Follistatin-like 1 suppresses sensory afferent transmission by activating Na+,K+-ATPase

Na+/K+-ATPase: ion pump, signal transducer, or cytoprotective protein, and novel biological functions

Na+/K+-ATPase is a transmembrane protein that has important roles in the maintenance of electrochemical gradients across cell membranes by transporting three Na+ out of and two K+ into cells. Additionally, Na+/K+-ATPase participates in Ca2+-signaling transduction and neurotransmitter release by coordinating the ion concentration gradient across the cell membrane. Na+/K+-ATPase works synergistically with multiple ion channels in the cell membrane to form a dynamic network of ion homeostatic regulation and affects cellular communication by regulating chemical signals and the ion balance among different types of cells. Therefore, it is not surprising that Na+/K+-ATPase dysfunction has emerged as a risk factor for a variety of neurological diseases. However, published studies have so far only elucidated the important roles of Na+/K+-ATPase dysfunction in disease development, and we are lacking detailed mechanisms to clarify how Na+/K+-ATPase affects cell function. Our recent studies revealed that membrane loss of Na+/K+-ATPase is a key mechanism in many neurological disorders, particularly stroke and Parkinson's disease. Stabilization of plasma membrane Na+/K+-ATPase with an antibody is a novel strategy to treat these diseases. For this reason, Na+/K+-ATPase acts not only as a simple ion pump but also as a sensor/regulator or cytoprotective protein, participating in signal transduction such as neuronal autophagy and apoptosis, and glial cell migration. Thus, the present review attempts to summarize the novel biological functions of Na+/K+-ATPase and Na+/K+-ATPase-related pathogenesis. The potential for novel strategies to treat Na+/K+-ATPase-related brain diseases will also be discussed.

Identification of FXYD6 as the novel biomarker for glioma based on differential expression and DNA methylation

OBJECTIVE

As a single-transmembrane protein of the FXYD family, FXYD6 plays different roles under physiological and pathological status, especially in the nervous system. This study aims to identify FXYD6 as a biomarker for glioma, by analyzing its expression and methylation patterns.

METHODS

Using TCGA and GTEx datasets, we analyzed FXYD6 expression in various tissues, confirming its levels in normal brain and different glioma grades via immunoblotting and immunostaining. FXYD6 biological functions were explored through enrichment analysis, and tumor immune infiltration was assessed using ESTIMATE and TIMER algorithms. Pearson correlation analysis probed FXYD6 associations with biological function-related genes. A glioma detection model was developed using FXYD6 methylation data from TCGA and GEO. Consistently, a FXYD6 methylation-based prognostic model was constructed for glioma via LASSO Cox regression.

RESULTS

FXYD6 was observed to be downregulated in GBM and implicated in a range of cellular functions, including synapse formation, cell junctions, immune checkpoint, ferroptosis, EMT, and pyroptosis. Hypermethylation of specific FXYD6 CpG sites in gliomas was identified, which could be used to build a diagnostic model. Additionally, FXYD6 methylation-based prognostic model could serve as an independent factor as well.

CONCLUSIONS

FXYD6 is a promising biomarker for the diagnosis and prognosis of glioma, with its methylation-based prognostic model serving as an independent factor. This highlights its potential in clinical application for glioma management.

Terpenes in Cannabis sativa Inhibit Capsaicin Responses in Rat DRG Neurons via Na+/K+ ATPase Activation

Terpenes in Cannabis sativa exert analgesic effects, but the mechanisms are uncertain. We examined the effects of 10 terpenes on capsaicin responses in an established model of neuronal hypersensitivity. Adult rat DRG neurons cultured with neurotrophic factors NGF and GDNF were loaded with Fura2AM for calcium imaging, and treated with individual terpenes or vehicle for 5 min, followed by 1 µMol capsaicin. In vehicle treated control experiments, capsaicin elicited immediate and sustained calcium influx. Most neurons treated with terpenes responded to capsaicin after 6-8 min. Few neurons showed immediate capsaicin responses that were transient or normal. The delayed responses were found to be due to calcium released from the endoplasmic reticulum, as they were maintained in calcium/magnesium free media, but not after thapsigargin pre-treatment. Terpene inhibition of calcium influx was reversed after washout of medium, in the absence of terpenes, and in the presence of the Na+/K+ ATPase inhibitor ouabain, but not CB1 or CB2 receptor antagonists. Thus, terpenes inhibit capsaicin evoked calcium influx by Na+/K+ ATPase activation. Immunofluorescence showed TRPV1 co-expression with α1β1 Na+/K+ ATPase in most neurons while others were either TRPV1 or α1β1 Na+/K+ ATPase positive.

Assessing genomic diversity and selective pressures in Bashan cattle by whole-genome sequencing data

Specific ecological environments and domestication have continuously influenced the physiological characteristics of Chinese indigenous cattle. Among them, Bashan cattle belongs to one of the indigenous breeds. However, the genomic diversity of Bashan cattle is still unknown. Published whole-genome sequencing (WGS) data of 13 Bashan cattle and 48 worldwide cattle were used to investigate the genetic composition and selection characteristics of Bashan cattle. The population structure analysis revealed that Bashan cattle harbored ancestries with East Asian taurine and Chinese indicine. Genetic diversity analysis implied the relatively high genomic diversity in Bashan cattle. Through the identification of containing >5 nsSNPs or frameshift mutations genes in Bashan cattle, a large number of pathways related to sensory perception were discovered. CLR, θπ ratio, FST, and XP-EHH methods were used to detect the candidate signatures of positive selection in Bashan cattle. Among the identified genes, most of the enriched signal pathways were related to environmental information processing, biological systems, and metabolism. We mainly reported genes related to the nervous system (HCN1, KATNA1, FSTL1, GRIK2, and CPLX2), immune (CD244, SLAMF1, LY9, and CD48), and reproduction (AKR1C1, AKR1C3, AKR1C4, and TUSC3). Our findings will be significant in understanding the molecular basis underlying phenotypic variation of breed-related traits and improving productivity in Bashan cattle.

Neuropathic pain: From actual pharmacological treatments to new therapeutic horizons

Neuropathic pain, caused by a lesion or disease affecting the somatosensory system, affects between 3 and 17% of the general population. The treatment of neuropathic pain is challenging due to its heterogeneous etiologies, lack of objective diagnostic tools and resistance to classical analgesic drugs. First-line treatments recommended by the Special Interest Group on Neuropathic Pain (NeuPSIG) and European Federation of Neurological Societies (EFNS) include gabapentinoids, tricyclic antidepressants (TCAs) and selective serotonin noradrenaline reuptake inhibitors (SNRIs). Nevertheless these treatments have modest efficacy or dose limiting side effects. There is therefore a growing number of preclinical and clinical studies aim at developing new treatment strategies to treat neuropathic pain with better efficacy, selectivity, and less side effects. In this review, after a brief description of the mechanisms of action, efficacy, and limitations of current therapeutic drugs, we reviewed new preclinical and clinical targets currently under investigation, as well as promising non-pharmacological alternatives and their potential co-use with pharmacological treatments.

