Association of Posttraumatic Stress Disorder and Race on Readmissions After Stroke

BACKGROUND

There is limited research on outcomes of patients with posttraumatic stress disorder (PTSD) who also develop stroke, particularly regarding racial disparities. Our goal was to determine whether PTSD is associated with the risk of hospital readmission after stroke and whether racial disparities existed.

METHODS

The analytical sample consisted of all veterans receiving care in the Veterans Health Administration who were identified as having a new stroke requiring inpatient admission based on the International Classification of Diseases codes. PTSD and comorbidities were identified using the International Classification of Diseases codes and given the date of first occurrence. The retrospective cohort data were obtained from the Veterans Affairs Corporate Data Warehouse. The main outcome was any readmission to Veterans Health Administration with a stroke diagnosis. The hypothesis that PTSD is associated with readmission after stroke was tested using Cox regression adjusted for patient characteristics including age, sex, race, PTSD, smoking status, alcohol use, and comorbidities treated as time-varying covariates.

RESULTS

Our final cohort consisted of 93 651 patients with inpatient stroke diagnosis and no prior Veterans Health Administration codes for stroke starting from 1999 with follow-up through August 6, 2022. Of these patients, 12 916 (13.8%) had comorbid PTSD. Of the final cohort, 16 896 patients (18.0%) with stroke were readmitted. Our fully adjusted model for readmission found an interaction between African American veterans and PTSD with a hazard ratio of 1.09 ([95% CI, 1.00-1.20] P=0.047). In stratified models, PTSD has a significant hazard ratio of 1.10 ([95% CI, 1.02-1.18] P=0.01) for African American but not White veterans (1.05 [95% CI, 0.99-1.11]; P=0.10).

CONCLUSIONS

Among African American veterans who experienced stroke, preexisting PTSD was associated with increased risk of readmission, which was not significant among White veterans. This study highlights the need to focus on high-risk groups to reduce readmissions after stroke.

Skeletal muscle as a molecular and cellular biomarker of disease progression in amyotrophic lateral sclerosis: a narrative review

Amyotrophic lateral sclerosis is a fatal multisystemic neurodegenerative disease with motor neurons being a primary target. Although progressive weakness is a hallmark feature of amyotrophic lateral sclerosis, there is considerable heterogeneity, including clinical presentation, progression, and the underlying triggers for disease initiation. Based on longitudinal studies with families harboring amyotrophic lateral sclerosis-associated gene mutations, it has become apparent that overt disease is preceded by a prodromal phase, possibly in years, where compensatory mechanisms delay symptom onset. Since 85-90% of amyotrophic lateral sclerosis is sporadic, there is a strong need for identifying biomarkers that can detect this prodromal phase as motor neurons have limited capacity for regeneration. Current Food and Drug Administration-approved therapies work by slowing the degenerative process and are most effective early in the disease. Skeletal muscle, including the neuromuscular junction, manifests abnormalities at the earliest stages of the disease, before motor neuron loss, making it a promising source for identifying biomarkers of the prodromal phase. The accessibility of muscle through biopsy provides a lens into the distal motor system at earlier stages and in real time. The advent of "omics" technology has led to the identification of numerous dysregulated molecules in amyotrophic lateral sclerosis muscle, ranging from coding and non-coding RNAs to proteins and metabolites. This technology has opened the door for identifying biomarkers of disease activity and providing insight into disease mechanisms. A major challenge is correlating the myriad of dysregulated molecules with clinical or histological progression and understanding their relevance to presymptomatic phases of disease. There are two major goals of this review. The first is to summarize some of the biomarkers identified in human amyotrophic lateral sclerosis muscle that have a clinicopathological correlation with disease activity, evidence of a similar dysregulation in the SOD1G93A mouse during presymptomatic stages, and evidence of progressive change during disease progression. The second goal is to review the molecular pathways these biomarkers reflect and their potential role in mitigating or promoting disease progression, and as such, their potential as therapeutic targets in amyotrophic lateral sclerosis.

Poly(ADP-ribose) mediates bioenergetic defects and redox imbalance in neurons following oxygen and glucose deprivation

PARP-1 over-activation results in cell death via excessive PAR generation in different cell types, including neurons following brain ischemia. Glycolysis, mitochondrial function, and redox balance are key cellular processes altered in brain ischemia. Studies show that PAR generated after PARP-1 over-activation can bind hexokinase-1 (HK-1) and result in glycolytic defects and subsequent mitochondrial dysfunction. HK-1 is the neuronal hexokinase and catalyzes the first reaction of glycolysis, converting glucose to glucose-6-phosphate (G6P), a common substrate for glycolysis, and the pentose phosphate pathway (PPP). PPP is critical in maintaining NADPH and GSH levels via G6P dehydrogenase activity. Therefore, defects in HK-1 will not only decrease cellular bioenergetics but will also cause redox imbalance due to the depletion of GSH. In brain ischemia, whether PAR-mediated inhibition of HK-1 results in bioenergetics defects and redox imbalance is not known. We used oxygen-glucose deprivation (OGD) in mouse cortical neurons to mimic brain ischemia in neuronal cultures and observed that PARP-1 activation via PAR formation alters glycolysis, mitochondrial function, and redox homeostasis in neurons. We used pharmacological inhibition of PARP-1 and adenoviral-mediated overexpression of wild-type HK-1 (wtHK-1) and PAR-binding mutant HK-1 (pbmHK-1). Our data show that PAR inhibition or overexpression of HK-1 significantly improves glycolysis, mitochondrial function, redox homeostasis, and cell survival in mouse cortical neurons exposed to OGD. These results suggest that PAR binding and inhibition of HK-1 during OGD drive bioenergetic defects in neurons due to inhibition of glycolysis and impairment of mitochondrial function.

RNA regulation of inflammatory responses in glia and its potential as a therapeutic target in central nervous system disorders

A major hallmark of neuroinflammation is the activation of microglia and astrocytes with the induction of inflammatory mediators such as IL-1β, TNF-α, iNOS, and IL-6. Neuroinflammation contributes to disease progression in a plethora of neurological disorders ranging from acute CNS trauma to chronic neurodegenerative disease. Posttranscriptional pathways of mRNA stability and translational efficiency are major drivers for the expression of these inflammatory mediators. A common element in this level of regulation centers around the adenine- and uridine-rich element (ARE) which is present in the 3' untranslated region (UTR) of the mRNAs encoding these inflammatory mediators. (ARE)-binding proteins (AUBPs) such as Human antigen R (HuR), Tristetraprolin (TTP) and KH- type splicing regulatory protein (KSRP) are key nodes for directing these posttranscriptional pathways and either promote (HuR) or suppress (TTP and KSRP) glial production of inflammatory mediators. This review will discuss basic concepts of ARE-mediated RNA regulation and its impact on glial-driven neuroinflammatory diseases. We will discuss strategies to target this novel level of gene regulation for therapeutic effect and review exciting preliminary studies that underscore its potential for treating neurological disorders.

MicroRNA-183-5p regulates TAR DNA-binding protein 43 neurotoxicity via SQSTM1/p62 in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that selectively attacks motor neurons, and leads to progressive muscle weakness and death. A common pathological feature is the misfolding, aggregation, and cytoplasmic mislocalization of TAR DNA-binding protein 43 (TDP-43) proteins in more than 95% of ALS patients, suggesting a universal role TDP-43 proteinopathy in ALS. Mutations in SQSTM1/p62 have been identified in familial and sporadic cases of ALS. MicroRNAs (miRNAs) are small non-coding RNAs that post-transcriptionally regulate their target genes. Emerging evidence indicates that miRNA dysregulation is associated with neuronal toxicity and mitochondrial dysfunction, and also plays a pivotal role in ALS pathogenesis. Here, we report the first evidence that miR-183-5p is aberrantly upregulated in spinal cords of patients with ALS. Using luciferase reporter assays and miR-183-5p agomirs, we demonstrate that miR-183-5p regulates the SQSTM1/p62 3'-untranslated region to suppress expression. A miR-183-5p agomir attenuated SOSTM1/p62 expression and led to an increase in TDP-43 protein levels in neuronal and non-neuronal cells. In contrast, a miR-183-5p antagomir decreased TDP-43 but increased SQSTM1/p62 protein levels. The antagomir repressed formation of stress granules and aggregated TDP43 protein in neuronal cells under stress-induced conditions and protected against cytotoxicity. Knockdown of SQSTM1/p62 decreased total ubiquitination and increased TDP-43 protein aggregation, indicating that SQSTM1/p62 may play a protective role in cells. In summary, our study reveals a novel mechanism of TDP-43 proteinopathy mediated by the miR-183-5p and provides a molecular link between aberrant RNA processing and protein degradation, two major pillars in ALS pathogenesis.

