Hypomyelination, hypodontia and craniofacial abnormalities in a Polr3b mouse model of leukodystrophy

RNA polymerase III (Pol III)-related hypomyelinating leukodystrophy (POLR3-HLD), also known as 4H leukodystrophy, is a severe neurodegenerative disease characterized by the cardinal features of hypomyelination, hypodontia and hypogonadotropic hypogonadism. POLR3-HLD is caused by biallelic pathogenic variants in genes encoding Pol III subunits. While approximately half of all patients carry mutations in POLR3B encoding the RNA polymerase III subunit B, there is no in vivo model of leukodystrophy based on mutation of this Pol III subunit. Here, we determined the impact of POLR3BΔ10 (Δ10) on Pol III in human cells and developed and characterized an inducible/conditional mouse model of leukodystrophy using the orthologous Δ10 mutation in mice. The molecular mechanism of Pol III dysfunction was determined in human cells by affinity purification-mass spectrometry and western blot. Postnatal induction with tamoxifen induced expression of the orthologous Δ10 hypomorph in triple transgenic Pdgfrα-Cre/ERT; R26-Stopfl-EYFP; Polr3bfl mice. CNS and non-CNS features were characterized using a variety of techniques including microCT, ex vivo MRI, immunofluorescence, immunohistochemistry, spectral confocal reflectance microscopy and western blot. Lineage tracing and time series analysis of oligodendrocyte subpopulation dynamics based on co-labelling with lineage-specific and/or proliferation markers were performed. Proteomics suggested that Δ10 causes a Pol III assembly defect, while western blots demonstrated reduced POLR3BΔ10 expression in the cytoplasm and nucleus in human cells. In mice, postnatal Pdgfrα-dependent expression of the orthologous murine mutant protein resulted in recessive phenotypes including severe hypomyelination leading to ataxia, tremor, seizures and limited survival, as well as hypodontia and craniofacial abnormalities. Hypomyelination was confirmed and characterized using classic methods to quantify myelin components such as myelin basic protein and lipids, results which agreed with those produced using modern methods to quantify myelin based on the physical properties of myelin membranes. Lineage tracing uncovered the underlying mechanism for the hypomyelinating phenotype: defective oligodendrocyte precursor proliferation and differentiation resulted in a failure to produce an adequate number of mature oligodendrocytes during postnatal myelinogenesis. In summary, we characterized the Polr3bΔ10 mutation and developed an animal model that recapitulates features of POLR3-HLD caused by POLR3B mutations, shedding light on disease pathogenesis, and opening the door to the development of therapeutic interventions.

Biallelic pathogenic variants in POLR3D alter tRNA transcription and cause a hypomyelinating leukodystrophy: A case report

RNA polymerase III-related leukodystrophy (POLR3-related leukodystrophy) is a rare, genetically determined hypomyelinating disease arising from biallelic pathogenic variants in genes encoding subunits of RNA polymerase III (Pol III). Here, we describe the first reported case of POLR3-related leukodystrophy caused by biallelic pathogenic variants in POLR3D, encoding the RPC4 subunit of Pol III. The individual, a female, demonstrated delays in walking and expressive and receptive language as a child and later cognitively plateaued. Additional neurological features included cerebellar signs (e.g., dysarthria, ataxia, and intention tremor) and dysphagia, while non-neurological features included hypodontia, hypogonadotropic hypogonadism, and dysmorphic facial features. Her MRI was notable for diffuse hypomyelination with myelin preservation of early myelinating structures, characteristic of POLR3-related leukodystrophy. Exome sequencing revealed the biallelic variants in POLR3D, a missense variant (c.541C > T, p.P181S) and an intronic splice site variant (c.656-6G > A, p.?). Functional studies of the patient's fibroblasts demonstrated significantly decreased RNA-level expression of POLR3D, along with reduced expression of other Pol III subunit genes. Notably, Pol III transcription was also shown to be aberrant, with a significant decrease in 7SK RNA and several distinct tRNA genes analyzed. Affinity purification coupled to mass spectrometry of the POLR3D p.P181S variant showed normal assembly of Pol III subunits yet altered interaction of Pol III with the PAQosome chaperone complex, indicating the missense variant is likely to alter complex maturation. This work identifies biallelic pathogenic variants in POLR3D as a novel genetic cause of POLR3-related leukodystrophy, expanding the molecular spectrum associated with this disease, and proposes altered tRNA homeostasis as a factor in the underlying biology of this hypomyelinating disorder.