Follistatin-like 1 and its paralogs in heart development and cardiovascular disease

Cardiovascular diseases (CVDs) are a group of disorders affecting the heart and blood vessels and a leading cause of death worldwide. Thus, there is a need to identify new cardiokines that may protect the heart from damage as reported in GBD 2017 Causes of Death Collaborators (2018) (The Lancet 392:1736-1788). Follistatin-like 1 (FSTL1) is a cardiokine that is highly expressed in the heart and released to the serum after cardiac injury where it is associated with CVD and predicts poor outcome. The action of FSTL1 likely depends not only on the tissue source but also post-translation modifications that are target tissue- and cell-specific. Animal studies examining the effect of FSTL1 in various models of heart disease have exploded over the past 15 years and primarily report a protective effect spanning from inhibiting inflammation via transforming growth factor, preventing remodeling and fibrosis to promoting angiogenesis and hypertrophy. A better understanding of FSTL1 and its homologs is needed to determine whether this protein could be a useful novel biomarker to predict poor outcome and death and whether it has therapeutic potential. The aim of this review is to provide a comprehensive description of the literature for this family of proteins in order to better understand their role in normal physiology and CVD.

The mouse resource at National Resource Center for Mutant Mice

Mouse models are essential for dissecting disease mechanisms and defining potential drug targets. There are more than 18,500 mouse strains available for research communities in National Resource Center for Mutant Mice (NRCMM) of China, affiliated with Model Animal Research Center of Nanjing University and Gempharmatech Company. In 2019, Gempharmatech launched the Knockout All Project (KOAP) aiming to generate null mutants and gene floxed strains for all protein-coding genes in mouse genome within 5 years. So far, KOAP has generated 8,004 floxed strains and 9,769 KO (knockout) strains (updated to Oct, 2021). NRCMM also created hundreds of Cre transgenic lines, mutant knock-in models, immuno-deficient models, and humanized mouse models. As a member of the international mouse phenotyping consortium (IMPC), NRCMM provides comprehensive phenotyping services for mouse models. In summary, NRCMM will continue to support biomedical community with new mouse models as well as related services.

Xylazole inhibits NO-cGMP pathway in fetal rat nerve cells

Background

Xylazole (Xyl) is a veterinary anesthetic that is structurally and functionally similar to xylazine. However, the effects of Xyl in vitro remain unknown.

Objectives

This study aimed to investigate the anesthetic mechanism of Xyl using fetal rat nerve cells treated with Xyl.

Methods

Fetal rat nerve cells cultured for seven days were treated with 10, 20, 30, and 40 μg/ mL Xyl for 0, 5, 10, 15, 20, 25, 30, 45, 60, 90, and 120 min. Variations of amino acid neurotransmitters (AANTs), Nitric oxide-Cyclic GMP (NO-cGMP) signaling pathway, and ATPase were evaluated.

Results

Xyl decreased the levels of cGMP and NO in nerve cells. Furthermore, Xyl affected the AANT content and Na⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase activity in nerve cells. These findings suggested that Xyl inhibited the NO-cGMP signaling pathway in nerve cells in vitro.

Conclusions

This study provided new evidence that the anesthetic and analgesic effects of Xyl are related to the inhibition of the NO-cGMP signaling pathway.

Follistatin-Like 1 Induces the Activation of Type 2 Innate Lymphoid Cells to Promote Airway Inflammation in Asthma

Asthma is a chronic disease closely related to airway inflammation. It has been proven that type 2 innate lymphoid cells (ILC2s) play an essential role in airway inflammation in asthma. Furthermore, there is growing evidence that Follistatin-like 1 (FSTL1) can participate in various inflammatory reactions mediated by the JAK/STAT signaling pathway, among others. Therefore, we put forward a new hypothesis: FSTL1 promotes asthmatic airway inflammation by activating ILC2. This study generated an ovalbumin-sensitized asthma model in C57BL/6 and Fstl1^+/- mice. The results showed that the absolute number and the proportion of ILC2 in the ovalbumin-challenged Fstl1^+/- group were lower than in the ovalbumin-challenged wild-type group. We also measured the levels of Th2-type cytokines in the serum and bronchoalveolar lavage fluid (BALF) of mice and found that the corresponding cytokines in the Fstl1^+/- were lower than in the wild-type groups. Finally, we tested whether MEK-JAK-STAT-GATA3 is the specific pathway for FSTL1 to activate ILC2, and further tested our working hypothesis by adding various inhibitors of proteins from this pathway. Overall, these findings reveal that FSTL1 can activate ILC2 through MEK-JAK-STAT-GATA3 to promote airway inflammation and participate in the pathogenesis of asthma.

Follistatin-Like Proteins: Structure, Functions and Biomedical Importance

Main forms of cellular signal transmission are known to be autocrine and paracrine signaling. Several cells secrete messengers called autocrine or paracrine agents that can bind the corresponding receptors on the surface of the cells themselves or their microenvironment. Follistatin and follistatin-like proteins can be called one of the most important bifunctional messengers capable of displaying both autocrine and paracrine activity. Whilst they are not as diverse as protein hormones or protein kinases, there are only five types of proteins. However, unlike protein kinases, there are no minor proteins among them; each follistatin-like protein performs an important physiological function. These proteins are involved in a variety of signaling pathways and biological processes, having the ability to bind to receptors such as DIP2A, TLR4, BMP and some others. The activation or experimentally induced knockout of the protein-coding genes often leads to fatal consequences for individual cells and the whole body as follistatin-like proteins indirectly regulate the cell cycle, tissue differentiation, metabolic pathways, and participate in the transmission chains of the pro-inflammatory intracellular signal. Abnormal course of these processes can cause the development of oncology or apoptosis, programmed cell death. There is still no comprehensive understanding of the spectrum of mechanisms of action of follistatin-like proteins, so the systematization and study of their cellular functions and regulation is an important direction of modern molecular and cell biology. Therefore, this review focuses on follistatin-related proteins that affect multiple targets and have direct or indirect effects on cellular signaling pathways, as well as to characterize the directions of their practical application in the field of biomedicine.

FSTL1 aggravates OVA-induced inflammatory responses by activating the NLRP3/IL-1β signaling pathway in mice and macrophages

OBJECTIVE

Asthma, a well-known disease with high morbidity, is characterized by chronic airway inflammation. However, the allergic inflammation mechanisms of follistatin-like protein 1 (FSTL1) have not been elucidated. This study aims to investigate the effects of FSTL1 in ovalbumin (OVA)-induced mice and macrophages on nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3)/interleukin-1β (IL-1β) signaling pathway.

METHODS

Mice were randomly divided into control-WT, OVA-WT, control-Fstl1±, OVA-Fstl1±. Histological changes were assessed by HE and PAS staining. The protein levels of Muc-5AC, FSTL1, NLRP3, and IL-1β in lung tissue were detected by immunohistochemistry and ELISA. The bronchoalveolar lavage fluid (BALF) in mice and human serum samples were detected by ELISA. Then, mice were grouped into control, FSTL1, MCC950 + FSTL1 to further investigate the relationship between FSTL1 and NLRP3/IL-1β. Alveolar macrophage cells (MH-S cells) were separated into control, OVA, FSTL1, OVA + FSTL1, OVA + siNC, OVA + siFSTL1, MCC950, and FSTL1 + MCC950 groups to explore the effect of FSTL1 on the NLRP3/IL-1β signaling. The protein expression of NLRP3 and IL-1β in MH-S cells was detected by Western blot analysis.

