Autoantibodies to calcium channels in type 1 diabetes mediate autonomic dysfunction by different mechanisms in colon and bladder and are neutralized by antiidiotypic antibodies

Autonomic dysfunction detected by skin sympathetic response in Lambert-Eaton myasthenic syndrome: a case report

Background

Lambert-Eaton myasthenic syndrome (LEMS) is a type of paraneoplastic syndrome that may initially manifest itself with proximal weakness and gait abnormalities. Approximately up to 50% of LEMS patients have a primary autonomic dysfunction.

Case presentation

We present here a case of a 75-year-old male with symmetric proximal muscle weakness, dry mouth and constipation. The cutaneous response to scratch and upright tilt-table testing were positive. A repetitive nerve stimulation test showed that there was a decremental response of compound muscle action potential (CMAP) amplitude at 3 Hz while an incremental response at 20 Hz. The presence of antibodies against voltage-gated calcium channels (VGCC) confirmed the diagnosis. Because of the prominent symptom of autonomic disorder, the patient further underwent the test of skin sympathetic response (SSR). Lower amplitude and longer response duration were found in palms, while it evoked no response in soles.

Conclusions

In this case, we present the detailed results of SSR test on a patient suffering LEMS with autonomic disorder. Since autonomic dysfunction has a significant impact on clinical management and SSR test is an effective detection method, we recommend that SSR test be performed on patients with LEMS regularly.

Neuroimmunogastroenterology: At the Interface of Neuroimmunology and Gastroenterology

The central nervous system (CNS) is an important regulator of the gastrointestinal tract, and CNS dysfunction can result in significant and disabling gastrointestinal symptom manifestation. For patients with neuroimmunologic and neuroinflammatory conditions, the recognition of gastrointestinal symptoms is under-appreciated, yet the gastrointestinal manifestations have a dramatic impact on quality of life. The current treatment strategies, often employed independently by the neurologist and gastroenterologist, raise the question of whether such patients are being treated optimally when siloed in one specialty. Neuroimmunogastroenterology lies at the borderlands of medical specialties, and there are few resources to guide neurologists in this area. Here, we provide an overview highlighting the potential mechanisms of crosstalk between immune-mediated neurological disorders and gastrointestinal dysfunction.

Enteric neuroplasticity and dysmotility in inflammatory disease: key players and possible therapeutic targets

Intestinal functions, including motility and secretion, are locally controlled by enteric neural networks housed within the wall of the gut. The fidelity of these functions depends on the precision of intercellular signaling among cellular elements, including enteric neurons, epithelial cells, immune cells, and glia, all of which are vulnerable to disruptive influences during inflammatory events. This review article describes current knowledge regarding inflammation-induced neuroplasticity along key elements of enteric neural circuits, what is known about the causes of these changes, and possible therapeutic targets for protecting and/or repairing the integrity of intrinsic enteric neurotransmission. Changes that have been detected in response to inflammation include increased epithelial serotonin availability, hyperexcitability of intrinsic primary afferent neurons, facilitation of synaptic activity among enteric neurons, and attenuated purinergic neuromuscular transmission. Dysfunctional propulsive motility has been detected in models of colitis, where causes include the changes described above, and in models of multiple sclerosis and other autoimmune conditions, where autoantibodies are thought to mediate dysmotility. Other cells implicated in inflammation-induced neuroplasticity include muscularis macrophages and enteric glia. Targeted treatments that are discussed include 5-hydroxytryptamine receptor 4 agonists, cyclooxygenase inhibitors, antioxidants, B cell depletion therapy, and activation of anti-inflammatory pathways.

Serum biomarkers for diagnosis and prediction of type 1 diabetes

Type 1 diabetes (T1D) culminates in the autoimmune destruction of the pancreatic βcells, leading to insufficient production of insulin and development of hyperglycemia. Serum biomarkers including a combination of glucose, glycated molecules, C-peptide, and autoantibodies have been well established for the diagnosis of T1D. However, these molecules often mark a late stage of the disease when ∼90% of the pancreatic insulin-producing β-cells have already been lost. With the prevalence of T1D increasing worldwide and because of the physical and psychological burden induced by this disease, there is a great need for prognostic biomarkers to predict T1D development or progression. This would allow us to identify individuals at high risk for early prevention and intervention. Therefore, considerable efforts have been dedicated to the understanding of disease etiology and the discovery of novel biomarkers in the last few decades. The advent of high-throughput and sensitive "-omics" technologies for the study of proteins, nucleic acids, and metabolites have allowed large scale profiling of protein expression and gene changes in T1D patients relative to disease-free controls. In this review, we briefly discuss the classical diagnostic biomarkers of T1D but mainly focus on the novel biomarkers that are identified as markers of β-cell destruction and screened with the use of state-of-the-art "-omics" technologies.

