Mutation of mouse Mayp/Pstpip2 causes a macrophage autoinflammatory disease

m6A epitranscriptomic and epigenetic crosstalk in liver fibrosis: Special emphasis on DNA methylation and non-coding RNAs

Liver fibrosis is a pathological process caused by a variety of chronic liver diseases. Currently, therapeutic options for liver fibrosis are very limited, highlighting the urgent need to explore new treatment approaches. Epigenetic modifications and epitranscriptomic modifications, as reversible regulatory mechanisms, are involved in the development of liver fibrosis. In recent years, researches in epitranscriptomics and epigenetics have opened new perspectives for understanding the pathogenesis of liver fibrosis. Exploring the epigenetic mechanisms of liver fibrosis may provide valuable insights into the development of new therapies for chronic liver diseases. This review primarily focus on the regulatory mechanisms of N6-methyladenosine (m6A) modification, non-coding RNA, and DNA methylation in organ fibrosis. It discusses the interactions between m6A modification and DNA methylation, as well as between m6A modification and non-coding RNA, providing a reference for understanding the interplay between epitranscriptomics and epigenetics.

PSTPIP2 ameliorates aristolochic acid nephropathy by suppressing interleukin-19-mediated neutrophil extracellular trap formation

Aristolochic acid nephropathy (AAN) is a progressive kidney disease caused by herbal medicines. Proline-serine-threonine phosphatase-interacting protein 2 (PSTPIP2) and neutrophil extracellular traps (NETs) play important roles in kidney injury and immune defense, respectively, but the mechanism underlying AAN regulation by PSTPIP2 and NETs remains unclear. We found that renal tubular epithelial cell (RTEC) apoptosis, neutrophil infiltration, inflammatory factor, and NET production were increased in a mouse model of AAN, while PSTPIP2 expression was low. Conditional knock-in of Pstpip2 in mouse kidneys inhibited cell apoptosis, reduced neutrophil infiltration, suppressed the production of inflammatory factors and NETs, and ameliorated renal dysfunction. Conversely, downregulation of Pstpip2 expression promoted kidney injury. In vivo, the use of Ly6G-neutralizing antibody to remove neutrophils and peptidyl arginine deiminase 4 (PAD4) inhibitors to prevent NET formation reduced apoptosis, alleviating kidney injury. In vitro, damaged RTECs released interleukin-19 (IL-19) via the PSTPIP2/nuclear factor (NF)-κB pathway and induced NET formation via the IL-20Rβ receptor. Concurrently, NETs promoted apoptosis of damaged RTECs. PSTPIP2 affected NET formation by regulating IL-19 expression via inhibition of NF-κB pathway activation in RTECs, inhibiting RTEC apoptosis, and reducing kidney damage. Our findings indicated that neutrophils and NETs play a key role in AAN and therapeutic targeting of PSTPIP2/NF-κB/IL-19/IL-20Rβ might extend novel strategies to minimize Aristolochic acid I-mediated acute kidney injury and apoptosis.

Colchicine-responsive chronic recurrent multifocal osteomyelitis associated with familial Mediterranean fever in the presence of MEFV mutation: A case report

A 38-year-old female was referred with a history of fever, polyarthralgia, and bone pain. She was diagnosed with chronic recurrent multifocal osteomyelitis based on imaging and biopsy findings. Non-steroidal anti-inflammatory drugs and bisphosphonate caused no improvement. Then, she developed recurrent diarrhoea and abdominal pain. Genetic testing revealed MEFV mutation. Based on the symptoms and genetic mutation results that emerged during the course of these events, she was diagnosed with familial Mediterranean fever. All symptoms, including bone pain, improved with daily colchicine administration. This case was considered familial Mediterranean fever complicated with a clinical diagnosis of chronic recurrent multifocal osteomyelitis, which is included in the spectrum of pyrine autoinflammatory diseases. Considering this case, patients with chronic recurrent multifocal osteomyelitis with MEFV gene variants may respond to colchicine.

Skin manifestations help identifying different phenotypes of paediatric SAPHO syndrome

OBJECTIVES

to evaluate whether the heterogeneous skin manifestations might influence the disease presentation and outcome of a cohort of SAPHO children.

METHODS

the clinical, serological, imaging and therapeutic data of 14 SAPHO patients, followed between 2001 and 2022 at the Unit for Autoinflammatory diseases at the Gaslini Hospital, were reviewed. According to their cutaneous manifestations, patients were divided into 2 groups: the acne-hidradenitis suppurativa (HS) and the Palmo-Plantar Pustulosis (PPP) group. Data were retrieved from the Eurofever database.

RESULTS

all patients presented bone involvement characterized by Chronic Recurrent multifocal Osteomyelitis (CRMO): 8 patients presented acne-HS while 6 patients had PPP. In the PPP group, all patients were female, characterized by a prepuberal disease onset with osteoarticular manifestations, followed by the appearance of PPP in the following 6 months. This group responded well to the treatments. In the acne-HS group, 7/8 patients were male: the disease onset was characterized by skin manifestations in pubertal age, followed by osteoarticular manifestations in the following year. This group presented a severe refractory skin disease that required in most cases the addition of biological therapies. A literature review confirmed our data highlighting the association males-acne-puberal age and female-PPP-prepuberal age.

CONCLUSION

paediatric SAPHO patients should be mainly stratified according to their skin involvement. In fact, our data suggest that two different skin phenotypes may be identified in SAPHO: the first is constituted by prepuberal females with PPP and a prevalent osteoarticular involvement, while the second by puberal males with a difficult-to-treat acne-HS.

Pediatric autoinflammatory bone disorders-a mini review with special focus on pathogenesis and inborn errors of immunity

Autoinflammatory bone disorders are a group of diseases characterized by sterile osteomyelitis. This includes chronic nonbacterial osteomyelitis and the monogenic forms, Majeed syndrome and deficiency of the interleukin-1 receptor antagonist. These disorders result from innate immune system dysregulation and cytokine imbalance that triggers inflammasome activation causing downstream osteoclastogenesis and excessive bone remodeling. In this review, we will summarize the immunopathogenesis of pediatric autoinflammatory bone diseases with a special focus on the genetics and inborn errors of immunity, while briefly touching on the clinical manifestations and management of each disease as well as areas for future research.

PSTPIP2 alleviates obesity associated adipose tissue inflammation and insulin resistance in diabetes mice through promoting M2 macrophage polarization via activation of PPARγ

BACKGROUND

Proline-serine-threonine phosphatase-interacting protein 2 (PSTPIP2) plays a role in inflammatory disease. In diabetes, very little is known about PSTPIP2 until now. Hence, this study aimed to determine PSTPIP2 functional role in diabetes.

METHODS

Diabetes mouse model was constructed by feeding high fat diet (HFD). Intraperitoneal glucose tolerance test and intraperitoneal insulin tolerance test were examined the glucose and insulin tolerance. The expression of genes and proteins was detected by quantitative real time PCR, immunohistochemistry and western blotting. The pathological changes of epididymal adipose tissues were examined by hematoxylin-eosin staining. RAW264.7 macrophages were treated with GW9662 (PPARγ antagonist). Flow cytometry examined the proportion of M1/M2 macrophages.

RESULTS

HFD enhanced the body weight, glucose and insulin tolerance, and inhibited PSTPIP2 expression in mice. PSTPIP2 overexpression alleviated glucose and insulin tolerance, reduced inflammation and macrophage accumulation in the epididymal adipose tissues of diabetic mice. The expression of iNOS and TNF-α was increased, the expression of IL-10 and Arg-1 was decreased in diabetic mice, which was abrogated by PSTPIP2 overexpression. In vitro, PSTPIP2 overexpression reduced the proportions of iNOS-positive cells and enhanced the proportions of CD206-positive cells in RAW264.7 cells. PPARγ and p-STAT6 were up-regulated, STAT6 was down-regulated in RAW264.7 cells. GW9662 impaired PSTPIP2 overexpression-mediated up-regulation of Arg-1, YM-1 and FIZZ1 in RAW264.7 cells.