Transcriptomic analysis of human ALS skeletal muscle reveals a disease-specific pattern of dysregulated circRNAs

Circular RNAs are abundant, covalently closed transcripts that arise in cells through back-splicing and display distinct expression patterns across cells and developmental stages. While their functions are largely unknown, their intrinsic stability has made them valuable biomarkers in many diseases. Here, we set out to examine circRNA patterns in amyotrophic lateral sclerosis (ALS). By RNA-sequencing analysis, we first identified circRNAs and linear RNAs that were differentially abundant in skeletal muscle biopsies from ALS compared to normal individuals. By RT-qPCR analysis, we confirmed that 8 circRNAs were significantly elevated and 10 were significantly reduced in ALS, while the linear mRNA counterparts, arising from shared precursor RNAs, generally did not change. Several of these circRNAs were also differentially abundant in motor neurons derived from human induced pluripotent stem cells (iPSCs) bearing ALS mutations, and across different disease stages in skeletal muscle from a mouse model of ALS (SOD1G93A). Interestingly, a subset of the circRNAs significantly elevated in ALS muscle biopsies were significantly reduced in the spinal cord samples from ALS patients and ALS (SOD1G93A) mice. In sum, we have identified differentially abundant circRNAs in ALS-relevant tissues (muscle and spinal cord) that could inform about neuromuscular molecular programs in ALS and guide the development of therapies.

Life-Long Steroid Responsive Familial Myopathy With Docking Protein 7 Mutation

Docking protein 7 (DOK7) congenital myasthenic syndrome (CMS) is characterized by limb-girdle weakness and lack of fluctuating fatigability simulating many familial myopathies. Albuterol is the first line of therapy in view of consistent improvement. Two brothers with progressive predominant biceps weakness for 1-3 years responded to prednisone treatment for 40-50 years. Various studies including muscle biopsy and many laboratory studies were unsuccessful for the definite diagnosis. Gene study, 40 years after the initial evaluation, confirmed the diagnosis of DOK7 CMS. These are the first reported cases of DOK7 CMS associated with a sustained benefit from corticosteroids.

Targeting the TREM1-positive myeloid microenvironment in glioblastoma

Background

Tumor cellular and molecular heterogeneity is a hallmark of glioblastoma and underlies treatment resistance and recurrence. This manuscript investigated the myeloid-derived microenvironment as a driver of glioblastoma heterogeneity and provided a pharmacological pathway for its suppression.

Methods

Transcriptomic signatures of glioblastoma infiltrated myeloid-derived cells were assessed using R2: genomic platform, Ivy Glioblastoma Spatial Atlas, and single-cell RNA-seq data of primary and recurrent glioblastomas. Myeloid-derived cell prints were evaluated in five PDX cell lines using RNA-seq data. Two immunocompetent mouse glioblastoma models were utilized to isolate and characterize tumor-infiltrated myeloid-derived cells and glioblastoma/host cell hybrids. The ability of an inhibitor of HuR dimerization SRI42127 to suppress TREM1⁺-microenvironment and glioblastoma/myeloid-derived cell interaction was assessed in vivo and in vitro.

Results

TREM1⁺-microenvironment is enriched in glioblastoma peri-necrotic zones. TREM1 appearance is enhanced with tumor grade and associated with poor patient outcomes. We confirmed an expression of a variety of myeloid-derived cell markers, including TREM1, in PDX cell lines. In mouse glioblastoma models, we demonstrated a reduction in the TREM1⁺-microenvironment and glioblastoma/host cell fusion after treatment with SRI42127. In vitro assays confirmed inhibition of cell fusion events and reduction of myeloid-derived cell migration towards glioblastoma cells by SRI42127 and TREM1 decoy peptide (LP17) versus control treatments.

Conclusions

TREM1⁺-myeloid-derived microenvironment promulgates glioblastoma heterogeneity and is a therapeutic target. Pharmacological inhibition of HuR dimerization leads to suppression of the TREM1⁺-myeloid-derived microenvironment and the neoplastic/non-neoplastic fusogenic cell network.

Inhibition of the RNA Regulator HuR by SRI-42127 Attenuates Neuropathic Pain After Nerve Injury Through Suppression of Neuroinflammatory Responses

Microglial activation with the production of pro-inflammatory mediators such as IL-6, TNF-α, and IL-1β, is a major driver of neuropathic pain (NP) following peripheral nerve injury. We have previously shown that the RNA binding protein, HuR, is a positive node of regulation for many of these inflammatory mediators in glia and that its chemical inhibition or genetic deletion attenuates their production. In this report, we show that systemic administration of SRI-42127, a novel small molecule HuR inhibitor, attenuates mechanical allodynia, a hallmark of NP, in the early and chronic phases after spared nerve injury in male and female mice. Flow cytometry of lumbar spinal cords in SRI-42127-treated mice shows a reduction in infiltrating macrophages and a concomitant decrease in microglial populations expressing IL-6, TNF-α, IL-1β, and CCL2. Immunohistochemistry, ELISA, and qPCR of lumbar spinal cord tissue indicate suppression of these cytokines and other inflammatory mediators. ELISA of plasma samples in the acute phase also shows attenuation of inflammatory responses. In summary, inhibition of HuR by SRI-42127 leads to the suppression of neuroinflammatory responses and allodynia after nerve injury and represents a promising new direction in the treatment of NP.

Smad8 Is Increased in Duchenne Muscular Dystrophy and Suppresses miR-1, miR-133a, and miR-133b

Duchenne muscular dystrophy (DMD) is an X-linked recessive disease characterized by skeletal muscle instability, progressive muscle wasting, and fibrosis. A major driver of DMD pathology stems from aberrant upregulation of transforming growth factor β (TGFβ) signaling. In this report, we investigated the major transducers of TGFβ signaling, i.e., receptor Smads (R-Smads), in DMD patient skeletal muscle and observed a 48-fold increase in Smad8 mRNA. Smad1, Smad2, Smad3, and Smad5 mRNA were only minimally increased. A similar pattern was observed in the muscle from the mdx5cv mouse. Western blot analysis showed upregulation of phosphorylated Smad1, Smad5, and Smad8 compared to total Smad indicating activation of this pathway. In parallel, we observed a profound diminishment of muscle-enriched microRNAs (myomiRs): miR-1, miR-133a, and miR-133b. The pattern of Smad8 induction and myomiR suppression was recapitulated in C2C12 muscle cells after stimulation with bone morphogenetic protein 4 (BMP4), a signaling factor that we found upregulated in DMD muscle. Silencing Smad8 in C2C12 myoblasts derepressed myomiRs and promoted myoblast differentiation; there was also a concomitant upregulation of myogenic regulatory factors (myogenin and myocyte enhancer factor 2D) and suppression of a pro-inflammatory cytokine (interleukin-6). Our data suggest that Smad8 is a negative regulator of miR-1, miR-133a, and miR-133b in muscle cells and that the BMP4-Smad8 axis is a driver of dystrophic pathology in DMD.

The versatile role of HuR in Glioblastoma and its potential as a therapeutic target for a multi-pronged attack

Glioblastoma (GBM) is a malignant and aggressive brain tumor with a median survival of ∼15 months. Resistance to treatment arises from the extensive cellular and molecular heterogeneity in the three major components: glioma tumor cells, glioma stem cells, and tumor-associated microglia and macrophages. Within this triad, there is a complex network of intrinsic and secreted factors that promote classic hallmarks of cancer, including angiogenesis, resistance to cell death, proliferation, and immune evasion. A regulatory node connecting these diverse pathways is at the posttranscriptional level as mRNAs encoding many of the key drivers contain adenine- and uridine rich elements (ARE) in the 3' untranslated region. Human antigen R (HuR) binds to ARE-bearing mRNAs and is a major positive regulator at this level. This review focuses on basic concepts of ARE-mediated RNA regulation and how targeting HuR with small molecule inhibitors represents a plausible strategy for a multi-pronged therapeutic attack on GBM.

A Neuroscience Primer for Integrating Geroscience With the Neurobiology of Aging

Neuroscience has a rich history of studies focusing on neurobiology of aging. However, much of the aging studies in neuroscience occur outside of the gerosciences. The goal of this primer is 2-fold: first, to briefly highlight some of the history of aging neurobiology and second, to introduce to geroscientists the broad spectrum of methodological approaches neuroscientists use to study the neurobiology of aging. This primer is accompanied by a corresponding geroscience primer, as well as a perspective on the current challenges and triumphs of the current divide across these 2 fields. This series of manuscripts is intended to foster enhanced collaborations between neuroscientists and geroscientists with the intent of strengthening the field of cognitive aging through inclusion of parameters from both areas of expertise.