A cell-based assay for the detection of pathogenic anti-voltage-gated calcium channel autoantibodies in immunoglobulin G from patients with type 1 diabetes

Recent studies have postulated the presence of functional autoantibodies (Abs) against L-type voltage gated calcium channels (VGCCs) in the serum of patients with type 1 diabetes, with various proposed physiological consequences, both islet cell associated and extra-glandular. Arguably, the most potentially damaging effect reported for these Abs is induction of apoptosis in pancreatic beta (β) cells, yet a convincing pathogenic mechanism remains to be demonstrated. In the current study, we report an assay of reactive oxygen species (ROS) stress induction in the rat insulinoma cell line Rin A12, as determined by 2', 7'-Dichlorofluorescein diacetate (DCF-DA) fluorescence detection by flow cytometry. We demonstrate that incubation of Rin A12 cells with immunoglobulin G (IgG) containing anti-VGCC activity from patients with T1D mediates a significant increase in ROS, with subsequent induction of apoptosis, as determined by positivity for annexin V expression. Neither T1D patient-derived IgG lacking anti-VGCC activity or IgG from healthy donors altered ROS or annexin V expression, indicating the new assay is specific for the detection of functional anti-VGCC Abs. Subsequent screening of IgG samples derived from individual patients indicated a prevalence of approximately 75% in a cohort of 20 patients with T1D. The new cell-based assay provides, for the first time, experimental evidence supporting a plausible pathophysiological mechanism underlying anti-VGCC Ab-mediated apoptosis induction in β cells. Additionally, the assay is a considerable advance on previously published methods for detecting and characterising the functional activity of anti-VGCC Abs in patient-derived samples.

Anti-serum with anti-autoantibody activity decreases autoantibody-positive B lymphocytes and type 1 diabetes of female NOD mice

Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by an autoimmune-mediated loss of insulin secreting β-cells. Each B lymphocyte clone that escapes immune tolerance produces a specific antibody. No specific treatment against autoantibodies is available for autoimmune diseases. We have developed a strategy to produce an antiserum against autoantibodies for the treatment of T1DM. Non-obese diabetic (NOD) but not Balb/c mouse serum contains autoantibodies. Antisera were produced by immunizing Balb/c mice with affinity-purified IgG from NOD or BALB/c mice along with the immune adjuvant (hereafter, NIgG or BIgG, respectively). A bolus administration of NIgG significantly reduced serum autoantibodies, autoantibody-positive B lymphocytes in the spleens of NOD mice, mortality and morbidity of diabetes, blood glucose and islet immune infiltration, whereas it increased islet mass in NOD mice for at least 26 weeks. NIgG antiserum treatment has no significant effect on CD3(+), CD4(+) or CD8(+) T cells and B220(+) or CD19(+) B cells. BIgG also imparted a moderate therapeutic effect, although it was considerably lower than that of NIgG. NIgG did not cross-react with allogeneic serum. NIgG showed no effect on Balb/c mice. The results show the feasibility of producing antiserum against autoantibodies to prevent and treat autoimmune-induced T1DM with a single bolus administration.

Autonomic neuropathy in experimental models of diabetes mellitus

Autonomic neuropathy complicates diabetes by increasing patient morbidity and mortality. Surprisingly, considering its importance, development and exploitation of animal models has lagged behind the wealth of information collected for somatic symmetrical sensory neuropathy. Nonetheless, animal studies have resulted in a variety of insights into the pathogenesis, neuropathology, and pathophysiology of diabetic autonomic neuropathy (DAN) with significant and, in some cases, remarkable correspondence between rodent models and human disease. Particularly in the study of alimentary dysfunction, findings in intrinsic intramural ganglia, interstitial cells of Cajal and the extrinsic parasympathetic and sympathetic ganglia serving the bowel vie for recognition as the chief mechanism. A body of work focused on neuropathologic findings in experimental animals and human subjects has demonstrated that axonal and dendritic pathology in sympathetic ganglia with relative neuron preservation represents one of the neuropathologic hallmarks of DAN but it is unlikely to represent the entire story. There is a surprising selectivity of the diabetic process for subpopulations of neurons and nerve terminals within intramural, parasympathetic, and sympathetic ganglia and innervation of end organs, afflicting some while sparing others, and differing between vascular and other targets within individual end organs. Rather than resulting from a simple deficit in one limb of an effector pathway, autonomic dysfunction may proceed from the inability to integrate portions of several complex pathways. The selectivity of the diabetic process appears to confound a simple global explanation (e.g., ischemia) of DAN. Although the search for a single unifying pathogenetic hypothesis continues, it is possible that autonomic neuropathy will have multiple pathogenetic mechanisms whose interplay may require therapies consisting of a cocktail of drugs. The role of multiple neurotrophic substances, antioxidants (general or pathway specific), inhibitors of formation of advanced glycosylation end products and drugs affecting the polyol pathway may be complex and therapeutic elements may have both salutary and untoward effects. This review has attempted to present the background and current findings and hypotheses, focusing on autonomic elements including and beyond the typical parasympathetic and sympathetic nervous systems to include visceral sensory and enteric nervous systems.

