The homeostatic function of Regnase-2 restricts neuroinflammation.

The precise physiological functions and mechanisms regulating RNase Regnase-2 (Reg-2/ZC3H12B/MCPIP2) activity remain enigmatic. We found that Reg-2 actively modulates neuroinflammation in nontransformed cells, including primary astrocytes. Downregulation of Reg-2 in these cells results in increased mRNA levels of proinflammatory cytokines IL-1ß and IL-6. In primary astrocytes, Reg-2 also regulates the mRNA level of Regnase-1 (Reg-1/ZC3H12A/MCPIP1). Reg-2 is expressed at high levels in the healthy brain, but its expression is reduced during neuroinflammation as well as glioblastoma progression. This process is associated with the upregulation of Reg-1. Conversely, overexpression of Reg-2 is accompanied by the downregulation of Reg-1 in glioma cells in a nucleolytic NYN/PIN domain-dependent manner. Interestingly, low levels of Reg-2 and high levels of Reg-1 correlate with poor-glioblastoma patients' prognoses. While Reg-2 restricts the basal levels of proinflammatory cytokines in resting astrocytes, its expression is reduced in IL-1ß-activated astrocytes. Following IL-1ß exposure, Reg-2 is phosphorylated, ubiquitinated, and degraded by proteasomes. Simultaneously, the Reg-2 transcript is destabilized by tristetraprolin (TTP) and Reg-1 through the AREs elements and conservative stem-loop structure present in its 3'UTR. Thus, the peer-control loop, of Reg-1 and Reg-2 opposing each other, exists. The involvement of TTP in Reg-2 mRNA turnover is confirmed by the observation that high TTP levels correlate with the downregulation of the Reg-2 expression in high-grade human gliomas. Additionally, obtained results reveal the importance of Reg-2 in inhibiting human and mouse glioma cell proliferation. Our current studies identify Reg-2 as a critical regulator of homeostasis in the brain.

Yin Yang 1 controls cerebellar astrocyte maturation.

Diverse subpopulations of astrocytes tile different brain regions to accommodate local requirements of neurons and associated neuronal circuits. Nevertheless, molecular mechanisms governing astrocyte diversity remain mostly unknown. We explored the role of a zinc finger transcription factor Yin Yang 1 (YY1) that is expressed in astrocytes. We found that specific deletion of YY1 from astrocytes causes severe motor deficits in mice, induces Bergmann gliosis, and results in simultaneous loss of GFAP expression in velate and fibrous cerebellar astrocytes. Single cell RNA-seq analysis showed that YY1 exerts specific effects on gene expression in subpopulations of cerebellar astrocytes. We found that although YY1 is dispensable for the initial stages of astrocyte development, it regulates subtype-specific gene expression during astrocyte maturation. Moreover, YY1 is continuously needed to maintain mature astrocytes in the adult cerebellum. Our findings suggest that YY1 plays critical roles regulating cerebellar astrocyte maturation during development and maintaining a mature phenotype of astrocytes in the adult cerebellum.

Cellular inhibitor of apoptosis 2 (cIAP2) restricts neuroinflammation during experimental autoimmune encephalomyelitis.

BACKGROUND: Immune activation, neuroinflammation, and cell death are the hallmarks of multiple sclerosis (MS), which is an autoimmune demyelinating disease of the central nervous system (CNS). It is well-documented that the cellular inhibitor of apoptosis 2 (cIAP2) is induced by inflammatory stimuli and regulates adaptive and innate immune responses, cell death, and the production of inflammatory mediators. However, the impact of cIAP2 on neuroinflammation associated with MS and disease severity remains unknown. METHODS: We used experimental autoimmune encephalomyelitis (EAE), a widely used mouse model of MS, to assess the effect of cIAP2 deletion on disease outcomes. We performed a detailed analysis on the histological, cellular, and molecular levels. We generated and examined bone-marrow chimeras to identify the cIAP2-deficient cells that are critical to the disease outcomes. RESULTS: cIAP2-/- mice exhibited increased EAE severity, increased CD4+ T cell infiltration, enhanced proinflammatory cytokine/chemokine expression, and augmented demyelination. This phenotype was driven by cIAP2-deficient non-hematopoietic cells. cIAP2 protected oligodendrocytes from cell death during EAE by limiting proliferation and activation of brain microglia. This protective role was likely exerted by cIAP2-mediated inhibition of the non-canonical NLRP3/caspase-8-dependent myeloid cell activation during EAE. CONCLUSIONS: Our findings suggest that cIAP2 is needed to modulate neuroinflammation, cell death, and survival during EAE. Significantly, our data demonstrate the critical role of cIAP2 in limiting the activation of microglia during EAE, which could be explored for developing MS therapeutics in the future.