RESULTS

The present results uncovered that Fstl1± significantly ameliorated OVA-induced Muc-5AC production and mucus hypersecretion. Fstl1± was also found to decrease the production of inflammatory cytokines and inflammatory cell infiltration in OVA-induced asthmatic mice. Meanwhile, the serum concentrations of FSTL1 and IL-1β were higher in  asthma subjects than the health subjects, and Fstl1± ameliorated the production of NLRP3 and IL-1β in OVA-induced asthmatic mice. Furthermore, mice by injected FSTL1 substantially stimulated the expression of NLRP3 and IL-1β, while pretreatment with MCC950 in mice significantly weakened the production of NLRP3 and IL-1β induced by injection FSTL1. Pretreatment with siFSTL1 or MCC950 significantly reduced the production of NLRP3 and IL-1β induced by OVA or FSTL1 in MH-S cells.

CONCLUSIONS

The study results showed that FSTL1 played an important role in allergic airway inflammation by activating NLRP3/IL-1β. Hence, inhibition FSTL1 could be applied as a therapeutic agent against asthma.

FXYD6 promotes thermal nociception by regulating TRPV1

FXYD6, an unnecessary auxiliary subunit of Na⁺,K⁺-ATPase, is expressed in the nervous system. However, its functions remain largely unclear. In the present study, we find that FXYD6 is involved in the thermal nociception. FXYD6 was mainly expressed in small-diameter DRG neurons expressing transient receptor potential channel V1 (TRPV1). In the SNS-Cre/Fxyd6^F/F mice, loss of FXYD6 in these sensory neurons impaired the behavioral responses to noxious heat stimulus and intraplantar injection of capsaicin. The capsaicin-induced and TRPV1-mediated currents were decreased in the FXYD6–deficient DRG neurons. Heterologous expression of FXYD6 could increase the TRPV1 capsaicin-sensitive currents in HEK293 cells. Furthermore, we found that the negatively charged PGDEE motif in C-terminal of FXYD6 is required for the FXYD6/TRPV1 interaction and FXYD6-mediated enhancement of TRPV1. Disrupting the FXYD6/TRPV1 interaction with the TAT-PGDEE peptide could elevate the threshold of thermal nociception. Therefore, FXYD6 maintains the thermal nociception via interacting with TRPV1 channel in nociceptors.

Input-output signal processing plasticity of vagal motor neurons in response to cardiac ischemic injury

Vagal stimulation is emerging as the next frontier in bioelectronic medicine to modulate peripheral organ health and treat disease. The neuronal molecular phenotypes in the dorsal motor nucleus of the vagus (DMV) remain largely unexplored, limiting the potential for harnessing the DMV plasticity for therapeutic interventions. We developed a mesoscale single-cell transcriptomics data from hundreds of DMV neurons under homeostasis and following physiological perturbations. Our results revealed that homeostatic DMV neuronal states can be organized into distinguishable input-output signal processing units. Remote ischemic preconditioning induced a distinctive shift in the neuronal states toward diminishing the role of inhibitory inputs, with concomitant changes in regulatory microRNAs miR-218a and miR-495. Chronic cardiac ischemic injury resulted in a dramatic shift in DMV neuronal states suggestive of enhanced neurosecretory function. We propose a DMV molecular network mechanism that integrates combinatorial neurotransmitter inputs from multiple brain regions and humoral signals to modulate cardiac health.

FSTL1 aggravates cigarette smoke-induced airway inflammation and airway remodeling by regulating autophagy

BACKGROUND

Cigarette smoke (CS) is a major risk factor for Chronic Obstructive Pulmonary Disease (COPD). Follistatin-like protein 1 (FSTL1), a critical factor during embryogenesis particularly in respiratory lung development, is a novel mediator related to inflammation and tissue remodeling. We tried to investigate the role of FSTL1 in CS-induced autophagy dysregulation, airway inflammation and remodeling.

METHODS

Serum and lung specimens were obtained from COPD patients and controls. Adult female wild-type (WT) mice, FSTL1^± mice and FSTL1^flox/+ mice were exposed to room air or chronic CS. Additionally, 3-methyladenine (3-MA), an inhibitor of autophagy, was applied in CS-exposed WT mice. The lung tissues and serum from patients and murine models were tested for FSTL1 and autophagy-associated protein expression by ELISA, western blotting and immunohistochemical. Autophagosome were observed using electron microscope technology. LTB4, IL-8 and TNF-α in bronchoalveolar lavage fluid of mice were examined using ELISA. Airway remodeling and lung function were also assessed.

RESULTS

Both FSTL1 and autophagy biomarkers increased in COPD patients and CS-exposed WT mice. Autophagy activation was upregulated in CS-exposed mice accompanied by airway remodeling and airway inflammation. FSTL1^± mice showed a lower level of CS-induced autophagy compared with the control mice. FSTL1^± mice can also resist CS-induced inflammatory response, airway remodeling and impaired lung function. CS-exposed WT mice with 3-MA pretreatment have a similar manifestation with CS-exposed FSTL1^± mice.

CONCLUSIONS

FSTL1 promotes CS-induced COPD by modulating autophagy, therefore targeting FSTL1 and autophagy may shed light on treating cigarette smoke-induced COPD.

Knockdown of Follistatin-like 1 disrupts synaptic transmission in hippocampus and leads to cognitive impairments

Follistatin-like 1 (FSTL1), also named transforming growth factor (TGF)-β1-inducible gene, is a secreted extracellular glycoprotein expressing widely in nervous system. Several recent studies have revealed that FSTL1 plays an essential role in neurological diseases including neuropathic pain and ischemic stroke. It proves that FSTL1 suppresses synaptic transmission by activating Na/K-ATPase in DRG neurons and inhibits neuronal apoptosis by phosphorylation AKT signaling. However, it is not clear whether FSTL1 can play a role in other type of neuron or neurodegenerative diseases. In this study, we found that the mice with Fstl1 genetic knockdown showed not only the impairments of learning and memory abilities, but also abnormal neural oscillations and synaptic plasticity in the hippocampus. Subsequently, we identified broad transcriptional changes including 55 up-regulated and 184 down-regulated genes in Fstl1 knockdown mice by RNA-Seq analysis, as well as neurotransmitter transport, synaptic transmission and disease-related genes. The expression changes of some DEGs were further validated via quantitative Realtime PCR (qRT-PCR). Further patch-clamp whole cell recording showed that Fstl1^+/- mice displayed a significant decrease in glutamatergic synaptic transmission and increase in GABAergic synaptic transmission, which were consistent with the RNA-Seq analysis. Taken together, our results provide an evidence and a possibly underlying mechanism for the critical role of FSTL1 in the hippocampus on learning and memory and normal neural oscillations, suggesting that FSTL1 may plays an important role in neurodegenerative diseases related to cognitive impairments.

Angiocrine FSTL1 (Follistatin-Like Protein 1) Insufficiency Leads to Atrial and Venous Wall Fibrosis via SMAD3 Activation

OBJECTIVE

Angiocrine factors, mediating the endothelial-mural cell interaction in vascular wall construction as well as maintenance, are incompletely characterized. This study aims to investigate the role of endothelial cell-derived FSTL1 (follistatin-like protein 1) in vascular homeostasis. Approach and Results: Using conditional knockout mouse models, we show that loss of FSTL1 in endothelial cells (Fstl1^ECKO) led to an increase of pulmonary vascular resistance, resulting in the heart regurgitation especially with tricuspid valves. However, this abnormality was not detected in mutant mice with Fstl1 knockout in smooth muscle cells or hematopoietic cells. We further showed that there was excessive αSMA (α-smooth muscle actin) associated with atrial endocardia, heart valves, veins, and microvessels after the endothelial FSTL1 deletion. There was also an increase in collagen deposition, as demonstrated in livers of Fstl1^ECKO mutants. The SMAD3 (mothers against decapentaplegic homolog 3) phosphorylation (pSMAD3) was significantly enhanced, and pSMAD3 staining was colocalized with αSMA in vein walls, suggesting the activation of TGFβ (transforming growth factor β) signaling in vascular mural cells of Fstl1^ECKO mice. Consistently, treatment with a TGFβ pathway inhibitor reduced the abnormal association of αSMA with the atria and blood vessels in Fstl1^ECKO mutant mice.