SRI-42127, a novel small molecule inhibitor of the RNA regulator HuR, potently attenuates glial activation in a model of lipopolysaccharide-induced neuroinflammation

Glial activation with the production of pro-inflammatory mediators is a major driver of disease progression in neurological processes ranging from acute traumatic injury to chronic neurodegenerative diseases such as amyotrophic lateral sclerosis and Alzheimer's disease. Posttranscriptional regulation is a major gateway for glial activation as many mRNAs encoding pro-inflammatory mediators contain adenine- and uridine-rich elements (ARE) in the 3' untranslated region which govern their expression. We have previously shown that HuR, an RNA regulator that binds to AREs, plays a major positive role in regulating inflammatory cytokine production in glia. HuR is predominantly nuclear in localization but translocates to the cytoplasm to exert a positive regulatory effect on RNA stability and translational efficiency. Homodimerization of HuR is necessary for translocation and we have developed a small molecule inhibitor, SRI-42127, that blocks this process. Here we show that SRI-42127 suppressed HuR translocation in LPS-activated glia in vitro and in vivo and significantly attenuated the production of pro-inflammatory mediators including IL1β, IL-6, TNF-α, iNOS, CXCL1, and CCL2. Cytokines typically associated with anti-inflammatory effects including TGF-β1, IL-10, YM1, and Arg1 were either unaffected or minimally affected. SRI-42127 suppressed microglial activation in vivo and attenuated the recruitment/chemotaxis of neutrophils and monocytes. RNA kinetic studies and luciferase studies indicated that SRI-42127 has inhibitory effects both on mRNA stability and gene promoter activation. In summary, our findings underscore HuR's critical role in promoting glial activation and the potential for SRI-42127 and other HuR inhibitors for treating neurological diseases driven by this activation.

The pathogenic role of c-Kit+ mast cells in the spinal motor neuron-vascular niche in ALS

Degeneration of motor neurons, glial cell reactivity, and vascular alterations in the CNS are important neuropathological features of amyotrophic lateral sclerosis (ALS). Immune cells trafficking from the blood also infiltrate the affected CNS parenchyma and contribute to neuroinflammation. Mast cells (MCs) are hematopoietic-derived immune cells whose precursors differentiate upon migration into tissues. Upon activation, MCs undergo degranulation with the ability to increase vascular permeability, orchestrate neuroinflammation and modulate the neuroimmune response. However, the prevalence, pathological significance, and pharmacology of MCs in the CNS of ALS patients remain largely unknown. In autopsy ALS spinal cords, we identified for the first time that MCs express c-Kit together with chymase, tryptase, and Cox-2 and display granular or degranulating morphology, as compared with scarce MCs in control cords. In ALS, MCs were mainly found in the niche between spinal motor neuron somas and nearby microvascular elements, and they displayed remarkable pathological abnormalities. Similarly, MCs accumulated in the motor neuron-vascular niche of ALS murine models, in the vicinity of astrocytes and motor neurons expressing the c-Kit ligand stem cell factor (SCF), suggesting an SCF/c-Kit-dependent mechanism of MC differentiation from precursors. Mechanistically, we provide evidence that fully differentiated MCs in cell cultures can be generated from the murine ALS spinal cord tissue, further supporting the presence of c-Kit+ MC precursors. Moreover, intravenous administration of bone marrow-derived c-Kit+ MC precursors infiltrated the spinal cord in ALS mice but not in controls, consistent with aberrant trafficking through a defective microvasculature. Pharmacological inhibition of c-Kit with masitinib in ALS mice reduced the MC number and the influx of MC precursors from the periphery. Our results suggest a previously unknown pathogenic mechanism triggered by MCs in the ALS motor neuron-vascular niche that might be targeted pharmacologically.

FGF23, a novel muscle biomarker detected in the early stages of ALS

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive muscle weakness. Skeletal muscle is a prime source for biomarker discovery since it is one of the earliest sites to manifest disease pathology. From a prior RNA sequencing project, we identified FGF23 as a potential muscle biomarker in ALS. Here, we validate this finding with a large collection of ALS muscle samples and found a 13-fold increase over normal controls. FGF23 was also increased in the SOD1G93A mouse, beginning at a very early stage and well before the onset of clinical symptoms. FGF23 levels progressively increased through end-stage in the mouse. Immunohistochemistry of ALS muscle showed prominent FGF23 immunoreactivity in the endomysial connective tissue and along the muscle membrane and was significantly higher around grouped atrophic fibers compared to non-atrophic fibers. ELISA of plasma samples from the SOD1G93A mouse showed an increase in FGF23 at end-stage whereas no increase was detected in a large cohort of ALS patients. In conclusion, FGF23 is a novel muscle biomarker in ALS and joins a molecular signature that emerges in very early preclinical stages. The early appearance of FGF23 and its progressive increase with disease progression offers a new direction for exploring the molecular basis and response to the underlying pathology of ALS.

Fat mass loss correlates with faster disease progression in amyotrophic lateral sclerosis patients: Exploring the utility of dual-energy x-ray absorptiometry in a prospective study

Background/objective

Weight loss is a predictor of shorter survival in amyotrophic lateral sclerosis (ALS). We performed serial measures of body composition using Dual-energy X-ray Absorptiometry (DEXA) in ALS patients to explore its utility as a biomarker of disease progression.

Methods

DEXA data were obtained from participants with ALS (enrollment, at 6- and 12- months follow ups) and Parkinson’s disease (enrollment and at 4-month follow up) as a comparator group. Body mass index, total lean mass index, appendicular lean mass index, total fat mass index, and percentage body fat at enrollment were compared between the ALS and PD cohorts and age-matched normative data obtained from the National Health and Nutrition Examination Survey database. Estimated monthly changes of body composition measures in the ALS cohort were compared to those of the PD cohort and were correlated with disease progression measured by the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R).

Results

The ALS cohort (N = 20) had lower baseline total and appendicular lean mass indices compared to the PD cohort (N = 20) and general population. Loss in total and appendicular lean masses were found to be significantly associated with follow-up time. Low baseline percentage body fat (r = 0.72, p = 0.04), loss of percentage body fat (r = 0.81, p = 0.01), and total fat mass index (r = 0.73, p = 0.04) during follow up correlated significantly with monthly decline of ALSFRS-R scores in ALS cohort who had 2 or more follow-ups (N = 8).

Conclusion

Measurement of body composition with DEXA might serve as a biomarker for rapid disease progression in ALS.

Targeting the HuR Oncogenic Role with a New Class of Cytoplasmic Dimerization Inhibitors

The development of novel therapeutics that exploit alterations in the activation state of key cellular signaling pathways due to mutations in upstream regulators has generated the field of personalized medicine. These first-generation efforts have focused on actionable mutations identified by deep sequencing of large numbers of tumor samples. We propose that a second-generation opportunity exists by exploiting key downstream "nodes of control" that contribute to oncogenesis and are inappropriately activated due to loss of upstream regulation and microenvironmental influences. The RNA-binding protein HuR represents such a node. Because HuR functionality in cancer cells is dependent on HuR dimerization and its nuclear/cytoplasmic shuttling, we developed a new class of molecules targeting HuR protein dimerization. A structure-activity relationship algorithm enabled development of inhibitors of HuR multimer formation that were soluble, had micromolar activity, and penetrated the blood-brain barrier. These inhibitors were evaluated for activity validation and specificity in a robust cell-based assay of HuR dimerization. SRI-42127, a molecule that met these criteria, inhibited HuR multimer formation across primary patient-derived glioblastoma xenolines (PDGx), leading to arrest of proliferation, induction of apoptosis, and inhibition of colony formation. SRI-42127 had favorable attributes with central nervous system penetration and inhibited tumor growth in mouse models. RNA and protein analysis of SRI-42127-treated PDGx xenolines across glioblastoma molecular subtypes confirmed attenuation of targets upregulated by HuR. These results highlight how focusing on key attributes of HuR that contribute to cancer progression, namely cytoplasmic localization and multimerization, has led to the development of a novel, highly effective inhibitor. SIGNIFICANCE: These findings utilize a cell-based mechanism of action assay with a structure-activity relationship compound development pathway to discover inhibitors that target HuR dimerization, a mechanism required for cancer promotion.