CONCLUSION

PSTPIP2 alleviates obesity associated adipose tissue inflammation and insulin resistance in diabetic mice through promoting M2 macrophage polarization via activation of PPARγ, suggesting that PSTPIP2 is a prospective target for diabetes treatment.

Rare missense variants in the SH3 domain of PSTPIP1 are associated with hidradenitis suppurativa

Hidradenitis suppurativa (HS) is a chronic, debilitating skin disease for which few treatment options are available. While most HS is sporadic, some rare kindred show a high-penetrance, autosomal-dominant inheritance. We wanted to identify rare variants that could contribute to HS risk in sporadic cases using candidate gene sequencing. We ultimately identified 21 genes for our capture panel. We included genes of the γ-secretase complex (n = 6) because rare variants in these genes sometimes cause familial HS. We added Notch receptor and ligand genes (n = 13) because γ-secretase is critical for processing Notch receptor signaling. Clinically, some people with PAPA (pyogenic arthritis, pyoderma gangrenosum, and acne) syndrome, a rare inflammatory disease, have concurrent HS. Rare variants in PSTPIP1 are known to cause PAPA syndrome, so we included PSTPIP1 and PSTPIP2 in the capture panel. We screened 117 individuals with HS for rare variations and calculated the expected burden using Genome Aggregation Database (gnomAD) allele frequencies. We discovered two pathogenic loss-of-function variants in NCSTN. This class of NCSTN variant can cause familial HS. There was no increased burden of rare variations in any γ-secretase complex gene. We did find that individuals with HS had a significantly increased number of rare missense variants in the SH3 domain of PSTPIP1. This finding, therefore, implicates PSTPIP1 variation in sporadic HS and further supports dysregulated immunity in HS. Our data also suggests that population-scale HS genetic research will yield valuable insights into disease pathology.

Chronic Recurrent Multifocal Osteomyelitis (CRMO) and Juvenile Spondyloarthritis (JSpA): To What Extent Are They Related?

Chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory disease occurring mainly in the pediatric age group (before 16 years) and generally presents as a separate entity. Synovitis, acne, pustulosis, hyperostosis and osteitis (SAPHO) syndrome combines osteoarticular and cutaneous involvement, similar to CRMO, and falls into the spectrum of spondyloarthritis (SpA). The fact that a patient can progress from one disease to another raises the question of whether CRMO, like SAPHO, could fall within the spectrum of SpA, ranging from a predominantly osteoarticular form to an enthesitic form with more or less marked skin involvement. In this review, we set out to discuss this hypothesis by highlighting the differences and similarities between CRMO and juvenile SpA in clinical, radiological and pathophysiological aspects. A common hypothesis could potentially consider intestinal dysbiosis as the origin of these different inflammatory diseases. Interindividual factors such as gender, environment, genetics and/or epigenetic background could act as combined disease modifiers. This is why we suggest that pathophysiology, rather than clinical phenotype, be used to reclassify these diseases.

PSTPIP2 regulates synovial macrophages polarization and dynamics via ERβ in the joint microenvironment

Background

The cytoskeletal protein, PSTPIP2, is associated with inflammation and is predominantly expressed in macrophages. Previous data have shown that PSTPIP2 inhibits articular bone damage in arthritic rats. The aim of this study is to explore the molecular mechanism of PSTPIP2’s resistance to bone erosion.

Methods

In the current study, peripheral blood and surgically excised synovial tissue from RA patients, DBA/1 mice, Pstpip2^CreR26-ZsGreen reporter mice, and Esr2^fl/fl/Adgre-Cre tool mice were used for in vivo studies. Adeno-associated viral vector was used to overexpress PSPTIP2 protein in vivo.

Results

We found that The level of PSTPIP2 in synovial macrophages is negatively correlated with RA disease activity, which is mediated by synovial macrophages polarization. PSTPIP2^hi synovial macrophages form a tight immunological barrier in the lining layer. Notably, the ability of PSTPIP2 to regulate synovial macrophages polarization is dependent on ERβ. Additionally, PSTPIP2 regulates the dynamics of synovial macrophages via ERβ.

Conclusions

Together, this study reveals that PSTPIP2 regulates synovial macrophages polarization and dynamics via ERβ to form an immunological barrier (F4/80⁺PSTPIP2^hi cell-enriched zone) for the joints. Thus, local modulation of PSTPIP2 expression in the joint microenvironment may be a potential strategy for controlling bone erosion in rheumatoid arthritis.

Graphical Abstract

PSTPIP2 regulates synovial macrophages polarization and dynamics via ERβ to form F4/80⁺PSTPIP2^hi cellular barrier in joint microenvironment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02939-y.

GNAS mutation analysis assists in differentiating chronic diffuse sclerosing osteomyelitis from fibrous dysplasia in the jaw

Chronic diffuse sclerosing osteomyelitis of the mandible (DSOM) and fibrous dysplasia (FD) are distinct lesions with overlapping clinicopathological features that complicate their diagnosis. This study aimed to evaluate the efficacy of GNAS mutation analysis in differentiating between these two conditions. DNA samples from patients with DSOM (n = 35) and FD (n = 29) were collected to analyze the presence of GNAS mutations in exons 8 and 9, the two previously reported hotspot regions, using polymerase chain reaction and direct sequencing. Twenty-four of 29 patients (83%) with FD showed missense mutations in codon 201 in exon 8, whereas no mutation was detected in exon 9. No mutations were found in any of the 35 cases with DSOM. We also identified one case with an uncertain diagnosis due to overlapping clinicopathological features of DSOM and FD. A Q227H mutation was detected in this case, that confirmed the diagnosis of FD. Taken together, the findings indicate that mutational analysis of the GNAS is a reliable approach to differentiate between DSOM and FD of the jaw.

PSTPIP1-LYP phosphatase interaction: structural basis and implications for autoinflammatory disorders

Mutations in the adaptor protein PSTPIP1 cause a spectrum of autoinflammatory diseases, including PAPA and PAMI; however, the mechanism underlying these diseases remains unknown. Most of these mutations lie in PSTPIP1 F-BAR domain, which binds to LYP, a protein tyrosine phosphatase associated with arthritis and lupus. To shed light on the mechanism by which these mutations generate autoinflammatory disorders, we solved the structure of the F-BAR domain of PSTPIP1 alone and bound to the C-terminal homology segment of LYP, revealing a novel mechanism of recognition of Pro-rich motifs by proteins in which a single LYP molecule binds to the PSTPIP1 F-BAR dimer. The residues R228, D246, E250, and E257 of PSTPIP1 that are mutated in immunological diseases directly interact with LYP. These findings link the disruption of the PSTPIP1/LYP interaction to these diseases, and support a critical role for LYP phosphatase in their pathogenesis.

DNMT3a-mediated methylation of PSTPIP2 enhances inflammation in alcohol-induced liver injury via regulating STAT1 and NF-κB pathway

Alcohol-induced liver injury (ALI) is associated with inflammatory responses regulated by macrophages. Activation of macrophages plays a crucial role in ALI while DNA methylation-regulated gene silencing is associated with inflammation processes in macrophages. Proline-Serine-Threonine Phosphatase Interacting Protein 2 (PSTPIP2), which belongs to the Fes/CIP4 homology-Bin/Amphiphysin/Rvs domain family of proteins and plays a role in macrophages. Previous studies have shown that Pstpip2 can be methylated. Herein, its expression was found to be significantly downregulated in primary liver macrophages isolated from EtOH-fed mice and EtOH-induced RAW264.7 cells. Overexpression of PSTPIP2 using liver-specific recombinant AAV serotype 9 (rAAV9)-PSTPIP2 in EtOH-fed mice dramatically alleviated liver injury and inflammatory responses. In addition, silencing of PSTPIP2 aggravated the alcohol-induced inflammatory response in vitro. Mechanistically, PSTPIP2 might affect macrophage-induced inflammatory responses by regulating the STAT1 and NF-κB signaling pathways. The downregulation of PSTPIP2 in ALI may be associated with DNA methylation. Methylation-specific PCR and western blotting analyses showed that EtOH induced abnormal DNA methylation patterns and increased the protein expression levels of DNMT1, DNMT3a, and DNMT3b. The chromatin immunoprecipitation assay showed that DNMT3a could directly bind to the Pstpip2 promoter and act as a principal regulator of PSTPIP2 expression. Moreover, silencing of DNMT3a significantly restored the EtOH-induced low expression of PSTPIP2 and inhibited EtOH-induced inflammation. Overall, these findings provide a detailed understanding of the possible functions and mechanisms of PSTPIP2 in ALI, thus providing new substantive research to elucidate the pathogenesis of ALI and investigate potential targeted treatment strategies.

