The role of TNF-α and its receptors in the production of Src-suppressed C kinase substrate by rat primary type-2 astrocytes

Etanercept-Induced Anti-Glomerular Basement Membrane Disease

Anti-glomerular basement membrane (anti-GBM) disease is a rare form of small-vessel vasculitis that typically causes rapidly progressive glomerulonephritis with or without alveolar haemorrhage. Previously, there has only been one reported case of tumour necrosis factor-α (TNF-α) antagonist-induced anti-GBM disease. Here, we describe the first reported case of etanercept-induced anti-GBM disease. A 55-year-old Caucasian man was referred to our tertiary specialist renal centre with a history of painless macroscopic haematuria. The patient has been receiving weekly etanercept injections over the past 12 months for psoriatic arthropathy. The serum immunology panel results highlighted a significantly raised anti-GBM titre (370.1 U). Etanercept was stopped, and the patient was empirically commenced on pulsed methylprednisolone, cyclophosphamide, and plasma exchange. A renal biopsy showed crescentic glomerulonephritis. Few days after admission, he tested positive for coronavirus disease 2019 (COVID-19), and a decision was made to withhold cyclophosphamide. There was further decline in renal function with hyperkalaemia for which he received 2 sessions of haemodialysis. He was restarted on cyclophosphamide upon discharge. The patient was switched to rituximab treatment afterwards as he developed leucopenia 2 weeks following the commencement of cyclophosphamide. The serum creatinine level continued to improve and remained dialysis-independent. In conclusion, with the increased use of etanercept and other TNF-α antagonists, the prescribing clinician must be aware of the rare but life-threatening drug-induced vasculitis. We recommend careful monitoring of renal indices with the use of this class of medications.

SSeCKS/AKAP12 scaffolding functions suppress B16F10-induced peritoneal metastasis by attenuating CXCL9/10 secretion by resident fibroblasts

SSeCKS/Gravin/AKAP12 (SSeCKS) is a kinase scaffolding protein known to suppress metastasis by attenuating tumor-intrinsic PKC- and Src-mediated signaling pathways [1]. In addition to downregulation in metastatic cells, in silico analyses identified SSeCKS downregulation in prostate or breast cancer-derived stroma, suggesting a microenvironmental cell role in controlling malignancy. Although orthotopic B16F10 and SM1WT1[Braf^V600E] mouse melanoma tumors grew similarly in syngeneic WT or SSeCKS-null (KO) mice, KO hosts exhibited 5- to 10-fold higher levels of peritoneal metastasis, and this enhancement could be adoptively transferred by pre-injecting naïve WT mice with peritoneal fluid (PF), but not non-adherent peritoneal cells (PC), from naïve KO mice. B16F10 and SM1WT1 cells showed increased chemotaxis to KO-PF compared to WT-PF, corresponding to increased PF levels of multiple inflammatory mediators, including the Cxcr3 ligands, Cxcl9 and 10. Cxcr3 knockdown abrogated enhanced chemotaxis to KO-PF and peritoneal metastasis in KO hosts. Conditioned media from KO peritoneal membrane fibroblasts (PMF), but not from KO-PC, induced increased B16F10 chemotaxis over controls, which could be blocked with Cxcl10 neutralizing antibody. KO-PMF exhibited increased levels of the senescence markers, SA-β-galactosidase, p21^waf1 and p16^ink4a, and enhanced Cxcl10 secretion induced by inflammatory mediators, lipopolysaccharide, TNFα, IFNα and IFNγ. SSeCKS scaffolding-site mutants and small molecule kinase inhibitors were used to show that the loss of SSeCKS-regulated PKC, PKA and PI3K/Akt pathways are responsible for the enhanced Cxcl10 secretion. These data mark the first description of a role for stromal SSeCKS/AKAP12 in suppressing metastasis, specifically by attenuating signaling pathways that promote secretion of tumor chemoattractants in the peritoneum.

A novel infection- and inflammation-associated molecular signature in peripheral blood of myasthenia gravis patients