The vitamin D activator CYP27B1 is upregulated in muscle fibers in denervating disease and can track progression in amyotrophic lateral sclerosis

Extra-renal expression of Cytochrome P450 Family 27 Subfamily B Member 1 (CYP27B1) has been well recognized and reflects the importance of intracrine/paracrine vitamin D signaling in different tissues under physiological and pathological conditions. In a prior RNA sequencing project, we identified CYP27B1 mRNA as upregulated in muscle samples from patients with amyotrophic lateral sclerosis (ALS) compared to normal controls. Our aims here were: (1) to validate this finding in a larger sample set including disease controls, (2) to determine which cell type is expressing CYP27B1 protein in muscle tissue, (3) to correlate CYP27B1 mRNA expression with disease progression in the SOD1G93A ALS mouse and in ALS patients. We assessed CYP27B1 expression by qPCR, western blot, and immunohistochemistry in a repository of muscle samples from ALS, disease controls (myopathy and non-ALS neuropathic disease), normal subjects, and muscle samples from the SOD1G93A mouse. Eight ALS patients were studied prospectively over 6-12 months with serial muscle biopsies. We found that CYP27B1 mRNA and protein levels were significantly increased in ALS versus normal and myopathy muscle samples. Neuropathy samples had increased CYP27B1 mRNA and protein expression but at a lower level than the ALS group. Immunohistochemistry showed that CYP27B1 localized to myofibers, especially those with features of denervation. In the SOD1G93A mouse, CYP27B1 mRNA and protein were detected in skeletal muscle in early pre-symptomatic stages and increased through end-stage. In the human study, increases in CYP27B1 mRNA in muscle biopsies correlated with disease progression rates over the same time period. In summary, we show for the first time that CYP27B1 mRNA and protein expression are elevated in muscle fibers in denervating disease, especially ALS, where mRNA levels can potentially serve as a surrogate marker for tracking disease progression. Its upregulation may reflect a local perturbation of vitamin D signaling, and further characterization of this pathway may provide insight into underlying molecular processes linked to muscle denervation.

Schwann cells orchestrate peripheral nerve inflammation through the expression of CSF1, IL-34, and SCF in amyotrophic lateral sclerosis

Distal axonopathy is a recognized pathological feature of amyotrophic lateral sclerosis (ALS). In the peripheral nerves of ALS patients, motor axon loss elicits a Wallerian-like degeneration characterized by denervated Schwann cells (SCs) together with immune cell infiltration. However, the pathogenic significance of denervated SCs accumulating following impaired axonal growth in ALS remains unclear. Here, we analyze SC phenotypes in sciatic nerves of ALS patients and paralytic SOD1^G93A rats, and identify remarkably similar and specific reactive SC phenotypes based on the pattern of S100β, GFAP, isolectin and/or p75^NTR immunoreactivity. Different subsets of reactive SCs expressed colony-stimulating factor-1 (CSF1) and Interleukin-34 (IL-34) and closely interacted with numerous endoneurial CSF-1R-expressing monocyte/macrophages, suggesting a paracrine mechanism of myeloid cell expansion and activation. SCs bearing phagocytic phenotypes as well as endoneurial macrophages expressed stem cell factor (SCF), a trophic factor that attracts and activates mast cells through the c-Kit receptor. Notably, a subpopulation of Ki67+ SCs expressed c-Kit in the sciatic nerves of SOD1^G93A rats, suggesting a signaling pathway that fuels SC proliferation in ALS. c-Kit+ mast cells were also abundant in the sciatic nerve from ALS donors but not in controls. Pharmacological inhibition of CSF-1R and c-Kit with masitinib in SOD1^G93A rats potently reduced SC reactivity and immune cell infiltration in the sciatic nerve and ventral roots, suggesting a mechanism by which the drug ameliorates peripheral nerve pathology. These findings provide strong evidence for a previously unknown inflammatory mechanism triggered by SCs in ALS peripheral nerves that has broad application in developing novel therapies.

Deletion of the RNA regulator HuR in tumor-associated microglia and macrophages stimulates anti-tumor immunity and attenuates glioma growth

Glioblastoma is a malignant brain tumor that portends a poor prognosis. Its resilience, in part, is related to a remarkable capacity for manipulating the microenvironment to promote its growth and survival. Microglia/macrophages are prime targets, being drawn into the tumor and stimulated to produce factors that support tumor growth and evasion from the immune system. Here we show that the RNA regulator, HuR, plays a key role in the tumor-promoting response of microglia/macrophages. Knockout (KO) of HuR led to reduced tumor growth and proliferation associated with prolonged survival in a murine model of glioblastoma. Analysis of tumor composition by flow cytometry showed that tumor-associated macrophages (TAMs) were decreased, more polarized toward an M1-like phenotype, and had reduced PD-L1 expression. There was an overall increase in infiltrating CD4⁺ cells, including Th1 and cytotoxic effector cells, and a concomitant reduction in tumor-associated polymorphonuclear myeloid-derived suppressor cells. Molecular and cellular analyses of HuR KO TAMs and cultured microglia showed changes in migration, chemoattraction, and chemokine/cytokine profiles that provide potential mechanisms for the altered tumor microenvironment and reduced tumor growth in HuR KO mice. In summary, HuR is a key modulator of pro-glioma responses by microglia/macrophages through the molecular regulation of chemokines, cytokines, and other factors. Our findings underscore the relevance of HuR as a therapeutic target in glioblastoma.

Quality of Care for Veterans With In-Hospital Stroke

Veterans who develop an in-hospital stroke and those who present to the emergency department with stroke symptoms received similar care, but some differences suggest the need to better standardize stroke care regardless of care setting.

Abstract 147: Deletion of the RNA regulator HuR in microglia/macrophages promotes an anti-tumor microenvironment in glioblastoma

Glioblastoma is a malignant brain tumor that portends a poor prognosis. Its resilience, in part, is related to a remarkable capacity for manipulating the microenvironment to promote its growth and survival. Microglia/macrophages are a prime target, being drawn into the tumor and stimulated to produce factors that support tumor growth and immune system evasion. Here we show that the RNA regulator, HuR, plays a key role in the tumor-promoting response of microglia/macrophages. Knockout of HuR in microglia/macrophages led to reduced tumor growth and prolonged survival in a murine model of glioblastoma. Analysis of tumor composition by flow cytometry showed that tumor associated macrophages were decreased, more polarized toward an M1-like phenotype, and had attenuated PD-L1 expression. There was a concomitant reduction in tumor-associated polymorphonuclear myeloid-derived suppressor cells, but an increase in Treg cells. In vitro assays showed reduced migration of HuR-/- microglia toward secreted factors derived from glioblastoma cells, and a decrease in migration of glioblastoma cells toward secreted factors derived from HuR-/- microglia. The molecular response of HuR-/- microglia was altered including reduced CXCL1, 2, MMP2, PD-L1 and VEGF expression and an increase in CXCL10 and several MMPs. There was a mixed effect on cytokines and other factors associated with both proinflammatory and alternatively activated phenotypes. In summary, HuR is a key modulator of the tumor microenvironment in glioblastoma, promoting tumor progression through its molecular regulation of factors produced by microglia/macrophages. These findings underscore the relevance of HuR as a therapeutic target in glioblastoma.

Citation Format: Jiping Wang, Jianmei Leavenworth, Anita Hjelmeland, Ben Borg, Peter H. King. Deletion of the RNA regulator HuR in microglia/macrophages promotes an anti-tumor microenvironment in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 147.

Anti-cancer effects of the HuR inhibitor, MS-444, in malignant glioma cells

Glioblastoma is a highly malignant and typically fatal tumor of the central nervous system. The tumor is characterized by marked cellular and molecular heterogeneity, including a subpopulation of brain tumor initiating cells (BTICs) that are highly resistant to radiation and chemotherapy. We previously reported that the RNA-binding protein HuR is: (1) overexpressed in glioblastoma, (2) necessary for tumor growth in vivo, and (3) a positive regulator of tumor-promoting genes in glioblastoma. These findings provide strong evidence that HuR might be a viable therapeutic target in glioblastoma. In this report, we investigated the effects of MS-444, a small molecule inhibitor of HuR, in xenograft-derived human glioblastoma cells and BTICs. We found that MS-444 treatment of glioblastoma cells resulted in loss of viability and induction of apoptosis, with evidence implicating death receptor 5. BTICs were particularly sensitive to MS-444. At sub-lethal doses, MS-444 attenuated invasion of glioblastoma cells and BTICs in a transwell model. At the molecular level, MS-444 treatment led to an attenuation of mRNAs in different tumor promoting pathways including angiogenesis, immune evasion and suppression of apoptosis. Although cytoplasmic HuR was reduced with MS-444 treatment, the attenuation of mRNAs could not be explained by RNA destabilization. In summary, this report provides proof of concept that small molecule inhibition of HuR could be a viable approach for treatment of glioblastoma.

