Thapsigargin-induced Ca2+ increase inhibits TGFβ1-mediated Smad2 transcriptional responses via Ca2+/calmodulin-dependent protein kinase II

Electrical stimulation of cochlear implant promotes activation of macrophages and fibroblasts under inflammation

Objectives

The implanted electrodes deliver electric signals to spiral ganglion neurons, conferring restored hearing of cochlear implantation (CI) recipients. Postimplantation intracochlear fibrosis, which is observed in most CI recipients, disturbs the electrical signals and impairs the long-term outcome of CI. The macrophages and fibroblasts activation is critical for the development of intracochlear fibrosis. However, the effect of electric stimulation of cochlear implant (ESCI) on the activity of macrophages and fibroblasts was unclear. In the present study, a human cochlear implant was modified to stimulate cultured macrophages and fibroblasts.

Methods

By measuring cellular marker and the expression level of cytokine production, the polarization and activity of macrophages and fibroblasts were examined with or without ESCI.

Results

Our data showed that ESCI had little effects on the morphology, density, and distribution of culturing macrophages and fibroblasts. Furthermore, ESCI alone did not affect the polarization of macrophages or the function of fibroblasts without the treatment of inflammatory factors. However, in the presence of LPS or IL-4, ESCI further promoted the polarization of macrophages, and increased the expression of pro-inflammatory or anti-inflammatory factors, respectively. For fibroblasts, ESCI further increased the collagen I synthesis induced by TGF-β1 treatment. Nifedipine inhibited ESCI induced calcium influx, and hereby abolished the promoted polarization and activation of macrophages and fibroblasts.

Conclusion

Our results suggest that acute inflammation should be well inhibited before the activation of cochlear implants to control the postoperative intracochlear fibrosis. The voltage-gated calcium channels could be considered as the targets for reducing postimplantation inflammation and fibrosis.

Level of Evidence

NA.

Irrespective of Plaque Activity, Multiple Sclerosis Brain Periplaques Exhibit Alterations of Myelin Genes and a TGF-Beta Signature

In a substantial share of patients suffering from multiple sclerosis (MS), neurological functions slowly deteriorate despite a lack of radiological activity. Such a silent progression, observed in either relapsing-remitting or progressive forms of MS, is driven by mechanisms that appear to be independent from plaque activity. In this context, we previously reported that, in the spinal cord of MS patients, periplaques cover large surfaces of partial demyelination characterized notably by a transforming growth factor beta (TGF-beta) molecular signature and a decreased expression of the oligodendrocyte gene NDRG1 (N-Myc downstream regulated 1). In the present work, we re-assessed a previously published RNA expression dataset in which brain periplaques were originally used as internal controls. When comparing the mRNA profiles obtained from brain periplaques with those derived from control normal white matter samples, we found that, irrespective of plaque activity, brain periplaques exhibited a TGF-beta molecular signature, an increased expression of TGFB2 (transforming growth factor beta 2) and a decreased expression of the oligodendrocyte genes NDRG1 (N-Myc downstream regulated 1) and MAG (myelin-associated glycoprotein). From these data obtained at the mRNA level, a survey of the human proteome allowed predicting a protein-protein interaction network linking TGFB2 to the down-regulation of both NDRG1 and MAG in brain periplaques. To further elucidate the role of NDRG1 in periplaque-associated partial demyelination, we then extracted the interaction network linking NDRG1 to proteins detected in human central myelin sheaths. We observed that such a network was highly significantly enriched in RNA-binding proteins that notably included several HNRNPs (heterogeneous nuclear ribonucleoproteins) involved in the post-transcriptional regulation of MAG. We conclude that both brain and spinal cord periplaques host a chronic process of tissue remodeling, during which oligodendrocyte myelinating functions are altered. Our findings further suggest that TGFB2 may fuel such a process. Overall, the present work provides additional evidence that periplaque-associated partial demyelination may drive the silent progression observed in a subset of MS patients.