CONCLUSIONS

The findings imply that endothelial FSTL1 is critical for the homeostasis of vascular walls, and its insufficiency may favor cardiovascular fibrosis leading to heart failure.

Nerve Injury-Induced Neuronal PAP-I Maintains Neuropathic Pain by Activating Spinal Microglia

Pancreatitis-associated proteins (PAPs) display multiple functions in visceral diseases. Previous studies showed that the expression level of PAP-I was low in the DRG of naive rats but was de novo expressed after peripheral nerve injury. However, its role in neuropathic pain remains unknown. We found that PAP-I expression was continuously upregulated in the DRG neurons from rat spared nerve injury models, and transported toward the spinal dorsal horn to act as a proinflammatory factor. Intrathecal delivery of PAP-I enhanced sensory hyperalgesia, whereas PAP-I deficiency by either gene knockout or antibody application alleviated tactile allodynia at the maintenance phase after spared nerve injury. Furthermore, PAP-I functioned by activating the spinal microglia via C-C chemokine receptor Type 2 that participated in neuropathic pain. Inhibition of either microglial activation or C-C chemokine receptor Type 2 abolished the PAP-I-induced hyperalgesia. Thus, PAP-I mediates the neuron-microglial crosstalk after peripheral nerve injury and contributes to the maintenance of neuropathic pain.SIGNIFICANCE STATEMENT Neuropathic pain is maladaptive pain condition, and the maintaining mechanism is largely unclear. Here we reveal that, after peripheral nerve injury, PAP-I can be transported to the spinal dorsal horn and is crucial in the progression of neuropathic pain. Importantly, we prove that PAP-I mainly functions through activating the spinal microglia via the CCR2-p38 MAPK pathway. Furthermore, we confirm that the proinflammatory effect of PAP-I is more prominent after the establishment of neuropathic pain, thus indicating that microglia also participate in the maintenance phase of neuropathic pain.

Structural and functional study of FK domain of Fstl1

Fstl1 is a TGF-β superfamily binding protein which involved in many pathological processes. The function of Fstl1 has been widely elucidated, but its structural characterization has not been explored. Here we solved the high-resolution crystal structure of FK domain of murine Fstl1, analyzed its unique characteristics, and investigated its contribution to the function of full-length Fstl1. We found that Fstl1-FK forms a stable dimer in both solution and crystal, which suggest that this protein may function as a dimer during its interaction with TGF-β, a molecule known to form dimer during activation process. We also found this FK domain is indispensable for the proper function of Fstl1 during the transduction of TGF-β signaling. These observations provide important insights into the understanding of Fstl1 and may facilitate the exploration of this molecule in clinical study.

Identifying pathogenic variants in the Follistatin-like 1 gene (FSTL1) in patients with skeletal and atrioventricular valve disorders

BACKGROUND

Follistatin-like 1 (Fstl1) is a glycoprotein expressed throughout embryonic development. Homozygous loss of Fstl1 in mice results in skeletal and respiratory defects, leading to neonatal death due to a collapse of the trachea. Furthermore, Fstl1 conditional deletion from the endocardial/endothelial lineage results in postnatal death due to heart failure and profound atrioventricular valve defects. Here, we investigated patients with phenotypes similar to the phenotypes observed in the transgenic mice, for variants in FSTL1.

METHODS

In total, 69 genetically unresolved patients were selected with the following phenotypes: campomelic dysplasia (12), small patella syndrome (2), BILU (1), and congenital heart disease patients (54), of which 16 also had kyphoscoliosis, and 38 had valve abnormalities as their main diagnosis. Using qPCR, none of 69 patients showed copy number variations in FSTL1. The entire gene body, including microRNA-198 and three validated microRNA-binding sites, were analyzed using Sanger sequencing.

RESULTS

No variants were found in the coding region. However, 8 intronic variants were identified that differed significantly in their minor allele frequency compared to controls. Variant rs2272515 was found to significantly correlate (p < 0.05) with kyphoscoliosis.

CONCLUSION

We conclude that pathogenic variants in FSTL1 are unlikely to be responsible for skeletal or atrioventricular valve anomalies in humans.

Cell biology and dynamics of Neuronal Na+/K+-ATPase in health and diseases

Neuronal Na⁺/K⁺-ATPase is responsible for the maintenance of ionic gradient across plasma membrane. In doing so, in a healthy brain, Na⁺/K⁺-ATPase activity accounts for nearly half of total brain energy consumption. The α3-subunit containing Na⁺/K⁺-ATPase expression is restricted to neurons. Heterozygous mutations within α3-subunit leads to Rapid-onset Dystonia Parkinsonism, Alternating Hemiplegia of Childhood and other neurological and neuropsychiatric disorders. Additionally, proteins such as α-synuclein, amyloid-β, tau and SOD1 whose aggregation is associated to neurodegenerative diseases directly bind and impair α3-Na⁺/K⁺-ATPase activity. The review will provide a summary of neuronal α3-Na⁺/K⁺-ATPase functional properties, expression pattern, protein-protein interactions at the plasma membrane, biophysical properties (distribution and lateral diffusion). Lastly, the role of α3-Na⁺/K⁺-ATPase in neurological and neurodegenerative disorders will be discussed. This article is part of the special issue entitled 'Mobility and trafficking of neuronal membrane proteins'.

Innate immune activation of astrocytes impairs neurodevelopment via upregulation of follistatin-like 1 and interferon-induced transmembrane protein 3

BACKGROUND

Polyriboinosinic-polyribocytidylic acid (polyI:C) triggers a strong innate immune response that mimics immune activation by viral infections. Induction of interferon-induced transmembrane protein 3 (Ifitm3) in astrocytes has a crucial role in polyI:C-induced neurodevelopmental abnormalities. Through a quantitative proteomic screen, we previously identified candidate astroglial factors, such as matrix metalloproteinase-3 (Mmp3) and follistatin-like 1 (Fstl1), in polyl:C-induced neurodevelopmental impairment. Here, we characterized the Ifitm3-dependent inflammatory processes focusing on astrocyte-derived Fstl1 following polyI:C treatment to assess the neuropathologic role of Fstl1.

METHODS

Astrocytes were treated with PBS (control) or polyI:C (10 μg/mL). The conditioned medium was collected 24 h after the polyI:C treatment and used as astrocyte condition medium (ACM). The expression of Fstl1 mRNA and extracellular Fstl1 protein levels were analyzed by quantitative PCR and western blotting, respectively. For functional studies, neurons were treated with ACM and the effects of ACM on dendritic elongation were assayed. To examine the role of Fstl1, recombinant Fstl1 protein and siRNA for Fstl1 were used. To investigate the expression of Fstl1 in vivo, neonatal mice were treated with vehicle or polyI:C on postnatal day 2 to 6.