Mast cells and neutrophils mediate peripheral motor pathway degeneration in ALS

Neuroinflammation is a recognized pathogenic mechanism underlying motor neuron degeneration in amyotrophic lateral sclerosis (ALS), but the inflammatory mechanisms influencing peripheral motor axon degeneration remain largely unknown. A recent report showed a pathogenic role for c-Kit-expressing mast cells mediating inflammation and neuromuscular junction denervation in muscles from SOD1G93A rats. Here, we have explored whether mast cells infiltrate skeletal muscles in autopsied muscles from ALS patients. We report that degranulating mast cells were abundant in the quadriceps muscles from ALS subjects but not in controls. Mast cells were associated with myofibers and motor endplates and, remarkably, interacted with neutrophils forming large extracellular traps. Mast cells and neutrophils were also abundant around motor axons in the extensor digitorum longus muscle, sciatic nerve, and ventral roots of symptomatic SOD1G93A rats, indicating that immune cell infiltration extends along the entire peripheral motor pathway. Postparalysis treatment of SOD1G93A rats with the tyrosine kinase inhibitor drug masitinib prevented mast cell and neutrophil infiltration, axonal pathology, secondary demyelination, and the loss of type 2B myofibers, compared with vehicle-treated rats. These findings provide further evidence for a yet unrecognized contribution of immune cells in peripheral motor pathway degeneration that can be therapeutically targeted by tyrosine kinase inhibitors.

Morphology of Emoleptalea Nwanedi n. Sp. from Schilbe Intermedius from Nwanedi-Luphephe Dam, Limpopo Province, South Africa

A new species, Emoleptalea nwanedi n. sp. is described from the intestine of Schilbe intermedius, the silver catfish or butter barbel, from the Nwanedi-Luphephe Dam in the Limpopo Province of South Africa. Fish were collected using gill nets where after they were euthanised and dissected. The parasites were sampled, fixed in 70 % EtOH and stained with Van Cleave’s haematoxylin. This species represents an addition to the African cluster of Emoleptalea species previously described and differs from the known species due to its unique size, equal size of oral and ventral suckers, position of ovary and seminal receptacle, number of vitelline follicles and their size, as well as the unique ciliated receptors on the wall of the acetabulum. This is the first record of this parasite from the silver catfish and from southern Africa.

Transgenic expression of HuR increases vasogenic edema and impedes functional recovery in rodent ischemic stroke

BACKGROUND AND PURPOSE

Ischemic stroke produces significant morbidity and mortality, and acute interventions are limited by short therapeutic windows. Novel approaches to neuroprotection and neurorepair are necessary. HuR is an RNA-binding protein (RBP) which modulates RNA stability and translational efficiency of genes linked to ischemic stroke injury.

METHODS

Using a transgenic (Tg) mouse model, we examined the impact of ectopic HuR expression in astrocytes on acute injury evolution after transient middle cerebral artery occlusion (tMCAO).

RESULTS

HuR transgene expression was detected in astrocytes in perilesional regions and contralaterally. HuR Tg mice did not improve neurologically 72h after injury, whereas littermate controls did. In Tg mice, increased cerebral vascular permeability and edema were observed. Infarct volume was not affected by the presence of the transgene.

CONCLUSIONS

Ectopic expression of HuR in astrocytes worsens outcome after transient ischemic stroke in mice in part by increasing vasogenic cerebral edema. These findings suggest that HuR could be a therapeutic target in cerebral ischemia/reperfusion.

HuR promotes the molecular signature and phenotype of activated microglia: Implications for amyotrophic lateral sclerosis and other neurodegenerative diseases

In neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), chronic activation of microglia contributes to disease progression. Activated microglia produce cytokines, chemokines, and other factors that normally serve to clear infection or damaged tissue either directly or through the recruitment of other immune cells. The molecular program driving this phenotype is classically linked to the transcription factor NF-κB and characterized by the upregulation of proinflammatory factors such as IL-1β, TNF-α, and IL-6. Here, we investigated the role of HuR, an RNA-binding protein that regulates gene expression through posttranscriptional pathways, on the molecular and cellular phenotypes of activated microglia. We performed RNA sequencing of HuR-silenced microglia and found significant attenuation of lipopolysaccharide-induced IL-1β and TNF-α inflammatory pathways and other factors that promote microglial migration and invasion. RNA kinetics and luciferase reporter studies suggested that the attenuation was related to altered promoter activity rather than a change in RNA stability. HuR-silenced microglia showed reduced migration, invasion, and chemotactic properties but maintained viability. MMP-12, a target exquisitely sensitive to HuR knockdown, participates in the migration/invasion phenotype. HuR is abundantly detected in the cytoplasmic compartment of activated microglia from ALS spinal cords consistent with its increased activity. Microglia from ALS-associated mutant SOD1 mice demonstrated higher migration/invasion properties which can be blocked with HuR inhibition. These findings underscore an important role for HuR in sculpting the molecular signature and phenotype of activated microglia, and as a possible therapeutic target in ALS and other neurodegenerative diseases.

RNA Binding Protein Human Antigen R Is Translocated in Astrocytes following Spinal Cord Injury and Promotes the Inflammatory Response

Inflammation plays a prominent role in the events following traumatic injury to the central nervous system (CNS). The initial inflammatory response is driven by mediators such as tumor necrosis factor α and interleukin 1β, which are produced by activated astrocytes and microglia at the site of injury. These factors are regulated post-transcriptionally by RNA binding proteins (RBP) that interact with adenylate and uridylate-rich elements (ARE) in the 3'-untranslated region of the messenger RNA (mRNA). Human antigen R (HuR) is one of these RBPs and generally functions as a positive regulator of ARE-containing mRNAs. Here, we hypothesized that HuR plays an important role in the induction of cytokine and chemokines in astrocytes following traumatic injury. Using a mouse model of spinal cord injury, we found HuR to be extensively translocated to the cytoplasm in astrocytes at the level of injury, consistent with its activation. In an in vitro stretch injury model of CNS trauma, we observed a similar cytoplasmic shift of HuR in astrocytes and an attenuation of cytokine induction with HuR knockdown. RNA kinetics and luciferase assays suggested that the effect was more related to transcription than RNA destabilization. A small molecule inhibitor of HuR suppressed cytokine induction of injured astrocytes and reduced chemoattraction for neutrophils and microglia. In summary, HuR is activated in astrocytes in the early stages of CNS trauma and positively regulates the molecular response of key inflammatory mediators in astrocytes. Our findings suggest that HuR may be a therapeutic target in acute CNS trauma for blunting secondary tissue injury triggered by the inflammatory response.

Transforming Growth Factor Beta (TGF-β) Is a Muscle Biomarker of Disease Progression in ALS and Correlates with Smad Expression

We recently identified Smads1, 5 and 8 as muscle biomarkers in human ALS. In the ALS mouse, these markers are elevated and track disease progression. Smads are signal transducers and become activated upon receptor engagement of ligands from the TGF-β superfamily. Here, we sought to characterize ligands linked to activation of Smads in ALS muscle and their role as biomarkers of disease progression. RNA sequencing data of ALS muscle samples were mined for TGF-β superfamily ligands. Candidate targets were validated by qRT-PCR in a large cohort of human ALS muscle biopsy samples and in the G93A SOD1 mouse. Protein expression was evaluated by Western blot, ELISA and immunohistochemistry. C2C12 muscle cells were used to assess Smad activation and induction. TGF-β1, 2 and 3 mRNAs were increased in ALS muscle samples compared to controls and correlated with muscle strength and Smads1, 2, 5 and 8. In the G93A SOD1 mouse, the temporal pattern of TGF-β expression paralleled the Smads and increased with disease progression. TGF-β1 immunoreactivity was detected in mononuclear cells surrounding muscle fibers in ALS samples. In muscle cells, TGF-β ligands were capable of activating Smads. In conclusion, TGF-β1, 2 and 3 are novel biomarkers of ALS in skeletal muscle. Their correlation with weakness in human ALS and their progressive increase with advancing disease in the ALS mouse suggest that they, as with the Smads, can track disease progression. These ligands are capable of upregulating and activating Smads and thus may contribute to the Smad signaling pathway in ALS muscle.

Role of KSRP in control of type I interferon and cytokine expression

Cytokines and chemokines are key participants in pathways that drive inflammatory, immune, and other cellular responses to exogenous insults such as infection, trauma, and physiological stress. Persistent and aberrant expression of these factors has been linked to autoimmune, degenerative, and neoplastic diseases. Consequently, cytokine and chemokine expression is tightly governed at each level of gene regulation. Recent studies have demonstrated a role for KH-type splicing regulatory protein (KSRP) in curtailing cytokine and chemokine expression through transcriptional and post-transcriptional mechanisms, including promotion of microRNA maturation. Understanding the role of KSRP in cytokine mRNA metabolism should identify promising targets for the modulation of immune and inflammatory responses.