Hypomyelination caused by a novel homozygous pathogenic variant in FOLR1: complete clinical and radiological recovery with oral folinic acid therapy and review of the literature

BACKGROUND

Neurodegeneration due to cerebral folate transport deficiency is a rare autosomal recessive disorder caused by biallelic pathogenic variants in FOLR1. Onset typically occurs in late infancy and is characterized by psychomotor regression, epilepsy, and a hypomyelinating leukodystrophy on magnetic resonance imaging. If left untreated, progressive neurodegeneration occurs. However, early treatment with folinic acid has been shown to stabilize or reverse neurological features. Approximately thirty patients have been described worldwide. Here, we report the first two cases with genetically proven cerebral folate transport deficiency from South-Eastern Europe, describe the effect of oral folinic acid therapy on clinical and neuroradiological features and review the literature.

RESULTS

Two siblings presented in childhood with clinical and radiological findings consistent with a hypomyelinating leukodystrophy. Exome sequencing revealed a novel homozygous pathogenic variant in FOLR1 (c.465_466delinsTG; p.W156G), confirming the diagnosis of neurodegeneration due to cerebral folate transport deficiency. Folinic acid treatment was promptly initiated in both patients. The younger sibling was treated early in disease course at 2 years of age, and demonstrated complete recovery in clinical and MRI features. The older sibling, who was 8 years of age at the time of diagnosis and treatment, demonstrated partial but substantial improvements.

CONCLUSION

We present the first account in the literature that early treatment initiation with oral folinic acid alone can result in complete neurological recovery of both clinical and radiological abnormalities in neurodegeneration due to cerebral folate deficiency. Moreover, through the report of these patients along with review of the literature, we provide information about the natural history of the disease with comparison of treatment effects at different stages of disease progression. This report also reinforces the importance of universal access to genetic testing to ensure prompt diagnoses for treatable disorders.

Solving inherited white matter disorder etiologies in the neurology clinic: Challenges and lessons learned using next-generation sequencing

Introduction

Rare neurodevelopmental disorders, including inherited white matter disorders or leukodystrophies, often present a diagnostic challenge on a genetic level given the large number of causal genes associated with a range of disease subtypes. This study aims to demonstrate the challenges and lessons learned in the genetic investigations of leukodystrophies through presentation of a series of cases solved using exome or genome sequencing.

Methods

Each of the six patients had a leukodystrophy associated with hypomyelination or delayed myelination on MRI, and inconclusive clinical diagnostic genetic testing results. We performed next generation sequencing (case-based exome or genome sequencing) to further investigate the genetic cause of disease.

Results

Following different lines of investigation, molecular diagnoses were obtained for each case, with patients harboring pathogenic variants in a range of genes including TMEM106B, GJA1, AGA, POLR3A, and TUBB4A. We describe the lessons learned in reaching the genetic diagnosis, including the importance of (a) utilizing proper multi-gene panels in clinical testing, (b) assessing the reliability of biochemical assays in supporting diagnoses, and (c) understanding the limitations of exome sequencing methods in regard to CNV detection and region coverage in GC-rich areas.

Discussion

This study illustrates the importance of applying a collaborative diagnostic approach by combining detailed phenotyping data and metabolic results from the clinical environment with advanced next generation sequencing analysis techniques from the research environment to increase the diagnostic yield in patients with genetically unresolved leukodystrophies.

Protection from radiation-induced neuroanatomical deficits by CCL2-deficiency is dependent on sex

PURPOSE

Cranial radiation therapy for the treatment of paediatric brain tumours results in changes to brain development that are detectable with magnetic resonance imaging (MRI). We have previously demonstrated similar structural changes in both humans and mice. The goal of the current study was to examine the role of inflammation in this response. Since neuroanatomical volume deficits in paediatric survivors are more pronounced in females, we also evaluated possible dependence on sex.