RelB controls adaptive responses of astrocytes during sterile inflammation.

In response to brain injury or infections, astrocytes become reactive, undergo striking morphological and functional changes, and secrete and respond to a spectrum of inflammatory mediators. We asked whether reactive astrocytes also display adaptive responses during sterile IL-1ß-induced neuroinflammation, which may limit tissue injury associated with many disorders of the central nervous system. We found that astrocytes display days-to-weeks long specific tolerance of cytokine genes, which is coordinated by NF-κB family member, RelB. However, in contrast to innate immune cells, astrocytic tolerance does not involve epigenetic silencing of the cytokine genes. Establishment of tolerance depends on persistent higher levels of RelB in tolerant astrocytes and its phosphorylation on serine 472. Mechanistically, this phosphorylation prevents efficient removal of RelB from cytokine promoters by IκBα and helps to establish tolerance. Importantly, ablation of RelB from astrocytes in mice abolishes tolerance during experimental neuroinflammation in vivo.

A detrimental role of RelB in mature oligodendrocytes during experimental acute encephalomyelitis.

BACKGROUND: Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system (CNS). It is firmly established that overactivation of the p65 (RelA) nuclear factor kappa B (NF-κB) transcription factor upregulates expression of inflammatory mediators in both immune and non-immune resident CNS cells and promotes inflammation during MS. In contrast to p65, NF-κB family member RelB regulates immune cell development and can limit inflammation. Although RelB expression is induced during inflammation in the CNS, its role in MS remains unknown. METHODS: To examine the role of RelB in non-immune CNS cells, we generated mice with RelB specifically deleted in astrocytes (RelBΔAST), oligodendrocytes (RelBΔOLIGO), or neural progenitor-derived cells (RelBΔNP). We used experimental autoimmune encephalomyelitis (EAE), an accepted mouse model of MS, to assess the effect of RelB deletion on disease outcomes and performed analysis on the histological, cellular, and molecular level. RESULTS: Despite being a negative regulator of inflammation, conditional knockout of RelB in non-immune resident CNS cells surprisingly decreased the severity of EAE. This protective effect was recapitulated by conditional deletion of RelB in oligodendrocytes but not astrocytes. Deletion of RelB in oligodendrocytes reduced disease severity, promoted survival of mature oligodendrocytes, and correlated with increased activation of p65 NF-κB. CONCLUSIONS: These findings suggest that RelB fine tunes inflammation and cell death/survival during EAE. Importantly, our data points out the detrimental role RelB plays in controlling survival of mature oligodendrocytes, which could be explored as a viable option to treat MS in the future.

Ocular pyoderma gangrenosum: A systematic review.

BACKGROUND: Pyoderma gangrenosum (PG) is a rare, ulcerative cutaneous disorder. Ophthalmic involvement in PG is atypical, but can have devastating consequences. OBJECTIVE: We sought to characterize ocular PG to allow for earlier diagnosis and therapy. To our knowledge, this is the first systematic review summarizing this clinical variant. METHODS: A systematic review was conducted using PubMed and Web of Science. Data were extracted and studies were qualitatively assessed and analyzed. RESULTS: We identified all 34 cases of PG involving the eye and periorbital area, and categorized them into 4 different subtypes. Common presenting signs include ulceration, peripheral ulcerative keratitis, and decreased visual acuity. Although it is often difficult to biopsy ocular PG, histologic features are nonspecific. Combined therapy using corticosteroids and further surgical reconstruction as needed is the mainstay of treatment. Cases of the eye/orbit in particular should be treated aggressively, as these are more likely to relapse compared with cases of the periorbital area. LIMITATIONS: Use of case reports, paucity of ocular PG cases, and heterogeneity of studies are limitations. CONCLUSION: PG should be considered in the differential diagnosis of ulceration of ocular/periocular tissues. An aggressive, early, multimodal treatment strategy should be used to prevent relapse, especially in cases of the eye/orbit.

Sphingosine-1-phosphate inhibits IL-1-induced expression of C-C motif ligand 5 via c-Fos-dependent suppression of IFN-ß amplification loop.