Myasthenia gravis (MG) is a T-cell dependent autoimmune disorder of the neuromuscular junction, characterised by muscle weakness and fatigability. Autoimmunity is thought to initiate in the thymus of acetylcholine receptor (AChR)-positive MG patients; however, the molecular mechanisms linking intra-thymic MG pathogenesis with autoreactivity via the circulation to the muscle target organ are poorly understood. Using whole-transcriptome sequencing, we compared the transcriptional profile of peripheral blood mononuclear cells from AChR-early onset MG (AChR-EOMG) patients with healthy controls: 178 coding transcripts and 229 long non-coding RNAs, including 11 pre-miRNAs, were differentially expressed. Among the 178 coding transcripts, 128 were annotated of which 17% were associated with the 'infectious disease' functional category and 46% with 'inflammatory disease' and 'inflammatory response-associated' categories. Validation of selected transcripts by qPCR indicated that of the infectious disease-related transcripts, ETF1, NFKB2, PLK3, and PPP1R15A were upregulated, whereas CLC and IL4 were downregulated in AChR-EOMG patients; in the 'inflammatory' categories, ABCA1, FUS, and RELB were upregulated, suggesting a contribution of these molecules to immunological dysfunctions in MG. Data selection and validation were also based on predicted microRNA-mRNA interactions. We found that miR-612, miR-3654, and miR-3651 were increased, whereas miR-612-putative AKAp12 and HRH4 targets and the miR-3651-putative CRISP3 target were downregulated in AChR-EOMG, also suggesting altered immunoregulation. Our findings reveal a novel peripheral molecular signature in AChR-EOMG, reflecting a critical involvement of inflammatory- and infectious disease-related immune responses in disease pathogenesis.

VAV1 and BAFF, via NFκB pathway, are genetic risk factors for myasthenia gravis

Objective

To identify novel genetic loci that predispose to early-onset myasthenia gravis (EOMG) applying a two-stage association study, exploration, and replication strategy.

Methods

Thirty-four loci and one confirmation loci, human leukocyte antigen (HLA)-DRA, were selected as candidate genes by team members of groups involved in different research aspects of MG. In the exploration step, these candidate genes were genotyped in 384 EOMG and 384 matched controls and significant difference in allele frequency were found in eight genes. In the replication step, eight candidate genes and one confirmation loci were genotyped in 1177 EOMG patients and 814 controls, from nine European centres.

Results

Allele frequency differences were found in four novel loci: CD86, AKAP12, VAV1, B-cell activating factor (BAFF), and tumor necrosis factor-alpha (TNF-α), and these differences were consistent in all nine cohorts. Haplotype trend test supported the differences in allele frequencies between cases and controls. In addition, allele frequency difference in female versus male patients at HLA-DRA and TNF-α loci were observed.

Interpretation

The genetic associations to EOMG outside the HLA complex are novel and of interest as VAV1 is a key signal transducer essential for T- and B-cell activation, and BAFF is a cytokine that plays important roles in the proliferation and differentiation of B-cells. Moreover, we noted striking epistasis between the predisposing VAV1 and BAFF haplotypes; they conferred a greater risk in combination than alone. These, and CD86, share the same signaling pathway, namely nuclear factor-kappaB (NFκB), thus implicating dysregulation of proinflammatory signaling in predisposition to EOMG.

Expression of SRC suppressed C kinase substrate in rat neural tissues during inflammation

Src-suppressed C kinase substrate (SSeCKS), an in vivo and in vitro protein kinase C substrate, is a major lipopolysaccharide (LPS) response protein which markedly upregulated in several organs, including brain, lung, heart, kidney etc., indicating a possible role of SSeCKS in inflammatory process. However, the expression and biological function of SSeCKS during neuronal inflammation remains to be elucidated, so we established an inflammatory model injected with LPS to investigate the gene expression patterns of SSeCKS in neural tissues by using TaqMan quantitative real-time PCR and immunohistochemistry in rat. Real-time PCR showed that LPS stimulated the expression of SSeCKS mRNA in a dose- and time-dependent manner in sciatic nerves, spinal cords and dorsal root ganglions. Immunohistochemistry showed that SSeCKS colocalized with nerve fibers in sciatic nerve after LPS administration, but there was no colocalization between SSeCKS and Schwann cells. In addition, SSeCKS colocalized with neurons which existed in dorsal root ganglions and spinal cords. These findings indicated that SSeCKS might play some important roles in sciatic nerve fibers and neurons in spinal cords and dorsal root ganglions after LPS injection.

Novel biomarkers for the progression of diabetic nephropathy: soluble TNF receptors

Despite 2 decades of advances in therapy of diabetic patients, the prevalence of diabetic nephropathy among patients with diabetes has not decreased. However, large-scale multicenter studies have achieved great success in terms of the reduction of albuminuria, suggesting that albuminuria might not be an accurate surrogate marker for slowing the rate of renal function decline. It is important to be able to identify individuals at high risk for renal function decline, or ultimately, end-stage kidney disease (ESKD) and its associated cardiovascular disease (CVD). More sensitive early biomarkers, other than albuminuria and the estimated glomerular filtration rate (eGFR), should be required. Recently, serum concentrations of soluble tumor necrosis factor (TNF), receptor 1 (TNFR1), and TNFR2 have predicted future GFR loss and ESKD in patients of a wide variety of stages and both types of diabetes. Longitudinal interventional studies are needed to validate these biomarkers in a broad range of populations prior to implementation in routine diabetes management.

