Autoantibodies Against Dihydrolipoamide S-Acetyltransferase in Immune-Mediated Neuropathies

BACKGROUND AND OBJECTIVES

This study aimed to identify disease-related autoantibodies in the serum of patients with immune-mediated neuropathies including chronic inflammatory demyelinating polyneuropathy (CIDP) and to investigate the clinical characteristics of patients with these antibodies.

METHODS

Proteins extracted from mouse brain tissue were used to react with sera from patients with CIDP by western blotting (WB) to determine the presence of common bands. Positive bands were then identified by mass spectrometry and confirmed for reactivity with patient sera using enzyme-linked immunosorbent assay (ELISA) and WB. Reactivity was further confirmed by cell-based and tissue-based indirect immunofluorescence assays. The clinical characteristics of patients with candidate autoantibody-positive CIDP were analyzed, and their association with other neurologic diseases was also investigated.

RESULTS

Screening of 78 CIDP patient sera by WB revealed a positive band around 60-70 kDa identified as dihydrolipoamide S-acetyltransferase (DLAT) by immunoprecipitation and mass spectrometry. Serum immunoglobulin G (IgG) and IgM antibodies' reactivity to recombinant DLAT was confirmed using ELISA and WB. A relatively high reactivity was observed in 29 of 160 (18%) patients with CIDP, followed by patients with sensory neuropathy (6/58, 10%) and patients with MS (2/47, 4%), but not in patients with Guillain-Barré syndrome (0/27), patients with hereditary neuropathy (0/40), and healthy controls (0/26). Both the cell-based and tissue-based assays confirmed reactivity in 26 of 33 patients with CIDP. Comparing the clinical characteristics of patients with CIDP with anti-DLAT antibodies (n = 29) with those of negative cases (n = 131), a higher percentage of patients had comorbid sensory ataxia (69% vs 37%), cranial nerve disorders (24% vs 9%), and malignancy (20% vs 5%). A high DLAT expression was observed in human autopsy dorsal root ganglia, confirming the reactivity of patient serum with mouse dorsal root ganglion cells.

DISCUSSION

Reactivity to DLAT was confirmed in patient sera, mainly in patients with CIDP. DLAT is highly expressed in the dorsal root ganglion cells, and anti-DLAT antibody may serve as a biomarker for sensory-dominant neuropathies.

Granuloma, vasculitis, and demyelination in sarcoid neuropathy

BACKGROUND

Despite the suggestion that direct compression by granuloma and ischemia resulting from vasculitis can cause nerve fiber damage, the mechanisms underlying sarcoid neuropathy have not yet been fully clarified.

METHODS

We examined the clinicopathological features of sarcoid neuropathy by focusing on electrophysiological and histopathological findings of sural nerve biopsy specimens. We included 18 patients with sarcoid neuropathy who had non-caseating epithelioid cell granuloma in their sural nerve biopsy specimens.

RESULTS

Although electrophysiological findings suggestive of axonal neuropathy were observed, particularly in the lower limbs, all but three patients showed ≥1 abnormalities in nerve conduction velocity or distal motor latency. Additionally, a conduction block was observed in 11 of the 16 patients for whom waveforms were assessed; five of them fulfilled motor nerve conduction criteria strongly supportive of demyelination as defined in the European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) guideline for chronic inflammatory demyelinating polyneuropathy (CIDP). In most patients, sural nerve biopsy specimens revealed a mild to moderate degree of myelinated fiber loss. Fibrinoid necrosis was observed in one patient, and electron microscopy analysis revealed demyelinated axons close to granulomas in six patients.

CONCLUSIONS

Patients with sarcoid neuropathy may meet the EAN/PNS electrophysiological criteria for CIDP due to the frequent presence of conduction blocks. Based on our results, in addition to the ischemic damage resulting from granulomatous inflammation, demyelination may play an important role in the mechanism underlying sarcoid neuropathy.