Erythropoietin Nanobots: Their Feasibility for the Controlled Release of Erythropoietin and Their Neuroprotective Bioequivalence in Central Nervous System Injury

Background: Erythropoietin (EPO) plays important roles in neuroprotection in central nervous system injury. Due to the limited therapeutic time window and coexistence of hematopoietic/extrahematopoietic receptors displaying heterogenic and phylogenetic differences, fast, targeted delivery agents, such as nanobots, are needed. To confirm the feasibility of EPO-nanobots (ENBs) as therapeutic tools, the authors evaluated controlled EPO release from ENBs and compared the neuroprotective bioequivalence of these substances after preconditioning sonication. Methods: ENBs were manufactured by a nanospray drying technique with preconditioning sonication. SH-SY5Y neuronal cells were cotreated with thapsigargin and either EPO or ENBs before cell viability, EPO receptor activation, and endoplasmic reticulum stress-related pathway deactivation were determined over 24 h. Results: Preconditioning sonication (50–60 kHz) for 1 h increased the cumulative EPO release from the ENBs (84% versus 25% at 24 h). Between EPO and ENBs at 24 h, both neuronal cell viability (both > 65% versus 15% for thapsigargin alone) and the expression of the proapoptotic/apoptotic biomolecular markers JAK2, PDI, PERK, GRP78, ATF6, CHOP, TGF-β, and caspase-3 were nearly the same or similar. Conclusion: ENBs controlled EPO release in vitro after preconditioning sonication, leading to neuroprotection similar to that of EPO at 24 h.

Heme Induces Endoplasmic Reticulum Stress (HIER Stress) in Human Aortic Smooth Muscle Cells

Accumulation of damaged or misfolded proteins resulted from oxidative protein modification induces endoplasmic reticulum (ER) stress by activating the pathways of unfolded protein response. In pathologic hemolytic conditions, extracellular free hemoglobin is submitted to rapid oxidation causing heme release. Resident cells of atherosclerotic lesions, after intraplaque hemorrhage, are exposed to heme leading to oxidative injury. Therefore, we raised the question whether heme can also provoke ER stress. Smooth muscle cells are one of the key players of atherogenesis; thus, human aortic smooth muscle cells (HAoSMCs) were selected as a model cell to reveal the possible link between heme and ER stress. Using immunoblotting, quantitative polymerase chain reaction and immunocytochemistry, we quantitated the markers of ER stress. These were: phosphorylated eIF2α, Activating transcription factor-4 (ATF4), DNA-damage-inducible transcript 3 (also known as C/EBP homology protein, termed CHOP), X-box binding protein-1 (XBP1), Activating transcription factor-6 (ATF6), GRP78 (glucose-regulated protein, 78kDa) and heme responsive genes heme oxygenase-1 and ferritin. In addition, immunohistochemistry was performed on human carotid artery specimens from patients who had undergone carotid endarterectomy. We demonstrate that heme increases the phosphorylation of eiF2α in HAoSMCs and the expression of ATF4. Heme also enhances the splicing of XBP1 and the proteolytic cleavage of ATF6. Consequently, there is up-regulation of target genes increasing both mRNA and protein levels of CHOP and GRP78. However, TGFβ and collagen type I decreased. When the heme binding proteins, alpha-1-microglobulin (A1M) and hemopexin (Hpx) are present in cell media, the ER stress provoked by heme is inhibited. ER stress pathways are also retarded by the antioxidant N-acetyl cysteine (NAC) indicating that reactive oxygen species are involved in heme-induced ER stress. Consistent with these findings, elevated expression of the ER stress marker GRP78 and CHOP were observed in smooth muscle cells of complicated lesions with hemorrhage compared to either atheromas or healthy arteries. In conclusion, heme triggers ER stress in a time- and dose-dependent manner in HAoSMCs. A1M and Hpx as well as NAC effectively hamper heme-induced ER stress, supporting their use as a potential therapeutic approach to reverse such a deleterious effects of heme toxicity.

