Genetic basis of tissue specificity of vasculitis in MRL/lpr mice

Emerging Molecular and Synaptic Targets for the Management of Chronic Pain Caused by Systemic Lupus Erythematosus

Patients with systemic lupus erythematosus (SLE) frequently experience chronic pain due to the limited effectiveness and safety profiles of current analgesics. Understanding the molecular and synaptic mechanisms underlying abnormal neuronal activation along the pain signaling pathway is essential for developing new analgesics to address SLE-induced chronic pain. Recent studies, including those conducted by our team and others using the SLE animal model (MRL/lpr lupus-prone mice), have unveiled heightened excitability in nociceptive primary sensory neurons within the dorsal root ganglia and increased glutamatergic synaptic activity in spinal dorsal horn neurons, contributing to the development of chronic pain in mice with SLE. Nociceptive primary sensory neurons in lupus animals exhibit elevated resting membrane potentials, and reduced thresholds and rheobases of action potentials. These changes coincide with the elevated production of TNFα and IL-1β, as well as increased ERK activity in the dorsal root ganglion, coupled with decreased AMPK activity in the same region. Dysregulated AMPK activity is linked to heightened excitability in nociceptive sensory neurons in lupus animals. Additionally, the increased glutamatergic synaptic activity in the spinal dorsal horn in lupus mice with chronic pain is characterized by enhanced presynaptic glutamate release and postsynaptic AMPA receptor activation, alongside the reduced activity of glial glutamate transporters. These alterations are caused by the elevated activities of IL-1β, IL-18, CSF-1, and thrombin, and reduced AMPK activities in the dorsal horn. Furthermore, the pharmacological activation of spinal GPR109A receptors in microglia in lupus mice suppresses chronic pain by inhibiting p38 MAPK activity and the production of both IL-1β and IL-18, as well as reducing glutamatergic synaptic activity in the spinal dorsal horn. These findings collectively unveil crucial signaling molecular and synaptic targets for modulating abnormal neuronal activation in both the periphery and spinal dorsal horn, offering insights into the development of analgesics for managing SLE-induced chronic pain.

Activation of microglial GPR109A alleviates thermal hyperalgesia in female lupus mice by suppressing IL-18 and glutamatergic synaptic activity

Many patients with systemic lupus erythematosus (SLE) live with chronic pain despite advances in medical management in reducing mortality related to SLE. Few animal studies have addressed mechanisms and treatment for chronic pain caused by SLE. In this study, we provide the first evidence for the analgesic effects of a GPR109A specific agonist (MK1903) and its action mechanisms in thermal hyperalgesia in female MRL/lpr mice, an SLE mouse model. Specifically, we show that MRL/lpr mice had a higher sensitivity to thermal stimuli at age 11-16 weeks, which was accompanied with significantly microglial and astrocytic activation, increases in p38 MAPK and glutamatergic synaptic activities in the spinal dorsal horn. We demonstrate that thermal hyperalgesia in MRL/lpr mice was significantly attenuated by intrathecal injection of MK1903. GPR109A was expressed in spinal microglia but not astrocytes or neurons. Its expression was significantly increased in MRL/lpr mice with thermal hyperalgesia. Activation of GPR109A receptors in microglia attenuated glutamatergic synaptic activity via suppressing production of interleukin-18 (IL-18). We provide evidence that activation of GPR109A attenuated thermal hyperalgesia in the SLE animal model via suppressing p38 MAPK activity and production of IL-18. Our study suggests that targeting the microglial GPR109A is a potent approach for reversing spinal neuroinflammation, abnormal excitatory synaptic activity, and management of thermal hyperalgesia caused by SLE.

Immune Relevant and Immune Deficient Mice: Options and Opportunities in Translational Research

In 1989 ILAR published a list and description of immunodeficient rodents used in research. Since then, advances in understanding of molecular mechanisms; recognition of genetic, epigenetic microbial, and other influences on immunity; and capabilities in manipulating genomes and microbiomes have increased options and opportunities for selecting mice and designing studies to answer important mechanistic and therapeutic questions. Despite numerous scientific breakthroughs that have benefitted from research in mice, there is debate about the relevance and predictive or translational value of research in mice. Reproducibility of results obtained from mice and other research models also is a well-publicized concern. This review summarizes resources to inform the selection and use of immune relevant mouse strains and stocks, aiming to improve the utility, validity, and reproducibility of research in mice. Immune sufficient genetic variations, immune relevant spontaneous mutations, immunodeficient and autoimmune phenotypes, and selected induced conditions are emphasized.