Early ultrastructural lesions of anti-neutrophil cytoplasmic antibody- versus complement-associated vasculitis

This study aims to describe electron microscopic findings of vasculitis associated with anti-neutrophil cytoplasmic antibody (ANCA) and complement. Sural nerve biopsy specimens were obtained from 10 patients with microscopic polyangiitis (MPA), a representative ANCA-associated vasculitis, and six patients with nonsystemic vasculitic neuropathy (NSVN), who were negative for ANCA but positive for complement deposition. In patients with MPA, attachment of neutrophils to epineurial vascular endothelial cells, migration of neutrophils to the extravascular space via the penetration of the endothelial layer, and release of neutrophil components to the extracellular space were observed. Such neutrophil-associated lesions were not observed in patients with NSVN. Nonetheless, morphological changes in epineurial vascular endothelial cells, such as increases in cytoplasmic organelles and cytoplasmic protrusions into the vascular lumen, were observed in patients with NSVN. Since these findings were observed where light microscopy-based findings suggestive of vasculitis (e.g., the disruption of vascular structures and fibrinoid necrosis) were absent, they were considered early lesions that preceded the formation of the so-called necrotizing vasculitis. In conclusion, this study enabled the visualization of distinctive early ultrastructural lesions associated with ANCA and complement. Further studies are needed to elucidate the molecular basis of the induction of these fine structural changes, which will contribute to the development of targeted therapies based on specific mechanisms of vasculitis.

Role of complement components in vasculitic neuropathy associated with systemic lupus erythematosus and rheumatoid arthritis

INTRODUCTION/AIMS

The mechanism of complement-mediated neurological injury in vasculitic neuropathy associated with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) is unknown. The current study aimed to investigate the local activation of the complement system in vasculitic neuropathy associated with SLE and RA.

METHODS

We analyzed sural nerve biopsy specimens collected from patients with SLE (n = 12) and RA (n = 12). The deposition of complement components comprising the classical and lectin pathways was assessed via immunohistochemistry.

RESULTS

The disease duration was longer in the RA group than in the SLE group (median [interquartile range]: 11.5 [5.5-31.0] and 4 [2-10] y, respectively). Complement components were found in the epineurial blood vessel walls in patients with SLE and RA, but not in controls. Deposition of the classical pathway component C1q in the blood vessel wall was more commonly observed in the SLE group (71.3% [25.6-85.8]) than in the RA group (20.1% [10.5-35.6]). As for the lectin pathway component, the incidence of ficolin-3 deposition in the blood vessel wall was higher in the SLE group (42.3% [25.7-51.3]) than in the RA group (17.2% [10.3-26.8]). On the contrary, the mannose-binding lectin level was higher in the RA group (37.5% [21.7-51.4]) than in the SLE group (17.8% [11.4-31.0]).

DISCUSSION

The classical and lectin pathways of the complement system may be involved in vasculitic neuropathy associated with SLE and RA.

ANCA-Associated Vasculitic Neuropathies: A Review

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a systemic disorder that frequently affects the peripheral nervous system and consists of three distinct conditions: microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA, previously Wegener’s granulomatosis), and eosinophilic granulomatosis with polyangiitis (EGPA, previously Churg-Strauss syndrome). The neuropathic features associated with this condition usually include mononeuritis multiplex, which reflects the locality of lesions. Findings suggestive of vasculitis are usually found in the epineurium and occur diffusely throughout the nerve trunk. Nerve fiber degeneration resulting from ischemia is sometimes focal or asymmetric and tends to become conspicuous at the middle portion of the nerve trunk. The attachment of neutrophils to endothelial cells in the epineurial vessels is frequently observed in patients with ANCA-associated vasculitis; neutrophils play an important role in vascular inflammation by binding of ANCA. The positivity rate of ANCA in EGPA is lower than that in MPA and GPA, and intravascular and tissue eosinophils appear to participate in neuropathy. Immunotherapy for ANCA-associated vasculitis involves the induction and maintenance of remission to prevent the relapse of the disease. A combination of glucocorticoids along with cyclophosphamide, rituximab, methotrexate, or mycophenolate mofetil is considered depending on the severity of the condition of the organ to induce remission. A combination of low-dose glucocorticoids and azathioprine, rituximab, methotrexate, or mycophenolate mofetil is recommended to maintain remission. The efficacy of anti-interleukin-5 therapy (i.e., mepolizumab) was demonstrated in the case of refractory or relapsing EGPA. Several other new agents, including avacopan, vilobelimab, and abatacept, are under development for the treatment of ANCA-associated vasculitis. Multidisciplinary approaches are required for the diagnosis and management of the disorder because of its systemic nature. Furthermore, active participation of neurologists is required because the associated neuropathic symptoms can significantly disrupt the day-to-day functioning and quality of life of patients with ANCA-associated vasculitis.

