Different Contributions of CDKAL1, KIF21B, and LRRK2/MUC19 Polymorphisms to SAPHO Syndrome, Rheumatoid Arthritis, Ankylosing Spondylitis, and Seronegative Spondyloarthropathy

Family aggregation and prevalence of other autoimmune diseases in SAPHO syndrome

Objective

SAPHO (Synovitis, Acne, Pustulosis, Hyperostosis and Osteitis) syndrome is a heterogeneous disease that clinically manifests as chronic inflammatory osteoarticular and dermatological lesions. Few reports have described familial clustering of SAPHO syndrome cases. This research aimed to illustrate the family aggregation of SAPHO syndrome and investigate the prevalence of autoimmune disorders among SAPHO syndrome patients and first-degree relatives in a large cohort.

Methods

We retrospectively reviewed the medical records of 233 SAPHO patients diagnosed at Peking Union Medical College Hospital. Direct phone calls were made to each first-degree relatives. All relatives of the patients who reported SAPHO syndrome were asked for a detailed outpatient evaluation.

Results

A total of 233 patients and 1227 first-degree relatives were recruited. Six (2.6 %) patients had positive SAPHO family history, including four mother-daughter pairs and two sister pairs. Twenty-one (9.0 %) patients presented at least one kind of autoimmune disease, including 12 rheumatoid arthritis and 4 ulcerative colitis cases. Fifty-eight (24.9 %) SAPHO syndrome patients had 68 (5.5 %) first-degree relatives with at least one autoimmune disorder. The palmoplantar pustulosis, psoriasis vulgaris, and rheumatoid arthritis prevalence in our subjects were each higher than reference rates.

Conclusion

This is the first evaluation of familial aggregation for SAPHO syndrome in a large cohort. SAPHO syndrome has a weak familial aggregation. There is a relatively high prevalence of coexisting autoimmune disease among patients with SAPHO syndrome and their first-degree relatives. These results would prompt physicians to screen SAPHO syndrome patients and their family members for concomitant autoimmune diseases.

Keypoints

This study suggesting a potential genetic component in the pathogenesis of SAPHO syndrome. This study is the first to evaluate the family aggregation of SAPHO syndrome in a large cohort.

SAPHO Syndrome Complicated by Ankylosing Spondylitis Successfully Treated With Tofacitinib: A Case Report

Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome, a type of chronic inflammatory disease, is rare and difficult to treat. Osteoarthropathy with skin involvement is the primary clinical manifestation of SAPHO syndrome. The unknown pathogenesis of SAPHO syndrome is speculated to be related to individual genetic differences, immune levels, microorganisms, and environmental factors. Tofacitinib, a novel small-molecule Janus kinase (JAK) inhibitor, has been used to treat rheumatoid arthritis. However, it also has great potential for the treatment of other immune diseases, including SAPHO syndrome. A 36-year-old man with chest and back pain for more than two months was admitted to our hospital. After admission, the patient developed a pustular rash and enteritis. SAPHO syndrome was diagnosed based on the above clinical manifestations, computed tomography (CT), and bone scintigraphy findings. Notably, the patient also had ankylosing spondylitis. Tofacitinib significantly improved the patient’s skin symptoms while preventing worsening of chest and back pain when adalimumab was discontinued. We report the first case of ankylosing spondylitis with SAPHO syndrome. In addition, it is also the first successful treatment thereof with tofacitinib. We hope to provide valuable information regarding the pathogenesis and treatment of SAPHO syndrome in this case.

Involvement of Cdkal1 in the etiology of type 2 diabetes mellitus and microvascular diabetic complications: a review

Diabetes Mellitus, being a polygenic disorder, have a set of risk genes involved in the onset of the insulin resistance, obesity and impaired insulin synthesis. Recent genome wide association studies (GWAS) shows the intimacy of CDK5 regulatory subunit Associated protein 1-Like 1 (Cdkal1) with the pathophysiology of the diabetes mellitus and its complications, although the exact molecular relation is still unknown. In this short review, we have summarized all the diverse biological roles of Cdkal1 in relation to the onset of diabetes mellitus. Variations in the Cdkal1 transcript are responsible for the accumulation of misfolded insulin and thus generating oxidative and ER stress in the pancreatic β-cells, leading to their destruction. Recent studies have shown that Cdkal1 has an intrinsic thiomethyl transferase activity, which is essential for proper posttranslational processing of pre-proinsulin to produce mature insulin. Moreover, Cdkal1 has also been claimed as an endogenous inhibitor of cdk5, which prevents the cdk5-induced interruption in insulin synthesis through PDX1 translocation from nucleus to cytosol. Recent clinical studies have identified the risk single nucleotide polymorphisms (SNPs) of Cdkal1 as one of the root causes for the onset of diabetic complications. To the best of our knowledge, it is the first comprehensive review which elaborates most of the potential Cdkal1-dependent molecular mechanisms studied yet. In this review, we present a compiled and concise summary about all the diverse roles of Cdkal1 in the context of type 2 diabetes mellitus and its associated complications. This review will be helpful to target Cdkal1 as a potential option for the management of type 2 diabetes mellitus in future.