Abstract W P270: Quality of In-Hospital Stroke Care in Veterans Affairs Hospitals

Introduction: Increasing focus is being placed on quality metrics for stroke care in an effort to improve outcomes. This study aims to examine if quality of stroke care is the same for Veterans experiencing an in-hospital stroke compared to patients presenting through the emergency department (ED).

Methods: We analyzed data from an 11-site VA quality improvement study, where 30 months of ICD-9 defined stroke admissions were chart reviewed by a central, trained group of abstractors to assess stroke diagnosis, clinical data, and eligibility and passing for 11 stroke quality indicators (QIs; 8 Joint Commission and 3 others). Stroke severity was determined by retrospective NIHSS scoring of the admission exam. Strokes were classified as presenting to the ED or in-hospital (already admitted for another diagnosis). Transfers (N = 362) were excluded. We compared clinical and QI data between the in-hospital and ER groups using Student’s t-tests and Chi-square tests.

Results: There were 35 in-hospital and 1788 ED strokes. The two groups did not differ with respect to age, race or sex, however in-hospital strokes had higher stroke severity (mean 11.1 vs 5.1, p=0.002), increased length of stay (12.8 vs 7.3, p=0.003), and were less likely to be discharged home (34.3% vs 63.8%, p<0.001). QI results are shown in the Table; those with in-hospital stroke were more likely to be eligible for tPA, but received less dysphagia screening.

Conclusions: Veterans who develop an in-hospital stroke receive similar quality of care as patients presenting to the ED although fewer in-hospital patients had dysphagia screening. Interestingly, tPA eligibility and utilization were higher for in-hospital strokes although utilization did not reach significance. While it is reassuring that in-hospital strokes are receiving similar quality of care, there is still room for improvement in all patient care settings and in-hospital stroke patients should be included in future QI processes.

Smads as muscle biomarkers in amyotrophic lateral sclerosis

OBJECTIVE

To identify molecular signatures in muscle from patients with amyotrophic lateral sclerosis (ALS) that could provide insight into the disease process and serve as biomarkers.

METHODS

RNA sequencing was performed on ALS and control muscle samples to identify Smad family members as potential markers of disease. Validation studies were performed in a cohort of 27 ALS patients and 33 controls. The markers were assessed in the G93A superoxide dismutase (SOD)1 mouse at different stages of disease and in a model of sciatic nerve injury.

RESULTS

Smad8, and to a lesser extent Smad1 and 5, mRNAs were significantly elevated in human ALS muscle samples. The markers displayed a remarkably similar pattern in the G93A SOD1 mouse model of ALS with increases detected at preclinical stages. Expression at the RNA and protein levels as well as protein activation (phosphorylation) significantly increased with disease progression in the mouse. The markers were also elevated to a lesser degree in gastrocnemius muscle following sciatic nerve injury, but then reverted to baseline during the muscle reinnervation phase.

INTERPRETATION

These data indicate that Smad1, 5, 8 mRNA and protein levels, as well as Smad phosphorylation, are elevated in ALS muscle and could potentially serve as markers of disease progression or regression.

Hu antigen R (HuR) is a positive regulator of the RNA-binding proteins TDP-43 and FUS/TLS: implications for amyotrophic lateral sclerosis

Posttranscriptional gene regulation is governed by a network of RNA-binding proteins (RBPs) that interact with regulatory elements in the mRNA to modulate multiple molecular processes, including splicing, RNA transport, RNA stability, and translation. Mounting evidence indicates that there is a hierarchy within this network whereby certain RBPs cross-regulate other RBPs to coordinate gene expression. HuR, an RNA-binding protein we linked previously to aberrant VEGF mRNA metabolism in models of SOD1-associated amyotrophic lateral sclerosis, has been identified as being high up in this hierarchy, serving as a regulator of RNA regulators. Here we investigated the role of HuR in regulating two RBPs, TDP-43 and FUS/TLS, that have been linked genetically to amyotrophic lateral sclerosis. We found that HuR promotes the expression of both RBPs in primary astrocytes and U251 cells under normal and stressed (hypoxic) conditions. For TDP-43, we found that HuR binds to the 3' untranslated region (UTR) and regulates its expression through translational efficiency rather than RNA stability. With HuR knockdown, there was a shift of TDP-43 and FUS mRNAs away from polysomes, consistent with translational silencing. The TDP-43 splicing function was attenuated upon HuR knockdown and could be rescued by ectopic TDP-43 lacking the 3' UTR regulatory elements. Finally, conditioned medium from astrocytes in which HuR or TDP-43 was knocked down produced significant motor neuron and cortical neuron toxicity in vitro. These findings indicate that HuR regulates TDP-43 and FUS/TLS expression and that loss of HuR-mediated RNA processing in astrocytes can alter the molecular and cellular landscape to produce a toxic phenotype.

Expression of PRMT5 correlates with malignant grade in gliomas and plays a pivotal role in tumor growth in vitro

Protein arginine methyltransferase 5 (PRMT5) catalyzes the formation of ω-NG,N'G-symmetric dimethylarginine residues on histones as well as other proteins. These modifications play an important role in cell differentiation and tumor cell growth. However, the role of PRMT5 in human glioma cells has not been characterized. In this study, we assessed protein expression profiles of PRMT5 in control brain, WHO grade II astrocytomas, anaplastic astrocytomas, and glioblastoma multiforme (GBM) by immunohistochemistry. PRMT5 was low in glial cells in control brain tissues and low grade astrocytomas. Its expression increased in parallel with malignant progression, and was highly expressed in GBM. Knockdown of PRMT5 by small hairpin RNA caused alterations of p-ERK1/2 and significantly repressed the clonogenic potential and viability of glioma cells. These findings indicate that PRMT5 is a marker of malignant progression in glioma tumors and plays a pivotal role in tumor growth.

Mutant tristetraprolin: a potent inhibitor of malignant glioma cell growth

Malignant gliomas rely on the production of certain critical growth factors including VEGF, interleukin (IL)-6 and IL-8, to fuel rapid tumor growth, angiogenesis, and treatment resistance. Post-transcriptional regulation through adenine and uridine-rich elements of the 3' untranslated region is one mechanism for upregulating these and other growth factors. In glioma cells, we have shown that the post-transcriptional machinery is optimized for growth factor upregulation secondary to overexpression of the mRNA stabilizer, HuR. The negative regulator, tristetraprolin (TTP), on the other hand, may be suppressed because of extensive phosphorylation. Here we test that possibility by analyzing the phenotypic effects of a mutated form of TTP (mt-TTP) in which 8 phosphoserine residues were converted to alanines. We observed a significantly enhanced negative effect on growth factor expression in glioma cells at the post-transcriptional and transcriptional levels. The protein became stabilized and displayed significantly increased antiproliferative effects compared to wild-type TTP. Macroautophagy was induced with both forms of TTP, but inhibition of autophagy did not affect cell viability. We conclude that glioma cells suppress TTP function through phosphorylation of critical serine residues which in turn contributes to growth factor upregulation and tumor progression.

Epidemiological features of amyotrophic lateral sclerosis in a large clinic-based African American population

Our objective was to identify the main clinical and epidemiological features of ALS in a large cohort of African American (AA) patients and compare them to Caucasian (CA) patients in a clinic-based population. We retrospectively identified 207 patients who were diagnosed with ALS based on the revised El Escorial criteria (60 AA and 147 CA subjects). Patients were seen in the Neuromuscular Division at the University Medical Center. We compared epidemiological and clinical features of these two groups, focusing on age of onset and diagnosis, clinical presentation and survival. Results showed that AA patients had a significantly younger age of disease onset (55 years vs. 61 years for CA, p = 0.011) and were diagnosed at an earlier age (56 years vs. 62 years, p = 0.012). In younger ALS patients (< 45 years of age), there was a significant difference in gender frequency, with females predominating in the AA population and males in the CA population (p = 0.025). In a multivariable Cox proportional hazard model, survival rates were not different between the groups. In both groups, survival significantly increased with younger age. In conclusion, AA patients presented at an earlier age, but there was no difference in survival compared to CA patients. A gender reversal occurred in younger ALS patients, with AA patients more likely to be female and CA patients more likely to be male.

