LncRNA Tincr regulates PKCɛ expression in a miR-31-5p-dependent manner in cardiomyocyte hypertrophy

Cardiomyocyte hypertrophy is a fatal factor in heart disease resulting in heart failure and even mortality. Although many studies have been focusing on the pathogenesis of cardiomyocyte hypertrophy, the exact molecular mechanisms are still unexclusive. In this study, we first found that the expression level of lncRNA Tincr was significantly decreased in the myocardial tissues of TAC mouse models of cardiomyocyte hypertrophy, and this result was further confirmed in H9C2 cells, a widely used rat myoblast cell lines. More intriguingly, we demonstrated that the aberration of Tincr is essential to the pathogenesis of cardiomyocyte hypertrophy, indicated by the re-induction of Tincr improving the heart functions of hypertrophic mice. In mechanism, we identified miR-31-5p as a direct target of Tincr using a widely used online bioinformatics tool StarBase, and this result was further experimentally validated using dual-luciferase reporter assay and real-time PCR. Also, we identified PRKCE as a direct target of miR-31-5p, and loss function of miR-31-5p significantly blocks the positive regulatory effect of Tincr on PRKCE expression in H9C2 cells. The knockdown of Tincr resulted in increased cardiomyocyte size, and, however, inhibition of miR-31-5p or overexpression of PRKCE significantly reversed the increased cardiomyocyte size. Taken together, our study showed that a novel Tincr-miR-31-5p axis targeting PRKCE was involved in cardiomyocyte hypertrophy, indicating that it may provide potential therapy in cardiomyocyte hypertrophy.

Loss in PKC Epsilon Causes Downregulation of MnSOD and BDNF Expression in Neurons of Alzheimer's Disease Hippocampus

Oxidative stress and amyloid-β (Aβ) oligomers have been implicated in Alzheimer's disease (AD). The growth and maintenance of neuronal networks are influenced by brain derived neurotrophic factor (BDNF) expression, which is promoted by protein kinase C epsilon (PKCɛ). We investigated the reciprocal interaction among oxidative stress, Aβ, and PKCɛ levels and subsequent PKCɛ-dependent MnSOD and BDNF expression in hippocampal pyramidal neurons. Reduced levels of PKCɛ, MnSOD, and BDNF and an increased level of Aβ were also found in hippocampal neurons from autopsy-confirmed AD patients. In cultured human primary hippocampal neurons, spherical aggregation of Aβ (amylospheroids) decreased PKCɛ and MnSOD. Treatment with t-butyl hydroperoxide (TBHP) increased superoxide, the oxidative DNA/RNA damage marker, 8-OHG, and Aβ levels, but reduced PKCɛ, MnSOD, BDNF, and cultured neuron density. These changes were reversed with the PKCɛ activators, bryostatin and DCPLA-ME. PKCɛ knockdown suppressed PKCɛ, MnSOD, and BDNF but increased Aβ. In cultured neurons, the increase in reactive oxygen species (ROS) associated with reduced PKCɛ during neurodegeneration was inhibited by the SOD mimetic MnTMPyP and the ROS scavenger NAc, indicating that strong oxidative stress suppresses PKCɛ level. Reduction of PKCɛ and MnSOD was prevented with the PKCɛ activator bryostatin in 5-6-month-old Tg2576 AD transgenic mice. In conclusion, oxidative stress and Aβ decrease PKCɛ expression. Reciprocally, a depression of PKCɛ reduces BDNF and MnSOD, resulting in oxidative stress. These changes can be prevented with the PKCɛ-specific activators.

Flow-Responsive Vascular Endothelial Growth Factor Receptor-Protein Kinase C Isoform Epsilon Signaling Mediates Glycolytic Metabolites for Vascular Repair

AIMS

Hemodynamic shear stress participates in maintaining vascular redox status. Elucidating flow-mediated endothelial metabolites enables us to discover metabolic biomarkers and therapeutic targets. We posited that flow-responsive vascular endothelial growth factor receptor (VEGFR)-protein kinase C isoform epsilon (PKCɛ)-6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) signaling modulates glycolytic metabolites for vascular repair.

