Nuclear factor-kappaB is a critical mediator of Ste20-like proline-/alanine-rich kinase regulation in intestinal inflammation

Target inhibition of SPAK in choroid plexus attenuates T cell infiltration and demyelination in experimental autoimmune encephalomyelitis

BACKGROUND

Disease-modifying therapies (DMTs) that prevent immune cell infiltration into the brain have demonstrated efficacy in multiple sclerosis (MS) treatment. However, their unpredictable adverse effects necessitate the development of safer therapeutic alternatives. The choroid plexus (ChP) functions as a crucial barrier against immune cell invasion, and previous studies have shown that preventing immune cell infiltration across the ChP reduces brain lesion in MS animal models. Understanding ChP barrier regulation is therefore essential for identifying novel therapeutic targets for MS. Here, we explored the role of Ste20-related proline/alanine-rich kinase (SPAK) in experimental autoimmune encephalomyelitis (EAE).

METHODS

We examined the expression patterns of SPAK signaling in ChP using immunofluorescence in the EAE model. To investigate the roles of SPAK, matrix metalloproteinase (MMP) 2 and MMP9 in EAE pathology, we performed ChP-specific gene manipulation via intracerebroventricular (ICV) injection of recombinant adeno-associated virus 2/5 (rAAV2/5). T cell infiltration into the central nervous system (CNS) was analyzed using CD4 immunostaining and flow cytometry. We employed cell immunofluorescence, transwell assays, and rescue experiments in vitro to study SPAK's effects on ChP epithelial barrier integrity. We also evaluated the protective effects of SPAK-Na-K-2Cl cotransporter-1 (NKCC1) inhibitors (ZT-1a and bumetanide) on immune invasion and demyelination during EAE using pharmacological approaches.

RESULTS

Following EAE induction, we observed progressive increases in both total and phosphorylated SPAK levels in ChP epithelium. Notably, ChP-specific SPAK knockdown significantly reduced T cell invasion and ameliorated EAE pathology, while SPAK overexpression exacerbated these effects. Bulk RNA sequencing and subsequent qPCR validation revealed that SPAK knockdown decreased the expression of MMP2 and MMP9, MMPs that compromise barrier integrity by degrading tight junction proteins. In vitro studies demonstrated that SPAK overexpression impaired ChP barrier function through the activator protein-1 (AP-1)-MMP2/9-zonula occludens-1 (ZO-1) axis. Furthermore, ChP-specific knockdown of either MMP2 or MMP9 protected against EAE pathology. Additionally, we identified SPAK-NKCC1 antagonists (bumetanide and ZT-1a) as promising therapeutic candidates for MS/EAE treatment.

CONCLUSIONS

Our findings demonstrate that targeting ChP-SPAK signaling represents a novel therapeutic strategy for MS treatment.

PTEN mutations impair CSF dynamics and cortical networks by dysregulating periventricular neural progenitors

Enlargement of the cerebrospinal fluid (CSF)-filled brain ventricles (ventriculomegaly) is a defining feature of congenital hydrocephalus (CH) and an under-recognized concomitant of autism. Here, we show that de novo mutations in the autism risk gene PTEN are among the most frequent monogenic causes of CH and primary ventriculomegaly. Mouse Pten-mutant ventriculomegaly results from aqueductal stenosis due to hyperproliferation of periventricular Nkx2.1+ neural progenitor cells (NPCs) and increased CSF production from hyperplastic choroid plexus. Pten-mutant ventriculomegalic cortices exhibit network dysfunction from increased activity of Nkx2.1+ NPC-derived inhibitory interneurons. Raptor deletion or postnatal everolimus treatment corrects ventriculomegaly, rescues cortical deficits and increases survival by antagonizing mTORC1-dependent Nkx2.1+ NPC pathology. Thus, PTEN mutations concurrently alter CSF dynamics and cortical networks by dysregulating Nkx2.1+ NPCs. These results implicate a nonsurgical treatment for CH, demonstrate a genetic association of ventriculomegaly and ASD, and help explain neurodevelopmental phenotypes refractory to CSF shunting in select individuals with CH.

Evaluation of the Choroid Plexus Epithelium Inflammation TLR4/NF-κB/NKCC1 Signal Pathway Activation in the Development of Hydrocephalus

BACKGROUND

Hydrocephalus is characterized by secretion, circulation, and absorption disorder of cerebrospinal fluid (CSF) with high morbidity and complication rate. The relationship between inflammation and abnormal secretion of CSF by choroid plexus epithelium (CPE) had received more attention. In this study, we aim to detect the role of Toll-like receptor 4/nuclear factor-kappa B/Na+/K+/2Cl-cotransporter 1(TLR4/NF-κB/NKCC1) signal pathway in the development of hydrocephalus.

METHOD

Hydrocephalus was induced in adult rats (8 weeks) by intracisternal kaolin injection, then pyrrolidinedithiocarbamate (PDTC) and bumetanide were administrated to the rats mode. Then the rat model was evaluated, and ventricular volume was calculated at different time points. Then CPE, cortex, preventricular tissue, and CSF were obtained. Protein expressions of TLR-4, NKCC/serine-threonine STE20/SPS1-related, proline-alanine-rich kinase (SPAK), pNKCC1, pSPAK, GFAP, AQP1, and AQP4 were measured by RT-PCR, western blot, and immunofluorescence (IF) stains in CPE, respectively.

RESULT

Our data showed that inflammation factors tumor necrosis factor-(TNF-α), interleukin 18(IL-18), and glial fibrillary acidic protein (GFAP) concentrations were significantly higher in the model group than in controls. The TLR4/NF-κB/NKCC1 signal pathway were actived by NF-κB-p65, NKCC1, pNKCC1- pSPAK complex, and Aquaporin1 (AQP1) high expression. PDTC and bumetanide use can help regular TLR4/NF-κB/NKCC1 expression and reduced AQP1 expression by down-regulate NF-B-p65 and inhibiting NKCC1, respectively. As a result, the treatment groups alleviated CPE abnormal secretion and ventricle enlargement.