RESULTS

ACM prepared with polyI:C (polyI:C ACM) contained significantly higher Fstl1 protein than control ACM, but no increase in Fstl1 was observed in polyI:C ACM derived from Ifitm3-deficient astrocytes. We found that the production of Fstl1 involves the inflammatory responsive molecule Ifitm3 in astrocytes and influences neuronal differentiation. In agreement, the levels of Fstl1 increased in the hippocampus of polyI:C-treated neonatal mice. COS7 cells co-transfected with both Fstl1 and Ifitm3 had higher extracellular levels of Fstl1 than the cells transfected with Fstl1 alone. Treatment of primary cultured hippocampal neurons with recombinant Fstl1 impaired dendritic elongation, and the deleterious effect of polyI:C ACM on dendritic elongation was attenuated by knockdown of Fstl1 in astrocytes.

CONCLUSIONS

The extracellular level of Fstl1 is regulated by Ifitm3 in astrocytes, which could be involved in polyI:C-induced neurodevelopmental impairment.

Region-Resolved Quantitative Proteome Profiling Reveals Molecular Dynamics Associated With Chronic Pain in the PNS and Spinal Cord

To obtain a thorough understanding of chronic pain, large-scale molecular mapping of the pain axis at the protein level is necessary, but has not yet been achieved. We applied quantitative proteome profiling to build a comprehensive protein compendium of three regions of the pain neuraxis in mice: the sciatic nerve (SN), the dorsal root ganglia (DRG), and the spinal cord (SC). Furthermore, extensive bioinformatics analysis enabled us to reveal unique protein subsets which are specifically enriched in the peripheral nervous system (PNS) and SC. The immense value of these datasets for the scientific community is highlighted by validation experiments, where we monitored protein network dynamics during neuropathic pain. Here, we resolved profound region-specific differences and distinct changes of PNS-enriched proteins under pathological conditions. Overall, we provide a unique and validated systems biology proteome resource (summarized in our online database painproteome.em.mpg.de), which facilitates mechanistic insights into somatosensory biology and chronic pain—a prerequisite for the identification of novel therapeutic targets.

Multiple myosin motors interact with sodium/potassium-ATPase alpha 1 subunits

The alpha1 (α1) subunit of the sodium/potassium ATPase (i.e., Na⁺/K⁺-ATPase α1), the prototypical sodium pump, is expressed in each eukaryotic cell. They pump out three sodium ions in exchange for two extracellular potassium ions to establish a cellular electrochemical gradient important for firing of neuronal and cardiac action potentials. We hypothesized that myosin (myo or myh) motor proteins might interact with Na⁺/K⁺-ATPase α1 subunits in order for them to play an important role in the transport and trafficking of sodium pump. To this end immunoassays were performed to determine whether class II non-muscle myosins (i.e., NMHC-IIA/myh9, NMHC-IIB/myh10 or NMHC-IIC/myh14), myosin Va (myoVa) and myosin VI (myoVI) would interact with Na⁺/K⁺-ATPase α1 subunits. Immunoprecipitation of myh9, myh10, myh14, myoVa and myoVI from rat brain tissues led to the co-immunoprecipitation of Na⁺/K⁺-ATPase α1 subunits expressed there. Heterologous expression studies using HEK293 cells indicated that recombinant myh9, myh10, myh14 and myoVI interact with Na⁺/K⁺-ATPase α1 subunits expressed in HEK293 cells. Additional results indicated that loss of tail regions in recombinant myh9, myh10, myh14 and myoVI did not affect their interaction with Na⁺/K⁺-ATPase α1 subunits. However, recombinant myh9, myh10 and myh14 mutants having reduced or no actin binding ability, as a result of loss of their actin binding sites, displayed greatly reduced or null interaction with Na⁺/K⁺-ATPase α1 subunits. These results suggested the involvement of the actin binding site, but not tail regions, of NMHC-IIs in their interaction with Na⁺/K⁺-ATPase α1 subunits. Overall these results suggest a role for these diverse myosins in the trafficking and transport of sodium pump in neuronal and non-neuronal tissues.

Follistatin-like 1 in development and human diseases

Follistatin-like 1 (FSTL1) is a secreted glycoprotein displaying expression changes during development and disease, among which cardiovascular disease, cancer, and arthritis. The cardioprotective role of FSTL1 has been intensively studied over the last years, though its mechanism of action remains elusive. FSTL1 is involved in multiple signaling pathways and biological processes, including vascularization and regulation of the immune response, a feature that complicates its study. Binding to the DIP2A, TLR4 and BMP receptors have been shown, but other molecular partners probably exist. During cancer progression and rheumatoid arthritis, controversial data have been reported with respect to the proliferative, apoptotic, migratory, and inflammatory effects of FSTL1. This controversy might reside in the extensive post-transcriptional regulation of FSTL1. The FSTL1 primary transcript also encodes for a microRNA (miR-198) in primates and multiple microRNA-binding sites are present in the 3'UTR. The switch between expression of the FSTL1 protein and miR-198 is an important regulator of tumour metastasis and wound healing. The glycosylation state of FSTL1 is a determinant of biological activity, in cardiomyocytes the glycosylated form promoting proliferation and the non-glycosylated working anti-apoptotic. Moreover, the glycosylation state shows differences between species and tissues which might underlie the differences observed in in vitro studies. Finally, regulation at the level of protein secretion has been described.

The Correlation between FSTL1 Expression and Airway Remodeling in Asthmatics

Background

Asthma is characterized by airway remodeling. Follistatin-like protein 1 (FSTL1) is an extracellular glycoprotein. Recent studies suggest that FSTL1 may participate in the pathogenesis of asthma.

Objectives

To analyze the association between FSTL1 and some parameters and inspect the role of FSTL1 in asthma.

Methods

We examined FSTL1 levels in 32 asthmatics and 25 controls. All subjects enrolled had routine blood tests, spirometry, and impulse oscillometry performed. Additionally, 15 of the 32 asthmatics underwent fibre optic bronchoscopy. Spearman rank analysis was performed to detect the correlation between FSTL1 and other parameters.

Results

Plasma FSTL1 levels were higher in asthmatics (130.762 ± 46.029 ng/mL) than in controls (95.408 ± 33.938 ng/mL) (p = 0.009). Plasma FSTL1 levels were associated with fibrosis levels around the airways (rs = 0.529, p = 0.043) and α-smooth muscle actin (α-SMA) (rs = 0.554, p = 0.032). FSTL1 levels in bronchoalveolar lavage fluid were associated with collagen I (rs = 0.536, p = 0.040), α-SMA (rs = 0.561, p = 0.029), fibrosis levels (rs = 0.779, p = 0.001), and the thickness of the airway reticular basement membrane (RBM) (rs = 0.660, p = 0.007).

Conclusions

FSTL1 levels in asthmatics were linked with increased smooth muscle mass and thickened RBM. FSTL1 may contribute to airway remodeling in asthmatics.

Deletion of Fstl1 (Follistatin-Like 1) From the Endocardial/Endothelial Lineage Causes Mitral Valve Disease

OBJECTIVE

Fstl1 (Follistatin-like 1) is a secreted protein that is expressed in the atrioventricular valves throughout embryonic development, postnatal maturation, and adulthood. In this study, we investigated the loss of Fstl1 in the endocardium/endothelium and their derived cells.