EXPERIMENTAL DESIGN

Male mice deficient in the C-C chemokine ligand 2 gene (Ccl2; previously Mcp-1) have been shown by others to have a muted neuroinflammatory response after irradiation. We irradiated Ccl2^-/- (HOM; females[f]=12, males[m]=13), Ccl2^+/- (HET; f=13, m=16), and Ccl2^+/+ (WT; f=11, m=13) mice with a whole brain dose of 7 Gy during infancy. Control mice (with approximately equal groups sizes) were anaesthetized but not irradiated. In vivo MR images were acquired at 4 time points up to 3 months following irradiation, and deformation-based morphometry was used to identify volume differences.

RESULTS

Irradiation of WT mice resulted in a deficit in neuroanatomical growth with limited sex dependence. HOM and HET males were significantly protected from this radiation-induced damage, while HOM and HET females were not. We conclude that interventions aimed at mitigating the effects of cranial radiation therapy in paediatric cancer survivors by modulating inflammatory response will need to consider patient sex.

Distinguishing severe phenotypes associated with pathogenic variants in POLR3A

A recent report by Majethia and Girisha described a patient with biallelic pathogenic variants in POLR3A and Wiedemann-Rautenstrauch syndrome. In this correspondence, we compare the features of this patient to that of a cohort of patients with severe POLR3-related leukodystrophy and a similar genotype and clinical course. We comment on the phenotyping and classification of POLR3-related disorders.

POLR3-Related Leukodystrophy: Exploring Potential Therapeutic Approaches

Leukodystrophies are a class of rare inherited central nervous system (CNS) disorders that affect the white matter of the brain, typically leading to progressive neurodegeneration and early death. Hypomyelinating leukodystrophies are characterized by the abnormal formation of the myelin sheath during development. POLR3-related or 4H (hypomyelination, hypodontia, and hypogonadotropic hypogonadism) leukodystrophy is one of the most common types of hypomyelinating leukodystrophy for which no curative treatment or disease-modifying therapy is available. This review aims to describe potential therapies that could be further studied for effectiveness in pre-clinical studies, for an eventual translation to the clinic to treat the neurological manifestations associated with POLR3-related leukodystrophy. Here, we discuss the therapeutic approaches that have shown promise in other leukodystrophies, as well as other genetic diseases, and consider their use in treating POLR3-related leukodystrophy. More specifically, we explore the approaches of using stem cell transplantation, gene replacement therapy, and gene editing as potential treatment options, and discuss their possible benefits and limitations as future therapeutic directions.

Endocrine and Growth Abnormalities in 4H Leukodystrophy Caused by Variants in POLR3A, POLR3B, and POLR1C

CONTEXT

4H or POLR3-related leukodystrophy is an autosomal recessive disorder typically characterized by hypomyelination, hypodontia, and hypogonadotropic hypogonadism, caused by biallelic pathogenic variants in POLR3A, POLR3B, POLR1C, and POLR3K. The endocrine and growth abnormalities associated with this disorder have not been thoroughly investigated to date.

OBJECTIVE

To systematically characterize endocrine abnormalities of patients with 4H leukodystrophy.

DESIGN

An international cross-sectional study was performed on 150 patients with genetically confirmed 4H leukodystrophy between 2015 and 2016. Endocrine and growth abnormalities were evaluated, and neurological and other non-neurological features were reviewed. Potential genotype/phenotype associations were also investigated.

SETTING

This was a multicenter retrospective study using information collected from 3 predominant centers.

PATIENTS

A total of 150 patients with 4H leukodystrophy and pathogenic variants in POLR3A, POLR3B, or POLR1C were included.

MAIN OUTCOME MEASURES

Variables used to evaluate endocrine and growth abnormalities included pubertal history, hormone levels (estradiol, testosterone, stimulated LH and FSH, stimulated GH, IGF-I, prolactin, ACTH, cortisol, TSH, and T4), and height and head circumference charts.