Changes in GAD65Ab-specific antiidiotypic antibody levels correlate with changes in C-peptide levels and progression to islet cell autoimmunity

CONTEXT

The previously reported absence of 65-kDa glutamate decarboxylase antibody (GAD65Ab)-specific antiidiotypic antibodies (anti-Id) in type 1 diabetes (T1D) patients at clinical onset could be due to an inability to mount an antibody response to GAD65Ab or a longitudinal decline in anti-Id levels.

OBJECTIVE AND DESIGN

We investigated anti-Id levels in longitudinal samples obtained from T1D patients (n = 41) (clinical diagnosis - 12 months), and latent autoimmune diabetes in adults (LADA) patients (n = 32) who received alum-formulated human recombinant GAD65 (baseline - 12 months). We also determined anti-Id levels in a small cohort of Type 2 diabetes patients during their development of autoimmune T cell responses.

RESULTS

At clinical onset T1D patients presented no or low anti-Id levels. However, 22/41 T1D patients showed ≥50% increase in GAD65Ab-specific anti-Id levels during follow-up; peaking at 3 (n = 1), 6 (n = 10), 9 (n = 10), or 12 (n = 1) months. Increasing anti-Id levels marked patients who experienced a temporary increase in C-peptide levels. Anti-Id levels correlated significantly with glycated hemoglobin and C-peptide levels at 6 and 9 months (P values ranged from <0.001 to <0.05). In LADA patients receiving placebo, anti-Id levels declined in seven of nine patients, whereas four of five patients receiving 20 μg alum-formulated human recombinant GAD65 showed increasing anti-Id levels. Changes in anti-Id and C-peptide levels closely correlated (P < 0.0001). The significant decline in anti-Id levels (P = 0.03) in T2D patients developing T cell autoimmune responses supports our hypothesis that declining anti-Id levels are associated with developing islet autoimmunity.

CONCLUSIONS

The close association between GAD65Ab-specific anti-Id levels and β-cell function may provide a novel marker for the progression of autoimmune diabetes.

A novel impedance-based cellular assay for the detection of anti-calcium channel autoantibodies in type 1 diabetes

We have recently postulated that functional autoantibodies (Abs) against L-type voltage-gated calcium channels (VGCCs) contribute to autonomic dysfunction in type 1 diabetes (T1D). Previous studies based on whole-organ assays have proven valuable in establishing the mechanism of anti-VGCC Ab activity, but are complex and unsuitable for screening large patient cohorts. In the current study, we used real-time dynamic monitoring of cell impedance to demonstrate that anti-VGCC Abs from patients with T1D inhibit the adherence of Rin A12 cells. The functional effect of the anti-VGCC Abs was mimicked by the dihydropyridine agonist, Bay K8644, and reversed by the antagonist, nicardipine, providing a pharmacological link to the whole-organ studies. IVIg neutralized the effect on cell adhesion of the anti-VGCC Abs, consistent with the presence of anti-idiotypic Abs in IVIg that may prevent the emergence of pathogenic Abs in healthy individuals. The cell impedance assay can be performed in a 96 well plate format, and represents a simple method for detecting the presence of anti-VGCC activity in patient immunoglobulin (IgG). The new cell assay should prove useful for further studies to determine the prevalence of the Ab and its association with symptoms of autonomic dysfunction in patients with T1D.

Potentiation of a functional autoantibody in narcolepsy by a cholinesterase inhibitor