Graphical abstract

Kinesin-4 KIF21B limits microtubule growth to allow rapid centrosome polarization in T cells

When a T cell and an antigen-presenting cell form an immunological synapse, rapid dynein-driven translocation of the centrosome toward the contact site leads to reorganization of microtubules and associated organelles. Currently, little is known about how the regulation of microtubule dynamics contributes to this process. Here, we show that the knockout of KIF21B, a kinesin-4 linked to autoimmune disorders, causes microtubule overgrowth and perturbs centrosome translocation. KIF21B restricts microtubule length by inducing microtubule pausing typically followed by catastrophe. Catastrophe induction with vinblastine prevented microtubule overgrowth and was sufficient to rescue centrosome polarization in KIF21B-knockout cells. Biophysical simulations showed that a relatively small number of KIF21B molecules can restrict mirotubule length and promote an imbalance of dynein-mediated pulling forces that allows the centrosome to translocate past the nucleus. We conclude that proper control of microtubule length is important for allowing rapid remodeling of the cytoskeleton and efficient T cell polarization.

The immune system is composed of many types of cells that can recognize foreign molecules and pathogens so they can eliminate them. When cells in the body become infected with a pathogen, they can process the pathogen’s proteins and present them on their own surface. Specialized immune cells can then recognize infected cells and interact with them, forming an ‘immunological synapse’. These synapses play an important role in immune response: they activate the immune system and allow it to kill harmful cells.

To form an immunological synapse, an immune cell must reorganize its internal contents, including an aster-shaped scaffold made of tiny protein tubes called microtubules. The center of this scaffold moves towards the immunological synapse as it forms. This re-orientation of the microtubules towards the immunological synapse is known as 'polarization' and it happens very rapidly, but it is not yet clear how it works.

One molecule involved in the polarization process is called KIF21B, a protein that can walk along microtubules, building up at the ends and affecting their growth. Whether KIF21B makes microtubules grow more quickly, or more slowly, is a matter of debate, and the impact microtubule length has on immunological synapse formation is unknown.

Here, Hooikaas, Damstra et al. deleted the gene for KIF21B from human immune cells called T cells to find out how it affected their ability to form an immunological synapse. Without KIF21B, the T cells grew microtubules that were longer than normal, and had trouble forming immunological synapses. When the T cells were treated with a drug that stops microtubule growth, their ability to form immunological synapses was restored, suggesting a role for KIF21B. To explore this further, Hooikaas, Damstra et al. replaced the missing KIF21B gene with a gene that coded for a version of the protein that could be seen using microscopy. This revealed that, when KIF21B reaches the ends of microtubules, it stops their growth and triggers their disassembly. Computational modelling showed that cells find it hard to reorient their microtubule scaffolding when the individual tubes are too long. It only takes a small number of KIF21B molecules to shorten the microtubules enough to allow the center of the scaffold to move.

Research has linked the KIF21B gene to autoimmune conditions like multiple sclerosis. Microtubules also play an important role in cell division, a critical process driving all types of cancer. Drugs that affect microtubule growth are already available, and a deeper understanding of KIF21B and microtubule regulation in immune cells could help to improve treatments in the future.

S-adenosylmethionine tRNA modification: unexpected/unsuspected implications of former/new players

S-adenosylmethionine supplies methyl groups to many acceptors, including lipids, proteins, RNA, DNA, and a wide range of small molecules. It acts as the precursor in the biosynthesis of metal ion chelating compounds, such as nicotianamine and phytosiderophores, of the polyamines spermidine and spermine and of some plant hormones. Finally, it is the source of catalytic 5′-deoxyadenosyl radicals.

Radical S-adenosylmethionine (SAM) enzymes (RS) represent one of the most abundant groups (more than 100,000) of enzymes, exerting a plethora of biological functions, some of which are still unknown.

In this work, we will focus on two RS: CDK5RAP1 and CDKAL1, both of which are involved in tRNA modifications that result in important tRNA folding and stability and in maintaining high translational fidelity. Based on this crucial role, their impairment can be important in the development of different human diseases.