CONCLUSION

These results confirmed that the inflammatory reaction contributes TLR4/NF-κB/NKCC1 mediated CPE abnormal secretion and consequent hydrocephalus. Regulation of TLR4/NF-κB/NKCC1 and AQP1 can prevent this process. Our study provides a strong rationale for further exploring alleviating CPE abnormal secretion as a therapeutic perspective of hydrocephalus.

SPAK inhibitor ZT-1a attenuates reactive astrogliosis and oligodendrocyte degeneration in a mouse model of vascular dementia

BACKGROUND

Astrogliosis and white matter lesions (WML) are key characteristics of vascular contributions to cognitive impairment and dementia (VCID). However, the molecular mechanisms underlying VCID remain poorly understood. Stimulation of Na-K-Cl cotransport 1 (NKCC1) and its upstream kinases WNK (with no lysine) and SPAK (the STE20/SPS1-related proline/alanine-rich kinase) play a role in astrocytic intracellular Na+ overload, hypertrophy, and swelling. Therefore, in this study, we assessed the effect of SPAK inhibitor ZT-1a on pathogenesis and cognitive function in a mouse model of VCID induced by bilateral carotid artery stenosis (BCAS).

METHODS

Following sham or BCAS surgery, mice were randomly assigned to receive either vehicle (DMSO) or SPAK inhibitor ZT-1a treatment regimen (days 14-35 post-surgery). Mice were then evaluated for cognitive functions by Morris water maze, WML by ex vivo MRI-DTI analysis, and astrogliosis/demyelination by immunofluorescence and immunoblotting.

RESULTS

Compared to sham control mice, BCAS-Veh mice exhibited chronic cerebral hypoperfusion and memory impairments, accompanied by significant MRI DTI-detected WML and oligodendrocyte (OL) death. Increased activation of WNK-SPAK-NKCC1-signaling proteins was detected in white matter tissues and in C3d+ GFAP+ cytotoxic astrocytes but not in S100A10+ GFAP+ homeostatic astrocytes in BCAS-Veh mice. In contrast, ZT-1a-treated BCAS mice displayed reduced expression and phosphorylation of NKCC1, decreased astrogliosis, OL death, and WML, along with improved memory functions.

CONCLUSION

BCAS-induced upregulation of WNK-SPAK-NKCC1 signaling contributes to white matter-reactive astrogliosis, OL death, and memory impairment. Pharmacological inhibition of the SPAK activity has therapeutic potential for alleviating pathogenesis and memory impairment in VCID.

The choroid plexus links innate immunity to CSF dysregulation in hydrocephalus

The choroid plexus (ChP) is the blood-cerebrospinal fluid (CSF) barrier and the primary source of CSF. Acquired hydrocephalus, caused by brain infection or hemorrhage, lacks drug treatments due to obscure pathobiology. Our integrated, multi-omic investigation of post-infectious hydrocephalus (PIH) and post-hemorrhagic hydrocephalus (PHH) models revealed that lipopolysaccharide and blood breakdown products trigger highly similar TLR4-dependent immune responses at the ChP-CSF interface. The resulting CSF "cytokine storm", elicited from peripherally derived and border-associated ChP macrophages, causes increased CSF production from ChP epithelial cells via phospho-activation of the TNF-receptor-associated kinase SPAK, which serves as a regulatory scaffold of a multi-ion transporter protein complex. Genetic or pharmacological immunomodulation prevents PIH and PHH by antagonizing SPAK-dependent CSF hypersecretion. These results reveal the ChP as a dynamic, cellularly heterogeneous tissue with highly regulated immune-secretory capacity, expand our understanding of ChP immune-epithelial cell cross talk, and reframe PIH and PHH as related neuroimmune disorders vulnerable to small molecule pharmacotherapy.

WNK1 in Malignant Behaviors: A Potential Target for Cancer?

Metastasis is the major cause of mortality in cancer patients. Analyses of mouse models and patient data have implicated the protein kinase WNK1 as one of a handful of genes uniquely linked to a subset of invasive cancers. WNK1 signaling pathways are widely implicated in the regulation of ion co-transporters and in controlling cell responses to osmotic stress. In this review we will discuss its actions in tumor malignancy in human cancers and present evidence for its function in invasion, migration, angiogenesis and mesenchymal transition.

CpG Single-Site Methylation Regulates TLR2 Expression in Proinflammatory PBMCs From Apical Periodontitis Individuals

Introduction

Apical periodontitis (AP) is a common oral disease caused by the inflammatory destruction of the periapical tissues due to the infection of the root canal system of the tooth. It also contributes to systemic bacterial translocation, where peripheric mononuclear blood cells (PBMCs) can act as carriers. Toll-like receptor (TLR) 2 mediates the response to infection and activates inflammatory responses. DNA methylation can be induced by bacteria and contributes to the modulation of this response. Despite the evidence that supports the participation of PBMCs in immune-inflammatory disorders, the inflammatory profile and epigenetic regulatory mechanisms of PBMCs in AP individuals are unknown.

Aim

To determine TLR2 gene methylation and inflammatory profiles of PBMCs in AP.

Methods

Cross-sectional exploratory study. Otherwise, healthy individuals with AP (n=27) and controls (n=30) were included. PMBCs were isolated by a Ficoll gradient, cultured for 24 hours, and both RNA and DNA were extracted. DNA was bisulfite-treated, and specific sites at the promoter region of the TLR2 gene were amplified by qPCR using validated primers. To verify its amplification, agarose gels were performed. Then, the PCR product was sequenced. mRNA expression of TLR2 was determined by qPCR. The soluble levels of 105 inflammatory mediators were first explored with Proteome Profiler Human Cytokine Array Kit. Consequently, tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-10, IL-6Rα, IL-1β, and IL-12p70 levels were measured by Multiplex assay.