Monitoring of Blood Vessel Density Using Contrast-Enhanced High Frequency Ultrasound May Facilitate Early Diagnosis of Lymph Node Metastasis

Time-dependent alterations in the ultrasonography characteristics of lymph nodes during early-stage metastasis have not been compared with those of tumor-draining lymph nodes that do not develop tumor; this is partly due to the absence of an appropriate experimental model. In a previous study of lymph nodes with experimental early-stage metastasis, we used contrast-enhanced high-frequency ultrasound to demonstrate that an increase in lymph node blood vessel density preceded any changes in lymph node volume. In the present study, we used an experimental model of lymph node metastasis in which tumor cells metastasized from the subiliac lymph node to the proper axillary lymph node (the tumor-draining lymph node). We utilized contrast-enhanced high-frequency ultrasound to perform a longitudinal analysis of tumor-draining lymph nodes, comparing those at an early-stage of metastasis with those that did not develop detectable metastasis. We found that the normalized blood vessel density of an early-stage metastatic lymph node exhibited a progressive rise, whereas that of a tumor-draining lymph node not containing tumor began to increase later. For both types of lymph nodes, the normalized blood vessel density on the final day of experiments showed a trend towards being higher than that measured in controls. We further found that mice with an initially low value for lymph node blood vessel density subsequently showed a larger increase in the blood vessel density of the metastatic lymph node; this differed significantly from measurements in controls. The present study indicates that a longitudinal analysis of the blood vessel densities of tumor-draining lymph nodes, made using contrast-enhanced high-frequency ultrasound imaging, may be a potentially promising method for detecting early-stage lymph node metastasis in selected patients. Furthermore, our findings suggest that tumor in an upstream lymph node may induce alteration of the vascular structures in draining lymph nodes that do not contain tumor.

Chronic pain and impaired glial glutamate transporter function in lupus-prone mice are ameliorated by blocking macrophage colony-stimulating factor-1 receptors

Systemic lupus erythematosus (SLE) is a multi-organ disease of unknown etiology in which the normal immune responses are directed against the body's own healthy tissues. Patients with SLE often suffer from chronic pain. Currently, no animal studies have been reported about the mechanisms underlying pain in SLE. In this study, the development of chronic pain in MRL lupus-prone (MRL/lpr) mice, a well-established lupus mouse model, was characterized for the first time. We found that female MRL/lpr mice developed thermal hyperalgesia at the age of 13 weeks, and mechanical allodynia at the age of 16 weeks. MRL/lpr mice with chronic pain had activation of microglia and astrocytes, over-expression of macrophage colony-stimulating factor-1 (CSF-1) and interleukin-1 beta (IL-1β), as well as suppression of glial glutamate transport function in the spinal cord. Intrathecal injection of either the CSF-1 blocker or IL-1 inhibitor attenuated thermal hyperalgesia in MRL/lpr mice. We provide evidence that the suppressed activity of glial glutamate transporters in the spinal dorsal horn in MRL/lpr mice is caused by activation of the CSF-1 and IL-1β signaling pathways. Our findings suggest that targeting the CSF-1 and IL-1β signaling pathways or the glial glutamate transporter in the spinal cord is an effective approach for the management of chronic pain caused by SLE.

[Systemic vasculitides: some debatable aspects of the problem]

A new nomenclature of systemic vasculitides (SV) and current approaches to their treatment have necessitated the discussion of some debatable questions on this condition. The paper gives the data of examining 325 patients with different forms of SV, followed up in the Interregional Consulting Center for SV patients, and the results of testing the American College of Rheumatology classification criteria for SV and the authors' criteria, by taking into account the International Chapel Hill Consensus Conference, USA (1994 and 2011) guidelines for CV nomenclature. It discusses the etiological factors and pathogenetic components of SV, morphological aspects, and relationships between the local and systemic forms of SV. The findings were compared with the data available in the literature. It is concluded that differentially diagnostic criteria for CV should be elaborated to specify the stage of the disease, the activity and use of adapted therapy regimens.