The neuroinflammation associated with multiple sclerosis involves activation of astrocytes that secrete and respond to inflammatory mediators such as IL-1. IL-1 stimulates expression of many chemokines, including C-C motif ligand (CCL) 5, that recruit immune cells, but it also stimulates sphingosine kinase-1, an enzyme that generates sphingosine-1-phosphate (S1P), a bioactive lipid mediator essential for inflammation. We found that whereas S1P promotes IL-1-induced expression of IL-6, it inhibits IL-1-induced CCL5 expression in astrocytes. This inhibition is mediated by the S1P receptor (S1PR)-2 via an inhibitory G-dependent mechanism. Consistent with this surprising finding, infiltration of macrophages into sites of inflammation increased significantly in S1PR2(-/-) animals. However, activation of NF-κB, IFN regulatory factor-1, and MAPKs, all of which regulate CCL5 expression in response to IL-1, was not diminished by the S1P in astrocytes. Instead, S1PR2 stimulated inositol 1,4,5-trisphosphate-dependent Ca(++) release and Elk-1 phosphorylation and enhanced c-Fos expression. In our study, IL-1 induced the IFNß production that supports CCL5 expression. An intriguing finding was that S1P induced c-Fos-inhibited CCL5 directly and also indirectly through inhibition of the IFN-ß amplification loop. We propose that in addition to S1PR1, which promotes inflammation, S1PR2 mediates opposing inhibitory functions that limit CCL5 expression and diminish the recruitment of immune cells.

Real-world socioeconomic determinants of corneal crosslinking in a national cohort.

PURPOSE: To characterize recent socioeconomic trends in patients with keratoconus/corneal ectasias undergoing corneal crosslinking (CXL). SETTING: A deidentified administrative medical claims database comprised commercial and Medicare Advantage health claims from across the United States. DESIGN: Population-based retrospective cohort study. METHODS: This study identified 552 patients with keratoconus/corneal ectasia who underwent CXL and 2723 matched controls who did not undergo CXL based on Current Procedural Terminology coding from a U.S. national insurance claims database from 2016 to 2020. For each patient, characteristics, including sex, race, age, household net worth, education level, insurance plan type, and geographic region, were extracted. Multivariate logistic regression was conducted to determine the odds of undergoing crosslinking. RESULTS: Age 30 years or older (odds ratio [OR], 0.34, P < .001) was associated with decreased likelihood of undergoing CXL. Sex, race, education, and patient income were not associated with odds of undergoing CXL. Patients with health maintenance organization insurance had lower odds of undergoing CXL (OR, 0.64, P = .047). Geographically, patients on the east coast (OR, 0.37, P < .001) and Lower Midwest (OR, 0.31, P < .001) had statistically lower odds of undergoing crosslinking. CONCLUSIONS: This is the first study to identify socioeconomic determinants of CXL, and it highlights that geographic location and insurance type may limit accessibility to patients.

The association of stroke with herpes zoster ophthalmicus.

BACKGROUND/OBJECTIVES: Studies have reported an association between herpes zoster ophthalmicus (HZO) and stroke. We sought to validate this association with rigorous controls for both medical comorbidities and social factors using a nationwide U.S. administrative medical claims database. SUBJECTS/METHODS: A two-step approach was taken: first a retrospective case-control study was performed, followed by a self-controlled case series (SCCS). For the case control study, cox proportional hazard regression with inverse proportional treatment weighting assessed the hazard for stroke. In the SCCS, incidence of stroke was compared prior to and after the diagnosis of HZO. RESULTS: For the case-control study, 25,720 cases and 75,924 controls met our eligibility criteria. 1712 (6.7%) and 4544 (6.0%) strokes occurred in the case and control groups respectively, conferring an 18% increased risk of stroke in the observed 1-year post-HZO period (HR = 1.18, 95% CI: 1.12-1.25, p < 0.001). SCCS analysis showed the risk for stroke was highest in the month immediately after HZO episode compared to any other time range (1-30 days after, relative risk 1.58, p < 0.001) and even higher when assessing time more distal time points prior to the HZO diagnosis (days 1-30 after HZO diagnosis had RR = 1.69 (95% CI: 1.38-2.07) and RR = 1.93 (95% CI: 1.55-2.39) compared with days -120 to -91 and -150 to -121 prior to index, respectively (p < 0.001). CONCLUSIONS: After accounting for stroke risk factors, our analysis confirms the association between HZO and stroke, with highest risk in the immediate month after an episode.

Ocular Manifestations of the NAA10-Related Syndrome.

The NAA10-related syndrome is a rare X-linked neurodevelopmental condition that was first described in 2011. The disorder is caused by pathogenic variants in the NAA10 gene located on chromosome X at position Xq28. Clinical features typically include severe psychomotor developmental delay, cardiac disease, dysmorphic features, postnatal growth failure, and hypotonia, although there is significant variability in the severity of the phenotype among affected individuals. We describe a 5-year-old female with the syndrome; massively parallel exome sequencing and analysis revealed the c.247C>T (p.Arg83Cys) pathogenic variant that has been previously reported in ten affected individuals. Ocular manifestations of the NAA10-related syndrome are not uncommon, although they have not been well characterized in literature reports. From a systematic review of previously published cases to date, ocular abnormalities are present in more than half of patients with the syndrome. Common ocular findings reported include astigmatism, hyperopia, cortical vision impairment, microphthalmia/anophthalmia, and hypertelorism. Our patient presented with growth restriction, dysmorphic features, and hypotonia. Ocular manifestations identified in this child include downslanting palpebral fissures, myopic astigmatism, nystagmus, and exotropia. We speculate that the type and severity of ocular defects present in individuals with the NAA10-related syndrome are dependent on the specific NAA10 pathogenic variant involved.