KSRP: a checkpoint for inflammatory cytokine production in astrocytes

Chronic inflammation in the central nervous system (CNS) is a central feature of many neurodegenerative and autoimmune diseases. As an immunologically competent cell, the astrocyte plays an important role in CNS inflammation. It is capable of expressing a number of cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) that promote inflammation directly and through the recruitment of immune cells. Checkpoints are therefore in place to keep tight control over cytokine production. Adenylate/uridylate-rich elements (ARE) in the 3' untranslated region of cytokine mRNAs serve as a major checkpoint by regulating mRNA stability and translational efficiency. Here, we examined the impact of KH-type splicing regulatory protein (KSRP), an RNA binding protein which destabilizes mRNAs via the ARE, on cytokine expression and paracrine phenotypes of primary astrocytes. We identified a network of inflammatory mediators, including TNF-α and IL-1β, whose expression increased 2 to 4-fold at the RNA level in astrocytes isolated from KSRP(-/-) mice compared to littermate controls. Upon activation, KSRP(-/-) astrocytes produced TNF-α and IL-1β at levels that exceeded control cells by 15-fold or more. Conditioned media from KSRP(-/-) astrocytes induced chemotaxis and neuronal cell death in vitro. Surprisingly, we observed a prolongation of half-life in only a subset of mRNA targets and only after selective astrocyte activation. Luciferase reporter studies indicated that KSRP regulates cytokine gene expression at both transcriptional and post-transcriptional levels. Our results outline a critical role for KSRP in regulating pro-inflammatory mediators and have implications for a wide range of CNS inflammatory and autoimmune diseases.

Sex hormone-dependent attenuation of EAE in a transgenic mouse with astrocytic expression of the RNA regulator HuR

In experimental autoimmune encephalomyelitis (EAE) and other neurodegenerative diseases, astrocytes play an important role in promoting or attenuating the inflammatory response through induction of different cytokines and growth factors. HuR plays a major role in regulating many of these factors by modulating RNA stability and translational efficiency. Here, we engineered transgenic mice to express HuR in astrocytes using the human glial fibrillary acidic protein promoter and found that female transgenic mice had significantly less clinical disability and histopathological changes in the spinal cord. Ovariectomy prior to EAE induction abrogated the protective effect. Our findings support a role for the astrocyte and posttranscriptional regulation in hormonally-mediated attenuation of EAE.

Abstract 3872: Transgenic HuR in Astrocytes Increases Ischemic Lesion Size in Mice

Introduction: Stroke is a serious neurological disorder that affects more than 800,000 Americans each year. HuR, an mRNA binding protein, regulates gene expression by modulating the stability and translational efficiency of mRNAs containing adenine-uridine rich elements in the 3’ untranslated region. Genes implicated in neuroprotection and post-ischemic repair may be regulated by HuR. The current investigation utilizes transgenic mice engineered to express Flag-HuR in astrocytes using the glial fibrillary acidic protein (GFAP) promoter. We hypothesized that modulation of mRNA stability in astrocytes would change the outcome from transient cerebral ischemia.

Methods: Four mouse cohorts were studied: male or female and transgenic (TG) or wild-type (WT). Mice underwent 30-minute transient right middle cerebral artery occlusion (MCAO) and survived for 24 or 72h. Neurological scores were recorded after ischemia and prior to euthanasia, and brain tissue was sectioned for histology and immunolabeling. In a blinded fashion, Flag-HuR expressing nuclei were counted in peri-lesional regions of interest (ROI) and contralateral mirror ROIs, and ischemic/contralateral indices were calculated. Representative lesion size was determined in hematoxylin-eosin sections at the level of Bregma 1.10 mm.

Results:HuR-Flag expression: The transgene was expressed in peri-lesional astrocytes. 24h after MCAO, hormonally intact female mice had higher levels of Flag-HuR expression: Flag-HuR index was 5.9 ± 1.9 in females (n = 7) vs. 2.0 ± 0.7 in males (n = 6), p = 0.002, Mann-Whitney rank sum test. 72h after MCAO, TG expression declined in females to levels comparable to those of males.

Lesion size: There was no difference in lesion size between sex-matched TG and WT mice 24h post-MCAO, but at 72h lesion size was larger in TG females than WT females: 47% ± 12 (n = 10) vs. 22% ± 11 (n = 5), respectively, p = 0.002, t-test. Analysis of neurological scores, sex hormone levels, and long term survival is ongoing.

Discussion: We hypothesized that altering mRNA stability in ischemic astrocytes would change outcome from cerebral ischemia. Initial characterization of TG mice in which HuR was expressed under control of the GFAP promoter showed that ischemia results in peri-lesional upregulation of the transgene, which is more robust in females than males 24h after MCAO and comparable to males 72h after MCAO. Transgene expression correlated with increased lesion size in females 72h after MCAO. While the mechanism of this effect requires elucidation, our results suggest that HuR is a viable novel target for further investigation in cerebral ischemia.

The RNA-binding protein HuR promotes glioma growth and treatment resistance

Posttranscriptional regulation is a critical control point for the expression of genes that promote or retard tumor growth. We previously found that the mRNA-binding protein, ELAV 1 (HuR), is upregulated in primary brain tumors and stabilizes growth factor mRNAs such as VEGF and IL-8. To better understand the role of HuR in brain tumor growth, we altered levels of HuR in glioma cells by short hairpin RNA or ectopic expression and measured tumor cell phenotype using in vitro and in vivo models. In HuR-silenced cells, we found a significant decrease in anchorage-independent growth and cell proliferation with a concomitant induction of apoptosis. Using an intracranial tumor model with primary glioblastoma cells, HuR silencing produced a significant decrease in tumor volume. In contrast, overexpression of HuR produced in vitro chemoresistance to standard glioma therapies. Because bcl-2 is abundantly expressed in glioma and associated with tumor growth and survival, we determined the impact of HuR on its regulation as a molecular validation to the cellular and animal studies. Using UV cross-linking and RNA immunoprecipitation, we show that HuR bound to the 3'-untranslated region of all bcl-2 family members. Silencing of HuR led to transcript destabilization and reduced protein expression. Polysome profiling indicated loss of HuR from the translational apparatus. In summary, these findings reveal a HuR-dependent mechanism for cancer cell survival and sensitivity to chemotherapeutic drugs suggesting that HuR should be considered as a new therapeutic target.

Abstract 4070: Mutant tristetraprolin enhances growth factor downregulation and inhibition of cell growth in malignant glioma

Background: Tristetraprolin (TTP) negatively regulates short-lived mRNAs by binding to AU-rich elements in the 3′ untranslated region (3′UTR). A number of mRNA targets, including vascular endothelial growth factor (VEGF), and interleukin (IL)-8, play an important role in tumor progression. We have shown previously that TTP downregulates IL-8 and VEGF in malignant glioma (MG) cells via RNA destabilization. In primary glioblastoma tumors, TTP is heavily phosphorylated which may render the protein less active. Hypothesis: We postulate that the destabilizing effect of TTP on target growth factor mRNAs is held in check by hyperphosphorylation which leads to altered subcellular localization and protein stability. Methods: Wild-type TTP and two mutant forms in which select serines were exchanged with alanines were cloned with a Flag epitope into pTRE2 and pEGFP vectors. U251 Tet On MG cells were transfected with pTRE2–TTP plasmids to produce stable clones. TTP expression was induced using doxycycline. Cellular location was assessed by fluorescence microscopy and Western blotting. Protein stability was measured by assessment of TTP levels following cycloheximide treatment. VEGF and IL-8 mRNA and protein levels were measured by qRT-PCR and ELISA. For assessment of RNA half-lives, cells were treated with actinomycin D. Cell growth, proliferation and cell viability were assessed using biochemical assays, soft agar, and Trypan Blue method. Results: Both IL-8 and VEGF mRNA levels were significantly lowered in the mutant TTP clones compared to wild-type. Half-lives of these mRNAs were also shortened, and ELISA analysis showed a correspondingly greater decrease in protein expression. There was a marked impact on cellular phenotype with greater inhibition of proliferation and loss of cell viability. A Soft agar colony formation was decreased by five-fold in mutant clones versus wild-type and a greater than ten-fold decrease versus the parent cell line. With TNF-α, there was a significant shift of mutant TTP to the nuclear compartment compared to WT TTP. Treatment with cycloheximide revealed that the WT TTP was less stable compared to dephosphorylated mutant. Conclusion: Removal of key serine residues from TTP enhances its function as an RNA destabilizer of VEGF and IL-8 mRNs and as a negative regulator of tumor cell growth in MG.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4070.