RESULTS

Bidirectional oscillatory flow (oscillatory shear stress [OSS]: 0.1 ± 3 dyne·cm-2 at 1 Hz) upregulated VEGFR-dependent PKCɛ expression to a greater degree than did unidirectional pulsatile flow (pulsatile shear stress [PSS]: 23 ± 8 dyne·cm-2 at 1 Hz) in human aortic endothelial cells (p < 0.05, n = 3). PSS and OSS further upregulated PKCɛ-dependent PFKFB3 expression for glycolysis (p < 0.05, n = 4). Constitutively active PKCɛ increased, whereas dominant-negative PKCɛ reduced both basal and maximal extracellular acidification rates for glycolytic flux (p < 0.01, n = 4). Metabolomic analysis demonstrated an increase in PKCɛ-dependent glycolytic metabolite, dihydroxyacetone (DHA), but a decrease in gluconeogenic metabolite, aspartic acid (p < 0.05 vs. control, n = 6). In a New Zealand White rabbit model, both PKCɛ and PFKFB3 immunostaining was prominent in the PSS- and OSS-exposed aortic arch and descending aorta. In a transgenic Tg(flk-1:EGFP) zebrafish model, GATA-1a morpholino oligonucleotide injection (to reduce viscosity-dependent shear stress) impaired vascular regeneration after tail amputation (p < 0.01, n = 20), which was restored with PKCɛ messenger RNA (mRNA) rescue (p < 0.05, n = 5). As a corollary, siPKCɛ inhibited tube formation and vascular repair, which were restored by DHA treatment in our Matrigel and zebrafish models. Innovation and Conclusion: Flow-sensitive VEGFR-PKCɛ-PFKFB3 signaling increases the glycolytic metabolite, dihydroxyacetone, to promote vascular repair. Antioxid. Redox Signal. 28, 31-43.

Myofibroblasts have an impact on expression, dimerization and signaling of different ErbB receptors in OSCC cells

INTRODUCTION

Receptors of the ErbB family belong to the key players in cancer development and are targets of several therapeutic approaches. Their functional dependency on the tumor microenvironment, especially on CAFs is albeit still poorly understood. Our objective was to investigate the impact of CAF secretome on ErbB receptor expression and signaling behavior in OSCC.

METHODS

Stimulation of PE/CA-PJ15 OSCC cells with conditioned media of TGF-β1-activated fibroblasts was used as model system for CAF to cancer cell communication. Thereby costimulation with inhibitors against matrix metalloproteinases (MMPs), epidermal growth factor receptor (EGFR), MAPK/ERK kinase (MEK), phosphoinositide-3 kinase (PI3-K), signal transducer and activator of transcription 3 (Stat3) or knockdown of Her3 by siRNA was utilized for detailed investigation of the expression, dimerization and signaling pattern of ErbB in western blot and coimmunoprecipitation.

RESULTS

Our results show that soluble factors in activated fibroblast secretome stimulate metalloproteinase activity in the membrane of cancer cells. Thereby ligands are released that activate EGFR and subsequently upregulates EGFR expression via the STAT3 pathway. Simultaneously, the expression of PKCɛ was enhanced via a PI3-kinase/Akt-mediated pathway and a negative feedback regulation loop on EGFR downstream signaling generated. Furthermore, the activated fibroblasts secretome stimulated the highly oncogenic hetero-dimerization between HER3 and p95HER2. That protein association is inversely dependent on the expression level of HER3.

CONCLUSIONS

Our results demonstrate that the activated fibroblasts secretome can induce a counterbalanced regulation of protein expression, downstream signaling and the dimerization patterns of different ErbB receptor subtypes in the cancer cell. Thus, the combinatorial targeting of CAFs and selective ErbB receptor subtype inhibitors may provide a useful approach in cancer therapy.