Two distinct mechanisms of neuropathy in immunoglobulin light chain (AL) amyloidosis

INTRODUCTION

Although polyneuropathy in patients with immunoglobulin light chain (AL) amyloidosis has been considered to be attributable to axonal degeneration resulting from amyloid deposition, patients with nerve conduction parameters indicating demyelination that mimics chronic inflammatory demyelinating polyneuropathy (CIDP) have also been reported anecdotally.

METHODS

We evaluated the electrophysiological and pathological features of 8 consecutive patients with AL amyloidosis who were referred for sural nerve biopsy.

RESULTS

Although findings of axonal neuropathy predominantly in the lower limbs were the cardinal feature, all patients showed one or more abnormalities of nerve conduction velocities or distal motor latencies. In particular, 2 of these patients fulfilled the definite electrophysiological for CIDP defined by the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS). On electron microscopic examination of sural nerve biopsy specimens, Schwann cells apposed to amyloid fibrils became atrophic in all patients, suggesting that amyloid deposits directly affect neighboring tissues. Additionally, detachment of the neurilemma from the outermost compacted myelin lamella was seen where amyloid fibrils were absent in 4 patients. Electrophysiological findings suggestive of demyelination were more conspicuous in these patients compared with the other patients. The detachment of the neurilemma from the outermost compacted myelin lamella was particularly conspicuous in patients who fulfilled the definite EFNS/PNS electrophysiological criteria for CIDP.

CONCLUSION

Abnormalities of myelinated fibers unrelated to amyloid deposition may frequently occur in AL amyloidosis. Disjunction between myelin and the neurilemma may induce nerve conduction abnormalities suggestive of demyelination.

[Effect of weekly docetaxel in patients with recurrent breast cancer]

A pilot trial was conducted to assess the tolerability and efficacy of a regimen with weekly docetaxel (TXT) in patients with metastatic breast cancer. The chemotherapy regimen consisted of a 30-minute weekly intravenous infusion of docetaxel (22-33 mg/m2/wk). Each 8-week cycle included 6 weekly treatments, followed by two weeks of rest. Thirteen patients were treated. All patients were evaluable for response: 0 CR (0%), 7 PR (53.8%), 3 NC (23.1%), 3 PD (23.1%). These results are almost the same as those with the administration of TXT (60 mg/m2) q3 wks. Toxicities observed were mild (< or = grade 2) and reversible, and included fatigue, nausea, neutropenia, and alopecia. This preliminary experience suggests a high level of clinical activity and excellent tolerability of the chemotherapy regimen at the given dose and schedule in patients with metastatic breast cancer.

EGF regulates early embryonic mouse gut development in chemically defined organ culture