Results

PBMCs from individuals with AP demonstrated a proinflammatory profile showing higher soluble levels of TNF-α, IL-6, and IL-1β compared to controls (p<0.05). Higher TLR2 expression and higher global methylation pattern of the promoter region of the gene were found in AP compared to controls (p<0.05). The CpGs single-sites at positions -166 and -146 were completely methylated, while the site -102 was totally unmethylated, independently of the presence of AP. DNA methylation of CpG single-sites in positions -77 and +24 was positively associated with TLR2 expression.

Conclusions

PBMCs from AP subjects show a hyperinflammatory phenotype and TLR2 upregulation in association with single CpG-sites’ methylation from the TLR2 gene promoter, thereby contributing to a sustained systemic inflammatory load in individuals with periapical endodontic diseases.

NF-κB Signaling-Mediated Activation of WNK-SPAK-NKCC1 Cascade in Worsened Stroke Outcomes of Ang II-Hypertensive Mice

BACKGROUND

Worsened stroke outcomes with hypertension comorbidity are insensitive to blood pressure-lowering therapies. In an experimental stroke model with comorbid hypertension, we investigated causal roles of ang II (angiotensin II)-mediated stimulation of the brain WNK (with no lysine [K] kinases)-SPAK (STE20/SPS1-related proline/alanine-rich kinase)-NKCC1 (Na-K-Cl cotransporter) complex in worsened outcomes.

METHODS

Saline- or ang II-infused C57BL/6J male mice underwent stroke induced by permanent occlusion of the distal branches of the middle cerebral artery. Mice were randomly assigned to receive either vehicle dimethyl sulfoxide/PBS (2 mL/kg body weight/day, IP), a novel SPAK inhibitor, 5-chloro-N-(5-chloro-4-((4-chlorophenyl)(cyano)methyl)-2-methylphenyl)-2-hydroxybenzamide (ZT-1a' 5 mg/kg per day, IP) or a NF-κB (nuclear factor-κB) inhibitor TAT-NBD (transactivator of transcription-NEMO-binding domain' 20 mg/kg per day, IP). Activation of brain NF-κB and WNK-SPAK-NKCC1 cascade as well as ischemic stroke outcomes were examined.

RESULTS

Stroke triggered a 2- to 5-fold increase of WNK (isoforms 1, 2, 4), SPAK/OSR1 (oxidative stress-responsive kinase 1), and NKCC1 protein in the ang II-infused hypertensive mouse brains at 24 hours after stroke, which was associated with increased nuclear translocation of phospho-NF-κB protein in the cortical neurons (a Pearson correlation r of 0.77, P<0.005). The upregulation of WNK-SPAK-NKCC1 cascade proteins resulted from increased NF-κB recruitment on Wnk1, Wnk2, Wnk4, Spak, and Nkcc1 gene promoters and was attenuated by NF-κB inhibitor TAT-NBD. Poststroke administration of SPAK inhibitor ZT-1a significantly reduced WNK-SPAK-NKCC1 complex activation, brain lesion size, and neurological function deficits in the ang II-hypertensive mice without affecting blood pressure and cerebral blood flow.

CONCLUSIONS

The ang II-induced stimulation of NF-κB transcriptional activity upregulates brain WNK-SPAK-NKCC1 cascade and contributes to worsened ischemic stroke outcomes, illustrating the brain WNK-SPAK-NKCC1 complex as a therapeutic target for stroke with comorbid hypertension.

Role of SPAK-NKCC1 signaling cascade in the choroid plexus blood-CSF barrier damage after stroke

BACKGROUND

The mechanisms underlying dysfunction of choroid plexus (ChP) blood-cerebrospinal fluid (CSF) barrier and lymphocyte invasion in neuroinflammatory responses to stroke are not well understood. In this study, we investigated whether stroke damaged the blood-CSF barrier integrity due to dysregulation of major ChP ion transport system, Na+-K+-Cl- cotransporter 1 (NKCC1), and regulatory Ste20-related proline-alanine-rich kinase (SPAK).

METHODS

Sham or ischemic stroke was induced in C57Bl/6J mice. Changes on the SPAK-NKCC1 complex and tight junction proteins (TJs) in the ChP were quantified by immunofluorescence staining and immunoblotting. Immune cell infiltration in the ChP was assessed by flow cytometry and immunostaining. Cultured ChP epithelium cells (CPECs) and cortical neurons were used to evaluate H2O2-mediated oxidative stress in stimulating the SPAK-NKCC1 complex and cellular damage. In vivo or in vitro pharmacological blockade of the ChP SPAK-NKCC1 cascade with SPAK inhibitor ZT-1a or NKCC1 inhibitor bumetanide were examined.

RESULTS

Ischemic stroke stimulated activation of the CPECs apical membrane SPAK-NKCC1 complex, NF-κB, and MMP9, which was associated with loss of the blood-CSF barrier integrity and increased immune cell infiltration into the ChP. Oxidative stress directly activated the SPAK-NKCC1 pathway and resulted in apoptosis, neurodegeneration, and NKCC1-mediated ion influx. Pharmacological blockade of the SPAK-NKCC1 pathway protected the ChP barrier integrity, attenuated ChP immune cell infiltration or neuronal death.

CONCLUSION

Stroke-induced pathological stimulation of the SPAK-NKCC1 cascade caused CPECs damage and disruption of TJs at the blood-CSF barrier. The ChP SPAK-NKCC1 complex emerged as a therapeutic target for attenuating ChP dysfunction and lymphocyte invasion after stroke.

SPAK Deficiency Attenuates Chemotherapy-Induced Intestinal Mucositis

Introduction

Ste20-related protein proline/alanine-rich kinase (SPAK) affects cell proliferation, differentiation, and transformation, and sodium and chloride transport in the gut. However, its role in gut injury pathogenesis is unclear.

Objective

We determined the role of SPAK in chemotherapy-induced intestinal mucositis using in vivo and in vitro models.

Methods

Using SPAK-knockout (KO) mice, we evaluated the severity of intestinal mucositis induced by 5-fluorouracil (5-FU) by assessing body weight loss, histological changes in the intestinal mucosa, length of villi in the small intestine, pro-inflammatory cytokine levels, proliferative indices, and apoptotic indices. We also evaluated changes in gut permeability and tight junction-associated protein expression. Changes in cell permeability, proliferation, and apoptosis were assessed in SPAK siRNA-transfected 5FU-treated IEC-6 cells.