Tumor necrosis factor receptors: biology and therapeutic potential in kidney diseases

The major evolutionary advance represented in the human immune system is a mechanism of antigen-directed immunity in which tumor necrosis factor (TNF)-α and TNF receptors (TNFRs) play essential roles. Binding of TNF-α to the 55-kDa type I TNFR (TNFR1, TNFRSF1A, CD120a, p55) or the 75-kDa type II TNFR (TNFR2, TNFRSF1B, CD120b, p75) activates signaling pathways controlling inflammatory, immune and stress responses, as well as host defense and apoptosis. Multiple studies have investigated the role of TNFRs in the development of early and late renal failure (diabetic nephropathy, nephroangiosclerosis, acute kidney transplant rejection, renal cell carcinoma, glomerulonephritis, sepsis and obstructive renal injury). This article reviews the general characteristics, the analytical aspects and the biology of TNFRs in this domain. In addition, the potential therapeutic application of specific TNFR blockers is discussed.

Involvement of SRC-suppressed C kinase substrate in neuronal death caused by the lipopolysaccharide-induced reactive astrogliosis

Src-suppressed C kinase substrate (SSeCKS), a protein kinase C substrate, is a major lipopolysaccharide (LPS) response protein, regulating the inflammatory process. In the process of spinal inflammatory diseases by LPS intraspinal injection, expression of SSeCKS in the spinal cord was increased, mainly in active astrocytes and neurons. Induced SSeCKS was colabeled with terminal deoxynucleotidyl transferase-mediated biotinylated-dUTP nick-end labeling (an apoptosis maker) in the late inflammation processes. These results indicated that SSeCKS might correlate with the inflammatory reaction and late neurodegeneration after LPS injection. A cell type-specific action for SSeCKS was further studied within C6 cells and PC12 cells. Knockdown of SSeCKS by small-interfering RNAs (siRNAs) blocked the LPS-induced inducible nitric oxide synthase (iNOS) expression in C6 cells, while overexpression SSeCKS enhanced iNOS expression. SSeCKS is also participated in regulation of PC12 cell viability. Loss of SSeCKS rescued PC12 cell viability, and excessive SSeCKS exacerbated the cell death upon conditioned medium and tumor necrosis factor-alpha exposure. This study delineates that SSeCKS may be important for host defenses in spinal inflammation and suggests a valuable molecular mechanism by which astrocytes modify neuronal viability during pathological states.

Involvement of Src-suppressed C kinase substrate in experimental autoimmune encephalomyelitis: a link between release of astrocyte proinflammatory factor and oligodendrocyte apoptosis

Src-suppressed C kinase substrate (SSeCKS) is involved in inflammation in the central nervous system (CNS), and plays a role in control of cell signaling and cytoskeletal arrangement. However, the expression and function of SSeCKS and its function in multiple sclerosis (MS) and its common animal model, experimental autoimmune encephalomyelitis (EAE) remained to be elucidated. In the present study, we first reported that SSeCKS was remarkably increased in astrocytes of EAE rats in vivo. TNF-alpha and NO were significantly induced in astrocytes stimulated with LPS/IFN-gamma in vitro, which was blocked in astrocytes transfected with SSeCKS siRNA. These results indicated that SSeCKS played a role in the production of TNF-alpha and NO in astrocytes with inflammatory stimulation. As excessive release of TNF-alpha and NO were major mediators in autoimmune diseases and correlated with oligodendrocyte cell death, we further investigated whether SSeCKS participated in oligodendrocyte apoptosis. Conditioned media (CM) from astrocytes treated with LPS/IFN-gamma decreased oligodendrocyte cell viability, while siRNA targeted to SSeCKS in astrocytes inhibited oligodendrocyte cell death. The results from antibody neutralization and NO inhibition suggested that the oligodendrocyte apoptosis may be due to the production of astrocyte-derived proinflammatory factors (TNF-alpha and NO). These findings revealed that there was a pathogenic interaction between SSeCKS expression in astrocytes and oligodendrocyte apoptosis. Understanding the mechanism of SSeCKS in the pathogenesis of EAE may contribute to the development of new therapeutic strategies against EAE and MS.

Age-dependent maintenance of motor control and corticostriatal innervation by death receptor 3

Death receptor 3 is a proinflammatory member of the immunomodulatory tumor necrosis factor receptor superfamily, which has been implicated in several inflammatory diseases such as arthritis and inflammatory bowel disease. Intriguingly however, constitutive DR3 expression has been detected in the brains of mice, rats, and humans, although its neurological function remains unknown. By mapping the normal brain expression pattern of DR3, we found that DR3 is expressed specifically by cells of the neuron lineage in a developmentally regulated and region-specific pattern. Behavioral studies on DR3-deficient (DR3(ko)) mice showed that constitutive neuronal DR3 expression was required for stable motor control function in the aging adult. DR3(ko) mice progressively developed behavioral defects characterized by altered gait, dyskinesia, and hyperactivity, which were associated with elevated dopamine and lower serotonin levels in the striatum. Importantly, retrograde tracing showed that absence of DR3 expression led to the loss of corticostriatal innervation without significant neuronal loss in aged DR3(ko) mice. These studies indicate that DR3 plays a key nonredundant role in the retention of normal motor control function during aging in mice and implicate DR3 in progressive neurological disease.