Amyotrophic lateral sclerosis-linked mutant SOD1 sequesters Hu antigen R (HuR) and TIA-1-related protein (TIAR): implications for impaired post-transcriptional regulation of vascular endothelial growth factor

Down-regulation of vascular endothelial growth factor (VEGF) in the mouse leads to progressive and selective degeneration of motor neurons similar to amyotrophic lateral sclerosis (ALS). In mice expressing ALS-associated mutant superoxide dismutase 1 (SOD1), VEGF mRNA expression in the spinal cord declines significantly prior to the onset of clinical manifestations. In vitro models suggest that dysregulation of VEGF mRNA stability contributes to that decline. Here, we show that the major RNA stabilizer, Hu Antigen R (HuR), and TIA-1-related protein (TIAR) colocalize with mutant SOD1 in mouse spinal cord extracts and cultured glioma cells. The colocalization was markedly reduced or abolished by RNase treatment. Immunoanalysis of transfected cells indicated that colocalization occurred in insoluble aggregates and inclusions. RNA immunoprecipitation showed a significant loss of VEGF mRNA binding to HuR and TIAR in mutant SOD1 cells, and there was marked depletion of HuR from polysomes. Ectopic expression of HuR in mutant SOD1 cells more than doubled the mRNA half-life of VEGF and significantly increased expression to that of wild-type SOD1 control. Cellular effects produced by mutant SOD1, including impaired mitochondrial function and oxidative stress-induced apoptosis, were reversed by HuR in a gene dose-dependent pattern. In summary, our findings indicate that mutant SOD1 impairs post-transcriptional regulation by sequestering key regulatory RNA-binding proteins. The rescue effect of HuR suggests that this impairment, whether related to VEGF or other potential mRNA targets, contributes to cytotoxicity in ALS.

Mutant copper-zinc superoxide dismutase associated with amyotrophic lateral sclerosis binds to adenine/uridine-rich stability elements in the vascular endothelial growth factor 3'-untranslated region

Vascular endothelial growth factor (VEGF) is a neurotrophic factor essential for maintenance of motor neurons. Loss of this factor produces a phenotype similar to amyotrophic lateral sclerosis (ALS). We recently showed that ALS-producing mutations of Cu/Zn-superoxide dismutase (SOD1) disrupt post-transcriptional regulation of VEGF mRNA, leading to significant loss of expression [Lu et al., J. Neurosci.27 (2007), 7929]. Mutant SOD1 was present in the ribonucleoprotein complex associated with adenine/uridine-rich elements (ARE) of the VEGF 3'-untranslated region (UTR). Here, we show by electrophoretic mobility shift assay that mutant SOD1 bound directly to the VEGF 3'-UTR with a predilection for AREs similar to the RNA stabilizer HuR. SOD1 mutants A4V and G37R showed higher affinity for the ARE than L38V or G93A. Wild-type SOD1 bound very weakly with an apparent K(d) 11- to 72-fold higher than mutant forms. Mutant SOD1 showed an additional lower shift with VEGF ARE that was accentuated in the metal-free state. A similar pattern of binding was observed with AREs of tumor necrosis factor-alpha and interleukin-8, except only a single shift predominated. Using an ELISA-based assay, we demonstrated that mutant SOD1 competes with HuR and neuronal HuC for VEGF 3'-UTR binding. To define potential RNA-binding domains, we truncated G37R, G93A and wild-type SOD1 and found that peptides from the N-terminal portion of the protein that included amino acids 32-49 could recapitulate the binding pattern of full-length protein. Thus, the strong RNA-binding affinity conferred by ALS-associated mutations of SOD1 may contribute to the post-transcriptional dysregulation of VEGF mRNA.

Cercariae developing in Lymnaea natalensis Krauss, 1848 collected in the vicinity of Pretoria, Gauteng Province, South Africa

Freshwater snails are known to serve as first intermediate hosts for various parasitic diseases such as schistosomosis and fasciolosis. Snails were collected on several occasions in the proximity of Pretoria, South Africa and their cercarial sheddings were studied. This article describes three different types of cercariae shed by the freshwater snail, Lymnaea natalensis, viz. a fork-tailed cercaria of a Trichobilharzia sp., an avian parasite belonging to the family Schistosomatidae, an echinostomatid cercaria of the family Echinostomatidae, also avian parasites and a xiphidiocercaria of the family Plagiorchiidae which parasitise avians and amphibians. The morphology of these cercariae was studied by light and scanning electron microscopy.

Alterations in RNA-binding activities of IRES-regulatory proteins as a mechanism for physiological variability and pathological dysregulation of IGF-IR translational control in human breast tumor cells

The type I insulin-like growth factor receptor (IGF-IR) is integrally involved in the control of cellular proliferation and survival. An internal ribosomal entry site (IRES) within the 1,038 nucleotide 5'-untranslated region of the human IGF-IR mRNA helps to provide the tight control of IGF-IR expression necessary for maintenance of normal cellular and tissue homeostasis. The IRES maps to a discrete sequence of 85 nucleotides positioned just upstream of the IGF-IR initiation codon, allowing the ribosome to bypass the highly structured regions of the 5'-UTR as well as the upstream open reading frame. The authenticity of the IGF-IR IRES has been confirmed by its sensitivity to deletion of the promoter from a bicistronic reporter construct, and its resistance in a monocistronic reporter construct to co-expression of a viral 2A protease. We previously characterized HuR as a potent repressor of IGF-IR translation. Here we demonstrate that hnRNP C competes with HuR for binding the IGF-IR 5'-UTR and enhances IRES-mediated translation initiation in a concentration-dependent manner. We observed changes in binding of hnRNP C versus HuR to the IGF-IR 5'-UTR in response to physiological alterations in cellular environment or proliferative status. Furthermore, we have found distinct alterations in the pattern of protein binding to the IGF-IR 5'-UTR in human breast tumor cells in which IGF-IR IRES activity and relative translational efficiency are aberrantly increased. These results suggest that dysregulation of the IGF-IR IRES through changes in the activities of RNA-binding translation-regulatory proteins could be responsible for IGF-IR overexpression in a proportion of human breast tumors.

Tristetraprolin down-regulates interleukin-8 and vascular endothelial growth factor in malignant glioma cells

Malignant gliomas are highly aggressive tumors of the central nervous system that rely on production of growth factors for tumor progression. Vascular endothelial growth factor (VEGF), interleukin-8 (IL-8), and tumor necrosis factor-alpha, for example, are up-regulated in these tumors to promote angiogenesis and proliferation. RNA stability, mediated through adenine and uridine-rich elements (ARE) in the 3' untranslated region, is a critical control point for regulating these growth factors. RNA half-life is predominantly governed by a balance between stabilizing and destabilizing factors that bind to ARE. We have previously shown that the stabilizing factor HuR is overexpressed in malignant gliomas and linked to RNA stabilization of angiogenic growth factors. Here, we report that the destabilizing factor tristetraprolin (TTP) is also ubiquitously expressed in primary malignant glioma tissues and cell lines. In contrast to benign astrogliotic tissues, however, the protein was hyperphosphorylated, with evidence implicating the p38/mitogen-activated protein kinase (MAPK) pathway. Conditional overexpression of TTP as a transgene in malignant glioma cells led to RNA destabilization of IL-8 and VEGF and down-regulation of protein production. Analysis of in vivo RNA binding indicated a shift of mRNA toward ectopic TTP and away from endogenous HuR. This biochemical phenotype was associated with a decrease in cell proliferation, loss of cell viability, and apoptosis. We postulate that hyperphosphorylation of TTP via p38/MAPK promotes progression of malignant gliomas by negatively regulating its RNA destabilizing function.

Mutant Cu/Zn-superoxide dismutase associated with amyotrophic lateral sclerosis destabilizes vascular endothelial growth factor mRNA and downregulates its expression

Vascular endothelial growth factor (VEGF) plays a neuroprotective role in mice harboring mutations of copper-zinc superoxide dismutase 1 (SOD1) in familial amyotrophic lateral sclerosis (ALS). Conversely, the loss of VEGF expression through genetic depletion can give rise to a phenotype resembling ALS independent of SOD1 mutations. Here, we observe a profound downregulation of VEGF mRNA expression in spinal cords of G93A SOD1 mice that occurred early in the course of the disease. Using an in vitro culture model of glial cells expressing mutant SOD1, we demonstrate destabilization and downregulation of VEGF RNA with concomitant loss of protein expression that correlates with level of transgene expression. Using a luciferase reporter assay, we show that this molecular effect is mediated through a portion of the VEGF 3'-untranslated region (UTR) that harbors a class II adenylate/uridylate-rich element. Other mutant forms of SOD1 produced a similar negative effect on luciferase RNA and protein expression. Mobility shift assay with a VEGF 3'-UTR probe reveals an aberrantly migrating complex that contains mutant SOD1. We further show that the RNA stabilizing protein, HuR (human antigen R), is translocated from nucleus to cytoplasm in mutant SOD1 cells in vitro and mouse motor neurons in vivo. In summary, our data suggest that mutant SOD1 gains a novel function, possibly by altering the ribonucleoprotein complex with the VEGF 3'-UTR. We postulate that the resultant dysregulation of VEGF posttranscriptional processing critically reduces the level of this neuroprotective growth factor and accelerates the neurodegenerative process in ALS.