A polygene network model for the complex pathological phenotypes of collagen disease

Almost 70 years after the description of 'collagen disease' by P. Klemperer et al., it is still controversial whether the diversity and similarity of pathological manifestations among the collagen diseases depends on ambiguity in diagnosis or is an intrinsic quality of the collagen diseases themselves. A genome wide analysis of the MRL mouse models of collagen disease may shed some light on the complex pathological manifestations. Study of the susceptibility loci to each type ofcollagen disease (such as glomerulonephritis, vasculitis, arthritis, sialoadenitis and dacryoadenitis) in the mice, revealed that these lesions developed because of a cumulative effect of multiple gene loci, none of which can induce the related phenotype alone. This may indicate that collagen disease develops in 'a polygenic system', as proposed by K. Mather in 1949. Each lesion in the mice developed because of an additive effect of the polygenes, which is also, in part, hierarchical. Some of the polygenes seemed to be common to those in other collagen diseases as well. Some of the positional candidate genes involved an allelic polymorphism in the coding or promoter regions, thus possibly causing a qualitative or quantitative difference in their function, respectively. As a result, a particular combination of the polygenes with such an allelic polymorphism may thus play a critical role in leading the cascade reaction to developing collagen disease, and also the regular variation in the pathological manifestations. We herein describe this as a polygene network of collagen disease.

Susceptibility Loci to Coronary Arteritis in Animal Model of Kawasaki Disease Induced withCandida albicans-Derived Substances

We have established an animal model of coronary arteritis which is histopathologically similar to that observed in cases of Kawasaki disease (KD), is a well-known childhood vasculitis syndrome. Coronary arteritis in this mouse model has been induced by intraperitoneal injection of Candida albicans -derived substances (CADS). Arteritis varied by mouse strain with the highest incidence by 71.1% (27/38) found in C3H/HeN mice, but absent in CBA/JN mice (0%, 0/27), suggesting association of genomic background to develop the disease. The present study aims to elucidate the susceptibility loci associated with coronary arteritis by using this animal model. The association of the onset of arteritis with polymorphic microsatellite markers between the two strains was examined using one hundred and fifteen of N1 backcross progeny [(CBAxC3H)F1xC3H]. Based on our analysis, arteritis-susceptibility loci with suggestive linkage were mapped on D1Mit171 and D1Mit245(map position 20.2 cM) on chromosome 1 (P=0.0019). These loci include several kinds of inflammatory cytokine receptors, such as interleukin 1 receptor and tumor necrosis factor receptor. We also found the cytokine response against CADS, levels of inflammatory cytokines interleukin-1 beta, tumor necrosis factor-alpha, and interleukin-6 in sera increased within 24 hr after CADS injection. Our results may indicate based on genomics that ligand-receptor interaction between these inflammatory cytokines and the receptors of these cytokines may affect the onset of arteritis.

Multiparametric and semiquantitative scoring systems for the evaluation of mouse model histopathology--a systematic review

BACKGROUND

Histopathology has initially been and is still used to diagnose infectious, degenerative or neoplastic diseases in humans or animals. In addition to qualitative diagnoses semiquantitative scoring of a lesion`s magnitude on an ordinal scale is a commonly demanded task for histopathologists. Multiparametric, semiquantitative scoring systems for mouse models histopathology are a common approach to handle these questions and to include histopathologic information in biomedical research.

RESULTS

Inclusion criteria for scoring systems were a first description of a multiparametric, semiquantiative scoring systems which comprehensibly describe an approach to evaluate morphologic lesion. A comprehensive literature search using these criteria identified 153 originally designed semiquantitative scoring systems for the analysis of morphologic changes in mouse models covering almost all organs systems and a wide variety of disease models. Of these, colitis, experimental autoimmune encephalitis, lupus nephritis and collagen induced osteoarthritis colitis were the disease models with the largest number of different scoring systems. Closer analysis of the identified scoring systems revealed a lack of a rationale for the selection of the scoring parameters or a correlation between scoring parameter value and the magnitude of the clinical symptoms in most studies.

CONCLUSION

Although a decision for a particular scoring system is clearly dependent on the respective scientific question this review gives an overview on currently available systems and may therefore allow for a better choice for the respective project.