The profound intestinal epithelial defects in the newborn epidermal growth factor receptor (EGFR) knockout mouse suggests that EGFR signaling plays important roles in embryonic gut development. Herein, we further elucidated the function of EGFR signaling on early embryonic gut development by comparing the effects of 1-10 ng/mL of exogenous epidermal growth factor (EGF) or 10-25 microM of the tyrphostin 3,4,5 trihydroxybenzene malononitrile, a specific inhibitor of EGFR tyrosine kinase, on intact E12 Swiss-Webster mouse midgut grown in chemically defined organ culture using Fitton-Jackson BGJb medium for 4 or 6 d. Intestinal development during culture was assayed by morphometry, histology, reverse transcription/competitive PCR for villin and intestinal fatty acid binding protein mRNA, and immunohistochemistry for epithelial proliferative markers. During organ culture, control specimens grew in length, developed smooth muscle, simple columnar epithelial and goblet cell phenotypes, showed early villus formation in the proximal intestine, and increased expression of villin and intestinal fatty acid binding protein mRNA. EGF failed to significantly alter small intestinal lengthening, whereas EGF 10 ng/mL inhibited colonic length growth. Tyrphostin 25 microM resulted in regional losses of stromal and smooth muscle cells in the small intestine and absent colonic goblet cells. In controls, cellular proliferation initially occurred throughout the small intestinal epithelium but became increasingly localized to the intervillus crypt regions. This sequestration of epithelial proliferation into crypts was much more apparent in EGF-treated versus tyrphostin-treated specimens. EGFR activation, therefore, appears to accelerate the maturation rate of goblet cells and the differential crypt/villus proliferation pattern in early embryonic mouse gut.

Postoperative intussusception after surgery for malrotation and appendicectomy in a newborn

Postoperative intussusception in the newborn is an infrequent condition. A 17-day-old female with duodenal stenosis and malrotation underwent excision of the membrane in the duodenum and incidental appendicectomy. Postoperatively, a ceco-colic type of intussusception occurred, necessitating a right hemicolectomy. We speculate that the causative factors are twofolds: the embedded appendiceal stump, a polyp-like protrusion that became a lead point, and the non-fixation of the ileocecal mesentery, which facilitated a ceco-colic type of invagination.

Reappraisal of lateral cervical cysts in neonates: pyriform sinus cysts as an anatomy-based nomenclature

BACKGROUND/PURPOSE

Cervical cysts in neonates are recognized as rare branchial remnants. This term includes many different derivatives of the branchial cleft and sinus.

METHODS

A retrospective review was performed in seven neonates with lateral cervical cysts seen at a single institution between 1975 and 1996. Two patients underwent simple excision of the cyst before 1987. Since 1987, five underwent complete excision of the sinus with or without esophagoscopic assistance to identify the orifice of the pyriform sinus.

RESULTS

All of the cysts were located on the left side of the neck, anterior to the sternocleidomastoid muscle. Five had large cysts containing air. In four patients, a large orifice of the pyriform sinus was identified by the esophagoscopy. In six of seven patients, the histological examination showed thyroid or thymic tissue in the wall of the cysts, which is compatible with a clinical entity of "pyriform sinus fistula" commonly seen in older children.

CONCLUSION

We propose that this anomaly be called a pyriform sinus cyst, which is an anatomic term based on their draining orifice.

Effect of growth hormone on wound healing in protein-malnourished rats treated with corticosteroids

This study was designed to evaluate the efficacy of human growth hormone (GH) in improving the tensile strength of wounds weakened by chronic protein malnourishment and corticosteroid (CS) administration. Eighty-six female Sprague-Dawley rats, weighing 80 to 100 g, were divided into five groups. Group 1 (control) received 23.4% protein chow for 8 weeks before surgery. Groups 2, 3, 4, and 5 received nonprotein chow on alternate days for the same duration. Groups 3 and 5 received prednisolone (2 mg/kg/d intramuscularly) for 3 weeks preoperatively and for 5 days postoperatively. Groups 4 and 5 were given GH (somatotropin, 1 IU/d) for 5 days postoperatively. All the animals underwent a precise 4-cm midline celiotomy. Wound testing was performed on the sixth postoperative day, after removal of the sutures. The bursting strength (BS, mean +/- SD) for group 1 was 145 +/- 16 mm Hg. The BS for groups 4 (137 +/- 13 mm Hg) and 5 (134 +/- 7 mm Hg) were significantly stronger than those for groups 2 (115 +/- 15 mm Hg) and 3 (91 +/- 16 mm Hg). The authors conclude that postoperative systemic GH restored the wound BS in protein-malnourished animals treated with CS, to the level of the normally nourished controls.