A Comprehensive Review of Local Pharmacologic Therapy for Pyoderma Gangrenosum.

Pyoderma gangrenosum (PG) is a rare, ulcerative inflammatory skin disease that most commonly occurs in patients with inflammatory bowel disease, rheumatologic diseases, or hematologic diseases. Successful treatment of PG often requires immunosuppression and appropriate wound care. Systemic corticosteroids and cyclosporine are the first-line treatments for PG. However, chronic use of these systemic agents places patients at risk for developing significant side effects, including hyperglycemia, osteoporosis, hypertension, and weight gain. Furthermore, when treating small or superficial PG ulcers, the use of local agents as monotherapies or adjuvant treatments can be ideal to control inflammation and promote healing without placing the patient at risk for many severe side effects that can be seen with long-term use of systemic agents. This literature review assesses all available local therapies in order to summarize the use and reported efficaciousness of the broad range of local treatments available for PG.

RelB acts as a molecular switch driving chronic inflammation in glioblastoma multiforme.

Glioblastoma multiforme (GBM) is a primary brain tumor characterized by extensive necrosis and immunosuppressive inflammation. The mechanisms by which this inflammation develops and persists in GBM remain elusive. We identified two cytokines interleukin-1ß (IL-1) and oncostatin M (OSM) that strongly negatively correlate with patient survival. We found that these cytokines activate RelB/p50 complexes by a canonical NF-κB pathway, which surprisingly drives expression of proinflammatory cytokines in GBM cells, but leads to their inhibition in non-transformed astrocytes. We discovered that one allele of the gene encoding deacetylase Sirtuin 1 (SIRT1), needed for repression of cytokine genes, is deleted in 80% of GBM tumors. Furthermore, RelB specifically interacts with a transcription factor Yin Yang 1 (YY1) in GBM cells and activates GBM-specific gene expression programs. As a result, GBM cells continuously secrete proinflammatory cytokines and factors attracting/activating glioma-associated microglia/macrophages and thus, promote a feedforward inflammatory loop.

Pyoderma Gangrenosum of the Scalp: A Rare Clinical Variant.

Pyoderma gangrenosum (PG) is a rare, neutrophil-predominant dermatosis that usually presents as a papule or pustule and progresses into a painful ulcer. Clinical and histopathological features are nonspecific, making PG a challenging condition to diagnose. Lesions may occur anywhere on the body; however, the lower extremity is the most common location. Solitary lesions in atypical locations such as the scalp are uncommon, making this clinical variant especially difficult to recognize and diagnose. Although the clinical features and subsequent management of scalp PG might be different from other anatomic sites, the typical presentation and treatment of scalp PG is still unclear. The authors present a recent case of a 34-year-old woman with scalp PG and summarize 16 other cases documented in the literature. This case report and literature review illustrate several similarities and differences between scalp PG and classic PG: (1) scalp PG occurs in a wider age demographic of patients; (2) as with classic PG, inflammatory bowel disease and pregnancy are associated conditions, but head injury and preexisting inflammatory skin conditions of the scalp may be additional predisposing factors for scalp PG; and (3) as with classic PG, scalp PG generally responds well to corticosteroids and immunosuppressive therapy. Scarring occurs in all conditions, though disfigurement and psychosomatic effects may be disproportionately higher in scalp PG.

Severe and acute complications of biologics in psoriasis.

Biologic therapies have revolutionized the approach to immune-mediated diseases such as psoriasis. Due to their favorable safety profiles and excellent efficacy, biologic agents are considered the gold standard for moderate-to-severe psoriasis. The aim of this paper is to saliently review the severe and acute complications of the Food and Drug Administration (FDA) approved biologic agents for psoriasis. Reviewed agents include tumor necrosis factor alpha inhibitors (etanercept, infliximab, and adalimumab), interleukin 12/23 inhibitors (ustekinumab), and interleukin 17 (IL-17) inhibitors (secukinumab and ixekizumab). While malignancies, serious infections, and major adverse cardiovascular events have been reported, their association with biologic therapy are not hypothesized as causal. However, IL-17 inhibitors appear to cause exacerbations and new cases of inflammatory bowel disease. While more long-term studies are warranted in understanding the biologic's long-term side effect profile, short-term studies have confirmed that the biologics are some of the safest treatment options for psoriasis. Nevertheless, certain populations yield higher risk to acute complications with the biologics than others - physicians must use their judgement and vigilance when monitoring and treating patients undergoing therapy with biological agents.