Repurposed drug screen identifies cardiac glycosides as inhibitors of TGF-β-induced cancer-associated fibroblast differentiation

The tumor microenvironment, primarily composed of myofibroblasts, directly influences the progression of solid tumors. Through secretion of growth factors, extracellular matrix deposition, and contractile mechanotransduction, myofibroblasts, or cancer-associated fibroblasts (CAFs), support angiogenesis and cancer cell invasion and metastasis. The differentiation of fibroblasts to CAFs is primarily induced by TGF-β from cancer cells. To discover agents capable of blocking CAF differentiation, we developed a high content immunofluorescence-based assay to screen repurposed chemical libraries utilizing fibronectin expression as an initial CAF marker. Screening of the Prestwick chemical library and NIH Clinical Collection repurposed drug library, totaling over 1700 compounds, identified cardiac glycosides as particularly potent CAF blocking agents. Cardiac glycosides are traditionally used to regulate intracellular calcium by inhibiting the Na+/K+ ATPase to control cardiac contractility. Herein, we report that multiple cardiac glycoside compounds, including digoxin, are able to inhibit TGF-β-induced fibronectin expression at low nanomolar concentrations without undesirable cell toxicity. We found this inhibition to hold true for multiple fibroblast cell lines. Using real-time qPCR, we determined that digoxin prevented induction of multiple CAF markers. Furthermore, we report that digoxin is able to prevent TGF-β-induced fibroblast contraction of extracellular matrix, a major phenotypic consequence of CAF differentiation. Assessing the mechanism of inhibition, we found digoxin reduced SMAD promoter activity downstream of TGF-β, and we provide data that the effect is through inhibition of its known target, the Na+/K+ ATPase. These findings support a critical role for calcium signaling during CAF differentiation and highlight a novel, repurposable modality for cancer therapy.

Thapsigargin-induced activation of Ca(2+)-CaMKII-ERK in brainstem contributes to substance P release and induction of emesis in the least shrew

Cytoplasmic calcium (Ca(2+)) mobilization has been proposed to be an important factor in the induction of emesis. The selective sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA) inhibitor thapsigargin, is known to deplete intracellular Ca(2+) stores, which consequently evokes extracellular Ca(2+) entry through cell membrane-associated channels, accompanied by a prominent rise in cytosolic Ca(2+). A pro-drug form of thapsigargin is currently under clinical trial as a targeted cancer chemotherapeutic. We envisioned that the intracellular effects of thapsigargin could cause emesis and planned to investigate its mechanisms of emetic action. Indeed, thapsigargin did induce vomiting in the least shrew in a dose-dependent and bell-shaped manner, with maximal efficacy (100%) at 0.5 mg/kg (i.p.). Thapsigargin (0.5 mg/kg) also caused increases in c-Fos immunoreactivity in the brainstem emetic nuclei including the area postrema (AP), nucleus tractus solitarius (NTS) and dorsal motor nucleus of the vagus (DMNX), as well as enhancement of substance P (SP) immunoreactivity in DMNX. In addition, thapsigargin (0.5 mg/kg, i.p.) led to vomit-associated and time-dependent increases in phosphorylation of Ca(2+)/calmodulin kinase IIα (CaMKIIα) and extracellular signal-regulated protein kinase 1/2 (ERK1/2) in the brainstem. We then explored the suppressive potential of diverse chemicals against thapsigargin-evoked emesis including antagonists of: i) neurokinin-1 receptors (netupitant), ii) the type 3 serotonin receptors (palonosetron), iii) store-operated Ca(2+) entry (YM-58483), iv) L-type Ca(2+) channels (nifedipine), and v) SER Ca(2+)-release channels inositol trisphosphate (IP3Rs) (2-APB)-, and ryanodine (RyRs) (dantrolene)-receptors. In addition, the antiemetic potential of inhibitors of CaMKII (KN93) and ERK1/2 (PD98059) were investigated. All tested antagonists/blockers attenuated emetic parameters to varying degrees except palonosetron, however a combination of non-effective doses of netupitant and palonosetron exhibited additive antiemetic efficacy. A low-dose combination of nifedipine and 2-APB plus dantrolene mixture completely abolished thapsigargin-evoked vomiting, CaMKII-ERK1/2 activation and SP elevation. In addition, pretreatment with KN93 or PD98059 suppressed thapsigargin-induced increases in SP and ERK1/2 activation. Intracerebroventricular injection of netupitant suppressed vomiting caused by thapsigargin which suggests that the principal site of evoked emesis is the brainstem. In sum, this is the first study to demonstrate that thapsigargin causes vomiting via the activation of the Ca(2+)-CaMKII-ERK1/2 cascade, which is associated with an increase in the brainstem tissue content of SP, and the evoked emesis occurs through SP-induced activation of neurokinin-1 receptors.