New advances of DNA/RNA methylation modification in liver fibrosis

Liver fibrosis is a complex pathological process caused by multiple pathogenic factors，such as ethanol, viruses, toxins, drugs or cholestasis, and it can eventually develop into liver cirrhosis without effective treatment. Activation of hepatic stellate cells (HSCs) is a pivotal cellular event in the pathogenesis of liver fibrosis. However, the pathogenesis of liver fibrosis has not been fully elucidated. DNA/RNA methylation can regulate gene expression without alteration in its sequence, and numerous studies have shown the involvement of DNA methylation in the activation of HSCs and then promote the progression of liver fibrosis. In addition, RNA methylation has recently been reported to play a regulatory role in this process. In this review, we focus on the aberrant DNA/RNA methylation of selected genes and explore their functional mechanism in regulating HSCs activation and liver fibrogenesis. All of these findings will enhance our understanding of DNA/RNA methylation and their roles in liver fibrosis and provide the basis to identify effective therapeutic targets.

Role of the F-BAR Family Member PSTPIP2 in Autoinflammatory Diseases

Proline-serine-threonine-phosphatase-interacting protein 2 (PSTPIP2) belongs to the Fes/CIP4 homology-Bin/Amphiphysin/Rvs (F-BAR) domain family. It exhibits lipid-binding, membrane deformation, and F-actin binding activity, suggesting broader roles at the membrane–cytoskeleton interface. PSTPIP2 is known to participate in macrophage activation, neutrophil migration, cytokine production, and osteoclast differentiation. In recent years, it has been observed to play important roles in innate immune diseases and autoinflammatory diseases (AIDs). Current research indicates that the protein tyrosine phosphatase PTP-PEST, Src homology domain-containing inositol 5’-phosphatase 1 (SHIP1), and C‐terminal Src kinase (CSK) can bind to PSTPIP2 and inhibit the development of AIDs. However, the mechanisms underlying the function of PSTPIP2 have not been fully elucidated. This article reviews the research progress and mechanisms of PSTPIP2 in AIDs. PSTPIP2 also provides a new therapeutic target for the treatment of AIDs.

Psoriatic Dactylitis: Current Perspectives and New Insights in Ultrasonography and Magnetic Resonance Imaging

Dactylitis, one of the most typical features of psoriatic arthritis (PsA), is the diffuse swelling of the digits and is determined by the involvement of different anatomic structures, including: the subcutaneous fibrous tissue “accessory pulley” system; flexor tendons, with their related structures; the articular synovium; the small enthesis of the hands. Dactylitis is currently considered both a marker of disease activity and severe prognosis and its importance in PsA is emphasized by the inclusion in the classification criteria of PsA. This review focuses on the role of imaging in the management of PsA patients with dactylitis in clinical practice and in a research setting. Furthermore, imaging could be a valuable tool to assist in unravelling some of the underlying mechanisms of the onset and chronicization of dactylitis in PsA patients.

Proline-Serine-Threonine Phosphatase-Interacting Protein 2 Alleviates Diabetes Mellitus-Osteoarthritis in Rats through Attenuating Synovial Inflammation and Cartilage Injury

Objective

To explore the possible way of proline‐serine–threonine phosphatase‐interacting protein 2 (PSTPIP2) influencing diabetes mellitus‐osteoarthritis (DM‐OA) progression.

Methods

In vivo, eight‐week‐old male Sprague Dawley rats were induced with DM‐OA by intraperitoneal injection of streptozotocin with high‐fat diet feeding and intra‐articular injection of monoiodoacetate. PSTPIP2 overexpression was achieved by intra‐articular injection of lentivirus vectors. PSTPIP2 expression was verified by real‐time polymerase chain reaction and Western blotting. Histological changes were examined by hematoxylin/eosin and safranin‐O/fast‐green staining. In vitro, rat synovial fibroblasts were induced DM‐OA by stimulation of high glucose (HG) and interleukin (IL)‐1β. PSTPIP2 overexpression was achieved by lentivirus infection. U0126 was added as an ERK inhibitor. Levels of tumor necrosis factor (TNF)‐α, IL‐6, and IL‐1β were detected using enzyme‐linked immunosorbent assay. Expression of matrix metalloproteinase (MMP)‐3, MMP‐13, aggrecanase‐2 (ADAMTS‐5), intercellular cell adhesion molecule (ICAM)‐1, extracellular regulated protein kinase (ERK) and phospho‐ERK (p‐ERK) was detected by Western blotting.

Results

In DM‐OA rats, PSTPIP2 relative messenger RNA (mRNA) level was significantly decreased compared to control rats. The protein expression was also decreased obviously. Inflammation score in synovium was dramatically increased, accompanying with increased TNF‐α, IL‐6, and IL‐1β levels. Osteoarthritis research society international (OARSI) score in cartilage was markedly increased, along with increased MMP‐3, MMP‐13, ADAMTS‐5, ICAM‐1, ERK and p‐ERK expression. In PSTPIP2‐overexpressed DM‐OA rats, PSTPIP2 mRNA level and protein expression was increased compared to DM‐OA rats received negative‐control lentivirus vectors. The inflammation score, as well as TNF‐α, IL‐6, and IL‐1β levels were dramatically decreased. Also, the OARSI score and protein expression of MMP‐3, MMP‐13, ADAMTS‐5, ICAM‐1, ERK and p‐ERK were decreased. In HG+IL‐1β‐treated rat synovial fibroblasts, PSTPIP2 protein expression was decreased compared to normal glucose (NG)‐treated cells. Levels of TNF‐α, IL‐6, and IL‐1β, as well as expression of MMP‐3, MMP‐13, ADAMTS‐5, ICAM‐1, ERK and p‐ERK were increased. After cells were infected with PSTPIP2‐overexpressed lentivirus, levels of TNF‐α, IL‐6, and IL‐1β, and expression of MMP‐3, MMP‐13, ADAMTS‐5, ICAM‐1, ERK and p‐ERK were obviously decreased compared to cells infected with NC lentivirus. In addition, ERK inhibitor U0126 treatment also decreased the TNF‐α, IL‐6, and IL‐1βlevels and MMP‐3, MMP‐13, ADAMTS‐5, ICAM‐1, ERK and p‐ERK expression in HG + IL‐1β treated rat synovial fibroblasts.

Conclusion

Overexpression of PSTPIP2 alleviates synovial inflammation and cartilage injury during DM‐OA progression via inhibiting ERK phosphorylation.