RESULTS

The most common endocrine abnormalities were delayed puberty (57/74; 77% overall, 64% in males, 89% in females) and short stature (57/93; 61%), when evaluated according to physician assessment. Abnormal thyroid function was reported in 22% (13/59) of patients.

CONCLUSIONS

Our results confirm pubertal abnormalities and short stature are the most common endocrine features seen in 4H leukodystrophy. However, we noted that endocrine abnormalities are typically underinvestigated in this patient population. A prospective study is required to formulate evidence-based recommendations for management of the endocrine manifestations of this disorder.

Migration Stimulating Factor (MSF): Its Role in the Tumour Microenvironment

Migration Stimulating Factor (MSF) is a 70 kDa truncated isoform of fibronectin (FN); its mRNA is generated from the FN gene by an unusual two-stage processing. Unlike full-length FN, MSF is not a matrix molecule but a soluble protein which displays cytokine-like activities not displayed by any other FN isoform due to steric hindrance. There are two isoforms of MSF; these are referred to as MSF+aa and MSF-aa, while the term MSF is used to include both.MSF was first identified as a motogen secreted by foetal and cancer-associated fibroblasts in tissue culture. It is also produced by sprouting (angiogenic) endothelial cells, tumour cells and activated macrophages. Keratinocytes and resting endothelial cells secrete inhibitors of MSF that have been identified as NGAL and IGFBP-7, respectively. MSF+aa and MSF-aa show distinct functionality in that only MSF+aa is inhibited by NGAL.MSF is present in 70-80% of all tumours examined, expressed by the tumour cells as well as by fibroblasts, endothelial cells and macrophages in the tumour microenvironment (TME). High MSF expression is associated with tumour progression and poor prognosis in all tumours examined, including breast carcinomas, non-small cell lung cancer (NSCLC), salivary gland tumours (SGT) and oral squamous cell carcinomas (OSCC). Epithelial and stromal MSF carry independent prognostic value. MSF is also expressed systemically in cancer patients, being detected in serum and produced by fibroblast from distal uninvolved skin. MSF-aa is the main isoform associated with cancer, whereas MSF+aa may be expressed by both normal and malignant tissues.The expression of MSF is not invariant; it may be switched on and off in a reversible manner, which requires precise interactions between soluble factors present in the TME and the extracellular matrix in contact with the cells. MSF expression in fibroblasts may be switched on by a transient exposure to several molecules, including TGFβ1 and MSF itself, indicating an auto-inductive capacity.Acting by both paracrine and autocrine mechanisms, MSF stimulates cell migration/invasion, induces angiogenesis and cell differentiation and alters the matrix and cellular composition of the TME. MSF is also a survival factor for sprouting endothelial cells. IGD tri- and tetra-peptides mimic the motogenic and angiogenic activities of MSF, with both molecules inhibiting AKT activity and requiring αvβ3 functionality. MSF is active at unprecedently low concentrations in a manner which is target cell specific. Thus, different bioactive motifs and extracellular matrix requirements apply to fibroblasts, endothelial cells and tumour cells. Unlike other motogenic and angiogenic factors, MSF does not affect cell proliferation but it stimulates tumour growth through its angiogenic effect and downstream mechanisms.The epithelial-stromal pattern of expression and range of bioactivities displayed puts MSF in the unique position of potentially promoting tumour progression from both the "seed" and the "soil" perspectives.

Expanding the phenotypic and molecular spectrum of RNA polymerase III-related leukodystrophy

Objective

To expand the phenotypic spectrum of severity of POLR3-related leukodystrophy and identify genotype-phenotype correlations through study of patients with extremely severe phenotypes.

Methods

We performed an international cross-sectional study on patients with genetically proven POLR3-related leukodystrophy and atypical phenotypes to identify 6 children, 3 males and 3 females, with an extremely severe phenotype compared with that typically reported. Clinical, radiologic, and molecular features were evaluated for all patients, and functional and neuropathologic studies were performed on 1 patient.