Intracellular Protein Shuttling: A Mechanism Relevant for Myelin Repair in Multiple Sclerosis?

A prominent feature of demyelinating diseases such as multiple sclerosis (MS) is the degeneration and loss of previously established functional myelin sheaths, which results in impaired signal propagation and axonal damage. However, at least in early disease stages, partial replacement of lost oligodendrocytes and thus remyelination occur as a result of resident oligodendroglial precursor cell (OPC) activation. These cells represent a widespread cell population within the adult central nervous system (CNS) that can differentiate into functional myelinating glial cells to restore axonal functions. Nevertheless, the spontaneous remyelination capacity in the adult CNS is inefficient because OPCs often fail to generate new oligodendrocytes due to the lack of stimulatory cues and the presence of inhibitory factors. Recent studies have provided evidence that regulated intracellular protein shuttling is functionally involved in oligodendroglial differentiation and remyelination activities. In this review we shed light on the role of the subcellular localization of differentiation-associated factors within oligodendroglial cells and show that regulation of intracellular localization of regulatory factors represents a crucial process to modulate oligodendroglial maturation and myelin repair in the CNS.

Inflammation and pancreatic cancer: molecular and functional interactions between S100A8, S100A9, NT-S100A8 and TGFβ1

BACKGROUND

In order to gain further insight on the crosstalk between pancreatic cancer (PDAC) and stromal cells, we investigated interactions occurring between TGFβ1 and the inflammatory proteins S100A8, S100A9 and NT-S100A8, a PDAC-associated S100A8 derived peptide, in cell signaling, intracellular calcium (Cai2+) and epithelial to mesenchymal transition (EMT). NF-κB, Akt and mTOR pathways, Cai2+ and EMT were studied in well (Capan1 and BxPC3) and poorly differentiated (Panc1 and MiaPaCa2) cell lines.

RESULTS

NT-S100A8, one of the low molecular weight N-terminal peptides from S100A8 to be released by PDAC-derived proteases, shared many effects on NF-κB, Akt and mTOR signaling with S100A8, but mainly with TGFβ1. The chief effects of S100A8, S100A9 and NT-S100A8 were to inhibit NF-κB and stimulate mTOR; the molecules inhibited Akt in Smad4-expressing, while stimulated Akt in Smad4 negative cells. By restoring Smad4 expression in BxPC3 and silencing it in MiaPaCa2, S100A8 and NT-S100A8 were shown to inhibit NF-κB and Akt in the presence of an intact TGFβ1 canonical signaling pathway. TGFβ1 counteracted S100A8, S100A9 and NT-S100A8 effects in Smad4 expressing, not in Smad4 negative cells, while it synergized with NT-S100A8 in altering Cai2+ and stimulating PDAC cell growth. The effects of TGFβ1 on both EMT (increased Twist and decreased N-Cadherin expression) and Cai2+ were antagonized by S100A9, which formed heterodimers with TGFβ1 (MALDI-TOF/MS and co-immuno-precipitation).

CONCLUSIONS

The effects of S100A8 and S100A9 on PDAC cell signaling appear to be cell-type and context dependent. NT-S100A8 mimics the effects of TGFβ1 on cell signaling, and the formation of complexes between TGFβ1 with S100A9 appears to be the molecular mechanism underlying the reciprocal antagonism of these molecules on cell signaling, Cai2+ and EMT.