APPROACH AND RESULTS

We conditionally ablated Fstl1 from the endocardial lineage using a transgenic Tie2-Cre mouse model. These mice showed a sustained Bmp and Tgfβ signaling after birth. This resulted in ongoing proliferation and endocardial-to-mesenchymal transition and ultimately in deformed nonfunctional mitral valves and a hypertrophic dilated heart. Echocardiographic and electrocardiographic analyses revealed that loss of Fstl1 leads to mitral regurgitation and left ventricular diastolic dysfunction. Cardiac function gradually deteriorated resulting in heart failure with preserved ejection fraction and death of the mice between 2 and 4 weeks after birth.

CONCLUSIONS

We report on a mouse model in which deletion of Fstl1 from the endocardial/endothelial lineage results in deformed mitral valves, which cause regurgitation, heart failure, and early cardiac death. The findings provide a potential molecular target for the clinical research into myxomatous mitral valve disease.

Presynaptic inhibition of nociceptive neurotransmission by somatosensory neuron-secreted suppressors

Noxious stimuli cause pain by activating cutaneous nociceptors. The Aδ- and C-fibers of dorsal root ganglion (DRG) neurons convey the nociceptive signals to the laminae I-II of spinal cord. In the dorsal horn of spinal cord, the excitatory afferent synaptic transmission is regulated by the inhibitory neurotransmitter γ-aminobutyric acid and modulators such as opioid peptides released from the spinal interneurons, and by serotonin, norepinepherine and dopamine from the descending inhibitory system. In contrast to the accumulated evidence for these central inhibitors and their neural circuits in the dorsal spinal cord, the knowledge about the endogenous suppressive mechanisms in nociceptive DRG neurons remains very limited. In this review, we summarize our recent findings of the presynaptic suppressive mechanisms in nociceptive neurons, the BNP/NPR-A/PKG/BKCa channel pathway, the FSTL1/α1Na⁺-K⁺ ATPase pathway and the activin C/ERK pathway. These endogenous suppressive systems in the mechanoheat nociceptors may also contribute differentially to the mechanisms of nerve injury-induced neuropathic pain or inflammation-induced pain.

Autophagy plays a role in FSTL1-induced epithelial mesenchymal transition and airway remodeling in asthma

Asthma is a chronic disease related to airway hyperresponsiveness and airway remodeling. Airway remodeling is the important reason of refractory asthma and is associated with differentiation of airway epithelia into myofibroblasts via epithelial-mesenchymal transition (EMT) to increase the process of subepithelial fibrosis. There is growing evidence that autophagy modulates remodeling. However, the underlying molecular mechanisms of these effects are still unclear. In this study, we hypothesized that Follistatin-like 1 (FSTL1) promotes EMT and airway remodeling by intensifying autophagy. With the use of transmission electron microscopy (TEM), double-membrane autophagosomes were detected in the airways of patients and mice. More autophagosomes were in patients with asthma and OVA-challenged mice compared with healthy controls. The expression of FSTL1 and beclin-1 was upregulated in the airways of patients with asthma and OVA-challenged mice, accompanied by airway EMT and remodeling. In OVA-challenged Fstl1^+/- mice, the degree of airway remodeling and autophagy was decreased compared with control mice. The effects of FSTL1 on autophagy and EMT were also tested in 16HBE cells in vitro. Additionally, inhibition of autophagy by using LY-294002 and siRNA-ATG5 reduced the FSTL1-induced EMT in 16HBE cells, as measured by E-cadherin, N-cadherin, and vimentin expression. In line herewith, administration of LY-294002 reduced the expression of autophagy, EMT, and airway remodeling markers in FSTL1-challenged WT mice. Taken together, our study suggests that FSTL1 may induce EMT and airway remodeling by activating autophagy. These findings may provide novel avenues for therapeutic research targeting the autophagy and FSTL1 pathway, which may be beneficial to patients with refractory asthma.

Up-Regulation of Follistatin-Like 1 By the Androgen Receptor and Melanoma Antigen-A11 in Prostate Cancer

BACKGROUND

High affinity androgen binding to the androgen receptor (AR) activates genes required for male sex differentiation and promotes the development and progression of prostate cancer. Human AR transcriptional activity involves interactions with coregulatory proteins that include primate-specific melanoma antigen-A11 (MAGE-A11), a coactivator that increases AR transcriptional activity during prostate cancer progression to castration-resistant/recurrent prostate cancer (CRPC).

METHODS

Microarray analysis and quantitative RT-PCR were performed to identify androgen-regulated MAGE-A11-dependent genes in LAPC-4 prostate cancer cells after lentivirus shRNA knockdown of MAGE-A11. Chromatin immunoprecipitation was used to assess androgen-dependent AR recruitment, and immunocytochemistry to localize an androgen-dependent protein in prostate cancer cells and tissue and in the CWR22 human prostate cancer xenograft.

RESULTS

Microarray analysis of androgen-treated LAPC-4 prostate cancer cells indicated follistatin-like 1 (FSTL1) is up-regulated by MAGE-A11. Androgen-dependent up-regulation of FSTL1 was inhibited in LAPC-4 cells by lentivirus shRNA knockdown of AR or MAGE-A11. Chromatin immunoprecipitation demonstrated AR recruitment to intron 10 of the FSTL1 gene that contains a classical consensus androgen response element. Increased levels of FSTL1 protein in LAPC-4 cells correlated with higher levels of MAGE-A11 relative to other prostate cancer cells. FSTL1 mRNA levels increased in CRPC and castration-recurrent CWR22 xenografts in association with predominantly nuclear FSTL1. Increased nuclear localization of FSTL1 in prostate cancer was suggested by predominantly cytoplasmic FSTL1 in benign prostate epithelial cells and predominantly nuclear FSTL1 in epithelial cells in CRPC tissue and the castration-recurrent CWR22 xenograft. AR expression studies showed nuclear colocalization of AR and endogenous FSTL1 in response to androgen.

CONCLUSION

AR and MAGE-A11 cooperate in the up-regulation of FSTL1 to promote growth and progression of CRPC. Prostate 77:505-516, 2017. © 2016 Wiley Periodicals, Inc.

High frequency stimulation induces sonic hedgehog release from hippocampal neurons

Sonic hedgehog (SHH) as a secreted protein is important for neuronal development in the central nervous system (CNS). However, the mechanism about SHH release remains largely unknown. Here, we showed that SHH was expressed mainly in the synaptic vesicles of hippocampus in both young postnatal and adult rats. High, but not low, frequency stimulation, induces SHH release from the neurons. Moreover, removal of extracellular Ca²⁺, application of tetrodotoxin (TTX), an inhibitor of voltage-dependent sodium channels, or downregulation of soluble n-ethylmaleimide-sensitive fusion protein attachment protein receptors (SNAREs) proteins, all blocked SHH release from the neurons in response to HFS. Our findings suggest a novel mechanism to control SHH release from the hippocampal neurons.