Chronic nonbacterial osteomyelitis (CNO) and chronic recurrent multifocal osteomyelitis (CRMO)

Chronic nonbacterial osteomyelitis (CNO) is an inflammatory bone disorder that most frequently affects children and adolescents. Chronic recurrent multifocal osteomyelitis (CRMO) is a severe form of CNO, usually characterized by symmetrical inflammatory bone lesions and its waxing and waning character. Sometimes severe and chronic pain can significantly affect the quality of life and psychosocial development of individuals affected. In the absence of prospectively tested and widely accepted diagnostic criteria or disease biomarkers, CNO remains a diagnosis of exclusion, and infections, malignancy and other differentials require consideration (1). The pathophysiology of CNO is not fully understood, but imbalanced cytokine expression and increased inflammasome activation in monocytes from CNO patients contribute to a pro-inflammatory phenotype that contributes to bone inflammation (2). Currently, no medications are licensed for the use in CNO. Most patients show at least some response to nonsteroidal anti-inflammatory drugs, others require more aggressive treatment that can include corticosteroids, cytokine-blocking agents and/or bisphosphonates (3). While under the care of an experienced team and sufficient treatment, the prognosis is good, but some patients will develop sequalae which can include vertebral compression fractures (1).

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CNO is an autoinflammatory bone disorder mostly affecting children and adolescents.

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Dysregulated cytokine expression and pathological activation of inflammasomes play a central role.

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Treatment is based on experience from case series and expert consensus treatment plans.

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Understanding the exact molecular pathophysiology will allow patient stratification and individualized treatment.

Majeed Syndrome: A Review of the Clinical, Genetic and Immunologic Features

Majeed syndrome is a multi-system inflammatory disorder affecting humans that presents with chronic multifocal osteomyelitis, congenital dyserythropoietic anemia, with or without a neutrophilic dermatosis. The disease is an autosomal recessive disorder caused by mutations in LPIN2, the gene encoding the phosphatidic acid phosphatase LIPIN2. It is exceedingly rare. There are only 24 individuals from 10 families with genetically confirmed Majeed syndrome reported in the literature. The early descriptions of Majeed syndrome reported severely affected children with recurrent fevers, severe multifocal osteomyelitis, failure to thrive, and marked elevations of blood inflammatory markers. As more affected families have been identified, it has become clear that there is significant phenotypic variability. Data supports that disruption of the phosphatidic acid phosphatase activity in LIPIN2 results in immune dysregulation due to aberrant activation of the NLRP3 inflammasome and overproduction of proinflammatory cytokines including IL-1β, however, these findings did not explain the bone phenotype. Recent studies demonstrate that LPIN2 deficiency drives pro-inflammatory M2-macrophages and enhances osteoclastogenesis which suggest a critical role of lipin-2 in controlling homeostasis at the growth plate in an inflammasome-independent manner. While there are no approved medications for Majeed syndrome, pharmacologic blockade of the interleukin-1 pathway has been associated with rapid clinical improvement.

PSTPIP2 inhibits cisplatin-induced acute kidney injury by suppressing apoptosis of renal tubular epithelial cells

Cisplatin (CP) is an effective chemotherapeutic agent widely used in the treatment of various solid tumours. However, CP nephrotoxicity is an important limitation for CP use; currently, there is no method to ameliorate cisplatin-induced acute kidney injury (AKI). Recently, we identified a specific role of proline-serine-threonine phosphatase-interacting protein 2 (PSTPIP2) in cisplatin-induced AKI. PSTPIP2 was reported to play an important role in a variety of diseases. However, the functions of PSTPIP2 in experimental models of cisplatin-induced AKI have not been extensively studied. The present study demonstrated that cisplatin downregulated the expression of PSTPIP2 in the kidney tissue. Administration of AAV-PSTPIP2 or epithelial cell-specific overexpression of PSTPIP2 reduced cisplatin-induced kidney dysfunction and inhibited apoptosis of renal tubular epithelial cells. Small interfering RNA-based knockdown of PSTPIP2 expression abolished PSTPIP2 regulation of epithelial cell apoptosis in vitro. Histone acetylation may impact gene expression at the epigenetic level, and histone deacetylase (HDAC) inhibitors were reported to prevent cisplatin-induced nephrotoxicity. The UCSC database was used to predict that acetylation of histone H3 at lysine 27 (H3K27ac) induces binding to the PSTPIP2 promoter, and this prediction was validated by a ChIP assay. Interestingly, an HDAC-specific inhibitor (TSA) was sufficient to potently upregulate PSTPIP2 in epithelial cells. Histone acetylation-mediated silencing of PSTPIP2 may contribute to cisplatin nephrotoxicity. PSTPIP2 may serve as a potential therapeutic target in the prevention of cisplatin nephrotoxicity.

Pathophysiology, assessment and treatment of psoriatic dactylitis

Dactylitis is diffuse swelling of the digits that is usually related to an underlying inflammatory or infiltrative disorder. Psoriatic arthritis (PsA) is the most common severe disease thought to cause dactylitis. Our understanding of the pathogenesis of PsA-related dactylitis comes from experimental animal models of PsA-like disease, as well as advances in imaging and other clinical studies. Clinical trials in PsA have increasingly included dactylitis as an important secondary outcome measure. These studies indicate that cytokines drive multi-locus microanatomical pan-digital pathology. Given the importance of pro-inflammatory cytokines, the pathogenesis of dactylitis is best understood as an initial aberrant innate immune response to biomechanical stress or injury, with subsequent adaptive immune mechanisms amplifying the dactylitis inflammatory response. Regarding the treatment of dactylitis, no studies have been conducted using dactylitis as the primary outcome measure, and the current knowledge comes from analysis of dactylitis as a secondary outcome measure.

ZBP1 and TAK1: Master Regulators of NLRP3 Inflammasome/Pyroptosis, Apoptosis, and Necroptosis (PAN-optosis)

Cell death is central to development, organismal homeostasis, and immune responses. The cell death field has experienced tremendous progress by delineating the molecular programs specific to each of the apoptotic and inflammatory cell death pathways. Moreover, the discovery of the inflammasomes and pyroptosis and necroptosis pathway regulators have provided the genetic basis for the programmed inflammatory cell death pathways. Earlier research highlighted the unique regulation of each of these pathways, but emerging studies discovered co-regulation and crosstalk between these seemingly different cell death complexes. The progress in this area has led to an idea that master regulators play central roles in orchestrating multiple cell death pathways. Here, we provide a brief review of the master regulators, the innate immune sensor ZBP1 and the essential cell survival kinase TAK1, that play vital roles in the regulation of RIPK1/RIPK3-FADD-caspase-8 cell death complex assembly and its versatility in executing Pyroptosis, Apoptosis, and Necroptosis, which we dubbed here as PAN-optosis. Furthermore, we discuss the implications and therapeutic potential of targeting these master regulators in health and disease.

One Sentence Summary

ZBP1 and TAK1 regulate PAN-optosis.

The nonreceptor tyrosine kinase SYK drives caspase-8/NLRP3 inflammasome-mediated autoinflammatory osteomyelitis

Chronic recurrent multifocal osteomyelitis (CRMO) in humans can be modeled in Pstpip2^cmo mice, which carry a missense mutation in the proline-serine-threonine phosphatase-interacting protein 2 (Pstpip2) gene. As cmo disease in mice, the experimental model analogous to human CRMO, is mediated specifically by IL-1β and not by IL-1α, delineating the molecular pathways contributing to pathogenic IL-1β production is crucial to developing targeted therapies. In particular, our earlier findings support redundant roles of NLR family pyrin domain-containing 3 (NLRP3) and caspase-1 with caspase-8 in instigating cmo However, the signaling components upstream of caspase-8 and pro-IL-1β cleavage in Pstpip2^cmo mice are not well-understood. Therefore, here we investigated the signaling pathways in these mice and discovered a central role of a nonreceptor tyrosine kinase, spleen tyrosine kinase (SYK), in mediating osteomyelitis. Using several mutant mouse strains, immunoblotting, and microcomputed tomography, we demonstrate that absent in melanoma 2 (AIM2), receptor-interacting serine/ threonine protein kinase 3 (RIPK3), and caspase recruitment domain-containing protein 9 (CARD9) are each dispensable for osteomyelitis induction in Pstpip2^cmo mice, whereas genetic deletion of Syk completely abrogates the disease phenotype. We further show that SYK centrally mediates signaling upstream of caspase-1 and caspase-8 activation and principally up-regulates NF-κB and IL-1β signaling in Pstpip2^cmo mice, thereby inducing cmo These results provide a rationale for directly targeting SYK and its downstream signaling components in CRMO.