Synovitis, acne, pustulosis, hyperostosis, and osteitis syndrome: review and update

Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome is a spectrum of heterogeneous diseases characterized by osteoarticular and dermatological manifestations. Osteitis and hyperostosis are core clinical manifestations in SAPHO syndrome, typically affecting multiple areas and possibly progressing to irreversible osteoarticular damage. Most patients with SAPHO have cutaneous involvement, mainly manifested as palmoplantar pustulosis and severe acne. Systemic manifestations are uncommon but occasionally reported. Epidemiological studies suggest the annual prevalence of SAPHO syndrome varies from 0.00144 in 100,000 in Japanese individuals to fewer than 1 in 10,000 in White individuals. The precise etiopathogenesis of SAPHO remains unclear, but it is generally considered an autoinflammatory syndrome that may be related to various etiologies, such as immune dysfunction, infection and genetic predisposition. Owing to the relapsing-remitting disease course, the goal of management is to improve clinical symptoms and prevent disease progression. Various treatments, including nonsteroidal anti-inflammatory drugs, conventional disease-modifying antirheumatic drugs, bisphosphonates, biologics, and antibiotics, are promising options for alleviating the disease.

Exosomal proteome from the serum, bone marrow, and palm and toe pustular skin tissues of a single patient with SAPHO syndrome

Exosome proteomic analysis may reveal differentially abundant proteins that are of significance for clarifying the pathogenesis of SAPHO (Synovitis, Acne, Pustulosis, Hyperostosis and Osteitis) syndrome. Exosomes were isolated from the serum, bone marrow and skin tissue of the palm and toe pustular areas in a unique patient with SAPHO syndrome. The exosomes were not different from those of healthy subjects in size (114.1 ± 73.7 nm) or morphology. Label-free exosome proteomic analysis identified 198 more abundant proteins and 183 less abundant compared with those of healthy subjects. Gene ontology enrichment analysis revealed that these proteins were involved in binding with a variety of biological molecules and participated in biological processes related to autoimmunity or inflammation. A total of 243 KEGG (Kyoto Encyclopedia of Gene and Genomes) pathways were enriched, of which 43 were related to immune function. It was speculated that five differentially abundant proteins, Mitogen-activated protein kinase 1 (MAPK1/MK01), Tyrosine protein kinase (SYK), Integrin beta-3 (ITB3), Serine/threonine-protein phosphatase 2a catalytic subunit alpha isoform (PP2AA) and Serine/threonine-protein phosphatase 2a 65 kDa regulatory subunit A beta isoform (2AAB), associated with multiple KEGG pathways, forms an interaction network that may be involved in the occurrence, development and prognosis of SAPHO syndrome. SIGNIFICANCE: Exosomes of SAPHO syndrome patient were not significantly different from those of healthy subjects in size and morphology. Label-free proteomic analysis of exosomal proteins in patient with SAPHO syndrome speculated 5 proteins MAPK1, SYK, ITB3, PP2AA and 2AAB, which may be involved in the occurrence, development and prognosis of SAPHO syndrome by binding with other biological molecules. It is speculated for the first time that proteins Histone H2A type 1-J and Histone H4 were related to SAPHO syndrome. Clinic relevance. Exosome proteomics can suggest novel pathological data in patients with SAPHO.

The tRNA-associated dysregulation in immune responses and immune diseases

Transfer RNA (tRNA), often considered as a housekeeping molecule, mainly participates in protein translation by transporting amino acids to the ribosome. Nevertheless, accumulating evidence has shown that tRNAs are closely related to various physiological and pathological processes. The proper functioning of the immune system is the key to human health. The aim of this review is to investigate the relationships between tRNAs and the immune system. We detail the biogenesis and structure of tRNAs and summarize the pathogen tRNA-mediated infection and host responses. In addition, we address recent advances in different aspects of tRNA-associated dysregulation in immune responses and immune diseases, such as tRNA molecules, tRNA modifications, tRNA derivatives and tRNA aminoacylation. Therefore, tRNAs play an important role in immune regulation. Although our knowledge of tRNAs in the context of immunity remains, for the most part, unknown, this field deserves in-depth research to provide new ideas for the treatment of immune diseases.

Gene expression analysis of vascular pathophysiology related to anti-TNF treatment in rheumatoid arthritis

OBJECTIVES

Impaired vascular pathophysiology and increased cardiovascular (CV) mortality are associated with rheumatoid arthritis (RA). To date, no genomic analysis of RA- and RA treatment-related vascular pathophysiology has been published. In this pilot study, we performed gene expression profiling in association with vascular pathophysiology in RA patients.