Results

5-FU-treated SPAK-KO mice exhibited milder intestinal mucositis, reduced pro-inflammatory cytokine expression, increased villus length, good maintenance of proliferative indices of villus cells, decreased apoptotic index of enterocytes, reduced gut permeability, and restoration of tight junction protein expression (vs. 5-FU-treated wild-type mice). Under in vitro conditions, siRNA-mediated SPAK-knockdown in IEC-6 cells decreased cell permeability and maintained homeostasis following 5-FU treatment.

Conclusion

SPAK deficiency attenuated chemotherapy-induced intestinal mucositis by modulating gut permeability and tight junction-associated protein expression and maintaining gut homeostasis in murine small intestinal tissues following gut injury. The expression of SPAK may influence the pathogenesis of chemotherapy-induced intestinal mucositis.

Macrophages on the margin: choroid plexus immune responses

The choroid plexus (ChP), an epithelial bilayer containing a network of mesenchymal, immune, and neuronal cells, forms the blood-cerebrospinal fluid (CSF) barrier (BCSFB). While best recognized for secreting CSF, the ChP is also a hotbed of immune cell activity and can provide circulating peripheral immune cells with passage into the central nervous system (CNS). Here, we review recent studies on ChP immune cells, with a focus on the ontogeny, development, and behaviors of ChP macrophages, the principal resident immune cells of the ChP. We highlight the implications of immune cells for ChP barrier function, CSF cytokines and volume regulation, and their contribution to neurodevelopmental disorders, with possible age-specific features to be elucidated in the future.

Inflammation in acquired hydrocephalus: pathogenic mechanisms and therapeutic targets

Hydrocephalus is the most common neurosurgical disorder worldwide and is characterized by enlargement of the cerebrospinal fluid (CSF)-filled brain ventricles resulting from failed CSF homeostasis. Since the 1840s, physicians have observed inflammation in the brain and the CSF spaces in both posthaemorrhagic hydrocephalus (PHH) and postinfectious hydrocephalus (PIH). Reparative inflammation is an important protective response that eliminates foreign organisms, damaged cells and physical irritants; however, inappropriately triggered or sustained inflammation can respectively initiate or propagate disease. Recent data have begun to uncover the molecular mechanisms by which inflammation - driven by Toll-like receptor 4-regulated cytokines, immune cells and signalling pathways - contributes to the pathogenesis of hydrocephalus. We propose that therapeutic approaches that target inflammatory mediators in both PHH and PIH could address the multiple drivers of disease, including choroid plexus CSF hypersecretion, ependymal denudation, and damage and scarring of intraventricular and parenchymal (glia-lymphatic) CSF pathways. Here, we review the evidence for a prominent role of inflammation in the pathogenic mechanism of PHH and PIH and highlight promising targets for therapeutic intervention. Focusing research efforts on inflammation could shift our view of hydrocephalus from that of a lifelong neurosurgical disorder to that of a preventable neuroinflammatory condition.

WNK pathways in cancer signaling networks

Background

The with no lysine [K] (WNK) pathway consists of the structurally unique WNK kinases, their downstream target kinases, oxidative stress responsive (OSR)1 and SPS/Ste20-related proline-alanine-rich kinase (SPAK), and a multitude of OSR1/SPAK substrates including cation chloride cotransporters.

Main body

While the best known functions of the WNK pathway is regulation of ion transport across cell membranes, WNK pathway components have been implicated in numerous human diseases. The goal of our review is to draw attention to how this pathway and its components exert influence on the progression of cancer, specifically by detailing WNK signaling intersections with major cell communication networks and processes.

Conclusion

Here we describe how WNKs and associated proteins interact with and influence PI3K-AKT, TGF-β, and NF-κB signaling, as well as its unanticipated role in the regulation of angiogenesis.

Paclitaxel Sensitivity of Ovarian Cancer Can be Enhanced by Knocking Down Pairs of Kinases that Regulate MAP4 Phosphorylation and Microtubule Stability

Purpose: Most patients with ovarian cancer receive paclitaxel chemotherapy, but less than half respond. Pre-treatment microtubule stability correlates with paclitaxel response in ovarian cancer cell lines. Microtubule stability can be increased by depletion of individual kinases. As microtubule stability can be regulated by phosphorylation of microtubule-associated proteins (MAPs), we reasoned that depletion of pairs of kinases that regulate phosphorylation of MAPs could induce microtubule stabilization and paclitaxel sensitization.Experimental Design: Fourteen kinases known to regulate paclitaxel sensitivity were depleted individually in 12 well-characterized ovarian cancer cell lines before measuring proliferation in the presence or absence of paclitaxel. Similar studies were performed by depleting all possible pairs of kinases in six ovarian cancer cell lines. Pairs that enhanced paclitaxel sensitivity across multiple cell lines were studied in depth in cell culture and in two xenograft models.Results: Transfection of siRNA against 10 of the 14 kinases enhanced paclitaxel sensitivity in at least six of 12 cell lines. Dual knockdown of IKBKB/STK39 or EDN2/TBK1 enhanced paclitaxel sensitivity more than silencing single kinases. Sequential knockdown was superior to concurrent knockdown. Dual silencing of IKBKB/STK39 or EDN2/TBK1 stabilized microtubules by inhibiting phosphorylation of p38 and MAP4, inducing apoptosis and blocking cell cycle more effectively than silencing individual kinases. Knockdown of IKBKB/STK39 or EDN2/TBK1 enhanced paclitaxel sensitivity in two ovarian xenograft models.Conclusions: Sequential knockdown of dual kinases increased microtubule stability by decreasing p38-mediated phosphorylation of MAP4 and enhanced response to paclitaxel in ovarian cancer cell lines and xenografts, suggesting a strategy to improve primary therapy. Clin Cancer Res; 24(20); 5072-84. ©2018 AACR.