Update on the genetics of nonbacterial osteomyelitis in humans

PURPOSE OF REVIEW

To summarize the current advances in our understanding or the genetic basis of nonbacterial osteomyelitis.

RECENT FINDINGS

Chronic recurrent multifocal osteomyelitis (CRMO) is a complex genetic disorder. Past discoveries identified several single gene defects (LPIN2, Pstpip2 and IL1RN) that cause IL-1-mediated sterile multifocal osteomyelitis. Recently Lorden et al.'s studies show that LIPIN2 deficiency can activate the NLRP3 inflammasome through alterations in the function of P2X7 receptor providing evidence that Majeed syndrome is an NLRP3 inflammasomopathy. New gene discoveries include the identification of FBLIM1 as a CRMO susceptibility gene. Mutations in FBLIM1 were found in a consanguineous family with CRMO. Fblim1 is one of the most significantly differentially expressed gene in bone from chronic multifocal osteomyelitis (cmo) mice, plays a role in IL-10-driven anti-inflammatory responses, and is involved in the physiology of bone remodeling. Lastly, new data on the putative CRMO susceptibility locus on chromosome 18 is presented here. Using Sanger sequencing, rather than microsatellite analysis, the DS18S60 susceptibility region could not be replicated in a larger cohort.

SUMMARY

CRMO occurs in humans, nonhuman primates, dogs and mice. There is a genetic component to disease but the genetic basis has only been identified for a small percentage of all cases.

PSTPIP2 attenuates joint damage and suppresses inflammation in adjuvant-induced arthritis

Proline-serine-threonine-phosphatase-interacting protein 2 (PSTPIP2) is related to inflammation. In this study, we investigated the function of PSTPIP2 in adjuvant-induced arthritis (AIA) by using adeno-associated virus (AAV) to overexpress PSTPIP2 in rat. AIA rats were developed by injecting Lewis rats with complete Freund's adjuvant (CFA) on day 0. AAV-empty or AAV-PSTPIP2, or PBS was administered intraarticularly into each knee joint on day 8 postinduction. All animals were killed at day 18 after adjuvant injection. WB was used to detect the expression of PSTPIP2 in rat synovial tissues. Fluorescence microscopy showed the transduction efficiency in synovial tissue. The morphology of arthritic joints was examined by HE, safranin O/fast green, or Toluidine blue staining. The bone destruction was examined via X-ray and micro-CT analysis. Immunohistochemical analysis or TRAP staining were used to investigate the role of PSTPIP2 in osteoclasts and the expression of PSTPIP2 in synovial tissue. RT-qPCR and ELISA were used to examine the expression of pro-inflammatory cytokines in synovial tissue or serum. AIA rats were found to have decreased PSTPIP2 expression and AIA-associated bone loss and inflammatory infiltration. We showed that administration of AAV-PSTPIP2 before arthritis onset significantly reduces the severity of AIA. PSTPIP2 was highly expressed in synovial cells. In addition, inflammatory responses and the number of osteoclasts were reduced with AAV-PSTPIP2 treatment. These findings demonstrate that PSTPIP2 may improve the severity of AIA by inhibiting the function of fibroblast-like synoviocytes, suppressing inflammation and reducing the number of osteoclasts.

Gain-of-function mutations in a member of the Src family kinases cause autoinflammatory bone disease in mice and humans

Chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory bone disease that presents with bone destruction occurring primarily in children. In a mouse ENU mutagenesis screen, the Ali18 strain was isolated because of spontaneous inflammation in the joints and bones. Sequencing candidate genes in the Ali18 critical region identified a missense mutation in the C-terminal regulatory region of the Src family kinase (SFK) member, Fgr. Genome editing revealed Fgr dependency of the inflammatory phenotype in Ali18 mice. Further, whole exome sequencing in our CRMO cohort identified two patients with missense mutations in FGR. In vitro functional assays confirm altered protein function. This work identifies FGR as a CRMO susceptibility gene and suggests that targeting SFKs may be useful in its treatment.

Autoinflammatory syndromes are characterized by dysregulation of the innate immune response with subsequent episodes of acute spontaneous inflammation. Chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory bone disorder that presents with bone pain and localized swelling. Ali18 mice, isolated from a mutagenesis screen, exhibit a spontaneous inflammatory paw phenotype that includes sterile osteomyelitis and systemic reduced bone mineral density. To elucidate the molecular basis of the disease, positional cloning of the causative gene for Ali18 was attempted. Using a candidate gene approach, a missense mutation in the C-terminal region of Fgr, a member of Src family tyrosine kinases (SFKs), was identified. For functional confirmation, additional mutations at the N terminus of Fgr were introduced in Ali18 mice by CRISPR/Cas9-mediated genome editing. N-terminal deleterious mutations of Fgr abolished the inflammatory phenotype in Ali18 mice, but in-frame and missense mutations in the same region continue to exhibit the phenotype. The fact that Fgr null mutant mice are morphologically normal suggests that the inflammation in this model depends on Fgr products. Furthermore, the levels of C-terminal negative regulatory phosphorylation of Fgr^Ali18 are distinctly reduced compared with that of wild-type Fgr. In addition, whole-exome sequencing of 99 CRMO patients including 88 trios (proband and parents) identified 13 patients with heterozygous coding sequence variants in FGR, including two missense mutant proteins that affect kinase activity. Our results strongly indicate that gain-of-function mutations in Fgr are involved in sterile osteomyelitis, and thus targeting SFKs using specific inhibitors may allow for efficient treatment of the disease.

Chronic non-bacterial osteomyelitis in the jaw

Chronic recurrent multifocal osteomyelitis (CRMO) is one of the most severe form of chronic non-bacterial osteomyelitis (CNO), which could result in bone and related tissue damage. This autoinflammatory bone disorder (ABD) is very difficult for its clinical diagnosis because of no diagnostic criteria or biomarkers. CRMO in the jaw must be suspected in the differential diagnosis of chronic and recurrent bone pain in the jaw, and a bone biopsy should be considered in chronic and relapsing bone pain with swelling that is unresponsive to treatment. The early diagnosis of CRMO in the jaw will prevent unnecessary and prolonged antibiotic usage or unnecessary surgical intervention. The updated researches for the identification of genetic and molecular alterations in CNO/CRMO should be studied more for its correct pathophysiological causes and proper treatment guidelines. Although our trial consisted of reporting items from Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), there are very few articles of randomized controlled trials. This article was summarized based on the author's diverse clinical experiences. This paper reviews the clinical presentation of CNO/CRMO with its own pathogenesis, epidemiology, recent research studies, and general medications. Treatment and monitoring of the jaw are essential for the clear diagnosis and management of CNO/CRMO patients in the field of dentistry and maxillofacial surgery.

PSTPIP2 Inhibits the Inflammatory Response and Proliferation of Fibroblast-Like Synoviocytes in vitro

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease and its pathogenesis remains unclear. Fibroblast-like synoviocytes (FLSs) play an important role in the pathogenesis of RA. Proline-serine-threonine phosphatase interacting protein 2 (PSTPIP2) is an adaptor protein, which is associated with auto-inflammatory disease. In this study, we selected adjuvant-induced arthritis (AIA) as animal model to study the role of PSTPIP2 in FLSs. We found that the expression of PSTPIP2 was significantly down-regulated in synovial tissues and FLSs of AIA rat compared with normal group. And overexpression of PSTPIP2 could inhibit the proliferation and inflammatory response of FLSs. Moreover, the proliferation and inflammatory response of FLSs were promoted with PSTPIP2 silencing treatment. In terms of mechanism, we found that the expression of PSTPIP2 was closely related to NF-κB signaling pathway. Overall, our results suggested that PSTPIP2 inhibits the proliferation and inflammatory response of FLSs, which might be closely related to NF-κB signaling pathway.