Application of viral vectors to the study of neural connectivities and neural circuits in the marmoset brain

It is important to study the neural connectivities and functions in primates. For this purpose, it is critical to be able to transfer genes to certain neurons in the primate brain so that we can image the neuronal signals and analyze the function of the transferred gene. Toward this end, our team has been developing gene transfer systems using viral vectors. In this review, we summarize our current achievements as follows. 1) We compared the features of gene transfer using five different AAV serotypes in combination with three different promoters, namely, CMV, mouse CaMKII (CaMKII), and human synapsin 1 (hSyn1), in the marmoset cortex with those in the mouse and macaque cortices. 2) We used target‐specific double‐infection techniques in combination with TET‐ON and TET‐OFF using lentiviral retrograde vectors for enhanced visualization of neural connections. 3) We used an AAV‐mediated gene transfer method to study the transcriptional control for amplifying fluorescent signals using the TET/TRE system in the primate neocortex. We also established systems for shRNA mediated gene targeting in a neocortical region where a gene is significantly expressed and for expressing the gene using the CMV promoter for an unexpressed neocortical area in the primate cortex using AAV vectors to understand the regulation of downstream genes. Our findings have demonstrated the feasibility of using viral vector mediated gene transfer systems for the study of primate cortical circuits using the marmoset as an animal model. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 354–372, 2017

Follistatin-like 1 promotes osteoclast formation via RANKL-mediated NF-κB activation and M-CSF-induced precursor proliferation

Follistatin-like 1 (FSTL1) functions as a pivotal modulator of inflammation and is implicated in many inflammatory diseases such as rheumatoid arthritis. Here, we report that FSTL1 is strongly upregulated and secreted during osteoclast differentiation of bone marrow-derived macrophages (BMMs) and that FSTL1 positively regulates osteoclast formation induced by RANKL and M-CSF. The overexpression of FSTL1 or treatment with recombinant FSTL1 (rFSTL1) in BMMs enhances the formation of multinuclear osteoclasts and the induction of c-Fos and NFATc1, transcription factors important for osteoclastogenesis. Conversely, knockdown of FSTL1 using a small hairpin RNA suppresses osteoclast formation and the expression of these transcription factors. While FSTL1 does not affect RANKL-stimulated activation of p38 MAPK, phosphorylation of IκBα, JNK, and ERK were increased by overexpression or addition of rFSTL1. Furthermore, rFSTL1 increased RANKL-induced NF-κB transcriptional activity in a dose-dependent manner. In addition to its role in osteoclastogenesis, FSTL1 promotes proliferation of osteoclast precursors by increasing M-CSF-induced ERK activation, which in turn leads to accelerated osteoclast formation. Together, our findings demonstrate that FSTL1 is a secreted osteoclastogenic factor that plays a critical role in osteoclast formation via the NF-κB and MAPKs signaling pathways.

The neuronal porosome complex in health and disease

Cup-shaped secretory portals at the cell plasma membrane called porosomes mediate the precision release of intravesicular material from cells. Membrane-bound secretory vesicles transiently dock and fuse at the base of porosomes facing the cytosol to expel pressurized intravesicular contents from the cell during secretion. The structure, isolation, composition, and functional reconstitution of the neuronal porosome complex have greatly progressed, providing a molecular understanding of its function in health and disease. Neuronal porosomes are 15 nm cup-shaped lipoprotein structures composed of nearly 40 proteins, compared to the 120 nm nuclear pore complex composed of >500 protein molecules. Membrane proteins compose the porosome complex, making it practically impossible to solve its atomic structure. However, atomic force microscopy and small-angle X-ray solution scattering studies have provided three-dimensional structural details of the native neuronal porosome at sub-nanometer resolution, providing insights into the molecular mechanism of its function. The participation of several porosome proteins previously implicated in neurotransmission and neurological disorders, further attest to the crosstalk between porosome proteins and their coordinated involvement in release of neurotransmitter at the synapse.

Somatosensory neuron types identified by high-coverage single-cell RNA-sequencing and functional heterogeneity

Sensory neurons are distinguished by distinct signaling networks and receptive characteristics. Thus, sensory neuron types can be defined by linking transcriptome-based neuron typing with the sensory phenotypes. Here we classify somatosensory neurons of the mouse dorsal root ganglion (DRG) by high-coverage single-cell RNA-sequencing (10 950 ± 1 218 genes per neuron) and neuron size-based hierarchical clustering. Moreover, single DRG neurons responding to cutaneous stimuli are recorded using an in vivo whole-cell patch clamp technique and classified by neuron-type genetic markers. Small diameter DRG neurons are classified into one type of low-threshold mechanoreceptor and five types of mechanoheat nociceptors (MHNs). Each of the MHN types is further categorized into two subtypes. Large DRG neurons are categorized into four types, including neurexophilin 1-expressing MHNs and mechanical nociceptors (MNs) expressing BAI1-associated protein 2-like 1 (Baiap2l1). Mechanoreceptors expressing trafficking protein particle complex 3-like and Baiap2l1-marked MNs are subdivided into two subtypes each. These results provide a new system for cataloging somatosensory neurons and their transcriptome databases.

Fstl1 is involved in the regulation of radial glial scaffold development

Background

Radial glial cells (RGCs), the instructive scaffolds for neuronal migration, are well characterized by their unique morphology and polarization; these cells extend elongated basal processes to the pial basement membrane (BM) and parallel to one another. However, little is known about the mechanisms that underlie the developmental regulation and maintenance of this unique morphology.

Results

Here, by crossing Fstl1^fl/fl mice with an EIIa-Cre line, we identified a new role for the secreted glycoprotein Follistatin like-1 (FSTL1). The ablation of Fstl1 in both of its cortical expression domains, the ventricular zone (VZ) and the pia mater, resulted in RGC morphologic disruption; basal processes were not parallel to each other, and endfeet exhibited greater density and branching. However, Fstl1 deletion in only the VZ in the Emx1^IREScre; Fstl1^fl/fl line did not affect RGC morphology, indicating that FSTL1 derived from the pia mater might be more important for RGC morphology. In addition, upper-layer projection neurons, not deeper-layer projection neurons, failed to reach their appropriate positions. We also found that BMP, AKT/PKB, Cdc42, GSK3β, integrin and reelin signals, which have previously been reported to regulate RGC development, were unchanged, indicating that Fstl1 may function through a unique mechanism.

Conclusions

In the present study, we identified a new role for FSTL1 in the development of radial glial scaffolds and the neuronal migration of upper-layer projection neurons. Our findings will improve understanding of the regulation of RGC development and neuronal migration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13041-015-0144-8) contains supplementary material, which is available to authorized users.

Fstl1 Promotes Asthmatic Airway Remodeling by Inducing Oncostatin M

Chronic asthma is associated with airway remodeling and decline in lung function. In this article, we show that follistatin-like 1 (Fstl1), a mediator not previously associated with asthma, is highly expressed by macrophages in the lungs of humans with severe asthma. Chronic allergen-challenged Lys-Cre(tg) /Fstl1(Δ/Δ) mice in whom Fstl1 is inactivated in macrophages/myeloid cells had significantly reduced airway remodeling and reduced levels of oncostatin M (OSM), a cytokine previously not known to be regulated by Fstl1. The importance of the Fstl1 induction of OSM to airway remodeling was demonstrated in murine studies in which administration of Fstl1 induced airway remodeling and increased OSM, whereas administration of an anti-OSM Ab blocked the effect of Fstl1 on inducing airway remodeling, eosinophilic airway inflammation, and airway hyperresponsiveness, all cardinal features of asthma. Overall, these studies demonstrate that the Fstl1/OSM pathway may be a novel pathway to inhibit airway remodeling in severe human asthma.