Effects of SPAK on vascular reactivity and nitric oxide production in endotoxemic mice

Vasoplegia impedes therapeutic interventions to restore vascular tone, leading to severe hypotension, poor tissue perfusion, and multiple organ failure in septic shock. High levels of circulating nitric oxide (NO) play a crucial role in endotoxin-induced vascular hyporeactivity. Proinflammatory cytokines have been implicated in the induction of inducible NO synthase and overproduction of NO. Anti-inflammatory therapy can diminish NO formation and improve vascular hyporeactivity in septic shock. STE20/SPS1-realted proline/alanine-rich kinase (SPAK) has been reported to activate mitogen-activated protein kinase and contribute to intestinal inflammation. Thus, we evaluated the roles of SPAK in NO production and vascular hyporeactivity in endotoxemic animals. Male wild-type and SPAK deficiency mice were intraperitoneally administered vehicle or Escherichia coli lipopolysaccharide (LPS, 50mg/kg). The changes of systolic blood pressure and plasma nitrate and nitrite levels were measured during the experimental period. Thoracic aortas were exercised to assess vascular reactivity and SPAK expression. In the present study, mice in endotoxin model showed severe hypotension and hyporeactivity to serotonin, phenylephrine (PE), and acetylcholine in the aortic rings. Phosphorylated SPAK expression in the aorta and NO levels in the plasma were also increased in animals with endotoxic shock. However, deletion of SPAK not only reduced the elevation of NO levels but also improved vascular hyporeactivity to serotonin and PE in endotoxemic mice. Taken together, SPAK could be involved in the NO overproduction and vascular hyporesponsiveness to vasoconstrictors in endotoxic shock. Thus, inhibition of SPAK could be useful in the prevention of endotoxin-induced vascular hyporeactivity.

Inflammation-dependent cerebrospinal fluid hypersecretion by the choroid plexus epithelium in posthemorrhagic hydrocephalus

The choroid plexus epithelium (CPE) secretes higher volumes of fluid (cerebrospinal fluid, CSF) than any other epithelium and simultaneously functions as the blood-CSF barrier to gate immune cell entry into the central nervous system. Posthemorrhagic hydrocephalus (PHH), an expansion of the cerebral ventricles due to CSF accumulation following intraventricular hemorrhage (IVH), is a common disease usually treated by suboptimal CSF shunting techniques. PHH is classically attributed to primary impairments in CSF reabsorption, but little experimental evidence supports this concept. In contrast, the potential contribution of CSF secretion to PHH has received little attention. In a rat model of PHH, we demonstrate that IVH causes a Toll-like receptor 4 (TLR4)- and NF-κB-dependent inflammatory response in the CPE that is associated with a ∼3-fold increase in bumetanide-sensitive CSF secretion. IVH-induced hypersecretion of CSF is mediated by TLR4-dependent activation of the Ste20-type stress kinase SPAK, which binds, phosphorylates, and stimulates the NKCC1 co-transporter at the CPE apical membrane. Genetic depletion of TLR4 or SPAK normalizes hyperactive CSF secretion rates and reduces PHH symptoms, as does treatment with drugs that antagonize TLR4-NF-κB signaling or the SPAK-NKCC1 co-transporter complex. These data uncover a previously unrecognized contribution of CSF hypersecretion to the pathogenesis of PHH, demonstrate a new role for TLRs in regulation of the internal brain milieu, and identify a kinase-regulated mechanism of CSF secretion that could be targeted by repurposed US Food and Drug Administration (FDA)-approved drugs to treat hydrocephalus.

Pharmacological targeting of SPAK kinase in disorders of impaired epithelial transport

The mammalian SPS1-related proline/alanine-rich serine-threonine kinase SPAK (STK39) modulates ion transport across and between epithelial cells in response to environmental stimuli such osmotic stress and inflammation. Research over the last decade has established a central role for SPAK in the regulation of ion and water transport in the distal nephron, colonic crypts, and pancreatic ducts, and has implicated deregulated SPAK signaling in NaCl-sensitive hypertension, ulcerative colitis and Crohn's disease, and cystic fibrosis. Areas covered: We review recent advances in our understanding of the role of SPAK kinase in the regulation of epithelial transport. We highlight how SPAK signaling - including its upstream Cl- sensitive activators, the WNK kinases, and its downstream ion transport targets, the cation- Cl- cotransporters contribute to human disease. We discuss prospects for the pharmacotherapeutic targeting of SPAK kinase in specific human disorders that feature impaired epithelial homeostasis. Expert opinion: The development of novel drugs that antagonize the SPAK-WNK interaction, inhibit SPAK kinase activity, or disrupt SPAK kinase activation by interfering with its binding to MO25α/β could be useful adjuncts in essential hypertension, inflammatory colitis, and cystic fibrosis.

WNK Kinase Signaling in Ion Homeostasis and Human Disease

WNK kinases, along with their upstream regulators (CUL3/KLHL3) and downstream targets (the SPAK/OSR1 kinases and the cation-Cl- cotransporters [CCCs]), comprise a signaling cascade essential for ion homeostasis in the kidney and nervous system. Recent work has furthered our understanding of the WNKs in epithelial transport, cell volume homeostasis, and GABA signaling, and uncovered novel roles for this pathway in immune cell function and cell proliferation.