PKC-epsilon activation is required for recognition memory in the rat

Activation of PKCɛ, an abundant and developmentally regulated PKC isoform in the brain, has been implicated in memory throughout life and across species. Yet, direct evidence for a mechanistic role for PKCɛ in memory is still lacking. Hence, we sought to evaluate this in rats, using short-term treatments with two PKCɛ-selective peptides, the inhibitory ɛV1-2 and the activating ψɛRACK, and the novel object recognition task (NORT). Our results show that the PKCɛ-selective activator ψɛRACK, did not have a significant effect on recognition memory. In the short time frames used, however, inhibition of PKCɛ activation with the peptide inhibitor ɛV1-2 significantly impaired recognition memory. Moreover, when we addressed at the molecular level the immediate proximal signalling events of PKCɛ activation in acutely dissected rat hippocampi, we found that ψɛRACK increased in a time-dependent manner phosphorylation of MARCKS and activation of Src, Raf, and finally ERK1/2, whereas ɛV1-2 inhibited all basal activity of this pathway. Taken together, these findings present the first direct evidence that PKCɛ activation is an essential molecular component of recognition memory and point toward the use of systemically administered PKCɛ-regulating peptides as memory study tools and putative therapeutic agents.

Effects of NSAIDs and paracetamol (acetaminophen) on protein kinase C epsilon translocation and on substance P synthesis and release in cultured sensory neurons

Celecoxib, diclofenac, ibuprofen, and nimesulide are nonsteroidal anti-inflammatory drugs (NSAIDs) very commonly used for the treatment of moderate to mild pain, together with paracetamol (acetaminophen), a very widely used analgesic with a lesser anti-inflammatory effect. In the study reported here, we tested the efficacy of celecoxib, diclofenac, and ibuprofen on preprotachykinin mRNA synthesis, substance P (SP) release, prostaglandin E₂ (PGE₂) release, and protein kinase C epsilon (PKCɛ) translocation in rat cultured sensory neurons from dorsal root ganglia (DRGs). The efficacy of these NSAIDs was compared with the efficacy of paracetamol and nimesulide in in vitro models of hyperalgesia (investigated previously). While nimesulide and paracetamol, as in previous experiments, decreased the percentage of cultured DRG neurons showing translocation of PKCɛ caused by 100 nM thrombin or 1 μM bradykinin in a dose-dependent manner, the other NSAIDs tested did not have a significant effect. The amount of SP released by peptidergic neurons and the expression level of preprotachykinin mRNA were assessed in basal conditions and after 70 minutes or 36 hours of stimulation with an inflammatory soup (IS) containing potassium chloride, thrombin, bradykinin, and endothelin-1. The release of SP at 70 minutes was inhibited only by nimesulide, while celecoxib and diclofenac were effective at 36 hours. The mRNA basal level of the SP precursor preprotachykinin expressed in DRG neurons was reduced only by nimesulide, while the increased levels expressed during treatment with the IS were significantly reduced by all drugs tested, with the exception of ibuprofen. All drugs were able to decrease basal and IS-stimulated PGE₂ release. Our study demonstrates novel mechanisms of action of commonly used NSAIDS.

Nimesulide inhibits protein kinase C epsilon and substance P in sensory neurons - comparison with paracetamol

In this paper we describe new actions of nimesulide and paracetamol in cultured peripheral neurons isolated from rat dorsal root ganglia (DRG). Both drugs were able to decrease in a dose-dependent fashion the number of cultured DRG neurons showing translocation of protein kinase C epsilon (PKCɛ) caused by exposure to 1 μM bradykinin or 100 nM thrombin. In addition, the level of substance P (SP) released by DRG neurons and the level of preprotachykinin mRNA expression were measured in basal conditions and after 70 minutes or 36 hours of stimulation with nerve growth factor (NGF) or with an inflammatory soup containing bradykinin, thrombin, endothelin-1, and KCl. Nimesulide (10 μM) significantly decreased the mRNA levels of the SP precursor preprotachykinin in basal and in stimulated conditions, and decreased the amount of SP released in the medium during stimulation of neurons with NGF or with the inflammatory soup. The effects of paracetamol (10 μM) on such response was lower. Nimesulide completely inhibited the release of prostaglandin E2 (PGE2) from DRG neurons, either basal or induced by NGF and by inflammatory soup, while paracetamol decreased PGE2 release only partially. Our data demonstrate, for the first time, a direct effect of two drugs largely used as analgesics on DRG neurons. The present results suggest that PKCɛ might be a target for the effect of nimesulide and paracetamol, while inhibition of SP synthesis and release is clearly more relevant for nimesulide than for paracetamol mechanism of action.