Genomics of vasculitis: lessons from mouse models

A genome analysis of mouse models may shed some light on the complex clinicopathological manifestations of systemic vasculitis. In the study of susceptibility loci to vasculitis in MRL mouse models, we found that systemic vasculitis developed through the cumulative effect of multiple gene loci, each of which by itself did not have a significant effect in inducing the related phenotype, thus indicating a polygenic system. The mice developed vasculitis in an additive manner with a hierarchical effect. Some of the susceptibility loci seemed to be common to those in other collagen diseases. Moreover, the loci controlling tissue specificity of vasculitis were present. One of the positional candidate genes for vasculitis showed an allelic polymorphism in the coding region, thus possibly causing a qualitative difference in its function. As a result, a particular combination of polygenes with such an allelic polymorphism may thus play a critical role in leading the cascade reaction to develop vasculitis, and also a regular variation of systemic vasculitis. This is designated as the polygene network in systemic vasculitis. (J Jpn Coll Angiol, 2009, 49: 11-16).

Polygene network in collagen disease

The pathological findings in collagen disease, which was originally proposed by Klemperer et al. in 1942, show complex lesions with glomerulonephritis, vasculitis, polyarthritis and/or sialoadenitis etc. It is still controversial whether such diversity and similarity of the lesions among collagen diseases depend on an ambiguity in diagnosis or an intrinsic quality of the diseases. In the study of susceptibility loci to collagen disease in MRL mouse models, we learned that several lesions such as glomerulonephritis, vasculitis, arthritis and sialoadenitis developed in a cumulative effect of multiple gene loci, each of which by itself did not have a significant effect to induce the related phenotype, thus indicating a polygenic system. The mice developed each lesion in an additive manner with a hierarchical effect. Some of the susceptibility loci seemed to be common to those in other collagen diseases as well. Some of the positional candidate genes showed an allelic polymorphism in the coding region, possibly causing a qualitative difference in their function. As a result, a particular combination of polygenes with such an allelic polymorphism may thus play a critical role in leading the cascade reaction to develop lesions, and also a regular variation of collagen disease. This is designated as the polygene network in collagen disease.

A genetic locus controlling aging-sensitive regression of B lymphopoiesis in an autoimmune-prone MRL/lpr strain of mice

Aging readily affects immune system under the influence of environmental and/or intrinsic factors while accelerating the development of various immune disorders including autoimmune diseases. Little is known about molecular and cellular mechanisms connecting between immune senescence and development of autoimmune diseases. Here, we first show strain-specific and aging-sensitive onset of B-cell abnormality in a lupus-prone MRL/Mp.Fas(lpr) (MRL/lpr) strain of mice. This abnormality was characterized by the regression of B lymphopoiesis in the bone marrow of this strain. We next examined the association between the B-cell regression and onset of autoimmune diseases in aged (MRL/lpr x C3H/He.Fas(lpr)) F2 mice, in which pathologic phenotypes, such as glomerulonephritis, vasculitis, sialoadenitis and arthritis, variously developed. We also searched whole genome to identify genetic loci linked to the B-cell regression by using the same F2 mice. The B-cell regression manifested in the spleen of F2 mice was retrospectively evaluated by reverse transcriptase-based PCR quantification. The results demonstrated that the onset of autoimmune diseases in the F2 mice was not associated with the aging-sensitive B-cell regression. The genetic study identified a significant locus responsible for the B-cell regression in the vicinity of D5Mit233 (29 cM). This is first evidence for the presence of a genetic locus that affects B lymphopoiesis in an aging-sensitive manner.

A proposal concept of a polygene network in systemic vasculitis: lessons from MRL mouse models

In addition to the studies of cellular and molecular events in the pathogenesis of systemic vasculitis, a genome analysis of mouse models may shed some light on the complex clinicopathological manifestations of systemic vasculitis. In the study of susceptibility loci to vasculitis in MRL mouse models, we learned that systemic vasculitis developed in a cumulative effect of multiple gene loci, each of which by itself did not have a significant effect to induce the related phenotype, thus indicating a polygenic system. The mice developed vasculitis in an additive manner of multiple genes with a hierarchical effect. Some of the susceptibility loci seemed to be common to those in other collagen diseases as well. Moreover, the loci controlling tissue specificity of vasculitis were present. One of the positional candidate genes for vasculitis showed an allelic polymorphism in the coding region, thus possibly causing a qualitative difference in its function. As a result, a particular combination of polygenes with such an allelic polymorphism may thus play a critical role in leading the cascade reaction to develop vasculitis, and also a regular variation of systemic vasculitis. This is designated as the polygene network in systemic vasculitis.

