogren's syndrome (SS), of autoantibodies that acutely inhibit M(3) muscarinic receptor (M3R)-mediated bladder contractions is difficult to reconcile with the fact that symptoms of detrusor overactivity and other features of cholinergic hyperresponsiveness occur in this disease. This study was undertaken to examine the in vivo effects of these autoantibodies on bladder function by examining bladder responsiveness and compliance following passive transfer of patient IgG to mice.

METHODS

Contractile responses of isolated bladder strips both to the muscarinic agonist carbachol and to electrically evoked acetylcholine release were measured 48 hours after injection of mice with patient or control IgG. A whole bladder assay with intact neuronal pathways was developed to assess bladder wall compliance on filling cystometry. Expression of M3R in bladders from IgG-injected mice was assessed by immunohistochemistry.

RESULTS

Passive transfer of SS IgG with inhibitory anti-M3R activity produced a paradoxical increase in contractile responses of detrusor strips to cholinergic stimulation. Cystometry of whole bladders revealed a corresponding decrease in bladder wall compliance and phasic detrusor contractions upon filling, replicating the urodynamic features of an overactive bladder. The features of cholinergic hyperresponsiveness were associated with increased postsynaptic M3R expression and were reproduced by injecting mice with a rabbit antibody against the second extracellular loop of M3R.

CONCLUSION

These findings are consistent with the notion that there is initial inhibition of parasympathetic neurotransmission by antagonistic autoantibodies to M3R, which produces a compensatory increase in M3R expression in vivo. The enhanced cholinergic responses during bladder distention result in detrusor overactivity. We conclude that the overactive bladder associated with SS is an autoantibody-mediated disorder of the autonomic nervous system, which may be part of a wider spectrum of cholinergic hyperresponsiveness.