Peripheral gene expression profile of mechanical hyperalgesia induced by repeated cold stress in SHRSP5/Dmcr rats

Repeated cold stress (RCS) is known to transiently induce functional disorders associated with hypotension and hyperalgesia. In this study, we investigated the effects of RCS (24 and 4 °C alternately at 30-min intervals during the day and 4 °C at night for 2 days, followed by 4 °C on the next 2 consecutive nights) on the thresholds for cutaneous mechanical pain responses and on peripheral expression of "pain-related genes" in SHRSP5/Dmcr rats, which are derived from stroke-prone spontaneously hypertensive rats. To define genes peripherally regulated by RCS, we detected changes in the expression of pain-related genes in dorsal root ganglion cells by PCR-based cDNA subtraction analysis or DNA microarray analysis, and confirmed the changes by RT-PCR. We found significantly changed expression in eight pain-related genes (upregulated: Fyn, St8sia1, and Tac 1; downregulated: Ctsb, Fstl1, Itpr1, Npy, S100a10). At least some of these genes may play key roles in hyperalgesia induced by RCS.

Simulation of alcohol action upon a detailed Purkinje neuron model and a simpler surrogate model that runs >400 times faster

BACKGROUND

An approach to investigate brain function/dysfunction is to simulate neuron circuits on a computer. A problem, however, is that detailed neuron descriptions are computationally expensive and this handicaps the pursuit of realistic network investigations, where many neurons need to be simulated.

RESULTS

We confront this issue; we employ a novel reduction algorithm to produce a 2 compartment model of the cerebellar Purkinje neuron from a previously published, 1089 compartment model. It runs more than 400 times faster and retains the electrical behavior of the full model. So, it is more suitable for inclusion in large network models, where computational power is a limiting issue. We show the utility of this reduced model by demonstrating that it can replicate the full model's response to alcohol, which can in turn reproduce experimental recordings from Purkinje neurons following alcohol application.

CONCLUSIONS

We show that alcohol may modulate Purkinje neuron firing by an inhibition of their sodium-potassium pumps. We suggest that this action, upon cerebellar Purkinje neurons, is how alcohol ingestion can corrupt motor co-ordination. In this way, we relate events on the molecular scale to the level of behavior.

Follistatin-like protein 1 and its role in inflammation and inflammatory diseases

Follistatin-like protein 1 (FSTL1) is a secreted glycoprotein produced mainly by cells of mesenchymal origin. FSTL1 has been shown to play an important role during embryogenesis; FSTL1-deficient mice die at birth from multiple developmental abnormalities. In the last decade, FSTL1 has been identified as a novel inflammatory protein, enhancing synthesis of proinflammatory cytokines and chemokines by immune cells in vitro and in vivo. FSTL1 mediates proinflammatory events in animal models of inflammatory diseases, particularly in collagen-induced arthritis in mice. FSTL1 is elevated in various inflammatory conditions and decreased during the course of treatment. FSTL1 may therefore be a valuable biomarker for such diseases. Moreover, a variety of experiments suggest that targeting of FSTL1 may be useful in the treatment of diseases in which inflammation plays a central role.

Fibroblast growth factor 7 is a nociceptive modulator secreted via large dense-core vesicles

Fibroblast growth factor (FGF) 7, a member of FGF family, is initially found to be secreted from mesenchymal cells to repair epithelial tissues. However, its functions in the nervous system are largely unknown. The present study showed that FGF7 was a neuromodulator localized in the large dense-core vesicles (LDCVs) in nociceptive neurons. FGF7 was mainly expressed in small-diameter neurons of the dorsal root ganglion and could be transported to the dorsal spinal cord. Interestingly, FGF7 was mostly stored in LDCVs that did not contain neuropeptide substance P. Electrophysiological recordings in the spinal cord slice showed that buffer-applied FGF7 increased the amplitude of excitatory post-synaptic current evoked by stimulating the sensory afferent fibers. Behavior tests showed that intrathecally applied FGF7 potentiated the formalin-induced acute nociceptive response. Moreover, both acute and inflammatory nociceptive responses were significantly reduced in Fgf7-deficient mice. These results suggest that FGF7 exerts an excitatory modulation of nociceptive afferent transmission.

FXYD2, a γ subunit of Na⁺, K⁺-ATPase, maintains persistent mechanical allodynia induced by inflammation

Na⁺, K⁺-ATPase (NKA) is required to generate the resting membrane potential in neurons. Nociceptive afferent neurons express not only the α and β subunits of NKA but also the γ subunit FXYD2. However, the neural function of FXYD2 is unknown. The present study shows that FXYD2 in nociceptive neurons is necessary for maintaining the mechanical allodynia induced by peripheral inflammation. FXYD2 interacted with α1NKA and negatively regulated the NKA activity, depolarizing the membrane potential of nociceptive neurons. Mechanical allodynia initiated in FXYD2-deficient mice was abolished 4 days after inflammation, whereas it persisted for at least 3 weeks in wild-type mice. Importantly, the FXYD2/α1NKA interaction gradually increased after inflammation and peaked on day 4 post inflammation, resulting in reduction of NKA activity, depolarization of neuron membrane and facilitation of excitatory afferent neurotransmission. Thus, the increased FXYD2 activity may be a fundamental mechanism underlying the persistent hypersensitivity to pain induced by inflammation.

Effect of infrared-C radiation on skin temperature, electrodermal conductance and pain in hemiparetic stroke patients

PURPOSE

A novel application of infrared-C (IR-C) radiation (3-1000 μm) on hemiparetic stroke patients was evaluated. Hot compresses (HC) were used on the paretic shoulders of patients in this placebo-controlled trial to investigate the effects of IR-C on skin temperature, electrodermal conductance (EC) and pain relief.

MATERIALS AND METHODS

Skin temperature at the center of the middle deltoid (CMD), Quchi (LI11), and the center of the third metacarpal bone on dorsum of hand (COT) of the subjects at Brunnstrom stage 3-5 before and after IR-C HC, were examined. Meanwhile, EC was measured on Hegu (LI4), Quchi and Juanyu (LI15). Pain intensity was evaluated before and after treatment.

RESULTS

Skin temperature increased significantly at the CMD and COT on the paretic side in males. In females after treatment, similar skin temperatures were found in each measured region on both the paretic and non-paretic sides. The EC on the paretic side tended to be higher than the non-paretic side before treatment. After treatment, the EC on paretic side declined in both sexes and became even lower than the non-paretic side in females. Pain intensity was lessened after treatment especially in males, which appeared to correspond with an increase in skin temperature and a decrease in EC.

CONCLUSION

IR-C hot compress is a promising method for stroke patients in rehabilitation. Physiological mechanisms of this treatment were proposed and summarized from this research.

Opioid receptor trafficking and interaction in nociceptors

Opiate analgesics such as morphine are often used for pain therapy. However, antinociceptive tolerance and dependence may develop with long-term use of these drugs. It was found that μ-opioid receptors can interact with δ-opioid receptors, and morphine antinociceptive tolerance can be reduced by blocking δ-opioid receptors. Recent studies have shown that μ- and δ-opioid receptors are co-expressed in a considerable number of small neurons in the dorsal root ganglion. The interaction of μ-opioid receptors with δ-opioid receptors in the nociceptive afferents is facilitated by the stimulus-induced cell-surface expression of δ-opioid receptors, and contributes to morphine tolerance. Further analysis of the molecular, cellular and neural circuit mechanisms that regulate the trafficking and interaction of opioid receptors and related signalling molecules in the pain pathway would help to elucidate the mechanism of opiate analgesia and improve pain therapy.

LINKED ARTICLES

This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.