SPAK plays a pathogenic role in IgA nephropathy through the activation of NF-κB/MAPKs signaling pathway

Sterile 20/SPS1-related proline/alanine-rich kinase (SPAK) can stimulate production of proinflammatory cytokines and interact with inflammation-related molecules. However, it has yet to be determined whether SPAK plays a pathophysiological role in the complicated pathological mechanisms of IgA nephropathy (IgAN), which is mainly characterized by mesangial cell (MC) proliferation and is the most common form of glomerulonephritis. In the present study, we examined the pathophysiological role of SPAK in IgAN using a mouse model and cell models. Our results clearly showed that (1) SPAK deficiency prevents the development of IgAN and inhibits production of immune/inflammatory mediators and T cell activation and proliferation; and (2) when primed with IgA immune complexes (IgA IC), both peritoneal macrophages and primary MCs from SPAK knockout mice show markedly reduced production of proinflammatory cytokines and inhibition of NF-κB/MAPKs activation. We proposed that activation of SPAK and the NF-κB/MAPKs signaling pathway in MCs, macrophages and T cells of the glomerulus may be a mechanism underlying the pathogenesis of IgAN. The activation of SPAK in renal tubuloepithelial cells either directly by IgA IC or an indirect action of the activated MCs or infiltrating mononuclear leukocytes seen in the kidney may further aggravate the disease process of IgAN. Our results suggest that SPAK is a potential therapeutic target for the glomerular disorder.

With-No-Lysine Kinase 4 Mediates Alveolar Fluid Regulation in Hyperoxia-Induced Lung Injury

OBJECTIVES

To investigate mechanisms involved in the regulation of epithelial ion channels and alveolar fluid clearance in hyperoxia-induced lung injury.

DESIGN

Laboratory animal experiments.

SETTING

Animal care facility procedure room in a medical center.

SUBJECTS

Wild-type, STE20/SPS1-related proline/alanine-rich kinase knockout (SPAK(-/-)), and with-no-lysine kinase 4 knockin (WNK4(D561A/+)) mice.

INTERVENTIONS

Mice were exposed to room air or 95% hyperoxia for 60 hours.

MEASUREMENTS AND MAIN RESULTS

Exposure to hyperoxia for 60 hours increased the lung expression of with-no-lysine kinase 4 and led to STE20/SPS1-related proline/alanine-rich kinase and sodium-potassium-chloride cotransporter phosphorylation, which resulted in the suppression of alveolar fluid clearance and increase of lung edema. WNK4(D561A/+) mice at the baseline presented an abundance of epithelium sodium channel and high levels of STE20/SPS1-related proline/alanine-rich kinase and sodium-potassium-chloride cotransporter phosphorylation. Compared with the wild-type group, hyperoxia caused greater epithelium sodium channel expression in WNK4(D561A/+) mice, but no significant difference in STE20/SPS1-related proline/alanine-rich kinase and sodium-potassium-chloride cotransporter phosphorylation. The functional inactivation of sodium-potassium-chloride cotransporter by gene knockout in SPAK(-/-) mice yielded a lower severity of lung injury and longer animal survival, whereas constitutive expression of with-no-lysine kinase 4 exacerbated the hyperoxia-induced lung injury. Pharmacologic inhibition of sodium-potassium-chloride cotransporter by inhaled furosemide improved animal survival in WNK4(D561A/+) mice. By contrast, inhibition of epithelium sodium channel exacerbated the hyperoxia-induced lung injury and animal death.

CONCLUSIONS

With-no-lysine kinase 4 plays a crucial role in the regulation of epithelial ion channels and alveolar fluid clearance, mainly via phosphorylation and activation of STE20/SPS1-related proline/alanine-rich kinase and sodium-potassium-chloride cotransporter.

Claudin-2 downregulation by KSHV infection is involved in the regulation of endothelial barrier function

BACKGROUND

Kaposi sarcoma (KS), caused by the infection of Kaposi sarcoma-associated herpesvirus (KSHV), is a disease manifested mainly by dark purple skin and mouth nodules. Cancer care studies showed that co-infection of KSHV and human immunodeficiency virus (HIV) was able to increase the patients' survival, but the underlying mechanisms are still elusive.

METHODS

To understand the mechanism underlying the prolonged survival in KSHV-HIV co-infected patients, we performed microarray analysis on RNA extracted from biopsies from KS tumors and adjacent healthy tissues in four KS patients. Subsequently, we performed hierarchical clustering, gene ontology (GO) and ingenuity pathway analysis. We then characterized the roles of tight junction protein claudin-2 in the endothelial barrier function.

RESULTS

Three hundred and forty-three differentially expressed genes were identified, of which 246 genes exhibited significantly increased expression in the tumor compared to the adjacent healthy tissue and 97 genes showed downregulated expression, including claudin-2. Knockdown of claudin-2 in cultured endothelial cells enhances barrier function by altering the charge selectivity, but not the size selectivity.

CONCLUSION

Claudin-2 expression is decreased in KS tumors from patients co-infected with KSHV and HIV. Decreased claudin-2 enhances endothelial barrier function and may play a role in the prolonged survival of patients with KSHV and HIV co-infection.

The enterocyte-associated intestinal microbiota of breast-fed infants and adults responds differently to a TNF-α-mediated pro-inflammatory stimulus

Co-evolved as an integral component of our immune system, the gut microbiota provides specific immunological services at different ages, supporting the immune education during our infancy and sustaining a well-balanced immunological homeostasis during the course of our life. In order to figure out whether this involves differences in the microbial groups primarily interacting with the host immune system, we developed a non-invasive HT29 cell-based minimal model to fingerprint the enterocyte-associated microbiota fraction in infants and adults. After depicting the fecal microbial community of 12 breast-fed infants and 6 adults by 16S rDNA amplicon pools 454 pyrosequencing, their respective HT29 cell-associated gut microbiota fractions were characterized by the universal phylogenetic array platform HTF-Microbi.Array, both in the presence and absence of a tumor necrosis factor-alpha (TNF-α)-mediated pro-inflammatory stimulus. Our data revealed remarkable differences between the enterocyte-associated microbiota fractions in breast-fed infants and adults, being dominated by Bifidobacterium and Enterobacteriaceae the first and Bacteroides-Prevotella and Clostridium clusters IV and XIVa the second. While in adults TNF-α resulted in a profound impairment of the structure of the enterocyte-associated microbiota fraction, in infants it remained unaffected. Differently from the adult-type gut microbial community, the infant-type microbiota is structured to cope with inflammation, being co-evolved to prime the early immune response by means of transient inflammatory signals from gut microorganisms.