PSTPIP2 connects DNA methylation to macrophage polarization in CCL4-induced mouse model of hepatic fibrosis

Macrophages play a crucial role in the progression of hepatic fibrosis (HF). In macrophages, epigenetic mechanisms are increasingly being recognized as crucial controllers of their phenotype. However, the functions of macrophage DNA methylation in experimental models of hepatic fibrosis have not been fully addressed. Here, we analyzed isolated hepatic macrophages DNA methylation from CCL4-induced (4 weeks) mice using reduced representation bisulfite sequencing (RRBS). We identified and validated the methylation status of 26 gene promoter regions associated with CpG islands. We further investigated the function of PSTPIP2 in HF by hepatic-adeno-associated virus (AAV9)-PSTPIP2 overexpression. The molecular mechanisms underlying PSTPIPS2-regulated HF were further explored in mice and RAW264.7 cell line. RRBS results show hypermethylation of PSTPIP2 (chr18: 77,843,840-77,843,968) in the 5'-UTR region. PSTPIP2 expression was significantly decreased in isolated hepatic macrophages from CCL4-induced mice. PSTPIP2 hypermethylation is mediated by the methyltransferases DNMT3a and DNMT3b in LPS-induced RAW264.7 cell line. Further investigation indicated that specific overexpression of PSTPIP2 in C57BL/6 mice reduced the inflammatory response and ameliorated liver fibrosis. These data indicated that hypermethylation of PSTPIP2 caused a mixed induction of hepatic classical macrophage (M1) and alternative macrophage (M2) biomarkers in CCL4-induced HF mice. Furthermore, overexpression of PSTPIP2 inhibited the expression of M1 markers by suppressing STAT1 activity, and enhanced the expression of M2 markers by promoting STAT6 activity. In contrast, knockdown of PSTPIP2 promoted M1 polarization and suppressed M2 polarization in vitro. Adding PSTPIP2 expression alleviates liver fibrosis and hepatic inflammation in mice by regulating macrophage polarization.

Function and regulation of IL-1α in inflammatory diseases and cancer

The interleukin (IL)-1 family of cytokines is currently comprised of 11 members that have pleiotropic functions in inflammation and cancer. IL-1α and IL-1β were the first members of the IL-1 family to be described, and both signal via the same receptor, IL-1R. Over the last decade, much progress has been made in our understanding of biogenesis of IL-1β and its functions in human diseases. Studies from our laboratory and others have highlighted the critical role of nod-like receptors (NLRs) and multi-protein complexes known as inflammasomes in the regulation of IL-1β maturation. Recent studies have increased our appreciation of the role played by IL-1α in inflammatory diseases and cancer. However, the mechanisms that regulate the production of IL-1α and its bioavailability are relatively understudied. In this review, we summarize the distinctive roles played by IL-1α in inflammatory diseases and cancer. We also discuss our current knowledge about the mechanisms that control IL-1α biogenesis and activity, and the major unanswered questions in its biology.

Dealing with Chronic Non-Bacterial Osteomyelitis: a practical approach

BACKGROUND

Chronic Non-Bacterial Osteomyelitis (CNO) is an inflammatory disorder that primarily affects children. Although underestimated, its incidence is rare. For these reasons, no diagnostic and no therapeutic guidelines exist. The manuscript wants to give some suggestions on how to deal with these patients in the every-day clinical practice.

MAIN BODY

CNO is characterized by insidious onset of bone pain with local swelling. Systemic symptoms such as fever, skin involvement and arthritis may be sometimes present. Radiological findings are suggestive for osteomyelitis, in particular if multiple sites are involved. CNO predominantly affects metaphyses of long bones, but clavicle and mandible, even if rare localizations of the disease, are very consistent with CNO diagnosis. CNO pathogenesis is still unknown, but recent findings highlighted the crucial role of cytokines such as IL-1β and IL-10 in disease pathogenesis. Moreover, the presence of non-bacterial osteomyelitis among autoinflammatory syndromes suggests that CNO could be considered an autoinflammatory disease itself. Differential diagnosis includes infections, malignancies, benign bone tumors, metabolic disorders and other autoinflammatory disorders. Radiologic findings, either with Magnetic Resonance or with Computer Scan, may be very suggestive. For this reason in patients in good clinical conditions, with multifocal localization and very consistent radiological findings bone biopsy could be avoided. Non-Steroidal Anti-Inflammatory Drugs are the first-choice treatment. Corticosteroids, methotrexate, bisphosphonates, TNFα-inhibitors and IL-1 blockers have also been used with some benefit; but the choice of the second line treatment depends on bone lesions localizations, presence of systemic features and patients' clinical conditions.

CONCLUSION

CNO may be difficult to identify and no consensus exist on diagnosis and treatment. Multifocal bone lesions with characteristic radiological findings are very suggestive of CNO. No data exist on best treatment option after Non-Steroidal Anti-Inflammatory Drugs failure.

Chronic Recurrent Multifocal Osteomyelitis (CRMO): Presentation, Pathogenesis, and Treatment

PURPOSE OF REVIEW

Chronic non-bacterial osteomyelitis (CNO) with its most severe form chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory bone disorder. We summarize the clinical presentation, diagnostic approaches, most recent advances in understanding the pathophysiology, and available treatment options and outcomes in CNO/CRMO.

RECENT FINDINGS

Though the exact molecular pathophysiology of CNO/CRMO remains somewhat elusive, it appears likely that variable defects in the TLR4/MAPK/inflammasome signaling cascade result in an imbalance between pro- and anti-inflammatory cytokine expressions in monocytes from CNO/CRMO patients. In this context, we present previously unpublished data on cytokine and chemokine expression in monocytes and tissues. CNO/CRMO is an autoinflammatory bone disorder resulting from imbalanced cytokine expression from innate immune cells. Though the exact molecular pathophysiology remains unclear, variable molecular defects appear to result in inflammasome activation and pro-inflammatory cytokine expression in monocytes from CNO/CRMO patients. Recent advances suggest signaling pathways and single molecules as biomarkers for CNO/CRMO as well as future treatment targets.

An Update on the Pathogenesis and Treatment of Chronic Recurrent Multifocal Osteomyelitis in Children

Chronic recurrent multifocal osteomyelitis (CRMO), also known as chronic non-bacterial osteomyelitis (CNO), is a rare inflammatory disorder that primarily affects children. It is characterized by pain, local bone expansion, and radiological findings suggestive of osteomyelitis, usually at multiple sites. CRMO predominantly affects the metaphyses of long bones, but involvement of the clavicle or mandible are suggestive of the diagnosis. CRMO is a diagnosis of exclusion, and its pathogenesis remains unknown. Differential diagnosis includes infection, malignancies, benign bone tumors, metabolic disorders, and other autoinflammatory disorders. Biopsy of the bone lesion is not often required but could be necessary in unclear cases, especially for differentiation from bone neoplasia. Non-steroidal anti-inflammatory drugs (NSAIDs) are the first-line treatment. Alternative therapies have been used, including corticosteroids, methotrexate, bisphosphonates, and tumor necrosis factor (TNF)-α inhibitors. No guidelines have been established regarding diagnosis and treatment options. This manuscript gives an overview of the most recent findings on the pathogenesis of CRMO and clinical approaches for patients with the condition.

Chronic Recurrent Multifocal Osteomyelitis and Related Diseases-Update on Pathogenesis

PURPOSE OF REVIEW

We focus on recent advances in the understanding of the genetic, molecular, immunologic, and environmental factors implicated in the pathogenesis of autoinflammatory bone diseases including the syndromic and non-syndromic forms of chronic recurrent multifocal osteomyelitis (CRMO).