The ontogeny of gene expression of progestin receptors in the female rat brain

The postnatal development of the progestin receptor (PR) system in the rat brain is a region-specific and stage-related process. In an attempt to analyze the molecular mechanism by which the dramatic change of gene expression of the PR occurs we have examined the level of PR mRNAs in the hypothalamus-preoptic area (HPOA) and cerebral cortex in development from fetal to postnatal stages of female rats. We used polymerase chain reaction to clone, from uterine cDNA, the cDNA corresponding to the steroid-binding domain of the PR forms 'A' and 'B' mRNA as well as the region around the translation-initiation site (ATG1) of the putative PR form 'B' mRNA. A quantitative reverse transcription-polymerase chain reaction assay was used to measure the level of mRNAs for PR forms 'A' and 'B' (total PR mRNAs) and PR form 'B'. There was a regional difference in the intracerebral distribution between the total and form 'B' mRNAs, indicating possible distinct mechanisms responsible for regulating the expression of the PR mRNAs. The PR mRNAs in the brain, already detectable 2 days before birth, increased at early neonatal stages. The total PR mRNAs in the cortex developed in a manner essentially similar to the PR protein at the early stages, but, surprisingly, unlike the receptor, the messages remained high at the later stages from day 18 to 8 weeks of life. On the other hand, the ontogeny of the cortical mRNA for form 'B', which predominantly existed in the region, resembled that of the cortical PR protein. In the HPOA the postnatal development of the form 'B' mRNAs was also roughly similar to the PR. These results suggest region-specific and stage-related gene expression of the PR isoform system in the developing brain: gene expression of form 'B' seems to be predominantly, first, "turned on" around birth, followed by form 'A' mRNA expression around days 8-12. Moreover, lowered levels of the cortical PR mRNAs in the propylthiouracil-induced hypothyroid rat, together with suppressed PR level, indicate a possible regulatory role of thyroid hormone on gene expression of the cortical receptor.

A one-step sandwich enzyme immunoassay for human matrix metalloproteinase 2 (72-kDa gelatinase/type IV collagenase) using monoclonal antibodies

A one-step sandwich enzyme immunoassay (EIA) for human matrix metalloproteinase 2 (MMP-2, 72-kDa gelatinase/type IV collagenase, EC 3.4.24.24) was established with a pair of monoclonal antibodies prepared against the precursor form of MMP-2 (proMMP-2) purified from the conditioned medium of human skin fibroblasts or against a synthetic peptide corresponding to the N-terminal domain of proMMP-2. ProMMP-2 in samples was allowed to simultaneously react with both solid-phase and peroxidase-labeled antibodies. Sensitivity of this EIA system was 2.4 pg/assay (0.24 microgram/l) and linearity was obtained between 10 and 5,000 pg/assay (1.0-500 micrograms/l). The EIA system recognized both the free form of proMMP-2 and its complex form with TIMP-2 with the same degree of immunoreactivity. ProMMP-2 levels in human sera from patients in various disease states were analyzed. In sera from patients with hyperthyroidism (12), primary biliary cirrhosis (8) and hepatocellular carcinoma (11), 749 +/- 166, 716 +/- 135 and 686 +/- 236 micrograms/l of proMMP-2 were detected, respectively and these were significantly higher than that observed in 213 normal human sera (570 +/- 118 micrograms/l). In contrast, the levels in sera from 33 patients with osteoarthritis (449 +/- 72 micrograms/l), 45 with rheumatoid arthritis (408 +/- 139 micrograms/l), 13 with stomach cancer (427 +/- 103 micrograms/l) and 10 with pancreatic cancer (422 +/- 130 micrograms/l) were significantly lower than that found in normal sera. Immunoblot and gel filtration analyses showed that human sera contain several MMP-2 species in addition to proMMP-2 which exist in a complex form with TIMP-2.