Knockout of Ste20-like proline/alanine-rich kinase (SPAK) attenuates intestinal inflammation in mice

Inflammatory bowel diseases are characterized by epithelial barrier disruption and alterations in immune regulation. Ste20-like proline/alanine-rich kinase (SPAK) plays a role in intestinal inflammation, but the underlying mechanisms need to be defined. Herein, SPAK knockout (KO) C57BL/6 mice exhibited significant increases in intestinal transepithelial resistance, a marked decrease in paracellular permeability to fluorescence isothiocyanate-dextran, and altered apical side tight junction sodium ion selectivity, compared with wild-type mice. Furthermore, the expression of junction protein, claudin-2, decreased. In contrast, expressions of occludin, E-cadherin, β-catenin, and claudin-5 increased significantly, whereas no obvious change of claudin-1, claudin-4, zonula occludens protein 1, and zonula occludens protein 2 expressions was observed. In murine models of colitis induced by dextran sulfate sodium and trinitrobenzene sulfuric acid, KO mice were more tolerant than wild-type mice, as demonstrated by colonoscopy features, histological characteristics, and myeloperoxidase activities. Consistent with these findings, KO mice showed increased IL-10 levels and decreased proinflammatory cytokine secretion, ameliorated bacterial translocation on treatment with dextran sulfate sodium, and regulation of with no lysine (WNK) kinase activity. Together, these features may reduce epithelial permeability. In conclusion, SPAK deficiency increases intestinal innate immune homeostasis, which is important for control or attenuation of pathological responses in inflammatory bowel diseases.

Molecular physiology of SPAK and OSR1: two Ste20-related protein kinases regulating ion transport

SPAK (Ste20-related proline alanine rich kinase) and OSR1 (oxidative stress responsive kinase) are members of the germinal center kinase VI subfamily of the mammalian Ste20 (Sterile20)-related protein kinase family. Although there are 30 enzymes in this protein kinase family, their conservation across the fungi, plant, and animal kingdom confirms their evolutionary importance. Already, a large volume of work has accumulated on the tissue distribution, binding partners, signaling cascades, and physiological roles of mammalian SPAK and OSR1 in multiple organ systems. After reviewing this basic information, we will examine newer studies that demonstrate the pathophysiological consequences to SPAK and/or OSR1 disruption, discuss the development and analysis of genetically engineered mouse models, and address the possible role these serine/threonine kinases might have in cancer proliferation and migration.

RNA splicing is responsive to MBNL1 dose

Myotonic dystrophy (DM1) is a highly variable, multi-system disorder resulting from the expansion of an untranslated CTG tract in DMPK. In DM1 expanded CUG repeat RNAs form hairpin secondary structures that bind and aberrantly sequester the RNA splice regulator, MBNL1. RNA splice defects resulting as a consequence of MBNL1 depletion have been shown to play a key role in the development of DM1 pathology. In patient populations, both the number and severity of DM1 symptoms increase broadly as a function of CTG tract length. However significant variability in the DM1 phenotype is observed in patients encoding similar CTG repeat numbers. Here we demonstrate that a gradual decrease in MBNL1 levels results both in the expansion of the repertoire of splice defects and an increase in the severity of the splice alterations. Thus, MBNL1 loss does not have an all or none outcome but rather shows a graded effect on the number and severity of the ensuing splice defects. Our results suggest that once a critical threshold is reached, relatively small dose variations of free MBNL1 levels, which may reflect modest changes in the size of the CUG tract or the extent of hairpin secondary structure formation, can significantly alter the number and severity of splice abnormalities and thus contribute to the phenotype variability observed in DM1 patients.

Tumor necrosis factor alpha modulates the dynamics of the plasminogen-mediated early interaction between Bifidobacterium animalis subsp. lactis and human enterocytes

The capacity to intervene with the host plasminogen system has recently been considered an important component in the interaction process between Bifidobacterium animalis subsp. lactis and the human host. However, its significance in the bifidobacterial microecology within the human gastrointestinal tract is still an open question. Here we demonstrate that human plasminogen favors the B. animalis subsp. lactis BI07 adhesion to HT29 cells. Prompting the HT29 cell capacity to activate plasminogen, tumor necrosis factor alpha (TNF-α) modulated the plasminogen-mediated bacterium-enterocyte interaction, reducing the bacterial adhesion to the enterocytes and enhancing migration to the luminal compartment.

Overexpression of Ste20-related proline/alanine-rich kinase exacerbates experimental colitis in mice

Inflammatory bowel disease, mainly Crohn's disease and ulcerative colitis, are characterized by epithelial barrier disruption and altered immune regulation. Colonic Ste20-like proline/alanine-rich kinase (SPAK) plays a role in intestinal inflammation, but its underlying mechanisms need to be defined. Both SPAK-transfected Caco2-BBE cells and villin-SPAK transgenic (TG) FVB/6 mice exhibited loss of intestinal barrier function. Further studies demonstrated that SPAK significantly increased paracellular intestinal permeability to FITC-dextran. In vivo studies using the mouse models of colitis induced by dextran sulfate sodium (DSS) and trinitrobenzene sulfonic acid showed that TG FVB/6 mice were more susceptible to DSS and trinitrobenzene sulfonic acid treatment than wild-type FVB/6 mice, as demonstrated by clinical and histological characteristics and enzymatic activities. Consistent with this notion, we found that SPAK increased intestinal epithelial permeability, which likely facilitated the production of inflammatory cytokines in vitro and in vivo, aggravated bacterial translocation in TG mice under DSS treatment, and consequently established a context favorable for the triggering of intestinal inflammation cascades. In conclusion, overexpression of SPAK inhibits maintenance of intestinal mucosal innate immune homeostasis, which makes regulation of SPAK important to attenuate pathological responses in inflammatory bowel disease.