Results

Each patient presented between 1 and 3 months of age with failure to thrive, severe dysphagia, and developmental delay. Four of the 6 children died before age 3 years. MRI of all patients revealed a novel pattern with atypical characteristics, including progressive basal ganglia and thalami abnormalities. Neuropathologic studies revealed patchy areas of decreased myelin in the cerebral hemispheres, cerebellum, brainstem, and spinal cord, with astrocytic gliosis in the white matter and microglial activation. Cellular vacuolization was observed in the thalamus and basal ganglia, and neuronal loss was evident in the putamen and caudate. Genotypic similarities were also present between all 6 patients, with one allele containing a POLR3A variant causing a premature stop codon and the other containing a specific intronic splicing variant (c.1771-7C>G), which produces 2 aberrant transcripts along with some wild-type transcript.

Conclusions

We describe genotype-phenotype correlations at the extreme end of severity of the POLR3-related leukodystrophy spectrum and shed light on the complex disease pathophysiology.

One-pot polymer brush synthesis via simultaneous isocyanate coupling chemistry and “grafting from” RAFT polymerization

One-pot ‘grafting from’ of polystyrene on polydopamine particles was investigated using a newly developed carbonyl-azide reversible addition–fragmentation chain transfer (RAFT) agent.

Adiponectin, an anti-carcinogenic hormone? A systematic review on breast, colorectal, liver and prostate cancer

Adiponectin is an adipose tissue-derived hormone, expressed almost exclusively in adipose tissue, with significant antidiabetic, anti-atherosclerotic, anti-inflammatory and anti-proliferative properties. The anti-carcinogenic effects of adiponectin result from two main mechanisms: a modulation in the signaling pathways involved in proliferation process and a subtle regulation of the apoptotic response. In this review, we present recent findings on the association of adiponectin with the risk of several malignancies (breast, colorectal, liver and prostate cancers), as well as data on underlying molecular mechanisms by which adiponectin plays a substantial role in cancer pathogenesis.

[Headaches in a 21-year-old man with Goodpasture disease]

The case of a 21-year old man who died due to an intracranial thrombosis just after diagnosis of Goodpasture's disease, is reported. Discussion deals with the putative mechanisms, which could be responsible for the thrombosis.

Assessment of vascularity as an index of angiogenesis in periradicular granulomas. Comparison with oral carcinomas and normal tissue counterparts

AIM

To quantify vascularity in periradicular granulomas using different endothelial markers, and assess its value as an index of angiogenesis by comparing granulomas with healthy periodontal ligament (PDL). To use oral tumours, compared with adjacent normal mucosa, as positive controls.

METHODOLOGY

Paraffin-embedded sections were stained with antibodies to von Willebrand factor (vWF), a pan-endothelial marker, and CD105, a putative marker for angiogenic vessels. Vascularity was quantified by different methods reflecting vessel volume and density.

RESULTS

Irrespective of the marker or method used, vascularity values were similar in periradicular granuloma and PDL. Both tissues were highly vascularized, with levels similar to those found in oral squamous cell carcinoma. Vascularity was significantly higher in the latter than in normal mucosa. Fewer vessels were positive for CD105 than for vWF in the normal mucosa, whereas similar numbers were found in the other tissues examined.

CONCLUSIONS

A comparison of vascularity in oral tumours and normal oral mucosa provided evidence of angiogenesis in the former. Staining with CD105 added limited value to staining with vWF in these tissues. In contrast, a comparison of periradicular granuloma and PDL failed to demonstrate evidence of angiogenesis in the granuloma. As all vessels were similarly stained with vWF and CD105 in granuloma and PDL, a possible hypothesis is that all vessels are newly formed in these tissues. A more plausible alternative is that CD105 expression may reflect the metabolic activity or intrinsic characteristics of the tissues, rather than the presence of angiogenic vessels.