RECENT FINDINGS

Evidence implicating the IL-1 pathway in the pathogenesis of the Mendelian forms of CRMO is growing. LIPIN2 can regulate the NLRP3 inflammasome by affecting P2X7 receptor activation, and intracellular cholesterol can modulate P2X7R currents. Work in a mouse model of CRMO demonstrates that dietary manipulation can alter the microbiome and protect these mice from the development of sterile osteomyelitis in vivo. Although the genetic and immunologic basis of non-syndromic CRMO remains only partially understood, the IL-1 pathway is central to the pathogenesis in the syndromic autoinflammatory bone disorders. Recent work implicates lipids and the microbiome in sterile osteomyelitis.

Recessive coding and regulatory mutations in FBLIM1 underlie the pathogenesis of chronic recurrent multifocal osteomyelitis (CRMO)

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare, pediatric, autoinflammatory disease characterized by bone pain due to sterile osteomyelitis, and is often accompanied by psoriasis or inflammatory bowel disease. There are two syndromic forms of CRMO, Majeed syndrome and DIRA, for which the genetic cause is known. However, for the majority of cases of CRMO, the genetic basis is unknown. Via whole-exome sequencing, we detected a homozygous mutation in the filamin-binding domain of FBLIM1 in an affected child with consanguineous parents. Microarray analysis of bone marrow macrophages from the CRMO murine model (cmo) determined that the Fblim1 ortholog is the most differentially expressed gene, downregulated over 20-fold in the cmo mouse. We sequenced FBLIM1 in 96 CRMO subjects and found a second proband with a novel frameshift mutation in exon 6 and a rare regulatory variant. In SaOS2 cells, overexpressing the regulatory mutation showed the flanking region acts as an enhancer, and the mutation ablates enhancer activity. Our data implicate FBLIM1 in the pathogenesis of sterile bone inflammation and our findings suggest CRMO is a disorder of chronic inflammation and imbalanced bone remodeling.

Serum Interleukin-6 and CCL11/Eotaxin May Be Suitable Biomarkers for the Diagnosis of Chronic Nonbacterial Osteomyelitis

OBJECTIVES

Chronic recurrent multifocal osteomyelitis (CRMO), the most severe form of chronic nonbacterial osteomyelitis (CNO), is an autoinflammatory bone disorder. In the absence of diagnostic criteria or biomarkers, CNO/CRMO remains a diagnosis of exclusion. The aim of this study was to identify biomarkers for diagnosing multifocal disease (CRMO).

STUDY DESIGN

Sera from 71 pediatric CRMO patients, 11 patients with osteoarticular infections, 62 patients with juvenile idiopathic arthritis (JIA), 7 patients with para-infectious or reactive arthritis, and 43 patients with acute leukemia or lymphoma, as well as 59 healthy individuals were collected. Multiplex analysis of 18 inflammation- and/or bone remodeling-associated serum proteins was performed. Statistical analysis included univariate ANOVA, discriminant analysis, univariate receiver operating characteristic (ROC) analysis, and logistic regression analyses.

RESULTS

For 14 of 18 blood serum proteins, significant differences were determined between CRMO patients, at least one alternative diagnosis, or healthy controls. Multi-component discriminant analysis delivered five biomarkers (IL-6, CCL11/eotaxin, CCL5/RANTES, collagen Iα, sIL-2R) for the diagnosis of CRMO. ROC analysis allowed further reduction to a core set of 2 biomarkers (CCL11/eotaxin, IL-6) that are sufficient to discern between CRMO, healthy controls, and alternative diagnoses.

CONCLUSION

Serum biomarkers CCL11/eotaxin and IL-6 differentiate between patients with CRMO, healthy controls, and alternative diagnoses (leukemia and lymphoma, osteoarticular infections, para-infectious arthritis, and JIA). Easily accessible biomarkers may aid in diagnosing CRMO. Further studies testing biomarkers in larger unrelated cohorts are warranted.

BAR Proteins PSTPIP1/2 Regulate Podosome Dynamics and the Resorption Activity of Osteoclasts

Bone resorption in vertebrates relies on the ability of osteoclasts to assemble F-actin-rich podosomes that condense into podosomal belts, forming sealing zones. Sealing zones segregate bone-facing ruffled membranes from other membrane domains, and disassemble when osteoclasts migrate to new areas. How podosome/sealing zone dynamics is regulated remains unknown. We illustrate the essential role of the membrane scaffolding F-BAR-Proline-Serine-Threonine Phosphatase Interacting Proteins (PSTPIP) 1 and 2 in this process. Whereas PSTPIP2 regulates podosome assembly, PSTPIP1 regulates their disassembly. PSTPIP1 recruits, through its F-BAR domain, the protein tyrosine phosphatase non-receptor type 6 (PTPN6) that de-phosphophorylates the phosphatidylinositol 5-phosphatases SHIP1/2 bound to the SH3 domain of PSTPIP1. Depletion of any component of this complex prevents sealing zone disassembly and increases osteoclast activity. Thus, our results illustrate the importance of BAR domain proteins in podosome structure and dynamics, and identify a new PSTPIP1/PTPN6/SHIP1/2-dependent negative feedback mechanism that counterbalances Src and PI(3,4,5)P3 signalling to control osteoclast cell polarity and activity during bone resorption.

Analysis of gene expression profile identifies potential biomarkers for atherosclerosis

The present study aimed to identify potential biomarkers for atherosclerosis via analysis of gene expression profiles. The microarray dataset no. GSE20129 was downloaded from the Gene Expression Omnibus database. A total of 118 samples from the peripheral blood of female patients was used, including 47 atherosclerotic and 71 non‑atherosclerotic patients. The differentially expressed genes (DEGs) in the atherosclerosis samples were identified using the Limma package. Gene ontology term and Kyoto Encyclopedia of Genes and Genomes pathway analyses for DEGs were performed using the Database for Annotation, Visualization and Integrated Discovery tool. The recursive feature elimination (RFE) algorithm was applied for feature selection via iterative classification, and support vector machine classifier was used for the validation of prediction accuracy. A total of 430 DEGs in the atherosclerosis samples were identified, including 149 up‑ and 281 downregulated genes. Subsequently, the RFE algorithm was used to identify 11 biomarkers, whose receiver operating characteristic curves had an area under curve of 0.92, indicating that the identified 11 biomarkers were representative. The present study indicated that APH1B, JAM3, FBLN2, CSAD and PSTPIP2 may have important roles in the progression of atherosclerosis in females and may be potential biomarkers for early diagnosis and prognosis as well as treatment targets for this disease.

Chronic Nonbacterial Osteomyelitis: Pathophysiological Concepts and Current Treatment Strategies

Chronic nonbacterial osteomyelitis (CNO) is an autoinflammatory bone disorder, covering a clinical spectrum with asymptomatic inflammation of single bones at the one end, and chronic recurrent multifocal osteomyelitis (CRMO) at the other end. The exact molecular pathophysiology of CNO remains largely unknown. Provided familial clusters and the association with inflammatory disorders of the skin and intestine suggest a genetic predisposition. Recently, profound dysregulation of cytokine responses was demonstrated in CRMO. Failure to produce antiinflammatory cytokines interleukin (IL)-10 and IL-19 contributes to activation of inflammasomes and subsequent IL-1β release. In IL-10-deficient and in CNO-prone chronic multifocal osteomyelitis mice, IL-1β was linked to bone inflammation. Further, alterations to the gut microbiome were suggested in contributing to IL-1β release from innate immune cells in mice, offering an interesting target in the search for molecular mechanisms in CNO. Here, we summarize clinical presentation and treatment options in CNO/CRMO, current pathophysiological concepts, available mouse models, and promising future scientific directions.

Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome - A challenging diagnosis not to be missed

SAPHO syndrome manifests as chronic inflammation of bones and joints, which may or may not be accompanied by skin changes. The term SAPHO is an acronym that stands for synovitis, acne, pustulosis (usually palmoplantar), hyperostosis and osteitis. The bones most commonly affected are those in the anterior chest wall (mainly the sternum, clavicles and sternocostoclavicular joints), the vertebrae and the sacroiliac joints, but peripheral and flat bones may also be involved, especially in children. There are no validated diagnostic criteria for SAPHO, and diagnosis is based on clinical and radiological findings. One of the main challenges in diagnosis is that the clinical features may occur many years apart. Additionally, patients may not develop all manifestations. Delayed diagnosis, as a result of a lack of awareness of SAPHO, can lead to patients suffering ongoing pain and disfiguring skin manifestations. One theory is that Propionibacterium acnes (isolated from bone biopsies in many SAPHO patients) triggers an auto-immune mediated chronic inflammation in genetically predisposed individuals. Treatment involves the use of nonsteroidal anti-inflammatory drugs, intra-articular steroids, bisphosphonates and biologicals. The course of SAPHO is often prolonged but, despite the challenges in diagnosis and treatment, the long-term prognosis is good.

Microbiota and caspase-1/caspase-8 regulate IL-1β-mediated bone disease

A leucine-to-proline missense mutation at residue 98 in the proline-serine-threonine phosphatase interacting protein 2 (Pstpip2) gene leads to autoinflammatory disease that is characterized by splenomegaly, necrosis, and spontaneous development of osteomyelitis in mice (Pstpip2^cmo). Disease progression in these mice resembles that of chronic recurrent multifocal osteomyelitis in humans. Our group and others have shown that disease progression in Pstpip2^cmo mice is mediated by the cytokine IL-1β, independently of inflammasomes or IL-1α. Our recent publication highlighted herein establishes that diet-induced changes in intestinal microbiota provide protection against the development of osteomyelitis in Pstpip2^cmo mice. Moreover, the proteases caspase-1 and caspase-8 have redundant roles in cleaving IL-1β and promoting disease. This addendum reviews the current literature on the Pstpip2^cmo murine disease model and the clinical significance of the role of PSTPIP2 in regulating autoinflammatory osteomyelitis, which is mediated by innate components of immune cells.

NLRP3 inflammasome plays a redundant role with caspase 8 to promote IL-1β-mediated osteomyelitis

Missense mutation in the proline-serine-threonine phosphatase-interacting protein 2 (Pstpip2) gene results in the development of spontaneous chronic bone disease characterized by bone deformity and inflammation that is reminiscent of patients with chronic multifocal osteomyelitis (cmo). Interestingly, this disease is specifically mediated by IL-1β but not IL-1α. The precise molecular pathways that promote pathogenic IL-1β production inPstpip2(cmo)mice remain unidentified. Furthermore, how IL-1β provokes inflammatory bone disease inPstpip2(cmo)mice is not known. Here, we demonstrate that double deficiency of Nod like receptor family, pyrin domain containing 3 (NLRP3) and caspase 8 inPstpip2(cmo)mice provides similar protection as observed in caspase-1 and caspase-8-deficientPstpip2(cmo)mice, demonstrating redundant roles for the NLRP3 inflammasome and caspase 8 in provoking osteomyelitic disease inPstpip2(cmo)mice. Consistently, immunofluorescence studies exhibited distinct caspase-1 and caspase-8 puncta in diseasedPtpn6(spin)neutrophils. Data from our chimera studies demonstrated that IL-1β produced by hematopoietic cells is sensed by the radioresistant compartment to promote bone disease. Furthermore, our results showed that the IL-1β signaling is unidirectional and feedback signaling of IL-1β onto the hematopoietic compartment is not important for disease induction. In conclusion, our studies have uncovered the combined actions of the NLRP3 inflammasome and caspase 8 leading to IL-1β maturation and the directionality of IL-1β in driving disease inPstpip2(cmo)mice.

Interleukin-1 Family Cytokines in Liver Diseases

The gene encoding IL-1 was sequenced more than 30 years ago, and many related cytokines, such as IL-18, IL-33, IL-36, IL-37, IL-38, IL-1 receptor antagonist (IL-1Ra), and IL-36Ra, have since been identified. IL-1 is a potent proinflammatory cytokine and is involved in various inflammatory diseases. Other IL-1 family ligands are critical for the development of diverse diseases, including inflammatory and allergic diseases. Only IL-1Ra possesses the leader peptide required for secretion from cells, and many ligands require posttranslational processing for activation. Some require inflammasome-mediated processing for activation and release, whereas others serve as alarmins and are released following cell membrane rupture, for example, by pyroptosis or necroptosis. Thus, each ligand has the proper molecular process to exert its own biological functions. In this review, we will give a brief introduction to the IL-1 family cytokines and discuss their pivotal roles in the development of various liver diseases in association with immune responses. For example, an excess of IL-33 causes liver fibrosis in mice via activation and expansion of group 2 innate lymphoid cells to produce type 2 cytokines, resulting in cell conversion into pro-fibrotic M2 macrophages. Finally, we will discuss the importance of IL-1 family cytokine-mediated molecular and cellular networks in the development of acute and chronic liver diseases.

Primary Chronic Osteomyelitis of the Jaws in Children: An Update on Pathophysiology, Radiological Findings, Treatment Strategies, and Prospective Analysis of Two Cases

Objective. Primary chronic osteomyelitis (PCO) of the jaws in children is associated with pain, trismus, and swelling. In children, temporomandibular joint involvement is rare and few studies have been published due to the relatively low incidence. This paper presents two cases of mandibular PCO in children with the involvement of the collum mandibulae. In addition, a review of the literature regarding demographic data, histological, radiological, and laboratory findings, and treatment strategies of PCO was also performed. Material and Methods. Prospective analyses of two PCO cases. A PubMed search was used and the articles were sorted according to their corresponding key area of focus. Results. Review of the literature revealed twenty-four cases of PCO with two cases of mandibular condyle involvement. The mean age was 18 years; the male to female ratio was 1 : 3. Most of the patients were treated with anti-inflammatory drugs in combination with decortication. Clinical recurrence was seen in 7 cases. Conclusion. A combination of anti-inflammatory drugs and surgical intervention appears to be the first choice of treatment. However, surgical removal of necrotic tissue adjacent to collum mandibulae has its limitations in children. Further investigations are of utmost importance in order to increase our knowledge and understanding of this disease.

PSTPIP2, a Protein Associated with Autoinflammatory Disease, Interacts with Inhibitory Enzymes SHIP1 and Csk

Mutations in the adaptor protein PSTPIP2 are the cause of the autoinflammatory disease chronic multifocal osteomyelitis in mice. This disease closely resembles the human disorder chronic recurrent multifocal osteomyelitis, characterized by sterile inflammation of the bones and often associated with inflammation in other organs, such as the skin. The most critical process in the disease's development is the enhanced production of IL-1β. This excessive IL-1β is likely produced by neutrophils. In addition, the increased activity of macrophages, osteoclasts, and megakaryocytes has also been described. However, the molecular mechanism of how PSTPIP2 deficiency results in this phenotype is poorly understood. Part of the PSTPIP2 inhibitory function is mediated by protein tyrosine phosphatases from the proline-, glutamic acid-, serine- and threonine-rich (PEST) family, which are known to interact with the central part of this protein, but other regions of PSTPIP2 not required for PEST-family phosphatase binding were also shown to be indispensable for PSTPIP2 function. In this article, we show that PSTPIP2 binds the inhibitory enzymes Csk and SHIP1. The interaction with SHIP1 is of particular importance because it binds to the critical tyrosine residues at the C terminus of PSTPIP2, which is known to be crucial for its PEST-phosphatase-independent inhibitory effects in different cellular systems. We demonstrate that in neutrophils this region is important for the PSTPIP2-mediated suppression of IL-1β processing and that SHIP1 inhibition results in the enhancement of this processing. We also describe deregulated neutrophil response to multiple activators, including silica, Ab aggregates, and LPS, which is suggestive of a rather generalized hypersensitivity of these cells to various external stimulants.