METHODS

Sixteen and 19 biologic-naïve RA patients were included in study 1 and study 2, respectively. In study 1, genetic signatures determined by microarray were related to flow-mediated vasodilation (FMD), pulse-wave velocity (PWV), and common carotid intima-media thickness (IMT) of patients. In study 2, clinical response (cR) vs non-response (cNR) to 1-year etanercept (ETN) or certolizumab pegol (CZP) treatment, as well as "vascular" response (vR) vs non-response (vNR) to biologics, were also associated with genomic profiles. Multiple testing could not be performed due to the relatively small number of patients; therefore, our pilot study may lack power.

RESULTS

In study 1, multiple genes were up- or downregulated in patients with abnormal vs normal FMD, IMT, and PWV. In study 2, there were 13 cR and 6 cNR anti-tumor necrosis factor (TNF)-treated patients. In addition, 10, 9, and 8 patients were FMD-20%, IMT-20%, and PWV-20% responders. Again, vascular responder status was associated with changes of the expression of various genes. The highest number of genes showing significant enrichment were involved in positive regulation of immune effector process, regulation of glucose transport, and Golgi vesicle budding.

CONCLUSION

Differential expression of multiple genetic profiles may be associated with vascular pathophysiology associated with RA. Moreover, distinct genetic signatures may also be associated with clinical and vascular responses to 1-year anti-TNF treatment.

Hidradenitis Suppurativa: A Systematic Review Integrating Inflammatory Pathways Into a Cohesive Pathogenic Model

Background: The pathogenesis of hidradenitis suppurativa (HS) is not fully understood. This systematic review examined the latest evidence for molecular inflammatory pathways involved in HS as a chronic inflammatory skin disease.

Methods: A systematic literature search was performed in PubMed/Medline and EMBASE from January 2013 through September 2017, according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA). Findings on HS pathogenesis were also compared with those of other immune-mediated inflammatory diseases (IMIDs) in a non-systematic review. In addition, current therapeutic options for HS are briefly discussed on the basis of the findings for the inflammatory pathways involved in HS.

Results: A total of 32 eligible publications were identified by the systematic search; these were supplemented with three additional publications. The extracted data indicated that four key themes underlie the pathogenesis of HS and related syndromic conditions. First, nicastrin (NCSTN) and PSTPIP1 mutations are directly associated with auto-inflammatory disease. Secondly, the up-regulation of several cytokines including tumor necrosis factor-α and T helper-17/interleukin-23 are connected to auto-inflammatory mechanisms in the pathogenesis of HS. Thirdly, the microbiome of lesional skin differs significantly vs. normal-appearing skin. Fourthly, HS risk is enhanced through physiological and environmental factors such as smoking, obesity, and mechanical friction. There is significant overlap between the pathogenesis of HS, its syndromic forms and other IMIDs, particularly with respect to aberrations in the innate immune response.

Conclusions: The evidence presented in this review supports HS as an auto-inflammatory skin disorder associated with alterations in the innate immune system. Based on these most recent data, an integrative viewpoint is presented on the pathogenesis of HS. Current management strategies on HS consist of anti-inflammatory therapies, surgical removal of chronic lesions, and lifestyle changes such as smoking cessation and weight loss. As large gaps remain in the understanding of the pathogenesis of HS, further research is warranted to ultimately improve the management and treatment of patients with HS and related syndromic conditions.

Axonal transport deficits in multiple sclerosis: spiraling into the abyss

The transport of mitochondria and other cellular components along the axonal microtubule cytoskeleton plays an essential role in neuronal survival. Defects in this system have been linked to a large number of neurological disorders. In multiple sclerosis (MS) and associated models such as experimental autoimmune encephalomyelitis (EAE), alterations in axonal transport have been shown to exist before neurodegeneration occurs. Genome-wide association (GWA) studies have linked several motor proteins to MS susceptibility, while neuropathological studies have shown accumulations of proteins and organelles suggestive for transport deficits. A reduced effectiveness of axonal transport can lead to neurodegeneration through inhibition of mitochondrial motility, disruption of axoglial interaction or prevention of remyelination. In MS, demyelination leads to dysregulation of axonal transport, aggravated by the effects of TNF-alpha, nitric oxide and glutamate on the cytoskeleton. The combined effect of all these pathways is a vicious cycle in which a defective axonal transport system leads to an increase in ATP consumption through loss of membrane organization and a reduction in available ATP through inhibition of mitochondrial transport, resulting in even further inhibition of transport. The persistent activity of this positive feedback loop contributes to neurodegeneration in MS.