Functional characterisation of the regulation of CAAT enhancer binding protein alpha by GSK-3 phosphorylation of Threonines 222/226

BACKGROUND

Glycogen Synthase Kinase-3 (GSK3) activity is repressed following insulin treatment of cells. Pharmacological inhibition of GSK3 mimics the effect of insulin on Phosphoenolpyruvate Carboxykinase (PEPCK), Glucose-6 Phosphatase (G6Pase) and IGF binding protein-1 (IGFBP1) gene expression. CAAT/enhancer binding protein alpha (C/EBPalpha) regulates these gene promoters in liver and is phosphorylated on two residues (T222/T226) by GSK3, although the functional outcome of the phosphorylation has not been established. We aimed to establish whether CEBPalpha is a link between GSK3 and these gene promoters.

RESULTS

C/EBPalpha represses the IGFBP1 thymine-rich insulin response element (TIRE), but mutation of T222 or T226 of C/EBPalpha to non-phosphorylatable alanines has no effect on C/EBPalpha activity in liver cells (towards the TIRE or a consensus C/EBP binding sequence). Phosphorylation of T222/T226 is decreased by GSK3 inhibition, suggesting GSK3 does phosphorylate T222/226 in intact cells. However, phosphorylation was not altered by treatment of liver cells with insulin. Meanwhile C/EBPalpha activity in 3T3 L1 preadipocytes was enhanced by mutation of T222/T226 and/or S230 to alanine residues. Finally, we demonstrate that C/EBPalpha is a very poor substrate for GSK3 in vitro and in cells.

CONCLUSION

The work demonstrates an important role for this domain in the regulation of C/EBPalpha activity in adipocytes but not hepatocytes, however GSK3 phosphorylation of these residues does not mediate regulation of this C/EBP activity. In short, we find no evidence that C/EBPalpha activity is regulated by direct phosphorylation by GSK3.

IL-1ra and IL-1 production in human oral mucosal epithelial cells in culture: differential modulation by TGF-beta1 and IL-4

Regulatory cytokines mediate the participation of oral mucosal epithelial cells (OMEC) in local immune responses. The aim of this study was to characterize the isoforms of IL-1 receptor antagonist (IL-1ra) in cultured human primary OMECs and to compare its production with that of IL-1 alpha (IL-1alpha) and IL-1 beta (IL-1beta). Western blot analysis showed that IL-1ra was 22 kDa in size hence slightly smaller than monocyte IL-1ra (25 kDa). A minor form of 20 kDa was also found in unstimulated cell culture lysates. In culture supernatants, IL-1 bioactivity increased after IL-1ra neutralization, indicating that the baseline production of IL-1ra is biologically relevant. Immunohistochemistry showed a relation between IL-1ra and involucrin expressions, suggesting that intracytoplasmic IL-1ra may be involved in cell terminal differentiation. In unstimulated culture lysates, there was far more IL-1ra than IL-1alpha and IL-1beta. TGF-beta1 markedly increased the IL-1ra/IL-1beta ratio from 93.6 : 1 to 300 : 1. IL-4, which is generally described as an anti-inflammatory cytokine, increased IL-1 but not IL-1ra production. TNF-alpha increased intracellular production of the three IL-1 members. IL-1ra levels were lower in supernatants than in lysates of cultured cells. Our results show that human OMECs constitutively produce significant amounts of a biologically active form of IL-1ra. TGF-beta1 mu(p)-regulation points to a positive amplification loop and IL-4 to a down-regulation loop, both including Th2 cells and OMECs. They may be important in oral tolerance and IgA production, respectively.

Increased serum levels of interleukin 10 in Sjögren's syndrome; correlation with increased IgG1

OBJECTIVE

To determine levels of interleukin 10 (IL-10) and IgG subclasses in serum from 53 patients with primary Sjögren's syndrome (SS).

METHODS

Serum levels of IL-10 were measured using specific sandwich ELISA in 25 patients with "definite" SS, 28 with "possible" SS, and 32 healthy controls. Interferon-gamma (IFN-gamma) and transforming growth factor-beta1 (TGF-beta1) were also measured by immunoassays. Immunoglobulin classes, IgG subclasses, and C-reactive protein were measured by nephelometry.