We have recently reported the presence of an immunoglobulin G (IgG) autoantibody (Ab) in patients with narcolepsy with cataplexy that abolishes spontaneous colonic migrating motor complexes (CMMCs) and increases smooth muscle tension and atropine-sensitive phasic contractions in a physiological assay of an isolated colon. In this study, we used the cholinesterase inhibitor, neostigmine, to explore the mechanism of the narcoleptic IgG-mediated disruption of enteric motor function in four patients with narcolepsy with cataplexy and to identify a pharmacological mimic of the Ab. Neostigmine potentiated the narcoleptic IgG-mediated increase in smooth muscle resting tension and phasic smooth muscle contractions by an atropine-sensitive mechanism but exerted no effect on resting tension in the presence of control IgG. Decreased frequency of CMMCs mediated by IgG with anti-M3R activity was reversed by neostigmine. Therefore, a challenge with a cholinesterase inhibitor improves the specificity of the CMMC assay for narcoleptic IgG. Tetrodotoxin (TTX), a neuronal sodium channel blocker, also abolished CMMCs and increased resting tone, and a similar potentiation was observed with neostigmine; thus, TTX is a mimic of the functional effects of the narcoleptic IgG in this bioassay. These findings provide a link to pharmacological studies of canine narcolepsy and are consistent with a functional blockade of both excitatory and inhibitory motor neurons by the narcoleptic Ab, similar to the TTX mimic, presumably by binding to an autoantigenic target expressed in both populations of neurons.

Peripheral blood mononuclear cell gene array profiles in patients with overactive bladder

OBJECTIVES

To investigate the utility of using peripheral blood mononuclear cells (PBMC) as a marker for patients with overactive bladder (OAB). Patients with OAB may suffer from varying degrees of symptoms such as frequency, urgency, nocturia, and incontinence; however, there is no definitive test for OAB at this time. Questionnaires may provide useful tools for screening patients for OAB but often clinicians may need to rely on more invasive procedures to confirm the diagnosis. We have previously demonstrated that PBMC can provide a reporter function in solid organ retroperitoneal disease.

METHODS

Twenty-one patients were assessed for OAB. PBMC was obtained from whole blood of the patients, and RNA was subjected to microarray gene chip analysis.

RESULTS

Microarray analysis revealed that 16 genes were differentially regulated (8 upregulated and 8 downregulated) in all patients with OAB in comparison with healthy controls. A sex-based analysis demonstrated 74 genes that were differentially regulated in males (25 upregulated and 49 downregulated), and 30 in females (13 upregulated and 17 downregulated). Of these platelet-derived growth factors, microfibrillar-associated protein and tropomyosin were downregulated in all sets that were analyzed.

CONCLUSIONS

Microarray analysis revealed many genes that were differentially regulated in PBMC from OAB patients, including regulatory elements and genes encoding structural proteins, which may be important in regulating structural integrity of the bladder and supporting tissues. These data suggest that PBMC can provide a reporter function for patients with OAB and may serve as a diagnostic marker and elucidate genes involved in this condition.

Probiotics and immunity

Probiotics are defined as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host, including the gastrointestinal tract. While this beneficial effect was originally thought to stem from improvements in the intestinal microbial balance, there is now substantial evidence that probiotics can also provide benefits by modulating immune functions. In animal models, probiotic supplementation is able to provide protection from spontaneous and chemically induced colitis by downregulating inflammatory cytokines or inducing regulatory mechanisms in a strain-specific manner. In animal models of allergen sensitization and murine models of asthma and allergic rhinitis, orally administered probiotics can strain-dependently decrease allergen-specific IgE production, in part by modulating systemic cytokine production. Certain probiotics have been shown to decrease airway hyperresponsiveness and inflammation by inducing regulatory mechanisms. Promising results have been obtained with probiotics in the treatment of human inflammatory diseases of the intestine and in the prevention and treatment of atopic eczema in neonates and infants. However, the findings are too variable to allow firm conclusions as to the effectiveness of specific probiotics in these conditions.

An autoantibody in narcolepsy disrupts colonic migrating motor complexes

Despite strong circumstantial evidence for the autoimmune hypothesis of narcolepsy, conventional immunological methods have failed to detect an autoantibody. This study investigated the real-time effects of narcoleptic immunoglobulins on a spontaneous colonic migrating motor complex (CMMC) preparation. IgG from patients with narcolepsy with cataplexy or healthy controls was added directly to isolated mouse colons undergoing CMMC activity to test for autoantibodies that disrupt colonic motility. The effect of immunoglobulins prepared for clinical intravenous treatment (IVIg) on autoantibody-mediated colonic disruption was also assessed. Narcoleptic IgGs markedly reduced the frequency of CMMCs or irreversibly abolished them. Abrogation of CMMCs was followed by an increase in the resting tension of the colon preparation and appearance of atropine-sensitive phasic smooth muscle contractions. IVIg partially neutralized the inhibitory effect of narcoleptic IgG on the CMMCs. The dramatic effect of narcoleptic IgG on CMMC generation is consistent with an autoantibody-mediated disruption of enteric neural pathways. The ex vivo whole-organ approach allows real-time examination of the physiological effects of the narcoleptic autoantibody and offers a new avenue for exploring the autoimmune basis of narcolepsy. The neutralizing effect of IVIg on the autoantibody provides a rationale for the reported clinical improvement in cataplexy when IVIg are given at disease onset.