Inhibition of osteoporosis in autoimmune disease prone MRL/Mpj-Fas(lpr) mice by N-3 fatty acids

OBJECTIVE

Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease involving the breakdown of cartilage and juxta-articular bone, which is often accompanied by decreased bone mineral density (BMD) and increased risk of fracture. Anti-inflammatory omega-3 fatty acids may prevent arthritis and bone loss in MRL/lpr mice model of arthritis and in humans.

METHODS

In this study, the effect of long term feeding of 10% dietary n-3 (fish oil (FO)) and n-6 (corn oil (CO)) fatty acids begun at 6 weeks of age on bone mineral density (BMD) in different bone regions in an MRL/lpr female mouse model of RA was measured at 6, 9, and 12 months of age by dual energy x-ray absorptiometry (DEXA). After sacrificing the mice at 12 months of age, antioxidant enzyme activities were measured in spleen, mRNA for receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG) was measured by RT-PCR in lymph nodes, and synovitis was measured in leg joints.

RESULTS

At 6, 9 and 12 months of age, BMD was significantly higher (p < 0.05) in distal femur, proximal tibia, and lumbar spine of FO fed mice than those of CO fed mice. Spleen catalase (CAT) and superoxide dismutase (SOD) activities were also significantly higher (p < 0.01) in FO fed mice than in CO fed mice. Histology of knee joints revealed mild synovitis in CO fed mice, which was not present in FO fed mice. RT-PCR analysis of lymph nodes revealed decreased RANKL mRNA (p < 0.001) expression and enhanced OPG mRNA expression (p < 0.01) in FO fed mice compared to CO fed mice.

CONCLUSIONS

These results suggest beneficial effects of long-term FO feeding in maintaining higher BMD and lower synovitis in this mouse model. These beneficial effects may be due, in part, to increased activity of antioxidant enzymes, decreased expression of RANKL, and increased expression of OPG in FO fed mice thereby altering the RANKL/OPG ratio. These significant beneficial effects on BMD suggest that FO may serve as an effective dietary supplement to prevent BMD loss in patients with RA.

Accelerating effect of an MRL gene locus on the severity and onset of arthropathy in DBA/1 mice

OBJECTIVE

To analyze the influence of the genetic background of an arthritis-prone strain of mice, MRL, on the spontaneous development of arthropathy in DBA/1 mice, which histopathologically resembles enthesopathy in humans, and to clarify the strain-specific gene loci and their interactions that confer susceptibility to arthropathy.

METHODS

MRL, DBA/1, (MRL x DBA/1)F(1), and (MRL x DBA/1)F(2) intercross mice were prepared, and the severity and onset of arthropathy of the ankle joints in individual mice were quantified (0-3 and 0-5 scale, respectively). A genome-wide scan of 271 male F(2) intercross mice with polymorphic microsatellite markers was performed.

RESULTS

Only male DBA/1, (MRL x DBA/1)F(1), and (MRL x DBA/1)F(2) mice developed arthropathy. The macroscopic and histopathologic findings of arthropathy in the F(2) mice were similar to those in the parental DBA/1 mice, but the onset was significantly earlier. In the quantitative trait locus analysis of male F(2) mice, 1 susceptibility locus for both the severity and early onset of the disease in the region of an MRL allele, Amd1, was located at marker D10Mit259 (map position 40.0 cM), which was common to 1 of the sialadenitis susceptibility loci in MRL mice, Asm1. Another susceptibility locus for the severity and early onset of arthropathy in the region of a DBA allele, Amd2, was located at D3Mit46 (29.5 cM). These loci manifested an additive effect on the development of arthropathy.

CONCLUSION

Arthropathy in DBA/1 mice is under the control of an allelic combination of gene loci, one of which is common to the locus for sialadenitis in MRL/MpJ-lpr/lpr mice.