RESULTS

Circulating IL-10 was elevated in 25 patients. The increase reached significance in the group with possible SS (p = 0.03) versus controls. In the group with definite SS, IL-10 level was correlated with IgG1 level (p = 0.01, r = 0.67) and with focus score (p = 0.01). IFN-gamma was undetectable in most patients. TGF-beta1 was higher (not significantly) in possible SS than in definite SS.

CONCLUSION

IL-10 is increased in SS and may account for the overproduction of IgG1 in the syndrome. High IL-10 in the absence of increased IgG1 in possible SS suggests that IL-10 may be necessary but not sufficient for IgG1 overproduction and that other factors are involved. Whereas the correlation of IL-10 level with focus score was expected, it is intriguing that IL-10 was more frequently increased in the incomplete (possible) form of SS than the complete (definite) form. Elevated IL-10 may characterize the lower stage of eccrine dysfunction and perhaps contributes to limiting its severity.

IL-1 receptor antagonist (IL-1RA) gene polymorphism in Sjögren's syndrome and rheumatoid arthritis

The gene encoding interleukin-1 receptor antagonist (IL-1ra) has a variable allelic polymorphism. The IL1RN*2 allele was recently described as a factor of severity in several autoimmune diseases and was paradoxically associated with increased production of IL-1ra by monocytes in vitro. We studied this polymorphism in 36 patients with possible or definite primary Sjögren's syndrome and found that IL1RN*2 was significantly more frequent in the definite than in the possible form. In rheumatoid arthritis, the frequency of the allele was not different from that of controls. The serum levels of IL-1ra were markedly higher in Sjögren patients than in those of healthy subjects. By contrast, the salivary IL-1ra levels were decreased. Patients with the allele generally had lower salivary levels and higher serum levels than patients without the allele. In the group of patients with the definite syndrome, CRP and TGF-beta 1, two in vitro stimulators of IL-1ra production, were correlated with IL-1ra serum levels. Our results suggest that IL1RN*2 is a marker of more severe forms of Sjögren's syndrome. Its effect on salivary and serum IL-1ra may be distinct, suggesting separate regulatory mechanisms.

IL-1 receptor antagonist in saliva; characterization in normal saliva and reduced concentration in Sjögren's syndrome (SS)

The characterization of a salivary factor cross-reacting with IL-1 receptor antagonist (IL-1Ra) is described. The apparent molecular weights of two species were 23 kD, consistent with the secreted peptide (sIL-1Ra), and 20 kD, consistent with the intracellular peptide (icIL-1Ra). It had an inhibitory activity on IL-1-stimulated fibroblasts, which is characteristic of IL-1Ra. Its source was the oral mucosa and not the salivary glands. Saliva from patients with SS contained significantly less IL-1Ra than saliva from controls. The decrease was marked in patients with early dental loss but whose xerostomia was still partial. In SS, the salivary IL-1/IL-1Ra imbalance may promote inflammatory lesions in the mouth and impede mucosal cell differentiation.

Preexposure of mouse peritoneal macrophages to lipopolysaccharide and other stimuli enhances the nitric oxide response to secondary stimuli

The aim of this study was to compare the regulation of the production of tumor necrosis factor-alpha (TNF-alpha) and secondary nitric oxide (NO) in macrophages submitted to a sequence of two stimulations. Pre-exposure for 18 h of mouse thioglycollate-elicited peritoneal macrophages to low doses (1-10 ng/ml) of lipopolysaccharide (LPS), in the presence or absence of serum, induces on one hand a desensitization (endotoxin tolerance) for secondary TNF-alpha responses to LPS and, on the other hand, a 4 fold increase (priming) of secondary NO responses. Preexposure to components from Gram-positive bacteria (lipoteichoic acid, peptidoglycan) and to a synthetic lipid structurally related to lipid A (compound M4), induced similar effects. In contrast to the desensitization for TNF-alpha secretion, the priming for NO production was not mimicked by sodium nitroprusside, a generator of NO. The results suggest that concomitant but distinct activation pathways induced by LPS and other agents can be dissociated by serum-independent modulation processes elicited by pre-exposure of the cells to LPS itself, or to other stimuli.