11beta-Hydroxysteroid dehydrogenase type 1 is an important regulator at the interface of obesity and inflammation

Systemic glucocorticoid excess, as exemplified by the Cushing syndrome, leads to obesity and all further symptoms of the metabolic syndrome. The current obesity epidemic, however, is not characterized by increased plasma cortisol concentrations, but instead comes along with chronic low-grade inflammation in adipose tissue and concomitant increased levels of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1, gene HSD11B1), a parameter known to cause obesity in a mouse model. 11beta-HSD1 represents an intracellular amplifier of active glucocorticoid, thus enhances the associated effects on the inflammatory response as well as on nutrient and energy metabolism, and may therefore cause and exacerbate obesity by local increase of glucocorticoid concentrations. Obtained by extensive literature and database searching, the present review includes comprehensive lists of primary glucocorticoid-sensitive genes and gene products as well as of the thus far known regulators of HSD11B1 expression with implication in inflammation and metabolic disease. Collectively, the data clearly show that, in addition to amplifying active glucocorticoid and thus profoundly modulating inflammation and nutrient metabolism, 11beta-HSD1 is subject to tight control of multiple additional immunomodulatory and metabolic regulators. Hence, 11beta-HSD1 acts at the interface of inflammation and obesity and represents an efficient integrator and effector of local inflammatory and metabolic state.

A Critical Role of Src-Suppressed C Kinase Substrate in Rat Astrocytes After Chronic Constriction Injury

Src-suppressed C kinase substrate (SSeCKS), is an in vivo and in vitro protein kinase C substrate that may have a role in both mitogenic regulation and cytoskeletal arrangement. In this study, we mainly investigated the mRNA and protein expression and cellular localization of SSeCKS during chronic constriction injury (CCI). Reverse transcriptase-mediated PCR and western blot analysis revealed that SSeCKS was present in normal whole spinal cord. It gradually increased, and reached a peak at 2 weeks for its mRNA level and 7 days for its protein level after CCI. The protein expression of SSeCKS was further analyzed by immunohistochemistry. The positively stained areas for SSeCKS changed with the similar pattern to that of protein expression detected by immunoblotting analysis. Double immunofluorescence staining showed SSeCKS immunoreactivity was mostly co-localized with neurons, partly with activated astrocytes and rarely with microglia in the superficial laminar of spinal dorsal horn. In cell culture, the expression of pro-inflammation cytokines, p-ERK, and SSeCKS was increased in the spinal astrocytes after stimulated by damaged sensory neurons. However, SSeCKS gene silencing by siRNA inhibited the up-regulation of p-ERK and the pro-inflammation cytokines. Taken together, activated astrocytes released cytokines and iNOS after neuropathic pain via SSeCKS-ERK signaling. SSeCKS might be critical for the activation of astrocytes in the neuropathic pain.

HIV-1 Tat co-operates with IFN-gamma and TNF-alpha to increase CXCL10 in human astrocytes

HIV-associated neurological disorders (HAND) are estimated to affect 60% of the HIV infected population. HIV-encephalitis (HIVE), the pathological correlate of the most severe form of HAND is often characterized by glial activation, cytokine/chemokine dysregulation, and neuronal damage and loss. However, the severity of HIVE correlates better with glial activation rather than viral load. One of the characteristic features of HIVE is the increased amount of the neurotoxic chemokine, CXCL10. This chemokine can be released from astroglia activated with the pro-inflammatory cytokines IFN-γ and TNF-α, in conjunction with HIV-1 Tat, all of which are elevated in HIVE. In an effort to understand the pathogenesis of HAND, this study was aimed at exploring the regulation of CXCL10 by cellular and viral factors during astrocyte activation. Specifically, the data herein demonstrate that the combined actions of HIV-1 Tat and the pro-inflammatory cytokines, IFN-γ and TNF-α, result in the induction of CXCL10 at both the RNA and protein level. Furthermore, CXCL10 induction was found to be regulated transcriptionally by the activation of the p38, Jnk, and Akt signaling pathways and their downstream transcription factors, NF-κB and STAT-1α. Since CXCL10 levels are linked to disease severity, understanding its regulation could aid in the development of therapeutic intervention strategies for HAND.