Inflammation-induced up-regulation of TLR2 expression in human endothelial cells is independent of differential methylation in the TLR2 promoter CpG island

Toll-like receptors play an important role in endothelial inflammation; however, little is known on the mechanisms regulating their expression. Differential promoter DNA methylation is an increasingly recognized mechanism that determines a switch between gene silencing and gene transcription. We hypothesized that epigenetic mechanisms are involved in the regulation of endothelial TLR2 expression because of the localization of the TLR2 promoter on a CpG-island. Resting human umbilical vein endothelial cells (HUVECs) displayed rather low TLR2 mRNA expression, while a strong expression increase occurred under inflammatory conditions. We examined the TLR2 promoter methylation pattern in resting HUVECs and compared it to cells treated either with the inflammatory cytokine TNF-α or the DNA-demethylating agent 5-azacytidine. DNA bisulfite conversion was followed by either genomic sequencing or single nucleotide primer extension (SNuPE) HPLC. Results of both techniques showed a low- or non-methylated TLR2 promoter in resting HUVECs and no alteration of the methylation pattern under inflammatory conditions. Whereas 5-azacytidine significantly increased the mRNA expression of the epigenetically regulated gene H19, TLR2 expression was not affected. Taken together, employing different methodological approaches, our data show no implication of methylation pattern changes in inflammatory induction of TLR2 expression in human endothelial cells.

DNA demethylation at specific CpG sites in the IL1B promoter in response to inflammatory cytokines in human articular chondrocytes

OBJECTIVE

To determine whether changes in the DNA methylation status in the promoter region of the gene encoding interleukin-1beta (IL-1beta) account for expression of IL1B messenger RNA (mRNA) after long-term treatment of human articular chondrocytes with inflammatory cytokines.

METHODS

IL-1beta, tumor necrosis factor alpha (TNFalpha) plus oncostatin M (OSM), or 5-azadeoxycytidine (5-aza-dC) was added twice weekly for 4-5 weeks to primary cultures of normal human articular chondrocytes derived from the femoral head cartilage of patients with a fracture of the femoral neck. Expression of MMP13, IL1B, TNFA, and DNMT1 was determined by SYBR Green-based quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis of genomic DNA and total RNA extracted from the same sample before and after culture. Bisulfite modification was used to identify which CpG sites in the IL1B promoter showed differential methylation between IL1B-expressing and IL1B-nonexpressing cells. The percentages of cells that were methylated at that critical CpG site (-299 bp) were quantified by a method that depended on methylation-sensitive restriction enzymes and real-time RT-PCR. Secretion of IL-1beta into the culture media was assessed by enzyme-linked immunosorbent assay.

RESULTS

Healthy chondrocytes did not express IL1B mRNA, but the levels were increased 5-fold by treatment with 5-aza-dC and were increased 100-1,000-fold by treatment with TNFalpha/OSM. The percentage CpG methylation was decreased by 5-aza-dC treatment but was reduced considerably more by IL-1beta and was almost abolished by TNFalpha/OSM. The mRNA was translated into protein in cytokine-treated chondrocytes.

CONCLUSION

These novel findings indicate that inflammatory cytokines can change the DNA methylation status at key CpG sites, resulting in long-term induction of IL1B in human articular chondrocytes.

Ste20-related proline/alanine-rich kinase (SPAK) regulated transcriptionally by hyperosmolarity is involved in intestinal barrier function

The Ste20-related protein proline/alanine-rich kinase (SPAK) plays important roles in cellular functions such as cell differentiation and regulation of chloride transport, but its roles in pathogenesis of intestinal inflammation remain largely unknown. Here we report significantly increased SPAK expression levels in hyperosmotic environments, such as mucosal biopsy samples from patients with Crohn's disease, as well as colon tissues of C57BL/6 mice and Caco2-BBE cells treated with hyperosmotic medium. NF-kappaB and Sp1-binding sites in the SPAK TATA-less promoter are essential for SPAK mRNA transcription. Hyperosmolarity increases the ability of NF-kappaB and Sp1 to bind to their binding sites. Knock-down of either NF-kappaB or Sp1 by siRNA reduces the hyperosmolarity-induced SPAK expression levels. Furthermore, expression of NF-kappaB, but not Sp1, was upregulated by hyperosmolarity in vivo and in vitro. Nuclear run-on assays showed that hyperosmolarity increases SPAK expression levels at the transcriptional level, without affecting SPAK mRNA stability. Knockdown of SPAK expression by siRNA or overexpression of SPAK in cells and transgenic mice shows that SPAK is involved in intestinal permeability in vitro and in vivo. Together, our data suggest that SPAK, the transcription of which is regulated by hyperosmolarity, plays an important role in epithelial barrier function.

Effects of trefoil peptide 3 on expression of TNF-alpha, TLR4, and NF-kappaB in trinitrobenzene sulphonic acid induced colitis mice

The trefoil factor (TFF) peptides are major secretory products of mucus cells of the gastrointestinal tract. There were evidences that administration of recombinant human TFF3 is effective in treatment of models of colitis, but the mechanism of the effects of rTFF3 is not fully understood. The main aims of this study is to evaluate effects of intraperitoneal injection recombinant human TFF3 on the expression of tumour necrosis factor alpha (TNF-alpha), toll-like receptor 4(TLR4), and nuclear factor kappaB (NF-kappaB) in trinitrobenzene sulphonic acid (TNBS) induced colitis mice. Distal colitis was induced in BALB/C mice by intracolonic administration of TNBS in ethanol. Treated with administration rhTFF3 for treatment group(5 mg/ml; approximately 0.5 mg/mouse), and normal saline for control for 5 consecutive days. Colonic damage score, tissue myeloperoxidase (MPO) activity, TLR4, NF-kappaB mRNA expression, and tissue TNF-alpha, TLR4, NF-kappaB production were determined, respectively. Once daily application of hTFF3 for 5 days after TNBS/ethanol had been injected, both microscopic and macroscopic injury and inflammatory index had been reduced compared with controls. In addition, decreased tissue TNF-alpha, TLR4, NF-kappaB production, and TLR4, NF-kappaB mRNA expression had been found. This study has shown that hTFF3 may have therapeutic potential in the treatment of inflammatory bowel disease, and one of the mechanisms may related to inhibit the TLR4/NF-kappaB signaling pathways.